Analysis of a Multimedia Stream using Stochastic Process Algebra

It is now well recognised that the next generation of distributed systems will be distributed multimedia systems. Central to multimedia systems is quality of service, which defines the non-functional requirements on the system. In this paper we investigate how stochastic process algebra can be used in order to determine the quality of service properties of distributed multimedia systems. We use a simple multimedia stream as our basic example. We describe it in the Stochastic Process Algebra PEPA and then we analyse whether the stream satisfies a set of quality of service parameters: throughput, end-to-end latency, jitter and error rates

Structural Materials and Fuels for Space Power Plants

A fission reactor combined with Stirling convertor power generation is one promising candidate in on-going Fission Surface Power (FSP) studies for future lunar and Martian bases. There are many challenges for designing and qualifying space-rated nuclear power plants. In order to have an affordable and sustainable program, NASA and DOE designers want to build upon the extensive foundation in nuclear fuels and structural materials. This talk will outline the current Fission Surface Power program and outline baseline design options for a lunar power plant with an emphasis on materials challenges. NASA first organized an Affordable Fission Surface Power System Study Team to establish a reference design that could be scrutinized for technical and fiscal feasibility. Previous papers and presentations have discussed this study process in detail. Considerations for the reference design included that no significant nuclear technology, fuels, or material development were required for near term use. The desire was to build upon terrestrial-derived reactor technology including conventional fuels and materials. Here we will present an overview of the reference design, Figure 1, and examine the materials choices. The system definition included analysis and recommendations for power level and life, plant configuration, shielding approach, reactor type, and power conversion type. It is important to note that this is just one concept undergoing refinement. The design team, however, understands that materials selection and improvement must be an integral part of the system development

Active Camera Stabilization from High Altitude Balloons

Many applications of High Altitude Ballooning (HAB) require maintaining a bearing in a non-inertial frame of reference, for example keeping a camera continuously pointed at the sun from a HAB payload in motion. Maintaining a consistent bearing is especially difficult on a HAB flight because it is hard to accurately measure and compensate the relative motion of the payload. In addition, friction, conservation of angular momentum, and errors in relative bearing measurement complicate the solution. This project aims to solve these issues using a combination of accelerometer data, gyro data, and a stepper motor-driven platform. It was launched as part of the Far Horizons project at the Adler Planetarium, whose mission is bringing real space exploration down to Earth and into the hands of students, volunteers, and the public. The initial design was built for use in the 2017 Eclipse mission, but will be also be used in missions such as mapping light pollution from a HAB platform. The system expands capabilities of general HAB missions and can be open-sourced to provide the HAB community with a solution to a unique problem in High Altitude Ballooning

Virus-host co-evolution under a modified nuclear genetic code

Among eukaryotes with modified nuclear genetic codes, viruses are unknown. However, here we provide evidence of an RNA virus that infects a fungal host (Scheffersomyces segobiensis) with a derived nuclear genetic code where CUG codes for serine. The genomic architecture and phylogeny are consistent with infection by a double-stranded RNA virus of the genus Totivirus. We provide evidence of past or present infection with totiviruses in five species of yeasts with modified genetic codes. All but one of the CUG codons in the viral genome have been eliminated, suggesting that avoidance of the modified codon was important to viral adaptation. Our mass spectroscopy analysis indicates that a congener of the host species has co-opted and expresses a capsid gene from totiviruses as a cellular protein. Viral avoidance of the host’s modified codon and host co-option of a protein from totiviruses suggest that RNA viruses co-evolved with yeasts that underwent a major evolutionary transition from the standard genetic code

Facile Fabrication of Spherical Nanoparticle-Tipped AFM Probes for Plasmonic Applications.

We wish to acknowledge the support of grants UK EPSRC EP/G060649/1, EP/H007024/1, a Marie Curie Intra-European Fellowship (FP7-PEOPLE-2011-IEF 298012 to L.Z.), ERC LINASS 320503, and Royal Society IE120879. R.W.B. thanks Queens’ College, Cambridge for financial support.This is the final published version. It originally appeared in Particle & Particle Systems Characterization and is available in http://onlinelibrary.wiley.com/doi/10.1002/ppsc.201400104/abstract

A one-piece 3D printed flexure translation stage for open-source microscopy.

Open source hardware has the potential to revolutionise the way we build scientific instruments; with the advent of readily available 3D printers, mechanical designs can now be shared, improved, and replicated faster and more easily than ever before. However, printed parts are typically plastic and often perform poorly compared to traditionally machined mechanisms. We have overcome many of the limitations of 3D printed mechanisms by exploiting the compliance of the plastic to produce a monolithic 3D printed flexure translation stage, capable of sub-micron-scale motion over a range of 8 × 8 × 4 mm. This requires minimal post-print clean-up and can be automated with readily available stepper motors. The resulting plastic composite structure is very stiff and exhibits remarkably low drift, moving less than 20 μm over the course of a week, without temperature stabilisation. This enables us to construct a miniature microscope with excellent mechanical stability, perfect for time-lapse measurements in situ in an incubator or fume hood. The ease of manufacture lends itself to use in containment facilities where disposability is advantageous and to experiments requiring many microscopes in parallel. High performance mechanisms based on printed flexures need not be limited to microscopy, and we anticipate their use in other devices both within the laboratory and beyond.We would like to thank Paula Rudall (Jodrell Laboratory, Royal Botanic Gardens, Kew, UK) for preparing the Pollia condensata samples. RWB was supported by Research Fellowships from Queens’ College, Cambridge and the Royal Commission for the Exhibition of 1851, and partial support was provided by EPSRC EP/L027151/1, the University Teaching and Learning Innovation Fund and the SynBioFund initiative.This is the final version of the article. It first appeared from AIP Publishing via http://dx.doi.org/10.1063/1.4941068 Data supporting this publication is available at http://www.repository.cam.ac.uk/handle/1810/253294. Design files and assembly instructions are available at http://docubricks.com/projects/ openflexure-microscope

Nanometer control in plasmonic systems through discrete layer-by-layer macrocycle-cation deposition.

In this work, we demonstrate that coordination interactions between Fe3+ and cucurbit[7]uril (CB[7]) can be utilised to build up defined nanoscale spacing layers in metallic nanosystems. We begin by characterising the layer-by-layer deposition of CB[7] and FeCl3·6H2O coordination layers through the use of a Quartz-Crystal Microbalance (QCM) and contact angle measurements. We then apply this layered structure to accurately control the spacing, and thus optical properties, of gold nanoparticles in a Nanoparticle-on-Mirror (NPoM) structure, which is demonstrated via normalising plasmon resonance spectroscopy.European Commission for a Marie Curie Fellowship (NANOSPHERE, 658360) ERC starting investigator grant (ASPiRe 240629) RC acknowledges support from the Dr. Manmohan Singh scholarship from St. John’s College BdN acknowledges support from the Leverhulme Trust and the Isaac Newton trust ECF

SERS of individual nanoparticles on a mirror : size does matter, but so does shape

The authors thank Javier Aizpurua (CSIC − UPV/EHU/DIPC) for helpful discussions. We acknowledge financial support from EPSRC Grants EP/G060649/1, EP/K028510/1, EP/L027151/1, ERC Grant LINASS 320503. F.B. acknowledges support from the Winton Programme for the Physics of Sustainability. R.C. acknowledges support from the Dr. Manmohan Singh scholarship from St. John’s College.Coupling noble metal nanoparticles by a 1 nm gap to an underlying gold mirror confines light to extremely small volumes, useful for sensing on the nanoscale. Individually measuring 10 000 of such gold nanoparticles of increasing size dramatically shows the different scaling of their optical scattering (far-field) and surface-enhanced Raman emission (SERS, near-field). Linear red-shifts of the coupled plasmon modes are seen with increasing size, matching theory. The total SERS from the few hundred molecules under each nanoparticle dramatically increases with increasing size. This scaling shows that maximum SERS emission is always produced from the largest nanoparticles, irrespective of tuning to any plasmonic resonances. Changes of particle facet with nanoparticle size result in vastly weaker scaling of the near-field SERS, without much modifying the far-field, and allows simple approaches for optimizing practical sensing.Publisher PDFPeer reviewe

Linking the progressive expansion of reducing conditions to a stepwise mass extinction event in the late Silurian oceans

The late Ludlow Lau Event was a severe biotic crisis in the Silurian, characterized by resurgent microbial facies and faunal turnover rates otherwise only documented during the "big five" mass extinctions. This asynchronous late Silurian marine extinction event preceded an associated positive carbon isotope excursion (CIE), the Lau CIE, although a mechanism for this temporal offset remains poorly constrained. Here, we report thallium isotope data from locally reducing late Ludlow strata within the Baltic Basin to document the earliest onset of global marine deoxygenation. The initial expansion of anoxia coincided with the onset of the extinction and therefore preceded the Lau CIE. Additionally, sulfur isotope data record a large positive excursion parallel to the Lau CIE, interpreted to indicate an increase in pyrite burial associated with the widely documented CIE. This suggests a possible global expansion of euxinia (anoxic and sulfidic water column) following deoxygenation. These data are the most direct proxy evidence of paleoredox conditions linking the known extinction to the Lau CIE through the progressive expansion of anoxia, and most likely euxinia, across portions of the late Silurian oceans

RNAi gene knockdown in the poultry red mite, Dermanyssus gallinae (De Geer 1778), a tool for functional genomics

The authors gratefully acknowledge funding for this project from the Scottish Government Rural Affairs, Food and the Environment (RAFE) Strategic Research Portfolio 2016-2021. DRGP is supported by a research fellowship provided by the Moredun Foundation. WC is supported by a studentship provided by the University of Aberdeen and the Moredun Foundation.Peer reviewedPublisher PD