ALBERT

Beschreibung: In response to solar wind disturbances, radiation belt (a few hundreds of keV to several MeV) electron fluxes can be depleted significantly over the entire equatorial pitch-angle range. The frequently mentioned cyclotron resonant scattering is applicable only for electrons mirroring off the equator. Here we propose a new physical mechanism, nonlinear Landau resonance with oblique electromagnetic ion cyclotron (EMIC) waves, to effectively scatter the near-equatorially mirroring electrons. Our test-particle simulations show that the nonlinear Landau trapping can occur over a wide energy range and yield the net decrease in equatorial pitch-angle Δ α e q ≈10 ∘ within several seconds. Our parametric studies further reveal that this nonlinear Landau trapping process is favored by a low plasma density, an intense wave field, a high wave frequency close to ion gyro-frequencies and a large wave normal angle.

Beschreibung: Three new alkaloids, 3- O -acetylveralkamine ( 1 ), veralkamine 3 - ( β - D -glucopyranoside) ( 2 ), and 6,7-epoxyverdine ( 3 ), together with five known alkaloids, veramitaline, veralkamine ( 4 ), angeloylzygadenine, veratroylzygadenine, and veramiline 3 - ( β - D -glucopyranoside), were isolated from the whole plants of Veratrum taliense. Their structures were elucidated on the basis of spectroscopic analysis, and the NMR data of veralkamine ( 4 ) are given for the first time. In addition, the cytotoxic activities of all isolated compounds, except for veramitaline, were tested.

Beschreibung: A phytochemical investigation on bulbs of Lycoris radiata resulted in the isolation of three new Amaryllidaceae alkaloids, named 5,6-dehydrodihydrolycorine ( 1 ), 6 β -acetoxycrinamine ( 2 ), and (+)-8- O -acetylhomolycorine α - N -oxide ( 3 ), together with eleven known alkaloids, 4 – 14 . The structures of the new alkaloids were established by means of spectroscopic methods, and the known compounds were identified by comparison of their data with those in the literature. Compound 2 showed cytotoxicity against HL-60, A-549, and MCF-7 cells, with IC 50 values of 8.1, 24.3, and 15.0 μ M , respectively.

Beschreibung: We present high-precision measurements of iron (Fe) and magnesium (Mg) isotopic compositions of olivine, orthopyroxene and chromite separates from harzburgites, dunites and chromitites in the mantle section of the Luobusa ophiolite, southern Tibet, to investigate the origins of podiform chromitite. Two harzburgites in the Zedong ophiolite, southern Tibet, are also reported for comparison. The olivine and orthopyroxene in the Luobusa and Zedong harzburgites have similar Fe and Mg isotopic compositions, with δ 56 Fe values ranging from 0‰ to +0.083‰ in olivine, from -0.034‰ to +0.081‰ in orthopyroxene and δ 26 Mg values ranging from -0.25‰ to -0.20‰ in olivine, from -0.29‰ to -0.26‰ in orthopyroxene, respectively. The olivines of two dunites from the Luobusa display small Fe and Mg isotopic variations, with δ 56 Fe values of +0.014‰ and +0.116‰ and δ 26 Mg values of -0.21‰ and -0.29‰. All chromites in the Luobusa chromitites have lighter Fe isotopic compositions than the coexisting olivines, with δ 56 Fe values ranging from -0.247‰ to +0.043‰ in chromite and from -0.146‰ to +0.215‰ in olivine (Δ 56 Fe Chr-Ol =-0.294 to -0.101‰). The chromite δ 26 Mg values span a significant range from -0.41‰ to +0.14‰. Large disequilibrium Fe and Mg isotope fractionation between chromite and olivine, as well as positive correlation of chromite δ 56 Fe values with their MgO contents, could be attributed to Fe-Mg exchange between chromite and olivine. In the disseminated chromitites, the higher modal abundances of olivine than chromite would result in a more extensive Fe-Mg exchange, whereas chromite in the massive chromitite where olivine is rare could not be affected by this process. This article is protected by copyright. All rights reserved.

Beschreibung: To evaluate the role of subducted oceanic crust in the genesis of potassium-rich magmas, we report high-precision Mg isotopic data for a set of Cenozoic volcanic rocks from Northeast China. These rocks overall are lighter in Mg isotopic composition than the normal mantle, and display considerable Mg isotopic variations, with δ 26 Mg ranging from -0.61 to -0.23. The covariation of δ 26 Mg with TiO 2 in these rocks suggests their light Mg isotopic compositions were derived from recycled oceanic crust in the form of carbonated eclogite in the source region. The strong correlations between δ 26 Mg and (Gd/Yb) N ratio as well as Sr-Pb isotopes further indicate a multicomponent and multistage origin of these rocks. Magnesium isotopes may thus be used as a novel tracer of recycled oceanic crust in the source region of mantle-derived magmas.

Beschreibung: Minerals, Vol. 8, Pages 230: Timing of Secondary Hydrothermal Alteration of the Luobusa Chromitites Constrained by Ar/Ar Dating of Chrome Chlorites Minerals doi: 10.3390/min8060230 Authors: Wei Guo Huaiyu He Youjuan Li Xiujuan Bai Fei Su Yan Liu Rixiang Zhu Chrome chlorites are usually found as secondary phases formed by hydrothermal alteration of chromite deposits and associated mafic/ultramafic rocks. Here, we report the 40Ar/39Ar age of chrome chlorites separated from the Luobusa massive chromitites which have undergone secondary alteration by CO2-rich hydrothermal fluids. The dating results reveal that the intermediate heating steps (from 4 to 10) of sample L7 generate an age plateau of 29.88 ± 0.42 Ma (MSWD = 0.12, plateau 39Ar = 74.6%), and the plateau data points define a concordant inverse isochron age of 30.15 ± 1.05 Ma (MSWD = 0.08, initial 40Ar/36Ar = 295.8 ± 9.7). The Ar release pattern shows no evidence of later degassing or inherited radiogenic component indicated by an atmospheric intercept, thus representing the age of the hydrothermal activity. Based on the agreement of this hydrothermal age with the ~30 Ma adakitic plutons exposed in nearby regions (the Zedong area, tens of kilometers west Luobusa) and the extensive late Oligocene plutonism distributed along the southeastern Gangdese magmatic belt, it is suggested that the hydrothermal fluids are likely related to the ~30 Ma magmatism. The hydrothermal fluid circulation could be launched either by remote plutons (such as the Sangri granodiorite, the nearest ~30 Ma pluton west Luobusa) or by a similar coeval pluton in the local Luobusa area (inferred, not found or reported so far). Our results provide important clues for when the listwanites in Luobusa were formed.

Beschreibung: Plant δ 13 C–temperature (δ-T) relation has been established in many systems and is often used as paleotemperature transfer function. However, it is still unclear about the exact contributions of temperature variation to plant 13 C discrimination because of covariation between temperature and precipitation (aridity), which reduces confidence in reconstruction of paleoclimate. In this study, we measured carbon isotope composition (δ 13 C) of 173 samples of C3 perennial herbs from 22 sites across a temperature gradient along the 400 mm isohyet in the farming-pastoral zone of North China. The results showed that precipitation obviously affected the correlations of temperatures and foliar δ 13 C. After removing the influence of precipitation by analysis of covariance (ANCOVA), a more strongly positive relationship was obtained between site-mean foliar δ 13 C and annual mean temperature (AMT), with a regression coefficient of 0.1636‰/°C ( p  =   .0024). For widespread species, Artemisia lavandulaefolia and Artemisia capillaries , the slopes (or coefficients) of foliar δ 13 C and AMT were significantly steeper (larger) than those of foliar δ 13 C and AMT where the precipitation influence was not excluded, whereas the δ-T coefficients of Polygonum persicaria and Leymus chinensis showed little change across the transect after deducting the precipitation effect. Moreover, the positive relationship between temperature and δ 13 C over the transect could be explained by soil moisture availability related to temperature. Our results may afford new opportunities for investigating the nature of past climate variability. Plant δ 13 C–temperature (δ-T) relation has been established in many systems and is often used as paleotemperature transfer function. However, it is still unclear about the exact contributions of temperature variation to plant 13 C discrimination because of covariation between temperature and precipitation. After removing the influence of precipitation by analysis of covariance (ANCOVA), a more strongly positive relationship was obtained between site-mean foliar δ 13 C and annual mean temperature (AMT), with a coefficient of 0.1636‰/°C.

Beschreibung: The concept of ecosystem health is a way to assess the holistic operations and development potential of urban ecosystems. Accelerated by the practical need for integrated ecosystem management, assessment of urban ecosystem health has been greatly developed and extensively applied in urban planning and management. Development is aimed at comprehensively evaluating the performance of urban ecosystems, identifying the limiting factors, and providing suggestions for urban regulation. The time has come for reviewing and establishing an instructional framework for urban ecosystem health assessment to shed light on certain essential issues of urban ecosystem health. Based on literature reviews and series of practice, a holistic framework of urban ecosystem health assessment is proposed. The framework covers the essential elements of urban ecosystem health and integrates three dimensions: theoretical foundation, assessment method, and practical application. Concrete assessment methods are also established, focusing on both external performance and internal metabolic processes. The practice of urban ecosystem health assessment in China is illustrated to briefly demonstrate the application of the established framework and methods. Some prospects are discussed for urban ecosystem health assessment and its application in urban planning and management.

Beschreibung: Minerals, Vol. 8, Pages 62: Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton Minerals doi: 10.3390/min8020062 Authors: Yang Bai Ben-Xun Su Yan Xiao Davide Lenaz Patrick Asamoah Sakyi Zi Liang Chen Chen Sai-Hong Yang We conducted petrological and mineral chemistry investigations of Cr-spinel in ultramafic rocks of the Yanmenguan mafic–ultramafic complex in the North China Craton. The Cr-spinel grains occur as inclusions in enstatite, tschermakite, phlogopite, and olivine, or as interstitial grains among the aforementioned silicate minerals, and show concentric or asymmetrical textures. Back-scattered electron and elemental images and compositional profiles of the spinel grains indicate the presence of Cr- and Fe-rich cores and Al- and Mg-rich rims. The host silicate minerals display a decrease in Al and Mg contents accompanied by an increase in Cr and Fe away from the spinel. These textures and compositional variations suggest that subsolidus elemental exchange more likely gave rise to the compositional zonation, resulting in the transfer of Al and Mg from the silicate minerals to the spinel. The Mn, Ni, and Ti contents in spinel and the major elements of olivine-hosted spinel are relatively stable during subsolidus elemental diffusion and thus are more reliable tracers of primary high-temperature processes. The temperature estimates reveal that the subsolidus diffusion might have occurred at 600–720 °C, which could be linked to the regional metamorphic event.