Compositional changes on GaN surfaces under low-energy ion bombardment studied by synchrotron-based spectroscopies

We have investigated compositional changes on GaNsurfaces under Ar-ion bombardment using synchrotron-based high-resolution x-rayphotoemission (PES) and near-edge x-ray absorption fine structure(NEXAFS)spectroscopy. The low-energy ion bombardment of GaN produces a Ga-rich surface layer which transforms into a metallic Ga layer at higher bombarding energies. At the same time, the photoemissionspectra around N 1s core levels reveal the presence of both uncoordinated nitrogen and nitrogen interstitials, which we have analyzed in more details by x-rayabsorption measurements at N K edge. We have demonstrated that PES and NEXAFS provide a powerful combination for studying the compositional changes on GaNsurfaces. A mechanism for the relocation and loss of nitrogen during ion bombardment in agreement with some recent experimental and theoretical studies of defect formation in GaN has been proposed.P.N.K.D. is grateful for the financial support of the Australian Research Council

Explaining Snapshots of Network Diffusions: Structural and Hardness Results

Much research has been done on studying the diffusion of ideas or technologies on social networks including the \textit{Influence Maximization} problem and many of its variations. Here, we investigate a type of inverse problem. Given a snapshot of the diffusion process, we seek to understand if the snapshot is feasible for a given dynamic, i.e., whether there is a limited number of nodes whose initial adoption can result in the snapshot in finite time. While similar questions have been considered for epidemic dynamics, here, we consider this problem for variations of the deterministic Linear Threshold Model, which is more appropriate for modeling strategic agents. Specifically, we consider both sequential and simultaneous dynamics when deactivations are allowed and when they are not. Even though we show hardness results for all variations we consider, we show that the case of sequential dynamics with deactivations allowed is significantly harder than all others. In contrast, sequential dynamics make the problem trivial on cliques even though it's complexity for simultaneous dynamics is unknown. We complement our hardness results with structural insights that can help better understand diffusions of social networks under various dynamics.Comment: 14 pages, 3 figure

Rubber friction on (apparently) smooth lubricated surfaces

We study rubber sliding friction on hard lubricated surfaces. We show that even if the hard surface appears smooth to the naked eye, it may exhibit short wavelength roughness, which may give the dominant contribution to rubber friction. That is, the observed sliding friction is mainly due to the viscoelastic deformations of the rubber by the substrate surface asperities. The presented results are of great importance for rubber sealing and other rubber applications involving (apparently) smooth surfaces.Comment: 7 pages, 15 figure

PI-tuned UPFC damping controllers design for multi-machine power system

This paper presents an adaptive multi-objective algorithm based Unified Power Flow Controller (UPFC) tuned for damping oscillations in two-area multi-machine system formulated as multi- objective optimization problem. The algorithms such as, Non-dominated Sorting Genetic Algorithm-II (NSGA-II) and Modified Non-dominated Sorting Genetic Algorithm-II (MNSGA-II) are proposed for tuning the damping controller with speed deviation and control input as conflicting objectives. The proposed algorithm is implemented in the two area multi-machine system using MATLAB Simulink model, and the simulation results were obtained with respect to the characteristics of damping oscillations and the dynamic stability of power systems. The performance measures such as Integral Time Squared Error (ITSE) and Integral Squared Error (ISE) are considered as the objective functions. The results of the two proposed algorithm has been compared and the outcome shows that the MNSGA-II algorithm performs better compared to the NSGA-II algorithm

P Wave Meson Spectrum in a Relativistic Model with Instanton Induced Interaction

On the basis of the phenomenological relativistic harmonic models for quarks we have obtained the masses of P wave mesons. The full Hamiltonian used in the investigation has Lorentz scalar + vector confinement potential, along with one gluon exchange potential (OGEP) and the instanton-induced quark-antiquark interaction (III). A good agreement is obtained with the experimental masses. The respective role of III and OGEP for the determination of the meson masses is discussed.Comment: Corrected typo

Evaluation of granisetron as an antiemetic in patients undergoing abdominal hysterectomy under spinal anaesthesia

Background: PONV most common complications related to surgery and anaesthesia despite major advances in spinal, epidural and combined spinal-epidural anesthesia techniques IONV are still present in a significant number of patients. Ondansetron, used for controlling PONV induced by chemotherapy or radiation. Recently 5HT3 receptor antagonist granisetron has more potent, selective and longer acting activity than ondansetron. Granisetron is more active for control of PONV in cisplatin induced vomiting than ondansetron. It also reduces PONV in strabismus repair, tonsillectomy, and general surgeries, it has less side effects as compared to ondansetron. Objective of the study was to study efficacy and safety of granisetron and compare it with ondansetron for prevention of IONV and PONV.Methods: 80 ASA grade I and II women undergoing abdominal hysterectomy under spinal anaesthesia were studied. Patients in group A received injection granisetron 2 mg and group B injection ondansetron 4 mg,10 minutes prior to induction of spinal anaesthesia. Main outcome measures were occurrence of nausea, retching or vomiting in intraoperative and postoperative period at 6, 12, 18 and 24 hours’ post-surgery. The response of patient to therapy and side effects were evaluated in both groups. The results were analyzed by ‘z’ test (p<0.5) considered significant.Results: Demographic characteristics of both groups were comparable patients in granisetron (80%) had more complete response as compared to ondansetron (47.5%). Adverse effects were lower in granisetron group.Conclusions: Granisetron 2 Mg has better efficacy and safety profile than ondansetron 4 Mg

Method for Generating Long-Range Correlations for Large Systems

We propose a new method to generate a sequence of random numbers with long-range power-law correlations that overcomes known difficulties associated with large systems. The new method presents an improvement on the commonly-used methods. We apply the algorithm to generate enhanced diffusion, isotropic and anisotropic self-affine surfaces, and isotropic and anisotropic correlated percolation.Comment: 4 pages, REVTEX, figures available upon request from [email protected]