Partially reversible photochromic behavior of organic-inorganic perovskites with copper(Ⅱ)chloride

We report that the ultraviolet(UV)light induced photochromic behavior of layered organic-inorganic perovskite material of(C4H9NH3)2CuCl4,changed from yellow to brown after irradiation with UV light(10 mW/cm2)and partially recovered through storage in the dark.(C4H9NH3)2CuCl4 exhibited two distinct absorption bands centered at 286 nm(band Ⅰ)and 384 nm band Ⅱ),which were attributed to the photo-induced exciton formed in 2D inorganic layers sandwiched by organic layers.The blue shift of band Ⅰ from 287 to 269 nm as well as the decrease of the intensity of band Ⅰ and band Ⅱ could be found when samples were irradiated under UV light for djfferent length of time.The simultaneous weakening of the intensity of the N-H…Clhydrogen bond as well as the vibration of the long Cu-Cl bond in the distorted CuCl64- octahedron could be detected from the Fourier transform infrared(FTIR)spectra,which resulted the change of charge distribution of the dissymmetric Cl-Cu…Cl bond and the resulting photochromic behavior.     

负载钨硅酸的复合薄膜的光致变色行为和机理

A novel reversible photochromic nanocomposite film based on a hybrid inorganic-organic matrix in which heteropolyacid H4SiW12O40 （SiWA） was entrapped in Si-O-Ti network was prepared. Structure, photochromic behaviors and mechanism of the film were investigated by means of infrared spectroscopy （IR）, ultraviolet-visible （UV-Vis） absorption spectra and electron spin resonance （ESR）. The results showed that heteropolyanion i.e. SiW12O^4- 40 （SiW12）, maintained a Keggin structure in the film and there was a strong interaction between anion SiW12 and cation R-NH^＋3 （R=link of hybrid composite）. The photochromic properties of the composite film originated from reversible charge transfer between the anions and cations. Under UV irradiation, the anion would be reduced via one-electron step with simultaneous oxidation of the cation, accompanied by a color change from colorless to blue. Bleaching could occur when the film was in contact with ambient air or 02 in the dark.     

A Monte Cado Model of Ught Propagation in Nontransparent Tissue

To sharpen the imaging of structures, it is vital to develop a convenient and efficient quantitative algorithm of the optical coherence tomography (OCT) sampling. In this paper a new Monte Carlo model is set up and how light propagates in bio-tissue is analyzed in virtue of mathematics and physics equations. The relations,in which light intensity of Class I and Class 2 light with different wavelengths changes with their permeation depth ,and in which Class I light intensity (signal light intensity) changes with the probing depth, and in which angularly resolved diffuse reflectance and diffuse transmittance change with the exiting angle, are studied. The results show that Monte Carlo simulation results are consistent with the theory data.     

Switchable 2,3-dithienylmaleimide bonded to different fluorophores:synthesis and photochromic properties

A series of photochromic diarylethene derivatives containing different fluorophores was synthesized by the Sonogashira coupling reaction and characterized by ^1H nuclear magnetic resonance （NMR）, ^13C NMR and mass spectroscopy. Photochromic conversion of Cz-MS was observed and its structural change was confirmed by proton NMR, Switchable absorption and emission phenomena were observed for these molecules. These phenomena were attributed to the reversible photochromic fluorescence resonance energy transfer （pcFRET） process. The design of this novel photochromic system of Py-4MS enables information to be processed in a non-destructive manner. This overcomes the problem of the destructive nature of tracking photochromism using ultraviolet （UV）-vis spectroscopy.     

Novel photocatalytic reactor for degradation of DDT in water and its optimization model

A novel photocatalytic reactor was developed to remove （1,1-bis（4-chlorophenyl）-2,2,2-trichloroethane） （DDT） from water. In the reactor, a cenosphere was used to support TiO2 film made by means of sol-gel. Because the cenospheres were coated with TiO2, their specific gravity was slightly increased from the original 0.6-0.8 to 0.8-0.9, so that they were able to be suspended in water. With the mixed operation of a bubbler, the water in the reactor was in a well-fluidized state. The bottom of the reactor is a sand filter bed, which can be used to prevent the photocatalyst from being lost. A mathematical model of the reactor has been developed in the two primary influential factors： ultraviolet （UV） light intensity and photocatalyst concentration. With such a model, the reactor can be designed more reasonably.     

Effects of SO2 and SO3 on the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans by de novo synthesis

The effects of SO2, SO3 on de novo synthesis of polychlorinated dibenzo-p-dioxins （PCDDs） and dibenzofurans （PCDFs） were studied using model fly ashes incorporating copper oxide and activated carbon. It was found that the inhibitive effect of SO2 on PCDD/Fs formation is similar to that of SO3. To investigate the inhibition mechanism, CuSO4 formations from both CuO and CuCl2 were examined. The ability of SO3 to convert CuCl2 and CuO on a silica support into sulfate is much stronger than that of SO2. However, replacing silica by activated carbon leads to a much high conversion of CuCl2 to CuSO4 in the presence of SO2. The promotion by activated carbon is explained by the reduction of CuCl2 to Cu2Cl2 and the eventual conversion of Cu2Cl2 into CuSO4 is the main inhibition mechanism of SO2 on de novo synthesis of PCDD/Fs.     

Evaluation of the teaching guide as an instrument for adaptation to the new European credit system： Case analysis

This paper presents the evaluation of the teaching guide application for the subject of management control in the Business Management and Administration Degree. The evaluation began with the analysis of a questionnaire which aimed to collect the perceptions of learners who have studied this subject in two groups （morning and afternoon） during the first semester of the current academic year. The intention of this analysis was to obtain information that would meet two objectives： to continue upgrading the teaching-learning process and to revise and improve all the components in the teaching guide. There is an analysis of the degree of difficulty involved in the activities proposed and the degree to which specific objectives for different competencies have been attained. Likewise, we have carried out a global assessment of the different methodologies applied in the teaching-learning process, and an assessment of the evaluation system as well as of other aspects that could have hindered reaching the objectives stated in the guide. Furthermore, the relevance of this questionnaire has been vindicated for obtaining the information necessary to adjust the learner＇s workload to the European credit.     

Practice on assessing grammar and vocabulary： The case of the TOEFL

The Test of English as a Foreign Language （TOEFL） brings tremendous influence to EFL （English as a Foreign Language） learners worldwide. TOEFL 2000 project claims that TOEFL, as a more reflective of communicative model, could provide more information about international students＇ language ability that it is supposed to measure. However, after detailed analyzing an authentic paper-based test paper in May, 2001 in China as a sample from four aspects--test reliability, construct validity, authenticity and interactiveness respectively, it is found that the test puts too much emphasis on vocabulary and grammar knowledge within almost every session of the test paper, in which ＂structure and written expression＂ could be the most disputed part. The content could not fully demonstrate its validity and communicative purposes so that it is suspected that test takers could meet the later demands in academic study abroad. Nevertheless, this is a powerful explanation about the current revolutionized change in the framework and content of TOEFL to meet the principles of designing a test, which could provide more information and guidance for later test designs.     

Microwave-assisted rapid synthesis of alumina nanoparticles using tea,coffee and triphala extracts

Alumina nanoparticles （A1NP） were synthe- sized from aluminium nitrate using extracts of tea, coffee and triphala--a well known herbal plant as well as a non- toxic and eco--friendly green material. The synthesis was carried out taking 1：4 ratio of metal salt and these extracts under microwave irradiations at 540 W, which gave better yield of nanoparticles. Water was taken as solvent medium. The formations of A1NP were initially monitored by the colour changes occurring in the reaction mixture during the incubation period. As synthesized nanoparticles were characterized by scanning electron microscope （SEM）, UV-Visible （UV-Vis） spectroscopy and Fourier transform infrared spectroscopy （FTIR）. The A1NP were found to be spherical in shape in case of tea and coffee extracts with a size of 50-200 nm and to be oval shaped in case of triphala extract with an average size of 200-400 nm. The formation of A1NP with the microwave-assistance using these plant extracts has proved to be very faster than any other methods. In addition, excellent reproducibility of these nanoparticles, without the use of any additional capping agent or stabilizer will have great advantages in compari- son with microbial synthesis, avoiding all the tedious and hygienic complications.     

Active Control of Free Paraboloidal Membrane Shells Using Photostrictive Actuators

The paraboloidal membrane shell with free boundary condition is actively controlled using photostrictive actuators which can provide contactless actuation under the illumination of ultraviolet light. The governing equations of the paraboloidal shell laminated with paired photostrictive actuators are established based on membrane approximation. The modal control actions of meridional/circumferential actuators are respectively formulated and evaluated by case studies. Constant light intensity related to the velocity of the shell is adopted, and then the governing equations are written in a closed-loop form which can be solved with Newmark-β method. Considering the multi-field coupling behavior of photostrictive actuators, time histories of transverse displacement and control light intensity are simulated and evaluated. The results show that photostrictive actuators can effectively control the vibration of the paraboloidal membrane shell, and the photostrictive actuators oriented along circumferential direction can give better control effect than photostrictive actuators placed along the meridional direction.     

Effects of nitrogen form on growth,CO2 assimilation,chlorophyll fluorescence,and photosynthetic electron allocation in cucumber and rice plants

Cucumber and rice plants with varying ammonium (NH₄ ⁺) sensitivities were used to examine the effects of different nitrogen (N) sources on gas exchange, chlorophyll (Chl) fluorescence quenching, and photosynthetic electron allocation. Compared to nitrate (NO₃ ⁻)-grown plants, cucumber plants grown under NH₄ ⁺-nutrition showed decreased plant growth, net photosynthetic rate, stomatal conductance, intercellular carbon dioxide (CO₂) level, transpiration rate, maximum photochemical efficiency of photosystem II, and O₂-independent alternative electron flux, and increased O₂-dependent alternative electron flux. However, the N source had little effect on gas exchange, Chl a fluorescence parameters, and photosynthetic electron allocation in rice plants, except that NH₄ ⁺-grown plants had a higher O₂-independent alternative electron flux than NO₃ ⁻-grown plants. NO₃ ⁻ reduction activity was rarely detected in leaves of NH₄ ⁺-grown cucumber plants, but was high in NH₄ ⁺-grown rice plants. These results demonstrate that significant amounts of photosynthetic electron transport were coupled to NO₃ ⁻ assimilation, an effect more significant in NO₃ ⁻-grown plants than in NH₄ ⁺-grown plants. Meanwhile, NH₄ ⁺-tolerant plants exhibited a higher demand for the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) for NO₃ ⁻ reduction, regardless of the N form supplied, while NH₄ ⁺-sensitive plants had a high water-water cycle activity when NH₄ ⁺ was supplied as the sole N source.     

柠檬酸含量对溶胶凝胶自燃烧法制备的钡铁氧体磁性能的影响

BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5.     

Sensitized Up—Conversion Luminescence of Ho^3＋ in Nd^3＋—Yb^3＋—Ho^3＋ Co—doped ZrF4—Based Glass

Up-conversion processes for the blue, green and red emissions were found two-photon phenomenon, known as the cooperative phenomenon. This phenomenon was assisted by Nd³⁺ → Yb³⁺ → Ho³⁺ energy transfer. The strong green emission due to the Ho³⁺ : (⁵F₄, ⁵S₂)→ ⁵I₈ transitions was observed in Nd³⁺-Ho³⁺ co-doped ZrF₄-based fluoride glasses under 800 nm excitation. As an attempt to enhance Ho³⁺ up-conversion luminescences in the Nd³⁺ – Ho³⁺ co-doped ZrF₄-based glasses, Yb³⁺ ions were added to the glasses. As a result it was found that, in 800 nm excitation of 60 ZrF₄. 30BaF2. (8-x)LaF₃. lNdF₃. xYbF₃. 1HoF₃ glasses (x=0 to 7), sensitized up-conversion luminescences are observed at around 490 nm (blue), 545 nm (green), and 650 nm (red), which correspond to the Ho³⁺ : ⁵F₃ → ⁵I₈, ( ⁵F₄, ⁵S₂)→⁵I₈ and ⁵F₅→ ⁵I₈ transitions respectively. The intensities of the green and red emissions in a 3 mol % YbF₃-containing glass were about 50 times stronger than those glasses without YbF₃. This is based on sensitization due to Yb³⁺ ions. In particular, the green emission was extremely strong and the Nd³⁺-Yb³⁺-Ho³⁺ co-doped ZrF₄-based glasses have a high possibility of realizing a green up-conversion laser glass. In this paper the up-conversion mechanism in the glasses is discussed in detail.     

Ethylene polymerization with novel silicon bridged homo-dinuclear cyanoethyl cyclopentadienyl complexes of titanium and zirconium

Novel homo-dinuclear silicon bridged cyanoethyl cyclopentadienyl complexes of titanium and zirconium (CH₃)₂Si((η⁵ ? C₅H₃CH₂CH₂CN)(C₅H₅)MCl₂)₂(M = Ti(1), Zr(2)) were synthesized and developed for the polymerization of ethylene. Compared with their corresponding mononuclear complexes (η⁵ ? C₅H₄CH₂CH₂CN)(C₅H₅)MCl₂(M = Ti(3), Zr(4)), the dinuclear complexes had higher catalytic activity. And the polyethylene produced had a higher molecular weight than that obtained with mononuclear catalysts. Effects of conditions on the ethylene polymerization catalyzed by (2)/MAO (methylaluminoxane) were studied in detail. The catalyst showed a very high activity (> 10⁶ g PE/mol Zr·h) under low catalyst concentration and high molar ratio of Al/Zr.     

Science Letters： New solutions of shear waves in piezoelectric cubic crystals

Acoustic wave propagation in piezoelectric crystals of classes?43m and 23 is studied. The crystals Tl3VS4 and Tl3TaSe4 (43m) of the Chalcogenide family and the crystal Bi12TiO20 (23) possess strong piezoelectric effect. Because the surface Bleustein-Gulyaev waves cannot exist in piezoelectric cubic crystals, it was concluded that new solutions for shear-horizontal surface acoustic waves (SH-SAWs) are found in the monocrystals using different electrical boundary conditions such as electri- cally “short” and “open” free-surfaces for the unique [101] direction of wave propagation. For the crystal Tl3TaSe4 with coefficient of electromechanical coupling (CEMC) Ke2=e2/(C×g)～1/3, the phase velocity Vph for the new SH-SAWs can be calculated with the following formula: Vph=(Va Vt)/2, where Vt is the speed of bulk SH-wave, Vt=Vt4(1 Ke2)1/2, Va=aKVt4, aK=2[Ke(1 Ke2)1/2-Ke2]1/2, and Vt4=(C44/ρ)1/2. It was found that the CEMC K2 evaluation for Tl3TaSe4 gave the value of K2=2(Vf–Vm)/Vf～0.047 (～4.7%), where Vf～848 m/s and Vm~828 m/s are the new-SAW velocities for the free and metallized surfaces, respectively. This high value of K2(Tl3TaSe4) is significantly greater than K2(Tl3VS4)～3% and about five times that of K2(Bi12TiO20).     

Ammonium affects cell viability to inhibit root growth in Arabidopsis

Ammonium (NH₄ ⁺) is an important form of nitrogen nutrient for most plants, yet is also a stressor for many of them. However, the primary events of NH₄ ⁺ toxicity at the cellular level are still unclear. Here, we showed that NH₄ ⁺ toxicity can induce the root cell death in a temporal pattern which primarily occurs in the cells of root maturation and elongation zones, and then spreads to the cells in the meristem and root cap. The results from the NH₄ ⁺-hypersensitive mutant hsn1 further confirmed our findings. Taken together, NH₄ ⁺ toxicity inhibits primary root growth by inhibiting cell elongation and division and inducing root cell death.     

Comparison of the effects of copper and lead on soil microbial biomass carbon and nitrogen in red soil

A laboratory incubation experiment was conducted to study the effect of copper as cupric sulfate (CuSO₄.5H₂O), and lead as lead acetate (Pb (OAc)₂) on the size of the microbial biomass in red soil. The metals were applied, separately at six different levels: Cu at 50, 100, 200, 300, 400, and 600 μg·g⁻¹ soil and Pb at 100, 200, 400, 600, 800, and 1000 μg·g⁻¹ soil. In comparison to uncontaminated soil, the microbial biomass carbon (C_mic) and biomass nitrogen (N_mic) decreased sharply in soils contaminated with Cu and Pb. The microbial biomass C:N ratio in the metal contaminated soil was observed to be considerably higher than that in untreated control. Between the two tested metals, Cu displayed greater biocidal effect on microbial biomass carbon and nitrogen than Pb, showing their relative toxicity in the order: Cu≫Pb. Project (No. 49671050) supported by National Natural Science Foundation of China. Wa’el Mohamad—Former Ph. D. Student of Zhejiang University and is working in Ministry Of Agriculture (P. O. box. 2099), Amman, Jordan.     

二芳基乙烯化合物的合成及光致变色性能研究

在氮气保护下,制备了3种二芳基乙烯化合物1o、2o 和3o,通过核磁共振进行结构表征,运用紫外-可见吸收光谱对其光致变色性能进行研究。在紫外光照射下,3种化合物在可见光区均出现了特征的关环吸收峰,最大吸收波长分别为440、511和605nm,溶液的颜色分别由无色变为黄色、红色和蓝色,到达光稳态时间分别为150、160和600s。到达光稳态的溶液在可见光照射下,发生开环反应,溶液颜色由有色恢复到无色。实验结果表明,乙烯环与二芳基不同位点的连接影响着二芳基乙烯分子的π-π共轭性,从而影响化合物的光致变色性能。     

Chemically processed Nb-doped SrTiO3 films and properties

Homogeneous, crack-free SrNb_xTi_1−x O₃ thin films on (110) silicon substrates were successfully fabricated by sol-gel processing. The optimum route and conditions were systematically investigated. Sr(OAc)₂ glacial acctic acid solution, after being refluxed and reacted with tartrate, formed Sr(OAc)₂(C₄H₆O₆)₂; Ti(OBu)₄ formed Ti(OAc)_4−x (AcAc)_x after having the ligand partially exchanged with AcAc, while Nb(OC₂H₅)₅ formed (OAc)₂Nb(AcAc) (C₄H₆O₆) by exchanging of ligand in glacial acetic acid with (CH₃CO)₂O. All the metal species after undergoing partial hydrolysis and polymerization with hydroxyl or oxygen, formed SrNb_xTi_1−x O₁₃ cluster sol. Methyl cellulose (MCL) caused SrNb_xTi_1−x O₃ sol to have polymeric structure and easily form films. SrNb_xTi_1−x O₃ films with perovskite were subsequently formed after being annealed at 650∼750 °C for 60 min in 25% N₂+75% H₂ (volume ratio) atmosphere. Resistivity of the SrNb_0.1Ti_0.9O₃ films at room temperature was 64 μω·cm, a particular T ² temperature dependence of the resistivity, from 25 K up to room temperature, was observed. Project (No. 2002CB613305) supported by the National Basic Research Program (973) of China     

Effects of ammonium application rate on uptake of soil adsorbed amino acids by rice

In recent years, excessive use of chemical nitrogen (N) fertilizers has resulted in the accumulation of excess ammonium (NH ₄ ⁺ ) in many agricultural soils. Though rice is known as an NH ₄ ⁺ -tolerant species and can directly absorb soil intact amino acids, we still know considerably less about the role of high exogenous NH ₄ ⁺ content on rice uptake of soil amino acids. This experiment examined the effects of the exogenous NH ₄ ⁺ concentration on rice uptake of soil adsorbed glycine in two different soils under sterile culture. Our data showed that the sorption capacity of glycine was closely related to soils;’ physical and chemical properties, such as organic matter and cation exchange capacity. Rice biomass was significantly inhibited by the exogenous NH ₄ ⁺ content at different glycine adsorption concentrations. A three-way analysis of variance demonstrated that rice glycine uptake and glycine nutritional contribution were not related to its sorption capacity, but significantly related to its glycine:NH ₄ ⁺ concentration ratio. After 21-d sterile cultivation, the rice uptake of adsorbed glycine accounted for 8.8%;–22.6% of rice total N uptake, which indicates that soil adsorbed amino acids theoretically can serve as an important N source for plant growth in spite of a high NH ₄ ⁺ application rate. However, further studies are needed to investigate the extent to which this bioavailability is realized in the field using the ¹³C, ¹⁵N double labeling technology.