Spawning of major carps in the lower Halda River,Bangladesh     

Chu-fa Tsai  M. Nazrul Islam  Rezaul Karim MD  K. U. M. Shahidur Rahman 《Estuaries and Coasts》1981,4(2):127-138

Spawning biology and spawn fishery of three valuable species of Indian major carps,Catla catla, Labeo rohita andCirrhinus mrigala, in the lower Halda River, Bangladesh, were studied in 1978. The major carps spawned only in the Sonairchar oxbow-bend from April to June on or near the dates of the full moon and the new moon. The tide was then at its highest level, and there was heavy flood water runoff from the hill region with sharp increases in water level, turbidity and current velocity, as well as decreases in water temperature, dissolved oxygen, and hydrogen ion concentration. These three heterogeneric species, as a result of parallelism or convergence in evolution, overlap in their environmental requirements for spawning. The nursery ground of the major carp fry spawned in the Halda River was found to be in the Bay of Bengal. The brood stock origin is suspected to be at the Shankha River, 40 miles south of the Karnafuli River. The spawn fishery in the Halda River was intensive but inefficient. Engineering works and water management schemes are threatening the spawning habitat.  相似文献   

大兴安岭北段塔河辉长岩的岩石学特征及其构造意义   总被引：9，自引：2，他引：9  

周长勇  葛文春  吴福元 《吉林大学学报(地球科学版)》2005,35(2):143-149

塔河辉长岩是大兴安岭北段塔河地区最具代表性的辉长岩体.该岩体主要由橄榄辉长岩、浅色橄榄辉长岩、淡色辉长岩(斜长岩)、橄长岩及辉长岩组成,以橄榄辉长岩和橄长岩为主.其主要造岩矿物由斜长石、橄榄石、单斜辉石及少量角闪石组成,具反应边结构和包含嵌晶结构.电子探针分析结果表明,其橄榄石Fo平均为77,属贵橄榄石.单斜辉石全部落入透辉石区.斜长石An平均为85,为倍长石.岩相学特征表明,该岩体为典型的堆晶辉长岩体.根据An-Fo及AlZ -TiO2 图解可以判别该岩体形成于活动大陆边缘/岛弧的构造环境中,属于I型弧堆晶辉长岩,其形成可能与古亚洲洋闭合过程中板块俯冲-流体交代作用有关,是研究古亚洲洋闭合历史的一个重要岩石学标志.  相似文献   

Assessing income-wise household environmental conditions and disease profile in urban areas: Study of an Indian city     

Atiqur Rahman 《GeoJournal》2006,65(3):211-227

The main objectives of the present study are: (i) to assess the income-wise household environmental conditions of the sampled households in Aligarh city, (ii) to examine income-wise disease profile of the population, (iii) to assess the relationship between income and four most occurring diseases, (iv) draw out inter-relationship between income, non-ideal household environmental conditions and environment related diseases. The quality of life and diseases in any urban areas get reflected by the immediate neighborhood in different parts of the city which depends upon the income strata of the households, their way of living, and their understanding of their household environment. This is because it is the household environment, which exerts the most and immediate influence on the life of the people. This study was carried out in order to assess household environmental conditions (i.e. housing conditions, bathroom and sanitation conditions, water supply conditions, water logging conditions, household garbage and solid waste, household pests, indoor air and indoor noise pollution) and their effect on the health of the resident population of Aligarh city. The method includes household survey of Aligarh city using questionnaires. The sampled households were classified into five income groups from very low to very high. Relationship was tested between income and household environmental conditions and also between income and diseases using Chi-Square technique. About 55% of the total sampled households suffer from diarrhea/dysentery, 43% jaundice, 42% malaria and 41% respiratory diseases. About 40% suffer from skin diseases, small pox/chicken pox. All these diseases are a result of poor household environmental conditions. Whereas 35% people reported other diseases (i.e. heart disease, hypertension and diabetes), only 14.42% households reported of tuberculosis. The study concludes that there exists a significant positive relationship between income level and household environmental conditions, and also between income and various diseases among sampled households of Aligarh city.  相似文献   

Conditions leading to the onset of the Indian monsoon: A satellite perspective   总被引：1，自引：0，他引：1  

B. Simon  S. H. Rahman  P. C. Joshi 《Meteorology and Atmospheric Physics》2006,93(3-4):201-210

Summary The summer monsoon onset-2004 over the Kerala Coast (Southern tip of the Indian Peninsula) was monitored in real-time using the Tropical Rainfall Measuring Mission (TRMM)/TMI derived total precipitable water vapor, wind speed and sea surface temperature (SST), National Centre for Environmental Prediction (NCEP) and QuikScat wind data. The 2004 onset was of a gradual type, with an early start (24 May), followed by slow growth to full strength (10 June). Hence, the unambiguous forecasting of such onsets becomes very difficult. The water vapor build up over the western Arabian Sea is one of the necessary conditions that gives us a lead time of two and half weeks for the onset of monsoon. The strength of the Hadley cell (monitored using NCEP meridional wind), which is associated with a large convective heat source is also used as a predictive parameter with a lead-time of two weeks. The other dynamical conditions considered are the early May propagation of the Madden Julian Oscillation (MJO) followed by a second MJO, which began in the Western Indian Ocean (WIO) and the kinetic energy over the South East Arabian Sea, with an early start around 24 May (50 m²/s²) and strengthening around 10 June (80 m²/s²). The setting of large-scale monsoon current using various satellite derived parameters and the distinct features for the year 2004 have been delineated.  相似文献   

伽师地震区地壳细结构及发震断层的初步研究   总被引：17，自引：7，他引：17       下载免费PDF全文

李松林  张先康  W.D.Mooney  赖晓玲  A.J.Michael  段永红 《地球物理学报》2002,45(1):76-82

199年至1998年伽师地区共出现9次震级为6.1-6.8级的强震. 在一个非常短的时间间隔内和非常小的地区范围内接连出现这么多次震级非常接近的地震,确实非常罕见. 为研究伽师强震区的深部构造背景和孕震机制,本文对伽师地震区的余震观测资料进行了分析处理. 利用联合反演技术同时得到了地震震源位置和地震区地壳三维速度结构. 余震震中沿一北北东向条带分布,与强震分布的两个条带中的北东向条带位置基本重合. 三维反演得到的速度结构结果表明,在地下12 km以下存在一条北北东向和一条北北西向的低速条带. 上述两低速条带与强震分布的两个条带位置很接近. 初步推测,低速条带对应了地壳深部的两条断裂. 在我们观测期间,北北东向断裂有微震活动,北北西向断裂相对平静.  相似文献   

Flood assessment and early warning of the reoccurrence of river blockage at the Baige landslide     

GAO Yunjian  ZHAO Siyuan  DENG Jianhui  YU Zhiqiu  RAHMAN Mahfuzur 《地理学报(英文版)》2021,31(11):1694-1712

On 10th Oct.and 3rd Nov.2018,two successive landslides occurred in the Jinsha River catchment at Baige Village,Tibet Autonomous Region,China.The landslides blocked the major river and formed the barrier lake,which finally caused the huge flood disaster loss.The hillslope at Baige landslide site has been still deforming after the 2018 slidings,which is likely to fail and block the Jinsha River again in the future.Therefore the investigation of 2018 flood disaster at the Baige landslide is of a great significance to provide a classic case for flood assessment and early warning for the future disaster.The detailed survey revealed that the outstanding inundations induced bank collapse disasters upstream the Baige landslide dams,and the field investigations and hydrological simulation suggested that the downstream of the Baige landslide were seriously flooded due to the two periods of the outburst floods.On these bases,the early warning process of potential outburst floods at the Baige landslide was advised,which contains four stages:Outburst Flood Simulating Stage,Outburst Flood Fore-casting Stage,Emergency Plan and Emergency Evacuation Stage.The study offers a con-ceptual model for the mitigation of landslides and flood disasters in the high-relief mountain-ous region in Tibet.  相似文献   

Age, growth and reproduction of the sand smelt Atherina boyeri Risso, 1810 in the Gomishan wetland – southeast Caspian Sea     

Rahman Patimar  Morteza Yousefi  Seyyed Morteza Hosieni 《Estuarine, Coastal and Shelf Science》2009,81(4):457-462

A total of 2256 specimens of Atherina boyeri caught in Gomishan wetland (a marsh lagoon located at the southeast Caspian Sea) during spawning season from February to August 2007 were examined for life-history attributes. The population has a 4-year life cycle. Length–weight relationship was estimated as W = 0.0053TL^3.0181 for males and W = 0.0050TL^3.063 for females, being allometrically positive for both sexes. The von Bertalanffy growth function fitted to back-calculated size at age data was: Lt = 155.17[1 − exp − 0.28(t + 0.738)] and Lt = 162.77[1 − exp − 0.27(t + 0.727)] for males and females respectively. The sex ratio was 1:1.30 in favor of females. The reproductive season, evaluated from GSI, extended from March to July, with a peak in March. The average absolute and relative fecundities were 2976 eggs and 874 eggs g⁻¹ of body weight respectively. The diameter of oocytes ranged from 0.03 to 0.20 mm with a mean value of 0.68. The life-history patterns of A. boyeri in the population under study imply that the population of this species in the southeast Caspian Sea differs markedly from those of other localities of its range distribution. The differences were thought to be due to differences in geographical locations.  相似文献   

Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections     

Abdul Rahman Ashraf  Ashok Sahni 《世界地质(英文版)》2003,6(1)

The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism.  相似文献   

Evolution of geophysical parameters over the Indian Ocean region during contrasting monsoon years of 2002 and 2003 using TRMM/TMI data     

S. H. Rahman  B. Simon  P. C. Joshi 《Theoretical and Applied Climatology》2007,89(3-4):211-227

Summary The evolution of geophysical parameters over Indian Ocean during two contrasting monsoon years 2002 (drought) and 2003 (normal) were studied using TRMM/TMI satellite data. Analysis indicates that there was a lack of total water vapour (TWV) build up over Western Indian Ocean (WIO) during May 2002 (drought) when compared to 2003 (normal). Negative (positive) TWV anomalies were found over the WIO in May 2002 (2003). In 2002, negative SST anomaly of ∼1.5 °C is found over entire WIO when compared to 2003. Anomalously high sea surface wind speed (SWS) anomaly over the South West Indian Ocean (SWIO) and WIO would have resulted in cooling of the sea surface in May 2002 in comparison to 2003. In 2003 the wind speed anomaly over entire WIO and Arabian Sea (AS) was negative, whereas sea surface temperature (SST) anomaly was positive over the same region, which would have resulted in higher moisture availability over these regions. A negative (positive) TWV anomaly over Eastern Arabian Sea (EAS) and positive (negative) anomaly over WIO forms a dipole structure. In the month of June no major difference is seen in all these parameters over the Indian Ocean. In July 2002 the entire WIO and AS was drier by 10–15 mm as compared to 2003. The pentad (5 day) average TWV values shows high (>55 mm) TWV convergence over EAS and Bay of Bengal (BoB) during active periods of 2003, which gives high rainfall over these regions. However, during 2002 although TWV over BoB was >55 mm but it was ∼45–55 mm over EAS during entire July and hence less rainfall. The evaporation has been calculated from the bulk aerodynamic formula using TRMM/TMI geophysical products. It has been seen that the major portion of evaporative moisture flux is coming from southern Indian Ocean (SIO) between 15 and 25° S. Evaporation in June was more over AS and SIO in 2003 when compared to 2002 which may lead to reduce moisture supply in July 2002 and hence less rainfall compared to July 2003.  相似文献   

CENOZOIC ALLUVIUM IN SINGAPORE: ITS PALEOENVIRONMENT RECONSTRUCTED FROM A SECTION     

Avijit Gupta  M.A.  PH.D.    Ausafur Rahman  MSc.  Ph.D.  P.P. Wong  M.A.  Ph.D. 《Singapore journal of tropical geography》1980,1(2):40-46

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