粘弹性数值模拟龙门山断裂带应力积累及大震复发周期

2008年5月12日在低地形变速率的龙门山断裂带上突发汶川强震,引发人们对该地震孕震机制的思考。本文根据GPS观测资料确定边界条件,通过三维粘弹性数值模拟探讨了汶川地震的孕震机理,计算了该区域岩石圈的应力增加速率和积累过程,以及汶川地震同震应力变化与震后应力松弛,在此基础上估算了汶川8.0级大地震的复发周期。数值模拟结果表明:印度板块对欧亚板块的推挤造成青藏高原的物质东流,高原中、下地壳物质在龙门山断裂带处遭到相对坚硬的四川盆地的阻挡之后,部分中、下地壳物质在龙门山断裂带下堆积产生应力集中。两个重要因素为应力集中提供了重要控制作用:其一是青藏高原中、下地壳较低的粘滞系数与四川盆地中、下地壳较高的粘滞系数的差异,其二是从青藏高原到四川盆地的Moho面深度在龙门山断裂带的突变。低应变速率的龙门断裂带岩石圈在数千年时间尺度的应力积累过程中,脆性上地壳的应力随时间近乎线性增长,并且上地壳深部的应力增长率超过浅部,6000年内应力积累最大量达到-21.6MPa,应力增长速率为-0.0036MPa/a;而柔性的中、下地壳以及岩石圈上地幔的应力在增长一段时间之后趋于稳定。在空间上,龙门山断裂带受到的压应力从断层西南向北东方向逐渐减小,而剪应力从西南到北东方向逐渐增大,应力状态有利于地震发生时断层的破裂方式从西南的逆冲运动向北东的逆冲兼走滑运动的方式发展。通过应力积累与地震应力降的计算得到汶川8.0级大地震的复发周期约为5400年。

Depression risk in patients with coronary heart disease in Germany

AIM To determine the prevalence of depression and its risk factors among patients with coronary heart disease(CHD) treated in German primary care practices.METHODS Longitudinal data from nationwide general practices in Germany(n = 1072) were analyzed.Individuals initially diagnosed with CHD(2009-2013) were identified,and 59992 patients were included and matched(1:1) to 59992 controls.The primary outcome measure was an initial diagnosis of depression within five years after the index date among patients with and without CHD.Cox proportional hazards models were used to adjust for confounders.RESULTS Mean age was equal to 68.0 years(SD = 11.3).A total of 55.9% of patients were men.After a five-year follow-up,21.8% of the CHD group and 14.2% of the control group were diagnosed with depression(P < 0.001).In the multivariate regression model,CHD was a strong risk factor for developing depression(HR =1.54,95%CI:1.49-1.59,P < 0.001).Prior depressive episodes,dementia,and eight other chronic conditions were associated with a higher risk of developing depression.Interestingly,older patients and women were also more likely to be diagnosed with depression compared with younger patients and men,respectively.CONCLUSION The risk of depression is significantly increased among patients with CHD compared with patients without CHD treated in primary care practices in Germany.CHD patients should be routinely screened for depression to ensure improved treatment and management.

Arsenic in Drinking Water Toxicological Risk Assessment in the North Region of Burkina Faso

Human health risks assessment were estimated by determining the nature and probability of adverse health effects in the North region’s populations who are now exposed to arsenic from drinking water or will be exposed in the future. Several questions were addressed in this study: what types of health problems may be caused by arsenic from drinking water? What is the chance that people will experience health problems when exposed to different levels of arsenic? What arsenic level are people exposed to and for how long? To answers these questions we have first identified the hazard by evaluating arsenic concentration in thirty-four (34) bore-hole water points among the region based on the assumption of clinical cases related to drinking water. Arsenic concentration ranged from 0 up to 87.8 micrograms per liter. Next we assessed the dose-response of exposure to arsenic. Dose-response relationship describes how the likelihood and severity of adverse health effects are related to the amount and condition of exposure to arsenic. This required us to choose toxicity reference values (TRVs) above which adverse effects may occur for noncarcinogenic and for carcinogenic effects. Exposure factors have been calculated in two scenarios: people from 0 to 14 years old and people from 15 to 70 years. Exposure has been estimated indirectly through consideration of measured concentrations of arsenic in drinking water. This study show that people in the Yatenga, Zondoma and Passore provinces are at very high risk for developing several pathologies such as hyper pigmentation, keratosis, cancer, etc. due by chronic exposure to arsenic in drinking water.

Floristic diversity and structural parameters of the Brazzaville Patte d’Oie forest, Congo

The flora of the Patte d’Oie forest of Brazzaville is studied according to three plots of 0.5 ha, corresponding each to one of the islet, currently constituting it. With an original area of 240 ha, put in reserve in 1938, the natural forest of the Patte d’Oie of Brazzaville covers 95 ha, less than 39% compared to initial area. Because the other main forests of Brazzaville have disappeared without delivering their biodiversity, this study is the first one which emphasizes the flora of this single ecosystem of Congo. The total floristic inventory revealed 459 trees of dbh≥10 cm on 1.5 ha;it is an average of 306 trees?ha?1. 31 species are listed for 17 families, and the best represented of which (Fabaceae, Euphorbiaceae and Rubiaceae) have a diversity varying from 13% to 19% of the inventory and a tree number oscillating from 15% to 36%. The Shannon (H') biological diversity index of the three plots is of 2.6 on average, for a maximum diversity (H'max) average of 2.9 versus an average true diversity of 15. The Pielou index is on average 0.9, whereas that of Simpson is 0.9. The coefficients of similarity of Jaccard (41.4% to 57.1%) and of the coefficient of S?rensen (58.5% to 72.7%) show the variations in the floristic composition. The followed ecological parameters show that this ecosystem is very few diversified compared to the tropical wet dense forests on the one hand, and, on the other hand, a non constant floristic composition is not. The analysis of the diametric structure by plot and the dominant and/or characteristic species give erratic curves, evidence of an insufficiency of the regenerative potential. Indeed, approximately 70% of the species are characteristic of the disturbed ecosystems (Macaranga sp.,Caloncoba welwitschii,Hymenocardia ulmoides,and Anthocleista sp.).

Natural Regeneration of Marker Species of the Tropical Dense Humid Ecosystems in the Loukaya Peri-Urban Forest, Brazzaville-Congo

The study aimed at evaluating the natural regeneration of some characteristic species in the Loukaya peri-urban forest was carried out in Brazzaville, over three surveys of one hectare each. The botanical inventory of the 23 species monitored covers the subjects of 2 ≤ d0.20 < 10 cm and d1.30 ≥ 10 cm. The study shows 1255 individuals of which 68.27% are 2 ≤ d0.20 < 10 cm. While being tropophilic and mesophilic, this ecosystem is pauciflorous and paucispecific. The phytoecological data show that this formation, which is a link in the African dense humid forest, presents values far below those known elsewhere;while being faithful to the forests of the Cataractes Plateau. As for the rate of natural regeneration, this index is greater than or equal to 100 for 69.56% of the taxa. Sarcochores and heliophytes are the taxa that best support this natural regeneration. This high rate of regeneration would be correlated with the high level of anthropization, whose large canopy gaps are accompanied by a flow of light conducive to the installation of seedlings.

DET1-mediated COP1 regulation avoids HY5 activity over second-site gene targets to tune plant photomorphogenesis

DE-ETIOLATED 1(DET1)and CONSTITUTIVE PHOTOMORPHOGENESIS 1(COP1)are two essential repressors of Arabidopsis photomorphogenesis.These proteins can associate with CULLIN4 to form independent CRL4-based E3 ubiquitin ligases that mediate the degradation of several photomorphogenic transcription factors,including ELONGATED HYPOCOTYL 5(HY5),thereby controlling multiple gene-regulatory networks.Despite extensive biochemical and genetic analyses of their multi-subunit complexes,the functional links between DET1 and COP1 have long remained elusive.Here,we report that DET1 associates with COP1 in vivo,enhances COP1-HY5 interaction,and promotes COP1 destabilization in a process that dampens HY5 protein abundance.By regulating its accumulation,DET1 avoids HY5 association with hundreds of second-site genomic loci,which are also frequently targeted by the skotomorphogenic transcription factor PHYTOCHROME-INTERACTING FACTOR 3.Accordingly,ectopic HY5 chromatin enrichment favors local gene repression and can trigger fusca-like phenotypes.This study therefore shows that DET1-mediated regulation of COP1 stability tunes down the HY5 cistrome,avoiding hyper-photomorphogenic responses that might compromise plant viability.

Water reorientation in the hydration shells of hydrophilic and hydrophobic solutes

We discuss some key aspects of our recent theoretical work on water reorientation dynamics,which is important in a wide range of phenomena,including aqueous phase chemical reactions,protein folding,and drug binding to proteins and DNA. It is shown that,contrary to the standard conception that these dynamics are diffusional,the reorientation of a water molecule occurs by sudden,large amplitude angular jumps. The mechanism involves the exchange of one hydrogen bond for another by the reorienting water,and the process can be fruitfully viewed as a chemical reaction. The results for reorientation times,which can be well described analytically,are discussed in the context of the molecular level interpretation of recent ultrafast infrared spectroscopic results,focusing on the concepts of structure making/breaking and solvent 'icebergs'.

High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices

Free-space optical communication is a very promising alternative to fiber communication systems,in terms of ease of deployment and costs.Midinfrared light has several features of utter relevance for free-space applications:low absorption when propagating in the atmosphere even under adverse conditions,robustness of the wavefront during long-distance propagation,and absence of regulations and restrictions for this range of wavelengths.A proof-of-concept of high-speed transmission taking advantage of intersubband devices has recently been demonstrated,but this effort was limited by the short-distance optical path(up to 1 m).In this work,we study the possibility of building a long-range link using unipolar quantum optoelectronics.Two different detectors are used:an uncooled quantum cascade detector and a nitrogen-cooled quantum well-infrared photodetector.We evaluate the maximum data rate of our link in a back-to-back configuration before adding a Herriott cell to increase the length of the light path up to 31 m.By using pulse shaping,pre-and post-processing,we reach a record bitrate of 30 Gbit s−1 for both two-level(OOK)and four-level(PAM-4)modulation schemes for a 31-m propagation link and a bit error rate compatible with error-correction codes.

A systematic approach to generating accurate neural network potentials:the case of carbon

Availability of affordable and widely applicable interatomic potentials is the key needed to unlock the riches of modern materials modeling.Artificial neural network-based approaches for generating potentials are promising;however,neural network training requires large amounts of data,sampled adequately from an often unknown potential energy surface.Here we propose a selfconsistent approach that is based on crystal structure prediction formalism and is guided by unsupervised data analysis,to construct an accurate,inexpensive,and transferable artificial neural network potential.Using this approach,we construct an interatomic potential for carbon and demonstrate its ability to reproduce first principles results on elastic and vibrational properties for diamond,graphite,and graphene,as well as energy ordering and structural properties of a wide range of crystalline and amorphous phases.

Macroscale fluorescence imaging against autofluorescence under ambient light

Macroscale fluorescence imaging is increasingly used to observe biological samples.However,it may suffer from spectral interferences that originate from ambient light or autofluorescence of the sample or its support.In this manuscript,we built a simple and inexpensive fluorescence macroscope,which has been used to evaluate the performance of Speed OPIOM(Out of Phase Imaging after Optical Modulation),which is a reference-free dynamic contrast protocol,to selectively image reversibly photoswitchable fluorophores as labels against detrimental autofluorescence and ambient light.By tuning the intensity and radial frequency of the modulated illumination to the Speed OPIOM resonance and adopting a phase-sensitive detection scheme that ensures noise rejection,we enhanced the sensitivity and the signal-to-noise ratio for fluorescence detection in blot assays by factors of 50 and 10,respectively,over direct fluorescence observation under constant illumination.Then,we overcame the strong autofluorescence of growth media that are currently used in microbiology and realized multiplexed fluorescence observation of colonies of spectrally similar fluorescent bacteria with a unique configuration of excitation and emission wavelengths.Finally,we easily discriminated fluorescent labels from the autofluorescent and reflective background in labeled leaves,even under the interference of incident light at intensities that are comparable to sunlight.The proposed approach is expected to find multiple applications,from biological assays to outdoor observations,in fluorescence macroimaging.