Development of 5-[(3-aminopropyl)phosphinooxy]-2-(hydroxymethyl)-4H-pyran-4-one as a novel whitening agent

A stable derivative of kojic acid, 5-[(3-aminopropyl)phosphinooxy]-2-(hydroxymethyl)-4H-pyran-4-one (Kojyl-APPA), was synthesized in good yield. The effects of Kojyl-APPA on tyrosinase activity and melanin synthesis were investigated. Kojyl-APPA showed tyrosinase inhibition effect (30%) in situ, but not in vitro. Kojyl-APPA inhibited tyrosinase activity significantly at 24 h after treatment in normal human melanocytes. It means that Kojyl-APPA is not a direct inhibitor of tyrosinase itself, but it is converted to a potential inhibitor kojic acid enzymatically in cells. In addition, Kojyl-APPA decreased melanin content to 75% of control in melanoma cells and decreased neomelanin synthesis to 43% of control in normal human melanocytes. Its permeation through skin increased by about 8 times as compared with kojic acid.     

X-ray photoelectron spectra and Auger studies of the surface oxidation of cobalt

Surface oxidation of Co has been investigated at different temperatures in the 300–600 K range at oxygen exposures upto 10⁶ L by XPES and AES techniques. In the XPES, both the valence band and core level bands have been employed to monitor the oxidation while in the AES, metal Auger intensity ratios as well as O(KLL)/Co(L₂₃M₄₅M₄₅) ratios have been examined. Only CoO is formed on the surface at high oxygen exposures at and above 500 K. Communication No. 62 from the Solid State and Structural Chemistry Unit.     

Overlap contribution to57Fe3+ isomer shifts in fluorides and oxides

We have calculated the overlap contribution to the contact charge density at the⁵⁷Fe³⁺ site in fluoride and oxide lattices, FeF₃, CaFe₂O₄, CaBaFe₄O₈ and KFeO₂. The trend in isomer shifts in going from one lattice to another is explained in terms of the overlap effects. The experimental values of the change in isomer shift from lattice to lattice is used to obtain the change in nuclear size. The values of r/r _N are found to lie between –0.81×10^–4 and –1.56×10^–4.     

Determination of relaxation characteristics during preacute stage of lysophosphatidyl choline-induced demyelinating lesion in rat brain: an animal model of multiple sclerosis

Relaxation time measurements were carried out during the preacute stage of lesion progression in an animal model of demyelination created in the internal capsule (ic) area of the rat brain using lysophosphatidyl choline (LPC). T1 and T2 were determined both before and after 36 h of lesion creation. Histology carried out on the rats after MR measurements showed focal demyelinating lesion and surrounding edema with prominent infiltration of inflammatory cells. Both T1 and T2 were statistically higher for the lesion compared to that determined before lesion creation. Percentage increase in T2 was found to be higher by approximately 45% compared to before lesion creation while T1 showed about 25% increase. Increase in T1 and T2 may be attributed to the early acute inflammatory response due to LPC. The beginning of the inflammatory response following LPC injection may also be a contributing factor. The study demonstrates that the quantitative estimate of MR relaxation provides useful information on the pathological events occurring during the early phase of the progression of demyelination.     

Electrodeposited carbon-supported nickel sulfide thin films with enhanced stability in acid medium as hydrogen evolution reaction electrocatalyst

A single-step electrochemical deposition of NiS thin films incorporating various carbon nanomaterials as support is described. Advantages of this method are as follows: It is simpler and can be easily scaled up, the precursors employed are cheaper, and the deposition method is energy effective requiring no further heat treatments. Benefits of carbon nanomaterials as catalyst support are manifold including high conductivity and stability. The carbon-supported thin films exhibit high hydrogen evolution activity, low Tafel slopes, and improved double layer capacitance. A remarkable enhancement in the stability of the thin films in the acid medium has been observed. Specifically, NiS/carbon nanofibers have shown the highest activity, lowest Tafel slope, and retained more than 90% of its initial activity after the stability tests.

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Graphical abstract NiS/carbon thin films were fabricated through a highly energy-efficient method as active and highly stable electrocatalysts in acid medium for hydrogen evolution reaction.

     

Electrodeposited Co<Subscript>1-x</Subscript>Mo<Subscript>x</Subscript>S thin films as highly efficient electrocatalysts for hydrogen evolution reaction in acid medium

Efficient and cost-effective electrocatalysts for hydrogen evolution reaction (HER) are significant for the advancement of effective water splitting reaction. Herein, we describe the growth of cobalt molybdenum sulfide (CoMoS) at different composites of tightly packed nanocrystals, prepared by one step process of simple electrodeposition method on fluorine-doped tin oxide (FTO) substrate as highly active and low-cost HER electrocatalyst. The prepared electrocatalysts were characterized via various analytical techniques. The HER activity was evaluated through electrochemical methods such as cyclic voltammetry technique and impedance analysis. Exhaustive electrochemical examinations show that the Co_0.95Mo_0.05S achieved higher cathodic current density value of 14.3 mA/cm² at η?=?250 mV with a lowest Tafel slope value towards HER. Furthermore, the active surface area of the as-deposited composite materials has been calculated by cyclic voltammetry analysis. Hence, the present work illustrates that the Co_0.95Mo_0.05S composite can serve as an encouraging cost-effective substitute to platinum-based electrocatalyst for HER.     

Second moment in wide-line proton magnetic resonance and its relation to packing density of protons in the unit cell

Analysis of the proton magnetic resonance second moment data of more than 60 organic and biological compounds has been carried out. It is shown that with certain classification schemes, such as compounds involving groups of protons (triplets and doublets), the second moment exhibits an approximate linear correlation with the proton density in the unit cell, defined as the number of protons per unit volume in the particular packing adopted by the structure.Contribution No. 562 from the department of Crystallography and Biophysics, University of Madras, Guindry Campus, Madras-600025, India.     

Refinement of the crystal structure of malonic acid,C3H4O4

A reinvestigation of the X-ray crystal structure of malonic acid (C₃H₄O₄) has been made in the light of some observations arising from solid-state¹³C NMR studies on this compound. The unit cell parameters are:a=5.156(1),b=5.341(1),c=8.407(1) Å, =71.48^o (2), =76.12^o (2), =85.09^o (2), space group ,Z=2. The structure was solved by direct methods and refined by full-matrix least-squares refinement to a finalR value of 0.038 for 711 unique reflections withl>3. The packing of the molecules involves dimeric hydrogen bonded association of each carboxyl group with a centrosymmetrically related neighbor. The angles O–C–O (123.3^o and 124.8^o, respectively) for the two carboxyl groups agree qualitatively with the values predicted from a linear relationship relating the observed ₂₂ component of the Carbon-13 NMR chemical shielding tensor for the carboxyl carbon atom to the bond angle O–C–O at the carbon atom.Contribution No. 825.     

A 36 fps SXGA 3-D Display Processor Embedding a Programmable 3-D Graphics Rendering Engine

In this paper, a 3D display processor embedding a programmable 3D graphics rendering engine is proposed. The proposed processor combines a 3D graphics rendering engine and a 3D image synthesis engine to support both true realism and interactivity for the future multimedia applications. Using high coherence between 3D graphics data and 3D display inputs, both pipelines are merged by sharing buffers such that a 3D display engine directly uses the output of a 3D graphics rendering engine. The merged architecture has synergetic coupling effects such as freely providing various rendering effects to 3D images and easily computing disparities without complex extraction processes. In the 3D image synthesis engine, we adopt view interpolation algorithm and propose real-time synthesis method, pixel-by-pixel process. The view interpolation algorithm reduces the number of images to be rendered, resulting in the reduction of external memory size to 64.8% compared to conventional synthesis process. The proposed pixel-by-pixel process synthesizes 3D images at 36 fps through bandwidth reduction of 26.7% and decreases internal memory size to 64.2% compared to typical image-by-image process. The 3D graphics rendering engine is programmable and supports the instruction sets of the latest 3D graphics standard APIs, Pixel Shader 3.0 and OpenGL|ES 2.0. The die contains about 1.7 M transistors, occupies 5 mm times 5 mm in 0.18 mum CMOS and dissipates 379 mW at 1.85 V.     

Giant magnetoresistance (GMR) and ferromagnetic properties of DC and pulse electrodeposited Cu–Co alloys

Cu–Co ferromagnetic alloys occurring as granular films and exhibiting giant magnetoresistance (GMR) property have been synthesized using both DC and pulse electrodeposition techniques. The growth process of these electrodeposits comprising multiple granules of disparate morphology, magnetic features exhibits critical dependence on electrodeposition conditions. Using ferromagnetic resonance and magnetic hysteresis data, we have attempted a correlation between evolution of these electrodeposits and their ferromagnetic properties with special emphasis on GMR property.