Biosynthesis Coupled to the Extraction of Geranyl Acetate in a Liquid-Gas System: Optimization of the Transesterification Reaction and Modeling of the Transfer

The objective of this paper was to study the production and the mass transfer of geranyl acetate known for its interesting green odor properties. Lipase-catalyzed geranyl acetate production via transesterification reaction with ethyl acetate in organic solvent was investigated. The production was catalyzed by using immobilized lipase from Rhizomucor miehei, and the recovery was achieved by using solid phase microextraction (SPME) fiber system (50/30 μm DVB/Carboxen/PDMS Coating). The effects of different reaction parameters on transesterification including the enzyme concentration, the substrate molar ratio, the added water, and the reaction time were firstly optimized. A higher yield of 82 % was achieved under near-anhydrous conditions at 55 °C by using an enzyme concentration of 6 % (w/w reactants), a molar ratio of geraniol to ethyl acetate of 1:5, and a reaction time of 6 h. Immobilized lipase was repeatedly used for four cycles with no decrease in reaction yield. The mass transfer of geranyl acetate from the organic to gas phase was studied theoretically and experimentally, and a transfer yield of 52.3 % was obtained. The simulation showed that the Fuller-Schettler-Giddings model exhibited good correlation with the experimental data

Estimating time-varying effects for overdispersed recurrent events data with treatment switching

In the analysis of multivariate event times, frailty models assuming time-independent regression coefficients are often considered, mainly due to their mathematical convenience. In practice, regression coefficients are often time dependent and the temporal effects are of clinical interest. Motivated by a phase III clinical trial in multiple sclerosis, we develop a semiparametric frailty modelling approach to estimate time-varying effects for overdispersed recurrent events data with treatment switching. The proposed model incorporates the treatment switching time in the time-varying coefficients. Theoretical properties of the proposed model are established and an efficient expectation-maximization algorithm is derived to obtain the maximum likelihood estimates. Simulation studies evaluate the numerical performance of the proposed model under various temporal treatment effect curves. The ideas in this paper can also be used for time-varying coefficient frailty models without treatment switching as well as for alternative models when the proportional hazard assumption is violated. A multiple sclerosis dataset is analysed to illustrate our methodology

Surface Effects on Anisotropic Photoluminescence in One-Dimensional Organic Metal Halide Hybrids

One-dimensional (1D) organic metal halide hybrids exhibit strongly anisotropic optical properties, highly efficient light emission, and large Stokes shift, holding promises for novel photodetection and lighting applications. However, the fundamental mechanisms governing their unique optical properties and in particular the impacts of surface effects are not understood. Here, we investigate 1D C4N2H14PbBr4 by polarization-dependent time-averaged and time-resolved photoluminescence (TRPL) spectroscopy, as a function of photoexcitation energy. Surprisingly, we find that the emission under photoexcitation polarized parallel to the 1D metal halide chains can be either stronger or weaker than that under perpendicular polarization, depending on the excitation energy. We attribute the excitation-energy-dependent anisotropic emission to fast surface recombination, supported by first-principles calculations of optical absorption in this material. The fast surface recombination is directly confirmed by TRPL measurements, when the excitation is polarized parallel to the chains. Our comprehensive studies provide a more complete picture for a deeper understanding of the optical anisotropy in 1D organic metal halide hybrids

A new thiocyanoacetamide (2-cyano-2-p-nitrophenyl-N-benzylthioamide) reduces doxorubicin-induced in vitro toxicity in Sertoli cells by decreasing apoptosis and autophagy

Despite conflicting data on doxorubicin (DOX) reproductive toxicity, its chemotherapeutic potential sustains its use to treat different types of cancer. This work was designed to study the protective effect of a newly synthesized thiocyanoacetamide (TA), in comparison with selenium (Se), against doxorubicin-induced in vitro toxicity in rat Sertoli cells (SCs). DOX was administered alone or in combination with Se or TA. The possible protective role of increased concentrations of TA (0.25, 0.5 and 1 mM) or Se (12, 25 and 50 mu M) on SCs was tested against 1 mu M of DOX. From this screening, only the least toxic doses of TA and Se were used for further analysis. DOX cytotoxicity, as well as its impact on SCs viability, mitochondria) membrane potential (Delta Psi(m)), oxidative stress biomarkers, apoptosis and autophagy were assessed. Our results showed that DOX exerted its cytotoxic effect through a significant increase in cell death. DOX-mediated cell death was not related to autophagy nor to an overproduction of reactive oxygen species. It was rather due to apoptosis, as shown by the increased number of apoptotic cells and increased activity of caspase-3, or due to necrosis, as shown by the increase in lactate dehydrogenase (LDH) extracellular activity. Still, Bax and Bcl-2 protein expression levels, as well as Delta Psi(m) were not altered by the different treatments. Some individual doses of Se or TA induced a significant toxicity in SCs, however, when combined with DOX, there was a decrease in cell death, LDH extracellular activity, number of apoptotic cells and caspase-3 activity. Overall, our results indicate that DOX-mediated apoptosis in cultured SCs can possibly be averted through its association with specific doses of Se or TA. Nevertheless, TA showed a higher efficiency than Se in reducing DOX-induced toxicity in SCs by decreasing not only apoptosis, but also necrosis and autophagy. (C) 2019 Elsevier Inc. All rights reserved

A causal roadmap for generating high-quality real-world evidence

Increasing emphasis on the use of real-world evidence (RWE) to support clinical policy and regulatory decision-making has led to a proliferation of guidance, advice, and frameworks from regulatory agencies, academia, professional societies, and industry. A broad spectrum of studies use real-world data (RWD) to produce RWE, ranging from randomized trials with outcomes assessed using RWD to fully observational studies. Yet, many proposals for generating RWE lack sufficient detail, and many analyses of RWD suffer from implausible assumptions, other methodological flaws, or inappropriate interpretations. The Causal Roadmap is an explicit, itemized, iterative process that guides investigators to prespecify study design and analysis plans; it addresses a wide range of guidance within a single framework. By supporting the transparent evaluation of causal assumptions and facilitating objective comparisons of design and analysis choices based on prespecified criteria, the Roadmap can help investigators to evaluate the quality of evidence that a given study is likely to produce, specify a study to generate high-quality RWE, and communicate effectively with regulatory agencies and other stakeholders. This paper aims to disseminate and extend the Causal Roadmap framework for use by clinical and translational researchers; three companion papers demonstrate applications of the Causal Roadmap for specific use cases

Voie de la lipoxygénase : valorisation d’huiles végétales et biosynthèse de flaveurs

Lipoxygenase pathway: valorization of plant oils and aroma biosynthesis. This article is a review on the lipoxygenase pathway in plants, and its application in aroma compound synthesis from plant oils. Raw material used by this pathway is plant oils rich in poly-unsaturated fatty acids. Then, lipase-catalyzed hydrolysis followed by lipoxygenation, hydroperoxyde-lyase and alcohol-dehydrogenase act successively producing respectively aldehyde and alcohol. Several papers and patents described the production of aroma as hexenal(s), nonenal(s) and nonadienal(s) as well as their corresponding alcohols using enzymes of this pathway from different sources. The reaction sequence uses enzymatic systems of different characteristics, as well as raw material and intermediary and final products having specific properties. In order to improve the efficiency of the application of the lipoxygenase pathway, different studies used multi-enzymatic systems in compartimentalized media for the bioconversion

Reactivity of Phosphonothioamidates with Acid Chlorides and Primary Amines: Synthesis and Conformational Study of N-Acylated Phosphonothioamidates and Phosphonoamidines

<div><p></p><p>Various <i>N</i>-acyl phosphonothioamidate derivatives, <b>2</b>, were obtained from <i>N</i>-acylation of phosphonothioamidates, <b>1</b>, with different acid chlorides. Phosphonoamidines, <b>3</b>, were prepared in high yields by reacting phosphonothioamidates, <b>1</b>, with primary amines at room temperature, ro short reaction periods. All compounds were characterized on the basis of IR and NMR spectroscopy (¹H, ¹³C, ¹⁹F and ³¹P) and in some cases by elemental analysis and calculations using Density Functional Theory (DFT)-B3LYP// 3-21G+** and evolution study by ³¹P-NMR and ¹⁹F-NMR spectroscopy using an external lock with D₂O. </p><p></p><p></p></div