Preparation of poly(vinylbenzyltriphenylphosphonium perbromide) and its application in the bromination of organic compounds

Insoluble poly(vinylbenzyltriphenylphosphonium perbromide) was prepared by the chemical modification of 2% crosslinked poly(p-bromomethylstyrene) with triphenylphosphine followed by treatment of the obtained polymeric salt with bromine. The activity of the resulting polymeric brominating reagent was compared with that of the low molecular weight model reagent in the direct brominations of alkenes and carbonyl compounds. In addition to the excellent yields of the brominated products and the ease and simplicity of the method, the resulting polymeric by-product could be simply regenerated to give the reagent without loss of activity.     

Light absorption of CrIII in two host lattices of pyroxene and spinel type

The light absorption of Cr³⁺ – doped diopside CaMgSi₂O₆ and spinel ZnGaAlO₄ was measured spectrophotometrically. Two absorption bands corresponding to the electron transition: ⁴A_2g → ⁴T_2g (low frequency band) and ⁴A_2g → ⁴T_1g (high frequency band) were obtained. Generally, the value of the estimated ligand field parameters Δ and B showed that the Cr? O bond in the studied two structures is of different character.     

On the use of discrete wavelet transform for solving integral equations of acoustic scattering

In this paper, the discrete wavelet transform (DWT) is used to solve the dense system of equations which arises from integral equation of acoustic scattering. The DWT using appropriate wavelet family for acquiring larger sparsification of the system matrix is used to obtain a sparse approximation to the transformed matrix that is used in place of the original matrix in an iterative solver. Alternatively DWT is also used to design sparse preconditioners for an iterative method. Also, DWT-based preconditioners are constructed to accelerate iterative Krylov subspace methods. Convergence rates and number of operations are discussed for each case.

     

The importance of longer wavelength reheating in dual-pulse laser-induced breakdown spectroscopy

Dual-pulse laser-induced breakdown spectroscopy (LIBS) provides improved sensitivity compared to conventional single-pulse LIBS. We used a combination of Nd: yttrium aluminum garnet (YAG) and CO₂ lasers to improve the sensitivity of LIBS. Significant emission intensity enhancement is noticed for both excited neutral lines and ionic lines for dual-pulse LIBS compared to single-pulse LIBS. However, the enhancement factor is found to be dependend on the energy levels of the lines, and resonance lines provided maximum enhancement. Our results indicate that IR reheating will cause significant improvement in sensitivity, regardless of the conditions, even with an unfocused reheating beam. The improved sensitivity with a YAG-CO₂ laser combination is caused by the effective reheating of the pre-plume with a longer wavelength laser is due to efficient inverse Bremsstrahlung absorption. The role of the spot sizes, inter-pulse delay times, energies of the preheating and reheating pulses on the LIBS sensitivity improvements are discussed.     

A photodissociation study of CH2BrCl in the A-band using the time-sliced ion velocity imaging method

Employing a high-resolution (velocity resolution deltanu/nu<1.5%) time-sliced ion velocity imaging apparatus, we have examined the photodissociation of CH2BrCl in the photon energy range of 448.6-618.5 kJ/mol (193.3-266.6 nm). Precise translational and angular distributions for the dominant Br(2P32) and Br(2P12) channels have been determined from the ion images observed for Br(2P32) and Br(2P12). In confirmation with the previous studies, the kinetic-energy distributions for the Br(2P12) channel are found to fit well with one Gaussian function, whereas the kinetic- energy distributions for the Br(2P32) channel exhibit bimodal structures and can be decomposed into a slow and a fast Gaussian component. The observed kinetic-energy distributions are consistent with the conclusion that the formation of the Br(2P32) and Br(2P12) channels takes place on a repulsive potential-energy surface, resulting in a significant fraction (0.40-0.47) of available energy to appear as translational energy for the photo fragments. On the basis of the detailed kinetic-energy distributions and anisotropy parameters obtained in the present study, together with the specific features and relative absorption cross sections of the excited 2A', 1A", 3A', 4A', and 2A" states estimated in previous studies, we have rationalized the dissociation pathways of CH2BrCl in the A-band, leading to the formation of the Br(2P32) and Br(2P12) channels. The analysis of the ion images observed at 235 nm for Cl(2P(32,12)) provides strong evidence that the formation of Cl mainly arises from the secondary photodissociation process CH2Cl + hnu --> CH2 + Cl.     

Working group report: Heavy-ion physics and quark-gluon plasma

This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported.     

Spatial and temporal variations of electron temperatures and densities from EUV-emitting lithium plasmas

Planar slabs of pure Li were irradiated with 1.064 nm, 6 ns Nd:YAG laser pulses. Determination of plasma densities at both the earliest times of plasma formation and near the target surface was performed using Nomarski interferometry. The plasma parameters at later times were evaluated using optical emission spectroscopy. The space- and time-dependent electron densities and temperatures of the plasma were determined from their Stark broadening and the relative intensities of the spectral lines, respectively. The advantages and disadvantages of both of these techniques are evaluated and discussed.     

Zur Kenntnis des Härtungsprozesses von Phenol-Formaldehyd-Harzen

Zusammenfassung Mono-und Di-hydroxymethyl-Verbindungen von p-Hydroxybenzoesäureestern wurden dargestellt, in die entsprechenden Chlor- und Phenylamino-methyl-Derivate verwandelt, ihr Verhalten bei der Härtung studiert, die Harze zur Harzsäure verseift und deren Wiederveresterbarkeit gezeigt.     

Absorption Spectra of CrIII in some lattices of spinel and pseudo-brookite Type

Spinel mixed crystals ZnCr_xAl_2?xO₄, Cd_yZn_1?yCrAlO₄, Cd_0.5Zn_0.5Cr_0.4Ga_1.6O₄ and pseudo-brookite compounds Al_2?xGe_yCr_xTi_1?yO₅ were synthesized and x-rayed. The reflectance spectra were measured. The Δ-dependent absorption band was shifted towards IR-region in case of the spinels, whereas it remains nearly unshifted in pseudo-brookite. Generally, the results are discussed with the help of the ligand field parameters Δ and B.     

Phosphate,phosphoric acid and phosphogypsum natural radioactivity and radiological hazards parameters

Journal of Radioanalytical and Nuclear Chemistry - The concentrations of 238U, 226Ra, 232Th and 40K maintained in phosphate rock (PR), phosphoric acid (PA) and phosphogypsum (PG) samples and its...