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

Structures of type IV pilins from Thermus thermophilus demonstrate similarities with type II secretion system pseudopilins

AbstractType IV pilins are proteins which form polymers that extend from the surface of the bacterial cell; they are involved in mediating a wide variety of functions, including adhesion, motility and natural competence. Here we describe the determination of the crystal structures of three type IVa pilins proteins from the thermophile Thermus thermophilus. They form part of a cluster of pilus-like proteins within the genome; our results show that one, Tt1222, is very closely related to the main structural type IV pilin, PilA4. The other two, Tt1218 and Tt1219, also adopt canonical pilin-like folds but, interestingly, are most closely related to the structures of the type II secretion system pseudopilins, EpsI/GspI and XcpW/GspJ. GspI and GspJ have been shown to form a complex with another pseudopilin, GspK, and this heterotrimeric complex is known to play a key role in initiating assembly of a pseudopilus which is thought to drive the secretion process. The structural similarity of Tt1218 and Tt1219 to GspI and GspJ suggests that they might work in a similar way, to deliver functions associated with type IV pili in T. thermophilus, such as natural competence

The historically enduring gap in death penalty support: Re-examining the role of context in the recent history of the black-white divide

This paper evaluates four racial‑ecological theories regarding the historically enduring racial divide in public opinion regarding death penalty support. Using geo‑coded data from the 20th century, this research examines the relative representation of African Americans, the level of black‑white economic inequality, and the extent of racial residential segregation on race‑spe‑ cific odds of supporting the death penalty. The research finds support for aspects of racial social context accounting for a portion of the black-white gap in death penalty support at the time. We find differential effects, by race, of representation and segregation as mediators of public opinion regarding the death penalty

Superantigen recognition and interactions: functions, mechanisms and applications

Superantigens are unconventional antigens which recognise immune receptors outside their usual recognition sites e.g. complementary determining regions (CDRs), to elicit a response within the target cell. T-cell superantigens crosslink T-cell receptors and MHC Class II molecules on antigen-presenting cells, leading to lymphocyte recruitment, induction of cytokine storms and T-cell anergy or apoptosis among many other effects. B-cell superantigens, on the other hand, bind immunoglobulins on B-cells, affecting opsonisation, IgG-mediated phagocytosis, and driving apoptosis. Here, through a review of the structural basis for recognition of immune receptors by superantigens, we show that their binding interfaces share specific physicochemical characteristics when compared with other protein-protein interaction complexes. Given that antibody-binding superantigens have been exploited extensively in industrial antibody purification, these observations could facilitate further protein engineering to optimize the use of superantigens in this and other areas of biotechnology

Functional analysis of the accumulation associated protein (Aap) of Staphylococcus epidermidis

S. epidermidis is one of the primary opportunistic pathogens associated within dwelling medical devices such as intravenous catheters and artificial heart valves and joints. S. epidermidis is also a permanent commensal resident on human skin and mucus membranes providing a large potential reservoir for the contamination of medical implants. Persistent colonisation of implants occurs via biofilm formation and infected implants must usually be replaced. The surface bound protein, accumulation associated protein (Aap), is one of the main biofilm promoting surface molecules on S. epidermidis. Aap is a LPXTG protein with a repetitive B-region, thought to promote biofilm formation as well as providing a stalk structure to project the A-domain away from the cell surface. Aap is expressed in lateral tufts of fibrils on the surface of a sub-population of strain NCTC 11047 and, here, similar sub-populations are shown to be present in other S. epidermidis strains. In order to determine the function of specific domains of Aap in adhesion and biofilm formation Aap constructs with and without the A-domain and with varying numbers of B-repeats were expressed on the surface of Lactococcus lactis MG1363 and Staphylococcus aureus. The expression of Aap with the A-domain on the surface of L. lactis increased corneocyte adhesion 20-fold compared to L. lactis carrying Aap without an A domain. Several S. epidermidis isolates also used the A-domain of Aap to adhere to corneocytes, emphasizing the role of Aap in skin adhesion. In addition, Aap promoted adhesion to polystyrene although only the A-domain additionally promoted adhesion to tissue culture treated polystyrene. Furthermore, biofilms were cultivated under flow conditions and analyzed by confocal microscopy. Aap, with the A-domain on the surface of both L. lactis and S. aureus, enhanced microcolony formation suggesting a potential role for the A domain in the early stage of biofilm formation. The A-domain of Aap is therefore multifunctional because, in addition to mediating adhesion to corneocytes it can promote initial attachment to polystyrene and functions in the early accumulation stage of biofilm formation.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Stellar intensity interferometry: Experimental steps toward long-baseline observations

Experiments are in progress to prepare for intensity interferometry with arrays of air Cherenkov telescopes. At the Bonneville Seabase site, near Salt Lake City, a testbed observatory has been set up with two 3-m air Cherenkov telescopes on a 23-m baseline. Cameras are being constructed, with control electronics for either off- or online analysis of the data. At the Lund Observatory (Sweden), in Technion (Israel) and at the University of Utah (USA), laboratory intensity interferometers simulating stellar observations have been set up and experiments are in progress, using various analog and digital correlators, reaching 1.4 ns time resolution, to analyze signals from pairs of laboratory telescopes.Comment: 12 pages, 3 figur

The Identification and Synthesis of Lead Apatite Minerals Formed in Lead Water Pipes

Phosphate is added to drinking water in the UK to minimise the release of lead from lead water pipes. The phosphate encourages the formation of insoluble lead apatites on the walls of the pipe. Hydroxylpyromorphite Pb5(PO4)3OH is the lead apatite that is most often used to model lead levels in tap water; however, its presence has not been confirmed. Our aims were to identify the lead pipe apatite and synthesise it. The synthetic mineral would then be used in future solubility studies to produce better predictions of lead levels in tap water. XRD and FTIR were used to characterise the minerals on a range of lead pipes. Pyromorphite and hydroxylpyromorphite were absent and instead a range of mixed calcium lead apatites were present. For every five lead ions in the general formula Pb5(PO4)3X between one and two ions were replaced with calcium and there was evidence of substitution of by either or . Calcium lead apatites with similar unit cell dimensions to those found on lead water pipes were then synthesised. The calcium : lead ratio in these reaction mixtures was in excess of 500 : 1 and the resulting crystals were shown by TEM to be nanosized rods and flakes. The synthetic apatites that most closely resembled the unit cell dimensions of the apatites on lead water pipes were shown to be Pb3.4Ca1.3(PO4)3Cl0.03OH0.97, Pb3.6Ca1.2(PO4)3Cl0.07OH0.93, and Pb3.6Ca1.2(PO4)3Cl0.27OH0.73

Structural Evaluation of the Spike Glycoprotein Variants on SARS-CoV-2 Transmission and Immune Evasion

From MDPI via Jisc Publications RouterHistory: accepted 2021-07-07, pub-electronic 2021-07-10Publication status: PublishedFunder: Universiti Sains Malaysia; Grant(s): 1001/PPSP/8012382Abstract: The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents significant social, economic and political challenges worldwide. SARS-CoV-2 has caused over 3.5 million deaths since late 2019. Mutations in the spike (S) glycoprotein are of particular concern because it harbours the domain which recognises the angiotensin-converting enzyme 2 (ACE2) receptor and is the target for neutralising antibodies. Mutations in the S protein may induce alterations in the surface spike structures, changing the conformational B-cell epitopes and leading to a potential reduction in vaccine efficacy. Here, we summarise how the more important variants of SARS-CoV-2, which include cluster 5, lineages B.1.1.7 (Alpha variant), B.1.351 (Beta), P.1 (B.1.1.28/Gamma), B.1.427/B.1.429 (Epsilon), B.1.526 (Iota) and B.1.617.2 (Delta) confer mutations in their respective spike proteins which enhance viral fitness by improving binding affinity to the ACE2 receptor and lead to an increase in infectivity and transmission. We further discuss how these spike protein mutations provide resistance against immune responses, either acquired naturally or induced by vaccination. This information will be valuable in guiding the development of vaccines and other therapeutics for protection against the ongoing coronavirus disease 2019 (COVID-19) pandemic