168 research outputs found
High-Resolution Observations in B1-IRS: ammonia, CCS and water masers
We present a study of the structure and dynamics of the star forming region
B1-IRS (IRAS 03301+3057) using the properties of different molecules at high
angular resolution (~4''). We have used VLA observations of NH3, CCS, and H2O
masers at 1 cm. CCS emission shows three clumps around the central source, with
a velocity gradient from red to blueshifted velocities towards the protostar,
probably due to the interaction with outflowing material. Water maser emission
is elongated in the same direction as a reflection nebula detected at 2micron
by 2MASS, with the maser spots located in a structure of some hundreds of AU
from the central source, possibly tracing a jet. We propose a new outflow model
to explain all our observations, consisting of a molecular outflow near the
plane of the sky. Ammonia emission is extended and anticorrelated with CCS. We
have detected for the first time this anticorrelation at small scales (1400 AU)
in a star forming region.Comment: 6 pages, 3 figures. To appear in the Proceedings of the 2004 European
Workshop: "Dense Molecular Gas around Protostars and in Galactic Nuclei",
Eds. Y.Hagiwara, W.A.Baan, H.J.van Langevelde, 2004, a special issue of ApSS,
Kluwe
Solar Images Processing in Parallel Environment
This paper presents the PVA-BDA project (Processing, Visualization and Analysis in ParallelEnvironment of the BDA Data) that has been developed for processing of solar images that will be captured bythe BDA (Brazilian Decimetric Array), a radio telescope under development at the National Institute for SpaceResearch (INPE). In a joint effort between the Department of Computer Science at Federal University of SãoCarlos (DC/UFSCar), the Astrophysics Division (DAS) and Associated Laboratory for Computing and AppliedMathematics (LAC) at INPE, a high performance parallel system is being developed with capacity to supportrealistic applications, involving a reasonable amount of parallel processing, in order to carry out the processing,visualization and analysis of solar images captured by BDA, in real time. The aim is to create the conditions forstarting a study of the solar weather forecast. The forecast of solar explosions are important as they may causeserious perturbations in terrestrial communication systems. An application for 3D reconstruction of X-raytomographic images of the solar atmosphere was developed at DC/UFSCar. Due to the need for the 3Dreconstruction of solar magnetic structures, in real-time, this application was implemented to execute in a parallelmachine using DSPs
Driven Diffusion in the Two-Dimensional Lattice Coulomb Gas; A Model for Flux Flow in Superconducting Networks
We carry out driven diffusion Monte Carlo simulations of the two dimensional
classical lattice Coulomb gas in an applied uniform electric field, as a model
for vortex motion due to an applied d.c. current, in a periodic superconducting
network. A finite-size version of dynamic scaling is used to extract the
dynamic critical exponent z, and infer the non-linear response at the
transition temperature. We consider the f=0 and f=1/2 cases, corresponding to
no applied magnetic field, and to one half flux quantum per unit cell of the
network respectively.Comment: 25 pages, 7 figures (available from [email protected]),
RevTex3.0, URST12
Search for Kosterlitz-Thouless transition in a triangular Ising antiferromagnet with further-neighbour ferromagnetic interactions
We investigate an antiferromagnetic triangular Ising model with anisotropic
ferromagnetic interactions between next-nearest neighbours, originally proposed
by Kitatani and Oguchi (J. Phys. Soc. Japan {\bf 57}, 1344 (1988)). The phase
diagram as a function of temperature and the ratio between first- and second-
neighbour interaction strengths is thoroughly examined. We search for a
Kosterlitz-Thouless transition to a state with algebraic decay of correlations,
calculating the correlation lengths on strips of width up to 15 sites by
transfer-matrix methods. Phenomenological renormalization, conformal invariance
arguments, the Roomany-Wyld approximation and a direct analysis of the scaled
mass gaps are used. Our results provide limited evidence that a
Kosterlitz-Thouless phase is present. Alternative scenarios are discussed.Comment: 10 pages, RevTeX 3; 11 Postscript figures (uuencoded); to appear in
Phys. Rev. E (1995
Phase transitions in the antiferromagnetic XY model with a kagome lattice
The ground state of the antiferromagnetic XY model with a kagome lattice is
characterized by a well developed accidental degeneracy. As a consequence the
phase transition in this system consists in unbinding of pairs of fractional
vortices. Addition of the next-to-nearest neighbors (NNN) interaction leads to
stabilization of the long-range order in chirality (staggered chirality). We
show that the phase transition, related with destruction of this long-range
order, can happen as a separate phase transition below the temperature of the
fractional vortex pairs unbinding only if the NNN coupling is extremely weak,
and find how the temperature of this transition depends on coupling constants.
We also demonstarte that the antiferromagnetic ordering of chiralities and,
accordingly, the presence of the second phase transition are induced by the
free energy of spin wave fluctuations even in absence of the NNN coupling.Comment: 10 pages (Revtex) + 8 figures (in 2 postscript files
Velocity-force characteristics of an interface driven through a periodic potential
We study the creep dynamics of a two-dimensional interface driven through a
periodic potential using dynamical renormalization group methods. We find that
the nature of weak-drive transport depends qualitatively on whether the
temperature is above or below the equilibrium roughening transition
temperature . Above , the velocity-force characteristics is Ohmic,
with linear mobility exhibiting a jump discontinuity across the transition. For
, the transport is highly nonlinear, exhibiting an interesting
crossover in temperature and weak external force . For intermediate drive,
, we find near a power-law velocity-force characteristics
, with , and well-below ,
, with . In the limit
of vanishing drive () the velocity-force characteristics crosses over
to , and is controlled by soliton nucleation.Comment: 18 pages, submitted to Phys. Rev.
Measuring the ß-decay Properties of Neutron-rich Exotic Pm, Sm, Eu, and Gd Isotopes to Constrain the Nucleosynthesis Yields in the Rare-earth Region
The ß-delayed neutron-emission probabilities of 28 exotic neutron-rich isotopes of Pm, Sm, Eu, and Gd were measured for the first time at RIKEN Nishina Center using the Advanced Implantation Detector Array (AIDA) and the BRIKEN neutron detector array. The existing ß-decay half-life (T1/2) database was significantly increased toward more neutron-rich isotopes, and uncertainties for previously measured values were decreased. The new data not only constrain the theoretical predictions of half-lives and ß-delayed neutron-emission probabilities, but also allow for probing the mechanisms of formation of the high-mass wing of the rare-earth peak located at A ˜ 160 in the r-process abundance distribution through astrophysical reaction network calculations. An uncertainty quantification of the calculated abundance patterns with the new data shows a reduction of the uncertainty in the rare-earth peak region. The newly introduced variance-based sensitivity analysis method offers valuable insight into the influence of important nuclear physics inputs on the calculated abundance patterns. The analysis has identified the half-lives of 168Sm and of several gadolinium isotopes as some of the key variables among the current experimental data to understand the remaining abundance uncertainty at A = 167–172.Peer ReviewedPostprint (published version
Sp110 transcription is induced and required by Anaplasma phagocytophilum for infection of human promyelocytic cells
<p>Abstract</p> <p>Background</p> <p>The tick-borne intracellular pathogen, <it>Anaplasma phagocytophilum </it>(Rickettsiales: Anaplasmataceae) causes human granulocytic anaplasmosis after infection of polymorphonuclear leucocytes. The human Sp110 gene is a member of the nuclear body (NB) components that functions as a nuclear hormone receptor transcriptional coactivator and plays an important role in immunoprotective mechanisms against pathogens in humans. In this research, we hypothesized that Sp110 may be involved in the infection of human promyelocytic HL-60 cells with <it>A. phagocytophilum</it>.</p> <p>Methods</p> <p>The human Sp110 and <it>A. phagocytophilum msp4 </it>mRNA levels were evaluated by real-time RT-PCR in infected human HL-60 cells sampled at 0, 12, 24, 48, 72 and 96 hours post-infection. The effect of Sp110 expression on <it>A. phagocytophilum </it>infection was determined by RNA interference (RNAi). The expression of Sp110 was silenced in HL-60 cells by RNAi using pre-designed siRNAs using the Nucleofector 96-well shuttle system (Amaxa Biosystems, Gaithersburg, MD, USA). The <it>A. phagocytophilum </it>infection levels were evaluated in HL-60 cells after RNAi by real-time PCR of <it>msp4 </it>and normalizing against human <it>Alu </it>sequences.</p> <p>Results</p> <p>While Sp110 mRNA levels increased concurrently with <it>A. phagocytophilum </it>infections in HL-60 cells, the silencing of Sp110 expression by RNA interference resulted in decreased infection levels.</p> <p>Conclusion</p> <p>These results demonstrated that Sp110 expression is required for <it>A. phagocytophilum </it>infection and multiplication in HL-60 cells, and suggest a previously undescribed mechanism by which <it>A. phagocytophilum </it>modulates Sp110 mRNA levels to facilitate establishment of infection of human HL-60 cells.</p
Applications of yeast flocculation in biotechnological processes
A review on the main aspects associated with yeast flocculation and its application
in biotechnological processes is presented. This subject is addressed following three
main aspects – the basics of yeast flocculation, the development of “new” flocculating yeast
strains and bioreactor development. In what concerns the basics of yeast flocculation, the
state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast
flocculation is reported. The construction of flocculating yeast strains includes not only the
recombinant constitutive flocculent brewer’s yeast, but also recombinant flocculent yeast
for lactose metabolisation and ethanol production. Furthermore, recent work on the
heterologous β-galactosidase production using a recombinant flocculent Saccharomyces
cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties,
mainly associated with a high solid phase hold-up, a section dedicated to its operation is
presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor
hydrodynamics and mass transfer properties of flocculating cell cultures are considered.
Finally, the paper concludes describing some of the applications of high cell density
flocculation bioreactors and discussing potential new uses of these systems.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI - BD11306/97
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