Network analyses of Y-chromosomal types in Europe, northern Africa, and western Asia reveal specific patterns of geographic distribution

In a study of 908 males from Europe, northern Africa, and western Asia, the variation of four Y-linked dinucleotide microsatellites was analyzed within three "frames" that are defined by mutations that are nonrecurrent, or nearly so. The rapid generation and extinction of new dinucleotide length variants causes the haplotypes within each lineage to diverge from one another. We constructed networks of "adjacent" haplotypes within each frame, by assuming changes of a single dinucleotide unit. Two small and six large networks were obtained, the latter including 94.9% of the sampled Y chromosomes. We show that the phenetic relationships among haplotypes, represented as a network, result largely from common descent and subsequent molecular radiation. The grouping of haplotypes of the same network thus fits an evolutionarily relevant criterion. Notably, this method allows the total diversity within a sample to be partitioned. Networks can be considered optimal markers for population studies, because reliable frequency estimates can be obtained in small samples. We present synthetic maps describing the incidence of different Y-chromosomal lineages in the extant human populations of the surveyed areas. Dinucleotide diversity also was used to infer time intervals for the coalescence of each network.     

Synthesis and tribological behaviors of Ti3SiC2 material prepared by vacuum sintering technique

The bulk Ti₃SiC₂ specimens with less than 1 wt% TiC impurity were prepared by vacuum sintering technique, and the average grain size was about 5–6 μm in the elongated direction. When the sintering temperature, soaking time and heating rate were 1 400 °C, 1 h and 10 °C·min^?1, respectively, the highest relative density of Ti₃SiC₂ specimens could reach 97.8%. Meanwhile, the lowest coefficient of friction (COF) and wear rate (WR) of the Ti₃SiC₂ samples were 0.55 and 1.37×10^?3 mm³(Nm)^?1 at a sliding speed of 0.35 m/s, load pressure of 10 N and ambient condition, respectively. The COF of the Ti₃SiC₂ sample reduced with the increasing of the load pressure, while the WRs fluctuated little. The WR increased with the increasing of the sliding speed, and weakly influenced the COF. These changing behaviors could be attributed to the presence and coverage of the amorphous mixture oxide film of Ti, Si, Al, and Fe on the Ti₃SiC₂ friction surface. The self-antifriction mechanism led to reducing of the COF. The increasing of the WR was attributed to the wearing consumption.     

用时空CE/SE方法求解微溶一维间歇结晶模型(英文)

This article is concerned with the numerical investigation of one-dimensional population balance models for batch crystallization process with fines dissolution. In batch crystal ization, dissolution of smaller unwanted nu-clei below some critical size is of vital importance as it improves the quality of product. The crystal growth rates for both size-independent and size-dependent cases are considered. A delay in recycle pipe is also included in the model. The space–time conservation element and solution element method, originally derived for non-reacting flows, is used to solve the model. This scheme has already been applied to a range of PDEs, mainly in the area of fluid mechanics. The numerical results are compared with those obtained from the Koren scheme, showing that the proposed scheme is more efficient.     

The crystal structure of a class II fructose-1,6-bisphosphate aldolase shows a novel binuclear metal-binding active site embedded in a familiar fold

BACKGROUND: [corrected] Aldolases catalyze a variety of condensation and cleavage reactions, with exquisite control on the stereochemistry. These enzymes, therefore, are attractive catalysts for synthetic chemistry. There are two classes of aldolase: class I aldolases utilize Schiff base formation with an active-site lysine whilst class II enzymes require a divalent metal ion, in particular zinc. Fructose-1,6-bisphosphate aldolase (FBP-aldolase) is used in gluconeogenesis and glycolysis; the enzyme controls the condensation of dihydroxyacetone phosphate with glyceraldehyde-3-phosphate to yield fructose-1,6-bisphosphate. Structures are available for class I FBP-aldolases but there is a paucity of detail on the class II enzymes. Characterization is sought to enable a dissection of structure/activity relationships which may assist the construction of designed aldolases for use as biocatalysts in synthetic chemistry. RESULTS: The structure of the dimeric class II FBP-aldolase from Escherichia coli has been determined using data to 2.5 A resolution. The asymmetric unit is one subunit which presents a familiar fold, the (alpha/beta)8 barrel. The active centre, at the C-terminal end of the barrel, contains a novel bimetallic-binding site with two metal ions 6.2 A apart. One ion, the identity of which is not certain, is buried and may play a structural or activating role. The other metal ion is zinc and is positioned at the surface of the barrel to participate in catalysis. CONCLUSIONS: Comparison of the structure with a class II fuculose aldolase suggests that these enzymes may share a common mechanism. Nevertheless, the class II enzymes should be subdivided into two categories on consideration of subunit size and fold, quaternary structure and metal-ion binding sites.     

Comparative photocatalytic study of two selected pesticide derivatives, indole-3-acetic acid and indole-3-butyric acid in aqueous suspensions of titanium dioxide

Heterogeneous photocatalysed degradation of two selected pesticide derivatives such as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) has been investigated in aqueous suspensions of titanium dioxide by monitoring the change in substrate concentration employing UV spectroscopic analysis technique and depletion in total organic carbon (TOC) content as a function of irradiation time. The degradation kinetics was studied under different conditions such as pH, types of TiO_2, substrate and catalyst concentration, and in the presence of electron acceptor such as hydrogen peroxide (H₂O₂) besides molecular oxygen. The degradation rates were found to be strongly influenced by all the above parameters. The photocatalyst Degussa P25 showed comparatively highest photocatalytics. The pesticide derivative, indole-3-acetic acid was found to degrade slightly faster than indole-3-butyric acid.     

ROS-mediated genotoxicity of asbestos-cement in mammalian lung cells <Emphasis Type="Italic">in vitro</Emphasis>

Asbestos is a known carcinogen and co-carcinogen. It is a persisting risk in our daily life due to its use in building material as asbestos-cement powder. The present study done on V79-cells (Chinese hamster lung cells) demonstrates the cytotoxic and genotoxic potential of asbestos-cement powder (ACP) in comparison with chrysotile asbestos. A co-exposure of chrysotile and ACP was tested using the cell viability test and the micronucleus assay. The kinetochore analysis had been used to analyse the pathway causing such genotoxic effects. Thiobarbituric acid-reactive substances were determined as evidence for the production of reactive oxygen species. Both, asbestos cement as well as chrysotile formed micronuclei and induced loss of cell viability in a concentration- and time- dependent way. Results of TBARS analysis and iron chelator experiments showed induction of free radicals in ACP- and chrysotile exposed cultures. CaSO₄ appeared to be a negligible entity in enhancing the toxic potential of ACP. The co-exposure of both, ACP and chrysotile, showed an additive effect in enhancing the toxicity. The overall study suggests that asbestos-cement is cytotoxic as well as genotoxic in vitro. In comparison to chrysotile the magnitude of the toxicity was less, but co-exposure increased the toxicity of both.     

Confined growth and dispersion of FeP nanoparticles in highly mesoporous carbons as efficient electrocatalysts for the hydrogen evolution reaction

We report the performance of a series of iron monophosphide (FeP) catalysts supported on highly mesoporous carbons (HMCs) with distinct mesopore size (6–17 nm) and mesopore volume (2–3 cm³ g^?1) for the hydrogen evolution reaction (HER). Our findings suggest that the mesopore size of the carbon is a key design parameter. The mesopores serve as nanoreactors and control the growth and the dispersion of FeP nanoparticles, which, in turn, determine the HER performance of the electrode. Carbons with smaller mesopore sizes confine and control the size of FeP leading to finely dispersed and fairly small (<5 nm) FeP nanocrystals, while carbons with larger mesopore size result in agglomerated, larger nanoparticles (>10 nm) and, thus, less active electrocatalysts. Electrocatalysts based on FeP immobilized on the mesoporous carbons show lower overpotential and lower Tafel slope and outperform those based on FeP immobilized on commercial activated carbon. This study establishes for the first time some correlations between HER performance and mesopore size and pore volume of the carbon. The findings provide further understanding and might pave the way towards a rational design of highly active electrocatalysts by delineating key design parameters for materials development.     

Effect of Compression and Decompression Rates of High Hydrostatic Pressure on Inactivation of Staphylococcus aureus in Different Matrices

Staphylococcus aureus ATCC6538 was inoculated in skimmed milk, orange juice, and Tris buffer samples. Inoculated samples were subjected to high hydrostatic pressure (HHP) treatments at 700 MPa for 5 min at 4 °C starting temperature with fast, medium, and slow rates of compression and decompression. The objective of this study was to determine the effects of changing rates of compression and decompression on inactivation of S. aureus during HHP processing. Immediate effect of different HHP treatments was not significantly different. However, during subsequent storage in refrigeration, highest microbial inactivation was the result of treatments with fast compression and slow decompression rates in all matrices.     

Power budget analysis of dual/single feeder fiber WDMPON

This paper investigates how to reduce the cost of wavelength division multiplexing passive optical network （WDM- PON） by comparing the transmission performance of bidirectional single feeder fiber and dual feeder fiber. Comparison is performed on the basis of power budgeting and cost of both arrangements. Simulation results using Optisystem show that the performance of a single feeder fiber is almost equivalent to that of a dual feeder fiber. Therefore, the single feeder fiber WDM-PON can efficiently replace the dual feeder fiber WDM-PON with the minimum deterioration in system performance and reduction in cost.