RAFT polymerization of N‐vinyl pyrrolidone using prop‐2‐ynyl morpholine‐4‐carbodithioate as a new chain transfer agent

RAFT polymerization of N‐vinyl pyrrolidone (NVP) has been investigated in the presence of chain transfer agent (CTA), i.e., prop‐2‐ynyl morpholine‐4‐carbodithioate (PMDC). The influence of reaction parameters such as monomer concentration [NVP], molar ratio of [CTA]/[AIBN, i.e., 2,2′‐azobis (2‐methylpropionitrile)] and [NVP]/[CTA], and temperature have been studied with regard to time and conversion limit. This study evidences the parameters leading to an excellent control of molecular weight and molar mass dispersity. NVP has been polymerized by maintaining molar ratio [NVP]: [PMDC]: [AIBN] = 100 : 1 : 0.2. Kinetics of the reaction was strongly influenced by both temperature and [CTA]/[AIBN] ratio and to a lesser extent by monomer concentration. The activation energy (E_a = 31.02 kJ mol^?1) and enthalpy of activation (ΔH^?= 28.29 kJ mol^?1) was in a good agreement to each other. The negative entropy of activation (ΔS^? = ?210.16 J mol^‐1K^‐1) shows that the movement of reactants are highly restricted at transition state during polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biomimetic peptide nanosensors

The development of a miniaturized sensing platform tailored for sensitive and selective detection of a variety of biochemical analytes could offer transformative fundamental and technological opportunities. Due to their high surface-to-volume ratios, nanoscale materials are extremely sensitive sensors. Likewise, peptides represent robust substrates for selective recognition due to the potential for broad chemical diversity within their relatively compact size. Here we explore the possibilities of linking peptides to nanosensors for the selective detection of biochemical targets. Such systems raise a number of interesting fundamental challenges: What are the peptide sequences, and how can rational design be used to derive selective binders? What nanomaterials should be used, and what are some strategies for assembling hybrid nanosensors? What role does molecular modeling play in elucidating response mechanisms? What is the resulting performance of these sensors, in terms of sensitivity, selectivity, and response time? What are some potential applications? This Account will highlight our early attempts to address these research challenges. Specifically, we use natural peptide sequences or sequences identified from phage display as capture elements. The sensors are based on a variety of nanomaterials including nanowires, graphene, and carbon nanotubes. We couple peptides to the nanomaterial surfaces via traditional surface functionalization methods or self-assembly. Molecular modeling provides detailed insights into the hybrid nanostructure, as well as the sensor detection mechanisms. The peptide nanosensors can distinguish chemically camouflaged mixtures of vapors and detect chemical warfare agents with sensitivities as low as parts-per-billion levels. Finally, we anticipate future uses of this technology in biomedicine: for example, devices based on these sensors could detect disease from the molecular components in human breath. Overall, these results provide a novel platform for the development of highly sensitive and selective "nanoelectronic noses".     

Hydrotreating of Gas Oil,Jatropha Oil,and Their Blends Using a Carbon Supported Cobalt-Molybdenum Catalyst

Hydrotreating of Jatropha oil and Jatropha oil blended gas oil feeds were studied under diesel hydrotreating conditions using Cobalt-Molybdenum catalyst on activated carbon. The experiments were carried out in pilot plant for more than 90 days first with gas oil, followed by 5%, 10%, and 20% Jatropha oil in gas oil and finally with Jatropha oil alone. Deactivation of the catalyst was not observed up to hydrotreating of 20 wt% Jatropha oil in gas oil, but, the reactor pressure shoots up after seven days of running neat Jatropha oil. The liquid products were characterized by GC-MS analysis, distillation, density, sulfur, nitrogen, and Cetane Index.     

Materials‐Scale Implications of Solvent and Temperature on [6,6]‐Phenyl‐C61‐butyric Acid Methyl Ester (PCBM): A Theoretical Perspective

The ability to detail how molecules pack in the bulk and at the various materials interfaces in the active layer of an organic solar cell is important to further understanding overall device performance. Here, [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM), a preferred electron‐acceptor material in organic solar cells, is studied through molecular dynamics (MD) simulations; the goal is to examine the effects of temperature and trace solvents on the packing and morphological features of bulk PCBM. Solubility (miscibility) parameters, melting and order‐disorder transitions, surface energies, and orientational distributions as a function of different starting configurations are discussed. On the basis of the derived morphologies, electronic structure calculations and a kinetic Monte Carlo approach are combined to evaluate the parameters impacting electron mobility in crystalline and amorphous PCBM structures.     

Polyphenylglyoxamide-Based Amphiphilic Small Molecular Peptidomimetics as Antibacterial Agents with Anti-Biofilm Activity

The rapid emergence of drug-resistant bacteria is a major global health concern. Antimicrobial peptides (AMPs) and peptidomimetics have arisen as a new class of antibacterial agents in recent years in an attempt to overcome antibiotic resistance. A library of phenylglyoxamide-based small molecular peptidomimetics was synthesised by incorporating an N-alkylsulfonyl hydrophobic group with varying alkyl chain lengths and a hydrophilic cationic group into a glyoxamide core appended to phenyl ring systems. The quaternary ammonium iodide salts 16d and 17c showed excellent minimum inhibitory concentration (MIC) of 4 and 8 μM (2.9 and 5.6 μg/mL) against Staphylococcus aureus, respectively, while the guanidinium hydrochloride salt 34a showed an MIC of 16 μM (8.5 μg/mL) against Escherichia coli. Additionally, the quaternary ammonium iodide salt 17c inhibited 70% S. aureus biofilm formation at 16 μM. It also disrupted 44% of pre-established S. aureus biofilms at 32 μM and 28% of pre-established E. coli biofilms 64 μM, respectively. A cytoplasmic membrane permeability study indicated that the synthesised peptidomimetics acted via disruption and depolarisation of membranes. Moreover, the quaternary ammonium iodide salts 16d and 17c were non-toxic against human cells at their therapeutic dosages against S. aureus.     

Assessment of Crohn's disease lesions in wireless capsule endoscopy images

Capsule endoscopy (CE) provides noninvasive access to a large part of the small bowel that is otherwise inaccessible without invasive and traumatic treatment. However, it also produces large amounts of data (approximately 50,000 images) that must be then manually reviewed by a clinician. Such large datasets provide an opportunity for application of image analysis and supervised learning methods. Automated analysis of CE images has only focused on detection, and often only for bleeding. Compared to these detection approaches, we explored assessment of discrete disease for lesions created by mucosal inflammation in Crohn's disease (CD). Our work is the first study to systematically explore supervised classification for CD lesions, a classifier cascade to classify discrete lesions, as well as quantitative assessment of lesion severity. We used a well-developed database of 47 studies for evaluation of these methods. The developed methods show high agreement with ground truth severity ratings manually assigned by an expert, and good precision ( > 90% for lesion detection) and recall ( > 90%) for lesions of varying severity.     

Effect of Particle Size on the Microwave Dielectric Properties of Alumina-Filled PTFE Substrates

α-alumina of different particle sizes of 50 nm, 0.4, 3, and 7 μm have been incorporated into the PTFE matrix to prepare flexible composite substrates. A proprietary process comprising of sigma mixing, extrusion, and calendering, followed by hot pressing (SMECH process) has been used to obtain dimensionally stable ceramic-filled PTFE substrates. Variation of the dielectric constant, loss tangent and moisture absorption of filled PTFE composites has been ascertained as a result of filler loading.     

Effect of plasma treatment on the seed germination and seedling growth of radish (Raphanus sativus)

The effect on the germination and seedling growth of radish (Raphanus sativus) seeds were examined employing a dielectric barrier discharge (DBD) at atmospheric pressure and room temperature for various treatment time. DBD plasma using argon gas of flow rate 2 l m−1 was employed in this study. Radish seeds were treated with DBD plasma for 1–5 min, respectively. Germination characteristics, seedling growth parameters, the contact angle of the seed coat, water uptake capacity, mass loss, the temperature of the seeds, chlorophyll, and carotenoid contents of the seedlings were measured before and after the DBD plasma treatments. Plasma treatment of radish seeds significantly increased germination-related characters, including germination percentage, fresh and dry weight, vigor index, and total carotenoids contents. However, the cumulative production rate was found to be decreased. Results from the experiment indicate an acceleration in the water uptake of the radish seeds and make the seed surface hydrophilic by plasma treatment. Scanning electron microscopy analysis showed that etching effects on the seed coat occurred after the argon plasma treatments, which affected the wettability of the radish seed. The experimental findings showed that seeds being treated by DBD plasma for 2 and 3 min had a positive effect on the germination and seedling growth of radish.     

Physical and chemical response of 145 MeV Ne ion irradiated polymethylmethacrylate (PMMA) polymer

Characterization of ion induced modifications in the physical, chemical and structural properties of polymethylmethacrylate (PMMA) polymer induced by 145 MeV Ne⁶⁺ ions has been carried out by FTIR, UV-Visible, Differential scanning calorimetry (DSC) and X-ray diffraction. Heavy ion irradiation was carried out under a vacuum of ∼10⁻⁶ torr at Variable Energy Cyclotron Centre, Kolkata, India using a low beam current (∼15 nA). Ion fluences of 10¹⁰, 10¹¹, 10¹², 10¹³ ions/cm² were used. The optical band gap (E_g), calculated from the absorption edge of the UV-Vis spectra of these films in 200-800 nm region varied from 2.167 eV to 1.512 eV for virgin and irradiated samples. In FTIR spectra appreciable changes have been observed after irradiation, indicating the molecular fragmentation, cross-linking, formation of unsaturated groups and free radicals. DSC thermograms give information about the thermal stability and type of thermal reactions (exothermic/endothermic) on the application of heat to the polymer. XRD analyses show slight shift of peak position and significant changes in peak intensity. XRD results show a decrease of ∼4.12% in crystallite size of irradiated sample at the higher fluence of 10¹² ions/cm².     

Effects of phase lags on wave propagation in an infinite solid due to a continuous line heat source

The present work is concerned with the wave propagation in a homogeneous, isotropic and unbounded solid due to a continuous line heat source under the theory of thermoelasticity with three phase-lags (Roychoudhari in J Therm Stress 30:231?C238, 2007). For the solution of the problem, we employ a potential function approach together with Laplace and Hankel transform method. Analytical expressions for the distributions of different fields like temperature, displacement and stresses inside the medium are derived by inverting Laplace transforms in an approximate manner for small values of time. The problem is illustrated by computing numerical values of the field variables for a particular material. The theoretical as well as numerical results are compared with the corresponding results for other theories of thermoelasticity reported earlier.