Flavouring and odorant thiols from renewable natural resources by In-catalysed hydrothioacetylation and lipase-catalysed solvolysis

A chemoenzymatic access to thiol compounds, including ethyl 3-thiobutanoate, 3-thio-p-menthene and 8-thio-p-menthan-2-one, three compounds of interest in flavour and fragrance chemistry presenting various fruity notes, is proposed. It involves an indium(III)-catalysed hydrothioacetylation of renewable precursors followed by an enzymatic solvolysis of the obtained thioesters by lipases in aqueous or organic solvents.     

Weak shock waves and its interaction with characteristic shocks in polyatomic gas

We present Lie symmetry analysis for investigating the shock‐wave structure of hyperbolic differential equations of polyatomic gases. With the application of symmetry analysis, we derive particular exact group invariant solutions for the governing system of partial differential equations (PDEs). In the next step, the evolutionary behavior of weak shock along with the characteristic shock and their interaction is investigated. Finally, the amplitudes of reflected wave, transmitted wave, and the jump in shock acceleration influenced by the incident wave after interaction are evaluated for the considered system of equations.     

Mathematical studies of the solution of Burgers' equations by Adomian decomposition method

In this paper, a novel Adomian decomposition method (ADM) is developed for the solution of Burgers' equation. While high level of this method for differential equations are found in the literature, this work covers most of the necessary details required to apply ADM for partial differential equations. The present ADM has the capability to produce three different types of solutions, namely, explicit exact solution, analytic solution, and semi-analytic solution. In the best cases, when a closed-form solution exists, ADM is able to capture this exact solution, while most of the numerical methods can only provide an approximation solution. The proposed ADM is validated using different test cases dealing with inviscid and viscous Burgers' equations. Satisfactory results are obtained for all test cases, and, particularly, results reported in this paper agree well with those reported by other researchers.     

Insights into colloid-mediated trace element release at the soil/water interface

Organic or inorganic colloids play a major role in the mobilization of trace elements in soils and waters. Environmental physicochemical parameters (pH, redox potential, temperature, pressure, ionic strength, etc.) are the controlling factors of the colloidal mobilization. This study was dedicated to follow the colloid-mediated mobilization of trace elements through time at the soil/water interface by means of an experimental approach. Soil column experiments were carried out using percolating synthetic solutions. The percolated solutions were ultrafiltrated with various decreasing cutoff thresholds to separate the different colloidal phases in which the dissolved organic carbon and trace element concentrations were measured. The major results which stem from this study are the following: (i) The data can be divided into different groups of organic compounds (microbial metabolites, fulvic acids, humic acids) with regard to their respective aromaticity and molecular weight. (ii) Three groups of elements can be distinguished based on their relationships with the colloidal phases: the first one corresponds to the so-called "truly" dissolved group (Li, B, K, Na, Rb, Si, Mg, Sr, Ca, Mn, Ba, and V). The second one can be considered as an intermediate group (Cu, Cd, Co, and Ni), while the third group gathers Al, Cr, U, Mo, Pb, Ti, Th, Fe, and rare earth elements (REE) carried by the organic colloidal pool. (iii) The data demonstrate that the fulvic acids seem to be a major organic carrier phase for trace elements such as Cu, Cd, Co, and Ni. By contrast, the trace elements belonging to the so-called colloidal pool were mostly mobilized by humic acids containing iron nanoparticles. Lead, Ti, and U were mobilized by iron nanoparticles bound to these humic acids. Thus, humic substances allowed directly or indirectly a colloidal transport of many insoluble trace elements either by binding trace elements or by stabilizing a ferric carrier phase. (iv) Finally, the results demonstrated also that REE were mostly mobilized by humic substances. The REE normalized patterns showed a middle REE downward concavity. Therefore, as previously shown elsewhere humic substances are a major control of REE speciation and REE fractionation patterns as well since the humic substance/metal ratio was the key parameter controlling the REE pattern shape.     

锦灯笼果实的化学成分研究

从锦灯笼中分离得到5个甾体类化合物,分别鉴定为酸浆素A(1,alkekengilin A)、酸浆素B(2,alkekengilin B)、酸浆苦素D(3,physalin D)、酸浆苦素P(4,physalin P)、4,7-二去氢新酸浆苦素B(5,4,7-didehydro-neophysalin B).其中酸浆素A(1,alkekengilin A)和酸浆素B(2,alkekengilin B)为新的天然产物.运用现代波谱技术对上述化合物的结构进行了确证.     

Analysis of soybean protein-derived peptides and the effect of cultivar, environmental conditions, and processing on lunasin concentration in soybean and soy products

Soybean, an important source of food proteins, has received increasing interest from the public because of its reported health benefits. These health benefits are attributed to its components, including isoflavones, saponins, proteins, and peptides. Lunasin, Bowman-Birk inhibitor, lectin, and beta-conglycinin are some of the biologically active peptides and proteins found in soybean. This article provides a comprehensive review on the recently used techniques in the analysis and characterization of food bioactive peptides, with emphasis on soybean peptides. The methods used to isolate and purify lunasin from defatted soybean flour were ion-exchange chromatography, ultrafiltration, and gel filtration chromatography. The identity of lunasin was established by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot, matrix-assisted laser desorption ionization-time of flight, and liquid chromatography. The results on the effect of soybean cultivar and environmental factors on lunasin concentration are also reported. The highest lunasin concentration, 11.7 +/- 0.3 mg/g flour, was found in Loda soybean cultivar grown at 23 degrees C; the lowest concentration, 5.4 +/- 0.4 mg/g flour, was found in Imari soybean cultivar grown at 28 degrees C. Lunasin concentration was affected by cultivar-temperature, cultivar-soil moisture, and cultivar-temperature-soil moisture interactions. The variation on lunasin concentration suggests that its content can be improved by breeding, and by optimization of growing conditions. In summary, bioactive peptides can be accurately identified and quantified by using different techniques and conditions. In addition, lunasin concentration in soybean depends mainly on cultivar and to some extent on environmental factors, particularly temperature. Lunasin concentration in soy products was also affected by processing conditions.     

Synthesis and structure of mycolactone E isolated from frog mycobacterium

The structure of mycolactone E, isolated from the frog pathogen Mycobacterium liflandii, was established via organic synthesis. Within the mycolactone family of metabolites, a structural variation has been seen only at the unsaturated fatty acid moiety thus far, and mycolactone E follows this observation. Interestingly, the absolute configuration of its unsaturated fatty acid matches that of the mycolactones from human mycobacteria, rather than the structurally more closely related mycolactone F from fish mycobacteria.     

结扎家兔颈总动脉和椎动脉后额区皮质超微结构变化──突触和突起

成年家兔１５只,分实验组和对照组。实验组动物结扎双侧颈总动脉和一侧椎动脉后分成Ⅰ,Ⅱ,Ⅲ组,分别存活３０ｍｉｎ,１ｈ和２４ｈ．对两侧大脑半球额区皮质的相同部位进行了电镜观察。突触活性区（突触前、后膜和突触间隙）电子密度增加,分辨不清突触间隙,在Ⅱ组这种突     

Study of the tensile constrained recovery behavior of a Fe-Mn-Si shape memory alloy

Free- and constrained recovery behaviors of a Fe-23.3 Mn-2.8 Si (wt.%) Shape Memory Alloy (SMA) were revealed by uncoiling experiments and tensile tests, respectively. With the enhancement of plastic deformation degree, including by additionally elongating the hot rolled specimens, the increase of the amount of ε stress induced martensite (SIM) plates in the detriment if γ austenite, was emphasized by means of optical microscopy and XRD. The tensile-stress variation was analyzed during complex cycling by constrained recovery of the alloy under study, with a tensile strength of 670 MPa and an ultimate strain of 8%. The cycles were composed of: (i) room temperature (RT) loading; (ii) RT partial unloading; (iii) constant strain heating and (iv) constant strain cooling to RT. During the cycles, characterized by average maximum stresses above 500 MPa and recovery stresses above 260 MPa, the observed stress-temperature evolution confirmed the four stage stress variation reported in literature [Z.Z. Dong et al., Acta Mater. 53, 4009 (2005)]. In order to maintain the above stress levels, constrained-recovery strain had to be increased with an average of 1.1% per cycle, between 1 and 3%.     

Board structure and firm technical efficiency: Evidence from Canadian state-owned enterprises

The objective of the study is to analyze the board–performance relationship for a group of 14 Canadian SOEs. This context is unique because SOEs do not have major control devices other than the board. As the interaction effect, if any, between the board and other corporate governance structures is expected to be low, we do not have to fully control for the potential impact of different control devices, or to disentangle them completely from influencing board composition. The performance is also measured using data envelopment analysis (DEA), a linear programming method used for the first time in this research area. As such, this study contributes to the operational research literature while applying DEA method to untraditional fields of research.