Grid services for the MAGIC experiment

Exploring signals from the outer space has become an observational science under fast expansion. On the basis of its advanced technology the MAGIC telescope is the natural building block for the first large scale ground based high energy gamma-ray observatory. The low energy threshold for gamma-rays together with different background sources leads to a considerable amount of data. The analysis will be done in different institutes spread over Europe. Therefore MAGIC offers the opportunity to use the Grid technology to setup a distributed computational and data intensive analysis system with the nowadays available technology. Benefits of Grid computing for the MAGIC telescope are presented.Comment: 5 pages, 1 figures, to be published in the Proceedings of the 6th International Symposium ''Frontiers of Fundamental and Computational Physics'' (FFP6), Udine (Italy), Sep. 26-29, 200

Asymptotic stability of the Cauchy and Jensen functional equations

The aim of this note is to investigate the asymptotic stability behaviour of the Cauchy and Jensen functional equations. Our main results show that if these equations hold for large arguments with small error, then they are also valid everywhere with a new error term which is a constant multiple of the original error term. As consequences, we also obtain results of hyperstability character for these two functional equations

L’ambiente carsico e l’idrogeologia dei gessi di Sassalbo (MS)

Nel Canale dell’Acqua Torbida (Alta Lunigiana), si trova il maggiore affioramento di evaporiti triassiche della Toscana. Rispetto ai gessi dell’Alta val Secchia (RE), di cui sono il lembo meridionale, appaiono molto meno tettonizzati. L’area carsica, che comprende in prevalenza calcari cavernosi, ha una superficie complessiva di circa 2,2 km2 in cui sono ben rappresentate forme carsiche superficiali, sia macro che micro. Anche i fenomeni carsici sotterranei sembrano essere ben sviluppati: la loro genesi è stata attribuita a periodi di avanzata e arretramento dei ghiacciai durante l’ultimo glaciale. Attualmente nel catasto toscano sono registrate 5 cavità, di cui 4 rilevate. Nell’ambito del Progetto Trias II (studio interdisciplinare svolto dalla Società Speleologica Italiana per conto del Parco Nazionale dell’Appennino Tosco-Emiliano) è stato possibile studiare l’area dal punto di vista morfologico, speleologico e idrochimico, monitorando in continuo alcune delle principali risorgenti carsiche parallelamente ai torrenti cui esse potevano risultare connesse. Nel presente lavoro, dopo breve illustrazione delle morfologie epigee ed ipogee, vengono presentati i risultati del monitoraggio idrologico. Le analisi hanno permesso di evidenziare come in molti casi le acque del carso di Sassalbo siano chimicamente molto simili a quelle del sistema ad ansa ipogea del Tanone della Gacciolina in Alta val di Secchia. Fanno eccezione altre sorgenti, alimentate quasi esclusivamente dalla serie marnoso arenacea e dal macigno, che presentano comportamenti idrodinamici differenti in funzione dei loro specifici bacini di alimentazione.Karst and hydrology of the Sassalbo Gypsa (Massa Carrara – Italy) The largest triassic evaporitic outcrop of Tuscany is located inside the Acqua Torbida creek (Upper Lunigiana). They represent the southernmost and less tectonized part of the Upper Secchia Gypsa (RE). The karst area (some 2,2) consists mostly of limestone (Calcari Cavernosi) with well developed macro – and micro – forms. The underground phenomena are mainly related to the mouventes of glacial tongues during the last Glacial. 5 cavities are presently known and inserted in the Tuscany Cadaster, 4 of which mapped. In the framework of the Trias II Project (an interdisciplinary study sponsored by the Appennino Tosco-Emiliano National Park and performed by the Italian Speleological Society) this area has been investigated from the morphological, speleological, hydrochemical point of view while some of the major springs and related rivers were monitored. In the paper after a short description of the epigean and hypogean forms, the achieved result during the hydrological study are presented. This study evidenced that in many occurrences the behavior of the Sassalbo karst waters is very similar to that of the Tanone della Gacciolina cave in the Upper Secchia Valley. Only a few springs exhibit a different behavior being rather completely fed by the marnoso-arenacea and macigno formations

Suspended SU-8 structures for monolithic microfluidic channels

SU-8 photoresist is commonly used in the field of microfabrication as structural material or for molding of microfluidic devices. One major limitation, however, is the difficulty to process partially freestanding SU-8 structures or monolithic closed cavities and channels on-chip. We propose here a simple method for the fabrication of suspended structures, in particular of monolithic SU-8 microchannels. The method is based on the processing of a SU-8 double-layer. Appropriate modification of the optical properties of the upper layer allows for selective crosslinking in the layer sandwich. This process is suitable for versatile layouts comprising open and hollow SU-8 structures on the same chi

Intercalation of graphene on SiC(0001) via ion-implantation

Electronic devices based on graphene technology are catching on rapidly and the ability to engineer graphene properties at the nanoscale is becoming, more than ever, indispensable. Here, we present a new procedure of graphene functionalization on SiC(0001) that paves the way towards the fabrication of complex graphene electronic chips. The procedure resides on the well-known ion-implantation technique. The efficiency of the working principle is demonstrated by the intercalation of the epitaxial graphene layer on SiC(0001) with Bi atoms, which was not possible following standard procedures. Our results put forward the ion-beam lithography to nanostructure and functionalize desired graphene chips

Direct evidence for efficient ultrafast charge separation in epitaxial WS2_2/graphene heterostructure

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS$_2$ and graphene. This heterostructure combines the benefits of a direct gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS$_2$, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS$_2$ layer. The resulting charge transfer state is found to have a lifetime of $\sim1$\,ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS$_2$ and graphene bands as revealed by high resolution ARPES. In combination with spin-selective excitation using circularly polarized light the investigated WS$_2$/graphene heterostructure might provide a new platform for efficient optical spin injection into graphene.Comment: 28 pages, 14 figure

Direct evidence for efficient ultrafast charge separation in epitaxial WS₂/graphene heterostructures

We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS2 and graphene. This heterostructure combines the benefits of a direct-gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS2, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS2 layer. The resulting charge-separated transient state is found to have a lifetime of ∼1 ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS2 and graphene bands as revealed by high-resolution ARPES. In combination with spin-selective optical excitation, the investigated WS2/graphene heterostructure might provide a platform for efficient optical spin injection into graphene

Approximate Homomorphisms of Ternary Semigroups

A mapping $f:(G_1,[ ]_1)\to (G_2,[ ]_2)$ between ternary semigroups will be called a ternary homomorphism if $f([xyz]_1)=[f(x)f(y)f(z)]_2$. In this paper, we prove the generalized Hyers--Ulam--Rassias stability of mappings of commutative semigroups into Banach spaces. In addition, we establish the superstability of ternary homomorphisms into Banach algebras endowed with multiplicative norms.Comment: 10 page