450 research outputs found

    U(N|M) quantum mechanics on Kaehler manifolds

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    We study the extended supersymmetric quantum mechanics, with supercharges transforming in the fundamental representation of U(N|M), as realized in certain one-dimensional nonlinear sigma models with Kaehler manifolds as target space. We discuss the symmetry algebra characterizing these models and, using operatorial methods, compute the heat kernel in the limit of short propagation time. These models are relevant for studying the quantum properties of a certain class of higher spin field equations in first quantization.Comment: 21 pages, a reference adde

    Heterotic-Type II duality in the hypermultiplet sector

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    We revisit the duality between heterotic string theory compactified on K3 x T^2 and type IIA compactified on a Calabi-Yau threefold X in the hypermultiplet sector. We derive an explicit map between the field variables of the respective moduli spaces at the level of the classical effective actions. We determine the parametrization of the K3 moduli space consistent with the Ferrara-Sabharwal form. From the expression of the holomorphic prepotential we are led to conjecture that both X and its mirror must be K3 fibrations in order for the type IIA theory to have an heterotic dual. We then focus on the region of the moduli space where the metric is expressed in terms of a prepotential on both sides of the duality. Applying the duality we derive the heterotic hypermultiplet metric for a gauge bundle which is reduced to 24 point-like instantons. This result is confirmed by using the duality between the heterotic theory on T^3 and M-theory on K3. We finally study the hyper-Kaehler metric on the moduli space of an SU(2) bundle on K3.Comment: 27 pages; references added, typos correcte

    Preclinical atherosclerosis, metabolic syndrome and risk of cardiovascular events

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    Atherosclerotic disease is a chronic disorder developing insidiously throughout the life and usually progressing to an advanced stage by the time symptoms occur. In order to realize cardiovascular (CV) prevention, the detection of asymptomatic but diseased patients is crucial for an early intervention, since in these subjects there are opportunities to alter the progression of disease and the outcome (1). However, the simply analysis of risk factors don’t permits to identify always these subjects since it doesn’t informs about the effect that risk factors (RF) had already provoked and may more provoke on the individual vasculature. Besides, the risk factors known predict can explain only the 90 percent of cardiovascular disease (CVD) and traditional algorithms for prediction of CV risk failed to predict a proportion of cardiovascular events (CVE), realizing a “risk factors prediction gap” (2). It may be explained by several reasons: the epidemiology-derived models, based on the prediction of long-term risk, may not accurately predict short-term events, they don’t take into consideration emerging and novel risk factors; risk algorithms don’t identify, among patients with neither a previous history of CVD nor an high risk for atherosclerotic disease, those who will develop acute myocardial infarction and/or sudden coronary death as first CVD manifestation, and this may be due to the fact that the factors responsible of plaque formation and growth are not necessarily the same responsible of its instability and rupture, being the latter related to inflammation, thrombosis and plaque morphology (3).So, a possible approach to evaluate the individual global cardiovascular risk with more accurateness is to identify risk factors combination that more easily produces vascular damage, or alternatively, to evaluate directly the arterial wall and its damage degree. The former approach is performed by the evaluation of metabolic syndrome, the latter by the non-invasive study of pre-ATS markers

    Respiratory syncytial virus: diagnosis, prevention and management.

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    Respiratory syncytial virus (RSV) is responsible for a large burden of disease globally and can present as a variety of clinical syndromes in children of all ages. Bronchiolitis in infants under 1 year of age is the most common clinical presentation hospitalizing 24.2 per 1000 infants each year in the United Kingdom. RSV has been shown to account for 22% of all episodes of acute lower respiratory tract infection in children globally. RSV hospitalization, that is, RSV severe disease, has also been associated with subsequent chronic respiratory morbidity. Routine viral testing in all children is not currently recommended by the United Kingdom National Institute for Health and Care Excellence (NICE) or the American Academy of Pediatrics (AAP) guidance and management is largely supportive. There is some evidence for the use of ribavirin in severely immunocompromised children. Emphasis is placed on prevention of RSV infection through infection control measures both in hospital and in the community, and the use of the RSV-specific monoclonal antibody, palivizumab, for certain high-risk groups of infants. New RSV antivirals and vaccines are currently in development. Ongoing work is needed to improve the prevention of RSV infection, not only because of the acute morbidity and mortality, but also to reduce the associated chronic respiratory morbidity after severe infection

    A new device to seal large coronary aneurysms: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>Coronary artery aneurysm is an uncommon disease. It is defined as a coronary artery dilatation, exceeding the diameter of the normal adjacent segment or the diameter of the patient's largest coronary vessel by 1.5 to 2 times. Coronary artery aneurysms are typically diagnosed by coronary angiography. The prognosis of coronary artery aneurysm is not well known and the management is challenging.</p> <p>Case presentation</p> <p>A 68-year-old Italian-Caucasian man presented to our hospital with angina. Coronary angiography revealed a large coronary aneurysm of the right coronary artery, which was successfully treated by the percutaneous implantation of an MGuard™stent.</p> <p>Conclusion</p> <p>This case report provides evidence that coronary artery aneurysms, even if very large, can be safely treated by MGuard™stent implantation. We strongly emphasize the high flexibility and good deliverability of this device, which leads to the complete exclusion of the aneurysm mediated by the process of endothelization of its thin mesh sleeves.</p

    Inflammatory myoglandular polyp of the cecum: case report and review of literature

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    <p>Abstract</p> <p>Background</p> <p>Inflammatory myoglandular polyp (IMGP) is a rare non-neoplastic polyp of the large bowel, commonly with a distal localization (rectosigmoid), obscure in its pathogenesis. Up till now, 60 cases of IMGP have been described in the literature, but none located in the cecum.</p> <p>Case presentation</p> <p>We report a case of a 53-year-old man who was admitted to our hospital for further evaluation of positive fecal occult blood test associated to anemia. A colonoscopy identified a red, sessile, lobulated polyp of the cecum, 4.2 cm in diameter, partially ulcerated. The histological examination of the biopsy revealed the presence of inflammatory granulation tissue with lymphocytic and eosinophil infiltration associated to a fibrous stroma: it was diagnosed as inflammatory fibroid polyp. Considering the polyp's features (absence of a peduncle and size) that could increase the risk of a polypectomy, a surgical resection was performed. Histological examination of the specimen revealed inflammatory granulation tissue in the lamina propria, hyperplastic glands with cystic dilatations, proliferation of smooth muscle and multiple erosions on the polyp surface: this polyp was finally diagnosed as IMGP. There was also another little polyp next to the ileocecal valve, not revealed at the colonoscopy, 0.8 cm in diameter, diagnosed as tubulovillous adenoma with low grade dysplasia.</p> <p>Conclusions</p> <p>This is the first case of IMGP of the cecum. It is a benign lesion of unknown pathogenesis and must be considered different from other non-neoplastic polyps of the large bowel such as inflammatory cap polyps (ICP), inflammatory cloacogenic polyps, juvenile polyps (JP), inflammatory fibroid polyps (IFP), polyps secondary to mucosal prolapse syndrome (MPS), polypoid prolapsing mucosal folds of diverticular disease. When symptomatic, IMGP should be removed endoscopically, whereas surgical resection is reserved only in selected patients as in our case.</p

    Methodological approach for the assessment of ultrasound reproducibility of cardiac structure and function: a proposal of the study group of Echocardiography of the Italian Society of Cardiology (Ultra Cardia SIC) Part I

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    When applying echo-Doppler imaging for either clinical or research purposes it is very important to select the most adequate modality/technology and choose the most reliable and reproducible measurements. Quality control is a mainstay to reduce variability among institutions and operators and must be obtained by using appropriate procedures for data acquisition, storage and interpretation of echo-Doppler data. This goal can be achieved by employing an echo core laboratory (ECL), with the responsibility for standardizing image acquisition processes (performed at the peripheral echo-labs) and analysis (by monitoring and optimizing the internal intra- and inter-reader variability of measurements). Accordingly, the Working Group of Echocardiography of the Italian Society of Cardiology decided to design standardized procedures for imaging acquisition in peripheral laboratories and reading procedures and to propose a methodological approach to assess the reproducibility of echo-Doppler parameters of cardiac structure and function by using both standard and advanced technologies. A number of cardiologists experienced in cardiac ultrasound was involved to set up an ECL available for future studies involving complex imaging or including echo-Doppler measures as primary or secondary efficacy or safety end-points. The present manuscript describes the methodology of the procedures (imaging acquisition and measurement reading) and provides the documentation of the work done so far to test the reproducibility of the different echo-Doppler modalities (standard and advanced). These procedures can be suggested for utilization also in non referall echocardiographic laboratories as an "inside" quality check, with the aim at optimizing clinical consistency of echo-Doppler data
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