Sample records for laboratory natural selection

  1. natural selection

    NSDL National Science Digital Library

    David Joiner

    Charles Darwin's theory of natural selection was the first plausible mechanism to explain the change of species over time, however, in it's original form it did not explain how new traits could form, or how traits that had formed could be passed on to successive generations. The rise in modern genetics helped to modify biologists understanding of evolution by attributing the origin of new traits in a species to random genetic processes of mutation and sexual recombination, with the survivability of species with the new traits subject to natural selection. This combination of random mutation and natural selection is often referred to as Neodarwinism.

  2. A Natural Selection

    NSDL National Science Digital Library

    Katherine M. Nielsen

    2005-10-01

    The high school science laboratory provides a natural environment for students to learn through scientist-teacher partnerships. A dynamic learning community, authentic inquiry, a deeper understanding of the nature of science, and learning about scientific careers are all benefits of scientist-teacher partnerships. This article focuses on the benefits of partnerships while describing how one specific partnership team developed a natural selection laboratory to integrate with a high school biology curriculum.

  3. THE NATURE AND EXTENT OF LABORATORY INSTRUCTION IN SELECTED MODERN HIGH SCHOOL BIOLOGY CLASSES.

    ERIC Educational Resources Information Center

    BARNES, LEHMAN WILDER, JR.

    ANALYZED WAS THE RELATIONSHIP BETWEEN THE DEGREE TO WHICH LABORATORY ACTIVITIES CONFORMED TO LABORATORY ACTIVITIES RECOMMENDED BY BIOLOGICAL SCIENCES CURRICULUM STUDY (BSCS) AND THREE SPECIFIC VARIABLES WHICH WERE (1) AVAILABLE LABORATORY FACILITIES, (2) ACCEPTANCE OF BSCS OBJECTIVES, AND (3) CLASS GAIN IN THE UNDERSTANDING OF SCIENCE. DATA WERE…

  4. Laboratory Activities to Support Student Understanding of the Molecular Mechanisms of Mutation & Natural Selection

    ERIC Educational Resources Information Center

    Hubler, Tina; Adams, Patti; Scammell, Jonathan

    2015-01-01

    The molecular basis of evolution is an important and challenging concept for students to understand. In a previous article, we provided some of the scientific background necessary to teach this topic. This article features a series of laboratory activities demonstrating that molecular events can alter the genomes of organisms. These activities are…

  5. Evolution by Natural Selection

    NSDL National Science Digital Library

    Jennifer Doherty

    Principles of natural selection are demonstrated by a simulation that involves different color pom-poms and student feeders equipped with different types of feeding implements. Students analyze results to see how different traits contribute to fitness in different habitats. Additional examples and questions help students to understand the process of natural selection, including three necessary conditions for natural selection to take place.

  6. Natural Resource Ecology Laboratory

    NSDL National Science Digital Library

    The Natural Resource Ecology Laboratory (NREL) at Colorado State University conducts multi-disciplinary research in ecosystem science, with the purpose of improving knowledge of "the complex interactions between humans, management activities, and ecosystems." The recently launched homepage, which is still under construction, includes background information on NREL; descriptions of research projects (a substantial and diverse list); publications, reports, and data; teaching and outreach; and contact information.

  7. Natural Selection Lesson

    NSDL National Science Digital Library

    David Joiner

    The Natural Selection lesson uses a Monte Carlo model of spot size with variability between generations in an environment with predators to study how variation and environment can affect a species over time.

  8. ``Evolution without Natural Selection''

    Microsoft Academic Search

    Charles Dixon

    1885-01-01

    BELIEVING as I do that the words of a reviewer should be final, it is with no small amount of hesitation that I pen the following few remarks on the review of my little work entitled ``Evolution without Natural Selection,'' which appeared in NATURE of November 12 (p. 26). The curious way in which my book has been misunderstood, and

  9. Darwin's Second Idea Natural Selection

    E-print Network

    Darwin's Second Idea ­ Natural Selection · Evolution: controversial? · Natural selection ­ Darwin · 15 species · Differences in beak size, shape #12;Darwin's Finches Can natural selection account's postulates ­ Controversial? ­ Two examples of NS #12;Charles Darwin Darwin's Ideas 1. Species evolve over

  10. Natural Selection and Geology 230

    E-print Network

    Kammer, Thomas

    ;Natural Selection · The theory of natural selection was proposed by Charles Darwin in 1859, in his book;Darwin drew an analogy between artificial selection and natural selection. Here we see dog breedsNatural Selection and Evolution Geology 230 Fossils and Evolution #12;The Study of Evolution

  11. Lamarck and Natural Selection

    NSDL National Science Digital Library

    Charles Darwin defined natural selection in "On the Origin of Species," however, Darwin did not invent the idea of evolution and not everyone saw his ideas as original. The shadow of Lamarckian theory which Darwin wanted desperately to escape is a genuine scientific precursor and what has become known as the Lamarckian Heresy has maintained a presence on the fringes of biology to this day. This radio broadcast explores who Lamarck was, how natural selection escaped from his shadow and gained acceptance from the scientific establishment, and whether any evidence has emerged that might challenge the elegant simplicity of natural selection. There is discussion about whether what is passed on to descendants may be affected by experience and environment; the experiments performed by Mendel that led to genetics; the role of DNA, gene mutations, and networks of genes in epigenetics; and how there seem to be fewer genes in humans than expected. The 2003 broadcast is 57 minutes in length.

  12. Introduction to Natural Selection

    NSDL National Science Digital Library

    Science Netlinks

    2002-03-28

    This lesson is an introduction to natural selection and is suited to any student who is just beginning his or her discovery of evolution. The motivation introduces a species of bird that became (over millions of years) numerous species, through adaptation. The development is a hands-on activity that demonstrates how populations change little by little, generation by generation, due to survival of species that have traits that are beneficial in an environment.

  13. Natural Selection Simulation

    NSDL National Science Digital Library

    2012-05-29

    This classroom activity introduces the concept of natural selection and how it relates to evolution. Students will use a variety of utensils including clothespins, tweezers and spoons to mimic animals with differently shaped mouths. The class will go through several trials, picking up at least twenty beans in one minute with their assigned utensil. If they fail to do so, their creature has died, demonstrating what happens to animals that cannot compete in the wild. Several discussion questions are included along with the activity.

  14. Investigating Natural Selection: Elementary School

    NSDL National Science Digital Library

    2010-01-01

    This lesson plan is designed for fourth and fifth grade students learning about natural selection. The class will investigate the predator-prey relationship as an example of how natural selection occurs in a population. Students will work in groups of three or four and observe how predators select their prey, and how this affects the subsequent populations of a species. The concept of camouflage is also covered in the material. This lesson is designed to take about sixty minutes of class time.

  15. Modeling Natural Selection

    NSDL National Science Digital Library

    Christine Lotter

    2011-02-01

    In their research, scientists generate, test, and modify scientific models. These models can be shared with others and demonstrate a scientist's understanding of how the natural world works. Similarly, students can generate and modify models to gain a bet

  16. ``Evolution without Natural Selection''

    Microsoft Academic Search

    Charles Dixon

    1885-01-01

    Two or three points in Mr. Romanes's letter in your issue of December 3 (p. 100), leave me no other alternative than to again ask you to insert the following few remarks. I beg to inform Mr. Romanes that with Darwinism my book has very little to do. It neither attempts to refute nor confirm the Darwinian hypothesis of Natural

  17. Natural Selection: How Evolution Works

    NSDL National Science Digital Library

    Douglas Futuyma (State University of New York at Stony Brook; )

    2004-12-01

    The issue-focused interview demonstrates how natural selection is a very efficient, predictable mechanism of evolution. It illustrates how species adapt to their environment, the reproductive success of a species, design in nature and presents evidence of evolution in action, e.g., antibiotic resistance.

  18. Natural Selection Promotes Antigenic Evolvability

    PubMed Central

    Graves, Christopher J.; Ros, Vera I. D.; Stevenson, Brian; Sniegowski, Paul D.; Brisson, Dustin

    2013-01-01

    The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed ‘cassettes’ that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections. PMID:24244173

  19. Friendship and natural selection.

    PubMed

    Christakis, Nicholas A; Fowler, James H

    2014-07-22

    More than any other species, humans form social ties to individuals who are neither kin nor mates, and these ties tend to be with similar people. Here, we show that this similarity extends to genotypes. Across the whole genome, friends' genotypes at the single nucleotide polymorphism level tend to be positively correlated (homophilic). In fact, the increase in similarity relative to strangers is at the level of fourth cousins. However, certain genotypes are also negatively correlated (heterophilic) in friends. And the degree of correlation in genotypes can be used to create a "friendship score" that predicts the existence of friendship ties in a hold-out sample. A focused gene-set analysis indicates that some of the overall correlation in genotypes can be explained by specific systems; for example, an olfactory gene set is homophilic and an immune system gene set is heterophilic, suggesting that these systems may play a role in the formation or maintenance of friendship ties. Friends may be a kind of "functional kin." Finally, homophilic genotypes exhibit significantly higher measures of positive selection, suggesting that, on average, they may yield a synergistic fitness advantage that has been helping to drive recent human evolution. PMID:25024208

  20. Friendship and natural selection

    PubMed Central

    Christakis, Nicholas A.; Fowler, James H.

    2014-01-01

    More than any other species, humans form social ties to individuals who are neither kin nor mates, and these ties tend to be with similar people. Here, we show that this similarity extends to genotypes. Across the whole genome, friends’ genotypes at the single nucleotide polymorphism level tend to be positively correlated (homophilic). In fact, the increase in similarity relative to strangers is at the level of fourth cousins. However, certain genotypes are also negatively correlated (heterophilic) in friends. And the degree of correlation in genotypes can be used to create a “friendship score” that predicts the existence of friendship ties in a hold-out sample. A focused gene-set analysis indicates that some of the overall correlation in genotypes can be explained by specific systems; for example, an olfactory gene set is homophilic and an immune system gene set is heterophilic, suggesting that these systems may play a role in the formation or maintenance of friendship ties. Friends may be a kind of “functional kin.” Finally, homophilic genotypes exhibit significantly higher measures of positive selection, suggesting that, on average, they may yield a synergistic fitness advantage that has been helping to drive recent human evolution. PMID:25024208

  1. Introduction. Modelling natural action selection.

    PubMed

    Prescott, Tony J; Bryson, Joanna J; Seth, Anil K

    2007-09-29

    Action selection is the task of resolving conflicts between competing behavioural alternatives. This theme issue is dedicated to advancing our understanding of the behavioural patterns and neural substrates supporting action selection in animals, including humans. The scope of problems investigated includes: (i) whether biological action selection is optimal (and, if so, what is optimized), (ii) the neural substrates for action selection in the vertebrate brain, (iii) the role of perceptual selection in decision-making, and (iv) the interaction of group and individual action selection. A second aim of this issue is to advance methodological practice with respect to modelling natural action section. A wide variety of computational modelling techniques are therefore employed ranging from formal mathematical approaches through to computational neuroscience, connectionism and agent-based modelling. The research described has broad implications for both natural and artificial sciences. One example, highlighted here, is its application to medical science where models of the neural substrates for action selection are contributing to the understanding of brain disorders such as Parkinson's disease, schizophrenia and attention deficit/hyperactivity disorder. PMID:17428783

  2. Natural Selection and Developmental Constraints

    E-print Network

    Monteiro, Antónia

    , scaling relationships are shaped by strong natural selection. Among species, populations, and even sexes) and exhibit lineage-specific, seasonal morph­specific, or sex-specific scaling relationships associated,1 *. Bas J. Zwaan,1 David L. Stern,2 Paul M. Brakefield1 In animals, scaling relationships between

  3. Natural Selection and Applied Genetics

    NSDL National Science Digital Library

    2010-01-01

    Natural Selection and Applied Genetics is a graduate-level professional development course designed to enhance your understanding and teaching of life science. In two sessions, you will investigate life science topics using hands-on activities and online resources including video segments, interactive activities, readings, and other multimedia materials. These resources are drawn from Teachers' Domain, WGBH's digital library service.

  4. Natural selection and glucocorticoid physiology.

    PubMed

    Patterson, S H; Hahn, T P; Cornelius, J M; Breuner, C W

    2014-02-01

    Glucocorticoid hormones are considered potent modulators of trade-offs between reproduction and survival. As such, selection should affect glucocorticoid physiology, although relatively little is known about how selection may act on glucocorticoid profiles. In general, the evolution of physiology is less studied and less well understood than morphological or life history traits. Here, we used a long-term data set from a population of mountain white-crowned sparrows to estimate natural selection on glucocorticoid profiles. Our study suggests that survival selection favours higher hormone concentrations for multiple components of glucocorticoid physiology (both baseline and stress-induced glucocorticoid levels). Fecundity selection varies depending on the component of hypothalamic-pituitary-adrenal physiology; greater reproductive output was associated with higher baseline glucocorticoid levels, but lower stress-induced glucocorticoid levels. Additionally, the selection gradient was greater for glucocorticoids than for a morphological trait (wing length). These results support the hypothesis that stress-induced glucocorticoids increase survival over reproduction within a wild population (the CORT-trade-off hypothesis). Taken together, these results add to our knowledge of how selection operates on physiological traits and also provide an evolutionary and ecological perspective on several key open issues in the field of glucocorticoid physiology. PMID:24341364

  5. Argonne National Laboratory's Natural Convection

    E-print Network

    Kemner, Ken

    will incorporate passive safety systems, many in the form of natural circulation loops, to ensure safe and long temperature measurement system augments the NSTF's conventional instrumentation, supporting: · High--confirms the performance of reactor cavity cooling systems (RCCS) and similar passive confinement or containment decay heat

  6. Natural Selection 9-149 Chapter 9. NATURAL SELECTION AND BIOLOGICAL

    E-print Network

    Richerson, Peter J.

    created. B. Darwin's Contribution Natural selection is a model of how evolution works. Darwin is sometimes selection into the category of a discovery. Charles Darwin developed his basic theory of evolutionNatural Selection 9-149 Chapter 9. NATURAL SELECTION AND BIOLOGICAL EVOLUTION Which beginning

  7. Natural Selection Because of Different Color: Camouflage

    NSDL National Science Digital Library

    2012-11-14

    In this activity (p.5-6 of PDF), learners investigate natural selection. Learners discover that natural selection, which takes place over decades, can lead to altered populations within a species. Use this activity to explain the role of pollution and how humans can impact populations as well as compare natural selection to the development of antibiotic resistance in bacteria, which occurs much more quickly.

  8. Natural Selection: Exploring Variation and Heritability

    NSDL National Science Digital Library

    This lesson has students think about two important components of Darwin's model of natural selection in greater detail. First, they will have an opportunity to explore the natural variations present in a variety of organisms. Specifically, they will examine sunflower seeds and Wisconsin Fast Plants. Next, they will use data and graphs of that data from an artificial selection experiment to consider the role of heredity in natural selection. They will answer questions related to a graph and review the statistical concepts of mean, median, mode, and range and will work in groups to examine and answer questions about graphs. The site includes instructional notes for the teacher and the required student handouts.

  9. Experiencing Natural Selection: Will You Survive?

    NSDL National Science Digital Library

    2012-06-11

    This video from the Teaching Channel demonstrates the concept of natural selection. The engaging classroom activity, led by instructor Ceri Evans, addresses survival and natural selection and relates these ideas to the larger concept of evolution. The video may be shown to students to demonstrate these concepts, or may be used as the basis for a similar classroom activity. Running time for the video is 27:29.

  10. Evoll - A Computer Based Natural Selection Game

    ERIC Educational Resources Information Center

    Wright, Ramil C.

    1972-01-01

    Describes a computer-generated natural selection game which deals with various factors influencing survival and speciation processes. Variation of population size, growth rate, brood size, and selection pressure are permitted by the program, which is written in ASA Basic FORTRAN IV. (PR)

  11. Natural Selection: Understanding Paley's Model

    NSDL National Science Digital Library

    This information is intended to introduce students to the ideas proposed by William Paley in 1802 in the book Natural Theology. His model invokes the supernatural to explain adaptation and is a particularly clear example of the intelligent design ideas that were prevalent at that time. Students will have an opportunity to come to an understanding of the phenomena he was trying to explain, in part by reading an excerpt of his original writing. As an optional activity, students will have direct experience examining the structure of the mammalian eye that figured prominently in Paley's writing. Finally, they will work in groups to imagine some of the prior knowledge and beliefs that were central in Paley's thinking. This site includes detailed instructional notes for the teacher and all of the student handouts that are required.

  12. Clippy Island: An Investigation into Natural Selection

    NSDL National Science Digital Library

    Lauren Furness

    2012-04-09

    In this activity, leaners will observe the process of natural selection on a population of birds called 'Springbeaks' over four seasons of breeding on an isolated environment called 'Clippy Island.' Learners will simulate feeding in a timed exercise to illustrate how a limited food supply and the introduction of genetic variants can lead to natural selection and adaptation. Learners will examine whether or not beak size affects the ability of a Springbeak to gather food and how this variation can affect successive generations in the population. This activity is designed for large groups of 30 learners but can work for smaller groups of at least 16 learners.

  13. Density-dependent natural selection in Drosophila: Adaptation to adult crowding

    E-print Network

    Rose, Michael R.

    Density-dependent natural selection in Drosophila: Adaptation to adult crowding AMITABH JOSHI,à WAN, Irvine, CA 92697-2525, USA Summary The eects of adult crowding on two components of ®tness were studied-dependent natural selection in the laboratory for over 50 generations. Three days of crowding, early in adult life

  14. Ocean waves, nearshore ecology, and natural selection

    Microsoft Academic Search

    Mark W. Denny

    2006-01-01

    Although they are subjected to one of the most stressful physical environments on earth, wave-swept rocky shores support a highly diverse community of plants and animals. The surprising presence of such diversity amidst severe environmental adversity provides a unique opportunity for exploration of the role of extreme water flows in community ecology and natural selection. Methods are described by which

  15. Sir Wyville Thomson and Natural Selection

    Microsoft Academic Search

    Charles Darwin

    1880-01-01

    I AM sorry to find that Sir Wyville Thomson does not under stand the principle of natural selection, as explained by Mr.Wallace and. myself. If he had done so, he could not have written the following sentence in the Introduction to the Voyage of the Challenger:-``The character of the abyssal fauna refuses to give the least support to the theory

  16. Natural selection of mammalian brain components

    Microsoft Academic Search

    William M. Brown

    2001-01-01

    The debate about whether the brain and accompanying cognitive architecture were designed by natural selection or by some other process originated with Alfred Russel Wallace and Charles Darwin. Today, this debate is no longer about vitalism verses mechanism, as it was for Wallace and Darwin, rather it is between the adaptationist and developmental constraints accounts of internal brain organization. New

  17. A Lesson on Evolution & Natural Selection

    ERIC Educational Resources Information Center

    Curtis, Anthony D.

    2010-01-01

    I describe three activities that allow students to explore the ideas of evolution, natural selection, extinction, mass extinction, and rates of evolutionary change by engaging a simple model using paper, pens, chalk, and a chalkboard. As a culminating activity that supports expository writing in the sciences, the students write an essay on mass…

  18. BOOK REVIEW Evolution Despite Natural Selection? Emergence

    E-print Network

    Badyaev, Alex

    BOOK REVIEW Evolution Despite Natural Selection? Emergence Theory and the Ever Elusive Link Between subsequently sorting this variation. Robert G. B. Reid's thought provoking and authoritative new book and adaptability. The book's main focus is emergence theory--the generation of stable novel structures that can

  19. Darwin's explanation of design: from natural theology to natural selection.

    PubMed

    Ayala, Francisco J

    2010-08-01

    Copernicus, Galileo, Newton and other physical scientists ushered in a conception of the universe as matter in motion governed by natural laws. Their discoveries brought about a fundamental revolution, namely a commitment to the postulate that the universe obeys immanent laws that can account for natural phenomena. The workings of the universe were brought into the realm of science: explanation through natural laws. Darwin completed the Copernican revolution by extending it to the living world. Darwin demonstrated the evolution of organisms. More important yet is that he discovered natural selection, the process that explains the "design" of organisms. The adaptations and diversity of organisms, the origin of novel and complex species, even the origin of mankind, could now be explained by an orderly process of change governed by natural laws. The origin of species and the exquisite features of organisms had previously been explained as special creations of an Omniscient God. Darwin brought them into the domain of science. Evolution is a creative process that produces genuine novelty. The creative power of evolution arises from a distinctive interaction between chance and necessity, between random mutation and natural selection. PMID:19800418

  20. A Selected Bibliography on Microbiological Laboratory Design.

    ERIC Educational Resources Information Center

    Laboratory Design Notes, 1967

    1967-01-01

    Reference sources on microbiological laboratory design are cited. Subjects covered include--(1) policies and general requirements, (2) ventilated cabinets, (3) animal isolation equipment, (4) air handling, ventilation, and filtration, (5) germicidal ultraviolet irradiation, (6) aerosol test facilities, (7) process production of microorganisms, and…

  1. [Perspectives of selective laboratory screening in children with joint pathology].

    PubMed

    2014-01-01

    The article highlights the problematic issues of the laboratory diagnostic possibilities in children with joint pathology with moden tests (anti-cyclic citrullinated peptide antibodies and antibodies to mutated citrullinated vimentin). The expediency and effectiveness of the proposed laboratory tests is justified for improvement of the early differential diagnosis, joint pathology treatment optimization, and discuss the prospect of selective laboratory screening in families burdened by rheumatic diseases genealogy. PMID:25796875

  2. Symbiogenesis, natural selection, and the dynamic Earth.

    PubMed

    Kutschera, U

    2009-08-01

    One century ago, Constantin S. Mereschkowsky introduced the symbiogenesis theory for the origin of chloroplasts from ancient cyanobacteria which was later supplemented by Ivan E. Wallin's proposal that mitochondria evolved from once free-living bacteria. Today, this Mereschkowsky-Wallin principle of symbiogenesis, which is also known as the serial primary endosymbiosis theory, explains the evolutionary origin of eukaryotic cells and hence the emergence of all eukaryotes (protists, fungi, animals and plants). In 1858, the concept of natural selection was described independently by Charles Darwin and Alfred R. Wallace. In the same year, Antonio Snider-Pellegrini proposed the idea of shifting continents, which was later expanded by Alfred Wegener, who published his theory of continental drift eight decades ago. Today, directional selection is accepted as the major cause of adaptive evolution within natural populations of micro- and macro-organisms and the theory of the dynamic Earth (plate tectonics) is well supported. In this article, I combine the processes and principles of symbiogenesis, natural selection and the dynamic Earth and propose an integrative 'synade-model' of macroevolution which takes into account organisms from all five Kingdoms of life. PMID:19399544

  3. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Selection for validation inspection-laboratory responsibilities...Program § 493.565 Selection for validation inspection—laboratory responsibilities... A laboratory selected for a validation inspection must do the...

  4. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Selection for validation inspection-laboratory responsibilities...Program § 493.565 Selection for validation inspection—laboratory responsibilities... A laboratory selected for a validation inspection must do the...

  5. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Selection for validation inspection-laboratory responsibilities...Program § 493.565 Selection for validation inspection—laboratory responsibilities... A laboratory selected for a validation inspection must do the...

  6. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...2013-10-01 false Selection for validation inspection-laboratory responsibilities...Program § 493.565 Selection for validation inspection—laboratory responsibilities... A laboratory selected for a validation inspection must do the...

  7. 42 CFR 493.565 - Selection for validation inspection-laboratory responsibilities.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...2014-10-01 false Selection for validation inspection-laboratory responsibilities...Program § 493.565 Selection for validation inspection—laboratory responsibilities... A laboratory selected for a validation inspection must do the...

  8. Mate Choice in Soldier Beetles: Field & Laboratory Experiments that Demonstrate Sexual Selection in Action

    ERIC Educational Resources Information Center

    Eason, Perri K.; Sherman, Peter T.

    2003-01-01

    Although the theory of evolution is the foundation of modern biology, students too rarely have an opportunity to watch selection operate in natural populations of animals. This lack may be partially responsible for the unfortunate ignorance of many people regarding the significance of evolution in biology. Laboratory exercises that directly study…

  9. Natural Codeswitching Knocks on the Laboratory Door

    ERIC Educational Resources Information Center

    Myers-Scotton, Carol

    2006-01-01

    This contribution discusses findings and hypotheses from empirical data of naturally-occurring codeswitching. The discussion is framed by some comparisons of the approaches of contact linguists and psycholinguists to bilingual production data. However, it emphasizes the relevance of naturally-occurring codeswitching to the theoretical questions…

  10. Respirator selection for clandestine methamphetamine laboratory investigation.

    PubMed

    Nelson, Gary O; Bronder, Gregory D; Larson, Scott A; Parker, Jay A; Metzler, Richard W

    2012-01-01

    First responders to illicit drug labs may not always have SCBA protection available. Air-purifying respirators using organic vapor cartridges with P-100 filters may not be sufficient. It would be better to use a NIOSH-approved CBRN respirator with its required multi-purpose cartridge system, which includes a P-100 filter. This would remove all the primary drug lab contaminants—organic vapors, acid gases, ammonia, phosphine, iodine, and airborne meth particulates. To assure the proper selection and use of a respirator, it is recommended that the contaminants present be identified and quantified and the OSHA 29 CFR 1910.134 respirator protection program requirements followed. PMID:22571884

  11. Natural language processing Laboratory Plan: An essential for Persian language

    Microsoft Academic Search

    Mohammad Azadnia; Sina Rezagholizadeh; Alireza Yari

    2010-01-01

    Prevalent use of human language in computer systems and language oriented document processing, especially in the web, caused creating the need of designing mechanisms for developing natural language processing. In this paper, a survey in Natural Language Processing Laboratory has been done and a proposed framework for its development is suggested. Achieving this goal, the specifications, structures and activities of

  12. Natural Resource Management Plan for Brookhaven National Laboratory

    Microsoft Academic Search

    2011-01-01

    This comprehensive Natural Resource Management Plan (NRMP) for Brookhaven National Laboratory (BNL) was built on the successful foundation of the Wildlife Management Plan for BNL, which it replaces. This update to the 2003 plan continues to build on successes and efforts to better understand the ecosystems and natural resources found on the BNL site. The plan establishes the basis for

  13. Summer Field Assistant (Two positions) Natural Resource Ecology Laboratory

    E-print Network

    measurements, Rocky Mountain plant identification, and forest ecology is desired. The successful candidate must University The Natural Resource Ecology Laboratory is seeking two seasonal field assistants to support forest, Ecology, or Natural Resource Management. Experience in backpacking, GIS, GPS and/or orienteering, forest

  14. Natural Selection: Comparison of the Models

    NSDL National Science Digital Library

    This lesson provides an opportunity for students to extend their understanding of the three models studied in previous lessons by using them to explain phenomena and by comparing them to one another. Students will work in groups to use the models of Paley, Lamarck, and Darwin to explain the origin of complex structures like the eye, the existence of fossils, and the variety of pigeon breeds. They will confer with another group to share ideas and participate in a class discussion comparing the models and develop written explanations for phenomena based on their understanding of the three models. This lesson represents a turning point in the unit as students conclude their examination of the ideas of Paley and Lamarck and prepare for a more in-depth study of Darwin's model of natural selection. The site also includes instructional notes for teachers and the required student handouts.

  15. Recoding of the stop codon UGA to glycine by a BD1-5/SN-2 bacterium and niche partitioning between Alpha- and Gammaproteobacteria in a tidal sediment microbial community naturally selected in a laboratory chemostat

    PubMed Central

    Hanke, Anna; Hamann, Emmo; Sharma, Ritin; Geelhoed, Jeanine S.; Hargesheimer, Theresa; Kraft, Beate; Meyer, Volker; Lenk, Sabine; Osmers, Harald; Wu, Rong; Makinwa, Kofi; Hettich, Robert L.; Banfield, Jillian F.; Tegetmeyer, Halina E.; Strous, Marc

    2014-01-01

    Sandy coastal sediments are global hotspots for microbial mineralization of organic matter and denitrification. These sediments are characterized by advective porewater flow, tidal cycling and an active and complex microbial community. Metagenomic sequencing of microbial communities sampled from such sediments showed that potential sulfur oxidizing Gammaproteobacteria and members of the enigmatic BD1-5/SN-2 candidate phylum were abundant in situ (>10% and ~2% respectively). By mimicking the dynamic oxic/anoxic environmental conditions of the sediment in a laboratory chemostat, a simplified microbial community was selected from the more complex inoculum. Metagenomics, proteomics and fluorescence in situ hybridization showed that this simplified community contained both a potential sulfur oxidizing Gammaproteobacteria (at 24 ± 2% abundance) and a member of the BD1-5/SN-2 candidate phylum (at 7 ± 6% abundance). Despite the abundant supply of organic substrates to the chemostat, proteomic analysis suggested that the selected gammaproteobacterium grew partially autotrophically and performed hydrogen/formate oxidation. The enrichment of a member of the BD1-5/SN-2 candidate phylum enabled, for the first time, direct microscopic observation by fluorescent in situ hybridization and the experimental validation of the previously predicted translation of the stop codon UGA into glycine. PMID:24904545

  16. Recoding of the stop codon UGA to glycine by a BD1-5/SN-2 bacterium and niche partitioning between Alpha- and Gammaproteobacteria in a tidal sediment microbial community naturally selected in a laboratory chemostat

    SciTech Connect

    Hanke, Anna [Max Planck Institute for Marine Microbiology; Hamann, Emmo [Max Planck Institute for Marine Microbiology; Sharma, Ritin [ORNL; Geelhoed, Jeanine [Max Planck Institute for Marine Microbiology; Hargesheimer, Theresa [Max Planck Institute for Marine Microbiology; Kraft, Beate [Max Planck Institute for Marine Microbiology; Meyer, Volker [Max Planck Institute for Marine Microbiology; Lenk, Sabine [Max Planck Institute for Marine Microbiology; Osmers, Harald [Max Planck Institute for Marine Microbiology; Wu, Rong [Delft University of Technology, Delft, Netherlands; Makinwa, Kofi [Delft University of Technology, Delft, Netherlands; Hettich, Robert {Bob} L [ORNL; Banfield, Jillian F. [University of California, Berkeley; Tegetmeyer, Halina [Max Planck Institute for Marine Microbiology; Strouss, Marc [University of Calgary, ALberta, Canada

    2014-01-01

    Sandy coastal sediments are global hot spots for microbial mineralization of organic matter and denitrification. These sediments are characterized by advective pore water flow, tidal cycling and an active and complex microbial community. Metagenomic sequencing of microbial communities sampled from such sediments showed that potential sulfuroxidizing Gammaproteobacteria and members of the enigmaticBD1-5/ SN-2 candidatephylumwereabundantinsitu (>10% and 2% respectively). By mimicking the dynamic oxic/anoxic environmental conditions of the sedimentin a laboratory chemostat, a simplified microbial community was selected from the more complex inoculum. Metagenomics, proteomics and fluorescenceinsituhybridization showed that this simplified community contained both a potential sulfuroxidizing Gamma proteobacteria (at 24 2% abundance) and a member of the BD1-5 / SN-2candidatephylum (at 7 6%abundance). Despite the abundant supply of organic substrates to the chemostat, proteomic analysis suggested that the selected gamma proteobacterium grew partially auto trophically and performed hydrogen/formate oxidation. The enrichment of a member of the BD1-5/SN-2candidatephylum enabled, for the first time, direct microscopic observation by fluorescent insitu hybridization and the experimental validation of the previously predicted translation of the stop codon UGA into glycine.

  17. Selecting Landing Sites for the 2009 Mars Science Laboratory

    Microsoft Academic Search

    J. A. Grant; M. P. Golombek; A. R. Vasavada; M. M. Watkins

    2006-01-01

    Landing site selection for the 2009 Mars Science Laboratory (MSL) is underway and includes a series of open workshops for soliciting science community input regarding the landing site. The first workshop was held in Spring 2006 and focused on prioritizing 33 proposed sites for imaging by orbital spacecraft. It should be noted that the number of potential landing sites is

  18. Reproduction of natural corrosion by accelerated laboratory testing methods

    SciTech Connect

    Luo, J.S.; Wronkiewicz, D.J.; Mazer, J.J.; Bates, J.K.

    1996-05-01

    Various laboratory corrosion tests have been developed to study the behavior of glass waste forms under conditions similar to those expected in an engineered repository. The data generated by laboratory experiments are useful for understanding corrosion mechanisms and for developing chemical models to predict the long-term behavior of glass. However, it is challenging to demonstrate that these test methods produce results that can be directly related to projecting the behavior of glass waste forms over time periods of thousands of years. One method to build confidence in the applicability of the test methods is to study the natural processes that have been taking place over very long periods in environments similar to those of the repository. In this paper, we discuss whether accelerated testing methods alter the fundamental mechanisms of glass corrosion by comparing the alteration patterns that occur in naturally altered glasses with those that occur in accelerated laboratory environments. This comparison is done by (1) describing the alteration of glasses reacted in nature over long periods of time and in accelerated laboratory environments and (2) establishing the reaction kinetics of naturally altered glass and laboratory reacted glass waste forms.

  19. Microbial Resistance to Triclosan: A Case Study in Natural Selection

    ERIC Educational Resources Information Center

    Serafini, Amanda; Matthews, Dorothy M.

    2009-01-01

    Natural selection is the mechanism of evolution caused by the environmental selection of organisms most fit to reproduce, sometimes explained as "survival of the fittest." An example of evolution by natural selection is the development of bacteria that are resistant to antimicrobial agents as a result of exposure to these agents. Triclosan, which…

  20. Natural selection stops the evolution of male attractiveness

    PubMed Central

    Hine, Emma; McGuigan, Katrina; Blows, Mark W.

    2011-01-01

    Sexual selection in natural populations acts on highly heritable traits and tends to be relatively strong, implicating sexual selection as a causal agent in many phenotypic radiations. Sexual selection appears to be ineffectual in promoting phenotypic divergence among contemporary natural populations, however, and there is little evidence from artificial selection experiments that sexual fitness can evolve. Here, we demonstrate that a multivariate male trait preferred by Drosophila serrata females can respond to selection and results in the maintenance of male mating success. The response to selection was associated with a gene of major effect increasing in frequency from 12 to 35% in seven generations. No further response to selection, or increase in frequency of the major gene, was observed between generations 7 and 11, indicating an evolutionary limit had been reached. Genetic analyses excluded both depletion of genetic variation and overdominance as causes of the evolutionary limit. Relaxing artificial selection resulted in the loss of 52% of the selection response after a further five generations, demonstrating that the response under artificial sexual selection was opposed by antagonistic natural selection. We conclude that male D. serrata sexually selected traits, and attractiveness to D. serrata females conferred by these traits, were held at an evolutionary limit by the lack of genetic variation that would allow an increase in sexual fitness while simultaneously maintaining nonsexual fitness. Our results suggest that sexual selection is unlikely to cause divergence among natural populations without a concomitant change in natural selection, a conclusion consistent with observational evidence from natural populations. PMID:21321197

  1. Good genes sexual selection in nature

    PubMed Central

    Byers, John A.; Waits, Lisette

    2006-01-01

    Whether the mate sampling and choice performed by females in nature influences offspring performance is a controversial issue in theory and an open empirical question. Pronghorn (Antilocapra americana) females engage in an obvious and energetically expensive mate sampling process to identify vigorous males. Although individual females sample independently, their choices converge on a small proportion of males that sire most young. Offspring of attractive males were more likely to survive to weaning and to age classes as late as 5 years, resulting in a selection differential, calculated by expected differences in lifetime number of offspring weaned, of 0.32 against random mating. Enhanced survival to weaning appeared to be accomplished by faster growth rates. Females compensated for matings with a less attractive mate by elevating rates of milk delivery to their young. Because pronghorn males do not have costly ornaments, we conclude that female choice for good genes can exist in the absence of ornaments. Furthermore, female choice may be important and unrecognized as a force that can lower population genetic load. PMID:17060640

  2. Natural selection and the elusiveness of happiness.

    PubMed Central

    Nesse, Randolph M

    2004-01-01

    The quest for happiness has expanded from a focus on relieving suffering to also considering how to promote happiness. However, both approaches have yet to be conducted in an evolutionary framework based on the situations that shaped the capacities for happiness and sadness. Because of this, the emphasis has almost all been on the disadvantages of negative states and the benefits of positive states, to the nearly total neglect of 'diagonal psychology', which also considers the dangers of unwarranted positive states and the benefits of negative emotions in certain situations. The situations that arise in goal pursuit contain adaptive challenges that have shaped domain-general positive and negative emotions that were partially differentiated by natural selection to cope with the more specific situations that arise in the pursuit of different kinds of goals. In cultures where large social groups give rise to specialized and competitive social roles, depression may be common because regulation systems are pushed far beyond the bounds for which they were designed. Research on the evolutionary origins of the capacities for positive and negative emotions is urgently needed to provide a foundation for sensible decisions about the use of new mood-manipulating technologies. PMID:15347525

  3. Good genes sexual selection in nature.

    PubMed

    Byers, John A; Waits, Lisette

    2006-10-31

    Whether the mate sampling and choice performed by females in nature influences offspring performance is a controversial issue in theory and an open empirical question. Pronghorn (Antilocapra americana) females engage in an obvious and energetically expensive mate sampling process to identify vigorous males. Although individual females sample independently, their choices converge on a small proportion of males that sire most young. Offspring of attractive males were more likely to survive to weaning and to age classes as late as 5 years, resulting in a selection differential, calculated by expected differences in lifetime number of offspring weaned, of 0.32 against random mating. Enhanced survival to weaning appeared to be accomplished by faster growth rates. Females compensated for matings with a less attractive mate by elevating rates of milk delivery to their young. Because pronghorn males do not have costly ornaments, we conclude that female choice for good genes can exist in the absence of ornaments. Furthermore, female choice may be important and unrecognized as a force that can lower population genetic load. PMID:17060640

  4. Understanding Natural Selection: Essential Concepts and Common Misconceptions

    Microsoft Academic Search

    T. Ryan Gregory

    2009-01-01

    Natural selection is one of the central mechanisms of evolutionary change and is the process responsible for the evolution\\u000a of adaptive features. Without a working knowledge of natural selection, it is impossible to understand how or why living things\\u000a have come to exhibit their diversity and complexity. An understanding of natural selection also is becoming increasingly relevant\\u000a in practical contexts,

  5. SERUM ALBUMIN POLYMORPHISMS IN NATURAL AND LABORATORY POPULATIONS OF PEROMYSCUS

    E-print Network

    Brown, James H.

    SERUM ALBUMIN POLYMORPHISMS IN NATURAL AND LABORATORY POPULATIONS OF PEROMYSCUS JAMES H. BROWN AND CARL F. WELSER ABSTRACT.-Electrophoresisof serum from 14 species of Peromyscus revealed albumin polymorphismsin samples of P. maniculatus, P. leucopus, P. truei, P. difficilis, P. megalops, and P. floridanus

  6. The Nature of Laboratory Learning Experiences in Secondary Science Online

    ERIC Educational Resources Information Center

    Crippen, Kent J.; Archambault, Leanna M.; Kern, Cindy L.

    2013-01-01

    Teaching science to secondary students in an online environment is a growing international trend. Despite this trend, reports of empirical studies of this phenomenon are noticeably missing. With a survey concerning the nature of laboratory activities, this study describes the perspective of 35-secondary teachers from 15-different U.S. states who…

  7. Peppered Moth Scavenger Hunt Activity Standard: Adaptation and natural selection.

    E-print Network

    Peppered Moth Scavenger Hunt Activity Grade: 4th Standard: Adaptation and natural selection. Supplements: Peppered Moth introduction slides http://www.techapps.net/interactives/pepperMoths.swf Materials

  8. Frequency selective bolometer development at Argonne National Laboratory

    Microsoft Academic Search

    Aaron Datesman; John Pearson; Gensheng Wang; Volodymyr Yefremenko; Ralu Divan; Thomas Downes; Clarence Chang; Jeff McMahon; Stephan Meyer; John Carlstrom; Daniel Logan; Thushara Perera; Grant Wilson; Valentyn Novosad

    2008-01-01

    We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four

  9. NATURAL RESOURCE MANAGEMENT PLAN FOR BROOKHAVEN NATIONAL LABORATORY.

    SciTech Connect

    GREEN,T.ET AL.

    2003-12-31

    Brookhaven National Laboratory (BNL) is located near the geographic center of Long Island, New York. The Laboratory is situated on 5,265 acres of land composed of Pine Barrens habitat with a central area developed for Laboratory work. In the mid-1990s BNL began developing a wildlife management program. This program was guided by the Wildlife Management Plan (WMP), which was reviewed and approved by various state and federal agencies in September 1999. The WMP primarily addressed concerns with the protection of New York State threatened, endangered, or species of concern, as well as deer populations, invasive species management, and the revegetation of the area surrounding the Relativistic Heavy Ion Collider (RHIC). The WMP provided a strong and sound basis for wildlife management and established a basis for forward motion and the development of this document, the Natural Resource Management Plan (NRMP), which will guide the natural resource management program for BNL. The body of this plan establishes the management goals and actions necessary for managing the natural resources at BNL. The appendices provide specific management requirements for threatened and endangered amphibians and fish (Appendices A and B respectively), lists of actions in tabular format (Appendix C), and regulatory drivers for the Natural Resource Program (Appendix D). The purpose of the Natural Resource Management Plan is to provide management guidance, promote stewardship of the natural resources found at BNL, and to integrate their protection with pursuit of the Laboratory's mission. The philosophy or guiding principles of the NRMP are stewardship, adaptive ecosystem management, compliance, integration with other plans and requirements, and incorporation of community involvement, where applicable.

  10. Sexual selection and natural selection in bird speciation

    PubMed Central

    Price, T.

    1998-01-01

    The role of sexual selection in speciation is investigated, addressing two main issues. First, how do sexually selected traits become species recognition traits? Theory and empirical evidence suggest that female preferences often do not evolve as a correlated response to evolution of male traits. This implies that, contrary to runaway (Fisherian) models of sexual selection, premating isolation will not arise as an automatic side effect of divergence between populations in sexually selected traits. I evaluate premating isolating mechanisms in one group, the birds. In this group premating isolation is often a consequence of sexual imprinting, whereby young birds learn features of their parents and use these features in mate choice. Song, morphology and plumage are known recognition cues. I conclude that perhaps the main role for sexual selection in speciation is in generating differences between populations in traits. Sexual imprinting then leads to these traits being used as species recognition mechanisms. The second issue addressed in this paper is the role of sexual selection in adaptive radiation, again concentrating on birds. Ecological differences between species include large differences in size, which may in themselves be sufficient for species recognition, and differences in habitat, which seem to evolve frequently and at all stages of an adaptive radiation. Differences in habitat often cause song and plumage patterns to evolve as a result of sexual selection for efficient communication. Therefore sexual selection is likely to have an important role in generating premating isolating mechanisms throughout an adaptive radiation. It is also possible that sexual selection, by creating more allopatric species, creates more opportunity for ecological divergence to occur. The limited available evidence does not support this idea. A role for sexual selection in accelerating ecological diversification has yet to be demonstrated.

  11. Towards Fully Integrated Natural and Virtual Hydrologic Laboratories

    NASA Astrophysics Data System (ADS)

    Vivoni, E. R.

    2014-12-01

    A key challenge facing hydrologic research and education is the integrated use of natural and virtual laboratories to advance theory and process understanding, develop and test new modeling approaches and provide compelling materials for educational and outreach activities. Too often, the experimental and modeling activities in the hydrologic community are carried out in isolation of each other. This talk will describe our long-term efforts in building two natural watershed laboratories in the Sonoran and Chihuahuan Deserts for the purpose of studying the hydrologic effects of woody plant encroachment. Through the common use of environmental sensor networks, unmanned areal vehicles and spatial sampling methods, the two small watersheds provide unprecedented detail on the hydrologic responses to the bimodal precipitation regime in the southwestern United States in the presence of varying woody plant cover. By designing each natural laboratory using hydrologic modeling criteria, sensor and remote sensing data products and their analyses have been immediately useful for testing and developing meaningful applications of a distributed hydrologic model, the Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator (tRIBS). After building confidence in the model applications, the virtual laboratories at each site are used to test hypotheses on the spatial controls on hydrologic patterns and to infer underlying hydrologic mechanisms. Furthermore, the model-data comparisons allow for detailed investigation of the model improvements that are required related processes, parameters or forcings. Examples are provided to illustrate the information content of the natural and virtual laboratories, the identification of model deficiencies and their resolution, and the process understanding gained from combining the distributed observations and modeling approaches.

  12. BSL-3 Laboratory Practices in the United States: Comparison of Select Agent and Non–Select Agent Facilities

    PubMed Central

    Pompei, Victoria C.; Anderson, Alice

    2014-01-01

    New construction of biosafety level 3 (BSL-3) laboratories in the United States has increased in the past decade to facilitate research on potential bioterrorism agents. The Centers for Disease Control and Prevention inspect BSL-3 facilities and review commissioning documentation, but no single agency has oversight over all BSL-3 facilities. This article explores the extent to which standard operating procedures in US BSL-3 facilities vary between laboratories with select agent or non–select agent status. Comparisons are made for the following variables: personnel training, decontamination, personal protective equipment (PPE), medical surveillance, security access, laboratory structure and maintenance, funding, and pest management. Facilities working with select agents had more complex training programs and decontamination procedures than non–select agent facilities. Personnel working in select agent laboratories were likely to use powered air purifying respirators, while non–select agent laboratories primarily used N95 respirators. More rigorous medical surveillance was carried out in select agent workers (although not required by the select agent program) and a higher level of restrictive access to laboratories was found. Most select agent and non–select agent laboratories reported adequate structural integrity in facilities; however, differences were observed in personnel perception of funding for repairs. Pest management was carried out by select agent personnel more frequently than non–select agent personnel. Our findings support the need to promote high quality biosafety training and standard operating procedures in both select agent and non–select agent laboratories to improve occupational health and safety. PMID:24552359

  13. Darwin and Natural Selection One of the most

    E-print Network

    Kammer, Thomas

    Darwin and Natural Selection #12;One of the most famous books of science. #12;Darwin's home, Down;Charles Darwin in 1837, age 28, after voyage of the Beagle #12;Age 40 Age 45 #12;Charles Darwin, age 60, 1996, Fernandina Volcano #12;Biologists are still studying natural selection in the Galapagos Islands

  14. EVOLUTION WITHOUT NATURAL SELECTION: FURTHER IMPLICATIONS OF THE DAISYWORLD PARABLE

    E-print Network

    Saunders, Peter

    of the model with those of systems that evolved solely by natural selection. Natural selection inherently there is life on Mars. In thinking of experiments for the Viking probes to carry out, Hitchcock and Lovelock (1966) realized that it was not actually necessary to go to Mars. All that was needed was to determine

  15. Natural Selection in the Field and the Classroom

    ERIC Educational Resources Information Center

    Andrews, Tessa Marie

    2012-01-01

    This dissertation examined natural selection in westslope cutthroat trout ("Oncorhynchus clarkii lewisi") and undergraduate learning in the subject area natural selection. Translocation--moving individuals to a new habitat to establish, re-establish or supplement a population--is a crucial management strategy for cutthroat trout. One of…

  16. Administration of Substances to Laboratory Animals: Equipment Considerations, Vehicle Selection, and Solute Preparation

    PubMed Central

    Turner, Patricia V; Pekow, Cynthia; Vasbinder, Mary Ann; Brabb, Thea

    2011-01-01

    Administration of substances to laboratory animals requires careful consideration and planning to optimize delivery of the agent to the animal while minimizing potential adverse experiences from the procedure. The equipment selected to deliver substances to animals depends on the length of the study and the nature of the material being administered. This selection provides a significant opportunity for refining animal treatment. Similarly, when substances are administered as solutions or suspensions, attention should be given to selection of vehicles and methods used for preparing the solutions and suspensions. The research team, veterinarian, technical personnel, and IACUC members should be aware of reasons underlying selection of equipment for substance delivery and should consider carefully how substances will be prepared and stored prior to administration to animals. Failure to consider these factors during experimental planning may result in unintentional adverse effects on experimental animals and confounded results. PMID:22330706

  17. The selective adsorption of hydrogen sulfide from natural gas streams 

    E-print Network

    Fails, James Clayton

    1959-01-01

    possible commercial application of the molecular sieves in sweetening sour natural gas streams' 50 COHCIiUSIOHS CONCLUSIONS The molecular sieves show a decided selectivity in adsorbing hydrogen sulfide from natural ges streamers This seleotivity... capaoity that may be expected decreases as the concentration of carbon dioxide increases' The selectivity shown by the molecular sieves ind1cates a possible commercial application in "sweetening" sour natural gas streams' 52 BIBLIOGRAPHY...

  18. Pollinator-mediated natural selection in Penstemon digitalis

    PubMed Central

    Kessler, André

    2010-01-01

    Measuring the agents of natural selection is important because it allows us to understand not only which traits are expected to evolve but also why they will evolve. Natural selection by pollinators on floral traits is often assumed because in outcrossing animal-pollinated plants flowers are generally thought to function as advertisements of rewards directed at pollinators. We tested the role of bee pollinators in selection on Penstemon digitalis and found that pollinators were driving selection for larger and more flowers. However, what makes our publication unique is the additional information we gained from reviewing the few other studies that also directly tested whether pollinators were agents of selection on floral traits. As we would expect if pollinators are important agents of selection, selection on floral traits was significantly stronger when pollinators were present than when their choices were experimentally removed. Taken together, these results suggest that pollinators can be important drivers of selection in contemporary populations. PMID:21150291

  19. Natural selection on floral morphology can be influenced by climate.

    PubMed

    Campbell, Diane R; Powers, John M

    2015-06-01

    Climate has the potential to influence evolution, but how it influences the strength or direction of natural selection is largely unknown. We quantified the strength of selection on four floral traits of the subalpine herb Ipomopsis sp. in 10 years that differed in precipitation, causing extreme temporal variation in the date of snowmelt in the Colorado Rocky Mountains. The chosen floral traits were under selection by hummingbird and hawkmoth pollinators, with hawkmoth abundance highly variable across years. Selection for flower length showed environmental sensitivity, with stronger selection in years with later snowmelt, as higher water resources can allow translation of pollination success into fitness based on seed production. Selection on corolla width also varied across years, favouring narrower corolla tubes in two unusual years with hawkmoths, and wider corollas in another late snowmelt year. Our results illustrate how changes in climate could alter natural selection even when the primary selective agent is not directly influenced. PMID:25972465

  20. A Simulation Study of Truncation Selection for a Quantitative Trait Opposed by Natural Selection

    PubMed Central

    Minvielle, Francis

    1980-01-01

    A quantitative character controlled at one locus with two alleles was submitted to artificial (mass) selection and to three modes of opposing natural selection (directional selection, overdominance and underdominance) in a large random-mating population. The selection response and the limits of the selective process were studied by deterministic simulation. The lifetime of the process was generally between 20 and 100 generations and did not appear to depend on the mode of natural selection. However, depending on the values of the parameters (initial gene frequency, selection intensity, ratio of the effect of the gene to the environmental standard deviation, fitness values) the following outcomes of selection were observed: fixation of the allele favored by artificial selection, stable nontrivial equilibrium, unstable equilibrium and loss of the allele favored by artificial selection. Finally, the results of the simulation were compared to the results of selection experiments. PMID:7439681

  1. Natural gas price deregulation: a selected bibliography

    SciTech Connect

    White, A.G.

    1984-01-01

    Congress has not been enthusiastic about natural gas deregulation, particularly those members from states whose voters are tied to natural-gas systems heavily for space-heating, i.e., the Mid-West and Northeast. A 1978 law gradually deregulates some of those prices, depending upon the depth at which the gas comes from and how old the discovery is (and thus came under regulation). The President has backed away somewhat from rapid decontrol of natural gas prices, especially in an election year. As the 1983 Congressional session ended, bills that would have made changes were left in committee. The implications for public administration are that natural gas deregulation presents a case study of the difficulties of making substantial administrative changes in politically-sensitive and recessionary times. 197 references.

  2. The Role of Metaphor in the Darwin Debates: Natural Theology, Natural Selection, and Christian Production of Counter-Metaphor 

    E-print Network

    Neumann, Juliet

    2012-07-16

    "nature," "evolution," "natural theology," and "natural selection" is examined?within Christianity prior to Darwin, in Darwin's writing of the Origin, and in the responses of three Victorian Christian critics of science. "Natural selection...

  3. 164 nature physics | VOL 5 | MARCH 2009 | www.nature.com/naturephysics A quantum of natural selection

    E-print Network

    Loss, Daniel

    of natural selection Seth Lloyd The modern evolutionary synthesis, which marries Darwin's theory of natural of natural selection. Perhaps the most surprising aspect of the book is that Darwin was able to construct his1 , much has been made of what Charles Darwin knew and did not know in formulating the theory

  4. Bayesian natural selection and the evolution of perceptual systems.

    PubMed Central

    Geisler, Wilson S; Diehl, Randy L

    2002-01-01

    In recent years, there has been much interest in characterizing statistical properties of natural stimuli in order to better understand the design of perceptual systems. A fruitful approach has been to compare the processing of natural stimuli in real perceptual systems with that of ideal observers derived within the framework of Bayesian statistical decision theory. While this form of optimization theory has provided a deeper understanding of the information contained in natural stimuli as well as of the computational principles employed in perceptual systems, it does not directly consider the process of natural selection, which is ultimately responsible for design. Here we propose a formal framework for analysing how the statistics of natural stimuli and the process of natural selection interact to determine the design of perceptual systems. The framework consists of two complementary components. The first is a maximum fitness ideal observer, a standard Bayesian ideal observer with a utility function appropriate for natural selection. The second component is a formal version of natural selection based upon Bayesian statistical decision theory. Maximum fitness ideal observers and Bayesian natural selection are demonstrated in several examples. We suggest that the Bayesian approach is appropriate not only for the study of perceptual systems but also for the study of many other systems in biology. PMID:12028784

  5. Darwinian Evolution -Adaptive Evolution/Natural Selection

    E-print Network

    Dever, Jennifer A.

    is occurring in this population #12;3 Evolutionary tree estimated from similarities and differences in DNA selection is based on differences in fitness among individuals Darwinian fitness = ability of an individual to reproductive success! Components of fitness: Female red backed spider with two male suitors ü Probability

  6. Problems in Learning the Concept of Natural Selection.

    ERIC Educational Resources Information Center

    Brumby, Margaret

    1979-01-01

    Investigates the level of students' understanding of the concept of evolution of natural selection. Sixty-three first year British university students with an advanced-level biology background participated in this study. (HM)

  7. Genetic Programming { Computers using \\Natural Selection" to generate programs

    E-print Network

    Fernandez, Thomas

    Genetic Programming { Computers using \\Natural Selection" to generate programs William B. Langdon themselves"; science fact or #12;ction? Genetic Programming uses novel optimisation techniques to \\evolve] - is automatic program generation. Genetic Programming applies GAs to a \\population" of programs - typically

  8. Genetic Programming Computers using "Natural Selection" to generate programs

    E-print Network

    Fernandez, Thomas

    Genetic Programming ­ Computers using "Natural Selection" to generate programs William B. Langdon themselves"; science fact or fiction? Genetic Programming uses novel optimisation techniques to "evolve] - is automatic program generation. Genetic Programming applies GAs to a "population" of programs - typically

  9. The Unit of Natural Selection: Groups, Families, Individuals, or Genes?

    ERIC Educational Resources Information Center

    Reiss, Michael J.

    1985-01-01

    Offers perspectives on natural selection and the phenomenon of altruism. Presents evidence for and against the theories that evolution acts essentially on genes, on individuals, on kin, or on larger groups. (ML)

  10. Natural Selection Is a Sorting Process: What Does that Mean?

    ERIC Educational Resources Information Center

    Price, Rebecca M.

    2013-01-01

    To learn why natural selection acts only on existing variation, students categorize processes as either creative or sorting. This activity helps students confront the misconception that adaptations evolve because species need them.

  11. Selective chemical labelling of natural T modifications in DNA

    E-print Network

    Hardisty, Robyn E.; Kawasaki, Fumiko; Sahakyan, Aleksandr B.; Balasubramanian, Shankar

    2015-05-06

    Selective Chemical Labeling of Natural T Modifications in DNA Robyn E. Hardisty,† Fumiko Kawasaki,† Aleksandr B. Sahakyan,† and Shankar Balasubramanian*,†,‡,§ †Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U...

  12. Student Conceptions of Natural Selection and Its Role in Evolution.

    ERIC Educational Resources Information Center

    Bishop, Beth A.; Anderson, Charles W.

    1990-01-01

    Discussed are the results of a test administered to nonmajor biology students on the topic of natural selection. The description of student conceptions, effects of instruction, and the effects of a belief in evolution are included. (KR)

  13. Selection of the Mars Science Laboratory landing site

    USGS Publications Warehouse

    Golombek, M.; Grant, J.; Kipp, D.; Vasavada, A.; Kirk, Randolph L.; Fergason, Robin L.; Bellutta, P.; Calef, F.; Larsen, K.; Katayama, Y.; Huertas, A.; Beyer, R.; Chen, A.; Parker, T.; Pollard, B.; Lee, S.; Hoover, R.; Sladek, H.; Grotzinger, J.; Welch, R.; Dobrea, E. Noe; Michalski, J.; Watkins, M.

    2012-01-01

    The selection of Gale crater as the Mars Science Laboratory landing site took over five years, involved broad participation of the science community via five open workshops, and narrowed an initial >50 sites (25 by 20 km) to four finalists (Eberswalde, Gale, Holden and Mawrth) based on science and safety. Engineering constraints important to the selection included: (1) latitude (±30°) for thermal management of the rover and instruments, (2) elevation (<-1 km) for sufficient atmosphere to slow the spacecraft, (3) relief of <100-130 m at baselines of 1-1000 m for control authority and sufficient fuel during powered descent, (4) slopes of <30° at baselines of 2-5 m for rover stability at touchdown, (5) moderate rock abundance to avoid impacting the belly pan during touchdown, and (6) a radar-reflective, load-bearing, and trafficable surface that is safe for landing and roving and not dominated by fine-grained dust. Science criteria important for the selection include the ability to assess past habitable environments, which include diversity, context, and biosignature (including organics) preservation. Sites were evaluated in detail using targeted data from instruments on all active orbiters, and especially Mars Reconnaissance Orbiter. All of the final four sites have layered sedimentary rocks with spectral evidence for phyllosilicates that clearly address the science objectives of the mission. Sophisticated entry, descent and landing simulations that include detailed information on all of the engineering constraints indicate all of the final four sites are safe for landing. Evaluation of the traversabilty of the landing sites and target “go to” areas outside of the ellipse using slope and material properties information indicates that all are trafficable and “go to” sites can be accessed within the lifetime of the mission. In the final selection, Gale crater was favored over Eberswalde based on its greater diversity and potential habitability.

  14. Selective feeding of four zooplankton species on natural lake phytoplankton

    Microsoft Academic Search

    Karin Knisely; Walter Geller

    1986-01-01

    Grazing experiments evaluated by microscopical counting were conducted with different size classes of Daphnia hyalina, D. galeata, Eudiaptomus gracilis, and Cyclops sp., all from Lake Constance, using natural lake phytoplankton as food. Species-specific grazing selectivity coefficients were calculated for the dominant phytoplankton species from weekly experiments. Specific selectivities were found to be largely invariant through the growing season. All zooplankters

  15. Frequency selective bolometer development at Argonne National Laboratory.

    SciTech Connect

    Datesman, A.; Pearson, J.; Wang, G.; Yefremenko, V.; Divan, R.; Downes, T.; Chang, C.; McMahon, J.; Meyer, S.; Carlstrom, J.; Logan, D.; Perera, T.; Wilson, G.; Novosad, V.; Univ. of Chicago; Univ. of Massachusetts

    2008-07-01

    We discuss the development, at Argonne National Laboratory, of a four-pixel camera suitable for photometry of distant dusty galaxies located by Spitzer and SCUBA, and for study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich (SZ) effect in clusters, and galactic dust. Utilizing Frequency Selective Bolometers (FSBs) with superconducting Transition-Edge Sensors (TESs), each of the camera's four pixels is sensitive to four colors, with frequency bands centered approximately at 150, 220, 270, and 360 GHz. The current generation of these devices utilizes proximity effect superconducting bilayers of Mo/Au or Ti/Au for TESs, along with frequency selective circuitry on membranes of silicon nitride 1 cm across and 1 micron thick. The operational properties of these devices are determined by this circuitry, along with thermal control structures etched into the membranes. These etched structures do not perforate the membrane, so that the device is both comparatively robust mechanically and carefully tailored in terms of its thermal transport properties. In this paper, we report on development of the superconducting bilayer TES technology and characterization of the FSB stacks. This includes the use of new materials, the design and testing of thermal control structures, the introduction of desirable thermal properties using buried layers of crystalline silicon underneath the membrane, detector stability control, and optical and thermal test results. The scientific motivation, FSB design, FSB fabrication, and measurement results are discussed.

  16. Natural selection and the genetics of adaptation in threespine stickleback

    PubMed Central

    Schluter, Dolph; Marchinko, Kerry B.; Barrett, R. D. H.; Rogers, Sean M.

    2010-01-01

    Growing knowledge of the molecular basis of adaptation in wild populations is expanding the study of natural selection. We summarize ongoing efforts to infer three aspects of natural selection—mechanism, form and history—from the genetics of adaptive evolution in threespine stickleback that colonized freshwater after the last ice age. We tested a mechanism of selection for reduced bony armour in freshwater by tracking genotype and allele frequency changes at an underlying major locus (Ectodysplasin) in transplanted stickleback populations. We inferred disruptive selection on genotypes at the same locus in a population polymorphic for bony armour. Finally, we compared the distribution of phenotypic effect sizes of genes underlying changes in body shape with that predicted by models of adaptive peak shifts following colonization of freshwater. Studies of the effects of selection on genes complement efforts to identify the molecular basis of adaptive differences, and improve our understanding of phenotypic evolution. PMID:20643737

  17. Natural water loss in selected drainage basins

    USGS Publications Warehouse

    Williams, Gordon R.

    1940-01-01

    Determinations of areal rainfall, run-off, and water loss, comprising largely evaporation from land surfaces and transpiration by vegetation, are essential in indicating the hydrologic characteristics of river basins. This report is primarily a statistical study that presents the results of computations of annual water loss, or annual rainfall minus annual run-off, for river basins in the humid or semiarid regions east of the Rocky Mountains. The basic period for which the computations are made is the water year or year ending September 30. As it is impractical to present in this report all the basic data used in arriving at the results, only sample computations are given. The various steps in the computations and the probable accuracy of the results are discussed. The drainage areas for which data are presented are those above river-measuring stations that have records for 3 years or more. For each area there are determinations of annual rainfall, annual run-off, and annual water loss for each year of record .as well as the means for the period of record. Results are given for about 200 drainage areas with an aggregate period of record of more than 2,000 years. As an illustration of the magnitude involved, the annual water loss from the eastern streams draining directly into the Atlantic Ocean varies more or less closely with latitude from about 20 inches as an average in northern New England to about 30 inches in Georgia. As the annual water loss from a basin is affected by the temperature, a supplemental study was made of the relation between water loss and temperature. For 28 drainage areas selected in various parts 8f eastern and central United States, average temperatures were computed for each year of the period shown in table 1. The results indicate a relation between average annual water loss and average annual temperature.

  18. Discrepancies Between Laboratory Shock Experiments on Minerals and Natural Events

    NASA Astrophysics Data System (ADS)

    de Carli, P. S.; Xie, Z.; Sharp, T. G.

    2009-12-01

    Numerous laboratory shock recovery experiments performed over the past 50 years have provided substantial data on the effects of shock waves on rocks and minerals. However, it has become increasingly clear that the pressure "calibrations" based on shock effects observed in these experiments are inconsistent with interpretations based on static high-pressure data. A fundamental question is whether shock pressures are somehow different from static high pressures. Fifty years ago, many journal reviewers doubted that phase transformations could take place on a sub-microsecond time scale. Shock wave workers responded by invoking "special" properties of shock compression. However, all available evidence is consistent with the hypothesis that phase transitions under shock pressure are no different from phase transitions under static high pressures. The discrepancies noted above result from the fact that the parameter space, especially shock pressure duration, accessible to shock recovery experiments is so small by comparison with natural events. Furthermore virtually all shock recovery experiments on rocks and minerals have used high impedance sample containers, with the result that the samples have been subjected to thermodynamic loading paths substantially from a natural event. Consider the case of a chondritic meteorite made up of minerals having a wide range of shock properties. In a natural shock event the transient (nano-second scale) shock pressure at the shock front can vary by as much as an order of magnitude from grain to grain or even within a single grain. There are corresponding local differences in shock temperature. Assuming a mineral grain size of about a mm, the pressure inhomogeneities will equilibrate in less than a microsecond, wheras the temperature inhomogenities will require seconds to equilibrate. Recent studies of high-pressure phases in meteorites have provided evidence for pressure durations in the range of seconds, long enough for high pressure phases to crystallize from a melt or transform via solid-solid mechanisms. In contrast, the sample shock loaded in a laboratory experiment in a high impedance container reaches peak pressure via a series of shock reflections. As a result, shock and post-shock temperatures correspond to a sample naturally shocked to a substantially lower ( 20-60 %, dependent on sample mineralogy and porosity) equilibrium pressure. The effect of differences in the shock properties of the individual minerals is also greatly reduced. Shock pressure durations in the range of seconds have been inferred from studies of naturally shocked meteorites, whereas the effective duration of a shock recovery experiment is about a microsecond. Shock effects that involve reconstructive phase transformations, and therefore nucleation and growth, are highly dependent on both temperature and duration. Finally, the laboratory experiments are conducted on a small scale; samples cool from their equilibrium post-shock temperature in seconds. In a large natural event, the cooling time can be thousands of years.

  19. Natural selection opposing artificial selection: a two-locus deterministic simulation.

    PubMed

    Minvielle, F

    1981-05-01

    A two-locus, two-allele metric trait was submitted to artificial truncation selection and to three types of opposing natural selection (two-locus extensions of directional selection, overdominance and underdominance) by numerical simulation in a large random-mating population. Limits to selection were generally reached by generation 100. Intermediate selection plateaus were found, with minor genes, for all three modes of opposing natural selection, but they were least frequent with underdominance. Multiple outcomes were common. In particular, fixation of the genotype favored by artificial selection was often associated with fixation of another genotype and/or with a central equilibrium; the end point actually reached depended on the genetic starting point of the simulation. In general, when the alleles favored by truncation selection were combined (positive linkage disequilibrium) in the base population, or when the trait was determined by major genes, artificial selection would prevail. Limitations inherent to this type of work are discussed, and possible avenues for further work on the antagonism between artificial and natural selection are proposed. PMID:17249086

  20. Natural Selection Opposing Artificial Selection: A Two-Locus Deterministic Simulation

    PubMed Central

    Minvielle, Francis

    1981-01-01

    A two-locus, two-allele metric trait was submitted to artificial truncation selection and to three types of opposing natural selection (two-locus extensions of directional selection, overdominance and underdominance) by numerical simulation in a large random-mating population. Limits to selection were generally reached by generation 100. Intermediate selection plateaus were found, with minor genes, for all three modes of opposing natural selection, but they were least frequent with underdominance. Multiple outcomes were common. In particular, fixation of the genotype favored by artificial selection was often associated with fixation of another genotype and/or with a central equilibrium; the end point actually reached depended on the genetic starting point of the simulation. In general, when the alleles favored by truncation selection were combined (positive linkage disequilibrium) in the base population, or when the trait was determined by major genes, artificial selection would prevail. Limitations inherent to this type of work are discussed, and possible avenues for further work on the antagonism between artificial and natural selection are proposed. PMID:17249086

  1. Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection

    NASA Astrophysics Data System (ADS)

    Thagard, Paul; Findlay, Scott

    2010-06-01

    Darwin’s theory of evolution by natural selection is central to modern biology, but is resisted by many people. This paper discusses the major psychological obstacles to accepting Darwin’s theory. Cognitive obstacles to adopting evolution by natural selection include conceptual difficulties, methodological issues, and coherence problems that derive from the intuitiveness of alternative theories. The main emotional obstacles to accepting evolution are its apparent conflict with valued beliefs about God, souls, and morality. We draw on the philosophy of science and on a psychological theory of cognitive and emotional belief revision to make suggestions about what can be done to improve acceptance of Darwinian ideas.

  2. Laboratory observation of naturally occurring dust-density waves

    NASA Astrophysics Data System (ADS)

    Flanagan, Tim; Goree, John

    2010-11-01

    Dust-density waves are electrostatic compressional waves that propagate in dusty plasma. Compared to the more familiar ion-acoustic waves, in dust-density waves, inertia is provided by dust particles (instead of ions) while pressure is provided by the ions as well as electrons (not just electrons). In a laboratory experiment, we observed dust density waves in a 3D void-free dusty plasma. The waves occur naturally due to an ion-flow instability. Dust particles (4.8 microns) are levitated within the volume of a glass box that rests atop an electrode in a radio-frequency glow discharge plasma. Horizontal confinement of dust particles is provided by the plasma's natural electric field that is enhanced by the walls of the glass box, while vertical confinement is due to the electrode's sheath. We observed dust-density waves with planar wave fronts propagating in alignment with flowing ions. By directly imaging the dust particles with a 500 frame-per-second camera, we monitor the dust density modulations in both space and time. A typical wave propagates at 40 mm/s with a frequency of 24 Hz. In this work, we characterize these waves and their growth as they propagate.

  3. Problems in learning the concept of natural selection

    Microsoft Academic Search

    Margaret Brumby

    1979-01-01

    In a written test investigating the level of understanding of the concept of natural selection, only 18 per cent of a group of first-year university students with an Advanced-level biology background were consistently able to apply this concept to common environmental problems. In their explanations, over half the students mistakenly formulated a ‘theory of adaptation by induced mutation’ instead of

  4. 2006 Nature Publishing Group Sexual reproduction selects for robustness and

    E-print Network

    Azevedo, Ricardo

    © 2006 Nature Publishing Group Sexual reproduction selects for robustness and negative epistasis recombination brings them together into single genomes1 . This explanation requires negative epistasis, a type to identify the mechanistic and evolutionary bases of negative epistasis. Here we show that negative epistasis

  5. Natural Selection: It's Not Darwin's (Or Wallace'S) Theory

    Microsoft Academic Search

    Milton Wainwright

    2008-01-01

    For nearly 150 years, since soon after the appearance of the On the Origin of Species, we have known that neither Charles Darwin nor Alfred Russel Wallace originated the theory of natural selection. This certainty is based on the fact that both of these great naturalists admitted that they were beaten to the theory by at least two other naturalists.

  6. How was Wallace led to the Discovery of Natural Selection?

    Microsoft Academic Search

    A. B. Meyer

    1895-01-01

    THE reviewer of Osborn's ``From the Greeks to Darwin'' (antea p. 362) says that Marshall quotes the fact of Wallace's being led ``to the discovery of natural selection as he lay ill of intermittent fever at Ternate,'' and refers one to the abridged form of the ``Life and Letters of Charles Darwin'' for this statement. Having only the original edition

  7. Using Different Examples of Natural Selection When Teaching Biology.

    ERIC Educational Resources Information Center

    Perry, Robert T.

    1993-01-01

    Describes the following examples of natural selection for use in science instruction: sickle-cell anemia and human beings, clogged crabs, the rounding of the human head, shell color in land snails, pollinator behavior and flower color, copper tolerance in a grass, lizards and quick change, and Darwin's finches. (PR)

  8. Natural selection: Evolution of lifespan in C. elegans

    Microsoft Academic Search

    David W. Walker; Gawain McColl; Nicole L. Jenkins; Jennifer Harris; Gordon J. Lithgow

    2000-01-01

    It was proposed almost 50 years ago that ageing is non-adaptive and is the consequence of a decline in the force of natural selection with age. This led to the theory that ageing results from detrimental effects late in life of genes that act beneficially in early life, so any genetic alteration that increases lifespan might be expected to reduce

  9. Neo-Darwinism Modern Synthesis (Mendelian Genetics + Natural Selection)

    E-print Network

    Dever, Jennifer A.

    , Fisher, Wright, Haldane · natural selection is the driving force of evolution, mutation simply provides become fixed due to genetic drift #12;3 evolution by genetic drift: The field of molecular evolution has substitution rates for four proteins; constant rate over millions of years Some genes have very slow clocks

  10. Partial Support for Winter Wheat Laboratory Marker-Assisted-Selection Program Phil Bruckner, Winter Wheat Breeder

    E-print Network

    Maxwell, Bruce D.

    Partial Support for Winter Wheat Laboratory Marker-Assisted-Selection Program Phil Bruckner, Winter Wheat Breeder Project Description Marker-assisted selection (MAS) is an established plant breeding with limited technological capabilities such as ours. The MSU winter wheat program conducted a laboratory MAS

  11. Viability selection prior to trait expression is an essential component of natural selection

    PubMed Central

    Mojica, Julius P.; Kelly, John K.

    2010-01-01

    Natural selection operates throughout the life cycle of an organism. Correlative studies typically fail to consider the effects of viability selection prior to trait expression. A 3-year field experiment on the wildflower Mimulus guttatus demonstrates that this unmeasured component of selection can be very strong. As in previous studies, we find that fecundity is positively related to flower size. However, survival to flowering is much lower in large-flowered genotypes than in small-flowered genotypes. Aggregating viability and fecundity, lifetime fitness through female function generally favoured smaller flowered genotypes. This result differs from the great majority of field studies, which suggest strong positive selection on flower size. It has important cautionary implications for studies of natural and sexual selection on adult characters generally, in both plants and animals. PMID:20462906

  12. Biological Fitness and the Fundamental Theorem of Natural Selection.

    PubMed

    Grafen, Alan

    2015-07-01

    Fisher's fundamental theorem of natural selection is proved satisfactorily for the first time, resolving confusions in the literature about the nature of reproductive value and fitness. Reproductive value is defined following Fisher, without reference to genetic variation, and fitness is the proportional rate of increase in an individual's contribution to the demographic population size. The mean value of fitness is the same in each age class, and it also equals the population's Malthusian parameter. The statement and derivation are regarded as settled here, and so the general biological significance of the fundamental theorem can be debated. The main purpose of the theorem is to find a quantitative measure of the effect of natural selection in a Mendelian system, thus founding Darwinism on Mendelism and identifying the design criterion for biological adaptation, embodied in Fisher's ingenious definition of fitness. The relevance of the newly understood theorem to five current research areas is discussed. PMID:26098334

  13. Survey and analysis of materials research and development at selected federal laboratories

    SciTech Connect

    Reed, J.E.; Fink, C.R.

    1984-04-01

    This document presents the results of an effort to transfer existing, but relatively unknown, materials R and D from selected federal laboratories to industry. More specifically, recent materials-related work at seven federal laboratories potentially applicable to improving process energy efficiency and overall productiviy in six energy-intensive manufacturing industries was evaluated, catalogued, and distributed to industry representatives to gauge their reaction. Laboratories surveyed include: Air Force Wright Aeronautical Laboratories Material Laboratory (AFWAL). Pacific Northwest Laboratory (PNL), National Aeronautics and Space Administration Marshall Flight Center (NASA Marshall), Oak Ridge National Laboratory (ORNL), Brookhaven National Laboratory (BNL), Idaho National Engineering Laboratory (INEL), and Jet Propulsion Laboratory (JPL). Industries included in the effort are: aluminum, cement, paper and allied products, petroleum, steel and textiles.

  14. The Slumgullion Natural Laboratory for Observing Slip Phenomena

    NASA Astrophysics Data System (ADS)

    Gomberg, J. S.; Schulz, W. H.; Bodin, P.; Kean, J. W.; Wang, G.; Coe, J. A.; MacQueen, P.; Foster, K.; Creager, K.

    2009-12-01

    Many natural systems release stresses by failure and sliding across surfaces; examples include landslides, glaciers, crustal- and plate-scale faults. Observational advances continue to reveal diversity in the seismic signals associated with fault slip and how such stress relaxation can occur, even on a single fault system. A particularly rich example are the episodes of slow fault slip near major subduction and transform plate boundaries that manifest as geodetically observed aseismic deformation abetted by a family of seismic signals depleted in high-frequencies relative to those from earthquakes (named ‘episodic tremor and slip’ or ETS). While the driving forces and scales differ, there are striking parallels between some observations and models of ETS and of landslide behaviors; e.g. in both, postulated key controls include rate-dependent friction and strength modulated by pore-pressure changes, dilatancy during rapid shear, and subsequent consolidation. To explore common features and the underlying processes we are studying the Slumgullion landslide, an ideal natural laboratory for observing fault slip and associated seismic and aseismic phenomena. Unlike crustal- or plate-scale studies significant deformation can be measured within a single field season, because the Slumgullion moves at average rates of cm/day. Moreover, pore pressures, displacements, material properties, and environmental variables may be measured directly and continuously at several locations on the landslide (albeit not at the basal sliding surface). We have just completed a field experiment on the Slumgullion to test several hypotheses, particularly that slip along the basal surface and side-bounding faults occurs with comparable richness of aseismic and seismic modes as crustal- and plate-scale boundaries. To do so from August 18-26, 2009 we continuously monitored the displacement-field using a robotic electronic displacement meter and the seismic radiation with 88 vertical-component seismographs [see Bodin et al., companion abstract]. Although we have only begun examining the data thus far, the seismic data contain an abundance of network-wide coherent signals with an amazing variety of characteristics. Significant unsteady movement in the displacement field is evident in the geodetic data, as well as fluctuations in the pore-pressures and relevant environmental parameters. Schulz et al. (companion abstract) presents initial landslide observations. We will form and present implications for understanding the likely mechanisms of failure and slip within natural systems.

  15. Genome-wide polymorphisms show unexpected targets of natural selection

    PubMed Central

    Pespeni, Melissa H.; Garfield, David A.; Manier, Mollie K.; Palumbi, Stephen R.

    2012-01-01

    Natural selection can act on all the expressed genes of an individual, leaving signatures of genetic differentiation or diversity at many loci across the genome. New power to assay these genome-wide effects of selection comes from associating multi-locus patterns of polymorphism with gene expression and function. Here, we performed one of the first genome-wide surveys in a marine species, comparing purple sea urchins, Strongylocentrotus purpuratus, from two distant locations along the species' wide latitudinal range. We examined 9112 polymorphic loci from upstream non-coding and coding regions of genes for signatures of selection with respect to gene function and tissue- and ontogenetic gene expression. We found that genetic differentiation (FST) varied significantly across functional gene classes. The strongest enrichment occurred in the upstream regions of E3 ligase genes, enzymes known to regulate protein abundance during development and environmental stress. We found enrichment for high heterozygosity in genes directly involved in immune response, particularly NALP genes, which mediate pro-inflammatory signals during bacterial infection. We also found higher heterozygosity in immune genes in the southern population, where disease incidence and pathogen diversity are greater. Similar to the major histocompatibility complex in mammals, balancing selection may enhance genetic diversity in the innate immune system genes of this invertebrate. Overall, our results show that how genome-wide polymorphism data coupled with growing databases on gene function and expression can combine to detect otherwise hidden signals of selection in natural populations. PMID:21993504

  16. Evolution of particle angularity in natural and laboratory debris flows

    NASA Astrophysics Data System (ADS)

    Mclaughlin, M. K.; Arabnia, O.; Sklar, L. S.

    2014-12-01

    The sizes of particles entrained in debris flows influence flow dynamics, affecting erosive power and runout distance. Particle size distributions evolve due to wear by abrasion and fracturing, and by gains or losses of sediment mass during transport. To tease apart these factors, we need a better understanding of the controls on rates and patterns of particle wear in debris flows. Here we focus on changes in particle angularity with travel distance, combining laboratory experiments with field study of a rocky debris flow at Inyo Creek, Sierra Nevada California. Angularity can indicate proximity to sediment source, assuming abrasion leads to progressive smoothing of particle surfaces. However, particle fracture can create fresh angular surfaces, confounding estimates of travel distance from angularity. This study is a component of an ongoing set of experiments using a 4 m diameter rotating drum to create near-prototype-scale debris flows. We load the drum with 1.7 Mg of highly angular granodiorite clasts, with median b-axis diameter of 100 mm. The 0.75 m deep, shearing mass flows at 1 m/s. After each 250 m travel distance, we measure mass and length of principal axes for every particle >19 mm, and sieve all smaller particles, to track evolution of the size distribution. We document the angularity of subsamples of selected particle sizes, using several techniques, including analysis of 2D photographs, 3D laser scans, and hand-placed equilibrium points. We use the same techniques in analyzing particles collected in the field study of the downstream evolution of rock clasts along a 1 km length of Inyo Creek. In this catchment, underlain by granodiorite, sediment transport is dominated by debris flows, which leave deposits on the bed and channel margins at slopes >20%. Preliminary laboratory results show rapid smoothing of large particle surfaces combined with creation of smaller angular particles by fracture. In contrast, downstream evolution of angularity in the field is more variable, possibly due to mixing of particles from multiple source areas. Results suggest that downstream changes in angularity contain information about proximity to sources and intensity of particle interactions in transport, and may be useful for constraining predictive relations for particle size evolution in debris flows.

  17. Immunology (1955–1975): The Natural Selection Theory, the Two Signal Hypothesis and Positive Repertoire Selection

    Microsoft Academic Search

    Donald R. Forsdyke

    Observations suggesting the existence of natural antibody prior to exposure of an organism to the corresponding antigen, led\\u000a to the natural selection theory of antibody formation of Jerne in 1955, and to the two signal hypothesis of Forsdyke in 1968.\\u000a Aspects of these were not only first discoveries but also foundational discoveries in that they influenced contemporaries\\u000a in a manner

  18. Natural selection as a paradigm of opportunism in biology

    Microsoft Academic Search

    Joseph Esfandiar Hannon Bozorgmehr; Hannon Bozorgmehr

    2012-01-01

    The success of extant species is largely due to their ability to adapt in the face of constantly changing environmental conditions.\\u000a Natural selection is the biological mechanism that takes advantage of opportunities to promote spontaneous variations and\\u000a facilitate evolutionary development. The character of this biological opportunism is considered here, placing it firmly within\\u000a the context of various social and economic

  19. Programed Death is Favored by Natural Selection in Spatial Systems

    NASA Astrophysics Data System (ADS)

    Werfel, Justin; Ingber, Donald E.; Bar-Yam, Yaneer

    2015-06-01

    Standard evolutionary theories of aging and mortality, implicitly based on mean-field assumptions, hold that programed mortality is untenable, as it opposes direct individual benefit. We show that in spatial models with local reproduction, programed deaths instead robustly result in long-term benefit to a lineage, by reducing local environmental resource depletion via spatiotemporal patterns causing feedback over many generations. Results are robust to model variations, implying that direct selection for shorter life span may be quite widespread in nature.

  20. Birth-order differences can drive natural selection on aging.

    PubMed

    Gillespie, Duncan O S; Trotter, Meredith V; Krishna-Kumar, Siddharth; Tuljapurkar, Shripad D

    2014-03-01

    Senescence-the deterioration of survival and reproductive capacity with increasing age-is generally held to be an evolutionary consequence of the declining strength of natural selection with increasing age. The diversity in rates of aging observed in nature suggests that the rate at which age-specific selection weakens is determined by species-specific ecological factors. We propose that, in iteroparous species, relationships between parental age, offspring birth order, and environment may affect selection on senescence. Later-born siblings have, on average, older parents than do first borns. Offspring born to older parents may experience different environments in terms of family support or inherited resources, factors often mediated by competition from siblings. Thus, age-specific selection on parents may change if the environment produces birth-order related gradients in reproductive success. We use an age-and-stage structured population model to investigate the impact of sibling environmental inequality on the expected evolution of senescence. We show that accelerated senescence evolves when later-born siblings are likely to experience an environment detrimental to lifetime reproduction. In general, sibling inequality is likely to be of particular importance for the evolution of senescence in species such as humans, where family interactions and resource inheritance have important roles in determining lifetime reproduction. PMID:24274174

  1. Birth-order differences can drive natural selection on aging

    PubMed Central

    Gillespie, Duncan O. S.; Trotter, Meredith V.; Krishna-Kumar, Siddharth; Tuljapurkar, Shripad D.

    2014-01-01

    Senescence—the deterioration of survival and reproductive capacity with increasing age—is generally held to be an evolutionary consequence of the declining strength of natural selection with increasing age. The diversity in rates of aging observed in nature suggests that the rate at which age-specific selection weakens is determined by species-specific ecological factors. We propose that, in iteroparous species, relationships between parental age, offspring birth order and environment may affect selection on senescence. Later-born siblings have, on average, older parents than do first-borns. Offspring born to older parents may experience different environments in terms of family support or inherited resources, factors often mediated by competition from siblings. Thus, age-specific selection on parents may change if the environment produces birth-order related gradients in reproductive success. We use an age-and-stage structured population model to investigate the impact of sibling environmental inequality on the expected evolution of senescence. We show that accelerated senescence evolves when later-born siblings are likely to experience an environment detrimental to lifetime reproduction. In general, sibling inequality is likely to be of particular importance for the evolution of senescence in species such as humans, where family interactions and resource inheritance have important roles in determining lifetime reproduction. PMID:24274174

  2. Using natural laboratories and modeling to decipher lithospheric rheology

    NASA Astrophysics Data System (ADS)

    Sobolev, Stephan

    2013-04-01

    Rheology is obviously important for geodynamic modeling but at the same time rheological parameters appear to be least constrained. Laboratory experiments give rather large ranges of rheological parameters and their scaling to nature is not entirely clear. Therefore finding rheological proxies in nature is very important. One way to do that is finding appropriate values of rheological parameter by fitting models to the lithospheric structure in the highly deformed regions where lithospheric structure and geologic evolution is well constrained. Here I will present two examples of such studies at plate boundaries. One case is the Dead Sea Transform (DST) that comprises a boundary between African and Arabian plates. During the last 15- 20 Myr more than 100 km of left lateral transform displacement has been accumulated on the DST and about 10 km thick Dead Sea Basin (DSB) was formed in the central part of the DST. Lithospheric structure and geological evolution of DST and DSB is rather well constrained by a number of interdisciplinary projects including DESERT and DESIRE projects leaded by the GFZ Potsdam. Detailed observations reveal apparently contradictory picture. From one hand widespread igneous activity, especially in the last 5 Myr, thin (60-80 km) lithosphere constrained from seismic data and absence of seismicity below the Moho, seem to be quite natural for this tectonically active plate boundary. However, surface heat flow of less than 50-60mW/m2 and deep seismicity in the lower crust ( deeper than 20 km) reported for this region are apparently inconsistent with the tectonic settings specific for an active continental plate boundary and with the crustal structure of the DSB. To address these inconsistencies which comprise what I call the "DST heat-flow paradox", a 3D numerical thermo-mechanical model was developed operating with non-linear elasto-visco-plastic rheology of the lithosphere. Results of the numerical experiments show that the entire set of observations for the DSB can be explained within the classical pull-apart model assuming that (1) the lithosphere has been thermally eroded at about 20 Ma, just before the active faulting at the DST, and (2) the uppermost mantle in the region have relatively weak rheology consistent with the experimental data for wet olivine or pyroxenite. Another example is modeling of the collision of India and Eurasia in Tibet. Our recent thermo-mechanical model (see abstract by Tympel et al) reproduce well many important features of this orogeny, including observed convergence and distance of underthrusting of Indian lithosphere beneath Tibet, if long-term friction at India-Eurasia interface is about 0.04- 0.05, which is typical for oceanic subduction zones, but is unexpected low for continental setting.

  3. Safety in the Chemical Laboratory: The Selection of Eyewash Stations for Laboratory Use.

    ERIC Educational Resources Information Center

    Walters, Douglas B.; And Others

    1988-01-01

    Evaluates and compares common eyewash stations currently being used in laboratories. Discusses types available, installation, water supply needs, and maintenance. Lists current OSHA eyewash station standards. (ML)

  4. Natural selection in the field and the classroom

    NASA Astrophysics Data System (ADS)

    Andrews, Tessa Marie

    This dissertation examined natural selection in westslope cutthroat trout (Oncorhynchus clarkii lewisi) and undergraduate learning in the subject area natural selection. Translocation---moving individuals to a new habitat to establish, re-establish or supplement a population---is a crucial management strategy for cutthroat trout. One of the major questions managers face in a translocation is which population(s) should contribute individuals? Unfortunately, we often know little about the differences among potential contributing population. The goal of the first half of this dissertation was to look for differences in performance among individuals from five populations of westslope cutthroat trout. I assessed survival, growth, and condition (Chapter 2) and dispersal (Chapter 3) following the translocation of embryos from these five populations to six introduction sites in Cherry Creek. No differences existed among these populations in relative survival, growth, or condition at age 1 or 2. In contrast, statistically significant differences existed in dispersal distance among these populations. These differences were consistent across some, but not all, introduction locations. As our knowledge of evolutionary biology has continued to grow, so too has our knowledge of how students learn evolution. Students taught using active learning strategies can learn substantially more about complex scientific concepts than students taught using primarily lectures. The goal of the second half of this dissertation was to further examine how students learn natural selection and how instructors facilitate that learning. I conducted a national survey of the relationship between an instructor's use of active learning strategies and how much students learned about natural selection (Chapter 4). I used a random sample of instructors from the largest and most prestigious universities in the country so that my results could be inferred to this large population of instructors. The degree to which instructors used active learning was NOT associated with student learning in this population of typical biology instructors. However, I found that a discussion of contemporary human evolution that used active learning strategies could effectively facilitate student learning of natural selection (Chapter 5).

  5. Laboratory treatability testing of selected oil shale process wastewaters

    SciTech Connect

    Lewis, R.C.; Rawlings, G.D.

    1982-01-01

    Gas condensate wastewaters are generated by cooling of retort offgases produced by in situ facilities. These waters are characterized by high concentrations of ammonia and alkalinity, and contain moderate concentrations of dissolved organic materials. Metallic elements are present in low concentrations. Location of retorting facilities in arid areas of the western United States is expected to increase utilization of wastewater recycle/reuse options, with treatment requirements depending upon end use quality requirements. Laboratory-scale experiments were conducted with an actual modified in-situ gas condensate to assess performance of steam stripping, the activated sludge process and activated carbon adsorption for upgrading the quality of this wastewater. Steam stripping experiments were carried out with a laboratory-scale, packed tower which contacted preheated, raw gas condensate with low pressure steam in a countercurrent manner. A bench-scale, continuous-flow activated sludge system was operated to evaluate the capability of this treatment technology for removal of dissolved organics. Continuous-flow tests were conducted with steam-stripped gas condensate and effluent from the activated sludge system to assess the ability of carbon adsorption for removal of dissolved organics. A field test configuration for treatment of gas condensate wastewaters has been developed, and pilot-scale units of each treatment technology will be procured during 1981. This mobile pilot equipment will be tested at retorting facilities to demonstrate control technology performance under actual retort operating conditions.

  6. Natural selection on fecundity variance in subdivided populations: kin selection meets bet hedging.

    PubMed

    Lehmann, Laurent; Balloux, François

    2007-05-01

    In a series of seminal articles in 1974, 1975, and 1977, J. H. Gillespie challenged the notion that the "fittest" individuals are those that produce on average the highest number of offspring. He showed that in small populations, the variance in fecundity can determine fitness as much as mean fecundity. One likely reason why Gillespie's concept of within-generation bet hedging has been largely ignored is the general consensus that natural populations are of large size. As a consequence, essentially no work has investigated the role of the fecundity variance on the evolutionary stable state of life-history strategies. While typically large, natural populations also tend to be subdivided in local demes connected by migration. Here, we integrate Gillespie's measure of selection for within-generation bet hedging into the inclusive fitness and game theoretic measure of selection for structured populations. The resulting framework demonstrates that selection against high variance in offspring number is a potent force in large, but structured populations. More generally, the results highlight that variance in offspring number will directly affect various life-history strategies, especially those involving kin interaction. The selective pressures on three key traits are directly investigated here, namely within-generation bet hedging, helping behaviors, and the evolutionary stable dispersal rate. The evolutionary dynamics of all three traits are markedly affected by variance in offspring number, although to a different extent and under different demographic conditions. PMID:17339208

  7. Laboratory Experiences in an Introduction to Natural Science Course.

    ERIC Educational Resources Information Center

    Barnard, Sister Marquita

    1984-01-01

    Describes a two-semester course designed to meet the needs of future elementary teachers, home economists, and occupational therapists. Laboratory work includes homemade calorimeters, inclined planes, and computing. Content areas of the course include measurement, physics, chemistry, astronomy, biology, geology, and meteorology. (JN)

  8. [Liver cell function test based on selective laboratory studies].

    PubMed

    Sliwi?ska-Przyjemska, H; Pilawska, H

    1981-01-01

    Laboratory tests have been carried out in 517 workers of a Chemical Fibres Plant. This was aimed at the detection of the changes resulting from cumulative exposure to caprolactam, dowtherm and physical factors. There have been performed hematological investigations, uninalyses and biochemical tests: total protein level, activity of enzymes: ASPAT, ALAT, PA, ChE, thymol test. The results have been analysed as the mean values for particular divisions and workstands; then they have been compared with standards. In order to evaluate the degree of occupational exposure of particular groups of workers, an index of the liver cell damage has been calculated. It was expressed in % of the results exceeding the standards in relation to all results in a given group of workers. The highest values of the index were those in the group employed at the polymerization division. The authoresses promote the advisability of special care for this group of workers. PMID:7289867

  9. Genetic variation as a test of natural selection.

    PubMed Central

    Nevo, E; Dessauer, H C; Chuang, K C

    1975-01-01

    Allozymic variation encoded by 26 loci was analyzed electrophoretically in 507 specimens representing 12 populations of green toads, Bufo viridis, in Israel and the Vis Adriatic Island. Genetic variation in Bufo viridis is higher than in any vertebrate yet studied. Mean heterozygosity per locus per individual (H) is 0.133 (range, 0.105 to 0.159). H is higher in central populations as compared with isolates, and varies among four major protein classes, being highest in transferases and hydrolases and lowest in oxidoreductases and nonenzymatic proteins. Differential gene frequencies among polymorphisms was tested as an indicator of natural selection. Significant heterogeneity between loci in their apparent inbreeding coefficients Fe=S-2p/P(1-p) was found for all alleles and for each of the four major classes of proteins tested, which may be taken as evidence of selection. Both uniform and diversifying selection are suggested by the low and high Fe values, respectively. The general pattern of high heterozygosity in Bufo viridis is best explained as an adaptive strategy in heterogeneous environments. PMID:1056019

  10. Use of Laboratory-Supplied Natural Gas in Breakthrough Phenomena.

    ERIC Educational Resources Information Center

    Eiceman, G. A.; And Others

    1985-01-01

    Natural gas from regular commercial lines contains enough carbon-8 and above hydrocarbon contaminants to serve as a satisfactory sample for breakthrough experiments. Procedures used, typical results obtained, and theoretical background information are provided. (JN)

  11. Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 885 CLASSIC PROTOCOL

    E-print Network

    Cai, Long

    © Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.11 | NOVEMBER 2005 | 885 CLASSIC PROTOCOL PUBLISHED IN ASSOCIATION WITH COLD SPRING HARBOR LABORATORY PRESS Long and accurate polymerase chain reaction In 1992, investigators working on mixing and fusing various domains of different DNA

  12. Testing sediment biological effects with the freshwater amphipod Hyalella azteca: the gap between laboratory and nature

    Microsoft Academic Search

    Feiyue Wang; Richard R. Goulet; Peter M. Chapman

    2004-01-01

    The freshwater amphipod, Hyalella azteca, is widely used in laboratory sediment toxicity and bioaccumulation tests. However, its responses in the laboratory are probably very different from those in the field. A review of the literature indicates that in its natural habitat this species complex is primarily epibenthic, derives little nutrition from the sediments, and responds primarily to contaminants in the

  13. Exploring the nature of collisionless shocks under laboratory conditions

    PubMed Central

    Stockem, A.; Fiuza, F.; Bret, A.; Fonseca, R. A.; Silva, L. O.

    2014-01-01

    Collisionless shocks are pervasive in astrophysics and they are critical to understand cosmic ray acceleration. Laboratory experiments with intense lasers are now opening the way to explore and characterise the underlying microphysics, which determine the acceleration process of collisionless shocks. We determine the shock character – electrostatic or electromagnetic – based on the stability of electrostatic shocks to transverse electromagnetic fluctuations as a function of the electron temperature and flow velocity of the plasma components, and we compare the analytical model with particle-in-cell simulations. By making the connection with the laser parameters driving the plasma flows, we demonstrate that shocks with different and distinct underlying microphysics can be explored in the laboratory with state-of-the-art laser systems. PMID:24488212

  14. Exploring the nature of collisionless shocks under laboratory conditions.

    PubMed

    Stockem, A; Fiuza, F; Bret, A; Fonseca, R A; Silva, L O

    2014-01-01

    Collisionless shocks are pervasive in astrophysics and they are critical to understand cosmic ray acceleration. Laboratory experiments with intense lasers are now opening the way to explore and characterise the underlying microphysics, which determine the acceleration process of collisionless shocks. We determine the shock character - electrostatic or electromagnetic - based on the stability of electrostatic shocks to transverse electromagnetic fluctuations as a function of the electron temperature and flow velocity of the plasma components, and we compare the analytical model with particle-in-cell simulations. By making the connection with the laser parameters driving the plasma flows, we demonstrate that shocks with different and distinct underlying microphysics can be explored in the laboratory with state-of-the-art laser systems. PMID:24488212

  15. Laboratory study of selected personal inhalable aerosol samplers.

    PubMed

    Görner, Peter; Simon, Xavier; Wrobel, Richard; Kauffer, Edmond; Witschger, Olivier

    2010-03-01

    Assessment of inhalable dust exposure requires reliable sampling methods in order to measure airborne inhalable particles' concentrations. Many inhalable aerosol samplers can be used but their performances widely vary and remain unknown in some cases. The sampling performance of inhalable samplers is strongly dependent on particle size and ambient air velocity. Five inhalable aerosol samplers have been studied in two laboratory wind tunnels using polydisperse glass-beads' test aerosol. Samplers tested were IOM sampler (UK), two versions of CIP 10-I sampler, v1 and v2 (F), 37-mm closed face cassette sampler (USA), 37-mm cassette fitted up with an ACCU-CAP insert (USA), and Button sampler (USA). Particle size-dependent sampling efficiencies were measured in a horizontal wind tunnel under a 1 m s(-1) wind velocity and in a vertical tunnel under calm air, using a specific method with Coulter(R) counter particle size number distribution determinations. Compared with CEN-ISO-ACGIH sampling criteria for inhalable dust, the experimental results show fairly high sampling efficiency for the IOM and CIP 10-I v2 samplers and slightly lower efficiencies for the Button and CIP 10-I v1 samplers. The closed face cassette (4-mm orifice) produced the poorest performances of all the tested samplers. This can be improved by using the ACCU-CAP internal capsule, which prevents inner wall losses inside the cassette. Significant differences between moving air and calm air sampling efficiency were observed for all the studied samplers. PMID:20147627

  16. Direct laboratory tensile testing of select yielding rock bolt systems

    SciTech Connect

    VandeKraats, J.D.; Watson, S.O.

    1996-08-01

    Yielding rock bolt support systems have been developed to accommodate ground movement in shifting ground such as in coal operations; in creeping ground such as salt, trona, and potash; and in swelling ground associated with some clays. These systems, designed to remain intact despite ground movement, should enhance mine safety and help contain costs in areas where rebolting of rigid non-yielding systems is typically required. Four such systems were tested in straight tensile pulls in the laboratory. They include the Slip Nut System from Dywidag Systems International USA, Inc., Ischebeck`s bolt mounted Titan Load Indicator, Rocky Mountain Bolt Company`s Yielding Cable Bolt, and a rock bolt installed variation of the yielding steel post developed by RE/SPEC Inc. The first two systems are currently marketed products and the latter two are prototype systems. Each system responds to load and displacement by yielding in an unique manner. All are designed to yield at predetermined loads. A description of each system and its yield function is provided. Each system was tested over its prescribed yield range in a test machine. At least five tests were performed on each system. Each system yielded and continued to provide support according to its design. Each shows promise for ground control use in shifting or creeping rock. This work helps to illustrate the comparative differences in performance between these specialized systems and the applications where they may be most useful.

  17. Direct laboratory tensile testing of select yielding rock bolt systems

    SciTech Connect

    VandeKraats, J.D.; Watson, S.O. [Westinghouse Electric Corp., Carlsbad, NM (United States)

    1996-12-01

    Yielding rock bolt support systems have been developed to accommodate ground movement in shifting ground such as in coal operations; in creeping ground such as salt, trona, and potash; and in swelling ground associated with some clays. These systems, designed to remain intact despite ground movement, should enhance mine safety and help contain costs in areas where revolting of rigid non-yielding systems is typically required. Four such systems were tested in straight tensile pulls in the laboratory. They include the Slip Nut System from Dywidag Systems International USA, Inc., Ischebeck`s bolt mounted Titan Load Indicator, Rocky Mountain Bolt Company`s Yielding Cable Bolt, and a rock bolt installed variation of the yielding steel post developed by RE/SPEC Inc. The first two systems are currently marketed products and the latter two are prototype systems. Each system responds to load and displacement by yielding in a unique manner. All are designed to yield at predetermined loads. A description of each system and its yield function is provided. Each system was tested over its prescribed yield range in a test machine. At least five tests were performed on each system. Each system yielded and continued to provide support according to its design. Each shows promise for ground control use in shifting or creeping rock. This work helps to illustrate the comparative differences in performance between these specialized systems and the applications where they may be most useful.

  18. Field Botany Laboratory Renewable Natural Resources 230L

    E-print Network

    Smith, Steven E.

    : (Knowledge and Concepts) 1. Be able to apply the hierarchical nature of taxonomic systems and the principles in the vegetation of Arizona. 6. Be able to collect, describe and preserve plant material for identification. 7 an indifferent man that one sometimes gladly exchanges the society of one for that of the other." ~William

  19. Effect of Insecticide Resistance on Development, Longevity and Reproduction of Field or Laboratory Selected Aedes aegypti Populations

    PubMed Central

    Bellinato, Diogo Fernandes; Peixoto, Alexandre Afranio; Valle, Denise; Lima, José Bento Pereira

    2012-01-01

    Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost. PMID:22431967

  20. Effect of insecticide resistance on development, longevity and reproduction of field or laboratory selected Aedes aegypti populations.

    PubMed

    Martins, Ademir Jesus; Ribeiro, Camila Dutra e Mello; Bellinato, Diogo Fernandes; Peixoto, Alexandre Afranio; Valle, Denise; Lima, José Bento Pereira

    2012-01-01

    Aedes aegypti dispersion is the major reason for the increase in dengue transmission in South America. In Brazil, control of this mosquito strongly relies on the use of pyrethroids and organophosphates against adults and larvae, respectively. In consequence, many Ae. aegypti field populations are resistant to these compounds. Resistance has a significant adaptive value in the presence of insecticide treatment. However some selected mechanisms can influence important biological processes, leading to a high fitness cost in the absence of insecticide pressure. We investigated the dynamics of insecticide resistance and its potential fitness cost in five field populations and in a lineage selected for deltamethrin resistance in the laboratory, for nine generations. For all populations the life-trait parameters investigated were larval development, sex ratio, adult longevity, relative amount of ingested blood, rate of ovipositing females, size of egglaying and eggs viability. In the five natural populations, the effects on the life-trait parameters were discrete but directly proportional to resistance level. In addition, several viability parameters were strongly affected in the laboratory selected population compared to its unselected control. Our results suggest that mechanisms selected for organophosphate and pyrethroid resistance caused the accumulation of alleles with negative effects on different life-traits and corroborate the hypothesis that insecticide resistance is associated with a high fitness cost. PMID:22431967

  1. Mosquito management in the face of natural selection.

    PubMed

    Agusto, Folashade B; Bewick, Sharon; Parshad, Rana D

    2012-09-01

    The sterile insect technique (SIT) is an appealing method for managing mosquito populations while avoiding the environmental and social costs associated with more traditional control strategies like insecticide application. Success of SIT, however, hinges on sterile males being able to compete for females. As a result, heavy and/or continued use of SIT could potentially diminish its efficacy if prolonged treatments result in selection for female preference against sterile males. In this paper we extend a general differential equation model of mosquito dynamics to consider the role of female choosiness in determining the long-term usefulness of SIT as a management option. We then apply optimal control theory to our model and show how natural selection for female choosiness fundamentally alters management strategies. Our study calls into question the benefits associated with developing SIT as a management strategy, and suggests that effort should be spent studying female mate choice in order to determine its relative importance and how likely it is to impact SIT treatment goals. PMID:22617381

  2. MEASUREMENTS OF NATURAL SELECTION ON FLORAL TRAITS IN WILD RADISH (RAPHANUS RAPHANISTRUM). I. SELECTION THROUGH LIFETIME FEMALE FITNESS

    Microsoft Academic Search

    JEFFREY K. CONNER; PETER JENNET; E. Healey

    Although the role of natural selection in the evolution of floral traits has been of great interest to biologists since Darwin, studies of selection on floral traits through differences in lifetime fitness have been rare. We measured selection acting on flower number, flower size, stigma exsertion, and ovule number per flower using field data on lifetime female fitness (seed production)

  3. Correlation of selected rock and fluid properties with residual oil saturation obtained by laboratory waterfloods 

    E-print Network

    Edgington, Jason Monroe

    1968-01-01

    CORRELATION OF SELECTED ROCK AND FLUID PROPERTIES NITH RESIDUAL OIL SATURATION OBTAINED BY LABORATORY HATERFLOODS A Thesis By JASON NONROE EDGLNGTON Subxi t ted to the Graduate College of the Texas AKi University in partial fulfi' leant... of the recuire~aents for the deSree of iEASTER OF SCIENCE January 1)68 NaJor Su'bract. Petroleum?' EnpineerinS CORRELATION OF SELECTED ROCK AND FLUID PROPERTIES WITH RESIDUAL OIL SATURATION OBTAINED BY LABORATORY ?ATERFLOODS A Thesis JASON MONROE...

  4. Definition of experiments and instruments for a communication/navigation research laboratory. Volume 2: Experiment selection

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The selection and definition of candidate experiments and the associated experiment instrumentation requirements are described. Information is presented that addresses the following study objectives: (1) determine specific research and technology needs in the comm/nav field through a survey of the scientific/technical community; (2) develop manned low earth orbit space screening criteria and compile lists of potential candidate experiments; (3) in Blue Book format, define and describe selected candidate experiments in sufficient detail to develop laboratory configuration designs and layouts; and (4) develop experiment time phasing criteria and recommend a payload for sortie can/early laboratory missions.

  5. On the Deformation of UHP Eclogite: From Laboratory to Nature

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Green, H. W.

    2007-05-01

    Eclogites from orogens often show strong plastic deformation together with the surrounding country rocks represented by felsic gneisses. Eclogite rheology is an important piece of information for understanding the subduction of continental crust to great depth and then return to the surface. In the past two decades, there have been numerous studies of naturally deformed eclogites using a combination of optical microscopy, scanning electron microscopy (SEM), electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM). Most of these studies suggest that omphacite accommodates most of the strain imposed on eclogite and develops strong lattice preferred orientations (LPOs); garnet crystals generally behave as rigid grains. However, there have been some recent controversies regarding the ductility of garnet and LPO development in omphacite. Natural garnets deformed by dislocation creep and by grain boundary processes have both been proposed based on a variety of observations and other evidence. The variation of S-type and L-type fabric in omphacite has been attributed to drastically different mechanisms, such as dislocation creep, diffusion-assisted grain growth and space-group transformation. We present here the comparison side by side of deformation microstructures, fabrics, and seismic properties between naturally deformed and experimentally deformed eclogites synthesized from the same natural rocks. Our results suggest remarkable similarities despite the large difference in conditions (e.g. strain rates, stress, temperature, etc.) responsible for producing them. We conclude that: 1) In dry eclogite, omphacites accommodate most of the deformation while garnets behave as essentially rigid bodies; 2) In wet eclogite, the deformation is accommodated by shape change in both garnet and omphacite; 3) In both cases, omphacites develop pronounced S-type or L-type microfabrics arising from dislocation creep and variation of the geometry and orientation of the finite strain ellipsoid; 4) Garnets develop no LPO in either case; 5) The seismic properties of eclogites are controlled by both garnet and omphacite but their anisotropy patterns of P-wave velocity are controlled only by the LPO of omphacite.

  6. Chiral Selective Chemistry Induced by Natural Selection of Spin-Polarized Electrons.

    PubMed

    Rosenberg, Richard A; Mishra, Debabrata; Naaman, Ron

    2015-06-15

    The search to understand the origin of homochirality in nature has been ongoing since the time of Pasteur. Previous work has shown that DNA can act as a spin filter for low-energy electrons and that spin-polarized secondary electrons produced by X-ray irradiation of a magnetic substrate can induce chiral selective chemistry. In the present work it is demonstrated that secondary electrons from a substrate that are transmitted through a chiral overlayer cause enantiomeric selective chemistry in an adsorbed adlayer. We determine the quantum yields (QYs) for dissociation of (R)- or (S)-epichlorohydrin adsorbed on a chiral self-assembled layer of DNA on gold and on bare gold (for control). The results show that there is a significant difference in the QYs between the two enantiomers when adsorbed on DNA, but none when they are adsorbed on bare Au. We propose that the effect results from natural spin filtering effects cause by the chiral monolayer. PMID:25950284

  7. Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

    ERIC Educational Resources Information Center

    Kalinowski, Steven T.; Leonard, Mary J.; Andrews, Tessa M.; Litt, Andrea R.

    2013-01-01

    Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural…

  8. Materials research at selected Japanese laboratories. Based on a 1992 visit: Overview, summary of highlights, notes on laboratories and topics

    SciTech Connect

    Not Available

    1994-02-01

    I visited Japan from June 29 to August 1, 1992. The purpose of this visit was to assess the status of materials science research at selected governmental, university and industrial laboratories and to established acquaintances with Japanese researchers. The areas of research covered by these visits included ceramics, oxide superconductors, intermetallics alloys, superhard materials and diamond films, high-temperature materials and properties, mechanical properties, fracture, creep, fatigue, defects, materials for nuclear reactor applications and irradiation effects, high pressure synthesis, self-propagating high temperature synthesis, microanalysis, magnetic properties and magnetic facilities, and surface science.

  9. The Origin of Mutants Under Selection: How Natural Selection Mimics Mutagenesis (Adaptive Mutation).

    PubMed

    Maisnier-Patin, Sophie; Roth, John R

    2015-01-01

    Selection detects mutants but does not cause mutations. Contrary to this dictum, Cairns and Foster plated a leaky lac mutant of Escherichia coli on lactose medium and saw revertant (Lac(+)) colonies accumulate with time above a nongrowing lawn. This result suggested that bacteria might mutagenize their own genome when growth is blocked. However, this conclusion is suspect in the light of recent evidence that revertant colonies are initiated by preexisting cells with multiple copies the conjugative F'lac plasmid, which carries the lac mutation. Some plated cells have multiple copies of the simple F'lac plasmid. This provides sufficient LacZ activity to support plasmid replication but not cell division. In nongrowing cells, repeated plasmid replication increases the likelihood of a reversion event. Reversion to lac(+) triggers exponential cell growth leading to a stable Lac(+) revertant colony. In 10% of these plated cells, the high-copy plasmid includes an internal tandem lac duplication, which provides even more LacZ activity-sufficient to support slow growth and formation of an unstable Lac(+) colony. Cells with multiple copies of the F'lac plasmid have an increased mutation rate, because the plasmid encodes the error-prone (mutagenic) DNA polymerase, DinB. Without DinB, unstable and stable Lac(+) revertant types form in equal numbers and both types arise with no mutagenesis. Amplification and selection are central to behavior of the Cairns-Foster system, whereas mutagenesis is a system-specific side effect or artifact caused by coamplification of dinB with lac. Study of this system has revealed several broadly applicable principles. In all populations, gene duplications are frequent stable genetic polymorphisms, common near-neutral mutant alleles can gain a positive phenotype when amplified under selection, and natural selection can operate without cell division when variability is generated by overreplication of local genome subregions. PMID:26134316

  10. Selectivity of Three Miticides to Spider Mite Predator, Phytoseius plumifer (Acari: Phytoseiidae) Under Laboratory Conditions

    Microsoft Academic Search

    Nadimi Ahmad; Kamali Karim; Arbabi Masoud; Abdoli Fateme

    2009-01-01

    The predatory mite, Phytoseius plumifer (Canestrini & Fanzago), is one of the most abundant natural enemies and efficient predator of phytophagous mites in Iran. The miticides hexythiazox (Nisorun®, EC 10%), fenpyroximate (Ortus®, SC 5%), and abamectin (Vertimec®, EC 1.8%) were tested in the laboratory for their side effects on P. plumifer. The miticides were applied at the highest field recommended

  11. Natural Energy Laboratory of Hawaii Authority (NELHA): Hawaii Ocean Science & Technology Park; Kailua-Kona, Hawaii

    DOE Data Explorer

    Olson, K.; Andreas, A.

    A partnership with the Natural Energy Laboratory of Hawaii Authority and U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to collect solar data to support future solar power generation in the United States. The measurement station monitors global horizontal horizontal irradiance to define the amount of solar energy that hits this particular location. The solar measurement instrumentation is also accompanied by meteorological monitoring equipment to provide scientists with a complete picture of the solar power possibilities.

  12. Natural Energy Laboratory of Hawaii Authority (NELHA): Hawaii Ocean Science & Technology Park; Kailua-Kona, Hawaii

    SciTech Connect

    Olson, K.; Andreas, A.

    2012-11-01

    A partnership with the Natural Energy Laboratory of Hawaii Authority and U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to collect solar data to support future solar power generation in the United States. The measurement station monitors global horizontal horizontal irradiance to define the amount of solar energy that hits this particular location. The solar measurement instrumentation is also accompanied by meteorological monitoring equipment to provide scientists with a complete picture of the solar power possibilities.

  13. Artificial selection for structural color on butterfly wings and comparison with natural evolution

    PubMed Central

    Wasik, Bethany R.; Liew, Seng Fatt; Lilien, David A.; Dinwiddie, April J.; Noh, Heeso; Cao, Hui; Monteiro, Antónia

    2014-01-01

    Brilliant animal colors often are produced from light interacting with intricate nano-morphologies present in biological materials such as butterfly wing scales. Surveys across widely divergent butterfly species have identified multiple mechanisms of structural color production; however, little is known about how these colors evolved. Here, we examine how closely related species and populations of Bicyclus butterflies have evolved violet structural color from brown-pigmented ancestors with UV structural color. We used artificial selection on a laboratory model butterfly, B. anynana, to evolve violet scales from UV brown scales and compared the mechanism of violet color production with that of two other Bicyclus species, Bicyclus sambulos and Bicyclus medontias, which have evolved violet/blue scales independently via natural selection. The UV reflectance peak of B. anynana brown scales shifted to violet over six generations of artificial selection (i.e., in less than 1 y) as the result of an increase in the thickness of the lower lamina in ground scales. Similar scale structures and the same mechanism for producing violet/blue structural colors were found in the other Bicyclus species. This work shows that populations harbor large amounts of standing genetic variation that can lead to rapid evolution of scales’ structural color via slight modifications to the scales’ physical dimensions. PMID:25092295

  14. Variation in natural selection for growth and phlorotannins in the brown alga Fucus vesiculosus

    Microsoft Academic Search

    V. Jormalainen; T. Honkanen

    2004-01-01

    Directional selection for plant traits associated with resistance to herbivory tends to eliminate genetic variation in such traits. On the other hand, balancing selection arising from trade-offs between resistance and growth or spatially variable selection acts against the elimination of genetic variation. We explore both the amount of genetic variation and variability of natural selection for growth and concentration of

  15. Reference site selection report for the advanced liquid metal reactor at the Idaho National Engineering Laboratory

    SciTech Connect

    Sivill, R.L.

    1990-03-01

    This Reference Site Selection Report was prepared by EG G, Idaho Inc., for General Electric (GE) to provide information for use by the Department of Energy (DOE) in selecting a Safety Test Site for an Advanced Liquid Metal Reactor. Similar Evaluation studies are planned to be conducted at other potential DOE sites. The Power Reactor Innovative Small Module (PRISM) Concept was developed for ALMR by GE. A ALMR Safety Test is planned to be performed on a DOE site to demonstrate features and meet Nuclear Regulatory Commission Requirements. This study considered possible locations at the Idaho National Engineering Laboratory that met the ALMR Prototype Site Selection Methodology and Criteria. Four sites were identified, after further evaluation one site was eliminated. Each of the remaining three sites satisfied the criteria and was graded. The results were relatively close. Thus concluding that the Idaho National Engineering Laboratory is a suitable location for an Advanced Liquid Metal Reactor Safety Test. 23 refs., 13 figs., 9 tabs.

  16. Natural Pathogens of Laboratory Mice, Rats, and Rabbits and Their Effects on Research

    PubMed Central

    Baker, David G.

    1998-01-01

    Laboratory mice, rats, and rabbits may harbor a variety of viral, bacterial, parasitic, and fungal agents. Frequently, these organisms cause no overt signs of disease. However, many of the natural pathogens of these laboratory animals may alter host physiology, rendering the host unsuitable for many experimental uses. While the number and prevalence of these pathogens have declined considerably, many still turn up in laboratory animals and represent unwanted variables in research. Investigators using mice, rats, and rabbits in biomedical experimentation should be aware of the profound effects that many of these agents can have on research. PMID:9564563

  17. Laboratory selection of resistance to spinosad in Culex quinquefasciatus (Diptera: Culicidae).

    PubMed

    Su, Tianyun; Cheng, Min-Lee

    2014-03-01

    A southern house mosquito Culex quinquefasciatus Say colony was established from surviving late instars and pupae from a semifield evaluation on Natular XRG (a granular formulation containing 2.5% spinosad). The initial lethal levels ofNatular XRG against this colony were determined in the laboratory for the first-generation progeny (designated as F1). Selection pressure was applied at LC70-90 levels to 10,000-15,000 late third- and early fourth-instar larvae of each generation with Natular XRG. Susceptibility changes in response to selection were determined every other generation, where a gradual and steady decline in susceptibility occurred from generation F1 to F35, followed by significant decline from generations F37 to F45 For reference purposes, susceptibility of freshly collected wild populations as well as a laboratory colony of the same species was also determined concurrently, which fluctuated within a slightly wider range for the wild populations and a tighter range for the laboratory colony. By comparing with wild populations and laboratory reference colony, tolerance to spinosad was observed from generations up to F9 in the selected population. Resistance levels increased gradually from generation F11 to F35, and elevated significantly from generations F37 to F45, when resistance ratios reached 1,415.3- to 2,229.9-fold at LC50 and 9,613.1- to 17,062.6-fold at LC90. Possible mechanisms of resistance development to spinosad were discussed. PMID:24724292

  18. Sexual dichromatism in frogs: natural selection, sexual selection and unexpected diversity

    PubMed Central

    Bell, Rayna C.; Zamudio, Kelly R.

    2012-01-01

    Sexual dichromatism, a form of sexual dimorphism in which males and females differ in colour, is widespread in animals but has been predominantly studied in birds, fishes and butterflies. Moreover, although there are several proposed evolutionary mechanisms for sexual dichromatism in vertebrates, few studies have examined this phenomenon outside the context of sexual selection. Here, we describe unexpectedly high diversity of sexual dichromatism in frogs and create a comparative framework to guide future analyses of the evolution of these sexual colour differences. We review what is known about evolution of colour dimorphism in frogs, highlight alternative mechanisms that may contribute to the evolution of sexual colour differences, and compare them to mechanisms active in other major groups of vertebrates. In frogs, sexual dichromatism can be dynamic (temporary colour change in males) or ontogenetic (permanent colour change in males or females). The degree and the duration of sexual colour differences vary greatly across lineages, and we do not detect phylogenetic signal in the distribution of this trait, therefore frogs provide an opportunity to investigate the roles of natural and sexual selection across multiple independent derivations of sexual dichromatism. PMID:22993253

  19. Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students

    PubMed Central

    Kalinowski, Steven T.; Leonard, Mary J.; Andrews, Tessa M.; Litt, Andrea R.

    2013-01-01

    Students in introductory biology courses frequently have misconceptions regarding natural selection. In this paper, we describe six activities that biology instructors can use to teach undergraduate students in introductory biology courses how natural selection causes evolution. These activities begin with a lesson introducing students to natural selection and also include discussions on sexual selection, molecular evolution, evolution of complex traits, and the evolution of behavior. The set of six topics gives students the opportunity to see how natural selection operates in a variety of contexts. Pre- and postinstruction testing showed students’ understanding of natural selection increased substantially after completing this series of learning activities. Testing throughout this unit showed steadily increasing student understanding, and surveys indicated students enjoyed the activities. PMID:24006396

  20. Preventing and Removing Contamination in a Natural Radiocarbon Sample Preparation Laboratory

    SciTech Connect

    Zermeno, P; Kurdyla, D K; Buchholz, B A; Heller, S J; Frantz, B R; Brown, T A; Kashgarian, M

    2002-10-25

    The introduction of elevated {sup 14}C contamination into a natural radiocarbon sample preparation laboratory can occur through many different pathways. The most difficult to control is the introduction of contaminated samples from outside labs. Laboratories can remain {sup 14}C contaminated as a result of earlier tracer based research, even if ''hot'' work has not occurred in the laboratories in decades. Prior to accepting samples from outside collaborators, it is recommended that the collaborators test their labs for {sup 14}C contamination. Any surface in a lab that has high use by multiple people has the potential to be contaminated. The standard procedure for determining whether a collaborator's lab is contaminated consists of swiping lab surfaces with small glass fiber filters wetted with alcohol and measuring them for {sup 14}C content using AMS. Volatile {sup 14}C can be detected by using aerosol monitors consisting of fine soot that is depleted in {sup 14}C. These monitors can be set out in the laboratory in question to check for volatile {sup 14}C contamination. In the event that a hot sample is introduced in the natural radiocarbon sample prep laboratory, all sample submission should be stopped until the lab is declared clean. Samples already being processed should be completed along with {sup 14}C depleted material and measured by AMS. This will help determine if the contaminated samples have affected other samples in the laboratory. After a contamination event, the laboratory and associated equipment requires cleaning or disposal. All surfaces and equipment should be wiped down with acetone or ethanol. All chemicals in use should be disposed of in the appropriate waste containers and those waste containers removed from the lab. Once the natural radiocarbon laboratory has been thoroughly ''cleaned'', several background samples consisting of {sup 14}C depleted material should be processed through the lab and measured by AMS before unknown samples are processed again.

  1. Human Fertility, Molecular Genetics, and Natural Selection in Modern Societies

    PubMed Central

    Tropf, Felix C.; Stulp, Gert; Barban, Nicola; Visscher, Peter M.; Yang, Jian; Snieder, Harold; Mills, Melinda C.

    2015-01-01

    Research on genetic influences on human fertility outcomes such as number of children ever born (NEB) or the age at first childbirth (AFB) has been solely based on twin and family-designs that suffer from problematic assumptions and practical limitations. The current study exploits recent advances in the field of molecular genetics by applying the genomic-relationship-matrix based restricted maximum likelihood (GREML) methods to quantify for the first time the extent to which common genetic variants influence the NEB and the AFB of women. Using data from the UK and the Netherlands (N = 6,758), results show significant additive genetic effects on both traits explaining 10% (SE = 5) of the variance in the NEB and 15% (SE = 4) in the AFB. We further find a significant negative genetic correlation between AFB and NEB in the pooled sample of –0.62 (SE = 0.27, p-value = 0.02). This finding implies that individuals with genetic predispositions for an earlier AFB had a reproductive advantage and that natural selection operated not only in historical, but also in contemporary populations. The observed postponement in the AFB across the past century in Europe contrasts with these findings, suggesting an evolutionary override by environmental effects and underscoring that evolutionary predictions in modern human societies are not straight forward. It emphasizes the necessity for an integrative research design from the fields of genetics and social sciences in order to understand and predict fertility outcomes. Finally, our results suggest that we may be able to find genetic variants associated with human fertility when conducting GWAS-meta analyses with sufficient sample size. PMID:26039877

  2. Current Biology 16, 580585, March 21, 2006 2006 Elsevier Ltd All rights reserved DOI 10.1016/j.cub.2006.01.065 Natural Selection Drives Extremely

    E-print Network

    Jiggins, Francis

    .cub.2006.01.065 Report Natural Selection Drives Extremely Rapid Evolution in Antiviral RNAi Genes Darren J RNA interference (RNAi) is perhaps best known as a laboratory tool. However, RNAi-related pathways protect themselves by suppressing RNAi [2­4], inter- action between RNA viruses and host RNAi may re

  3. 113 Lab Learning Objectives Week 12: Information and Natural Selection lab #7

    E-print Network

    Campbell, A. Malcolm

    antibiotic resistant bacteria can appear quickly in the population. · Design directed evolution process to select antibiotic resistant bacteria. · Formulate an hypothesis how antibiotic resistant bacteria evolve outside the laboratory. · Propose a mechanism that allows bacteria to evolve rapidly when exposed

  4. Statistical Genetics of an Annual Plant, Impatiens Capensis. II. Natural Selection

    PubMed Central

    Mitchell-Olds, T.; Bergelson, J.

    1990-01-01

    Measurement of natural selection on correlated characters provides valuable information on fitness surfaces, patterns of directional, stabilizing, or disruptive selection, mechanisms of fitness variation operating in nature, and possible spatial variation in selective pressures. We examined effects of seed weight, germination date, plant size, early growth, and late growth on individual fitness. Path analysis showed that most characters had direct or indirect effects on individual fitness, indicating directional selection. For most early life-cycle characters, indirect effects via later characters exceed the direct causal effect on fitness. Selection gradients were uniform across the experimental site. There was no evidence for stabilizing or disruptive selection. We discuss several definitions of stabilizing and disruptive selection. Although early events in the life of an individual have important causal effects on subsequent characters and fitness, there is no detectable genetic variance for most of these characters, so little or no genetic response to natural selection is expected. PMID:2307362

  5. The size of beaks of Darwin's finches on the Galpagos Islands is influenced by natural selection.

    E-print Network

    Emlen, Douglas J.

    The size of beaks of Darwin's finches on the Galápagos Islands is influenced by natural selection Studies in the Wild Natural Selection Learning Objectives · Describe the di erences between directional rates of fish populations. Charles Darwin managedto visit only a handful of the Galápa- gos Islands

  6. Can natural selection favour altruism between species? G. A. K. WYATT*, S. A. WEST* & A. GARDNER*

    E-print Network

    West, Stuart

    Can natural selection favour altruism between species? G. A. K. WYATT*, S. A. WEST* & A. GARDNER; relatedness. Abstract Darwin suggested that the discovery of altruism between species would anni- hilate his theory of natural selection. However, it has not been formally shown whether between-species altruism can

  7. Quantifying the strength of natural selection of a motif Chen-Hsiang Yeang1

    E-print Network

    Yeang, Chen-Hsiang

    Quantifying the strength of natural selection of a motif sequence Chen-Hsiang Yeang1 Institute a method of evaluating the strength of natural selection of a motif from a family of aligned sequences as transcription factor binding motifs) from sequence data. However, most existing methods either target specific

  8. Heritability, covariation and natural selection on 24 traits of common evening primrose (Oenothera biennis) from

    E-print Network

    Agrawal, Anurag

    Heritability, covariation and natural selection on 24 traits of common evening primrose (Oenothera must be heritable for natural selection to result in evolutionary change within populations. Second future adaptive evolution. A number of studies have now considered the heritability Correspondence: Marc

  9. Visions of Evolution: Self-organization proposes what natural selection disposes David Batten1*

    E-print Network

    Boschetti, Fabio

    ." Charles Darwin SUMMARY This paper reviews the seven "visions" of evolution proposed by Depew and Weber1 Visions of Evolution: Self-organization proposes what natural selection disposes David Batten1 drives evolution; (2) self-organization drives evolution, or (3) natural selection and self

  10. Darwin's Principles of Divergence and Natural Selection: Why Fodor was Almost Right

    E-print Network

    Richards, Robert J.

    0 Darwin's Principles of Divergence and Natural Selection: Why Fodor was Almost Right Robert J. Richards University of Chicago Abstract Darwin maintained that the principles of natural selection as to be classifiable in the Linnaean taxonomic categories of variety, species, genus, and so on. Darwin's formulation

  11. Examining undergraduate understanding of natural selection and evolution

    NASA Astrophysics Data System (ADS)

    Balgopal, Meena Michelle

    2007-12-01

    This dissertation explores the understanding of evolution and natural selection by zoology and biological sciences education majors in two upper-division undergraduate courses. To date, there has been little research on evolution misconceptions held by these two populations. Students' misconceptions regarding evolution typically revolve around teleological and Lamarckian explanations for adaptations, origin of variation, and fitness. There are other misconceptions, however, that are described in this dissertation. The overarching objective of the dissertation was to identify variables that might influence the conceptual change. A mixed-method analysis was developed to identify instances of conceptual change that go undetected when only quantitative analyses are used. Through interpretations of in-depth interviews, written discourse, diagnostic tests, instructor interviews, and field notes, it was discovered that students' professional and personal affiliations influenced their motivation to resolve misconceptions. There were three main findings of this doctoral study. First, the effects of direct instruction on misconceptions enabled students to identify incorrect teleological wording but did not necessarily change students' writing about evolution. Higher-achieving students with career interests in biology were more likely to resolve their teleological misconceptions than lower-achieving students. Second, zoology student written discourse could be divided into subjective, objective, and authentic categories based on personal and professional connections that students made in their writing. Students who wrote authentically expressed intentions of pursuing professional biological research. Third, biological sciences education students were found to have composite identities based on personal and professional affiliations, which either hindered or enhanced their motivation to resolve evolution misconceptions. Students' personal affiliations to religious communities of practice did not hinder their motivation to understand evolution. However, students' fears of (a) not being able to resolve competing religious and scientific explanations for diversity of life and/or (b) not being prepared to defend evolution concepts to their employers and students were factors that influenced their motivation to learn. Biological sciences education students appeared to identify themselves as "sharers of scientific knowledge," not as "producers of scientific knowledge." I posit that identity plays a role in the conceptual change process.

  12. Toxicity of naturally-contaminated manganese soil to selected crops.

    PubMed

    Ková?ik, Jozef; Št?rbová, Dagmar; Babula, Petr; Švec, Pavel; Hedbavny, Josef

    2014-07-23

    The impact of manganese excess using naturally contaminated soil (Mn-soil, pseudototal Mn 6494 vs 675 ?g g(-1) DW in control soil) in the shoots of four crops was studied. Mn content decreased in the order Brassica napus > Hordeum vulgare > Zea mays > Triticum aestivum. Growth was strongly depressed just in Brassica (containing 13696 ?g Mn g(-1) DW). Some essential metals (Zn, Fe) increased in Mn-cultured Brassica and Zea, while macronutrients (K, Ca, Mg) decreased in almost all species. Toxic metals (Ni and Cd) were rather elevated in Mn-soil. Microscopy of ROS, NO, lipid peroxidation, and thiols revealed stimulation in all Mn-cultured crops, but changes were less visible in Triticum, a species with low shoot Mn (2363 ?g g(-1) DW). Antioxidative enzyme activities were typically enhanced in Mn-cultured plants. Soluble phenols increased in Brassica only while proteins rather decreased in response to Mn excess. Inorganic anions (chloride, sulfate, and phosphate) were less accumulated in almost all Mn-cultured crops, while the nitrate level rather increased. Organic anions (malate, citrate, oxalate, acetate, and formate) decreased or remained unaffected in response to Mn-soil culture in Brassica, Hordeum, and Triticum but not in Zea. However, the role of organic acids in Mn uptake in these species is not assumed. Because control and Mn-soil differed in pH (6.5 and 3.7), we further studied its impact on Mn uptake in solution culture (using Mn concentration ?5 mM deducted from water-soluble fraction of Mn-soil). Shoot Mn contents in Mn-treated plants were similar to those observed in soil culture (high in Brassica and low in Triticum) and pH had negligible impact. Fluorescence indicator of "general ROS" revealed no extensive or pH-dependent impact either in control or Mn-cultured roots. Observed toxicity of Mn excess to common crops urges for selection of cultivars with higher tolerance. PMID:24965550

  13. Predator-mediated natural selection on the wings of the damselfly Calopteryx splendens: differences in selection among trait types.

    PubMed

    Kuchta, Shawn R; Svensson, Erik I

    2014-07-01

    Traits that increase mating success in males may come at a cost, such as an increased risk of predation. However, predator-mediated selection is challenging to document in natural populations, hampering our understanding of the trade-offs between sexual selection and predation. Here we report on a study of predator-mediated natural selection on wing traits in the damselfly Calopteryx splendens, the males of which possess conspicuous wing patches. Wagtails (genus Motacilla) are important avian predators of C. splendens, capturing them in flight and removing the wings prior to consumption. Using geometric morphometric techniques, we quantified the strength and mode of selection on wing traits by comparing wings from depredated individuals with the standing variation present in the population. Our results reveal that predator-mediated selection is stronger on secondary sexual characters than on size and shape, suggesting that traits related to flight performance are closer to their adaptive peaks. This could be a consequence of the long-term evolutionary association with avian predators, whereas stronger selection on conspicuous secondary sexual traits may reflect trade-offs between sexual and natural selection. Finally, even though C. splendens possesses nearly identical fore- and hindwings, we found evidence for divergent selection between them. PMID:24921603

  14. Polycyclic aromatic hydrocarbons at selected burning grounds at Los Alamos National Laboratory

    SciTech Connect

    Harris, B.W.; Minor, L.K.M.; Flucas, B.J.

    1998-02-01

    A commercial immunoassay field test (IFT) was used to rapidly assess the total concentrations of polycyclic aromatic hydrocarbons (PAHs) in the soil at selected burning grounds within the explosives corridor at Los Alamos National Laboratory (LANL). Results were compared with analyses obtained from LANL Analytical Laboratory and from a commercial laboratory. Both used the Environmental Protection Agency`s (EPA`s) Methods 8270 and 8310. EPA`s Method 8270 employs gas chromatography and mass spectral analyses, whereas EPA`s Method 8310 uses an ultraviolet detector in a high-performance liquid chromatography procedure. One crude oil sample and one diesel fuel sample, analyzed by EPA Method 8270, were included for references. On an average the IFT results were lower for standard samples and lower than the analytical laboratory results for the unknown samples. Sites were selected to determine whether the PAHs came from the material burned or the fuel used to ignite the burn, or whether they are produced by a high-temperature chemical reaction during the burn. Even though the crude oil and diesel fuel samples did contain measurable quantities of PAHs, there were no significant concentrations of PAHs detected in the ashes and soil at the burning grounds. Tests were made on fresh soil and ashes collected after a large burn and on aged soil and ashes known to have been at the site more than three years. Also analyzed were twelve-year-old samples from an inactive open burn cage.

  15. Modeling Natural Action Selection Proceedings of an International Workshop

    E-print Network

    Bryson, Joanna J.

    . Thompson Combining action selection models with a five factor theory 16 Mark Witkowski On compromise strategies for action selection with proscriptive goals 24 Frederick Crabbe He/she-you-I formalism, Russell Hill, and Brian Logan Tolerance and sexual attraction in despotic societies: A replication

  16. LIFETIME SELECTION ON HERITABLE LIFE-HISTORY TRAITS IN A NATURAL POPULATION OF RED SQUIRRELS

    Microsoft Academic Search

    D. Réale; D. Berteaux; A. G. McAdam; S. Boutin

    2003-01-01

    Despite their importance in evolutionary biology, heritability and the strength of natural selection have rarely been estimated in wild populations of iteroparous species or have usually been limited to one particular event during an organism's lifetime. Using an animal-model restricted maximum likelihood and phenotypic selection models, we estimated quantitative genetic parameters and the strength of lifetime selection on parturition date

  17. North American Natural Gas Markets: Selected technical studies. Volume 3

    SciTech Connect

    Huntington, H.G.; Schuler, G.E. [eds.

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  18. North American Natural Gas Markets: Selected technical studies

    SciTech Connect

    Huntington, H.G.; Schuler, G.E. (eds.)

    1989-04-01

    The Energy Modeling Forum (EMF) was established in 1976 at Stanford University to provide a structural framework within which energy experts, analysts, and policymakers could meet to improve their understanding of critical energy problems. The ninth EMF study, North American Natural Gas Markets, was conducted by a working group comprised of leading natural gas analysts and decision-makers from government, private companies, universities, and research and consulting organizations. The EMF 9 working group met five times from October 1986 through June 1988 to discuss key issues and analyze natural gas markets. This third volume includes technical papers that support many of the conclusions discussed in the EMF 9 summary report (Volume 1) and full working group report (Volume 2). These papers discuss the results from the individual models as well as some nonmodeling analysis related to US natural gas imports and industrial natural gas demand. Individual papers have been processed separately for inclusion in the Energy Science and Technology Database.

  19. Selective whole genome amplification for resequencing target microbial species from complex natural samples.

    PubMed

    Leichty, Aaron R; Brisson, Dustin

    2014-10-01

    Population genomic analyses have demonstrated power to address major questions in evolutionary and molecular microbiology. Collecting populations of genomes is hindered in many microbial species by the absence of a cost effective and practical method to collect ample quantities of sufficiently pure genomic DNA for next-generation sequencing. Here we present a simple method to amplify genomes of a target microbial species present in a complex, natural sample. The selective whole genome amplification (SWGA) technique amplifies target genomes using nucleotide sequence motifs that are common in the target microbe genome, but rare in the background genomes, to prime the highly processive phi29 polymerase. SWGA thus selectively amplifies the target genome from samples in which it originally represented a minor fraction of the total DNA. The post-SWGA samples are enriched in target genomic DNA, which are ideal for population resequencing. We demonstrate the efficacy of SWGA using both laboratory-prepared mixtures of cultured microbes as well as a natural host-microbe association. Targeted amplification of Borrelia burgdorferi mixed with Escherichia coli at genome ratios of 1:2000 resulted in >10(5)-fold amplification of the target genomes with <6.7-fold amplification of the background. SWGA-treated genomic extracts from Wolbachia pipientis-infected Drosophila melanogaster resulted in up to 70% of high-throughput resequencing reads mapping to the W. pipientis genome. By contrast, 2-9% of sequencing reads were derived from W. pipientis without prior amplification. The SWGA technique results in high sequencing coverage at a fraction of the sequencing effort, thus allowing population genomic studies at affordable costs. PMID:25096321

  20. Natural selection and rational decision: two concepts of optimization

    Microsoft Academic Search

    Elias L. Khalil

    2009-01-01

    There are two different kinds of optimization: “selection” and “rationality” optimization. Selection optimization characterizes\\u000a competition in human and nonhuman societies sharing the same market or niche. “Rationality optimization”, on the other hand,\\u000a characterizes human and nonhuman decision making processes. The two kinds of optimization generate the same result: agents\\u000a end up behaving efficiently. Nonetheless, we should not downplay the differences

  1. The Slumgullion Natural Laboratory: Landsliding Mechanisms Inferred from Seismic and Geodetic Observations

    NASA Astrophysics Data System (ADS)

    Schulz, W. H.; Kean, J. W.; Gomberg, J. S.; Bodin, P.; Wang, G.; Coe, J. A.; MacQueen, P.; Foster, K.; Creager, K.

    2009-12-01

    Effective mitigation of landslide hazards requires accurate characterization of landslide subsurface geometry and failure mode, both of which are difficult to obtain. To evaluate a new geophysical approach for landslide and faulting characterization in a natural setting, we recently deployed an array of 88 single-channel seismometers complemented by geodetic measurements made using GPS and a robotic total-station theodolite at the 3.9-km-long Slumgullion landslide in southwestern Colorado. This landslide was selected because of its size, nearly continuous movement, and the documentation of its failure modes from previous continuous monitoring and laboratory testing. Our previous studies identified that the landslide material (soil and weathered rock) dilates during shear and has very low permeability. These characteristics result in generation of excess negative pore-water pressures along shear surfaces that restrain movement by increasing effective normal stresses. We’ve also observed that lateral shear boundaries episodically relocate, forming new shear surfaces. Although we have only just completed the data-gathering phase, we’ve identified that landslide movement varies considerably, sometimes occurring aseismically and other times producing seismic tremor and localized slidequakes. Our working hypothesis is that steady aseismic slip occurs where shear-zone porosity is at critical state, tremor radiates from areas where increased effective stress from shear-zone dilation sporadically resists movement, and slidequakes are produced from similarly dilating areas, especially where and when new shear surfaces are formed. Complex rearrangements between individual kinematic units comprising the landslide may also affect its mode of failure and slip and consequent observables. Further analyses of geodetic, seismic, and environmental data will refine our hypotheses. Location estimates of the large number of observed seismic events may constrain the geometry of the landslide’s basal shear zone. Conventional geophysical techniques such as seismic refraction have proven ineffective for imaging the base of the Slumgullion and other landslides because landslide materials do not adequately differ from underlying materials. Our findings should help understand landslides in general, as well as other phenomena that involve naturally occurring shear failure of soil and rock, such as earthquakes, glacier movement, and volcanic eruptions.

  2. Caprylate-thallous agar medium for selectively isolating Serratia and its utility in the clinical laboratory.

    PubMed Central

    Starr, M P; Grimont, P A; Grimont, F; Starr, P B

    1976-01-01

    A defined agar medium (hereinafter designated caprylate-thallous [CT5 agar) containing 0.01% yeast extract, 0.1% caprylic (n-octanoic) acid, and 0.025% thallous sulfate is highly selective for all Serratia species and effectively discriminates against most non-Serratia strains likely to be in the same habitats. The selectivity of CT agar is demonstrated by the very high efficiency of colony formation (mean, 80.7% of that on a nonselective complex medium) on CT agar by known Serratia strains and the very low efficiency of colony formation (close to zero) on CT agar by bacterial strains known not to be Serratia. The utility of this medium in actual clinical laboratory practice is demonstrated by the more rapid and higher recovery of Serratia on this selective medium as compared to conventional procedures of in-tandem runs of 513 consecutive urine, feces, and sputum specimens. Pigmented and nonpigmented Serratia strains deliberately added to fecal specimens can be selectively and quantitatively recovered on CT agar. CT agar compares favorably with, or in some cases is an improvement over, other selective media which have been recommended for isolating Serratia. This selective CT agar medium could be quite useful in ecological surveys, especially those related to hospital-acquired infections. PMID:972193

  3. Assessing the alignment of sexual and natural selection using radiomutagenized seed beetles.

    PubMed

    Power, D J; Holman, L

    2015-05-01

    A major unsolved question in evolutionary biology concerns the relationship between natural and sexual selection. Sexual selection might augment natural selection, for example if mutations that harm female fecundity also reduce male mating success. Conversely, sexual selection might favour traits that impair naturally selected fitness components. We induced detrimental mutations in Callosobruchus maculatus beetles using X-ray irradiation and then experimentally measured the effect of precopulatory sexual selection on offspring number and survival rate. Sexual selection treatment had a negative effect on egg-to-adult survivorship, although the number of progeny reaching adulthood was unaffected, perhaps because eggs and juveniles that failed to develop lessened competition on the survivors. We hypothesize that the negative effect of sexual selection arose because sexually competitive males transmitted a smaller nuptial gift or carried alleles that conferred reduced survival. Although we found no evidence that sexual selection on males can purge alleles that are detrimental to naturally selected fitness components, such benefits might exist in other environmental or genetic contexts. PMID:25808294

  4. Spatial patterns of variation due to natural selection in humans

    PubMed Central

    Novembre, John; Di Rienzo, Anna

    2013-01-01

    Empowered by technology and sampling efforts designed to facilitate genome-wide association mapping, human geneticists are now studying the geography of genetic variation with unprecedented detail. With high genomic coverage and geographic resolution, these studies are identifying loci with spatial signatures of selection, such as extreme levels of differentiation and correlations with environmental variables. Collectively, patterns at these loci are beginning to provide novel insights into the process of human adaptation. Here we review the challenges of these studies and emerging results, including how human population structure has influenced the response to novel selective pressures. PMID:19823195

  5. Antarctic circumpolar wave impact on marine biology: A natural laboratory for climate change study

    Microsoft Academic Search

    Corinne Le Quéré; Laurent Bopp; Ina Tegen

    2002-01-01

    We use the observed variations in ocean surface chlorophyll, temperature and height caused by the Antarctic Circumpolar Wave (ACW) as a natural laboratory to determine how marine biology responds to changes in ocean stratification in the Southern Ocean. Interannual variations of surface chlorophyll (±5%) observed by SeaWiFS satellite during 1997–2001 vary in phase over the entire Southern Ocean in spite

  6. Natural history of sensitization, symptoms and occupational diseases in apprentices exposed to laboratory animals

    Microsoft Academic Search

    D. Gautrin; H. Ghezzo; C. Infante-Rivard; J. L. Malo

    2001-01-01

    The natural history of the development of sensitization and disease due to high-molecular-weight allergens is not well characterized. This study describes the time- course of the incidence of work-related symptoms, skin reactivity and occupational rhinoconjunctivitis (RC) and asthma (OA); and assesses the predictive value of skin testing and RC symptoms in apprentices exposed to laboratory animals, in a 3-4-yr programme.

  7. Laboratory coating evaluation and its relationship with the selection to protect pipeline against external corrosion

    SciTech Connect

    Rodriguez, V.; Perozo, E.; Castafieda, L.; Alvarez, E. [INTEVEP, S.A., Caracas (Venezuela). Material Technology Dept.

    1998-12-31

    There are several pipeline external coatings classified into different types, among them are extruded and tape polyethylene, fusion bonded epoxy (FBE), coal tar enamel, coal tar epoxy, polyurethane, wax, cementitious epoxy and multilayer systems. These coatings are assumed to protect the pipeline for a certain period of time. In order to select the most appropriate coating, several accelerated laboratory tests need to be carried out to obtain their properties and correlate them with the performance in the field. Cathodic disbonding tests at different temperatures and voltages, adhesion at different temperatures, impact resistance, loss of adhesion against time under water immersion conditions, differential scanning calorimetry analysis and water uptake are the most important tests to carry out in this study. The results indicate that coatings perform differently in each test. For this reason the selection must be done according to the soil characteristics, considering the results obtained in laboratory. This paper will provide a guideline to select a coating for a specific environment and the results that should be expected in the field. For example, the multilayer system presented the best performance like low cathodic disbonding, excellent adhesion, high impact resistance, excellent behavior under hot water immersion and high temperature resistance. This system can be used in all types of soil with high life time expectancy in protecting the pipeline. On the other hand, the polyurethane coating presented high impact resistance but very low adhesion and high cathodic disbonding that limits its use in corrosive soil.

  8. Charles Kingsley and the Theological Interpretation of Natural Selection

    Microsoft Academic Search

    David M. Levy; Sandra J. Peart

    2006-01-01

    Synopsis  This paper questions the common view that Darwinian biology is a straighforward extension of classical political economy. Our analysis contrasts the economists’ classification scheme – whereby all humans were presumed natural kinds, to be equally competent for economic and political decision making – with the post-Darwinian classification scheme that developed. When the tools of political economy were imported into biology,

  9. Mortality among Plants and its Bearing on Natural Selection

    Microsoft Academic Search

    R. Weatherall

    1931-01-01

    I HAVE read with great interest the letters from Prof. Salisbury and Dr. J. Phillips which have appeared in NATURE dealing with mortality in plants at different stages of their life histories. The observations are of the greatest importance, but I doubt whether the interpretation advanced by Prof. Salisbury in his letter of May 31, 1930, is supported by the

  10. Selected References on Asbestos: Its Nature, Hazards, Detection, and Control.

    ERIC Educational Resources Information Center

    National Education Association, Washington, DC.

    This document provides teachers with sources of information about the nature, hazards, detection, and control of asbestos. Because many school buildings include asbestos-containing materials, teachers and other school personnel must be aware of the potential dangers to students and to themselves and take steps to have asbestos hazards contained or…

  11. Biochemical characterization of chlorantraniliprole and spinetoram resistance in laboratory-selected obliquebanded leafroller, Choristoneura rosaceana (Harris)(Lepidoptera:Tortricidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Neonate larvae of obliquebanded leafroller, Choristoneura rosaceana, from a laboratory colony were exposed to two reduced-risk insecticides, chlorantraniliprole and spinetoram. After nine generations of selection, significant levels of resistance to each insecticide were observed. Biochemical assa...

  12. Genetic drift or natural selection? Hybridization and asymmetric mitochondrial introgression in two Caribbean lizards

    E-print Network

    Rodríguez, Javier A.

    University, Durham, NC, USA Keywords: Caribbean Sea; DNAH3; evolutionary diversification; hybridizationGenetic drift or natural selection? Hybridization and asymmetric mitochondrial introgression in two Caribbean lizards (Anolis pulchellus and Anolis krugi) T. JEZKOVA*, M. LEAL & J. A. RODRI

  13. When Natural Selection Favors Imitation Richard McElreath and Pontus Strimling

    E-print Network

    McElreath, Richard

    307 When Natural Selection Favors Imitation of Parents Richard McElreath and Pontus Strimling evolutionary dynamics (Cavalli-Sforza and Feldman 1981; Boyd and Richerson 1985; Barth 1990). Debates ranging

  14. Mouse Strain Type is Not Selective for a Laboratory-adapted Strain of Schistosoma mansoni

    PubMed Central

    Liu, Shi Fan; Prasad, Jayendra; Blanton, Ronald E.

    2013-01-01

    We genotyped pooled adult worms of Schistosoma mansoni from infected CF1, C57BL/6, BALB/c, and BALB/c interferon gamma knockout mice in order to investigate if mouse strain differences selected for parasite genotypes. We also compared differentiation in eggs collected from liver and intestines to determine if there was differential distribution of parasite strains in the vertebrate host that might account for any genotype selection. We found that mouse strains with differing immune responses did not differ in resistance to infection and did not select for parasite genotypes. S. mansoni genotypes were also equally distributed in tissues and there was no difference between adult and egg allele frequencies. Differing immune responses in these mouse strains does not significantly affect the degree or the nature of host resistance to schistosomes. PMID:21506771

  15. Natural selection of altruism in inelastic viscous homogeneous populations

    Microsoft Academic Search

    Alan Grafen; Marco Archetti

    2008-01-01

    Biological explanations are given of three main uninterpreted theoretical results on the selection of altruism in inelastic viscous homogeneous populations, namely that non-overlapping generations hinder the evolution of altruism, fecundity effects are more conducive to altruism than survival effects, and one demographic regime (so-called death–birth) permits altruism whereas another (so-called birth–death) does not. The central idea is ‘circles of compensation’,

  16. Genome Sequencing Reveals Loci under Artificial Selection that Underlie Disease Phenotypes in the Laboratory Rat

    PubMed Central

    Atanur, Santosh S.; Diaz, Ana Garcia; Maratou, Klio; Sarkis, Allison; Rotival, Maxime; Game, Laurence; Tschannen, Michael R.; Kaisaki, Pamela J.; Otto, Georg W.; Ma, Man Chun John; Keane, Thomas M.; Hummel, Oliver; Saar, Kathrin; Chen, Wei; Guryev, Victor; Gopalakrishnan, Kathirvel; Garrett, Michael R.; Joe, Bina; Citterio, Lorena; Bianchi, Giuseppe; McBride, Martin; Dominiczak, Anna; Adams, David J.; Serikawa, Tadao; Flicek, Paul; Cuppen, Edwin; Hubner, Norbert; Petretto, Enrico; Gauguier, Dominique; Kwitek, Anne; Jacob, Howard; Aitman, Timothy J.

    2013-01-01

    Summary Large numbers of inbred laboratory rat strains have been developed for a range of complex disease phenotypes. To gain insights into the evolutionary pressures underlying selection for these phenotypes, we sequenced the genomes of 27 rat strains, including 11 models of hypertension, diabetes, and insulin resistance, along with their respective control strains. Altogether, we identified more than 13 million single-nucleotide variants, indels, and structural variants across these rat strains. Analysis of strain-specific selective sweeps and gene clusters implicated genes and pathways involved in cation transport, angiotensin production, and regulators of oxidative stress in the development of cardiovascular disease phenotypes in rats. Many of the rat loci that we identified overlap with previously mapped loci for related traits in humans, indicating the presence of shared pathways underlying these phenotypes in rats and humans. These data represent a step change in resources available for evolutionary analysis of complex traits in disease models. PaperClip PMID:23890820

  17. Natural selection constrains neutral diversity across a wide range of species.

    PubMed

    Corbett-Detig, Russell B; Hartl, Daniel L; Sackton, Timothy B

    2015-04-01

    The neutral theory of molecular evolution predicts that the amount of neutral polymorphisms within a species will increase proportionally with the census population size (Nc). However, this prediction has not been borne out in practice: while the range of Nc spans many orders of magnitude, levels of genetic diversity within species fall in a comparatively narrow range. Although theoretical arguments have invoked the increased efficacy of natural selection in larger populations to explain this discrepancy, few direct empirical tests of this hypothesis have been conducted. In this work, we provide a direct test of this hypothesis using population genomic data from a wide range of taxonomically diverse species. To do this, we relied on the fact that the impact of natural selection on linked neutral diversity depends on the local recombinational environment. In regions of relatively low recombination, selected variants affect more neutral sites through linkage, and the resulting correlation between recombination and polymorphism allows a quantitative assessment of the magnitude of the impact of selection on linked neutral diversity. By comparing whole genome polymorphism data and genetic maps using a coalescent modeling framework, we estimate the degree to which natural selection reduces linked neutral diversity for 40 species of obligately sexual eukaryotes. We then show that the magnitude of the impact of natural selection is positively correlated with Nc, based on body size and species range as proxies for census population size. These results demonstrate that natural selection removes more variation at linked neutral sites in species with large Nc than those with small Nc and provides direct empirical evidence that natural selection constrains levels of neutral genetic diversity across many species. This implies that natural selection may provide an explanation for this longstanding paradox of population genetics. PMID:25859758

  18. Phenotypic heterogeneity is a selected trait in natural yeast populations subject to environmental stress

    PubMed Central

    Holland, Sara L; Reader, Tom; Dyer, Paul S; Avery, Simon V

    2014-01-01

    Populations of genetically uniform microorganisms exhibit phenotypic heterogeneity, where individual cells have varying phenotypes. Such phenotypes include fitness-determining traits. Phenotypic heterogeneity has been linked to increased population-level fitness in laboratory studies, but its adaptive significance for wild microorganisms in the natural environment is unknown. Here, we addressed this by testing heterogeneity in yeast isolates from diverse environmental sites, each polluted with a different principal contaminant, as well as from corresponding control locations. We found that cell-to-cell heterogeneity (in resistance to the appropriate principal pollutant) was prevalent in the wild yeast isolates. Moreover, isolates with the highest heterogeneity were consistently observed in the polluted environments, indicating that heterogeneity is positively related to survival in adverse conditions in the wild. This relationship with survival was stronger than for the property of mean resistance (IC50) of an isolate. Therefore, heterogeneity could be the major determinant of microbial survival in adverse conditions. Indeed, growth assays indicated that isolates with high heterogeneities had a significant competitive advantage during stress. Analysis of yeasts after cultivation for ??500 generations additionally showed that high heterogeneity evolved as a heritable trait during stress. The results showed that environmental stress selects for wild microorganisms with high levels of phenotypic heterogeneity. PMID:24000788

  19. Selection of yeasts with multifunctional features for application as starters in natural black table olive processing.

    PubMed

    Bonatsou, S; Benítez, A; Rodríguez-Gómez, F; Panagou, E Z; Arroyo-López, F N

    2015-04-01

    Yeasts are unicellular eukaryotic microorganisms with a great importance in the elaboration on many foods and beverages. In the last years, researches have focused their attention to determine the favourable effects that these microorganisms could provide to table olive processing. In this context, the present study assesses, at laboratory scale, the potential technological (resistance to salt, lipase, esterase and ?-glucosidase activities) and probiotic (phytase activity, survival to gastric and pancreatic digestions) features of 12 yeast strains originally isolated from Greek natural black table olive fermentations. The multivariate classification analysis carried out with all information obtained (a total of 336 quantitative input data), revealed that the most promising strains (clearly discriminated from the rest of isolates) were Pichia guilliermondii Y16 (which showed overall the highest resistance to salt and simulated digestions) and Wickerhamomyces anomalus Y18 (with the overall highest technological enzymatic activities), while the rest of strains were grouped together in two clearly differentiated clusters. Thus, this work opens the possibility for the evaluation of these two selected yeasts as multifunctional starters, alone or in combination with lactic acid bacteria, in real table olive fermentations. PMID:25475268

  20. Life-history QTLS and natural selection on flowering time in Boechera stricta, a perennial relative of Arabidopsis.

    PubMed

    Anderson, Jill T; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

    2011-03-01

    Plants must precisely time flowering to capitalize on favorable conditions. Although we know a great deal about the genetic basis of flowering phenology in model species under controlled conditions, the genetic architecture of this ecologically important trait is poorly understood in nonmodel organisms. Here, we evaluated the transition from vegetative growth to flowering in Boechera stricta, a perennial relative of Arabidopsis thaliana. We examined flowering time QTLs using 7920 recombinant inbred individuals, across seven laboratory and field environments differing in vernalization, temperature, and photoperiod. Genetic and environmental factors strongly influenced the transition to reproduction. We found directional selection for earlier flowering in the field. In the growth chamber experiment, longer winters accelerated flowering, whereas elevated ambient temperatures delayed flowering. Our analyses identified one large effect QTL (nFT), which influenced flowering time in the laboratory and the probability of flowering in the field. In Montana, homozygotes for the native allele at nFT showed a selective advantage of 6.6%. Nevertheless, we found relatively low correlations between flowering times in the field and the growth chambers. Additionally, we detected flowering-related QTLs in the field that were absent across the full range of laboratory conditions, thus emphasizing the need to conduct experiments in natural environments. PMID:21083662

  1. Patterns of Population Differentiation and Natural Selection on the Celiac Disease Background Risk

    E-print Network

    Cochran-Stafira, D. Liane

    Patterns of Population Differentiation and Natural Selection on the Celiac Disease Background Risk Biology, Cornell University, Ithaca, New York, United States of America Abstract Celiac disease Selection on the Celiac Disease Background Risk Network. PLoS ONE 8(7): e70564. doi:10.1371/journal

  2. The relative influence of natural selection and geography on gene flow in guppies

    Microsoft Academic Search

    ERIKA CRISPO; PAUL BENTZEN; DAVID N. R EZNICK; MICHAEL T. K INNISON; ANDREW P. H ENDRY

    Two general processes may influence gene flow among populations. One involves divergent selection, wherein the maladaptation of immigrants and hybrids impedes gene flow between ecological environments (i.e. ecological speciation). The other involves geographic features that limit dispersal. We determined the relative influence of these two processes in natural populations of Trinidadian guppies ( Poecilia reticulata ). If selection is important,

  3. From Ends to Causes (and Back Again) by Metaphor: The Paradox of Natural Selection

    ERIC Educational Resources Information Center

    Blancke, Stefaan; Schellens, Tammy; Soetaert, Ronald; Van Keer, Hilde; Braeckman, Johan

    2014-01-01

    Natural selection is one of the most famous metaphors in the history of science. Charles Darwin used the metaphor and the underlying analogy to frame his ideas about evolution and its main driving mechanism into a full-fledged theory. Because the metaphor turned out to be such a powerful epistemic tool, Darwin naturally assumed that he could also…

  4. Natural selection of altruism in inelastic viscous homogeneous populations.

    PubMed

    Grafen, Alan; Archetti, Marco

    2008-06-21

    Biological explanations are given of three main uninterpreted theoretical results on the selection of altruism in inelastic viscous homogeneous populations, namely that non-overlapping generations hinder the evolution of altruism, fecundity effects are more conducive to altruism than survival effects, and one demographic regime (so-called death-birth) permits altruism whereas another (so-called birth-death) does not. The central idea is 'circles of compensation', which measure how far the effects of density dependence extend from a focal individual. Relatednesses can then be calculated that compensate for density dependence. There is very generally a 'balancing circle of compensation', at which the viscosity of the population slows up selection of altruism, but does not affect its direction, and this holds for altruism towards any individual, not just immediate neighbours. These explanations are possible because of recent advances in the theory of inclusive fitness on graphs. The assumption of node bitransitivity in that recent theory is relaxed to node transitivity and symmetry of the dispersal matrix, and new formulae show how to calculate relatedness from dispersal and vice versa. PMID:18371985

  5. Natural selection reduces energy metabolism in the garden snail, helix aspersa (cornu aspersum).

    PubMed

    Artacho, Paulina; Nespolo, Roberto F

    2009-04-01

    Phenotypic selection is widely recognized as the primary cause of adaptive evolution in natural populations, a fact that has been documented frequently over the last few decades, mainly in morphological and life-history traits. The energetic definition of fitness predicts that natural selection will maximize the residual energy available for growth and reproduction, suggesting that energy metabolism could be a target of selection. To address this problem, we chose the garden snail, Helix aspersa (Cornu aspersum). We performed a seminatural experiment for measuring phenotypic selection on standard metabolic rate (SMR), the minimum cost of maintenance in ectotherm organisms. To discount selection on correlated traits, we included two additional whole-organism performance traits (mean speed and maximum force of dislodgement). We found a combination of linear (negative directional selection, beta=-0.106 +/- 0.06; P= 0.001) and quadratic (stabilizing selection, gamma=-0.012 +/- 0.033; P= 0.061) selection on SMR. Correlational selection was not significant for any possible pair of traits. This suggests that individuals with average-to-reduced SMRs were promoted by selection. To the best of our knowledge, this is the first study showing significant directional selection on the obligatory cost of maintenance in an animal, providing support for the energetic definition of fitness. PMID:19236475

  6. Developments of the Price equation and natural selection under uncertainty.

    PubMed

    Grafen, A

    2000-06-22

    Many approaches to the study of adaptation, following Darwin, centre on the number of offspring of individuals. Population genetics theory makes clear that predicting gene frequency changes requires more detailed knowledge, for example of linkage and linkage disequilibrium and mating systems. Because gene frequency changes underlie adaptation, this can lead to a suspicion that approaches ignoring these sophistications are approximate or tentative or wrong. Stochastic environments and sexual selection are two topics in which there are widespread views that focusing on number of offspring of individuals is not enough, and that proper treatments require the introduction of further details, namely variability in offspring number and linkage disequilibrium, respectively. However, the bulk of empirical research on adaptation and a great deal of theoretical work continue to employ these approaches. Here, a new theoretical development arising from the Price equation provides a formal justification in very general circumstances for focusing on the arithmetic average of the relative number of offspring of individuals. PMID:10902688

  7. The Nature of Irac-selected Extremely Red Objects

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Huang, J.; Gu, Q.

    2010-05-01

    Using deep U-8um photometry from GEMs, MUSYC and SIMPLE surveys, we investigate properties of a large sample of IRAC-selected extremely red galaxies(IEROs). The sample comprises 304 brightest IEROs distributed over the GEMS field with a total area of 800 arcmin2, which satisfy ([3.6]+[4.5]/2)<21.2 and z-[3.6] > 3.25). Combined with the deepest Chandra and Spitzer surveys in this field, we are able to determine relative contributions of AGNs, (dusty) star-forming galaxies and passively evolving systems to the RED population; 51 sources are detected in at least one of three X-ray bands, leaving 253 non-Xray sources with 179 detected in 24um( 20uJy, 3sigma), indicating that at most 25% of these IEROs are passively evolving.We derive and examine photometric redshift using different methods; their redshift range from 1 to 2.6 with the median value at 1.5. Stellar masses of non-Xray sources are also derived with SED fitting methods, achieving a median value of 0.4*1011 Msun for a chrabrier initial mass function. The properties of best-fitting BC03 models are consistent with templates used for estimating redshifts, which have on average E(B-V) of 0.5 for 24um-deteced galaxies. The corresponding star-formation rates of these star-forming galaxies through SED fitting are within 40-100 Msun yr-1, consistent with that derived from their 24?m flux, which show a median total infrared luminosity 1*1011Lsun. We argue that such selected IEROs may represent a transient population from ULIRGs to LIRGs, and are likely descents of SMGs or DOGs.

  8. Heterochrony in limb evolution: developmental mechanisms and natural selection.

    PubMed

    Richardson, Michael K; Gobes, Sharon M H; van Leeuwen, Anne C; Polman, Japke A E; Pieau, Claude; Sánchez-Villagra, Marcelo R

    2009-09-15

    The tetrapod limb provides several examples of heterochrony-changes in the timing of developmental events. These include species differences in the sequence of skeletal chondrogenesis, in gene transcription in the developing limbs, and in the relative time at which forelimb and hind limb buds develop. Here, we examine (i) phylogenetic trends in limb heterochrony; (ii) changes in developmental mechanisms that may lead to heterochrony; and (iii) the possible role that heterochrony plays in generating adaptive traits. We analyze the published literature and present preliminary data on turtle (Emys orbicularis) and bat (Rousettus amplexicaudatus) limb development. Teleosts, marsupials, and some urodeles show extreme timing differences between forelimb (or pectoral fin) and hind limb (or pelvic fin) development; this heterochrony may, in some cases, be adaptive. Published data on limb chondrogenesis reveal sequence elements that are strongly conserved (possibly owing to constraints); and others that vary between higher taxa (for unknown reasons). We find little evidence that chondrogenic sequences are modified by selection for limb functional traits. There are a few examples of developmental mechanisms that may be modified under heterochrony to produce adaptive changes in the limb (e.g. some cases of hyperphalangy or limb reduction). In conclusion, numerous examples of limb heterochrony have been recorded. However, few cases are obviously adaptive. Indeed, current data and methodologies make it difficult to identify the developmental changes, or selective pressures, that may underlie limb heterochrony. More integrative studies, including studies of heterochrony within populations, are needed to assess the role of timing shifts in limb evolution. PMID:19130597

  9. The paradoxical advantages and disadvantages of natural selection: the case history of Charles Darwin.

    PubMed

    Lieb, J

    2007-01-01

    The biology of natural selection is an enduring mystery, as is the nature of Charles Darwin's chronic illness. Of the theories advanced to explain the latter, Oedipal conflicts and Chagas' disease are preeminent. Hypomania, however, propelled Darwin to the pinnacle of scientific achievement and good health, the depression that followed condemning him to intellectual stagnation, lethargy, impaired memory and concentration, and incapacitating gastrointestinal disorders. Examples of natural selection in humans are much sought after when, ironically, one need look no further than Darwin himself. PMID:17499450

  10. SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES

    SciTech Connect

    Nigel Clark; Gregory Thompson; Richard Atkinson; Chamila Tissera; Matt Swartz; Emre Tatli; Ramprabhu Vellaisamy

    2005-01-01

    The research program conducted at the West Virginia University Engine and Emissions Research Laboratory (EERL) is working towards the verification and optimization of an approach to remove nitric oxides from the exhaust gas of lean burn natural gas engines. This project was sponsored by the US Department of Energy, National Energy Technology Laboratory (NETL) under contract number: DE-FC26-02NT41608. Selective NOx Recirculation (SNR) involves three main steps. First, NOx is adsorbed from the exhaust stream, followed by periodic desorption from the aftertreatment medium. Finally the desorbed NOx is passed back into the intake air stream and fed into the engine, where a percentage of the NOx is decomposed. This reporting period focuses on the NOx decomposition capability in the combustion process. Although researchers have demonstrated NOx reduction with SNR in other contexts, the proposed program is needed to further understand the process as it applies to lean burn natural gas engines. SNR is in support of the Department of Energy goal of enabling future use of environmentally acceptable reciprocating natural gas engines through NOx reduction under 0.1 g/bhp-hr. The study of decomposition of oxides of nitrogen (NOx) during combustion in the cylinder was conducted on a 1993 Cummins L10G 240 hp lean burn natural gas engine. The engine was operated at different air/fuel ratios, and at a speed of 800 rpm to mimic a larger bore engine. A full scale dilution tunnel and analyzers capable of measuring NOx, CO{sub 2}, CO, HC concentrations were used to characterize the exhaust gas. Commercially available nitric oxide (NO) was used to mimic the NOx stream from the desorption process through a mass flow controller and an injection nozzle. The same quantity of NOx was injected into the intake and exhaust line of the engine for 20 seconds at various steady state engine operating points. NOx decomposition rates were obtained by averaging the peak values at each set point minus the baseline and finding the ratio between the injected NO amounts. It was observed that the air/fuel ratio, injected NO quantity and engine operating points affected the NOx decomposition rates of the natural gas engine. A highest NOx decomposition rate of 27% was measured from this engine. A separate exploratory tests conducted with a gasoline engine with a low air/fuel ratio yielded results that suggested, that high NOx decomposition rates may be possible if a normally lean burn engine were operated at conditions closer to stoichiometric, with high exhaust gas recirculation (EGR) for a brief period of time during the NOx decomposition phase and with a wider range of air/fuel ratios. Chemical kinetic model predictions using CHEMKIN were performed to relate the experimental data with the established rate and equilibrium models. NOx decomposition rates from 35% to 42% were estimated using the CHEMKIN software. This provided insight on how to maximize NOx decomposition rates for a large bore engine. In the future, the modeling will be used to examine the effect of higher NO{sub 2}/NO ratios that are associated with lower speed and larger bore lean burn operation.

  11. Natural selection in the water: freshwater invasion and adaptation by water colour in the Amazonian pufferfish.

    PubMed

    Cooke, G M; Chao, N L; Beheregaray, L B

    2012-07-01

    Natural selection and ecological adaptation are ultimately responsible for much of the origin of biodiversity. Yet, the identification of divergent natural selection has been hindered by the spatial complexity of natural systems, the difficulty in identifying genes under selection and their relationship to environment, and the confounding genomic effects of time. Here, we employed genome scans, population genetics and sequence-based phylogeographic methods to identify divergent natural selection on population boundaries in a freshwater invader, the Amazonian pufferfish, Colomesus asellus. We sampled extensively across markedly different hydrochemical settings in the Amazon Basin and use 'water colour' to test for ecological isolation. We distinguish the relative contribution of natural selection across hydrochemical gradients from biogeographic history in the origin and maintenance of population boundaries within a single species and across a complex ecosystem. We show that spatially distinct population structure generated by multiple forces (i.e. water colour and vicariant biogeographic history) can be identified if the confounding effects of genetic drift have not accumulated between selective populations. Our findings have repercussions for studies aimed at identifying engines of biodiversity and assessing their temporal progression in understudied and ecologically complex tropical ecosystems. PMID:22551113

  12. 1000 Genomes Selection Browser 1.0: a genome browser dedicated to signatures of natural selection in modern humans

    PubMed Central

    Pybus, Marc; Dall’Olio, Giovanni M.; Luisi, Pierre; Uzkudun, Manu; Carreño-Torres, Angel; Pavlidis, Pavlos; Laayouni, Hafid; Bertranpetit, Jaume; Engelken, Johannes

    2014-01-01

    Searching for Darwinian selection in natural populations has been the focus of a multitude of studies over the last decades. Here we present the 1000 Genomes Selection Browser 1.0 (http://hsb.upf.edu) as a resource for signatures of recent natural selection in modern humans. We have implemented and applied a large number of neutrality tests as well as summary statistics informative for the action of selection such as Tajima’s D, CLR, Fay and Wu’s H, Fu and Li’s F* and D*, XPEHH, ?iHH, iHS, FST, ?DAF and XPCLR among others to low coverage sequencing data from the 1000 genomes project (Phase 1; release April 2012). We have implemented a publicly available genome-wide browser to communicate the results from three different populations of West African, Northern European and East Asian ancestry (YRI, CEU, CHB). Information is provided in UCSC-style format to facilitate the integration with the rich UCSC browser tracks and an access page is provided with instructions and for convenient visualization. We believe that this expandable resource will facilitate the interpretation of signals of selection on different temporal, geographical and genomic scales. PMID:24275494

  13. Redox-sensitivity and mobility of selected pharmaceutical compounds in a laboratory column experiment

    NASA Astrophysics Data System (ADS)

    Banzhaf, S.; Nödler, K.; Licha, T.; Krein, A.; Scheytt, T.

    2012-04-01

    Laboratory column experiments are suitable to investigate the sediment water interaction and to study the transport behaviour of solutes. Processes like retardation and degradation can be identified and quantified. The conducted experiment, which is closely connected to a field study in Luxembourg, investigated the transport behaviour of selected pharmaceutical compounds and their redox-dependent metabolism under water saturated conditions. Fine-grained natural sediment with a low hydraulic conductivity from a study site in Luxembourg was filled into the column. The water for the experiment was taken from a small stream at the same fieldsite. It was spiked with four pharmaceutical compounds (carbamazepine, diclofenac, ibuprofen, sulfamethoxazole) with concentrations between 170 and 300 ng/L for the different substances. The chosen pharmaceuticals were also detected in groundwater and surface water samples at the study site and used to qualify exchange/mixing of surface water and groundwater (BANZHAF et al., 2011). As some of the substances are known to exhibit redox-sensitive degradation, the redox-conditions were systematically varied throughout the experiment. This was realised by adding nitrate at the inflow of the column. During the experiment, which lasted for 2.5 months, four different nitrate concentrations (20-130 mg/L) were applied, beginning with the highest concentration. During the experiment water from the reservoir tank was sampled daily in order to detect a potential degradation of the pharmaceutical compounds before they enter the column. The effluent water was sampled every three hours to guarantee a maximum resolution for the analysis of the pharmaceuticals where necessary. In addition, major ions were analysed in the influent and effluent samples. Throughout the experiment physicochemical parameters (oxidation reduction potential (ORP), dissolved oxygen, electrical conductivity, and pH-value) were measured and logged at the outflow of the column. At the beginning, the ORP was positive (200 mV) and then dropped continuously. Negative values were reached after 1 month and at the end of the experiment -300 mV were measured. Apart from nitrate and nitrite no significant changes in ion concentrations were detected in the effluent. However, the added pharmaceuticals showed very different behaviour in the column. Diclofenac and especially carbamazepine were highly absorbed by the sediment. They were detected significantly later at the outflow of the column than sulfamethoxazole and ibuprofen. Sulfamethoxazole was heavily influenced by the redox-conditions. Its time variation curve in the effluent is negatively correlated with nitrite and nitrate: during nitrite formation the concentrations of sulfamethoxazole dropped considerably. The presented experiment yields a better understanding of the processes influencing the occurrence and transport behaviour of the studied compounds. In addition, some general findings on redox-dependent transport behaviour and metabolism of the antibiotic sulfamethoxazole are gained. This emphasizes the role of the ORP as a key parameter for the behaviour of this compound, which has to be considered. BANZHAF, S., KREIN, A. & SCHEYTT, T. (2011). Investigative approaches to determine exchange processes in the hyporheic zone of a low permeability riverbank. Hydrogeology Journal 19 (3), pp. 591-601.

  14. 113 Lab Learning Objectives Week 13: Information and Natural Selection lab #8

    E-print Network

    Campbell, A. Malcolm

    of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly in the population. · Design directed evolution process to select antibiotic resistant bacteria. · Formulate an hypothesis how antibiotic resistant bacteria evolve outside the laboratory. · Propose a mechanism that allows

  15. Effects of selected bioactive natural products on the vascular endothelium.

    PubMed

    Ahmad, Ajaz; Khan, Rao M A; Alkharfy, Khalid M

    2013-08-01

    The endothelium, a highly active structure, regulates vascular homeostasis through the release of numerous vasoactive factors that control vascular tone and vascular smooth cell proliferation. A larger number of medicinal plants and their isolated chemical constituents have been shown to beneficially affect the endothelium. For example, flavonoids in black tea, green tea, and concord grape cause a vasodilation possibly through their antioxidant properties. Allicin, a by-product of the enzyme alliinase, has been proposed to be the main active metabolite and responsible for most of the biological activities of garlic, including a dose-dependent dilation on the isolated coronaries. Thymoquinone, the principal phytochemical compound found in the volatile oil of the black seed, and the hawthorn extract have also been shown to improve aging-related impairment of endothelium-dependent relaxations in animal models. In this review, the effect of some of the natural products, including Camellia sinensis (black tea and green tea), Vitis labrusca (concord grape), Allium sativum (garlic), and Nigella sativa (black seed) and Crataegus ssp (hawthorn extract), is explored. The molecular mechanisms behind these potential therapeutic effects are also discussed. PMID:23599064

  16. The 'Natural Laboratory', a tool for deciphering growth, lifetime and population dynamics in larger benthic foraminifera

    NASA Astrophysics Data System (ADS)

    Hohenegger, Johann

    2015-04-01

    The shells of symbiont-bearing larger benthic Foraminifera (LBF) represent the response to physiological requirements in dependence of environmental conditions. All compartments of the shell such as chambers and chamberlets accommodate the growth of the cell protoplasm and are adaptations for housing photosymbiotic algae. Investigations on the biology of LBF were predominantly based on laboratory studies. The lifetime of LBF under natural conditions is still unclear. LBF, which can build >100 chambers during their lifetime, are thought to live at least one year under natural conditions. This is supported by studies on population dynamics of eulittoral foraminifera. In species characterized by a time-restricted single reproduction period the mean size of specimens increases from small to large during lifetime simultaneously reducing individual number. This becomes more complex when two or more reproduction times are present within a one-year cycle leading to a mixture of abundant small individuals with few large specimens during the year, while keeping mean size more or less constant. This mixture is typical for most sublittoral megalospheric (gamonts or schizonts) LBF. Nothing is known on the lifetime of agamonts, the diploid asexually reproducing generation. In all hyaline LBF it is thought to be significantly longer than 1 year based on the large size and considering the mean chamber building rate of the gamont/schizonts. Observations on LBF under natural conditions have not been performed yet in the deeper sublittoral. This reflects the difficulties due to intense hydrodynamics that hinder deploying technical equipment for studies in the natural environment. Therefore, studying growth, lifetime and reproduction of sublittoral LBF under natural conditions can be performed using the so-called 'natural laboratory' in comparison with laboratory investigations. The best sampling method in the upper sublittoral from 5 to 70 m depth is by SCUBA diving. Irregular sampling intervals caused by differing weather conditions may range from weeks to one month, whereby the latter represents the upper limit: larger intervals could render the data set worthless. The number of sampling points at the location must be more than 4, randomly distributed and approximately 5m apart to smooth the effects of patchy distributions, which are typical for most LBF. Only three simple measurements are necessary to determine chamber building rate and population dynamics under natural conditions. These are the number of individuals, number of chambers and the largest diameter of the individual. The determination of a standardized sample surface area, which is necessary for population dynamic investigations, depends on the sampling method. Reproduction and longevity can be estimated based on shell size using the date where the mean abundance of specimens with minimum size (expected after a one month's growth) characterizes the reproduction period. Then the difference to the date with the mean abundance of specimens characterized by large size indicating readiness for reproduction marks the life time. Calculation of the chamber-building rate based on chamber number is more complex and depends on the reproduction period and longevity. This can be fitted with theoretical growth functions (e.g. Michaelis Menten Function). According to the above mentioned methods, chamber building rates, longevity and population dynamics can be obtained for the shallow sublittoral symbiont-bearing LBF using the 'natural laboratory'.

  17. A highly selective biosynthetic pathway to non-natural C50 carotenoids assembled from moderately selective enzymes.

    PubMed

    Furubayashi, Maiko; Ikezumi, Mayu; Takaichi, Shinichi; Maoka, Takashi; Hemmi, Hisashi; Ogawa, Takuya; Saito, Kyoichi; Tobias, Alexander V; Umeno, Daisuke

    2015-01-01

    Synthetic biology aspires to construct natural and non-natural pathways to useful compounds. However, pathways that rely on multiple promiscuous enzymes may branch, which might preclude selective production of the target compound. Here, we describe the assembly of a six-enzyme pathway in Escherichia coli for the synthesis of C50-astaxanthin, a non-natural purple carotenoid. We show that by judicious matching of engineered size-selectivity variants of the first two enzymes in the pathway, farnesyl diphosphate synthase (FDS) and carotenoid synthase (CrtM), branching and the production of non-target compounds can be suppressed, enriching the proportion of C50 backbones produced. We then further extend the C50 pathway using evolved or wild-type downstream enzymes. Despite not containing any substrate- or product-specific enzymes, the resulting pathway detectably produces only C50 carotenoids, including ?90% C50-astaxanthin. Using this approach, highly selective pathways can be engineered without developing absolutely specific enzymes. PMID:26168783

  18. Natural selection in a population group of Andaman and Nicobar Islands

    PubMed Central

    Kapoor, Anup K.; Kaur, Jaspreet

    2012-01-01

    Background: Natural selection is a continuous process that operates in populations to weed out deleterious genes and preserve the genes that increase the chances of survival, procreation, and multiplication. The fitness of a population group is measured in terms of its differential fertility and mortality. These are the most fundamental events through which the natural selection is operative. Selection intensity, which is a measure of the fitness of a population, is expressed in terms of differential fertility, and differential mortality, assuming that the heritability of fitness is complete and that the birth and death rates are all selective. These indices are influenced by a number of socio-cultural conditions, religious, ethnic, and environmental factors which have been studied by different researchers in different parts of the world, including India. Objective: In this paper, an attempt was made to study the index of total selection, index of selection due to mortality, and index of selection due to fertility among the Andaman Indians, an island population of Andaman and Nicobar Islands and we highlight the variability of selection intensity in different ecological zones of India, namely the island, coastal, plains and plateau, Himalayan region, and the desert ecologies. Materials and Methods: Data were collected on pre-designed questionnaire, from women aged 40 + years, on various demographic parameters. Results: The value of the Index of Total Selection was found to be 1.263, the component due to fertility was 1.020, and that of mortality was found to be 0.120 PMID:22690055

  19. Natural hazard management high education: laboratory of hydrologic and hydraulic risk management and applied geomorphology

    NASA Astrophysics Data System (ADS)

    Giosa, L.; Margiotta, M. R.; Sdao, F.; Sole, A.; Albano, R.; Cappa, G.; Giammatteo, C.; Pagliuca, R.; Piccolo, G.; Statuto, D.

    2009-04-01

    The Environmental Engineering Faculty of University of Basilicata have higher-level course for students in the field of natural hazard. The curriculum provides expertise in the field of prediction, prevention and management of earthquake risk, hydrologic-hydraulic risk, and geomorphological risk. These skills will contribute to the training of specialists, as well as having a thorough knowledge of the genesis and the phenomenology of natural risks, know how to interpret, evaluate and monitor the dynamic of environment and of territory. In addition to basic training in the fields of mathematics and physics, the course of study provides specific lessons relating to seismic and structural dynamics of land, environmental and computational hydraulics, hydrology and applied hydrogeology. In particular in this course there are organized two connected examination arguments: Laboratory of hydrologic and hydraulic risk management and Applied geomorphology. These course foresee the development and resolution of natural hazard problems through the study of a real natural disaster. In the last year, the work project has regarded the collapse of two decantation basins of fluorspar, extracted from some mines in Stava Valley, 19 July 1985, northern Italy. During the development of the course, data and event information has been collected, a guided tour to the places of the disaster has been organized, and finally the application of mathematical models to simulate the disaster and analysis of the results has been carried out. The student work has been presented in a public workshop.

  20. Chemical composition of selected core samples, Idaho National Engineering Laboratory, Idaho

    SciTech Connect

    Knobel, L.L.; Cecil, L.D.; Wood, T.R.

    1995-11-01

    This report presents chemical compositions determined from 84 subsamples and 5 quality-assurance split subsamples of basalt core from the eastern Snake River Plain. The 84 subsamples were collected at selected depths from 5 coreholes located on the Idaho National Engineering Laboratory, Idaho. This report was jointly prepared by Lockheed Idaho Technologies Company and the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, Idaho Operations Office. Ten major elements and as many as 32 trace elements were determined for each subsample either by wavelength dispersive X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, or by both methods. Descriptive statistics for each element were calculated and tabulated by analytical method for each corehole.

  1. Host selection and lethality of attacks by sea lampreys (Petromyzon marinus) in laboratory studies

    USGS Publications Warehouse

    Swink, W.D.

    2003-01-01

    Parasitic-phase sea lampreys (Petromyzon marinus) are difficult to study in the wild. A series of laboratory studies (1984-1995) of single attacks on lake trout (Salvelinus namaycush), rainbow trout (Oncorhynchus mykiss), and burbot (Lota lota) examined host size selection; determined the effects of host size, host species, host strain, and temperature on host mortality; and estimated the weight of hosts killed per lamprey. Rainbow trout were more able and burbot less able to survive attacks than lake trout. Small sea lampreys actively selected the larger of two small hosts; larger sea lampreys attacked larger hosts in proportion to the hosts' body sizes, but actively avoided shorter hosts (??? 600 mm) when larger were available. Host mortality was significantly less for larger (43-44%) than for smaller hosts (64%). However, the yearly loss of hosts per sea lamprey was less for small hosts (range, 6.8-14.2 kg per sea lamprey) than larger hosts (range, 11.4-19.3 kg per sea lamprey). Attacks at the lower of two temperature ranges (6.1-11.8??C and 11.1-15.0??C) did not significantly reduce the percentage of hosts killed (54% vs. 69%, p > 0.21), but longer attachment times at lower temperatures reduced the number of hosts attacked (33 vs. 45), and produced the lowest loss of hosts (6.6 kg per sea lamprey). Low temperature appeared to offset other factors that increase host mortality. Reanalysis of 789 attacks pooled from these studies, using forward stepwise logistic regression, also identified mean daily temperature as the dominant factor affecting host mortality. Observations in Lakes Superior, Huron, and Ontario support most laboratory results.

  2. Host selection and lethality of attacks by sea lampreys (Petromyzon marinus) in laboratory studies

    USGS Publications Warehouse

    Swink, William D.

    2003-01-01

    Parasitic-phase sea lampreys (Petromyzon marinus) are difficult to study in the wild. A series of laboratory studies (1984-1995) of single attacks on lake trout (Salvelinus namaycush), rainbow trout (Oncorhynchus mykiss), and burbot (Lota lota) examined host size selection; determined the effects of host size, host species, host strain, and temperature on host mortality; and estimated the weight of hosts killed per lamprey. Rainbow trout were more able and burbot less able to survive attacks than lake trout. Small sea lampreys actively selected the larger of two small hosts; larger sea lampreys attacked larger hosts in proportion to the hosts' body sizes, but actively avoided shorter hosts (a?? 600 mm) when larger were available. Host mortality was significantly less for larger (43-44%) than for smaller hosts (64%). However, the yearly loss of hosts per sea lamprey was less for small hosts (range, 6.8-14.2 kg per sea lamprey) than larger hosts (range, 11.4-19.3 kg per sea lamprey). Attacks at the lower of two temperature ranges (6.1-11.8A?C and 11.1-15.0A?C) did not significantly reduce the percentage of hosts killed (54% vs. 69%, p > 0.21), but longer attachment times at lower temperatures reduced the number of hosts attacked (33 vs. 45), and produced the lowest loss of hosts (6.6 kg per sea lamprey). Low temperature appeared to offset other factors that increase host mortality. Reanalysis of 789 attacks pooled from these studies, using forward stepwise logistic regression, also identified mean daily temperature as the dominant factor affecting host mortality. Observations in Lakes Superior, Huron, and Ontario support most laboratory results.

  3. Mobile laboratory measurements of atmospheric emissions from agriculture, oil, and natural gas activities in northeastern Colorado

    NASA Astrophysics Data System (ADS)

    Eilerman, S. J.; Peischl, J.; Neuman, J. A.; Ryerson, T. B.; Wild, R. J.; Perring, A. E.; Brown, S. S.; Aikin, K. C.; Holloway, M.; Roberts, O.

    2014-12-01

    Atmospheric emissions from agriculture are important to air quality and climate, yet their representation in inventories is incomplete. Increased fertilizer use has lead to increased emissions of nitrogen compounds, which can adversely affect ecosystems and contribute to the formation of fine particulates. Furthermore, extraction and processing of oil and natural gas continues to expand throughout northeastern Colorado; emissions from these operations require ongoing measurement and characterization. This presentation summarizes initial data and analysis from a summer 2014 campaign to study emissions of nitrogen compounds, methane, and other species in northeastern Colorado using a new mobile laboratory. A van was instrumented to measure NH3, N2O, NOx, NOy, CH4, CO, CO2, O3, and bioaerosols with high time resolution. By sampling in close proximity to a variety of emissions sources, the mobile laboratory facilitated accurate source identification and quantification of emissions ratios. Measurements were obtained near agricultural sites, natural gas and oil operations, and other point sources. Additionally, extensive measurements were obtained downwind from urban areas and along roadways. The relationship between ammonia and other trace gases is used to characterize sources and constrain emissions inventories.

  4. The response of natural enemies to selective insecticides applied to soybean.

    PubMed

    Varenhorst, A J; O'Neal, M E

    2012-12-01

    Natural enemies of the invasive pest Aphis glycines Matsumura can prevent its establishment and population growth. However, current A. glycines management practices include the application of broad-spectrum insecticides that affect pests and natural enemies that are present in the field at the time of application. An alternative is the use of selective insecticides that affect the targeted pest species, although having a reduced impact on the natural enemies. We tested the effects of esfenvalerate, spirotetramat, imidacloprid, and a combination of spirotetramat and imidacloprid on the natural enemies in soybean during the 2009 and 2010 field season. The natural enemy community that was tested differed significantly between 2009 and 2010 (F = 87.41; df = 1, 598; P < 0.0001). The most abundant natural enemy in 2009 was Harmonia axyridis (Pallas) (56.0%) and in 2010 was Orius insidiosus (Say) (41.0%). During 2009, the abundance of natural enemies did not vary between the broad-spectrum and selective insecticides; however, the abundance of natural enemies was reduced by all insecticide treatments when compared with the untreated control. In 2010, the selective insecticide imidacloprid had more natural enemies than the broad-spectrum insecticide. Although we did not observe a difference in the abundance of the total natural enemy community in 2009, we did observe more H. axyridis in plots treated with spirotetramat. In 2010, we observed more O. insidiosus in plots treated with imidacloprid. We suggest a couple of mechanisms to explain how the varying insecticides have different impacts on separate components of the natural enemy community. PMID:23321105

  5. Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Tests - 2011

    SciTech Connect

    Pawloski, G A

    2011-02-28

    This report evaluates collapse evolution for selected Lawrence Livermore National Laboratory (LLNL) underground nuclear tests at the Nevada National Security Site (NNSS, formerly called the Nevada Test Site). The work is being done at the request of National Security Technologies, LLC (NSTec) and supports the Department of Energy, National Nuclear Security Administration for the Nevada Site Office Borehole Management Program (BMP). The primary objective of this program is to close (plug) weapons program legacy boreholes that are deemed no longer useful. Safety decisions must be made before a crater area, or potential crater area, can be reentered for any work. Our statements on cavity collapse and crater formation are input into their safety decisions. The BMP is an on-going program to address hundreds of boreholes at the NTS. Each year NSTec establishes a list of holes to be addressed. They request the assistance of the Lawrence Livermore National Laboratory and Los Alamos National Laboratory Containment Programs to provide information related to the evolution of collapse history and make statements on completeness of collapse as relates to surface crater stability. These statements do not include the effects of erosion that may modify the collapse craters over time. They also do not address possible radiation dangers that may be present. Subject matter experts from the LLNL Containment Program who had been active in weapons testing activities performed these evaluations. Information used included drilling and hole construction, emplacement and stemming, timing and sequence of the selected test and nearby tests, geology, yield, depth of burial, collapse times, surface crater sizes, cavity and crater volume estimations, ground motion, and radiological release information. Both classified and unclassified data were reviewed. Various amounts of information are available for these tests, depending on their age and other associated activities. Lack of data can hamper evaluations and introduce uncertainty. We make no attempt to quantify this uncertainty. The following unclassified summary statements describe collapse evolution and crater stability in response to a recent request to review 3 LLNL test locations in areas 2 and 12: Kennebec in U2af, Cumberland in U2e, and Yuba in U12b.10.

  6. Gas detection and migration in geological media: lessons learned from the Roselend Natural Laboratory (Invited)

    NASA Astrophysics Data System (ADS)

    Pili, E.; Guillon, S.; Agrinier, P.; Sabroux, J.; Adler, P. M.

    2013-12-01

    The Roselend Natural Laboratory (French Alps) is a unique facility for studying gas transport in the subsurface and across the geosphere-atmosphere interface. At 55 m depth, a sealed cavity allows for gas release experiments across fractured porous rocks in the unsaturated zone. While many parameters controlling the state of the geological system are known, analogous gas-tracer experiments were conducted at the field-scale with SF6 and 3He. Water infiltration, permeability and the concentrations of many gases, naturally occurring or injected, are recorded via long-term and high-resolution monitoring. The fracture network is characterized thanks to extensive drilling, logging and modeling. These experiments are used to determine the physical and chemical processes that would control the noble gas source term after an underground nuclear explosion in the framework of the Comprehensive nuclear-Test-Ban Treaty (CTBT) and to develop and validate the corresponding numerical models. The Roselend Natural Laboratory also provides a test bed for sampling protocols and instrument developments. Detection of gases relevant to CTBT issues requires that their baseline concentration is understood. Experiments and subsequent modeling demonstrated that baselines are a highly dynamical process resulting from gas sources, sinks and modulation by barometric pressure and water movements. Gas migration from underground cavities occurs as early venting through fractures due to advection driven by gas overpressure. It is associated with very large dilution which requires very low detection limits. Late-time seepage occurs through fractured porous media thanks to barometric pumping, which is only efficient for a narrow window of parameter values. Full calculation for real fractured porous media is now available.

  7. Laboratory and field evaluation of spinosad, a biorational natural product, against larvae of Culex mosquitoes.

    PubMed

    Jiang, Yongxing; Mulla, Mir S

    2009-12-01

    Spinosad, a fermentation product from the naturally occurring soil actinomycete bacterium Saccharopolyspora spinosa, has been reported to have a high level of activity against phytophagous insects and insects impacting human and animal health. It has low mammalian toxicity and a favorable environmental profile, including low persistence and no toxicity to fish and wildlife at mosquito larvicidal rates. In order to determine the activity and efficacy of spinosad against larvae of Culex mosquitoes, technical powder and liquid formulations of spinosad were tested against mosquito larvae under laboratory and field conditions. In the laboratory, spinosad powder was highly active against 2nd and 4th instars of Culex quinquefasciatus after 24 h of exposure. The extent of mortality increased slightly after 48 h of exposure. Second instars were slightly more susceptible than 4th instars. The liquid formulation showed somewhat higher activity (about 2x) than the technical powder material at both the LCs50 and LC90 levels. In field microcosm tests against natural populations of mosquitoes, the liquid formulation yielded excellent control of immature Culex spp. for 21 days at concentrations of 0.05 mg (AI)/liter and 35 days at 0.1 to 0.5 mg (AI)/liter in outdoor tubs. This formulation also yielded excellent control of natural Culex mosquitoes for 14 days or longer at 0.025 to 0.1 mg (AI)/liter in outdoor ponds. From our data, it appears that spinosad as a new mode of action has a good potential for controlling mosquito larvae. PMID:20099593

  8. Synergism of natural selection and introgression in the origin of a new species.

    PubMed

    Grant, Peter R; Grant, B Rosemary

    2014-05-01

    This article explores how introgressive hybridization enhances the evolutionary effects of natural selection and how, reciprocally, natural selection can enhance the evolutionary effects of introgression. Both types of interaction were observed during a 40-year study of Darwin's finches (Geospiza) on the small Galápagos island of Daphne Major. Hybrids, produced rarely by Geospiza fortis (medium ground finch) breeding with Geospiza scandens (cactus finch) and Geospiza fuliginosa (small ground finch), survived and bred as well as the parental species in the past 3 decades. By backcrossing, they increased the standing genetic variation and thereby the evolutionary responsiveness of the populations to natural selection. Natural selection occurred in droughts and oscillated in direction as a result of climatically induced fluctuations in food composition. Introgressive hybridization has led to the formation of a new lineage. It was initiated by a large, introgressed, hybrid male with a unique song and genetic marker that immigrated from the nearby island of Santa Cruz and bred with local hybrids and with G. fortis. All members of the lineage died in the 2003-2005 drought except a brother and a sister, who then bred with each other. Subsequent increase in the lineage was facilitated by selective mortality of the largest G. fortis. Breeding endogamously, the lineage is behaving as a biological species. PMID:24739199

  9. Maintenance of a genetic polymorphism with disruptive natural selection in stickleback.

    PubMed

    Marchinko, Kerry B; Matthews, Blake; Arnegard, Matthew E; Rogers, Sean M; Schluter, Dolph

    2014-06-01

    The role of natural selection in the maintenance of genetic variation in wild populations remains a major problem in evolution. The influence of disruptive natural selection on genetic variation is especially interesting because it might lead to the evolution of assortative mating or dominance [1, 2]. In theory, variation can persist at a gene under disruptive natural selection, but the process is little studied and there are few examples [3, 4]. We report a stable polymorphism in the bony armor of threespine stickleback maintained with a deficit of heterozygotes at the major underlying gene, Ectodysplasin (Eda) [5]. The deficit vanishes at the embryo life stage only to re-emerge in adults, indicating that disruptive natural selection, rather than nonrandom mating, is the cause. The mechanism enabling long-term persistence of the polymorphism is unknown, but disruptive selection is predicted to be frequency dependent, favoring homozygous genotypes when they become rare. Further research on the ecological and evolutionary processes affecting individual genes will ultimately lead to a better understanding of the causes of genetic variation in populations. PMID:24856211

  10. Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

    Microsoft Academic Search

    Nigel N. Clark

    2006-01-01

    Nitric oxide (NO) and nitrogen dioxide (NO2) generated by internal combustion (IC) engines are implicated in adverse environmental and health effects. Even though lean-burn natural gas engines have traditionally emitted lower oxides of nitrogen (NOx) emissions compared to their diesel counterparts, natural gas engines are being further challenged to reduce NOx emissions to 0.1 g\\/bhp-hr. The Selective NOx Recirculation (SNR)

  11. Strong natural selection during plant restoration favors an unexpected suite of plant traits

    PubMed Central

    Kulpa, Sarah M; Leger, Elizabeth A

    2013-01-01

    Restoration is an opportunity to study natural selection: One can measure the distribution of traits in source propagules used to found populations, compare this with the distribution of traits in successful recruits, and determine the strength and direction of selection on potentially adaptive traits. We investigated whether natural selection influenced seedling establishment during postfire restoration in the Great Basin, an area where large-scale restoration occurs with a few widely available cultivars planted over a large range of environmental conditions. We collected seeds from established plants of the perennial grass Elymus elymoides ssp. californicus (squirreltail) at two restoration sites and compared the distribution of phenotypic traits of surviving plants with the original pool of restoration seeds. Seeds were planted in common gardens for two generations. Plants grown from seeds that established in the field were a nonrandom subset of the original seeds, with directional selection consistently favoring a correlated suite of traits in both field sites: small plant and seed size, and earlier flowering phenology. These results demonstrate that natural selection can affect restoration establishment in strong and predictable ways and that adaptive traits in these sites were opposite of the current criteria used for selection of restoration material in this system. PMID:23745142

  12. Strong natural selection during plant restoration favors an unexpected suite of plant traits.

    PubMed

    Kulpa, Sarah M; Leger, Elizabeth A

    2013-04-01

    RESTORATION IS AN OPPORTUNITY TO STUDY NATURAL SELECTION: One can measure the distribution of traits in source propagules used to found populations, compare this with the distribution of traits in successful recruits, and determine the strength and direction of selection on potentially adaptive traits. We investigated whether natural selection influenced seedling establishment during postfire restoration in the Great Basin, an area where large-scale restoration occurs with a few widely available cultivars planted over a large range of environmental conditions. We collected seeds from established plants of the perennial grass Elymus elymoides ssp. californicus (squirreltail) at two restoration sites and compared the distribution of phenotypic traits of surviving plants with the original pool of restoration seeds. Seeds were planted in common gardens for two generations. Plants grown from seeds that established in the field were a nonrandom subset of the original seeds, with directional selection consistently favoring a correlated suite of traits in both field sites: small plant and seed size, and earlier flowering phenology. These results demonstrate that natural selection can affect restoration establishment in strong and predictable ways and that adaptive traits in these sites were opposite of the current criteria used for selection of restoration material in this system. PMID:23745142

  13. Contemporary evolution during invasion: evidence for differentiation, natural selection, and local adaptation.

    PubMed

    Colautti, Robert I; Lau, Jennifer A

    2015-05-01

    Biological invasions are 'natural' experiments that can improve our understanding of contemporary evolution. We evaluate evidence for population differentiation, natural selection and adaptive evolution of invading plants and animals at two nested spatial scales: (i) among introduced populations (ii) between native and introduced genotypes. Evolution during invasion is frequently inferred, but rarely confirmed as adaptive. In common garden studies, quantitative trait differentiation is only marginally lower (~3.5%) among introduced relative to native populations, despite genetic bottlenecks and shorter timescales (i.e. millennia vs. decades). However, differentiation between genotypes from the native vs. introduced range is less clear and confounded by nonrandom geographic sampling; simulations suggest this causes a high false-positive discovery rate (>50%) in geographically structured populations. Selection differentials (¦s¦) are stronger in introduced than in native species, although selection gradients (¦?¦) are not, consistent with introduced species experiencing weaker genetic constraints. This could facilitate rapid adaptation, but evidence is limited. For example, rapid phenotypic evolution often manifests as geographical clines, but simulations demonstrate that nonadaptive trait clines can evolve frequently during colonization (~two-thirds of simulations). Additionally, QST -FST studies may often misrepresent the strength and form of natural selection acting during invasion. Instead, classic approaches in evolutionary ecology (e.g. selection analysis, reciprocal transplant, artificial selection) are necessary to determine the frequency of adaptive evolution during invasion and its influence on establishment, spread and impact of invasive species. These studies are rare but crucial for managing biological invasions in the context of global change. PMID:25891044

  14. Natural Selection

    NSDL National Science Digital Library

    The Concord Consortium

    2011-12-11

    The concept of interdependence in an ecosystem and its effect on the evolution of populations is further explored through a model of a dam. Students build a dam in the middle of the field, dividing the ecosystem in half to illustrate the affects of geographic isolation. They watch as the grass and then the rabbit populations in that region shift to one variant in the population. When students remove the dam, they observe the ecosystem slowly return to its original state.

  15. Natural and laboratory compaction bands in porous carbonates: a three-dimensional characterization using synchrotron X-ray computed microtomography

    NASA Astrophysics Data System (ADS)

    Cilona, A.; Arzilli, F.; Mancini, L.; Emanuele, T.

    2014-12-01

    Porous carbonates form important reservoirs for water and hydrocarbons. The fluid flow properties of carbonate reservoirs may be affected by post-depositional processes (e.g., mechanical and chemical), which need to be quantified. Field-based studies described bed-parallel compaction bands (CBs) within carbonates with a wide range of porosities. These burial-related structures accommodate volumetric strain by grain rotation, translation, pore collapse and pressure solution. Recently, the same structures have been reproduced for the first time in the laboratory by performing triaxial compaction experiments on porous grainstones. These laboratory studies characterized and compared the microstructures of natural and laboratory CBs, but no analysis of pore connectivity has been performed. In this paper, we use an innovative approach to characterize the pore networks (e.g. porosity, connectivity) of natural and laboratory CBs and compare them with the host rock one. We collected the data using the synchrotron X-ray computed microtomography technique at the SYRMEP beamline of the Elettra-Sincrotrone Trieste Laboratory (Italy). Quantitative analyses of the samples were performed with the Pore3D software library. The porosity was calculated from segmented 3D images of pristine and deformed carbonates. A process of skeletonization was then applied to quantify the number of connected pores within the rock volume. The analysis of the skeleton allowed us to highlight the differences between natural and laboratory CBs, and to investigate how pore connectivity evolves as a function of different deformation pathways. Both pore volume and connectivity are reduced within the CBs respect to the pristine rock and the natural CB has a lower porosity with respect to the laboratory one. The grain contacts in the natural CB are welded, whereas in the laboratory one they have more irregular shapes and grain crushing is the predominant process.

  16. Elimination of laboratory-acquired cadmium by the oyster Crassostrea virginica in the natural environment

    SciTech Connect

    Mowdy, D.E.

    1981-03-01

    Many productive shellfish-growing areas along the coast of the United States are closed because of pollution from domestic and industrial wastes. Many estuarine areas that are closed to shellfish harvesting because of bacterial pollution contain productive shellfish beds. These shellfish can be used as commercial food products after they have been relayed to approved growing waters and allowed to eliminate the polluting organisms. Relaying is not presently applied to shellfish contaminated with toxic metals for several reasons: There are no standards to control metal pollution (other than mercury) in seafood; few public health problems in this country involve toxic levels of trace metals in oysters; and not enough information is available to indicate the feasibility of such a project. This study demonstrates the feasibility of relaying cadmium-contaminated oysters to observe cadmium elimination. Because oysters containing naturally acquired cadmium were not readily available, oysters containing laboratory-incurred cadmium were studied.

  17. 3D Magnetic Reconnection and Turbulence Study on Natural and Laboratory Plasmas at RSX

    NASA Astrophysics Data System (ADS)

    Liu, D. T.; Intrator, T. P.; Weber, T. E.; Sears, J. A.; Adams, C. S.; Los Alamos Nat'l Lab Team

    2011-10-01

    In natural and laboratory plasmas, magnetic reconnection and turbulence are difficult 3-dimensional problems and data from the Reconnection Scaling Experiment (RSX) can help address these questions. The data from RSX are fully 3D (no symmetries)and capture the unsteady, dynamic plasma physics of colliding flux ropes that reconnect and form turbulent modes. Data obtained from RSX via B-dot and triple Langmuir probes will be used to determine the time-integrated magnetic field, plasma density, floating potential, and electrostatic field. Additionally, there exist related reconnection and turbulence data from spacecraft that must be downloaded and distilled from large, cumbersome datasets, a process hampered by low telemetry rates. Simulated spacecraft trajectories through the RSX datasets provide insight for data acquisition, analysis, and download aboard spacecraft missions. Supported by US DOE OFES under a National Undergraduate Fellowship, DE-AC52-06NA25396 and NASA grant NNH10A044.

  18. Laser system for natural gas detection. Phase 1: Laboratory feasibility studies

    NASA Technical Reports Server (NTRS)

    Grant, W. B.; Hinkley, E. D., Jr.

    1982-01-01

    This project demonstrated the feasibility of using laser remote sensing technology as a tool for leak survey work in natural gas distribution systems. A laboratory device was assembled using a pair of helium neon (HeNe) lasers to measure methane. One HeNe laser emits radiation at a wavelength of 3.3922 micrometers, which corresponds to a strong absorption feature of methane, while the other emits radiation at a wavelength of 3.3911 micrometers, which corresponds to a weak absorption by methane. As a particular area is scanned for leaks, the laser is pointed at convenient topographic targets within its operating range, about 25 m. A portion of the backscattered radiation is collected by a receiver and focused onto an indium antimonide (InSb) photodetector, cooled to 77K. Methane concentrations were determined from the differential absorption at the two wavelengths for the backscattered radiation.

  19. Misconceptions about the Concept of Natural Selection by Medical Biology Students.

    ERIC Educational Resources Information Center

    Brumby, Margaret N.

    1984-01-01

    Examined Australian medical school students' (N=150) conceptual frameworks and reasoning patterns related to natural selection. Results indicate that the majority believed that evolutionary changes occur as a result of need. Implications related to student learning and to science and medical education are considered. (JN)

  20. Mutation pressure, natural selection, and the evolution of base composition in Drosophila

    Microsoft Academic Search

    Hiroshi Akashi; Richard M. Kliman

    1998-01-01

    Genome sequencing in a number of taxa has revealed variation in nucleotide composition both among regions of the genome and among functional classes of sites in DNA. Mutational biases, biased gene conversion, and natural selection have been proposed as causes of this variation. Here, we review patterns of base composition in Drosophila DNA. Nucleotide composition in Drosophila melanogastervarys regionally, and

  1. Young children can be taught basic natural selection using a picture-storybook intervention.

    PubMed

    Kelemen, Deborah; Emmons, Natalie A; Seston Schillaci, Rebecca; Ganea, Patricia A

    2014-04-01

    Adaptation by natural selection is a core mechanism of evolution. It is also one of the most widely misunderstood scientific processes. Misconceptions are rooted in cognitive biases found in preschoolers, yet concerns about complexity mean that adaptation by natural selection is generally not comprehensively taught until adolescence. This is long after untutored theoretical misunderstandings are likely to have become entrenched. In a novel approach, we explored 5- to 8-year-olds' capacities to learn a basic but theoretically coherent mechanistic explanation of adaptation through a custom storybook intervention. Experiment 1 showed that children understood the population-based logic of natural selection and also generalized it. Furthermore, learning endured 3 months later. Experiment 2 replicated these results and showed that children understood and applied an even more nuanced mechanistic causal explanation. The findings demonstrate that, contrary to conventional educational wisdom, basic natural selection is teachable in early childhood. Theory-driven interventions using picture storybooks with rich explanatory structure are beneficial. PMID:24503874

  2. Genetic Programming as a Means for Programming Computers by Natural Selection

    E-print Network

    Fernandez, Thomas

    Genetic Programming as a Means for Programming Computers by Natural Selection JOHN R. KOZA Computer developed genetic programming paradigm described herein provides a way to search the space of possible) a surprising variety of different problems from different fields. In genetic programming, populations

  3. The natural history of hypotheses about the selection task: towards a philosophy of science

    E-print Network

    van Lambalgen, Michiel

    The natural history of hypotheses about the selection task: towards a philosophy of science of the dif- ficulties subjects have with the task are closely related to Popper's philosophy of science in the intervening years. Pop- per's philosophy of science is widely believed to be an at best partial account

  4. Instructional Design Consequences of an Analogy between Evolution by Natural Selection and Human Cognitive Architecture

    ERIC Educational Resources Information Center

    Sweller, John

    2004-01-01

    Evolution by natural selection may be characterized as a system in which a large store of genetic information will persist indefinitely while it remains coordinated with its environment but will continuously produce small random variations that are tested for environmental effectiveness. In any environment, effective variations will persist while…

  5. 2002 Nature Publishing Group Selective cell suicide is crucial for sculpting the embryo,

    E-print Network

    Gauthier, Eric

    © 2002 Nature Publishing Group REVIEWS Selective cell suicide is crucial for sculpting the embryo apoptosis is a crucial step in tumorigenesis. Indeed, a defective suicide programme endows nascent-being and decide whether the suicide pro- gramme should be activated? Re-evaluation of this hotly debated issue8

  6. The Interface Theory of Perception: Natural Selection Drives True Perception To Swift Extinction

    E-print Network

    Stanford, Kyle

    The Interface Theory of Perception: Natural Selection Drives True Perception To Swift Extinction Donald D. Hoffman #12;#12;1 The Interface Theory of Perception A goal of perception is to estimate true shaped our senses to this end. These three assumptions motivate much work on human perception. I here

  7. Aging is Neither a Failure nor an Achievement of Natural Selection.

    PubMed

    Aledo, Juan Carlos; Blanco, Jose Maria

    2015-01-01

    In contraposition to the view of aging as a stochastic time-dependent accumulation of damage, phenoptotic theories of aging postulate that senescence may provide supra-individual advantages, and therefore it might have been promoted by natural selection. We reason that although programmed aging theories are subjectively appealing because they convey a cure for aging, they also raise a number of objections that need to be dealt with, before we may be entitled to contemplate aging as an adaptive function evolved through natural selection. As an alternative view, we present metabolism as an endless source of by-products and errors causing cellular damage. Although this damage accumulation event is a spontaneous entropy-driven process, its kinetics can be genetically and environmentally modulated, giving place to the wide range of lifespans we observe. Mild forms of damage may be accumulating during a long enough period of time to allow reproduction before the fatal failure happens. Hence, aging would be a stochastic process out of the reach of natural selection. However, those genetic pathways influencing the rate of aging and consequently determining longevity may be targets of natural selection and may contribute to shaping the optimal strategy according to the ecological context. In this sense, short- and long-lived organisms represent two extreme strategies that, in terms of biological fitness, can perform equally well, each within its own niche. PMID:26054343

  8. Natural selection and genetic differentiation of behaviour between parasitoids from wild

    E-print Network

    van Nouhuys, Saskya

    Pieridae. In the study area the only host of C. glomerata is the Small Cabbage White Butter¯y [Pieris rapae adaptation of wasps to either habitat. Keywords: Cotesia glomerata, evolution, foraging behaviour, Pieris rapae, tritrophic interaction. Introduction Natural selection in dierent habitat types can lead

  9. Human vs. Computer Diagnosis of Students' Natural Selection Knowledge: Testing the Efficacy of Text Analytic Software

    ERIC Educational Resources Information Center

    Nehm, Ross H.; Haertig, Hendrik

    2012-01-01

    Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements (or Key Concepts) that comprise undergraduate students' explanatory models of natural selection with…

  10. Impact of gene expression noise on organismal fitness and the efficacy of natural selection

    E-print Network

    Zhang, Jianzhi

    Impact of gene expression noise on organismal fitness and the efficacy of natural selection Zhi, and approved February 24, 2011 (received for review January 5, 2011) Gene expression noise is a universal overexpres- sion. (ii) Higher sensitivity of fitness to the expression fluctuations of essential genes than

  11. Supervised and Unsupervised Feature Selection for Inferring Social Nature of Telephone Conversations

    E-print Network

    Shafran, Izhak

    Supervised and Unsupervised Feature Selection for Inferring Social Nature of Telephone of telephone conversations opens up a variety of applications, ranging from designing context-sensitive user of everyday telephone conversations collected from eight residences over the duration of a year, we

  12. Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

    NASA Astrophysics Data System (ADS)

    Gomberg, Joan; Schulz, William; Bodin, Paul; Kean, Jason

    2011-09-01

    We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

  13. Seismic and geodetic signatures of fault slip at the Slumgullion Landslide Natural Laboratory

    USGS Publications Warehouse

    Gomberg, J.; Schulz, W.; Bodin, P.; Kean, J.

    2011-01-01

    We tested the hypothesis that the Slumgullion landslide is a useful natural laboratory for observing fault slip, specifically that slip along its basal surface and side-bounding strike-slip faults occurs with comparable richness of aseismic and seismic modes as along crustal- and plate-scale boundaries. Our study provides new constraints on models governing landslide motion. We monitored landslide deformation with temporary deployments of a 29-element prism array surveyed by a robotic theodolite and an 88-station seismic network that complemented permanent extensometers and environmental instrumentation. Aseismic deformation observations show that large blocks of the landslide move steadily at approximately centimeters per day, possibly punctuated by variations of a few millimeters, while localized transient slip episodes of blocks less than a few tens of meters across occur frequently. We recorded a rich variety of seismic signals, nearly all of which originated outside the monitoring network boundaries or from the side-bounding strike-slip faults. The landslide basal surface beneath our seismic network likely slipped almost completely aseismically. Our results provide independent corroboration of previous inferences that dilatant strengthening along sections of the side-bounding strike-slip faults controls the overall landslide motion, acting as seismically radiating brakes that limit acceleration of the aseismically slipping basal surface. Dilatant strengthening has also been invoked in recent models of transient slip and tremor sources along crustal- and plate-scale faults suggesting that the landslide may indeed be a useful natural laboratory for testing predictions of specific mechanisms that control fault slip at all scales.

  14. In situ and laboratory toxicity of coalbed natural gas produced waters with elevated sodium bicarbonate

    USGS Publications Warehouse

    Farag, Aida M.; Harper, David D.; Skaar, Don

    2014-01-01

    Some tributaries in the Powder River Structural Basin, USA, were historically ephemeral, but now contain water year round as a result of discharge of coalbed natural gas (CBNG)-produced waters. This presented the opportunity to study field sites with 100% effluent water with elevated concentrations of sodium bicarbonate. In situ experiments, static renewal experiments performed simultaneously with in situ experiments, and static renewal experiments performed with site water in the laboratory demonstrated that CBNG-produced water reduces survival of fathead minnow (Pimephales promelas) and pallid sturgeon (Scaphirhynchus albus). Age affected survival of fathead minnow, where fish 2 d posthatch (dph) were more sensitive than 6 dph fish, but pallid sturgeon survival was adversely affected at both 4 and 6 dph. This may have implications for acute assays that allow for the use of fish up to 14 dph. The survival of early lifestage fish is reduced significantly in the field when concentrations of NaHCO3 rise to more than 1500?mg/L (also expressed as >1245?mg HCO3 (-) /L). Treatment with the Higgin's Loop technology and dilution of untreated water increased survival in the laboratory. The mixing zones of the 3 outfalls studied ranged from approximately 800?m to 1200?m below the confluence. These experiments addressed the acute toxicity of effluent waters but did not address issues related to the volumes of water that may be added to the watershed.

  15. Selection of an omnivorous diet by the mangrove tree crab Aratus pisonii in laboratory experiments

    NASA Astrophysics Data System (ADS)

    Erickson, Amy A.; Feller, Ilka C.; Paul, Valerie J.; Kwiatkowski, Lisa M.; Lee, Woody

    2008-02-01

    Observational studies on leaf damage, gut content analyses, and crab behaviour have demonstrated that like numerous other mangrove and salt-marsh generalists, the mangrove tree crab Aratus pisonii feeds on a variety of food resources. This study is the first that experimentally tests feeding preferences of A. pisonii, as well as the first to test experimentally whether chemical composition of food resources is responsible for food selection. Feeding preferences were determined among a variety of plant, algal, and animal resources available in the field both in Florida and Belize, using multiple-choice feeding assays, where male and female crabs simultaneously were offered a variety of food items. To test whether chemistry of food resources was responsible for feeding preferences, chemical extracts of food resources were incorporated in an agar-based artificial food, and used in feeding assays. Results of feeding assays suggest that crabs prefer animal matter from ˜ 2.5 to 13× more than other available resources, including leaves of the red mangrove Rhizophora mangle, which contribute the most to their natural diet. Artificial feeding assays also demonstrated that chemical cues were responsible for selection of animal matter, up to 25× more than other available resources. Non-polar extracts (derived from extraction in 1:1 ethyl actetate:methanol) stimulated feeding the most, suggesting that fatty acids, triglycerides, or sterols may be important for growth, reproduction, or survival. Results for both sexes were similar across most assays. While chemical composition of food resources appears to play some role in selection, this does not discount the potential role of other factors, such as resource availability, competition, predation, or reproductive requirements in influencing feeding preferences. Bioassay-guided fractionation of extracts should aid in determining chemical constituents that play the greatest role in determining feeding preferences.

  16. The realized effect of postpollination sexual selection in a natural plant population.

    PubMed Central

    Krauss, S L

    2000-01-01

    The ultimate importance of postpollination sexual selection has remained elusive, largely because of the difficulty of assigning paternity in the field. Here I use a powerful new molecular marker (AFLP) for paternity analysis in a natural population of the outcrossing angiosperm Persoonia mollis (Proteaceae) to assess male reproductive success following equal pollination of 15 pollen donors on each of 6310 pistils. These results were contrasted with male reproductive success of these same plants following natural mating. Following equal pollination, there was a significant departure from equal siring success, indicating a potential for postpollination sexual selection. The most successful pollen donor sired more than twice the expected number of seeds, and this was largely consistent across recipient plants. However, siring success following natural mating was significantly different from siring success following artificial pollination and showed that the reproductive gains to be made from superior pollen performance did not translate into increased reproductive success following natural mating. As the ecological context for post-pollination sexual selection is strong in P. mollis, I suggest that pollen competition may ultimately have only a weak effect on non-random male mating success under natural conditions because the realized opportunities for pollen competition within pistils are limited. PMID:11075703

  17. Coevolutionary information, protein folding landscapes, and the thermodynamics of natural selection

    PubMed Central

    Morcos, Faruck; Schafer, Nicholas P.; Cheng, Ryan R.; Onuchic, José N.; Wolynes, Peter G.

    2014-01-01

    The energy landscape used by nature over evolutionary timescales to select protein sequences is essentially the same as the one that folds these sequences into functioning proteins, sometimes in microseconds. We show that genomic data, physical coarse-grained free energy functions, and family-specific information theoretic models can be combined to give consistent estimates of energy landscape characteristics of natural proteins. One such characteristic is the effective temperature Tsel at which these foldable sequences have been selected in sequence space by evolution. Tsel quantifies the importance of folded-state energetics and structural specificity for molecular evolution. Across all protein families studied, our estimates for Tsel are well below the experimental folding temperatures, indicating that the energy landscapes of natural foldable proteins are strongly funneled toward the native state. PMID:25114242

  18. The GIST Model for Selection and Modification of Scientific Research for the College Teaching Laboratory Based on Root Competition Investigations

    ERIC Educational Resources Information Center

    Elliott, Shannon Snyder

    2007-01-01

    The purpose of this study is to first develop an 8-week college teaching module based on root competition literature. The split-root technique is adapted for the teaching laboratory, and the Sugar Ann English pea (Pisum sativum var. Sugar Ann English) is selected as the species of interest prior to designing experiments, either original or…

  19. Unweaving misconceptions: Guided learning, simulations, and misconceptions in learning principles of natural selection

    NASA Astrophysics Data System (ADS)

    Weeks, Brian E.

    College students often come to the study of evolutionary biology with many misconceptions of how the processes of natural selection and speciation occur. How to relinquish these misconceptions with learners is a question that many educators face in introductory biology courses. Constructivism as a theoretical framework has become an accepted and promoted model within the epistemology of science instruction. However, constructivism is not without its skeptics who see some problems of its application in lacking necessary guidance for novice learners. This study within a quantitative, quasi-experimental format tested whether guided online instruction in a video format of common misconceptions in evolutionary biology produced higher performance on a survey of knowledge of natural selection versus more constructivist style learning in the form of student exploration of computer simulations of the evolutionary process. Performances on surveys were also explored for a combination of constructivist and guided techniques to determine if a consolidation of approaches produced higher test scores. Out of the 94 participants 95% displayed at least one misconception of natural selection in the pre-test while the study treatments produced no statistically significant improvements in post-test scores except within the video (guided learning treatment). These overall results demonstrated the stubbornness of misconceptions involving natural selection for adult learners and the difficulty of helping them overcome them. It also bolsters the idea that some misconceptions of natural selection and evolution may be hardwired in a neurological sense and that new, more long-term teaching techniques may be warranted. Such long-term strategies may not be best implemented with constructivist techniques alone, and it is likely that some level of guidance may be necessary for novice adult learners. A more substantial, nuanced approach for undergraduates is needed that consolidates successful teaching strategies to adult students that is based on current research.

  20. Natural selection influences AFLP intraspecific genetic variability and introgression patterns in Atlantic eels.

    PubMed

    Gagnaire, P A; Albert, V; Jónsson, B; Bernatchez, L

    2009-04-01

    Investigating patterns of genetic variation in hybridizing species provides an opportunity to understand the impact of natural selection on intraspecific genetic variability and interspecific gene exchange. The Atlantic eels Anguilla rostrata and A. anguilla each occupy a large heterogeneous habitat upon which natural selection could differentially shape genetic variation. They also produce viable hybrids only found in Iceland. However, the possible footprint of natural selection on patterns of genetic variation within species and introgressive hybridization in Icelandic eels has never been assessed. We revisited amplified fragment length polymorphism data collected previously using population genomics and admixture analyses to test if (i) genetic variation could be influenced by non-neutral mechanisms at both the intra- and interspecific levels, and if (ii) selection could shape the spatio-temporal distribution of Icelandic hybrids. We first found candidate loci for directional selection within both species. Spatial distributions of allelic frequencies displayed by some of these loci were possibly related with the geographical patterns of life-history traits in A. rostrata, and could have been shaped by natural selection associated with an environmental gradient along European coasts in A. anguilla. Second, we identified outlier loci at the interspecific level. Non-neutral introgression was strongly suggested for some of these loci. We detected a locus at which typical A. rostrata allele hardly crossed the species genetic barrier, whereas three other loci showed accelerated patterns of introgression into A. anguilla in Iceland. Moreover, the level of introgression at these three loci increased from the glass eel to the yellow eel stage, supporting the hypothesis that differential survival of admixed genotypes partly explains the spatio-temporal pattern of hybrid abundance previously documented in Iceland. PMID:19302349

  1. Lifetime selection on heritable life-history traits in a natural population of red squirrels.

    PubMed

    Réale, D; Berteaux, D; McAdam, A G; Boutin, S

    2003-10-01

    Despite their importance in evolutionary biology, heritability and the strength of natural selection have rarely been estimated in wild populations of iteroparous species or have usually been limited to one particular event during an organism's lifetime. Using an animal-model restricted maximum likelihood and phenotypic selection models, we estimated quantitative genetic parameters and the strength of lifetime selection on parturition date and litter size at birth in a natural population of North American red squirrels, Tamiasciurus hudsonicus. Litter size at birth and parturition date had low heritabilities (h2 = 0.15 and 0.16, respectively). We considered potential effects of temporal environmental covariances between phenotypes and fitness and of spatial environmental heterogeneity in estimates of selection. Selection favored early breeders and females that produced litter sizes close to the population average. Stabilizing selection on litter size at birth may occur because of a trade-off between number of offspring produced per litter and offspring survival or a trade-off between a female's fecundity and her future reproductive success and survival. PMID:14628929

  2. Natural attenuation of pharmaceuticals and an illicit drug in a laboratory column experiment.

    PubMed

    Greenhagen, Andrew M; Lenczewski, Melissa E; Carroll, Monica

    2014-11-01

    Trace amounts of pharmaceutical compounds have been detected in waters across the United States. Many compounds are released as the result of human ingestion and subsequent excretion of over-the-counter and prescription medications, and illicit drugs. This research utilized columns (30×30cm) of sand and undisturbed fine-grained sediments to simulate injection of wastewater containing pharmaceuticals and an illicit drug, such as would be found in a septic system, leaky sewer, or landfill. The columns were placed in a temperature-controlled laboratory and each was injected with natural groundwater containing known concentrations of caffeine, methamphetamine, and acetaminophen. Natural attenuation of each chemical was observed in all columns. The highest amount removed (approximately 90%) occurred in the undisturbed column injected with methamphetamine, compared with little reduction in the sand column. When the suite of drugs was injected, loss of methamphetamine was less than when methamphetamine was injected alone. The subsurface sediments exhibit the ability to remove a substantial amount of the injected pharmaceuticals and illicit drug; however, complete removal was not achieved. There was little attenuation of injected pharmaceuticals in the sand column which demonstrates a concern for water quality in the environment if pharmaceuticals were to contaminate a sandy aquifer. Understanding the transport of pharmaceuticals in the subsurface environment is an important component of protecting drinking water supplies from contamination. PMID:24594486

  3. Joint phenotypes, evolutionary conflict and the fundamental theorem of natural selection

    PubMed Central

    Queller, David C.

    2014-01-01

    Multiple organisms can sometimes affect a common phenotype. For example, the portion of a leaf eaten by an insect is a joint phenotype of the plant and insect and the amount of food obtained by an offspring can be a joint trait with its mother. Here, I describe the evolution of joint phenotypes in quantitative genetic terms. A joint phenotype for multiple species evolves as the sum of additive genetic variances in each species, weighted by the selection on each species. Selective conflict between the interactants occurs when selection takes opposite signs on the joint phenotype. The mean fitness of a population changes not just through its own genetic variance but also through the genetic variance for its fitness that resides in other species, an update of Fisher's fundamental theorem of natural selection. Some similar results, using inclusive fitness, apply to within-species interactions. The models provide a framework for understanding evolutionary conflicts at all levels. PMID:24686940

  4. The Role of Natural Selection in Genetic Differentiation of Worldwide Populations of Drosophila ananassae

    PubMed Central

    Baines, John F.; Das, Aparup; Mousset, Sylvain; Stephan, Wolfgang

    2004-01-01

    The main evolutionary forces leading to genetic differentiation between populations are generally considered to be natural selection, random genetic drift, and limited migration. However, little empirical evidence exists to help explain the extent, mechanism, and relative role of these forces. In this study, we make use of the differential migration behavior of genes located in regions of low and high recombination to infer the role and demographic distribution of natural selection in Drosophila ananassae. Sequence data were obtained from 13 populations, representing almost the entire range of cosmopolitan D. ananassae. The pattern of variation at a 5.1-kb fragment of the furrowed gene, located in a region of very low recombination, appears strikingly different from that of 10 noncoding DNA fragments (introns) in regions of normal to high recombination. Most interestingly, two main haplotypes are present at furrowed, one being fixed in northern populations and the other being fixed or in high frequency in more southern populations. A cline in the frequency of one of these haplotypes occurs in parallel latitudinal transects. Taken together, significant clinal variation and a test against alternative models of natural selection provide evidence of two independent selective sweeps restricted to specific regions of the species range. PMID:15611169

  5. The role of natural selection in genetic differentiation of worldwide populations of Drosophila ananassae.

    PubMed

    Baines, John F; Das, Aparup; Mousset, Sylvain; Stephan, Wolfgang

    2004-12-01

    The main evolutionary forces leading to genetic differentiation between populations are generally considered to be natural selection, random genetic drift, and limited migration. However, little empirical evidence exists to help explain the extent, mechanism, and relative role of these forces. In this study, we make use of the differential migration behavior of genes located in regions of low and high recombination to infer the role and demographic distribution of natural selection in Drosophila ananassae. Sequence data were obtained from 13 populations, representing almost the entire range of cosmopolitan D. ananassae. The pattern of variation at a 5.1-kb fragment of the furrowed gene, located in a region of very low recombination, appears strikingly different from that of 10 noncoding DNA fragments (introns) in regions of normal to high recombination. Most interestingly, two main haplotypes are present at furrowed, one being fixed in northern populations and the other being fixed or in high frequency in more southern populations. A cline in the frequency of one of these haplotypes occurs in parallel latitudinal transects. Taken together, significant clinal variation and a test against alternative models of natural selection provide evidence of two independent selective sweeps restricted to specific regions of the species range. PMID:15611169

  6. The importance of selection at the level of the pair over 25 years in a natural population of birds

    PubMed Central

    Björklund, Mats; Gustafsson, Lars

    2013-01-01

    Knowledge of the pattern of selection in natural populations is fundamental for our understanding of the evolutionary process. Selection at higher levels has gained considerable theoretical support in recent years, and one possible level of selection is the breeding pair where fitness is a function of the pair and cannot be reduced to single individuals. We analyzed the importance of pair-level selection over 25 years in a natural population of the collared flycatcher. Pair-level selection was significant in five and probably in another 9 years. The relative importance of pair-level selection varied over years and can have stronger or the same strength as directional selection. This means that selection can act on the combination of the breeding pair in addition to selection on each individual separately. Overall, the conservative estimates obtained here show that this is a potentially important form of selection. PMID:24340199

  7. On Theoretical Models of Gene Expression Evolution with Random Genetic Drift and Natural Selection

    PubMed Central

    Ogasawara, Osamu; Okubo, Kousaku

    2009-01-01

    Background The relative contributions of natural selection and random genetic drift are a major source of debate in the study of gene expression evolution, which is hypothesized to serve as a bridge from molecular to phenotypic evolution. It has been suggested that the conflict between views is caused by the lack of a definite model of the neutral hypothesis, which can describe the long-run behavior of evolutionary change in mRNA abundance. Therefore previous studies have used inadequate analogies with the neutral prediction of other phenomena, such as amino acid or nucleotide sequence evolution, as the null hypothesis of their statistical inference. Methodology/Principal Findings In this study, we introduced two novel theoretical models, one based on neutral drift and the other assuming natural selection, by focusing on a common property of the distribution of mRNA abundance among a variety of eukaryotic cells, which reflects the result of long-term evolution. Our results demonstrated that (1) our models can reproduce two independently found phenomena simultaneously: the time development of gene expression divergence and Zipf's law of the transcriptome; (2) cytological constraints can be explicitly formulated to describe long-term evolution; (3) the model assuming that natural selection optimized relative mRNA abundance was more consistent with previously published observations than the model of optimized absolute mRNA abundances. Conclusions/Significance The models introduced in this study give a formulation of evolutionary change in the mRNA abundance of each gene as a stochastic process, on the basis of previously published observations. This model provides a foundation for interpreting observed data in studies of gene expression evolution, including identifying an adequate time scale for discriminating the effect of natural selection from that of random genetic drift of selectively neutral variations. PMID:19936214

  8. Identification of innate immunity elicitors using molecular signatures of natural selection

    PubMed Central

    McCann, Honour C.; Nahal, Hardeep; Thakur, Shalabh; Guttman, David S.

    2012-01-01

    The innate immune system is an ancient and broad-spectrum defense system found in all eukaryotes. The detection of microbial elicitors results in the up-regulation of defense-related genes and the elicitation of inflammatory and apoptotic responses. These innate immune responses are the front-line barrier against disease because they collectively suppress the growth of the vast majority of invading microbes. Despite their critical role, we know remarkably little about the diversity of immune elicitors. To address this paucity, we reasoned that hosts are more likely to evolve recognition to “core” pathogen proteins under strong negative selection for the maintenance of essential cellular functions, whereas repeated exposure to host–defense responses will impose strong positive selective pressure for elicitor diversification to avoid host recognition. Therefore, we hypothesized that novel bacterial elicitors can be identified through these opposing forces of natural selection. We tested this hypothesis by examining the genomes of six bacterial phytopathogens and identifying 56 candidate elicitors that have an excess of positively selected residues in a background of strong negative selection. We show that these positively selected residues are atypically clustered, similar to patterns seen in the few well-characterized elicitors. We then validated selected candidate elicitors by showing that they induce Arabidopsis thaliana innate immunity in functional (virulence suppression) and cellular (callose deposition) assays. These finding provide targets for the study of host–pathogen interactions and applied research into alternative antimicrobial treatments. PMID:22323605

  9. Natural selection on synonymous sites is correlated with gene length and recombination in Drosophila.

    PubMed Central

    Comeron, J M; Kreitman, M; Aguadé, M

    1999-01-01

    Evolutionary analysis of codon bias in Drosophila indicates that synonymous mutations are not neutral, but rather are subject to weak selection at the translation level. Here we show that the effectiveness of natural selection on synonymous sites is strongly correlated with the rate of recombination, in accord with the nearly neutral hypothesis. This correlation, however, is apparent only in genes encoding short proteins. Long coding regions have both a lower codon bias and higher synonymous substitution rates, suggesting that they are affected less efficiently by selection. Therefore, both the length of the coding region and the recombination rate modulate codon bias. In addition, the data indicate that selection coefficients for synonymous mutations must vary by a minimum of one or two orders of magnitude. Two hypotheses are proposed to explain the relationship among the coding region length, the codon bias, and the synonymous divergence and polymorphism levels across the range of recombination rates in Drosophila. The first hypothesis is that selection coefficients on synonymous mutations are inversely related to the total length of the coding region. The second hypothesis proposes that interference among synonymous mutations reduces the efficacy of selection on these mutations. We investigated this second hypothesis by carrying out forward simulations of weakly selected mutations in model populations. These simulations show that even with realistic recombination rates, this interference, which we call the "small-scale" Hill-Robertson effect, can have a moderately strong influence on codon bias. PMID:9872963

  10. Cyclone Tolerance in New World Arecaceae: Biogeographic Variation and Abiotic Natural Selection

    PubMed Central

    Griffith, M. Patrick; Noblick, Larry R.; Dowe, John L.; Husby, Chad E.; Calonje, Michael A.

    2008-01-01

    Background and Aims Consistent abiotic factors can affect directional selection; cyclones are abiotic phenomena with near-discrete geographic limits. The current study investigates selective pressure of cyclones on plants at the species level, testing for possible natural selection. Methods New World Arecaceae (palms) are used as a model system, as plants with monopodial, unbranched arborescent form are most directly affected by the selective pressure of wind load. Living specimens of known provenance grown at a common site were affected by the same cyclone. Data on percentage mortality were compiled and analysed in biogeographic and phylogenetic contexts. Key Results Palms of cyclone-prone provenance exhibited a much lower (one order of magnitude) range in cyclone tolerance, and significantly lower (P < 0·001) mean percentage mortality than collections from cyclone-free areas. Palms of cyclone-free provenance had much greater variation in tolerance, and significantly greater mean percentage mortality. A test for serial independence recovered no significant phylogenetic autocorrelation of percentage mortality. Conclusions Variation in cyclone tolerance in New World Arecaceae correlates with biogeography, and is not confounded with phylogeny. These results suggest natural selection of cyclone tolerance in cyclone-prone areas. PMID:18669575

  11. Natural Selection and the Frequency Distributions of ``silent'' DNA Polymorphism in Drosophila

    PubMed Central

    Akashi, H.; Schaeffer, S. W.

    1997-01-01

    In Escherichia coli, Saccharomyces cerevisiae, and Drosophila melanogaster, codon bias may be maintained by a balance among mutation pressure, genetic drift, and natural selection favoring translationally superior codons. Under such an evolutionary model, silent mutations fall into two fitness categories: preferred mutations that increase codon bias and unpreferred changes in the opposite direction. This prediction can be tested by comparing the frequency spectra of synonymous changes segregating within populations; natural selection will elevate the frequencies of advantageous mutations relative to that of deleterious changes. The frequency distributions of preferred and unpreferred mutations differ in the predicted direction among 99 alleles of two D. pseudoobscura genes and five alleles of eight D. simulans genes. This result confirms the existence of fitness classes of silent mutations. Maximum likelihood estimates suggest that selection intensity at silent sites is, on average, very weak in both D. pseudoobscura and D. simulans (|N(e)s| & 1). Inference of evolutionary processes from within-species sequence variation is often hindered by the assumption of a stationary frequency distribution. This assumption can be avoided when identifying the action of selection and tested when estimating selection intensity. PMID:9136019

  12. Natural Gamma Emitters after a Selective Chemical Separation of a TENORM residue: Preliminary Results

    NASA Astrophysics Data System (ADS)

    de Freitas, Antonio Alves; dos Santos, Adir Janete Godoy; Pecequilo, Brigitte Roxana Soreanu; Abrão, Alcídio

    2008-08-01

    An analytical procedure was established in order to obtain selective fractions containing radium isotopes (228Ra), thorium (232Th), and rare earths from RETOTER (REsíduo de TÓrio e TErras Raras), a solid residue rich in rare earth elements, thorium isotopes and small amount of natural uranium generated from the operation of a thorium pilot plant for purification and production of pure thorium nitrate at IPEN -CNEN/SP. The paper presents preliminary results of 228Ra, 226Ra, 238U, 210Pb, and 40K concentrations in the selective fractions and total residue determined by high-resolution gamma spectroscopy, considering radioactive equilibrium of the samples.

  13. Material selection for wellhead equipment exposed to chlorinated and natural seawater

    SciTech Connect

    Olsen, S.; Nice, P.; Strandmyr, O. [Statoil, Stavanger (Norway); Maligas, M.; Vicic, J. [FMC Corp., Houston, TX (United States). Wellhead Equipment Div.

    1996-08-01

    Corrosion resistant alloys have been used in marine environments for their corrosion resistance. However, some of these materials are prone to localized corrosion, in particular crevice and pitting corrosion, in natural seawater. Injection water normally consists of de-oxygenated seawater, but, more recently either continuously or batch chlorinated and fully oxygenated seawater has been selected for this purpose because of their cost benefits. This investigation covers testing of corrosion resistant materials to aid in the selection of materials for wellhead equipment in an oxygenated and chlorinated seawater injection environment.

  14. Variation in mycorrhizal performance in the epiphytic orchid Tolumnia variegata in vitro : the potential for natural selection

    Microsoft Academic Search

    J. Tupac Otero; Paul Bayman; James D. Ackerman

    2005-01-01

    Symbiotic seed germination is a critical stage in orchid life histories. Natural selection may act to favor plants that efficiently use mycorrhizal fungi. However, the necessary conditions for natural selection – variation, heritability, and differences in fitness – have not been demonstrated for either orchid or fungus. With the epiphytic orchid Tolumnia variegata as a model system, we ask the

  15. LABORATORY PROCESS CONTROLLER USING NATURAL LANGUAGE COMMANDS FROM A PERSONAL COMPUTER

    NASA Technical Reports Server (NTRS)

    Will, H.

    1994-01-01

    The complex environment of the typical research laboratory requires flexible process control. This program provides natural language process control from an IBM PC or compatible machine. Sometimes process control schedules require changes frequently, even several times per day. These changes may include adding, deleting, and rearranging steps in a process. This program sets up a process control system that can either run without an operator, or be run by workers with limited programming skills. The software system includes three programs. Two of the programs, written in FORTRAN77, record data and control research processes. The third program, written in Pascal, generates the FORTRAN subroutines used by the other two programs to identify the user commands with the user-written device drivers. The software system also includes an input data set which allows the user to define the user commands which are to be executed by the computer. To set the system up the operator writes device driver routines for all of the controlled devices. Once set up, this system requires only an input file containing natural language command lines which tell the system what to do and when to do it. The operator can make up custom commands for operating and taking data from external research equipment at any time of the day or night without the operator in attendance. This process control system requires a personal computer operating under MS-DOS with suitable hardware interfaces to all controlled devices. The program requires a FORTRAN77 compiler and user-written device drivers. This program was developed in 1989 and has a memory requirement of about 62 Kbytes.

  16. A signal integration model of thymic selection and natural regulatory T cell commitment.

    PubMed

    Khailaie, Sahamoddin; Robert, Philippe A; Toker, Aras; Huehn, Jochen; Meyer-Hermann, Michael

    2014-12-15

    The extent of TCR self-reactivity is the basis for selection of a functional and self-tolerant T cell repertoire and is quantified by repeated engagement of TCRs with a diverse pool of self-peptides complexed with self-MHC molecules. The strength of a TCR signal depends on the binding properties of a TCR to the peptide and the MHC, but it is not clear how the specificity to both components drives fate decisions. In this study, we propose a TCR signal-integration model of thymic selection that describes how thymocytes decide among distinct fates, not only based on a single TCR-ligand interaction, but taking into account the TCR stimulation history. These fates are separated based on sustained accumulated signals for positive selection and transient peak signals for negative selection. This spans up the cells into a two-dimensional space where they are either neglected, positively selected, negatively selected, or selected as natural regulatory T cells (nTregs). We show that the dynamics of the integrated signal can serve as a successful basis for extracting specificity of thymocytes to MHC and detecting the existence of cognate self-peptide-MHC. It allows to select a self-MHC-biased and self-peptide-tolerant T cell repertoire. Furthermore, nTregs in the model are enriched with MHC-specific TCRs. This allows nTregs to be more sensitive to activation and more cross-reactive than conventional T cells. This study provides a mechanistic model showing that time integration of TCR-mediated signals, as opposed to single-cell interaction events, is needed to gain a full view on the properties emerging from thymic selection. PMID:25392533

  17. Materials from the Cell Factory Nature is a laboratory for particularly intelligent materials.This is what motivates Joachim Spatz,

    E-print Network

    . Such materials may be capable of regenera- tion. Today, research into these kinds of self-healing materialsMaterials from the Cell Factory Nature is a laboratory for particularly intelligent materials materials. Along the way, he anticipates new discoveries about the behavior of cells in tissues. TEXT ROLAND

  18. Reassigning the Structures of Natural Products Using NMR Chemical Shifts Computed with Quantum Mechanics: A Laboratory Exercise

    ERIC Educational Resources Information Center

    Palazzo, Teresa A.; Truong, Tiana T.; Wong, Shirley M. T.; Mack, Emma T.; Lodewyk, Michael W.; Harrison, Jason G.; Gamage, R. Alan; Siegel, Justin B.; Kurth, Mark J.; Tantillo, Dean J.

    2015-01-01

    An applied computational chemistry laboratory exercise is described in which students use modern quantum chemical calculations of chemical shifts to assign the structure of a recently isolated natural product. A pre/post assessment was used to measure student learning gains and verify that students demonstrated proficiency of key learning…

  19. Life history QTLs and natural selection on flowering time in Boechera stricta, a perennial relative of Arabidopsis

    PubMed Central

    Anderson, Jill T.; Lee, Cheng-Ruei; Mitchell-Olds, Thomas

    2011-01-01

    Plants must precisely time flowering to capitalize on favorable conditions. Although we know a great deal about the genetic basis of flowering phenology in model species under controlled conditions, the genetic architecture of this ecologically-important trait is poorly understood in non-model organisms. Here, we evaluated the transition from vegetative growth to flowering in Boechera stricta, a perennial relative of Arabidopsis thaliana. We examined flowering time QTLs using 7,920 recombinant inbred individuals, across seven lab and field environments differing in vernalization, temperature, and photoperiod. Genetic and environmental factors strongly influenced the transition to reproduction. We found directional selection for earlier flowering in the field. In the growth chamber experiment, longer winters accelerated flowering, whereas elevated ambient temperatures delayed flowering. Our analyses identified one large effect QTL (nFT), which influenced flowering time in both experiments and the probability of flowering in the field. In Montana, homozygotes for the native allele at nFT showed a selective advantage of 6.6%. Nevertheless, we found relatively low correlations between flowering times in the field and the growth chambers. Additionally, we detected flowering-related QTLs in the field which were absent across the full range of laboratory conditions, thus emphasizing the need to conduct experiments in natural environments. PMID:21083662

  20. Mutation pressure, natural selection, and the evolution of base composition in Drosophila

    Microsoft Academic Search

    Hiroshi Akashi; Richard M. Kliman; Adam Eyre-Walker

    1998-01-01

    Genome sequencing in a number of taxa has revealed variation in nucleotide composition both among regions of the genome and\\u000a among functional classes of sites in DNA. Mutational biases, biased gene conversion, and natural selection have been proposed\\u000a as causes of this variation. Here, we review patterns of base composition in Drosophila DNA. Nucleotide composition in Drosophila\\u000a melanogaster varys regionally,

  1. On the moulding of senescence by natural selection in sexual and partly sexual populations

    Microsoft Academic Search

    Ilan Eshel; Beverly Sackler

    1990-01-01

    Under a wide variety of dynamic environmental conditions, natural selection appears to favor reproductive investment in a\\u000a sexually produced offspring, carrying only half of the mother’s genes, over the investment in an asexually produced offspring,\\u000a genetically identical to her. It is maintained that the same environmental conditions must affect the evolutionary cost and\\u000a benefit of an investment in the prolongation

  2. Can natural selection maintain long-distance dispersal? Insight from a stream salamander system

    Microsoft Academic Search

    Winsor H. LoweMark; Mark A. McPeek

    Dispersal distributions are often characterized by many individuals that stay close to their origin and large variation in\\u000a the distances moved by those that leave. This variation in dispersal distance can strongly influence demographic, ecological,\\u000a and evolutionary processes. However, a lack of data on the fitness and phenotype of individual dispersers has impeded research\\u000a on the role of natural selection

  3. Natural Image Coding in V1: How Much Use is Orientation Selectivity?

    Microsoft Academic Search

    Jan Eichhorn; Fabian Sinz; Matthias Bethge

    2008-01-01

    Orientation selectivity is the most striking feature of simple cell coding in V1 which has been shown to emerge from the reduction of higher-order correlations in natural images in a large variety of statistical image models. The most parsimonious one among these models is linear Independent Component Analysis (ICA), whereas second-order decorrelation transformations such as Principal Component Analysis (PCA) do

  4. Natural and synthetic geiparvarins are strong and selective MAO-B inhibitors. Synthesis and SAR studies.

    PubMed

    Carotti, Angelo; Carrieri, Antonio; Chimichi, Stefano; Boccalini, Marco; Cosimelli, Barbara; Gnerre, Carmela; Carotti, Andrea; Carrupt, Pierre Alain; Testa, Bernard

    2002-12-16

    Natural geiparvarin 1 and a number of its analogues were prepared and tested as inhibitors of both monoamine oxidase isoforms, MAO-B and MAO-A. The desmethyl congener 6 of geiparvarin, proved potent and selective MAO-B inhibitor (pIC(50)=7.55 vs 4.62). X-ray crystallography and molecular modelling studies helped the understanding of the observed structure-activity relationships. PMID:12443774

  5. Trace metals in natural iron oxides from laterites: A study using selective kinetic extraction

    Microsoft Academic Search

    Fabienne Trolard; Guilhem Bourrie; Emmanuel Jeanroy; Adrien J. Herbillon; Henri Martin

    1995-01-01

    To determine the extent of metal association in natural iron oxides, a combination of XRD and chemical selective dissolution techniques was applied to four samples from laterites developed on peridotites in East Africa. The reagents used were dithionite-citrate-bicarbonate (DCB), citrate-bicarbonate (CB), hydroxylamine hydrochloride (HH), and oxalic acid-oxalate (Tamm). From the results obtained, it appears that: (1) the difference DCB minus

  6. Form and nature of precopulatory sexual selection in both sexes of a moth.

    PubMed

    Xu, Jin; Wang, Qiao

    2010-07-01

    Sexual selection is a process that operates through intrasexual competition and intersexual choice for reproduction in both sexes. Here, we report our work on a polygamous moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), aiming to infer the form and nature of precopulatory sexual selection in males and females. We show that, although a number of traits measured in each sex are correlated with mating success, the primary selection trait in females appears to be abdominal thickness and that in males is aedeagus length. As the female's abdominal thickness is a reliable signal about the number and developmental stage of eggs, males who select females with thicker abdomens for mating will gain reproductive benefit, i.e., fertilizing more mature eggs. For females, earlier maturation of their eggs makes the females more likely to achieve mating earlier in an uncertain world where there is no guarantee that they will find more males in the future. Sexual selection appears to be the important force behind the evolution of fast egg maturation in females. We show that, under a male-biased sex ratio, more than 20% of mating fails within a few minutes after the aedeagus has penetrated into the female's genitalia, suggesting that females can assess the features of the male aedeagus before allowing insemination to occur. Dissection and examination of both sexes suggest that a longer aedeagus enhances mating and fertilization efficiency in this species, supporting the notion that sexual selection is a primary force in the evolution of genital variance. PMID:20473478

  7. Field and laboratory tests on nitrate treatment for potential use in natural gas operations

    SciTech Connect

    Morris, E.A.; Derr, R.M.; Kenney, T.M.; Pope, D.H.

    1995-12-01

    A variety of treatment products containing forms of nitrate have become available for use in optimizing microbial activities in a manner that results in improved system performance. While many of the traditional approaches to microbiological control have involved the use of biocides to achieve overall reduction in bacteria levels, the nitrate approach involves promoting growth of {open_quotes}beneficial{close_quotes} organisms which can negate the effects of, or out-compete the offending organisms. Suppliers of products, as well as systems operators in the natural gas industry, have reported the approach successful in a wide variety of applications including mitigation of downhole and above-ground produced water sulfide-souring, enhanced recovery of hydrocarbons in production reservoirs, and expediting cleanup of wastewater. In a study sponsored by the Gas Research Institute (GRI), Chicago Illinois, nitrate-based treatment strategies were assessed in field tests for efficacy in wastewater cleanup and mitigation of sulfide-souring in a produced water containment facility. In addition, laboratory tests were done to assess nitrate treatment for its potential for mitigation of downhole sulfide-souring using a test loop containing formation core material which was colonized by microbes producing sour water. Details on the test results, discussion of potential advantages/disadvantages of nitrate treatment, and criteria for determining if nitrate treatment is appropriate are provided herein.

  8. Laboratory chemical remanent magnetization in a natural claystone: a record of two magnetic polarities

    NASA Astrophysics Data System (ADS)

    Cairanne, G.; Aubourg, C.; Pozzi, J.-P.; Moreau, M.-G.; Decamps, T.; Marolleau, G.

    2004-12-01

    A record of two magnetic polarities during the acquisition by heating of a laboratory chemical remanent magnetization (CRM) in a natural pyrite-rich claystone was investigated. The samples were heated for 22 hr at 250 °C in a controlled magnetic field (1.0 mT) under an argon atmosphere. We interpret the origin of CRM as the surface oxidation of pyrite to magnetite, which in turn is progressively oxidized into haematite. We carried out experiments under a constant-polarity magnetic field and under two opposite polarities. The resulting CRM was measured after cooling in zero field: it is parallel to the applied field and has the direction of the last polarity. Thermal demagnetization under an argon atmosphere isolates an unexpected low-unblocking-temperature component (TUB < 220 °C). This component probably results from thermal alteration of magnetic carriers during subsequent thermal demagnetization. In the one-polarity experiments, thermal demagnetization of CRM above 220 °C isolates a well-defined component parallel to the imparted field direction. In the experiments with two magnetic polarities thermal demagnetization of CRM reveals two components of opposite polarity. The component which is parallel to the direction of the last applied field is well defined, while the other component, which has the polarity of the first applied field, is ill defined. Oppositely directed components are also detected by using alternating field demagnetization.

  9. Experimental and theoretical study of microalgal competition in laboratory and natural ecosystems

    NASA Astrophysics Data System (ADS)

    Pisman, T. I.; Somova, L. A.

    An important aspect of studying mixed cultures of microalgae is the artificial ecosystems containing algal culture as a regeneration link and a source of vegetable substances. The peculiarities of studying the stability of microalgae mixed cultures in the laboratory and natural environment have been considered in the work. The role of factors most essentially affecting the species structure of phytoplankton community (temperature factor, light intensity, pH environments, elements of mineral nutrition, algal metabolites, predation and fluctuation of environmental conditions) has been displayed. As a result of experimental and theoretical modelling of the microalgae Chlorella vulgaris and Scenedesmus quadricauda competition under limitation on nitrogen, the impossibility of their co-existence has been revealed. Under these conditions Chl. vulgaris turned out to be less competitive than Sc. quadricauda. The influence of the ratio of biogenic elements concentration in the environment, which should be recognized as an independent regulatory factor limiting growth of populations in the community and, thus affecting its structure, has been analyzed.

  10. Sexual Selection: Furthering the "Evolution" Metaphor Computational evolution is based on biological evolution, primarily using the features of natural

    E-print Network

    Meeden, Lisa A.

    Sexual Selection: Furthering the "Evolution" Metaphor Cynthia Ma 5/9/2014 Abstract Computational driving force behind the diversity and complexity of the natural world is sexual selection. Previous computational evolution. This study focuses on exploring a different aspect of sexual select - the need

  11. Tropolones As Lead-Like Natural Products: The Development of Potent and Selective Histone Deacetylase Inhibitors

    PubMed Central

    2013-01-01

    Natural products have long been recognized as a rich source of potent therapeutics but further development is often limited by high structural complexity and high molecular weight. In contrast, at the core of the thujaplicins is a lead-like tropolone scaffold characterized by relatively low molecular weight, ample sites for diversification, and metal-binding functionality poised for targeting a range of metalloenzyme drug targets. Here, we describe the development of this underutilized scaffold for the discovery of tropolone derivatives that function as isozyme-selective inhibitors of the validated anticancer drug target, histone deacetylase (HDAC). Several monosubstituted tropolones display remarkable levels of selectivity for HDAC2 and potently inhibit the growth of T-cell lymphocyte cell lines. The tropolones represent a new chemotype of isozyme-selective HDAC inhibitors. PMID:24900743

  12. Natural selection for the Duffy-null allele in the recently admixed people of Madagascar.

    PubMed

    Hodgson, Jason A; Pickrell, Joseph K; Pearson, Laurel N; Quillen, Ellen E; Prista, António; Rocha, Jorge; Soodyall, Himla; Shriver, Mark D; Perry, George H

    2014-08-22

    While gene flow between distantly related populations is increasingly recognized as a potentially important source of adaptive genetic variation for humans, fully characterized examples are rare. In addition, the role that natural selection for resistance to vivax malaria may have played in the extreme distribution of the protective Duffy-null allele, which is nearly completely fixed in mainland sub-Saharan Africa and absent elsewhere, is controversial. We address both these issues by investigating the evolution of the Duffy-null allele in the Malagasy, a recently admixed population with major ancestry components from both East Asia and mainland sub-Saharan Africa. We used genome-wide genetic data and extensive computer simulations to show that the high frequency of the Duffy-null allele in Madagascar can only be explained in the absence of positive natural selection under extreme demographic scenarios involving high genetic drift. However, the observed genomic single nucleotide polymorphism diversity in the Malagasy is incompatible with such extreme demographic scenarios, indicating that positive selection for the Duffy-null allele best explains the high frequency of the allele in Madagascar. We estimate the selection coefficient to be 0.066. Because vivax malaria is endemic to Madagascar, this result supports the hypothesis that malaria resistance drove fixation of the Duffy-null allele in mainland sub-Saharan Africa. PMID:24990677

  13. Footprints of divergent selection in natural populations of Castanopsis fargesii (Fagaceae).

    PubMed

    Li, C; Sun, Y; Huang, H W; Cannon, C H

    2014-12-01

    Given predicted rapid climate change, an understanding of how environmental factors affect genetic diversity in natural populations is important. Future selection pressures are inherently unpredictable, so forest management policies should maintain both overall diversity and identify genetic markers associated with the environmental factors expected to change most rapidly, like temperature and rainfall. In this study, we genotyped 648 individuals in 28 populations of Castanopsis fargesii (Fagaceae) using 32 expressed sequence tag (EST)-derived microsatellite markers. After removing six loci that departed from Hardy-Weinberg equilibrium, we measured genetic variation, population structure and identified candidate loci putatively under selection by temperature and precipitation. We found that C. fargesii populations possessed high genetic diversity and moderate differentiation among them, indicating predominant outcrossing and few restrictions to gene flow. These patterns reduce the possible impact of stochastic effects or the influence of genetic isolation. Clear footprints of divergent selection at four loci were discovered. Frequencies of five alleles at these loci were strongly correlated with environmental factors, particularly extremes in precipitation. These alleles varied from being near fixation at one end of the gradient to being completely absent at the other. Our study species is an important forest tree in the subtropical regions of China and could have a major role in future management and reforestation plans. Our results demonstrate that the gene flow is widespread and abundant in natural populations, maintaining high diversity, while diversifying selection is acting on specific genomic regions. PMID:24984608

  14. Does natural selection organize ecosystems for the maintenance of high productivity and diversity?

    PubMed Central

    Leigh, Egbert Giles; Vermeij, Geerat Jacobus

    2002-01-01

    Three types of evidence suggest that natural ecosystems are organized for high productivity and diversity: (i) changes not previously experienced by a natural ecosystem, such as novel human disturbances, tend to diminish its productivity and/or diversity, just as 'random' changes in a machine designed for a function usually impair its execution of that function; (ii) humans strive to recreate properties of natural ecosystems to enhance productivity of artificial ones, as farmers try to recreate properties of natural soils in their fields; and (iii) productivity and diversity have increased during the Earth's history as a whole, and after every major biotic crisis. Natural selection results in ecosystems organized to maintain high productivity of organic matter and diversity of species, just as competition among individuals in Adam Smith's ideal economy favours high production of wealth and diversity of occupations. In nature, poorly exploited energy attracts more efficient users. This circumstance favours the opening of new ways of life and more efficient recycling of resources, and eliminates most productivity-reducing 'ecological monopolies'. Ecological dominants tend to be replaced by successors with higher metabolism, which respond to more stimuli and engage in more varied interactions. Finally, increasingly efficient predators and herbivores favour faster turnover of resources. PMID:12079531

  15. Laboratory Constraints on the Stability of Petroleum at Elevated Temperatures: Implications for the Origin of Natural Gas

    SciTech Connect

    Seewald, Jeffrey, S.

    2011-03-14

    Results of prior DOE supported research conducted at the Woods Hole Oceanographic Institution have demonstrated the participation of sedimentary minerals and water as reactants and catalysts in chemical transformations associated with the degradation of oil and the formation of low molecular weight organic compounds. The occurrence of such processes in natural environments can be difficult to recognize because the composition of organic alteration products may not be substantially different than those produced by thermal cracking. The goals of this study were the development of diagnostic tools based on hydrogen and carbon isotopes that can be used to identify geochemical processes responsible for the formation of thermogenic natural gas. In addition, our activities were expanded to include experimental investigation of CO2 reduction in aqueous systems at elevated temperature and pressures and an assessment of microbial activity in relatively low temperature (<70°C) natural gas reservoirs in southeastern Oklahoma. Specific objectives included: ? A laboratory investigation of geochemical processes that regulate the hydrogen isotope composition of low molecular weight hydrocarbons in natural gas at elevated temperatures and pressures. ? A laboratory investigation of factors that regulate the carbon isotope composition of organic acids in basinal brines. ? A laboratory assessment of the role of methanol during reduction of CO2 to CH4 under hydrothermal conditions. ? Characterization of microbial ecosystems in coproduced fluids from the Potato Hills gas field to assess the role of microbes in the generation of natural gas.

  16. Targeted activation of silent natural product biosynthesis pathways by reporter-guided mutant selection.

    PubMed

    Guo, Fang; Xiang, Sihai; Li, Liyuan; Wang, Bin; Rajasärkkä, Johanna; Gröndahl-Yli-Hannuksela, Kirsi; Ai, Guomin; Metsä-Ketelä, Mikko; Yang, Keqian

    2015-03-01

    The continuously increasing genome sequencing data has revealed numerous cryptic pathways, which might encode novel secondary metabolites with interesting biological activities. However, utilization of this hidden potential has been hindered by the observation that many of these gene clusters remain silent (or poorly expressed) under laboratory conditions. Here we present reporter-guided mutant selection (RGMS) as an effective and widely applicable method for targeted activation of silent gene clusters in the native producers. The strategy takes advantage of genome-scale random mutagenesis for generation of genetic diversity and a reporter-guided selection system for the identification of the desired target-activated mutants. It was first validated in the re-activation of jadomycin biosynthesis in Streptomyces venezuelae ISP5230, where high efficiency of activation was achieved. The same strategy was then applied to a hitherto unactivable pga gene cluster in Streptomyces sp. PGA64 leading to the identification of two new anthraquinone aminoglycosides, gaudimycin D and E. PMID:25554073

  17. Complex selection associated with Hox genes in a natural population of lizards.

    PubMed

    Schwartz, T S; Perrin, C; Wapstra, E; Uller, T; Olsson, M

    2011-11-01

    Hox genes are recognized for their explanatory power of bilateral development. However, relatively little is known about natural variation in, and the evolutionary dynamics of, Hox genes within wild populations. Utilizing a natural population of sand lizards (Lacerta agilis), we screened HoxA13 for genetic variation and an association with incidence of offspring malformations. We found significant effects of parental genetic similarity and offspring sex, and their interaction, on risk of hatching malformed as an offspring. We also found within population genetic variation in HoxA13, and identified a significant effect of a three-way interaction among Hox genotype, parental genetic similarity, and offspring sex on the risk of hatching malformation. Since malformed offspring in this population do not survive to maturity, this study reveals complex and ongoing selection associated with Hox genes in a wild reptile population. Importantly, this demonstrates the utility of natural populations in unveiling microevolutionary processes shaping variation in highly conserved genes. PMID:21883611

  18. Good Laboratory Practice (GLP) Regulations: Interpretation Techniques and Review of Selected Compliance Issues

    Microsoft Academic Search

    Christine S. Lee; John Y. Lee

    2006-01-01

    The Food and Drug Administration (FDA) good laboratory practice (GLP) inspections in fiscal year 2003 increased significantly at a level of 71% over the previous year. A review and analysis of recently issued FDA warning letters for nonclinical laboratory studies found that the two major GLP compliance deficiencies were study director responsibility and authority (21 CFR §58.33) and the quality

  19. Laboratory Evaluation of Ion-Selective Electrodes for Simultaneous Analysis of Macronutrients in Hydroponic Solution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Automated sensing of macronutrients in hydroponic solution would allow more efficient management of nutrients for crop growth in closed hydroponic systems. Ion-selective microelectrode technology requires an ion-selective membrane or a solid metal material that responds selectively to one analyte in...

  20. Field and laboratory arsenic speciation methods and their application to natural-water analysis

    USGS Publications Warehouse

    Bednar, A.J.; Garbarino, J.R.; Burkhardt, M.R.; Ranville, J.F.; Wildeman, T.R.

    2004-01-01

    The toxic and carcinogenic properties of inorganic and organic arsenic species make their determination in natural water vitally important. Determination of individual inorganic and organic arsenic species is critical because the toxicology, mobility, and adsorptivity vary substantially. Several methods for the speciation of arsenic in groundwater, surface-water, and acid mine drainage sample matrices using field and laboratory techniques are presented. The methods provide quantitative determination of arsenite [As(III)], arsenate [As(V)], monomethylarsonate (MMA), dimethylarsinate (DMA), and roxarsone in 2-8min at detection limits of less than 1??g arsenic per liter (??g AsL-1). All the methods use anion exchange chromatography to separate the arsenic species and inductively coupled plasma-mass spectrometry as an arsenic-specific detector. Different methods were needed because some sample matrices did not have all arsenic species present or were incompatible with particular high-performance liquid chromatography (HPLC) mobile phases. The bias and variability of the methods were evaluated using total arsenic, As(III), As(V), DMA, and MMA results from more than 100 surface-water, groundwater, and acid mine drainage samples, and reference materials. Concentrations in test samples were as much as 13,000??g AsL-1 for As(III) and 3700??g AsL-1 for As(V). Methylated arsenic species were less than 100??g AsL-1 and were found only in certain surface-water samples, and roxarsone was not detected in any of the water samples tested. The distribution of inorganic arsenic species in the test samples ranged from 0% to 90% As(III). Laboratory-speciation method variability for As(III), As(V), MMA, and DMA in reagent water at 0.5??g AsL-1 was 8-13% (n=7). Field-speciation method variability for As(III) and As(V) at 1??g AsL-1 in reagent water was 3-4% (n=3). ?? 2003 Elsevier Ltd. All rights reserved.

  1. Natural Selection in a Bangladeshi Population from the Cholera-Endemic Ganges River Delta

    PubMed Central

    Karlsson, Elinor K.; Harris, Jason B.; Tabrizi, Shervin; Rahman, Atiqur; Shlyakhter, Ilya; Patterson, Nick; O'Dushlaine, Colm; Schaffner, Stephen F.; Gupta, Sameer; Chowdhury, Fahima; Sheikh, Alaullah; Shin, Ok Sarah; Ellis, Crystal; Becker, Christine E.; Stuart, Lynda M.; Calderwood, Stephen B.; Ryan, Edward T.; Qadri, Firdausi; Sabeti, Pardis C.; LaRocque, Regina C.

    2015-01-01

    As an ancient disease with high fatality, cholera has likely exerted strong selective pressure on affected human populations. We performed a genome-wide study of natural selection in a population from the Ganges River Delta, the historic geographic epicenter of cholera. We identified 305 candidate selected regions using the Composite of Multiple Signals (CMS) method. The regions were enriched for potassium channel genes involved in cyclic AMP-mediated chloride secretion and for components of the innate immune system involved in NF-?B signaling. We demonstrate that a number of these strongly selected genes are associated with cholera susceptibility in two separate cohorts. We further identify repeated examples of selection and association in an NF-kB / inflammasome-dependent pathway that is activated in vitro by Vibrio cholerae. Our findings shed light on the genetic basis of cholera resistance in a population from the Ganges River Delta and present a promising approach for identifying genetic factors influencing susceptibility to infectious diseases. PMID:23825302

  2. Highly variable recombinational landscape modulates efficacy of natural selection in birds.

    PubMed

    Gossmann, Toni I; Santure, Anna W; Sheldon, Ben C; Slate, Jon; Zeng, Kai

    2014-08-01

    Determining the rate of protein evolution and identifying the causes of its variation across the genome are powerful ways to understand forces that are important for genome evolution. By using a multitissue transcriptome data set from great tit (Parus major), we analyzed patterns of molecular evolution between two passerine birds, great tit and zebra finch (Taeniopygia guttata), using the chicken genome (Gallus gallus) as an outgroup. We investigated whether a special feature of avian genomes, the highly variable recombinational landscape, modulates the efficacy of natural selection through the effects of Hill-Robertson interference, which predicts that selection should be more effective in removing deleterious mutations and incorporating beneficial mutations in high-recombination regions than in low-recombination regions. In agreement with these predictions, genes located in low-recombination regions tend to have a high proportion of neutrally evolving sites and relaxed selective constraint on sites subject to purifying selection, whereas genes that show strong support for past episodes of positive selection appear disproportionally in high-recombination regions. There is also evidence that genes located in high-recombination regions tend to have higher gene expression specificity than those located in low-recombination regions. Furthermore, more compact genes (i.e., those with fewer/shorter introns or shorter proteins) evolve faster than less compact ones. In sum, our results demonstrate that transcriptome sequencing is a powerful method to answer fundamental questions about genome evolution in nonmodel organisms. PMID:25062920

  3. Highly Variable Recombinational Landscape Modulates Efficacy of Natural Selection in Birds

    PubMed Central

    Gossmann, Toni I.; Santure, Anna W.; Sheldon, Ben C.; Slate, Jon; Zeng, Kai

    2014-01-01

    Determining the rate of protein evolution and identifying the causes of its variation across the genome are powerful ways to understand forces that are important for genome evolution. By using a multitissue transcriptome data set from great tit (Parus major), we analyzed patterns of molecular evolution between two passerine birds, great tit and zebra finch (Taeniopygia guttata), using the chicken genome (Gallus gallus) as an outgroup. We investigated whether a special feature of avian genomes, the highly variable recombinational landscape, modulates the efficacy of natural selection through the effects of Hill–Robertson interference, which predicts that selection should be more effective in removing deleterious mutations and incorporating beneficial mutations in high-recombination regions than in low-recombination regions. In agreement with these predictions, genes located in low-recombination regions tend to have a high proportion of neutrally evolving sites and relaxed selective constraint on sites subject to purifying selection, whereas genes that show strong support for past episodes of positive selection appear disproportionally in high-recombination regions. There is also evidence that genes located in high-recombination regions tend to have higher gene expression specificity than those located in low-recombination regions. Furthermore, more compact genes (i.e., those with fewer/shorter introns or shorter proteins) evolve faster than less compact ones. In sum, our results demonstrate that transcriptome sequencing is a powerful method to answer fundamental questions about genome evolution in nonmodel organisms. PMID:25062920

  4. Patterns of population differentiation and natural selection on the celiac disease background risk network.

    PubMed

    Sams, Aaron; Hawks, John

    2013-01-01

    Celiac disease is a common small intestinal inflammatory condition induced by wheat gluten and related proteins from rye and barley. Left untreated, the clinical presentation of CD can include failure to thrive, malnutrition, and distension in juveniles. The disease can additionally lead to vitamin deficiencies, anemia, and osteoporosis. Therefore, CD potentially negatively affected fitness in past populations utilizing wheat, barley, and rye. Previous analyses of CD risk variants have uncovered evidence for positive selection on some of these loci. These studies also suggest the possibility that risk for common autoimmune conditions such as CD may be the result of positive selection on immune related loci in the genome to fight infection. Under this evolutionary scenario, disease phenotypes may be a trade-off from positive selection on immunity. If this hypothesis is generally true, we can expect to find a signal of natural selection when we survey across the network of loci known to influence CD risk. This study examines the non-HLA autosomal network of gene loci associated with CD risk in Europe. We reject the null hypothesis of neutrality on this network of CD risk loci. Additionally, we can localize evidence of selection in time and space by adding information from the genome of the Tyrolean Iceman. While we can show significant differentiation between continental regions across the CD network, the pattern of evidence is not consistent with primarily recent (Holocene) selection across this network in Europe. Further localization of ancient selection on this network may illuminate the ecological pressures acting on the immune system during this critically interesting phase of our evolution. PMID:23936230

  5. Low pH Springs - A Natural Laboratory for Ocean Acidification

    NASA Astrophysics Data System (ADS)

    Derse, E.; Rebolledo-Vieyra, M.; Potts, D. C.; Paytan, A.

    2009-12-01

    Recent increases in atmospheric carbon dioxide of 40% above pre-industrial levels has resulted in rising aqueous CO2 concentrations that lower the pH of the oceans. Currently, the surface ocean has an average pH between 8.1 and 8.2: it is estimated that over the next 100 years this value will decrease by ~0.4 pH units. Previous studies have highlighted the negative impacts that changes in pH (and the resulting CaCO3 saturation state) have on marine organisms; however, to date, very little is known about the long-term impacts of ocean acidification on ecosystems as a whole. The Yucatán Peninsula of Quintana Roo, Mexico, represents an ecosystem where naturally low pH groundwater (7.25-8.07) has been discharging offshore at highly localized points (called ojos) since the last deglaciation. We present preliminary chemical and biological data on a selection of ojos from lagoon sites in Puerto Morelos, Mexico. We address the potential long-term implications of low pH waters on marine ecosystems.

  6. Foraminiferal Range Expansions: The Mediterranean Sea as a natural laboratory for climate induced invasions

    NASA Astrophysics Data System (ADS)

    Hortense Mouanga, Gloria; Langer, Martin R.

    2015-04-01

    Climate change and biological invasions are key processes that modify biodiversity. One of the most severely affected areas of global change is the Mediterranean Sea, where global warming and the opening of the Suez Canal triggered a mass invasion of tropical Red Sea taxa into Mediterranean territories. Climate models prognosticate that the Mediterranean Sea will be one of the most affected ocean regions and may thus serve as a natural laboratory of future global changes. Among the key taxa that are rapidly expanding their latitudinal range in the Mediterranean Sea are symbiont-bearing foraminifera of the genus Amphistegina. Their range expansion strongly correlates with rising sea surface temperatures and mirrors processes of global change. Amphisteginid foraminifera are among the most prolific foraminiferal species and contribute significantly to shallow-water carbonate sediments. Given their prominent environmental role, rapid biogeographic range expansion, and impact on native ecosystems, amphisteginid range expansion and invasion into new territory are likely to trigger changes in ecosystem functioning. Among the uncertainties, it is not known whether all parts of the Mediterranean will be affected equally and to what extent amphisteginid invasions will impact native biotas. We have initiated a new baseline study to explore the effects of invasive amphisteginids on native foraminiferal biotas and to monitor expansion rates and effects on ecosystem functioning along the current range expansion front. We will present new data on recent shift along the range expansion front and discuss cascading effects on community structures and species richness of native foraminiferal biotas. The magnitude and effects that climate change will have on the Mediterranean foraminiferal faunas may ultimately serve as an example of what would happen along expansion fronts in global oceans.

  7. A simple method for estimating the strength of natural selection on overlapping genes.

    PubMed

    Wei, Xinzhu; Zhang, Jianzhi

    2015-01-01

    Overlapping genes, where one DNA sequence codes for two proteins with different reading frames, are not uncommon in viruses and cellular organisms. Estimating the direction and strength of natural selection acting on overlapping genes is important for understanding their functionality, origin, evolution, maintenance, and potential interaction. However, the standard methods for estimating synonymous (dS) and nonsynonymous (dN) nucleotide substitution rates are inapplicable here because a nucleotide change can be simultaneously synonymous and nonsynonymous when both reading frames involved are considered. We have developed a simple method that can estimate dN/dS and test for the action of natural selection in each relevant reading frame of the overlapping genes. Our method is an extension of the modified Nei-Gojobori method previously developed for nonoverlapping genes. We confirmed the reliability of our method using extensive computer simulation. Applying this method, we studied the longest human sense-antisense overlapping gene pair, LRRC8E and ENSG00000214248. Although LRRC8E (leucine-rich repeat containing eight family, member E) is known to regulate cell size, the function of ENSG00000214248 is unknown. Our analysis revealed purifying selection on ENSG00000214248 and suggested that it originated in the common ancestor of bony vertebrates. PMID:25552532

  8. Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict.

    PubMed

    Brennan, Patricia L R; Prum, Richard O

    2015-01-01

    Genital coevolution between the sexes is expected to be common because of the direct interaction between male and female genitalia during copulation. Here we review the diverse mechanisms of genital coevolution that include natural selection, female mate choice, male-male competition, and how their interactions generate sexual conflict that can lead to sexually antagonistic coevolution. Natural selection on genital morphology will result in size coevolution to allow for copulation to be mechanically possible, even as other features of genitalia may reflect the action of other mechanisms of selection. Genital coevolution is explicitly predicted by at least three mechanisms of genital evolution: lock and key to prevent hybridization, female choice, and sexual conflict. Although some good examples exist in support of each of these mechanisms, more data on quantitative female genital variation and studies of functional morphology during copulation are needed to understand more general patterns. A combination of different approaches is required to continue to advance our understanding of genital coevolution. Knowledge of the ecology and behavior of the studied species combined with functional morphology, quantitative morphological tools, experimental manipulation, and experimental evolution have been provided in the best-studied species, all of which are invertebrates. Therefore, attention to vertebrates in any of these areas is badly needed. PMID:26134314

  9. Evidence of natural selection acting on a polymorphic hybrid incompatibility locus in Mimulus.

    PubMed

    Sweigart, Andrea L; Flagel, Lex E

    2015-02-01

    As a common cause of reproductive isolation in diverse taxa, hybrid incompatibilities are fundamentally important to speciation. A key question is which evolutionary forces drive the initial substitutions within species that lead to hybrid dysfunction. Previously, we discovered a simple genetic incompatibility that causes nearly complete male sterility and partial female sterility in hybrids between the two closely related yellow monkeyflower species Mimulus guttatus and M. nasutus. In this report, we fine map the two major incompatibility loci-hybrid male sterility 1 (hms1) and hybrid male sterility 2 (hms2)-to small nuclear genomic regions (each <70 kb) that include strong candidate genes. With this improved genetic resolution, we also investigate the evolutionary dynamics of hms1 in a natural population of M. guttatus known to be polymorphic at this locus. Using classical genetic crosses and population genomics, we show that a 320-kb region containing the hms1 incompatibility allele has risen to intermediate frequency in this population by strong natural selection. This finding provides direct evidence that natural selection within plant species can lead to hybrid dysfunction between species. PMID:25428983

  10. Select Agent and Toxin Regulations: Beyond the Eighth Edition of the Guide for the Care and Use of Laboratory Animals

    PubMed Central

    Kastenmayer, Robin J; Moore, Rashida M; Bright, Allison L; Torres-Cruz, Rafael; Elkins, William R

    2012-01-01

    In the interval between the publication of the seventh and eighth editions of the Guide for the Care and Use of Laboratory Animals (Guide), much has changed with regard to the regulation and funding of highly pathogenic biologic agents and toxins (Select Agents). Funding of research involving highly pathogenic agents has increased dramatically during this time, thus increasing the demand for facilities capable of supporting this work. The eighth edition of the Guide briefly mentions Select Agents and provides a limited set of references. Here we provide some background information regarding the relevant laws and regulations, as well as an overview of the programmatic requirements pertaining to the use of Select Agents, with a focus on use in animals. PMID:22776191

  11. Epigenetics as an answer to Darwin's "special difficulty," Part 2: natural selection of metastable epialleles in honeybee castes.

    PubMed

    Ruden, Douglas M; Cingolani, Pablo E; Sen, Arko; Qu, Wen; Wang, Luan; Senut, Marie-Claude; Garfinkel, Mark D; Sollars, Vincent E; Lu, Xiangyi

    2015-01-01

    In a recent perspective in this journal, Herb (2014) discussed how epigenetics is a possible mechanism to circumvent Charles Darwin's "special difficulty" in using natural selection to explain the existence of the sterile-fertile dimorphism in eusocial insects. Darwin's classic book "On the Origin of Species by Means of Natural Selection" explains how natural selection of the fittest individuals in a population can allow a species to adapt to a novel or changing environment. However, in bees and other eusocial insects, such as ants and termites, there exist two or more castes of genetically similar females, from fertile queens to multiple sub-castes of sterile workers, with vastly different phenotypes, lifespans, and behaviors. This necessitates the selection of groups (or kin) rather than individuals in the evolution of honeybee hives, but group and kin selection theories of evolution are controversial and mechanistically uncertain. Also, group selection would seem to be prohibitively inefficient because the effective population size of a colony is reduced from thousands to a single breeding queen. In this follow-up perspective, we elaborate on possible mechanisms for how a combination of both epigenetics, specifically, the selection of metastable epialleles, and genetics, the selection of mutations generated by the selected metastable epialleles, allows for a combined means for selection amongst the fertile members of a species to increase colony fitness. This "intra-caste evolution" hypothesis is a variation of the epigenetic directed genetic error hypothesis, which proposes that selected metastable epialleles increase genetic variability by directing mutations specifically to the epialleles. Natural selection of random metastable epialleles followed by a second round of natural selection of random mutations generated by the metastable epialleles would allow a way around the small effective population size of eusocial insects. PMID:25759717

  12. Epigenetics as an answer to Darwin’s “special difficulty,” Part 2: natural selection of metastable epialleles in honeybee castes

    PubMed Central

    Ruden, Douglas M.; Cingolani, Pablo E.; Sen, Arko; Qu, Wen; Wang, Luan; Senut, Marie-Claude; Garfinkel, Mark D.; Sollars, Vincent E.; Lu, Xiangyi

    2015-01-01

    In a recent perspective in this journal, Herb (2014) discussed how epigenetics is a possible mechanism to circumvent Charles Darwin’s “special difficulty” in using natural selection to explain the existence of the sterile-fertile dimorphism in eusocial insects. Darwin’s classic book “On the Origin of Species by Means of Natural Selection” explains how natural selection of the fittest individuals in a population can allow a species to adapt to a novel or changing environment. However, in bees and other eusocial insects, such as ants and termites, there exist two or more castes of genetically similar females, from fertile queens to multiple sub-castes of sterile workers, with vastly different phenotypes, lifespans, and behaviors. This necessitates the selection of groups (or kin) rather than individuals in the evolution of honeybee hives, but group and kin selection theories of evolution are controversial and mechanistically uncertain. Also, group selection would seem to be prohibitively inefficient because the effective population size of a colony is reduced from thousands to a single breeding queen. In this follow-up perspective, we elaborate on possible mechanisms for how a combination of both epigenetics, specifically, the selection of metastable epialleles, and genetics, the selection of mutations generated by the selected metastable epialleles, allows for a combined means for selection amongst the fertile members of a species to increase colony fitness. This “intra-caste evolution” hypothesis is a variation of the epigenetic directed genetic error hypothesis, which proposes that selected metastable epialleles increase genetic variability by directing mutations specifically to the epialleles. Natural selection of random metastable epialleles followed by a second round of natural selection of random mutations generated by the metastable epialleles would allow a way around the small effective population size of eusocial insects. PMID:25759717

  13. Natural selection on floral traits of female Silene dioica by a sexually transmitted disease.

    PubMed

    Giles, Barbara E; Pettersson, Tor Mikael; Carlsson-Granér, Ulla; Ingvarsson, Pär K

    2006-01-01

    Floral traits endowing high reproductive fitness can also affect the probability of plants contracting sexually transmitted diseases. We explore how variations in floral traits influence the fitness of Silene dioica females in their interactions with pollinators carrying pollen or spores of the sterilizing anther-smut fungus Microbotryum violaceum. We collected healthy and infected plants in a highly diseased population and grew them under conditions that 'cure' infected individuals, and used standard regression methods to detect natural selection on floral traits. Narrow-sense heritabilities, coefficients of additive genetic variation (CV(A)) and genetic correlations among traits were estimated from paternal half-sib groups. Pollinator preferences imposed strong direct and directional selection on traits affecting female attractiveness and pollen-/spore-capturing abilities. Levels of additive genetic variance were high in these traits, suggesting that rapid responses to selection are possible. By considering our results in the light of spatial and temporal heterogeneity resulting from the colonization dynamics typical for this species, we suggest that the conflicting selective effects of pollen/spore loads lead to the maintenance of genetic variation in these traits. PMID:16441754

  14. Impact of natural cleaning on the selection of a washing system for solar collectors

    NASA Astrophysics Data System (ADS)

    Kerstein, A.

    1981-04-01

    The desired optical properties (reflectivity, transmissivity, etc.) of solar energy collector surfaces such as mirrors and photovoltaic surfaces are degraded over time by soiling. Cost benefit evaluation of alternative methods for washing the surface or retarding the optical degradation must take into account natural cleaning processes such as precipitation and frost, which impact the scheduling as well as the benefits of washing. A probabilistic method developed to address this question is used to compare truck-mounted versus mirror-mounted washing systems for central receiver plants. The comparison of these systems is shown to be sensitive to the seasonally-varying frequency and effectiveness of natural cleaning processes. The implications of this analysis for such diverse issues as cost/benefit evaluation of soil-retardant mirror coatings and formulation of plant site selection criteria are noted.

  15. Automated ion-selective electrode method for determining fluoride in natural waters

    USGS Publications Warehouse

    Erdmann, D.E.

    1975-01-01

    An automated fluoride method which uses AutoAnalyzer modules in conjunction with a fluoride ion-selective electrode was evaluated. The results obtained on 38 natural water samples are in excellent agreement with those determined by a similar manual method (average difference = 0.026 mg/l). An average fluoride concentration of 0.496 mg/l was found when several natural water samples were spiked with 0.50 mg/l fluoride. Aluminum is the only significant interfering substance, and it can be easily tolerated if its concentration does not exceed 2 mg/l. Thirty samples were analyzed per hour over a concentration range of 0-2 mg/l.

  16. Fish sperm cryopreservation in France: from laboratory studies to application in selective breeding programs

    Microsoft Academic Search

    Pierrick Haffray; Catherine Labbe; Gérard MaIsse

    Application of sperm cryopreservation by the fish farming industry is still limited, despite great interest in optimising genetic resource conservation; limiting risks associated with horizontal disease transmission; increasing genetic progress; and accelerating genetic selection from prime specimens, as in other livestock production. Several factors are listed. With the aim of developing coherent broodstock selection programmes, SYSAAF (Union of the French

  17. INSECTICIDE RESISTANCE MECHANISMS AFTER LABORATORY SELECTION WITH CYPERMETHRIN IN THE GERMAN COCKROACH, BLATTELLA GERMANICA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A cross resistant strain of German cockroach (Marietta) expressing multiple resistance mechanisms was subjected to intense cypermethrin selection pressure. Resistance to cypermethrin increased incrementally from 3.6-fold in the parental strain to 35-fold after 4 rounds of selection. Piperonyl butox...

  18. Reference site selection report for the advanced liquid metal reactor at the Idaho National Engineering Laboratory

    Microsoft Academic Search

    Sivill

    1990-01-01

    This Reference Site Selection Report was prepared by EG G, Idaho Inc., for General Electric (GE) to provide information for use by the Department of Energy (DOE) in selecting a Safety Test Site for an Advanced Liquid Metal Reactor. Similar Evaluation studies are planned to be conducted at other potential DOE sites. The Power Reactor Innovative Small Module (PRISM) Concept

  19. On the causal efficacy of natural selection: A response to Richards' critique of the standard interpretation.

    PubMed

    Sullivan-Clarke, Andrea

    2013-12-01

    Given the amount of literature devoted to the reasoning used in Darwin's Origin of Species, an interpretation seeking to revise the standard take on Darwin's methodology is unexpected. Yet, Richards (1997, 1998, 2005) challenges the view that Darwin drew an analogy in the Origin on the grounds that such a strategy could not support the possibility of a new species emerging. I suggest, however, that how one interprets causal efficacy is intimately connected with Darwin's use of analogy. A more robust conception of natural selection, as found in the Origin, supports the standard interpretation, significantly weakening Richards' charge of a paradox. PMID:24231184

  20. Can natural phenotypic variances be estimated reliably under homogeneous laboratory conditions?

    PubMed

    St Juliana, J R; Janzen, F J

    2007-07-01

    The phenotypic variance is assumed to be greater in a more heterogeneous environment. The validity of this assumption is important for microevolutionists to extrapolate results from the laboratory to field environments. We subjected clutches of eggs from common snapping turtles (Chelydra serpentina) to a split-family design to evaluate the variability in incubation time and four size traits of neonates from eggs incubated in the laboratory and those left in situ. Mean size measurements were similar between the laboratory and the field, but incubation time was systematically longer in the field. We found no tendency among clutches for hatchlings resulting from eggs incubated in laboratory or field environments to demonstrate greater variability. Also contrary to expectation, clutches that experienced greater thermal variation in the field did not exhibit greater variation in phenotypic traits. Consequently, extrapolating results from the laboratory to the field may not always be problematic for microevolutionary analyses. PMID:17584235

  1. Effects of ultraviolet radiation on early larval stages of the Alpine newt, Triturus alpestris , under natural and laboratory conditions

    Microsoft Academic Search

    Alexander M. Nagl; Rudolf Hofer

    1997-01-01

    Although Alpine newts (Triturus alpestris) are found at altitudes up to 2500 m, their larvae proved to be extremely sensitive to UV radiation when exposed in clear\\u000a tapwater to natural sunlight or to comparable artificial UV-B radiation in the laboratory. The experiments revealed severe\\u000a skin damages (lysis of epithelial cells) and mortality after a few days of exposure. In their

  2. Culture and maintenance of selected invertebrates in the laboratory and classroom.

    PubMed

    Smith, Stephen A; Scimeca, Joseph M; Mainous, Mary E

    2011-01-01

    Invertebrate species have been used for many years in the laboratory and teaching environment. We discuss some of the most commonly maintained invertebrates--the nematode (Caenorhabditis elegans), the California sea hare (Aplysia californica), the fruit fly (Drosophila melanogaster), terrestrial hermit crabs, the horseshoe crab (Limulus polyphemus), and cephalopods--and briefly describe general techniques for culturing them in captivity. The aim of this article is to give potential users an idea of the materials, methods, and effort required to maintain each type of organism in a laboratory or classroom setting. PMID:21709308

  3. ORGANOTIN TOXICITY STUDIES CONDUCTED WITH SELECTED MARINE ORGANISMS AT EPA'S ENVIRONMENTAL RESEARCH LABORATORY, GULF BREEZE, FLORIDA

    EPA Science Inventory

    Studies on effect of bis(tri-n-butyltin)oxide (TBTO) and other organotins on marine species have been conducted at the U.S. Environmental Protection Agency's laboratory at Gulf Breeze, Florida, since 1983. First studies were done on two species of algae, Skeletonema costatum and ...

  4. Laboratory toxicity and field efficacy of selected insecticides against fall armyworm (Lepidoptera: Notctuidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fall armyworm, Spodoptera frugiperda (J. E. Smith), is an occasional but often serious pest of several southern row crops, including: cotton, field corn, and grain sorghum. The objective of these studies was to generate baseline dose-mortality responses for fall armyworm larvae in laboratory bioas...

  5. Mineralogy of selected sedimentary interbeds at or near the Idaho National Engineering Laboratory, Idaho

    Microsoft Academic Search

    M. F. Reed; R. C. Bartholomay

    1994-01-01

    The US Geological Survey`s (USGS) Project Office at the Idaho National Engineering Laboratory (INEL) analyzed 66 samples from sedimentary interbed cores during a 38-month period beginning in October 1990 to determine bulk and clay mineralogy. These cores had been collected from 19 sites in the Big Lost River Basin, 2 sites in the Birch Creek Basin, and 1 site in

  6. Novel Experiments in Physics. A Selection of Laboratory Notes Now Used in Colleges and Universities.

    ERIC Educational Resources Information Center

    American Association of Physics Teachers, Washington, DC.

    The present volume was compiled by the AAPT Committee on Apparatus for Educational Institutions and by the AAPT-AIP Center for Education Apparatus in Physics to assist physics departments in the never-ending task of keeping their undergraduate laboratories up to date. The purpose of the book is to put before physics teachers for their…

  7. 75 FR 53277 - Notice of Intent To Terminate Selected National Voluntary Laboratory Accreditation Program (NVLAP...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-31

    ...includes the following areas of testing: paints and related coatings, paper and related...includes the following areas of testing: paints and related coatings, paper and related...laboratories are also accredited for plastic and paint testing in support of plumbing...

  8. Evaluation of toxicity of selected insecticides against thrips on cotton in laboratory bioassays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adult vial technique (AVT) and spray table bioassays were conducted to evaluate toxicity of selected insecticides against immature and adult Western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae). In AVT, technical insecticides comprising of organophosphates (d...

  9. Isolating "Unknown" Bacteria in the Introductory Microbiology Laboratory: A New Selective Medium for Gram-Positives.

    ERIC Educational Resources Information Center

    McKillip, John L.; Drake, MaryAnne

    1999-01-01

    Describes the development, preparation, and use of a medium that can select against a wide variety of Gram-negative bacteria while still allowing growth and differentiation of a wide range of Gram-positives. (WRM)

  10. Darwinian natural selection for orange bioluminescent color in a Jamaican click beetle.

    PubMed

    Stolz, Uwe; Velez, Sebastian; Wood, Keith V; Wood, Monika; Feder, Jeffrey L

    2003-12-01

    The Jamaican click beetle Pyrophorus plagiophthalamus (Coleoptera: Elateridae) is unique among all bioluminescent organisms in displaying a striking light color polymorphism [Biggley, W. H., Lloyd, J. E. & Seliger, H. H. (1967) J. Gen. Physiol. 50, 1681-1692]. Beetles on the island vary in the color of their ventral light organs from yellow-green to orange and their dorsal organs from green to yellow-green. The genetic basis for the color variation involves specific amino acid substitutions in the enzyme luciferase. Here, we show that dorsal and ventral light color in P. plagiophthalamus are under separate genetic control, we resolve the allelic basis for color variation, and, through analyses of luciferase sequence variation, we demonstrate that natural selection has produced a long-term adaptive trend for longer wavelength (more orange) ventral light on Jamaica. Our results constitute a novel example connecting the selective fixation of specific nucleotides in nature to their precisely determined phenotypic effects. We also present evidence suggesting that a recently derived ventral orange luciferase allele on the island has deterministically increased in frequency. Thus, the current luciferase polymorphism for P. plagiophthalamus appears to be mirroring the long-term anagenic trend on Jamaica, revealing a possible ongoing adaptive color transition in progress. PMID:14623957

  11. Complementary effect of natural and sexual selection against immigrants maintains differentiation between locally adapted fish.

    PubMed

    Plath, Martin; Riesch, Rüdiger; Oranth, Alexandra; Dzienko, Justina; Karau, Nora; Schiessl, Angela; Stadler, Stefan; Wigh, Adriana; Zimmer, Claudia; Arias-Rodriguez, Lenin; Schlupp, Ingo; Tobler, Michael

    2010-08-01

    Adaptation to ecologically heterogeneous environments can drive speciation. But what mechanisms maintain reproductive isolation among locally adapted populations? Using poeciliid fishes in a system with naturally occurring toxic hydrogen sulfide, we show that (a) fish from non-sulfidic sites (Poecilia mexicana) show high mortality (95 %) after 24 h when exposed to the toxicant, while locally adapted fish from sulfidic sites (Poecilia sulphuraria) experience low mortality (13 %) when transferred to non-sulfidic water. (b) Mate choice tests revealed that P. mexicana females exhibit a preference for conspecific males in non-sulfidic water, but not in sulfidic water, whereas P. sulphuraria females never showed a preference. Increased costs of mate choice in sulfidic, hypoxic water, and the lack of selection for reinforcement due to the low survival of P. mexicana may explain the absence of a preference in P. sulphuraria females. Taken together, our study may be the first to demonstrate independent-but complementary-effects of natural and sexual selection against immigrants maintaining differentiation between locally adapted fish populations. PMID:20574847

  12. Complementary effect of natural and sexual selection against immigrants maintains differentiation between locally adapted fish

    NASA Astrophysics Data System (ADS)

    Plath, Martin; Riesch, Rüdiger; Oranth, Alexandra; Dzienko, Justina; Karau, Nora; Schießl, Angela; Stadler, Stefan; Wigh, Adriana; Zimmer, Claudia; Arias-Rodriguez, Lenin; Schlupp, Ingo; Tobler, Michael

    2010-08-01

    Adaptation to ecologically heterogeneous environments can drive speciation. But what mechanisms maintain reproductive isolation among locally adapted populations? Using poeciliid fishes in a system with naturally occurring toxic hydrogen sulfide, we show that (a) fish from non-sulfidic sites ( Poecilia mexicana) show high mortality (95 %) after 24 h when exposed to the toxicant, while locally adapted fish from sulfidic sites ( Poecilia sulphuraria) experience low mortality (13 %) when transferred to non-sulfidic water. (b) Mate choice tests revealed that P. mexicana females exhibit a preference for conspecific males in non-sulfidic water, but not in sulfidic water, whereas P. sulphuraria females never showed a preference. Increased costs of mate choice in sulfidic, hypoxic water, and the lack of selection for reinforcement due to the low survival of P. mexicana may explain the absence of a preference in P. sulphuraria females. Taken together, our study may be the first to demonstrate independent—but complementary—effects of natural and sexual selection against immigrants maintaining differentiation between locally adapted fish populations.

  13. Natural selection in utero induced by mass layoffs: the hCG evidence.

    PubMed

    Catalano, Ralph; Margerison-Zilko, Claire; Goldman-Mellor, Sidra; Pearl, Michelle; Anderson, Elizabeth; Saxton, Katherine; Bruckner, Tim; Subbaraman, Meenakshi; Goodman, Julia; Epstein, Mollie; Currier, Robert; Kharrazi, Martin

    2012-12-01

    Evolutionary theory, when coupled with research from epidemiology, demography, and population endocrinology, suggests that contracting economies affect the fitness and health of human populations via natural selection in utero. We know, for example, that fetal death increases more among males than females when the economy unexpectedly contracts; that unexpected economic contraction predicts low secondary sex ratios; and that males from low sex ratio birth cohorts live, on average, longer than those from high sex ratio cohorts. We also know that low levels of human chorionic gonadotropin (i.e., hCG) measured in the serum of pregnant women predict fetal death. We do not, however, know whether male survivors of conception cohorts subjected to contracting economies exhibit, as theory predicts, higher hCG than those from other cohorts. We show, in 71 monthly conception cohorts including nearly two million California births, that they do. We thereby add to the literature suggesting that the economy, a phenomenon over which we collectively exercise at least some control, affects population health. Our findings imply that the effect arises via natural selection - a mechanism we largely ignore when attempting to explain, or alter, how collective choice affects our biology. PMID:23346225

  14. Moving from the laboratory to the field: Adding natural environmental conditions to toxicology testing

    EPA Science Inventory

    While laboratory toxicology tests are generally easy to perform, cost effective and readily interpreted, they have been criticized for being unrealistic. In contrast, field tests are considered realistic while producing results that are difficult to interpret and expensive. To ...

  15. Vegetation-derived cues for the selection of oviposition substrates by Anopheles albimanus under laboratory conditions.

    PubMed

    Torres-Estrada, José Luis; Meza-Alvarez, R Amanda; Cibrián-Tovar, Juan; Rodríguez-López, Mario H; Arredondo-Jiménez, Juan I; Cruz-López, Leopoldo; Rojas-Leon, Julio C

    2005-12-01

    Oviposition response of gravid Anopheles albimanus Wiedemman (Diptera: Culicidae) females to water containing Brachiaria mutica, Cynodon dactylon, Jouvea straminea, Fimbristylis spadicea, and Ceratophyllum demersum was investigated. Gravid An. albimanus females deposited similar egg numbers in cups containing natural plants in water from natural breeding sites and in cups containing natural plants in distilled water. Gravid mosquitoes deposited significantly more eggs in cups containing natural plants in water from natural breeding sites than in cups containing artificial plants in water from the corresponding natural breeding sites. These results were confirmed in experiments conducted in a wind tunnel, indicating that female response is mediated by chemical cues from plants. Bioassays with organic extracts of all 5 plant species indicated that these extracts at 100%, 10%, and 1% concentrations had an oviposition repellent effect, while attractiveness was observed at 0.1%, 0.01%, and 0.001%. Gas chromatography and mass spectrometry analysis of the organic extracts found in all 5 plants showed a mixture of terpenoid and alcohol compounds, among them: guaiacol, phenol, isoeugenol, longifolene, caryophyllene, phenyl ethyl alcohol, and p-cresol. These results suggest that middle-range volatiles from plants may function as chemical cues for the female's oviposition response in this mosquito species. PMID:16506557

  16. Natural selection on a measure of parasite resistance varies across ages and environmental conditions in a wild mammal

    E-print Network

    Lummaa, Virpi

    Natural selection on a measure of parasite resistance varies across ages and environmental Individuals in natural populations are under constant threat of infection from parasitic organisms that have detrimental effects on host condition and fitness (Poulin, 2007). Infection and damage by parasites may

  17. Negative frequency-dependent selection or alternative reproductive tactics: maintenance of female polymorphism in natural populations

    PubMed Central

    2013-01-01

    Background Sex-limited polymorphisms have long intrigued evolutionary biologists and have been the subject of long-standing debates. The coexistence of multiple male and/or female morphs is widely believed to be maintained through negative frequency-dependent selection imposed by social interactions. However, remarkably few empirical studies have evaluated how social interactions, morph frequencies and fitness parameters relate to one another under natural conditions. Here, we test two hypotheses proposed to explain the maintenance of a female polymorphism in a species with extreme geographical variation in morph frequencies. We first elucidate how fecundity traits of the morphs vary in relation to the frequencies and densities of males and female morphs in multiple sites over multiple years. Second, we evaluate whether the two female morphs differ in resource allocation among fecundity traits, indicating alternative tactics to maximize reproductive output. Results We present some of the first empirical evidence collected under natural conditions that egg number and clutch mass was higher in the rarer female morph. This morph-specific fecundity advantage gradually switched with the population morph frequency. Our results further indicate that all investigated fecundity traits are negatively affected by relative male density (i.e. operational sex ratio), which confirms male harassment as selective agent. Finally, we show a clear trade-off between qualitative (egg mass) and quantitative (egg number) fecundity traits. This trade-off, however, is not morph-specific. Conclusion Our reported frequency- and density-dependent fecundity patterns are consistent with the hypothesis that the polymorphism is driven by a conflict between sexes over optimal mating rate, with costly male sexual harassment driving negative frequency-dependent selection on morph fecundity. PMID:23822745

  18. ON THE NATURE OF THE FIRST GALAXIES SELECTED AT 350 mum

    SciTech Connect

    Khan, Sophia A. [Pontificia Universidad Catolica, Departamento de AstronomIa y Astrofisica, 4860 Vicuna Mackenna, Casilla 306, Santiago 22 (Chile); Chanial, Pierre F.; Clements, David L.; Sumner, Timothy J. [Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom); Willner, S. P.; Ashby, M. L. N.; Fazio, G. G.; Huang, J.-S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Pearson, Chris P. [Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Benford, Dominic J.; Moseley, S. Harvey; Shafer, Richard A.; Staguhn, Johannes [Observational Cosmology Laboratory (Code 665), NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Dye, Simon [School of Physics and Astronomy, Cardiff University, Queens Buildings, Cardiff, CF24 3AA (United Kingdom); Farrah, Duncan [Astronomy Centre, University of Sussex, Falmer, Brighton (United Kingdom); Lebouteiller, V. [Department of Astronomy, Cornell University, 610 Space Sciences Building, Ithaca, NY 14853 (United States); Le Floc'h, Emeric [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96815 (United States); Mainetti, Gabriele [Department of Astronomy, University of Padova, Vicolo Osservatorio 3, I-35122, Padova (Italy); Negrello, Mattia; Serjeant, Stephen [Department of Physics and Astronomy, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    2009-11-20

    We present constraints on the nature of the first galaxies selected at 350 mum. The sample includes galaxies discovered in the deepest blank-field survey at 350 mum (in the Booetes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 mum position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 mum counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 < z < 3 predominantly powered by star formation. The first spectrum of a 350 mum selected galaxy provides an additional confirmation, showing prominent dust grain features typically associated with star-forming galaxies. Compared to submillimeter galaxies selected at 850 and 1100 mum, galaxies selected at 350 mum have a similar range of far-infrared color temperatures. However, no 350 mum selected sources are reliably detected at 850 or 1100 mum. Galaxies in our sample with redshifts 1 < z < 2 show a tight correlation between the far- and mid-infrared flux densities, but galaxies at higher redshifts show a large dispersion in their mid- to far-infrared colors. This implies a limit to which the mid-IR emission traces the far-IR emission in star-forming galaxies. The 350 mum flux densities (15 < S{sub 350} < 40 mJy) place these objects near the Herschel/SPIRE 350 mum confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 mum contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 mum background-star-forming galaxies in the epoch of peak star formation in the universe-could be more effectively probed using ground-based instruments with their angular resolution and sensitivity offering significant advantages over space-based imaging.

  19. Learning Natural Selection in 4th Grade with Multi-Agent-Based Computational Models

    NASA Astrophysics Data System (ADS)

    Dickes, Amanda Catherine; Sengupta, Pratim

    2013-06-01

    In this paper, we investigate how elementary school students develop multi-level explanations of population dynamics in a simple predator-prey ecosystem, through scaffolded interactions with a multi-agent-based computational model (MABM). The term "agent" in an MABM indicates individual computational objects or actors (e.g., cars), and these agents obey simple rules assigned or manipulated by the user (e.g., speeding up, slowing down, etc.). It is the interactions between these agents, based on the rules assigned by the user, that give rise to emergent, aggregate-level behavior (e.g., formation and movement of the traffic jam). Natural selection is such an emergent phenomenon, which has been shown to be challenging for novices (K16 students) to understand. Whereas prior research on learning evolutionary phenomena with MABMs has typically focused on high school students and beyond, we investigate how elementary students (4th graders) develop multi-level explanations of some introductory aspects of natural selection—species differentiation and population change—through scaffolded interactions with an MABM that simulates predator-prey dynamics in a simple birds-butterflies ecosystem. We conducted a semi-clinical interview based study with ten participants, in which we focused on the following: a) identifying the nature of learners' initial interpretations of salient events or elements of the represented phenomena, b) identifying the roles these interpretations play in the development of their multi-level explanations, and c) how attending to different levels of the relevant phenomena can make explicit different mechanisms to the learners. In addition, our analysis also shows that although there were differences between high- and low-performing students (in terms of being able to explain population-level behaviors) in the pre-test, these differences disappeared in the post-test.

  20. Artificial natural selection: can supplemental feeding domesticate mosquitoes and control mosquito-borne diseases?

    PubMed

    Egeth, Marc; Kurzban, Robert

    2012-01-01

    A new method is proposed for controlling mosquito-borne diseases. In particular, instead of trying to kill mosquitoes, we suggest provisioning them with food from artificial feeders. Because mosquito populations are frequently limited by ecological factors other than blood meals, such as the availability of egg-laying sites, feeding mosquitoes would not necessarily increase the total number of mosquitoes, but could reduce the number of human-drawn mosquito meals. Like mosquito traps, feeders could divert biting mosquitoes away from people by means of lures, but, after diversion, prevent subsequent human bites by satiating the mosquitoes instead of killing them. Mosquito feeders might reduce the problem of the evolution of resistance to control: in an ecology with mosquito feeders, which provide safe and abundant calories for adult female mosquitoes, there could be selection for preferring (rather than avoiding) feeders, which could eventually lead to a population of feeder-preferring mosquitoes. Artificial feeders also offer the chance to introduce novel elements into the mosquito diet, such as anti- malarial or other anti-parasitic agents. Feeders might directly reduce human bites and harnesses the power of natural selection by selectively favoring feeder-preferring (rather than trap-resistant) mosquitoes. PMID:22947681

  1. Laboratory mating trials indicate incipient speciation by sexual selection among populations of the cichlid fish Pseudotropheus zebra from Lake Malawi.

    PubMed Central

    Knight, Mairi E.; Turner, George F.

    2004-01-01

    It has been suggested that sexual selection may have played a major role in the rapid evolution of hundreds of species of cichlid fishes in Lake Malawi. We report the results of a laboratory test of assortative mating among Lake Malawi cichlid fishes from five closely related geographical populations differing in male courtship colour. Paternity of clutches was tested using microsatellite DNA typing of offspring. Out of 1955 offspring typed, 1296 (66.3%) were sired by the male from the same population as the female, which is more than three times the rate expected if females do not differentiate among males of the different populations (20%). This result indicates that mate preferences of geographical races are strongly differentiated, consistent with the races representing incipient geographical species diverging under sexual selection exerted by female preferences for different male courtship colours. PMID:15209099

  2. Genome-wide Comparison of African-Ancestry Populations from CARe and Other Cohorts Reveals Signals of Natural Selection

    PubMed Central

    Bhatia, Gaurav; Patterson, Nick; Pasaniuc, Bogdan; Zaitlen, Noah; Genovese, Giulio; Pollack, Samuela; Mallick, Swapan; Myers, Simon; Tandon, Arti; Spencer, Chris; Palmer, Cameron D.; Adeyemo, Adebowale A.; Akylbekova, Ermeg L.; Cupples, L. Adrienne; Divers, Jasmin; Fornage, Myriam; Kao, W.H. Linda; Lange, Leslie; Li, Mingyao; Musani, Solomon; Mychaleckyj, Josyf C.; Ogunniyi, Adesola; Papanicolaou, George; Rotimi, Charles N.; Rotter, Jerome I.; Ruczinski, Ingo; Salako, Babatunde; Siscovick, David S.; Tayo, Bamidele O.; Yang, Qiong; McCarroll, Steve; Sabeti, Pardis; Lettre, Guillaume; De Jager, Phil; Hirschhorn, Joel; Zhu, Xiaofeng; Cooper, Richard; Reich, David; Wilson, James G.; Price, Alkes L.

    2011-01-01

    The study of recent natural selection in human populations has important applications to human history and medicine. Positive natural selection drives the increase in beneficial alleles and plays a role in explaining diversity across human populations. By discovering traits subject to positive selection, we can better understand the population level response to environmental pressures including infectious disease. Our study examines unusual population differentiation between three large data sets to detect natural selection. The populations examined, African Americans, Nigerians, and Gambians, are genetically close to one another (FST < 0.01 for all pairs), allowing us to detect selection even with moderate changes in allele frequency. We also develop a tree-based method to pinpoint the population in which selection occurred, incorporating information across populations. Our genome-wide significant results corroborate loci previously reported to be under selection in Africans including HBB and CD36. At the HLA locus on chromosome 6, results suggest the existence of multiple, independent targets of population-specific selective pressure. In addition, we report a genome-wide significant (p = 1.36 × 10?11) signal of selection in the prostate stem cell antigen (PSCA) gene. The most significantly differentiated marker in our analysis, rs2920283, is highly differentiated in both Africa and East Asia and has prior genome-wide significant associations to bladder and gastric cancers. PMID:21907010

  3. Wavelength selection and spectral discrimination for paddy rice, with laboratory measurements of hyperspectral leaf reflectance

    NASA Astrophysics Data System (ADS)

    Song, Shalei; Gong, Wei; Zhu, Bo; Huang, Xin

    2011-09-01

    The objective of this research is to select the most sensitive wavelengths for the discrimination of the imperceptible spectral variations of paddy rice under different cultivation conditions. The paddy rice was cultivated under four different nitrogen cultivation levels and three water irrigation levels. There are 2151 hyperspectral wavelengths available, both in hyperspectral reflectance and energy space transformed spectral data. Based on these two data sets, the principal component analysis (PCA) and band-band correlation methods were used to select significant wavelengths with no reference to leaf biochemical properties, while the partial least squares (PLS) method assessed the contribution of each narrow band to leaf biochemical content associated with each loading weight across the nitrogen and water stresses. Moreover, several significant narrow bands and other broad bands were selected to establish eight kinds of wavelength (broad-band) combinations, focusing on comparing the performance of the narrow-band combinations instead of broad-band combinations for rice supervising applications. Finally, to investigate the capability of the selected wavelengths to diagnose the stress conditions across the different cultivation levels, four selected narrow bands (552, 675, 705 and 776 nm) were calculated and compared between nitrogen-stressed and non-stressed rice leaves using linear discriminant analysis (LDA). Also, wavelengths of 1158, 1378 and 1965 nm were identified as the most useful bands to diagnose the stress condition across three irrigation levels. Results indicated that good discrimination was achieved. Overall, the narrow bands based on hyperspectral reflectance data appear to have great potential for discriminating rice of differing cultivation conditions and for detecting stress in rice vegetation; these selected wavelengths also have great potential use for the designing of future sensors.

  4. Compilation of minimum and maximum isotope ratios of selected elements in naturally occurring terrestrial materials and reagents

    USGS Publications Warehouse

    Coplen, T.B.; Hopple, J.A.; Böhlke, J.K.; Peiser, H.S.; Rieder, S.E.; Krouse, H.R.; Rosman, K.J.R.; Ding, T.; Vocke, R.D., Jr.; Revesz, K.M.; Lamberty, A.; Taylor, P.; De Bievre, P.

    2002-01-01

    Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope abundance variations potentially are large enough to result in future expansion of their atomic weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope-abundance variations in materials of natural terrestrial origin are too small to have a significant effect on their standard atomic weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio. There are no internationally distributed isotopic reference materials for the elements zinc, selenium, molybdenum, palladium, and tellurium. Preparation of such materials will help to make isotope ratio measurements among laboratories comparable. The minimum and maximum concentrations of a selected isotope in naturally occurring terrestrial materials for selected chemical elements reviewed in this report are given below: Isotope Minimum mole fraction Maximum mole fraction -------------------------------------------------------------------------------- 2H 0 .000 0255 0 .000 1838 7Li 0 .9227 0 .9278 11B 0 .7961 0 .8107 13C 0 .009 629 0 .011 466 15N 0 .003 462 0 .004 210 18O 0 .001 875 0 .002 218 26Mg 0 .1099 0 .1103 30Si 0 .030 816 0 .031 023 34S 0 .0398 0 .0473 37Cl 0 .240 77 0 .243 56 44Ca 0 .020 82 0 .020 92 53Cr 0 .095 01 0 .095 53 56Fe 0 .917 42 0 .917 60 65Cu 0 .3066 0 .3102 205Tl 0 .704 72 0 .705 06 The numerical values above have uncertainties that depend upon the uncertainties of the determinations of the absolute isotope-abundance variations of reference materials of the elements. Because reference materials used for absolute isotope-abundance measurements have not been included in relative isotope abundance investigations of zinc, selenium, molybdenum, palladium, and tellurium, ranges in isotopic composition are not listed for these elements, although such ranges may be measurable with state-of-the-art mass spectrometry. This report is available at the url: http://pubs.water.usgs.gov/wri014222.

  5. Elucidating the role of genetic drift and natural selection in cork oak differentiation regarding drought tolerance.

    PubMed

    Ramírez-Valiente, J A; Lorenzo, Z; Soto, A; Valladares, F; Gil, L; Aranda, I

    2009-09-01

    Drought is the main selection agent in Mediterranean ecosystems and it has been suggested as an important evolutionary force responsible for population diversification in these types of environments. However, population divergence in quantitative traits can be driven by either natural selection, genetic drift or both. To investigate the roles of these forces on among-population divergence in ecophysiological traits related to drought tolerance (carbon isotope discrimination, specific leaf area, leaf size and leaf nitrogen content), we compared molecular and quantitative genetic differentiation in a common garden experiment including thirteen cork oak (Quercus suber L.) populations across a gradient of rainfall and temperature. Population differentiation for height, specific leaf area, leaf size and nitrogen leaf content measured during a dry year far exceeded the molecular differentiation measured by six nuclear microsatellites. Populations from dry-cool sites showed the lowest nitrogen leaf content and the smallest and thickest leaves contrasting with those from humid-warm sites. These results suggest (i) these traits are subjected to divergence selection and (ii) the genetic differences among populations are partly due to climate adaptation. By contrast, the low among-population divergence found in basal diameter, annual growth and carbon isotopic discrimination (a surrogate for water use efficiency) suggests low or no divergence selection for these traits. Among-population differentiation for neutral markers was not a good predictor for differentiation regarding the quantitative traits studied here, except for leaf size. The correlation observed between the genetic differentiation for leaf size and that for molecular markers was exclusively due to the association between leaf size and the microsatellite QpZAG46, which suggests a possible linkage between QpZAG46 and genes encoding for leaf size. PMID:19732337

  6. Comparison of laboratory delignification methods, their selectivity, and impacts on physiochemical characteristics of cellulosic biomass

    E-print Network

    California at Riverside, University of

    , and information for less recalci- trant lignocellulosic feedstocks and pretreated biomass is scarce. Furthermore. " Various raw and pretreated biomass solids and pure cellulose were used. " Delignification selectivity, and pine sawdust; pop- lar subjected to AFEX, controlled pH, lime, and SO2 pretreatments; and the cellulose

  7. Allergic reactions to glove materials Gloves are common in research laboratories. The selection

    E-print Network

    Shull, Kenneth R.

    -immune reaction affecting the skin, and should not be confused with an allergy. Exposure to glove materials can to natural rubber latex proteins and/or synthetic chemicals in the glove material. Latex allergy is an Ig a protein. Latex products can cause Type I allergy as well as Type IV allergy. Type I allergy to latex

  8. Influence of the nature of the quaternary ammonium base on the sensitivity and selectivity of membrane thiocyanate-selective electrodes

    SciTech Connect

    Tulyupa, F.M.; Fedchuk, T.M.

    1987-11-10

    A study has been made of the properties of 10 thiocyanate-selective electrodes based on the thiocyanates of quaternary ammonium bases. It has been established that the sensitivity and selectivity of the electrodes is determined by the critical micelle concentration (CMC) of the ionic association entering into the composition of the membrane: the lower the CMC is, the lower the limit of detection of thiocyanate ions is and the higher the selectivity of the electrodes is relative to other anions.

  9. A Study of the Relative Effectiveness of Selected Laboratory and Classroom Programs in Driver and Traffic Safety Education. Washington Driver and Traffic Safety Education Project.

    ERIC Educational Resources Information Center

    McDaniel, Charles E.

    In their study of driver education practices, the authors investigated the relative effectiveness of four selected driver and traffic safety education laboratory programs, three selected driver and traffic safety education classroom programs, and sought to determine if the effectiveness of a program is affected by the sex of the student. The…

  10. Investigating the genetics of Bti resistance using mRNA tag sequencing: application on laboratory strains and natural populations of the dengue vector Aedes aegypti

    PubMed Central

    Paris, Margot; Marcombe, Sebastien; Coissac, Eric; Corbel, Vincent; David, Jean-Philippe; Després, Laurence

    2013-01-01

    Mosquito control is often the main method used to reduce mosquito-transmitted diseases. In order to investigate the genetic basis of resistance to the bio-insecticide Bacillus thuringiensis subsp. israelensis (Bti), we used information on polymorphism obtained from cDNA tag sequences from pooled larvae of laboratory Bti-resistant and susceptible Aedes aegypti mosquito strains to identify and analyse 1520 single nucleotide polymorphisms (SNPs). Of the 372 SNPs tested, 99.2% were validated using DNA Illumina GoldenGate® array, with a strong correlation between the allelic frequencies inferred from the pooled and individual data (r = 0.85). A total of 11 genomic regions and five candidate genes were detected using a genome scan approach. One of these candidate genes showed significant departures from neutrality in the resistant strain at sequence level. Six natural populations from Martinique Island were sequenced for the 372 tested SNPs with a high transferability (87%), and association mapping analyses detected 14 loci associated with Bti resistance, including one located in a putative receptor for Cry11 toxins. Three of these loci were also significantly differentiated between the laboratory strains, suggesting that most of the genes associated with resistance might differ between the two environments. It also suggests that common selected regions might harbour key genes for Bti resistance. PMID:24187584

  11. [Surgical stress: clinical-and-laboratory parallels under activation of the natural stress-limiting systems].

    PubMed

    Gvak, G V; Eremenko, V G; Ivanov, E A; Smantser, V A

    2004-01-01

    Three hundred and eighty-seven patients, who were operated on the scheduled basis for different surgical pathologies, were examined. The purpose of the case study was definition of the clinical-and-laboratory parallels related with pronouncement of surgical stress in an advanced variation of neuroleptanalgesia. PMID:15468552

  12. Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.12 | DECEMBER 2005 | 997 CLASSIC PROTOCOL

    E-print Network

    Cai, Long

    to Southern blotting, which is used to analyze DNA. This protocol describes the transfer of RNA from agarose PROTOCOL PUBLISHED IN ASSOCIATION WITH COLD SPRING HARBOR LABORATORY PRESS Northern blotting: transfer of denatured RNA to membranes Northern blotting and hybridization are used to study gene expression

  13. Cold Spring Harbor Laboratory Press NATURE METHODS | VOL.2 NO.9 | SEPTEMBER 2005 | 719 CLASSIC PROTOCOL

    E-print Network

    Cai, Long

    , the genomic DNA is subjected to Southern blot analysis. If a probe derived from the DNA fragment hybridizes electrophoresis and Southern blot analysis. PROCEDURE 1| Pellet ~108 cells at 300g at 4 °C for 10 min PROTOCOL PUBLISHED IN ASSOCIATION WITH COLD SPRING HARBOR LABORATORY PRESS Micrococcal nuclease­Southern

  14. Natural Selection Canalizes Expression Variation of Environmentally Induced Plasticity-Enabling Genes

    PubMed Central

    Shaw, Joseph R.; Hampton, Thomas H.; King, Benjamin L.; Whitehead, Andrew; Galvez, Fernando; Gross, Robert H.; Keith, Nathan; Notch, Emily; Jung, Dawoon; Glaholt, Stephen P.; Chen, Celia Y.; Colbourne, John K.; Stanton, Bruce A.

    2014-01-01

    Many organisms survive fluctuating and extreme environmental conditions by manifesting multiple distinct phenotypes during adulthood by means of developmental processes that enable phenotypic plasticity. We report on the discovery of putative plasticity-enabling genes that are involved in transforming the gill of the euryhaline teleost fish, Fundulus heteroclitus, from its freshwater to its seawater gill-type, a process that alters both morphology and function. Gene expression that normally enables osmotic plasticity is inhibited by arsenic. Gene sets defined by antagonistic interactions between arsenic and salinity show reduced transcriptional variation among individual fish, suggesting unusually accurate and precise regulatory control of these genes, consistent with the hypothesis that they participate in a canalized developmental response. We observe that natural selection acts to preserve canalized gene expression in populations of killifish that are most tolerant to abrupt salinity change and that these populations show the least variability in their transcription of genes enabling plasticity of the gill. We found that genes participating in this highly canalized and conserved plasticity-enabling response had significantly fewer and less complex associations with transcriptional regulators than genes that respond only to arsenic or salinity. Collectively these findings, which are drawn from the relationships between environmental challenge, plasticity, and canalization among populations, suggest that the selective processes that facilitate phenotypic plasticity do so by targeting the regulatory networks that gives rise to the response. These findings also provide a generalized, conceptual framework of how genes might interact with the environment and evolve toward the development of plastic traits. PMID:25158801

  15. Characterizing selection on phenotypic plasticity in response to natural environmental heterogeneity.

    PubMed

    Baythavong, Brooke S; Stanton, Maureen L

    2010-10-01

    Adaptive genetic differentiation and adaptive phenotypic plasticity can increase the fitness of plant lineages in heterogeneous environments. We examine the relative importance of genetic differentiation and plasticity in determining the fitness of the annual plant, Erodium cicutarium, in a serpentine grassland in California. Previous work demonstrated that the serpentine sites within this mosaic display stronger dispersal-scale heterogeneity than nonserpentine sites. We conducted a reciprocal transplant experiment among six sites to characterize selection on plasticity expressed by 180 full-sibling families in response to natural environmental heterogeneity across these sites. Multivariate axes of environmental variation were constructed using a principal components analysis of soil chemistry data collected at every experimental block. Simple linear regressions were used to characterize the intercept, and slope (linear and curvilinear) of reaction norms for each full-sibling family in response to each axis of environmental variation. Multiple linear regression analyses revealed significant selection on trait means and slopes of reaction norms. Multivariate analyses of variance demonstrated genetic differentiation between serpentine and nonserpentine lineages in the expression of plasticity in response to three of the five axes of environmental variation considered. In all but one case, serpentine genotypes expressed a stronger adaptive plastic response than nonserpentine genotypes. PMID:20649815

  16. Rhythmic natural selection over intertidal and brackish water genotypes: simple formulations for testing hypothesis.

    PubMed

    Lara, M; Binder, P M; Figueredo-Fernández, M A

    2014-04-01

    Tidal cycles at benthic habitats induce a set of periodic environmental changes in variables like salinity, temperature and sediment water content which are able to stress benthic organisms. Consequently, a natural selection temporally correlated with tides affects the fitness of genotypes (wi) depending on their adaptation degree. Classic population genetics demonstrate that (1) rhythmic wi is more restrictive than equivalent spatial variations to preserve genetic variance, and (2) mean fitness of the population (w¯) does not have to be enhanced by genetic variance (?(2)w). The present study develops a simple replicator dynamics-based model of continuous selection, where wi of multiple asexual genotypes fluctuates as a sinusoid. The amplitude of w was set as 0.5 (1-wmin), whereas the ratio of tide period to generation time (h) was defined. Overall, the model shows that if h>1, then the success of an advantageous genotype is exposed to randomness, and w¯ may decrease over generations. In contrast, if h<1 the success is deterministic, is limiting co-dominance, and only depends on wmin. The amount of different genotypes buffers the decay of ?(2)w and hence increases cohesiveness. Finally, the reliability of the model is analyzed for a set of target intertidal and brackish water organisms. PMID:24412494

  17. Reduced disease in black abalone following mass mortality: phage therapy and natural selection

    PubMed Central

    Friedman, Carolyn S.; Wight, Nathan; Crosson, Lisa M.; VanBlaricom, Glenn R.; Lafferty, Kevin D.

    2014-01-01

    Black abalone, Haliotis cracherodii, populations along the NE Pacific ocean have declined due to the rickettsial disease withering syndrome (WS). Natural recovery on San Nicolas Island (SNI) of Southern California suggested the development of resistance in island populations. Experimental challenges in one treatment demonstrated that progeny of disease-selected black abalone from SNI survived better than did those from naïve black abalone from Carmel Point in mainland coastal central California. Unexpectedly, the presence of a newly observed bacteriophage infecting the WS rickettsia (WS-RLO) had strong effects on the survival of infected abalone. Specifically, presence of phage-infected RLO (RLOv) reduced the host response to infection, RLO infection loads, and associated mortality. These data suggest that the black abalone: WS-RLO relationship is evolving through dual host mechanisms of resistance to RLO infection in the digestive gland via tolerance to infection in the primary target tissue (the post-esophagus) coupled with reduced pathogenicity of the WS-RLO by phage infection, which effectively reduces the infection load in the primary target tissue by half. Sea surface temperature patterns off southern California, associated with a recent hiatus in global-scale ocean warming, do not appear to be a sufficient explanation for survival patterns in SNI black abalone. These data highlight the potential for natural recovery of abalone populations over time and that further understanding of mechanisms governing host–parasite relationships will better enable us to manage declining populations. PMID:24672512

  18. [Selective feeding in fish: Effect of feeding and defensive motivations evoked by natural odors].

    PubMed

    Kasumyan, A O; Marusov, E A

    2015-01-01

    The effect of feeding and defensive motivations evoked by natural olfactory signals (the food odor, the alarm pheromone) on choice and consumption of food items different in color and taste, and the manifestation of foraging behavior were examined in fish (koi Cyprinus carpio, roach Rutilus rutilus). The agar-agar pellets of red and green color having one of the amino acids (glycine, L-proline, L-alanine; all in concentration of 0.1 M) were simultaneously offered to single fishes in pure water, and in water extract of Chironomidae larvae or in water extract of fish skin. It was found out that odors used have different effects on fish foraging activity and on pellet selection for both pellet choice and consumption. On background of food odor, fish grasped pellets more often than in pure water. The equal choice of red and green pellets in pure water shifted to the preference of red ones in the presence of food odor. Despite the increase in the absolute number of pellets grasped, the relative consumption reduced and was replaced by selective consumption of pellets with glycine regardless of their color. Increasing demand for the food quality, due to the increased feeding motivation in response to food odor, is an important adaptation enhancing selection and consumption of food with more appropriate sensory qualities for fish. Defensive motivation caused by alarm pheromone suppressed predisposition. of fish to feed. Fish grasped pellets several times less often than in pure water and refused most of them. Any changes in the color or taste preferences were absent. Feeding behavior of fish of both species was characterized by repeated intraoral pellet testing, but in koi handling was less typical than in roach. In both species, handling activity was higher in those cases when the pellet was finally rejected. This activity was enhanced also on the background of food odor. PMID:26201217

  19. Multi-robots to micro-surgery: Selected robotic applications at Sandia National Laboratories

    SciTech Connect

    Bennett, P.C. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Systems and Robotics Center

    1996-11-01

    The Intelligent Systems and Robotics Center (ISRC) at Sandia National Laboratories is a multi-program organization, pursuing research, development and applications in a wide range of field. Activities range from large-scale applications such as nuclear facility dismantlement for the US Department of Energy (DOE), to aircraft inspection and refurbishment, to automated script and program generation for robotic manufacturing and assembly, to miniature robotic devices and sensors for remote sensing and micro-surgery. This paper describes six activities in the large and small scale that are underway and either nearing technology transfer stage or seeking industrial partners to continue application development. The topics of the applications include multiple arm coordination for intuitively maneuvering large, ungainly work pieces; simulation, analysis and graphical training capability for CP-5 research reactor dismantlement; miniature robots with volumes of 16 cubic centimeters and less developed for inspection and sensor deployment; and biomedical sensors to enhance automated prosthetic device production and fill laparoscopic surgery information gap.

  20. Intense natural selection caused a rapid morphological transition in a living marine snail.

    PubMed

    Seeley, R H

    1986-09-01

    Shell shape and shell thickness of the intertidal snail Littorina obtusata changed markedly between 1871 and 1984 in northern New England. Shells collected prior to 1900 were high-spired with thin walls, whereas shells collected in 1982-84 were low-spired with thick walls. An intertidal crab (Carcinus maenas) which preys on L. obtusata expanded its range into northern New England around 1900. This suggests that the change in snail shell form was a response to predation by Carcinus. Field and laboratory experiments demonstrated that the high-spired form of L. obtusata, which can still be found in some Maine localities, is more vulnerable to predation by Carcinus than is the low-spired form of L. obtusata. Electrophoretic comparisons of high- and low-spired populations of L. obtusata confirmed that these populations represent different morphological forms of L. obtusata rather than different species [Nei's D (unbiased measure of genetic distance) = 0.003]. These data demonstrate that classical Darwinian selection can produce a rapid morphological transition without speciation. PMID:16593760

  1. Natural attenuation of metals and radionuclides: Report from a workshop held by Sandia National Laboratories

    SciTech Connect

    Brady, P.V.; Borns, D.J. [Sandia National Labs., Albuquerque, NM (United States). Geochemistry Dept.

    1997-11-01

    Natural attenuation is increasingly applied to remediate contaminated soils and ground waters. Roughly 25% of Superfund groundwater remedies in 1995 involved some type of monitored natural attenuation, compared to almost none 5 years ago. Remediation by natural attenuation (RNA) requires clear evidence that contaminant levels are decreasing sufficiently over time, a defensible explanation of the attenuation mechanism, long-term monitoring, and a contingency plan at the very least. Although the primary focus of implementation has to date been the biodegradation of organic contaminants, there is a wealth of scientific evidence that natural processes reduce the bioavailability of contaminant metals and radionuclides. Natural attenuation of metals and radionuclides is likely to revolve around sorption, solubility, biologic uptake and dilution controls over contaminant availability. Some of these processes can be applied to actively remediate sites. Others, such as phytoremediation, are likely to be ineffective. RNA of metals and radionuclides is likely to require specialized site characterization to construct contaminant and site-specific conceptual models of contaminant behavior. Ideally, conceptual models should be refined such that contaminant attenuation can be confidently predicted into the future. The technical approach to RNA of metals and radionuclides is explored here.

  2. Did RNA editing in plant organellar genomes originate under natural selection or through genetic drift?

    PubMed Central

    Jobson, Richard W; Qiu, Yin-Long

    2008-01-01

    Background The C?U substitution types of RNA editing have been observed frequently in organellar genomes of land plants. Although various attempts have been made to explain why such a seemingly inefficient genetic mechanism would have evolved, no satisfactory explanation exists in our view. In this study, we examined editing patterns in chloroplast genomes of the hornwort Anthoceros formosae and the fern Adiantum capillus-veneris and in mitochondrial genomes of the angiosperms Arabidopsis thaliana, Beta vulgaris and Oryza sativa, to gain an understanding of the question of how RNA editing originated. Results We found that 1) most editing sites were distributed at the 2nd and 1st codon positions, 2) editing affected codons that resulted in larger hydrophobicity and molecular size changes much more frequently than those with little change involved, 3) editing uniformly increased protein hydrophobicity, 4) editing occurred more frequently in ancestrally T-rich sequences, which were more abundant in genes encoding membrane-bound proteins with many hydrophobic amino acids than in genes encoding soluble proteins, and 5) editing occurred most often in genes found to be under strong selective constraint. Conclusion These analyses show that editing mostly affects functionally important and evolutionarily conserved codon positions, codons and genes encoding membrane-bound proteins. In particular, abundance of RNA editing in plant organellar genomes may be associated with disproportionately large percentages of genes in these two genomes that encode membrane-bound proteins, which are rich in hydrophobic amino acids and selectively constrained. These data support a hypothesis that natural selection imposed by protein functional constraints has contributed to selective fixation of certain editing sites and maintenance of the editing activity in plant organelles over a period of more than four hundred millions years. The retention of genes encoding RNA editing activity may be driven by forces that shape nucleotide composition equilibrium in two organellar genomes of these plants. Nevertheless, the causes of lineage-specific occurrence of a large portion of RNA editing sites remain to be determined. Reviewers This article was reviewed by Michael Gray (nominated by Laurence Hurst), Kirsten Krause (nominated by Martin Lercher), and Jeffery Mower (nominated by David Ardell). PMID:18939975

  3. Natural Selection on Coding and Noncoding DNA Sequences Is Associated with Virulence Genes in a Plant Pathogenic Fungus

    PubMed Central

    Rech, Gabriel E.; Sanz-Martín, José M.; Anisimova, Maria; Sukno, Serenella A.; Thon, Michael R.

    2014-01-01

    Natural selection leaves imprints on DNA, offering the opportunity to identify functionally important regions of the genome. Identifying the genomic regions affected by natural selection within pathogens can aid in the pursuit of effective strategies to control diseases. In this study, we analyzed genome-wide patterns of selection acting on different classes of sequences in a worldwide sample of eight strains of the model plant-pathogenic fungus Colletotrichum graminicola. We found evidence of selective sweeps, balancing selection, and positive selection affecting both protein-coding and noncoding DNA of pathogenicity-related sequences. Genes encoding putative effector proteins and secondary metabolite biosynthetic enzymes show evidence of positive selection acting on the coding sequence, consistent with an Arms Race model of evolution. The 5? untranslated regions (UTRs) of genes coding for effector proteins and genes upregulated during infection show an excess of high-frequency polymorphisms likely the consequence of balancing selection and consistent with the Red Queen hypothesis of evolution acting on these putative regulatory sequences. Based on the findings of this work, we propose that even though adaptive substitutions on coding sequences are important for proteins that interact directly with the host, polymorphisms in the regulatory sequences may confer flexibility of gene expression in the virulence processes of this important plant pathogen. PMID:25193312

  4. Algal food selection and digestion by larvae of the pestiferous chironomid Chironomus Crassicaudatus under laboratory conditions.

    PubMed

    Frouz, Jan; Ali, Arshad; Lobinske, Richard J

    2004-12-01

    Feeding preference of Chironomus crassicaudatus 4th instars when fed on 5 algal species, Anabaena flos-aquae, Botryococcus braunii, Lyngbia cf. aeruginosa, Microcystis sp., and Scenedesmus quadricauda was studied under laboratory conditions. The various algal species were mixed in pairs at 1:1 ratio (fresh weight) to create 10 possible test combinations. The larvae were allowed to feed individually for 8 h on each algal mixture in tissue culture plates having 4 replicates. Four identical algal mixtures were simultaneously used without larvae as controls. After feeding, larvae and excrement were removed, and remaining algae from feeding trials and controls were fixed with Lugol's solution; the final ratio of algal species in each mixture was determined microscopically. Feeding preferences of C. crassicaudatus early 4th instars, in descending order, was L. cf. aeruginosa, A. flos-aquae, B. braunii, Microcystis sp., and S. quadricaudata. To evaluate algal digestibility, larval excrement was collected and the proportion of live and dead cells was determined by microscopic observations with the use of visible and ultraviolet light (epifluorescence). Anabaena flos-aquae and L. cf. aeruginosa were the easiest to digest, followed by Microcystis sp. and S. quadricaudata, whereas no digestion of B. braunii was observed. Cultures of larval excrement revealed the presence of some viable cells of all 5 tested algal species. PMID:15669393

  5. Evaluation of Macroinvertebrate Communities and Habitat for Selected Stream Reaches at Los Alamos National Laboratory

    SciTech Connect

    L.J. Henne; K.J. Buckley

    2005-08-12

    This is the second aquatic biological monitoring report generated by Los Alamos National Laboratory's (LANL's) Water Quality and Hydrology Group. The study has been conducted to generate impact-based assessments of habitat and water quality for LANL waterways. The monitoring program was designed to allow for the detection of spatial and temporal trends in water and habitat quality through ongoing, biannual monitoring of habitat characteristics and benthic aquatic macroinvertebrate communities at six key sites in Los Alamos, Sandia, Water, Pajarito, and Starmer's Gulch Canyons. Data were collected on aquatic habitat characteristics, channel substrate, and macroinvertebrate communities during 2001 and 2002. Aquatic habitat scores were stable between 2001 and 2002 at all locations except Starmer's Gulch and Pajarito Canyon, which had lower scores in 2002 due to low flow conditions. Channel substrate changes were most evident at the upper Los Alamos and Pajarito study reaches. The macroinvertebrate Stream Condition Index (SCI) indicated moderate to severe impairment at upper Los Alamos Canyon, slight to moderate impairment at upper Sandia Canyon, and little or no impairment at lower Sandia Canyon, Starmer's Gulch, and Pajarito Canyon. Habitat, substrate, and macroinvertebrate data from the site in upper Los Alamos Canyon indicated severe impacts from the Cerro Grande Fire of 2000. Impairment in the macroinvertebrate community at upper Sandia Canyon was probably due to effluent-dominated flow at that site. The minimal impairment SCI scores for the lower Sandia site indicated that water quality improved with distance downstream from the outfall at upper Sandia Canyon.

  6. Finding Fingerprints of Selection in Poplar Genomes

    SciTech Connect

    Tuskan, Gerald

    2014-10-02

    Jerry Tuskan of Oak Ridge National Laboratory and the DOE JGI talks about poplar trees as models for selective adaptation to an environment. This video complements a study published ahead online August 24, 2014 in Nature Genetics.

  7. Finding Fingerprints of Selection in Poplar Genomes

    ScienceCinema

    Tuskan, Gerald

    2014-10-28

    Jerry Tuskan of Oak Ridge National Laboratory and the DOE JGI talks about poplar trees as models for selective adaptation to an environment. This video complements a study published ahead online August 24, 2014 in Nature Genetics.

  8. Evidence for divergent natural selection of a Lake Tanganyika cichlid inferred from repeated radiations in body size.

    PubMed

    Takahashi, T; Watanabe, K; Munehara, H; Rüber, L; Hori, M

    2009-07-01

    Divergent natural selection is thought to play a vital role in speciation, but clear, measurable examples from nature are still few. Among the many possible sources of divergent natural selection, predation pressure may be important because predators are ubiquitous in food webs. Here, we show evidence for divergent natural selection in a Lake Tanganyika cichlid, Telmatochromis temporalis, which uses burrows under stones or empty snail shells as shelters. This species contains normal and dwarf morphs at several localities. The normal morph inhabits rocky shorelines, whereas the dwarf morph invariably inhabits shell beds, where empty snail shells densely cover the lake bottom. Genetic evidence suggested that the dwarf morph evolved independently from the normal morph at two areas, and morphological analysis and evaluation of habitat structure revealed that the body sizes of morphs closely matched the available shelter sizes in their habitats. These findings suggest that the two morphs repeatedly evolved through divergent natural selection associated with the strategy for sheltering from predators. PMID:19549109

  9. The Great Smoky Mountains National Park: Its Use as a Natural Laboratory for General Biology.

    ERIC Educational Resources Information Center

    Adams, Harold S.; Lipford, Michael L.

    Extended field trips have the potential to provide students with direct experience in learning about the natural world, as well as opportunities for the development of group cohesiveness. This document describes a program developed by a community college in which general biology students spend 3 days in the Great Smoky Mountains National Park. The…

  10. I. ASCRC General Education Form Group Group XI Natural Science (non laboratory)

    E-print Network

    Vonessen, Nikolaus

    method is used within the discipline to draw scientific conclusions. This course explores the field to a hypothesis and then to a validated scientific theory. The scientific method as it is applied in physical://www.umt.edu/facultysenate/ASCRCx/Adocuments/GE_Criteria5-1-08.htm Courses explore a discipline in the natural sciences and demonstrate how the scientific

  11. Effect of Weak Acid Hypochlorous Solution on Selected Viruses and Bacteria of Laboratory Rodents

    PubMed Central

    Taharaguchi, Motoko; Takimoto, Kazuhiro; Zamoto-Niikura, Aya; Yamada, Yasuko K.

    2014-01-01

    Weak acid hypochlorous solution (WAHS) is known to have efficacy for inactivating pathogens and to be relatively safe with respect to the live body. Based on these advantages, many animal facilities have recently been introducing WAHS for daily cleaning of animal houses. In this study, we determined the effect of WAHS in inactivating specific pathogens of laboratory rodents and pathogens of opportunistic infection. WAHS with an actual chloride concentration of 60 ppm and a pH value of 6.0 was generated using purpose-built equipment. One volume of mouse hepatitis virus (MHV), Sendai virus, lymphocytic choriomeningitis virus, Bordetella bronchiseptica, Pasteurella pneumotropica, Corynebacterium kutscheri, Staphylococcus aureus, and Pseudomonas aeruginosa was mixed with 9 or 99 volumes of WAHS (×10 and ×100 reaction) for various periods (0.5, 1, and 5 min) at 25°C. After incubation, the remaining infectious viruses and live bacteria were determined by plaque assay or culture. In the ×100 reaction mixture, infectious viruses and live bacteria could not be detected for any of the pathogens examined even with the 0.5-min incubation. However, the effects for MHV, B. bronchiseptica, and P. aeruginosa were variable in the ×10 reaction mixture with the 0.5- and 1-min incubations. Sufficient effects were obtained by elongation of the reaction time to 5 min. In the case of MHV, reducing organic substances in the virus stock resulted in the WAHS being completely effective. WAHS is recommended for daily cleaning in animal facilities but should be used properly in order to obtain a sufficient effect, which includes such things as using a large enough volume to reduce effects of organic substances. PMID:24770639

  12. Mars-GRAM Applications for Mars Science Laboratory Mission Site Selection Processes

    NASA Technical Reports Server (NTRS)

    Justh, Hilary; Justus, C. G.

    2007-01-01

    An overview is presented of the Mars-Global Reference Atmospheric Model (Mars-GRAM 2005) and its new features. One important new feature is the "auxiliary profile" option, whereby a simple input file is used to replace mean atmospheric values from Mars-GRAM's conventional (General Circulation Model) climatology. An auxiliary profile can be generated from any source of data or alternate model output. Results are presented using auxiliary profiles produced from mesoscale model output (Southwest Research Institute's Mars Regional Atmospheric Modeling System (MRAMS) model and Oregon State University's Mars mesoscale model (MMM5) model) for three candidate Mars Science Laboratory (MSL) landing sites (Terby Crater, Melas Chasma, and Gale Crater). A global Thermal Emission Spectrometer (TES) database has also been generated for purposes of making 'Mars-GRAM auxiliary profiles. This data base contains averages and standard deviations of temperature, density, and thermal wind components, averaged over 5-by-5 degree latitude bins and 15 degree L(sub S) bins, for each of three Mars years of TES nadir data. Comparisons show reasonably good consistency between Mars-GRAM with low dust optical depth and both TES observed and mesoscale model simulated density at the three study sites. Mean winds differ by a more significant degree. Comparisons of mesoscale and TES standard deviations' with conventional Mars-GRAM values, show that Mars-GRAM density perturbations are somewhat conservative (larger than observed variability), while mesoscale-modeled wind variations are larger than Mars-GRAM model estimates. Input parameters rpscale (for density perturbations) and rwscale (for wind perturbations) can be used to "recalibrate" Mars-GRAM perturbation magnitudes to better replicate observed or mesoscale model variability.

  13. Tandem Duplications and the Limits of Natural Selection in Drosophila yakuba and Drosophila simulans

    PubMed Central

    Rogers, Rebekah L.; Cridland, Julie M.; Shao, Ling; Hu, Tina T.; Andolfatto, Peter; Thornton, Kevin R.

    2015-01-01

    Tandem duplications are an essential source of genetic novelty, and their variation in natural populations is expected to influence adaptive walks. Here, we describe evolutionary impacts of recently-derived, segregating tandem duplications in Drosophila yakuba and Drosophila simulans. We observe an excess of duplicated genes involved in defense against pathogens, insecticide resistance, chorion development, cuticular peptides, and lipases or endopeptidases associated with the accessory glands across both species. The observed agreement is greater than expectations on chance alone, suggesting large amounts of convergence across functional categories. We document evidence of widespread selection on the D. simulans X, suggesting adaptation through duplication is common on the X. Despite the evidence for positive selection, duplicates display an excess of low frequency variants consistent with largely detrimental impacts, limiting the variation that can effectively facilitate adaptation. Standing variation for tandem duplications spans less than 25% of the genome in D. yakuba and D. simulans, indicating that evolution will be strictly limited by mutation, even in organisms with large population sizes. Effective whole gene duplication rates are low at 1.17 × 10?9 per gene per generation in D. yakuba and 6.03 × 10?10 per gene per generation in D. simulans, suggesting long wait times for new mutations on the order of thousands of years for the establishment of sweeps. Hence, in cases where adaptation depends on individual tandem duplications, evolution will be severely limited by mutation. We observe low levels of parallel recruitment of the same duplicated gene in different species, suggesting that the span of standing variation will define evolutionary outcomes in spite of convergence across gene ontologies consistent with rapidly evolving phenotypes. PMID:26176952

  14. Warning signal brightness variation: sexual selection may work under the radar of natural selection in populations of a polytypic poison frog.

    PubMed

    Crothers, Laura R; Cummings, Molly E

    2013-05-01

    Though theory predicts consistency of warning signals in aposematic species to facilitate predator learning, variation in these signals often occurs in nature. The strawberry poison frog Dendrobates pumilio is an exceptionally polytypic (populations are phenotypically distinct) aposematic frog exhibiting variation in warning color and brightness. In the Solarte population, males and females both respond differentially to male brightness variation. Here, we demonstrate through spectrophotometry and visual modeling that aposematic brightness variation within this population is likely visible to two putative predators (crabs, snakes) and conspecifics but not to the presumed major predator (birds). This study thus suggests that signal brightness within D. pumilio populations can be shaped by sexual selection, with limited opportunity for natural selection to influence this trait due to predator sensory constraints. Because signal brightness changes can ultimately lead to changes in hue, our findings at the within-population level can provide insights into understanding this polytypism at across-population scales. PMID:23594556

  15. Comment on "Bateman in nature: predation on offspring reduces the potential for sexual selection".

    PubMed

    Bergeron, P; Martin, A M; Garant, D; Pelletier, F

    2013-05-01

    Byers and Dunn (Reports, 9 November 2012, p. 802) claimed that predation on offspring reduced the potential for sexual selection in pronghorn. We argue that the potential for sexual selection is not affected by random offspring mortality when relative reproductive success is considered and increases when measured with the opportunity for selection, a metric that describes the potential for selection. PMID:23641093

  16. The dynamic and ever-changing volcanic nature of Iceland -An outdoor laboratory for education on natural processes and the human impacts on them-

    NASA Astrophysics Data System (ADS)

    Petursdottir, Thorunn; Finger, David

    2015-04-01

    "Tell me and I will forget, show me and I may remember, involve me and I will understand" (Chinese Proverb). Throughout the global history fundamental knowledge on utilizing natural resources, nowadays known as ecoliteracy, was passed on to next generations by our ancestors. Nevertheless, their practices were often unsustainable and lead directly or indirectly to severe ecosystem degradation. Nowadays, overexploitation of natural resources is still a global main driver for ecological degradation, water quality decrease and climate change. While ecoliteracy is still an essential knowledge, the societal structures required to maintain the knowledge have diminished. Today, about 80% of the population in Western countries lives in urban areas dominated by concrete structures with frequently only isolated green spaces. Environmental education is dominated by theoretical concepts taught using a wide range of multimedia technologies to simulate direct experiences of natural processes. Nevertheless, these technologies can only provide a superficial insight into the functioning of natural processes. Only direct on-sight investigations can provide a thorough experience of the dynamic, ever-changing environmental processes. Iceland is a 103,000 km2 large island, located on the Mid Atlantic Ridge just south of the Arctic Circle. In that area the earth crust is only a few km thick, leading to frequent volcanic eruptions and seismic activity. Due to the long winter and the wet climate glaciers formed on all major peaks and cover 11% of the island. Most riverbeds are in their pristine state and water quality is in general excellent. The Icelandic nature may look pristine but is indeed severely degraded. Unsustainable landuse, namely deforestation and overgrazing, in an environment characterized by harsh winters and volcanic activities had devastating effects on the nature. Since settlement 1100 years ago 40% of its vegetation and soil have been lost. Soil conservation and restoration has been a governmental objective for over a century. Iceland has thus gained tremendous knowledge on ecosystem degradation and restoration. This knowledge is highly valuable for educational purposes, particularly to demonstrate the interactions of natural processes within functional and dysfunctional ecosystems. Iceland has a population of roughly 325'000 whereof only 6% live in rural areas. Although fishing and agriculture are predominant industries in rural areas, in recent years tourism and heavy industry have become increasingly important drivers for economic development. Iceland is a representative democracy with a governmental structure similar to other North European countries. All these factors make Iceland an ideal place to study ecoliteracy and learn about social and ecological systems. In this presentation we will present examples of training schools where the Icelandic nature is used as an outdoor laboratory for environmental education. We will also discuss how the interaction between human and nature in Iceland can be used to demonstrate the importance of linking geoscience to relevant social and ecological systems and how it can feed in to build up resilience-based management of natural resources.

  17. Selection of indigenous isolates of entomopathogenic soil fungus Metarhizium anisopliae under laboratory conditions.

    PubMed

    Skalický, Aleš; Bohatá, Andrea; Šimková, Jana; Osborne, Lance S; Landa, Zden?k

    2014-07-01

    Eight native isolates of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin were obtained by monitoring soils cultivated in a conventional manner. These isolates were compared in three areas: (a) conidial germination, (b) radial growth and sporulation and (c) ability of conidia to infect Tenebrio molitor larvae. All bioassays were carried out at constant temperatures of 10, 15, and 20 °C. Conidia of individual isolates demonstrated differences in germination after a 24-h long incubation at all evaluated temperatures. At 20 °C, the germination ranged from 67 to 100 % and at 15 °C from 5.33 to 46.67 %. At 10 °C, no germination was observed after 24 h; nevertheless, it was 8.67-44.67 % after 48 h. In terms of radial growth, the culture diameters and the associated production of spores of all isolates increased with increasing temperature. At 10 °C, sporulation was observed in three isolates while all remaining cultures appeared sterile. Three weeks post-inoculation, conidia of all assessed isolates caused 100 % cumulative mortality of treated larvae of T. molitor at 15 and 20 °C with the exception of isolate 110108 that induced 81.33 % mortality at 15 °C. At 10 °C, larval cumulative mortality ranged from 6.67 to 85.33 % depending on the isolate. Isolates 110108 and 110111 showed significantly slower outset and a much lower rate of infection at all temperatures compared to other tested isolates of M. anisopliae. The bioassays were carried out with the purpose to sort and select indigenous isolates of M. anisopliae useful as biocontrol agents in their original habitat. PMID:24338078

  18. Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Underground Nuclear Tests - 2011, Part 2

    SciTech Connect

    Pawloski, G A

    2012-01-30

    This report evaluates collapse evolution for selected Lawrence Livermore National Laboratory (LLNL) underground nuclear tests at the Nevada National Security Site (NNSS, formerly called the Nevada Test Site). The work is being done to support several different programs that desire access to the ground surface above expended underground nuclear tests. The programs include: the Borehole Management Program, the Environmental Restoration Program, and the National Center for Nuclear Security Gas-Migration Experiment. Safety decisions must be made before a crater area, or potential crater area, can be reentered for any work. Evaluation of cavity collapse and crater formation is input into the safety decisions. Subject matter experts from the LLNL Containment Program who participated in weapons testing activities perform these evaluations. Information used included drilling and hole construction, emplacement and stemming, timing and sequence of the selected test and nearby tests, geology, yield, depth of burial, collapse times, surface crater sizes, cavity and crater volume estimations, ground motion, and radiological release information. Both classified and unclassified data were reviewed. The evaluations do not include the effects of erosion that may modify the collapse craters over time. They also do not address possible radiation dangers that may be present. Various amounts of information are available for these tests, depending on their age and other associated activities. Lack of data can hamper evaluations and introduce uncertainty. We make no attempt to quantify this uncertainty. Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Underground Nuclear Tests - 2011 was published on March 2, 2011. This report, considered Part 2 of work undertaken in calendar year 2011, compiles evaluations requested after the March report. The following unclassified summary statements describe collapse evolution and crater stability in response to a recent request to review 6 LLNL test locations in Yucca Flat, Rainier Mesa, and Pahute Mesa. They include: Baneberry in U8d; Clearwater in U12q; Wineskin in U12r, Buteo in U20a and Duryea in nearby U20a1; and Barnwell in U20az.

  19. Molecular Phylogeography of a Human Autosomal Skin Color Locus Under Natural Selection

    PubMed Central

    Canfield, Victor A.; Berg, Arthur; Peckins, Steven; Wentzel, Steven M.; Ang, Khai Chung; Oppenheimer, Stephen; Cheng, Keith C.

    2013-01-01

    Divergent natural selection caused by differences in solar exposure has resulted in distinctive variations in skin color between human populations. The derived light skin color allele of the SLC24A5 gene, A111T, predominates in populations of Western Eurasian ancestry. To gain insight into when and where this mutation arose, we defined common haplotypes in the genomic region around SLC24A5 across diverse human populations and deduced phylogenetic relationships between them. Virtually all chromosomes carrying the A111T allele share a single 78-kb haplotype that we call C11, indicating that all instances of this mutation in human populations share a common origin. The C11 haplotype was most likely created by a crossover between two haplotypes, followed by the A111T mutation. The two parental precursor haplotypes are found from East Asia to the Americas but are nearly absent in Africa. The distributions of C11 and its parental haplotypes make it most likely that these two last steps occurred between the Middle East and the Indian subcontinent, with the A111T mutation occurring after the split between the ancestors of Europeans and East Asians. PMID:24048645

  20. Molecular phylogeography of a human autosomal skin color locus under natural selection.

    PubMed

    Canfield, Victor A; Berg, Arthur; Peckins, Steven; Wentzel, Steven M; Ang, Khai Chung; Oppenheimer, Stephen; Cheng, Keith C

    2013-11-01

    Divergent natural selection caused by differences in solar exposure has resulted in distinctive variations in skin color between human populations. The derived light skin color allele of the SLC24A5 gene, A111T, predominates in populations of Western Eurasian ancestry. To gain insight into when and where this mutation arose, we defined common haplotypes in the genomic region around SLC24A5 across diverse human populations and deduced phylogenetic relationships between them. Virtually all chromosomes carrying the A111T allele share a single 78-kb haplotype that we call C11, indicating that all instances of this mutation in human populations share a common origin. The C11 haplotype was most likely created by a crossover between two haplotypes, followed by the A111T mutation. The two parental precursor haplotypes are found from East Asia to the Americas but are nearly absent in Africa. The distributions of C11 and its parental haplotypes make it most likely that these two last steps occurred between the Middle East and the Indian subcontinent, with the A111T mutation occurring after the split between the ancestors of Europeans and East Asians. PMID:24048645

  1. Gene Flow and Natural Selection in the Origin of Drosophila Pseudoobscura and Close Relatives

    PubMed Central

    Wang, R. L.; Wakeley, J.; Hey, J.

    1997-01-01

    The divergence of Drosophila pseudoobscura and close relatives D. persimilis and D. pseudoobscura bogotana has been studied using comparative DNA sequence data from multiple nuclear loci. New data from the Hsp82 and Adh regions, in conjunction with existing data from Adh and the Period locus, are examined in the light of various models of speciation. The principal finding is that the three loci present very different histories, with Adh indicating large amounts of recent gene flow among the taxa, while little or no gene flow is apparent in the data from the other loci. The data were compared with predictions from several isolation models of divergence. These models include no gene flow, and they were found to be incompatible with the data. Instead the DNA data, taken together with other evidence, seem consistent with divergence models in which natural selection acts against gene flow at some loci more than at others. This family of models includes some sympatric and parapatric speciation models, as well as models of secondary contact and subsequent reinforcement of sexual isolation. PMID:9383055

  2. Naturally acquired Mycobacterium tuberculosis complex in laboratory pig-tailed macaques

    PubMed Central

    Engel, Gregory A; Wilbur, Alicia K; Westmark, Andrew; Horn, Dara; Johnson, Jordan; Jones-Engel, Lisa

    2012-01-01

    Here we present a case series from a primate research facility. The index case, a 4-year-old pig-tailed macaque (Macaca nemestrina) experimentally infected with chimeric simian-human immunodeficiency virus (SHIVSF162 P4), developed weight loss and was euthanized. Based on necropsy results the animal was diagnosed with opportunistic atypical mycobacteriosis associated with simian AIDS (SAIDS). Subsequently, tissues from the index animal, as well as tissues and oral mucosal swabs from six SHIV-infected contacts, were analyzed using molecular methods and found to contain nucleic acid sequences characteristic of Mycobacterium tuberculosis complex (MTBC). These data suggest that existing protocols fail to reliably detect MTBC infection in laboratory primates used as experimental models.

  3. Science, evolution and natural selection: in praise of Darwin at the Stazione Zoologica Anton Dohrn of Naples.

    PubMed

    Ayala, Francisco J

    2015-01-01

    Copernicus, Galileo, Newton and other physical scientists ushered in a conception of the universe as matter in motion governed by natural laws. Their discoveries brought about a fundamental revolution, namely a commitment to the postulate that the universe obeys immanent laws that can account for natural phenomena. The workings of the universe were brought into the realm of science: explanation through natural laws. Darwin completed the Copernican revolution by extending it to the living world. Darwin demonstrated the evolution of organisms. More important yet is that he discovered natural selection, the process that explains the 'design' of organisms. The adaptations and diversity of organisms, the origin of novel and complex species, even the origin of mankind, could now be explained by an orderly process of change governed by natural laws. The origin of species and the exquisite features of organisms had previously been explained as special creations of an omniscient God. Darwin brought them into the domain of science. PMID:26013200

  4. Unravelling floods selection mechanisms for vegetation from laboratory experiments and implications for river restoration efficiency

    NASA Astrophysics Data System (ADS)

    Perucca, Eliana; Molnar, Peter; Francis, Robert; Perona, Paolo

    2010-05-01

    The establishment and evolution of vegetation in organized patterns on river bar alluvial sediment are active morphodynamic processes governed by flow hydrology. Although this is well documented in literature, how do time scales between the arrival of flow disturbances and vegetation growth interact to determine the survival of certain vegetation characteristics is still unclear. We started to explore such dynamics within the research project RIVERINE (RIver - VEgetation interactions and Reproduction of Island Nuclei formation and Evolution), funded by the Hydralab III European Framework Programme. Laboratory experiments are important tools which allow comprehensive observations of the feedbacks between flow, channel morphology and vegetation, which are otherwise difficult to observe at the real scale. In this work we present the results of novel flume experiments that we carried out at the Total Environment Simulator (TES) of the University of Hull, United Kingdom. Starting from an initial levelled slope of 1%, the channel was seeded with Avena Sativa at a uniform density. A number of days after seeding, the flume was flooded daily for 4 days with a flood disturbance which lasted 15 minutes. Different flood magnitudes as well as times between seeding and the first disturbance and flume geometries (i.e., parallel and convergent walls) were investigated. After each disturbance the eroded material (sediment, seeds and plants) was collected at the channel bottom and corresponding statistics for main root length, number of roots and stem height were calculated. At the same time, random samples of non-eroded plants were sampled from the flume and the same statistics were computed for a control run. After every flood disturbance, the channel bed surface was measured with a laser scanner and photographed. Since flooding frequencies were comparable with the plant root germination and growth time scales, vegetation and flood disturbances were in direct competition. Results show that while non-eroded plants continue to grow in successive runs, flow erosion acts preferentially on plants that have a weaker root system. In particular, a direct linkage between flow magnitude and the first statistical moment of the distribution of the eroded plants seems not to depend on successive runs as long as the distributions of the eroded and the non-eroded plants overlap. Channel geometry influences specific stream power, which in turn would affect the limit where colonization by vegetation in a converging channel is successful. Although the collected data at present have an explorative value only, our findings can be useful for river restoration practice. We show that the timescale of flood disturbance and that of root growth interact in determining whether a particular vegetation species can be successful in the colonization of a given river system. Moreover, the analysis of the influence of channel shape can be useful to identify the best location for plant establishment.

  5. The Case Study: I'm Looking over a White-Striped Clover--A Case of Natural Selection

    ERIC Educational Resources Information Center

    Krufka, Alison; Evarts, Susan; Wilson, Chester

    2007-01-01

    The case presented in this article is an exploration of the process of natural selection using white clover ("Trifolium repens") as an example. In general, two forms of white clover can be found around the world in various habitats. One type has plain green leaves and the other type produces cyanide as a defense against herbivores and signals the…

  6. Does natural selection alter genetic architecture? An evaluation of quantitative genetic variation among populations of Allonemobiussocius and A. fasciatus

    Microsoft Academic Search

    Roff; Mousseau

    1999-01-01

    To make long-term predictions using present quantitative genetic theory it is necessary to assume that the genetic variance-covariance matrix (G) remains constant or at least changes by a constant fraction. In this paper we examine the stability of the genetic architecture of two traits known to be subject to natural selection; femur length and ovipositor length in two species of

  7. Intrapopulation variation in predator-avoidance performance of Galápagos lava lizards: The interaction of sexual and natural selection

    Microsoft Academic Search

    Howard L. Snell; Randy D. Jennings; Heidi M. Snell; Sylvia Harcourt

    1988-01-01

    Summary The interaction of sexual and natural selection in shaping variation in defensive behavior was explored via three steps. (1) Three predictions from the hypothesis that varying responses to predation account for intrapopulation variation in locomotory performance and wariness were tested. One measure of locomotory performance and two measures of wariness were compared between lava lizards (Tropidurus albemarlensis) inhabiting sparsely

  8. Evidence that Accumulation of Mutants in a Biofilm Reflects Natural Selection Rather than Stress-Induced Adaptive Mutation

    Microsoft Academic Search

    Jeffrey A. Banas; Justin D. Miller; Meghan E. Fuschino; Karsten R. O. Hazlett; Wendy Toyofuku; Kristen A. Porter; Sarah B. Reutzel; Matthew A. Florczyk; Kathleen A. McDonough; Suzanne M. Michalek

    2007-01-01

    The accumulation of mutant genotypes within a biofilm evokes the controversy over whether the biofilm environment induces adaptive mutation or whether the accumulation can be explained by natural selection. A comparison of the virulence of two strains of the dental pathogen Streptococcus mutans showed that rats infected with one of the strains accumulated a high proportion (average, 22%) of organisms

  9. In making his case for the role of natural selection in evolution, Darwin started by pointing to the enormous

    E-print Network

    Arnold, Frances H.

    In making his case for the role of natural selection in evolution, Darwin started by pointing. In Darwin's day, the importance of good breeding practices in determining the productivity and quality of a farmer's stock or the crop size of a pigeon fancier's prize bird was clear to all, and Darwin

  10. Natural Selection: 2006 E. coli Recall of Fresh Spinach A Case Study by The Food Industry Center

    E-print Network

    Weiblen, George D

    also helps illustrate the complexity of the food supply chain and the food recall process. A similar1 Natural Selection: 2006 E. coli Recall of Fresh Spinach A Case Study by The Food Industry Center. While every food recall is important and unique, the contamination of fresh spinach with the bacteria

  11. Evidence that Accumulation of Mutants in a Biofilm Reflects Natural Selection Rather than Stress-Induced Adaptive Mutation?

    PubMed Central

    Banas, Jeffrey A.; Miller, Justin D.; Fuschino, Meghan E.; Hazlett, Karsten R. O.; Toyofuku, Wendy; Porter, Kristen A.; Reutzel, Sarah B.; Florczyk, Matthew A.; McDonough, Kathleen A.; Michalek, Suzanne M.

    2007-01-01

    The accumulation of mutant genotypes within a biofilm evokes the controversy over whether the biofilm environment induces adaptive mutation or whether the accumulation can be explained by natural selection. A comparison of the virulence of two strains of the dental pathogen Streptococcus mutans showed that rats infected with one of the strains accumulated a high proportion (average, 22%) of organisms that had undergone a deletion between two contiguous and highly homologous genes. To determine if the accumulation of deletion mutants was due to selection or to an increased mutation rate, accumulations of deletion mutants within in vitro planktonic and biofilm cultures and within rats inoculated with various proportions of deletion organisms were quantified. We report here that natural selection was the primary force behind the accumulation of the deletion mutants. PMID:17085702

  12. Evidence that accumulation of mutants in a biofilm reflects natural selection rather than stress-induced adaptive mutation.

    PubMed

    Banas, Jeffrey A; Miller, Justin D; Fuschino, Meghan E; Hazlett, Karsten R O; Toyofuku, Wendy; Porter, Kristen A; Reutzel, Sarah B; Florczyk, Matthew A; McDonough, Kathleen A; Michalek, Suzanne M

    2007-01-01

    The accumulation of mutant genotypes within a biofilm evokes the controversy over whether the biofilm environment induces adaptive mutation or whether the accumulation can be explained by natural selection. A comparison of the virulence of two strains of the dental pathogen Streptococcus mutans showed that rats infected with one of the strains accumulated a high proportion (average, 22%) of organisms that had undergone a deletion between two contiguous and highly homologous genes. To determine if the accumulation of deletion mutants was due to selection or to an increased mutation rate, accumulations of deletion mutants within in vitro planktonic and biofilm cultures and within rats inoculated with various proportions of deletion organisms were quantified. We report here that natural selection was the primary force behind the accumulation of the deletion mutants. PMID:17085702

  13. Teaching Evolution & the Nature of Science via the History of Debates about the Levels at Which Natural Selection Operates

    ERIC Educational Resources Information Center

    Stansfield, William D.

    2013-01-01

    Students should not graduate from high school without understanding that scientific debates are essential components of scientific methodology. This article presents a brief history of ongoing debates regarding the hypothesis that group selection is an evolutionary mechanism, and it serves as an example of the role that debates play in correcting…

  14. Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

    SciTech Connect

    Nigel N. Clark

    2006-12-31

    Nitric oxide (NO) and nitrogen dioxide (NO2) generated by internal combustion (IC) engines are implicated in adverse environmental and health effects. Even though lean-burn natural gas engines have traditionally emitted lower oxides of nitrogen (NOx) emissions compared to their diesel counterparts, natural gas engines are being further challenged to reduce NOx emissions to 0.1 g/bhp-hr. The Selective NOx Recirculation (SNR) approach for NOx reduction involves cooling the engine exhaust gas and then adsorbing the NOx from the exhaust stream, followed by the periodic desorption of NOx. By sending the desorbed NOx back into the intake and through the engine, a percentage of the NOx can be decomposed during the combustion process. SNR technology has the support of the Department of Energy (DOE), under the Advanced Reciprocating Engine Systems (ARES) program to reduce NOx emissions to under 0.1 g/bhp-hr from stationary natural gas engines by 2010. The NO decomposition phenomenon was studied using two Cummins L10G natural gas fueled spark-ignited (SI) engines in three experimental campaigns. It was observed that the air/fuel ratio ({lambda}), injected NO quantity, added exhaust gas recirculation (EGR) percentage, and engine operating points affected NOx decomposition rates within the engine. Chemical kinetic model predictions using the software package CHEMKIN were performed to relate the experimental data with established rate and equilibrium models. The model was used to predict NO decomposition during lean-burn, stoichiometric burn, and slightly rich-burn cases with added EGR. NOx decomposition rates were estimated from the model to be from 35 to 42% for the lean-burn cases and from 50 to 70% for the rich-burn cases. The modeling results provided an insight as to how to maximize NOx decomposition rates for the experimental engine. Results from this experiment along with chemical kinetic modeling solutions prompted the investigation of rich-burn operating conditions, with added EGR to prevent preignition. It was observed that the relative air/fuel ratio, injected NO quantity, added EGR fraction, and engine operating points affected the NO decomposition rates. While operating under these modified conditions, the highest NO decomposition rate of 92% was observed. In-cylinder pressure data gathered during the experiments showed minimum deviation from peak pressure as a result of NO injections into the engine. A NOx adsorption system, from Sorbent Technologies, Inc., was integrated with the Cummins engine, comprised a NOx adsorbent chamber, heat exchanger, demister, and a hot air blower. Data were gathered to show the possibility of NOx adsorption from the engine exhaust, and desorption of NOx from the sorbent material. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a benchtop adsorption system was constructed. The temperature of this apparatus was controlled while data were gathered on the characteristics of the sorbent material for development of a system model. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passed over fresh sorbent material. A mass heat transfer analysis was conducted to analyze the possibility of using hot exhaust gas for the desorption process. It was found in the adsorption studies, and through literature review, that NO adsorption was poor when the carrier gas was nitrogen, but that NO in the presence of oxygen was adsorbed at levels exceeding 1% by mass of the sorbent. From the three experimental campaigns, chemical kinetic modeling analysis, and the scaled benchtop NOx adsorption system, an overall SNR system model was developed. An economic analysis was completed, and showed that the system was impractical in cost for small engines, but that economies of scale favored the technology.

  15. Field and laboratory investigations into the persistence of glutaraldehyde and acrolein in natural gas storage operations

    SciTech Connect

    Morris, E.A. III; Pope, D.H. [Bioindustrial Technologies, Inc., Georgetown, TX (United States)

    1994-12-31

    The persistence of biocides formulated in glutaraldehyde and acrolein were tested in different produced water environments using a calorimetric general aldehyde detection method based on metaphenylenediamine. The objective of Phase 1 (laboratory study) was to characterize the persistence of acrolein and glutaraldehyde in water samples representative of the environments to which the biocides has been applied. To validate the test results, some duplicate samples were analyzed using gas chromatographic (GC) methods and repeat trials were done on certain tests. The objective of Phase 2 (field assessment) was to compare the Phase 1 results on formation waters to actual field data. At the study site, monitoring of biocide residuals had been done by the chemical vendor at all treated wells. The data provided information on glutaraldehyde and acrolein residuals for one gas withdrawal (winter) season. The data were compiled so that persistence/degradation graphs could be constructed for the biocides in each formation. These field data were then compared to the Phase 1 results. The persistence of the biocides in each environment tested was shown to be unique, but repeatable.

  16. Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; arsenic speciation in natural-water samples using laboratory and field methods

    USGS Publications Warehouse

    Garbarino, John R.; Bednar, Anthony J.; Burkhardt, Mark R.

    2002-01-01

    Analytical methods for the determination of arsenite [As(III)], arsenate [As(V)], dimethylarsinate (DMA), monomethylarsonate (MMA), and roxarsone in filtered natural-water samples are described. Various analytical methods can be used for the determination, depending on the arsenic species being determined. Arsenic concentration is determined by using inductively coupled plasma-mass spectrometry (ICP-MS) as an arsenic-specific detector for all methods. Laboratory-speciation methods are described that use an ion chromatographic column to separate the arsenic species; the column length, column packing, and mobile phase are dependent on the species of interest. Regardless of the separation technique, the arsenic species are introduced into plasma by eithe rpneumatic nebulization or arsine generation. Analysis times range from 2 to 8 minutes and method detection limits range from 0.1 to 0.6 microgram-arsenic per liter (ug-As/L), 10 to 60 picograms absolute (for a 100-microliter injection), depending on the arsenic species determined and the analytical method used. A field-generation specciation method also is described that uses a strong anion exchange cartridge to separate As(III) from As(V) in the field. As(III) in the eluate and the As(V) in the cartridge extract are determined by direct nebulization ICP-MS. Methylated arsenic species that also are retained on the cartridge will positively bias As(V) results without further laboratory separations. The method detection limit for field speciation is 0.3 ug-As/L. The distribution of arsenic species must be preserved in the field to eliminate changes caused by photochemical oxidation or metal oxyhydroxide precipitation. Preservation techniques, such as refrigeration, the addition of acides, or the additoin of ethylene-diaminetetraacetic acid (EDTA) and the effects of ambient light were tested. Of the preservatives evaluated, EDTA was found to work best with the laboratory- and field-speciation methods for all sample matrices tested. Storing the samples in opaque polytethylene bottles eliminated the effects of photochemical oxidation. The percentage change in As(III):As(V) ratios for an EDTA-preserved acid mine drainage (AMD) sample and ground-water sample during a 3-month period was -5 percent and +3 percent, respectively. The bias and variability of the methods were evaluated by comparing results for total arsenic and As(III), As(V), DMA, and MMA concentrations in ground water, AMD, and surface water. Seventy-one ground-water, 10 AMD, and 24 surface-water samples were analyzed. Concentrations in ground-water samples reached 720 ug-As/L for As(III) and 1080 ug-As/L for As(V); AMD samples reached 12800 ug-As/L for As(III) and 7050 ug-As/L for As(V); and surface-water samples reached 5 ug-As/L for As(III) and As(V). Inorganic arsenic species distribution in the samples ranged from 0 to 90 percent As(III). DMA and MMA were present only in surface-water samples from agricultural areas where the herbicide monosodium methylarsonate was applied; concentrations never exceeded 6 ug-As/L. Statistical analyses indicated that the difference between As(III) and As(V) concentrations for samples preserved with EDTA in opaque bottles and field-speciation results were analytically insignificant at the 95-percent confidence interval. There was no significant difference among the methods tested for total arsenic concentration. Percentage recovery for field samples spiked at 50 ug-As/L and analyzed by the laboratory-speciation method (n=2) ranged from 82 to 100 percent for As(III), 97 to 102 percent for As(V), 90 to 104 percent for DMA, and 81 to 96 percent for MMA; recoveries for samples spiked at 100 ug-As/L and analyzed by the field-speciation method ranged from 102 to 107 percent for As(III) and 105 to 106 percent for As(V). Laboratory-speciation results for Environment Canada reference material SLRS-2 closely matched reported concentrations. Laboratory-speciation metho

  17. The impact of natural selection on health and disease: uses of the population genetics approach in humans

    PubMed Central

    Vasseur, Estelle; Quintana-Murci, Lluis

    2013-01-01

    Investigations of the legacy of natural selection in the human genome have proved particularly informative, pinpointing functionally important regions that have participated in our genetic adaptation to the environment. Furthermore, genetic dissection of the intensity and type of selection acting on human genes can be used to predict involvement in different forms and severities of human diseases. We review here the progress made in population genetics studies toward understanding the effects of selection, in its different forms and intensities, on human genome diversity. We discuss some outstanding, robust examples of genes and biological functions subject to strong dietary, climatic and pathogen selection pressures. We also explore the possible relationship between cancer and natural selection, a topic that has been largely neglected because cancer is generally seen as a late-onset disease. Finally, we discuss how the present-day incidence of some diseases of modern societies may represent a by-product of past adaptation to other selective forces and changes in lifestyle. This perspective thus illustrates the value of adopting a population genetics approach in delineating the biological mechanisms that have played a major evolutionary role in the way humans have genetically adapted to different environments and lifestyles over time. PMID:23789027

  18. Selective Removal of Natural Occlusal Caries by Coupling Near-infrared Imaging with a CO2 Laser

    PubMed Central

    Tao, You-Chen; Fried, Daniel

    2011-01-01

    Laser removal of dental hard tissue can be combined with optical, spectral or acoustic feedback systems to selectively ablate dental caries and restorative materials. Near-infrared (NIR) imaging has considerable potential for the optical discrimination of sound and demineralized tissue. Last year we successfully demonstrated that near-IR images can be used to guide a CO2 laser ablation system for the selective removal of artificial caries lesions on smooth surfaces. The objective of this study was to test the hypothesis that two-dimensional near-infrared images of natural occlusal caries can be used to guide a CO2 laser for selective removal. Two-dimensional NIR images were acquired at 1310-nm of extracted human molar teeth with occlusal caries. Polarization sensitive optical coherence tomography (PS-OCT) was also used to acquire depth-resolved images of the lesion areas. An imaging processing module was developed to analyze the NIR imaging output and generate optical maps that were used to guide a CO2 laser to selectively remove the lesions at a uniform depth. Post-ablation NIR images were acquired to verify caries removal. Based on the analysis of the NIR images, caries lesions were selectively removed with a CO2 laser while sound tissues were conserved. However, the removal rate varied markedly with the severity of decay and multiple passes were required for caries removal. These initial results are promising but indicate that the selective removal of natural caries is more challenging than the selective removal of artificial lesions due to varying tooth geometry, the highly variable organic/mineral ratio in natural lesions and more complicated lesion structure. PMID:21909225

  19. Just like the rest of evolution in Mother Nature, the evolution of cancers may be driven by natural selection, and not by haphazard mutations.

    PubMed

    Zhang, Ju; Lou, Xiaomin; Zellmer, Lucas; Liu, Siqi; Xu, Ningzhi; Liao, D Joshua

    2014-01-01

    Sporadic carcinogenesis starts from immortalization of a differentiated somatic cell or an organ-specific stem cell. The immortalized cell incepts a new or quasinew organism that lives like a parasite in the patient and usually proceeds to progressive simplification, constantly engendering intermediate organisms that are simpler than normal cells. Like organismal evolution in Mother Nature, this cellular simplification is a process of Darwinian selection of those mutations with growth- or survival-advantages, from numerous ones that occur randomly and stochastically. Therefore, functional gain of growth- or survival-sustaining oncogenes and functional loss of differentiation-sustaining tumor suppressor genes, which are hallmarks of cancer cells and contribute to phenotypes of greater malignancy, are not drivers of carcinogenesis but are results from natural selection of advantageous mutations. Besides this mutation-load dependent survival mechanism that is evolutionarily low and of an asexual nature, cancer cells may also use cell fusion for survival, which is an evolutionarily-higher mechanism and is of a sexual nature. Assigning oncogenes or tumor suppressor genes or their mutants as drivers to induce cancer in animals may somewhat coerce them to create man-made oncogenic pathways that may not really be a course of sporadic cancer formations in the human. PMID:25594068

  20. Just like the rest of evolution in Mother Nature, the evolution of cancers may be driven by natural selection, and not by haphazard mutations

    PubMed Central

    Zhang, Ju; Lou, Xiaomin; Zellmer, Lucas; Liu, Siqi; Xu, Ningzhi; Liao, D. Joshua

    2014-01-01

    Sporadic carcinogenesis starts from immortalization of a differentiated somatic cell or an organ-specific stem cell. The immortalized cell incepts a new or quasinew organism that lives like a parasite in the patient and usually proceeds to progressive simplification, constantly engendering intermediate organisms that are simpler than normal cells. Like organismal evolution in Mother Nature, this cellular simplification is a process of Darwinian selection of those mutations with growth- or survival-advantages, from numerous ones that occur randomly and stochastically. Therefore, functional gain of growth- or survival-sustaining oncogenes and functional loss of differentiation-sustaining tumor suppressor genes, which are hallmarks of cancer cells and contribute to phenotypes of greater malignancy, are not drivers of carcinogenesis but are results from natural selection of advantageous mutations. Besides this mutation-load dependent survival mechanism that is evolutionarily low and of an asexual nature, cancer cells may also use cell fusion for survival, which is an evolutionarily-higher mechanism and is of a sexual nature. Assigning oncogenes or tumor suppressor genes or their mutants as drivers to induce cancer in animals may somewhat coerce them to create man-made oncogenic pathways that may not really be a course of sporadic cancer formations in the human. PMID:25594068

  1. Semi-automatic laboratory goniospectrometer system for performing multi-angular reflectance and polarization measurements for natural surfaces

    NASA Astrophysics Data System (ADS)

    Sun, Z. Q.; Wu, Z. F.; Zhao, Y. S.

    2014-01-01

    In this paper, the design and operation of the Northeast Normal University Laboratory Goniospectrometer System for performing multi-angular reflected and polarized measurements under controlled illumination conditions is described. A semi-automatic arm, which is carried on a rotated circular ring, enables the acquisition of a large number of measurements of surface Bidirectional Reflectance Factor (BRF) over the full hemisphere. In addition, a set of polarizing optics enables the linear polarization over the spectrum from 350 nm to 2300 nm. Because of the stable measurement condition in the laboratory, the BRF and linear polarization has an average uncertainty of 1% and less than 5% depending on the sample property, respectively. The polarimetric accuracy of the instrument is below 0.01 in the form of the absolute value of degree of linear polarization, which is established by measuring a Spectralon plane. This paper also presents the reflectance and polarization of snow, soil, sand, and ice measured during 2010-2013 in order to illustrate its stability and accuracy. These measurement results are useful to understand the scattering property of natural surfaces on Earth.

  2. Semi-automatic laboratory goniospectrometer system for performing multi-angular reflectance and polarization measurements for natural surfaces.

    PubMed

    Sun, Z Q; Wu, Z F; Zhao, Y S

    2014-01-01

    In this paper, the design and operation of the Northeast Normal University Laboratory Goniospectrometer System for performing multi-angular reflected and polarized measurements under controlled illumination conditions is described. A semi-automatic arm, which is carried on a rotated circular ring, enables the acquisition of a large number of measurements of surface Bidirectional Reflectance Factor (BRF) over the full hemisphere. In addition, a set of polarizing optics enables the linear polarization over the spectrum from 350 nm to 2300 nm. Because of the stable measurement condition in the laboratory, the BRF and linear polarization has an average uncertainty of 1% and less than 5% depending on the sample property, respectively. The polarimetric accuracy of the instrument is below 0.01 in the form of the absolute value of degree of linear polarization, which is established by measuring a Spectralon plane. This paper also presents the reflectance and polarization of snow, soil, sand, and ice measured during 2010-2013 in order to illustrate its stability and accuracy. These measurement results are useful to understand the scattering property of natural surfaces on Earth. PMID:24517791

  3. A theory for the origin of a self-replicating chemical system. I: Natural selection of the autogen from short, random oligomers.

    PubMed

    White, D H

    1980-12-01

    A theory is described for the origin of a simple chemical system named an autogen, consisting of two short oligonucleotide sequences coding for two simple catalytic peptides. If the theory is valid, under appropriate conditions the autogen would be capable of self-reproduction in a truly genetic process involving both replication and translation. Limited catalytic ability, short oligomer sequences, and low selectivities leading to sloppy information transfer processes are shown to be adequate for the origin of the autogen from random background oligomers. A series of discrete steps, each highly probable if certain minimum requirements and boundary conditions are satisfied, lead to exponential increase in population of all components in the system due to autocatalysis and hypercyclic organization. Nucleation of the components and exponential increase to macroscopic amounts could occur in times on the order of weeks. The feasibility of the theory depends on a number of factors, including the capability of simple protoenzymes to provide moderate enhancements of the accuracies of replication and translation and the likelihood of finding an environment where all of the required processes can occur simultaneously. Regardless of whether or not the specific form proposed for the autogen proves to be feasible, the theory suggests that the first self-replicating chemical systems may have been extremely simple, and that the period of time required for chemical evolution prior to Darwinian natural selection may have been far shorter than generally assumed. Due to the short time required, this theory, unlike others on the origin of genetic processes, is potentially capable of direct experimental verification. A number of prerequisites leading up to such an experiment are suggested, and some have been fulfilled. If successful, such an experiment would be the first laboratory demonstration of the spontaneous emergence by natural selection of a genetic, self-replicating, and evolving molecular system, and might represent the first step in the prebiotic environment of true Darwinian evolution toward a living cell. PMID:6162031

  4. Characterizing the Phyllosilicates and Amorphous Phases Found by MSL Using Laboratory XRD and EGA Measurements of Natural and Synthetic Materials

    NASA Technical Reports Server (NTRS)

    Rampe, Elizabeth B.; Morris, Richard V.; Chipera, Steve; Bish, David L.; Bristow, Thomas; Archer, Paul Douglas; Blake, David; Achilles, Cherie; Ming, Douglas W.; Vaniman, David; Crisp, Joy A.; DesMarais, David J.; Downs, Robert; Farmer, Jack D.; Morookian, John Michael; Morrison, Shaunna; Sarrazin, Philippe; Spanovich, Nicole; Treiman, Allan H.; Yen, Albert S.

    2013-01-01

    The Curiosity Rover landed on the Peace Vallis alluvial fan in Gale crater on August 5, 2012. A primary mission science objective is to search for past habitable environments, and, in particular, to assess the role of past water. Identifying the minerals and mineraloids that result from aqueous alteration at Gale crater is essential for understanding past aqueous processes at the MSL landing site and hence for interpreting the site's potential habitability. X-ray diffraction (XRD) data from the CheMin instrument and evolved gas analyses (EGA) from the SAM instrument have helped the MSL science team identify phases that resulted from aqueous processes: phyllosilicates and amorphous phases were measure in two drill samples (John Klein and Cumberland) obtained from the Sheepbed Member, Yellowknife Bay Fm., which is believed to represent a fluvial-lacustrine environment. A third set of analyses was obtained from scoop samples from the Rocknest sand shadow. Chemical data from the APXS instrument have helped constrain the chemical compositions of these secondary phases and suggest that the phyllosilicate component is Mg-enriched and the amorphous component is Fe-enriched, relatively Si-poor, and S- and H-bearing. To refine the phyllosilicate and amorphous components in the samples measured by MSL, we measured XRD and EGA data for a variety of relevant natural terrestrial phyllosilicates and synthetic mineraloids in laboratory testbeds of the CheMin and SAM instruments. Specifically, Mg-saturated smectites and vermiculites were measured with XRD at low relative humidity to understand the behavior of the 001 reflections under Mars-like conditions. Our laboratory XRD measurements suggest that interlayer cation composition affects the hydration state of swelling clays at low RH and, thus, the 001 peak positions. XRD patterns of synthetic amorphous materials, including allophane, ferrihydrite, and hisingerite were used in full-pattern fitting (FULLPAT) models to help determine the types and abundances of amorphous phases in the martian rocks and sand shadow. These models suggest that the rocks and sand shadow are composed of approx 30% amorphous phases. Sulfate-adsorbed allophane and ferrihydrite were measured by EGA to further understand the speciation of the sulfur present in the amorphous component. These data indicate that sulfate adsorbed onto the surfaces of amorphous phases could explain a portion of the SO2 evolution in the Rocknest SAM data. The additional constraints placed on the mineralogy and chemistry of the aqueous alteration phases through our laboratory measurements can help us better understand the nature of the fluids that affected the different samples and devise a history of aqueous alteration for the Sheepbed Member of the Yellowknife Bay Fm. at Gale crater.

  5. Laboratory studies using naturally occurring "green rust" to aid metal mine water remediation.

    PubMed

    Bearcock, Jenny M; Perkins, William T; Pearce, Nicholas J G

    2011-06-15

    Green rust, an Fe (II) and (III) oxyhydroxy salt, can alter the aqueous oxidation state, mobility and toxicity, of inorganic contaminants and thus could have applications in water treatment. This paper discusses a series of stirred, open batch experiments designed to evaluate green rust, and its oxidised equivalent in this context comparing it to a ferrihydrite/goethite 'ochre'. Natural green rust was added to different mine waters as either a wet, reduced material or a dry, partially oxidised material. Experiments showed that the addition of either form accelerated the removal of potentially harmful elements from solution. Within one hour Fe, Al and Cu were completely removed from mine waters with initial concentrations of 80, 70 and 8.5mg/L, respectively, and Zn was reduced from 60 to <5mg/L. These experiments show the potential of green rust in mine water treatment, especially as it is able to remove problematic elements such as Al and Zn. The material is effective even after being dried and mostly oxidised. Changes to the pH and ORP of the mine waters and surface catalysis are the suggested mechanisms of accelerated removal of contaminants. PMID:21497995

  6. Mean Observer Metamerism and the Selection of Display Mark D. Fairchild and David R. Wyble, Rochester Institute of Technology, Munsell Color Science Laboratory, Rochester, NY/USA

    E-print Network

    Fairchild, Mark D.

    Mean Observer Metamerism and the Selection of Display Primaries Mark D. Fairchild and David R. Wyble, Rochester Institute of Technology, Munsell Color Science Laboratory, Rochester, NY/USA Abstract provide accurate estimates of population-mean color matching functions, they can never predict accurate

  7. Settling dynamics of natural ash particles: insight from laboratory high speed imaging

    NASA Astrophysics Data System (ADS)

    Del Bello, Elisabetta; Andronico, Daniele; Duc, Alix Vu; Kueppers, Ulrich; Cristaldi, Antonio; Ricci, Tullio; Scarlato, Piergiorgio; Scollo, Simona; Taddeucci, Jacopo

    2015-04-01

    Existing experimental and numerical models of ash sedimentation from volcanic plumes consider aerodynamic properties of particles as a function of their shape, density and size. However, rather than individually, particles are often observed to settle through zones of high particle concentration associated with gravitational instabilities (e.g., particle-rich fingers) where sedimentation is controlled by the properties of the bulk down-flow of settling particles. In order to investigate the differences in the aerodynamic behaviour of ash particles when settling individually or in mass, we performed systematic large-scale ash settling experiments. Natural basaltic ash from Etna (Italy, sampled in July 2014) and trachytic, pumiceous ash from Laacher See (Germany, 12.900 y BP) was used as starting material. For Etna, we used particles in the classes 0-125 and 125-500 µm, for Laacher See, we used 40-90 and 500-1000 µm. For each class, we released 40-500 g of sample from heights of 2 to 5 m with different, controlled volumetric flow rates, in an unconstrained open space and at minimal air movement. All experiments were recorded with a high-speed camera at 2000 fps. A vertical laser sheet crossing the flow enhanced visibility of particles. After release, particles were observed to cluster, leading to locally enhanced fall velocities. High-speed imaging, manual and automatic tracking analyses are being used to provide full characterization of particle settling dynamics as a function of particle concentration in the flow, density and particle size. SEM analysis will provide particle shape characterization. The main results are i) measured settling velocities of individual particles increase with increasing particle concentration; ii) particle sorting during sedimentation is observed. This suggests that particle dispersion during fallout may be one reason explaining larger than theoretical depletion rates of fine particles from volcanic ash clouds.

  8. Natural Selection and Functional Potentials of Human Noncoding Elements Revealed by Analysis of Next Generation Sequencing Data

    PubMed Central

    Xu, Shuhua

    2015-01-01

    Noncoding DNA sequences (NCS) have attracted much attention recently due to their functional potentials. Here we attempted to reveal the functional roles of noncoding sequences from the point of view of natural selection that typically indicates the functional potentials of certain genomic elements. We analyzed nearly 37 million single nucleotide polymorphisms (SNPs) of Phase I data of the 1000 Genomes Project. We estimated a series of key parameters of population genetics and molecular evolution to characterize sequence variations of the noncoding genome within and between populations, and identified the natural selection footprints in NCS in worldwide human populations. Our results showed that purifying selection is prevalent and there is substantial constraint of variations in NCS, while positive selectionis more likely to be specific to some particular genomic regions and regional populations. Intriguingly, we observed larger fraction of non-conserved NCS variants with lower derived allele frequency in the genome, indicating possible functional gain of non-conserved NCS. Notably, NCS elements are enriched for potentially functional markers such as eQTLs, TF motif, and DNase I footprints in the genome. More interestingly, some NCS variants associated with diseases such as Alzheimer's disease, Type 1 diabetes, and immune-related bowel disorder (IBD) showed signatures of positive selection, although the majority of NCS variants, reported as risk alleles by genome-wide association studies, showed signatures of negative selection. Our analyses provided compelling evidence of natural selection forces on noncoding sequences in the human genome and advanced our understanding of their functional potentials that play important roles in disease etiology and human evolution. PMID:26053627

  9. Inspection of selected travel policy and procedures at the Department of Energy`s Lawrence Livermore Laboratory

    SciTech Connect

    Not Available

    1994-09-01

    The Federal Acquisition Regulation (FAR) describes the allowable costs for transportation, lodging, meals, and incidental expenses incurred by government contractors, personnel traveling on official company business. According to the FAR, state institutions are allowed to follow their own institutional policy and procedures to administer travel costs incurred under Federal Government contracts. The Department of Energy`s Lawrence Livermore National Laboratory (Livermore) is operated by a State institution, the University of California (University), under a Department of Energy (Department)-management and operating (M&O) contract. According to a Livermore Travel Accounting Office official, between October 1, 1989, and July 31, 1993, travel costs incurred at Livermore were about $100 million. The purpose of this inspection was to review selected travel policies and procedures for reimbursing travel expenses at Livermore. The objectives of this inspection were: (1) to determine the appropriate criteria for reimbursing Livermore travel expenses involving trips for thirty consecutive days but less than six months; (2) to review whether University travel policy and procedures were generally being followed at Livermore; and (3) to evaluate whether the Department`s Oakland Operations Office (OAK) officials were carrying out their contract management responsibilities for travel practices at Livermore, as required by Federal and Departmental regulations.

  10. After the bottleneck: Genome-wide diversification of the Mycobacterium tuberculosis complex by mutation, recombination, and natural selection

    PubMed Central

    Namouchi, Amine; Didelot, Xavier; Schöck, Ulrike; Gicquel, Brigitte; Rocha, Eduardo P.C.

    2012-01-01

    Many of the most virulent bacterial pathogens show low genetic diversity and sexual isolation. Accordingly, Mycobacterium tuberculosis, the deadliest human pathogen, is thought to be clonal and evolve by genetic drift. Yet, its genome shows few of the concomitant signs of genome degradation. We analyzed 24 genomes and found an excess of genetic diversity in regions encoding key adaptive functions including the type VII secretion system and the ancient horizontally transferred virulence-related regions. Four different approaches showed evident signs of recombination in M. tuberculosis. Recombination tracts add a high density of polymorphisms, and many are thus predicted to arise from outside the clade. Some of these tracts match Mycobacterium canettii sequences. Recombination introduced an excess of non-synonymous diversity in general and even more in genes expected to be under positive or diversifying selection, e.g., cell wall component genes. Mutations leading to non-synonymous SNPs are effectively purged in MTBC, which shows dominance of purifying selection. MTBC mutation bias toward AT nucleotides is not compensated by biased gene conversion, suggesting the action of natural selection also on synonymous changes. Together, all of these observations point to a strong imprint of recombination and selection in the genome affecting both non-synonymous and synonymous positions. Hence, contrary to some other pathogens and previous proposals concerning M. tuberculosis, this lineage may have come out of its ancestral bottleneck as a very successful pathogen that is rapidly diversifying by the action of mutation, recombination, and natural selection. PMID:22377718

  11. Spatial variability of shelf sediments in the STRATAFORM natural laboratory, Northern California

    USGS Publications Warehouse

    Goff, J.A.; Wheatcroft, R.A.; Lee, H.; Drake, D.E.; Swift, D.J.P.; Fan, S.

    2002-01-01

    The "Correlation Length Experiment", an intensive box coring effort on the Eel River shelf (Northern California) in the summer of 1997, endeavored to characterize the lateral variability of near-surface shelf sediments over scales of meters to kilometers. Coring focused on two sites, K60 and S60, separated by ??? 15 km along the 60 m isobath. The sites are near the sand-to-mud transition, although K60 is sandier owing to its proximity to the Eel River mouth. Nearly 140 cores were collected on dip and strike lines with core intervals from < 10m to 1 km. Measurements on each core included bulk density computed from gamma-ray attenuation, porosity converted from resistivity measurements, and surficial grain size. Grain size was also measured over the full depth range within a select subset of cores. X-radiograph images were also examined. Semi-variograms were computed for strike, dip, and down-hole directions at each site. The sand-to-mud transition exerts a strong influence on all measurements: on average, bulk density increases and porosity decreases with regional increases in mean grain size. Analysis of bulk density measurements indicates very strong contrasts in the sediment variability at K60 and S60. No coherent bedding is seen at K60; in the strike direction, horizontal variability is "white" (fully uncorrelated) from the smallest scales examined (a few meters) to the largest (8 km), with a variance equal to that seen within the cores. In contrast, coherent bedding exists at S60 related to the preservation of the 1995 flood deposit. A correlatable structure is found in the strike direction with a decorrelation distance of ??? 800 m, and can be related to long-wavelength undulations in the topography and/or thickness of the flood layer or overburden. We hypothesize that the high degree of bulk density variability at K60 is a result of more intense physical reworking of the seabed in the sandier environment. Without significant averaging, the resistivity-based porosity measurements are only marginally correlated to gamma-ray-bulk density measurements, and are largely independent of mean grain size. Furthermore, porosity displays a high degree of incoherent variability at both sites. Porosity, with a much smaller sample volume than bulk density, may therefore resolve small-scale biogenic variability which is filtered out in the bulk density measurement. ?? 2002 Elsevier Science Ltd. All rights reserved.

  12. 29/03/2010 17:03Institute of Biological Engineering Altruism and natural selection Page 1 of 3http://blog.ibe.org/?p=78

    E-print Network

    Gardner, Andy

    29/03/2010 17:03Institute of Biological Engineering » Altruism and natural selection Page 1 of 3 The IBE Blog: What's hot in Biological Engineering Home About Announcements Altruism and natural selection source of altruism in relatives. If a gene is carried by a young individual also appears in its relatives

  13. Development of a van-portable remote-sensing laser system for selective detection of natural gas leaks

    NASA Astrophysics Data System (ADS)

    Rosengreen, A.; Vanderlaan, J.

    1984-04-01

    A mobile leak-survey system was developed for gas mains buried in the street that is faster and more efficient than existing systems. The feasibility of the laser remote-sensing technique for selective detection of leaking natural gas was demonstrated. A laser breadboard system was developed using a spectral differential absorption technique for detection of ethane from natural gas leaks. The system was then successfully demonstrated using an outdoor simulated gas leak. To estimate system performance, a preliminary system analysis was performed.

  14. 113 Lab Learning Objectives Week 11: Information and Natural Selection lab #6

    E-print Network

    Campbell, A. Malcolm

    of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly in the population. · Design directed evolution process to select antibiotic resistant bacteria. #12;

  15. Use of hydrogen peroxide treatment and crystal violet agar plates for selective recovery of bacteriophages from natural environments

    SciTech Connect

    Asghari, A.; Farrah, S.R.; Bitton, G. (Univ. of Florida, Gainesville (United States))

    1992-04-01

    Hydrogen peroxide inactivated bacteriophages and bacteria at different rates. A concentration of 0.1% hydrogen peroxide reduced the numbers of several bacteria by an average of 94% but caused an average of 25% inactivation in the numbers of bacteriophages tested. Treating natural samples with hydrogen peroxide selectively reduced the indigenous bacterial flora and permitted better visualization of plaques of lawns of Escherichia coli C-3000. In some cases indigenous gram-positive bacteria were relatively resistant to hydrogen peroxide, but their growth could be limited by incorporation of crystal violet into the bottom agar used for plaque assays. The use of hydrogen peroxide treatment and crystal violet-containing plates permitted recovery of more phages from natural samples than did other procedures, such as chloroform pretreatment or the use of selective plating agar such as EC medium.

  16. Selected Aspects of the Natural History of Gila Chub Fisheries Research Report 02-06

    E-print Network

    Bonar, Scott A.

    United States Geological Survey School of Natural Resources University of Arizona 104 Biological Sciences........................................................................ 24 Rock/Boulder cover............................................ 25 Algal cover

  17. A comparative analysis of the Darwin-Wallace papers and the development of the concept of natural selection

    Microsoft Academic Search

    U. Kutschera

    2003-01-01

    Summary  The classical theory of descent with modification by means of natural selection had no mother, but did have two English fathers,\\u000a Charles Darwin (1809–1882) and Alfred Russel Wallace (1823–1913). In 1858, the Linnean Society of London published two contributions\\u000a of these naturalists and acknowledged both authors as the proponents of a novel hypothesis on the driving force of organismic\\u000a evolution.

  18. Darwin vs. Wallace: When Poetry Dies and When Poetry Survives in the Not-So-Natural Selection of Memetic Evolution

    Microsoft Academic Search

    Bryce Christensen

    2011-01-01

    The theory of memetic evolution – explaining the reproduction of cultural units called memes – illuminates the decline of poetry as a cultural presence by clarifying the contrasting attitudes towards poetry manifested by the co-discoverers of natural selection: Charles Darwin and Alfred Wallace. Darwin’s eventual indifference to poetry can be traced to an all-absorbing faith in science that extinguishes poetry-favouring

  19. The annual habitat selection of released Père David’s Deer in Dafeng Milu National Nature Reserve

    Microsoft Academic Search

    Baolei Wu; Yifan Ji; Jinli Wang; Pei Qin

    2011-01-01

    The number of Père David’s (Elaphurus davidinus) deer which have been released into the wild is over one hundred in the third core area of Dafeng Milu National Nature Reserve. Annual habitat selection of released Père David’s deer was studied from November 2008 to November 2009. The results of our research showed that: in autumn and winter released Père David’s

  20. Natural killer cell activity and lymphocyte activation: Investigating the effects of a selection of essential oils and components in vitro

    Microsoft Academic Search

    M. D. Standen; Paul A Connellan; David N Leach

    2006-01-01

    A selection of essential oils and components were tested in vitro for potential immunomodulating effects on natural killer cell activity (NKCA) and lymphocyte activation through CD69 expression.\\u000aMatricaria recutita, Boswellia carteri, Pelargonium graveolens, Lavandula angustifolia, Citrus limon, Melaleuca alternifolia, Melaleuca viridiflora, Santalum spicatum, Cedrus atlantica, and Thymus vulgaris ct. linalool essential oils were solubilised with ethanol and methylated â-cyclodextrin 1:5:25

  1. Rapid shifts in the chemical composition of aspen forests: an introduced herbivore as an agent of natural selection

    Microsoft Academic Search

    Joseph K. Bailey; Jennifer A. Schweitzer; Brian J. Rehill; Duncan J. Irschick; Thomas G. Whitham; Richard L. Lindroth

    2007-01-01

    The global ecological impacts of introduced and exotic species can be dramatic, leading to losses in biodiversity and ecosystem\\u000a “meltdown”, however, the evolutionary impacts of introduced species are much less understood. Further, very few studies have\\u000a examined whether mammalian herbivores can act as agents of natural selection for plant traits. We examined the hypothesis\\u000a that variation in aspen phytochemistry resulted

  2. Determination of antiplasmodial activity and binding affinity of selected natural products towards PfTrxR and PfGR.

    PubMed

    Munigunti, Ranjith; Becker, Katja; Brun, Reto; Calderón, Angela I

    2013-08-01

    In our study, the binding affinities of selected natural products towards PfTrxR, PfGR, human TrxR and human GR were determined using a mass spectrometry based ligand binding assay. The in vitro antimalarial activity and cytotoxicity of these ligands were also determined. Catharanthine, 11-(OH)-coronaridine, hernagine, vobasine and hispolone displayed antiplasmodial activity against PfK1 (IC50 = 0.996-3.63 microg/mL). PMID:24079187

  3. Laboratory and realized host ranges of Chaetorellia succinea (Diptera: Tephritidae), an unintentionally introduced natural enemy of yellow starthistle.

    PubMed

    Balciunas, Joe K; Villegas, Baldo

    2007-08-01

    In 1999, we reported our discovery, in California and Oregon, of Chaetorellia succinea (Costa) (Diptera: Tephritidae) destroying the seeds of yellow starthistle, Centaurea solstitialis L., one of the worst weeds in the western United States. This fly, an unintentional introduction from Greece, dispersed rapidly throughout California and the northwest, and there is interest in using this adventive fly as a classical biological control agent for this weed. Because the host range of Ch. succinea has not been studied, this fly might pose a risk to other members of the thistle tribe Cardueae, especially the many thistle species native to California and other parts of the western United States. We determined the physiological host range of this fly in the laboratory by exposing it under no-choice conditions to 14 potential Cardueae hosts. Two introduced weed species and the native American basketflower (Centaurea americana Nuttall) were laboratory hosts. Under less restrictive choice test conditions, yellow starthistle was highly preferred, but there was a small amount of oviposition, and a few adult Ch. succinea emerged from all three of these plant species. Because Ch. succinea is now widespread throughout California, we collected flower heads from 24 potential host plant species at 111 sites to determine the realized host range in the field. These collections did not include American basketflower, which does not occur naturally in California. Ch. succinea emerged only from the other two known hosts: Ce. melitensis and Ce. sulfurea. Our results suggest that American basketflower growing in the southwestern United States may be at risk if Ch. succinea expands its range into that region. PMID:17716475

  4. Notice of Release of Zapata Germplasm Rio Grande Clammyweed Selected Class of Natural Germplasm

    Microsoft Academic Search

    Paula D Maywald; Shelly D Maher; Juan Garza; John Lloyd-Reilley; Forrest S Smith; Andrew W. Scott; Keith A Pawelek

    2010-01-01

    : A selected germplasm of Rio Grande clammyweed (Polanisia dodecandra (L.) DC. ssp. riograndensis Iltis [Capparaceae]) has been released for rangeland restoration and wildlife habitat enhancement plantings in south Texas. Zapata Germplasm Rio Grande clammyweed is a warm-season annual forb originating from seed collected from native plants in Dimmitt and Zapata counties of south Texas. Collections were selected based on

  5. Selecting networks of nature reserves: methods do affect the long-term outcome

    PubMed Central

    Virolainen, K. M.; Virola, T.; Suhonen, J.; Kuitunen, M.; Lammi, A.; ki, P. Siikam

    1999-01-01

    Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodiversity over time. However, the random selection of lakes seems to be the most inefficient option for a reserve network. In general, reserve selection methods seem to favour lakes that maximize one aspect of diversity at the time of selection, but the network may not be the best option for maintaining the maximum diversity over time. The reserve selection methods do affect the long-term outcome but it is impossible to recommend one method over the others unequivocally.

  6. Conservation of natural enemies through use of selective insecticides: recent developments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been well established that the use of selective insecticides promotes the critical role of biological control in the successful management of Bemisia tabaci within the Arizona Cotton IPM program. An increasing number of putatively selective insecticides have been introduced in recent years, ...

  7. Positive Selection of Natural Poly-Reactive B Cells in the Periphery Occurs Independent of Heavy Chain Allelic Inclusion

    PubMed Central

    Xing, Ying; Ji, Qiuhe; Lin, Ying; Fu, Meng; Gao, Jixin; Zhang, Ping; Hu, Xingbin; Feng, Lei; Liu, Yufeng; Han, Hua; Li, Wei

    2015-01-01

    Natural autoreactive B cells are important mediators of autoimmune diseases. Receptor editing is known to play an important role in both central and peripheral B cell tolerance. However, the role of allelic inclusion in the development of natural autoreactive B cells is not clear. Previously, we generated ? chain (TgVH3B4I) and ?/? chains (TgVH/L3B4) transgenic mice using transgene derived from the 3B4 hybridoma, which produce poly-reactive natural autoantibodies. In this study, we demonstrate that a considerable population of B cells edited their B cells receptors (BCRs) via light chain or heavy chain allelic inclusion during their development in TgVH3B4I mice. Additionally, allelic inclusion occurred more frequently in the periphery and promoted the differentiation of B cells into marginal zone or B-1a cells in TgVH3B4I mice. B cells from TgVH/L3B4 mice expressing the intact transgenic 3B4 BCR without receptor editing secreted poly-reactive 3B4 antibody. Interestingly, however, B cell that underwent allelic inclusion in TgVH3B4I mice also produced poly-reactive autoantibodies in vivo and in vitro. Our findings suggest that receptor editing plays a minor role in the positive selection of B cells expressing natural poly-reactive BCRs, which can be positively selected through heavy chain allelic inclusion to retain their poly-reactivity in the periphery. PMID:25993514

  8. Population genomic footprints of selection and associations with climate in natural populations of Arabidopsis halleri from the Alps

    PubMed Central

    Fischer, Martin C; Rellstab, Christian; Tedder, Andrew; Zoller, Stefan; Gugerli, Felix; Shimizu, Kentaro K; Holderegger, Rolf; Widmer, Alex

    2013-01-01

    Natural genetic variation is essential for the adaptation of organisms to their local environment and to changing environmental conditions. Here, we examine genomewide patterns of nucleotide variation in natural populations of the outcrossing herb Arabidopsis halleri and associations with climatic variation among populations in the Alps. Using a pooled population sequencing (Pool-Seq) approach, we discovered more than two million SNPs in five natural populations and identified highly differentiated genomic regions and SNPs using FST-based analyses. We tested only the most strongly differentiated SNPs for associations with a nonredundant set of environmental factors using partial Mantel tests to identify topo-climatic factors that may underlie the observed footprints of selection. Possible functions of genes showing signatures of selection were identified by Gene Ontology analysis. We found 175 genes to be highly associated with one or more of the five tested topo-climatic factors. Of these, 23.4% had unknown functions. Genetic variation in four candidate genes was strongly associated with site water balance and solar radiation, and functional annotations were congruent with these environmental factors. Our results provide a genomewide perspective on the distribution of adaptive genetic variation in natural plant populations from a highly diverse and heterogeneous alpine environment. PMID:24102711

  9. Essential oils as potential adulticides against two populations of Aedes aegypti , the laboratory and natural field strains, in Chiang Mai province, northern Thailand

    Microsoft Academic Search

    Dana Chaiyasit; Wej Choochote; Eumporn Rattanachanpichai; Udom Chaithong; Prasong Chaiwong; Atchariya Jitpakdi; Pongsri Tippawangkosol; Doungrat Riyong; Benjawan Pitasawat

    2006-01-01

    Essential oils derived from five plant species, celery (Apium graveolens), caraway (Carum carvi), zedoary (Curcuma zedoaria), long pepper (Piper longum), and Chinese star anise (Illicium verum), were subjected to investigation of adulticidal activity against mosquito vectors. Two populations of Aedes aegypti, the laboratory and natural field strains, collected in Chiang Mai province, northern Thailand were tested in pyrethroid-susceptibility bioassays. The

  10. 113 Lab Learning Objectives Week 14: Information and Natural Selection lab #9

    E-print Network

    Campbell, A. Malcolm

    of evolution based on lab experiences. · Explain how antibiotic resistant bacteria can appear quickly evolution of antibiotic resistance in bacteria. · Formulate an hypothesis how antibiotic resistant bacteria evolve outside the laboratory. · Propose a mechanism that allows bacteria to evolve rapidly when exposed

  11. Natural selection acting on body size, growth rate and compensatory growth: an empirical

    E-print Network

    Hendry, Andrew

    seasons in wild brown trout (Salmo trutta) by estimating selection acting on individual size, growth-history trade-offs, Salmo trutta. * Address all correspondence to Stephanie Carlson, School of Aquatic

  12. [Natural selection associated with color vision defects in some population groups of Eurasia].

    PubMed

    Evsiukov, A N

    2014-01-01

    Fitness coefficients and other quantitative parameters of selection associated with the generalized color blindness gene CB+ were obtained for three ethnogeographic population groups, including Belarusians from Belarus, ethnic populations of the Volga-Ural region, and ethnic populations of Siberia and the Far East of Russia. All abnormalities encoded by the OPN1LW and OPN1MW loci were treated as deviations from normal color perception. Coefficients were estimated from an approximation of the observed CB+ frequency distributions to the theoretical stationary distribution for the Wright island model. This model takes into account the pressure of migrations, selection, and random genetic drift, while the selection parameters are represented in the form of the distribution parameters. In the populations of Siberia and Far East, directional selection in favor of normal color vision and the corresponding allele CB- was observed. In the Belarusian and ethnic populations of the Volga-Ural region, stabilizing selection was observed. The selection intensity constituted 0.03 in the Belarusian; 0.22 in the ethnic populations of the Volga-Ural region; and 0.24 in ethnic populations of Siberia and Far East. PMID:25711015

  13. Selection of a Data Acquisition and Controls System Communications and Software Architecture for Johnson Space Center's Space Environment Simulation Laboratory Thermal and Vacuum Test Facilities

    NASA Technical Reports Server (NTRS)

    Jordan, Eric A.

    2004-01-01

    Upgrade of data acquisition and controls systems software at Johnson Space Center's Space Environment Simulation Laboratory (SESL) involved the definition, evaluation and selection of a system communication architecture and software components. A brief discussion of the background of the SESL and its data acquisition and controls systems provides a context for discussion of the requirements for each selection. Further framework is provided as upgrades to these systems accomplished in the 1990s and in 2003 are compared to demonstrate the role that technological advances have had in their improvement. Both of the selections were similar in their three phases; 1) definition of requirements, 2) identification of candidate products and their evaluation and testing and 3) selection by comparison of requirement fulfillment. The candidates for the communication architecture selection embraced several different methodologies which are explained and contrasted. Requirements for this selection are presented and the selection process is described. Several candidates for the software component of the data acquisition and controls system are identified, requirements for evaluation and selection are presented, and the evaluation process is described.

  14. Essential oils as potential adulticides against two populations of Aedes aegypti, the laboratory and natural field strains, in Chiang Mai province, northern Thailand.

    PubMed

    Chaiyasit, Dana; Choochote, Wej; Rattanachanpichai, Eumporn; Chaithong, Udom; Chaiwong, Prasong; Jitpakdi, Atchariya; Tippawangkosol, Pongsri; Riyong, Doungrat; Pitasawat, Benjawan

    2006-11-01

    Essential oils derived from five plant species, celery (Apium graveolens), caraway (Carum carvi), zedoary (Curcuma zedoaria), long pepper (Piper longum), and Chinese star anise (Illicium verum), were subjected to investigation of adulticidal activity against mosquito vectors. Two populations of Aedes aegypti, the laboratory and natural field strains, collected in Chiang Mai province, northern Thailand were tested in pyrethroid-susceptibility bioassays. The results revealed that the natural field strain of A. aegypti was resistant to permethrin, with mortality rates ranging from 51 to 66%. A mild susceptibility, with mortality rates ranging from 82 to 88%, was observed in the natural field strain of A. aegypti exposed to lambdacyhalothrin, which suggested that this strain was tolerant and might be resistant to this insecticide. However, laboratory-reared A. aegypti exposed to discriminating dosages of permethrin and lambdacyhalothrin induced 100% mortality in all cases, thus indicating complete susceptibility of this strain to these insecticides. The adulticidal activity determined by topical application revealed that all five essential oils exerted a promising adulticidal efficacy against both laboratory and natural field strains of A. aegypti. Although the laboratory strain was slightly more susceptible to these essential oils than the natural field strain, no statistically significant difference was observed. Moreover, comparison of the adulticidal activity indicated that the performance of these essential oils against the two strains of A. aegypti was similar. The highest potential was established from caraway, followed by zedoary, celery, long pepper, and Chinese star anise, with an LC(50) in the laboratory strain of 5.44, 5.94, 5.96, 6.21, and 8.52 microg/mg female, respectively, and 5.54, 6.02, 6.14, 6.35, and 8.83 microg/mg female, respectively, in the field strain. These promising essential oils are, therefore, an alternative in developing and producing mosquito adulticides as an effective measure used in controlling and eradicating mosquito vectors. PMID:16738885

  15. Genetic variability and natural selection at the ligand domain of the Duffy binding protein in brazilian Plasmodium vivax populations

    PubMed Central

    2010-01-01

    Background Plasmodium vivax malaria is a major public health challenge in Latin America, Asia and Oceania, with 130-435 million clinical cases per year worldwide. Invasion of host blood cells by P. vivax mainly depends on a type I membrane protein called Duffy binding protein (PvDBP). The erythrocyte-binding motif of PvDBP is a 170 amino-acid stretch located in its cysteine-rich region II (PvDBPII), which is the most variable segment of the protein. Methods To test whether diversifying natural selection has shaped the nucleotide diversity of PvDBPII in Brazilian populations, this region was sequenced in 122 isolates from six different geographic areas. A Bayesian method was applied to test for the action of natural selection under a population genetic model that incorporates recombination. The analysis was integrated with a structural model of PvDBPII, and T- and B-cell epitopes were localized on the 3-D structure. Results The results suggest that: (i) recombination plays an important role in determining the haplotype structure of PvDBPII, and (ii) PvDBPII appears to contain neutrally evolving codons as well as codons evolving under natural selection. Diversifying selection preferentially acts on sites identified as epitopes, particularly on amino acid residues 417, 419, and 424, which show strong linkage disequilibrium. Conclusions This study shows that some polymorphisms of PvDBPII are present near the erythrocyte-binding domain and might serve to elude antibodies that inhibit cell invasion. Therefore, these polymorphisms should be taken into account when designing vaccines aimed at eliciting antibodies to inhibit erythrocyte invasion. PMID:21092207

  16. Mandevilles Ship: Theistic Design and Philosophical History in Charles Darwins Vision of Natural Selection

    Microsoft Academic Search

    Stephen G. Alter

    2008-01-01

    This essay examines the analogy of a savage observing a sailing ship found in the final chapter of Darwin’s Origin of Species, an image that summed up his critique of British natural theology’s “design” thesis. Its inspiration drawn from works by Mandeville and Hume, and Darwin’s experience on the Beagle voyage, the ship illustration shows how Darwin conceived of natural

  17. A National Natural Laboratory.

    ERIC Educational Resources Information Center

    Cohn, Jeffrey P.

    1994-01-01

    Describes the Savannah River Site, a national environmental research park that shelters wild animals and idle nuclear reactors. Outlines research conducted at the site that focuses on the recovery of ecosystems after disturbance related to the operation of nuclear reactors and other land uses. (LZ)

  18. Organic synthesis: the art and science of replicating the molecules of living nature and creating others like them in the laboratory

    PubMed Central

    Nicolaou, K. C.

    2014-01-01

    Synthetic organic chemists have the power to replicate some of the most intriguing molecules of living nature in the laboratory and apply their developed synthetic strategies and technologies to construct variations of them. Such molecules facilitate biology and medicine, as they often find uses as biological tools and drug candidates for clinical development. In addition, by employing sophisticated catalytic reactions and appropriately designed synthetic processes, they can synthesize not only the molecules of nature and their analogues, but also myriad other organic molecules for potential applications in many areas of science, technology and everyday life. After a short historical introduction, this article focuses on recent advances in the field of organic synthesis with demonstrative examples of total synthesis of complex bioactive molecules, natural or designed, from the author’s laboratories, and their impact on chemistry, biology and medicine. PMID:24611027

  19. Natural selection among Kinnaura of the Himalayan highland: A comparative analysis with other Indian and Himalayan populations

    PubMed Central

    Gautam, Rajesh K.; Kapoor, Anup K.; Kshatriya, G. K.

    2009-01-01

    The present investigation on fertility and mortality differential among Kinnaura of the Himalayan highland is based on data collected from 160 post-menopausal women belonging to the middle and high altitude region of Kinnaur district of Himachal Pradesh (Indian Himalayas). Selection potential based on differential fertility and mortality was computed for middle-and high-altitude women. Irrespective of the methodology, the total index of selection was found to be highest among middle-altitude women (0.386) as compared with high-altitude (0.370) women, whereas for the total population it is estimated to be 0.384. It was found that the Kinnaura of the Himalayan highland showing moderate index of total selection and relative contribution of the mortality component (Im) to the index of total selection is higher than the corresponding fertility component (If). The analysis of embryonic and post-natal mortality components shows that the post-natal mortality components are higher in comparison with the embryonic mortality components among highlanders and needs special intervention and health care. The present findings are compared with other Indian tribes as well as non-tribes of the Himalayan region and other parts of the country. It reveals that this index among Kinnaura is moderate than the other population groups; among the Himalayan population, the highest was reported for Galong (It = 1.07) of Arunachal, whereas the lowest was reported from Ahom (It = 0.218) of Manipur. The correlation and regression analysis between total index of selection (It) and fertility (If) and mortality (Im) components for pooled data of populations of the Indian Himalayan states show that If and Im account for 21.6 and 29.1% variability, respectively. In Crow's total index of selection (It) along with strong association, which is significant at the 1% level, this indicates that mortality plays a greater role in natural selection in comparison with fertility among populations of the Indian Himalayas. PMID:21088718

  20. Natural selection in a postglacial range expansion: the case of the colour cline in the European barn owl.

    PubMed

    Antoniazza, Sylvain; Kanitz, Ricardo; Neuenschwander, Samuel; Burri, Reto; Gaigher, Arnaud; Roulin, Alexandre; Goudet, Jérôme

    2014-11-01

    Gradients of variation--or clines--have always intrigued biologists. Classically, they have been interpreted as the outcomes of antagonistic interactions between selection and gene flow. Alternatively, clines may also establish neutrally with isolation by distance (IBD) or secondary contact between previously isolated populations. The relative importance of natural selection and these two neutral processes in the establishment of clinal variation can be tested by comparing genetic differentiation at neutral genetic markers and at the studied trait. A third neutral process, surfing of a newly arisen mutation during the colonization of a new habitat, is more difficult to test. Here, we designed a spatially explicit approximate Bayesian computation (ABC) simulation framework to evaluate whether the strong cline in the genetically based reddish coloration observed in the European barn owl (Tyto alba) arose as a by-product of a range expansion or whether selection has to be invoked to explain this colour cline, for which we have previously ruled out the actions of IBD or secondary contact. Using ABC simulations and genetic data on 390 individuals from 20 locations genotyped at 22 microsatellites loci, we first determined how barn owls colonized Europe after the last glaciation. Using these results in new simulations on the evolution of the colour phenotype, and assuming various genetic architectures for the colour trait, we demonstrate that the observed colour cline cannot be due to the surfing of a neutral mutation. Taking advantage of spatially explicit ABC, which proved to be a powerful method to disentangle the respective roles of selection and drift in range expansions, we conclude that the formation of the colour cline observed in the barn owl must be due to natural selection. PMID:25294501

  1. Selective targeting of PPAR? by the natural product chelerythrine with a unique binding mode and improved antidiabetic potency

    PubMed Central

    Zheng, Weili; Qiu, Lin; Wang, Rui; Feng, Xuhui; Han, Yaping; Zhu, Yanlin; Chen, Dezhou; Liu, Yijie; Jin, Lihua; Li, Yong

    2015-01-01

    Type 2 diabetes mellitus (T2DM) is a pervasive metabolic syndrome that is characterized by insulin resistance, hyperglycemia and dyslipidemia. As full agonists of PPAR?, thiazolidinedione (TZD) drugs elicit antidiabetic effects by targeting PPAR? but is accompanied by weight gain, fluid retention and cardiovascular risk associated with their transcriptional agonism potency. We here identify a natural product chelerythrine as a unique selective PPAR modulator (SPPARM) with a potent PPAR? binding activity but much less classical receptor transcriptional agonism. Structural analysis reveals that chelerythrine exhibits unique binding in parallel with H3 of PPAR?. Unlike TZDs, chelerythrine destabilizes helix 12, especially residue tyrosine 473, resulting in a loose configuration of AF-2 and a selective cofactor profile distinct from TZDs, leading to a differential target gene profile in adipogenesis in db/db diabetic mice. Moreover, chelerythrine improved insulin sensitivity by more potently blocking the phosphorylation of PPAR? by CDK5 compared to TZDs. These data fundamentally elucidate the mechanism by which chelerythrine retains the benefits of improving insulin sensitivity while reducing the adverse effects of TZDs, suggesting that the natural product chelerythrine is a very promising pharmacological agent by selectively targeting PPAR? for further development in the clinical treatment of insulin resistance. PMID:26183621

  2. The Earth Microbiome Project: Meeting report of the “1st EMP meeting on sample selection and acquisition” at Argonne National Laboratory October 6th 2010.

    PubMed Central

    Gilbert, Jack A.; Meyer, Folker; Jansson, Janet; Gordon, Jeff; Pace, Norman; Tiedje, James; Ley, Ruth; Fierer, Noah; Field, Dawn; Kyrpides, Nikos; Glöckner, Frank-Oliver; Klenk, Hans-Peter; Wommack, K. Eric; Glass, Elizabeth; Docherty, Kathryn; Gallery, Rachel; Stevens, Rick; Knight, Rob

    2010-01-01

    This report details the outcome the first meeting of the Earth Microbiome Project to discuss sample selection and acquisition. The meeting, held at the Argonne National Laboratory on Wednesday October 6th 2010, focused on discussion of how to prioritize environmental samples for sequencing and metagenomic analysis as part of the global effort of the EMP to systematically determine the functional and phylogenetic diversity of microbial communities across the world. PMID:21304728

  3. Nature

    NSDL National Science Digital Library

    Nature is a weekly international journal publishing the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance, and surprising conclusions. Nature also provides rapid, authoritative, insightful and arresting news and interpretation of topical and coming trends affecting science, scientists and the wider public. Nature publishes more articles than any other multidisciplinary journal, and retains its position as the most cited weekly science journal. The site provides free access to news stories in the latest issue; access to research articles, and to the Nature archive, is by subscription.

  4. Demography and weak selection drive patterns of transposable element diversity in natural populations of Arabidopsis lyrata

    PubMed Central

    Lockton, Steven; Ross-Ibarra, Jeffrey; Gaut, Brandon S.

    2008-01-01

    Transposable elements (TEs) are the major component of most plant genomes, and characterizing their population dynamics is key to understanding plant genome complexity. Yet there have been few studies of TE population genetics in plant systems. To study the roles of selection, transposition, and demography in shaping TE population diversity, we generated a polymorphism dataset for six TE families in four populations of the flowering plant Arabidopsis lyrata. The TE data indicated significant differentiation among populations, and maximum likelihood procedures suggested weak selection. For strongly bottlenecked populations, the observed TE band-frequency spectra fit data simulated under neutral demographic models constructed from nucleotide polymorphism data. Overall, we propose that TEs are subjected to weak selection, the efficacy of which varies as a function of demographic factors. Thus, demographic effects could be a major factor driving distributions of TEs among plant lineages. PMID:18772373

  5. Selective elimination of human pluripotent stem cells by a marine natural product derivative.

    PubMed

    Kuo, Ting-Fang; Mao, Di; Hirata, Nao; Khambu, Bilon; Kimura, Yasuhisa; Kawase, Eihachiro; Shimogawa, Hiroki; Ojika, Makoto; Nakatsuji, Norio; Ueda, Kazumitsu; Uesugi, Motonari

    2014-07-16

    One of the current obstacles to stem cell therapy is the tumorigenic potential of residual undifferentiated stem cells. The present study reports rediscovery of a synthetic derivative of okadaic acid, a marine polyether toxin, as a reagent that selectively induces the death of human pluripotent stem cells. Cell-based screening of 333 cytotoxic compounds identified methyl 27-deoxy-27-oxookadaate (molecule 1) as a substrate of two ATP-binding cassette (ABC) transporters, ABCB1 (MDR1) and ABCG2 (BCRP), whose expression is repressed in human embryonic stem cells and induced pluripotent stem cells. The results demonstrate that selective elimination of human pluripotent stem cells can be achieved by designing cytotoxic small molecules with appropriate ABC-transporter selectivity. PMID:24992689

  6. MORTALITY COSTS OF SEXUAL SELECTION AND PARENTAL CARE IN NATURAL POPULATIONS OF BIRDS

    Microsoft Academic Search

    András Liker; Tamás Székely

    2005-01-01

    Is the cost of reproduction different between males and females? On the one hand, males typically compete intensely for mates, thus sexual selection theory predicts higher cost of reproduction for males in species with intense male-male competition. On the other hand, care provisioning such as incubating the eggs and raising young may also be costly, thus parental care theory predicts

  7. Changes in Landscape Greenness: Anthropogenic or Natural: Proof of Concept, Selected Study Areas

    EPA Science Inventory

    We selected four National Forest areas that span east to west of USA to conduct the study over the 25-year period from 1989 through 2013: GWJ (Virginia), Chatt-O (Georgia), Kisatchie (Louisiana), Hemlock Restoration (California). The Normalized Difference Vegetation Index (NDV...

  8. Copyright 2003 by the Genetics Society of America Natural Selection Drives Drosophila Immune System Evolution

    E-print Network

    Begun, David

    selection may often play a role in the evolution of host immune system proteins. However, there have been few attempts to make general population genetic inferences on the basis of analysis of several immune-system to function in the innate immune system of Drosophila simulans and compare these data to those from 28

  9. SELECTION ON LOCOMOTOR PERFORMANCE CAPACITY IN A NATURAL POPULATION OF GARTER SNAKES

    Microsoft Academic Search

    BRUCE C. JAYNE; ALBERT F. BENNETT

    Abstrad-Selection on locomotor performance was determined for a series of marked and recap- tured individuals from a population of garter snakes (Thamnophis sirtalis &hi) in Northern California. We measured snake length and mass, burst speed, endurance on a treadmill, and the distance crawled around a stationary circular track. Size-corrected values (residuals) of mass and locomotor performance were generated from the

  10. Natural selection for resistance to the allelopathic effects of invasive plants

    Microsoft Academic Search

    RAGAN M. CALLAWAY; WENDY M. RIDENOUR; TREVOR LABOSKI; TIFFANY WEIR; JORGE M. VIVANCO

    2005-01-01

    Summary 1 Exotic plant invasions often cause high mortality in native populations and therefore have the potential to be a powerful selective force. 2 We found that surviving individuals from North American communities that have experienced extensive invasion by Centaurea maculosa have higher tolerances to the Eurasian invader than individuals from communities that did not experience invasion. 3 Some native

  11. Natural Choice in Chimpanzees ("Pan troglodytes"): Perceptual and Temporal Effects on Selective Value

    ERIC Educational Resources Information Center

    Beran, Michael J.; Ratliff, Chasity L.; Evans, Theodore A.

    2009-01-01

    In three experiments, four chimpanzees made choices between two visible food options to assess the validity of the "selective value effect" (the assignment of value to only the most preferred type of food presented in a comparison). In Experiment 1, we established that all chimpanzees preferred single banana pieces to single apple pieces before…

  12. Male infanticide and paternity analyses in a socially natural herd of Przewalski's horses: Sexual selection?

    Microsoft Academic Search

    C. Feh; B. Munkhtuya

    2008-01-01

    The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions

  13. The magnitude and selectivity of natural and multiple anthropogenic mortality causes in hunted brown bears

    Microsoft Academic Search

    Richard Bischof; Jon E. Swenson; Nigel G. Yoccoz; Atle Mysterud; Olivier Gimenez

    2009-01-01

    Summary 1. The population dynamic and evolutionary effects of harvesting are receiving growing attention among biologists. Cause-specific estimates of mortality are necessary to determine and compare the magnitude and selectivity of hunting and other types of mortalities. In addition to the logistic and financial constraints on longitudinal studies, they are complicated by the fact that nonhunting mortality in managed populations

  14. Demography and weak selection drive patterns of transposable element diversity in natural populations of Arabidopsis lyrata

    Microsoft Academic Search

    Steven Lockton; Jeffrey Ross-Ibarra; Brandon S. Gaut

    2008-01-01

    Transposable elements (TEs) are the major component of most plant genomes, and characterizing their population dynamics is key to understanding plant genome complexity. Yet there have been few studies of TE population genetics in plant systems. To study the roles of selection, transposition, and demography in shaping TE population diversity, we generated a polymorphism dataset for six TE families in

  15. Evolution in an Afternoon: Rapid Natural Selection and Adaptation of Bacterial Populations

    ERIC Educational Resources Information Center

    Delpech, Roger

    2009-01-01

    This paper describes a simple, rapid and low-cost technique for growing bacteria (or other microbes) in an environmental gradient, in order to determine the tolerance of the microbial population to varying concentrations of sodium chloride ions, and suggests how the evolutionary response of a microbial population to the selection pressure of the…

  16. Visual search for natural grains in pigeons (Columba livia): Search images and selective attention

    Microsoft Academic Search

    Cynthia M. Langley; Donald A. Riley; Alan B. Bond; Namni Goel

    1996-01-01

    The experiments reported here were designed to test the suggestion of many researchers that selective attention to visual features of a prey can account for search-image effects. In 3 experiments pigeons ate wheat and vetch grains presented on multicolored and gray gravel trays. In Experiment 1 search-image effects were evident when grains were cryptic but not when they were conspicuous.

  17. Natural selection on unpalatable species imposed by state-dependent foraging behaviour

    Microsoft Academic Search

    Thomas N. Sherratt; Michael P. Speed; Graeme D. Ruxton

    2004-01-01

    Müllerian mimicry is typically thought to arise as a consequence of defended prey species adopting a similar way of signalling their unprofitability, thereby reducing the costs of predator education. Here we consider subsequent selection on the morphology of prey species, in the potentially lengthy period of time when predators are generally aware of the noxious qualities of their prey (and

  18. Tardigrades living in extreme environments have naturally selected prerequisites useful to space conquer

    Microsoft Academic Search

    Roberto Guidetti; Altiero Tiziana; Michele Cesari; Angela Maria Rizzo; Roberto Bertolani; Giuseppe Galletta; Maurizio Dalessandro; Lorena Rebecchi

    2010-01-01

    Extreme habitats are highly selective and can host only living organisms possessing specific adaptations to stressors. Among extreme habitats, space environment has particular charac-teristics of radiations, vacuum, microgravity and temperature, which induce rapid changes in living systems. Consequently, the response of multicellular complex organisms, able to colo-nize extreme environments, to space stresses can give very useful information on the ability

  19. Prolactin and helping in birds: has natural selection strengthened helping behavior?

    Microsoft Academic Search

    Jerram L. Brown; Carol M. Vleck

    1998-01-01

    The evolution of helping behavior in birds has been hotly debated. Hamilton's inclusive fitness theory has received much support from ecological cost-benefit studies; however, the hypothesis that helping has not been selected per se but is simply a phenotypically plastic response to altered social conditions has been proposed. In this view helping by nonbreeding birds occurs when at independence they

  20. Interspecific competition alters natural selection on shade avoidance phenotypes in Impatiens capensis

    Microsoft Academic Search

    Brechann V. McGoey; John R. Stinchcombe

    2009-01-01

    Summary • Shade avoidance syndrome is a known adaptive response for Impatiens capensis growing in dense intraspecific competition. However, I. capensis also grow with dominant interspecific competitors in marshes. Here, we compare the I. capensis shade-avoidance phenotypes produced in the absence and presence of heterospecific competitors, as well as selection on those traits.  Two treatments were established in a

  1. Sex ratio dynamics and fluctuating selection pressures in natural populations of the Trinidadian guppy, Poecilia reticulata

    Microsoft Academic Search

    Lars B. Pettersson; Indar W. Ramnarine; S. Anette Becher; Rajindra Mahabir; Anne E. Magurran

    2004-01-01

    In many species, population sex ratios have far-reaching consequences for a wide variety of population-level and behavioural processes and can directly influence sexual selection through differential effects on male and female mating behaviour. Although sex ratios are often treated as more or less stable population characteristics, recent theoretical evidence suggests that sex ratios fluctuate under many conditions, and that the

  2. CYANIDIN-3-RUTINOSIDE, A NATURAL POLYPHENOL ANTIOXIDANT, SELECTIVELY KILLS LEUKEMIC CELLS BY INDUCTION OF OXIDATIVE STRESS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Anthocyanins are a group of naturally occurring phenolic compounds widely available in fruits and vegetables of human diets. They have broad biological activities including anti-mutagenesis and anti-carcinogenesis, which are generally attributed to their antioxidant activities. We studied the effe...

  3. Improved Conservation of Natural Enemies with Selective Management Systems for Bemisia tabaci (Homoptera: Aleyrodidae) in Cotton

    Microsoft Academic Search

    Steven E. Naranjo; James R. Hagler; Peter C. Ellsworth

    2003-01-01

    A large-scale study was conducted in 1996 to evaluate and demonstrate strategies for pest management of Bemisia tabaci (Gennadius) in cotton involving different insecticide regimes, application methods, and action thresholds. Here we examined the effects of the various management systems on the abundance and activity of native natural enemies. Population densities of 18 out of 20 taxa of arthropod predators

  4. Selected Aspects Of Personal Values And Interpersonal Needs As They Relate To Philosophies Of Human Nature

    Microsoft Academic Search

    Rosario Miguel Bautista

    1982-01-01

    Purpose. The purpose of this study was to determine the extent to which creativity and expressed interpersonal needs correlate with philosophies of human nature.Procedure. The respondents were 64 students who were enrolled in four EDP 101: Introduction to Education classes and two doctoral seminars, EED 695 and ELI 695, in the School of Education and Allied Professions, during the Fall

  5. Impact of natural cleaning on the selection of a washing system for solar collectors

    Microsoft Academic Search

    A. Kerstein

    1981-01-01

    The desired optical properties (reflectivity, transmissivity, etc.) of solar energy collector surfaces such as mirrors and photovoltaic surfaces are degraded over time by soiling. Cost benefit evaluation of alternative methods for washing the surface or retarding the optical degradation must take into account natural cleaning processes such as precipitation and frost, which impact the scheduling as well as the benefits

  6. Functional group classification and target species selection for Yancheng Nature Reserve, China

    Microsoft Academic Search

    Hongguang Zhu; Pei Qin; Hui Wang

    2004-01-01

    Yancheng Nature Reserve in east China is of great importance to the protection of biodiversity. It is a principal refuge for Red-crowned Cranes (Grus japonensis) and many other rare species, an important station for migrant waterfowls in the Asian Pacific, and a captive breeding base for Milu (Elaphurus davidianus). However, since the late 1980s, serious losses of biodiversity have been

  7. KEY CRITERIA AND SELECTION OF SENSITIVITY ANALYSIS METHODS APPLIED TO NATURAL RESOURCE MODELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Integrated natural resource models (e.g., APSIM) are typically large and complex, thus, it can be difficult to prioritize parameters that are most promising with respect to system management goals. It is important to evaluate how a model responds to changes in its inputs as part of the process of m...

  8. Unusual selection on the KIR3DL1\\/S1 natural killer cell receptor in Africans

    Microsoft Academic Search

    Laurent Abi-Rached; Ketevan Gendzekhadze; Daniel Korbel; Michael Gleimer; Don Rowley; Dan Bruno; Christine V F Carrington; Dasdayanee Chandanayingyong; Yih-Hsin Chang; Catalina Crespí; Güher Saruhan-Direskeneli; Patricia A Fraser; Kamran Hameed; Giorgi Kamkamidze; Kwadwo A Koram; Zulay Layrisse; Nuria Matamoros; Joan Milà; Myoung Hee Park; Ramasamy M Pitchappan; D Dan Ramdath; Ming-Yuh Shiau; Henry A F Stephens; Siske Struik; David H Verity; Robert W Vaughan; Dolly Tyan; Ronald W Davis; Eleanor M Riley; Mostafa Ronaghi; Paul J Norman; Peter Parham

    2007-01-01

    Interactions of killer cell immunoglobulin-like receptors (KIRs) with major histocompatibility complex (MHC) class I ligands diversify natural killer cell responses to infection. By analyzing sequence variation in diverse human populations, we show that the KIR3DL1\\/S1 locus encodes two lineages of polymorphic inhibitory KIR3DL1 allotypes that recognize Bw4 epitopes of protein\\

  9. The selection of natural scales in 2D images using adaptive Gabor filtering

    Microsoft Academic Search

    J. Fdez-Valdivia; J. A. Garcia; J. Martinez-Baena; Xose R. Fdez-Vidal

    1998-01-01

    This paper analyzes how the natural scales of the shapes in 2D images can be extracted. Spatial information is analyzed by multiple units sensitive to both spatial and spatial-frequency variables. Scale estimates of the relevant shapes are constructed only from strongly responding detectors. The meaningful structures in the response of a detector (computed through 2D Gabor filtering) are, at their

  10. Natural Genetic Variation in Selected Populations of Arabidopsis thaliana Is Associated with Ionomic Differences

    Microsoft Academic Search

    Elizabeth Buescher; Tilman Achberger; Idris Amusan; Anthony Giannini; Cherie Ochsenfeld; Ana Rus; Brett Lahner; Owen Hoekenga; Elena Yakubova; Jeffrey F. Harper; Mary Lou Guerinot; Min Zhang; David E. Salt; Ivan R. Baxter; Pär K. Ingvarsson

    2010-01-01

    Controlling elemental composition is critical for plant growth and development as well as the nutrition of humans who utilize plants for food. Uncovering the genetic architecture underlying mineral ion homeostasis in plants is a critical first step towards understanding the biochemical networks that regulate a plant's elemental composition (ionome). Natural accessions of Arabidopsis thaliana provide a rich source of genetic

  11. KEY CRITERIA AND SELECTION OF SENSITIVITY ANALYSIS METHODS APPLIED TO NATURAL RESOURCE MODELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Integrated natural resource models (e.g., APSIM)are typically large and complex, thus, it can be difficult to prioritize parameters that are most promising with respect to system management goals. It is important to evaluate how a model responds to changes in its inputs as part of the process of mo...

  12. Management of natural hazards in Europe: The role of spatial planning in selected EU member states

    Microsoft Academic Search

    Stefan Greiving; Mark Fleischhauer; Sylvia Wanczura

    2006-01-01

    This paper presents the results of an assessment made as a part of the research project, Applied Multi-Risk Mapping of Natural Hazards for Impact Assessment (ARMONIA). The aim was to identify which aspects in the so-called disaster management cycle are covered by spatial planning in planning practice in the European Union's member states of Finland, France, Germany, Greece, Italy, Poland,

  13. Inferring natural selection signals in Plasmodium vivax-encoded proteins having a potential role in merozoite invasion.

    PubMed

    Garzón-Ospina, Diego; Forero-Rodríguez, Johanna; Patarroyo, Manuel A

    2015-07-01

    Detecting natural selection signals in Plasmodium parasites antigens might be used for identifying potential new vaccine candidates. Fifty-nine Plasmodium vivax-Sal-I genes encoding proteins having a potential role in invasion were used as query for identifying them in recent P. vivax strain genome sequences and two closely-related Plasmodium species. Several measures of DNA sequence variation were then calculated and selection signatures were detected by using different approaches. Our results may be used for determining which genes expressed during P. vivax merozoite stage could be prioritised for further population genetics or functional studies for designing a P. vivax vaccine which would avoid allele-specific immune responses. PMID:25943417

  14. Natural soil microbes alter flowering phenology and the intensity of selection on flowering time in a wild Arabidopsis relative

    PubMed Central

    Wagner, Maggie R.; Lundberg, Derek S.; Coleman-Derr, Devin; Tringe, Susannah G.; Dangl, Jeffery L.; Mitchell-Olds, Thomas

    2014-01-01

    Plant phenology is known to depend on many different environmental variables, but soil microbial communities have rarely been acknowledged as possible drivers of flowering time. Here we tested separately the effects of four naturally occurring soil microbiomes and their constituent soil chemistries on flowering phenology and reproductive fitness of Boechera stricta, a wild relative of Arabidopsis. Flowering time was sensitive to both microbes and the abiotic properties of different soils; varying soil microbiota also altered patterns of selection on flowering time. Thus, soil microbes potentially contribute to phenotypic plasticity of flowering time and to differential selection observed between habitats. We also describe a method to dissect the microbiome into single axes of variation that can help identify candidate organisms whose abundance in soil correlates with flowering time. This approach is broadly applicable to search for microbial community members that alter biological characteristics of interest. PMID:24698177

  15. Natural soil microbes alter flowering phenology and the intensity of selection on flowering time in a wild Arabidopsis relative.

    PubMed

    Wagner, Maggie R; Lundberg, Derek S; Coleman-Derr, Devin; Tringe, Susannah G; Dangl, Jeffery L; Mitchell-Olds, Thomas

    2014-06-01

    Plant phenology is known to depend on many different environmental variables, but soil microbial communities have rarely been acknowledged as possible drivers of flowering time. Here, we tested separately the effects of four naturally occurring soil microbiomes and their constituent soil chemistries on flowering phenology and reproductive fitness of Boechera stricta, a wild relative of Arabidopsis. Flowering time was sensitive to both microbes and the abiotic properties of different soils; varying soil microbiota also altered patterns of selection on flowering time. Thus, soil microbes potentially contribute to phenotypic plasticity of flowering time and to differential selection observed between habitats. We also describe a method to dissect the microbiome into single axes of variation that can help identify candidate organisms whose abundance in soil correlates with flowering time. This approach is broadly applicable to search for microbial community members that alter biological characteristics of interest. PMID:24698177

  16. Positive natural selection of TRIB2, a novel gene that influences visceral fat accumulation, in East Asia.

    PubMed

    Nakayama, Kazuhiro; Ogawa, Ayumi; Miyashita, Hiroshi; Tabara, Yasuharu; Igase, Michiya; Kohara, Katsuhiko; Miki, Tetsuro; Kagawa, Yasuo; Yanagisawa, Yoshiko; Katashima, Mitsuhiro; Onda, Tomohiro; Okada, Koichi; Fukushima, Shogo; Iwamoto, Sadahiko

    2013-02-01

    Accumulation of visceral fat increases cardiovascular mortality in industrialized societies. However, during the evolution of the modern human, visceral fat may have acted as energy storage facility to survive in times of famine. Therefore, past natural selection might contribute to shaping the variation of visceral fat accumulation in present populations. Here, we report that the gene encoding tribbles homolog 2 (TRIB2) influenced visceral fat accumulation and was operated by recent positive natural selection in East Asians. Our candidate gene association analysis on 11 metabolic traits of 5,810 East Asians revealed that rs1057001, a T/A transversion polymorphism in 3'untranslated region (UTR) of TRIB2, was strongly associated with visceral fat area (VFA) and waist circumference adjusted for body mass index (P = 2.7 × 10(-6) and P = 9.0 × 10(-6), respectively). rs1057001 was in absolute linkage disequilibrium with a conserved insertion-deletion polymorphism in the 3'UTR and was associated with allelic imbalance of TRIB2 transcript levels in adipose tissues. rs1057001 showed high degree of interpopulation variation of the allele frequency; the low-VFA-associated A allele was found with high frequencies in East Asians. Haplotypes containing the rs1057001 A allele exhibited a signature of a selective sweep, which may have occurred 16,546-27,827 years ago in East Asians. Given the predominance of the thrifty gene hypothesis, it is surprising that the apparently non-thrifty allele was selectively favored in the evolution of modern humans. Environmental/physiological factors other than famine would be needed to explain the non-neutral evolution of TRIB2 in East Asians. PMID:23108367

  17. Genetic Programming as a Means for Programming Computers by Natural Selection 1 Revised September 17, 1993 for Statistics and Computing journal.

    E-print Network

    Fernandez, Thomas

    Genetic Programming as a Means for Programming Computers by Natural Selection 1 Revised September 17, 1993 for Statistics and Computing journal. Genetic Programming as a Means for Programming fit individual computer program. The recently developed genetic programming paradigm described herein

  18. Relationship of organizational communication methods and leaders' perceptions of the 2002 Farm Bill: a study of selected commodity-specific, general agricultural, and natural resources organizations

    E-print Network

    Catchings, Christa Leigh

    2005-11-01

    The purpose of this study was to determine perceptions of organizational communication methods used by selected commodity-specific, general agricultural and, conservation or natural resources organizations to disseminate information about the Farm...

  19. Relationship of organizational communication methods and leaders' perceptions of the 2002 Farm Bill: a study of selected commodity-specific, general agricultural, and natural resources organizations 

    E-print Network

    Catchings, Christa Leigh

    2005-11-01

    The purpose of this study was to determine perceptions of organizational communication methods used by selected commodity-specific, general agricultural and, conservation or natural resources organizations to disseminate ...

  20. Male infanticide and paternity analyses in a socially natural herd of Przewalski's horses: sexual selection?

    PubMed

    Feh, C; Munkhtuya, B

    2008-07-01

    The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions were not the genetic fathers in four cases out of five, stallions present at birth did not significantly attempt to kill unrelated foals. Infanticide did not reduce birth intervals; only in one case out of five was the infanticidal stallion, the father of the next foal; mothers whose foals were attacked subsequently avoided associating with infanticidal stallions. Therefore, evidence for the sexual selection hypothesis was weak. The "human disturbance" hypothesis received some support, as only zoo bred stallions which grew up in unnatural social groups attacked foals of mares which were pregnant during takeovers. PMID:18328636

  1. Distinct Roles for Eye and Head Movements in Selecting Salient Image Parts during Natural Exploration

    Microsoft Academic Search

    Wolfgang Einhäuser; Frank Schumann; Johannes Vockeroth; Klaus Bartl; Moran Cerf; Jonathan Harel; Erich Schneider; Peter König

    2009-01-01

    Humans adjust gaze by eye, head, and body movements. Certain stimulus properties are therefore elevated at the gaze center, but the relative contribution of eye-in-head and head-in-world movements to this selection process is unknown. Gaze- and head- centered videos recorded with a wearable device (EyeSeeCam) during free exploration are reanalyzed with respect to responses of a face-detection algorithm. In line

  2. Reproduction and Immunity-Driven Natural Selection in the Human WFDC Locus

    PubMed Central

    Ferreira, Zélia; Seixas, Susana; Andrés, Aida M.; Kretzschmar, Warren W.; Mullikin, James C.; Cherukuri, Praveen F.; Cruz, Pedro; Swanson, Willie J.; Clark, Andrew G.; Green, Eric D.; Hurle, Belen

    2013-01-01

    The whey acidic protein (WAP) four-disulfide core domain (WFDC) locus located on human chromosome 20q13 spans 19 genes with WAP and/or Kunitz domains. These genes participate in antimicrobial, immune, and tissue homoeostasis activities. Neighboring SEMG genes encode seminal proteins Semenogelin 1 and 2 (SEMG1 and SEMG2). WFDC and SEMG genes have a strikingly high rate of amino acid replacement (dN/dS), indicative of responses to adaptive pressures during vertebrate evolution. To better understand the selection pressures acting on WFDC genes in human populations, we resequenced 18 genes and 54 noncoding segments in 71 European (CEU), African (YRI), and Asian (CHB + JPT) individuals. Overall, we identified 484 single-nucleotide polymorphisms (SNPs), including 65 coding variants (of which 49 are nonsynonymous differences). Using classic neutrality tests, we confirmed the signature of short-term balancing selection on WFDC8 in Europeans and a signature of positive selection spanning genes PI3, SEMG1, SEMG2, and SLPI. Associated with the latter signal, we identified an unusually homogeneous-derived 100-kb haplotype with a frequency of 88% in Asian populations. A putative candidate variant targeted by selection is Thr56Ser in SEMG1, which may alter the proteolytic profile of SEMG1 and antimicrobial activities of semen. All the well-characterized genes residing in the WDFC locus encode proteins that appear to have a role in immunity and/or fertility, two processes that are often associated with adaptive evolution. This study provides further evidence that the WFDC and SEMG loci have been under strong adaptive pressure within the short timescale of modern humans. PMID:23292442

  3. Fluorescence of the natural dye saffron: Selective reaction with eosinophil leucocyte granules

    Microsoft Academic Search

    Clara Isabel Trigoso; Juan Carlos Stockert

    1995-01-01

    Treatment of methanol-fixed chicken, rat, horse and human blood smears with saturated solutions of saffron in borate buffer at pH 10 results in a bright yellow-green fluorescence reaction of the acidophilic cytoplasm granules in mammalian eosinophils and chicken heterophils under violet-blue exciting light. Spectral characteristics of saffron (emission peak at 543 nm under 436 nm excitation) and its selective fluorescence

  4. Phenology of Agromyzid (Diptera) leafminers and their natural enemies on selected Texas native plants

    E-print Network

    Praetorius, Richard Leonhardt

    1990-01-01

    Enemies on Selected Texas Native Plants. (December 1990) Richard Leonhardt Praetorius, B. S. , Central Missouri State University; Chair of Advisory Committee: Dr. Robert Wharton The two annual bluebonnet species, Lupinus texensis and L. subcarnosus... germinate in October with secondary leaves being available for agromyzid oviposition by January. Both species begin their reproductive stage in mid March. Lupinus subcarnosus plants had died by April while L. texensis continued through June. Activity...

  5. Engineering development of advanced physical fine coal cleaning for premium fuel applications. Task 6 -- Selective agglomeration laboratory research and engineering development for premium fuels

    SciTech Connect

    Moro, N.; Jha, M.C.

    1997-06-27

    The primary goal of this project is the engineering development of two advanced physical fine coal cleaning processes, column flotation and selective agglomeration, for premium fuel applications. The project scope included laboratory research and benchscale testing on six coals to optimize these processes, followed by the design, construction, and operation of a 2 t/hr process development unit (PDU). The project began in October, 1992, and is scheduled for completion by September 1997. This report represents the findings of Subtask 6.5 Selective Agglomeration Bench-Scale Testing and Process Scale-up. During this work, six project coals, namely Winifrede, Elkhorn No. 3, Sunnyside, Taggart, Indiana VII, and Hiawatha were processed in a 25 lb/hr continuous selective agglomeration bench-scale test unit.

  6. Quantitative trait locus mapping in laboratory mice derived from a replicated selection experiment for open-field activity.

    PubMed Central

    Turri, M G; Henderson, N D; DeFries, J C; Flint, J

    2001-01-01

    Bidirectional selection in rodents has been used to derive animal models of human behavior. An important question is whether selection for behavior operates on a limited number of QTL or whether the number and individual contribution of QTL varies between selection experiments. To address this question, we mapped QTL in two large F2 intercrosses (N = 815 and 821) from the four lines derived from a replicated selection experiment for open-field activity, an animal model for susceptibility to anxiety. Our analyses indicate that selection operated on the same relatively small number of loci in both crosses. Haplotype information and the direction of effect of each QTL allele were used to confirm that the QTL mapped in the two crosses lie in the same chromosomal regions, although we were unable to determine whether QTL in the two crosses represent the same genes. We conclude that the genetic architecture of the selected strains is similar and relatively simple. PMID:11454769

  7. Selection of natural health products for clinical trials: a preclinical template.

    PubMed

    Vohra, S; Adams, D; Hudson, J B; Moore, J A; Vimalanathan, S; Sharma, M; Burt, A J; Lamont, E; Lacaze, N; Arnason, J T; Lee, T D G

    2009-05-01

    In preparation for a clinical trial on the efficacy of Echinacea products with a pediatric population, a rational method for selection of test products was developed, based on phytochemical and bioassay evaluation. Ten currently available commercial products of Echinacea angustifolia (EA) or Echinacea purpurea (EP) were selected, and 3 bottles of each of 2 different lots were purchased for each product. Investigators were blinded to product identity before phytochemical analysis. Lot-to-lot variation was small, but product variation due to species and formulation was large. Products derived from ethanol extracts had low polysaccharide content and high levels of alkamides (EA), echinacoside (EA), cynarin (EA), cichoric acid (EP), and caftaric acid (EP). These products possessed high antiviral activities that differed between EA and EP products, but limited immune activation properties. In contrast, products derived without ethanol extraction had higher polysaccharide levels, but low levels of other components. These aqueous compounds showed immunostimulant activity as measured in a mouse macrophage model and a somewhat different antiviral profile. The choice of Echinacea product for clinical trial must therefore consider the impact of immune enhancement, the specific viral infection targeted, and the potential to reduce symptoms via antiinflammatory activity. Product selection may also depend on whether the intent of the trial is prophylaxis or treatment. PMID:19448735

  8. Adaptation of Drosophila enzymes to temperature IV. Natural selection at the alcohol-dehydrogenase locus

    Microsoft Academic Search

    S. N. Alahiotis

    1982-01-01

    Studies were carried out on the temperature-dependent kinetic properties (Km, Q10, Ea, thermostability) of alcohol-dehydrogenase allozymes from D. melanogaster. It was shown that there is a parallelism between the biochemical properties of the enzymes and the behaviour of the genes in natural and cage populations. Furthermore, the relationship between the temperature-dependent kinetic properties of alcohol dehydrogenase and assay temperature was

  9. Selection at Work in Self-Incompatible Arabidopsis lyrata: Mating Patterns in a Natural Population

    Microsoft Academic Search

    Mikkel H. Schierup; Jesper S. Bechsgaard; Lene H. Nielsen; Freddy B. Christiansen

    2006-01-01

    Identification and characterization of the self-incompatibility genes in Brassicaceae species now allow typing of self-incompatibility haplotypes in natural populations. In this study we sampled and mapped all 88 individualsinasmallpopulationofArabidopsislyratafromIceland.Theself-incompatibilityhaplotypesatthe SRK gene weretypedforall theplants andsomeof their progenyand usedtoinvestigate therealizedmating patternsinthepopulation.Theobservedfrequenciesofhaplotypeswerefoundtochangeconsiderablyfrom the parentgeneration to the offspring generationaround their deterministic equilibriaas determined from the known dominance relations among haplotypes. We provide direct evidence

  10. A study of the antimicrobial activity of selected synthetic and naturally occurring quinolines

    Microsoft Academic Search

    F. O’Donnell; T. J. P. Smyth; V. N. Ramachandran; W. F. Smyth

    2010-01-01

    The antimicrobial activities of 60 naturally occurring and synthetic quinolines were studied. The quinolines were organised into seven structural subgroups and, using an in-house microtitre assay, were tested against a range of Gram-positive and Gram-negative bacteria, including a hospital isolate of meticillin-resistant Staphylococcus aureus (MRSA). The quinolines exhibiting good bioactivity [i.e. low minimum inhibitory concentration (MIC)] against two S. aureus

  11. A study of the antimicrobial activity of selected naturally occurring and synthetic coumarins

    Microsoft Academic Search

    T. Smyth; V. N. Ramachandran; W. F. Smyth

    2009-01-01

    The antimicrobial activities of 43 naturally occurring and synthetic coumarins were studied. Using a microtitre assay developed in-house, a range of Gram-positive and Gram-negative bacteria, including a hospital isolate of methicillin-resistant Staphylococcus aureus (MRSA),were utilised. The coumarins exhibiting good bioactivity (i.e. a lowminimum inhibitory concentration) against two S. aureus strains were then assessed for their antimicrobial activities against a range

  12. DAILY GROWTH OF THE JUVENILE FISH (MENIDIA MENIDIA) IN THE NATURAL HABITAT COMPARED WITH JUVENILES REARED IN THE LABORATORY

    EPA Science Inventory

    The Atlantic Silverside (Menidia menidia) is an abundant annual fish in Rhode Island, USA, waters and is being cultured in the Narragansett Laboratory of EPA for use in toxicological bioassays following culture techniques described by Beck (1977). It is desirable for laboratory-r...

  13. Contrasted Patterns of Selection on MHC-Linked Microsatellites in Natural Populations of the Malagasy Plague Reservoir

    PubMed Central

    Tollenaere, Charlotte; Ivanova, Svilena; Duplantier, Jean-Marc; Loiseau, Anne; Rahalison, Lila; Rahelinirina, Soanandrasana; Brouat, Carine

    2012-01-01

    Plague (Yersinia pestis infection) is a highly virulent rodent disease that persists in many natural ecosystems. The black rat (Rattus rattus) is the main host involved in the plague focus of the central highlands of Madagascar. Black rat populations from this area are highly resistant to plague, whereas those from areas in which the disease is absent (low altitude zones of Madagascar) are susceptible. Various lines of evidence suggest a role for the Major Histocompatibility Complex (MHC) in plague resistance. We therefore used the MHC region as a candidate for detecting signatures of plague-mediated selection in Malagasy black rats, by comparing population genetic structures for five MHC-linked microsatellites and neutral markers in two sampling designs. We first compared four pairs of populations, each pair including one population from the plague focus and one from the disease-free zone. Plague-mediated selection was expected to result in greater genetic differentiation between the two zones than expected under neutrality and this was observed for one MHC-class I-linked locus (D20Img2). For this marker as well as for four other MHC-linked loci, a geographic pattern of genetic structure was found at local scale within the plague focus. This pattern would be expected if plague selection pressures were spatially variable. Finally, another MHC-class I-linked locus (D20Rat21) showed evidences of balancing selection, but it seems more likely that this selection would be related to unknown pathogens more widely distributed in Madagascar than plague. PMID:22403713

  14. Joint effects of natural selection and recombination on gene flow between Drosophila ananassae populations.

    PubMed

    Chen, Y; Marsh, B J; Stephan, W

    2000-07-01

    We estimated DNA sequence variation in a 5.7-kb fragment of the furrowed (fw) gene region within and between four populations of Drosophila ananassae; fw is located in a chromosomal region of very low recombination. We analyzed gene flow between these four populations along a latitudinal transect on the Indian subcontinent: two populations from southern, subtropical areas (Hyderabad, India, and Sri Lanka) and two from more temperate zones in the north (Nepal and Burma). Furthermore, we compared the pattern of differentiation at fw with published data from Om(1D), a gene located in a region of normal recombination. While differentiation at Om(1D) shows an isolation-by-distance effect, at fw the pattern of differentiation is quite different such that the frequencies of single nucleotide polymorphisms are homogenized over extended geographic regions (i.e., among the two populations of the northern species range from Burma and Nepal as well as among the two southern populations from India and Sri Lanka), but strongly differentiated between the northern and southern populations. To examine these differences in the patterns of variation and differentiation between the Om(1D) and fw gene regions, we determine the critical values of our previously proposed test of the background selection hypothesis (henceforth called F(ST) test). Using these results, we show that the pattern of differentiation at fw may be inconsistent with the background selection model. The data depart from this model in a direction that is compatible with the occurrence of recent selective sweeps in the northern as well as southern populations. PMID:10880480

  15. Joint effects of natural selection and recombination on gene flow between Drosophila ananassae populations.

    PubMed Central

    Chen, Y; Marsh, B J; Stephan, W

    2000-01-01

    We estimated DNA sequence variation in a 5.7-kb fragment of the furrowed (fw) gene region within and between four populations of Drosophila ananassae; fw is located in a chromosomal region of very low recombination. We analyzed gene flow between these four populations along a latitudinal transect on the Indian subcontinent: two populations from southern, subtropical areas (Hyderabad, India, and Sri Lanka) and two from more temperate zones in the north (Nepal and Burma). Furthermore, we compared the pattern of differentiation at fw with published data from Om(1D), a gene located in a region of normal recombination. While differentiation at Om(1D) shows an isolation-by-distance effect, at fw the pattern of differentiation is quite different such that the frequencies of single nucleotide polymorphisms are homogenized over extended geographic regions (i.e., among the two populations of the northern species range from Burma and Nepal as well as among the two southern populations from India and Sri Lanka), but strongly differentiated between the northern and southern populations. To examine these differences in the patterns of variation and differentiation between the Om(1D) and fw gene regions, we determine the critical values of our previously proposed test of the background selection hypothesis (henceforth called F(ST) test). Using these results, we show that the pattern of differentiation at fw may be inconsistent with the background selection model. The data depart from this model in a direction that is compatible with the occurrence of recent selective sweeps in the northern as well as southern populations. PMID:10880480

  16. LESSONS LEARNED FROM IMPLEMENTATION OF MONITORED NATURAL ATTENUATION FOR AN AEROBIC TRICHLOROETHENE PLUME AT THE IDAHO NATIONAL ENGINEERING AND ENVIRONMENTAL LABORATORY

    Microsoft Academic Search

    R. A. Wymore; L. N. Peterson; L. O. Nelson; K. S. Sorenson

    The Test Area North (TAN) Facility of the Idaho National Engineering and Environmental Laboratory (INEEL) is the site of a 3-km-long trichloroethene (TCE) plume resulting from past waste injections into the deep fractured basalt aquifer. An in-depth natural attenuation field evaluation showed that aerobic TCE degradation was occurring with a half-life of 9 to 21 years (1) in the plume's

  17. Investigations on the biology, epidemiology, pathology and control of Tunga penetrans in Brazil. VI. Natural history of the infestation in laboratory-raised Wistar rats

    Microsoft Academic Search

    Hermann Feldmeier; Lars Witt; Stefan Schwalfenberg; Pedro M. Linardi; Ronaldo A. Ribeiro; Raphael A. C. Capaz; Eric Van Marck; Oliver Meckes; Heinz Mehlhorn; Norbert Mencke; Jörg Heukelbach

    2007-01-01

    Tungiasis is endemic in many countries in Latin America, the Caribbean and sub-Saharan Africa, and it is associated with severe\\u000a morbidity. The pathophysiological and immunological characteristics of the ectoparasitosis are not well understood, and no\\u000a effective therapy is currently available. The aim of this study was to describe the natural history of tungiasis in laboratory-raised\\u000a Wistar rats. The rats were

  18. 9 CFR 381.189 - Provisions inapplicable to specimens for laboratory examination, etc., or to naturally inedible...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...as inedible when they leave the establishment. (c) To parts of poultry carcasses that are naturally inedible by humans, such as entrails and feathers in their natural state. [40 FR 55310, Nov. 28,...

  19. 9 CFR 381.189 - Provisions inapplicable to specimens for laboratory examination, etc., or to naturally inedible...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...as inedible when they leave the establishment. (c) To parts of poultry carcasses that are naturally inedible by humans, such as entrails and feathers in their natural state. [40 FR 55310, Nov. 28,...

  20. 9 CFR 381.189 - Provisions inapplicable to specimens for laboratory examination, etc., or to naturally inedible...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...as inedible when they leave the establishment. (c) To parts of poultry carcasses that are naturally inedible by humans, such as entrails and feathers in their natural state. [40 FR 55310, Nov. 28,...