Garnet: a middleware architecture for distributing data streams originating in wireless sensor networks

We present an architectural framework, Garnet, which provides a data stream centric abstraction to encourage the manipulation and exploitation of data generated in sensor networks. By providing middleware services to allow mutually-unaware applications to manipulate sensor behaviour, a scalable, extensible platform is provided. We focus on sensor networks with transmit and receive capabilities as this combination poses greater challenges for managing and distributing sensed data. Our approach allows simple and sophisticated sensors to coexist, and allows data consumers to be mutually unaware of each other This also promotes the use of middleware services to mediate among consumers with potentially conflicting demands for shared data. Garnet has been implemented in Java, and we report on our progress to date and outline some likely scenarios where the use of our distributed architecture and accompanying middleware support enhances the task of sharing data in sensor network environments

Protist predation can favour cooperation within bacterial species

Here, we studied how protist predation affects cooperation in the opportunistic pathogen bacterium Pseudomonas aeruginosa, which uses quorum sensing (QS) cell-to-cell signalling to regulate the production of public goods. By competing wild-type bacteria with QS mutants (cheats), we show that a functioning QS system confers an elevated resistance to predation. Surprisingly, cheats were unable to exploit this resistance in the presence of cooperators, which suggests that resistance does not appear to result from activation of QS-regulated public goods. Instead, elevated resistance of wild-type bacteria was related to the ability to form more predation-resistant biofilms. This could be explained by the expression of QS-regulated resistance traits in densely populated biofilms and floating cell aggregations, or alternatively, by a pleiotropic cost of cheating where less resistant cheats are selectively removed from biofilms. These results show that trophic interactions among species can maintain cooperation within species, and have further implications for P. aeruginosa virulence in environmental reservoirs by potentially enriching the cooperative and highly infective strains with functional QS system

Inhomogeneous Structures in Holographic Superfluids: II. Vortices

We study vortex solutions in a holographic model of Herzog, Hartnoll, and Horowitz, with a vanishing external magnetic field on the boundary, as is appropriate for vortices in a superfluid. We study relevant length scales related to the vortices and how the charge density inside the core of the vortex behaves as a function of temperature or chemical potential. We extract the critical superfluid velocity from the vortex solutions, study how it behaves as a function of the temperature, and compare it to earlier studies and to the Landau criterion. We also comment on the possibility of a Berezinskii-Kosterlitz-Thouless vortex confinement-deconfinement transition.Comment: 32 pages, 10 figures, typos corrected, references adde

Ex vivo analysis of local orientation of collagen fiber bundles in 3D in posterior horn human meniscus using micro-computed tomography

Abstract. Objective: Knee osteoarthritis (OA) is an increasingly relevant joint disease affecting mostly aged population in developed countries. However, there is currently no treatment for OA and increasing the knowledge of the disease with the help of micro-computed tomography (µCT) imaging could offer help in finding the solution. The objective of this thesis was to quantitatively analyze the microstructural organization of human posterior horn meniscus samples in 3D using hexamethyldisilazane (HMDS) based µCT imaging. In addition, this study aims to compare the local microstructural organization of meniscus between OA patients and healthy references. Method: We collected medial and lateral posterior horns of human menisci from 10 endstage medial compartment knee OA patients undergoing total knee replacement surgery and from 10 deceased donors without diagnosed knee OA to act as healthy reference. The posterior horns were dissected and fixed in formalin, dehydrated in ascending alcohol concentrations, treated with HMDS, and scanned with a desktop µCT. Furthermore, we performed local orientation analysis of collagenous microstructure in 3D to all samples, by calculating local structure tensors from greyscale gradients withing a selected integration window to determine the polar angle for each voxel. Moreover, distribution of angles and mean estimated average angles were statistically compared. Results: Collagen fiber bundles in HMDS-treated meniscal samples were depicted in 3D using µCT. In the quantitative local orientation analysis, medial OA had overall lowest orientation angles compared to all other groups: mean estimated differences versus medial OA were -24° [95%CI -31°, -18°] in medial donor, -25° [95%CI -34°, -15°] in lateral OA, and -25° [95%CI -35°, -16°] in lateral donor groups. Distribution and mean angles between lateral OA and lateral donor menisci were similar with a mean difference of 2°. Conclusions: In this study, we were able to quantitatively analyze collagen fiber bundles and their orientations in 3D in the posterior horn of human meniscus using HMDS-based µCT imaging. Furthermore, collagen disorganization increased in the medial OA meniscus, suggesting a relationship between collagenous microstructure disorganization and meniscus degradation.Ihmisen nivelkierukan takasarven kollageenisäiekimppujen kolmi-ulotteinen lokaaliorientaatioanalyysi mikrotietokonetomografian avulla. Tiivistelmä. Tarkoitus: Nivelrikko on yleinen sairaus vanhenevassa yhteiskunnassa, mutta sairauden monimuotoisuuden vuoksi sen hoitaminen on vaikeaa. Sairauden vahvempi ymmärtäminen voisi auttaa hoidon kehittämisessä sairautta vastaan. Tämän pro gradu -tutkielman tavoitteena oli analysoida kvantitatiivisesti ihmisen nivelkierukkanäytteiden mikrorakenteiden orientaatiota kolmiulotteisesti käyttäen heksametyylidisilatsaaniin (HMDS) perustuvaa näytteenkäsittelytekniikkaa mikrotietokonetomografiakuvantamisessa (µCT). Lisäksi tässä työssä verrataan kierukan lokaalimikrorakenneorganisaatiota nivelrikkoisten potilaiden ja terveiden verrokkien välillä. Menetelmä: Keräsimme mediaali- ja lateraalipuolen nivelkierukan takasarvet kymmeneltä nivelrikon loppuvaiheen potilaalta, joille tehtiin polven tekonivelleikkaus, ja 10 menehtyneeltä oikeuslääketieteen potilaalta, joilla ei ollut diagnosoitua polven nivelrikkoa. Nivelkierukoiden posterioriset sarvet leikattiin, käsiteltiin formaliinilla, kuivattiin nousevissa etanolipitoisuuksissa, käsiteltiin HMDS:llä ja kuvattiin µCT-laitteella. Lisäksi teimme näytteille kolmiulotteisen orientaatioanalyysin, jolla mitataan näytteiden kollageenisen mikrorakenteen orientaatiota. Analyysi laskee µCT-kuvien harmaasävygradienttien avulla jokaiselle vokselille paikallisen rakennetensorin, joiden purkamisesta saadaan laskettua vokselin anisotropian määrä ja sen pienimmän vektorin suunta. Pienin arvo ja sen suunta voidaan määrittää vokselin pääasialliseksi orientaatioksi. Kulmien jakautumista ja keskimääräisiä kulmia verrattiin tilastollisesti terveiden ja nivelrikkopotilaiden mediaali- ja lateraalipuolten välillä. Tulokset: Nivelkierukan kollageenikimput kuvattiin kolmiulotteisesti µCT:llä käyttäen HMDS-käsiteltyjä nivelkierukkanäytteitä. Kvantitatiivisessa orientaatioanalyysissä todettiin mediaalipuolen nivelrikkoisilla nivelkierukoilla yleisesti enemmän disorganisaatiota kaikkiin muihin ryhmiin verrattuna: mediaalipuolen nivelrikkoryhmässä orientaatioiden ero verrattuna mediaaliverrokkiryhmään oli -24° [95%CI -31°, -18°], -25° [95%CI -34°, -15°] verrattuna lateraalipuolen nivelrikkoryhmään ja -25° [95%CI -35°, -16°] verrattuna lateraalipuolen luovuttajaryhmän välillä. Lisäksi lateraalipuolen luovuttaja- ja lateraalipuolen nivelrikkoryhmän välillä kulmien jakauma ja keskiarvo olivat samanlaiset keskimäärisen eron ollessa 2°. Johtopäätökset: Tässä tutkimuksessa onnistuimme kuvaamaan ihmisen nivelkierukan kollageenikimput sekä kvantitatiivisesti analysoimaan niiden kolmiulotteista orientaatiota käyttäen HMDS-pohjaista µCT-kuvantamista. Lisäksi kollageenin disorganisaatio oli suurin mediaalipuolen nivelrikkoisessa nivelkierukassa, mikä viittaa kollageenisen mikrorakenteen disorganisaatioon ja nivelkierukan degeneraation väliseen vahvaan suhteeseen

Sparse image reconstruction on the sphere: implications of a new sampling theorem

We study the impact of sampling theorems on the fidelity of sparse image reconstruction on the sphere. We discuss how a reduction in the number of samples required to represent all information content of a band-limited signal acts to improve the fidelity of sparse image reconstruction, through both the dimensionality and sparsity of signals. To demonstrate this result we consider a simple inpainting problem on the sphere and consider images sparse in the magnitude of their gradient. We develop a framework for total variation (TV) inpainting on the sphere, including fast methods to render the inpainting problem computationally feasible at high-resolution. Recently a new sampling theorem on the sphere was developed, reducing the required number of samples by a factor of two for equiangular sampling schemes. Through numerical simulations we verify the enhanced fidelity of sparse image reconstruction due to the more efficient sampling of the sphere provided by the new sampling theorem.Comment: 11 pages, 5 figure

Implications for compressed sensing of a new sampling theorem on the sphere

A sampling theorem on the sphere has been developed recently, requiring half as many samples as alternative equiangular sampling theorems on the sphere. A reduction by a factor of two in the number of samples required to represent a band-limited signal on the sphere exactly has important implications for compressed sensing, both in terms of the dimensionality and sparsity of signals. We illustrate the impact of this property with an inpainting problem on the sphere, where we show the superior reconstruction performance when adopting the new sampling theorem compared to the alternative.Comment: 1 page, 2 figures, Signal Processing with Adaptive Sparse Structured Representations (SPARS) 201

Large-scale surface reconstruction energetics of Pt(100) and Au(100) by all-electron DFT

The low-index surfaces of Au and Pt all tend to reconstruct, a fact that is of key importance in many nanostructure, catalytic, and electrochemical applications. Remarkably, some significant questions regarding their structural energies remain even today, in particular for the large-scale quasihexagonal reconstructed (100) surfaces: Rather dissimilar reconstruction energies for Au and Pt in available experiments, and experiment and theory do not match for Pt. We here show by all-electron density-functional theory that only large enough "(5 x N)" approximant supercells capture the qualitative reconstruction energy trend between Au(100) and Pt(100), in contrast to what is often done in the theoretical literature. Their magnitudes are then in fact similar, and closer to the measured value for Pt(100); our calculations achieve excellent agreement with known geometric characteristics and provide direct evidence for the electronic reconstruction driving force.Comment: updated version - also includes EPAPS information as auxiliary file; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm