Energy dependence of fission-fragment neutron multiplicity in 235U(n,f)^{235}\textrm{U}(n,f)

A consistent framework for treating the energy dependence of fission-fragment neutron multiplicities is presented. The shape evolution of the compound nucleus towards scission is treated in the strong damping limit using the Metropolis walk method. The available excitation energy at scission is then divided statistically between the two fragments using microscopic level densities. Deformation energies, which contribute to the excitation energy when the fragments relax to their ground-state shapes, are also computed. From the total fragment excitation energies, the number of emitted neutrons is obtained and illustrated for neutron-induced fission of $^{235}\textrm{U}$.Comment: 8 pages, 4 figures, Proceeding of the XXV Nuclear Physics Workshop, Kazimierz, Poland, 2018; minor typos correcte

Holistic debugging - enabling instruction set simulation for software quality assurance

We present holistic debugging, a novel method for observing execution of complex and distributed software. It builds on an instruction set simulator, which provides reproducible experiments and non-intrusive probing of state in a distributed system. Instruction set simulators, however, only provide low-level information, so a holistic debugger contains a translation framework that maps this information to higher abstraction level observation tools, such as source code debuggers. We have created Nornir, a proof-of-concept holistic debugger, built on the simulator Simics. For each observed process in the simulated system, Nornir creates an abstraction translation stack, with virtual machine translators that map machine-level storage contents (e.g. physical memory, registers) provided by Simics, to application-level data (e.g. virtual memory contents) by parsing the data structures of operating systems and virtual machines. Nornir includes a modified version of the GNU debugger (GDB), which supports non-intrusive symbolic debugging of distributed applications. Nornir's main interface is a debugger shepherd, a programmable interface that controls multiple debuggers, and allows users to coherently inspect the entire state of heterogeneous, distributed applications. It provides a robust observation platform for construction of new observation tools

Weed problems and possibilities for their control in salix for biomass

Salix is a dedicated arable bioenergy crop that is presently grown on 12,000 ha in Sweden. It has probably the best environmental profile among the arable bioenergy crops grown in Sweden partly because neither fungicides nor insecticides are used in the production. However, herbicides are used routinely, because salix plants are very sensitive, especially during the first growing season, to competition from weeds. Hence, to improve the environmental profile of salix even further, alternative weed control methods that complement or for substitute the use of herbicides are desired. Some of these alternatives might be to improve the mechanical weeding techniques, using cover crops, applying herbicides more accurately or to breed for weed competitiveness. The purpose of this introductory paper is therefore to review what is known about weeds in relation to biomass salix. To put this subject into context there will first be a general overview of salix and the current production system

N=1 supersymmetric sigma model with boundaries, I

We study an N=1 two-dimensional non-linear sigma model with boundaries representing, e.g., a gauge fixed open string. We describe the full set of boundary conditions compatible with N=1 superconformal symmetry. The problem is analyzed in two different ways: by studying requirements for invariance of the action, and by studying the conserved supercurrent. We present the target space interpretation of these results, and identify the appearance of partially integrable almost product structures.Comment: 24 pages, LaTeX. v2: minor clarification in section 3.2, reference added. v3: section added on N=2 supersymmetry. v4: typos corrected, published versio

On the Poisson-Lie T-plurality of boundary conditions

Conditions for the gluing matrix defining consistent boundary conditions of two-dimensional nonlinear sigma-models are analyzed and reformulated. Transformation properties of the right-invariant fields under Poisson-Lie T-plurality are used to derive a formula for the transformation of the boundary conditions. Examples of transformation of D-branes in two and three dimensions are presented. We investigate obstacles arising in this procedure and propose possible solutions.Comment: 25 pages, LaTeX; major revision, discussion of boundary fields added; author's version of the published pape

Worldsheet boundary conditions in Poisson-Lie T-duality

We apply canonical Poisson-Lie T-duality transformations to bosonic open string worldsheet boundary conditions, showing that the form of these conditions is invariant at the classical level, and therefore they are compatible with Poisson-Lie T-duality. In particular the conditions for conformal invariance are automatically preserved, rendering also the dual model conformal. The boundary conditions are defined in terms of a gluing matrix which encodes the properties of D-branes, and we derive the duality map for this matrix. We demonstrate explicitly the implications of this map for D-branes in two non-Abelian Drinfel'd doubles.Comment: 20 pages, Latex; v2: typos and wording corrected, references added; v3: three-dimensional example added, reference added, discussion clarified, published versio

E8 Quiver Gauge Theory and Mirror Symmetry

We show that the Higgs branch of a four-dimensional Yang-Mills theory, with gauge and matter content summarised by an E_8 quiver diagram, is identical to the generalised Coulomb branch of a four-dimensional superconformal strongly coupled gauge theory with E_8 global symmetry. This is the final step in showing that there is a Higgs-Coulomb identity of this kind for each of the cases {0}, A_1, A_2, D_4, E_6, E_7 and E_8. This series of equivalences suggests the existence of a mirror symmetry between the quiver theories and the strongly coupled theories. We also discuss how to interpret the parameters of the quiver gauge theory in terms of the Hanany-Witten picture.Comment: 19 pages, 3 figures, references adde

Impact and control of weeds in biomass willow clones

Willow (Salix spp.) grown on arable land as short-rotation coppice (SRC) produces renewable energy in the form of woody biomass. This perennial crop has a high ratio of energy output to input and a good environmental profile. However, weed control is mostly dependent on herbicide use. Therefore, this thesis examined the possibility to further improve the environmental profile of willow SRC by omitting the use of herbicides during establishment. If genetic variation in willow competitiveness to weeds exists, more weed-competitive cultivars might be bred. However, in a study performed at three different sites in southern Sweden, only small differences were found between 12 clones tested for their ability to compete with weeds. Depending on site, weeds reduced stem biomass yield by between 68 and 94% after the first harvest cycle and increased plant mortality at all sites. The practice of cutting the first-year shoots either reduced or did not affect the ability of the willow plants to compete with weeds. Hence, this measure should be omitted provided this is compatible with other management actions. A study on the efficiency and economic returns from four different non-chemical weed control methods during willow establishment of two different cultivars showed that it is possible to establish an agriculturally and economically viable willow plantation without the use of herbicides. The most promising non-chemical weed control method involved repeated passes with a row crop cultivator equipped with torsion weeders, while the least promising method was a living clover cover crop. Yield data were obtained from the weed competition study for the willow SRC clones when subjected to thorough weeding. Cultivars Sven and Tordis were found to be among the highest yielding at all three sites, although site x clone interactions were found. However, these two clones did not yield significantly more than two more recently bred clones, Klara and Linnea, at any site. Biomass estimates from destructive and non-destructive methods have been shown to differ and the magnitude of these differences may depend on clone. A study with six different clones showed that assumptions regarding harvest height and dry matter content of clones might explain part of these differences