Effect of the Twisting Motion on the Nonunifornities of Transmyocardial Fiber Mechanics and Energy Demand A Theoretical Study

The contraction of the left ventricle (LV) is manifested by a distribution of strains and strain rates throughout the muscle thickness. Using a nested shell spheroidal model of the LV, which accounts for a fiber angle distribution from + 60°at the endocardium to ?60° at the epicardium, and the radial electrical activation pattern from the endocardium to the epicardium, it can be shown that endocardial layers undergo higher strains than the epicardial layers throughout the cardiac cycle, and higher length changes characterize the endocardial sarcomeres relative to the epicardial sarcomeres. However, the calculated nonuniformities in the sarcomeres' shortening are significantly moderated when the physiological twisting motion of the LV around the longitudinal axis is accounted for. Thus, the twisting motion of the heart is a basic mechanism by which the sarcomere function is maintained within its physiological range.     

A Surprise Party (on Your Computer)?

Iv?n Arce of Core Security Technologies looks at the current state of malware and introduces the articles he selected for this special issue.     

Symbolic parametrization of curves

If algebraic varieties like curves or surfaces are to be manipulated by computers, it is essential to be able to represent these geometric objects in an appropriate way. For some applications an implicit representation by algebraic equations is desirable, whereas for others an explicit or parametric representation is more suitable. Therefore, transformation algorithms from one representation to the other are of utmost importance.We investigate the transformation of an implicit representation of a plane algebraic curve into a parametric representation. Various methods for computing a rational parametrization, if one exists, are described. As a new idea we introduce the concept of working with classes of conjugate (singular or simple) points on curves. All the necessary operations, like determining the multiplicity and the character of the singular points or passing a linear system of curves through these points, can be applied to such classes of conjugate points. Using this idea one can parametrize a curve if one knows only one simple point on it. We do not propose any new method for finding such a simple point. By classical methods a rational point on a rational curve can be computed, if such a point exists. Otherwise, one can express the coordinates of such a point in an algebraic extension of degree 2 over the ground field.     

Surface chemistry of tribochemical reactions explored in ultrahigh vacuum conditions

The thermal decomposition of model extreme-pressure lubricant additives on clean iron was studied in ultrahigh vacuum conditions using molecular beam strategies. Methylene chloride and chloroform react to deposit a solid film consisting of FeCl₂ and carbon, and evolve only hydrogen into the gas phase. No gas-phase products and less carbon on the surface are detected in the case of carbon tetrachloride. Dimethyl and diethyl disulfide react on clean iron to deposit a saturated sulfur plus carbon layer at low temperatures (∼600 K) and an iron sulfide film onto a Fe + C underlayer at higher temperatures (∼950 K). Methane is the only gas-phase product when dimethyl disulfide reacts with iron. Ethylene and hydrogen are detected when diethyl disulfide is used.     

Material constant sensitivity boundary integral equation for anisotropic solids

In this paper, the material constant sensitivity boundary integral equation is presented, and its numerical solution proposed, based on boundary element techniques. The formulation deals with plane problems with general rectilinear anisotropy. Expressions for the computation of sensitivities for displacements, tractions, strains and stresses are derived, both for boundary and interior points. The sensitivities can be computed with respect to the bulk material properties or to the properties of part of the domain (inclusions, coatings, etc.). To assess the accuracy of the proposed approach, the computed results are compared to analytical ones derived from exact solutions obtained by complex potential theory, when possible, or finite difference derivatives otherwise. Copyright © 2005 John Wiley & Sons, Ltd.     

An analysis of the Slapper worm

We can prove that the Slapper is a variation of the Apache Scalper worm by comparing the source code. Modifications introduced in the Slapper worm improved the robustness and efficiency of its predecessor's simplistic P2P networking capabilities. Slapper's author also removed certain features from the original-either because they were redundant or to reduce the perception that it was a tool developed to cause direct harm to networks. Among the features the author removed from the Slapper were capabilities to update itself from a remotely specified Web server (perhaps to prevent someone else from replacing this version with a new one), to attack and infect a host specified with a controlling program, and to send spans. Interestingly, the ability to execute distributed denial-of-service attacks on a controlling user's behalf was kept intact. Slapper's author attempted to make communications with a remote controlling program as stealthy and untraceable as possible by removing several commands to query status and obtain feedback from Slapper nodes.     

Monitoring of lineage-specific chimaerism allows early prediction of response following donor lymphocyte infusions for relapsed chronic myeloid leukaemia

Thrombogenesis in the left atrial appendage (LAA) has been related to the special morphology of this cavity and to its size and degree of dysfunction. However, no study has focused on LAA function in conjunction with left atrial (LA) function in both sinus rhythm (SR) and nonrheumatic idiopathic atrial fibrillation (AF) in relation to clinical status (cardioembolic stroke). Forty-three patients in SR (14 patients with stroke, 29 control subjects) and 45 patients in AF (27 patients with stroke, 18 control subjects) were examined by transthoracic and transesophageal echocardiography. Baseline clinical characteristics and standard transthoracic and transesophageal measurements of the LA and LAA (size, fractional area change, flow measurements, spontaneous echo contrast, and thrombus) were recorded and compared in relation to cardiac rhythm. Patients in the stroke-SR group showed a significant decrease of fractional area change in the LA (32%+/-15%) and LAA (34%+/-15%) in relation to control subjects (43%+/-10%, p = 0.035, 49%+/-13%, p = 0.006, respectively). Patients in the stroke-AF group showed significant reduction of appendage flow measurements (outward velocity = 22+/-13 vs 33+/-19 cm/sec, p = 0.036), whereas no differences were detected in the center of the LA. In multiple regression analysis, the presence of cardioembolic stroke was positively associated with the presence of spontaneous echo contrast (p = 0.0253) and spontaneous echo contrast negatively associated with appendage inward flow velocity (p<0.001). Cardioembolic stroke in patients in SR is associated with a global decrease of shortening in both cavities and in patients with AF, with a reduction of LAA flow parameters. Patients with spontaneous echo contrast, thrombus, or both showed further reduction of shortening and flow velocities in both cavities, indicating a more advanced stage of dysfunction.