804 research outputs found
Thermal diagnostic of the Optical Window on board LISA Pathfinder
Vacuum conditions inside the LTP Gravitational Reference Sensor must comply
with rather demanding requirements. The Optical Window (OW) is an interface
which seals the vacuum enclosure and, at the same time, lets the laser beam go
through for interferometric Metrology with the test masses. The OW is a
plane-parallel plate clamped in a Titanium flange, and is considerably
sensitive to thermal and stress fluctuations. It is critical for the required
precision measurements, hence its temperature will be carefully monitored in
flight. This paper reports on the results of a series of OW characterisation
laboratory runs, intended to study its response to selected thermal signals, as
well as their fit to numerical models, and the meaning of the latter. We find
that a single pole ARMA transfer function provides a consistent approximation
to the OW response to thermal excitations, and derive a relationship with the
physical processes taking place in the OW. We also show how system noise
reduction can be accomplished by means of that transfer function.Comment: 20 pages, 14 figures; accepted for publication in Class. Quantum Gra
A new special class of Petrov type D vacuum space-times in dimension five
Using extensions of the Newman-Penrose and Geroch-Held-Penrose formalisms to
five dimensions, we invariantly classify all Petrov type vacuum solutions
for which the Riemann tensor is isotropic in a plane orthogonal to a pair of
Weyl alligned null directionsComment: 4 pages, 1 table, no figures. Contribution to the proceedings of the
Spanish Relativity Meeting 2010 held in Granada (Spain
The LISA PathFinder DMU and Radiation Monitor
The LISA PathFinder DMU (Data Management Unit) flight model was formally
accepted by ESA and ASD on 11 February 2010, after all hardware and software
tests had been successfully completed. The diagnostics items are scheduled to
be delivered by the end of 2010. In this paper we review the requirements and
performance of this instrumentation, specially focusing on the Radiation
Monitor and the DMU, as well as the status of their programmed use during
mission operations, on which work is ongoing at the time of writing.Comment: 11 pages, 7 figures, prepared for the Proceedings of the 8th
International LISA Symposium, Classical and Quantum Gravit
Brucella abortus ure2 region contains an acid-activated urea transporter and a nickel transport system
<p>Abstract</p> <p>Background</p> <p>Urease is a virulence factor that plays a role in the resistance of <it>Brucella </it>to low pH conditions, both <it>in vivo </it>and <it>in vitro</it>. <it>Brucella </it>contains two separate urease gene clusters, <it>ure1 </it>and <it>ure2</it>. Although only <it>ure1 </it>codes for an active urease, <it>ure2 </it>is also transcribed, but its contribution to <it>Brucella </it>biology is unknown.</p> <p>Results</p> <p>Re-examination of the <it>ure2 </it>locus showed that the operon includes five genes downstream of <it>ureABCEFGDT </it>that are orthologs to a <it>nikKMLQO </it>cluster encoding an ECF-type transport system for nickel. <it>ureT </it>and <it>nikO </it>mutants were constructed and analyzed for urease activity and acid resistance. A non-polar <it>ureT </it>mutant was unaffected in urease activity at neutral pH but showed a significantly decreased activity at acidic pH. It also showed a decreased survival rate to pH 2 at low concentration of urea when compared to the wild type. The <it>nikO </it>mutant had decreased urease activity and acid resistance at all urea concentrations tested, and this phenotype could be reverted by the addition of nickel to the growth medium.</p> <p>Conclusions</p> <p>Based on these results, we concluded that the operon <it>ure2 </it>codes for an acid-activated urea transporter and a nickel transporter necessary for the maximal activity of the urease whose structural subunits are encoded exclusively by the genes in the <it>ure1 </it>operon.</p
Theory and modeling of the magnetic field measurement in LISA PathFinder
The magnetic diagnostics subsystem of the LISA Technology Package (LTP) on
board the LISA PathFinder (LPF) spacecraft includes a set of four tri-axial
fluxgate magnetometers, intended to measure with high precision the magnetic
field at their respective positions. However, their readouts do not provide a
direct measurement of the magnetic field at the positions of the test masses,
and hence an interpolation method must be designed and implemented to obtain
the values of the magnetic field at these positions. However, such
interpolation process faces serious difficulties. Indeed, the size of the
interpolation region is excessive for a linear interpolation to be reliable
while, on the other hand, the number of magnetometer channels does not provide
sufficient data to go beyond the linear approximation. We describe an
alternative method to address this issue, by means of neural network
algorithms. The key point in this approach is the ability of neural networks to
learn from suitable training data representing the behavior of the magnetic
field. Despite the relatively large distance between the test masses and the
magnetometers, and the insufficient number of data channels, we find that our
artificial neural network algorithm is able to reduce the estimation errors of
the field and gradient down to levels below 10%, a quite satisfactory result.
Learning efficiency can be best improved by making use of data obtained in
on-ground measurements prior to mission launch in all relevant satellite
locations and in real operation conditions. Reliable information on that
appears to be essential for a meaningful assessment of magnetic noise in the
LTP.Comment: 10 pages, 8 figures, 2 tables, submitted to Physical Review
Application of genomic and quantitative genetic tools to identify candidate resistance genes for brown rot resistance in peach.
The availability of a complete peach genome assembly and three different peach genome sequences created by our group provide new opportunities for application of genomic data and can improve the power of the classical Quantitative Trait Loci (QTL) approaches to identify candidate genes for peach disease resistance. Brown rot caused by Monilinia spp., is the most important fungal disease of stone fruits worldwide. Improved levels of peach fruit rot resistance have been identified in some cultivars and advanced selections developed in the UC Davis and USDA breeding programs. Whole genome sequencing of the Pop-DF parents lead to discovery of high-quality SNP markers for QTL genome scanning in this experimental population. Pop-DF created by crossing a brown rot moderately resistant cultivar 'Dr. Davis' and a brown rot resistant introgression line, 'F8,1-42', derived from an initial almond × peach interspecific hybrid, was evaluated for brown rot resistance in fruit of harvest maturity over three seasons. Using the SNP linkage map of Pop-DF and phenotypic data collected with inoculated fruit, a genome scan for QTL identified several SNP markers associated with brown rot resistance. Two of these QTLs were placed on linkage group 1, covering a large (physical) region on chromosome 1. The genome scan for QTL and SNP effects predicted several candidate genes associated with disease resistance responses in other host-pathogen systems. Two potential candidate genes, ppa011763m and ppa026453m, may be the genes primarily responsible for M. fructicola recognition in peach, activating both PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI) responses. Our results provide a foundation for further genetic dissection, marker assisted breeding for brown rot resistance, and development of peach cultivars resistant to brown rot
LISA and LISA PathFinder, the endeavour to detect low frequency GWs
This is a review about LISA and its technology demonstrator, LISA PathFinder.
We first describe the conceptual problems which need to be overcome in order to
set up a working interferometric detector of low frequency Gravitational Waves
(GW), then summarise the solutions to them as currently conceived by the LISA
mission team. This will show that some of these solutions require new
technological abilities which are still under development, and which need
proper test before being fully implemented. LISA PathFinder (LPF) is the the
testbed for such technologies. The final part of the paper will address the
ideas and concepts behind the PathFinder as well as their impact on LISA.Comment: 25 pages, 21 figures, presented at the Spanish Relativity Meeting,
Mallorca September 2006. Will be published in Journal of Physics: Conference
Series, IOP. To be published in Journal of Physics: Conference Series, IO
Estudio piloto sobre la prescripción en situaciones excepcionales. Uso de medicamentos de humana en medicina veterinaria
En este trabajo se ha realizado una revisión de los medicamentos de uso humano prescritos para animales de compañía (perros y gatos) con el fin de comprobar el cumplimiento por parte del veterinario del supuesto de "prescripción excepcional". Para ello se llevó a cabo un estudio piloto transversal retrospectivo durante un periodo de 2 años de los medicamentos de uso humano prescritos para animales de compañía y su alternativa en medicina veterinaria. Los datos han sido obtenidos a partir de los registros en el libro recetario de tres Oficinas de Farmacia de la Comunidad de Madrid. Como conclusión de este estudio piloto, podemos señalar que para algunos de los medicamentos de uso humano prescritos en pequeños animales existen medicamentos de uso veterinario que podría ser la primera alternativa terapéutica
Petrov D vacuum spaces revisited: Identities and Invariant Classification
For Petrov D vacuum spaces, two simple identities are rederived and some new
identities are obtained, in a manageable form, by a systematic and transparent
analysis using the GHP formalism. This gives a complete involutive set of
tables for the four GHP derivatives on each of the four GHP spin coefficients
and the one Weyl tensor component. It follows directly from these results that
the theoretical upper bound on the order of covariant differentiation of the
Riemann tensor required for a Karlhede classification of these spaces is
reduced to two.Comment: Proof about the Karlhede upper bound improved and discussion of case
IIIA re-written. Acknowledgments section expanded. To appear in Classical and
Quantum Gravit
Effects of nodular extracts of Alnus glutinosa (L.) Gaertn. on nitrogen fixation (Acetylene reduction assay) and denitrification in different soils
European alder (Alnus glutinosa [L.] Gaertn) nodules were maintained under conditions that allow their exudation (water stress). The effect of this nodular extracts colected on free nitrogen fixation (acetylene reduction assay [ARA]) and denitrification, was evaluated in three soils of significativelydifferent physico-chemicalcharacteristics. The comparisons with controls having different concentrations of glucose as carbon source suggest that, in the assayed conditions, the nodular european alder extracts activate ARA (up to 9.97% respect water control) and produces a partial inhibition of denitrification. The effects do not seem to be due neither to organic carbon nor to nitrate, but rather to specific activator(s) and inhibitor(s) of the processes considered.Nódulos radicales de aliso europeo [Alnusglutinosa (L.)Gaertn.] fueron mantenidos en condiciones que optimizan el proceso de exudación (estrés hídrico). Se evaluó el efecto de dichos extractos sobre la fijación libre de nitrógeno (ARA) y desnitrificación en tres suelos con diferencias significativas en sus características físico-químicas. Las comparaciones con diferentes controles, muestran que los extractos activan (en un 9.97%) el ARA y promueven una inhibición parcial de la desnitrificación. Los efectos no parecen causados por el aporte de carbono orgánico o de nitrato por parte de los exudados, sino por algún activador o inhibidor especifico de los procesos considerados
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