646 research outputs found
Lanza v. Drexel & 9 & Co and Rule 10b-5 Approaching the Scienter Controversy in Private Actions
On the variability of hemispheric scale energy parameters
Includes bibliographical references.January 1975.USAEC Report No. C00-1340-41.Hemispheric scale energy parameters have been computed and their variability on an annual time scale and a scale of a few weeks is identified and discussed. Based on data for 15 winter seasons, the annual variability of available potential energy is linked to fluctuations of elements of the general circulation, such as the jet streams. This link establishes a relationship between simply computed hemispheric scale parameters and regional weather conditions affecting man's economic wellbeing. Daily statistics on three winter seasons of hemispheric energy modes have been analyzed with the ultimate goal of understanding and reproducing the behavior of the hemispheric energy cycle. Two phenomena are discussed: (1) A strong 22-26 day cycle in the energy modes which may be linked to synoptic scale systems and the atmospheric index cycle; and (2) A large midwinter "dip" in zonal available potential energy which is tentatively linked to a possible movement of the Hadley cell. This "dip" is shown to have a profound effect on the meridional temperature gradient, particularly in midlatitudes.Support for the analysis work performed from NSF Grant GA - 42215. Investigation of hemispheric circulation features supported by USAEC under Contract AT(11-1) - 1340. A number of the calculations described were accomplished at the NCAR Computing Facility funded by the National Science Foundation
Cooperative Carbon Dioxide Adsorption in Alcoholamine- and Alkoxyalkylamine-Functionalized Metal-Organic Frameworks.
A series of structurally diverse alcoholamine- and alkoxyalkylamine-functionalized variants of the metal-organic framework Mg2 (dobpdc) are shown to adsorb CO2 selectively via cooperative chain-forming mechanisms. Solid-state NMR spectra and optimized structures obtained from van der Waals-corrected density functional theory calculations indicate that the adsorption profiles can be attributed to the formation of carbamic acid or ammonium carbamate chains that are stabilized by hydrogen bonding interactions within the framework pores. These findings significantly expand the scope of chemical functionalities that can be utilized to design cooperative CO2 adsorbents, providing further means of optimizing these powerful materials for energy-efficient CO2 separations
Exploring Holographic General Gauge Mediation
We study models of gauge mediation with strongly coupled hidden sectors,
employing a hard wall background as an holographic dual description. The
structure of the soft spectrum depends crucially on the boundary conditions one
imposes on bulk fields at the IR wall. Generically, vector and fermion
correlators have poles at zero momentum, leading to gauge mediation by massive
vector messengers and/or generating Dirac gaugino masses. Instead, non-generic
choices of boundary conditions let one cover all of GGM parameter space.
Enriching the background with R-symmetry breaking scalars, the SSM soft term
structure becomes more constrained and similar to previously studied top-down
models, while retaining the more analytic control the present bottom-up
approach offers.Comment: 28 pages, 4 figures; v2: typos corrected and refs adde
Observation of modified radiative properties of cold atoms in vacuum near a dielectric surface
We have observed a distance-dependent absorption linewidth of cold Rb
atoms close to a dielectric-vacuum interface. This is the first observation of
modified radiative properties in vacuum near a dielectric surface. A cloud of
cold atoms was created using a magneto-optical trap (MOT) and optical molasses
cooling. Evanescent waves (EW) were used to observe the behavior of the atoms
near the surface. We observed an increase of the absorption linewidth with up
to 25% with respect to the free-space value. Approximately half the broadening
can be explained by cavity-quantum electrodynamics (CQED) as an increase of the
natural linewidth and inhomogeneous broadening. The remainder we attribute to
local Stark shifts near the surface. By varying the characteristic EW length we
have observed a distance dependence characteristic for CQED.Comment: 6 pages, 6 figures, some minor revision
Cascades with Adjoint Matter: Adjoint Transitions
A large class of duality cascades based on quivers arising from non-isolated
singularities enjoy adjoint transitions - a phenomenon which occurs when the
gauge coupling of a node possessing adjoint matter is driven to strong coupling
in a manner resulting in a reduction of rank in the non-Abelian part of the
gauge group and a subsequent flow to weaker coupling. We describe adjoint
transitions in a simple family of cascades based on a Z2-orbifold of the
conifold using field theory. We show that they are dual to Higgsing and produce
varying numbers of U(1) factors, moduli, and monopoles in a manner which we
calculate. This realizes a large family of cascades which proceed through
Seiberg duality and Higgsing. We briefly describe the supergravity limit of our
analysis, as well as a prescription for treating more general theories. A
special role is played by N=2 SQCD. Our results suggest that additional light
fields are typically generated when UV completing certain constructions of
spontaneous supersymmetry breaking into cascades, potentially leading to
instabilities.Comment: 29 pages, a few typos fixed, improved discussion, added figure; now
there is 1 figur
Anisotropic Spin Diffusion in Trapped Boltzmann Gases
Recent experiments in a mixture of two hyperfine states of trapped Bose gases
show behavior analogous to a spin-1/2 system, including transverse spin waves
and other familiar Leggett-Rice-type effects. We have derived the kinetic
equations applicable to these systems, including the spin dependence of
interparticle interactions in the collision integral, and have solved for
spin-wave frequencies and longitudinal and transverse diffusion constants in
the Boltzmann limit. We find that, while the transverse and longitudinal
collision times for trapped Fermi gases are identical, the Bose gas shows
diffusion anisotropy. Moreover, the lack of spin isotropy in the interactions
leads to the non-conservation of transverse spin, which in turn has novel
effects on the hydrodynamic modes.Comment: 10 pages, 4 figures; submitted to PR
Soft branes in supersymmetry-breaking backgrounds
We revisit the analysis of effective field theories resulting from
non-supersymmetric perturbations to supersymmetric flux compactifications of
the type-IIB superstring with an eye towards those resulting from the
backreaction of a small number of anti-D3-branes. Independently of the
background, we show that the low-energy Lagrangian describing the fluctuations
of a stack of probe D3-branes exhibits soft supersymmetry breaking, despite
perturbations to marginal operators that were not fully considered in some
previous treatments. We take this as an indication that the breaking of
supersymmetry by anti-D3-branes or other sources may be spontaneous rather than
explicit. In support of this, we consider the action of an anti-D3-brane
probing an otherwise supersymmetric configuration and identify a candidate for
the corresponding goldstino.Comment: 36+5 pages. References added, minor typos correcte
Cooperative Electronic and Structural Regulation in a Bioinspired Allosteric Photoredox Catalyst
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