Development of a floating tidal energy system suitable for use in shallow water

A proposal is made for the use of a traditional streamwaterwheel suspended between two floating catamaranNPL series demi-hulls as means of generating electricalpower. Two prototype devices, of lengths 1.6m and 4.5m,have been developed, constructed and tested. It was foundthat the concept is sound although greater investment isrequired with regards to the materials and bothhydrodynamic and aerodynamic design of the waterwheelto ensure an economically viable system. The workpresented concentrates on practical aspects associated withdesign, construction and trial testing in Southampton waterof the 4.5m prototype. The relatively low cost, ease ofdeployment, and the fact that conventional boat mooringsystems are effective, combine to make this an attractivealternative energy solution for remote communities

Assessment of Alternative Energy Technologies and Recommendations for a National Energy Policy

The objective of this IQP is to analyze the current state of energy production by all major energy sources, explore the technical and economic feasibility of individual alternatives, and to develop a set of public policy recommendations that can be implemented at the federal level to address this situation over the next few decades

Functional asymmetry in the lysyl-tRNA synthetase explored by molecular dynamics, free energy calculations and experiment

BACKGROUND: Charging of transfer-RNA with cognate amino acid is accomplished by the aminoacyl-tRNA synthetases, and proceeds through an aminoacyl adenylate intermediate. The lysyl-tRNA synthetase has evolved an active site that specifically binds lysine and ATP. Previous molecular dynamics simulations of the heat-inducible Escherichia coli lysyl-tRNA synthetase, LysU, have revealed differences in the binding of ATP and aspects of asymmetry between the nominally equivalent active sites of this dimeric enzyme. The possibility that this asymmetry results in different binding affinities for the ligands is addressed here by a parallel computational and biochemical study. RESULTS: Biochemical experiments employing isothermal calorimetry, steady-state fluorescence and circular dichroism are used to determine the order and stoichiometries of the lysine and nucleotide binding events, and the associated thermodynamic parameters. An ordered mechanism of substrate addition is found, with lysine having to bind prior to the nucleotide in a magnesium dependent process. Two lysines are found to bind per dimer, and trigger a large conformational change. Subsequent nucleotide binding causes little structural rearrangement and crucially only occurs at a single catalytic site, in accord with the simulations. Molecular dynamics based free energy calculations of the ATP binding process are used to determine the binding affinities of each site. Significant differences in ATP binding affinities are observed, with only one active site capable of realizing the experimental binding free energy. Half-of-the-sites models in which the nucleotide is only present at one active site achieve their full binding potential irrespective of the subunit choice. This strongly suggests the involvement of an anti-cooperative mechanism. Pathways for relaying information between the two active sites are proposed. CONCLUSIONS: The asymmetry uncovered here appears to be a common feature of oligomeric aminoacyl-tRNA synthetases, and may play an important functional role. We suggest a manner in which catalytic efficiency could be improved by LysU operating in an alternating sites mechanism

A Formalization of the Theorem of Existence of First-Order Most General Unifiers

This work presents a formalization of the theorem of existence of most general unifiers in first-order signatures in the higher-order proof assistant PVS. The distinguishing feature of this formalization is that it remains close to the textbook proofs that are based on proving the correctness of the well-known Robinson's first-order unification algorithm. The formalization was applied inside a PVS development for term rewriting systems that provides a complete formalization of the Knuth-Bendix Critical Pair theorem, among other relevant theorems of the theory of rewriting. In addition, the formalization methodology has been proved of practical use in order to verify the correctness of unification algorithms in the style of the original Robinson's unification algorithm.Comment: In Proceedings LSFA 2011, arXiv:1203.542

Biomimetic Behaviours in Hydrogel Artificial Cells through Embedded Organelles

Artificial cells are biomimetic structures formed from molecular building blocks that replicate biological processes, behaviors, and architectures. Of these building blocks, hydrogels have emerged as ideal, yet underutilized candidates to provide a gel-like chassis in which to incorporate both biological and nonbiological componentry which enables the replication of cellular functionality. Here, we demonstrate a microfluidic strategy to assemble biocompatible cell-sized hydrogel-based artificial cells with a variety of different embedded functional subcompartments, which act as engineered synthetic organelles. The organelles enable the recreation of increasingly biomimetic behaviors, including stimulus-induced motility, content release through activation of membrane-associated proteins, and enzymatic communication with surrounding bioinspired compartments. In this way, we showcase a foundational strategy for the bottom–up construction of hydrogel-based artificial cell microsystems which replicate fundamental cellular behaviors, paving the way for the construction of next-generation biotechnological devices

Characteristics of young people accessing recently implemented Community Forensic Child and Adolescent Mental Health Services (F:CAMHS) in England: insights from national service activity data

Children and young people in contact with forensic child and adolescent mental health services present with more complex needs than young people in the general population. Recent policy in child and adolescent mental health has led to the implementation of new workstreams and programmes to improve service provision. This research examines the characteristics of children and young people referred to recently commissioned Community Forensic Child and Adolescent Services (F:CAMHS) and service activity during the frst 24 months of service. The study is a national cohort study to describe the population and investigate service provision and access across England. Secondary data on 1311 advice cases and 1406 referrals are included in analysis. Findings show that 71.9% of the sample had accessed mainstream CAMHS before their referral, 50.9% had experienced/witnessed multiple traumatic events and 58.4% of young people presented with multiple difculties. The results of the study highlight the complexity of the cohort and a need for interagency trauma-informed working. This is the frst study to describe the characteristics of children and young people referred to Community F:CAMHS and provides valuable information on pathways and needs to inform service policy and provision

Several types of types in programming languages

Types are an important part of any modern programming language, but we often forget that the concept of type we understand nowadays is not the same it was perceived in the sixties. Moreover, we conflate the concept of "type" in programming languages with the concept of the same name in mathematical logic, an identification that is only the result of the convergence of two different paths, which started apart with different aims. The paper will present several remarks (some historical, some of more conceptual character) on the subject, as a basis for a further investigation. The thesis we will argue is that there are three different characters at play in programming languages, all of them now called types: the technical concept used in language design to guide implementation; the general abstraction mechanism used as a modelling tool; the classifying tool inherited from mathematical logic. We will suggest three possible dates ad quem for their presence in the programming language literature, suggesting that the emergence of the concept of type in computer science is relatively independent from the logical tradition, until the Curry-Howard isomorphism will make an explicit bridge between them.Comment: History and Philosophy of Computing, HAPOC 2015. To appear in LNC

RPO, Second-order Contexts, and Lambda-calculus

First, we extend Leifer-Milner RPO theory, by giving general conditions to obtain IPO labelled transition systems (and bisimilarities) with a reduced set of transitions, and possibly finitely branching. Moreover, we study the weak variant of Leifer-Milner theory, by giving general conditions under which the weak bisimilarity is a congruence. Then, we apply such extended RPO technique to the lambda-calculus, endowed with lazy and call by value reduction strategies. We show that, contrary to process calculi, one can deal directly with the lambda-calculus syntax and apply Leifer-Milner technique to a category of contexts, provided that we work in the framework of weak bisimilarities. However, even in the case of the transition system with minimal contexts, the resulting bisimilarity is infinitely branching, due to the fact that, in standard context categories, parametric rules such as the beta-rule can be represented only by infinitely many ground rules. To overcome this problem, we introduce the general notion of second-order context category. We show that, by carrying out the RPO construction in this setting, the lazy observational equivalence can be captured as a weak bisimilarity equivalence on a finitely branching transition system. This result is achieved by considering an encoding of lambda-calculus in Combinatory Logic.Comment: 35 pages, published in Logical Methods in Computer Scienc