Human CD4+ T Cell Recognition of Influenza A Haemagglutinin

Imperial Users onl

Tracing and Debugging of Lazy Functional Programs - A Comparative Evaluation of Three Systems

In this paper we compare three systems for tracing and debugging Haskell programs: Freja, the Redex Trail System and Hood. We identify the similarities and differences of these systems and we evaluate their usefulness in practice by applying them to a number of small to medium programs in which errors had deliberately been introduced

Needs assessment of gossamer structures in communications platform end-of-life disposal

The use of a gossamer structure is considered in application to end-of-life disposal of communications platforms. A wide-ranging survey of end-of-life disposal techniques and strategies is presented for comparison against a gossamer structure prior to a down-selection of viable competing techniques; solar sailing, high and low-thrust propulsion, and electrodynamic tethers. A parametric comparison of the down-selection competing techniques is presented where it was found that exploiting solar radiation pressure on the gossamer structure was of limited value. In general terms, it was found that if a spacecraft propulsion system remains functioning at the end-of-life then this will likely provide the most efficient means of re-orbiting, especially when the propulsion system is only used to lower the orbit to a point where atmospheric drag will cause the orbit to decay within the required timeframe. Atmospheric drag augmentation was found to be of most benefit for end-of-life disposal when an entirely passive means is required, allowing the device to act as a ‘fail-safe’, which if the spacecraft suffers a catastrophic failure would activate. The use of an atmospheric drag augmentation system is applicable to only low and medium mass spacecraft, or spacecraft that are unlikely to survive atmospheric re-entry, hence minimizing risk to human life

Multiple-View Tracing for Haskell: a New Hat

Different tracing systems for Haskell give different views of a program at work. In practice, several views are complementary and can productively be used together. Until now each system has generated its own trace, containing only the information needed for its particular view. Here we present the design of a trace that can serve several views. The trace is generated and written to file as the computation proceeds. We have implemented both the generation of the trace and several different viewers

Fine-grained visualization pipelines and lazy functional languages

The pipeline model in visualization has evolved from a conceptual model of data processing into a widely used architecture for implementing visualization systems. In the process, a number of capabilities have been introduced, including streaming of data in chunks, distributed pipelines, and demand-driven processing. Visualization systems have invariably built on stateful programming technologies, and these capabilities have had to be implemented explicitly within the lower layers of a complex hierarchy of services. The good news for developers is that applications built on top of this hierarchy can access these capabilities without concern for how they are implemented. The bad news is that by freezing capabilities into low-level services expressive power and flexibility is lost. In this paper we express visualization systems in a programming language that more naturally supports this kind of processing model. Lazy functional languages support fine-grained demand-driven processing, a natural form of streaming, and pipeline-like function composition for assembling applications. The technology thus appears well suited to visualization applications. Using surface extraction algorithms as illustrative examples, and the lazy functional language Haskell, we argue the benefits of clear and concise expression combined with fine-grained, demand-driven computation. Just as visualization provides insight into data, functional abstraction provides new insight into visualization

Multi-cultural visualization : how functional programming can enrich visualization (and vice versa)

The past two decades have seen visualization flourish as a research field in its own right, with advances on the computational challenges of faster algorithms, new techniques for datasets too large for in-core processing, and advances in understanding the perceptual and cognitive processes recruited by visualization systems, and through this, how to improve the representation of data. However, progress within visualization has sometimes proceeded in parallel with that in other branches of computer science, and there is a danger that when novel solutions ossify into `accepted practice' the field can easily overlook significant advances elsewhere in the community. In this paper we describe recent advances in the design and implementation of pure functional programming languages that, significantly, contain important insights into questions raised by the recent NIH/NSF report on Visualization Challenges. We argue and demonstrate that modern functional languages combine high-level mathematically-based specifications of visualization techniques, concise implementation of algorithms through fine-grained composition, support for writing correct programs through strong type checking, and a different kind of modularity inherent in the abstractive power of these languages. And to cap it off, we have initial evidence that in some cases functional implementations are faster than their imperative counterparts

The role of proteolytic processing of the 220kDa polyprotein of African swine fever virus and aggresomes during virion assembly

African swine fever virus (ASFV) is a large double stranded DNA virus causing a lethal haemorrhagic disease in domestic pigs. The 170kbp genome encodes 150 open reading frames and virions contain more than 50 different proteins. ASFV uses a 220kDa polyprotein (pp220) to produce major structural proteins p150, p37, p34 and p14. This thesis investigates the subcellular distribution and regulation of pp220 processing. Antibodies specific for p150 and p34 were generated and characterised. Western blot analysis showed that approximately 35% of the intracellular pool of pp220 associated with membranes, the remainder was cytosolic. The membrane bound pool was processed via intermediates to p34 and p150. p34 and p150, but not the polyprotein, or the processing intermediates, were enveloped and released in virions. The cytosolic pool was processed incorrectly and failed to produce structural proteins. The correct processing of pp220 occurs at 4 Gly-Gly-X motifs, however the polyprotein contains 19 Gly-Gly-X motifs. It was concluded that membrane association is required for correct processing. In the absence of membrane association the polyprotein maybe cleaved at all 19 Gly-Gly-X motifs. Aggresomes are a major site of proteolysis in cells and their role in ASFV assembly was investigated. Aggresomes are pericentriolar structures enriched for chaperones, proteasomes and ubiquitin. They are enclosed in a vimentin cage surrounded by mitochondria. ASFV assembly occurs in perinuclear structures called viral factories and the possibility that these derive from aggresomes was investigated. Immunofluorescence experiments showed viral factories close to the centriole and surrounded by vimentin cages and mitochondria. Furthermore, inhibitors of aggresome proteolysis and the over expression of misfolded proteins in the cytosol blocked viral replication. It is possible that ASFV uses aspects of the aggresomes to concentrate viral proteins during assembly

Speaking indirectly : theories of non-literal speech in Indian philosophy

textHow do hearers recognize when someone is speaking figuratively, and how do they recover the content--whatever it is--of an utterance? "Speaking Indirectly" explores this question in Indian philosophy, showing along the way that it is a helpful conversation partner with Western philosophy of language. Focusing on the debate between ninth-century Indian philosophers Mukulabhatt̤a and Ānandavardhana about competing explanations of non-literal meaning, I argue that Mukulabhatt̤a's proposal can be understood in the spirit of Gricean pragmatics, and is broadly successful. I also show that he tacitly appeals to reasoning known as arthāpatti to explain the interpretive process, a process which I conclude is a version of inference to the best explanation. I also employ contemporary conceptual tools, such as the theory of sort-shifting, to illustrate the plausibility of Mukulabhatt̤a's analysis of non-literal speech. A significant aspect of my dissertation is a new, philosophically informed, English translation of Mukulabhatt̤a's Sanskrit text, the Abhidhā-vṛtta-mātṛkā (Fundamentals of the Communicative Function).Philosoph

Sin and human responsibility in the theology of Emil Brunner

Brunner's theology is one of reaction and reformulation; reaction against the "objectivism" of Orthodoxy and Roman Catholicism, and against the "subjectivism" of liberal theology, and a reformulation of the basic tenets of the Christian faith in accordance with the sola gratia perspective of the Reformers. The reformulation contrasts the competing tendencies in philosophy, psychology and ethics, and relates these to the basic contradiction of human life, which the Christian faith calls 'sin', with the aid of Kantian criticism, and particularly Kantian moral theory, the Kierkegaardian dialectic of time and eternity, and the I-Thou framework developed by Ebner and Buber. Within this comprehensive formulation, our concern is the question of sin and human responsibility.Theologically, the issue is the seriousness of sin, and has been answered traditionally by contrasting man's creation in the image of God with the loss of that image through sin. Brunner's contention that Scripture presents two concepts of the image is most plausible, but his designation of these as a formal and a material concept of the image seems to set the distinction within man himself, whereas the Scriptural distinction seems to be between an Old Testament image which is predicated of man and a New Testament image which is Christ. We must also question his contention that Irenaeus distinguished between imago and similitudo in a manner similar to the medieval natural-supernatural distinction, but his summation of the Reformers' predicament, that their equation of the image with the justitia originalis and corresponding doctrine of total depravity renders their concept of a 'relic' of the image illegitimate, is essentially plausible. Brunner's solution to this predicament is not greatly clarified in the controversy with Barth, although Barth's subsequent charge, that Brunner teaches a neutral freedom, is instructive. Brunner's insistence on a concept of an analogia entis involving an analogy of proportionality, likeness in basic unlikeness, is understandable, but his relational interpretation of this suggests that his distinction between a formal and a material sense of the image is facilitated by an ambiguity in the term 'responsibility'.The term 'responsibility' seems to have at least three basic meanings in Brunner's theology - responsiveness, accountability, and ability to respond. Behind this is the more basic question of the distinction between moral and religious responsibility. His enthusiasm for Kant's development of the concept suggests that he overlooks the basically rational nature of the Kantian Imperative, and his content- -ion that Kant was torn between autonomy and theonomy suggests that he minimises the rational perspective from which Kant viewed Christianity. Kierkegaard's teleological suspension of the ethical, with its inseparability of command and commanded, reveals the difficulty in the formal Kantian Imperative which Brunner applauds. Further, Brunner's contention that Kant's concept of 'radical evil' is rationally discerned, and his appreciation for Schelling's treatment of evil, cast doubt on the seriousness of his affirmation of the irrationality of sin, and also illuminate the ambiguity in the moral and religious uses of the term 'responsibility' in his writings. There seem to be two strands in Brunner's presentation - a basic allegiance to the Reformers, and a certain sympathy with moral idealism.The conflict is climaxed in Brunner's treatment of the Fall and Original Sin. His rejection of a literal interpretation of Genesis III is understandable, but his contention that there is no real conflict here with modem science indicates an oversimplification of the problem. His rejection of a causal explanation of sin is understandable, but his rejection of every temporal explanation suggests a confusion between causal and temporal. His late admission that he taught a Platonic doctrine of the Fall suggests that he never really came to grips with the basic problems of the doctrine. His concern has been with the fallenness of man, in which he attempts to correct the one-sidedness of the Augustinian doctrine with an emphasis on responsibility. Here the conflict between the two strands in Brunner's theology is pronounced. His reversal of Kierkegaard's formula for the relation between individuals and humanity, whereby the special term 'Individual' is subordinated to an individualistic concept of 'each of us', conflicts with his concern for solidarity and his appreciation for the I-Thou framework, but agrees with his emphasis on responsibility and his refusal to consider a temporal origin of sin. Ultimately it is the universality of sin, and not solidarity in sin, which prevails in Brunner's theology. As this fails to provide an adequate statement of the totality of sin in terms of the race, so his emphasis on sin as 'act' fails to give adequate account of the totality of sin in terms of the individual. The concern to emphasise responsibility for sin suggests that this is a total responsibility which is predicated of men in general, and thus indicates a violation of the Reformation perspective.In his basic allegiance to the Reformation perspective, Brunner's development of the sola gratia principle involves an opposition to synergism in Orthodoxy, Roman Catholicism and liberal theology, and to passivism in the Reformers themselves. His defence of the personal over against the rational, in terms of the I-Thou framework, raises questions as to the significance of the 'It'dimension of life and the nature of the relation between I and Thou. The two questions are answered in Brunner's presentation of the respective roles of the imperative and the indicative in the relation. The former reveals a basic divergence between Brunner and Luther on 'Law' in that Brunner divests Luther's Law of all content and reintroduces it as the formal Imperative, thus indicating that Law is an 'It' which has no integral place in the I-Thou framework. The indicative of the once-for-all act of God in Christ is equally embarrassing to the I-Thou, although it represents a constant emphasis in Brunner's theology. Luther's concern for the man who stands between the demand of the Law and the comfort of the Gospel becomes, in Brunner, the concern to relate this dialectic to the self-understanding of natural man. He accomplishes this with the relatively modern word 'responsibility' which can refer both to man as an independent moral agent and to man's ultimate obligation to God. In so far as man is addressed as a moral agent, and called to account prior to the proclamation of grace, the Reformation perspective is violated. It is strange that Brunner has not applied his recognition of the profound gulf separating modern man from former ages to this relatively modern concept of 'responsibility'