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961.
Are Subject-Specific Musculoskeletal Models Robust to the Uncertainties in Parameter Identification?
Giordano Valente Lorenzo Pitto Debora Testi Ajay Seth Scott L. Delp Rita Stagni Marco Viceconti Fulvia Taddei 《PloS one》2014,9(11)
Subject-specific musculoskeletal modeling can be applied to study musculoskeletal disorders, allowing inclusion of personalized anatomy and properties. Independent of the tools used for model creation, there are unavoidable uncertainties associated with parameter identification, whose effect on model predictions is still not fully understood. The aim of the present study was to analyze the sensitivity of subject-specific model predictions (i.e., joint angles, joint moments, muscle and joint contact forces) during walking to the uncertainties in the identification of body landmark positions, maximum muscle tension and musculotendon geometry. To this aim, we created an MRI-based musculoskeletal model of the lower limbs, defined as a 7-segment, 10-degree-of-freedom articulated linkage, actuated by 84 musculotendon units. We then performed a Monte-Carlo probabilistic analysis perturbing model parameters according to their uncertainty, and solving a typical inverse dynamics and static optimization problem using 500 models that included the different sets of perturbed variable values. Model creation and gait simulations were performed by using freely available software that we developed to standardize the process of model creation, integrate with OpenSim and create probabilistic simulations of movement. The uncertainties in input variables had a moderate effect on model predictions, as muscle and joint contact forces showed maximum standard deviation of 0.3 times body-weight and maximum range of 2.1 times body-weight. In addition, the output variables significantly correlated with few input variables (up to 7 out of 312) across the gait cycle, including the geometry definition of larger muscles and the maximum muscle tension in limited gait portions. Although we found subject-specific models not markedly sensitive to parameter identification, researchers should be aware of the model precision in relation to the intended application. In fact, force predictions could be affected by an uncertainty in the same order of magnitude of its value, although this condition has low probability to occur. 相似文献
962.
William J. Sames Terry A. Klein Heung Chul Kim Sung Tae Chong In Yong Lee Se Hun Gu Yon Mi Park Ji Hye Jeong Jin‐Won Song 《Journal of vector ecology》2009,34(2):225-231
The Twin Bridges Training Area (TBTA) in the Republic of Korea consists of dirt roads, barren training areas, and forested hillsides adjacent to linear and broad expanses of tall grasses, herbaceous, and scrub vegetation. Of the six species of small mammals, the striped field mouse, Apodemus agrarius, was the most frequently captured (96.1%). Apodemus agrarius capture rates varied from 17.7 to 33.2% during three trapping periods. Gravid females were observed during November‐December 2006 (8.4%) and March 2007 (5.1%). In 2005, the overall seroprevalence of Hantaan virus (HTNV) was high (34.4%) and lower during surveys in 2006 (14.2%) and 2007 (13.8%). Seroprevalence was directly correlated with weight increase of A. agrarius. 相似文献
963.
Heidi Goodrich-Blair Jean-Michel Ané James D. Bever Seth R. Bordenstein Monika Bright John M. Chaston Keith Clay Cameron R. Currie Angela E. Douglas Nicole Gerardo Maria J. Harrison Ruth E. Ley Margaret McFall-Ngai Arijit Mukherjee Bethany Rader Kenneth F. Raffa Edward G. Ruby Mary Beth Saffo Marc-André Selosse Justin L. Sonnenburg S. Patricia Stock Garret Suen Katarzyna Turnau Michael Udvardi Karen L. Visick Virginia M. Weis 《Symbiosis (Philadelphia, Pa.)》2010,51(1):1-12
Symbiosis, the intimate association between two or more organisms, is a fundamental component of biological systems. Our ability to understand the processes involved in the establishment and function of Symbiosis has critical consequences for the health of humans and the world we live in. For example, a deeper understanding of how legumes and insects have harnessed the nitrogen-fixing capacity of microbes can pave the way toward novel strategies to decrease fertilizer use. Also, using insect models to elucidate links between diet, gut microbiota, and toxin sensitivity not only has implications for biological control strategies, but also will lend insights into similar links in the human gut ecosystem. These types of ideas were presented and discussed at the 6th International Symbiosis Society Congress held in Madison, Wisconsin August, 2009. Over 300 participants from 20 countries attended the 7-day event, which featured cutting-edge symbiosis research from many different perspectives and disciplines. The conference was organized thematically, with oral sessions focused on Evolution, Ecology, Metabolism, the Host-Microbe Interface, Threats to Earth Systems, Symbiosis Models and the Human Microbiome, Viruses and Organelles, and Symbiosis Education. World-renowned scientists, post-doctoral fellows, and students were given the opportunity to describe their most recent discoveries. Session chairs provided overviews of their programs which highlight how the comparative analysis of different systems reveal common trends underlying symbiotic associations, what tools and theory are being developed that may be applied more broadly in symbiosis research, how symbiosis research contributing solutions to global issues such as emerging antibiotic resistance, a need for alternative energy sources, the pursuit of sustainable agriculture and natural resources, and how symbiotic systems are ideal for educating people about the fascinating natural world around us. The following paragraphs provide an overview of the research and discussions that took place during the congress. 相似文献
964.
Terry Yin Timothy E. Lindley Gregory W. Albert Raheel Ahmed Peter B. Schmeiser M. Sean Grady Matthew A. Howard Michael J. Welsh 《PloS one》2013,8(8)
Traumatic brain injury (TBI) is a common cause of morbidity and mortality in people of all ages. Following the acute mechanical insult, TBI evolves over the ensuing minutes and days. Understanding the secondary factors that contribute to TBI might suggest therapeutic strategies to reduce the long-term consequences of brain trauma. To assess secondary factors that contribute to TBI, we studied a lateral fluid percussion injury (FPI) model in mice. Following FPI, the brain cortex became acidic, consistent with data from humans following brain trauma. Administering HCO3
− after FPI prevented the acidosis and reduced the extent of neurodegeneration. Because acidosis can activate acid sensing ion channels (ASICs), we also studied ASIC1a−/− mice and found reduced neurodegeneration after FPI. Both HCO3
− administration and loss of ASIC1a also reduced functional deficits caused by FPI. These results suggest that FPI induces cerebral acidosis that activates ASIC channels and contributes to secondary injury in TBI. They also suggest a therapeutic strategy to attenuate the adverse consequences of TBI. 相似文献
965.
D J Cruickshank P B Terry W T Fullerton 《The International journal of biological markers》1991,6(4):247-252
Seventy four consecutive patients with epithelial ovarian cancer have been followed up longitudinally with serial serum CA125 for up to 48 months. From this database, the CA125 changes in small volume disease have been evaluated. For long term complete responders (n = 12), the mean plateau level of CA125 was 7.2 U/ml (95% confidence interval; 5.6 to 9.2 U/ml). The natural half-life of CA125 at 5.1 days (range 3.8 to 7 days) was calculated from five patients with Stage I and II disease who underwent complete surgical excision. A mean lead time of 99 days (range 14 to 255 days) was demonstrated between marker detection of disease progression and clinically apparent progressive disease in 12 out of 13 patients (92%) who relapsed after chemotherapy induced complete remission. The threshold of tumour volume detection with CA125 is unlikely to be determined by an arbitrary cut-off level. The kinetics of CA125 provide more useful information and the potential to define complete response or indeed cure with CA125 parameters requires further investigation. 相似文献
966.
Spatial changes in structural and functional characteristics of fish and macroinvertebrate communities in eastern Kentucky
were investigated in a drainage system chronically exposed to high levels of chloride salts from nearby oilfield operations.
Salinity levels at biological monitoring stations ranged from 0.12–31.3‰. Lotic regions with salinities greater than 10‰ were
dominated by larvae of the dipterans Ephydra and Culicoides. In regions with salinities less than 10‰ species richness increased more or less linearly with decreasing levels of chloride
salts. Ephemeropterans appeared to be one of the major invertebrate groups least tolerant of elevated NaCl levels and were
absent in regions with salinities greater than 2‰ Availability of food resources, such as periphyton and particulate organic
matter, did not appear to be grossly altered in disturbed regions, and it is suggested that the observed distribution of macroinvertebrate
fauna was largely in response to taxonomic differences in salt tolerance. Fish seemed to be more tolerant of highly saline
conditions, and several species were observed in regions experiencing salinities as high as 15‰. Accordingly, assemblages
of fish taxa along the salinity gradient may have been influenced by trophic factors, such as spatial limitations in availability
of invertebrate prey. 相似文献
967.
Seth H. Weinberg 《PloS one》2013,8(11)
High-frequency (HF) stimulation has been shown to block conduction in excitable cells including neurons and cardiac myocytes. However, the precise mechanisms underlying conduction block are unclear. Using a multi-scale method, the influence of HF stimulation is investigated in the simplified FitzhHugh-Nagumo and biophysically-detailed Hodgkin-Huxley models. In both models, HF stimulation alters the amplitude and frequency of repetitive firing in response to a constant applied current and increases the threshold to evoke a single action potential in response to a brief applied current pulse. Further, the excitable cells cannot evoke a single action potential or fire repetitively above critical values for the HF stimulation amplitude. Analytical expressions for the critical values and thresholds are determined in the FitzHugh-Nagumo model. In the Hodgkin-Huxley model, it is shown that HF stimulation alters the dynamics of ionic current gating, shifting the steady-state activation, inactivation, and time constant curves, suggesting several possible mechanisms for conduction block. Finally, we demonstrate that HF stimulation of a network of neurons reduces the electrical activity firing rate, increases network synchronization, and for a sufficiently large HF stimulation, leads to complete electrical quiescence. In this study, we demonstrate a novel approach to investigate HF stimulation in biophysically-detailed ionic models of excitable cells, demonstrate possible mechanisms for HF stimulation conduction block in neurons, and provide insight into the influence of HF stimulation on neural networks. 相似文献
968.
Esa T. Jarvi Prasad S. Sunkara Terry L. Bowlin 《Nucleosides, nucleotides & nucleic acids》2013,32(5-6):1111-1114
Abstract 2′-difluoro and 3′-difluoro dideoxynucleosides containing thymine and cytosine as the base were synthesized. These compounds inhibited HeLa cell growth and Moloney leukemia virus to a modest degree. 相似文献
969.
970.
A fungal endophyte defensive symbiosis affects plant-nematode interactions in cotton 总被引:1,自引:0,他引:1
Wenqing Zhou Terry A. Wheeler James L. Starr Cesar U. Valencia Gregory A. Sword 《Plant and Soil》2018,422(1-2):251-266