3,800 research outputs found
The 1958 Pekeris-Accad-WEIZAC Ground-Breaking Collaboration that Computed Ground States of Two-Electron Atoms (and its 2010 Redux)
In order to appreciate how well off we mathematicians and scientists are
today, with extremely fast hardware and lots and lots of memory, as well as
with powerful software, both for numeric and symbolic computation, it may be a
good idea to go back to the early days of electronic computers and compare how
things went then. We have chosen, as a case study, a problem that was
considered a huge challenge at the time. Namely, we looked at C.L. Pekeris's
seminal 1958 work on the ground state energies of two-electron atoms. We went
through all the computations ab initio with today's software and hardware, with
a special emphasis on the symbolic computations which in 1958 had to be made by
hand, and which nowadays can be automated and generalized.Comment: 8 pages, 2 photos, final version as it appeared in the journa
Norway's ambiguous approach towards Israel and Palestine:Forum: The occupation of Palestinian territories since 1967: an analysis of Europe’s role
A randomized clinical trial of the immunogenicity of 7-valent pneumococcal conjugate vaccine compared to 23-valent polysaccharide vaccine in frail, hospitalized elderly
Background: Elderly people do not mount strong immune responses to vaccines. We compared 23-valent capsular polysaccharide (23vPPV) alone versus 7-valent conjugate (PCV7) vaccine followed by 23vPPV 6 months later in hospitalized elderly. Methods: Participants were randomized to receive 23vPPV or PCV7-23vPPV. Antibodies against serotypes 3, 4, 6A, 6B, 9V, 14, 18C, 19A, 19F, 23F were measured by enzyme-linked immunosorbent (ELISA) and opsonophagocytic (OPA) assays at baseline, 6 months and 12 months. Results: Of 312 recruited, between 40% and 72% of subjects had undetectable OPA titres at baseline. After one dose, PCV7 recipients had significantly higher responses to serotypes 9V (both assays) and 23F (OPA only), and 23vPPV recipients had significantly higher responses to serotype 3 (ELISA), 19F and 19A (OPA only). In subjects with undetectable OPA titres at baseline, a proportionately greater rise in OPA titre (P<0.01) was seen for all serotypes after both vaccines. The GMT ratio of OPA was significantly higher at 12 months in the PCV7-23vPPV group for serotypes 6A, 9V, 18C and 23F. OPA titre levels for these serotypes increased moderately after 6 months, whereas immunity waned in the 23vPPV only arm. Conclusion: We did not show overwhelming benefit of one vaccine over the other. Low baseline immunity does not preclude a robust immune response, reiterating the importance of vaccinating the frail elderly. A schedule of PCV7-23vPPV prevents waning of antibody, suggesting that both vaccines could be useful in the elderly. Follow up studies are needed to determine persistence of immunity. Trial Registration: The Australian Clinical Trials Registry ACTRN12607000387426 © 2014 MacIntyre et al
All-optical switching in granular ferromagnets caused by magnetic circular dichroism
Magnetic recording using circularly polarised femto-second laser pulses is an emerging technology that would allow write speeds much faster than existing field driven methods. However, the mechanism that drives the magnetisation switching in ferromagnets is unclear. Recent theories suggest that the interaction of the light with the magnetised media induces an opto-magnetic field within the media, known as the inverse Faraday effect. Here we show that an alternative mechanism, driven by thermal excitation over the anisotropy energy barrier and a difference in the energy absorption depending on polarisation, can create a net magnetisation over a series of laser pulses in an ensemble of single domain grains. Only a small difference in the absorption is required to reach magnetisation levels observed experimentally and the model does not preclude the role of the inverse Faraday effect but removes the necessity that the opto-magnetic field is 10 s of Tesla in strength
Planet Sensitivity from Combined Ground- and Space-based Microlensing Observations
To move one step forward toward a Galactic distribution of planets, we
present the first planet sensitivity analysis for microlensing events with
simultaneous observations from space and the ground. We present this analysis
for two such events, OGLE-2014-BLG-0939 and OGLE-2014-BLG-0124, which both show
substantial planet sensitivity even though neither of them reached high
magnification. This suggests that an ensemble of low to moderate magnification
events can also yield significant planet sensitivity and therefore probability
to detect planets. The implications of our results to the ongoing and future
space-based microlensing experiments to measure the Galactic distribution of
planets are discussed.Comment: 10 pages, 5 figures, 1 table; ApJ in pres
OGLE-2005-BLG-153: Microlensing Discovery and Characterization of A Very Low Mass Binary
The mass function and statistics of binaries provide important diagnostics of
the star formation process. Despite this importance, the mass function at low
masses remains poorly known due to observational difficulties caused by the
faintness of the objects. Here we report the microlensing discovery and
characterization of a binary lens composed of very low-mass stars just above
the hydrogen-burning limit. From the combined measurements of the Einstein
radius and microlens parallax, we measure the masses of the binary components
of and . This discovery
demonstrates that microlensing will provide a method to measure the mass
function of all Galactic populations of very low mass binaries that is
independent of the biases caused by the luminosity of the population.Comment: 6 pages, 3 figures, 1 tabl
OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?
We combine all available information to constrain the nature of
OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first
in a high-magnification event. These include photometric and astrometric
measurements from Hubble Space Telescope, as well as constraints from higher
order effects extracted from the ground-based light curve, such as microlens
parallax, planetary orbital motion and finite-source effects. Our primary
analysis leads to the conclusion that the host of Jovian planet
OGLE-2005-BLG-071Lb is an M dwarf in the foreground disk with mass M= 0.46 +/-
0.04 Msun, distance D_l = 3.3 +/- 0.4 kpc, and thick-disk kinematics v_LSR ~
103 km/s. From the best-fit model, the planet has mass M_p = 3.8 +/- 0.4 M_Jup,
lies at a projected separation r_perp = 3.6 +/- 0.2 AU from its host and so has
an equilibrium temperature of T ~ 55 K, i.e., similar to Neptune. A degenerate
model less favored by \Delta\chi^2 = 2.1 (or 2.2, depending on the sign of the
impact parameter) gives similar planetary mass M_p = 3.4 +/- 0.4 M_Jup with a
smaller projected separation, r_\perp = 2.1 +/- 0.1 AU, and higher equilibrium
temperature T ~ 71 K. These results from the primary analysis suggest that
OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that
is hosted by an M dwarf. However, the formation of such high-mass planetary
companions in the outer regions of M-dwarf planetary systems is predicted to be
unlikely within the core-accretion scenario. There are a number of caveats to
this primary analysis, which assumes (based on real but limited evidence) that
the unlensed light coincident with the source is actually due to the lens, that
is, the planetary host. However, these caveats could mostly be resolved by a
single astrometric measurement a few years after the event.Comment: 51 pages, 12 figures, 3 tables, Published in Ap
Expected Performance of the ATLAS Experiment - Detector, Trigger and Physics
A detailed study is presented of the expected performance of the ATLAS
detector. The reconstruction of tracks, leptons, photons, missing energy and
jets is investigated, together with the performance of b-tagging and the
trigger. The physics potential for a variety of interesting physics processes,
within the Standard Model and beyond, is examined. The study comprises a series
of notes based on simulations of the detector and physics processes, with
particular emphasis given to the data expected from the first years of
operation of the LHC at CERN
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
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