211 research outputs found
Singular behavior of fluctuations in a relaxation process
Carrying out explicitly the computation in a paradigmatic model of
non-interacting systems, the Gaussian Model, we show the existence of a
singular point in the probability distribution of an extensive variable
. Interpreting as a thermodynamic potential of a dual system obtained
from the original one by applying a constraint, we discuss how the
non-analytical point of is the counterpart of a phase-transition in the
companion system. We show the generality of such mechanism by considering both
the system in equilibrium or in the non-equilibrium state following a
temperature quench.Comment: 8 pages, 2 figures. arXiv admin note: text overlap with
arXiv:1404.397
Heat exchanges in coarsening systems
This paper is a contribution to the understanding of the thermal properties
of aging systems where statistically independent degrees of freedom with
largely separated timescales are expected to coexist. Focusing on the
prototypical case of quenched ferromagnets, where fast and slow modes can be
respectively associated to fluctuations in the bulk of the coarsening domains
and to their interfaces, we perform a set of numerical experiments specifically
designed to compute the heat exchanges between different degrees of freedom.
Our studies promote a scenario with fast modes acting as an equilibrium
reservoir to which interfaces may release heat through a mechanism that allows
fast and slow degrees to maintain their statistical properties independent.Comment: 12 pages, 8 figure
Heat exchanges in a quenched ferromagnet
The off-equilibrium probability distribution of the heat exchanged by a
ferromagnet in a time interval after a quench below the critical point is
calculated analytically in the large-N limit. The distribution is characterized
by a singular threshold Qc < 0, below which a macroscopic fraction of heat is
released by the k = 0 Fourier component of the order parameter. The
mathematical structure producing this phenomenon is the same responsible of the
order parameter condensation in the equilibrium low temperature phase. The heat
exchanged by the individual Fourier modes follows a non trivial pattern, with
the unstable modes at small wave vectors warming up the modes around a
characteristic finite wave vector kM. Two internal temperatures, associated to
the k = 0 and k = kM modes, rule the heat currents through a fluctuation
relation similar to the one for stationary systems in contact with two thermal
reservoirs.Comment: 5 pages, 2 figures. New version with improved and extended tex
Frictional Active Brownian Particles
Frictional forces affect the rheology of hard-sphere colloids, at high shear
rate. Here we demonstrate, via numerical simulations, that they also affect the
dynamics of active Brownian particles, and their motility induced phase
separation. Frictional forces increase the angular diffusivity of the
particles, in the dilute phase, and prevent colliding particles from resolving
their collision by sliding one past to the other. This leads to qualitatively
changes of motility-induced phase diagram in the volume-fraction motility
plane. While frictionless systems become unstable towards phase separation as
the motility increases only if their volume fraction overcomes a threshold,
frictional system become unstable regardless of their volume fraction. These
results suggest the possibility of controlling the motility induced phase
diagram by tuning the roughness of the particles
Monotonicity Principle in Tomography of Nonlinear Conducting Materials
We treat an inverse electrical conductivity problem which deals with the
reconstruction of nonlinear electrical conductivity starting from boundary
measurements in steady currents operations. In this framework, a key role is
played by the Monotonicity Principle, which establishes a monotonic relation
connecting the unknown material property to the (measured) Dirichlet-to-Neumann
operator (DtN). Monotonicity Principles are the foundation for a class of
non-iterative and real-time imaging methods and algorithms. In this article, we
prove that the Monotonicity Principle for the Dirichlet Energy in nonlinear
problems holds under mild assumptions. Then, we show that apart from linear and
-Laplacian cases, it is impossible to transfer this Monotonicity result from
the Dirichlet Energy to the DtN operator. To overcome this issue, we introduce
a new boundary operator, identified as an Average DtN operator.Comment: 28 pages, 6 figure
The emergency and delay management in total talus extrusion: Case report and review of literature after 24 months of follow up
Abstract Total talus extrusion is a rare and severe injury. It is burdened by many complications as avascular necrosis and osteomyelitis even if a proper debridement of extruded talus is performed. Few case reports or case series were published, and because of the rarity of this event, there are no guidelines for treatment. We report the first case on an octogenarian man providing a long-term follow-up performing contrast enhanced magnetic resonances. The authors report the case of an octogenarian man who fell from an olive tree reporting a total talus extrusion associated with the fracture of the medial malleolus. After an accurate debridement and washing of the wound, the talus was anatomically repositioned and the fracture was treated with an external fixator. The wound healed with difficulty after 12 months and the patient developed a chronic osteomyelitis of the talar dome and avascular necrosis of talar head. We followed the patient for 24 months performing contrast enhanced magnetic resonances and evaluating the development of the avascular necrosis. Even if we encountered these complications, the treatment allowed the patient to walk without pain, using a talus type shoe and one crutch. Although the literature suggests that an anatomic replacement of talus allows avoiding main complications, we deem that the patient's age is an important biological feature to consider in the prognostic stratification. Moreover, primary talectomy and tibio-calcaneal fusion should be reserved as a salvage procedure. Talus replacement allows an overall good outcome for the patients, retaining height, and allowing a good quality of life
Resistant Hypertension, Time-Updated Blood Pressure Values and Renal Outcome in Type 2 Diabetes Mellitus
BACKGROUND: Apparent treatment resistant hypertension (aTRH) is highly prevalent in patients with type 2 diabetes mellitus (T2D) and entails worse cardiovascular prognosis. The impact of aTRH and long-term achievement of recommended blood pressure (BP) values on renal outcome remains largely unknown. We assessed the role of aTRH and BP on the development of chronic kidney disease in patients with T2D and hypertension in real-life clinical practice.METHODS AND RESULTS: Clinical records from a total of 29 923 patients with T2D and hypertension, with normal baseline estimated glomerular filtration rate and regular visits during a 4-year follow-up, were retrieved and analyzed. The association between time-updated BP control (ie, 75% of visits with BP <140/90 mm Hg) and the occurrence of estimated glomerular filtration rate <60 and/or a reduction 6530% from baseline was assessed. At baseline, 17% of patients had aTRH. Over the 4-year follow-up, 19% developed low estimated glomerular filtration rate and 12% an estimated glomerular filtration rate reduction 6530% from baseline. Patients with aTRH showed an increased risk of developing both renal outcomes (adjusted odds ratio, 1.31 and 1.43; P<0.001 respectively), as compared with those with non-aTRH. No association was found between BP control and renal outcomes in non-aTRH, whereas in aTRH, BP control was associated with a 30% (P=0.036) greater risk of developing the renal end points.CONCLUSIONS: ATRH entails a worse renal prognosis in T2D with hypertension. BP control is not associated with a more-favorable renal outcome in aTRH. The relationship between time-updated BP and renal function seems to be J-shaped, with optimal systolic BP values between 120 and 140 mm Hg
The role of PIAS3, p-STAT3 and ALR in colorectalcancer: new translational molecular features for an old disease
OBJECTIVE: Human colorectal cancer (CRC) is characterized by a sequence of biological events that determine its induction and progression. Gut microbiota has an impor-tant role in this multistep model of carcinogen-esis, as well as constitutive activation of Signal Transducer and Activator Factors 3 (p-STAT3) and Protein Inhibitor of Activated STAT3 (PIAS3), which negatively controls STAT3. It has been re-ported that a liver growth factor, the Augmenter of Liver Regeneration (ALR), an anti-apoptotic, anti-metastatic factor, exerts protective/cell sur-vival and anti-metastatic activities and has been detected highly expressed in neoplastic cells. PATIENTS AND METHODS: To evaluate, by immunohistochemistry, p-STAT3, PIAS3 and ALR expression in neoplastic human tissues from CRC patients, grouping the data in accord-ance with the histological alterations (G1, G2 and G3) and metastasis presence. Western blot (WB) analysis of ALR was also determined in ne-oplastic and surrounding tissues. Finally, cell proliferation (Ki-67) and apoptosis (Bcl-2) were determined. RESULTS : Colon cancer tissue samples showed: (1) ALR and p-STAT3 strongly over-ex-pression in 100% of G1 tissue samples, reducing in G2 and G3 tissue samples; (2) PIAS3 immuno-logical determination was poorly expressed in G1 tissue samples and highly expressed in the 100% of colorectal tissues from group G2 and G3. Ki-67 progressively increases with the im-portance of the anatomic-pathological altera-tions and Bcl-2 resulted higher in G3 tissue sam-ples compared to G1 neoplastic tissues. WB data evidenced, in neoplastic tissues, compared to the tumour-surrounding tissues, ALR over-ex-pressed in G1 neoplastic tissues and down-ex-pressed in G3 neoplastic tissues.CONCLUSIONS: Our data demonstrate a dif-ferent dynamism of the investigated factors in relation to the severity of CRC histological find-ings. We hypothesize that the positive expres-sion of ALR and p-STAT3 in the neoplastic tis-sue samples from CRC G1 group, associated to the absence of PIAS3, could be useful marker to identify an early stage of the disease. Based on these data and on our previous studies on gut microbiota in precancerous intestinal lesions, we are confident that, after microbial priming, a cascade of molecular events is started. So, the detectable molecules acting in these initial steps should be considered for the study of CRC progression and therapy
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