Nuclear isotope thermometry

We discuss different aspects which could influence temperatures deduced from experimental isotopic yields in the multifragmentation process. It is shown that fluctuations due to the finite size of the system and distortions due to the decay of hot primary fragments conspire to blur the temperature determination in multifragmentation reactions. These facts suggest that caloric curves obtained through isotope thermometers, which were taken as evidence for a first-order phase transition in nuclear matter, should be investigated very carefully.Comment: 9 pages, 7 figure

An adaptive controller for photovoltaic emulator using artificial neural network

The photovoltaic (PV) emulator is a nonlinear power supply that features the similar characteristic of the PV module. However, the nonlinear characteristic of the PV module causes instability of the PV emulator output. The conventional solution is to operate the PV emulator in the overdamped condition which results in a poor dynamic performance. This drawback is solved by manipulating the proportional and integral gains of the proportional-integral (PI) controller. In this paper, the artificial neural network is used in the adaptive PI controller to maintain a stable and fast dynamic response of the PV emulator. This has been simulated with varied output resistance and irradiance. By comparing the proposed control strategy with the conventional method during start-up response of the photovoltaic emulator, the dynamic performance of the output current has shown an improvement of up to 80 % faster than the conventional method

Association Between Vestibular Migraine and Migraine Headache: Yet to Explore.

ObjectivesTo evaluate if patients with a diagnosis of vestibular migraine (VM) by the International Classification of Headache Disorders (ICHD) criteria have meaningful differences in symptomatology and disease characteristics when compared to patients with concurrent vestibular symptoms and migraine that do not meet ICHD criteria.MethodsPatients who presented for the evaluation of vertigo were provided a detailed questionnaire about dizziness and migraine symptoms. Patients were assigned to either VM cohort (met ICHD criteria for VM) or migraine headache (MH) cohort (met ICHD criteria for migraine with or without aura but not VM). Disease characteristics, symptomatology, quality of life, and perceived stress score were compared between the cohorts.ResultsThe VM cohort demonstrated a shorter duration of vertigo episodes, 11 ± 22 hours versus 84 ± 146 hours in the MH cohort. In the VM cohort, 81% reported experiencing migraine headaches during episodes of vertigo, versus 61% in the MH cohort. All patients in the VM cohort reported a previous diagnosis of migraine headache, whereas 9% of the MH cohort had not been previously diagnosed by another physician. There was no difference in quality of life or perceived stress scores between the cohorts.ConclusionsA large proportion of vertigo patients with migrainous features do not meet the ICHD criteria for VM. The differences between cohorts represent selection bias rather than meaningful features unique to the cohorts. As such, VM and MH with vestibular symptoms may exist on a spectrum of the same disease process and may warrant the same treatment protocols

Aharonov-Bohm oscillations of a tunable quantum ring

With an atomic force microscope a ring geometry with self-aligned in-plane gates was directly written into a GaAs/AlGaAs-heterostructure. Transport measurements in the open regime show only one transmitting mode and Aharonov-Bohm oscillations with more than 50% modulation are observed in the conductance. The tuning via in-plane gates allows to study the Aharonov-Bohm effect in the whole range from the open ring to the Coulomb-blockade regime.Comment: 3 pages, 3 figure

The Morphotropic Phase Boundary in the (1-x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] Perovskite Solid Solution

Ceramics in the (1-x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] solid solution system with 0.48 x 0.56 were investigated. A morphotropic phase boundary separating rhombohedral and tetragonal perovskite phases was identified at x = 0.52. This composition displays the maximum remanent polarization Pr of 40.7 μC/cm2 and the best piezoelectric coefficient d33 of 311 pC/N in the pseudo-binary system. However, the Curie temperature Tc for this MPB composition is 291 °C, much lower than initially expected

Study of intermixing in a GaAs/AlGaAs quantum-well structure using doped spin-on silica layers

The effect of two different dopants, P and Ga, in spin-on glass (SOG) films on impurity-free vacancy disordering (IFVD) in GaAs/AlGaAs quantum-well structures has been investigated. It is observed that by varying the annealing and baking temperatures, P-doped SOG films created a similar amount of intermixing as the undoped SOG films. This is different from the results of other studies of P-doped SiO₂ and is ascribed to the low doping concentration of P, indicating that the doping concentration of P in the SiO₂ layer is one of the key parameters that may control intermixing. On the other hand, for all the samples encapsulated with Ga-doped SOG layers, significant suppression of the intermixing was observed, making them very promising candidates with which to achieve the selective-area defect engineering that is required for any successful application of IFVD.One of the authors (H.H.T.) acknowledges a fellowship awarded to him by the Australian Research Council

Spin Susceptibility of a 2D Electron System in GaAs towards the Weak Interaction Region

We determine the spin susceptibility $\chi$ in the weak interaction regime of a tunable, high quality, two-dimensional electron system in a GaAs/AlGaAs heterostructure. The band structure effects, modifying mass and g-factor, are carefully taken into accounts since they become appreciable for the large electron densities of the weak interaction regime. When properly normalized, $\chi$ decreases monotonically from 3 to 1.1 with increasing density over our experimental range from 0.1 to $4\times10^{11} cm^{-2}$. In the high density limit, $\chi$ tends correctly towards $\chi\to 1$ and compare well with recent theory.Comment: Submitted to Physical Review