26,363 research outputs found
Nodal involvement evaluation in advanced cervical cancer: a single institutional experience
Purpose: To assess the usefulness of different imaging techniques in the detection of nodal involvement in patients with advanced
cervical carcinoma. Moreover, to analyze the correlation between the presurgical (FIGO) and postsurgical (pTNM) staging classifications.
Materials and Methods: All patients diagnosed with advanced cervical cancer (FIGO Stages IIB-IV) from 2005 to 2012 were
selected. The medical charts of 51 patients that underwent presurgical assessment with posterior surgical staging by means of paraaortic
lymphadenectomy, were reviewed. Nodal status assessment by computed tomography scan (CT scan), magnetic resonance
imaging (MRI), positron emission tomography (PET), and sonography was compared, as well as the size given in imaging techniques
compared to the final pathologic report information. Results: Presurgical analysis by CT scan, MRI, PET, and sonography showed
pelvic nodal involvement in 51.3% of patients, and para-aortic involvement in 30.8% of cases. CT scan showed positive pelvic nodes
in 35% of cases, but pathologic confirmation was observed in just 17.6% of cases. However, MRI resulted in higher rates of up to
48.8% of cases. Concerning para-aortic nodal involvement, CT scan showed positive nodes in 25% of cases, MRI in 3.2% of cases,
and the pathologic report in 15.6% of cases. The authors found significant differences between staging groups among both classifications
(FIGO vs. pTNM; p < 0.001). Eight cases (15.7%) were understaged by FIGO classification. Conclusions: Despite all imaging
techniques available, none has demonstrated to be efficient enough to avoid the systematic study of para-aortic nodal status by
means of surgical evaluatio
Bio-logic: gene expression and the laws of combinatorial logic
Original article can be found at: http://www.mitpressjournals.org/ Copyright MIT Press DOI: 10.1162/artl.2008.14.1.121At the heart of the development of fertilized eggs into fully formed organisms and the adaptation of cells to changed conditions are genetic regulatory networks (GRNs). In higher multi-cellular organisms, signal selection and multiplexing is performed at the cis-regulatory domains of genes, where combinations of transcription factors (TFs) regulate the rates at which the genes are transcribed into mRNA. To be able to act as activators or repressors of gene transcription, TFs must first bind to target sequences on the regulatory domains. Two TFs that act in concert may bind entirely independently of each other, but more often binding of the first one will alter the affinity of the other for its binding site. This paper presents a systematic investigation into the effect of TF binding dependencies on the predicted regulatory function of this “bio-logic”. Four extreme scenarios, commonly used to classify enzyme activation and inhibition patterns, for the binding of two TFs were explored: independent (the TFs bind without affecting each other’s affinities), competitive (the TFs compete for the same binding site), ordered (the TFs bind in a compulsory order), and joint binding (the TFs either bind as a preformed complex, or binding of one is virtually impossible in the absence of the other). The conclusions are: 1) the laws of combinatorial logic hold only for systems with independently binding TFs; 2) systems formed according to the other scenarios can mimic the functions of their Boolean logical counterparts, but cannot be combined or decomposed in the same way; and 3) the continuously scaled output of systems consisting of competitively binding activators and repressors can be more robustly controlled than that of single TF or (quasi-) logical multi-TF systems. Keywords: Transcription regulation, Genetic regulatory networks, Enzyme kinetics, Combinatorial logic, Non-Boolean continuous logic, Modelling.Peer reviewe
Random laser from engineered nanostructures obtained by surface tension driven lithography
The random laser emission from the functionalized thienyl-S,S-dioxide
quinquethiophene (T5OCx) in confined patterns with different shapes is
demonstrated. Functional patterning of the light emitter organic material in
well defined features is obtained by spontaneous molecular self-assembly guided
by surface tension driven (STD) lithography. Such controlled supramolecular
nano-aggregates act as scattering centers allowing the fabrication of
one-component organic lasers with no external resonator and with desired shape
and efficiency. Atomic force microscopy shows that different geometric pattern
with different supramolecular organization obtained by the lithographic process
tailors the coherent emission properties by controlling the distribution and
the size of the random scatterers
Experimental evidence of replica symmetry breaking in random lasers
Spin-glass theory is one of the leading paradigms of complex physics and
describes condensed matter, neural networks and biological systems, ultracold
atoms, random photonics, and many other research fields. According to this
theory, identical systems under identical conditions may reach different states
and provide different values for observable quantities. This effect is known as
Replica Symmetry Breaking and is revealed by the shape of the probability
distribution function of an order parameter named the Parisi overlap. However,
a direct experimental evidence in any field of research is still missing. Here
we investigate pulse-to-pulse fluctuations in random lasers, we introduce and
measure the analogue of the Parisi overlap in independent experimental
realizations of the same disordered sample, and we find that the distribution
function yields evidence of a transition to a glassy light phase compatible
with a replica symmetry breaking.Comment: 10 pages, 5 figure
Nucleosynthesis Predictions for Intermediate-Mass AGB Stars: Comparison to Observations of Type I Planetary Nebulae
Type I planetary nebulae (PNe) have high He/H and N/O ratios and are thought
to be descendants of stars with initial masses of ~3-8Msun. These
characteristics indicate that the progenitor stars experienced proton-capture
nucleosynthesis at the base of the convective envelope, in addition to the slow
neutron capture process operating in the He-shell (the s-process). We compare
the predicted abundances of elements up to Sr from models of intermediate-mass
asymptotic giant branch (AGB) stars to measured abundances in Type I PNe. In
particular, we compare predictions and observations for the light trans-iron
elements Se and Kr, in order to constrain convective mixing and the s-process
in these stars. A partial mixing zone is included in selected models to explore
the effect of a 13C pocket on the s-process yields. The solar-metallicity
models produce enrichments of [(Se, Kr)/Fe] < 0.6, consistent with Galactic
Type I PNe where the observed enhancements are typically < 0.3 dex, while lower
metallicity models predict larger enrichments of C, N, Se, and Kr. O
destruction occurs in the most massive models but it is not efficient enough to
account for the > 0.3 dex O depletions observed in some Type I PNe. It is not
possible to reach firm conclusions regarding the neutron source operating in
massive AGB stars from Se and Kr abundances in Type I PNe; abundances for more
s-process elements may help to distinguish between the two neutron sources. We
predict that only the most massive models would evolve into Type I PNe,
indicating that extra-mixing processes are active in lower-mass stars
(3-4Msun), if these stars are to evolve into Type I PNe.Comment: 39 pages, accepted for publication in Ap
Frequency dynamics of gain-switched injection-locked semiconductor lasers
The frequency dynamics of gain-switched singlemode semiconductor lasers subject to optical injection is investigated. The requirements for low time jitter and reduced frequency chirp operation are studied as a function of the frequency mismatch between the master and slave lasers. Suppression of the power overshoot, typical during gain-switched operation, can be achieved for selected frequency detunings
Symmetries of Two Higgs Doublet Model and CP violation
We use the invariance of physical picture under a change of Lagrangian, the
reparametrization invariance in the space of Lagrangians and its particular
case -- the rephrasing invariance, for analysis of the two-Higgs-doublet
extension of the SM. We found that some parameters of theory like tan beta are
reparametrization dependent and therefore cannot be fundamental. We use the
Z2-symmetry of the Lagrangian, which prevents a phi_1 phi_2 transitions,
and the different levels of its violation, soft and hard, to describe a
physical content of the model. In general, the broken Z2-symmetry allows for a
CP violation in the physical Higgs sector. We argue that the 2HDM with a soft
breaking of Z2-symmetry is a natural model in the description of EWSB. To
simplify an analysis we choose among different forms of Lagrangian describing
the same physical reality a specific one, in which the vacuum expectation
values of both Higgs fields are real. A possible CP violation in the Higgs
sector is described by using a two-step procedure with the first step identical
to a diagonalization of mass matrix for CP-even fields in the CP conserved
case. We find very simple necessary and sufficient condition for a CP violation
in the Higgs sector. We determine the range of parameters for which CP
violation and Flavor Changing Neutral Current effects are naturally small,what
corresponds to a small dimensionless mass parameter nu= Re m_{12}^2/(2v1v2). We
discuss how for small nu some Higgs bosons can be heavy, with mass up to about
0.6 TeV, without violating of the unitarity constraints. We discuss main
features of the large nu case, which corresponds for nu -> infty to a
decoupling of heavy Higgs bosons.Comment: 27 pages, extended discussion, references added, one figure, Revtex
Evolution and nucleosynthesis of helium-rich asymptotic giant branch models
There is now strong evidence that some stars have been born with He mass
fractions as high as (e.g., in Centauri). However,
the advanced evolution, chemical yields, and final fates of He-rich stars are
largely unexplored. We investigate the consequences of He-enhancement on the
evolution and nucleosynthesis of intermediate-mass asymptotic giant branch
(AGB) models of 3, 4, 5, and 6 M with a metallicity of
([Fe/H] ). We compare models with He-enhanced compositions
() to those with primordial He (). We find that the
minimum initial mass for C burning and super-AGB stars with CO(Ne) or ONe cores
decreases from above our highest mass of 6 M to 4-5 M
with . We also model the production of trans-Fe elements via the slow
neutron-capture process (s-process). He-enhancement substantially reduces the
third dredge-up efficiency and the stellar yields of s-process elements (e.g.,
90% less Ba for 6 M, ). An exception occurs for 3 M,
where the near-doubling in the number of thermal pulses with leads to
50% higher yields of Ba-peak elements and Pb if the C neutron
source is included. However, the thinner intershell and increased temperatures
at the base of the convective envelope with probably inhibit the
C neutron source at this mass. Future chemical evolution models with our
yields might explain the evolution of s-process elements among He-rich stars in
Centauri.Comment: 21 pages, 16 figures, accepted for publication by MNRAS. Stellar
yields included as online data table
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