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Available Knowledge (available + knowledge)
Selected AbstractsEcological implications of plants' ability to tell the timeECOLOGY LETTERS, Issue 6 2009Víctor Resco Abstract The circadian clock (the endogenous mechanism that anticipates diurnal cycles) acts as a central coordinator of plant activity. At the molecular and organism level, it regulates key traits for plant fitness, including seed germination, gas exchange, growth and flowering, among others. In this article, we explore current evidence on the effect of the clock for the scales of interest to ecologists. We begin by synthesizing available knowledge on the effect of the clock on biosphere,atmosphere interactions and observe that, at least in the systems where it has been tested, the clock regulates gas exchange from the leaf to the ecosystem level, and we discuss its implications for estimates of the carbon balance. Then, we analyse whether incorporating the action of the clock may help in elucidating the effects of climate change on plant distributions. Circadian rhythms are involved in regulating the range of temperatures a species can survive and affects plant interactions. Finally, we review the involvement of the clock in key phenological events, such as flowering time and seed germination. Because the clock may act as a common mechanism affecting many of the diverse branches of ecology, our ultimate goal is to stimulate further research into this pressing, yet unexplored, topic. [source] Navigating toward Fetal and Maternal Health: The Challenge of Treating Epilepsy in PregnancyEPILEPSIA, Issue 10 2004Torbjörn Tomson Summary:, A rational approach to the treatment of women of childbearing potential with epilepsy has been hampered by the lack of conclusive data on the comparative teratogenic potential of different antiepileptic drugs (AEDs). Although, several cohort studies on birth defects associated with AED use during pregnancy have been published, these have generally failed to demonstrate differences in malformation rates between AEDs, probably mainly due to insufficient power. In particular, pregnancies with new generation AEDs have been too few. In recent years, pregnancy registries have been introduced to overcome this problem,EURAP (an international collaboration), the North American, and the U.K. AED and pregnancy registries are observational studies that prospectively assess pregnancy outcome after AED exposure using slightly different methods. Each has enlisted 3,5,000 pregnancies in women with epilepsy, and the North American and the U.K. have released preliminary observations. Thus the U.K. registry reported a higher malformation rate with valproate, 5.9% (4.3,8.2%; 95% CI), than with carbamazepine, 2.3% (1.4,3.7%), and lamotrigine, 2.1% (1.0,4.0%). Most of the more recent cohort studies have also identified a nonsignificant trend toward a higher teratogenicity with valproate. These signals need to be interpreted with some caution since none of the studies to date have fully assessed the impact of possible confounders, such as type of epilepsy, family history of birth defects, etc. However, with increasing number of pregnancies it should be possible in the near future for the pregnancy registries to take such confounding factors into account and thus make more reliable assessments of the causal relationship between exposure to specific AEDs and teratogenic risks. While awaiting more conclusive results, it appears reasonable to be cautious in prescribing valproate to women considering to become pregnant if other suitable treatment alternatives, and with less teratogenic potential, are available. Any attempt to change treatment should, however, be accomplished well before conception. The importance of maintained seizure control must also be kept in mind, and the woman who needs valproate to control her seizures should not be discouraged from pregnancy, provided that counseling at the best of available knowledge is given. [source] Lamina propria dendritic cells: For whom the bell TOLLs?EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2008Maria Rescigno PhD. Abstract One of the major tasks of the mucosal immune system is to discriminate between dangerous and harmless antigens that are encountered daily at mucosal sites. In the gastrointestinal tract, immune cells have to tolerate food antigens and commensal microbes but at the same time have to induce a prompt response against invasive pathogens, when needed. In this issue of the European Journal of Immunology, it is shown that intestinal dendritic cell (DC) populations can be distinguished based on the expression level of Toll-like receptors (TLR) and on the response of these TLR to their microbial ligands. DC either do not express TLR or they express them but respond in a non-inflammatory mode. In this commentary, these findings are discussed in the context of available knowledge on lamina propria DC. See accompanying article http://dx.doi.org/10.1002/eji.200737909 [source] Diagnostic expert systems: a method for engineering knowledge used in sequential diagnosisEXPERT SYSTEMS, Issue 4 2000Silvano Mussi The paper presents a method for helping knowledge engineers in modelling the knowledge involved in sequential diagnosis. In particular, we consider sequential diagnosis as a process which occurs in the following type of scenario: (1) there exist some candidate hypotheses which are to be pursued; (2) for each hypothesis there are some alternative tests which might be executed to pursue it; (3) the available knowledge about the world precludes projecting into the future (in other words, the available knowledge about the world does not afford the information needed for planning sequences of tests, i.e. for projecting the consequences of possible sequences of actions and picking the best sequence); (4) the choice of the next test (or tests) is made on the basis of the current state of knowledge; (5) the outcome of a test execution is affected by uncertainty. The suggested method addresses the problem of engineering the knowledge experts use for making decisions under uncertainty. A practical example of the method is also presented: at any time of the diagnostic process the expert is provided with a dynamically updated list of suggested tests in order to support him or her in the decision-making problem about which test to execute next. [source] Bacteria as computers making computersFEMS MICROBIOLOGY REVIEWS, Issue 1 2009Antoine Danchin Abstract Various efforts to integrate biological knowledge into networks of interactions have produced a lively microbial systems biology. Putting molecular biology and computer sciences in perspective, we review another trend in systems biology, in which recursivity and information replace the usual concepts of differential equations, feedback and feedforward loops and the like. Noting that the processes of gene expression separate the genome from the cell machinery, we analyse the role of the separation between machine and program in computers. However, computers do not make computers. For cells to make cells requires a specific organization of the genetic program, which we investigate using available knowledge. Microbial genomes are organized into a paleome (the name emphasizes the role of the corresponding functions from the time of the origin of life), comprising a constructor and a replicator, and a cenome (emphasizing community-relevant genes), made up of genes that permit life in a particular context. The cell duplication process supposes rejuvenation of the machine and replication of the program. The paleome also possesses genes that enable information to accumulate in a ratchet-like process down the generations. The systems biology must include the dynamics of information creation in its future developments. [source] Simulation and quantification of enrichment and retention processes in the southern Benguela upwelling ecosystemFISHERIES OCEANOGRAPHY, Issue 5 2006CHRISTOPHE LETT Abstract Important environmental processes for the survival and recruitment of early life stages of pelagic fishes have been synthesized through Bakun's fundamental triad as enrichment, concentration and retention processes (A. Bakun, 1996, Patterns in the Ocean. Ocean Processes and Marine Population Dynamics. San Diego, CA, USA: University of California Sea Grant). This conceptual framework states that from favourable spawning habitats, eggs and larvae would be transported to and/or retained in places where food originating from enrichment areas would be concentrated. We propose a method for quantifying two of the triad processes, enrichment and retention, based on the Lagrangian tracking of particles transported within water velocity fields generated by a three-dimensional hydrodynamic model. We apply this method to the southern Benguela upwelling ecosystem, constructing putative maps of enrichment and retention. We comment on these maps regarding main features of the circulation in the region, and investigate seasonal variability of the processes. We finally discuss the results in relation to available knowledge on the reproductive strategies of two pelagic clupeoid species abundant in the southern Benguela, anchovy (Engraulis encrasicolus) and sardine (Sardinops sagax). Our approach is intended to be sufficiently generic so as to allow its application to other upwelling systems. [source] Radial profiles of seismic attenuation in the upper mantle based on physical modelsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2008Fabio Cammarano SUMMARY Thermally activated, viscoelastic relaxation of the Earth's materials is responsible for intrinsic attenuation of seismic waves. Seismic observations have been used to define layered radially symmetric attenuation models, independent of any constraints on temperature and composition. Here, we interpret free-oscillation and surface wave attenuation measurements in terms of physical structures, by using the available knowledge on the physical mechanisms that govern attenuation at upper-mantle (<400 km) conditions. We find that observations can be explained by relatively simple thermal and grain-size structures. The 1-D attenuation models obtained do not have any sharp gradients below 100 km, but fit the data equally well as the seismic models. The sharp gradients which characterize these models are therefore not required by the data. In spite of the large sensitivity of seismic observations to temperature, a definitive interpretation is limited by the unknown effects of pressure on anelasticity. Frequency dependence of anelasticity, as well as trade-offs with deeper attenuation structure and dependence on the elastic background model, are less important. Effects of water and dislocations can play an important role as well and further complicate the interpretation. Independent constraints on temperature and grain size expected around 100 km depth, help to constrain better the thermal and grain-size profiles at greater depth. For example, starting from a temperature of 1550 K at 100 km and assuming that the seismic attenuation is governed by the Faul & Jackson's (2005) mechanism, we found that negative thermal gradients associated with several cm grain sizes (assuming low activation volume) or an adiabatic gradient associated with ,1 cm grain size, can explain the data. A full waveform analysis, combining the effects on phase and amplitude of, respectively, elasticity and anelasticity, holds promise for further improving our knowledge on the average composition and thermal structure of the upper mantle. [source] Management of heart failure in elderly peopleINTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 2 2008M. Imazio Summary Aims:, To review currently available knowledge on presentation, clinical features and management of heart failure (HF) in elderly people. Methods:, To review currently available evidence, we performed a thorough search of several evidence-based sources of information, including Cochrane Database of Systematic Reviews, Clinical Evidence, Evidence-based guidelines from National Guidelines Clearinghouse and a comprehensive MEDLINE search with the MeSH terms: ,heart failure', ,elderly' and ,management'. Results:, A number of features of ageing may predispose elderly people to HF, and may impair the ability to respond to injuries. Another hallmark of elderly patients is the increasing prevalence of multiple coexisting chronic conditions and geriatric syndromes that may complicate the clinical presentation and evolution of HF. Although diagnosis may be challenging, because atypical symptoms and presentations are common, and comorbid conditions may mimic or complicate the clinical picture, diagnostic criteria do not change in elderly people. Drug treatment is not significantly different from that recommended in younger patients, and largely remains empiric, because clinical trials have generally excluded elderly people and patients with comorbid conditions. Disease management programmes may have the potential to reduce morbidity and mortality for patients with HF. Conclusions:, Heart failure is the commonest reason for hospitalisation and readmission among older adults. HF shows peculiar features in elderly people, and is usually complicated by comorbidities, presenting a significant financial burden worldwide, nevertheless elderly people have been generally excluded from clinical trials, and thus management largely remains empiric and based on evidence from younger age groups. [source] An isolate and sequence database of infectious haematopoietic necrosis virus (IHNV)JOURNAL OF FISH DISEASES, Issue 6 2010S P Jonstrup Abstract In the field of fish diseases, the amount of relevant information available is enormous. Internet-based databases are an excellent tool for keeping track of the available knowledge in the field. Fishpathogens.eu was launched in June 2009 with the aim of collecting, storing and sorting data on fish pathogens. The first pathogen to be included was the rhabdovirus, viral haemorrhagic septicaemia virus (VHSV). Here, we present an extension of the database to also include infectious haematopoietic necrosis virus (IHNV). The database is developed, maintained and managed by the European Community Reference Laboratory for Fish Diseases and collaborators. It is available at http://www.fishpathogens.eu/ihnv. [source] Elucidation and decisional risk in a multi-criteria decision based on a Choquet integral aggregation,a cybernetic frameworkJOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 5-6 2005J. Montmain Abstract The authors are developing multi-criteria Decision-making support systems (DMSS) for project teams in charge of selecting a technical solution among alternatives. They propose a cybernetic framework to emphasize the link between decision-making (DM) and knowledge management processes in such projects. These DMSSs rely on the tracking of the accompanying knowledge production of long-term decisional processes by a collective with many actors. Based on knowledge-production management, this paper explains how to design decisional risk evaluation, monitoring and control aids and traceability functions for strategic choices and logical argumentation. The DMSS is seen as a recommender system for the project manager. Each possible solution involved in the decision-making process (DMP) is evaluated by means of a set of criteria. The evaluation results from an interpretation of the knowledge items in terms of satisfaction scores of the solutions according to the considered criteria. Aggregating these partial scores provides a ranking of all the possible solutions by order of preference. As criteria are sometimes interacting, the aggregation has to be based on adapted operators, i.e. Choquet integrals. Evaluating possible solutions by the knowledge contained in the knowledge base (KB) opens the way to automating the argumentation of the project team's decisions: the argumentation principle underlying this approach is based naturally on coupling a knowledge dynamical management system (KDMS) with the DMSS. The DMSS also evaluates the decisional risk that reflects the eventuality of a wrong selection due to the insufficiency of available knowledge at a given time in order to adopt a reliable solution. Decisional risk assessment corresponds to sensitivity analyses. These analyses are then exploited to control the decisional risk in time: they enable to identify the crucial information points for which additional and deeper investigations would be of great interest to improve the stability of the selection in the future. The knowledge management of a collective project is represented as a control loop: the KDMS is the actuator, the risk accompanying the decision is the controlled variable and is strongly linked to the entropy of the KB managed by the KDMS. Each of the three phases,intelligence, design, choice,of the DMP is identified to a function of the control loop: actuator, process and regulator. This cybernetic framework for decision has its origin in knowledge management activities for a great-scale project,the EtLD project of the French Atomic Commission (CEA) that concerns the management of high-level long-life radioactive waste in France. Copyright © 2007 John Wiley & Sons, Ltd. [source] Antinociceptive efficacy of levetiracetam in a mice model for painful diabetic neuropathyACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2008M. OZCAN Background and Objective: Despite important advances in available knowledge, management of neuropathic pain remains incomplete, and results from experimental and clinical studies indicate that some anticonvulsants show promise for treating neuropathic pain. The aim of this study was to assess the antinociceptive efficacy of levetiracetam (LEV, ucb L059) in a mice model for painful diabetic neuropathy using the in vivo nociceptive behavioral ,hot-plate test.' Methods: The hot-plate test consisted of placing individual mice (adult male Balb/C) on the hot plate at 50±0.1 °C and timing the delay for the first hind paw lift (nociceptive threshold). After obtaining control values, diabetes was induced by injection of streptozotocin [200 mg/kg intraperitoneally (i.p.)] and 2 weeks after induction of diabetes (serum glucose ,400 mg/dL) LEV was administered i.p. and hot-plate tests were repeated. Pain threshold values were determined and analyzed by Kruskal,Wallis one-way analysis of variance (ANOVA) followed by a pairwise comparison using a Dunnett's t -test on the ranked data. Results: LEV (60, 300 and 900 mg/kg) had no significant effect on the nociceptive threshold in normal mice (n=8 for each dose, P>0.05). There were significant decreases in pain threshold latency in diabetic mice compared with the normal healthy group and these were significantly and dose-dependently restored by much lower doses of LEV (20, 100 and 200 mg/kg) in a reversible manner. Conclusion: Results obtained from the in vivo behavioral test lend support to the validation of the promising therapeutic potential of the novel antiepileptic agent LEV in the treatment of neuropathic pain. [source] On Defending Controversial Viewpoints: Debates of Sixth Graders About the Desirability of Early 20th-Century American ImmigrationLEARNING DISABILITIES RESEARCH & PRACTICE, Issue 3 2002Charles A. MacArthur Sixth-grade students with and without mild disabilities participated in an eight-week project-based investigation about immigration to the United States in the late 19th and early 20th centuries. Students' investigations were designed to promote their understanding of the perspectives of immigrants and Americans who opposed immigration, as well as the "ways of life" that gave impetus to immigration and often resulted in conflict between these groups. At the conclusion of these investigations, students were assigned the role of the immigrants or opponents of immigration and were asked to debate the desirability of immigration to the United States during this historical period. The primary focus of this article is on the opportunities afforded by, and the limitations of, these classroom debates. The debates promoted high levels of engagement and equal participation by students with and without disabilities as well as by boys and girls. Analyses of content and structure showed that students' discourse was influenced by the knowledge they gained during their investigations, but the use of this knowledge was shaped by the competitive rhetorical goal of defending a particular viewpoint. Later rounds of the debates were more balanced and drew more on the breadth of available knowledge than did earlier rounds. Overall, the debates were more typical of everyday arguments than academic arguments. The implications of our findings for the design of instructional opportunities in the social studies in inclusive classrooms are discussed. [source] T cell-mediated immunoregulation in the gastrointestinal tractALLERGY, Issue 4 2009L. Saurer In the intestinal tract, only a single layer of epithelial cells separates innate and adaptive immune effector cells from a vast amount of antigens. Here, the immune system faces a considerable challenge in tolerating commensal flora and dietary antigens while preventing the dissemination of potential pathogens. Failure to tightly control immune reactions may result in detrimental inflammation. In this respect, ,conventional' regulatory CD4+ T cells, including naturally occurring and adaptive CD4+ CD25+ Foxp3+ T cells, Th3 and Tr1 cells, have recently been the focus of considerable attention. However, regulatory mechanisms in the intestinal mucosa are highly complex, including adaptations of nonhaematopoietic cells and innate immune cells as well as the presence of unconventional T cells with regulatory properties such as resident TCR,, or TCR,, CD8+ intraepithelial lymphocytes. This review aims to summarize the currently available knowledge on conventional and unconventional regulatory T cell subsets (Tregs), with special emphasis on clinical data and the potential role or malfunctioning of Tregs in four major human gastrointestinal diseases, i.e. inflammatory bowel diseases, coeliac disease, food allergy and colorectal cancer. We conclude that the clinical data confirms some but not all of the findings derived from experimental animal models. [source] Application of fast-digitizer card Acqiris DP-240 in positron lifetime spectroscopyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2009Martin Petriska Abstract Based on the available knowledge base in positron annihilation measurements, new software for digital positron lifetime spectrometry has been designed within the frame of joint activity between STU Bratislava and JRC Petten. The tests of the new positron digital-life time setup have been carried out. Detectors with BaF2 scintillators and fast-dynode outputs were chosen for such studies. As the digitiser unit, the card Acqiris DP240 was fully tested. Originally, start and stop timing signals were sampled to digital waveforms separately at a rate of 1 GS/s in 8 bit resolution. However, due to limited quality of collected waveforms which significantly affected post-processing of data, the joined delayed channel mode with 2 GS/s sampling rate was applied for further studies. The full setup was benchmarked by a series of calibration measurements of two high purity materials, specifically Si and Ni. The inter-comparison of conventional analogue- and digital-based processing are discussed in detail. Further, the optimisation of main parameters for waveform-processing are analysed too. Such a new approach in the digital life-time spectroscopy will help to improve the resolution of existing methodology which might enhance the capabilities of this technique for further applications, especially in materials science. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Plant's Capacity in Regulating Resource DemandPLANT BIOLOGY, Issue 6 2005R. Matyssek Abstract: Regulation of resource allocation in plants is the key to integrate understanding of metabolism and resource flux across the whole plant. The challenge is to understand trade-offs as plants balance allocation between different and conflicting demands, e.g., for staying competitive with neighbours and ensuring defence against parasites. Related hypothesis evaluation can, however, produce equivocal results. Overcoming deficits in understanding underlying mechanisms is achieved through integrated experimentation and modelling the various spatio-temporal scaling levels, from genetic control and cell metabolism towards resource flux at the stand level. An integrated, interdisciplinary research concept on herbaceous and woody plants and its outcome to date are used, while drawing attention to currently available knowledge. This assessment is based on resource allocation as driven through plant-pathogen and plant-mycorrhizosphere interaction, as well as competition with neighbouring plants in stands, conceiving such biotic interactions as a "unity" in the control of allocation. Biotic interaction may diminish or foster effects of abiotic stress on allocation, as changes in allocation do not necessarily result from metabolic re-adjustment but may obey allometric rules during ontogeny. Focus is required on host-pathogen interaction under variable resource supply and disturbance, including effects of competition and mycorrhization. Cost/benefit relationships in balancing resource investments versus gains turned out to be fundamental in quantifying competitiveness when related to the space, which is subject to competitive resource exploitation. A space-related view of defence as a form of prevention of decline in competitiveness may promote conversion of resource turnover across the different kinds of biotic interaction, given their capacity in jointly controlling whole plant resource allocation. [source] A Clinical Imperative: Assisting Patients Who Smoke to Reduce Their Risk of Cardiovascular DiseasePREVENTIVE CARDIOLOGY, Issue 2007Chris Bullen MBChB The role of tobacco smoking as a cause of cardiovascular disease is now unequivocal and well-documented in literally hundreds of epidemiologic and biomedical studies over the past 50 years. Cessation of smoking, on the other hand, swiftly and profoundly reduces the risks of a cardiovascular event. Thus, smoking cessation should be seen as perhaps the most effective lifesaving intervention in the physician's armamentarium. Despite this widely available knowledge, and evidence that most smokers want to quit, relatively few physicians offer cessation support to their smoking patients, even those at high risk for a cardiovascular event. This article reviews the links between tobacco smoking and cardiovascular disease, argues for a greater role for physicians in assisting smokers to quit, and highlights the most effective interventions currently available. [source] How Much Ecology Do We Need to Know to Restore Mediterranean Ecosystems?RESTORATION ECOLOGY, Issue 3 2007Fernando Valladares Abstract Despite important advances in ecological knowledge of Mediterranean-type ecosystems, advances in restoration ecology have not seen a parallel increase in these systems. Although some concepts such as positive plant,plant interaction (facilitation) have received attention in the restoration ecology community, others such as phenotypic plasticity have not. Some concepts (e.g., environmental heterogeneity) are mature enough for a wide use in restoration, whereas available knowledge on others (e.g., facilitation, plasticity) is less conclusive. However, the scientific knowledge is in general enough to significantly improve the guidelines for restoration of Mediterranean ecosystems. Our review suggests that (1) the extent of facilitation in dry ecosystems is partially understood, with supporting, but somewhat contradictory empirical evidence for its potential use in restoration; (2) the influence of habitat heterogeneity on plant performance and plasticity is only beginning to be understood, with a strong bias toward patterns of structural heterogeneity and negligible information on functional heterogeneity; and (3) sound evaluations of phenotypic plasticity might be useful to increase the success of restoration practices in patchy Mediterranean environments. Future global change scenarios involving temperature rise, reduced precipitation, increased frequency of extreme climatic events, and important land use changes and fragmentation must be particularly considered when restoring Mediterranean ecosystems. Further research on how to incorporate results on facilitation, environmental heterogeneity, and plasticity within a global change framework is clearly needed. [source] Lost in knowledge translation: Time for a map?THE JOURNAL OF CONTINUING EDUCATION IN THE HEALTH PROFESSIONS, Issue 1 2006Ian D. Graham PhD Abstract There is confusion and misunderstanding about the concepts of knowledge translation, knowledge transfer, knowledge exchange, research utilization, implementation, diffusion, and dissemination. We review the terms and definitions used to describe the concept of moving knowledge into action. We also offer a conceptual framework for thinking about the process and integrate the roles of knowledge creation and knowledge application. The implications of knowledge translation for continuing education in the health professions include the need to base continuing education on the best available knowledge, the use of educational and other transfer strategies that are known to be effective, and the value of learning about planned-action theories to be better able to understand and influence change in practice settings. [source] Photodynamic therapy: a targeted therapy in periodonticsAUSTRALIAN DENTAL JOURNAL, Issue 2009M Raghavendra Abstract The oral cavity is colonized by a large number and highly diversified communities of micro-organisms. Bacterial biofilm present on tooth or root surface is a major cause of gingivitis and periodontitis. Chemical antimicrobial agents are widely used in prophylactic and therapeutic regimens for dental plaque related diseases, which are among the most common human infections. As these agents are difficult to maintain at therapeutic concentrations in the oral cavity and can be rendered ineffective by resistance development in target organisms, there is a need for an alternative antimicrobial approach. A novel approach, photodynamic therapy (PDT), could be a solution to these problems. Lethal photosensitization of many bacteria, both Gram positive and Gram negative was found in many studies. The advantage of this new approach includes rapid bacterial elimination, minimal chance of resistance development and safety of adjacent host tissue and normal microflora. Thus, the available knowledge of photodynamic therapy should encourage a more clinically oriented application of this technique. [source] Better library design: data-driven protein engineeringBIOTECHNOLOGY JOURNAL, Issue 2 2007Javier F. Chaparro-Riggers Abstract Data-driven protein engineering is increasingly used as an alternative to rational design and combinatorial engineering because it uses available knowledge to limit library size, while still allowing for the identification of unpredictable substitutions that lead to large effects. Recent advances in computational modeling and bioinformatics, as well as an increasing databank of experiments on functional variants, have led to new strategies to choose particular amino acid residues to vary in order to increase the chances of obtaining a variant protein with the desired property. Strategies for limiting diversity at each position, design of small sub-libraries, and the performance of scouting experiments, have also been developed or even automated, further reducing the library size. [source] Herpetofaunal Diversity and Abundance in Tropical Upland Forests of Cameroon and Panama,BIOTROPICA, Issue 1 2001Ulrich Hofer ABSTRACT Two tropical upland forests, Mount Kupe in Cameroon and Bosque Protector Palo Seco in Panama, were compared in terms of herpetofaunal species richness and density of individuals. Based on rarefaction, whereby samples are standardized for abundance, Palo Seco had significantly more species of frogs and lizards. Extrapolations to total local species richness, by fitting the Michaelis,Menten equation to the species accumulation curves and by using Chao's estimator, yielded divergent results: more lizard species on Mount Kupe, and an equal number of frogs at both sites. These disparities can be accounted for by differences in evenness, which was higher in Palo Seco. Frog density was significantly higher on Mount Kupe, snake density significantly higher in Palo Seco, and lizards exhibited no density difference. Overall, the results revealed a less consistent pattern and more moderate differences than what is known from southeast Asian,-Central American comparisons. This outcome is discussed in the light of available knowledge, but quantitative data from African forests are too sparse to allow general conclusions. Se comparó la herpetofauna de dos bosques tropicales húmedos ubicados en las montañas, Mount Kupe en Camerún y Bosque Protector Palo Seco en Panamá, en relación a la riqueza especifica y la densidad de individuos. Con base en el método de rarefacción, en el cual los muestreos se estandarizan en base a su abudancia, Palo Seco presenta significativamente mas especies de anuros y lagartos. Extrapolaciones con respecto a la riqueza especifica total de los sitios, mediante un ajuste de la ecuación de Michaelis-Menten a las curvas de acumulación de especies, y utilizando el índice de Chao, produjeron resultados divergentes: más especies de lagartos en Mount Kupe, y el mismo número de especies de anuros en ambos sitios. Dichas diferencias pueden resultar de una equitatividad más alta en Palo Seco. La densidad de anuros resultó significativamente más alta en Mount Kupe, mientras que la densidad de serpientes fue significativamente más alta en Palo Seco, y no se encontró una diferencia entre k densidad de lagartos en ambos sitios. En general los resultados muestran patrones menos consistentes y diferencias mis moderadas de las que se conocen entre el Sureste de Asia y Centroamerica. Se discuten los resultados con base en la información disponible, sin embargo, la existencia de datos cuantitativos para bosques africanos es demasiado escaza como para permitir conclusiones generales. RESUMES Se comparó la herpetofauna de dos bosques tropicales húmedos ubicados en las montañas, Mount Kupe en Camerún y Bosque Protector Palo Seco en Panamá, en relación a la riqueza especifica y la densidad de individuos. Con base en el método de rarefacción, en el cual los muestreos se estandarizan en base a su abudancia, Palo Seco presenta significativamente mas especies de anuros y lagartos. Extrapolaciones con respecto a la riqueza especifica total de los sitios, mediante un ajuste de la ecuación de Michaelis-Menten a las curvas de acumulación de especies, y utilizando el índice de Chao, produjeron resultados divergentes: más especies de lagartos en Mount Kupe, y el mismo número de especies de anuros en ambos sitios. Dichas diferencias pueden resultar de una equitatividad más alta en Palo Seco. La densidad de anuros resultó significativamente más alta en Mount Kupe, mientras que la densidad de serpientes fue significativamente más alta en Palo Seco, y no se encontró una diferencia entre k densidad de lagartos en ambos sitios. En general los resultados muestran patrones menos consistentes y diferencias mis moderadas de las que se conocen entre el Sureste de Asia y Centroamerica. Se discuten los resultados con base en la información disponible, sin embargo, la existencia de datos cuantitativos para bosques africanos es demasiado escaza como para permitir conclusiones generales. [source] | |||||||||||||||||||