3,690 research outputs found
The state space of short-range Ising spin glasses: the density of states
The state space of finite square and cubic Ising spin glass models is
analysed in terms of the global and the local density of states. Systems with
uniform and gaussian probability distribution of interactions are compared.
Different measures for the local state density are presented and discussed. In
particular the question whether the local density of states grows exponentially
or not is considered. The direct comparison of global and local densities leads
to consequences for the structure of the state space.Comment: 18 pages (including 6 figures); submitted to Z.f.Physik
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots
We report on the development and testing of a coplanar stripline antenna that
is designed for integration in a magneto-photoluminescence experiment to allow
coherent control of individual electron spins confined in single self-assembled
semiconductor quantum dots. We discuss the design criteria for such a structure
which is multi-functional in the sense that it serves not only as microwave
delivery but also as electrical top gate and shadow mask for the single quantum
dot spectroscopy. We present test measurements on hydrogenated amorphous
silicon, demonstrating electrically detected magnetic resonance using the
in-plane component of the oscillating magnetic field created by the coplanar
stripline antenna necessary due to the particular geometry of the quantum dot
spectroscopy. From reference measurements using a commercial electron spin
resonance setup in combination with finite element calculations simulating the
field distribution in the structure, we obtain an average magnetic field of
~0.2mT at the position where the quantum dots would be integrated into the
device. The corresponding pi-pulse time of ~0.3us fully meets the requirements
set by the high sensitivity optical spin read-out scheme developed for the
quantum dot
Quasi-two-dimensional Fermi surfaces of the heavy-fermion superconductor CePdIn
We report low-temperature de Haas-van Alphen (dHvA) effect measurements in
magnetic fields up to 35 T of the heavy-fermion superconductor CePdIn.
The comparison of the experimental results with band-structure calculations
implies that the 4 electrons are itinerant rather than localized. The
cyclotron masses estimated at high field are only moderately enhanced, 8 and 14
, but are substantially larger than the corresponding band masses. The
observed angular dependence of the dHvA frequencies suggests
quasi-two-dimensional Fermi surfaces in agreement with band-structure
calculations. However, the deviation from ideal two dimensionality is larger
than in CeCoIn, with which CePdIn bears a lot of similarities. This
subtle distinction accounts for the different superconducting critical
temperatures of the two compounds.Comment: accepted to Phys. Rev.
Influence of body water distribution on skin thickness: measurements using high-frequency ultrasound
Reliable quantification of 1,2-dihydroxynaphthalene in urine using a conjugated reference compound for calibration.
After environmental and occupational exposure to naphthalene, 1,2-dihydroxynaphthalene (1,2-DHN) was shown to be one major metabolite in human naphthalene metabolism. However, the instability of free 1,2-DHN complicates the reliable determination of this promising biomarker in urine. To solve this stability problem, glucuronide conjugates of 1,2-DHN and the corresponding isotopically labelled D-6-1,2-dihydroxynaphthalene (D-6-1,2-DHN) were synthesised and applied as reference material and internal standard in a gas chromatographic-tandem mass spectrometric (GC-MS/MS) method. The determination of 1- and 2-naphthol (1-MHN, 2-MHN) was included in the procedure to enable a comprehensive assessment of naphthalene metabolism and exposure. The results of the validation showed a high reliability and sensitivity of the method. The detection limits range from 0.05 to 0.16 mu g/L. Precision and repeatability were determined to range from 1.4 to 6.6% for all parameters. The simultaneous determination of 1- and 2-MHN as additional parameters besides 1,2-DHN enables the application of the method for further metabolism and kinetic studies on naphthalene. The use of glucuronide-derivative reference substances and the application of structurally matched isotopic-labelled internal standards for each substance guarantee a reliable quantification of the main naphthalene metabolites 1,2-DHN and 1- and 2-MHN
A Review of the Biology, Ecology and Behavior of Velvety Tree Ants of North America
Ants belonging to the genus Liometopum are regionally distributed across North America, Europe and Asia. L. apiculatum Mayr, L. luctuosum Wheeler, and L. occidentale Emery are found in western North America and are referred to as velvety tree ants. Very little is known about the biology of these species, but they are similar. They are typically associated with trees and shrubs and are frequently found tending hemipterans. All three species are are easily disturbed and and resort to highly aggressive behaviors including the use of strong alarm odors. The following review is intended to summarize the literature regarding the biology and control of these species. Special emphasis has been given to factors that might be important in their control and gaps in our current knowledge
A Review of the Biology, Ecology and Behavior of Velvety Tree Ants of North America
Ants belonging to the genus Liometopum are regionally distributed across North America, Europe and Asia. L. apiculatum Mayr, L. luctuosum Wheeler, and L. occidentale Emery are found in western North America and are referred to as velvety tree ants. Very little is known about the biology of these species, but they are similar. They are typically associated with trees and shrubs and are frequently found tending hemipterans. All three species are are easily disturbed and and resort to highly aggressive behaviors including the use of strong alarm odors. The following review is intended to summarize the literature regarding the biology and control of these species. Special emphasis has been given to factors that might be important in their control and gaps in our current knowledge.</span
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