Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia

Although facies models of braided, meandering and anastomosing rivers have provided the cornerstones of fluvial sedimentology for several decades, the depositional processes and external controls on sheetflow fluvial systems remain poorly understood. Sheetflow fluvial systems represent a volumetrically significant part of the non‐marine sedimentary record and documented here are the lithofacies, depositional processes and possible roles of rapid subsidence and arid climate in generating a sheetflow‐dominated fluvial system in the Cenozoic hinterland of the central Andes. A 6500 m thick succession comprising the Late Eocene–Oligocene Potoco Formation is exposed continuously for >100 km along the eastern limb of the Corque syncline in the high Altiplano plateau of Bolivia. Fluvial sandstone and mudstone units were deposited over an extensive region (>10 000 km²) with remarkably few incised channels or stacked‐channel complexes. The Potoco succession provides an exceptional example of rapid production of accommodation sustained over a prolonged period of time in a non‐marine setting (>0·45 mm year⁻¹ for 14 Myr). The lower ≈4000 m of the succession coarsens upward and consists of fine‐grained to medium‐grained sandstone, mudstone and gypsum deposits with palaeocurrent indicators demonstrating eastward transport. The upper 2500 m also coarsens upward, but contains mostly fine‐grained to medium‐grained sandstone that exhibits westward palaeoflow. Three facies associations were identified from the Potoco Formation and are interpreted to represent different depositional environments in a sheetflow‐dominated system. (i) Playa lake deposits confined to the lower 750 m are composed of interbedded gypsum, gypsiferous mudstone and sandstone. (ii) Floodplain deposits occur throughout the succession and include laterally extensive (>200 m) laminated to massive mudstone and horizontally stratified and ripple cross‐stratified sandstone. Pedogenic alteration and root casts are common. (iii) Poorly confined channel and unconfined sheet sandstone deposits include laterally continuous beds (50 to >200 m) that are defined primarily by horizontally stratified and ripple cross‐stratified sandstone encased in mudstone‐rich floodplain deposits. The ubiquitous thin‐sheet geometry and spatial distribution of individual facies within channel sandstone and floodplain deposits suggest that confined to unconfined, episodic (flash) flood events were the primary mode of deposition. The laterally extensive deposition and possible distributary nature of this sheetflow‐dominated system are attributed to fluvial fan conditions in an arid to semi‐arid, possibly seasonal, environment. High rates of sediment accumulation and tectonic subsidence during early Andean orogenesis may have favoured the development and long‐term maintenance of a sheetflow system rather than a braided, meandering or anastomosing fluvial style. It is suggested here that rapidly produced accommodation space and a relatively arid, seasonal climate are critical conditions promoting the generation of sheetflow‐dominated fluvial systems.     

基于NB-IoT技术的地震预警信息发布终端设备研制

天津市地震局于2015年通过首都圈预警示范工程项目建设，完成地震预警信息服务网络建设，并选取6所学校安装地震预警信息发布装置，提供地震预警信息示范服务，但由于信息发布装置安装复杂且价格偏高，在一定程度上影响终端设备的普及，制约地震预警信息社会化服务进程。同时，已有终端设备如同黑箱，不利于二次开发应用，存在安全隐患，影响服务质量。因此，天津市地震局积极推进基于NB-IoT技术的地震预警信息发布终端设备研制，实现低成本、低功耗、低延时目标及地震预警信息社会化服务。     

激光法气相合成纳米Si/C/N复相粉体

用大功率５ｋＷＣＯ２激光器为能源,以六甲基二硅胺烷［（ＣＨ３）３Ｓｉ］２ＮＨ（简称ＨＭＤＳ）和ＮＨ３为原料,合成纳米非晶Ｓｉ／Ｃ／Ｎ复相粉体。研究了ＨＭＤＳ流量和ＮＨ３对纳米复相粉体组成的影响。ＮＨ３的加入可以大幅度降低纳米复相粉体的碳含量,提高氮含量。Ｓｉ／Ｃ／Ｎ纳米复相粉体的粒径分布范围为１０～５０ｎｍ,为非晶态。     

Water shortage and associated changes in organic nitrogen betweenPappophorum caespitosum(Gramineae) provenances

Three provenances ofPappophorum caespitosum, a forage native grass from the temperate arid region of Argentina, were studied to gain a physiological knowledge of the seasonal organic N status in response to adequate water supply and water stress conditions; and to assess the extent to which variations in the N status between these provenances arise under different water regimes. Plant part samples were analysed for free and bound organic N fractions. Water shortage resulted in a significant depression of plant growth in all provenances. Total N concentration declined along the annual cycle in both water treatments, but it was higher under water stress. The size of the free N pool was very large, suggesting that it may act like an osmoticum. Nitrogen use efficiency increases along the growing period, while the rate of N intake and the specific leaf N content decrease. Variability was found between provenances in most of the physiological and biochemical traits examined under both water regimes.     

氧化铬柱支撑蒙脱石的制备研究

以浙江和新疆的膨润土为原料合成了氧化铝柱支撑蒙脱石,成柱溶液以Na2CO3为碱水解铝盐溶液制得。因为制备含有大聚羟基铬阳离子的成柱溶液是获得具有大的基面间距的柱支撑粘土的关键,我们详细研究了CO32-／Cr3＋值、水解温度和水解时间对所得柱支撑蒙脱石性质的影响。聚羟基铬阳离子通过阳离子交换引入蒙脱石,所得产物用X射线衍射分析和BET氮比表面等方法研究。所得氧化铝柱支撑蒙脱石（简称Cr－mont）的基面间距为2．55nm,BET氮比表面积为190～230m2／g。     

基于Windows 2003远程终端服务的气象信息共享平台的开发和应用

Windows 2003 Server提供的远程终端服务功能实现了多用户同时操作,远程终端多用户通过远程终端功能可以同时在远程终端服务上运行程序、保存文件和使用网络资源等,为业务应用提供了便捷.介绍利用Windows Server 2003远程终端(包括远程桌面和终端服务),开发了气象业务中多用户共享MICAPS20、雷达PUP产品及其它气象应用系统的信息服务平台,在实际应用中发挥了很好的应用效果.     

Assessment of δ13C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Lateglacial isolation basin sediments,northwest Scotland

Carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea‐level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between δ¹³C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of δ¹³C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between δ¹³C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO₂ concentration, poor vegetation development and temperature influence δ¹³C values during this period. Copyright © 2007 John Wiley & Sons, Ltd.     

Bayesian modelling of the cool core galaxy group NGC 4325

We present an X-ray analysis of the radio-quiet cool-core galaxy group NGC 4325  ( z = 0.026)  based on Chandra and ROSAT observations. The Chandra data were analysed using xspec deprojection, 2D spectral mapping and forward-fitting with parametric models. Additionally, a Markov Chain Monte Carlo method was used to perform a joint Bayesian analysis of the Chandra and ROSAT data. The results of the various analysis methods are compared, particularly those obtained by forward-fitting and deprojection. The spectral mapping reveals the presence of cool gas displaced up to 10 kpc from the group centre. The Chandra X-ray surface brightness shows the group core to be highly disturbed, and indicates the presence of two small X-ray cavities within 15 kpc of the group core. The xspec deprojection analysis shows that the group has a particularly steep entropy profile, suggesting that an active galactic nucleus (AGN) outburst may be about to occur. With the evidence of prior AGN activity, but with no radio emission currently observed, we suggest that the group in a pre-outburst state, with the cavities and displaced gas providing evidence of a previous, weak AGN outburst.     

Recent discoveries of supersoft X‐ray sources in M 31

Classical novae (CNe) have recently been reported to represent the major class of supersoft X‐ray sources (SSSs) in the central area of our neighbouring galaxy M 31. This paper presents a review of results from recent X‐ray observations of M 31 with XMM‐Newton and Chandra. We carried out a dedicated optical and X‐ray monitoring program of CNe and SSSs in the central area ofM 31. We discovered the first SSSs in M 31 globular clusters (GCs) and their connection to the very first discovered CN in a M 31 GC. This result may have an impact on the CN rate in GCs. Furthermore, in our optical and X‐ray monitoring data we discovered the CN M3 1N 2007‐11a, which shows a very short SSS phase of 29–52 days. Short SSS states (durations ≤ 100 days) of CNe indicate massive white dwarfs (WDs) that are candidate progenitors of supernovae type Ia. In the case of M31N 2007‐11a, the optical and X‐ray light curves suggest a binary containing a WD with M_WD > 1.0 M_⊙. Finally, we present the discovery of the SSS counterpart of the CN M31N 2006‐04a. The X‐ray light curve of M31N 2006‐04a shows short‐time variability, which might indicate an orbital period of about 2 hours (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

利用氮氧同位素研究桂林寨底地下河硝酸盐来源

工农业生产的迅速发展使地下水硝酸盐氮(NO3-—N)污染成为世界性的环境问题。地下水中硝酸盐的来源研究在水文地质结构特殊的西南岩溶地区就显得尤为重要。稳定氮同位素和氧同位素在地下水硝酸盐的来源示踪研究中有着广泛的应用。本研究选取岩溶地区典型地下河——广西桂林寨底地下河为研究对象,通过氮氧同位素数据,判断寨底地下河硝酸盐来源是以动物粪便为主的农家肥,为该区地下水的保护和利用提供科学依据。