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581.
The system (Fe0.88Mn0.12
1–x
Al
x
has been investigated in a concentration range from 5 to 14 at.% Al. We applied Mössbauer spectroscopy in the temperature range from 4 up to 900 K and X-ray diffractometry at room temperature. The as-cast samples show a bcc phase for all concentrations and exhibit broadened six-line Mössbauer spectra typical for disordered alloys. The Mössbauer spectra during a high temperature treatment show dramatic changes. These are due to ordering processes appearing at temperatures above 700 K. As an example of the observed changes, we present results obtained for the alloy withx= 14 at.% Al. 相似文献
582.
Tobias LieseVolker Radisch Inga KnorrMichael Reese Peter GroßmannKlaus Mann Hans-Ulrich Krebs 《Applied Surface Science》2011,257(12):5138-5141
As a novel approach, the combination of pulsed laser deposition and focused ion beam was applied to fabricate different types of multilayer zone plate structures for soft X-ray applications. For this purpose, high quality non-periodic ZrO2/Ti multilayers were deposited by pulsed laser deposition on planar Si substrates and on rotating steel wires with layer thicknesses according to the Fresnel zone plate law. Linear focusing optics were fabricated by cutting slices out of the multilayers by focused ion beam and placing them directly over pinholes within Si3N4 substrates. Additionally, it was shown that laser deposition of depth-graded multilayers on a wire is also a promising way for building up multilayer zone plates with point focus. First experiments using a table-top X-ray source based on a laser-induced plasma show that the determined focal length and spatial resolution of the fabricated multilayer Laue lens corresponds to the designed optic. 相似文献
583.
Considering four aromatic copolymers as an example, it was shown that the Kuhn segment of those random copolymers calculated by Monte Carlo method had a nonlinear dependence on the copolymer’s composition. It was also shown that the behavior of glass transition temperature, free volume, and dielectric permittivity versus conformational rigidity was similar to the behavior of aromatic homopolymers. 相似文献
584.
Cai Z Riedel H Thaw Saw NM Kütük O Mewis I Jäger H Knorr D Smetanska I 《Applied biochemistry and biotechnology》2011,164(4):443-453
Plant cell cultures provide a large potential for the production of secondary metabolites. Through the application of different
physical and chemical cell stress factors, we investigated the production of the secondary metabolites in plant cell cultures.
The effects of pulsed electric field (PEF) and ethephon on growth and secondary metabolism, particularly anthocyanins and
phenolic acids synthesis, were investigated by using suspension culture of Vitis vinifera L. cv. Gamay Fréaux as a model system. Anthocyanins were measured by spectrophotometer and extracellular phenolic acids were
determined by high-performance liquid chromatography. The compounds were identified by liquid chromatography–mass spectrometry
and nuclear magnetic resonance. After the treatments with PEF and ethephon, the concentrations of anthocyanins and phenolic
acids in cell culture were higher than in the control, without loss of biomass. The combination of PEF treatment and ethephon
improved secondary metabolites formation. Production levels of extracellular phenolic acids, 3-O-glucosyl-resveratrol were increased by PEF and ethephon treatments. The results show that PEF induced a defense response
of plant cells and may have altered the cell/membrane’s dielectric properties. PEF, an external stimulus or stress, is proposed
as a promising new abiotic elicitor for stimulating secondary metabolites biosynthesis in plant cell cultures. 相似文献
585.
Gratz SR Ciolino LA Mohrhaus AS Gamble BM Gracie JM Jackson DS Roetting JP McCauley HA Heitkemper DT Fricke FL Krol WJ Arsenault TL White JC Flottmeyer MM Johnson YS 《Journal of AOAC International》2011,94(5):1601-1616
A rapid, sensitive, and accurate method for the screening and determination of polycyclic aromatic hydrocarbons (PAHs) in edible seafood is described. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction and HPLC with fluorescence detection (FLD). The method was developed and validated in response to the massive Deepwater Horizon oil spill in the Gulf of Mexico. Rapid and highly sensitive PAH screening methods are critical tools needed for oil spill response; they help to assess when seafood is safe for harvesting and consumption. Sample preparation involves SPE of edible seafood portions with acetonitrile, followed by the addition of salts to induce water partitioning. After centrifugation, a portion of the acetonitrile layer is filtered prior to analysis via HPLC-FLD. The chromatographic method uses a polymeric C18 stationary phase designed for PAH analysis with gradient elution, and it resolves 15 U.S. Environmental Protection Agency priority parent PAHs in fewer than 20 min. The procedure was validated in three laboratories for the parent PAHs using spike recovery experiments at PAH fortification levels ranging from 25 to 10 000 microg/kg in oysters, shrimp, crab, and finfish, with recoveries ranging from 78 to 99%. Additional validation was conducted for a series of alkylated homologs of naphthalene, dibenzothiophene, and phenanthrene, with recoveries ranging from 87 to 128%. Method accuracy was further assessed based on analysis of National Institute of Standards and Technology Standard Reference Material 1974b. The method provides method detection limits in the sub to low ppb (microg/kg) range, and practical LOQs in the low ppb (microg/kg) range for most of the PAH compounds studied. 相似文献
586.
Inga M. Aladzheva Dmitrii I. Lobanov Ol'ga V. Bykhovskaya Pavel V. Petrovskii Konstantin A. Lyssenko Tatyana A. Mastryukova 《Heteroatom Chemistry》2003,14(7):596-602
A novel facile one‐pot synthesis of the 1,2‐azaphospholanes by intramolecular alkylation of 3‐halopropyl amides of tricoordinate phosphorus has been suggested. Using this method, a series of the differently N‐substituted 1,2‐azaphospholanium salts were synthesized. 3‐Aminopropylphosphine oxides were obtained by hydrolysis of the salts. A probable mechanism of the 1,2‐azaphospholanium salts formation is discussed. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:596–602, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10209 相似文献
587.
588.
Stanislav I. Klenin Inga A. Baranovskaya Vladimir O. Aseyev 《Macromolecular Symposia》1996,106(1):205-217
High molecular weight polyelectrolyte: poly(dimethylaminoethyl methacrylate) [PDMAEMA] with molecular weights MW = 28.0×106, 20.0×106, 15.0×106 was investigated in dilute solution by light scattering, flow birefringence and viscometry (at different rate gradients) in a water-acetone system by varying the weight fraction of acetone r in the mixture. At r=0.76 the polymer undergoes a reversible coil-globule transition accompanied by a drastic decrease in intrinsic viscosity [n], mean-square radius of gyration R2z1/2 and second virial coefficient A2, with no change in molecular weight. The coil asymmetry parameter p (p=2.5 at r=0.50) decreases with increasing r and attains unity (completely symmetrical particle) at the transition point (r=0.76). The anomalous behavior of the viscosity of PDMAEMA-water-acetone solutions, detected near the transition point (r=0.6+0.7), is interpreted by formation of local knots of compactization on the molecular chain under the influence of a hydrodynamic field. 相似文献
589.
Martin Maiwald Jrg Fricke Arnim Ginolas Johannes Pohl Bernd Sumpf Gtz Erbert Günther Trnkle 《Laser \u0026amp; Photonics Reviews》2013,7(4):L30-L33
A dual‐wavelength monolithic Y‐branch distributed Bragg reflection (DBR) diode laser at 671 nm is presented. The device is realized with deeply etched surface DBR gratings by one‐step epitaxy. A maximum optical output power of 110 mW is obtained in cw‐operation for each laser cavity. The emission wavelengths of the device are 670.5 nm and 671.0 nm with a spectral width of 13 pm (0.3 cm−1) and a mean spectral distance of 0.46 nm (10.2 cm−1) over the whole operating range. Together with a free running power stability of ± 1.1% this most compact diode laser is ideally suited as an excitation light source for portable shifted excitation Raman difference spectroscopy (SERDS). 相似文献