Periodic orbits based on geometric structure of center manifold around Lagrange points

This study proposes an analytical method that determines the center manifold and identifies the reduced system on the center manifold. The proposed method expresses the center manifold through general equations containing only state variables, and not functions with respect to time. This is the so-called geometric structure of the center manifold. The location of periodic or quasi-periodic orbits is identified after the geometric structure of the center manifold is determined. The reduced system on the center manifold is described using ordinary differential equations, so that periodic or quasi-periodic orbits can be computed by numerically integrating the reduced system. The results indicate that the analytical method proposed in this study has higher precision compared with the Lindstedt-Poincaré method of the same order.     

Partizansky base-metal skarn deposit, Dal’negorsk ore district, Russia: Stages of ore formation, mineral assemblages, and typomorphism of fahlore

As indicated by mineralogical, geochemical, and structural-textural data, the base-metal skarn ore at the Partizansky deposit was formed during two stages (base-metal skarn and silver-sulfosalt), which were separated by intrusion of basaltic dikes. The bulk of the base-metal ore was deposited at the first stage, which comprises four sequential mineral assemblages: skarn-silicate, quartz-arsenopyrite, productive galena-sphalerite, and pyrrhotite-pyrite-chalcopyrite. The mineralization of the second stage was mainly confined to the upper margins of orebodies and pertains to the sulfosalt-galena-chalcopyrite assemblage, which was super-imposed on minerals of the first stage. The vertical mineralogical-geochemical zoning of the deposit is telescopic (related to the formation of the late silver-sulfosalt mineralization) and facies (typical of the early skarn and base-metal assemblages). The zoning of the skarn-silicate assemblage is expressed in the metasomatic replacement of skarn by quartz and calcite in the uppermost zone of skarn bodies and is emphasized by variation of the mineral composition throughout the skarn column, for instance, by the distinct updip enrichment of hedenbergite in manganese. The vertical zoning of the productive assemblage is emphasized by variations in the ratio of sphalerite to galena (the Pb/Zn ratio in the ore increases upward from 0.1 to 1), changes in mineral assemblages, and compositional variation of major ore-forming and minor minerals. In particular, galena from the deep levels is extremely enriched in Bi and Ag, while that from the upper levels is almost completely devoid of isomorphic admixtures. Fahlore displays updip enrichment in Sb, Ag, and Fe and corresponding depletion in Cu and Zn. The vertical chemical variations in fahlore are caused by the specific geological setting of ore deposition, the composition of the ore-forming solutions, and the physicochemical conditions of their transportation and ore deposition.     

INFLUENCE OF A CONDUCTING SHIELD IN THE ONE-LOOP VERSION OF THE TRANSIENT PULSE INDUCTION METHOD*

The transient response of a conductive shell-shell model in the one-loop version was obtained analytically. The results indicate that four zones, namely early, late early, intermediate, and late zone can be identified in the total transient characteristic of the model. In case the measurements are carried out in the late early zone, a conductive target appears as a resistive one. It is suggested that the optimum time of measurement should be so selected as to fall in the intermediate zone.     

61～50kaBP亚洲季风百年尺度气候振荡的黔西南石笋记录

12个U/Th年龄测试结果显示,黔西南普安县雾露洞长度分别为667mm和830mm的两支石笋覆盖了61～50kaBP时段。据两支石笋999个δ18O数据建立了平均分辨率达15年的亚洲夏季风强度变化序列。雾露洞δ18O记录揭示了4个振幅达1.7‰的千年尺度季风增强事件,对应于格陵兰冰心DO17—DO14事件。在总体特征上,该记录峰谷振荡特征及振幅与贵州董歌洞、南京葫芦洞记录一致,进一步证实亚洲季风区大气降水同位素组成变化在大范围空间内具有一致性。在百年尺度上,亚洲季风区石笋δ18O清晰记录了MIS3早期6个DO亚旋回事件,而且在更短时间尺度上具有类似高纬气温振荡特征。这种低纬季风系统与北高纬气候变化的耦合关系表明,大气环流快速重组和传输可能是连接高低纬DO旋回及亚旋回气候变化的主要纽带。     

Heavy-mineral variability in bottom sediments of the lower Chesapeake Bay,Virginia

Heavy minerals in bottom-sediment samples of the lower Chesapeake Bay show distribution patterns and interrelationships that denote characteristic mineral suites associated with defined geographic provinces. The Baymouth province has a garnet—hornblende—pyroxene suite, which is largely attributed to the influx of littoral and shelf sediments; the Eastern Shore province has a similar suite, derived largely from coastal erosion of the Eastern Shore peninsula. The Northern and Combined River provinces have a zircon—tourmaline—staurolite assemblage, which reflects derivation from an Appalachian Piedmont—Atlantic Coastal Plain sourceland. The Western Shore province is associated with a zircon—epidote—staurolite assemblage, apparently derived jointly from tributary influx and coastal erosion of the western shore. Factor analysis identified two major factors that account for 63% of the total variation in the relative amounts of the seven most common heavy minerals. The dominant factor (44%) is based on a zircon—hornblende—staurolite—pyroxene relationship, which indicates that mineral stability, as influenced by sediment maturity, is a major contributing factor. The second factor (19%) based on a tourmaline—epidote—staurolite—garnet relationship indicates that provenance is another major cause of heavy-mineral variability within the lower bay.     

Untersuchung der Sorptionseigenschaften des Kationenaustauschers KB-2M mit Makronetzstruktur zur Abtrennung von Zinkionen aus Ab- und Spülwässern

Study of Sorptional Properties of the Cation Exchanger KB-2M with Macroreticular Structure for Recovery of Zinc Ions from Sewage and Rinsing Water Although a number of ion-exchange methods have been employed for the recovery of some transition metals from industrial effluents, knowledge about ion-exchange resins with macroreticular structure is poor. The present paper describes the mechanism of sorption on such exchangers and their application for recovery of zinc from sewage rinsing water. Ion exchanger of macroreticular structure are polymers with long-chained cross-linking agents. We have synthesized carboxylic ion-exchange resins by hydrolysis of copolymerisates of methyl acrylate with different cross-linking agents: divinylbenzene, divinyl sulfide, divinyl ester of ethylene glycol and divinyl ester of di- or triethylene glycol. The sorption process on modifications of the carboxylic resins KB-2 of various structure was studied with different methods: potentiometric titration, infrared spectroscopy, electron microscopy, X-ray structural analysis. The initial zinc concentration in rinsing water was 0.05 mol/L at pH from 3 to 6. For the sorption, 0.2…1.0 g of resin were equilibrated with 100 mL of zinc solution. After equilibrium (12 h), the resin was separated from solution. The zinc ions were determined by atomic absorption spectrometry after stripping with 100 mL of 10% sulfuric acid. The distribution ratio D was calculated (D: mmole of Zn sorbed per gram of resin divided by mmole of Zn per millilitre of solution). By means of infrared spectroscopy, the mechanism of sorption of zinc ions from rinsing water was determined. There may be a possibility of the formation of complexes in the cation-exchange resin phase. It was found out in this paper that the cation-exchanger KB-2M of macroreticular structure is the most effective for the sorption of the Zn²⁺-ions from sewage and rinsing water.     

Activated release of alkalis during the vesiculation of molten basalts under high vacuum: implications for lunar volcanism

Knudsen cell-quadrupole mass spectrometry was used to study the high-temperature vaporization of Hawaiian basalts, plagioclase, tektites, and samples from the Allende meteorite. Procedures are described by which mass loss rates and vapor pressures of Na and K were measured quantitatively.Gas-rich glassy basalts were observed to vesiculate under vacuum over the 900–1000°C region and simultaneously evaporate alkalis in nonequilibrium fashion at rates (units of μg/g/hr) of approximately 200–300 Na and 75–250 K. Degassed residues of the same basalts demonstrated equilibrium evaporation rates (over the same temperature range) of 60–120 Na and 30–60 K. The gas-deficient plagioclase and tektite sample showed only equilibrium vaporization with rates of 60 Na, 10 K (plagioclase) and 10 Na, 5K (tektites) at 900–1000°C. The Allende meteorite vaporized at rates of 2400 Na and 200 K at 900–1000°C, possibly by the reaction of Na₂O and K₂O with C or S₂, or by the thermal decomposition of nepheline or sodalite.The nonequilibrium vaporization of alkalis from the gas-rich basalts is attributed to vigorous agitation of the melt during its vesiculation by a gas phase composed principally of SO₂, CO₂, H₂O, CO, and H₂S. The major gases released from the Allende meteorite at 900–1000°C are, in order of decreasing abundance, CO, S₂, CO₂, H₂O, SO₂, and H₂S.It is proposed that nonequilibrium vaporization of alkalis during the vesiculation of lunar lavas was responsible for the production of alkali-rich vapors which subsequently deposited plagioclase crystals in the vugs of lunar rocks. The vesiculative, nonequilibrium vaporization of Na and K during a lunar volcanic eruption should be expected to occur at a high rate upon initial extrusion of the lava into vacuum but then decrease by a factor of approximately three when degassing is nearing completion. Vaporization losses remain inadequate to explain the uniformly low alkali concentrations in lunar basalts.     

Climate and human health: synthesizing environmental complexity and uncertainty

Broad relationships between weather and human health have long been recognized, and there is currently a large body of research examining the impacts of climate change on human health. Much of the literature in this area examines climate–health relationships at global or regional levels, incorporating mostly generalized responses of pathogens and vectors to broad changes in climate. Far less research has been done to understand the direct and indirect climate-mediated processes involved at finer scales. Thus, some studies simplify the role of climate and may over- or under-estimate the potential response, while others have begun to highlight the subtle and complex role for climate that is contingent on other relevant processes occurring in natural and social environments. These fundamental processes need to be understood to determine the effects of past, current and future climate variation and change on human health. We summarize the principal climate variables and climate-dependent processes that are believed to impact human health across a representative set of diseases, along with key uncertainties in these relationships.