Si doped GaAs/AlGaAs terahertz detector and phonon effect on the responsivity

Terahertz detection capability of an n-type heterojunction interfacial work function internal photoemission (HEIWIP) detector is demonstrated. Threshold frequency, f₀, of 3.2 THz (93 μm) was obtained by using n-type GaAs emitter doped to 1 × 10¹⁸ cm⁻³ and Al_0.04Ga_0.96As single barrier structure. The detector shows a broad spectral response from 30 to 3.2 THz (10–93 μm) with peak responsivity of 6.5 A/W at 7.1 THz under a forward bias field of 0.7 kV/cm at 6 K. The peak quantum efficiency and peak detectivity are 19% and 5.5 × 10⁸ Jones, respectively under a bias field of 0.7 kV/cm at 6 K. In addition, the detector can be operated up to 25 K.     

A simple approach for synthesis of TiO2 nanotubes with through‐hole morphology

The present work reports a simple approach for fabrication of self‐standing titania (TiO₂) nanotube membranes with through‐hole morphology. The method is hydrofluoric acid free and the pore opening of TiO₂ nanotubes is performed by electrochemical thinning of the oxide barrier layer. A reduction of anodization voltage was applied at the end of the anodization process to cause a successful removal of the remaining barrier layer from the TiO₂ nanotubes during their detachment from the underlying titanium substrate. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An in-plane insensitive multiaperture speckle shear interferometer for slope measurement

A modified two-aperture speckle shear interferometer that eliminates the contribution of the in-plane component and its derivative to the phase change, and yields a fringe pattern corresponding to the first-order partial derivatives of the out-of-plane displacement component, is reported in this note. In this method, two laterally sheared object points are viewed axially. The wave fields from these points are independently combined at the image plane of the imaging system.     

Cation disorder and structural studies on Bi4−x Nd x Ti3O12 (0.0≤x≤2.0)

Here we report the results of combined powder X-ray and neutron diffraction studies of Bi_4?x Nd _x Ti₃O₁₂ (0.0 ≤ x ≤ 2.0) compositions. The parent Bi₄Ti₃O₁₂ has an orthorhombic lattice (space group: B2cb) with unit cell parameters a = 5.4432(5) Å, b = 5.4099(5) Å and c = 32.821(2) Å, and V = 966.5(1) ų. This orthorhombic lattice is retained in all the studied compositions. The unit cell parameters gradually decrease with Nd³⁺ ion concentration with a discontinuity at x = 0.75. Orthorhombicity of the lattice decreases with increase in Nd³⁺ content in the lattice. The orthorhombic unit cell parameters for a representative Bi₂Nd₂Ti₃O₁₂ composition are: a = 5.3834(9), b = 5.3846(9) and c = 32.784(1) Å. The observed orthorhombic distortion at x = 2.0 is very small and thus the crystal structure apparently has a pseudo-tetragonal lattice. In addition, Nd³⁺ preferentially substitutes in the perovskite slab of the Aurivillius structure. The fraction of Nd³⁺ in the fluorite slab increases with increase in Nd³⁺ contents.     

Molecular conformation and liquid structure of 2-propanol through neutron diffraction

The neutron diffraction data analysis of deuterated liquid 2-propanol at room temperature to define its molecular conformation is presented. 2-Propanol being a large molecule with twelve atomic sites, the conformation analysis is tricky and an improved method of data analysis is given. The intermolecular structural correlations, i.e., hydrogen-bonded liquid structure, can be modelled accurately to extract the nature of the average hydrogen-bonded molecular association in liquid state at room temperature. Like other alcohols these are mostly hexamer ring chain (HRC) clusters. The cluster analysis of recent X-ray data available in the literature also support the same liquid structure.     

Range‐independent background subtraction algorithm for recovery of Raman spectra of biological tissue

An important requirement for the use of Raman spectroscopy for tissue diagnostic applications is an appropriate algorithm that can faithfully retrieve weak tissue Raman signals from the measured raw Raman spectra. Although iterative modified polynomial‐fitting‐based automated algorithms are widely used, these are sensitive to the choice of the fitting range, thereby leading to significantly different Raman spectra for different start and stop wavenumber selection. We report here an algorithm for automated recovery of the weak Raman signal, which is range independent. Given a raw Raman spectrum and the choice of the start and the stop wavenumbers, the algorithm first truncates the spectrum to include the raw data within this wavenumber range, linearly extrapolates the truncated raw spectrum beyond the points of truncation on the two sides by using coefficients of linear least‐square fit, adds two Gaussian peaks of appropriate height and width on the extrapolated linear wings on either side and then iteratively smoothens the data with all these add‐ons such that the smaller of the ordinate values of the smoothed and the starting raw data serve as the input to each successive round of iterative smoothing until the added Gaussian peaks are fully recovered. The algorithm was compared with the modified polynomial‐based algorithms using mathematically simulated Raman spectrum as well as experimentally measured Raman spectra from various biological samples and was found to yield consistently range‐independent and artifact‐free Raman signal with zero baseline. Copyright © 2012 John Wiley & Sons, Ltd.     

Therapeutics for COVID-19: from computation to practices—where we are,where we are heading to

Molecular Diversity - After the 1918 Spanish Flu pandemic caused by the H1N1 virus, the recent coronavirus disease 2019 (COVID-19) brought us to the time of serious global health catastrophe....     

Electroweak tests with τ leptons at LEP

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z⁰ pole. From measurements of the τ polarization in e⁺ e^?→τ ⁺ τ ^?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg _{v e} /g _{a e} =0.066±0.015 andg _{V τ} /g _{A τ} =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG _τ /G _μ =0.996±0.008.