Synthesis,crystal growth,structural, spectral,optical, thermal and dielectric studies of a new nonlinear optical material: 4-Hydroxy-l-proline-l-tartaric acid (1:1)

Single crystals of a new organic material, 4-hydroxy-l-proline-l-tartaric acid (HPTA) adduct, were grown by slow evaporation of an aqueous solution containing equimolar concentrations of 4-hydroxy-l-proline and l-tartaric acid at room temperature. Formation of new crystal has been confirmed by single crystal X-ray diffraction and NMR spectroscopic techniques. The single crystal XRD analysis shows that a molecule of 4-hydroxy-l-proline and a molecule of free l-tartaric acid both of which are interlinked to each other by two types of H-bonding interactions, namely O(6)–H(6)⋯O(2) and N(1)–H(1B)⋯O(10). The title compound (HPTA) crystallizes in monoclinic crystal system with non-centrosymmetric space group P2₁. The suitability of the crystal for optical applications was studied by UV–Vis–NIR spectroscopy. Fourier transform infrared (FT-IR) spectral analysis was used to confirm the presence of various functional groups in the grown crystals. The thermal stability of the compound was investigated by thermogravimetric and differential thermal analyses. The dielectric constant and dielectric loss of the crystal were studied as a function of frequency and temperature. The fluorescence spectral analysis of the title crystal shows an indigo emission. The second order nonlinear optical (NLO) property of the crystal was confirmed by the modified Kurtz–Perry powder second harmonic generation (SHG) test.     

Fabrication and Characterization of Cytochrome C Modified Poly(3-Aminobenzoic Acid) Thin Film

The electropolymerized poly(3-aminobenzoic acid) (PABA) film on indium tin oxide electrode was used for fabrication of cytochrome c (Cyt c) modified PABA thin film upon immobilization of Cyt c onto the PABA surface. The obtained Cyt c modified PABA thin film was characterized by UV-vis spectroscopy, XPS, AFM, and SEM-EDX techniques. Shifts of the UV-vis absorption peaks were observed from Cyt c modified PABA thin film compared with Cyt c solution and PABA thin film. The formation of the covalent amide bond between the carboxylic groups of PABA and amine groups in Cyt c was observed from XPS results.     

Synthesis and characterization of acetylated sept-D-glucopyranose carbamate as an oligosaccharide donor简

An oligosaccharide donor, acetylated sept-o-glucopyranose tetradecyl carbamate, was designed and synthesized. This compound could be easily linked to hydroxyl-containing compounds through an Oglycosidic bond. Characterization of all the oligosaccharide intermediates and the final product was thoroughly discussed.     

Photo-induced Synthesis and Characterization of Poly（methyl methacrylate） Grafted Sodium Salt of Partially Carboxymethylated Guar Gum

Photo-induced graft copolymerization of methyl methacrylate（MMA） onto sodium salt of partially carboxymethylated guar gum（Na-PCMGG, DS = 0.291） was carried out in an aqueous medium using ceric ammonium nitrate（CAN） as photoinitiator to synthesize a novel graft copolymer, Na-PCMGG-g-PMMA, which may find its potential application as a metal adsorbent. The influences of synthesis variables such as concentrations of photoinitiator（CAN）, nitric acid and monomer（MMA） as well as reaction time, temperature and amount of substrate on the grafting yields were studied and the reaction conditions for optimum photo-grafting were evaluated. At optimum concentration, the maximum values of the grafting yields achieved were G = 271.61% and GE = 63.89%. The experimental results were found to be in very good agreement with the proposed kinetic scheme. The photo-graft copolymerization of MMA onto Na-PCMGG（ DS = 0.291） was also carried out in the presence and absence of ultraviolet radiation for studying the efficiency of the photoinitiator. The influence of carboxymethyl groups introduced onto the guar gum molecules with regard to its behavior towards ultra-violet radiation induced grafting with MMA was also investigated. Photo-grafting process was confirmed and the products were characterized with the help of the spectroscopic（1H-NMR and FTIR） and SEM techniques.     

Characterization of tension set behavior of a silicone rubber at different loads and temperatures via digital image correlation

This work aims to determine the tensile set behavior of a silicone rubber under different stress magnitudes and temperatures through digital image correlation implemented in an improved creep experimental set-up. Creep-recovery strains were measured with time at 20, 40 and 60 °C under tensile strengths of 98.1, 196.2 and 394.3 kPa, respectively. The behavior of creep and recovery strain with time at the different stress magnitudes and temperatures was successfully obtained by the experiments. The corresponding elastic and viscous components of the material for each condition were determined from the results. Overall, all obtained creep behaviors matched with the behavior of a four-element model of creep-recovery. The increase of temperature generated an increase of creep compliance at the three loads, but the increase of tensile load produced a decrease of creep compliance for the three temperatures. The strain was not recovered entirely in any case for the test time stated.     

长碳链聚酰胺及其共聚物的拉伸诱导结晶

长碳链聚酰胺(LCPA)作为聚酰胺的特殊品种,较长的亚甲基链和极性酰胺基团使其兼具聚烯烃和聚酰胺的双重特性.在加工或使用过程中,拉伸诱导结晶现象对长碳链聚酰胺及其共聚物的强度和弹性行为具有重要影响,深入认识其在外场下的微观结构响应对该材料的设计及制备具有重要意义.围绕拉伸诱导结晶作用,该专论主要基于本团队2010年以来在长碳链聚酰胺及其共聚物的拉伸诱导结晶工作,并综述了国内外的相关研究,涉及拉伸诱导结晶现象、拉伸诱导结晶的影响因素、拉伸诱导结晶与力学性能的构效关系及拉伸诱导结晶的表征方法等方面.     

Recent advances in short peptide self-assembly: from rational design to novel applications

Owing to their structural simplicity and robust self-assembled nanostructures, short peptides prove to be an ideal system to explore the physical processes of self-assembly, hydrogels, semi-flexible polymers, quenched disorder, and reptation. Rational design in peptide sequences facilitates cost-effective manufacturing, but the huge number of possible peptides has imposed obstacles for their characterization to establish functional connections to the primary, secondary, and tertiary structures. This review aims to cover recent advances in the self-assembly of designed short peptides, with a focus on physical driving forces, design rules, characterization methods, and exemplar applications. Super-resolution microscopy in combination with modern image analysis have been applied to quantify the structure and dynamics of peptide hydrogels, while small-angle neutron scattering and solid-state nuclear magnetic resonance continue to provide valuable information on structures over complementary length scales. Short peptides are attractive in biomedicine and nanotechnology, e.g., as antimicrobials, anticancer agents, vehicles for controlled drug release, peptide bioelectronics, and responsive cell culture materials.     

Study of new cellulosic dressing with enhanced antibacterial performance grafted with a biopolymer of chitosan and myrrh polysaccharide extract

The treatment of chronic wounds represents a major interest for public health both medically and economically. Hence the need for a modern wound dressing that actively promotes the physiological process specific to healing. In this perspective we have studied the development of a new dressing able to offer a serious contribution to the dilemma of the various chronic wounds. A dressing grafted with two natural polysaccharides known for their multiple biological effects, chitosan and a carbohydrate polymer extracted from Commiphora myrrha (CMP). We began by studying the grafting of the two natural biopolymers onto cellulose dressings, via a polyacrylic acid as a crosslinking agent. An optimization study, revealed the different grafting parameters, the polymer concentration as well as the heat-setting time and temperature. After, different characterization techniques were carried out in order to evaluate the effectiveness of our grafting. The swelling test revealed a hydrophilicity enhancement which increased with the degree of grafting, a desired property for effective dressings. Infrared characterization as well as thermogravimetric analysis (TGA and DTA) confirmed the binding mode and the permanence of our grafting. XRD and mechanical characterization showed no change in the crystallinity or in the original mechanical properties of the functionalized dressings. Morphological SEM study, confirmed the presence of our grafting as well as its mode of distribution. Finally, a bacteriological study conducted, showed a clear improvement of the antimicrobial behavior of cellulosic wound dressings functionalized by our combined natural biopolymers.     

Numerical study of induction heating in melt growth systems—Frequency selection

A set of 2D finite element numerical simulation of induction heating process for an oxide Czochralski crystal growth system has been made for a range of f=1–100 kHz applied frequency of driving current. It was shown that the frequency selection has a marked effect in all basic induction phenomena, including electromagnetic field distribution, skin depth, coil efficiency, and intensity and structure of heating in the growth setup.     

New organotin(IV) complexes with N(4)-methylthiosemicarbazone derivatives prepared from 2,3-dihydroxybenzaldehyde and 2-hydroxy-5-methylbenzaldehyde: synthesis,characterization, and cytotoxic activity

Abstract

The N(4)-methylthiosemicarbazone derivatives H₂DDMT (1) and H₂DMMT (2) have been prepared from the reaction of 4-methylthiosemicarbazide with 2,3-dihydroxybenzaldehyde and 2-hydroxy-5-methylbenzaldehyde, respectively. Six new organotin(IV) complexes, [MeSnCl(DDMT)] (3), [BuSnCl(DDMT)] (4), [PhSnCl(DDMT)] (5), [MeSnCl(DMMT)] (6), [BuSnCl(DMMT)] (7), and [PhSnCl(DMMT)] (8) have been synthesized by direct reaction of corresponding organotin(IV) chloride(s) with these ligands. The ligands and their compounds have been characterized by elemental analysis, molar conductivity, UV–Vis, FT-IR, and NMR (¹H, ¹³C, and ¹¹⁹Sn) spectroscopy. The molecular structures of 1 and 2 were determined by X-ray crystallography. Spectroscopic data suggested that the ligands were coordinated to tin(IV) as dinegative tridentate via phenoxide-O, azomethine-N, and thiolate-S atoms. The crystal structures revealed that the ligands exist in thione form in the solid state. In vitro cytotoxicity assays were carried out for all the compounds against MCF-7 cancer cell line. The results have shown that different organotin(IV) groups showed characteristic differences in their biological activity.