Hydrogen storage on cation-decorated biphenylene carbon and nitrogenated holey graphene

Hydrogen storage on cation-decorated biphenylene carbon (BPC) and nitrogenated holey graphene (C₂N) layered materials are addressed by dispersion-corrected density functional theory calculations. Maximum storage capacity and adsorption energy of a gas-phase H₂ monolayer adsorbed on both sides of (Li⁺, Na⁺, Mg²⁺, Ca²⁺)-doped layers are investigated. We find that cations distribute homogeneously on BPC and C₂N with a maximum densities of 1.9 and 1.7 ion/nm², respectively. The H₂ adsorption on cation-decorated BPC shows binding energies that vary from ?0.14 to ?0.26 eV/H₂, depending on whether the cation is single or double charged, where the storage capacity are calculated to be around 10 wt%. Whereas, for cation-doped C₂N, the H₂ binding energies vary from ?0.11 to ?0.31 eV/H₂, with storage capacity between 7.3 and 8.8 wt%. Our results suggest that cation-doped C₂N is the most stable material, providing both reversibility and high capacity for hydrogen storage at operational conditions.     

Aeromyocological survey in the Santiago Western district (author''s transl)

It has not been determined whether Rho (D)-negative infants born of Rho (D)-positive mothers are sensitized during gestation or during parturition. Sensitization before use precludes the efficacious use of human Rho immune globulin as a prophylactic. The purpose of the present study is to identify the time of sensitization. Cord blood was collected from the placentas of 68 Rho (D)-negative infants whose mothers were Rho (D)-positive. Sixty-three of the 68 infants had one blood sample obtained between 1 and 9 months later. The paired samples were analyzed for anti-D by standard Coombs test and by automated antibody detection techniques. With the technique of automated antibody detection, we have been unable to demonstrate antibody in cord blood of the Rho (D)-negative infants of whom at least 7 of 63 (11%) had detectable anti-D between 1 and 9 months of age. These data show that Rho (D)-negaitve infants do not have detectable antibody at birth but may develop detectable anti-D in the first months of life. This observation suggests that the sensitizing dose of Rho (D) antigen occurs at parturition rather than during gestation.     

Direct grafting of long-lived luminescent indicator dyes to GaN light-emitting diodes for chemical microsensor development

Two new methods for covalent functionalization of GaN based on plasma activation of its surface are presented. Both of them allow attachment of sulfonated luminescent ruthenium(II) indicator dyes to the p- and n-type semiconductor as well as to the surface of nonencapsulated chips of GaN light-emitting diodes (blue LEDs). X-ray photoelectron spectroscopy analysis of the functionalized semiconductor confirms the formation of covalent bonds between the GaN surface and the dye. Confocal fluorescence microscopy with single-photon-timing (SPT) detection has been used for characterization of the functionalized surfaces and LED chips. While the ruthenium complex attached to p-GaN under an oxygen-free atmosphere gives significantly long mean emission lifetimes for the indicator dye (ca. 2000 ns), the n-GaN-functionalized surfaces display surprisingly low values (600 ns), suggesting the occurrence of a quenching process. A photoinduced electron injection from the dye to the semiconductor conduction band, followed by a fast back electron transfer, is proposed to be responsible for the excited ruthenium dye deactivation. This process invalidates the use of the n-GaN/dye system for sensing applications. However, for p-GaN/dye materials, the luminescence decay accelerates in the presence of O(2). The moderate sensitivity is attributed to the fact that only a monolayer of indicator dye is anchored to the semiconductor surface but serves as a demonstrator device. Moreover, the luminescence decays of the functionalized LED chip measured with excitation of either an external (laser) source or the underlying LED emission (from p-GaN/InGaN quantum wells) yield the same mean luminescence lifetime. These results pave the way for using advanced LEDs to develop integrateable optochemical microsensors for gas analysis.     

GABAergic Regulation of Astroglial Gliotransmission through Cx43 Hemichannels

Gamma-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain. It is produced by interneurons and recycled by astrocytes. In neurons, GABA activates the influx of Cl^- via the GABA_A receptor or efflux or K⁺ via the GABA_B receptor, inducing hyperpolarization and synaptic inhibition. In astrocytes, the activation of both GABA_A and GABA_B receptors induces an increase in intracellular Ca²⁺ and the release of glutamate and ATP. Connexin 43 (Cx43) hemichannels are among the main Ca²⁺-dependent cellular mechanisms for the astroglial release of glutamate and ATP. However, no study has evaluated the effect of GABA on astroglial Cx43 hemichannel activity and Cx43 hemichannel-mediated gliotransmission. Here we assessed the effects of GABA on Cx43 hemichannel activity in DI NCT1 rat astrocytes and hippocampal brain slices. We found that GABA induces a Ca²⁺-dependent increase in Cx43 hemichannel activity in astrocytes mediated by the GABA_A receptor, as it was blunted by the GABA_A receptor antagonist bicuculline but unaffected by GABA_B receptor antagonist {"type":"entrez-protein","attrs":{"text":"CGP55845","term_id":"875097176","term_text":"CGP55845"}}CGP55845. Moreover, GABA induced the Cx43 hemichannel-dependent release of glutamate and ATP, which was also prevented by bicuculline, but unaffected by CGP. Gliotransmission in response to GABA was also unaffected by pannexin 1 channel blockade. These results are discussed in terms of the possible role of astroglial Cx43 hemichannel-mediated glutamate and ATP release in regulating the excitatory/inhibitory balance in the brain and their possible contribution to psychiatric disorders.