3,238 research outputs found
Effect of Ga Content on Defect States in CuIn\u3csub\u3e1-x\u3c/sub\u3eGa\u3csub\u3ex\u3c/sub\u3eSe\u3csub\u3e2\u3c/sub\u3e Photovoltaic Devices
Defects in the band gap of CuIn1-xGaxSe2 have been characterized using transient photocapacitance spectroscopy. The measured spectra clearly show response from a band of defects centered around 0.8 eV from the valence band edge as well as an exponential distribution of band tail states. Despite Ga contents ranging from Ga/(In+Ga)=0.0 to 0.8, the defect bandwidth and its position relative to the valence band remain constant. This defect band may act as an important recombination center, contributing to the decrease in device efficiency with increasing Ga content
The role of domiciliary nebulizers in managing patients with severe COPD
AbstractThe difficulty of assessing nebulizer responses in chronic obstructive pulmonary disease (COPD) has been demonstrated before. This study aims to re-examine both the role of domiciliary nebulizers in COPD and also bronchodilator (BD) assessment in individuals. In a double-blind, randomized, cross-over trial, 19 stable patients with severe COPD were given the following medication 6-hourly for 2-week periods: (1) nebulized salbutamol 2·5 mg with ipratropium 0·5 mg and placebo inhalers (MDI) with spacer; (2) placebo nebules and inhaled salbutamol 400 μ g with ipratropium 80 μ g via MDI with spacer; (3) inhaled salbutamol 400 μ g with ipratropium 80 μ g via MDI with spacer (but no placebo nebulized drugs).Both nebulized and MDI drugs produced highly significant improvements in forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), specific airways conductance, 6-min walking distance (6MWD) and residual volume. There were no significant differences between BD responses obtained after active nebulized and active MDI BDs. From the diary cards, 2 weeks of active nebulized BDs produced a slightly higher median peak expiratory flow (PEF) than active MDI BDs (236 and 219 l m−1, respectively, P=0·01) and slightly less extra inhaler use (0·8 and 1·1 puffs, respectively, P<0·05) but no significant difference in dyspnoea or quality of life (QOL) scores. There were significant correlations between domiciliary PEF and acute BD-induced changes in FVC and 6MWD, and also between domiciliary dyspnoea scores and acute changes in both total lung capacity and 6MWD.In conclusion, nebulized medication conferred little clinical advantage over the regular use of inhalers with spacers in this group of patients with severe COPD. However, acute changes in total lung capacity, FVC and 6MWD may be useful predictors of the longer-term effects of nebulized BDs in individual patients
Analogue Cosmological Particle Creation: Quantum Correlations in Expanding Bose Einstein Condensates
We investigate the structure of quantum correlations in an expanding Bose
Einstein Condensate (BEC) through the analogue gravity framework. We consider
both a 3+1 isotropically expanding BEC as well as the experimentally relevant
case of an elongated, effectively 1+1 dimensional, expanding condensate. In
this case we include the effects of inhomogeneities in the condensate, a
feature rarely included in the analogue gravity literature. In both cases we
link the BEC expansion to a simple model for an expanding spacetime and then
study the correlation structure numerically and analytically (in suitable
approximations). We also discuss the expected strength of such correlation
patterns and experimentally feasible BEC systems in which these effects might
be detected in the near future.Comment: Reference adde
General anesthesia reduces complexity and temporal asymmetry of the informational structures derived from neural recordings in Drosophila
We apply techniques from the field of computational mechanics to evaluate the
statistical complexity of neural recording data from fruit flies. First, we
connect statistical complexity to the flies' level of conscious arousal, which
is manipulated by general anesthesia (isoflurane). We show that the complexity
of even single channel time series data decreases under anesthesia. The
observed difference in complexity between the two states of conscious arousal
increases as higher orders of temporal correlations are taken into account. We
then go on to show that, in addition to reducing complexity, anesthesia also
modulates the informational structure between the forward- and reverse-time
neural signals. Specifically, using three distinct notions of temporal
asymmetry we show that anesthesia reduces temporal asymmetry on
information-theoretic and information-geometric grounds. In contrast to prior
work, our results show that: (1) Complexity differences can emerge at very
short timescales and across broad regions of the fly brain, thus heralding the
macroscopic state of anesthesia in a previously unforeseen manner, and (2) that
general anesthesia also modulates the temporal asymmetry of neural signals.
Together, our results demonstrate that anesthetized brains become both less
structured and more reversible.Comment: 14 pages, 6 figures. Comments welcome; Added time-reversal analysis,
updated discussion, new figures (Fig. 5 & Fig. 6) and Tables (Tab. 1
Low Tensor Rank Learning of Neural Dynamics
Learning relies on coordinated synaptic changes in recurrently connected
populations of neurons. Therefore, understanding the collective evolution of
synaptic connectivity over learning is a key challenge in neuroscience and
machine learning. In particular, recent work has shown that the weight matrices
of task-trained RNNs are typically low rank, but how this low rank structure
unfolds over learning is unknown. To address this, we investigate the rank of
the 3-tensor formed by the weight matrices throughout learning. By fitting RNNs
of varying rank to large-scale neural recordings during a motor learning task,
we find that the inferred weights are low-tensor-rank and therefore evolve over
a fixed low-dimensional subspace throughout the entire course of learning. We
next validate the observation of low-tensor-rank learning on an RNN trained to
solve the same task by performing a low-tensor-rank decomposition directly on
the ground truth weights, and by showing that the method we applied to the data
faithfully recovers this low rank structure. Finally, we present a set of
mathematical results bounding the matrix and tensor ranks of gradient descent
learning dynamics which show that low-tensor-rank weights emerge naturally in
RNNs trained to solve low-dimensional tasks. Taken together, our findings
provide novel constraints on the evolution of population connectivity over
learning in both biological and artificial neural networks, and enable reverse
engineering of learning-induced changes in recurrent network dynamics from
large-scale neural recordings.Comment: The last two authors contributed equall
A review of the Helophorus frater-praenanus group of species, with description of a new species and additional faunal records of Helophorus Fabricius from China and Bhutan (Coleoptera: Helophoridae)
The six species of the East Palaearctic Helophorus frater-praenanus group (Coleoptera: Helophoridae) are reviewed and a new species, H. aquila sp.n. is described from China (Qinghai). Habitus,
head and pronotum and aedeagophores are figured for all the species and a key for their identification
is given. Four further species which could be confused with the H. frater-praenanus group are
discussed and illustrated. These are H. croaticus KUWERT, 1886, H. pumilio ERICHSON, 1837, H.
pitcheri ANGUS, 1970 and H. shatrovskyi ANGUS, 1985. Additional faunal records of Helophorus
FABRICIUS species from the Tibetan Plateau and other areas of China are given. Helophorus
tuberculatus GYLLENHAL, 1808 is recorded from Bhutan for the first time©Wiener Coleopterologenverein (WCV). The attached paper is the published pdf. https://www.zobodat.at/pdf/KOR_84_2014_0209-0219.pd
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