12,349 research outputs found
Motion of Vacancies in a Pinned Vortex Lattice: Origin of the Hall Anomaly
Physical arguments are presented to show that the Hall anomaly is an effect
of the vortex many-body correlation rather than that of an individual vortex.
Quantitatively, the characteristic energy scale in the problem, the vortex
vacancy formation energy, is obtained for thin films. At low temperatures a
scaling relation between the Hall and longitudinal resistivities is found, with
the power depending on sample details. Near the superconducting transition
temperature and for small magnetic fields the Hall conductivity is found to be
proportional to the inverse of the magnetic field and to the quadratic of the
difference between the measured and the transition temperatures.Comment: minor change
Phase slip in a superfluid Fermi gas near a Feshbach resonance
In this paper, we study the properties of a phase slip in a superfluid Fermi
gas near a Feshbach resonance. The phase slip can be generated by the phase
imprinting method. Below the superfluid transition temperature, it appears as a
dip in the density profile, and becomes more pronounced when the temperature is
lowered. Therefore the phase slip can provide a direct evidence of the
superfluid state. The condensation energy of the superfluid state can be
extracted from the density profile of the phase slip, due to the unitary
properties of the Fermi gas near the resonance. The width of the phase slip is
proportional to the square root of the difference between the transition
temperature and the temperature. The signature of the phase slip in the density
profile becomes more robust across the BCS-BEC crossover.Comment: 5 pages, 2 figures, the density profile of a phase slip under
experimental conditions was calculate
Invalidity of Classes of Approximated Hall Effect Calculations
In this comment, I point out a number of approximated derivations for the
effective equation of motion, now been applied to d-wave superconductors by
Kopnin and Volovik are invalid. The major error in those approximated
derivations is the inappropriate use of the relaxation time approximation in
force-force correlation functions, or in force balance equations, or in similar
variations. This approximation is wrong and unnecessary.Comment: final version, minor changes, to appear in Phys. Rev. Let
Hydrographic Study of Peirce Island Wastewater Treatment Plant Effluent in the Piscataqua River of Portsmouth, New Hampshire: Report of Findings from the December 10 – 14, 2012 Study Period
In order to assist the New Hampshire Department of Environmental Services (NHDES) evaluate the impact of treated wastewater effluent from Peirce Island Wastewater Treatment Plant (WWTP) to the Lower Piscataqua River and Portsmouth Harbor a hydrographic dye study was conducted in December 2012 in Portsmouth, NH. Eight (8) shellfish cages with American oysters (Crassostrea virginica) and blue mussels (Mytilus edulis) were deployed both upstream and downstream of the Peirce Island WWTP in the Piscataqua River, Little Harbor, and the entrance of Little Bay. Eight (8) mini CTDs that monitor conductivity/salinity, temperature, and depth, and six (6) moored fluorometers, which measure dye tagged effluent from the Peirce Island WWTP were attached to the subsurface cages. A fifty (50) gallon mixture of Rhodamine WT dye and distilled water was injected into WWTP on December 11, 2012 for a half tidal cycle (approximately 12.4 hours). Additionally, boat tracking fluorometers connected with a mobile geographic information system (GIS) were used to measure dye levels on the surface in situ and in real time. Microbiological analyses of fecal coliform (FC), male-specific coliphage (MSC), Norovirus (NoV) genogroup I (GI) and genogroup II (GII), and Adenovirus (AdV) were conducted on WWTP influent and effluent composite samples collected with automated samplers to determine the WWTP efficiency in reducing indicator bacteria and viruses. Microbiological sampling and testing of oysters and mussels from the eight (8) sentinel cages was conducted to assess the impact of WWTP effluent on shellfish growing areas and growing area classifications. Prior to conducting the study, the assumption was that the FDA’s recommended minimum dilution of 1000:1was not applicable in this situation because the recommended dilution is based on a WWTP having at least secondary treatment. The microbiological findings in shellfish samples, wastewater samples from the Peirce Island WWTP, and the results of the dye study, confirm that a minimum of 1,000:1 dilution with respect to Peirce Island WWTP is currently not applicable for this WWTP. The FDA and NHDES recommend continued MSC testing of wastewater samples from the WWTP before and after the WWTP upgrade. The FDA and NHDES recommend a future field study after the WWTP upgrade in order to delineate the 1,000:1 dilution zone
Reply to Comment "Invalidity of classes of approximate Hall effect calculations."
We reply to the criticism raised by Ao in his Comment (cond-mat/9801180).
Being unable to properly treat the Hall conductivity in a mixed state of
superconductors, Ao is looking for possible mistakes in microscopic and
phenomenological calculations, as well as in the corresponding experiments. The
errors in his treatment of the problem (cond-mat/9704247) are analized. We
indicate where the approach advocated by him fails to properly account for the
interaction with impurities and other sources of relaxation.Comment: reply to Comment by Ao (cond-mat/9801180) on our paper in PRL, 79,
1377 (1997), revtex file, 1 page, no figure
Learning from mistakes
A willingness to acknowledge and learn from failure is essential for all progress, writes Professor Geoff Masters AO
Achievement gaps - the continuing challenge
Professor Geoff Masters AO discusses the challenges of closing achievement gaps
Focus on the larger purpose of schooling and improvement may follow
Success in schools may best be achieved not by pursuing it directly, but as a ‘side-effect’ of an unwavering dedication to the larger educational purpose, writes Professor Geoff Masters AO
Principal Performance Improvement Tool
What is a highly effective school principal, and what do they do that makes them so effective? The Principal Performance Improvement Tool sets out to answer these questions. It provides a point of reference that principals can use to reflect on their current practices and to identify areas in which their work could be still more effective
Stationary states of an electron in periodic structures in a constant uniform electrical field
On the basis of the transfer matrix technique an analytical method to
investigate the stationary states, for an electron in one-dimensional periodic
structures in an external electrical field, displaying the symmetry of the
problem is developed. These solutions are shown to be current-carrying. It is
also shown that the electron spectrum for infinite structures is continuous,
and the corresponding wave functions do not satisfy the symmetry condition of
the problem.Comment: 10 pages (Latex), no figures, in the revised variant some mistakes in
the English text are corrected and also the first two paragraphs in the
Conclusion are refined (Siberian physical-technical institute at the Tomsk
state university, Tomsk, Russia
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