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Struck T, Volmer M, Visser L, Offermann T, Xue R, Tu JS, Trellenkamp S, Cywiński Ł, Bluhm H, Schreiber LR. Spin-EPR-pair separation by conveyor-mode single electron shuttling in Si/SiGe. Nat Commun 2024; 15:1325. [PMID: 38351007 PMCID: PMC10864332 DOI: 10.1038/s41467-024-45583-7] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Accepted: 01/29/2024] [Indexed: 02/16/2024] Open
Abstract
Long-ranged coherent qubit coupling is a missing function block for scaling up spin qubit based quantum computing solutions. Spin-coherent conveyor-mode electron-shuttling could enable spin quantum-chips with scalable and sparse qubit-architecture. Its key feature is the operation by only few easily tuneable input terminals and compatibility with industrial gate-fabrication. Single electron shuttling in conveyor-mode in a 420 nm long quantum bus has been demonstrated previously. Here we investigate the spin coherence during conveyor-mode shuttling by separation and rejoining an Einstein-Podolsky-Rosen (EPR) spin-pair. Compared to previous work we boost the shuttle velocity by a factor of 10000. We observe a rising spin-qubit dephasing time with the longer shuttle distances due to motional narrowing and estimate the spin-shuttle infidelity due to dephasing to be 0.7% for a total shuttle distance of nominal 560 nm. Shuttling several loops up to an accumulated distance of 3.36 μm, spin-entanglement of the EPR pair is still detectable, giving good perspective for our approach of a shuttle-based scalable quantum computing architecture in silicon.
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Affiliation(s)
- Tom Struck
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
- ARQUE Systems GmbH, Aachen, Germany
| | - Mats Volmer
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
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- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Tobias Offermann
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Ran Xue
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
| | - Jhih-Sian Tu
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, Jülich, Germany
| | - Stefan Trellenkamp
- Helmholtz Nano Facility (HNF), Forschungszentrum Jülich, Jülich, Germany
| | - Łukasz Cywiński
- Institute of Physics, Polish Academy of Sciences, Warsaw, Poland
| | - Hendrik Bluhm
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany
- ARQUE Systems GmbH, Aachen, Germany
| | - Lars R Schreiber
- JARA-FIT Institute for Quantum Information, Forschungszentrum Jülich GmbH and RWTH Aachen University, Aachen, Germany.
- ARQUE Systems GmbH, Aachen, Germany.
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Volmer M, Marder M. Zur Theorie der linearen Kristallisationsgeschwindigkeit unterkühlter Schmelzen und unterkühlter fester Modifikationen. ACTA ACUST UNITED AC 2017. [DOI: 10.1515/zpch-1931-15405] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Volmer M, Mahnert P. Über die Auflösung fester Körper in Flüssigkeitsoberflächen und die Eigenschaften der dabei entstehenden Schichten. ACTA ACUST UNITED AC 2017. [DOI: 10.1515/zpch-1925-11518] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Volmer M. Molargewichtsbestimmung im Gaszustand bei sehr niedrigen Drucken nach den Experimentalarbeiten von S. Heller und K. Neumann. ACTA ACUST UNITED AC 2017. [DOI: 10.1515/zpch-1931-s190] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Volmer M, Czodrowski B, Stratmann M. Electron Spectroscopic and Electrochemical Investigations of Chemically Modified Iron Surfaces. ACTA ACUST UNITED AC 2014. [DOI: 10.1002/bbpc.198800321] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [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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Abstract
In this paper we present a micromagnetic approach to describe the detection of magnetic nanobeads using planar Hall effect sensors. The magnetic beads polarized by a dc magnetic field generate a field, which can affect the magnetization state of spin-valve sensor, leading in principle, to a detectable signal. For magnetic nanobeads we assumed a superparamagnetic behaviour. Three detection geometries are discussed and some specific behaviours were highlighted by micromagnetic simulations. We found that when the polarising field is applied parallel with the sensor surface a very weak signal can be obtained. This is because at working fields, for which the magnetic nanobeads are magnetised, the sensor saturates. We identified other setups that can overcome this shortcoming and deliver a net signal.
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Affiliation(s)
- M Volmer
- Transilvania University of Brasov, Eroilor 29, Brasov 500036, Romania
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Oosterhuis WP, van der Horst M, van Dongen K, Ulenkate HJLM, Volmer M, Wulkan RW. [Prospective comparison of the flow chart for laboratory investigations for anaemia from the Dutch College of General Practitioners' guideline 'Anaemia' with a self-developed, substantive and logistical alternative flow chart]. Ned Tijdschr Geneeskd 2007; 151:2326-2332. [PMID: 18064935] [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] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
OBJECTIVE To compare the flow diagram for the diagnosis of anaemia from the guideline 'Anaemia' from the Dutch College of General Practitioners (NHG) with a substantive and logistical alternative protocol. DESIGN Prospective. METHOD For evaluation of anaemia, 124 patients from primary care reported to the laboratories of the St. Elisabeth Hospital in Tilburg (n = 94) and the Scheper Hospital in Emmen (n = 30), the Netherlands. Two flow charts were used: the NHG's flow chart and a self-developed chart in which not mean corpuscular volume, but ferritin concentration occupies the central position. All the laboratory tests mentioned in both flow charts were carried out in every patient with, for practical reasons, the exception of Hgb electrophoresis and bone marrow investigations. General practitioners were approached and patient dossiers were consulted to obtain further clinical data. RESULTS According to the NHG protocol, on the grounds of the laboratory investigations, 64 (52%) of patients could not be put in a specific category. The majority were patients with normocytary anaemia who did not fulfil the criteria for iron deficiency anaemia or the anaemia of chronic disease. According to the alternative chart, in 36 (29%) patients no diagnosis was made. These were patients in whom no abnormal laboratory findings were observed, other than low haemoglobin values. The majority of the patients had normocytary anaemia, in some cases this was interpreted as the anaemia of chronic disease, but more often the anaemia could not be assigned to a particular category. A large number ofpatients had a raised creatinine value. This value did not appear in the NHG protocol. In 15% of patients, more than one cause for anaemia was found. The NHG protocol did not enable these multiple diagnoses to be made. Accordingly, the NHG protocol was difficult to implement in the laboratory. CONCLUSION Using the NHG flow diagram a large percentage of patients could not be assigned to a particular category. Using the alternative flow diagram, which procedure is easier to carry out in the laboratory, it was possible to make multiple diagnoses.
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Affiliation(s)
- W P Oosterhuis
- Atrium Medisch Centrum, afd. Klinische Chemie, Postbus 4446, 6401 CX Heerlen.
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Sternemann C, Huotari S, Vankó G, Volmer M, Monaco G, Gusarov A, Lustfeld H, Sturm K, Schülke W. Correlation-induced double-plasmon excitation in simple metals studied by inelastic x-ray scattering. Phys Rev Lett 2005; 95:157401. [PMID: 16241758 DOI: 10.1103/physrevlett.95.157401] [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: 04/14/2005] [Indexed: 05/05/2023]
Abstract
We report a new type of peaklike structure observed in the tail of the dynamic structure factor of simple metals, measured by inelastic x-ray scattering. Based on the momentum-transfer dependence of the energy position and the intensity of this structure, it has been unambiguously attributed to intrinsic plasmon-plasmon excitations, an electronic correlation effect that was theoretically predicted by many-body perturbation theory of the homogeneous-electron-gas model beyond the random-phase approximation. This signature appears to be largely unaffected by electron-ion interaction effects. Thus a structure that is primarily caused by correlation effects in the electron gas has been found experimentally in the dynamic structure factor of simple metals.
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Affiliation(s)
- C Sternemann
- Institute of Physics, University of Dortmund, D-44221 Dortmund, Germany
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Fuchs S, Tibesku CO, Genkinger M, Volmer M, Laass H, Rosenbaum D. Clinical and functional comparison of bicondylar sledge prostheses retaining all ligaments and constrained total knee replacement. Clin Biomech (Bristol, Avon) 2004; 19:263-9. [PMID: 15003341 DOI: 10.1016/j.clinbiomech.2003.11.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [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] [Received: 04/17/2002] [Accepted: 11/14/2003] [Indexed: 02/07/2023]
Abstract
OBJECTIVE Comparison of different total knee replacements regarding clinical and functional differences with respect to gait and electromyographic analyses. DESIGN Retrospective, comparative, clinical and functional study. METHODS Three groups (control group of 11 healthy subjects, 15 patients with bicondylar sledge prostheses retaining all ligaments (cemented unicondylar prostheses in both the medial and lateral compartment), 15 patients with constrained total knee replacement sacrificing all cruciate and collateral ligaments (cemented total knee prosthesis with intramedullary stems and a large intercondylar tibial post) were compared by clinical evaluation using a number of clinical evaluation scores, a pain scale, surface electromyographic examinations of the lower limb, and gait analysis. RESULTS Clinical scores revealed significantly worse results for patients with constrained prostheses. Both patient groups had significantly lower clinical scores compared to the control group. Gait analysis and electromyographic parameters revealed no significant differences between both patient groups. Compared to the control group, patients revealed significantly impaired parameters. Electromyography also demonstrated significant differences between patients and controls: mean electromyographic activities were reduced in vastus medialis and lateralis, semitendinosus, tibialis anterior and gastrocnemius. Peak activities were reduced in all muscles but rectus femoris. CONCLUSION Clinical scores demonstrated significantly better results in bicondylar sledge than in constrained prostheses. Nevertheless, gait and electromyographic analyses did not reveal significant differences. RELEVANCE Retaining of ligaments in bicondylar sledge prostheses apparently improved the activities of daily living but is not reflected in gait and electromyographic parameters.
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Affiliation(s)
- S Fuchs
- Department of Orthopaedics, University Hospital Muenster, Albert-Schweitzer-Str 33, 48129 Muenster, Germany.
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Volmer M, de Vries JC, Goldschmidt HM. Infrared analysis of urinary calculi by a single reflection accessory and a neural network interpretation algorithm. Clin Chem 2001; 47:1287-96. [PMID: 11427461] [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: 02/20/2023]
Abstract
BACKGROUND Preparation of KBr tablets, used for Fourier transform infrared (FT-IR) analysis of urinary calculus composition, is time-consuming and often hampered by pellet breakage. We developed a new FT-IR method for urinary calculus analysis. This method makes use of a Golden Gate Single Reflection Diamond Attenuated Total Reflection sample holder, a computer library, and an artificial neural network (ANN) for spectral interpretation. METHODS The library was prepared from 25 pure components and 236 binary and ternary mixtures of the 8 most commonly occurring components. The ANN was trained and validated with 248 similar mixtures and tested with 92 patient samples, respectively. RESULTS The optimum ANN model yielded root mean square errors of 1.5% and 2.3% for the training and validation sets, respectively. Fourteen simple expert rules were added to correct systematic network inaccuracies. Results of 92 consecutive patient samples were compared with those of a FT-IR method with KBr tablets, based on an initial computerized library search followed by visual inspection. The bias was significantly different from zero for brushite (-0.8%) and the concomitantly occurring whewellite (-2.8%) and weddellite (3.8%), but not for ammonium hydrogen urate (-0.1%), carbonate apatite (0.5%), cystine (0.0%), struvite (0.4%), and uric acid (-0.1%). The 95% level of agreement of all results was 9%. CONCLUSIONS The new Golden Gate method is superior because of its smaller sample size, user-friendliness, robustness, and speed. Expert knowledge for spectral interpretation is minimized by the combination of a library search and ANN prediction, but visual inspection remains necessary.
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Affiliation(s)
- M Volmer
- Department of Pathology and Laboratory Medicine, University Hospital Groningen (UHG), PO Box 30001, 9700 RB Groningen, The Netherlands
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Volmer M, Kingma AW, Borsboom PC, Wolthers BG, Kema IP. Investigation of applicability of a mid-infrared spectroscopic method using an attenuated total reflection accessory and a new near-infrared transmission method for determination of faecal fat. Ann Clin Biochem 2001; 38:256-63. [PMID: 11392501 DOI: 10.1258/0004563011900489] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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: 11/18/2022]
Abstract
In many laboratories, the titrimetric method of Van de Kamer is used for the analysis of faecal fat content of patients suspected of steatorrhoea. We investigated the applicability of a mid-infrared (MIR) spectroscopic method, using an attenuated total reflection (ATR) accessory, and a new near-infrared (NIR) spectroscopic method. For the NIR method, sealed plastic bags containing the stool samples were used as transmission cells. Standardization was obtained using a previously described MIR method, with a NaCl flow-cell, as reference method. Partial least-squares regression was used for the calibration of each method. Full cross-validation of the calibration set was used for the internal validation of each method. Fifteen per cent of the stool samples could not be estimated with the ATR method within reasonable accuracy limits compared with the reference. The standard error of prediction of the NIR method was 1.1 g/dL. We conclude that the new NIR method is a promising technique for routine use. However, further experiments need to be done with triplicate measurements of each sample and the use of an external validation set.
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Affiliation(s)
- M Volmer
- Department of Pathology and Laboratory Medicine, University Hospital Groningen, The Netherlands.
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Swaanenburg JC, Loef BG, Volmer M, Boonstra PW, Grandjean JG, Mariani MA, Epema AH. Creatine kinase MB, troponin I, and troponin T release patterns after coronary artery bypass grafting with or without cardiopulmonary bypass and after aortic and mitral valve surgery. Clin Chem 2001; 47:584-7. [PMID: 11238316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
Affiliation(s)
- J C Swaanenburg
- Department of Pathology and Laboratory Medicine, Thoracic Center, University Hospital Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
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Abstract
AIM OF THE STUDY To assess the clinical and functional outcome after implantation of a constrained knee arthroplasty. MATERIAL AND METHODS 14 patients with a revision of the primary prostheses with constrained knee arthroplasties ("Genesis constrained" and "Blauth") were evaluated in the operated and non operated leg at an average follow-up of 8.5 months (range 6.5 to 61.4 months). The study included clinical examinations as well as gait analysis and surface electromyography. The results were compared with a group of healthy volunteers. The clinical examinations were scored with the HSS, the Knee Society Score, the Tegner Activity Score, the Patella Score and the Visual Analogue Scale. Gait analysis was performed with a three dimensional motion analysis system. Surface electromyography was evaluated bilaterally from the rectus femoris, vastus medialis and lateralis, semitendinosus, biceps femoris (long head), tibialis anterior and gastrocnemius (medial head). RESULTS The comparison between the healthy volunteers and the patients showed significant functional deficits in the patient group. The electromyography demonstrated significantly lower peak amplitudes in 5 of 7 muscles. In all parameters--except for knee extension--gait analysis resulted in significant differences between the patient and control group. The comparison between the operated and non operated leg showed a significant difference only for knee extension. The patients revealed a bilateral functional deficit so that gait symmetry was preserved. CONCLUSION The presented results indicate that the functional deficits may be caused by preoperative deficits and are not only due to the operation. It can be supposed that the gastrocnemius is more important because of the high correlation with the clinical results. The value of pre- and postoperative rehabilitation programs to prevent postoperative functional deficits can be concluded.
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Affiliation(s)
- S Fuchs
- Westfälische Wilhelms Universität Münster, Klinik und Poliklinik für Allgemeine Orthopädie, Albert-Schweitzer-Strasse 33, 48129 Münster.
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Meijer WG, Kema IP, Volmer M, Willemse PH, de Vries EG. Discriminating capacity of indole markers in the diagnosis of carcinoid tumors. Clin Chem 2000; 46:1588-96. [PMID: 11017936] [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: 02/17/2023]
Abstract
BACKGROUND We evaluated the discriminating capacity of the indole markers urinary 5-hydroxyindoleacetic acid (5-HIAA), urinary serotonin, and platelet serotonin in the diagnosis of carcinoid tumors. METHODS Indole markers were measured in 688 patients with suspected carcinoid disease. The initial values of indole markers from patients in whom a carcinoid tumor was confirmed during follow-up (n = 98) were used for ROC analysis. Two groups served as reference populations. The first consisted of 45 healthy individuals ("healthy controls"). The second was a random sample of 40 patients, drawn from the 590 (688 minus 98) patients with carcinoid-like symptoms but without a carcinoid tumor ("clinically suspected patients"). RESULTS ROC curve analysis showed platelet serotonin to have the highest discriminating capacity, especially in foregut carcinoids. Cutoff values for platelet serotonin obtained from ROC analysis with healthy controls as reference group (5.4 nmol/10(9) platelets) gave a sensitivity of 74%, specificity of 91%, positive predictive value of 63%, and negative predictive value of 95% when applied to the initial 688 patients. Using the cutoff value with the clinically suspected patients as the reference group (9.3 nmol/10(9) platelets) gave a sensitivity of 63%, specificity of 99%, positive predictive value of 89%, and negative predictive value of 93%. Indole markers were increased in 169 (25%) of 688 patients. In 76 (45%) of these 169 patients, a carcinoid tumor was present. Slight increases of markers were associated with non-carcinoid neuroendocrine tumors, non-neuroendocrine tumors, and disturbed bowel motility. CONCLUSIONS ROC curve analysis shows that platelet serotonin is the most discriminating indole marker for the diagnosis of carcinoid tumors. Platelet serotonin especially improves the diagnosis of carcinoids producing small amounts of serotonin.
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Affiliation(s)
- W G Meijer
- Departments of Medical Oncology and Pathology and Laboratory Medicine, University Hospital Groningen, 9700 RB Groningen, The Netherlands
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van der Mei J, Volmer M, Boersma ER. Growth and survival of low birthweight infants from 0 to 9 years in a rural area of Ghana. Comparison of moderately low (1,501-2,000 g) and very low birthweight (1,000-1,500 g) infants and a local reference population. Trop Med Int Health 2000; 5:571-7. [PMID: 10995099 DOI: 10.1046/j.1365-3156.2000.00604.x] [Citation(s) in RCA: 7] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
This prospective and descriptive study was conducted to evaluate the growth and survival of 105 low birthweight (LBW, 1,000-2,000 g) infants discharged during a 4-year period from Agogo Hospital, Ghana, and followed from birth until the age of 4-9 years. Thirty-two babies were very low birthweight children (VLBW, 1,000-1,500 g) and 73 (70%) were of moderately low birthweight (MLBW, 1,501-2,000 g). At the age of 3 years, 15 children (14.2%) had not come for follow-up; of the remaining 90 children, nine (10%) had died, five during the first 3 months of life. At follow-up from 4 to 9 years of age, two more children could not be traced and another two had died. Compared to a local reference population and the WHO standard, growth of survivors lagged behind and caught up only slightly during the first 3 years of life. From 3 to 9 years of age, median growth impairment increased, which either suggests impaired growth potential or poor health and inadequate nutrition. This long-term study confirms that LBW (1,000-2,000 g) infants, particularly VLBW children, are at high risk.
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Affiliation(s)
- J van der Mei
- Paediatric Department, Agogo Hospital, Presbyterian Church of Ghana
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Jakobs BS, Volmer M, Hofs MT, Swinkels DW. Enhanced time-saving extraction procedure for the analysis of fecal fat by Fourier transform infrared spectroscopy. Clin Chem 2000; 46:1019-20. [PMID: 10894855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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Jakobs BS, Volmer M, Swinkels DW, Hofs MT, Donkervoort S, Joosting MM, Wolthers BG, de Peinder P, Voorbij HA. New method for faecal fat determination by mid-infrared spectroscopy, using a transmission cell: an improvement in standardization. Ann Clin Biochem 2000; 37 ( Pt 3):343-9. [PMID: 10817249 DOI: 10.1258/0004563001899258] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [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: 11/18/2022]
Abstract
Current techniques used in clinical laboratories for faecal fat determination, such as the Van de Kamer method, are not very accurate or precise. This became apparent when results obtained by different laboratories were compared, and could explain the disappointing performance of near-infrared and mid-infrared spectroscopy since the accuracy of these techniques depends upon the accuracy of the calibration used (i.e. inaccurate wet chemical analysis). In order to improve standardization, we developed and tested a new quantitative method in three laboratories, based on Fourier transform infrared (FT-IR) spectroscopy. Fatty acids were extracted from faecal samples with acidified petroleum ether-ethanol and the extracts were dried and dissolved in chloroform. An infrared spectrum of the extracts was recorded in the range 4000-650 cm(-1), using an infrared transmission cell. Standard mixtures of stearic and palmitic acids (65:35) were used for calibration. Quantification was based on the absorbance band of the CH2 group (2855 cm(-1)) of free fatty acids and fatty acid glycerol esters. The calibration curve showed excellent linearity. The correlation coefficient between the titrimetric Van de Kamer and FT-IR methods was 0.96 (y = 1.12x-0.02, standard error of prediction = 0.89 g% fat). No significant difference was found when the FT-IR results of 28 faecal samples from patients were compared between two different university hospital laboratories. The new FT-IR method, using primary standards, is simple and rapid, and provides satisfactory intra- and inter-laboratory precision for the diagnosis and monitoring of steatorrhoea.
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Affiliation(s)
- B S Jakobs
- Department of Clinical Chemistry, University Hospital Nijmegen St Radboud, The Netherlands.
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van der Dijs FP, Volmer M, van Gijssel-Wiersma DG, Smit JW, van Veen R, Muskiet FA. Predictive value of cord blood hematological indices and hemoglobin Barts for the detection of heterozygous alpha-thalassemia-2 in an African-Caribbean population. Clin Chem 1999; 45:1495-500. [PMID: 10471652] [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: 02/13/2023]
Abstract
BACKGROUND Cord blood hemoglobin Barts (HbBarts) and hemocytometric indices may be used for classification of newborns into those without alpha-thalassemia-2 (alphaalpha/alphaalpha) and with heterozygous alpha-thalassemia-2 (-alpha(3.7)/alphaalpha). We investigated by logistic regression analysis whether the combination of HbBarts and hemocytometric indices improves classification compared with classification based on a single analyte. METHODS HbBarts percentages and hemocytometric indices were determined in cord blood of 208 consecutive newborns in Curaçao (Netherlands Antilles). Of these, 157 had alphaalpha/alphaalpha and 51 had -alpha(3.7)/alphaalpha, as established by DNA analysis. RESULTS Between-group differences were significant for erythrocytes, mean cell volume, mean cell hemoglobin (MCH), mean cell hemoglobin concentration, platelets, hemoglobin F(0) (HbF(0)), and HbBarts. The Logit equation of the logistic regression model, using MCH (pg) and HbBarts (%), was: 42.7164 + 5.7916(HbBarts) - 1.3110(MCH). A sensitivity of 100% was reached at a Logit value of -3.70. The corresponding specificity was 62.2%, and the predictive value of a positive test (PV+) was 46.3% (95% confidence interval, 37.0-55.7%). The relative information gains were as follows: 88% for the HbBarts-MCH combination, 26% for MCH (not significant), and 0% for HbBarts compared with the 24.6% -alpha(3.7)/alphaalpha prevalence. CONCLUSION Combined use of cord blood HbBarts and MCH improves classification compared with classification based on single hemocytometric indices.
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Swaanenburg JC, Dejongste MJ, Volmer M, Kema IP. Analytical aspects of the automated CKMB1,2 and CKMM1,2,3 isoform determination and its relation to other biochemical markers. Scand J Clin Lab Invest 1998; 58:167-76. [PMID: 9587170 DOI: 10.1080/00365519850186760] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [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: 02/07/2023]
Abstract
The automated (CK)MB1,2/MM1,2,3 isoform measurement, based on electrophoresis, has been simplified to the point that it has become possible to perform this analysis on a 24-h routine basis. We studied analytical aspects of this analysis and its clinical relevance in relation to other biochemical markers (CK total, CKMB activity, CKMB mass, myoglobin, Troponin I and Troponin T) in patients with acute myocardial infarction (AMI), patients with unstable angina pectoris (UAP), and healthy donors. Furthermore, the additional significance of the analysis was evaluated in patients with clinically unexpected, raised CKMB/CK total activities. The storage of serum at 4 degrees C does not influence the MB2/MB1 ratios, whereas storage at 20 degrees C changes them significantly. MM3/MM1 and normal MB2/MB1 ratios show lower coefficients of variation than increased MB2/MB1 ratios. Between 2 and 30 h after myocardial tissue damage, AMI patients showed a characteristic change in CK isoform patterns. At a mean time of 3.6 h after the onset of symptoms we found raised MB2/MB1 ratios in 94% of these patients. With the information of the CK isoform analysis unexpected abnormal CK activities could explained by CK macro enzymes (Ig-bound and mitochondrial), insufficient CK clearance capacity, enzyme activities 4 h after (re-)infarction and raised CK activity 15 h after skeletal muscle damage. We conclude that the CK isoforms are relatively simply to assess; they are adequate tools with which to indicate the CK kinetics over a period lasting between 2 and 30 h after tissue damage with a single blood sample and a single analysis; the CK isoform analysis has additional value in explaining inappropriate CKMB/CK total activities, and the MB2/MB1 ratios show to be one of the best early parameters for discriminating patients with AMI on admission to hospital.
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Affiliation(s)
- J C Swaanenburg
- Central Clinical Chemical Laboratory, University Hospital Groningen, The Netherlands
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45
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Abstract
Cytarabine is intracellularly activated and correlations have been established between the pharmacokinetic behaviour of active metabolites and their antileukemic effect. Recently, a good response to high-dose treatment of leukemias has additionally been attributed to a so-called low deamination phenotype of cytarabine inactivation. Consequently, these findings would support plasma level monitoring of cytarabine and its metabolite uracil arabinoside in high-dose cytarabine regimens. This pharmacokinetic study presents data attempting to reevaluate these observations. Thirty-seven patients were treated by 3-h high-dose cytarabine infusions (9 patients 1000 mg/m2, 28 patients 3000 mg/m2) as part of their treatment for acute leukemia. Serial blood samples during and post infusion were analysed for cytarabine (araC) and its deamination product uracil arabinoside (araU) using HPLC with UV-detection. Considerable interindividual variation was observed in end-infusion plasma concentrations of araC (1000 mg/m2: 2.1-fold, 3000 mg/m2: 5.5-fold) and araU (1000 mg/m2: 2.7-fold, 3000 mg/m2: 2.9-fold). The median ratio of end infusion concentrations araU/araC (on a molar basis) was 5.6 (S.D. 3.0), extreme ratio values were 2 and 14. No differences of the araU/araC ratio were found between the two dosages used. Minimum plasma araC concentrations at the end of infusion were 10.5 micromol/l and 22.0 micromol/l at a dose of 1000 and 3000 mg/m2, respectively. In our European study population a "fast" deamination phenotype of cytarabine (araU/araC ratio > 14) was not be observed.
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Affiliation(s)
- M Burk
- Clinic of Hematology, Oncology and Clinical Immunology, Heinrich Heine University, Düsseldorf, Germany
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46
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Brouwer DA, Leerink CB, Steward HN, Kroon TA, Suverkropp GH, Römer JW, Volmer M, Muskiet FA. Lipids, apolipoprotein-E genotypes and other risk factors of patients with coronary artery disease in Curaçao. W INDIAN MED J 1997; 46:47-52. [PMID: 9260534] [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: 02/05/2023]
Abstract
We studied lipids, apolipoprotein-E (apo-epsilon) genotypes and other coronary artery disease (CAD) risk factors of 67 CAD patients (male/female ratio 5) in Curaçao. Compared with 57 controls, male CAD patients had higher cholesterol, triglycerides, LDL-cholesterol, apo-B and decreased HDL-cholesterol and HDL-cholesterol/cholesterol concentrations. Other CAD risk factors were: increased fasting glucose and HbA1c concentrations, decreased creatinine clearance, and increased prevalences of lipoprotein (a) concentration > 500 mg/l, renal disease, hyperhomocysteinaemia, diabetes mellitus type II (DM-II), positive CAD family history and cigarette smoking. Male CAD patients had higher plasma alpha-tocopheroleq. Compared with 29 female controls, female CAD patients had higher fasting plasma glucose and HbA1c concentrations, and prevalence of DM-II. Predicting factors for CAD development in the whole CAD group were: DM-II, cigarette smoking, apo-epsilon 3/epsilon 4 and apo-epsilon 4/epsilon 4 Apo-epsilon 4 was associated with lower HDL- and higher LDL-cholesterol concentrations. There is a need for local studies on improvement of diabetic control, reference values of lipoprotein (a) and homocysteine concentrations, on apolipoprotein (a) phenotypes, causes of hyperhomocysteinaemia, and dietary influences on CAD development in subjects who carry the apo-epsilon 4 allele.
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Affiliation(s)
- D A Brouwer
- Central Laboratory for Clinical Chemistry, University Hospital Gröningen, The Netherlands
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47
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Wolthers BG, Kema IP, Volmer M, Wesemann R, Westermann J, Manz B. Evaluation of urinary metanephrine and normetanephrine enzyme immunoassay (ELISA) kits by comparison with isotope dilution mass spectrometry. Clin Chem 1997; 43:114-20. [PMID: 8990232] [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: 02/03/2023]
Abstract
Determination of urinary 3-O-methylated catecholamines (metanephrines) is generally considered a principal test for the clinical chemical diagnosis of pheochromocytoma and is currently performed predominantly with chromatographic techniques such as gas-liquid chromatography and HPLC. Enzyme immunoassays based on microtiter plate technology have recently been developed for the quantitative determination of urinary metanephrine (M) and normetanephrine (NM). We compared the results for urinary M and NM determined by these ELISA methods with those obtained by a recently developed isotope dilution mass spectrometric method. From this comparative study we can conclude that the investigated ELISA methods are applicable in the quantification of urinary M and thus can be successfully used to establish the diagnosis of pheochromocytoma. These relatively simple methods can be executed in any clinical laboratory and in time may replace the present, more complicated, chromatographic techniques.
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Affiliation(s)
- B G Wolthers
- Central Laboratory for Clinical Chemistry, University Hospital, Groningen, The Netherlands
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48
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Burk M, Volmer M, Fartash K, Schneider W. Ion-pair liquid chromatography of cytarabine and uracil-arabinoside in human plasma. Arzneimittelforschung 1995; 45:616-9. [PMID: 7612064] [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] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
An ion-pair high pressure liquid chromatographic method is described for the determination of cytarabine (CAS 147-94-4, araC) in human plasma. Complete separation is achieved within 10 min using a reversed stationary phase and an isocratic eluent containing 0.4 mmol/l heptane sulfonic acid as modifier. Detection by UV-absorption occurs at 270 nm. Quantification of cytarabine and of its main plasma metabolite uracil arabinoside (araU) is achieved by means of internal standardisation using adenine arabinoside (araA). Retention times of araU, araC, and araA are 3.9, 5.9 and 9.4 min, respectively. Detection limits of araC and araU are 10 and 15 ng/ml, resp. During a pharmacokinetic study of high-dose cytarabine treatment no interferences could be observed in plasma samples.
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Affiliation(s)
- M Burk
- Department of Internal Medicine, Heinrich Heine University, Düsseldorf, Germany
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49
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Volmer M, Wolthers BG, Metting HJ, de Haan TH, Coenegracht PM, van der Slik W. Artificial neural network predictions of urinary calculus compositions analyzed with infrared spectroscopy. Clin Chem 1994; 40:1692-7. [PMID: 8070077] [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: 01/28/2023]
Abstract
Infrared (IR) spectroscopy is used to analyze urinary calculus (renal stone) constituents. However, interpretation of IR spectra for quantifying urinary calculus constituents in mixtures is difficult, requiring expert knowledge by trained technicians. In our laboratory IR spectra of unknown calculi are compared with references spectra in a computerized library search of 235 reference spectra from various mixtures of constituents in different proportions, followed by visual interpretation of band intensities for more precise semiquantitative determination of the composition. To minimize the need for this last step, we tested artificial neural network models for detecting the most frequently occurring compositions of urinary calculi. Using constrained mixture designs, we prepared various samples containing ammonium hydrogen urate, brushite, carbonate apatite, cystine, struvite, uric acid, weddellite, and whewellite for use as a training set. We assayed known artificial mixtures as well as selected patients' samples from which the semiquantitative compositions were determined by computerized library search followed by visual interpretation. Neural network analysis was more accurate than the library search and required less expert knowledge because careful visual inspection of the band intensities could be omitted. We conclude that neural networks are promising tools for routine quantification of urinary calculus compositions and for other related types of analyses in the clinical laboratory.
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Affiliation(s)
- M Volmer
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
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50
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Volmer M, Wolthers BG, Metting HJ, de Haan TH, Coenegracht PM, van der Slik W. Artificial neural network predictions of urinary calculus compositions analyzed with infrared spectroscopy. Clin Chem 1994. [DOI: 10.1093/clinchem/40.9.1692] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [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]
Abstract
Abstract
Infrared (IR) spectroscopy is used to analyze urinary calculus (renal stone) constituents. However, interpretation of IR spectra for quantifying urinary calculus constituents in mixtures is difficult, requiring expert knowledge by trained technicians. In our laboratory IR spectra of unknown calculi are compared with references spectra in a computerized library search of 235 reference spectra from various mixtures of constituents in different proportions, followed by visual interpretation of band intensities for more precise semiquantitative determination of the composition. To minimize the need for this last step, we tested artificial neural network models for detecting the most frequently occurring compositions of urinary calculi. Using constrained mixture designs, we prepared various samples containing ammonium hydrogen urate, brushite, carbonate apatite, cystine, struvite, uric acid, weddellite, and whewellite for use as a training set. We assayed known artificial mixtures as well as selected patients' samples from which the semiquantitative compositions were determined by computerized library search followed by visual interpretation. Neural network analysis was more accurate than the library search and required less expert knowledge because careful visual inspection of the band intensities could be omitted. We conclude that neural networks are promising tools for routine quantification of urinary calculus compositions and for other related types of analyses in the clinical laboratory.
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Affiliation(s)
- M Volmer
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
| | - B G Wolthers
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
| | - H J Metting
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
| | - T H de Haan
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
| | - P M Coenegracht
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
| | - W van der Slik
- Central Laboratory for Clinical Chemistry, University Hospital Groningen, The Netherlands
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