78,277 research outputs found
Spontaneous formation of a chiral (Mo2O2S2)2+-based cluster driven by dimeric {Te2O6}-based templates
Utilization of [Mo2S2O2(H2O)6]2+ and a tellurite anion led to the formation of three new clusters, 1–3, with unique structural features. The tellurite anion not only templated the formation of [(Mo2O2S2)4(TeO3)(OH)9]3− 1 and [(Mo2O2S2)12(TeO3)4(TeO4)2 (OH)18]10− 3, but also the in situ generation of two different types of dimeric {Te2O6} based moieties induced the spontaneous assembly of the chiral [(Mo2O2S2)10(TeO3)(Te2O6)2(OH)18]8− anionic cluster, 2
Nonperiodic Flux to Voltage Conversion of an Arithmetic Series Array of dc SQUIDs
A theoretical study on the voltage response function of a series array of
dc SQUIDs is presented in which the elementary dc SQUID loops vary in size and,
possibly, in orientation. Such series arrays of two-junction SQUIDs possess
voltage response functions vs. external magnetic field B that differ
substantially from those of corresponding regular series arrays with identical
loop-areas, while maintaining a large voltage swing as well as a low noise
level. Applications include the design of current amplifiers and quantum
interference filters.Comment: 3 pages, 3 figure
Anisotropic Superconducting Properties of MgB2 Single Crystals
In-plane electrical transport properties of MgB2 single crystals grown under
high pressure of 4-6 GPa and temperature of 1400-1700oC in Mg-B-N system have
been measured. For all specimens we found sharp superconducting transition
around 38.1-38.3K with transition width within 0.2-0.3K. Estimated resistivity
value at 40K is about 1 mkOhmcm and resistivity ratio R(273K)/R(40K) of about
4.9. Results of measurements in magnetic field up to 5.5T perpendicular to Mg
and B planes and up to 9T in parallel orientation show temperature dependent
anisotropy of the upper critical field with anisotropy ratio increasing from
2.2 close to Tc up to about 3 below 30K. Strong deviation of the angular
dependence of Hc2 from anisotropic mass model has been also found.Comment: 10pages, including 5 figures,submitted to Physica C (in press
Electronic redistribution around oxygen atoms in silicate melts by ab initio molecular dynamics simulation
The structure around oxygen atoms of four silicate liquids (silica, rhyolite,
a model basalt and enstatite) is evaluated by ab initio molecular dynamics
simulation. Thanks to the use of maximally localized Wannier orbitals to
represent the electronic ground state of the simulated system, one is able to
quantify the redistribution of electronic density around oxygen atoms as a
function of the cationic environment and melt composition. It is shown that the
structure of the melt in the immediate vicinity of the oxygen atoms modulates
the distribution of the Wannier orbitals associated with oxygen atoms. In
particular the evaluation of the distances between the oxygen-core and the
orbital Wannier centers and their evolution with the nature of the cation
indicates that the Al-O bond in silicate melts is certainly less covalent than
the Si-O bond while for the series Mg-O, Ca-O, Na-O and K-O the covalent
character of the M-O bond diminishes rapidly to the benefit of the ionic
character. Furthermore it is found that the distribution of the oxygen dipole
moment coming from the electronic polarization is only weakly dependent on the
melt composition, a finding which could explain why some empirical force fields
can exhibit a high degree of transferability with melt composition.Comment: 27 pages, 7 figures. To be published in Journal of Non-Crystalline
Solid
The Nernst effect in high- superconductors
The observation of a large Nernst signal in an extended region above
the critical temperature in hole-doped cuprates provides evidence that
vortex excitations survive above . The results support the scenario that
superfluidity vanishes because long-range phase coherence is destroyed by
thermally-created vortices (in zero field), and that the pair condensate
extends high into the pseudogap state in the underdoped (UD) regime. We present
a series of measurements to high fields which provide strong evidence for
this phase-disordering scenario.Comment: 21 pages, 28 figure
F-wave versus P-wave Superconductivity in Organic Conductors
Current experimental results suggest that some organic quasi-one-dimensional
superconductors exhibit triplet pairing symmetry. Thus, we discuss several
potential triplet order parameters for the superconducting state of these
systems within the functional integral formulation. We compare weak spin-orbit
coupling , , and symmetries via several thermodynamic
quantities. For each symmetry, we analyse the temperature dependences of the
order parameter, condensation energy, specific heat, and superfluid density
tensor.Comment: 5 pages, 4 figure
Drainage of a nanoconfined simple fluid: rate effects on squeeze-out dynamics
We investigate the effect of loading rate on drainage in molecularly thin
films of a simple fluid made of quasi-spherical molecules
(octamethylcyclotetrasiloxane, OMCTS). We find that (i) rapidly confined OMCTS
retains its tendency to organize into layers parallel to the confining
surfaces, and (ii) flow resistance in such layered films can be described by
bulklike viscous forces if one accounts for the existence of one monolayer
immobilized on each surfaces. The latter result is fully consistent with the
recent work of Becker and Mugele, who reached a similar conclusion by analyzing
the dynamics of squeeze-out fronts in OMCTS [T. Becker and F. Mugele, Phys.
Rev. Lett. {\bf 91} 166104(2003)]. Furthermore, we show that the confinement
rate controls the nature of the thinning transitions: layer-by-layer expulsion
of molecules in metastable, slowly confined films proceeds by a
nucleation/growth mechanism, whereas deeply and rapidly quenched films are
unstable and undergo thinning transitions akin to spinodal decomposition
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