391 research outputs found
Anti de Sitter quantum field theory and a new class of hypergeometric identities
We use Anti-de Sitter quantum field theory to prove a new class of identities
between hypergeometric functions related to the K\"all\'en-Lehmann
representation of products of two Anti-de Sitter two-point functions. A rich
mathematical structure emerges. We apply our results to study the decay of
unstable Anti-de Sitter particles. The total amplitude is in this case finite
and Anti-de Sitter invariant
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Energy efficiency study of single-wide manufactured homes
This Cooperative Research and Development Agreement (CRADA) was among Tennessee Technological University, Clayton Homes, Inc., and Oak Ridge National Laboratory (ORNL). Manufactured homes now make up a substantial portion of the new home market, and improving the energy efficiency of these homes would save significant amounts of energy. This project explored the impact of differing levels of attic insulation, the use of evacuated insulation panels, and the application of a solar reflective roof coating. The performance of the installed roof cavity insulation compared favorably with that predicted by laboratory measurements. The more heavily insulated of the two units used about 30% less energy over the period of the project than the standard unit. Based on the experimental data, computer simulations for nine cities were completed for a single-wide manufactured home with the solar reflective roof coating. Annual electric power savings ranged from 894 kWh in Rapid City to 2119 kWh for the same roof area in Los Angeles. The field performance of vacuum insulation panels was compared with laboratory performance. The panels will perform as expected if protected from puncture
Trapping Long-Lifetime Excitons in a Two-Dimensional Harmonic Potential
We report an important step forward for the goal of unambiguous observation
of Bose-Einstein condensation of excitons in semiconductors. We have
demonstrated a system in which excitons live for microseconds, much longer than
their thermalization time, move over distances of hundreds of microns, and can
be trapped in a harmonic potential exactly analous to the traps for atomic
condensates. We also report recent results of a new method for observing
evidence of Bose-Einstein condensation, by angular resolution of the emitted
luminescence.Comment: Invited paper for International Conference on Spontaneous Coherence
in Excitonic Systems, Seven Springs, PA, May 2004. To appear in Solid State
Communication
The 13-C(p,d) Reaction at 120 MeV
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
Star and Planet Formation with ALMA: an Overview
Submillimeter observations with ALMA will be the essential next step in our
understanding of how stars and planets form. Key projects range from detailed
imaging of the collapse of pre-stellar cores and measuring the accretion rate
of matter onto deeply embedded protostars, to unravelling the chemistry and
dynamics of high-mass star-forming clusters and high-spatial resolution studies
of protoplanetary disks down to the 1 AU scale.Comment: Invited review, 8 pages, 5 figures; to appear in the proceedings of
"Science with ALMA: a New Era for Astrophysics". Astrophysics & Space
Science, in pres
Possible origins of macroscopic left-right asymmetry in organisms
I consider the microscopic mechanisms by which a particular left-right (L/R)
asymmetry is generated at the organism level from the microscopic handedness of
cytoskeletal molecules. In light of a fundamental symmetry principle, the
typical pattern-formation mechanisms of diffusion plus regulation cannot
implement the "right-hand rule"; at the microscopic level, the cell's
cytoskeleton of chiral filaments seems always to be involved, usually in
collective states driven by polymerization forces or molecular motors. It seems
particularly easy for handedness to emerge in a shear or rotation in the
background of an effectively two-dimensional system, such as the cell membrane
or a layer of cells, as this requires no pre-existing axis apart from the layer
normal. I detail a scenario involving actin/myosin layers in snails and in C.
elegans, and also one about the microtubule layer in plant cells. I also survey
the other examples that I am aware of, such as the emergence of handedness such
as the emergence of handedness in neurons, in eukaryote cell motility, and in
non-flagellated bacteria.Comment: 42 pages, 6 figures, resubmitted to J. Stat. Phys. special issue.
Major rewrite, rearranged sections/subsections, new Fig 3 + 6, new physics in
Sec 2.4 and 3.4.1, added Sec 5 and subsections of Sec
Observational diagnostics of gas in protoplanetary disks
Protoplanetary disks are composed primarily of gas (99% of the mass).
Nevertheless, relatively few observational constraints exist for the gas in
disks. In this review, I discuss several observational diagnostics in the UV,
optical, near-IR, mid-IR, and (sub)-mm wavelengths that have been employed to
study the gas in the disks of young stellar objects. I concentrate in
diagnostics that probe the inner 20 AU of the disk, the region where planets
are expected to form. I discuss the potential and limitations of each gas
tracer and present prospects for future research.Comment: Review written for the proceedings of the conference "Origin and
Evolution of Planets 2008", Ascona, Switzerland, June 29 - July 4, 2008. Date
manuscript: October 2008. 17 Pages, 6 graphics, 134 reference
A systematic review of the effects of exercise interventions on body composition in HIV+ adults
Over the years, physical activity and exercise have been used to positively impact the health and quality of life of persons infected with HIV and, more recently, has been associated with a spectrum of body composition changes. The aim of this review was to examine the effects of various exercise interventions on body composition in HIV positive adults, using a search strategy of randomized, controlled trials (RCTs). A systematic review was performed by five independent reviewers using a predetermined protocol adapted from previous research for assessing the articles for inclusion, the extracted data, and methodological quality. Eight RCTs involving 430 (26% female) HIV positive adults performing exercise a minimum of thrice weekly for at least six weeks were finally selected: Four were progressive resistance training (PRT) studies, three were aerobic training (AT) studies, and one involved yoga. In the PRT studies, there were significant increases in three anthropometric measures, namely, body mass, sum of skinfolds and sum of limb girths. In the AT studies, significant decreases were found in seven anthropometric measures, namely, body mass index, waist-hip ratio, body mass, triceps skinfold, waist circumference and sum of skinfolds. With yoga, the changes were nonsignificant. Exercise contributes to improved body composition and, when applied safely, appears to be beneficial for adults living with HIV/AIDS. However, these findings should be interpreted cautiously due to the relatively few RCTs published to date. Future studies would benefit from increased attention to sample size, female participants, participant follow-up, complete statistical analysis and intention-to-treat analysis.Scopu
Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV
Results are presented from a search for a W' boson using a dataset
corresponding to 5.0 inverse femtobarns of integrated luminosity collected
during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV.
The W' boson is modeled as a heavy W boson, but different scenarios for the
couplings to fermions are considered, involving both left-handed and
right-handed chiral projections of the fermions, as well as an arbitrary
mixture of the two. The search is performed in the decay channel W' to t b,
leading to a final state signature with a single lepton (e, mu), missing
transverse energy, and jets, at least one of which is tagged as a b-jet. A W'
boson that couples to fermions with the same coupling constant as the W, but to
the right-handed rather than left-handed chiral projections, is excluded for
masses below 1.85 TeV at the 95% confidence level. For the first time using LHC
data, constraints on the W' gauge coupling for a set of left- and right-handed
coupling combinations have been placed. These results represent a significant
improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
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