138 research outputs found
Interactions measurement payload for Shuttle
The Interactions Measurement Payload for Shuttle (IMPS) consisted of engineering experiments to determine the effects of the space environment on projected Air Force space systems. Measurements by IMPS on a polar-orbit Shuttle flight will lead to detailed knowledge of the interaction of the low-altitude polar-auroral environment on materials, equipment and technologies to be used in future large, high-power space systems. The results from the IMPS measurements will provide direct input to MIL-STD design guidelines and test standards that properly account for space-environment effects
Numerical program for analysis of three-dimensional supersonic exhaust flow fields (CHAR 3D)
Choice of reference plane orientation depends on specific nozzle geometry, with different configurations requiring different reference plane systems. In addition, for given configuration several reference systems may be used in different regions of flow field, so each system is locally aligned with flow
Measurement of high-voltage and radiation-damage limitations to advanced solar array performance
A description is given of the reconfigured Photovoltaic Array Space Power (PASP) Plus experiment: its objectives, solar-array complement, and diagnostic sensors. Results from a successful spaceflight will lead to a better understanding of high-voltage and radiation-damage limitations in the operation of new-technology solar arrays
A Unified Approach to Solvable Models of Dilaton Gravity in Two-Dimensions Based on Symmetry
A large class of solvable models of dilaton gravity in two space-time
dimensions, capable of describing black hole geometry, are analyzed in a
unified way as non-linear sigma models possessing a special symmetry. This
symmetry, which can be neatly formulated in the target-space-covariant manner,
allows one to decompose the non-linearly interacting dilaton-gravity system
into a free field and a field satisfying the Liouville equation with in general
non-vanishing cosmological term. In this formulation, all the existent models
are shown to fall into the category with vanishing cosmological constant.
General analysis of the space-time structureinduced by a matter shock wave is
performed and new models, with and without the cosmological term, are
discussed.Comment: 29 pages, LaTe
Nonanomalous Discrete R-Symmetry and Light Gravitino
We discuss nonanomalous R-symmetry in the supersymmetric grand unified
theories. In particular, we explore anomaly-free solutions predicting the
gravitino mass in the range of 10^{-3} eV \lsim m_{3/2} \lsim 1 TeV when the
-parameter is fixed to be . In the minimal SU(5) GUT, we
have shown that is obtained only if the gravitino is
ultralight with mass . If extra fields or are introduced, many solutions
predicting m_{3/2} \gsim 10^{-3} eV are found. The R-parity is violated due
to the vacuum expectation value of the superpotential, but it is controlled by
the discrete R-symmetry. We find that the R-parity violating couplings are
naturally suppressed much below the experimental bounds for some charge
assignments. These charge assignments predict light gravitino with masses of
order --. These discrete R-symmetries
can be considered as solutions to the -problem in low energy supersymmetry
breaking models such as the gauge mediation.Comment: 20 pages, no figure. v2: minor corrections, references added, "Note
Added" in Summary adde
Extra Dimensions and Higgs Pair Production at Photon Colliders
We show that new physics effects due to extra dimensions can dramatically
affect Higgs pair production at photon colliders. We find that the cross
section due to extra dimensions with the scale of new physics around 1.5
TeV, the cross section can be as large as 0.11 pb (1.5pb) for monochromatic
photon collision, , with the collider energy TeV for Higgs mass of 100 (350) GeV. The cross section can be 3 fb
(2.7 fb) for the same parameters for collisions using photon beams from
electron or positron back scattered by laser. These cross sections are much
larger than those predicted in the Standard Model. Higgs pair production at
photon colliders can provide useful tests for new physics due to extra
dimensions.Comment: Typos corrected and updated references, Rev-Tex, 11 pages with one
figur
A burst with double radio spectrum observed up to 212 GHz
We study a solar flare that occurred on September 10, 2002, in active region
NOAA 10105 starting around 14:52 UT and lasting approximately 5 minutes in the
radio range. The event was classified as M2.9 in X-rays and 1N in H\alpha.
Solar Submillimeter Telescope observations, in addition to microwave data give
us a good spectral coverage between 1.415 and 212 GHz. We combine these data
with ultraviolet images, hard and soft X-rays observations and full-disk
magnetograms. Images obtained from Ramaty High Energy Solar Spectroscopic
Imaging data are used to identify the locations of X-ray sources at different
energies and to determine the X-ray spectrum, while ultra violet images allow
us to characterize the coronal flaring region. The magnetic field evolution of
the active region is analyzed using Michelson Doppler Imager magnetograms. The
burst is detected at all available radio-frequencies. X-ray images (between 12
keV and 300 keV) reveal two compact sources and 212 GHz data, used to estimate
the radio source position, show a single compact source displaced by 25" from
one of the hard X-ray footpoints. We model the radio spectra using two
homogeneous sources, and combine this analysis with that of hard X-rays to
understand the dynamics of the particles. Relativistic particles, observed at
radio wavelengths above 50 GHz, have an electron index evolving with the
typical soft-hard-soft behaviour.Comment: Submitted to Solar Physics, 20 pages, 8 fugure
Clomiphene, Metformin, or Both for Infertility in the Polycystic Ovary Syndrome
Background
The polycystic ovary syndrome is a common cause of infertility. Clomiphene and insulin sensitizers are used alone and in combination to induce ovulation, but it is unknown whether one approach is superior. Methods We randomly assigned 626 infertile women with the polycystic ovary syndrome to receive clomiphene citrate plus placebo, extended-release metformin plus placebo, or a combination of metformin and clomiphene for up to 6 months. Medication was discontinued when pregnancy was confirmed, and subjects were followed until delivery.
Results
The live-birth rate was 22.5% (47 of 209 subjects) in the clomiphene group, 7.2% (15 of 208) in the metformin group, and 26.8% (56 of 209) in the combinationtherapy group (P\u3c0.001 for metformin vs. both clomiphene and combination therapy; P=0.31 for clomiphene vs. combination therapy). Among pregnancies, the rate of multiple pregnancy was 6.0% in the clomiphene group, 0% in the metformin group, and 3.1% in the combination-therapy group. The rates of first-trimester pregnancy loss did not differ significantly among the groups. However, the conception rate among subjects who ovulated was significantly lower in the metformin group (21.7%) than in either the clomiphene group (39.5%, P=0.002) or the combinationtherapy group (46.0%, P\u3c0.001). With the exception of pregnancy complications, adverse-event rates were similar in all groups, though gastrointestinal side effects were more frequent, and vasomotor and ovulatory symptoms less frequent, in the metformin group than in the clomiphene group.
Conclusions
Clomiphene is superior to metformin in achieving live birth in infertile women with the polycystic ovary syndrome, although multiple birth is a complication. (ClinicalTrials.gov number, NCT00068861.
The origin of the matter-antimatter asymmetry
Although the origin of matter-antimatter asymmetry remains unknown,
continuing advances in theory and improved experimental limits have ruled out
some scenarios for baryogenesis, for example the sphaleron baryogenesis at the
electroweak phase transition in the standard model. At the same time, the
success of cosmological inflation and the prospects for discovering
supersymmetry at the LHC have put some other models in sharper focus. We review
the current state of our understanding of baryogenesis with the emphasis on
those scenarios that we consider most plausible.Comment: submitted to Reviews of Modern Physics; 38 pages; 9 figure
Effects of Extra Dimensions on Unitarity and Higgs Boson Mass
We study the unitarity constraint on the two body Higgs boson elastic
scattering in the presence of extra dimensions. The contributions from exchange
of spin-2 and spin-0 Kaluza-Klein states can have large effect on the partial
wave amplitude. Unitarity condition restrict the maximal allowed value for the
ratio of the center of mass energy to the gravity scale to be less than
one. Although the constraint on the standard Higgs boson mass for of order
one is considerably relaxed, for small the constraint is similar to that in
the Standard Model. The resulting bound on the Higgs boson mass is not
dramatically altered if perturbative calculations are required to be valid up
to the maximal allowed value for .Comment: References added, RevTex, 9 pages with two figure
- …