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1.
Knobbe N Vogl J Pritzkow W Panne U Fry H Lochotzke HM Preiss-Weigert A 《Analytical and bioanalytical chemistry》2006,386(1):104-108
The stable carbon and nitrogen isotopic composition of urine and milk samples from cattle under different feeding regimes
were analysed over a period of six months. The isotope ratios were measured with isotope ratio mass spectrometry (IRMS). The
δ
13C values of milk and urine were dependent on different feeding regimes based on C3 or C4 plants. The δ
13C values are more negative under grass feeding than under maize feeding. The δ
13C values of milk are more negative compared to urine and independent of the feeding regime. Under grass feeding the analysed
milk and urine samples are enriched in 13C relative to the feed, whereas under maize feeding the 13C/12C ratio of urine is in the same range and milk is depleted in 13C relative to the diet. The difference between the 15N/14N ratios for the two feeding regimes is less pronounced than the 13C/12C ratios. The δ
15N values in urine require more time to reach the new equilibrium, whereas the milk samples show no significant differences
between the two feeding regimes. 相似文献
2.
The effects of high-energy electron beam and pulsed excimer laser irradiation on the magnetic properties of Fe80B20 amorphous alloy are investigated by means of transmission and conversion electron Mössbauer spectroscopy (CEMS) and scanning electron microscopy (SEM). Both types of irradiation were found to induce changes in the magnetic anisotropy of Fe80B20, but the influence of high-energy electron beam irradiation was weaker. Depending on the number of applied laser pulses and repetition rate, controlled magnetic anisotropy and/or relaxation of internal stresses could be obtained by excimer laser irradiation. The presence of molten zones subsequently solidified and of laser-induced internal stresses supports the model of closúre domain structure. 相似文献
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5.
Dou K. Knobbe E.T. Parkhill R.L. Irwin B. Matthews L. Church K.H. 《Applied Physics A: Materials Science & Processing》2003,76(3):303-307
Surface structuring and compositioning in aluminum alloy 2024-T3 were demonstrated using a femtosecond pulse laser. Surface
nanostructuring was developed as a function of laser parameters and the surface micrographs of the scanning electron microscopy
were characterized as a function of incident laser fluence. Surface compositioning was performed by selectively removing the
elements on the surface of the sample. Femtosecond studies of highly excited electrons were performed by a pump–probe technique,
and the thermalization time was found to be in a range of 1.5–3 ps, increasing with incident fluence. The time-resolved measurement
is well matched to the numerical calculation.
Received: 6 September 2001 / Accepted: 18 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. Fax: +1-405/744-6811, E-mail: dou@okstate.edu 相似文献
6.
H. C. J. Hoefsloot H. W. Hoogstraten L. P. B. M. Janssen J. W. Knobbe 《Applied Scientific Research》1992,49(2):161-173
The neutral-stability analysis presented by Hoefsloot et al. [3] is completed by computing the growth factorsβ for the normal modes and by showing that the neutral states (Re(β)=0) are stationary (Im(β)=0) rather than oscillatory (Im(β)≠0). 相似文献
7.
Although confocal fluorescence microscopes are widely used in biology and have been proven to be promising diagnostic tools in dermatologic diagnostics, they are at present uncommon in medical practice. This is mainly due to high costs of acquisition and their large and complex outline. With the integration of a MEMS scanner we present a demonstration system of a confocal fluorescence laser scanning microscope which is affordable and portable. It has a field of view of 500 μm × 500 μm and is mainly composed of off-the-shelf components. 相似文献
8.
V.A. Guzenko A. Bringer J. Knobbe H. Hardtdegen Th. Schäpers 《Applied Physics A: Materials Science & Processing》2007,87(3):577-584
An overview is given on the Rashba effect in GaxIn1-xAs/InP quantum wires. First, the effect of Rashba spin–orbit coupling on the energy level spectrum of quantum wires with different
shapes of the confining potential is theoretically investigated. The wave functions as well as the spin densities in the quantum
wire are analyzed for different magnetic fields. It is found that, owing to the additional geometrical confinement, a modification
of the characteristic beating pattern in the magnetoresistance can be expected. The theoretical findings are compared to measurements
on two different types of wires: First, single wires and, second, sets of parallel wires. A characteristic beating pattern
in the Shubnikov–de Haas oscillations is observed for wires with an effective width down to approximately 400 nm. The beating
pattern is significantly better resolved for the samples with sets of parallel wires, owing to the effective suppression of
conductance fluctuations. A comparison with theoretical simulations confirms that the strength of the Rashba effect is basically
not affected by the geometrical confinement of the wires. However, for wires with a very small effective width the strong
carrier confinement leads to a suppression of the characteristic beating pattern in the Shubnikov–de Haas oscillations.
PACS 71.70.Ej; 73.63.-b; 71.70.Di 相似文献
9.
H. C. J. Hoefsloot H. W. Hoogstraten L. P. B. M. Janssen J. W. Knobbe 《Applied Scientific Research》1992,49(1):161-173
The neutral-stability analysis presented by Hoefsloot et al. [3] is completed by computing the growth factors for the normal modes and by showing that the neutral states (Re()=0) are stationary (Im()=0) rather than oscillatory (Im()0). 相似文献
10.
V.A. Guzenko Th. Schpers K.M. Indlekofer J. Knobbe 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):333
Magnetotransport properties of quasi-one-dimensional (quasi-1D) quantum wires based on InGaAs/InP heterojunctions were studied. The influence of the wire width as well as of the temperature on the weak antilocalization was investigated. A crossover from the weak antilocalization to the weak localization regime was observed in the very narrow wires. The analysis of the characteristic scattering lengths suggests a strong effect of the electron confinement and diffusive boundary scattering on the suppression of the weak antilocalization. 相似文献