Interplay between localization and absorption in disordered waveguides

This work presents results of ab-initio simulations of continuous wave transport in disordered absorbing waveguides. Wave interference effects cause deviations from diffusive picture of wave transport and make the diffusion coefficient position- and absorption-dependent. As a consequence, the true limit of a zero diffusion coefficient is never reached in an absorbing random medium of infinite size, instead, the diffusion coefficient saturates at some finite constant value. Transition to this absorption-limited diffusion exhibits a universality which can be captured within the framework of the self-consistent theory (SCT) of localization. The results of this work (i) justify use of SCT in analyses of experiments in localized regime, provided that absorption is not weak; (ii) open the possibility of diffusive description of wave transport in the saturation regime even when localization effects are strong.Comment: 10 pages, 3 figure

Position-dependent diffusion of light in disordered waveguides

Diffusion has been widely used to describe a random walk of particles or waves, and it requires only one parameter -- the diffusion constant. For waves, however, diffusion is an approximation that disregards the possibility of interference. Anderson localization, which manifests itself through a vanishing diffusion coefficient in an infinite system, originates from constructive interference of waves traveling in loop trajectories -- pairs of time-reversed paths returning to the same point. In an open system of finite size, the return probability through such paths is reduced, particularly near the boundary where waves may escape. Based on this argument, the self-consistent theory of localization and the supersymmetric field theory predict that the diffusion coefficient varies spatially inside the system. A direct experimental observation of this effect is a challenge because it requires monitoring wave transport inside the system. Here, we fabricate two-dimensional photonic random media and probe position-dependent diffusion inside the sample from the third dimension. By varying the geometry of the system or the dissipation which also limits the size of loop trajectories, we are able to control the renormalization of the diffusion coefficient. This work shows the possibility of manipulating diffusion via the interplay of localization and dissipation.Comment: 24 pages, 6 figure

Relation between Transmission and Energy Stored in Random Media with Gain

In this work, we investigate a possibility of using the ratio between optical transmission, T, and energy stored inside the system, E, as a quantitative measure of the enhanced mesoscopic corrections to diffusive transport of light through a random medium with gain. We obtain an expression for T/E as a function of amplification strength in the diffusive approximation and show that it does not a have tendency to diverge when the threshold for random lasing is approached, as both T and E do. Furthermore, we find that a change in T/E signifies a change in the electric field distribution inside the random medium. In the localization regime, we also investigate the correlations between transmission and energy stored in the medium with and without amplification. Our results suggest that T/E is a promising parameter which can help characterize the nature of wave transport in random medium with gain

Influx of Calcium through L-type Calcium Channels in Early Postnatal Regulation of Chloride Transporters in the Rat Hippocampus

During the early postnatal period, GABAB receptor activation facilitates L-type calcium current in rat hippocampus. One developmental process that L-type current may regulate is the change in expression of the K+Cl− co-transporter (KCC2) and N+K+2Cl− co-transporter (NKCC1), which are involved in the maturation of the GABAergic system. The present study investigated the connection between L-type current, GABAB receptors, and expression of chloride transporters during development. The facilitation of L-type current by GABAB receptors is more prominent in the second week of development, with the highest percentage of cells exhibiting facilitation in cultures isolated from 7 day old rats (37.5%). The protein levels of KCC2 and NKCC1 were investigated to determine the developmental timecourse of expression as well as expression following treatment with an L-type channel antagonist and a GABAB receptor agonist. The time course of both chloride transporters in culture mimics that seen in hippocampal tissue isolated from various ages. KCC2 levels increased drastically in the first two postnatal weeks while NKCC1 remained relatively stable, suggesting that the ratio of the chloride transporters is important in mediating the developmental change in chloride reversal potential. Treatment of cultures with the L-type antagonist nimodipine did not affect protein levels of NKCC1, but significantly decreased the upregulation of KCC2 during the first postnatal week. In addition, calcium current facilitation occurs slightly before the large increase in KCC2 expression. These results suggest that the expression of KCC2 is regulated by calcium influx through L-type channels in the early postnatal period in hippocampal neurons

Editorial Board

Objective: The internally validated fulIPIERS model predicts adverse maternal outcomes in women with pre-eclampsia within 48 h after eligibility. Our objective was to assess generalizability of this prediction model. Study design: External validation study using prospectively collected data from two tertiary care obstetric centers. Methods: The existing PETRA dataset, a cohort of women (n = 216) with severe early-onset pre-eclampsia, eclampsia, HELLP syndrome or hypertension-associated fetal growth restriction was used. The fulIPIERS model equation was applied to all women in the dataset using values collected within 48 h after inclusion. The performance (ROC area and R-squared) of the model, risk stratification and calibration were assessed from 48 h up to a week after inclusion. Results: Of 216 women in the PETRA trial, 73 (34%) experienced an adverse maternal outcome(s) at any time after inclusion. Adverse maternal outcome was observed in 32 (15%) cases within 48 h and 62 (29%) within 7 days after inclusion. The fulIPIERS model predicted adverse maternal outcomes within 48 h (AUC ROC 0.97, 95% CI: 0.87-0.99) and up to 7 days after inclusion (AUC ROC 0.80, 95% CI: 0.70-0.87). Conclusions: The fullPIERS model performed well when applied to the PETRA dataset. These results confirm the usability of the fulIPIERS prediction model as a 'rule-in' test for women admitted with severe pre-eclampsia, eclampsia, HELLP syndrome or hypertension-associated fetal growth restriction. Future research should focus on intervention studies that assess the clinical impact of strategies using the fullPIERS model. (C) 2014 Elsevier Ireland Ltd. All rights reserved

Age-related references in national public health, technology appraisal and clinical guidelines and guidance: documentary analysis

$\textbf{BACKGROUND}$: older people may be less likely to receive interventions than younger people. Age bias in national guidance may influence entire public health and health care systems. We examined how English National Institute for Health & Care Excellence (NICE) guidance and guidelines consider age. $\textbf{METHODS}$: we undertook a documentary analysis of NICE public health ($\textit{n}$ = 33) and clinical ($\textit{n}$ = 114) guidelines and technology appraisals ($\textit{n}$ = 212). We systematically searched for age-related terms, and conducted thematic analysis of the paragraphs in which these occurred ('age-extracts'). Quantitative analysis explored frequency of age-extracts between and within document types. Illustrative quotes were used to elaborate and explain quantitative findings. $\textbf{RESULTS}$: 2,314 age-extracts were identified within three themes: age documented as an $\textit{a-priori}$ consideration at scope-setting (518 age-extracts, 22.4%); documentation of differential effectiveness, cost-effectiveness or other outcomes by age (937 age-extracts, 40.5%); and documentation of age-specific recommendations (859 age-extracts, 37.1%). Public health guidelines considered age most comprehensively. There were clear examples of older-age being considered in both evidence searching and in making recommendations, suggesting that this can be achieved within current processes. $\textbf{CONCLUSIONS}$: we found inconsistencies in how age is considered in NICE guidance and guidelines. More effort may be required to ensure age is consistently considered. Future NICE committees should search for and document evidence of age-related differences in receipt of interventions. Where evidence relating to effectiveness and cost-effectiveness in older populations is available, more explicit age-related recommendations should be made. Where there is a lack of evidence, it should be stated what new research is needed.This work was supported by the National Institute for Health Research's School for Public Health Research (NIHR SPHR http://sphr.nihr.ac.uk/). J.A. & M.W. are members of the Centre for Diet and Activity Research (CEDAR) a UKCRC Public Health Research Centre of Excellence

Diagonal splittings of toric varieties and unimodularity

We use a polyhedral criterion for the existence of diagonal splittings to investigate which toric varieties X are diagonally split. Our results are stated in terms of the vector configuration given by primitive generators of the 1-dimensional cones in the fan defining X. We show, in particular, that X is diagonally split at all q if and only if this configuration is unimodular, and X is not diagonally split at any q if this configuration is not 2-regular. We also study implications for the possibilities for the set of q at which a toric variety X is diagonally split.Comment: 11 pages v2: minor revisions, to appear in Proc. Amer. Math. So

Age and provenance of the Cryogenian to Cambrian passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil

The Paraguay Belt in central South America\ud developed in response to the collision of\ud the Amazonian craton, the São Francisco\ud craton, and the Paranapanema block. The\ud alleged “Brasiliano” age (ca. 620 Ma) of\ud orogenesis has recently been questioned by\ud paleo magnetic and radioisotopic ages that\ud indicate the closing stages of orogenesis occurred\ud well into the Cambrian. We investigated\ud the timing of deposition and source\ud areas for these sedimentary rocks overlying\ud the Amazonian craton using integrated\ud U-Pb and Hf isotope data of detrital zircons\ud from within this sequence. In total, 742 detrital\ud zircon U-Pb ages were analyzed from\ud samples taken from the base to the top of this\ud sedimentary succession. Maximum depositional\ud ages from the uppermost part of this\ud sequence of rocks, the Diamantino Formation,\ud indicate that fi nal deposition began no\ud earlier than 560 ± 13 Ma and possibly as\ud young as the Cambrian. Given that zircon\ud inheritance in these rocks continues up until\ud this age and that known Amazonian craton\ud ages are older than ca. 950 Ma, we considered\ud other potential sources for these sediments.\ud This was achieved by integrating the\ud U-Pb detrital zircon data with Hf isotopic\ud data from these zircons that have εHf values\ud ranging from –18 to 12. The εHf signature is\ud consistent, with a predominantly Amazonian\ud source until the early Neoproterozoic, at\ud which point the signal becomes signifi cantly\ud more evolved. These data, when combined\ud with other evidence discussed here, are\ud consistent with an ocean to the east of the\ud present-day Amazonian craton that did not\ud close until the latest Ediacaran–Cambrian