1,788 research outputs found
Circularly polarized waves in a plasma with vacuum polarization effects
The theory for large amplitude circularly polarized waves propagating along
an external magnetic field is extended in order to include also vacuum
polarization effects. A general dispersion relation, which unites previous
results, is derived.Comment: 5 pages (To appear in Physics of Plasmas
Odin observations of ammonia in the Sgr A +50 km/s Cloud and Circumnuclear Disk
Context. The Odin satellite is now into its sixteenth year of operation, much
surpassing its design life of two years. One of the sources which Odin has
observed in great detail is the Sgr A Complex in the centre of the Milky Way.
Aims. To study the presence of NH3 in the Galactic Centre and spiral arms.
Methods. Recently, Odin has made complementary observations of the 572 GHz NH3
line towards the Sgr A +50 km/s Cloud and Circumnuclear Disk (CND). Results.
Significant NH3 emission has been observed in both the +50 km/s Cloud and the
CND. Clear NH3 absorption has also been detected in many of the spiral arm
features along the line of sight from the Sun to the core of our Galaxy.
Conclusions. The very large velocity width (80 km/s) of the NH3 emission
associated with the shock region in the southwestern part of the CND may
suggest a formation/desorption scenario similar to that of gas-phase H2O in
shocks/outflows.Comment: 5 pages, 3 figures, 3 table
A measurement of the differential cross section for the two-body photodisintegration of 3He at theta_LAB = 90deg using tagged photons in the energy range 14 -- 31 MeV
The two-body photodisintegration of 3He has been investigated using tagged
photons with energies from 14 -- 31 MeV at MAX-lab in Lund, Sweden. The
two-body breakup channel was unambiguously identified by the (nonsimultaneous)
detection of both protons and deuterons. This approach was made feasible by the
over-determined kinematic situation afforded by the tagged-photon technique.
Proton- and deuteron-energy spectra were measured using four silicon
surface-barrier detector telescopes located at a laboratory angle of 90deg with
respect to the incident photon-beam direction. Average statistical and
systematic uncertainties of 5.7% and 6.6% in the differential cross section
were obtained for 11 photon-energy bins with an average width of 1.2 MeV. The
results are compared to previous experimental data measured at comparable
photon energies as well as to the results of two recent Faddeev calculations
which employ realistic potential models and take into account three-nucleon
forces and final-state interactions. Both the accuracy and precision of the
present data are improved over the previous measurements. The data are in good
agreement with most of the previous results, and favor the inclusion of
three-nucleon forces in the calculations.Comment: 12 pages, 13 figures; further Referee comments addresse
New Measurement of Compton Scattering from the Deuteron and an Improved Extraction of the Neutron Electromagnetic Polarizabilities
The electromagnetic polarizabilities of the nucleon are fundamental
properties that describe its response to external electric and magnetic fields.
They can be extracted from Compton-scattering data --- and have been, with good
accuracy, in the case of the proton. In contradistinction, information for the
neutron requires the use of Compton scattering from nuclear targets. Here we
report a new measurement of elastic photon scattering from deuterium using
quasimonoenergetic tagged photons at the MAX IV Laboratory in Lund, Sweden.
These first new data in more than a decade effectively double the world
dataset. Their energy range overlaps with previous experiments and extends it
by 20 MeV to higher energies. An analysis using Chiral Effective Field Theory
with dynamical \Delta(1232) degrees of freedom shows the data are consistent
with and within the world dataset. After demonstrating that the fit is
consistent with the Baldin sum rule, extracting values for the isoscalar
nucleon polarizabilities and combining them with a recent result for the
proton, we obtain the neutron polarizabilities as \alpha_n = [11.55 +/-
1.25(stat) +/- 0.2(BSR) +/- 0.8(th)] X 10^{-4} fm^3 and \beta_n = [3.65 -/+
1.25(stat) +/- 0.2(BSR) -/+ 0.8(th)] X 10^{-4} fm3, with \chi^2 = 45.2 for 44
degrees of freedom.Comment: 6 pages, 3 figures, comments from Physical Review Letters Referees
addresse
Superconducting single-mode contact as a microwave-activated quantum interferometer
The dynamics of a superconducting quantum point contact biased at subgap
voltages is shown to be strongly affected by a microwave electromagnetic field.
Interference among a sequence of temporally localized, microwave-induced
Landau-Zener transitions between current carrying Andreev levels results in
energy absorption and in an increase of the subgap current by several orders of
magnitude. The contact is an interferometer in the sense that the current is an
oscillatory function of the inverse bias voltage. Possible applications to
Andreev-level spectroscopy and microwave detection are discussed
Bioluminescence Enhanced Enzyme Immunoassay. New Ultrasensitive Detection Systems for Enzyme Immunoassays, II.
Peer Reviewe
Shell-like configuration in O<sup>+</Sup> ion velocity distribution at high altitudes in the dayside magnetosphere observed by Cluster/CIS
Legislative History: An Act to Allow an Income Tax Credit for School Tuition (HP364)(LD 509)
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