377 research outputs found
Two-dimensional kinematics of SLACS lenses: I. Phase-space analysis of the early-type galaxy SDSS J2321-097 at z=0.1
We present the first results of a combined VLT VIMOS integral-field unit and
Hubble Space Telescope (HST)/ACS study of the early-type lens galaxy SDSS
J2321-097 at z=0.0819, extending kinematic studies to a look-back time of 1
Gyr. This system, discovered in the Sloan Lens ACS Survey (SLACS), has been
observed as part of a VLT Large Programme with the goal of obtaining
two-dimensional stellar kinematics of 17 early-type galaxies to z~0.35 and Keck
spectroscopy of an additional dozen lens systems. Bayesian modelling of both
the surface brightness distribution of the lensed source and the
two-dimensional measurements of velocity and velocity dispersion has allowed
us, under the only assumptions of axisymmetry and a two-integral stellar
distribution function (DF) for the lens galaxy, to dissect this galaxy in three
dimensions and break the classical mass--anisotropy, mass-sheet and
inclination--oblateness degeneracies. Our main results are that the galaxy (i)
has a total density profile well described by a single power-law rho propto
r^{-gamma'} with gamma'=2.06^{+0.03}_{-0.06}; (ii) is a very slow rotator
(specific stellar angular momentum parameter lambda_R = 0.075); (iii) shows
only mild anisotropy (delta ~ 0.15); and (iv) has a dark matter contribution of
~30 per cent inside the effective radius. Our first results from this large
combined imaging and spectroscopic effort with the VLT, Keck and HST show that
the structure of massive early-type galaxies beyond the local Universe can now
be studied in great detail using the combination of stellar kinematics and
gravitational lensing. Extending these studies to look-back times where
evolutionary effects become measurable holds great promise for the
understanding of formation and evolution of early-type galaxies.Comment: 16 pages, 12 figures; accepted for publication in MNRAS; corrected
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Landau Theory of the Phase Transitions in Half Doped Manganites: Interplay of Magnetic, Charge and Structural Orders
The order parameters of the magnetic, charge and structural orders at
half-doped manganites are identified. A corresponding Landau theory of the
phase transitions is formulated. Many structural and thermodynamical behaviors
are accounted for and clarified within the framework. In particular, the theory
provides a unified picture for the scenario of the phase transitions and their
nature with respect to the variation of the tolerance factor of the manganites.
It also accounts for the origin of the incommensurate nature of the orbital
order and its subsequently accompanying antiferromagnetic order.Comment: 4 pages, 3 eps figures, Revtex, Phys. Rev. B61, 200
Neutron-gamma discrimination by pulse analysis with superheated drop detector
Superheated drop detector (SDD) consisting of drops of superheated liquid of
halocarbon is irradiated to neutrons and gamma-rays from 252Cf fission neutron
source and 137Cs gamma source separately. The analysis of pulse height of the
signals in the neutron and gamma-ray sensitive temperature provides strong
information on the identification of neutron and gamma-ray induced events.Comment: 19 pages with 8 figures, Accepted in Nucl. Instrum. Meth.
The SWELLS Survey. I. A large spectroscopically selected sample of edge-on late-type lens galaxies
The relative contribution of baryons and dark matter to the inner regions of
spiral galaxies provides critical clues to their formation and evolution, but
it is generally difficult to determine. For spiral galaxies that are strong
gravitational lenses, however, the combination of lensing and kinematic
observations can be used to break the disk-halo degeneracy. In turn, such data
constrain fundamental parameters such as i) the mass density profile slope and
axis ratio of the dark matter halo, and by comparison with dark matter-only
numerical simulations the modifications imposed by baryons; ii) the mass in
stars and therefore the overall star formation efficiency, and the amount of
feedback; iii) by comparison with stellar population synthesis models, the
normalization of the stellar initial mass function. In this first paper of a
series, we present a sample of 16 secure, 1 probable, and 6 possible strong
lensing spiral galaxies, for which multi-band high-resolution images and
rotation curves were obtained using the Hubble Space Telescope and Keck-II
Telescope as part of the Sloan WFC Edge-on Late-type Lens Survey (SWELLS). The
sample includes 8 newly discovered secure systems. [abridged] We find that the
SWELLS sample of secure lenses spans a broad range of morphologies (from
lenticular to late-type spiral), spectral types (quantified by Halpha
emission), and bulge to total stellar mass ratio (0.22-0.85), while being
limited to M_*>10^{10.5} M_sun. The SWELLS sample is thus well-suited for
exploring the relationship between dark and luminous matter in a broad range of
galaxies. We find that the deflector galaxies obey the same size-mass relation
as that of a comparison sample of elongated non-lens galaxies selected from the
SDSS survey. We conclude that the SWELLS sample is consistent with being
representative of the overall population of high-mass high-inclination disky
galaxies.Comment: 21 pages, 6 figures, MNRAS, in pres
Grey and white matter correlates of recent and remote autobiographical memory retrieval:Insights from the dementias
The capacity to remember self-referential past events relies on the integrity of a distributed neural network. Controversy exists, however, regarding the involvement of specific brain structures for the retrieval of recently experienced versus more distant events. Here, we explored how characteristic patterns of atrophy in neurodegenerative disorders differentially disrupt remote versus recent autobiographical memory. Eleven behavioural-variant frontotemporal dementia, 10 semantic dementia, 15 Alzheimer's disease patients and 14 healthy older Controls completed the Autobiographical Interview. All patient groups displayed significant remote memory impairments relative to Controls. Similarly, recent period retrieval was significantly compromised in behavioural-variant frontotemporal dementia and Alzheimer's disease, yet semantic dementia patients scored in line with Controls. Voxel-based morphometry and diffusion tensor imaging analyses, for all participants combined, were conducted to investigate grey and white matter correlates of remote and recent autobiographical memory retrieval. Neural correlates common to both recent and remote time periods were identified, including the hippocampus, medial prefrontal, and frontopolar cortices, and the forceps minor and left hippocampal portion of the cingulum bundle. Regions exclusively implicated in each time period were also identified. The integrity of the anterior temporal cortices was related to the retrieval of remote memories, whereas the posterior cingulate cortex emerged as a structure significantly associated with recent autobiographical memory retrieval. This study represents the first investigation of the grey and white matter correlates of remote and recent autobiographical memory retrieval in neurodegenerative disorders. Our findings demonstrate the importance of core brain structures, including the medial prefrontal cortex and hippocampus, irrespective of time period, and point towards the contribution of discrete regions in mediating successful retrieval of distant versus recently experienced events
Sperm cryodamage occurs after rapid freezing phase: flow cytometry approach and antioxidant enzymes activity at different stages of cryopreservation
Abstract\ud
\ud
Background\ud
In order to improve the efficiency of bovine sperm cryopreservation process, it is important to understand how spermatozoa respond to differences in temperature as well as the ability to recover its own metabolism. The combination between flow cytometry approach and antioxidant enzymes activity allows a more sensible evaluation of sperm cell during cryopreservation. The aim of this study was to evaluate sperm attributes and antioxidant enzymes activity during different stages of cryopreservation process. Semen samples from Holstein bulls (n = 4) were separated in 3 treatments: fresh (37 °C); cooled (5 °C); and thawed. Evaluation occurred at 0 h and 2 h after incubation. Membrane integrity, mitochondrial membrane potential (MMP) and DNA damages were evaluated by flow cytometry; activities of antioxidant enzymes such as catalase, superoxide dismutase and gluthatione peroxidase were measured by spectrofotometry.\ud
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Results\ud
There was an increase in the percentage of sperm with DNA damage in the thawed group, compared to fresh and cooled, and for 2 hs of incubation when compared to 0Â h. Considering MMP, there was an increase in the percentage of cells with medium potential in thawed group when compared to fresh and cooled groups. Opposingly, a decrease was observed in the thawed group considering high mitochondrial potential. Also in the thawed group, there was an increase on cells with damaged acrosome and membrane when compared to fresh and cooled groups. Significant correlations were found between antioxidant enzymes activity and membrane or mitochondrial parameters.\ud
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Conclusion\ud
Based on our results, we conclude that cryopreservation affects cellular and DNA integrity and that the critical moment is when sperm cells are exposed to freezing temperature. Also, our study indicates that intracellular antioxidant machinery (SOD and GPX enzymes) is not enough to control cryodamage.This study was supported by SĂŁo Paulo Research Foundation (FAPESP),\ud
process number 2010/18978-9 and 2007/58487-1
The NOD2-Smoking Interaction in Crohn's Disease is likely Specific to the 1007fs Mutation and may be Explained by Age at Diagnosis:A Meta-Analysis and Case-Only Study
Background: NOD2 and smoking are risk factors for Crohn's disease. We meta-analyzed NOD2-smoking interactions in Crohn's disease (Phase 1), then explored the effect of age at diagnosis on NOD2-smoking interactions (Phase 2).
Methods: Phase 1: MEDLINE and EMBASE were searched for studies (n = 18) providing data on NOD2 and smoking in Crohn's disease. NOD2-smoking interactions were estimated using odds ratios (ORs) and 95% confidence intervals (CIs) calculated using random effects models. Phase 2: A case-only study compared the proportion of smokers and carriers of the 1007 fs variant across ages at diagnosis (≤16, 17–40, >40 years).
Findings: Phase 1: Having ever smoked was less common among carriers of the 1007 fs variant of NOD2 (OR 0.74, 95%CI:0.66–0.83). There was no interaction between smoking and the G908R (OR 0.96, 95%CI:0.82–1.13) or the R702W variant (OR 0.89, 95%CI:0.76–1.05). Phase 2: The proportion of patients (n = 627) carrying the 1007 fs variant decreased with age at diagnosis (≤16 years: 15%; 17–40: 12%; >40: 3%; p = 0.003). Smoking was more common in older patients (≤16 years: 4%; 17–40: 48%; >40: 71%; p < 0.001).
Interpretation: The negative NOD2-smoking interaction in Crohn's disease is specific to the 1007Â fs variant. However, opposing rates of this variant and smoking across age at diagnosis may explain this negative interaction
Simulation of Special Bubble Detectors for PICASSO
The PICASSO project is a cold dark matter (CDM) search experiment relying on
the superheated droplet technique. The detectors use superheated freon liquid
droplets (active material) dispersed and trapped in a polymerized gel. This
detection technique is based on the phase transition of superheated droplets at
about room temperature and ambient pressure. The phase transition is induced by
nuclear recoils when an atomic nucleus in the droplets interacts with incoming
subatomic particles. This includes CDM particles candidate as the neutralino (a
yet-to-discover particle predicted in extensions of the Standard Model of
particle physics). Simulations performed to understand the detector response to
neutrons and alpha particles are presented along with corresponding data
obtained at the Montreal Laboratory.Comment: 13 pages, 4 figures. To appear in the Proceedings of the 14th
International Conference on Solid State Dosimetry, June 27 - July 2 2004,
Yale University, New Haven, CT, US
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