33,792 research outputs found
Hierarchical strategies for efficient fault recovery on the reconfigurable PAnDA device
A novel hierarchical fault-tolerance methodology for reconfigurable devices is presented. A bespoke multi-reconfigurable FPGA architecture, the programmable analogue and digital array (PAnDA), is introduced allowing fine-grained reconfiguration beyond any other FPGA architecture currently in existence. Fault blind circuit repair strategies, which require no specific information of the nature or location of faults, are developed, exploiting architectural features of PAnDA. Two fault recovery techniques, stochastic and deterministic strategies, are proposed and results of each, as well as a comparison of the two, are presented. Both approaches are based on creating algorithms performing fine-grained hierarchical partial reconfiguration on faulty circuits in order to repair them. While the stochastic approach provides insights into feasibility of the method, the deterministic approach aims to generate optimal repair strategies for generic faults induced into a specific circuit. It is shown that both techniques successfully repair the benchmark circuits used after random faults are induced in random circuit locations, and the deterministic strategies are shown to operate efficiently and effectively after optimisation for a specific use case. The methods are shown to be generally applicable to any circuit on PAnDA, and to be straightforwardly customisable for any FPGA fabric providing some regularity and symmetry in its structure
Stem cell mechanobiology
Stem cells are undifferentiated cells that are capable of proliferation, self-maintenance and differentiation towards specific cell phenotypes. These processes are controlled by a variety of cues including physicochemical factors associated with the specific mechanical environment in which the cells reside. The control of stem cell biology through mechanical factors remains poorly understood and is the focus of the developing field of mechanobiology. This review provides an insight into the current knowledge of the role of mechanical forces in the induction of differentiation of stem cells. While the details associated with individual studies are complex and typically associated with the stem cell type studied and model system adopted, certain key themes emerge. First, the differentiation process affects the mechanical properties of the cells and of specific subcellular components. Secondly, that stem cells are able to detect and respond to alterations in the stiffness of their surrounding microenvironment via induction of lineage-specific differentiation. Finally, the application of external mechanical forces to stem cells, transduced through a variety of mechanisms, can initiate and drive differentiation processes. The coalescence of these three key concepts permit the introduction of a new theory for the maintenance of stem cells and alternatively their differentiation via the concept of a stem cell 'mechano-niche', defined as a specific combination of cell mechanical properties, extracellular matrix stiffness and external mechanical cues conducive to the maintenance of the stem cell population.<br/
Gravitational effects in ultrahigh-energy string scattering
Ultrahigh-energy string scattering is investigated to clarify the relative
role of string and gravitational effects, and their possible contributions to
nonlocal behavior. Different regimes can be characterized by varying the impact
parameter at fixed energy. In the regime where momentum transfers reach the
string scale, string effects appear subdominant to higher-loop gravitational
processes, approximated via the eikonal. At smaller impact parameters,
"diffractive" or "tidal" string excitation leads to processes dominated by
highly excited strings. However, new evidence is presented that these
excitation effects do not play a direct role in black hole formation, which
corresponds to breakdown of gravitational perturbation theory and appears to
dominate at sufficiently small impact parameters. The estimated amplitudes
violate expected bounds on high-energy behavior for local theories.Comment: 19 pages, harvmac. v2: fixed typos, added refs and discussion of
longitudinal spread. v3: minor changes to agree with published versio
Perfluorocarbon Enhanced Glasgow Oxygen Level Dependent (GOLD) magnetic resonance metabolic imaging identifies the penumbra following acute ischemic stroke
The ability to identify metabolically active and potentially salvageable ischaemic penumbra is crucial for improving treatment decisions in acute stroke patients. Our solution involves two complementary novel MRI techniques (Glasgow Oxygen Level Dependant (GOLD) Metabolic Imaging), which when combined with a perfluorocarbon (PFC) based oxygen carrier and hyperoxia can identify penumbra due to dynamic changes related to continued metabolism within this tissue compartment. Our aims were (i) to investigate whether PFC offers similar enhancement of the second technique (Lactate Change) as previously demonstrated for the T2*OC technique (ii) to demonstrate both GOLD metabolic imaging techniques working concurrently to identify penumbra, following administration of Oxycyte® (O-PFC) with hyperoxia.
Methods: An established rat stroke model was utilised. Part-1: Following either saline or PFC, magnetic resonance spectroscopy was applied to investigate the effect of hyperoxia on lactate change in presumed penumbra. Part-2; rats received O-PFC prior to T2*OC (technique 1) and MR spectroscopic imaging, which was used to identify regions of tissue lactate change (technique 2) in response to hyperoxia. In order to validate the techniques, imaging was followed by [14C]2-deoxyglucose autoradiography to correlate tissue metabolic status to areas identified as penumbra.
Results: Part-1: PFC+hyperoxia resulted in an enhanced reduction of lactate in the penumbra when compared to saline+hyperoxia. Part-2: Regions of brain tissue identified as potential penumbra by both GOLD metabolic imaging techniques utilising O-PFC, demonstrated maintained glucose metabolism as compared to adjacent core tissue.
Conclusion: For the first time in vivo, enhancement of both GOLD metabolic imaging techniques has been demonstrated following intravenous O-PFC+hyperoxia to identify ischaemic penumbra. We have also presented preliminary evidence of the potential therapeutic benefit offered by O-PFC. These unique theranostic applications would enable treatment based on metabolic status of the brain tissue, independent of time from stroke onset, leading to increased uptake and safer use of currently available treatment options
NFAT5 genes are part of the osmotic regulatory system in Atlantic salmon (Salmo salar)
Acknowledgements This study was supported by a grant from the Biotechnology and Biological Sciences Research Council (BBSRC, BB/H008063/1), UK to DGH and SAM. Funding also came from Research Council Norway for project number 241016 for DGH and EJ. This work was carried out as part of a PhD thesis funded by the Marine Alliance of Science and Technology Scotland (MASTS).Peer reviewedPublisher PD
The factorisation of glue and mass terms in SU(N) gauge theories
In this paper we investigate the structure of the glue in Zwanziger's gauge
invariant expansion for the A^2-type mass term in Yang-Mills theory. We show
how to derive this expansion, in terms of the inverse covariant Laplacian, and
extend it to higher orders. In particular, we give an explicit expression, for
the first time, for the next to next to leading order term. We further show
that the expansion is not unique and give examples of the resulting ambiguity.Comment: 22 page
Cross-link governed dynamics of biopolymer networks
Cytoskeletal networks of biopolymers are cross-linked by a variety of
proteins. Experiments have shown that dynamic cross-linking with physiological
linker proteins leads to complex stress relaxation and enables network flow at
long times. We present a model for the mechanical properties of transient
networks. By a combination of simulations and analytical techniques we show
that a single microscopic timescale for cross-linker unbinding leads to a broad
spectrum of macroscopic relaxation times, resulting in a weak power-law
dependence of the shear modulus on frequency. By performing rheological
experiments, we demonstrate that our model quantitatively describes the
frequency behavior of actin network cross-linked with -Actinin- over
four decades in frequency.Comment: 4 page
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