Amorphous silicon/langmuir-blodgett film mis devices

Hetal-inaulator-ieniconductor (MIS) structure based on glow discharge produced, hydrogenated amorphous silicon (a-Si:H), and incorporating Langmuir-Blodgett (LB) film inaulating layers, have been investigated. Two distinct types of MIS diode have been considered : tunnelling diodes (insulator thickness 10 nm). A preliminary study of insulated-gate field-effect-tranaistors (igfet's) has also been undertaken. Simple Schottky barrier (MS) structures, which are effectively a first step towards tunnelling MIS devices, have been made and characterised : results showed that these were 'state-of-the-art' devices. A preparation procedure has been developed which facilitates the successful deposition of LB film materials onto a-Si:H. Tunnelling MIS diodes containing diacetylene polymer LB insulating films have been fabricated, and capacitance measurements showed that the films were of reasonable quality. The current-voltage characteristics of these diodes were rather non-ideal and, it is thought, were dominated by the effects of two distinct levels of surface states. The appearance of peaks in the illuminated conductance-voltage curves supports this interpretation. Solar cells with an HIS structure can show an enhanced efficiency compared with MS (Schottky) cells. By using varying numbers of LB monolayers, the effects of increasing insulator thickness on a-Si:H solar cell parameters have been ascertained. Though the results closely parallel those of other researchers, the presence of a surface 'oxide' layer of ~ 4 nm thickness (as a result of the pre-LB film deposition etch) prevented optimisation of the cell efficiency. Further work is necessary in order to capitalise on the effect which has been demonstrated e.g. the development of a more suitable etch treatment, the use of different LB film materials.Non-tunnelling MIS diodes were made using cadmium stearate/stearic acid LB films. The capacitance-voltage curves were very similar to those which have been reported for conventional MIS devices on single crystal semiconductors. The LB films, although of slightly poorer structural quality than is possible on single crystal substrates, were nonetheless reproducible. An unusual In J v V(^½) current-voltage dependence was found, which, it is suggested, was due to image-force effects. Large hysteresis was observed in the device characteristics due to polarisation or ionic motion. The characteristics were also influenced by the presence, in the upper half of the a-Si:H mobility gap, of a band of surface or bulk states. These simple structures could possibly be used as gas detectors, since the penetration of a gas into the LB film may well result in measureable changes in the device parameters. For the first time, an igfet based upon the a-Si:H/LB film system has been produced. The device showed a change in source-drain current of almost three orders of magnitude for a gate voltage change of lOV. This compares well with the early results of other workers using more conventional insulators. It is thought that the device performance was limited by the poor semiconducting properties of the surface region of the a-Si:H, and that an alternative FET configuration would lead to improvements. Possible applications include the switching of large area liquid crystal displays (using FET arrays) or, more tentatively, the exploitation of the 'molecular tailoring' qualities of LB films to produce specific biological and chemical FET sensors

Mucociliary clearance in COPD can be increased by both a D2/β2 and a standard β2 agonists

SummaryIn addition to breathlessness and cough, excessive mucus production is one of the main symptoms of chronic obstructive pulmonary disease (COPD). Excess mucus coupled with deteriorating mucociliary clearance is associated with a decline in lung function and an increased risk of death from pulmonary infection. The effect of ViozanTM (Sibenadet HCI, AR-C68397AA), a novel dual D2 dopamine receptor, β2-adrenoceptor agonist, on mucociliary clearance was investigated together with that of a β2-adrenoceptor agonist, salbutamol. Using a double blind, parallel group study design, 15 patients with COPD, all habitual smokers, were randomised to receive nebulised sidenadet (3mg tid; n=7) or salbutamol (5mg tid; n=8) for 10 days. Lung mucociliary clearance rates were measured, by a standard radioaerosol technique, before and after the treatment period, as were 24-h sputum volumes. Both sibenadet and salbutamol therapies resulted in significant (P<0.02) enhancement of lung mucociliary clearance. The 24-h sputum volume was significantly reduced following sibenadet therapy (P<0.03) whereas salbutamol therapy had no effect. Our results, in addition to illustrating the effects of a standard β2 agonist on mucociliary clearance, strongly suggest the potential dual benefit of dual-agonist compounds in lessening sputum production whilst simultaneously enhancing mucociliary clearance. For reasons unconnected with the present study, development work on this specific formulation is no longer proceeding

A Discrete Four Stroke Quantum Heat Engine Exploring the Origin of Friction

The optimal power performance of a first principle quantum heat engine model shows friction-like phenomena when the internal fluid Hamiltonian does not commute with the external control field. The model is based on interacting two-level-systems where the external magnetic field serves as a control variable.Comment: 4 pages 3 figure

Tendency to Maximum Complexity in a Non-Equilibrium Isolated System

The time evolution equations of a simplified isolated ideal gas, the "tetrahe- dral" gas, are derived. The dynamical behavior of the LMC complexity [R. Lopez-Ruiz, H. L. Mancini, and X. Calbet, Phys. Lett. A 209, 321 (1995)] is studied in this system. In general, it is shown that the complexity remains within the bounds of minimum and maximum complexity. We find that there are certain restrictions when the isolated "tetrahedral" gas evolves towards equilibrium. In addition to the well-known increase in entropy, the quantity called disequilibrium decreases monotonically with time. Furthermore, the trajectories of the system in phase space approach the maximum complexity.Comment: 22 pages, 0 figures. Published in Phys. Rev. E 63, 066116(9) (2001

Hamiltonian light-front field theory within an AdS/QCD basis

Non-perturbative Hamiltonian light-front quantum field theory presents opportunities and challenges that bridge particle physics and nuclear physics. Fundamental theories, such as Quantum Chromodynmamics (QCD) and Quantum Electrodynamics (QED) offer the promise of great predictive power spanning phenomena on all scales from the microscopic to cosmic scales, but new tools that do not rely exclusively on perturbation theory are required to make connection from one scale to the next. We outline recent theoretical and computational progress to build these bridges and provide illustrative results for nuclear structure and quantum field theory. As our framework we choose light-front gauge and a basis function representation with two-dimensional harmonic oscillator basis for transverse modes that corresponds with eigensolutions of the soft-wall AdS/QCD model obtained from light-front holography.Comment: To appear in the proceedings of Light-Cone 2009: Relativistic Hadronic and Particle Physics, July 8-13, 2009, Sao Jose dos Campos, Brazi

Mapping crustal shear wave velocity structure and radial anisotropy beneath West Antarctica using seismic ambient noise

Using 8‐25s period Rayleigh and Love wave phase velocity dispersion data extracted from seismic ambient noise, we (i) model the 3D shear wave velocity structure of the West Antarctic crust and (ii) map variations in crustal radial anisotropy. Enhanced regional resolution is offered by the UK Antarctic Seismic Network. In the West Antarctic Rift System (WARS), a ridge of crust ~26‐30km thick extending south from Marie Byrd Land separates domains of more extended crust (~22km thick) in the Ross and Amundsen Sea Embayments, suggesting along‐strike variability in the Cenozoic evolution of the WARS. The southern margin of the WARS is defined along the southern Transantarctic Mountains (TAM) and Haag Nunataks‐Ellsworth Whitmore Mountains (HEW) block by a sharp crustal thickness gradient. Crust ~35‐40km is modelled beneath the Haag Nunataks‐Ellsworth Mountains, decreasing to ~30‐32km km thick beneath the Whitmore Mountains, reflecting distinct structural domains within the composite HEW block. Our analysis suggests that the lower crust and potentially the mid crust is positively radially anisotropic (VSH > VSV) across West Antarctica. The strongest anisotropic signature is observed in the HEW block, emphasising its unique provenance amongst West Antarctica's crustal units, and conceivably reflects a ~13km thick metasedimentary succession atop Precambrian metamorphic basement. Positive radial anisotropy in the WARS crust is consistent with observations in extensional settings, and likely reflects the lattice‐preferred orientation of minerals such as mica and amphibole by extensional deformation. Our observations support a contention that anisotropy may be ubiquitous in continental crust

Longitudinal Results With Intratympanic Dexamethasone in the Treatment of Ménière’s Disease

To assess patient satisfaction with vertigo control using intratympanic (IT) dexamethasone (12 mg/mL) for medically refractory unilateral Meniere's disease. STUDY DESIGN: Retrospective study. SETTING: Tertiary referral neurotology clinic. PATIENTS: One hundred twenty-nine subjects diagnosed with unilateral Meniere's disease still having vertigo despite medical therapy. INTERVENTION: IT dexamethasone injections as needed to control vertigo attacks. MAIN OUTCOME MEASURE: A Kaplan-Meier time-to-event method was used to determine the rate of "survival," meaning sufficient satisfaction with vertigo control that the subject did not wish to have subsequent ablative treatment. "Failure" was defined as poor control and the choice to proceed to ablative treatment. RESULTS: Acceptable vertigo control ("survival") was achieved in 117 (91%) of 129 subjects. Vertigo control required only one dexamethasone injection in 48 (37%), 2 injections in 26 (20%), 3 injections in 18 (14%), and 4 injections in 10 (8%). More than 4 injections were needed in 15 subjects (21%). Of 12 failures (9%), 9 occurred within 6 months of the first IT dexamethasone injection. Follow-up data for 2 years were available for 96 subjects. Of these, 87 (91%) had vertigo control with IT dexamethasone, of whom 61 (70)% required no further injections after 2 years, 23 (26%) continued to receive IT dexamethasone injections, and 3 (3%) chose IT gentamicin treatment. CONCLUSION: IT dexamethasone injection therapy on an as-needed outpatient basis can provide vertigo control that is satisfactory in patients with Meniere's disease. The Kaplan-Meier method addresses the need for an outcome measure suited to repeated treatments and variable lengths of follow-up. However, due to the retrospective nature of this study, the presence of bias caused by loss of subjects from follow-up cannot be ruled out

Non-leftmost Unfolding in Partial Evaluation of Logic Programs with Impure Predicates

Abstract. Partial evaluation of logic programs which contain impure predicates poses non-trivial challenges. Impure predicates include those which produce side-effects, raise errors (or exceptions), and those whose truth value varies according to the degree of instantiation of arguments 4. In particular, non-leftmost unfolding steps can produce incorrect results since the independence of the computation rule no longer holds in the presence of impure predicates. Existing proposals allow non-leftmost unfolding steps, but at the cost of accuracy: bindings and failure are not propagated backwards to predicates which are potentially impure. In this work we propose a partial evaluation scheme which substantially reduces the situations in which such backpropagation has to be avoided. With this aim, our partial evaluator takes into account the information about purity of predicates expressed in terms of assertions. This allows achieving some optimizations which are not feasible using existing partial evaluation techniques. We argue that our proposal goes beyond existing ones in that it is a) accurate, since the classification of pure vs impure is done at the level of atoms instead of predicates, b) extensible, as the information about purity can be added to programs using assertions without having to modify the partial evaluator itself, and c) automatic, since (backwards) analysis can be used to automatically infer the required assertions. Our approach has been implemented in the context of CiaoPP, the abstract interpretation-based preprocessor of the Ciao logic programming system.

Entanglement Dynamics in 1D Quantum Cellular Automata

Several proposed schemes for the physical realization of a quantum computer consist of qubits arranged in a cellular array. In the quantum circuit model of quantum computation, an often complex series of two-qubit gate operations is required between arbitrarily distant pairs of lattice qubits. An alternative model of quantum computation based on quantum cellular automata (QCA) requires only homogeneous local interactions that can be implemented in parallel. This would be a huge simplification in an actual experiment. We find some minimal physical requirements for the construction of unitary QCA in a 1 dimensional Ising spin chain and demonstrate optimal pulse sequences for information transport and entanglement distribution. We also introduce the theory of non-unitary QCA and show by example that non-unitary rules can generate environment assisted entanglement.Comment: 12 pages, 8 figures, submitted to Physical Review