耒宜高速公路路堑边坡变形破坏特征及其综合治理

耒宜高速公路修建于山岭重丘区 ,沿线地形、地质条件差异较大 ,路堑开挖边坡类型较多 ,特征不一。本文介绍了路堑边坡的主要特征、边坡失稳的主要原因及治理对策。     

The microwave heating of two-dimensional slabs with small Arrhenius absorptivity

The microwave heating of two-dimensional slabs in a long rectangularwaveguide propagating the TE₁₀ mode is examined. The temperaturedependency of the electrical conductivity and the thermal absorptivityis assumed to be governed by the Arrhenius law, while both theelectrical permittivity and the magnetic permeability are assumedconstant. The governing equations are the forced heat equationand the steady-state version of Maxwell's equation while theboundary conditions take into account both convective and radiativeheat loss. Approximate analytical solutions, valid for smallthermal absorptivity, are found for the temperature and theelectric-field amplitude using the Galerkin method. As the Arrheniuslaw is not amenable analytically, it is approximated by a rational-cubicfunction. At the steady state the temperature versus power relationshipis found to be multivalued; at the critical power level thermalrunaway occurs when the temperature jumps from the lower (cool)temperature branch to the upper (hot) temperature branch ofthe solution. In the steady-state limit the approximate analyticalsolutions are compared with the numerical solutions of the governingequations for various special cases. These are the limits ofsmall and large heat loss and an intermediate case involvingradiative heat loss. Results are also presented for a case wheredifferential cooling occurs on the different sides on the slab.An alternative heating scenario, where one end of the waveguideis blocked by a short, is also considered. The approximate solutionsare found for this geometry and compared in the small Biot-numberlimit to Kriegsmann (1997). Also, a control process is presented,which allows thermal runaway to be avoided and the desired finalsteady state to be reached. Various special cases of the feedbackparameters associated with the control process are examined.     

New routes to low-coordinate iron hydride complexes: The binuclear oxidative addition of H2

The oxidative addition and reductive elimination reactions of H₂ on unsaturated transition-metal complexes are crucial in utilizing this important molecule. Both biological and man-made iron catalysts use iron to perform H₂ transformations, and highly unsaturated iron complexes in unusual geometries (tetrahedral and trigonal planar) are anticipated to give unusual or novel reactions. In this paper, two new synthetic routes to the low-coordinate iron hydride complex [L^tBuFe(μ-H)]₂ are reported. Et₃SiH was used as the hydride source in one route by taking advantage of the silaphilicity of the fluoride ligand in three-coordinate L^tBuFeF. The other synthetic method proceeded through the binuclear oxidative addition of H₂ or D₂ to a putative Fe(I) intermediate. Deuteration was verified through reduction of an alkyne and release of the deuterated alkene product. Mössbauer spectra of [L^tBuFe(μ-H)]₂ indicate that the samples are pure, and that the iron(II) centers are high-spin.     

Evidence that microbially produced alkaline materials are involved in coal biosolubilization

Applied Biochemistry and Biotechnology - The biosolubilities (susceptibility to being attacked and solubilized by microbes) of 17 coals by 9 microbes were evaluated, as were solubilities of these...     

Dynamic monitoring of glucagon secretion from living cells on a microfluidic chip

A rapid microfluidic based capillary electrophoresis immunoassay (CEIA) was developed for on-line monitoring of glucagon secretion from pancreatic islets of Langerhans. In the device, a cell chamber containing living islets was perfused with buffers containing either high or low glucose concentration. Perfusate was continuously sampled by electroosmosis through a separate channel on the chip. The perfusate was mixed on-line with fluorescein isothiocyanate-labeled glucagon (FITC-glucagon) and monoclonal anti-glucagon antibody. To minimize sample dilution, the on-chip mixing ratio of sampled perfusate to reagents was maximized by allowing reagents to only be added by diffusion. Every 6 s, the reaction mixture was injected onto a 1.5-cm separation channel where free FITC-glucagon and the FITC-glucagon–antibody complex were separated under an electric field of 700 V cm⁻¹. The immunoassay had a detection limit of 1 nM. Groups of islets were quantitatively monitored for changes in glucagon secretion as the glucose concentration was decreased from 15 to 1 mM in the perfusate revealing a pulse of glucagon secretion during a step change. The highly automated system should be enable studies of the regulation of glucagon and its potential role in diabetes and obesity. The method also further demonstrates the potential of rapid CEIA on microfluidic systems for monitoring cellular function.     

Electric quadrupole moments and strong interaction effects in pionic atoms of 165Ho, 175Lu, 176Lu, 179Hf and 181Ta

The effective quadrupole moments Q_eff of the nuclei of ¹⁶⁵Ho, ¹⁷⁵Lu, ¹⁷⁶Lu, ¹⁷⁹Hf and ¹⁸¹Ta were accurately measured by detecting the pionic atom 5g-4f X-rays of the elements. The spectroscopic quadropole moments, Q_spec, were obtained by correcting Q_eff for nuclear finite size effect, distortion of the pion wave function by the pion-nucleus strong interaction, and contribution to the energy level splittings by the strong interaction. The intrinsic quadrupole moments, Q₀, were obtained by projecting Q_spec into the frame of reference fixed on the nucleus. The shift, ε₀, and broadening, Γ₀, of the 4f energy level due to the strong interaction between the pion and the nucleons for all the elements were also measured. Theoretical values of ε₀ and Γ₀ were calculated and compared to the experimental values. The measured values of Q₀ were compared with existing results in muonic and pionic atoms. The measured values of ε₀ and Γ₀ were also compared with existing values.     

Rotational excitations in residual nuclei produced by stopped negative pions on targets of Ho, Lu, Lu, Hf, and Ta

Reactions produced by stopped negative pions on targets of ¹⁶⁵Ho, ¹⁷⁵Lu, ¹⁷⁶Lu, ¹⁷⁹Hf, and ¹⁸¹Ta are investigated by measuring photons coincident with the stopped pions. These photons were detected with an 80 cm³ Ge(Li) detector and identified as pionic X-rays or rotational γ-rays from the residual nuclei. Pion capture is found to result in the excitation of high-spin states. Yields for the residual nuclei are inferred from the observed γ-transitions and compared to calculations based on the exciton model for pre-equilibrium emission followed by particle evaporation. Preliminary results of a pion stop, γn coincidence experiment are presented and compared to the calculations.     

Bi-directional modulation of AMPA receptor unitary conductance by synaptic activity

Background  

Knowledge of how synapses alter their efficiency of communication is central to the understanding of learning and memory. The most extensively studied forms of synaptic plasticity are long-term potentiation (LTP) and its counterpart long-term depression (LTD) of AMPA receptor-mediated synaptic transmission. In the CA1 region of the hippocampus, it has been shown that LTP often involves a rapid increase in the unitary conductance of AMPA receptor channels. However, LTP can also occur in the absence of any alteration in AMPA receptor unitary conductance. In the present study we have used whole-cell dendritic recording, failures analysis and non-stationary fluctuation analysis to investigate the mechanism of depotentiation of LTP.