Broadband time-reversing array retrofocusing in noisy environments

Acoustic time reversal is a promising technique for spatial and temporal focusing of sound in unknown environments. Acoustic time reversal can be implemented with an array of transducers that listens to a remote sound source and then transmits a time-reversed version of what was heard. In a noisy environment, the performance of such a time-reversing array (TRA) will be degraded because the array will receive and transmit noise, and the intended signal may be masked by ambient noise at the retrofocus location. This article presents formal results for the signal-to-noise ratio at the intended focus (SNRf) for TRAs that receive and send finite-duration broadband signals in noisy environments. When the noise is homogeneous and uncorrelated, and a broadcast power limitation sets the TRA's electronic amplification, the formal results can be simplified to an algebraic formula that includes the characteristics of the signal, the remote source, the TRA, and the noisy environment. Here, SNRf is found to be proportional to the product of the signal bandwidth and the duration of the signal pulse after propagation through the environment. Using parabolic-equation propagation simulations, the formal results for SNRf are illustrated for a shallow water environment at source-array ranges of 1 to 40 km and bandwidths from several tens of Hz to more than 500 Hz for a signal center frequency of 500 Hz. Shallow-water TRA noise rejection is predicted to be superior to that possible in free space because TRAs successfully exploit multipath-propagation.     

Surface tensions and surface heats of mixing of mixtures of 1,2-dibromoethane with cyclohexane,benzene, toluene, o-xylene, m-xylene,and p-xylene at 298.15, 303.15, And 308.15 K

Surface tensions of mixtures of 1,2-dibromoethane+cyclohexane, benzene, +toluene, +o-xylene, +m-xylene, and +p-xylene have been measured as a function of composition at 298.15, 303.15 and 308.15 K. Interchange energies and surface heats of mixing in these mixtures were computed.     

Atomic structure calculations for F-like tungsten

Energy levels, wavefunction compositions and lifetimes have been computed for all levels of 1s22s22p5, 1s22s2p6,1s22s22p43 s, 1s22s22p43 p, and 1s22s22p43 d configurations in highly charged F-like tungsten ion. The multiconfigurational Dirac–Fock method(MCDF) is adopted to generate the wavefunctions. We have also presented the transition wavelengths,oscillator strengths, transition probabilities, and line strengths for the electric dipole(E1) and magnetic quadrupole(M2)transition from the 1s22s22p5 ground configuration. We have performed parallel calculations with the flexible atomic code(FAC) for comparing the atomic data. The reliability of present data is assessed by comparison with other theoretical and experimental data available in the literature. Good agreement is found between our results and those obtained using different approaches confirm the quality of our results. Additionally, we have predicted some new atomic data for F-like W that were not available so far and may be important for plasma diagnostic analysis in fusion plasma.     

CH overtone spectrum of nitromethane: a C3V coupled oscillator analysis using local mode parameters

The near infrared overtone absorption spectrum of liquid phase nitromethane in the spectral region deltaV = 2-5 is reported. The observed spectrum is analysed using local mode model. It is shown that the observed CH local mode overtones and local-local combinations are well predicted by a C(3V) coupled oscillator Hamiltonian.     

Sol–gel spin coating assisted room temperature operated nanostructured ZnO ethanol sensor with behavior transformation

In this paper, zinc oxide (ZnO) thin film sensor has been fabricated using different sol–gel spin coating route to detect very low concentration (2?ppm) of ethanol vapors at room temperature (RT). The sensor shows appreciable response ~60% for 100?ppm of ethanol (C₂H₅OH) vapors at RT under humidity level ~55% RH. Various sensing parameters viz. % response, selectivity, stability, response/recovery time, repeatability, and reproducibility have been studied successfully. Structural and morphological properties have been studied via X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD reveals the wurtzite structure of polycrystalline ZnO thin film. AFM, SEM, and TEM results confirm the wavy structure of well-shaped and slackly distributed ZnO nanograins with average particle size in range ~15–25?nm. The analyte sensing properties at room temperature can be ascribed to higher specific surface area due to nanograins formation. The significant effect of operating temperature on sensor’s performance is also analysed in order to obtain the optimum temperature (T_opt) of the sensor device. Response reaches to 321.7% for 100?ppm of ethanol vapors at T_opt (175?°C). The transformation in the behavior of sensing layer is observed which is described on the basis of experimental studies.

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Rapid screening for S-adenosylmethionine-dependent methylation products by enzyme-transferred isotope patterns analysis

We report here an isotopic labeling and mass spectrometric method to rapidly identify S-adenosylmethionine (AdoMet)-dependent methylation products. In the presence of CH(3)- and CD(3)-labeled AdoMet, a methyl transfer product appears as a doublet separated by 3 Da in a mass spectrum, while other compounds show their normal isotopic distribution. Based on this unique isotopic pattern, methylation product(s) can be easily detected even from a mixture of cellular components. To validate our method, the product of human thiopurine methyltransferase (TPMT, EC 2.1.1.67) has been successfully identified from both an in vitro assay and a whole-cell assay. This method is generally applicable to AdoMet-dependent transmethylation and other group-transfer reactions, and constitutes the first example of a general strategy of enzyme-transferred isotope patterns (ETIPs) analysis.     

Assessment of Chinese medicinal herb metabolite profiles by UPLC-MS-based methodology for the detection of aristolochic acids

In this study, aristolochic acid in different herbal medicines containing a mixture of varying herb species was identified through fingerprint pattern similarities. Aristolochic acid I and II are nephrotoxic compounds naturally present in the Aristolochia plant species that are commonly used in Chinese herbal medicines. Twenty-four commercially available herbal formulations were extracted into an aqueous solution and injected into a UPLC-MS system. All the samples were analysed by multiple reaction monitoring (MRM) to check for the presence of aristolochic acids I and II. The same samples were then fingerprinted using two different gradient methods and the chromatograms deconvoluted into retention time (RT) and masses for the chemicals present taking concentration into account. Statistical analysis of this data revealed that samples were highly heterogeneous, and that the main differences between the preparations were concentrations of polar compounds. A model was constructed where the samples could be separated into two groups differentiated by the presence of the two forms of aristolochic acid.     

Cellulose nanocrystal treatment of aligned short hemp fibre mats for reinforcement in polypropylene matrix composites

Cellulose - Oriented short hemp fibre mats were produced using dynamic sheet forming (DSF) incorporating cellulose nanocrystals (CNCs) to improve their integrity. The CNCs were found to act as a...     

Common fixed points for weakly compatible maps

The purpose of this paper is to prove a common fixed point theorem, from the class of compatible continuous maps to a larger class of maps having weakly compatible maps without appeal to continuity, which generalizes the results of Jungck [3], Fisher [1], Kang and Kim [8], Jachymski [2], and Rhoades [9].     

The formation of NO+ from the reaction of N2(2+) with O2

We have studied the potentially ionospherically significant reaction between N(2)2+ with O2 using position-sensitive coincidence spectroscopy. We observe both nondissociative and dissociative electron transfer reactions as well as two channels involving the formation of NO+. The NO+ product is formed together with either N+ and O in one bond-forming channel or O+ and N in the other bond-forming channel. Using the scattering diagrams derived from the coincidence data, it seems clear that both bond-forming reactions proceed via a collision complex [N2O2]2+. This collision complex then decays by loss of a neutral atom to form a daughter dication (NO2(2+) or N2O2+), which then decays by charge separation to yield the observed products.