Stability shear stress and equilibrium cross-sectional geometry of sheltered tidal channels

This study relates tidal channel cross-sectional area (A) to peak spring discharge (Q) via a physical mechanism, namely the stability shear stress ( tau sub(S)) just necessary to maintain a zero gradient in net along-channel sediment transport. It is assumed that if bed shear stress ( tau ) is greater than tau sub(S), net erosion will occur, increasing A, and reducing tau similar to (Q/A) super(2) back toward tau sub(S). If tau < tau sub(S) there will be net deposition, reducing A and increasing tau toward tau sub(S). A survey of the literature allows estimates of Q and A at 242 sections in 26 separate sheltered tidal systems. Assuming a single value of tau sub(S) characterizes the entire length of a given tidal channel, it is predicted that along-channel geometry will follow the relation Ah sub(R) super(1) super(/) super(6) similar to Q. Along-channel regressions of the form Ah sub(R) super(1) super(/) super(6) similar to Q super( beta ) give a mean observed value for beta of 1.00 plus or minus 0.06, which is consistent with this concept. Results indicate that a lower bound on tau sub(S) (and an upper bound on A) for stable channels is provided by the critical shear stress ( tau sub(C)) just capable of initiating sediment motion. Observed tau sub(S) is found to vary among all systems as a function of spring tidal range (R sub(sp)) according to the relation tau sub(S) approximately 2.3 R sub(sp) super(0.79) tau sub(C). Observed deviations from uniform tau sub(S) along individual channels are associated with along-channel variation in the direction of maximum discharge (i.e., flood-versus ebb-dominance).

A ternary supramolecular compound of p-sulfonatocalix[8]arene with 1D channels

A ternary supramolecular complex of [Ni(bipy)(2)(H2O)](4)(C8AS)center dot 17.6(H2O) (bipy=4,4'-dimethyl-2,2'-bipyridine and C8AS = p-sulfonatocalix[8]arene) has been synthesized by a hydrothermal method and characterized by FT-IR spectroscopy, TG-DTA analysis and single crystal X-ray diffraction. In the structure. the water-soluble p-sulfonatocalix[8]arene molecule adopts a double partial cone conformation and is coordinated by four nickel atoms each of which is bonded by two 4,4'-dimethyl-2,2'-bipyridine molecules and one water molecule at the same time. The tetranuclear Subunits are stacked into an extended 3D structure with 1D water-filled channels via hydrogen bonds and C-H center dot center dot center dot pi interactions.

Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis

By incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C-2']picolinate (Flrpic) for blue emission and bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1 H-benzoimidazol-N,C-3) iridium(acetylacetonate) ((fbi)(2)Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5 lm W-1, corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8 cd A(-1). Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density-voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of Flrpic and (fbi)(2)Ir(acac) are, respectively, host-guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses.

PH-Dependent syntheses and structures of two Copper(II)/Phenanthroline/p-Sulfonatocalix[4]arene supramolecular compounds with 1D water-filled channels

Two copper-organic framework supramolecular assemblies of p-sulfonatocalix[4]arene and 1,10-phenanthroline Cu-2[C12H8N2][C28H20S4O16][H2O](23.5) (1) and Cu-3[C12H8N2](3)[C28H19S4O16]Cl[H2O](17.6) (2) were obtained by pH-dependent synthesis at room temperature. Both structures show ID water-filled channels (rectangular shape in I and triangular in 2) with the solvent-accessible volume occupying 30.8% (1) and 24.2% (2) of the unit-cell volume, respectively. The calixarene molecules in both structures assume analogous cone shapes of C-2 nu symmetry instead of the conventional C-4 nu symmetry. Their connecting to different amounts of copper/phenanthroline cations leads to the formation of different structures.

Synthesis and structure of a novel open-framework zincophosphate with intersecting three-dimensional helical channels

A new open-framework zincophosphate, Zn-0.5(H2PO4).0.5H(2)O (denoted as FJ-13), possessing intersecting three-dimensional helical channels, has been synthesized under solvothermal conditions.

Electrochemical study of gramicidin D forming ion-permeable channels in the bilayer lipid membranes

Gramicidin within the lipid bilayer matrix is a well-known channel-forming polypeptide, but the mechanism of the ions across the membrane induced by gramicidin is not well understood. We found that at very low concentration of gramicidin in a bilayer lipid membrane, the channel behavior was controlled by the voltage applied across the membrane. When the voltage is higher than 75 mV, the channel is closing, while lower than 75 mV, the channel is opening. But when the concentration of the gramicidin in the BLMs is high, the channel behavior is changed into voltage-independent. (C) 1998 Elsevier Science Ltd. All rights reserved.

INVESTIGATION ON SELECTIVE DOPING OF POLYANILINE ENCAPSULATED IN THE CHANNELS OF ZEOLITE MOLECULAR-SIEVES

The aniline encapsulated in the channels of zeolite molecular sieves was polymerized electrochemically. The doping reaction of polyaniline was studied in 12-Molybdophosphoric acid and sulfuric acid solution. The results indicate the zeolite modified ele

Improving Ship Detection with Polarimetric SAR based on Convolution between Co-polarization Channels

The convolution between co-polarization amplitude only data is studied to improve ship detection performance. The different statistical behaviors of ships and surrounding ocean are characterized a by two-dimensional convolution function (2D-CF) between different polarization channels. The convolution value of the ocean decreases relative to initial data, while that of ships increases. Therefore the contrast of ships to ocean is increased. The opposite variation trend of ocean and ships can distinguish the high intensity ocean clutter from ships' signatures. The new criterion can generally avoid mistaken detection by a constant false alarm rate detector. Our new ship detector is compared with other polarimetric approaches, and the results confirm the robustness of the proposed method.

Study on the GABA gated channels in the neurosecretory cells of MTXO in the eyestalks of Eriocheir sinensis

The responses to rapid application of gamma-aminobutyric acid (GABA) and the GABA receptor characteristics of MTXO neurosecretory cells in the eyestalks of Chinese mitten-handed crab (Eriocheir sinensis) were examined by whole-cell patch clamp. Under current clamp mode, the depolarization and hyperpolarization were evoked from the three types of neurosecretory cells in response to the GABA (0.1 mmol/L) depending on the Nernst Cl- potential. Under voltage clamp mode, the inward Cl- channel currents (I-GABA) were resolved from all three types of neurosecretory cells in response to GABA (0.01similar to5 mmol/L). The GABA currents were activated within 1 200 ms and peaked within 800 ms. No obviously desensitization was observed during GABA application. The dose-response curve showed usual S-shape, with a just-discernible effect at 0.01 mmol/L and near-saturation at 0.5 mmol/L. The GABA currents had reversal potentials that followed Nernst Cl- potentials when [Cl-] was varied. The pharmacological results revealed that the GABA receptor of the crab neurosecretory cells was sensitive to the Cl- channel blockers picrotoxin and niflumic acid (0.5 mmol/L), insensitive to GABA(A) receptor antagonist bicuculline and GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA 1 mmol/L) and trans-4-aminocrotonic (TACA 1 mmol/L).

GABAA receptor chloride channels are involved in the neuroprotective role of GABA following oxygen and glucose deprivation in the rat cerebral cortex but not in the hippocampus.

Assays on "ex vivo" sections of rat hippocampus and rat cerebral cortex, subjected to oxygen and glucose deprivation (OGD) and a three-hour reperfusion-like (RL) recovery, were performed in the presence of either GABA or the GABA(A) receptor binding site antagonist, bicuculline. Lactate dehydrogenase (LDH) and propidium iodide were used to quantify cell mortality. We also measured, using real-time quantitative polymerase chain reaction (qPCR), the early transcriptional response of a number of genes of the glutamatergic and GABAergic systems. Specifically, glial pre- and post-synaptic glutamatergic transporters (namely GLAST1a, EAAC-1, GLT-1 and VGLUT1), three GABAA receptor subunits (α1, β2 and γ2), and the GABAergic presynaptic marker, glutamic acid decarboxylase (GAD65), were studied. Mortality assays revealed that GABAA receptor chloride channels play an important role in the neuroprotective effect of GABA in the cerebral cortex, but have a much smaller effect in the hippocampus. We also found that GABA reverses the OGD-dependent decrease in GABA(A) receptor transcript levels, as well as mRNA levels of the membrane and vesicular glutamate transporter genes. Based on the markers used, we conclude that OGD results in differential responses in the GABAergic presynaptic and postsynaptic systems.

Formation of channels for fast-ion diffusion in alkali silicate melts: A quasielastic neutron scattering study

Kargl, Florian; Meyer, A.; Koza, M.M.; Schober, H., (2006) 'Formation of channels for fast-ion diffusion in alkali silicate melts: A quasielastic neutron scattering study', Physical Review B: Condensed Matter and Materials Physics 74 pp.14304 RAE2008

Parallel Auditory Filtering By Sustained and Transient Channels Separates Coarticulated Vowels and Consonants

A neural model of peripheral auditory processing is described and used to separate features of coarticulated vowels and consonants. After preprocessing of speech via a filterbank, the model splits into two parallel channels, a sustained channel and a transient channel. The sustained channel is sensitive to relatively stable parts of the speech waveform, notably synchronous properties of the vocalic portion of the stimulus it extends the dynamic range of eighth nerve filters using coincidence deteectors that combine operations of raising to a power, rectification, delay, multiplication, time averaging, and preemphasis. The transient channel is sensitive to critical features at the onsets and offsets of speech segments. It is built up from fast excitatory neurons that are modulated by slow inhibitory interneurons. These units are combined over high frequency and low frequency ranges using operations of rectification, normalization, multiplicative gating, and opponent processing. Detectors sensitive to frication and to onset or offset of stop consonants and vowels are described. Model properties are characterized by mathematical analysis and computer simulations. Neural analogs of model cells in the cochlear nucleus and inferior colliculus are noted, as are psychophysical data about perception of CV syllables that may be explained by the sustained transient channel hypothesis. The proposed sustained and transient processing seems to be an auditory analog of the sustained and transient processing that is known to occur in vision.

Simulation of multigate SOI transistors with silicon, germanium and III-V channels

In this work by employing numerical three-dimensional simulations we study the electrical performance and short channel behavior of several multi-gate transistors based on advanced SOI technology. These include FinFETs, triple-gate and gate-all-around nanowire FETs with different channel material, namely Si, Ge, and III-V compound semiconductors, all most promising candidates for future nanoscale CMOS technologies. Also, a new type of transistor called “junctionless nanowire transistor” is presented and extensive simulations are carried out to study its electrical characteristics and compare with the conventional inversion- and accumulation-mode transistors. We study the influence of device properties such as different channel material and orientation, dimensions, and doping concentration as well as quantum effects on the performance of multi-gate SOI transistors. For the modeled n-channel nanowire devices we found that at very small cross sections the nanowires with silicon channel are more immune to short channel effects. Interestingly, the mobility of the channel material is not as significant in determining the device performance in ultrashort channels as other material properties such as the dielectric constant and the effective mass. Better electrostatic control is achieved in materials with smaller dielectric constant and smaller source-to-drain tunneling currents are observed in channels with higher transport effective mass. This explains our results on Si-based devices. In addition to using the commercial TCAD software (Silvaco and Synopsys TCAD), we have developed a three-dimensional Schrödinger-Poisson solver based on the non-equilibrium Green’s functions formalism and in the framework of effective mass approximation. This allows studying the influence of quantum effects on electrical performance of ultra-scaled devices. We have implemented different mode-space methodologies in our 3D quantum-mechanical simulator and moreover introduced a new method to deal with discontinuities in the device structures which is much faster than the coupled-mode-space approach.

Interaction between 3’,5’-cyclic monophosphate, volume-regulated anion channels and the Na+-HCO3- cotransporter NBCe1 in the regulation of nutrient- and hypotonicity-induced insulin release from rat pancreatic islets and tumoral insulin-producing BRIN-BD11 cells

info:eu-repo/semantics/published