Photoluminescence study of homoepitaxial N-polar GaN grown on differently misoriented single crystal substrates

We report results of a photoluminescence (PL) study of homoepitaxial N-polar GaN films grown by metal-organic chemical vapour deposition on vicinal GaN single crystal substrates. Off-angles of 2° and 4° towards the direction as well as 4° in the direction were investigated. Along with a remarkable improvement of the epilayer morphology, a significant reduction of the unintentional/intrinsic donor concentration is achieved for all considered misorientations. As a consequence, PL spectra with narrow bound and free excitonic lines were observed. The misorientation of 4° towards the direction results in an N-polar epilayer of the best optical quality.     

Photoinitiators and photoinitiation, 12. The aromatic ketone/t-amine Type-II photoinitiating system. Identification of the initiating species

The system benzophenone/N,N-dimethylaniline (DMA) representing a typical Type-II photoinitiating system is irradiated in the presence of 1,1-di(p-tolyl)ethylene (DTE) as a non-polymerising model substrate. In the presence of DMA the excited triplet state of benzophenone is not quenched by DTE and N-[3,3-di(p-tolyl)propyl]-N-methylaniline is isolated as the major product, indicating the DMA derived radical as the main initiating species in such Type-II systems. The mechanism of the reaction and its implications are discussed.     

High spin level structure of 63 143 Eu80

The level scheme of ¹⁴³ Eu has been extended to I=75/2 in an experiment with the NORDBALL Compton-suppressed Ge detector array and the ¹¹⁰ Pd(³⁷ Cl, 4n) reaction. Most of the scheme shows irregular structure of multiparticle excitations. A strongly populated straight cascade of more than 10 stretched E2 transitions suggests the onset of collectivity.     

High-spin states in 232U investigated with the 232Th(α, 4nγ) reaction

The ground-state rotational band of ²³²U is established up to I^π = 16⁺ (tentatively 18⁺) through a study of the ²³²Th(α, 4nγ) reaction. Conversion electron spectroscopy is found to be especially useful in circumventing the difficulties caused by strong fission competition.     

Selective pressurized liquid extraction of three classes of halogenated contaminants in fish

Pressurized liquid extraction (PLE) combined with in-cell clean-up of co-extracts, so-called selective-PLE (S-PLE), is a fast and accepted method for the analysis of halogenated organic contaminants in fish. However, many of the existing methods were optimized for use with single classes of contaminants. The main objective of this research was to develop an S-PLE method that elutes a minimal amount of fats while simultaneously extracting halogenated pesticides, polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) from fat-rich fish. The optimized method uses n-hexane:dichloromethane (75:25, v/v) as the extraction solvent, a 0.0078 fat to fat-retainer ratio (FFR) with Florisil as the fat retainer, three individual 5-min extractions with flush volumes of 150% and a selection of labeled surrogate standards (isotope dilution). This method resulted in a mean recovery of 77% for all target analytes in spiked samples and an average relative standard deviation of 6.3%. The method was validated with a certified reference material; the mean measured analyte concentrations agreed with the reference values except in the case of individual endosulfan isomers. It is likely that interconversion from the beta- to alpha-endosulfan isomer had occurred in the CRM, resulting in low measured concentrations for beta-endosulfan and high measured concentrations for alpha-endosulfan when compared with the reference values. Finally, the method was tested on three fish species with varying fat content. Different contaminant patterns were observed in the various species.     

The FT-IR study of the brain tissue of Labeo rohita due to arsenic intoxication

The brain is believed to be particularly vulnerable to arsenic due to its high oxygen consumption rate and high level of polyunsaturated fatty acids and relatively high rate of oxygen free radical generate without commensurable level of arsenic. Hence, in the present work an attempt is made to study the changes in the biochemical contents in the brain tissues of edible fish Labeo rohita due to arsenic intoxication using Fourier Transform Infrared (FT-IR) spectroscopy. FT-IR spectra reveal significant differences in absorbance intensities between the control and arsenic intoxicated brain tissues, reflecting an alteration on the major biochemical constituents, such as lipids, proteins and nucleic acids of the brain tissues of L. rohita due to arsenic intoxication. Further, the administration of antidote DMSA improves the protein and lipid contents significantly in the brain tissues when compared to arsenic intoxicated tissues. The decrease in α-helix structure due to arsenic intoxication might be responsible for the increase in β-sheet secondary structures, which is consistent with the mechanism of β-sheet formation.