Relationship between structure and gas permeation properties of polyimides prepared from oxydiphthalic dianhydride

Gas permeability coefficients of a series of aromatic polyimides, which were prepared from oxydiphthalic dianhydride (ODPA) with various aromatic diamines, with respect to H-2, CO2, O-2, N-2, and CH4 were measured under 10 atm and in the temperature range from 30 to 150 degrees C. A significant change in gas permeability and permselectivity resulting from systematic variation of the chemical structure of the polyimides was found. Among the polyimides which were prepared from phenylenediamine and its derivatives as well as bridged diamines without side groups on the benzene rings of the diamine residues, the increase of the gas permeability is accompanied by a decrease of the permselectivity. However, both the gas permeability and the permselectivity of the polyimides which were prepared from bridged diamines with methyl or methoxy groups on the benzene rings of the diamine residues simultaneously increase.

Structure/permeability and permselectivity relationship of polyetherimides from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride .2.

Gas permeability coefficients of a series of aromatic polyetherimides, which were prepared from 1,4-bis(3,4-dicarboxyphenoxy) benzene dianhydride (HQDPA) with various aromatic diamines, to H-2, O-2 and N-2 have been measured under 7 atm and at the temperature range 30-100 degrees C. A significant change in the permeability and permselectivity resulting from the systematic variation in chemical structure of the polyetherimides was found. Among the polyetherimides, that were prepared from phenylenediamine and methyl substituted phenylenediamines, the increase of permeability is accompanied by a decrease of permselectivity. The polyetherimides that were prepared from 3,5-diaminobenzoic esters have lower permselectivity than the others. However, the polyetherimide from 3,5-diaminobenzoic acid possesses much higher permselectivity than the others due to cross-linking. Copyright (C) 1996 Elsevier Science Ltd

C-118 from fullerenols: Formation, structure and intermolecular nC(2) transfer reactions in mass spectrometry

In fast atom bombardment, two fullerenols C-60(OH)(x) (x=13-15) and C-60(OH)(x) (x-24-26) gave rise to a group of ions centered at C-118 with intervals of 24 mass units in the high mass region. In contrast, no such ions appeared in the mass spectra of pure C-60, C-70 and other fullerene derivatives such as C-60(C6H5)(10), under the same conditions. It is proposed that the pinacol rearrangement of C-60(OH)(2), resulting from partial rupture of the polyhydroxy molecules, produces C-59 with two carbon atoms bearing an unpaired electron, and that dimerization of this reactive intermediate is responsible for the formation of the predominant product C-118. An intermolecular nC(2) transfer process is used to explain the symmetrical abundance distribution of these product ions in the spectra of fullerenols.

COMPARATIVE-STUDIES ON PERIODATOCUPRATE(II, III) AND TELLURATOCUPRATE(II, III)

The crystal structures, electronic spectra, and Cu2p XPS of Cu(III) complexes Na4H[Cu(H2TeO6)(2)]. 17H(2)O and Na4K[Cu(HlO(6))(2)]. 12H(2)O have been described. The characterizations of a Cu(III) atom in a complex are as follows: (i) In a square-planar coordination, the average bond length of Cu-O is 0.183 nm, shorter than the 0.190-0.200 nm found for a Cu(II) complex. (2) The ''blue shift'' occurs for d-d transitions in the electronic spectrum of the Cu(III) complex compared to those of its related Cu(II) complex, resulting from the higher valence state. (3) Cu(III) compounds with CuO4 square-planar coordination are expected to be diamagnetic whereas Cu(II) compounds to be paramagnetic. (4) Comprehensive investigations on Cu2p XPS show that the binding energy of Cu2p(3/2) of a pure Cu(III) compound is about 2.0 eV higher than that of its corresponding Cu(II) compound: the shake-up satellites do not appear in the Cu2p XPS for a pure diamagnetic Cu(III) compound, the same as found for a diamagnetic Ni(II) compound: the FWHM of the signal of Cu2p XPS may become broader for Cu(III) compound because its core hole's lifetime shortens due to the higher valence state of copper. (C) 1995 Academic Press, Inc.

5,7-Dihydroxy-5,6,7,8-tetrahydro-1H-azocin-2-one from a marine-derived Streptomyces sp.

In the course of a screening program, we have isolated the new natural product, 5,7-dihydroxy-5,6,7,8-tetrahydroazocin-2(IH)-one (1), from the staurosporine producing marine-derived Streptomyces sp. strain QD518. Here we report the isolation and structure elucidation of 1 and the artifacts 3 and 4 resulting from I by acid catalyzed intra- and inter-molecular reactions.

Roles of equatorial waves and western boundary reflection in the seasonal circulation of the equatorial Indian Ocean

An ocean general circulation model (OGCM) is used to study the roles of equatorial waves and western boundary reflection in the seasonal circulation of the equatorial Indian Ocean. The western boundary reflection is defined as the total Kelvin waves leaving the western boundary, which include the reflection of the equatorial Rossby waves as well as the effects of alongshore winds, off-equatorial Rossby waves, and nonlinear processes near the western boundary. The evaluation of the reflection is based on a wave decomposition of the OGCM results and experiments with linear models. It is found that the alongshore winds along the east coast of Africa and the Rossby waves in the off-equatorial areas contribute significantly to the annual harmonics of the equatorial Kelvin waves at the western boundary. The semiannual harmonics of the Kelvin waves, on the other hand, originate primarily from a linear reflection of the equatorial Rossby waves. The dynamics of a dominant annual oscillation of sea level coexisting with the dominant semiannual oscillations of surface zonal currents in the central equatorial Indian Ocean are investigated. These sea level and zonal current patterns are found to be closely related to the linear reflections of the semiannual harmonics at the meridional boundaries. Because of the reflections, the second baroclinic mode resonates with the semiannual wind forcing; that is, the semiannual zonal currents carried by the reflected waves enhance the wind-forced currents at the central basin. Because of the different behavior of the zonal current and sea level during the reflections, the semiannual sea levels of the directly forced and reflected waves cancel each other significantly at the central basin. In the meantime, the annual harmonic of the sea level remains large, producing a dominant annual oscillation of sea level in the central equatorial Indian Ocean. The linear reflection causes the semiannual harmonics of the incoming and reflected sea levels to enhance each other at the meridional boundaries. In addition, the weak annual harmonics of sea level in the western basin, resulting from a combined effect of the western boundary reflection and the equatorial zonal wind forcing, facilitate the dominance by the semiannual harmonics near the western boundary despite the strong local wind forcing at the annual period. The Rossby waves are found to have a much larger contribution to the observed equatorial semiannual oscillations of surface zonal currents than the Kelvin waves. The westward progressive reversal of seasonal surface zonal currents along the equator in the observations is primarily due to the Rossby wave propagation.

地下水位上升造成的黄土远程滑坡形成机理与数值模拟研究

Based on field survey, laboratory testing and numerical modeling, engineering characteristics of undisturbed loess and the mechanism of long-runout loess landslides caused by underground water level rise, as well as the formation conditions and spatial distribution of landslides, are systematically studied and analyzed. Loess landslides at south Plateau of Jingyang County are mainly classified as flowslide, slide and fall. Flowslide is the main type characteristic of high velocity, long runout and multi-stages. The steep relief composed of loose structured loess-old aged soil serials and the rise of groundwater table are the predominant conditions for landslides in the study area. To study loess mechanic poperties and loess landslides mechanisims, isotropically and anisotropically consolidated undrained compression(ICU and ACU) tests and constant-deviator-drained compression (CQD) tests were carried out on undisturbed samples. The results of undrained compression tests performed at the in-situ stress level show that the soils are of consistently strain-softening in the stress-strain relations and cause high excess pore pressure. The steady-state line and the potential region of instability are obtained from ICU and ACU test results. A necessary condition for liquefaction is that the soil state initially lies in or is brought into the potential instability region. In addition, a strong strain-softening model is also formed. CQD tests demonstrate that the mobilized friction angle is far less than the steady-state angle and that the soil experiences undrained contractive failure suddenly at very small strains when its stress path during drained loading tries to cross the potential instability region，thus validates the proposed instability region. Based on the location of the region of potential instability and the stress state of slope soil, a method of static liquefaction analysis is proposed for loess landslides caused by rise in groundwater table. Compared with other liquefaction analysis methods, this method overcomes the limitations inherent in conventional slope stability method and undrained brittleness index method. Triaxial tests composed of constant water content (CW) and wetting tests at constant deviator stress are performed on undisturbed unsaturated samples. The stress-strain relation of CW tests takes on strain-hardening behavior; The results of wetting tests at constant deviator stress designed to study the mechanics of failure of unsaturated loess caused by an increase in the degree of saturation (wetting) shows that a contractive failure occurs in the undisturbed samples. On the basis of the above triaxial test results, the initiation of static liquefaction is presented for long-runout loess landslides caused by rise in groundwater table, that is, the loess slope soil gradually transfer from unsaturated to saturated state under the infiltration of irrigation. A contractive failure occurs in the local region at very small strain by increasing the pore-water pressure at constant deviator stresses under drained conditons. It is the contractive failrue resulting from rise of pore pressure that leads to high excess pore pressure in the neighbour soil which reduces shear resistance of soil. The neighbour soils also fail due to the rapid increase in pore-water pressure. Thus a connected failure surface is developed quickly and a flowslide occurs. Based on the saturated-unsaturated seepage theory, transient seepage is computed using the finite element method on loess slope under groundwater table rise. Pore-water pressure distribution for every time step after irrigation are obtained. The phreatic surface in the slope increases with the groundwater table. Pore-water pressure distribution within 8m above the phreatic surface changes very quickly，but the water content and pore water pressure in the region ranging from 8m above the phreatic surface up to ground surface is almost not affected and the matric suction usually is kept at 100～120 kPa. Based on the results of laboratory tests and seepage flow analysis, the development process of loess landslide is modeled considering groundwater table rise. The shearing plastic zone first occurs at the slope toe where the soil is soaked for long term during rise in groundwater table. As irrigation continues, the shearing plastic zone gradually extends to the interior soils, with the results that the tensile plastic zone occurs at the slope crown. As time goes on, both the shearing plastic zone and tensile plastic zone continue to extend. Then a connected plastic zone is formed and fowslide occurs. In comparision to laboratory test results, the results of numerical simulation quite well verify the presented mechanism of static liquefaction of long-runout loess landslides caused by rise in groundwater table.

地震波模拟：非规则网格离散的数值解法、吸收边界及其实际应用

This dissertation presents a series of irregular-grid based numerical technique for modeling seismic wave propagation in heterogeneous media. The study involves the generation of the irregular numerical mesh corresponding to the irregular grid scheme, the discretized version of motion equations under the unstructured mesh, and irregular-grid absorbing boundary conditions. The resulting numerical technique has been used in generating the synthetic data sets on the realistic complex geologic models that can examine the migration schemes. The motion equation discretization and modeling are based on Grid Method. The key idea is to use the integral equilibrium principle to replace the operator at each grid in Finite Difference scheme and variational formulation in Finite Element Method. The irregular grids of complex geologic model is generated by the Paving Method, which allow varying grid spacing according to meshing constraints. The grids have great quality at domain boundaries and contain equal quantities of nodes at interfaces, which avoids the interpolation of parameters and variables. The irregular grid absorbing boundary conditions is developed by extending the Perfectly Matched Layer method to the rotated local coordinates. The splitted PML equations of the first-order system is derived by using integral equilibrium principle. The proposed scheme can build PML boundary of arbitrary geometry in the computational domain, avoiding the special treatment at corners in a standard PML method and saving considerable memory and computation cost. The numerical implementation demonstrates the desired qualities of irregular grid based modeling technique. In particular, (1) smaller memory requirements and computational time are needed by changing the grid spacing according to local velocity; (2) Arbitrary surfaces and interface topographies are described accurately, thus removing the artificial reflection resulting from the stair approximation of the curved or dipping interfaces; (3) computational domain is significantly reduced by flexibly building the curved artificial boundaries using the irregular-grid absorbing boundary conditions. The proposed irregular grid approach is apply to reverse time migration as the extrapolation algorithm. It can discretize the smoothed velocity model by irregular grid of variable scale, which contributes to reduce the computation cost. The topography. It can also handle data set of arbitrary topography and no field correction is needed.

碎屑锆石年龄和Nd-Hf同位素组成对扬子基底演化的制约

The South China craton was formed by the collision of the Yangtze and Cathaysia blocks during the Neoproterozoic Jiangnan orogeny (also termed as the Jingnin or Sibao orogeny in Chinese literature). Basement rocks within the Yangtze block consist mainly of Proterozoic sediments of the Lengjiaxi and Banxi Groups. U-Pb ages of detrital zircons obtained by the LA-ICP-MS dating technique imply that the deposition of the Lengjiaxi Group continued until the Neoproterozoic. The youngest detrital zircons suggest a maximum deposition age of ~830 Ma for the Lengjiaxi Group, consistent with the initiation time of the deposition of the overlying Banxi Group, likely indicating continuous deposition of these two groups and a short temporal hiatus (~10 Ma) between the Neoproterozoic sedimentary rocks distributed in the South China craton. Detrital zircons from both the Lengjiaxi and Banxi Groups have a wide range of εHf(t) values from -12 to 14.2 and a continuous Nd and Hf model age spectrum from ~820 Ma to 2200 Ma. Some grains have model ages ranging up to ca. 2.9-3.5 Ga, indicating that both juvenile mantle material and ancient crust provided sedimentary detritus. This is also consistent with the Nd isotopic signature of sedimentary rocks recorded in the Lengjiaxi Group, suggesting a back-arc tectonic setting. The Banxi Group has slightly enriched Nd isotopic signatures relative to the Lengjiaxi Group, implying a higher percentage of old continental material in the sedimentary source. Combined with previously published data, new results can help us to reconstruct the Neoproterozoic tectonic evolution of the South China craton. The age spectrum of detrital zircons and Nd-Hf isotopic composition suggests a two-stage collision: Between 1000 Ma to 870 Ma, a continental magmatic arc was build up along the eastern margin of the Yangtze block. Convergence led to continent-based back-arc extension, subsidence and formation of a back-arc basin. Detritus originating from arc-related magmatic and old basement rocks was transported into this back-arc basin resulting in formation of the Lengjiaxi Group and its equivalents. At around 870 Ma, a second (oceanic) arc was formed by extension of an inter-arc basin, subduction subsequently led to the first collision and the emplacement of the blueschist mélange. Accretion of the magmatic arc lasted until the closure of an oceanic basin between the Yangtze and Cathaysia blocks at about 830 Ma. Shortly after the collision, subsequent uplift, further extension of the former back-arc basin and post-collisional granitoid magmatism caused a tilting of the Lengjiaxi sediments. Between 830 Ma and 820 Ma, subsequent closure of the oceanic back-arc basin and formation of the Jiangnan orogen took place, leaving a regional unconformity above the Lengjiaxi Group. Above this unconformity the Banxi Group was immediately deposited during the post-tectonic stage.

石笋微层序列的断代和信号研究

Based on chronological and climatologic analysis of many young stalagmites in Shihua Cave at Beijing and Water Cave in Benxi, Liaoning Province, this dissertation aims to discuss some key points on quantitative reconstruction of high resolution climate change from micro bands time series in young stalagmites. On chronological aspect of micro bands time series in young stalagmite, the uppermost micro bands were testified formed in the sampling year or the year before sampling from long term and in situ experiment in Shihua Cave at Beijing. Have been observed detailed under microscope, the micro bands were counted and compared with high resolution TIMS-230Th or ICP-MS U series dating, the results show that the micro bands are annual bands. The microscopic characteristics of annual bands in North China is as follows after studying lots of young stalagmites: the interface appears to be carved, and there is a light line adjacent to it, which moves back and forth slightly when adjusting the microscope slide. The cross dating of annual bands from different stalagmites is experimented in this thesis. On climatologically aspect of micro bands times series in young stalagmites, one significant problem is that the deposition trend resulting from the variation of the stalagmite shape. Various deposition trends have been discussed and corrected before climatologically analysis of micro bands series. And the whole year in situ observation and analysis of dripping water in Shihua Cave provide us new evidence for climate information reserved in stalagmites micro bands. The stalagmites in the same cave may contain different climate information due to the micro hydrological condition. The annual bands of young stalagmites collected from North China can be used to reconstruct past climate changes quantitatively. The warm season temperature (May, June, July, August) is reconstructed using two annual bands time series from Shihua Cave, Beijing, which corresponds to the warm/cool periods very well in Chinese history documents. The precipitation record of past 500 years is reconstructed using two stalagmite annual bands series from Shihua Cave, which is consistent to the dryness/wetness records derived from historical documents too.

岱海岩芯沉积的粒度组成与湖区全新世降水变化历史

Sediment cores DH99a and DH99b recovered in the central part of Daihai Lake in north-central China were analysed at 2- to 4-crn intervals for grain-size distribution. Grain-size distributions of the lake sediments are inferred to be a proxy for past changes in East Asian monsoon precipitation, such that greater silt-size percentage and higher median grain size reflect increased monsoonal precipitation rates. The grain-size record of Daihai Lake sediments spanning the last ca 11,000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages: the Early, Middle and Late Holocene. During the Early Holocene before ca 7900 cal yr BP, the median grain size (Md) and the silt-fraction content were relatively low and constant, suggesting relatively low precipitation over the lake region. The Middle Holocene between ca 7900 and 3100 cal yr BP was marked by intensified and highly variable monsoonal precipitation, as indicated by high and variable Md values and silt contents of the lake sediments. During this period, average precipitation rate gradually increased from ca 7900 to 6900 cal yr BP, displayed intense oscillations between ca 6900 and 4400 cal yr BP, and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr BP Although generally high during the Middle Holocene, both the Md and the silt content assumed distinctly low values at the short intervals of ca 6500-6400, 6000-5900, 5700-5600, 4400-4200 cal yr BP, implying that monsoonal precipitation might have been significantly reduced during these intervals. During the Late Holocene since ca 3100 cal yr BP, grain-size values suggest that precipitation decreased. However, during the Late Holocene, relatively higher Md values and silt contents occurring between ca 1700 to 1000 cal yr BP may denote an intensification of hydrological cycles in the lake area. Changes in the East Asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the Earth's orbital parameters, but also may have been closely related to variations in the temperature and size of the Western Pacific Warm Pool, in the intensity of the El Nino-Southern Oscillation, and in the path and strength of the North Equatorial Current in the western Pacific.

Structure of glasses and melts

Wilding, M. C., Benmore, C. J. (2006). Structure and Glasses and Melts. reviews in Mineralogy and Geochemistry, 63 (1), 275-311 RAE2008

An experimental study of the peeling of dough from solid surfaces

Binding, David; Couch, M.A., (2003) 'An experimental study of the peeling of dough from solid surfaces', Journal of Food Engineering 58(2) pp.299-309 RAE2008

Les tribulations parisiennes de l’officier écrivain : l’oeuvre autobiographique de Yasmina Khadra et son accueil en France

This article describes Yasmina Khadra’s autobiographical work composed of two books: "L’écrivain" and "L’imposture des mots" and its reception in France. The main purpose of this study was to establish the literary genre of these books, which implies determining whether Khandra’s work represents an autobiography or an autofiction with reference to P. Lejeune’s and V. Colonna’s theoretical studies. The dividing line between two genres in Khandra’s works refl ects his inner split between being either a solder or a writer. The presentation will also help to understand the controversy resulting from Khandra’s participation in Algerian civil war. Moreover the analysis is related to modern Algerian history.

A influência dos principais factores de risco cardiovascular nos AVCs e consequente perturbação da linguagem adquirida

Trabalho de Projeto apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Terapêutica da Fala, área de especialização em Linguagem no Adulto