1,204 research outputs found
Yersiniosis outbreak in rainbow trout at fish farm in Oromia Regional State, Ethiopia
This study presents the results of an investigation conducted on an outbreak of Yersiniosis (Enteric red mouth disease) caused by Yersinia ruckeri at a rainbow trout farm situated at Adaba, Oromia Regional State, Ethiopia. Seven diseased rainbow trout fish having average weight 80 - 100 grams and aged 9 months, were brought to the National Animal Health Diagnostic and Investigation Center (NAHDIC) for further examination and laboratory testing. The young sick fish showed clinical signs of darkening of the skin, loss of appetite and gasping at the surface of the water before death. The fish were sacrificed and examined thoroughly externally for the presence of visible lesions. Scrapings were collected from the skin especially from areas around the fins and observed under the stereomicroscope and also under the low power objective of the compound microscope. Bacteriological tests were carried out on samples from the kidney, liver and spleen. It was concluded that the fish were affected by Yersinia ruckeri based on colony morphology during growth on Tryptose Soy Agar (yellow colonies, gram negative and rodshaped) and distinctive biochemical characteristics. Y. ruckeri is identified from sick fish for the first time in Ethiopia. The protozoan parasites Trichodina species were also recovered in large colonies from the skin scrapings and histopathological sections of the gills. The pathological lesions recorded included high degree anaemia of oral and branchial mucosa, congested gills, kidney and spleen and pale liver, congestion, extensive necrosis in the kidney and spleen, and infiltration with inflammatory cells. Antibiogram test conducted on the bacteria showed that the Y. ruckeri strain were susceptible to Oxytetracycline, Furazolidone, Trimethoprim and Streptomycin. This study showed the importance of stress induced by higher temperature and poor water quality associated with infestations by Trichodina species as predisposing factors to bacterial diseases in intensive fish farming practices. Key words: bacterial culture, histopathology, rainbow trout, Yersinia ruckeri, Trichodina specie
Kinematics and morphology of ionized gas in Hickson Compact Group 18
We present new observations of emission in the Hickson Compact
Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The
velocity field does not show motions of individual group members but, instead,
a complex common velocity field for the whole group. The gas distribution is
very asymmetric with clumps of maximum intensity coinciding with the optically
brightest knots. Comparing and HI data we conclude that HCG 18 is
not a compact group but instead a large irregular galaxy with several clumps of
star formation.Comment: Accepted for publication in Astronomical Journal (13p 6 figures
Effects of a 75-km mountain ultra-marathon on heart rate variability in amateur runners
BACKGROUND: This study examined the effects of a mountain ultra-marathon (MUM) on the activity of the autonomous nervous system through heart rate variability (HRV) monitoring and determined whether this variable related to final performance.
METHODS: Heart rate and HRV were measured in eight male amateur runners (aged 37-60 years). Measurements were recorded before and after the event, in resting conditions, as well as continuously throughout the whole MUM. In addition, percentage (%) of heart rate reserve (HRres) and partial and total times during the race were analyzed.
RESULTS: Average heart rate (HRavg) measured at rest was increased after the event (+37%). Standard deviation of successive differences (SDSD) and the square root of the mean squared differences of successive NN intervals (RMSSD) were reduced after the MUM (-56% and -59%, respectively). There was a positive relationship between the frequency-domain index normalized low frequency power (PLFn) measured at rest before the event and race time (0.79) while there was a negative relationship between race time and the difference in HRavg before and after the event. In the last half of the event, there was a high correlation (Spearman coefficient of correlation >0.9) between race time and the standard deviation of the NN intervals (SDNN) registered during the race.
CONCLUSIONS: Autonomous cardiac regulation can be related to the performance in a mountain ultra-marathon. HRV monitoring could represent a practical tool for the evaluation of the relationship between the autonomous nervous system activity and performance in a mountain ultra-marathon
Gap, a mycobacterial specific integral membrane protein, is required for glycolipid transport to the cell surface
The cell envelope of mycobacteria is a complex multilaminar structure that protects the cell from stresses encountered in the environment, and plays an important role against the bactericidal activity of immune system cells. The outermost layer of the mycobacterial envelope typically contains species-specific glycolipids. Depending on the mycobacterial species, the major glycolipid localized at the surface can be either a phenolglycolipid or a peptidoglycolipid (GPL). Currently, the mechanism of how these glycolipids are addressed to the cell surface is not understood. In this study, by using a transposon library of Mycobacterium smegmatis and a simple dye assay, six genes involved in GPLs synthesis have been characterized. All of these genes are clustered in a single genomic region of approximately 60 kb. We show by biochemical analyses that two non-ribosomal peptide synthetases, a polyketide synthase, a methyltransferase and a member of the MmpL family are required for the biosynthesis of the GPLs backbone. Furthermore, we demonstrate that a small integral membrane protein of 272 amino acids named Gap (gap: GPL addressing protein) is specifically required for the transport of the GPLs to the cell surface. This protein is predicted to contain six transmembrane segments and possesses homologues across the mycobacterial genus, thus delineating a new protein family. This Gap family represents a new paradigm for the transport of small molecules across the mycobacterial envelope, a critical determinant of mycobacterial virulence
The integral equation approach to kinematic dynamo theory and its application to dynamo experiments in cylindrical geometry
The conventional magnetic induction equation that governs hydromagnetic
dynamo action is transformed into an equivalent integral equation system. An
advantage of this approach is that the computational domain is restricted to
the region occupied by the electrically conducting fluid and to its boundary.
This integral equation approach is first employed to simulate kinematic dynamos
excited by Beltrami-like flows in a finite cylinder. The impact of externally
added layers around the cylinder on the onset of dynamo actions is
investigated. Then it is applied to simulate dynamo experiments within
cylindrical geometry including the von Karman sodium (VKS) experiment and the
Riga dynamo experiment. A modified version of this approach is utilized to
investigate magnetic induction effects under the influence of externally
applied magnetic fields which is also important to measure the proximity of a
given dynamo facility to the self-excitation threshold.Comment: 22 pages, 14 figure
Quasilinear theory of the 2D Euler equation
We develop a quasilinear theory of the 2D Euler equation and derive an
integro-differential equation for the evolution of the coarse-grained
vorticity. This equation respects all the invariance properties of the Euler
equation and conserves angular momentum in a circular domain and linear impulse
in a channel. We show under which hypothesis we can derive a H-theorem for the
Fermi-Dirac entropy and make the connection with statistical theories of 2D
turbulence.Comment: 4 page
Scaling laws and vortex profiles in 2D decaying turbulence
We use high resolution numerical simulations over several hundred of turnover
times to study the influence of small scale dissipation onto vortex statistics
in 2D decaying turbulence. A self-similar scaling regime is detected when the
scaling laws are expressed in units of mean vorticity and integral scale, as
predicted by Carnevale et al., and it is observed that viscous effects spoil
this scaling regime. This scaling regime shows some trends toward that of the
Kirchhoff model, for which a recent theory predicts a decay exponent .
In terms of scaled variables, the vortices have a similar profile close to a
Fermi-Dirac distribution.Comment: 4 Latex pages and 4 figures. Submitted to Phys. Rev. Let
Long-time discrete particle effects versus kinetic theory in the self-consistent single-wave model
The influence of the finite number N of particles coupled to a monochromatic
wave in a collisionless plasma is investigated. For growth as well as damping
of the wave, discrete particle numerical simulations show an N-dependent long
time behavior resulting from the dynamics of individual particles. This
behavior differs from the one due to the numerical errors incurred by Vlasov
approaches. Trapping oscillations are crucial to long time dynamics, as the
wave oscillations are controlled by the particle distribution inhomogeneities
and the pulsating separatrix crossings drive the relaxation towards thermal
equilibrium.Comment: 11 pages incl. 13 figs. Phys. Rev. E, in pres
Perpendicular momentum injection by lower hybrid wave in a tokamak
The injection of lower hybrid waves for current drive into a tokamak affects
the profile of intrinsic rotation. In this article, the momentum deposition by
the lower hybrid wave on the electrons is studied. Due to the increase in the
poloidal momentum of the wave as it propagates into the tokamak, the parallel
momentum of the wave increases considerably. The change of the perpendicular
momentum of the wave is such that the toroidal angular momentum of the wave is
conserved. If the perpendicular momentum transfer via electron Landau damping
is ignored, the transfer of the toroidal angular momentum to the plasma will be
larger than the injected toroidal angular momentum. A proper quasilinear
treatment proves that both perpendicular and parallel momentum are transferred
to the electrons. The toroidal angular momentum of the electrons is then
transferred to the ions via different mechanisms for the parallel and
perpendicular momentum. The perpendicular momentum is transferred to ions
through an outward radial electron pinch, while the parallel momentum is
transferred through collisions.Comment: 22 pages, 4 figure
Beyond scaling and locality in turbulence
An analytic perturbation theory is suggested in order to find finite-size
corrections to the scaling power laws. In the frame of this theory it is shown
that the first order finite-size correction to the scaling power laws has
following form , where
is a finite-size scale (in particular for turbulence, it can be the Kolmogorov
dissipation scale). Using data of laboratory experiments and numerical
simulations it is shown shown that a degenerate case with can
describe turbulence statistics in the near-dissipation range , where
the ordinary (power-law) scaling does not apply. For moderate Reynolds numbers
the degenerate scaling range covers almost the entire range of scales of
velocity structure functions (the log-corrections apply to finite Reynolds
number). Interplay between local and non-local regimes has been considered as a
possible hydrodynamic mechanism providing the basis for the degenerate scaling
of structure functions and extended self-similarity. These results have been
also expanded on passive scalar mixing in turbulence. Overlapping phenomenon
between local and non-local regimes and a relation between position of maximum
of the generalized energy input rate and the actual crossover scale between
these regimes are briefly discussed.Comment: extended versio
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