5,764 research outputs found
Gender homophily from spatial behavior in a primary school: a sociometric study
We investigate gender homophily in the spatial proximity of children (6 to 12
years old) in a French primary school, using time-resolved data on face-to-face
proximity recorded by means of wearable sensors. For strong ties, i.e., for
pairs of children who interact more than a defined threshold, we find
statistical evidence of gender preference that increases with grade. For weak
ties, conversely, gender homophily is negatively correlated with grade for
girls, and positively correlated with grade for boys. This different evolution
with grade of weak and strong ties exposes a contrasted picture of gender
homophily
De Novo Genome Assembly of Phormia regina (Diptera: Calliphoridae)
poster abstractPhormia regina (Meigen), commonly known as the black blow fly, is a dipteran that belongs to the family Calliphoridae (blow flies). Calliphorids play an important role in various research fields like ecology, medical studies, veterinary and forensic sciences. P. regina is one of the common forensically relevant insects in North America and is typically used to assist in estimating post-mortem intervals (PMI).
To better understand the roles it plays in the numerous research fields, we aim to re-construct its genome using next generation sequencing technologies. We are specifically focusing on generating a reference genome by de novo assembly then use the genomic data to identify genetic markers (microsatellites, single nucleotide polymorphisms) that contribute to intra- and inter-population variation with regards to geographic location.
DNA was extracted from five adult male and female flies and was sequenced using the Illumina HiSeq2000 sequencing platform. More than 250 million high quality reads were produced from each sex. These reads were used in the de novo genome assembly of the female, male and combined sexes. The assembled draft genomes produced approximately 251,115 contigs, 306,273 contigs, and 325,664 contigs respectively. The assembled genome sizes totaled to ~524 Mbp and ~508 Mbp for the female and male flies, respectively. Compared to the estimated genome sizes from a previous study of 529 Mbp for females and 517 Mbp for males, we can conclude that a majority of the genome sequence (~99%) is included in the assembly. Gene prediction and annotation of the draft genomes are currently in progress.
The draft reference genomes assembled from this study will provide an important resource for analyzing genetic basis of variations between and among blow fly species, which will ultimately facilitate ongoing studies in various areas of research that utilize blow flies as study models. It will also be a source where reliable genomic data can be readily available and used in downstream analysis to increase the understanding of the genetic, molecular and cellular processes of blow flies
Comparative genomics of the sheep blow fly Lucilia cuprina
poster abstractInsects employ different adaptive strategies in response to selective pressures, such as competition for limited resources. Carrion insects provide the ideal case to study these fundamental processes of adaptive evolution due to the intense selective pressures placed on developing larvae with limited food resources, their widespread and abundant distributions, and the presence of geographically distinct populations with specialized adaptations. One adaptation is facultative ectoparasitism, where the insect strikes a healthy animal and feeds on the living flesh, providing a developmental advantage over competitor fly species, but causing significant harm to the host.
Lucilia species, which hybridize in the wild and form geographically distinct subpopulations in other regions, are diverging, meaning that we can observe and quantify early biological adaptive processes that govern speciation as they are occurring over hundreds, instead of millions, of years. The draft genome of a North American male Lucilia cuprina fly (carrion breeder) was assembled using a combination of short and long read sequences. This genome is compared to an existing Australian draft genome (ectoparasite) by elucidating genomic structure in key adaptive processes (i.e. immune system evasion) via high-throughput re-sequencing of parasitic specimens, gene prediction and annotation. The carcass colonized by or animal parasitized by both species, with some geographic overlap, provides a semi-controlled environment within the larger context of the ecosystem to sample a large number of individuals with similar life history strategies, allowing for direct comparative studies to elucidate the correlation between structure and function in the genomes of carrion flies – allowing us to understand biological adaptation and speciation
Retrospective study on the incidence of Salmonella isolations in animals in South Africa, 1996 to 2006
A retrospective study that involves the analysis of laboratory diagnostic data collected during the period 1996-2006 was conducted. A total of 3417 Salmonella isolations involving 183 different serotypes was recorded from 1999-2006, inclusive, at the Onderstepoort Veterinary Institute, Agricultural Research Council, South Africa. The most common serotypes were Salmonella enterica subspecies enterica serovar Typhimurium (917 incidents), Salmonella enterica subspecies enterica serovar Dublin (248 incidents), Salmonella enterica subspecies enterica serovar Enteritidis (232 incidents), Salmonella enterica subspecies enterica serovar Muenchen (164 incidents), Salmonella enterica subspecies enterica serovar Heidelberg (118 incidents) and Salmonella enterica subspecies enterica serovar Chester (113 incidents). The number of recorded Salmonella isolations over the period 1996 to 2006 varies considerably from year to year. The peak of 693 isolations was recorded in 1997, and the lowest, 108 incidents, in 2001. Of the total incidents recorded during the period of survey, 2410 (70.5 %) occurred in poultry and other birds, 641 (18.75 %) occurred in cattle, 255 (7.46) in pigs and 111 (3.24 %) in sheep. Despite the large number of serotypes isolated (183), 52% of incidents were due to only 6 serotypes in decreasing order of prevalence : S. Typhimurium, S. Dublin, S. Enteritidis, S. Muenchen, S. Heidelberg and S. Chester. Serovar Typhimurium was the most common serotype and was detected in all animal species sampled, with, 65 % (598) of the incidents occurring in poultry and 20 % (187) occurring in cattle. Of the total of 248 incidents of S. Dublin serotype, 95.6 % (237) of incidents occurred in cattle and of the 232 isolates of S. Enteritidis, 223 (96 %) originated from poultry. Serovar Choleraesuis was identified in 16 isolates from pigs. The following 4 serotypes were each recorded in more than 50 incidents : S. Hadar (102), S. Schwarzengrund (99), S. Mbandaka (94) and S. Sandiego (73). The trends of annual incidence of Salmonella infection in cattle, sheep, pigs, poultry and other birds during the 11-year period and the distribution of the main serotypes in individual species of animals from 1996-2006 are discussed
Water Vapour Effects in Mass Measurement
Water vapour inside the mass comparator enclosure is a critical parameter. In
fact, fluctuations of this parameter during mass weighing can lead to errors in
the determination of an unknown mass. To control that, a proposal method is
given and tested. Preliminary results of our observation of water vapour
sorption and desorption processes from walls and mass standard are reported
Deep Radio Imaging of Globular Clusters and the Cluster Pulsar Population
We have obtained deep multifrequency radio observations of seven globular
clusters using the Very Large Array and the Australia Telescope Compact Array.
Five of these, NGC 6440, NGC 6539, NGC 6544, NGC 6624 and Terzan 5 had
previously been detected in a shallower survey for steep spectrum radio sources
in globular clusters (Fruchter and Goss 1990). The sixth, the rich globular
cluster, Liller 1, had heretofore been undetected in the radio, and the
seventh, 47 Tucanae, was not included in our original survey. High resolution 6
and 20 cm images of three of the clusters, NGC 6440, NGC 6539, NGC 6624 reveal
only point sources coincident with pulsars which have been discovered
subsequent to our first imaging survey. 21 and 18 cm images reveal several
point sources within a few core-radii of the center of 47 Tuc. Two of these are
identified pulsars, and a third, which is both variable and has a steep
spectrum, is also most likely a pulsar previously identified by a pulsed
survey. However, the 6, 20 and 90 cm images of NGC 6544, Liller 1 and Terzan 5
display strong steep-spectrum emission which cannot be associated with known
pulsars. The image of the rich cluster Terzan 5 displays numerous point sources
within , or 4 core radii of the cluster center. The density of these
objects rises rapidly toward the core, where an elongated region of emission is
found. The brightest individual sources, as well as the extended emission,
possess the steep spectra expected of pulsars. Furthermore, the flux
distribution of the sources agrees well with the standard pulsar luminosity
function. The total luminosity and number of objects observed suggest that
Terzan 5 contains more pulsars than any other Galactic globular cluster.Comment: 33 pages, 6 Postscript figures; Accepted for publication in the
Astrophysical Journal; abstract abridged. PDF version also available at
http://nemesis.stsci.edu/~fruchter/fg99/fg99.pd
Semiclassical and quantum Liouville theory
We develop a functional integral approach to quantum Liouville field theory
completely independent of the hamiltonian approach. To this end on the sphere
topology we solve the Riemann-Hilbert problem for three singularities of finite
strength and a fourth one infinitesimal, by determining perturbatively the
Poincare' accessory parameters. This provides the semiclassical four point
vertex function with three finite charges and a fourth infinitesimal. Some of
the results are extended to the case of n finite charges and m infinitesimal.
With the same technique we compute the exact Green function on the sphere on
the background of three finite singularities. Turning to the full quantum
problem we address the calculation of the quantum determinant on the background
of three finite charges and of the further perturbative corrections. The zeta
function regularization provides a theory which is not invariant under local
conformal transformations. Instead by employing a regularization suggested in
the case of the pseudosphere by Zamolodchikov and Zamolodchikov we obtain the
correct quantum conformal dimensions from the one loop calculation and we show
explicitly that the two loop corrections do not change such dimensions. We then
apply the method to the case of the pseudosphere with one finite singularity
and compute the exact value for the quantum determinant. Such results are
compared to those of the conformal bootstrap approach finding complete
agreement.Comment: 12 pages, 1 figure, Contributed to 5th Meeting on Constrained
Dynamics and Quantum Gravity (QG05), Cala Gonone, Sardinia, Italy, 12-16 Sep
200
Liouville field theory with heavy charges. II. The conformal boundary case
We develop a general technique for computing functional integrals with fixed
area and boundary length constraints. The correct quantum dimensions for the
vertex functions are recovered by properly regularizing the Green function.
Explicit computation is given for the one point function providing the first
one loop check of the bootstrap formula.Comment: LaTeX 26 page
H(3)+ correlators from Liouville theory
We prove that arbitrary correlation functions of the H(3)+ model on a sphere
have a simple expression in terms of Liouville theory correlation functions.
This is based on the correspondence between the KZ and BPZ equations, and on
relations between the structure constants of Liouville theory and the H(3)+
model. In the critical level limit, these results imply a direct link between
eigenvectors of the Gaudin Hamiltonians and the problem of uniformization of
Riemann surfaces. We also present an expression for correlation functions of
the SL(2)/U(1) coset model in terms of correlation functions in Liouville
theory.Comment: 24 pages, v3: minor changes, references adde
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