Mobility and glass transition temperature of polymer nanospheres

Recent studies have illustrated a decoupling between cooperative segmental mobility and the glass transition temperature (T_g) of thin polymer films and nanocomposites. Here, we use dielectric spectroscopy to probe the cooperative segmental mobility and capacitive dilatometry to determine the T_g of films of polystyrene nanospheres with diameters (d) less than 400 nm. We find that both capacitive dilatometry and calorimetry revealed nearly identical suppressions in T_g as the size of the nanospheres was reduced. While T_g was impacted by confinement, in the range 130 nm ≤ d ≤ 400 nm, in stark contrast, the cooperative segmental mobility, i.e., the peak position of the α-relaxation process was not. Furthermore, when d ≤ 200 nm, an additional molecular relaxation process, not observed in bulk, was present. We interpret these findings as evidence of a decoupling between T_g and cooperative segmental mobility in nanospheres. That is, the latter may be impacted by confinement under conditions in which the former is not.     

Lipidosterolic Extract of Serenoa Repens Modulates the Expression of Inflammation Related-Genes in Benign Prostatic Hyperplasia Epithelial and Stromal Cells

Despite the high prevalence of histological Benign Prostatic Hypeplasia (BPH) in elderly men, little is known regarding the molecular mechanisms and networks underlying the development and progression of the disease. Here, we explored the effects of a phytotherapeutic agent, Lipidosterolic extract of the dwarf palm plant Serenoa repens (LSESr), on the mRNA gene expression profiles of two representative models of BPH, BPH1 cell line and primary stromal cells derived from BPH. Treatment of these cells with LSESr significantly altered gene expression patterns as assessed by comparative gene expression profiling on gene chip arrays. The expression changes were manifested three hours following in vitro administration of LSESr, suggesting a rapid action for this compound. Among the genes most consistently affected by LSESr treatment, we found numerous genes that were categorized as part of proliferative, apoptotic, and inflammatory pathways. Validation studies using quantitative real-time PCR confirmed the deregulation of genes known to exhibit key roles in these biological processes including IL1B, IL1A, CXCL6, IL1R1, PTGS2, ALOX5, GAS1, PHLDA1, IL6, IL8, NFkBIZ, NFKB1, TFRC, JUN, CDKN1B, and ERBB3. Subsequent analyses also indicated that LSESr treatment can impede the stimulatory effects of certain proinflammatory cytokines such as IL6, IL17, and IL15 in these cells. These results suggest that LSESr may be useful to treat BPH that manifest inflammation characteristics. This also supports a role for inflammation in BPH presumably by mediating the balance between apoptosis and proliferation.     

Network Rearrangement in AgI‐Doped GeTe4 Glasses

The structure of (GeTe₄)_1?x(AgI)_x (x = 0.15 and 0.25) glasses has been investigated by X‐ray and neutron diffraction as well as extended X‐ray absorption spectroscopy (EXAFS) and Raman spectroscopy. Large‐scale structural models have been obtained by fitting simultaneously the experimental datasets in the framework of the reverse Monte Carlo simulation technique (RMC). Short‐range order parameters have been calculated and compared with that of GeTe₄. Doping with AgI affects the structure of the host GeTe₄ matrix in two ways. First, while Te is essentially twofold coordinated in GeTe_4, its coordination number is as high as ~2.9 ± 0.3 for x = 0.25. The change is mainly due to the increased fraction of Te–Te bonds. Second, Ge atoms remain fourfold coordinated but the tetrahedral symmetry is distorted due to the elongation of some Ge–Te bonds. The incorporation of AgI in the GeTe₄‐based host covalent matrix and the Te coordination increase explains the enhanced thermal stability of (GeTe₄)_1?x(AgI)_x in the supercooled liquid‐state hindering the crystallization of Te found in case of GeTe₄ glass.     

Ribbon-like Foldamers for Cellular Uptake and Drug Delivery

Different intracellular delivery systems of bioactive compounds have been developed, including cell-penetrating peptides. Although usually nontoxic and biocompatible, these vectors share some of the general drawbacks of peptides, notably low bioavailability and susceptibility to protease degradation, that limit their use. Herein, the conversion of short peptide sequences into poly-α-amino-γ-lactam foldamers that adopt a ribbon-like structure is investigated. This template is used to distribute critical cationic and/or hydrophobic groups on both sides of the backbone, leading to potent short, cell-permeable foldamers with a low positive-charge content. The lead compound showed dramatically improved protease resistance and was able to efficiently deliver a biologically relevant cargo inside cells. This study provided a simple strategy to convert short peptide sequences into efficient protease-resistant cell-penetrating foldamers.     

Polypyrrole material for the electrostatic discharge sensitivity mitigation of Al/SnO2 energetic composites

Nanothermites are composite energetic materials made of fuel and oxidizer nanoparticles characterized by impressive exothermic reactions (highly flame temperatures and impressive heat combustion releases). However, nanothermites suffer from their high electrostatic discharge (ESD) sensitivity that may be at the origin of accidental ignitions during handling. The present study deals with the use of doped-polypyrrole conducting polymer in aluminum/tin (IV) oxide energetic formulation (Al/SnO₂). X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, conductivity measurements, sensitivities and combustion tests were implemented to characterize the polypyrrole-doped Al/SnO₂ energetic composite. The results revealed a significant gradual ESD desensitization of the nanothermite (<0.14 mJ to 246.40 mJ) as a function of the doped-polypyrrole amount (0 to 15 wt%). The reactive properties of the polypyrrole-enriched Al/SnO₂ nanothermite were verified and an acceptable reactive behavior was claimed. The successful adding of doped-polypyrrole conducting polymer within energetic nanocomposites is reported for the first time.     

Alginate grafted with poly(ε‐caprolactone): effect of enzymatic degradation on physicochemical properties

The paper discusses the enzymatic behaviour of a series of copolymers composed of alginate grafted with poly(ε‐caprolactone) (PCL) of various lengths and degrees of substitution. The study is focused on viscosity measurements and pyrene probe fluorescence with or without two enzymes: alginate lyase, which breaks the alginate backbone; and esterase, which breaks PCL pendent groups. Alginate lyase is inactive at pH = 3.8 and degrades quickly all copolymers at pH = 6.3. The degradation is not complete and is slowed down by the presence of PCL. Esterase degrades only copolymers with long pendent PCL groups. It has no effect on copolymers when PCL has a length of 530 g mol^?1. These systems are good candidates for controlled release of drugs using an enzymatic method. Copyright © 2012 Society of Chemical Industry     

Fish Oil and Microalga Omega-3 as Dietary Supplements: A Comparative Study on Cardiovascular Risk Factors in High-Fat Fed Rats

Dietary supplementation with marine omega‐3 polyunsaturated fatty acids (n‐3 PUFA) can have beneficial effects on a number of risk factors for cardiovascular disease (CVD). We compared the effects of two n‐3 PUFA rich food supplements (freeze‐dried Odontella aurita and fish oil) on risk factors for CVD. Male rats were randomly divided into four groups of six animals each and fed with the following diets: control group (C) received a standard diet containing 7 % lipids; second group (HF high fat) was fed with a high‐fat diet containing 40 % lipids; third group (HFFO high fat+fish oil) was fed with the high‐fat diet supplemented with 0.5 % fish oil; and fourth group (HFOA high fat+O. aurita) received the high‐fat diet supplemented with 12 % of freeze‐dried O. aurita. After 8 weeks rats fed with the high‐fat diet supplemented with O. aurita displayed a significantly lower bodyweight than those in the other groups. Both the microalga and the fish oil significantly reduced insulinemia and serum lipid levels. O. aurita was more effective than the fish oil in reducing hepatic triacyglycerol levels and in preventing high‐fat diet‐induced steatosis. O. aurita and fish oil also reduced platelet aggregation and oxidative status induced by high fat intake. After an OA supplementation, the adipocytes in the HFOA group were smaller than those in the HF group. Freeze‐dried O. aurita showed similar or even greater biological effects than the fish oil. This could be explained by a potential effect of the n‐3 PUFA but also other bioactive compounds of the microalgae.     

X‐ray photoelectron spectroscopy analysis of Ge–Sb–Se pulsed laser deposited thin films

Pulsed laser deposition was used to prepare amorphous thin films from (GeSe₂)_100?x(Sb₂Se₃)_x system (x = 0, 5, 10, 20, 30, 40, 50, and 60). From a wide variety of chalcogenide glass‐forming systems, Ge–Sb–Se one, especially in thin films form, already proved to offer a great potential for photonic devices such as chemical sensors. This system has a large glass‐forming region which gives the possibility to adjust the chemical composition of the glasses according to required physical characteristics. The chemical composition of fabricated thin films was analyzed via X‐ray photoelectron spectroscopy (XPS) and compared to energy dispersive spectroscopy (EDS) data. The results of both techniques agree well: a small deficiency in chalcogen element and an excess of antimony was found. The structure of as‐deposited thin films has been investigated by XPS. The presence of the two main structural units, [GeSe₄] and [SbSe₃] proposed by Raman scattering spectroscopy data analysis, was confirmed by XPS. Moreover, XPS core level spectra analysis revealed the presence of M–M bonds (M = Ge, Sb) in (Ge,Sb)–Ge–(Se)₃ and (Ge,Sb)–Sb–(Se)₂ entities that could correspond to Ge‐based tetrahedra and Sb‐based pyramids where one of its Se atoms at corners is substituted by Ge or Sb ones. The content of depicted M–M bonds tends to increase with introduction of antimony in the amorphous network of as‐deposited thin films from x = 0 to x = 40 and then it decreases. XPS analysis of as‐deposited thin films shows also the presence of the (Ge,Sb)–Se–(Ge,Sb) and Se–Se–(Ge,Sb) entities.     

Experimental study of laminar flames obtained by the homogenization of three forest fuels

This work aims to improve the understanding of the parameters involved in the burning of vegetative fuels. As the role of the surface-to-volume ratio is already known, we focused on the influence of other parameters. Three Mediterranean species (Pinus pinaster, Erica arborea and Cistus monspeliensis) were crushed in order to decrease the surface-to-volume ratio effects. The burning of these fuel samples produces unsteady, axisymmetric, non-premixed, laminar flames. The thermal properties and the mass loss of the crushed fuels, the distribution of temperature inside the sample and in the flame, the gases released by the fuels and the flame geometry were investigated. Thanks to these experimental data, the influence of the different fuel properties was underlined. We observed that the mass burning rate of the samples mainly controls the flame dynamics. However, the combustion kinetics in the flame depends on the degradation gases released by the fuels: the reaction zone is shifted and the flame height is changed. It appears that the composition of the degradation gases has to be taken into account to improve forest fire modeling.     

4th generation synchrotron source boosts crystalline imaging at the nanoscale

New 4th-generation synchrotron sources,with their increased brilliance,promise to greatly improve the performances of coherent X-ray microscopy.This perspective...