Multifunctional Optical Terminals for Microsatellite Clusters – Design Tradeoffs

We study optical terminals with both communication and ranging capabilities for their potential use in short range free-space applications, typically encountered within a cluster of microsatellites. For our considerations we assume satellites with a unit mass between 10 kg and 100 kg, with mutual distances on the order of a few km, and per link data rates range from a few kbits/s to some 100 Mbit/s. We discuss possible network topologies and multiple access methods, andcompare the performance characteristics of different intensity modulation formats, taking into account not only the task of communication but also that of accurate intra-cluster distance measurement. Our considerations revealbasic tradeoffs to be observed when designing such multifunctional optical terminals.     

The relationship between cognitive deficits and everyday functional activities in multiple sclerosis.

Considerable evidence indicates that cognitive dysfunction and impairments in everyday life activities are common in multiple sclerosis (MS). However, the relationship between these cognitive and functional deficits has not been thoroughly investigated. The purpose of this study was to examine the role of cognitive dysfunction in the functional status of individuals with MS. Participants were 74 adults with MS and 35 healthy comparison participants (HCs) who underwent neuropsychological testing and completed the Executive Functions Performance Test (EFPT; Baum, Morrison, Hahn, & Edwards, 2003), an objective measure of everyday life activities. Between-groups comparisons and correlational analyses were conducted to examine the relationship between cognition and functional capacity. Significant differences in EFPT performance were revealed between individuals with MS with and without cognitive impairment and HCs. In individuals with MS, performance on cognitive constructs was related to performance on the EFPT. Furthermore, a linear regression model comprised of indices of cognitive functioning explained a significant portion of the variance in everyday life activities. Findings suggest that individuals with and without cognitive impairment differ in functional status and that aspects of cognition are predictive of functional status in MS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sensitivity enhancement of optical receivers by impulsive coding

A theory for the signal-to-noise ratio (SNR) of optical direct-detection receivers employing return-to-zero (RZ) coding (and possibly optical preamplification) is developed. The results are valid for both signal-independent noise limited and signal-dependent noise limited receivers, as well as for arbitrary optical pulse shapes and receiver filter characteristics. Even if the same receiver bandwidth is used, RZ coding is seen to perform better than nonreturn-to-zero (NRZ) coding. Asymptotic expressions for the SNR in case of very high and very low receiver bandwidths show that the full sensitivity enhancement potential of RZ coding is exhausted at fairly moderate duty cycles. A realistic example taking into account intersymbol interference (ISI) shows that a receiver sensitivity gain (compared to NRZ coding) of, e.g., 3.2 dB can be obtained in a signal-independent noise limited receiver with a bandwidth of 80% of the data rate, using a duty cycle of three     

Cellular Chaperone Function of Intrinsically Disordered Dehydrin ERD14

Disordered plant chaperones play key roles in helping plants survive in harsh conditions, and they are indispensable for seeds to remain viable. Aside from well-known and thoroughly characterized globular chaperone proteins, there are a number of intrinsically disordered proteins (IDPs) that can also serve as highly effective protecting agents in the cells. One of the largest groups of disordered chaperones is the group of dehydrins, proteins that are expressed at high levels under different abiotic stress conditions, such as drought, high temperature, or osmotic stress. Dehydrins are characterized by the presence of different conserved sequence motifs that also serve as the basis for their categorization. Despite their accepted importance, the exact role and relevance of the conserved regions have not yet been formally addressed. Here, we explored the involvement of each conserved segment in the protective function of the intrinsically disordered stress protein (IDSP) A. thaliana’s Early Response to Dehydration (ERD14). We show that segments that are directly involved in partner binding, and others that are not, are equally necessary for proper function and that cellular protection emerges from the balanced interplay of different regions of ERD14.     

Size-Exclusion Chromatography Separation Reveals That Vesicular and Non-Vesicular Small RNA Profiles Differ in Cell Free Urine

Urinary extracellular vesicles (EVs) and their RNA cargo are a novel source of biomarkers for various diseases. We aimed to identify the optimal method for isolating small (<200 nm) EVs from human urine prior to small RNA analysis. EVs from filtered healthy volunteer urine were concentrated using three methods: ultracentrifugation (UC); a precipitation-based kit (PR); and ultrafiltration (UF). EVs were further purified by size-exclusion chromatography (SEC). EV preparations were analysed with transmission electron microscopy (TEM), Western blotting, nanoparticle tracking analysis (NTA) and an Agilent Bioanalyzer Small RNA kit. UF yielded the highest number of particles both before and after SEC. Small RNA analysis from UF-concentrated urine identified two major peaks at 10–40 nucleotides (nt) and 40–80 nt. In contrast, EV preparations obtained after UC, PR or SEC combined with any concentrating method, contained predominantly 40–80 nt sized small RNA. Protein fractions from UF+SEC contained small RNA of 10–40 nt in size (consistent with miRNAs). These data indicate that most of the microRNA-sized RNAs in filtered urine are not associated with small-sized EVs, and highlights the importance of removing non-vesicular proteins and RNA from urine EV preparations prior to small RNA analysis.     

Information Processing Deficits in Multiple Sclerosis: Does Choice of Screening Instrument Make a Difference?

Objective: To examine the clinical utility of the Letter-Number Sequencing (LNS) subtest of the Wechsler Adult Intelligence Scale-III and the Paced Auditory Serial Addition Test (PASAT) to detect cognitive decline in persons with multiple sclerosis (MS). Design: Case-control study. Setting: Outpatient rehabilitation research institution. Participants: Fifty-two adults with clinically definite MS. Main Outcome Measures: LNS standard score and number correct on the PASAT. Results: The PASAT was more sensitive to information processing deficits in persons with MS than was the LNS, perhaps due to a significant processing speed component in the former. Conclusions: The PASAT and the LNS have differential clinical utility, inasmuch as the PASAT assesses not only working memory ability but processing speed as well. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-dose radiography of scoliosis in children. A comparison of methods

STUDY DESIGN: Records of 1,582 conventional and computed radiographic examinations performed to evaluate scoliosis were reviewed and compared to determine differences in total radiation burden. OBJECTIVE: This study evaluated the impact of computed radiographic imaging (CRI) on radiation exposure in children undergoing serial spinal radiographs for scoliosis assessment and compared exposure from CRI with that of low-dose film-screen combinations. SUMMARY OF BACKGROUND DATA: CRI permits diagnostic radiographic studies to be performed with a dose reduction of 80%-95% compared to conventional film-screen systems. High speed film-screen systems also permit a significantly lower exposure. Each approach has unique advantages and disadvantages. METHODS: Over 6 years, we performed 1,582 spinal examinations in children 4-14 years old using reduced dosage techniques with computed radiography. The images were obtained with Fuji FCR 101 and Philips PCR/SP systems. The adequacy of diagnostic image quality in the serial evaluation of scoliosis at different exposure levels was evaluated and compared with regular and film-screen systems with speeds ranging from 250 to 1,200. RESULTS: Diagnostic-quality images for evaluating scoliosis can be obtained with doses of 5% or less than required with conventional film-screen systems. Computed radiography provides image quality and dose reduction comparable to a 1,200-speed film-screen system. CONCLUSION: CRI gives satisfactory images at 5% reduction of the standard film-screen dose. Based on comparison with a 1,200 speed film-screen system, CRI provides equal or better image quality at a similar radiation dose. The cost of CRI is higher than for film-screen radiography, but wide latitude and the ability to tailor dose with requirements for image quality are significant advantages for CRI.     

Antimony doped tin oxides and their composites with tin pyrophosphates as catalyst supports for oxygen evolution reaction in proton exchange membrane water electrolysis

Proton exchange membrane water electrolysers operating at typically 80 °C or at further elevated temperatures suffer from insufficient catalyst activity and durability. In this work, antimony doped tin oxide nanoparticles were synthesized and further doped with an inorganic proton conducting phase based on tin pyrophosphates as the catalyst support. The materials showed an overall conductivity of 0.57 S cm⁻¹ at 130 °C under the water vapor atmosphere with a contribution of the proton conduction. Using this composite support, iridium oxide nanoparticle catalysts were prepared and characterized in sulfuric and phosphoric acid electrolytes, showing much enhanced catalytic activity. Electrolyzer tests were conducted at both 80 °C with an Aquivion^™ membrane and at 130 °C with a phosphoric acid doped Aquivion^™ membrane. Significant improvement in the anodic kinetics was achieved on the composite supported catalysts at 130 °C although the electrolyzer cells showed higher ohmic resistance primarily from the membrane and catalyst layer. A durability test of electrolyzer cells was carried out at 130 °C under a current density of 400 mA cm⁻² in a period of up to 760 h, showing rather good stability of the system.