1
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Szadkowska M, Olewniczak M, Kloska A, Jankowska E, Kapusta M, Rybak B, Wyrzykowski D, Zmudzinska W, Gieldon A, Kocot A, Kaczorowska AK, Nierzwicki L, Makowska J, Kaczorowski T, Plotka M. A Novel Cryptic Clostridial Peptide That Kills Bacteria by a Cell Membrane Permeabilization Mechanism. Microbiol Spectr 2022; 10:e0165722. [PMID: 36094301 PMCID: PMC9602519 DOI: 10.1128/spectrum.01657-22] [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] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Accepted: 08/23/2022] [Indexed: 12/31/2022] Open
Abstract
This work reports detailed characteristics of the antimicrobial peptide Intestinalin (P30), which is derived from the LysC enzyme of Clostridium intestinale strain URNW. The peptide shows a broader antibacterial spectrum than the parental enzyme, showing potent antimicrobial activity against clinical strains of Gram-positive staphylococci and Gram-negative pathogens and causing between 3.04 ± 0.12 log kill for Pseudomonas aeruginosa PAO1 and 7.10 ± 0.05 log kill for multidrug-resistant Acinetobacter baumannii KPD 581 at a 5 μM concentration. Moreover, Intestinalin (P30) prevents biofilm formation and destroys 24-h and 72-h biofilms formed by Acinetobacter baumannii CRAB KPD 205 (reduction levels of 4.28 and 2.62 log CFU/mL, respectively). The activity of Intestinalin is combined with both no cytotoxicity and little hemolytic effect against mammalian cells. The nuclear magnetic resonance and molecular dynamics (MD) data show a high tendency of Intestinalin to interact with the bacterial phospholipid cell membrane. Although positively charged, Intestinalin resides in the membrane and aggregates into small oligomers. Negatively charged phospholipids stabilize peptide oligomers to form water- and ion-permeable pores, disrupting the integrity of bacterial cell membranes. Experimental data showed that Intestinalin interacts with negatively charged lipoteichoic acid (logK based on isothermal titration calorimetry, 7.45 ± 0.44), causes membrane depolarization, and affects membrane integrity by forming large pores, all of which result in loss of bacterial viability. IMPORTANCE Antibiotic resistance is rising rapidly among pathogenic bacteria, becoming a global public health problem that threatens the effectiveness of therapies for many infectious diseases. In this respect, antimicrobial peptides appear to be an interesting alternative to combat bacterial pathogens. Here, we report the characteristics of an antimicrobial peptide (of 30 amino acids) derived from the clostridial LysC enzyme. The peptide showed killing activity against clinical strains of Gram-positive and Gram-negative pathogens. Experimental data and computational modeling showed that this peptide forms transmembrane pores, directly engaging the negatively charged phospholipids of the bacterial cell membrane. Consequently, dissipation of the electrochemical gradient across cell membranes affects many vital processes, such as ATP synthesis, motility, and transport of nutrients. This kind of dysfunction leads to the loss of bacterial viability. Our firm conviction is that the presented study will be a helpful resource in searching for novel antimicrobial peptides that could have the potential to replace conventional antibiotics.
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Affiliation(s)
- Monika Szadkowska
- Laboratory of Extremophiles Biology, Department of Microbiology, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Michal Olewniczak
- Department of Physical Chemistry, Gdansk University of Technology, Gdansk, Poland
| | - Anna Kloska
- Department of Medical Biology and Genetics, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Elzbieta Jankowska
- Department of Biomedical Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Malgorzata Kapusta
- Department of Plant Cytology and Embryology, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Bartosz Rybak
- Department of Environmental Toxicology, Faculty of Health Sciences with Institute of Maritime and Tropical Medicine, Medical University of Gdansk, Gdansk, Poland
| | - Dariusz Wyrzykowski
- Department of General and Inorganic Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Wioletta Zmudzinska
- Laboratory of Biopolymer Structure, Intercollegiate Faculty of Biotechnology, University of Gdansk and Medical University of Gdansk, Gdansk, Poland
| | - Artur Gieldon
- Laboratory of Simulation of Polymers, Department of Theoretical Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Aleksandra Kocot
- Laboratory of Extremophiles Biology, Department of Microbiology, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Anna-Karina Kaczorowska
- Collection of Plasmids and Microorganisms, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Lukasz Nierzwicki
- Department of Physical Chemistry, Gdansk University of Technology, Gdansk, Poland
| | - Joanna Makowska
- Department of General and Inorganic Chemistry, Faculty of Chemistry, University of Gdansk, Gdansk, Poland
| | - Tadeusz Kaczorowski
- Laboratory of Extremophiles Biology, Department of Microbiology, Faculty of Biology, University of Gdansk, Gdansk, Poland
| | - Magdalena Plotka
- Laboratory of Extremophiles Biology, Department of Microbiology, Faculty of Biology, University of Gdansk, Gdansk, Poland
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2
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Rams-Baron M, Kramarczyk D, Knapik-Kowalczuk J, Hachula B, Kocot A, Paluch M. Broadband-dielectric-spectroscopy study of molecular dynamics in a mixture of itraconazole and glycerol in glassy, smectic-A, and isotropic phases. Phys Rev E 2021; 104:034702. [PMID: 34654189 DOI: 10.1103/physreve.104.034702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Accepted: 08/17/2021] [Indexed: 11/07/2022]
Abstract
Itraconazole (ITZ) is a thermotropic liquid crystal that exhibits isotropic, nematic, and smectic phases on cooling towards the glass transition upon melting. Over the years, new aspects regarding the liquid-crystalline ordering of this antifungal drug were systematically revealed. It has been shown recently that the temperature range of individual mesophases in ITZ can be modified by adding a small amount of glycerol (GLY). Moreover, above the critical concentration of 5% w/w, a smectic to nematic transition can be avoided. Here we go one step further, and we used broadband dielectric spectroscopy to investigate the new phase behavior of the ITZ-GLY mixture (5% w/w). To confirm the phase transformations of the ITZ-GLY mixture, differential scanning calorimetry was also employed. The analysis of molecular dynamics of the ITZ-GLY mixture in the glassy and isotropic phases revealed features similar to those observed for neat ITZ. Two relaxation processes were identified in the smectic-A phase, with similar temperature dependence, most likely related to the fast rotations around the long axis of a molecule. Additionally, the derivative analysis revealed another low-frequency process hidden under DC conductivity ascribed to the slow rotations about a short axis. We will show that the differences in the molecular organization in the smectic-A and isotropic phases leave a clear fingerprint on the temperature behavior of relaxation times and other dielectric parameters, such as DC conductivity and dielectric strength, for which a pretransition effect has been detected.
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Affiliation(s)
- M Rams-Baron
- August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.,Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland
| | - D Kramarczyk
- August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.,Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland
| | - J Knapik-Kowalczuk
- August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.,Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland
| | - B Hachula
- Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice, Poland
| | - A Kocot
- Institute of Materials Engineering, University of Silesia, 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland
| | - M Paluch
- August Chełkowski Institute of Physics, University of Silesia, 75 Pulku Piechoty 1, 41-500 Chorzow, Poland.,Silesian Center for Education and Interdisciplinary Research, 75 Pulku Piechoty 1a, 41-500 Chorzow, Poland
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3
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Abstract
The combination of a severe urethral sphincter defect with simultaneous development of recurrent bladder outlet obstruction characterizes a "devastated bladder outlet", which often is not surgically reconstructable. Clinically, quality of life is considerably compromised in affected patients with a wide variance of symptoms, mostly complete incontinence, but also urinary retention. This condition is usually preceded by multiple endoscopic interventions or even open surgical procedures, occasionally also in combination with radiotherapy of the pelvic region as part of multimodal oncological therapy. Treatment of these cases is complex and limited to few promising procedures. A potential therapy should primarily include the decision about the possibility of preserving the urinary bladder. In individual cases, this can result in simple therapy options while at the same time maintaining an acceptable quality of life for those affected. If there is no possibility of a refunctionalization of the original bladder, supravesical urinary diversion is indicated as a last-resort therapy. This paper provides a review as well as the limits and possibilities of conservative and surgical treatment options for a devastated bladder outlet.
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Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius Maximilians Universität Würzburg, Oberdürrbacher Str. 6, 97080, Würzburg, Deutschland.
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4
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Swaminathan V, Panov VP, Kocot A, Vij JK. Molecular orientational distribution function of a chiral de Vries smectic liquid crystal from birefringence measurements. J Chem Phys 2019; 150:084901. [PMID: 30823765 DOI: 10.1063/1.5080222] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
An alternative method for determining the orientational distribution function and the order parameter from the electric field-induced birefringence measurements of a chiral liquid crystal compound in its Smectic A* is being introduced. A chiral mesogen based on a 5-phenyl-pyrimidine benzoate core terminated by a trisiloxane group on one side and the chiral alkyloxy chain on its opposite side is designed and synthesized to exhibit the "de Vries" smectic characteristics. The compound exhibits first order Smectic A*-Smectic C* phase transition, evidenced by the results of differential scanning calorimetry. The material is being investigated by electro-optical experiment in its smectic phases. We present a model that incorporates the generalised Langevin-Debye model which includes the Maier-Saupe effective mean-field potential term in order to explain the change in birefringence with the electric field. A good agreement between the experimental results and the predictions from the model leads to the determination of the molecular orientational distribution function in Smectic A phase. Furthermore, the temperature dependency of the Saupe orientational order parameter ⟨P2⟩ is obtained using the parameters of the model. Based on the experimental and theoretical results, we show that de Vries Smectic A* phase exhibits a broad volcano-like tilt angle distribution with the two maxima occurring at finite tilt angles closer to the Smectic A*-Smectic C* transition temperature, and a sugarloaf-like distribution occurs in the tilt for temperatures close to the Isotropic-Smectic A* phase transition.
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Affiliation(s)
- V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - A Kocot
- Faculty of Computer Material Sciences, Institute of Technology and Mechatronics, Silesian University, Katowice, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
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5
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Merkel K, Kocot A, Welch C, Mehl GH. Soft modes of the dielectric response in the twist–bend nematic phase and identification of the transition to a nematic splay bend phase in the CBC7CB dimer. Phys Chem Chem Phys 2019; 21:22839-22848. [DOI: 10.1039/c9cp04952e] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Two collective processes resulting from distortion of the heliconical structure of the twist–bend nematic phase of an achiral dimer: one tilt mode due to distortions of the conical angle and second related to long range fluctuation of the cone phase.
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Affiliation(s)
- K. Merkel
- Faculty of Computer Science and Material Science
- Institute of Technology and Mechatronics
- University of Silesia in Katowice
- Poland
| | - A. Kocot
- Faculty of Computer Science and Material Science
- Institute of Technology and Mechatronics
- University of Silesia in Katowice
- Poland
| | - C. Welch
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
| | - G. H. Mehl
- Department of Chemistry
- University of Hull
- Hull HU6 7RX
- UK
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6
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Merkel K, Kocot A, Vij JK, Shanker G. Distortions in structures of the twist bend nematic phase of a bent-core liquid crystal by the electric field. Phys Rev E 2018; 98:022704. [PMID: 30253534 DOI: 10.1103/physreve.98.022704] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Indexed: 05/16/2023]
Abstract
The dielectric spectra of the twist bend nematic phase (N_{TB}) of an achiral asymmetric bent-core liquid crystalline compound are studied for determining the various relaxation modes. Dielectric measurements are also carried out under the bias field E up to 8 V/µm. Two molecular and two collective relaxation processes are observed. The orientational order parameters with respect to the local and the main directors determined using molecular modes are used to find the heliconical angle. The results also show that the order parameter with reference to the main director reverses its trend from increasing to decreasing at temperatures of a few degrees above the N_{TB} to N transition. The collective relaxation modes are assigned to (a) distortions of the local director by the electric field at a frequency of ∼100kHz while the periodic helical structure remains unaltered (mode attributed to flexoelectricity); (b) changes in the periodic structure arising from a coupling of the dielectric anisotropy with the electric field at the lowest frequency in the range of 100 Hz-10 kHz. Frequency of the higher frequency collective mode (∼100kHz) depends primarily on the heliconical angle and has anomalous softeninglike behavior at the N-N_{TB} transition. The lowest frequency mode is studied under the bias field E; the modulus of the wave vector gradually vanishes on increasing E (except for an initial behavior, E^{2}<0.1V^{2}/μm^{2}, which is just the opposite). The transition from the twist bend to splay bend structure is observed by a sudden drop in the frequency of this mode, followed by a linear decrease in frequency by increasing E. The results agree with the predictions made from the currently proposed models for a periodically distorted N_{TB} phase.
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Affiliation(s)
- K Merkel
- Institute of Material Science, Silesian University, Katowice 40-007, Poland
| | - A Kocot
- Institute of Material Science, Silesian University, Katowice 40-007, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, School of Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - G Shanker
- Department of Studies in Chemistry, Jnana Bharathi Campus, Sneha Bhavan, Bangalore University, Bangalore 560056, India
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7
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Caloone J, Huissoud C, Kocot A, Vincenot J, Dehay C, Giroud P, Misery P, Allias F, Rudigoz RC, Melodelima D. Non-invasive high-intensity focused ultrasound treatment of the placenta: a preliminary in-vivo study using a simian model. Ultrasound Obstet Gynecol 2017; 50:635-641. [PMID: 27804180 DOI: 10.1002/uog.17350] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 10/23/2016] [Accepted: 10/24/2016] [Indexed: 06/06/2023]
Abstract
OBJECTIVE To demonstrate the feasibility and efficacy of high-intensity focused ultrasound (HIFU) for the non-invasive creation of placental lesions in a simian model. METHODS Eight pregnant monkeys were exposed to HIFU treatment after anesthesia, using a toroidal HIFU 2.5-MHz transducer with an integrated ultrasound imaging probe. Lesions on the placental tissue were created non-invasively by placing the HIFU probe on the skin surface. Fetal and maternal parameters, such as maternal heart rate, fetal heart rate and subcutaneous and intra-amniotic fluid temperature, were recorded during HIFU exposure. Cesarean section was performed immediately after the procedure to extract the placenta and examine the fetus and the maternal abdominal cavity. Placental HIFU lesions were assessed by ultrasound, gross pathology and histology. RESULTS The mean gestational age of the monkeys was 72 ± 4 days. In total, 13 HIFU procedures were performed. The acoustic power and exposure time were increased progressively. This gradual increase in total energy delivered was used to determine a set of parameters to create reproducible lesions in the placenta without complications. Five placental lesions were observed with average diameters of 6.4 ± 0.5 mm and 7.8 ± 0.7 mm and an average depth of 3.8 ± 1.5 mm. Ultrasound examination of the placentae revealed hyperechoic regions that correlated well with macroscopic analysis of the HIFU lesions. Necrosis of placental tissue exposed to HIFU was confirmed with macroscopic and microscopic analysis. There was no significant variation in maternal and fetal parameters during HIFU exposure. CONCLUSIONS This study demonstrates the feasibility of HIFU applied non-invasively to the placental unit in an in-vivo pregnant monkey model. The technique is safe in the immediate short term and is potentially translatable to human pregnancy. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.
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Affiliation(s)
- J Caloone
- Inserm, U1032, Laboratory of Therapeutic Applications of Ultrasound, Lyon, France
- Université de Lyon, Lyon, France
- Department of Obstetrics and Gynecology, Croix Rousse University Hospital, Lyon, France
| | - C Huissoud
- Department of Obstetrics and Gynecology, Croix Rousse University Hospital, Lyon, France
- Stem Cell and Brain Research Institute, Institut National de la Sante et de la Recherche Médicale U846, Bron, France
| | - A Kocot
- Inserm, U1032, Laboratory of Therapeutic Applications of Ultrasound, Lyon, France
- Université de Lyon, Lyon, France
| | - J Vincenot
- Inserm, U1032, Laboratory of Therapeutic Applications of Ultrasound, Lyon, France
- Université de Lyon, Lyon, France
| | - C Dehay
- Stem Cell and Brain Research Institute, Institut National de la Sante et de la Recherche Médicale U846, Bron, France
| | - P Giroud
- Stem Cell and Brain Research Institute, Institut National de la Sante et de la Recherche Médicale U846, Bron, France
| | - P Misery
- Stem Cell and Brain Research Institute, Institut National de la Sante et de la Recherche Médicale U846, Bron, France
| | - F Allias
- Université de Lyon, Lyon, France
- Department of Pathology, Croix Rousse University Hospital, Lyon, France
| | - R C Rudigoz
- Department of Obstetrics and Gynecology, Croix Rousse University Hospital, Lyon, France
| | - D Melodelima
- Inserm, U1032, Laboratory of Therapeutic Applications of Ultrasound, Lyon, France
- Université de Lyon, Lyon, France
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8
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Kocot A, Vij JK, Perova TS, Merkel K, Swaminathan V, Sreenilayam SP, Yadav N, Panov VP, Stevenson PJ, Panov A, Rodriguez-Lojo D. Observation of the de Vries behavior in SmA * phase of a liquid crystal using polarised Raman scattering and infrared spectroscopy. J Chem Phys 2017; 147:094903. [PMID: 28886626 DOI: 10.1063/1.4999792] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Two approaches exist in the literature for describing the orientational distribution function (ODF) of the molecular directors in SmA* phase of liquid crystals, though several models are recently proposed in the literature for explaining the de Vries behaviour. These ODFs correspond to either the conventional unimodal arrangements of molecular directors arising from the mean field theory that leads to the broad or sugar-loaf like distribution or to the "diffuse-cone-shaped" type distribution proposed by de Vries. The hypothesis by de Vries provides for a realistic explanation as to how at a molecular level, a first-order SmA* to SmC* transition can occur where the uniform molecular director azimuthal distributions condense to values lying within a narrow range of angles; finally these condense to a single value while at the same time ensuring a little or no concomitant shrinkage in the layer spacing. The azimuthal distribution of the in-layer directors is probed using IR and polarized Raman spectroscopic techniques. The latter allows us to obtain the ODF and the various order parameters for the uniaxial and the biaxial phases. Based on the results of these measurements, we conclude that the "cone-shaped" (or volcano-shaped) de Vries type of distribution can most preferably describe SmA* where "a first-order phase transition from SmA* to SmC*" and a low layer shrinkage can both be easily explained.
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Affiliation(s)
- A Kocot
- Institute of Physics, Silesian University, Katowice, Poland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - T S Perova
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - K Merkel
- Central Mining Institute, Katowice, Poland
| | - V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - N Yadav
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - P J Stevenson
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
| | - A Panov
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
| | - D Rodriguez-Lojo
- School of Chemistry and Chemical Engineering, Queen's University Belfast, Northern Ireland, United Kingdom
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9
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Sreenilayam SP, Agra-Kooijman DM, Panov VP, Swaminathan V, Vij JK, Panarin YP, Kocot A, Panov A, Rodriguez-Lojo D, Stevenson PJ, Fisch MR, Kumar S. Phase behavior and characterization of heptamethyltrisiloxane-based de Vries smectic liquid crystal by electro-optics, x rays, and dielectric spectroscopy. Phys Rev E 2017; 95:032701. [PMID: 28415229 DOI: 10.1103/physreve.95.032701] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Indexed: 11/07/2022]
Abstract
A heptamethyltrisiloxane liquid crystal (LC) exhibiting I-SmA^{*}-SmC^{*} phases has been characterized by calorimetry, polarizing microscopy, x-ray diffraction, electro-optics, and dielectric spectroscopy. Observations of a large electroclinic effect, a large increase in the birefringence (Δn) with electric field, a low shrinkage in the layer thickness (∼1.75%) at 20 °C below the SmA^{*}-SmC^{*} transition, and low values of the reduction factor (∼0.40) suggest that the SmA^{*} phase in this material is of the de Vries type. The reduction factor is a measure of the layer shrinkage in the SmC^{*} phase and it should be zero for an ideal de Vries. Moreover, a decrease in the magnitude of Δn with decreasing temperature indicates the presence of the temperature-dependent tilt angle in the SmA^{*} phase. The electro-optic behavior is explained by the generalized Langevin-Debye model as given by Shen et al. [Y. Shen et al., Phys. Rev. E 88, 062504 (2013)10.1103/PhysRevE.88.062504]. The soft-mode dielectric relaxation strength shows a critical behavior when the system goes from the SmA^{*} to the SmC^{*} phase.
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Affiliation(s)
- S P Sreenilayam
- Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
| | | | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
| | - V Swaminathan
- Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland
| | - Yu P Panarin
- Department of Electronic and Electrical Engineering, Trinity College, The University of Dublin, Dublin 2, Ireland.,School of Electrical and Electronic Engineering, Dublin Institute of Technology, Dublin 8, Ireland
| | - A Kocot
- Institute of Physics, Silesian University, Katowice 40-007, Poland
| | - A Panov
- School of Chemistry and Chemical Engineering, Queens University, Belfast, BT7 1NN, United Kingdom
| | - D Rodriguez-Lojo
- School of Chemistry and Chemical Engineering, Queens University, Belfast, BT7 1NN, United Kingdom
| | - P J Stevenson
- School of Chemistry and Chemical Engineering, Queens University, Belfast, BT7 1NN, United Kingdom
| | - Michael R Fisch
- College of Applied Engineering Sustainability and Technology, Kent State University, Kent, Ohio 44242, USA
| | - Satyendra Kumar
- Department of Physics, Kent State University, Kent, Ohio 44242, USA.,Division of Research and Department of Physics, University at Albany, Albany, New York 12222, USA
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10
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Abstract
BACKGROUND Radiotherapy plays a substantial role in the treatment of malignancies. More than 2/3 of all oncologic patients undergo radiotherapy during their specific treatment. Besides manifold side effects of radiotherapy, radiogenic fistulas of the urogenital tract are a potential severe complication. These fistulas might affect the female genital tract and the urinary tract. THERAPY Potential manifold variety of radiogenic urogenital fistulas requires a specific therapy. Radiation tissue damage includes severely disturbed local blood supply. Consequently, in some cases extremely complex reconstructive techniques are necessary to restore the functionality of the urinary tract. CONCLUSION The treatment of radiogenic urogenital fistulas is challenging. A successful therapy can only be achieved by local improvement of the blood supply in the damaged area.
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Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius Maximilians Universität Würzburg, Oberdürrbacher Str. 6, 97080, Würzburg, Deutschland.
| | - H Riedmiller
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius Maximilians Universität Würzburg, Oberdürrbacher Str. 6, 97080, Würzburg, Deutschland
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11
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Vincenot J, Kocot A, Vignot A, Chavrier F, Blanc E, Dupré A, Rivoire M, Chapelon J, Melodelima D. Toroidal Transducer for Intraoperative Thermal Ablation of Pancreatic Tumours by High-Intensity Focused Ultrasound. First In Vitro Experiments. Ing Rech Biomed 2016. [DOI: 10.1016/j.irbm.2016.02.001] [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: 10/22/2022]
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12
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Caloone J, Huissoud C, Vincenot J, Kocot A, Dehay C, Chapelon JY, Rudigoz RC, Melodelima D. High-intensity focused ultrasound applied to the placenta using a toroidal transducer: a preliminary ex-vivo study. Ultrasound Obstet Gynecol 2015; 45:313-319. [PMID: 24723334 DOI: 10.1002/uog.13374] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 03/04/2014] [Accepted: 03/14/2014] [Indexed: 06/03/2023]
Abstract
OBJECTIVE To demonstrate in an ex-vivo model the feasibility of applying high-intensity focused ultrasound (HIFU) using a toroidal transducer for the creation of placental lesions. METHODS In this study we used a toroidal transducer, composed of 32 ring-shaped emitters with an ultrasound probe at the center, operating at a frequency of 2.5 MHz. We examined 45 human placentae, following either normal vaginal delivery or medical termination of pregnancy between 17 and 40 gestational weeks. First, the attenuation coefficients of 12 human placentae were measured and integrated into a numerical model for simulating HIFU lesions. Then, using acoustic parameters from this preliminary study, we performed ex-vivo experiments with 33 human placentae, each overlain with an animal abdominal wall to simulate the maternal wall. We created single HIFU lesions in 25 of these placentae, and a series of six juxtaposed lesions in eight, studying these both sonographically and macroscopically. RESULTS Human placental attenuation coefficients of the 12 human placentae ranged from 0.072 to 0.098 Np/cm/MHz, according to gestational age. The 25 single HIFU lesions created had an average diameter of 7.1 ± 3.2 mm and an average depth of 8.2 ± 3.1 mm. The average diameter of the eight series of six juxtaposed HIFU lesions was 23.0 ± 5.0 mm and the average depth was 11.0 ± 4.7 mm. The average thickness of the abdominal walls was 10.5 ± 1.8 mm. No lesions or damage were observed in intervening tissues. CONCLUSION This study demonstrates, using an ex-vivo model, the feasibility, reproducibility, harmlessness and effectiveness of HIFU applied to the human placenta.
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Affiliation(s)
- J Caloone
- Inserm, U1032, LabTau, Lyon, France; Université de Lyon, Lyon, France; Department of Obstetrics and Gynecology, Croix Rousse University Hospital, Lyon, France
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Balachandran R, Panov VP, Vij JK, Shanker G, Tschierske C, Merkel K, Kocot A. Dielectric and electro-optic studies of a bimesogenic liquid crystal composed of bent-core and calamitic units. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 90:032506. [PMID: 25314464 DOI: 10.1103/physreve.90.032506] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Indexed: 06/04/2023]
Abstract
A bimesogen, BR1, composed of a bent-core and calamitic unit, linked laterally via a flexible spacer is investigated by dielectric and electro-optic techniques. X-ray results show the presence of clusters in the nematic phase, and the cluster size is of the order of the thickness of a single layer. The splitting of the small-angle scattering Δχ/2 is about 50°, which indicates SmC like clusters with a significant tilt of the molecules in the quasilayers. The sign reversal of the dielectric anisotropy Δε' is observed as a function of frequency; the behavior is rather similar to that exhibited by the conventional dual frequency nematics, composed of a calamitic mesogen, with the exception that it occurs at much lower frequencies in this material. Interestingly, as the bimesogen enters its nematic phase, the average permittivity decreases as the temperature is lowered. This indicates the onset of antiparallel association of some of the dipoles in the system, and this type of association is much more prominent in BR1 in comparison to other bent-core liquid crystalline systems composed of the same bisbenzoate core unit. The analysis of the dielectric spectra using the Maier-Meier model confirms the onset of an antiparallel correlation of dipoles occurring at the isotropic to nematic phase transition temperature. Additionally these results support a model of the cluster where the transverse dipole moments in the neighboring layers are antiparalleled to each other.
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Affiliation(s)
- R Balachandran
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - V P Panov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland and School of Physics and Astronomy, University of Manchester, M13 9PL Manchester, United Kingdom
| | - J K Vij
- Department of Electronic and Electrical Engineering, Trinity College Dublin, The University of Dublin, Dublin 2, Ireland
| | - G Shanker
- Institute of Chemistry, Organic Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120 Halle, Germany and BMS R&D Centre, BMS College of Engineering, Bull Temple Road, Bangalore-560019, India
| | - C Tschierske
- Institute of Chemistry, Organic Chemistry, Martin-Luther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120 Halle, Germany
| | - K Merkel
- Central Mining Institute, Katowice, Poland
| | - A Kocot
- Institute of Physics, Silesian University, Katowice, Poland
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14
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Kocot A, Riedmiller H. [Management and prevention of complications in open urethral surgery. End-to-end anastomosis and buccal mucosa urethroplasty]. Urologe A 2014; 53:1006-10. [PMID: 24927779 DOI: 10.1007/s00120-014-3513-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Open operative procedures for urethral reconstruction (i.e. stricture resection with primary end-to-end anastomosis and buccal mucosa urethroplasty) are established and proven techniques with a low complication profile and high success rates. The aim of this operative technique is removal of the urethral obstruction to avoid far-reaching complications for the whole urinary tract. Despite excellent long-term results, complications are not completely avoidable in both techniques. A successful complication management requires the complete spectrum of reconstructive techniques in addition to appropriate operative expertise in order to be able to achieve the optimal result even in cases of complications. Simultaneously the recognition of potential risks contributes to a further reduction of early and delayed complications both in the approach to the operative intervention as well as intraoperatively.
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Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius-Maximilians-Universität, Oberdürrbacher Str. 6, 97080, Würzburg, Deutschland,
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15
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Tarnacka M, Adrjanowicz K, Kaminska E, Kaminski K, Grzybowska K, Kolodziejczyk K, Wlodarczyk P, Hawelek L, Garbacz G, Kocot A, Paluch M. Molecular dynamics of itraconazole at ambient and high pressure. Phys Chem Chem Phys 2013; 15:20742-52. [PMID: 24196752 DOI: 10.1039/c3cp52643g] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Comprehensive molecular dynamics studies of vitrified and cryogrounded itraconazole (Itr) were performed at ambient and elevated pressure. DSC measurements yielded besides melting and glass transition observed during heating and cooling of both samples two further endothermic events at around T = 363 K and T = 346 K. The nature of these transitions was investigated using X-ray diffraction, broadband dielectric spectroscopy and Density Functional Theory calculations. The X-ray measurements indicated that extra ordering in itraconazole is likely to occur. Based on calculations and theory derived by Letz et al. the transition observed at T = 363 K was discussed in the context of formation of the nematic mesophase. In fact, additional FTIR measurements revealed that order parameter variation in Itr shows a typical sequence of liquid crystal phases with axially symmetric orientational order; i.e. a nematic phase in the temperature range 361.7 K to 346.5 K and a smectic A phase below 346.5. Moreover, dielectric measurements demonstrated that except for the structural relaxation process, there is also slower mode above the glass transition temperature in both vitrified and cryogrounded samples. We considered the origin of this mode taking into account DFT calculations, rod like shape of itraconazole and distribution of its dipole moment vectors. For the dielectric data collected at elevated pressure, evolution of the steepness index versus pressure was determined. Finally, the pressure coefficient of the glass transition temperature was evaluated to be equal to 190 K GPa(-1).
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Affiliation(s)
- M Tarnacka
- Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40-007 Katowice, Poland.
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Abstract
To increase the donor and recipient pool in living related renal transplantation, kidneys from expanded criteria living donors are used more frequently to reduce the general problem of organ shortage. This article presents an overview of the current literature concerning this topic to further improve donor selection and transplant decision making.
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Affiliation(s)
- A Kocot
- Department of Urology and Pediatric Urology, Julius-Maximilians-University Medical School, Würzburg, Germany.
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17
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Aziz A, Gierth M, Fritsche HM, May M, Otto W, Denzinger S, Wieland WF, Merseburger A, Riedmiller H, Kocot A, Burger M. Oncological outcome of primary versus secondary muscle-invasive bladder cancer is comparable after radical cystectomy. Urol Int 2013; 91:97-102. [PMID: 23751372 DOI: 10.1159/000350232] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/15/2013] [Indexed: 11/19/2022]
Abstract
BACKGROUND High-risk non-muscle-invasive bladder cancer (NMIBC) progressing to muscle-invasive bladder cancer (MIBC) is associated with adverse tumour biology. It is unclear, however, whether outcome of NMIBC progressing to MIBC is adverse compared to primary MIBC and whether NMIBC of higher risk of progression to MIBC is adverse compared to NMIBC of lower risk. OBJECTIVE Our objective was to assess cancer-specific survival (CSS) following radical cystectomy (RC) for primary MIBC and for NMIBC progressing to MIBC in dependence of EORTC risk score. MATERIALS AND METHODS Clinical and histopathological characteristics and CSS of 150 patients were assessed. Secondary MIBCs were stratified by EORTC risk score at the last transurethral resection of bladder tumour for NMIBC. RESULTS CSS did not differ significantly between primary and secondary MIBC (p = 0.521). Secondary MIBC with high EORTC score had significantly shorter CSS compared to secondary MIBC with intermediate EORTC score (p = 0.029). In multivariable analysis, pathological tumour stage (HR = 3.77; p = 0.020) and lymph node stage (HR = 2.34; p = 0.022) were significantly correlated with CSS. CONCLUSION While the outcome of secondary MIBC is not generally adverse compared to primary MIBC, the EORTC risk score not only reflects high risk of progression of NMIBC to MIBC, but also worse outcome following RC for secondary MIBC. Timely RC should thus be debated in high-risk NMIBC.
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Affiliation(s)
- A Aziz
- Department of Urology, Caritas-St. Josef Medical Centre, University of Regensburg, Germany.
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18
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Papoutsoglou N, Tappe D, Demmer P, Kocot A, Riedmiller H. Urinary incontinence due to the presence of necrotic adult Schistosoma haematobium parasite in the bladder following travel to Egypt. Travel Med Infect Dis 2012; 10:205-7. [PMID: 22658784 DOI: 10.1016/j.tmaid.2012.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 04/30/2012] [Accepted: 05/08/2012] [Indexed: 11/25/2022]
Abstract
A case of seronegative urinary Schistosomiasis is reported in a 68-year-old Caucasian male presenting with urgency of micturition and incontinence several months after bathing in a chlorinated pool of a first class hotel in Egypt. The symptoms were initiated by a necrotic adult Schistosoma haematobium parasite found in the urinary bladder following a cystoscopic examination. The purpose of this report is to describe this probable and uncommon source of Schistosomiasis, to demonstrate that Schistosoma parasites can also be found in the urinary bladder and to emphasize the importance of travel history.
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Affiliation(s)
- N Papoutsoglou
- Department of Urology and Pediatric Urology, Julius Maximilian University Medical School, Würzburg, Germany.
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20
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Merkel K, Nagaraj M, Kocot A, Kohlmeier A, Mehl GH, Vij JK. Biaxial order and a rotation of the minor director in the nematic phase of an organo-siloxane tetrapode by the electric field. J Chem Phys 2012; 136:094513. [PMID: 22401458 DOI: 10.1063/1.3690108] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Biaxiality in the nematic phase for a liquid crystalline tetrapode made up of organo-siloxanes mesogens is investigated using polarized infrared spectroscopy. An ordering of the minor director for the homeotropically aligned sample is found to depend on the amplitude of the in-plane electric field. On increasing the in-plane electric field, the minor director, lying initially along the rubbing direction, rotates to the direction of the applied field. The scalar order parameters of the second rank tensor are found to depend significantly on the strength of the electric field. A most significant increase is found in the nematic order parameter and in the parameter that characterizes the phase biaxiality.
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Affiliation(s)
- K Merkel
- Central Mining Institute, Plac Gwarkow 1, Katowice, Poland
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21
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Jang Y, Panov VP, Kocot A, Lehmann A, Tschierske C, Vij JK. Short-range correlations seen in the nematic phase of bent-core liquid crystals by dielectric and electro-optic studies. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 84:060701. [PMID: 22304031 DOI: 10.1103/physreve.84.060701] [Citation(s) in RCA: 7] [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] [Received: 08/18/2011] [Indexed: 05/31/2023]
Abstract
Three bent-core nematic liquid crystals having the same core but with different terminal groups, short (C4) and long (C7,C9) tails, are investigated by dielectric and electro-optic contrast spectroscopic techniques. C4 shows sign reversal in the dielectric anisotropy Δε' as a function of both temperature and frequency, whereas C9 shows only negative Δε' in the entire mesophasic region. The behavior of C7 is intermediate of the two. Results of a dielectric study show that both C7 and C9 exhibit strong short-range polar correlations normal to the director. The correlation lengths of these interactions are found to be similar to those from the x-ray scattering. An increased hindered rotation for C9 compared to C4 moves the dielectric dispersion for ε(|') to much lower frequencies, such that C9 shows only negative Δε' over the entire temperature range.
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Affiliation(s)
- Yun Jang
- Department of Electronic and Electrical Engineering, Trinity College Dublin, Dublin 2, Ireland
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22
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Kocot A, Spahn M, Loeser A, Riedmiller H. [Recto-vesico-cutaneous fistula following salvage cryotherapy of the prostate due to recurrent localized prostate cancer]. Urologe A 2011; 50:1428-30. [PMID: 21811839 DOI: 10.1007/s00120-011-2653-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
For patients with recurrent prostate cancer after initial external beam radiation salvage cryotherapy is considered as an alternative to salvage prostatectomy. We report a serious complication of salvage cryotherapy in a 72-year-old man suffering from a severe recto-vesico-cutaneous fistula 6 weeks after salvage cryotherapy. To manage this situation salvage cystoprostatectomy and continent urinary diversion with creation of an ileocaecal pouch with cutaneous stoma had to be performed.
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Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius-Maximilians-Universität Würzburg, Oberdürrbacher Straße 6, Würzburg, Germany.
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23
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Kocot A, Giessing M, Fornara P, Engehausen D, Heynemann H, Wunderlich H, Dreikorn K, Riedmiller H. [18th Annual Congress of the Renal Transplantation Working Group of the German Society of Urology: Würzburg, 18-20 November 2010]. Urologe A 2011; 50:846-9. [PMID: 21678106 DOI: 10.1007/s00120-011-2600-0] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie , Zentrum Operative Medizin Würzburg, Oberdürrbacher Straße 6, 97080 Würzburg, Deutschland.
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24
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Kocot A, Gerharz EW, Riedmiller H. Urological complications of laparoscopic inguinal hernia repair: a case series. Hernia 2010; 15:583-6. [PMID: 20602131 DOI: 10.1007/s10029-010-0696-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2009] [Accepted: 06/15/2010] [Indexed: 02/03/2023]
Abstract
OBJECTIVES To illustrate urological complications of laparoscopic inguinal hernia repair and discuss their management. PATIENTS Between April 2002 and February 2004, four men (aged 38-63 years) were treated for serious complications 2 days to 11 years after unilateral (1 patient) or bilateral (3 patients) laparoscopic inguinal hernioplasty. RESULTS In all cases (extra and intraperitoneal bladder injury, purulent urocystitis due to mesh-erosion of the bladder, secondary retroperitoneal fibrosis) open revision with complete drainage of the urinary tract was chosen as an efficacious therapeutic strategy. CONCLUSIONS Awareness of rare complications of laparoscopic inguinal hernia repair may lead to early diagnosis and appropriate management.
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Affiliation(s)
- A Kocot
- Department of Urology, Julius-Maximilians-University Medical School, Oberduerrbacher Strasse 6, 97080 Wuerzburg, Germany.
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25
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Abstract
Excision with primary anastomosis is an excellent reconstructive option for short bulbar and membranous urethral strictures. With adequate patient selection including history, physical examination, and radiographic staging success rates between 90 and 95% in appropriately selected patients can be achieved. Success with this reliable method is based on adequate excision of the complete urethral stricture and sufficient mobilization of the urethra with tension-free anastomosis. Complications affecting ejaculation or penile sensitivity are rare and might be avoided by appropriate surgical techniques. Resection of the stricture and urethral end-to-end anastomosis represents the "gold-standard" in the treatment of bulbar and membraneous strictures up to a length of 3 cm.
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Affiliation(s)
- M Spahn
- Klinik und Poliklinik für Urologie und Kinderurologie, Universitätsklinik Würzburg, Oberdürrbacher Strasse 6, 97080, Würzburg, Germany.
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Gorkunov MV, Osipov MA, Kocot A, Vij JK. Molecular model of biaxial ordering in nematic liquid crystals composed of flat molecules with four mesogenic groups. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 81:061702. [PMID: 20866427 DOI: 10.1103/physreve.81.061702] [Citation(s) in RCA: 7] [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] [Received: 01/19/2010] [Revised: 05/17/2010] [Indexed: 05/29/2023]
Abstract
Relative stability of uniaxial and biaxial nematic phases is analyzed in a model nematic liquid crystal composed of flat molecules of C2h symmetry with four mesogenic groups rigidly linked to the same center. The generalized effective quadrupole mean-field potential is proposed and its constants are evaluated numerically for the pair intermolecular potential based on Gay-Berne interaction between mesogenic groups. The dependencies of the constants on molecular shape parameters are systematically analyzed. Order parameters of the uniaxial and biaxial nematic phases are evaluated by direct minimization of the free energy at different temperatures. The corresponding phase diagrams are obtained enabling one to study the effects of molecular model parameters on the stability regions of uniaxial and biaxial phases. The results are used to clarify the nature of experimentally observed biaxial ordering in nematic liquid crystals composed of tetrapode molecules with the same symmetry.
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Affiliation(s)
- M V Gorkunov
- Department of Electronic and Electrical Engineering, Trinity College Dublin, Dublin 2, Ireland
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Abstract
For patients with end-stage renal disease and dysfunctional or absent lower urinary tract, complex therapeutic strategies are necessary combining kidney transplantation and - if possible - continent urinary diversion. In this concept urinary diversion is the first step in a two-stage procedure followed by renal transplantation. Meticulous preoperative diagnostics, careful patient selection and life-long close surveillance are critical for the success of this concept. The published data concerning long-term graft and patient survival are promising.
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Affiliation(s)
- A Kocot
- Klinik und Poliklinik für Urologie und Kinderurologie, Julius-Maximilians-Universität, Oberdürrbacherstrasse 6, 97080, Würzburg, Deutschland.
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Gösswein T, Kocot A, Emmert G, Kreuz W, Martinez-Saguer I, Aygören-Pürsün E, Rusicke E, Bork K, Oldenburg J, Müller CR. Mutational spectrum of the C1INH (SERPING1) gene in patients with hereditary angioedema. Cytogenet Genome Res 2008; 121:181-8. [PMID: 18758157 DOI: 10.1159/000138883] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/22/2008] [Indexed: 11/19/2022] Open
Abstract
Hereditary angioedema (HAE) is an autosomal dominant disease that manifests as intermittent acute swellings of the skin and mucosal surfaces, which, in the gastrointestinal tract and larynx, may even be fatal. HAE results from functional deficiency of the C1 inhibitor (C1INH) protein, which plays a key role in the classical pathway of complement activation. C1INH is the sole inhibitor of the activated proteases C1r and C1s, and is the major regulator of activated coagulation Factor XII and plasma kallikrein, which limits the generation of the vasoactive peptide bradykinin. In this paper, we report on the genetic analysis of 173 families (including 326 members) with a clinical diagnosis of HAE. Direct sequencing, Southern blotting and quantitative PCR by the MLPA method were used to screen for mutations in C1INH (SERPING1). In 142 families (82.1%), a causative C1INH gene mutation could be identified. A total of 80 novel point mutations of C1INH not published previously were detected in 96 pedigrees (including 172 members). Our results corroborate C1INH (SERPING1) deficiency as a disease of extreme allelic heterogeneity with almost each individual family carrying their own mutation. Routine molecular genetic analysis is an effective way of confirming the clinical diagnosis and identifying mutation carriers early on before any clinical manifestation becomes apparent. It is, therefore, a valuable tool in prevention and adequate treatment of acute and life-threatening oedema.
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Affiliation(s)
- T Gösswein
- Department of Human Genetics, University of Wurzburg, Wurzburg, Germany
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Hayashi N, Kocot A, Linehan MJ, Fukuda A, Vij JK, Heppke G, Naciri J, Kawada S, Kondoh S. Experimental demonstration, using polarized Raman and infrared spectroscopy, that both conventional and de Vries smectic-A phases may exist in smectic liquid crystals with a first-order A-C* transition. Phys Rev E Stat Nonlin Soft Matter Phys 2006; 74:051706. [PMID: 17279925 DOI: 10.1103/physreve.74.051706] [Citation(s) in RCA: 8] [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] [Received: 10/21/2005] [Revised: 04/07/2006] [Indexed: 05/13/2023]
Abstract
Two models exist for the orientational distribution of the long molecular axes in smectic-A liquid crystals: the conventional unimodal distribution and the "cone-shaped" de Vries distribution. The de Vries hypothesis provides a plausible picture of how, at a molecular level, a first-order Sm-A to Sm-C* transition may occur, especially if there is little or no concomitant shrinkage of the layer spacing. This work investigates two materials with such transitions: C7 and TSiKN65. The azimuthal distribution of in-layer directors is probed using IR and polarized Raman spectroscopy, which allows us to obtain orientational order parameters. In C7, we observe a discontinuous change in the order parameter, the magnitude of which is small compared with the corresponding change in the in-layer director tilt angle Theta . Assuming that the smectic-A liquid crystal is of the de Vries type, we calculate the Theta required to reproduce the apparent order parameter <P2>app, obtained from IR, by using the true order parameter <P2>, obtained from polarized Raman scattering. The results indicate that, for C7, the tilt angle so calculated is much smaller than that in the Sm-C* angle and hence de Vries behavior may not be the appropriate explanation in this case. Conversely, we find that TSiKN65 shows a different behavior to C7, which can be explained in terms of the de Vries concept. Thus, we conclude that either type of distribution may exist in Sm-A phases which undergo a first-order transition to the Sm-C* phase. We also discuss the changes in the smectic layer spacing and the orientational order parameters across the Sm-A-Sm-C* phase transition, together with changes in birefringence with applied electric field.
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Affiliation(s)
- Naoki Hayashi
- Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
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Vij JK, Kocot A, Kruk G, Wrzalik R, Zentel R. Infrared Dichroism and Vibrational Spectroscopy of a Side Chain Polyacrylate Liquid Crystalline Polymer. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/10587259308030148] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Jastrzebska M, Zalewska-Rejdak J, Mróz I, Barwinski B, Wrzalik R, Kocot A, Nozynski J. Atomic force microscopy and FT-IR spectroscopy investigations of human heart valves. Gen Physiol Biophys 2006; 25:231-44. [PMID: 17197723] [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: 05/13/2023]
Abstract
Human aortic, mitral, tricuspid and pulmonary heart valves were investigated by the contact mode atomic force microscopy (AFM) in air, and using FT-IR spectroscopy in the frequency range 950-4000 cm(-1). Heart valves were collected post mortem from 65-78 years old patients who died from non-cardiac diseases. All of the examined valves showed considerable heterogeneity in the surface topography of collagen fibrils as well as in their organization on the tissue surface. The AFM images revealed areas with significantly different spatial organization of the collagen fibril bundles. We observed zones with multidirectional, stacked collagen fibrils as well as areas of thin fibrils packed regularly, densely and "in phase". The majority of the collagen fibrils reproduced the typical transverse D-banding pattern, with the band interval varying in rather wide range of 70-90 nm. Using AFM imaging, objects that correspond to some pathological states of heart valves at their early stages, i.e. some forms of mineral deposits, were observed. The FT-IR spectra allowed us to recognize main components, i.e. collagen and elastin, in di.erent layers (ventricularis, fibrosa) of the valve leaflets as well as they gave also support for the presence of mineral deposits on the valve surface. The presented results showed, that the AFM imaging and FT-IR spectroscopy can be applied as a complementary methods for structural characterization of heart valves at the molecular and supramolecular levels.
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Affiliation(s)
- M Jastrzebska
- Department of Biophysics, Faculty of Pharmacy, Medical University of Silesia, Ostrogórska 30, 41-200 Sosnowiec, Poland.
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Affiliation(s)
- J.K. Vij
- a Department of Microelectronics and Electrical Engineering , Trinity College , Dublin 2 , Ireland
| | - T. Grochulski
- a Department of Microelectronics and Electrical Engineering , Trinity College , Dublin 2 , Ireland
- b Institute of Physics, Polish Academy of Sciences , Warsaw , Poland
| | - A. Kocot
- a Department of Microelectronics and Electrical Engineering , Trinity College , Dublin 2 , Ireland
- c Institute of Physics, University of Silesia , Katowice , Poland
| | - F. Hufnagel
- a Department of Microelectronics and Electrical Engineering , Trinity College , Dublin 2 , Ireland
- d Institute of Physics, Mainz University , 6500 , Mainz , Federal Republic of Germany
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Jastrzebska M, Zalewska-Rejdak J, Wrzalik R, Kocot A, Mroz I, Barwinski B, Turek A, Cwalina B. Tannic acid-stabilized pericardium tissue: IR spectroscopy, atomic force microscopy, and dielectric spectroscopy investigations. J Biomed Mater Res A 2006; 78:148-56. [PMID: 16619255 DOI: 10.1002/jbm.a.30717] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [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: 11/11/2022]
Abstract
Infrared (IR) spectroscopy, atomic force microscopy (AFM), and dielectric spectroscopy methods were employed to study structural and dynamic changes in the tannic acid (TA)-stabilized pericardium tissue. Chemically stabilized pericardium tissue is widely used in construction of the tissue derived bioprostheses. IR spectra recorded in the range 400-4000 cm-1 allowed us to recognize different types of TA-collagen interactions. Formation of hydrogen bonds between amine as well as amide NH groups from collagen and hydroxyl groups of TA was analyzed. The AFM imaging showed that the stabilization procedure with TA introduces considerable changes in both surface topography and thickness of collagen fibrils as well as in fibril arrangement on the tissue surface. It was found, that these structural changes have an impact on the dielectric behavior of the TA-stabilized tissue. The dielectric spectra for the native and TA-stabilized tissues were measured in the frequency and temperature ranges of 10(-1) -10(7) Hz and 120-270 K, respectively. The dielectric spectra revealed the relaxation process due to orientation of bound water supplemented by the fluctuation of collagen polar side groups. At the temperatures above approximately 210 K, the relaxation due to ion migration process was observed. It was found that both relaxation processes were influenced by the TA-collagen interaction.
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Affiliation(s)
- M Jastrzebska
- Department of Biophysics, Faculty of Pharmacy, Medical University of Silesia, Ostrogorska 30, 41-200 Sosnowiec, Poland.
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Merkel K, Kocot A, Vij JK, Mehl GH, Meyer T. Orientational order and dynamics of the dendritic liquid crystal organo-siloxane tetrapodes determined using dielectric spectroscopy. Phys Rev E Stat Nonlin Soft Matter Phys 2006; 73:051702. [PMID: 16802949 DOI: 10.1103/physreve.73.051702] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 12/08/2005] [Indexed: 05/10/2023]
Abstract
The dielectric measurements have been carried out on the two zeroth generation dendrimers with four branched arms (called tetrapodes) based on the siloxane cores. The results are analyzed in the framework of the molecular theory of dielectric permittivity by Maier and Meier for nematogens. At least four molecular processes are resolved in the dielectric relaxation spectra in the nematic phase for each of the two tetrapodes. Three of them are assigned to the reorientation of the monomeric unit whereas the fourth is assigned to the rotation of the molecular segments in the individual arms of the monomeric unit around the long molecular axis. The dielectric relaxation strength of the low frequency process has been used to calculate the orientational order parameter. The dynamics of the resolved processes has been quantitatively analyzed using the results of the microscopic model of the rotational diffusion, given by Coffey and Kalmykov [W. T. Coffey and Yu. P. Kalmykov, Adv. Chem. Phys. 113, 487 (2000)] using the calculated order parameter. All molecular processes: the rotation around the short molecular axis (end-over-end rotation), precession around the director and the rotation around the long molecular axis (also called the spinning motion) are shown to have successfully been reproduced by the model. The anisotropy of the rotational diffusion coefficients gradually increases with a reduction in temperature, to a factor of 3 in the nematic phase relative to its isotropic phase.
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Affiliation(s)
- K Merkel
- Laboratory of Advanced Materials, Department of Electronic Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Korlacki R, Fukuda A, Vij JK, Kocot A, Görtz V, Hird M, Goodby JW. Self-assembly of biaxial ordering and molecular tilt angle of chiral smectic liquid crystals in homeotropically aligned cells investigated using infrared spectroscopy. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:041704. [PMID: 16383399 DOI: 10.1103/physreve.72.041704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2005] [Revised: 04/21/2005] [Indexed: 05/05/2023]
Abstract
Temperature dependences of the infrared absorbance have been measured for the four chiral liquid crystal samples in the homeotropic cell configuration. It is shown that the values of the orientational order parameter obtained using this method exhibit a remarkable similarity to the x-ray diffraction results of the smectic layer spacing and lead to accurate values of the molecular tilt angle. This has important consequences for the existing interpretation of the x-ray data. The proposed method, in many cases, may be considered as a valuable alternative to the x-ray diffraction, giving additional, important information about the orientations and the ordering of the molecular fragments. It is found that if the experimentally obtained order parameter is low, then the molecular biaxiality is exceptionally large. The average phenyl ring plane is found to lie close to the molecular tilt plane.
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Affiliation(s)
- R Korlacki
- Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Merkel K, Kocot A, Vij JK, Korlacki R, Mehl GH, Meyer T. Thermotropic biaxial nematic phase in liquid crystalline organo-siloxane tetrapodes. Phys Rev Lett 2004; 93:237801. [PMID: 15601203 DOI: 10.1103/physrevlett.93.237801] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2004] [Indexed: 05/24/2023]
Abstract
Infrared absorbance measurements have been carried out on two liquid crystalline organo-siloxane tetrapodes. Results unambiguously show the existence of a biaxial nematic phase below a uniaxial nematic phase. The three components of IR absorbance are used to calculate the various order parameters. On cooling, a weak first-order transition from isotropic to nematic is observed, followed by a second-order phase transition to biaxial nematic where the biaxiality parameters are found to be significantly large. Results are supported by observations from conoscopy and texture. Temperature dependences of the order parameters are well explained by the mean-field model for a biaxial phase.
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Affiliation(s)
- K Merkel
- Trinity College, University of Dublin, Dublin 2, Ireland
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Ossowska-Chruściel MD, Korlacki R, Kocot A, Wrzalik R, Chruściel J, Zalewski S. Infrared study of orientational order parameters of a ferroelectric liquid crystal. Phys Rev E Stat Nonlin Soft Matter Phys 2004; 70:041705. [PMID: 15600423 DOI: 10.1103/physreve.70.041705] [Citation(s) in RCA: 9] [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] [Received: 01/21/2004] [Revised: 06/09/2004] [Indexed: 05/24/2023]
Abstract
A method of determining the set of four order parameters S , D , P , and C for a ferroelectric liquid crystal, using complementary results for different sample geometries, is presented. IR measurements have been performed for homeotropic, planar heterogeneous and, planar homogenous sample geometries. Orientational order parameters were determined in two frames of reference to obtain complete information on molecular arrangement. Results for the D , P , and C parameters indicate the importance of both the intrinsic and extrinsic biaxialities. The molecular rotation around the long molecular axis is not free, and the carbonyl dipole and plane of the central phenyl ring are oriented close to the tilt plane. It has been found that transition dipole moments show significant correlations, antiparallel for longitudinal dipoles and parallel for transversal ones.
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Merkel K, Kocot A, Vij JK, Mehl GH, Meyer T. The orientational order parameters of a dendritic liquid crystal organo-siloxane tetrapode oligomer, determined using polarized infrared spectroscopy. J Chem Phys 2004; 121:5012-21. [PMID: 15332938 DOI: 10.1063/1.1769355] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The observed macroscopic anisotropic properties such as the components of infrared (IR) absorbances of liquid crystals are expressed in terms of the order parameters of the long molecular axis, molecular, and phase biaxiality. The order parameters of the organo-siloxane tetrapode liquid crystal of zero dendritic order (G0) in its nematic and smectic phases have been determined using results of the polarized IR spectroscopic measurements on a planar homogenously and hometropic aligned cells. The spatial components of the absorbances for the vibrational bands (in the mesogenic unit, terminal chains, and spacer) have been measured and analyzed. For the laboratory reference system, the apparent orientational order parameter S of the mesogen unit shows a significant drop in the transition from the nematic to the smectic phase while the phase biaxiality order parameter P increases to almost 0.4 in the smectic phase. This result shows that the director is tilted out of the sample plane in the smectic phase. The molecular biaxiality parameter D is found to be positive both for the nematic and smectic phases. This suggests that the carbonyl dipoles are oriented close to the tilt plane. For the vibrational bands in the chains, low values of S and D indicative of their low orientational order are obtained. As a result of the interaction among the molecules in the tilted smectic phases, the transition dipoles show positive correlations for the transversal and negative for the longitudinal dipoles.
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Affiliation(s)
- K Merkel
- Laboratory of Advanced Materials, Department of Electronic and Electrical Engineering, Trinity College, University of Dublin, Dublin 2, Ireland
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Jastrzebska M, Kocot A. Ionic diffusion and space charge polarization in structural characterization of biological tissues. Eur Phys J E Soft Matter 2004; 14:137-142. [PMID: 15254833 DOI: 10.1140/epje/i2003-10143-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In this study, a new approach to the analysis of the low-frequency (1-10(7) Hz) dielectric spectra of biological tissue, has been described. The experimental results are interpreted in terms of ionic diffusion and space charge polarization according to Sawada's theory. The new presentation of dielectric spectra, i.e. ([Formula: see text]) [Formula: see text] has been used. This method results in peaks which are narrower and better resolved than both the measured loss peaks and an alternative loss quantity [Formula: see text]. The presented method and Sawada's expression have been applied to the analysis of changes in the spatial molecular structure of a collagen fibril network in pericardium tissue exposed to glutaraldehyde (GA), with respect to the native tissue. The diffusion coefficient of ions was estimated on the basis of a dielectric dispersion measurement for an aqueous NaCl solution with a well-calibrated distance between the electrodes. The fitting procedure of a theoretical function to the experimental data allowed us to determine three diffusive relaxation regions with three structural distance parameters d(s), describing the spatial arrangement of collagen fibrils in pericardium tissue. It has been found that a significant decrease in the structural distance d(s) from 87 nm to 45 nm may correspond to a reduction in the interfibrillar distance within GA cross-linked tissue.
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Affiliation(s)
- M Jastrzebska
- Medical University of Silesia, Department of Biophysics, Faculty of Pharmacy, 41-200 Sosnowiec, Ostrogorska 30, Poland.
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Tajber L, Kocot A, Vij JK, Merkel K, Zalewska-Rejdak J, Mehl GH, Elsässer R, Goodby JW, Veith M. Orientational Order and Dynamics of Nematic Multipodes Based on Carbosilazane Cores Using Optical and Dielectric Spectroscopy. Macromolecules 2002. [DOI: 10.1021/ma020714p] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wrzalik R, Merkel K, Kocot A, Cieplak B. Analysis of experimental and simulated vibrational spectra for the antiferroelectric liquid crystal 12OBBB1M6. J Chem Phys 2002. [DOI: 10.1063/1.1498464] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
The photoconductivity effect in synthetic dopa-melanin polymer with relation to the charge hopping conduction has been investigated. Measurements of the rise and decay of photocurrents upon visible radiation (400-800 nm) and at temperatures of 293-326 K allowed the determination of the major trapping levels as follows: 56, 35 and 26 kJ/mol. Spectral response of the steady-state photocurrent in the range 367-1100 nm showed significant departures from the absorption spectrum of melanin. The high concentration of traps or recombination centers can explain the long time-constants calculated from the photocurrent rise and decay curves. The results obtained can support the postulated earlier polarons and hopping model of conductivity in synthetic dopa-melanin.
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Affiliation(s)
- M Jastrzebska
- Department of Biophysics, Faculty of Pharmacy, Medical University of Silesia, Ostrogórska 30, 41-200 Sosnowiec, Poland.
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Orgasinska B, Perova T, Merkel K, Kocot A, Vij J. Surface phenomena in discotic liquid crystals investigated using polarized FTIR transmission spectroscopy. Materials Science and Engineering: C 1999. [DOI: 10.1016/s0928-4931(99)00067-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Orgasińska B, Kocot A, Merkel K, Wrzalik R, Ziolo J, Perova T, Vij J. Infrared study of the orientational order of the mesogen in discotic phases of hexapentyloxytriphenylene and hexaheptyloxytriphenylene. J Mol Struct 1999. [DOI: 10.1016/s0022-2860(99)00167-2] [Citation(s) in RCA: 3] [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: 10/18/2022]
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Perova T, Kocot A, Vij J. Study of orientational ordering in discotic liquid-crystalline thin films by using Fourier transform infra-red spectroscopy. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0968-5677(97)00038-2] [Citation(s) in RCA: 4] [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: 10/18/2022]
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Kocot A. Raman scattering study of the orientational dynamics of the methyl bromide. J Mol Liq 1996. [DOI: 10.1016/0167-7322(96)00939-7] [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: 11/27/2022]
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Kocot A, Wrzalik R, Vij JK, Brehmer M, Zentel R. Dielectric and electro-optical studies of a ferroelectric copolysiloxane. Phys Rev B Condens Matter 1994; 50:16346-16356. [PMID: 9976019 DOI: 10.1103/physrevb.50.16346] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Godlewska M, Kocot A, Sciesińska E, Sciensiński J. Mid-infrared study of the polymorphism of 4,4′-di-n-butyloxyazoxybenzene. J Mol Struct 1992. [DOI: 10.1016/0022-2860(92)80197-p] [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: 10/17/2022]
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