Crystallization dynamics of supersaturated NaClO4 aerosols studied by high-speed photography

Single supersaturated NaClO4 aerosol droplets on a quartz substrate were observed by a high-speed video camera for their morphologic changes with decreasing relative humidity （RH）. The supersaturated droplets were found to form anhydrous NaClO4 at -10% RH. Three stages were roughly observed in this process, i.e., the main stem appearance, primary and secondary branches growth, and the deep dehydration. The main stem grew steadily and finished in 120 ms. Affected by both crystal precipitation and water evaporation, primary branches grew for 1200 ms, accompanied by a slower growth of secondary branches. The deep dehydration was more complicated, and lasted for a longer time.     

Size distribution and element composition of dust aerosol in Chinese Otindag Sandland

Dust aerosol is one important component of atmos-pheric aerosols, and plays important roles in the Earth’s climate system and the biogeochemical cycle. Large amounts of dust aerosols produced from windblown soils and deserts are emitted annually into the atmosphere and transported over long distance to downwind land and ocean areas[1]. The deserts and desertification soils in northern China are important sources of East Asia dust aerosols. It is estimated that 800 Mt of dust aerosols emit-t…     

Chemical leaching of an Indian bituminous coal and characterization of the products by vibrational spectroscopic techniques

High volatile bituminous coal was demineralized by a chemical method. The vibrations of the "aromatics" structure of graphite, crystalline or non-crystalline, were observed in the spectra at the 1600 cm-1 region. The band at 1477 cm-1 is assigned as V_R band, the band at 1392 cm-1 as V_L band and the band at 1540 cm-1 as G_R band. Graphite structure remains after chemical leaching liberates oxygenated functional groups and mineral groups. The silicate bands between 1010 and 1100 cm-1 are active in the infrared (IR) spectrum but inactive in the Raman spectrum. Absorption arising from C-H stretching in alkenes occurs in the region of 3000 to 2840 cm-1. Raman bands because of symmetric stretch of water molecules were also observed in the spectrum at 3250 cm-1 and 3450 cm-1. Scanning electron microscopy analysis revealed the presence of a graphite layer on the surface. Leaching of the sample with hydrofluoric acid decreases the mineral phase and increases the carbon content. The ash content is reduced by 84.5wt% with leaching from its initial value by mainly removing aluminum and silicate containing minerals.     

Crystallization kinetics of sea-salt aerosols studied by high-speed photography

Morphological changes with decreasing relative humidity(RH) of supersaturated sea-salt aerosol droplets on a quartz substrate were observed using a high-speed video-camera.Stable gypsum(CaSO4·2H2O) or the metastable hemihydrate(CaSO4·0.5H2O) were precipitated as the RH decreased.The dynamic process of crystal growth under steady-state humidity was studied by controlling the RH;the metastable hemihydrate was precipitated at 70.5%-77.1% RH,and the apparent crystal growth rate was between 1.42 and 2.33 μm3/s.Stable gypsum was formed at 80.7%-82.2% RH,and the apparent crystal growth rate was between 0.70 and 0.81 μm3/s.     

Smog chamber studies of ozone formation potentials for isopentane

The incremental reactivity and ozone formation potential of isopentane have been studied with chamber experiments and computer simulations. The chemical mechanism used in the computer simulations is an isopentane sub-mechanism from the Master Chemical Mechanism （MCM）. The results from the chamber experiments suggest that the MCM can well simulate i-C5H12-NOx chamber experiments. The heterogeneous reaction of NO2 and water is an important source for OH radicals in the chamber experiments. The photolysis of HONO is responsible for the initiation of isopentane in photochemical reactions. The reaction rate constant for NO2 → HONO was determined to be 3.9×10-4―5.9×10-3 min-1 by conducting 3 sets of CO-NOx-air irradiations. 5 sets of isopentane-NOx irradiations under different conditions were performed in our chamber. Compared with the experiment with a low relative humidity （RH）, an increase in RH can increase the reaction rate of NO2 with H2O, so that the peak ozone occurs earlier. When isopentane is predominant over NOx, the peak ozone concentration is largely dependent on NOx concentrations.     

Investigation of the interfacial water structure on poly[2-（dimethylamino）ethyl methacrylate] at the air/water interface by sum frequency generation vibrational spectroscopy

The effect of pH on the conformation of surface alkyl groups and the structure of interfacial water molecules on poly[2-(dime-thylamino)ethyl methacrylate](PDEM) at the air/water interface were investigated with sum frequency generation vibrational spectroscopy(SFG-VS).At pH 4.1,the hydrogen bonding SFG spectra were similar to that of the air/pure water interface.As the pH increased from 5.4 to 9.6,the SFG intensities of both highly ordered hydrogen bonding(3200 cm-1 band) and less-ordered hydrogen bonding(3400 cm-1 band) were enhanced because of the charge-induced effect of deprotonated PDEM.The free OH peak disappeared completely because it was replaced by interfacial PDEM molecules.At pH 11.5,a new spectral band appeared at about 3580 cm-1 in the ppp and sps spectra,and this could be assigned to the C2v asymmetric stretching mode of the water molecules through molecular symmetry simulation.These hydrogen bonding structures are fully consistent with the conformational change of PDEM alkyl groups,and PDEM molecules act as a Hofmeister solvent.PDEM molecules are kosmotropic when they are charged and become more chaotropic as the pH increases.     

Electrocatalytic oxidation of H<Subscript>2</Subscript>O<Subscript>2</Subscript> at a carbon paste electrode modified with a nickel (II)-5, 11, 17, 23-tetra-tert-butyl-25, 27-bis(Diethylcarbamoylmethoxy) calix[4] arene complex and its application

Electrochemical behavior of a carbon paste electrode (CPE) modified with nickel(II)-5, 11, 17, 23-tetra-tert-butyl-25, 27-bis(diethylcarbamoylmethoxy) calix[4]arene (Ni (II)-L) complex and its electrocatalytic activity towards the oxidation of hydrogen peroxide were investigated by cyclic voltammetric technique in a 5.0×10⁻² mol/L NaClO₄+1.0×10⁻³ mol/L NaOH solution. It was found that Ni(II)-L acts as an effective catalyst for the oxidation of hydrogen peroxide. The modified electrode exhibited a linear response over a hydrogen peroxide concentrations in the range of 2.0×10⁻⁵−1.0×10⁻⁴ mol/L with a detection limit as low as 1.0×10⁻⁶ mol/L. The relative standard deviation was 3.5% for 5 successive determinations of H₂O₂ at 1.0×10⁻⁵ mol/L. The modified electrode was used successfully in rainwater analysis. Foundation item: Supported by the Natural Science Foundation of Hubei Province (98J040). Biography: Li Chun ya(1972-), Ph. D. candidate, research direction: electroanalysis and electrosynthesis.     

Effect of irrigation with saline water on soil water-salt dynamics and maize yield in Arid Northwest China

An experiment was conducted in non-weighing lysimeters to study the effect of irrigation with saline water on water movement and salt accumulation and maize yield. The experiment was carried out in northwest China,both sufficient and insufficient irrigation were applied in the first year,and only sufficient treatments in the second year. Irrigation with solute concentration of 9 g·L-1 and 6 g·L-1 led to salt accumulation about 6-8 dS·m-1 in certain depths,even downwards to 160 cm received about 4 dS·m-1 for 9 g·L-1 and 2 dS·m-1 for 6 g·L-1,which was two times more than initial. Salt-affected water extracted from soil behaved as low evapotranspiration under sufficient irrigation,and more water was left in the soil. Yield of spring maize was not affected when saturated soil paste electrical conductivity did not exceeded 1.2 dS·m-1.     

Nb5N6 thin film on silicon and silicon oxide: A good material for terahertz detection

Voltage responsivity of bolometer will benefit from high temperature coefficient of resistance （TCR） of the material. The Nb5N6 thin solid films we proposed in this paper have high TCR, compared with the commonly-used materials such as Nb and Bi. The films were sputtered on Si（100）, SiO2/Si（100）, SiO2 substrates by using radio frequency （rt） magnetron sputtering. The deposition conditions have been optimized to get high TCR. The highest TCR is over 0.91% K^-1 at 300 K and up to 4.5% K^-1 -7% K^-1 at 78 K, which is good enough to be used in terahertz detection and thermometer fabrication in the range from 78 K to 300 K.     

Coordination behavior between zinc salts and L-α-methionine

The solubility properties of ZnCl\-2/ZnAc\-2/ZnSO\-4_Met_H\-2O systems at 25℃ in the whole cocentration range have been investigated by phase equilibrium method. The results indicate that ZnAc\-2 and ZnSO\-4 systems are both simple systems, which do not exist any compound; there are 2 complexes formed in ZnCl\-2 system: Zn(Met)Cl\-2 and Zn(Met)\-2Cl\-2·2H\-2O. Under the direction of phase equilibrium result, 2 solid complexes have been prepared in water and characterized by chemical analysis, IR, X_ray diffraction. Their combustion energies have also been determined by means of a RBC_type_1 rotating_bomb calorimeter, and their standard enthalpies of formation, Δ f, coor(s)H O-, have been calculated which are (-828.32±3.00) kJ·mol -1 and (-1 117.08±6.15) kJ·mol -1, respectively.     

硫酸盐体系中阳离子对水分子氢键破坏效应

利用拉曼光谱对室温下Na2SO4-H2O、MgSO4-H2O、ZnSO4-H2O、Fe2(SO4)3-H2O体系中水分子的O-H伸缩振动情况开展研究。首先,通过对频谱中2 800~4 000 cm^-1区间,特别是3 400 cm^-1附近主峰拉曼位移的移动幅度和3 200 cm^-1附近肩峰强弱的考察,研究了拉曼光谱中不同阳离子浓度和类型对水分子中O-H伸缩振动的影响规律。其次,借助高斯拟合分峰的方法考察了各阳离子对水分子不同氢键结构类型的破坏效应。最后,系统分析了配合物的生成和阳离子破坏效应的共同作用。结果表明：不同阳离子的硫酸盐溶液对水分子氢键的破坏能力规律为：Na2SO4> Fe2(SO4)3> MgSO4> ZnSO4。     

Crystal structure and negative thermal expansion of solid solution Lu<Subscript>2</Subscript>W<Subscript>3−<Emphasis Type="Italic">x</Emphasis></Subscript>Mo<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>12</Subscript>

A new series of solid solutions Lu₂W_3−x Mo _x O₁₂ (0.5≤x≤2.5) were successfully synthesized by the solid-state method. Their crystal structure and negative thermal expansion properties were studied using high-temperature X-ray powder diffraction and the Rietveld method. All samples of rare-earth tungstates and molybdates are found to crystallize in the same orthorhombic structure with space group Pnca and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure. Thermal expansion coefficients (TEC) of Lu₂W_3−x Mo _x O₁₂ are determined as −20.0×10⁻⁶ K⁻¹ for x=0.5 and −16.1×10⁻⁶ K⁻¹ for x=2.5 but -18.6×10⁻⁶ and −16.9×10⁻⁶ K⁻¹ for unsubstituted Lu₂W₃O₁₂ and Lu₂Mo₃O₁₂ in the identical temperature range of 200 to 800°C. High-temperature X-ray diffraction (XRD) data and bond length analysis suggest that the difference between W-O and Mo-O bond is responsible for the change of TECs after the element substitution in this series of solid solutions.     

In-situ Mg77Cu12Zn5Y6 bulk metallic glass matrix composite with extraordinary plasticity

Mg base BMG alloys have attracted a great deal of attention for its low density and relative low cost. To date, BMG alloys with millimeter scale have been fab- ricated by using conventional copper cast and die cast method in Mg-Ni-Ce[1], Mg-Ni-La[2], Mg-C…     

Evidence of the 1991 Pinatubo volcanic eruption in South Polar snow

Traces of tephra and increased sulfate (SO ₄ ²⁻ ) concentrations were identified in the 1992–1994 snow layers in 2 firn cores from South Pole. The deposition of the Pinatubo SO ₄ ²⁻ aerosol was delayed due to the long transport to the high south latitudes and its initial existence at high altitudes in the Antarctic atmosphere. Electron microscopic analyses show that the element composition of the tephra is identical to that of volcanic ash found near the Pinatubo volcano in Philippines. Detailed stratigraphic snow sampling resolved the Pinatubo signal from that of Cerro Hudson eruption during August 1991 in Chile. The South Pole sulfate flux from Pinatubo is calculated to be (10.9±1.1) kg·km⁻², while the Hudson sulfate flux is (3.2±1.1) kg·km⁻². This information will be useful to estimating the magnitudes of the past volcanic eruptions recorded in Antarctic ice core.     

Decarburization rate of RH refining for ultra low carbon steel

The decarburization behaviors of ultra low carbon steel in a 210-t RH vacuum degasser were investigated under practical operating conditions. According to the apparent decarburization rate constant (K_C) calculated by the carbon content in the samples taken from the hot melt in a ladle at an interval of 1–2 min, it is observed that the total decarburization reaction period in RH can be divided into the quick decarburization period and the stagnant decarburization period, which is quite different from the traditional one with three stages. In this study, the average apparent decarburization rate constant during the quick decarburization period is 0.306 min-1, and that of the stagnant period is 0.072 min-1. Increasing the initial carbon content and enhancing the exhausting capacity can increase the apparent decarburization rate constant in the quick decarburization period. The decarburization reaction comes into the stagnant decarburization period when the carbon content in molten steel is less than 14×10-6 after 10 min of decarburization.     

Fluxes of carbon dioxide and methane from swamp and impact factors in Sanjiang Plain,China

Incomplete decomposition of organic matter results in the accumulation of the carbon and other nutriments in wetlands. The wetland ecosystem gains a large amount of carbon from atmosphere CO2 by photosynthesis, and it loses much of which back into the atmosphere as CO2 and CH4 emission through the decomposition and respiration. Climate change, such as global warming and reduction of precipitation could drive the wetlands from carbon sink to source[1,2]. Wetland plays an important role in car…     

Properties of garnet-type Li6La3ZrTaO12 solid electrolyte films fabricated by aerosol deposition method

The garnet-type Li_6La_3ZrTaO_(12)(LLZT) solid electrolyte films were fabricated by aerosol deposition(AD)method.Ball-milled LLZT powder with a cubic garnet structure and a particle size of 1-2 urn was used as raw material and deposited directly on a SUS316L or a glass substrate via impact consolidation.As-deposited LLZT film has a cubic garnet structure but contains Li_2CO_3 and La_2Zr_2O_7 phases.SEM observation revealed that the film consists of LLZT particles fractured into submicron size.The impurity phase formation during AD process was caused by the local heating by the collision between LLZT particles and deposition surface and reaction with CO_2.The Li~+ ion conductivity of LLZT film was estimated to be 0.24 × 10~(-5)S cm~(-1) at room temperature.Electronic conductivity of LLZT film was confirmed to be around 10~(-12) S cm~(-1),indicating the dominant Li~+ ion conduction of LLZT film.     

Natural gas geochemistry of low evolutionary stage of medium- and small-sized basins in Yunnan Province, southwestern China

The biogenic gas and premature-low mature associated gases in some medium and small-sized basins of Yannan Province, such as Luliang, Yanglin, Baoshan and Jinggu basins, have beed researched. The results show that the biogenic-gas consists mainly of methane which is more than 99% in gasous hydrocarbons and of lighter carbon isotopic composition with δ13C1 values from -60.0‰ to - 75.4‰. The methane carbon isotopic compositions in the Baoshan Basin is relatively heavy (δ13C1 - 60‰- - 65‰), but those in Luliang and Yanglin basins are lighter (δ13C1, less than -70‰), which implies that the gas field of the Baoshan Basin formed earlier than the others. In the Jinggu Basin, where crude oil is premature-lower mature, the natural gas of associated oil relatively wet and the relative content of methane about 58%-95% in gasous hydrocarbons. Constituently the gas composition is much similar to associated one, but the methane carbon isotopic compositions from - 53.8‰ to - 57.8‰ are obviously richer in 12C than those of general oil fields and similarly characterize the biothermo-catalytic transitional zone gas. Their ethane carbon isotopic compositions from - 34.6‰ to -29.0‰ show that they may be derived from type Ⅰ or Ⅱ source rock. But for the associated gas from lower evolutionary stage, the heavier ethane carbon isotopic composition as well as the reversed order among the carbon isotopic composition of ethane, propylane and butane also implies that some gases from the type Ⅲ organic matter are mixed. The δ13CCo2 of the samples essentially less than - 10‰ may be generated from organic matter.     

Origin of middle Miocene leucogranites and rhyolites on the Tibetan Plateau: Constraints on the timing of crustal thickening and uplift of its northern boundary

Leucogranites play a significant role in understanding crustal thickening, melting within continental collisional belts, and plateau uplift. Field investigations show that Miocene igneous rocks from the Hoh Xil Lake area mainly consist of two-mica leucogranites and rhyolites. We studied the Bukadaban two-mica leucogranites and the Kekao Lake, Malanshan and Hudongliang rhyolites by zircon U-Pb, muscovite and sanidine 40Ar/39Ar geochronology, and whole-rock geochemical and Sr-Nd isotopic analysis. Results yielded crystallization and cooling ages for the Bukadaban leucogranites of 9.7±0.2 and 6.88±0.19 Ma, respectively. Extrusive ages of the Kekao Lake and Malanshan rhyolites are 14.5±0.8 and 9.37±0.30 Ma, respectively. All rocks are enriched in SiO2 (70.99%-73.59%), Al2O3 (14.39%-15.25%) and K2O (3.78%-5.50%) but depleted in Fe2O3 (0.58%-1.56%), MgO (0.11%- 0.44%) and CaO (0.59%-1.19%). The rocks are strongly peraluminous (A/CNK=1.11?1.21) S-type granites characterized by negative Eu anomalies (δ Eu=0.18-0.39). In also considering their Sr-Nd isotopic compositions (87Sr/86Sri=0.7124 to 0.7143; δ Nd (9 Ma) =-5.5 to -7.1), we propose that these igneous rocks were generated through dehydration melting of muscovite in the thickened middle or lower crust of northern Tibet. Melting was probably triggered by localized E-W stretching decompression in the horse tails of Kunlun sinistral strike-slip faults. Reactivation of the Kunlun strike-slip faults, accompanied by emplacement of leucogranite and eruption of rhyolite in the Hoh Xil Lake area, indicates that large-scale crustal shortening and thickening in northern Tibet mainly occurred before 15 Ma. In addition, these findings suggest that the northern Tibetan Plateau attained its present elevation (~5000 m) at least 15 Ma ago.     

Binding and endocytosis of monoterbium transferrin by K562 cells

Human serum apotransferrin is the major iron-tran- sport protein in blood. The protein binds iron as Fe3+ at two similar, but not identical, high-affinity binding sites. Although iron bound to human serum apotransferrin is less then 0.1% (~3 mg) of the total body iron, dynamically it is the most important iron pool with the highest rate of turnover. The turnover of transferrin iron is in the order of 30 mg per day and, normally, about 80% of this iron are transported to the bone marrow for hem…