Quantum mechanics as quantum information,mostly

Abstract

In this paper, I try to cause some good-natured trouble. The issue is, when will we ever stop burdening the taxpayer with conferences devoted to the quantum foundations? The suspicion is expressed that no end will be in sight until a means is found to reduce quantum theory to two or three statements of crisp physical (rather than abstract, axiomatic) significance. In this regard, no tool appears better calibrated for a direct assault than quantum information theory. Far from a strained application of the latest fad to a time-honoured problem, this method holds promise precisely because a large part—but not all—of the structure of quantum theory has always concerned information. It is just that the physics community needs reminding.     

An Automated Monitoring System for an Experimental Coal Gasifier

ABSTRACT

A data acquisition system has been developed for the analysis of the performance of an experimental reactor unit for coal gasification. Pertinent data such as gas concentrations, temperatures, and pressures at several locations inside the reactor, and the flow rate of supply gases are collected. An automated calibration procedure of the gas analysis system is included. A minicomputer controls the time sequences of the individual events, allowing a high degree of flexibility. The intervals between two gas analyses can be made as short as 30 sec, the other data can be taken arbitrarily often. The system is suitable for expansion to monitor more physical quantities and to increase the number of observation points inside the reactor.     

Microstructure and phase composition of cordierite-based co-clinker

The aim of this work is to study the effect of phase composition and microstructure of cordierite-based co-clinkers on the electrical properties and coefficient of thermal expansion of cordierite briquettes. To achieve this aim talc and kaolinite samples were collected from quarries in the Egyptian desert. The samples are characterized using XRD, XRF, polarized light, cathodoluminescence and SEM microscopy attached with EDAX, in addition to X-ray micro-computed tomography (3D- µXCT). The electrical properties and coefficient of thermal expansion of the cordierite briquettes are determined using HiTESTER instrument and automatic Netzsch DIL402 PC dilatometer, respectively.Five talc-based batches were shaped and fired in the temperature range 1000–1350 °C for 2 h. The microstructural and physical characteristics of the resulted cordierite-based co-clinkers depend mainly on the viscosity of the liquid phase developed during firing. The microchemistry of the cordierite briquettes confirms their enrichment of both cordierite and ferroan-cordierite crystallized directly from locally developed melts. The dielectric constant and loss factor values for cordierite briquettes allow their possible use as insulator components in electronic applications.     

Diffractive optical isolator made of high-efficiency dielectric gratings only

The working principle of an optical isolator made of two corrugated dielectric gratings is introduced. One grating acts as a polarizer, and the other acts as a quarter-wave plate used in conical incidence converting linearly polarized light into circularly polarized light. Global maxima of diffraction efficiency for surface-corrugated gratings with binary, sinusoidal, and pyramidal ridge shapes with dependence on the material index are identified. Regarding technological feasibility for use in the visible wavelength range, high-frequency gratings with a binary shape were realized. With these gratings, an extinction ratio of more than 40 dB for the polarizer is theoretically possible, and more than 20 dB was experimentally achieved. A good correlation between theoretically calculated efficiencies and birefringences based on rigorous methods and the experimental results is demonstrated.     

一种高精度超声测距方法的研究

本文介绍了一种基于超声波循环反射测量原理的高精度超声测距方法 ,并给出了以单片机为核心的测距系统的组成 .本测量法克服了多次反射法中对回波脉冲个数的限制 ,经温度补偿后测量精度得到了明显改善 .     

Explicit exact analysis of infinite periodic structures under general loading

This paper deals with the explicit analysis of infinite periodic structures under arbitrary loadings. In the context or structural stiffness optimization, with its inherent problem of multiple reanalysis, the purpose is to obtain expressions for the stress resultants anywhere in the infinite structure as an explicit function of the stiffnesses of the elements. Following the method of the representative cell the analysis of an infinite structures is reduced to the analysis of single module under transformed loading and boundary conditions by using the discrete Fourier transform. This produces the equilibrium, strain-displacements and constitutive equations in terms of complex-valued displacements, generalized strains and generalized stresses transforms. Next an existing formula is used to write the stress resultants transforms explicitly in terms of the stiffnesses. Finally one computes the stress resultants wherever needed in the real structure by means of the inverse Fourier transform. The exact formula for the stress resultants is usually impractical due to the large number of terms involved in the analytical expressions. What makes the approach practical herein is the very reduced size of the repeating module that is to be analysed, which renders the analytical formula more tractable in many cases. The technique is illustrated with the explicit analysis of an infinite truss with 1D translational symmetry and of an infinite grid of orthogonal beams on elastic supports with 2D translational symmetry. Received December 4, 2000     

Electronic Structure and Superconductivity of Nonmagnetic Transition Metal Borocarbides

The electronic structure of tetragonal (RC(N))_m(TB)₂, m=1–3, compounds, with R= Y,Lu,La, T=Ni,Pt is studied. Total and partial densities of states N(E) are calculated and compared with orbital resolved x-ray absorption data. Special attention is paid to the structure of N(E) near the Fermi-level and its consequences for thermodynamic properties in the superconducting and the normal states. A medium el-ph coupling constant 0.5 1.2 is found. There is no simple correlation between N(0) and T _c . The analysis of the upper critical field reveals the presence of at least two groups of electrons with quite different Fermi velocities v _F in accord with dHvA data, and with calculated distributions of v _F around the Fermi surface     

Stoichiometrically bound beta-carotene in the cytochrome b6f complex of oxygenic photosynthesis protects against oxygen damage

The cytochrome b6f complex of oxygenic photosynthesis carries out "dark reactions" of electron transfer that link the light-driven reactions of the reaction centers, and coupled proton transfer that generates part of the electrochemical potential utilized for ATP synthesis. In contrast to the bc1 complex of the respiratory chain, with which there are many structural and functional homologies, the b6f complex contains bound pigment molecules. Along with the specifically bound chlorophyll a previously found to be bound stoichiometrically in the dimeric b6f complex, it was found in the present study that beta-carotene is also present in the b6f complex at stoichiometric levels or nearly so. Chlorophyll and carotenoid pigments were quantitatively extracted from b6f complex purified from (i) the thermophilic cyanobacterium, Mastigocladus laminosus, (ii) spinach chloroplasts, and (iii) the green alga, Chlamydomonas reinhardtii. Visible and mass spectra showed the carotenoid to be a beta-carotene of molecular weight = 536, with a stoichiometry of 1. 0:1 relative to cytochrome f in the highly active M. laminosus complex but somewhat lower stoichiometries, 0.77 and 0.55, in the b6f complex obtained from spinach chloroplasts and C. reinhardtii. A photoprotective function for the beta-carotene was inferred from the findings that the rate of photobleaching of the chlorophyll a bound in the complex was found to vary inversely with beta-carotene content and to decrease markedly in the presence of ambient N2 instead of air. The presence of beta-carotene in the b6f complex, and not in the related bc1 complexes of the mitochondrial respiratory chain and photosynthetic bacteria, suggests that an additional function is to protect the protein complexes in oxygenic photosynthetic membranes against toxic effects of intramembrane singlet O2.     

Solution structure of the sodium channel inactivation gate

The sodium channel initiates action potentials by opening in response to membrane depolarization. Fast channel inactivation, which is required for proper physiological function, is mediated by a cytoplasmic loop proposed to occlude the ion pore via a hinged lid mechanism with the triad IFM serving as a hydrophobic "latch". The NMR solution structure of the isolated inactivation gate reveals a stably folded core comprised of an alpha-helix capped by an N-terminal turn, supporting a model in which the tightly folded core containing the latch motif pivots on a more flexible hinge region to occlude the pore during inactivation. The structure, in combination with substituted cysteine mutagenesis experiments, indicates that the IFM triad and adjacent Thr are essential components of the latch and suggests differing roles for the residues of the IFMT motif in fast inactivation.