Eco-friendly heterogeneous solid acids as novel and recyclable catalysts in ionic medium for tetrahydropyranols

A variety of aldehydes and homoallylic alcohols undergo smoothly Prins-cyclization on the surface of solid acids such as H-ZSM-5 zeolite or Amberlyst-15^® ion-exchange resin in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to afford the corresponding tetrahydropyranols in high yields with cis-diastereoselectivity. The recovered ionic liquid containing solid acid was recycled in subsequent runs without loss of activity.     

Two new bromotyrosine-derived metabolites from the sponge Psammaplysilla purpurea

Two new bromotyrosine-derived metabolites (1, 2) have been isolated along with the known compounds 3,5-dibromo-4-methoxyphenylacetonitrile, 3-bromo-4-methoxyphenylacetonitrile, 3-bromo-4-hydroxyphenylacetonitrile, 1-hydroxyuracil, 1-methoxyhemibastadin 2, purpuramine H and a steroid 5alpha,8alpha-epidioxycholest-6-en-3beta-ol from the sponge Psammaplysilla purpurea. Compounds 1 and 2 were characterized by interpretation of their spectral data. The antibacterial activity of these compounds is summarized.     

Novel triterpenoid saponins from Mimusops elengi

Two novel triterpenoid saponins, mimusopin ( 3-O-β-D-glucopyranosyl-2β, 3β, 6β, 23-tetrahydroxyolean-12-en-28-oic acid 28-O--L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)[a-L-rhamnopyranosyl-(1→ 3)]--L-rhamnopyranosyl-(1→2)--L-arabinopyranoside)(1) and mimusopsin 3-O-[β-D-glucopyranosyl-(1→3)β-D-gluco-pyranosyl]-2β, 3β, 6β, 23-tetrahydroxyolean-12-en-28-oic acid 28-O--L-rhamnopyranosyl-(1→3)-β-D-xylopyranosyl-(1→4)--L-rhamnopyranosyl-(1→2)--L-arabinopyranoside (2) were isolated from the seeds of Mimusops elengi. Their structures were elucidated by a combination of 2D-NMR (COSY, HOHAHA, HETCOR, HMBC and NOESY), FAB-MS/MS and strategic chemical degradation. In addition, molecular mechanics and dynamics studies showed that the lack of a ¹³C glycosylation shift at the C-4 of the inner rhamnose in 1 could be correlated with distortion in the corresponding torsion angles.     

KMS states and complex multiplication

We construct a quantum statistical mechanical system which generalizes the Bost–Connes system to imaginary quadratic fields K of arbitrary class number and fully incorporates the explicit class field theory for such fields. This system admits the Dedekind zeta function as partition function and the idèle class group as group of symmetries. The extremal KMS states at zero temperature intertwine this symmetry with the Galois action on the values of the states on the arithmetic subalgebra. The geometric notion underlying the construction is that of commensurability of K-lattices.     

Subfemtomole detection of small molecules with microsphere sensors

We investigated the feasibility of using a silica microsphere sensor for detection of small molecules. Using the silica molecules (60 Da) at the sphere's surface as a model system, we measured the spectral shifts in the whispering-gallery modes (WGMs) when the sphere size was decreased by a hydrofluoric acid (HF) solution. The results demonstrate that our sensor is capable of detecting a 4 pm (or 0.01 layer of silica) decrease in sphere radius, corresponding to a change of 0.4 fmol silica molecule. These results suggest that small molecules can be detected in trace quantities at the surface of an optical microsphere sensor.     

Simple 3-designs and PSL(2, q) with q ≡ 1 (mod 4)

In this paper, we consider the action of (2, q) on the finite projective line for q ≡ 1 (mod 4) and construct several infinite families of simple 3-designs which admit PSL(2, q) as an automorphism group. Some of the designs are also minimal. We also indicate a general outline to obtain some other algebraic constructions of simple 3-designs.      

Biomimetic preparation of polymer-supported free radical scavenging, cytocompatible and antimicrobial "green" silver nanoparticles using aqueous extract of Citrus sinensis peel

In the pursuit of making the nanoscale-research greener, the utilization of the reductive potency of a common byproduct of food processing industry i.e. orange peel is reported here to prepare biopolymer-templated "green" silver nanoparticles. Aqueous extract of orange peel at basic pH was exploited to prepare starch supported nanoparticles under ambient conditions. The compositional abundance of pectins, flavonoids, ascorbic acid, sugars, carotenoids and myriad other flavones may be envisaged for the effective reductive potential of orange peel to generate silver nanoparticles. The nanoparticles were distributed within a narrow size spectrum of (3-12 nm) with characteristic Bragg's reflection planes of fcc structure, and surface plasmon resonance peak at 404 nm. Anti-lipid peroxidation assay using goat liver homogenate and DPPH scavenging test established the anti-oxidant potency of the silver nanoparticles. Their synergy with rifampicin against Bacillus subtilis MTCC 736 and cytocompatibility with the human leukemic monocytic cell line, THP-1 were also investigated. Thus, the present work deals with the preparation of starch assisted anti-microbial, cytocompatible and free radical scavenging "green" silver nanoparticles.     

Bio‐based Biodegradable and Biocompatible Hyperbranched Polyurethane: A Scaffold for Tissue Engineering

Hyperbranched polyurethanes are synthesized using TDI, PCL diol, butanediol, and pentaerythritol (1–5 wt%) as the B₄ reactant with and without the monoglyceride of sunflower oil. The biodegradation, physico‐mechanical, and thermal properties are found to be tailored by varying the percentage weight of the branching unit. An MTT/hemolytic assay and subcutaneous implantation in Wistar rats followed by cytokine/ALP assay and histopathology studies confirm a better biocompatibility of HBPU with MG than without MG. HBPU supports the proliferation of dermatocytes with no toxic effect in major organs, in addition the in vitro degraded products are non‐toxic. Cell adherence and proliferation endorse the bio‐based HBPU as a prospective scaffold material in the niche of tissue engineering.

     

Bio‐based hyperbranched polyurethane/Fe3O4 nanocomposites as shape memory materials

The bio‐based shape memory polymers have generated immense interest as advanced smart materials. Mesua ferrea L. seed oil‐based hyperbranched polyurethane (HBPU)/Fe₃O₄ nanocomposites were prepared by the in‐situ polymerization technique. The transmission electron microscopy confirmed the homogeneous distribution of the Fe₃O₄ nanoparticles in polymer matrix, whereas Fourier transform infrared spectroscopic study revealed the presence of strong interfacial interactions between them. The incorporation of Fe₃O₄ (0 to 10 wt%) into the HBPU resulted in an increase in tensile strength (5.5–15 MPa) and scratch resistance (3–6 kg). The thermo‐gravimetric analysis indicated the improvement of thermal stability (240–270°C) of the nanocomposites. The nanocomposites exhibited full shape fixity, as well as almost full shape recovery under the microwave stimulus. The shape recovery speed increased with the increase of Fe₃O₄ nanoparticles content in the nanocomposites. Thus, the studied nanocomposites might be used as advanced shape memory materials in different potential fields. Copyright © 2013 John Wiley & Sons, Ltd.     

Polymeric Foaming with Nanoscale Nucleants: A Surface Nanobubble Mechanism

The dimensionally restricted, diffusion‐driven volumetric change of almost flat nucleated surface nanobubbles hosted on dispersed nanoscale surfaces is proposed as the probable mechanism of heterogeneous bubble generation during polymer–nanoscale‐nucleant suspension foaming. By conducting numerical simulations, this hypothesis is used to predict the final bubble sizes upon polymeric foaming with nanoscale nucleants and to compare them with reported experimentally determined values. The volumetric change in the bubble hosted on the miniscule surface is envisaged to occur due to two parallel diffusion processes: 1) through the contact line of the bubble cap with the surface, and 2) through the curved gas–polymer interface. The foaming conditions determine the direction and molar rate of both these diffusions. The mechanism explains the relative nucleating efficiency of nanoscale surfaces experimentally observed during reactive and nonreactive polymeric foaming by predicting the growth or dissolution of the bubble. In the case of nonreactive thermoplastic foaming, the size of the bubbles released to the bulk from the nanoscale surface varies in a near linear fashion with respect to the size of the nucleants, limited to a maximum nucleant size. Beyond this maximum, the size of bubble generated is independent of the nucleant size. However, increase in the initial nanoscopic contact angle does not significantly affect the bubble size upon detachment from the surface.