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排序方式: 共有329条查询结果,搜索用时 31 毫秒
31.
32.
Eoghan M Cunnane John JE Mulvihill Hilary E Barrett Michael T Walsh 《Biomedical engineering online》2015,14(Z1):S7
Background
Due to the limited number of experimental studies that mechanically characterise human atherosclerotic plaque tissue from the femoral arteries, a recent trend has emerged in current literature whereby one set of material data based on aortic plaque tissue is employed to numerically represent diseased femoral artery tissue. This study aims to generate novel vessel-appropriate material models for femoral plaque tissue and assess the influence of using material models based on experimental data generated from aortic plaque testing to represent diseased femoral arterial tissue.Methods
Novel material models based on experimental data generated from testing of atherosclerotic femoral artery tissue are developed and a computational analysis of the revascularisation of a quarter model idealised diseased femoral artery from a 90% diameter stenosis to a 10% diameter stenosis is performed using these novel material models. The simulation is also performed using material models based on experimental data obtained from aortic plaque testing in order to examine the effect of employing vessel appropriate material models versus those currently employed in literature to represent femoral plaque tissue.Results
Simulations that employ material models based on atherosclerotic aortic tissue exhibit much higher maximum principal stresses within the plaque than simulations that employ material models based on atherosclerotic femoral tissue. Specifically, employing a material model based on calcified aortic tissue, instead of one based on heavily calcified femoral tissue, to represent diseased femoral arterial vessels results in a 487 fold increase in maximum principal stress within the plaque at a depth of 0.8 mm from the lumen.Conclusions
Large differences are induced on numerical results as a consequence of employing material models based on aortic plaque, in place of material models based on femoral plaque, to represent a diseased femoral vessel. Due to these large discrepancies, future studies should seek to employ vessel-appropriate material models to simulate the response of diseased femoral tissue in order to obtain the most accurate numerical results.33.
Background
Representation of independent biophysical sources using Fourier analysis can be inefficient because the basis is sinusoidal and general. When complex fractionated atrial electrograms (CFAE) are acquired during atrial fibrillation (AF), the electrogram morphology depends on the mix of distinct nonsinusoidal generators. Identification of these generators using efficient methods of representation and comparison would be useful for targeting catheter ablation sites to prevent arrhythmia reinduction.Method
A data-driven basis and transform is described which utilizes the ensemble average of signal segments to identify and distinguish CFAE morphologic components and frequencies. Calculation of the dominant frequency (DF) of actual CFAE, and identification of simulated independent generator frequencies and morphologies embedded in CFAE, is done using a total of 216 recordings from 10 paroxysmal and 10 persistent AF patients. The transform is tested versus Fourier analysis to detect spectral components in the presence of phase noise and interference. Correspondence is shown between ensemble basis vectors of highest power and corresponding synthetic drivers embedded in CFAE.Results
The ensemble basis is orthogonal, and efficient for representation of CFAE components as compared with Fourier analysis (p ≤ 0.002). When three synthetic drivers with additive phase noise and interference were decomposed, the top three peaks in the ensemble power spectrum corresponded to the driver frequencies more closely as compared with top Fourier power spectrum peaks (p ≤ 0.005). The synthesized drivers with phase noise and interference were extractable from their corresponding ensemble basis with a mean error of less than 10%.Conclusions
The new transform is able to efficiently identify CFAE features using DF calculation and by discerning morphologic differences. Unlike the Fourier transform method, it does not distort CFAE signals prior to analysis, and is relatively robust to jitter in periodic events. Thus the ensemble method can provide a useful alternative for quantitative characterization of CFAE during clinical study. 相似文献34.
35.
Thornberg C Vesanen R Wallström E Zvonova I Jesko T Balonov M Mattsson S 《Radiation and environmental biophysics》2005,44(2):97-106
In 1990, a joint Nordic-Russian project was initiated in order to make independent estimations of the effective dose to selected
groups of inhabitants in a highly contaminated area around the city of Novozybkov in the western Bryansk region of Russia.
The inhabitants were living in six villages with initial contamination levels of 137Cs between 0.9 and 2.7 MBq m−2. Some villages had been decontaminated, others not. Both school children and adults participated in the study. The external
irradiation of 100–130 inhabitants was determined during 1 month in September-October each year from 1990 to 2000 (except
1999), using individual thermoluminescent dosemeters. The body burden of 137,134Cs was determined by in vivo measurements in about 500 inhabitants annually from 1991 to 2000, and for a subgroup also with
analysis of the 137Cs concentration in urine. The mean effective dose (E) from external and internal irradiation due to 137,134Cs deposition varied between 2.5 and 1.2 mSv per year between 1990 and 2000. The total mean E decreased, on average, by 9% per year, while the mean external dose decreased by 16% per year. The dose rate from internal
radiation decreased more slowly than the dose rate from external radiation, and also showed an irregular time variation. The
contribution from the internal dose to the total E was 30–50%, depending on the village. Predictions for the long-term changes in the effective dose to people living in the
areas are presented. The cumulated E for the 70 years following the accident was estimated to be about 90 mSv with the assumption that both internal and external
dose decrease by 2% per year after year 2000. The highest E during a life-time received by single individuals living in the area may amount to around 500 mSv considering the individual
variations in E. 相似文献
36.
Ryser-Degiorgis MP Hofmann-Lehmann R Leutenegger CM af Segerstad CH Mörner T Mattsson R Lutz H 《Journal of wildlife diseases》2005,41(1):58-66
Serum samples from 106 Eurasian lynx (Lynx lynx) from across Sweden, found dead or shot by hunters in 1993-99, were investigated for presence of antibodies to feline parvovirus (FPV), feline coronavirus, feline calicivirus, feline herpesvirus, feline immunodeficiency virus, Francisella tularensis, and Anaplasma phagocytophila, and for feline leukemia virus antigen. In addition, tissue samples from 22 lynx submitted in 1999 were analyzed by real-time polymerase chain reaction (PCR) to detect nucleic acids specific for viral agents and A. phagocytophila. Except for FPV antibodies in one lynx and A. phagocytophila in four lynx, all serology was negative. All PCR results also were negative. It was concluded that free-ranging Swedish lynx do not have frequent contact with the infectious agents considered in this study. 相似文献
37.
Similar to murine models with compromised CD22/SHP-1 function, flaky skin (fsn) mutant mice exhibit lymphocyte hyperactivation and an autoimmune phenotype characterized by circulating autoantibodies to dsDNA and glomerulonephritis. Immunophenotyping of fsn/fsn splenic B cells was performed to determine if abnormalities in CD22 expression contributed to the phenotype. We identified an expansion of an IgM(bright) CD22lo population consistent with immature B-lymphocytes. While normal B-lymphocytes require IL-4 to achieve down-modulation of CD22 expression in response to BCR cross-linking, culture with anti-IgM alone led to reduced CD22 expression in fsn/fsn mice. Furthermore, when IL-4 was added to fsn/fsn cultures, no further reduction in CD22 expression was observed. This suggested that fsn/fsn B cells were pre-activated in vivo by chronic IL-4 exposure. A portion of these CD22lo cells expressed the B-1 surface marker CD11b. We contend that decreased activation thresholds among CD22lo B-lymphocytes contributes to the expansion of immature and B-1 B cell populations and to the development of autoimmune pathology in fsn/fsn mice. 相似文献
38.
M Matsuda A Tazumi S Kagawa T Sekizuka O Murayama JE Moore BC Millar 《BMC veterinary research》2006,2(1):1-4
Background
At present, six accessible sequences of 16S rDNA from Taylorella equigenitalis (T. equigenitalis) are available, whose sequence differences occur at a few nucleotide positions. Thus it is important to determine these sequences from additional strains in other countries, if possible, in order to clarify any anomalies regarding 16S rDNA sequence heterogeneity. Here, we clone and sequence the approximate full-length 16S rDNA from additional strains of T. equigenitalis isolated in Japan, Australia and France and compare these sequences to the existing published sequences.Results
Clarification of any anomalies regarding 16S rDNA sequence heterogeneity of T. equigenitalis was carried out. When cloning, sequencing and comparison of the approximate full-length 16S rDNA from 17 strains of T. equigenitalis isolated in Japan, Australia and France, nucleotide sequence differences were demonstrated at the six loci in the 1,469 nucleotide sequence. Moreover, 12 polymorphic sites occurred among 23 sequences of the 16S rDNA, including the six reference sequences.Conclusion
High sequence similarity (99.5% or more) was observed throughout, except from nucleotide positions 138 to 501 where substitutions and deletions were noted. 相似文献39.
Liljander M Sällström MA Andersson S Andersson A Holmdahl R Mattsson R 《Arthritis research & therapy》2006,8(2):R45-6
Collagen-induced arthritis in mice is one of the most commonly used autoimmune experimental models, with many similarities
to rheumatoid arthritis. Since collagen-induced arthritis is a complex polygenic disease there is a need for identification
of several major disease-controlling genes. Because rheumatoid arthritis particularly affects aged women, we have in the present
study identified new genetic regions critical for collagen-induced arthritis by studying aged female mice of a cross between
NFR/N and B10.Q (H-2q haplotype). The mice in the present study had different reproductive histories, which did not significantly affect the onset,
incidence or severity of the disease. A total of 200 female mice were used in a total genome-wide screening with 125 microsatellite
markers. We found one new significant quantitative trait locus affecting the arthritis incidence, severity and day of onset
on chromosome 11 (denoted Cia40), which colocalizes with a locus controlling pregnancy failure. Furthermore, a quantitative trait locus of suggestive significance
associated with the incidence, severity and day of onset was identified on chromosome 1. Finally, a suggestively significant
quantitative trait locus associated with collagen type II antibody titers was identified on chromosome 13. This study indicates
that several gene loci control arthritis in aged multiparous females, and that at least one of these loci coincides with pregnancy
failure. 相似文献
40.