The simulation of ionospheric conditions for space vehicles

Plasma wind tunnel to simulate ionospheric conditions for space vehicle

School reform, school size, and student achievement

An estimation of the effect of school size on student achievement, with the results suggesting that market-based school reform could enhance student performance if the reform reduced school size.Education

Photovoltaic Oscillations Due to Edge-Magnetoplasmon Modes in a Very-High Mobility 2D Electron Gas

Using very-high mobility GaAs/AlGaAs 2D electron Hall bar samples, we have experimentally studied the photoresistance/photovoltaic oscillations induced by microwave irradiation in the regime where both 1/B and B-periodic oscillations can be observed. In the frequency range between 27 and 130 GHz we found that these two types of oscillations are decoupled from each other, consistent with the respective models that 1/B oscillations occur in bulk while the B-oscillations occur along the edges of the Hall bars. In contrast to the original report of this phenomenon (Ref. 1) the periodicity of the B-oscillations in our samples are found to be independent of L, the length of the Hall bar section between voltage measuring leads.Comment: 4 pages, 4 figure

Techniques for the realization of ultrareliable spaceborne computers Interim scientific report

Error-free ultrareliable spaceborne computer

Neutron Star Properties with Hyperons

In the light of the recent discovery of a neutron star with a mass accurately determined to be almost two solar masses, it has been suggested that hyperons cannot play a role in the equation of state of dense matter in $\beta$-equilibrium. We re-examine this issue in the most recent development of the quark-meson coupling model. Within a relativistic Hartree-Fock approach and including the full tensor structure at the vector-meson-baryon vertices, we find that not only must hyperons appear in matter at the densities relevant to such a massive star but that the maximum mass predicted is completely consistent with the observation.Comment: Minor correction

The spectral-curvature parameter: an alternative tool for the analysis of synchrotron spectra

The so-called Spectral Curvature Parameter(SCP), when plotted versus the high-frequency spectral index ($alpha_{high}$) of synchrotron sources, provides crucial parameters on the continuum spectrum of synchrotron radiation without the more complex modeling of spectral ageing scenarios. An important merit of the SCP-$alpha$ diagram is the enhanced reliability of extracting multiple injection spectra, $alpha_{inj}$. Different from the colour-colour diagram, tracks of different $alpha_{inj}$s, especially when the synchrotron particles are young, exhibit less overlap and less smearing in the SCP-$alpha$ diagram. Three giant radio galaxies(GRGs) and a sample of Compact steep spectrum(CSS) souces are presented. GRGs exhibit asymmetries of their injection spectral indices $alpha_{inj}$ in the SCP-$alpha_{high}$ diagram. The obtained $alpha_{inj}$s and the trends in the sources are cross-checked with the literature and show remarkable confidence. Besides the spectral steepening, spectral flattening is prominent in the radio lobes. The spectral flattening is a clue to efficient re-acceleration processes in the lobes. It implies interaction with the surrounding intergalactic or intra-cluster medium is an important characteristic of GRGs. In the SW lobe of DA240, there is a clear sign of CI and KP/JP bifurcation at the source extremity. This indicates a highly relativistic energy transportation from the core or in situ acceleration in this typical FR I lobe. Our analysis proves, if exists, KP spectra imply the existence of strong $B_{sync}$ field with $B_{sync} > B_{CMB}$. In the CSS sources, our result confirms the CI model and $B_{sync} >> B_{CMB}$. The synchrotron self-absorption is significant in the CSS sample.Comment: to be published in A&

Weak Localization Coexisting with a Magnetic Field in a Normal-Metal--Superconductor Microbridge

A random-matrix theory is presented which shows that breaking time-reversal symmetry by itself does {\em not} suppress the weak-localization correction to the conductance of a disordered metal wire attached to a superconductor. Suppression of weak localization requires applying a magnetic field as well as raising the voltage, to break both time-reversal symmetry and electron-hole degeneracy. A magnetic-field dependent contact resistance obscured this anomaly in previous numerical simulations.Comment: 8 pages, REVTeX-3.0, 1 figur