Detailed kinetic analysis of the impact of nucleation behavior and particle size distribution on the configurations of carbon black

Journal of Nanoparticle Research - Dextrans are widely used as additives in food, pharmaceutical, and cosmetics because of their hydrophilicity, biocompatibility, and low toxicity. These features...     

Rational Synthesis of Antiaromatic 5,15‐Dioxaporphyrin and Oxidation into β,β‐Linked Dimers

5,15‐Dioxaporphyrin was synthesized for the first time by a nucleophilic aromatic substitution reaction of a nickel bis(α,α′‐dibromodipyrrin) complex with benzaldoxime, followed by an intramolecular annulation of the α‐hydroxy‐substituted intermediate. This unprecedented molecule is a 20π‐electron antiaromatic system, in terms of Hückel's rule of aromaticity, because lone pair electrons of oxygen atoms are incorporated into the 18π‐electron conjugated system of the porphyrin. A theoretical analysis based on the gauge‐including magnetically induced current method confirmed its antiaromaticity and a dominant inner ring pathway for the ring current. The unique reactivity of 5,15‐dioxaporphyrin forming a β,β‐linked dimer upon oxidation was also revealed.     

Hydrothermal synthesis of MoS2 nanowires

The MoS₂ nanowires with diameters of 4 nm and lengths of 50 nm were synthesized by a hydrothermal method using 0.36 g MoO₃ and 1.8 g Na₂S as precursors in 0.4 mol/l HCl solution at 260°C. The products are characterized by XRD, XPS, TEM, HTEM and BET. Results show that the as-prepared MoS₂ nanowires consist of 1–10 sulfide layers with BET surface areas of 107 m²/g. The possible reaction route and the formation mechanism of the MoS₂ nanowires are discussed. The effects of exterior conditions such as pH value, temperature, concentration of precursors and additives on the particle size and morphology of MoS₂ crystallites were investigated.     

Influence of a high vertical magnetic field on Te dopant segregation in InSb grown by the vertical gradient freeze method

A vertical gradient freeze apparatus was set up to investigate the influence of a vertical magnetc field on Te dopant segregation in InSb. Te-doped InSb crystals were grown in the presence and absence of an 80.0 kG magnetic field. The axial profile of the Te concentration in the crystal grown in the magnetic field was observed to be more uniform than that grown without magnetic field, which was attributed to the influence of the high magnetic field on Te dopant segregation by reducing convection in the melt.     

Crystal growth of Ce: PrF3 by micro-pulling-down method

Micro-pulling-down (μ-PD) growth apparatus was modified for fluoride crystals. PrF₃ was grown with various concentrations of Ce³⁺ from 0–100%. The crystals were transparent and colorless (CeF₃) or greenish and 3 mm in diameter and 15–50 mm in length. Neither visible inclusions nor cracks were observed. Radioluminescence spectra and decay kinetics were measured for the sample set at room temperature. In comparison to the Czochralski or Bridgman method, the μ-PD method allows to produce single crystalline material in a faster thus more economic way. Once it is established for the fluoride crystals, it is an efficient tool for exploring the field of new functional fluorides.     

Exact SDP relaxations of quadratically constrained quadratic programs with forest structures

Journal of Global Optimization - We study the exactness of the semidefinite programming (SDP) relaxation of quadratically constrained quadratic programs (QCQPs). With the aggregate sparsity matrix...     

Transient Heat Transfer for Forced Convection Flow of Helium Gas Over a Horizontal Plate

Transient heat transfer coefficients for helium gas flowing over a horizontal plate (ribbon) were measured under wide experimental conditions. The platinum plate with a thickness of 0.1 mm was used as the test heater and heated by electric current. The heat generation rate was exponentially increased with a function of Q₀ exp(t/τ). The gas flow velocities ranged from 4 to 10 m/s, the gas temperatures ranged from 290 to 353 K, and the periods of heat generation rate, τ, ranged from 50 ms to 17 s. The surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. Empirical correlation for transient heat transfer was also obtained based on the experimental data.