6,368 research outputs found
Two-step rocket engine bipropellant valve Patent
Solenoid two-step valve for bipropellant flow rate control to rocket engin
Two-step rocket engine bipropellant valve concept
Initiating combustion of altitude control rocket engines in a precombustion chamber of ductile material reduces high pressure surges generated by hypergolic propellants. Two-step bipropellant valve concepts control initial propellant flow into precombustion chamber and subsequent full flow into main chamber
No evidence yet for hadronic TeV gamma-ray emission from SNR RX J1713.7-3946
Recent TeV-scale gamma-ray observations with the CANGAROO II telescope have
led to the claim that the multi-band spectrum of RX J1713.7-3946 cannot be
explained as the composite of a synchrotron and an inverse Compton component
emitted by a population of relativistic electrons. It was argued that the
spectrum of the high-energy emission is a good match to that predicted by pion
decay, thus providing observational evidence that protons are accelerated in
SNR to at least TeV energies. In this Letter we discuss the multi-band spectrum
of RX J1713.7-3946 under the constraint that the GeV-scale emission observed
from the closely associated EGRET source 3EG J1714-3857 is either associated
with the SNR or an upper limit to the gamma-ray emission of the SNR. We find
that the pion-decay model adopted by Enomoto et al. is in conflict with the
existing GeV data. We have examined the possibility of a modified proton
spectrum to explain the data, and find that we cannot do so within any existing
theoretical framework of shock acceleration models.Comment: in press as Letter to Astronomy & Astrophysic
Charged Current Neutrino Nucleus Interactions at Intermediate Energies
We have developed a model to describe the interactions of neutrinos with
nucleons and nuclei, focusing on the region of the quasielastic and Delta(1232)
peaks. We describe neutrino nucleon collisions with a fully relativistic
formalism which incorporates state-of-the-art parametrizations of the form
factors for both the nucleon and the N-Delta transition. The model has then
been extended to finite nuclei, taking into account nuclear effects such as
Fermi motion, Pauli blocking (both within the local density approximation),
nuclear binding and final state interactions. The in-medium modification of the
Delta resonance due to Pauli blocking and collisional broadening have also been
included. Final state interactions are implemented by means of the
Boltzmann-Uehling-Uhlenbeck (BUU) coupled-channel transport model. Results for
charged current inclusive cross sections and exclusive channels as pion
production and nucleon knockout are presented and discussed.Comment: 26 pages, 24 figures; v2: 2 figures and discussion added, version
accepted for publication in Phys. Rev.
How Reliable is Medical Malpractice Law? A Review of Medical Malpractice and the American Jury: Confronting the Myths about Jury Incompetence, Deep Pockets, and Outrageous Damage Awards by Neil Vidmar
How Reliable is Medical Malpractice Law? A Review of Medical Malpractice and the American Jury: Confronting the Myths about Jury Incompetence, Deep Pockets, and Outrageous Damage Awards by Neil Vidmar
Strong-coupling effects in the relaxation dynamics of ultracold neutral plasmas
We describe a hybrid molecular dynamics approach for the description of
ultracold neutral plasmas, based on an adiabatic treatment of the electron gas
and a full molecular dynamics simulation of the ions, which allows us to follow
the long-time evolution of the plasma including the effect of the strongly
coupled ion motion. The plasma shows a rather complex relaxation behavior,
connected with temporal as well as spatial oscillations of the ion temperature.
Furthermore, additional laser cooling of the ions during the plasma evolution
drastically modifies the expansion dynamics, so that crystallization of the ion
component can occur in this nonequilibrium system, leading to lattice-like
structures or even long-range order resulting in concentric shells
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