Key Constructions Research Articles

HOM-ALGEBRAS AND HOM-COALGEBRAS

The aim of this paper is to develop the theory of Hom-coalgebras and related structures. After reviewing some key constructions and examples of quasi-deformations of Lie algebras involving twisted derivations and giving rise to the class of quasi-Lie algebras incorporating Hom–Lie algebras, we describe the notion and some properties of Hom-algebras and provide examples. We introduce Hom-coalgebra structures, leading to the notions of Hom-bialgebra and Hom–Hopf algebras, and prove some fundamental properties and give examples. Finally, we define the concept of Hom–Lie admissible Hom-coalgebra and provide their classification based on subgroups of the symmetric group.

Gender, gender roles and completion of nursing education: A longitudinal study

The current worldwide nursing shortage and high attrition of nursing students remain a challenge for the nursing profession. The aim of this paper was to investigate how key psychological attributes and constructions differentiate between completers and non-completers of nursing education. A questionnaire including measures of gender role identity and perceived gender appropriateness of careers was administered to 384 students early in the first year of the course. At the end of the programme attrition rates were obtained. The findings indicate that males were more likely to leave the course than females. Furthermore, those who completed the course tended to view nursing as more appropriate for women, in contrast to the non-completers who had less gender typed views. The female-dominated nature of nursing, prevalent stereotypes and gender bias inherent in nursing education seem to make this an uncomfortable place for males and those with less gendered typed views. Whilst it is acknowledged that attrition is undoubtedly a complex issue with many contributing factors, the nursing profession need to take steps to address this bias to ensure their profession is open equally to both female and male recruits.

Alternative Interpretations: Exceptional Circumstances and the Bluestone Development in Pembrokeshire Coast National Park

This paper focuses on the debate around the planning application to build a major holiday village in a National Park, an application complicated by the fact that the proposed site straddled the boundaries of two planning authorities driven by very different policy agendas and attitudes towards sustainability which acted as lenses for their interpretation of the term “exceptional circumstances”. The situation was further exacerbated by extensive cross-membership of the two planning authorities with elected members from the local authority forming the majority of members on the National Park authority without reciprocal membership from the National Park authority on the local authority. Thus, local authority policies bled across the boundary into the National Park authority. Planning permission was granted and, although its legality was later challenged in court, was subsequently upheld. Through convergent and semi-structured interviews with key stakeholders different discursive constructions of the term exceptional circumstances, which enabled stakeholders to rationalise their reactions to the proposal and their subsequent support (or not) for it, crystallised. The paper concludes that for cross-boundary proposals with very different policy drivers each side of the boundary, as is the case for a local authority and a National Park authority, that planning applications must be referred for external, independent scrutiny.

Anonymous RFID authentication supporting constant-cost key-lookup against active adversaries

In the absence of sufficiently optimised public key constructions, anonymous authentication for Radio-Frequency Identification Devices (RFIDs) requires state synchronisation between tags and a trusted server. Active adversaries disrupt this synchrony, making a recovery strategy necessary. In some protocols, tags recover by replaying previously used values, thus compromising unlinkability of their transcripts; other schemes require servers to search through the set of issued keys, incurring costs that are not constant with the number of legitimate tags. This article describes an approach based on a lightweight trapdoor one-way function from modular squaring. The solution exploits the fact that synchrony can be recovered even if tags are endowed with only the ability to perform public-key operations, whilst the trusted server is capable of trapdoor computations. The construction is provably secure and generic, transforming any anonymous, challenge-response RFID authentication protocol into another that is robust against active adversaries and supports constant key-lookup cost.

Photocycloaddition in Natural Product Synthesis

AbstractThe application of photocycloaddition to natural product synthesis continues to produce innovative and effective strategies for key bond constructions in the complex molecule environment. This Microreview surveys the recent literature for examples that illustrate the power and versatility of photocycloaddition chemistry, drawing from [2+2], [3+2], [4+2], [5+2] and [4+4] reactions. The discussion is confined to natural product syntheses, and will include photocycloaddition key steps in both completed routes and those in progress.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Interpretivism and Conventionalism: Contributions to the Critical Assessment of Contemporary Methodological Legal Positivism

The essay provides a critical analysis of certain versions of legal positivism that combine interpretivism with (jurisprudential) conventionalism. The first sections of the essay are devoted to clarifying the key conceptual constructions around which the analysis revolves. Interpretivism is taken as a methodological programme for legal theory that is based on the idea that the nature of law is to be clarified by way of interpreting information gathered from participant communication about law. Jurisprudential conventionalism refers to the theoretical claim that normativity of law can be traced back to an interdependent convergence of behaviour among the officials of legal systems that gives rise to a duty-imposing conventional rule (commonly called the rule of recognition). Directives become normative as legal standards if they meet the conditions of legality set out by that conventional rule. Herbert Hart is taken as the paradigmatic representative of the criticised version of legal positivism. The essay argues that the core idea of interpretivism is sound and worth preserving, but, for interpretivist legal theories, jurisprudential conventionalism is to be rejected. The problem for accounts of law that combine interpretivism with conventionalism is that they cannot account for the distinctive normativity of law. The reason being that they cannot deny the central conceptual significance of the legal obligations imposed on the ordinary citizens of the legal system (it is a fact that participant communication attributes to law that ability to obligate ordinary citizens), but no conventions generated by the convergence of the behaviour of officials can provide the normative basis for such obligations. The essay tries to provide a detailed analysis of Hart's efforts to overcome the problems of jurisprudential conventionalism. The closing section aims at showing the way the position taken by the author is to be distinguished from the familiar claims of natural lawyers.

Total Syntheses of (+)-Lyconadin A and (−)-Lyconadin B

The enantioselective syntheses of (+)-lyconadin A and (−)-lyconadin B are described. Key bond constructions include a strategy-level intramolecular aldol/conjugate addition cascade, an olefin amino...

건축턴키공사 초기 단계에서의 클레임 방지를 위한 클레임요인 분석 및 대응방안에 관한 연구 - 국내공사 사례중심으로 -

In the inner turn key constructions the problems of uniform types are repeatedly occurred, and, especially, many problems happen up to the stage of pre-construction(from a bid to a contract) owing to the specialties of the turn key constructions. So the claim factors of the Korean turn key constructions were abstracted through the literature searches, the site document examinations, the case studies and the interviews with the experts. When the technicians meeting the interior turn key constructions for the first time and working here now are well acquainted with only these factors, many claims will be prevented. By analysing the degree of claims by claims factors through the questionnaires to the experts about the abstracted factors and surveying the amount of the claims through the case studies, what factors exerted how much of influence on the claims was tested and analyzed. Proposing the response devices to the factors affecting the claims much led the technicians in charge of internal turn key constructions to the prevention and the proper solution of the site claims.

Discursive constructions of ‘eating disorders nursing’: an analysis of nurses' accounts of nursing eating disorder patients

The contribution of nurses is a significant but notably under-researched aspect of hospital-based eating disorders treatment. This paper reports a qualitative interview-based study in which 15 nurses were interviewed about nursing children and adolescents diagnosed with eating disorder. A discourse analytic methodology was employed to analyse the resulting interview transcripts and focuses, in particular, on elucidating the various ways in which ‘eating disorders nursing’ was construed in participants' accounts. Three key constructions were revealed in which ‘eating disorders nursing’ was discursively constituted (i) as ‘loving’ or empathetic support, (ii) as a surveillance and disciplining of patients and (iii) as a constant and ever-present care. The implications of these constructions are discussed. Copyright © 2006 John Wiley & Sons, Ltd and Eating Disorders Association.

Interface Tracking for Axisymmetric Flows

A front tracking method for inviscid gas dynamics is presented. The key constructions and algorithms used in the code are described and the interrelations between shock capturing, interface dynamics, computational geometry, grid construction, and parallelism are discussed for the code as a whole. Validation is carried out by comparing the single mode bubble velocity for Rayleigh--Taylor instability with theoretical models and experimental results. The calculations are validated by mesh refinement studies and by the comparison of the asymptotic limit of the minimum radius $r_{\rm min} \rightarrow \infty$ to a pure planar computation in two dimensions.

Bounds And Constructions For Threshold Shared Generation Of Authenticators

Shared generation of authenticator systems (or SGA-systems) generalise Simmons' traditional authentication codes when authenticators for source states are produced by collaboration of a group of senders, rather than a single sender. In this paper we study threshold SGA-systems. We derive information-theoretic and combinatorial lower bounds on the probability of success and the size of the key space, and give two key efficient constructions for SGA-systems based on den Boer A-codes and error-correcting codes. We also give a recursive construction method using perfect hash families to construct SGA-systems for large groups.

Performance testing of side chairs

Although a number of methods have been developed, both domestically and internationally, to evaluate the performance characteristics of side chairs, these tests, in general, do not provide quantitative measures of the strength and durability of the key structural elements and constructions which are needed for engineering design purposes. In addition, such tests also do not provide straightforward procedures for translating historical performance data into quantitative acceptance levels. This paper presents a series of performance tests for chairs which were developed to eliminate these shortcomings. Basically, these tests provide a means of determining the strength and durability of chairs in an unambiguous manner. Thus, they provide a rational means of determining the inherent strength characteristics of specific chair constructions. In addition, they provide a means of evaluating chairs with proven service histories and thereby establishing a database of service histories which can in turn be used to set up meaningful performance acceptance levels for chairs. Through the use of these tests, manufacturers are able to design and produce and consumers are able to select chairs with the strength and durability characteristics needed to survive in any specified service environment.

Applications of Vinylogous Mannich Reactions. Concise Enantiospecific Total Syntheses of (+)-Croomine

Because the vinylogous Mannich reaction of substituted furans with iminium ions is a useful construction in alkaloid synthesis, it is important to know what effects substituents on the two reacting partners have upon the stereoselectivity of the reaction. Toward this end, the additions of the methylated furans 9a−h to the iminium ion generated in situ from the ethoxy carbamate 10 were examined. Generally, mixtures (3−24:1) of the threo and erythro adducts 11a−h and 12a−h were obtained in 50−96% combined yields, with the threo isomers being the major products. Two extraordinarily concise asymmetric syntheses of (+)-croomine (1) have been completed using a novel strategy, highlighted by two vinylogous Mannich reactions as key constructions. The first such reaction involved the addition of 5-(4-bromobut-1-yl)-3-methyl-2-(triisopropylsilyloxy)furan to the N-acyliminium salt derived from the l-pyroglutamic acid derivative 17 to give the adduct [5(S),2‘(S),5‘(S)]-5-(4‘ ‘-bromobut-1‘ ‘yl)-5-[N-(tert-butoxycarbonyl)-2‘-(methoxycarbonyl)-pyrrolidin-5‘-yl]-3-methyl-2(5H)-furanone (18) as the major product. Refunctionalization of 18 led to the tricyclic intermediate [3‘S-[3‘α,9‘α(S*),9‘aα]]-decahydro-4-methyl-5-oxospiro[furan-2(3H),9‘-[9H]pyrrolo[1,2-a]azepin]-3‘-carboxylic acid, hydrobromide salt, which was, in turn, converted to an iminium salt that underwent a second vinylogous Mannich reaction to give [3‘S-[3‘α(R*),9‘α(S*),9‘aα]]-3‘-(2,5-dihydro-4-methyl-5-oxo-2-furanyl)decahydro-4-methylspiro[furan-2(5H),9‘-[9H]pyrrolo[1,2-a]azepin-5-one (24) as the major adduct. Stereoselective reduction of the unsaturated lactone 24 gave 1, completing a synthesis that required a total of only 11 chemical steps from commercially available starting materials. In a second approach, the initial Mannich adduct [5(S),2‘(S),5‘(S)]-5-(4‘ ‘-bromobut-1‘ ‘-yl)-5-[2‘-(methoxycarbonyl)pyrrolidin-5‘-yl]-3-methyl-2(5H)-furanone was transformed into the unsaturated tricyclic intermediate [3‘S-[3‘α(R*),9‘α(S*),9‘aα]]-3‘-(2,5-dihydro-4-methyl-5-oxo-2-furanyl)-1‘,2‘,3‘,5‘,6‘,7‘,8‘-octahydro-4-methylspiro[furan-2(5H),9‘-[9H]pyrrolo[1,2-a]azepin]-5-one, which underwent hydrogenation to give 1 as the only isolable product, thereby completing a synthesis that required only 10 steps.