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991.
K. Totsuka 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):705-717
Novel massive quantum states appearing in spin chains under a strong magnetic field are discussed. These states lead to plateaus in magnetization
curves. When the systems are axially symmetric and the field is applied parallel to the symmetry-axis, the phenomena are analogous
to metal-insulator transitions. Striking features of the plateau phenomena - exactness and rationality - are explained as
consequences the commensurability condition to the underlying lattice. The effects of the planar anisotropy are also discussed
in detail.
Received: 16 February 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
992.
I. P. Smorchkova J. M. Kikkawa N. Samarth D. D. Awschalom 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
Magneto-transport and magneto-optical probes are used to interrogate spin-dependent transport in magnetic heterostructures wherein a two dimensional electron gas (2DEG) is exchange-coupled to local moments. At low temperatures, the significant s–d exchange-enhanced spin splitting in these “magnetic” 2DEGs is responsible for the observation of unusual transport properties such as a complete spin polarization of the gas at large Landau level filling factors and a pronounced, non-monotonic background magneto-resistance. Magneto-transport measurements of gated samples performed in a parallel field geometry are used to systematically study the variation of the magneto-resistance with sheet concentration, yielding new insights into the dependence of spin transport on the Fermi energy of the majority spin carriers. 相似文献
993.
M A Brown 《Magnetic resonance imaging》1985,3(1):3-10
Paramagnetic metal ions have shown promise as contrast agents for nuclear magnetic resonance (NMR) imaging. Their ability depends upon modification of the relaxation times (T1 and T2) through dipolar interactions. These interactions cause the effectiveness of the agents to be sensitive to the operating magnetic field. Studies are presented of the operating field dependence (frequency dispersion) of two metal-chelate complexes, Gd+3-ethylenediaminetetraacetate (EDTA) and Mn+2-EDTA, in a physiologically balanced electrolyte solution. Inversion recovery experiments were performed on two concentrations of each metal-chelate complex at five resonant frequencies. The frequency dispersion curves were similar in appearance for those of the corresponding aqueous solutions. The Mn+2 complex showed no unusual concentration effects. The Gd+3 complex showed an unexpected concentration dependence in the dispersion behavior. This is attributed to a difference in the dipolar correlation time between the two solutions. With its unique correlation time in electrolyte solutions, predictions of relaxation rate changes in studies in vivo may be easier for the Mn+2-EDTA complex. 相似文献
994.
Gd2O3 particles (less than 2 microns) in suspension were evaluated as a potential contrast agent for liver-spleen imaging with magnetic resonance. The agent was administered IV to rabbits in doses ranging from 10 to 120 mumol/kg and the tissues removed after sacrifice for in vitro T1 and T2 analysis. The temporal response was determined in liver and spleen samples of rabbits given a fixed dose (60 mumol/kg) and sacrificed at intervals from 15 min to 60 hr later. Documentation of the subanatomic location of Gd2O3 particles in tissue was accomplished by electron microscopy and x-ray dispersion microanalysis. T1 weighted images were obtained at 0.12T on a prototype resistive scanner. The liver, spleen, and lung relaxation times are very responsive to Gd2O3 IV and the effect is dose related. A peak effect is observed between 3-7 hr after injection and relaxation times may normalize by 60 hr. By electron microscopic and x-ray analysis, Gd2O3 is most prominently found in the hepatic and splenic sinusoids. The images show marked enhancement of liver and splenic tissues, aiding in the clear delineation of these tissues from neighboring structures. 相似文献
995.
The results of a time-of-flight experiment are presented, in which the total cross-sections for 2–400 eV positrons on H2, D2, N2, and CO were measured.
Paper F7 presented at 3rd Internat'l. Conf. Positron Annihilation. Otaniemi, Finland (August 1973). 相似文献
996.
Lyubimov AV Carr SN Brown AP Art JJ Crowell JA Levine BS 《Journal of photochemistry and photobiology. B, Biology》2005,80(3):225-234
The knowledge of intracellular spatial distribution of pH in prostates in animal models reflective of human prostate may have implications for drug development upon pH dependent drug delivery and activity. Freshly dissected prostate tissues (in vitro) or the entire prostate gland (in vivo) were loaded with fluorescent dyes and viewed using confocal microscopy. Images were initially taken in tissues perfused with RPMI-1640 medium. Calibration in situ was performed with high potassium buffers of known pH containing nigericin. Acetoxymethyl ester carboxy-SNARF-1 was visible in epithelial cells (but not stroma) in rat and dog prostates. The pH of lysosomes in prostate epithelial cells was 5.2 as determined by fluorescence of Lyso Sensor Green DND-189. A method of in situ confirmation of tissue viability was developed by a secondary loading and visualization of the BCECF fluorescent dye. Besides the direct measurement of the pH in rat and dog tissues (pH ≈ 7.0), a method of pH measurement in prostate tissue (rather than in cell culture) was developed. 相似文献
997.
The combination of headspace solid phase microextraction (HS-SPME) [1] with fast chromatographic pre-separation by means of multi-capillary columns (MCC) coupled to an ion mobility spectrometer equipped with a 10.6 eV photoionisation source was applied to rapid on-site monitoring of ground and surface water contaminations. Under field conditions, water contaminants were directly detectable down to the upper g/L range. The potential of the developed method is illustrated by measurements of BTEX, naphthalene, chlorinated alkenes and chlorinated benzenes in water. Practical results from investigations of contaminated groundwater at a former gasworks site and groundwater from the site of a metal processing plant, focusing on the key substances benzene, naphthalene and tetrachloroethene, demonstrate the feasibility of the system for field studies.Dedicated to the memory of Wilhelm Fresenius. One of the authors (D. Klockow) feels very much indebeted to Prof. Fresenius because of the steady support and advice he received through him, as a professional and as a private person. 相似文献
998.
Density,viscosity, conductance,and transference number of concentrated aqueous magnesium chloride at 25°C 总被引:1,自引:0,他引:1
The density, viscosity, conductance, and transference number of aqueous magnesium chloride at 298.15°K are reported for the concentration range 0 to 5.7m. The transference numbers were determined using the emf method. It was found that the viscosity, conductance, and transference number of aqueous magnesium chloride are similar to those for aqueous nickel chloride. It was therefore tentatively concluded that incomplete dissociation and complex formation was unlikely to be of importance in nickel chloride solutions. 相似文献
999.
J. W. F. Dorleijn W. F. Druyvesteyn 《Applied Physics A: Materials Science & Processing》1973,1(3):167-169
In the bubble collapse technique the domain wall mobility is evaluated by measuring the shortest time for which a magnetic
bubble collapses. The way in which this evaluation should be carried out is discussed. 相似文献
1000.
N D Sen Gupta 《Pramana》1973,1(4):165-171
The phenomenon of magnetic resonance is studied by considering the transverse oscillatory field as superposition of two oppositely
rotating fields. One of the rotating fields is taken as strong and the other relatively weak. 相似文献