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Fundamental Problems (fundamental + problem)
Selected AbstractsA Fundamental Problem with Amino-Acid-Sequence Characters for Phylogenetic AnalysesCLADISTICS, Issue 3 2000Mark P. Simmons Protein-coding genes may be analyzed in phylogenetic analyses using nucleotide-sequence characters and/or amino-acid-sequence characters. Although amino-acid-sequence characters "correct" for saturation (parallelism), amino-acid-sequence characters are subject to convergence and ignore phylogenetically informative variation. When all nucleotide-sequence characters have a consistency index of 1, characters coded using the amino acid sequence may have a consistency index of less than 1. The reason for this is that most amino acids are specified by more than one codon. If two different codons that both code for the same amino acid are derived independent of one another in divergent lineages, nucleotide-sequence characters may not be homoplasious when amino-acid-sequence characters may be homoplasious. Not only may amino-acid-sequence characters support groupings that are not supported by nucleotide-sequence characters, they may support contradictory groupings. Because this convergence is a problem of character delimitation, it affects the results of all tree-construction methods (maximum likelihood, neighbor joining, parsimony, etc.). In effect, coding amino-acid-sequence characters instead of nucleotide-sequence characters putatively corrects for saturation and definitely causes a convergence problem. An empirical example from the Mhc locus is given. [source] Two-point dixon fat,water separation: Improving reliability and accuracy in phase correction algorithmsJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2008Maria A. Schmidt PhD Abstract Purpose To propose an advanced phase-correction region-growing algorithm for two-point fat,water separation suitable for parotid assessment, and to evaluate the general performance of phase-correction algorithms. Materials and Methods Two region-growing algorithms were evaluated in test objects and in head images: the original phase-correction algorithm (OPC) and the advanced phase-correction algorithm with voxel size manipulation (VSM) which includes: 1) starting the region-growing process from images of lower resolution and subsequently stepping toward the original matrix size, and 2) limiting the use of low-pass filters to fat,water interfaces with partial volume effects Results Fundamental problems relate to biological tissue spectrum being poorly approximated by two discrete peaks for fat and water. The VSM algorithm was shown to be less noise-sensitive, faster, and to produce a better approximation for the field inhomogeneity map. In head images (6 volunteers, 10 slices each) 43 errors were found with the OPC algorithm and only 6 errors with the VSM algorithm. Only the OPC algorithm produced errors surrounding the parotids (10 errors). Conclusion The VSM algorithm provides a more accurate and less noise-sensitive fat,water separation. This highly significant performance improvement allows the application of phase-correction algorithms to a wider range of clinical applications. J. Magn. Reson. Imaging 2008. © 2008 Wiley-Liss, Inc. [source] Choosing Rhetorical Structures To Plan Instructional TextsCOMPUTATIONAL INTELLIGENCE, Issue 3 2000Leila Kosseim This paper discusses a fundamental problem in natural language generation: how to organize the content of a text in a coherent and natural way. In this research, we set out to determine the semantic content and the rhetorical structure of texts and to develop heuristics to perform this process automatically within a text generation framework. The study was performed on a specific language and textual genre: French instructional texts. From a corpus analysis of these texts, we determined nine senses typically communicated in instructional texts and seven rhetorical relations used to present these senses. From this analysis, we then developed a set of presentation heuristics that determine how the senses to be communicated should be organized rhetorically in order to create a coherent and natural text. The heuristics are based on five types of constraints: conceptual, semantic, rhetorical, pragmatic, and intentional constraints. To verify the heuristics, we developed the spin natural language generation system, which performs all steps of text generation but focuses on the determination of the content and the rhetorical structure of the text. [source] The lateral intercellular space as osmotic coupling compartment in isotonic transportACTA PHYSIOLOGICA, Issue 1 2009E. H. Larsen Abstract Solute-coupled water transport and isotonic transport are basic functions of low- and high-resistance epithelia. These functions are studied with the epithelium bathed on the two sides with physiological saline of similar composition. Hence, at transepithelial equilibrium water enters the epithelial cells from both sides, and with the reflection coefficient of tight junction being larger than that of the interspace basement membrane, all of the water leaves the epithelium through the interspace basement membrane. The common design of transporting epithelia leads to the theory that an osmotic coupling of water absorption to ion flow is energized by lateral Na+/K+ pumps. We show that the theory accounts quantitatively for steady- and time dependent states of solute-coupled fluid uptake by toad skin epithelium. Our experimental results exclude definitively three alternative theories of epithelial solute,water coupling: stoichiometric coupling at the molecular level by transport proteins like SGLT1, electro-osmosis and a ,junctional fluid transfer mechanism'. Convection-diffusion out of the lateral space constitutes the fundamental problem of isotonic transport by making the emerging fluid hypertonic relative to the fluid in the lateral intercellular space. In the Na+ recirculation theory the ,surplus of solutes' is returned to the lateral space via the cells energized by the lateral Na+/K+ pumps. We show that this theory accounts quantitatively for isotonic and hypotonic transport at transepithelial osmotic equilibrium as observed in toad skin epithelium in vitro. Our conclusions are further developed for discussing their application to solute,solvent coupling in other vertebrate epithelia such as small intestine, proximal tubule of glomerular kidney and gallbladder. Evidence is discussed that the Na+ recirculation theory is not irreconcilable with the wide range of metabolic cost of Na+ transport observed in fluid-transporting epithelia. [source] On the analytical solution of the Bejan-Khair equation arising in free convection in porous mediaHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2010V.J. Bansod Abstract This paper revisits the fundamental problem of free convection heat and mass transfer over a heated vertical surface embedded in a porous medium using analytical techniques. An integral procedure is applied to the boundary layer similar equation for the combined heat and mass transfer from a vertical surface in a porous medium. The analytical approximations have covered a wide range of governing parameters of the problem. The results for both Nusselt and Sherwood numbers agree well with numerical results published in the literature. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20297 [source] States, Social Policies and Globalisations Arguing on the Right Terrain?IDS BULLETIN, Issue 4 2000Mick Moore Summaries The debate about future social policies in OECD countries is framed in the light of rich country concerns, notably of a ,welfare state at risk'. Because globalisation processes can plausibly be presented as a major source of threat, there is a temptation to generalise the analysis globally, and to assume that social policy issues in poor countries are fundamentally the same as in OECD states. The debate about the future of social policy in poor countries should not be framed in terms of OECD concerns. Three more specific points underpin this general argument: (a) Economic globalisation is not necessarily a threat. There are good historical reasons for believing that it may create political pressures to extend as well as to shrink social provision in poor countries; (b) There is a fundamental problem of state incapacity in much of the poor world that makes many OECD-based arguments about the proper role of the state appear redundant. Greater state capacity will itself lead to more effective social policies; and (c) It makes little sense for poor countries to resist, on grounds of potential adverse impacts on social policy, the trends toward the adoption of either New Public Management practices or the broader shift from ,positive' to regulatory states. Whatever changes occur in the architecture of poor states, more effective regulation will remain an urgent need. [source] Exploring the maximum capability of adaptive feedbackINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 5 2002Lei Guo Abstract The main purpose of adaptive feedback is to deal with dynamical systems with internal and/or external uncertainties, by using the on-line observed information. Thus, a fundamental problem in adaptive control is to understand the maximum capability (and limits) of adaptive feedback. This paper gives a survey of some basic ideas and results developed recently in this direction, for several typical classes of uncertain dynamical systems including parametric and non-parametric non-linear systems, sampled-data systems and time-varying systems. Copyright © 2002 John Wiley & Sons, Ltd. [source] Optimization of tree-shaped flow distribution structures over a disc-shaped areaINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2003S. Lorente Abstract In this paper, we review the fundamental problem of how to design a flow path with minimum overall resistance between one point (O) and many points situated equidistantly on a circle centred at O. This is a fundamental problem in energy engineering: the distribution of fluid, energy, electric power, etc., from points to surrounding areas. This problem is also fundamental in heat transfer and electronics cooling: how to bathe and cool with a single stream of coolant a disc-shaped area or volume that generates heat at every point. This paper outlines, first, a direct route to the construction of effective tree-shaped flow structures. The starting point is the optimization of the shape of each elemental area, such that the length of the flow path housed by the element is minimized. Proceeding towards larger and more complex structures,from elements to first constructs, second constructs, etc.,the paper develops tree-shaped flow structures between one point and a straight line, as an elemental problem, and a circle and its centre. We also consider the equivalent tree-shaped networks obtained by minimizing the pressure drop at every step of the construction, in accordance with geometric constraints. The construction method is applied to a fluid flow configuration with laminar fully developed flow. It is shown that there is little difference between the two methods. The minimal-length structures perform very close to the fully optimized designs. These results emphasize the robustness of optimized tree-shaped flows. Copyright © 2003 John Wiley & Sons, Ltd. [source] A dynamic key management solution to access hierarchyINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 6 2007Xukai Zou Hierarchical access control (HAC) has been a fundamental problem in computer and network systems. Since Akl and Taylor proposed the first HAC scheme based on number theory in 1983, cryptographic key management techniques for HAC have appeared as a new and promising class of solutions to the HAC problem. Many cryptographic HAC schemes have been proposed in the past two decades. One common feature associated with these schemes is that they basically limited dynamic operations at the node level. In this paper, by introducing the innovative concept of ,access polynomial' and representing a key value as the sum of two polynomials in a finite field, we propose a new key management scheme for dynamic access hierarchy. The newly proposed scheme supports full dynamics at both the node level and user level in a uniform yet efficient manner. Furthermore, the new scheme allows access hierarchy to be a random structure and can be flexibly adapted to many other access models such as ,transfer down' and ,depth-limited transfer'. Copyright © 2007 John Wiley & Sons, Ltd. [source] Aid, Relief, and Containment: The First Asylum Country and BeyondINTERNATIONAL MIGRATION, Issue 5 2002B.S. Chimni A fundamental problem that confronts the European Union today is how it can maintain its commitment to the institution of asylum while checking irregular migration and the abuse of its asylum system. In order to explore a response to this dilemma the paper addresses the following questions: what role can relief and aid policies play in influencing migration patterns? What should be the appropriate approach to the granting of relief and aid to developing countries of first asylum? Should it be viewed as a part of the larger problem of development or be treated as a distinct issue? What kind of a relief/aid model will help refugees return to post,conflict societies and stop the conflict from reproducing itself? The paper examines two different approaches to address these questions: the alliance,containment approach and the distributive,developmental approach. It also looks at some empirical evidence, which reveals that at present it is a conservative alliance,containment approach that informs EU relief and aid practices. This approach, however, does not help achieve the stated objective of checking abuse of asylum and migration procedures while sustaining a commitment to a liberal asylum regime. The paper goes on to identify the gaps in EU policy and the lessons that can be drawn. It concludes by looking at different policy alternatives and suggesting the adoption of a reformist distributive,developmental model. The implementation of this model holds out the hope of reverting to a more liberal asylum regime while controlling irregular migration and "bogus" asylum seekers, for the reformist distributive developmental model takes a more long,term view of migration trends and also seeks to address the growing North,South divide. [source] An educational process to strengthen primary care nursing practices in São Paulo, BrazilINTERNATIONAL NURSING REVIEW, Issue 4 2007A.M. Chiesa rn Objective:, To describe the experience of a registered nurse (RN) training process related to the Family Health Program (FHP) developed in the city of São Paulo, Brazil. Background:, The FHP is a national, government strategy to restructure primary care services. It focuses on the family in order to understand its physical and social structure in regards to the health,illness process. In the FHP, the RN is a member of a team with the same number as medical doctors , an unprecedented situation. The FHP requires a discussion of the RNs' practice, by qualifying and empowering them with tools and knowledge. Methods:, The training process was based on Freire's approach founded on critical pedagogy in order to address the fundamental problem of inequalities in health. The first phase included workshops and the second one included a course. The workshops identified the following problems related to the RN's work: lack of tools to identify the population's needs; overload of work due to the accumulation of management and assistance activities; difficulties regarding teamwork; lack of tools to evaluate the impact of nursing interventions; lack of tools to improve the participation of the community. The course was organized to tackle these problems under five thematic headings. Results:, The RN's training process allowed the group to reflect deeply on its work. This experience led to the need for the construction of tools to intervene in the reality, mainly against social exclusion, rescuing and adapting of the knowledge accumulated in the healthcare practice, identifying settings which demand institutional solutions and engaging the RN in research groups in order to develop projects according to the complexity of the primary care services. Conclusion:, The application of the concept of equity in the health sector represented a reaction against the processes of social exclusion, starting from performance at a local level to become a reality in the accomplishments achieved by the Brazilian National Health System. This training process allowed us to evaluate that partnership, which has produced many concrete results in addressing both parts of the Inequalities in Health dilemma and which is a productive way of building up a new model of health. [source] A REVIEW OF GEOLOGICAL DATA THAT CONFLICT WITH THE PARADIGM OF CATAGENIC GENERATION AND MIGRATION OF OILJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2005H. Hugh Wilson The majority of petroleum geologists today agree that the complex problems that surround the origin, generation, migration and accumulation of hydrocarbons can be resolved by accepting the geochemical conclusion that the process originates by catagenic generation in deeply-buried organically-rich source rocks. These limited source rock intervals are believed to expel hydrocarbons when they reach organic maturity in oil kitchens. The expelled oil and gas then follow migration pathways to traps at shallower levels. However, there are major geological obstacles that cast doubt upon this interpretation. The restriction of the source rock to a few organically rich levels in a basin forces the conclusion that the basin plumbing system is leaky and allows secondary horizontal and vertical migration through great thicknesses of consolidated sedimentary rocks in which there are numerous permeability barriers that are known to effectively prevent hydrocarbon escape from traps. The sourcing of lenticular traps points to the enclosing impermeable envelope as the logical origin of the trapped hydrocarbons. The lynch-pin of the catagenic theory of hydrocarbon origin is the expulsion mechanism from deeply-buried consolidated source rock under high confining pressures. This mechanism is not understood and is termed an "enigma". Assuming that expulsion does occur, the pathways taken by the hydrocarbons to waiting traps can be ascertained by computer modelling of the basin. However, subsurface and field geological support for purported migration pathways has yet to be provided. Many oilfield studies have shown that oil and gas are preferentially trapped in synchronous highs that were formed during, or very shortly after, the deposition of the charged reservoir. An unresolved problem is how catagenically generated hydrocarbons, expelled during a long-drawn-out maturation period, can have filled synchronous highs but have avoided later traps along the assumed migration pathways. From many oilfield studies, it has also been shown that the presence of hydrocarbons inhibits diagenesis and compaction of the reservoir rock. This "Füchtbauer effect" points to not only the early charging of clastic and carbonate reservoirs, but also to the development of permeability barriers below the early-formed accumulations. These barriers would prevent later hydrocarbon additions during the supposed extended period of expulsion from an oil kitchen. Early-formed traps that have been sealed diagenetically will retain their charge even if the trap is opened by later structural tilting. Diagenetic traps have been discovered in clastic and carbonate provinces but their recognition as viable exploration targets is discouraged by present-day assumptions of late hydrocarbon generation and a leaky basin plumbing system. Because there are so many geological realities that cast doubt upon the assumptions that devolve from the paradigm of catagenic generation, the alternative concept of early biogenic generation and accumulation of immature oil, with in-reservoir cracking during burial, is again worthy of serious consideration. This concept envisages hydrocarbon generation by bacterial activity in many anoxic environments and the charging of synchronous highs from adjacent sources. The resolution of the fundamental problem of hydrocarbon generation and accumulation, which is critical to exploration strategies, should be sought in the light of a thorough knowledge of the geologic factors involved, rather than by computer modelling which may be guided by questionable geochemical assumptions. [source] Creative Destruction, Economic Insecurity, Stress, and Epidemic ObesityAMERICAN JOURNAL OF ECONOMICS AND SOCIOLOGY, Issue 3 2010Jon D. Wisman The percentage of Americans who are obese has doubled since 1980. Most attempts to explain this "obesity epidemic" have been found inadequate, including the "Big Two" (the increased availability of inexpensive food and the decline of physical exertion). This article explores the possibility that the obesity epidemic is substantially due to growing insecurity, stress, and a sense of powerlessness in modern society where high-sugar and high-fat foods are increasingly omnipresent. Those suffering these conditions may suffer less control over other domains of their lives. Insecurity and stress have been found to increase the desire for high-fat and high-sugar foods. After exploring the evidence of a link between stress and obesity, the increasing pace of capitalism's creative destruction and its generation of greater insecurity and stress are addressed. The article ends with reflections on how epidemic obesity is symptomatic of a social mistake,the seeking of maximum efficiency and economic growth even in societies where the fundamental problem of material security has been solved. I confess I am not charmed with the ideal of life held out by those who think that the normal state of human beings is that of struggling to get on; that the trampling, crushing, elbowing, and treading on each other's heels, which form the existing type of social life, are the most desirable lot of humankind, or anything but the disagreeable symptoms of one of the phases of industrial progress. (Mill 1848: 748) Thus we have been expressly evolved by nature,with all our impulses and deepest instincts,for the purpose of solving the economic problem ["the struggle for subsistence"]. If the economic problem is solved, mankind will be deprived of its traditional purpose . . . Will this be a benefit? If one believes at all in the real values of life, the prospect at least opens up the possibility of benefit. Yet I think with dread of the readjustment of the habits and instincts of the ordinary man, bred into him for countless generations, which he may be asked to discard within a few decades. (Keynes 1932: 366) [source] Power Sharing and Leadership Dynamics in Authoritarian RegimesAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 2 2009Milan W. Svolik I examine a fundamental problem of politics in authoritarian regimes: the dictator and the ruling coalition must share power and govern in an environment where political influence must be backed by a credible threat of violence. I develop a model of authoritarian politics in which power sharing is complicated by this conflict of interest: by exploiting his position, the dictator may acquire more power at the expense of the ruling coalition, which may attempt to deter such opportunism by threatening to stage a coup. Two power-sharing regimes, contested and established dictatorships, may emerge as a result of strategic behavior by the dictator and the ruling coalition. This theory accounts for the large variation in the duration of dictators' tenures and the concentration of power in dictatorships over time, and it contributes to our understanding of the dynamics of power sharing and accountability in authoritarian regimes. [source] THE VICE OF SNOBBERY: AESTHETIC KNOWLEDGE, JUSTIFICATION AND VIRTUE IN ART APPRECIATIONTHE PHILOSOPHICAL QUARTERLY, Issue 239 2010Matthew Kieran Apparently snobbery undermines justification for and legitimacy of aesthetic claims. It is also pervasive in the aesthetic realm, much more so than we tend to presume. If these two claims are combined, a fundamental problem arises: we do not know whether or not we are justified in believing or making aesthetic claims. Addressing this new challenge requires an epistemological story which underpins when, where and why snobbish judgement is problematic, and how appreciative claims can survive. This leads towards a virtue-theoretic account of art appreciation and aesthetic justification, as contrasted with a purely reliabilist one , a new direction for contemporary aesthetics. [source] A critique of Emanuel's hurricane model and potential intensity theoryTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 632 2008Roger K. Smith Abstract We present a critique of Emanuel's steady-state hurricane model, which is a precursor to his theory for hurricane potential intensity (PI). We show that a major deficiency of the theory is the tacit assumption of gradient wind balance in the boundary layer, a layer that owes its existence to gradient wind imbalance in the radial momentum equation. If a more complete boundary-layer formulation is included using the gradient wind profiles obtained from Emanuel's theory, the tangential wind speed in the boundary layer becomes supergradient, invalidating the assumption of gradient wind balance. We show that the degree to which the tangential wind is supergradient depends on the assumed boundary-layer depth. The full boundary-layer solutions require a knowledge of the tangential wind profile above the boundary layer in the outer region where there is subsidence into the layer and they depend on the breadth of this profile. This effect is not considered in Emanuel's theory. We argue that a more complete theory for the steady-state hurricane would require the radial pressure gradient above the boundary layer to be prescribed or determined independently of the boundary layer. The issues raised herein highlight a fundamental problem with Emanuel's theory for PI, since that theory makes the same assumptions as in the steady-state hurricane model. Our current findings together with recent studies examining intense hurricanes suggest a way forward towards a more consistent theory for hurricane PI. Copyright © 2008 Royal Meteorological Society [source] Effective Corporatisation Legislation: The Fundamental Issue in Port ManagementAUSTRALIAN JOURNAL OF PUBLIC ADMINISTRATION, Issue 3 2003Sophia Everett It is now some seven years since the restructure of Australian ports and their transformation into corporatised entities. This strategy was adopted in an endeavour to improve efficiency by distancing government from day to day operations - that element that was perceived to be the cause of sub-optimal performance. While there is widespread agreement that port performance has improved significantly, dissatisfaction persists and the belief that continued political intervention is preventing ports' commercial potential from being realised. This paper investigates these issues but argues that political intervention per se should not be the focus of research as the fundamental cause of sub-optimal performance. Rather political intervention is an effect of a more fundamental problem , an inappropriate legislative framework , and the focus of research should be on the legislation and corporatisation model in which political intervention is mandatory. [source] A porcine model of bladder outlet obstruction incorporating radio-telemetered cystometryBJU INTERNATIONAL, Issue 1 2007Matthew B. Shaw OBJECTIVE To present a novel porcine model of bladder outlet obstruction (BOO) with a standardized bladder outlet resistance and real-time ambulatory radio-telemetered cystometry, as BOO is a common condition with many causes in both adults and children, with significant morbidity and occasional mortality, but attempts to model this condition in many animal models have the fundamental problem of standardising the degree of outlet resistance. MATERIALS AND METHODS BOO was created in nine castrated male pigs by dividing the mid-urethra; outflow was allowed through an implanted bladder drainage catheter containing a resistance valve, allowing urine to flow across the valve only when a set pressure differential was generated across the valve. An implantable radio-telemetered pressure sensor monitored the pressure within the bladder and abdominal cavity, and relayed this information to a remote computer. Four control pigs had an occluded bladder drainage catheter and pressure sensor placed, but were allowed to void normally through the native urethra. Intra-vesical pressure was monitored by telemetry, while the resistance valve was increased weekly, beginning with 2 cmH2O and ultimately reaching 10 cmH2O. The pigs were assessed using conventional cystometry under anaesthesia before death, and samples conserved in formalin for haematoxylin and eosin staining. RESULTS The pigs had radio-telemetered cystometry for a median of 26 days. All telemetry implants functioned well for the duration of the experiment, but one pig developed a urethral fistula and was excluded from the study. With BOO the bladder mass index (bladder mass/body mass × 10 000) increased from 9.7 to 20 (P = 0.004), with a significant degree of hypertrophy of the detrusor smooth muscle bundles. Obstructed bladders were significantly less compliant than control bladders (8.3 vs 22.1 mL/cmH2O, P = 0.03). Telemetric cystometry showed that there was no statistically significance difference in mean bladder pressure between obstructed and control pigs (4.8 vs 6.7 cmH2O, P = 0.7), but that each void was longer in the pigs with BOO. CONCLUSION This new model of BOO provides a method of reliably and precisely defining the bladder outlet resistance; it induces the changes classically seen with BOO, including increased bladder mass, increased smooth muscle bundle size and decreased compliance. [source] ANALYZING MYOPIC APPROACHES FOR MULTI-AGENT COMMUNICATIONCOMPUTATIONAL INTELLIGENCE, Issue 1 2009Raphen Becker Choosing when to communicate is a fundamental problem in multi-agent systems. This problem becomes particularly challenging when communication is constrained and each agent has different partial information about the overall situation. We take a decision-theoretic approach to this problem that balances the benefits of communication against the costs. Although computing the exact value of communication is intractable, it can be estimated using a standard myopic assumption,that communication is only possible at the present time. We examine specific situations in which this assumption leads to poor performance and demonstrate an alternative approach that relaxes the assumption and improves performance. The results provide an effective method for value-driven communication policies in multi-agent systems. [source] The CCA core specification in a distributed memory SPMD frameworkCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 5 2002Benjamin A. Allan Abstract We present an overview of the Common Component Architecture (CCA) core specification and CCAFFEINE, a Sandia National Laboratories framework implementation compliant with the draft specification. CCAFFEINE stands for CCA Fast Framework Example In Need of Everything; that is, CCAFFEINE is fast, lightweight, and it aims to provide every framework service by using external, portable components instead of integrating all services into a single, heavy framework core. By fast, we mean that the CCAFFEINE glue does not get between components in a way that slows down their interactions. We present the CCAFFEINE solutions to several fundamental problems in the application of component software approaches to the construction of single program multiple data (SPMD) applications. We demonstrate the integration of components from three organizations, two within Sandia and one at Oak Ridge National Laboratory. We outline some requirements for key enabling facilities needed for a successful component approach to SPMD application building. Copyright © 2002 John Wiley & Sons, Ltd. [source] Endoderm development in vertebrates: fate mapping, induction and regional specificationDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 6 2005Kimiko Fukuda The formation of the vertebrate body plan begins with the differentiation of cells into three germ layers: ectoderm, mesoderm and endoderm. Cells in the endoderm give rise to the epithelial lining of the digestive tract, associated glands and respiratory system. One of the fundamental problems in developmental biology is to elucidate how these three primary germ layers are established from the homologous population of cells in the early blastomere. To address this question, ectoderm and mesoderm development have been extensively analyzed, but study of endoderm development has only begun relatively recently. In this review, we focus on the ,where', ,when' and ,how' of endoderm development in four vertebrate model organisms: the zebrafish, Xenopus, chick and mouse. We discuss the classical fate mapping of the endoderm and the more recent progress in characterizing its induction, segregation and regional specification. [source] The Swedish Deep Drilling Program: the quest for the Earth's inner secretsGEOLOGY TODAY, Issue 6 2009Henning Lorenz The Swedish Deep Drilling Program (SDDP) has been initiated to study fundamental problems of the dynamic Earth system, its natural history and evolution. Many key scientific questions can be addressed through in situ investigations only, requiring deep continental drilling. Some are unique to Scandinavia, most are of international interest and significance. At present, five core projects (Fig. 1) with international teams are integrating scientific problems with societal and industrial applications. If SDDP succeeds to attract the funding required, Sweden will have a number of world-class boreholes at key locations by 2020. Figure 1. Locations of SDDP drilling project proposals. PFDP,Postglacial Fault Drilling Project; PaMVAS,Palaeoproterozoic mineralized volcanic arc systems: the Skellefte District; COSC,Collisional Orogeny in the Scandinavian Caledonides; DRL,The Dellen Impact Crater, a geoscientific deep rock laboratory; SELHO,Svecofennian accretion, an example of the early structural evolution in a large hot orogen; CISP,Concentric Impact Structures in the Palaeozoic: the Lockne and Siljan craters. Background and inset image from Blue Marble Next Generation data set (NASA Earth Observatory, http://earthobservatory.nasa.gov/Features/BlueMarble/). [source] Public Provision for Urban Water: Getting Prices and Governance RightGOVERNANCE, Issue 4 2008EDUARDO ARARAL Public sector monopolies are often associated with inefficiencies and inability to meet rising demand. Scholars attribute this to fundamental problems associated with public provision: (1) a tradition of below-cost pricing due to populist pressures, (2) owner,regulator conflicts of interest, and (3) perverse organizational incentives arising from non-credible threat of bankruptcy, weak competition, rigidities, and agency and performance measurement problems. Many governments worldwide have shifted to private provision, but recent experience in urban water utilities in developing countries has shown their limitations because of weak regulatory regimes compounded by inherent problems of information, incentives, and commitment. This article examines the paradoxical case of the Phnom Penh Water Supply in Cambodia to illustrate how public provision of urban water can be substantially improved by getting prices and governance right. Findings have implications for the search for solutions to provide one billion people worldwide with better access to potable water. [source] Shared challenges in object perception for robots and infantsINFANT AND CHILD DEVELOPMENT, Issue 1 2008Paul Fitzpatrick Abstract Robots and humans receive partial, fragmentary hints about the world's state through their respective sensors. These hints,tiny patches of light intensity, frequency components of sound, etc.,are far removed from the world of objects which we feel and perceive so effortlessly around us. The study of infant development and the construction of robots are both deeply concerned with how this apparent gap between the world and our experience of it is bridged. In this paper, we focus on some fundamental problems in perception which have attracted the attention of researchers in both robotics and infant development. Our goal was to identify points of contact already existing between the two fields, and also important questions identified in one field that could fruitfully be addressed in the other. We start with the problem of object segregation: how do infants and robots determine visually where one object ends and another begins? For object segregation, both the fields have examined the idea of using ,key events' where perception is in some way simplified and the infant or robot acquires knowledge that can be exploited at other times. We propose that the identification of the key events themselves constitutes a point of contact between the fields. Although the specific algorithms used in robots do not necessarily map directly to infant strategies, the overall ,algorithmic skeleton' formed by the set of algorithms needed to identify and exploit key events may in fact form the basis for mutual dialogue. We then look more broadly at the role of embodiment in humans and robots, and see the opportunities it affords for development. Copyright © 2008 John Wiley & Sons, Ltd. [source] Improving node behaviour in a QoS control environment by means of load-dependent resource redistributions in LANs,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2005Bernd E. Wolfinger Abstract An important means to guarantee an acceptable quality of service in networks with real-time communication requirements is the reservation of resources at connection setup time. However, such reserved resources, e.g. transmission bandwidth, may be unused as a consequence of the variations in the actual resource demands. Therefore, a more efficient resource utilization is possible if communicating stations or end-users dynamically hand over some of the free resources temporarily to the other communication partners, e.g. of a ,broadcast network'. This paper concentrates on two fundamental problems of such a demand-based sharing of resources: on the one hand, estimation of the current resource requirement on the basis of load measurements is investigated and, on the other hand, we elaborate efficient algorithms for resource sharing respecting real-time requirements. The algorithms proposed for load estimation and for resource sharing are evaluated analytically with respect to their efficiency for worst-case, average-case and realistic load scenarios. Our approach suggested for resource and traffic management allows one to achieve significantly better utilization of network resources. Copyright © 2005 John Wiley & Sons, Ltd. [source] Design aspects of satellite,cellular hybrid wireless systemsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2002Tamer ElBatt Abstract In this paper we investigate various issues related to the design of satellite,cellular hybrid systems. First, we review the fundamental problems of channel partitioning and call admission/assignment. Second, we study the impact of different frequency reuse constraints, in both layers, on the optimum channel partitioning. Third, we investigate, analytically and via simulation, the effect of reducing the cell size. We emphasize the blocking-forced termination probabilities trade-off for pure cellular and satellite,cellular hybrid systems. Accordingly, an optimization problem with respect to the cell size is formulated. Finally, we search for the optimum dynamic call re-assignment policy that improves the system capacity at the expense of the complexity associated with tearing down a connection in one system and setting-up an alternative one in the other system. For a small hybrid system, we characterized the optimum re-assignment policies that minimize the blocking probability, dropping probability, and a weighted cost function of these probabilities. Copyright © 2002 John Wiley & Sons, Ltd. [source] Epistemology and the socio-cognitive perspective in information scienceJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 4 2002Birger Hjørland This article presents a socio-cognitive perspective in relation to information science (IS) and information retrieval (IR). The differences between traditional cognitive views and the socio-cognitive or domain-analytic view are outlined. It is claimed that, given elementary skills in computer-based retrieval, people are basically interacting with representations of subject literatures in IR. The kind of knowledge needed to interact with representations of subject literatures is discussed. It is shown how different approaches or "paradigms" in the represented literature imply different information needs and relevance criteria (which users typically cannot express very well, which is why IS cannot primarily rely on user studies). These principles are exemplified by comparing behaviorism, cognitivism, psychoanalysis, and neuroscience as approaches in psychology. The relevance criteria implicit in each position are outlined, and empirical data are provided to prove the theoretical claims. It is further shown that the most general level of relevance criteria is implied by epistemological theories. The article concludes that the fundamental problems of IS and IR are based in epistemology, which therefore becomes the most important allied field for IS. [source] Cell-free expression and selective isotope labelling in protein NMRMAGNETIC RESONANCE IN CHEMISTRY, Issue S1 2006David Staunton Abstract Isotope labelling is a very powerful tool in NMR studies of proteins and has been employed in various ways for over 40 years. 15N and 13C incorporation, using recombinant expression systems, is now commonplace because heteronuclear experiments assist with the fundamental problems of peak resolution and assignment. The use of selective labelling for peak assignment has been restricted by the scrambling of isotope label through metabolic pathways within the expression host organism. The availability of efficient cell-free expression systems with low levels of metabolic conversion allow the increasing use of selective isotope labelling as a tool in protein NMR. We describe two examples, one where a selective labelling scheme can identify backbone amide peaks from unassigned 1H15N HSQC and HNCO spectra of a 84 residue protein, and another where a specific backbone amide in a 198 residue construct of the ninth and tenth Type III repeats from human fibronectin can be labelled and rapidly identified using a simple HSQC experiment. Copyright © 2006 John Wiley & Sons, Ltd. [source] Cellular mechanisms of potassium transport in plantsPHYSIOLOGIA PLANTARUM, Issue 4 2008Dev T. Britto Potassium (K+) is the most abundant ion in the plant cell and is required for a wide array of functions, ranging from the maintenance of electrical potential gradients across cell membranes, to the generation of turgor, to the activation of numerous enzymes. The majority of these functions depend more or less directly upon the activities and regulation of membrane-bound K+ transport proteins, operating over a wide range of K+ concentrations. Here, we review the physiological aspects of potassium transport systems in the plasma membrane, re-examining fundamental problems in the field such as the distinctions between high- and low-affinity transport systems, the interactions between K+ and other ions such as NH4+ and Na+, the regulation of cellular K+ pools, the generation of electrical potentials and the problems involved in measurement of unidirectional K+ fluxes. We place these discussions in the context of recent discoveries in the molecular biology of K+ acquisition and produce an overview of gene families encoding K+ transporters. [source] Hydroxyapatite as a filler for biosynthetic PHB homopolymer and P(HB,HV) copolymersPOLYMER INTERNATIONAL, Issue 7 2003Antje Bergmann Abstract This paper deals with some of the fundamental problems encountered when using a semicrystalline polymer as the matrix phase for a particulate-filled composite. As our model system we adopted poly-(R)-3-hydroxybutyrate, PHB, and two copolymers of (R)-3-hydroxybutyrate and (R)-3-hydroxyvalerate, P(HB,HV), for the matrix phase, and the mineral calcium hydroxyapatite as a particulate filler. The structure and properties of compression-moulded films of various compositions were investigated by polarized light microscopy, wide-angle X-ray scattering and mechanical testing. It was found that the degree of crystallinity of the matrix was lower in filled samples, and that the spherulitic crystallization of the matrix appeared to cause the filler particles to form agglomerates, which would not be as effective a reinforcement as finely dispersed primary filler particles. The tensile strength, strain-to-break and tensile modulus of samples of different compositions were analysed using well-known theories for composite behaviour. Copyright © 2003 Society of Chemical Industry [source] | ||||||||||||||||||||||||||||||||||