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Barrat JL, Hansen JP, Totsuji H. Collective modes and single-particle motion in Yukawa fluids near freezing. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/21/25/003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
This review summarizes and assesses recent theoretical and experimental advances, with special emphasis on the effective interaction between charge-stabilized colloids, in the bulk or in confined geometries, and on the ambiguities of defining an effective charge of the colloidal particles. Some consideration is given to the often neglected discrete solvent effects.
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Louis AA, Bolhuis PG, Hansen JP, Meijer EJ. Can polymer coils Be modeled as "Soft colloids"? PHYSICAL REVIEW LETTERS 2000; 85:2522-2525. [PMID: 10978097 DOI: 10.1103/physrevlett.85.2522] [Citation(s) in RCA: 277] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2000] [Indexed: 05/23/2023]
Abstract
We map dilute or semidilute solutions of nonintersecting polymer chains onto a fluid of "soft" particles interacting via a concentration dependent effective pair potential, by inverting the pair distribution function of the centers of mass of the initial polymer chains. A similar inversion is used to derive an effective wall-polymer potential; these potentials are combined to successfully reproduce the calculated exact depletion interaction induced by nonintersecting polymers between two walls. The mapping opens up the possibility of large-scale simulations of polymer solutions in complex geometries.
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Wildman RD, Huntley JM, Hansen JP, Parker DJ, Allen DA. Single-particle motion in three-dimensional vibrofluidized granular beds. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:3826-3835. [PMID: 11088900 DOI: 10.1103/physreve.62.3826] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2000] [Indexed: 05/23/2023]
Abstract
A technique to probe the interior of three-dimensional dynamic granular systems is presented. Positron emission particle tracking (PEPT) allows a single tracer particle to be followed around a three dimensional vibrofluidized granular bed for periods up to six hours. At present the technique is able to resolve the position of the grains to +/-4 mm, with an average temporal resolution of about 7 ms. Packing fraction profiles are calculated by making use of the ergodicity of the system, and granular temperature profiles are obtained, in the dilute case, from the short time behavior of the mean squared displacement. At longer times, the mean squared displacement shows a range of behavior which can be explained by the presence of strong gradients in the packing fraction. Convection currents were observed, but were sufficiently small in magnitude to be ignored during the analysis of grain motion. The system was modeled using the Smoluchowski equation, which was solved numerically, and the results compared with the experimentally determined displacement probability density functions. Good agreement between experiment and numerical results was achieved using Brownian motion relationships modified to accommodate differences between granular systems and thermal systems.
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Wang JB, Hansen JP, Dubois A. Spin anisotropy for excitation in collisions between two one-electron atoms. PHYSICAL REVIEW LETTERS 2000; 85:1638-1641. [PMID: 10970577 DOI: 10.1103/physrevlett.85.1638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2000] [Indexed: 05/23/2023]
Abstract
The singlet and triplet contributions of excitation cross sections are studied theoretically for collisions between various two one-electron atoms. The spin anisotropy is shown to have a general behavior in the important impact energy range. At low energies triplet cross sections dominate completely over the singlet ones while the opposite is true when the active electron and projectile velocities are comparable. Beyond the matching velocity regime singlet and triplet contributions become identical. We propose a general dynamical interpretation based on the analysis of the time dependency of the electron probability density and probability current density.
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Goulding D, Hansen JP, Melchionna S. Size selectivity of narrow pores. PHYSICAL REVIEW LETTERS 2000; 85:1132-1135. [PMID: 10991492 DOI: 10.1103/physrevlett.85.1132] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2000] [Indexed: 05/23/2023]
Abstract
The selectivity of micropores and ion channels is examined for simple pore topologies within the framework of density functional theory of highly confined fluids. In an infinite cylindrical pore purely steric (excluded volume) effects are shown to lead to strong, nontrivial size selectivity, which is highly sensitive to the pore radius. A crude modeling of electrostatic effects does not alter the relative absorbance of Na+ and K+ ions in a significant way.
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Weile B, Hansen BF, Hägerstrand I, Hansen JP, Krasilnikoff PA. Interobserver variation in diagnosing coeliac disease. A joint study by Danish and Swedish pathologists. APMIS 2000; 108:380-4. [PMID: 10937777 DOI: 10.1034/j.1600-0463.2000.d01-72.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
There is an almost 40-fold difference in incidence rates of symptomatic coeliac disease between Denmark and Sweden. In an attempt to explain this difference, the present study focused on the interobserver agreement when pathologists were assessing small intestinal biopsy specimens from children suspected of suffering from coeliac disease. The study was performed on 90 biopsy specimens from 73 children. Most of the biopsies came from children who turned out not to suffer from coeliac disease after a clinical evaluation including small intestinal biopsy. Using the kappa methodology, the interobserver agreement between two Danish pathologists and one Swedish pathologist, all of whom were experienced, was "moderate" to "substantial" or 0.57-0.75. Kappa indices when the pathologists evaluated selected histological elements were in the interval from 0.24 to 0.67. A comparison of a previous routine diagnostic assessment of the 90 biopsies (14 pathologists) with the results of the experienced pathologists in the present study gave kappa indices of from 0.53 to 0.57. The study could prove no major differences in the histopathological assessment of small intestinal biopsy specimens made by Danish and Swedish pathologists. The difference in clinical presentation of coeliac disease in Denmark and Sweden does not relate to differences in the histopathological assessment of small intestinal biopsies.
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Louis AA, Finken R, Hansen JP. Crystallization and phase separation in nonadditive binary hard-sphere mixtures. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:R1028-R1031. [PMID: 11046530 DOI: 10.1103/physreve.61.r1028] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/1999] [Indexed: 05/23/2023]
Abstract
We calculate for the first time the full phase diagram of an asymmetric nonadditivehard-sphere mixture. The nonadditivity strongly affects the crystallization and the fluid-fluid phase separation. The global topology of the phase diagram is controlled by an effective size ratio y(eff), while the fluid-solid coexistence scales with the depth of the effective potential well.
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Wildman RD, Huntley JM, Hansen JP. Self-diffusion of grains in a two-dimensional vibrofluidized bed. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 60:7066-75. [PMID: 11970646 DOI: 10.1103/physreve.60.7066] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/1999] [Revised: 07/07/1999] [Indexed: 04/18/2023]
Abstract
The analogy of vibrofluidized granular beds with a thermal gas of hard discs has been tested. Analysis of the mean squared displacement behavior of the grains allowed comparison of the measured diffusion with the predicted value at a particular combination of granular temperature and packing fraction. High speed photography, image analysis, and particle tracking software enabled accurate location of the grains. Appropriate analysis of the three mean squared displacement regimes, ballistic, diffusive, and crossover between the two extremes, allowed both the diffusion coefficient and the granular temperature to be measured at the same packing fraction. Broad agreement between Chapman-Enskog theory relating temperature to self-diffusion and observation was observed up to packing fractions of eta approximately equal to 0.7. At higher packing fractions the grains showed evidence of caging and jump diffusion, with the observed diffusion rapidly diverging from that predicted by theory. Measurement of self-diffusion coefficients and subsequent use of kinetic theory was found to be an accurate method to determine the granular temperature for intermediate packing fractions (eta=0.4-0.6), and would be particularly suitable for those situations where the time resolution of the experimental facility is insufficient to resolve the speed of the grain between collisions.
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Xu H, Hansen JP. Plasma-insulator transition of spin-polarized hydrogen. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1999; 60:R9-R12. [PMID: 11969868 DOI: 10.1103/physreve.60.r9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/1999] [Indexed: 04/18/2023]
Abstract
A mixed classical-quantum density functional theory is used to calculate pair correlations and the free energy of a spin-polarized hydrogen plasma. A transition to an atomic insulator phase is estimated to occur around r(s)=2.5 at T=10(4) K, and a pressure P is approximately equal to 0.5 Mbar. Spin polarization is imposed to prevent the formation of H2 molecules.
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Bohn J, Hansen JP, Menné T. Ulcerative lichen planus-like dermatitis due to long-term hydroxyurea therapy. J Eur Acad Dermatol Venereol 1998; 10:187-9. [PMID: 9553923 DOI: 10.1111/j.1468-3083.1998.tb00726.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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37
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Hansen JP, Futch DB. Chiropractic services in a staff model HMO: utilization and satisfaction. HMO PRACTICE 1997; 11:39-42. [PMID: 10165554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Utilization of chiropractic services was assessed in the continuously enrolled, non-Medicaid membership of Group Health Cooperative of South Central Wisconsin in 1993 and 1994. In addition, a random sample of 500 members using chiropractic services in the last quarter of 1994 was surveyed about satisfaction with the services. A total of 5.1% and 5.3% of members used the services in 1993 and 1994, respectively. Highest utilization occurred among women aged 35 to 49, with rates of 9.5% and 9.9%. Satisfaction levels were high in all areas; 95.8% indicated overall satisfaction with chiropractic care and services.
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Kohanoff J, Hansen JP. Statistical properties of the dense hydrogen plasma: An ab initio molecular dynamics investigation. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1996; 54:768-781. [PMID: 9965124 DOI: 10.1103/physreve.54.768] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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39
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Dijkstra M, Hansen JP, Madden PA. Gelation of a clay colloid suspension. PHYSICAL REVIEW LETTERS 1995; 75:2236-2239. [PMID: 10059248 DOI: 10.1103/physrevlett.75.2236] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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40
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Lock-Andersen J, Hou-Jensen K, Hansen JP, Jensen NK, Søgaard H, Andersen PK. Observer variation in histological classification of cutaneous malignant melanoma. SCANDINAVIAN JOURNAL OF PLASTIC AND RECONSTRUCTIVE SURGERY AND HAND SURGERY 1995; 29:141-8. [PMID: 7569811 DOI: 10.3109/02844319509034330] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To evaluate the variations within and between observers in the interpretation of important histological prognostic factors, a series of 96 melanoma patients was randomly selected from a database of 1691 patients with cutaneous malignant melanoma. The stained sections were examined on two occasions by four experienced pathologists. Analysis by observed agreement and kappa statistics showed maximal tumour thickness to be the best reproducible variable, with ulceration the second best. Regression was the least reproducible, with level of invasion and type of melanoma in the mid range. Intra-observer variation was uniformly less than inter-observer variation for each variable. For tumour thickness a variance component analysis was done to quantify the variability further. The clinician should not base his choice of treatment entirely on the microscopic classification but take into consideration the clinical course and appearance of the tumour.
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Trizac E, Hansen JP. Dynamic scaling behavior of ballistic coalescence. PHYSICAL REVIEW LETTERS 1995; 74:4114-4117. [PMID: 10058419 DOI: 10.1103/physrevlett.74.4114] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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42
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Hansen AC, Kristensen IB, Dragsholt C, Hansen JP. [Alcohol, drugs and narcotics in suicides in the Aarhus police district]. Ugeskr Laeger 1995; 157:1524-7. [PMID: 7725551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
For a period of one year all suicides in Aarhus police district were investigated with a view to identifying the presence of alcohol or drugs in the body of the deceased. Fifty-one suicides occurred, 46 of which were examined. One third of the suicides were due to poisoning and one fourth to hanging. Alcohol was detected in 20% and drugs or narcotics were found in approximately 60%. The most frequent findings were benzodiazepines, analgetics, antidepressants and carbon monoxide. Approximately 40% of the deceased had received psychiatric treatment.
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Kohanoff J, Hansen JP. Ab Initio Molecular Dynamics of Metallic Hydrogen at High Densities. PHYSICAL REVIEW LETTERS 1995; 74:626-629. [PMID: 10058807 DOI: 10.1103/physrevlett.74.626] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Wewer V, Christiansen KM, Andersen LP, Henriksen FW, Hansen JP, Tvede M, Krasilnikoff PA. Helicobacter pylori infection in children with recurrent abdominal pain. Acta Paediatr 1994; 83:1276-81. [PMID: 7734870 DOI: 10.1111/j.1651-2227.1994.tb13015.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Helicobacter pylori was cultured and Helicobacter-like organisms (HLO) were seen in 6 (16%) of 37 children with recurrent abdominal pain. Five children had concomitant histological inflammation, but none had endoscopic changes. All 6 children demonstrated positive serology. Compared with the total group, they were more often from developing countries, larger families and lower social groups. Treatment with phenoxymethyl penicillin and colloidal bismuth subcitrate did not result in side effects or elevated serum levels of serum bismuth. Three children demonstrated metronidazole-resistant strains and the treatment of these children remained an unsolved problem. Among the 31 H. pylori/HLO negative children 8 (26%) demonstrated histological changes, 5 (16%) endoscopic changes and 11 (35%) had positive serology. In conclusion, pathological findings at upper gastrointestinal endoscopy are common in children with recurrent abdominal pain. Because of disconcordance between endoscopy, histology and culture, we recommend that biopsies should always be taken to clarify the diagnosis.
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Andersen LP, Wewer AV, Christiansen KM, Tvede M, Hansen JP, Henriksen FW, Krasilnikoff PA. The humoral immune response to Helicobacter pylori infection in children with recurrent abdominal pain. APMIS 1994; 102:457-64. [PMID: 8068306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The systemic humoral immune response to Helicobacter pylori antigens was investigated in 36 children with recurrent abdominal pain (RAP). H. pylori was cultured and Helicobacter-like organisms (HLO) were seen in six children, three of whom had active and two inactive chronic gastritis. None of these children had endoscopic abnormalities. All sex children had increased IgG antibodies to heat-stable H. pylori antigens which were of the IgG1 and IgG3 subclasses. Using six other IgG tests, four of which were commercially available, two to five H. pylori-positive children were found seropositive. Five of six H. pylori-negative children with inactive chronic gastritis and no endoscopic abnormalities had increased IgM antibody levels in addition to increased or borderline increased IgG antibody levels to H. pylori, indicating activity in a chronic H. pylori infection. Five children without H. pylori and with no morphological changes, but with gastritis or duodenitis by endoscopy, had significantly lower IgG and IgA antibody levels compared to other groups. Six of nineteen children without H. pylori, and with no morphological or endoscopic changes had increased IgG and IgM antibody levels to H. pylori. All H. pylori-negative children were seronegative by the four commercial kits. Overall, 12 (33%) of 36 children with RAP were either H. pylori positive by culture and microscopy or had increased IgG antibody levels to H. pylori, which is significantly different from the 10-14% seropositive rate of asymptomatic children. H. pylori may therefore be a cause of RAP in one quarter to one third of the children with RAP in whom other etiologies of RAP are excluded. Further studies on a large number of children are needed for an extended evaluation of the humoral immune response to H. pylori and for further examination of commercial kits which seem to give a high number of false-negative results.
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Hansen JP. After Reykjavik. ARCTIC MEDICAL RESEARCH 1993; 52:142. [PMID: 7905735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Hansen JP, Taulbjerg K. Partial cross sections for single- and double-electron capture by multiply charged ions colliding with He. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1993; 47:2987-2994. [PMID: 9909270 DOI: 10.1103/physreva.47.2987] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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48
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Hansen JP, Nielsen SE, Dubois A. Trajectory-interference effects in ion-atom collisions. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 46:R5331-R5333. [PMID: 9908887 DOI: 10.1103/physreva.46.r5331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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49
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Harvald B, Hansen JP. What will become of Arctic medical research? ARCTIC MEDICAL RESEARCH 1992; 51:114-5. [PMID: 1503577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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50
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Aumayr F, Gieler M, Schweinzer J, Winter H, Hansen JP. Electron capture in He2+ collisions with aligned Na*(3p) atoms. PHYSICAL REVIEW LETTERS 1992; 68:3277-3280. [PMID: 10045661 DOI: 10.1103/physrevlett.68.3277] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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