Equilibrium on the hydrolysis of boron trifluoride in large amount of water

In order to clarify the equilibrium components in the hydrolysis solution of boron trifluoride(BF_3-H_2O),the BF_3-H_2O was prepared by mixing BF_3-CH_3OH with large amount of water,in which the stoichiometric concentration of BF_3 is less than 0.1 mol/L.Two ionic equilibrium models were proposed to simulate the hydrolysis equilibrium of BF_3 and tested by special acid-base titration technique.The most accurate ion equilibrium constants were determined.The model,which was assumed to have no HF,was proved to be more representative for the real system and used to simulate the hydrolysis equilibrium of BF_3.The simulation suggested that H~+,BF_4~-,BF_3OH~- and H_3BO_3 were the main species in the dilute hydrolysis solution,while BF_2(OH)_2~- and F~- were insignificant species whose concentrations were both in the order of 10~(-4) mol/L magnitude,and BF(OH)_3~- could be omitted because its concentration almost equaled zero.Meanwhile,the equilibrium constant of the overall ionic reaction at 25℃ was obtained as 161.6.     

Determination of boron trifluoride in boron trifluoride complex by fluoride ion selective electrode

A method was proposed to determine boron trifluoride in boron trifluoride complex using fluoride ion selective electrode(ISE). Hydroxide was chosen to mask aluminum for the determination of 0.01—0.1 mol/L of fluoride. The simulation indicated that the permissible aluminum masked at a certain p H value was limited and hardly related to F-concentration and boric acid. It is better to control p H value below 11.5 and the aluminum concentration within 0.025 mol/L to minimize the interference of hydroxide to the fluoride ISE. The decomposition conditions of boron trifluoride by aluminum chloride were investigated. It is found that the F-detection ratio will approach 1.0 if the Al/F molar ratio is 0.3—0.7 and aluminum concentration is no more than 0.02 mol/L when heated at 80 ℃ for 10 min. In one word, hydroxide is quite fit to mask aluminum for samples which contain high content of fluoride and aluminum and the BF3 content can be successfully determined by this method.     

Preparation and electrochemical application of praseodymium modified TiO<Subscript>2</Subscript>-NTs/SnO<Subscript>2</Subscript>-Sb anode by cyclic voltammetry method

A Pr-doped TiO₂-NTs/SnO₂-Sb electrode was prepared by a simple method, cyclic voltammetry(CV). The methyl orange(MO)aqueous solution was selected as a simulated wastewater. The ordered microstructural TiO₂-NTs substrate was synthesized by an electrochemical method to obtain large specific surface area and high space utilization. The phase structure, electrode surface morphology and electrochemical properties of electrodes were characterized by XRD, SEM and electrochemical technology, respectively. The results showed that praseodymium oxide was successfully doped into the SnO₂-Sb film by CV method. Due to the doped Pr, the oxygen evolution potential increased from 2.25 V to 2.40 V. The degradation of MO was investigated by UV-vis. The C _t /C ₀ (φ) was studied as a function to obtain the optimal parameters, such as the amount of doped Pr, current density and initial dye concentration. In addition, the degradation process followed pseudo-first-order reaction kinetics and the rate constant was 0.099 3 min^-1. The result indicated that the introduction of Pr reduced the formation of oxygen vacancies or enhanced the formation of adsorbed hydroxyl radical groups on the surface, thus leading to better activity and stability.     

Effects of astaxanthin on oxidative stress induced by Cu<Superscript>2+</Superscript> in prostate cells

Astaxanthin (AST), a carotenoid molecule extensively found in marine organisms and increasingly used as a dietary supplement, has been reported to have beneficial effects against oxidative stress. In the current paper, the effects of AST on viability of prostate cells were investigated by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay; cell apoptosis and intracellular reactive oxygen species (ROS) levels were determined by flow cytometry; the mitochondrial membrane potential (MMP) was measured by fluorospectrophotometer; and activities of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were evaluated by a detection kit. The results show that copper ion (Cu²⁺) induced apoptosis, along with the accumulation of intracellular ROS and MDA, in both prostate cell lines (RWPE-1 and PC-3). AST treatments could decrease the MDA levels, increase MMP, and keep ROS stable in RWPE-1 cell line. An addition of AST decreased the SOD, GSH-Px, and CAT activities in PC-3 cell line treated with Cu²⁺, but had a contrary reaction in RWPE-1 cell lines. In conclusion, AST could contribute to protecting RWPE-1 cells against Cu²⁺-induced injuries but could cause damage to the antioxidant enzyme system in PC-3 cells.     

Study on the effect of doxorubicin on expressions of genes encoding myocardial sarcoplasmic reticulum Ca<Superscript>2+</Superscript> transport proteins and the effect of taurine on myocardial protection in rabbits

To investigate the effect of doxorubicin(DOX) on gene expression of the myocardial sarcoplasmic reticulum (SR) Ca²⁺ transport proteins and the mechanism of taurine(Tau) protecting cardiac muscle cells, 9 rabbits were injected with DOX, 8 rabbits with DOX and Tau, and 9 rabbits with normal saline. Cardiac function, concentration of calcium in cardiomycocytes (Myo [Ca²⁺] _i ), activity of SR Ca²⁺-ATPase (SERCA2a), level of SERCA2a mRNA and Ca²⁺ released channels (RYR2) mRNA were detected. The left ventricle tissues were observed by electron microscopy. The results showed that cardiac index, left ventricular systolic pressure, activity of SR Ca²⁺-ATPase and level of SERCA2a mRNA decreased, while Myo[Ca²⁺] _i increased in DOX-treated rabbits. DOX could not affect the level of RYR2 mRNA. Tau intervention could alleviate the increase of left ventricular diastolic pressure, Myo[Ca²⁺] _i and the decrease of SERCA2a mRNA induced by doxorubicin. The results suggested that downregulation of SERCA2a gene expression was an important mechanism of DOX-induced cardiomyopathy and that Tau could partially improve the heart function by reducing calcium overload and alleviating downregulation of SERCA2a mRNA.     

Conversion of CO<Subscript>2</Subscript> to useful substances with composite iron,nickel, and copper catalysts

Composite materials of Fe/Al₂O₃, which consist of small particles of iron supported by thermally stable alumina even at 500–700 °C, have been widely used in the water-gas shift reaction for natural gas reforming. Therefore, Fe/Al₂O₃ is one of the promising candidates for re-transformation of exhausted CO₂ into fuels such as alcohols and hydrocarbons. The development of a CO₂ reforming system using the composite materials of Fe/Al₂O₃ through CO₂ reduction to CO, dissociation of water into hydrogen, and methanol synthesis has been investigated. It was found that dry and steam (i.e. wet) reforming of CO₂ produced almost the same amount of CO. At a temperature above 500 °C, maximal and saturated yields of CO and H₂ from CO₂ and water were obtained. However, this CO₂ reforming system requires higher-pressure conditions from several tens to hundreds standard atmospheric pressure in order to achieve high yield and selectivity for methanol production. In this study we developed the modified CO₂ reforming system by the utilization of Ni and/or Cu instead of Fe in order to obtain other types of useful products such as CO, CH₄, and carbon, more efficiently and selectively under atmospheric pressure. When Ni or Cu was used, conversion of CO₂ was reduced to 76%, while 9% of methane was detected in the case of Ni. On the other hand, though the CO₂ conversion reduced half of the Fe, the selectivity of CO from CO₂ increased to 95% in the case of Cu.     

Synthesis of Novel Ionic Liquid （[C4CNmim]^＋PF6^-） and Application to Preparation of Polyketone

N-valeronitrile-N’-methylimidazolium hexafluorophosphate ([C 4 CNmim]+ PF 6),as a novel ionic liquid with polar nitrile functional group,was prepared.The structure of the ionic liquid was characterized by using IR and 1 H NMR.As a medium,the ionic liquid plays an important role in copolymerization of carbon monoxide (CO) with styrene (St).Some synthetic conditions were determined,including the usage of ionic liquid,palladium composite catalyst and methanol,CO pressure,reaction time and reaction temperature.The influence of these factors on catalytic activity was analyzed.The results show that the catalytic activity has reached 1 724.1 gStCO/(gPd·h) and the catalyst could be reused 5 times under the optimal condition:composite catalyst 0.015 mmol,ionic liquid 3 mL,methanol 0.75 mL,CO pressure 2MPa,reaction time 2 h and reaction temperature 70℃.This CO/St copolymerization within [C 4 CNmim]+ PF 6 system could facilitate ionic liquids with efficient and economical applications to polymeric materials.     

Study of transport behavior for Fe-doping La<Subscript>0.67</Subscript>Ca<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> perovskite manganese

Systematic studies of the transport properties of La_0.67Ca_0.33Mn_1?xFe _x O₃ (x=0–0.3) systems showed that with increasing Fe-doping contentx the resistance increases and the insulator-metal transition temperature moves to lower temperature. For small doping content, the transport property satisfies metal transport behavior below the transition temperature, and above the transition temperature it satisfies the small polaron model. This behavior can be explained by Fe³⁺ doping, which easily forms Fe³⁺?O^2??Mn⁴⁺ channel, suppressing the double exchange Mn³⁺?O^2??Mn⁴⁺ channel and enhancing the spin scattering of Mn ions induced by antiferromagnetic clusters of Fe ions.     

Preparation and characterization of high purity enriched <Superscript>10</Superscript>B boric acid via anti-solvent recrystallization

Self-made enriched ¹⁰B boric acid as raw material was purified by recrystallization. The effects of final crystallization temperature, crystallization time, stirring speed, crystallization frequency and other factors on the purity were investigated. The appropriate operating condition was that the final crystallization temperature and time were 5°C and 10 h respectively under a low-speed stirring for crystallizing twice, which would make the purity and yield of boric acid reach 99.94% and 95.36%, respectively. Taking this as foundation, recrystallization process was optimized with acetone as anti-solvent, whose amount was the most important index. The boric acid solution was added into acetone and recrystallized under the same condition, and the purity and yield of boric acid would reach 99.98% and 99.61%, respectively. The product detected by XRD was confirmed as boric acid crystal. Main ion concentration in the product was detected by ICP, which basically met the national standard of high purity. Crystal morphology of boric acid was observed by SEM.     

Mutagenic effects of chromium trioxide on root tip cells of <Emphasis Type="Italic">Vicia faba</Emphasis>

In this study on the mutagenic effects of different concentrations of chromium trioxide (CrO₃) on Vicia faba root tip, micronucleus assay and chromosome aberration assay were used to determine the mitotic indexes, micronucleus rate and chromosome aberration rate of Vicia faba root tip cells. The results showed that the effects of CrO₃ concentration on the mitotic indexes were complicated. CrO₃ increases the micronucleus rate of Vicia faba root tip cells. It was found that within certain range of CrO₃ concentration the micronucleus rate increased systematically with increased concentration of CrO₃, but that the micronucleus rate decreased at higher level of CrO₃ and that CrO₃ also caused various types of chromosome aberration at a rate which increased systematically with increased concentration of CrO₃. We concluded that CrO₃ has significant mutagenic effect on Vicia faba root tip cells. Project supported by Wenzhou Technology Bureau (No. S2002A015) and Wenzhou “551” Talented People Fund of China     

Uptake,transport and distribution of molybdenum in two oilseed rape (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) cultivars under different nitrate/ammonium ratios

Objectives

To investigate the effects of different nitrate sources on the uptake, transport, and distribution of molybdenum (Mo) between two oilseed rape (Brassica napus L.) cultivars, L0917 and ZS11.

Methods

A hydroponic culture experiment was conducted with four nitrate/ammonium (NO₃ ^?:NH₄ ⁺) ratios (14:1, 9:6, 7.5:7.5, and 1:14) at a constant nitrogen concentration of 15 mmol/L. We examined Mo concentrations in roots, shoots, xylem and phloem sap, and subcellular fractions of leaves to contrast Mo uptake, transport, and subcellular distribution between ZS11 and L0917.

Results

Both the cultivars showed maximum biomass and Mo accumulation at the 7.5:7.5 ratio of NO₃ ^?:NH₄ ⁺ while those were decreased by the 14:1 and 1:14 treatments. However, the percentages of root Mo (14.8% and 15.0% for L0917 and ZS11, respectively) were low under the 7.5:7.5 treatment, suggesting that the equal NO₃ ^?:NH₄ ⁺ ratio promoted Mo transportation from root to shoot. The xylem sap Mo concentration and phloem sap Mo accumulation of L0917 were lower than those of ZS11 under the 1:14 treatment, which suggests that higher NO₃ ^?:NH₄ ⁺ ratio was more beneficial for L0917. On the contrary, a lower NO₃ ^?:NH₄ ⁺ ratio was more beneficial for ZS11 to transport and remobilize Mo. Furthermore, the Mo concentrations of both the cultivars’ leaf organelles were increased but the Mo accumulations of the cell wall and soluble fraction were reduced significantly under the 14:1 treatment, meaning that more Mo was accumulated in organelles under the highest NO₃ ^?:NH₄ ⁺ ratio.

Conclusions

This investigation demonstrated that the capacities of Mo absorption, transportation and subcellular distribution play an important role in genotype-dependent differences in Mo accumulation under low or high NO₃ ^?:NH₄ ⁺ ratio conditions.

     

Theoretical study of NO adsorbed on the surface of TiO<Subscript>2</Subscript> (110) cluster model

The chemisorption properties of N¹⁸O adsorption on TiO₂(110) surface were investigated by experimental and theoretical methods. The results of temperature programmed desorption (TPD) indicated that the temperatures of the three desorption peaks of the main N₂ molecules were at (low) temperature of 230 K, 450 K and (high) temperature of 980 K. This meant that N¹⁸O decomposed and recombined during the process of N₂ desorption after N¹⁸O was exposed. Analysis of the stable combination and orbital theory calculation of the surface reaction of NO adsorption on the TiO₂(110) cluster model showed that there was clear preference for the Ti-NO orientation.     

Fabrication of LaAlO<Subscript>3</Subscript> film by sol-gel process with corresponding inorganic

Well-cubic perovskite lanthanum aluminate (LaAlO₃) film on (110) silicon substrate was fabricated by sol-gel method with corresponding inorganic salts. Lanthanum acetate and aluminum acetate glacial acetic acid solutions were prepared via ligand exchange starting from lanthanum nitrate hexahydrate and aluminum nitrate hexahydrate after being refluxed. (CH₃CO)₂O removed nitrates and the crystallized H₂O completely, acetylacetone (AcAc) was partially bidentated with metallic ion of the metallic acetates and formed La(OAc)_3−x (AcAc) _x which were hydrolyzed into La(AcAc)_3−x(OH) _x by adding 10 ml 0.4% methyl cellulose (MCL) solution. The La(AcAc)_3−x (OH) _x , polymerizing and combining with MCL, formed the LaAlO₃ sol precursor with heteropolymeric structure and formed film easily. The epitaxial LaAlO₃ film on Si(110) substrate was crystallized after being annealed in thermal annealing furnace for 650–750 °C/30 min. The morphologies and microstructures were characterized. The refractive index of the LAO film was 1.942 to 2.007; the dielectric constant and the dissipation factors were estimated to be 23–26 and 2.1×10⁻⁴−2.4×10⁻⁴ respectively. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China     

Physical and chemical characteristics of PM<Subscript>2.5</Subscript> and its toxicity to human bronchial cells BEAS-2B in the winter and summer

With the increasing occurrence of haze during the summer, the physicochemical characteristics and toxicity differences in PM_2.5 in different seasons are of great concern. Hangzhou is located in an area that has a subtropical monsoon climate where the humidity is very high during both the summer and winter. However, there are limited studies on the seasonal differences in PM_2.5 in these weather conditions. In this test, PM_2.5 samples were collected in the winter and summer, the morphology and chemical composition of PM_2.5 were analyzed, the toxicity of PM_2.5 to human bronchial cells BEAS-2B was compared, and the correlation between PM_2.5 toxicity and the chemical composition was discussed. The results showed that during both the winter and summer, the main compounds in the PM_2.5 samples were water-soluble ions, particularly SO₄^2?, NO₃^?, and NH₄⁺, followed by organic components, while heavy metals were present at lower levels. The higher the mass concentration of PM_2.5, the greater its impact on cell viability and ROS levels. However, when the mass concentration of PM_2.5 was similar, the water extraction from the summer samples showed a greater impact on BEAS-2B than that from the winter samples. The cytotoxicity of PM_2.5 was closely associated with heavy metals and organic pollutants but less related to water-soluble ions.     

Density functional theory study of the adsorption of elemental mercury on a 1T-MoS<Subscript>2</Subscript> monolayer

Elemental mercury has become a global concern because of its significant impact on human health and the ecosystem. A lot of effort has been put towards the removal of elemental mercury from the 2H-MoS₂ (prismatic structure of MoS₂). However, the mechanism of 1T-MoS₂ (polytype structure of MoS₂) in Hg⁰ capture remains unexplored. In this study, density functional theory (DFT) was adopted to investigate the adsorption mechanism of Hg on a 1T-MoS₂ monolayer. The different possible adsorption positions on the 1T-MoS₂ were examined. For different adsorption configurations, the changes in electronic property were also studied to understand the adsorption process. The results elucidated that chemisorption dominates the adsorption between Hg⁰ atoms and the 1T-MoS₂. It was found that the T_Mo (on top of the Mo atom) position is the strongest adsorption configuration among all the possible adsorption positions. The adsorption of Hg⁰ atoms on the 1T-MoS₂ monolayer is influenced by adjacent S and Mo atoms. The adsorbate Hg0 atom is found being oxidized on the T_Mo position of the 1T-MoS₂ with an adsorption energy of ?1.091 eV. From the partial density of states (PDOS) analysis of the atoms, the strong interaction between Hg⁰ and the 1T-MoS₂ surface is caused by the significant overlap among the d orbitals of the mercury atom and the s orbital of the S atom and p and d orbitals of the Mo atom.     

On some projectively flat polynomial （α,β）-metrics

In this paper, we consider some polynomial (α,β)-metrics, and discuss the sufficient and necessary conditions for a Finsler metric in the form F=α a1β a2β2/α a4β4/α3 to be projectively flat, where ai (i=1,2,4) are constants with a1≠0, α is a Riemannian metric and β is a 1-form. By analyzing the geodesic coefficients and the divisibility of certain polynomials, we obtain that there are only five projectively flat cases for metrics of this type. This gives a classification for such kind of Finsler metrics.     

The polymerization of methyl methacrylate with a new Tin-bridged yttrocene/Al(I-Bu)3

A new catalyst composed of Tin-bridged yttrocene Ph₂Sn(MeCp)₂YCI (MeCp=methylcyclopentadienyl) and Al (i-Bu)₃ was successfully developed for the polymerization of methyl methacrylate (MMA). Detailed study of factors (such as the molar ratio of Al/Cat., catalyst concentration, various solvents, temperature and time) influencing polymerization reaction indicated that the catalytic active species may be still somewhat stable at high temperature and still have a long catalytic lifetime.¹H NMR spectrum showed about 65% syndiotactic content in the polymethyl methacrylate (PMMA) prepared. From kinetic studies, the polymerization rate equation may be expressed as Rp=Kp[Cat.]^2.4. The overall activation energy of polymerization is 20.9±3.1 kJ/mol. Project(29774021) supported by the Natural Science Foundation of China and National Laboratory of Element-Organic Chemistry, Nakai, University.     

Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> as indicator of heavy metal enrichment in Zhujiang (Pearl River) estuary sediments

A part of the heavy metals in estuary and coastal zone occurs naturally in the environment; the other part is due to human activity; so the directly measured concentration of heavy metal does not automatically indicate anthropogenic enrichment. Fe₂O₃ was used in this study as conservative tracer to distinguish natural components from anthropogenic components of heavy metal sediment concentration in the Zhujiang estuary. Compared with clay and Al₂O₃, Fe₂O₃ is more suitable as reference element. The final results showed that two zones in the Zhujiang estuary were seriously contaminated by heavy metals. One nearby the Humen mouth; the other around the west coast of the estuary. The horizontal distribution of heavy metals indicates that Zn, Ni and Cu have wider contaminating areas than TiO₂, V and Cr in the estuary.     

在室温和常压下用机械合金化方法制备Fe5C2金属间化合物

Single phase Fe5C2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X-ray differaction spectrum. The decomposing temperature of the Fe5C2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure.     

Three AMIGO<Superscript>3</Superscript>s: Using “Anchored modular inquiry” to help prepare future teachers

We discuss three case studies associated with Vanderbilt’s PT3 (Preparing Tomorrow’s Teachers to Use Technology) grant. The studies explore some initial effects of attempts to enhance the education of preservice teachers in three areas: (a) How People Learn, (b) Mathematics, and (c) Adolescent Psychology. The case studies to be described each build on Vanderbilt’s AMIGO³ project, which involves technology architecture for flexible modular design that was developed to be consistent with principles of How People Learn. Three different research teams used the AMIGO³ architecture and rationale to design, implement, and study their own courses. All teams agreed on some basic guidelines, but then proceeded independently of one another. The purpose of this report is to compare similarities and differences in the experiences of the teams. The PT3 group: Primary Investigator—John Bransford; Project Director—Bob Plants; How People Learn Course—John Bransford, Nancy Vye, Kay Burgess, and Sean Brophy; Adolescent Psychology—Helen Bateman, and Christopher J. Bateman; Mathematics—Paul Cobb, Chrystal Dean, and Lori Tyler; Development Team—Tim Altman, Jason Adair, Hank Clark, Bill Corbin, John Harwood, Elliott Mitchell, and Carolyn Stalcup. Vanderbilt PT3 Partners: AACTE, Apple Computers, Bankstreet College, Concord Consortium, Little Planet Software, Middle Tennessee University, University of Illinois-Chicago, University of Minnesota, and University of Vermont. Research presented in this article was supported by grants: The Department of Education Preparing tomorrow’s teachers to use technology (PT3) Catalyst grant, #P342A990348, The National Science Foundation VaNTH Bioengineering grant, #EEC 9876363, and the Atlantic Philanthropic Association K-12 Learning Consortium (no assigned grant number).