Distributed computational fluid dynamics

Computational fluid dynamics simulations of relevance to jet-engine design, for instance, are extremely computationally demanding and the use of large-scale distributed computing will allow the solution of problems that cannot be tackled using current resources. It is often appropriate to leave the large datasets generated by CFD codes local to the compute resource in use at the time. This naturally leads to a distributed database of results that will need to be federated as a coherent resource for the engineering community. We describe the use of Globus and Condor within Cambridge for sharing computer resources, progress on defining XML standards for the annotation of CFD datasets and a distributed database framework for them

Determination of the Gyrotropic Characteristics of Hexaferrite Ceramics From 75 to 600 GHz

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Skeletal muscle glucose uptake during treadmill exercise in neuronal nitric oxide synthase-μ knockout mice

Nitric oxide influences intramuscular signaling that affects skeletal muscle glucose uptake during exercise. The role of the main NO-producing enzyme isoform activated during skeletal muscle contraction, neuronal nitric oxide synthase-μ (nNOSμ), in modulating glucose uptake has not been investigated in a physiological exercise model. In this study, conscious and unrestrained chronically catheterized nNOSμ+/+ and nNOSμ−/− mice either remained at rest or ran on a treadmill at 17 m/min for 30 min. Both groups of mice demonstrated similar exercise capacity during a maximal exercise test to exhaustion (17.7 ± 0.6 vs. 15.9 ± 0.9 min for nNOSμ+/+ and nNOSμ−/−, respectively, P &gt; 0.05). Resting and exercise blood glucose levels were comparable between the genotypes. Very low levels of NOS activity were detected in skeletal muscle from nNOSμ−/− mice, and exercise increased NOS activity only in nNOSμ+/+ mice (4.4 ± 0.3 to 5.2 ± 0.4 pmol·mg−1·min−1, P &lt; 0.05). Exercise significantly increased glucose uptake in gastrocnemius muscle (5- to 7-fold) and, surprisingly, more so in nNOSμ−/− than in nNOSμ+/+ mice ( P &lt; 0.05). This is in parallel with a greater increase in AMPK phosphorylation during exercise in nNOSμ−/− mice. In conclusion, nNOSμ is not essential for skeletal muscle glucose uptake during exercise, and the higher skeletal muscle glucose uptake during exercise in nNOSμ−/− mice may be due to compensatory increases in AMPK activation. </jats:p

An In Vitro Model of Latency and Reactivation of Varicella Zoster Virus in Human Stem Cell-Derived Neurons

Varicella zoster virus (VZV) latency in sensory and autonomic neurons has remained enigmatic and difficult to study, and experimental reactivation has not yet been achieved. We have previously shown that human embryonic stem cell (hESC)-derived neurons are permissive to a productive and spreading VZV infection. We now demonstrate that hESC-derived neurons can also host a persistent non-productive infection lasting for weeks which can subsequently be reactivated by multiple experimental stimuli. Quiescent infections were established by exposing neurons to low titer cell-free VZV either by using acyclovir or by infection of axons in compartmented microfluidic chambers without acyclovir. VZV DNA and low levels of viral transcription were detectable by qPCR for up to seven weeks. Quiescently-infected human neuronal cultures were induced to undergo renewed viral gene and protein expression by growth factor removal or by inhibition of PI3-Kinase activity. Strikingly, incubation of cultures induced to reactivate at a lower temperature (34°C) resulted in enhanced VZV reactivation, resulting in spreading, productive infections. Comparison of VZV genome transcription in quiescently-infected to productively-infected neurons using RNASeq revealed preferential transcription from specific genome regions, especially the duplicated regions. These experiments establish a powerful new system for modeling the VZV latent state, and reveal a potential role for temperature in VZV reactivation and disease

Role of domain walls in the abnormal photovoltaic effect in BiFeO3

Recently, the anomalous photovoltaic (PV) effect in BiFeO3 (BFO) thin films, which resulted in open circuit voltages (V-oc) considerably larger than the band gap of the material, has generated a revival of the entire field of photoferroelectrics. Here, via temperature-dependent PV studies, we prove that the bulk photovoltaic (BPV) effect, which has been studied in the past for many non-centrosymmetric materials, is at the origin of the anomalous PV effect in BFO films. Moreover, we show that irrespective of the measurement geometry, V-oc as high as 50V can be achieved by controlling the conductivity of domain walls (DW). We also show that photoconductivity of the DW is markedly higher than in the bulk of BFO

Photocatalytic polymers of intrinsic microporosity for hydrogen production from water

The most common strategy for introducing porosity into organic polymer photocatalysts has been the synthesis of cross-linked conjugated networks or frameworks. Here, we study the photocatalytic performance of a series of linear conjugated polymers of intrinsic microporosity (PIMs) as photocatalysts for hydrogen production from water in the presence of a hole scavenger. The best performing materials are porous and wettable, which allows for the penetration of water into the material. One of these polymers of intrinsic microporosity, P38, showed the highest sacrificial hydrogen evolution rate of 5226 μmol h−1 g−1 under visible irradiation (λ > 420 nm), with an external quantum efficiency of 18.1% at 420 nm, placing it among the highest performing polymer photocatalysts reported to date for this reaction

Outcomes of total hip arthroplasty, as a salvage procedure, following failed internal fixation of intracapsular fractures of the femoral neck: a systematic review and meta-analysis.

AIMS: The optimal management of intracapsular fractures of the femoral neck in independently mobile patients remains open to debate. Successful fixation obviates the limitations of arthroplasty for this group of patients. However, with fixation failure rates as high as 30%, the outcome of revision surgery to salvage total hip arthroplasty (THA) must be considered. We carried out a systematic review to compare the outcomes of salvage THA and primary THA for intracapsular fractures of the femoral neck. PATIENTS AND METHODS: We performed a Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) compliant systematic review, using the PubMed, EMBASE and Cochrane libraries databases. A meta-analysis was performed where possible, and a narrative synthesis when a meta-analysis was not possible. RESULTS: Our analyses revealed a significantly increased risk of complications including deep infection, early dislocation and peri-prosthetic fracture with salvage THA when compared with primary THA for an intracapsular fracture of the femoral neck (overall risk ratio of 3.15). Functional outcomes assessment using EuroQoL (EQ)-5D were not significantly different (p = 0.3). CONCLUSION: Salvage THA carries a significantly higher risk of complications than primary THA for intracapsular fractured neck of femur. Current literature is still lacking well designed studies to provide a full answer to the question. TAKE HOME MESSAGE: Salvage THA is associated with more complications than primary THA for intracapsular neck of femur fractures

Multiscale analysis of materials with anisotropic microstructure as micropolar continua

Multiscale procedures are often adopted for the continuum modeling of materials composed of a specific micro-structure. Generally, in mechanics of materials only two-scales are linked. In this work the original (fine) micro-scale description, thought as a composite material made of matrix and fibers/particles/crystals which can interact among them, and a scale-dependent continuum (coarse) macro-scale are linked via an energy equivalence criterion. In particular the multiscale strategy is proposed for deriving the constitutive relations of anisotropic composites with periodic microstructure and allows us to reduce the typically high computational cost of fully microscopic numerical analyses. At the microscopic level the material is described as a lattice system while at the macroscopic level the continuum is a micropolar continuum, whose material particles are endowed with orientation besides position. The derived constitutive relations account for shape, texture and orientation of inclusions as well as internal scale parameters, which account for size effects even in the elastic regime in the presence of geometrical and/or load singularities. Applications of this procedure concern polycrystals, wherein an important descriptor of the underlying microstructure gives the orientation of the crystal lattice of each grain, fiber reinforced composites, as well as masonry-like materials. In order to investigate the effects of micropolar constants in the presence of material non central symmetries, some numerical finite element simulations, with elements specifically formulated for micropolar media, are presented. The performed simulations, which extend several parametric analyses earlier performed [1], involve two-dimensional media, in the linear framework, subjected to compression loads distributed in a small portion of the medium