Influence of carbon enrichment on electrical conductivity and processing of polycarbosilane derived ceramic for MEMS applications

An analysis about the effect of carbon enrichment of allylhydridopolycarbosilane SMP10® with divinylbenzene (DVB) as a promising material for electrical conductive micro-electrical mechanical systems (MEMS) is presented. The liquid precursors can be micropipetted and cured in polytetrafluoroethylene (PTFE) molds to produce 14 mm diameter disc shaped samples. The effect of pyrolysis temperature and carbon content on the electrical conductivity is discussed. The addition of 28.7 wt.% of DVB was found to be the optimum amount. Carbon was preserved in the microstructure during pyrolysis and the ceramic yield increased from 77.5 to 80.5 wt.%. The electrical conductivity increased from 10−6 to 1 S/cm depending on the annealing temperature. Furthermore, the ceramic samples obtained with this composition were found to be in many cases crack free or with minimal cracks in contrast with the behavior of pure SMP10. Using the same process we demonstrate that also microsized ceramic samples can be produced.

New strategies in laser processing of TCOs for light management improvement in thin-film silicon solar cells

Light confinement strategies play a crucial role in the performance of thin-film (TF) silicon solar cells. One way to reduce the optical losses is the texturing of the transparent conductive oxide (TCO) that acts as the front contact. Other losses arise from the mismatch between the incident light spectrum and the spectral properties of the absorbent material that imply that low energy photons (below the bandgap value) are not absorbed, and therefore can not generate photocurrent. Up-conversion techniques, in which two sub-bandgap photons are combined to give one photon with a better matching with the bandgap, were proposed to overcome this problem. In particular, this work studies two strategies to improve light management in thin film silicon solar cells using laser technology. The first one addresses the problem of TCO surface texturing using fully commercial fast and ultrafast solid state laser sources. Aluminum doped Zinc Oxide (AZO) samples were laser processed and the results were optically evaluated by measuring the haze factor of the treated samples. As a second strategy, laser annealing experiments of TCOs doped with rare earth ions are presented as a potential process to produce layers with up-conversion properties, opening the possibility of its potential use in high efficiency solar cells.

Expression, stability, and membrane integration of truncation mutants of bovine rhodopsin

Premature termination of protein synthesis by nonsense mutations is at the molecular origin of a number of inherited disorders in the family of G protein-coupled seven-helix receptor proteins. To understand how such truncated polypeptides are processed by the cell, we have carried out COS-1 cell expression studies of mutants of bovine rhodopsin truncated at the first 1, 1.5, 2, 3, or 5 transmembrane segments (TMS) of the seven present in wild-type opsin. Our experiments show that successful completion of different stages in the cellular processing of the protein [membrane insertion, N-linked glycosylation, stability to proteolytic degradation, and transport from the endoplasmic reticulum (ER) membrane] requires progressively longer lengths of the polypeptide chain. Thus, none of the truncations affected the ability of the polypeptides to be integral membrane proteins. C-terminal truncations that generated polypeptides with fewer than two TMS resulted in misorientation and prevented glycosylation at the N terminus, whereas truncations that generated polypeptides with fewer than five TMS greatly destabilized the protein. However, all of the truncations prevented exit of the polypeptide from the ER. We conclude that during the biogenesis of rhodopsin, proper integration into the ER membrane occurs only after the synthesis of at least two TMS is completed. Synthesis of the next three TMS confers a gradual increase in stability, whereas the presence of more than five TMS is necessary for exit from the ER.

Processing of the leader mRNA plays a major role in the induction of thrS expression following threonine starvation in Bacillus subtilis.

The threonyl-tRNA synthetase gene, thrS, is a member of a family of Gram-positive genes that are induced following starvation for the corresponding amino acid by a transcriptional antitermination mechanism involving the cognate uncharged tRNA. Here we show that an additional level of complexity exists in the control of the thrS gene with the mapping of an mRNA processing site just upstream of the transcription terminator in the thrS leader region. The processed RNA is significantly more stable than the full-length transcript. Under nonstarvation conditions, or following starvation for an amino acid other than threonine, the full-length thrS mRNA is more abundant than the processed transcript. However, following starvation for threonine, the thrS mRNA exists primarily in its cleaved form. This can partly be attributed to an increased processing efficiency following threonine starvation, and partly to a further, nonspecific increase in the stability of the processed transcript under starvation conditions. The increased stability of the processed RNA contributes significantly to the levels of functional RNA observed under threonine starvation conditions, previously attributed solely to antitermination. Finally, we show that processing is likely to occur upstream of the terminator in the leader regions of at least four other genes of this family, suggesting a widespread conservation of this phenomenon in their control.

Flight evaluation of various phugoid dynamics and 1/Th values for the landing-approach task.

"This is the second in a series of two reports dealing with longitudinal handling qualities in the landing approach." (see also TL/711/L3/C43+)

Flight evaluations of the effect of variable spiral damping in a JTB-26B airplane.

"Contract no. NO(s) 56-793-c."

Flight text of an autopilot installation as a lateral gust alleviator in a PT-26 airplane.

"Aeronautical Research Laboratory. Contract No. AF 33(038)-10480, Task 70171, Project 1366."

Soft solution processing of cerium hydroxysulfate powders with different morphologies

Polycrystalline cerium hydroxysulfate powders have been prepared by soft solution processing using various basic solvents. The crystals prepared have varying morphologies, spherical and flaky, depending on the solvent used. The crystals obtained from distilled water-pyridine and aqueous ammonia solvent mixtures are spherical, whereas those obtained from mixtures of distilled water and ethylenediamine or hydrazine hydrate are flaky. All the crystalline cerium hydroxysulfate samples display luminescence properties. It was found that the flaky crystals generally show a much stronger luminescence than their spherical counterparts.

Processing of a 22 kDa precursor protein to produce the circular protein tricyclon A

Cyclotides are a family of plant proteins that have the unusual combination of head-to-tail backbone cyclization and a cystine knot motif. They are exceptionally stable and show resistance to most chemical, physical, and enzymatic treatments. The structure of tricyclon A, a previously unreported cyclotide, is described here. In this structure, a loop that is disordered in other cyclotides forms a beta sheet that protrudes from the globular core. This study indicates that the cyclotide fold is amenable to the introduction of a range of structural elements without affecting the cystine knot core of the protein, which is essential for the stability of the cyclotides. Tricyclon A does not possess a hydrophobic patch, typical of other cyclotides, and has minimal hemolytic activity, making it suitable for pharmaceutical applications. The 22 kDa precursor protein of tricyclon A was identified and provides clues to the processing of these fascinating miniproteins.

HRT and everyday memory at menopause: A comparison of two samples of mid-aged women

Research on the effect of hormone replacement therapy (HRT) on memory in mid-aged women is equivocal although findings indicate that oestrogen may enhance verbal memory. Mood may mediate the relationship between HRT and memory. This study examined the effect of HRT on mood and everyday memory in two samples of women between ages 40 and 60 years. In the cross-sectional comparison (N = 124), HRT users performed significantly better on tests of everyday and verbal memory. A within-woman comparison of 17 women showed that everyday memory, working memory, and delayed verbal memory improved after 3 months of HRT use. The improvement in memory was not mediated by mood. These results suggest that any effect of HRT on mood may be short-term but that some aspects of everyday memory are enhanced, particularly verbal memory. The development of the everyday memory construct and future investigation are discussed.

Discovery and characterization of a linear cyclotide from Viola odorata: Implications for the processing of circular proteins

Cyclotides are mini-proteins of 28-37 amino acid residues that have the unusual feature of a head-to-tail cyclic backbone surrounding a cystine knot. This molecular architecture gives the cyclotides heightened resistance to thermal, chemical and enzymatic degradation and has prompted investigations into their use as scaffolds in peptide therapeutics. There are now more than 80 reported cyclotide sequences from plants in the families Rubiaceae, Violaceae and Cucurbitaceae, with a wide variety of biological activities observed. However, potentially limiting the development of cyclotide-based therapeutics is a lack of understanding of the mechanism by which these peptides are cyclized in vivo. Until now, no linear versions of cyclotides have been reported, limiting our understanding of the cyclization mechanism. This study reports the discovery of a naturally occurring linear cyclotide, violacin A, from the plant Viola odorata and discusses the implications for in vivo cyclization of peptides. The elucidation of the cDNA clone of violacin A revealed a point mutation that introduces a stop codon, which inhibits the translation of a key Asn residue that is thought to be required for cyclization. The three-dimensional solution structure of violacin A was determined and found to adopt the cystine knot fold of native cyclotides. Enzymatic stability assays on violacin A indicate that despite an increase in the flexibility of the structure relative to cyclic counterparts, the cystine knot preserves the overall stability of the molecule. (c) 2006 Elsevier Ltd. All rights reserved.

Reactive processing of polymers:effect of bifunctional and tri-functional comonomers on melt grafting of glycidyl methacrylate onto polypropylene

Two reactive comonomers, divinyl benzene (DVB) and trimethylolpropane triacrylate (TRIS), were evaluated for their role in effecting the melt free radical grafting reaction of the monomer glycidyl methacrylate (GMA) onto polypropylene (PP). The characteristics of the GMA-grafting systems in the presence and absence of DVB or TRIS were examined and compared in terms of the yield of the grafting reaction and the extent of the main side reactions, namely homopolymerisation of GMA (poly-GMA) and polymer degradation, using different chemical compositions of the reactive systems and processing conditions. In the absence of the comonomers, i.e. in a conventional system, high initiator concentrations of peroxides were typically required to achieve the highest possible GMA grafting levels which were found to be generally low. Concomitantly, both poly-GMA and degradation of the polymer by chain scission takes place with increasing initiator amounts. On the other hand, the presence of a small amount of the comonomers, DVB or Tris, in the GMA-grafting system, was shown to bring about a significant increase in the grafting level paralleled by a large reduction in poly-GMA and PP degradation. In the presence of these highly reactive comonomers, the optimum grafting system requires a much lower concentration of the peroxide initiator and, consequently, would lead to the much lower degree of polymer degradation observed in these systems. The differences in the effects of the presence of DVB and that of TRIS in the grafting systems on the rate of the GMA-grafting and homopolymerisation reactions, and the extent of PP degradation (through melt flow changes), were compared and contrasted with a conventional GMA-grafting system.

Fast pyrolysis processing of surfactant washed Miscanthus

Miscanthus × giganteus was subjected to pre-treatment with deionised water, hydrochloric acid or Triton X-100 surfactant, and subsequently fast pyrolysed in a fluidised bed reactor at 535 °C to obtain bio-oil. Triton X-100 surfactant was identified as a promising pre-treatment medium for removal of inorganic matter because its physicochemical nature was expected to mobilise inorganic matter in the biomass matrix. The influence of different concentrations of Triton X-100 pre-treatment solutions on the quality of bio-oil produced from fast pyrolysis was studied, as defined by a single phase bio-oil, viscosity index and water content index. The highest concentration of Triton X-100 surfactant produced the best quality bio-oil with high organic yield and low reaction water content. The calculated viscosity index from the accelerated ageing test showed that bio-oil stability improved as the concentration of Triton X-100 increased. © 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license.

The influence of variations in eating disorder-related symptoms on processing of emotional faces in a non-clinical female sample:an eye-tracking study

This study aimed to: i) determine if the attention bias towards angry faces reported in eating disorders generalises to a non-clinical sample varying in eating disorder-related symptoms; ii) examine if the bias occurs during initial orientation or later strategic processing; and iii) confirm previous findings of impaired facial emotion recognition in non-clinical disordered eating. Fifty-two females viewed a series of face-pairs (happy or angry paired with neutral) whilst their attentional deployment was continuously monitored using an eye-tracker. They subsequently identified the emotion portrayed in a separate series of faces. The highest (n=18) and lowest scorers (n=17) on the Eating Disorders Inventory (EDI) were compared on the attention and facial emotion recognition tasks. Those with relatively high scores exhibited impaired facial emotion recognition, confirming previous findings in similar non-clinical samples. They also displayed biased attention away from emotional faces during later strategic processing, which is consistent with previously observed impairments in clinical samples. These differences were related to drive-for-thinness. Although we found no evidence of a bias towards angry faces, it is plausible that the observed impairments in emotion recognition and avoidance of emotional faces could disrupt social functioning and act as a risk factor for the development of eating disorders.

Signal processing of physiological signals for automated assessment of stress in computer users

The need to provide computers with the ability to distinguish the affective state of their users is a major requirement for the practical implementation of affective computing concepts. This dissertation proposes the application of signal processing methods on physiological signals to extract from them features that can be processed by learning pattern recognition systems to provide cues about a person's affective state. In particular, combining physiological information sensed from a user's left hand in a non-invasive way with the pupil diameter information from an eye-tracking system may provide a computer with an awareness of its user's affective responses in the course of human-computer interactions. In this study an integrated hardware-software setup was developed to achieve automatic assessment of the affective status of a computer user. A computer-based "Paced Stroop Test" was designed as a stimulus to elicit emotional stress in the subject during the experiment. Four signals: the Galvanic Skin Response (GSR), the Blood Volume Pulse (BVP), the Skin Temperature (ST) and the Pupil Diameter (PD), were monitored and analyzed to differentiate affective states in the user. Several signal processing techniques were applied on the collected signals to extract their most relevant features. These features were analyzed with learning classification systems, to accomplish the affective state identification. Three learning algorithms: Naïve Bayes, Decision Tree and Support Vector Machine were applied to this identification process and their levels of classification accuracy were compared. The results achieved indicate that the physiological signals monitored do, in fact, have a strong correlation with the changes in the emotional states of the experimental subjects. These results also revealed that the inclusion of pupil diameter information significantly improved the performance of the emotion recognition system. ^