Double-layer shocks in a magnetized quantum plasma

The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves (QIAWs) obliquely to an external magnetic field is reported in a quantum electron-positron-ion (e-p-i) plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter $H$ associated with the Bohm potential and the positron to electron density ratio $\delta$. The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.Comment: 4 pages, 1 figure (to appear in Physical Review E

Quantum effects in linear and non-linear transport of T-shaped ballistic junction

We report low-temperature transport measurements of three-terminal T-shaped device patterned from GaAs/AlGaAs heterostructure. We demonstrate the mode branching and bend resistance effects predicted by numerical modeling for linear conductance data. We show also that the backscattering at the junction area depends on the wave function parity. We find evidence that in a non-linear transport regime the voltage of floating electrode always increases as a function of push-pull polarization. Such anomalous effect occurs for the symmetric device, provided the applied voltage is less than the Fermi energy in equilibrium

Transient Thermal Modeling of an Axial Flux Permanent Magnet (AFPM) Machine Using a Hybrid Thermal Model

This paper presents the development of a hybrid thermal model for the EVO Electric AFM 140 Axial Flux Permanent Magnet (AFPM) machine as used in hybrid and electric vehicles. The adopted approach is based on a hybrid lumped parameter and finite difference method. The proposed method divides each motor component into regular elements which are connected together in a thermal resistance network representing all the physical connections in all three dimensions. The element shape and size are chosen according to the component geometry to ensure consistency. The fluid domain is lumped into one region with averaged heat transfer parameters connecting it to the solid domain. Some model parameters are obtained from Computation Fluid Dynamic (CFD) simulation and empirical data. The hybrid thermal model is described by a set of coupled linear first order differential equations which is discretised and solved iteratively to obtain the temperature profile. The computation involved is low and thus the model is suitable for transient temperature predictions. The maximum error in temperature prediction is 3.4% and the mean error is consistently lower than the mean error due to uncertainty in measurements. The details of the model development, temperature predictions and suggestions for design improvements are presented in this paper.Accepted versio

Quantized Dispersion of Two-Dimensional Magnetoplasmons Detected by Photoconductivity Spectroscopy

We find that the long-wavelength magnetoplasmon, resistively detected by photoconductivity spectroscopy in high-mobility two-dimensional electron systems, deviates from its well-known semiclassical nature as uncovered in conventional absorption experiments. A clear filling-factor dependent plateau-type dispersion is observed that reveals a so far unknown relation between the magnetoplasmon and the quantum Hall effect.Comment: 5 pages, 3 figure

Photoemission results on intralayer insertion at III-V/III-V junctions: A critical appraisal of the different interpretations

Several researchers have proposed that band discontinuities at semiconductor heterojunctions may be "tuned" by inserting very thin layers of foreign atoms at the interface which are thought to induce an "interface dipole." Modifications of the apparent valence-band offset, as measured by photoelectron spectroscopy (PES), have been indeed observed upon Si insertion at GaAs–AlAs interfaces, and they have been generally interpreted as real band-offset changes. However, there is an alternative explanation of the photoemission results in terms of band-bending effects. Here, we present results of PES experiments designed to test the two opposing interpretations. We have examined the effect of Si insertion at polar (100) and nonpolar (110) interfaces, and we have studied the insertion of Si (n-type) and Be (p-type) intralayers. Similar results are obtained for polar and nonpolar interfaces, and effects of opposite sign are observed for Si and Be intralayers. These results can be readily interpreted in terms of a band-bending profile modification upon Si or Be insertion. Additional PES experiments performed at different substrate temperatures have allowed us to test the proposed band profiles. From the surface photovoltage effects induced at low temperature, we obtain evidence for sample band bending which is consistent with the room-temperature band profiles proposed. Hence, our results can be completely understood within a "band-bending interpretation," calling into question the interpretation in terms of a "band-offset tuning effect.

Si and Be intralayers at GaAs/AlAs and GaAs/GaAs junctions: Low-temperature photoemission measurements

In order to distinguish between conflicting interpretations regarding the effect of intralayer insertion at semiconductor junctions, we have carried out synchrotron-radiation photoemission studies of GaAs/AlAs(100) heterojunctions and GaAs/GaAs(110) homojunctions, with and without a Si or a Be intralayer, at room temperature and at low temperature. The synchrotron light induces photovoltage effects at low temperature, which are found to be consistent with the room-temperature band profiles we have previously proposed for these heterojunctions [M. Moreno et al., Phys. Rev. B 58, 13 767 (1998)], assuming a doping role for the intralayer atoms. Band discontinuities play an important role in determining the type of photovoltage effects induced. Our experimental observations can be fully understood in terms of intralayer-induced changes of the bandbending profile, and the occurrence of photovoltage effects at low temperature, calling into question the previous interpretation of room-temperature photoemission results from GaAs/AlAs heterojunctions in terms of intralayer-induced "band-offset" changes

Towards quality control in cancer chemotherapy.

A survey of all hospital pharmacies in the former North Western Regional Health Authority has revealed that hospital personnel continue to prepare cytotoxic drugs in suboptimal conditions, despite the widespread introduction of pharmacy cytotoxic reconstitution services. Other concerns include the lack of formal training for medical staff in the administration of these agents and the frequent absence of written procedures for dealing with extravasation and chemotherapy errors

More on the Narrowing of Impact Broadened Radio Recombination Lines at High Principal Quantum Number

Recently Alexander and Gulyaev have suggested that the apparent decrease in impact broadening of radio recombination lines seen at high principal quantum number n may be a product of the data reduction process, possibly resulting from the presence of noise on the telescope spectra that is not present on the calculated comparison spectra. This is an interesting proposal. However, there are serious problems with their analysis that need to be pointed out. Perhaps the most important of these is the fact that for principal quantum numbers below n = 200, where the widths are not in question, their processed generated profile widths do not fit the widths of the processed lines obtained at the telescope. After processing, the halfwidths of the generated and telescope profiles must agree below n = 200 if we are to believe that the processed generated linewidths above n = 200 are meaningful. Theirs do not. Furthermore, we find that after applying the linewidth reduction factors found by Alexander and Gulyaev for their noise added profiles to our generated profiles to simulate their noise adding effect, the processed widths we obtain still do not come close to explaining the narrowing seen in the telescope lines for n values in the range 200 < n < 250. It is concluded that what is needed to solve this mystery is a completely new approach using a different observing technique instead of simply a further manipulation of the frequency-switched data.Comment: Six pages with 4 figures. Accepted for publication in Astrophysics and Space Scienc