BED SHEAR IN EVOLVING SCOUR AT A CYLINDER:A THEORETICAL APPROACH

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ANALYSIS OF SURFACE AIR TEMPERATURE RECORDED IN LAHORE AND MIANWALI OVER THE PAST THREE DECADES

Surface air temperatures recorded over the past three decades at the weather stations located in Lahore (anindustrialized and densely populated city) and Mianwali (a small and sparsely populated city) were analyzed in order tostudy their climatic trend.Lahore,where meteorological data are recorded at two weather stations (city station and air-port station) indicates a cooling trend,of about 0.5℃ per record period of 1953—1992,for the airport station (31°31′N,74°24′E) and a slight warming trend,of about 0.2℃,for the city station (31°33′N,74°20′E) for the record period of 1950—1992.The Mianwali weather station (32°33′N,71°31′E) also shows a slight cooling trend,of about 0.4℃ per recordperiod of 1959—1992.The climatic variability at these stations was studied by computing seasonal and annual tempera-ture anomalies.The results are explained in terms of the local environmental conditions.     

第四纪红砂层的热释光年代测量——斯里兰卡海岸砂丘的研究实例

通常人们认为,占据湿热带海岸大片地区的红砂层年代是无法测定的。本文根据热释光法取得了这些沉积物绝对年龄的初步成果,同时讨论了热释光法应用在了解环境地球化学情况方面的重要性。有关斯里兰卡海岸地区研究的结果表明,该区70,000年以来海平面可能受到过区域地质构造运动的影响。根据在现场发现红砂中的具有几何图形的细石器来看,可认为其年龄约为距今25,000年,这表明它确实比到目前为止人们所认为的年龄更老。     

挪威西部Вjфrкedalen的变质榴辉岩矿物相之间的Sr交代和分离

在挪威西部片麻岩地区的(?)橄榄岩研究中,变质榴辉岩显示异常的Sr浓缩,在全岩分析中SrO最大为2.4％。在变质榴辉岩矿物中存在的最大Sr浓度是:斜长石9.6％ SrO,绿帘石8.5％,黝帘石7.4％斜黝帘石4.7％,杆沸石6.65％,磷灰石1.5％,葡萄石0.5％,榍石0.3％,角闪石0.2％以及Sr-长石22.6％。锶异常是由于榴辉岩在角闪岩化作用期间Sr带入而形成的。被带入的Sr的来源或许是邻近的角闪岩和在晚加里东期带入的。晶体化学研究表明,根据晶体化学现有的知识和痕量元素分布很可能能够预见在矿物相之间Sr的分布。     

横向均匀介质中地震走时的正演和反演

横向均匀介质可由若干水平分层足够好地逼近,本文引入零厚度层来描述成层介质,从而建立了回折波、反射波、首波和直达波统一的时距关系以及地震走时随模型参数变化的公式。本文详细讨论了水平分层介质里地震走时曲线的特征,合成地震走时的试验表明了由地震走时,用阻尼最小二乘法可以成功地反演速度模型参数,所反演的模型含有速度梯度层,也可以含有低速层。     

混合式三维电磁模拟方法

在地球物理文献中对三维电磁问题讨论过有限的几种数值解。这些数值解是利用积分方程,有限元法或有限差分技术获得的。莱尼斯和乔尼斯(Lines和Jones,1973)以及雷戴等人(Reddy等,1977)分别应用有限差分和有限元技术提出了关于三维大地电磁     

藏高原雪冰电导率与降水碱度以及大气粉尘载荷变化的关系

对青藏高原小冬克玛底冰川和古里雅冰帽上的数个雪坑和浅冰芯的观测,得出其碱度(OH-)剖面、雪坑和冰芯的液态电导率(EC)变化与OH-之间呈良好线性相关(r≥0.8).分析表明,无论在季节、年际或百年际时间尺度上,EC与OH-间的相关性以及EC与可溶离子总量(TDS)间的相关程度是大致相当的.EC的波动主要取决于粉尘来源的碱性盐类(尤其Ca2+)的变化.因此,EC参量运用到深冰芯研究中,可反映历史时期大气粉尘载荷的变化,对反演沙漠演化、大气环流有重要意义.古里雅冰芯记录表明,大气粉尘的中、长期变化可能取决于气候参量的组合特征"冷-干"气候阶段粉尘量上升,EC和OH-值高;"暖-湿"阶段粉尘量下降,EC和OH-值低.20世纪初以来,随着藏北高原气候呈现暖湿化趋势,大气粉尘载荷明显下降.因此,EC可作为显示大气尘埃载荷变化的宏观标尺,是气候波动的"指示器".     

ENCORE: the effect of nutrient enrichment on coral reefs. Synthesis of results and conclusions

Coral reef degradation resulting from nutrient enrichment of coastal waters is of increasing global concern. Although effects of nutrients on coral reef organisms have been demonstrated in the laboratory, there is little direct evidence of nutrient effects on coral reef biota in situ. The ENCORE experiment investigated responses of coral reef organisms and processes to controlled additions of dissolved inorganic nitrogen (N) and/or phosphorus (P) on an offshore reef (One Tree Island) at the southern end of the Great Barrier Reef, Australia. A multi-disciplinary team assessed a variety of factors focusing on nutrient dynamics and biotic responses. A controlled and replicated experiment was conducted over two years using twelve small patch reefs ponded at low tide by a coral rim. Treatments included three control reefs (no nutrient addition) and three + N reefs (NH4Cl added), three + P reefs (KH2PO4 added), and three + N + P reefs. Nutrients were added as pulses at each low tide (ca twice per day) by remotely operated units. There were two phases of nutrient additions. During the initial, low-loading phase of the experiment nutrient pulses (mean dose = 11.5 microM NH4+; 2.3 microM PO4(-3)) rapidly declined, reaching near-background levels (mean = 0.9 microM NH4+; 0.5 microM PO4(-3)) within 2-3 h. A variety of biotic processes, assessed over a year during this initial nutrient loading phase, were not significantly affected, with the exception of coral reproduction, which was affected in all nutrient treatments. In Acropora longicyathus and A. aspera, fewer successfully developed embryos were formed, and in A. longicyathus fertilization rates and lipid levels decreased. In the second, high-loading, phase of ENCORE an increased nutrient dosage (mean dose = 36.2 microM NH4+; 5.1 microM PO4(-3)) declining to means of 11.3 microM NH4+ and 2.4 microM PO4(-3) at the end of low tide) was used for a further year, and a variety of significant biotic responses occurred. Encrusting algae incorporated virtually none of the added nutrients. Organisms containing endosymbiotic zooxanthellae (corals and giant clams) assimilated dissolved nutrients rapidly and were responsive to added nutrients. Coral mortality, not detected during the initial low-loading phase, became evident with increased nutrient dosage, particularly in Pocillopora damicornis. Nitrogen additions stunted coral growth, and phosphorus additions had a variable effect. Coral calcification rate and linear extension increased in the presence of added phosphorus but skeletal density was reduced, making corals more susceptible to breakage. Settlement of all coral larvae was reduced in nitrogen treatments, yet settlement of larvae from brooded species was enhanced in phosphorus treatments. Recruitment of stomatopods, benthic crustaceans living in coral rubble, was reduced in nitrogen and nitrogen plus phosphorus treatments. Grazing rates and reproductive effort of various fish species were not affected by the nutrient treatments. Microbial nitrogen transformations in sediments were responsive to nutrient loading with nitrogen fixation significantly increased in phosphorus treatments and denitrification increased in all treatments to which nitrogen had been added. Rates of bioerosion and grazing showed no significant effects of added nutrients. ENCORE has shown that reef organisms and processes investigated in situ were impacted by elevated nutrients. Impacts were dependent on dose level, whether nitrogen and/or phosphorus were elevated and were often species-specific. The impacts were generally sub-lethal and subtle and the treated reefs at the end of the experiment were visually similar to control reefs. Rapid nutrient uptake indicates that nutrient concentrations alone are not adequate to assess nutrient condition of reefs. Sensitive and quantifiable biological indicators need to be developed for coral reef ecosystems. The potential bioindicators identified in ENCORE should be tested in future research on coral reef/nutrient interactions. Synergistic and cumulative effects of elevated nutrients and other environmental parameters, comparative studies of intact vs. disturbed reefs, offshore vs. inshore reefs, or the ability of a nutrient-stressed reef to respond to natural disturbances require elucidation. An expanded understanding of coral reef responses to anthropogenic impacts is necessary, particularly regarding the subtle, sub-lethal effects detected in the ENCORE studies.     

特大地震大小的快速估计法

将根据初至地震P波的宽带记录(即在宽频范围内的记录)得出的体波震级m_B重新引入国际地震实践中能更快地估计大地震的大小。国际地震学与地球内部物理学协会(IASPEI)震级测定工作组做出的这一建议以及与未来震级测量标准相关的其他建议于2005年10月2～8日在智利召开的IASPEI大会上被IASPEI地震观测与解释委员会采纳。