Prototyping Incentive-based Resource Assignment for Clouds in Community Networks

Wireless community networks are a successful example of a collective where communities operate ICT infrastructure and provide IP connectivity based on the principle of reciprocal resource sharing of network bandwidth. This sharing, however, has not extended to computing and storage resources, resulting in very few applications and services which are currently deployed within community networks. Cloud computing, as in today's Internet, has made it common to consume resources provided by public clouds providers, but such cloud infrastructures have not materialized within community networks. We analyse in this paper socio-technical characteristics of community networks in order to derive scenarios for community clouds. Based on an architecture for such a community cloud, we implement a prototype for the incentive-driven resource assignment component, deploy it in a testbed of community network nodes, and evaluate its behaviour experimentally. Our evaluation gives insight into how the deployed prototype components regulate the consumption of cloud resources taking into account the users' contributions, and how this regulation affects the system usage. Our results suggest a further integration of this regulation component into current cloud management platforms in order to open them up for the operation of an ecosystem of community cloud

Support Service for Reciprocal Computational Resource Sharing in Wireless Community Networks

In community networks, individuals and local organizations from a geographic area team up to create and run a community-owned IP network to satisfy the community's demand for ICT, such as facilitating Internet access and providing services of local interest. Most current community networks use wireless links for the node interconnection, applying off-the-shelf wireless equipment. While IP connectivity over the shared network infrastructure is successfully achieved, the deployment of applications in community networks is surprisingly low. To address the solution of this problem, we propose in this paper a service to incentivize the contribution of computing and storage as cloud resources to community networks, in order to stimulate the deployment of services and applications. Our final goal is the vision that in the long term, the users of community networks will not need to consume applications from the Internet, but find them within the wireless community network

Accessing the topological susceptibility via the Gribov horizon

The topological susceptibility, $\chi^4$, following the work of Witten and Veneziano, plays a key role in identifying the relative magnitude of the $\eta^{\prime}$ mass, the so-called $U(1)_{A}$ problem. A nonzero $\chi^4$ is caused by the Veneziano ghost, the occurrence of an unphysical massless pole in the correlation function of the topological current. In a recent paper (Phys.Rev.Lett.114 (2015) 24, 242001), an explicit relationship between this Veneziano ghost and color confinement was proposed, by connecting the dynamics of the Veneziano ghost, and thus the topological susceptibility, with Gribov copies. However, the analysis is incompatible with BRST symmetry (Phys.Rev.D 93 (2016) no.8, 085010). In this paper, we investigate the topological susceptibility, $\chi^4$, in SU(3) and SU(2) Euclidean Yang-Mills theory using an appropriate Pad\'e approximation tool and a non-perturbative gluon propagator, within a BRST invariant framework and by taking into account Gribov copies in a general linear covariant gauge.Comment: 17 pages, 4 figures. v2: corrected typos, new figures, improved style of presentatio

Entanglement, Holography and Causal Diamonds

We argue that the degrees of freedom in a d-dimensional CFT can be re-organized in an insightful way by studying observables on the moduli space of causal diamonds (or equivalently, the space of pairs of timelike separated points). This 2d-dimensional space naturally captures some of the fundamental nonlocality and causal structure inherent in the entanglement of CFT states. For any primary CFT operator, we construct an observable on this space, which is defined by smearing the associated one-point function over causal diamonds. Known examples of such quantities are the entanglement entropy of vacuum excitations and its higher spin generalizations. We show that in holographic CFTs, these observables are given by suitably defined integrals of dual bulk fields over the corresponding Ryu-Takayanagi minimal surfaces. Furthermore, we explain connections to the operator product expansion and the first law of entanglement entropy from this unifying point of view. We demonstrate that for small perturbations of the vacuum, our observables obey linear two-derivative equations of motion on the space of causal diamonds. In two dimensions, the latter is given by a product of two copies of a two-dimensional de Sitter space. For a class of universal states, we show that the entanglement entropy and its spin-three generalization obey nonlinear equations of motion with local interactions on this moduli space, which can be identified with Liouville and Toda equations, respectively. This suggests the possibility of extending the definition of our new observables beyond the linear level more generally and in such a way that they give rise to new dynamically interacting theories on the moduli space of causal diamonds. Various challenges one has to face in order to implement this idea are discussed.Comment: 84 pages, 12 figures; v2: expanded discussion on constraints in section 7, matches published versio

VERITAS Observations of Extragalactic Non-Blazars

During the 2007/2008 season, VERITAS was used for observations at E>200 GeV of several extragalactic non-blazar objects such as galaxy clusters, starburst and interacting galaxies, dwarf galaxies, and nearby galaxies. In these proceedings, we present preliminary results from our observations of dwarf galaxies and M87. Results from observation of other non-blazar sources are presented in separate papers in the proceedings.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

VERITAS Distant Laser Calibration and Atmospheric Monitoring

As a calibrated laser pulse propagates through the atmosphere, the intensity of the Rayleigh scattered light arriving at the VERITAS telescopes can be calculated precisely. This allows for absolute calibration of imaging atmospheric Cherenkov telescopes (IACT) to be simple and straightforward. In these proceedings, we present the comparison between laser data and simulation to estimate the light collection efficiencies of the VERITAS telescopes, and the analysis of multiple laser data sets taken in different months for atmospheric monitoring purpose.Comment: Submitted to Proceedings of "4th Heidelberg International Symposium on High Energy Gamma-Ray Astronomy 2008

Morphology and hardness ratio exploitation under limited statistics

Gamma-ray astronomy has produced for several years now sky maps for low photon statistics, non-negligible background and comparatively poor angular resolution. Quantifying the significance of spatial features remains difficult. Besides, spectrum extraction requires regions with large statistics while maps in energy bands allow only qualitative interpretation. The two main competing mechanisms in the VHE domain are the Inverse-Compton emission from accelerated electrons radiating through synchrotron in the X-ray domain and the interactions between accelerated hadrons and the surrounding medium, leading to the production and subsequent decay of Pi0 mesons. The spectrum of the VHE emission from leptons is predicted to steepen with increasing distance from the acceleration zone, owing to synchrotron losses (i.e. cooled population). It would remain approximately constant for hadrons. Ideally, spectro-imaging analysis would have the same spatial scale in the TeV and X-ray domains, to distinguish the local emission mechanisms. More realistically, we investigate here the possibility of improving upon the currently published HESS results by using more sophisticated tools.Comment: 4 pages, 6 figures, Proceeding for a poster at the GAMMA08 Heidelberg Symposiu

Clonal Composition of Human Adrenocortical Neoplasms

The mechanisms of tumorigenesis of adrenocortical neoplasms are still not understood. Tumor formation may be the result of spontaneous transformation of adrenocortical cells by somatic mutations. Another factor stimulating adrenocortical cell growth and potentially associated with formation of adrenal adenomas and, less frequently, carcinomas is the chronic elevation of proopiomelanocortin-derived peptides in diseases like ACTH-dependent Cushing's syndrome and congenital adrenal hyperplasia. To further investigate the pathogenesis of adrenocortical neoplasms, we studied the clonal composition of such tumors using X-chromosome inactivation analysis of the highly polymorphic region Xcen-Xp11.4 with the hybridization probe M27ß, which maps to a variable number of tandem repeats on the X-chromsome. In addition, polymerase chain reaction amplification of a phosphoglycerokinase gene polymorphism was performed. After DNA extraction from tumorous adrenal tissue and normal leukocytes in parallel, the active X-chromosome of each sample was digested with the methylation-sensitive restriction enzyme HpaII. A second digestion with an appropriate restriction enzyme revealed the polymorphism of the region Xcen-Xp11.4 and the phosphoglycerokinase locus. Whereas in normal polyclonal tissue both the paternal and maternal alleles are detected, a monoclonal tumor shows only one of the parental alleles. A total of 21 female patients with adrenal lesions were analyzed; 17 turned out to be heterozygous for at least one of the loci. Our results were as follows: diffuse (n = 4) and nodular (n = 1) adrenal hyperplasia in patients with ACTH-dependent Cushing's syndrome, polyclonal pattern; adrenocortical adenomas (n = 8), monoclonal (n = 7), as well as polyclonal (n = 1); adrenal carcinomas (n = 3), monoclonal pattern. One metastasis of an adrenocortical carcinoma showed a pattern most likely due to tumor-associated loss of methylation. In the special case of a patient with bilateral ACTH-independent macronodular hyperplasia, diffuse hyperplastic areas and a small nodule showed a polyclonal pattern, whereas a large nodule was monoclonal. We conclude that most adrenal adenomas and carcinomas are monoclonal, whereas diffuse and nodular adrenal hyperplasias are polyclonal. The clonal composition of ACTH-independent massive macronodular hyperplasia seems to be heterogeneous, consisting of polyclonal and monoclonal areas