Valence band offset of InN/AlN heterojunctions measured by X-ray photoelectron spectroscopy

The valence band offset of wurtzite-InN/AlN (0001) heterojunctions is determined by x-ray photoelectron spectroscopy to be 1.52±0.17 eV. Together with the resulting conduction band offset of 4.0±0.2 eV, a type-I heterojunction forms between InN and AlN in the straddling arrangement

Universality of electron accumulation at wurtzite c- and a-plane and zinc-blende InN surfaces

Electron accumulation is found to occur at the surface of wurtzite (112¯0), (0001), and (0001¯) and zinc-blende (001) InN using x-ray photoemission spectroscopy. The accumulation is shown to be a universal feature of InN surfaces. This is due to the low Г-point conduction band minimum lying significantly below the charge neutrality level

Radiography of a normal fault system by 64,000 high-precision earthquake locations: The 2009 L'Aquila (central Italy) case study

We studied the anatomy of the fault system where the 2009 L'Aquila earthquake (M_W 6.1) nucleated by means of ~64 k high-precision earthquake locations spanning 1 year. Data were analyzed by combining an automatic picking procedure for P and S waves, together with cross-correlation and double-difference location methods reaching a completeness magnitude for the catalogue equal to 0.7 including 425 clusters of similar earthquakes. The fault system is composed by two major faults: the high-angle L'Aquila fault and the listric Campotosto fault, both located in the first 10 km of the upper crust. We detect an extraordinary degree of detail in the anatomy of the single fault segments resembling the degree of complexity observed by field geologists on fault outcrops. We observe multiple antithetic and synthetic fault segments tens of meters long in both the hanging wall and footwall along with bends and cross fault intersections along the main fault and fault splays. The width of the L'Aquila fault zone varies along strike from 0.3 km where the fault exhibits the simplest geometry and experienced peaks in the slip distribution, up to 1.5 km at the fault tips with an increase in the geometrical complexity. These characteristics, similar to damage zone properties of natural faults, underline the key role of aftershocks in fault growth and co-seismic rupture propagation processes. Additionally, we interpret the persistent nucleation of similar events at the seismicity cutoff depth as the presence of a rheological (i.e., creeping) discontinuity explaining how normal faults detach at depth

Transition from electron accumulation to depletion at InGaN surfaces

The composition dependence of the Fermi-level pinning at the oxidized (0001) surfaces of n-type InxGa1−xN films (0<=x<=1) is investigated using x-ray photoemission spectroscopy. The surface Fermi-level position varies from high above the conduction band minimum (CBM) at InN surfaces to significantly below the CBM at GaN surfaces, with the transition from electron accumulation to depletion occurring at approximately x=0.3. The results are consistent with the composition dependence of the band edges with respect to the charge neutrality level

Structure of adsorbed Fe on Ni{111}

Using photoelectron diffraction in the scanned energy mode we have established that Fe atoms adsorb in the fcc hollow sites of the Ni{111} surface even at low temperatures. Total-energy calculations had suggested that the hcp hollow sites were more stable

Software that goes with the flow in systems biology

A recent article in BMC Bioinformatics describes new advances in workflow systems for computational modeling in systems biology. Such systems can accelerate, and improve the consistency of, modeling through automation not only at the simulation and results-production stages, but also at the model-generation stage. Their work is a harbinger of the next generation of more powerful software for systems biologists

Engineered swift equilibration of a Brownian particle

A fundamental and intrinsic property of any device or natural system is its relaxation time relax, which is the time it takes to return to equilibrium after the sudden change of a control parameter [1]. Reducing $tau$ relax , is frequently necessary, and is often obtained by a complex feedback process. To overcome the limitations of such an approach, alternative methods based on driving have been recently demonstrated [2, 3], for isolated quantum and classical systems [4--9]. Their extension to open systems in contact with a thermostat is a stumbling block for applications. Here, we design a protocol,named Engineered Swift Equilibration (ESE), that shortcuts time-consuming relaxations, and we apply it to a Brownian particle trapped in an optical potential whose properties can be controlled in time. We implement the process experimentally, showing that it allows the system to reach equilibrium times faster than the natural equilibration rate. We also estimate the increase of the dissipated energy needed to get such a time reduction. The method paves the way for applications in micro and nano devices, where the reduction of operation time represents as substantial a challenge as miniaturization [10]. The concepts of equilibrium and of transformations from an equilibrium state to another, are cornerstones of thermodynamics. A textbook illustration is provided by the expansion of a gas, starting at equilibrium and expanding to reach a new equilibrium in a larger vessel. This operation can be performed either very slowly by a piston, without dissipating energy into the environment, or alternatively quickly, letting the piston freely move to reach the new volume

Importance of implant technique on risk of major paravalvular leak (PVL) after St. Jude mechanical heart valve replacement: a report from the Artificial Valve Endocarditis Reduction Trial (AVERT)

Objective: To examine risk factors for major paravalvular leak (PVL) events after mechanical heart valve replacement. Methods: We analyzed outcome of 807 patients randomized into the Artificial Valve Endocarditis Reduction Trial (AVERT). The mean follow-up time was 30.6 months and 21 major PVL events were reported. Three additional major PVL events associated with endocarditis were excluded from analysis. All baseline medical history variables, as well as operative parameters (including use of pledgets and suture technique) were examined using Cox regression. Results: Major PVL was reported after 11 aortic, 9 mitral, and 1 double valve replacement. 6/404 (1.5%) patients with conventional valves experienced a major PVL event versus 15/403 (3.7%) in the Silzone group. 10/172 (5.8%) patients with valve suture technique without pledgets experienced a major PVL event versus 11/635 (1.7%) patients with pledgets. Final multivariable model showed that only suture technique without pledgets (p = 0.005) was an independent significant risk factor for major PVL events. Silzone cuff showed a strong trend (p = 0.055). Conclusions: Suture technique without pledgets is an independent significant risk factor for major PVL events. In this study, use of pledgets during valve replacement had a protective effect against subsequent paravalvular leak, supporting the use of buttress reinforcement for valve suture. The use of Silzone cuff, although not statistically significant, showed a strong trend as a risk facto

Adsorption site and orientation of pyridine on Cu{110} determined by photoelectron diffraction

The local adsorption geometry of pyridine on Cu{110} has been determined quantitatively using photoelectron diffraction in the scanned-energy mode. At high coverages the molecule adsorbs nearly atop a Cu atom in the close-packed rows with a N–Cu bond length of 2.00 Å. Moreover, the Cu–N axis and the molecular (C2) axis are inclined by 8° and 20°, respectively, to the surface normal. The result shows that not only the adsorption site of the emitter (in this case the N atom) but also the position of relatively light scatterers (the C atoms) can be determined by photoelectron diffraction

Local adsorption geometry of acetylene on Si(100)(2×1)

Using C 1s scanned-energy-mode photoelectron diffraction the local adsorption geometry of acetylene on the Si(100)(2x1) surface has been determined and the results are compared with those of a similar study of ethylene adsorption on this surface. Both molecules bond to the surface along the Si-Si dimers with the C-C bonds parallel to the surface such that the C atoms are in off-atop sites relative to the Si dimer atoms. In both cases the Si-Si bond length (2.36±0.21 Å for ethylene and 2.44±0.58 Å for acetylene) is compatible only with the dimer remaining intact after adsorption and not with the Si-Si distance of an ideally terminated undimerized Si(100) surface (3.84 Å)