Accuracy and Responsiveness of CPU Sharing Using Xen's Cap Values

The accuracy and responsiveness of the Xen CPU Scheduler is evaluated using the "cap value" mechanism provided by Xen. The goal of the evaluation is to determine whether state-of-the-art virtualization technology, and in particular Xen, enables CPU sharing that is sufficiently accurate and responsive for the purpose of enabling "flexible resource allocations" in virtualized cluster environments

Constraining the Origin of Local Positrons with HAWC TeV Gamma-Ray Observations of Two Nearby Pulsar Wind Nebulae

The HAWC Gamma-Ray Observatory has reported the discovery of TeV gamma-ray emission extending several degrees around the positions of Geminga and B0656+14 pulsars. Assuming these gamma rays are produced by inverse Compton scattering off low-energy photons in electron halos around the pulsars, we determine the diffusion of electrons and positrons in the local interstellar medium. We will present the morphological and spectral studies of these two VHE gamma-ray sources and the derived positron spectrum at Earth.Comment: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contribution

Statistical Modeling of Resource Availability in Desktop Grids

Desktop grids are compute platforms that aggregate and harvest the idle CPU cycles of individually owned personal computers and workstations. A challenge for using these platforms is that the compute resources are volatile. Due to this volatility the vast majority of desktop grid applications are embarrassingly parallel and high-throughput. Deeper understanding of the nature of resource availability is needed to enable the use of desktop grids for a broader class of applications. In this document we further this understanding thanks to statistical analysis of availability traces collected on real-world desktop grid platforms

Resource Allocation using Virtual Clusters

In this report we demonstrate the utility of resource allocations that use virtual machine technology for sharing parallel computing resources among competing users. We formalize the resource allocation problem with a number of underlying assumptions, determine its complexity, propose several heuristic algorithms to find near-optimal solutions, and evaluate these algorithms in simulation. We find that among our algorithms one is very efficient and also leads to the best resource allocations. We then describe how our approach can be made more general by removing several of the underlying assumptions

Alexander-Conway polynomial state model and link homology

This paper shows how the Formal Knot Theory state model for the Alexander-Conway polynomial is related to Knot Floer Homology. In particular we prove a parity result about the states in this model that clarifies certain relationships of the model with Knot Floer Homology.Ministerio de Ciencia e InnovaciónJunta de Andalucía (Consejería de Innovación, Ciencia y Empresa)Fondo Europeo de Desarrollo Regiona

Biological activity of glucosinolate derived compounds isolated from seed meal of Brassica crops and evaluated as plant and food protection agents

Glucosinolates are amino acid derived allelochemicals characteristic of plants of the order Capparales. These compounds are present in seeds of agriculturally common Brassica crops in varying quantities depending on the species (ref). The use of the remaining seed cake after oil extraction has traditionally been limited by the concentration of these compounds. However, the extraction of glucosinolates from seed meal is nowadays possible and it further contributes to an increased quality of the seed meal for feed (Sørensen et al., this conference). Glucosinolates are hydrolysed by endogenous enzymes (myrosinases; EC 3.2.1.147) and a number of compounds are produced depending on the parent glucosinolate and the environmental conditions.1 Among these compounds, oxazolidine-2-thiones are known for their antinutritional effects on monogastric animals, whereas isothiocyanates are fungicidal, nematocidal and herbicidal.2,3 The possibility for using glucosinolates as precursors for environmental friendly biocides therefore exists, which could contribute to increase the value of the Brassica seed meal

Modeling the gamma-ray emission produced by runaway cosmic rays in the environment of RX J1713.7-3946

Diffusive shock acceleration in supernova remnants is the most widely invoked paradigm to explain the Galactic cosmic ray spectrum. Cosmic rays escaping supernova remnants diffuse in the interstellar medium and collide with the ambient atomic and molecular gas. From such collisions gamma-rays are created, which can possibly provide the first evidence of a parent population of runaway cosmic rays. We present model predictions for the GeV to TeV gamma-ray emission produced by the collisions of runaway cosmic rays with the gas in the environment surrounding the shell-type supernova remnant RX J1713.7-3946. The spectral and spatial distributions of the emission, which depend upon the source age, the source injection history, the diffusion regime and the distribution of the ambient gas, as mapped by the LAB and NANTEN surveys, are studied in detail. In particular, we find for the region surrounding RX J1713-3946, that depending on the energy one is observing at, one may observe startlingly different spectra or may not detect any enhanced emission with respect to the diffuse emission contributed by background cosmic rays. This result has important implications for current and future gamma-ray experiments.Comment: version published on PAS

Molecular Clouds as Cosmic-Ray Barometers

The advent of high sensitivity, high resolution gamma-ray detectors, together with a knowledge of the distribution of the atomic hydrogen and especially of the molecular hydrogen in the Galaxy on sub-degree scales creates a unique opportunity to explore the flux of cosmic rays in the Galaxy. We here present the new data on the distribution of the molecular hydrogen from a large region of the inner Galaxy obtained by the NANTEN Collaboration. We then introduce a methodology which aims to provide a test bed for current and future gamma-ray observatories to explore the cosmic ray flux at various positions in our Galaxy. In particular, for a distribution of molecular clouds, as provided by the NANTEN survey, and local cosmic ray density as measured at the Earth, we estimate the expected GeV to TeV gamma-ray signal, which can then be compared with observations and use to test the cosmic ray flux.Comment: PASJ (in press