Self-powered sensor for naked-eye detection of serum trypsin

Here, we report a device for the detection of the proteolytic enzyme trypsin, which is a biomarker for pancreatitis. The sensor is self-powered, easy to use, and signals the presence of trypsin via a light-emitting diode (LED) that is visible to the unaided eye. Assay time is ～3 h, and the limit of detection is 0.5 μg/mL, which is within the range required for detection of trypsin at levels signaling acute pancreatitis. The sensing mechanism relies on trypsin digestion of a gelled protein layer. Partial digestion of the protein layer permits hydroxide penetration and subsequent etching of an underlying Al membrane. Degradation of both the protein and Al layers exposes an underlying Mg anode and closes an electrochemical circuit that produces ～2.2 V. This is sufficient voltage to illuminate the LED. A logarithmic relationship is observed between the time required for LED illumination and trypsin concentration. The device is equally effective for trypsin dissolved in buffer or serum media.     

Role of a disperse carbon interlayer on the performances of tandem a-Si solar cells

Abstract

We report the effect of a disperse carbon interlayer between the n-a-Si:H layer and an aluminium zinc oxide (AZO) back contact on the performance of amorphous silicon solar cells. Carbon was incorporated to the AZO film as revealed by x-ray photoelectron spectroscopy and energy-dispersive x-ray analysis. Solar cells fabricated on glass substrates using AZO in the back contact performed better when a disperse carbon interlayer was present in their structure. They exhibited an initial efficiency of 11%, open-circuit voltage V_oc = 1.6 V, short-circuit current J_SC = 11 mA cm^?2 and a filling factor of 63%, that is, a 10% increase in the J_SC and 20% increase in the efficiency compared to a standard solar cell.     

Layered rare-earth hydroxide and oxide nanoplates of the Y/Tb/Eu system: phase-controlled processing,structure characterization and color-tunable photoluminescence via selective excitation and efficient energy transfer

Abstract

Well-crystallized (Y_0.97?xTb_0.03Eu_x)₂(OH)₅NO₃·nH₂O (x = 0–0.03) layered rare-earth hydroxide (LRH) nanoflakes of a pure high-hydration phase have been produced by autoclaving from the nitrate/NH₄OH reaction system under the optimized conditions of 100 °C and pH ～7.0. The flakes were then converted into (Y_0.97?xTb_0.03Eu_x)₂O₃ phosphor nanoplates with color-tunable photoluminescence. Detailed structural characterizations confirmed that LRH solid solutions contained NO₃^? anions intercalated between the layers. Characteristic Tb³⁺ and Eu³⁺ emissions were detected in the ternary LRHs by selectively exciting the two types of activators, and the energy transfer from Tb³⁺ to Eu³⁺ was observed. Annealing the LRHs at 1100 °C produced cubic-lattice (Y_0.97?xTb_0.03Eu_x)₂O₃ solid-solution nanoplates with exposed 222 facets. Multicolor, intensity-adjustable luminescence was attained by varying the excitation wavelength from ～249 nm (the charge transfer excitation band of Eu³⁺) to 278 nm (the 4f⁸–4f⁷5d¹ transition of Tb³⁺). Unitizing the efficient Tb³⁺ to Eu³⁺ energy transfer, the emission color of (Y_0.97?xTb_0.03Eu_x)₂O₃ was tuned from approximately green to yellowish-orange by varying the Eu³⁺/Tb³⁺ ratio. At the optimal Eu³⁺ content of x = 0.01, the efficiency of energy transfer was ～91% and the transfer mechanism was suggested to be electric multipole interactions. The phosphor nanoplates developed in this work may be incorporated in luminescent films and find various lighting and display applications.     

Directionality from anisotropic phonon production in solid state dark matter detection

We present results from computer simulations of the events immediately following the scattering of a dark matter particle off a nucleus in a crystal detector. Our simulations show that with NaF as the target, the recoil produces solitary waves that decay slowly, resulting in a narrow wake of phonons. The phonon wake allows a determination of direction of the nuclear recoil.     

Rheology of polypropylene in the solid state

The tensile behaviour of a commercial grade of isotactic polypropylene was tested in a temperature range between 20 and 150 °C with a video-controlled testing system which is capable of imposing a constant true strain-rate within the neck automatically. The results are displayed in the form of effective stress-strain curves and modelled by a constitutive equation in a multiplicative form. It is thus shown that, for each temperature, the plastic response can be described up to very large strains ( 2.0) by a set of four parameters. The assumptions introduced in this modelling are critically discussed in order to check the validity of the simplifying hypotheses (strain homogeneity, isochoric deformation, etc.). The constitutive equation thus obtained was utilized in a finite difference code in order to predict the development of stretching instabilities of polypropylene. The simulation gives access to the engineering stress-strain response of the stretched test piece and to the detailed kinetics of the incipient neck. It is found that the severity of the instabilities is less at room temperature than near the melting point because of the decrease of the strain-hardening and of the strain-rate sensitivity with temperature.     

Study of omeprazole-gamma-cyclodextrin complexation in the solid state

The possibility of obtaining inclusion complexes between omeprazole (OME) and γ-cyclodextrin (γ-CD) by kneading, spray-drying, coprecipitation, and freeze-drying was evaluated. All these methods lead to the isolation of a true inclusion compound, as evidenced by differential scanning calorimetry (DSC), infrared spectroscopy, and X-ray diffractometry on powder (PXRD). Moreover, PXRD and scanning electron microscopy (SEM) afforded data concerning crystallinity and surface characteristics of the solid phases obtained. In all cases, a significant increase of the release rate with respect to the drug alone was found, and it was attributed to the formation of an inclusion compound. Among the solid phases obtained, the coprecipitated product presented the highest dissolution rate.     

Relevance of liquid state to solid state properties

We outline in this talk the beginning of a new programme to study physical properties of crystalline solids. It is based on considering the latter, a broken symmetry phase, in terms of the higher symmetry liquid phase. The solid is a calculable perturbation on the fluid. This is exactly opposite to the standard approach which relates mechanical properties to the behaviour of defects (mainly dislocations) etc., in an otherwise perfect crystalline solid. However, most other broken symmetry phases (e.g. ferromagnets) are discussed starting from a symmetric Hamiltonian or a free energy functional, and earlier work by one of the authors shows that the liquid-solid transition is well described, qualitatively and quantitatively, by this approach. On the other hand, defect theories of melting have a long record of nonsuccess. In the first part of the talk, the density wave theory of freezing will be outlined, and it will be shown how properties such as Debye Waller factor, entropy change of freezing etc. can be calculated with no or one free parameter. The problem of calculating shear elastic constants and dislocation core structures as well as energies in terms only of observable liquid state properties will be set up, and results presented. The method will be contrasted with zero temperature ‘atomistic’ models which obscure the essential dependence on structure and flounder in a mass of detail. The concluding part will describe further proposed applications, some suggestive experimental results extant in the literature, and some speculations. Only a summary is presented.     

The rotating solid disk in the fully plastic state

Subject of the investigation is the distribution of stress, displacement, and plastic strain in a rotating solid disk of elastic-plastic material with linear strain-hardening in the fully plastic state. In order to obtain a realistic model of the rotating disk one may not neglect hardening. Since the onset of plastic flow occurs at the axis of the disk the corresponding image-point lies in a corner of Tresca's hexagon. As in related cases, the plastic zone of the rotating disk is composed of two parts, the image points of the outer part lying on one side of the hexagon. It is demonstrated that the boundary between the two regions approaches a limit for unbounded growth of the angular velocity. Residual stress remaining in the disk after the standstill is discussed.     

Elastic stiffness of crystalline cellulose in the folded-chain solid state

In previous papers the axial stiffness of crystalline native cellulose has been calculated for two proposed configurations of the cellulose chains within the elementary fibrils: an extended chain configuration, and a configuration in which the chains are folded to form a ribbon which in turn is helically wound into a rather open, spring-like structure. In the present paper two additional folded-chain configurations are treated: a more tightly wound helical configuration in which axial secondary bonds are formed between adjacent turns of the helix; and a configuration in which the chains are folded rather infrequently and remain in a fully-dense close-packed arrangement. It is shown that this last configuration is mechanically equivalent to the extended chain configuration so far as axial stiffness is concerned, and that either helical configuration has a substantially lower axial stiffness than that of the extended chain.The investigation reported in this paper (No. 69-8-64) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Effect of water on monetite synthesis in the solid state

Synthesis of calcium hydrogen phosphate CaHPO₄ can be carried out with a milling apparatus into which solid calcium dihydrogen phosphate Ca(H₂PO₄)₂.H₂O and tricalcium phosphate Ca₃(PO₄)₂.1/6H₂O mixtures are introduced. The effect of water vapor pressure P_H2O on this reaction has been investigated. At a given temperature (60°C) the curves of degree of conversion as a function of milling time depend on P_H2O. Formation of brushite CaHPO₄.2H₂O during the course of reaction can be noted for a particular range of water vapor pressure.If some amounts of brushite are added to the initial mixture, the kinetics of the reaction developed under water vapor are increased. Experiments on the evolution of products after a milling treatment give evidence of the important dependence of the reaction rate on water vapor pressure.     

Quantum computing in the solid state: the challenge of decoherence

The current status of solid-state implementations of quantum computing is briefly described. There are numerous candidate proposals, but only comparatively recently have some of them begun to progress to the point of demonstrating coherent motion of the individual quantum bits (qubits), and the controlled coupling of more than one qubit remains a significant challenge. We also present a generalization of the fluctuation-dissipation theorem that provides a relationship between the coherent evolution entangling two spatially separated qubits, and the associated irreducible decoherence. This relationship may be used to bound the maximum attainable figures of merit in proposed two-qubit gates.     

A solid state Pomeranchuk refrigerator

Recently we have shown that YbInCu₄ and related compounds present a solid state Pomeranchuk effect. At their first order volume transition, a local moment phase coexist with a renormalized Fermi liquid in analogy with ³He at its melting curve. This structural transition can be affected by pressure and magnetic field. We show here that as in ³He the Pomeranchuk effect can be used to produce cooling. We discuss the efficiency and different ways of implementing the solid state Pomeranchuk refrigerator.     

火灾条件下气溶胶灭火剂固体微粒沉降过程分析

对火灾下气溶胶灭火剂固体微粒的空间分布特点及沉降过程进行了非稳态分析,给出了微粒粒径对其运动状态的影响特征,对固体微粒在流场中的稳定性及滞留时间进行了研究,获得了微粒到达火源表面的临界粒径表达式。结果表明,微粒沉降过程其沉降的雷诺数与粒子直径相关,且基本处于低雷诺数状态,沉降速度与微粒粒径的平方成正比。当微粒直径小于100μm时,将在很短时间内达到相对稳定的流动状态;当微粒直径达到1μm时,可在空间中长期滞留,并通过卷吸进入火焰区域,达到灭火的效果。     

Material state remapping in computational solid mechanics

A computational procedure for remapping material state information from one finite element mesh to another is described. The procedure is useful in connection with evolving meshes for inelastic problems, as for example occur in the context of fracture simulation and adaptive mesh refinement. The proposed method is based on weak enforcement of equality between corresponding fields on the two meshes, where piecewise‐constant fields on both meshes are generalized from the quadrature‐point values. The essential algorithmic problem is that of calculating the volume partition of an arbitrary convex region with respect to a covering set of disjoint convex regions. Instead of geometrically resolving the associated intersections, the problem is herein approximated by a constrained optimization problem, which may be readily and efficiently solved computationally. This formulation is a main contribution of the paper. Computational examples are given that illustrate the effectiveness of the proposed procedure. Copyright © 2002 John Wiley & Sons, Ltd.     

Stress-strain state of solid railway wheels

A method for the design of railway wheels, which is based on use of the semianalytical finite-element method and which makes it possible to account for both the forces of contact interaction between the wheel and rail and negative production clearance during the press fitting of wheels, is developed.Translated from Problemy Prochnosti, No. 10, pp. 75–78, October, 1990.     

Role of stacking faults in solid state transformations

This article illustrates the two different roles played by stacking faults in solid state transformations viz. (i) in accommodating part of the transformation strains as observed in the noble metal-based alloys undergoing martensitic transformations, and (ii) in providing a mechanism for changing the stacking sequence of layers in a variety of materials like SiC, ZnS, Co and its alloys, and certain steels. Diffraction patterns taken from the martensitic phases of noble-metal-based alloys as well as from SiC and ZnS crystals undergoing transformation from one close-packed modification to another reveal the presence of characteristic diffuse streaks. It is shown that from a theoretical analysis of the observed intensity distribution along streaked reciprocal lattice rows in terms of physically plausible models for the geometry and distribution of faults, one can make a choice between various possible routes for transformation. From simple computer simulation studies, it is shown that the observed arrest of transformations in SiC is essentially due to the insertion of stacking faults in a random space and time sequence leading to an irregular distribution of solitons.