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1

A Natural Selection: Partnering Teachers and Scientists in the Classroom Laboratory Creates a Dynamic Learning Community  

ERIC Educational Resources Information Center

The high school science laboratory provides a natural environment for students to learn through scientist-teacher partnerships. Scientists represent an excellent resource for teachers and students: They possess specialized knowledge and skills, have access to laboratory equipment and materials, and are immersed in a culture of collaborative…

Siegel, Marcelle A.; Mlynarczyk-Evans, Susanna; Brenner, Tamara J.; Nielsen, Katherine M.

2005-01-01

2

Natural Selection  

NSDL National Science Digital Library

Learners simulate the process of natural selection using a variety of beans and a bowl with a hole cut into it. The variety of beans represents the variation in a population of microbes, and the bowl with a hole represents an antibiotic or some other selective pressure on the population. Only the beans that survive (don't fall through the hole) are allowed to reproduce for the next generation. Learners record and plot the number of each kind of bean through multiple generations. This activity also addresses the process of scientific investigation as learners are encouraged to design their own method of experimentation, make a hypothesis, record data, and share their results.

Thiel-Cobbey, Heather

2012-01-01

3

Adaptive Value of Phenological Traits in Stressful Environments: Predictions Based on Seed Production and Laboratory Natural Selection  

PubMed Central

Phenological traits often show variation within and among natural populations of annual plants. Nevertheless, the adaptive value of post-anthesis traits is seldom tested. In this study, we estimated the adaptive values of pre- and post-anthesis traits in two stressful environments (water stress and interspecific competition), using the selfing annual species Arabidopsis thaliana. By estimating seed production and by performing laboratory natural selection (LNS), we assessed the strength and nature (directional, disruptive and stabilizing) of selection acting on phenological traits in A. thaliana under the two tested stress conditions, each with four intensities. Both the type of stress and its intensity affected the strength and nature of selection, as did genetic constraints among phenological traits. Under water stress, both experimental approaches demonstrated directional selection for a shorter life cycle, although bolting time imposes a genetic constraint on the length of the interval between bolting and anthesis. Under interspecific competition, results from the two experimental approaches showed discrepancies. Estimation of seed production predicted directional selection toward early pre-anthesis traits and long post-anthesis periods. In contrast, the LNS approach suggested neutrality for all phenological traits. This study opens questions on adaptation in complex natural environment where many selective pressures act simultaneously.

Glorieux, Cedric; Cuguen, Joel; Roux, Fabrice

2012-01-01

4

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

ERIC Educational Resources Information Center

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…

BARNES, LEHMAN WILDER, JR.

5

Evolution by Natural Selection  

NSDL National Science Digital Library

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.

Doherty, Jennifer; Waldron, Ingrid

6

Cultural artifacts: a comparison of senescence in natural, laboratory-adapted and artificially selected lines of Drosophila melanogaster  

Microsoft Academic Search

When animals are kept in the laboratory in non-overlapping generations, a high load of mutations with late-acting effects can accumulate over time. This may lead, in turn, to a gradual but steady decline in life expectancy. Selection experiments designed to extend longevity in laboratory-adapted lines may, in fact, simply restore the vigour that was lost from the original lines after

Catherine Linnen; Marc Tatar; Daniel Promislow

2001-01-01

7

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.

2007-05-06

8

Introduction to Natural Selection  

NSDL National Science Digital Library

This lesson will help students develop an understanding of natural selection, specifically, how it unfolds from generation to generation. The Motivation section introduces a species of bird that became (over millions of years) numerous species, through adaptation. The Development section 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. Students will learn why organisms evolve over time, how natural selection works, and how certain factors determine survival and differences in organisms.

9

Multicellular microorganisms: laboratory versus nature  

PubMed Central

Our present in-depth knowledge of the physiology and regulatory mechanisms of microorganisms has arisen from our ability to remove them from their natural, complex ecosystems into pure liquid cultures. These cultures are grown under optimized laboratory conditions and allow us to study microorganisms as individuals. However, microorganisms naturally grow in conditions that are far from optimal, which causes them to become organized into multicellular communities that are better protected against the harmful environment. Moreover, this multicellular existence allows individual cells to differentiate and acquire specific properties, such as forming resistant spores, which benefit the whole population. The relocation of natural microorganisms to the laboratory can result in their adaptation to these favourable conditions, which is accompanied by complex changes that include the repression of some protective mechanisms that are essential in nature. Laboratory microorganisms that have been cultured for long periods under optimized conditions might therefore differ markedly from those that exist in natural ecosystems.

Palkova, Zdena

2004-01-01

10

Reinventing Natural Selection  

ERIC Educational Resources Information Center

Although many research studies report students' Lamarckian misconceptions, only a few studies present learning and teaching strategies that focus on the successful development of the concept of natural selection. The learning and teaching strategy for upper secondary students (aged 15-16) presented in this study conducted in The Netherlands is…

Geraedts, Caspar L.; Boersma, Kerst Th.

2006-01-01

11

Reinventing Natural Selection  

NASA Astrophysics Data System (ADS)

Although many research studies report students’ Lamarckian misconceptions, only a few studies present learning and teaching strategies that focus on the successful development of the concept of natural selection. The learning and teaching strategy for upper secondary students (aged 15 16) presented in this study conducted in The Netherlands is based on the idea of guided reinvention, rather than on the conceptual change strategy. In guided reinvention, students reinvent the concept of natural selection by answering a sequence of questions based on the logical nature of Darwin’s theory. The results show that few Lamarckian explanations for evolution were recorded in the study and that the majority of the students developed a Darwinian or neo-Darwinian conception. The status of Lamarckian misconceptions is challenged.

Geraedts, Caspar L.; Boersma, Kerst Th.

2006-06-01

12

Investigating Natural Selection  

NSDL National Science Digital Library

In this activity, students experience one mechanism for evolution through a simulation that models the principles of natural selection and helps answer the question 'how might biological change have occurred and been reinforced over time?' Students will discover that species evolve over time and evolution is the consequence of the interaction of the potential for a species to increase in number, the genetic variability of offspring due to mutation and recombination of genes, a finite supply of the resources required for life, and the ensuing selection of those offspring better able to survive and leave offspring in a particular environment. Natural selection and its evolutionary consequences provide a scientific explanation for the fossil record of ancient life forms, as well as for the striking molecular similarities observed among the diverse species of living organisms. The site also contains a list of materials and all information and instructions required to complete this activity.

13

Introduction to Natural Selection  

NSDL National Science Digital Library

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.

Science Netlinks;

2002-03-28

14

Natural Selection Simulation  

NSDL National Science Digital Library

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.

2012-05-29

15

Natural selection in the laboratory for a change in resistance by Drosophila melanogaster to the parasitoid wasp Asobara tabida  

Microsoft Academic Search

The selection response of the polymorphic hostD. melanogaster (Meigen) to the braconid waspA. tabida (Nees) is addressed. Cages of flies with and without wasps were initiated with a population ofD. melanogaster that exhibited variation both in larval foraging behavior and in encapsulation ability. Encapsulation ability was measured as the proportion of parasitized larvae that produce a hardened capsule which encapsulates

Kimberley Hughes; Marla B. Sokolowski

1996-01-01

16

Visualizing and quantifying natural selection  

Microsoft Academic Search

Modern methods of analysis are enabling researchers to study natural selection at a new level of detail. Multivariate statistical techniques can Identify specific targets of selection and provide parameter estimates that fit into equations for evolutionary change. A more Intuitive understanding of the form of selection can be provided through graphical representation of selection surfaces. Combinations of quantitative and visual

Edmund D. Brodie; Allen J. Moore; Fredric J. Janzen

1995-01-01

17

Modeling Natural Selection  

ERIC Educational Resources Information Center

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 better understanding of the content, process, and nature of science (Kenyon, Schwarz, and Hug…

Bogiages, Christopher A.; Lotter, Christine

2011-01-01

18

Investigating Natural Selection: Elementary School  

NSDL National Science Digital Library

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.

2010-01-01

19

Evolution Through Natural Selection  

NSDL National Science Digital Library

This workbook simulates the population genetics of a single gene with two alleles, allowing the user to set the initial allele frequencies and enter parameters for a variety of different selection models; the program then tracks the population through up to 10,000 generations.

Tim Comar (Benedictine University;Mathematics)

2005-04-17

20

A quantum of natural selection  

NASA Astrophysics Data System (ADS)

The modern evolutionary synthesis, which marries Darwin's theory of natural selection with Mendel's genetics, was developed around the same time as quantum mechanics. Is there any connection between the two?

Lloyd, Seth

2009-03-01

21

Charles Darwin II: Natural selection  

NSDL National Science Digital Library

This is the second in a series of modules which detail the research of Charles Darwin and evolutionary theory. This module continues with a discussion of the processes that led to Darwin's formulation of the theory of natural selection.

Rosenberger, Alfred

2004-02-12

22

Natural Selection: How Evolution Works  

NSDL National Science Digital Library

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.

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

2004-12-01

23

Natural Selection Promotes Antigenic Evolvability  

PubMed Central

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.

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

2013-01-01

24

The cost of natural selection  

Microsoft Academic Search

Summary  Unless selection is very intense, the number of deaths needed to secure the substitution, by natural selection, of one gene\\u000a for another at a locus, is independent of the intensity of selection. It is often about 30 times the number of organisms in\\u000a a generation. It is suggested that, in horotelic evolution, the mean time taken for each gene substitution

J. B. S. Haldane

1957-01-01

25

Natural Selection in the Brain  

Microsoft Academic Search

\\u000a This chapter explores the possibility that natural selection takes place in the brain. We review the theoretical and experimental\\u000a evidence for selectionist and competitive dynamics within the brain. We propose that in order to explain human problem-solving,\\u000a selectionist mechanisms demand extension to encompass the full Darwinian dynamic that arises from introducing replication\\u000a of neuronal units of selection. The algorithmic advantages

Chrisantha Fernando; Eörs Szathmáry

26

Laboratory Selection Quickly Erases Historical Differentiation  

PubMed Central

The roles of history, chance and selection have long been debated in evolutionary biology. Though uniform selection is expected to lead to convergent evolution between populations, contrasting histories and chance events might prevent them from attaining the same adaptive state, rendering evolution somewhat unpredictable. The predictability of evolution has been supported by several studies documenting repeatable adaptive radiations and convergence in both nature and laboratory. However, other studies suggest divergence among populations adapting to the same environment. Despite the relevance of this issue, empirical data is lacking for real-time adaptation of sexual populations with deeply divergent histories and ample standing genetic variation across fitness-related traits. Here we analyse the real-time evolutionary dynamics of Drosophila subobscura populations, previously differentiated along the European cline, when colonizing a new common environment. By analysing several life-history, physiological and morphological traits, we show that populations quickly converge to the same adaptive state through different evolutionary paths. In contrast with other studies, all analysed traits fully converged regardless of their association with fitness. Selection was able to erase the signature of history in highly differentiated populations after just a short number of generations, leading to consistent patterns of convergent evolution.

Lopes-Cunha, Miguel; Lima, Margarida; Kellen, Barbara; Barbaro, Margarida; Santos, Josiane; Rose, Michael R.; Santos, Mauro; Matos, Margarida

2014-01-01

27

Natural Selection and Applied Genetics  

NSDL National Science Digital Library

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.

2010-01-01

28

Natural Selection: A Cumulative Process  

NSDL National Science Digital Library

A common criticism of natural selection is: How can it produce novel complex useful structures by pure random chance? Darwin argued that selection is not a random process, and furthermore, it is cumulative. This lesson provides a way for students to actually compare the cumulative non-random selection of Darwin with the non-cumulative version so often erroneously implied. Students attempt to produce a full sequence of 13 cards of one suit (ace - to king). This must be done by shuffling the suit of cards for each round, then checking the cards. Half the teams must look for the full sequence each time, and repeat the process until this is accomplished. The other teams start to build their sequence by pulling the ace when it first appears as the top card, then adding to the stack whenever the next card for the sequence is shuffled to the top. Discussion reveals how the second method mimics Darwinian natural selection, while the first does not.

Heim, Werner

29

Scavenger Hunt: Simulating Natural Selection  

NSDL National Science Digital Library

This kinesthetic activity simulates the process of evolution by natural selection. Students take on the roles of crab-like predators that exhibit one of four variants of feeding appendage: a spoon, fork, knife, and chopsticks. The simulation runs for three trials, as the predators use their appendages to harvest pinto beans, with varying success. Students track the frequency of each appendage type through three generations. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

30

Simulate Natural Selection With Beetles  

NSDL National Science Digital Library

In this simulation activity, students experiment with a population of M&M candies or paper dot "beetles" to test how well each color is adapted to survive on a field of colorful wrapping paper or fabric. Students act as predators and see that camouflaged beetles survive predation preferentially. Students reflect on how the activity could be modified to better simulate the process of predation-based natural selection. This activity is supported by a textbook chapter, "Origin of Species," part of the unit, "Losing Biodiversity," in Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

31

Interaction between Natural Selection for Heterozygotes and Directional Selection  

PubMed Central

When directional selection for an additively inherited trait is opposed by natural selection favoring heterozygous genotypes a selection plateau may be reached where genetic variance is present. The amount of response when this plateau is reached is a simple function of the selection response in the first generation and the intensity of natural selection. When selection is practiced in small populations, the sizes of the initial equilibrium gene frequencies are at least as important as the intensity of natural selection in determining the probability of fixing desirable alleles.

Verghese, Margrith Wehrli

1974-01-01

32

Selection of a Site Adapted to the Realization of an Underground Laboratory in Clay Formations.  

National Technical Information Service (NTIS)

Research carried out in Italy by ENEA for site selection of an underground laboratory in a clay formation are presented. Mine roadways, abandoned tunnels, natural or artificial escarpments are prospected. The Pasquasia potash mine in Sicily was selected. ...

F. Benvegnu

1984-01-01

33

The Nature of Naive Explanations of Natural Selection.  

ERIC Educational Resources Information Center

Suggests that misconceptions about natural selection arise from mistaken categorization. Proposes that students often fail to understand the ontological features of equilibrium processes. Contains 32 references. (DDR)

Ferrari, Michel; Chi, Michelene T. H.

1998-01-01

34

Natural Selection Because of Different Color: Camouflage  

NSDL National Science Digital Library

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.

Cavanagh, Dave; Pickup, Nikki; Cavanagh, Laura

2012-11-14

35

Natural Selection in a Petri Dish.  

ERIC Educational Resources Information Center

Presents an activity to teach natural selection that involves students in a microbiological investigation. Students discover that a change in environmental conditions tests a species' range of adaptations. (DDR)

McCarty, Robbie V.; Marek, Edmund A.

1997-01-01

36

Experiencing Natural Selection: Will You Survive?  

NSDL National Science Digital Library

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.

2011-01-01

37

The Natural Selection of Stick-Worms  

NSDL National Science Digital Library

This lesson teaches students that traits are usually favored by natural selection only when they result in more reproductively successful offspring. Students go out onto the school lawn and play the role of birds, picking up toothpick stick worms which have been previously scattered in equal numbers of green-stained and unstained. Birds are chased away before the worm population drops too low. Back in the classroom, the number of green and non-green worms are compared individually and for the whole class. Discussion relates the experience to the elements of natural selection. As presented here, it does not lend itself to demonstrating the effects of selection over multiple generations.

Dutton, Don; Fisher, Fred; Flammer, Larry

38

From nature to the laboratory and into the clinic.  

PubMed

Natural products possess a broad diversity of structure and function, and they provide inspiration for chemistry, biology, and medicine. In this review article, we highlight and place in context our laboratory's total syntheses of, and related studies on, complex secondary metabolites that were clinically important drugs, or have since been developed into useful medicines, namely amphotericin B (1), calicheamicin gamma(1)(I) (2), rapamycin (3), Taxol (4), the epothilones [e.g., epothilones A (5) and B (6)], and vancomycin (7). We also briefly highlight our research with other selected inspirational natural products possessing interesting biological activities [i.e., dynemicin A (8), uncialamycin (9), eleutherobin (10), sarcodictyin A (11), azaspiracid-1 (12), thiostrepton (13), abyssomicin C (14), platensimycin (15), platencin (16), and palmerolide A (17)]. PMID:19028103

Nicolaou, K C; Chen, Jason S; Dalby, Stephen M

2009-03-15

39

Comparing Patterns of Natural Selection Across Species Using Selective Signatures  

SciTech Connect

Comparing gene expression profiles over many different conditions has led to insights that were not obvious from single experiments. In the same way, comparing patterns of natural selection across a set of ecologically distinct species may extend what can be learned from individual genome-wide surveys. Toward this end, we show how variation in protein evolutionary rates, after correcting for genome-wide effects such as mutation rate and demographic factors, can be used to estimate the level and types of natural selection acting on genes across different species. We identify unusually rapidly and slowly evolving genes, relative to empirically derived genome-wide and gene family-specific background rates for 744 core protein families in 30 gamma-proteobacterial species. We describe the pattern of fast or slow evolution across species as the 'selective signature' of a gene. Selective signatures represent a profile of selection across species that is predictive of gene function: pairs of genes with correlated selective signatures are more likely to share the same cellular function, and genes in the same pathway can evolve in concert. For example, glycolysis and phenylalanine metabolism genes evolve rapidly in Idiomarina loihiensis, mirroring an ecological shift in carbon source from sugars to amino acids. In a broader context, our results suggest that the genomic landscape is organized into functional modules even at the level of natural selection, and thus it may be easier than expected to understand the complex evolutionary pressures on a cell.

Alm, Eric J.; Shapiro, B. Jesse; Alm, Eric J.

2007-12-18

40

Comparing Patterns of Natural Selection across Species Using Selective Signatures  

SciTech Connect

Comparing gene expression profiles over many different conditions has led to insights that were not obvious from single experiments. In the same way, comparing patterns of natural selection across a set of ecologically distinct species may extend what can be learned from individual genome-wide surveys. Toward this end, we show how variation in protein evolutionary rates, after correcting for genome-wide effects such as mutation rate and demographic factors, can be used to estimate the level and types of natural selection acting on genes across different species. We identify unusually rapidly and slowly evolving genes, relative to empirically derived genome-wide and gene family-specific background rates for 744 core protein families in 30 c-proteobacterial species. We describe the pattern of fast or slow evolution across species as the"selective signature" of a gene. Selective signatures represent aprofile of selection across species that is predictive of gene function: pairs of genes with correlated selective signatures are more likely to share the same cellular function, and genes in the same pathway can evolve in concert. For example,glycolysis and phenylalanine metabolism genes evolve rapidly in Idiomarina loihiensis, mirroring an ecological shift in carbon source from sugars to amino acids. In a broader context, our results suggest that the genomic landscape is organized into functional modules even at the level of natural selection, and thus it may be easier than expected to understand the complex evolutionary pressures on a cell.

Shapiro, Jesse; Alm, Eric J.

2007-12-01

41

Microsatellites as Targets of Natural Selection  

PubMed Central

The ability to survey polymorphism on a genomic scale has enabled genome-wide scans for the targets of natural selection. Theory that connects patterns of genetic variation to evidence of natural selection most often assumes a diallelic locus and no recurrent mutation. Although these assumptions are suitable to selection that targets single nucleotide variants, fundamentally different types of mutation generate abundant polymorphism in genomes. Moreover, recent empirical results suggest that mutationally complex, multiallelic loci including microsatellites and copy number variants are sometimes targeted by natural selection. Given their abundance, the lack of inference methods tailored to the mutational peculiarities of these types of loci represents a notable gap in our ability to interrogate genomes for signatures of natural selection. Previous theoretical investigations of mutation-selection balance at multiallelic loci include assumptions that limit their application to inference from empirical data. Focusing on microsatellites, we assess the dynamics and population-level consequences of selection targeting mutationally complex variants. We develop general models of a multiallelic fitness surface, a realistic model of microsatellite mutation, and an efficient simulation algorithm. Using these tools, we explore mutation-selection-drift equilibrium at microsatellites and investigate the mutational history and selective regime of the microsatellite that causes Friedreich’s ataxia. We characterize microsatellite selective events by their duration and cost, note similarities to sweeps from standing point variation, and conclude that it is premature to label microsatellites as ubiquitous agents of efficient adaptive change. Together, our models and simulation algorithm provide a powerful framework for statistical inference, which can be used to test the neutrality of microsatellites and other multiallelic variants.

Haasl, Ryan J.; Payseur, Bret A.

2013-01-01

42

Clippy Island: An Investigation into Natural Selection  

NSDL National Science Digital Library

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.

Furness, Lauren; Sutherland, Louise; Chalk, Hannah; Bulleid, Susan; Bamford, Amanda; Mcghie, Henry

2012-04-09

43

Natural selection. IV. The Price equation*  

PubMed Central

The Price equation partitions total evolutionary change into two components. The first component provides an abstract expression of natural selection. The second component subsumes all other evolutionary processes, including changes during transmission. The natural selection component is often used in applications. Those applications attract widespread interest for their simplicity of expression and ease of interpretation. Those same applications attract widespread criticism by dropping the second component of evolutionary change and by leaving unspecified the detailed assumptions needed for a complete study of dynamics. Controversies over approximation and dynamics have nothing to do with the Price equation itself, which is simply a mathematical equivalence relation for total evolutionary change expressed in an alternative form. Disagreements about approach have to do with the tension between the relative valuation of abstract versus concrete analyses. The Price equation’s greatest value has been on the abstract side, particularly the invariance relations that illuminate the understanding of natural selection. Those abstract insights lay the foundation for applications in terms of kin selection, information theory interpretations of natural selection, and partitions of causes by path analysis. I discuss recent critiques of the Price equation by Nowak and van Veelen.

Frank, Steven A.

2012-01-01

44

The Natural Selection of Bean Hunters  

NSDL National Science Digital Library

This lesson on natural selection shows students that population characteristics can change as a result of selective pressures operating over several generations. In the lesson, groups of students go hunting for beans in the lawn. Each group has a different tool (e.g. hand, spoon, fork, etc). There are three different colors of beans. The hunting goes for three rounds (generations), with extinctions and reproduction occurring between rounds.

45

Natural selection. VII. History and interpretation of kin selection theory.  

PubMed

Kin selection theory is a kind of causal analysis. The initial form of kin selection ascribed cause to costs, benefits and genetic relatedness. The theory then slowly developed a deeper and more sophisticated approach to partitioning the causes of social evolution. Controversy followed because causal analysis inevitably attracts opposing views. It is always possible to separate total effects into different component causes. Alternative causal schemes emphasize different aspects of a problem, reflecting the distinct goals, interests and biases of different perspectives. For example, group selection is a particular causal scheme with certain advantages and significant limitations. Ultimately, to use kin selection theory to analyse natural patterns and to understand the history of debates over different approaches, one must follow the underlying history of causal analysis. This article describes the history of kin selection theory, with emphasis on how the causal perspective improved through the study of key patterns of natural history, such as dispersal and sex ratio, and through a unified approach to demographic and social processes. Independent historical developments in the multivariate analysis of quantitative traits merged with the causal analysis of social evolution by kin selection. PMID:23662923

Frank, S A

2013-06-01

46

Natural Selection and Sickle Cell Disease  

NSDL National Science Digital Library

This high school lesson planâÂÂaimed to accommodate students with disabilities who are included in standard biology or environmental science classesâÂÂhelps students understand the concept of natural selection in relation to genetic variations like sickle cell trait.

Selin Mammen (Seneca Valley High School;); Anita OâÂÂNeill (Montgomery County Public Schools;)

2010-05-28

47

A Lesson on Evolution & Natural Selection  

ERIC Educational Resources Information Center

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…

Curtis, Anthony D.

2010-01-01

48

Natural selection on male wealth in humans.  

PubMed

Although genomic studies suggest that natural selection in humans is ongoing, the strength of selection acting on particular characteristics in human populations has rarely been measured. Positive selection on male wealth appears to be a recurrent feature of human agrarian and pastoralist societies, and there is some evidence of it in industrial populations, too. Here we investigate the strength of selection on male wealth, first in contemporary Britain using data from the National Child Development Study and then across seven other varied human societies. The British data show positive selection on male income driven by increased childlessness among low-income men but a negative association between personal income and reproductive success for women. Across cultures, selection gradients for male wealth are weakest in industrial countries and strongest in subsistence societies with extensive polygyny. Even the weakest selection gradients observed for male wealth in humans are as strong as or stronger than selection gradients reported from field studies of other species. Thus, selection on male wealth in contemporary humans appears to be ubiquitous and substantial in strength. PMID:18808363

Nettle, Daniel; Pollet, Thomas V

2008-11-01

49

THE LANGUAGE LABORATORY--SELECTED READINGS.  

ERIC Educational Resources Information Center

THIS PACKET OF ARTICLES AND BOOKLETS, PUBLISHED FROM 1961 TO 1965, IS DESIGNED FOR PERSONS INTERESTED IN THE USE OF THE LANGUAGE LABORATORY IN THEIR FOREIGN LANGUAGE PROGRAMS. INCLUDED ARE--(1) "A DOZEN DO'S AND DON'TS FOR PLANNING AND OPERATING A LANGUAGE LAB OR AN ELECTRONIC CLASSROOM IN A HIGH SCHOOL," (2) "MODERN FOREIGN LANGUAGES IN HIGH…

Modern Language Association of America, New York, NY.

50

A Selected Bibliography on Microbiological Laboratory Design.  

ERIC Educational Resources Information Center

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…

Laboratory Design Notes, 1967

1967-01-01

51

Laboratory evaluation of selected tar sand asphalts  

SciTech Connect

Three tar sand asphalts of similar grades prepared from one syncrude by three different refining methods were characterized by tests commonly used to specify paving asphalts together with certain special tests. Asphalt-aggregate mixtures were prepared using these asphalts and tested in the laboratory to determine strength stiffness stability, tensile properties, temperature effects and water susceptibility. Comparison of the tar sand asphalt properties to conventional petroleum asphalt properties reveal no striking differences.

Button, J.W.; Epps, J.A.; Gallaway, B.M.

1980-12-01

52

Investigating Natural Selection: Middle and High School  

NSDL National Science Digital Library

This lesson plan is designed for middle or high school students learning about natural selection. Students will learn how predators select their prey, and how the survival of members of a species with certain qualities can affect subsequent populations of that species. Several discussion questions are included which can be used as a post-activity quiz or to support a larger classroom discussion. The activity may be changed to suit either middle or high school grade levels. The activity is intended to take about sixty minutes of class time.

2010-01-01

53

Natural Selection of Antibiotic Resistant Bacteria  

NSDL National Science Digital Library

In this activity (p.3-4 of PDF), learners learn about disease transmission and antibiotic resistance. In this activity, an educator shows what could happen if one learner has not washed his/her hands properly before lunch and becomes ill as a result. The educator uses beans to illustrate both disease transmission and the development of antibiotic resistant bacteria. Use this activity to discuss the importance of proper hygiene, disease transmission, and both natural and artificial selection.

Cavanagh, Dave; Pickup, Nikki; Cavanagh, Laura

2012-06-26

54

Symbiogenesis, natural selection, and the dynamic Earth.  

PubMed

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

Kutschera, U

2009-08-01

55

Respirator selection for clandestine methamphetamine laboratory investigation.  

PubMed

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

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

2012-01-01

56

NVLAP (National Voluntary Laboratory Accreditation Program) Assessor Selection and Training,  

National Technical Information Service (NTIS)

The role and importance of 'peer' assessors in the National Voluntary Laboratory Accreditation Program (NVLAP) is discussed. Procedures for identification, evaluation, and selection of assessors are described, and the elements of assessor orientation and ...

H. W. Berger

1987-01-01

57

Selection of Four Landing Sites for the Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

This abstract describes the four landing sites under consideration and the selection process for the Mars Science Laboratory (MSL) after discussion of seven downselected sites at the third Landing Site Workshop and a subsequent project meeting.

Golombek, M.; Grant, J.; Vasavada, A. R.; Grotzinger, J.; Watkins, M.; Kipp, D.; Noe Dobrea, E. Z.; Griffes, J.; Parker, T. J.

2009-03-01

58

Beneficiation of Coal by Selective Flocculation, A Laboratory Study.  

National Technical Information Service (NTIS)

The Bureau of Mines conducted a laboratory scale investigation of the process of selective flocculation with the objective of developing a method to effect separations on suspensions consisting predominately of ultra-fine-size (minus-400-mesh) particles o...

R. E. Hucko

1977-01-01

59

Phytoestrogens: the "natural" selective estrogen receptor modulators?  

PubMed

Phytoestrogens are diphenolic compounds that are present in several plants eaten by human beings. Soybeans and flaxseed are particularly abundant source of phytoestrogens. When ingested in relatively large amounts, phytoestrogens have been shown to have significant estrogen agonists/antagonists effects in animals and humans. There is epidemiological, laboratory and clinical evidence which indicates that phytoestrogens, like certain selective estrogen receptor mudulators, have an antiproliferative effect on the breast, and positive effects on the lipoprotein profile and bone density. They might also improve some of the climacteric symptoms. This evidence is critically reviewed, and the possible benefit of dietary intervention with phytoestrogen-rich food for woman's health is discussed. PMID:10428321

Brzezinski, A; Debi, A

1999-07-01

60

Natural Selection: Developing a Darwinian Explanation  

NSDL National Science Digital Library

This lesson asks students to take their understanding of Darwin's model of natural selection and begin to think about how it can be used to explain natural phenomena. They will do this by first attempting individually to explain the case of lizard camouflage to provide a concrete example from which to work. Next, they will work within their groups to compile an explanation based on all of their work and, finally, they will be asked to develop a set of criteria for acceptable explanations. Each individual student will develop a Darwinian explanation and each group will write a complete explanation and a list of criteria for a good explanation. The site includes instructional notes for teachers and a student handout.

61

Natural selection and cultural rates of change  

PubMed Central

It has been claimed that a meaningful theory of cultural evolution is not possible because human beliefs and behaviors do not follow predictable patterns. However, theoretical models of cultural transmission and observations of the development of societies suggest that patterns in cultural evolution do occur. Here, we analyze whether two sets of related cultural traits, one tested against the environment and the other not, evolve at different rates in the same populations. Using functional and symbolic design features for Polynesian canoes, we show that natural selection apparently slows the evolution of functional structures, whereas symbolic designs differentiate more rapidly. This finding indicates that cultural change, like genetic evolution, can follow theoretically derived patterns.

Rogers, Deborah S.; Ehrlich, Paul R.

2008-01-01

62

Laboratory parameters in the natural history of liver cirrhosis  

Microsoft Academic Search

Summary  The aim of the present study was to evaluate the changes of common laboratory parameters in the natural evolution of liver\\u000a cirrhosis, as well as their relationships with the occurrence of ascites onset and death. Routine laboratory findings of 458\\u000a patients suffering from liver cirrhosis admitted to a 9-year follow-up period were retrospectively investigated, but only\\u000a data of the 138

Alessandro Milani; Laura Marra; Massimo Siciliano; Lodovico Rossi

1989-01-01

63

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

ERIC Educational Resources Information Center

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…

Eason, Perri K.; Sherman, Peter T.

2003-01-01

64

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

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

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

65

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

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.

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

66

Reproduction of natural corrosion by accelerated laboratory testing methods  

SciTech Connect

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.

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

1996-05-01

67

Pervasive Natural Selection in the Drosophila Genome?  

PubMed Central

Over the past four decades, the predominant view of molecular evolution saw little connection between natural selection and genome evolution, assuming that the functionally constrained fraction of the genome is relatively small and that adaptation is sufficiently infrequent to play little role in shaping patterns of variation within and even between species. Recent evidence from Drosophila, reviewed here, suggests that this view may be invalid. Analyses of genetic variation within and between species reveal that much of the Drosophila genome is under purifying selection, and thus of functional importance, and that a large fraction of coding and noncoding differences between species are adaptive. The findings further indicate that, in Drosophila, adaptations may be both common and strong enough that the fate of neutral mutations depends on their chance linkage to adaptive mutations as much as on the vagaries of genetic drift. The emerging evidence has implications for a wide variety of fields, from conservation genetics to bioinformatics, and presents challenges to modelers and experimentalists alike.

Sella, Guy; Petrov, Dmitri A.; Przeworski, Molly; Andolfatto, Peter

2009-01-01

68

The Nature of Laboratory Learning Experiences in Secondary Science Online  

ERIC Educational Resources Information Center

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…

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

2013-01-01

69

A Working Model of Natural Selection Illustrated by Table Tennis  

ERIC Educational Resources Information Center

Natural selection is one of the most important topics in biology and it helps to clarify the variety and complexity of organisms. However, students in almost every stage of education find it difficult to understand the mechanism of natural selection and they can develop misconceptions about it. This article provides an active model of natural…

Dinc, Muhittin; Kilic, Selda; Aladag, Caner

2013-01-01

70

Selective particle ingestion by oyster larvae ( Crassostrea virginica ) feeding on natural seston and cultured algae  

Microsoft Academic Search

I investigated selective particle ingestion by oyster larvae (Crassostrea virginica) feeding on natural seston from Chesapeake Bay and laboratory-cultured algae of different sizes or chemical content. In 15 of 16 experiments with complex natural suspensions as food, small(150 µm) larvae selected most strongly for small (2 to 4 µm) food particles, but in the presence of a large (>10 µm)-cell

B. S. Baldwin

1995-01-01

71

Compressed natural gas and liquefied petroleum gas conversions: The National Renewable Energy Laboratory`s experience  

Microsoft Academic Search

The National Renewable Energy Laboratory (NREL) contracted with conversion companies in six states to convert approximately 900 light-duty Federal fleet vehicles to operate on compressed natural gas (CNG) or liquefied petroleum gas (LPG). The contracts were initiated in order to help the Federal government meet the vehicle acquisition requirements of the Energy Policy Act of 1992 (EPACT) during a period

R. C. Motta; K. J. Kelly; W. W. Warnock

1996-01-01

72

NATURAL SELECTION ON COLOR PATTERNS IN POECILIA RETICULATA  

Microsoft Academic Search

All too often in evolutionary biology we are led to speculate or infer the mode of action of natural selection; we usually do not know why some individuals are more adaptive than others. Very often attempts to measure natural selection are unsuc- cessful, leading to heated arguments about the relative importance of selection, ge- netic drift, and epistasis in evolution

JOHN A. ENDLER

1980-01-01

73

Microbial Resistance to Triclosan: A Case Study in Natural Selection  

ERIC Educational Resources Information Center

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…

Serafini, Amanda; Matthews, Dorothy M.

2009-01-01

74

Seal formation in arid soil under natural and laboratory conditions  

NASA Astrophysics Data System (ADS)

Runoff is of considerable importance in the functioning of a desert ecosystem. The hydrological characteristics of runoff developing on arid soil under natural field conditions and those of runoff occurring in laboratory-controlled rain simulation experiments using the same type of soil were investigated. Runoff and erosion measurements were carried out in small plots (0.2-0.8 m2) on a south-facing hillslope in the northern Negev, Israel (90 mm ave. annual rainfall). Soil from the area near to the runoff plots was collected for the rain simulation experiments conducted in the laboratory. The soil was collected from 0-1 cm and 1-5 cm depths, and then placed within boxes (1.16 m long and 0.55 m wide) in the laboratory in the same order as they had been in the field. Representative surface stones were collected in the field and scattered randomly on the soil surface in the laboratory boxes. In some of the laboratory experiments soil, 5 cm in depth, was placed on a geotechnical sheet on a metal screen, while in other experiments, soil of 5 cm depth was placed on a Terzaghi filter. Rain simulator used had a rotating disk with a tilted nozzle to simulate raindrop size dispersion and kinetic energy of natural rain. The sprinkling intensity was set at a rate of 18 mm/hour. Soil crusts in the field were more stable than those created in the lab for two standard tests: Emerson - immersion test, and the 'single water drop' test. Whereas weak activity of microphytes was found in the field there was no such activity in the lab. The rain depth until runoff in the field was less than under laboratory conditions, while the sediment yield was greater in the field than in the laboratory (8.64 g/m2 versus 0.58 g/m2). The rain simulator experiments that had included a Terzaghi filter showed significantly higher final infiltration rate (7.5 mm/h versus 4.2 mm/h), shorter accumulated watering depth until stabilization of soil seal formation (100-200 mm versus 50 mm), and smaller fraction of clay in the crust (4.2% versus 6.8%), than the experiments that done without this filter. Therefore, it is conceivable that there is a suction of thin material from the surface while capillary pressures are activated, result in sub-surface seal formation (washed-in layer). This can lead to differences between runoff-forming processes existing in the laboratory set-up and processes that occur under natural field conditions.

Sarah, Pariente; Sachs, Eyal

2013-04-01

75

Patterns and Power of Phenotypic Selection in Nature  

NSDL National Science Digital Library

This article from the July/August 2007 issue of BioScience is about natural selection and quantifies the strength of selection in nature. Phenotypic selection occurs when individuals with certain characteristics produce more surviving offspring than individuals with other characteristics. Although selection is regarded as the chief engine of evolutionary change, scientists have only recently begun to measure its action in the wild. These studies raise numerous questions: How strong is selection, and do different types of traits experience different patterns of selection? Is selection on traits that affect mating success as strong as selection on traits that affect survival? Does selection tend to favor larger body size, and, if so, what are its consequences? We explore these questions and discuss the pitfalls and future prospects of measuring selection in natural populations.

Joel G. Kingsolver, David W. Pfennig (;)

2007-07-01

76

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

77

ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES  

SciTech Connect

In 2003 the US Department of Energy (DOE) embarked on a project to explore an innovative approach to remediation of subsurface contaminant plumes that focused on introducing mechanisms for augmenting natural attenuation to achieve site closure. Termed enhanced attenuation (EA), this approach has drawn its inspiration from the concept of monitored natural attenuation (MNA).

Vangelas, K; W. H. Albright, W; E. S. Becvar, E; C. H. Benson, C; T. O. Early, T; E. Hood, E; P. M. Jardine, P; M. Lorah, M; E. Majche, E; D. Major, D; W. J. Waugh, W; G. Wein, G; O. R. West, O

2007-05-15

78

Natural Selection, Nutrition Research, and Science Teaching.  

ERIC Educational Resources Information Center

Provides examples of the teaching of hypothesis generation and scientific inquiry in biology. Specifically, the author applies the selection paradigm to considerations of the human nutrient-handling apparatus, finally suggesting a model of the selective forces that may have operated on the human genome since hunting-gathering and primitive…

Nelson, Darby

1980-01-01

79

The Nature of Laboratory Learning Experiences in Secondary Science Online  

NASA Astrophysics Data System (ADS)

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 are teaching science online. The type and frequency of reported laboratory activities are consistent with the tradition of face-to-face instruction, using hands-on and simulated experiments. While provided examples were student-centered and required the collection of data, they failed to illustrate key components of the nature of science. The features of student-teacher interactions, student engagement, and nonverbal communications were found to be lacking and likely constitute barriers to the enactment of inquiry. These results serve as a call for research and development focused on using existing communication tools to better align with the activity of science such that the nature of science is more clearly addressed, the work of students becomes more collaborative and authentic, and the formative elements of a scientific inquiry are more accessible to all participants.

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

2013-06-01

80

Evidence for somatic selection of natural autoantibodies  

PubMed Central

Natural autoantibodies are primarily immunoglobulin M (IgM) antibodies that bind to a variety of self-antigens, including self-IgG. Accounting for a large proportion of the early B cell repertoire, such polyspecific autoantibodies are speculated to contribute to the homeostasis and/or competence of the primary humoral immune system. Recent studies indicate that the leukemia cells from most patients with chronic lymphocytic leukemia (CLL) also express such IgM autoantibodies. Similarly, the leukemia cells from many CLL patients react with murine monoclonal antibodies (mAbs) specific for crossreactive idiotypes (CRIs) associated with human IgM autoantibodies. In particular, leukemic cells frequently react with G6, a mAb specific for an Ig heavy chain (H chain)-associated CRI, and/or with 17.109, a mAb that defines a kappa light chain (L chain)- associated CRI. Generated against IgM rheumatoid factor (RF) paraproteins, G6 and 17.109 each recognize a major CRI that is present in many IgM RF paraproteins. Furthermore, over 90% of the IgM paraproteins found to bear both H and L chain-associated CRIs also are found to have RF activity. Molecular characterization of these CRIs demonstrates that each is a serologic marker for expression of a highly conserved Ig V gene. As such, the frequent production of IgM polyspecific autoantibodies in CLL simply may reflect the frequent use of such highly conserved autoantibody-encoding Ig V genes with little or no somatic mutation. To test this hypothesis, we generated murine transfectomas to pair the 17.109-reactive kappa L chain of SMI, a 17.109/G6-reactive CLL population, with the Ig H chain of SMI or other G6-reactive leukemia cells or tonsillar lymphocytes. Cotransfection of vectors encoding the Ig H and L chains of SMI generated transfectomas that produce IgM kappa RF autoantibodies reactive with human IgG1 and IgG4. In contrast to G6/17.109-reactive IgM kappa RF Waldenstrom's paraproteins, the SMI IgM kappa also reacts with several other self- antigens, including myoglobin, actin, and ssDNA. However, cotransfection of the SMI L chain with a vector encoding any one of 10 different G6-reactive Ig H chains generated transfectomas that produce IgM kappa antibodies without detectable polyspecific autoantibody activity. These results indicate that polyspecific antiself-reactivity of G6/17.019-reactive Ig is dependent on the somatically generated Ig third complementarity determining region. Collectively, these studies imply that selection may be responsible for the frequent expression of polyspecific autoantibodies in CLL and early B cell ontogeny.

1992-01-01

81

Development and Evaluation of the Conceptual Inventory of Natural Selection.  

ERIC Educational Resources Information Center

Presents a diagnostic test to assess students' understanding of natural selection. Field-tests the Conceptual Inventory of Natural Selection (CINS) with nonmajors and biology majors at community colleges. Compares test scores of nonmajors with performances in interviews and discusses the correlation between the test scores and the interview…

Anderson, Dianne L.; Fisher, Kathleen M.; Norman, Gregory J.

2002-01-01

82

Are Humans Still Evolving? A Natural Selection Discussion Lesson  

ERIC Educational Resources Information Center

A study is conducted to develop sound comprehension of natural selection theory by prompting students to use its concept to explain the evolutionary status of humans. In relation to the current existence of human it is stated that human populations currently undergo microevolutionary changes in allele frequencies due to natural selection and other…

Shields, Martin

2004-01-01

83

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection  

ERIC Educational Resources Information Center

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…

Thagard, Paul; Findlay, Scott

2010-01-01

84

Laboratory annoyance and skin conductance responses to some natural sounds  

NASA Astrophysics Data System (ADS)

The influences of spectral properties of sounds on annoyance and electrodermal activity reactions have been studied. In two laboratory experiments, subjects were exposed to some natural sounds in semi-anechoic conditions. Skin conductance and annoyance reactions were determined. The results suggest that electrodermal activity increases when the A-weighted equivalent sound pressure level exceeds 70 dB(A). It is concluded that the width of the spectrum is relevant, and that the greater the fundamental frequency of the harmonic spectrum the more annoying the sound.

Björk, E. A.

1986-09-01

85

Natural Selection: Introduction to the Nature of Explanatory Models  

NSDL National Science Digital Library

This information is designed to connect what students have learned about scientific arguments to the role and nature of explanatory models in science. They will be asked to read and discuss a brief handout about scientific models and their function in science. They will discover that models are ideas that scientists use to explain patterns they see in the natural world, a model is an idea that has predictive and explanatory power and is consistent with other ideas about how the world works, and that models can be compared based on data, the inferences made in the model, and the prior knowledge and beliefs upon which they are based. This site includes instructional notes for the teacher and student handouts.

86

Chemistry and biology of selected natural products  

Microsoft Academic Search

Natural products often offer excitement, stimulation, challenges and op- portunities for chemists, biologists and medical investigators. The study of their chemistry, biology and medicine provides, more often than not, rewards imagined and unimagined, and is still a major frontier in organic chemistry. In this article we summa- rize some of our recent work in this area and project ahead to

K. C. Nicolaou; E. A. Theodorakis; C. F. Claiborne

1996-01-01

87

Laboratory selection for an accelerated mosquito sexual development rate  

PubMed Central

Background Separating males and females at the early adult stage did not ensure the virginity of females of Anopheles arabiensis (Dongola laboratory strain), whereas two years earlier this method had been successful. In most mosquito species, newly emerged males and females are not able to mate successfully. For anopheline species, a period of 24 h post-emergence is generally required for the completion of sexual maturation, which in males includes a 180° rotation of the genitalia. In this study, the possibility of an unusually shortened sexual maturity period in the laboratory-reared colony was investigated. Methods The effect of two different sex-separation methods on the virginity of females was tested: females separated as pupae or less than 16 h post-emergence were mated with males subjected to various doses of radiation. T-tests were performed to compare the two sex-separation methods. The rate of genitalia rotation was compared for laboratory-reared and wild males collected as pupae in Dongola, Sudan, and analysed by Z-tests. Spermatheca dissections were performed on females mated with laboratory-reared males to determine their insemination status. Results When the sex-separation was performed when adults were less than 16 h post-emergence, expected sterility was never reached for females mated with radio-sterilized males. Expected sterility was accomplished only when sexes were separated at the pupal stage. Observation of genitalia rotation showed that some males from the laboratory strain Dongola were able to successfully mate only 11 h after emergence and 42% of the males had already completed rotation. A small proportion of the same age females were inseminated. Wild males showed a much slower genitalia rotation rate. At 17 h post-emergence, 96% of the laboratory-reared males had completed genitalia rotation whereas none of the wild males had. Conclusion This colony has been cultured in the laboratory for over one hundred generations, and now has accelerated sexual maturation when compared with the wild strain. This outcome demonstrates the kinds of selection that can be expected during insect colonization and maintenance, particularly when generations are non-overlapping and similar-age males must compete for mates.

2011-01-01

88

The Strength of Phenotypic Selection in Natural Populations  

Microsoft Academic Search

How strong is phenotypic selection on quantitative traits in the wild? We reviewed the literature from 1984 through 1997 for studies that estimated the strength of linear and quadratic selection in terms of standardized selection gradients or differentials on natural variation in quantitative traits for field populations. We tabulated 63 published studies of 62 species that reported over 2,500 estimates

J. G. Kingsolver; H. E. Hoekstra; J. M. Hoekstra; D. Berrigan; S. N. Vignieri; C. E. Hill; A. Hoang; P. Gibert; P. Beerli

2001-01-01

89

BSL-3 laboratory practices in the United States: comparison of select agent and non-select agent facilities.  

PubMed

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

Richards, Stephanie L; Pompei, Victoria C; Anderson, Alice

2014-01-01

90

Using the FAR Guide to Teach Simulations: An Example with Natural Selection  

ERIC Educational Resources Information Center

Engaging students in a predator-prey simulation to teach natural selection is a common activity in secondary biology classrooms. The purpose of this article is to demonstrate how the authors have changed their approach to teaching this activity from a laboratory investigation to a class-constructed simulation. Specifically, the authors drew upon a…

Sickel, Aaron J.; Friedrichsen, Patricia J.

2012-01-01

91

Laboratory facility design and microbial indoor air quality in selected hospital laboratories.  

PubMed

Hospital laboratory is one of workplace areas contaminated with a variety of biohazards. A cross sectional study was conducted to assess the microbial air quality and facility design in the laboratories of four selected governmental hospitals (Hospitals A, B, C, and D) in Bangkok, Thailand. One hundred eighty-eight indoor air samples were collected from 40 laboratory rooms to investigate bacterial and fungal counts using the Millipore air tester. Forty air samples were collected from the waiting areas of those laboratories, and 16 outdoor air samples were collected to use for comparison. Additionally, those laboratory facilities were assessed following biosafety facility design (10 items). Results indicated that the facility design of laboratory in the Hospital A met most of items of the biosafety facility criteria. The rest met only seven items of the criteria. Means +/- standard deviation (SD) of bacterial counts of 253.1 +/- 247.7 cfu/m3, 236.8 +/- 200.1 cfu/m3, 304.4 +/- 264.2 cfu/m3, and 146.7 +/- 127.0 cfu/m3, and fungal counts of 500.8 +/- 64.2 cfu/ m3, 425.0 +/- 21.2 cfu/m3, 357.0 +/- 121.2 cfu/m3, and 355.7 +/- 86.8 cfu/m3 were found in hospital laboratories A, B, C and D, respectively. The isolated colonies of bacteria and fungi were identified as group or genus. It was found that the most common bacteria was Staphylococcus spp (84.1%, 76.0%, 72.1% and 80.5%, respectively), whereas, the most common fungi were Aspergillus spp and septate hyphae fungi (42.0%, 37.5%, 39.5%, and 45.7%; vs 38.6%, 56.2%, 52.1%, and 37.2%, respectively). These data may be valuable to develop interventions to improve the microbial indoor air quality among hospital laboratories and for preventing the laboratory-acquired infections. PMID:24974659

Luksamijarulkul, Pipat; Kiennukul, Nuchanard; Vatthanasomboon, Pisit

2014-05-01

92

Natural Selection in Protected and Unprotected Populations  

NSDL National Science Digital Library

In this simulation, learners model two elephant seal populations and how they change over time. Learners start with cards representing a variety of seals. Each generation, some seals survive to reproduce, passing on their traits to new seals. The amount of variation in the protected seal population stays high, while the unprotected population becomes more limited by selective pressure. In the related activity, learners can graph their data about the seal populations to show how they change over time.

Huffard, Crissy

2011-01-01

93

Canine Evolution in Sabretoothed Carnivores: Natural Selection or Sexual Selection?  

PubMed Central

The remarkable elongated upper canines of extinct sabretoothed carnivorous mammals have been the subject of considerable speculation on their adaptive function, but the absence of living analogues prevents any direct inference about their evolution. We analysed scaling relationships of the upper canines of 20 sabretoothed feliform carnivores (Nimravidae, Barbourofelidae, Machairodontinae), representing both dirk-toothed and scimitar-toothed sabretooth ecomorphs, and 33 non-sabretoothed felids in relation to body size in order to characterize and identify the evolutionary processes driving their development, using the scaling relationships of carnassial teeth in both groups as a control. Carnassials display isometric allometry in both sabretooths and non-sabretooths, supporting their close relationship with meat-slicing, whereas the upper canines of both groups display positive allometry with body size. Whereas there is no statistical difference in allometry of upper canine height between dirk-toothed and scimitar-toothed sabretooth ecomorphs, the significantly stronger positive allometry of upper canine height shown by sabretooths as a whole compared to non-sabretooths reveals that different processes drove canine evolution in these groups. Although sabretoothed canines must still have been effective for prey capture and processing by hypercarnivorous predators, canine morphology in these extinct carnivores was likely to have been driven to a greater extent by sexual selection than in non-sabretooths. Scaling relationships therefore indicate the probable importance of sexual selection in the evolution of the hypertrophied sabretooth anterior dentition.

Randau, Marcela; Carbone, Chris; Turvey, Samuel T.

2013-01-01

94

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

PubMed Central

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.

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

2011-01-01

95

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

PubMed Central

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.

Minvielle, Francis

1980-01-01

96

Darwin, microbes and evolution by natural selection.  

PubMed

Born 200 years ago, Darwin's revolutionary ideas were derived largely from his observations on life forms that evolved relatively recently, including various flowering plants, worms, birds and domesticated animals. Yet, life appeared on planet earth close to 4 billion years ago in the form of unicellular organisms collectively called bacteria. It was only shortly after "On the Origin of Species" was published (1859) that the "germ theory" of infectious diseases was formulated. Microbes (viruses, bacteria, fungi and microparasites) received scant mention in Darwin's writings, although pioneers of the Golden Age of Bacteriology, such as Louis Pasteur (1822-1895), were contemporaries. Today, microbes offer extraordinary testimony and powerful model systems of direct relevance to the essentials of Darwinian selection, such as understanding microbial-host interactions, the evolution of pathogens and the emergence of drug- or vaccine-related resistance. PMID:21120720

Moxon, E Richard

2011-01-01

97

Laboratory Evidence for Microbially Mediated Silicate Mineral Dissolution in Nature  

SciTech Connect

Bacteria may potentially enhance or inhibit silicate mineral dissolution in nature by a variety of mechanisms. In the laboratory, some microbial metabolites enhanced dissolution rates by a factor of ten above the expected proton-promoted rate by an additional ligand-promoted mechanism focused principally at Al sites at the mineral surface. In investigations with bacteria, it was found that organic acids are produced in organic-rich/nutrient-poor cultures, resulting in increased mineral dissolution rates compared to abiotic controls. Alginate and poly-aspartate inhibited dissolution rates either by a reduction in surface reactivity or reactive surface area (or both). Bacteria may also influence dissolution rates by creating and maintaining microenvironments where metabolite concentrations are higher than in the bulk solution.

Ullman, W. J.; Kirchman, D. L.; Welch, S. A.; Vandevivere, P.

1996-01-01

98

Selection of the Mars Science Laboratory landing site  

USGS Publications Warehouse

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.

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

99

Thermal Conductivity of Soft Vulcanized Natural Rubber: Selected Values.  

National Technical Information Service (NTIS)

The published literature on the thermal conductivity of natural rubber was assembled and the results critically evaluated. Best values of thermal conductivity as a function of temperature were selected. These are presented in both graphical and tabular fo...

L. C. K. Carwile H. J. Hoge

1966-01-01

100

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

ERIC Educational Resources Information Center

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.

Price, Rebecca M.

2013-01-01

101

Laboratory observation of naturally occurring dust-density waves  

NASA Astrophysics Data System (ADS)

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.

Flanagan, Tim; Goree, John

2010-11-01

102

Laboratory demonstration of real time frame selection with Magellan AO  

NASA Astrophysics Data System (ADS)

The Magellan AO system combines a pyramid wavefront sensor and high-order adaptive secondary mirror, and will see first light on the Magellan Clay telescope in November 2012. With a 24 cm projected actuator pitch, this powerful system will enable good correction in the optical (0.5 to 1 ?m). Realistic laboratory testing has produced Strehl ratios greater than 40% in i’ (0.765 ?m) on bright simulated stars. On fainter stars our visible AO camera, VisAO, will work in the partially corrected regime with only short moments of good correction. We have developed a form of lucky imaging, called real time frame selection, which uses a fast shutter to block moments of bad correction, and quickly opens the shutter when the correction is good, enabling long integrations on a conventional CCD while maximizing Strehl ratio and resolution. The decision to open or shut is currently based on reconstructed WFS telemetry. Here we report on our implementation and testing of this technique in the Arcetri test tower in Florence, Italy, where we showed that long exposure i’ Strehl could be improved from 16% to 26% when the selection threshold was set to the best 10% of instantaneous Strehl.

Males, Jared R.; Close, Laird M.; Kopon, Derek; Quiros-Pacheco, Fernando; Riccardi, Armando; Xompero, Marco; Puglisi, Alfio; Gasho, Victor; Morzinski, Katie M.; Follette, Katherine B.

2012-07-01

103

Effective Assessment: Probing Students' Understanding of Natural Selection  

ERIC Educational Resources Information Center

Evolution by natural selection provides the conceptual framework upon which much of modern biology is based: therefore understanding core ideas about biological evolution is an essential part of scientific literacy. Nonetheless, research repeatedly shows that high school and college students have difficulties understanding the notion of natural…

Stern, Luli

2004-01-01

104

Annotated selected references on natural resources investigations, Collier County, Florida  

USGS Publications Warehouse

A data base for future natural resources investigations in Collier County, Fla., was initiated by compiling a selected annotated bibliography. This report provides references and annotations for selected reports released between 1950 and 1978. The references are presented by subject material as follows: biologic, ecologic, geologic, geochemical, and hydrologic. (USGS)

Swayze, L. J.

1981-01-01

105

Selective feeding of four zooplankton species on natural lake phytoplankton  

Microsoft Academic Search

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

Karin Knisely; Walter Geller

1986-01-01

106

NATURAL RESOURCE MANAGEMENT PLAN FOR BROOKHAVEN NATIONAL LABORATORY  

Microsoft Academic Search

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

2003-01-01

107

Natural and sexual selection in a monogamous historical human population.  

PubMed

Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760-1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species. PMID:22547810

Courtiol, Alexandre; Pettay, Jenni E; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

2012-05-22

108

Natural and sexual selection in a monogamous historical human population  

PubMed Central

Whether and how human populations exposed to the agricultural revolution are still affected by Darwinian selection remains controversial among social scientists, biologists, and the general public. Although methods of studying selection in natural populations are well established, our understanding of selection in humans has been limited by the availability of suitable datasets. Here, we present a study comparing the maximum strengths of natural and sexual selection in humans that includes the effects of sex and wealth on different episodes of selection. Our dataset was compiled from church records of preindustrial Finnish populations characterized by socially imposed monogamy, and it contains a complete distribution of survival, mating, and reproductive success for 5,923 individuals born 1760–1849. Individual differences in early survival and fertility (natural selection) were responsible for most variation in fitness, even among wealthier individuals. Variance in mating success explained most of the higher variance in reproductive success in males compared with females, but mating success also influenced reproductive success in females, allowing for sexual selection to operate in both sexes. The detected opportunity for selection is in line with measurements for other species but higher than most previous reports for human samples. This disparity results from biological, demographic, economic, and social differences across populations as well as from failures by most previous studies to account for variation in fitness introduced by nonreproductive individuals. Our results emphasize that the demographic, cultural, and technological changes of the last 10,000 y did not preclude the potential for natural and sexual selection in our species.

Courtiol, Alexandre; Pettay, Jenni E.; Jokela, Markus; Rotkirch, Anna; Lummaa, Virpi

2012-01-01

109

Nonconsumptive predator-driven mortality causes natural selection on prey.  

PubMed

Predators frequently exert natural selection through differential consumption of their prey. However, predators may also cause prey mortality through nonconsumptive effects, which could cause selection if different prey phenotypes are differentially susceptible to this nonconsumptive mortality. Here we present an experimental test of this hypothesis, which reveals that nonconsumptive mortality imposed by predatory dragonflies causes selection on their damselfly prey favoring increased activity levels. These results are consistent with other studies of predator-driven selection, however, they reveal that consumption alone is not the only mechanism by which predators can exert selection on prey. Uncovering this mechanism also suggests that prey defensive traits may represent adaptations to not only avoid being consumed, but also for dealing with other sources of mortality caused by predators. Demonstrating selection through both consumptive and nonconsumptive predator mortality provides us with insight into the diverse effects of predators as an evolutionary force. PMID:24152082

Siepielski, Adam M; Wang, Jason; Prince, Garrett

2014-03-01

110

Getting to Darwin: Obstacles to Accepting Evolution by Natural Selection  

NASA Astrophysics Data System (ADS)

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.

Thagard, Paul; Findlay, Scott

2010-06-01

111

The Role of Natural Selection in the Origin of Life  

Microsoft Academic Search

It is commonly accepted among origin-of-life scientists that the emergence of life was an evolutionary process involving at\\u000a one stage or other the working of natural selection. Researchers disagree, however, on the nature of the chemical infrastructure\\u000a that could have formed prebiotically, enabling the evolutionary process. The division of the origin-of-life research community\\u000a into ‘geneticists’ and ‘metabolists’ usually revolves around

Iris Fry

2011-01-01

112

Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards.  

PubMed Central

Both sexual selection and natural selection can influence the form of dimorphism in secondary sexual traits. Here, we used a comparative approach to examine the relative roles of sexual selection and natural selection in the evolution of sexually dimorphic coloration (dichromatism) and ornamentation in agamid lizards. Sexual dimorphism in head and body size were used as indirect indicators of sexual selection, and habitat type (openness) as an index of natural selection. We examined separately the dichromatism of body regions "exposed to" and "concealed from" visual predators, because these body regions are likely to be subject to different selection pressures. Dichromatism of "exposed" body regions was significantly associated with habitat type: males were typically more conspicuously coloured than females in closed habitats. By contrast, dichromatism of "concealed" body regions and ornament dimorphism were positively associated with sexual size dimorphism (SSD). When we examined male and female ornamentation separately, however, both were positively associated with habitat openness in addition to snout-vent length and head SSD. These results suggest that natural selection constrains the evolution of elaborate ornamentation in both sexes as well as sexual dichromatism of body regions exposed to visual predators. By contrast, dichromatism of "concealed" body regions and degree of ornament dimorphism appear to be driven to a greater degree by sexual selection.

Stuart-Fox, Devi M.; Ord, Terry J.

2004-01-01

113

The Chips Are Down: A Natural Selection Simulation  

NSDL National Science Digital Library

This lesson demonstrates how natural selection operates, using different colored paper chips to represent prey and a piece of fabric as a background (the environment). The predator (student) will hunt (select chips) to show that the best adapted, by color, are NOT chosen, and others which are poorly adapted (by standing out) ARE chosen (removed). Thus, the best adapted survive and reproduce to pass on their traits. Survivors then reproduce and subsequent generations are preyed upon.

Digiovanni, Nick

114

Selection at 6-PGD locus in laboratory populations of Bactrocera oleae.  

PubMed

We have previously shown that laboratory populations of the olive fruitfly Bactrocera oleae come to equilibrium with allele frequencies at the 6-phosphogluconate dehydrogenase (6-PGD) locus markedly different from those of wild populations. In this study, we present new evidence from perturbation experiments in support of the notion that the locus is under selective pressure under laboratory conditions. Eleven populations were started with frequencies at the 6-PGD locus different from the laboratory equilibrium. Over 12 generations, the populations showed a return to the previous equilibrium, indicating a direct and powerful selection pressure on the naturally occurring allozymes of this locus. That is, a marked increase of the F allele followed by a compensatory decrease of allele I. Populations were set up to minimize the effects of associative overdominance, and we discuss the possible influence of this factor. Nucleotide sequence for the 6-PGD F and I alleles revealed two missense mutations at positions 501 and 730 leading to different amino acids among the two alleles. PMID:19061528

Cosmidis, Nikos; Goulielmos, George; Eliopoulos, Elias; Loukas, Michael

2008-10-01

115

Natural selection on floral volatile production in Penstemon digitalis  

PubMed Central

Natural selection is thought to have shaped the evolution of floral scent; however, unlike other floral characters, we have a rudimentary knowledge of how phenotypic selection acts on scent. We found that floral scent was under stronger selection than corolla traits such as flower size and flower color in weakly scented Penstemon digitalis. Our results suggest that to understand evolution in floral phenotypes, including scent in floral selection, studies are crucial. For P. digitalis, linalool was the direct target of selection in the scent bouquet. Therefore, we determined the enantiomeric configuration of linalool because interacting insects may perceive the enantiomers differentially. We found that P. digitalis produces only (S)-(+)-linalool and, more interestingly, it is also taken up into the nectar. Because the nectar is scented and flavored with (S)-(+)-linalool, it may be an important cue for pollinators visiting P. digitalis flowers.

Parachnowitsch, Amy L.; Burdon, Rosalie C. F.; Raguso, Robert A.; Kessler, Andre

2013-01-01

116

Assessing the effect of natural selection in malaria parasites  

Microsoft Academic Search

There are few concepts that have been used across disciplines; one of them is natural selection. The impact that this process has on parasite genetic diversity is reviewed here by discussing examples on drug resistance and vaccine antigens. Emphasis is made on how mechanisms need to be addressed rather than associations, and how such investigations were out of reach of

Ananias A. Escalante; Omar E. Cornejo; Ascanio Rojas; Venkatachalam Udhayakumar; Altaf A. Lal

2004-01-01

117

Using Different Examples of Natural Selection When Teaching Biology.  

ERIC Educational Resources Information Center

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)

Perry, Robert T.

1993-01-01

118

Detecting natural selection in high-altitude human populations  

Microsoft Academic Search

High-altitude natives have distinctive biological characteristics that appear to offset the stress of hypoxia. Evolutionary theory reasons that they reflect genetic adaptations resulting from natural selection on traits with heritable variation. Furthermore, high-altitude natives of the Andean and Tibetan Plateaus differ from one another, perhaps resulting from different evolutionary histories. Three approaches have developed a case for the possibility of

Cynthia M. Beall

2007-01-01

119

Signatures of natural selection in the human genome  

Microsoft Academic Search

During their dispersal from Africa, our ancestors were exposed to new environments and diseases. Those who were better adapted to local conditions passed on their genes, including those conferring these benefits, with greater frequency. This process of natural selection left signatures in our genome that can be used to identify genes that might underlie variation in disease resistance or drug

Michael Bamshad; Stephen P. Wooding

2003-01-01

120

Selected Topics in Laboratory Animal Medicine. Volume VIII. Parasitology.  

National Technical Information Service (NTIS)

The major parasites of laboratory animals are divided into eight groups: Insects, arachnids, pentastomes, acanthocephalids, unicellular parasites (protozoan), cestodes, trematodes, and nematodes. A broad review is presented of the major characteristics th...

G. W. Irving

1972-01-01

121

Selection on protein-coding genes of natural cyanobacterial populations.  

PubMed

We examined the distribution of synonymous and non-synonymous changes in 12 protein-coding genes of natural populations of cyanobacteria to infer changes in gene functionality. By comparing mutation distributions within and across species using the McDonald-Kreitman test, we found data sets to contain evidence for purifying selection (hetR of Trichodesmium, nifH of Cylindrospermopsis raceborskii and rpoC1 of Anabaena lemmermannii) and positive selection (kaiC of Microcoleus chthonoplastes and rbcX of Anabaena and Aphanizomenon sp.). Other genes from the same set of clonal isolates (petB and rbcL in M. chthonoplastes and Anabaena/Aphanizomenon, respectively) did not harbour evidence for either form of selection. The results of branch models of codon evolution agreed fully with the results of the McDonald-Kreitman test in terms of significance and absolute value of the dN/dS estimates. The high frequency of gene-specific mutation patterns and their association with branches that separate closely related cyanobacterial genera suggest that evolutionary tests are suited to uncover gene-specific selective differentiation in cyanobacterial genomes. At the same time, given the lack of information about the history of cyanobacteria, analysis of larger numbers of protein-coding genes of clonal cyanobacterial isolates will produce more detailed pictures of the effects of natural selection. PMID:16913914

Mes, Ted H M; Doeleman, Marije; Lodders, Nicole; Nübel, Ulrich; Stal, Lucas J

2006-09-01

122

Parasite-mediated disruptive selection in a natural Daphnia population  

PubMed Central

Background A mismatch has emerged between models and data of host-parasite evolution. Theory readily predicts that parasites can promote host diversity through mechanisms such as disruptive selection. Yet, despite these predictions, empirical evidence for parasite-mediated increases in host diversity remains surprisingly scant. Results Here, we document parasite-mediated disruptive selection on a natural Daphnia population during a parasite epidemic. The mean susceptibility of clones collected from the population before and after the epidemic did not differ, but clonal variance and broad-sense heritability of post-epidemic clones were significantly greater, indicating disruptive selection and rapid evolution. A maximum likelihood method that we developed for detecting selection on natural populations also suggests disruptive selection during the epidemic: the distribution of susceptibilities in the population shifted from unimodal prior to the epidemic to bimodal after the epidemic. Interestingly, this same bimodal distribution was retained after a generation of sexual reproduction. Conclusion These results provide rare empirical support for parasite-driven increases in host genetic diversity, and suggest that this increase can occur rapidly.

2008-01-01

123

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

ERIC Educational Resources Information Center

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)

Walters, Douglas B.; And Others

1988-01-01

124

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

SciTech Connect

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.

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

1984-04-01

125

Natural selection and infectious disease in human populations.  

PubMed

The ancient biological 'arms race' between microbial pathogens and humans has shaped genetic variation in modern populations, and this has important implications for the growing field of medical genomics. As humans migrated throughout the world, populations encountered distinct pathogens, and natural selection increased the prevalence of alleles that are advantageous in the new ecosystems in both host and pathogens. This ancient history now influences human infectious disease susceptibility and microbiome homeostasis, and contributes to common diseases that show geographical disparities, such as autoimmune and metabolic disorders. Using new high-throughput technologies, analytical methods and expanding public data resources, the investigation of natural selection is leading to new insights into the function and dysfunction of human biology. PMID:24776769

Karlsson, Elinor K; Kwiatkowski, Dominic P; Sabeti, Pardis C

2014-06-01

126

Stick insect genomes reveal natural selection's role in parallel speciation.  

PubMed

Natural selection can drive the repeated evolution of reproductive isolation, but the genomic basis of parallel speciation remains poorly understood. We analyzed whole-genome divergence between replicate pairs of stick insect populations that are adapted to different host plants and undergoing parallel speciation. We found thousands of modest-sized genomic regions of accentuated divergence between populations, most of which are unique to individual population pairs. We also detected parallel genomic divergence across population pairs involving an excess of coding genes with specific molecular functions. Regions of parallel genomic divergence in nature exhibited exceptional allele frequency changes between hosts in a field transplant experiment. The results advance understanding of biological diversification by providing convergent observational and experimental evidence for selection's role in driving repeatable genomic divergence. PMID:24833390

Soria-Carrasco, Víctor; Gompert, Zachariah; Comeault, Aaron A; Farkas, Timothy E; Parchman, Thomas L; Johnston, J Spencer; Buerkle, C Alex; Feder, Jeffrey L; Bast, Jens; Schwander, Tanja; Egan, Scott P; Crespi, Bernard J; Nosil, Patrik

2014-05-16

127

Natural selection shaped regional mtDNA variation in humans  

Microsoft Academic Search

Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have

Dan Mishmar; Eduardo Ruiz-Pesini; Pawel Golik; Vincent Macaulay; Andrew G. Clark; Seyed Hosseini; Martin Brandon; Kirk Easley; Estella Chen; Michael D. Brown; Rem I. Sukernik; Antonel Olckers; Douglas C. Wallace

2002-01-01

128

Competition and natural selection in a mathematical model of cancer  

Microsoft Academic Search

A malignant tumor is a dynamic amalgamation of various cell phenotypes, both cancerous (parenchyma) and healthy (stroma).\\u000a These diverse cells compete over resources as well as cooperate to maintain tumor viability. Therefore, tumors are both an\\u000a ecological community and an integrated tissue. An understanding of how natural selection operates in this unique ecological\\u000a context should expose unappreciated vulnerabilities shared by

John D. Nagy

2004-01-01

129

Use of Laboratory-Supplied Natural Gas in Breakthrough Phenomena.  

ERIC Educational Resources Information Center

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)

Eiceman, G. A.; And Others

1985-01-01

130

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

Microsoft Academic Search

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

Donald R. Forsdyke

131

Survival and catabolic activity of natural and genetically engineered bacteria in a laboratory-scale activated-sludge unit  

Microsoft Academic Search

The survival of selected naturally occurring and genetically engineered bacteria in a fully functional laboratory-scale activated-sludge unit (ASU) was investigated. The effect of the presence of 3-chlorobenzoate (3CB) on the survival of Pseudomonas putida UWC1, with or without a chimeric plasmid, pD10, which encodes 3CB catabolism, was determined. P. putida UWC1(pD10) did not enhance 3CB breakdown in the ASU, even

N. C. McClure; J. C. Fry; A. J. Weightman

1991-01-01

132

Selective MAO-B inhibitors: a lesson from natural products.  

PubMed

Monoamine oxidases (MAOs) are mitochondrial bound enzymes, which catalyze the oxidative deamination of monoamine neurotransmitters. Inside the brain, MAOs are present in two isoforms: MAO-A and MAO-B. The activity of MAO-B is generally higher in patients affected by neurodegenerative diseases like Alzheimer's and Parkinson's. Therefore, the search for potent and selective MAO-B inhibitors is still a challenge for medicinal chemists. Nature has always been a source of inspiration for the discovery of new lead compounds. Moreover, natural medicine is a major component in all traditional medicine systems. In this review, we present the latest discoveries in the search for selective MAO-B inhibitors from natural sources. For clarity, compounds have been classified on the basis of structural analogy or source: flavonoids, xanthones, tannins, proanthocyanidins, iridoid glucosides, curcumin, alkaloids, cannabinoids, and natural sources extracts. MAO inhibition values reported in the text are not always consistent due to the high variability of MAO sources (bovine, pig, rat brain or liver, and human) and to the heterogeneity of the experimental protocols used. PMID:24218136

Carradori, Simone; D'Ascenzio, Melissa; Chimenti, Paola; Secci, Daniela; Bolasco, Adriana

2014-02-01

133

Maintaining life and health by natural selection of protein molecules.  

PubMed

A concept for a life and health-preserving principle is presented, with reference to evolutionary, medical, and biochemical observations. Life comprises two basic phenomena: it unfolds over longer periods at the population level, and is sustained for the duration of individual life spans. The evolution of life within populations by means of natural selection of individuals is central to Darwin's theory of evolution. An important component of maintaining individual life is proposed here to be the natural selection of molecular components-the proteins, a process of preferred removal of denatured and old, synonymous with the selection of younger, functional molecules. The proteins of the cell are committed to fulfilling all the tasks programmed by the genome while continuously maintaining all appropriate cellular functions, including protecting the DNA. Physiological and environmental influences accelerate the breakdown of aged protein molecules, driving this renewal process so that the cell can maintain its protein stock at high-performance levels. The principle of selection makes the incredible dynamics of continual protein turnover, and hence not only the preservation of life, but the maintenance of health in individual beings, comprehensible. Arguments are presented to counter the hypothesis that protein breakdown is a stochastic, random process governed by first-order kinetics. PMID:10534437

Pirlet, K; Arthur-Goettig, A

1999-11-01

134

The role of natural selection in circadian behaviour: a molecular-genetic approach.  

PubMed

Circadian rhythms (~24 h) in biochemistry, physiology and behaviour are found in almost all eukaryotes and some bacteria. The elucidation of the molecular components of the 24 h circadian clock in a number of model organisms in recent years has provided an opportunity to assess the adaptive value of variation in clock genes. Laboratory experiments using artificially generated mutants reveal that the circadian period is adaptive in a 24 h world. Natural genetic variation can also be studied, and there are a number of ways in which the signature of natural selection can be detected. These include the study of geographical patterns of genetic variation, which provide a first indication that selection may be at work, and the use of sophisticated statistical neutrality tests, which examine whether the pattern of variation observed is consistent with a selective rather than a neutral (or drift) scenario. Finally, examining the probable selective agents and their differential effects on the circadian phenotype of the natural variants provides the final compelling evidence for selection. We present some examples of how these types of analyses have not only enlightened the evolutionary study of clocks, but have also contributed to a more pragmatic molecular understanding of the function of clock proteins. PMID:21819385

Rosato, Ezio; Kyriacou, Charalambos P

2011-06-30

135

Exploring the nature of collisionless shocks under laboratory conditions  

PubMed Central

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.

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

2014-01-01

136

Laboratory selection for an accelerated mosquito sexual development rate  

Microsoft Academic Search

Background  Separating males and females at the early adult stage did not ensure the virginity of females of Anopheles arabiensis (Dongola laboratory strain), whereas two years earlier this method had been successful. In most mosquito species, newly emerged\\u000a males and females are not able to mate successfully. For anopheline species, a period of 24 h post-emergence is generally\\u000a required for the

Clelia F Oliva; Mark Q Benedict; Guy Lempérière; Jérémie Gilles

2011-01-01

137

Male Mating Success: Preference or Prowess? Investigating Sexual Selection in the Laboratory Using "Drosophila melanogaster"  

ERIC Educational Resources Information Center

Sexual selection is the primary force affecting the evolution of the elaborate sexual displays common in animals, yet sexual selection experiments are largely absent from introductory biology laboratories. Here we describe the rationale, methodology, and results of several experiments using "Drosophila melanogaster" to demonstrate sexual selection…

Coleman, Seth; Jensen, Jeffrey

2007-01-01

138

Population thinking and natural selection in dual-inheritance theory.  

PubMed

A deflationary perspective on theories of cultural evolution, in particular dual-inheritance theory, has recently been proposed by Lewens. On this 'pop-culture' analysis, dual-inheritance theorists apply population thinking to cultural phenomena, without claiming that cultural items evolve by natural selection. This paper argues against this pop-culture analysis of dual-inheritance theory. First, it focuses on recent dual-inheritance models of specific patterns of cultural change. These models exemplify population thinking without a commitment to natural selection of cultural items. There are grounds, however, for doubting the added explanatory value of the models in their disciplinary context-and thus grounds for engaging in other potentially explanatory projects based on dual-inheritance theory. One such project is suggested by advocates of the theory. Some of the motivational narratives that they offer can be interpreted as setting up an adaptationist project with regard to cumulative change in cultural items. We develop this interpretation here. On it, dual-inheritance theory features two interrelated selection processes, one on the level of genetically inherited learning mechanisms, another on the level of the cultural items transmitted through these mechanisms. This interpretation identifies a need for further modelling efforts, but also offers scope for enhancing the explanatory power of dual-inheritance theory. PMID:22523438

Houkes, Wybo

2012-05-01

139

Transport and selective uptake of radium into natural clay minerals  

NASA Astrophysics Data System (ADS)

Understanding of the environmental behavior of Ra is important from the viewpoint of the long-termed repository safety of radioactive waste, but investigation of Ra behavior in natural environment is difficult to detect. We found isotopic evidence of Ra transportation and its selective uptake into clay minerals from Pb isotopic analyses. Illite grains found in calcite veins included in sandstone near the Oklo uranium deposit, Republic of Gabon, show extremely low 207Pb/ 206Pb (˜ 0.0158) isotopic ratios. Although the Pb isotopic ratios of calcite and quartz coexisting with illite indicate the formation age of each component, those of illite do not. In addition, illite grains having low 207Pb/ 206Pb isotopic ratios contain a strongly large amount of Ba (1230 to 6010 ppm) in contrast with low contents of Ba in calcite and quartz (< 0.26 ppm). Considering the chemical similarity between Ba and Ra, the 207Pb/ 206Pb isotopic data suggest an excess of 206Pb due to selective adsorption of 226Ra (and also Ba) into illite grains. This is a very rare example to show evidence of the selective adsorption behavior of Ra from the isotopic excesses of 206Pb, although the adsorption ability of Ra itself in nature was largely reported.

Hidaka, Hiroshi; Horie, Kenji; Gauthier-Lafaye, Françoise

2007-12-01

140

Discrepancy in HbA1c measurements performed at different local laboratories and at a selected central reference laboratory.  

PubMed

As participants in a general practice intervention study, 66 patients had their HbA1c measured both at a local and at a selected central reference laboratory. A discrepancy in the results was observed, as 97% of the results measured locally were lower than the centrally determined results. Bias (as calculated from mean value of measured HbA1c) between local laboratories and the central laboratory was measured to -1.47% HbA1c. A bias of this magnitude gave "problems" both to the general practitioners, patients and laboratories. To reduce the "problems" a bias of 0.5% HbA1c is estimated to be acceptable. But, to avoid these "problems" totally, a bias of 0.25% HbA1c is estimated to be the highest allowed bias. For HbA1c, a control system for both control of method standardisation and for specificity is described. PMID:7974856

Jensen, O N; de Fine Olivarius, N; Petersen, P H; Klitgaard, N A; Blaabjerg, O; Hørder, M

1993-01-01

141

Natural Attenuation of Cr(VI) Contamination in Laboratory Mesocosms  

Microsoft Academic Search

The processes leading to the natural attenuation of hexavalent chromium (Cr(VI)) in marine systems are not well understood. To determine the rate at which Cr(VI) could be reduced and the effect of Cr(VI) on bacterial communities in marine sediments, we performed mesocosm experiments with 37.85 L aquaria containing San Diego Bay sandy sediments and seawater. Constant levels of 0, 0.25

Y. Meriah Arias; Anna Obraztsova; Bradley M. Tebo; Carlos Green-Ruiz

2003-01-01

142

Laboratory simulation studies of uranium mobility in natural waters  

NASA Astrophysics Data System (ADS)

The effects of imposed variations of pH and Eh on aqueous uranium mobility at 25°C have been studied in three simulations of natural water systems. Constituents tested for their effect on uranium mobility were: (a) hydrous ferric oxide, to represent adsorptive solids which precipitate or dissolve in response to variations in pH and Eh. (b) kaolinite, representing minerals which, although modified by pH and Eh changes, are present as solids over the pH-Eh range of natural waters. (c) carbonate, to represent a strong uranium-complexing species. Uranium mobility measurements from each simulation were regressed against pH and Eh within a range appropriate to natural waters. Hydrous ferric oxide and kaolinite each affected uranium mobility, but in separate pH-Eh domains. Aqueous carbonate increased mobility of uranium, and adsorption of UO 2(CO 3) 34- caused colloidal dispersion of hydrous ferric oxide, possibly explaining the presence of 'hydrothermal hematite' in some uranium deposits. Enhanced uranium mobility observed in the pH-Eh domains of thermodynamically insoluble uranium oxides could be explained if the oxides were present as colloids. Uranium persisting as a mobile species, even after reduction, has implications for the near surface genesis of uranium ores.

Giblin, A. M.; Batts, B. D.; Swaine, D. J.

1981-05-01

143

Exploring natural selection to guide breeding for agriculture.  

PubMed

Climate change threatens reduced crop production and poses major challenges to food security. The breeding of climate-resilient crop varieties is increasingly urgent. Wild plant populations evolve to cope with changes in their environment due to the forces of natural selection. This adaptation may be followed over time in populations at the same site or explored by examining differences between populations growing in different environments or across an environmental gradient. Survival in the wild has important differences to the objective of agriculture to maximize crop yields. However, understanding the nature of adaptation in wild populations at the whole genome level may suggest strategies for crop breeding to deliver agricultural production with more resilience to climate variability. PMID:24975385

Henry, Robert James; Nevo, Eviatar

2014-08-01

144

Natural selection of stellar civilizations by the limits of growth  

NASA Astrophysics Data System (ADS)

Evolution occurs in any system that possesses degrees of freedom to allow the appearance of new entities and constraints to select a few of them to become part of the system which in this manner continues to evolve. The limits of growth in a finite system, which will be imposed on all stellar civilizations by the colossal distances that separate the stars, will become the constraint that will affect the natural selection of these civilizations. Those that will manage to overcome their innate tendencies toward continuous material growth and replace them with non-material goals will be the only ones to survive this crisis. As a result the entire galaxy in a cosmically short period will become populated by stable, highly ethical and spiritual civilizations.

Papagiannis, M. D.

1983-10-01

145

The natural selection of fidelity in social learning  

PubMed Central

Social learning mechanisms are usually assumed to explain both the spread and the persistence of cultural behavior. In a recent article, we showed that the fidelity of social learning commonly found in transmission chain experiments is not high enough to explain cultural stability. Here we want to both enrich and qualify this conclusion by looking at the case of song transmission in song birds, which can be faithful to the point of being true replication. We argue that this high fidelity results from natural selection pressure on cognitive mechanisms. This observation strengthens our main argument. Social learning mechanisms are unlikely to be faithful enough to explain cultural stability because they are generally selected not for high fidelity but for generalization and adjustment to the individual’s needs, capacities and situation.

Sperber, Dan

2010-01-01

146

Salvinorin A: A potent naturally occurring nonnitrogenous ? opioid selective agonist  

PubMed Central

Salvia divinorum, whose main active ingredient is the neoclerodane diterpene Salvinorin A, is a hallucinogenic plant in the mint family that has been used in traditional spiritual practices for its psychoactive properties by the Mazatecs of Oaxaca, Mexico. More recently, S. divinorum extracts and Salvinorin A have become more widely used in the U.S. as legal hallucinogens. We discovered that Salvinorin A potently and selectively inhibited 3H-bremazocine binding to cloned ? opioid receptors. Salvinorin A had no significant activity against a battery of 50 receptors, transporters, and ion channels and showed a distinctive profile compared with the prototypic hallucinogen lysergic acid diethylamide. Functional studies demonstrated that Salvinorin A is a potent ? opioid agonist at cloned ? opioid receptors expressed in human embryonic kidney-293 cells and at native ? opioid receptors expressed in guinea pig brain. Importantly, Salvinorin A had no actions at the 5-HT2A serotonin receptor, the principal molecular target responsible for the actions of classical hallucinogens. Salvinorin A thus represents, to our knowledge, the first naturally occurring nonnitrogenous opioid-receptor subtype-selective agonist. Because Salvinorin A is a psychotomimetic selective for ? opioid receptors, ? opioid-selective antagonists may represent novel psychotherapeutic compounds for diseases manifested by perceptual distortions (e.g., schizophrenia, dementia, and bipolar disorders). Additionally, these results suggest that ? opioid receptors play a prominent role in the modulation of human perception.

Roth, Bryan L.; Baner, Karen; Westkaemper, Richard; Siebert, Daniel; Rice, Kenner C.; Steinberg, SeAnna; Ernsberger, Paul; Rothman, Richard B.

2002-01-01

147

Brookhaven National Laboratory Selected Cryogenic Data Notebook. Volume 2. Sections 10-18.  

National Technical Information Service (NTIS)

The Selected Cryogenic Data Notebook has been designed to meet the general needs of the engineers and scientists working with cryogenic systems at Brookhaven National Laboratory. The objective in the preparation of this collection of data tables and chart...

A. G. Prodell H. Brechna J. E. Jensen R. B. Stewart W. A. Tuttle

1980-01-01

148

Preventing and Removing Contamination in a Natural Radiocarbon Sample Preparation Laboratory  

Microsoft Academic Search

The introduction of elevated ¹⁴C 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 ¹⁴C contaminated as a result of earlier tracer based research, even if ''hot'' work has not occurred in the laboratories in decades. Prior to

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

2002-01-01

149

Laboratory study of selected personal inhalable aerosol samplers.  

PubMed

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

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

2010-03-01

150

Evidence for natural selection in a fern hybrid zone.  

PubMed

Morphological characters, chloroplast DNA, and allozymes were used to analyze the distribution of individuals within a hybrid population of the ferns Polystichum munitum and P. imbricans in northwestern California. Microsites within the population were characterized according to soil moisture and light levels reaching the plants. In sites with low soil moisture and high light levels, all of the ferns were genetically and morphologically like P. imbricans. In contrast, ferns with the genetic and morphological identity of P. munitum predominated in moist shady sites. Intermediate sites supported very few P.munitum, a wide variety of hybrid recombinants, and a majority of ferns with P. imbricans characteristics. The pattern of variation within the population is noteworthy because of the close proximity of the habitat extremes and the long-range dispersal of fern spores. We conclude that natural selection along environmental gradients must be a major factor in determining the ecological and genetic associations within the hybrid zone. The results of this study are evaluated in the context of the fern life cycle and compared to the assumptions of models explaining the establishment and maintenance of hybrid zones, which vary in the role attributed to environmentally mediated natural selection. PMID:10948001

Kentner, E K; Mesler, M R

2000-08-01

151

The cycling of iron in natural environments: Considerations based on laboratory studies of heterogeneous redox processes  

Microsoft Academic Search

The various pathways for the oxygenation of ferrous iron and for the dissolution of Fe(III) (hydr) oxides, especially by reducing ligands with oxygen donor atoms in thermal and photochemical processes, are assessed on the basis of laboratory experiments for application to natural systems. The typically large specific surface area of Fe-bearing solids in natural systems and the ability of these

Werner Stumm; Barbara Sulzberger

1992-01-01

152

More than Meets the Eye--a Simulation of Natural Selection.  

ERIC Educational Resources Information Center

Presents experiments using wild birds as predators and pastry as prey and colored stones as background to demonstrate natural selection. Describes the exercise as an exercise in simulating natural selection. (Author/CW)

Allen, J. A.; And Others

1987-01-01

153

Signatures of natural selection in a primate bitter taste receptor.  

PubMed

Bitter taste receptors (TAS2Rs) enable animals to detect and avoid toxins in the environment, including noxious defense compounds produced by plants. This suggests that TAS2Rs are under complex pressures from natural selection. To investigate these pressures, we examined signatures of selection in the primate TAS2R38 gene. Whole-gene (1,002 bp) sequences from 40 species representing all major primate taxa uncovered extensive variation. Nucleotide substitutions occurred at 448 positions, resulting in 201 amino acid changes. Two single-nucleotide deletions, one three-nucleotide in-frame deletion, and one premature stop codon were also observed. The rate of non-synonymous substitution (? = dN/dS), was high in TAS2R38 (? = 0.60) compared to other genes, but significantly lower than expected under neutrality (P = 4.0 × 10(-9)), indicating that purifying selection has maintained the basic structure of the receptor. However, differences were present among receptor subregions. Non-synonymous rates were significantly lower than expected in transmembrane domains (? = 0.55, P = 1.18 × 10(-12)) and internal loops (? = 0.51, P = 7.04 × 10(-5)), but not external loops (? = 1.16, P = 0.53), and evidence of positive selection was found in external loop 2, which exhibited a high rate (? = 2.53) consistent with rapid shifts in ligand targeting. These patterns point to a history of rapid yet constrained change in bitter taste responses in the course of primate evolution. PMID:22218679

Wooding, Stephen

2011-12-01

154

Genetic improvement of Amblyseius finlandicus (Acari: Phytoseiidae): laboratory selection for resistance to azinphosmethyl and dimethoate  

Microsoft Academic Search

Amblyseius finlandicus (Oudemans) was selected in the laboratory for resistance to azinphosmethyl and dimethoate by subjecting adult females to increasing concentrations of dried residues of dimethoate and azinphosmethyl on detached bean leaves. The first eight selections were done with dimethoate. Slide-dip bioassays indicated selection with dimethoate increased dimethoate resistance 1.8-fold and azinphosmethyl resistance 2.6-fold. These resistances appeared to be quite

Tuomas Kostiainen; Marjorie A. Hoy

1994-01-01

155

Optimization of a Ribosomal Structural Domain by Natural Selection†  

PubMed Central

A conserved, independently folding domain in the large ribosomal subunit consists of 58 nt of rRNA and a single protein, L11. The tertiary structure of an rRNA fragment carrying the E. coli sequence is marginally stable in vitro but can be substantially stabilized by mutations found in other organisms. To distinguish between possible reasons why natural selection has not evolved a more stable rRNA structure in E. coli, mutations affecting the rRNA tertiary structure were assessed for their in vitro effects on rRNA stability and L11 affinity (in the context of an rRNA fragment) or in vivo effects on cell growth rate and L11 content of ribosomes. The rRNA fragment stabilities ranged from ?4 to +9 kcal/mol relative to the wild type sequence. Variants in the range of ?4 to +5 kcal/mol had almost no observable effect in vivo, while more destabilizing mutations (> 7 kcal/mol) were not tolerated. The data suggest that the in vivo stability of the complex is roughly ?6 kcal/mol, and that any single tertiary interaction is dispensable for function as long as a minimum stability of the complex is maintained. Based on these data, it seems that the evolution of this domain has not been constrained by inherent structural or functional limits on stability. The estimated stability corresponds to only a few ribosomes per bacterial cell dissociated from L11 at any time; thus the selective advantage for any further increase in stability may be so small as to be outweighed by other competing selective pressures.

Maeder, Corina; Conn, Graeme L.; Draper, David E.

2008-01-01

156

Natural selection shaped regional mtDNA variation in humans  

PubMed Central

Human mtDNA shows striking regional variation, traditionally attributed to genetic drift. However, it is not easy to account for the fact that only two mtDNA lineages (M and N) left Africa to colonize Eurasia and that lineages A, C, D, and G show a 5-fold enrichment from central Asia to Siberia. As an alternative to drift, natural selection might have enriched for certain mtDNA lineages as people migrated north into colder climates. To test this hypothesis we analyzed 104 complete mtDNA sequences from all global regions and lineages. African mtDNA variation did not significantly deviate from the standard neutral model, but European, Asian, and Siberian plus Native American variations did. Analysis of amino acid substitution mutations (nonsynonymous, Ka) versus neutral mutations (synonymous, Ks) (ka/ks) for all 13 mtDNA protein-coding genes revealed that the ATP6 gene had the highest amino acid sequence variation of any human mtDNA gene, even though ATP6 is one of the more conserved mtDNA proteins. Comparison of the ka/ks ratios for each mtDNA gene from the tropical, temperate, and arctic zones revealed that ATP6 was highly variable in the mtDNAs from the arctic zone, cytochrome b was particularly variable in the temperate zone, and cytochrome oxidase I was notably more variable in the tropics. Moreover, multiple amino acid changes found in ATP6, cytochrome b, and cytochrome oxidase I appeared to be functionally significant. From these analyses we conclude that selection may have played a role in shaping human regional mtDNA variation and that one of the selective influences was climate.

Mishmar, Dan; Ruiz-Pesini, Eduardo; Golik, Pawel; Macaulay, Vincent; Clark, Andrew G.; Hosseini, Seyed; Brandon, Martin; Easley, Kirk; Chen, Estella; Brown, Michael D.; Sukernik, Rem I.; Olckers, Antonel; Wallace, Douglas C.

2003-01-01

157

Numerical, Laboratory And Field Studiesof Gas Production FromNatural Hydrate Accumulations in Geologic Media  

SciTech Connect

We discuss the range of activities at Lawrence BerkeleyNational Laboratory in support of gas production from natural hydrates.Investigations of production from the various classes of hydrate depositsby numerical simulation indicate their significant promise as potentialenergy sources. Laboratory studies are coordinated with the numericalstudies and are designed to address knowledge gaps that are important tothe prediction of gas production. Our involvement in field tests is alsobriefly discussed.

Moridis, George J.; Kneafsey, Timothy J.; Kowalsky, Michael; Reagan, Matthew

2006-10-17

158

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

PubMed Central

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.

Baker, David G.

1998-01-01

159

Exploring Variation and Natural Selection with Fast Plants  

NSDL National Science Digital Library

This Immersion Unit provides a coherent series of lessons designed to guide students in developing deep conceptual understanding that is aligned with the standards, key science concepts, and essential features of classroom inquiry (as defined by the National Science Education Standards). The Unit's overarching concepts are:- Naturally occurring variations of traits in a population are influenced by genetic and environmental factors and evolve over generations by selective processes.- Science knowledge advances through inquiry.Unit Supporting Concepts:- The variation of organisms within a species increases the likelihood that at least some members of the species will survive under changed environmental conditions.- Individual organisms with certain traits are more likely than others to survive and have offspring. Changes in environmental conditions can affect the survival of individual organisms and entire species.- Some variation in heritable characteristics exists within every species. One of these characteristics gives individuals an advantage over others in surviving and reproducing, and the advantaged offspring, in turn,are more likely than others to survive and reproduce.- New varieties of cultivated plants and domestic animals have resulted from selective breeding for particular traits.- Scientists differ greatly in whatphenomena they study and how they go about their work. Although there is nofixed set of steps that all scientists follow, scientific investigations usually involve the collection of relevant evidence, the use of logical reasoning, and the application of imagination in devising hypotheses and explanations to make sense of the collected evidence.- Important contributions to the advancement of science, mathematics, and technology have been made by different kinds of people, in different cultures, at different times.In Immersion Units, students learn academic content by working like scientists: making observations, asking questions, doing further investigations to explore and explain natural phenomena, and communicating results based on evidence. Immersion Units are intended to support teachers in building a learning culture in their classrooms to sustain students enthusiasm for engaging in scientific habits of thinking while learning rigorous science content.The first step of this unit engages students in developing a class criteria for effective record-keeping in science by guiding an inquiry into scientists' notebooks.The unit includes very complete implementation instructions (Teacher's Guide pages), student pages, and formative and summative assessments.Students investigate:- how variation within a population is influenced by environmental factors- how environmental factors influence reproductive success in a populationThis unit was developed through the large Math and Science Partnership project called System-wide Change for All Learners and Educators (SCALE), involving a collaboration among Los Angeles School District educators, California State University science and education faculty, and UW-Madison SCALE staff.

Program, The W.

160

Food selection by laboratory-reared larvae of the scaled sardine Harengula pensacolae (Pisces, Clupeidae) and the bay anchovy Anchoa mitchilli (Pisces, Engraulidae)  

Microsoft Academic Search

Food selection by laboratory-reared larvae of scaled sardines Harengula pensacolae, and bay anchovies Anchoa mitchilli, was compared. Natural plankton was fed to the larvae during the 22 days following hatching. Food levels in the rearing tanks were maintained at an average of 1,600 to 1,800 potential food organisms per liter. Larvae of both species selected as food copepod nauplii, copepodites,

R. Detwyler; E. D. Houde

1970-01-01

161

Preventing and Removing Contamination in a Natural Radiocarbon Sample Preparation Laboratory  

SciTech Connect

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.

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

2002-10-25

162

Selective predation by a sculpin and a stonefly on two chironomids in laboratory feeding trials  

Microsoft Academic Search

Sculpin and stonefly predators fed selectively on the larvae of the chironomids Paratendipes over Cricotopus in laboratory stream microcosms. In these experiments, Cricotopus were usually tube-dwelling, whereas Paratendipes were usually free-living. Paratendipes were also bright red, which may have influenced selectivity by visual feeding sculpin, but tactile feeding stoneflies were most likely influenced only by the difference in tube-dwelling behavior

Anne E. Hershey; Stanley I. Dodson

1985-01-01

163

Molluscan Natural Products as Biological Models: Chemical Ecology, Histology and Laboratory Culture  

Microsoft Academic Search

known for centuries. However, only recently have modern technologies and advances in the fields of chemistry, chemical ecology, anatomy, histology, and laboratory culture allowed the exploitation of new, unprecedented applications of natural products. Recent studies have dealt with (a) the role that these compounds have in the sea in protecting the animals (e.g., chemical defense), or in mediating their intraspecific

Conxita Avila

164

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

Microsoft Academic Search

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.

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

2004-01-01

165

Six Classroom Exercises to Teach Natural Selection to Undergraduate Biology Students  

ERIC Educational Resources Information Center

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…

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

2013-01-01

166

Modifying effects of phenotypic plasticity on interactions among natural selection, adaptation and gene flow  

Microsoft Academic Search

Divergent natural selection, adaptive divergence and gene flow may interact in a number of ways. Recent studies have focused on the balance between selection and gene flow in natural populations, and empirical work has shown that gene flow can constrain adaptive divergence, and that divergent selection can constrain gene flow. A caveat is that phenotypic diversification may be under the

E. CRISPO

2008-01-01

167

Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes  

Microsoft Academic Search

Identifying regions of the human genome that have been targets of natural selection will provide important insights into human evolutionary history and may facilitate the identification of complex disease genes. Although the signature that natural selection imparts on DNA sequence variation is difficult to disentangle from the effects of neutral processes such as population demographic history, selective and demographic forces

Joshua M. Akey; Michael A. Eberle; Mark J. Rieder; Christopher S. Carlson; Mark D. Shriver; Deborah A. Nickerson; Leonid Kruglyak

2004-01-01

168

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

Microsoft Academic Search

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

Pawloski

2011-01-01

169

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

PubMed

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

Su, Tianyun; Cheng, Min-Lee

2014-03-01

170

Genetic Load in Natural Populations: Is It Compatible with the Hypothesis That Many Polymorphisms Are Maintained by Natural Selection?  

PubMed Central

Recent studies of genetically controlled enzyme variation lead to an estimation that at least 30 to 60% of the structural genes are polymorphic in natural populations of many vertebrate and invertebrate species. Some authors have argued that a substantial proportion of these polymorphisms cannot be maintained by natural selection because this would result in an unbearable genetic load. If many polymorphisms are maintained by heterotic natural selection, individuals with much greater than average proportion of homozygous loci should have very low fitness. We have measured in Drosophila melanogaster the fitness of flies homozygous for a complete chromosome relative to normal wild flies. A total of 37 chromosomes from a natural population have been tested using 92 experimental populations. The mean fitness of homozygous flies is 0.12 for second chromosomes, and 0.13 for third chromosomes. These estimates are compatible with the hypothesis that many (more than one thousand) loci are maintained by heterotic selection in natural populations of D. melanogaster.

Tracey, Martin L.; Ayala, Francisco J.

1974-01-01

171

Idaho National Laboratory Materials and Fuels Complex Natural Phenomena Hazards Flood Assessment  

SciTech Connect

This report presents the results of flood hazards analyses performed for the Materials and Fuels Complex (MFC) and the adjacent Transient Reactor Experiment and Test Facility (TREAT) located at Idaho National Laboratory. The requirements of these analyses are provided in the U.S. Department of Energy Order 420.1B and supporting Department of Energy (DOE) Natural Phenomenon Hazard standards. The flood hazards analyses were performed by Battelle Energy Alliance and Pacific Northwest National Laboratory. The analyses addressed the following: • Determination of the design basis flood (DBFL) • Evaluation of the DBFL versus the Critical Flood Elevations (CFEs) for critical existing structures, systems, and components (SSCs).

Gerald Sehlke; Paul Wichlacz

2010-12-01

172

Toxicity of naturally-contaminated manganese soil to selected crops.  

PubMed

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 13?696 ?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

Ková?ik, Jozef; St?rbová, Dagmar; Babula, Petr; Svec, Pavel; Hedbavny, Josef

2014-07-23

173

Examining undergraduate understanding of natural selection and evolution  

NASA Astrophysics Data System (ADS)

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.

Balgopal, Meena Michelle

174

North American Natural Gas Markets: Selected technical studies  

SciTech Connect

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.

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

1989-04-01

175

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

SciTech Connect

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.

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

1989-04-01

176

Six classroom exercises to teach natural selection to undergraduate biology students.  

PubMed

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

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

2013-01-01

177

Mini-conference on Angular Momentum Transport in Laboratory and Nature  

SciTech Connect

This paper provides a concise summary of the current status of the research and future perspectives discussed in the Mini-Conference on Angular Momentum Transport in Laboratory and Nature. This Mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society's Division of Plasma Physics 2007 Annual Meeting (November 12{16, 2007). This Mini-conference covers a wide range of phenomena happening in fluids and plasmas, either in laboratory or in nature. The purpose of this paper is not to comprehensively review these phenomena, but to provide a starting point for interested readers to refer to related research in areas other than their own.

Hantao Ji, Philipp Kronberg, Stewart C. Prager, and Dmitri A. Uzdensky

2008-05-06

178

Parallel shifts in ecology and natural selection in an island lizard  

PubMed Central

Background Natural selection is a potent evolutionary force that shapes phenotypic variation to match ecological conditions. However, we know little about the year-to-year consistency of selection, or how inter-annual variation in ecology shapes adaptive landscapes and ultimately adaptive radiations. Here we combine remote sensing data, field experiments, and a four-year study of natural selection to show that changes in vegetation structure associated with a severe drought altered both habitat use and natural selection in the brown anole, Anolis sagrei. Results In natural populations, lizards increased their use of vegetation in wet years and this was correlated with selection on limb length but not body size. By contrast, a die-back of vegetation caused by drought was followed by reduced arboreality, selection on body size, and relaxed selection on limb length. With the return of the rains and recovery of vegetation, selection reverted back to pre-drought pattern of selection acting on limb length but not body size. To test for the impact of vegetation loss on natural selection during the drought, we experimentally removed vegetation on a separate study island in a naturally wet year. The experiment revealed similar inter-annual changes in selection on body size but not limb length. Conclusion Our results illustrate the dynamic nature of ecology driving natural selection on Anolis morphology and emphasize the importance of inter-annual environmental variation in shaping adaptive variation. In addition, results illustrate the utility of using remote sensing data to examine ecology's role in driving natural selection.

Calsbeek, Ryan; Buermann, Wolfgang; Smith, Thomas B

2009-01-01

179

Regularities in transient modes in the seismic process according to the laboratory and natural modeling  

Microsoft Academic Search

Regularities in the excitation and relaxation of rock failure were revealed in a series of laboratory experiments. Similar\\u000a regularities are found also in natural conditions. A physical idea and its mathematical description are suggested for explaining\\u000a the obtained experimental data. The aim of the experiments was to understand the character of excitation of the failure, triggered\\u000a by the external impact,

V. B. Smirnov; A. V. Ponomarev; P. Benard; A. V. Patonin

2010-01-01

180

A laboratory-based procedure for measuring emotional expression from natural speech  

Microsoft Academic Search

Despite dramatic advances in the sophistication of tools for measuring prosodic and content channels of expression from natural\\u000a speech, methodological issues have limited the simultaneous measurement of those channels for laboratory research. This is\\u000a particularly unfortunate, considering the importance of emotional expression in daily living and how it can be disrupted in\\u000a many psychological disorders (e.g., schizophrenia). The present study

Alex S. Cohen; Kyle S. Minor; Gina M. Najolia; S. Lee Hong

2009-01-01

181

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

Microsoft Academic Search

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.

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

2001-01-01

182

Clients and clinician satisfaction with laboratory services at selected government hospitals in eastern Ethiopia  

PubMed Central

Background In clinical laboratory service, patients and clinical service providers are the primary focus of survey of satisfaction in many countries. The objective of the study was to assess clients’ and clinicians’ satisfaction with laboratory services at selected government hospitals in eastern Ethiopia from May to June, 2010. Findings A cross sectional study was conducted at Dil Chora, Jugal, Hiwot Fana and Bisidimo hospitals. Data were collected from 429 patients and 54 clinical service providers. A statistical analysis was conducted using Likert Scale and SPSS Version 16 software. Most of the patients (87.6%) were satisfied with the laboratory services. The lowest [2.48?±?1.39] and highest [4.27?±?0.83] rate satisfaction were on cleanness of latrine to collect specimens and availability of laboratory staff on working hours respectively. The extent of the patients’ satisfaction was different among the study hospitals (P-value?laboratory services. The lowest [3.02?±?1.36] and highest [3.78?±?1.03] rate of satisfaction were found on critical value notification and timely test results for HIV/AIDS patients care respectively. Conclusion The overall degree of customers’ satisfaction with laboratory services was high. But there were some services such as the cleanness of latrines, information given during specimen collection outside laboratory and critical value notification which need attention. Therefore, the hospital administrations and the laboratory departments should work harder and closely to solve the identified problems. Further study with a larger sample size and more factors is recommended.

2013-01-01

183

Dynamic Viscoelastic Properties of Selected Natural-Neoprene Rubber Blends.  

National Technical Information Service (NTIS)

This report provides the results of measuring the various viscoelastic properties of specially formulated natural-neoprene rubber samples. Each sample is described in terms of its unique formulation, resulting specific gravity, Young's modulus, tensile st...

W. M. Madigosky

1990-01-01

184

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

SciTech Connect

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.

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

1998-02-01

185

Dynamics of extinction and the selection of nature reserves.  

PubMed Central

Familiar quantitative reserve-selection techniques are tailored to simple decision problems, where the representation of species is sought at minimum cost. However, conservationists have begun to ask whether representing species in reserve networks is sufficient to avoid local extinctions within selected areas. An attractive, but previously untested idea is to model current species' probabilities of occurrence as an estimate of local persistence in the near future. Using distribution data for passerine birds in Great Britain, we show that (i) species' probabilities of occurrence are negatively related to local probabilities of extinction, at least when a particular 20-year period is considered, and (ii) local extinctions can be reduced if areas are selected to maximize current species' probabilities of occurrence We suggest that more extinctions could be avoided if even a simple treatment of persistence were to be incorporated within reserve selection methods.

Araujo, Miguel B; Williams, Paul H; Fuller, Robert J

2002-01-01

186

Development of impactor size-selective dust samplers at the Elliot Lake Laboratory.  

PubMed

The Elliot Lake Laboratory designs and uses impactor size selectors for respirable and other dust samplers both in the laboratory and in mines. Advantages of the selectors are compact size, reproducibility of size-selection performance based on the high precision of drill manufacture and use, flexibility in design and layout, and manufacturing ease in a machine shop. The major problems in design and performance were secondary deposition of dust and overloading with coarse dust. Secondary deposition modified the calculated size selection and either limited the spacing between adjacent orifices or orifices and other features or required a final calibration. Overloading of the coarse dust deposition zone led to changes in size-selection characteristics as the dust load increased, giving a definite limit to acceptable dust collection quantities. The use of multiple stages increased the coarse dust-holding capability manyfold. All the dust samplers developed at the Elliot Lake Laboratory used two or more successive stages to increase dust-holding capacity. PMID:2069124

Knight, G

1991-04-01

187

A Hands-On Exercise to Demonstrate Evolution by Natural Selection & Genetic Drift  

ERIC Educational Resources Information Center

Although students "learn" (i.e., hear about) the components of evolution by natural selection in high school biology courses, few of them truly understand or remember them. Evolution by natural selection, although seemingly simple, requires that several conditions be met. The trait of concern must exhibit variation within the population; this…

Young, Helen J.; Young, Truman P.

2003-01-01

188

Evolution of Students' Ideas about Natural Selection through a Constructivist Framework  

ERIC Educational Resources Information Center

Educating students about the process of evolution through natural selection is vitally important because not only is it the unifying theory of biological science, it is also widely regarded as difficult for students to fully comprehend. Anderson and colleagues (2002) describe alternative ideas and misconceptions about natural selection as highly…

Baumgartner, Erin; Duncan, Kanesa

2009-01-01

189

Interaction between natural and sexual selection during the evolution of mate recognition.  

PubMed Central

The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.

Blows, Mark W

2002-01-01

190

Selection against inbred song sparrows during a natural population bottleneck  

Microsoft Academic Search

THE genetic and demographic consequences of population subdivision have received considerable attention from conservation biologists. In particular, losses of genetic variability and reduced viability and fecundity due to inbreeding (inbreeding depression) are of concern1-3. Studies of domestic, laboratory4,5 and zoo populations2,6,7 have shown inbreeding depression in a variety of traits related to fitness. Consequently, inbreeding depression is widely accepted as

Lukas F. Keller; Peter Arcese; James N. M. Smith; Wesley M. Hochachka; Stephen C. Stearns

1994-01-01

191

Predator-Mediated Natural Selection on the Wings of the Damselfly Calopteryx splendens: Differences in Selection among Trait Types.  

PubMed

Abstract 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

Kuchta, Shawn R; Svensson, Erik I

2014-07-01

192

Natural selection of mitochondria during somatic lifetime promotes healthy aging  

PubMed Central

Stimulation of mitochondrial biogenesis during life-time challenges both eliminates disadvantageous properties and drives adaptive selection of advantageous phenotypic variations. Intermittent fission and fusion of mitochondria provide specific targets for health promotion by brief temporal stressors, interspersed with periods of recovery and biogenesis. For mitochondria, the mechanisms of selection, variability, and heritability, are complicated by interaction of two independent genomes, including the multiple copies of DNA in each mitochondrion, as well as the shared nuclear genome of each cell. The mechanisms of stress-induced fission, followed by recovery-induced fusion and biogenesis, drive the improvement of mitochondrial functions, not only as directed by genotypic variations, but also as enabled by phenotypic diversity. Selective adaptation may explain unresolved aspects of aging, including the health effects of exercise, hypoxic and poisonous preconditioning, and tissue-specific mitochondrial differences. We propose that intermittent purposeful enhancement of mitochondrial biogenesis by stressful episodes with subsequent recovery paradoxically promotes adaptive mitochondrial health and continued healthy aging.

Rodell, Anders; Rasmussen, Lene J.; Bergersen, Linda H.; Singh, Keshav K.; Gjedde, Albert

2013-01-01

193

I'm Looking Over a White-Striped Clover: A Natural Selection Case  

NSDL National Science Digital Library

This case study examines the process of natural selection, using the example of white clover. Students will learn the concepts of variation, natural selection, fitness, selection pressure, evolution, and adaptation.The lesson would be useful for high school or lower level undergraduate students studying biology or botany. The case study and teaching notes may be downloaded in PDF format. The site also includes a section for instructor feedback where general comments may be read and contributed.

Evarts, Susan; Krufka, Alison; Wilson, Chester

2006-11-28

194

Comparison of in situ and laboratory gamma spectroscopy of natural radionuclides in desert soil.  

PubMed

In situ and laboratory gamma spectroscopy were used to characterize natural background levels of radiation in the soil at eight sites around the Yucca Mountain Range. The purpose of this practical field analysis was to determine if published empirical in situ calibration factors would yield accurate quantitative specific activities (Bq kg(-1)) in a desert environment. Corrections were made to the in situ calibration factors to account for the on-axis response of a detector with a thin beryllium end window. The in situ gamma spectroscopy results were compared to laboratory gamma spectroscopy of soil samples gathered from each site. Five natural radionuclides were considered: 40K, 214Pb, 214Bi, 208Tl, and 228Ac. The in situ determined specific activities were consistently within +/-15% of the laboratory soil sample results. A quantitative discussion of the factors contributing to the uncertainty in the in situ and laboratory results is included. Analysis on the specific activity data using statistical hypothesis tests determined that three nuclides, 214Pb, 214Bi, and 228Ac showed a weak site dependence while the other two nuclides, 40K and 208Tl, did not exhibit a site dependence. Differing radiation background levels from site to site along with in situ and laboratory uncertainties in excess of 10% are two factors that account for the weak site dependence. Despite the good correlation between data, it was recommended that the in situ detector be calibrated by a detector-specific Monte Carlo code which would accurately model more complex geometries and source distributions. PMID:9228170

Benke, R R; Kearfott, K J

1997-08-01

195

Natural Selection Favors a Newly Derived timeless Allele in Drosophila melanogaster  

Microsoft Academic Search

Circadian and other natural clock-like endogenous rhythms may have evolved to anticipate regular temporal changes in the environment. We report that a mutation in the circadian clock gene timeless in Drosophila melanogaster has arisen and spread by natural selection relatively recently in Europe. We found that, when introduced into different genetic backgrounds, natural and artificial alleles of the timeless gene

Eran Tauber; Mauro Zordan; Federica Sandrelli; Mirko Pegoraro; Nicolò Osterwalder; Carlo Breda; Andrea Daga; Alessandro Selmin; Karen Monger; Clara Benna; Ezio Rosato; Charalambos P. Kyriacou; Rodolfo Costa

2007-01-01

196

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

ERIC Educational Resources Information Center

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…

National Education Association, Washington, DC.

197

SEXUAL SIZE DIMORPHISM IN SHOREBIRDS, GULLS, AND ALCIDS: THE INFLUENCE OF SEXUAL AND NATURAL SELECTION  

Microsoft Academic Search

Charadrii (shorebirds, gulls, and alcids) have an unusual diversity in their sexual size dimorphism, ranging from monomorphism to either male-biased or female-biased dimorphism. We use comparative analyses to investigate whether this variation relates to sexual selection through competition for mates or natural selection through different use of resources by males and females. As predicted by sexual selection theory, we found

Tamás Székely; John D. Reynolds; Jordi Figuerola

2000-01-01

198

Gene flow and the limits to natural selection  

Microsoft Academic Search

In general, individuals who survive to reproduce have genotypes that work relatively well under local conditions. Migrating or dispersing offspring elsewhere is likely to decrease an individual's or its offspring's fitness, not to mention the intrinsic costs and risks of dispersal. Gene flow into a population can counteract gene frequency changes because of selection, imposing a limit on local adaptation.

Thomas Lenormand

2002-01-01

199

Evaluation of selected neutralizing agents for the treatment of uranium tailings leachates. Laboratory progress report  

SciTech Connect

Laboratory experiments were conducted to evaluate the performance of selected neutralizing agents for the treatment of uranium tailings solutions. Highly acidic tailings solutions (pH<2) from the Lucky Mc Mill in Gas Hills, Wyoming and the Exxon Highlands Mill near Casper, Wyoming were neutralized to a pH of 7 or greater using seven neutralizing agents. Reagents used included: Fly Ash from Boardman Coal Plant, Boardman, Oregon; Fly Ash from Wyodak Coal Plant, Gillette, Wyoming; Calcium carbonate (CaCO/sub 3/) reagent grade; Calcium hydroxide (Ca(OH)/sub 2/) reagent grade; Magnesium oxide (MgO) reagent grade; Sodium carbonate (Na/sub 2/CO/sub 3/) reagent grade; and Sodium hydroxide (NaOH) reagent grade. Evaluation of the effectiveness for the treatment of uranium tailings solutions for the selected neutralizing agents under controlled laboratory conditions was based on three criteria. The criteria are: (1) treated effluent water quality, (2) neutralized sludge handling and hydraulic properties, and (3) reagent costs and acid neutralizing efficiency. On the basis of these limited laboratory results calcium hydroxide or its dehydrated form CaO (lime) appears to be the most effective option for treatment of uranium tailings solutions.

Sherwood, D.R.; Serne, R.J.

1983-02-01

200

Survival and catabolic activity of natural and genetically engineered bacteria in a laboratory-scale activated-sludge unit  

SciTech Connect

The survival of selected naturally occurring and genetically engineered bacteria in a fully functional laboratory-scale activated-sludge unit (ASU) was investigated. The effect of the presence of 3-chlorobenzoate (3CB) on the survival of Pseudomonas putida UWC1, with or without a chimeric plasmid, pD10, which encodes 3CB catabolism, was determined. P. putida UWC1(pD10) did not enhance 3CB breakdown in the ASU, even following inoculation at a high concentration (3 x 10(8) CFU/ml). The emergence of a natural, 3CB-degrading population appeared to have a detrimental effect on the survival of strain UWC1 in the ASU. The fate of two 3CB-utilizing bacteria, derived from activated-sludge microflora, was studied in experiments in which these strains were inoculated into the ASU. Both strains, AS2, an unmanipulated natural isolate which flocculated readily in liquid media, and P. putida ASR2.8, a transconjugant containing the recombinant plasmid pD10, survived for long periods in the ASU and enhanced 3CB breakdown at 15 degrees C. The results reported in this paper illustrate the importance of choosing strains which are well adapted to environmental conditions if the use of microbial inoculants for the breakdown of target pollutants is to be successful.

McClure, N.C.; Fry, J.C.; Weightman, A.J. (Univ. of Wales College of Cardiff (Wales))

1991-02-01

201

Fault healing promotes high-frequency earthquakes in laboratory experiments and on natural faults  

USGS Publications Warehouse

Faults strengthen or heal with time in stationary contact and this healing may be an essential ingredient for the generation of earthquakes. In the laboratory, healing is thought to be the result of thermally activated mechanisms that weld together micrometre-sized asperity contacts on the fault surface, but the relationship between laboratory measures of fault healing and the seismically observable properties of earthquakes is at present not well defined. Here we report on laboratory experiments and seismological observations that show how the spectral properties of earthquakes vary as a function of fault healing time. In the laboratory, we find that increased healing causes a disproportionately large amount of high-frequency seismic radiation to be produced during fault rupture. We observe a similar connection between earthquake spectra and recurrence time for repeating earthquake sequences on natural faults. Healing rates depend on pressure, temperature and mineralogy, so the connection between seismicity and healing may help to explain recent observations of large megathrust earthquakes which indicate that energetic, high-frequency seismic radiation originates from locations that are distinct from the geodetically inferred locations of large-amplitude fault slip

McLaskey, Gregory C.; Thomas, Amanda M.; Glaser, Steven D.; Nadeau, Robert M.

2012-01-01

202

Design and validation of laboratory-scale simulations for selecting tribomaterials and surface treatments  

SciTech Connect

Engineering approaches to solving tribology problems commonly involve friction, lubrication, or wear testing, either in the field or in a laboratory setting. Since wear and friction are properties of the materials in the larger context of the tribosystem, the selection of appropriate laboratory tribotesting procedures becomes critically important. Laboratory simulations must exhibit certain key characteristics of the application in order for the test results to be relevant, but they may not have to mimic all operating conditions. The current paper illustrates a step-by-step method to develop laboratory-scale friction and wear simulations based on a tribosystem analysis. Quantitative or qualitative metrics are established and used to validate the effectiveness of the tribosimulation. Sometimes standardized test methods can be used, but frequently a new type of test method or procedure must be developed. There are four factors to be addressed in designing effective simulations: (1) contact macrogeometry and the characteristics of relative motion, (2) pressure--velocity relationships, (3) thermal and chemical environment (including type of lubrication), and (4) the role of third-bodies. In addition, there are two typical choices of testing philosophy: (1) the worst-case scenario and, (2) the nominal-operations scenario. Examples of the development and use of simulative friction and wear tests are used to illustrate major points.

Blau, P.J. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1997-05-01

203

Naturally occurring high chloride coal and superheater corrosion - a laboratory study  

SciTech Connect

The fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals was investigated. The results of the laboratory and field tests were previously reported. In a supplementary phase of the program, the effect of chloride on similar alloys while firing a naturally occurring high chloride Midwestern bituminous coal in the same laboratory furnace were studied. On the basis of exposure in the convection pass at temperatures from 1100 to 1700 F, Inconel Alloy 690 was very good while Incoloy 800 and Tp-310 S.S. were good transitional materials. Poor materials were T-22, 316S.S., Inconel 617, and Inconel 671. 4 refs.

Plumley, A.L.; Roczniak, W.R.

1981-01-01

204

Population Genetics of Drosophila Amylase. IV. Selection in Laboratory Populations Maintained on Different Carbohydrates  

PubMed Central

Two polymorphic systems impinging on ?-amylase in Drosophila pseudoobscura have been studied in laboratory populations maintained on medium in which the only carbohydrate source was starch (the substrate of amylase) and replicas maintained on medium in which the only carbohydrate source was maltose (the product of amylase). The two polymorphic systems were alleles at the structural gene (Amy) coding for the enzyme (allozymes) and variation in the tissue-specific expression along the adult midgut controlled by several genes. In the seven populations on maltose medium little consistent change was noted in either system. In the seven populations on starch medium, both polymorphisms exhibited selective changes. A midgut pattern of very limited expression of amylase rose in frequency in all starch populations, as did the frequency of the "fast" (1.00) Amy allele. The overall specific amylase activity did not differ between starch-adapted and maltose-adapted flies.—The results, along with previous studies, indicate that when a gene-enzyme system is specifically stressed in laboratory populations, allozymes often exhibit selective differences. Such results make the selectionist hypothesis at least tenable. Furthermore, the fact that both types of polymorphisms responded to selection indicates the role of structural gene vs. gene regulation changes in adaptive evolution is not an either/or question but one of relative roles and interactions.

Powell, Jeffrey R.; Andjelkovic, Marko

1983-01-01

205

Nucleation of Laboratory Earthquakes: Observation, Characterization, and Scaling up to the Natural Earthquakes Dimensions  

NASA Astrophysics Data System (ADS)

In this work we observe the nucleation phase of in-plane ruptures in the laboratory and characterize its dynamics. We use a laboratory toy-model, where mode II shear ruptures are produced on a pre-cut fault in a plate of polycarbonate. The fault is cut at the critical angle that allows a stick-slip behavior under uniaxal loading. The ruptures are thus naturally nucleated. The material is birefringent under stress, so that the rupture propagation can be followed by ultra-rapid elastophotometry. A network of acoustic sensors and accelerometers is disposed on the plate to measure the radiated wavefield and record laboratory near-field accelograms. The far field stress level is also measured using strain gages. We show that the nucleation is composed of two distinct phases, a quasi-static and an acceleration stage, followed by dynamic propagation. We propose an empirical model which describes the rupture length evolution: the quasi-static phase is described by an exponential growth while the acceleration phase is described by an inverse power law of time. The transition from quasistatic to accelerating rupture is related to the critical nucleation length, which scales inversely with normal stress in accordance with theoretical predictions, and to a critical surfacic power, which may be an intrinsic property of the interface. Finally, we discuss these results in the frame of previous studies and propose a scaling up to natural earthquake dimensions. Three spontaneously nucleated laboratory earthquakes at increasingly higher normal pre-stresses, visualized by photo-elasticity. The red curves highlight the position of rupture tips as a function of time. We propose an empirical model that describes the dynamics of rupture nucleation and discuss its scaling with the initial normal stress.

Latour, S.; Schubnel, A.; Nielsen, S. B.; Madariaga, R. I.; Vinciguerra, S.

2013-12-01

206

What can abnormal environments tell us about normal people? Polar stations as natural psychology laboratories.  

PubMed

The psychological effects of unusual environments reveal different aspects of behaviour from those seen in more customary situations. Such environments provide natural laboratories in which many questions of psychological interest, varying with the specific environment, may be studied. This paper uses isolated polar stations to illustrate this point. In such settings, the usual parameters that control a variety of psychological processes are drastically changed, and confounding variables are stripped away. Consequently, the environment offers unique perspectives on environmental perception and cognition; adaptation to and use of the environment; environmental bonding; social interaction; and coping with environmental challenge. PMID:11541914

Suedfeld, P

1998-03-01

207

Geographical structure and differential natural selection among North European populations  

PubMed Central

Population structure can provide novel insight into the human past, and recognizing and correcting for such stratification is a practical concern in gene mapping by many association methodologies. We investigate these patterns, primarily through principal component (PC) analysis of whole genome SNP polymorphism, in 2099 individuals from populations of Northern European origin (Ireland, United Kingdom, Netherlands, Denmark, Sweden, Finland, Australia, and HapMap European-American). The major trends (PC1 and PC2) demonstrate an ability to detect geographic substructure, even over a small area like the British Isles, and this information can then be applied to finely dissect the ancestry of the European-Australian and European-American samples. They simultaneously point to the importance of considering population stratification in what might be considered a small homogeneous region. There is evidence from FST-based analysis of genic and nongenic SNPs that differential positive selection has operated across these populations despite their short divergence time and relatively similar geographic and environmental range. The pressure appears to have been focused on genes involved in immunity, perhaps reflecting response to infectious disease epidemic. Such an event may explain a striking selective sweep centered on the rs2508049-G allele, close to the HLA-G gene on chromosome 6. Evidence of the sweep extends over a 8-Mb/3.5-cM region. Overall, the results illustrate the power of dense genotype and sample data to explore regional population variation, the events that have crafted it, and their implications in both explaining disease prevalence and mapping these genes by association.

McEvoy, Brian P.; Montgomery, Grant W.; McRae, Allan F.; Ripatti, Samuli; Perola, Markus; Spector, Tim D.; Cherkas, Lynn; Ahmadi, Kourosh R.; Boomsma, Dorret; Willemsen, Gonneke; Hottenga, Jouke J.; Pedersen, Nancy L.; Magnusson, Patrik K.E.; Kyvik, Kirsten Ohm; Christensen, Kaare; Kaprio, Jaakko; Heikkila, Kauko; Palotie, Aarno; Widen, Elisabeth; Muilu, Juha; Syvanen, Ann-Christine; Liljedahl, Ulrika; Hardiman, Orla; Cronin, Simon; Peltonen, Leena; Martin, Nicholas G.; Visscher, Peter M.

2009-01-01

208

The Use of Decision Analysis Tools for the Selection of Clinical Laboratory Tests: Developing Diagnostic and Forecasting Models Using Laboratory Evidence  

Microsoft Academic Search

\\u000a The number and complexity of available laboratory tests continues to increase at a rapid pace. Staying current with accepted\\u000a standards for laboratory testing for diagnosis, monitoring and prognosis is extremely challenging, particularly for nonspecialists\\u000a who see a diverse patient population. Decision support tools to aid physicians in appropriate test selection and interpretation\\u000a are widely available and will become increasingly important.

Ji Yeon Kim; Elizabeth M. Van Cott; Kent B. Lewandrowski

209

A Nature of Gravitation and the Problem of the Laboratory Gravitational Waves Generation  

NASA Astrophysics Data System (ADS)

This work sheds light on nature of gravitation and vacuum structure to offer new possibilities for the laboratory HFGWs generation, since neither Einstein's GR nor any another theory of gravity not make answer on this question. Well-known hypothesis about non-materiality of gravitation field unambiguously leads to representation that the elemental particles (EPs) are gravitational stabilized substance. By their nature EPs would constitute microscopic black holes with extreme curved space-time into their bulk and in the vicinity. Since EPs birth take place at interaction of photons with polarized vacuum, this latter represents medium consisting from massless gravitational skeletons of known EPs. So the particle can be not born without its antiparticle and vacuum is gravitationally neutral, particle and antiparticle skeleton, must possess gravitation and antigravitation, correspondingly. GWs would be represented oscillations of the EPs gravitational and antigravitational skeletons around the common centre and in consequence they would be transverse. The high penetrating ability of GWs is a result that neither vacuum, in which HFGWs are propagated, nor HFGWs, does not have mass (energy). In the concept frameworks a new RTG, which must be confirmed these representations, is developed. However, already the fact by itself the laboratory generation of GWs is the direct proof of correctness of these representations.

Kanibolotsky, Valentyn

2010-01-01

210

Composition of Bacterial Communities Associated with Natural and Laboratory Populations of Asobara tabida Infected with Wolbachia? †  

PubMed Central

Asobara tabida wasps are fly endoparasitoids that naturally harbor three Wolbachia strains, which induce cytoplasmic incompatibility and control oogenesis. To investigate whether other bacteria play a role in wasp biology, we surveyed the bacterial communities of wild A. tabida populations originating from different regions of France and of laboratory colonies using PCR-denaturing gradient gel electrophoresis and culture methods. Proteobacteria and Firmicutes were found to be the main phyla represented in these populations. Among these were several cultured and uncultured representatives of the genera Acetobacter, Acidomonas, Bacillus, Brevibacillus, Duganella, Herbaspirillum, Pseudomonas, Staphylococcus, and Streptococcus. In addition to Wolbachia, wild individuals harbored Rickettsia, which tended to be lost when insects were reared in the laboratory. The antibiotic treatment used to generate wasp sublines singly infected with Wolbachia also affected the overall bacterial composition, with most fingerprint sequences being characteristic of the family Enterobacteriaceae. We also screened for potentially heritable endosymbionts by PCR and fluorescence in situ hybridization in stable laboratory lines, with only Wolbachia being consistently found in wasp ovaries.

Zouache, Karima; Voronin, Denis; Tran-Van, Van; Mavingui, Patrick

2009-01-01

211

Epistasis and natural selection shape the mutational architecture of complex traits.  

PubMed

The evolutionary trajectories of complex traits are constrained by levels of genetic variation as well as genetic correlations among traits. As the ultimate source of all genetic variation is mutation, the distribution of mutations entering populations profoundly affects standing variation and genetic correlations. Here we use an individual-based simulation model to investigate how natural selection and gene interactions (that is, epistasis) shape the evolution of mutational processes affecting complex traits. We find that the presence of epistasis allows natural selection to mould the distribution of mutations, such that mutational effects align with the selection surface. Consequently, novel mutations tend to be more compatible with the current forces of selection acting on the population. These results suggest that in many cases mutational effects should be seen as an outcome of natural selection rather than as an unbiased source of genetic variation that is independent of other evolutionary processes. PMID:24828461

Jones, Adam G; Bürger, Reinhard; Arnold, Stevan J

2014-01-01

212

Evaluation of Selected Laboratory Components of a Comprehensive Periodic Health Evaluation for Veterans With Spinal Cord Injury and Disorders  

Microsoft Academic Search

Choi H, Binder DS, Oropilla ML, Bernotus EE, Konya D, Nee MA, Tammaro EA, Sabharwal S. Evaluation of selected laboratory components of a comprehensive periodic health evaluation for veterans with spinal cord injury and disorders.

Howard Choi; David S. Binder; Marjorie L. Oropilla; Ervin E. Bernotus; Deniz Konya; Maura A. Nee; Elizabeth A. Tammaro; Sunil Sabharwal

2006-01-01

213

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

PubMed

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

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

2014-06-01

214

Evidence that Natural Selection on Codon Usage in Drosophila pseudoobscura Varies Across Codons  

PubMed Central

Like other species of Drosophila, Drosophila pseudoobscura has a distinct bias toward the usage of C- and G-ending codons. Previous studies have indicated that this bias is due, at least in part, to natural selection. Codon bias clearly differs among amino acids (and other codon classes) in Drosophila, which may reflect differences in the intensity of selection on codon usage. Ongoing natural selection on synonymous codon usage should be reflected in the shapes of the site frequency spectra of derived states at polymorphic positions. Specifically, regardless of other demographic effects on the spectrum, it should be shifted toward higher values for changes from less-preferred to more-preferred codons, and toward lower values for the converse. If the intensity of natural selection is increased, shifts in the site frequency spectra should be more pronounced. A total of 33,729 synonymous polymorphic sites on Chromosome 2 in D. pseudoobscura were analyzed. Shifts in the site frequency spectra are consistent with differential intensity of natural selection on codon usage, with stronger shifts associated with higher codon bias. The shifts, in general, are greater for polymorphic synonymous sites than for polymorphic intron sites, also consistent with natural selection. However, unlike observations in D. melanogaster, codon bias is not reduced in areas of low recombination in D. pseudoobscura; the site frequency spectrum signal for selection on codon usage remains strong in these regions. However, diversity is reduced, as expected. It is possible that estimates of low recombination reflect a recent change in recombination rate.

Kliman, Richard M.

2014-01-01

215

Selective attention and heart rate responses to natural and urban environments  

Microsoft Academic Search

We tested the hypothesis that exposure to nature stimuli restores depleted voluntary attention capacity and affects selective attention. Before viewing a video of either a natural or an urban environment, 28 subjects first completed a proofreading task to induce mental load and then performed Posner's attention-orienting task. After viewing the video they performed the attention-orienting task a second time. Cardiac

Karin Laumann; Tommy Gärling; Kjell Morten Stormark

2003-01-01

216

Selecting healthy volunteers in specific populations: a retrospective analysis of clinical and laboratory screening.  

PubMed

Healthy volunteers must undergo a medical examination before enrollment in a clinical trial. An increasing number of trials include specific populations designed to match the target populations of the drugs tested. Our study aimed at evaluating which investigations are the most appropriate in different sub-populations of healthy volunteers. Data from 350 healthy volunteers who attended our Research Center from 1997 to 2004 were retrospectively analysed. Volunteers were distributed into five sub-populations: young men, senior men, overweight men, young women, postmenopausal women. The screening procedure comprised a review of medical history, physical examination, electrocardiogram and laboratory tests. Ineligibility criteria were classified as non-medical causes, protocol specific medical causes and non-specific medical causes. A total of 148 subjects (42%) were not-eligible, mainly because of non-specific medical causes (111 subjects), including abnormal medical history (34.5% of all ineligibilities). Blood pressure abnormalities were frequent in all sub-populations except young women. Electrocardiographic abnormalities led to ineligibility of only five overweight men and one menopausal woman. Abnormal laboratory tests accounted for 19.6% of ineligibilities. In senior subjects and overweight men, serologies, liver function tests and lipid profile contributed importantly to the selection process. Low red cells count was the most frequent laboratory abnormality in young women. Erythrocyte sedimentation rate, phosphocalcic metabolism and standard clotting tests led to frequent insignificant and non-contributive abnormalities. Our study confirms that a complete review of medical history is essential and determines the major part of ineligibilities. Complementary laboratory tests are always needed and may be adjusted to the population considered. PMID:19686534

Roux, Clarisse; Chevassus, Hugues; Farret, Anne; Costa, Françoise; Petit, Pierre; Galtier, Florence

2010-02-01

217

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

218

Evaluating the role of natural selection in the evolution of gene regulation  

Microsoft Academic Search

Surveys of gene expression reveal extensive variability both within and between a wide range of species. Compelling cases have been made for adaptive changes in gene regulation, but the proportion of expression divergence attributable to natural selection remains unclear. Distinguishing adaptive changes driven by positive selection from neutral divergence resulting from mutation and genetic drift is critical for understanding the

J C Fay; P J Wittkopp

2008-01-01

219

Evaluating the role of natural selection in the evolution of gene regulation  

Microsoft Academic Search

Surveys of gene expression reveal extensive variability both within and between a wide range of species. Compelling cases have been made for adaptive changes in gene regulation, but the proportion of expression divergence attributable to natural selection remains unclear. Distinguish- ing adaptive changes driven by positive selection from neutral divergence resulting from mutation and genetic drift is critical for understanding

JC Fay; PJ Wittkopp

2007-01-01

220

The Nature of Selection and Judging for the Teacher of the Year Award.  

ERIC Educational Resources Information Center

This paper reports on the investigation of the operation of the Teacher of the Year Award program in 28 states. It focuses on the method of selection for recipients of this award, and explores the nature of the judging process used in selecting candidates at both the state and national levels. Specific objectives are: (1) to determine the criteria…

McKenna, Bonnie; And Others

221

Reduced Natural Selection Associated with Low Recombination in Drosophila melanogaster 1  

Microsoft Academic Search

for translational efficiency. We link this model of varying selection intensity to the population-genetics prediction that the effectiveness of natural selection is decreased under reduced recombination. In analyses of 385 D. melunoguster loci, we find that codon bias is reduced in regions of low recombination (i.e., near centromeres and telomeres and on the fourth chromosome). The effect does not appear

Richard Ml Kliman; Jody Hey

222

The Beanbag Genetics Controversy: Towards a synthesis of opposing views of natural selection  

Microsoft Academic Search

The beanbag genetics controversy can be traced from the dispute between Fisher and Wright, through Mayr's influential promotion of the issue, to the contemporary units of selection debate. It centers on the claim that genic models of natural selection break down in the face of epistatic interactions among genes during phenotypic development. This claim is explored from both a conceptual

WILLEM DE WINTER

1997-01-01

223

Synonymous Codon Usage in Drosophila melanogaster: Natural Selection and Translational Accuracy  

Microsoft Academic Search

I present evidence that natural selection biases synonymous codon usage to enhance the accuracy of protein synthesis in Drosophila melanogaster. Since the fitness cost of a translational misincorporation will depend on how the amino acid substitution affects protein function, selection for translational accuracy predicts an association between codon usage in DNA and functional constraint at the protein level. The frequency

Hiroshi Akashi

1994-01-01

224

How selection pressure changes the nature of social dilemmas in structured populations  

NASA Astrophysics Data System (ADS)

When members of a population engage in dyadic interactions reflecting a prisoner's dilemma game, the evolutionary dynamics depends crucially on the population structure, described by means of graphs and networks. Here, we investigate how selection pressure contributes to change the fate of the population. We find that homogeneous networks, in which individuals share a similar number of neighbors, are very sensitive to selection pressure, whereas strongly heterogeneous networks are more resilient to natural selection, dictating an overall robust evolutionary dynamics of coordination. Between these extremes, a whole plethora of behaviors is predicted, showing how selection pressure can change the nature of dilemmas populations effectively face. We further show how the present results for homogeneous networks bridge the existing gap between analytic predictions obtained in the framework of the pair-approximation from very weak selection and simulation results obtained from strong selection.

Pinheiro, Flávio L.; Santos, Francisco C.; Pacheco, Jorge M.

2012-07-01

225

SELECTIVE NOx RECIRCULATION FOR STATIONARY LEAN-BURN NATURAL GAS ENGINES  

SciTech Connect

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.

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

2005-01-01

226

Assessment of laboratory logistics management information system practice for HIV/AIDS and tuberculosis laboratory commodities in selected public health facilities in Addis Ababa, Ethiopia  

PubMed Central

Introduction Logistics management information system for health commodities remained poorly implemented in most of developing countries. To assess the status of laboratory logistics management information system for HIV/AIDS and tuberculosis laboratory commodities in public health facilities in Addis Ababa. Methods A cross-sectional descriptive study was conducted from September 2010-January 2011 at selected public health facilities. A stratified random sampling method was used to include a total of 43 facilities which, were investigated through quantitative methods using structured questionnaires interviews. Focus group discussion with the designated supply chain managers and key informant interviews were conducted for the qualitative method. Results There exists a well-designed logistics system for laboratory commodities with trained pharmacy personnel, distributed standard LMIS formats and established inventory control procedures. However, majority of laboratory professionals were not trained in LMIS. Majority of the facilities (60.5%) were stocked out for at least one ART monitoring and TB laboratory reagents and the highest stock out rate was for chemistry reagents. Expired ART monitoring laboratory commodities were found in 25 (73.5%) of facilities. Fifty percent (50%) of the assessed hospitals and 54% of health centers were currently using stock/bin cards for all HIV/AIDS and TB laboratory commodities in main pharmacy store, among these only 25% and 20.8% of them were updated with accurate information matching with the physical count done at the time of visit for hospitals and health centers respectively. Conclusion Even though there exists a well designed laboratory LMIS, keeping quality stock/bin cards and LMIS reports were very low. Key ART monitoring laboratory commodities were stock out at many facilities at the day of visit and during the past six months. Based on findings, training of laboratory personnel's managing laboratory commodities and keeping accurate inventory control procedures were recommended.

Desale, Adino; Taye, Bineyam; Belay, Getachew; Nigatu, Alemayehu

2013-01-01

227

Acoustic and resistivity measurements on rock samples containing tetrahydrofuran hydrates: laboratory analogues to natural gas hydrate deposits  

Microsoft Academic Search

In this paper we report laboratory acoustic velocity and electrical resistivity measurements on Berea Sandstone and Austin Chalk samples saturated with a stoichiometric mixture of tetrahydofuran (THF) and water. The and water is an excellent experimental analogue to natural gas hydrates because THF solutions form hydrates similar to natural gas hydrates readily at atmospheric pressures. Hydrate formation in both the

C. Pearson; J. Murphy; R. Hermes

1986-01-01

228

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

PubMed

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

Artacho, Paulina; Nespolo, Roberto F

2009-04-01

229

Emergence of life: from functional RNA selection to natural selection and beyond.  

PubMed

This study tracks the rise, evolution and post-evolution of the genetic information system through emergence of life. The major stages traversed include prebiotic synthesis, functional RNA selection by metabolite, RNA World, peptidated RNA world, co-evolution of genetic code and amino acid biosynthesis, last universal common ancestor, Darwinian evolution and synthetic life. PMID:24896340

Wong, Jeffrey Tze-Fei

2014-01-01

230

Natural Selection Affects Multiple Aspects of Genetic Variation at Putatively Neutral Sites across the Human Genome  

PubMed Central

A major question in evolutionary biology is how natural selection has shaped patterns of genetic variation across the human genome. Previous work has documented a reduction in genetic diversity in regions of the genome with low recombination rates. However, it is unclear whether other summaries of genetic variation, like allele frequencies, are also correlated with recombination rate and whether these correlations can be explained solely by negative selection against deleterious mutations or whether positive selection acting on favorable alleles is also required. Here we attempt to address these questions by analyzing three different genome-wide resequencing datasets from European individuals. We document several significant correlations between different genomic features. In particular, we find that average minor allele frequency and diversity are reduced in regions of low recombination and that human diversity, human-chimp divergence, and average minor allele frequency are reduced near genes. Population genetic simulations show that either positive natural selection acting on favorable mutations or negative natural selection acting against deleterious mutations can explain these correlations. However, models with strong positive selection on nonsynonymous mutations and little negative selection predict a stronger negative correlation between neutral diversity and nonsynonymous divergence than observed in the actual data, supporting the importance of negative, rather than positive, selection throughout the genome. Further, we show that the widespread presence of weakly deleterious alleles, rather than a small number of strongly positively selected mutations, is responsible for the correlation between neutral genetic diversity and recombination rate. This work suggests that natural selection has affected multiple aspects of linked neutral variation throughout the human genome and that positive selection is not required to explain these observations.

Lohmueller, Kirk E.; Albrechtsen, Anders; Li, Yingrui; Kim, Su Yeon; Korneliussen, Thorfinn; Vinckenbosch, Nicolas; Tian, Geng; Huerta-Sanchez, Emilia; Feder, Alison F.; Grarup, Niels; J?rgensen, Torben; Jiang, Tao; Witte, Daniel R.; Sandbaek, Annelli; Hellmann, Ines; Lauritzen, Torsten; Hansen, Torben

2011-01-01

231

Darwin's principles of divergence and natural selection: Why Fodor was almost right.  

PubMed

Darwin maintained that the principles of natural selection and divergence were the "keystones" of his theory. He introduced the principle of divergence to explain a fundamental feature of living nature: that organisms cluster into hierarchical groups, so as to be classifiable in the Linnaean taxonomic categories of variety, species, genus, and so on. Darwin's formulation of the principle of divergence, however, induces many perplexities. In his Autobiography, he claimed that he had neglected the problem of divergence in his Essay of 1844 and only solved it in a flash during a carriage ride in the 1850s; yet he does seem to have stated the problem in the Essay and provided the solution. This initial conundrum sets three questions I wish to pursue in this essay: (1) What is the relationship of the principle of divergence to that of natural selection? Is it independent of selection, derivative of selection, or a type of selection, perhaps comparable to sexual selection? (2) What is the advantage of divergence that the principle implies-that is, why is increased divergence beneficial in the struggle for life? And (3) What led Darwin to believe he had discovered the principle only in the 1850s? The resolution of these questions has implications for Darwin's other principle, natural selection, and permits us to readjust the common judgment made about Jerry Fodor's screed against that latter principle. PMID:22326095

Richards, Robert J

2012-03-01

232

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

233

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

USGS Publications Warehouse

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.

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

2011-01-01

234

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

SciTech Connect

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.

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

1995-11-01

235

Laboratory selection for and characteristics of pyrethroid resistance in the malaria vector Anopheles funestus.  

PubMed

A laboratory colony of Anopheles funestus Giles (Diptera: Culicidae) was established in 2000 from material collected from southern Mozambique where pyrethroid resistance had been demonstrated in the wild population. A subsample of the colony was selected for pyrethroid resistance using 0.1% lambda-cyhalothrin. Bioassay susceptibility tests in subsequent generations F(2) to F(4) showed increased resistance with each successive generation. Survival of individual mosquitoes fed only on 10% sugar solution, increased with age up to 4 days, but by day 10 had decreased significantly. However, females that had been mated and given bloodmeals showed no such increase in mortality with age. Biochemical analysis of resistant and susceptible individuals showed increased monooxygenase and glutathione S-transferase activity but no significant correlation with age of the mosquitoes. PMID:16134975

Hunt, R H; Brooke, B D; Pillay, C; Koekemoer, L L; Coetzee, M

2005-09-01

236

Natural infection of murine norovirus in conventional and specific pathogen-free laboratory mice  

PubMed Central

Noroviruses cause most cases of acute viral gastroenteritis worldwide. The lack of a cell culture infection model for human norovirus necessitates the use of molecular methods and/or viral surrogate models amenable to cell culture to predict norovirus inactivation. Murine norovirus (MNV) may be used to construct a small animal model for studying the biology and pathogenesis of noroviruses because MNV is the only norovirus that replicates in cell culture and a small animal model. However, recent studies have shown that natural MNV infection is widespread in laboratory mouse colonies. We investigated MNV infection in both conventional and specific pathogen-free (SPF) genetically modified mice from Japan and the US, and commercial mice from several animal breeders in Japan, using serological and molecular techniques. MNV antibodies were detected in 67.3% of conventional mice and 39.1% of SPF mice from Japan and 62.5% of conventional mice from the US. MNV antibodies were also found in 20% of commercial SPF C57BL/6 mice from one of three breeders. Partial gene amplification of fecal isolates from infected animals showed that the isolates were homologous to reported MNV sequences. These results suggest that both conventional and SPF laboratory mice, including commercial mice, are widely infected with MNV, which might require considerable attention as an animal model of human disease.

Ohsugi, Takeo; Matsuura, Kumi; Kawabe, Satomi; Nakamura, Naoko; Kumar, Jerald M.; Wakamiya, Makoto; Morikawa, Saki; Urano, Toru

2013-01-01

237

Natural Selection  

NSDL National Science Digital Library

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.

Consortium, The C.

2011-12-11

238

Natural Selection  

ERIC Educational Resources Information Center

For education administrators, summer break is the time to regroup and prepare facilities for the next influx of students. Ensuring that facilities are equipped with proper furnishings is part of this preparation. Through careful research and planning, education administrators can choose furniture that will become a lasting investment. This article…

Hall, Julie

2006-01-01

239

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

PubMed

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

Varenhorst, A J; O'Neal, M E

2012-12-01

240

An investigation of Zimbabwe high school chemistry students' laboratory work-based images of the nature of science  

NASA Astrophysics Data System (ADS)

This study investigates the proximal and distal images of the nature of science (NOS) that A-level students develop from their participation in chemistry laboratory work. We also explored the nature of the interactions among the students' proximal and distal images of the NOS and students' participation in laboratory work. Students' views of the NOS and the nature of their chemistry laboratory work were elicited through students' responses to an open-ended questionnaire and semistructured interviews. The results suggest that students build some understandings of the NOS from their participation in laboratory work. Students' proximal NOS understandings appear to build into and interact with their understandings of the nature and practice of professional science. This interaction appears to be mediated by the nature of instruction. It is posited that each student's conceptual ecological system is replete with interactions, which govern attenuation of proximal understandings into distal images. Methodologically, the study illustrates how students' laboratory work-based proximal and distal images of the NOS can be identified and extracted through analyzing and interpreting their responses to protocols. Implications for A-level Chemistry instruction and curriculum development are raised.

Vhurumuku, Elaosi; Holtman, Lorna; Mikalsen, Oyvind; Kolsto, Stein D.

2006-02-01

241

Evidence that Natural Selection on Codon Usage in Drosophila pseudoobscura Varies Across Codons.  

PubMed

Like other species of Drosophila, Drosophila pseudoobscura has a distinct bias toward the usage of C- and G-ending codons. Previous studies have indicated that this bias is due, at least in part, to natural selection. Codon bias clearly differs among amino acids (and other codon classes) in Drosophila, which may reflect differences in the intensity of selection on codon usage. Ongoing natural selection on synonymous codon usage should be reflected in the shapes of the site frequency spectra of derived states at polymorphic positions. Specifically, regardless of other demographic effects on the spectrum, it should be shifted toward higher values for changes from less-preferred to more-preferred codons, and toward lower values for the converse. If the intensity of natural selection is increased, shifts in the site frequency spectra should be more pronounced. A total of 33,729 synonymous polymorphic sites on Chromosome 2 in D. pseudoobscura were analyzed. Shifts in the site frequency spectra are consistent with differential intensity of natural selection on codon usage, with stronger shifts associated with higher codon bias. The shifts, in general, are greater for polymorphic synonymous sites than for polymorphic intron sites, also consistent with natural selection. However, unlike observations in D. melanogaster, codon bias is not reduced in areas of low recombination in D. pseudoobscura; the site frequency spectrum signal for selection on codon usage remains strong in these regions. However, diversity is reduced, as expected. It is possible that estimates of low recombination reflect a recent change in recombination rate. PMID:24531731

Kliman, Richard M

2014-01-01

242

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines  

Microsoft Academic Search

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)

Nigel N. Clark

2006-01-01

243

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

PubMed

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

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

2014-06-01

244

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

PubMed

Abstract 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

Grant, Peter R; Grant, B Rosemary

2014-05-01

245

USING POPULATION GENOMICS TO DETECT SELECTION IN NATURAL POPULATIONS: KEY CONCEPTS AND METHODOLOGICAL CONSIDERATIONS  

PubMed Central

Natural selection shapes patterns of genetic variation among individuals, populations, and species, and it does so differentially across genomes. The field of population genomics provides a comprehensive genome-scale view of the action of selection, even beyond traditional model organisms. However, even with nearly complete genomic sequence information, our ability to detect the signature of selection on specific genomic regions depends on choosing experimental and analytical tools appropriate to the biological situation. For example, processes that occur at different timescales, such as sorting of standing genetic variation, mutation-selection balance, or fixed interspecific divergence, have different consequences for genomic patterns of variation. Inappropriate experimental or analytical approaches may fail to detect even strong selection or falsely identify a signature of selection. Here we outline the conceptual framework of population genomics, relate genomic patterns of variation to evolutionary processes, and identify major biological factors to be considered in studies of selection. As data-gathering technology continues to advance, our ability to understand selection in natural populations will be limited more by conceptual and analytical weaknesses than by the amount of molecular data. Our aim is to bring critical biological considerations to the fore in population genomics research and to spur the development and application of analytical tools appropriate to diverse biological systems.

Hohenlohe, Paul A.; Phillips, Patrick C.; Cresko, William A.

2010-01-01

246

Germination of Ocotea pulchella (Nees) Mez (Lauraceae) seeds in laboratory and natural restinga environment conditions.  

PubMed

The germination response of Ocotea pulchella (Nees) Mez seeds to light, temperature, water level and pulp presence is introduced. The laboratory assays were carried out in germination chambers and thermal-gradient apparatus, whereas the field assays were performed in environments with distinct light, temperature and soil moisture conditions within a permanent parcel of Restinga forest of the Parque Estadual da Ilha do Cardoso, Cananéia, São Paulo. The seeds do not exhibit dormancy, they are non photoblastic, and a loss of viability in dry stored seeds can be related to a decrease in water content of the seed. The presence of the pulp and the flooded substratum influenced negatively the germination of O. pulchella seeds tested in the laboratory. Otherwise, light and temperature probably are not limiting factors of the germination of O. pulchella seeds in the natural environment of Restinga. The optimum temperature range for germination of Ocotea pulchella seeds was 20 to 32 degrees C, the minimum or base temperature estimated was 11 degrees C and the maximum ranged between 33 and 42 degrees C. The isotherms exhibited a sigmoidal pattern well described by the Weibull model in the sub-optimal temperature range. The germinability of O. pulchella seeds in the understorey, both in wet and dry soil, was higher than in gaps. Germination was not affected by fluctuations in soil moisture content in the understorey environment, whereas in gaps, germination was higher in wet soils. Thus, the germination of this species involves the interaction of two or more factors and it cannot be explained by a single factor. PMID:19802455

Pires, L A; Cardoso, V J M; Joly, C A; Rodrigues, R R

2009-08-01

247

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

NASA Astrophysics Data System (ADS)

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 employ it as an educational tool to inform his contemporaries about his findings. Moreover, by using the metaphor Darwin was able to bring his theory in accordance with both the dominant philosophy of science in his time and the respected tradition of natural theology. However, as he introduced his theory of evolution by natural selection in On the origin of species in 1859, the metaphor also turned out to have a serious downside. Because of its intentional overtones, his contemporaries systematically misunderstood his metaphor not as a natural mechanism causing evolution to occur but as an agent who works towards particular ends. The difference in success between natural selection as an epistemic tool and its failure as an educational tool is labelled as a paradox. We explain the paradox from a cognitive perspective and discuss the implications for teaching evolution.

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

2014-04-01

248

West Florida Shelf: A natural laboratory for the study of ocean acidificiation  

USGS Publications Warehouse

Declining oceanic pH and carbonate-ion concentrations are well-known consequences of increased atmospheric and surface-ocean partial pressure of carbon dioxide (pCO2). The possible subject of shifts in seawater carbonate chemistry on biocalcification and survival rates of marine organisms provides questions amenable to both experimental and field study (Kleypas and Langdon, 2006). To date, limited quantitative data exist with which to formalize and test hypotheses regarding such impacts, particularly in continental-shelf settings. The continental shelves of Florida provide an ideal natural laboratory in which to test latitudinal (and temperature and depth) shifts in habitat ranges of calcifying organisms. Both the east and west Florida shelves extend from warm temperate to subtropical latitudes; additionally, the west Florida shelf has very little siliciclastic influx to mask the carbonate production. This study utilizes the natural laboratory of the west and southwest Florida shelf (fig 1.1) to examine the transition from foramol (predominately foraminifera and molluscan) carbonate sediments, characteristic of the west-central Florida shelf, to chlorozoan (algal and coral) sediments characteristic of the southwest Florida shelf. The west Florida shelf is a mixed siliciclastic carbonate ramp that to the south transitions to the carbonate-dominated southwest Florida shelf (Enos, 1977; Brooks and others, 2003). The west Florida shelf is a distally steepened carbonate ramp that is ~250 kilometers (km) wide (Read, 1985). It is covered by a veneer of unconsolidated sediment consisting of mainly biogenic carbonate and quartz in the near shore, with subordinate amounts of phosphate. The sediment-distribution pattern is largely a function of proximity to source, with physical processes playing a minor role in distribution. The carbonate sand-and-gravel fraction is produced by organisms within the depositional basin of the west Florida shelf (Brooks and others, 2003). The southwest Florida shelf is a rimmed carbonate margin where organisms produce virtually all of the substrate; it also exhibits a greater sediment thickness as compared to the west Florida shelf (Enos, 1977). Temperature, which is usually associated with latitude, plays a major role in locations of foramol versus chlorozoan assemblages, but other factors beyond latitude influence temperature on the west and southwest Florida shelves. The potential of cooler, deep-water upwelling and transport over the bottom waters of the shelf may have a significant role in the species assemblage at the sediment/water interface and ultimately on location of foramol versus chlorozoan production. Deep water transported onto and over the shelf may also have environmental ramifications beyond temperature by bringing in water of different chemistry.

Hallock, Pamela; Robbins, Lisa L.; Larson, Rebekka; Beck, Tanya; Schwing, Patrick; Martinez-Colon, Michael; Gooch, Brad

2010-01-01

249

Using a semi-natural stream to produce young sturgeons for conservation stocking: Maintaining natural selection during spawning and rearing  

USGS Publications Warehouse

Young sturgeons used for conservation stocking are presently produced using the same methods used for commercial culture. To determine if young sturgeons could be produced without relaxing natural selection factors, we developed a semi-natural stream where we annually studied mating of wild shortnose sturgeon (Acipenser brevirostrum) observed movement of gametes released freely during spawning, and estimated the number of larvae produced by various densities of spawned eggs. The stream had a bottom area of 18.8m2, a rubble-gravel bottom, and a mean bottom current at 0.6 depth during spawning of 48cms-1 (range, 17-126cms-1). Wild adults successfully spawned in the stream each year for 7years (2002-2008). Some females and males were more successful during spawning than others, suggesting an unequal fitness during spawning among wild individuals, which is different than the controlled spawning fitness of individuals in hatcheries. Male and female gametes spawned naturally must connect quickly in the fast current or fail, a selection factor absent in hatcheries. The number of larvae produced was inversely related to spawned egg densitym-2 (R2=0.65) and the maximum number of larvae produced was 8000-16000 (425-851larvaem-2 of bottom). Artificial spawning streams have the potential to contribute to sturgeon restoration. ?? 2011 Blackwell Verlag, Berlin.

Kynard, B.; Pugh, D.; Parker, T.; Kieffer, M.

2011-01-01

250

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

NASA Astrophysics Data System (ADS)

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.

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

2008-02-01

251

LABORATORY PROCESS CONTROLLER USING NATURAL LANGUAGE COMMANDS FROM A PERSONAL COMPUTER  

NASA Technical Reports Server (NTRS)

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.

Will, H.

1994-01-01

252

Laboratory studies of groundwater degassing in replicas of natural fractured rock for linear flow geometry  

SciTech Connect

Laboratory experiments to simulate two-phase (gas and water) flow in fractured rock evolving from groundwater degassing were conducted in transparent replicas of natural rock fractures. These experiments extend the work by Geller et al. (1995) and Jarsjo and Geller (1996) that tests the hypothesis that groundwater degassing caused observed flow reductions in the Stripa Simulated Drift Experiment (SDE). Understanding degassing effects over a range of gas contents is needed due to the uncertainty in the gas contents of the water at the SDE. The main objectives of this study were to: (1) measure the effect of groundwater degassing on liquid flow rates for lower gas contents than the values used in Geller for linear flow geometry in the same fracture replicas of Geller; (2) provide a data set to develop a predictive model of two-phase flow in fractures for conditions of groundwater degassing; and (3) improve the certainty of experimental gas contents (this effort included modifications to the experimental system used by Geller et al. and separate gas-water equilibration tests). The Stripa site is being considered for a high-level radioactive waste repository.

Geller, J.T.

1998-02-01

253

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

NASA Astrophysics Data System (ADS)

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.

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

254

Estimating hydroxyl radical photochemical formation rates in natural waters during long-term laboratory irradiation experiments.  

PubMed

In this study it was observed that, during long-term irradiations (>1 day) of natural waters, the methods for measuring hydroxyl radical (?OH) formation rates based upon sequentially determined cumulative concentrations of photoproducts from probes significantly underestimate actual ?OH formation rates. Performing a correction using the photodegradation rates of the probe products improves the ?OH estimation for short term irradiations (<1 day), but not long term irradiations. Only the 'instantaneous' formation rates, which were obtained by adding probes to aliquots at each time point and irradiating these sub-samples for a short time (?2 h), were found appropriate for accurately estimating ?OH photochemical formation rates during long-term laboratory irradiation experiments. Our results also showed that in iron- and dissolved organic matter (DOM)-rich water samples, ?OH appears to be mainly produced from the Fenton reaction initially, but subsequently from other sources possibly from DOM photoreactions. Pathways of ?OH formation in long-term irradiations in relation to H2O2 and iron concentrations are discussed. PMID:24513701

Sun, Luni; Chen, Hongmei; Abdulla, Hussain A; Mopper, Kenneth

2014-03-27

255

Pedagogy and performativity: Rendering laboratory lives in the documentary "Naturally obsessed: the making of a scientist".  

PubMed

A recently released documentary on life in a protein crystallography laboratory offers an exemplary opportunity to examine how a popular account of scientific training models narrowly defined norms of masculinity and mentorship and simultaneously sets these as the tacit conditions for success in science. Rather than treating this documentary as a good or bad representation of what life in the lab is actually like, this analysis draws attention to how the scientists featured in the film perform for the camera and how the filmmakers splice together the action to animate an engaging story. This essay shows how this popular and widely circulating documentary frames science as a game to be won and stages scientific success on an agonistic playing field. Those who can "make it" are those who are tough enough and those who are willing and able to get entangled in the taunting, jesting, and jostling relationships that appear to be required for mentorship in this lab. The essay argues that this documentary tethers this model of success in science to restrictive norms of masculinity and in so doing promotes a pedagogical culture that fosters competition, rivalry, and ritualized shame. Feminist theories of performativity are engaged to consider the iterative processes through which narrowly circumscribed masculinities and styles of pedagogy are sedimented and naturalized. This essay aims to spur renewed attention to the care historians and anthropologists might take to examine the often hidden tropes that are lurking inside the stories about science that we find so salient. PMID:21409989

Myers, Natasha

2010-12-01

256

The Laboratory Opossum (Monodelphis domestica) as a Natural Mammalian Model for Human Cancer Research  

PubMed Central

This study established that human cancer cells (A375 melanoma, HT-29 colon cancer, PC-3p prostate cancer) that were xenografted into suckling opossums could proliferate and globally metastasize as early as 11 days after injection. Light and electron microscopic examinations (HT-29 colon cancer) determined that the cellular features exhibited by the xenogeneic human tumors grown in laboratory opossums were consistent with those observed in tumors removed from humans. The tumor induction rate, patterns of tumor growth and regression, and types of host immune responses against the xenografted tumors were influenced by injection dosages, injection sites and injection ages of suckling opossums. The results highlight the value of the opossum model as a natural in vivo system for investigating human cancer growth, metastasis and apoptosis at the cellular and molecular levels; enhancing identification of tumor associated antigens or T cell epitopes through use of humoral and cellular expression cloning techniques; elucidating mechanisms utilized by tumor cells to evade host immunosurveillance; and devising diagnostic and therapeutic methods for cancer treatment.

Wang, Zhiqiang; Hubbard, Gene B.; Clubb, Fred J.; VandeBerg, John L.

2009-01-01

257

The Future of Natural Selection Knowledge Measurement: A Reply to Anderson et al. (2010)  

ERIC Educational Resources Information Center

The development of rich, reliable, and robust measures of the composition, structure, and stability of student thinking about core scientific ideas (such as natural selection) remains a complex challenge facing science educators. In their recent article (Nehm & Schonfeld 2008), the authors explored the strengths, weaknesses, and insights provided…

Nehm, Ross H.; Schonfeld, Irvin Sam

2010-01-01

258

Common Garden and Natural Selection Experiments Support Ecotypic Differentiation in the Dominican Anole ( Anolis oculatus )  

Microsoft Academic Search

The theory behind ecotypic differentiation and ecological speciation assumes a predominant role for natural selection working on characteristics with genetic variance, but experimental support for these assumptions is limited. Lesser Antillean anoles show marked ecotypic variation within islands and the potential for ecological spe- ciation. Common garden rearing experiments on the Dominican anole (Anolis oculatus) suggest that the characters showing

Anita Malhotra

2005-01-01

259

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

Microsoft Academic Search

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

Antonio Alves de Freitas; Adir Janete Godoy Dos Santos; Brigitte Roxana Soreanu Pecequilo

2008-01-01

260

Were neandertal and modern human cranial differences produced by natural selection or genetic drift?  

Microsoft Academic Search

Most evolutionary explanations for cranial differences between Neandertals and modern humans emphasize adaptation by natural selection. Features of the crania of Neandertals could be adaptations to the glacial climate of Pleistocene Europe or to the high mechanical strains produced by habitually using the front teeth as tools, while those of modern humans could be adaptations for articulate speech production. A

Timothy D. Weaver; Charles C. Roseman; Chris B. Stringer

2007-01-01

261

Darwin's Rehabilitation of Teleology Versus Williams' Replacement of Teleology by Natural Selection  

Microsoft Academic Search

Williams argued that Darwin replaced teleology by natural selection. This article argues that this idea is based on a misunderstanding of Darwin's critique of the argument from design. Darwin did not replace teleology by evolutionary explanations but showed that we can understand teleology without referring to a Designer. He eliminated the concept of design and rehabilitated Aristotelian teleological explanations. The

Harry Smit

2010-01-01

262

Ecological selection against hybrids in natural populations of sympatric threespine sticklebacks  

Microsoft Academic Search

Experimental work has provided evidence for extrinsic post-zygotic isolation, a phenomenon unique to ecological speciation. The role that ecological components to reduced hybrid fitness play in promoting speciation and maintaining species integrity in the wild, however, is not as well understood. We addressed this problem by testing for selection against naturally occurring hybrids in two sympatric species pairs of benthic

J. L. GOW; C. L. PEICHEL; E. B. TAYLOR

2007-01-01

263

Approximating Nature's Variation: Selecting and Using Reference Information in Restoration Ecology  

Microsoft Academic Search

Restoration ecologists use reference information to define restoration goals, determine the restoration po- tential of sites, and evaluate the success of restoration efforts. Basic to the selection and use of reference in- formation is the need to understand temporal and spatial variation in nature. This is a challenging task: variation is likely to be scale dependent; ecosystems vary in complex

Peter S. White; Joan L. Walker

1997-01-01

264

The Power of Natural Selection: A Guided Investigation of Three Case Studies  

ERIC Educational Resources Information Center

I describe a quantitative approach to three case studies in evolution that can be used to challenge college freshmen to explore the power of natural selection and ask questions that foster a deeper understanding of its operation and relevance. Hemochromatosis, the peppered moth, and hominid cranial capacity are investigated with a common algebraic…

Beachly, William

2010-01-01

265

Darwin's Arguments in Favour of Natural Selection and against Special Creationism  

ERIC Educational Resources Information Center

In many places in "The Origin of Species", Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as "Inference to the Best Explanation". The first part of this paper is methodological. It considers Whewell's notion of…

Nola, Robert

2013-01-01

266

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

ERIC Educational Resources Information Center

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…

Nehm, Ross H.; Haertig, Hendrik

2012-01-01

267

Reasoning about Natural Selection: Diagnosing Contextual Competency Using the ACORNS Instrument  

ERIC Educational Resources Information Center

Studies of students' thinking about natural selection have revealed that the scenarios in which students reason evoke different types, magnitudes, and arrangements of knowledge elements and misconceptions. Diagnostic tests are needed that probe students' thinking across a representative array of evolutionary contexts. The ACORNS is a diagnostic…

Nehm, Ross H.; Beggrow, Elizabeth P.; Opfer, John E.; Ha, Minsu

2012-01-01

268

Developing Conceptual Understanding of Natural Selection: The Role of Interest, Efficacy, and Basic Prior Knowledge  

ERIC Educational Resources Information Center

Changes in high school students' (n = 94) conceptions of natural selection were examined as a function of motivational beliefs (individual interest, academic self-efficacy), basic prior knowledge, and gender across three assessments (pre, post, follow-up). Results from variable-centered analyses suggested that these variables had relatively little…

Linnenbrink-Garcia, Lisa; Pugh, Kevin J.; Koskey, Kristin L. K.; Stewart, Victoria C.

2012-01-01

269

Interrogating a High-Density SNP Map for Signatures of Natural Selection  

Microsoft Academic Search

Identifying genomic regions that have been targets of natural selection remains one of the most important and challenging areas of research in genetics. To this end, we report an analysis of 26,530 single nucleotide polymorphisms (SNPs) with allele frequencies that were determined in three populations. Specifically, we calculated a measure of genetic differentiation, FST, for each locus and examined its

Joshua M. Akey; Ge Zhang; Kun Zhang; Li Jin; Mark D. Shriver

2002-01-01

270

Influences of Teleological and Lamarckian Thinking on Student Understanding of Natural Selection  

ERIC Educational Resources Information Center

Previous research has demonstrated creationist, Lamarckian, and teleological reasoning in high school and college students. These lines of thinking conflict with the Darwinian notion of natural selection, which serves as the primary catalyst for biological evolution. The current study assessed evolutionary conceptions in non-science majors,…

Stover, Shawn K.; Mabry, Michelle L.

2007-01-01

271

Natural selection retains overrepresented out-of-frame stop codons against frameshift peptides in prokaryotes  

Microsoft Academic Search

BACKGROUND: Out-of-frame stop codons (OSCs) occur naturally in coding sequences of all organisms, providing a mechanism of early termination of translation in incorrect reading frame so that the metabolic cost associated with frameshift events can be reduced. Given such a functional significance, we expect statistically overrepresented OSCs in coding sequences as a result of a widespread selection. Accordingly, we examined

Herman Tse; James J Cai; Hoi-Wah Tsoi; Esther PT Lam; Kwok-Yung Yuen

2010-01-01

272

Student Conceptions of Natural Selection and Its Role in Evolution, Research Series No. l65.  

ERIC Educational Resources Information Center

Pretests and posttests on the topic of evolution through natural selection were administered to students in a college nonmajors' biology course. Analysis of test responses revealed that most students understood evolution as a process in which species respond to environmental conditions by changing gradually over time. Student thinking differed…

Bishop, Beth A.; Anderson, Charles W.

273

Selection of proteins with desired properties from natural proteome libraries using mRNA display  

Microsoft Academic Search

mRNA display is a powerful yet challenging in vitro selection technique that can be used to identify proteins with desired properties from both natural proteome and combinatorial polypeptide libraries. The physical conjugation between a protein and its own RNA presents unique challenges in manipulating the displayed proteins at a low nanomolar scale in an RNase-free environment. The following protocol outlines

Steven W Cotten; Jianwei Zou; C Alexander Valencia; Rihe Liu

2011-01-01

274

Examining beginning biology teachers' knowledge, beliefs, and practice for teaching natural selection  

NASA Astrophysics Data System (ADS)

The teacher is the most important school-based factor in student learning. Thus, in order to improve student learning, we must examine how teachers learn to teach. My overarching research agenda centers upon K-16 science teacher learning and development. Within this agenda, I conduct studies focused on two strands of research: 1) How teachers learn to teach science using constructivist and inquiry-oriented teaching strategies; and 2) How teachers learn to teach biological evolution. This dissertation merges the two strands together, and consists of four related manuscripts that address how beginning biology teachers learn to teach natural selection using constructivist and inquiry-oriented teaching strategies. In the first manuscript, I reviewed the evolution education literature focused on K-12 teachers’ knowledge, beliefs, and practice for teaching evolution. Based upon findings across the studies, I articulated five goals for preparing teachers to teach evolution. The second and third manuscripts are longitudinal empirical studies focused on three beginning biology teachers learning to teach natural selection using the 5E instructional model and interactive classroom simulations. The fourth manuscript is a practitioner article that explains how to teach natural selection simulations using a constructivist, analogy-based teaching strategy. Findings that cut across the four manuscripts are organized into the following themes: (A) The participants developed some common types of knowledge for teaching natural selection, yet also developed in unique ways. All participants developed knowledge of the horizontal curriculum. Yet, participants also developed different types of knowledge. For example, participants who had taken an evolution course developed more integrated pedagogical content knowledge for teaching the core concepts of natural selection. The participant who integrated discipline-level knowledge for teaching science through inquiry with topic-level knowledge for teaching natural selection had taken an undergraduate evolution course and possessed a student-centered orientation, demonstrating the importance of both subject matter preparation and orientations for teaching science in reform-based ways. Differences I observed among the participants highlight the need for more in-depth case studies in addition to large-scale studies to understand beginning science teacher development. (B) Beliefs about science teaching and learning shaped the participants’ knowledge and practice for teaching natural selection. Participants who possessed student-centered science teaching orientations developed more integrated pedagogical content knowledge for teaching natural selection. However, one participant with a student-centered orientation possessed beliefs in which it was the students’ role to discover natural selection with little intervention from the teacher. This finding supports the need to help teachers develop constructivist orientations to facilitate students’ conceptual understandings of science in addition to engaging in inquiry processes. (C) Learning to teach evolution requires a complex amalgam of knowledge, beliefs, and practice. The literature highlights the types of knowledge and beliefs that teachers must develop to be willing to teach evolution, including content knowledge, understandings of the nature of science, and knowledge of teaching controversial topics. In addition, teachers need to develop pedagogical content knowledge for teaching evolution in ways that support students’ conceptual understanding of evolution. Based upon my review of the literature, secondary science majors should be required to take a course designed for teaching evolution, with the following goals: 1) Develop content knowledge of evolution; 2) Accept evolution as scientifically valid; 3) Develop understandings of the nature of science related to evolution; 4) Develop strategies for handling the public controversy; and 5) Develop pedagogical content knowledge for teaching evolution. This collection of work has implications f

Sickel, Aaron J.

275

Using Avida to test the effects of natural selection on phylogenetic reconstruction methods.  

PubMed

Phylogenetic trees group organisms by their ancestral relationships. There are a number of distinct algorithms used to reconstruct these trees from molecular sequence data, but different methods sometimes give conflicting results. Since there are few precisely known phylogenies, simulations are typically used to test the quality of reconstruction algorithms. These simulations randomly evolve strings of symbols to produce a tree, and then the algorithms are run with the tree leaves as inputs. Here we use Avida to test two widely used reconstruction methods, which gives us the chance to observe the effect of natural selection on tree reconstruction. We find that if the organisms undergo natural selection between branch points, the methods will be successful even on very large time scales. However, these algorithms often falter when selection is absent. PMID:15107228

Hagstrom, George I; Hang, Dehua H; Ofria, Charles; Torng, Eric

2004-01-01

276

Genetic polymorphism and natural selection of Duffy binding protein of Plasmodium vivax Myanmar isolates  

PubMed Central

Background Plasmodium vivax Duffy binding protein (PvDBP) plays an essential role in erythrocyte invasion and a potential asexual blood stage vaccine candidate antigen against P. vivax. The polymorphic nature of PvDBP, particularly amino terminal cysteine-rich region (PvDBPII), represents a major impediment to the successful design of a protective vaccine against vivax malaria. In this study, the genetic polymorphism and natural selection at PvDBPII among Myanmar P. vivax isolates were analysed. Methods Fifty-four P. vivax infected blood samples collected from patients in Myanmar were used. The region flanking PvDBPII was amplified by PCR, cloned into Escherichia coli, and sequenced. The polymorphic characters and natural selection of the region were analysed using the DnaSP and MEGA4 programs. Results Thirty-two point mutations (28 non-synonymous and four synonymous mutations) were identified in PvDBPII among the Myanmar P. vivax isolates. Sequence analyses revealed that 12 different PvDBPII haplotypes were identified in Myanmar P. vivax isolates and that the region has evolved under positive natural selection. High selective pressure preferentially acted on regions identified as B- and T-cell epitopes of PvDBPII. Recombination may also be played a role in the resulting genetic diversity of PvDBPII. Conclusions PvDBPII of Myanmar P. vivax isolates displays a high level of genetic polymorphism and is under selective pressure. Myanmar P. vivax isolates share distinct types of PvDBPII alleles that are different from those of other geographical areas. These results will be useful for understanding the nature of the P. vivax population in Myanmar and for development of PvDBPII-based vaccine.

2012-01-01

277

The effect of natural selection on the performance of maximum parsimony  

PubMed Central

Background Maximum parsimony is one of the most commonly used and extensively studied phylogeny reconstruction methods. While current evaluation methodologies such as computer simulations provide insight into how well maximum parsimony reconstructs phylogenies, they tell us little about how well maximum parsimony performs on taxa drawn from populations of organisms that evolved subject to natural selection in addition to the random factors of drift and mutation. It is clear that natural selection has a significant impact on Among Site Rate Variation (ASRV) and the rate of accepted substitutions; that is, accepted mutations do not occur with uniform probability along the genome and some substitutions are more likely to occur than other substitutions. However, little is know about how ASRV and non-uniform character substitutions impact the performance of reconstruction methods such as maximum parsimony. To gain insight into these issues, we study how well maximum parsimony performs with data generated by Avida, a digital life platform where populations of digital organisms evolve subject to natural selective pressures. Results We first identify conditions where natural selection does affect maximum parsimony's reconstruction accuracy. In general, as we increase the probability that a significant adaptation will occur in an intermediate ancestor, the performance of maximum parsimony improves. In fact, maximum parsimony can correctly reconstruct small 4 taxa trees on data that have received surprisingly many mutations if the intermediate ancestor has received a significant adaptation. We demonstrate that this improved performance of maximum parsimony is attributable more to ASRV than to non-uniform character substitutions. Conclusion Maximum parsimony, as well as most other phylogeny reconstruction methods, may perform significantly better on actual biological data than is currently suggested by computer simulation studies because of natural selection. This is largely due to specific sites becoming fixed in the genome that perform functions associated with an improved fitness.

Hang, Dehua; Torng, Eric; Ofria, Charles; Schmidt, Thomas M

2007-01-01

278

Volcanic Plumes in the South Atlantic Ocean: A Natural Laboratory for the Study of Aerosol-Cloud Interactions  

Microsoft Academic Search

Because marine cloud properties are most sensitive to changes in aerosol concentration, they provide an ideal natural laboratory for aerosol-cloud interaction studies. However, direct observations of effects of aerosols on cloud properties in remote marine areas are difficult to detect and to analyze. Probably the only examples thoroughly studied are the smoke plumes from commercial ships. Ship-tracks demonstrate how high

S. Gassó

2006-01-01

279

Index of opportunity for natural selection among the Gowdas of Kodagahalli village, Karnataka, India  

PubMed Central

BACKGROUND: In order to understand how selection is operating in the Gowda population, the index of opportunity for selection was calculated and the present findings were compared with some related findings from other South Indian (SI) populations. MATERIALS AND METHODS: Crow (1958) and the modified method by Johnston and Kensinger (1971) were used for the present purpose. RESULTS AND DISCUSSION: The index of total selection intensity (I) was found to be moderate taking into consideration the range for many Indian populations. Considering certain differences in fertility and mortality heritable, it appears that natural selection play an important role in shaping the genetic constitution of the Gowda population. Analysis of data indicates that the index due to fertility seems to contribute more towards selection than mortality. This trend might be because of better living condition and health-care system among the Gowdas which have a positive impact on the lower contribution of mortality for the evolution mechanism of the Gowda population through natural selection.

Sohkhlet, Bhaboklang

2013-01-01

280

Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Underground Nuclear Tests - 2011, Part 2  

Microsoft Academic Search

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

Pawloski

2012-01-01

281

Evaluation of Cavity Collapse and Surface Crater Formation for Selected Lawrence Livermore National Laboratory Underground Nuclear Tests - 2010  

Microsoft Academic Search

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 Navarro-Interra LLC, and supports environmental restoration efforts by the Department of Energy, National Nuclear Security Administration for the Nevada Site Office. Safety decisions

Pawloski

2011-01-01

282

Low pH Springs - A Natural Laboratory for Ocean Acidification  

NASA Astrophysics Data System (ADS)

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.

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

2009-12-01

283

Selection of natural Gas Fired Advanced Turbine Systems (GFATS) program - Task 3. Topical report  

SciTech Connect

Research continued on natural gas-fired turbines.The objective of Task 3 was to perform initial trade studies and select one engine system (Gas-Fired Advanced Turbine System [GFATS]) that the contractor could demonstrate, at full scale, in the 1998 to 2000 time frame. This report describes the results of the selection process. This task, including Allison internal management reviews of the selected system, has been completed. Allison`s approach to ATS is to offer an engine family that is based on the newest T406 high technology engine. This selection was based on a number of parameters including return on investment (ROI), internal rate of return (IRR) market size and potential sales into that market. This base engine family continues a history at Allison of converting flight engine products to industrial use.

NONE

1994-06-01

284

RTK/ERK Pathway under Natural Selection Associated with Prostate Cancer  

PubMed Central

Prostate cancer (PCa) is a global disease causing large numbers of deaths every year. Recent studies have indicated the RTK/ERK pathway might be a key pathway in the development of PCa. However, the exact association and evolution-based mechanism remain unclear. This study was conducted by combining genotypic and phenotypic data from the Chinese Consortium for Prostate Cancer Genetics (ChinaPCa) with related databases such as the HapMap Project and Genevar. In this analysis, expression of quantitative trait loci (eQTLs) analysis, natural selection and gene-based pathway analysis were involved. The pathway analysis confirmed the positive relationship between PCa risk and several key genes. In addition, combined with the natural selection, it seems that 4 genes (EGFR, ERBB2, PTK2, and RAF1) with five SNPs (rs11238349, rs17172438, rs984654, rs11773818, and rs17172432) especially rs17172432, might be pivotal factors in the development of PCa. The results indicate that the RTK/ERK pathway under natural selection is a key link in PCa risk. The joint effect of the genes and loci with positive selection might be one reason for the development of PCa. Dealing with all the factors simultaneously might give insight into prevention and aid in predicting the success of potential therapies for PCa.

Xu, Jianfeng; Yu, Xiaoxiang; Li, Tianyu; Mo, Zengnan; Hu, Yanling

2013-01-01

285

Natural and Synthetic Alleles Provide Complementary Insights Into the Nature of Selection Acting on the Men Polymorphism of Drosophila melanogaster  

PubMed Central

Two malic enzyme alleles, Men113A and Men113G, occur at approximately equal frequency in North American populations of Drosophila melanogaster, while only Men113A occurs in African populations. We investigated the population genetics, biochemical characteristics, and selective potential of these alleles. Comparable levels of nucleotide polymorphism in both alleles suggest that the Men113G allele is not recently derived, but we find no evidence in the DNA sequence data for selection maintaining the polymorphism. Interestingly, the alleles differ in both Vmax and Km for the substrate malate. Triglyceride concentration and isocitrate dehydrogenase (IDH) and glucose-6-phosphate dehydrogenase (G6PD) activities are negatively correlated with the in vivo activities of the Men alleles. We examined the causality of the observed correlations using P-element excision-derived knockout alleles of the Men gene and found significant changes in the maximum activities of both IDH and G6PD, but not in triglyceride concentration, suggesting compensatory interactions between MEN, IDH, and G6PD. Additionally, we found significantly higher than expected levels of MEN activity in knockout heterozygotes, which we attribute to transvection effects. The distinct differences in biochemistry and physiology between the naturally occurring alleles and between the engineered alleles suggest the potential for selection on the Men locus.

Merritt, Thomas J. S.; Duvernell, David; Eanes, Walter F.

2005-01-01

286

Effects of Heterogeneous Adsorption Affinity on Natural Organic Matter (NOM) Transport in Laboratory Sand Columns  

NASA Astrophysics Data System (ADS)

Transport of reactive sorbing solutes through porous media is commonly quantified by implementing an effective retardation coefficient in the advection-dispersion equation (ADE), which describes dispersion in accordance with Fick's law. However, anomalous (non-Fickian) transport behavior can be observed in systems with heterogeneous retardation coefficients (Dentz & Castro, 2009). In such systems, the ADE is unable to reproduce the non-Fickian nature of plume shapes and breakthrough curves, motivating the development and application of alternative solute transport theories, such as the continuous time random walk (CTRW) or multi-rate mass transfer (MRMT). Heterogeneity in retardation coefficients in practice arises from variability in the geochemical properties controlling sorption-desorption kinetics between the solute and mineral surfaces. These distributions have been described in the context of heterogeneity of the porous medium, but to date little attention has been given to the potential role of a geochemically heterogeneous solute. In this work, we consider a system in which anomalous transport arises during the passage of natural organic matter (NOM), a polydisperse mixture of compounds derived from the breakdown of plants and microorganisms in the environment, through homogeneous laboratory sand columns. NOM solutions were passed through columns containing either hematite, corundum, or a naturally-coated quartz sand at a variety of pH and ionic strength conditions. Influent and effluent NOM concentration was measured as UV absorbance at 254 nm. The resulting breakthrough curves are non-Fickian, displaying power-law tailing at late times. Such curves cannot be predicted by the ADE model. Reactivity of NOM components is known to be related to their molecular weight (MW), which tends to be log-normally distributed in aquatic NOM isolates (Cabaniss et al., 2000). Low-MW compounds are more water-soluble, have a higher diffusion coefficient, and due to their smaller structure, are able to enter nanopores which exclude macromolecules. Conversely, high-MW components are hydrophobic, less mobile, and have a greater affinity for metal binding than their smaller counterparts. By analyzing the transport of different NOM components in the effluent solution over time we see that there is a clear heterogeneity in the retardation of the different NOM components. Using the approaches of Dentz & Castro (2009) and Dentz & Bolster (2011) we can show that the effective upscaled transport can be modeled as a CTRW. To this end we demonstrate that the CTRW and MRMT models (which can be shown to be intricately related) can indeed faithfully capture the observed behavior. From a practical perspective, our experiments demonstrate increased mobility of low-MW fractions of NOM relative to high-MW fractions, which - given the ability of NOM to bind to organic compounds, metals, and radionuclides - could have important implications for contaminant transport in groundwater systems.

McInnis, D. P.; Bolster, D.; Maurice, P. A.

2012-12-01

287

Selective extraction of PAHs from a sediment with structural preservation of Natural Organic Matter.  

PubMed

Selective extraction of Polycyclic Aromatic Hydrocarbons (PAH) without structural modification of the Natural Organic Matter (NOM) from a heavily contaminated sediment was investigated using various solvents mixtures. Structural modification of the NOM was monitored after extraction using 3D-fluorescence spectroscopy. Better results were obtained with a 15-h PAH extraction under reflux with a dichloromethane/cyclohexane 20/80 mixture. The experimental procedure was validated with NOM standard materials before to be applied on natural sediments. It could be applied to any environmental solid sample such as sediments and soils. PMID:24434170

Merdy, Patricia; Achard, Romain; Samaali, Ismahen; Lucas, Yves

2014-07-01

288

Identification of innate immunity elicitors using molecular signatures of natural selection  

PubMed Central

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.

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

2012-01-01

289

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

SciTech Connect

An analytical procedure was established in order to obtain selective fractions containing radium isotopes ({sup 228}Ra), thorium ({sup 232}Th), and rare earths from RETOTER (REsiduo de TOrio 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 {sup 228}Ra, {sup 226}Ra, {sup 238}U, {sup 210}Pb, and {sup 40}K concentrations in the selective fractions and total residue determined by high-resolution gamma spectroscopy, considering radioactive equilibrium of the samples.

Alves de Freitas, Antonio; Abrao, Alcidio [Centro de Quimica e do Meio Ambiente (Brazil); Godoy dos Santos, Adir Janete; Pecequilo, Brigitte Roxana Soreanu [Centro de Metrologia das Radiacoes Instituto de Pesquisas Energeticas e Nucleares Av. Prof. Lineu Prestes, 2242-Cidade Universitaria-Zip Code 05508-000 Sao Paulo-SP (Brazil)

2008-08-07

290

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

NASA Astrophysics Data System (ADS)

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.

de Freitas, Antonio Alves; Dos Santos, Adir Janete Godoy; Pecequilo, Brigitte Roxana Soreanu; Abra~O, Alcídio

2008-08-01

291

Life History of Acetabularia acetabulum (=Mediterranea) in the Laboratory and in Nature.  

National Technical Information Service (NTIS)

The authors compare the life cycle of Acetabularia acetabulum (Dasycladaceae) grown under artificial or under natural conditions. New evidence is presented, supporting the view that in nature Acetabularia behaves as a 'pluriannual' plant.

S. Bonotto G. Arapis M. Paques

1984-01-01

292

The Role of Selection in Shaping Diversity of Natural M. tuberculosis Populations  

PubMed Central

Mycobacterium tuberculosis (M.tb), the cause of tuberculosis (TB), is estimated to infect a new host every second. While analyses of genetic data from natural populations of M.tb have emphasized the role of genetic drift in shaping patterns of diversity, the influence of natural selection on this successful pathogen is less well understood. We investigated the effects of natural selection on patterns of diversity in 63 globally extant genomes of M.tb and related pathogenic mycobacteria. We found evidence of strong purifying selection, with an estimated genome-wide selection coefficient equal to ?9.5×10?4 (95% CI ?1.1×10?3 to ?6.8×10?4); this is several orders of magnitude higher than recent estimates for eukaryotic and prokaryotic organisms. We also identified different patterns of variation across categories of gene function. Genes involved in transport and metabolism of inorganic ions exhibited very low levels of non-synonymous polymorphism, equivalent to categories under strong purifying selection (essential and translation-associated genes). The highest levels of non-synonymous variation were seen in a group of transporter genes, likely due to either diversifying selection or local selective sweeps. In addition to selection, we identified other important influences on M.tb genetic diversity, such as a 25-fold expansion of global M.tb populations coincident with explosive growth in human populations (estimated timing 1684 C.E., 95% CI 1620–1713 C.E.). These results emphasize the parallel demographic histories of this obligate pathogen and its human host, and suggest that the dominant effect of selection on M.tb is removal of novel variants, with exceptions in an interesting group of genes involved in transportation and defense. We speculate that the hostile environment within a host imposes strict demands on M.tb physiology, and thus a substantial fitness cost for most new mutations. In this respect, obligate bacterial pathogens may differ from other host-associated microbes such as symbionts.

Pepperell, Caitlin S.; Casto, Amanda M.; Kitchen, Andrew; Granka, Julie M.; Cornejo, Omar E.; Holmes, Eddie C.; Birren, Bruce; Galagan, James; Feldman, Marcus W.

2013-01-01

293

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

Microsoft Academic Search

Our study examines the efficacy of Computer Assisted Scoring (CAS) of open-response text relative to expert human scoring\\u000a within the complex domain of evolutionary biology. Specifically, we explored whether CAS can diagnose the explanatory elements\\u000a (or Key Concepts) that comprise undergraduate students’ explanatory models of natural selection with equal fidelity as expert\\u000a human scorers in a sample of >1,000 essays.

Ross H. Nehm; Hendrik Haertig

2011-01-01

294

Darwin's passionate environmentalism or the dangerous fallacy of the 'All-sufficiency of natural selection' theory.  

PubMed

Following his last edition of the Origin of Species in 1872, Darwin spent much of the rest of his life searching for possible mechanisms, such as the pangenes in the blood, which would communicate information from the environment to the genome. In each of his six editions of the 'Origin', he stated that there were two forces in evolution - natural selection and conditions of existence. Of the two, he claims that the latter is the more powerful. In so doing, he recognized that natural selection could only operate within the bounds of possibility, that is the environment. August Weismann claimed that conditions of existence had no place in evolution. His publication, the 'All-sufficiency of natural selection', was based on mutilation (cutting tails of rodents and watching the next generation grow tails), which has nothing to do with Darwin's concept of conditions of existence. Nonetheless, evolutionary biologists in general followed the line of the 'all sufficiency' theory and ignored Darwin's conditions of existence, which in other words means the environment. Natural selection has a weak predictive power as it is based on random events. However, the conditions of existence have, by contrast, strong predictive powers that can be tested. The environmental views of two of the greatest evolutionists, Lamarck and Darwin, have been consistently ignored by most evolution theorists who came after them, continuing for over 200 years. Looking at the fossil record through the eyes of Darwin's conditions of existence, not to mention the recent changes in height and shape over the last century, it is possible to draw important conclusions about the past and predictions of the future. With new knowledge of epigenetics, it is perhaps time that Darwin's conditions of existence were given a second hearing. PMID:22544777

Marsh, David

2012-01-01

295

Natural selection theory in non-majors' biology: Instruction, assessment and conceptual difficulty  

NASA Astrophysics Data System (ADS)

Evolution by natural selection is the dominant and unifying theme in biology, yet many college students hold alternative conceptions about the topic even after completing general biology. To develop effective instructional strategies and track conceptual understanding, it is useful to have a detailed assessment tool easily used with large classes. This study presents the Conceptual Inventory of Natural Selection (CINS), a distractor-driven twenty item multiple-choice test that assesses understanding of ten concepts related to natural selection: biotic potential, stable populations, limited natural resources, limited survival, variation within a population, variation inherited, differential survival, change in populations, origin of variation, and origin of species. Development, refinement, and field-testing of individual CINS items are presented, and validity, readability, reliability and factor analysis of the CINS are described. There was significant correlation between student performance on the posttest CINS and end-of-semester interviews suggesting that the CINS is a useful classroom tool. The CINS was used as both a pretest and posttest to determine relative difficulty of the concepts among college students. The three most challenging concepts were random origin of variation, how populations change over time due to changing proportions of alleles, and how new species originate. Many students chose distractors including "need" as a driving force. Results support the use of non-traditional methods, as only students in such classes demonstrated any improvement on the CINS posttest. Pre and posttesting with the CINS was also used to assess relative effectiveness of using two types of supplemental reading materials (selections from narrative, non-textbook sources or from other general biology textbooks) in a general biology course. These results suggest that specific content of readings was more important than style of the readings. Implications for teaching both students and pre-service teachers are described.

Anderson, Dianne L.

296

Natural selection and the molecular basis of electrophoretic variation at the coagulation F13B locus  

Microsoft Academic Search

Electrophoretic analysis of protein variation at the coagulation F13B locus has previously revealed three alleles, with alleles 1, 2, and 3 each being at high frequency in European, African, and Asian populations, respectively. To determine if this unusual pattern of interpopulation differentiation reflects local natural selection or neutral genetic drift, we re-sequenced 4.6 kb of the gene, encompassing all exons,

Anthony W Ryan; David A Hughes; Kun Tang; Dermot P Kelleher; Thomas Ryan; Ross McManus; Mark Stoneking

2009-01-01

297

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

Microsoft Academic Search

An analytical procedure was established in order to obtain selective fractions containing radium isotopes (228Ra), thorium (232Th), and rare earths from RETOTER (REsi´duo de TO´rio 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

Antonio Alves de Freitas; Adir Janete Godoy dos Santos; Brigitte Roxana Soreanu Pecequilo; Alci´dio Abrão

2008-01-01

298

How Some Major Components of Religion Could Have Evolved by Natural Selection?  

Microsoft Academic Search

Religion is a broad concept that is difficult to define, as each definition has exceptions. As a result, it is difficult to\\u000a ask how religion as a whole could have evolved by natural selection\\u000a . An alternative is to divide religion into its components – behavior, beliefs, values, moods, and feelings. One can then\\u000a ask the same question of these

Jay R. Feierman

299

Darwin's Arguments in Favour of Natural Selection and Against Special Creationism  

NASA Astrophysics Data System (ADS)

In many places in The Origin of Species, Darwin compares his own theory of Natural Selection favourably with Special Creationism which comes off as a bad second best. He does this using some version of the argument form known as `Inference to the Best Explanation'. The first part of this paper is methodological. It considers Whewell's notion of consilience, that is, the way in which theories can get additional confirmation through unifying otherwise disparate and independent facts. Then it considers various forms of inference to the best explanation. The second part of the paper applies these methodological considerations to an analysis of some of the many passages in Origin where Darwin presents his case in favour of Natural Selection. This gives a far superior explanation of biological facts compared with Special Creationism which provides either an inferior explanation or no explanation at all. Contrary to the view that Creationism should not be taught, the passages from Darwin show at least that it should be understood if only to show that it offers no explanation of a wide range of obvious biological facts. As such the passages in Origin in which Darwin presents his case against Creationism can serve as a series of excellent exercises in getting students to think about Natural Selection as opposed to Creationism. For this reason alone they ought to be better known. In addition, Darwin's point in these passages can only be understood using principles of scientific method, such as inference to the best explanation, which are essential in showing that Natural Selection is to be preferred to Creationism.

Nola, Robert

2013-02-01

300

Integrated data search and access to geophysical data for Geohazards Supersites and Natural Laboratories  

NASA Astrophysics Data System (ADS)

The Geohazards Supersites and Natural Laboratories (GSNL) are committed to sharing space-based and ground-based geophysical data and building collaborations to better understand Earth processes and mitigate the societal hazards related to the dynamic Earth. GSNL is global with locations in Turkey, Japan, China, Italy, Haiti the United States (e.g. Hawaii and the western U.S.) and elsewhere. The UNAVCO Data Center in Boulder, Colorado, archives and distributes geodesy data and products in the GPS/GNSS, InSAR, and LiDAR domains. UNAVCO has an open access data policy and strives to provide catalogs and data access tools for all users. In an effort to create a unified data and metadata access capability for geodesy data centers in general and for GSNL in particular, UNAVCO and our partners, have designed and implemented software for simplified access called the Geodesy Seamless Archive Centers (GSAC). GSAC is a web services based technology to facilitate data discovery and access. The GSAC technology leverages several well-accepted geodesy data and metadata formats, and identifies a relatively small set of required and recommended metadata for the basic installation. Additional optional metadata can be defined at individual data centers. The GSAC services utilize a repository layer implemented at each data center, and a service layer to identify and present the required metadata elements along with any data center-specific services and capabilities. The software for the GSAC is available through SourceForge, and any geodesy data archive can download the code and implement GSAC services for their repository; doing so will provide the data center's users with the ability to use common query and access mechanisms with other GSAC data centers. Further, optional federation of individual GSAC data centers is facilitated through the GSAC software. GSAC would significantly simplify data access and integration, while enhancing data sharing around the world. GSAC is an excellent tool for advancing the goals of GSNL and helping to make the world a safer place through simple data integration.

Rowan, L.; Baker, S.; Wier, S.; Boler, F. M.; Meertens, C. M.; Amelung, F.

2013-12-01

301

Probing feature selectivity of neurons in primary visual cortex with natural stimuli  

NASA Astrophysics Data System (ADS)

One way to characterize neural feature selectivity is to model the response probability as a nonlinear function of the output of a set of linear filters applied to incoming signals. Traditionally these linear filters are measured by probing neurons with correlated Gaussian noise ensembles and calculating correlation functions between incoming signals and neural responses. It is also important to derive these filters in response to natural stimuli, which have been shown to have strongly non-Gaussian spatiotemporal correlations. An information-theoretic method has been proposed recently for reconstructing neural filters using natural stimuli in which one looks for filters whose convolution with the stimulus ensemble accounts for the maximal possible part of the overall information carried the sequence of neural responses. Here we give a first-time demonstration of this method on real neural data, and compare responses of neurons in cat primary visual cortex driven with natural stimuli, noise ensembles, and moving gratings. We show that the information-theoretic method achieves the same quality of filter reconstruction for natural stimuli as that of well-established white-noise methods. Major parameters of neural filters derived from noise ensembles and natural stimuli, as well as from moving gratings are consistent with one another. We find that application of the reverse correlation method to natural stimuli ensembles leads to significant distortions in filters for a majority of studied cells with non-zero reverse-correlation filter.

Sharpee, Tatyana; Sugihara, Hiroki; Kurgansky, A. V.; Rebrik, S.; Stryker, M. P.; Miller, Kenneth D.

2004-05-01

302

Measuring Knowledge of Natural Selection: A Comparison of the CINS, an Open-Response Instrument, and an Oral Interview  

ERIC Educational Resources Information Center

Growing recognition of the central importance of fostering an in-depth understanding of natural selection has, surprisingly, failed to stimulate work on the development and rigorous evaluation of instruments that measure knowledge of it. We used three different methodological tools, the Conceptual Inventory of Natural Selection (CINS), a modified…

Nehm, Ross H.; Schonfeld, Irvin Sam

2008-01-01

303

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

NASA Astrophysics Data System (ADS)

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.

Xu, Jin; Wang, Qiao

2010-07-01

304

Selecting the Best Mobile Information Service with Natural Language User Input  

NASA Astrophysics Data System (ADS)

Information services accessed via mobile phones provide information directly relevant to subscribers’ daily lives and are an area of dynamic market growth worldwide. Although many information services are currently offered by mobile operators, many of the existing solutions require a unique gateway for each service, and it is inconvenient for users to have to remember a large number of such gateways. Furthermore, the Short Message Service (SMS) is very popular in China and Chinese users would prefer to access these services in natural language via SMS. This chapter describes a Natural Language Based Service Selection System (NL3S) for use with a large number of mobile information services. The system can accept user queries in natural language and navigate it to the required service. Since it is difficult for existing methods to achieve high accuracy and high coverage and anticipate which other services a user might want to query, the NL3S is developed based on a Multi-service Ontology (MO) and Multi-service Query Language (MQL). The MO and MQL provide semantic and linguistic knowledge, respectively, to facilitate service selection for a user query and to provide adaptive service recommendations. Experiments show that the NL3S can achieve 75-95% accuracies and 85-95% satisfactions for processing various styles of natural language queries. A trial involving navigation of 30 different mobile services shows that the NL3S can provide a viable commercial solution for mobile operators.

Feng, Qiangze; Qi, Hongwei; Fukushima, Toshikazu

305

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

PubMed

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

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

306

Genome-wide detection of natural selection in African Americans pre- and post-admixture  

PubMed Central

It is particularly meaningful to investigate natural selection in African Americans (AfA) due to the high mortality their African ancestry has experienced in history. In this study, we examined 491,526 autosomal single nucleotide polymorphisms (SNPs) genotyped in 5210 individuals and conducted a genome-wide search for selection signals in 1890 AfA. Several genomic regions showing an excess of African or European ancestry, which were considered the footprints of selection since population admixture, were detected based on a commonly used approach. However, we also developed a new strategy to detect natural selection both pre- and post-admixture by reconstructing an ancestral African population (AAF) from inferred African components of ancestry in AfA and comparing it with indigenous African populations (IAF). Interestingly, many selection-candidate genes identified by the new approach were associated with AfA-specific high-risk diseases such as prostate cancer and hypertension, suggesting an important role these disease-related genes might have played in adapting to a new environment. CD36 and HBB, whose mutations confer a degree of protection against malaria, were also located in the highly differentiated regions between AAF and IAF. Further analysis showed that the frequencies of alleles protecting against malaria in AAF were lower than those in IAF, which is consistent with the relaxed selection pressure of malaria in the New World. There is no overlap between the top candidate genes detected by the two approaches, indicating the different environmental pressures AfA experienced pre- and post-population admixture. We suggest that the new approach is reasonably powerful and can also be applied to other admixed populations such as Latinos and Uyghurs.

Jin, Wenfei; Xu, Shuhua; Wang, Haifeng; Yu, Yongguo; Shen, Yiping; Wu, Bailin; Jin, Li

2012-01-01

307

Identifying Signatures of Natural Selection in Tibetan and Andean Populations Using Dense Genome Scan Data  

PubMed Central

High-altitude hypoxia (reduced inspired oxygen tension due to decreased barometric pressure) exerts severe physiological stress on the human body. Two high-altitude regions where humans have lived for millennia are the Andean Altiplano and the Tibetan Plateau. Populations living in these regions exhibit unique circulatory, respiratory, and hematological adaptations to life at high altitude. Although these responses have been well characterized physiologically, their underlying genetic basis remains unknown. We performed a genome scan to identify genes showing evidence of adaptation to hypoxia. We looked across each chromosome to identify genomic regions with previously unknown function with respect to altitude phenotypes. In addition, groups of genes functioning in oxygen metabolism and sensing were examined to test the hypothesis that particular pathways have been involved in genetic adaptation to altitude. Applying four population genetic statistics commonly used for detecting signatures of natural selection, we identified selection-nominated candidate genes and gene regions in these two populations (Andeans and Tibetans) separately. The Tibetan and Andean patterns of genetic adaptation are largely distinct from one another, with both populations showing evidence of positive natural selection in different genes or gene regions. Interestingly, one gene previously known to be important in cellular oxygen sensing, EGLN1 (also known as PHD2), shows evidence of positive selection in both Tibetans and Andeans. However, the pattern of variation for this gene differs between the two populations. Our results indicate that several key HIF-regulatory and targeted genes are responsible for adaptation to high altitude in Andeans and Tibetans, and several different chromosomal regions are implicated in the putative response to selection. These data suggest a genetic role in high-altitude adaption and provide a basis for future genotype/phenotype association studies necessary to confirm the role of selection-nominated candidate genes and gene regions in adaptation to altitude.

Bigham, Abigail; Bauchet, Marc; Pinto, Dalila; Mao, Xianyun; Akey, Joshua M.; Mei, Rui; Scherer, Stephen W.; Julian, Colleen G.; Wilson, Megan J.; Lopez Herraez, David; Brutsaert, Tom; Parra, Esteban J.; Moore, Lorna G.; Shriver, Mark D.

2010-01-01

308

Assessment Laboratory Model. Firefighter Selection Examination Developed for City of Palo Alto, California.  

National Technical Information Service (NTIS)

The assessment laboratory function is supplementary and subsequent to the usual mass testing procedures. It is designed to elicit information not furnished by older, more traditional methods, e.g., assessment of personal attributes, communication skills, ...

J. D. Harris D. S. Macrae

1975-01-01

309

Natural Product Total Synthesis in the Organic Laboratory: Total Synthesis of Caffeic Acid Phenethyl Ester (CAPE), a Potent 5-Lipoxygenase Inhibitor from Honeybee Hives  

ERIC Educational Resources Information Center

Natural products play a critical role in modern organic synthesis and learning synthetic techniques is an important component of the organic laboratory experience. In addition to traditional one-step organic synthesis laboratories, a multistep natural product synthesis is an interesting experiment to challenge students. The proposed three-step…

Touaibia, Mohamed; Guay, Michel

2011-01-01

310

Laboratory methods for evaluating migrated high molecular weight hydrocarbons in marine sediments at naturally occurring oil seeps  

Microsoft Academic Search

A laboratory study has been conducted to determine the best methods for the detection of C10–C40 hydrocarbons at naturally occurring oil seeps in marine sediments. The results indicate that a commercially available method using n-C6 to extract sediments and gas chromatography–flame ionization detection (GC–FID) to screen the resulting extract is effective at recognizing the presence of migrated hydrocarbons at concentrations

Graham A. Logan; Michael A. Abrams; Nicola F. Dahdah; Emmanuelle Grosjean

2009-01-01

311

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

PubMed Central

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.

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

2011-01-01

312

Natural Image Coding in V1: How Much Use Is Orientation Selectivity?  

PubMed Central

Orientation selectivity is the most striking feature of simple cell coding in V1 that 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 not yield oriented filters. Because of this finding, it has been suggested that the emergence of orientation selectivity may be explained by higher-order redundancy reduction. To assess the tenability of this hypothesis, it is an important empirical question how much more redundancy can be removed with ICA in comparison to PCA or other second-order decorrelation methods. Although some previous studies have concluded that the amount of higher-order correlation in natural images is generally insignificant, other studies reported an extra gain for ICA of more than 100%. A consistent conclusion about the role of higher-order correlations in natural images can be reached only by the development of reliable quantitative evaluation methods. Here, we present a very careful and comprehensive analysis using three evaluation criteria related to redundancy reduction: In addition to the multi-information and the average log-loss, we compute complete rate–distortion curves for ICA in comparison with PCA. Without exception, we find that the advantage of the ICA filters is small. At the same time, we show that a simple spherically symmetric distribution with only two parameters can fit the data significantly better than the probabilistic model underlying ICA. This finding suggests that, although the amount of higher-order correlation in natural images can in fact be significant, the feature of orientation selectivity does not yield a large contribution to redundancy reduction within the linear filter bank models of V1 simple cells.

Bethge, Matthias

2009-01-01

313

Aggression and feeding of hatchery-reared and naturally reared steelhead (Oncorhynchus mykiss) fry in a laboratory flume and a comparison with observations in natural streams  

USGS Publications Warehouse

We quantified the aggression and feeding of naturally reared steelhead (Oncorhynchus mykiss) fry stocked into a laboratory flume with naturally reared fry or hatchery-reared fry from conventional and enriched rearing environments at three densities in the presence and absence of predators, and compared the aggression and feeding observed in the flume to that observed in two streams. Steelhead fry attack rate increased with density and was reduced in the presence of predators, but was not affected by rearing treatment. Threat rate appeared to increase with density and was significantly affected by rearing treatment combination, but was not significantly affected by predator presence. Feeding rate was not affected by density or rearing treatment, but was reduced in the presence of predators. The rate of aggression by steelhead fry in two streams was lower than that observed in the laboratory and did not increase with density. Rates of aggression and feeding of hatchery-reared and wild steelhead fry were not significantly different in the streams. Overall, we found no evidence that hatchery rearing environments caused higher aggression in steelhead fry. Laboratory observations of salmonid aggression, particularly at high density, may not reflect aggression levels in the wild. ?? 2005 NRC.

Riley, S. C.; Tatara, C. P.; Scheurer, J. A.

2005-01-01

314

DEVELOPMENT OF A SELECTIVE CESIUM AND STRONTIUM REMOVAL SYSTEM FOR THE JAERI TOKAI-MURA SITE - LABORATORY TESTS  

Microsoft Academic Search

New selective inorganic ion exchange medias, CsTreat ® and SrTreat ® , were tested in laboratory using minicolumns and simulated waste liquid for the treatment of medium-active reprocessing waste effluents. The test results indicated that decontamination factors (DF) in the range of 1000- 10,000 could be obtained for 137 Cs and 90 Sr, which is well above the required purification

R. Harjula; J. Lehto; L. Brodkin; E. Tusa; A. Keskinen; T. Mimori; K. Miyajima; H. Tajiri; H. Mizubayashi

2000-01-01

315

A laboratory study of survival of selected microorganisms after heat treatment of biowaste used in biogas plants  

Microsoft Academic Search

The aim of the study was to assess the effect of pasteurisation, as set by the European regulation EC 1774\\/2002, on selected pathogens and indicator organisms.Unpasteurised substrate (biowaste), including animal by-products from a full-scale biogas plant was heat treated under laboratory conditions at 70°C and 55°C for 30min and 60min.Heat treatment at 55°C for 60min was not sufficient to achieve

Leena Sahlström; Elisabeth Bagge; Eva Emmoth; Annika Holmqvist; Marie-Louise Danielsson-Tham; Ann Albihn

2008-01-01

316

Genetic Drift and Natural Selection in an Isolated Zapotec-Speaking Community in the Valley of Oaxaca, Southern Mexico  

Microsoft Academic Search

Genetic drift and natural selection were analyzed in a genetically isolated Zapotec-speaking community in the Valley of Oaxaca, southern Mexico. Moderately intense genetic drift and selection potentials were found. Potential for drift was related to (1) the small effective size of the population, and (2) the exceptionally low number of migrants into the population. Potential for selection was due to

Bertis B. Little; Robert M. Malina

1989-01-01

317

Natural selection in a bangladeshi population from the cholera-endemic ganges river delta.  

PubMed

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 adenosine monophosphate-mediated chloride secretion and for components of the innate immune system involved in nuclear factor ?B (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-?B/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

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

2013-07-01

318

Chemoselective Reactions of Citral: Green Syntheses of Natural Perfumes for the Undergraduate Organic Laboratory  

ERIC Educational Resources Information Center

Chemoselectivity is a central concept in organic synthesis and may be readily appreciated in the context of the fragrant, polyfunctional natural product citral. We describe three single-step reactions students may perform on citral to synthesize other natural perfumes: citronellal, geraniol, nerol, or epoxycitral. Each of the reactions uses a…

Cunningham, Anna D.; Ham, Eun Y.; Vosburg, David A.

2011-01-01

319

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

PubMed Central

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.

Sams, Aaron; Hawks, John

2013-01-01

320

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

PubMed

Two established delignification methods employing sodium chlorite-acetic acid (SC/AA) and peracetic acid (PAA) are often used, and are reportedly highly selective. However, these reports are mostly for highly recalcitrant and unpretreated softwoods and hardwoods species, and information for less recalcitrant lignocellulosic feedstocks and pretreated biomass is scarce. Furthermore, the effects on cellulose structure are not documented. Thus, in this study, delignification kinetics and selectivity were evaluated when SC/AA and PAA were applied to untreated switchgrass, poplar, corn stover, and pine sawdust; poplar subjected to AFEX, controlled pH, lime, and SO(2) pretreatments; and the cellulose model compounds. Both methods proved effective in removing >90% lignin, but selectivity for lignin and carbohydrates removal was substrate and pretreatment dependent. For untreated biomass, PAA was more selective in removing lignin than SC/AA; however, both methods were less selective for pretreated solids. Cellulose characterizations revealed that PAA had less pronounced impacts on cellulose structure. PMID:23313683

Kumar, Rajeev; Hu, Fan; Hubbell, Christopher A; Ragauskas, Arthur J; Wyman, Charles E

2013-02-01

321

Comprehensive features of natural and in vitro selected GNRA tetraloop-binding receptors  

PubMed Central

Specific recognitions of GNRA tetraloops by small helical receptors are among the most widespread long-range packing interactions in large ribozymes. However, in contrast to GYRA and GAAA tetraloops, very few GNRA/receptor interactions have yet been identified to involve GGAA tetraloops in nature. A novel in vitro selection scheme based on a rigid self-assembling tectoRNA scaffold designed for isolation of intermolecular interactions with A-minor motifs has yielded new GGAA tetraloop-binding receptors with affinity in the nanomolar range. One of the selected receptors is a novel 12 nt RNA motif, (CCUGUG … AUCUGG), that recognizes GGAA tetraloop hairpin with a remarkable specificity and affinity. Its physical and chemical characteristics are comparable to those of the well-studied ‘11nt’ GAAA tetraloop receptor motif. A second less specific motif (CCCAGCCC … GAUAGGG) binds GGRA tetraloops and appears to be related to group IC3 tetraloop receptors. Mutational, thermodynamic and comparative structural analysis suggests that natural and in vitro selected GNRA receptors can essentially be grouped in two major classes of GNRA binders. New insights about the evolution, recognition and structural modularity of GNRA and A-minor RNA–RNA interactions are proposed.

Geary, Cody; Baudrey, Stephanie; Jaeger, Luc

2008-01-01

322

Out of the Laboratory: A Case Study with the IRUS Natural Language Interface.  

National Technical Information Service (NTIS)

DARPA's Strategic Computing Program in the application area of Navy Battle Management has provided us several challenges and opportunities in natural language processing research and development. At the beginning of the effort, a set of domain-independent...

D. Ayuso E. Walker J. Bruin K. Koile R. M. Weischedel

1986-01-01

323

LABORATORY STUDIES ON THE STABILITY AND TRANSPORT OF INORGANIC COLLOIDS THROUGH NATURAL AQUIFER MATERIAL  

EPA Science Inventory

The stability and transport of radio-labeled Fe2O3 particles were studied using laboratory batch and column techniques. Core material collected from shallow sand and gravel aquifer was used as the immobile column matrix material. Variables in the study included flow rate, pH, i...

324

PROJECTS IN IMAGINATIVE NATURE EDUCATION, SURVEY REPORT AND OUTDOOR LABORATORY PLAN.  

ERIC Educational Resources Information Center

THIS PLAN SUGGESTS HOW THE MID HUDSON-CATSKILLS MUSEUM CAN WORK CREATIVELY WITH COOPERATING SCHOOL DISTRICTS TO STRENGTHEN THEIR CURRICULUMS THROUGH OUTDOOR EDUCATION. THE RESULT OF THIS COOPERATIVE ENDEAVOR IS TO BE AN OUTDOOR LABORATORY CALLED "GATEWAY CENTER" LOCATED NEAR NEW PALTZ, NEW YORK. PART 1 CONTAINS (1) BACKGROUND INFORMATION, (2)…

National Audubon Society, New York, NY.

325

Role of the Special Librarian in a Federal Natural Resources Research Laboratory.  

ERIC Educational Resources Information Center

The function of a Federal research library reflects the purpose of the laboratory it serves and the philosophy of the librarian. Libraries at the Fish and Wildlife Service research centers must rely on small specialized collections, supplemented by a large amount of cooperation among agency libraries and other subject-related collections. Due to…

Eaton, Deborah A.

326

Laser system for natural gas detection. Phase I. Laboratory feasibility studies  

Microsoft Academic Search

Laboratory and field tests successfully proved the feasibility of laser remote sensing as a leak-survey tool in gas distribution systems. Using a pair of helium neon lasers to measure methane, the device exhibited at a 43-ft range a methane detection limit of 3 ppm in a gas plume with a 3.3-ft path length.

W. B. Grant; E. D. Hinkley

1981-01-01

327

Laser system for natural gas detection. Phase I. Laboratory Feasibility studies  

Microsoft Academic Search

Laboratory and field tests successfully proved the feasibility of laser remote sensing as a leak-survey tool in gas distribution systems, Using a pair of helium-neon lasers to measure methane, the device exhibited at a 43-ft range a methane detection limit of 3 ppm in a gas plume with a 3.3-ft path length.

W. B. Grant; E. D. Hinkley

1981-01-01

328

Animal genetic resources in Brazil: result of five centuries of natural selection.  

PubMed

Brazil has various species of domestic animals, which developed from breeds brought by the Portuguese settlers soon after their discovery. For five centuries, these breeds have been subjected to natural selection in specific environments. Today, they present characteristics adapted to the specific Brazilian environmental conditions. These breeds developed in Brazil are known as "Crioulo," "local," or naturalized. From the beginning of the 20th century, some exotic breeds, selected in temperate regions, have begun to be imported. Although more productive, these breeds do not have adaptive traits, such as resistance to disease and parasites found in breeds considered to be "native." Even so, little by little, they replaced the native breeds, to such an extent that the latter are in danger of extinction. In 1983, to avoid the loss of this important genetic material, the National Research Center for Genetic Resources and Biotechnology (Cenargen) of the Brazilian Agricultural Research Corporation (Embrapa) decided to include conservation of animal genetic resources in its research program Conservation and Utilization of Genetic Resources. Until this time, they were only concerned with conservation of native plants. Conservation has been carried out by various research centers of Embrapa, universities, state research corporations, and private farmers, with a single coordinator at the national level, Cenargen. Specifically, conservation is being carried out by conservation nuclei, which are specific herds in which the animals are being conserved, situated in the habitats where the animals have been subjected to natural selection. This involves storage of semen and embryos from cattle, horses, buffaloes, donkeys, goats, sheep, and pigs. The Brazilian Animal Germplasm Bank is kept at Cenargen, which is responsible for the storage of semen and embryos of various breeds of domestic animals threatened with extinction, where almost 45,000 doses of semen and more than 200 embryos exist presently. An important challenge for this program is to make the different segments of society realize the importance of the conservation of animal genetic resources. PMID:11775972

Mariante, A da S; Egito, A A

2002-01-01

329

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

Microsoft Academic Search

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

1996-01-01

330

SELECTION AND GENETIC ANALYSIS OF LABORATORY MUTANTS OF BOTRYOTINIA FUCKELIANA RESISTANT TO FENHEXAMID  

Microsoft Academic Search

SUMMARY Ten monoascosporic strains of Botryotinia fuckeliana were used in mycelium growth tests to evaluate baseline sensitivity to Fenhexamid, a fungicide recently intro- duced in the control of grey mould. Their response to the fungicide was EC 50 = 0.1-0.3 µg ml -1 and MIC = 0.3-3 µg ml -1 . Eight laboratory mutants resistant to the fungicide were obtained

M. A. De Guido; R. M. De; Miccolis Angelini; S. Pollastro; A. Santomauro; F. Faretra

2007-01-01

331

Assessment Laboratory Model. Fire Fighter Selection Examination Developed for City of Palo Alto, California.  

ERIC Educational Resources Information Center

The assessment laboratory function is supplementary and subsequent to the usual mass testing procedures. It is designed to elicit information not furnished by older more traditional methods, e.g., assessment of personal attributes, communication skills, etc. The exam involved participation by the candidates in both individual and group exercises.…

Harris, J. David; Macrae, Donald S.

332

Environmental cost-effectiveness analysis in intertemporal natural resource policy: evaluation of selective fishing gear.  

PubMed

In most decision-making involving natural resources, the achievements of a given policy (e.g., improved ecosystem or biodiversity) are rather difficult to measure in monetary units. To address this problem, the current paper develops an environmental cost-effectiveness analysis (ECEA) to include intangible benefits in intertemporal natural resource problems. This approach can assist managers in prioritizing management actions as least cost solutions to achieve quantitative policy targets. The ECEA framework is applied to a selective gear policy case in Danish mixed trawl fisheries in Kattegat and Skagerrak. The empirical analysis demonstrates how a policy with large negative net benefits might be justified if the intangible benefits are included. PMID:24184529

Kronbak, Lone Grønbæk; Vestergaard, Niels

2013-12-15

333

Identification of a neuroprotective and selective butyrylcholinesterase inhibitor derived from the natural alkaloid evodiamine.  

PubMed

Two sets of carbamates based on the natural alkaloid evodiamine were designed, synthesized and evaluated as potential butyrylcholinesterase inhibitors. Although a set of carbamates of 3-hydroxyevodiamine (10a-f) is inactive both at AChE and BChE, carbamates of 5-deoxo-3-hydroxyevodiamine (11a-f) exhibit much better potency with selectivity toward BChE. The heptyl carbamate of 5-deoxo-3-hydroxyevodiamine (11c) shows the best potency with an IC50 value of 77 nM and very good selectivity over AChE. ORAC and cell-based assays indicate 11c owns pronounced antioxidant properties with 1.75 Trolox equivalents and strong neuroprotection even from 1 ?M onwards. These combined activities might enable compound 11c to be a potential candidate for treatment of Alzheimer's disease. PMID:24819955

Huang, Guozheng; Kling, Beata; Darras, Fouad H; Heilmann, Jörg; Decker, Michael

2014-06-23

334

Immobilization of selected heavy metals in sewage sludge by natural zeolites.  

PubMed

This contribution presents the possibility of application of natural sorbent (Transcarpathian clinoptylolite (KL)) for immobilization of selected heavy metals in the sewage sludge. The influence of ion-exchange parameters (e.g. time, amount of zeolite) were discussed. Process of immobilization was performed using a static method (Batch). It was found that best possible conditions for immobilization of heavy metal ions were as follows: zeolite fraction 0.7-1.0mm, 5h of shaking, zeolite/sewage sludge ratio 2/98. PMID:18083511

Kosobucki, Przemys?aw; Kruk, Magdalena; Buszewski, Bogus?aw

2008-09-01

335

The age-specific force of natural selection and biodemographic walls of death  

PubMed Central

W. D. Hamilton’s celebrated formula for the age-specific force of natural selection furnishes predictions for senescent mortality due to mutation accumulation, at the price of reliance on a linear approximation. Applying to Hamilton’s setting the full nonlinear demographic model for mutation accumulation recently developed by Evans, Steinsaltz, and Wachter, we find surprising differences. Nonlinear interactions cause the collapse of Hamilton-style predictions in the most commonly studied case, refine predictions in other cases, and allow walls of death at ages before the end of reproduction. Haldane’s principle for genetic load has an exact but unfamiliar generalization.

Wachter, Kenneth W.; Evans, Steven N.; Steinsaltz, David

2013-01-01

336

Taming of a superbase for selective phenol desilylation and natural product isolation.  

PubMed

Hydroxyl moieties are highly prevalent in natural products. We previously reported a chemoselective strategy for enrichment of hydroxyl-functionalized molecules by formation of a silyl ether bond to a resin. To generate smaller pools of molecules for analysis, we developed cleavage conditions to promote stepwise release of phenolic silyl ethers followed by aliphatic silyl ethers with a "tamed" version of the superbase 1,1,3,3-tetramethylguanadine. We demonstrate this as a general strategy for selective deprotection of phenolic silyl ethers under neutral conditions at room temperature. PMID:23815363

Trader, Darci J; Carlson, Erin E

2013-07-19

337

Waterborne Disease Outbreaks: Selected Reprints of Articles on Epidemiology, Surveillance, Investigation, and Laboratory Analysis.  

National Technical Information Service (NTIS)

The publication is Volume II of a series of articles based on selected presentations made at the U.S. Environmental Protection Agency (EPA) and Association of State Drinking Water Administrators Workshop on Methods for Investigation of Waterborne Disease ...

G. F. Craun

1990-01-01

338

REtools: A laboratory program for restriction enzyme work: enzyme selection and reaction condition assistance  

PubMed Central

Background Restriction enzymes are one of the everyday tools used in molecular biology. The continuously expanding panel of known restriction enzymes (several thousands) renders their optimal use virtually impossible without computerized assistance. Several manufacturers propose on-line sites that assist scientists in their restriction enzyme work, however, none of these sites meet all the actual needs of laboratory workers, and they do not take into account the enzymes actually present in one's own laboratory. Results Using FileMaker Pro, we developed a stand-alone application which can run on both PCs and Macintoshes. We called it REtools, for Restriction Enzyme tools. This program, which references all currently known enzymes (>3500), permits the creation and update of a personalized list of restriction enzymes actually available in one's own laboratory. Upon opening the program, scientists will be presented with a user friendly interface that will direct them to different menus, each one corresponding to different situations that restriction enzyme users commonly encounter. We particularly emphasized the ease of use to make REtools a solution that laboratory members would actually want to use. Conclusion REtools, a user friendly and easily customized program to organize any laboratory enzyme stock, brings a software solution that will make restriction enzyme use and reaction condition determination straightforward and efficient. The usually unexplored potential of isoschizomers also becomes accessible to all, since REtools proposes all possible enzymes similar to the one(s) chosen by the user. Finally, many of the commonly overlooked subtleties of restriction enzyme work, such as methylation requirement, unusual reaction conditions, or the number of flanking bases required for cleavage, are automatically provided by REtools.

Martin, Patrick; Boulukos, Kim E; Pognonec, Philippe

2006-01-01

339

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

PubMed

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

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

2006-01-01

340

Seasonal and diel habitat selection by bluegills in a shallow natural lake  

USGS Publications Warehouse

Habitat use by bluegill Lepomis macrochirus may be dictated by the avoidance of predators and the availability of prey. Previous work suggests that bluegills large enough to avoid predators will select habitats based on foraging profitability. However, these studies focused on smaller fish (200 mm total length [TL]) bluegills in a shallow (mean depth = 1.2 m), 332-ha, natural lake (Pelican Lake, Nebraska) with both emergent and submergent vegetation distributed throughout. A total of 78 bluegills (200-273 mm TL) were implanted with radio transmitters and relocated daily for 6 d per month (April-September); up to 20 of the tagged fish were relocated every 2 h for a 24-h period once each month. Regardless of diel period, bluegills used open-water, emergent vegetation, submergent vegetation, and mixed emergent - submergent vegetation habitat types in similar proportions. During April, June, and July, male bluegills positively selected emergent vegetation, whereas female bluegills showed no vegetation selection preference during any month. Throughout the study period, bluegills never avoided open-water habitats, suggesting that larger individuals may continue to use open-water habitats in proportion to their availability. In addition, emergent vegetation appeared to be important, particularly for male bluegills. Although the mechanism for the positive selection of emergent vegetation by males was unclear, the protection or enhancement of such habitats may facilitate the preservation of quality bluegill populations in shallow lakes.

Paukert, C. P.; Willis, D. W.

2002-01-01

341

Inspection of the handling of selected chemicals at Lawrence Livermore National Laboratory  

SciTech Connect

The subject report is provided to inform of our findings and recommendations as a result of our inspection, and to give an opportunity to comment. The purpose of this inspection was to examine the potential for manufacture and/or diversion of 49 selected chemicals which were either controlled drugs or precursors that could be illegally used for the manufacture of such drugs, and to determine whether controls in place were adequate to detect misuse of these selected chemicals.

Not Available

1988-02-19

342

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

SciTech Connect

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.

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

1997-11-01

343

Genetic drift and natural selection in an isolated Zapotec-speaking community in the Valley of Oaxaca, southern Mexico.  

PubMed

Genetic drift and natural selection were analyzed in a genetically isolated Zapotec-speaking community in the Valley of Oaxaca, southern Mexico. Moderately intense genetic drift and selection potentials were found. Potential for drift was related to (1) the small effective size of the population, and (2) the exceptionally low number of migrants into the population. Potential for selection was due to (1) an unusually high variance in fertility, and (2) a high contribution of prereproductive mortality. Significant potential for genetic evolution was found due to genetic drift and natural selection. PMID:2759638

Little, B B; Malina, R M

1989-01-01

344

Naturally occurring high-chloride coal and superheater corrosion - a laboratory study  

SciTech Connect

An investigation was carried out on the fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals. The results of these laboratory and field tests were reported previously. In some supplementary tests, the effect of chloride was investigated on similar alloys while firing a high-chloride mid-western US bituminous coal in the same laboratory furnace. On the basis of exposure in the convection pass at temperatures from 1100-1700 F, Inconel Alloy 690 was found to have very good corrosion resistance, while Incoloy 800 H and Tp-310 s.s. were good transitional materials. Poor materials were T-22, 316 s.s., Inconel 617 and Inconel 671.

Plumley, A.L.; Roczniak, W.R.

1982-10-01

345

The Nature of Pre-service Science Teachers’ Argumentation in Inquiry-oriented Laboratory Context  

Microsoft Academic Search

The aim of this study was to investigate the kinds of argumentation schemes generated by pre-service elementary science teachers (PSTs) as they perform inquiry-oriented laboratory tasks, and to explore how argumentation schemes vary by task as well as by experimentation and discussion sessions. The model of argumentative and scienti?c inquiry was used as a design framework in the present study.

Yasemin Ozdem; Hamide Ertepinar; Jale Cakiroglu; Sibel Erduran

2011-01-01

346

Vermicompost as natural adsorbent for removing metal ions from laboratory effluents  

Microsoft Academic Search

The use of vermicompost as an adsorbent to remove Cd(II), Cu(II), Pb(II) and Zn(II) ions from laboratory effluents is proposed. Parameters such as adsorption pH, vermicompost amount, flow rate and particle size range were studied. An optimum pH range (2.5–5.0) was found for metal removal. The flow rate affected only slightly the removal of Cd(II) ions (about 10%). A decrease

G. D Matos; M. A. Z Arruda

2003-01-01

347

Soil organic carbon content estimation with laboratory-based visible-near-infrared reflectance spectroscopy: feature selection.  

PubMed

This study, with Yixing (Jiangsu Province, China) and Honghu (Hubei Province, China) as study areas, aimed to compare the successive projection algorithm (SPA) and the genetic algorithm (GA) in spectral feature selection for estimating soil organic carbon (SOC) contents with visible-near-infrared (Vis-NIR) reflectance spectroscopy and further to assess whether the spectral features selected from one site could be applied to another site. The SOC content and Vis-NIR reflectance spectra of soil samples were measured in the laboratory. Savitzky-Golay smoothing and log10(1/R) (R is reflectance) were used for spectral preprocessing. The reflectance spectra were resampled using different spacing intervals ranging from 2 to 10 nm. Then, SPA and GA were conducted for selecting the spectral features of SOC. Partial least square regression (PLSR) with full-spectrum PLSR and the spectral features selected by SPA (SPA-PLSR) and GA (GA-PLSR) were calibrated and validated using independent datasets, respectively. Moreover, the spectral features selected from one study area were applied to another area. Study results showed that, for the two study areas, the SPA-PLSR and GA-PLSR improved estimation accuracies and reduced spectral variables compared with the full spectrum PLSR in estimating SOC contents; GA-PLSR obtained better estimation results than SPA-PLSR, whereas SPA was simpler than GA, and the spectral features selected from Yixing could be well applied to Honghu, but not the reverse. These results indicated that the SPA and GA could reduce the spectral variables and improve the performance of PLSR model and that GA performed better than SPA in estimating SOC contents. However, SPA is simpler and time-saving compared with GA in selecting the spectral features of SOC. The spectral features selected from one dataset could be applied to a target dataset when the dataset contains sufficient information adequately describing the variability of samples of the target dataset. PMID:25061784

Shi, Tiezhu; Chen, Yiyun; Liu, Huizeng; Wang, Junjie; Wu, Guofeng

2014-08-01

348

The nature of laboratory domestication changes in freshly isolated Escherichia coli strains.  

PubMed

Adaptation of environmental bacteria to laboratory conditions can lead to modification of important traits, what we term domestication. Little is known about the rapidity and reproducibility of domestication changes, the uniformity of these changes within a species or how diverse these are in a single culture. Here, we analysed phenotypic changes in nutrient-rich liquid media or on agar of four Escherichia coli strains newly isolated through minimal steps from different sources. The laboratory-cultured populations showed changes in metabolism, morphotype, fitness and in some phenotypes associated with the sigma factor RpoS. Domestication events and phenotypic diversity started to emerge within 2-3 days in replicate subcultures of the same ancestor. In some strains, increased amino acid usage and higher fitness under nutrient limitation resembled those in mutants with the GASP (growth advantage in stationary phase) phenotype. The domestication changes are not uniform across a species or even within a single domesticated population. However, some parallelism in adaptation within repeat cultures was observed. Differences in the laboratory environment also determine domestication effects, which differ between liquid and solid media or with extended stationary phase. Important lessons for the handling and storage of organisms can be based on these studies. PMID:23889812

Eydallin, Gustavo; Ryall, Ben; Maharjan, Ram; Ferenci, Thomas

2014-03-01

349

Genetic signatures of natural selection in response to air pollution in red spruce (Picea rubens, Pinaceae).  

PubMed

One of the most important drivers of local adaptation for forest trees is climate. Coupled to these patterns, however, are human-induced disturbances through habitat modification and pollution. The confounded effects of climate and disturbance have rarely been investigated with regard to selective pressure on forest trees. Here, we have developed and used a population genetic approach to search for signals of selection within a set of 36 candidate genes chosen for their putative effects on adaptation to climate and human-induced air pollution within five populations of red spruce (Picea rubens Sarg.), distributed across its natural range and air pollution gradient in eastern North America. Specifically, we used FST outlier and environmental correlation analyses to highlight a set of seven single nucleotide polymorphisms (SNPs) that were overly correlated with climate and levels of sulphate pollution after correcting for the confounding effects of population history. Use of three age cohorts within each population allowed the effects of climate and pollution to be separated temporally, as climate-related SNPs (n = 7) showed the strongest signals in the oldest cohort, while pollution-related SNPs (n = 3) showed the strongest signals in the youngest cohorts. These results highlight the usefulness of population genetic scans for the identification of putatively nonneutral evolution within genomes of nonmodel forest tree species, but also highlight the need for the development and application of robust methodologies to deal with the inherent multivariate nature of the genetic and ecological data used in these types of analyses. PMID:24118331

Bashalkhanov, Stanislav; Eckert, Andrew J; Rajora, Om P

2013-12-01

350

Sexual size dimorphism in shorebirds, gulls, and alcids: the influence of sexual and natural selection.  

PubMed

Charadrii (shorebirds, gulls, and alcids) have an unusual diversity in their sexual size dimorphism, ranging from monomorphism to either male-biased or female-biased dimorphism. We use comparative analyses to investigate whether this variation relates to sexual selection through competition for mates or natural selection through different use of resources by males and females. As predicted by sexual selection theory, we found that in taxa with socially polygynous mating systems, males were relatively larger than females compared with less polygynous species. Furthermore, evolution toward socially polyandrous mating systems was correlated with decreases in relative male size. These patterns depend on the kinds of courtship displays performed by males. In taxa with acrobatic flight displays, males are relatively smaller than in taxa in which courtship involves simple flights or displays from the ground. This result remains significant when the relationship with mating system is controlled statistically, thereby explaining the enigma of why males are often smaller than females in socially monogamous species. We did not find evidence that evolutionary changes in sexual dimorphism relate to niche division on the breeding grounds. In particular, biparental species did not have greater dimorphism in bill lengths than uniparental species, contrary to the hypothesis that selection for ecological divergence on the breeding grounds has been important as a general explanation for patterns of bill dimorphism. Taken together, these results strongly suggest that sexual selection has had a major influence on sexual size dimorphism in Charadrii, whereas divergence in the use of feeding resources while breeding was not supported by our analyses. PMID:11005306

Székely, T; Reynolds, J D; Figuerola, J

2000-08-01

351

Natural selection drives the accumulation of amino acid tandem repeats in human proteins  

PubMed Central

Amino acid tandem repeats are found in a large number of eukaryotic proteins. They are often encoded by trinucleotide repeats and exhibit high intra- and interspecies size variability due to the high mutation rate associated with replication slippage. The extent to which natural selection is important in shaping amino acid repeat evolution is a matter of debate. On one hand, their high frequency may simply reflect their high probability of expansion by slippage, and they could essentially evolve in a neutral manner. On the other hand, there is experimental evidence that changes in repeat size can influence protein–protein interactions, transcriptional activity, or protein subcellular localization, indicating that repeats could be functionally relevant and thus shaped by selection. To gauge the relative contribution of neutral and selective forces in amino acid repeat evolution, we have performed a comparative analysis of amino acid repeat conservation in a large set of orthologous proteins from 12 vertebrate species. As a neutral model of repeat evolution we have used sequences with the same DNA triplet composition as the coding sequences—and thus expected to be subject to the same mutational forces—but located in syntenic noncoding genomic regions. The results strongly indicate that selection has played a more important role than previously suspected in amino acid tandem repeat evolution, by increasing the repeat retention rate and by modulating repeat size. The data obtained in this study have allowed us to identify a set of 92 repeats that are postulated to play important functional roles due to their strong selective signature, including five cases with direct experimental evidence.

Mularoni, Loris; Ledda, Alice; Toll-Riera, Macarena; Alba, M. Mar

2010-01-01

352

Out of the Laboratory: Teaching about the History and Nature of Science and Technology.  

ERIC Educational Resources Information Center

Identifies and discusses six themes for teaching "History and Nature of Science and Technology" developed by a teacher enhancement workshop. The themes are designed to provide instructional guidelines for teachers developing courses in this area. Includes sample project descriptions, learning outcomes, and instructional activities. (MJP)

Singleton, Laurel R.

1997-01-01

353

Detection and characterization of Wolbachia infections in laboratory and natural populations of different species of tsetse flies (genus Glossina)  

PubMed Central

Background Wolbachia is a genus of endosymbiotic ?-Proteobacteria infecting a wide range of arthropods and filarial nematodes. Wolbachia is able to induce reproductive abnormalities such as cytoplasmic incompatibility (CI), thelytokous parthenogenesis, feminization and male killing, thus affecting biology, ecology and evolution of its hosts. The bacterial group has prompted research regarding its potential for the control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. Results In the present study, we employed a Wolbachia specific 16S rRNA PCR assay to investigate the presence of Wolbachia in six different laboratory stocks as well as in natural populations of nine different Glossina species originating from 10 African countries. Wolbachia was prevalent in Glossina morsitans morsitans, G. morsitans centralis and G. austeni populations. It was also detected in G. brevipalpis, and, for the first time, in G. pallidipes and G. palpalis gambiensis. On the other hand, Wolbachia was not found in G. p. palpalis, G. fuscipes fuscipes and G. tachinoides. Wolbachia infections of different laboratory and natural populations of Glossina species were characterized using 16S rRNA, the wsp (Wolbachia Surface Protein) gene and MLST (Multi Locus Sequence Typing) gene markers. This analysis led to the detection of horizontal gene transfer events, in which Wobachia genes were inserted into the tsetse flies fly nuclear genome. Conclusions Wolbachia infections were detected in both laboratory and natural populations of several different Glossina species. The characterization of these Wolbachia strains promises to lead to a deeper insight in tsetse flies-Wolbachia interactions, which is essential for the development and use of Wolbachia-based biological control methods.

2012-01-01

354

Detection and characterization of Wolbachia infections in laboratory and natural populations of different species of tsetse flies (genus Glossina).  

PubMed

BACKGROUND: Wolbachia is a genus of endosymbiotic ?-Proteobacteria infecting a wide range of arthropods and filarial nematodes. Wolbachia is able to induce reproductive abnormalities such as cytoplasmic incompatibility (CI), thelytokous parthenogenesis, feminization and male killing, thus affecting biology, ecology and evolution of its hosts. The bacterial group has prompted research regarding its potential for the control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. RESULTS: In the present study, we employed a Wolbachia specific 16S rRNA PCR assay to investigate the presence of Wolbachia in six different laboratory stocks as well as in natural populations of nine different Glossina species originating from 10 African countries. Wolbachia was prevalent in Glossina morsitans morsitans, G. morsitans centralis and G. austeni populations. It was also detected in G. brevipalpis, and, for the first time, in G. pallidipes and G. palpalis gambiensis. On the other hand, Wolbachia was not found in G. p. palpalis, G. fuscipes fuscipes and G. tachinoides. Wolbachia infections of different laboratory and natural populations of Glossina species were characterized using 16S rRNA, the wsp (Wolbachia Surface Protein) gene and MLST (Multi Locus Sequence Typing) gene markers. This analysis led to the detection of horizontal gene transfer events, in which Wobachia genes were inserted into the tsetse flies fly nuclear genome. CONCLUSIONS: Wolbachia infections were detected in both laboratory and natural populations of several different Glossina species. The characterization of these Wolbachia strains promises to lead to a deeper insight in tsetse flies-Wolbachia interactions, which is essential for the development and use of Wolbachia-based biological control methods. PMID:22376025

Doudoumis, Vangelis; Tsiamis, George; Wamwiri, Florence; Brelsfoard, Corey; Alam, Uzma; Aksoy, Emre; Dalaperas, Stelios; Abd-Alla, Adly; Ouma, Johnson; Takac, Peter; Aksoy, Serap; Bourtzis, Kostas

2012-01-18

355

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines  

SciTech Connect

Selective NOx Recirculation (SNR) involves cooling the engine exhaust gas and then adsorbing the oxides of nitrogen (NOx) from the exhaust stream, followed by the periodic desorption of NOx. By returning the desorbed, concentrated NOx into the engine intake and through the combustion chamber, a percentage of the NOx is decomposed during the combustion process. An initial study of NOx decomposition during lean-burn combustion was concluded in 2004 using a 1993 Cummins L10G 240hp natural gas engine. It was observed that the air/fuel ratio, injected NO (nitric oxide) quantity and engine operating points affected NOx decomposition rates of the engine. Chemical kinetic modeling results were also used to determine optimum NOx decomposition operating points and were published in the 2004 annual report. A NOx decomposition rate of 27% was measured from this engine under lean-burn conditions while the software model predicted between 35-42% NOx decomposition for similar conditions. A later technology 1998 Cummins L10G 280hp natural gas engine was procured with the assistance of Cummins Inc. to replace the previous engine used for 2005 experimental research. The new engine was equipped with an electronic fuel management system with closed-loop control that provided a more stable air/fuel ratio control and improved the repeatability of the tests. The engine was instrumented with an in-cylinder pressure measurement system and electronic controls, and was adapted to operate over a range of air/fuel ratios. The engine was connected to a newly commissioned 300hp alternating current (AC) motoring dynamometer. The second experimental campaign was performed to acquire both stoichiometric and slightly rich (0.97 lambda ratio) burn NOx decomposition rates. Effects of engine load and speed on decomposition were quantified, but Exhaust Gas Recirculation (EGR) was not varied independently. Decomposition rates of up to 92% were demonstrated. Following recommendations at the 2004 ARES peer review meeting at Argonne National Laboratories, in-cylinder pressure was measured to calculate engine indicated mean effective pressure (IMEP) changes due to NOx injections and EGR variations, and to observe conditions in the cylinder. The third experimental campaign gathered NOx decomposition data at 800, 1200 and 1800 rpm. EGR was added via an external loop, with EGR ranging from zero to the point of misfire. The air/fuel ratio was set at both stoichiometric and slightly rich conditions, and NOx decomposition rates were calculated for each set of runs. Modifications were made to the engine exhaust manifold to record individual exhaust temperatures. The three experimental campaigns have provided the data needed for a comprehensive model of NOx decomposition during the combustion process, and data have confirmed that there was no significant impact of injected NO on in-cylinder pressure. The NOx adsorption system provided by Sorbent Technologies Corp. (Twinsburg, OH), comprised a NOx adsorber, heat exchanger and a demister. These components were connected to the engine, and data were gathered to show both the adsorption of NOx from the engine, and desorption of NOx from the carbon-based sorbent material back into the engine intake, using a heated air stream. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a bench top adsorption system was constructed and instrumented with thermocouples and the system output was fed into a NOx analyzer. The temperature of this apparatus was controlled while gathering data on the characteristics of the sorbent material. These data were required for development of a system model. Preliminary data were gathered in 2005, and will continue in early 2006. To assess the economic benefits of the proposed SNR technology the WVU research team has been joined in the last quarter by Dr Richard Turton (WVU-Chemical Engineering), who is modeling, sizing and costing the major components. The tasks will address modeling and preliminary design of the heat exchanger, demister and NOx sorbent chamber s

Nigel Clark; Gregory Thompson; Richard Atkinson; Richard Turton; Chamila Tissera; Emre Tatli; Andy Zimmerman

2005-12-28

356

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

NASA Astrophysics Data System (ADS)

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.

Dickes, Amanda Catherine; Sengupta, Pratim

2013-06-01

357

Genetic and Phenotypic Selection Affect Natural (Auto-) Antibody Reactivity of Chickens  

PubMed Central

Specificity, antibody isotype distribution and levels of natural antibodies (NAb) may be potential informative parameters for immune mediated natural disease resistance, immune modulation, and maintenance of physiological homeostasis. A large proportion of mammalian NAb have affinity for or are directed against self-antigens; so called natural auto antibodies (N(A)Ab). In the present study we showed the presence and typed levels and isotypes (total immunoglobulins, IgG and IgM) of N(A)Ab in plasma binding the ‘auto-antigen’ complex chicken liver cell lysate (CLL) of one-year old chickens from different genotype and phenotype backgrounds by ELISA and quantitative Western blotting. Higher levels of N(A)Ab binding CLL were found in plasma from chickens genetically selected for high specific antibody responses. In all birds, extensive staining patterns of plasma antibodies binding CLL were found for all isotypes, with IgG binding the highest number of CLL antigens and also showing the highest variation in staining patterns between individuals. Patterns of IgM antibodies binding CLL appeared to be more similar in all lines. Significant differences of binding patterns of N(A)Ab (antigen fragments of CLL and staining intensity) were detected between the different chicken lines, and lines could be clustered on the basis of their auto-antibody profile. In addition, also individual differences within lines were found. The present results indicate that analysis of the levels and the N(A)Ab repertoire of poultry like in mammals could provide a new way of distinguishing differences of immune competence and immune maturation between individuals, and could provide tools to select birds for health traits, or optimize hygiene and husbandry procedures.

de Jong, Britt G.; Lammers, Aart; Oberendorf, Leonora A. A.; Nieuwland, Mike G. B.; Savelkoul, Huub F. J.; Parmentier, Henk K.

2013-01-01

358

Size-selective grazing on bacteria by natural assemblages of estuarine flagellates and ciliates.  

PubMed Central

The small average cell size of in situ bacterioplankton, relative to cultured cells, has been suggested to be at least partly a result of selection of larger-sized cells by bacterivorous protozoa. In this study, we determined the relative rates of uptake of fluorescence-labeled bacteria (FLB), of various cell sizes and cell types, by natural assemblages of flagellates and ciliates in estuarine water. Calculated clearance rates of bacterivorous flagellates had a highly significant, positive relationship with size of FLB, over a range of average biovolume of FLB of 0.03 to 0.08 microns3. Bacterial cell type or cell shape per se did not appear to affect flagellate clearance rates. The dominant size classes of flagellates which ingested all types of FLB were 3- to 4-microns cells. Ciliates also showed a general preference for larger-sized bacteria. However, ciliates ingested a gram-positive enteric bacterium and a marine bacterial isolate at higher rates than they did a similarly sized, gram-negative enteric bacterium or natural bacterioplankton, respectively. From the results of an experiment designed to test whether the addition of a preferentially grazed bacterial strain stimulated clearance rates of natural bacterioplankton FLB by the ciliates, we hypothesized that measured differences in rates of FLB uptake were due instead to differences in effective retention of bacteria by the ciliates. In general, clearance rates for different FLB varied by a factor of 2 to 4. Selective grazing by protozoa of larger bacterioplankton cells, which are generally the cells actively growing or dividing, may in part explain the small average cell size, low frequency of dividing cells, and low growth rates generally observed for assemblages of suspended bacteria.

Gonzalez, J M; Sherr, E B; Sherr, B F

1990-01-01

359

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

ERIC Educational Resources Information Center

This second volume, a compilation of reprints of experimental notes in physics, was prepared by the American Association of Physics Teachers (AAPT) Committee on Apparatus and by the AAPT Executive Office in response to requests received by the Association for a completely new edition. The goal of the Committee was to provide a selection of…

American Association of Physics Teachers, Washington, DC.

360

Allocating structure to function: the strong links between neuroplasticity and natural selection.  

PubMed

A central question in brain evolution is how species-typical behaviors, and the neural function-structure mappings supporting them, can be acquired and inherited. Advocates of brain modularity, in its different incarnations across scientific subfields, argue that natural selection must target domain-dedicated, separately modifiable neural subsystems, resulting in genetically-specified functional modules. In such modular systems, specification of neuron number and functional connectivity are necessarily linked. Mounting evidence, however, from allometric, developmental, comparative, systems-physiological, neuroimaging and neurological studies suggests that brain elements are used and reused in multiple functional systems. This variable allocation can be seen in short-term neuromodulation, in neuroplasticity over the lifespan and in response to damage. We argue that the same processes are evident in brain evolution. Natural selection must preserve behavioral functions that may co-locate in variable amounts with other functions. In genetics, the uses and problems of pleiotropy, the re-use of genes in multiple networks have been much discussed, but this issue has been sidestepped in neural systems by the invocation of modules. Here we highlight the interaction between evolutionary and developmental mechanisms to produce distributed and overlapping functional architectures in the brain. These adaptive mechanisms must be robust to perturbations that might disrupt critical information processing and action selection, but must also recognize useful new sources of information arising from internal genetic or environmental variability, when those appear. These contrasting properties of "robustness" and "evolvability" have been discussed for the basic organization of body plan and fundamental cell physiology. Here we extend them to the evolution and development, "evo-devo," of brain structure. PMID:24431995

Anderson, Michael L; Finlay, Barbara L

2014-01-01

361

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

PubMed Central

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.

2013-01-01

362

Winter habitat selection of mule deer before and during development of a natural gas field  

USGS Publications Warehouse

Increased levels of natural gas exploration, development, and production across the Intermountain West have created a variety of concerns for mule deer (Odocoileus hemionus) populations, including direct habitat loss to road and well-pad construction and indirect habitat losses that may occur if deer use declines near roads or well pads. We examined winter habitat selection patterns of adult female mule deer before and during the first 3 years of development in a natural gas field in western Wyoming. We used global positioning system (GPS) locations collected from a sample of adult female mule deer to model relative frequency or probability of use as a function of habitat variables. Model coefficients and predictive maps suggested mule deer were less likely to occupy areas in close proximity to well pads than those farther away. Changes in habitat selection appeared to be immediate (i.e., year 1 of development), and no evidence of well-pad acclimation occurred through the course of the study; rather, mule deer selected areas farther from well pads as development progressed. Lower predicted probabilities of use within 2.7 to 3.7 km of well pads suggested indirect habitat losses may be substantially larger than direct habitat losses. Additionally, some areas classified as high probability of use by mule deer before gas field development changed to areas of low use following development, and others originally classified as low probability of use were used more frequently as the field developed. If areas with high probability of use before development were those preferred by the deer, observed shifts in their distribution as development progressed were toward less-preferred and presumably less-suitable habitats.

Sawyer, H.; Nielson, R. M.; Lindzey, F.; McDonald, L. L.

2006-01-01

363

Copy number variants and selective sweeps in natural populations of the house mouse (Mus musculus domesticus)  

PubMed Central

Copy–number variants (CNVs) may play an important role in early adaptations, potentially facilitating rapid divergence of populations. We describe an approach to study this question by investigating CNVs present in natural populations of mice in the early stages of divergence and their involvement in selective sweeps. We have analyzed individuals from two recently diverged natural populations of the house mouse (Mus musculus domesticus) from Germany and France using custom, high–density, comparative genome hybridization arrays (CGH) that covered almost 164 Mb and 2444 genes. One thousand eight hundred and sixty one of those genes we previously identified as differentially expressed between these populations, while the expression of the remaining genes was invariant. In total, we identified 1868 CNVs across all 10 samples, 200 bp to 600 kb in size and affecting 424 genic regions. Roughly two thirds of all CNVs found were deletions. We found no enrichment of CNVs among the differentially expressed genes between the populations compared to the invariant ones, nor any meaningful correlation between CNVs and gene expression changes. Among the CNV genes, we found cellular component gene ontology categories of the synapse overrepresented among all the 2444 genes tested. To investigate potential adaptive significance of the CNV regions, we selected six that showed large differences in frequency of CNVs between the two populations and analyzed variation in at least two microsatellites surrounding the loci in a sample of 46 unrelated animals from the same populations collected in field trappings. We identified two loci with large differences in microsatellite heterozygosity (Sfi1 and Glo1/Dnahc8 regions) and one locus with low variation across the populations (Cmah), thus suggesting that these genomic regions might have recently undergone selective sweeps. Interestingly, the Glo1 CNV has previously been implicated in anxiety–like behavior in mice, suggesting a differential evolution of a behavioral trait.

Bryk, Jaroslaw; Tautz, Diethard

2014-01-01

364

A Review of the Natural History and Laboratory Culture Methods for the Yellow Dung Fly, Scathophaga stercoraria  

PubMed Central

The yellow dung fly Scathophaga stercoraria (L.) (Diptera: Scathophagidae) is a widespread and locally abundant fly associated with the dung of large mammals, especially farm animals. This species has recently become a standard test organism for evaluating toxic effects of veterinary pharmaceuticals in livestock dung. In this context, a review of its natural history and a general description of the field and laboratory rearing methods of this species are provided here to benefit the scientific community as well as government regulators and applicants of eco-toxicological studies. For guidance, means and ranges are included for all relevant standard life history traits stemming from previously published data on Swiss populations.

Blanckenhorn, WU; Pemberton, AJ; Bussiere, LF; Roembke, J; Floate, KD

2010-01-01

365

On the Nature of the First Galaxies Selected at 350 Micrometers  

NASA Technical Reports Server (NTRS)

We present constraints on the nature of the first galaxies selected at 350 micrometers. The sample includes galaxies discovered in the deepest blank-field survey at 350 micrometers (in the Bo6tes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 lam 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 micrometer 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 micrometer 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 micrometers, galaxies selected at 350 micrometers have a similar range of far-infrared color temperatures. However, no 350 micrometer selected sources are reliably detected at 850 or 1100 micrometers. 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 micrometer flux densities (15 < S(sub 350) < 40 mJy) place these objects near the Herschel/SPIRE 350 micrometer confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 micrometers contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 micrometers 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. Key words: galaxies: high-redshift galaxies: starburst infrared: galaxies submillimeter

Khan, Sophia A.; Chanial, Pierre F.; Willner, S. P.; Pearson, Chris P.; Ashby, M. L. N.; Benford, Dominic J.; Clements, David L.; Dye, Simon; Farrah, Duncan; Fazio, G. G.; Huang, J. S.; Lebouteiller, V.; Le Floc'H, Emeric; Mainetti, Gabriele; Harvey Moseley, S.; Negrello, Mattia; Serjeant, Stephen; Shafer, Richard A.; Staguhn, Johannes; Sumner, Timothy J.; Vaccari, Mattia

2009-01-01

366

[Quantitative analysis method of natural gas combustion process combining wavelength selection and outlier spectra detection].  

PubMed

The present paper uses a combination method of wavelength selection and outlier spectra detection for quantitative analysis of nature gas combustion process based on its near infrared spectra. According to the statistical distribution of partial least squares (PLS) model coefficients and prediction errors, the method realized wavelength selection and outlier spectra detection, respectively. In contrast with PLS, PLS after leave-one-out for outlier detection (LOO-PLS), uninformative variable elimination by PLS (UVE-PLS) and UVE-PLS after leave-one-out for outlier detection (LOO-UVE-PLS), the root-mean-squared error of prediction (RMSEP) based on the method for CH4 prediction model is reduced by 14.33%, 14.33%, 10.96% and 12.21%; the RMSEP value for CO prediction model is reduced by 67.26%, 72.58%, 11.32% and 4.52%; the RMSEP value for CO2 prediction model is reduced by 5.95%, 19.7%, 36.71% and 4.04% respectively. Experimental results demonstrate that the method can significantly decrease the number of selected wavelengths, reduce model complexity and effectively detect outlier spectra. The established prediction model of analytes is more accurate as well as robust. PMID:23285890

Cao, Hui; Hu, Luo-Na; Zhou, Yan

2012-10-01

367

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

PubMed

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

Egeth, Marc; Kurzban, Robert

2012-01-01

368

Selection, characterization and genetic analysis of laboratory mutants of Botryotinia fuckeliana ( Botrytis cinerea ) resistant to the fungicide boscalid  

Microsoft Academic Search

Resistance to the fungicide boscalid in laboratory mutants of Botryotinia fuckeliana (Botrytis cinerea) was investigated. The baseline sensitivity to boscalid was evaluated in terms of colony growth (EC50?=?0.3–3 µg ml?1; MIC?=?10–30 µg ml?1) and conidial germination (EC50?=?0.03–0.1 µg ml?1; MIC?=?1–3 µg ml?1) tests. Mutants were selected in vitro from wild-type strains of the fungus on a fungicide-amended medium containing acetate as a carbon source. Mutants showed\\u000a two

Rita M. De Miccolis Angelini; Wassim Habib; Caterina Rotolo; Stefania Pollastro; Francesco Faretra

2010-01-01

369

Multi-modal hard x-ray imaging with a laboratory source using selective reflection from a mirror  

PubMed Central

Multi-modal hard x-ray imaging sensitive to absorption, refraction, phase and scattering contrast is demonstrated using a simple setup implemented with a laboratory source. The method is based on selective reflection at the edge of a mirror, aligned to partially reflect a pencil x-ray beam after its interaction with a sample. Quantitative scattering contrast from a test sample is experimentally demonstrated using this method. Multi-modal imaging of a house fly (Musca domestica) is shown as proof of principle of the technique for biological samples.

Pelliccia, Daniele; Paganin, David M.

2014-01-01

370

Multi-modal hard x-ray imaging with a laboratory source using selective reflection from a mirror.  

PubMed

Multi-modal hard x-ray imaging sensitive to absorption, refraction, phase and scattering contrast is demonstrated using a simple setup implemented with a laboratory source. The method is based on selective reflection at the edge of a mirror, aligned to partially reflect a pencil x-ray beam after its interaction with a sample. Quantitative scattering contrast from a test sample is experimentally demonstrated using this method. Multi-modal imaging of a house fly (Musca domestica) is shown as proof of principle of the technique for biological samples. PMID:24761297

Pelliccia, Daniele; Paganin, David M

2014-04-01

371

Naturally occurring high-chloride coal and superheater corrision laboratory study  

SciTech Connect

Commerical boiler tube alloys were tested for the corrosive effect of chloride while firing a naturally occurring high chloride Midwestern bituminous coal. On the basis of exposure in the convection pass at temperatures from 1100-1700/sup 0/F, Inconel Alloy 690 was found to have very good resistance to corrosion while Incoloy 800H and Tp-310 s. s. were good transitional materials. Poor materials were T-22, 316 s. s., Inconel 617, and Inconel 671.

Plumley, A.L.; Roczniak, W.R.

1982-10-01

372

Laboratory process control using natural language commands from a personal computer  

NASA Technical Reports Server (NTRS)

PC software is described which provides flexible natural language process control capability with an IBM PC or compatible machine. Hardware requirements include the PC, and suitable hardware interfaces to all controlled devices. Software required includes the Microsoft Disk Operating System (MS-DOS) operating system, a PC-based FORTRAN-77 compiler, and user-written device drivers. Instructions for use of the software are given as well as a description of an application of the system.

Will, Herbert A.; Mackin, Michael A.

1989-01-01

373

Detection of the signature of natural selection in humans: evidence from the Duffy blood group locus.  

PubMed Central

The Duffy blood group locus, which encodes a chemokine receptor, is characterized by three alleles-FY*A, FY*B, and FY*O. The frequency of the FY*O allele, which corresponds to the absence of Fy antigen on red blood cells, is at or near fixation in most sub-Saharan African populations but is very rare outside Africa. The FST value for the FY*O allele is the highest observed for any allele in humans, providing strong evidence for the action of natural selection at this locus. Homozygosity for the FY*O allele confers complete resistance to vivax malaria, suggesting that this allele has been the target of selection by Plasmodium vivax or some other infectious agent. To characterize the signature of directional selection at this locus, we surveyed DNA sequence variation, both in a 1.9-kb region centered on the FY*O mutation site and in a 1-kb region 5-6 kb away from it, in 17 Italians and in a total of 24 individuals from five sub-Saharan African populations. The level of variation across both regions is two- to threefold lower in the Africans than in the Italians. As a result, the pooled African sample shows a significant departure from the neutral expectation for the number of segregating sites, whereas the Italian sample does not. The FY*O allele occurs on two major haplotypes in three of the five African populations. This finding could be due to recombination, recurrent mutation, population structure, and/or mutation accumulation and drift. Although we are unable to distinguish among these alternative hypotheses, it is likely that the two major haplotypes originated prior to selection on the FY*O mutation.

Hamblin, M T; Di Rienzo, A

2000-01-01

374

Preliminary delineation of natural geochemical reactions, Snake River Plain aquifer system, Idaho National Engineering Laboratory and vicinity, Idaho  

SciTech Connect

The U.S. Geological Survey, in cooperation with the U.S. Department of Energy, is conducting a study to determine the natural geochemistry of the Snake River Plain aquifer system at the Idaho National Engineering Laboratory (INEL), Idaho. As part of this study, a group of geochemical reactions that partially control the natural chemistry of ground water at the INEL were identified. Mineralogy of the aquifer matrix was determined using X-ray diffraction and thin-section analysis and theoretical stabilities of the minerals were used to identify potential solid-phase reactants and products of the reactions. The reactants and products that have an important contribution to the natural geochemistry include labradorite, olivine, pyroxene, smectite, calcite, ferric oxyhydroxide, and several silica phases. To further identify the reactions, analyses of 22 representative water samples from sites tapping the Snake River Plain aquifer system were used to determine the thermodynamic condition of the ground water relative to the minerals in the framework of the aquifer system. Principal reactions modifying the natural geochemical system include congruent dissolution of olivine, diopside, amorphous silica, and anhydrite; incongruent dissolution of labradorite with calcium montmorillonite as a residual product; precipitation of calcite and ferric oxyhydroxide; and oxidation of ferrous iron to ferric iron. Cation exchange reactions retard the downward movement of heavy, multivalent waste constituents where infiltration ponds are used for waste disposal.

Knobel, L.L.; Bartholomay, R.C.; Orr, B.R.

1997-05-01

375

Market power and the sale of Ontario residential natural gas: An institutional analysis and a laboratory experiment  

NASA Astrophysics Data System (ADS)

The Ontario residential natural gas market underwent a significant institutional change in 1986, after the federal government decontrolled natural gas prices. Currently, consumers may sign up for fixed-cost natural gas from a broker, or they may continue to be served by the regulated distribution company. This thesis examines the economic effects on consumers of the institutional change, and particularly whether or not market power was enhanced by the change. In the thesis, I first present the industrial organization of the residential natural gas sector, and explain the institutional evolution using an institutional economic approach. I then construct a model of the market environment, with sellers acting as middlemen in a well-defined Bertrand oligopoly setting with no production constraints and single-unit consumer demands. In this model, the only Nash equilibrium in the one-period game is the joint profit maximizing price, and its likelihood of obtaining depends on the nature of the cost of signing up new customers. I then take a version of this model into the laboratory with human subject sellers and simulated buyers and run six replications each of a balanced treatment design under a unique information mechanism that parallels individual customer canvassing used by sellers in the naturally-occurring market. Treatment variables are: number of sellers, number of simulated at-cost sellers present, and presence of input cost uncertainty for sellers. I find that adding any seller to the market has about the same impact on market price, irrespective of whether it is a human subject or a simulated at-cost seller. Although increasing the number of sellers does decrease the market price somewhat, it does not bring about the competitive outcome predicted by the benchmark microeconomic model. This research contributes to the literature on policy making and energy market design, as well as to experimental methodology aimed at policy evaluation.

Bloemhof, Barbara Lynn

376

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

USGS Publications Warehouse

The U.S. Geological Survey (USGS) Project Office at the Idaho National Engineering Laboratory (INEL), in cooperation with the U.S. Department of Energy and Idaho State University, 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 the Mud Lake Basin, and were archived at the USGS lithologic core library at the INEL. Mineralogy data indicate that the core samples from the Big Lost River Basin have larger mean and median percentages of quartz, total feldspar, and total clay minerals, but smaller mean and median percentages of calcite than the core samples from the Birch Creek Basin. Core samples from the Mud Lake Basin have abundant quartz, total feldspar, calcite, and total clay minerals.

Reed, Michael F.; Bartholomay, Roy C.

1994-01-01

377

The quest for natural selection in the age of comparative genomics.  

PubMed

Continued genome sequencing has fueled progress in statistical methods for understanding the action of natural selection at the molecular level. This article reviews various statistical techniques (and their applicability) for detecting adaptation events and the functional divergence of proteins. As large-scale automated studies become more frequent, they provide a useful resource for generating biological null hypotheses for further experimental and statistical testing. Furthermore, they shed light on typical patterns of lineage-specific evolution of organisms, on the functional and structural evolution of protein families and on the interplay between the two. More complex models are being developed to better reflect the underlying biological and chemical processes and to complement simpler statistical models. Linking molecular processes to their statistical signatures in genomes can be demanding, and the proper application of statistical models is discussed. PMID:17848974

Anisimova, M; Liberles, D A

2007-12-01

378

Salience: the key to the selection problem in natural language generation  

SciTech Connect

The authors argue that in domains where a strong notion of salience can be defined, it can be used to provide: (1) an elegant solution to the selection problem, i.e. the problem of how to decide whether a given fact should or should not be mentioned in the text; and (2) a simple and direct control framework for the entire deep generation process, coordinating proposing, planning, and realization. (Deep generation involves reasoning about conceptual and rhetorical facts, as opposed to the narrowly linguistic reasoning that takes place during realization.) The authors report on an empirical study of salience in pictures of natural scenes, and its use in a computer program that generates descriptive paragraphs comparable to those produced by people. 13 references.

Conklin, E.J.; McDonald, D.D.

1982-01-01

379

The Formulation of Explanations: An Invitation to Inquiry on Natural Selection  

NSDL National Science Digital Library

This activity uses the concept of natural selection to introduce the idea of formulating and testing scientific hypotheses. Through a focused discussion approach, the teacher provides information and allows students time to think, interact with peers, and propose explanations for observations described by the teacher. While working on this activity, students will be able to: identify questions that can be answered through scientific investigations, design and conduct a scientific investigation, and use appropriate tools and techniques to gather, analyze, and interpret data. They will also have an opportunity to develop descriptions, explanations, predictions, and models using evidence and think critically and logically to make relationships between evidence and explanations. This site contains all information and instructions to complete the activity.

380

A method for detecting centres of natural selection in protein structures: potential for predicting the location of functional areas.  

PubMed

A simple method has been developed to detect protein microenvironments which are likely to be the focus of natural selection, and thereby important for function. It relies on distinguishing between the probability of an amino acid type arising by genetic mutation and the probability that it will be chosen by natural selection. When applied to proteins of known tertiary structure, the method revealed that major differences exist in the balance between neutral and selected change, and also that functional sites can be highlighted. PMID:3254431

Dufton, M J; Bladon, P

1988-10-01

381

High Fitness of Heterokaryotypic Individuals Segregating Naturally within a Long-Standing Laboratory Population of Drosophila silvestris  

PubMed Central

Natural populations of Drosophila silvestris are polymorphic for inversions in one or more of four of the five major chromosome arms; laboratory stocks tend to retain this heterozygosity. A laboratory stock, U28T2, was started from a single naturally inseminated wild female caught at Kilauea Forest Reserve, Hawaii, in January 1977. Polytene analysis in 1980 showed the presence of three natural inversions in chromosome 4: k 2 is distal, t is central and l2 is proximal. The inversions are short but only short uncovered euchromatic sections exist at the distal and proximal ends. Periodic examinations through 1986 showed all three inversions to be persistent at moderately high frequencies. In 1984, a series of tests of mating performance of caged, mature males, taken at random as they eclosed from the stock, were followed by cytological testcrosses to females from a homokaryotypic stock. Only three of the eight possible haplotypes, k2/t/+ (A), +/+/l2 ( a) and +/+/+ (a') were present. Tests of crossing over show none in males; in females, there is about 1% in each of the two regions between the inversions. Only one such apparent crossover haplotype was found among 1084 examined in samples from this stock. Thus, chromosome arrangements A, a and a' virtually behave as wholechromosome alleles in both sexes. Of 146 males marked and tested in cages, 61 produced progeny; the others failed to reproduce. Of 58 males and 80 females producing progeny and analyzed cytologically, there were, respectively, 49 and 59 heterokaryotypes. On the basis of frequencies calculated for fertilized eggs, 33.6 males and 46.3 females are expected. The facts suggest that individual males with the Aa karyotype are particularly successful in production of offspring. Adult females show an excess of Aa' as well as Aa. Such high fitness of heterokaryotypes in the effective breeding adults could be a major factor in the maintenance of stable chromosomal polymorphisms both in laboratory stocks and in nature. Although some of this heterosis is clearly ascribable to differential survival, the facts suggest that there is a substantial opportunity, indeed a likelihood, for a contribution from differential mating among surviving adults.

Carson, Hampton L.

1987-01-01

382

Natural abundance nitrogen-15 nuclear magnetic resonance spectral studies on selected donors  

NASA Astrophysics Data System (ADS)

The natural abundance 15N-NMR chemical shifts of selected aliphatic amines, 2-substituted pyridine type compounds, bialicyclic tertiary amines have been measured as a function of the nature of the solvent. In the case of cyclic aliphatic amines, like piperidine, morpholine, piperazine, thiomorpholine, the nitrogen is more shielded in concentrated solution compared to that in dilute solution whereas in the hydrogen bonding and protonating solvents there is a prominent deshielding. 2-Substituted pyridines studied can be further divided into four sub groups. The site of hydrogen bonding and protonation in 2-amino, 2-hydroxy and 2-mercapto pyridines have been conclusively proved from the 15N-NMR chemical shifts and the well-known tautomeric forms of the above compounds. Similarly in the case of 2-(2-thienyl)pyridine and 2-(3-thienyl)pyridine, the site of donation has been proved as the nitrogen of the pyridine ring in both the compounds. In a similar manner, the site of hydrogen bonding and protonation in two individual compounds 2-anilinopyridine and 2-(2-pyridyl)benzimidazole have also been established. Among the bialicyclic amines, 1,2-diazabicyclo[2.2.2]octane (DABCO) behaved differently from the other two compounds. In both 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), it was possible to show that N 1-nitrogen in both the compounds is the site of donation. The effect of the second donor site on the 15N-NMR chemical shift, the site of donation in the selected compounds and some typical compounds reported in literature have been presented and discussed.

Someswara Rao, N.; Babu Rao, G.; Murthy, B. N.; Das, M. Maria; Prabhakar, T.; Lalitha, M.

2002-10-01

383

THE zCOSMOS-SINFONI PROJECT. I. SAMPLE SELECTION AND NATURAL-SEEING OBSERVATIONS  

SciTech Connect

The zCOSMOS-SINFONI project is aimed at studying the physical and kinematical properties of a sample of massive z {approx} 1.4-2.5 star-forming galaxies, through SINFONI near-infrared integral field spectroscopy (IFS), combined with the multiwavelength information from the zCOSMOS (COSMOS) survey. The project is based on one hour of natural-seeing observations per target, and adaptive optics (AO) follow-up for a major part of the sample, which includes 30 galaxies selected from the zCOSMOS/VIMOS spectroscopic survey. This first paper presents the sample selection, and the global physical characterization of the target galaxies from multicolor photometry, i.e., star formation rate (SFR), stellar mass, age, etc. The H{alpha} integrated properties, such as, flux, velocity dispersion, and size, are derived from the natural-seeing observations, while the follow-up AO observations will be presented in the next paper of this series. Our sample appears to be well representative of star-forming galaxies at z {approx} 2, covering a wide range in mass and SFR. The H{alpha} integrated properties of the 25 H{alpha} detected galaxies are similar to those of other IFS samples at the same redshifts. Good agreement is found among the SFRs derived from H{alpha} luminosity and other diagnostic methods, provided the extinction affecting the H{alpha} luminosity is about twice that affecting the continuum. A preliminary kinematic analysis, based on the maximum observed velocity difference across the source and on the integrated velocity dispersion, indicates that the sample splits nearly 50-50 into rotation-dominated and velocity-dispersion-dominated galaxies, in good agreement with previous surveys.

Mancini, C.; Renzini, A. [INAF-OAPD, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Foerster Schreiber, N. M.; Hicks, E. K. S.; Genzel, R.; Tacconi, L.; Davies, R. [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Cresci, G. [Osservatorio Astrofisico di Arcetri (OAF), INAF-Firenze, Largo E. Fermi 5, I-50125 Firenze (Italy); Peng, Y.; Lilly, S.; Carollo, M.; Oesch, P. [Institute of Astronomy, Department of Physics, Eidgenossische Technische Hochschule, ETH Zurich CH-8093 (Switzerland); Vergani, D.; Pozzetti, L.; Zamorani, G. [INAF-Bologna, Via Ranzani, I-40127 Bologna (Italy); Daddi, E. [CEA-Saclay, DSM/DAPNIA/Service d'Astrophysique, F-91191 Gif-Sur Yvette Cedex (France); Maraston, C. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, PO1 3HE Portsmouth (United Kingdom); McCracken, H. J. [IAP, 98bis bd Arago, F-75014 Paris (France); Bouche, N. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Shapiro, K. [Aerospace Research Laboratories, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); and others

2011-12-10

384

The Number of Mutations Selected During Adaptation in a Laboratory Population of Saccharomyces cerevisiae  

PubMed Central

There is currently limited empirical and theoretical support for the prevailing view that adaptation typically results from the fixation of many mutations, each with small phenotypic effects. Recent theoretical work suggests that, on the contrary, most of the phenotypic change during an episode of adaptation can result from the selection of a few mutations with relatively large effects. I studied the genetics of adaptation by populations of budding yeast to a culture regime of daily hundredfold dilution and transfer in a glucose-limited minimal liquid medium. A single haploid genotype isolated after 2000 generations showed a 76% fitness increase over its ancestor. This evolved haploid was crossed with its ancestor, and tetrad dissections were used to isolate a complete series of six meiotic tetrads. The Castle-Wright estimator of the number of loci at which adaptive mutations had been selected, modified to account for linkage and variation among mutations in the size of their effect, is 4.4. The estimate for a second haploid genotype, isolated from a separate population and with a fitness gain of 60%, was 2.7 loci. Backcrosses to the ancestor with the first evolved genotype support the inference that adaptation resulted primarily from two to five mutations. These backcrosses also indicated that deleterious mutations had hitchhiked with adaptive mutations in this evolved genotype.

Zeyl, Clifford

2005-01-01

385

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

USGS Publications Warehouse

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.

Coplen, T. B.; Hopple, J. A.; Bohlke, 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

386

Gravito-electrodynamics, Ehd and Their Applications To Natural Hazards and Laboratory Devices  

NASA Astrophysics Data System (ADS)

For the past two decades, theory of dusty and dirty plasmas in space and in the labo - ratory has been developed on the basis of both unconventional gravito-electrody- nam ics and a new EHD (electrohydrodynamics) with novel concepts of electric re- connection and critical ionization velocity as well as modern concepts of self-organ- ization and chaos and has been applied to explanations of a variety of new dust-re- lated and meteorologyico-electric phenomena such as planetary (Saturn's and Jupi- ter's) dust layer or ring formation, terrestrial dust layer formation, terrestrial light - ning including winter thunderstorms, rocket and tower triggered lightning, planetary (Saturn's, Jupiter's, and Io's) lightning, nebular lightning, ball lightning, tornadic thunderstorms, whirlwinds, cloud-to-ionosphere discharges, pre-earthquake atmo- sphereic and ionospheric effects, and new laboratory devices such as electric undu - lators, a universal electric-cusp type plasma reactor for basic laboratory studies, sim- ulations of atmospheric phenomena and pollution control and gas cleaning, plasma processing and new material production for industrial applications, and new devices such as towards cancer treatment for biological and medical applications. Reference H. Kikuchi, Electrohydrodynamics in Dusty and Dirty plasmas, Kluwer Academic Publishers, Dordrecht/The Netherlands, 2001. For describing any plasmas, particle dynamics plays always fundamental and impor - tant roles in understanding all of plasma behaviors. A variety of descriptions in a magnetic field such as a guiding center approach have well been developed as a test-particle approach particularly for a base of MHD. This is still true for EHD or EMHD, but additional factors become significant due to the existence of space charges and electric fields for EHD or EMHD in dielectric or semiconducting fluids. In cosmic plasmas, the existence of double layers, electric and magnetic dipoles or quadru-poles often affects the particle motions drastically even if particles are uncharged, and can play a crucial role in planetary dust layer or ring formation. This is a new discov-ery and has been discussed in detail for the past several EGS meetings. In the presenc e of quadrupole-like charged cloud configurations which constitute electric cusps and mirrors, a neutral or uncharged particle can be accelerated in an electric cusp, reaching a maximum speed near a cusp boundary, if the environment is a tenuous gas whatever it may be neutral or ionized, and also can be reflected back at a mirror point. Otherwise, a dust in an electric cusp is capable for a source origin of plasma layer formation, gas discharges or lightnings due to additional effect of `criti-cal velocity' if the local electric fields around the dust produced by quadrupole-like charged clouds are sufficiently high beyond a gas-breakdown threshold. Then electric reconnection through the dust is followed by streamer or leader formation due to the critical ionization effect and consequent gas discharges or lightnings. One of major features of new electrodynamics, gravito-electrodynamics, and EHD is a new addition of two basic concepts of electric reconnection and critical ionization . First, one may recall that a distribution of scattered charged clouds is so ubiquitous in space and in the laboratory, even in our daily life, whatever they are of large-scale or small-scale, like thunderclouds in the atmosphere, charged clouds in interstellar space, charges on the belt of Van de Graff generator, and a system of miniature thunder-clouds produced by frictional electricity almost everywhere, typically on human hairs. All those cases are capable for electric reconnection. Whenever electric reconnection occurs through dusts in the atmosphere, it can be accompanied by a critical ioniza-tion flow . In this way, electric reconnection and critical ionization could be a signifi-cant cause of electrification and electric discharge and play important roles in a varie-ty of phenomena in meteorologico-electric, dusty and dirty plasma environmen

Kikuchi, H.

387

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

PubMed

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

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

2014-01-01

388

Insights into cation exchange selectivity of a natural clinoptilolite by means of dielectric relaxation spectroscopy  

NASA Astrophysics Data System (ADS)

Purified natural clinoptilolite from the Tasajeras deposit, Cuba, and some of its metal exchanged forms are studied, at the dehydrated state, by means of dielectric relaxation spectroscopy (DRS) using two different modus operandi: complex impedance spectroscopy and dielectric dynamic thermal analysis. Data analysis yields the determination of the extra-framework cation (EFC) population into the various possible crystallographic sites of the zeolitic framework as well as of the activation energy characterizing the localized hopping mechanism of EFC. First, it is shown that the DRS responses obtained here match well with the previous reported data, which were previously localized EFCs in positions close to M1 and M2 sites when the clinoptilolite is modified to almost homoionic form. From this outcome, it can be concluded that all EFCs are in the same crystallographic situation regarding solvation or, in other terms, that no steric effect can be taken into account to explain cationic selectivity. Second, based on the assumption that the activation energy for EFC hopping is directly connected to the EFC/framework interaction and on simple thermodynamics consideration, we show this interaction does not govern the EFC exchange reaction. So, it is emphasized that EFC/H2O interaction is the key factor for cation exchange selectivity.

Rodríguez-Fuentes, Gerardo; Devautour-Vinot, Sabine; Diaby, Sekou; Henn, François

2011-09-01

389

Acute selective ablation of rat insulin promoter-expressing (RIPHER) neurons defines their orexigenic nature  

PubMed Central

Rat insulin promoter (RIP)-expressing neurons in the hypothalamus control body weight and energy homeostasis. However, genetic approaches to study the role of these neurons have been limited by the fact that RIP expression is predominantly found in pancreatic ?-cells, which impedes selective targeting of neurons. To define the function of hypothalamic RIP-expressing neurons, we set out to acutely and selectively eliminate them via diphtheria toxin-mediated ablation. Therefore, the diphtheria toxin receptor transgene was specifically expressed upon RIP-specific Cre recombination using a RIP-Cre line first described by Herrera (RIPHER-Cre) [Herrera PL (2000) Development 127:2317–2322]. Using proopiomelanocortin–expressing cells located in the arcuate nucleus of the hypothalamus and in the pituitary gland as a model, we established a unique protocol of intracerebroventricular application of diphtheria toxin to efficiently ablate hypothalamic cells with no concomitant effect on pituitary proopiomelanocortin–expressing corticotrophs in the mouse. Using this approach to ablate RIPHER neurons in the brain, but not in the pancreas, resulted in decreased food intake and loss of body weight and fat mass. In addition, ablation of RIPHER neurons caused increased c-Fos immunoreactivity of neurons in the paraventricular nucleus (PVN) of the hypothalamus. Moreover, transsynaptic tracing of RIPHER neurons revealed labeling of neurons located in the PVN and dorsomedial hypothalamic nucleus. Thus, our experiments indicate that RIPHER neurons inhibit anorexigenic neurons in the PVN, revealing a basic orexigenic nature of these cells.

Rother, Eva; Belgardt, Bengt F.; Tsaousidou, Eva; Hampel, Brigitte; Waisman, Ari; Myers, Martin G.; Bruning, Jens C.

2012-01-01

390

Extractive fixed-site polymer sorbent for selective boron removal from natural water.  

PubMed

Water contamination by boron is a widespread environmental problem. The World Health Organization (WHO) recommends maximum boron concentration of 2.4 mg L(-1) for drinking water. The paper presents a simple method for preparation of functionalized sheet sorbent for selective extraction of boron from natural water. The pores of commercially available poly(propylene) membrane were functionalized by room temperature in situ crosslinking of poly(vinylbenzyl chloride) with a cyclic diamine piperazine. The precursor membranes were chemically modified with N-methyl D-glucamine which is selective for boron. Characterization of membrane was carried out using scanning electron microscopy (SEM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) techniques. The functionalized membrane has been characterized in terms of parameters that influence the sorption of boron from aqueous streams like pH, uptake capacity, contact time, effects of competing ions and reusability. The maximum boron sorption capacity determined experimentally was 28 mg g(-1). The studies showed that trace concentrations of boron were quantitatively removed from water at neutral pH. The developed fixed site polymer sorbent exhibited high sorption capacity and fast kinetics as compared to various sorbents reported in literature. It was successfully applied for the removal of boron from ground water and seawater samples in presence of high concentration of interfering ions. PMID:23892170

Thakur, Neha; Kumar, Sanjukta A; Shinde, Rakesh N; Pandey, Ashok K; Kumar, Sangita D; Reddy, A V R

2013-09-15

391

Selective removal of copper (II) from natural waters by nanoporous sorbents functionalized with chelating diamines  

PubMed Central

Copper has been identified as a pollutant of concern by the Environmental Protection Agency (EPA) because of its widespread occurrence and toxic impact in the environment. Three nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu2+ adsorption from natural waters -- ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS®), ethylenediamine functionalized activated carbon (AC-CH2-EDA), and 1,10-Phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu2+ sorption, Cu2+ sorption capacities, rates, and selectivity of the sorbents were determined and compared with those of commercial sorbents (Chelex-100 ion exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed excellent Cu2+ removal (~95–99%) from river water and sea water over the pH range of 6.0–8.0. EDA-SAMMS and AC-CH2-EDA demonstrated rapid Cu2+ sorption kinetics (minutes) and good sorption capacities (26 and 17 mg Cu/g sorbent, respectively) in sea water, while Phen-FMC had excellent selectivity for Cu2+ over other metal ions (e.g. Ca2+, Fe2+, Ni2+, and Zn2+) and was able to achieve Cu levels below the EPA standards for river and sea waters.

Chouyyok, Wilaiwan; Shin, Yongsoon; Davidson, Joseph; Samuels, William D.; LaFemina, Nikki H.; Rutledge, Ryan D.; Fryxell, Glen E.; Sangvanich, Thanapon; Yantasee, Wassana

2010-01-01

392

Effects of Novel Isoform-Selective Phosphoinositide 3-Kinase Inhibitors on Natural Killer Cell Function  

PubMed Central

Phosphoinositide 3-kinases (PI3Ks) are promising targets for therapeutic development in cancer. The class I PI3K isoform p110? has received considerable attention in oncology because the gene encoding p110? (PIK3CA) is frequently mutated in human cancer. However, little is known about the function of p110? in lymphocyte populations that modulate tumorigenesis. We used recently developed investigational inhibitors to compare the function of p110? and other isoforms in natural killer (NK) cells, a key cell type for immunosurveillance and tumor immunotherapy. Inhibitors of all class I isoforms (pan-PI3K) significantly impaired NK cell-mediated cytotoxicity and antibody-dependent cellular cytotoxicity against tumor cells, whereas p110?-selective inhibitors had no effect. In NK cells stimulated through NKG2D, p110? inhibition modestly reduced PI3K signaling output as measured by AKT phosphorylation. Production of IFN-? and NK cell-derived chemokines was blocked by a pan-PI3K inhibitor and partially reduced by a p110?inhibitor, with lesser effects of p110? inhibitors. Oral administration of mice with MLN1117, a p110? inhibitor in oncology clinical trials, had negligible effects on NK subset maturation or terminal subset commitment. Collectively, these results support the targeting of PIK3CA mutant tumors with selective p110? inhibitors to preserve NK cell function.

Yea, Sung Su; So, Lomon; Mallya, Sharmila; Lee, Jongdae; Rajasekaran, Kamalakannan; Malarkannan, Subramaniam; Fruman, David A.

2014-01-01

393

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

SciTech Connect

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.

L.J. Henne; K.J. Buckley

2005-08-12

394

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

SciTech Connect

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 the Mud Lake Basin, and were archived at the USGS lithologic core library at the INEL. Mineralogy data indicate that core samples from the Big Lost River Basin have larger mean and median percentages of quartz, total feldspar, and total clay minerals, but smaller mean and median percentages of calcite than the core samples from the Birch Creek Basin. Core samples from the Mud Lake Basin have abundant quartz, total feldspar, calcite, and total clay minerals. Identification of the mineralogy of the Snake River Plain is needed to aid in the study of the hydrology and geochemistry of subsurface waste disposal.

Reed, M.F.; Bartholomay, R.C.

1994-08-01

395

Natural selection among Eurasians at genomic regions associated with HIV-1 control  

PubMed Central

Background HIV susceptibility and pathogenicity exhibit both interindividual and intergroup variability. The etiology of intergroup variability is still poorly understood, and could be partly linked to genetic differences among racial/ethnic groups. These genetic differences may be traceable to different regimes of natural selection in the 60,000 years since the human radiation out of Africa. Here, we examine population differentiation and haplotype patterns at several loci identified through genome-wide association studies on HIV-1 control, as determined by viral-load setpoint, in European and African-American populations. We use genome-wide data from the Human Genome Diversity Project, consisting of 53 world-wide populations, to compare measures of FST and relative extended haplotype homozygosity (REHH) at these candidate loci to the rest of the respective chromosome. Results We find that the Europe-Middle East and Europe-South Asia pairwise FST in the most strongly associated region are elevated compared to most pairwise comparisons with the sub-Saharan African group, which exhibit very low FST. We also find genetic signatures of recent positive selection (higher REHH) at these associated regions among all groups except for sub-Saharan Africans and Native Americans. This pattern is consistent with one in which genetic differentiation, possibly due to diversifying/positive selection, occurred at these loci among Eurasians. Conclusions These findings are concordant with those from earlier studies suggesting recent evolutionary change at immunity-related genomic regions among Europeans, and shed light on the potential genetic and evolutionary origin of population differences in HIV-1 control.

2011-01-01

396

Geospatial Toolkits and Resource Maps for Selected Countries from the National Renewable Energy Laboratory (NREL)  

DOE Data Explorer

NREL developed the Geospatial Toolkit (GsT) ù a map-based software application that integrates resource data and geographic information systems (GIS) ù for integrated resource assessment. A variety of agencies within countries and global datasets provided country-specific data. For some countries, NREL has developed a HOMER GsT version of the toolkit, which contains all of the features of the standard Geospatial Toolkit and also integrates HOMER, an optimization model for distributed power. Countries for which Geospatial Toolkits have been developed are: • Afghanistan • Bangladesh • Bhutan • Brazil • China • El Salvador • Ghana • Guatemala • Honduras • India (Northwest) • Mexico (Oaxaca) • Nicaragua • Pakistan • Sri Lanka NREL also has developed high-resolution resource maps and data products for selected, individual countries using its Geospatial Toolkit. Countries with both a GsT product and related maps and data products are Afghanistan, Bhutan, Northwest India, and Pakistan. [Taken and edited from http://www.nrel.gov/international/geospatial_toolkits.html

397

Photosynthetic acclimation responses of maize seedlings grown under artificial laboratory light gradients mimicking natural canopy conditions.  

PubMed

In this study we assessed the ability of the C4 plant maize to perform long-term photosynthetic acclimation in an artificial light quality system previously used for analyzing short-term and long-term acclimation responses (LTR) in C3 plants. We aimed to test if this light system could be used as a tool for analyzing redox-regulated acclimation processes in maize seedlings. Photosynthetic parameters obtained from maize samples harvested in the field were used as control. The results indicated that field grown maize performed a pronounced LTR with significant differences between the top and the bottom levels of the plant stand corresponding to the strong light gradients occurring in it. We compared these data to results obtained from maize seedlings grown under artificial light sources preferentially exciting either photosystem II or photosystem I. In C3 plants, this light system induces redox signals within the photosynthetic electron transport chain which trigger state transitions and differential phosphorylation of LHCII (light harvesting complexes of photosystem II). The LTR to these redox signals induces changes in the accumulation of plastid psaA transcripts, in chlorophyll (Chl) fluorescence values F \\rm s/F \\rm m, in Chl a/b ratios and in transient starch accumulation in C3 plants. Maize seedlings grown in this light system exhibited a pronounced ability to perform both short-term and long-term acclimation at the level of psaA transcripts, Chl fluorescence values F \\rm s/F \\rm m and Chl a/b ratios. Interestingly, maize seedlings did not exhibit redox-controlled variations of starch accumulation probably because of its specific differences in energy metabolism. In summary, the artificial laboratory light system was found to be well-suited to mimic field light conditions and provides a physiological tool for studying the molecular regulation of the LTR of maize in more detail. PMID:24062753

Hirth, Matthias; Dietzel, Lars; Steiner, Sebastian; Ludwig, Robert; Weidenbach, Hannah; And, Jeannette Pfalz; Pfannschmidt, Thomas

2013-01-01

398

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

NASA Technical Reports Server (NTRS)

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.

Justh, Hilary; Justus, C. G.

2007-01-01

399

Examining tellurium geochemistry using laboratory-based sorption studies and spectroscopic investigation of natural samples  

NASA Astrophysics Data System (ADS)

Increased use of tellurium, a toxic metalloid, in CdTe-based solar panels and other high-tech applications highlights the need for improved understanding of the geochemical controls over Te released in the near-surface environment. Many ore minerals and industrially important Te species are reduced (e.g., AuTe, BixTey, Te metal, CdTe) making them vulnerable to oxidation under surface conditions to tellurate (TeO42-) and tellurite (TeO32-) oxyanions. Understanding the geochemistry of Te oxyanions is an important first step understanding Te behavior in the near-surface environment. As with the geochemically similar selenium, our geochemical sorption models for tellurium oxyanions indicate a strong affinity for ferrihydrite. In addition, we used X-ray absorption spectroscopy to examine the sorption geometry of a tellurite-ferrihydrite complex, which yielded a Te-O bond distance of 1.97 Å. We also examined tellurium speciation in copper mine tailings and determined that, while most of the Te is in a bismuth telluride (Te-Bi bond distance is 3.07 Å), a small fraction of Te is bonded to oxygen, indicating that Te in these tailings is beginning to oxidize. These types of analysis are important to understanding the fundamental geochemistry of Te as well as determining what forms of Te occur in the natural environment.

Hayes, S.; Foster, A. L.; Balistrieri, L. S.

2011-12-01

400

Selected stratigraphic contacts for drill holes in LANL (Los Alamos National Laboratory) use areas of Yucca Flat, NTS (Nevada Test Site)  

Microsoft Academic Search

This report is a compilation of selected stratigraphic contacts in drill holes in areas of Yucca Flat, Nevada Test Site (NTS), used by the Los Alamos National Laboratory (LANL). Data presented for each drill hole includes the following: (1) hole name; (2) total depth (TD) of drill hole at completion of drilling; (3) depth below surface to selected stratigraphic contacts;

S. L. Jr. Drellack; A. P. Cavazos

1986-01-01

401

Selection of indigenous isolates of entomopathogenic soil fungus Metarhizium anisopliae under laboratory conditions.  

PubMed

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

Skalický, Aleš; Bohatá, Andrea; Simková, Jana; Osborne, Lance S; Landa, Zden?k

2014-07-01

402

Scanning electron microscopy investigations of laboratory-grown gas clathrate hydrates formed from melting ice, and comparison to natural hydrates  

USGS Publications Warehouse

Scanning electron microscopy (SEM) was used to investigate grain texture and pore structure development within various compositions of pure sI and sII gas hydrates synthesized in the laboratory, as well as in natural samples retrieved from marine (Gulf of Mexico) and permafrost (NW Canada) settings. Several samples of methane hydrate were also quenched after various extents of partial reaction for assessment of mid-synthesis textural progression. All laboratory-synthesized hydrates were grown under relatively high-temperature and high-pressure conditions from rounded ice grains with geometrically simple pore shapes, yet all resulting samples displayed extensive recrystallization with complex pore geometry. Growth fronts of mesoporous methane hydrate advancing into dense ice reactant were prevalent in those samples quenched after limited reaction below and at the ice point. As temperatures transgress the ice point, grain surfaces continue to develop a discrete "rind" of hydrate, typically 5 to 30 ??m thick. The cores then commonly melt, with rind microfracturing allowing migration of the melt to adjacent grain boundaries where it also forms hydrate. As the reaction continues under progressively warmer conditions, the hydrate product anneals to form dense and relatively pore-free regions of hydrate grains, in which grain size is typically several tens of micrometers. The prevalence of hollow, spheroidal shells of hydrate, coupled with extensive redistribution of reactant and product phases throughout reaction, implies that a diffusion-controlled shrinking-core model is an inappropriate description of sustained hydrate growth from melting ice. Completion of reaction at peak synthesis conditions then produces exceptional faceting and euhedral crystal growth along exposed pore walls. Further recrystallization or regrowth can then accompany even short-term exposure of synthetic hydrates to natural ocean-floor conditions, such that the final textures may closely mimic those observed in natural samples of marine origin. Of particular note, both the mesoporous and highly faceted textures seen at different stages during synthetic hydrate growth were notably absent from all examined hydrates recovered from a natural marine-environment setting.

Stern, L. A.; Kirby, S. H.; Circone, S.; Durham, W. B.

2004-01-01

403

The Earth-Moon-Sun natural laboratory for testing of gravitational and electromagnetic fields coupling  

NASA Astrophysics Data System (ADS)

Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on VSU test ground, at Main Geophysical Observa-tory(St. Petersburg), on Kamchatka pen., on Lake Baikal. The distance spaced reception of electrical and magnetic fields will allow to analyze more widely the nature of the investigated interactions. Monitoring of electromagnetic fields in the ELF range is being realized. The work is connected with search of interconnection of the electromagnetic field of the atmosphere boundary layer with the gravitational Compact Binaries wave fields. For analyzing Compact Binaries were taken with ELF of GW-radiation: J 0700+6418, J 1012+5307, J 1537+1155, J 1959+2048, J 2130+1210, J 1915+1606, J 1910+0004, J 1910+0004, J 1748-2446A.For analyz-ing the spectrum of the magnetic fields there was used the information of VSU station and the monitoring information of Japanese geomagnetic stations Kakioka and Mambetsu. The aim of such investigations is connected with displaying tide processes (the Moon tides) and gravita-tional wave influence of Compact Binaries in the electromagnetic fields.On the first stage of the investigations a correlative spectral analysis of the experimental data was being carried out. There was factually extracted the influence of the atmosphere lower layer electromagnetic field of the thermogravitational solar tides and a number of gravitational: M1, M2, N2. It was ob-tained that astrophysical sources GV-6, GV-3,GV-4, GV-8, GV-9 have the most probability of non-casual of events. The subsequent investigations are connected with search of main features accompanying such influences. They are signal modulations by diurnal and year's rotation of the Earth. Such modulations are peculiar to sources of non-terrestrial origin. We are planning an extraction of the radiation frequency change of the source because of energy loss for the radiation of GW. Such investigations turned out to be possible after developing the method of scanning experimental signal of electromagnetic field into non-correlated components. There is shown efficiency of using latent vectors of covariance matrixes to expose complex periodical component of time series, including the ease when such components don't have energetic dom-inate in time series.The work was carried out with supporting of grants RFBR 09-05-08176, Program DSPHS 2.1.1/5660.

Grunskaya, Lubov; Isakevich, Valiriy; Efimov, Vladislav; Zakirov, Alexander

404

Modulation of gap-junctional intercellular communication by a series of cyanobacterial samples from nature and laboratory cultures.  

PubMed

Cyanobacterial extracts have been recently shown to alter two in vitro biomarkers of tumor promotion, namely to cause inhibition of gap-junctional intercellular communication (GJIC) and activation of mitogen-activated protein kinases (Blaha et al., 2010a). In the present study, we investigated GJIC-inhibitory potencies of 10 laboratory strains representing common water bloom-forming cyanobacteria (Anabaena, Aphanizomenon, Cylindrospermopsis, Microcystis and Planktothrix) and six natural water bloom samples (dominated by Aphanizomenon sp. or Microcystis). The most pronounced inhibitions of GJIC in a model rat liver epithelial cell line WB-F344 were caused by methanolic extracts of Anabaena flos-aquae UTEX 1444, Aphanizomenon flos-aquae SAG 31.87, Aphanizomenon gracile RCX 06, Microcystis aeruginosa PCC 7806, Cylindrospermopsis raciborskii SAG 1.97, Planktothrix agardhii CCALA 159 and SAG 32.79, whereas weaker effects were induced by Aphanizomenon klebahnii CCALA 009 and no inhibition was induced by extracts of Aph. flos-aquae PCC 7905 and Aph. gracile SAG 31.79. Exudates of the laboratory cultured strains concentrated by solid phase extraction also induced species-specific inhibitory effects, but they did not necessarily correlate with the inhibitory potencies of extracts from the corresponding species. Interestingly, the GJIC-inhibitory effects may not be restricted to cyanobacteria, since exudates of two green alga species also affected GJIC, although their extracts caused no effects. The extracts from different natural water blooms inhibited GJIC with different potencies without apparent relation to bloom-species composition. Since the observed effects on GJIC did not correlate with the content of cyanotoxins microcystins and cylindrospermopsin in the tested samples, they were most likely induced by unknown compound(s). Our results indicate that putative tumor promoting compound(s) could be associated with different species of bloom-forming cyanobacteria, but their production is probably species- and strain-specific. PMID:21619891

Nováková, Kate?ina; Babica, Pavel; Adamovský, Ond?ej; Bláha, Lud?k

2011-07-01

405

A laboratory study of survival of selected microorganisms after heat treatment of biowaste used in biogas plants.  

PubMed

The aim of the study was to assess the effect of pasteurisation, as set by the European regulation EC 1774/2002, on selected pathogens and indicator organisms. Unpasteurised substrate (biowaste), including animal by-products from a full-scale biogas plant was heat treated under laboratory conditions at 70 degrees C and 55 degrees C for 30 min and 60 min. Heat treatment at 55 degrees C for 60 min was not sufficient to achieve a hygienically acceptable product. Heat treatment at 70 degrees C for 30 min and 60 min was effective in reducing pathogenic bacteria, Ascaris suum eggs, Swine vesicular disease virus and indicator organisms. However, this level of pasteurisation will still not reduce the quantity of Clostridia spores, or completely inactivate heat-resistant viruses such as Porcine parvovirus or Salmonella phage 28B. The results still give cause for some concern regarding the use of digested residue from biogasplants in agriculture. PMID:18513960

Sahlström, Leena; Bagge, Elisabeth; Emmoth, Eva; Holmqvist, Annika; Danielsson-Tham, Marie-Louise; Albihn, Ann

2008-11-01

406

Laboratory test reactor for the investigation of liquid reducing agents in the selective catalytic reduction of NOx  

NASA Astrophysics Data System (ADS)

A test reactor was designed and built for investigating liquid reducing agents in the selective catalytic reduction (SCR) process in the laboratory. The design of the experimental setup is described in detail and its performance was evaluated. Using a glass nebulizer, liquid reducing agents were sprayed directly onto a catalyst positioned in a heated glass reactor with a length of 250 mm and an internal diameter of 20.4 mm or 40 mm. Model exhaust gases were mixed from individual gas components and were heated up to 450 °C in a heat exchanger before entering the reactor. The off-gas was analyzed using two complimentary techniques, a multi-component online FTIR gas analysis and a liquid quench gas absorption setup, to detect higher molecular compounds and aerosols. Due to the versatility of construction, processes not related to SCR, but involving three-phase reactions with gases, liquids and a catalyst, can also be investigated.

Peitz, D.; Bernhard, A.; Elsener, M.; Kröcher, O.

2011-08-01

407

Comparison of longevity between a laboratory strain and a natural population of Anastrepha Fraterculus (Diptera: Tephritidae) under field cage conditions  

SciTech Connect

The South American fruit fly Anastrepha fraterculus (Wiedemann) is one of the most destructive fruit pests in this region, infesting major fruit crops. Implementation of the sterile insect technique (SIT) as part of an area-wide integrated approach against this species requires information on the survival of mass-reared and sterilized insects in the field and their ability to mate with wild females. The survival rates in field cages of both non-irradiated and irradiated laboratory flies were compared with that of wild flies. Both types of laboratory flies survived longer than their wild counterparts over the 8 days under the experimental conditions. The irradiation dose (70 Gy) did not affect survival of the laboratory reared flies. Our results improve the prospect of integrating the SIT into the control of A. fraterculus populations in Argentina. (author) [Spanish] Anastrepha fraterculus (Wiedemann), la mosca sudamericana de la fruta, es una de las plagas mas destructivas en la region que infesta a los principales cultivos de frutas. La implementacion de la Tecnica del Insecto Esteril (TIE) como parte de un manejo integrado en areas extensivas contra esta especie requiere ensayos que demuestren que los insectos producidos en forma masiva y esterilizados son capaces de sobrevivir en el campo y aparearse con las hembras silvestres. Se comparo la supervivencia de individuos de una linea de laboratorio, tanto irradiados como no irradiados con la de individuos de una poblacion natural. Los dos tratamientos de moscas de laboratorio sobrevivieron mas tiempo que las salvajes durante los 8 dias y en las condiciones ensayadas. La dosis de radiacion (70 Gy.) no afecto la supervivencia de las moscas criadas en laboratorio. Nuestros resultados mejoran las perspectivas de integrar la TIE en el control de las poblaciones argentinas de A. fraterculus. (author)

Gomez Cendra, P.; Vilardi, J. [Depto. Ecologia, Genetica y Evolucion, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, (1428) Buenos Aires (Argentina); Segura, D.; Cladera, J. [Instituto de Genetica, INTA Castelar, CC25, (1712), Buenos Aires (Argentina); Allinghi, A. [Comision Nacional de Energia Atomica, CNEA, Buenos Aires (Argentina)

2007-03-15

408

Selective removal of copper (II) from natural waters by nanoporous sorbents functionalized with chelating diamines  

SciTech Connect

The essential trace metal copper has been identified as a pollutant of concern by the Environmental Protection Agency (EPA) because of its widespread occurrence in the environment, often being found in concentrations capable of causing problems in organisms in that ecosystem. In this work, three different nanoporous sorbents containing chelating diamine functionalities were evaluated for Cu2+ adsorption in natural waters; these sorbents are ethylenediamine functionalized self-assembled monolayers on mesoporous supports (EDA-SAMMS®, SAMMS is a registered trademark of Steward Advanced Materials), ethylenediamine functionalized activated carbon (AC-CH2-EDA), and 1,10-Phenanthroline functionalized mesoporous carbon (Phen-FMC). The pH dependence of Cu2+ sorption and the Cu2+ sorption capacities of sorbents were determined. The Cu2+ adsorption rates and metal ion selectivity of these sorbents were compared to those of commercial sorbents (Chelex-100 ion exchange resin and Darco KB-B activated carbon). All three chelating diamine sorbents showed the excellent Cu2+ removal (~ 95-99%) from river water and sea water over the pH range of 6.0-8.0. Even under acidic conditions (e.g. pH of 3), AC-CH2-EDA and Phen-FMC were able to remove approximately ~49-58% of Cu2+ in sea water. EDA-SAMMS and AC-CH2-EDA demonstrated rapid Cu2+ sorption kinetics (reaching equilibrium within 5 min) and large adsorption capacities (26 and 17 mg Cu/g sorbent, respectively) in sea water. They also showed good selectivity for Cu2+ over other metal ions (e.g. Ca2+, Fe2+, Ni2+, and Zn2+) in sea water.

Chouyyok, Wilaiwan; Shin, Yongsoon; Davidson, Joseph D.; Samuels, William D.; LaFemina, Nikki H.; Rutledge, Ryan D.; Fryxell, Glen E.; Sangvanich, Thanapon; Yantasee, Wassana

2010-04-13

409

Natural selection of the major histocompatibility complex (Mhc) in Hawaiian honeycreepers (Drepanidinae)  

USGS Publications Warehouse

The native Hawaiian honeycreepers represent a classic example of adaptive radiation and speciation, but currently face one the highest extinction rates in the world. Although multiple factors have likely influenced the fate of Hawaiian birds, the relatively recent introduction of avian malaria is thought to be a major factor limiting honeycreeper distribution and abundance. We have initiated genetic analyses of class II ?? chain Mhc genes in four species of honeycreepers using methods that eliminate the possibility of sequencing mosaic variants formed by cloning heteroduplexed polymerase chain reaction products. Phylogenetic analyses group the honeycreeper Mhc sequences into two distinct clusters. Variation within one cluster is high, with dN > d S and levels of diversity similar to other studies of Mhc (B system) genes in birds. The second cluster is nearly invariant and includes sequences from honeycreepers (Fringillidae), a sparrow (Emberizidae) and a blackbird (Emberizidae). This highly conserved cluster appears reminiscent of the independently segregating Rfp-Y system of genes defined in chickens. The notion that balancing selection operates at the Mhc in the honeycreepers is supported by transpecies polymorphism and strikingly high dN/dS ratios at codons putatively involved in peptide interaction. Mitochondrial DNA control region sequences were invariant in the i'iwi, but were highly variable in the 'amakihi. By contrast, levels of variability of class II ?? chain Mhc sequence codons that are hypothesized to be directly involved in peptide interactions appear comparable between i'iwi and 'amakihi. In the i'iwi, natural selection may have maintained variation within the Mhc, even in the face of what appears to a genetic bottleneck.

Jarvi, S. I.; Tarr, C. L.; Mcintosh, C. E.; Atkinson, C. T.; Fleischer, R. C.

2004-01-01

410

Selective toxin-lipid membrane interactions of natural, haemolytic Scyphozoan toxins analyzed by surface plasmon resonance.  

PubMed

A comparison of the molecular interaction of natural Scyphozoan lysins with their bioactivity in a haemolytic assay was performed by establishing an efficient, automatable and reproducible procedure for the measurement of protein-membrane interactions. The toxin-membrane interactions were analyzed utilising a chip-based technology with immobilized liposomes as artificial cell membranes. The technique was established with streptolysin O as a cholesterol-selective model toxin and its cholesterol-selectivity has been proven. The haemolytic potency of protein fractions derived from the venom of the jellyfish Aurelia aurita and Cyanea capillata was tested and EC50 values of 35.3mug/mL and 43.1mug/mL against sheep and 13.5mug/mL and 8.8mug/mL against rabbit erythrocytes were measured. Cell membrane binding as a first step in the haemolytic process was analyzed using the Biacore((R)) technology. Major cell membrane lipids (cholesterol, sphingomyelin and phosphatidylcholine) were immobilized as pure liposomes and in binary mixtures. A preference for cholesterol and sphingomyelin of both jellyfish species was demonstrated. The specificity of the method was proven with a non-haemolytic A. aurita protein fraction that did not express a lipid binding. Additionally, an inactivated C. capillata lysine with negligible haemolytic activity showed a remaining but reduced adsorption onto lipid layers. The binding level of the lytic venom fraction of these dominant boreal jellyfish species increased as a function of protein concentration. The binding strength was expressed in RU50 values ranging from 12.4mug/mL to 35.4mug/mL, which were in the same order of magnitude as the EC50 values in the haemolytic assay. PMID:20599534

Helmholz, Heike

2010-10-01

411

Development of selective social buffering of the plasma cortisol response in laboratory-reared male guinea pigs (Cavia porcellus).  

PubMed

The authors examined the effect of different classes of females on the plasma cortisol response of male guinea pigs (Cavia porcellus) from shortly after weaning through full adulthood. Males housed under standard laboratory conditions with artificial harems of 2 unrelated females of similar age were tested at 4 age ranges (approximately Days 40, 120, 180, and 240). At each age range, males were placed into a novel environment for 2 hr on 4 separate occasions: while alone, with 1 female cage mate, with the other female cage mate, or with an unfamiliar female. Relative preference for the 2 female cage mates was determined from observations in the home cage. Puberty was estimated by plasma testosterone levels. At the 3 youngest ages, the more preferred, less preferred, and unfamiliar females did not differentially reduce the plasma cortisol response. At 240 days of age, only the presence of the more preferred female was able to significantly reduce cortisol levels. These results demonstrate a very selective social buffering effect on the plasma cortisol response in a nonmonogamous species. This effect emerges well after sexual maturity and can be observed under standard laboratory housing. PMID:19331458

Maken, Deborah S; Hennessy, Michael B

2009-04-01

412

Thoracic size-selective sampling of fibres: performance of four types of thoracic sampler in laboratory tests.  

PubMed

The counting of fibres on membrane filters could be facilitated by using size-selective samplers to exclude coarse particulate and fibres that impede fibre counting. Furthermore, the use of thoracic size selection would also remove the present requirement to discriminate fibres by diameter during counting. However, before thoracic samplers become acceptable for sampling fibres, their performance with fibres needs to be determined. This study examines the performance of four thoracic samplers: the GK2.69 cyclone, a Modified SIMPEDS cyclone, the CATHIA sampler (inertial separation) and the IOM thoracic sampler (porous foam pre-selector). The uniformity of sample deposit on the filter samples, which is important when counts are taken on random fields, was examined with two sizes of spherical particles (1 and 10 microm) and a glass fibre aerosol with fibres spanning the aerodynamic size range of the thoracic convention. Counts by optical microscopy examined fields on a set scanning pattern. Hotspots of deposition were detected for one of the thoracic samplers (Modified SIMPEDS with the 10 microm particles and the fibres). These hotspots were attributed to the inertial flow pattern near the port from the cyclone pre-separator. For the other three thoracic samplers, the distribution was similar to that on a cowled sampler, the current standard sampler for fibres. Aerodynamic selection was examined by comparing fibre concentration on thoracic samples with those measured on semi-isokinetic samples, using fibre size (and hence calculated aerodynamic diameter) and number data obtained by scanning electron microscope evaluation in four laboratories. The size-selection characteristics of three thoracic samplers (GK2.69, Modified SIMPEDS and CATHIA) appeared very similar to the thoracic convention; there was a slight oversampling (relative to the convention) for d(ae) < 7 microm, but that would not be disadvantageous for comparability with the cowled sampler. Only the IOM thoracic sampler tended to undersample the fibres relative to the thoracic convention. With the data divided into four classes based on fibre length, the size-selection characteristics appeared to be unaffected by fibre length for GK2.69, Modified SIMPEDS and CATHIA. Only the IOM thoracic sampler (with the foam selector) showed slightly lower selection for longer length classes of fibres. These results indicate that the tested samplers follow the thoracic sampling convention for fibres, and may be used to improve the quality and reliability of samples that are taken when there is likely to be significant background dust. PMID:15790615

Jones, A D; Aitken, R J; Fabriès, J F; Kauffer, E; Liden, G; Maynard, A; Riediger, G; Sahle, W

2005-08-01

413