中国北方上新世降温事件及其对温度纬度梯度变化的影响

中晚上新世是现代气候形成过程根据在同一地区(剖面)获得的古地磁年代资料,发现山西榆社及河北泥河湾的孢粉资料记录了在松山/高斯极性事件界线附近(约2.5 Ma)的一次明显的降温事件.山西榆社的孢粉资料还记录了在约2.7 Ma-2.8 Ma的一次降温事件.这些降温事件主要是因为全球性气候变化引起的,北极圈附近和西伯利亚的冷高压大大地降低了我国,特别是我国北方的冬季气温.与此同时,位于北极圈附近的阿拉斯加发生了更为强烈的降温事件.比较两地相当时期的降温幅度,可以发现因为不同纬度的降温幅度不同使得温度的纬度变化梯度比降温事件发生前大大增加了,由原来的纬度每增加一度降低约0.3℃增大到约0.5℃.     

Highly potent and selective NaV1.7 inhibitors for use as intravenous agents and chemical probes

The discovery and selection of a highly potent and selective Na_V1.7 inhibitor PF-06456384, designed specifically for intravenous infusion, is disclosed. Extensive in vitro pharmacology and ADME profiling followed by in vivo preclinical PK and efficacy model data are discussed. A proposed protein–ligand binding mode for this compound is also provided to rationalise the high levels of potency and selectivity over inhibition of related sodium channels. To further support the proposed binding mode, potent conjugates are described which illustrate the potential for development of chemical probes to enable further target evaluation.     

Impact of Grazing Intensity and Seasons on Greenhouse Gas Emissions in Tropical Grassland

Greenhouse gases (GHG) can be affected by grazing intensity, soil, and climate variables. This study aimed at assessing GHG emissions from a tropical pasture of Brazil to evaluate (i) how the grazing intensity affects the magnitude of GHG emissions; (ii) how season influences GHG production and consumption; and (iii) what are the key driving variables associated with GHG emissions. We measured under field conditions, during two years in a palisade-grass pasture managed with 3 grazing intensities: heavy (15 cm height), moderate (25 cm height), and light (35 cm height) N₂O, CH₄ and CO₂ fluxes using static closed chambers and chromatographic quantification. The greater emissions occurred in the summer and the lower in the winter. N₂O, CH₄, and CO₂ fluxes varied according to the season and were correlated with pasture grazing intensity, temperature, precipitation, % WFPS (water-filled pores space), and soil inorganic N. The explanatory variables differ according to the gas and season. Grazing intensity had a negative linear effect on annual cumulative N₂O emissions and a positive linear effect on annual cumulative CO₂ emissions. Grazing intensity, season, and year affected N₂O, CH₄, and CO₂ emissions. Tropical grassland can be a large sink of N₂O and CH₄. GHG emissions were explained for different key driving variables according to the season.     

In Situ Rhamnolipid Production at an Abandoned Petroleum Refinery

A simple screening method was developed to detect in situ biosurfactant production by exploiting the relationship between surface tension (ST) and surfactant concentration. Filtered groundwater from contaminated wells with ST values of 60 to 70 dynes/cm decreased to 29 dynes/cm after being concentrated 10 to 15 times in a rotary evaporator, indicating that biosurfactants in the sample reached the critical micelle concentration (CMC). Samples from uncon-taminated groundwater concentrated 25 times showed no decrease in ST below 72 dynes/cm, suggesting that biosurfactants were not present. Microorganisms from soil cores were cultured on diesel fuel and identified using fatty acid methyl ester (FAME) analysis. Pseudomonas aeruginosa was found at very low numbers in uncontami-nated soil but was the dominant species in contaminated soil, indicating that hydrocarbon release impacted microbial diversity significantly. High-performance liquid chromatography (HPLC) was used to quantify rhamnolipids, biosurfactants produced by P. aeruginosa, in concentrated ground-water samples. Rhamnolipid concentrations in samples from contaminated soil were observed equal to their CMC (50 mg/L), but were not detected in samples from un-contaminated wells. We conclude that biosurfactant production may be an indicator of intrinsic bioremediation.     

Co-regulation of alternative splicing by diverse splicing factors in Caenorhabditis elegans

Regulation of alternative splicing is controlled by pre-mRNA sequences (cis-elements) and trans-acting protein factors that bind them. The combinatorial interactions of multiple protein factors with the cis-elements surrounding a given alternative splicing event lead to an integrated splicing decision. The mechanism of multifactorial splicing regulation is poorly understood. Using a splicing-sensitive DNA microarray, we assayed 352 Caenorhabditis elegans alternative cassette exons for changes in embryonic splicing patterns between wild-type and 12 different strains carrying mutations in a splicing factor. We identified many alternative splicing events that are regulated by multiple splicing factors. Many splicing factors have the ability to behave as splicing repressors for some alternative cassette exons and as splicing activators for others. Unexpectedly, we found that the ability of a given alternative splicing factor to behave as an enhancer or repressor of a specific splicing event can change during development. Our observations that splicing factors can change their effects on a substrate during development support a model in which combinatorial effects of multiple factors, both constitutive and developmentally regulated ones, contribute to the overall splicing decision.     

Free radical grafting onto cellulose in homogeneous conditions 1. Modified cellulose–acrylonitrile system

Synthesis of cellulose–polyacrylonitrile copolymers has been studied in a homogeneous solution of N,N-dimethylacetamide/LiCl. The method is based on the preliminary reaction of a portion of OH cellulosic groups with acryloyl chloride to give cellulose with a certain number of pendant double bonds. Successively, acrylonitrile is grafted onto the unsaturated groups by free radical polymerization using azobisisobutyronitrile as initiator. The optimum grafting conditions are evaluated by changing reaction temperature, as well as monomer/initiator and monomer/unsaturated group molar ratios. The products are characterized by size exclusion chromatography, i.r. and ¹³C n.m.r. spectroscopy and a possible reaction mechanism is deduced.     

Quantifying Biomolecule Diffusivity Using an Optimal Bayesian Method

We propose a Bayesian method to extract the diffusivity of biomolecules evolving freely or inside membrane microdomains. This approach assumes a model of motion for the particle considered, namely free Brownian motion or confined diffusion. In each framework, a systematic Bayesian scheme is provided for estimating the diffusivity. We show that this method reaches the best performances theoretically achievable. Its efficiency overcomes that of widely used methods based on the analysis of the mean-square displacement. The approach presented here also gives direct access to the uncertainty on the estimation of the diffusivity and predicts the number of steps of the trajectory necessary to achieve any desired precision. Its robustness with respect to noise on the position of the biomolecule is also investigated.