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General Principles (general + principle)
Selected AbstractsAnalysis of single rock blocks for general failure modes under conservative and non-conservative forcesINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 14 2007F. Tonon Abstract After describing the kinematics of a generic rigid block subjected to large rotations and displacements, the Udwadia's General Principle of Mechanics is applied to the dynamics of a rigid block with frictional constraints to show that the reaction forces and moments are indeterminate. Thus, the paper presents an incremental-iterative algorithm for analysing general failure modes of rock blocks subject to generic forces, including non-conservative forces such as water forces. Consistent stiffness matrices have been developed that fully exploit the quadratic convergence of the adopted Newton,Raphson iterative scheme. The algorithm takes into account large block displacements and rotations, which together with non-conservative forces make the stiffness matrix non-symmetric. Also included in the algorithm are in situ stress and fracture dilatancy, which introduces non-symmetric rank-one modifications to the stiffness matrix. Progressive failure is captured by the algorithm, which has proven capable of detecting numerically challenging failure modes, such as rotations about only one point. Failure modes may originate from a limit point or from dynamic instability (divergence or flutter); equilibrium paths emanating from bifurcation points are followed by the algorithm. The algorithm identifies both static and dynamic failure modes. The calculation of the factor of safety comes with no overhead. Examples show the equilibrium path of a rock block that undergoes slumping failure must first pass through a bifurcation point, unless the block is laterally constrained. Rock blocks subjected to water forces (or other non-conservative forces) may undergo flutter failure before reaching a limit point. Copyright © 2007 John Wiley & Sons, Ltd. [source] A warm welcome for destination quality brands: the example of the Pays Cathare regionINTERNATIONAL JOURNAL OF TOURISM RESEARCH, Issue 4 2003Megan Woods Abstract In this paper, the salient complexities characterising quality management at the tourism destination are outlined, and in light of these, a number of quality principles are deemed particularly appropriate for the further investigation of destination quality management (DQM). The complexities include the significant number of services provided at the destination, the highly fragmented nature of the tourism destination product and the large number of small businesses that go to comprise this product. General principles are drawn from the SERVQUAL, Kano and EFQM Business Excellence models in order to provide a tentative framework for investigating how one destination has striven to overcome these challenges. The example of the Pays Cathare Region in southern France, which has been recognised by the European Commission as an example of best practice in integrated quality management (IQM), shows how these quality tenets can be translated from the theoretical framework into actual practice by means of its destination quality brand. Copyright © 2003 John Wiley &Sons, Ltd. [source] Lactate transport and transporters: General principles and functional roles in brain cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 1-2 2005Leif Hertz Abstract Lactate is transported across cell membranes by diffusional, saturable cotransport with protons, mediated by monocarboxylate transporters (MCTs). This transport is bidirectional and in the absence of a transcellular H+ gradient, it can increase the intracellular concentration of lactate up to but not beyond the extracellular level (or vice versa). If extra- and intracellular pH differ, however, the equilibrium level is determined by the gradients of both lactate anions and protons. Rates of lactate uptake are determined most often by measuring uptake of labeled lactate, e.g., [U- 14C]lactate. In the case of lactate and other compounds that are metabolized, errors are introduced easily because continuing inwardly directed diffusional net transport of label can be achieved by intracellular metabolism, reducing the intracellular level of the nonmetabolized lactate and thus maintaining a concentration gradient between extra- and intracellular concentrations of the nonmetabolized compound (metabolism-driven uptake). For measurement of facilitated diffusion kinetics, it is essential that the period during which the uptake is measured is short enough that little or no metabolism-driven uptake contributes to the measured uptake (or that first-order regression analysis is carried out to obtain initial uptake rates from nonlinear traces). To achieve initial uptake rates, incubation periods well below 1 min are generally required. Lactate uptake is fast in astrocytes, which express powerful, low-affinity MCTs, i.e., MCT1 and MCT4. Due to the low affinity of these transporters, they respond to increased lactate gradients with enhanced transporter activity. The predominant MCT in neurons is the high-affinity MCT2, which can only increase its activity to a limited extent in the face of an increased lactate gradient. This is reflected by a high-affinity lactate uptake, although most investigators also have demonstrated a component of lactate uptake with lower affinity. In both neurons and astrocytes, however, facilitated diffusion is fast enough that under most conditions lactate fluxes will be determined mainly by the rate of metabolism-driven uptake, and MCT-mediated transport only will be rate-limiting after establishment of large transmembrane gradients. © 2004 Wiley-Liss, Inc. [source] General principles to enhance practice patterns in gastrointestinal endoscopyALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2002A. Sonnenberg To develop general rules on how to pursue a therapeutic goal of interventional endoscopy without getting lost in abundant details. Methods: The influences of various medical interventions on the survival of a patient with gastrointestinal haemorrhage are modelled by an influence diagram. Survival is the focal point of multiple influences affecting its overall strength. Any downstream influence can represent the focal point of other preceding upstream influences. The mathematics underlying the influence diagram are similar to those of a decision tree with some notable exceptions. Its formalism allows one to consider inhibitory and additive influences and to include in the same analysis non-commensurable qualities, such as correct diagnosis, haemostasis or survival. Results: The analysis reveals five general rules. First, the large number of factors involved in successful endoscopy render the influence of each individual factor less important. Second, a single factor that exerts its influence on many subsequent factors tends to be associated with an overall greater relevance. Third, remote influences are of lesser relevance than those directly linked to the final outcome. Fourth, factors multiplied by several consecutive probabilities lose their influence. Fifth, endoscopists need to assess the relevance of individual factors with respect to the immediate goals of endoscopy, as well as the general goals of patient well-being. Conclusions: The influence model of endoscopic haemostasis reveals several general principles that can be utilized as tools in endoscopy training. [source] Interlaboratory evaluation of two Reverse-transcriptase Polymeric Chain Reaction-based methods for detection of four fruit tree virusesANNALS OF APPLIED BIOLOGY, Issue 1 2009S. Massart Abstract Recent technological development of molecular methods has led to the proliferation of new rapid PCR or reverse-transcriptase (RT)-PCR-derived diagnostic tests for plant viruses. Nevertheless, for routine use, the reliability of all these new methods is not widely established and there is still an apprehension to adopt them in official diagnostic for certification of plant material. This is partly because of the lack of confidence in the obtained results and the poor knowledge on the reproducibility and limits of the RT-PCR protocols. There is a lack of information on the adequate risk assessment in the use of this new technology. An interlaboratory evaluation of two RT-PCR duplex protocols for the detection of four different fruit tree viruses was performed to address these questions. Identical samples were sent as crude extract preparation to each of the participant laboratories. Samples were coded to ensure a double-blind test. General principles of result analysis are described, for example calculation of parameters such as specificity, sensitivity, repeatability, reproducibility, likelihood ratios and post-test probabilities. These parameters and the integration of the protocols within official certification scheme are discussed. Finally, guidelines for researchers desirous of validating their new plant virus diagnostic protocols through interlaboratory evaluation are suggested. [source] General principles regarding the use of adult stem cellsCELL PROLIFERATION, Issue 2008I. Carrasco de Paula In the vast world of scientific investigation, few disciplines can boast of having realized documents of such ethical rigour, and respect for the integrity and intrinsic value of the human person has been one of the cardinal principles of the researcher. Research is intrinsic to the medical profession; the reward of research is knowledge and its techniques are ordered towards maintenance of human health. Since this end concerns human beings, it demands an extremely rigorous ethical approach. Ethical aspects are present from the first moments of the experimental project and occur on three levels: choice of the objectives, selection and use of the appropriate means for the study, and application of resultant new discoveries. Today, our moral attention cannot be reduced to a cost,benefit analysis. Biomedical sciences and medicine have overlapping areas of interest that can be sources of tension: the good of the subject versus scientific utility; profit versus complexity of research; liberty versus ethical and juridical bonds; the public versus the private; and the individual versus the community. Here, I attempt to formulate some essential principles that should guarantee humane measures for research on humans. [source] 4251: General principles of autoinflammation and autoimmunityACTA OPHTHALMOLOGICA, Issue 2010F WILLERMAIN Purpose In this talk, the definition and the molecular mechanisms of autoinflammation and autoimmunity will be introduced. Methods Defense against invading microorganisms is one of the main challenges of life. Very early in the evolution, a series of germline-encoded protein capable to detect pathogen associated molecular patterns (PAMP) have evolved. PAMPs include toll-like receptors, NOD like receptors and C-type lectin. Their activation converges to the rapid stimulation of proinflammatory pathways. Results PAMPs are at the basis of the innate immune response which represent the first line of defense and will shape the nature of the adaptive immune system. The latter is mediated by clonal selection and expansion of antigen specific T and B lymphocytes. It is now well described that dysregulations of those two arms of the immune system are associated with distinct clinical diseases. Conclusion Various anomalies of the innate immune system have been found in a series of disease grouped under the name autoinflammatory syndromes. This term highlight the distinction between those diseases and classical autoimmune diseases, characterized by an abnormal adaptive immune response with the presence of autoantibodies and/or autoreactive T cells. [source] Pentadentate Ligands for the 1:1 Coordination of Lanthanide(III) Salts,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007Markus Albrecht Abstract Three hydrazone type ligands, namely 2 -H, 3, and 4, which were designed to form 1:1 complexes with lanthanoid(III) ions, are presented. Although the tetradentate ligand 2, leads to an interesting complex [(2)(2 -H)YCl2] with yttrium(III), a more general principle for the coordination of the metal ions by hydrazone-type ligands can be found with ligand 3, where 1:1 complexes are obtained with an effective coordination of the metal salts by the ligand. The stabledimer [{(3)Nd(CF3SO3)}2(,-CF3SO3)3]CF3SO3 was characterized by X-ray structure determination. Depending on the size of the metal ion, additional co-ligands can also be bound to the metal centers. This is observed in the molecular structures of [(3)Pr(NO3)2(MeOH)2](NO3), [(3)NdCl2(MeOH)(EtOH)]Cl, [(3)ErCl2(MeOH)]Cl, and [(3)LuCl2]Cl. The solid-state molecular structures of 4 and 4·HCl show the helicating ability of this ligand upon metal coordination. The corresponding lanthanide complexes of 4 are characterized by standard techniques such as NMR and CD spectroscopy and mass spectrometry.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] The Function of the Proportionality Principle in EU LawEUROPEAN LAW JOURNAL, Issue 2 2010Tor-Inge Harbo In this article the author assesses the proportionality principle in EU law from a legal theoretical and constitutional perspective with the aim of discovering the function of the principle. Having first discussed the implications of the proportionality principle being a general principle of law, and what function it has,namely to secure legitimacy for judicial decisions,the author suggests that there are several ways in which the principle can be interpreted. There is, nevertheless, a limit to this interpretation determined by the proposed function of the principle. In the third part of the article, the European Court of Justice's (ECJ's) interpretation of the principle is assessed. The assessment clearly shows that the ECJ is interpreting the principle in different distinguishable ways. The question could, however, be raised as to whether the ECJ in some areas is interpreting the principle in a way that undermines the very function of it. [source] Suppression of sidelobes in OFDM systems by multiple-choice sequences,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 6 2006Ivan Cosovic In this paper, we consider the problem of out-of-band radiation in orthogonal frequency-division multiplexing (OFDM) systems caused by high sidelobes of the OFDM transmission signal. Suppression of high sidelobes in OFDM systems enables higher spectral efficiency and/or co-existence with legacy systems in the case of OFDM spectrum sharing systems. To reduce sidelobes, we propose a method termed multiple-choice sequences (MCS). It is based on the idea that transforming the original transmit sequence into a set of sequences and choosing that sequence out of the set with the lowest power in the sidelobes allows to reduce the out-of-band radiation. We describe the general principle of MCS and out of it we derive and compare several practical MCS algorithms. In addition, we shortly consider the combination of MCS sidelobe suppression method with existing sidelobe suppression methods. Numerical results show that with MCS approach OFDM sidelobes can be reduced significantly while requiring only a small amount of signalling information to be sent from transmitter to receiver. For example, in an OFDM overlay scenario sidelobes power is reduced by around 10,dB with a signalling overhead of only 14%. Copyright © 2006 AEIT. [source] Vigilance and fitness in grey partridges Perdix perdix: the effects of group size and foraging-vigilance trade-offs on predation mortalityJOURNAL OF ANIMAL ECOLOGY, Issue 2 2007MARK WATSON Summary 1Vigilance increases fitness by improving predator detection but at the expense of increasing starvation risk. We related variation in vigilance among 122 radio-tagged overwintering grey partridges Perdix perdix (L.) across 20 independent farmland sites in England to predation risk (sparrowhawk Accipiter nisus L., kill rate), use of alternative antipredation behaviours (grouping and use of cover) and survival. 2Vigilance was significantly higher when individuals fed in smaller groups and in taller vegetation. In the covey period (in early winter when partridges are in flocks), vigilance and use of taller vegetation was significantly higher at sites with higher sparrowhawk predation risk, but tall vegetation was used less by larger groups. Individuals were constrained in reducing individual vigilance by group size and habitat choice because maximum group size was determined by overall density in the area during the covey period and by the formation of pairs at the end of the winter (pair period), when there was also a significant twofold increase in the use of tall cover. 3Over the whole winter individual survival was higher in larger groups and was lower in the pair period. However, when controlling for group size, mean survival decreased as vigilance increased in the covey period. This result, along with vigilance being higher at sites with increasing with raptor risk, suggests individual vigilance increases arose to reduce short-term predation risk from raptors but led to long-term fitness decreases probably because high individual vigilance increased starvation risk or indicated longer exposure to predation. The effect of raptors on survival was less when there were large groups in open habitats, where individual partridges can probably both detect predators and feed efficiently. 4Our study suggests that increasing partridge density and modifying habitat to remove the need for high individual vigilance may decrease partridge mortality. It demonstrates the general principle that antipredation behaviours may reduce fitness long-term via their effects on the starvation,predation risk trade-off, even though they decrease predation risk short-term, and that it may be ecological constraints, such as poor habitat (that lead to an antipredation behaviour compromising foraging), that cause mortality, rather than the proximate effect of an antipredation behaviour such as vigilance. [source] Plant neurobiology and green plant intelligence: science, metaphors and nonsenseJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2008Paul C Struik Abstract This paper analyses the recent debates on the emerging science of plant neurobiology, which claims that the individual green plant should be considered as an intelligent organism. Plant neurobiology tries to use elements from animal physiology as elegant metaphors to trigger the imagination in solving complex plant physiological elements of signalling, internal and external plant communication and whole-plant organisation. Plant neurobiology proposes useful concepts that stimulate discussions on plant behaviour. To be considered a new science, its added value to existing plant biology needs to be presented and critically evaluated. A general, scientific approach is to follow the so-called ,parsimony principle', which calls for simplest ideas and the least number of assumptions for plausible explanation of scientific phenomena. The extent to which plant neurobiology agrees with or violates this general principle needs to be examined. Nevertheless, innovative ideas on the complex mechanisms of signalling, communication, patterning and organisation in higher plants are badly needed. We present current views on these mechanisms and the specific role of auxins in regulating them. Copyright © 2007 Society of Chemical Industry [source] Echinococcus multilocularis metacestode extract triggers human basophils to release interleukin-4PARASITE IMMUNOLOGY, Issue 10 2004E. Aumüller SUMMARY Infections with parasitic helminths are associated with a T helper 2 (Th2) immune response and IgE production. The underlying mechanism, however, is only partially understood. Recently we have isolated a protein from extracts of Schistosoma mansoni eggs that triggers human basophils from non-sensitized donors to release interleukin-4 (IL-4), the key cytokine of a Th2 response. We called this protein IPSE (for IL-4-inducing principle from Schistosoma mansoni eggs). Supposing that IPSE-like IL-4-inducing activities might be a general principle shared among different helminth species, we investigated extracts from the cestode E. multilocularis for its effect on human basophils. Our results showed that extracts from metacestodes of E. multilocularis cause basophil degranulation, as well as the secretion of histamine, IL-4 and IL-13, in a dose-dependent manner. IgE stripping and resensitization of basophils indicated that the mechanism of IL-4 induction requires the presence of IgE on the cells. Since analogous properties have been demonstrated earlier for IPSE, we think that S. mansoni and E. multilocularis may induce a Th2 response in their hosts via a related mechanism, namely, by the induction of IL-4 release from basophils. [source] HOTELLING'S BEACH WITH LINEAR AND QUADRATIC TRANSPORTATION COSTS: EXISTENCE OF PURE STRATEGY EQUILIBRIA,AUSTRALIAN ECONOMIC PAPERS, Issue 1 2007ALAIN EGLI In Hotelling type models consumers have the same transportation cost function. We deviate from this assumption and introduce two consumer types. Some consumers have linear transportation costs, while the others have quadratic transportation costs. If at most half the consumers have linear transportation costs, a subgame perfect equilibrium in pure strategies exists for all symmetric locations. Furthermore, no general principle of differentiation holds. With two consumer types, the equilibrium pattern ranges from maximum to intermediate differentiation. The degree of product differentiation depends on the fraction of consumer types. [source] A Flexible Approach to Measurement Error Correction in Case,Control StudiesBIOMETRICS, Issue 4 2008A. Guolo Summary We investigate the use of prospective likelihood methods to analyze retrospective case,control data where some of the covariates are measured with error. We show that prospective methods can be applied and the case,control sampling scheme can be ignored if one adequately models the distribution of the error-prone covariates in the case,control sampling scheme. Indeed, subject to this, the prospective likelihood methods result in consistent estimates and information standard errors are asymptotically correct. However, the distribution of such covariates is not the same in the population and under case,control sampling, dictating the need to model the distribution flexibly. In this article, we illustrate the general principle by modeling the distribution of the continuous error-prone covariates using the skewnormal distribution. The performance of the method is evaluated through simulation studies, which show satisfactory results in terms of bias and coverage. Finally, the method is applied to the analysis of two data sets which refer, respectively, to a cholesterol study and a study on breast cancer. [source] Improvement of low-temperature caseinolytic activity of a thermophilic subtilase by directed evolution and site-directed mutagenesisBIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009Chuan-Qi Zhong Abstract By directed evolution and subsequent site-directed mutagenesis, cold-adapted variants of WF146 protease, a thermophilic subtilase, have been successfully engineered. A four-amino acid substitution variant RTN29 displayed a sixfold increase in caseinolytic activity in the temperature range of 15,25°C, a down-shift of optimum temperature by ,15°C, as well as a decrease in thermostability, indicating it follows the general principle of trade-off between activity and stability. Nevertheless, to some extent RTN29 remained its thermophilic nature, and no loss of activity was observed after heat-treatment at 60°C for 2,h. Notably, RTN29 exhibited a lower hydrolytic activity toward suc-AAPF-pNA, due to an increase in Km and a decrease in kcat, in contrast to other artificially cold-adapted subtilases with increased low-temperature activity toward small synthetic substrates. All mutations (S100P, G108S, D114G, M137T, T153A, and S246N) identified in the cold-adapted variants occurred within or near the substrate-binding region. None of these mutations, however, match the corresponding sites in naturally psychrophilic and other artificially cold-adapted subtilases, implying there are multiple routes to cold adaptation. Homology modeling and structural analysis demonstrated that these mutations led to an increase in mobility of substrate-binding region and a modulation of substrate specificity, which seemed to account for the improvement of the enzyme's catalytic activity toward macromolecular substrates at lower temperatures. Our study may provide valuable information needed to develop enzymes coupling high stability and high low-temperature activity, which are highly desired for industrial use. Biotechnol. Bioeng. 2009; 104: 862,870. © 2009 Wiley Periodicals, Inc. [source] A fast triangle to triangle intersection test for collision detectionCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 5 2006Oren Tropp Abstract The triangle-to-triangle intersection test is a basic component of all collision detection data structures and algorithms. This paper presents a fast method for testing whether two triangles embedded in three dimensions intersect. Our technique solves the basic sets of linear equations associated with the problem and exploits the strong relations between these sets to speed up their solution. Moreover, unlike previous techniques, with very little additional cost, the exact intersection coordinates can be determined. Finally, our technique uses general principles that can be applied to similar problems such as rectangle-to-rectangle intersection tests, and generally to problems where several equation sets are strongly related. We show that our algorithm saves about 20% of the mathematical operations used by the best previous triangle-to-triangle intersection algorithm. Our experiments also show that it runs 18.9% faster than the fastest previous algorithm on average for typical scenarios of collision detection (on Pentium 4). Copyright © 2006 John Wiley & Sons, Ltd. [source] Ethical problems in cytologyCYTOPATHOLOGY, Issue 1 2004. Znidar Great advances in medical science have raised a number of ethical issues, many of which affect cytopathology. Some of the main issues addressed in this paper relate to the organization of a cytology laboratory: internal and external quality control, adequate staffing levels and staff education, cytopathology reporting format and contents, confidentiality issues, relationship with the clinicians and involvement of cytopathologists in clinical management teams. Quality control has to be provided within cytology departments but external quality assurance is also essential, with national monitoring. New technologies should be used according to the best scientific methods, following cytological analysis. Scientific work in cytology has to respect the general principles of scientific ethics. The patient's interest has to be the main reason for such work. [source] Optical imaging of infants' neurocognitive development: Recent advances and perspectivesDEVELOPMENTAL NEUROBIOLOGY, Issue 6 2008Yasuyo Minagawa-Kawai Abstract Near-infrared spectroscopy (NIRS) provides a unique method of monitoring infant brain function by measuring the changes in the concentrations of oxygenated and deoxygenated hemoglobin. During the past 10 years, NIRS measurement of the developing brain has rapidly expanded. In this article, a brief discussion of the general principles of NIRS, including its technical advantages and limitations, is followed by a detailed review of the role played so far by NIRS in the study of infant perception and cognition, including language, and visual and auditory functions. Results have highlighted, in particular, the developmental changes of cerebral asymmetry associated with speech acquisition. Finally, suggestions for future studies of neurocognitive development using NIRS are presented. Although NIRS studies of the infant brain have yet to fulfill their potential, a review of the work done so far indicates that NIRS is likely to provide many unique insights in the field of developmental neuroscience. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] Foraging behavior of an estuarine predator, the blue crab Callinectes sapidus in a patchy environmentECOGRAPHY, Issue 1 2000Mary E. Clark To define general principles of predator-prey dynamics in an estuarine subtidal environment, we manipulated predator density (the blue crab, Callinectes sapidus) and prey (the clam, Macoma balthica) patch distribution in large field enclosures in the Rhode River subestuary of the central Chesapeake Bay. The primary objectives were to determine whether predators forage in a way that maximizes prey consumption and to assess how their foraging success is affected by density of conspecifics. We developed a novel ultrasonic telemetry system to observe behavior of individual predators with unprecedented detail. Behavior of predators was more indicative of optimal than of opportunistic foraging. Predators appeared responsive to the overall quality of prey in their habitat. Rather than remaining on a prey patch until depletion, predators appeared to vary their patch use with quality of the surrounding environment. When multiple (two) prey patches were available, residence time of predators on a prey patch was shorter than when only a single prey patch was available. Predators seemed to move among the prey patches fairly regularly, dividing their foraging time between the patches and consuming prey from each of them at a similar rate. That predators more than doubled their consumption of prey when we doubled the number of prey (by adding the second patch) is consistent with optimizing behaviors - rather than with an opportunistic increase in prey consumption brought about simply by the addition of more prey. Predators at high density, however, appeared to interfere with each other's foraging success, reflected by their lower rates of prey consumption. Blue crabs appear to forage more successfully (and their prey to experience higher mortality) in prey patches located within 15,20 meters of neighboring patch, than in isolated patches. Our results are likely to apply, at least qualitatively, to other crustacean-bivalve interactions, including those of commercial interest; their quantitative applicability will depend on the mobility of other predators and the scale of patchiness they perceive. [source] When density dependence is not instantaneous: theoretical developments and management implicationsECOLOGY LETTERS, Issue 2 2008Irja I. Ratikainen Abstract Most organisms live in changing environments or do not use the same resources at different stages of their lives or in different seasons. As a result, density dependence will affect populations differently at different times. Such sequential density dependence generates markedly different population responses compared to the unrealistic assumption that all events occur simultaneously. Various field studies have also shown that the conditions that individuals experience during one period can influence success and per capita vital rates during the following period. These carry-over effects further complicate any general principles and increase the diversity of possible population dynamics. In this review, we describe how studies of sequential density dependence have diverged in directions that are both taxon-specific and have non-overlapping terminology, despite very similar underlying problems. By exploring and highlighting these similarities, we aim to improve communication between fields, clarify common misunderstandings, and provide a framework for improving conservation and management practices, including sustainable harvesting theory. [source] Comparing tropical forest tree size distributions with the predictions of metabolic ecology and equilibrium modelsECOLOGY LETTERS, Issue 5 2006Helene C. Muller-Landau Abstract Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the ,2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality. [source] UNDERSTANDING THE OTHER/UNDERSTANDING OURSELVES: TOWARD A CONSTRUCTIVE DIALOGUE ABOUT "PRINCIPLES' IN EDUCATIONAL RESEARCHEDUCATIONAL THEORY, Issue 3 2005Pamela A. Moss The recent federal interest in advancing "scientifically based research," along with the National Research Council's 2002 report Scientific Research in Education (SRE), have provided space and impetus for a more general dialogue across discourse boundaries within the field of educational research. The goal of this article is to develop and illustrate principles for an educative dialogue across research discourses. I have turned to Gadamer's philosophical hermeneutics and the critical dialogue that surrounds it to seek guidance about how we might better understand one another's perspectives and learn more about ourselves through the encounter. To illustrate these principles, I consider the dialogue between SRE authors and critics that was published in Educational Researcher shortly after the release of the report. I focus in particular on one of the many issues about which misunderstandings seem to arise , the nature, status, and role of generalizations , and point to some instructive challenges that each of the articles seems to raise for the others. Finally, I propose what I argue is a more prudent aspiration for general principles in educational research: developing the principles through which open critique and debate across differences might occur and through which sound decisions about particular programs for research might be made. [source] Hair growth inhibition by psychoemotional stress: a mouse model for neural mechanisms in hair growth controlEXPERIMENTAL DERMATOLOGY, Issue 1 2006Eva M. J. Peters Abstract:, Stress has long been discussed controversially as a cause of hair loss. However, solid proof of stress-induced hair growth inhibition had long been missing. If psychoemotional stress can affect hair growth, this must be mediated via definable neurorendocrine and/or neuroimmunological signaling pathways. Revisiting and up-dating relevant background data on neural mechanisms of hair growth control, we sketch essentials of hair follicle (HF) neurobiology and discuss the modulation of murine hair growth by neuropeptides, neurotransmitters, neurotrophins, and mast cells. Exploiting an established mouse model for stress, we summarize recent evidence that sonic stress triggers a cascade of molecular events including plasticity of the peptidergic peri- and interfollicular innervation and neuroimmune crosstalk. Substance P (SP) and NGF (nerve growth factor) are recruited as key mediators of stress-induced hair growth-inhibitory effects. These effects include perifollicular neurogenic inflammation, HF keratinocyte apoptosis, inhibition of proliferation within the HF epithelium, and premature HF regression (catagen induction). Intriguingly, most of these effects can be abrogated by treatment of stressed mice with SP-receptor neurokinin-1 receptor (NK-1) antagonists or NGF-neutralizing antibodies , as well as, surprisingly, by topical minoxidil. Thus there is now solid in vivo -evidence for the existence of a defined brain- HF axis. This axis can be utilized by psychoemotional and other stressors to prematurely terminate hair growth. Stress-induced hair growth inhibition can therefore serve as a highly instructive model for exploring the brain-skin connection and provides a unique experimental model for dissecting general principles of skin neuroendocrinology and neuroimmunology well beyond the HF. [source] Crawfish Tails: A Curious Tale of Foreign Trade Policy MakingFOREIGN POLICY ANALYSIS, Issue 2 2007CAMERON G. THIES This paper presents a case study of the demand for and supply of protectionism upon exposure to international trade. The examination of the crawfish industry demonstrates that theories of the demand for protectionism often provide inadequate or incomplete explanations of outcomes. The curious aspect of this case is that crawfish producers failed to organize to demand protection despite having many factors working in their favor. In fact, political representatives at the state level organized demand from federal agencies on their behalf, thus supplying protection without any real organized demand. In the end, only a handful of crawfish processors (not producers) received any benefits from protection, and Chinese imports still dominate the U.S. crawfish market. The result is consistent with the notion that the U.S. system of trade regulation is designed to produce the appearance, but not the substance of protection in order to uphold general principles of freer trade while making elected officials look responsive to their constituents. [source] COMPARING INVASIVE NETWORKS: CULTURAL AND POLITICAL BIOGRAPHIES OF INVASIVE SPECIES,GEOGRAPHICAL REVIEW, Issue 2 2004PAUL ROBBINS ABSTRACT. Under what cultural and political conditions do certain species become successful invaders? What impact does species invasion have on human culture and politics? The work assembled in this special issue of the Geographical Review suggests complex interspecies interactions that complicate any answer to these questions. It demonstrates the need to advance a more integrative human/environment approach to species invasion than has hitherto been seen. Reviewing the concepts demonstrated in these articles and applying them to case histories of Mimosaceae (a family that includes genera such as Acacia, Prosopis, and Mimosa) invasion, two general principles become clear. The status and identification of any species as an invader, weed, or exotic are conditioned by cultural and political circumstances. Furthermore, because the human "preparation of landscape" is a prerequisite for most cases of invasion, and because species invasions impact local culture and politics in ways that often feed back into the environmental system, specific power-laden networks of human and non-human actors tend to create the momentum for invasion. It is therefore possible to argue a more general cultural and political account of contemporary species expansion: It is not species but sociobiological networks that are invasive. [source] Pregnancy and rare bleeding disordersHAEMOPHILIA, Issue 5 2009R. KADIR Summary., Rare bleeding disorders include deficiency of fibrinogen, prothrombin, factor V, factor VII, factor X, factor XI and factor XIII together with combined deficiency disorders, factor V+VIII deficiency, and deficiency of the vitamin K-dependent factors (factor II, VII, IX and X). They account for 3,5% of all inherited coagulation disorders. Due to their rarity, information about pregnancy complications and management is limited and mostly derived from case reports. Deficiency of fibrinogen and FXIII are both found to be strongly associated with increased risk of recurrent miscarriage and placental abruption. Factor replacement is used to reduce these risks. However, the risk of miscarriage and ante-partum complications is less clear in women with other bleeding disorders. Haemostatic abnormalities in women with rare bleeding disorders seem to persist throughout pregnancy especially if the defect is severe. Therefore women affected with these disorders are at risk of post-partum haemorrhage. The fetus can also be affected and potentially at risk of bleeding complications. Specialised multidisciplinary management is essential to minimise the potential maternal and neonatal complications and ensure an optimal outcome. This paper presents literature review for pregnancy complications in each of the rare bleeding disorders. In addition general principles for management of pregnancy, labour and delivery are discussed. [source] Practical questions in liver metastases of colorectal cancer: general principles of treatmentHPB, Issue 4 2007Héctor Daniel González Abstract Liver metastases of colorectal cancer are currently treated by multidisciplinary teams using strategies that combine chemotherapy, surgery and ablative techniques. Many patients classically considered non-resectable can now be rescued by neoadjuvant chemotherapy followed by liver resection, with similar results to those obtained in initial resections. While many of those patients will recur, repeat resection is a feasible and safe approach if the recurrence is confined to the liver. Several factors that until recently were considered contraindications are now recognized only as adverse prognostic factors and no longer as contraindications for surgery. The current evaluation process to select patients for surgery is no longer focused on what is to be removed but rather on what will remain. The single most important objective is to achieve a complete (R0) resection within the limits of safety in terms of quantity and quality of the remaining liver. An increasing number of patients with synchronous liver metastases are treated by simultaneous resection of the primary and the liver metastatic tumours. Multilobar disease can also be approached by staged procedures that combine neoadjuvant chemotherapy, limited resections in one lobe, embolization or ligation of the contralateral portal vein and a major resection in a second procedure. Extrahepatic disease is no longer a contraindication for surgery provided that an R0 resection can be achieved. A reverse surgical staged approach (liver metastases first, primary second) is another strategy that has appeared recently. Provided that a careful selection is made, elderly patients can also benefit from surgical treatment of liver metastases. [source] The learning organization information system (LOIS): looking for the next generationINFORMATION SYSTEMS JOURNAL, Issue 1 2001Adrian Williamson Abstract. This paper explores the notion that the next generation of information systems will focus on supporting organizational learning. The paper suggests that the increasingly successful automation of procedural work will lead to pressure on organizations to improve performance through enhanced support for knowledge work. A set of outline requirements for the learning organization information system (LOIS) is then proposed using recent research findings from computer supported co-operative working and organizational learning. The computerized on-line journal from this research is described. This journal provides transparent capture of episodes of work and it is argued that the general principles established could support LOIS by helping to provide a richly defined organizational memory. The journal supports collaborative working through the use of groupware, which manages the sharing of, and learning from, journal contents. This can facilitate the retention of not only data and information, but also the inquiry process that produced them. The paper concludes that LOIS will be a self-organizing system, focussing on knowledge work, learning and using advanced technologies drawn from ubiquitous computing. A view of a system that moves towards this aim is presented. Future topics for research are identified, and a natural language approach to knowledge asset management is discussed briefly. In closing, it is argued that LOIS is an important future vision for organizations operating in the information age. [source] Agricultural Biotechnology and Regime Formation: A Constructivist Assessment of the ProspectsINTERNATIONAL STUDIES QUARTERLY, Issue 4 2002William D. Coleman Controversies surrounding the appropriate use and diffusion of agricultural biotechnologies are giving rise to questions about governance at the international level. This article investigates the likelihood that a single, international regime or multiple regimes governing this technology will form by way of negotiation. We show that four normative,institutional arrangements, organized around distinct general principles, have a potential governance role: world food security and safety, liberalized trade, protection of intellectual property, and conservation and sustainable use of biodiversity. We argue that an adequate amount of compatibility between the principles and norms of these arrangements is required to support the type of communicative action or truth,seeking needed to develop the intersubjective understanding for a regime. Using a framework for assessing normative compatibility, we find not one, but two nascent understandings rooted in the trade and biodiversity areas competing to form the foundation for governance. Further analysis of levels of institutional density between the two developing regimes reveals they are presently too low to support a negotiated resolution of normative conflict. Finally, we demonstrate that recent framing attempts at the international level to decrease areas of tension and incompatibility in principles/norms between the regimes have neglected to create the crucial normative background conditions needed to avert a scenario of increased political conflict in the near future. [source] | |||||||||||||||||||||||||||||||||||||