1,692 research outputs found
The perturbation and its geometric interpretation
Starting from the recently-discovered -perturbed
Lagrangians, we prove that the deformed solutions to the classical EoMs for
bosonic field theories are equivalent to the unperturbed ones but for a
specific field-dependent local change of coordinates. This surprising geometric
outcome is fully consistent with the identification of
-deformed 2D quantum field theories as topological
JT gravity coupled to generic matter fields. Although our conclusion is valid
for generic interacting potentials, it first emerged from a detailed study of
the sine-Gordon model and in particular from the fact that solitonic
pseudo-spherical surfaces embedded in are left invariant by the
deformation. Analytic and numerical results concerning the perturbation of
specific sine-Gordon soliton solutions are presented.Comment: v2 : Expanded version with new comments, numerical results and 16
figures added. Minor typos corrected. Extra references added. 25 pages. 4
figures v3 : JHEP version. Section 6 added. Minor typos corrected. Extra
reference added. 30 pages. 5 figure
Conserved currents and irrelevant deformations of 2D integrable field theories
It has been recently discovered that the deformation
is closely-related to Jackiw-Teitelboim gravity. At classical level, the
introduction of this perturbation induces an interaction between the
stress-energy tensor and space-time and the deformed EoMs can be mapped,
through a field-dependent change of coordinates, onto the corresponding
undeformed ones. The effect of this perturbation on the quantum spectrum is
non-perturbatively described by an inhomogeneous Burgers equation. In this
paper, we point out that there exist infinite families of models where the
geometry couples instead to generic combinations of local conserved currents
labelled by the Lorentz spin. In spirit, these generalisations are similar to
the model as the resulting theories and the
corresponding scattering phase factors are not Lorentz invariant. The link with
the model is discussed in detail. While the classical
setup described here is very general, we shall use the sine-Gordon model and
its CFT limit as explanatory quantum examples. Most of the final equations and
considerations are, however, of broader validity or easily generalisable to
more complicated systems.Comment: 39 pages, 3 figures. v2: typos corrected, extended version with more
results on the link between the classical and the quantum analysi
Endothelial effects of antihypertensive treatment: focus on irbesartan
The endothelium is characterized by a wide range of important homeostatic functions. It participates in the control of hemostasis, blood coagulation and fibrinolysis, platelet and leukocyte interactions with the vessel wall, regulation of vascular tone, and of blood pressure. Many crucial vasoactive endogenous compounds are produced by the endothelial cells to control the functions of vascular smooth muscle cells and of circulating blood cells. These complex systems determine a fine equilibrium which regulates the vascular tone. Impairments in endothelium-dependent vasodilation lead to the so called endothelial dysfunction. Endothelial dysfunction is then characterized by unbalanced concentrations of vasodilating and vasoconstricting factors, the most important being represented by nitric oxide (NO) and angiotensin II (AT II). High angiotensin-converting enzyme (ACE) activity leads to increased AT II generation, reduced NO levels with subsequent vasoconstriction. The net acute effect results in contraction of vascular smooth muscle cells and reduced lumen diameter. Furthermore, when increased ACE activity is chronically sustained, increase in growth, proliferation and differentiation of the vascular smooth muscle cells takes place; at the same time, a decrease in the anti-proliferative action by NO, a decrease in fibinolysis and an increase in platelets aggregation may be observed. AT II is then involved not only in the regulation of blood pressure, but also in vascular inflammation, permeability, smooth muscle cells remodelling, and oxidative stress which in turn lead to atherosclerosis and increased cardiovascular risk. Given the pivotal role exerted by AT II in contributing to alteration of endothelial function, treatment with ACE inhibitors or angiotensin receptor blockers (ARBs) may be of particular interest to restore a physiological activity of endothelial cells. In this view, the blockade of the renin-angiotensin system (RAS), has been shown to positively affect the endothelial function, beyond the antihypertensive action displayed by these compounds. In this review, attention has been specifically focused on an ARB, irbesartan, to examine its effects on endothelial function
Selenium and thyroid autoimmunity
The trace element selenium (Se) occurs in the form of the amino acid selenocysteine in selenoproteins. Selenoproteins exerts multiple physiological effects in human health, many of which are related with regulation of reduction-oxidation processes. In fact, the selenoenzyme families of glutathione peroxidase (GPx) and thioredoxin reductase (TRx) display the ability to act as antioxidants, protecting cells from oxidative damage. Furthermore, another class of selenoproteins are the iodothyronine deiodinase enzymes (DIO), which catalyze the conversion of thyroxine (T4) in triiodothyronine (T3), then exerting a fine tuned control on thyroid hormones metabolism. Several studies have investigated the potential positive effects of Se supplementation in thyroid diseases, characterized by increased levels of hydrogen peroxide and free radicals, like autoimmune chronic thyroiditis. These studies have supplied evidences indicating that Se supplementation, maximizing the antioxidant enzymes activity, may reduce the thyroid inflammatory status. Then, it may be postulated that Se could play a therapeutical role in thyroid autoimmune diseases. Despite the fact that recent studies seem to be concordant about Se beneficial effects in decreasing thyroid peroxidase antibodies (TPOAb) titers and ameliorating the ultrasound echogenicity pattern, several doubts have to be still clarified, before advising Se supplementation in chronic autoimmune thyroiditis
Generalised Born-Infeld models, Lax operators and the perturbation
Surprising links between the deformation of 2D quantum field theories induced
by the composite operator, effective string
models and the CFT correspondence, have recently emerged. The purpose of
this article is to discuss various classical aspects related to the deformation
of 2D interacting field theories. Special attention is given to the
sin(h)-Gordon model, for which we were able to construct the -deformed Lax pair. We consider the Lax pair formulation to be
the first essential step toward a more satisfactory geometrical interpretation
of this deformation within the integrable model framework.
Furthermore, it is shown that the 4D Maxwell-Born-Infeld theory, possibly
with the addition of a mass term or a derivative-independent potential,
corresponds to a natural extension of the 2D examples. Finally, we briefly
comment on 2D Yang-Mills theory and propose a modification of the heat kernel,
for a generic surface with genus and boundaries, which fully accounts
for the contribution.Comment: 22 pages, 2 figures, v2: new comments, hyperlinks and minor typos
correcte
Wood-Based Composites: Innovation towards a Sustainable Future
The term wood-based composite (WBC) is used to define a wide range of products in which wood is bonded together with other wooden or non-wooden materials [...
The first, holistic immunological model of COVID‐19: Implications for prevention, diagnosis, and public health measures
The natural history of COVID-19 caused by SARS-CoV-2 is extremely variable, ranging from asymptomatic or mild infection, mainly in children, to multi-organ failure, eventually fatal, mainly in the eldest. We propose here the first model explaining how the outcome of first, crucial 10-15 days after infection, depends on the balance between the cumulative dose of viral exposure and the efficacy of the local innate immune response (natural IgA and IgM antibodies, mannose-binding lectin). If SARS-CoV-2 runs the blockade of this innate immunity and spreads from the upper airways to the alveoli in the early phases of the infections, it can replicate with no local resistance, causing pneumonia and releasing high amounts of antigens. The delayed and strong adaptive immune response (high-affinity IgM and IgG antibodies) that follows, causes severe inflammation and triggers mediator cascades (complement, coagulation, and cytokine storm), leading to complications often requiring intensive therapy and being, in some patients, fatal. Low-moderate physical activity can still be recommended. However, extreme physical activity and oral breathing with hyperventilation during the incubation days and early stages of COVID-19 facilitates re-inhalation and early direct penetration of high numbers of own virus particles in the lower airways and the alveoli, without impacting on the airway's mucosae covered by neutralizing antibodies ("viral auto-inhalation" phenomenon). This allows the virus to bypass the efficient immune barrier of the upper airway mucosa in already infected, young, and otherwise healthy athletes. In conclusion, whether the virus or the adaptive immune response reaches the lungs first is a crucial factor deciding the fate of the patient. This "quantitative and time-/sequence-dependent" model has several implications for prevention, diagnosis, and therapy of COVID-19 at all ages
The Generalised Born Oscillator and the Berry-Keating Hamiltonian
In this study, we introduce and investigate a family of quantum mechanical
models in 0+1 dimensions, known as generalized Born quantum oscillators. These
models represent a one-parameter deformation of a specific system obtained by
reducing the Nambu-Goto theory to 0+1 dimensions. Despite these systems showing
significant similarities with -type
perturbations of two-dimensional relativistic models, our analysis reveals
their potential as interesting regularizations of the Berry-Keating theory. We
quantize these models using the Weyl quantization scheme up to very high orders
in . By examining a specific scaling limit, we observe an intriguing
connection between the generalized Born quantum oscillators and the
Riemann-Siegel function.Comment: 23+16 pages; 8 figures; Published versio
Drug-resistant chronic cluster headache successfully treated with supraorbital plus occipital nerve stimulation. A rare case report
Chronic cluster headache (CCH) is a rare and extremely disabling headache syndrome with a recent clinical systematization of its clinical frame from the European Headache Federation [1]. We present a case of a young man affected by drug-resistant chronic CH (rCCH) who showed improvement after a two-time combined supraorbital and occipital nerve stimulation (S-ONS). The clinical improvement was still present at 6-month follow-up
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