Development of a Quality of Service Framework for Multimedia Streaming Applications

By the year 2012, it is expected that the majority of all Internet traffic will be video content. Coupled with this is the increasing availability of Wireless Local Area Networks (WLANs) due to their ease of deployment, flexibility and reducing roll out costs. Unfortunately the contention based access mechanism utilised by IEEE 802.11 WLANs does not suit the non-uniform or bursty bandwidth profile of a video stream which can lead to a reduced quality of service (QoS) being experienced by the end-user. In 2005, the IEEE 802.11e protocol was ratified in an attempt to solve this emerging problem. It provides for an access prioritization mechanism based upon four separate traffic classes or access categories (ACs). Each AC is characterised by a set of access parameters that determine its level of access priority which is turn determines the amount of bandwidth available to it. Computer simulation studies have shown that AC prioritisation can yield significant improvements in the QoS delivered over a WLAN. However, these studies have been based upon the use of static access parameters for the ACs. In practice, this is not a viable solution owing to the dynamic and unpredictable nature of the operating conditions on WLANs. In this thesis, an experimental study of AC prioritisation based upon adaptive tuning of the access parameters is presented. This new approach to bandwidth provisioning for video streaming is shown to yield significant improvements in the QoS under a wide range of different operating conditions. For example, it is shown that by adaptively tuning the access control parameters in response to the network conditions, the number of video frames delivered that satisfy QoS requirements is more than doubled

Sands through the hourglass the structural and functional diversity of major intrinsic proteins

Major Intrinsic Proteins (MIPs) are an ancient family of integral membrane proteins that mediate the bidirectional flux of water and small solutes across cellular membranes. Genomic and phylogenetic analyses indicate that plants contain more MIP genes than their animal and microbial counterparts. An analysis of MIP structure also indicates that plant MIPs structurally diverse at the regions that control selectivity of these proteins. Homology modeling was performed using all 35 members of the MIP family from Arabidopsis thaliana. This analysis revealed that MIPs can be divided into 8 functional subgroups based on the amino acids in their selectivity determining ar/R regions. A broader phylogenetic analysis of all available MIP sequences indicates that 92 ar/R regions exist in this dataset, and that much of the diversity arises from plant sources.Homology modeling indicated that the Nodulin 26-like intrinsic protein (NIP) family of Arabidopsis could be divided into two subgroups based on ar/R classification: NIP subgroup I and II. Functional analysis indicates that these two subgroups are functionally distinct. NIP subgroup I forms aquaglyceroporin channels that are also permeable to ammonia, while NIP subgroup II channels are impermeable to water and capable of transporting larger solutes, such as urea. Site-directed mutagenesis studies were used to rationally interconvert the selectivity of these proteins by amino acid substitutions in the ar/R region. Finally, it was demonstrated that members of NIP subgroup II in Arabidopsis form physiologically relevant boric acid channels at the plasma membrane. Nodulin 26, the archetypal NIP, is phosphorylated by a calcium dependant protein kinase (CDPK) at Ser 262 in its C-terminus. This study demonstrates that nodulin 26 phosphorylation increases the water permeability of the channel.In addition, the C-terminus was found to constitute a protein interaction site for nodule cytosolic glutamine synthetase. Finally, the study was extended to characterize MIP channels from the common pea aphid (ApAQP1 and ApAQP2). The results indicate that ApAQP1 is a water-selective aquaporin that is involved in aphid gut osmoregulation, while ApAQP2 is a water channel that is permeable to an array of linear polyols. The potential physiological function of this channel is also discussed

British academics and war with Germany 1914 - 1918

Before 1914 the German university system and German scholarship occupied a position of special prestige. The outbreak of the First World War not only severed ties of friendship and common endeavour between British and German scholars, but also seriously undermined the reputation of German Wissenschaft* British academics, hitherto admirers of German achievements, now claimed to have long harboured doubts as to the tone of German academic life. Others, like Lord Bryce, who had worked to promote Anglo- German understanding now joined the propaganda battle against Germany. Intellectuals in all belligerent states saw the war as a great ideological contest. British philosophers provided an ideo¬ logical exegesis for German policy, although the legacy of Hegel gave considerable difficulties for the neo-Xdealist school then dominant in British universities. The historian's traditional explanation of Britain's role in the world was given greater impor¬ tance by the German claim that the war was a contest for world empire. The war also posed an intellectual problem for academics. Before 1914 there had been little discussion of the questions of war and peace amongst British academics. When war forced liberal academics to face moral issues, only Bertrand Russell stood out in total opposition to government policy. Gilbert Murray and Lowes Dickinson provide more typical examples of the behaviour of liberal intellectuals under the stress of war. In Britain the eulogy of war may have been more muted than it was in Germany or France, the persecution of academic "dissenters" less intense than in the United States, but the involvement of academics as publicists and propagandists of the national cause was not less marked than in other belligerent states. However, the theme is not one of "betrayal". The commitment of British academics to value-free objective enquiry before the war was, in reality, as illusory as the similar claims of their German colleagues

A study of the effect of neutral salts upon the dissociation of benzoic acid by means of the catalytic decomposition of ethyl diazoacetate

ChemistryDoctor of Philosophy (PhD

CURIOS: Connecting Community Heritage through Linked Data

Peer reviewedPostprin

Child abuse registration, fetal growth, and preterm birth: a population based study

Objectives: To study the relation of intra-uterine growth and gestational age with child protection registration in a 20 year whole population birth cohort. Setting: West Sussex area of England. Study design: Retrospective whole population birth cohort. Outcomes: Child protection registration; individual categories of registration—sexual abuse, physical abuse, emotional abuse, and neglect. Population and participants: 119 771 infants born in West Sussex between January 1983 and December 2001 with complete data including birth weight, gestational age, maternal age, and postcode. Results: In all categories of registration a linear trend was noted such that the lower the birth weight z score the higher the likelihood of child protection registration. Similar trends were noted for gestational age. All these trends were robust to adjustment for maternal age and socioeconomic status. Conclusions: The results of this study suggest that lower levels of fetal growth and shorter gestational duration are associated with increased likelihood of child protection registration in all categories including sexual abuse independent of maternal age or socioeconomic status. This study does not permit comment on whether poor fetal growth or preterm birth predispose to child abuse and neglect or the association arises because they share a common pathway

Effects of Lline Rate on vVideo QoS over Wireless Networks: an Experimental Approach

Video streaming over Wireless Local Area Networks (WLANS) is becoming an increasingly popular service. However, end user OoS is highly influenced by many factors. These include the video codec used, the packetization scheme, error concealment and correction techniques, the complexity of the video, propagation losses, and the line rate. In this paper the effect of the line rate on the capacity of the network when streaming multimedia content is analyzed experimentally. It is shown that as the line rate decreases the bandwidth load of the video stream dramatically increases leading to poor QoS at the client side. As automatic line rate adaptation schemes are typically employed in the majority of WLAN adapters, clients have no control over the line rate of their connection and consequently can suffer from a poor QoS for their video streaming services

A first direct measurement of the intergalactic medium temperature around a quasar at z=6

The thermal state of the intergalactic medium (IGM) provides an indirect probe of both the HI and HeII reionisation epochs. Current constraints on the IGM temperature from the Lya forest are restricted to the redshift range 2<z<4.5, limiting the ability to probe the thermal memory of HI reionisation toward higher redshift. In this work, we present the first direct measurement of the IGM temperature around a z=6 quasar by analysing the Doppler widths of Lya absorption lines in the proximity zone of SDSS J0818+1722. We use a high resolution (R= 40000) Keck/HIRES spectrum in combination with detailed numerical modelling to obtain the temperature at mean density, T_0=23600\pm^5000_6900K (\pm^9200_9300K) at 68 (95) per cent confidence assuming a prior probability 13500K<T_0<38500 K following HI and HeII reionisation. This enables us to place an upper limit on the redshift of HI reionisation, z_H, within 33 comoving Mpc of SDSS J0818+1722. If the quasar reionises the HeII in its vicinity, then in the limit of instantaneous reionisation we infer z_H<9.0 (11.0) at 68 (95) per cent confidence assuming photoheating is the dominant heat source and that HI reionisation is driven by ionising sources with soft spectra, typical of population II stars. If the HI and HeII in the IGM around SDSS J0818+1722 are instead reionised simultaneously by a population of massive metal-free stars, characterised by very hard ionising spectra, we obtain a tighter upper limit of z_H<8.4 (9.4). Initiating reionisation at higher redshifts produces temperatures which are too low with respect to our constraint unless the HI ionising sources or the quasar itself have spectra significantly harder than typically assumed.Comment: 15 pages, 9 figures, accepted to MNRA

THE SCOTCH-IRISH OF PROVINCIAL NEW HAMPSHIRE

This dissertation examines the Scotch-Irish as a distinct ethnic group in eighteenth-century New Hampshire. The Scotch-Irish are seen in light of their ethnicity as well as the role they played in the growth and development of provincial New Hampshire. When the first wave of Presbyterians from Ulster came to New England in 1718, they were confused with native, Catholic Irish. Boston rejected them, and they were sent to frontier areas in Maine and central Massachusetts, where they suffered at the hands of land speculators, unsympathetic neighbors, and hostile Indians. In New Hampshire, a substantial number of New England\u27s Scotch-Irish immigrants found a haven in the vicinity of Nutfield, or Londonderry. Yet it was a haven threatened by conflicting interpretations of town and provincial boundaries. The Scotch-Irish story in Londenderry had both ethnic and political dimensions. The Scotch-Irish proprietors of Londonderry sought to control town affairs in order to preserve their community\u27s ethnic identity. Toward that end, they encouraged emigrants from Ulster to join them. Yet out of political necessity, town proprietors had to align themselves with New Hampshire\u27s political leaders. Officials in Londonderry and Portsmouth worked together in order to prevent New Hampshire from being absorbed by its much larger southern neighbor. In the end, they succeeded. New Hampshire not only survived, but the boundary decision of 1740 expanded New Hampshire at the expense of Massachusetts. Ironically, political victory led to assimilation. As Scotch-Irish settlers left Londonderry to settle townships in western New Hampshire, ethnic barriers broke down