4,771 research outputs found
Topological transitions of the generalized Pancharatnam-Berry phase
Distinctfrom the dynamicalphase,in a cyclicevolution,a system’sstate may acquire an additionalcomponent,a.k.a.geometricphase.Recently, it has beendemonstrated that geometricphasescan be inducedby a sequenceof generalizedmeasurementsimplementedon a singlequbit.Furthermore, it has beenpredictedthat thesegeometricphasesmay exhibita topologicaltransitionas a functionof the measurementstrength.We demon-strate and studythis transitionexperimentallyby usingan opticalplatformwhere the qubitis representedbythe polarization of lightand the weak measurementis performedby meansof couplingwiththe spatial degreeof freedom.Our protocolcan be interpretedin termsof environment-inducedgeometricphases,whosevaluesare topologicallydeterminedby the environment-system couplingstrength.Our resultsshow that the two limitsof geometricphaseinducedby sequencesof eitherweak or projective measurementsare topologicallydistinct
Star Formation and Selective Dust Extinction in Luminous Starburst Galaxies
We investigate the star formation and dust extinction properties of very
luminous infrared galaxies whose spectra display a strong Hdelta line in
absorption and a moderate [OII] emission (e[a] spectrum). This spectral
combination has been suggested to be a useful method to identify dusty
starburst galaxies at any redshift on the basis of optical data alone. We
compare the average e(a) optical spectrum with synthetic spectra that include
both the stellar and the nebular contribution, allowing dust extinction to
affect differentially the stellar populations of different ages. We find that
reproducing the e(a) spectrum requires the youngest stellar generations to be
significantly more extinguished by dust than older stellar populations, and
implies a strong ongoing star formation activity at a level higher than in
quiescent spirals. A model fitting the optical spectrum does not necessarily
produce the observed FIR luminosity and this can be explained by the existence
of stellar populations which are practically obscured at optical wavelengths.
Models in which dust and stars are uniformly mixed yield a reddening of the
emerging emission lines which is too low compared to observations: additional
foreground reddening is required.Comment: 17 pages, 4 Postscript figures, ApJ in pres
Separating Agent-Functioning and Inter-Agent Coordination by Activated Modules: The DECOMAS Architecture
The embedding of self-organizing inter-agent processes in distributed
software applications enables the decentralized coordination system elements,
solely based on concerted, localized interactions. The separation and
encapsulation of the activities that are conceptually related to the
coordination, is a crucial concern for systematic development practices in
order to prepare the reuse and systematic integration of coordination processes
in software systems. Here, we discuss a programming model that is based on the
externalization of processes prescriptions and their embedding in Multi-Agent
Systems (MAS). One fundamental design concern for a corresponding execution
middleware is the minimal-invasive augmentation of the activities that affect
coordination. This design challenge is approached by the activation of agent
modules. Modules are converted to software elements that reason about and
modify their host agent. We discuss and formalize this extension within the
context of a generic coordination architecture and exemplify the proposed
programming model with the decentralized management of (web) service
infrastructures
A retrosynthetic co-templating method for the preparation of silicoaluminophosphate molecular sieves
This work has been supported by Johnson Matthey PLC, UK. Solid-state NMR spectra were obtained at the EPSRC UK National Solid-state NMR Service at Durham.A retrosynthetic method has been developed to design the synthesis of target zeotypes whose frameworks belong to the ABC-6 structural family and which contain gme cages. This permits the preparation of silicoaluminophosphate versions of AFX (SAPO-56), SFW (STA- 18) and GME (STA-19) topology types. The method makes simultaneous use of two organic structure directing agents (SDAs) to promote the formation of structural features such as cages or channels of the target framework. Computational modelling was used to identify SDAs for gme and other cages or channels in the target structures. The trimethylammonium cation was found to be the most favourable SDA for the gme cage while bisdiazabicyclooctane (DABCO) alkane cations and quaternary ammonium oligomers of DABCO with connecting polymethylene chain lengths of 4 to 8 methylene units acted as 1 templates for the additional cages or channels, respectively. The incorporation of each of the co-SDAs in the as-prepared materials was confirmed by chemical analysis, 13C MAS NMR and Rietveld refinement combined with computational modeling. Calcination of the SAPO- 56, STA-18 and some of the STA-19 materials gives microporous, fully tetrahedrally- coordinated framework solids with AFX, SFW and GME topologies: other STA-19 samples convert topotactically to SAPO-5. These results show that SAPOs in the ABC-6 family can be prepared via a targeted co-templating approach.PostprintPostprintPeer reviewe
Synthetic indole and melatonin derivatives exhibit antimalarial activity on the cell cycle of the human malaria parasite Plasmodium falciparum
Discovering the mechanisms by which cell signaling controls the cell cycle of the human malaria parasite Plasmodium falciparum is fundamental to designing more effective antimalarials. To better understand the impacts of melatonin structure and function on the cell cycle of P. falciparum, we have synthesized two families of structurally-related melatonin compounds (7–11 and 12–16). All synthesized melatonin analogs were assayed in P. falciparum culture and their antimalarial activities were measured by flow cytometry. We have found that the chemical modification of the carboxamide group attached at C-3 position of the indole ring of melatonin (6) was crucial for the action of the indole-related compounds on the P. falciparum cell cycle. Among the melatonin derivatives, only the compounds 12, 13 and 14 were capable of inhibiting the P. falciparum growth in low micromolar IC50. These results open good perspectives for the development of new drugs with novel mechanisms of action
Recurrence quantification analysis as a tool for the characterization of molecular dynamics simulations
A molecular dynamics simulation of a Lennard-Jones fluid, and a trajectory of
the B1 immunoglobulin G-binding domain of streptococcal protein G (B1-IgG)
simulated in water are analyzed by recurrence quantification, which is
noteworthy for its independence from stationarity constraints, as well as its
ability to detect transients, and both linear and nonlinear state changes. The
results demonstrate the sensitivity of the technique for the discrimination of
phase sensitive dynamics. Physical interpretation of the recurrence measures is
also discussed.Comment: 7 pages, 8 figures, revtex; revised for review for Phys. Rev. E
(clarifications and expansion of discussion)-- addition of the 8 postscript
figures previously omitted, but unchanged from version
Damping of supernova neutrino transitions in stochastic shock-wave density profiles
Supernova neutrino flavor transitions during the shock wave propagation are
known to encode relevant information not only about the matter density profile
but also about unknown neutrino properties, such as the mass hierarchy (normal
or inverted) and the mixing angle theta_13. While previous studies have
focussed on "deterministic" density profiles, we investigate the effect of
possible stochastic matter density fluctuations in the wake of supernova shock
waves. In particular, we study the impact of small-scale fluctuations on the
electron (anti)neutrino survival probability, and on the observable spectra of
inverse-beta-decay events in future water-Cherenkov detectors. We find that
such fluctuations, even with relatively small amplitudes, can have significant
damping effects on the flavor transition pattern, and can partly erase the
shock-wave imprint on the observable time spectra, especially for
sin^2(theta_13) > O(10^-3).Comment: v2 (23 pages, including 6 eps figures). Typos removed, references
updated, matches the published versio
High precision astrometry mission for the detection and characterization of nearby habitable planetary systems with the Nearby Earth Astrometric Telescope (NEAT)
(abridged) A complete census of planetary systems around a volume-limited
sample of solar-type stars (FGK dwarfs) in the Solar neighborhood with uniform
sensitivity down to Earth-mass planets within their Habitable Zones out to
several AUs would be a major milestone in extrasolar planets astrophysics. This
fundamental goal can be achieved with a mission concept such as NEAT - the
Nearby Earth Astrometric Telescope. NEAT is designed to carry out space-borne
extremely-high-precision astrometric measurements sufficient to detect
dynamical effects due to orbiting planets of mass even lower than Earth's
around the nearest stars. Such a survey mission would provide the actual
planetary masses and the full orbital geometry for all the components of the
detected planetary systems down to the Earth-mass limit. The NEAT performance
limits can be achieved by carrying out differential astrometry between the
targets and a set of suitable reference stars in the field. The NEAT instrument
design consists of an off-axis parabola single-mirror telescope, a detector
with a large field of view made of small movable CCDs located around a fixed
central CCD, and an interferometric calibration system originating from
metrology fibers located at the primary mirror. The proposed mission
architecture relies on the use of two satellites operating at L2 for 5 years,
flying in formation and offering a capability of more than 20,000
reconfigurations (alternative option uses deployable boom). The NEAT primary
science program will encompass an astrometric survey of our 200 closest F-, G-
and K-type stellar neighbors, with an average of 50 visits. The remaining time
might be allocated to improve the characterization of the architecture of
selected planetary systems around nearby targets of specific interest (low-mass
stars, young stars, etc.) discovered by Gaia, ground-based high-precision
radial-velocity surveys.Comment: Accepted for publication in Experimental Astronomy. The full member
list of the NEAT proposal and the news about the project are available at
http://neat.obs.ujf-grenoble.fr. The final publication is available at
http://www.springerlink.co
Diversity across Major and Candidate Genes in European Local Pig Breeds
In the frame of the European TREASURE* project, the genetic characterization of 20 local pig breeds is being performed with genetic and genomic tools. The objectives are the study of genetic diversity in these populations and the identification of useful markers for authentication, traceability, conservation and breeding programs. In first place, a candidate gene approach has been applied and the most relevant genes and mutations associated with pig productive, meat quality, reproductive and disease resistance traits have been prioritized and analyzed. Two OpenArray® chips of 32 and 16 SNPs were designed and genotyped in 48 animals from each one of 20 breeds included in the project (Alentejana, Apulo Calabrese, Basque, Bísaro, Black Majorcan, Black Sicilian, Black Slavonian, Casertana, Cinta Senese, Gascon, Iberian, Krskopolje, Lithuanian indigenous wattle, Mangalitsa, Mora Romagnola, Moravka, Old Lithuanian White, Sarda, Schwäbisch Hällisches, Turopolje). Forty SNPs located in 34 genes were successfully genotyped (MC1R, TYRP1, NR6A, PCK1, RYR1, IGF2, MC4R, PHKG1, SCD, GBP5, TAS2R39, TAS2R4, MUC4, ESR1, CYP2E1, LEP, CAST, MTTP, CYB5A, FTO, PPARGC1A, CAPN1, PPARD, CTSL, LEPR, PRKAG3, ACACA, KIT, ACSL4, ADIPOQ, FASN, AHR, FUT1, MSTN). Results provide relevant information regarding genetic diversity and segregation of SNPs responsible for specific production and quality traits. Coat color and morphological trait-genes, showing low level of segregation, and fixed SNPs may be useful for traceability. On the other hand, we detected SNPs which may be useful for breeding programs. For instance, we observed predominance of unfavorable alleles for disease resistance and boar taint genes in most breeds, and segregation of many genes involved in meat quality, fatness and growth. These results joint with ongoing genomic assays, will provide essential information regarding genetic diversity, structure, selective signatures and biological processes responsible for specific production and quality traits
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