Low Intensity Decameter Emissions from Jupiter

Low intensity decameter emissions from Jupite

Measurements of antenna impedance in the ionosphere. II. Observing frequency greater than the electron gyro frequency

Short dipole antenna impedance measurements in ionosphere at observing frequency above electron gyrofrequenc

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

An assessment of key model parametric uncertainties in projections of Greenland Ice Sheet behavior

Lack of knowledge about the values of ice sheet model input parameters introduces substantial uncertainty into projections of Greenland Ice Sheet contributions to future sea level rise. Computer models of ice sheet behavior provide one of several means of estimating future sea level rise due to mass loss from ice sheets. Such models have many input parameters whose values are not well known. Recent studies have investigated the effects of these parameters on model output, but the range of potential future sea level increases due to model parametric uncertainty has not been characterized. Here, we demonstrate that this range is large, using a 100-member perturbed-physics ensemble with the SICOPOLIS ice sheet model. Each model run is spun up over 125 000 yr using geological forcings and subsequently driven into the future using an asymptotically increasing air temperature anomaly curve. All modeled ice sheets lose mass after 2005 AD. Parameters controlling surface melt dominate the model response to temperature change. After culling the ensemble to include only members that give reasonable ice volumes in 2005 AD, the range of projected sea level rise values in 2100 AD is ~40 % or more of the median. Data on past ice sheet behavior can help reduce this uncertainty, but none of our ensemble members produces a reasonable ice volume change during the mid-Holocene, relative to the present. This problem suggests that the model's exponential relation between temperature and precipitation does not hold during the Holocene, or that the central-Greenland temperature forcing curve used to drive the model is not representative of conditions around the ice margin at this time (among other possibilities). Our simulations also lack certain observed physical processes that may tend to enhance the real ice sheet's response. Regardless, this work has implications for other studies that use ice sheet models to project or hindcast the behavior of the Greenland Ice Sheet

Non-perturbative corrections to mean-field behavior: spherical model on spider-web graph

We consider the spherical model on a spider-web graph. This graph is effectively infinite-dimensional, similar to the Bethe lattice, but has loops. We show that these lead to non-trivial corrections to the simple mean-field behavior. We first determine all normal modes of the coupled springs problem on this graph, using its large symmetry group. In the thermodynamic limit, the spectrum is a set of $\delta$-functions, and all the modes are localized. The fractional number of modes with frequency less than $\omega$ varies as $\exp (-C/\omega)$ for $\omega$ tending to zero, where $C$ is a constant. For an unbiased random walk on the vertices of this graph, this implies that the probability of return to the origin at time $t$ varies as $\exp(- C' t^{1/3})$, for large $t$, where $C'$ is a constant. For the spherical model, we show that while the critical exponents take the values expected from the mean-field theory, the free-energy per site at temperature $T$, near and above the critical temperature $T_c$, also has an essential singularity of the type $\exp[ -K {(T - T_c)}^{-1/2}]$.Comment: substantially revised, a section adde

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

Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting

We present a detailed investigation of the magnetic and magnetotransport properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion implantation and pulsed-laser melting (II-PLM). The field and temperature-dependent magnetization, magnetic anisotropy, temperature-dependent resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have all of the characteristic signatures of the strong p-d interaction of holes and Mn ions observed in the dilute hole-mediated ferromagnetic phase. The ferromagnetic and electrical transport properties of II-PLM films correspond to the peak substitutional Mn concentration meaning that the non-uniform Mn depth distribution is unimportant in determining the film properties. Good quantitative agreement is found with films grown by low temperature molecular beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition. Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from interstitial Mn_I because of the high temperature processing. At high Mn implantation doses the kinetics of solute redistribution during solidification alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs giving evidence for this being an intrinsic property of the carrier-mediated ferromagnetic phase

Automated Retrieval of Non-Engineering Domain Solutions to Engineering Problems

Organised by: Cranfield UniversityBiological inspiration for engineering design has occurred through a variety of techniques such as creation and use of databases, keyword searches of biological information in natural-language format, prior knowledge of biology, and chance observations of nature. This research focuses on utilizing the reconciled Functional Basis function and flow terms to identify suitable biological inspiration for function based design. The organized search provides two levels of results: (1) associated with verb function only and (2) narrowed results associated with verb-noun (function-flow). A set of heuristics has been complied to promote efficient searching using this technique. An example for creating smart flooring is also presented and discussed.Mori Seiki – The Machine Tool Compan