一株来源于水库的浮游蓝丝藻SK3株的生长及产毒特性

浮游蓝丝藻是水华蓝藻的常见种属,但对其生长和产毒特性认识不多本文首次对我国水体中的浮游蓝丝藻进行了研究.从广东省一重要供水水库中分离到一株丝状蓝藻,经形态特征鉴定为阿氏浮游蓝丝藻,并在不同的光照和温度下对该藻株进行了培养.结果表明,适合于该藻生长的光强和温度分别为20μmol/(m~2·s)和30℃;该藻株具有mcyE基因,能产生微囊藻毒素MCRR,产量为0.06μg/mg(DW).     

羊屎沟铁岭组大理岩鞘褶皱的变形特征分析

在羊屎沟铁岭组大理岩上发现鞘褶皱垂直于最大主应变轴X轴和垂直于中间应变主轴Y轴的切面,并对其变形特征及形成机制进行了考察和分析,认为,鞘褶皱所反映的韧性剪切作用方向大致为SSE方向150°～160°,且晚于铁岭组大理岩的形成时间。     

Effects of core formation

Two sets of earth models have been generated which simulate the process of core formation in the earth. The results allow the evaluation of the distribution of energy release by core formation and thus an estimate of the early temperature profile following core formation. The process itself is likely to have taken 20 Ma or less, although a longer induction period during which some metal phase exists as a melt is probable. Much of the energy (half or more) ends up in a hot core with the mantle relatively cold. These results suggest the occurrence of mantle wide convection, leading to homogenization and the possible stripping of some elements from the mantle.     

The chemistry of star formation

Understanding the chemistry of molecular clouds is now realized to be fundamental to our understanding of the whole star-formation process. A two-day meeting was held within NAM2002 to bring together chemists and astronomers to discuss this complex subject. Derek Ward-Thompson, Helen Fraser and Jonathan Rawlings report.  

     

The formation of ice sails

Debris-covered glaciers are prone to the formation of a number of supraglacial geomorphological features, and generally speaking, their upper surfaces are far from level surfaces. Some of these features are due to radiation screening or enhancing properties of the debris cover, but theoretical explanations of the consequent surface forms are in their infancy. In this paper we consider a theoretical model for the formation of “ice sails”, which are regularly spaced bare ice features which are found on debris-covered glaciers in the Karakoram.     

Dynamical features of fracture formation

We analyze the results of a series of experiments on studying the dynamical pattern of fracture growth. The failure of the rocks under long loading with the use of nonexplosive demolition agent (NDA) is studied. Due to the long (about 2 days) loading, the experiment closely reproduces the natural conditions. It is shown that a single center of failure is absent. The coordinates of the sources of acoustic emission are calculated. The failure zone where the fracture is formed is identified. The combined analysis of the migration of strong acoustic events (AC_max) with the determination of their coordinates together with the deformation observations provide an insight into the kinetics of evolution of the source zone.     

Core formation in terrestrial planets

Calculations of the radial distribution of the energy released in core formation indicate that the cores of all the terrestrial planets may be expected to receive a disproportionate share of the gravitational energy released. Since the model of the process used in these calculations favors transfer of energy to the mantle, it is likely that other reasonable models of the process will result in even more energy being deposited in the cores of the early planets. The calculations also show that it is necessary for a certain amount of core phase to separate and accumulate, before the energy released by gravitational settling is sufficient to supply the latent heat of fusion of the core phase. The amount of melting required to reach this point varies according to the total mass of the planet, and mass fraction of core, but is not particularly great (<5% for the Earth to ～ 37% for the Moon). In the case of the Moon, this amount of segregation, although large, amounts to a surface layer about 260 km thick, similar to the proposed depth of early wholesale melting. Core separation in terrestrial planets appears to be a self-sustaining process even for fairly small bodies, provided that a small amount of a dense potential core phase is present. Although it seems likely to occur rapidly (within 10⁶–10⁷ years) even for small (Moon-size) bodies, detailed kinetic models will be necessary to specify the time scale.     

Point-defect formation parameters in olivine

The formation internal energy and volume of the point-defect species in olivine are derived for a number of approximate charge-neutrality conditions. The formation parameters of an effectively charged point defect are a function of the approximate condition of charge neutrality. Since the approximate charge-neutrality condition depends upon the partial pressure of oxygen and the activity of enstatite in olivine, changes in the magnitude of these thermodynamic-state variables result in different values of the formation parameters if the charge-neutrality regime is altered. The fractional change in the formation internal energies of the energetically unfavorable defects, such as Si vacancies, is small between the charge-neutrality regions while the fractional change for the favorable defects, such as Mg vacancies, is large.     

Phenomenology of seismic macrofracture formation

A phenomenological scheme is proposed for the formation of a seismic macrofracture in the crust through multiscale avalanche-like crack coalescence of the inverse cascade type. Relations connecting fractal dimensions of crack sets and the concentration criterion of coalescence of cracks that are required for the onset of multiscale fracture are obtained. It is shown that the enlargement of cracks from micro-to macroscales includes a relatively small number of hierarchical coalescence stages.     

On surface seismic waves formation

Summary The interpretation of surface seismic waves records is rather complicated as they include a superposition of oscillations of the fundamental mode and higher modes. Besides recorded oscillations depend on spectral characteristics of motions in earthquakes sources. The consideration of these problems is based on results of surface waves two-dimensional modelling [1]³. Some physical ideas about their formation deals with the change of the nature of the oscillation propagating with dispersion. This report represents a condensate of several independent works. , , . , . , . () . .Scientific communication presented to the IASPEI Assembly, Madrid, 1969.     

川东南茅口组缝洞型储层地球物理响应特征及形成机制研究

为深入认识川东南茅口组缝洞型储层的地球物理响应特征并分析其形成机制,以钻井、测井资料为基础,采用离散合成记录与地质剖面对比、正演模拟的方法开展茅口组储层地震一地质特征分析,建立了四类缝洞型储层地球物理响应特征并分析了其地质形成机制,指出茅口组上部的波状反射和顶部空白反射反映缝洞体在茅口组上部或顶部发育,为较可靠的含气缝...     

On the formation of couplet-style stratifications

Couplet-style stratifications refer to the sedimentary sequences that consist of alternating coarse-grain-dominated bed and fine-grain-dominated bed, with or without a sandwiched middle-sized bed. The formation mechanism is complicated due to the interplays of varying driving force （s）, sediment supply ＆ transport and topographic configurations. This paper presents a comprehensive overview of such characteristic bedforms, which emerge during the transport and deposition of non-uniform sediments. The leading formative models include water-stage variation, gravel-overpassing process, superimposition of bedload sheets and avalanching process （inverse grading）. Each process might produce similar or distinct sedimentological features with respect to grading, matrix content, grain attitude, bounding faces between beds and internal longitudinal/transverse geometry. The couplet-style stratified strata might play an active role in landscape evolution.     

The formation of porphyry copper deposits

Copper is a moderately incompatible chalcophile element.Its behavior is strongly controlled by sulfides.The speciation of sulfur is controlled by oxygen fugacity.Therefore,porphyry Cu deposits are usually oxidized(with oxygen fugacities AFMQ +2)(Mungall 2002;Sun et al.2015).The problem is that while most of the magmas at convergent margins are highly oxidized,porphyry Cu deposits are very rare,suggesting that high oxygen fugacity alone is not sufficient.Partial melting of mantle peridotite even at very high oxygen fugacities forms arc magmas with initial Cu contents too low to form porphyry Cu deposits directly(Lee et al.2012;Wilkinson 2013).Here we show that partial melting of subducted young oceanic slabs at high oxygen fugacity(AFMQ +2) may form magmas with initial Cu contents up to 500 ppm,favorable for porphyry mineralization.Pre-enrichment of Cu through sulfide saturation and accumulation is not necessarily beneficial to porphyry Cu mineralization.In contrast,remelting of porphyritic hydrothermal sulfide associated with iron oxides may have major contributions to porphyry deposits.Thick overriding continental crust reduces the "leakage" of hydrothermal fluids,thereby promoting porphyry mineralization.Nevertheless,it is also more difficult for ore forming fluids to penetrate the thick continental crust to reach the depths of 2—4 km where porphyry deposits form.     

Star formation timescales in M82

Richard de Grijs reviews the picture of starbirth presented in this nearby, prototype starburst galaxy, a well-studied example of processes that must be widespread in the early universe.
The last tidal encounter between M82 and M81, some 500 Myr ago, had a major impact on what was probably an otherwise normal, quiescent disk galaxy. It caused a concentrated burst of star formation in the form of massive star clusters that decreased rapidly, within a few 100 Myr. The current starburst in the centre of the galaxy is likely to arise from large-scale propagating star formation. Alternatively, it may be related to late infall of tidally disrupted debris from M82 itself. Star formation here overall may, in fact, come from a combination of these two mechanisms, in the sense that the star formation in the active core is actively propagating, whilst the overall evolution of the starburst depends on tidal debris raining back onto the disk of the galaxy, giving rise to the present-day starburst.     

Sand wave formation by stationary waves

In this paper we develop a new hypothesis which relates the formation of sand waves in open flow to the effect of stationary (lee) waves on flow with smooth nonhomogeneous downstream depth or behind an obstacle. The lee wave moves upstream with the phase velocity equal to the absolute value of the flow velocity, hence the wave crest does not move. Results of our experiments show that sand waves on the flow bed appear only below the lee waves and characteristics of sand waves are determined by the wave properties. We investigated the nonlinear stationary waves for subcritical and supercritical Froude numbers. These results allow us to predict sand waves characteristics for a particular flow.     

Stable isotopic characterisation of francolite formation

Stable isotopic data are presented for 112 samples of francolite from 18 separate phosphate deposits. Values ofδ¹³C andδ³⁴S in most offshore deposits suggest formation within oxic or suboxic environments either by carbonate replacement or direct precipitation of francolite from water of normal marine compositions. The exceptions are concretionary francolite from Namibia, which has an isotopic composition in keeping with its formation within organic-rich sediments, and that from offshore Morocco, which has an isotopic signature of the anoxic/suboxic interface. Onshore deposits from Jordan, Mexico, South Africa and, possibly, the Permian Phosphoria Formation in the western U.S.A., are substantially depleted in¹⁸O: they appear to be too altered for deductions to be made about their environments of formation. In other onshore deposits which are unaltered, or minimally altered, the isotopic composition suggests that some formed within sulphate-reducing sediments (Sedhura, Morocco) whilst francolite from the Georgina Basin of Australia formed at the oxic/anoxic boundary, where oxidation of biogenic H₂S decreases theδ³⁴S of pore water. In general, pelletal samples show non-oxic isotopic signatures, whilst non-pelletal samples show oxic isotopic signatures, but samples from Namibia, Peru (Ica Plateau) and the Californian and Moroccan margins are exceptions to this rule. Morphology may therefore be a misleading indicator of francolite genesis as no definitive relation exists between phosphorite type and isotopic signature.     

La formation des Nuages Altocumulus Translucidus

Résumé Dans cette étude l'explication de la formation des nuages Ac tra part de la supposition que l'air dans ce type de nuages est plus froid que l'air environnant, ce qui provoque certains courants convectifs dans la région du nuage. Ces courants ressemblent à ceux qui sont supposés par la théorie thermoconvective actuelle. D'après notre avis se trouvent des courants descendants audessous des petits nuages qui composent l'Ac tra, et les petits nuages qui forment l'Ac tra sont des corps séparés dont la température est moindre que la température de l'air environnant: c'est pour cela qu'ils tombent. Au contraire, d'après la théorie thermoconvective actuelle, l'air audessous de petits nuages monte et dans la distribution de la température des discontinuités n'existent pas.

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Summary In this paper the explanation of the formation of clouds Ac tra is based on the assumption that the air in the cloud is colder than the surrounding air, causing convective currents in the region of the cloud. These currents are not unlike those assumed by the existing thermoconvective theory. According to the author's view there are descending currents under the cloudlets of which the Ac tra is made, and these cloudlets are separate bodies at a lower temperature than that of the surrounding air, so that the cloudlets fall. On the contrary, according to the existing thermoconvective theory, the air under the cloudlets rises and there are no discontinuities in the distribution of the temperature.

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Rapport présenté le 26 Avril 1962 à la Xème Assemblée Générale de laSocietà Italiana di Geofisica e Meteorologia (26–28 Avril 1962)     

Field observations of nearshore bar formation

The formation of an inner nearshore bar was observed during a high‐energy event at the sandy beach of Vejers, Denmark. The bar accreted in situ during surf zone conditions and the growth of the bar was associated with the development of a trough landward of the bar. Measurements of hydrodynamics and sediment fluxes were obtained from electromagnetic current meters and optical backscatter sensors. These process measurements showed that a divergence in sediment transport occurred at the location of the developing trough, and observed gradients in cross‐shore net sediment flux were consistent with the morphological development. The main cause for the flux gradients were cross‐shore gradients in offshore‐directed mean current (undertow) speed which depended upon local relative wave height and local bed slope. Copyright © 2007 John Wiley & Sons, Ltd.