6,470 research outputs found
Intercomparison of numerical models of flaring coronal loops
The proposed Benchmark Problem consists of an infinitesimal magnetic flux tube containing a low-beta plasma. The field strength is assumed to be so large that the plasma can move only along the flux tube, whose shape remains invariant with time (i.e., the fluid motion is essentially one-dimensional). The flux tube cross section is taken to be constant over its entire length. In planar view the flux tube has a semi-circular shape, symmetric about its midpoint s = s sub max and intersecting the chromosphere-corona interface (CCI) perpendicularly at each foot point. The arc length from the loop apex to the CCI is 10,000 km. The flux tube extends an additional 2000 km below the CCI to include the chromosphere, which initially has a uniform temperature of 8000 K. The temperature at the top of the loop was fixed initially at 2 X 1 million K. The plasma is assumed to be a perfect gas (gamma = 5/3), consisting of pure hydrogen which is considered to be fully ionized at all temperatures. For simplicity, moreover, the electron and ion temperatures are taken to be everywhere equal at all times (corresponding to an artificially enhanced electron-ion collisional coupling). While there was more-or-less unanimous agreement as to certain global properties of the system behavior (peak temperature reached, thermal-wave time scales, etc.), no two groups could claim satisfactory accord when a more detailed comparison of solutions was attempted
Two experiments for the price of one? -- The role of the second oscillation maximum in long baseline neutrino experiments
We investigate the quantitative impact that data from the second oscillation
maximum has on the performance of wide band beam neutrino oscillation
experiments. We present results for the physics sensitivities to standard three
flavor oscillation, as well as results for the sensitivity to non-standard
interactions. The quantitative study is performed using an experimental setup
similar to the Fermilab to DUSEL Long Baseline Neutrino Experiment (LBNE). We
find that, with the single exception of sensitivity to the mass hierarchy, the
second maximum plays only a marginal role due to the experimental difficulties
to obtain a statistically significant and sufficiently background-free event
sample at low energies. This conclusion is valid for both water Cherenkov and
liquid argon detectors. Moreover, we confirm that non-standard neutrino
interactions are very hard to distinguish experimentally from standard
three-flavor effects and can lead to a considerable loss of sensitivity to
\theta_{13}, the mass hierarchy and CP violation.Comment: RevTex 4.1, 23 pages, 10 figures; v2: Typos corrected, very minor
clarifications; matches published version; v3: Fixed a typo in the first
equation in sec. III
Real-Time Operating System/360
RTOS has a cost savings advantage for real-time applications, such as those with random inputs requiring a flexible data routing facility, display systems simplified by a device independent interface language, and complex applications needing added storage protection and data queuing
Laparo-endoscopic single-site (LESS) radical nephrectomy with renal vein thrombectomy: initial report
Abstract Background By combining trocar sites and extraction incision, Laparo-endoscopic Single-site Surgery (LESS) may provide less morbidity than traditional laparoscopy. Concerns continue about LESS for locally advanced tumors. We present our experience with LESS-radical nephrectomy with renal vein thrombectomy (LESS-RN-RVT) Case Presentation Between 5-6/2009, 2 patients underwent LESS-RN-RVT (1 right-/1 left-side). Standard steps of multi-site laparoscopic radical nephrectomy were performed, including stapled renal vein thrombectomy and intact specimen extraction. Both cases were successfully completed by LESS without complications. Mean tumor size was 7.8 cm, incision size 4.5 cm, operative time 152 min, EBL 100 ml, and hospital stay 2.5 days. Both patients had negative margins, and are alive at time of last follow-up. One did not require postoperative opiates. Conclusions LESS-RN-RVT is safe and feasible in selected patients with renal vein thrombi. Further accumulation of data and comparison to multiport laparoscopic technique are requisite
Considerations for an Ac Dipole for the LHC
Following successful experience at the BNL AGS, FNAL Tevatron, and CERN SPS,
an AC Dipole will be adopted at the LHC for rapid measurements of ring optics.
This paper describes some of the parameters of the AC dipole for the LHC,
scaling from performance of the FNAL and BNL devices.Comment: proceedings of the 2007 Particle Accelerator Conferenc
Interface-induced d-wave pairing
We discuss a scenario for interface-induced superconductivity involving
pairing by dipolar excitations proximate to a two-dimensional electron system
controlled by a transverse electric field. If the interface consists of
transition metal oxide materials, the repulsive on-site Coulomb interaction is
typically strong and a superconducting state is formed via exchange of
non-local dipolar excitations in the d-wave channel. Perspectives to enhance
the superconducting transition temperature are discussed.Comment: 4 pages, 3 figure
Spin-Waves in the Mid-Infrared Spectrum of Antiferromagnetic YBaCuO
The mid-infrared spin-wave spectrum of antiferromagnetic
YBaCuO\ was determined by infrared transmission and reflection
measurements (\bbox{k} \!\! \parallel c) at ~K.\@ Excitation of
single magnons of the optical branch was observed at
~meV.\@ Two further peaks at ~meV
() and ~meV
() both belong to the two-magnon spectrum. Linear
spin wave theory is in good agreement with the measured two-magnon spectrum,
and allows to determine the exchange constant to be about ~meV,
whereas the intrabilayer coupling is approximately .Comment: 3 figures in uuencoded for
On 32-GHz cryogenically cooled HEMT low-noise amplifiers
The cryogenic noise temperature performance of a two-stage and a three-stage 32 GHz High Electron Mobility Transistor (HEMT) amplifier was evaluated. The amplifiers employ 0.25 micrometer conventional AlGaAs/GaAs HEMT devices, hybrid matching input and output microstrip circuits, and a cryogenically stable dc biasing network. The noise temperature measurements were performed in the frequency range of 31 to 33 GHz over a physical temperature range of 300 K down to 12 K. Across the measurement band, the amplifiers displayed a broadband response, and the noise temperature was observed to decrease by a factor of 10 in cooling from 300 K to 15 K. The lowest noise temperature measured for the two-stage amplifier at 32 GHz was 35 K with an associated gain of 16.5 dB, while the three-stage amplifier measured 39 K with an associated gain of 26 dB. It was further observed that both amplifiers were insensitive to light
RHESSI images and spectra of two small flares
We studied the evolution of two small flares (GOES class C2 and C1) that
developed in the same active region with different morphological
characteristics: one is extended and the other is compact. We analyzed the
accuracy and the consistency of different algorithms implemented in RHESSI
software to reconstruct the image of the emitting sources, for energies between
3 and 12 keV. We found that all tested algorithms give consistent results for
the peak position whil the other parameters can differ at most by a factor 2.
Pixon and Forward-fit generally converge to similar results but Pixon is more
reliable for reconstructing a complex source. We investigated the spectral
characteristics of the two flares during their evolution in the 3--25 keV
energy band. We found that a single thermal model of the photon spectrum is
inadequate to fit the observations and we needed to add either a non-thermal
model or a hot thermal one.The non-thermal and the double thermal fits are
comparable. If we assume a non-thermal model, the non-thermal energy is always
higher than the thermal one.Only during the very final decay phase a single
thermal model fits fairly well the observed spectrum.Comment: 26 pages, 11 figures, accepted by Solar Physic
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