9,332 research outputs found
Quasi-saddles as relevant points of the potential energy surface in the dynamics of supercooled liquids
The supercooled dynamics of a Lennard-Jones model liquid is numerically
investigated studying relevant points of the potential energy surface, i.e. the
minima of the square gradient of total potential energy . The main findings
are: ({\it i}) the number of negative curvatures of these sampled points
appears to extrapolate to zero at the mode coupling critical temperature ;
({\it ii}) the temperature behavior of has a close relationship with the
temperature behavior of the diffusivity; ({\it iii}) the potential energy
landscape shows an high regularity in the distances among the relevant points
and in their energy location. Finally we discuss a model of the landscape,
previously introduced by Madan and Keyes [J. Chem. Phys. {\bf 98}, 3342
(1993)], able to reproduce the previous findings.Comment: To be published in J. Chem. Phy
Hierarchy from Baryogenesis
We study a recently proposed mechanism to solve the hierarchy problem in the
context of the landscape, where the solution of the hierarchy problem is
connected to the requirement of having baryons in our universe via Electroweak
Baryogenesis. The phase transition is triggered by the fermion condensation of
a new gauge sector which becomes strong at a scale Lambda determined by
dimensional transmutation, and it is mediated to the standard model by a new
singlet field. In a ``friendly'' neighborhood of the landscape, where only the
relevant operators are ``scanned'' among the vacua, baryogenesis is effective
only if the higgs mass m_h is comparable to this low scale Lambda, forcing m_h
to be of order Lambda, and solving the hierarchy problem. A new CP violating
phase is needed coupling the new singlet and the higgs field to new matter
fields. We study the constraints on this model given by baryogenesis and by the
electron electric dipole moment (EDM), and we briefly comment on gauge coupling
unification and on dark matter relic abundance. We find that next generation
experiments on the EDM will be sensitive to essentially the entire viable
region of the parameter space, so that absence of a signal would effectively
rule out the model.Comment: 28 pages, 4 figures. v2: Added comments and references. Corrected one
typo in eq.(81). Conclusions unaltere
Trismus as the first manifestation of cholangiocarcinoma
The initial presentation of a cholangiocarcinoma (CC) as trismus due to metastasis to the parotid gland is extremely rare and no previous reports have been found in the literature. A 29-year-old woman presented trismus that initiated 2 months before admission, just after superior left third molar extraction. Physical examination revealed severe trismus and a mass in the parotid gland. Computed tomography (CT) showed a heterogeneous mass in the left parotid gland. The next day she presented jaundice, bilirubinuria, and fever, followed by massive bleeding, intravascular disseminated coagulation, and respiratory insufficiency. Two days later she died. At autopsy, the parotid tumor was identified as a metastasis from a CC of the extrabiliary tract. To our knowledge, this is the first reported case of a metastatic CC that initially presented as trismus due to a mass in the parotid gland. This case represents a rare but important diagnosis that otolaryngologists and oral surgeons should add to the catalog of uncommon causes of trismus
Activated processes and Inherent Structure dynamics of finite-size mean-field models for glasses
We investigate the inherent structure (IS) dynamics of mean-field {\it
finite-size} spin-glass models whose high-temperature dynamics is described in
the thermodynamic limit by the schematic Mode Coupling Theory for super-cooled
liquids. Near the threshold energy the dynamics is ruled by activated processes
which induce a logarithmic slow relaxation. We show the presence of aging in
both the IS correlation and integrated response functions and check the
validity of the one-step replica symmetry breaking scenario in the presence of
activated processes. Our work shows: 1) The violation of the
fluctuation-dissipation theorem is given by the configurational entropy, 2) The
intermediate time regime () in mean-field theory automatically
includes activated processes opening the way to analytically investigate
activated processes by computing corrections beyond mean-field.Comment: 8 pages, 3 postscript figures, EPL format, improved versio
Vibrational origin of the fast relaxation processes in molecular glass-formers
We study the interaction of the relaxation processes with the density
fluctuations by molecular dynamics simulation of a flexible molecule model for
o-terphenyl (oTP) in the liquid and supercooled phases. We find evidence,
besides the structural relaxation, of a secondary vibrational relaxation whose
characteristic time, few ps, is slightly temperature dependent. This i)
confirms the result by Monaco et al. [Phys. Rev, E 62, 7595 (2000)] of the
vibrational nature of the fast relaxation observed in Brillouin Light
Scattering (BLS) experiments in oTP; and ii) poses a caveat on the
interpretation of the BLS spectra of molecular systems in terms of a purely
center of mass dynamics.Comment: RevTeX, 5 pages, 4 eps figure
A new p65 isoform that bind the glucocorticoid hormone and is expressed in inflammation liver diseases and COVID-19
Inflammation is a physiological process whose deregulation causes some diseases including cancer. Nuclear Factor kB (NF-kB) is a family of ubiquitous and inducible transcription factors, in which the p65/p50 heterodimer is the most abundant complex, that play critical roles mainly in inflammation. Glucocorticoid Receptor (GR) is a ligand-activated transcription factor and acts as an anti-inflammatory agent and immunosuppressant. Thus, NF-kB and GR are physiological antagonists in the inflammation process. Here we show that in mice and humans there is a spliced variant of p65, named p65 iso5, which binds the corticosteroid hormone dexamethasone amplifying the effect of the glucocorticoid receptor and is expressed in the liver of patients with hepatic cirrhosis and hepatocellular carcinoma (HCC). Furthermore, we have quantified the gene expression level of p65 and p65 iso5 in the PBMC of patients affected by SARS-CoV-2 disease. The results showed that in these patients the p65 and p65 iso5 mRNA levels are higher than in healthy subjects. The ability of p65 iso5 to bind dexamethasone and the regulation of the glucocorticoid (GC) response in the opposite way of the wild type improves our knowledge and understanding of the anti-inflammatory response and identifies it as a new therapeutic target to control inflammation and related diseases
Topological Description of the Aging Dynamics in Simple Glasses
We numerically investigate the aging dynamics of a monatomic Lennard-Jones
glass, focusing on the topology of the potential energy landscape which, to
this aim, has been partitioned in basins of attraction of stationary points
(saddles and minima). The analysis of the stationary points visited during the
aging dynamics shows the existence of two distinct regimes: i) at short times,
t<t_c, the system visits basins of saddles whose energies and orders decrease
with t; ii) at long times, t>t_c, the system mainly lies in basins pertaining
to minima of slowly decreasing energy. The dynamics for t>t_c can be
represented by a simple random walk on a network of minima with a jump
probability proportional to the inverse of the waiting time.Comment: 4 pages, 5 postscript figure
High frequency dynamics in a monatomic glass
The high frequency dynamics of glassy Selenium has been studied by Inelastic
X-ray Scattering at beamline BL35XU (SPring-8). The high quality of the data
allows one to pinpoint the existence of a dispersing acoustic mode for
wavevectors () of nm, helping to clarify a previous
contradiction between experimental and numerical results. The sound velocity
shows a positive dispersion, exceeding the hydrodynamic value by 10%
at nm. The dependence of the sound attenuation
, reported for other glasses, is found to be the low- limit of a
more general law which applies also to the
higher region, where no longer holds.Comment: Phys. Rev. Lett. (Accepted
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