Tuning electrochemical potential of LiCoO2 with cation substitution: first-principles predictions and electronic origin

With a goal to improve the performance of LiCoO₂ as a cathode material in Li-ion batteries, we simulate substitution of various elements (X = Be, Mg, Al, Ga, Si and Ti) for Co using first-principles density functional theory and predict changes in its electrochemical potential. While the electrochemical potential of LiCoO₂ is enhanced with substitution of Be, Mg, Al and Ga for Co, an opposite effect is predicted of Si and Ti substitution. We determine the electronic origin of these changes in electrochemical potential using (a) Bader method of topological analysis of charge density, (b) partial density of electronic states to estimate oxidation states of metal and oxygen, and charge re-distribution upon lithiation. We find that the distribution of electronic charge donated by Li is influenced by the nature of the X–O bond. A larger electron transfer to O (in XO₆ octahedron) upon lithiation leads to stronger Li intercalation and thereby higher electrochemical voltage. Our findings provide a platform for a rational design of cathode materials in Li batteries with enhanced voltage.     

Microfluidics in the “Open Space” for Performing Localized Chemistry on Biological Interfaces

Local interactions between (bio)chemicals and biological interfaces play an important role in fields ranging from surface patterning to cell toxicology. These interactions can be studied using microfluidic systems that operate in the “open space”, that is, without the need for the sealed channels and chambers commonly used in microfluidics. This emerging class of techniques localizes chemical reactions on biological interfaces or specimens without imposing significant “constraints” on samples, such as encapsulation, pre‐processing steps, or the need for scaffolds. They therefore provide new opportunities for handling, analyzing, and interacting with biological samples. The motivation for performing localized chemistry is discussed, as are the requirements imposed on localization techniques. Three classes of microfluidic systems operating in the open space, based on microelectrochemistry, multiphase transport, and hydrodynamic flow confinement of liquids are presented.     

LESSER KNOWN MIRACLES OF BURGERS EQUATION Dedicated to Professor Constantine M. Dafermos on the occasion of his 70th birthday

This article is a short introduction to the surprising appearance of Burgers equation in some basic probabilistic models.     

Droplet shape analysis and permeability studies in droplet lipid bilayers

We apply optical manipulation to prepare lipid bilayers between pairs of water droplets immersed in an oil matrix. These droplet pairs have a well-defined geometry allowing the use of droplet shape analysis to perform quantitative studies of the dynamics during bilayer formation and to determine time-dependent values for the droplet volumes, bilayer radius, bilayer contact angle, and droplet center-line approach velocity. During bilayer formation, the contact angle rises steadily to an equilibrium value determined by the bilayer adhesion energy. When there is a salt concentration imbalance between droplets, there is a measurable change in the droplet volume. We present an analytical expression for this volume change and use this expression to calculate the bilayer permeability to water.     

Dopant induced morphologies of ZnS nanoparticles

We have reported the synthesis of cubic (zinc blende) phase ZnS: Ni²⁺ nanoparticles using a simple wet‐chemical method. Synthesized ZnS: Ni²⁺ nanoparticles had been characterized by X‐ray diffraction (XRD) and Energy Dispersive X‐ray (EDX) analysis. Surface morphologies were studied using Scanning Electron Microscopy (SEM). Fourier Transform Infrared (FTIR) spectra of selected samples were also carried out to confirm the presence of capping agent on the surface of the material. We have demonstrated that various morphologies like spherical, tetrapods, sheet and long‐armed multipods are emerged by simple chemical route without any vigorous reaction parameters and changing the concentration of dopant ions only. The probable mechanism for such morphologies has also been suggested.     

Observation of bulk like magnetic ordering below the blocking temperature in nanosized zinc ferrite

We investigated the magnetic behavior of nanosized zinc ferrite with the help of vibrating sample magnetometry and in-field Mössbauer spectroscopy. The nanoparticles of zinc ferrite with crystallite size ranging from 10 to 62 nm were synthesized by a nitrate method. The structure and phase were determined with the help of X-ray diffraction. Attributes of cation inversion were found with the calculated values of lattice parameter. The saturation magnetization decreases with the increase in crystallite size at room temperature, while these values are almost the same at 10 K for all the samples except the one with crystallite size of 10 nm. The thermal magnetization measurement shows a decrease in blocking temperature with increase in particle size for these samples. The synthesized samples exhibit the presence of antiferromagnetic ordering below the blocking temperature as investigated by in-field Mössbauer spectroscopy.     

Synthesis,characterization and antimicrobial activities of new bis-hydrazonothioxothiazolidinone derivatives

New bis-hydrazonothioxothiazolidinone derivatives based on 2-thioxothiazolidin-4-one were synthesized in good yields using a simplified experimental condition. The structure of synthesized compounds was established with the help of common physico-chemical analysis and various spectroscopic techniques like FT-IR, mass and ¹H NMR. The results of characterizations are in good agreement with the proposed structure of all the synthesized compounds. Further, the antimicrobial (antibacterial and antifungal) activities of all the synthesized derivatives were carried out against various species like Bacillus subtilis, Escherichia coli, Aspergillous niger and Aspergillous flavus by using agar-cup method. The results of antimicrobial screening showed that all the compounds have mild to moderate activity. However, some of the compounds (3a, 3b, 3d, 3e, 3f, 3g, 3i and 3j) have shown better activity than the other.     

Selective reductive transformations using samarium diiodide-water

Samarium diiodide (SmI(2)) is one of the most important reductive electron transfer reagents available in the laboratory. Key to the popularity of SmI(2) is the ability of additives and co-solvents to tune the properties of the reagent. Over the last decade water has emerged as a particularly valuable additive, opening up new chemical space and leading to the discovery of unprecedented selectivity and new reactions promoted by SmI(2). In this Feature Article we review recent progress in the application of SmI(2)-H(2)O systems, with an emphasis on mechanistic considerations and the development of new transformations.     

New parasite inhibitors encompassing novel conformationally-locked 5'-acyl sulfamoyl adenosines

We describe the design, synthesis and biological evaluation of conformationally-locked 5'-acyl sulfamoyl adenosine derivatives as new parasitic inhibitors against Trypanosoma and Leishmania. The conformationally-locked (3'-endo, North-type) nucleosides have been synthesized by covalently attaching a 4'-CH(2)-O-2' bridge () across C2'-C4' of adenosine in order to reduce the conformational flexibility of the pentose ring. This is designed to decrease the entropic penalty for complex formation with the target protein, which may improve free-energy of stabilization of the complex leading to improved potency. Conformationally-locked 5'-acyl sulfamoyl adenosine derivatives (16-22) were tested against parasitic protozoans for the first time in this work, and showed potent inhibition of Trypanosoma cruzi, Trypanosoma brucei, Trypanosoma rhodesiense and Leishmania infantum with IC(50) = 0.25-0.51 μM. In particular, the potent 5'-pentanyl acyl sulfamoyl adenosine derivative 17 (IC(50) = 0.25 μM) against intracellular L. infantum amastigotes and Trypanosoma subspecies is interesting in view of its almost insignificant cytotoxicity in murine macrophage host cells (CC(50) >4 μM) and in diploid human fibroblasts MRC-5 cell lines (CC(50) 4 μM). This work also suggests that variable alkyl chain length of the acyl group on the acylsulfamoyl side chain at 5' can modulate the toxicity of 5'-O-sulfamoylnucleoside analogues. This conformationally-locked sulfamoyl adenosine scaffold presents some interesting possibilities for further drug design and lead optimization.     

Conformal Fluctuations of the Interior Schwarzschild Solution

The basic formalism for conformal fluctuations of the gravitational field is presented. After developing a master propagator for the interior Schwarzschild solution, the time development of the gravitational wave function is considered. The effect of the two classical singularities (resp. pseudo-singularities) of the Schwarzschild solution on the quantum wave function for the gravitational field is studied using a wave function initially localized on the classical solution. While the true singularity at r = 0 imparts consequences on the wave function that cannot be ignored, the pseudo-singularity at the event horizon does not seem to cause any divergences on the interior fluctuations of the Schwarzschild solution.