994 research outputs found
Topological aspects in the photonic crystal analog of single-particle transport in quantum Hall systems
We present a perturbative approach to derive the semiclassical equations of
motion for the two-dimensional electron dynamics under the simultaneous
presence of static electric and magnetic fields, where the quantized Hall
conductance is known to be directly related to the topological properties of
translationally invariant magnetic Bloch bands. In close analogy to this
approach, we develop a perturbative theory of two-dimensional photonic
transport in gyrotropic photonic crystals to mimic the physics of quantum Hall
systems. We show that a suitable permittivity grading of a gyrotropic photonic
crystal is able to simulate the simultaneous presence of analog electric and
magnetic field forces for photons, and we rigorously derive the
topology-related term in the equation for the electromagnetic energy velocity
that is formally equivalent to the electronic case. A possible experimental
configuration is proposed to observe a bulk photonic analog to the quantum Hall
physics in graded gyromagnetic photonic crystals.Comment: to be published in Phys Rev
Groups with restriction on non-normal subgroups
This thesis contains a study of groups with restrictions on non-normal subgroups and of groups whose subgroups not satisfying a property X have finitely many normalizers
On The Weak-Coupling Limit for Bosons and Fermions
In this paper we consider a large system of Bosons or Fermions. We start with
an initial datum which is compatible with the Bose-Einstein, respectively
Fermi-Dirac, statistics. We let the system of interacting particles evolve in a
weak-coupling regime. We show that, in the limit, and up to the second order in
the potential, the perturbative expansion expressing the value of the
one-particle Wigner function at time , agrees with the analogous expansion
for the solution to the Uehling-Uhlenbeck equation. This paper follows in
spirit the companion work [\rcite{BCEP}], where the authors investigated the
weak-coupling limit for particles obeying the Maxwell-Boltzmann statistics:
here, they proved a (much stronger) convergence result towards the solution of
the Boltzmann equation
Macroscopic Forces driven by Resonant Neutrino Conversion
We show that neutrino oscillations in matter are always accompanied by
collective forces on the medium. This effect may produce interesting
consequences for the background and the neutrino oscillations themselves. The
force is maximal in the case of resonant neutrino conversion in the adiabatic
regime. We study here the forces driven by and
MSW conversion and shortly discuss their possible relevance for
the dynamics of a type II supernova.Comment: 9 LaTeX pages, 1 ps figure file. Format changed. One formula
corrected. Some comments added to the text. Accepted for publication on Phys.
Lett.
Sexual Minority Status, Anxiety–Depression, and Academic Outcomes: The Role of Campus Climate Perceptions among Italian Higher Education Students
Students from sexual minorities generally describe Higher Education contexts as
unwelcoming and chilly environments. Based on the Minority Stress theory, these disparities
in climate perceptions may lead sexual minority students to negative health and academic outcomes.
To date, research documenting the experience of sexual minority students within European Higher
Education Institutions is limited. Framed within campus climate literature, the current study aimed
to expand on previous knowledge by investigating the associations between sexual minority status,
students’ perceptions of campus climate and psychological (i.e., anxiety–depression), and academic
outcomes (i.e., intellectual and academic success and considering leaving the university) using a
self-selected sample of 868 Italian university students (17.9% sexual minority students). The results
showed that sexual minority status was associated with negative perceptions of campus climate,
which, in turn, were associated with higher levels of anxiety–depression symptoms, lowered academic
success, and a high probability of considering leaving university. Further research is needed to
investigate the experience of sexual minority students within European Higher Education contexts
and to explore possible actions that could contribute to fostering a greater sense of belonging to the
campus community for all students, and particularly for students from sexual minority groups
Recognition of Daily Gestures with Wearable Inertial Rings and Bracelets
Recognition of activities of daily living plays an important role in monitoring elderly people and helping caregivers in controlling and detecting changes in daily behaviors. Thanks to the miniaturization and low cost of Microelectromechanical systems (MEMs), in particular of Inertial Measurement Units, in recent years body-worn activity recognition has gained popularity. In this context, the proposed work aims to recognize nine different gestures involved in daily activities using hand and wrist wearable sensors. Additionally, the analysis was carried out also considering different combinations of wearable sensors, in order to find the best combination in terms of unobtrusiveness and recognition accuracy. In order to achieve the proposed goals, an extensive experimentation was performed in a realistic environment. Twenty users were asked to perform the selected gestures and then the data were off-line analyzed to extract significant features. In order to corroborate the analysis, the classification problem was treated using two different and commonly used supervised machine learning techniques, namely Decision Tree and Support Vector Machine, analyzing both personal model and Leave-One-Subject-Out cross validation. The results obtained from this analysis show that the proposed system is able to recognize the proposed gestures with an accuracy of 89.01% in the Leave-One-Subject-Out cross validation and are therefore promising for further investigation in real life scenarios
Mediterranean diet, endothelial function and vascular inflammatory markers.
AbstractObjectivesTo discuss present knowledge about the relation between adipose tissue, inflammation and the Mediterranean-style diet.DesignReview of the literature and personal perspectives.Setting and resultsRecent studies indicate that adipose tissue is an endocrine organ producing numerous proteins, collectively referred to as adipokines, with broad biological activity, which play an important autocrine role in obesity-associated complications. Adipose tissue in general and visceral fat in particular are thought to be key regulators of inflammation which is heavily involved in the onset and development of atherothrombotic disease. Moreover, chronic inflammation may also represent a triggering factor in the origin of the metabolic syndrome and type 2 diabetes mellitus. An increased release of proinflammatory adipokines from the visceral adipose tissue, associated with a reduced secretion of anti-inflammatory adipokines and cytokines, could determine a low-grade chronic inflammatory state which might play a role in the future development of the metabolic syndrome, diabetes and atherosclerosis through both insulin resistance and endothelial dysfunction. Interventions aimed at decreasing weight loss and improving adherence to a Mediterranean-style diet in people with obesity or metabolic syndrome decrease the inflammatory milieu and ameliorate both insulin resistance and endothelial dysfunction.ConclusionsAppropriate dietary patterns, as those associated with the eating model of Mediterranean-type diets, represent therapeutic strategies to reduce inflammation and the associated metabolic and cardiovascular risk
Sexual dysfunction and the Mediterranean diet.
AbstractObjectivesTo discuss present knowledge about the relation between sexual dysfunction, metabolic factors and the Mediterranean-style diet.DesignReview of the literature and personal perspectives.Setting and resultsSexual problems appear to be widespread in society, influenced by both health-related and psychosocial factors, and are associated with impaired quality of life. Epidemiological studies suggest that modifiable health behaviours, including physical activity and leanness, are associated with a reduced risk for erectile dysfunction (ED) among men. Data from other surveys also indicate a higher prevalence of impotence in obese men. Obesity and the metabolic syndrome may be a risk factor for ED. The high prevalence of ED in patients with cardiovascular risk factors suggests that abnormalities of the vasodilator system of penile arteries play an important role in the pathophysiology of ED. We have shown that one-third of obese men with ED can regain their sexual activity after 2 years of adopting health behaviours, including a Mediterranean-style diet associated with regular exercise.ConclusionsWestern societies actually spend a huge part of their health care costs on chronic disease treatment and interventions for risk factors. The adoption of healthy lifestyles can reduce the prevalence of obesity and the metabolic syndrome, and hopefully the burden of sexual dysfunction
L’USO DELL’ENDOMICROSCOPIA CONFOCALE NELLO STUDIO IN VIVO DELLA CARATTERISTICHE TUMORALI CON PARTICOLARE RIGUARDO ALLA NEO-ANGIOGENESI
AIM:
Tumour neoangiogenesis is a key factor in tumour progression and metastatic spread and the possibility to assess tumour angiogenesis might provide prognostic information. The aim of this study was to establish the role of probe-based confocal laser endomicroscopy (p-CLE) in the identification of vascular architecture and specific morphological patterns in normal colorectal mucosa and malignant lesions during routine endoscopy.
METHOD:
Fourteen consecutive patients with colorectal cancer were included. The following features were identified and then compared between normal and neoplastic mucosa on p-CLE images: vessel shape (straight vs irregular) vessel diameter the 'branching patterns' vessel permeability (fluorescein leakage) and blood flow (normal vs defective flux). Immunohistochemistry was used to confirm the presence and to study the morphology of vascular structures (CD-34 staining) and 'neo-vessels' (WT-1 staining) on tumour and normal mucosal sections.
RESULTS:
Tumour vessels appeared as irregular, ectatic and with a highly variable calibre and branching patterns on p-CLE images. The mean diameter of tumour vessels was significantly larger than those in normal mucosa (weighted mean difference 3.38, 95% CI 2.65-4.11, P = 0.01). Similarly, 'vessel branching' (OR 2.74, 95% CI 1.23-6.14, P = 0.01), fluorescent dye 'extravasation' (OR 3.46, 95% CI 1.39-8.57, P = 0.01) were significantly more frequent in colorectal cancer than in normal colorectal mucosa. Immunohistochemistry corroborated the p-CLE findings, showing higher vascularity in tumour sections due to neoformed vessels, presenting irregular patterns.
CONCLUSION:
Probe-based confocal laser endomicroscopy provides a noninvasive characterization of the microvascular architecture of colonic mucosa. Different morphological patterns have been described, discriminating normal and malignant microvascular networks in colorectal mucosa
Complementarity between Quantum and Classical Mechanics in Chemical Modeling. The H + HeH+ → H2+ + He Reaction: A Rigourous Test for Reaction Dynamics Methods
In this work we present a dynamical study of the H + HeH+ → H2+ + He reaction in a collision energy range from 0.1 meV to 10 eV, suitable to be used in applicative models. The paper extends and complements a recent work [ Phys. Chem. Chem. Phys. 2014, 16, 11662 ] devoted to the characterization of the reactivity from the ultracold regime up to the three-body dissociation breakup. In particular, the accuracy of the quasi-classical trajectory method below the three-body dissociation threshold has been assessed by a detailed comparison with previous calculations performed with different reaction dynamics methods, whereas the reliability of the results in the high energy range has been checked by a direct comparison with the available experimental data. Integral cross sections for several HeH+ roto-vibrational states have been analyzed and used to understand the extent of quantum effects in the reaction dynamics. By using the quasi-classical trajectory method and quantum mechanical close coupling data, respectively, in the high and low collision energy ranges, we obtain highly accurate thermal rate costants until 15 000 K including all (178) the roto-vibrational bound and quasi-bound states of HeH+. The role of the collision-induced dissociation is also discussed and explicitly calculated for the ground roto-vibrational state of HeH+
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