A note on some early radiosonde temperature observations in the Antarctic lower stratosphere

The behaviour of the Southern Hemisphere stratosphere has attracted considerable interest, and been compared with the Northern Hemisphere, since the International Geophysical Year (1957–58) when the sudden (explosive or accelerated) springtime warming phenomenon in the Antarctic was first observed. Over the years studies of upper air temperature and wind observations have been made, principally through the spring months when the polar vortex breakdown occurs, utilising both ground-based (rawinsonde, rocket) and more recently, satellite-derived data. Although the radiosonde-derived temperature data are limited both by the number of reporting stations, and the practical difficulty of securing observations much above the 100 hPa level, useful records exist from 1956 or 1957. These have shown that in the 1959 southern spring, the lower stratosphere was relatively colder, and the warming rate through the season was essentially more regular, with little evidence of the marked but short-lived temperature fluctuations usually found. Similar, but not quite such wide-spread conditions occurred again in the 1961 spring. In another study, 30 hPa temperature fields over the Antarctic continent, which could be drawn for the 1967 spring, showed the complexity of the polar vortex breakdown. These features are recalled because extension of the 100 hPa springtime temperature series for the Australian Antarctic station at Casey (66.3°S, 110.5°E) shows that in 1985 and part of 1986, the temperature behaviour there was similar to, but not quite so extreme as that which occurred at Mirny (66.5°S, 93.0°E) in 1959.     

Wharf embankment and strengthening program at the Port of Oakland

The wharf and embankment strengthening program (WESP) is a structural modification project involving approximately 12,000 linear feet of pile-supported, marginal wharf structures. WESP is necessary because the Port of Oakland plans to deepen its berths from −42′ mean lower low water (MLLW) to −52′ MLLW, in conjunction with a Federal Government-sponsored channel dredging project. Unless they are structurally reinforced prior to the dredging, the waterfront components (i.e. wharves and embankments) will be weakened by the berth deepening project. WESP is a three-phase program that establishes the existing structural and seismic capacities of waterfront components, develops designs for improvements necessary to maintain these capacities after the berth deepening, and constructs the improvements. WESP also includes consideration of seismic upgrade improvements. The Port is currently completing the first phase of the WESP program. This paper will describe the design criteria, project phasing, construction type of waterfront components, project organization, and results to date for WESP.     

长江中下游地震同青藏高原北部地震的相关性

本文对比了1910—1987年发生的长江中下游地震和青藏高原北部地震,发现两者有比较好的对应关系。一般是,青藏高原北部先发生M≥6级地震,而后长江中下游地区发生M≥19/4级地震。对1910年以来的21次地震进行了统计分析,得到复相关系数R=0.74,能够在很高的显著性水平上通过F检验。地震活动在时间、空间、强度上的相关,现代构造运动及应力场等事实表明,长江中下游地震活动可能主要受青藏高原向东的横向推移运动的影响。     

Explosion seismic reflections from the Earth’s core

Recent seismological studies have presented evidence for the existence of a layer with ultra-low seismic velocities at the core-mantle boundary at ca. 2900 km depth. We report high-amplitude, high-frequency, and laterally coherent seismic arrivals from three nuclear explosions in Siberia. With recording station intervals of 15 km, the seismic phases are readily correlated and show the presence of a thin, ultra-low velocity zone in a region where it was not previously reported. The duration and complexity of the arrivals are inconsistent with a simple core-mantle boundary and require a hitherto unidentified, kilometre-scale, fine structure in the ultra-low velocity zone. The observations may be explained by a ca. 7 km thick, two-layer, ultra-low velocity zone with exceptional low velocities, which indicate the presence of high percentages of melt (>15%), in particular in the lower part of the zone. Waveform variation implies lateral change in the thickness and physical properties of the ultra-low velocity zone with a wavelength of less than 100 km.     

1990s长江下游干流径流量演变趋势

利用M-K相关分析方法和大通站1950-2000年逐月径流资料,研究了长江下游干流径流的趋势变化.研究结果表明:1950s以来长江下游径流量呈增加趋势,1990s平均径流量(30415.3 m³/s)比所有其他年代平均径流都大,为近50a以来的最大值;就季节和月份而言,秋季径流明显减少;夏、冬两季径流量,增加的趋势明显,尤以冬季枯水季节径流增加最为突出.洪水、枯水季节径流增加明显,但以枯水季节径流增加占优势.冬季枯水径流的增加,可能在一定程度上能够缓解长江口生态环境的巨大压力.1990s径流量的增加与全球变暖、水循环加快、长江流域降水量增加密切相关.     

富营养化浅水湖泊沉水水生植被的衰退与恢复

对国外近年来有关富营养化浅水湖泊的退化与恢复方面的研究进展以及生物操纵作用作了述评,对有关富营养化湖泊沉水植被衰退的有代表性的３种假说也作了介绍。根据“八五”期间武汉东湖水生植被重建的研究工作和多年积累的湖泊水生植被调查资料,提出了长江中下游浅湖富营养化过程中沉水植被演替的模式。     

双源CT Flash双低技术手动触发扫描在冠状动脉CTA的可行性研究

目的:对比常规前瞻性心电触发扫描及对比剂用量方案,探讨在双源CT Flash扫描模式下,低k V、低对比剂用量、手动触发扫描方案在低体重、低心率患者行冠脉CTA检查的可行性。方法:48例患者分为两组:A组:24例,体重<65kg,45次/min≤心率≤65次/min,对比剂流速和用量分别为5.0 mL/s和20 mL (350 mg I/m L),行Flash扫描,管电压采用70 kV;B组:24例,体重<65 kg,48次/min≤心率≤65次/min,对比剂流速和剂量分别为5.0 mL/s和50 mL (350 mg I/m L),行前瞻性心电触发扫描,管电压采用100k V。对原始数据进行SAFIRE迭代重建。比较两组患者的性别、年龄、心率、体重、BMI、CTDI_VOL、DLP和ED,测量并比较两组图像主动脉根部、左主干、冠脉三大支近段管腔内的CT值、噪声、信噪比及主动脉根部的对比噪声比。两组冠脉图像质量采用4级评分法进行比较。结果:两组患者在性别、年龄、心率、体重、BMI及两组图像主动脉根部、左主干、冠脉三大支近段的CT值、噪声、信噪比、主动脉根部对比噪声比无显著性差异(P>0.05),在CTDI_VOL、DLP和ED方面两组图像有显著性差异(P<0.05)。两组冠脉图像质量等级无显著性差异,冠脉可评价节段率均>96%。结论:双源CT在低体重、低心率患者应用70 kV超低管电压和低对比剂用量的方案进行冠状动脉CTA检查可以获得满足临床诊断的图像质量,较常规方案的放射剂量和对比剂用量显著减低。     

FRICTIONAL SLIDING OF PLAGIOCLASE GOUGE UNDER LOWER-CRUST TEMPERATURE AND RELATIVELY LOW EFFECTIVE NORMAL STRESS

The discovery of tremors on the lower crust portion of the San Andreas Fault has attracted more attention on the mechanical properties of the lower crust in recent years, and some experimental studies have been carried out to understand the mechanical behavior. Previous experiments under effective normal stresses of 200MPa have shown that pyroxene and plagioclase mineral separated from the gabbro and their mixtures all show velocity weakening in the lower-crust temperature range, which results in unstable slip when frictional sliding is the dominant deformation mechanism. This work is to examine whether the velocity-weakening behavior of plagioclase gouge also applies to relatively lower effective normal stress. Our experiments were performed under effective normal stress of about 100MPa, with a constant confining pressure control, with pore pressure of 30MPa and temperature of 100℃ to 600℃. We found that the frictional sliding of plagioclase are basically the same with the previous results obtained under effective normal stress of 200MPa, both of which show velocity weakening over the entire temperature range. The only difference is the out-of-trend drop of constitutive parameter a at 600℃ for the lower effective normal stress of 100MPa. It is thus concluded that reducing the effective normal stress has little effect on the sliding stability of plagioclase, and the previous conclusion made for mechanical behavior of the lower crust that unstable slips are possible therein also applies to the lower effective normal stress of 100MPa.     

Impact of global change on transmission of human infectious diseases

Global change,which refers to large-scale changes in the earth system and human society,has been changing the outbreak and transmission mode of many infectious diseases.Climate change affects infectious diseases directly and indirectly.Meteorological factors including temperature,precipitation,humidity and radiation influence infectious disease by modulating pathogen,host and transmission pathways.Meteorological disasters such as droughts and floods directly impact the outbreak and transmission of infectious diseases.Climate change indirectly impacts infectious diseases by altering the ecological system,including its underlying surface and vegetation distribution.In addition,anthropogenic activities are a driving force for climate change and an indirect forcing of infectious disease transmission.International travel and rural-urban migration are a root cause of infectious disease transmission.Rapid urbanization along with poor infrastructure and high disease risk in the rural-urban fringe has been changing the pattern of disease outbreaks and mortality.Land use changes,such as agricultural expansion and deforestation,have already changed the transmission of infectious disease.Accelerated air,road and rail transportation development may not only increase the transmission speed of outbreaks,but also enlarge the scope of transmission area.In addition,more frequent trade and other economic activities will also increase the potential risks of disease outbreaks and facilitate the spread of infectious diseases.     

S-wave crustal and upper mantle's velocity structure in the eastern Tibetan Plateau——Deep environment of lower crustal flow

A teleseismic profile consisting of 26 stations was deployed along 30°N latitude in the eastern Tibetan Plateau. By use of the inversion of P-wave receiver function, the S-wave velocity structures at depth from surface to 80 km beneath the profile have been determined. The inversion results reveal that there is significant lateral variation of the crustal structure between the tectonic blocks on the profile. From Linzhi north of the eastern Himalayan Syntaxis, the crust is gradually thickened in NE direction; the crustal thickness reaches to the maximum value (~72 km) at the Bangong-Nujiang suture, and then decreased to 65 km in the Qiangtang block, to 57―64 km in the Bayan Har block, and to 40―45 km in the Sichuan Basin. The eastern segment of the teleseismic profile (to the east of Batang) coincides geographically with the Zhubalong-Zizhong deep seismic sounding profile carried out in 2000, and the S-wave velocity structure determined from receiver functions is consistent with the P-wave velocity structure obtained by deep seismic sounding in respect of the depths of Moho and major crustal interfaces. In the Qiangtang and the Bayan Har blocks, the lower velocity layer is widespread in the lower crust (at depth of 30―60 km) along the profile, while there is a normal velocity distribution in lower crust in the Sichuan Basin. On an average, the crustal velocity ratio (Poisson ratio) in tectonic blocks on the profile is 1.73 (σ = 0.247) in the Lhasa block, 1.78 (σ = 0.269) in the Banggong-Nujiang suture, 1.80 (σ = 0.275) in the Qiangtang block, 1.86 (σ = 0.294) in the Bayan Har blocks, and 1.77 (σ = 0.265) in the Yangtze block, respectively. The Qiangtang and the Bayan Har blocks are characterized by lower S-wave velocity anomaly in lower crust, complicated Moho transition, and higher crustal Poisson ratio, indicating that there is a hot and weak medium in lower crust. These are considered as the deep environment of lower crustal flow in the eastern Tibetan Plateau. Flowage of the ductile material in lower crust may be attributable to the variation of the gravitational potential energy in upper crust from higher on the plateau to lower off plateau.