The role of the cytoskeleton in capacitaftive calcium entry in myenteric glia

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73680/1/j.1365-2982.2003.00406.x.pd

Use of dead and living fungal biomass for removal of hexavalent chromium

The removal of hexavalent chromium from aqueous solution was carried out in batch experiments using dead and living biomass of Aspergillus niger. The effects of the operating parameters such as influent Cr(VI) concentration, influent pH and biomass concentration on the Cr(VI) reduction were investigated. The results indicates that the removal rate of Cr(VI) increased with a decrease in pH or with increase of Cr(VI) and biomass concentrations. For chromium bioaccumulation along with nutrients the process is the most intensive within the first 5 days of mycelium formation. For biosorption, the greatest binding of this metal is achieved within the first 4 days of the process

Biological removal of Cr(VI) ions from aqueous solutions by trichoderma viride

The paper presents biological removing of Cr(VI) ions from aqueous solution by applying autochtonic fungi seedling of Trichoderma viride originated from chromium mud samples. The growth of organism and removing of chromium(VI) was performed in aqueous solution of various chromium(VI) contents and at optimal value of pH. During 14 days of incubation, samples of 5 cm3 each were collected every day for determination of chromium(VI) in solution and the efficiency of biological removal was specified. Since removal of chromium(VI) from aqueous solution may occur because of reduction, biosorption or bioaccumulation processes, to determine which one occurred, the Cr(III) contents were determined in samples of the medium as well in ooze after mycelium irrigating and in mycelium

Hydroprocessing of Maya vacuum residue using a NiMo catalyst supported on Cr-doped alumina

6 figures, 7 tables.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Mesoporous alumina was doped with Cr using a co-precipitation method to prepare a support for hydrocracking catalysts. Ni and Mo were then impregnated on Cr-doped mesoporous alumina (NiMo/Al2O3-Cr). Catalytic activity was tested in hydrodeasphaltenisation (HDA), hydrodesulfurisation (HDS) and hydrodemetallisation (HDM) of Maya vacuum residue in a batch reactor and compared with NiMo supported on mesoporous alumina not doped with Cr (NiMo/Al2O3). Following activation and initial carbon deposition, experiments involving contact of the catalysts with fresh feed were performed. Greater HDA extent and maltene to asphaltene ratios were obtained with NiMo/Al2O3-Cr than NiMo/Al2O3 despite a larger amount of coke deposits. Significant activity of both NiMo/Al2O3-Cr and NiMo/Al2O3 towards HDS and HDM were also observed. Alumina textural properties remained relatively unaffected by the co-precipitation of Cr. X-ray photoelectron spectroscopy (XPS) showed that the catalysts contained Cr3+ and after reduction all Ni was present in metallic state at least in the near-surface region, while Mo6+ was reduced to Mo4+ and Moδ+ (0 ≤ δ ≤ 3) to a larger extent in NiMo/Al2O3-Cr. Lower reduction temperatures in the presence of Cr were determined, suggesting a larger number of metal sites available in reduced form at operating conditions. It was found that Cr aided metal dispersion in catalyst synthesis and coke dispersion during reaction. Spent catalysts showed reductions in surface area and pore volume. However, while spent NiMo/Al2O3 catalysts had a decrease in average pore diameter (APD), NiMo/Al2O3-Cr maintained the fresh material APD, which may explain the sustained catalytic activity.H.P. thanks the support of CONACYT Mexico for the award of her PhD grant. Founding from Skolkovo Foundation and BP through UNIHEAT Project is gratefully acknowledged.Peer reviewe

Electronic structure of zinc-blende Zn0.5Co0.5Se: theoretical study.

In this paper we present a comprehensive study of the tetrahedral semiconductor ZnSe crystallizing in the zincblende structure. The electronic structure of ZnSe has been determined first using the ab initio self-consistent linear muffin-tin orbital method with a local-density form of the exchange-correlation functional. Then it has been adjusted to reproduce the experimental energy positions of the Zn 3d bands and of the optical gap. The adjusted electronic structure, densities of states and interband optical properties are presented and compared with previous calculations. Good agreement with experimental photoemission and bremsstrahlung isochromat measurements was found after including an energy-dependent lifetime broadening. We measured the reflectivity of ZnSe with high resolution from 4 to 30 eV and the high-energy region of the spectra has been interpreted on the basis of the present calculation

Electronic structure of zincblende ZnSe: theory and experiment

In this paper we present a comprehensive study of the tetrahedral semiconductor ZnSe crystallizing in the zincblende structure. The electronic structure of ZnSe has been determined first using the ab initio self-consistent linear muffin-tin orbital method with a local-density form of the exchange-correlation functional. Then it has been adjusted to reproduce the experimental energy positions of the Zn 3d bands and of the optical gap. The adjusted electronic structure, densities of states and interband optical properties are presented and compared with previous calculations. Good agreement with experimental photoemission and bremsstrahlung isochromat measurements was found after including an energy-dependent lifetime broadening. We measured the reflectivity of ZnSe with high resolution from 4 to 30 eV and the high-energy region of the spectra has been interpreted on the basis of the present calculation

The influence of transition metals on the electronic structure of ZnSe host crystal: fundamental reflectivity analysis

The optical properties of the semiconducting compounds Zn1-xMexSe (Me = Ti, V, Cr, Mn, Fe, Co, and Ni) crystallizing in the zinc-blende structure have been investigated. Reflectivity spectra of these materials have been taken at room and liquid nitrogen temperatures. The measurements have been performed in the 4-25 eV energy range using synchrotron radiation from the ADONE storage ring in Frascati. Comparisons between the reflectivity spectra of the ternary systems and those of the host crystal ZnSe have been made, and models explaining the influence of the transition metal ions on the electronic structure of the host crystal ZnSe have been discussed

Inactivation and tachyphylaxis of heat-evoked inward currents in nociceptive primary sensory neurones of rats

Membrane currents evoked by repeated noxious heat stimuli (43–47 °C) of 3 s duration were investigated in acutely dissociated dorsal root ganglion (DRG) neurones of adult rats. The heat stimuli generated by a fast solution exchanger had a rise time of 114 ± 6 ms and a fall time of 146 ± 13 ms.When heat stimuli were applied to heat-sensitive small (≤ 32·5 μm) DRG neurones, an inward membrane current (Iheat) with a mean peak of 2430 ± 550 pA was observed (n = 19). This current started to activate and deactivate with no significant latency with respect to the heat stimulus. The peak of Iheat was reached with a rise time of 625 ± 115 ms. When the heat stimulus was switched off Iheat deactivated with a fall time of 263 ± 17 ms.During constant heat stimulation Iheat decreased with time constants of 4–5 s (inactivation). At the end of a 3 s heat stimulus the peak current was reduced by 44 ± 5 % (n = 19).Current-voltage curves revealed outward rectifying properties of Iheat and a reversal potential of −6·3 ± 2·2 mV (n = 6). Inactivation was observed at all membrane potentials investigated (−80 to 60 mV); however, inactivation was more pronounced for inward currents (37 ± 5 %) than for outward currents (23 ± 6 %, P < 0·05).When neurones were investigated with repeated heat stimuli (3 to 5 times) of the same temperature, the peak current relative to the first Iheat declined by 48 ± 6 % at the 3rd stimulus (n = 19) and by 54 ± 18 % at the 5th stimulus (n = 4; tachyphylaxis).In the absence of extracellular Ca2+ (buffered with 10 mm EGTA) inactivation (by 53 ± 6 %) and tachyphylaxis (by 42 ± 7 % across three stimuli) were still observed (n = 8). The same was true when intracellular Ca2+ was buffered by 10 mm BAPTA (inactivation by 49 ± 4 %, tachyphylaxis by 52 ± 7 % across three stimuli; n = 13). Thus, inactivation and tachyphylaxis were mainly independent of intra- and extracellular Ca2+.These results indicate that inactivation and tachyphylaxis of heat-evoked inward currents can be observed in vitro, similar to adaptation and suppression of action potential discharges elicited by comparably fast heat stimuli in vivo. Whereas the voltage dependence of Iheat resembles that of capsaicin-induced membrane currents (ICaps), the independence of inactivation and tachyphylaxis of Iheat from calcium is in clear contrast to ICaps. A similar difference in calcium dependence of inactivation has been reported between heat-evoked and capsaicin-induced currents through the cloned capsaicin receptor channel VR1. Thus, the properties of Iheat and of VR1 largely account for the adaptation and suppression of heat-evoked nociceptor discharges