Diet and feeding strategies of round goby,Neogobius melanostomus (Pallas, 1814) from the invasion front in the Danube River tributaries (Bulgaria): ontogenetic shift and seasonal variation

The round goby Neogobius melanostomus is one of the most successful Ponto-Caspian fish invaders, established in a variety of aquatic ecosystems throughout Europe and North America. Diet and feeding strategies of N. melanostomus from three recently invaded tributaries of the Lower Danube River (Bulgaria) were investigated. Research design is based on monthly examination of the round goby diet and macroinvertebrate density. The results show that the round goby consume a wide range of different organisms – 76 taxa in total (identified to family, genus or species level). The most common prey taxa in all three rivers were Chironomidae (Orthocladius/Cricotopus spp., Tanytarsini g. sp.), Trichoptera larvae (Psychomyiidae g. sp., Hydropsyche spp.) and Ephemeroptera nymphs (Baetis spp.). Only in one of the rivers, a predominant feeding on crustaceans (Gammarus spp.) was observed. The taxonomical composition of consumed invertebrates suggests that the round goby prefers the ecological group of “sprawling/walking” insect larvae associated to coarse substratum. Feeding activity was observed throughout the whole year, even during low-temperature months. Three seasonal and four size-depended shifts in the species’ diet were determined. Generalization feeding tactics predominated in all three rivers. Specialization was rare and specific for each tributary, where a few individuals consumed invertebrates from fine substratum and/or submerged vegetation. Possible relationships between the spread of N. melanostomus and the recent invasion of the Asian clam (Corbicula fluminea) in the Bulgarian Danube tributaries were discussed. Generalisation and feeding plasticity contribute to the round goby’s establishment success in the Danube tributaries and might facilitate its further upstream spread.     

Magnetotail dipolarization fronts and particle acceleration: A review

In this paper, the particle acceleration processes around magnetotail dipolarization fronts(DFs) were reviewed. We summarize the spacecraft observations(including Cluster, THEMIS, MMS) and numerical simulations(including MHD, testparticle, hybrid, LSK, PIC) of these processes. Specifically, we(1) introduce the properties of DFs at MHD scale, ion scale, and electron scale,(2) review the properties of suprathermal electrons with particular focus on the pitch-angle distributions,(3)define the particle-acceleration process and distinguish it from the particle-heating process,(4) identify the particle-acceleration process from spacecraft measurements of energy fluxes, and(5) quantify the acceleration efficiency and compare it with other processes in the magnetosphere(e.g., magnetic reconnection and radiation-belt acceleration processes). We focus on both the acceleration of electrons and ions(including light ions and heavy ions). Regarding electron acceleration, we introduce Fermi,betatron, and non-adiabatic acceleration mechanisms;regarding ion acceleration, we present Fermi, betatron, reflection, resonance, and non-adiabatic acceleration mechanisms. We also discuss the unsolved problems and open questions relevant to this topic, and suggest directions for future studies.     

海洋锋区的一种声速计算模式及其在声传播影响研究中的应用

利用穿过海洋锋区断面的实测CTD数据,确定了锋面的宽度、所在的位置以及陡度等特征参数,建立了海洋锋区声速计算理论模式。结果表明,此模式可以用来描述选定断面的锋面特性。将理论计算结果与实测数据进行比较,二者符合较好。进而利用二维PE模型,研究了通过海洋锋面的声传播特性。结果表明,在声源深度为50m和发射频率为150 Hz的情形下,对不同接收深度,有锋面与无锋面时传播损失的差别最大约为20 dB左右。     

滦平盆地桑园营子露头剖面沉积层序的Markov链模拟

桑园营子露头剖面具有同沉积断层控制的近源、粗粒、陡坡型浅水扇三角洲体系的沉积特征。根据 Markov过程的基本原理 ,认识到桑园营子剖面出露完整的扇三角洲前缘沉积组合( C — C 旋回 )各岩性相之间的转移具有 Markov性质 ,利用转移概率矩阵法及差值矩阵法对该沉积组合进行 Markov链模拟 ,得出了理想的垂向沉积层序模式图。该模式图与实际地层层序吻合较好 ,反映了各岩性相的空间展布特征 ,建立了沉积环境的演化序列。     

Satellite infrared remote sensing observation of surface circulation of the northeast South China Sea in winter

I~IOX \The investigation of physical oceanography in the South China Sea dates from early in the17th century and was carried out by scientists from many countries, including the United StateS,the United Kingdoms, Japan, .Russia and so on, but the survey area was rather limited at thattime and the data which were collected were still fragmentary. Since the 20th century, the investigation on the sleuth China Sea has made great progreSS not only in the scale of survey, but alsoin the depth …     

99.8.11山东特大暴雨能量分析

本文用能量天气学方法分析了１９９９年８月１１日－－１２日发生在鲁东南的特大暴雨天气过程。分析发现：能量锋区产生在高低空干冷空气与暖湿空气的交汇处。特大暴雨产生在能量锋区的右侧高能舌附近,此处是位势不稳定能量的大值区,由云图和雷达回波可以看出也是水汽聚集和上升运动最强烈的地区,且位势不稳定能量中心的移动对未来１２小时暴雨落区有较好的指示性。     

西南天山柯坪推覆构造柯坪塔格山前逆断裂东段晚第四纪的古地震

柯坪推覆构造系是西南天山前陆推覆构造的重要组成部分。文中试图通过对柯坪推覆构造区的影像解译和野外观察、断错地貌的实测和探槽开挖,探讨柯坪塔格山前断裂东段晚第四纪以来的古地震活动。在三岔口以西的五道班—三间房一带和三岔口以东的大山口道班一带,除现代洪积扇外,明显可见2期保存较完整的洪积扇被断错。五道班—三间房地段的3个探槽揭露出了晚更新世末期以来该破裂段发生的4次事件,其参考年代为:距今22、14、6·5和4·4ka;重复间隔时间约为:8、7和2ka左右。间隔时间长的事件垂直位移量约1~1·2m,缩短量约1·3~1·4m;间隔时间短的事件,垂直位移量0·20~0·30m,缩短量0·6~0·7m。大山口道班段探槽揭露出了晚更新世末期以来的2次事件,分别发生在稍早于距今13ka和稍晚于距今6ka。重复间隔时间约7ka。同震垂直位移量约50cm,缩短量130cm左右     

南印度洋测控海域大风分析

在辽阔的东南印度洋上的“远望号”测量船为中国卫星和载人飞船执行测控服务。该海域风大浪急,缺乏海洋水文气象资料。本文利用1980~1990年的部分历史资料(包括地面图和卫星云图)进行了分析研究,指出有三类天气系统容易引起测控海域的大风巨浪:冷锋、中纬度气旋和强梯度带。该结论有助于东南印度洋的远洋气象保障。     

乌鲁木齐头屯河区急性心肌梗塞发病率与气象关系的分析

从1979～1996年17年新疆钢铁公司职工医院收住的急性心肌梗塞（简称心梗）168个病例,结合相应的气象资料,分析了心梗发病的季节特征和5种天气类型,指出冬春季是心梗的多发季节;在5种天气类型中,以高压低温和低压高温两种类型发病率最高,而低压低温型最低。     

桂西一次强降水过程的物理量演变特征分析

利用Ｔ１０６数值预报产品物理量分析场资料, 对１９９８ 年７ 月２３～２５ 日百色地区持续性的暴雨天气过程进行分析, 揭示了暴雨发生前后影响系统及物理量场的分布与演变特征、影响系统和各种物理量的相互配置与暴雨的关系, 指出能量锋的出现与暴雨落区的形成关系特别密切。