The habenular nuclei: a conserved asymmetric relay station in the vertebrate brain

The dorsal diencephalon, or epithalamus, contains the bilaterally paired habenular nuclei and the pineal complex. The habenulae form part of the dorsal diencephalic conduction (DDC) system, a highly conserved pathway found in all vertebrates. In this review, we shall describe the neuroanatomy of the DDC, consider its physiology and behavioural involvement, and discuss examples of neural asymmetries within both habenular circuitry and the pineal complex. We will discuss studies in zebrafish, which have examined the organization and development of this circuit, uncovered how asymmetry is represented at the level of individual neurons and determined how such left–right differences arise during development

Anomalous diffusion and the first passage time problem

We study the distribution of first passage time (FPT) in Levy type of anomalous diffusion. Using recently formulated fractional Fokker-Planck equation we obtain three results. (1) We derive an explicit expression for the FPT distribution in terms of Fox or H-functions when the diffusion has zero drift. (2) For the nonzero drift case we obtain an analytical expression for the Laplace transform of the FPT distribution. (3) We express the FPT distribution in terms of a power series for the case of two absorbing barriers. The known results for ordinary diffusion (Brownian motion) are obtained as special cases of our more general results.Comment: 25 pages, 4 figure

Effects of columnar disorder on flux-lattice melting in high-temperature superconductors

The effect of columnar pins on the flux-lines melting transition in high-temperature superconductors is studied using Path Integral Monte Carlo simulations. We highlight the similarities and differences in the effects of columnar disorder on the melting transition in YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) and the highly anisotropic Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (BSCCO) at magnetic fields such that the mean separation between flux-lines is smaller than the penetration length. For pure systems, a first order transition from a flux-line solid to a liquid phase is seen as the temperature is increased. When adding columnar defects to the system, the transition temperature is not affected in both materials as long as the strength of an individual columnar defect (expressed as a flux-line defect interaction) is less than a certain threshold for a given density of randomly distributed columnar pins. This threshold strength is lower for YBCO than for BSCCO. For higher strengths the transition line is shifted for both materials towards higher temperatures, and the sharp jump in energy, characteristic of a first order transition, gives way to a smoother and gradual rise of the energy, characteristic of a second order transition. Also, when columnar defects are present, the vortex solid phase is replaced by a pinned Bose glass phase and this is manifested by a marked decrease in translational order and orientational order as measured by the appropriate structure factors. For BSCCO, we report an unusual rise of the translational order and the hexatic order just before the melting transition. No such rise is observed in YBCO.Comment: 32 pages, 13 figures, revte

NOx or VOC Limitation in East German Ozone Plumes?

The ozone forming potential of VOCs and NO sub x for plumes observed from several cities and a power plant in eastern Germany was investigated. A closed box model with a gas phase photochemical reaction mechanism was employed to simulate several scenarios based upon aircraft observations. In several of the scenarios, the initial concentrations of NO sub x VOCs, and SO2, were reduced to study the factors limiting the O3 production. Ozone production was limited by the initial VOC concentrations for all of the simulated plumes. Higher O3 concentrations were produced with reduced initial NO sub x. In one sample with high SO2 mixing ratios (> 100 ppb), SO2 was also identified as a significant contributor to the production of O3

Blood pressure and heart rate during tonic immobility in the black tipped reef shark, Carcharhinus melanoptera

Tonic immobility was induced in black tipped reef sharks (Carcharhinus melanoptera) and heart rate and ventral aortic blood pressure recorded. Without branchial irrigation, tonic immobility was correlated with a significant depression in blood pressure and heart rate irrespective of the sharks being in air or in water. Tonic immobility with branchial irrigation resulted in a significant increase in blood pressure in sharks in air, but not in water. Heart rate was unchanged when the gills were irrigated. Intra-arterial injections of atropine abolished the bradycardia and blood pressure rise associated with tonic immobility. We conclude that, during tonic immobility, sharks are able to receive afferent information from the ventilatory system and make appropriate responses via the vagus nerve

Messung der Verteilung flugzeugbedingter Spurengase in der oberen Troposphaere und unteren Stratosphaere Abschlussbericht

During the summer and winter 1994, the research aircraft Falcon of the German Aerospace Research Establishment (DLR) Oberpfaffenhofen flew a total of 8 missions in the region of the transatlantic main flight corridor off the shores of Great Britain and Ireland. Besides the meteorological parameters temperature, humidity and wind (2-d), the measurements covered the mixing ratios of 0_3, NO_2, NO_y, CO, CO_2 and some volatile hydrocarbons (VOC) as well as the photolyserates of ozone. Cruising flight in this region occurs in clean air masses from the middle and upper troposphere, partly in air masses with marked stratospheric character and partly even in convection carried air masses from the lower troposphere. In most cases a very heterogeneous composition and mixing of different types of air masses was observed. Against this heterogeneous background individual exhaust plumes from airliners were detected during all flights. These trails are characterized as enrichments of the nitrogen oxide concentrations. Other trace gas measurements were not able to identify the trails. As a result of wind transportation the trails occur isolated in most cases. In few cases, when the wind vector ran parallel to the flight routes, the influence of air traffic on the nitrogen oxide concentrations was identified even in higher regions of 30 km horizontal extension or 200 m vertical extension. The results were interpreted by means of a photochemical box model specifically developed for this purpose. The model predictions of the ratios NO/NO_y and NO_x/NO_y in the trails correlated very well with the measurement results. The model results indicate that HNO_3 is created within the trails already at short time intervals after the emission, which being a relatively stable trace gas should remain as the signature of the aircraft emissions. In addition to this, at least for the period under investigation (up to one hour after emission of the exhaust gases), under the conditions of high solar irradiation the influence of the trails on the oxidation capacity of the atmosphere is not significant. (orig.)SIGLEAvailable from TIB Hannover: RR 1618(38) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman