Improvement of the physical properties of ZnO/CdTe core-shell nanowire arrays by CdCl2 heat treatment for solar cells

CdTe is an important compound semiconductor for solar cells, and its use in nanowire-based heterostructures may become a critical requirement, owing to the potential scarcity of tellurium. The effects of the CdCl₂ heat treatment are investigated on the physical properties of vertically aligned ZnO/CdTe core-shell nanowire arrays grown by combining chemical bath deposition with close space sublimation. It is found that recrystallization phenomena are induced by the CdCl₂ heat treatment in the CdTe shell composed of nanograins: its crystallinity is improved while grain growth and texture randomization occur. The presence of a tellurium crystalline phase that may decorate grain boundaries is also revealed. The CdCl₂ heat treatment further favors the chlorine doping of the CdTe shell with the formation of chlorine A-centers and can result in the passivation of grain boundaries. The absorption properties of ZnO/CdTe core-shell nanowire arrays are highly efficient, and more than 80% of the incident light can be absorbed in the spectral range of the solar irradiance. The resulting photovoltaic properties of solar cells made from ZnO/CdTe core-shell nanowire arrays covered with CuSCN/Au back-side contact are also improved after the CdCl₂ heat treatment. However, recombination and trap phenomena are expected to operate, and the collection of the holes that are mainly photo-generated in the CdTe shell from the CuSCN/Au back-side contact is presumably identified as the main critical point in these solar cells.     

Second-generation iminoxylitol-based pharmacological chaperones for the treatment of Gaucher disease

A series of O-alkyl iminoxylitol derivatives was synthesized and evaluated as β-glucocerebrosidase (GCase) inhibitors. This structure-activity study shows a dramatic influence of the position of the alkyl chain (α-C1, O2, O3, or O4) on human GCase inhibition. Remarkably, 1,2-shift of the alkyl chain from C1 to O2 was found to maintain high inhibitory potency toward GCase as well as chaperone activity at sub-inhibitory concentration (10?nM). Removal of the stereogenic center at the pseudo-anomeric position led to shorter and more practical synthetic sequences. 2-O-Alkyl iminoxylitol derivatives constitute a new promising class of leads for the treatment of Gaucher disease by means of pharmacological chaperone therapy.     

A combined neural network and DEA for measuring efficiency of large scale datasets

Data Envelopment Analysis (DEA) is one of the most widely used methods in the measurement of the efficiency and productivity of Decision Making Units (DMUs). DEA for a large dataset with many inputs/outputs would require huge computer resources in terms of memory and CPU time. This paper proposes a neural network back-propagation Data Envelopment Analysis to address this problem for the very large scale datasets now emerging in practice. Neural network requirements for computer memory and CPU time are far less than that needed by conventional DEA methods and can therefore be a useful tool in measuring the efficiency of large datasets. Finally, the back-propagation DEA algorithm is applied to five large datasets and compared with the results obtained by conventional DEA.     

Alcoholism and social isolation.

To control for biases in prior research, undiagnosed alcoholics (N = 238) were compared with nonalcoholics (N = 176) on social isolation. Both groups were patients given medical diagnoses by physicians instructed to diagnose all alcoholics admitted to the emergency service of a large general hospital. However, the undiagnosed alcoholics were rated alcoholic by separate criteria. Data were also available on all diagnosed alcoholics (N = 200). Standard biographical information, used to estimate current close contacts, stability in maintaining social involvement, and use of community resources, showed alcoholics to be more isolated than controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Understanding children''s perceptions— a classroom experiment

This paper describes an experiment concerned with children's perceptions of everyday objects. The experiment drew upon personal construct theory. As well as investigating how children construe objects the experiment compared the children's perceptions of designed objects with those of their teachers. The experiment also provided a structured means for classroom discussion of the design of various objects. The results showed some marked differences between the constructs used by boys and by girls, perhaps due to the different design education experiences the boys and girls had had previously. The assessments of the objects for ‘good’ design showed the girls' assessments as similar to their teachers', but the boys' as different; the girls were also better at guessing what their teachers' assessments would be. Classroom procedures based on the experiment could help to clarify discussion of design concepts.     

Recent Advances on InAs/InP Quantum Dash Based Semiconductor Lasers and Optical Amplifiers Operating at 1.55 μm

This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm² per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T₀ larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time-jitter characteristics when QD lasers are actively mode-locked. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications     

Impact of Lithographic Grid Irregularity Assessed on Photonic Crystal Device Selectivity

The gridding irregularities of electron beam lithography may deterministically disorder photonic crystals (PhC). Their practical impact is addressed on a PhC wavelength selective device using a large grid size of 8 nm. The device operation, based on confined resonances and propagation mini-stopbands in a multimode waveguide, is deterministically blurred. Scattering length scales are correspondingly discussed. Strategies for higher throughput lithography are proposed accordingly     

Effect of nitrogen fertiliser supply and winter cutting on morphological composition and herbage digestibility of a Dactylis glomerata L sward in spring

The aim of this study was to improve the prediction of sward digestibility in spring as affected by nitrogen supply and winter cutting, taking into account their effects on the leaf:stem ratio and the digestibility of the plant parts. Two nitrogen treatments (120 kg ha⁻¹ and nil) and two cutting regimes were studied over three growing seasons. Herbage digestibility measurements were made about 2 weeks before and after the heading stage. Nitrogen deficiency always decreased the proportion of stem in the herbage yield significantly, mainly because it reduced or delayed the number of tillers which reach the double‐ridge stage. The stem digestibility was higher when no nitrogen was supplied. We show that it decreased with increasing stem length, whatever the sampling date and the growing season. Morever, for a given stem length we noticed a positive effect of herbage nitrogen status, probably because the stem weight per unit length was lower when N was supplied. Green lamina digestibility decreased more slowly than that of stem, but at a different rate according to the growing season. At the whole herbage level, nitrogen supply always decreased the herbage digestibility, and sometimes cutting in winter increased it. These trends resulted mainly from the effect of nitrogen supply on the proportion of stem in the herbage and its digestibility. © 2000 Society of Chemical Industry     

Conversion of 18∶3 Δ9cis, 12cis, 15trans in rat liver microsomes

Several years ago, it was established that the Δ15 trans isomer of α-linolenic acid is converted in vivo into fatty acids containing 20 and 22 carbons (geometrical isomers of eicosapentaenoic and docosahexaenoic acids). The present study focused on the in vitro Δ6 desaturation, the first step of the biosynthesis of the n-3 long-chain polyunsaturated fatty acids from 18:3n-3. For that purpose, rat liver microsomes were prepared and incubated with radiolabeled 18∶3 Δ9cis, 12cis, 15cis (18∶3 c,c,c) or 18∶3 Δ9cis, 12cis, 15trans (18∶3c,c,t) under desaturation conditions. The data show that 18∶3c,c,t is converted at a lower rate compared with α-linolenic acid. The product of conversion of 18∶3 c,c,t may be 18∶4 Δ6cis, 9cis, 12cis, 15trans resulting from a Δ6 desaturation of the trans substrate. Moreover, the conversion of radiolabeled 18∶3c,c,t was strongly decreased by the presence of 18∶3c,c,c (up to 48%) while the 18∶3c,c,t only slightly decreased the conversion of radiolabeled 18∶3c,c,c. Thus, the desaturation enzyme presented a higher affinity for the native all-cis n-3 substrate.     

“Green labelled” pectins with gelling and emulsifying properties can be extracted by enzymatic way from unexploited sources

Functional properties of “green labelled” pectins extracted with enzymes from chicory root, citrus peel and cauliflower by-products were assessed. Chicory and citrus pectins were selected to study their gelling properties, while cauliflower pectin was chosen to investigate its emulsifying ability. High methoxy chicory and citrus pectins were shown to gel in the presence of sucrose at acidic pH, whereas their corresponding low methoxy pectins were able to gel in the presence of calcium. Additionally, HM cauliflower pectin exhibited emulsifying ability. Atomic Force Microscopy was used to better understand the gelling mechanism of pectins and particularly the first steps of gel setting. The present work demonstrates that “green labelled” enzyme-extracted pectins can be successfully used as gelling or emulsifying agents. The present study allows enhancing the value of “green” extraction of pectins, since such extraction leads to products with good functional properties that can directly be used for food and non-food purposes.