Possibilities of collagen adsorption on some polymeric matrices based on styrene copolymers

Seven matrices based on polystyrene and styrene copolymers, with acrylic and methacrylic acid, acryl‐ and methacrylamide, and acrylonitrile and maleic anhydride, are tested in respect of their capacity of collagen adsorption. The aim of the study is to correlate the collagen coupling capacity by the nature of the monomers and the ability of functional groups to obtain biomaterials. The prepared vinylic polymers are relatively hydrophobic. These hydrophobic properties, together with the large mesh interstices, hinder smooth‐cell seeding. In contrast, collagen offers the advantage of specific cell interactions and hydrophilicity. Therefore, synthetic polymers and collagen have been hybridized to combine their advantages. The biocompatibilization process consists of physical immobilization of the protein onto the synthesized matrice surfaces. The content of the adsorbed protein was correlated with the conditions of capture, solution pH, and sorption temperature, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3554–3561, 2006     

Hyperbranched polycarbosiloxanes and polycarbosilanes via bimolecular non-linear hydrosilylation polymerization

The syntheses and selected structure–property relationships of two series of polycarbosiloxanes (HB-PCSOX) and polycarbosilanes (HB-PCS) prepared by the platinum-catalyzed bimolecular non-linear hydrosilylation polymerizations of commercially available 1,3-diallyl- or 1,3-divinyl- disiloxanes or disilanes and tri- or tetra-functional siloxysilanes or silanes (i.e., A_x + B_y polymerization systems where x = 2 and y = 3 or 4) are described. The polymerizations were controlled to avoid gelation and ensure preparation of non-crosslinked soluble polymer products by adjusting the molar ratios of the reacting A (allylsilyl, Si–CH₂–CHCH₂, or vinylsilyl, Si–CHCH₂) and B (silyl, Si–H) reactive functional groups such that r ≤ 1/[(x ? 1)(y ? 1)] or r ≥ (x ? 1)(y ? 1) where r = [A]/[B]. The polymers were characterized by IR, ¹H, ¹³C and ²⁹Si NMR, SEC, DSC and TGA. Their molecular weights were found to increase in the following order of the side-group substitution in the 1,3-divinyldisiloxane monomer used: EtO > Me > MePh > Ph₂, consistent with the increased electron-donation to the vinyl groups causing their increased reactivity in hydrosilylation. These polymers represent unique yet easily and economically available multifunctional nanoscopic dendritic building blocks for more complex 3D nano-structured materials for a variety of applications in electronics, photonics, lithography, specialty coatings, etc.     

Synthesis,Structure, and Explosive Properties of a New Trinitrate Derivative of an Unexpected Condensation Product of Nitromethane with Glyoxal

In the condensation reaction of nitromethane with glyoxal carried out in an aqueous solution of sodium hydroxide, 3,6‐dinitro‐cyclohexane‐1,2,4,5‐tetraol was obtained (the expected product, described in the literature) and, unexpectedly, also tricyclic nitro‐triol (6b‐nitrohexahydro‐2H‐1,3,5‐trioxacyclopenta[cd]‐pentalene‐2,4,6‐triol), which has been unknown until now, was obtained as the main product. The structure of the compound was confirmed with ¹H NMR and ¹³C NMR spectroscopy, LR, and HR‐MS techniques and with single‐crystal X‐ray diffractometry. The tricyclic triol (formally a hemiacetal) was transformed into 6b‐nitrohexahydro‐2H‐1,3,5‐trioxacyclopenta[cd]‐pentalene‐2,4,6‐triyl trinitrate by reaction with 98 % HNO₃. Some explosive properties of this compound were determined including: friction and impact sensitivity, activation energy, detonation velocity, heat of combustion in an oxygen atmosphere and enthalpy of formation. The nitrate ester is a powerful explosive with performance close to that of pentaerythritol tetranitrate (PETN).     

Establishment of High Pressure Pneumatic Standard up to 40?MPa at NPLI

The current paper describes the successful establishment of high pressure pneumatic secondary standard for the realization of national pneumatic pressure scale up to 40?MPa from the previously existing 12?MPa. The traceability as well as the uncertainty in measurement was established through a continuous chain of measurements from very low pressures starting with the ultrasonic interferometer manometer and successive extension in overlapping pressure ranges. For this purpose a piston cylinder assembly designated as NPLI-40, with a pressure range of 0.2?C40?MPa was coupled to a mechanical gas booster through a high gas pressure controller. We have experimentally estimated the zero pressure effective area of piston as well as the distortion coefficient which is traceable to the international system of unit SI. The CMC for the same is now on the BIPM website. The results obtained are discussed in detail.     

Magnetic composites obtainment based on styrene polymers

Three styrene‐based matrices for hybrid composites with ferrite have been obtained by emulsion polymerization in the presence of a tensioactive system: sodium n‐dodecylbenzene sulfate (C₁₂H₂₅C₆H₄SO₃Na) as anionic agent and poly(oxyethylene) nonylphenyl ether [C₉H₁₉C₆H₄(OCH₂CH₂)₃₀OH] as nonionic tensioactive agent. The system assures the steadiness of the emulsion during the reaction and the stability of the latices. The surfactants act as a protective colloid component and thickening agents determining an optimum viscosity and conditions for the further catching of the inorganic oxide with magnetic properties. The obtained polystyrene and styrene copolymers with acrylamide and methacrylamide were analyzed by elemental analysis, IR spectroscopy, DSC, and their viscosity data have been characterized. The size as well as the magnetic properties of composites were also appreciated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4133–4141, 2006     

A low cost laser-raman spectrometer

A Jobin Yvon-Spex (HR640) monochromator with a notch filter (514·5 nm) and Ar⁺ ion laser has been used to set up a low cost laser Raman spectrometer. The selection and setup of the various optical components used in the present work has been solely carried out in our laboratory. The calibration of the monochromator was established from the studies of various standard mercury lines and the obtained data fitted with the reported data. Raman signals have been recorded for a number of samples e.g. diamond, ruby, carbon tetrachloride (CCI₄), benzene (C₆H₆) and ethanol (C₂H₅OH). The obtained results are found to be in excellent agreement with the reported values for these materials in the literature.     

Video viewing: do auditory salient events capture visual attention?

We assess whether salient auditory events contained in soundtracks modify eye movements when exploring videos. In a previous study, we found that, on average, nonspatial sound contained in video soundtracks impacts on eye movements. This result indicates that sound could play a leading part in visual attention models to predict eye movements. In this research, we go further and test whether the effect of sound on eye movements is stronger just after salient auditory events. To automatically spot salient auditory events, we used two auditory saliency models: the discrete energy separation algorithm and the energy model. Both models provide a saliency time curve, based on the fusion of several elementary audio features. The most salient auditory events were extracted by thresholding these curves. We examined some eye movement parameters just after these events rather than on all the video frames. We showed that the effect of sound on eye movements (variability between eye positions, saccade amplitude, and fixation duration) was not stronger after salient auditory events than on average over entire videos. Thus, we suggest that sound could impact on visual exploration not only after salient events but in a more global way.     

Direct gene delivery to synovium. An evaluation of potential vectors in vitro and in vivo

OBJECTIVE: To assess the abilities of various vectors to transfer genes to the synovial lining of joints. METHODS: Vectors derived from retrovirus, adenovirus, and herpes simplex virus as well as cationic liposomes and naked plasmid DNA were evaluated. Each construct contained the lac Z marker gene; and one retroviral construct, and one plasmid also contained a gene encoding human interleukin-1 receptor antagonist. Gene expression was under the control of the human cytomegalovirus promoter in all vectors except the retrovirus, where the endogenous 5' long terminal repeat was retained as the promoter. Cultures of rabbit synovial fibroblasts were exposed to these vectors and stained with X-gal to identify lac Z+ cells. Vectors were then injected directly into rabbits' knee joints, and gene transfer and expression were assessed by X-gal staining and polymerase chain reaction (PCR). RESULTS: Adenovirus was a highly effective vector both in vitro and in vivo, with lac Z gene expression persisting for at least 28 days. However, an inflammatory response was noted in vivo. Cells infected in vitro and in vivo with herpes simplex virus also expressed the lac Z gene at high levels, but expression was limited by cytotoxicity. Retroviruses, in contrast, were effective only under in vitro conditions, permitting cell division. Liposomes gave variable in vitro results; when injected into joints in vivo, gene expression was low and was detectable for only a few days, even though a PCR signal persisted for at least 28 days. Unexpectedly, plasmid DNA was captured by the synoviocytes and expressed transiently following intraarticular injection. CONCLUSION: None of the vectors was ideal for in vivo gene delivery to synovium, although adenovirus was clearly the most effective of those tested. Retroviruses, although poor vectors for in vivo gene delivery, are well suited for ex vivo gene transfer to the synovial lining of joints.     

Proposals for Peace Facilitation in Central America

This paper is an abbreviated version of two interconnected proposals first presented in October and November 1983, to apply transdisciplinary problem-solving skills to the conflicts in Central America. One calls for a survey of key international policy makers and opinion leaders who influence or determine long-range future directions in El Salvador. The other calls for a series of meetings of opinion leaders with a team of facilitators. Agreements to participate have been obtained from some of the principal participants for an initial meeting.     

Cauliflower‐shaped ternary nanocomposites with enhanced power and energy density for supercapacitors

The present research work aimed to study the electrochemical performance of the rGO/PPY/PANI ternary nanocomposite electrodes for supercapacitor applications. The nanocomposites have been prepared by physical blending of rGO with conducting polymers PANI and PPY in five different ratios. The prepared nanocomposites were examined by XRD, IR, Raman, SEM, and XAS characterizations, and from the results, it was found that ternary nanocomposites formed in cauliflower shape, in which PPY and PANI nanoparticles are decorated on to the rGO matrix. In addition, the electrochemical performance of the prepared nanocomposites were studied using cyclic voltammetry, galvanostatic charge‐discharge, and electrochemical impedance spectroscopic studies. The highest values of capacitance, energy density, and power density values achieved were 317.5 F/g, 254 Wh/kg, and 1508.9 W/kg for nanocomposite, respectively, as expected from the synergistic properties of two types of electrode materials resulting in the nanocomposites with hybrid and improved properties. Further, the cyclic stability was also analyzed by performing 4000 long cycles, and the retained capacitance during such long cycles indicates the high potential of rGO/PPY/PANI ternary nanocomposites as electrodes for future energy requirement.