The role of two anatomically separate olfactory bulbs in shark food odor tracking

Most sharks have well-developed olfactory systems and depend to a large degree on odor information to locate food, home and navigate, and possibly detect predators and mates. The aim of this investigation is to determine the behavioral function of two paired bilateral olfactory bulbs in the smooth dogfish shark, Mustelus canis. The paired olfactory bulbs are a rare and unique feature among elasmobranchs and are absent in bony fishes. Given that the olfactory system of bony fishes contains lateral and medial nerve bundles with behavioral functions in feeding and social behavior respectively, we hypothesize that sharks have an elaborate functional division in which the medial bulb is processing social odors and the lateral bulb food odors. This functional division would parallel the division into an olfactory and an accessory olfactory system, also known as the vomeronasal organ or Jacobson’s organ, which evolved in tetrapods. Our study is based on the behavioral effects of selective transection of the two olfactory tracts to reveal how the brain is processing input from two anatomically distinct olfactory systems. The results show that animals with lateral tract transections showed impaired ability to track a food odor plume while those with medial transections showed no change. Attempts to identify a reliable social odor (pheromone) were not successful, preventing us from determining the deficits expected from medial tract lesions

The q-harmonic oscillators, q-coherent states and the q-symplecton

The recently introduced notion of a quantum group is discussed conceptually and then related to deformed harmonic oscillators ('q-harmonic oscillators'). Two developments in applying q-harmonic oscillators are reviewed: q-coherent states and the q-symplecton

Nonlinear self-flipping of polarization states in asymmetric waveguides

Waveguides of subwavelength dimensions with asymmetric geometries, such as rib waveguides, can display nonlinear polarization effects in which the nonlinear phase difference dominates the linear contribution, provided the birefringence is sufficiently small. We demonstrate that self-flipping polarization states can appear in such rib waveguides at low (mW) power levels. We describe an optical power limiting device with optimized rib waveguide parameters that can operate at low powers with switching properties

Degenerate Topological Vortex solutions from a generalized Abelian Higgs Model with a Chern-Simons term

We consider a generalization of the abelian Higgs model with a Chern-Simons term by modifying two terms of the usual Lagrangian. We multiply a dielectric function with the Maxwell kinetic energy term and incorporate nonminimal interaction by considering generalized covariant derivative. We show that for a particular choice of the dielectric function this model admits topological vortices satisfying Bogomol'nyi bound for which the magnetic flux is not quantized even though the energy is quantized. Furthermore, the vortex solution in each topological sector is infinitely degenerate.Comment: 13 pages (one figure not included), Revtex, IP/BBSR/93-5

Efficient third harmonic generation in photonic nanowires

In a photonic nanowire the strong optical confinement allows for the phase matching of nonlinear interactions that would not normally be phase matched, while the large longitudinal component of the electric field serves to further enhance the effective nonlinearity. Thus such waveguides are good choices for studying nonlinear effects such as third harmonic generation. In this paper we analyse third harmonic generation analytically and present the criteria for optimal harmonic generation. In addition we analyse the inverse process of 1/3 harmonic generation and show that efficient parametric amplifiers can be made which would be a high brightness source of entangled photons for producing GHZ states

Spin dynamics of low-dimensional excitons due to acoustic phonons

We investigate the spin dynamics of excitons interacting with acoustic phonons in quantum wells, quantum wires and quantum disks by employing a multiband model based on the $4\times4$ Luttinger Hamiltonian. We also use the Bir-Pikus Hamiltonian to model the coupling of excitons to both longitudinal acoustic phonons and transverse acoustic phonons, thereby providing us with a realistic framework in which to determine details of the spin dynamics of excitons. We use a fractional dimensional formulation to model the excitonic wavefunctions and we demonstrate explicitly the decrease of spin relaxation time with dimensionality. Our numerical results are consistent with experimental results of spin relaxation times for various configurations of the GaAs/Al$_{0.3}$Ga$_{0.7}$As material system. We find that longitudinal and transverse acoustic phonons are equally significant in processes of exciton spin relaxations involving acoustic phonons.Comment: 24 pages, 3 figure

Exact BPS monopole solution in a self-dual background

An exact one monopole solution in a uniform self-dual background field is obtained in the BPS limit of the SU(2) Yang-Mills-Higgs theory by using the inverse scattering method.Comment: 10 page

RNA from a simple-tandem repeat is required for sperm maturation and male fertility in Drosophila melanogaster.

Tandemly-repeated DNAs, or satellites, are enriched in heterochromatic regions of eukaryotic genomes and contribute to nuclear structure and function. Some satellites are transcribed, but we lack direct evidence that specific satellite RNAs are required for normal organismal functions. Here, we show satellite RNAs derived from AAGAG tandem repeats are transcribed in many cells throughout Drosophila melanogaster development, enriched in neurons and testes, often localized within heterochromatic regions, and important for viability. Strikingly, we find AAGAG transcripts are necessary for male fertility, and that AAGAG RNA depletion results in defective histone-protamine exchange, sperm maturation and chromatin organization. Since these events happen late in spermatogenesis when the transcripts are not detected, we speculate that AAGAG RNA in primary spermatocytes 'primes' post-meiosis steps for sperm maturation. In addition to demonstrating essential functions for AAGAG RNAs, comparisons between closely related Drosophila species suggest that satellites and their transcription evolve quickly to generate new functions

Solitons in systems of coupled scalar fields

We present a method to obtain soliton solutions to relativistic system of coupled scalar fields. This is done by examining the energy associated to static field configurations. In this case we derive a set of first-order differential equations that solve the equations of motion when the energy saturates its lower bound. To illustrate the general results, we investigate some systems described by polynomial interactions in the coupled fields.Comment: RevTex4, 5 page

Generalized Zeta Functions and One-loop Corrections to Quantum Kink Masses

A method for describing the quantum kink states in the semi-classical limit of several (1+1)-dimensional field theoretical models is developed. We use the generalized zeta function regularization method to compute the one-loop quantum correction to the masses of the kink in the sine-Gordon and cubic sinh-Gordon models and another two ${\rm P}(\phi)_2$ systems with polynomial self-interactions.Comment: 29 pages, 4 figures; version to appear in Nucl. Phys.