23,226 research outputs found
Burrowing apparatus
A soil burrowing mole is described in which a housing has an auger blade wound around a front portion. This portion is rotatable about a housing longitudinal axis relative to an externally finned housing rear portion upon operation of driving means to cause an advance through soil and the like. The housing carries a sensor sensitive to deviation from a predetermined path and to which is coupled means for steering the housing to maintain the path
Better bound on the exponent of the radius of the multipartite separable ball
We show that for an m-qubit quantum system, there is a ball of radius
asymptotically approaching kappa 2^{-gamma m} in Frobenius norm, centered at
the identity matrix, of separable (unentangled) positive semidefinite matrices,
for an exponent gamma = (1/2)((ln 3/ln 2) - 1), roughly .29248125. This is much
smaller in magnitude than the best previously known exponent, from our earlier
work, of 1/2. For normalized m-qubit states, we get a separable ball of radius
sqrt(3^(m+1)/(3^m+3)) * 2^{-(1 + \gamma)m}, i.e. sqrt{3^{m+1}/(3^m+3)}\times
6^{-m/2} (note that \kappa = \sqrt{3}), compared to the previous 2 * 2^{-3m/2}.
This implies that with parameters realistic for current experiments, NMR with
standard pseudopure-state preparation techniques can access only unentangled
states if 36 qubits or fewer are used (compared to 23 qubits via our earlier
results). We also obtain an improved exponent for m-partite systems of fixed
local dimension d_0, although approaching our earlier exponent as d_0
approaches infinity.Comment: 30 pp doublespaced, latex/revtex, v2 added discussion of Szarek's
upper bound, and reference to work of Vidal, v3 fixed some errors (no effect
on results), v4 involves major changes leading to an improved constant, same
exponent, and adds references to and discussion of Szarek's work showing that
exponent is essentially optimal for qubit case, and Hildebrand's alternative
derivation for qubit case. To appear in PR
On Exact Superpotentials, Free Energies and Matrix Models
We discuss exact results for the full nonperturbative effective
superpotentials of four dimensional supersymmetric U(N) gauge
theories with additional chiral superfield in the adjoint representation and
the free energies of the related zero dimensional bosonic matrix models with
polynomial potentials in the planar limit using the Dijkgraaf-Vafa matrix model
prescription and integrating in and out. The exact effective superpotentials
are produced including the leading Veneziano-Yankielowicz term directly from
the matrix models. We also discuss how to use integrating in and out as a tool
to do random matrix integrals in the large limit.Comment: 14 pages; v2: typos corrected; v3: the scheme for computing exact
superpotentials including both the Veneziano-Yankielowicz term and all
instanton corrections directly using matrix models is emphasized and
references added, to appear in JHE
Properties of Intercalated 2H-NbSe2, 4Hb-TaS2 and 1T-TaS2
The layered compounds 2H-NbSe, 24Hb-TaS, 2and 1T-TaS2 have been intercalated with organic molecules; and the resulting crystal structure, heat capacity, conductivity, and superconductivity have been studied. The coordination in the disulfide layers was found to be unchanged in the product phase. Resistance minima appear and the superconducting transition temperature is reduced in the NbSe2 complex. Conversely, superconductivity is induced in the 4Hb-TaS2 complex. Corresponding evidence of a large change of the density of states, negative for 2H-NbSe2 and positive for 4Hb-TaS2, was also observed upon intercalation. The transport properties of all the intercalation complexes show a pronounced dependence upon the coordination of the transition metal
Conditions for CP-Violation in the General Two-Higgs-Doublet Model
The most general Higgs potential of the two-Higgs-doublet model (2HDM)
contains three squared-mass parameters and seven quartic self-coupling
parameters. Among these, one squared-mass parameter and three quartic coupling
parameters are potentially complex. The Higgs potential explicitly violates CP
symmetry if and only if no choice of basis exists in the two-dimensional Higgs
``flavor'' space in which all the Higgs potential parameters are real. We
exhibit four independent potentially complex invariant (basis-independent)
combinations of mass and coupling parameters and show that the reality of all
four invariants provides the necessary and sufficient conditions for an
explicitly CP-conserving 2HDM scalar potential. Additional potentially complex
invariants can be constructed that depend on the Higgs field vacuum expectation
values (vevs). We demonstrate how these can be used together with the
vev-independent invariants to distinguish between explicit and spontaneous
CP-violation in the Higgs sector.Comment: 46 pages, minor typographical errors corrected, accepted for
publication in Phys. Rev.
White mold
White mold, caused by the fungus Sclerotinia (Whetzelinia) sclerotiorum, is distributed worldwide and has more than 300 hosts. It infects flowers, cotyledons, seeds, leaves, or injured plant tissue. The disease can be controlled by crop rotation, flooding, reduced seeding rates, fewer irrigations, and destruction of bean- cull screenings containing sclerotia. Other control measures include chemical products in the middle of the flowering period, modifying plant architecture, and using resistant var. Many soil microorganisms are associated with sclerotia and may cause them to degrade or fail to germinate. The symptoms and damage caused by the disease are illustrated in color. (CIAT)El moho blanco causado por el hongo Sclerotinia (Whetzelinia) sclerotiorum se halla presente en todo el mundo, con mas de 300 plantas hospedantes del patogeno; infecta las flores, cotiledones, semillas, hojas o tejido lesionado. El control de la enfermedad se puede hacer por rotacion de cultivos, inundacion del terreno, menos riego y destruccion de residuos con esclerocios y utilizacion de menor cantidad de semilla en la siembra. Otras medidas de control incluyen la aplicacion de productos quimicos a mediados de la floracion, la modificacion de la arquitectura de la planta y la utilizacion de var. resistentes. Muchos microorganismos del suelo se asocian con los esclerocios y pueden causar degradacion e impedir que estos germinen. Se ilustran a color los sintomas y danos causados por la enfermedad. (CIAT
El moho blanco
White mold, caused by the fungus Sclerotinia (Whetzelinia) sclerotiorum, is distributed worldwide and has more than 300 hosts. It infects flowers, cotyledons, seeds, leaves or injured plant tissue. The disease can be controlled by crop rotation, flooding, reduced seeding rates, application of chemical products in the middle of the flowering period, modifying plant architecture and the use of resistant var. Many soil microorganisms are associated with sclerotia and may cause them to degrade or fan to germinate. The symptoms and damage caused by the disease are illustrated in color. (CIAT)El moho blanco causado por el hongo Sclerotinia (Whetzelinia) sclerotiorum se halla presente en todo el mundo y mas de 300 plantas son hospedantes del patogeno; infecta las flores, cotiledones, semillas, hojas o tejido herido. El control de la enfermedad se puede hacer por: rotacion de cultivos, inundacion del terreno, utilizacion de menor cantidad de semilla en la siembra, aplicacion de productos quimicos a mediados de la floracion, modificando la arquitectura de la planta y utilizando var resistentes; muchos microorganismos del suelo estan asociados con los esclerosios y pueden causar degradacion e impedir que estos germinen. Se ilustran en color los sintomas y danos causados por la enfermedad. (CIAT
The unreasonable effectiveness of equilibrium-like theory for interpreting non-equilibrium experiments
There has been great interest in applying the results of statistical
mechanics to single molecule experiements. Recent work has highlighted
so-called non-equilibrium work-energy relations and Fluctuation Theorems which
take on an equilibrium-like (time independent) form. Here I give a very simple
heuristic example where an equilibrium result (the barometric law for colloidal
particles) arises from theory describing the {\em thermodynamically}
non-equilibrium phenomenon of a single colloidal particle falling through
solution due to gravity. This simple result arises from the fact that the
particle, even while falling, is in {\em mechanical} equilibrium (gravitational
force equal the viscous drag force) at every instant. The results are
generalized by appeal to the central limit theorem. The resulting time
independent equations that hold for thermodynamically non-equilibrium (and even
non-stationary) processes offer great possibilities for rapid determination of
thermodynamic parameters from single molecule experiments.Comment: 6 page
EC1231 Managing the Home Orchard
Extension circular 1231 is about managing the home orchard
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