Brine-Mediated Efficient Benzoylation of Primary Amines and Amino Acids

Benzoylation of primary amines and amino acids is efficiently carried out in a brine solution using a stoichiometric amount of benzoyl chloride followed by trituration with aqueous saturated bicarbonate solution.     

Anomalous diffusion in an electrolyte saturated paper matrix

Diffusion of colored dye on water saturated paper substrates has been traditionally exploited with great skill by renowned water color artists. The same physics finds more recent practical applications in paper-based diagnostic devices deploying chemicals that react with a bodily fluid yielding colorimetric signals for disease detection. During spontaneous imbibition through the tortuous pathways of a porous electrolyte saturated paper matrix, a dye molecule undergoes diffusion in a complex network of pores. The advancing front forms a strongly correlated interface that propagates diffusively but with an enhanced effective diffusivity. We measure this effective diffusivity and show that it is several orders of magnitude greater than the free solution diffusivity and has a significant dependence on the solution pH and salt concentration in the background electrolyte. We attribute this to electrically mediated interfacial interactions between the ionic species in the liquid dye and spontaneous surface charges developed at porous interfaces, and introduce a simple theory to explain this phenomenon.     

Application of multilayered strategy for variable selection in QSAR modeling of PET and SPECT imaging agents as diagnostic agents for Alzheimer’s disease

Structural Chemistry - Non-invasive imaging of amyloid beta (Aβ) and tau fibrils in the brain may support an early and precise diagnosis of Alzheimer’s disease. Molecular imaging...     

Esterification and ketalization of levulinic acid with desilicated zeolite β and pseudo-homogeneous model for reaction kinetics

To maximize the production of esters (E), keto (K) and keto-ester (KE) by esterification and ketalization of levulinic acid (LA) has been reacted using diols such as 1,2-propane diol (PDOL),1,2-ethane diol (EDOL), and 1,2,3-propane triol or glycerol (TRIOL) with desilicated Hβ. This work aims to assess the conversion and selectivity for the production of esters using conventional and microwave-irradiated (MWI) reactors. Catalysts characterizations were performed using NH₃-temperature programme desorption, Brunauer, Emmett and Teller surface area (BET), Barrett, Joyner, and Halenda (BJH), scanning electron microscope, transmission electron microscope, and dynamic light scattering. Operating parameters such as reaction temperature (170–180°C), reaction time (20–80 min), feed composition (LA:PDOL/EDOL/TRIOL, 1:8/10/12), and microwave energy (300–500 watt) have been systematically investigated. Note that 99–100% conversion was achieved with the product selectivity of E (40%), K (30%), and KE (30%) with1,2-EDOL; E (56%), K (2%), and KE (17%) with 1,2-PDOL; E (69%), K(0%), and KE (22%) with TRIOL using D-Hβ as a solid catalyst in an MWI reactor. Reaction paths and kinetics were studied using pseudo-homogeneous (PH) model.     

Direct Participation of Solvent Molecules in the Formation of Supramolecular Polymers

This article reports supramolecular polymerization of two bis-amide functionalized naphthalene-diimide (NDI) building blocks (NDI−L and NDI−C) in two solvents, namely n-heptane (Hep) and methylcyclohexane (MCH). NDI−L and NDI−C differ only by the peripheral hydrocarbon wedges, consisting of linear C7 chains or cyclic methylcyclohexane rings, respectively. UV/Vis and FTIR spectroscopy studies reveal distinct internal order and H-bonding pattern for NDI−L and NDI−C aggregates irrespective of the solvent system, indicating the dominant role of the intrinsic packing parameters of the individual building block, possibly influenced by the peripheral steric crowding. However, NDI−L produces a significantly stronger gel in Hep compared to MCH as evident from the rheological and thermal properties. In contrast, NDI−C exhibits a clear preference for MCH, producing gel with moderate strength but in Hep it fails to produce 1D morphology or gelation. All-atom molecular dynamics (MD) simulation studies corroborate with the experimental observation and provide the rationale for the observed solvent-shape effect by revealing a quantitative estimate regarding the thermodynamics of self-assembly in these four combinations. Such clear-cut shape-matching effect (between the peripheral hydrocarbon wedge and the solvent system) unambiguously support a direct participation of the solvent molecules during supramolecular polymerization and presence of a closely-adhered solvent shell around the supramolecular polymers, similar to the first layer of water molecules around the protein surface. Solvent induced CD experiments support this hypothesis as induced CD band was observed only from a chiral co-solvent of matching shape. This is reconfirmed by the higher de-solvation temperature of the shape-matching NDI/solvent system combination compared to the shape mis-match combination in variable temperature UV/Vis experiments, revealing transformation to a different aggregate at higher temperatures rather than disassembly to the monomer for all four combinations.     

Polarization encoded all-optical quaternary R-S flip-flop using binary latch

The developments of different multi-valued logic (MVL) systems have received considerable interests in recent years all over the world. In electronics, efforts have already been made to incorporate multi-valued system in logic and arithmetic data processing. But, very little efforts have been given in realization of MVL with optics. In this paper we present novel designs of certain all-optical circuits that can be used for realizing multi-valued logic functions. Polarization encoded all-optical quaternary (4-valued) R-S flip-flop is proposed and described. Two key circuits (all-optical encoder/decoder and a binary latch) are designed first. They are used to realize quaternary flip-flop in all-optical domain. Here the different quaternary logical states are represented by different polarized state of light. Terahertz Optical Asymmetric Demultiplexer (TOAD) based interferometric switch can take an important role. Computer simulation result confirming described methods and conclusion are given in this paper.     

Surface and interfacial structural characterization of MBE grown Si/Ge multilayers

Si/Ge multilayer structures have been grown by solid source molecular beam epitaxy (MBE) on Si (1 1 1) and (1 0 0) substrates and were characterized by high-resolution X-ray diffraction (XRD), atomic force microscopy (AFM), high-depth-resolution secondary ion mass spectroscopy (SIMS) and cross-section high-resolution transmission electron microscopy (HRTEM). A reasonably good agreement has been obtained for layer thickness, interfacial structure and diffusion between SIMS and HRTEM measurements. Epitaxial growth and crystalline nature of the individual layer have been probed using cross-sectional HRTEM and XRD measurements. Surface and interface morphological studies by AFM and HRTEM show island-like growth of both Si and Ge nanostructures.     

Energy Conditions,Cosmological Solutions and Cosmic No-Hair Conjecture in Gauss-Bonnet Theory

A detailed investigation of Gauss-Bonnet theory has been done from a different perspective. At first, the standard energy conditions are discussed and modified forms have been presented. Then some cosmological solutions have been obtained in 5D for perfect fluid assuming that the extra dimensional metric coefficient decreases with time. For some particular choice of the parameters, exponential solutions are obtained and finally, Cosmic No-Hair Conjecture has been proved for Gauss-Bonnet dilatonic scalar coupled to Einstein gravity with coupling parameter growing linearly in time.