New thermoelastic technique for detection of residual stress distribution in solids

I.IntroductionNondestructiveeva1uationofstressdistributioninmaterialandmovingor1oadedcompo-nentsisveryimportantinmaterialscienccandengineering.Theultrasonictechnique['l,Ramanspectroscope['l,X-ray['landneutrondiffrac1iontcchnique[4]areusua1lyusedtodetectthestressdistributioninanopaquesample.RecentlytheScanningE1ectronAcousticMicroscopy(SEAM)[s]andphotoacoustictcchniquc[6]havebccnrcportedasncwtechniquetodeterminetheresidualstressdistribution.Itisshownthatthethermalwavealsocanbeusedtomcasure…     

Empirical mathematical model for dynamic manganese-enhanced MRI of the murine pancreas for assessment of β-cell function

Autoimmune ablation of pancreatic β-cells and alteration of its microvasculature may be a predictor of Type I diabetes development. A dynamic manganese-enhanced MRI (MEMRI) approach and an empirical mathematical model were developed to monitor whole pancreatic β-cell function and vasculature modifications in mice. Normal and streptozotocin-induced diabetic FVB/N mice were imaged on a 9.4 T MRI system using a 3D magnetization prepared rapid acquisition gradient echo pulse sequence to characterize low dose manganese kinetics in the pancreas head, body and tail. Average signal enhancement in the pancreas (head, body, and tail) as a function of time was fit by a novel empirical mathematical model characterizing contrast uptake/washout rates and yielding parameters describing peak signal, initial slope, and initial area under the curve. Signal enhancement from glucose-induced manganese uptake was fit by a linear function. The results demonstrated that the diabetic pancreatic tail had a significantly lower contrast uptake rate, smaller initial slope/initial area under the curve, and a smaller rate of Mn uptake following glucose activation (p < 0.05) compared to the normal pancreatic tail. These observations parallel known patterns of β-cell loss and alteration in supportive vasculature associated with diabetes. Dynamic MEMRI is a promising technique for assessing β-cell functionality and vascular perfusion with potential applications for monitoring diabetes progression and/or therapy.     

Novel Formalism for Energy Eigenvalue Problem with Hamiltonian Expressible as Function of Angular Mometum

We present a novel formalism for energy eigenvalue problems when the corresponding Hamiltonians can be expressed as a function of an angular momentum.The problems are turned into finding operator polynomials by solving a c-number differential equation.Simple and efficient computer-aided analytical and numerical methods may e developed based on the formalism.     

Potential application of Al-doped ZnO nanotube as an electronic sensor for β-keto-amphetamine drug

The β-keto-amphetamine (β-KA) drug abuse causes numerous deaths worldwide. Thus, finding a proper sensor for β-KA drug detection is of great importance. Here, potential application of pristine and Al-doped ZnO nanotubes (ZN) was investigated in detection of β-KA using density functional theory calculations. Based on our AIM analysis, the β-KA drug physically adsorbed on the pristine ZN with adsorption energy (E_ad) of −4.7 kcal/mol. The sensing response of ZN to the β-KA drug is very small about 3.9 at 298 K. By substituting a Zn atom of ZN by an Al atom, the E_ad of β-KA drug increased to −22.9 kcal/mol and the nature of interaction changes from the physisorption to a highly polar covalent chemisorption. Also, the sensing response increased to 315.9, indicating that the Al-doping makes the ZN a promising sensor for β-KA. A recovery time of 19.0 s was predicted for the Al-ZN.     

Raman spectroscopy of Chinese human skin in vivo

A novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology (VPT) holographic system, and NIR intensified charge-coupled device (CCD). Signal-to-noise ratio (SNR) and resolution are improved compared with ordinary acquisition method by a specially designed optical fiber detector and the spectrograph image aberration correction with a parabolic-line fiber array. In 1-5 s, Raman spectra of different parts of Chinese human skin are acquired. Autofluorescence is subtracted from the raw spectrum by polynomial fitting and skin Raman spectrum is then smoothed for further analysis.     

Heterogeneous catalysis in solution at high pressures lactose hydrolysis over an immobilized β-galactosidase

Abstract

The hydrolysis of lactose over an immobilized β-galactos-idase was studied under pressures up to 98 MPa. The data were analyzed on the basis of a Michaelis-Menten type kinetic model. A model for the transition state complex is proposed by analyzing kinetic parameters.     

Spectral editing for in vivo ¹³C magnetic resonance spectroscopy

In vivo detection of carboxylic/amide carbons is a promising technique for studying cerebral metabolism and neurotransmission due to the very low RF power required for proton decoupling. In the carboxylic/amide region, however, there is severe spectral overlap between acetate C1 and glutamate C5, complicating studies that use acetate as an astroglia-specific substrate. There are no known in vivo MRS techniques that can spectrally resolve acetate C1 and glutamate C5 singlets. In this study, we propose to spectrally separate acetate C1 and glutamate C5 by a two-step J-editing technique after introducing homonuclear (13)C-(13)C scalar coupling between carboxylic/amide carbons and aliphatic carbons. By infusing [1,2-(13)C(2)]acetate instead of [1-(13)C]acetate the acetate doublet can be spectrally edited because of the large separation between acetate C2 and glutamate C4 in the aliphatic region. This technique can be applied to studying acetate transport and metabolism in brain in the carboxylic/amide region without spectral interference.     

Carbon nanotube β-cyclodextrin-modified electrode for quantification of cocaine in seized street samples

Ionics - Detection and quantification of cocaine is a key tool in fields such as police apprehensions and the fight against drug trafficking. Thus, a simple, fast and inexpensive electroanalytical...     

Effects of sonochemical approach and induced contraction of core–shell bismuth sulfide/graphitic carbon nitride as an efficient electrode materials for electrocatalytic detection of antibiotic drug in foodstuffs

Ultrasonic-enhanced surface-active bismuth trisulfide based core–shell nanomaterials were developed and used as an efficient modified electrode material to construct a highly sensitive antibiotic sensor. The core–shell Bi₂S₃@GCN electrode material was directly synthesized by in-situ growth of GCN on Bi₂S₃ to form core–shell like nanostar (Ti-horn, 30 kHz, and 70 W/cm²). The electrocatalyst of Bi₂S₃@GCN nanocomposites was efficaciously broadened towards electrochemical applications. As synthesized Bi₂S₃@GCN promoted the catalytic ability and electrons of GCN to transfer to Bi₂S₃. The single-crystalline GCN layers were uniformly grown on the surface of the Bi₂S₃ nanostars. Under the optimal conditions of electrochemical analysis, the CPL sensor exhibited responses directly proportional to concentrations (toxic chemical) over a range of 0.02–374.4 μM, with a nanomolar detection limit of 1.2 nM (signal-to-noise ratio S/N = 3). In addition, the modified sensor has exhibited outstanding selectivity under high concentrations of interfering chemicals and biomolecules. The satisfactory CPL recoveries in milk product illustrated the credible real-time application of the proposed Bi₂S₃@GCN sensors for real samples, indicating promising potential in food safety department and control. Additionally, the proposed electrochemical antibiotic sensor exhibited outstanding performance of anti-interfering ability, high stability and reproducibility.     

Design of the thermal neutron detection system for CJPL-Ⅱ

A low background thermal neutron flux detection system has been designed to measure the ambient thermal neutron flux of the second phase of the China Jinping Underground Laboratory(CJPL-Ⅱ),right after completion of the rock bolting work.A ~3He proportional counter tube combined with an identical ~4He proportional counter tube was employed as the thermal neutron detector,which has been optimised in energy resolution,wall effect and radioactivity of construction materials for low background performance.The readout electronics were specially designed for long-term stable operation and easy maintenance in an underground laboratory under construction.The system was installed in Lab Hall No.3 of CJPL-Ⅱ and accumulated data for about 80 days.The ambient thermal neutron flux was determined under the assumption that the neutron field is fully thermalized,uniform and isotropic at the measurement position.     

Error detection using mode information of macroblocks for video transmission

When video signals are transmitted over noisy chan-nels such as wireless networks, there will be errors inthe transmitted bit stream. Traditional coding methodsmake video more sensitive to channel errors because ofspatial and temporal propagation due to using variablelength codes (VLC) and motion compensation, respec-tively. Error detection and concealment are extremelyimportant components of error robust video codec. Theprocess of error detection can be divided into two steps.First, video b…     

Performance comparison of interferometer topologies for carrier-envelope phase detection

Performance and noise immunity of different interferometer set-ups for carrier-envelope phase detection are compared. The frequently used Mach–Zehnder interferometer is found to be easily corrupted by acoustic noise contributions and air streaks, whereas a quasi-common-path variant of the f-to-2f interferometer exhibits a 40% reduction of residual noise. This comparative analysis also provides deeper insight into additional mechanisms that are currently limiting the performance of carrier-envelope phase stabilization schemes.     

Optimal structure for resonant THz detection of plasmons–polaritons in the 2D quantum wells

We investigate terahertz plasmon?Cpolariton (PP) resonances for hetero-structures (AlGaN/GaN, SiGe/Si/SiGe, AlGaAs/GaAs, and InAlN/GaN) with a grating coupler in order to find the overall optimal structure showing the strongest absorption for terahertz detection (THz). We show by a parametric study (influence of geometric dimensions, electron concentration, temperature, etc.) that refined and intense resonances can be obtained at specific frequency. GaN based heterostructures present the higher PP resonances at room temperature. The roles of the finite thicknesses of lossy metal grating and a two-dimensional gas (2DEG) layer on observed absorption are also investigated. Absorption spectra for three kinds of heterogeneous charge density profiles (piecewise, linear, and parabolic) of 2DEG was investigated and compared for an AlGaAs/GaAs structure because some physical parameters such as the Fermi level pinning at the interface semiconductor/air are well established only for this heterostructure. We show that the PP resonance (amplitude and frequency position) is modulated by the charge concentration but also by the metallization biasing.     

A DR-WFOI fusion system for the real-time molecular imaging in vivo

Digital radiography(DR)and whole-body fluorescent optical imaging(WFOI)have been widely applied in the field of molecular imaging,with the advantages in tissues and functional imaging.The integration of them contributes to the development and discovery of medicine.We introduce an equipment,performance of which is better than that of another molecular imaging system manufactured by Kodak Corp.It can take real-time small animal imaging in vivo,with lower cost and shorter development cycle on the LabVIEW platform.At last,a paradigm experiment on a nude mouse with green fluorescent protein(GFP)transgenic tumor is given to present a real-time DR-WFOI fusion simultaneous image.     

First-principles study of lithium-ion diffusion in β-Li3PS4 for solid-state electrolytes

Understanding the role of partially occupied sites in Li-based superionic conductors is key to improving performance of solid-state electrolyte materials. We study the optimized structure of crystalline β-Li₃PS₄ and the Li-ion diffusion using first-principles calculations and the nudged elastic band method. Considering diffusion paths through both interstitial and vacancy exchanges, we calculate the migration energies of Li ions. We find that the phonon-mode softening and concurrent inversion symmetry breaking leads to a more stable structure with low symmetry. Atomic distortion from the phonon softening provides diffusion paths for Li ions with less migration energies than the ones in high-symmetry structures. Our results show that diffusion of Li ion is highly anisotropic through the armchair- or zigzag-shaped channels along the b-axis that contain Li-ion sites with fractional occupation.     

Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.     

The potential of CO2 laser photoacoustic spectrometry for?detection of methanol in alcoholic beverage

The first use of CO₂ laser photoacoustic measurements for detecting the methanol contents in alcohol-like solutions is presented. With an intracavity cell configuration, the minimum detectable concentration was ∼200 ppm for methanol and the linear range of the calibration curve for methanol was from 200 to 70000 ppm. For demonstrating the reliability of analysis in alcoholic beverages, a series of different concentrations of two-component samples was prepared and measured by the same procedures. The results showed the feasibility on determining methanol and ethanol contents accurately within a specific tolerance, limited mainly by background signal and laser stability. This potential method with no pre-treatment of samples takes only ∼10 min to finish one single measurement. It suggests that the PA detection is suitable for routine diagnosis of adulterated wines in commercial products.     

H2-induced changes in electrical conductance of β-Ga2O3 thin-film systems

H₂-induced changes of electrical conductivity in polycrystalline, undoped -Ga₂O₃ thin films in the temperature range of 400–650° C are described. The sheet conductance of these films depends reversibly, according to a power law p ^1/3, on the partial pressure of hydrogen in the ambient atmosphere of the Ga₂O₃ film. A bulk vacancy mechanism is excluded by experiments and it is shown that the interaction is based on a surface effect. Changes in conductance are discussed to result from the formation of an accumulation layer due to chemisorption on the grain surfaces. Typical coverages are determined to be approximately 10^–4 ML for pH₂=0.05 bar and T=600° C. A possible explanation of the p ^1/3 power law is provided.