Directionality of Solar Flare Accelerated Protons and Alpha Particles from Gamma-Ray Line Measurements

The energies and widths of gamma-ray lines emitted by ambient nuclei excited by flare-accelerated protons and alpha particles provide information on the ions directionality and spectra, and on the characteristics of the interaction region. We have measured the energies and widths of strong lines from de-excitations of 12C, 16O, and 20Ne in solar flares as a function of heliocentric angle. The line energies from all three nuclei exhibit ~1% redshifts for flares at small heliocentric angles, but are not shifted near the limb. The lines have widths of ~3% FWHM. We compare the 12C line measurements for flares at five different heliocentric angles with calculations for different interacting-particle distributions. A downward isotropic distribution (or one with a small upward component) provides a good fit to the line measurements. An angular distribution derived for particles that undergo significant pitch angle scattering by MHD turbulence in coronal magnetic loops provides comparably good fits

Photocatalytic Hydrogen Production at Titania-Supported Pt Nanoclusters that are Derived from Surface-Anchored Molecular Precursors

Degussa P-25 TiO2 bearing surface-anchored Pt(dcbpy)Cl-2 [dcbpy = 4,4\u27-dicarboxylic acid-2,2\u27-bipyridine] prepared with systematically varied surface coverage produced Pt-0 nanoparticles under bandgap illumination in the presence of methanol hole scavengers. Energy-dispersive X-ray spectroscopy confirmed the presence of elemental platinum in the newly formed nanoparticles during scanning transmission electron microscopy (STEM) eleriments. According to the statistical analysis of numerous STEM images, the Pt-0 nanoclusters were distributed in a segregated manner throughout the titania surface, ranging in size from 1 to 3 nm in diameter. The final achieved nanoparticle size and net hydrogen production were determined as a function of the Pt(dcbpy)Cl-2 surface coverage as well as other systematically varied experimental parameters. The hybrid Pt/TiO2 nanomaterials obtained upon complete decomposition of the Pt(dcbpy)Cl-2 precursor displayed higher photocatalytic activity (300 mu mol/h) for hydrogen evolution in aqueous suspensions when compared with platinized TiO2 derived from H2PtCl6 precursors (130 mu mol/h), as ascertained through gas chromatographic analysis of the photoreactor headspace under identical experimental conditions. The conclusion that H-2 was evolved from Pt-0 sites rather than from molecular Pt(dcbpy)Cl-2 entities was independently supported by Hg and CO poisoning experiments. The formation of small Pt nanopartides (1.5 nm in diameter) prevail at low surface coverage of Pt(dcbpy)Cl-2 on TiO2 (0.5 to 2% by mass) that exhibit enhanced turnover frequencies with respect to all other materials investigated, induding those produced from the in situ photochemical reduction of H2PtCl6 center dot Pt-II precursor absorption in the ultraviolet region appeared to be partially responsible for attenuation of the H-2 evolution rate at higher Pt(dcbpy)Cl-2 surface coverage. The nanoparticle size and hydrogen evolution characteristics of the surface-anchored materials generated through photodeposition were directly compared with those derived from chemical reduction using NaBH4. Finally, Degussa P-25 thin films deposited on FTO substrates enabled electrochemically induced (-1.0 V vs Ag/AgCl, pH 7.0, phosphate buffer) electron trapping (TiO2(e(-))) throughout the titania. After removal of the applied bias and the anaerobic introduction of Pt(dcbpy)Cl-2, the accumulated electrons reduce this molecular species to Pt-0 nanoparticles on the titania electrode surface, as confirmed by TEM measurements, with the concomitant production of H-2 gas. The combined experiments illustrate that TiO2(e(-)) generated with bandgap excitation or via electrochemical bias affords the reduction of Pt(dcbpy)Cl-2 to Pt-0 nanoparticles that in turn are responsible for heterogeneous hydrogen gas evolution

Identification of a neurovascular signaling pathway regulating seizures in mice

ObjectiveA growing body of evidence suggests that increased blood–brain barrier (BBB) permeability can contribute to the development of seizures. The protease tissue plasminogen activator (tPA) has been shown to promote BBB permeability and susceptibility to seizures. In this study, we examined the pathway regulated by tPA in seizures.MethodsAn experimental model of kainate‐induced seizures was used in genetically modified mice, including mice deficient in tPA (tPA−/−), its inhibitor neuroserpin (Nsp−/−), or both (Nsp:tPA−/−), and in mice conditionally deficient in the platelet‐derived growth factor receptor alpha (PDGFRα).ResultsCompared to wild‐type (WT) mice, Nsp−/− mice have significantly reduced latency to seizure onset and generalization; whereas tPA−/− mice have the opposite phenotype, as do Nsp:tPA−/− mice. Furthermore, interventions that maintain BBB integrity delay seizure propagation, whereas osmotic disruption of the BBB in seizure‐resistant tPA−/− mice dramatically reduces the time to seizure onset and accelerates seizure progression. The phenotypic differences in seizure progression between WT, tPA−/−, and Nsp−/− mice are also observed in electroencephalogram recordings in vivo, but absent in ex vivo electrophysiological recordings where regulation of the BBB is no longer necessary to maintain the extracellular environment. Finally, we demonstrate that these effects on seizure progression are mediated through signaling by PDGFRα on perivascular astrocytes.InterpretationTogether, these data identify a specific molecular pathway involving tPA‐mediated PDGFRα signaling in perivascular astrocytes that regulates seizure progression through control of the BBB. Inhibition of PDGFRα signaling and maintenance of BBB integrity might therefore offer a novel clinical approach for managing seizures.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112290/1/acn3209.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112290/2/acn3209-sup-0001-TableS1.pd

The Intraflagellar Transport Protein IFT27 Promotes BBSome Exit from Cilia through the GTPase ARL6/BBS3

SummaryThe sorting of signaling receptors into and out of cilia relies on the BBSome, a complex of Bardet-Biedl syndrome (BBS) proteins, and on the intraflagellar transport (IFT) machinery. GTP loading onto the Arf-like GTPase ARL6/BBS3 drives assembly of a membrane-apposed BBSome coat that promotes cargo entry into cilia, yet how and where ARL6 is activated remains elusive. Here, we show that the Rab-like GTPase IFT27/RABL4, a known component of IFT complex B, promotes the exit of BBSome and associated cargoes from cilia. Unbiased proteomics and biochemical reconstitution assays show that, upon disengagement from the rest of IFT-B, IFT27 directly interacts with the nucleotide-free form of ARL6. Furthermore, IFT27 prevents aggregation of nucleotide-free ARL6 in solution. Thus, we propose that IFT27 separates from IFT-B inside cilia to promote ARL6 activation, BBSome coat assembly, and subsequent ciliary exit, mirroring the process by which BBSome mediates cargo entry into cilia

The reinforcing properties of ethanol are quantitatively enhanced in adulthood by peri-adolescent ethanol, but not saccharin, consumption in female alcohol-preferring (P) rats

Alcohol drinking during adolescence is associated in adulthood with heavier alcohol drinking and an increased rate of alcohol dependence. Past research in our laboratory has indicated that peri-adolescent ethanol consumption can enhance the acquisition and reduce the rate of extinction of ethanol self-administration in adulthood. Caveats of the past research include reinforcer specificity, increased oral consumption during peri-adolescence, and a lack of quantitative assessment of the reinforcing properties of ethanol. The current experiments were designed to determine the effects of peri-adolescent ethanol or saccharin drinking on acquisition and extinction of oral ethanol self-administration and ethanol seeking, and to quantitatively assess the reinforcing properties of ethanol (progressive ratio). Ethanol or saccharin access by alcohol-preferring (P) rats occurred during postnatal day (PND) 30-60. Animals began operant self-administration of ethanol or saccharin after PND 85. After 10 weeks of daily operant self-administration, rats were tested in a progressive ratio paradigm. Two weeks later, self-administration was extinguished in all rats. Peri-adolescent ethanol consumption specifically enhanced the acquisition of ethanol self-administration, reduced the rate of extinction for ethanol self-administration, and quantitatively increased the reinforcing properties of ethanol during adulthood. Peri-adolescent saccharin consumption was without effect. The data indicate that ethanol consumption during peri-adolescence results in neuroadaptations that may specifically enhance the reinforcing properties of ethanol during adulthood. This increase in the reinforcing properties of ethanol could be a part of biological sequelae that are the basis for the effects of adolescent alcohol consumption on the increase in the rate of alcoholism during adulthood