Radiation resistance of Ge, Ge0.93Si0.07, GaAs and Al0.08Ga0.92 as solar cells

Solar cells made of Ge, Ge(0.93)Si(0.07) alloys, GaAs and Al(0.08)Ga(0.92)As were irradiated in two experiments with 1-meV electrons at fluences as great as 1 x 10(exp 16) cm(exp-2). Several general trends have emerged. Low-band-gap Ge and Ge(0.93)Si(0.07) cells show substantial resistance to radiation-induced damage. The two experiments showed that degradation is less for Al(0.08)Ga(0.92)As cells than for similarly irradiated GaAs cells. Compared to homojunctions, cells with graded-band-gap emitters did not show the additional resistance to damage in the second experiment that had been seen in the first. The thickness of the emitter is a key parameter to limit the degradation in GaAs devices

Graded-bandgap AlGaAs solar cells for AlGaAs/Ge cascade cells

Some p/n graded-bandgap Al(x)Ga(1-x)As solar cells were fabricated and show AMO conversion efficiencies in excess of 15 percent without antireflection (AR) coatings. The emitters of these cells are graded between 0.008 is less than or equal to x is less than or equal to 0.02 during growth of 0.25 to 0.30 micron thick layers. The keys to achieving this performance were careful selection of organometallic sources and scrubbing oxygen and water vapor from the AsH3 source. Source selection and growth were optimized using time-resolved photoluminescence. Preliminary radiation-resistance measurements show AlGaAs cells degraded less than GaAs cells at high 1 MeV electron fluences, and AlGaAs cells grown on GaAs and Ge substrates degrade comparably

Experimental investigation of optical atom traps with a frequency jump

We study the evolution of a trapped atomic cloud subject to a trapping frequency jump for two cases: stationary and moving center of mass. In the first case, the frequency jump initiates oscillations in the cloud's momentum and size. At certain times we find the temperature is significantly reduced. When the oscillation amplitude becomes large enough, local density increases induced by the anharmonicity of the trapping potential are observed. In the second case, the oscillations are coupled to the center of mass motion through the anharmonicity of the potential. This induces oscillations with even larger amplitudes, enhancing the temperature reduction effects and leading to nonisotropic expansion rates while expanding freely.Comment: 8 figures, Journal of Physics B: At. Mol. Op. Phy

Electron irradiation effects on superconductivity in PdTe2_2: an application of a generalized Anderson theorem

Low temperature ($\sim$ 20~K) electron irradiation with 2.5 MeV relativistic electrons was used to study the effect of controlled non-magnetic disorder on the normal and superconducting properties of the type-II Dirac semimetal PdTe$_2$. We report measurements of longitudinal and Hall resistivity, thermal conductivity and London penetration depth using tunnel-diode resonator technique for various irradiation doses. The normal state electrical resistivity follows Matthiessen rule with an increase of the residual resistivity at a rate of $\sim$0.77$\mu \Omega$cm/$(\textrm{C}/\textrm{cm}^2)$. London penetration depth and thermal conductivity results show that the superconducting state remains fully gapped. The superconducting transition temperature is suppressed at a non-zero rate that is about sixteen times slower than described by the Abrikosov-Gor'kov dependence, applicable to magnetic impurity scattering in isotropic, single-band $s$-wave superconductors. To gain information about the gap structure and symmetry of the pairing state, we perform a detailed analysis of these experimental results based on insight from a generalized Anderson theorem for multi-band superconductors. This imposes quantitative constraints on the gap anisotropies for each of the possible pairing candidate states. We conclude that the most likely pairing candidate is an unconventional $A_{1g}^{+-}$ state. While we cannot exclude the conventional $A_{1g}^{++}$ and the triplet $A_{1u}$, we demonstrate that these states require additional assumptions about the orbital structure of the disorder potential to be consistent with our experimental results, e.g., a ratio of inter- to intra-band scattering for the singlet state significantly larger than one. Due to the generality of our theoretical framework, we think that it will also be useful for irradiation studies in other spin-orbit-coupled multi-orbital systems.Comment: 22 pages, 12 figure

Patterns of psychotropic prescribing and polypharmacy in older hospitalized patients in Ireland: the influence of dementia on prescribing

Neuropsychiatric Symptoms (NPS) are ubiquitous in dementia and are often treated pharmacologically. The objectives of this study were to describe the use of psychotropic, anti-cholinergic, and deliriogenic medications and to identify the prevalence of polypharmacy and psychotropic polypharmacy, among older hospitalized patients in Ireland, with and without dementia. All older patients (≥ 70 years old) that had elective or emergency admissions to six Irish study hospitals were eligible for inclusion in a longitudinal observational study. Of 676 eligible patients, 598 patients were recruited and diagnosed as having dementia, or not, by medical experts. These 598 patients were assessed for delirium, medication use, co-morbidity, functional ability, and nutritional status. We conducted a retrospective cross-sectional analysis of medication data on admission for 583/598 patients with complete medication data, and controlled for age, sex, and co-morbidity. Of 149 patients diagnosed with dementia, only 53 had a previous diagnosis. At hospital admission, 458/583 patients experienced polypharmacy (≥ 5 medications). People with dementia (PwD) were significantly more likely to be prescribed at least one psychotropic medication than patients without dementia (99/147 vs. 182/436; p < 0.001). PwD were also more likely to experience psychotropic polypharmacy (≥ two psychotropics) than those without dementia (54/147 vs. 61/436; p < 0.001). There were no significant differences in the prescribing patterns of anti-cholinergics (23/147 vs. 42/436; p = 0.18) or deliriogenics (79/147 vs. 235/436; p = 0.62). Polypharmacy and psychotropic drug use is highly prevalent in older Irish hospitalized patients, especially in PwD. Hospital admission presents an ideal time for medication reviews in PwD

A study protocol of a randomised controlled trial to measure the effects of an augmented prescribed exercise programme (APEP) for frail older medical patients in the acute setting

Background: Older adults experience functional decline in hospital leading to increased healthcare burden and morbidity. The benefits of augmented exercise in hospital remain uncertain. The aim of this trial is to measure the short and longer-term effects of augmented exercise for older medical in-patients on their physical performance, quality of life and health care utilisation. Design and Methods: Two hundred and twenty older medical patients will be blindly randomly allocated to the intervention or sham groups. Both groups will receive usual care (including routine physiotherapy care) augmented by two daily exercise sessions. The sham group will receive stretching and relaxation exercises while the intervention group will receive tailored strengthening and balance exercises. Differences between groups will be measured at baseline, discharge, and three months. The primary outcome measure will be length of stay. The secondary outcome measures will be healthcare utilisation, activity (accelerometry), physical performance (Short Physical Performance Battery), falls history in hospital and quality of life (EQ-5D-5 L). Discussion: This simple intervention has the potential to transform the outcomes of the older patient in the acute setting

Prolyl 4-hydroxlase activity is essential for development and cuticle formation in the human infective parasitic nematode Brugia malayi

Collagen prolyl 4-hydroxylases (C-P4H) are required for formation of extracellular matrices in higher eukaryotes. These enzymes convert proline residues within the repeat regions of collagen polypeptides to 4-hydroxyproline, a modification essential for the stability of the triple helix. C-P4Hs are most often oligomeric complexes, with enzymatic activity contributed by the α subunits, and the β subunits formed by protein disulfide isomerase (PDI). Here we characterise this enzyme class in the important human parasitic nematode Brugia malayi. All potential C-P4H subunits were identified by detailed bioinformatic analysis of sequence databases, function was investigated both by RNAi in the parasite and heterologous expression in Caenorhabditis elegans, while biochemical activity and complex formation were examined via co-expression in insect cells. Simultaneous RNAi of two B. malayi C-P4H α subunit-like genes resulted in a striking, highly penetrant body morphology phenotype in parasite larvae. This was replicated by single RNAi of a B. malayi C-P4H β subunit-like PDI. Surprisingly however, the B. malayi proteins were not capable of rescuing a C. elegans α subunit mutant, whereas the human enzymes could. In contrast, the B. malayi PDI did functionally complement the lethal phenotype of a C. elegans β subunit mutant. Comparison of recombinant and parasite derived material indicates that enzymatic activity may be dependent on a non-reducible, inter-subunit cross-link, present only in the parasite. We therefore demonstrate that C-P4H activity is essential for development of B. malayi and uncover a novel parasite-specific feature of these collagen biosynthetic enzymes that may be exploited in future parasite control

Integration of microRNA changes in vivo identifies novel molecular features of muscle insulin resistance in type 2 diabetes

Skeletal muscle insulin resistance (IR) is considered a critical component of type II diabetes, yet to date IR has evaded characterization at the global gene expression level in humans. MicroRNAs (miRNAs) are considered fine-scale rheostats of protein-coding gene product abundance. The relative importance and mode of action of miRNAs in human complex diseases remains to be fully elucidated. We produce a global map of coding and non-coding RNAs in human muscle IR with the aim of identifying novel disease biomarkers. We profiled &gt;47,000 mRNA sequences and &gt;500 human miRNAs using gene-chips and 118 subjects (n = 71 patients versus n = 47 controls). A tissue-specific gene-ranking system was developed to stratify thousands of miRNA target-genes, removing false positives, yielding a weighted inhibitor score, which integrated the net impact of both up- and down-regulated miRNAs. Both informatic and protein detection validation was used to verify the predictions of in vivo changes. The muscle mRNA transcriptome is invariant with respect to insulin or glucose homeostasis. In contrast, a third of miRNAs detected in muscle were altered in disease (n = 62), many changing prior to the onset of clinical diabetes. The novel ranking metric identified six canonical pathways with proven links to metabolic disease while the control data demonstrated no enrichment. The Benjamini-Hochberg adjusted Gene Ontology profile of the highest ranked targets was metabolic (P &lt; 7.4 × 10-8), post-translational modification (P &lt; 9.7 × 10-5) and developmental (P &lt; 1.3 × 10-6) processes. Protein profiling of six development-related genes validated the predictions. Brain-derived neurotrophic factor protein was detectable only in muscle satellite cells and was increased in diabetes patients compared with controls, consistent with the observation that global miRNA changes were opposite from those found during myogenic differentiation. We provide evidence that IR in humans may be related to coordinated changes in multiple microRNAs, which act to target relevant signaling pathways. It would appear that miRNAs can produce marked changes in target protein abundance in vivo by working in a combinatorial manner. Thus, miRNA detection represents a new molecular biomarker strategy for insulin resistance, where micrograms of patient material is needed to monitor efficacy during drug or life-style interventions

Performance analysis of AlGaAs/GaAs tunnel junctions for ultra-high concentration photovoltaics

An n(++)-GaAs/p(++)-AlGaAs tunnel junction with a peak current density of 10 100Acm(-2) is developed. This device is a tunnel junction for multijunction solar cells, grown lattice-matched on standard GaAs or Ge substrates, with the highest peak current density ever reported. The voltage drop for a current density equivalent to the operation of the multijunction solar cell up to 10 000 suns is below 5 mV. Trap-assisted tunnelling is proposed to be behind this performance, which cannot be justified by simple band-to-band tunnelling. The metal-organic vapour-phase epitaxy growth conditions, which are in the limits of the transport-limited regime, and the heavy tellurium doping levels are the proposed origins of the defects enabling trap-assisted tunnelling. The hypothesis of trap-assisted tunnelling is supported by the observed annealing behaviour of the tunnel junctions, which cannot be explained in terms of dopant diffusion or passivation. For the integration of these tunnel junctions into a triple-junction solar cell, AlGaAs barrier layers are introduced to suppress the formation of parasitic junctions, but this is found to significantly degrade the performance of the tunnel junctions. However, the annealed tunnel junctions with barrier layers still exhibit a peak current density higher than 2500Acm(-2) and a voltage drop at 10 000 suns of around 20 mV, which are excellent properties for tunnel junctions and mean they can serve as low-loss interconnections in multijunction solar cells working at ultra-high concentrations