Preparation of Lead Zirconate by Homogeneous Precipitation and Calcination

Antiferroelectric PbZrO₃ has been synthesized by homogeneous precipitation from aqueous solutions in the presence of urea (NH₂CONH₂) and calcination for 6 h at 700°C. SEM studies displayed the presence of submicrometer powder, with a significant degree of agglomeration.     

Temporal perspective on individual driver behavior using electronic records of undesirable events

This paper explores In-Vehicle Data Recorders (IVDRs) information about the count of undesirable driving events (such as hard braking, lane changing, and sharp turning) of 148 individuals. The information was logged over three years and included time stamp information about the occurrence of undesirable driving events in each trip (N = 573,238). The objective was to gain deeper understanding about the heterogeneity among drivers with respect to behavior change over time, the effect of trip duration and the distribution of events count. Our findings show that in some respects drivers are similar: for all drivers, the variance of the events count was larger than the mean, indicating that the negative binomial distribution is suitable to model the distribution of events count per trip. Most drivers (95%) had lower events rate during longer trips, suggesting that a ‘simple’ events rate index is problematic when comparing between those driving longer trips and drivers driving short trips. In addition, most drivers (87%) improved their driving behavior throughout the measurement period. However, there are important differences among drivers in terms of the frequency of behavior change and the trends in behavior over time. These findings demonstrate the need for personalized examination of individual drivers. Several tools for such personalized examination were developed and discussed in this study.     

Highly Active Metastable Ruthenium Nanoparticles for Hydrogen Production through the Catalytic Hydrolysis of Ammonia Borane

Late transition metal nanoparticles (NPs) with a favorably high surface area to volume ratio have garnered much interest for catalytic applications. Yet, these NPs are prone to aggregation in solution, which has been mitigated through attachment of surface ligands, additives or supports; unfortunately, protective ligands can severely reduce the effective surface area on the NPs available for catalyzing chemical transformations. The preparation of ‘metastable’ NPs can readily address these challenges. We report herein the first synthesis of monodisperse metastable ruthenium nanoparticles (RuNPs), having sub 5 nm size and an fcc structure, in aqueous media at room temperature, which can be stored for a period of at least 8 months. The RuNPs can subsequently be used for the catalytic, quantitative hydrolysis of ammonia‐borane (AB) yielding hydrogen gas with 21.8 turnovers per min at 25 °C. The high surface area available for hydrolysis of AB on the metastable RuNPs translated to an E_a of 27.5 kJ mol^‐1, which is notably lower than previously reported values for RuNP based catalysts.     

Ring-type plasmon resonance in metallic nanoshells

A simple, approximate theoretical model of surface plasmon resonance in two-dimensional metal nanoshells is developed. The model is based on the concept of short-range surface plasmons propagating around closed circular metal nanotubes. In this model, the plasmon resonance in a metal nanotube is treated as a propagating, self-interfering plasmonic wave, in a ring-type resonance, at plasmonic wavelengths matching an integer fraction of the nanotube's effective circumference. The model is validated by detailed computer simulations based on the finite-difference time-domain method and is shown to be in full agreement with the widely used plasmon hybridization model, which is based on the quasi-static approximation.     

New mollusc-specific alpha-conotoxins block Aplysia neuronal acetylcholine receptors

Two mollusc-specific neurotoxic peptides from the venom of the molluscivorous snail Conus pennaceus are described. These new toxins block acetylcholine receptors (AChR) of cultured Aplysia neurons. Bath application of 0.5-1 microM toxin induces 5-10-mV membrane depolarization, which recovers to the control level within 1-3 min in the presence of the toxin. This response is blocked by 1 mM hexamethonium. Concomitantly with the transient depolarization, the toxins block approximately 90% of the depolarizing responses evoked by brief iontophoretic application of acetylcholine. The pharmacology and amino acid sequences of the toxins (alpha PnIA, GCCSLPPCAANNPDYC-NH2; alpha PnIB, GCCSLPPCALSNPDYC-NH2) enable their classification as novel alpha-conotoxins. The sequences differ from those of previously described alpha-conotoxins in a number of features, the most striking of which is the presence of a single negatively charged residue in the C-terminal loop. This loop contains a positively charged residue in piscivorous venom alpha-conotoxins. In contrast to other alpha-conotoxins, which are selective for vertebrate skeletal muscle nicotinic ACh receptors, these Conus pennaceus toxins block neuronal ACh receptors in molluscs. As such they are new probes which can be used to define subtypes of ACh receptors, and they should be useful tools in the study of structure-function relationships in ACh receptors.     

酸驼奶的研究进展

在新疆,对于哈萨克族来说饮用发酵过的驼奶是传统的、普遍的.科学家和消费者们认为酸驼奶有抗菌和保健治疗的特性.概述酸驼奶的成分、微生态分布、抗菌性和医疗保健作用等方面内容.以便促进对酸驼奶的研究、开发和利用.     

Effects of meta-chlorophenylpiperazine infusions in patients with seasonal affective disorder and healthy control subjects. Diurnal responses and nocturnal regulatory mechanisms

BACKGROUND: Multiple lines of evidence suggest that brain serotonergic systems may be disturbed in seasonal affective disorder (SAD). Previously, we found that the serotonergic agent meta-chlorophenylpiperazine (m-CPP) produced increases in activation and euphoria in depressed patients with SAD, but not in patients with SAD following light treatment or in the summer, nor in healthy control subjects in any condition. In the present study, we attempted to replicate and extend this finding using better methods. METHODS: Seventeen outpatients with SAD and 15 control subjects underwent successive 3-week periods of bright light treatment and light avoidance in a randomized order. During the third week of each condition, on 2 different occasions, subjects were admitted to the hospital for a night of sleep (core temperatures were recorded), followed by infusions of m-CPP (0.08 mg/kg) or placebo the next morning. Dependent measures included the 24-item National Institute of Mental Health Self-Rating Scale, plasma corticotropin, cortisol, prolactin, growth hormone, and norepinephrine concentrations, and core temperatures. RESULTS: Meta-chlorophenylpiperazine produced (1) significant increases in "activation-euphoria" ratings only in depressed patients with SAD in the untreated condition and (2) blunted corticotropin and norepinephrine responses in patients with SAD compared with controls across both light treatment conditions. In both groups, light treatment was associated with significant reductions in nocturnal core temperatures, which were correlated with similarly significant reductions in mean diurnal growth hormone concentrations. In patients with SAD, (1) the reductions in nocturnal core temperatures also were correlated with the reductions in baseline depression ratings and (2) the reductions in mean growth hormone concentrations were significantly smaller compared with controls. CONCLUSIONS: The abnormal m-CPP-induced activation-euphoria responses represent a replicated state marker of winter depression in patients with SAD. The blunted m-CPP-induced responsiveness of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system may represent traitlike abnormalities. The improvements in mood following light treatment in patients with SAD seem to be associated with the lowering of nocturnal core temperatures. The findings, although not easily explained based on a uniform abnormality of serotonin receptors, are nonetheless compatible with the notion that selected regions of the central nervous system are deficient in serotonin transmission during winter depression.