A Roadmap to Pervasive Systems Verification

yesThe complexity of pervasive systems arises from the many different aspects that such systems possess. A typical pervasive system may be autonomous, distributed, concurrent and context-based, and may involve humans and robotic devices working together. If we wish to formally verify the behaviour of such systems, the formal methods for pervasive systems will surely also be complex. In this paper, we move towards being able to formally verify pervasive systems and outline our approach wherein we distinguish four distinct dimensions within pervasive system behaviour and utilise different, but appropriate, formal techniques for verifying each one.EPSR

Interplay between structure and magnetism in Mo12S9I9Mo_{12} S_9 I_9 nanowires

We investigate the equilibrium geometry and electronic structure of Mo$_{12}$S$_{9}$I$_{9}$ nanowires using ab initio Density Functional calculations. The skeleton of these unusually stable nanowires consists of rigid, functionalized Mo octahedra, connected by flexible, bi-stable sulphur bridges. This structural flexibility translates into a capability to stretch up to approximate 20% at almost no energy cost. The nanowires change from conductors to narrow-gap magnetic semiconductors in one of their structural isomers.Comment: 4 pages with PRL standards and 3 figure

Testing General Relativity with Atom Interferometry

The unprecedented precision of atom interferometry will soon lead to laboratory tests of general relativity to levels that will rival or exceed those reached by astrophysical observations. We propose such an experiment that will initially test the equivalence principle to 1 part in 10^15 (300 times better than the current limit), and 1 part in 10^17 in the future. It will also probe general relativistic effects--such as the non-linear three-graviton coupling, the gravity of an atom's kinetic energy, and the falling of light--to several decimals. Further, in contrast to astrophysical observations, laboratory tests can isolate these effects via their different functional dependence on experimental variables.Comment: 4 pages, 1 figure; v2: Minor changes made for publicatio

Disaster-Resilient Control Plane Design and Mapping in Software-Defined Networks

Communication networks, such as core optical networks, heavily depend on their physical infrastructure, and hence they are vulnerable to man-made disasters, such as Electromagnetic Pulse (EMP) or Weapons of Mass Destruction (WMD) attacks, as well as to natural disasters. Large-scale disasters may cause huge data loss and connectivity disruption in these networks. As our dependence on network services increases, the need for novel survivability methods to mitigate the effects of disasters on communication networks becomes a major concern. Software-Defined Networking (SDN), by centralizing control logic and separating it from physical equipment, facilitates network programmability and opens up new ways to design disaster-resilient networks. On the other hand, to fully exploit the potential of SDN, along with data-plane survivability, we also need to design the control plane to be resilient enough to survive network failures caused by disasters. Several distributed SDN controller architectures have been proposed to mitigate the risks of overload and failure, but they are optimized for limited faults without addressing the extent of large-scale disaster failures. For disaster resiliency of the control plane, we propose to design it as a virtual network, which can be solved using Virtual Network Mapping techniques. We select appropriate mapping of the controllers over the physical network such that the connectivity among the controllers (controller-to-controller) and between the switches to the controllers (switch-to-controllers) is not compromised by physical infrastructure failures caused by disasters. We formally model this disaster-aware control-plane design and mapping problem, and demonstrate a significant reduction in the disruption of controller-to-controller and switch-to-controller communication channels using our approach.Comment: 6 page

Low velocity quantum reflection of Bose-Einstein condensates

We studied quantum reflection of Bose-Einstein condensates at normal incidence on a square array of silicon pillars. For incident velocities of 2.5-26 mm/s observations agreed with theoretical predictions that the Casimir-Polder potential of a reduced density surface would reflect slow atoms with much higher probability. At low velocities (0.5-2.5 mm/s), we observed that the reflection probability saturated around 60% rather than increasing towards unity. We present a simple model which explains this reduced reflectivity as resulting from the combined effects of the Casimir-Polder plus mean field potential and predicts the observed saturation. Furthermore, at low incident velocities, the reflected condensates show collective excitations.Comment: 4 figure

IOME, A Toolkit for Distributed and Collaborative Computational Science and Engineering

The internet provides a media rich communications platform enabling communities to share content. Alongside the increased activity in collaborative work, recent developments on workflow tools are now enabling researchers from different disciplines to collaborate by feeding data and results between large multi-disciplinary, optimization problems. Researchers developing computational models require development kits and tools enabling them to provide simulations with a range of methods that facilitate collaboration. This paper presents a unique, multi-purpose tool-kit, enabling researchers to easily develop simulations which may be run as web services and accessed interactively. The development kit is based on a protocol that uses an XML markup called IOME ML, "the Interactive Object Management Environment Markup Language". The paper describes the IOME ML and it's development kit. We illustrate the capabilities of IOME with two case studies. Firstly, a medical image processing application which is wrapped as a web service and accessed through a web browser offering medical professionals image analysis tools. Secondly, a method of collaborative visualisation and computational steering of a tsunami simulation based on a shallow water wave model. The paper concludes with a review of further developments including refinements to the mark up language and the development of a service factory enabling dynamic invocation of published simulations as IOME web service applications

Elastomeric Osteoconductive Synthetic Scaffolds with Acquired Osteoinductivity Expedite the Repair of Critical Femoral Defects in Rats

Regenerative medicine aspires to reduce reliance on or overcome limitations associated with donor tissue-mediated repair. Structural bone allografts are commonly used in orthopedic surgery, with a high percentage of graft failure due to poor tissue integration. This problem is aggravated among elderly, those suffering from metabolic conditions, or those undergoing cancer therapies that compromise graft healing. Toward this end, we developed a synthetic graft named FlexBone, in which nanocrystalline hydroxyapatite (50-wt%) was structurally integrated with crosslinked poly(hydroxyethyl methacrylate) hydrogel, which provides dimensional stability and elasticity. It recapitulates the essential role of nanocrystalline hydroxyapatite in defining the osteoconductivity and biochemical microenvironment of bone because of its affinity for biomolecules. Here, we demonstrate that FlexBone effectively absorbed endogenously secreted signaling molecules associated with the inflammation/graft healing cascade upon being press-fit into a 5-mm rat femoral segmental defect. Further, when preabsorbed with a single dose of 400-ng recombinant human (rh) bone morphogenetic protein-2/7 heterodimer, it enabled the functional repair of the critical-sized defect by 8-12 weeks. FlexBone was stably encapsulated by the bridging bony callus and the FlexBone-callus interface was continuously remodeled. In summary, FlexBone combines the dimensional stability and osteoconductivity of structural bone allografts with desirable surgical compressibility and acquired osteoinductivity in an easy-to-fabricate and scalable synthetic biomaterial.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90480/1/ten-2Etea-2E2010-2E0274.pd

Experimental consequences of family unification

Theories of family unification predict four left-handed and four right-handed families of quarks and leptons, all with masses below 265 GeV. The lightest mirror quark has a mass of less than 140 GeV. All charged leptons are lighter than 55 GeV, and the lightest is below 40 GeV. All five new neutrinos have masses less than 40 GeV and contribute to the width of the Z0. We study the decays of these new families, and discuss rare processes such as μ→eγ. We also examine proton decay, and show that it can proceed into e+π0 at the observable but acceptable rate of 1032±1 yr