848 research outputs found
Towards Superinstructions for Java Interpreters
The Java Virtual Machine (JVM) is usually implemented by an interpreter or just-in-time (JIT) compiler. JITs provide the best performance, but interpreters have a number of advantages that make them attractive, especially for embedded systems. These advantages include simplicity, portability and lower memory requirements. Instruction dispatch is responsible for most of the running time of efficient interpreters, especially on pipelined processors. Superinstructions are an important optimisation to reduce the number of instruction dispatches. A superinstruction is a new Java instruction which performs the work of a common sequence of instructions. In this paper we describe work in progress on the design and implementation of a system of superinstructions for an efficient Java interpreter for connected devices and embedded systems. We describe our basic interpreter, the interpreter generator we use to automatically create optimised source code for superinstructions, and discuss Java specific issues relating to superinstructions. Our initial experimental results show that superinstructions can give large speedups on the SPECjvm98 benchmark suite
Role of active galactic nuclei in galaxy evolution
It is now believed that most, if not all, galaxies contain a supermassive black
hole (SMBH) and that these play a crucial role in their host galaxies' evolution.
Whilst accreting material, a SMBH (known as an active galactic nucleus, AGN,
during this growth phase) releases energy which may have the effect of quenching
star formation and constraining the growth of the galaxy. It is believed that
AGNs can be divided into two broad fundamental categories, each with its own
feedback mechanism. The radiative-mode of feedback occurs in gas-rich galaxies
when substantial star formation is occurring and their young AGNs are growing
rapidly through efficient accretion of cold gas. A fraction of the energy released
by an AGN is transferred into the surrounding gas, creating a thermal "energy-driven" wind or pressure "momentum-driven" wind. Gas and dust may be expelled
from the galaxy, so halting star formation but also cutting off the fuel supply to
the AGN itself. The jet-mode occurs thereafter. The SMBH has now attained a
large mass, but is accreting at a comparatively low level as gas slowly cools and
falls back into the galaxy. The accretion process generates two-sided jets that
generate shock fronts, so heating the gas surrounding the galaxy and partially
offsetting the radiative cooling. This restricts the inflow of gas into the galaxy,
so slowing the growth of the galaxy and SMBH.
There are several convincing theoretical arguments to support the existence of
these feedback mechanisms, although observational evidence has been hard to
obtain. A new radio telescope - the Low Frequency Array (LOFAR) - recently
started operations. LOFAR is especially suitable for investigating AGN feedback.
It has been designed to allow exploration of low radio frequencies, between 10
and 240 MHz, which are particularly relevant for research into AGN activity.
Also, with its large field-of-view and multi-beam capability, LOFAR is ideal for
conducting extensive radio surveys. A project to image deeply the ELAIS-N1
field was started in May 2013.
This thesis uses a number of surveys at different wavelengths, but particularly the
low-frequency radio observations of the ELAIS-N1 field, to improve our knowledge
of jet-mode AGN feedback and hence of the interplay between the complicated
processes involved in galaxy formation and evolution. The more important pieces
of research within the thesis are as follows:
- A sample of 576 AGNs in the nearby universe was assembled and used to
find a relationship between radio luminosity, X-ray luminosity and black
hole mass. Moreover, the relationship is valid over at least 15 orders
of magnitude in X-ray luminosity, strongly suggesting that the process
responsible for the launching of radio jets is scale-invariant.
- The established "Likelihood Ratio" technique was refined to incorporate
colour information in order to optimally match the radio sources in the
ELAIS-N1 field with their host galaxies.
- The resulting catalogue was used to investigate ways in which radio sources
can be matched automatically with their host galaxies (and so avoiding
laborious visual examination of each source). The conclusions have helped
the design of a pipeline for an extensive wide-area survey currently being
conducted by the LOFAR telescope.
- The catalogue was also used to investigate the evolution of jet-mode AGNs.
This involved: deriving source counts; obtaining redshifts for each object;
classifying the radio sources into the different populations of radiative-mode
AGNs, jet-mode AGNs and star-forming galaxies; and using the above
preparatory work in order to derive a luminosity function for jet-mode
AGNs.
- Key conclusions are that (1) feedback from jet-mode AGNs peaks at around
a redshift of 0.75, (2) the space density of jet-mode AGNs declines steadily
with redshift and (3) the typical luminosity of a jet-mode AGN increases
steadily with redshift
The role of RM for DMCs in the run up to the London Olympics 2012
This dissertation will implement The Process Model of Relationship Marketing (Parvatiyar and Sheth 2000) to analyse existing Relationship Marketing (RM) practices and attempt to compare findings to existing literature and academic best-practice in order to reveal managerial implications for MangoLondon.
Research objectives include:
• To identify criteria or a model through which to analyse the effectiveness of Relation Marketing practice
• To use this model to identify current management of these relationships at MangoLondon
• Make suggestions for the MangoLondon in view of the 2012 London Olympics
Qualitative interviews were carried out with management at the organisation and compared to interviews with customers and secondary data.
This dissertation reveals that MangoLondon effectively manages some aspects of the process model, such as communication and trust with its customers. However, there are shortfalls in current management and governance of RM processes.
Based on the findings of this dissertation managerial implications have been suggested which may inform the business plan for MangoLondon in the lead up to the 2012 Olympics in London
A comparative study on the effect of subtherapeutic tylosin administration on select feral or domestic porcine gut microflora grown in continuous-flow culture
Continuous now cultures of feral (culture FC) and domesticated (culture RPCF) pig gut microflora were established in steady state. Cultures, in duplicate, were continuously infused subtherapeutic (2S lJg/ml) levels of tylosin and sampled at intervals to assess effects on total culturable anaerobes, Bacteroides spp. and Enterococcus spp. via plating on serial 10-fold dilutions to anaerobic Brucella blood agar, Bacteroides bile esculin agar, and M Enterococcus agar supplemented without or with 100 lJg tylosin/ml, the later to assess bacterial sensitivity to tylosin Concentrations of total culturable anaerobes within culture FC decreased (P \u3c 0.05), albeit slightly, following 7 days tylosin administration. Concentrations of Bacteroides and Enterococcus decreased (P \u3c 0.05) to near or below detectable levels (1.0 log10 CFU/ml) in culture FC following 7 days tylosin administration, and tylosin-insensitive colonies were recovered at low numbers (~ 2 log10 CFU/ml) and did not persist
Innate Immune Response Induced in Gnotobiotic Piglets by a Mixed Culture of Commensal Bacteria
Our laboratory has developed a recombined porcine-derived mixed bacterial culture (RPCF) isolated from the ceca of a healthy, pathogen-free pig and have maintained it at steady state in a continuous-flow chemostat. The culture has been shown to protect neonatal and weaned pigs from infection and disease caused by Salmonella and E. coli. However, the mechanism of action of the protection from pathogens observed with the RPCF culture remains unclear
Automated Fourier space region-recognition filtering for off-axis digital holographic microscopy
Automated label-free quantitative imaging of biological samples can greatly
benefit high throughput diseases diagnosis. Digital holographic microscopy
(DHM) is a powerful quantitative label-free imaging tool that retrieves
structural details of cellular samples non-invasively. In off-axis DHM, a
proper spatial filtering window in Fourier space is crucial to the quality of
reconstructed phase image. Here we describe a region-recognition approach that
combines shape recognition with an iterative thresholding to extracts the
optimal shape of frequency components. The region recognition technique offers
fully automated adaptive filtering that can operate with a variety of samples
and imaging conditions. When imaging through optically scattering biological
hydrogel matrix, the technique surpasses previous histogram thresholding
techniques without requiring any manual intervention. Finally, we automate the
extraction of the statistical difference of optical height between malaria
parasite infected and uninfected red blood cells. The method described here
pave way to greater autonomy in automated DHM imaging for imaging live cell in
thick cell cultures
The potential for vaccines against scour worms of small ruminants
This review addresses the research landscape regarding vaccines against scour worms, particularly Trichostrongylus spp. and Teladorsagia circumcincta. The inability of past research to deliver scour-worm vaccines with reliable and reproducible efficacy has been due in part to gaps in knowledge concerning: (i) host-parasite interactions leading to development of type-2 immunity, (ii) definition of an optimal suite of parasite antigens, and (iii) rational formulation and administration to induce protective immunity against gastrointestinal nematodes (GIN) at the site of infestation. Recent ‘omics’ developments enable more systematic analyses. GIN genomes are reaching completion, facilitating “reverse vaccinology” approaches that have been used successfully for the Rhipicephalus australis vaccine for cattle tick, while methods for gene silencing and editing in GIN enable identification and validation of potential vaccine antigens. We envisage that any efficacious scour worm vaccine(s) would be adopted similarly to “Barbervax™” within integrated parasite management schemes. Vaccines would therefore effectively parallel the use of resistant animals, and reduce the frequency of drenching and pasture contamination. These aspects of integration, efficacy and operation require updated models and validation in the field. The conclusion of this review outlines an approach to facilitate an integrated research program
- …