Rostroconchia: a new class of bivalved mollusks

Four Paleozoic bivalved genera are assigned to the new molluscan class Rostroconchia: Eopteria, Euchasma, Conocardium, and Pseudoconocardium. These mollusks have ani uncoiled univalved larval shell; an untorted bivalved adult shell; no hinge teeth, ligament, or adductor muscles; and a fused, almost inflexible. hinge. Rostroconchianis developed separately from the pelecypods through the ribeirioids, but are regarded as more closely related to the Pelecypoda and Scaphopoda than to other known classes of mollusks.     

新型深水水下清管器发射装置

为解决传统深水海底管道的清管问题,结合海底管道的清管原理,设计了一种新型的水下清管器发射装置,从而有效地避免了平台发射清管器所带来的清管器回收和管道停输等问题。对水下清管器发射装置进行了详细的结构设计,主要包括连接器、保护框架、发射主体结构、上部开合机构和阀门控制系统;介绍了水下发射清管的作业流程,论述了该装置相对于传统清管器发射装置具有的诸多优势;最后对发射装置的储球筒和卡爪连接法兰这两个关键部件进行了数值分析,其结果显示满足设计要求。该装置为深水清管作业提供了一种新的行之有效的方法。（图8,参10）     

Bivalve mollusks: fluid dynamics of burrowing

When bivalves burrow into soft substrates the foot is first extended and then dilated to obtain a firm anchorage before retraction pulls the shell downward. Pedal dilation is principally caused by adduction of the valves. The hinged shell futnctions as a hydraulic machine in which the strength of the adductor muscles is transferred to the distal part of the foot by means of the body fluids.     

Hemocyanin respiratory pigment in bivalve mollusks

Hemocyanins, high molecular weight oxygen-binding proteins, were identified in two species of protobranch bivalve mollusks, Acila castrensis and Yoldia limatula. Although hemocyanins have been reported in chitons, gastropods, and cephalopods, they have not been observed in the Class Bivalvia. In A. castrensis the dissociation products of hemocyanin, characterized by gel electrophoresis, had a subunit molecular weight of approximately 250K. Negatively stained preparations of extracted hemocyanin formed protein aggregates in the shape of cylinders measuring 35 by 38 nanometers. X-ray microanalysis of hemocyanin aggregates in thin sections of Y. limatula demonstrated the presence of copper in the molecules. The discovery of hemocyanin in the protobranchs reinforces the primitive nature of the taxon and is further evidence that the major molluscan classes have a common ancestry.     

一种新型的果树栽培模式--草地果园

果树是一种重要的经济植物,但是传统的栽培模式都沿袭着“桃三李四梨五年”的传统观念,投产期与丰产期不能突破当年栽当年丰产或次年丰产的格局,本文介绍一种新型栽培模式草地果园,可以使许多果树,特别是落叶果树中的核果类及仁果类水果产期大大地往前推移,如桃葡萄可以做到当年栽培当年丰产,苹果、梨可以达到当年栽培次年丰产。     

一种新型设施草莓立体栽培模式的探讨

为提高设施草莓土地利用率,设计一种新型设施草莓立体栽培模式("新H型":即"H型"架下土壤栽培一层草莓,形成双层立体栽培模式),以‘红颜’草莓为试验材料,分析对比在"新H型"和传统栽培2种不同栽培模式下的光照条件、植株营养生长、果实产量与品质、经济效益等指标,并综合评价了"新H型"立体栽培模式实际生产性能。结果表明:单位面积土地上,"新H型"立体栽培模式比传统栽培模式种植株数多20%,投入增加44.455%,产量增加20.240%,总收入增加35.269%,纯利润增加25.876%。初步证实,"新H型"立体栽培模式整体表现优于传统栽培,提高了土地利用效率。     

新型液体肥施肥试验台的总体设计

针对液体肥料发展迅速和液体肥料施用装置发展不完善的现状,提出了一种可以准确测量液体肥施用装置主要部件的技术性能及参数的试验台的设计,可为液体肥料施用装置的研制提供准确的技术参数.     

Environmental and evolutionary stability in bivalve mollusks

There is no relationship between environmental stability [as indicated by infaunal (stable) versus epifaunal (unstable) habits] and the generic duration of extinct marine bivalve mollusks when the effects of cosmopolitanism (which is associated with long generic durations) and other paleontological "noise" are excluded. This is contrary to the "depauperate gene pool" hypothesis of extinctions.     

一种用于摩托车的新型行星齿轮自动变速器

介绍了一种可作为摩托车自动变速器使用、并具有优越的传动和变速性能的行星齿轮变速机构.该机构由2个齿轮参数完全相同的行星排,以及1个制动器、1个离合器和2个单向离合器,以适当方式连接而成,可得到按等比级数分配的3个传动比.它具有结构紧凑、传动效率高、换档平稳性好等特点.     

A new type of meteoritic diamond in the enstatite chondrite abee

Diamonds with delta(13)C values of -2 per mil and less than 50 parts per million (by mass) nitrogen have been isolated from the Abee enstatite chondrite by the same procedure used for concentrating Cdelta, the putative interstellar diamond found ubiquitously in primitive meteorites and characterized by delta(13)C values of -32 to -38 per mil, nitrogen concentrations of 2,000 to 12,500 parts per million, and delta(15)N values of -340 per mil. Because the Abee diamonds have typical solar system isotopic compositions for carbon, nitrogen, and xenon, they are presumably nebular in origin rather than presolar. Their discovery in an unshocked meteorite eliminates the possibility of origins normally invoked to account for diamonds in ureilites and iron meteorites and suggests a low-pressure synthesis. The diamond crystals are approximately 100 nanometers in size, are of an unusual lath shape, and represent approximately 100 parts per million of Abee by mass.     

Diversity of atlantic coastal plain mollusks since the pliocene

About 70 percent of tropical western Atlantic mollusk species have become extinct since the Pliocene, which has led to perceptions of a corresponding decline in diversity. However, a compilation of gastropod species from Plio-Pleistocene faunas of the United States Atlantic coastal plain and from Recent western Atlantic faunas indicates that regional diversity has not changed since the Pliocene. Gastropod diversity in the Pliocene Pinecrest Beds in Florida approximates that seen today on either coast of Florida. Gastropod diversity is not demonstrably different in the Recent tropical western Atlantic than in the Recent tropical eastern Pacific. High extinction rates must have been balanced by high origination rates.     

Physalia nematocysts: utilized by mollusks for defense

Nudibranchs Glaucus and Glaucilla store and utilize for their own defense the nematocysts of the venomous siphonophore Physalia.     

Rise and fall of species occupancy in Cenozoic fossil mollusks

In the time between speciation and extinction, a species' ecological and biogeographic footprint-its occupancy-will vary in response to macroecological drivers and historical contingencies. Despite their importance for understanding macroecological processes, general patterns of long-term species occupancy remain largely unknown. We documented the occupancy histories of Cenozoic marine mollusks from New Zealand. For both genera and species, these show a distinct pattern of increase to relatively short-lived peak occupancy at mid-duration, followed by a decline toward extinction. Thus, species at greatest risk for extinction are those that have already been in decline for a substantial period of time. This pattern of protracted rise and fall stands in contrast to that of incumbency, insofar as species show no general tendency to stay near maximal occupancy once established.