711 research outputs found
Absolutely continuous spectrum for the isotropic Maxwell operator with coefficients that are periodic in some directions and decay in others
The purpose of this paper is to prove that the spectrum of an isotropic
Maxwell operator with electric permittivity and magnetic permeability that are
periodic along certain directions and tending to a constant super-exponentially
fast in the remaining directions is purely absolutely continuous. The basic
technical tools is a new ``operatorial'' identity relating the Maxwell operator
to a vector-valued Schrodinger operator. The analysis of the spectrum of that
operator is then handled using ideas developed by the same authors in a
previous paper
Wegner estimate for discrete alloy-type models
We study discrete alloy-type random Schr\"odinger operators on
. Wegner estimates are bounds on the average number of
eigenvalues in an energy interval of finite box restrictions of these types of
operators. If the single site potential is compactly supported and the
distribution of the coupling constant is of bounded variation a Wegner estimate
holds. The bound is polynomial in the volume of the box and thus applicable as
an ingredient for a localisation proof via multiscale analysis.Comment: Accepted for publication in AHP. For an earlier version see
http://www.ma.utexas.edu/mp_arc-bin/mpa?yn=09-10
Further genetic heterogeneity for autosomal dominant human sutural cataracts
A unique sutural cataract was observed in a 4-generation German family to be transmitted as an isolated autosomal, dominant trait. Since mutations in the gamma-crystallin encoding CRYG genes have previously been demonstrated to be the most frequent reason for isolated congenital cataracts, all 4 active CRYG genes have been sequenced. A single base-pair change in the CRYGA gene has been shown, leading to a premature stop codon. This was not observed in 170 control individuals. However, it did not segregate with the disease phenotype. This is the first truncating mutation in an active CRYG gene without a dominant phenotype. As the CRYGA mutation did not explain the cataract, several other candidate loci (CCV, GJA8, CRYBB2, BFSP2, MIP, GJA8, central pouch-like, CRYBA1) were investigated by micro-satellite markers and linkage analysis, but they were excluded based on the combination of haplotype analysis and two-point linkage analysis. The phenotype in this family is due to a mutation in another sutural cataract gene yet to be identified
Low lying spectrum of weak-disorder quantum waveguides
We study the low-lying spectrum of the Dirichlet Laplace operator on a
randomly wiggled strip. More precisely, our results are formulated in terms of
the eigenvalues of finite segment approximations of the infinite waveguide.
Under appropriate weak-disorder assumptions we obtain deterministic and
probabilistic bounds on the position of the lowest eigenvalue. A Combes-Thomas
argument allows us to obtain so-called 'initial length scale decay estimates'
at they are used in the proof of spectral localization using the multiscale
analysis.Comment: Accepted for publication in Journal of Statistical Physics
http://www.springerlink.com/content/0022-471
Untersuchungen und Prozessbegleitung zur Praxiseinführung von Heißwassertauchanlagen im ökologischen Kernobstanbau
In general, organic grown apples (Malus x domestica Borkh.) are not treated with chemical fungicides to prevent storage decay and these fruits may suffer up to 30% decay during storage. Preliminary experiments had shown that hot water dipping of apples may be an alternative. To inhibit Gloeosporium rot (Pezicula alba, P. malicortis) water temperature may be of about 50°C and dipping time from 60 sec up to 180 sec. The present investigation was conducted to test different ranges of temperatures and dipping time periods in different apple cultivars over a three year investigation. The objective was to determinate the suitable hot water treatment that prevents decay incidence and maintains fruit quality (firmness, scale symptoms). For the reduction of post harvest decay the treatment 53°C and 180 sec is recommended; that was found suitable for `Topaz`. For cultivars with a sensitivity to skin disorders dips for 120 sec or 180 sec are recommended; that was found best for ´Elstar´(51°C), ´Ingrid Marie` (49°C), ´Holsteiner Cox´(51°C) und ´Boskoop´(51°C). A big box dipping machine was invented in northern Germany to improve the situation on the farms. The parameters we found in the trails were used as standards on the developing side. Today’s ma-chine runs with a precision temperature range of one K inside the box
Decorrelation estimates for the eigenlevels of the discrete Anderson model in the localized regime
The purpose of the present work is to establish decorrelation estimates for
the locally renormalized eigenvalues of the discrete Anderson model near two
distinct energies inside the localization region. In dimension one, we prove
these estimates at all energies. In higher dimensions, the energies are
required to be sufficiently far apart from each other
Insights in nutrition programs for the developing ruminant
As the world population grows and resources for food animal production become more limited, animal efficiency must increase. The dairy industry has made progress in reducing age at first calving from 27 to 25 mo., but heifers remain unproductive for over half of their life while still consuming resources. As pre-ruminants, offering restricted amounts of milk to neonatal heifers (conventional system) increases concentrate consumption which drives rumen development. However, accelerated milk programs improve pre-weaning growth rate and the balance between these two systems is still under continuous investigation. Solid feed is important for papillary and musculature development in addition to establishment of a microbial population, which increase transition success when calves are weaned gradually. Furthermore, the optimal target weight for calving is 550 kg at 23 to 24.5 mo., which increases 305-d lactation yield. Increased milk production is desired, but a costly rearing period without producing milk only increases as age at first calving increases, which also increases total number of replacement heifers and total herd green-house emissions. Strategies to achieve desired body weight and age at first calving while reducing input include, using compensatory growth, restricting intake and precision feeding. Compensatory growth can increase average daily gain and feed efficiency; moreover, precision feeding increases feed efficiency even further by reducing nutrient metabolic costs in comparison to ad- libitum systems. Restricting intake provides increased rumen retention time for fiber, non-structural carbohydrates, protein, and other nutrients to be highly digested. Nutrient digestibility is important when comparing these feeding methods because dry matter intake has the greatest impact on efficiency, specifically when different amounts of forages are fed. Using different strategies during the weaning, pre-pubertal and post-pubertal period of dairy heifers can significantly improve performance, nutrient and resources utilization during this conditioning growing phase of dairy cattle.A medida que la población mundial crece y los alimentos se vuelven más limitados, la eficiencia animal debe aumentar. La industria láctea ha progresado en la reducción de la edad al primer parto de 27 a 25 meses, pero las vaquillas siguen siendo improductivas durante más de la mitad de su vida mientras consumen recursos. Como pre-rumiantes, ofrecer cantidades restringidas de leche a las vaquillas neonatales (sistema convencional) aumenta el consumo de concentrado, lo que impulsa el desarrollo del rumen. Sin embargo, los programas acelerados de leche mejoran la tasa de crecimiento previo al destete y el equilibrio entre estos dos sistemas aún está bajo investigación continua. La alimentación sólida es importante para el desarrollo papilar y la musculatura, además del establecimiento de una población microbiana, que aumenta el éxito de la transición cuando los terneros se destetan gradualmente. El peso objetivo para el parto es 550 kg de 23 a 24.5 meses, lo que aumenta el rendimiento de lactancia de 305 días. Si no se reduce el periodo de cría, aumenta el número de vaquillas de reemplazo y las emisiones totales de gases invernadero. Las estrategias para lograr el peso corporal y la edad deseados al primer parto al tiempo que se reducen los insumos incluyen el uso de crecimiento compensatorio, la restricción de la ingesta y la alimentación de precisión. El crecimiento compensatorio puede aumentar la ganancia diaria promedio y la eficiencia alimenticia; Además, la alimentación de precisión aumenta aún más la eficiencia alimenticia al reducir los costos metabólicos de los nutrientes en comparación con los sistemas ad-libitum. La ingesta restringida proporciona un mayor tiempo de retención del rumen para que la fibra, los carbohidratos no estructurales, las proteínas y otros nutrientes sean altamente digeridos
New characterizations of the region of complete localization for random Schr\"odinger operators
We study the region of complete localization in a class of random operators
which includes random Schr\"odinger operators with Anderson-type potentials and
classical wave operators in random media, as well as the Anderson tight-binding
model. We establish new characterizations or criteria for this region of
complete localization, given either by the decay of eigenfunction correlations
or by the decay of Fermi projections. (These are necessary and sufficient
conditions for the random operator to exhibit complete localization in this
energy region.) Using the first type of characterization we prove that in the
region of complete localization the random operator has eigenvalues with finite
multiplicity
Periodic Jacobi operator with finitely supported perturbation on the half-lattice
We consider the periodic Jacobi operator with finitely supported
perturbations on the half-lattice. We describe all eigenvalues and resonances
of and give their properties. We solve the inverse resonance problem: we
prove that the mapping from finitely supported perturbations to the Jost
functions is one-to-one and onto, we show how the Jost functions can be
reconstructed from the eigenvalues, resonances and the set of zeros of
S(\l)-1, where S(\l) is the scattering matrix.Comment: 29 page
The influence of transition metal solutes on dislocation core structure and values of Peierls stress and barrier in tungsten
Several transition metals were examined to evaluate their potential for
improving the ductility of tungsten. The dislocation core structure and Peierls
stress and barrier of screw dislocations in binary
tungsten-transition metal alloys (WTM) were investigated using
first principles electronic structure calculations. The periodic quadrupole
approach was applied to model the structure of dislocation. Alloying
with transition metals was modeled using the virtual crystal approximation and
the applicability of this approach was assessed by calculating the equilibrium
lattice parameter and elastic constants of the tungsten alloys. Reasonable
agreement was obtained with experimental data and with results obtained from
the conventional supercell approach. Increasing the concentration of a
transition metal from the VIIIA group, i.e. the elements in columns headed by
Fe, Co and Ni, leads to reduction of the elastic constant and
increase of elastic anisotropy A=. Alloying W with a group
VIIIA transition metal changes the structure of the dislocation core from
symmetric to asymmetric, similar to results obtained for WRe
alloys in the earlier work of Romaner {\it et al} (Phys. Rev. Lett. 104, 195503
(2010))\comments{\cite{WRECORE}}. In addition to a change in the core symmetry,
the values of the Peierls stress and barrier are reduced. The latter effect
could lead to increased ductility in a tungsten-based
alloy\comments{\cite{WRECORE}}. Our results demonstrate that alloying with any
of the transition metals from the VIIIA group should have similar effect as
alloying with Re.Comment: 12 pages, 8 figures, 3 table
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