Thin Layer Chromatography for the Detection of Unexpected Reactions in Organometallic Combinatorial Catalysis

Thin layer chromatography (TLC) represents a fast and inexpensive alternative to NMR spectroscopy or analytical methods based on chromatography for the detection of unexpected products in organometallic combinatorial catalysis. This screening test led to the detection of the catalytic system [Ir(COD)Cl]₂/PPh₃ for isomerisation of diolefinic substrates instead the expected ring closing metathesis (RCM) reaction.     

Activated Carbon Fiber Cloth/Biomimetic Apatite: A Dual Drug Delivery System

A biomaterial that is both bioactive and capable of controlled drug release is highly attractive for bone regeneration. In previous works, we demonstrated the possibility of combining activated carbon fiber cloth (ACC) and biomimetic apatite (such as calcium-deficient hydroxyapatite (CDA)) to develop an efficient material for bone regeneration. The aim to use the adsorption properties of an activated carbon/biomimetic apatite composite to synthetize a biomaterial to be used as a controlled drug release system after implantation. The adsorption and desorption of tetracycline and aspirin were first investigated in the ACC and CDA components and then on ACC/CDA composite. The results showed that drug adsorption and release are dependent on the adsorbent material and the drug polarity/hydrophilicity, leading to two distinct modes of drug adsorption and release. Consequently, a double adsorption approach was successfully performed, leading to a multifunctional and innovative ACC-aspirin/CDA-tetracycline implantable biomaterial. In a second step, in vitro tests emphasized a better affinity of the drug (tetracycline or aspirin)-loaded ACC/CDA materials towards human primary osteoblast viability and proliferation. Then, in vivo experiments on a large cortical bone defect in rats was carried out to test biocompatibility and bone regeneration ability. Data clearly highlighted a significant acceleration of bone reconstruction in the presence of the ACC/CDA patch. The ability of the aspirin-loaded ACC/CDA material to release the drug in situ for improving bone healing was also underlined, as a proof of concept. This work highlights the possibility of bone patches with controlled (multi)drug release features being used for bone tissue repair.     

A new tribometer for measuring friction data at high temperature in a continuous operation

This paper describes a rotary tribometer that can function at high temperature in a pin-on-disc or ring-on-disc configuration. With this tribometer the tribological properties of ceramics (structural ceramics or coatings) and metallic alloys can be studied from room temperature to 900 °C. The sliding velocity can be varied from 0.1 to 1.5 m/s, and the normal load from 10 to 2000 N. The test apparatus is unique in terms of the wide range of loads which can be tested, and in its sensor and computer data acquisition system, which allows different test parameters, such as friction coefficient, vertical displacement of samples, and temperature near the interface, to be measured in one continuous operation.     

A survey on hygienic practices and their impact on the microbiological quality and safety in the Rwandan milk and dairy chain

This study assessed the status of hygienic practices in the Rwandan milk and dairy chain. Data collection was based on interviews with the help of a survey and site visits to farms, collection centres, milk processing companies, small‐scale cheese plants, wholesale points, supermarkets and milk shops. The observed status of good practices was further linked to actual microbiological data. It was concluded that there is a major gap in compliance with hygienic practices leading to higher levels of contaminated dairy products.     

The Signaling Role of CD40 Ligand in Platelet Biology and in Platelet Component Transfusion

The CD40 ligand (CD40L) is a transmembrane molecule of crucial interest in cell signaling in innate and adaptive immunity. It is expressed by a variety of cells, but mainly by activated T-lymphocytes and platelets. CD40L may be cleaved into a soluble form (sCD40L) that has a cytokine-like activity. Both forms bind to several receptors, including CD40. This interaction is necessary for the antigen specific immune response. Furthermore, CD40L and sCD40L are involved in inflammation and a panoply of immune related and vascular pathologies. Soluble CD40L is primarily produced by platelets after activation, degranulation and cleavage, which may present a problem for transfusion. Soluble CD40L is involved in adverse transfusion events including transfusion related acute lung injury (TRALI). Although platelet storage designed for transfusion occurs in sterile conditions, platelets are activated and release sCD40L without known agonists. Recently, proteomic studies identified signaling pathways activated in platelet concentrates. Soluble CD40L is a good candidate for platelet activation in an auto-amplification loop. In this review, we describe the immunomodulatory role of CD40L in physiological and pathological conditions. We will focus on the main signaling pathways activated by CD40L after binding to its different receptors.     

WorkSim: A Calibrated Agent-Based Model of the Labor Market Accounting for Workers’ Stocks and Gross Flows

This paper presents an agent-based model of the labor market. It simulates the market in the recent period at the aggregate level and at the level of the principal categories of labor, on the basis of the decisions of heterogeneous agents, firms and individuals, who interact. These decisions rely on individual computations of profits and utilities, although rationality is bounded in such a complex environment. The theoretical structure that underlies the decisions is the search concept. We apply this framework to the case of France in 2011. The model is at a scale of 1/4700. It is fairly detailed on the institutions of the labor market that constrain the agents’ decisions. Finally it is calibrated by a powerful algorithm to reproduce a large number of variables of interest. The calibrated model presents a consistent accounting system of the gross flows of the individuals between the main states, employment, distinguishing open ended contracts and fixed duration contracts, unemployment and inactivity. The simulation of the gross flows accounts enables us to analyze the patterns of mobility in a way that the observed statistics on gross flows, which are partial, cannot do. The model then characterizes the nature of the labor market under study, reproducing the high proportion of the fixed duration contracts in the hiring flows, and it points to a dualism of the French labor market.     

High‐Temperature Creep Behavior of SiOC Glass‐Ceramics: Influence of Network Carbon Versus Segregated Carbon

Three silicon oxycarbide samples with different carbon contents are analyzed in the present study with respect to their high‐temperature creep behavior. The tests were performed in compression at 1100°C, 1200°C, and 1300°C; in this temperature range the mechanism of creep relies on viscoelastic flow within the samples and has been modeled with the Jeffreys viscoelastic model. After the release of the applied mechanical stress, a viscoelastic recovery behavior was observed in all samples. The creep behavior of the investigated samples indicates two rheological contributions in SiOC: (i) a high viscous answer, coming from the silica‐rich network, and (ii) an elastic response from the segregated carbon phase within the samples. Furthermore, two distinct effects of the carbon phase on the HT creep behavior of SiOC were identified and are discussed in the present paper: the effect of the carbon presence within the SiOC network (the “carbidic” carbon), which induces a significant increase in the viscosity and a strong decrease in the activation energy for creep, as compared to vitreous silica; and the influence of the segregated carbon phase (the “free” carbon), which has been shown to affect the viscosity and the activation energy of creep and dominates the creep behavior in phase‐separated silicon oxycarbides.     

The impact of strain-induced crystallization on strain during mechanical cycling of cross-linked natural rubber

The improvement of X-ray diffraction techniques since the last ten years allowed a renewal of the study of strain-induced crystallization in natural rubber. In particular real-time measurements are now commonplace. However, due to experimental difficulties, the exploitation of the X-ray data as far as the strain state of the remaining molten fraction is concerned has been left aside. Indeed the knowledge of the local extension of the molten chains is crucial for understanding the peculiar stress behavior observed during the crystallization process. This paper presents a systematic study of this parameter during mechanical cycling performed at various temperatures. It is shown that crystallization limits the amplitude of strain endured by the molten fraction during traction. This process of strain regulation may be one explanation for the protective effect of crystallization against tearing. A precise evaluation of the contribution of the molten fraction to the retraction force during mechanical cycling is made. The role of crystallites as nanofillers may be quantified this way.