1,012 research outputs found
Subtle alterations in cerebrovascular reactivity in mild cognitive impairment detected by graph theoretical analysis and not by the standard approach.
There is growing support that cerebrovascular reactivity (CVR) in response to a vasodilatory challenge, also defined as the cerebrovascular reserve, is reduced in Alzheimer's disease dementia. However, this is less clear in patients with mild cognitive impairment (MCI). The current standard analysis may not reflect subtle abnormalities in CVR. In this study, we aimed to investigate vasodilatory-induced changes in the topology of the cerebral blood flow correlation (CBF javax.xml.bind.JAXBElement@6894b36 ) network to study possible network-related CVR abnormalities in MCI. For this purpose, four CBF javax.xml.bind.JAXBElement@389286d6 networks were constructed: two using CBF SPECT data at baseline and under the vasodilatory challenge of acetazolamide (ACZ), obtained from a group of 26 MCI patients; and two equivalent networks from a group of 26 matched cognitively normal controls. The mean strength of association ( javax.xml.bind.JAXBElement@58a7138c ) and clustering coefficient ( javax.xml.bind.JAXBElement@5f56d60d ) were used to evaluate ACZ-induced changes on the topology of CBF javax.xml.bind.JAXBElement@13cae62a networks. We found that cognitively normal adults and MCI patients show different patterns of javax.xml.bind.JAXBElement@3fc266b3 and javax.xml.bind.JAXBElement@5f9929b4 changes. The observed differences included the medial prefrontal cortices and inferior parietal lobe, which represent areas involved in MCI's cognitive dysfunction. In contrast, no substantial differences were detected by standard CVR analysis. These results suggest that graph theoretical analysis of ACZ-induced changes in the topology of the CBF javax.xml.bind.JAXBElement@36167af4 networks allows the identification of subtle network-related CVR alterations in MCI, which couldn't be detected by the standard approach
The effect of 12C + 12C rate uncertainties on the evolution and nucleosynthesis of massive stars
[Shortened] The 12C + 12C fusion reaction has been the subject of
considerable experimental efforts to constrain uncertainties at temperatures
relevant for stellar nucleosynthesis. In order to investigate the effect of an
enhanced carbon burning rate on massive star structure and nucleosynthesis, new
stellar evolution models and their yields are presented exploring the impact of
three different 12C + 12C reaction rates. Non-rotating stellar models were
generated using the Geneva Stellar Evolution Code and were later post-processed
with the NuGrid Multi-zone Post-Processing Network tool. The enhanced rate
causes core carbon burning to be ignited more promptly and at lower
temperature. This reduces the neutrino losses, which increases the core carbon
burning lifetime. An increased carbon burning rate also increases the upper
initial mass limit for which a star exhibits a convective carbon core. Carbon
shell burning is also affected, with fewer convective-shell episodes and
convection zones that tend to be larger in mass. Consequently, the chance of an
overlap between the ashes of carbon core burning and the following carbon shell
convection zones is increased, which can cause a portion of the ashes of carbon
core burning to be included in the carbon shell. Therefore, during the
supernova explosion, the ejecta will be enriched by s-process nuclides
synthesized from the carbon core s process. The yields were used to estimate
the weak s-process component in order to compare with the solar system
abundance distribution. The enhanced rate models were found to produce a
significant proportion of Kr, Sr, Y, Zr, Mo, Ru, Pd and Cd in the weak
component, which is primarily the signature of the carbon-core s process.
Consequently, it is shown that the production of isotopes in the Kr-Sr region
can be used to constrain the 12C + 12C rate using the current branching ratio
for a- and p-exit channels.Comment: The paper contains 17 figures and 7 tables. Table 7 will be published
in full online onl
Will Patients Benefit from Regionalization of Gynecologic Cancer Care?
OBJECTIVE: Patient chances for cure and palliation for a variety of malignancies may be greatly affected by the care provided by a treating hospital. We sought to determine the effect of volume and teaching status on patient outcomes for five gynecologic malignancies: endometrial, cervical, ovarian and vulvar carcinoma and uterine sarcoma. METHODS: The Florida Cancer Data System dataset was queried for all patients undergoing treatment for gynecologic cancers from 1990-2000. RESULTS: Overall, 48,981 patients with gynecologic malignancies were identified. Endometrial tumors were the most common, representing 43.2% of the entire cohort, followed by ovarian cancer (30.9%), cervical cancer (20.8%), vulvar cancer (4.6%), and uterine sarcoma (0.5%). By univariate analysis, although patients treated at high volume centers (HVC) were significantly younger, they benefited from an improved short-term (30-day and/or 90-day) survival for cervical, ovarian and endometrial cancers. Multivariate analysis (MVA), however, failed to demonstrate significant survival benefit for gynecologic cancer patients treated at teaching facilities (TF) or HVC. Significant prognostic factors at presentation by MVA were age over 65 (HR = 2.6, p<0.01), African-American race (HR = 1.36, p<0.01), and advanced stage (regional HR = 2.08, p<0.01; advanced HR = 3.82, p<0.01, respectively). Surgery and use of chemotherapy were each significantly associated with improved survival. CONCLUSION: No difference in patient survival was observed for any gynecologic malignancy based upon treating hospital teaching or volume status. Although instances of improved outcomes may occur, overall further regionalization would not appear to significantly improve patient survival
Bridging the gap between low and high mass dwarf galaxies
While the dark matter content within the most massive giant and smallest
dwarf galaxies has been probed -- spanning a range of over one million in mass
-- an important observational gap remains for galaxies of intermediate mass.
This gap covers K band magnitudes of approximately -16 > M_K > -18 (for which
dwarf galaxies have B--K ~ 2). On the high mass side of the gap are dwarf
elliptical (dE) galaxies, that are dominated by stars in their inner regions.
While the low mass side includes dwarf spheroidal (dSph) galaxies that are dark
matter-dominated and ultra compact dwarf (UCD) objects that are star-dominated.
Evolutionary pathways across the gap have been suggested but remain largely
untested because the `gap' galaxies are faint, making dynamical measurements
very challenging. With long exposures on the Keck telescope using the ESI
instrument we have succeeded in bridging this gap by measuring the dynamical
mass for five dwarf galaxies with M_K ~ -17.5 (M_B ~ --15.5). With the
exception of our brightest dwarf galaxy, they possess relatively flat velocity
dispersion profiles of around 20 km/s. By examining their 2D scaling relations
and 3D fundamental manifold, we found that the sizes and velocity dispersions
of these gap galaxies reveal continuous trends from dE to dSph galaxies. We
conclude that low-luminosity dwarf elliptical galaxies are dominated by stars,
not by dark matter, within their half light radii. This finding can be
understood if internal feedback processes are operating most efficiently in gap
galaxies, gravitationally heating the centrally-located dark matter to larger
radii. Whereas external environmental processes, which can strip away stars,
have a greater influence on dSph galaxies resulting in their higher dark matter
fractions. Abridged.Comment: 20 pages, includes 12 figures, accepted for publication in MNRA
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at , 2.76 and 7 TeV
Measurements of the sphericity of primary charged particles in minimum bias
proton--proton collisions at , 2.76 and 7 TeV with the ALICE
detector at the LHC are presented. The observable is linearized to be collinear
safe and is measured in the plane perpendicular to the beam direction using
primary charged tracks with GeV/c in . The
mean sphericity as a function of the charged particle multiplicity at
mid-rapidity () is reported for events with different
scales ("soft" and "hard") defined by the transverse momentum of the leading
particle. In addition, the mean charged particle transverse momentum versus
multiplicity is presented for the different event classes, and the sphericity
distributions in bins of multiplicity are presented. The data are compared with
calculations of standard Monte Carlo event generators. The transverse
sphericity is found to grow with multiplicity at all collision energies, with a
steeper rise at low , whereas the event generators show the
opposite tendency. The combined study of the sphericity and the mean with multiplicity indicates that most of the tested event generators
produce events with higher multiplicity by generating more back-to-back jets
resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with
tune PERUGIA-2011 exhibits a noticeable improvement in describing the data,
compared to the other tested generators.Comment: 21 pages, 9 captioned figures, 3 tables, authors from page 16,
published version, figures from
http://aliceinfo.cern.ch/ArtSubmission/node/308
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
Measurements of multi-particle azimuthal correlations (cumulants) for charged
particles in p-Pb and Pb-Pb collisions are presented. They help address the
question of whether there is evidence for global, flow-like, azimuthal
correlations in the p-Pb system. Comparisons are made to measurements from the
larger Pb-Pb system, where such evidence is established. In particular, the
second harmonic two-particle cumulants are found to decrease with multiplicity,
characteristic of a dominance of few-particle correlations in p-Pb collisions.
However, when a gap is placed to suppress such correlations,
the two-particle cumulants begin to rise at high-multiplicity, indicating the
presence of global azimuthal correlations. The Pb-Pb values are higher than the
p-Pb values at similar multiplicities. In both systems, the second harmonic
four-particle cumulants exhibit a transition from positive to negative values
when the multiplicity increases. The negative values allow for a measurement of
to be made, which is found to be higher in Pb-Pb collisions at
similar multiplicities. The second harmonic six-particle cumulants are also
found to be higher in Pb-Pb collisions. In Pb-Pb collisions, we generally find
which is indicative of a Bessel-Gaussian
function for the distribution. For very high-multiplicity Pb-Pb
collisions, we observe that the four- and six-particle cumulants become
consistent with 0. Finally, third harmonic two-particle cumulants in p-Pb and
Pb-Pb are measured. These are found to be similar for overlapping
multiplicities, when a gap is placed.Comment: 25 pages, 11 captioned figures, 3 tables, authors from page 20,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/87
Multiplicity dependence of jet-like two-particle correlations in p-Pb collisions at = 5.02 TeV
Two-particle angular correlations between unidentified charged trigger and
associated particles are measured by the ALICE detector in p-Pb collisions at a
nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum
range 0.7 5.0 GeV/ is examined,
to include correlations induced by jets originating from low
momen\-tum-transfer scatterings (minijets). The correlations expressed as
associated yield per trigger particle are obtained in the pseudorapidity range
. The near-side long-range pseudorapidity correlations observed in
high-multiplicity p-Pb collisions are subtracted from both near-side
short-range and away-side correlations in order to remove the non-jet-like
components. The yields in the jet-like peaks are found to be invariant with
event multiplicity with the exception of events with low multiplicity. This
invariance is consistent with the particles being produced via the incoherent
fragmentation of multiple parton--parton scatterings, while the yield related
to the previously observed ridge structures is not jet-related. The number of
uncorrelated sources of particle production is found to increase linearly with
multiplicity, suggesting no saturation of the number of multi-parton
interactions even in the highest multiplicity p-Pb collisions. Further, the
number scales in the intermediate multiplicity region with the number of binary
nucleon-nucleon collisions estimated with a Glauber Monte-Carlo simulation.Comment: 23 pages, 6 captioned figures, 1 table, authors from page 17,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/161
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
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