Finite element modelling of inter-ply delamination and intra-yarn cracking in textile laminates

The aim of the current study is to demonstrate the effect of inter-ply delamination on stiffness degradation of multi-ply woven composites. Such a demonstration becomes possible due to new technique of modelling textile laminates. It is based on set of boundary value problems for unit cell of a single ply, where boundary conditions imitate interaction with the other plies. Once these problems are solved, local stress distribution and stiffness of the laminate are determined analytically as function of number of the plies and local stress/strain fields obtained in these problems. Hence, it opens the road for an efficient modelling of delamination, which is described as gradual reduction of plies in the laminate

Impulsive aggressiveness of pregnant women affects the development of the fetal heart

Mounting evidence indicates that the development of the fetus is heavily influenced by the intra-uterine milieu during pregnancy, and that such influence may have life-long consequences for the individual. The intra- uterine milieu is not only influenced by nutritional factors, but also by maternal endocrine and autonomic activity. Such activity is prone to be affected by an individual's personality, but only little is known about influences of maternal personality on the development of the fetus. We tested pregnant women for their propensity for impulsive, uncontrollable outbursts of temper (referred to here as moderate Intermittent Explosive Disorder, mIED). After the women gave birth, we measured electrocardiograms (ECGs) from their newborn infants to compare ECGs between newborns of women with and without mIED. The data show that infants of women with mIED have larger QRS complexes in the electrocardiogram, and lower heart rate variability, compared to infants of women without mIED. These results reveal effects of maternal mIED on the fetal heart development. These effects may predispose the individual to increased risk for later cardio-vascular disease. The findings open perspectives for better risk prevention models for the unborn child

Voltage-induced defect mode interaction in a one-dimensional photonic crystal with a twisted-nematic defect layer

Defect modes are investigated in a band gap of an electrically tunable one-dimensional photonic crystal infiltrated with a twisted-nematic liquid crystal (1D PC/TN). Their frequency shift and interference under applied voltage are studied both experimentally and theoretically. We deal with the case where the defect layer thickness is much larger than the wavelength (Mauguin condition). It is shown theoretically that the defect modes could have a complex structure with the elliptic polarization. Two series of polarized modes interact with each other and exhibit an avoided crossing phenomenon in the case of opposite parity.Comment: 14 pages, 8 figures, sent to PR

Accuracy of patient recall of hand and elbow disability on the QuickDASH questionnaire over a two-year period

BACKGROUND: Patient self-reporting questionnaires such as the QuickDASH, a shortened version of the Disabilities of the Arm, Shoulder and Hand (DASH) outcome measure, are critical to current orthopaedic outcomes research. The use of these questionnaires could introduce recall bias in retrospective, case-control, and cross-sectional studies if no preoperative data has been collected prior to study inception. The purpose of this study was to quantify recall accuracy on the QuickDASH questionnaire as a function of the duration of the recall interval. METHODS: This cross-sectional study enrolled 140 patients with nontraumatic hand and elbow diseases. Patients were stratified into groups of thirty-five based on the time since their initial office visit (three months, six months, twelve months, or twenty-four months). All patients had completed the QuickDASH as part of a standard intake form at the time of the initial office visit (actual baseline score). Patients were contacted by phone and asked to recall their upper extremity disability from the time of the initial office visit with use of the QuickDASH questionnaire. Patients also completed the QuickDASH to rate their current disability. Actual and recalled QuickDASH scores for each group were statistically compared. Kruskal-Wallis analysis was used to determine any differences in recall accuracy between the groups. Pearson correlation coefficients quantified relations between recall accuracy and patient age and current function (absolute QuickDASH scores). RESULTS: Mean differences between recalled QuickDASH scores and actual scores were all less than the QuickDASH minimal clinically important difference (MCID) of 13 points at different time points: three months (–7.1, p < 0.01), six months (0.8, p = 0.79), twelve months (–2.3, p = 0.43), and twenty-four months (–2.8, p = 0.26). There were no significant differences in recall accuracy across the four groups (p = 0.77). Recalled QuickDASH scores were highly correlated with actual baseline values (r(p) ≥ 0.74). Recall accuracy was neither correlated with patient age nor current QuickDASH scores (r(p) ≤ 0.04). CONCLUSIONS: Patients with a nontraumatic hand or elbow diagnosis are able to recall prior level of function accurately for up to two years with the QuickDASH questionnaire. Although data collected prospectively remain optimal, our data suggest that research conducted with use of recalled QuickDASH scores produces reliable assessment of disability from common upper extremity diagnoses with acceptable recall bias. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence

Surface Quality of a Work Material Influence on Vibrations in a Cutting Process

The problem of stability in the machining processes is an important task. It is strictly connected with the final quality of a product. In this paper we consider vibrations of a tool-workpiece system in a straight turning process induced by random disturbances and their effect on a product surface. Basing on experimentally obtained system parameters we have done the simulations using one degree of freedom model. The noise has been introduced to the model by the Langevin equation. We have also analyzed the product surface shape and its dependence on the level of noise.Comment: 12 pages, PDF of figures can be obtained from http://archimedes.pol.lublin.pl/~raf/graf/fpic.pd

Generation of GeV protons from 1 PW laser interaction with near critical density targets

The propagation of ultra intense laser pulses through matter is connected with the generation of strong moving magnetic fields in the propagation channel as well as the formation of a thin ion filament along the axis of the channel. Upon exiting the plasma the magnetic field displaces the electrons at the back of the target, generating a quasistatic electric field that accelerates and collimates ions from the filament. Two-dimensional Particle-in-Cell simulations show that a 1 PW laser pulse tightly focused on a near-critical density target is able to accelerate protons up to an energy of 1.3 GeV. Scaling laws and optimal conditions for proton acceleration are established considering the energy depletion of the laser pulse.Comment: 26 pages, 8 figure