Self-avoiding walks on a bilayer Bethe lattice

We propose and study a model of polymer chains in a bilayer. Each chain is confined in one of the layers and polymer bonds on first neighbor edges in different layers interact. We also define and comment results for a model with interactions between monomers on first neighbor sites of different layers. The thermodynamic properties of the model are studied in the grand-canonical formalism and both layers are considered to be Cayley trees. In the core region of the trees, which we may call a bilayer Bethe lattice, we find a very rich phase diagram in the parameter space defined by the two activities of monomers and the Boltzmann factor associated to the interlayer interaction between bonds or monomers. Beside critical and coexistence surfaces, there are tricritical, bicritical and critical endpoint lines, as well as higher order multicritical points.Comment: 21 pages, 10 figures. Journal of Statistical Mechanics: Theory and Experiment (in press

Genetic insight into an extinct population of Asian elephants (Elephas maximus) in the Near East

The current range of the Asian elephant is fragmented and restricted to southern Asia. Its historical range was far wider and extended from Anatolia and the Levant to Central China. The fossil record from these peripheral populations is scant and we know little of their relationship to modern Asian elephants. To gain a first insight to the genetic affinity of an E. maximus population that once inhabited Turkey we sequenced ca. 570 bp mtDNA from four individuals dating to ~3500 cal. BP. We show that these elephants carried a rare haplotype previously only observed in one modern elephant from Thailand. These results clarify the taxonomic identity of specimens with indeterminate morphologies and show that this ancient population groups within extant genetic variation. By placing the age of the common ancestor of this haplotype in the interval 3.7–58.7 kya (mean = 23.5 kya) we show that range-wide connectivity occurred at some time or times since the start of MIS 3, ~57 kya, probably reflecting range and population expansion during a favourable climatic episode. The genetic data do not distinguish natural versus anthropogenic origin of the Near Eastern Bronze Age population, but together with archaeological and paleoclimatic data they allow the possibility of a natural westward expansion around that time

Near-field flow structure of a confined wall jet on flat and concave rough walls

Experimental results are presented of the mean flow and turbulence characteristics in the near field of a plane wall jet issuing from a nozzle onto flat and concave walls consisting of fixed sand beds. This is a flow configuration of interest for sediment erosion, also referred to as scouring. The measurements were made with an acoustic profiler that gives access to the three components of the instantaneous velocities. For the flat-wall flow, it is shown that the outer-layer spatial growth rate and the maxima of the Reynolds stresses approach the values accepted for the far field of a wall jet at a downstream distance x/b0 ≈ 8. These maxima are only about half the values of a plane free jet. This reduction in Reynolds stresses is also observed in the shear-layer region, x/b0 11, the maximum Reynolds shear stress approaches the value of a plane free jet. This change in Reynolds stresses is related to the mean vertical velocity that is negative for x/b0 < 8 and positive further downstream. The evolution of the inner region of the wall jet is found to be in good agreement with a previous model that explicitly includes the roughness length. On the concave wall, the mean flow and the Reynolds stresses are drastically changed by the adverse pressure gradient and especially by the development of Görtler vortices. On the downslope side of the scour hole, the flow is nearly separating with the wall shear stress tending to zero, whereas on the upslope side, the wall-friction coefficient is increased by a factor of about two by Görtler vortices. These vortices extend well into the outer layer and, just above the wall, cause a substantial increase in Reynolds shear stres

Chemical abundances of the metal-poor horizontal-branch stars CS 22186-005 and CS 30344-033

We report on a chemical-abundance analysis of two very metal-poor horizontal-branch stars in the Milky Way halo: CS 22186-005 ([Fe/H]=-2.70) and CS 30344-033 ([Fe/H]=-2.90). The analysis is based on high-resolution spectra obtained at ESO, with the spectrographs HARPS at the 3.6 m telescope, and UVES at the VLT. We adopted one-dimensional, plane-parallel model atmospheres assuming local thermodynamic equilibrium. We derived elemental abundances for 13 elements for CS 22186-005 and 14 elements for CS 30344-033. This study is the first abundance analysis of CS 30344-033. CS 22186-005 has been analyzed previously, but we report here the first measurement of nickel (Ni; Z = 28) for this star, based on twenty-two NiI lines ([Ni/Fe]=-0.21$\pm$0.02); the measurement is significantly below the mean found for most metal-poor stars. Differences of up to 0.5 dex in [Ni/Fe] ratios were determined by different authors for the same type of stars in the literature, which means that it is not yet possible to conclude that there is a real intrinsic scatter in the [Ni/Fe] ratios. For the other elements for which we obtained estimates, the abundance patterns in these two stars match the Galactic trends defined by giant and turnoff stars well. This confirms the value of horizontal-branch stars as tracers of the chemical properties of stellar populations in the Galaxy. Our radial velocities measurements for CS 22186-005 differ from previously published measurements by more than the expected statistical errors. More measurements of the radial velocity of this star are encouraged to confirm or refute its radial velocity variability

Genetic analysis of the complete G gene of viral hemorrhagic septicemia virus (VHSV) genotype Ie isolates from Turkey

Viral hemorrhagic septicemia virus (VHSV) is an enveloped non-segmented, single-stranded, negative-sense RNA virus that belongs to the Novirhabdovirus genus of the family Rhabdoviridae. This virus causes economically significant diseases in farmed rainbow trout, in Turkey, which is often associated with the transmission of pathogens from European resources. In this study, moribund rainbow trout (Oncorhynchus mykiss) samples were collected during an outbreak of VHSV in a rainbow trout fish farm in Bolu Province of Turkey in 2006. In addition, two VHSV strains were isolated from wild turbot (Scophthalmus maximus) in Trabzon Province of the Black Sea region of Turkey during a field survey. We have sequenced the full-length glycoprotein (G) gene of three VHSV isolates and compared them with 25 previously published gene sequences. Based on a complete gene nucleotide sequence, Turkish VHSV isolates were classified into class Ie of genotype I, which is closely related to GE-1.2 isolate (97.1-97.5% nucleotide identity and 98.2-98.4% amino acid identity) found in Georgia more than 30 years ago. These isolates could be an indigenous type of VHSV distributed in the Black Sea. On the other hand, Turkish isolates have 97.5-97.6% nucleotide identity and 98.8-99% amino acid identity with Finnish, Danish, and Norwegian isolates which are classified under Ib and Id. These results suggest that Turkish VHSV isolates may have orginated from Europe and co-circulated with indigenous strains which can threaten the aquaculture industry in Turkey

Characterization of Micrococcus luteus and Bacillus marisflavi Recovered from Common Dentex (Dentex dentex) Larviculture System

In this manuscript, thirty yellow-pigmented Gram-positive bacteria were isolated from natural intestine microflora and from sea water around the marine cage of a rearing tank of common dentex (Dentex dentex), in the Aegean Sea on the Turkish coast and were characterized. Eighteen isolates were assigned to the species Micrococcus luteus, the other twelve to the species Bacillus marisflavi. Eight representative strains, six from B. marisflavi and two from M. luteus, were chosen for further 16S rDNA analyses. A pathogenicity assay for the isolated bacterial strains was carried out in rainbow trout and it evidenced absence of pathogenicity in the tested strains. The isolated strains were tested for in vitro antagonistic activity against Listonella anguillarum, a pathogen bacterium diffused in Mediterranean aquaculture and affecting various fish species. The isolated bacterial strains showed antagonistic activity against the pathogenic bacterium, suggesting a possible role of isolates as probiotics. In this study, for the first time, bacterial strains of the species B. marisflavi, known as an environmental species, were recovered in the gut microbiota of a healthy fish. The use of the isolates characterized in this study, mainly the yellow-pigmented bacterium, is suggested as possible probiotics to improve fish health, along with alternative methods of maintaining a healthy environment

Observations of Lick Standard Stars Using the SCORPIO Multi-Slit Unit at the SAO 6-m Telescope

We present Lick line-index measurements of standard stars from the list of Worthey. The spectra were taken with the multi-slit unit of the SCORPIO spectrograph at the 6-m Special Astrophysical observatory telescope. We describe in detail our method of analysis and explain the importance of using the Lick index system for studying extragalactic globular clusters. Our results show that the calibration of our instrumental system to the standard Lick system can be performed with high confidence.Comment: 12 pages, 3 figure

Near-field flow structure of a confined wall jet on flat and concave rough walls

Experimental results are presented of the mean flow and turbulence characteristics in the near field of a plane wall jet issuing from a nozzle onto flat and concave walls consisting of fixed sand beds. This is a flow configuration of interest for sediment erosion, also referred to as scouring. The measurements were made with an acoustic profiler that gives access to the three components of the instantaneous velocities. For the flat-wall flow, it is shown that the outer-layer spatial growth rate and the maxima of the Reynolds stresses approach the values accepted for the far field of a wall jet at a downstream distance $x/{b}_{0}\approx8$. These maxima are only about half the values of a plane free jet. This reduction in Reynolds stresses is also observed in the shear-layer region, $x/{b}_{0}\ 11$, the maximum Reynolds shear stress approaches the value of a plane free jet. This change in Reynolds stresses is related to the mean vertical velocity that is negative for $x/{b}_{0}\ <8$ and positive further downstream. The evolution of the inner region of the wall jet is found to be in good agreement with a previous model that explicitly includes the roughness length.On the concave wall, the mean flow and the Reynolds stresses are drastically changed by the adverse pressure gradient and especially by the development of Görtler vortices. On the downslope side of the scour hole, the flow is nearly separating with the wall shear stress tending to zero, whereas on the upslope side, the wall-friction coefficient is increased by a factor of about two by Görtler vortices. These vortices extend well into the outer layer and, just above the wall, cause a substantial increase in Reynolds shear stress