215 research outputs found
Non-Abelian Chern-Simons theory from a Hubbard-like model
Here, we provide a simple Hubbard-like model of spin-1/2 fermions that gives rise to the SU(2)-symmetric Thirring model that is equivalent, in the low-energy limit, to the Yang-Mills-Chern-Simons model. First, we identify the regime that simulates the SU(2) Yang-Mills theory. Then, we suitably extend this model so that it gives rise to the SU(2) Chern-Simons theory with level k≥2 that can support non-Abelian anyons. This is achieved by introducing multiple fermionic species and modifying the Thirring interactions, while preserving the SU(2) symmetry. Our proposal provides the means to theoretically and experimentally probe non-Abelian SU(2) level k topological phases
Induced Topological Phases at the Boundary of 3D Topological Superconductors
We present tight-binding models of 3D topological superconductors in class DIII that support a variety of winding numbers. We show that gapless Majorana surface states emerge at their boundary in agreement with the bulk-boundary correspondence. At the presence of a Zeeman field, the surface states become gapped and the boundary behaves as a 2D superconductor in class D. Importantly, the 2D and 3D winding numbers are in agreement, signifying that the topological phase of the boundary is induced by the phase of the 3D bulk. Hence, the boundary of a 3D topological superconductor in class DIII can be used for the robust realization of localized Majorana zero modes
Extended formulations from communication protocols in output-efficient time
Deterministic protocols are well-known tools to obtain extended formulations,
with many applications to polytopes arising in combinatorial optimization.
Although constructive, those tools are not output-efficient, since the time
needed to produce the extended formulation also depends on the number of rows
of the slack matrix (hence, on the exact description in the original space). We
give general sufficient conditions under which those tools can be implemented
as to be output-efficient, showing applications to e.g.~Yannakakis' extended
formulation for the stable set polytope of perfect graphs, for which, to the
best of our knowledge, an efficient construction was previously not known. For
specific classes of polytopes, we give also a direct, efficient construction of
extended formulations arising from protocols. Finally, we deal with extended
formulations coming from unambiguous non-deterministic protocols
Has VZV epidemiology changed in Italy? Results of a seroprevalence study
The aim of the study was to evaluate if and how varicella prevalence has changed in Italy. In particular a seroprevalence study was performed, comparing it to similar surveys conducted in pre-immunization era. During 2013–2014, sera obtained from blood samples taken for diagnostic purposes or routine investigations were collected in collaboration with at least one laboratory/center for each region, following the approval of the Ethics Committee. Data were stratified by sex and age. All samples were processed in a national reference laboratory by an immunoassay with high sensitivity and specificity. Statutory notifications, national hospital discharge database and mortality data related to VZV infection were analyzed as well. A total of 3707 sera were collected and tested. In the studied period both incidence and hospitalization rates decreased and about 5 deaths per year have been registered. The seroprevalence decreased in the first year of life in subjects passively protected by their mother, followed by an increase in the following age classes. The overall antibody prevalence was 84%. The comparison with surveys conducted with the same methodology in 1996–1997 and 2003–2004 showed significant differences in age groups 1–19 y. The study confirms that in Italy VZV infection typically occurs in children. The impact of varicella on Italian population is changing. The comparison between studies performed in different periods shows a significant increase of seropositivity in age class 1–4 years, expression of vaccine interventions already adopted in some regions
Xcd - Modular, Realizable Software Architectures
Connector-Centric Design (Xcd) is centred around a new formal architectural description language, focusing mainly on complex connectors. Inspired by Wright and BIP, Xcd aims to cleanly separate in a modular manner the high-level functional, interaction, and control system behaviours. This can aid in both increasing the understandability of architectural specifications and the reusability of components and connectors themselves. Through the independent specification of control behaviours, Xcd allows designers to experiment more easily with different design decisions early on, without having to modify the functional behaviour specifications (components) or the interaction ones(connectors).
At the same time Xcd attempts to ease the architectural specification by following (and extending) a Design-by-Contract approach, which is more familiar to software developers than process algebras like CSP or languages like BIP that are closer to synchronous/hardware specification languages. Xcd extends Design-by-Contract (i) by separating component contracts into functional and interaction sub-contracts, and (ii) by allowing service consumers to specify their own contractual clauses. Xcd connector specifications are completely decentralized, foregoing Wright’s connector glue, to ensure their realizability by construction
Instances and connectors : issues for a second generation process language
This work is supported by UK EPSRC grants GR/L34433 and GR/L32699Over the past decade a variety of process languages have been defined, used and evaluated. It is now possible to consider second generation languages based on this experience. Rather than develop a second generation wish list this position paper explores two issues: instances and connectors. Instances relate to the relationship between a process model as a description and the, possibly multiple, enacting instances which are created from it. Connectors refers to the issue of concurrency control and achieving a higher level of abstraction in how parts of a model interact. We believe that these issues are key to developing systems which can effectively support business processes, and that they have not received sufficient attention within the process modelling community. Through exploring these issues we also illustrate our approach to designing a second generation process language.Postprin
Small cargo proteins and large aggregates can traverse the Golgi by a common mechanism without leaving the lumen of cisternae
Procollagen (PC)-I aggregates transit through the Golgi complex without leaving the lumen of Golgi cisternae. Based on this evidence, we have proposed that PC-I is transported across the Golgi stacks by the cisternal maturation process. However, most secretory cargoes are small, freely diffusing proteins, thus raising the issue whether they move by a transport mechanism different than that used by PC-I. To address this question we have developed procedures to compare the transport of a small protein, the G protein of the vesicular stomatitis virus (VSVG), with that of the much larger PC-I aggregates in the same cell. Transport was followed using a combination of video and EM, providing high resolution in time and space. Our results reveal that PC-I aggregates and VSVG move synchronously through the Golgi at indistinguishable rapid rates. Additionally, not only PC-I aggregates (as confirmed by ultrarapid cryofixation), but also VSVG, can traverse the stack without leaving the cisternal lumen and without entering Golgi vesicles in functionally relevant amounts. Our findings indicate that a common mechanism independent of anterograde dissociative carriers is responsible for the traffic of small and large secretory cargo across the Golgi stack
Il terremoto del 21 giugno 2013 in Lunigiana. Le attivitĂ del coordinamento Sismiko
Il 21 giugno 2013 alle ore 10.33 UTC è stato registrato dalla Rete Sismica Nazionale (RSN) [Amato e
Mele, 2008; Delladio, 2011] dell’Istituto Nazionale di Geofisica e Vulcanologia (INGV) un terremoto di
magnitudo (ML) 5.2 nel distretto sismico1 denominato “Alpi Apuane” tra i comuni di Minucciano in
provincia di Lucca e Fivizzano e Casola in provincia di Massa e Carrara, zona conosciuta come “Lunigiana”.
L’evento sismico, localizzato dai sismologi in turno presso la sala di sorveglianza sismica di Roma [Basili,
2011] con coordinate 44.153°N e 10.135° E e una profondità di circa 5 km è stato ben risentito in tutta la
penisola centro-settentrionale ed è stato seguito in poche ore da numerosi eventi anche di ML ≥ 3.0 (16 nelle
prime 72 ore). Storicamente l’area oggetto della sequenza sismica è stata interessata da numerosi terremoti di
magnitudo superiore a 5.0 il piĂą grande dei quali quello avvenuto nel 1920 nella zona della Garfagnana
(fonte dati: Catalogo Parametrico dei Terremoti Italiani - CPTI11 [Rovida et al., 2011]), ad una distanza di
circa 12 km dal mainshock odierno, interessata anch’essa da una piccola sequenza sismica a gennaio del
2013.
In considerazione dell’entità dell’evento e seguendo le procedure definite per le situazioni di
emergenza internamente all’INGV anche in accordo con l’Allegato A2 della Convenzione vigente 2012-
20203 fra l’ente e il Dipartimento di Protezione Civile (DPC), è stata attivata la Rete Sismica Mobile della
sede INGV di Roma (Re.Mo. [Moretti et al., 2010]). Nell’arco di tempo di poco più un’ora dall’accadimento
del mainshock è stata disposta l’installazione di una rete sismica temporanea costituita da sei stazioni a
integrazione delle reti sismiche permanenti giĂ presenti in area epicentrale (RSN e Regional Seismic network
of North-Western Italy – RSNI [Ferretti et al., 2008; 2010; Eva et al., 2010; Pasta et al., 2011]).
Nel contempo sono stati consultati tramite e-mail i referenti delle unitĂ di rete sismica mobile delle
altre sedi INGV che nell’ambito del coordinamento “Sismiko” [Moretti et al., 2012] negli ultimi due anni
hanno dato la propria disponibilitĂ , in termini di personale e strumentazione, ad intervenire in caso di
emergenza sismica; sono stati inoltre contattati i colleghi del Dipartimento di Scienze della Terra,
dell’Ambiente e della Vita, dell’Università degli Studi di Genova (DISTAV) i più vicini all’area epicentrale
e gestori della RSNI che hanno comunicato loro stessi l’intenzione di installare due stazioni temporanee, una
in real-time e una in configurazione stand-alone.
In questo lavoro viene descritta l’attività compiuta dalla Rete Sismica Mobile INGV, la tempistica
dell’intervento effettuato in sinergia con i colleghi dell’Università di Genova, i dettagli circa l'installazione e
la gestione delle stazioni sismiche temporanee nel primo mese di attivitĂ e una valutazione del dataset
acquisito
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