1,713 research outputs found
Constraints for the existence of flat and stable non-supersymmetric vacua in supergravity
We further develop on the study of the conditions for the existence of
locally stable non-supersymmetric vacua with vanishing cosmological constant in
supergravity models involving only chiral superfields. Starting from the two
necessary conditions for flatness and stability derived in a previous paper
(which involve the Kahler metric and its Riemann tensor contracted with the
supersymmetry breaking auxiliary fields) we show that the implications of these
constraints can be worked out exactly not only for factorizable scalar
manifolds, but also for symmetric coset manifolds. In both cases, the
conditions imply a strong restriction on the Kahler geometry and constrain the
vector of auxiliary fields defining the Goldstino direction to lie in a certain
cone. We then apply these results to the various homogeneous coset manifolds
spanned by the moduli and untwisted matter fields arising in string
compactifications, and discuss their implications. Finally, we also discuss
what can be said for completely arbitrary scalar manifolds, and derive in this
more general case some explicit but weaker restrictions on the Kahler geometry.Comment: 22 pages, Latex, no figure
Preliminary Investigation of Methods to Increase Base Pressure of Plug Nozzles at Mach 0.9
The effects of various afterbody changes on the base pressure of a nacelle-type isentropic plug nozzle installation operating at lower-than-design jet pressure ratios were investigated at a Mach number of 0.9. Although the estimates of the net propulsive force contain some uncertainties, the results indicate that both a plain-ring base shroud and a circular-arc boattail fairing reduced the loss in net propulsive force experienced with a cylindrical nacelle installation of the plug nozzle
Experimental Investigation of Drag of Afterbodies with Exiting Jet at High Subsonic Mach Numbers
Low-speed Longitudinal Aerodynamic Characteristics of a Twisted and Cambered Wing of 45 Degree Sweepback and Aspect Ratio 8 with and Without High-lift and Stall-control Devices and a Fuselage at Reynolds Numbers from 1.5 x 10(exp 6) to 4.8 x 10(exp 6
A Three-Dimensional Flow Expander as a Device to Increase the Mach Number in a Supersonic Wind Tunnel
A preliminary investigation of a simple 5 deg conical-flow expander was made to determine the feasibility of using this type of device to increase the Mach number in the test section of a supersonic wind tunnel. The inlet-to-exit area ratio of the nozzle was that required to increase one-dimensional flow from a Mach number of 3.88 to 5.5. The Mach numbers obtained at the expander exit varied from about 5.1 at the centerline to about 5.4 near the walls. No difficulty in operation of the main wind tunnel was experienced
Yaw Characteristics of a 52 Degree Sweptback Wing of NACA 64(sub 1)-112 Section with a Fuselage and with Leading-edge and Split Flaps at Reynolds Numbers from 1.93 x 10(exp 6) to 6.00 x 10(exp 6)
Effects of leading-edge devices and trailing-edge flaps on longitudinal characteristics of two 47.7 degree sweptback wings of aspect ratios 5.1 and 6.0 at a Reynolds number of 6.0 x 10(exp 6)
Pressure-distribution Measurements over an Extensible Leading-edge Flap on Two Wings Having Leading-edge Sweep of 42 Degrees and 52 Degrees
Survival of TNF antagonists in spondylarthritis is better than in rheumatoid arthritis. Data from the Spanish registry BIOBADASER
The aim of the present work is to compare drug survival and safety of infliximab, etanercept, and adalimumab (tumor necrosis factor [TNF] antagonists) in spondylarthritis (SpA) with those of rheumatoid arthritis (RA). To this purpose, we analysed the data in BIOBADASER (2000–2005), a drug registry launched in 2000 for long-term follow-up of the safety of these biologics in rheumatic diseases. The rates of drug discontinuation and adverse events (AEs) in SpA (n = 1,524) were estimated and compared with those of RA (n = 4,006). Cox regression analyses were used to adjust for independent factors. Total exposure to TNF antagonists for SpA was 2,430 patient-years and 7,865 for RA. Drug survival in SpA was significantly greater than in RA at 1, 2, and 3 years. The hazard ratio (HR) for discontinuation in SpA compared with RA was 0.66 (95% confidence interval [CI], 0.57–0.76) after adjustment for age, gender, and use of infliximab. The difference remained after controlling for the individual medication and its place in the sequence of treatment. There were fewer SpA patients with AEs (17%) than RA patients (26%; p < 0.001). The HR for AEs in SpA was 0.80 (95% CI, 0.70–0.91) compared with RA after adjustment for age, disease duration, and use of infliximab. In conclusion, due in part to a better safety profile, survival of TNF antagonists in SpA is better than in RA. TNF antagonists are at present a safe and effective therapeutic option for long-term treatment of patients with SpA failing to respond to traditional drugs. Because chronic therapy is necessary, continual review of this issue is necessary
A New Method for Finding Vacua in String Phenomenology
One of the central problems of string-phenomenology is to find stable vacua
in the four dimensional effective theories which result from compactification.
We present an algorithmic method to find all of the vacua of any given
string-phenomenological system in a huge class. In particular, this paper
reviews and then extends hep-th/0606122 to include various non-perturbative
effects. These include gaugino condensation and instantonic contributions to
the superpotential.Comment: 27 pages, 5 .eps figures. V2: Minor corrections, reference adde
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