First record of freshwater bryozoans (Bryozoa: Phylactolaemata) in the aquatic invertebrate fauna of Serbia

Species of freshwater bryozoans are newly recognized in the fauna of aquatic invertebrates in Serbia. This first record includes a total of five species of class Phylactolaemata found at eight localities during limnological investigations in the period from 2002 to 2006. Four species are assigned to family Plumatellidae (Plumatella casmiana, P. emarginata, P. geimermassardi and Hyalinella punctata). Family Cristatellidae is represented by one species (Cristatella mucedo). The freshwater bryozoans in the form of intact colonies and especially as dormant bodies were identified to the species level. The identification was done using scanning electron microscopy, analyzing resting bodies’ morphological ultrastructure.     

初至波菲涅尔体地震层析成像

根据地震波传播的有限频理论,对于某个特定震相的观测信息,不仅射线路径上的点对该信息具有影响,射线领域上的其他点对接收信息也具有影响,这种影响可以用核函数来表达.本文基于波动方程的Born近似与Rytov近似,给出了非均匀介质情况下初至地震波振幅与走时菲涅尔体层析成像单频、带限层析核函数的计算方法.通过对均匀介质情况下初至地震波菲涅尔体层析成像核函数解析表达式的理论模型实验与分析,给出了不同维度振幅、走时单频菲涅尔体的空间分布范围,进而给出了带限菲涅尔体边界的确定方法.将本文的走时菲涅尔体层析成像理论应用于表层速度结构反演中,理论模型试验与实际资料处理结果表明,初至波菲涅尔体地震层析成像方法比传统的初至波射线层析成像理论具有更高的反演精度.     

三维复杂地形近地表速度估算及地震层析静校正

在地表一致性模型的基础上提出一种可适用于宽线剖面、弯曲测线、传统的二维和目前广泛使用的三维地震观测.在地形及近地表低降速带地质结构复杂的探区，低降速带厚度及速度估算的精度是静校正处理的关键.本研究根据三维地震观测的初至走时数据，利用最小平方与QR分解相结合的算法，在三维空间重建近地表低降速带速度模型，根据重建速度模型实现了静校正长波长分量与短波长分量的同步计算.分析了复杂的近地表低降速带模型初至波的性质，在观测值的自动拾取以及理论值的计算中充分考虑了可能成为初至波的直达波、折射波和反射波的利用，提高了低降速带速度模型反演的精度.在初至走时观测数据的拾取中，本研究采用分形算法克服了初至波波形差异以及折射波相位反转导致的拾取误差，实现了三维初至拾取的大规模全自动化运算.在射线路径与初至波理论走时的计算中，本研究采用一种计算量与模型复杂程度无关的三维射线追踪方法，该方法以最小走时射线路径保证了与观测数据有同等意义的初至波的射线追踪及理论走时的计算.野外实际资料的处理结果表明了方法的有效性.     

Not a “forever model”: the curious case of graduation in Housing First

This article investigates how Housing First (HF) is practiced in Alberta, Canada, with a focus on the concept of graduation. The dominant HF model, Pathways, holds that client support should be time-unlimited. However, HF is highly mobile and increasingly characterized by ambiguity and drift away from Pathways principles. In Alberta, one prominent example of drift is the notion that clients can and should graduate – that is, “exit” HF programs after a certain time. Interviews conducted with 45 participants in three Alberta cities in 2014–15 revealed commonplace, but contested, graduation practices. Interviewees noted that graduation can be necessary to make room for new clients, and may be expected and encouraged by coordinating organizations. They expressed varied concerns about graduation, and the negative influence it could have on client relationships and housing stability. In particular, they emphasized clients’ ongoing dependence on rental subsidies, and the risk of relapse into homelessness.     

西沙群岛星虫类研究Ⅲ——石管星虫属Lithacrosiphon

本文连续报道南海西沙群岛星虫类的第三部分即石管星虫属(Lithacrosiphon)。本属系1902年由Shipley氏订立。据文献记载属中的种均分布于热带海,通常钻孔于珊瑚石中。作者仅鉴定了马岛石管星虫(Lithac-rosiphon maldivensis Shipley)一种。本属在中国海是首次记载。     

北太平洋海温与广西前汛期降水的联系

利用1979—2019年全国160站逐月降水资料、Hadley中心海温资料、NOAA以及NCEP/NCAR再分析资料,结合相关分析、信息流以及合成分析方法,分析了北太平洋海温异常与广西前汛期降水的同期联系,并初步探讨了前者对后者的影响及可能机制,结果表明：北太平洋关键区海温是广西前汛期降水的显著影响源,海温正位相(负位相)的异常分布在一定程度上导致了广西前汛期降水增多(减少).北太平洋关键区海温变化可以独立于赤道中东太平洋影响前汛期降水,而赤道中东太平洋海温变化可以起到调制作用,增强两者联系.北太平洋为正位相海温异常时,大气为“+-+”的经向三极型位势高度异常响应.与此同时,海温异常激发了向下游中高纬传播的Rossby波列,引起东亚沿岸位势高度正异常和反气旋环流异常.在上述机制下,贝加尔湖高压脊和东亚大槽均显著增强,使得中高纬冷空气更易南下.赤道中东太平洋海温的调制作用体现在对中低纬环流的影响.关键区海温正位相对应于赤道中东太平洋海温偏暖,后者引起局地异常上升运动,减弱Walker环流进而导致赤道西太平洋出现下沉异常,抑制了对流活动,在西北太平洋强迫出异常反气旋,使得副高加强西伸.副高的增强西伸增强了暖湿气流输送,这一方面有利于广西一带的水汽输送,水汽通量辐合增强;另一方面有利于冷暖空气在广西交汇,对流不稳定增强,促进上升运动,最终导致降水增多.北太平洋为负位相时上述异常形势相反,导致降水减少.

     

三河—平谷8.0级地震区地壳结构和活动断裂研究——利用单次覆盖深反射和浅层地震剖面

跨1679年三河—平谷8.0级地震区完成的单次覆盖深地震反射剖面和浅层地震反射剖面,揭示了三河—平谷地震区的地壳结构和断裂的深、浅构造特征.结果表明,该区地壳以TWT6~7 s左右的强反射带为界分为上地壳和下地壳,上地壳厚约18~21 km,下地壳厚约13~15 km.剖面揭示的地壳深断裂和浅部活动断裂具有上下一致的对应关系,其中,陡倾角的深断裂切割了下地壳和壳幔过渡带,向上延伸至上地壳,将地壳深部构造与浅部活动断裂联系在一起,这种深、浅共存的断裂构造体系是控制该区地震孕育和发生的重要因素,也是三河—平谷8.0级地震的深、浅构造背景.     

From fishing to farming: Shellfish aquaculture expansion and the complexities of ocean space on Canada's west coast

Ocean spaces are social and political, and just as with terrestrial governance, oceans governance is prone to ambiguity, contradiction, and contestation. The validity and dynamics of these claims will be demonstrated through a study of discourse and structured agreements employed to involve coastal First Nations in the expansion of the shellfish aquaculture sector in British Columbia. Analysis focuses on the West Coast of Vancouver Island, a region identified as having good biophysical potential for shellfish aquaculture and much of which is territorial home of the Nuu-chah-nulth First Nations. Through community interviews and document and discourse analysis, the article highlights that: seafood, including shellfish, is intimately connected with Nuu-chah-nulth identity; many Nuu-chah-nulth have long-engaged in subsistence and commercial harvests of wild-growing shellfish; and, there are important prospective differences between longer-standing shellfish harvests and shellfish aquaculture. Findings and discussion offer perspective on the sorts of choices that First Nations might encounter in the pursuit of shellfish aquaculture, as well as raise bigger questions about whether or how Nations might tradeoff territorial authority and collective harvest opportunities against leasing state-sanctioned private marine tenures.     

http://www.sciencedirect.com/science/article/pii/S1674987112001065

It has been thought that granitic crust,having been formed on the surface,must have survived through the Earth’s evolution because of its buoyancy.At subduction zones continental crust is predominantly created by arc magmatism and is returned to the mantle via sediment subduction,subduction erosion, and continental subduction.Granitic rocks,the major constituent of the continental crust,are lighter than the mantle at depths shallower than 270 km,but we show here,based on first principles calculations, that beneath 270 km they have negative buoyancy compared to the surrounding material in the upper mantle and transition zone,and thus can be subducted in the depth range of 270-660 km.This suggests that there can be two reservoirs of granitic material in the Earth,one on the surface and the other at the base of the mantle transition zone(MTZ).The accumulated volume of subducted granitic material at the base of the MTZ might amount to about six times the present volume of the continental crust.Our calculations also show that the seismic velocities of granitic material in the depth range from 270 to 660 km are faster than those of the surrounding mantle.This could explain the anomalous seismic-wave velocities observed around 660 km depth.The observed seismic scatterers and reported splitting of the 660 km discontinuity could be due to jadeite dissociation,chemical discontinuities between granitic material and the surrounding mantle,or a combination thereof.     

河南朝川矿一井突水因素分析

河南省汝州市朝川矿一井主采煤层二1煤底板隔水层薄、分布不稳定,底板灰岩承压含水层富水性强、水头压力高、补给来源丰富,开采至今已发生数十起突水事故,造成严重的经济损失。研究认为：矿井的主要充水水源为寒武系含水层,导水通道是断层、构造裂隙及采动裂隙,二1煤层底板隔水层仅在局部地段能起到隔水作用;矿井的充水方式主要是大气降水、地表水体通过石炭系和寒武系灰岩露头区渗漏补给,在煤层底板形成水头压力大的承压水而威胁矿井安全的。最后指出,在矿井生产中一定要严格遵守＂预测预报,有采必探,边探边掘,先治后采＂防治水方针。