Direct-writing of PbS nanoparticles inside transparent porous silica monoliths using pulsed femtosecond laser irradiation

Pulsed femtosecond laser irradiation at low repetition rate, without any annealing, has been used to localize the growth of PbS nanoparticles, for the first time, inside a transparent porous silica matrix prepared by a sol-gel route. Before the irradiation, the porous silica host has been soaked within a solution containing PbS precursors. The effect of the incident laser power on the particle size was studied. X-ray diffraction was used to identify the PbS crystallites inside the irradiated areas and to estimate the average particle size. The localized laser irradiation led to PbS crystallite size ranging between 4 and 8 nm, depending on the incident femtosecond laser power. The optical properties of the obtained PbS-silica nanocomposites have been investigated using absorption and photoluminescence spectroscopies. Finally, the stability of PbS nanoparticles embedded inside the host matrices has been followed as a function of time, and it has been shown that this stability depends on the nanoparticle mean size.     

Efficient Immobilization of Yeast Transketolase on Layered Double Hydroxides and Application for Ketose Synthesis

Transketolase (TK) from S. cerevisiae was successfully immobilized on layered double hydroxides (LDH) using simple, affordable and efficient adsorption and coprecipitation based immobilization procedures. Optimization of the preparation was performed using zinc aluminium nitrate (Zn₂Al‐NO₃) and magnesium aluminium nitrate (Mg₂Al‐NO₃) LDH as immobilization supports, and the protein‐to‐LDH weight ratio (Q) was varied. The highest immobilization yields (98–99%) and highest relative specific activities (4.2–4.4 U⋅mg⁻¹ for the immobilized enzyme compared to 4.5 U⋅mg⁻¹ for the free enzyme) were both achieved when using a protein‐to‐LDH weight ratio (Q) of 0.38. Efficient lyophilization of the LDH‐TK bionanocomposites thus synthesized was proven to allow easy use and storage of the supported TK with no significant loss of activity over a three‐month period. The kinetic parameters of the LDH‐TK enzyme were comparable to those of the free TK. The LDH‐TK enzyme was finally tested for the synthesis of L ‐erythrulose starting from hydroxypyruvate lithium salt (Li‐HPA) and glycolaldehyde (GA) as substrates. L ‐erythrulose was characterized and obtained with an isolated yield of 56% similar to that obtained with free TK. The reusability of the LDH‐TK biohybrid material was then investigated, and we found no loss of enzymatic activity over six cycles.     

Plant Chemical Defense Induced by a Seed-Eating Pollinator Mutualist

Plant-seed parasite pollination mutualisms involve a specific pollinator whose larvae develop by consuming a fraction of the host plant seeds. These mutualisms are stable only if the plant can control seed destruction by the larvae. Here, we studied the chemical response of the European globeflower Trollius europaeus to infestation by an increasing number of Chiastocheta fly larvae. We used liquid chromatographic analysis to compare the content of phenolic compounds in unparasitized and parasitized fruits collected in two natural populations of the French Alps, and mass spectrometry and nuclear magnetic resonance to elucidate the structure of adonivernith, a C-glycosyl-flavone. This compound is present in many of the organs of T. europaeus, but not found in other Trollius species. Furthermore, it is overproduced in the carpel walls of parasitized fruits, and this induced response to infestation by fly larvae is density-dependent (increases with larval number), and site-dependent (more pronounced in the high-altitude site). Mechanical damage did not induce adonivernith production. This tissue-specific and density-dependent response of T. europaeus to infestation by Chiastocheta larvae might be an efficient regulation mechanism of seed-predator mutualist population growth if it decreases survival or growth of the larvae.     

The Effect of Pore Morphology on Hot Spot Temperature

Composite explosives contain pores that collapse under shock wave interaction generating localized regions of heat known to be important in the initiation of high explosives. Understanding pore collapse under shock loading is essential to create predictive reactive flow models to simulate the initiation process. While spherical pore collapse has been thoroughly simulated, other geometries have been relatively neglected. Simulating microoscale hot spot nucleation, we analyze the effect of pore morphology on the post‐shock hot spot temperature. Several pore morphologies that yield higher temperatures than the spherical case are revealed and discussed. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE‐AC52‐07NA27344.     

Microporous network‐assisted formation of copper‐in‐polymer gradient composite film

In this article, a copper‐in‐polymer‐gradient composite film (CPGCF) was synthesized by electrochemical strategy via reducing a solvent‐swollen cathode film (SCF). The latex nanoparticles of a ternary copolymer including styrene, butyl acrylate, and acrylic acid structural units play the key role to form well‐graded copper distribution in this ternary copolymer matrix through the porous morphological structure developed by latex nanoparticle semimelt joining. The morphological structure along cross‐section of CPGCF includes three layers: (1) a dense copper layer in ternary copolymer matrix whose most outside was originally attached to cathode in electrochemical reactor, (2) a shrublike layer that grew from dense copper layer, and (3) a clear layer in which there is no obvious reduced copper phase whose most outside was originally contacted with liquid electrolyte medium in electrochemical reactor. As experimental aspects, the influences of emulsion polymerization conditions of ternary copolymer, predrying time and temperature of SCF, dc voltage in electrochemical reduction on CPGCF structure were investigated. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Calorimetric study of fluorinated methacrylic and vinyl polymer blends: part 2: correlation between miscibility, chemical structure and χ12 interaction parameter in binary systems

The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester-MMA) copolymers (MMA-MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA-MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA-MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory-Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ₁₂ increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ₁₂ values as compared to VDF-TFE or particularly to VDF-TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values.     

Acute Generalized Exanthematous Pustulosis: Pathogenesis,Genetic Background,Clinical Variants and Therapy

Acute generalized exanthematous pustulosis (AGEP) is a severe, usually drug-related reaction, characterized by an acute onset of mainly small non-follicular pustules on an erythematous base and spontaneous resolution usually within two weeks. Systemic involvement occurs in about 20% of cases. The course is mostly benign, and only in rare cases complications lead to life-threatening situations. Recent studies highlight the importance of genetic variations in interleukin-36 receptor antagonist gene (IL-36RN) in the pathogenesis of this disease. The physiopathology of AGEP remains unclear, but an involvement of innate and acquired immune cells together with resident cells (keratinocytes), which recruit and activate neutrophils via production of cytokines/chemokines such as IL-17, IL-36, granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor alpha (TNFα) and chemokine (C-X-C motif) ligand 8 (CXCL8)/IL-8, has been postulated. Treatment is based on the removal of the causative drug, supportive care, infection prevention and use of potent topical or systemic steroids.     

pH‐Cleavable Nucleoside Lipids: A New Paradigm for Controlling the Stability of Lipid‐Based Delivery Systems

Lipid‐based delivery systems are an established technology with considerable clinical acceptance and several applications in human. Herein, we report the design, synthesis and evaluation of novel orthoester nucleoside lipids (ONLs) for the modulation of liposome stability. The ONLs contain head groups with 3′‐orthoester nucleoside derivatives featuring positive or negative charges. The insertion of the orthoester function in the NL structures allows the formation of pH‐sensitive liposomes. ONL‐based liposomes can be hydrolyzed to provide nontoxic products, including nucleoside derivatives and hexadecanol. To allow the release to be tunable at different hydrolysis rates, the charge of the polar head structure is modulated, and the head group can be released at a biologically relevant pH. Crucially, when ONLs are mixed with natural phosphocholine lipids (PC), the resultant liposome evolves toward the formation of a hexadecanol/PC lamellar system. Biological evaluation shows that stable nucleic acid lipid particles (SNALPs) formulated with ONLs and siRNAs can effectively enter into tumor cells and release their nucleic acid payload in response to an intracellular acidic environment. This results in a much higher antitumor activity than conventional SNALPs. The ability to use pH‐cleavable nucleolipids to control the stability of lipid‐based delivery systems represents a promising approach for the intracellular delivery of drug cargos.     

THE USE OF A GAS CHROMATOGRAPH TO OBTAIN DRYING RATES DATA THROUGH SIMPLE LABORATORY EXPERIMENTS

Abstract

A method making use of a gas chromatograph was investigated to acquire bound solvent drying rates. The solid to be dried was used as stationary phase in a chromatographic column, and the TCD detector was used to follow the decrease of solvent content of the effluent as inert gas was flown through the column. The measurement of the break-through curve allows the evolution of drying rate with time or solvent content to be obtained. The comparison of the experimental results with numerical simulation leads to the determination, through parametric adjustment, of the internal mass-transfer coefficient as a function of the solvent content during the second stage of bound solvent drying period. This parameter can lead to the value of the diffusivity as a function of solvent content.