A simple and sensitive particle induced gamma-ray emission method for non-destructive quantification of lithium in lithium doped Nd2Ti2O7 ceramic sample

A particle induced gamma-ray emission method using proton beam in conjunction with in situ current normalization approach was standardized for non-destructive determination of low Z element lithium and was applied for quantification of Li in lithium doped neodymium dititanate (Nd₂Ti₂O₇) ceramic sample. Thick pellets of heat treated samples, their precursors and Li standards were prepared separately by homogeneously mixing with cellulose and fixed amount of F used for in situ current normalization. For validation of the method, four synthetic samples were also analyzed. Samples and standards were irradiated with 4?MeV proton beam (~5?nA current) from folded tandem ion accelerator (FOTIA) BARC, Mumbai. Characteristic ??-rays of 478?keV from ⁷Li to 197?keV from ¹⁹F were measured by high resolution ??-ray spectrometry. The Li concentrations determined in the six samples were in the range of 0.29?C0.85?wt%. The Li contents in heat treated samples gave the idea about loss of Li compared to their precursors.     

One-Pot Process to Produce Anthraquinone Derivatives: Prospective Wood Delignification Catalysts

Derivatives of 9,10-anthraquinone (AQ) are widely used chemicals but the currently practiced methods for their production are inefficient and environmentally harmful. In the present work, an innovative method for synthesis of substituted AQ from hydroquinone (HQ) and substituted dienes (2,3-dimethylbutadiene, DMB) was studied with the synthesis of 2,3,6,7-tetramethyl-9,10-AQ (TMAQ) as an example. A solution of high-vanadium heteropoly acid H₁₇P₃Mo₁₆V₁₀O₈₉ (HPA-10) was used as the bifunctional (acid and oxidative) catalyst for the new one-pot process. The influence of a number of factors on the key process parameters was studied. An insoluble mixture of two products (80% TMAQ and 20% DHTMAQ—an underoxidized dihydroderivative of TMAQ) was synthesized in 24 h under the chosen conditions. The mixture can be used as an effective catalyst for wood delignification. The results obtained offer real possibilities for developing low-waste processes of substituted AQ synthesis from HQ and substituted 1,3-dienes in the presence of HPA-10 solutions. The catalysts are highly active, stable and effective.     

Investigation of driving waveform and resonance pressure in piezoelectric inkjet printing

In order to improve the processing throughput and printing quality of inkjet printing technology, the droplet stability and ejection speed need to be well controlled. This paper investigates the relationship between the driving waveform and resonance pressure of piezoelectric inkjet printers using computational simulation and experiments. The detailed pressure history under various driving conditions is obtained. Furthermore, the individual contribution of each waveform parameter is evaluated.     

A nonlinear composite shell theory

A general nonlinear theory for the dynamics of elastic anisotropic circular cylindrical shells undergoing small strains and moderate-rotation vibrations is presented. The theory fully accounts for extensionality and geometric nonlinearities by using local stress and strain measures and an exact coordinate transformation, which result in nonlinear curvatures and strain-displacement expressions that contain the von Karman strains as a special case. Moreover, the linear part of the theory contains, as special cases, most of the classical linear theories when appropriate stress resultants and couples are defined. Parabolic distributions of the transverse shear strains are accounted for by using a third-order theory and hence shear correction factors are not required. Five third-order nonlinear partial differential equations describing the extension, bending, and shear vibrations of shells are obtained using the principle of virtual work and an asymptotic analysis. These equations show that laminated shells display linear elastic and nonlinear geometric couplings among all motions.     

Creep-bending facility and tests on large specimens

A creep-bending facility for large specimens is described herein. Some initial results of elastic-creep and elastic-plastic-creep tests on rectangular stainless-steel beams are presented. The beams are subjected to equal-and-opposite end moments at temperatures up to 1200°F in the 8-cu-ft capacity test facility. Initial test results are indicated.     

Three-dimensional nonlinear vibrations of composite beams — II. flapwise excitations

The nonlinear equations of motion derived in Part I are used to investigate the response of an inextensional, symmetric angle-ply graphite-epoxy beam to a harmonic base-excitation along the flapwise direction. The equations contain bending-twisting couplings and quadratic and cubic nonlinearities due to curvature and inertia. The analysis focuses on the case of primary resonance of the first flexural-torsional (flapwise-torsional) mode when its frequency is approximately one-half the frequency of the first out-of-plane flexural (chordwide) mode. A combination of the fundamental-matrix method and the method of multiple scales is used to derive four first-order ordinary-differential equations to describe the time variation of the amplitudes and phases of the interacting modes with damping, nonlinearity, and resonances. The eigenvalues of the Jacobian matrix of the modulation equations are used to determine the stability and bifurcations of their constant solutions, and Floquet theory is used to determine the stability and bifurcations of their limit-cycle solutions. Hopf bifurcations, symmetry-breaking bifurcations, period-multiplying sequences, and chaotic solutions of the modulation equations are studied. Chaotic solutions are identified from their frequency spectra, Poincaré sections, and Lyapunov's exponents. The results show that the beam motion may be nonplanar although the input force is planar. Nonplanar responses may be periodic, periodically modulated, or chaotically modulated motions.     

Multidimensional umbrella sampling and replica‐exchange molecular dynamics simulations for structure prediction of transmembrane helix dimers

Structural information of a transmembrane (TM) helix dimer is useful in understanding molecular mechanisms of important biological phenomena such as signal transduction across the cell membrane. Here, we describe an umbrella sampling (US) scheme for predicting the structure of a TM helix dimer in implicit membrane using the interhelical crossing angle and the TM–TM relative rotation angles as the reaction coordinates. This scheme conducts an efficient conformational search on TM–TM contact interfaces, and its robustness is tested by predicting the structures of glycophorin A (GpA) and receptor tyrosine kinase EphA1 (EphA1) TM dimers. The nuclear magnetic resonance (NMR) structures of both proteins correspond to the global free‐energy minimum states in their free‐energy landscapes. In addition, using the landscape of GpA as a reference, we also examine the protocols of temperature replica‐exchange molecular dynamics (REMD) simulations for structure prediction of TM helix dimers in implicit membrane. A wide temperature range in REMD simulations, for example, 250–1000 K, is required to efficiently obtain a free‐energy landscape consistent with the US simulations. The interhelical crossing angle and the TM–TM relative rotation angles can be used as reaction coordinates in multidimensional US and be good measures for conformational sampling of REMD simulations. © 2013 Wiley Periodicals, Inc.     

Using fluorescence measurement of zinc ions liberated from ZnS nanoparticle labels in bioassay for <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7

In this study, an alternative approach using ZnS nanoparticle biolabels as fluorescence signal transducers is reported for the immunoassay of E. coli O157:H7 in tap water samples. Instead of measuring the fluorescence of ZnS nanoparticles in the assay, the fluorescence signal is generated through the binding of zinc ions released from nanoparticle labels with zinc-ion sensitive fluorescence indicator Fluozin-3. In the assay, ZnS nanoparticles around 50 nm in diameter were synthesized, bioconjugated, and applied for the detection of E. coli O157:H7. The assay shows a detection range over two orders of magnitude and a detection limit around 1000 colony-forming units (cfu) of E. coli O157:H7.     

Mapping the reaction coordinates of enzymatic defluorination

The carbon-fluorine bond is the strongest covalent bond in organic chemistry, yet fluoroacetate dehalogenases can readily hydrolyze this bond under mild physiological conditions. Elucidating the molecular basis of this rare biocatalytic activity will provide the fundamental chemical insights into how this formidable feat is achieved. Here, we present a series of high-resolution (1.15-1.80 ?) crystal structures of a fluoroacetate dehalogenase, capturing snapshots along the defluorination reaction: the free enzyme, enzyme-fluoroacetate Michaelis complex, glycolyl-enzyme covalent intermediate, and enzyme-product complex. We demonstrate that enzymatic defluorination requires a halide pocket that not only supplies three hydrogen bonds to stabilize the fluoride ion but also is finely tailored for the smaller fluorine halogen atom to establish selectivity toward fluorinated substrates. We have further uncovered dynamics near the active site which may play pivotal roles in enzymatic defluorination. These findings may ultimately lead to the development of novel defluorinases that will enable the biotransformation of more complex fluorinated organic compounds, which in turn will assist the synthesis, detoxification, biodegradation, disposal, recycling, and regulatory strategies for the growing markets of organofluorines across major industrial sectors.     

Dependence of resistivity on structure and composition of AZO films fabricated by ion beam co-sputtering deposition

The correlation between the resistivity and the structure/composition in the aluminum doped zinc oxide (AZO) films fabricated by the ion beam co-sputtering deposition at room temperature was investigated. The various compositions of AZO films were controlled by the sputtered area ratio of Al to Zn target. The structure, Al concentrations and resistivities of the as-deposited films were determined by X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and four-point probe station, respectively. The lowest resistivity of the deposited film was 5.66 × 10⁻⁴ Ω-cm at the 0.7 wt.% aluminum concentration. The most intense ZnO (0 0 2) diffraction peak, the largest grain size, the longest mean free path, and the highest free carrier concentration in the film result in the lowest resistivity of 5.66 × 10⁻⁴ Ω-cm at room temperature; simultaneously, the thermal stability of the resistivity of the AZO film as a function of the sample temperature was investigated. Below 200 °C the film's resistivity was almost kept at a fixed value and the lowest resistivity of 4.64 × 10⁻⁴ Ω-cm at 247 °C was observed.