Thermal diffusivities of group V semimetals

A flash method, employing a pulsed flashlamp-pumped dye laser has been used to determine the thermal diffusivities of elemental arsenic, antimony, and bismuth. Measurements were made both on poly-crystalline samples and on oriented single crystal (111) wafers in the form of small disks 3.0?7.0 mm in diameter, and 0.43–1.33 mm thick. Thermocouples (0.076 mm dia) monitor the back surface temperature as a function of time after the front of the sample is exposed to a single laser pulse of pulse width (τ) <1.0 μsec. The room temperature thermal diffusivities α (cm²/sec) of polycrystalline As, Sb and Bi are respectively: 0.234, 0.182 and 0.0651. The diffusivities parallel to the trigonal crystal axis α₁ are: 0.119,0.142 and 0.0350. Measurements on polycrystalline Cu, Al and Ti yield 1.13, 0.96 and 0.085 cm²/sec, in agreement with literature values.     

Long range anemometry using a CO2 laser

A CO₂ laser anemometer is described which gives a real-time, continuous, measure of one component of wind velocity. Results are presented of a series of trials in which the laser anemometer is compared with a conventional propeller anemometer at ranges up to 50 m from the laser. Very good agreement is observed between the outputs of the two devices.     

Unilateral contact buckling of lightly profiled skin sheets under compressive or shearing loads

Thin, profiled steel sheets forming the skin of concrete-filled composite wall panels and similar members benefit from the unilateral (tensionless) restraint provided by fill of sufficient elastic modulus. This paper investigates the buckling of such skin sheets in panels subjected to compressive or shearing loads. The profiled skins are modelled as infinite, thin orthotropic plates resting on tensionless rigid foundations, allowing the local buckling response to be simulated by the single-wave buckling mode of an unrestrained plate section of appropriate aspect ratio. Solution of the governing differential equations leads to the determination of the plate buckling coefficients. Simplified formulas for the buckling coefficients in terms of the parameters describing the skin sheets are developed and shown to agree well with published results and finite element analyses for particular limiting cases.     

Particle-rotor-model calculations in 125I

Recent experimental data on ¹²⁵I has revealed several interesting structural features. These include the observation of a three quasiparticle band, prolate and oblate deformed bands, signature inversion in the yrast positive-parity band and identification of the unfavoured πh _11/2 band showing very large signature splitting. In the present work, particle-rotor-model calculations have been performed for the πh _11/2 band, using an axially symmetric deformed Nilsson potential. The calculations reproduce the experimental results well and predict a moderate prolate quadrupole deformation of about 0.2 for the band.     

[Bis­(di­phenyl­phosphino)­alkane](pentane‐2,4‐di­thionato) complexes of nickel(II)

The structures of a series of four‐coordinate nickel(II) complexes of the form [Ni(sacsac)L] PF₆ (sacsac = pentane‐2,4‐di­thione anion; L = (Ph₂P)₂(CH₂)_n, n = 1,2,3) have beendetermined. These are [bis­(di­phenyl­phosphino)­methane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₅H₂₂P₂)(C₅H₇S₂)]PF₆, [1,2‐bis­(di­phenylphosphino)­ethane](pentane‐2,4‐di­thionato–S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₆H₂₄P₂)(C₅H₇S₂)]PF₆, and [1,3‐bis­(di­phenyl­phosphino)­propane](pentane‐2,4‐di­thionato‐S,S′)­nickel(II) hexa­fluoro­phosphate, [Ni(C₂₇H₂₆P₂)(C₅H₇S₂)]PF₆. All have a distorted square‐planar arrangement about Ni with angles around Ni varying with the length of the hydro­carbon chain.     

Mechanism-based inactivation by aromatization of the transaminase BioA involved in biotin biosynthesis in Mycobaterium tuberculosis

BioA catalyzes the second step of biotin biosynthesis, and this enzyme represents a potential target to develop new antitubercular agents. Herein we report the design, synthesis, and biochemical characterization of a mechanism-based inhibitor (1) featuring a 3,6-dihydropyrid-2-one heterocycle that covalently modifies the pyridoxal 5'-phosphate (PLP) cofactor of BioA through aromatization. The structure of the PLP adduct was confirmed by MS/MS and X-ray crystallography at 1.94 ? resolution. Inactivation of BioA by 1 was time- and concentration-dependent and protected by substrate. We used a conditional knock-down mutant of M. tuberculosis to demonstrate the antitubercular activity of 1 correlated with BioA expression, and these results provide support for the designed mechanism of action.     

Synthesis of tetranuclear, four-coordinate manganese clusters with "pinned butterfly" geometry formed by metal-mediated N-N bond cleavage in diphenylhydrazine

The preparation of four-coordinate tetramanganese-amide-hydrazide clusters is described. Reaction of Mn(NR(2))(2) (R = SiMe(3)) with N,N'-diphenylhydrazine resulted in the formation of a black intermediary mixture that converted to a four-coordinate tetranuclear "pinned butterfly" cluster, Mn(4)(μ(3)-N(2)Ph(2))(2)(μ-N(2)Ph(2))(μ-NHPh)(2)(THF)(4). This compound was isolated in ~90% yield and identified by single-crystal X-ray diffraction analysis. In pyridine, the THF ligands were replaced, giving the pyridyl complex Mn(4)(μ(3)-N(2)Ph(2))(2)(μ-N(2)Ph(2))(μ-NHPh)(2)(py)(4). Charge counting considerations indicate that the clusters had gained two protons and two electrons in addition to the formative fragments. Isolation of the black mixture was achieved by extraction techniques from a reaction with a decreased loading of hydrazine run at low temperatures with decreased solvent polarity. The black mixture was characterized by FT-IR, UV-vis, and (1)H NMR spectroscopy. In addition, an isolable, colorless dimer, Mn(2)(μ-NHPh)(2)(NR(2))(2)(THF)(2), was present in the mixture and identified by single-crystal X-ray diffraction. These intermediates are discussed in light of possible mechanisms for formation of the tetranuclear cluster.     

Effect of Mg doping on morphology,photocatalytic activity and related biological properties of Zn1−xMgxO nanoparticles

The objective of this study is to synthesize ZnO and Mg doped ZnO (Zn_1−xMg_xO) nanoparticles via the sol-gel method, and characterize their structures and to investigate their biological properties such as antibacterial activity and hemolytic potential.Nanoparticles (NPs) were synthesized by the sol-gel method using zinc acetate dihydrate (Zn(CH₃COO)₂.2H₂O) and magnesium acetate tetrahydrate (Mg(CH₃COO)₂.4H₂O) as precursors. Methanol and monoethanolamine were used as solvent and sol stabilizer, respectively. Structural and morphological characterizations of Zn_1−xMg_xO nanoparticles were studied by using XRD and SEM-EDX, respectively. Photocatalytic activities of ZnO and selected Mg-doped ZnO (Zn_1−xMg_xO) nanoparticles were investigated by degradation of methylene blue (MeB). Results indicated that Mg doping (both 10% and 30%) to the ZnO nanoparticles enhanced the photocatalytic activity and a little amount of Zn0.90 Mg0.10 O photocatalyst (1.0 mg/mL) degraded MeB with 99% efficiency after 24 h of irradiation under ambient visible light. Antibacterial activity of nanoparticles versus Escherichia coli ( E. coli ) was determined by the standard plate count method. Hemolytic activities of the NPs were studied by hemolysis tests using human erythrocytes. XRD data proved that the average particle size of nanoparticles was around 30 nm. Moreover, the XRD results indicatedthat the patterns of Mg doped ZnO nanoparticles related to ZnO hexagonal wurtzite structure had no secondary phase for x ≤ 0.2 concentration. For 0 ≤ x ≤ 0.02, NPs showed a concentration dependent antibacterial activity against E. coli . While Zn_0.90Mg_0.10 O totally inhibited the growth of E. coli , upper and lower dopant concentrations did not show antibacterial activity.     

Spectralanalyse

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