Polarization Beam Splitter Based on Self-Collimation of a Hybrid Photonic Crystal

A photonic crystal polarization beam splitter based on photonic band gap and self-collimation effects is designed for optical communication wavelengths. The photonic crystal structure consists of a polarization-insensitive self-collimation region and a splitting region. TM- and TE-polarized waves propagate without diffraction in the self-collimation region, whereas they split by 90 degrees in the splitting region. Efficiency of more than 75% for TM- and TE-polarized light is obtained for a polarization beam splitter size of only 17 μm x 17 μm in a wavelength interval of 60 nm including 1.55 μm

Optoelectronic cooling of mechanical modes in a semiconductor nanomembrane

Optical cavity cooling of mechanical resonators has recently become a research frontier. The cooling has been realized with a metal-coated silicon microlever via photo-thermal force and subsequently with dielectric objects via radiation pressure. Here we report cavity cooling with a crystalline semiconductor membrane via a new mechanism, in which the cooling force arises from the interaction between the photo-induced electron-hole pairs and the mechanical modes through the deformation potential coupling. The optoelectronic mechanism is so efficient as to cool a mode down to 4 K from room temperature with just 50 uW of light and a cavity with a finesse of 10 consisting of a standard mirror and the sub-wavelength-thick semiconductor membrane itself. The laser-cooled narrow-band phonon bath realized with semiconductor mechanical resonators may open up a new avenue for photonics and spintronics devices.Comment: 5 pages, 4 figure

Reply to the Comment by B. Andresen

All the comments made by Andresen's comments are replied and are shown not to be pertinent. The original discussions [ABE S., Europhys. Lett. 90 (2010) 50004] about the absence of nonextensive statistical mechanics with q-entropies for classical continuous systems are reinforced.Comment: 5 pages. This is Reply to B. Andresen's Comment on the paper entitled "Essential discreteness in generalized thermostatistics with non-logarithmic entropy", Europhys. Lett. 90 (2010) 5000

Antimicrobial susceptibility of bacteria isolated from newborns with suspected or confirmed necrotising enterocolitis

Aim. This audit aimed to identify which bacteria were associated with necrotising enterocolitis (NEC) and determine their antibiotic sensitivities. Methods. A retrospective audit of all infants with a diagnosis of suspected NEC or confirmed NEC and a positive culture (blood/faeces/operative specimen or vascular access device) between January 2000 and September 2007 was performed. Results. Ninety nine infants had a diagnosis of suspected (45) or confirmed NEC (54). Seventeen patients had suspected (5) or confirmed (12) NEC and a positive culture result. 12 babies had positive blood cultures associated with their NEC. Only 4 of the 12 cases of NEC with a positive blood culture received adequate first line cover for their subsequently identified infecting organism. Conclusions. Due to the limitations of this study we are unable to make general recommendations on the first line antibiotic choice for babies with suspected or confirmed NEC. Our current regime of Ampicillin, Gentamicin and Metronidazole failed to adequately treat 8 of the 12 organisms subsequently isolated in blood cultures. Only the combination of Vancomycin and Meropenem would have adequately treated all the bacteria identified. The concern with this approach is the possible emergence of multi drug resistant bacteria

Feasibility study of a plastic helical coil heat exchanger for a domestic water storage tank

The main goal of this study is to investigate whether it is possible to use a polymeric helical coil heat exchanger as an alternative to conventional metallic helical coil. More specifically this work focuses on a helical coil design for a domestic water storage tank application. Corrosion and fouling resistance, scarcity of the materials, low weight and cost are the driving forces to consider designing polymeric heat exchangers rather than metallic heat exchangers. However, simply replacing the metallic material by the polymer material and applying the traditional design methods used for metallic heat exchangers do not lead to an acceptable design. If one wants to design a good polymer heat exchanger, heat transfer and structural problems have to be solved first. In addition, the pressure drop limitation should not be neglected. In order to reach this goal, a model is developed to predict the optimal design of a helical coil heat exchanger immersed in the water storage tank for a certain water mass flow rate and temperature. This design compensates for the low thermal conductivity and strength of the polymer.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016

The week after:Do the effects of imagined contact last over time?

The vast majority of studies assessing the prejudice reduction properties of imagined contact have focused so far on the immediate effects of the intervention. In an attempt to contribute to the literature examining the long-term effects of imagined contact, the two studies reported in this paper tested the immediate and long-term effects of imagined contact on outgroup attitudes, intergroup anxiety, and behavioral intentions in Experiment 1, and also on contact self-efficacy in Experiment 2. Both studies were conducted in a context of entrenched intergroup conflict, Cyprus. The results supported the effectiveness of imagined contact in eliciting more positive attitudes, lower levels of anxiety, more positive behavioral intentions, and higher contact self-efficacy when these were measured immediately after contact. However, evidence for the endurance of these effects was systematically found only for outgroup attitudes and intergroup anxiety. While these results speak to the ability of imagined contact to lead to long-term changes in important and commonly studied intergroup outcomes, lack of consistent evidence regarding its ability to yield lasting changes on variables pertaining to intended behavior toward the outgroup compose a challenge for the intervention

Combined In Silico, In Vivo, and In Vitro Studies Shed Insights into the Acute Inflammatory Response in Middle-Aged Mice

We combined in silico, in vivo, and in vitro studies to gain insights into age-dependent changes in acute inflammation in response to bacterial endotoxin (LPS). Time-course cytokine, chemokine, and NO2-/NO3- data from "middle-aged" (6-8 months old) C57BL/6 mice were used to re-parameterize a mechanistic mathematical model of acute inflammation originally calibrated for "young" (2-3 months old) mice. These studies suggested that macrophages from middle-aged mice are more susceptible to cell death, as well as producing higher levels of pro-inflammatory cytokines, vs. macrophages from young mice. In support of the in silico-derived hypotheses, resident peritoneal cells from endotoxemic middle-aged mice exhibited reduced viability and produced elevated levels of TNF-α, IL-6, IL-10, and KC/CXCL1 as compared to cells from young mice. Our studies demonstrate the utility of a combined in silico, in vivo, and in vitro approach to the study of acute inflammation in shock states, and suggest hypotheses with regard to the changes in the cytokine milieu that accompany aging. © 2013 Namas et al

The International Workshop on Osteoarthritis Imaging Knee MRI Segmentation Challenge: A Multi-Institute Evaluation and Analysis Framework on a Standardized Dataset

Purpose: To organize a knee MRI segmentation challenge for characterizing the semantic and clinical efficacy of automatic segmentation methods relevant for monitoring osteoarthritis progression. Methods: A dataset partition consisting of 3D knee MRI from 88 subjects at two timepoints with ground-truth articular (femoral, tibial, patellar) cartilage and meniscus segmentations was standardized. Challenge submissions and a majority-vote ensemble were evaluated using Dice score, average symmetric surface distance, volumetric overlap error, and coefficient of variation on a hold-out test set. Similarities in network segmentations were evaluated using pairwise Dice correlations. Articular cartilage thickness was computed per-scan and longitudinally. Correlation between thickness error and segmentation metrics was measured using Pearson's coefficient. Two empirical upper bounds for ensemble performance were computed using combinations of model outputs that consolidated true positives and true negatives. Results: Six teams (T1-T6) submitted entries for the challenge. No significant differences were observed across all segmentation metrics for all tissues (p=1.0) among the four top-performing networks (T2, T3, T4, T6). Dice correlations between network pairs were high (>0.85). Per-scan thickness errors were negligible among T1-T4 (p=0.99) and longitudinal changes showed minimal bias (<0.03mm). Low correlations (<0.41) were observed between segmentation metrics and thickness error. The majority-vote ensemble was comparable to top performing networks (p=1.0). Empirical upper bound performances were similar for both combinations (p=1.0). Conclusion: Diverse networks learned to segment the knee similarly where high segmentation accuracy did not correlate to cartilage thickness accuracy. Voting ensembles did not outperform individual networks but may help regularize individual models.Comment: Submitted to Radiology: Artificial Intelligence; Fixed typo

Bistability in Apoptosis by Receptor Clustering

Apoptosis is a highly regulated cell death mechanism involved in many physiological processes. A key component of extrinsically activated apoptosis is the death receptor Fas, which, on binding to its cognate ligand FasL, oligomerize to form the death-inducing signaling complex. Motivated by recent experimental data, we propose a mathematical model of death ligand-receptor dynamics where FasL acts as a clustering agent for Fas, which form locally stable signaling platforms through proximity-induced receptor interactions. Significantly, the model exhibits hysteresis, providing an upstream mechanism for bistability and robustness. At low receptor concentrations, the bistability is contingent on the trimerism of FasL. Moreover, irreversible bistability, representing a committed cell death decision, emerges at high concentrations, which may be achieved through receptor pre-association or localization onto membrane lipid rafts. Thus, our model provides a novel theory for these observed biological phenomena within the unified context of bistability. Importantly, as Fas interactions initiate the extrinsic apoptotic pathway, our model also suggests a mechanism by which cells may function as bistable life/death switches independently of any such dynamics in their downstream components. Our results highlight the role of death receptors in deciding cell fate and add to the signal processing capabilities attributed to receptor clustering.Comment: Accepted by PLoS Comput Bio