2,394 research outputs found
Three intermediate-mass YSOs with different properties emerging from the same natal cloud in IRAS 00117+6412
We observed with the VLA, PdBI, and SMA the centimeter and millimeter
continuum, N2H+(1-0), and CO(2-1) emission associated with a dusty cloud
harboring a nascent cluster with intermediate-mass protostars. At centimeter
wavelengths we found a strong source, tracing a UCHII region, at the eastern
edge of the dusty cloud, with a shell-like structure, and with the
near-infrared counterpart falling in the center of the shell. This is
presumably the most massive source of the forming cluster. About 15'' to the
west of the UCHII region and well embedded in the dusty cloud, we detected a
strong millimeter source, MM1, associated with centimeter and near-infrared
emission. MM1 seems to be driving a prominent high-velocity CO bipolar outflow,
and is embedded in a ridge of dense gas traced by N2H+. We estimated that MM1
is an intermediate-mass source in the Class 0/I phase. About 15'' to the south
of MM1, and still more deeply embedded in the dusty cloud, we detected a
compact millimeter source, MM2, with neither centimeter nor near-infrared
emission, but with water maser emission. MM2 is associated with a clump of
N2H+, whose kinematics reveal a clear velocity gradient and additionally we
found signposts of infall motions. MM2, being deeply embedded within the dusty
cloud, with an associated water maser but no hints of CO outflow emission, is
an intriguing object, presumably of intermediate mass. In conclusion, the UCHII
region is found at the border of a dusty cloud which is currently undergoing
active star formation. Two intermediate-mass protostars in the dusty cloud seem
to have formed after the UCHII region and have different properties related to
the outflow phenomenon.Comment: accepted to Astronomy and Astrophysic
CAT25 defines microsatellite instability in colorectal cancer by high-resolution melting PCR
Background: CAT25 (T25mononucleotide repeat of the Caspase 2 gene), is a promising DNA marker for detecting microsatellite instability (MSI) in colorectal cancer. CAT25 has the potential to be incorporated into the Bethesda panel, a commonly used panel of DNA microsatellites, or replace it in its entirety. We aimed to develop and validate a high-resolution melting-PCR (HRM-PCR) method for CAT25 instability detection in clinical samples. Methods: The instability of CAT25, BAT25 (a poly(A) tract occurring in c‐kit) and BAT26 (a poly(A) tract localized in hMSH2) microsatellites were assessed in DNA from tumour and peripheral blood obtained from 110 patients with colorectal cancer using HRM-PCR and capillary electrophoresis. Immunohistochemistry (IHC) staining for MSH2, MSH6, MLH1, and PMS2 enzymes was performed on tumours with jigj MSI. Allelic size variation of CAT25 was analysed on peripheral blood DNA from 208 healthy volunteers. Results: The HRM-PCR for CAT25 was validated in clinical samples. CAT25 showed a tight range of 64–66 base pairs. Of 110 tumours, 11 had High MSI, later confirmed by IHC. CAT25 defines MSI alone as well as when used together with BAT25 and BAT26. CAT25 results provided 100% predictive values and p < 0.0001 to classify a tumour as having high MSI. Conclusions: We developed and validated a new HRM-PCR assay to detect CAT25 instability. Our findings showed a limited allelic size variation of CAT25 and highlighted to CAT25 as a promising marker for MSI analysis.Fil: Sánchez, A.G.. Hospital Privado Universitario de Córdoba; Argentina. Instituto Universitario de Ciencias Biomédicas de Córdoba; ArgentinaFil: Juaneda, I.. Hospital Privado Universitario de Córdoba; ArgentinaFil: Eynard, H.. Hospital Privado Universitario de Córdoba; ArgentinaFil: Basquiera, Ana Lisa. Hospital Privado Universitario de Córdoba; ArgentinaFil: Palazzo, E.. Hospital Privado Universitario de Córdoba; ArgentinaFil: Calafat, P.. Hospital Privado Universitario de Córdoba; ArgentinaFil: Palla, V.. Hospital Privado Universitario de Córdoba; ArgentinaFil: Romagnoli, Pablo Alberto. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Grupo Vinculado Centro de Investigación en Medicina Traslacional Severo R. Amuchástegui - Cimetsa | Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Grupo Vinculado Centro de Investigación en Medicina Traslacional Severo R. Amuchástegui - Cimetsa | Instituto de Investigación Médica Mercedes y Martín Ferreyra. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Grupo Vinculado Centro de Investigación en Medicina Traslacional Severo R. Amuchástegui - Cimetsa; ArgentinaFil: Alvarellos, T.. Hospital Privado Universitario de Córdoba; Argentina. Instituto Universitario de Ciencias Biomédicas de Córdoba; Argentin
Statistical mechanics of topological phase transitions in networks
We provide a phenomenological theory for topological transitions in
restructuring networks. In this statistical mechanical approach energy is
assigned to the different network topologies and temperature is used as a
quantity referring to the level of noise during the rewiring of the edges. The
associated microscopic dynamics satisfies the detailed balance condition and is
equivalent to a lattice gas model on the edge-dual graph of a fully connected
network. In our studies -- based on an exact enumeration method, Monte-Carlo
simulations, and theoretical considerations -- we find a rich variety of
topological phase transitions when the temperature is varied. These transitions
signal singular changes in the essential features of the global structure of
the network. Depending on the energy function chosen, the observed transitions
can be best monitored using the order parameters Phi_s=s_{max}/M, i.e., the
size of the largest connected component divided by the number of edges, or
Phi_k=k_{max}/M, the largest degree in the network divided by the number of
edges. If, for example the energy is chosen to be E=-s_{max}, the observed
transition is analogous to the percolation phase transition of random graphs.
For this choice of the energy, the phase-diagram in the [,T] plane is
constructed. Single vertex energies of the form
E=sum_i f(k_i), where k_i is the degree of vertex i, are also studied.
Depending on the form of f(k_i), first order and continuous phase transitions
can be observed. In case of f(k_i)=-(k_i+c)ln(k_i), the transition is
continuous, and at the critical temperature scale-free graphs can be recovered.Comment: 12 pages, 12 figures, minor changes, added a new refernce, to appear
in PR
Crossing the Gould Belt in the Orion vicinity
We present a study of the large-scale spatial distribution of 6482 RASS X-ray
sources in approximately 5000 deg^2 in the direction of Orion. We examine the
astrophysical properties of a sub-sample of ~100 optical counterparts, using
optical spectroscopy. This sub-sample is used to investigate the space density
of the RASS young star candidates by comparing X-ray number counts with
Galactic model predictions. We characterize the observed sub-sample in terms of
spectral type, lithium content, radial and rotational velocities, as well as
iron abundance. A population synthesis model is then applied to analyze the
stellar content of the RASS in the studied area. We find that stars associated
with the Orion star-forming region do show a high lithium content. A population
of late-type stars with lithium equivalent widths larger than Pleiades stars of
the same spectral type (hence younger than ~70-100 Myr) is found widely spread
over the studied area. Two new young stellar aggregates, namely "X-ray Clump
0534+22" (age~2-10 Myr) and "X-ray Clump 0430-08" (age~2-20 Myr), are also
identified. The spectroscopic follow-up and comparison with Galactic model
predictions reveal that the X-ray selected stellar population in the direction
of Orion is characterized by three distinct components, namely the clustered,
the young dispersed, and the widespread field populations. The clustered
population is mainly associated with regions of recent or ongoing star
formation and correlates spatially with molecular clouds. The dispersed young
population follows a broad lane apparently coinciding spatially with the Gould
Belt, while the widespread population consists primarily of active field stars
older than 100 Myr. We expect the "bi-dimensional" picture emerging from this
study to grow in depth as soon as the distance and the kinematics of the
studied sources will become available from the future Gaia mission.Comment: 17 pages, 13 figures, 4 tables. Accepted for publication in Astronomy
and Astrophysics. Abstract shortene
Control of star formation by supersonic turbulence
Understanding the formation of stars in galaxies is central to much of modern
astrophysics. For several decades it has been thought that stellar birth is
primarily controlled by the interplay between gravity and magnetostatic
support, modulated by ambipolar diffusion. Recently, however, both
observational and numerical work has begun to suggest that support by
supersonic turbulence rather than magnetic fields controls star formation. In
this review we outline a new theory of star formation relying on the control by
turbulence. We demonstrate that although supersonic turbulence can provide
global support, it nevertheless produces density enhancements that allow local
collapse. Inefficient, isolated star formation is a hallmark of turbulent
support, while efficient, clustered star formation occurs in its absence. The
consequences of this theory are then explored for both local star formation and
galactic scale star formation. (ABSTRACT ABBREVIATED)Comment: Invited review for "Reviews of Modern Physics", 87 pages including 28
figures, in pres
Search for CP Violation in the Decay Z -> b (b bar) g
About three million hadronic decays of the Z collected by ALEPH in the years
1991-1994 are used to search for anomalous CP violation beyond the Standard
Model in the decay Z -> b \bar{b} g. The study is performed by analyzing
angular correlations between the two quarks and the gluon in three-jet events
and by measuring the differential two-jet rate. No signal of CP violation is
found. For the combinations of anomalous CP violating couplings, and , limits of \hat{h}_b < 0.59h^{\ast}_{b} < 3.02$ are given at 95\% CL.Comment: 8 pages, 1 postscript figure, uses here.sty, epsfig.st
Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at sqrt(s) = 7 TeV
A search for new physics is presented based on an event signature of at least
three jets accompanied by large missing transverse momentum, using a data
sample corresponding to an integrated luminosity of 36 inverse picobarns
collected in proton--proton collisions at sqrt(s)=7 TeV with the CMS detector
at the LHC. No excess of events is observed above the expected standard model
backgrounds, which are all estimated from the data. Exclusion limits are
presented for the constrained minimal supersymmetric extension of the standard
model. Cross section limits are also presented using simplified models with new
particles decaying to an undetected particle and one or two jets
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
Combined search for the quarks of a sequential fourth generation
Results are presented from a search for a fourth generation of quarks
produced singly or in pairs in a data set corresponding to an integrated
luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in
2011. A novel strategy has been developed for a combined search for quarks of
the up and down type in decay channels with at least one isolated muon or
electron. Limits on the mass of the fourth-generation quarks and the relevant
Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a
simple extension of the standard model with a sequential fourth generation of
fermions. The existence of mass-degenerate fourth-generation quarks with masses
below 685 GeV is excluded at 95% confidence level for minimal off-diagonal
mixing between the third- and the fourth-generation quarks. With a mass
difference of 25 GeV between the quark masses, the obtained limit on the masses
of the fourth-generation quarks shifts by about +/- 20 GeV. These results
significantly reduce the allowed parameter space for a fourth generation of
fermions.Comment: Replaced with published version. Added journal reference and DO
Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV
The t t-bar production cross section (sigma[t t-bar]) is measured in
proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS
experiment, corresponding to an integrated luminosity of 2.3 inverse
femtobarns. The measurement is performed in events with two leptons (electrons
or muons) in the final state, at least two jets identified as jets originating
from b quarks, and the presence of an imbalance in transverse momentum. The
measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/-
2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction
of the standard model.Comment: Replaced with published version. Included journal reference and DO
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