Synthesis and solution properties of comblike polymers from octadecyl methacrylate and acrylic acid

Amphiphilic polymers consisting of a statistical distribution of octadecyl methacrylate (ODMA) and acrylic acid in respective molar ratios of 83-22 and 17-78 mol% and in a molecular-weight range of 2.35-4.70᎒⁴ gmol^-1 have been synthesized. The series of polymers consisting of various mole fractions of ODMA and acrylic acid are expected to exhibit unique characteristics resembling ionomer to hydrophobically modified polyelectrolytes. The changes in the I₃/I₁ emission intensity ratios of pyrene, occurring in the presence of tetrahydrofuran (THF) solutions of the polymers have been taken as the main basis for inferring solution structures. The polymers are found to form random-coil to collapsed-coil/aggregated structures in THF solvent depending on the copolymer compositions. The polymer consisting of 83 mol% ODMA and 17 mol% acrylic acid behaves as an ionomer, capable of forming collapsed-coil structures at concentrations of 0.02 gml^-1 and above as shown by a very high I₃/I₁ of 1.20 (I₃/I₁ of pyrene in THF is 0.85). In contrast, the poly(octadecyl methacrylate) homopolymer and the sets of copolymers consisting of a very high proportion of acrylic acid to an extent of 73 mol% and above contribute to almost negligible or very small changes in I₃/I₁ similar to the homopolymer, poly(octadecyl methacrylate), suggesting the formation of random-coil structures.     

Practical and Chemoselective Reduction of Acyl Chloride to Alcohol by Borohydride in Aqueous Dichloromethane

A simple methodology for the reduction of acid chlorides to their corresponding alcohols has been developed. Various carboxylic acids were converted to alcohols in excellent yields using NaBH₄-K₂CO₃ in a mixed solvent system of dichloromethane and water (1:1) in the presence of a phase-transfer catalyst at low temperature. The importance of the work is its simplicity, selectivity, excellent yield, and very short reaction time. This new reduction condition has proved to be an excellent chemoselective method for a range of acid chlorides in the presence of various functional groups.     

Robust sampled‐data H∞ control for mechanical systems

This article addresses the issue of robust sampled‐data control for a class of uncertain mechanical systems with input delays and linear fractional uncertainties which appear in all the mass, damping, and stiffness matrices. Then, a novel Lyapunov–Krasovskii functional is constructed to obtain sufficient conditions under which the uncertain mechanical system is robustly, asymptotically stable with disturbance attenuation level about its equilibrium point for all admissible uncertainties. More precisely, Schur complement and Jenson's integral inequality are utilized to substantially simplify the derivation of the main results. In particular, a set of sampled‐data controller is designed in terms of the solution of certain linear matrix inequalities that can be solved effectively using available MATLAB software. Finally, a numerical example with simulation result is provided to show the effectiveness and less conservativeness of the proposed sampled‐data control scheme. © 2014 Wiley Periodicals, Inc. Complexity 20: 19–29, 2015     

Raman Imaging: An Impending Approach Towards Cancer Diagnosis

In accordance with the recent studies, Raman spectroscopy is well experimented as a highly sensitive analytical and imaging technique in biomedical research, mainly for various disease diagnosis including cancer. In comparison with other imaging modalities, Raman spectroscopy facilitate numerous assistances owing to its low background signal, immense spatial resolution, high chemical specificity, multiplexing capability, excellent photo stability and non-invasive detection capability. In cancer diagnosis Raman imaging intervened as a promising investigative tool to provide molecular level information to differentiate the cancerous vs non-cancerous cells, tissues and even in body fluids. Anciently, spontaneous Raman scattering is very feeble due to its low signal intensity and long acquisition time but new advanced techniques like coherent Raman scattering (CRS) and surface enhanced Raman scattering (SERS) gradually superseded these issues. So, the present review focuses on the recent developments and applications of Raman spectroscopy-based imaging techniques for cancer diagnosis.     

Theoretical and experimental studies on optically tunable hydrogen bonded liquid crystal complex derived from mesogenic and non-mesogenic aromatic compound

A novel hydrogen bonded liquid crystal (HBLC) complex is synthesized from non-mesogenic benzylmalonic acid (BMA) and mesogenic 4-nonyloxybenzoic acid (9OBA). Structural properties and optimized vibrational frequencies of BMA + 9OBA have been studied by FT-IR spectrum. The weak intermolecular interaction between the molecules is proved by NBO and Mulliken charge distribution analysis. The optical and thermal properties are investigated by POM, DSC, UV-Visible and PL techniques. The present HBLC complex exhibits schlieren textures of nematic, broken focal conic texture of smectic C and multicolored mosaic texture of smectic G phases respectively which is not observed in the pure mesogen (9OBA). The HBLC complex geometry is optimized by DFT method at the level of B3LYP basis set 6311G (d, p). The electronic properties of HBLC complex such as, NBO, HOMO-LUMO, ESP and Mulliken charge distribution are also studied. A noteworthy observation is brought out by identifying the presence of photoluminescence in nematic phase due to the variation in intermolecular interaction of the mesophase. The utility of the same complex is discussed. The phase width, thermal stability factor, tilt angle, phase transition temperature and its enthalpy values are reported.     

Ultrasound assisted,VOSO4 catalyzed synthesis of 4-thiazolidinones: Antimicrobial evaluation of indazole-4-thiazolidinone derivatives

A simple and expedient multicomponent protocol was developed to synthesize 4-thiazolidinones by employing VOSO₄ as a catalyst under ultrasonic irradiation. The significant features of this protocol includes shorter reaction time, high yields, low catalyst loading, and also the catalyst can be recovered and reused up to next four cycles without significant loss in catalytic activity. All the synthesized novel indazole compounds were evaluated for their antibacterial and anti-biofilm activities. Compounds 9n, 9o and 9q showed promising activity (MIC value of 3.9?µg/mL) against K. planticola (MTCC 530). They also exhibited significant bactericidal activity against K. planticola (MTCC 530) (MBC value of 15.6?µg/mL). Additionally, 9n, 9o and 9q inhibited biofilm formation (IC₅₀ values ranging between 20.28–20.79?μg/mL) in this organism.     

Single‐Cell Investigations of Silver Nanoparticle–Bacteria Interactions

Interaction of bacteria with citrate‐reduced silver nanoparticles (AgNPs) of size 25 nm ± 8.5 nm is studied using Raman spectroscopy in conjunction with plasmon resonance imaging of single bacterial cells. Distribution of isolated nanoparticles (NPs) inside Escherichia coli (ATCC 25922; E. coli) is observed by hyperspectral imaging (HSI) as a function of incubation time. Time‐dependent degradation of bacterial DNA upon incubation of AgNPs with E. coli is proven by Raman spectroscopic studies. While attachment of NPs is evident in HSI, molecular changes are evident from the surface‐enhanced Raman spectra of adsorbed DNA and its fragments. Distinct enhancement of DNA features is observed upon interaction of AgNPs and the number of such distinct features increases with incubation time, reaches a maximum, and decreases afterwards. This systematic interaction of DNA with the NPs system and its gradual chemical evolution is proven by investigating isolated plasmid DNA. A comparative Raman study with silver ions has shown that DNA features are observable only when bacteria are incubated with AgNPs. Energetics of interaction examined with microcalorimetry suggests the exothermicity of ?1.547 × 10¹⁰ cal mol^?1 for the NP–bacteria system. Specific interaction of AgNPs with exocyclic nitrogen present in the bases, adenine, guanine, and cytosine, leads to the changes in DNA.     

Raman spectroscopic study of medieval Indian art of 17th century

We report the first Raman spectroscopic investigations of medieval Indian art of 17th century. Three miniature paintings, belonging to Mogul and Rajput schools from the collections of the Madras Museum, were investigated by micro‐Raman spectroscopy using different excitation wavelengths. Many areas in the paintings exhibited rich spectra containing several intense Raman bands. The Raman bands were assigned on the basis of the reported reference spectra of the pigments. Evidences for the presence of massicot, red‐lead, lead‐white, vermilion, litharge, Indian yellow and anatase are found. In addition, tentative assignments of some of the Raman bands to atacamite and orpiment are also made. The present studies suggest that several mineral‐based unique pigments were popular among the Indian artists of this period. Copyright © 2010 John Wiley & Sons, Ltd.