2,294 research outputs found
Josephson squelch filter for quantum nanocircuits
We fabricated and tested a squelch circuit consisting of a copper powder
filter with an embedded Josephson junction connected to ground. For small
signals (squelch-ON), the small junction inductance attenuates strongly from DC
to at least 1 GHz, while for higher frequencies dissipation in the copper
powder increases the attenuation exponentially with frequency. For large
signals (squelch-OFF) the circuit behaves as a regular metal powder filter. The
measured ON/OFF ratio is larger than 50dB up to 50 MHz. This squelch can be
applied in low temperature measurement and control circuitry for quantum
nanostructures such as superconducting qubits and quantum dots.Comment: Corrected and completed references 6,7,8. Updated some minor details
in figure
Knotted Solitons in a Charged Two-Condensate Bose System
By making use of the decomposition of U(1) gauge potential theory and the
\phi mapping method, we propose that a charged two-condensate Bose system
possesses vortex lines and two classes of knotted solitons. The topological
charges of the vortex lines are characterized by the Hopf indices and the
Brower degrees of \phi-mapping, and the knotted solitons are described by the
nontrivial Hopf invariant and the BF action, respectively.Comment: 12 pages,0 figure
Mutation Analysis of the CYP21A2 Gene in the Iranian Population
Background: Defects in the CYP21A2 gene cause steroid 21-hydroxylase deficiency, which is the most frequent cause of congenital adrenal hyperplasia. Forty four affected families were investigated to identify the mutation spectrum of the CYP21A2 gene. Methods: Families were subjected to clinical, biochemical, and molecular analyses. Allele-specific polymerase chain reaction amplification was used for eight common mutations followed by dosage analysis to exclude CYP21A2 deletions. Results: The most frequent mutations detected were gene deletions and chimera (31.8). Other mutation frequencies were as follows: Q318X, 15.9; I2G, 14.8; I172N, 5.8; gene duplication, 5.7; R356W, 8; and E6 cluster mutations, 2.3. Direct sequencing of the CYP21A2 gene revealed R316X, P453S, c.484insT, and a change at the start codon. Different modules carried by patients were classified into five different haplotypes. The genotype phenotype correlation (positive predictive value) for group null, A, B, and C were 92.3, 85.7, 100, and 0, respectively. Conclusions: Methods used will be helpful for carrier detection and antenatal diagnosis, especially with inclusion of the multiplex ligation probe dependent amplification technique, which is easier for routine tests in comparison with other methods. Mutation frequencies indicate that Iranians are possible descendants of Asians and Europeans
Spacetime Covariant Form of Ashtekar's Constraints
The Lagrangian formulation of classical field theories and in particular
general relativity leads to a coordinate-free, fully covariant analysis of
these constrained systems. This paper applies multisymplectic techniques to
obtain the analysis of Palatini and self-dual gravity theories as constrained
systems, which have been studied so far in the Hamiltonian formalism. The
constraint equations are derived while paying attention to boundary terms, and
the Hamiltonian constraint turns out to be linear in the multimomenta. The
equivalence with Ashtekar's formalism is also established. The whole constraint
analysis, however, remains covariant in that the multimomentum map is evaluated
on {\it any} spacelike hypersurface. This study is motivated by the
non-perturbative quantization program of general relativity.Comment: 22 pages, plain Tex, no figures, accepted for publication in Nuovo
Cimento
Conformal Einstein equations and Cartan conformal connection
Necessary and sufficient conditions for a space-time to be conformal to an
Einstein space-time are interpreted in terms of curvature restrictions for the
corresponding Cartan conformal connection
Equivalence problem for the orthogonal webs on the sphere
We solve the equivalence problem for the orthogonally separable webs on the
three-sphere under the action of the isometry group. This continues a classical
project initiated by Olevsky in which he solved the corresponding canonical
forms problem. The solution to the equivalence problem together with the
results by Olevsky forms a complete solution to the problem of orthogonal
separation of variables to the Hamilton-Jacobi equation defined on the
three-sphere via orthogonal separation of variables. It is based on invariant
properties of the characteristic Killing two-tensors in addition to properties
of the corresponding algebraic curvature tensor and the associated Ricci
tensor. The result is illustrated by a non-trivial application to a natural
Hamiltonian defined on the three-sphere.Comment: 32 page
On certain relationships between cosmological observables in the Einstein-Cartan gravity
We show that in the Einstein-Cartan gravity it is possible to obtain a
relation between Hubble's expansion and the global rotation (vorticity) of the
Universe. Gravitational coupling can be reduced to dimensionless quantity of
order unity, fixing the scalar mass density and the resulting negative
cosmological constant at spacelike infinity. Current estimates of the expansion
and rotation (see also astro-ph/9703082) of the Universe favour the massive
spinning particles as candidate particles for cold and hot dark matter. Nodland
and Ralston vorticity (Phys. Rev. Lett. 78 (1997) 3043) overestimates the value
favoured by the Einstein-Cartan gravity for three orders of magnitude.Comment: 7 pages, LaTeX styl
Space-time defects and teleparallelism
We consider the class of space-time defects investigated by Puntigam and
Soleng. These defects describe space-time dislocations and disclinations
(cosmic strings), and are in close correspondence to the actual defects that
arise in crystals and metals. It is known that in such materials dislocations
and disclinations require a small and large amount of energy, respectively, to
be created. The present analysis is carried out in the context of the
teleparallel equivalent of general relativity (TEGR). We evaluate the
gravitational energy of these space-time defects in the framework of the TEGR
and find that there is an analogy between defects in space-time and in
continuum material systems: the total gravitational energy of space-time
dislocations and disclinations (considered as idealized defects) is zero and
infinit, respectively.Comment: 22 pages, no figures, to appear in the Class. Quantum Gravit
Massive Electrodynamics and Magnetic Monopoles
Including torsion in the geometric framework of the Weyl-Dirac theory we
build up an action integral, and obtain from it a gauge covariant (in the Weyl
sense) general relativistic massive electrodynamics. Photons having an
arbitrary mass, electric, and magnetic currents (Dirac's monopole) coexist
within this theory. Assuming that the space-time is torsionless, taking the
photons mass zero, and turning to the Einstein gauge we obtain Maxwell's
electrodynamics.Comment: LaTex File, 9 pages, no figure
Erratum: Linearly polarized probes of surface chirality [J. Chem. Phys. 103, 8296 (1995)]
We present a new nonlinear optical technique to study surface chirality. We demonstrate experimentally that the efficiency of second‐harmonic generation from isotropic chiral surfaces is different for excitation with fundamental light that is +45° and −45° linearly polarized with respect to the p‐polarized direction
- …