The role of inner and internal radiation on the melt growth of sapphire crystal

In this paper, for an inductively heated Czochralski furnace used to grow sapphire single crystal, influence of the inner (wall‐to‐wall) and crystal internal (bulk) radiation on the characteristics of the growth process such as temperature and flow fields, structure of heat transfer and crystal‐melt interface has been studied numerically using the 2D quasi‐steady state finite element method. The obtained results of global analysis demonstrate a strong dependence of thermal field, heat transport structure and crystal‐melt interface on both types of radiative heat transfer within the growth furnace.     

On equilibrium structures of the water molecule

Equilibrium structures are fundamental entities in molecular sciences. They can be inferred from experimental data by complicated inverse procedures which often rely on several assumptions, including the Born-Oppenheimer approximation. Theory provides a direct route to equilibrium geometries. A recent high-quality ab initio semiglobal adiabatic potential-energy surface (PES) of the electronic ground state of water, reported by Polyansky et al. [ ibid. 299, 539 (2003)] and called CVRQD here, is analyzed in this respect. The equilibrium geometries resulting from this direct route are deemed to be of higher accuracy than those that can be determined by analyzing experimental data. Detailed investigation of the effect of the breakdown of the Born-Oppenheimer approximation suggests that the concept of an isotope-independent equilibrium structure holds to about 3 x 10(-5) A and 0.02 degrees for water. The mass-independent [Born-Oppenheimer (BO)] equilibrium bond length and bond angle on the ground electronic state PES of water is r(e) (BO)=0.957 82 A and theta e (BO)=104.48(5) degrees , respectively. The related mass-dependent (adiabatic) equilibrium bond length and bond angle of H2 (16)O is r(e) (ad)=0.957 85 A and theta e (ad)=104.50(0) degrees , respectively, while those of D2 (16)O are r(e) (ad)=0.957 83 A and theta e (ad)=104.49(0) degrees . Pure ab initio prediction of J=1 and 2 rotational levels on the vibrational ground state by the CVRQD PESs is accurate to better than 0.002 cm(-1) for all isotopologs of water considered. Elaborate adjustment of the CVRQD PESs to reproduce all observed rovibrational transitions to better than 0.05 cm(-1) (or the lower ones to better than 0.0035 cm(-1)) does not result in noticeable changes in the adiabatic equilibrium structure parameters. The expectation values of the ground vibrational state rotational constants of the water isotopologs, computed in the Eckart frame using the CVRQD PESs and atomic masses, deviate from the experimentally measured ones only marginally, especially for A0 and B0. The small residual deviations in the effective rotational constants are due to centrifugal distortion, electronic, and non-Born-Oppenheimer effects. The spectroscopic (nonadiabatic) equilibrium structural parameters of H2 16O, obtained from experimentally determined A'0 and B'0 rotational constants corrected empirically to obtain equilibrium rotational constants, are r(e) (sp)=0.957 77 A and theta e (sp)=104.48 degrees .     

Analysis of hot D2O emission using spectroscopically determined potentials

Fourier transform emission spectra of D2O vapor were recorded at a temperature of 1500 degrees C in the wavenumber range 380-1880 cm(-1). 15 346 lines were measured, of which the majority were identified as belonging to D2O. The spectrum was analyzed using variational nuclear motion calculations based on spectroscopically determined potential-energy surfaces. Initial assignments were made using a potential surface obtained by fitting a high accuracy ab initio potential. The new assignments were used to refine the potential surface, resulting in additional assignments. A total of 6400 D2O transitions were assigned and 2144 new D2O energy levels were obtained. Transitions involving the 4nu2 and 5nu2 bending states, with band origins of 4589.30 (+/-0.02) and 5679.6 (+/-0.1) cm(-1), respectively, were assigned for the first time.     

Survival of Threshold Contact Processes

We consider the d-dimensional threshold contact process. Suppose that a vacant site becomes occupied at rate one when there are at least occupied sites in its neighborhood, and the death rate at any site is >0. We will explicitly give two integers ab with the following properties: For a the process survives starting from finite configurations when is small, but for >a the process dies out starting from any finite configuration with any positive death rate. For b the process has a nontrivial invariant measure when is small, but for >b the only invariant measure is the all-zero configuration for any positive death rate.     

Preparation of polyphenylsulfone/graphene nanocomposite membrane for the pervaporation separation of cumene from water

Polyphenylsulfone (PPSU) was applied for the first time in the hydrophobic PV process. Nanocomposite membranes of PPSU/graphene (Gr) nanosheets were prepared and used to separate isopropyl benzene (cumene) from water via pervaporation (PV). Analysis of the mechanical properties of the membranes showed that the tensile strength and Young's modulus had an increasing trend with the incorporation of Gr into PPSU. The water contact angle of the membranes had a rising trend with the addition of Gr, confirming the improved hydrophobicity of membranes. In the PV experiments, the membrane containing 3.5 wt% Gr provided the highest separation factor, which was 4.5-fold as much as that of the neat PPSU membrane. Cumene separation from water by the PPSU/3.5 wt% Gr membrane was associated with the total flux of 132.73 gMH, the separation factor of 1566.36, and the PSI of 208,124.8 gMH.     

Screening of hepatitis B virus DNA in the serum sample by a new sensitive electrochemical genosensor-based Pd-Al LDH substrate

Journal of Solid State Electrochemistry - Screening for hepatitis B is one of the most severe liver virus infections in the world, and due to the effect of early detection and treatment of...     

Water line lists close to experimental accuracy using a spectroscopically determined potential energy surface for H2(16)O, H2(17)O, and H2(18)O

Line lists of vibration-rotation transitions for the H(2) (16)O, H(2) (17)O, and H(2) (18)O isotopologues of the water molecule are calculated, which cover the frequency region of 0-20 000 cm(-1) and with rotational states up to J=20 (J=30 for H(2) (16)O). These variational calculations are based on a new semitheoretical potential energy surface obtained by morphing a high accuracy ab initio potential using experimental energy levels. This potential reproduces the energy levels with J=0, 2, and 5 used in the fit with a standard deviation of 0.025 cm(-1). Linestrengths are obtained using an ab initio dipole moment surface. That these line lists make an excellent starting point for spectroscopic modeling and analysis of rotation-vibration spectra is demonstrated by comparison with recent measurements of Lisak and Hodges [J. Mol. Spectrosc. (unpublished)]: assignments are given for the seven unassigned transitions and the intensity of the strong lines are reproduced to with 3%. It is suggested that the present procedure may be a better route to reliable line intensities than laboratory measurements.     

Green Synthesis of Imidazole Derivatives via Fe3O4‐MNPs as Reusable Catalyst

In this research, a one‐pot, efficient, and high yielding procedure for the synthesis of imidazole derivatives is investigated. The procedure was carried out via multicomponent reaction of isothiocyanate, alkyl bromides, N‐methylimidazole, and triphenylphosphine in the presence of magnetic iron oxide nanoparticles (Fe₃O₄‐MNPs) as reusable catalyst under solvent‐free conditions at 50°C. Also, Fe₃O₄‐MNPs were produced using green synthetic method by reduction of ferric chloride solution with Clover Leaf water extract. The nanoparticles generated using this procedure can potentially be important in different purposes such as organic synthesis. Easy, simple, rapid, and clean procedures for the synthesis of imidazole derivatives are the advantages of this study.     

Polyvinyl amine as a modified and grafted shell for Fe3O4 nanoparticles: As a strong solid base catalyst for the synthesis of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation

In this work, we reported one-step deposition of polyacrylamide on nano-magnetite surface via a simple and in situ polymerization of acryl amide to form n-Fe₃O₄/PAM nanocomposite. The amide (–CONH₂) groups could be converted easily to amine (–NH₂) groups through Hofmann degradation to introduce n-Fe₃O₄/PVAm as a highly efficient heterogeneous base catalyst. The obtained organic-inorganic nanocomposite exhibited high catalytic activity for the solvent-free syntheses of various dihydropyrano[2,3-c]pyrazole derivatives and the Knoevenagel condensation in high to excellent yields and in the following, a plausible mechanism for the synthesis of them has been proposed. Because of the polymer layer coated Fe₃O₄ nanoparticles, the catalyst has many catalytic units, and acceptable thermal stability and recyclability. Titration, FT-IR, SEM, TGA, VSM, and XRD analysis were used for characterization of the catalyst. Also, the nanocomposite can be easily recovered by a magnetic field and reused up to 9 times without distinct deterioration in catalytic activity.