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Jin J, Kaewsakul W, Noordermeer JWM, Dierkes WK, Blume A. MACRO- AND MICRO-DISPERSION OF SILICA IN TIRE TREAD COMPOUNDS: ARE THEY RELATED? Rubber Chemistry and Technology 2021. [DOI: 10.5254/rct.20.80365] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
The dispersion of rubber fillers, such as silica, can be divided into two categories: macro- and micro-dispersion. Both dispersions are important; however, to achieve the best reinforcement of rubber, micro-dispersion of silica is crucial. The common view is that these filler dispersions are strongly related. The micro-dispersion is understood as the consequence of the continuous breakdown of filler clusters from macro-dispersion. Yet, a large problem is that an objective unequivocal direct measurement method for micro-dispersion is not available. In this study, a set of parameters is defined that are anticipated to have an influence on the micro- as well as the macro-dispersion. Mixing trials are performed with varying silanization temperature and time, different amounts of silane coupling agent, and by using silicas with different structures and specific surface areas. The degrees of micro- and macro-dispersion are evaluated by measuring the Payne effect as an indirect method for micro-dispersion and using a dispergrader for quantitative measurement of macro-dispersion. The results show that the filler dispersion processes happen simultaneously but independently. These results are supported by earlier work of Blume and Uhrlandt, who stated as well that micro- and macro-dispersion are independent. The major influencing factors on micro- and macro-dispersion of silica are also identified.
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Affiliation(s)
- J. Jin
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
- Hankooktire Co., LTD., Main R&D Center, Material Department, 34127 Daejeon, Republic of Korea
| | - W. Kaewsakul
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
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Sattayanurak S, Sahakaro K, Kaewsakul W, Dierkes WK, Reuvekamp LAEM, Blume A, Noordermeer JWM. Elucidating the role of clay-modifier on the properties of silica- and silica/nanoclay-reinforced natural rubber tire compounds. EXPRESS POLYM LETT 2021. [DOI: 10.3144/expresspolymlett.2021.56] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Sattayanurak S, Sahakaro K, Kaewsakul W, Dierkes WK, Reuvekamp LAEM, Blume A, Noordermeer JWM. IMPROVEMENT OF SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS BY JOINT HYBRIDIZATION WITH SMALL AMOUNTS OF SECONDARY FILLERS AND POLYMERS. Rubber Chemistry and Technology 2020. [DOI: 10.5254/rct.20.79962] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
To improve the properties of silica-reinforced truck tire tread compounds, especially abrasion resistance, the effect of vinyl contents in butadiene rubber (BR) or solution styrene–butadiene rubber (SSBR) as secondary polymers in silica-filled natural rubber (NR) compounds at a ratio of 80/20 phr is investigated in the first part of this study. By increasing the levels of vinyl contents in BR in combination with NR, a better Payne effect, 300% modulus, reinforcement index, and tan delta at −20 and 0 ° C are obtained, whereas the tensile strength, elongation at break, and DIN abrasion resistance index decrease with increasing vinyl contents. Higher vinyl contents in SSBR result in improvements in Payne effect, 300% modulus, tan delta at −20 and 0 °C but only a small improvement in DIN abrasion resistance index. Combinations of secondary fillers and polymers in silica-filled NR are covered in the second part of present study. Silica/carbon black–filled NR/BR and NR/SSBR, respectively, and silica/organoclay–filled NR/BR and NR/SSBR show positive effects on scorch time and optimum cure time, with only slight changes in Payne effect, tensile properties, tan delta at −20 and 0 ° C and DIN abrasion resistance as compared with compounds with carbon black N134. The use of organoclay results in an enhanced Payne effect and tan delta at 60 °C, indicative of reduced filler–filler networking and consequently a lower rolling resistance of tire tread compounds as compared with the compound without organoclay. The specific combination of a small amount of organoclay replacing the same amount of silica, together with some of the NR replaced by high-vinyl BR, promises a substantial overall boost in wet and ice traction, abrasion, and wear resistance as compared with straight NR/silica tire treads. This new observation helps to overcome one of the main shortcomings of NR/silica compounds: their generally low wear resistance.
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Affiliation(s)
- S. Sattayanurak
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
| | - W. Kaewsakul
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521 PT Enschede, The Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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Sattayanurak S, Sahakaro K, Kaewsakul W, Dierkes WK, Reuvekamp LAEM, Blume A, Noordermeer JWM. ENHANCING PERFORMANCE OF SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS BY APPLYING ORGANOCLAY AS SECONDARY FILLER. Rubber Chemistry and Technology 2020. [DOI: 10.5254/rct.20.80373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
Silica-reinforced natural rubber (NR) tire tread compounds are investigated using organoclay (OC) as secondary filler. By varying mixer temperature settings at a silica/OC ratio of 45/10 phr, dump temperatures are reached of approximately 120, 140, 150, and 160 °C. The increased dump temperature leads to a better silanization reaction resulting in lower mixing torque, Mooney viscosity, and Payne effect. The optimum mixing dump temperature was found to be around 150 °C. By varying the loadings of OC in the silica-filled NR compounds from 0 to 36 wt% relative to total filler amount, the increased OC loadings decreased the Payne effect and compound viscosities, significantly shortened scorch and cure times, and raised the tan delta at −20 and 0 °C as indications for ice traction and wet skid resistance of tire treads made therefrom. The optimum loading of OC of 9 wt% relative to total filler content shows better Payne effect, cure rate index, tan delta at −20 and 60 °C indicative for rolling resistance, and DIN (German Institute of Standardization) abrasion resistance index. The results indicate that the use of this hybrid filler may provide tires with better wet traction and lower rolling resistance and wear resistance compared with the pure silica-filled system.
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Affiliation(s)
- S. Sattayanurak
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
| | - W. Kaewsakul
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521pt Enschede, The Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500ae Enschede, The Netherlands
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Hayichelaeh C, Reuvekamp LAEM, Dierkes WK, Blume A, Noordermeer JWM, Sahakaro K. SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS CONTAINING BIO-BASED PROCESS OILS. II: INFLUENCE OF EPOXIDE AND AMINO FUNCTIONAL GROUPS. Rubber Chemistry and Technology 2020. [DOI: 10.5254/rct.19.81461] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
The feasibility of the use of epoxidized palm oil (EPO) and amine-modified epoxidized palm oil (mEPO) as process oils in silica-reinforced natural rubber compounds is studied. The chemical structures of EPO and mEPO are characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy (1H-NMR). Amine modification for 3 and 5 h leads to mEPOs with 0.03 and 0.04 mmol of amine in 1 g of oil, referred to as 0.03 mEPO and 0.04 mEPO, respectively. The properties of rubber compounds containing modified palm oils are investigated by taking those with TDAE oil and those without oil as references. The use of process oils clearly enhances the processibility (i.e., lower mixing torque and complex viscosity) and mechanical and dynamic mechanical properties of the rubber compounds as compared with compounds without oil. The rubber compounds with EPO and 0.03 mEPO show a lower Payne effect (i.e., less filler–filler interaction) than the rubber compound with TDAE because of the shielding effect of the oils on the silica surface. The use of mEPO boosts the vulcanization reaction, resulting in much better cure torque difference, which indicates a higher crosslink density due to the amino groups present in mEPO as compared with TDAE. Therefore, rubber compounds with mEPOs have better mechanical properties (i.e., reinforcement index, tensile strength, and elongation at break) and better elastic response under dynamic deformation, as indicated by a lower loss tangent at 60 °C as compared with the mix with TDAE.
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Affiliation(s)
- C. Hayichelaeh
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521 PT Enschede, the Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
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Blume A, Snellgrove B, Steinert T. [Staffing levels and patient-related outcomes : Systematic literature review on international evidence]. Nervenarzt 2019; 90:40-44. [PMID: 30238232 DOI: 10.1007/s00115-018-0621-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The objective of this study was to systematically review the international literature with respect to significant links between staffing levels or qualification on the one hand and patient-related outcomes on the other. Of the initial 7778 abstracts identified by means of a complex search strand in PubMed and CINAHL, 51 could finally be included in a qualitative synthesis. A total of nine different patient-related outcome categories with significant associations on an at least ordinally scaled level were distinguished. None of the studies included had a (quasi-)experimental research design. Despite, in some instances, high numbers of cases at multiple sites and efforts to control obvious confounding variables by regression analysis, no evidence-based conclusions for health policy or clinical practice can be drawn from the available observational studies. There is therefore a considerable need for prospective randomized or at least quasi-experimental studies also as accompanying research on novel models of financing.
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Affiliation(s)
- A Blume
- Klinik für Psychiatrie und Psychotherapie I der Universität Ulm, Weissenau, ZfP Südwürttemberg, Weingartshofer Str. 2, 88214, Ravensburg, Deutschland.
| | - B Snellgrove
- Klinik für Psychiatrie und Psychotherapie I der Universität Ulm, Weissenau, ZfP Südwürttemberg, Weingartshofer Str. 2, 88214, Ravensburg, Deutschland
| | - T Steinert
- Klinik für Psychiatrie und Psychotherapie I der Universität Ulm, Weissenau, ZfP Südwürttemberg, Weingartshofer Str. 2, 88214, Ravensburg, Deutschland
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Vleugels N, Dierkes WK, Blume A, Reuvekamp LAEM, Noordermeer JWM. MAIN GOVERNING FACTORS INFLUENCING MECHANICAL PROPERTIES OF SHORT-CUT ARAMID FIBER–REINFORCED ELASTOMERS. Rubber Chemistry and Technology 2019. [DOI: 10.5254/rct.19.82593] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
This study concerns short-cut aramid fiber reinforcement of synthetic elastomer compounds and their influence on the processability and mechanical properties. Short-fiber reinforcement of elastomers is very complex, because it depends on many mutually interacting factors: fiber concentration, fiber orientation distribution, fiber length and distribution, fiber-matrix interfacial strength, and properties of the matrix. The relationship between these influencing factors is highlighted in an S-SBR compound by design of experiments. Two 3 mm long aramid fibers were used: an epoxy-amine–coated fiber and a virgin fiber without coating. To potentially achieve a fiber–matrix interaction, the following silane coupling agents were employed: bis-(triethoxysilylpropyl)-disulfane (TESPD), bis-(triethoxysilylpropyl)-tetrasulfane (TESPT), S-3-(triethoxysilylpropyl)-octanethioate (NXT), and an alkylpolyether-mercapto-silane (Si 363), all in combination with the adhesion-activated aramid fibers and in comparison with the virgin fibers. They are compared on equimolar basis with regard to the amount of reactive ethoxy groups versus TESPD, making use of a “design of experiments” approach of the experimental setup. The outcome shows that, contrary to common assumptions, the effect of the fiber–matrix interaction is grossly overshadowed by the effects of other factors (i.e., fiber concentration and orientation) on the vulcanization system. For each mechanical property response, an optimization prediction is calculated and confirmed with an experimental run, showing, for example, a 330% potential improvement in the Young's modulus.
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Affiliation(s)
- N. Vleugels
- University of Twente, Elastomer Technology and Engineering, P.O. Box 217, 7500AE Enschede, The Netherlands
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600AX Eindhoven, The Netherlands
| | - W. K. Dierkes
- University of Twente, Elastomer Technology and Engineering, P.O. Box 217, 7500AE Enschede, The Netherlands
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600AX Eindhoven, The Netherlands
| | - A. Blume
- University of Twente, Elastomer Technology and Engineering, P.O. Box 217, 7500AE Enschede, The Netherlands
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600AX Eindhoven, The Netherlands
| | - L. A. E. M. Reuvekamp
- University of Twente, Elastomer Technology and Engineering, P.O. Box 217, 7500AE Enschede, The Netherlands
| | - J. W. M. Noordermeer
- University of Twente, Elastomer Technology and Engineering, P.O. Box 217, 7500AE Enschede, The Netherlands
- Dutch Polymer Institute (DPI), P.O. Box 902, 5600AX Eindhoven, The Netherlands
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Jin J, Noordermeer JWM, Dierkes WK, Blume A. THE ORIGIN OF MARCHING MODULUS OF SILICA-FILLED TIRE TREAD COMPOUNDS. Rubber Chemistry and Technology 2019. [DOI: 10.5254/rct.19.80453] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
Silica-reinforced S-SBR/BR tire tread compounds often show characteristic vulcanization profiles that do not exhibit a distinct maximum in the cure curve nor a plateau profile within acceptable time scales (marching modulus). In such a situation, it is difficult to determine the optimum curing time, and as a consequence, the physical properties of the rubber compounds may vary. Previous studies stated that the curing behavior of silica-filled rubber compounds is related to the degree of filler dispersion, the silanization, and the filler–polymer coupling reaction, as well as to the donation of free sulfur from the silane coupling agent. Such results imply that these are the key factors for minimization of the marching modulus. Various silane coupling agents with different sulfur ranks and functionalities were mixed at varied silanization temperatures. The correlation between these factors and their effect on the marching modulus intensity (MMI) were investigated. The MMI was monitored by measuring the vulcanization rheograms using a rubber process analyzer at small (approximately 7%) and large (approximately 42%) strains to discriminate the effects of filler–filler and filler–polymer interactions on the marching modulus of the silica-filled rubber compounds. Both factors have an intricate influence on the marching modulus, determined by the degree of filler–filler interaction and the coupling agent.
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Affiliation(s)
- J. Jin
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
- Hankook Tire Co., Ltd, Main R&D Center, Material Department, 34127 Daejeon, Republic of Korea
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
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Hayichelaeh C, Reuvekamp LAEM, Dierkes WK, Blume A, Noordermeer JWM, Sahakaro K. SILICA-REINFORCED NATURAL RUBBER TIRE TREAD COMPOUNDS CONTAINING BIO-BASED PROCESS OILS. I: ASPECTS OF MIXING SEQUENCE AND EPOXIDE CONTENT. Rubber Chemistry and Technology 2019. [DOI: 10.5254/rct.19.81462] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
A bio-based process oil for rubber compounds is one of the compounding ingredients to be used toward an eco-friendly and more sustainable rubber technology. This work investigates epoxidized palm oil (EPO) as an alternative for petroleum-based process oil in silica-reinforced natural rubber (NR) tire tread compounds. The effect of different incorporating steps of EPO on the properties of the rubber compounds is first studied, taking into account that the polar functional groups in the oil molecules may interact with the silanol groups on the silica surface. The properties of silica-reinforced NR compounds with EPO oil are compared with that of reference mixes with treated distillate aromatic extract (TDAE) and without oil. The compounds with EPO show a lower viscosity, filler–filler interaction, and flocculation rate constant but higher cure reaction rate constants compared with the compound with TDAE. The results indicate that the epoxide groups in EPO interact with the silanol groups on the silica surface, promoting a greater shielding effect on the polar surface and thus better silica dispersion and less interference with the vulcanization reaction. The different incorporating steps of EPO show no significant effect on the viscosity, filler–filler interaction, or flocculation rate constant but clearly affect the extent of crosslinking, as indicated by the cure torque difference. The presence of EPO in an early stage of the mixing together with the first half addition of silica and silane results in the lowest cure torque difference, modulus, and tensile strength (i.e., the highest tan δ at 60 °C), which indicates a possible obstruction for the interaction between the silanol groups and silane coupling agent by the EPO molecules. Comparing EPO with different epoxide contents in the range of 1–3 mol%, the increase in epoxide content gives similar Payne effects but enhances the cure reaction, resulting in improved tensile properties and tan δ at 60 °C. The results clearly prove that EPO can be used as a TDAE alternative.
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Affiliation(s)
- C. Hayichelaeh
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521 PT Enschede, the Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
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Senkal A, Brückner-Bozetti P, Lingenfelder M, Blume A, Klode C, Steinert T. [Erratum to: Structural features and regional characteristics of psychiatric hospitals in Germany]. Nervenarzt 2019; 90:522-523. [PMID: 30367217 DOI: 10.1007/s00115-018-0632-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Affiliation(s)
- A Senkal
- Forum für Gesundheitswirtschaft gGmbH, Scharnhorststr. 76, 28211, Bremen, Deutschland.
| | - P Brückner-Bozetti
- Forum für Gesundheitswirtschaft gGmbH, Scharnhorststr. 76, 28211, Bremen, Deutschland
| | - M Lingenfelder
- Institut für Health Care Management, Philipps-Universität Marburg, Marburg, Deutschland
| | - A Blume
- Abteilung Versorgungsforschung, Zentrum für Psychiatrie Südwürttemberg, Ravensburg, Deutschland
| | - C Klode
- Forum für Gesundheitswirtschaft gGmbH, Scharnhorststr. 76, 28211, Bremen, Deutschland
| | - T Steinert
- Zentren für Psychiatrie Südwürttemberg, Klinik für Psychiatrie und Psychotherapie der Universität Ulm, Ulm, Deutschland
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Senkal A, Brückner-Bozetti P, Lingenfelder M, Blume A, Klode C, Steinert T. [Structural features and regional characteristics of psychiatric hospitals in Germany]. Nervenarzt 2019; 90:293-298. [PMID: 30143832 DOI: 10.1007/s00115-018-0600-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
BACKGROUND The German Law for the Development of Care and Funding for Psychiatric and Psychosomatic Services (PsychVVG) has established a new regulation for the mental healthcare system. In the future, characteristics of hospitals and catchment areas will be an elementary part of negotiations on remuneration. OBJECTIVE The aim of this study was to identify structural and regional characteristics of psychiatric hospitals in Germany that contribute to increased average costs according to the views of clinical managers and directors. METHODS In this study 37 guided expert interviews were conducted with business managers, financial controllers, leading medical and nursing personnel from psychiatric hospitals and the characteristics relevant for the budget and increased average costs were collated. RESULTS Important factors with top priority were hospital infrastructure, characteristics of the catchment area and specialties of inpatient services provided. Obligatory service for a defined catchment area, increased documentation requirements and infrastructure of buildings and grounds were estimated as being associated with the highest additional financial expenditure. CONCLUSION It is a challenge for clinics to prove increased average costs due to the respective hospital structural and regional characteristics. This study shows which characteristics should be considered as most cost-relevant from the perspective of hospital management.
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Affiliation(s)
- A Senkal
- Forum für Gesundheitswirtschaft gGmbH, Scharnhorststr. 76, 28211, Bremen, Deutschland.
| | - P Brückner-Bozetti
- Forum für Gesundheitswirtschaft gGmbH, Scharnhorststr. 76, 28211, Bremen, Deutschland
| | - M Lingenfelder
- Institut für Health Care Management, Philipps-Universität Marburg, Marburg, Deutschland
| | - A Blume
- Abteilung Versorgungsforschung, Zentrum für Psychiatrie Südwürttemberg, Ravensburg, Deutschland
| | - C Klode
- Institut für Health Care Management, Philipps-Universität Marburg, Marburg, Deutschland
| | - T Steinert
- Zentren für Psychiatrie Südwürttemberg, Klinik für Psychiatrie und Psychotherapie der Universität Ulm, Ulm, Deutschland
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Hayichelaeh C, Reuvekamp LAEM, Dierkes WK, Blume A, Noordermeer JWM, Sahakaro K. Enhancing the Silanization Reaction of the Silica-Silane System by Different Amines in Model and Practical Silica-Filled Natural Rubber Compounds. Polymers (Basel) 2018; 10:polym10060584. [PMID: 30966618 PMCID: PMC6403743 DOI: 10.3390/polym10060584] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 05/22/2018] [Accepted: 05/23/2018] [Indexed: 11/18/2022] Open
Abstract
Diphenyl guanidine (DPG) is an essential ingredient in silica-reinforced rubber compounds for low rolling resistance tires, as it not only acts as a secondary accelerator, but also as a catalyst for the silanization reaction. However, because of concern over the toxicity of DPG that liberates aniline during high-temperature processing, safe alternatives are required. The present work studies several amines as potential alternatives for DPG. Different amines (i.e., hexylamine, decylamine, octadecylamine, cyclohexylamine, dicyclohexylamine, and quinuclidine) are investigated in a model system, as well as in a practical rubber compound by taking the ones with DPG and without amine as references. The kinetics of the silanization reaction of the silica/silane mixtures are evaluated using model compounds. The mixtures with amines show up to 3.7 times higher rate constants of the primary silanization reaction compared to the compound without amine. Linear aliphatic amines promote the rate constant of the primary silanization reaction to a greater extent compared to amines with a cyclic structure. The amines with short-alkyl chains that provide better accessibility towards the silica surface, enhance the primary silanization reaction more than the ones with long-alkyl chains. The different amines have no significant influence on the rate constant of the secondary silanization reaction. The amine types that give a higher primary silanization reaction rate constant show a lower flocculation rate in the practical compounds. For the systems with a bit lower primary silanization reaction rate, but higher extent of shielding or physical adsorption that still promotes higher interfacial compatibility between the elastomer and the filler surface, the rubber compounds show a lower Payne effect which would indicate lower filler-filler interaction. However, the flocculation rate constant remained high.
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Affiliation(s)
- C Hayichelaeh
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani 94000, Thailand.
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. BOX 217, 7500AE Enschede, The Netherlands.
| | - L A E M Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. BOX 217, 7500AE Enschede, The Netherlands.
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521PT Enschede, The Netherlands.
| | - W K Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. BOX 217, 7500AE Enschede, The Netherlands.
| | - A Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. BOX 217, 7500AE Enschede, The Netherlands.
| | - J W M Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. BOX 217, 7500AE Enschede, The Netherlands.
| | - K Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani 94000, Thailand.
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Hayichelaeh C, Reuvekamp LAEM, Dierkes WK, Blume A, Noordermeer JWM, Sahakaro K. PROMOTING INTERFACIAL COMPATIBILITY OF SILICA-REINFORCED NATURAL RUBBER TIRE COMPOUNDS BY ALIPHATIC AMINE. Rubber Chemistry and Technology 2018. [DOI: 10.5254/rct.18.81630] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
Octadecylamine (OCT) as an alternative for diphenyl guanidine (DPG) in silica-reinforced NR tire compounds with bis-(triethoxysilyl-propyl)tetrasulfide (TESPT) as silane coupling agent was investigated with focus on the improvement of compatibility between the silica surface and rubber molecules, by taking the amine-free rubber compound as a reference. The quantity of OCT and DPG was varied in a range of 2.4–9.5 mmol per 100 parts of rubber by weight (i.e., 0.5–2.5 phr). Bound rubber contents, changes in heat capacity (ΔCp), and immobilized polymer layer (χim) data prove an enhanced interfacial compatibility as the amines are absorbed on the polar silica surface and catalyze the silanization reaction. Comparing the two different amine types, the rubber compounds with OCT show higher interfacial compatibility than the ones with DPG, because of an additional shielding effect promoted by the long alkyl chain that leads to more hydrophobicity. Thus, the rubber compounds with OCT show higher physically bound rubber contents and consequently higher total bound rubber, a higher immobilized polymer layer, as well as a lower Payne effect. However, the compounds with OCT show a higher flocculation rate constant because the physical interactions between amine and silanol groups decrease under thermal treatment. The compounds with OCT show a lower cure torque difference that indicates a lower crosslink density, but because of the good interfacial interaction combining both chemical and physical interactions, the vulcanized rubber with OCT at optimum loading shows better mechanical properties and tan δ at 60 °C when compared with the DPG counterpart. At high (excessive) loading of amines, the compounds with DPG clearly have higher crosslink density and thus higher modulus as well as tensile strength compared with the use of OCT.
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Affiliation(s)
- C. Hayichelaeh
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521PT Enschede, the Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
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Hayichelaeh C, Reuvekamp LAEM, Dierkes WK, Blume A, Noordermeer JWM, Sahakaro K. REINFORCEMENT OF NATURAL RUBBER BY SILICA/SILANE IN DEPENDENCE OF DIFFERENT AMINE TYPES. Rubber Chemistry and Technology 2017. [DOI: 10.5254/rct.82.83708] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
ABSTRACT
Diphenyl guanidine (DPG) is the most commonly used secondary accelerator in silica-reinforced rubber compounds because of its additional positive effect on the silanization reaction and deactivation of free silanol groups that are left over after the silanization. However, because of health and safety concerns about the use of DPG, which decomposes to give highly toxic aniline during high processing temperature, safe alternatives are required. This work investigates the effect of various types of aliphatic amines having alkyl or cyclic structures and similar pKa (i.e., hexylamine [HEX], decylamine [DEC], octadecylamine [OCT], cyclohexylamine [CYC], dicyclohexylamine [DIC], and quinuclidine [QUI]) on the properties of silica-reinforced natural rubber (NR) compounds by taking the ones with DPG and without amine as references. When compared with the compound without amine, the use of all amine types reduces filler–filler interaction (i.e., the Payne effect) and enhances filler–rubber interaction, as indicated by bound rubber content and decreased heat capacity increment. The amines with alkyl chains can reduce the Payne effect and enhance cure rate to a greater extent compared with the amines with cyclic rings as a result of better accessibility toward the silica surface and a shielding effect because of less steric hindrance. The longer carbon tails on linear aliphatic amines ranging from HEX, DEC, to OCT lead to a lower Payne effect, lower heat capacity increment, higher bound rubber content, and higher modulus as well as tensile strength. Overall, the use of OCT provides silica-reinforced NR compounds with properties closest to the reference one with DPG and can act as a potential alternative for DPG.
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Affiliation(s)
- C. Hayichelaeh
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - L. A. E. M. Reuvekamp
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
- Apollo Tyres Global R&D B.V., Colosseum 2, 7521PT Enschede, the Netherlands
| | - W. K. Dierkes
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - A. Blume
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - J. W. M. Noordermeer
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
| | - K. Sahakaro
- Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, 94000 Thailand
- Elastomer Technology and Engineering, Department of Mechanics of Solids, Surfaces and Systems (MS3), Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500AE Enschede, the Netherlands
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Abstract
Yawning often occurs during states of increased sleep propensity. Depression is associated with sleep problems and tiredness. The aim of this paper is to review the present knowledge about possible changes of yawning during an episode of major depression (MD) and to report data on yawning from an online depression forum comprising of 450,000 postings. A literature search did not reveal any study about yawning in people with MD when compared to controls. However, there is evidence for an increased frequency of yawning under the influence of antidepressants. Analysis of the depression forum postings revealed 63 people writing about increased yawning in the context of depression. However, all but one of them were treated with antidepressants; and yawning was not reported as a symptom of depression, but in most cases (N=56) as occurring as a result of treatment with antidepressants. These findings are in agreement with a tonic hyperarousal in typical depression which is reduced by all standard antidepressants. For clinicians, it would be of interest to know whether yawning is reduced in untreated depression and whether it predicts treatment outcome.
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Affiliation(s)
- T Hensch
- Department of Psychiatry and Psychotherapy, University of Leipzig, Leipzig, Germany
| | - A Blume
- Depression Research Centre of the German Depression Foundation, University of Leipzig, Leipzig, Germany
| | - D Böttger
- Depression Research Centre of the German Depression Foundation, University of Leipzig, Leipzig, Germany
| | - C Sander
- Department of Psychiatry and Psychotherapy, University of Leipzig, Leipzig, Germany
| | - N Niedermeier
- Medical Practice for Psychosomatic Disorders and Psychotherapy, München, Germany
| | - U Hegerl
- Department of Psychiatry and Psychotherapy, University of Leipzig, Leipzig, Germany
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Affiliation(s)
- D Vijeratnam
- Department of Genitourinary Medicine; St Mary's Hospital; Portsmouth UK
| | - J Woods
- Yorclinic; Monkgate Health Centre; York UK
| | - A Blume
- Department of Genitourinary Medicine; St Mary's Hospital; Portsmouth UK
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Blume A, Hübner W, Müller M, Bäuerle HD. Structure and Dynamics of Lipid Model Membranes: FT-IR- and2H-NMR-Spectroscopic Studies. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.198800242] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Corrieri S, Heider D, Conrad I, Blume A, Konig HH, Riedel-Heller SG. School-based prevention programs for depression and anxiety in adolescence: a systematic review. Health Promot Int 2013; 29:427-41. [DOI: 10.1093/heapro/dat001] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Blume A, Standerwick K, Tucker L, Harris S, Sheron N. Sexual assault and coincident alcohol use in attendees at a genitourinary medicine clinic in the south of England. Int J STD AIDS 2012; 23:115-9. [PMID: 22422686 DOI: 10.1258/ijsa.2011.011149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
To investigate the relationship between alcohol consumption and the experience of sexual assault, either as victim or perpetrator, among genitourinary (GU) medicine department attendees in Portsmouth, UK, we carried out a cross-sectional survey of consecutive patients attending the walk-in service when a researcher was available. Self-completed questionnaires were used and anonymized data were collected from 1186 participants (response rate 34%). Responses showed that 15.6% of female and 3.7% of male participants had ever being sexually assaulted. Women who reported sexual assault drank more on a heavy night out than those who did not report sexual assault (mean 21.3 versus 17.0 units, P = 0.041). Over half of the victims had been drinking prior to the relevant assault. Twenty-seven participants (2.3%) admitted to having sex with a person who was not fully willing. Of these, 59% had been drinking prior to the assault, and the majority believed alcohol had contributed to the assault. Any strategies aiming to reduce the incidence of sexual assault must address hazardous drinking as a high priority.
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Affiliation(s)
- A Blume
- Department of Genitourinary Medicine, St Mary's Hospital, Portsmouth, UK.
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Abstract
A small cluster of infectious syphilis among young heterosexuals aged under 25 years in south-east Hampshire has highlighted the limitations of effective partner notification, the challenges of providing effective awareness raising and the need for increased accessibility to genitourinary (GU) medicine services. Evaluation of awareness raising to both the target age group and health care professionals indicated that the strategies employed did not increase testing and had limited impact on young people in terms of seeking further information.
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Affiliation(s)
- E Morgan
- Hampshire and Isle of Wight Health Protection Unit, Whiteley
| | - A Blume
- Department of Genitourinary Medicine, Portsmouth Hospitals NHS Trust, Portsmouth
| | - R Carroll
- Public Health, NHS Hampshire, Eastleigh, UK
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Heuert U, Krumova M, Hempel G, Schiewek M, Blume A. NMR probe for pressure-jump experiments up to 250 bars and 3 ms jump time. Rev Sci Instrum 2010; 81:105102. [PMID: 21034114 DOI: 10.1063/1.3481164] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We describe the design and performance of a pressure-jump instrument for time-resolved NMR experiments. Initial pressure of up to 250 bars can be produced by means of a HPLC pump and distilled water as a pressure-transmitting liquid. Fast pressure release at a time resolution of 3 ms is achieved using a fast acting valve driven by a piezostack close to the sample chamber. The pressure-jump cell is placed together with two valves in an especially designed NMR probe, which can be used in standard spectrometers with wide-bore magnets. All functions of the instrument are personal computer controlled. The equipment is designed for investigations on systems of biological interest, especially lipid-water dispersions. A theoretical consideration implies that probably the limited speed of valve opening determines the lower boundary of the jump time. The performance is illustrated by time-resolved NMR spectra across the phase transition of a phospholipid-water dispersion after a pressure jump from 100 bars to atmospheric pressure.
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Affiliation(s)
- U Heuert
- Insitut für Physik, Martin-Luther University Halle-Wittenberg, Betty-Heimann-Str. 7, D-06120 Halle/Saale, Germany
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Abstract
There is currently a debate as to whether microscopy is necessary in asymptomatic men presenting for a sexual health screen. Arguments favouring microscopy include finding chlamydia in a significant proportion of sexual partners of men with non-specific urethritis (NSU) in studies that included symptomatic men. We aimed to investigate the proportion of partners of men with asymptomatic NSU who were diagnosed with a sexually transmitted infection. A retrospective case-note review was carried out for all men diagnosed with asymptomatic pathogen-negative NSU, and their traced sexual contacts, during a nine-month period. As a result of contact-tracing, we identified 42 partners who attended the clinic. Only one partner (2.4%) tested positive for chlamydia. A further two partners were diagnosed with a viral sexually transmitted infection (STI). The low level of chlamydia and other STIs in partners of asymptomatic men with pathogen-negative NSU does not support the routine use of microscopy to identify these patients.
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Affiliation(s)
- A Blume
- Department of GU Medicine, Royal South Hants Hospital
| | - C Main
- University of Southampton, Southampton, UK
| | - R Patel
- Department of GU Medicine, Royal South Hants Hospital
| | - E Foley
- Department of GU Medicine, Royal South Hants Hospital
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Monosrol A, Blume A, Manosrol J, Bauer KH. Thermodynamic Characteristics of A Human Insulin-Deae-Dextran Complex Entrapped in Liposomes. Drug Dev Ind Pharm 2008. [DOI: 10.3109/03639049009114913] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Cibis A, Bramesfeld A, Blume A, Havers I, Hegerl U. Optimierte Versorgung depressiv Erkrankter. Bundesgesundheitsblatt Gesundheitsforschung Gesundheitsschutz 2008; 51:430-5. [DOI: 10.1007/s00103-008-0511-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Birnbaum J, Lehmann C, Klotz E, Hein OV, Blume A, Jubin F, Polze N, Luther D, Spies CD. Effects of N-acetylcysteine and tirilazad mesylate on intestinal functional capillary density, leukocyte adherence, mesenteric plasma extravasation and cytokine levels in experimental endotoxemia in rats. Clin Hemorheol Microcirc 2008; 39:99-111. [PMID: 18503116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
INTRODUCTION The study's objective was to determine the effects of the administration of N-acetylcysteine (NAC) and of tirilazad mesylate (TM) on intestinal functional capillary density, mesenteric plasma extravasation, leukocyte adherence and on cytokine release during experimental endotoxemia in rats. METHODS In a prospective, randomized, controlled animal study, 80 male Wistar rats were examined in 2 test series. Both series were divided into 4 groups. Group 1 served as control group (CON group). Group 2 (LPS group), group 3 (NAC group) and group 4 (TM group) received endotoxin infusions (10 mg/kg over 2 h). In NAC group 150 mg/kg body weight NAC was administered after the first 30 minutes of endotoxemia intravenously. In TM group, 10 mg/kg body weight TM was administered after the first 30 minutes of endotoxemia intravenously. Animals of the series 1 underwent studies of leukocyte adherence on submucosal venular endothelium of the small bowel wall and intestinal functional capillary density (FCD) in the intestinal mucosa and the circular as well as the longitudinal muscle layer by intravital fluorescence microscopy (IVM). Plasma levels of interleukin 1beta (IL-1beta), interferone gamma (IFN-gamma) and soluble intercellular adhesion molecule1 (s-ICAM 1) as well as white blood cell count (WBC) were estimated. In the animals of the series 2 mesenteric plasma extravasation was determined by IVM and plasma levels of tumor necrosis factor alpha (TNF-alpha), IL-4, IL-6, IL-10 and malondialdehyde (MDA) were estimated. RESULTS After LPS administration, FCD in the villi intestinales was unchanged and in the longitudinal muscularis layer it was increased. There was no effect of NAC or TM administration on FCD.Although the plasma extravasation was not significantly influenced by LPS administration, TM administration resulted in a lower plasma extravasation in the TM group compared to the other groups. After endotoxin challenge, the firmly adherence of leukocytes to vascular endothelium as a parameter of leukocyte activation in endotoxemia was increased but NAC or TM administration had no influence on leukocyte adherence. The plasma levels of IL-1beta, IL-6, IL-10, TNF-alpha, IFN-gamma and sICAM-1 were increased in the endotoxemic groups (LPS group, NAC group and TM group) and the WBC was decreased compared to controls. IL-4 levels were unchanged during observation period. Plasma MDA levels were not influenced by LPS administration compared to controls. The administration of NAC resulted in lower sICAM-1 and MDA levels compared to the LPS group. The IL-1beta, IL-6, IL-10, TNF-alpha and IFN-gamma plasma levels were not influenced by NAC or TM administration. CONCLUSIONS In this posttreatment sepsis model in rats, NAC administration resulted in lower sICAM-1 and MDA levels compared to the LPS treated animals. TM administration reduced the plasma extravasation in this model.
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Affiliation(s)
- J Birnbaum
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité - Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany.
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Birnbaum J, Lehmann C, Klotz E, Hein OV, Blume A, Jubin F, Polze N, Luther D, Spies C. Effects of N-acetylcysteine and tirilazad mesylate on intestinal functional capillary density, leukocyte adherence, mesenteric plasma extravasation and cytokine levels in experimental endotoxemia in rats. Clin Hemorheol Microcirc 2008. [DOI: 10.3233/ch-2008-1073] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- J. Birnbaum
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - Ch. Lehmann
- Departments of Anesthesia, Pharmacology, Microbiology and Immunology, Dalhousie University, Victoria General Hospital, Halifax, NS, Canada
| | - E. Klotz
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - O. Vargas Hein
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - A. Blume
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - F. Jubin
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - N. Polze
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - D. Luther
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
| | - C.D. Spies
- Klinik für Anästhesiologie und operative Intensivmedizin, Charité – Universitätsmedizin Berlin, Campus Charité Mitte und Campus Virchow-Klinikum, Berlin, Germany
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Lopes DHJ, Meister A, Gohlke A, Hauser A, Blume A, Winter R. Mechanism of islet amyloid polypeptide fibrillation at lipid interfaces studied by infrared reflection absorption spectroscopy. Biophys J 2007; 93:3132-41. [PMID: 17660321 PMCID: PMC2025658 DOI: 10.1529/biophysj.107.110635] [Citation(s) in RCA: 163] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Islet amyloid polypeptide (IAPP) is a pancreatic hormone and one of a number of proteins that are involved in the formation of amyloid deposits in the islets of Langerhans of type II diabetes mellitus patients. Though IAPP-membrane interactions are known to play a major role in the fibrillation process, the mechanism and the peptide's conformational changes involved are still largely unknown. To obtain new insights into the conformational dynamics of IAPP upon its aggregation at membrane interfaces and to relate these structures to its fibril formation, we studied the association of IAPP at various interfaces including neutral as well as charged phospholipids using infrared reflection absorption spectroscopy. The results obtained reveal that the interaction of human IAPP with the lipid interface is driven by the N-terminal part of the peptide and is largely driven by electrostatic interactions, as the protein is able to associate strongly with negatively charged lipids only. A two-step process is observed upon peptide binding, involving a conformational transition from a largely alpha-helical to a beta-sheet conformation, finally forming ordered fibrillar structures. As revealed by simulations of the infrared reflection absorption spectra and complementary atomic force microscopy studies, the fibrillar structures formed consist of parallel intermolecular beta-sheets lying parallel to the lipid interface but still contain a significant number of turn structures. We may assume that these dynamical conformational changes observed for negatively charged lipid interfaces play an important role as the first steps of IAPP-induced membrane damage in type II diabetes.
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Affiliation(s)
- D H J Lopes
- University of Dortmund, Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, D-44227 Dortmund, Germany
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Simpson TL, Kaysen D, Bowen S, MacPherson LM, Chawla N, Blume A, Marlatt GA, Larimer M. PTSD symptoms, substance use, and vipassana meditation among incarcerated individuals. J Trauma Stress 2007; 20:239-49. [PMID: 17597132 DOI: 10.1002/jts.20209] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The present study evaluated whether Posttraumatic Stress Disorder (PTSD) symptom severity was associated with participation and treatment outcomes comparing a Vipassana meditation course to treatment as usual in an incarcerated sample. This study utilizes secondary data. The original study demonstrated that Vipassana meditation is associated with reductions in substance use. The present study found that PTSD symptom severity did not differ significantly between those who did and did not volunteer to take the course. Participation in the Vipassana course was associated with significantly greater reductions in substance use than treatment as usual, regardless of PTSD symptom severity levels. These results suggest that Vipassana meditation is worthy of further study for those with comorbid PTSD and substance use problems.
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Affiliation(s)
- T L Simpson
- VA Puget Sound Health Care System and Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA, USA.
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Förster G, Schwieger C, Faber F, Weber T, Blume A. Influence of poly(l-lysine) on the structure of dipalmitoylphosphatidylglycerol/water dispersions studied by X-ray scattering. Eur Biophys J 2006; 36:425-35. [PMID: 16909276 DOI: 10.1007/s00249-006-0087-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Revised: 06/15/2006] [Accepted: 06/26/2006] [Indexed: 10/24/2022]
Abstract
The interaction between the negatively charged phospholipid DPPG and positively charged poly(L: -lysine) (PLL) of different lengths was studied by X-ray scattering in the SAXS and WAXS region. As a reference pure DPPG (Na salt) was investigated over a wide temperature range (-30 to 70 degrees C). The phase behavior of DPPG in aqueous and in buffer/salt dispersions showed a metastable subgel phase at low temperatures and a recrystallization upon heating before reaching the liquid-crystalline phase. The presence of additional salt stabilizes the bilayer structure and decreases the recrystallization temperature. Large changes in the SAXS region are not connected with changes in chain packing. In DPPG/PLL samples, the PLL is inserted between adjacent headgroup layers and liberates counterions which give rise to a freezing point depression. In the complex with DPPG PLL form an alpha-helical secondary structure at pH 7 and temperatures below the gel to liquid-crystalline phase transition. This prevents DPPG from recrystallization and strongly increases the stacking order. The lamellar repeat distance is decreased and fixed by the helix conformation of PLL in the gel phase. PLL with n = 14 is too short to form helices and is squeezed out reversibly from the interbilayer space upon cooling by freezing of trapped water. In dispersions with longer PLLs (n > 400) at -20 degrees C a 1D crystallization of PLL alpha-helices in the aqueous layer between the headgroups takes place. A structural model is presented for the lateral periodic complex, which is similar to the known cationic lipid/DNA complex.
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Affiliation(s)
- G Förster
- Institute of Physical Chemistry, Martin-Luther-University Halle-Wittenberg, Halle, Germany
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Blume A, Blume A, Marx A, Fritzer G, Aldenhoff JB, Schiffelholz T. The early postnatal application of the NMDA antagonist MK–801 induces life long pathological changes in behaviour in rats. Pharmacopsychiatry 2005. [DOI: 10.1055/s-2005-918638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Hübner W, Blume A, Pushnjakova R, Dekhtyar Y, Hein HJ. The influence of X-ray radiation on the mineral/organic matrix interaction of bone tissue: an FT-IR microscopic investigation. Int J Artif Organs 2005; 28:66-73. [PMID: 15742312 DOI: 10.1177/039139880502800111] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fourier transform infrared microscopy was used to investigate human cortical bone samples before and after treatment with increasing doses of X-ray radiation. Especially the spectral region of the v1 and v3 phosphate vibrations of hydroxyapatite, the main mineral component of bone, and the region of the amide I and amide II vibrational bands due to the collagen extracellular matrix were examined. Major spectral changes in the phosphate region between 1250-1000 cm(-1) occur after irradiation doses between 1 and 4 Gray. These findings are explained by a decrease in size of mineral crystallites and by variances of the toichiometric/non-stoichiometric apatite composition. The Ca2+ /PO4(3-) /HPO4(2-) composition in the biological apatite is altered near the bone surface. The secondary structure of the collagen matrix is not affected by cumulative irradiation up to doses of 15 Gray as indicated by the unchanged frequency maximum and contour shape of the amide I band between 1600-1700 cm(-1) . However, side chain carboxylate groups of the collagen matrix that are involved in coordination with apatite bound calcium ions are partially removed by decarboxylation upon irradiation. Concomitantly, a loss of acidic phosphate groups due to a formation of phosphate groups with bound calcium is observed. These changes on a molecular level can be correlated with alterations in the mechanical properties of the bone samples, e.g. with an increased embrittlement as deduced from experiments with a scanning acoustic microscope.
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Affiliation(s)
- W Hübner
- Institute of Physical Chemistry, Martin-Luther-University, Halle-Wittenberg, Germany
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Hussain H, Kerth A, Blume A, Kressler J. Amphiphilic Block Copolymers of Poly(ethylene oxide) and Poly(perfluorohexylethyl methacrylate) at the Water Surface and Their Penetration into the Lipid Monolayer. J Phys Chem B 2004. [DOI: 10.1021/jp0495702] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- H. Hussain
- Department of Engineering Science and Department of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - A. Kerth
- Department of Engineering Science and Department of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - A. Blume
- Department of Engineering Science and Department of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - J. Kressler
- Department of Engineering Science and Department of Chemistry, Martin-Luther-University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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Littger R, Alke A, Tewes B, Gropp F, Asai T, Watanabe K, Kuromi K, Kurohane K, Ogino K, Taki T, Tsukada H, Nakayama J, Oku N, Babai I, Matyas G, Baranji L, Milosevits J, Alving CR, Bendas G, Rothe U, Scherphof GL, Kamps JAAM, Kessner S, Rothe U, Bendas G, Carafa M, Di Stefano A, Sozio P, Cacciatore I, Mosciatti B, Santucci E, Choice E, Harvie P, Galbraith T, Zunder E, Dutzar B, Anklesaria P, Paul R, Cocquyt J, De Cuyper M, Van der Meeren P, Cruz MEM, Gaspar MM, Silva MT, Dathe M, Nikolenko H, Wessolowski A, Schmieder P, Beyermann M, Bienert M, Santos ND, Cox KA, Allen C, Gallagher RC, Ickenstein L, Mayer LD, Bally MB, Fischer S, Margalit R, Freisleben HJ, Garidel P, Chen HC, Moore D, Mendelsohn R, Garidel P, Keller M, Hildebrand A, Blume A, Girão da Cruz MT, Simões S, Pedroso de Lima MC, Graser A, Nahde T, Fahr A, Müller R, Müller-Brüsselbach S, Harvie P, Dutzar B, Choice E, Cudmore S, O'Mahony D, Anklesaria P, Paul R, Hoving S, van Tiel ST, Seynhaeve ALB, Ambagtsheer G, Eggermont AMM, ten Hagen TLM, Høyrup P, Jensen SS, Jørgensen K, Iden D, Kuang H, Mullen P, Jacobs C, Roben P, Stevens T, Lollo C, Ishida T, Maeda R, Masuda K, Ichihara M, Kiwada H, Jung K, Reszka R, Kaiser N, Ohloff I, Linser-Haar S, Massing U, Schubert R, Kan P, Tsao CW, Chen WK, Wang AJ, Kimpfler A, Gerber C, Wieschollek A, Bruchelt G, Schubert R, Kobayashi T, Okada Y, Ishida T, Sone S, Harashima H, Maruyama K, Kiwada H, Kondo M, Lee CM, Tanaka T, Su W, Kitagawa T, Ito T, Matsuda H, Murai T, Miyasaka M, Junji K, Kondo M, Asai T, Ogino K, Taki T, Tsukada H, Baba K, Oku N, Koning GA, Wauben MHM, ten Hagen TLM, Vestweber D, Everts M, Kok RJ, Schraa AJ, Molema G, Schiffelers RM, Storm G, Kristl J, Šentjurc M, Abramović Z, Landry S, Perron S, Bestman-Smith J, Désormeaux A, Tremblay MJ, Bergeron MG, Madeira C, Loura LMS, Fedorov A, Prieto M, Aires-Barros MR, Marques CM, Simões SI, Cruz ME, Cevc G, Martins MB, Moreira JN, Gaspar R, Allen TM, Esposito C, Ortaggi G, Bianco A, Bonadies F, Malizia D, Napolitano R, Cametti C, Mossa G, Endert G, Essler F, Lutz S, Panzner S, Pastorino F, Brignole C, Pagnan G, Moase EH, Allen TM, Ponzoni M, Pavelic Z, Škalko-Basnet N, Jalšenjak I, Penacho N, Simões S, Pedroso de Lima MC, Pisano C, Bucci F, Serafini S, Martinelli R, Cupelli A, Marconi A, Ferrara FF, Santaniello M, Critelli L, Tinti O, Luisi P, Carminati P, Santaniello M, Bucci F, Tinti O, Pisano C, Critelli L, Galletti B, Luisi P, Carminati P, Sauer I, Nikolenko H, Dathe M, Schleef M, Voß C, Schmidt T, Flaschel E, König S, Wenger T, Dumond J, Bogetto N, Reboud-Ravaux M, Schramm HJ, Schramm W, Sheynis T, Rozner S, Kolusheva S, Satchell D, Jelnik R, Shigeta Y, Imanaka H, Ando H, Makino T, Kurohane K, Oku N, Baba N, Shimizu K, Asai T, Takada M, Baba K, Namba Y, Oku N, Simberg D, Danino D, Talmon Y, Minsky A, Ferrari ME, Wheeler CJ, Barenholz Y, Takada M, Shimizu K, Kuromi K, Asai T, Baba K, Oku N, Takeuchi Y, Kurohane K, North JR, Namba Y, Nango M, Oku N, Tewes B, Köchling T, Deissler M, Kühl C, Marx U, Strote G, Gropp F, Qualls MM, Kim JM, Thompson DH, Zhang ZY, Shum P, Collier JH, Hu BH, Ruberti JW, Messersmith PB, Thompson DH, Tsuruda T, Nakade A, Sadzuka Y, Hirota S, Sonobe T, Vorauer-Uhl K, Wagner A, Katinger H, Wagner A, Vorauer-Uhl K, Katinger H, Weeke-Klimp AH, Bartsch M, Meijer DKF, Scherphof GL, Kamps JAAM, Zeisig R, Walther W, Reß A, Fichtner I, Zschörnig O, Schiller J, Süß M, Bergmeier C, Arnold K, Nchinda G, Überla K, Zschörnig O. Poster Abstracts. J Liposome Res 2003. [DOI: 10.1081/lpr-120017490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Hait SK, Majhi PR, Blume A, Moulik SP. A Critical Assessment of Micellization of Sodium Dodecyl Benzene Sulfonate (SDBS) and Its Interaction with Poly(vinyl pyrrolidone) and Hydrophobically Modified Polymers, JR 400 and LM 200. J Phys Chem B 2003. [DOI: 10.1021/jp027379r] [Citation(s) in RCA: 160] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- S. K. Hait
- Centre for Surface Science, Department of Chemistry, Jadavpur University, Calcutta-700 032, India, and Institute of Physical Chemistry, Martin-Luther-Universitat Halle-Wittenberg, Muehlpforte 1, D-06108 Halle/Saale, Germany
| | - P. R. Majhi
- Centre for Surface Science, Department of Chemistry, Jadavpur University, Calcutta-700 032, India, and Institute of Physical Chemistry, Martin-Luther-Universitat Halle-Wittenberg, Muehlpforte 1, D-06108 Halle/Saale, Germany
| | - A. Blume
- Centre for Surface Science, Department of Chemistry, Jadavpur University, Calcutta-700 032, India, and Institute of Physical Chemistry, Martin-Luther-Universitat Halle-Wittenberg, Muehlpforte 1, D-06108 Halle/Saale, Germany
| | - S. P. Moulik
- Centre for Surface Science, Department of Chemistry, Jadavpur University, Calcutta-700 032, India, and Institute of Physical Chemistry, Martin-Luther-Universitat Halle-Wittenberg, Muehlpforte 1, D-06108 Halle/Saale, Germany
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Culman J, Blume A, Gohlke P, Unger T. The renin-angiotensin system in the brain: possible therapeutic implications for AT(1)-receptor blockers. J Hum Hypertens 2002; 16 Suppl 3:S64-70. [PMID: 12140731 DOI: 10.1038/sj.jhh.1001442] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Biochemical, physiological and functional studies suggest that the brain renin-angiotensin system (RAS) is regulated independently of the peripheral RAS. The classical actions of angiotensin II in the brain include blood pressure control, drinking behaviour, natriuresis and the release of vasopressin into the circulation. At least two subtypes of G-protein coupled receptors, the AT(1) and the AT(2) receptor, have been identified. Most of the classic actions of angiotensin II in the brain are mediated by AT(1) receptors. The AT(2) receptor is involved in brain development and neuronal regeneration and protection. Additionally, AT(2) receptors can modulate some of the classic angiotensin II actions in the brain. Selective non-peptide AT(1) receptor blockers, applied systemically, have been shown to inhibit both peripheral and brain AT(1)receptors. In genetically hypertensive rats, inhibition of brain AT(1) receptors may contribute to the blood pressure lowering effects of AT(1) receptor blockers. Animal studies have shown that AT(1) receptor antagonists enable endogenous angiotensin II to stimulate neuronal regeneration via activation of AT(2) receptors. In animal models, inhibition of the brain RAS proved to be beneficial with respect to stroke incidence and outcome. Blockade of brain and cerebrovascular AT(1) receptors by AT(1) receptor blockers prevents the reduction in blood flow during brain ischaemia, reduces the volume of ischaemic injury and improves neurological outcome after brain ischaemia. This paper reviews the actions of angiotensin II and its receptors in the brain, and discusses the possible consequences of AT(1) receptor blockade in neuroprotection, neuroregeneration, cerebral haemodynamics and ischaemia.
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Affiliation(s)
- J Culman
- Institute of Pharmacology, Christian-Albrechts-University of Kiel, Germany.
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Ovsitser O, Uchida Y, Mestl G, Weinberg G, Blume A, Jäger J, Dieterle M, Hibst H, Schlögl R. Molybdenum oxide based partial oxidation catalyst. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1381-1169(02)00128-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Blume A, Neumann C, Dorenkamp M, Culman J, Unger T. Involvement of adrenoceptors in the angiotensin II-induced expression of inducible transcription factors in the rat forebrain and hypothalamus. Neuropharmacology 2002; 42:281-8. [PMID: 11804625 DOI: 10.1016/s0028-3908(01)00177-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Angiotensin II (Ang II) acts as a neuromodulator/neurotransmitter in specific brain nuclei involved in the regulation of blood pressure and volume homeostasis. It also induces a highly differentiated transcription factor expression in these nuclei. We investigated whether adrenoceptors, which modulate other central actions of angiotensin II like the vasopressin release, also play a role in the AT1 receptor-mediated expression of the transcription factors (TF) c-Fos, c-Jun and Krox-24 in the rat brain. Ang II, injected intracerebroventricularly, induced the expression of c-Fos, c-Jun and Krox-24 in the hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei. Pretreatment with the alpha 1-adrenoceptor antagonist, prazosin, significantly inhibited the Ang II-induced transcription factor expression in the SON and PVN. The alpha 2-adrenoceptor antagonist, yohimbine, also reduced Ang II-stimulated transcription factors significantly in both nuclei. This inhibition was mainly localized in vasopressinergic magnocellular neurons in both nuclei. The beta-adrenoceptor antagonist, propranolol, did not influence the Ang II-induced expression of TF. Our results show that both, Ang II-induced vasopressin release and transcription factor expression, involve the same neuronal connections in the brain, implicating that the signal transduction pathways leading to the two different effects are at least to a certain degree convergent.
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Affiliation(s)
- A Blume
- Institute of Pharmacology, Christian-Albrechts-University of Kiel, Hospitalstrasse 4, 24105 Kiel, Germany.
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Abstract
Substance P, the principal neurokinin peptide in the mammalian brain and the natural ligand for the NK(1) tachykinin receptor, plays an integrative role in the regulation of cardiovascular, neuroendocrine and behavioural responses to stress. In rats, stimulation of periventricular NK(1) receptors in the forebrain induces a distinct pattern of cardiovascular responses which is accompanied by intense grooming behaviour. Ligands for NK(3) receptors induce a different pattern of cardiovascular and behavioural responses which comprises an increased release of vasopressin from the posterior pituitary and wet-dog shakes behaviour. To define the brain areas in the rat which respond to stimulation of forebrain NK(1) and NK(3) receptors and participate in the generation of these responses, the induction of c-Fos immunoreactivity was examined in brains following intracerebroventricular injections of substance P and neurokinin B in conscious rats. Stimulation of central NK(1) receptors by substance P (25, 100 and 500 pmol) injected into the lateral ventricle elicited grooming behaviour (face washing and hind limb grooming) and resulted in a marked c-Fos expression in the paraventricular, dorsomedial and parabrachial nuclei and in the medial thalamus. At 25 pmol, substance P did not significantly increase c-Fos expression, at 100 pmol, maximal c-Fos activation was induced in all four brain regions which responded to the peptide. Intracerebroventricular pretreatment of rats with the selective and high-affinity, non-peptide NK(1) receptor antagonist, RP 67580 (500 pmol), but not with its inactive enantiomer, RP 68651, completely abolished the behavioural response to substance P and reduced the substance P-induced c-Fos expression in all brain areas to nearly control levels. Intracerebroventricular injection of the natural ligand for NK(3) receptors, neurokinin B (500 pmol), elicited wet-dog shakes behaviour and activated c-Fos expression in localized regions of the forebrain including the organum vasculosum laminae terminalis, subfornical organ, median preoptic nucleus, paraventricular, supraoptic and anterior hypothalamic nuclei, medial thalamus and in the ventral tegmental area. These results demonstrate that the neurokinins, substance P and neurokinin B, induce specific and different patterns of c-Fos expression in distinct regions of the rat brain. Brain areas which selectively responded to substance P have been traditionally linked to the central regulation of cardiovascular and neuroendocrine reactions to stress or involved in the processing of nociceptive responses. On the other side, brain areas activated by neurokinin B are known to be involved in the central regulation of blood pressure, water and salt homeostasis or control of behaviour.
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MESH Headings
- Analgesics/pharmacology
- Animals
- Autonomic Nervous System/drug effects
- Autonomic Nervous System/metabolism
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Brain/drug effects
- Brain/metabolism
- Cardiovascular Physiological Phenomena/drug effects
- Dose-Response Relationship, Drug
- Immunohistochemistry
- Indoles/pharmacology
- Isoindoles
- Male
- Neurokinin B/metabolism
- Neurokinin B/pharmacology
- Neurokinin-1 Receptor Antagonists
- Neurons/drug effects
- Neurons/metabolism
- Neurosecretory Systems/drug effects
- Neurosecretory Systems/physiology
- Pain/metabolism
- Pain/physiopathology
- Proto-Oncogene Proteins c-fos/metabolism
- Rats
- Rats, Wistar
- Receptors, Neurokinin-1/agonists
- Receptors, Neurokinin-1/metabolism
- Receptors, Neurokinin-3/agonists
- Receptors, Neurokinin-3/antagonists & inhibitors
- Receptors, Neurokinin-3/metabolism
- Receptors, Tachykinin/agonists
- Receptors, Tachykinin/antagonists & inhibitors
- Receptors, Tachykinin/metabolism
- Stress, Physiological/metabolism
- Stress, Physiological/physiopathology
- Substance P/metabolism
- Substance P/pharmacology
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Affiliation(s)
- H Spitznagel
- German Institute for High Blood Pressure Research, 69120 Heidelberg, Germany
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Fitter J, Herrmann R, Dencher NA, Blume A, Hauss T. Activity and stability of a thermostable alpha-amylase compared to its mesophilic homologue: mechanisms of thermal adaptation. Biochemistry 2001; 40:10723-31. [PMID: 11524019 DOI: 10.1021/bi010808b] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To elucidate how enzymes adapt to extreme environmental conditions, a comparative study with a thermostable alpha-amylase from Bacillus licheniformis (BLA) and its mesophilic homologue from Bacillus amyloliquefaciens (BAA) was performed. We measured conformational stability, catalytic activity, and conformational fluctuations on the picosecond time scale for both enzymes as a function of temperature. The objective of this study is to analyze how these properties are related to each other. BLA shows its maximal catalytic activity at about 90-95 degrees C and a strongly reduced activity (only 20% of the maximum) at room temperature. Although B. licheniformis itself is a mesophilic organism, BLA shows an activity profile typical for a thermophilic enzyme. In contrast to this, BAA exhibits its maximal activity at about 80 degrees C but with a level of about 60% activity at room temperature. In both cases the unfolding temperatures T(m) are only 6 degrees C (BAA, T(m) = 86 degrees C) and 10 degrees C (BLA, T(m) = 103 degrees C), respectively, higher than the temperatures for maximal activity. In contrast to many previous studies on other thermophilic-mesophilic pairs, in this study a higher structural flexibility of the thermostable BLA was measured as compared to the mesophilic BAA. The findings of this study neither indicate a proportionality between the observed dynamics and the catalytic activity nor support the idea of more "rigid" thermostable proteins, as often proposed in the concept of "corresponding states".
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Affiliation(s)
- J Fitter
- Biologische Strukturforschung, Forschungszentrum Jülich, IBI-2, D-52425 Jülich, Germany
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Sandmann S, Yu M, Kaschina E, Blume A, Bouzinova E, Aalkjaer C, Unger T. Differential effects of angiotensin AT1 and AT2 receptors on the expression, translation and function of the Na+-H+ exchanger and Na+-HCO3- symporter in the rat heart after myocardial infarction. J Am Coll Cardiol 2001; 37:2154-65. [PMID: 11419902 DOI: 10.1016/s0735-1097(01)01287-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVES This study investigated the role of angiotensin receptor subtype 1 (AT1) and angiotensin receptor subtype 2 (AT2) in the regulation of Na+-H+ exchanger (NHE) and Na+-HCO3 symporter (NBC) in the infarcted myocardium. BACKGROUND The cardiac renin-angiotensin system is activated after myocardial infarction (MI), and both angiotensin AT1 and AT2 receptors are upregulated in the myocardium. METHODS Na+-H+ exchanger isoform-1 and NBC-1 gene expression were determined by reverse transcription polymerase chain reaction and Northern blot analysis; protein levels by Western blot analysis; and activity by measurement of H+ transport in left ventricular (LV) free wall, interventricular septum (IS) and right ventricle (RV) after induction of MI. Rats were treated with placebo, the angiotensin-converting enzyme inhibitor ramipril (1 mg/kg/day), the AT1 receptor antagonist valsartan (10 mg/kg/day) or the AT2 receptor antagonist PD 123319 (30 mg/kg/day). Treatment was started seven days before surgery. RESULTS Na+-H+ exchanger isoform-1 and NBC-1 messenger RNA (mRNA) expression and protein levels were increased twofold in the LV free wall after MI, whereas no changes were observed in the IS and RV. Na+-dependent H+ flux was increased in the LV free wall. Ramipril inhibited mRNA and protein upregulation of both transporters. Valsartan inhibited the upregulation of NHE-1 mRNA and protein but had no effect on NBC-1 mRNA expression and translation. In contrast, PD 123319 abolished the upregulation of NBC-1 mRNA and protein but had no effect on NHE-1 upregulation. Ramipril and valsartan prevented post-MI increase in NHE-1 activity, whereas ramipril and PD 123319 decreased NBC-1 activity. CONCLUSIONS Angiotensin II via its AT1 and AT2 receptors differentially controls transcriptional and translational regulation as well as the activity of NHE-1 and NBC-1 in the ischemic myocardium and contributes to the control of pH regulation in cardiac tissue.
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Affiliation(s)
- S Sandmann
- Institute of Pharmacology, University of Kiel, Germany
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Affiliation(s)
- J Culman
- Institute of Pharmacology, Christian-Albrechts-University of Kiel, Kiel, Germany.
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Moellenhoff E, Blume A, Culman J, Chatterjee B, Herdegen T, Lebrun CJ, Unger T. Effect of repetitive icv injections of ANG II on c-Fos and AT(1)-receptor expression in the rat brain. Am J Physiol Regul Integr Comp Physiol 2001; 280:R1095-104. [PMID: 11247832 DOI: 10.1152/ajpregu.2001.280.4.r1095] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
ANG II has been implicated in neuroplastic processes via stimulation of inducible transcription factors (ITF) in the brain. In the present study, we investigated the effects of acute vs. repetitive once daily intracerebroventricular injections of ANG II for 7 days on the expression of ITF and constitutive transcription factor (CTF) and the AT1 receptor in the median preoptic area (MnPO), the subfornical organ (SFO), and the hypothalamic paraventricular (PVN) and supraoptic nuclei (SON). After repetitive injections, the expression of c-Fos declined by approximately 50% in MnPO, SFO, PVN, and SON compared with controls injected once. The desensitization of c-Fos occurred on the transcriptional level as shown in the SON by RT-PCR. Apart from a novel expression of c-Jun in the SON, the ITF c-Jun, JunB, JunD, and Krox-24 did not change after repetitive stimulation. Neither were the CTF, calcium response element binding protein, activating transcription factor 2, and serum response factor altered after repetitive vs. single injections of ANG II. The AT1 receptor was coexpressed with c-Fos/c-Jun. Immunohistochemical stainings suggest an increase in AT1-receptor number in MnPO, SFO, PVN, and SON on chronic stimulation compared with once-injected controls. These findings demonstrate that repetitive periventricular stimulation with ANG II essentially alters the expression of transcription factors compared with acute stimulation and suggest c-Fos and c-Jun as major intermediates of the AT1-receptor transcription.
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MESH Headings
- Activating Transcription Factor 2
- Angiotensin II/administration & dosage
- Angiotensin II/pharmacology
- Animals
- Brain/drug effects
- Brain/physiology
- Cerebral Ventricles/drug effects
- Cerebral Ventricles/physiology
- Cyclic AMP Response Element-Binding Protein/metabolism
- DNA-Binding Proteins/metabolism
- Drosophila Proteins
- Drug Administration Schedule
- Genes, fos/drug effects
- Genes, jun/drug effects
- Injections, Intraventricular
- Male
- Membrane Proteins/metabolism
- Nuclear Proteins/metabolism
- Organ Specificity
- Paraventricular Hypothalamic Nucleus/drug effects
- Paraventricular Hypothalamic Nucleus/physiology
- Preoptic Area/drug effects
- Preoptic Area/physiology
- Proto-Oncogene Proteins c-fos/analysis
- Proto-Oncogene Proteins c-fos/genetics
- Rats
- Rats, Wistar
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/analysis
- Receptors, Angiotensin/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Serum Response Factor
- Subfornical Organ/drug effects
- Subfornical Organ/physiology
- Supraoptic Nucleus/drug effects
- Supraoptic Nucleus/physiology
- Time Factors
- Transcription Factors/metabolism
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Affiliation(s)
- E Moellenhoff
- Institute of Pharmacology, University of Kiel, Hospitalstrasse 4, 24105 Kiel, Germany
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Abstract
The signalling mechanisms and biological significance of the angiotensin II type 2 receptor have long been unknown. In recent years, studies, first in cell culture models but now increasingly also in vivo, have shed some light on the molecular events occurring after a stimulation of the receptor with its ligand as well as on its physiological effects and its significance for pathophysiological processes. There is increasing evidence that the angiotensin II type 2 receptor is involved in different pathophysiological processes, such as myocardial infarction, heart and kidney failure, and stroke.
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Affiliation(s)
- A Blume
- Institute of Pharmacology, University of Kiel, Germany
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