6,412 research outputs found
Exact Finite-Size-Scaling Corrections to the Critical Two-Dimensional Ising Model on a Torus
We analyze the finite-size corrections to the energy and specific heat of the
critical two-dimensional spin-1/2 Ising model on a torus. We extend the
analysis of Ferdinand and Fisher to compute the correction of order L^{-3} to
the energy and the corrections of order L^{-2} and L^{-3} to the specific heat.
We also obtain general results on the form of the finite-size corrections to
these quantities: only integer powers of L^{-1} occur, unmodified by logarithms
(except of course for the leading term in the specific heat); and the
energy expansion contains only odd powers of L^{-1}. In the specific-heat
expansion any power of L^{-1} can appear, but the coefficients of the odd
powers are proportional to the corresponding coefficients of the energy
expansion.Comment: 26 pages (LaTeX). Self-unpacking file containing the tex file and
three macros (indent.sty, eqsection.sty, subeqnarray.sty). Added discussions
on the results and new references. Version to be published in J. Phys.
Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines
A significant fraction of the molecular gas in star-forming regions is
irradiated by stellar UV photons. In these environments, the electron density
(n_e) plays a critical role in the gas dynamics, chemistry, and collisional
excitation of certain molecules. We determine n_e in the prototypical strongly
irradiated photodissociation region (PDR), the Orion Bar, from the detection of
new millimeter-wave carbon recombination lines (mmCRLs) and existing far-IR
[13CII] hyperfine line observations. We detect 12 mmCRLs (including alpha,
beta, and gamma transitions) observed with the IRAM 30m telescope, at ~25''
angular resolution, toward the H/H2 dissociation front (DF) of the Bar. We also
present a mmCRL emission cut across the PDR. These lines trace the C+/C/CO gas
transition layer. As the much lower frequency carbon radio recombination lines,
mmCRLs arise from neutral PDR gas and not from ionized gas in the adjacent HII
region. This is readily seen from their narrow line profiles (dv=2.6+/-0.4
km/s) and line peak LSR velocities (v_LSR=+10.7+/-0.2 km/s). Optically thin
[13CII] hyperfine lines and molecular lines - emitted close to the DF by trace
species such as reactive ions CO+ and HOC+ - show the same line profiles. We
use non-LTE excitation models of [13CII] and mmCRLs and derive n_e = 60-100
cm^-3 and T_e = 500-600 K toward the DF. The inferred electron densities are
high, up to an order of magnitude higher than previously thought. They provide
a lower limit to the gas thermal pressure at the PDR edge without using
molecular tracers. We obtain P_th > (2-4)x10^8 cm^-3 K assuming that the
electron abundance is equal or lower than the gas-phase elemental abundance of
carbon. Such elevated thermal pressures leave little room for magnetic pressure
support and agree with a scenario in which the PDR photoevaporates.Comment: Accepted for publication in A&A Letters (includes language editor
corrections
Relevance of p53 in the regulation of pro and antiapoptotic factors from the Bcl-2 family during the treatment with tirosine kinase inhibitors
Motivation:
Liver cancer is the sixth most common cancer and the fourth most frequent cause of cancer-related death worldwide [1]. Nowadays, only one third of patients diagnosed with HCC are in the earliest BCLC 0-A stages, with a high proportion being in more advanced stages of the disease (BCLC B-C). Patients with the presence of poor prognostic factors such as vascular invasion, extrahepatic metastases and/or impaired hepatic function are considered in the advanced stage of the disease (BCLC C). Sorafenib is the standard of care for advanced HCC stage demonstrated in two large-scale trials [2]. Other drugs have been developed to increase the therapeutic arsenal of treatments. A phase III clinical trial comparing Lenvatinib and Sorafenib demonstrated that Lenvatinib was statistically non-inferior to Sorafenib in overall survival as a first-line treatment in patients with advanced HCC. Regorafenib and Cabozantinib have been shown to be effective as second-line therapy. [2]
Methods:
Sorafenib, Regorafenib, Cabozantinib and Lenvatinib were obtained commercially from Carbosynth Limited (Berkshire, UK). HepG2, Hep3B and Huh7 cell lines were obtained from American Type Culture Collection (ATCC; LGC Standards, S.L.U., Barcelona, Spain). HCC cell lines were maintained in supplemented Minimum Essential Medium with Earle's Balanced Salts (MEM/EBSS) at 37°C in a humidified incubator with 5 % CO2. Cells were seeded at a density of 100,000 cells/cm2 in 2D culture. Different parameters related to cell death and proliferation were associated with the expression of proapoptotic (Bak, Bax, tBid and Bim) antiapoptotic (Bcl-2, Mcl-1 and Bcl-xL) and regulatory (Beclin-1) Bcl-2 family members assessed by Western-blot analysis.
Results:
The administration of tyrosine kinase inhibitors induced cell death and reduced cell proliferation. This effect was associated with an upregulation of tBid and Bim expression in liver cancer cells. This effect was not observed in Hep3B and Huh7 which were less responsiveness to the proapoptotic and antiproliferative properties of tyrosine kinase inhibitors.
Conclusions:
The induction of cell death and antiproliferative properties of tyrosine kinase inhibitors were associated with the increase of the expression of different proapoptotic Bcl-2 family members. This expression appeared to be regulated by p53
REAM intensity modulator-enabled 10Gb/s colorless upstream transmission of real-time optical OFDM signals in a single-fiber-based bidirectional PON architecture
Reflective electro-absorption modulation-intensity modulators (REAM-IMs) are utilized, for the first time, to experimentally demonstrate colorless ONUs in single-fiber-based, bidirectional, intensity-modulation and direct-detection (IMDD), optical OFDM PONs (OOFDM-PONs) incorporating 25km SSMFs and OLT-side-seeded CW optical signals. The colorlessness of the REAM-IMs is characterized, based on which optimum REAM-IM operating conditions are identified. In the aforementioned PON architecture, 10Gb/s colorless upstream transmissions of end-to-end realtime OOFDM signals are successfully achieved for various wavelengths within the entire C-band. Over such a wavelength window, corresponding minimum received optical powers at the FEC limit vary in a range as small as <0.5dB. In addition, experimental measurements also indicate that Rayleigh backscattering imposes a 2.8dB optical power penalty on the 10Gb/s over 25km upstream OOFDM signal transmission. Furthermore, making use of on-line adaptive bit and power loading, a linear trade-off between aggregated signal line rate and optical power budget is observed, which shows that, for the present PON system, a 10% reduction in signal line rate can improve the optical power budget by 2.6dB. © 2012 Optical Society of America
Test of nuclear level density inputs for Hauser-Feshbach model calculations
The energy spectra of neutrons, protons, and alpha-particles have been
measured from the d+59Co and 3He+58Fe reactions leading to the same compound
nucleus, 61$Ni. The experimental cross sections have been compared to
Hauser-Feshbach model calculations using different input level density models.
None of them have been found to agree with experiment. It manifests the serious
problem with available level density parameterizations especially those based
on neutron resonance spacings and density of discrete levels. New level
densities and corresponding Fermi-gas parameters have been obtained for
reaction product nuclei such as 60Ni,60Co, and 57Fe
Dynamic Critical Behavior of the Swendsen-Wang Algorithm: The Two-Dimensional 3-State Potts Model Revisited
We have performed a high-precision Monte Carlo study of the dynamic critical
behavior of the Swendsen-Wang algorithm for the two-dimensional 3-state Potts
model. We find that the Li-Sokal bound ()
is almost but not quite sharp. The ratio seems to diverge
either as a small power () or as a logarithm.Comment: 35 pages including 3 figures. Self-unpacking file containing the
LaTeX file, the needed macros (epsf.sty, indent.sty, subeqnarray.sty, and
eqsection.sty) and the 3 Postscript figures. Revised version fixes a
normalization error in \xi (with many thanks to Wolfhard Janke for finding
the error!). To be published in J. Stat. Phys. 87, no. 1/2 (April 1997
Irrelevant operators in the two-dimensional Ising model
By using conformal-field theory, we classify the possible irrelevant
operators for the Ising model on the square and triangular lattices. We analyze
the existing results for the free energy and its derivatives and for the
correlation length, showing that they are in agreement with the conformal-field
theory predictions. Moreover, these results imply that the nonlinear scaling
field of the energy-momentum tensor vanishes at the critical point. Several
other peculiar cancellations are explained in terms of a number of general
conjectures. We show that all existing results on the square and triangular
lattice are consistent with the assumption that only nonzero spin operators are
present.Comment: 32 pages. Added comments and reference
Microscopic entropy of the charged BTZ black hole
The charged BTZ black hole is characterized by a power-law curvature
singularity generated by the electric charge of the hole. The curvature
singularity produces ln r terms in the asymptotic expansion of the
gravitational field and divergent contributions to the boundary terms. We show
that these boundary deformations can be generated by the action of the
conformal group in two dimensions and that an appropriate renormalization
procedure allows for the definition of finite boundary charges.
In the semiclassical regime the central charge of the dual CFT turns out to
be that calculated by Brown and Henneaux, whereas the charge associated with
time translation is given by the renormalized black hole mass. We then show
that the Cardy formula reproduces exactly the Bekenstein-Hawking entropy of the
charged BTZ black hole.Comment: 9 pages, no figure
Critical energy flux and mass in solvable theories of 2d dilaton gravity
In this paper we address the issue of determining the semiclassical threshold
for black hole formation in the context of a one-parameter family of theories
which continuously interpolates between the RST and BPP models. We find that
the results depend significantly on the initial static configuration of the
spacetime geometry before the influx of matter is turned on. In some cases
there is a critical energy density, given by the Hawking rate of evaporation,
as well as a critical mass (eventually vanishing). In others there is
neither nor a critical flux.Comment: LaTeX file, 12 pages, 4 figure
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