5,160 research outputs found
Study of Giant Pairing Vibrations with neutron-rich nuclei
We investigate the possible signature of the presence of giant pairing states
at excitation energy of about 10 MeV via two-particle transfer reactions
induced by neutron-rich weakly-bound projectiles. Performing particle-particle
RPA calculations on Pb and BCS+RPA calculations on Sn, we
obtain the pairing strength distribution for two particles addition and removal
modes. Estimates of two-particle transfer cross sections can be obtained in the
framework of the 'macroscopic model'. The weak-binding nature of the projectile
kinematically favours transitions to high-lying states. In the case of (~^6He,
\~^4He) reaction we predict a population of the Giant Pairing Vibration with
cross sections of the order of a millibarn, dominating over the mismatched
transition to the ground state.Comment: Talk presented in occasion of the VII School-Semina r on Heavy Ion
Physics hosted by the Flerov Laboratory (FLNR/JINR) Dubna, Russia from May 27
to June 2, 200
Middle Convolution and Harnad Duality
We interpret the additive middle convolution operation in terms of the Harnad
duality, and as an application, generalize the operation to have a
multi-parameter and act on irregular singular systems.Comment: 50 pages; v2: Submitted version once revised according to referees'
comment
Adaptive latitudinal variation in Common Blackbird Turdus merula nest characteristics
Nest construction is taxonomically widespread, yet our understanding of adaptive
intraspecific variation in nest design remains poor. Nest characteristics are
expected to vary adaptively in response to predictable variation in spring temperatures
over large spatial scales, yet such variation in nest design remains largely
overlooked, particularly amongst open-cup-nesting birds. Here, we systematically
examined the effects of latitudinal variation in spring temperatures and precipitation
on the morphology, volume, composition, and insulatory properties of
open-cup-nesting Common Blackbirds’ Turdus merula nests to test the hypothesis
that birds living in cooler environments at more northerly latitudes would build
better insulated nests than conspecifics living in warmer environments at more
southerly latitudes. As spring temperatures increased with decreasing latitude, the
external diameter of nests decreased. However, as nest wall thickness also
decreased, there was no variation in the diameter of the internal nest cups. Only
the mass of dry grasses within nests decreased with warmer temperatures at lower
latitudes. The insulatory properties of nests declined with warmer temperatures at
lower latitudes and nests containing greater amounts of dry grasses had higher insulatory
properties. The insulatory properties of nests decreased with warmer temperatures
at lower latitudes, via changes in morphology (wall thickness) and
composition (dry grasses). Meanwhile, spring precipitation did not vary with latitude,
and none of the nest characteristics varied with spring precipitation. This suggests
that Common Blackbirds nesting at higher latitudes were building nests with
thicker walls in order to counteract the cooler temperatures. We have provided evidence
that the nest construction behavior of open-cup-nesting birds systematically
varies in response to large-scale spatial variation in spring temperatures
Torsion pairs and rigid objects in tubes
We classify the torsion pairs in a tube category and show that they are in
bijection with maximal rigid objects in the extension of the tube category
containing the Pruefer and adic modules. We show that the annulus geometric
model for the tube category can be extended to the larger category and
interpret torsion pairs, maximal rigid objects and the bijection between them
geometrically. We also give a similar geometric description in the case of the
linear orientation of a Dynkin quiver of type A.Comment: 25 pages, 13 figures. Paper shortened. Minor errors correcte
Sheaves on fibered threefolds and quiver sheaves
This paper classifies a class of holomorphic D-branes, closely related to
framed torsion-free sheaves, on threefolds fibered in resolved ADE surfaces
over a general curve C, in terms of representations with relations of a twisted
Kronheimer--Nakajima-type quiver in the category Coh(C) of coherent sheaves on
C. For the local Calabi--Yau case C\cong\A^1 and special choice of framing, one
recovers the N=1 ADE quiver studied by Cachazo--Katz--Vafa.Comment: 13 pages, 2 figures, minor change
Morse theory of the moment map for representations of quivers
The results of this paper concern the Morse theory of the norm-square of the
moment map on the space of representations of a quiver. We show that the
gradient flow of this function converges, and that the Morse stratification
induced by the gradient flow co-incides with the Harder-Narasimhan
stratification from algebraic geometry. Moreover, the limit of the gradient
flow is isomorphic to the graded object of the
Harder-Narasimhan-Jordan-H\"older filtration associated to the initial
conditions for the flow. With a view towards applications to Nakajima quiver
varieties we construct explicit local co-ordinates around the Morse strata and
(under a technical hypothesis on the stability parameter) describe the negative
normal space to the critical sets. Finally, we observe that the usual Kirwan
surjectivity theorems in rational cohomology and integral K-theory carry over
to this non-compact setting, and that these theorems generalize to certain
equivariant contexts.Comment: 48 pages, small revisions from previous version based on referee's
comments. To appear in Geometriae Dedicat
Tree modules and counting polynomials
We give a formula for counting tree modules for the quiver S_g with g loops
and one vertex in terms of tree modules on its universal cover. This formula,
along with work of Helleloid and Rodriguez-Villegas, is used to show that the
number of d-dimensional tree modules for S_g is polynomial in g with the same
degree and leading coefficient as the counting polynomial A_{S_g}(d, q) for
absolutely indecomposables over F_q, evaluated at q=1.Comment: 11 pages, comments welcomed, v2: improvements in exposition and some
details added to last sectio
Assessment of Stormflow and Water Quality from Undisturbed and Site Prepared Forest Land in East Texas (Final Report)
In 1979, nine small forested watersheds were instrumented in East Texas to determine the effect of intensive forest management practices
On water quantity and quality. Three replications of three treatments were used: 1) clearcutting - followed by shearing and windrowing, 2) clearcutting - followed by roller chopping and 3) undisturbed control. Following treatment, the sheared and windrowed sites exposed 57% of the surface soil compared to 16% for the chopped watersheds. During 1981, the first year after treatment, stormflow volumes increased with the intensity of the site disturbance. Sites sheared produced the greatest amount of stormflow (5.76 inches), followed by chopped (3.26 inches) and the undisturbed watersheds (1.03 inches). Stormflow volumes decreased 66% and 57% on the sheared and chopped watersheds the second year following treatment. Sediment losses were significantly higher on the sheared watersheds (2,620 lb/acre) than the chopped (22 lb/acre), during 1981. By the fall of 1982, the exposure of mineral soil on the sheared sites dropped to 20% and to 4% on the chopped sites. For this reason and the lower volume of runoff, sediment loss for 1982 dropped to 71.3, 4.9 and 4.5 lb/acre for the sheared, chopped and undisturbed watersheds, respectively.
Nitrate concentrations were significantly different between treatments during 1981: Sheared - 205 ppb, chopped - 96 ppb and control 10 ppb. During 1982, although nitrate concentrations were lower, the sheared watershed still had a significantly higher concentration. Total nitrogen concentration on the sheared sites was 2,155 ppb, which was significantly higher than the chopped (999 ppb) or the control sites (996 ppb) for 1981. The first year total nitrogen export from the sheared sites (2.79 lb/acre) was 3.5 times greater than the chopped loss (0.76 lb/acre) and 12 times greater than the loss on the control sites (0.24 lb/acre). The second year following treatment, total nitrogen concentrations were not significantly different and total nitrogen loss on the sheared areas was less than half of the loss recorded from the control sites during 1981. Total phosphorus concentrations for 1981 were 221, 85 and 54 ppb for the sheared, chopped and control watersheds, respectively. Total phosphorus loss for this period was only 0.297 lb/acre from the sheared treatments, but was significantly higher than the chopped or undisturbed treatments. A drop in sediment concentrations and runoff in 1982 reduced phosphorus losses on the sheared watersheds by over 90%. Calcium, potassium and sodium concentrations during 1981, were highest for the chopped treatments, while magnesium concentrations were highest on the sheared treatments. Export of these elements was greatest from the sheared sites, except for calcium, which was lost in greater quantities on the chopped sites. During 1982 there was no significant difference between treatments for Ca, Mg, K and Na concentrations.
The rapid revegetation and reduction in exposed mineral soil that occurred on both sheared and chopped treatments during 1982, resulted in a decrease in runoff and sediment and nutrient losses. As the stabilization of sites continues, treatment differences should diminish. Limiting shearing and windrowing activities to the more gentle slopes will reduce first year erosion and prevent increases in sediment and nutrient losses. Roller chopping on the other hand, appears to cause only minor changes to water yield and quality on slopes of up to 25%
Supplement 19, Part 2, Parasite-Subject Catalogue: Parasites: Protozoa
United States Department of Agriculture, Bureau of Animal Industry, Animal Parasitology Institute, Agricultural Research Servic
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