8,727 research outputs found
Resistojet systems studies directed to the space station/space base. Volume 2 - Biowaste resistojet system development program Final report
Space station/base biowaste resistojet system for orbit keeping and control moment gyro desaturation - systems developmen
Non-Fermi liquid behavior in nearly charge ordered layered metals
Non-Fermi liquid behavior is shown to occur in two-dimensional metals which
are close to a charge ordering transition driven by the Coulomb repulsion. A
linear temperature dependence of the scattering rate together with an increase
of the electron effective mass occur above T*, a temperature scale much smaller
than the Fermi temperature. It is shown that the anomalous temperature
dependence of the optical conductivity of the quasi-two-dimensional organic
metal alpha-(BEDT-TTF)2MHg(SCN)4, with M=NH4 and Rb, above T*=50-100 K, agrees
qualitatively with our predictions for the electronic properties of nearly
charge ordered two-dimensional metals.Comment: accepted in Phys. Rev. Let
Low-energy renormalization of the electron dispersion of high-T superconductors
High-resolution ARPES studies in cuprates have detected low-energy changes in
the dispersion and absorption of quasi-particles at low temperatures, in
particular, in the superconducting state. Based on a new 1/N expansion of the
t-J-Holstein model, which includes collective antiferromagnetic fluctuations
already in leading order, we argue that the observed low-energy structures are
mainly caused by phonons and not by spin fluctuations, at least, in the optimal
and overdoped regime.Comment: 6 pages, 3 figure
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Self-immolative linkers in polymeric delivery systems
There has been significant interest in the methodologies of controlled release for a diverse range of applications spanning drug delivery, biological and chemical sensors, and diagnostics. The advancement in novel substrate-polymer coupling moieties has led to the discovery of self-immolative linkers. This new class of linker has gained popularity in recent years in polymeric release technology as a result of stable bond formation between protecting and leaving groups, which becomes labile upon activation, leading to the rapid disassembly of the parent polymer. This ability has prompted numerous studies into the design and development of self-immolative linkers and the kinetics surrounding their disassembly. This review details the main concepts that underpin self-immolative linker technologies that feature in polymeric or dendritic conjugate systems and outlines the chemistries of amplified self-immolative elimination
Spin exchange and superconductivity in a model for two-dimensional quarter-filled systems
The effect of antiferromagnetic spin fluctuations on two-dimensional
quarter-filled systems is studied theoretically. An effective model on
a square lattice which accounts for checkerboard charge fluctuations and
next-nearest-neighbors antiferromagnetic spin fluctuations is considered. From
calculations based on large-N theory on this model it is found that the
exchange interaction, , increases the attraction between electrons in the
d channel only, so that both charge and spin fluctuations work
cooperatively to produce d pairing.Comment: 9 pages, 6 figure
INFLUENCE OF BED ROUGHNESS AND CROSS SECTION GEOMETRY ON MEDIUM AND MAXIMUM VELOCITY RATIO IN OPEN CHANNEL FLOW
The paper deals with the analytic-theoretical derivation of the relationships between the entropic quantity Φ(M), representing the ratio between the mean and maximum flow velocity, and the relative submergence and aspect ratio, using classical open channel flow equations. Φ(M) is found to be highly dependent on the relative submergence when large or intermediate roughness scale occur, while it might be assumed almost constant for a small roughness scale. Furthermore, considering the hydraulic geometry relationships, it is attempted to relate the relative submergence to the aspect ratio of flow through a log-relationship whose coefficients depend on the local bed slope, with an important implication for hydrological practices. Then, a practical relation between Φ(M) and aspect ratio is proposed and validated in the operative chain for discharge assessment, showing high robustness and stability. The proposed model has been applied to a set of experimental velocity data collected in gaged river sites with different geometric and hydraulic characteristics as well as low, medium and high flows
Magnetic Reconnection and Intermittent Turbulence in the Solar Wind
A statistical relationship between magnetic reconnection, current sheets and
intermittent turbulence in the solar wind is reported for the first time using
in-situ measurements from the Wind spacecraft at 1 AU. We identify
intermittency as non-Gaussian fluctuations in increments of the magnetic field
vector, , that are spatially and temporally non-uniform. The
reconnection events and current sheets are found to be concentrated in
intervals of intermittent turbulence, identified using the partial variance of
increments method: within the most non-Gaussian 1% of fluctuations in
, we find 87%-92% of reconnection exhausts and 9% of current
sheets. Also, the likelihood that an identified current sheet will also
correspond to a reconnection exhaust increases dramatically as the least
intermittent fluctuations are removed from the dataset. Hence, the turbulent
solar wind contains a hierarchy of intermittent magnetic field structures that
are increasingly linked to current sheets, which in turn are progressively more
likely to correspond to sites of magnetic reconnection. These results could
have far reaching implications for laboratory and astrophysical plasmas where
turbulence and magnetic reconnection are ubiquitous.Comment: 5 pages, 3 figures, submitted to Physical Review Letter
Scanning and data extraction from crop collecting mission documents
Poster presented at TDWG 2009, Montpellier (France). 9 - 13 Nov 2009
Dynamics of Phase Transitions in Asymmetric Nuclear Matter
We present several possibilities offered by the reaction dynamics of
dissipative heavy ion collisions to study in detail the symmetry term of the
nuclear equation of state, . In particular we discuss isospin effects on
the nuclear liquid-gas phase transition, {\it Isospin Distillation}, and on
collective flows. We stress the importance of a microscopic relativistic
structure of the effective interaction in the isovector channel. The
possibility of an {\it early} transition to deconfined matter in high isospin
density regions is also suggested. We finally select {\it Eleven} observables,
in different beam energy regions, that appear rather sensitive to the isovector
part of the nuclear , in particular in more exclusive experiments.Comment: 8 pages, 7 figures, ISPUN02 Conference, Halong-Vietnam, Nov.20-25
2002, to appear in Nucl.Phys.A. Elsevier Proceedings Styl
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