990 research outputs found
Solving the stellar 62Ni problem with AMS
An accurate knowledge of the neutron capture cross sections of 62,63Ni is
crucial since both isotopes take key positions which affect the whole reaction
flow in the weak s process up to A=90. No experimental value for the
63Ni(n,gamma) cross section exists so far, and until recently the experimental
values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12
and 37 mb. This latter discrepancy could now be solved by two activations with
following AMS using the GAMS setup at the Munich tandem accelerator which are
also in perfect agreement with a recent time-of-flight measurement. The
resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to
be 30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the
64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5
MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at
Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample
activated at 13.5 MeV revealed a cross section smaller by more than a factor of
2 compared to NON-SMOKER predictions.Comment: Proceedings of the 11th International Conference on Accelerator Mass
Spectrometry in Rome, Sept. 14-19, 2008; to be published in Nucl. Instr.
Meth.
HST Imaging of the BL Lacertae Object OJ 287
Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae object
OJ 287 and the surrounding field are presented. We find evidence of associated
extended nebulosity near OJ 287, as well as a small nebulosity to the West,
which may be spatially coincident with the position of previously observed
radio emission. The brightness of a host galaxy is difficult to determine due
to the brightness of the active nucleus, but it lies in the range -21.5 > M_R >
-23.1 (H_0 = 100 km s^{-1} Mpc^{-1}, q_0 = 0). No evidence is seen for the
previously reported optical ``jet'' at position angle 220 degrees to a surface
brightness limit of I = 24.3 mag arcsec^{-2}. There are several resolved and
unresolved objects within 17'' of OJ~287 in the field to limits of I=25 (point
source 5\sigma detections). The magnitudes and relative positions of these
objects are reported. An offset in the centroid position between the OJ 287
point source and the underlying nebulosity reported by Wurtz, Stocke and Yee is
confirmed and measured to be about 0.4 (1.2h^{-1} kpc at the redshift of
OJ~287). This offset is tentatively interpreted as evidence for recent merger
activity rather than a sign of gravitational microlensing.Comment: To appear in ApJ Letters, 3 jpg figure
Bone Plasticity in Response to Exercise Is Sex-Dependent in Rats
Purpose: To characterize the potential sexual dimorphism of bone in response to exercise.Methods: Young male and female Wistar rats were either submitted to 12 weeks of exercise or remained sedentary. the training load was adjusted at the mid-trial (week 6) by the maximal speed test. A mechanical test was performed to measure the maximal force, resilience, stiffness, and fracture load. the bone structure, formation, and resorption were obtained by histomorphometric analyses. Type I collagen (COL I) mRNA expression and tartrate-resistant acid phosphatase (TRAP) mRNA expression were evaluated by quantitative real-time PCR (qPCR).Results: the male and female trained rats significantly improved their maximum speed during the maximal exercise test (main effect of training; p<0.0001). the male rats were significantly heavier than the females, irrespective of training (main effect of sex; p<0.0001). Similarly, both the weight and length of the femur were greater for the male rats when compared with the females (main effect of sex; p<0.0001 and p<0.0001, respectively). the trabecular volume was positively affected by exercise in male and female rats (main effect of training; p = 0.001), whereas the trabecular thickness, resilience, mineral apposition rate, and bone formation rate increased only in the trained males (within-sex comparison; p<0.05 for all parameters), demonstrating the sexual dimorphism in response to exercise. Accordingly, the number of osteocytes increased significantly only in the trained males (within-sex comparison; p<0.05). Pearson's correlation analyses revealed that the COL I mRNA expression and TRAP mRNA expression were positively and negatively, respectively, related to the parameters of bone remodeling obtained from the histomorphometric analysis (r = 0.59 to 0.85; p<0.05).Conclusion: Exercise yielded differential adaptations with respect to bone structure, biomechanical proprieties, and molecular signaling in male and female rats.Univ São Paulo, Sch Med, Div Nephrol, São Paulo, BrazilUniv São Paulo, Sch Phys Educ & Sport, Dept Sports, São Paulo, BrazilUniv São Paulo, Inst Biomed Sci, Dept Anat, São Paulo, BrazilUniv São Paulo, Sch Med, Div Rheumatol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Physiol Sci, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Physiol Sci, São Paulo, BrazilWeb of Scienc
Comprometimento cognitivo leve: rastreio cognitivo ou avaliação neuropsicológica?
OBJECTIVE: To describe the neuropsychological profile of mild cognitive impairment subtypes (amnestic, non-amnestic and multiple-domain) of a clinical sample. We further address the diagnostic properties of the Mini-Mental State Examination and the Cambridge Cognitive Examination for the identification of the different mild cognitive impairment subtypes in clinical practice. METHOD: Cross-sectional clinical and neuropsychological evaluation of 249 elderly patients attending a memory clinic at a university hospital in Sao Paulo, Brazil. RESULTS: The performance of patients with mild cognitive impairment was heterogeneous across the different subtests of the neuropsychological battery, with a trend towards an overall worse performance for amnestic (particularly multiple domain) mild cognitive impairment as compared to non-amnestic subtypes. Screening tests for dementia (Mini-Mental State Examination and Cambridge Cognitive Examination) adequately discriminated cases of mild Alzheimer's disease from controls, but they were not accurate to discriminate patients with mild cognitive impairment (all subtypes) from control subjects. CONCLUSIONS: The discrimination of mild cognitive impairment subtypes was possible only with the aid of a comprehensive neuropsychological assessment. It is necessary to develop new strategies for mild cognitive impairment screening in clinical practice.OBJETIVO: Descrever o perfil neuropsicológico dos subtipos de comprometimento cognitivo leve, amnéstico, não-amnéstico e múltiplos domínios, de uma amostra clínica. Além disto, avaliou-se as propriedades diagnósticas do Mini-exame do Estado Mental e do Cambridge Cognitive Examination na identificação dos diferentes subtipos de comprometimento cognitivo leve na prática clínica. MÉTODO: Avaliação clínica e neuropsicológica transversal de 249 idosos em uma clínica de memória de um hospital universitário em São Paulo, Brasil. RESULTADOS: Testes de rastreio para demência (Mini-exame do Estado Mental e Cambridge Cognitive Examination) identificam corretamente casos de doença de Alzheimer leve, mas não apresentam boa acurácia para diferenciar os diversos subtipos de comprometimento cognitivo leve. A performance dos sujeitos portadores de comprometimento cognitivo leve foi heterogênea nos diferentes testes da bateria neuropsicológica, com uma tendência a uma pior performance global nos pacientes com o subtipo amnéstico (especialmente os com envolvimento de múltiplos domínios cognitivos) em relação ao comprometimento cognitivo leve não-amnéstico. CONCLUSÕES: A discriminação dos diferentes subtipos de comprometimento cognitivo leve foi possível somente a partir de uma avaliação neuropsicológica detalhada. Desta maneira, é necessário o desenvolvimento de novas estratégias de rastreio para esta condição na prática clínica
Geodetic VLBI Observations of EGRET Blazars
We present VLBI observations of the EGRET quasars 0202+149, CTA 26, and
1606+106, as well as additional analysis of VLBI observations of 1156+295
presented in Piner & Kingham (1997b). We have produced 8 and 2 GHz VLBI images
at 11 epochs, 8 epochs, and 12 epochs, spanning the years 1989 to 1996, of
0202+149, CTA 26, and 1606+106 respectively. The VLBI data have been taken from
the Washington VLBI correlator's geodetic database. We have measured the
apparent velocities of the jet components and find that CTA 26 and 1606+106 are
superluminal sources, with average apparent speeds of 8.9 and 2.9 h^{-1}c
respectively (H_{0}=100h km s^{-1} Mpc^{-1}, q_{0}=0.5). The components in
0202+149 are stationary, and we identify this source as a compact F double.
These sources all have apparently bent jets, and we detected non-radial motion
of components in CTA 26 and 1156+295. We have not yet detected any components
emerging subsequent to the gamma-ray flares in CTA 26, 1156+295, and 1606+106,
and we derive lower limits on the ejection times of any such components. The
misalignment angle distribution of the EGRET sources is compared to the
distribution for blazars as a whole, and we find that EGRET sources belong
preferentially to neither the aligned nor the misaligned population. We also
compare the average values for the apparent velocities and Doppler beaming
factors for the EGRET and non-EGRET blazars, and find no significant
differences. We thus find no indication, within the measurement errors, that
EGRET blazars are any more strongly beamed than their counterparts which have
not been detected in gamma-rays.Comment: 47 pages, including 13 figures; accepted for publication in the
Astrophysical Journa
Self-pruning acts synergistically with diageotropica to guide auxin responses and proper growth form
The SELF PRUNING (SP) gene is a key regulator of growth habit in tomato (Solanum lycopersicum). It is an ortholog of TERMINAL FLOWER1, a phosphatidylethanolamine-binding protein with antiflorigenic activity in Arabidopsis (Arabidopsis thaliana). A spontaneous loss-of-function mutation (sp) has been bred into several industrial tomato cultivars, as it produces a suite of pleiotropic effects that are favorable for mechanical harvesting, including determinate growth habit, short plant stature, and simultaneous fruit ripening. However, the physiological basis for these phenotypic differences has not been thoroughly explained. Here, we show that the sp mutation alters polar auxin transport as well as auxin responses, such as gravitropic curvature and elongation of excised hypocotyl segments. We also demonstrate that free auxin levels and auxin-regulated gene expression patterns are altered in sp mutants. Furthermore, diageotropica, a mutation in a gene encoding a cyclophilin A protein, appears to confer epistatic effects with sp. Our results indicate that SP affects the tomato growth habit at least in part by influencing auxin transport and responsiveness. These findings suggest potential novel targets that could be manipulated for controlling plant growth habit and improving productivity
Brown dwarf census with the Dark Energy Survey year 3 data and the thin disc scale height of early L types
27 pages, 18 figuresIn this paper we present a catalogue of 11 745 brown dwarfs with spectral types ranging from L0 to T9, photometrically classified using data from the Dark Energy Survey (DES) year 3 release matched to the Vista Hemisphere Survey (VHS) DR3 and Wide-field Infrared Survey Explorer (WISE) data, covering ≈2400 deg2 up to iAB = 22. The classification method follows the same phototype method previously applied to SDSS-UKIDSS-WISE data. The most significant difference comes from the use of DES data instead of SDSS, which allow us to classify almost an order of magnitude more brown dwarfs than any previous search and reaching distances beyond 400 pc for the earliest types. Next, we also present and validate the GalmodBD simulation, which produces brown dwarf number counts as a function of structural parameters with realistic photometric properties of a given survey. We use this simulation to estimate the completeness and purity of our photometric LT catalogue down to iAB = 22, as well as to compare to the observed number of LT types. We put constraints on the thin disc scale height for the early L (L0–L3) population to be around 450 pc, in agreement with previous findings. For completeness, we also publish in a separate table a catalogue of 20 863 M dwarfs that passed our colour cut with spectral types greater than M6. Both the LT and the late M catalogues are found at DES release page https://des.ncsa.illinois.edu/releases/other/y3-mlt.Peer reviewedFinal Published versio
Phenotypic redshifts with self-organizing maps: A novel method to characterize redshift distributions of source galaxies for weak lensing
Wide-field imaging surveys such as the Dark Energy Survey (DES) rely on
coarse measurements of spectral energy distributions in a few filters to
estimate the redshift distribution of source galaxies. In this regime, sample
variance, shot noise, and selection effects limit the attainable accuracy of
redshift calibration and thus of cosmological constraints. We present a new
method to combine wide-field, few-filter measurements with catalogs from deep
fields with additional filters and sufficiently low photometric noise to break
degeneracies in photometric redshifts. The multi-band deep field is used as an
intermediary between wide-field observations and accurate redshifts, greatly
reducing sample variance, shot noise, and selection effects. Our implementation
of the method uses self-organizing maps to group galaxies into phenotypes based
on their observed fluxes, and is tested using a mock DES catalog created from
N-body simulations. It yields a typical uncertainty on the mean redshift in
each of five tomographic bins for an idealized simulation of the DES Year 3
weak-lensing tomographic analysis of , which is a
60% improvement compared to the Year 1 analysis. Although the implementation of
the method is tailored to DES, its formalism can be applied to other large
photometric surveys with a similar observing strategy.Comment: 24 pages, 11 figures; matches version accepted to MNRA
On the geometrical origin of periodicity in blazar-type sources
Periodicities in blazar light curves may be related to helical trajectories
in extragalactic radio jets by differential Doppler boosting effects. We
consider ballistic and non-ballistic (i.e., radial) trajectories and discuss
three possible periodic driving mechanisms for the origin of helical jet paths,
namely, orbital motion in a binary black hole system (BBHS), jet precession,
and intrinsic jet rotation. It is shown that precessional-driven ballistic
motion is unlikely to result in observable periods of less than several tens of
years. We demonstrate that for non-ballistic helical motion the observed period
is generally strongly shortened relative to the real physical driving period
because of light-travel time effects. Internal jet rotation may thus account
for observed periods days. Periodicity due to
orbital-driven (non-ballistic) helical motion, on the other hand, is usually
constrained to periods of days, while Newtonian-driven
precession is unlikely to be responsible for periodicity on a timescale days but may well be associated with periods of yr.Comment: 10 pages, ApJ Letters in pres
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