10,426 research outputs found
A preliminary summary of the observations of the 16 February 1984 solar flare (STIP Interval XV, 12-21 February 1984)
The solar flare on 16 Feb. 1984 (0900 UT) and the associated photon and particle emissions were perhaps the most interesting solar and interplanetary phenomena during STIP Interval XV, 12 to 21 Feb. 1984. The X-ray and microwave radio emissions, as observed from the Earth, were relatively weak and no optical flare was reported. However, the hard X-ray and low energy gamma-ray observations made with the Pioneer Venus Orbiter spacecraft behind the west limb of the Sun indicate that the flare was, in reality, very intense. There is evidence that the flare was located approx 40 deg behind the west limb of the Sun and hence, for instruments located near the Earth, the most intense parts of the X-ray and microwave radio sources were occulted by the photosphere. However, the effect of occultation on the metric type II, type III, and type IV and decimetric (type DCIM) radio sources appeared to be relatively small. Following the flare, a large increase in the counting rates was recorded by several ground level neutron monitors and energetic particle detectors located in interplanetary space. A preliminary analysis of the 16 Feb. 1984 flare observations follows
Commuting, transitions and belonging: the experiences of students living at home in their first year at university
In this study, our cross-case analysis of students’ lives challenges the conventional home–university model of transition and highlights the importance of acknowledging the influence of this complex symbiotic relationship for students who attend university and live at home. We argue that as with stay-at-home holidays, or “staycations”, which are of such crucial importance to the tourism industry, so stay-at-home students or commuter students are vital to higher education and the term utilised here is “stayeducation”. Through the narratives of “stayeducation” students, we see how family and community aspects of students’ lives are far more significant than previously realised, and our study suggests that these heavily influence the development of a student sense of belonging. Drawing upon biographical narrative method, this paper introduces three first-year Business and Economics students enrolled at different universities in London and explores their journeys through their transition through home, school and early university life. Ways in which key themes play out in the transition stories of our students and the challenges and obstacles for the individual are drawn out through the cross-case analysis. Findings support the existing literature around gender, class and identity; however, new insights into the importance, for these students, of family, friendships and community are presented. Our work has implications for academic staff, those writing institutional policies, and argues for the creation of different spaces within which students can integrate into their new environment
Finite difference time domain implementation of surface impedance boundary conditions
Surface impedance boundary conditions are employed to reduce the solution volume during the analysis of scattering from lossy dielectric objects. In a finite difference solution, they also can be utilized to avoid using small cells, made necessary by shorter wavelengths in conducting media throughout the solution volume. The standard approach is to approximate the surface impedance over a very small bandwidth by its value at the center frequency, and then use that result in the boundary condition. Two implementations of the surface impedance boundary condition are presented. One implementation is a constant surface impedance boundary condition and the other is a dispersive surface impedance boundary condition that is applicable over a very large frequency bandwidth and over a large range of conductivities. Frequency domain results are presented in one dimension for two conductivity values and are compared with exact results. Scattering width results from an infinite square cylinder are presented as a 2-D demonstration. Extensions to 3-D should be straightforward
Wideband finite difference time domain implementation of surface impedance boundary conditions for good conductors
Surface impedance boundary conditions are used to reduce the solution volume during the analysis of scattering from lossy dielectric objects. In a finite difference solution, they also can be used to avoid using small cells, made necessary by shorter wavelengths in conducting media, throughout the solution volume. A one dimensional implementation is presented for a surface impedance boundary condition for good conductors in the Finite Difference Time Domain (FDTD) technique. In order to illustrate the FDTD surface impedance boundary condition, a planar air-lossy dielectric interface is considered
Do About Half the Top Quarks at FNAL Come From Gluino Decays?
We argue that it is possible to make a consistent picture of FNAL data
including the production and decay of gluinos and squarks. The additional cross
section is several pb, about the size of that for Standard Model (SM) top quark
pair production. If the stop squark mass is small enough, about half of the top
quarks decay to stop squarks, and the loss of SM top quark pair production rate
is compensated by the supersymmetric processes. This behavior is consistent
with the reported top quark decay rates in various modes and other aspects of
the data, and suggests several other possible decay signatures. This picture
can be tested easily with more data, perhaps even with the data in hand, and
demonstrates the potential power of a hadron collider to determine
supersymmetric parameters. It also has implications for the top mass
measurement and the interpretation of the LEP excess.Comment: 18 pages, including 4 Postscript figures, uses epsf.tex, also
available at http://www.hep.anl.gov/theory/mrenna
High-Field Electrical Transport in Single-Wall Carbon Nanotubes
Using low-resistance electrical contacts, we have measured the intrinsic
high-field transport properties of metallic single-wall carbon nanotubes.
Individual nanotubes appear to be able to carry currents with a density
exceeding 10^9 A/cm^2. As the bias voltage is increased, the conductance drops
dramatically due to scattering of electrons. We show that the current-voltage
characteristics can be explained by considering optical or zone-boundary phonon
emission as the dominant scattering mechanism at high field.Comment: 4 pages, 3 eps figure
Low energy supersymmetry with a neutralino LSP and the CDF ee\gamma\gamma + missing E_T event
We present a refined and expanded analysis of the CDF ee\gamma\gamma + \Et
event as superpartner production, assuming the lightest neutralino is the
lightest supersymmetric particle. A general low-energy Lagrangian is
constrained by a minimum cross section times branching ratio into two electrons
and two photons, kinematics consistent with the event, and LEP1-LEP130 data. We
examine how the supersymmetric parameters depend on the kinematics, branching
ratios and experimental predictions with a selectron interpretation of the
event, and discuss to what extent these are modified by other interpretations.
Predictions for imminent CERN LEP upgrades and the present and future Fermilab
Tevatron are presented. Finally, we briefly discuss the possible connection to
other phenomena including a light stop, the neutralino relic density, the shift
in and the associated shift in , and implications for the form
of the theory.Comment: 57 pages, LaTeX, uses epsf.sty, 19 figures. Version accepted for
publication in Phys. Rev. D, with minor changes and a few clarification
Dynamical electron transport through a nanoelectromechanical wire in a magnetic field
We investigate dynamical transport properties of interacting electrons moving
in a vibrating nanoelectromechanical wire in a magnetic field. We have built an
exactly solvable model in which electric current and mechanical oscillation are
treated fully quantum mechanically on an equal footing. Quantum mechanically
fluctuating Aharonov-Bohm phases obtained by the electrons cause nontrivial
contribution to mechanical vibration and electrical conduction of the wire. We
demonstrate our theory by calculating the admittance of the wire which are
influenced by the multiple interplay between the mechanical and the electrical
energy scales, magnetic field strength, and the electron-electron interaction
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