Micromechanical analysis of influence of voids and interface properties on ultimate strength of composite laminates

The influence of fiber-matrix interface fracture properties, fiber waviness, and voids on the response of fiber-reinforced composites are investigated in this paper via three dimensional finite element analysis. We specifically employ augmented finite element method (AFEM) to provide high-fidelity data on damage initiation and propagation along with micromechanical analysis. Stochastic process of model preparation is programmed in Python code and linked to the Abaqus software. Crack initiation and propagation in AFEM are autonomously determined based on the loading conditions, laminate configuration and properties, and distribution of defects and waviness. Within micromechanical analysis, the effects of fiber volume fractions, fiber shapes are also considered to capture the stochastic behavior of the composite under tensile loading. In order to investigate the effects of voids and defects on ultimate strength of composite, we carry out simulations with random voids and defects. These results strongly show the importance of including defects and voids in the finite element analysis. The results reveal that the response of RVE with constant interface properties overestimates the composite transverse strength. It is also seen that the damage initiation and propagation locations are controlled by the distributions of fracture properties, fibers’ shapes, and defects

Geometric approach to nonlinear coherent states using the Higgs model for harmonic oscillator

In this paper, we investigate the relation between the curvature of the physical space and the deformation function of the deformed oscillator algebra using non-linear coherent states approach. For this purpose, we study two-dimensional harmonic oscillators on the flat surface and on a sphere by applying the Higgs modell. With the use of their algebras, we show that the two-dimensional oscillator algebra on a surface can be considered as a deformed one-dimensional oscillator algebra where the effect of the curvature of the surface is appeared as a deformation function. We also show that the curvature of the physical space plays the role of deformation parameter. Then we construct the associated coherent states on the flat surface and on a sphere and compare their quantum statistical properties, including quadrature squeezing and antibunching effect.Comment: 12 pages, 7 figs. To be appeared in J. Phys.

Is the skin microbiota a modifiable risk factor for breast disease?: A systematic review

Purpose: High prevalence, unreliable risk discrimination and poor clinical outcomes are observed in malignant and benign breast diseases (BD). The involvement of microbial communities in the development of BD has become topical, and distal influences of microbial dysregulation in the breast have been well established. Despite advances, the role of the breast skin microbiota in BD remains unclear. Interactions between the skin microbiota and the underlying mucosal immune system are complex. In homeostasis, the skin offers a physical barrier protecting underlying breast tissue from skin commensals and noxious environmental triggers. Our review aims to illuminate the role of the skin microbiota in the development of BD. Methods: Adhering to the PRISMA protocol, a systematic review was conducted utilising the Medline and Embase search engines. Results: Through a comprehensive search of the last ten years, twenty-two studies satisfied the inclusion criteria. Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes were identified as the most prevalent phyla of both breast tissue and skin in healthy controls and BD. High abundance of skin commensals, specifically some species of Staphylococcus, have been linked in breast cancer and metastases. Similarly, dysregulated microbial abundance is also seen in inflammatory and implant-associated BD. These findings raise the hypothesis that the skin microbiota plays a role in tissue homeostasis and may contribute to a range of breast pathologies. Several mechanisms of microbial transfer to underlying tissue have been proposed, including retrograde transfer through ductal systems, breakdown of the skin barrier, and migration through nipple-aspirate fluid. Conclusion: Our review provides preliminary insights into the skin microbiota as a modifiable risk factor for BD. This raises opportunities for future studies in antimicrobials/probiotics as an adjunct to, or replacement of surgery; a diagnostic and/or prognostic tool for BD; and the possibility of conditioning the microbiota to manage BD

Antibacterial Activity of Iranian Green and Black Tea on Streptococcus Mutans: An In Vitro Study

Objective: Dental caries is a common infectious disease.Streptococcus mutans is the prevalent decay microorganism. The anti Streptococcus mutans activity of non fermented and semi-fermented tea has been shown. The aim of this study was to determine the anti Streptococcus mutans activity of Iranian green and black tea (non fermented and fermented type).Materials and Methods: The study was experimental. The aerial parts of wild-growing Camellia sinensis were collected from Lahijan province. The methanolic extract of green and black tea were examined on Streptococcus mutans (ATCC3566). Five different concentrations (50mg/ml, 100mg/ml, 200mg/ml, 300mg/ml and 400 mg/ml) of tea extracts were tested using the well assay method. The agar dilution method recommended by the NCCLS standards (National Committee for Clinical Laboratory Standards) was used. Theminimum inhibitory concentration (MIC) was determined as the lowest concentration of extract inhibiting visible growth of the organism on the agar media plate. Minimum bactericidal concentration (MBC) was detected from MIC.Results: The Iranian green and black tea had an antibacterial effect on 100 to 400 mg/ml concentrations. The minimum inhibitory concentration of green and black tea was 150 and 50 mg/ml, respectively. The mean diameter of inhibition zone were 9.5 mm and 10.9 mm for methanolic extract of green and black tea, respectively.Conclusion: Both Iranian non fermented (green tea) and fermented (black tea) have anti Streptococcus mutans activity in vitro. The anti Streptococcus mutans activity of black tea appears on a lower concentration than green tea

rf linewidth reduction in a quantum dot passively mode-locked laser subject to external optical feedback

International audienceThe effect of external optical feedback on an InAs/GaAs quantum dot passively mode-locked laser is investigated. The rf linewidth narrows from 8 KHz in the free-running situation to a value as low as 350 Hz under relatively low feedback. The rf linewidth characterization under resonant feedback at a multiple of the laser cavity length validates the prediction of a previous numerical simulation. It is also confirmed that the integrated rms timing jitter varies as the square root of the rf linewidth. The results are promising for the development of compact, monolithic semiconductor mode-locked lasers as low noise optoelectronic oscillators

Optical feedback instabilities in a monolithic InAs/GaAs quantum dot passively mode-locked laser

International audienceThe impact of optical feedback on the direct performance of a monolithic InAs/GaAs quantum dot passively mode-locked laser intended for applications such as multigigahertz interchip/intrachip clock distribution is experimentally investigated. Evaluation of the feedback resistance is an important feature, as the laser is to be monolithically integrated on chip with other devices, in which case optical isolation is difficult. This work shows that a feedback level on the order of −24 dB is detrimental for mode-locking operation, enhancing noise in the rf electrical signal, strongly narrowing the useful mode-locking region as well as causing central frequency shift, and severe instabilities

Evaluation of the role of conventional and tissue doppler imaging echocardiography in detection of acute cardiac allograft rejection in heart transplant recipients

Background: Endomyocardial Biopsy (EMB) is the gold standard test for diagnosis of acute allograft cardiac rejection. Objectives: The present study aimed to assess the role of echocardiographic parameters in discriminating patients with and without evidence of acute cardiac allograft rejection. Materials and Methods: In the present cross-sectional study, using convenience sampling, 63 EMB specimens were collected from the patients who had undergone biatrial orthotropic cardiac transplantation. The mean age of the recipients and donors was 30.46 ± 9.49 and 24.55 ± 7.64 years, respectively. There were 51(81) male recipients and 39(62) male donors. Echocardiographic examination was performed within the 24 hours of EMB. The data were entered into the SPSS statistical software, version 19 and were analyzed by chi-square test, student�s t-test, and one-way ANOVA as appropriated. All the data were two-tailed and P < 0.05 was considered to be statistically significant. Results: Among the 63 EMB specimens evaluated in the present study, mild and moderate acute rejections were seen in 19(30) and 5(8) cases, respectively. On Doppler examination, the three groups (without rejection, with mild rejection, and with moderate acute rejection) were significantly different only regarding trans-tricuspid E wave (P = 0.040). Pulsed-wave Tissue Doppler Imaging (TDI) also revealed a significant difference between the patients with and without allograft rejection regarding early diastolic tricuspid and mitral annular motion velocities (P = 0.005 and P = 0.02, respectively). Conclusions: It seems that echocardiographic parameters, including TDI, might be adjunct to, rather than substitution for, EMB findings for early diagnosis of acute allograft rejection. © 2016, Iranian Cardiovascular Research Journal. All right reserved

Measurement of pulmonary arterial elastance in patients with systolic heart failure using Doppler echocardiography

Objective: A reliable and easy-to-perform method for measuring right ventricular (RV) afterload is desirable when scheduling patients with systolic heart failure to undergo heart transplantation. The present study aimed to investigate the accuracy of echocardiographically-derived pulmonary arterial elastance as a measurement of pulmonary vascular resistance by comparing it with invasive measures. Methods: Thirty-one patients with moderate to severe systolic heart failure, including 22 (71) male patients, with a mean age of 41.16±15.9 years were enrolled in the study. Right heart catheterization and comprehensive echocardiography during the first hour after completion of cardiac catheterization were performed in all the patients. The pulmonary artery elastance was estimated using the ratio of end-systolic pressure (Pes) over the stroke volume (SV) by both cardiac catheterization Ea (PV)-C and echocardiography Ea (PV)-E. Results: The mean Ea (PV)-C and Ea (PV)-E were estimated to be 0.73±0.49 mm Hg/mL and 0.67±0.44 mm Hg/mL, respectively. There was a significant relation between Ea (PV)-E and Ea (PV)-C (r=0.897, p<0.001). Agreement between echocardiography and catheterization methods for estimating Ea (PV), investigated by the Bland-Altman method, showed a mean bias of -0.06, with 95% limits of agreement from -0.36 mm Hg/mL to 0.48 mm Hg/mL. Conclusion: Doppler echocardiography is an easy, non-invasive, and inexpensive method for measuring pulmonary arterial elastance, which provides accurate and reliable estimation of RV afterload in patients with systolic heart failure. © 2016 by Turkish Society of Cardiology

Back-action ground state cooling of a micromechanical membrane via intensity-dependent interaction

We propose a theoretical scheme to show the possibility of achieving the quantum ground state cooling of a vibrating micromechanical membrane inside a high finesse optical cavity by back-action cooling approach. The scheme is based on an intensity-dependent coupling of the membrane to the intracavity radiation pressure field. We find the exact expression for the position and momentum variances of the membrane by solving the linearized quantum Langevin equations in the steady-state, conditioned by the Routh-Hurwitz criterion. We show that by varying the Lamb-Dicke parameter and the membrane's reflectivity one can effectively control the mean number of excitations of vibration of the membrane and also cool down the system to micro-Kelvin temperatures