Twenty-four near-instabilities of Caspar-Klug viruses

Group theoretical arguments combined with normal mode analysis techniques are applied to a coarse-grained approximation of icosahedral viral capsids which incorporates areas of variable flexibility. This highlights a remarkable structure of the low-frequency spectrum in this approximation, namely, the existence of a plateau of 24 near zero modes with universal group theory content

Superconformal Algebras and Mock Theta Functions

It is known that characters of BPS representations of extended superconformal algebras do not have good modular properties due to extra singular vectors coming from the BPS condition. In order to improve their modular properties we apply the method of Zwegers which has recently been developed to analyze modular properties of mock theta functions. We consider the case of N=4 superconformal algebra at general levels and obtain the decomposition of characters of BPS representations into a sum of simple Jacobi forms and an infinite series of non-BPS representations. We apply our method to study elliptic genera of hyper-Kahler manifolds in higher dimensions. In particular we determine the elliptic genera in the case of complex 4 dimensions of the Hilbert scheme of points on K3 surfaces K^{[2]} and complex tori A^{[[3]]}.Comment: 28 page

Alcuni esempi di catalogazione e restauro nell’ambito della Collezione Storica degli Strumenti di Fisica dell’Università di Palermo

In questo articolo presenteremo e discuteremo della catalogazione e restauro e di alcuni strumenti scientifici di particolare interesse storico-didattico appartenenti alla Collezione Storica degli Strumenti di Fisica dell’Università di Palermo. La catalogazione è stata effettuata secondo le indicazioni fornite dell’Istituto Centrale per il Catalogo e la Documentazione, per mezzo della scheda per il patrimonio scientifico-tecnologico. Nell’articolo saranno discussi gli aspetti tecnici degli interventi di restauro effettuati e saranno indicate le linee guida generali per il proseguimento dell’attività avviata.The article deals with the cataloguing and restoration of some scientific instruments of particular historical and didactic interest belonging to the Historical Collection of the Physics Instruments of the University of Palermo. The restoration activities have been carried out side by side the cataloguing, which has been done following the instructions supplied by the Central Institute for Cataloguing and Documentation with the official form for the scientific and technological heritage. In the article, we will discuss the technical aspects of the work carried out and basic guidelines will be given for the continuation of the activity

First Evidence of Tris(catecholato)silicate Formation from Hydrolysis of an Alkyl Bis(catecholato)silicate

The hydrolysis of 3-ammoniumpropylbis(catecholato)silicate 1, giving two different silica-based materials containing different amounts of tris(catecholato)silicate, is reported. The latter species can be formed through an attack of catechol to the silicon atom in the pentacoordinate complex, in which the silicon-carbon bond is further activated toward electrophilic proton cleavage. The Knoevenagel reaction was used as a probe in order to test the availability of functional groups on the surface of such materials

Longevity: Lesson from model organisms

Research on longevity and healthy aging promises to increase our lifespan and decrease the burden of degenerative diseases with important social and economic effects. Many aging theories have been proposed, and important aging pathways have been discovered. Model organisms have had a crucial role in this process because of their short lifespan, cheap maintenance, and manipulation possibilities. Yeasts, worms, fruit flies, or mammalian models such as mice, monkeys, and recently, dogs, have helped shed light on aging processes. Genes and molecular mechanisms that were found to be critical in simple eukaryotic cells and species have been confirmed in humans mainly by the functional analysis of mammalian orthologues. Here, we review conserved aging mechanisms discovered in different model systems that are implicated in human longevity as well and that could be the target of anti-aging interventions in human

Prevalence of sexually transmitted infections and enteric protozoa among homosexual men in western Sicily (south Italy)

Introduction. In recent years an increase in the number of sexu- ally transmitted infections (STIs) in men who have sex with men (MSM) has been reported in different industrialised countries. Because few epidemiological data on the STIs/MSM population in Sicily are available, a survey was conducted to assess the preva- lence of STIs/enteric protozoa and risky sexual behaviours among MSM in western Sicily. Methods. In 2010, 74 MSM with median age of 30 years old, were recruited via networks. All participants to the study were interviewed by anonymous self-administered questionnaire in order to collect social/demographic information, clinic data and STI-related risky sexual behaviours. After completing the ques- tionnaire, blood samples were collected to determine HIV, HCV, HHV8 and Treponema pallidum antibodies; presence of Giardia duodenalis and Cryptosporidium parvum was also investigated in faecal samples by immunofluorescence assay. Results. HIV, HHV8, T. pallidum and Giardia prevalence were 8.1%, 16.2%, 21.6% and 16.4% respectively; all patients were negative for HCV and Cryptosporidium infections. The median values of sexual anal intercourse and oral sex per week were 2 and 1, respectively. 7% of participants always had unprotected anal sex, 50.7% sometimes used condom during sexual anal inter- course and 42.3% always had protected anal sex. All MSM-HIV+ and 7 (43.7%) syphilis seropositives were unaware of their own infection. Discussion. MSM in western Sicily are a high risk group for important STIs. It seems necessary that continuous interventions for preventing HIV/AIDS and other STIs and for improving the level of knowledge of symptoms are needed

Window-Based Energy Selecting X-ray Imaging and Charge Sharing in Cadmium Zinc Telluride Linear Array Detectors for Contaminant Detection

The spectroscopic and imaging performance of energy-resolved photon counting detectors, based on new sub-millimetre boron oxide encapsulated vertical Bridgman cadmium zinc telluride linear arrays, are presented in this work. The activities are in the framework of the AVATAR X project, planning the development of X-ray scanners for contaminant detection in food industry. The detectors, characterized by high spatial (250 µm) and energy (<3 keV) resolution, allow spectral X-ray imaging with interesting image quality improvements. The effects of charge sharing and energy-resolved techniques on contrast-to-noise ratio (CNR) enhancements are investigated. The benefits of a new energy-resolved X-ray imaging approach, termed window-based energy selecting, in the detection of low- and high-density contaminants are also shown