43,696 research outputs found
Summary of the Heavy Flavours Working Group
This is a summary of the contributions presented in the Heavy Flavours
Working Group of the DIS2006 Workshop.Comment: 14 pp, 8 figures. To appear in the proceedings of 14th International
Workshop on Deep Inelastic Scattering (DIS 2006), Tsukuba, Japan, 20-24 Apr
200
Keck Deep Fields. II. The UV Galaxy Luminosity Function at z~4, 3, and 2
We use very deep UGRI multi-field imaging obtained at the Keck telescope to
study the evolution of the rest-frame 1700A galaxy luminosity function as the
Universe doubles its age from z~4 to z~2. The depth of our imaging allows us to
constrain the faint end of the luminosity function reaching M_1700A ~ -18.5 at
z~3 (equivalent to ~1M_sun/yr) accounting for both N^1/2 uncertainty in the
number of galaxies and for cosmic variance. We carefully examine many potential
sources of systematic bias in our LF measurements before drawing the following
conclusions. We find that the luminosity function of Lyman Break Galaxies
evolves with time and that this evolution is likely differential with
luminosity. The result is best constrained between the epochs at z~4 and z~3,
where we find that the number density of sub-L* galaxies increases with time by
at least a factor of 2.3 (11sigma statistical confidence); while the faint end
of the LF evolves, the bright end appears to remain virtually unchanged,
indicating that there may be differential, luminosity-dependent evolution
significant at the 97% level. Potential systematic biases restric our ability
to draw strong conclusions about continued evolution of the luminosity function
to lower redshifts, z~2.2 and z~1.7, but, nevertheless, it appears certain that
the number density of z~2.2 galaxies at all luminosities we studied,
-22<M_1700A<-18, is at least as high as that of their counterparts at z~3.
While it is not yet clear what mechanism underlies the observed evolution, the
fact that this evolution is differential with luminosity opens up new avenues
of improving our understanding of how galaxies form and evolve at high
redshift.Comment: Accepted for publication in ApJ. Updated preprint to reflect this
final versio
Livelihood strategies and performance indicators: Understanding irrigation from water-users' perspectives: A Collaborative Research Project of the International Irrigation Management Institute, and the International Institute for Environment and Development
Water usersParticipatory rural appraisalFarmer participationPerformance indexesIrrigation managementGenderSocial aspectsHealthResearch methodsResearch projects
Echinococcus multilocularis coproantigen detection by enzyme-linked immunosorbent assay in fox, dog, and cat populations
A sandwich enzyme-linked immunosorbent assay (ELISA) for the detection of Echinococcus multilocularis coproantigens (EM-ELISA) was developed with polyclonal rabbit (solid phase) and chicken egg (catching) antibodies that were directed against E. multilocularis coproantigens and somatic worm antigens, respectively. In experimentally infected dogs and cats, coproantigens were first detectable 6-17 days postinfection (PI) in samples of 8 dogs (worm burdens at necropsy: 6,330-43,200) and from 11 days PI onward in samples of 5 cats infected with 20-6,833 worms. After anthelmintic treatment of 4 dogs and 5 cats at day 20 PI, coproantigen excretion disappeared within 3-5 days. The sensitivity of the ELISA was 83.6% in 55 foxes infected with 4-60,000 E. multilocularis, but reached 93.3% in the 45 foxes harboring more than 20 worms. The EM-ELISA was used in surveys of 'normal' dog and cat populations in Switzerland. Among 660 dogs and 263 cats, 5 dogs and 2 cats exhibited a positive reaction. In 2 of these dogs (0.30%) and 1 cat (0.38%), intestinal E. multilocularis infections were confirmed by necropsy, polymerase chain reaction PCR, or both. The specificities of the ELISA in these groups were found to be 99.5% and 99.6%, respectively, if positive ELISA results that could not be confirmed by other methods were classified as 'false positive' reactions
Keck Deep Fields. III. Luminosity-dependent Evolution of the Ultraviolet Luminosity and Star Formation Rate Densities at z~4, 3, and 2
We use the Keck Deep Fields UGRI catalog of z~4, 3, and 2 UV-selected
galaxies to study the evolution of the rest-frame 1700A luminosity density at
high redshift. The ability to reliably constrain the contribution of faint
galaxies is critical and our data do so as they reach to M*+2 even at z~4 and
deeper still at lower redshifts. We find that the luminosity density at high
redshift is dominated by the hitherto poorly studied galaxies fainter than L*,
and, indeed, the the bulk of the UV light in the high-z Universe comes from
galaxies in the luminosity range L=0.1-1L*. It is these faint galaxies that
govern the behavior of the total UV luminosity density. Overall, there is a
gradual rise in luminosity density starting at z~4 or earlier, followed by a
shallow peak or a plateau within z~3--1, and then followed by the well-know
plunge at lower redshifts. Within this total picture, luminosity density in
sub-L* galaxies evolves more rapidly at high redshift, z>~2, than that in more
luminous objects. However, this is reversed at lower redshifts, z<~1, a
reversal that is reminiscent of galaxy downsizing. Within the context of the
models commonly used in the observational literature, there seemingly aren't
enough faint or bright LBGs to maintain ionization of intergalactic gas even as
late as z~4. This is particularly true at earlier epochs and even more so if
the faint-end evolutionary trends we observe at z~3 and 4 continue to higher
redshifts. Apparently the Universe must be easier to reionize than some recent
studies have assumed. Nevertheless, sub-L* galaxies do dominate the total UV
luminosity density at z>~2 and this dominance further highlights the need for
follow-up studies that will teach us more about these very numerous but thus
far largely unexplored systems.Comment: Accepted for publication in the Astrophysical Journal. Abstract
abridge
Reaction cross-section predictions for nucleon induced reactions
A microscopic calculation of the optical potential for nucleon-nucleus
scattering has been performed by explicitly coupling the elastic channel to all
the particle-hole (p-h) excitation states in the target and to all relevant
pickup channels. These p-h states may be regarded as doorway states through
which the flux flows to more complicated configurations, and to long-lived
compound nucleus resonances. We calculated the reaction cross sections for the
nucleon induced reactions on the targets Ca, Ni, Zr and
Sm using the QRPA description of target excitations, coupling to all
inelastic open channels, and coupling to all transfer channels corresponding to
the formation of a deuteron. The results of such calculations were compared to
predictions of a well-established optical potential and with experimental data,
reaching very good agreement. The inclusion of couplings to pickup channels
were an important contribution to the absorption. For the first time,
calculations of excitations account for all of the observed reaction
cross-sections, at least for incident energies above 10 MeV.Comment: 6 pages, 6 figures. Submitted to INPC 2010 Conference Proceeding
BVRI Observations of the Optical Afterglow of GRB 990510
We present observations of the optical counterpart to the Gamma-Ray
Burst (GRB) 990510 obtained with the Las Campanas 1.0-m telescope between 15
and 48 hours after the burst. The temporal analysis of the data indicates
steepening decay, independent of wavelength, approaching asymptotically
at early times ( and at
late times, with the break time at . GRB 990510 is the
most rapidly fading of the well-documented GRB afterglows. It is also the first
observed example of broad-band break for a GRB optical counterpart. The optical
spectral energy distribution, corrected for significant Galactic reddening, is
well fitted by a single power-law with . However, when the
-band point is dropped from the fit, the power-law becomes , indicating a possible deviation from the power-law in the spectrum,
either intrinsic or due to additional extinction near the source or from an
intervening galaxy at . Broad-band break behavior broadly similar to
that observed in GRB 990510 has been predicted in some jet models of GRB
afterglows, thus supporting the idea that the GRB energy is beamed, at least in
some cases.Comment: submitted to the ApJ Letters, 13 pages, 5 tables, 3 figures;
additional data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB990510/
and through WWW at http://cfa-www.harvard.edu/cfa/oir/Research/GRB
Idealized Antenna Patterns for Use in Communication-satellite Interference Studies
Idealized antenna patterns for communication satellite interference studie
Particle transfer reactions with the time-dependent Hartree-Fock theory using a particle number projection technique
A particle-number projection technique is used to calculate transfer
probabilities in the O+Pb reaction below the fusion barrier. The
time evolution of the many-body wave function is obtained with the
time-dependent Hartree-Fock (TDHF) mean-field theory. The agreement with
experimental data for the sum of the proton-transfer channels is good,
considering that TDHF has no parameter adjusted on reaction mechanism. Some
perspectives for extensions beyond TDHF to include cluster-transfers are
discussed.Comment: Ref. 30 update
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