Patient-specific modeling of dyssynchronous heart failure: A case study

The development and clinical use of patient-specific models of the heart is now a feasible goal. Models have the potential to aid in diagnosis and support decision-making in clinical cardiology. Several groups are now working on developing multi-scale models of the heart for understanding therapeutic mechanisms and better predicting clinical outcomes of interventions such as cardiac resynchronization therapy. Here we describe the methodology for generating a patient-specific model of the failing heart with a myocardial infarct and left ventricular bundle branch block. We discuss some of the remaining challenges in developing reliable patient-specific models of cardiac electromechanical activity, and identify some of the main areas for focusing future research efforts. Key challenges include: efficiently generating accurate patient-specific geometric meshes and mapping regional myofiber architecture to them; modeling electrical activation patterns based on cellular alterations in human heart failure, and estimating regional tissue conductivities based on clinically available electrocardiographic recordings; estimating unloaded ventricular reference geometry and material properties for biomechanical simulations; and parameterizing systemic models of circulatory dynamics from available hemodynamic measurements.     

Patient-specific analyses of deep tissue loads post transtibial amputation in residual limbs of multiple prosthetic users

Active transtibial amputation (TTA) patients are at risk for developing pressure ulcers (PU) and deep tissue injury (DTI) while using their prosthesis. It is therefore important to obtain knowledge of the mechanical state in the internal soft tissues of the residuum, as well as knowledge of the mechanical state upon its surface. Our aim was to apply patient-specific MRI-based non-linear finite element (FE) models to quantify internal strains in TTA prosthetic users (n=5) during load-bearing. By further employing a strain injury threshold for skeletal muscle, we identified patients susceptible to DTI. The geometrical characteristics of the residuum of the TTA participants varied substantially between patients, e.g. the residuum lengths were 7.6, 8.1, 9.2, 11.5 and 13.3 cm. We generally found that internal strains were higher in the bone proximity than in the muscle flap periphery. The highest strains, which in some patients exceeded 50% (engineering strain) for compressive, tensile and shear strains, were found in the shortest residual limbs, i.e. the 7.6 and 8.1 cm-long limbs. Correspondingly, the lowest strains were found in the 13.3 cm-long residuum, which had the bulkiest muscle flap. Yet, even in the case of a long residuum, about a third of the soft tissue volume at the distal tibial proximity area was occupied by large (>5%) internal compressive, tensile and shear strains. For both patients with shorter residual limbs, the internal principal compressive strains above 5% occupied almost the entire distal tibial proximity area. For a patient whose distal tibial end was flat (non-beveled), internal strains were more uniformly distributed, compared to the strain distributions in the other models, where focal elevated strains accumulated in the bone proximity. We found no muscle strains above the immediate injury threshold, indicating that all patients were not at immediate risk for DTI. Two patients whose residuum fat padding was minimal to none, were the only ones identified as theoretically prone to DTI at long (>3 h) continuous weight-bearing periods. We conclude that there is a wide variability in internal mechanical conditions between residual limbs across subjects, which necessitates patient-specific quantitative analyses of internal mechanical states in TTA patients, to assess the mechanical performance of the reconstructed limb and in particular, the individual risk for deep PU or DTI.     

A case of colonization of a prosthetic mitral valve by Acremonium strictum

A case of colonization of a prosthetic mitral valve in a 73-year-old Spanish male by the fungus Acremonium strictum W. Gams is described. The valve was replaced due to paravalvular leak and severe insufficiency and the patient died of multiorgan failure. The identity of the fungus was determined by morphological studies and it was confirmed by the analysis of the ITS region sequence analysis. Molecular studies seem to demonstrate that A. strictum is a species complex. The case emphasizes the potential high risk of fungal infection for patients with prosthetic valves.     

Sensing DNA damage by PARP-like fingers

PARP-like zinc fingers are protein modules, initially described as nick-sensors of poly(ADP-ribosyl)-polymerases (PARPs), which are found at the N-terminus of different DNA repair enzymes. I chose to study the role of PARP-like fingers in AtZDP, a 3′ DNA phosphoesterase, which is the only known enzyme provided with three such finger domains. Here I show that PARP-like fingers can maintain AtZDP onto damaged DNA sites without interfering with its DNA end repair functions. Damage recognition by AtZDP fingers, in fact, relies on the presence of flexible joints within double-strand DNA and does not entail DNA ends. A single AtZDP finger is already capable of specific recognition. Two fingers strengthen the binding and extend the contacts on the bound DNA. A third finger further enhances the specific binding to damaged DNA sites. Unexpectedly, gaps but not nicks are bound by AtZDP fingers, suggesting that nicks on a naked DNA template do not provide enough flexibility for the recognition. Altogether these results indicate that AtZDP PARP-like fingers, might have a role in positioning the enzyme at sites of enhanced helical flexibility, where single-strand DNA breaks are present or are prone to occur.     

遥感和GIS支持的土地利用动态监测研究——以黄河三角洲垦利县为例

以黄河三角洲垦利县为例,对比分析了目视解译、机助分类等遥感土地利用信息提取方法,采用1981、1991和1995年3时相土地利用现状信息,研究确定了统一的监测分类系统,提出了土地利用面积及其空间分布动态监测方法.在此基础上,分析了垦利县地类面积增减变化,在GIS支持下分析了1981～1995年土地利用空间动态变化,同时进行了实地监测点土地利用变化分析,探明了该县土地利用动态变化规律.     

遥感和GIS支持的土地利用动态监测研究--以黄河三角洲垦利县为例

以黄河三角洲垦利县为例 ,对比分析了目视解译、机助分类等遥感土地利用信息提取方法 ,采用 1981、1991和 1995年 3时相土地利用现状信息 ,研究确定了统一的监测分类系统 ,提出了土地利用面积及其空间分布动态监测方法 .在此基础上 ,分析了垦利县地类面积增减变化 ,在GIS支持下分析了 1981～ 1995年土地利用空间动态变化 ,同时进行了实地监测点土地利用变化分析 ,探明了该县土地利用动态变化规律 .     

地形对植被生物量遥感反演的影响——以广州市为例

目前植被生物量遥感反演研究中的地形校正主要是校正地形变化对地表反射率的影响,较少考虑地形起伏引起的像元面积与实际地表面积的差异,而这种差异将导致植被生物量估算结果的偏差.在生物量遥感反演的基础上,结合地表面积计算模型和物质守恒定律,建立了生物量地形校正模型,定量分析和讨论了地形起伏对广州市植被类型面积提取和生物量准确估算的影响.结果表明:地形校正前后全市针叶林、阔叶林、草地、灌木林和园地面积分别增加6.18％、3.70％、2.86％、1.92％和1.29％;在综合分析区域生物量遥感反演中的各种不确定性的基础上,建立的各植被类型的生物量模型均具有较高精度,相关系数均接近或者超过0.9,可以满足生物量反演的要求;全市植被生物量呈现出东、北高,西、南低的分布格局,像元实际代表的林地(阔叶林和针叶林)平均生物量为61.86t/hm2,高于珠三角区域生物量平均值,但与亚热带林的顶级群落生物量水平有较大差距,林地生物量还有较大的增长空间;经过校正地形变化引起的像元面积和实际地表面积差异对生物量提取结果的影响后,植被总生物量比校正前增加了5.82％,5种植被类型的总生物量有不同程度的增加,阔叶林、针叶林、草地、灌木林和园地分别增加了7.74％,4.76％、3.34％、2.50％和1.58％.与其它的表面积计算模型相比,利用的像元地表面积模型具有较高的精度,可以满足生物量遥感估算中地形校正的需要.     

遥感和GIS支持的土地利用动态监测研究：以黄河三角洲垦利县 …

以黄河三角洲垦利县为例,对比分析了目视解译、机助分类等遥感土地利用信息提取方法,采用１９８１、１９９１和１９９５年３时相土地利用状信息,研究确定了统一的监测分类系统、提出了土地利用面积及其空间分布动态监测方法,在此基础上,分析了垦利县地类面积增减变化,在ＧＩＳ支持下分析了１９８１－１９９５年土地利用空间动态变化,同时进行了实地监测点土地利用变分析,探明了该县土地利用动态变化规律。     

Study of function of fingers by physiological tremor

1. 1. Physiological tremor is invisible mechanical vibration of body parts.

2. 2. It has two peak frequencies in the p ower spectrum. The origin of the peaks has not been well elucidated. Therefore, the mechanism and its application to labor science is studied in the paper.

3. 3. The effect of immersion of fingers in water and of loading weights on fingers are performed to elucidate the mechanism involved.

4. 4. It is found that the power spectrum output has two bands from the lower frequency band (1.5–18 Hz) from the CNS and the higher frequency band (18–50 Hz).

5. 5. These results are applied to the evaluation of fatigue of fingers in tapping and typing work.

6. 6. The total power, which is the sum of power spectrum in frequency range between 1.5 and 50 Hz, is employed as evaluational index. The change of total power explains finger fatigue during tapping and typing loads.

7. 7. Physiological tremor is an effective way of evaluating the function of fingers in human work.

Let your fingers do the walking: A simple spectral signature model for "remote" fossil prospecting

Even with the most meticulous planning, and utilizing the most experienced fossil-hunters, fossil prospecting in remote and/or extensive areas can be time-consuming, expensive, logistically challenging, and often hit or miss. While nothing can predict or guarantee with 100% assurance that fossils will be found in any particular location, any procedures or techniques that might increase the odds of success would be a major benefit to the field. Here we describe, and test, one such technique that we feel has great potential for increasing the probability of finding fossiliferous sediments - a relatively simple spectral signature model using the spatial analysis and image classification functions of ArcGIS^®10 that creates interactive thematic land cover maps that can be used for “remote” fossil prospecting. Our test case is the extensive Eocene sediments of the Uinta Basin, Utah - a fossil prospecting area encompassing ∼1200 square kilometers. Using Landsat 7 ETM+ satellite imagery, we “trained” the spatial analysis and image classification algorithms using the spectral signatures of known fossil localities discovered in the Uinta Basin prior to 2005 and then created interactive probability models highlighting other regions in the Basin having a high probability of containing fossiliferous sediments based on their spectral signatures. A fortuitous “post-hoc” validation of our model presented itself. Our model identified several paleontological “hotspots”, regions that, while not producing any fossil localities prior to 2005, had high probabilities of being fossiliferous based on the similarities of their spectral signatures to those of previously known fossil localities. Subsequent fieldwork found fossils in all the regions predicted by the model.     

Multidisciplinary population monitoring when demographic data are sparse: a case study of remote trout populations

The potential of genetic, genomic, and phenotypic metrics for monitoring population trends may be especially high in isolated regions, where traditional demographic monitoring is logistically difficult and only sporadic sampling is possible. This potential, however, is relatively underexplored empirically. Over eleven years, we assessed several such metrics along with traditional ecological knowledge and catch data in a socioeconomically important trout species occupying a large, remote lake. The data revealed largely stable characteristics in two populations over 2–3 generations, but possible contemporary changes in a third population. These potential shifts were suggested by reduced catch rates, reduced body size, and changes in selection implied at one gene‐associated single nucleotide polymorphism. A demographic decline in this population, however, was ambiguously supported, based on the apparent lack of temporal change in effective population size, and corresponding traditional knowledge suggesting little change in catch. We illustrate how the pluralistic approach employed has practicality for setting future monitoring efforts of these populations, by guiding monitoring priorities according to the relative merits of different metrics and availability of resources. Our study also considers some advantages and disadvantages to adopting a pluralistic approach to population monitoring where demographic data are not easily obtained.     

Patient-specific finite-element analyses of the proximal femur with orthotropic material properties validated by experiments

Patient-specific high order finite-element (FE) models of human femurs based on quantitative computer tomography (QCT) with inhomogeneous orthotropic and isotropic material properties are addressed. The point-wise orthotropic properties are determined by a micromechanics (MM) based approach in conjunction with experimental observations at the osteon level, and two methods for determining the material trajectories are proposed (along organs outer surface, or along principal strains). QCT scans on four fresh-frozen human femurs were performed and high-order FE models were generated with either inhomogeneous MM-based orthotropic or empirically determined isotropic properties. In vitro experiments were conducted on the femurs by applying a simple stance position load on their head, recording strains on femurs' surface and head's displacements. After verifying the FE linear elastic analyses that mimic the experimental setting for numerical accuracy, we compared the FE results to the experimental observations to identify the influence of material properties on models' predictions. The strains and displacements computed by FE models having MM-based inhomogeneous orthotropic properties match the FE-results having empirically based isotropic properties well, and both are in close agreement with the experimental results. When only the strains in the femoral neck are being compared a more pronounced difference is noticed between the isotropic and orthotropic FE result. These results lay the foundation for applying more realistic inhomogeneous orthotropic material properties in FEA of femurs.