360 research outputs found
UCDs as Probes of the Major and Minor Merger Histories of Galaxies
Two competing theories posit that Ultra Compact Dwarfs (UCDs) form either as
the stripped nuclei of dwarf galaxies or as giant globular clusters (GGCs)
associated with the largest globular cluster (GC) systems. By focussing on the
field and group environments where young UCDs may be most common, we have
discovered the first UCD that is clearly the result of recent (<4 Gyr ago)
stripping of a companion galaxy. However, we have also found a definitive case
of a multiple-UCD system created via GC formation processes, which are likely
associated with major galaxy mergers. We demonstrate that it is possible to
reliably distinguish the two types of UCD, thereby probing both the major and
minor merger histories of individual galaxies.Comment: 2 pages, 1 figure, to appear in the proceedings of the conference "A
Universe of Dwarf Galaxies" (Lyon, June 14-18, 2010
Hidrogenionic potential (pH) of the attractant, trap density and control threshold for Ceratitis capitata (Diptera: tephritidae) on Hamlin oranges in São Paulo central region, Brazil
This study evaluated the effect of initial pH values of 4.5, 6.5 and 8.5 of the attractant
(protein bait) Milhocina® and borax (sodium borate) in the feld, on the capture of fruit flies in McPhail
traps, using 1, 2, 4 and 8 traps per hectare, in order to estimate control thresholds in a Hamlin orange grove
in the central region of the state of São Paulo. The most abundant fruit fly species was Ceratitis capitata,
comprising almost 99% of the fruit flies captured, of which 80% were females. The largest captures of C.
capitata were found in traps baited with Milhocina® and borax at pH 8.5. Captures per trap for the four
densities were similar, indicating that the population can be estimated with one trap per hectare in areas
with high populations. It was found positive relationships between captures of C. capitata and the number
of Hamlin oranges damaged, 2 and 3 weeks after capture. It was obtained equations that correlate captures
and damage levels which can be used to estimate control thresholds. The average loss caused in Hamlin
orange fruits by C. capitata was 2.5 tons per hectare or 7.5% of production.Esta pesquisa teve como objetivos: avaliar o efeito do pH inicial, 4.5; 6.5 e 8.5, do atrativo
proteico Milhocina® e bórax (tetraborato de sódio) na captura de moscas-das-frutas em armadilhas McPhail;
estudar densidades de armadilhas, 1; 2; 4 e 8 por hectare, para estimar níveis de controle em laranja cv.
Hamlin, na região central de São Paulo. A espécie predominante, com 99% das moscas-das-frutas capturadas,
foi Ceratitis capitata, sendo 80% de fêmeas. As maiores capturas de C. capitata ocorreram nas armadilhas
com Milhocina® e bórax em pH 8.5. As capturas, nas 4 densidades, foram semelhantes, indicando que a
população pode ser estimada com uma armadilha por hectare em áreas de altas populações. Houve relações
positivas entre capturas de C. capitata e o número de frutos danificados, 2 e 3 semanas após a captura. Assim,
foram obtidas equações que relacionam a captura e o dano, possibilitando estimar níveis de controle desse
inseto. As perdas médias causadas por C. capitata em laranja cv. Hamlin chegaram a 2,5 toneladas de frutos
por hectare ou 7,5% da produção.info:eu-repo/semantics/publishedVersio
Cost Containment Through Disability Prevention: Preliminary Results of a Health Promotion Workshop for People with Physical Disabilities
The Disability Prevention Project at the University of Montana and the University of Kansas has developed and evaluated an eight week workshop and self-help manual that targets the prevention and management of secondary conditions among adults with spinal cord injuries. The preliminary results of this intervention are very encouraging
A SLUGGS and Gemini/GMOS combined study of the elliptical galaxy M60: wide-field photometry and kinematics of the globular cluster system
We present new wide-field photometry and spectroscopy of the globular clusters (GCs) around NGC 4649 (M60), the third brightest galaxy in the Virgo cluster. Imaging of NGC 4649 was assembled from a recently obtained Hubble Space Telescope/Advanced Camera for Surveys mosaic, and new Subaru/Suprime-Cam and archival Canada–France–Hawaii Telescope/MegaCam data. About 1200 sources were followed up spectroscopically using combined observations from three multi-object spectrographs: Keck/Deep Imaging Multi-Object Spectrograph, Gemini/Gemini Multi-Object Spectrograph and Multiple Mirror Telescope/Hectospec. We confirm 431 unique GCs belonging to NGC 4649, a factor of 3.5 larger than previous data sets and with a factor of 3 improvement in velocity precision. We confirm significant GC colour bimodality and find that the red GCs are more centrally concentrated, while the blue GCs are more spatially extended. We infer negative GC colour gradients in the innermost 20 kpc and flat gradients out to large radii. Rotation is detected along the galaxy major axis for all tracers: blue GCs, red GCs, galaxy stars and planetary nebulae. We compare the observed properties of NGC 4649 with galaxy formation models. We find that formation via a major merger between two gas-poor galaxies, followed by satellite accretion, can consistently reproduce the observations of NGC 4649 at different radii. We find no strong evidence to support an interaction between NGC 4649 and the neighbouring spiral galaxy NGC 4647. We identify interesting GC kinematic features in our data, such as counter-rotating subgroups and bumpy kinematic profiles, which encode more clues about the formation history of NGC 4649
Adaptive optics in high-contrast imaging
The development of adaptive optics (AO) played a major role in modern
astronomy over the last three decades. By compensating for the atmospheric
turbulence, these systems enable to reach the diffraction limit on large
telescopes. In this review, we will focus on high contrast applications of
adaptive optics, namely, imaging the close vicinity of bright stellar objects
and revealing regions otherwise hidden within the turbulent halo of the
atmosphere to look for objects with a contrast ratio lower than 10^-4 with
respect to the central star. Such high-contrast AO-corrected observations have
led to fundamental results in our current understanding of planetary formation
and evolution as well as stellar evolution. AO systems equipped three
generations of instruments, from the first pioneering experiments in the
nineties, to the first wave of instruments on 8m-class telescopes in the years
2000, and finally to the extreme AO systems that have recently started
operations. Along with high-contrast techniques, AO enables to reveal the
circumstellar environment: massive protoplanetary disks featuring spiral arms,
gaps or other asymmetries hinting at on-going planet formation, young giant
planets shining in thermal emission, or tenuous debris disks and micron-sized
dust leftover from collisions in massive asteroid-belt analogs. After
introducing the science case and technical requirements, we will review the
architecture of standard and extreme AO systems, before presenting a few
selected science highlights obtained with recent AO instruments.Comment: 24 pages, 14 figure
The baryonic collapse efficiency of galaxy groups in the RESOLVE and ECO surveys
We examine the z = 0 group-integrated stellar and cold baryonic (stars + cold atomic gas) mass functions (group SMF and CBMF) and the baryonic collapse efficiency (group cold baryonic to dark matter halo mass ratio) using the RESOLVE and ECO survey galaxy group catalogs and a GALFORM semi-analytic model (SAM) mock catalog. The group SMF and CBMF fall off more steeply at high masses and rise with a shallower low-mass slope than the theoretical halo mass function (HMF). The transition occurs at the group-integrated cold baryonic mass Mbary cold ~ 1011 M. The SAM, however, has significantly fewer groups at the transition mass ∼1011 M and a steeper low-mass slope than the data, suggesting that feedback is too weak in low-mass halos and conversely too strong near the transition mass. Using literature prescriptions to include hot halo gas and potential unobservable galaxy gas produces a group BMF with a slope similar to the HMF even below the transition mass. Its normalization is lower by a factor of ∼2, in agreement with estimates of warm-hot gas making up the remaining difference. We compute baryonic collapse efficiency with the halo mass calculated two ways, via halo abundance matching (HAM) and via dynamics (extended all the way to three-galaxy groups using stacking). Using HAM, we find that baryonic collapse efficiencies reach a flat maximum for groups across the halo mass range of Mhalo ~ 1011.4 - 12 M, which we label “nascent groups.” Using dynamics, however, we find greater scatter in baryonic collapse efficiencies, likely indicating variation in group hot-to-cold baryon ratios. Similarly, we see higher scatter in baryonic collapse efficiencies in the SAM when using its true groups and their group halo masses as opposed to friends-of-friends groups and HAM masses
Risk factors for household vector abundance using indoor CDC light traps in a high malaria transmission area of Northern Zambia
Malaria transmission is dependent on the density and distribution of mosquito vectors, but drivers of vector abundance have not been adequately studied across a range of transmission settings. To inform intervention strategies for high-burden areas, further investigation is needed to identify predictors of vector abundance. Active household (HH) surveillance was conducted in Nchelenge district, Luapula Province, northern Zambia, a high-transmission setting with limited impact ofmalaria control. Between April 2012 and July 2017,mosquitoeswere collected indoors during HH visits using CDC light traps. Demographic, environmental, and climatological correlates of vector abundance were identified using log-binomial regressionmodels with robust standard errors. The primarymalaria vectors in this setting were Anopheles funestus sensu stricto (s.s.) andAnopheles gambiae s.s. Anopheles funestus predominated inboth seasons, with a peak in the dry season. Anopheles gambiae peaked at lower numbers in the rainy season. Environmental, climatic, and demographic factors were correlated with HH vector abundance. Higher vector counts were found in rural areas with low population density and among HHs close to roads and small streams. Vector counts were lower with increasing elevation and slope. Anopheles funestus was negatively associated with rainfall at lags of 2-6weeks, and An. gambiae was positively associated with rainfall at lags of 3-10 weeks. Both vectors had varying relationships with temperature. These results suggest thatmalaria vector control in Nchelenge district should occur throughout the year, with an increased focus on dry-season transmission and rural areas
Classical capacity of quantum channels with general Markovian correlated noise
The classical capacity of a quantum channel with arbitrary Markovian
correlated noise is evaluated. For the general case of a channel with long-term
memory, which corresponds to a Markov chain which does not converge to
equilibrium, the capacity is expressed in terms of the communicating classes of
the Markov chain. For an irreducible and aperiodic Markov chain, the channel is
forgetful, and one retrieves the known expression for the capacity
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An update for the MuCool test area
Construction of a new facility known as the MuCool Test Area (MTA) has been completed at Fermi National Accelerator Laboratory. This facility supports research in new accelerator technologies for future endeavors such as a Neutrino Factory or Muon Collider. During the summer of 2004, an initial set of tests was completed for the filling of a convection-style liquid hydrogen absorber designed by KEK. The absorber contained 6.2 liquid liters of hydrogen and was tested for a range of heating conditions to quantify the absorber's heat exchanger performance. Future work at Fermilab includes the design, construction, and installation of a forced-flow absorber to be used with other components built to investigate the properties of a muon ionization cooling channel. A Tevatron-style refrigerator/compressor building is to be operational by spring of 2006 in support of the absorber tests and also to provide 5-K helium and liquid nitrogen to a 5-T solenoid magnet, an active element of the future test apparatus. The refrigerator will be configured in such a manner as to meet the 5 K and 14-20-K helium needs of the MTA. This paper reviews the challenges and successes of the past KEK absorber tests as well as looks into the future cryogenic capabilities and intentions of the site
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