A high efficiency input/output coupler for small silicon photonic devices

Coupling light from an optical fibre to small optical waveguides is particularly problematic in semiconductors, since the refractive index of the silica fibre is very different from that of a semiconductor waveguide. There have been several published methods of achieving such coupling, but none are sufficiently efficient whilst being robust enough for commercial applications. In this paper experimental results of our approach called a Dual-Grating Assisted Directional Coupler, are presented. The principle of coupling by this novel method has been successfully demonstrated, and a coupling efficiency of 55% measured

Energy level statistics of electrons in a 2D quasicrystal

A numerical study is made of the spectra of a tight-binding hamiltonian on square approximants of the quasiperiodic octagonal tiling. Tilings may be pure or random, with different degrees of phason disorder considered. The level statistics for the randomized tilings follow the predictions of random matrix theory, while for the perfect tilings a new type of level statistics is found. In this case, the first-, second- level spacing distributions are well described by lognormal laws with power law tails for large spacing. In addition, level spacing properties being related to properties of the density of states, the latter quantity is studied and the multifractal character of the spectral measure is exhibited.Comment: 9 pages including references and figure captions, 6 figures available upon request, LATEX, report-number els

Geometria e modellazione di un sistema di retro-scorrimenti attivosulla base di dati di geofisica marina ad alta risoluzione:la Dorsale di Amendolara (Golfo di Taranto).

Nuovi dati sismici ad alta (Sparker) ed altissima (Subbottm Chirp) risoluzione, acquisiti durante la Campagna Oceanografica “Teatioca_2010”, integrati da dati sismici multicanale ad alta penetrazione, pubblici disponibili sul sito www.videpi.com, calibrati con pozzi profondi, batimetrici multifascio e carotaggi, rivelano che la dorsale di Amendolara, estensione sottomarina della zona frontale del sistema a thrust dell’Appennino meridionale, è stata controllata nel Quaternario da un sistema di retro-scorrimenti e faglie transpressive (ATFS) che dislocano verso SW la catena mio-pliocenica NE-vergente. Il pacco di sequenze deposizionali attribuito, sulla base della facies sismica e della presenza di discordanze controllate dalle oscillazioni glacio-eustatiche, al Pleistocene medio-superiore risulta piegato in maniera consistente con le strutture desumibili dai profili multicanale. I dati morfometrici e sismici documentano che la dorsale, orientata NW-SE, è formata da 3 banchi lunghi ~10-20 km, cresciuti sopra rampe di sovrascorrimenti ciechi (~2 km) disposti en-echelon a formare un sistema segmentato. Sono stati individuati e modellati i segmenti di Amendolara a NW e Cariati a SE, collegati da una più piccola rampa laterale (segmento di Rossano). La modellazione numerica calibrata sui dati batimetrici e sismici indica che le rampe hanno inclinazione di ~45° e sono radicate a ~10 km di profondità a possibili scollamenti o strutture maggiori. I tassi di scorrimento negli ultimi 4-500 ka, calcolati per i segmenti sulla base degli strati di crescita nei bacini sin tettonici variano da 0.5-0-9 mm/a per il segmento di Amendolara a 0.35-0.5 mm/a per quello di Cariati. L’ATFS coincide con una fascia di moderata sismicità (Mw<4.7) con meccanismi focali inversi o transpressivi. L’orientazione degli assi di strain incrementale (sismico) e finito (geologico, come documentano i dati a terra) suggerisce per i segmenti dell’ATFS un movimento da inverso a obliquo sinistro. In base alla dimensione dei segmenti di faglia, nell’ipotesi di deformazione puramente elastica, si stima una magnitudo potenziale massima per l’ATFS di M~6.1-6.4, ma è verosimile che buona parte della deformazione sia asismica o microsismica. L’epicentro macrosismico del terremoto del 1988 (Mw=4.9) ricade su un tratto del segmento di Cariati che mostra rotture a fondo mare e possibile risalita di fluidi localizzata lungo strutture attive. La crescita dell’ATFS è stata verosimilmente controllata da un interfaccia meccanica tra la spessa crosta apula e la crosta ionica assottigliata o in parte oceanica, quando in tempi recenti la convergenza Adria-Europa ha prevalso sull’arretramento della cerniera della subduzione ionica

An active oblique-contractional belt at the transition between the Southern Apennines and Calabrian Arc: The Amendolara Ridge, Ionian Sea, Italy

High-resolution, single-channel seismic and multibeam bathymetry data collected at the Amendolara Ridge, a key submarine area marking the junction between the Apennine collision belt and the Calabrian subduction forearc, reveal active deformation in a supposedly stable crustal sector. New data, integrated with existing multichannel seismic profiles calibrated with oil-exploratory wells, show that middle to late Pleistocene sediments are deformed in growth folds above blind oblique-reverse faults that bound a regional pop-up. Data analysis indicates that ~10 to 20 km long banks that top the ~80 km long, NW-SE trending ridge are structural culminations above en echelon fault segments. Numeric modeling of bathymetry and stratigraphic markers suggests that three 45\ub0 dipping upper crustal (2\u201310km) fault segments underlie the ridge, with slip rates up to ~0.5mm/yr. Segments may be capable with M~ 6.1\u20136.3 earthquakes, although an unknown fraction of aseismic slip undoubtedly contributes to deformation. The fault array that bounds the southern flank of the ridge (Amendolara Fault System) parallels a belt of Mw<4.7 strike-slip and thrust earthquakes, which suggest current left-oblique reverse motion on the array. The eastern segment of the array shows apparent morphologic evidence of deformation and might be responsible for Mw 64 5.2 historic events. Late Pliocene-Quaternary growth of the oblique contractional belt is related to the combined effects of stalling of Adriatic slab retreat underneath the Apennines and subduction retreat of the Ionian slab underneath Calabria. Deformation localization was controlled by an inherited mechanical interface between the thick Apulian (Adriatic) platform crust and the attenuated Ionian Basin crust

Advanced technologies to target cardiac cell fate plasticity for heart regeneration

The adult human heart can only adapt to heart diseases by starting a myocardial remodeling process to compensate for the loss of functional cardiomyocytes, which ultimately develop into heart failure. In recent decades, the evolution of new strategies to regenerate the injured myocardium based on cellular reprogramming represents a revolutionary new paradigm for cardiac repair by targeting some key signaling molecules governing cardiac cell fate plasticity. While the indirect reprogramming routes require an in vitro engineered 3D tissue to be transplanted in vivo, the direct cardiac reprogramming would allow the administration of reprogramming factors directly in situ, thus holding great potential as in vivo treatment for clinical applications. In this framework, cellular reprogramming in partnership with nanotechnologies and bioengineering will offer new perspectives in the field of cardiovascular research for disease modeling, drug screening, and tissue engineering applications. In this review, we will summarize the recent progress in developing innovative therapeutic strategies based on manipulating cardiac cell fate plasticity in combination with bioengineering and nanotechnology-based approaches for targeting the failing heart

Cost Estimating Cases: Educational Tools for Cost Analysts

The goal of this research effort was to develop educational cases that would bridge the gap between the theory and principles of cost estimating currently taught in the Air Force Institute of Technology (AFIT) Graduate Cost Analysis (GCA) curriculum and the real world of cost estimating in the acquisition arena. To achieve these goals, the following research objectives were investigated (1) Identify cost estimating skills that graduates of the AFIT GCA curriculum are expected to possess. (2) Assess the relative importance of the identified cost estimating skills. (3) Select weapon system scenarios that are relevant, interesting, and facilitate student performance of identified cost estimating skills. (4) Provide cases based on realistic scenarios that will facilitate student learning of important cost estimating skills. The cases developed in this research effort were implemented in the summer quarter 1993 GCA seminar class. Feedback from seminar students and Air Force cost estimating organizations was collected to measure the overall effectiveness of these cases in facilitating student learning. The results show that the cases developed in this effort are effective in developing the AFIT GCA students\u27 abilities to apply cost estimating techniques