Nanoscale Zeeman localization of charge carriers in diluted magnetic semiconductor-permalloy hybrids

We investigate the possibility of charge carrier localization in magnetic semiconductors due to the presence of a highly inhomogeneous external magnetic field. As an example, we study in detail the properties of a magnetic semiconductor-permalloy disk hybrid system. We find that the giant Zeeman respose of the magnetic semiconductor in conjuction with the highly non-uniform magnetic field created by the vortex state of a permalloy disk can lead to Zeeman localized states at the interface of the two materials. These trapped state are chiral, with chirality controlled by the orientation of the core magnetization of the permalloy disk. We calculate the energy spectrum and the eigenstates of these Zeeman localized states, and discuss their experimental signatures in spectroscopic probes.Comment: 4 pages, 1 figur

Effects of CarbonDioxide on Rainbow Trout Larvae: Application for Invasive Fish Eradication

Currently, efforts are underway to eradicate invasive fish species that threaten the ecological integrity of aquatic ecosystems. Several studies have examined the effects of anesthetizing fish for easier handling, surgical procedures, tagging and management. Carbon Dioxide (CO2) is an approved and efficient anesthetic for adult fish in medicine and aquaculture and is favorable due to lack of residues, zero withdrawal period and does not need to be registered as its classification is generally regarded as safe (GRAS). Carbon dioxide has also shown to have lethal effects on other life history stages of fish. In this study, various early life stages of Rainbow trout (Oncorhynchus mykiss) larvae were exposed to CO2 in the form of dry ice pellets to determine the critical period of sensitivity for mortality in a model salmonid species. Studies were conducted in aluminum tanks (n = 3 tanks per treatment, with three chambers in each tank with 40 larvae per chamber) with 68 liters of filtered creek water (dissolved CO2 = 4 mg/l, dissolved O2 = 8.125 mg/l, pH = 7.78, temperature = 12.9°C, conductivity = -55 mV, Total alkalinity as CaCO3 = 160 mg/l). Larvae exposed at post hatch day 10 had increased susceptibility to CO2, when compared with earlier embryonic stages. The results of the experiment indicate that early rainbow trout life history stages are susceptible to CO2 but only at late embryonic stages and may have implications for systematically eradicating invasive salmonids

The Effects of Ultraviolet Light on Rainbow Trout Embryos

There currently exists a need to develop new approaches to control aquatic invasive and nuisance species. The effects of light radiation such as ultra-violet wavelengths of light have shown negative effects, such as increased embryo mortality in early embryonic salmonid larvae. This study explores the use of light radiation for eradication of invasive fish. Experiments were conducted to evaluate dose and critical period of sensitivity for mortality of rainbow trout (Oncorhynchus mykiss) embryos after exposure to visual and ultra-violet light radiation. Endpoints recorded include exposure intensity, effective distance from source, duration of exposure, malformations and mortality. Introduced light may be an effective and feasible eradication technique of early life history stages of fish and invertebrate invasive species in situ, as light can be implemented and removed with minimal environmental impact

Hybridized quadrupole-dipole exciton effects in Cu2OCu_2O - Organic Heterostructure

In the present work we discuss resonant hybridization of the $1S$ quadrupole Wannier-Mott exciton (WE) in a $Cu_2O$ quantum well with the Frenkel (FE) dipole exciton in an adjacent layer of organic DCM2:CA:PA. The coupling between excitons is due to interaction between the gradient of electric field induced by DCM2 Frenkel exciton and the quadrupole moment of the $1S$ transition in the cuprous oxide. The specific choice of the organic allows us to use the mechanism of 'solid state solvation' to dynamically tune the WE and FE into resonance during time $\approx 3.3 \: ns$ (comparable with the big life time of the WE) of the 'slow' phase of the solvation. The quadrupole-dipole hybrid utilizes the big oscillator strength of the FE along with the big lifetime of the quadrupole exciton, unlike dipole-dipole hybrid exciton which utilizes big oscillator strength of the FE and big radius of the dipole allowed WE. Due to strong spatial dispersion and big mass of the quadrupole WE the hybridization is not masked by the kinetic energy or the radiative broadening. The lower branch of the hybrid dispersion exhibits a pronounced minimum and may be used in applications. Also we investigate and report noticeable change in the coupling due to a induced 'Stark effect' from the strong local electric field of the FE. We investigated the fine energy structure of the quantum well confined ortho and para excitons in cuprous oxide

The D coefficient in neutron beta decay in effective field theory

In this paper we explore the time-reversal-odd triple-correlation coefficient in neutron beta decay, the so-called "D coefficient", using heavy-baryon effective field theory with photon degrees of freedom. We find that this framework allows us to reproduce the known results for the contribution which comes from final-state interactions, and also to discuss higher-order corrections. In particular we are able to show that in the heavy-baryon limit all electromagnetic contributions vanish. By calculating the leading correction to the known result, we give a final expression which is accurate to better than 1%. Hence we extend downwards the range over which the D coefficient could be used to explore time-violation from new physics.Comment: 12c pages, 3 eps figures Version accepted for publication in Physics Letters B; minor changes of wordin

Effects of Electricity and Altered Conductivity on Rainbow Trout Embryos: A Study to Determine Efficacy of Electricity for Eradication of Invasive Salmonids

Electricity has been an applied means of facilitating capture and removal of invasive fishes for many years. Current methods involve use of electrodes to establish a current through which passing fish will be susceptible to a brief shock to stun. This method, however, only affects free swimming individuals and is not inclusive of early life history stages such as embryos within spawning substrate. This study evaluates the susceptibility of embryonic and larval stage rainbow trout (Oncorhynchus mykiss) to direct DC current between 2-20v/cm in varying conductive waters to determine lethality for invasive salmonid eradication efforts. Rainbow trout embryos (n = 10 embryos/exposure) were initially exposed to homogeneous electric fields for 5 sec with a water conductivity of 220uS/cm from 1 day post fertilization (DPF)/ 27 temperature units (TU) to 15 DPF/405TU. Mortality was assessed 24 hours post exposure and the LV50 (lethal voltage) at 220uS/cm was determined for each TU. Embryos from six periods of development were then exposed to their respective LV50 voltages in varying conductive waters (20-600uS/cm). Susceptibility to direct DC voltages increased with voltage but overall susceptibility decreased with development. Susceptibility to a constant voltage increased with increasing conductivity and was consistent throughout early development (81TU-292TU), but the effects of increased conductivity were not enhanced in eyed embryos after 364TU. Results indicate that direct DC current applied prior to eyed embryonic stages, the period of greatest trout embryo susceptibility, is an effective means of eradicating invasive and nuisance salmonids

Analytical Estimate of the Critical Velocity for Vortex Pair Creation in Trapped Bose Condensates

We use a modified Thomas-Fermi approximation to estimate analytically the critical velocity for the formation of vortices in harmonically trapped BEC. We compare this analytical estimate to numerical calculations and to recent experiments on trapped alkali condensates.Comment: 12 page

Wormholes and Flux Tubes in 5D Kaluza-Klein Theory

In this paper spherically symmetric solutions to 5D Kaluza-Klein theory, with ``electric'' and/or ``magnetic'' fields are investigated. It is shown that the global structure of the spacetime depends on the relation between the ``electrical'' and ``magnetic'' Kaluza-Klein fields. For small ``magnetic'' field we find a wormhole-like solution. As the strength of the ``magnetic'' field is increased relative to the strength of the ``electrical'' field, the wormhole-like solution evolves into a finite or infinite flux tube depending on the strengths of the two fields. For the large ``electric'' field case we conjecture that this solution can be considered as the mouth of a wormhole, with the $G_{55}$, $G_{5t}$ and $G_{5\phi}$ components of the metric acting as the source of the exotic matter necessary for the formation of the wormhole's mouth. For the large ``magnetic'' field case a 5D flux tube forms, which is similar to the flux tube between two monopoles in Type-II superconductors, or the hypothesized color field flux tube between two quarks in the QCD vacuum.Comment: 12 pages, 5 eps.figures, REVTEX, Discussion about null surfaces ammended. References added. To be published in PR

Local gauge invariance implies Siegert's hypothesis

The nonrelativistic Ward-Takahashi identity, a consequence of local gauge invariance in quantum mechanics, shows the necessity of exchange current contributions in case of nonlocal and/or isospin-dependent potentials. It also implies Siegert's hypothesis: in the nonrelativistic limit, two-body charge densities identically vanish. Neither current conservation, which follows from global gauge invariance, nor the constraints of (lowest order) relativity are sufficient to arrive at this result. Furthermore, a low-energy theorem for exchange contributions is established.Comment: 5 pages, REVTE

Vortex nucleation in Bose-Einstein condensates in time-dependent traps

Vortex nucleation in a Bose-Einstein condensate subject to a stirring potential is studied numerically using the zero-temperature, two-dimensional Gross-Pitaevskii equation. It is found that this theory is able to describe the creation of vortices, but not the crystallization of a vortex lattice. In the case of a rotating, slightly anisotropic harmonic potential, the numerical results reproduce experimental findings, thereby showing that finite temperatures are not necessary for vortex excitation below the quadrupole frequency. In the case of a condensate subject to stirring by a narrow rotating potential, the process of vortex excitation is described by a classical model that treats the multitude of vortices created by the stirrer as a continuously distributed vorticity at the center of the cloud, but retains a potential flow pattern at large distances from the center.Comment: 22 pages, 7 figures. Changes after referee report: one new figure, new refs. No conclusions altere