Mechanism of film growth of pulsed electrodeposition of nanocrystalline copper in presence of thiourea

This article reports the effect of addition of small amount of thiourea on mechanism of film growth, levelling and grain refinement of pulsed electrodeposition of nanocrystalline copper on stainless steel substrate using simple aqueous acidic copper sulphate solution prepared from 0.25 M CuSO₄·5H₂O and 0.5 M H₂SO₄. The amount of thiourea used in the electrolyte is 0 and 36 mg/l. The results indicate the change in morphology of the deposits with addition of thiourea leading to dendrite free copper deposits. The growth mechanism of the copper deposition is found to change from Volmer–Weber type to Frank-Vander Merwe type making the deposits smoother when deposited with thiourea addition. A small amount (36 mg/l) of thiourea addition leads to decrease in the average grain size of copper from 1160 nm to 14 nm. The results clearly reveal the formation of nanocrystalline copper by addition of thiourea with three orders of magnitude reduction in grain size as compared to the sample deposited without thiourea. Preferential segregation of sulphur (present in thiourea) along the grain boundaries of nanocrystalline copper is shown by energy filter imaging using ultra high resolution transmission electron microscope (TEM), thereby restricting the growth of copper grains during pulsed electrodeposition.     

Optical solitons in (1 + 1) and (2 + 1) dimensions

This paper addresses the nonlinear Schrödinger's equation that serves as the model to study the propagation of optical solitons through nonlinear optical fibers. The main focus of this paper is the aspect of integrability. There are a couple of integration tools that are employed to obtain the exact solutions to the model. Fan's F-expansion approach is applied to extract several forms of solutions to the model. This integration mechanism displays cnoidal waves, snoidal waves and several other solutions; needless to mention that these solutions, in the limiting case, leads to bright, dark and singular soliton solutions. The study then rolls over to the (2 + 1)-dimensions where, in addition, the semi-inverse variational principle is applied to extract a bright soliton solution, along with the necessary constraint conditions. There is also a display of several numerical simulations.     

Combining Sparse and Dense Features to Improve Multi-Modal Registration for Brain DTI Images

A new solution to overcome the constraints of multimodality medical intra-subject image registration is proposed, using the mutual information (MI) of image histogram-oriented gradients as a new matching criterion. We present a rigid, multi-modal image registration algorithm based on linear transformation and oriented gradients for the alignment of T2-weighted (T2w) images (as a fixed reference) and diffusion tensor imaging (DTI) (b-values of 500 and 1250 s/mm²) as floating images of three patients to compensate for the motion during the acquisition process. Diffusion MRI is very sensitive to motion, especially when the intensity and duration of the gradient pulses (characterized by the b-value) increases. The proposed method relies on the whole brain surface and addresses the variability of anatomical features into an image stack. The sparse features refer to corners detected using the Harris corner detector operator, while dense features use all image pixels through the image histogram of oriented gradients (HOG) as a measure of the degree of statistical dependence between a pair of registered images. HOG as a dense feature is focused on the structure and extracts the oriented gradient image in the x and y directions. MI is used as an objective function for the optimization process. The entropy functions and joint entropy function are determined using the HOGs data. To determine the best image transformation, the fiducial registration error (FRE) measure is used. We compare the results against the MI-based intensities results computed using a statistical intensity relationship between corresponding pixels in source and target images. Our approach, which is devoted to the whole brain, shows improved registration accuracy, robustness, and computational cost compared with the registration algorithms, which use anatomical features or regions of interest areas with specific neuroanatomy. Despite the supplementary HOG computation task, the computation time is comparable for MI-based intensities and MI-based HOG methods.     

Dispersion-Managed Solitons in Multiple-Core Nonlinear Fiber Arrays

The variational principle is employed to obtain the evolution of the parameters of Gaussian and super-Gaussian chirped solitons that propagates through multiple-core nonlinear optical fiber arrays. This is governed by the dispersion-managed nonlinear Schrodinger's equation with strong dispersion management in the presence of linear coupling between the adjacent cores. The results are valid for any configuration of the cores.     

Analysis of Generalized Ghost Dark Energy in LQC and Galileon Gravity

A so-called ghost dark energy was recently proposed to explain the present acceleration of the universe.The energy density of ghost dark energy,which originates from Veneziano ghost of Quantum Chromodynamics(QCD),in a time dependent background,can be written in the form,ρD=αH + βH~2 where H is the Hubble parameter.We investigate the generalized ghost dark energy(GGDE) model in the setup of loop quantum Cosmology(LQC) and Galileon Cosmology.We study the cosmological implications of the models.We also obtain the equation of state and the deceleration parameters and differential equations governing the evolution of this dark energy model for LQC and Galileon Cosmology.     

Indigenous development of a 2 kW RF-excited fast axial flow CO<Subscript>2</Subscript> laser

RF-excited fast axial flow CO₂ lasers in kilowatt regime are presently being used for various new scientific applications in addition to laser material processing because of its versatility and superior beam quality. We have indigenously developed a compact 2 kW RF-excited fast axial flow CO₂ laser with moderate beam quality. In this paper the key design features of the laser and the associated high power capacitively coupled RF excitation technique are discussed in detail. Operational characteristics of this system are described along with the experimental findings.     

Flat principal bundles over an abelian variety

We prove that a principal G-bundle E_G over a complex abelian variety A, where G is a complex reductive algebraic group, admits a flat holomorphic connection if and only if E_G is isomorphic to all the translations of it by the group structure of A.