Band-gap and strain engineering in GeSn alloys using post-growth pulsed laser melting.

The pseudomorphic growth of Ge1-xSnxon Ge causes in-plane compressive strain, which degrades the superior properties of the Ge1-xSnxalloys. Therefore, efficient strain engineering is required. In this article, we present strain and band-gap engineering in Ge1-xSnxalloys grown on Ge a virtual substrate using post-growth nanosecond pulsed laser melting (PLM). Micro-Raman and x-ray diffraction (XRD) show that the initial in-plane compressive strain is removed. Moreover, for PLM energy densities higher than 0.5 J cm-2, the Ge0.89Sn0.11layer becomes tensile strained. Simultaneously, as revealed by Rutherford Backscattering spectrometry, cross-sectional transmission electron microscopy investigations and XRD the crystalline quality and Sn-distribution in PLM-treated Ge0.89Sn0.11layers are only slightly affected. Additionally, the change of the band structure after PLM is confirmed by low-temperature photoreflectance measurements. The presented results prove that post-growth ns-range PLM is an effective way for band-gap and strain engineering in highly-mismatched alloys.

Ellipsometric characterization of doped Ge0.95Sn0.05 films in the infrared range for plasmonic applications.

GeSn as a group-IV material opens up new possibilities for realizing photonic device concepts in Si-compatible fabrication processes. Here we present results of the ellipsometric characterization of highly p- and n-type doped Ge0.95Sn0.05 alloys deposited on Si substrates investigated in the wavelength range from 1 to 16 µm. We discuss the suitability of these films for integrated plasmonic applications in the infrared region.

GeSn/Ge multiquantum well photodetectors on Si substrates.

Vertical incidence GeSn/Ge multiquantum well (MQW) pin photodetectors on Si substrates were fabricated with a Sn concentration of 7%. The epitaxial structure was grown with a special low temperature molecular beam epitaxy process. The Ge barrier in the GeSn/Ge MQW was kept constant at 10 nm. The well width was varied between 6 and 12 nm. The GeSn/Ge MQW structures were grown pseudomorphically with the in-plane lattice constant of the Ge virtual substrate. The absorption edge shifts to longer wavelengths with thicker QWs in agreement with expectations from smaller quantization energies for the thicker QWs.

Nano-cones formation on a surface of Ge, Si crystals and Si1-xGe(x) solid solution by laser radiation.

The study of self-assembling nano-cones induced by irradiation of nanosecond Nd:YAG laser pulses on a surface of a Si1-xGe(x) solid solution is reported. It is shown that dynamics of nano-cones formation depends on concentration of Ge atoms (x) in Si lattice and on the intensity of laser radiation. Two different processes of nano-cones formation depending on x are observed. The first one-at higher concentration of Ge atoms x = 0.3-0.4 and the second one-at lower concentration of Ge atoms at x = 0.15 take place. At the first stage, similar processes of nano-cones formation occur. It means, at low intensity of laser radiation 1 < 2.0 MW/cm2 Ge atoms drift to the irradiated surface due to Thermo-gradient effect and Ge-rich phase is formed for both concentration ranges. The second stage is different for low and high Ge content ranges. At the higher concentration of Ge atoms and intensity of laser radiation 1 > 2.0 MW/cm2 nano-cones formation takes place by Stransky-Krastanov mode. On the same time, at lower concentration of Ge atoms cones look like "tree ring" growth due to melting of Ge separated islands on the irradiated surface at intensity of laser radiation 1 = 20 MW/cm2.

Self-assembly of nanohills in Si1-xGe(x)/Si hetero-epitaxial structure due to Ge redistribution induced by laser radiation.

The study is focused on formation and optical properties of nanostructures induced by laser radiation on the surface of Si1-xGe(x)/Si hetero-structures. Formation of self-assembling nanohills induced by irradiation of nanosecond Nd:YAG laser pulses on the Si0.7Ge0.3/Si hetero-epitaxial structures is reported. The atomic force microscope study of the irradiated surface morphology has shown a start of nanohills formation after laser irradiation of the intensity I = 7.0 MW/cm2. The huge "blue shift" of photoluminescence spectra with maximum intensity in region of 700-800 nm (1.76-1.54 eV) is explained by the quantum confinement effect in the nanohills. The maximum of this photoluminescence band slightly shifts to shorter wavelengths with the increase of the intensity of laser pulses used for sample treatment. Appearance of the 300 cm(-1) Ge-Ge vibration band in Raman scattering spectra for sample irradiated with I = 20.0 MW/cm2 is explained by Ge phase formation. Formation of the Ge-rich phase is explained by localization of Ge atoms drifting toward the irradiated surface under the thermal gradient due to strong absorption of laser radiation. Ellipsometric data confirm appearance of Ge-rich phase precipitates amounting to 7.1%, 6.4% of the total Ge content induced by laser radiation of intensities I1 = 20.0 MW/cm2, I2 = 7.0 MW/cm2 respectively.

Increased survival by feeding tetradecylthioacetic acid during a natural outbreak of heart and skeletal muscle inflammation in S0 Atlantic salmon, Salmo salar L.

We have previously documented increased survival by feeding tetradecylthioacetic acid (TTA) during a natural outbreak of infectious pancreatic necrosis in post-smolt S1 Atlantic salmon. The aim of the present study was to test the effects of dietary TTA in S0 smolt at a location where fish often experience natural outbreaks of heart and skeletal muscle inflammation (HSMI) during their first spring at sea. The experimental groups were fed a diet supplemented with 0.25% TTA for a 6-week period prior to a natural outbreak of HSMI in May 2007. Relative percent survival for the groups fed TTA was 45% compared with control diets, reducing mortality from 4.7% to 2.5%. Expression of genes related to lipid oxidation was higher in cardiac ventricles from salmon fed TTA compared with controls. In addition, salmon fed TTA had periodically reduced levels of plasma urea, and increased cardiosomatic index and growth. Reduced mortality and increased growth after administration of TTA may be related to a combination of anti-inflammatory effects, and an altered metabolic balance with better protein conservation because of increased lipid degradation.

[Care structures for drug dependent children and adolescents]. / Versorgungsstrukturen für drogenabhängige Kinder und Jugendliche.

Children and adolescents abusing drugs present a special challenge for our health system. Special risks for the development of drug dependence are psychic diseases of parents, familial addiction or multiply burdened families. The treatment of drug-addicted children and adolescents in child and youth psychiatry requires a highly individualised therapy programme as well as a pedagogic and therapeutic setting corresponding to age. 745 patients were examined in a retrospective study between 1998 and 2001. The results are shown below. 68% of the patients had a relevant psychiatric second diagnosis, 39 Patients of the examined drug addicted children and adolescents were diagnosed with an additional psychotic disturbance. A study of children and youth psychiatry clinics in the fall of 2001 showed that sufficient clinical care for drug-addicted children and adolescents is still lacking.

Study of the enantioselective elimination of four toxaphene congeners in rat after intravenous administration by high resolution gas chromatography negative ion mass spectrometry.

This study was performed to investigate the possible enantioselective metabolism of the four chlorinated bornanes: #26, #32, #50 and #62 (according to the Parlar nomenclature) by rats. Rats were exposed to a mixture of these toxaphenes by a single intravenous injection. Enantiomer ratios (ER) as well as the enantiomer fractions (EF) were determined in brain, adipose tissue and liver samples at six time intervals by high resolution gas chromatography (HRGC) coupled to negative ion chemical ionization (NICI) mass spectrometry (MS). Capillaries coated with heptakis-(2,3,6-O-tert-butyldimethylsilyl)-beta-cyclodextrin (TBDMS-CD) or octakis-(2,3,6-tri-O-ethyl)-gamma-cyclodextrin (TEG-CD) were used for the enantioselective separations. Significant time-dependent changes of ER and EF were found in all the three tissues for #26, #50 and #62. Greatest deviations from racemic composition were found in the liver, which is known to be the major metabolizing organ for toxaphenes. #32 was metabolized the fastest, but showed no changes in ER. Brief information is also included about the possible reasons for the different behaviors of the four congeners in the studied tissues.

Detection of chlordanes by positive ion chemical ionization in an ion trap: a comparative [correction of comparitive] study of the non-conventional reagents acetonitrile, acrylonitrile and dichloromethane.

The detection of some chlordane compounds (heptachlor, cis-/trans-chlordane and cis-/trans-nonachlor) by positive ion chemical ionization (PICI) in an ion trap was studied using acetonitrile, acrylonitrile and dichloromethane as non-conventional reagent gases. These reagent gases initiated specific fragmentation reactions and resulted in different response factors. All reagent gases enabled detection limits in the low-pg range for heptachlor, whereas the detection limits of cis-/trans-chlordane and cis-/trans-nonachlor were in the mid-pg range. Additionally, the acetonitrile and dichloromethane PICI mass spectra of the cis- and trans-stereoisomers of chlordane and nonachlor were different.

HPLC combined with multiple mass spectrometry (MSn): an alternative for the structure elucidation of compounds and artefacts found in smog chamber samples.

Ion trap multiple mass spectrometry combined with high-performance liquid chromatography (online HPLC-MSn) was used to identify carbonyl compounds and artefacts found in air samples of 2-3 L taken during the OH-radical reaction study of cis-3-acetyl-2,2-dimethylcyclobutylethanal (pinonal) or cis-3-acetyl-2,2-dimethylcyclobutylcarbaldehyde (nor-pinonal) in a smog chamber. Carbonyls were transformed into 2,4-dinitrophenylhydrazones. Detection of low picogram quantities was possible. Twenty-eight compounds could be identified based on the presence of structure characteristic fragments, a developed fragmentation scheme, comparison of retention times and a library of MSn spectra of selected carbonyls. Furthermore, the additional elucidation of the sub-structures of sixteen unknowns was possible. Details about the structure elucidation procedure and the formation of the observed fragments are presented.

Consequences of variable purity of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin determined by liquid chromatography-mass spectrometry on the enantioselective separation of polychlorinated compounds.

The composition of 10 batches of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (PM-CD) from different suppliers was determined by high-performance liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometry (MS). Considerable differences were found. Some batches consisted of more than 95% pure PM-CD, whereas others were not completely derivatised or contained a significant amount of by-products. Some suggestions about the structures of these impurities are given though neither nuclear magnetic resonance spectroscopy nor MS-MS investigations could completely reveal their nature. Capillaries for high-resolution gas chromatography were coated with the batches of most differing composition. They demonstrated widely varying column performance and separation properties for selected chiral polychlorinated substances such as chlordane compounds, o,p'-DDT, o,p'-DDD, alpha-hexachlorocyclohexane and atropisomeric polychlorinated biphenyls. The best enantioselectivity was obtained with the purest PM-CD. Compared to separations reported in the literature, a broader enantioselectivity was observed and also trans-heptachlor epoxide and oxychlordane could be resolved into enantiomers.

Quantification of derivatives of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) migrated from can coatings into tuna by HPLC/fluorescence and MS detection.

A reversed phase high performance liquid chromatographic method combined with fluorescence and mass spectrometric detection in series is presented for the separation and quantification of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) derivatives in extracts from food can coatings, tuna and oil. Fifteen samples of tuna cans bought in four European countries were investigated. Atmospheric pressure chemical ionization mass spectrometry in the positive ion mode (APCI(+)-MS) allowed to tentatively identify BADGE and NOGE related compounds originating from reactions of the glycidyl ethers with bisphenols, phenol, butanol, water and hydrochloric acid. Quantification was based on the external standard method and fluorescence detection. Mass fractions up to 3.7 micrograms/g were found for hydrochlorination products of bisphenol F diglycidyl ether (BFDGE + 2HCl) in tuna. Furthermore, total migration quantities of phenolic ether compounds were estimated. The highest values found were 20 micrograms/g in tuna and 43 micrograms/g in the oil phase.

Identification of derivatives of bisphenol A diglycidyl ether and novolac glycidyl ether in can coatings by liquid chromatography/ion trap mass spectrometry.

A reversed-phase liquid chromatographic method combined with fluorescence and multiple mass spectrometric detection in series is presented for the separation and structure elucidation of bisphenol A diglycidyl ether (BADGE) and novolac glycidyl ether (NOGE) derivatives. Atmospheric pressure chemical ionization in the positive ion mode and collision induced fragmentation in the ion trap allowed identification of BADGE- and NOGE-related compounds originating from reactions of the glycidyl ethers with bisphenols, solvents, and chain stoppers. Two extracts from food-can coatings were investigated in detail. It was possible to elucidate the structures of many substances and consequently to draw conclusions about the production of the lacquers.

Separation of toxaphene by high resolution gas chromatography.

A summary is given about the separation of toxaphenes by high resolution gas chromatography (HRGC). The suitability of different stationary phases for isomer and/or enantiomer-selective separations is compared. Multidimensional and tandem techniques are also presented. In addition, problems caused by thermal degradation in the injector and on the column are addressed. Furthermore, a brief survey is included about detection methods such as electron capture detection and different mass spectrometric methods.

Toxaphene in standard solutions and cleaned biota extracts--results of the first QUASIMEME interlaboratory studies. Quality Assurance of Information for Marine Environmental Monitoring in Europe.

Two interlaboratory studies on individual toxaphene congeners have been organised by the project Quality Assurance of Information for Marine Environmental Monitoring in Europe (QUASIMEME). Fifteen laboratories analysed two standard solutions in the first study and 13 laboratories analysed a standard solution and two cleaned biota extracts in the second study. The coefficients of variation obtained for the standard solutions were 6-21% and for the cleaned extracts 16-39%. Although the results were comparable to those of other studies, further improvement in the level of agreement between the participating laboratories was considered possible.

Quantitative determination and structure elucidation of type A- and B-trichothecenes by HPLC/ion trap multiple mass spectrometry.

A method is presented for the quantification and structure confirmation of trichothecenes in wheat by high-performance liquid chromatography combined with multiple mass spectrometry (MS(n)()). Nine type A- and B-trichothecenes were determined (nivalenol, deoxynivalenol, fusarenon-X, 3-acetyldeoxynivalenol, 15-acetyldeoxynivalenol, neosolaniol, diacetoxyscirpenol, HT-2 toxin, and T-2 toxin). Extraction was carried out with acetonitrile/water. The extract was purified on a MycoSep column. Quantification was based on an internal standard and atmospheric pressure chemical ionization in the positive ion mode. Recoveries from spiked wheat were in the range of 80-106% at levels of 500 ppb. The limits of quantification for the whole method were between 10 and 100 ppb. Ion adduct formation with ammonium and acetate ions and MS(n) experiments provided information about substitution and fragmentation behavior of the mycotoxins. A scheme has been established for the partial structure elucidation of type A- and B-trichothecenes in fungal cultures.

Isolation of diterpenoid alkaloids from herb and flowers of aconitum napellus ssp. vulgare and electrospray ion trap multiple MS study of these alkaloids

Chemical investigation of herb and flowers of Aconitum napellus L. ssp. vulgare led to the isolation of 12 diterpenoid alkaloids. Their chemical structures were identified on the basis of NMR and MS and of their complete ion trap multiple fragmentation mass spectrometry study.

Structure Elucidation of 2,4-Dinitrophenylhydrazone Derivatives of Carbonyl Compounds in Ambient Air by HPLC/MS and Multiple MS/MS Using Atmospheric Chemical Ionization in the Negative Ion Mode.

Ion trap multiple fragmentation mass spectrometry (MS(n)()) combined with high-performance liquid chromatography (HPLC) has been used for the structure elucidation and identification of 2,4-dinitrophenylhydrazone derivatives of carbonyl compounds in ambient air samples. Atmospheric pressure chemical ionization in the negative ion mode was the most suitable detection method. Different measures are described to decrease the MS background originating from the HPLC system. Low-picogram quantities were detectable in extracted mass chromatograms generated from full-scan records. Fragment ions produced by MS/MS allowed identification of substructures of the carbonyls. Detailed fragmentation paths were studied by MS(3) to MS(4) using reference compounds. A fragmentation scheme was established which enabled a structure confirmation and identification with 1-10 ng by HPLC/MS/MS. The identification of a compound coeluting with n-pentanal-DNPH and of a dimerization byproduct are given as examples.

Determination of levels of polychlorinated dibenzo-p-dioxins, dibenzofurans, biphenyls and pesticides in harp seals from the Greenland Sea.

The levels of polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF), biphenyls (PCB) and compounds of the DDT group were determined in individual seal blubber and brain samples from ten male and one female harp seals caught in the Greenland Sea. No data from this region and from harp seals have been reported before. The age of the animals varied between 1 and 18 years. PCDD/PCDF concentrations in the blubber (4-10 pg/g TEQ wet weight (w.w.), Nordic model) were somewhat lower than in ringed seals from the Arctic. Non-ortho substituted PCB (CB 77,126 and 169) showed TEQ levels in the blubber which were about 4-10-times higher. CB 77 dominated in most samples, but in a few cases CB 169 was the most abundant congener. p,p'-DDE (average 760 ng/g w.w.) and di-ortho substituted PCB concentrations (2560 ng/g w.w. expressed as sigma PCB) in the blubber were comparable to those found in ringed seals from the European and Canadian Artic. Levels of PCDD/PCDF in brain correspond to the detection limit (about. 0.1-0.6 pg/g w.w.) for most congeners. With one exception, PCB amounts in brain (w.w.) were one to two orders of magnitude lower. A highly significant correlation was found between age, p,p-DDE and di-ortho PCB as well as between single PCDD and coplanar PCB congeners. No relationship was observed between levels of PCDD/PCDF, age and di-ortho-PCB.

Concentrations of polychlorinated dibenzo-p-dioxins, dibenzofurans and non-ortho substituted biphenyls in polar bear milk from Svalbard (Norway).

Polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF) and non-ortho substituted biphenyls (PCB, CB) were determined in 6 polar bear milk samples from Svalbard (Norway). For these compounds, no data for polar bears have been reported before from this region. Most of the PCDD/PCDF congeners were found at detectable levels. Concentrations expressed as 2,3,7,8-TCDD equivalents (Nordic model) were in the order of 1-3 pg/g(-1) fat (0.2-1.6 pg ml(-1) milk) which is comparable with ringed and harp seal blubber from the same region. On whole milk basis, concentrations were similar to those found in human milk. An estimation of the daily uptake via milk showed that the intake is lower for polar bears compared to humans. As in human milk, relatively high levels of OCDD were found in some polar bear milk samples. The PCDD/PCDF congener pattern in the milk was different to that found in polar bear fat from the Canadian Arctic. Non-ortho substituted PCB levels in polar bear milk were similar to those found in polar bear fat from the Canadian North. However, CB 77 or 169 dominated in the milk while CB 126 was the most abundant congener in fat. PCDD/PCDF levels expressed as 2,3,7,8-TE were highly correlated with the fat content of the milk. No correlation between CB and PCDD/PCDF concentrations was found. Some data indicate that PCDD/PCDF concentrations in polar bear milk decrease with increasing time after delivery.