4,480 research outputs found
Direct Mediation and Metastable Supersymmetry Breaking for SO(10)
We examine a metastable Macroscopic SO(N) SQCD model of
Intriligator, Seiberg and Shih (ISS). We introduce various baryon and meson
deformations, including multitrace operators and explore embedding an SO(10)
parent of the standard model into two weakly gauged flavour sectors. Direct
fundamental messengers and the symmetric pseudo-modulus messenger mediate SUSY
breaking to the MSSM. Gaugino and sfermion masses are computed and compared for
each deformation type. We also explore reducing the rank of the magnetic quark
matrix of the ISS model and find an additional fundamental messenger.Comment: 43 pages, Latex. Version to appear in JHEP
A slice of AdS_5 as the large N limit of Seiberg duality
A slice of AdS_5 is used to provide a 5D gravitational description of 4D
strongly-coupled Seiberg dual gauge theories. An (electric) SU(N) gauge theory
in the conformal window at large N is described by the 5D bulk, while its
weakly coupled (magnetic) dual is confined to the IR brane. This framework can
be used to construct an N = 1 MSSM on the IR brane, reminiscent of the original
Randall-Sundrum model. In addition, we use our framework to study
strongly-coupled scenarios of supersymmetry breaking mediated by gauge forces.
This leads to a unified scenario that connects the extra-ordinary gauge
mediation limit to the gaugino mediation limit in warped space.Comment: 47 Pages, axodraw4j.st
TASI/PiTP/ISS Lectures on Moduli and Microphysics
I review basic forces on moduli that lead to their stabilization, for example
in the supercritical and KKLT models of de Sitter space in string theory, as
well as an model I include which is not published
elsewhere. These forces come from the classical dilaton tadpole in generic
dimensionality, internal curvature, fluxes, and branes and orientifolds as well
as non-perturbative effects. The resulting (A)dS solutions of string theory
make detailed predictions for microphysical entropy, whose leading behavior we
exhibit on the Coulomb branch of the system. Finally, I briefly review recent
developments concerning the role of velocity-dependent effects in the dynamics
of moduli. These lecture notes are based on material presented at various
stages in the 1999 TASI, 2002 PiTP, 2003 TASI, and 2003 ISS schools.Comment: 35 pages, harvmac bi
General Path Planning Methodology for Leader-Follower Robot Formations
This paper describes a robust algorithm for mobile robot formations based on the Voronoi Fast Marching path planning method. This is based on the propagation of a wave throughout the model of the environment, the wave expanding faster as the wave's distance from obstacles increases. This method provides smooth and safe trajectories and its computational efficiency allows us to maintain a good response time. The proposed method is based on a local-minima-free planner; it is complete and has an O(n) complexity order where n is the number of cells of the map. Simulation results show that the proposed algorithm generates good trajectories.Comunidad de Madri
Robot formation motion planning using Fast Marching
This paper presents the application of the Voronoi Fast Marching (VFM) method to path planning of mobile formation robots. The VFM method uses the propagation of a wave (Fast Marching) operating on the world model to determine a motion plan over a viscosity map (similar to the refraction index in optics) extracted from the updated map model. The computational efficiency of the method allows the planner to operate at high rate sensor frequencies. This method allows us to maintain good response time and smooth and safe planned trajectories. The navigation function can be classified as a type of potential field, but it has no local minima, it is complete (it finds the solution path if it exists) and it has a complexity of order n(O(n)), where n is the number of cells in the environment map. The results presented in this paper show how the proposed method behaves with mobile robot formations and generates trajectories of good quality without problems of local minima when the formation encounters non-convex obstacles.This work has been supported by the CAM Project S2009/DPI-1559/ROBOCITY2030 II,
developed by the research team RoboticsLab at the University Carlos III of Madrid.Publicad
De novo backbone and sequence design of an idealized α/β-barrel protein: evidence of stable tertiary structure
We have designed, synthesized, and characterized a 216 amino acid residue
sequence encoding a putative idealized α/β-barrel protein. The
design was elaborated in two steps. First, the idealized backbone was
defined with geometric parameters representing our target fold: a central
eight parallel-stranded β-sheet surrounded by eight parallel α-helices,
connected together with short structural turns on both sides of the barrel.
An automated sequence selection algorithm, based on the dead-end elimination
theorem, was used to find the optimal amino acid sequence fitting
the target structure. A synthetic gene coding for the designed sequence
was constructed and the recombinant artificial protein was expressed in
bacteria, purified and characterized. Far-UV CD spectra with prominent
bands at 222 nm and 208 nm revealed the presence of α-helix secondary
structures (50%) in fairly good agreement with the model. A pronounced
absorption band in the near-UV CD region, arising from immobilized aromatic
side-chains, showed that the artificial protein is folded in solution.
Chemical unfolding monitored by tryptophan fluorescence revealed a
conformational stability (ΔGH_2O) of 35 kJ/mol. Thermal unfolding monitored by near-UV CD revealed a cooperative transition with an apparent T_m of 65 °C. Moreover, the artificial protein did not exhibit any affinity
for the hydrophobic fluorescent probe 1-anilinonaphthalene-8-sulfonic
acid (ANS), providing additional evidence that the artificial barrel is not
in the molten globule state, contrary to previously designed artificial a/
b-barrels. Finally, ^1H NMR spectra of the folded and unfolded proteins
provided evidence for specific interactions in the folded protein. Taken
together, the results indicate that the de novo designed α/β-barrel protein
adopts a stable three-dimensional structure in solution. These encouraging
results show that de novo design of an idealized protein structure of
more than 200 amino acid residues is now possible, from construction of
a particular backbone conformation to determination of an amino acid
sequence with an automated sequence selection algorithm
Development and experimentation of LQR/APF guidance and control for autonomous proximity maneuvers of multiple spacecraft
http://dx.doi.org/10.1016/j.actaastro.2010.08.012This work introduces a novel control algorithm for close proximity multiple spacecraft autonomous maneuvers, based on hybrid linear quadratic regulator/artificial potential function (LQR/APF), for applications including autonomous docking, on-orbit assembly and spacecraft servicing. Both theoretical developments and experimental validation of the proposed approach are presented. Fuel consumption is sub-optimized in real-time through re-computation of the LQR at each sample time, while performing collision avoidance through the APF and a high level decisional logic. The underlying LQR/APF controller is integrated with a customized wall-following technique and a decision logic, overcoming problems such as local minima. The algorithm is experimentally tested on a four spacecraft simulators test bed at the Spacecraft Robotics Laboratory of the NAval Postgraduate School. The metrics to evaluate the control algorithm are: autonomy of the system in making decisions, successful completion of the maneuver, required time, and propellant consumption
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