Photoinduced phase transition accompanied with the changes in magnetic properties

Recently, many studies have been started in search for materials which show a photoinduced phase transition (PIPT). In this work, we review two systems as typical examples of PIPT accompanied with changes in magnetic characteristics; (1) organo-metal complex [Fe(2-pic)₃]Cl₂ EtOH (2-pic = 2-amino-methyl-pyridine) and (2) III-V based magnetic semiconductors (In_1-x , Mn _x )As. In the former case, we show several nonlinear characteristics in dynamical process of photoinduced spin state transition from low-spin to high-spin states. In the latter one, photocarrier-induced ferromagnetic order has been observed by both magnetic and transport measurements.     

Non-relativistic Limit of a Dirac Polaron in Relativistic Quantum Electrodynamics

A quantum system of a Dirac particle interacting with the quantum radiation field is considered in the case where no external potentials exist. Then the total momentum of the system is conserved and the total Hamiltonian is unitarily equivalent to the direct integral of a family of self-adjoint operators acting in the Hilbert space , where is the Hilbert space of the quantum radiation field. The fiber operator is called the Hamiltonian of the Dirac polaron with total momentum . The main result of this paper is concerned with the non-relativistic (scaling) limit of . It is proven that the non-relativistic limit of yields a self-adjoint extension of a Hamiltonian of a polaron with spin 1/2 in non-relativistic quantum electrodynamics.     

Charge density of Ga<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Al<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sb

Charge density calculations and electronic band structures for Ga _x Al_{1 − x} Sb with x = 1.0, 0.5 and 0.0 are presented in this work. The calculations are performed using the empirical pseudopotential method. The charge density is computed for a number of planes, i.e. z = 0.0, 0.125 and 0.25 A ₀ by generating the potential through a number of potential parameters available in the literature. The virtual crystal approximation was applied for the semiconducting alloy. The characteristics of the band structure and charge density are observed to be affected by the potential parameters. Calculated band gaps and the nature of gaps are in good agreement with the experimental data reported. The ionicity is also reasonably in good agreement with other scales proposed in the literature; however the formulation needs to be improved. The present work also demands indirect experimental band gap for the alloy.      

Catalytic and kinetic spectrophotometric method for determination of vanadium(V) by 2,3,4-trihydroxyacetophenonephenylhydrazone

A new catalytic and kinetic spectrophotometric method for the determination of vanadium(V) was studied using 2,3,4-trihydroxyacetophenonephenylhydrazone (THAPPH) as an analytical reagent. The present method was developed on the catalytic effect of vanadium on oxidation of THAPPH by hydrogen peroxide in hydrochloric acid–potassium chloride buffer (pH = 2.8) at the 20th minute. The metal ion has formed 1:2 (M:L) complex with THAPPH. Beer’s law was obeyed in the range 20–120 ng/mL of V(V) at λ_max 390 nm. The sensitivity of the method was calculated in terms of molar absorptivity (1.999 × 10⁵ L mol⁻¹cm⁻¹) and Sandell’s sensitivity (0.000254 μg cm⁻²), shows that this method is more sensitive. The standard deviation (0.0022), relative standard deviation (0.56%), confidence limit (±0.0015) and standard error (0.0007) revealed that the developed method has more precision and accuracy. The stability constant was calculated with the help of Asmu’s (9.411 × 10⁻¹¹) and Edmond’s & Birnbaum’s (9.504 × 10⁻¹¹) methods at room temperature. The interfering effect of various cations and anions was also studied. The present method was successfully applied for the determination of vanadium(V) in environmental and alloy samples. The method’s validity was checked by comparing the results obtained with atomic-absorption spectrophotometry and also by evaluation of results using F-test.     

An Improved Approach for Practical Synthesis of 5-Hydroxymethyl-2′-deoxycytidine (5hmdC) Phosphoramidite and Triphosphate

5-Hydroxymethyl-2′-deoxycytidine (5hmdC) phosphoramidite and triphosphate are important building blocks in 5hmdC-containing DNA synthesis for epigenetic studies. However, efficient and practical methods for the synthesis of these compounds are still limited. The current research provides an intensively improved synthetic method that enables the preparation of commercially available cyanoethyl-protected 5hmdC phosphoramidite with an overall yield of 39% on 5 g scale. On the basis of facile and efficient accesses to cyanoethyl protected-5hmdU and 5hmdC intermediates, two efficient synthetic routes for 5hmdC triphosphate were also developed.     

微弧氧化陶瓷膜封孔后处理及抗高温氧化性能的研究

在铝酸盐体系中,利用微等离体氧化脉冲电源在Ti-6Al-4V合金表面制备了以Al2TiO5为主晶相的陶瓷膜层,然后采用钛酸四丁酯/乙醇和硅酸钠溶液的封孔方法对微弧氧化陶瓷膜进行封孔后处理。通过SEM及高温氧化测试,分析比较了陶瓷膜层在封孔前后的表面形貌以及抗高温氧化性能的变化情况。结果表明:封孔后膜层孔洞明显变小。经700℃高温氧化测试,采用钛酸四丁酯/乙醇溶液封孔方法不仅没有带来抗高温氧化性能的提高反而下降,而硅酸钠溶液的封孔方法提高了抗高温氧化性能。     

Targeted deposition of Au aerosol nanoparticles on vertical nanowires for the creation of nanotrees

Complex tree-like nanostructures with controlled morphology are becoming increasingly important for the development of nanoscale devices. The position of branches on III–V semiconductor nanotrees is determined by the distribution of Au seed particles. Here we report the dependence of the distribution of Au aerosol nanoparticles on nanowires on parameters including distance between wires, particle size, wire length, wire diameter, III–V material and particle charge. It was observed that different wire lengths and separation distances as well as different particle polarities have a significant effect on the resulting particle distribution while different wire diameters, particle diameters, materials and deposition voltages do not.     

Note on the kinetic energy inequality leading to Lieb's negative ionization upper bound

The kinetic energy inequality is alternatively proved which yields Lieb's boundN < 2Z + 1 on the maximum negative ionization of an atom with nucleus chargeZ andN electrons when the kinetic energy operator is the nonrelativistic or relativistic magnetic Schrödinger operator. It is seen to follow from the free case where the vector potential vanishes. The proof applies to the Weyl quantized relativistic magnetic Schrödinger operator as well.Research partially supported by Grant-in-Aid for Scientific Research Nos. 04640141 and 05640165, Ministry of Education, Science and Culture, Japanese Government.     

Efficient removal of As(V) from simulated arsenic-contaminated wastewater via a novel metal–organic framework material: Synthesis,structure, and response surface methodology

A novel metal–organic framework material {[N(C₂H₅)₃][Zn₂(ptmda)₂(μ₂-H₂O)]·(H₂O)_0.5}_n { GUT-3 ; H₂ptmda is 4,4′-([p-tolylazanediyl]bis [methylene])dibenzoic acid} was successfully synthesized using the hydrothermal method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. GUT-3 has a two-dimensional network based on dinuclear [Zn₂(ptmda)₂(μ₂-H₂O)]⁻ building units which formed an eightfold interpenetration network in GUT-3 molecules. Hirshfeld surface analysis revealed that H–H, C–H, and O–H bonds accounted for the majority of intermolecular interactions. Moreover, the interactions between GUT-3 and As(V) – the form of As(V) is AsO₄³⁻ – were analyzed in aqueous solutions in a batch system to study the effect of pH, concentration, adsorbent dose, adsorption time, adsorption temperature, and shaking speed. The kinetic and isotherm data of arsenic adsorption on GUT-3 were accurately modeled by pseudo-second-order, Langmuir (q_m = 33.91 mg/g), and Freundlich models. The Box–Behnken response surface method was used to optimize the adsorption conditions of As(V) from the simulated arsenic-contaminated wastewater. The effect of various experimental parameters and optimal experimental conditions was ascertained using the quadratic model.