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Sample records for fast speciation alternative

  1. Fast voltammetry of metals at carbon-fiber microelectrodes: towards an online speciation sensor.

    PubMed

    Pathirathna, Pavithra; Siriwardhane, Thushani; McElmurry, Shawn P; Morgan, Stephen L; Hashemi, Parastoo

    2016-11-14

    Speciation controls the chemical behavior of trace metals. Thus, there is great demand for rapid speciation analysis in a variety of fields. In this study, we describe the application of fast scan cyclic voltammetry (FSCV) and fast scan adsorption controlled voltammetry (FSCAV) to trace metal speciation analysis. We show that Cu(2+) can be detected using FSCAV in different matrices. We find that matrices with different Cu(2+) binding ability do not affect the equilibrium of Cu(2+) adsorption onto CFMs, and thus are an excellent predictor for free Cu(2+) ([Cu(2+)]free) in solution. We modelled a correlation between the FSCV response, [Cu(2+)]free and log Kf for 15 different Cu(2+) complexes. Using our model, we rapidly predicted, and verified [Cu(2+)]free and Kf of a real groundwater sample spiked with Cu(2+). We thus highlight the potential of fast voltammetry as a rapid trace metal speciation sensor.

  2. Arsenic speciation in clinical samples: urine analysis using fast micro-liquid chromatography ICP-MS.

    PubMed

    Morton, Jackie; Leese, Elizabeth

    2011-02-01

    Arsenic speciation is a subject that is developing all the time both from improvements in analytical techniques and from increases in toxicological understanding. Despite speciation methods being widely developed, arsenic speciation is not routinely offered as an analysis in clinical laboratory. The work in this paper describes a simple routine method for arsenic speciation that could be easily implemented in clinical laboratories. The method described, a new, fast analytical method for arsenic speciation, is reported using micro-liquid chromatography hyphenated to an inductively coupled plasma mass spectrometer (μLC-ICP-MS). The method uses a low-pressure delivery six-port valve with a 5 cm anion exchange column, which allows a fully resolved separation of five arsenic species (arsenobetaine [AB], arsenite [As(3+)], arsenate [As(5+)], mono-methylarsonic acid [MMA(5+)] and dimethylarsinic acid [DMA(5+)]) in urine in just 6 min. This fast analytical method offers an arsenic speciation method that is feasible for a laboratory that does not have the capability for a dedicated arsenic speciation LC-ICP-MS instrument. The micro-LC system is small, easy to install and is fully integrated with the ICP-MS software. The results reported here are from urine samples from 65 workers in a semiconductor work providing a sample for their routine biological monitoring to assess workplace exposure. Control samples from 20 unexposed people were also determined. Results show that the semiconductor workers exhibit very low levels of arsenic in their urine samples, similar to the levels in the controls, and thus are not significantly exposed to arsenic. Care must be taken when interpreting urinary arsenic species results because it is not always possible to differentiate between dietary and other external sources of exposure.

  3. Mn, Fe, Zn and As speciation in a fast-growing ferromanganese marine nodule

    SciTech Connect

    Marcus, Matthew A.; Manceau, Alain; Kersten, Michael

    2004-04-01

    The speciation of Mn, Fe, As and Zn in a fast-growing (0.02mm/yr), shallow-marine ferromanganese nodule has been examined by micro X-ray fluorescence, micro X-ray diffraction, and micro X-ray absorption spectroscopy. This nodule exhibits alternating Fe-rich and Mn-rich layers reflecting redox variations in water chemistry. Fe occurs as two-line ferrihydrite. The As is strictly associated with Fe and is mostly pentavalent, with an environment similar to that of As sorbed on or coprecipitated with synthetic ferrihydrite. The Mn is in the form of turbostratic birnessite with {approx} 10 percent trivalent manganese in the layers and probably {approx} 8 percent corner-sharing metal octahedra in the interlayers. The Zn is enriched on the rim of the nodule, associated with Mn. The Zn is completely (>90 percent) tetrahedrally coordinated and sorbed in the interlayers of birnessite on vacant layer Mn sites. The Zn and Mn species are similar to ones found in soils, suggesting common structural principles, despite the differing formation conditions in these systems.

  4. Boosted Fast Flux Loop Alternative Cooling Assessment

    SciTech Connect

    Glen R. Longhurst; Donna Post Guillen; James R. Parry; Douglas L. Porter; Bruce W. Wallace

    2007-08-01

    The Gas Test Loop (GTL) Project was instituted to develop the means for conducting fast neutron irradiation tests in a domestic radiation facility. It made use of booster fuel to achieve the high neutron flux, a hafnium thermal neutron absorber to attain the high fast-to-thermal flux ratio, a mixed gas temperature control system for maintaining experiment temperatures, and a compressed gas cooling system to remove heat from the experiment capsules and the hafnium thermal neutron absorber. This GTL system was determined to provide a fast (E > 0.1 MeV) flux greater than 1.0E+15 n/cm2-s with a fast-to-thermal flux ratio in the vicinity of 40. However, the estimated system acquisition cost from earlier studies was deemed to be high. That cost was strongly influenced by the compressed gas cooling system for experiment heat removal. Designers were challenged to find a less expensive way to achieve the required cooling. This report documents the results of the investigation leading to an alternatively cooled configuration, referred to now as the Boosted Fast Flux Loop (BFFL). This configuration relies on a composite material comprised of hafnium aluminide (Al3Hf) in an aluminum matrix to transfer heat from the experiment to pressurized water cooling channels while at the same time providing absorption of thermal neutrons. Investigations into the performance this configuration might achieve showed that it should perform at least as well as its gas-cooled predecessor. Physics calculations indicated that the fast neutron flux averaged over the central 40 cm (16 inches) relative to ATR core mid-plane in irradiation spaces would be about 1.04E+15 n/cm2-s. The fast-to-thermal flux ratio would be in excess of 40. Further, the particular configuration of cooling channels was relatively unimportant compared with the total amount of water in the apparatus in determining performance. Thermal analyses conducted on a candidate configuration showed the design of the water coolant and

  5. Fast ion chromatography-ICP-QQQ for arsenic speciation

    PubMed Central

    Jackson, Brian

    2015-01-01

    Two methods for the fast separation of arsenic species are presented. The general approach is to modify existing methodology utilizing carbonate eluents for a small particle size, short column length Hamilton PRPX100 column which is interfaced with the Agilent 8800 ICP-QQQ using oxygen as reaction gas and detection of AsO at m/z 91. Using H2O2 in the extractant to oxidize As(III) to As(V) it is possible to separate arsenobetaine from DMA, MMA and As(V) in 1.5 minutes. Such a method may be useful where a measure of total inorganic As is sufficient, for example for regulatory compliance in food or beverage testing. It is possible to separate six As species. i.e the four above and arsenocholine and As(III) in 4.5 minutes using a gradient separation. Such a method could be useful analysis of urinary arsenic species. Coupling with high sensitivity of ICP-QQQ yields equivalent or better detection limits than conventional methods with run times up to 5 times faster, which is a significant benefit for sample throughput and method development. PMID:26366032

  6. Evolution of blind beetles in isolated aquifers: a test of alternative modes of speciation.

    PubMed

    Leijs, Remko; van Nes, Egbert H; Watts, Chris H; Cooper, Steven J B; Humphreys, William F; Hogendoorn, Katja

    2012-01-01

    Evidence is growing that not only allopatric but also sympatric speciation can be important in the evolution of species. Sympatric speciation has most convincingly been demonstrated in laboratory experiments with bacteria, but field-based evidence is limited to a few cases. The recently discovered plethora of subterranean diving beetle species in isolated aquifers in the arid interior of Australia offers a unique opportunity to evaluate alternative modes of speciation. This naturally replicated evolutionary experiment started 10-5 million years ago, when climate change forced the surface species to occupy geographically isolated subterranean aquifers. Using phylogenetic analysis, we determine the frequency of aquifers containing closely related sister species. By comparing observed frequencies with predictions from different statistical models, we show that it is very unlikely that the high number of sympatrically occurring sister species can be explained by a combination of allopatric evolution and repeated colonisations alone. Thus, diversification has occurred within the aquifers and likely involved sympatric, parapatric and/or microallopatric speciation.

  7. Speciation of Organic By-Products from the Thermal Decomposition of Alternative Automotive Fuels.

    PubMed

    Taylor, Philip H; Shanbhag, Santosh; Rubey, Wayne A; Dellinger, Barry; Bergin, Michelle

    1999-01-01

    The high-temperature thermal degradation of four alternative automotive fuels (methanol, ethanol, natural gas, and liquefied petroleum (LP) gas) have been examined as a function of fuel-oxygen equivalence ratio and exposure temperature using fused silica flow reactor instrumentation coupled to in-line GC-TCD and GC-MS detection. Organic speciation for methanol, natural gas, and LP gas were consistent with previous measurements. However, several previously undetected organic by-products were observed from ethanol oxidation and pyrolysis. Organic speciation was found to vary significantly between methanol and ethanol and less so between natural gas and LP gas. Non-methane organic gases (NMOG) and specific reactivities of the respective fuels were measured, and trends with respect to proposed reactivity adjustment factors are discussed. A qualitative comparison of NMOG quantified in the flow reactor tests with the results of recent vehicle tests is also reported. The most significant differences in the comparisons were observed for toxic compounds, including the lack of detection of acetalde-hyde, 1,3-butadiene, and benzene from flow reactor experiments of methanol degradation, and the lack of detection of 1,3-butadiene from flow reactor experiments of ethanol combustion. Possible sources for the formation of these compounds in vehicle tests are discussed.

  8. Oxygen speciation in upgraded fast pyrolysis bio-oils by comprehensive two-dimensional gas chromatography.

    PubMed

    Omais, Badaoui; Crepier, Julien; Charon, Nadège; Courtiade, Marion; Quignard, Alain; Thiébaut, Didier

    2013-04-21

    Biomass fast pyrolysis is considered as a promising route to produce liquid for the transportation field from a renewable resource. However, the derived bio-oils are mainly oxygenated (45-50%w/w O on a wet basis) and contain almost no hydrocarbons. Therefore, upgrading is necessary to obtain a liquid with lower oxygen content and characterization of oxygenated compounds in these products is essential to assist conversion reactions. For this purpose, comprehensive two-dimensional gas chromatography (GC × GC) can be investigated. Oxygen speciation in such matrices is hampered by the large diversity of oxygenated families and the complexity of the hydrocarbon matrix. Moreover, response factors must be taken into account for oxygenate quantification as the Flame Ionisation Detector (FID) response varies when a molecule contains heteroatoms. To conclude, no distillation cuts were accessible and the analysis had to cover a large range of boiling points (30-630 °C). To take up this analytical challenge, a thorough optimization approach was developed. In fact, four GC × GC column sets were investigated to separate oxygenated compounds from the hydrocarbon matrix. Both model mixtures and the upgraded biomass flash pyrolysis oil were injected using GC × GC-FID to reach a suitable chromatographic separation. The advantages and drawbacks of each column combination for oxygen speciation in upgraded bio-oils are highlighted in this study. Among the four sets, an original polar × semi-polar column combination was selected and enabled the identification by GC × GC-ToF/MS of more than 40 compounds belonging to eight chemical families: ketones, furans, alcohols, phenols, carboxylic acids, guaiacols, anisols, and esters. For quantification purpose, the GC × GC-FID chromatogram was divided into more than 60 blobs corresponding to the previously identified analyte and hydrocarbon zones. A database associating each blob to a molecule and its specific response factor (determined

  9. Teacher Perspectives on Their Alternative Fast-Track Induction

    ERIC Educational Resources Information Center

    Haim, Orly; Amdur, Lisa

    2016-01-01

    The purpose of this study was to explore the professional challenges and concerns of 30 second career teachers (SCTs) participating in an alternative fast-track induction program during their first year of teaching. Additionally, the study investigated their perspectives of the institutional support provided to them. The main source of data was…

  10. Dissolved phosphorus speciation of flash carbonization, slow pyrolysis, and fast pyrolysis biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pyrolysis of waste biomass is a promising technology to produce sterile and renewable organic phosphorus fertilizers. Systematic studies are necessary to understand how different pyrolysis platforms influence the chemical speciation of dissolved (bioavailable) phosphorus. This study employed solut...

  11. Development of alternate extractant systems for fast reactor fuel cycle

    SciTech Connect

    Vasudeva Rao, P.R.; Suresh, A.; Venkatesan, K.A.; Srinivasan, T.G.; Raj, Baldev

    2007-07-01

    Due to the limitations of TBP in processing of high burn-up, Pu-rich fast reactor fuels, there is a need to develop alternate extractants for fast reactor fuel processing. In this context, our Centre has been examining the suitability of alternate tri-alkyl phosphates. Third phase formation in the extraction of Th(IV) by TBP, tri-n-amyl phosphate (TAP) and tri-2-methyl-butyl phosphate (T2MBP) from nitric acid media has been investigated under various conditions to derive conclusions on their application for extraction of Pu at macro levels. The chemical and radiolytic degradation of tri-n-amyl-phosphate (TAP) diluted in normal paraffin hydrocarbon (NPH) in the presence of nitric acid has been investigated by the measurement of plutonium retention in organic phase. The potential application of room temperature ionic liquids (RTILs) for reprocessing of spent nuclear fuel has been explored. Extraction of uranium (VI) and palladium (II) from nitric acid medium by commercially available RTIL and tri-n-butyl phosphate solution in RTIL have been studied and the feasibility of electrodeposition of uranium as uranium oxide (UO{sub 2}) and palladium (II) as metallic palladium from the loaded organic phase have been demonstrated. This paper describes results of the above studies and discusses the suitability of the systems for fast reactor fuel reprocessing. (authors)

  12. Determinants of weight loss success with alternate day fasting.

    PubMed

    Varady, Krista A; Hoddy, Kristin K; Kroeger, Cynthia M; Trepanowski, John F; Klempel, Monica C; Barnosky, Adrienne; Bhutani, Surabhi

    2016-01-01

    This study examined what characteristics predict weight loss success with alternate day fasting (ADF). Four 8-week trials of ADF (n=121) were included in the analysis. Subjects aged 50-59 y achieved greater (P=0.01) weight loss than other age groups. Males and females achieved similar weight loss. Caucasian subjects achieved greater (P=0.03) weight loss than other races. Baseline body weight and baseline BMI did not predict degree of weight loss achieved with the diet. These findings may help clinicians to decide which population groups may benefit most from an ADF approach.

  13. Fast Reactor Alternative Studies: Effects of Transuranic Groupings on Metal and Oxide Sodium Fast Reactor Designs

    SciTech Connect

    R. Ferrer; M. Asgari; S. Bays; B. Forget

    2007-09-01

    A 1000 MWth commercial-scale Sodium Fast Reactor (SFR) design with a conversion ratio (CR) of 0.50 was selected in this study to perform perturbations on the external feed coming from Light Water Reactor Spent Nuclear Fuel (LWR SNF) and separation groupings in the reprocessing scheme. A secondary SFR design with a higher conversion ratio (CR=0.75) was also analyzed as a possible alternative, although no perturbations were applied to this model.

  14. Leveraging transcript quantification for fast computation of alternative splicing profiles

    PubMed Central

    Alamancos, Gael P.; Pagès, Amadís; Trincado, Juan L.; Bellora, Nicolás; Eyras, Eduardo

    2015-01-01

    Alternative splicing plays an essential role in many cellular processes and bears major relevance in the understanding of multiple diseases, including cancer. High-throughput RNA sequencing allows genome-wide analyses of splicing across multiple conditions. However, the increasing number of available data sets represents a major challenge in terms of computation time and storage requirements. We describe SUPPA, a computational tool to calculate relative inclusion values of alternative splicing events, exploiting fast transcript quantification. SUPPA accuracy is comparable and sometimes superior to standard methods using simulated as well as real RNA-sequencing data compared with experimentally validated events. We assess the variability in terms of the choice of annotation and provide evidence that using complete transcripts rather than more transcripts per gene provides better estimates. Moreover, SUPPA coupled with de novo transcript reconstruction methods does not achieve accuracies as high as using quantification of known transcripts, but remains comparable to existing methods. Finally, we show that SUPPA is more than 1000 times faster than standard methods. Coupled with fast transcript quantification, SUPPA provides inclusion values at a much higher speed than existing methods without compromising accuracy, thereby facilitating the systematic splicing analysis of large data sets with limited computational resources. The software is implemented in Python 2.7 and is available under the MIT license at https://bitbucket.org/regulatorygenomicsupf/suppa. PMID:26179515

  15. Testing alternative models for sexual isolation in natural populations of Littorina saxatilis: indirect support for by-product ecological speciation?

    PubMed

    Cruz, R; Carballo, M; Conde-Padín, P; Rolán-Alvarez, E

    2004-03-01

    Two ecotypes of the rough periwinkle Littorina saxatilis occur at different shore levels, showing assortative mating for size and partial reproductive isolation when they meet at the mid-shore. This system represents a putative case of incomplete speciation in sympatry. Two processes contribute to the assortative mating: morph-specific microhabitat aggregation and mate choice. The estimation of mate choice coefficients in nature and a simulation of the aggregation effects on sexual isolation were used to disentangle these processes as well as to test alternative mechanisms of mate choice. Mate choice significantly increased the frequency of within-morph pairs and significantly decreased the frequency of between-morph pairs, whereas those pairs including at least one hybrid morph mated randomly. These results allow us to reject a discriminant mate choice and support a model of evolution of sexual isolation as a side-effect of size-assortative mating in a context of divergent natural selection for size in the population. This mechanism is more compatible with a model of incomplete by-product ecological speciation, as suggested by previous evidence.

  16. Speciation rates decline through time in individual-based models of speciation and extinction.

    PubMed

    Wang, Shaopeng; Chen, Anping; Fang, Jingyun; Pacala, Stephen W

    2013-09-01

    A well-documented pattern in the fossil record is a long-term decline in the origination rate of new taxa after diversity rebounds from a mass extinction. The mechanisms for this pattern remain elusive. In this article, we investigate the macroevolutionary predictions of an individual-based birth-death model (BDI model) where speciation and extinction rates emerge from population dynamics. We start with the simplest neutral model in which every individual has the same per capita rates of birth, death, and speciation. Although the prediction of the simplest neutral model agrees qualitatively with the fossil pattern, the predicted decline in per-species speciation rates is too fast to explain the long-term trend in fossil data. We thus consider models with variation among species in per capita rates of speciation and a suite of alternative assumptions about the heritability of speciation rate. The results show that interspecific variation in per capita speciation rate can induce differences among species in their ability to resist extinction because a low speciation rate confers a small but important demographic advantage. As a consequence, the model predicts an appropriately slow temporal decline in speciation rates, which provides a mechanistic explanation for the fossil pattern.

  17. Fast alternating projection methods for constrained tomographic reconstruction.

    PubMed

    Liu, Li; Han, Yongxin; Jin, Mingwu

    2017-01-01

    The alternating projection algorithms are easy to implement and effective for large-scale complex optimization problems, such as constrained reconstruction of X-ray computed tomography (CT). A typical method is to use projection onto convex sets (POCS) for data fidelity, nonnegative constraints combined with total variation (TV) minimization (so called TV-POCS) for sparse-view CT reconstruction. However, this type of method relies on empirically selected parameters for satisfactory reconstruction and is generally slow and lack of convergence analysis. In this work, we use a convex feasibility set approach to address the problems associated with TV-POCS and propose a framework using full sequential alternating projections or POCS (FS-POCS) to find the solution in the intersection of convex constraints of bounded TV function, bounded data fidelity error and non-negativity. The rationale behind FS-POCS is that the mathematically optimal solution of the constrained objective function may not be the physically optimal solution. The breakdown of constrained reconstruction into an intersection of several feasible sets can lead to faster convergence and better quantification of reconstruction parameters in a physical meaningful way than that in an empirical way of trial-and-error. In addition, for large-scale optimization problems, first order methods are usually used. Not only is the condition for convergence of gradient-based methods derived, but also a primal-dual hybrid gradient (PDHG) method is used for fast convergence of bounded TV. The newly proposed FS-POCS is evaluated and compared with TV-POCS and another convex feasibility projection method (CPTV) using both digital phantom and pseudo-real CT data to show its superior performance on reconstruction speed, image quality and quantification.

  18. A novel fast gas chromatography method for higher time resolution measurements of speciated monoterpenes in air

    NASA Astrophysics Data System (ADS)

    Jones, C. E.; Kato, S.; Nakashima, Y.; Kajii, Y.

    2014-05-01

    Biogenic emissions supply the largest fraction of non-methane volatile organic compounds (VOC) from the biosphere to the atmospheric boundary layer, and typically comprise a complex mixture of reactive terpenes. Due to this chemical complexity, achieving comprehensive measurements of biogenic VOC (BVOC) in air within a satisfactory time resolution is analytically challenging. To address this, we have developed a novel, fully automated Fast Gas Chromatography (Fast-GC) based technique to provide higher time resolution monitoring of monoterpenes (and selected other C9-C15 terpenes) during plant emission studies and in ambient air. To our knowledge, this is the first study to apply a Fast-GC based separation technique to achieve quantification of terpenes in ambient air. Three chromatography methods have been developed for atmospheric terpene analysis under different sampling scenarios. Each method facilitates chromatographic separation of selected BVOC within a significantly reduced analysis time compared to conventional GC methods, whilst maintaining the ability to quantify individual monoterpene structural isomers. Using this approach, the C9-C15 BVOC composition of single plant emissions may be characterised within a 14.5 min analysis time. Moreover, in-situ quantification of 12 monoterpenes in unpolluted ambient air may be achieved within an 11.7 min chromatographic separation time (increasing to 19.7 min when simultaneous quantification of multiple oxygenated C9-C10 terpenoids is required, and/or when concentrations of anthropogenic VOC are significant). These analysis times potentially allow for a twofold to fivefold increase in measurement frequency compared to conventional GC methods. Here we outline the technical details and analytical capability of this chromatographic approach, and present the first in-situ Fast-GC observations of 6 monoterpenes and the oxygenated BVOC (OBVOC) linalool in ambient air. During this field deployment within a suburban forest

  19. Computer modelling of the chemical speciation of caesium, uranium(VI) and neptunium(V) in human duodenal fluids under fasting conditions.

    PubMed

    Jones, Paul W; Taylor, David M; Webb, Louise M; Williams, David R

    2002-08-01

    A model simulating the human duodenal contents under physiologically realistic, fasting conditions was developed using the joint expert speciation system (JESS) computer program and database and used to investigate the chemical speciation of caesium, uranium(VI) and neptunium(V). Over the pH range 5.0-9.0, and the concentration range 5 x 10(-15) x 10(-5) mol dm(-3), caesium was predicted to occur predominantly as the absorbable free monovalent cation Cs+ (approximately 95%) with species such as CsHPO4- and CsCl representing the remainder. The presence or absence of sulphate at 2.1 x 10(-3) mol dm(-3) did not influence the predicted speciation. Uranium was predicted to be present entirely as a soluble, highly charged species, both in the absence and in the presence of sulphate. Between pH 5.0 and approximately 6.5 the UO2H2(PO4)2(2-) predominated, above this pH carbonate species, either UO2(CO3)4(6-) or, possibly, UO2(CO3)5(8-). At pH 8.0, and in the presence of sulphate, neptunium(V) was predicted to exist solely as the tetrasulphate species, whilst in the absence of sulphate, an array of negatively charged soluble carbonate species predominated. Studies over the pH range 5.0-9.0 predicted the formation of a spectrum of negatively charged carbonate and phosphate species, approximately 40% of the total neptunium was predicted to be present as the electrically net-neutral species NpO2HCO3 at pH6.0, approximately 20% at pH 7.0, approximately 10% at pH 7.5 and approximately 1% at pH 8.0. The observed speciation patterns of uranium and neptunium did not change over the concentration range 5 x 10(-15) - 5 x 10(-5) mol dm(-3) and no solid species were predicted to occur under the conditions simulated. Whether the predicted electrically net-neutral neptunium species or the uranium pentacarbonate species do actually occur under true physiological conditions remains to be established. The observed speciation patterns for caesium and uranium are consistent with the observed

  20. A novel Fast Gas Chromatography based technique for higher time resolution measurements of speciated monoterpenes in air

    NASA Astrophysics Data System (ADS)

    Jones, C. E.; Kato, S.; Nakashima, Y.; Kajii, Y.

    2013-12-01

    Biogenic emissions supply the largest fraction of non-methane volatile organic compounds (VOC) from the biosphere to the atmospheric boundary layer, and typically comprise a complex mixture of reactive terpenes. Due to this chemical complexity, achieving comprehensive measurements of biogenic VOC (BVOC) in air within a satisfactory time resolution is analytically challenging. To address this, we have developed a novel, fully automated Fast Gas Chromatography (Fast-GC) based technique to provide higher time resolution monitoring of monoterpenes (and selected other C9-C15 terpenes) during plant emission studies and in ambient air. To our knowledge, this is the first study to apply a Fast-GC based separation technique to achieve quantification of terpenes in air. Three chromatography methods have been developed for atmospheric terpene analysis under different sampling scenarios. Each method facilitates chromatographic separation of selected BVOC within a significantly reduced analysis time compared to conventional GC methods, whilst maintaining the ability to quantify individual monoterpene structural isomers. Using this approach, the C10-C15 BVOC composition of single plant emissions may be characterised within a ~ 14 min analysis time. Moreover, in situ quantification of 12 monoterpenes in unpolluted ambient air may be achieved within an ~ 11 min chromatographic separation time (increasing to ~ 19 min when simultaneous quantification of multiple oxygenated C9-C10 terpenoids is required, and/or when concentrations of anthropogenic VOC are significant). This corresponds to a two- to fivefold increase in measurement frequency compared to conventional GC methods. Here we outline the technical details and analytical capability of this chromatographic approach, and present the first in situ Fast-GC observations of 6 monoterpenes and the oxygenated BVOC linalool in ambient air. During this field deployment within a suburban forest ~ 30 km west of central Tokyo, Japan, the

  1. Development of a fast capillary electrophoresis-time-of-flight mass spectrometry method for the speciation of organotin compounds under separation conditions of high electrical field strengths.

    PubMed

    Malik, Ashok Kumar; Grundmann, Marco; Matysik, Frank-Michael

    2013-11-15

    A novel approach has been developed for the separation of organotin species with capillary electrophoresis hyphenated to time-of-flight mass spectrometry. It has been applied to the development of a method for the determination and speciation of organotin compounds namely, dibutyltin (DBT), tributyltin (TBT), diphenyltin (DPT) and triphenyltin (TPT) in water samples. Experiments were made with a special laboratory constructed CE instrument. A non-aqueous buffer system compatible with TOF-MS has been developed using ammonium acetate-acetic acid (50 mM and 1 M) in acetonitrile: methanol (80:20). The total analysis time is less than 3 min for these compounds under the conditions developed. The method has been applied successfully to the determination of these compounds in river water samples. Detection limits of the CE-TOF-MS method were between 1 and 8×10(-7) M, and between 2 and 11×10(-9) M (0.46 to 3.2 µg L(-1)) when used in conjunction with solid phase extraction. The short analysis time as well as good sensitivity and selectivity make it a useful approach for the fast screening of organotin compounds.

  2. The drivers of tropical speciation.

    PubMed

    Smith, Brian Tilston; McCormack, John E; Cuervo, Andrés M; Hickerson, Michael J; Aleixo, Alexandre; Cadena, Carlos Daniel; Pérez-Emán, Jorge; Burney, Curtis W; Xie, Xiaoou; Harvey, Michael G; Faircloth, Brant C; Glenn, Travis C; Derryberry, Elizabeth P; Prejean, Jesse; Fields, Samantha; Brumfield, Robb T

    2014-11-20

    Since the recognition that allopatric speciation can be induced by large-scale reconfigurations of the landscape that isolate formerly continuous populations, such as the separation of continents by plate tectonics, the uplift of mountains or the formation of large rivers, landscape change has been viewed as a primary driver of biological diversification. This process is referred to in biogeography as vicariance. In the most species-rich region of the world, the Neotropics, the sundering of populations associated with the Andean uplift is ascribed this principal role in speciation. An alternative model posits that rather than being directly linked to landscape change, allopatric speciation is initiated to a greater extent by dispersal events, with the principal drivers of speciation being organism-specific abilities to persist and disperse in the landscape. Landscape change is not a necessity for speciation in this model. Here we show that spatial and temporal patterns of genetic differentiation in Neotropical birds are highly discordant across lineages and are not reconcilable with a model linking speciation solely to landscape change. Instead, the strongest predictors of speciation are the amount of time a lineage has persisted in the landscape and the ability of birds to move through the landscape matrix. These results, augmented by the observation that most species-level diversity originated after episodes of major Andean uplift in the Neogene period, suggest that dispersal and differentiation on a matrix previously shaped by large-scale landscape events was a major driver of avian speciation in lowland Neotropical rainforests.

  3. Are we analyzing speciation without prejudice?

    PubMed

    Johannesson, Kerstin

    2010-09-01

    Physical isolation has long been the null hypothesis of speciation, with exceptional evidence required to suggest speciation with gene flow. Following recent persuasive theoretical support and strong empirical examples of nonallopatric speciation, one might expect a changed view. However, a review of 73 recent empirical studies shows that when allopatric speciation is suggested, a nonallopatric alternative is rarely considered, whereas the opposite is true in studies suggesting sympatric speciation, indicating a biased treatment of different speciation models. Although increasing support for ecological speciation suggests natural selection as the most critical component of speciation, gene flow remains an issue. Methods for unbiased hypothesis testing are available, and the genetic and phylogeographic data required for appropriate tests can be generated. Focus on phylogenies and functions of individual genes have revealed strong idiosyncratic elements of speciation, such as single genes with possible allopatric origin that make significant contributions during nonallopatric phases of speciation. Hence a more complex picture of speciation is now emerging that will benefit from unbiased evaluation of both allopatric and sympatric mechanisms of speciation.

  4. Interdigitated pixel electrodes with alternating tilts for fast fringe-field switching of liquid crystals.

    PubMed

    Choi, Tae-Hoon; Woo, Jae-Hyeon; Choi, Yeongyu; Yoon, Tae-Hoon

    2016-11-28

    We propose an interdigitated pixel electrode structure with alternating tilts for fast fringe-field switching of liquid crystals (LCs). In contrast to an LC cell, where the pixel electrodes are parallel to the LC alignment direction, this device does not require a non-zero pretilt angle, owing to an obliquely applied electric field; thus, it can retain a much wider viewing angle by aligning the LCs without a pretilt. In addition to a short response time and wide viewing angle, the proposed device allows a much larger deviation of the LC alignment direction, which is essential for mass production. Moreover, LCs with negative dielectric anisotropy can be used to minimize the transmittance decrease.

  5. Alternate-day fasting diet improves fructose-induced insulin resistance in mice.

    PubMed

    Beigy, M; Vakili, S; Berijani, S; Aminizade, M; Ahmadi-Dastgerdi, M; Meshkani, R

    2013-12-01

    Increased fructose consumption is linked to insulin resistance, weight gain, hyperlipidemia and hypertension. Although the advantages of several dietary restriction regimens have been demonstrated, the effects of alternate-day fasting (ADF) on fructose-induced insulin resistance have not yet been studied. This study is based on a new modification on ADF by combining the fructose-rich solution (10% w/v) and regular mice diet. Mice were randomly allocated into four groups: ADF50% (50% restriction in chow food intake but ad libitum fructose drink), ADF100% (100% restriction for chow food but ad libitum fructose drink), control (ad libitum chow food intake plus tap water) and daily food and fructose (DFF) (had free access to both chow and fructose solution). Biweekly fasting blood sugar (FBS), glucose tolerance test (GTT) and insulin tolerance test (ITT) were conducted. All groups gained weight during the study (p < 0.05). Body weights of DFF and control groups did not differ from that of ADF groups, but ADF50% gained more (p < 0.01) weights than ADF100% through the study. Total calorie intake (feed + fast days) of ADF50% was higher than that of ADF100% (p < 0.001) and control (p < 0.03). In addition, ADF groups consumed more energy than the control and DFF groups in feed (ad libitum) days (p < 0.05). At the end of the study, the mean FBS levels in the control and ADF100% groups were similar and significantly lower in relation to that of DFF and ADF50% groups (p < 0.01). Measurements of area under the curve in GTT and ITT revealed that the ADF100% group was more insulin-sensitive than the DFF and ADF50% groups. In conclusion, these data suggest that the ADF100% improves fructose-induced insulin resistance in mice.

  6. Alternating high and low climate variability: The context of natural selection and speciation in Plio-Pleistocene hominin evolution.

    PubMed

    Potts, Richard; Faith, J Tyler

    2015-10-01

    Interaction of orbital insolation cycles defines a predictive model of alternating phases of high- and low-climate variability for tropical East Africa over the past 5 million years. This model, which is described in terms of climate variability stages, implies repeated increases in landscape/resource instability and intervening periods of stability in East Africa. It predicts eight prolonged (>192 kyr) eras of intensified habitat instability (high variability stages) in which hominin evolutionary innovations are likely to have occurred, potentially by variability selection. The prediction that repeated shifts toward high climate variability affected paleoenvironments and evolution is tested in three ways. In the first test, deep-sea records of northeast African terrigenous dust flux (Sites 721/722) and eastern Mediterranean sapropels (Site 967A) show increased and decreased variability in concert with predicted shifts in climate variability. These regional measurements of climate dynamics are complemented by stratigraphic observations in five basins with lengthy stratigraphic and paleoenvironmental records: the mid-Pleistocene Olorgesailie Basin, the Plio-Pleistocene Turkana and Olduvai Basins, and the Pliocene Tugen Hills sequence and Hadar Basin--all of which show that highly variable landscapes inhabited by hominin populations were indeed concentrated in predicted stages of prolonged high climate variability. Second, stringent null-model tests demonstrate a significant association of currently known first and last appearance datums (FADs and LADs) of the major hominin lineages, suites of technological behaviors, and dispersal events with the predicted intervals of prolonged high climate variability. Palynological study in the Nihewan Basin, China, provides a third test, which shows the occupation of highly diverse habitats in eastern Asia, consistent with the predicted increase in adaptability in dispersing Oldowan hominins. Integration of fossil, archeological

  7. Special Speciation

    ERIC Educational Resources Information Center

    Countryman, Lyn L.; Maroo, Jill D.

    2015-01-01

    Considerable anecdotal evidence indicates that some of the most difficult concepts that both high school and undergraduate elementary-education students struggle with are those surrounding evolutionary principles, especially speciation. It's no wonder that entry-level biology students are confused, when biologists have multiple definitions of…

  8. Fas-activated serine/threonine kinase (FAST K) synergizes with TIA-1/TIAR proteins to regulate Fas alternative splicing.

    PubMed

    Izquierdo, José M; Valcárcel, Juan

    2007-01-19

    The factors and mechanisms that mediate the effects of intracellular signaling cascades on alternative pre-mRNA splicing are poorly understood. TIA-1 (T-cell intracellular antigen 1) and TIAR (TIA-1-related) proteins regulate alternative pre-mRNA splicing by promoting the use of suboptimal 5' splice sites followed by uridine-rich intronic enhancer sequences. These proteins promote, for example, inclusion of Fas receptor exon 6, which leads to an mRNA encoding a pro-apoptotic form of the receptor at the expense of the form that skips exon 6, which encodes an anti-apoptotic form. Fas-activated serine/threonine kinase (FAST K) is known to interact with and phosphorylate TIA-1. Here we have tested the possibility that FAST K influences alternative pre-mRNA splicing by affecting the activity of TIA-1/TIAR. Depletion of FAST K form Jurkat cells leads to skipping of exon 6 from endogenous Fas transcripts. Conversely, FAST K overexpression enhances exon 6 inclusion of Fas reporters transfected in HeLa cells. Consistent with the possibility that the effects of FAST K are mediated by changes in the function of TIA-1/TIAR, the effects of FAST K overexpression (i) are largely suppressed by depletion of TIA-1 and TIAR and (ii) are significantly compromised by mutation of a TIA-1/TIAR-responsive enhancer present downstream of exon 6 5' splice site. Furthermore, in vitro phosphorylation of TIA-1 by FAST K results in enhanced U1 snRNP recruitment. Interestingly, this enhancement is not due to increased binding of TIA-1 to the pre-mRNA. Taken together, the results connect Fas signaling with the activity of splicing factors that modulate Fas alternative splicing, suggesting the existence of an autoregulatory loop that could serve to amplify Fas responses.

  9. Distinct Inter-Joint Coordination during Fast Alternate Keystrokes in Pianists with Superior Skill

    PubMed Central

    Furuya, Shinichi; Goda, Tatsushi; Katayose, Haruhiro; Miwa, Hiroyoshi; Nagata, Noriko

    2011-01-01

    Musical performance requires motor skills to coordinate the movements of multiple joints in the hand and arm over a wide range of tempi. However, it is unclear whether the coordination of movement across joints would differ for musicians with different skill levels and how inter-joint coordination would vary in relation to music tempo. The present study addresses these issues by examining the kinematics and muscular activity of the hand and arm movements of professional and amateur pianists who strike two keys alternately with the thumb and little finger at various tempi. The professionals produced a smaller flexion velocity at the thumb and little finger and greater elbow pronation and supination velocity than did the amateurs. The experts also showed smaller extension angles at the metacarpo-phalangeal joint of the index and middle fingers, which were not being used to strike the keys. Furthermore, muscular activity in the extrinsic finger muscles was smaller for the experts than for the amateurs. These findings indicate that pianists with superior skill reduce the finger muscle load during keystrokes by taking advantage of differences in proximal joint motion and hand postural configuration. With an increase in tempo, the experts showed larger and smaller increases in elbow velocity and finger muscle co-activation, respectively, compared to the amateurs, highlighting skill level-dependent differences in movement strategies for tempo adjustment. Finally, when striking as fast as possible, individual differences in the striking tempo among players were explained by their elbow velocities but not by their digit velocities. These findings suggest that pianists who are capable of faster keystrokes benefit more from proximal joint motion than do pianists who are not capable of faster keystrokes. The distinct movement strategy for tempo adjustment in pianists with superior skill would therefore ensure a wider range of musical expression. PMID:21660290

  10. Chronic Alternate Day Fasting Results in Reduced Diastolic Compliance and Diminished Systolic Reserve in Rats

    PubMed Central

    Ahmet, Ismayil; Wan, Ruiqian; Mattson, Mark P; Lakatta, Edward G.; Talan, Mark I.

    2010-01-01

    Background Based on animal experiments and limited data from few human trials, alternate day fasting (ADF) resulted in weight loss; prolonged life; reduced metabolic risk factors for diabetes and cardiovascular diseases; and reduced prevalence of age-related diseases. The present study is the first comprehensive examination of the long-term effects of ADF on general cardiovascular fitness in rats. Methods and Results Four months old male Sprague-Dawley rats were started on ADF or continued on ad libitum diets and followed for 6 months with serial echocardiography. A comprehensive hemodynamic evaluation including a combined dobutamine - volume stress test was performed at the end of the study, and hearts were harvested for histological assessment. The six-month long ADF diet resulted in a 9% reduction (p<0.01) of cardiomyocyte diameter and 3 fold increase in interstitial myocardial fibrosis. Left ventricular chamber size was not affected by ADF and ejection fraction was not reduced, but left atrial diameter was increased 16%, and the E/A in Doppler-measured mitral flow was reduced (p<0.01). Pressure-volume loop analyses revealed a “stiff” heart during diastole in ADF rats, while combined dobutamine and volume loading showed a significant reduction in LV diastolic compliance and a lack of increase in systolic pump function, indicating a diminished cardiac reserve. Conclusion Chronic ADF in rats results in development of diastolic dysfunction with diminished cardiac reserve. ADF is a novel and unique experimental model of diet-induced diastolic dysfunction. The deleterious effect of ADF in rats suggests that additional studies of ADF effects on cardiovascular functions in humans are warranted. PMID:20932467

  11. Pleistocene Speciation in North American Lichenized Fungi and the Impact of Alternative Species Circumscriptions and Rates of Molecular Evolution on Divergence Estimates

    PubMed Central

    Leavitt, Steven D.; Lumbsch, H. Thorsten; Stenroos, Soili; Clair, Larry L. St.

    2013-01-01

    Pleistocene climatic fluctuations influenced patterns of genetic variation and promoted speciation across a wide range of species groups. Lichens are commonly found in habitats that were directly impacted by glacial cycles; however, the role of Pleistocene climate in driving speciation in most lichen symbionts remains unclear. This uncertainty is due in part to limitations in our ability to accurately recognize independently evolving lichen-forming fungal lineages and a lack of relevant fossil calibrations. Using a coalescent-based species tree approach, we estimated divergence times for two sister clades in the genus Xanthoparmelia (Parmeliaceae) restricted to western North America. We assessed the influence of two different species circumscription scenarios and various locus-specific rates of molecular evolution on divergence estimates. Species circumscriptions were validated using the program BP&P. although speciation was generally supported in both scenarios, divergence times differed between traditional species circumscriptions and those based on genetic data, with more recent estimates resulting from the former. Similarly, rates of evolution for different loci resulted in variable divergence time estimates. However, our results unambiguously indicate that diversification in the sampled Xanthoparmelia clades occurred during the Pleistocene. Our study highlights the potential impact of ambiguous species circumscriptions and uncertain rates of molecular evolution on estimating divergence times within a multilocus species tree framework. PMID:24386465

  12. Pleistocene speciation in North American lichenized fungi and the impact of alternative species circumscriptions and rates of molecular evolution on divergence estimates.

    PubMed

    Leavitt, Steven D; Lumbsch, H Thorsten; Stenroos, Soili; St Clair, Larry L

    2013-01-01

    Pleistocene climatic fluctuations influenced patterns of genetic variation and promoted speciation across a wide range of species groups. Lichens are commonly found in habitats that were directly impacted by glacial cycles; however, the role of Pleistocene climate in driving speciation in most lichen symbionts remains unclear. This uncertainty is due in part to limitations in our ability to accurately recognize independently evolving lichen-forming fungal lineages and a lack of relevant fossil calibrations. Using a coalescent-based species tree approach, we estimated divergence times for two sister clades in the genus Xanthoparmelia (Parmeliaceae) restricted to western North America. We assessed the influence of two different species circumscription scenarios and various locus-specific rates of molecular evolution on divergence estimates. Species circumscriptions were validated using the program BP&P. although speciation was generally supported in both scenarios, divergence times differed between traditional species circumscriptions and those based on genetic data, with more recent estimates resulting from the former. Similarly, rates of evolution for different loci resulted in variable divergence time estimates. However, our results unambiguously indicate that diversification in the sampled Xanthoparmelia clades occurred during the Pleistocene. Our study highlights the potential impact of ambiguous species circumscriptions and uncertain rates of molecular evolution on estimating divergence times within a multilocus species tree framework.

  13. Alternative thermodiffusion interface for simultaneous speciation of organic and inorganic lead and mercury species by capillary GC-ICPMS using tri-n-propyl-lead chloride as an internal standard.

    PubMed

    Yan, Dong; Yang, Limin; Wang, Qiuquan

    2008-08-01

    An alternative thermodiffusion interface (TDI) was designed and constructed for the effective online coupling of capillary gas chromatography (cGC) and inductively coupled plasma mass spectrometry (ICPMS). Pb(2+), (CH3)3Pb(+), (C2H5)3Pb(+), Hg(2+), CH3Hg(+) and C2H5Hg(+) were derived as Pb(C4H9)4, (CH3)3PbC4H9, (C2H5)3PbC4H9, (C4H9)2Hg, CH3HgC4H9, and C2H5HgC4H9 when butyl magnesium bromide was employed as a derivatization reagent for a proof-of-concept study, avoiding the loss of their species specific information. All these derivatives together with the neutral fully saturated (CH3)4Pb and (C2H5)4Pb could be quantitatively separated within 7 min using a 15 m long capillary column, allowing the determination and speciation of organic and inorganic Pb and Hg species in a single run. The method detection limits (3sigma) for Me4Pb, Et4Pb, Me3Pb(3+), Pb(2+), MeHg(+), EtHg(+), and Hg(2+) are 0.07, 0.06, 0.04, 7.0, 0.09, 0.1, and 0.2 pg g(-1), respectively. Moreover, tri-n-propyl-lead chloride was synthesized and used as an alternative internal standard for the accurate and simultaneous speciation analysis of Pb and Hg in complicated environmental and biological samples for the first time. This cGC-TDI-ICPMS method was validated by analyzing Pb and Hg species in certified reference materials and then was applied to simultaneous speciation analysis of Pb and Hg in real-life samples. It is expected that these approaches can be extended to the speciation of other organometallic compounds after suitable modifications and so will aid in monitoring the occurrence, pathways, toxicity, and/or biological effects of these compounds in the environment and in organisms.

  14. Fast arsenic speciation in water by on-site solid phase extraction and high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Mihucz, Victor G.; Bencs, László; Koncz, Kornél; Tatár, Enikő; Weiszburg, Tamás; Záray, Gyula

    2017-02-01

    A method of high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS), combined with on-site separation/solid phase extraction (SPE) has been developed for the speciation of inorganic As (iAs) in geothermal and drinking water samples. The HR-CS-GFAAS calibration curves were linear up to 200 μg/L As, but using second order polynomial fitting, accurate calibration could be performed up to 500 μg/L. It has been demonstrated that sample pH should not be higher than 8 for an accurate speciation of As(V) with a recovery of ≈ 95%. Geothermal water had fairly high salt content (≈ 2200 mg/L) due to the presence of chlorides and sulfates at mg/L levels. Therefore, a two-fold dilution of these types of samples before SPE is recommended, especially, for total As determinations, when the As concentration is as high as 400 μg/L. For drinking water, sampled from public wells with records of As concentrations higher than the 10 μg/L in the past, the reduction of As contamination below the WHO's health limit value could be observed. However, the electrical conductivity was close to 2500 μS/cm, i.e., the guideline limit for drinking water, which was due to their higher chloride content. The proposed fit-for-purpose SPE-HR-CS-GFAAS method could be a candidate for screening drinking water quality.

  15. Obese mice on a high-fat alternate-day fasting regimen lose weight and improve glucose tolerance.

    PubMed

    Joslin, P M N; Bell, R K; Swoap, S J

    2016-06-08

    Alternate-day fasting (ADF) causes body weight (BW) loss in humans and rodents. However, it is not clear that ADF while maintaining a high-fat (HF) diet results in weight loss and the accompanying improvement in control of circulating glucose. We tested the hypotheses that a high-fat ADF protocol in obese mice would result in (i) BW loss, (ii) improved glucose control, (iii) fluctuating phenotypes on 'fasted' days when compared to 'fed' days and (iv) induction of torpor on 'fasted days'. We evaluated the physiological effects of ADF in diet-induced obese mice for BW, heart rate (HR), body temperature (Tb ), glucose tolerance, insulin responsiveness, blood parameters (leptin, insulin, free fatty acids) and hepatic gene expression. Diet-induced obese male C57BL/6J mice lost one-third of their pre-diet BW while on an ADF diet for 10 weeks consisting of HF food. The ADF protocol improved glucose tolerance and insulin sensitivity, although mice on a fast day were less glucose tolerant than the same mice on a fed day. ADF mice on a fast day had low circulating insulin, but had an enhanced response to an insulin-assisted glucose tolerance test, suggesting the impaired glucose tolerance may be a result of insufficient insulin production. On fed days, ADF mice were the warmest, had a high HR and displayed hepatic gene expression and circulating leptin that closely mimicked that of mice fed an ad lib HF diet. ADF mice never entered torpor as assessed by HR and Tb . However, on fast days, they were the coolest, had the slowest HR, and displayed hepatic gene expression and circulating leptin that closely mimicked that of Chow-Fed mice. Collectively, the ADF regimen with a HF diet in obese mice results in weight loss, improved blood glucose control, and daily fluctuations in selected physiological and biochemical parameters in the mouse.

  16. Cell-autonomous regulation of fast troponin T pre-mRNA alternative splicing in response to mechanical stretch.

    PubMed

    Schilder, Rudolf J; Kimball, Scot R; Jefferson, Leonard S

    2012-08-01

    How mechanochemical signals induced by the amount of weight borne by the skeletal musculature are translated into modifications to muscle sarcomeres is poorly understood. Our laboratory recently demonstrated that, in response to experimentally induced increases in the weight load borne by a rat, alternative splicing of the fast skeletal muscle troponin T (Tnnt3) pre-mRNA in gastrocnemius was adjusted in a correlated fashion with the amount of added weight. (Schilder RJ, Kimball SR, Marden JH, Jefferson LS. J Exp Biol 214: 1523-1532, 2011). Thus muscle load is perceived quantitatively by the body, and mechanisms that sense it appear to control processes that generate muscle sarcomere composition plasticity, such as alternative pre-mRNA splicing. Here we demonstrate how mechanical stretch (see earlier comment) of C2C12 muscle cells in culture results in changes to Tnnt3 pre-mRNA alternative splicing that are qualitatively similar to those observed in response to added weight in rats. Moreover, inhibition of Akt signaling, but not that of ERK1/2, prevents the stretch-induced effect on Tnnt3 pre-mRNA alternative splicing. These findings suggest that effects of muscle load on Tnnt3 pre-mRNA alternative splicing are controlled by a cell-autonomous mechanism, rather than systemically. They also indicate that, in addition to its regulatory role in protein synthesis and muscle mass plasticity, Akt signaling may regulate muscle sarcomere composition by modulating alternative splicing events in response to load. Manipulation of Tnnt3 pre-mRNA alternative splicing by mechanical stretch of cells in culture provides a model to investigate the biology of weight sensing by skeletal muscles and facilitates identification of mechanisms through which skeletal muscles match their performance and experienced load.

  17. Older women with dementia can perform fast alternating forearm movements and performance is correlated with tests of lower extremity function

    PubMed Central

    Bramell-Risberg, Eva; Jarnlo, Gun-Britt; Elmståhl, Sölve

    2013-01-01

    Background: The purpose of this work was to study the performance and reliability of a test of fast alternating forearm movements and its relationship with measures of lower extremity function in older women with dementia. Methods: Fast alternating movements was studied in 26 female patients (mean age 81.7 ± 5.9 years) with dementia and 34 controls (mean age 87.5 ± 4.7 years). Subgroup analyses for those aged 80–89 years were performed due to significant differences in the mean ages of the study groups. Test–retest reliability for alternating forearm movements was studied in 11 patients (mean age 80.3 ± 6.7 years) and 10 controls (mean age 87.4 ± 1.6 years). Pulses generated were transformed to an analog signal shown on a modified electrocardiogram. Numbers of cycles at 10 and 15 seconds were calculated for the right and left hand. Walking 2 × 15 m and the Get-Up-and Go (GUG) test were performed at self-selected and maximal speed. Associations between tests of upper and lower extremity function were sought in eight patients (mean age 85 ± 2.7 years) and 16 controls (mean age 85.1 ± 2.8 years) and also according to types of dementia in nine patients with probable Alzheimer’s disease and 10 patients with other types of dementia. Results: Patients with dementia could perform the test and had significantly fewer cycles (P = 0.02–0.006) at both 10 and 15 seconds compared with controls after age adjustment. A higher number of cycles was associated with higher self-selected walking speeds in patients (r = −0.79). Test–retest reliability for alternating forearm movements was high for both patients (intraclass correlation 0.88–0.94) and controls (intraclass correlation 0.74–0.94). Conclusion: Alternating forearm movements at fast speed can be used as a reliable test in both patients with dementia and healthy older subjects. The test can be used as a measure of bradykinesia and might be useful as a proxy for lower extremity function in older persons

  18. Speciation in fishes.

    PubMed

    Bernardi, Giacomo

    2013-11-01

    The field of speciation has seen much renewed interest in the past few years, with theoretical and empirical advances that have moved it from a descriptive field to a predictive and testable one. The goal of this review is to provide a general background on research on speciation as it pertains to fishes. Three major components to the question are first discussed: the spatial, ecological and sexual factors that influence speciation mechanisms. We then move to the latest developments in the field of speciation genomics. Affordable and rapidly available, massively parallel sequencing data allow speciation studies to converge into a single comprehensive line of investigation, where the focus has shifted to the search for speciation genes and genomic islands of speciation. We argue that fish present a very diverse array of scenarios, making them an ideal model to study speciation processes.

  19. SPECIATE - EPA'S DATABASE OF SPECIATED EMISSION PROFILES

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of total organic compound (TOC) and particulate matter (PM) speciation profiles for emissions from air pollution sources. The data base has recently been updated and an associated report has recently been re...

  20. 3D-spectral CDIs: a fast alternative to 3D inversion?

    NASA Astrophysics Data System (ADS)

    Macnae, James

    2015-09-01

    Virtually all airborne electromagnetic (AEM) data is interpreted using stitched 1D conductivity sections, derived from constrained inversion or fast but fairly accurate approximations. A small subset of this AEM data recently has been inverted using either block 3D models or thin plates, which processes have limitations in terms of cost and accuracy, and the results are in general strongly biased by the choice of starting models. Recent developments in spectral modelling have allowed fast 3D approximations of the EM response of both vortex induction and current gathering for simple geological target geometries. Fitting these spectral responses to AEM data should be sufficient to accurately locate current systems within the ground, and the behaviour of these local current systems can in theory approximately define a conductivity structure in 3D. This paper describes the results of initial testing of the algorithm in fitting vortex induction in a small target at the Forrestania test range, Western Australia, using results from a versatile time-domain electromagnetic (VTEM)-Max survey.

  1. Prevalence of insulin resistance and the metabolic syndrome with alternative definitions of impaired fasting glucose.

    PubMed

    Ford, Earl S; Abbasi, Fahim; Reaven, Gerald M

    2005-07-01

    We sought to evaluate the effect of the new definition of impaired fasting glucose (IFG = fasting glucose concentration 100-125 mg/dL among people without diabetes) on the ability to identify insulin resistance, as well as the prevalence of the metabolic syndrome in apparently healthy individuals. From the Stanford General Clinical Research Center data-base, we used data from 230 men and 260 women aged 19-79 years who had had an insulin suppression test to measure insulin resistance. From the Third National Health and Nutrition Examination Survey (1988-1994), we used data from 8814 participants aged > or =20 years to estimate the impact of adopting the new IFG criteria on the prevalence of the metabolic syndrome. Among the 490 participants, the prevalence of IFG increased from 5.5% under the old definition of IFG to 20.4% under the new definition. Using the old definition of IFG, the sensitivity, specificity, and positive predictive value (PPV) of IFG of identifying an individual as being insulin resistant were 10%, 97%, and 63%, respectively. Using the new definition, these parameters were 33%, 88%, and 61%, respectively. If the new IFG criteria were adopted, the prevalence of the metabolic syndrome would increase from 21.8% to 26.3%. The new definition of IFG expands the population with insulin resistance by almost four-fold and could expand the population with the metabolic syndrome by about 20%. The clinical and public health implications of the new IFG definition remain to be elucidated.

  2. Mechanisms by Which Phenotypic Plasticity Affects Adaptive Divergence and Ecological Speciation.

    PubMed

    Nonaka, Etsuko; Svanbäck, Richard; Thibert-Plante, Xavier; Englund, Göran; Brännström, Åke

    2015-11-01

    Phenotypic plasticity is the ability of one genotype to produce different phenotypes depending on environmental conditions. Several conceptual models emphasize the role of plasticity in promoting reproductive isolation and, ultimately, speciation in populations that forage on two or more resources. These models predict that plasticity plays a critical role in the early stages of speciation, prior to genetic divergence, by facilitating fast phenotypic divergence. The ability to plastically express alternative phenotypes may, however, interfere with the early phase of the formation of reproductive barriers, especially in the absence of geographic barriers. Here, we quantitatively investigate mechanisms under which plasticity can influence progress toward adaptive genetic diversification and ecological speciation. We use a stochastic, individual-based model of a predator-prey system incorporating sexual reproduction and mate choice in the predator. Our results show that evolving plasticity promotes the evolution of reproductive isolation under diversifying environments when individuals are able to correctly select a more profitable habitat with respect to their phenotypes (i.e., adaptive habitat choice) and to assortatively mate with relatively similar phenotypes. On the other hand, plasticity facilitates the evolution of plastic generalists when individuals have a limited capacity for adaptive habitat choice. We conclude that plasticity can accelerate the evolution of a reproductive barrier toward adaptive diversification and ecological speciation through enhanced phenotypic differentiation between diverging phenotypes.

  3. Effects of weight loss via high fat vs. low fat alternate day fasting diets on free fatty acid profiles.

    PubMed

    Varady, Krista A; Dam, Vi T; Klempel, Monica C; Horne, Matthew; Cruz, Rani; Kroeger, Cynthia M; Santosa, Sylvia

    2015-01-05

    Cardiovascular disease risk is associated with excess body weight and elevated plasma free fatty acid (FFA) concentrations. This study examines how an alternate-day fasting (ADF) diet high (HF) or low (LF) in fat affects plasma FFA profiles in the context of weight loss, and changes in body composition and lipid profiles. After a 2-week weight maintenance period, 29 women (BMI 30-39.9 kg/m(2)) 25-65 years old were randomized to an 8-week ADF-HF (45% fat) diet or an ADF-LF (25% fat) diet with 25% energy intake on fast days and ad libitum intake on feed days. Body weight, BMI and waist circumference were assessed weekly and body composition was measured using dual x-ray absorptiometry (DXA). Total and individual FFA and plasma lipid concentrations were measured before and after weight loss. Body weight, BMI, fat mass, total cholesterol, LDL-C and triglyceride concentrations decreased (P < 0.05) in both groups. Total FFA concentrations also decreased (P < 0.001). In the ADF-LF group, decreases were found in several more FFAs than in the ADF-HF group. In the ADF-HF group, FFA concentrations were positively correlated with waist circumference. Depending on the macronutrient composition of a diet, weight loss with an ADF diet decreases FFA concentrations through potentially different mechanisms.

  4. Fast stochastic simulation of biochemical reaction systems by alternative formulations of the chemical Langevin equation.

    PubMed

    Mélykúti, Bence; Burrage, Kevin; Zygalakis, Konstantinos C

    2010-04-28

    The Chemical Langevin Equation (CLE), which is a stochastic differential equation driven by a multidimensional Wiener process, acts as a bridge between the discrete stochastic simulation algorithm and the deterministic reaction rate equation when simulating (bio)chemical kinetics. The CLE model is valid in the regime where molecular populations are abundant enough to assume their concentrations change continuously, but stochastic fluctuations still play a major role. The contribution of this work is that we observe and explore that the CLE is not a single equation, but a parametric family of equations, all of which give the same finite-dimensional distribution of the variables. On the theoretical side, we prove that as many Wiener processes are sufficient to formulate the CLE as there are independent variables in the equation, which is just the rank of the stoichiometric matrix. On the practical side, we show that in the case where there are m(1) pairs of reversible reactions and m(2) irreversible reactions there is another, simple formulation of the CLE with only m(1) + m(2) Wiener processes, whereas the standard approach uses 2(m(1) + m(2)). We demonstrate that there are considerable computational savings when using this latter formulation. Such transformations of the CLE do not cause a loss of accuracy and are therefore distinct from model reduction techniques. We illustrate our findings by considering alternative formulations of the CLE for a human ether a-go-go related gene ion channel model and the Goldbeter-Koshland switch.

  5. Protein domain architectures provide a fast, efficient and scalable alternative to sequence-based methods for comparative functional genomics

    PubMed Central

    Koehorst, Jasper J.; Saccenti, Edoardo; Schaap, Peter J.; Martins dos Santos, Vitor A. P.; Suarez-Diez, Maria

    2016-01-01

    A functional comparative genome analysis is essential to understand the mechanisms underlying bacterial evolution and adaptation. Detection of functional orthologs using standard global sequence similarity methods faces several problems; the need for defining arbitrary acceptance thresholds for similarity and alignment length, lateral gene acquisition and the high computational cost for finding bi-directional best matches at a large scale. We investigated the use of protein domain architectures for large scale functional comparative analysis as an alternative method. The performance of both approaches was assessed through functional comparison of 446 bacterial genomes sampled at different taxonomic levels. We show that protein domain architectures provide a fast and efficient alternative to methods based on sequence similarity to identify groups of functionally equivalent proteins within and across taxonomic boundaries. As the computational cost scales linearly, and not quadratically with the number of genomes, it is suitable for large scale comparative analysis. Running both methods in parallel pinpoints potential functional adaptations that may add to bacterial fitness. PMID:27703668

  6. Validation of analytical methods in GMP: the disposable Fast Read 102® device, an alternative practical approach for cell counting

    PubMed Central

    2012-01-01

    Background The quality and safety of advanced therapy products must be maintained throughout their production and quality control cycle to ensure their final use in patients. We validated the cell count method according to the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use and European Pharmacopoeia, considering the tests’ accuracy, precision, repeatability, linearity and range. Methods As the cell count is a potency test, we checked accuracy, precision, and linearity, according to ICH Q2. Briefly our experimental approach was first to evaluate the accuracy of Fast Read 102® compared to the Bürker chamber. Once the accuracy of the alternative method was demonstrated, we checked the precision and linearity test only using Fast Read 102®. The data were statistically analyzed by average, standard deviation and coefficient of variation percentages inter and intra operator. Results All the tests performed met the established acceptance criteria of a coefficient of variation of less than ten percent. For the cell count, the precision reached by each operator had a coefficient of variation of less than ten percent (total cells) and under five percent (viable cells). The best range of dilution, to obtain a slope line value very similar to 1, was between 1:8 and 1:128. Conclusions Our data demonstrated that the Fast Read 102® count method is accurate, precise and ensures the linearity of the results obtained in a range of cell dilution. Under our standard method procedures, this assay may thus be considered a good quality control method for the cell count as a batch release quality control test. Moreover, the Fast Read 102® chamber is a plastic, disposable device that allows a number of samples to be counted in the same chamber. Last but not least, it overcomes the problem of chamber washing after use and so allows a cell count in a clean environment such as that in a Cell Factory. In a good

  7. Computer-Based Video Instruction to Teach the Use of Augmentative and Alternative Communication Devices for Ordering at Fast-Food Restaurants

    ERIC Educational Resources Information Center

    Mechling, Linda C.; Cronin, Beth

    2006-01-01

    In the study reported on here, the authors used computer-based video instruction (CBVI) to teach 3 high school students with moderate or severe intellectual disabilities how to order in fast-food restaurants by using an augmentative, alternative communication device. The study employed a multiple probe design to institute CBVI as the only…

  8. SPECIATE 4.2: speciation Database Development Documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Among the many uses of speciation data, these source profiles are used to: (1) create speciated emissions inve...

  9. Ecological speciation in marine v. freshwater fishes.

    PubMed

    Puebla, O

    2009-10-01

    molecular approaches to address specific questions related to the ecological hypothesis of speciation such as the nature of the genes underlying key ecological traits, the magnitude of their effect on phenotype and the mechanisms underlying their differential expression in different ecological contexts. The potential provided by molecular studies is fully realized when they are complemented with alternative (e.g. ecological, theoretical) approaches.

  10. SPECIATE 4.3: Addendum to SPECIATE 4.2--Speciation database development documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Among the many uses of speciation data, these source profiles are used to: (1) create speciated emissions inve...

  11. What Is Speciation?

    PubMed

    Shapiro, B Jesse; Leducq, Jean-Baptiste; Mallet, James

    2016-03-01

    Concepts and definitions of species have been debated by generations of biologists and remain controversial. Microbes pose a particular challenge because of their genetic diversity, asexual reproduction, and often promiscuous horizontal gene transfer (HGT). However, microbes also present an opportunity to study and understand speciation because of their rapid evolution, both in nature and in the lab, and small, easily sequenced genomes. Here, we review how microbial population genomics has enabled us to catch speciation "in the act" and how the results have challenged and enriched our concepts of species, with implications for all domains of life. We describe how recombination (including HGT and introgression) has shaped the genomes of nascent microbial, animal, and plant species and argue for a prominent role of natural selection in initiating and maintaining speciation. We ask how universal is the process of speciation across the tree of life, and what lessons can be drawn from microbes? Comparative genomics showing the extent of HGT in natural populations certainly jeopardizes the relevance of vertical descent (i.e., the species tree) in speciation. Nevertheless, we conclude that species do indeed exist as clusters of genetic and ecological similarity and that speciation is driven primarily by natural selection, regardless of the balance between horizontal and vertical descent.

  12. What Is Speciation?

    PubMed Central

    Shapiro, B. Jesse; Leducq, Jean-Baptiste; Mallet, James

    2016-01-01

    Concepts and definitions of species have been debated by generations of biologists and remain controversial. Microbes pose a particular challenge because of their genetic diversity, asexual reproduction, and often promiscuous horizontal gene transfer (HGT). However, microbes also present an opportunity to study and understand speciation because of their rapid evolution, both in nature and in the lab, and small, easily sequenced genomes. Here, we review how microbial population genomics has enabled us to catch speciation “in the act” and how the results have challenged and enriched our concepts of species, with implications for all domains of life. We describe how recombination (including HGT and introgression) has shaped the genomes of nascent microbial, animal, and plant species and argue for a prominent role of natural selection in initiating and maintaining speciation. We ask how universal is the process of speciation across the tree of life, and what lessons can be drawn from microbes? Comparative genomics showing the extent of HGT in natural populations certainly jeopardizes the relevance of vertical descent (i.e., the species tree) in speciation. Nevertheless, we conclude that species do indeed exist as clusters of genetic and ecological similarity and that speciation is driven primarily by natural selection, regardless of the balance between horizontal and vertical descent. PMID:27030977

  13. How does climate influence speciation?

    PubMed

    Hua, Xia; Wiens, John J

    2013-07-01

    Variation in climatic conditions over space and time is thought to be an important driver of speciation. However, the role of climate has not been explored in the theoretical literature on speciation, and the theory underlying empirical studies of climate and speciation has come largely from informal, verbal models. In this study, we develop a quantitative model to test a relatively new but theoretically untested model of speciation (speciation via niche conservatism) and to examine the climatic conditions under which speciation via niche conservatism and speciation via niche divergence are most plausible. Our results have three broad implications for the study of speciation: (1) ecological similarity over time (niche conservatism) can be an important part of speciation, despite the traditional emphasis on ecological divergence, (2) long-term directional climate change promotes speciation via niche conservatism for species with low climatic-niche lability, whereas climatic oscillations promote speciation via niche divergence for species with high climatic-niche lability, and (3) population extinction can be a key component of speciation.

  14. Characterization of Technetium Speciation in Cast Stone

    SciTech Connect

    Um, Wooyong; Jung, Hun Bok; Wang, Guohui; Westsik, Joseph H.; Peterson, Reid A.

    2013-11-11

    This report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, “Production and Long-Term Performance of Low Temperature Waste Forms” to provide additional information on technetium (Tc) speciation characterization in the Cast Stone waste form. To support the use of Cast Stone as an alternative to vitrification for solidifying low-activity waste (LAW) and as the current baseline waste form for secondary waste streams at the Hanford Site, additional understanding of Tc speciation in Cast Stone is needed to predict the long-term Tc leachability from Cast Stone and to meet the regulatory disposal-facility performance requirements for the Integrated Disposal Facility (IDF). Characterizations of the Tc speciation within the Cast Stone after leaching under various conditions provide insights into how the Tc is retained and released. The data generated by the laboratory tests described in this report provide both empirical and more scientific information to increase our understanding of Tc speciation in Cast Stone and its release mechanism under relevant leaching processes for the purpose of filling data gaps and to support the long-term risk and performance assessments of Cast Stone in the IDF at the Hanford Site.

  15. Effects of different degrees of insulin resistance on endothelial function in obese adults undergoing alternate day fasting

    PubMed Central

    Hoddy, Kristin K.; Bhutani, Surabhi; Phillips, Shane A.; Varady, Krista A.

    2016-01-01

    BACKGROUND: Obesity can have deleterious effects on insulin sensitivity leading to endothelial dysfunction. Whether alternate day fasting (ADF) can ameliorate insulin sensitivity in a way that improves endothelial function remains unknown. OBJECTIVE: This study examined the impact of ADF on endothelium dependent flow mediated dilation (FMD) in obese subjects with different degrees of insulin resistance. METHODS: Obese non-diabetic adults (n = 54) participated in an 8-week ADF protocol (25% energy intake “fast day”, alternated with ad libitum intake “feast day”). Subjects were divided into tertiles according to degree of insulin resistance based on HOMA-IR (Homeostatic model assessment-Insulin resistance): tertile 1 (0.8–2.4), tertile 2 (2.5–3.6), tertile 3 (3.7–12.4). RESULTS: Body weight decreased (P < 0.001) by 4% in each tertile. Fat mass, lean mass, and visceral fat mass also decreased (P < 0.001) similarly in each tertile. After 8 weeks of ADF, FMD and adiponectin differed (P < 0.05) between tertile 1 (3±0%; 26±23%) versus tertile 3 (–3±0%; –13±10%). Changes in leptin did not differ between tertiles (tertile 1: –23±7%; tertile 2: –20±7%; tertile 3: –9±7%). Fasting glucose did not change in any tertile. Fasting insulin and HOMA-IR differed (P < 0.05) between tertile 1 (10±11%; 11±11%) versus tertile 3 (–27±8%; –30±9%). Plasma lipids, blood pressure and heart rate did not change in any tertile. CONCLUSION: Our data suggest that ADF may be effective for decreasing insulin resistance in insulin resistant subjects, but these changes have no effect on endothelial function. PMID:28035343

  16. Effects of different degrees of insulin resistance on endothelial function in obese adults undergoing alternate day fasting.

    PubMed

    Hoddy, Kristin K; Bhutani, Surabhi; Phillips, Shane A; Varady, Krista A

    2016-10-27

    BACKGROUND: Obesity can have deleterious effects on insulin sensitivity leading to endothelial dysfunction. Whether alternate day fasting (ADF) can ameliorate insulin sensitivity in a way that improves endothelial function remains unknown. OBJECTIVE: This study examined the impact of ADF on endothelium dependent flow mediated dilation (FMD) in obese subjects with different degrees of insulin resistance. METHODS: Obese non-diabetic adults (n = 54) participated in an 8-week ADF protocol (25% energy intake "fast day", alternated with ad libitum intake "feast day"). Subjects were divided into tertiles according to degree of insulin resistance based on HOMA-IR (Homeostatic model assessment-Insulin resistance): tertile 1 (0.8-2.4), tertile 2 (2.5-3.6), tertile 3 (3.7-12.4). RESULTS: Body weight decreased (P < 0.001) by 4% in each tertile. Fat mass, lean mass, and visceral fat mass also decreased (P < 0.001) similarly in each tertile. After 8 weeks of ADF, FMD and adiponectin differed (P < 0.05) between tertile 1 (3±0%; 26±23%) versus tertile 3 (-3±0%; -13±10%). Changes in leptin did not differ between tertiles (tertile 1: -23±7%; tertile 2: -20±7%; tertile 3: -9±7%). Fasting glucose did not change in any tertile. Fasting insulin and HOMA-IR differed (P < 0.05) between tertile 1 (10±11%; 11±11%) versus tertile 3 (-27±8%; -30±9%). Plasma lipids, blood pressure and heart rate did not change in any tertile. CONCLUSION: Our data suggest that ADF may be effective for decreasing insulin resistance in insulin resistant subjects, but these changes have no effect on endothelial function.

  17. Speciation Mapping of Environmental Samples Using XANES Imaging

    EPA Science Inventory

    Fast X-ray detectors with large solid angles and high dynamic ranges open the door to XANES imaging, in which millions of spectra are collected to image the speciation of metals at micrometre resolution, over areas up to several square centimetres. This paper explores how such mu...

  18. Speciation in ancient lakes.

    PubMed

    Martens, K

    1997-05-01

    About a dozen lakes in the world are up to three orders of magnitude older than most others. Lakes Tanganyika (East Africa) and Baikal (Siberia) have probably existed in some form for 12-20 million years, maybe more. Such lakes can have different origins, sizes, shapes, depths and limnologies, but, in contrast to short-lived (mostly post-glacial) lakes, they have exceptionally high faunal diversity and levels of endemicity. A multitude of and processes accounting for these explosive radiations have recently been documented, most of them based on particular groups in certain lakes, but comparative research can detect repeated patterns. No special speciafion mechanism, exclusive to ancient lakes has been demonstrated, although cases of ultra-rapid speciation have been documented. Extant diversity results not by simple accumulation, but by a complex process of immigration, speciation and extinction.

  19. The evolutionary genetics of speciation.

    PubMed Central

    Coyne, J A; Orr, H A

    1998-01-01

    The last decade has brought renewed interest in the genetics of speciation, yielding a number of new models and empirical results. Defining speciation as 'the origin of reproductive isolation between two taxa', we review recent theoretical studies and relevant data, emphasizing the regular patterns seen among genetic analyses. Finally, we point out some important and tractable questions about speciation that have been neglected. PMID:9533126

  20. Arsenic Speciation in Groundwater: Role of Thioanions

    EPA Science Inventory

    The behavior of arsenic in groundwater environments is fundamentally linked to its speciation. Understanding arsenic speciation is important because chemical speciation impacts reactivity, bioavailability, toxicity, and transport and fate processes. In aerobic environments arsen...

  1. Can environmental change affect host/parasite-mediated speciation?

    PubMed

    Brunner, Franziska S; Eizaguirre, Christophe

    2016-08-01

    Parasitism can be a driver of species divergence and thereby significantly alter species formation processes. While we still need to better understand how parasite-mediated speciation functions, it is even less clear how this process is affected by environmental change. Both rapid and gradual changes of the environment can modify host immune responses, parasite virulence and the specificity of their interactions. They will thereby change host-parasite evolutionary trajectories and the potential for speciation in both hosts and parasites. Here, we summarise mechanisms of host-parasite interactions affecting speciation and subsequently consider their susceptibility to environmental changes. We mainly focus on the effects of temperature change and nutrient input to ecosystems as they are major environmental stressors. There is evidence for both disruptive and accelerating effects of those pressures on speciation that seem to be context-dependent. A prerequisite for parasite-driven host speciation is that parasites significantly alter the host's Darwinian fitness. This can rapidly lead to divergent selection and genetic adaptation; however, it is likely preceded by more short-term plastic and transgenerational effects. Here, we also consider how these first responses and their susceptibility to environmental changes could lead to alterations of the species formation process and may provide alternative pathways to speciation.

  2. Geographical range and speciation in fossil and living molluscs.

    PubMed Central

    Jablonski, David; Roy, Kaustuv

    2003-01-01

    The notion of a positive relation between geographical range and speciation rate or speciation probability may go back to Darwin, but a negative relation between these parameters is equally plausible. Here, we test these alternatives in fossil and living molluscan taxa. Late Cretaceous gastropod genera exhibit a strong negative relation between the geographical ranges of constituent species and speciation rate per species per million years; this result is robust to sampling biases against small-bodied taxa and is not attributable to phylogenetic effects. They also exhibit weak inverse or non-significant relations between geographical range and (i) the total number of species produced over the 18 million year timeframe, and (ii) the number of species in a single timeplane. Sister-group comparisons using extant molluscan species also show a non-significant relation between median geographical range and species richness of genera. These results support the view that the factors promoting broad geographical ranges also tend to damp speciation rates. They also demonstrate that a strong inverse relation between per-species speciation rate and geographical range need not be reflected in analyses conducted within a single timeplane, underscoring the inadequacy of treating net speciation as a proxy for raw per-taxon rates. PMID:12639320

  3. SPECIATE--EPA'S DATABASE OF SPECIATED EMISSION PROFILES

    EPA Science Inventory

    SPECIATE is EPA's repository of Total Organic Compound and Particulate Matter speciated profiles for a wide variety of sources. The profiles in this system are provided for air quality dispersion modeling and as a library for source-receptor and source apportionment type models. ...

  4. Effects of Age and Hindlimb Immobilization and Remobilization on Fast Troponin T Precursor mRNA Alternative Splicing in Rat Gastrocnemius Muscle

    PubMed Central

    Ravi, Suhana; Schilder, Rudolf J.; Berg, Arthur S.; Kimball, Scot R.

    2016-01-01

    Fast skeletal muscle Troponin T (TNNT3) is an important component of the skeletal muscle contractile machinery. The pre-mRNA encoding TNNT3 is alternatively spliced and changes in the pattern of TNNT3 splice form expression are associated with alterations in thin filament calcium sensitivity and force production during muscle contraction, thereby regulating muscle function. Interestingly, during aging, muscle force/cross sectional area is reduced, suggesting that loss of mass does not completely account for the impaired muscle function that develops during the aging process. Therefore, in the present study, we tested the hypothesis that age- and changes in muscle loading are associated with alterations in TNNT3 alternative splicing in the rat gastrocnemius muscle. We found that the relative abundance of several TNNT3 splice forms varied significantly with age among 2, 9, and 18-month old rats, and the pattern correlated with changes in body weight rather than muscle mass. Hindlimb immobilization for 7 days resulted in dramatic alterations in splice form relative abundance such that the pattern was similar to that observed in lighter animals. Remobilization for 7 days restored the splicing pattern toward that observed in the non-immobilized limb, even though muscle mass had not yet begun to recover. In conclusion, the results suggest that TNNT3 pre-mRNA alternative splicing is rapidly (i.e. within days) modulated in response to changes in the load placed on the muscle. Moreover, the results show that restoration of TNNT3 alternative splicing to control patterns is initiated prior to an increase in muscle mass. PMID:26799695

  5. To fast or feed: an alternative life history for anadromous brook trout Salvelinus fontinalis overwintering within a harbour.

    PubMed

    Spares, A D; Dadswell, M J; MacMillan, J; Madden, R; O'Dor, R K; Stokesbury, M J W

    2014-09-01

    The seasonal feeding pattern of sea-run brook trout Salvelinus fontinalis was studied from November to May 2010-2012 in Antigonish Harbour, Nova Scotia, Canada (45° 38' N; 61° 55' W). Sixty-three S. fontinalis (mean ± s.d. fork length = 330 ± 70 mm and mass = 536 ± 351 g) captured had fed predominantly on fishes (Fundulidae and Gasterosteidae). Percentage of empty stomachs was highest during autumn (18%) and winter (22%) and lowest in spring (7%). Stomach fullness increased from autumn to a maximum during winter, relating to near-zero body temperatures which may have effectively stopped gastric evacuation. Although feeding occurred during winter (December to March), consumption rates were calculated as negative values, and subsequently returned to positive values in spring (April to May). The over-winter life-history strategy of this sea-run S. fontinalis population appears to be a feeding marine migration in which fish continually increase body condition, representing an alternative to the more common overwintering strategy of starvation in fresh water until spring.

  6. Quantification of the boron speciation in alkali borosilicate glasses by electron energy loss spectroscopy

    PubMed Central

    Cheng, Shaodong; Yang, Guang; Zhao, Yanqi; Peng, MingYing; Skibsted, Jørgen; Yue, Yuanzheng

    2015-01-01

    Transmission electron microscopy and related analytical techniques have been widely used to study the microstructure of different materials. However, few research works have been performed in the field of glasses, possibly due to the electron-beam irradiation damage. In this paper, we have developed a method based on electron energy loss spectroscopy (EELS) data acquisition and analyses, which enables determination of the boron speciation in a series of ternary alkali borosilicate glasses with constant molar ratios. A script for the fast acquisition of EELS has been designed, from which the fraction of BO4 tetrahedra can be obtained by fitting the experimental data with linear combinations of the reference spectra. The BO4 fractions (N4) obtained by EELS are consistent with those from 11B MAS NMR spectra, suggesting that EELS can be an alternative and convenient way to determine the N4 fraction in glasses. In addition, the boron speciation of a CeO2 doped potassium borosilicate glass has been analyzed by using the time-resolved EELS spectra. The results clearly demonstrate that the BO4 to BO3 transformation induced by the electron beam irradiation can be efficiently suppressed by doping CeO2 to the borosilicate glasses. PMID:26643370

  7. Fast circulation of cerebrospinal fluid: an alternative perspective on the protective role of high intracranial pressure in ocular hypertension.

    PubMed

    Wostyn, Peter; De Groot, Veva; Van Dam, Debby; Audenaert, Kurt; Killer, Hanspeter Esriel; De Deyn, Peter Paul

    2016-05-01

    As ocular hypertension refers to a condition in which the intraocular pressure is consistently elevated but without development of glaucoma, study of it may provide important clues to factors that may play a protective role in glaucoma. β-amyloid, one of the key histopathological findings in Alzheimer's disease, has been reported to increase by chronic elevation of intraocular pressure in animals with experimentally induced ocular hypertension and to cause retinal ganglion cell death, pointing to similarities in molecular cell death mechanisms between glaucoma and Alzheimer's disease. On the other hand, recent studies have reported that intracranial pressure is higher in patients with ocular hypertension compared with controls, giving rise to the idea that elevated intracranial pressure may provide a protective effect for the optic nerve by decreasing the trans-lamina cribrosa pressure difference. The speculation that the higher intracranial pressure reported in ocular hypertension patients may protect against glaucoma mainly through a lower trans-lamina cribrosa pressure difference remains at least questionable. Here, we present an alternative viewpoint, according to which the protective effect of higher intracranial pressure could be due, at least in part, to a pressure-independent mechanism, namely faster cerebrospinal fluid production leading to increased cerebrospinal fluid turnover with enhanced removal of potentially neurotoxic waste products that accumulate in the optic nerve. This suggests a new hypothesis for glaucoma, which, just like Alzheimer's disease, may be considered then as an imbalance between production and clearance of neurotoxins, including β-amyloid. If confirmed, then strategies to improve cerebrospinal fluid flow are reasonable and could provide a new therapeutic approach for stopping the neurotoxic β-amyloid pathway in glaucoma.

  8. Fast food (image)

    MedlinePlus

    Fast foods are quick, reasonably priced, and readily available alternatives to home cooking. While convenient and economical for a busy lifestyle, fast foods are typically high in calories, fat, saturated ...

  9. Hitchhiking to Speciation

    PubMed Central

    Presgraves, Daven C.

    2013-01-01

    The modern evolutionary synthesis codified the idea that species exist as distinct entities because intrinsic reproductive barriers prevent them from merging together. Understanding the origin of species therefore requires understanding the evolution and genetics of reproductive barriers between species. In most cases, speciation is an accident that happens as different populations adapt to different environments and, incidentally, come to differ in ways that render them reproductively incompatible. As with other reproductive barriers, the evolution and genetics of interspecific hybrid sterility and lethality were once also thought to evolve as pleiotripic side effects of adaptation. Recent work on the molecular genetics of speciation has raised an altogether different possibility—the genes that cause hybrid sterility and lethality often come to differ between species not because of adaptation to the external ecological environment but because of internal evolutionary arms races between selfish genetic elements and the genes of the host genome. Arguably one of the best examples supporting a role of ecological adaptation comes from a population of yellow monkey flowers, Mimulus guttatus, in Copperopolis, California, which recently evolved tolerance to soil contaminants from copper mines and simultaneously, as an incidental by-product, hybrid lethality in crosses with some off-mine populations. However, in new work, Wright and colleagues show that hybrid lethality is not a pleiotropic consequence of copper tolerance. Rather, the genetic factor causing hybrid lethality is tightly linked to copper tolerance and spread to fixation in Copperopolis by genetic hitchhiking. PMID:23468596

  10. SPECIATE 4.0: SPECIATION DATABASE DEVELOPMENT DOCUMENTATION--FINAL REPORT

    EPA Science Inventory

    SPECIATE is the U.S. EPA's repository of total organic compounds (TOC) and particulate matter (PM) speciation profiles of air pollution sources. This report documents how EPA developed the SPECIATE 4.0 database that replaces the prior version, SPECIATE 3.2. SPECIATE 4.0 includes ...

  11. Ecological speciation in Gambusia fishes.

    PubMed

    Langerhans, R Brian; Gifford, Matthew E; Joseph, Everton O

    2007-09-01

    Although theory indicates that natural selection can facilitate speciation as a by-product, demonstrating ongoing speciation via this by-product mechanism in nature has proven difficult. We examined morphological, molecular, and behavioral data to investigate ecology's role in incipient speciation for a post-Pleistocene radiation of Bahamas mosquitofish (Gambusia hubbsi) inhabiting blue holes. We show that adaptation to divergent predator regimes is driving ecological speciation as a by-product. Divergence in body shape, coupled with assortative mating for body shape, produces reproductive isolation that is twice as strong between populations inhabiting different predator regimes than between populations that evolved in similar ecological environments. Gathering analogous data on reproductive isolation at the interspecific level in the genus, we find that this mechanism of speciation may have been historically prevalent in Gambusia. These results suggest that speciation in nature can result as a by-product of divergence in ecologically important traits, producing interspecific patterns that persist long after speciation events have completed.

  12. Chronic speciation in periodical cicadas.

    PubMed

    Ritchie, M G.

    2001-02-01

    Allochronic speciation and reproductive character displacement are two intuitively attractive models of speciation. The first proposes that changes in the timing of life cycles produce new species, whereas the second suggests that speciation is due to the exaggeration of sexual isolation in sympatric populations. Clear examples of either process in nature remain elusive, despite some extensive searches. Two recent studies of mtDNA markers and behaviour of periodical cicadas in North America have identified a new species of cicada that seems to provide good evidence for the involvement of both processes in its origin.

  13. Sexual selection drives speciation in an Amazonian frog

    USGS Publications Warehouse

    Boul, K.E.; Funk, W.C.; Darst, C.R.; Cannatella, D.C.; Ryan, M.J.

    2007-01-01

    One proposed mechanism of speciation is divergent sexual selection, whereby divergence in female preferences and male signals results in behavioural isolation. Despite the appeal of this hypothesis, evidence for it remains inconclusive. Here, we present several lines of evidence that sexual selection is driving behavioural isolation and speciation among populations of an Amazonian frog (Physalaemus petersi). First, sexual selection has promoted divergence in male mating calls and female preferences for calls between neighbouring populations, resulting in strong behavioural isolation. Second, phylogenetic analysis indicates that populations have become fixed for alternative call types several times throughout the species' range, and coalescent analysis rejects genetic drift as a cause for this pattern, suggesting that this divergence is due to selection. Finally, gene flow estimated with microsatellite loci is an average of 30 times lower between populations with different call types than between populations separated by a similar geographical distance with the same call type, demonstrating genetic divergence and incipient speciation. Taken together, these data provide strong evidence that sexual selection is driving behavioural isolation and speciation, supporting sexual selection as a cause for speciation in the wild. ?? 2006 The Royal Society.

  14. Determining Evapotranspiration with the Eddy Covariance Method: Fast-Response Dry- and Wet-Bulb Thermocouples for Humidity Measurements Can Provide a Cheap Alternative to Infrared Hygrometers.

    NASA Astrophysics Data System (ADS)

    Holwerda, F.; Alvarado-Barrientos, M. S.

    2014-12-01

    Field data on evapotranspiration are of crucial importance for ecohydrological and hydrometeorological studies in the tropics. Probably the most direct way to measure evapotranspiration is with the eddy covariance method, in which the latent heat flux (λE) is calculated from turbulent fluctuations of vertical wind velocity and humidity. The humidity fluctuations are typically measured with some type of fast-response infrared hygrometer. However, these sensors are expensive, which can be problematic if research budgets are limited. Turbulent fluctuations of humidity can also be measured with fast-response dry- and wet-bulb thermocouples, which can be constructed easily and at a fraction of the price of infrared sensors. The idea of using dry- and wet-bulb thermocouples for measuring λE with the eddy covariance method is not new, but hasn't been tested recently, possibly because experiments in the late seventies showed that this approach is not without problems due to the slow response of the wet-bulb thermocouple. In the present study, values of λE derived from dry- and wet-bulb thermocouple measurements were compared with those obtained using a fast-response KH20 hygrometer. Measurements were made above a shaded coffee plantation and a sugarcane crop in central Veracruz, Mexico. The agreement between λE obtained with the thermocouples (y) and the hygrometer (x) was very good for both vegetation covers: y = 0.98x + 5.0 (W m-2), r2 = 0.93 (coffee plantation); y = 0.99x - 13.3 (W m-2), r2 = 0.88 (sugarcane). However, the correction factor (CF) for high frequency loss in the wet-bulb temperature signal was considerably higher for the low-statured sugarcane crop (CF = 1.33) as compared to the taller shaded coffee plantation (CF = 1.09). Nevertheless, as long as care is taken in the derivation of this correction factor, reliable λE data can be obtained using the dry- and wet-bulb thermocouples, offering a cheap alternative to infrared hygrometers.

  15. CORRELATING METAL SPECIATION IN SOILS

    EPA Science Inventory

    Understanding bioavailability of metals from exposure to contaminated soils is a challenging aspect of environmental research. This presentation will examine three areas of research with respect to metal speciation in soils as it relates to bioavailability: 1) Pb immobilization a...

  16. Fast and simultaneous detection of heavy metals using a simple and reliable microchip-electrochemistry route: An alternative approach to food analysis.

    PubMed

    Chailapakul, Orawon; Korsrisakul, Sarawadee; Siangproh, Weena; Grudpan, Kate

    2008-01-15

    This paper reports, for the first, the fast and simultaneous detection of prominent heavy metals, including: lead, cadmium and copper using microchip CE with electrochemical detection. The direct amperometric detection mode for microchip CE was successfully applied to these heavy metal ions. The influences of separation voltage, detection potential, as well as the concentration and pH value of the running buffer on the response of the detector were carefully assayed and optimized. The results clearly show that reliable analysis for lead, cadmium, and copper by the degree of electrophoretic separation occurs in less than 3min using a MES buffer (pH 7.0, 25mM) and l-histidine, with 1.2kV separation voltage and -0.8V detection potential. The detection limits for Pb(2+), Cd(2+), and Cu(2+) were 1.74, 0.73 and 0.13microM (S/N=3). The %R.S.D. of each peak current was <6% and migration times <2% for prolonged operation. To demonstrate the potential and future role of microchip CE, analytical possibilities and a new route in the raw sample analysis were presented. The results obtained allow the proposed microchip CE-ED acts as an alternative approach for metal analysis in foods.

  17. Sexual conflict and speciation.

    PubMed Central

    Parker, G A; Partridge, L

    1998-01-01

    We review the significance of two forms of sexual conflict (different evolutionary interests of the two sexes) for genetic differentiation of populations and the evolution of reproductive isolation. Conflicting selection on the alleles at a single locus can occur in males and females if the sexes have different optima for a trait, and there are pleiotropic genetic correlations between the sexes for it. There will then be selection for sex limitation and hence sexual dimorphism. This sex limitation could break down in hybrids and reduce their fitness. Pleiotropic genetic correlations between the sexes could also affect the likelihood of mating in interpopulation encounters. Conflict can also occur between (sex-limited) loci that determine behaviour in males and those that determine behaviour in females. Reproductive isolation may occur by rapid coevolution of male trait and female mating preference. This would tend to generate assortative mating on secondary contact, hence promoting speciation. Sexual conflict resulting from sensory exploitation, polyspermy and the cost of mating could result in high levels of interpopulation mating. If females evolve resistance to make pre- and postmating manipulation, males from one population could be more successful with females from the other, because females would have evolved resistance to their own (but not to the allopatric) males. Between-locus sexual conflict could also occur as a result of conflict between males and females of different populations over the production of unfit hybrids. We develop models which show that females are in general selected to resist such matings and males to persist, and this could have a bearing on both the initial level of interpopulation matings and the likelihood that reinforcement will occur. In effect, selection on males usually acts to promote gene flow and to restrict premating isolation, whereas selection on females usually acts in the reverse direction. We review theoretical models

  18. Arabidopsis hybrid speciation processes

    PubMed Central

    Schmickl, Roswitha; Koch, Marcus A.

    2011-01-01

    The genus Arabidopsis provides a unique opportunity to study fundamental biological questions in plant sciences using the diploid model species Arabidopsis thaliana and Arabidopsis lyrata. However, only a few studies have focused on introgression and hybrid speciation in Arabidopsis, although polyploidy is a common phenomenon within this genus. More recently, there is growing evidence of significant gene flow between the various Arabidopsis species. So far, we know Arabidopsis suecica and Arabidopsis kamchatica as fully stabilized allopolyploid species. Both species evolved during Pleistocene glaciation and deglaciation cycles in Fennoscandinavia and the amphi-Beringian region, respectively. These hybrid studies were conducted either on a phylogeographic scale or reconstructed experimentally in the laboratory. In our study we focus at a regional and population level. Our research area is located in the foothills of the eastern Austrian Alps, where two Arabidopsis species, Arabidopsis arenosa and A. lyrata ssp. petraea, are sympatrically distributed. Our hypothesis of genetic introgression, migration, and adaptation to the changing environment during the Pleistocene has been confirmed: We observed significant, mainly unidirectional gene flow between the two species, which has given rise to the tetraploid A. lyrata. This cytotype was able to escape from the narrow ecological niche occupied by diploid A. lyrata ssp. petraea on limestone outcrops by migrating northward into siliceous areas, leaving behind a trail of genetic differentiation. PMID:21825128

  19. Possible incipient sympatric ecological speciation in blind mole rats (Spalax)

    PubMed Central

    Hadid, Yarin; Tzur, Shay; Pavlíček, Tomáš; Šumbera, Radim; Šklíba, Jan; Lövy, Matěj; Fragman-Sapir, Ori; Beiles, Avigdor; Arieli, Ran; Raz, Shmuel; Nevo, Eviatar

    2013-01-01

    Sympatric speciation has been controversial since it was first proposed as a mode of speciation. Subterranean blind mole rats (Spalacidae) are considered to speciate allopatrically or peripatrically. Here, we report a possible incipient sympatric adaptive ecological speciation in Spalax galili (2n = 52). The study microsite (0.04 km2) is sharply subdivided geologically, edaphically, and ecologically into abutting barrier-free ecologies divergent in rock, soil, and vegetation types. The Pleistocene Alma basalt abuts the Cretaceous Senonian Kerem Ben Zimra chalk. Only 28% of 112 plant species were shared between the soils. We examined mitochondrial DNA in the control region and ATP6 in 28 mole rats from basalt and in 14 from chalk habitats. We also sequenced the complete mtDNA (16,423 bp) of four animals, two from each soil type. Remarkably, the frequency of all major haplotype clusters (HC) was highly soil-biased. HCI and HCII are chalk biased. HC-III was abundant in basalt (36%) but absent in chalk; HC-IV was prevalent in basalt (46.5%) but was low (20%) in chalk. Up to 40% of the mtDNA diversity was edaphically dependent, suggesting constrained gene flow. We identified a homologous recombinant mtDNA in the basalt/chalk studied area. Phenotypically significant divergences differentiate the two populations, inhabiting different soils, in adaptive oxygen consumption and in the amount of outside-nest activity. This identification of a possible incipient sympatric adaptive ecological speciation caused by natural selection indirectly refutes the allopatric alternative. Sympatric ecological speciation may be more prevalent in nature because of abundant and sharply abutting divergent ecologies. PMID:23359700

  20. Speciation of animal fat: Needs and challenges.

    PubMed

    Hsieh, Yun-Hwa Peggy; Ofori, Jack Appiah

    2017-05-24

    The use of pork fat is a concern for Muslims and Jews, who for religious reasons avoid consuming anything that is pig-derived. The use of bovine materials, including beef fat, is prohibited in Hinduism and may also pose a risk of carrying the infectious agent for bovine spongiform encephalopathy. Vegetable oils are sometimes adulterated with animal fat or pork fat with beef fat for economic gain. The development of methods to determine the species origin of fat has therefore become a priority due to the complex and global nature of the food trade, which creates opportunities for the fraudulent use of these animal fats as food ingredients. However, determining the species origin of fats in processed foods or composite blends is an arduous task as the adulterant has a composition that is very similar to that of the original fat or oil. This review examines some of the methods that have been developed for fat speciation, including both fat-based and DNA-based methods, their shortcomings, and the need for additional alternatives. Protein-based methods, specifically immunoassays targeting residual proteins in adipose tissue, that are being explored by researchers as a new tool for fat speciation will also be discussed.

  1. Recombinase Polymerase Amplification Assay—A Simple, Fast and Cost-Effective Alternative to Real Time PCR for Specific Detection of Feline Herpesvirus-1

    PubMed Central

    Wang, Jianchang; Liu, Libing; Wang, Jinfeng; Sun, Xiaoxia; Yuan, Wanzhe

    2017-01-01

    Feline herpesvirus 1 (FHV-1), an enveloped dsDNA virus, is one of the major pathogens of feline upper respiratory tract disease (URTD) and ocular disease. Currently, polymerase chain reaction (PCR) remains the gold standard diagnostic tool for FHV-1 infection but is relatively expensive, requires well-equipped laboratories and is not suitable for field tests. Recombinase polymerase amplification (RPA), an isothermal gene amplification technology, has been explored for the molecular diagnosis of infectious diseases. In this study, an exo-RPA assay for FHV-1 detection was developed and validated. Primers targeting specifically the thymidine kinase (TK) gene of FHV-1 were designed. The RPA reaction was performed successfully at 39°C and the results were obtained within 20 min. Using different copy numbers of recombinant plasmid DNA that contains the TK gene as template, we showed the detection limit of exo-RPA was 102 copies DNA/reaction, the same as that of real time PCR. The exo-RPA assay did not cross-detect feline panleukopenia virus, feline calicivirus, bovine herpesvirus-1, pseudorabies virus or chlamydia psittaci, a panel of pathogens important in feline URTD or other viruses in Alphaherpesvirinae, demonstrating high specificity. The assay was validated by testing 120 nasal and ocular conjunctival swabs of cats, and the results were compared with those obtained with real-time PCR. Both assays provided the same testing results in the clinical samples. Compared with real time PCR, the exo-RPA assay uses less-complex equipment that is portable and the reaction is completed much faster. Additionally, commercial RPA reagents in vacuum-sealed pouches can tolerate temperatures up to room temperature for days without loss of activity, suitable for shipment and storage for field tests. Taken together, the exo-RPA assay is a simple, fast and cost-effective alternative to real time PCR, suitable for use in less advanced laboratories and for field detection of FHV-1

  2. Recombinase Polymerase Amplification Assay-A Simple, Fast and Cost-Effective Alternative to Real Time PCR for Specific Detection of Feline Herpesvirus-1.

    PubMed

    Wang, Jianchang; Liu, Libing; Wang, Jinfeng; Sun, Xiaoxia; Yuan, Wanzhe

    2017-01-01

    Feline herpesvirus 1 (FHV-1), an enveloped dsDNA virus, is one of the major pathogens of feline upper respiratory tract disease (URTD) and ocular disease. Currently, polymerase chain reaction (PCR) remains the gold standard diagnostic tool for FHV-1 infection but is relatively expensive, requires well-equipped laboratories and is not suitable for field tests. Recombinase polymerase amplification (RPA), an isothermal gene amplification technology, has been explored for the molecular diagnosis of infectious diseases. In this study, an exo-RPA assay for FHV-1 detection was developed and validated. Primers targeting specifically the thymidine kinase (TK) gene of FHV-1 were designed. The RPA reaction was performed successfully at 39°C and the results were obtained within 20 min. Using different copy numbers of recombinant plasmid DNA that contains the TK gene as template, we showed the detection limit of exo-RPA was 102 copies DNA/reaction, the same as that of real time PCR. The exo-RPA assay did not cross-detect feline panleukopenia virus, feline calicivirus, bovine herpesvirus-1, pseudorabies virus or chlamydia psittaci, a panel of pathogens important in feline URTD or other viruses in Alphaherpesvirinae, demonstrating high specificity. The assay was validated by testing 120 nasal and ocular conjunctival swabs of cats, and the results were compared with those obtained with real-time PCR. Both assays provided the same testing results in the clinical samples. Compared with real time PCR, the exo-RPA assay uses less-complex equipment that is portable and the reaction is completed much faster. Additionally, commercial RPA reagents in vacuum-sealed pouches can tolerate temperatures up to room temperature for days without loss of activity, suitable for shipment and storage for field tests. Taken together, the exo-RPA assay is a simple, fast and cost-effective alternative to real time PCR, suitable for use in less advanced laboratories and for field detection of FHV-1

  3. Mutation-order divergence by sexual selection: diversification of sexual signals in similar environments as a first step in speciation.

    PubMed

    Mendelson, Tamra C; Martin, Michael D; Flaxman, Samuel M

    2014-09-01

    The origin of species remains a central question, and recent research focuses on the role of ecological differences in promoting speciation. Ecological differences create opportunities for divergent selection (i.e. 'ecological' speciation), a Darwinian hypothesis that hardly requires justification. In contrast, 'mutation-order' speciation proposes that, instead of adapting to different environments, populations find different ways to adapt to similar environments, implying that speciation does not require ecological differences. This distinction is critical as it provides an alternative hypothesis to the prevailing view that ecological differences drive speciation. Speciation by sexual selection lies at the centre of debates about the importance of ecological differences in promoting speciation; here, we present verbal and mathematical models of mutation-order divergence by sexual selection. We develop three general cases and provide a two-locus population genetic model for each. Results indicate that alternative secondary sexual traits can fix in populations that initially experience similar natural and sexual selection and that divergent traits and preferences can remain stable in the face of low gene flow. This stable divergence can facilitate subsequent divergence that completes or reinforces speciation. We argue that a mutation-order process could explain widespread diversity in secondary sexual traits among closely related, allopatric species.

  4. How common is homoploid hybrid speciation?

    PubMed

    Schumer, Molly; Rosenthal, Gil G; Andolfatto, Peter

    2014-06-01

    Hybridization has long been considered a process that prevents divergence between species. In contrast to this historical view, an increasing number of empirical studies claim to show evidence for hybrid speciation without a ploidy change. However, the importance of hybridization as a route to speciation is poorly understood, and many claims have been made with insufficient evidence that hybridization played a role in the speciation process. We propose criteria to determine the strength of evidence for homoploid hybrid speciation. Based on an evaluation of the literature using this framework, we conclude that although hybridization appears to be common, evidence for an important role of hybridization in homoploid speciation is more circumscribed.

  5. Models of speciation: where are we now?

    PubMed

    Gavrilets, Sergey

    2014-01-01

    Theory building is an integral part of biological research, in general, and of speciation research, in particular. Here, I review the modeling work on speciation done in the last 10 years or so, assessing the progress made and identifying areas where additional effort is required. Specific topics considered include evolutionary dynamics of genetic incompatibilities, spatial and temporal patterns of speciation, links to neutral theory of biodiversity, effects of multidimensionality of phenotype, sympatric and parapatric speciation, adaptive radiation, speciation by sexual conflict, and models tailored for specific biological systems. Particularly challenging questions for future theoretical research identified here are 1) incorporating gene regulatory networks in models describing accumulation of genetic incompatibilities; 2) integrating models of community ecology with those developed in speciation theory; 3) building models providing better insights on the dynamics of parapatric speciation; 4) modeling speciation in multidimensional ecological niches with mating preferences based on multidimensional mating cues and sexual characters; 5) linking microevolutionary processes with macroevolutionary patterns as observed in adaptive radiations and paleontological record; 6) modeling speciation in specific systems studied by empirical biologists; and 7) modeling human origins. The insights from dynamic models of speciation should be useful in developing statistical tools that would enable empiricists to infer the history of past evolutionary divergence and speciation from genomic data.

  6. Combustion chemistry of ethanol: Ignition and speciation studies in a rapid compression facility [On the combustion chemistry of ethanol: Ignition and speciation studies in a rapid compression facility

    SciTech Connect

    Barraza-Botet, Cesar L.; Wagnon, Scott W.; Wooldridge, Margaret S.

    2016-08-31

    Here, ethanol remains the most important alternative fuel for the transportation sector. This work presents new experimental data on ethanol ignition, including stable species measurements, obtained with the University of Michigan rapid compression facility. Ignition delay times were determined from pressure histories of ignition experiments with stoichiometric ethanol–air mixtures at pressures of ~3–10 atm. Temperatures (880–1150 K) were controlled by varying buffer gas composition (Ar, N2, CO2). High-speed imaging was used to record chemiluminescence during the experiments, which showed homogeneous ignition events. The results for ignition delay time agreed well with trends on the basis of previous experimental measurements. Speciation experiments were performed using fast gas sampling and gas chromatography to identify and quantify ethanol and 11 stable intermediate species formed during the ignition delay period. Simulations were carried out using a chemical kinetic mechanism available in the literature, and the agreement with the experimental results for ignition delay time and the intermediate species measured was excellent for the majority of the conditions studied. From the simulation results, ethanol + HO2 was identified as an important reaction at the experimental conditions for both the ignition delay time and intermediate species measurements. Further studies to improve the accuracy of the rate coefficient for ethanol + HO2 would improve the predictive understanding of intermediate and low-temperature ethanol combustion.

  7. Estimating the duration of speciation from phylogenies.

    PubMed

    Etienne, Rampal S; Morlon, Hélène; Lambert, Amaury

    2014-08-01

    Speciation is not instantaneous but takes time. The protracted birth-death diversification model incorporates this fact and predicts the often observed slowdown of lineage accumulation toward the present. The mathematical complexity of the protracted speciation model has barred estimation of its parameters until recently a method to compute the likelihood of phylogenetic branching times under this model was outlined (Lambert et al. ). Here, we implement this method and study using simulated phylogenies of extant species how well we can estimate the model parameters (rate of initiation of speciation, rate of extinction of incipient and good species, and rate of completion of speciation) as well as the duration of speciation, which is a combination of the aforementioned parameters. We illustrate our approach by applying it to a primate phylogeny. The simulations show that phylogenies often do not contain enough information to provide unbiased estimates of the speciation-initiation rate and the extinction rate, but the duration of speciation can be estimated without much bias. The estimate of the duration of speciation for the primate clade is consistent with literature estimates. We conclude that phylogenies combined with the protracted speciation model provide a promising way to estimate the duration of speciation.

  8. Sensory drive in cichlid speciation.

    PubMed

    Maan, Martine E; Hofker, Kees D; van Alphen, Jacques J M; Seehausen, Ole

    2006-06-01

    The role of selection in speciation is a central yet poorly understood problem in evolutionary biology. The rapid radiations of extremely colorful cichlid fish in African lakes have fueled the hypothesis that sexual selection can drive species divergence without geographical isolation. Here we present experimental evidence for a mechanism by which sexual selection becomes divergent: in two sibling species from Lake Victoria, female mating preferences for red and blue male nuptial coloration coincide with their context-independent sensitivities to red and blue light, which in turn correspond to a difference in ambient light in the natural habitat of the species. These results suggest that natural selection on visual performance, favoring different visual properties in different spectral environments, may lead to divergent sexual selection on male nuptial coloration. This interplay of ecological and sexual selection along a light gradient may provide a mechanism of rapid speciation through divergent sensory drive.

  9. Homoploid hybrid speciation in animals.

    PubMed

    Mavárez, Jesús; Linares, Mauricio

    2008-10-01

    Among animals, evidence for homoploid hybrid speciation (HHS, i.e. the creation of a hybrid lineage without a change in chromosome number) was limited until recently to the virgin chub, Gila seminuda, and some controversial data in support of hybrid status for the red wolf, Canis rufus. This scarcity of evidence, together with pessimistic attitudes among zoologists about the evolutionary importance of hybridisation, prompted the view that HHS is extremely rare among animals, especially as compared with plants. However, in recent years, the literature on animal HHS has expanded to include several new putative examples in butterflies, ants, flies and fishes. We argue that this evidence suggests that HHS is far more common than previously thought and use it to provide insights into some of the genetic and ecological aspects associated with this type of speciation among animals.

  10. MODELING MONOMETHYLMERCURY AND TRIBUTYLTIN SPECIATION WITH EPA'S GEOCHEMICAL SPECIATION MODEL MINTEQA2

    EPA Science Inventory

    Given the complexity of the various, simultaneous (and competing) equilibrium reactions governing the speciation of ionic species in aquatic systems, EPA has developed and distributed the geochemical speciation model MINTEQA2 (Brown and Allison, 1987, Allison et al., 1991; Hydrog...

  11. Thermal adaptation and ecological speciation.

    PubMed

    Keller, I; Seehausen, O

    2012-02-01

    Ecological speciation is defined as the emergence of reproductive isolation as a direct or indirect consequence of divergent ecological adaptation. Several empirical examples of ecological speciation have been reported in the literature which very often involve adaptation to biotic resources. In this review, we investigate whether adaptation to different thermal habitats could also promote speciation and try to assess the importance of such processes in nature. Our survey of the literature identified 16 animal and plant systems where divergent thermal adaptation may underlie (partial) reproductive isolation between populations or may allow the stable coexistence of sibling taxa. In many of the systems, the differentially adapted populations have a parapatric distribution along an environmental gradient. Isolation often involves extrinsic selection against locally maladapted parental or hybrid genotypes, and additional pre- or postzygotic barriers may be important. Together, the identified examples strongly suggest that divergent selection between thermal environments is often strong enough to maintain a bimodal genotype distribution upon secondary contact. What is less clear from the available data is whether it can also be strong enough to allow ecological speciation in the face of gene flow through reinforcement-like processes. It is possible that intrinsic features of thermal gradients or the genetic basis of thermal adaptation make such reinforcement-like processes unlikely but it is equally possible that pertinent systems are understudied. Overall, our literature survey highlights (once again) the dearth of studies that investigate similar incipient species along the continuum from initial divergence to full reproductive isolation and studies that investigate all possible reproductive barriers in a given system.

  12. Speciation in fungal and oomycete plant pathogens.

    PubMed

    Restrepo, Silvia; Tabima, Javier F; Mideros, Maria F; Grünwald, Niklaus J; Matute, Daniel R

    2014-01-01

    The process of speciation, by definition, involves evolution of one or more reproductive isolating mechanisms that split a single species into two that can no longer interbreed. Determination of which processes are responsible for speciation is important yet challenging. Several studies have proposed that speciation in pathogens is heavily influenced by host-pathogen dynamics and that traits that mediate such interactions (e.g., host mobility, reproductive mode of the pathogen, complexity of the life cycle, and host specificity) must lead to reproductive isolation and ultimately affect speciation rates. In this review, we summarize the main evolutionary processes that lead to speciation of fungal and oomycete plant pathogens and provide an outline of how speciation can be studied rigorously, including novel genetic/genomic developments.

  13. Arsenic Speciation of Terrestrial Invertebrates

    SciTech Connect

    Moriarty, M.M.; Koch, I.; Gordon, R.A.; Reimer, K.J. ); )

    2009-07-01

    The distribution and chemical form (speciation) of arsenic in terrestrial food chains determines both the amount of arsenic available to higher organisms, and the toxicity of this metalloid in affected ecosystems. Invertebrates are part of complex terrestrial food webs. This paper provides arsenic concentrations and arsenic speciation profiles for eight orders of terrestrial invertebrates collected at three historical gold mine sites and one background site in Nova Scotia, Canada. Total arsenic concentrations, determined by inductively coupled plasma mass spectrometry (ICP-MS), were dependent upon the classification of invertebrate. Arsenic species were determined by high-performance liquid chromatography (HPLC) ICP-MS and X-ray absorption spectroscopy (XAS). Invertebrates were found by HPLC ICP-MS to contain predominantly arsenite and arsenate in methanol/water extracts, while XAS revealed that most arsenic is bound to sulfur in vivo. Examination of the spatial distribution of arsenic within an ant tissue highlighted the differences between exogenous and endogenous arsenic, as well as the extent to which arsenic is transformed upon ingestion. Similar arsenic speciation patterns for invertebrate groups were observed across sites. Trace amounts of arsenobetaine and arsenocholine were identified in slugs, ants, and spiders.

  14. Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    1998-01-01

    A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface.

  15. Dielectric-wall linear accelerator with a high voltage fast rise time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators

    DOEpatents

    Caporaso, G.J.; Sampayan, S.E.; Kirbie, H.C.

    1998-10-13

    A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface. 12 figs.

  16. Adaptive speciation theory: a conceptual review.

    PubMed

    Weissing, Franz J; Edelaar, Pim; van Doorn, G Sander

    2011-03-01

    Speciation-the origin of new species-is the source of the diversity of life. A theory of speciation is essential to link poorly understood macro-evolutionary processes, such as the origin of biodiversity and adaptive radiation, to well understood micro-evolutionary processes, such as allele frequency change due to natural or sexual selection. An important question is whether, and to what extent, the process of speciation is 'adaptive', i.e., driven by natural and/or sexual selection. Here, we discuss two main modelling approaches in adaptive speciation theory. Ecological models of speciation focus on the evolution of ecological differentiation through divergent natural selection. These models can explain the stable coexistence of the resulting daughter species in the face of interspecific competition, but they are often vague about the evolution of reproductive isolation. Most sexual selection models of speciation focus on the diversification of mating strategies through divergent sexual selection. These models can explain the evolution of prezygotic reproductive isolation, but they are typically vague on questions like ecological coexistence. By means of an integrated model, incorporating both ecological interactions and sexual selection, we demonstrate that disruptive selection on both ecological and mating strategies is necessary, but not sufficient, for speciation to occur. To achieve speciation, mating must at least partly reflect ecological characteristics. The interaction of natural and sexual selection is also pivotal in a model where sexual selection facilitates ecological speciation even in the absence of diverging female preferences. In view of these results, it is counterproductive to consider ecological and sexual selection models as contrasting and incompatible views on speciation, one being dominant over the other. Instead, an integrative perspective is needed to achieve a thorough and coherent understanding of adaptive speciation.

  17. Arsenic speciation in edible mushrooms.

    PubMed

    Nearing, Michelle M; Koch, Iris; Reimer, Kenneth J

    2014-12-16

    The fruiting bodies, or mushrooms, of terrestrial fungi have been found to contain a high proportion of the nontoxic arsenic compound arsenobetaine (AB), but data gaps include a limited phylogenetic diversity of the fungi for which arsenic speciation is available, a focus on mushrooms with higher total arsenic concentrations, and the unknown formation and role of AB in mushrooms. To address these, the mushrooms of 46 different fungus species (73 samples) over a diverse range of phylogenetic groups were collected from Canadian grocery stores and background and arsenic-contaminated areas. Total arsenic was determined using ICP-MS, and arsenic speciation was determined using HPLC-ICP-MS and complementary X-ray absorption spectroscopy (XAS). The major arsenic compounds in mushrooms were found to be similar among phylogenetic groups, and AB was found to be the major compound in the Lycoperdaceae and Agaricaceae families but generally absent in log-growing mushrooms, suggesting the microbial community may influence arsenic speciation in mushrooms. The high proportion of AB in mushrooms with puffball or gilled morphologies may suggest that AB acts as an osmolyte in certain mushrooms to help maintain fruiting body structure. The presence of an As(III)-sulfur compound, for the first time in mushrooms, was identified in the XAS analysis. Except for Agaricus sp. (with predominantly AB), inorganic arsenic predominated in most of the store-bought mushrooms (albeit with low total arsenic concentrations). Should inorganic arsenic predominate in these mushrooms from contaminated areas, the risk to consumers under these circumstances should be considered.

  18. Possible method for dissolved organic carbon speciation in forest soils

    NASA Astrophysics Data System (ADS)

    Drabek, O.; Tejnecký, V.; Ash, C.; Hubova, P.; Boruvka, L.

    2013-12-01

    Dissolved organic carbon (DOC) is a natural part of dissolved organic matter and it plays an important role in the biogeochemistry of soil processes. Low Molecular Mass Organic Acids (LMMOA) are an essential part of DOC. These acids play a key role in chemical processes that affect the entire soil environment. Knowing the amount of DOC and the speciation of LMMOA is required for realistic equilibrium modelling of soil chemical processes and transport mechanisms. There have been a number of proposed methods for the quantitative analysis of DOC and for speciation of LMMOA. The first aim of this contribution is to introduce and test a modified spectroscopic method for the determination of water-extractable organic carbon (WEOC) from forest soils. In general this method is based on the oxidization of WEOC by chromium-sulphuric acid. The presented method can be used as an economical alternative to the classical, more financially demanding elemental analysis. However, the main aim is to test the reliability of the method for LMMOA speciation. Ion exchange chromatography (IC) with hydroxide elution has proven to be a useful tool for the determination of LMMOA in many different water-based samples. However, the influence of multivalent cations (often present in environmental samples) on IC results has not yet been sufficiently studied. In order to assess the influence of Al, Fe, Mn, Mg and Ca on the amount of LMMOA determined by IC, an extensive set of model solutions was prepared and immediately analysed by means of IC. Moreover, the influence of pH on determined amounts of LMMOA in model solutions and representative soil aqueous extracts was investigated. These experimental results were compared to expected values and also to results provided by the chemical equilibrium model - PHREEQC. Based on the above listed research, some modifications to the common IC method for LMMOA speciation are presented.

  19. Speciation genetics: current status and evolving approaches

    PubMed Central

    Wolf, Jochen B. W.; Lindell, Johan; Backström, Niclas

    2010-01-01

    The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues. PMID:20439277

  20. Speciation in fungal and oomycete plant pathogens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The process of speciation by definition involves evolution of one or more reproductive isolating mechanisms that split a single species into two that can no longer interbreed. Determination of which processes are responsible for speciation is important yet challenging. Several studies have proposed ...

  1. Speciation genetics: current status and evolving approaches.

    PubMed

    Wolf, Jochen B W; Lindell, Johan; Backström, Niclas

    2010-06-12

    The view of species as entities subjected to natural selection and amenable to change put forth by Charles Darwin and Alfred Wallace laid the conceptual foundation for understanding speciation. Initially marred by a rudimental understanding of hereditary principles, evolutionists gained appreciation of the mechanistic underpinnings of speciation following the merger of Mendelian genetic principles with Darwinian evolution. Only recently have we entered an era where deciphering the molecular basis of speciation is within reach. Much focus has been devoted to the genetic basis of intrinsic postzygotic isolation in model organisms and several hybrid incompatibility genes have been successfully identified. However, concomitant with the recent technological advancements in genome analysis and a newfound interest in the role of ecology in the differentiation process, speciation genetic research is becoming increasingly open to non-model organisms. This development will expand speciation research beyond the traditional boundaries and unveil the genetic basis of speciation from manifold perspectives and at various stages of the splitting process. This review aims at providing an extensive overview of speciation genetics. Starting from key historical developments and core concepts of speciation genetics, we focus much of our attention on evolving approaches and introduce promising methodological approaches for future research venues.

  2. Rates of speciation in the fossil record.

    PubMed Central

    Sepkoski, J J

    1998-01-01

    Data from palaeontology and biodiversity suggest that the global biota should produce an average of three new species per year. However, the fossil record shows large variation around this mean. Rates of origination have declined through the Phanerozoic. This appears to have been largely a function of sorting among higher taxa (especially classes), which exhibit characteristic rates of speciation (and extinction) that differ among them by nearly an order of magnitude. Secular decline of origination rates is hardly constant, however; many positive deviations reflect accelerated speciation during rebounds from mass extinctions. There has also been general decline in rates of speciation within major taxa through their histories, although rates have tended to remain higher among members in tropical regions. Finally, pulses of speciation appear sometimes to be associated with climate change, although moderate oscillations of climate do not necessarily promote speciation despite forcing changes in species' geographical ranges. PMID:11541734

  3. Rates of speciation in the fossil record

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. J. Jr; Sepkoski JJ, J. r. (Principal Investigator)

    1998-01-01

    Data from palaeontology and biodiversity suggest that the global biota should produce an average of three new species per year. However, the fossil record shows large variation around this mean. Rates of origination have declined through the Phanerozoic. This appears to have been largely a function of sorting among higher taxa (especially classes), which exhibit characteristic rates of speciation (and extinction) that differ among them by nearly an order of magnitude. Secular decline of origination rates is hardly constant, however; many positive deviations reflect accelerated speciation during rebounds from mass extinctions. There has also been general decline in rates of speciation within major taxa through their histories, although rates have tended to remain higher among members in tropical regions. Finally, pulses of speciation appear sometimes to be associated with climate change, although moderate oscillations of climate do not necessarily promote speciation despite forcing changes in species' geographical ranges.

  4. Copper and nickel speciation in mine effluents by combination of two independent techniques.

    PubMed

    Chakraborty, Parthasarathi; Zhao, Jiujiang; Chakrabarti, C L

    2009-03-16

    To control potentially toxic metals in water resources it is necessary to know metal speciation and changes in the metal speciation that occur after aqueous effluents containing metals are discharged into freshwaters. This work explores the speciation of nickel and copper in metal-mining aqueous effluents. Diffusive gradients in thin films (DGT) technique and competing ligand exchange (CLE) method have been applied to determine the speciation of nickel and copper. The results of this investigation demonstrate that combination of two analytical techniques having complementary analytical capabilities can provide a better physicochemical picture of metal speciation than either one of the analytical technique can do alone. The combined use of these techniques revealed that copper formed labile complexes having slow diffusion coefficient along with the presence of small labile copper complexes. Nickel-dissolved organic complexes (DOC) complexes in the aqueous effluent have been found to have fast diffusion coefficient. The results are likely to have environmental significance for providing a link between the metal species in mine aqueous effluent and their bioavailability by determining the characteristics of copper and nickel complexes in metal-mine aqueous effluents. This knowledge is expected to promote a better understanding of the lability of DOC complexes of copper and nickel in mining effluents.

  5. Molecular evolutionary rates predict both extinction and speciation in temperate angiosperm lineages

    PubMed Central

    2010-01-01

    Background A positive relationship between diversification (i.e., speciation) and nucleotide substitution rates is commonly reported for angiosperm clades. However, the underlying cause of this relationship is often unknown because multiple intrinsic and extrinsic factors can affect the relationship, and these have confounded previous attempts infer causation. Determining which factor drives this oft-reported correlation can lend insight into the macroevolutionary process. Results Using a new database of 13 time-calibrated angiosperm phylogenies based on internal transcribed spacer (ITS) sequences, and controlling for extrinsic variables of life history and habitat, I evaluated several potential intrinsic causes of this correlation. Speciation rates (λ) and relative extinction rates (ε) were positively correlated with mean substitution rates, but were uncorrelated with substitution rate heterogeneity. It is unlikely that the positive diversification-substitution correlation is due to accelerated molecular evolution during speciation (e.g., via enhanced selection or drift), because punctuated increases in ITS rate (i.e., greater mean and variation in ITS rate for rapidly speciating clades) were not observed. Instead, fast molecular evolution likely increases speciation rate (via increased mutational variation as a substrate for selection and reproductive isolation) but also increases extinction (via mutational genetic load). Conclusions In general, these results predict that clades with higher background substitution rates may undergo successful diversification under new conditions while clades with lower substitution rates may experience decreased extinction during environmental stasis. PMID:20515493

  6. Molecular models for actinide speciation

    SciTech Connect

    Clark, D.L.; Watkin, J.G.; Morris, D.E.; Berg, J.M.

    1994-06-01

    Much effort has been devoted to the development of sensitive spectroscopic techniques for the study of actinide speciation based on the sensitivity of f-f electronic absorption bands to oxidation state and ligation of the actinide ions. These efforts assume that data obtained in such studies will be interpretable in terms of changes in complexation of the metal center. However, the current understanding of 5f electronic structure is based on data from solid state doped single crystals. In those studies, the local coordination geometry about the central actinide ion is maintained in an almost perfect high-symmetry environment and will have little relevance for species in solution where deviations from perfect high symmetry tend to be the rule rather than the exception. The authors have developed a vigorous research program in the systematic preparation and spectroscopic characterization of synthetic actinide complexes (Th, U, Np, and Pu) in which they can control nuclearity, oxidation state, and molecular structure. These complexes have been used to determine how observable electronic transitions are perturbed in response to structural changes in the complex in solution. From the spectra obtained for these model complexes, the authors have found that the f-f transitions naturally fall into obvious groupings by coordination number and symmetry by which they can now differentiate between monomeric, dimeric, and trimeric species in solution. The study of radionuclide speciation is fundamentally important to the determination of radionuclide solubility in the groundwater at Yucca Mountain.

  7. The speciation of behavior analysis

    PubMed Central

    Rider, David P.

    1991-01-01

    The relationship between the Experimental Analysis of Behavior (EAB) and Applied Behavior Analysis (ABA) has been the subject of several editorials and commentaries in recent years. Various authors have argued that researchers in these two fields (a) have become isolated from each other, (b) face different requirements for survival in their respective fields, and (c) possess different skills to meet those requirements. The present paper provides an allegory for the relationship between EAB and ABA in terms of biological speciation. The conditions that have changed the relationship between EAB and ABA are parallel to those responsible for biological speciation: (a) isolation of some members of a species from the rest of the population, (b) different contingencies of survival for members of the two separate groups, and (c) divergence in the adaptive characteristics displayed by the two groups. When members of two different groups, descendants of common ancestors, no longer are capable of producing viable offspring by interbreeding, the different groups then represent different species. To the extent that members of the EAB group and members of the ABA group interact with each other only trivially, they each represent allegorically different species. Changes in the relationship between EAB and ABA are part of a natural process that takes place in many other sciences, and the course of that process can hardly be reversed by us. PMID:22478096

  8. Bird song, ecology and speciation.

    PubMed Central

    Slabbekoorn, Hans; Smith, Thomas B

    2002-01-01

    The study of bird song dialects was once considered the most promising approach for investigating the role of behaviour in reproductive divergence and speciation. However, after a series of studies yielding conflicting results, research in the field slowed significantly. Recent findings, on how ecological factors may lead to divergence in both song and morphology, necessitate a re-examination. We focus primarily on species with learned song, examine conflicting results in the literature and propose some potential new directions for future studies. We believe an integrative approach, including an examination of the role of ecology in divergent selection, is essential for gaining insight into the role of song in the evolution of assortative mating. Habitat-dependent selection on both song and fitness-related characteristics can lead to parallel divergence in these traits. Song may, therefore, provide females with acoustic cues to find males that are most fit for a particular habitat. In analysing the role of song learning in reproductive divergence, we focus on post-dispersal plasticity in a conceptual framework. We argue that song learning may initially constrain reproductive divergence, while in the later stages of population divergence it may promote speciation. PMID:12028787

  9. Nanomaterial-based approaches for the detection and speciation of mercury.

    PubMed

    Xu, Xiaohan; Li, Yu-Feng; Zhao, Jiating; Li, Yunyun; Lin, Jing; Li, Bai; Gao, Yuxi; Chen, Chunying

    2015-12-07

    Mercury is toxic with widespread contamination. Highly sensitive and selective approaches for mercury analysis are desired. Although conventional techniques are accurate and sensitive in the determination of mercury, these procedures are time-consuming, labor-intensive and dependent heavily on expensive instrumentation. In recent years, nanomaterial-based approaches have been proved to be effective alternatives in the detection and speciation of mercury. In this review, the development of different nanomaterial-based approaches was summarized, as well as their utilization for the detection of mercury in environmental and biological samples, such as gold nanomaterials, carbon nanomaterials, quantum dots and so on. Moreover, the speciation of mercury using nanomaterials was also reviewed.

  10. How Fast Is Fast?

    ERIC Educational Resources Information Center

    Korn, Abe

    1994-01-01

    Presents an activity that enables students to answer for themselves the question of how fast a body must travel before the nonrelativistic expression must be replaced with the correct relativistic expression by deciding on the accuracy required in describing the kinetic energy of a body. (ZWH)

  11. US EPA's SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, volatile o...

  12. Environmental harshness, latitude and incipient speciation.

    PubMed

    Weir, Jason T

    2014-02-01

    Are rates of evolution and speciation fastest where diversity is greatest - the tropics? A commonly accepted theory links the latitudinal diversity gradient to a speciation pump model whereby the tropics produce species at a faster rate than extra-tropical regions. In this issue of Molecular Ecology, Botero et al. () test the speciation pump model using subspecies richness patterns for more than 9000 species of birds and mammals as a proxy for incipient speciation opportunity. Rather than using latitudinal centroids, the authors investigate the role of various environmental correlates of latitude as drivers of subspecies richness. Their key finding points to environmental harshness as a positive predictor of subspecies richness. The authors link high subspecies richness in environmental harsh areas to increased opportunities for geographic range fragmentation and/or faster rates of trait evolution as drivers of incipient speciation. Because environmental harshness generally increases with latitude, these results suggest that opportunity for incipient speciation is lowest where species richness is highest. The authors interpret this finding as incompatible with the view of the tropics as a cradle of diversity. Their results are consistent with a growing body of evidence that reproductive isolation and speciation occur fastest at high latitudes.

  13. Assessing when chromosomal rearrangements affect the dynamics of speciation: implications from computer simulations.

    PubMed

    Feder, Jeffrey L; Nosil, Patrik; Flaxman, Samuel M

    2014-01-01

    Many hypotheses have been put forth to explain the origin and spread of inversions, and their significance for speciation. Several recent genic models have proposed that inversions promote speciation with gene flow due to the adaptive significance of the genes contained within them and because of the effects inversions have on suppressing recombination. However, the consequences of inversions for the dynamics of genome wide divergence across the speciation continuum remain unclear, an issue we examine here. We review a framework for the genomics of speciation involving the congealing of the genome into alternate adaptive states representing species ("genome wide congealing"). We then place inversions in this context as examples of how genetic hitchhiking can potentially hasten genome wide congealing. Specifically, we use simulation models to (i) examine the conditions under which inversions may speed genome congealing and (ii) quantify predicted magnitudes of these effects. Effects of inversions on promoting speciation were most common and pronounced when inversions were initially fixed between populations before secondary contact and adaptation involved many genes with small fitness effects. Further work is required on the role of underdominance and epistasis between a few loci of major effect within inversions. The results highlight five important aspects of the roles of inversions in speciation: (i) the geographic context of the origins and spread of inversions, (ii) the conditions under which inversions can facilitate divergence, (iii) the magnitude of that facilitation, (iv) the extent to which the buildup of divergence is likely to be biased within vs. outside of inversions, and (v) the dynamics of the appearance and disappearance of exceptional divergence within inversions. We conclude by discussing the empirical challenges in showing that inversions play a central role in facilitating speciation with gene flow.

  14. Rates of speciation and morphological evolution are correlated across the largest vertebrate radiation.

    PubMed

    Rabosky, Daniel L; Santini, Francesco; Eastman, Jonathan; Smith, Stephen A; Sidlauskas, Brian; Chang, Jonathan; Alfaro, Michael E

    2013-01-01

    Several evolutionary theories predict that rates of morphological change should be positively associated with the rate at which new species arise. For example, the theory of punctuated equilibrium proposes that phenotypic change typically occurs in rapid bursts associated with speciation events. However, recent phylogenetic studies have found little evidence linking these processes in nature. Here we demonstrate that rates of species diversification are highly correlated with the rate of body size evolution across the 30,000+ living species of ray-finned fishes that comprise the majority of vertebrate biological diversity. This coupling is a general feature of fish evolution and transcends vast differences in ecology and body-plan organization. Our results may reflect a widespread speciational mode of character change in living fishes. Alternatively, these findings are consistent with the hypothesis that phenotypic 'evolvability'-the capacity of organisms to evolve-shapes the dynamics of speciation through time at the largest phylogenetic scales.

  15. Inferring the geographic mode of speciation by contrasting autosomal and sex-linked genetic diversity.

    PubMed

    Chu, Jui-Hua; Wegmann, Daniel; Yeh, Chia-Fen; Lin, Rong-Chien; Yang, Xiao-Jun; Lei, Fu-Min; Yao, Cheng-Te; Zou, Fa-Sheng; Li, Shou-Hsien

    2013-11-01

    When geographic isolation drives speciation, concurrent termination of gene flow among genomic regions will occur immediately after the formation of the barrier between diverging populations. Alternatively, if speciation is driven by ecologically divergent selection, gene flow of selectively neutral genomic regions may go on between diverging populations until the completion of reproductive isolation. It may also lead to an unsynchronized termination of gene flow between genomic regions with different roles in the speciation process. Here, we developed a novel Approximate Bayesian Computation pipeline to infer the geographic mode of speciation by testing for a lack of postdivergence gene flow and a concurrent termination of gene flow in autosomal and sex-linked markers jointly. We applied this approach to infer the geographic mode of speciation for two allopatric highland rosefinches, the vinaceous rosefinch Carpodacus vinaceus and the Taiwan rosefinch C. formosanus from DNA polymorphisms of both autosomal and Z-linked loci. Our results suggest that the two rosefinch species diverged allopatrically approximately 0.5 Ma. Our approach allowed us further to infer that female effective population sizes are about five times larger than those of males, an estimate potentially useful when comparing the intensity of sexual selection across species.

  16. Liquid phase microextraction for the analysis of trace elements and their speciation

    NASA Astrophysics Data System (ADS)

    Hu, Bin; He, Man; Chen, Beibei; Xia, Linbo

    2013-08-01

    Trace/ultra-trace elements and their speciation analysis in complex matrices usually require sample preparation procedures to achieve sample clean-up and analyte preconcentration. Sample preparation is often the bottleneck in trace elements and their speciation analysis which has a direct impact on accuracy, precision and limits of detection and is often the rate-determining step of the analytical process. Recent trends in sample preparation include miniaturization, automation, high-throughput performance and reduction in solvent/sample consumption and operation time. Liquid-phase microextraction (LPME) technique as a novel and promising alternative in sample preparation can meet these requirements and has become a very efficient sample preparation technique. This review updates the state of art of LPME for trace elements and their speciation analysis and discusses its promising prospects. The major thrust of the article highlights the applications of LPME including single-drop microextraction (SDME), hollow fiber-liquid phase microextraction (HF-LPME), dispersive liquid liquid microextraction (DLLME) and solidified floating organic drop microextraction (SFODME) to the fields of elemental and their speciation analysis by atomic spectrometry-based methods, especially inductively coupled plasma mass spectrometry. General and specific concepts, different extraction formats and characteristics of LPME are described and compared, along with examples of recent innovations and applications presented to demonstrate its potential for trace elements and their speciation analysis in biological and environmental fields. Moreover, the application potential and an outlook on the combination of LPME and atomic spectrometry-based techniques for inorganic analysis are commentated.

  17. CORRELATING METAL SPECIATION IN SOILS TO RISK

    EPA Science Inventory

    Understanding bioavailability of metals from exposure to contaminated soils is a challenging aspect of environmental research. This presentation will examine three areas of research with respect to metal speciation in soils as it relates to bioavailability: 1) Pb immobilization a...

  18. Diploid versus haploid models of neutral speciation.

    PubMed

    Schneider, David M; Baptestini, Elizabeth M; de Aguiar, Marcus A M

    2016-03-01

    Neutral models of speciation based on isolation by distance and assortative mating, termed topopatric, have shown to be successful in describing abundance distributions and species-area relationships. Previous works have considered this type of process in the context of haploid genomes. Here we discuss the implementation of two schemes of dominance to analyze the effects of diploidy: a complete dominance model in which one allele dominates over the other and a perfect codominant model in which heterozygous genotypes give rise to a third phenotype. In the case of complete dominance, we observe that speciation requires stronger spatial inbreeding in comparison to the haploid model. For perfect codominance, instead, speciation demands stronger genetic assortativeness. Nevertheless, once speciation is established, the three models predict the same abundance distributions even at the quantitative level, revealing the robustness of the original mechanism to describe biodiversity features.

  19. Physicochemical speciation of lead in drinking water.

    PubMed

    Harrison, R M; Laxen, D P

    1980-08-21

    Recent studies have highlighted the importance of drinking water as a route of human exposure to lead. Whilst there are ample data on lead concentrations in drinking water, little is known of its physical and chemical forms (physicochemical speciation). Such information is important as the speciation of ingested lead influences the efficiency of absorption from the gastrointestinal tract. Knowledge of speciation should also provide a fuller understanding of the factors controlling the solubility of lead in potable waters and hence assist in devising the most cost-effective means of plumbosolvency control. We have determined experimentally the speciation of lead in three different tapwaters and report here diverse forms of dissolved and particle-associated lead, dependent primarily on the chemical matrix of the raw water.

  20. Fast perfusion measurements in rat skeletal muscle at rest and during exercise with single-voxel FAIR (flow-sensitive alternating inversion recovery).

    PubMed

    Pohmann, Rolf; Künnecke, Basil; Fingerle, Jürgen; von Kienlin, Markus

    2006-01-01

    Non-invasive measurement of perfusion in skeletal muscle by in vivo magnetic resonance remains a challenge due to its low level and the correspondingly low signal-to-noise ratio. To enable accurate, quantitative, and time-resolved perfusion measurements in the leg muscle, a technique with a high sensitivity is required. By combining a flow-sensitive alternating inversion recovery (FAIR)-sequence with a single-voxel readout, we have developed a new technique to measure the perfusion in the rat gastrocnemius muscle at rest, yielding an average value of 19.4 +/- 4.8 mL/100 g/min (n = 22). In additional experiments, perfusion changes were elicited by acute ischemia and reperfusion or by exercise induced by electrical, noninvasive muscle stimulation with varying duration and intensity. The perfusion time courses during these manipulations were measured with a temporal resolution of 2.2 min, showing increases in perfusion of a factor of up to 2.5. In a direct comparison, the results agreed closely with values found with microsphere measurements in the same animals. The quantitative and noninvasive method can significantly facilitate the investigation of atherosclerotic diseases and the examination of drug efficacy.

  1. Fast Breeder Reactor studies

    SciTech Connect

    Till, C.E.; Chang, Y.I.; Kittel, J.H.; Fauske, H.K.; Lineberry, M.J.; Stevenson, M.G.; Amundson, P.I.; Dance, K.D.

    1980-07-01

    This report is a compilation of Fast Breeder Reactor (FBR) resource documents prepared to provide the technical basis for the US contribution to the International Nuclear Fuel Cycle Evaluation. The eight separate parts deal with the alternative fast breeder reactor fuel cycles in terms of energy demand, resource base, technical potential and current status, safety, proliferation resistance, deployment, and nuclear safeguards. An Annex compares the cost of decommissioning light-water and fast breeder reactors. Separate abstracts are included for each of the parts.

  2. Refining the conditions for sympatric ecological speciation.

    PubMed

    Débarre, F

    2012-12-01

    Can speciation occur in a single population when different types of resources are available, in the absence of any geographical isolation, or any spatial or temporal variation in selection? The controversial topics of sympatric speciation and ecological speciation have already stimulated many theoretical studies, most of them agreeing on the fact that mechanisms generating disruptive selection, some level of assortment, and enough heterogeneity in the available resources, are critical for sympatric speciation to occur. Few studies, however, have combined the three factors and investigated their interactions. In this article, I analytically derive conditions for sympatric speciation in a general model where the distribution of resources can be uni- or bimodal, and where a parameter controls the range of resources that an individual can exploit. This approach bridges the gap between models of a unimodal continuum of resources and Levene-type models with discrete resources. I then test these conditions against simulation results from a recently published article (Thibert-Plante & Hendry, 2011, J. Evol. Biol. 24: 2186-2196) and confirm that sympatric ecological speciation is favoured when (i) selection is disruptive (i.e. individuals with an intermediate trait are at a local fitness minimum), (ii) resources are differentiated enough and (iii) mating is assortative. I also discuss the role of mating preference functions and the need (or lack thereof) for bimodality in resource distributions for diversification.

  3. Evaluation of Alternate Materials for Coated Particle Fuels for the Gas-Cooled Fast Reactor. Laboratory Directed Research and Development Program FY 2006 Final Report

    SciTech Connect

    Paul A. Demkowicz; Karen Wright; Jian Gan; David Petti; Todd Allen; Jake Blanchard

    2006-09-01

    Candidate ceramic materials were studied to determine their suitability as Gas-Cooled Fast Reactor particle fuel coatings. The ceramics examined in this work were: TiC, TiN, ZrC, ZrN, AlN, and SiC. The studies focused on (i) chemical reactivity of the ceramics with fission products palladium and rhodium, (ii) the thermomechanical stresses that develop in the fuel coatings from a variety of causes during burnup, and (iii) the radiation resiliency of the materials. The chemical reactivity of TiC, TiN, ZrC, and ZrN with Pd and Rh were all found to be much lower than that of SiC. A number of important chemical behaviors were observed at the ceramic-metal interfaces, including the formation of specific intermetallic phases and a variation in reaction rates for the different ceramics investigated. Based on the data collected in this work, the nitride ceramics (TiN and ZrN) exhibit chemical behavior that is characterized by lower reaction rates with Pd and Rh than the carbides TiC and ZrC. The thermomechanical stresses in spherical fuel particle ceramic coatings were modeled using finite element analysis, and included contributions from differential thermal expansion, fission gas pressure, fuel kernel swelling, and thermal creep. In general the tangential stresses in the coatings during full reactor operation are tensile, with ZrC showing the lowest values among TiC, ZrC, and SiC (TiN and ZrN were excluded from the comprehensive calculations due to a lack of available materials data). The work has highlighted the fact that thermal creep plays a critical role in the development of the stress state of the coatings by relaxing many of the stresses at high temperatures. To perform ion irradiations of sample materials, an irradiation beamline and high-temperature sample irradiation stage was constructed at the University of Wisconsin’s 1.7MV Tandem Accelerator Facility. This facility is now capable of irradiating of materials to high dose while controlling sample temperature

  4. Selenium metabolism in cancer cells: the combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems.

    PubMed

    Weekley, Claire M; Aitken, Jade B; Finney, Lydia; Vogt, Stefan; Witting, Paul K; Harris, Hugh H

    2013-05-21

    Determining the speciation of selenium in vivo is crucial to understanding the biological activity of this essential element, which is a popular dietary supplement due to its anti-cancer properties. Hyphenated techniques that combine separation and detection methods are traditionally and effectively used in selenium speciation analysis, but require extensive sample preparation that may affect speciation. Synchrotron-based X-ray absorption and fluorescence techniques offer an alternative approach to selenium speciation analysis that requires minimal sample preparation. We present a brief summary of some key HPLC-ICP-MS and ESI-MS/MS studies of the speciation of selenium in cells and rat tissues. We review the results of a top-down approach to selenium speciation in human lung cancer cells that aims to link the speciation and distribution of selenium to its biological activity using a combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM). The results of this approach highlight the distinct fates of selenomethionine, methylselenocysteine and selenite in terms of their speciation and distribution within cells: organic selenium metabolites were widely distributed throughout the cells, whereas inorganic selenium metabolites were compartmentalized and associated with copper. New data from the XFM mapping of electrophoretically-separated cell lysates show the distribution of selenium in the proteins of selenomethionine-treated cells. Future applications of this top-down approach are discussed.

  5. Speciation of vanadium in soil.

    PubMed

    Połedniok, Justyna; Buhl, Franciszek

    2003-01-02

    A method for speciation of vanadium in soil is presented in this work. The sequential extraction analysis procedure of Tessier et al. for heavy metals was used for the vanadium separation. The method consists of sequential leaching of the soil samples to separate five fractions of metals: (1) exchangeable, (2) bound to carbonates, (3) bound to Fe-Mn oxides, (4) bound to organic matter and (5) residual. The leaching solutions of Tessier were used for the vanadium extraction, only for the residual fraction the HClO(4) was replaced with H(2)SO(4). The optimum conditions for leaching of vanadium from soil (weight of sample, concentration and volume of extractants, time of extraction) were chosen for each fraction. A sensitive, spectrophotometric method based on the ternary complex V(IV) with Chrome Azurol S and benzyldodecyldimethylammonium bromide (epsilon=7.1x10(4) l mol(-1) cm(-1)) was applied for the vanadium determination after separation of V(V) by solvent extraction using mesityl oxide and reduction of V(V) using ascorbic acid. This method was applied for vanadium speciation in soil from two different regions of Poland: Upper Silesia (industrial region) and Podlasie (agricultural region). The content of vanadium in the fractions of Upper Silesia soil was respectively (in 10(-3)%): I, 3.39; III, 4.53; IV, 10.70; V, 8.70 and it was the highest in the organic fraction, indicating input by anthropogenic activities. The content of vanadium in Podlasie soil was clearly lower and it was (in 10(-3)%): I, 2.07; III, 0.92; IV, 0.69; V, 1.23. The concentration of vanadium in fraction 2 of both soils was less than detection limit of applied method. The total content of vanadium in the five soil fractions was in good correlation with the total content of this element in both soils found after HF-H(2)SO(4) digestion. Analysis using the ICP-AES method gave comparable results.

  6. On speciation of VOC localization

    NASA Astrophysics Data System (ADS)

    Chen, S.; Chang, J.; Wang, J.

    2011-12-01

    Most of the gas-phase chemical mechanisms successfully used in gas-phase atmospheric chemical processes, such as CBM-Z, RADM2 or SAPRC-07, treat hundreds of VOC as lumped organic species by their chemical characteristics. Most of the model results are compared with total VOC observations, and it is not appropriate to compare lumped VOC simulations to observations even if there are separate VOC observations like Photochemical Assessment Monitoring Stations (PAMS). While the PAMS Air Quality Model (PAMS-AQM) is developed, separate organic species observed by PAMS without a doubt can be directly compared with model simulations. From the past case study (Chen et al., 2010), it shows a major and very significant finding in that detailed emissions of VOC in the existing emissions database are often in error in Taiwan or other countries due to the fact that the annual VOC emissions are classified into hundreds of species-specific emissions by using the speciation factors following the protocol of the U.S. EPA (AP-42). Based on all PAMS observations from 2006-2007, four base cases with well comparable meteorological simulations were selected for the unified correction for all sources in Taiwan. After the PAMS species emissions are modified, the diurnal patterns and simulation-observation correlation for most of the PAMS species are improved, and the concentration levels are more comparable with those of observations. More expanded case studies also revealed necessary corrections for the PAMS species emissions. Sensitivity analyses for lumped organic species with modified PAMS species emissions are also conducted. After modified PAMS emissions are added into lumped VOC emissions, there is an increase of only 10% of totally VOC emissions. While the sources of the lumped VOC emissions are changed, ozone formation shows no significant change with modified lumped VOC emissions. This helps to support the argument that for ozone simulation, the lumped VOC processes balance out

  7. Microextraction techniques for the non-chromatographic speciation of ultratraces of elements in waters: some significant cases

    NASA Astrophysics Data System (ADS)

    Lopez-Garcia, Ignacio; Vicente-Martinez, Yesica; Hernandez-Cordoba, Manuel; Martínez-Sanchez, Maria Jose; Perez-Sirvent, Carmen

    2015-04-01

    The speciation of very low concentrations of some elements in waters is of interest due to the different behaviour and toxicity the species can have. This task can be carried out by using liquid chromatographic techniques (LC) for separation together with inductively coupled plasma mass spectrometry (ICP-MS) for detection. However, this combination is not easily available in all laboratories mainly due to the relative high cost of acquisition and maintenance of the ICP-MS spectrometer, and so other alternatives are of practical interest. Present knowledge of microextraction techniques involving minimal (or none) amounts of organic solvents allows, in some cases, speciation to be carried out without the need of such an expensive instrument, and even avoiding the use of a chromatographic stage. The selectivity of the separation (fractionation or speciation) can be achieved by modifying the experimental conditions used for microextraction, and a sensitive final measurement be obtained by means of electrothermal atomic absorption spectrometry (ETAAS). In this way, since an ETAAS instrument is common (and sometimes underused) in all laboratories, the speciation procedures are made available to most laboratories worldwide. The high preconcentration factor achieved by means of the microextraction stage together with the high sensitivity inherent in ETAAS measurements result in extremely sensitive methods that permit the speciation at ultratrace levels. The advantages of this methodology are presented by discussing speciation of chromium and arsenic as representative examples.

  8. Is ecological speciation a major trend in aphids? Insights from a molecular phylogeny of the conifer-feeding genus Cinara

    PubMed Central

    2013-01-01

    Introduction In the past decade ecological speciation has been recognized as having an important role in the diversification of plant-feeding insects. Aphids are host-specialised phytophagous insects that mate on their host plants and, as such, they are prone to experience reproductive isolation linked with host plant association that could ultimately lead to species formation. The generality of such a scenario remains to be tested through macroevolutionary studies. To explore the prevalence of host-driven speciation in the diversification of the aphid genus Cinara and to investigate alternative modes of speciation, we reconstructed a phylogeny of this genus based on mitochondrial, nuclear and Buchnera aphidicola DNA sequence fragments and applied a DNA-based method of species delimitation. Using a recent software (PhyloType), we explored evolutionary transitions in host-plant genera, feeding sites and geographic distributions in the diversification of Cinara and investigated how transitions in these characters have accompanied speciation events. Results The diversification of Cinara has been constrained by host fidelity to conifer genera sometimes followed by sequential colonization onto different host species and by feeding-site specialisation. Nevertheless, our analyses suggest that, at the most, only half of the speciation events were accompanied by ecological niche shifts. The contribution of geographical isolation in the speciation process is clearly apparent in the occurrence of species from two continents in the same clades in relatively terminal positions in our phylogeny. Furthermore, in agreement with predictions from scenarios in which geographic isolation accounts for speciation events, geographic overlap between species increased significantly with time elapsed since their separation. Conclusions The history of Cinara offers a different perspective on the mode of speciation of aphids than that provided by classic models such as the pea aphid. In this

  9. Speciation by Symbiosis: the Microbiome and Behavior

    PubMed Central

    Shropshire, J. Dylan

    2016-01-01

    ABSTRACT Species are fundamental units of comparison in biology. The newly discovered importance and ubiquity of host-associated microorganisms are now stimulating work on the roles that microbes can play in animal speciation. We previously synthesized the literature and advanced concepts of speciation by symbiosis with notable attention to hybrid sterility and lethality. Here, we review recent studies and relevant data on microbes as players in host behavior and behavioral isolation, emphasizing the patterns seen in these analyses and highlighting areas worthy of additional exploration. We conclude that the role of microbial symbionts in behavior and speciation is gaining exciting traction and that the holobiont and hologenome concepts afford an evolving intellectual framework to promote research and intellectual exchange between disciplines such as behavior, microbiology, genetics, symbiosis, and speciation. Given the increasing centrality of microbiology in macroscopic life, microbial symbiosis is arguably the most neglected aspect of animal and plant speciation, and studying it should yield a better understanding of the origin of species. PMID:27034284

  10. Speciation by Symbiosis: the Microbiome and Behavior.

    PubMed

    Shropshire, J Dylan; Bordenstein, Seth R

    2016-03-31

    Species are fundamental units of comparison in biology. The newly discovered importance and ubiquity of host-associated microorganisms are now stimulating work on the roles that microbes can play in animal speciation. We previously synthesized the literature and advanced concepts of speciation by symbiosis with notable attention to hybrid sterility and lethality. Here, we review recent studies and relevant data on microbes as players in host behavior and behavioral isolation, emphasizing the patterns seen in these analyses and highlighting areas worthy of additional exploration. We conclude that the role of microbial symbionts in behavior and speciation is gaining exciting traction and that the holobiont and hologenome concepts afford an evolving intellectual framework to promote research and intellectual exchange between disciplines such as behavior, microbiology, genetics, symbiosis, and speciation. Given the increasing centrality of microbiology in macroscopic life, microbial symbiosis is arguably the most neglected aspect of animal and plant speciation, and studying it should yield a better understanding of the origin of species.

  11. Speciation without Pre-Defined Fitness Functions.

    PubMed

    Gras, Robin; Golestani, Abbas; Hendry, Andrew P; Cristescu, Melania E

    2015-01-01

    The forces promoting and constraining speciation are often studied in theoretical models because the process is hard to observe, replicate, and manipulate in real organisms. Most models analyzed to date include pre-defined functions influencing fitness, leaving open the question of how speciation might proceed without these built-in determinants. To consider the process of speciation without pre-defined functions, we employ the individual-based ecosystem simulation platform EcoSim. The environment is initially uniform across space, and an evolving behavioural model then determines how prey consume resources and how predators consume prey. Simulations including natural selection (i.e., an evolving behavioural model that influences survival and reproduction) frequently led to strong and distinct phenotypic/genotypic clusters between which hybridization was low. This speciation was the result of divergence between spatially-localized clusters in the behavioural model, an emergent property of evolving ecological interactions. By contrast, simulations without natural selection (i.e., behavioural model turned off) but with spatial isolation (i.e., limited dispersal) produced weaker and overlapping clusters. Simulations without natural selection or spatial isolation (i.e., behaviour model turned off and high dispersal) did not generate clusters. These results confirm the role of natural selection in speciation by showing its importance even in the absence of pre-defined fitness functions.

  12. Hydroxyl speciation in felsic magmas

    NASA Astrophysics Data System (ADS)

    Malfait, Wim J.; Xue, Xianyu

    2014-09-01

    The hydroxyl speciation of hydrous, metaluminous potassium and calcium aluminosilicate glasses was investigated by 27Al-1H cross polarization and quantitative 1H MAS NMR spectroscopy. Al-OH is present in both the potassium and the calcium aluminosilicate glasses and its 1H NMR partial spectrum was derived from the 27Al-1H cross polarization data. For the calcium aluminosilicate glasses, the abundance of Al-OH could not be determined because of the low spectral resolution. For the potassium aluminosilicate glasses, the fraction of Al-OH was quantified by fitting its partial spectrum to the quantitative 1H NMR spectra. The degree of aluminum avoidance and the relative tendency for Si-O-Si, Si-O-Al and Al-O-Al bonds to hydrolyze were derived from the measured species abundances. Compared to the sodium, lithium and calcium systems, potassium aluminosilicate glasses display a much stronger degree of aluminum avoidance and a stronger tendency for the Al-O-Al linkages to hydrolyze. Combining our results with those for sodium aluminosilicate glasses (Malfait and Xue, 2010a), we predict that the hydroxyl groups in rhyolitic and phonolitic magmas are predominantly present as Si-OH (84-89% and 68-78%, respectively), but with a significant fraction of Al-OH (11-16% and 22-32%, respectively). For both rhyolitic and phonolitic melts, the AlOH/(AlOH + SiOH) ratio is likely smaller than the Al/(Al + Si) ratio for the lower end of the natural temperature range but may approach the Al/(Al + Si) ratio at higher temperatures.

  13. Integrated Computational and Experimental Protocol for Understanding Rh(III) Speciation in Hydrochloric and Nitric Acid Solutions

    SciTech Connect

    Samuels, Alex C.; Boele, Cherilynn A.; Bennett, Kevin T.; Clark, Sue B.; Wall, Nathalie; Clark, Aurora E.

    2014-12-01

    A combined experimental and theoretical approach has investigated the complex speciation of Rh(III) in hydrochloric and nitric acid media, as a function of acid concentration. This has relevance to the separation and isolation of Rh(III) from dissolved spent nuclear fuel, which is an emergent and attractive alternative source of platinum group metals, relative to traditional mining efforts.

  14. Trace metal speciation in natural waters: Computational vs. analytical

    USGS Publications Warehouse

    Kirk, Nordstrom D.

    1996-01-01

    Improvements in the field sampling, preservation, and determination of trace metals in natural waters have made many analyses more reliable and less affected by contamination. The speciation of trace metals, however, remains controversial. Chemical model speciation calculations do not necessarily agree with voltammetric, ion exchange, potentiometric, or other analytical speciation techniques. When metal-organic complexes are important, model calculations are not usually helpful and on-site analytical separations are essential. Many analytical speciation techniques have serious interferences and only work well for a limited subset of water types and compositions. A combined approach to the evaluation of speciation could greatly reduce these uncertainties. The approach proposed would be to (1) compare and contrast different analytical techniques with each other and with computed speciation, (2) compare computed trace metal speciation with reliable measurements of solubility, potentiometry, and mean activity coefficients, and (3) compare different model calculations with each other for the same set of water analyses, especially where supplementary data on speciation already exist. A comparison and critique of analytical with chemical model speciation for a range of water samples would delineate the useful range and limitations of these different approaches to speciation. Both model calculations and analytical determinations have useful and different constraints on the range of possible speciation such that they can provide much better insight into speciation when used together. Major discrepancies in the thermodynamic databases of speciation models can be evaluated with the aid of analytical speciation, and when the thermodynamic models are highly consistent and reliable, the sources of error in the analytical speciation can be evaluated. Major thermodynamic discrepancies also can be evaluated by simulating solubility and activity coefficient data and testing various

  15. Monte Carlo simulations of parapatric speciation

    NASA Astrophysics Data System (ADS)

    Schwämmle, V.; Sousa, A. O.; de Oliveira, S. M.

    2006-06-01

    Parapatric speciation is studied using an individual-based model with sexual reproduction. We combine the theory of mutation accumulation for biological ageing with an environmental selection pressure that varies according to the individuals geographical positions and phenotypic traits. Fluctuations and genetic diversity of large populations are crucial ingredients to model the features of evolutionary branching and are intrinsic properties of the model. Its implementation on a spatial lattice gives interesting insights into the population dynamics of speciation on a geographical landscape and the disruptive selection that leads to the divergence of phenotypes. Our results suggest that assortative mating is not an obligatory ingredient to obtain speciation in large populations at low gene flow.

  16. Considerations in As analysis and speciation

    USGS Publications Warehouse

    Edwards, M.; Patel, S.; McNeil, L.; Chen, H.W.; Frey, M.; Eaton, A.D.; Antweiler, R.C.; Taylor, H.E.

    1998-01-01

    This article summarizes recent experiences in arsenic (As) quantification, preservation, and speciation developed during AWWA Research Foundation (AWWARF) and Water Industry Technical Action Fund (WITAF) projects. The goal of this article is to alert analysts and decision-makers to potential problems in As analysis and speciation, because there appear to be several unresolved problems with routine analytical approaches. In true split drinking water samples As was quantified by three accepted analytical methods in three laboratories. The techniques used were graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma mass spectrometry (ICP-MS), and hydride generation inductively coupled plasma-emission spectrometry (HG-ICP-AES). Experimental findings are organized into sections on As analysis, particulate As in water supplies, and examination of As speciation methods.

  17. EPAs SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of source category-specific particulate matter (PM), volatile organic gas, and other gas speciation profiles of air pollutant emissions. Abt Associates, Inc. developed SPECIATE 4.4 through a collaborat...

  18. SPECIATE Version 4.4 Database Development Documentation

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Some of the many uses of these source profiles include: (1) creating speciated emissions inventories for regi...

  19. Arsenic speciation in manufactured seafood products.

    PubMed

    Vélez, D; Montoro, R

    1998-09-01

    The literature on the speciation of arsenic (As) in seafoods was critically reviewed. Most research has been directed toward fresh seafood products with few papers dealing with As speciation in manufactured seafoods. Predictions concerning As species made on the basis of fresh seafood products cannot be extrapolated to manufactured seafoods. Therefore, due to the numerous species of As, the scarcity of data concerning their presence in foods, the transformations each species may undergo during industrial processing and cooking, and the lack of legislation on permitted As levels in seafood products, As species in manufactured seafood products need to be determined and quantified.

  20. Instrumentation for Aerosol and Gas Speciation

    NASA Technical Reports Server (NTRS)

    Coggiola, Michael J.

    1998-01-01

    Using support from NASA Grant No. NAG 2-963, SRI International successfully completed the project, entitled, 'Instrumentation for Aerosol and Gas Speciation.' This effort (SRI Project 7383) covered the design, fabrication, testing, and deployment of a real-time aerosol speciation instrument in NASA's DC-8 aircraft during the Spring 1996 SUbsonic aircraft: Contrail and Cloud Effects Special Study (SUCCESS) mission. This final technical report describes the pertinent details of the instrument design, its abilities, its deployment during SUCCESS and the data acquired from the mission, and the post-mission calibration, data reduction, and analysis.

  1. Demographic history of speciation in a Senecio altitudinal hybrid zone on Mt. Etna.

    PubMed

    Filatov, Dmitry A; Osborne, Owen G; Papadopulos, Alexander S T

    2016-06-01

    Hybrid zones typically form as a result of species coming into secondary contact, but can also be established in situ as an ecotonal hybrid zone, a situation which has been reported far less frequently. An altitudinal hybrid zone on Mount Etna between two ragwort species (the low elevation Senecio chrysanthemifolius and high elevation S. aethnensis) could potentially represent either of these possibilities. However, a scenario of secondary contact vs. speciation with gene flow has not been explicitly tested. Here, we test these alternatives and demonstrate that the data do not support secondary contact. Furthermore, we report that the previous analyses of speciation history of these species were based on admixed populations, which has led to inflated estimates of ongoing, interspecific gene flow. Our new analyses, based on 'pure' S. aethnensis and S. chrysanthemifolius populations, reveal gene exchange of less than one effective migrant per generation, a level low enough to allow the species to accumulate neutral, genomewide differences. Overall, our results are consistent with a scenario of speciation with gene flow and a divergence time which coincides with the rise of Mt. Etna to altitudes above 2000 m (~150 KY). Further work to quantify the role of adaptation to contrasting environments of high and low altitudes will be needed to support the scenario of recent ecological speciation in this system.

  2. The Fast Alternative Cryogenic Experiment Testbed

    NASA Astrophysics Data System (ADS)

    Nash, Alfred

    One of the challenges in the area of cryogenics for space exploration in the next millennium is providing the capability for inexpensive, frequent, access to space. Faced with this challenge during the International Space Station (ISS) build era, when other Space Shuttle manifesting opportunities are unavailable, a "proof of concept" cryostat has been developed to demonstrate the ability to accommodate low temperature science investigations within the constraints of the Hitchhiker siderail carrier. The Hitchhiker siderail carrier is available on a "mass available" basis during the ISS build era. In fact, several hitchhiker payloads flew with the deployment of the Unity module. Hitchhiker siderail carrier payloads have historically flown an average of about four times a year. A hybrid Solid Neon - Superfluid Helium cryostat has been developed with Janis Research Company to accommodate instruments of 16.5 cm diameter and 30 cm length. This hybrid approach was taken in part to provide adequate on-orbit lifetime for instruments with high (conducted) heat loads from the instrumentation wiring. Mass, volume, lifetime and the launch hold scenario were all design drivers. In addition, with Ball Aerospace and Technologies Corporation, a multi-channel VME architecture Germanium Resistance Thermometer (GRT) readout and heater control servo system has been developed. In a flight system, the cryostat and electronics payloads would be umbilically attached in a paired Hitchhiker siderail mount, and permit on-orbit command and telemetry capability. The results of performance tests of both the cryostat, and a helium sample instrument will be presented. The instrument features a self contained, miniaturized, nano-Kelvin resolution High Resolution Thermometer (HRT). This high level of thermal resolution is achieved through the utilization of a dc Superconducting Quantum Interference Device (SQUID). Although developed for the Low Temperature Microgravity Fundamental Physics investigator community, many design features are applicable in fields such as infrared and x-ray astronomy. This work was carried out by the Jet Propulsion Laboratory, California Institute of Technology under contract to the National Aeronautics and Space Administration. The work was funded by NASA Microgravity Research Division.

  3. The Fast Alternative Cryogenic Experiment Testbed

    NASA Technical Reports Server (NTRS)

    Nash, Alfred; Holmes, Warren

    2000-01-01

    One of the challenges in the area of cryogenics for space exploration in the next millennium is providing the capability for inexpensive, frequent, access to space. Faced with this challenge during the International Space Station (ISS) build era, when other Space Shuttle manifesting opportunities are unavailable, a "proof of concept" cryostat has been developed to demonstrate the ability to accommodate low temperature science investigations within the constraints of the Hitchhiker siderail carrier. The Hitchhiker siderail carrier is available on a "mass available" basis during the ISS build era. In fact, several hitchhiker payloads flew with the deployment of the Unity module. Hitchhiker siderail carrier payloads have historically flown an average of about four times a year. A hybrid Solid Neon - Superfluid Helium cryostat has been developed with Janis Research Company to accommodate instruments of 16.5 cm diameter and 30 cm. length. This hybrid approach was taken in part to provide adequate on-orbit lifetime for instruments with high (conducted) heat loads from the instrumentation wiring. Mass, volume, lifetime and the launch hold scenario were all design drivers. In addition, with Ball Aerospace and Technologies Corporation, a multichannel VME architecture Germanium Resistance Thermometer (GRT) readout and heater control servo system has been developed. In a flight system, the cryostat and electronics payloads would be umbilically attached in a paired Hitchhiker siderail mount, and permit on-orbit command and telemetry capability. The results of performance tests of both the cryostat, and a helium sample instrument will be presented. The instrument features a self contained, miniaturized, nano-Kelvin resolution High Resolution Thermometer (HRT). This high level of thermal resolution is achieved through the utilization of a dc Superconducting Quantum Interference Device (SQUID). Although developed for the Low Temperature Microgravity Fundamental Physics investigator community, many design features are applicable in fields such as infrared and x-ray astronomy.

  4. Speciation of trace elements in human serum by micro anion exchange chromatography coupled with inductively coupled plasma mass spectrometry.

    PubMed

    Malavolta, Marco; Piacenza, Francesco; Basso, Andrea; Giacconi, Robertina; Costarelli, Laura; Pierpaoli, Sara; Mocchegiani, Eugenio

    2012-02-01

    Speciation analysis of essential trace elements in human serum provides important information on nutritional status and homeostatic mechanisms regulating transport processes, acute phase reactions, and protection against oxidative damage. Anion exchange high-performance liquid chromatography (HPLC) combined with inductively coupled plasma mass spectrometry (ICP-MS) has proved to be a useful tool in speciation. Here we describe a fast method that can be applied to carry out the speciation of Fe, Cu, Zn, and Se in as little as 1 microl [corrected] of serum. The method employs monolithic anion exchange micro columns installed on a tandem HPLC system coupled on-line with an ICP-MS detector. The chromatographic separation is similar to those reported previously but with considerable gain in terms of time and sample requirement. Reproducibility is acceptable for most species. Using our method, we were able to find species-specific differences between different commercially available trace element reference materials. Because the method chosen to collect blood might interfere with speciation, the proposed methodology was used to compare heparinized plasma, ethylenediaminetetraacetic acid (EDTA) plasma, and serum from adult healthy volunteers. As expected, EDTA strongly affects speciation analysis (especially for Fe and Zn), whereas changes due to the use of lithium-heparin (Li-He) as anticoagulant appear to be minimized.

  5. Fast Reactors

    NASA Astrophysics Data System (ADS)

    Esposito, S.; Pisanti, O.

    The following sections are included: * Elementary Considerations * The Integral Equation to the Neutron Distribution * The Critical Size for a Fast Reactor * Supercritical Reactors * Problems and Exercises

  6. Biosensor for metal analysis and speciation

    DOEpatents

    Aiken, Abigail M.; Peyton, Brent M.; Apel, William A.; Petersen, James N.

    2007-01-30

    A biosensor for metal analysis and speciation is disclosed. The biosensor comprises an electron carrier immobilized to a surface of an electrode and a layer of an immobilized enzyme adjacent to the electrode. The immobilized enzyme comprises an enzyme having biological activity inhibited by a metal to be detected by the biosensor.

  7. EFFECT OF SCR CATALYST ON MERCURY SPECIATION

    EPA Science Inventory

    A pilot-scale research study was conducted to investigate the effect of selective catalytic reduction (SCR) on elemental mercury speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois bituminous coals and one Powder River Basin (PRB) coal...

  8. ARSENIC SPECIATION ANALYSIS IN HUMAN SALIVA

    EPA Science Inventory

    Background: Determination of arsenic species in human saliva is potentially useful for biomonitoring of human exposure to arsenic and for studying arsenic metabolism. However, there is no report on the speciation analysis of arsenic in saliva. Methods: Arsenic species in saliva ...

  9. Speciation through the learning of habitat features.

    PubMed

    Beltman, J B; Haccou, P

    2005-05-01

    Learning of environmental features can influence both mating behaviour and the location where young are produced. This may lead to speciation in three steps: (i) colonization of a new habitat, (ii) genetic divergence of the two groups by adaptation to the habitats, and (iii) a decrease of genetic mixing between the lineages (similar to reinforcement). In a previous paper we showed that steps (i) and (ii) occur readily for a wide range of fixed mating and habitat preferences. Here, we study whether this can ultimately lead to speciation through selective changes in these preferences. We show that this indeed occurs, and, furthermore, it is very general: for a large class of models there is selection toward producing young more frequently in the natal habitat. Once habitat preference is strong, there is selection toward stronger assortative mating. Even when steps (i) and (ii) initially fail, genetic divergence may succeed at a later evolutionary stage, after which a decrease of genetic mixing completes speciation. Our results show that speciation by the learning of habitat features is an extremely effective mechanism.

  10. Diploid hybrid speciation in Penstemon (Scrophulariaceae)

    PubMed Central

    Wolfe, Andrea D.; Xiang, Qiu-Yun; Kephart, Susan R.

    1998-01-01

    Hybrid speciation has played a significant role in the evolution of angiosperms at the polyploid level. However, relatively little is known about the importance of hybrid speciation at the diploid level. Two species of Penstemon have been proposed as diploid hybrid derivatives based on morphological data, artificial crossing studies, and pollinator behavior observations: Penstemon spectabilis (derived from hybridization between Penstemon centranthifolius and Penstemon grinnellii) and Penstemon clevelandii (derived from hybridization between P. centranthifolius and P. spectabilis). Previous studies were inconclusive regarding the purported hybrid nature of these species because of a lack of molecular markers sufficient to differentiate the parental taxa in the hybrid complex. We developed hypervariable nuclear markers using inter-simple sequence repeat banding patterns to test these classic hypotheses of diploid hybrid speciation in Penstemon. Each species in the hybrid complex was genetically distinct, separated by 10–42 species-specific inter-simple sequence repeat markers. Our data do not support the hybrid origin of P. spectabilis but clearly support the diploid hybrid origin of P. clevelandii. Our results further suggest that the primary reason diploid hybrid speciation is so difficult to detect is the lack of molecular markers able to differentiate parental taxa from one another, particularly with recently diverged species. PMID:9560237

  11. Actinide speciation in relation to biological processes.

    PubMed

    Ansoborlo, Eric; Prat, Odette; Moisy, Philippe; Den Auwer, Christophe; Guilbaud, Philippe; Carriere, M; Gouget, Barbara; Duffield, John; Doizi, Denis; Vercouter, Thomas; Moulin, Christophe; Moulin, Valérie

    2006-11-01

    In case of accidental release of radionuclides into the environment, actinides represent a severe health risk to human beings following internal contamination (inhalation, ingestion or wound). For a better understanding of the actinide behaviour in man (in term of metabolism, retention, excretion) and in specific biological systems (organs, cells or biochemical pathways), it is of prime importance to have a good knowledge of the relevant actinide solution chemistry and biochemistry, in particular of the thermodynamic constants needed for computing actinide speciation. To a large extent, speciation governs bioavailability and toxicity of elements and has a significant impact on the mechanisms by which toxics accumulate in cell compartments and organs and by which elements are transferred and transported from cell to cell. From another viewpoint, speciation is the prerequisite for the design and success of potential decorporation therapies. The purpose of this review is to present the state of the art of actinide knowledge within biological media. It is also to discuss how actinide speciation can be determined or predicted and to highlight the areas where information is lacking with the aim to encourage new research efforts.

  12. Sympatric speciation by allochrony in a seabird

    PubMed Central

    Friesen, V. L.; Smith, A. L.; Gómez-Díaz, E.; Bolton, M.; Furness, R. W.; González-Solís, J.; Monteiro, L. R.

    2007-01-01

    The importance of sympatric speciation (the evolution of reproductive isolation between codistributed populations) in generating biodiversity is highly controversial. Whereas potential examples of sympatric speciation exist for plants, insects, and fishes, most theoretical models suggest that it requires conditions that are probably not common in nature, and only two possible cases have been described for tetrapods. One mechanism by which it could occur is through allochronic isolation—separation of populations by breeding time. Oceanodroma castro (the Madeiran or band-rumped storm-petrel) is a small seabird that nests on tropical and subtropical islands throughout the Atlantic and Pacific Oceans. In at least five archipelagos, different individuals breed on the same islands in different seasons. We compared variation in five microsatellite loci and the mitochondrial control region among 562 O. castro from throughout the species' range. We found that sympatric seasonal populations differ genetically within all five archipelagos and have ceased to exchange genes in two. Population and gene trees all indicate that seasonal populations within four of the archipelagos are more closely related to each other than to populations from the same season from other archipelagos; divergence of the fifth sympatric pair is too ancient for reliable inference. Thus, seasonal populations appear to have arisen sympatrically at least four times. This is the first evidence for sympatric speciation by allochrony in a tetrapod, and adds to growing indications that population differentiation and speciation can occur without geographic barriers to gene flow. PMID:18006662

  13. Pervaporation: a useful tool for speciation analysis

    NASA Astrophysics Data System (ADS)

    Luque de Castro, M. D.; Papaefstathiou, I.

    1998-02-01

    The application of pervaporation as both an auxiliary and a fundamental device for speciation analysis in liquid and solid samples is discussed. Examples of various determinations, including the coupling of the technique to both a gas chromatograph and flow-injection configurations, applied mostly to environmental and biological samples, are presented, giving clear evidence of the double role of the pervaporation process.

  14. ELEMENTAL SPECIATION IN ENVIRONMENTAL EXPOSURE ASSESSMENT MATRICES

    EPA Science Inventory

    Arsenic and tin are two trace metals where exposure assessments have moved towards a speciation based approach because the toxicity is very chemical form dependent. This toxicity difference can be one of many factors which influence the formulation of certain regulations. For a...

  15. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids.

    PubMed

    Kautt, Andreas F; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-06-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  16. Multispecies Outcomes of Sympatric Speciation after Admixture with the Source Population in Two Radiations of Nicaraguan Crater Lake Cichlids

    PubMed Central

    Kautt, Andreas F.; Machado-Schiaffino, Gonzalo; Meyer, Axel

    2016-01-01

    The formation of species in the absence of geographic barriers (i.e. sympatric speciation) remains one of the most controversial topics in evolutionary biology. While theoretical models have shown that this most extreme case of primary divergence-with-gene-flow is possible, only a handful of accepted empirical examples exist. And even for the most convincing examples uncertainties remain; complex histories of isolation and secondary contact can make species falsely appear to have originated by sympatric speciation. This alternative scenario is notoriously difficult to rule out. Midas cichlids inhabiting small and remote crater lakes in Nicaragua are traditionally considered to be one of the best examples of sympatric speciation and lend themselves to test the different evolutionary scenarios that could lead to apparent sympatric speciation since the system is relatively small and the source populations known. Here we reconstruct the evolutionary history of two small-scale radiations of Midas cichlids inhabiting crater lakes Apoyo and Xiloá through a comprehensive genomic data set. We find no signs of differential admixture of any of the sympatric species in the respective radiations. Together with coalescent simulations of different demographic models our results support a scenario of speciation that was initiated in sympatry and does not result from secondary contact of already partly diverged populations. Furthermore, several species seem to have diverged simultaneously, making Midas cichlids an empirical example of multispecies outcomes of sympatric speciation. Importantly, however, the demographic models strongly support an admixture event from the source population into both crater lakes shortly before the onset of the radiations within the lakes. This opens the possibility that the formation of reproductive barriers involved in sympatric speciation was facilitated by genetic variants that evolved in a period of isolation between the initial founding

  17. Sample treatment in chromatography-based speciation of organometallic pollutants.

    PubMed

    Gómez-Riza, J L; Morales, E; Giráldez, I; Sánchez-Rodas, D; Velasco, A

    2001-12-14

    Speciation analysis is nowadays performed routinely in many laboratories to control the quality of the environment, food and health. Chemical speciation analyses generally include the study of different oxidation state of elements or individual organometallic compounds. The determination of the different chemical forms of elements is still an analytical challenge, since they are often unstable and concentrations in different matrices of interest are in the microg l(-1) or even in the ng l(-1) range (e.g., estuarine waters) or ng g(-1) in sediments and biological tissues. For this reason, sensitive and selective analytical atomic techniques are being used as available detectors for speciation, generally coupled with chromatography for the time-resolved introduction of analytes into the atomic spectrometer. The complexity of these instrumental couplings has a straightforward consequence on the duration of the analysis, but sample preparation to separate and transfer the chemical species present in the sample into a solution to be accepted readily by a chromatographic column is the more critical step of total analysis, and demands considerable operator skills and time cost. Traditionally, liquid-liquid extraction has been employed for sample treatment with serious disadvantages, such as consumption, disposal and long-term exposure to organic solvent. In addition, they are usually cumbersome and time-consuming. Therefore, the introduction of new reagents such as sodium tetraethylborate for the simultaneous derivatization of several elements has been proposed. Other possibilities are based in the implementation of techniques for efficient and accelerated isolation of species from the sample matrix. This is the case for microwave-assisted extraction, solid-phase extraction and microextraction, supercritical fluid extraction or pressurized liquid extraction, which offer new possibilities in species treatment, and the advantages of a drastic reduction of the extraction

  18. Alternative security

    SciTech Connect

    Weston, B.H. )

    1990-01-01

    This book contains the following chapters: The Military and Alternative Security: New Missions for Stable Conventional Security; Technology and Alternative Security: A Cherished Myth Expires; Law and Alternative Security: Toward a Just World Peace; Politics and Alternative Security: Toward a More Democratic, Therefore More Peaceful, World; Economics and Alternative Security: Toward a Peacekeeping International Economy; Psychology and Alternative Security: Needs, Perceptions, and Misperceptions; Religion and Alternative Security: A Prophetic Vision; and Toward Post-Nuclear Global Security: An Overview.

  19. Adding to the Mercury Speciation Toolbox

    NASA Astrophysics Data System (ADS)

    Fitts, J. P.; Northrup, P. A.; Chidambaram, D.; Kalb, P. D.

    2007-12-01

    Mercury was used to separate lithium-6 isotope for weapons production at the Y-12 Plant in Oak Ridge, TN in the 1950s and 1960s. A large portion of the waste Hg entered the environment and continues to move throughout the sub-surface and surface waters in the area. Environmental management of Hg contamination within this complex hydrologic system, where Hg speciation and the mobile fraction have been found to vary widely, will require ongoing characterization and predictive modeling of Hg speciation. State-of-the-art spectroscopic tools that can directly probe Hg speciation in preserved aqueous and sediment samples with greater sensitivity, however, are required to determine rates and mechanisms of biogeochemical reactions. We will present the first results demonstrating the use of x-ray absorption spectroscopy (XAS) at the Hg M5 edge (2295 eV) to fingerprint Hg species. Heavy-metal M5 absorption edges can have very sharp features due to local electron transitions, and therefore, we are developing this edge as a tool for quantitative measurement of Hg species. In addition, sulfur speciation using the sulfur K absorption edge, which is at a similar energy (2472 eV), can be measured in the same scan as the Hg M5 edge. Potentially important organic and inorganic sulfur species (sulfide, disulfide, elemental sulfur, sulfite and sulfate) are readily differentiated, and thereby, provides an independent method for monitoring the redox state of the system along with changes in S-Hg bonding. We will also present x-ray microprobe 2-D concentration maps of Hg and other elements at the grain and pore scales to identify its microscopic distribution and chemical associations. When used in combination with established sequential extraction and direct spectroscopic methods, the addition of XAS at the Hg M5 edge should provide a significant advancement in the determination of Hg speciation in complex biogeochemical environments.

  20. Arsenic Speciation in Geothermal Waters

    NASA Astrophysics Data System (ADS)

    Keller, N. S.; Stefansson, A.; Sigfusson, B.

    2011-12-01

    Various arsenic species have been observed or inferred in geothermal waters in recent years, in particular thio- and oxyanions. However their exact stoechiometry and their oxidation state has been subjected to a sustained debate over the last decade. Most of the As species seen in geothermal waters are unstable under laboratory conditions, thus it is crucial that appropriate sampling and analytical techniques are used in order to minimise post-sampling changes. The goals of this study were to determine how many As species can be seen in geothermal systems and how geochemical parameters control the number and relative abundance of the species. Furthermore, we tested the stability of the As-S compounds after sampling, in particular whether the traditionally used flash-freezing method quantitatively preserves the species. Samples were collected from wells at the Hellisheidi Power Plant and from natural hot springs in the Geysir Geothermal Area in SW Iceland. The samples were analysed on-site immediately after sampling by first separating the various As species by Ion Chromatography followed by quantification by Hydride-Generation Atomic Fluorescence Spectrometer (HG-AFS). Preliminary results show that analysis of the samples immediately after sampling is crucial, as sample storage and flash-freezing/thawing appear to modify the As speciation. Using the retention times of the analytes through the chromatographic column, a minimum of seven As species were observed. Two of the species are oxides of AsIII and AsV, based on the comparison of their retention times with standards. The other five species have yet to be unequivocally identified, but based on prior studies it is assumed that at least some of them are thioarsenic species with various S:O ratios, with longer retention times for increasing S:O. Clear differences can be seen between samples from Hellisheidi and Geysir. In the case of the oxyanions, only AsIII is present at Hellisheidi whereas both oxidation states

  1. Multiply associating electrolytes in the binding mean spherical approximation: Thermodynamic properties and speciation

    NASA Astrophysics Data System (ADS)

    Bernard, O.; Torres-Arenas, J.; Simonin, J.-P.

    2014-01-01

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  2. Multiply associating electrolytes in the binding mean spherical approximation: thermodynamic properties and speciation.

    PubMed

    Bernard, O; Torres-Arenas, J; Simonin, J-P

    2014-01-21

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  3. Multiply associating electrolytes in the binding mean spherical approximation: Thermodynamic properties and speciation

    SciTech Connect

    Bernard, O. Simonin, J.-P.; Torres-Arenas, J.

    2014-01-21

    Ionic solutions exhibiting multiple association are described within the binding mean spherical approximation (BiMSA). This model is based on the Wertheim formalism, in the framework of the primitive model at the McMillan-Mayer level. The cation and the anion form the various complexes according to stepwise complexation-equilibria. Analytic expressions for the Helmholtz energy, the internal energy, the speciation, and for the osmotic and activity coefficients are given considering a binary solution with an arbitrary number of association sites on one type of ion (polyion) and one site on the ions of opposite sign (counterions). As an alternative, mean field expressions, as developed in SAFT-type theories, are also presented. The result obtained from the latter approximate method exhibits a reasonable agreement with those from BiMSA for the speciation, and a remarkable one for the osmotic coefficient.

  4. Comparison of gas chromatographic hyphenated techniques for mercury speciation analysis.

    PubMed

    Nevado, J J Berzas; Martín-Doimeadios, R C Rodríguez; Krupp, E M; Bernardo, F J Guzmán; Fariñas, N Rodríguez; Moreno, M Jiménez; Wallace, D; Ropero, M J Patiño

    2011-07-15

    In this study, we evaluate advantages and disadvantages of three hyphenated techniques for mercury speciation analysis in different sample matrices using gas chromatography (GC) with mass spectrometry (GC-MS), inductively coupled plasma mass spectrometry (GC-ICP-MS) and pyrolysis atomic fluorescence (GC-pyro-AFS) detection. Aqueous ethylation with NaBEt(4) was required in all cases. All systems were validated with respect to precision, with repeatability and reproducibility <5% RSD, confirmed by the Snedecor F-test. All methods proved to be robust according to a Plackett-Burnham design for 7 factors and 15 experiments, and calculations were carried out using the procedures described by Youden and Steiner. In order to evaluate accuracy, certified reference materials (DORM-2 and DOLT-3) were analyzed after closed-vessel microwave extraction with tetramethylammonium hydroxide (TMAH). No statistically significant differences were found to the certified values (p=0.05). The suitability for water samples analysis with different organic matter and chloride contents was evaluated by recovery experiments in synthetic spiked waters. Absolute detection and quantification limits were in the range of 2-6 pg for GC-pyro-AFS, 1-4 pg for GC-MS, with 0.05-0.21 pg for GC-ICP-MS showing the best limits of detection for the three systems employed. However, all systems are sufficiently sensitive for mercury speciation in environmental samples, with GC-MS and GC-ICP-MS offering isotope analysis capabilities for the use of species-specific isotope dilution analysis, and GC-pyro-AFS being the most cost effective alternative.

  5. Phosphorous Speciation in WTR-treated Biosolids Using XANES

    NASA Astrophysics Data System (ADS)

    Zhang, T. Q.; Huff, D.; Lin, Z.-Q.

    2009-04-01

    The concept of co-application of biosolids and drinking water treatment residues (DWTRs) represents an environmentally sustainable and economically sound strategy for the management of municipal solid wastes. This study demonstrated the effectiveness of reducing water-soluble P in biosolids-amended agricultural soil by the addition of DWTRs. Results showed that total P in soil leachate was significantly reduced during the initial 42-days of a 200-day greenhouse study when biosolids (50 g kg-1) were applied along with DWTRs (40 g kg-1). Particulate P was the dominant fraction of P in the soil leachate, which decreases with increasing DWTR application rate. The application of DWTRs does not significantly decrease the growth and yield of wheat (Triticum aestivum L.). The primary P chemical composition in biosolids include cupper phytate [Cu(IP6)6], barium phytate [Ba6IP6], and cupper phosphate [Cu3(PO4)2]. The addition of DWTRs to biosolids alternated the P speciation, and the P speciation change became significant with increasing the incubation time of the mixture of biosolids and DWTRs. The chemical component of Cu3(PO4)2 became non significant (<5%) with the addition of DWTRs. During the 14-day incubation time period, the proportion of P that was adsorbed on amorphous Fe(OH)3 increased substantially from 8 to 46% and Ba6IP6 increased steadily from 30 to 50%, while the proportion of Cu(IP6)6 decreased significantly from 53 to 5%. The amorphous Fe(OH)3-adsorbed P and Ba6IP6 formed the dominant P chemical components in the mixture of biosolids and DWTRs.

  6. Fast CRCs

    DTIC Science & Technology

    2009-10-01

    Detecting Codes: General Theory and Their Application in Feedback Communication Systems. Kluwer Academic, 1995. [8] D.E. Knuth , The Art of Computer ... computation . Index Terms—Fast CRC, low-complexity CRC, checksum, error-detection code, Hamming code, period of polynomial, fast software implementation...simulations, and performance analysis of systems and networks. CRC implementation in software is desirable, because many computers do not have hardware

  7. Speciation Effect in the Penna Aging Model

    NASA Astrophysics Data System (ADS)

    Łaszkiewicz, A.; Szymczak, Sz.; Cebrat, S.

    We have simulated the evolution of diploid, sexually reproducing populations using the Penna model of aging. We have noted that diminishing the recombination frequency during the gamete production generates a specific diversity of genomes in the populations. When two populations independently evolving for some time were mixed in one environmental niche of the limited size and crossbreeding between them was allowed, the average lifespan of hybrids was significantly shorter than the lifespan of the individuals of parental lines. Another effect of higher hybrid mortality is the faster elimination of one parental line from the shared environment. The two populations living in one environment co-exist much longer if they are genetically separated — they compete as two species instead of crossbreeding. This effect can be considered as the first step to speciation — any barrier eliminating crossbreeding between these populations, leading to speciation, would favor the populations.

  8. Speciation in aqueous solutions of nitric acid.

    PubMed

    Hlushak, S; Simonin, J P; De Sio, S; Bernard, O; Ruas, A; Pochon, P; Jan, S; Moisy, P

    2013-02-28

    In this study, speciation in aqueous solutions of nitric acid at 25 °C was assessed in two independent ways. First, Raman experiments were carried out and interpreted in terms of free nitrate ions, ion pairs and neutral HNO(3) molecules. In parallel, a model was developed to account for the formation of these two kinds of pairs. It was based on an extension of the binding mean spherical approximation (BiMSA), or associative MSA (AMSA), in which the size and the charge of the ions in the chemical pair may differ from those of the free ions. A simultaneous fit of the osmotic coefficient and of the proportion of free ions (obtained from Raman spectroscopy experiments) led to an estimation of the speciation in nitric acid solutions. The result obtained using this procedure was compared with the estimation obtained from the Raman experiments.

  9. Does speciation matter for tungsten ecotoxicology?

    PubMed

    Strigul, Nikolay

    2010-09-01

    Tungsten is a widely used transition metal that has not been thoroughly investigated with regards to its ecotoxicological effects. Tungsten anions polymerize in environmental systems as well as under physiological conditions in living organisms. These polymerization/condensation reactions result in the development of several types of stable polyoxoanions. Certain chemical properties (in particular redox and acidic properties) differentiate these polyanions from monotungstates. However, our current state of knowledge on tungsten toxicology, biological and environmental effects is based entirely on experiments where monotungstates were used and assumed by the authors to be the form of tungsten that was present and that produced the observed effect. Recent discoveries indicate that tungsten speciation may be important to ecotoxicology. New results obtained by different research groups demonstrate that polytungstates develop and persist in environmental systems, and that polyoxotungstates are much more toxic than monotungstates. This paper reviews the available toxicological information from the standpoint of tungsten speciation and identifies knowledge gaps and pertinent future research directions.

  10. First passage time to allopatric speciation

    PubMed Central

    Yamaguchi, Ryo; Iwasa, Yoh

    2013-01-01

    Allopatric speciation is a mechanism to evolve reproductive isolation; it is caused by the accumulation of genetic differences between populations while they are geographically isolated. Here, we studied a simple stochastic model for the time until speciation caused by geographical isolation in fragmented populations that experience recurrent but infrequent migration between subpopulations. We assumed that mating incompatibility is controlled by a number of loci that behave as neutral characters in the accumulation of novel mutations within each population. Genetic distance between populations was defined as the number of incompatibility-controlling loci that differ between them. Genetic distance increases through the separate accumulation of mutations in different populations, but decreases after a successful migration event followed by genetic mixing between migrants and residents. We calculated the time to allopatric speciation, which occurs when the genetic distance exceeds a specified threshold. If the number of invasive individuals relative to the resident population is not very large, diffusion approximation provides an accurate prediction. There is an intermediate optimal rate of migration that maximizes the rate of species creation by recurrent invasion and diversification. We also examined cases that involved more than two populations. PMID:24516714

  11. Arsenic speciation and sorption in natural environments

    USGS Publications Warehouse

    Campbell, Kate M.; Nordstrom, D. Kirk

    2014-01-01

    Aqueous arsenic speciation, or the chemical forms in which arsenic exists in water, is a challenging, interesting, and complicated aspect of environmental arsenic geochemistry. Arsenic has the ability to form a wide range of chemical bonds with carbon, oxygen, hydrogen, and sulfur, resulting in a large variety of compounds that exhibit a host of chemical and biochemical properties. Besides the intriguing chemical diversity, arsenic also has the rare capacity to capture our imaginations in a way that few elements can duplicate: it invokes images of foul play that range from sinister to comedic (e.g., “inheritance powder” and arsenic-spiked elderberry wine). However, the emergence of serious large-scale human health problems from chronic arsenic exposure in drinking water has placed a high priority on understanding environmental arsenic mobility, toxicity, and bioavailability, and chemical speciation is key to these important questions. Ultimately, the purpose of arsenic speciation research is to predict future occurrences, mitigate contamination, and provide successful management of water resources.

  12. Speciation of challenging elements in food by atomic spectrometry.

    PubMed

    Ruzik, Lena

    2012-05-15

    The review addresses trends in speciation analysis of challenging - rather rarely examined despite their importance for human health - elements in foodstuffs with special attention prior to sample preparation. Elements of interest are cobalt, iodine, manganese, iron, zinc, copper and molybdenum belong to the group of elements still appealed for searching their speciation despite extremely small contents in foodstuffs. Advantages and weaknesses of recommended procedures are overviewed and discussed, highlighting state-of-the-art speciation methodologies developed so far in the field.

  13. Evaluation of Regenerated Catalyst for Mercury Speciation

    SciTech Connect

    Dennis Laudal

    2007-06-01

    In March of 2005, U.S. Environmental Protection Agency (EPA) promulgated the Clean Air Mercury Rule (CAMR). Mercury from coal-fired power plants was to be reduced from the current 48 to 38 tons/yr by 2010 and then 15 tons/yr by 2018. It is expected that the first phase reduction of {approx}21% will be achieved by cobenefits that will occur as a result of installing additional selective catalytic reduction (SCR) and flue gas desulfurization (FGD) systems to meet the new Clean Air Interstate Rule (CAIR). Detroit Edison (DTE) is installing SCR at all four units at its Monroe Station and will eventually install wet-FGD systems. As such, the Electric Power Research Institute (EPRI), the U.S. Department of Energy (DOE), and DTE have contracted with the Energy & Environmental Research Center (EERC) to determine the extent of mercury oxidation that occurs at Monroe Station. The EERC originally did mercury speciation sampling at Monroe Station in 2004 and then went back in 2005 to determine if any changes occurred as a result of catalyst aging. During the second test, in addition to measuring the mercury speciation at the inlet and outlet of the SCR, the EERC also completed sampling at a location between the catalyst layers. The results are shown in Table 1. In Table 1, the results show that {approx}40% of the Hg was in oxidized form (Hg{sup 2+}) at the inlet and nearly 100% Hg{sup 2+} at the outlet. The results at the midpoint were between 40% and 100%. As part of their overall strategy to reduce SCR costs, utilities and SCR vendors are attempting to regenerate catalyst layers that have degenerated over time. If these regenerated catalysts are used, the question remains as to the effect this process will have on the ability of these catalysts to oxidize mercury as well as reduce NO{sub x}. The current project is designed to measure the Hg speciation across an SCR using a regenerated catalyst. The results were compared to previous results to determine what, if any, changes

  14. Fast valve

    DOEpatents

    Van Dyke, W.J.

    1992-04-07

    A fast valve is disclosed that can close on the order of 7 milliseconds. It is closed by the force of a compressed air spring with the moving parts of the valve designed to be of very light weight and the valve gate being of wedge shaped with O-ring sealed faces to provide sealing contact without metal to metal contact. The combination of the O-ring seal and an air cushion create a soft final movement of the valve closure to prevent the fast air acting valve from having a harsh closing. 4 figs.

  15. Fast valve

    DOEpatents

    Van Dyke, William J.

    1992-01-01

    A fast valve is disclosed that can close on the order of 7 milliseconds. It is closed by the force of a compressed air spring with the moving parts of the valve designed to be of very light weight and the valve gate being of wedge shaped with O-ring sealed faces to provide sealing contact without metal to metal contact. The combination of the O-ring seal and an air cushion create a soft final movement of the valve closure to prevent the fast air acting valve from having a harsh closing.

  16. Application of Hyphenated Techniques in Speciation Analysis of Arsenic, Antimony, and Thallium

    PubMed Central

    Michalski, Rajmund; Szopa, Sebastian; Jabłońska, Magdalena; Łyko, Aleksandra

    2012-01-01

    Due to the fact that metals and metalloids have a strong impact on the environment, the methods of their determination and speciation have received special attention in recent years. Arsenic, antimony, and thallium are important examples of such toxic elements. Their speciation is especially important in the environmental and biomedical fields because of their toxicity, bioavailability, and reactivity. Recently, speciation analytics has been playing a unique role in the studies of biogeochemical cycles of chemical compounds, determination of toxicity and ecotoxicity of selected elements, quality control of food products, control of medicines and pharmaceutical products, technological process control, research on the impact of technological installation on the environment, examination of occupational exposure, and clinical analysis. Conventional methods are usually labor intensive, time consuming, and susceptible to interferences. The hyphenated techniques, in which separation method is coupled with multidimensional detectors, have become useful alternatives. The main advantages of those techniques consist in extremely low detection and quantification limits, insignificant interference, influence as well as high precision and repeatability of the determinations. In view of their importance, the present work overviews and discusses different hyphenated techniques used for arsenic, antimony, and thallium species analysis, in different clinical, environmental and food matrices. PMID:22654649

  17. Alternative Fuels

    EPA Pesticide Factsheets

    Alternative fuels include gaseous fuels such as hydrogen, natural gas, and propane; alcohols such as ethanol, methanol, and butanol; vegetable and waste-derived oils; and electricity. Overview of alternative fuels is here.

  18. Alternative Therapies

    MedlinePlus

    ... Late Effects of Poliomyelitis for Physicians and Survivors © Alternative Therapies Alternative therapies, also called complementary, can support ... of motion, pain, and fatigue are often reported. Energy work includes acupuncture and acupressure, traditional Chinese medicine ...

  19. Project FAST.

    ERIC Educational Resources Information Center

    Essexville-Hampton Public Schools, MI.

    Described are components of Project FAST (Functional Analysis Systems Training) a nationally validated project to provide more effective educational and support services to learning disordered children and their regular elementary classroom teachers. The program is seen to be based on a series of modules of delivery systems ranging from mainstream…

  20. Development of a new column switching method for simultaneous speciation of selenometabolites and selenoproteins in human serum.

    PubMed

    García-Sevillano, M A; García-Barrera, T; Gómez-Ariza, J L

    2013-11-29

    A method for the simultaneous speciation of selenoproteins and selenometabolites in human serum has been developed on the basis of in series three dimensional chromatography: size exclusion, affinity and anion exchange high performance liquid chromatography (3D/SE-AF-AEC-HPLC), using different columns of each type and hyphenation to inductively coupled plasma-(quadrupole) mass spectrometry (ICP-qMS). The method allows the quantitative simultaneous analysis of selenoprotein P (SeP), extracellular glutathione peroxidase (eGPx), selenoalbumin (SeAlb), selenite and selenate in human serum using species-unspecific isotope dilution (SUID). The 3D chromatographic separation is proposed to remove typical spectral interferences in this matrix from chloride and bromide on (77)Se ((40)Ar(37)Cl), (80)Se ((79)Br(1)H) and (82)Se ((81)Br(1)H). In addition, a previous method based on 2D/SE-AF-HPLC is proposed as a simple alternative when low molecular mass selenium species are absent in the samples. The method is robust, reliable and fast with typical chromatographic runtime less than 35min. Detection limits are in the range of 0.2-1.3ng of Seg(-1). Method accuracy for determination of total protein-bound to Se was assessed by analyzing an human serum reference material (BCR-637) certified for total Se content and method reliability checked in samples of human serum providing results in good agreement with the total selenium concentration. In addition, the application of the method to commercial human serum and plasma reference materials for quality control analysis, certified for total Se, has provided, for the first time, indicative levels of selenium containing proteins in these samples.

  1. Complementary arsenic speciation methods: A review

    NASA Astrophysics Data System (ADS)

    Nearing, Michelle M.; Koch, Iris; Reimer, Kenneth J.

    2014-09-01

    The toxicity of arsenic greatly depends on its chemical form and oxidation state (speciation) and therefore accurate determination of arsenic speciation is a crucial step in understanding its chemistry and potential risk. High performance liquid chromatography with inductively coupled mass spectrometry (HPLC-ICP-MS) is the most common analysis used for arsenic speciation but it has two major limitations: it relies on an extraction step (usually from a solid sample) that can be incomplete or alter the arsenic compounds; and it provides no structural information, relying on matching sample peaks to standard peaks. The use of additional analytical methods in a complementary manner introduces the ability to address these disadvantages. The use of X-ray absorption spectroscopy (XAS) with HPLC-ICP-MS can be used to identify compounds not extracted for HPLC-ICP-MS and provide minimal processing steps for solid state analysis that may help preserve labile compounds such as those containing arsenicsbnd sulfur bonds, which can degrade under chromatographic conditions. On the other hand, HPLC-ICP-MS is essential in confirming organoarsenic compounds with similar white line energies seen by using XAS, and identifying trace arsenic compounds that are too low to be detected by XAS. The complementary use of electrospray mass spectrometry (ESI-MS) with HPLC-ICP-MS provides confirmation of arsenic compounds identified during the HPLC-ICP-MS analysis, identification of unknown compounds observed during the HPLC-ICP-MS analysis and further resolves HPLC-ICP-MS by identifying co-eluting compounds. In the complementary use of HPLC-ICP-MS and ESI-MS, HPLC-ICP-MS helps to focus the ESI-MS selection of ions. Numerous studies have shown that the information obtained from HPLC-ICP-MS analysis can be greatly enhanced by complementary approaches.

  2. Investigations of copper speciation and bioavailability

    SciTech Connect

    Deaver, E.; Rodgers, J.H. Jr.

    1995-12-31

    Speciation, or form in which copper occurs, can effect the bioavailability and therefore, the toxicity of that element. One needs to determine the bioavailable forms of copper in sediment/water effects on organisms. In both water and sediment experiments, physical/chemical factors influencing copper speciation were evaluated and related to organism responses. Ten day aqueous experiments encompassing a range of pH (6.5--8.1), alkalinity (10--70 mg/L as CaCO{sub 3}), hardness (10--70 mg/L as CaCO{sub 3}) and conductivity (30--300 umhos/cm) were conducted using Hyalella azteca. Amphipod survival was evaluated relative to changes in water characteristics and concomitant changes in copper speciation as measured using atomic adsorption spectroscopy (AA) for acid extractable copper, and differential pulse anodic stripping voltammetry (DPASV) for labile copper. Ten day LC50s based on AA measured copper concentrations ranged from 42 to 142 ug/L Cu, and LC50s based on DPASV measured copper concentrations ranged from 17.4--24.8 ug/L Cu. Ten day sediment experiments encompassing a range of sediment pH, organic carbon content, acid volatile sulfides and redox concentrations were also conducted using H. azteca. Overlying water (AA and DPASV) and sediment copper concentrations (AA) were measured and evaluated relative to organism survival. Ten day sediment test LC50s based on DPASV measured copper concentrations in overlying water were 18.5 and 18 ug/L Cu for experiments in sandy and silty sediments, respectively. Organism survival, used as a measure of bioavailable copper, was evaluated in relation to measured copper species concentrations and used to develop guidelines for predicting copper toxicity in freshwater systems.

  3. Anthropogenic VOC speciation in emission inventories: a method for improvement and evaluation

    NASA Astrophysics Data System (ADS)

    von Schneidemesser, E.; D'angiola, A.; Granier, C.; Monks, P. S.; Law, K.

    2011-12-01

    Volatile organic compounds (VOCs) are important precursor compounds for the formation of ozone and other secondary organic aerosols. Anthropogenic sources of VOCs are dominated by industrial usage and transportation sources, the latter being extremely important in urban areas. Megacities and large urban conglomerations are emission hot spots that exert disproportionately large adverse health effects on the population and surrounding environment, owing to their high population density and concentrated emission sources. Exceedances of ozone air quality standards are a problem in many urban areas. Improvements in the modelling of ozone precursors would benefit our understanding of the impact of changes in emissions and the effect of future legislation on air quality. As many VOCs are extremely reactive in the atmosphere and have high ozone forming potential, improved speciation of VOCs in models could lead to better predictions of ozone levels and secondary organic aerosol formation. Previously, VOC and carbon monoxide (CO) data from urban areas around the world were compared. Significant differences in VOC concentrations were observed, however, when normalized to CO, the VOC-CO ratios were similar for many locations and over time, even as emission reductions were implemented. The largest variation was found in the lighter alkanes due to the use of alternative transportation fuels in various world regions. These ratios were grouped by region and used to develop a new speciation for surface emissions of VOCs, by applying the regional observed VOC-CO ratios to the CO emissions for the urban areas. Urban areas were defined as 150 inhabitants per km2 or greater. Model simulations were performed using the MOZART-4 chemistry transport model to assess the improved speciation of the VOC emissions. The model outputs were compared to urban observational data where available. The impact of the new speciation of the distribution of CO, OH and ozone at the global scale will be

  4. Biotic immigration events, speciation, and the accumulation of biodiversity in the fossil record

    NASA Astrophysics Data System (ADS)

    Stigall, Alycia L.; Bauer, Jennifer E.; Lam, Adriane R.; Wright, David F.

    2017-01-01

    Biotic Immigration Events (BIMEs) record the large-scale dispersal of taxa from one biogeographic area to another and have significantly impacted biodiversity throughout geologic time. BIMEs associated with biodiversity increases have been linked to ecologic and evolutionary processes including niche partitioning, species packing, and higher speciation rates. Yet substantial biodiversity decline has also been documented following BIMEs due to elevated extinction and/or reduced speciation rates. In this review, we develop a conceptual model for biodiversity accumulation that links BIMEs and geographic isolation with local (α) diversity, regional (β) diversity, and global (γ) diversity metrics. Within the model, BIME intervals are characterized by colonization of existing species within new geographic regions and a lack of successful speciation events. Thus, there is no change in γ-diversity, and α-diversity increases at the cost of β-diversity. An interval of regional isolation follows in which lineage splitting results in successful speciation events and diversity increases across all three metrics. Alternation of these two regimes can result in substantial biodiversity accumulation. We tested this conceptual model using a series of case studies from the paleontological record. We primarily focus on two intervals during the Middle through Late Ordovician Period (470-458 Ma): the globally pervasive BIMEs during the Great Ordovician Biodiversification Event (GOBE) and a regional BIME, the Richmondian Invasion. We further test the conceptual model by examining the Great Devonian Interchange, Neogene mollusk migrations and diversification, and the Great American Biotic Interchange. Paleontological data accord well with model predictions. Constraining the mechanisms of biodiversity accumulation provides context for conservation biology. Because α-, β-, and γ-diversity are semi-independent, different techniques should be considered for sustaining various

  5. Bayesian Estimation of Speciation and Extinction from Incomplete Fossil Occurrence Data

    PubMed Central

    Silvestro, Daniele; Schnitzler, Jan; Liow, Lee Hsiang; Antonelli, Alexandre; Salamin, Nicolas

    2015-01-01

    The temporal dynamics of species diversity are shaped by variations in the rates of speciation and extinction, and there is a long history of inferring these rates using first and last appearances of taxa in the fossil record. Understanding diversity dynamics critically depends on unbiased estimates of the unobserved times of speciation and extinction for all lineages, but the inference of these parameters is challenging due to the complex nature of the available data. Here, we present a new probabilistic framework to jointly estimate species-specific times of speciation and extinction and the rates of the underlying birth-death process based on the fossil record. The rates are allowed to vary through time independently of each other, and the probability of preservation and sampling is explicitly incorporated in the model to estimate the true lifespan of each lineage. We implement a Bayesian algorithm to assess the presence of rate shifts by exploring alternative diversification models. Tests on a range of simulated data sets reveal the accuracy and robustness of our approach against violations of the underlying assumptions and various degrees of data incompleteness. Finally, we demonstrate the application of our method with the diversification of the mammal family Rhinocerotidae and reveal a complex history of repeated and independent temporal shifts of both speciation and extinction rates, leading to the expansion and subsequent decline of the group. The estimated parameters of the birth-death process implemented here are directly comparable with those obtained from dated molecular phylogenies. Thus, our model represents a step towards integrating phylogenetic and fossil information to infer macroevolutionary processes. PMID:24510972

  6. Bayesian estimation of speciation and extinction from incomplete fossil occurrence data.

    PubMed

    Silvestro, Daniele; Schnitzler, Jan; Liow, Lee Hsiang; Antonelli, Alexandre; Salamin, Nicolas

    2014-05-01

    The temporal dynamics of species diversity are shaped by variations in the rates of speciation and extinction, and there is a long history of inferring these rates using first and last appearances of taxa in the fossil record. Understanding diversity dynamics critically depends on unbiased estimates of the unobserved times of speciation and extinction for all lineages, but the inference of these parameters is challenging due to the complex nature of the available data. Here, we present a new probabilistic framework to jointly estimate species-specific times of speciation and extinction and the rates of the underlying birth-death process based on the fossil record. The rates are allowed to vary through time independently of each other, and the probability of preservation and sampling is explicitly incorporated in the model to estimate the true lifespan of each lineage. We implement a Bayesian algorithm to assess the presence of rate shifts by exploring alternative diversification models. Tests on a range of simulated data sets reveal the accuracy and robustness of our approach against violations of the underlying assumptions and various degrees of data incompleteness. Finally, we demonstrate the application of our method with the diversification of the mammal family Rhinocerotidae and reveal a complex history of repeated and independent temporal shifts of both speciation and extinction rates, leading to the expansion and subsequent decline of the group. The estimated parameters of the birth-death process implemented here are directly comparable with those obtained from dated molecular phylogenies. Thus, our model represents a step towards integrating phylogenetic and fossil information to infer macroevolutionary processes.

  7. The Development and Uses of EPA's SPECIATE Database

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA) repository of volatile organic compounds (VOC) and particulate matter (PM) speciation profiles of air pollution sources. These source profiles can be used to (l) provide input to chemical mass balance (CMB) receptor mod...

  8. Speciation and release kinetics of zinc in contaminated paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zinc is an important nutrient for plants, but it can be toxic at high concentrations. The solubility and speciation of Zn is controlled by many factors, especially soil pH and Eh, which can vary in lowland rice culture. This study determined Zn speciation and release kinetics in Cd-Zn co-contamina...

  9. Arsenic speciation in natural sulfidic geothermal waters

    NASA Astrophysics Data System (ADS)

    Keller, Nicole S.; Stefánsson, Andri; Sigfússon, Bergur

    2014-10-01

    The speciation of arsenic in natural sulfidic geothermal waters was studied using chemical analyses and thermodynamic aqueous speciation calculations. Samples were collected in three geothermal systems in Iceland, having contrasting H2S concentrations in the reservoir (high vs. low). The sampled waters contained 7-116 ppb As and <0.01-77.6 ppm H2S with pH of 8.56-9.60. The analytical setup used for the determination of arsenic species (Ion Chromatography-Hydride Generation Atomic Fluorescence Spectrometry, IC-HG-AFS) was field-deployed and the samples analyzed within ∼5 min of sampling in order to prevent changes upon storage, which were shown to be considerable regardless of the sample storage method used. Nine aqueous arsenic species were detected, among others arsenite (HnAsO3n-3), thioarsenite (HnAsS3n-3), arsenate (HnAsO4n-3), monothioarsenate (HnAsSO3n-3), dithioarsenate (HnAsS2O2n-3), trithioarsenate (HnAsS3O) and tetrathioarsenate (HnAsS4n-3). The results of the measured aqueous arsenic speciation in the natural geothermal waters and comparison with thermodynamic calculations reveal that the predominant factors determining the species distribution are sulfide concentration and pH. In alkaline waters with low sulfide concentrations the predominant species are AsIII oxyanions. This can be seen in samples from a liquid-only well, tapping water that is H2S-poor and free of oxygen. At intermediate sulfide concentration AsIII and AsV thio species become important and predominate at high sulfide concentration, as seen in two-phase well waters, which have high H2S concentrations in the reservoir. Upon oxidation, for instance due to mixing of the reservoir fluid with oxygenated water upon ascent to the surface, AsV oxyanions form, as well as AsV thio complexes if the sulfide concentration is intermediate to high. This oxidation process can be seen in samples from hot springs in the Geysir geothermal area. While the thermodynamic modeling allows for a first

  10. Fast electrochemical actuator

    NASA Astrophysics Data System (ADS)

    Uvarov, I. V.; Postnikov, A. V.; Svetovoy, V. B.

    2016-03-01

    Lack of fast and strong microactuators is a well-recognized problem in MEMS community. Electrochemical actuators can develop high pressure but they are notoriously slow. Water electrolysis produced by short voltage pulses of alternating polarity can overcome the problem of slow gas termination. Here we demonstrate an actuation regime, for which the gas pressure is relaxed just for 10 μs or so. The actuator consists of a microchamber filled with the electrolyte and covered with a flexible membrane. The membrane bends outward when the pressure in the chamber increases. Fast termination of gas and high pressure developed in the chamber are related to a high density of nanobubbles in the chamber. The physical processes happening in the chamber are discussed so as problems that have to be resolved for practical applications of this actuation regime. The actuator can be used as a driving engine for microfluidics.

  11. Ephemeral ecological speciation and the latitudinal biodiversity gradient.

    PubMed

    Cutter, Asher D; Gray, Jeremy C

    2016-10-01

    The richness of biodiversity in the tropics compared to high-latitude parts of the world forms one of the most globally conspicuous patterns in biology, and yet few hypotheses aim to explain this phenomenon in terms of explicit microevolutionary mechanisms of speciation and extinction. We link population genetic processes of selection and adaptation to speciation and extinction by way of their interaction with environmental factors to drive global scale macroecological patterns. High-latitude regions are both cradle and grave with respect to species diversification. In particular, we point to a conceptual equivalence of "environmental harshness" and "hard selection" as eco-evolutionary drivers of local adaptation and ecological speciation. By describing how ecological speciation likely occurs more readily at high latitudes, with such nascent species especially prone to extinction by fusion, we derive the ephemeral ecological speciation hypothesis as an integrative mechanistic explanation for latitudinal gradients in species turnover and the net accumulation of biodiversity.

  12. Chapter A5. Section 6.4.A. Arsenic Speciation

    USGS Publications Warehouse

    Garbarino, John R.

    2005-01-01

    Two sample-processing methods (field speciation and laboratory speciation) used at the USGS National Water Quality Laboratory (NWQL) are specific to sample analysis by inductively coupled plasma-mass spectrometry (ICP-MS) for determining the concentration of inorganic and organic arsenic species in a water sample. The field-speciation method requires NWQL Schedule 1729. The laboratory-speciation method requires use either of NWQL Schedule 1730, 1731, or 1732, as appropriate for study objectives. For either the field- or laboratory-speciation method, prior knowledge is needed of sample matrix-composition characteristics (that is, major-ion concentrations in filtered samples). Major-ion data are necessary to determine (1) the volume of ethylenediaminetetraacetic acid (EDTA) that will be required for sample preservation, and (2) if sample dilution is required.

  13. Sympatric speciation as a consequence of male pregnancy in seahorses

    PubMed Central

    Jones, Adam G.; Moore, Glenn I.; Kvarnemo, Charlotta; Walker, DeEtte; Avise, John C.

    2003-01-01

    The phenomenon of male pregnancy in the family Syngnathidae (seahorses, pipefishes, and sea dragons) undeniably has sculpted the course of behavioral evolution in these fishes. Here we explore another potentially important but previously unrecognized consequence of male pregnancy: a predisposition for sympatric speciation. We present microsatellite data on genetic parentage that show that seahorses mate size-assortatively in nature. We then develop a quantitative genetic model based on these empirical findings to demonstrate that sympatric speciation indeed can occur under this mating regime in response to weak disruptive selection on body size. We also evaluate phylogenetic evidence bearing on sympatric speciation by asking whether tiny seahorse species are sister taxa to large sympatric relatives. Overall, our results indicate that sympatric speciation is a plausible mechanism for the diversification of seahorses, and that assortative mating (in this case as a result of male parental care) may warrant broader attention in the speciation process for some other taxonomic groups as well. PMID:12732712

  14. Wolbachia infections mimic cryptic speciation in two parasitic butterfly species, Phengaris teleius and P. nausithous (Lepidoptera: Lycaenidae).

    PubMed

    Ritter, Sylvia; Michalski, Stefan G; Settele, Josef; Wiemers, Martin; Fric, Zdenek F; Sielezniew, Marcin; Šašić, Martina; Rozier, Yves; Durka, Walter

    2013-01-01

    Deep mitochondrial divergence within species may result from cryptic speciation, from phylogeographic isolation or from endosymbiotic bacteria like Wolbachia that manipulate host reproduction. Phengaris butterflies are social parasites that spend most of their life in close relationship with ants. Previously, cryptic speciation has been hypothesised for two Phengaris species based on divergent mtDNA sequences. Since Phengaris species are highly endangered, the existence of cryptic species would have drastic consequences for conservation and management. We tested for cryptic speciation and alternative scenarios in P. teleius and P. nausithous based on a comprehensive sample across their Palaearctic ranges using COI gene sequences, nuclear microsatellites and tests for Wolbachia. In both species a deep mitochondrial split occurring 0.65-1.97 myrs ago was observed that did not correspond with microsatellite data but was concordant with Wolbachia infection. Haplotypes previously attributed to cryptic species were part of the Wolbachia-infected clades. In both species remaining phylogeographic structure was largely consistent between mitochondrial and nuclear genomes. In P. teleius several mitochondrial and nuclear groups were observed in East Asia while a single haplogroup and nuclear cluster prevailed across continental Eurasia. Neutrality tests suggested rapid demographic expansion into that area. In contrast, P. nausithous had several mitochondrial and nuclear groups in Europe, suggesting a complex phylogeographic history in the western part of the species range. We conclude that deep intraspecific divergences found in DNA barcode studies do not necessarily need to represent cryptic speciation but instead can be due to both infection by Wolbachia and phylogeographic structure.

  15. The rate test of speciation: estimating the likelihood of non-allopatric speciation from reproductive isolation rates in Drosophila.

    PubMed

    Yukilevich, Roman

    2014-04-01

    Among the most debated subjects in speciation is the question of its mode. Although allopatric (geographical) speciation is assumed the null model, the importance of parapatric and sympatric speciation is extremely difficult to assess and remains controversial. Here I develop a novel approach to distinguish these modes of speciation by studying the evolution of reproductive isolation (RI) among taxa. I focus on the Drosophila genus, for which measures of RI are known. First, I incorporate RI into age-range correlations. Plots show that almost all cases of weak RI are between allopatric taxa whereas sympatric taxa have strong RI. This either implies that most reproductive isolation (RI) was initiated in allopatry or that RI evolves too rapidly in sympatry to be captured at incipient stages. To distinguish between these explanations, I develop a new "rate test of speciation" that estimates the likelihood of non-allopatric speciation given the distribution of RI rates in allopatry versus sympatry. Most sympatric taxa were found to have likely initiated RI in allopatry. However, two putative candidate species pairs for non-allopatric speciation were identified (5% of known Drosophila). In total, this study shows how using RI measures can greatly inform us about the geographical mode of speciation in nature.

  16. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-01-01

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced field reflectors,'' is discussed and experimental results obtained with short wiggler models are presented.

  17. Fast excitation variable period wiggler

    SciTech Connect

    van Steenbergen, A.; Gallardo, J.; Romano, T.; Woodle, M.

    1991-12-31

    The design of an easily stackable, variable period length, fast excitation driven wiggler, making use of geometrically alternating substacks of Vanadium Permandur ferromagnetic laminations, interspaced with conductive, non magnetic, laminations which act as eddy current induced ``field reflectors,`` is discussed and experimental results obtained with short wiggler models are presented.

  18. Relative Bioavailability and Bioaccessability and Speciation of ...

    EPA Pesticide Factsheets

    Background: Assessment of soil arsenic (As) bioavailability may profoundly affect the extent of remediation required at contaminated sites by improving human exposure estimates. Because small adjustments in soil As bioavailability estimates can significantly alter risk assessments and remediation goals, convenient, rapid, reliable, and inexpensive tools are needed to determine soil As bioavailability. Objectives: We evaluated inexpensive methods for assessing As bioavailability in soil as a means to improve human exposure estimates and potentially reduce remediation costs. Methods: Nine soils from residential sites affected by mining or smelting activity and two National Institute of Standards and Technology standard reference materials were evaluated for As bioavailability, bioaccessibility, and speciation. Arsenic bioavailability was determined using an in vivo mouse model, and As bioaccessibility was determined using the Solubility/Bioavailability Research Consortium in vitro assay. Arsenic speciation in soil and selected soil physicochemical properties were also evaluated to determine whether these parameters could be used as predictors of As bio¬availability and bioaccessibility. Results: In the mouse assay, we compared bioavailabilities of As in soils with that for sodium arsenate. Relative bioavailabilities (RBAs) of soil As ranged from 11% to 53% (mean, 33%). In vitro soil As bioaccessibility values were strongly correlated with soil As RBAs (R

  19. A genomic perspective on hybridization and speciation

    PubMed Central

    Payseur, Bret A.; Rieseberg, Loren H.

    2016-01-01

    Hybridization among diverging lineages is common in nature. Genomic data provide a special opportunity to characterize the history of hybridization and the genetic basis of speciation. We review existing methods and empirical studies to identify recent advances in the genomics of hybridization, as well as issues that need to be addressed. Notable progress has been made in the development of methods for detecting hybridization and inferring individual ancestries. However, few approaches reconstruct the magnitude and timing of gene flow, estimate the fitness of hybrids or incorporate knowledge of recombination rate. Empirical studies indicate that the genomic consequences of hybridization are complex, including a highly heterogeneous landscape of differentiation. Inferred characteristics of hybridization differ substantially among species groups. Loci showing unusual patterns – which may contribute to reproductive barriers – are usually scattered throughout the genome, with potential enrichment in sex chromosomes and regions of reduced recombination. We caution against the growing trend of interpreting genomic variation in summary statistics across genomes as evidence of differential gene flow. We argue that converting genomic patterns into useful inferences about hybridization will ultimately require models and methods that directly incorporate key ingredients of speciation, including the dynamic nature of gene flow, selection acting in hybrid populations and recombination rate variation. PMID:26836441

  20. Speciation network in Laurasiatheria: retrophylogenomic signals.

    PubMed

    Doronina, Liliya; Churakov, Gennady; Kuritzin, Andrej; Shi, Jingjing; Baertsch, Robert; Clawson, Hiram; Schmitz, Juergen

    2017-03-15

    Rapid species radiation due to adaptive changes or occupation of new ecospaces challenges our understanding of ancestral speciation and the relationships of modern species. At the molecular level, rapid radiation with successive speciations over short time periods - too short to fix polymorphic alleles - is described as incomplete lineage sorting. Incomplete lineage sorting leads to random fixation of genetic markers and hence random signals of relationships in phylogenetic reconstructions. The situation is further complicated when you consider that the genome is a mosaic of ancestral and modern incompletely sorted sequence blocks that leads to reconstructed affiliations to one or the other relatives depending on the fixation of their shared ancestral polymorphic alleles. The laurasiatherian relationships among Chiroptera, Perissodactyla, Cetartiodactyla, and Carnivora present a prime example for such enigmatic affiliations. We performed whole-genome screenings for phylogenetically diagnostic retrotransposon insertions involving the representatives bat (Chiroptera), horse (Perissodactyla), cow (Cetartiodactyla), and dog (Carnivora), and extracted among 162 thousand preselected cases 102 virtually noise-free, phylogenetically informative retroelements to draw a complete picture of the highly complex evolutionary relations within Laurasiatheria. All possible evolutionary scenarios received considerable retrotransposon support, leaving us with a network of affiliations. However, the Cetartiodactyla-Carnivora relationship as well as the basal position of Chiroptera and an ancestral laurasiatherian hybridization process did exhibit some very clear, distinct signals. The significant accordance of retrotransposon presence/absence patterns and flanking nucleotide changes suggest an important influence of mosaic genome structures in the reconstruction of species histories.

  1. Gene regulation and speciation in house mice

    PubMed Central

    Mack, Katya L.; Campbell, Polly; Nachman, Michael W.

    2016-01-01

    One approach to understanding the process of speciation is to characterize the genetic architecture of post-zygotic isolation. As gene regulation requires interactions between loci, negative epistatic interactions between divergent regulatory elements might underlie hybrid incompatibilities and contribute to reproductive isolation. Here, we take advantage of a cross between house mouse subspecies, where hybrid dysfunction is largely unidirectional, to test several key predictions about regulatory divergence and reproductive isolation. Regulatory divergence between Mus musculus musculus and M. m. domesticus was characterized by studying allele-specific expression in fertile hybrid males using mRNA-sequencing of whole testes. We found extensive regulatory divergence between M. m. musculus and M. m. domesticus, largely attributable to cis-regulatory changes. When both cis and trans changes occurred, they were observed in opposition much more often than expected under a neutral model, providing strong evidence of widespread compensatory evolution. We also found evidence for lineage-specific positive selection on a subset of genes related to transcriptional regulation. Comparisons of fertile and sterile hybrid males identified a set of genes that were uniquely misexpressed in sterile individuals. Lastly, we discovered a nonrandom association between these genes and genes showing evidence of compensatory evolution, consistent with the idea that regulatory interactions might contribute to Dobzhansky-Muller incompatibilities and be important in speciation. PMID:26833790

  2. Alternative fuels

    SciTech Connect

    Not Available

    1991-07-01

    This paper presents the preliminary results of a review, of the experiences of Brazil, Canada, and New Zealand, which have implemented programs to encourage the use of alternative motor fuels. It will also discuss the results of a separate completed review of the Department of Energy's (DOE) progress in implementing the Alternative Motor Fuels Act of 1988. The act calls for, among other things, the federal government to use alternative-fueled vehicles in its fleet. The Persian Gulf War, environmental concerns, and the administration's National Energy Strategy have greatly heightened interest in the use of alternative fuels in this country.

  3. EPA’s SPECIATE 4.4 Database:Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA)repository of volatile organic gas and particulate matter (PM) speciation profiles for air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, VOC, total...

  4. EPA’s SPECIATE 4.4 Database: Bridging Data Sources and Data Users

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA)repository of volatile organic gas and particulate matter (PM) speciation profiles for air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, VOC, total...

  5. EPA’s SPECIATE 4.4 Database: Development and Uses

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency's (EPA)repository of volatile organic gas and particulate matter (PM) speciation profiles for air pollution sources. EPA released SPECIATE 4.4 in early 2014 and, in total, the SPECIATE 4.4 database includes 5,728 PM, VOC, total...

  6. Ecological speciation in an island snail: evidence for the parallel evolution of a novel ecotype and maintenance by ecologically dependent postzygotic isolation.

    PubMed

    Stankowski, Sean

    2013-05-01

    Speciation is the process by which reproductive isolation evolves between populations. Two general models of speciation have been proposed: ecological speciation, where reproductive barriers evolve due to ecologically based divergent selection, and mutation-order speciation, where populations fix different mutations as they adapt to similar selection pressures. I evaluate these alternative models and determine the progress of speciation in a diverse group of land snails, genus Rhagada, inhabiting Rosemary Island. A recently derived keeled-flat morphotype occupies two isolated rocky hills, while globose-shelled snails inhabit the surrounding plains. The study of one hill reveals that they are separated by a narrow hybrid zone. As predicted by ecological speciation theory, there are local and landscape level associations between shell shape and habitat, and the morphological transition coincides with a narrow ecotone between the two distinct environments. Microsatellite DNA revealed a cline of hybrid index scores much wider than the morphological cline, further supporting the ecological maintenance of the morphotypes. The hybrid zone does not run through an area of low population density, as is expected for mutation-order hybrid zones, and there is a unimodal distribution of phenotypes at the centre, suggesting that there is little or no prezygotic isolation. Instead, these data suggest that the ecotypes are maintained by ecologically dependent postzygotic isolation (i.e. ecological selection against hybrids). Mitochondrial and Microsatellite DNA indicate that the keeled-flat form evolved recently, and without major historical disruptions to gene flow. The data also suggest that the two keeled-flat populations, inhabiting similar rocky hills, have evolved in parallel. These snails provide a complex example of ecological speciation in its early stages.

  7. Genomic Islands of Speciation in Anopheles gambiae

    PubMed Central

    Hahn, Matthew W; Nuzhdin, Sergey V

    2005-01-01

    The African malaria mosquito, Anopheles gambiae sensu stricto (A. gambiae), provides a unique opportunity to study the evolution of reproductive isolation because it is divided into two sympatric, partially isolated subtaxa known as M form and S form. With the annotated genome of this species now available, high-throughput techniques can be applied to locate and characterize the genomic regions contributing to reproductive isolation. In order to quantify patterns of differentiation within A. gambiae, we hybridized population samples of genomic DNA from each form to Affymetrix GeneChip microarrays. We found that three regions, together encompassing less than 2.8 Mb, are the only locations where the M and S forms are significantly differentiated. Two of these regions are adjacent to centromeres, on Chromosomes 2L and X, and contain 50 and 12 predicted genes, respectively. Sequenced loci in these regions contain fixed differences between forms and no shared polymorphisms, while no fixed differences were found at nearby control loci. The third region, on Chromosome 2R, contains only five predicted genes; fixed differences in this region were also verified by direct sequencing. These “speciation islands” remain differentiated despite considerable gene flow, and are therefore expected to contain the genes responsible for reproductive isolation. Much effort has recently been applied to locating the genes and genetic changes responsible for reproductive isolation between species. Though much can be inferred about speciation by studying taxa that have diverged for millions of years, studying differentiation between taxa that are in the early stages of isolation will lead to a clearer view of the number and size of regions involved in the genetics of speciation. Despite appreciable levels of gene flow between the M and S forms of A. gambiae, we were able to isolate three small regions of differentiation where genes responsible for ecological and behavioral isolation are

  8. Lead Speciation in remote Mountain Lakes

    NASA Astrophysics Data System (ADS)

    Plöger, A.; van den Berg, C. M. G.

    2003-04-01

    In natural waters trace metals can become complexed by organic matter. This complexation can change the geochemistry of the metals by preventing them being scavenged, thereby increasing their residence time in the water column. The chemical speciation of trace metals also affects the bioavalability and their toxicological impact on organisms. It is therefore important to determine the chemical speciation of trace metals as well as their concentrations. Mountain lakes have been less studied in the past than other lakes- partly because of their remoteness and partly because they were perceived to be unpolluted and undisturbed. But work so far on mountain lakes has shown that most sites are affected and threatened, for example by transboundary air pollutants like trace metals. One of the important features that distinguishes these lakes from lowland lakes at similar latitudes is the fact that they may be isolated from the atmosphere for six months or more during the winter by a thick ice cover. Also, as these lakes are remote from direct anthropogenic influences, they reflect the regional distribution of pollutants transferred via the atmosphere. For this work, under the framework of the EMERGE (European Mountain lake Ecosystems: Regionalisation, diaGnostic and socio-economic Evaluation) programme, two remote mountain lakes have been studied in detail, with water sampling taking place at different times of the year to investigate possible seasonal differences in lead concentrations and speciation. Results so far have shown that lead-complexing ligand concentrations are in excess to dissolved lead concentrations, indicating that dissolved lead probably occurs fully complexed in these lakes. Therefore the toxic fraction is likely to be less than the dissolved lead concentration. Also, lead concentrations at the time of the spring thaw are higher than autumn concentrations just before ice cover, indicating that a significant proportion of fallout onto the lake catchment

  9. Pleasant Alternatives.

    ERIC Educational Resources Information Center

    Unks, Gerald

    1981-01-01

    The author feels that the current wave of political conservatism may prove beneficial to education if the national mood of decentralization and decontrol leads to a resurgence of community involvement and locally-developed alternatives. He cites several examples of successful urban alternative schools. (SJL)

  10. Alternative Schools.

    ERIC Educational Resources Information Center

    Annett, Larry D.

    A model is presented for the categorizing of alternative schools, then the nature of the free school, which represents the essence of the alternative school movement, is examined. Strengths and weaknesses of court, legislative, and administrative approaches to resolve governance issues are set forth. This is followed by an analysis of three…

  11. Alternative Assessment.

    ERIC Educational Resources Information Center

    Stefonek, Tom; And Others

    1991-01-01

    This special double issue focuses on the issue of alternative assessment and its place in educational reform. "Alternative Assessment: A National Perspective" (T. Stefonek) emphasizes that the fundamental purposes of new assessment methods are grounded in educational goals, meaningful outcomes, and curricular and instructional programs…

  12. A Japanese view on speciation: "Sumiwake" explosive speciation of the cichlids in Lake Victoria.

    PubMed

    Kawamiya, Nobuo

    2003-01-01

    Imanishi's "mental" (cerebral) view of speciation is presented, in Mizuhata's revision. The key concept here is the "ethological partition" of the species. Members of each species=society (etho-species) share the same mental (brain) software, irrespective of their genetic structure. Cerebral animals perform active programmed selection, not to be confused with passive, non-programmed "natural selection" as in Neo-Darwinism. The program includes mating-choice of peculiar characters, distinct from the Neo-Darwinian sexual selection supposed due to the specific choosy genes. Speciation can occur, as a "partition of species=society", with bifurcation of mate-choosing program in the parent species. A main promoter for this bifurcation is species-specific "passion" for especially significant characters: long necks, ornamental antlers, ocelli feathers, bright nuptial colors etc. The cichlids in Lake Victoria achieved explosive speciation, while retaining their genetic homogeneity completely. Therefore it is illogical to attribute this divergence to extraordinary mutations in "action controlling genes". The origin of species=society (etho-species) can trace along to the Cambrian Period.

  13. Genetics of ecological divergence during speciation

    PubMed Central

    Arnegard, Matthew E.; McGee, Matthew D.; Matthews, Blake; Marchinko, Kerry B.; Conte, Gina L.; Kabir, Sahriar; Bedford, Nicole; Bergek, Sara; Chan, Yingguang Frank; Jones, Felicity C.; Kingsley, David M.; Peichel, Catherine L.; Schluter, Dolph

    2014-01-01

    Ecological differences often evolve early in speciation as divergent natural selection drives adaptation to distinct ecological niches, leading ultimately to reproductive isolation. Though this process is a major generator of biodiversity, its genetic basis remains poorly understood. Here we investigate the genetic architecture of niche differentiation in a sympatric species pair of threespine stickleback fish by mapping the environment-dependent effects of phenotypic traits on hybrid feeding and performance under semi-natural conditions. We show that multiple, unlinked loci act largely additively to determine position along the major niche axis separating these recently diverged species. We also find that functional mismatch between phenotypic traits reduces growth of some stickleback hybrids beyond that expected from an intermediate phenotype, suggesting a role for epistasis between the underlying genes. This functional mismatch might lead to hybrid incompatibilities that are analogous to those underlying intrinsic reproductive isolation but that depend on the ecological context. PMID:24909991

  14. NICKEL SPECIATION OF URBAN PARTICULATE MATTER

    SciTech Connect

    Kevin C. Galbreath; Charlene R. Crocker; Carolyn M. Nyberg; Frank E. Huggins; Gerald P. Huffman

    2003-10-01

    A four-step sequential Ni extraction method, summarized in Table AB-1, was evaluated for identifying and quantifying the Ni species occurring in urban total suspended particulate (TSP) matter and fine particulate matter (<10 {micro}m [PM{sub 10}] and <2.5 {micro}m [PM{sub 2.5}] in aerodynamic diameter). The extraction method was originally developed for quantifying soluble, sulfidic, elemental, and oxidic forms of Ni that may occur in industrial atmospheres. X-ray diffraction (XRD) and x-ray absorption fine structure (XAFS) spectroscopy were used to evaluate the Ni species selectivity of the extraction method. Uncertainties in the chemical speciation of Ni in urban PM{sub 10} and PM{sub 2.5} greatly affect inhalation health risk estimates, primarily because of the large variability in acute, chronic, and cancer-causing effects for different Ni compounds.

  15. Horizontal Gene Transfer, Dispersal and Haloarchaeal Speciation

    PubMed Central

    Papke, R. Thane; Corral, Paulina; Ram-Mohan, Nikhil; de la Haba, Rafael R.; Sánchez-Porro, Cristina; Makkay, Andrea; Ventosa, Antonio

    2015-01-01

    The Halobacteria are a well-studied archaeal class and numerous investigations are showing how their diversity is distributed amongst genomes and geographic locations. Evidence indicates that recombination between species continuously facilitates the arrival of new genes, and within species, it is frequent enough to spread acquired genes amongst all individuals in the population. To create permanent independent diversity and generate new species, barriers to recombination are probably required. The data support an interpretation that rates of evolution (e.g., horizontal gene transfer and mutation) are faster at creating geographically localized variation than dispersal and invasion are at homogenizing genetic differences between locations. Therefore, we suggest that recurrent episodes of dispersal followed by variable periods of endemism break the homogenizing forces of intrapopulation recombination and that this process might be the principal stimulus leading to divergence and speciation in Halobacteria. PMID:25997110

  16. Mercury speciation in the Adriatic Sea.

    PubMed

    Kotnik, Jože; Horvat, Milena; Ogrinc, Nives; Fajon, Vesna; Žagar, Dušan; Cossa, Daniel; Sprovieri, Francesca; Pirrone, Nicola

    2015-07-15

    Mercury and its speciation were studied in surface and deep waters of the Adriatic Sea. Several mercury species (i.e. DGM – dissolved gaseous Hg, RHg – reactive Hg, THg – total Hg, MeHg – monomethyl Hg and DMeHg – dimethylmercury) together with other water parameters were measured in coastal and open sea deep water profiles. THg concentrations in the water column, as well as in sediments and pore waters, were the highest in the northern, most polluted part of the Adriatic Sea as the consequence of Hg mining in Idrija and the heavy industry of northern Italy. Certain profiles in the South Adriatic Pit exhibit an increase of DGM just over the bottom due to its diffusion from sediment as a consequence of microbial and/or tectonic activity. Furthermore, a Hg mass balance for the Adriatic Sea was calculated based on measurements and literature data.

  17. Carbon speciation and surface tension of fog

    USGS Publications Warehouse

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  18. Spatially Resolved Sulfur Speciation in Urban Soils

    NASA Astrophysics Data System (ADS)

    Brettholle, M.; Gleber, S.-C.; Mekiffer, B.; Legnini, D.; McNulty, I.; Vogt, S.; Wessolek, G.; Thieme, J.

    2011-09-01

    A combination of x-ray microscopy, elemental mapping, and XANES spectroscopy at the K-absorption edge of sulfur was used to analyze the elemental and particulate composition of an urban soil loaded with building rubble from WWII, exemplarily from Berlin, Germany. This combination of element specific high-resolution microscopy with high spectral resolution capabilities allows for the determination of elemental composition as well as chemical speciation and is therefore well suited for the analysis of highly heterogeneous environmental samples. Different soil and debris constituents could be assigned to elemental distribution patterns within collected fluorescence maps, allowing for a detailed analysis of the sulfur pool and release from war debris in subsequent studies. A detailed understanding of this sulfur lixiviation is central to preserve urban water quality.

  19. Chemical speciation of radionuclides migrating in groundwaters

    SciTech Connect

    Robertson, D.; Schilk, A.; Abel, K.; Lepel, E.; Thomas, C.; Pratt, S.; Cooper, E.; Hartwig, P.; Killey, R.

    1994-04-01

    In order to more accurately predict the rates and mechanisms of radionuclide migration from low-level waste disposal facilities via groundwater transport, ongoing studies are being conducted at field sites at Chalk River Laboratories to identify and characterize the chemical speciation of mobile, long-lived radionuclides migrating in groundwaters. Large-volume water sampling techniques are being utilized to separate and concentrate radionuclides into particular, cationic, anionic, and nonionic chemical forms. Most radionuclides are migrating as soluble, anionic species that appear to be predominantly organoradionuclide complexes. Laboratory studies utilizing anion exchange chromatography have separated several anionically complexed radionuclides, e.g., {sup 60}Co and {sup 106}Ru, into a number of specific compounds or groups of compounds. Further identification of the anionic organoradionuclide complexes is planned utilizing high resolution mass spectrometry. Large-volume ultra-filtration experiments are characterizing the particulate forms of radionuclides being transported in these groundwaters.

  20. Speciation of arsenic in sulfidic waters

    PubMed Central

    Wilkin, Richard T; Wallschläger, Dirk; Ford, Robert G

    2003-01-01

    Formation constants for thioarsenite species have been determined in dilute solutions at 25°C, ΣH2S from 10-7.5 to 10-3.0 M, ΣAs from 10-5.6 to 10-4.8 M, and pH 7 and 10. The principal inorganic arsenic species in anoxic aquatic systems are arsenite, As(OH)30, and a mononuclear thioarsenite with an S/As ratio of 3:1. Thioarsenic species with S/As ratios of 1 : 1,2 : 1, and 4 : 1 are lesser components in sulfidic solutions that might be encountered in natural aquatic environments. Thioarsenites dominate arsenic speciation at sulfide concentrations > 10-4.3 M at neutral pH. Conversion from neutral As(OH)30 to anionic thioarsenite species may regulate the transport and fate of arsenic in sulfate-reducing environments by governing sorption and mineral precipitation reactions.

  1. Aluminium speciation in effluents and receiving waters.

    PubMed

    Gardner, M J; Comber, S D W

    2003-12-01

    The respective speciation of aluminium in sewage effluent and in river water receiving effluent, has been examined. Results showed that concentrations of reactive aluminium changed over a timescale of hours and were controlled predominantly by pH. A minimum concentration of reactive aluminium occurred at a pH of approximately 6.8, coinciding with the prevalence of non-reactive, insoluble Al(OH)3 species. For receiving waters of low pH value, typically < pH 5, a large proportion of the 'naturally present' aluminium can be present in a reactive form at concentrations higher than the proposed Environmental Quality Standard (EQS). Mixing of waters of this type with effluent of a higher pH value leads to the precipitation of aluminium hydroxide. Mixing of effluent of pH value in the range 7.5-8.0 with river water in the same (or slightly higher) pH range appears to result in no appreciable change in the proportion of reactive aluminium; the change in concentration tends to be related simply to dilution. On the basis of a theoretical knowledge of aluminium speciation, results obtained in this work indicate that it is possible to make predictions about the proportion of reactive aluminium present in a receiving water, based on the pH values of the effluent water mixture and the concentration in the effluent. Reasonable comparisons between measured and predicted values were obtained at higher pH values, but the relationship was less certain at pH values less than 6.5 for which levels of reactive metal tended to be higher than the quality standard value.

  2. SPECIATE Version 4.5 Database Development Documentation

    EPA Science Inventory

    This product updated SPECIATE 4.4 with new emission profiles to address high priority Agency data gaps and to included new, more accurate emission profiles generated by research underway within and outside the Agency.

  3. A model of sympatric speciation through assortative mating

    NASA Astrophysics Data System (ADS)

    Bagnoli, Franco; Guardiani, Carlo

    2005-03-01

    A microscopic model is developed, within the frame of the theory of quantitative traits, to study the combined effect of competition and assortativity on the sympatric speciation process, i.e., speciation in the absence of geographical barriers. Two components of fitness are considered: a static one that describes adaptation to environmental factors not related to the population itself, and a dynamic one that accounts for interactions between organisms, e.g. competition. A simulated annealing technique was applied in order to speed up simulations. The simulations show that both in the case of flat and steep static fitness landscapes, competition and assortativity do exert a synergistic effect on speciation. We also show that competition acts as a stabilizing force against extinction due to random sampling in a finite population. Finally, evidence is shown that speciation can be seen as a phase transition.

  4. Male competition fitness landscapes predict both forward and reverse speciation.

    PubMed

    Keagy, Jason; Lettieri, Liliana; Boughman, Janette W

    2016-01-01

    Speciation is facilitated when selection generates a rugged fitness landscape such that populations occupy different peaks separated by valleys. Competition for food resources is a strong ecological force that can generate such divergent selection. However, it is unclear whether intrasexual competition over resources that provide mating opportunities can generate rugged fitness landscapes that foster speciation. Here we use highly variable male F2 hybrids of benthic and limnetic threespine sticklebacks, Gasterosteus aculeatus Linnaeus, 1758, to quantify the male competition fitness landscape. We find that disruptive sexual selection generates two fitness peaks corresponding closely to the male phenotypes of the two parental species, favouring divergence. Most surprisingly, an additional region of high fitness favours novel hybrid phenotypes that correspond to those observed in a recent case of reverse speciation after anthropogenic disturbance. Our results reveal that sexual selection through male competition plays an integral role in both forward and reverse speciation.

  5. PARTICLE SPECIATION AND EMISSION PROFILES OF SMALL 2-STROKE ENGINES

    EPA Science Inventory

    The Human Exposure and Atmospheric Sciences Division (HEASD) conducts studies designed to acquire information from emission sources for use in source apportionment studies. The objective of this work is to characterize a complete, speciated emission profile (PM and air toxics) ...

  6. Alternative Schools.

    ERIC Educational Resources Information Center

    Pritchett, Stanley; Kimsey, Steve

    2002-01-01

    Describes the design of the DeKalb Alternative School in Atlanta, Georgia, located in a renovated shopping center. Purchasing commercial land and renovating the existing building saved the school system time and money. (EV)

  7. Sulfur Speciation and Extraction in Jet A (Briefing Charts)

    DTIC Science & Technology

    2015-08-16

    collected with Agilent Technologies 6890N Gas Chromatography System and Agilent Technologies 355 Sulfur Chemiluminescence Detector attachment • Method ...Charts 3. DATES COVERED (From - To) July 2015-August 2015 4. TITLE AND SUBTITLE Sulfur Speciation and Extraction in Jet A (Briefing Charts) 5a...239.18 DISTRIBUTION A: Approved for public release. Distribution is unlimited. Sulfur Speciation and Extraction in Jet A 16 August 2015 Kevin

  8. Speciation, Ecological Opportunity, and Latitude (American Society of Naturalists Address).

    PubMed

    Schluter, Dolph

    2016-01-01

    Evolutionary hypotheses to explain the greater numbers of species in the tropics than the temperate zone include greater age and area, higher temperature and metabolic rates, and greater ecological opportunity. These ideas make contrasting predictions about the relationship between speciation processes and latitude, which I elaborate and evaluate. Available data suggest that per capita speciation rates are currently highest in the temperate zone and that diversification rates (speciation minus extinction) are similar between latitudes. In contrast, clades whose oldest analyzed dates precede the Eocene thermal maximum, when the extent of the tropics was much greater than today, tend to show highest speciation and diversification rates in the tropics. These findings are consistent with age and area, which is alone among hypotheses in predicting a time trend. Higher recent speciation rates in the temperate zone than the tropics suggest an additional response to high ecological opportunity associated with low species diversity. These broad patterns are compelling but provide limited insights into underlying mechanisms, arguing that studies of speciation processes along the latitudinal gradient will be vital. Using threespine stickleback in depauperate northern lakes as an example, I show how high ecological opportunity can lead to rapid speciation. The results support a role for ecological opportunity in speciation, but its importance in the evolution of the latitudinal gradient remains uncertain. I conclude that per capita evolutionary rates are no longer higher in the tropics than the temperate zone. Nevertheless, the vast numbers of species that have already accumulated in the tropics ensure that total rate of species production remains highest there. Thus, tropical evolutionary momentum helps to perpetuate the steep latitudinal biodiversity gradient.

  9. How humans drive speciation as well as extinction.

    PubMed

    Bull, J W; Maron, M

    2016-06-29

    A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation-and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon 'no net loss' conservation literature-considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity.

  10. How humans drive speciation as well as extinction

    PubMed Central

    Maron, M.

    2016-01-01

    A central topic for conservation science is evaluating how human activities influence global species diversity. Humanity exacerbates extinction rates. But by what mechanisms does humanity drive the emergence of new species? We review human-mediated speciation, compare speciation and known extinctions, and discuss the challenges of using net species diversity as a conservation objective. Humans drive rapid evolution through relocation, domestication, hunting and novel ecosystem creation—and emerging technologies could eventually provide additional mechanisms. The number of species relocated, domesticated and hunted during the Holocene is of comparable magnitude to the number of observed extinctions. While instances of human-mediated speciation are known, the overall effect these mechanisms have upon speciation rates has not yet been quantified. We also explore the importance of anthropogenic influence upon divergence in microorganisms. Even if human activities resulted in no net loss of species diversity by balancing speciation and extinction rates, this would probably be deemed unacceptable. We discuss why, based upon ‘no net loss’ conservation literature—considering phylogenetic diversity and other metrics, risk aversion, taboo trade-offs and spatial heterogeneity. We conclude that evaluating speciation alongside extinction could result in more nuanced understanding of biosphere trends, clarifying what it is we actually value about biodiversity. PMID:27358365

  11. Ecological Impacts of Reverse Speciation in Threespine Stickleback.

    PubMed

    Rudman, Seth M; Schluter, Dolph

    2016-02-22

    Young species are highly prone to extinction via increased gene flow after human-caused environmental changes. This mechanism of biodiversity loss, often termed reverse speciation or introgressive extinction, is of exceptional interest because the parent species are typically highly differentiated ecologically. Reverse speciation events are potentially powerful case studies for the role of evolution in driving ecological changes, as the phenotypic shifts associated with introgressive extinction can be large and they occur over particularly short timescales. Furthermore, reverse speciation can lead to novel phenotypes, which may in turn produce novel ecological effects. Here we investigate the ecological shift associated with reverse speciation in threespine stickleback fish using a field study and a replicated experiment. We find that an instance of introgressive extinction had cascading ecological consequences that altered the abundance of both aquatic prey and the pupating aquatic insects that emerged into the terrestrial ecosystem. The community and ecosystem impacts of reverse speciation were novel, and yet they were also predictable based on ecological and morphological considerations. The study suggests that knowledge about the community ecology and changes in functional morphology of a dominant species may lead to some predictive power for the ecological effects of evolutionary change. Moreover, the rapid nature and resultant ecological impacts associated with reverse speciation demonstrates the interplay between biodiversity, evolutionary change, and ecosystem function.

  12. Dynamic speciation analysis of atrazine in aqueous latex nanoparticle dispersions using solid phase microextraction (SPME).

    PubMed

    Benhabib, Karim; Town, Raewyn M; van Leeuwen, Herman P

    2009-04-09

    Solid phase microextraction (SPME) is applied in the dynamic speciation analysis of the pesticide atrazine in an aqueous medium containing sorbing latex nanoparticles. It is found that the overall rate of extraction of the analyte is faster than in the absence of nanoparticles and governed by the coupled diffusion of free and particle-bound atrazine toward the solid/sample solution interface. In the eventual equilibrium the total atrazine concentration in the solid phase is dictated by the solid phase/water partition coefficient (K(sw)) and the concentration of the free atrazine in the sample solution. These observations demonstrate that the nanoparticles do not enter the solid phase. The experimental data show that the rate of release of sorbed atrazine from the latex particles is fast on the effective time scale of the microextraction process. A lability criterion is derived to quantitatively describe the relative rates of these two processes. All together, the results indicate that SPME has a strong potential for dynamic speciation analysis of organic compounds in media containing sorbing nanoparticles.

  13. Breakdown in the Process of Incipient Speciation in Anopheles gambiae

    PubMed Central

    Nwakanma, Davis C.; Neafsey, Daniel E.; Jawara, Musa; Adiamoh, Majidah; Lund, Emily; Rodrigues, Amabelia; Loua, Kovana M.; Konate, Lassana; Sy, Ngayo; Dia, Ibrahima; Awolola, T. Samson; Muskavitch, Marc A. T.; Conway, David J.

    2013-01-01

    Understanding genetic causes and effects of speciation in sympatric populations of sexually reproducing eukaryotes is challenging, controversial, and of practical importance for controlling rapidly evolving pests and pathogens. The major African malaria vector mosquito Anopheles gambiae sensu stricto (s.s.) is considered to contain two incipient species with strong reproductive isolation, hybrids between the M and S molecular forms being very rare. Following recent observations of higher proportions of hybrid forms at a few sites in West Africa, we conducted new surveys of 12 sites in four contiguous countries (The Gambia, Senegal, Guinea-Bissau, and Republic of Guinea). Identification and genotyping of 3499 A. gambiae s.s. revealed high frequencies of M/S hybrid forms at each site, ranging from 5 to 42%, and a large spectrum of inbreeding coefficient values from 0.11 to 0.76, spanning most of the range expected between the alternative extremes of panmixia and assortative mating. Year-round sampling over 2 years at one of the sites in The Gambia showed that M/S hybrid forms had similar relative frequencies throughout periods of marked seasonal variation in mosquito breeding and abundance. Genome-wide scans with an Affymetrix high-density single-nucleotide polymorphism (SNP) microarray enabled replicate comparisons of pools of different molecular forms, in three separate populations. These showed strong differentiation between M and S forms only in the pericentromeric region of the X chromosome that contains the molecular form-specific marker locus, with only a few other loci showing minor differences. In the X chromosome, the M/S hybrid forms were more differentiated from M than from S forms, supporting a hypothesis of asymmetric introgression and backcrossing. PMID:23335339

  14. Speciation and Health Risks of Atmospheric Nanoparticulates

    NASA Astrophysics Data System (ADS)

    Nguyen, Kennedy

    Exposure to air pollution causes several adverse health effects such as asthma, respiratory disease, cardiovascular disease, cancer, and premature death; and the San Joaquin Valley is one of the most heavily polluted regions in the US. The mountains that surround the valley allow air pollution, including particulate matter, to remain stagnant, prolonging the exposure of valley populations to it. The primary sources of particulate matter for this region are aluminosilicate dust from agricultural activities, and soot emissions from diesel trucks and vehicular traffic. A substantial fraction of emitted material is nanoparticulate matter (<100 nm), which contains trace iron and polycyclic aromatic hydrocarbons that can traverse into human organs via the lungs, initiate inflammation, and lead to disease. The traditional approach of reducing the total mass of emitted material is beginning to reach its limit of effectiveness for mitigating the negative health impacts of particulate matter. There is a need for chemical speciation of particulate matter that will allow the identification of the chemical and physical properties of particulates by source, the creation of well-controlled proxy particles with those properties for testing in cell culture studies, and correlation of particulate properties and sources with their negative health impacts. These results can help identify the sources of air pollution to prioritize for mitigation for the greatest health benefit. In addition, further chemical speciation can help monitor the results of such mitigation efforts. Here, natural particulate matter samples from Merced and Fresno, two cities in the San Joaquin Valley, were analyzed. Ultrafine particles present were 40 to 50 nm in diameter and mostly composed of aluminum, silicon, oxygen, and iron hydroxide. XAS data confirmed the presence of the aluminosilicate as smectite clay and the iron hydroxide as ferrihydrite. Furthermore, a chemical speciation study investigated

  15. Not So F.A.S.T., Dr. Vickers!

    ERIC Educational Resources Information Center

    Deary, Ian J.; Caryl, Peter G.

    1997-01-01

    A critical review of the theoretical basis and empirical results of the frequency accrual speed test (FAST) developed by D. Vickers and others (1993) leads to the conclusion that the FAST is not appropriately described as an alternative to the inspection time (IT) task, and that results from FAST are not generalizable to IT. (SLD)

  16. A Note On Deletion Rules in Fast Speech.

    ERIC Educational Resources Information Center

    Hewlett, Nigel

    In fast speech, certain segments pronounced in careful speech may be deleted. Rules of a generative phonology have been used to account for fast speech forms. An alternative approach is suggested which views fast speech deletions as merely limiting cases of segment reduction, under conditions of increased tempo and/or casualness. To complement…

  17. Aluminum speciation in crustal fluids revisited

    NASA Astrophysics Data System (ADS)

    Tagirov, Boris; Schott, Jacques

    2001-11-01

    Aluminum speciation in crustal fluids is assessed by means of standard thermodynamic properties at 25°C, 1 bar, and revised Helgeson-Kirkham-Flowers (HKF) (Tanger J. C. IV and Helgeson H. C., "Calculation of the thermodynamic and transport properties of aqueous species at high pressures and temperatures: Revised equations of state for the standard partial molal properties of ions and electrolytes," Am. J. Sci. 288, 19-98, 1988) equations of state parameters for aqueous species in the system Al-O-H-Na-Si-Cl-F-SO 4 derived from recent experimental data with the help of isocoulombic reactions and correlations among parameters in the HKF model. In acidic to neutral hydrothermal solutions and for fluorine concentrations in excess of 1 ppm, the fluoride complexes AlF n3-n dominate Al speciation at temperature (T) < 100°C, whereas the hydroxide fluoride species Al(OH) 2F (aq)0 and AlOHF 20(aq) are dominant up to ˜400°C. In high-temperature (T > 300°C) hydrothermal and metamorphic fluids, aluminum mobility is considerably enhanced by formation of NaAl(OH) 3F (aq)0 and NaAl(OH) 2F 20(aq) ion paired mixed species. NaAl(OH) 2F 20(aq) controls Al transport in granite-derived fluids and during greisenization. At alkaline pH, Al(OH) 4-, Al(OH) 3H 3SiO 4-, and the NaAl(OH) 40(aq) ion-pair are the dominant Al species. Thermodynamic calculations show that as a result of strong interactions of Al(aq) with NaOH, NaF, HF, and SiO 2(aq) present in crustal fluids, the concentrations of aluminum in equilibrium with Al-bearing minerals can be several orders of magnitude higher than those calculated assuming that only Al hydroxyde complexes are formed. Interactions with these components are likely to be responsible for aluminum mobility during hydrothermal and metamorphic reactions.

  18. Element speciation during nuclear glass alteration

    NASA Astrophysics Data System (ADS)

    Galoisy, L.; Calas, G.; Bergeron, B.; Jollivet, P.; Pelegrin, E.

    2011-12-01

    Assessing the long-term behavior of nuclear glasses implies the prediction of their long-term performance. An important controlling parameter is their evolution during interaction with water under conditions simulating geological repositories. After briefly recalling the major characteristics of the local and medium-range structure of borosilicate glasses of nuclear interest, we will present some structural features of this evolution. Specific structural tools used to determine the local structure of glass surfaces include synchrotron-radiation x-ray absorption spectroscopy with total electron yield detection. The evolution of the structure of glass surface has been determined at the Zr-, Fe-, Si- and Al-K edges and U-LIII edge. During alteration in near- or under-saturated conditions, some elements such as Fe change coordination, as other elements such as Zr only suffer structural modifications in under-saturated conditions. Uranium exhibits a modification of its speciation from an hexa-coordinated U(VI) in the borosilicate glass to an uranyl group in the gel. These structural modifications may explain the chemical dependence of the initial alteration rate and the transition to the residual regime. They also illustrate the molecular-scale origin of the processes at the origin of the glass-to-gel transformation. Eventually, they explain the provisional trapping of U by the alteration gel: the uranium retention factors in the gel depend on the alteration conditions, and thus on the nature of the resulting gel and on the trapping conditions.

  19. Ice sheets promote speciation in boreal birds.

    PubMed

    Weir, Jason T; Schluter, Dolph

    2004-09-22

    The premise that Pleistocene ice ages played an important role in generating present-day species diversity has been challenged by genetic data indicating that most of the youngest terrestrial species on Earth coalesced long before major glacial advances. However, study has been biased towards faunas distributed at low latitudes that were not directly fragmented by advancing ice sheets. Using mitochondrial sequence divergence and a molecular clock, we compared the coalescence times of pairs of avian species belonging to superspecies complexes from the high-latitude boreal forest with those of sub-boreal and tropical avifaunas of the New World. Remarkably, all coalescence events in boreal superspecies date to the Pleistocene, providing direct evidence that speciation was commonly initiated during recent glacial periods. A pattern of endemism in boreal superspecies plausibly links the timing of divergence to the fragmentation of the boreal forest by ice sheets during the Mid- and Late Pleistocene. In contrast to the boreal superspecies, only 56% of sub-boreal and 46% of tropical superspecies members coalesced during the Pleistocene, suggesting that avifaunas directly fragmented by ice sheets experienced rapid rates of diversification, whereas those distributed farther south were affected to a lesser extent. One explanation for the absence of pre-Pleistocene superspecies in boreal avifaunas is that strong selection pressures operated in boreal refugia, causing superspecies members to achieve ecological differentiation at an accelerated rate.

  20. Ice sheets promote speciation in boreal birds.

    PubMed Central

    Weir, Jason T.; Schluter, Dolph

    2004-01-01

    The premise that Pleistocene ice ages played an important role in generating present-day species diversity has been challenged by genetic data indicating that most of the youngest terrestrial species on Earth coalesced long before major glacial advances. However, study has been biased towards faunas distributed at low latitudes that were not directly fragmented by advancing ice sheets. Using mitochondrial sequence divergence and a molecular clock, we compared the coalescence times of pairs of avian species belonging to superspecies complexes from the high-latitude boreal forest with those of sub-boreal and tropical avifaunas of the New World. Remarkably, all coalescence events in boreal superspecies date to the Pleistocene, providing direct evidence that speciation was commonly initiated during recent glacial periods. A pattern of endemism in boreal superspecies plausibly links the timing of divergence to the fragmentation of the boreal forest by ice sheets during the Mid- and Late Pleistocene. In contrast to the boreal superspecies, only 56% of sub-boreal and 46% of tropical superspecies members coalesced during the Pleistocene, suggesting that avifaunas directly fragmented by ice sheets experienced rapid rates of diversification, whereas those distributed farther south were affected to a lesser extent. One explanation for the absence of pre-Pleistocene superspecies in boreal avifaunas is that strong selection pressures operated in boreal refugia, causing superspecies members to achieve ecological differentiation at an accelerated rate. PMID:15347509

  1. Selenium speciation in flue desulfurization residues.

    PubMed

    Zhong, Liping; Cao, Yan; Li, Wenying; Xie, Kechang; Pan, Wei-Ping

    2011-01-01

    Flue gas from coal combustion contains significant amounts of volatile selenium (Se). The capture of Se in the flue gas desulfurization (FGD) scrubber unit has resulted in a generation of metal-laden residues. It is important to determine Se speciation to understand the environmental impact of its disposal. A simple method has been developed for selective inorganic Se(IV), Se(VI) and organic Se determination in the liquid-phase FGD residues by hydride generation atomic fluorescence spectrometry (AFS). It has been determined that Se(IV), Se(VI) and organic Se can be accurately determined with detection limits (DL) of 0.05, 0.06 and 0.06 microg/L, respectively. The accuracy of the proposed method was evaluated by analyzing the certified reference material, NIST CRM 1632c, and also by analyzing spiked tap-water samples. Analysis indicates that the concentration of Se is high in FGD liquid residues and primarily exists in a reduced state as selenite (Se(IV)). The toxicity of Se(IV) is the strongest of all Se species. Flue gas desulfurization residues pose a serious environmental risk.

  2. Speciated hydrocarbon emissions from small utility engines.

    PubMed

    Reisel, J R; Kellner, T A; Neusen, K F

    2000-04-01

    Partially speciated hydrocarbon (HC) emissions data from several small utility engines, as measured by a Fourier Transform Infrared analyzer, are presented. The engines considered have nominal horsepower ratings between 3.7 and 9.3 kW. Both side-valve and overhead-valve engines are studied, and four different fuels are used in the engines. The results indicate that the small HCs present in the exhaust tend to be in the form of either methane or unsaturated HCs. Other small alkanes, such as ethane and propane, are present in only relatively small concentrations. In terms of ozone formation potential, the HCs in the form of methane will lead to little ozone, but the distribution of the C2 and C3 species is not ideal from an ozone reduction stand-point. It is also found that the presence of oxygen in the fuels appears to lead to somewhat more complete combustion, although the effects are not large. Finally, the overhead-valve engines appear to have lower HC emissions than side-valve engines, which is primarily due to higher operating A/F ratios and the engine geometry.

  3. The biological speciation and toxicokinetics of aluminum.

    PubMed Central

    DeVoto, E; Yokel, R A

    1994-01-01

    This review discusses recent literature on the chemical and physiological factors that influence the absorption, distribution, and excretion of aluminum in mammals, with particular regard to gastrointestinal absorption and speciation in plasma. Humans encounter aluminum, a ubiquitous yet highly insoluble element in most forms, in foods, drinking water, and pharmaceuticals. Exposure also occurs by inhalation of dust and aerosols, particularly in occupational settings. Absorption from the gut depends largely on pH and the presence of complexing ligands, particularly carboxylic acids, with which the metal can form absorbable neutral aluminum species. Uremic animals and humans experience higher than normal body burdens of aluminum despite increased urinary clearance of the metal. In plasma, 80-90% of aluminum binds to transferrin, an iron-transport protein for which receptors exist in many tissue. The remaining fraction of plasma aluminum takes the form of small-molecule hydroxy species and small complexes with carboxylic acids, phosphate, and, to a much lesser degree, amino acids. Most of these species have not been observed in vivo but are predicted from equilibrium models derived from potentiometric methods and NMR investigations. These models predict that the major small-molecule aluminum species under plasma conditions are charged and hence unavailable for uptake into tissues. PMID:9738208

  4. Geographically multifarious phenotypic divergence during speciation

    PubMed Central

    Gompert, Zachariah; Lucas, Lauren K; Nice, Chris C; Fordyce, James A; Alex Buerkle, C; Forister, Matthew L

    2013-01-01

    Speciation is an important evolutionary process that occurs when barriers to gene flow evolve between previously panmictic populations. Although individual barriers to gene flow have been studied extensively, we know relatively little regarding the number of barriers that isolate species or whether these barriers are polymorphic within species. Herein, we use a series of field and lab experiments to quantify phenotypic divergence and identify possible barriers to gene flow between the butterfly species Lycaeides idas and Lycaeides melissa. We found evidence that L. idas and L. melissa have diverged along multiple phenotypic axes. Specifically, we identified major phenotypic differences in female oviposition preference and diapause initiation, and more moderate divergence in mate preference. Multiple phenotypic differences might operate as barriers to gene flow, as shown by correlations between genetic distance and phenotypic divergence and patterns of phenotypic variation in admixed Lycaeides populations. Although some of these traits differed primarily between species (e.g., diapause initiation), several traits also varied among conspecific populations (e.g., male mate preference and oviposition preference). PMID:23532669

  5. Speciation and distribution of cadmium and lead in salinized horizons of antrosols

    NASA Astrophysics Data System (ADS)

    Bulgariu, D.; Bulgariu, L.; Astefanei, D.

    2009-04-01

    soils have been estimated on the basis of Raman and FT-IR spectra, recorded for fractions obtained after each extraction step. These data were correlated with those obtained by chemical analysis and UV-VIS spectrometry, and were used for to establish the type and weight of Cd and Pb speciation forms in studied antrosol. Our studies have been show that in medium and inferior horizons of hortic antrosols, the heavy metals have a general accumulation tendency, preferential by binding on organic matter and organic-mineral complexes, components with higher abundance in such type of soils. The selectivity and complexation mechanisms are controlled by speciation forms of the two metals. This phenomenon has two important consequences, the strong fixation of heavy metals in hortic antrosol and significant modification of structure and conformation of organic macromolecules. A specific phenomenon of hortic antrosols is that the accumulation rate of heavy metals is higher than levigation rate, and the mobile forms of these have a higher biodisponibility, being relative easy assimilated by plants. The progressive salinization of superior horizons of soils from glass houses, determined a sever perturbation of equilibrium between Cd and Pb speciation forms. In consequence these will have an accentuated migration tendency in superior horizons, as complexes with inorganic ligands, with a high mobility and biodsiponibility. The accumulation of soluble salts in superior horizons, and the formation of frangipane horizon (horizon of geochemical segregation of hortic antrosols) modified the ionic strength from soil solution and the thermodynamic activity of cadmium and lead species. Under these conditions, the levigation rate of cadmium and lead is higher than the accumulation rate, which means that the migration of these metals in soil solution occurs fast and in high concentrations. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of

  6. Speciation of triphenyltin compounds using Moessbauer spectroscopy. Final report

    SciTech Connect

    Eng, G.

    1993-11-01

    Organotin compounds have been used widely as the active agent in antifouling marine paints. Organotin compounds, i.e., tributyltin compounds (TBTs) and triphenyltin compounds (TPTs) have been found to be effective in preventing the unwanted attachment and development of aquatic organisms such as barnacles, sea grass and hydroids on ships, hulls and underwater surfaces. However, these organotin compounds have been found to be toxic to non-targeted marine species as well. While speciation of tributyltins in environmental water systems has received much attention in the literature, little information concerning the speciation of triphenyltins is found. Therefore, it would be important to study the fate of TPTs in the aquatic environment, particularly in sediments, both oxic and anoxic, in order to obtain speciation data. Since marine estuaries consist of areas with varying salinity and pH, it is important to investigate the speciation of these compounds under varying salinity conditions. In addition, evaluation of the speciation of these compounds as a function of pH would give an insight into how these compounds might interact with sediments in waters where industrial chemical run-offs can affect the pH of the estuarine environment. Finally, since organotins are present in both salt and fresh water environments, the speciation of the organotins in seawater and distilled water should also be studied. Moessbauer spectroscopy would provide a preferred method to study the speciation of triphenyltins as they leach from marine paints into the aquatic environment. Compounds used in this study are those triphenyltin compounds that are commonly incorporated into marine paints such as triphenyltin fluoride (TPTF), triphenyltin acetate (TPTOAc), triphenyltin chloride (TPTCl) and triphenyltin hydroxide (TPTOH).

  7. Magnetostrictive Alternator

    NASA Technical Reports Server (NTRS)

    Dyson, Rodger; Bruder, Geoffrey

    2013-01-01

    This innovation replaces the linear alternator presently used in Stirling engines with a continuous-gradient, impedance-matched, oscillating magnetostrictive transducer that eliminates all moving parts via compression, maintains high efficiency, costs less to manufacture, reduces mass, and eliminates the need for a bearing system. The key components of this new technology are the use of stacked magnetostrictive materials, such as Terfenol-D, under a biased magnetic and stress-induced compression, continuous-gradient impedance-matching material, coils, force-focusing metallic structure, and supports. The acoustic energy from the engine travels through an impedancematching layer that is physically connected to the magnetostrictive mass. Compression bolts keep the structure under compressive strain, allowing for the micron-scale compression of the magnetostrictive material and eliminating the need for bearings. The relatively large millimeter displacement of the pressure side of the impedance-matching material is reduced to micron motion, and undergoes stress amplification at the magnetostrictive interface. The alternating compression and expansion of the magnetostrictive material creates an alternating magnetic field that then induces an electric current in a coil that is wound around the stack. This produces electrical power from the acoustic pressure wave and, if the resonant frequency is tuned to match the engine, can replace the linear alternator that is commonly used.

  8. ALTERNATIVE OXIDANTS

    EPA Science Inventory

    This chapter reports on the efforts of the USEPA to study chloramines, chlorine dioxide and ozone as alternative oxidants/disinfectants to chlorine for the control of disinfection by-rpdocuts (DBPs) in drinking water. It examines the control of DBPs like trihalomethanes and haloa...

  9. Alternative Thinking.

    ERIC Educational Resources Information Center

    Herman, Dan

    1999-01-01

    Explains how advances in diesel and alternative fuels has caused schools to reconsider their use for their bus fleets. Reductions in air pollution emissions, cost-savings developments, and the economies experienced from less downtime and maintenance requirements are explored. (GR)

  10. Divergence is focused on few genomic regions early in speciation: incipient speciation of sunflower ecotypes.

    PubMed

    Andrew, Rose L; Rieseberg, Loren H

    2013-09-01

    Early in speciation, as populations undergo the transition from local adaptation to incipient species, is when a number of transient, but potentially important, processes appear to be most easily detected. These include signatures of selective sweeps that can point to asymmetry in selection between habitats, divergence hitchhiking, and associations of adaptive genes with environments. In a genomic comparison of ecotypes of the prairie sunflower, Helianthus petiolaris, occurring at Great Sand Dunes National Park and Preserve (Colorado), we found that selective sweeps were mainly restricted to the dune ecotype and that there was variation across the genome in whether proximity to the nondune population constrained or promoted divergence. The major regions of divergence were few and large between ecotypes, in contrast with an interspecific comparison between H. petiolaris and a sympatric congener, Helianthus annuus. In general, the large regions of divergence observed in the ecotypic comparison swamped locus-specific associations with environmental variables. In both comparisons, regions of high divergence occurred in portions of the genetic map with high marker density, probably reflecting regions of low recombination. The difference in genomic distributions of highly divergent regions between ecotypic and interspecific comparisons highlights the value of studies spanning the spectrum of speciation in related taxa.

  11. Theoretical models of the influence of genomic architecture on the dynamics of speciation.

    PubMed

    Flaxman, Samuel M; Wacholder, Aaron C; Feder, Jeffrey L; Nosil, Patrik

    2014-08-01

    A long-standing problem in evolutionary biology has been determining whether and how gradual, incremental changes at the gene level can account for rapid speciation and bursts of adaptive radiation. Using genome-scale computer simulations, we extend previous theory showing how gradual adaptive change can generate nonlinear population transitions, resulting in the rapid formation of new, reproductively isolated species. We show that these transitions occur via a mechanism rooted in a basic property of biological heredity: the organization of genes in genomes. Genomic organization of genes facilitates two processes: (i) the build-up of statistical associations among large numbers of genes and (ii) the action of divergent selection on persistent combinations of alleles. When a population has accumulated a critical amount of standing, divergently selected variation, the combination of these two processes allows many mutations of small effect to act synergistically and precipitously split one population into two discontinuous, reproductively isolated groups. Periods of allopatry, chromosomal linkage among loci, and large-effect alleles can facilitate this process under some conditions, but are not required for it. Our results complement and extend existing theory on alternative stable states during population divergence, distinct phases of speciation and the rapid emergence of multilocus barriers to gene flow. The results are thus a step towards aligning population genomic theory with modern empirical studies.

  12. Inferring phylogeny and speciation of Gymnosporangium species, and their coevolution with host plants

    PubMed Central

    Zhao, Peng; Liu, Fang; Li, Ying-Ming; Cai, Lei

    2016-01-01

    Gymnosporangium species (Pucciniaceae, Pucciniales) cause serious diseases and significant economic losses to apple cultivars. Most of the reported species are heteroecious and complete their life cycles on two different plant hosts belonging to two unrelated genera, i.e. Juniperus and Malus. However, the phylogenetic relationships among Gymnosporangium species and the evolutionary history of Gymnosporangium on its aecial and telial hosts were still undetermined. In this study, we recognized species based on rDNA sequence data by using coalescent method of generalized mixed Yule-coalescent (GMYC) and Poisson Tree Processes (PTP) models. The evolutionary relationships of Gymnosporangium species and their hosts were investigated by comparing the cophylogenetic analyses of Gymnosporangium species with Malus species and Juniperus species, respectively. The concordant results of GMYC and PTP analyses recognized 14 species including 12 known species and two undescribed species. In addition, host alternations of 10 Gymnosporangium species were uncovered by linking the derived sequences between their aecial and telial stages. This study revealed the evolutionary process of Gymnosporangium species, and clarified that the aecial hosts played more important roles than telial hosts in the speciation of Gymnosporangium species. Host switch, losses, duplication and failure to divergence all contributed to the speciation of Gymnosporangium species. PMID:27385413

  13. The Interplay of Al and Mg Speciation in Advanced Mg Battery Electrolyte Solutions.

    PubMed

    See, Kimberly A; Chapman, Karena W; Zhu, Lingyang; Wiaderek, Kamila M; Borkiewicz, Olaf J; Barile, Christopher J; Chupas, Peter J; Gewirth, Andrew A

    2016-01-13

    Mg batteries are an attractive alternative to Li-based energy storage due to the possibility of higher volumetric capacities with the added advantage of using sustainable materials. A promising emerging electrolyte for Mg batteries is the magnesium aluminum chloride complex (MACC) which shows high Mg electrodeposition and stripping efficiencies and relatively high anodic stabilities. As prepared, MACC is inactive with respect to Mg deposition; however, efficient Mg electrodeposition can be achieved following an electrolytic conditioning process. Through the use of Raman spectroscopy, surface enhanced Raman spectroscopy, (27)Al and (35)Cl nuclear magnetic resonance spectroscopy, and pair distribution function analysis, we explore the active vs inactive complexes in the MACC electrolyte and demonstrate the codependence of Al and Mg speciation. These techniques report on significant changes occurring in the bulk speciation of the conditioned electrolyte relative to the as-prepared solution. Analysis shows that the active Mg complex in conditioned MACC is very likely the [Mg2(μ-Cl)3·6THF](+) complex that is observed in the solid state structure. Additionally, conditioning creates free Cl(-) in the electrolyte solution, and we suggest the free Cl(-) adsorbs at the electrode surface to enhance Mg electrodeposition.

  14. Constraints on speciation suggested by comparing lake-stream stickleback divergence across two continents.

    PubMed

    Berner, Daniel; Roesti, Marius; Hendry, Andrew P; Salzburger, Walter

    2010-11-01

    Adaptation to ecologically distinct environments can coincide with the emergence of reproductive barriers. The outcome of this process is highly variable and can range along a continuum from weak population differentiation all the way to complete, genome-wide divergence. The factors determining how far diverging taxa will move along this continuum remain poorly understood but are most profitably investigated in taxa under replicate divergence. Here, we explore determinants of progress towards speciation by comparing phenotypic and molecular divergence within young (<150 years) lake-stream stickleback pairs from Central Europe to divergence in older (thousands of years) archetypal lake-stream pairs from Vancouver Island, Canada. We generally find relatively weak divergence in most aspects of foraging morphology (gill raker number, body shape) in the European pairs, although substantial adaptive divergence is seen in gill raker length. Combined with striking overall phenotypic differences between the continents, this argues for genetic and time constraints on adaptive divergence in the European pairs. The European lake-stream pairs also do not display the strong habitat-related differentiation in neutral (microsatellite) markers seen in the Canadian watersheds. This indicates either the lack of strong reproductive barriers owing to weak adaptive divergence, or alternatively that neutral markers are poorly suited for detecting reproductive barriers if these emerge rapidly. Overall, our comparative approach suggests constraints on speciation due to genetic architecture and limited time for divergence. The relative importance of these factors remains to be quantified by future investigation.

  15. Genome‐wide tests for introgression between cactophilic Drosophila implicate a role of inversions during speciation

    PubMed Central

    Lohse, Konrad; Clarke, Magnus; Ritchie, Michael G.; Etges, William J.

    2015-01-01

    Models of speciation‐with‐gene‐flow have shown that the reduction in recombination between alternative chromosome arrangements can facilitate the fixation of locally adaptive genes in the face of gene flow and contribute to speciation. However, it has proven frustratingly difficult to show empirically that inversions have reduced gene flow and arose during or shortly after the onset of species divergence rather than represent ancestral polymorphisms. Here, we present an analysis of whole genome data from a pair of cactophilic fruit flies, Drosophila mojavensis and D. arizonae, which are reproductively isolated in the wild and differ by several large inversions on three chromosomes. We found an increase in divergence at rearranged compared to colinear chromosomes. Using the density of divergent sites in short sequence blocks we fit a series of explicit models of species divergence in which gene flow is restricted to an initial period after divergence and may differ between colinear and rearranged parts of the genome. These analyses show that D. mojavensis and D. arizonae have experienced postdivergence gene flow that ceased around 270 KY ago and was significantly reduced in chromosomes with fixed inversions. Moreover, we show that these inversions most likely originated around the time of species divergence which is compatible with theoretical models that posit a role of inversions in speciation with gene flow. PMID:25824653

  16. Inorganic arsenic speciation in natural mineral drinking waters by flow-through anodic stripping chronopotentiometry.

    PubMed

    Jedryczko, Dominika; Pohl, Pawel; Welna, Maja

    2016-04-01

    A simple and inexpensive method for chemical speciation of inorganic As in natural mineral drinking waters by using anodic stripping chronopotentiometry (ASCP) in an electrochemical flow-through cell with an Au wire as the working electrode was described in the present work. The presented method is an attractive alternative to laborious and time-consuming procedures requiring pre-separation of various forms of As before their detection by other flow-through and non flow-through stripping methods. The limits of detection were found to be 0.42 µg L(-1) for As(III) and 0.55 µg L(-1) for As(V), obtained at the deposition potentials of -350 mV and -1600 mV, respectively. The accuracy of the method was assessed by the spiking-and-recovery experiments for particular water samples and the recoveries found, being in range from 99% to 105% for As(III) and from 104% to 106% for As(V), respectively, were quantitative. The proposed method was successfully applied to speciation analysis of inorganic As in water samples with a high content of Cu.

  17. Fast weathering of olivine in high-energy shallow seas for cost-effective CO2 capture as a cheap alternative for CCS, and effective mitigation of ocean acidification

    NASA Astrophysics Data System (ADS)

    De Boer, P. L.; Schuiling, R. D.

    2013-12-01

    Spreading of olivine in high-energy shelf seas can counteract human CO2 emissions and ocean acidification against a price well below that of CCS and other methods. In the reaction: Mg(Fe)2SiO4 (olivine) + 4 H2O --> 2 Mg(Fe)2+ + 4 OH- + H4SiO4 followed by 4 OH- + 4 CO2 --> 4 HCO3-, CO2 is consumed, while Mg2+, Fe2+, H4SiO4 and HCO3- are produced. Contrary to the paradigm that olivine weathering in nature is a slow process, flume experiments mimicking high-energy shallow marine environments show a fast reaction, consuming CO2, and raising the pH at short notice. This must be because under immobile conditions a silica coating develops and retards or stops the reaction. In high-energy shallow marine environments such silica coatings are abraded so that the chemical reaction can continue. When kept in motion also large olivine grains and gravels rubbing and bumping against each other and against other sediment grains weather quickly. The experiments also show that fine micron- to silt-sized olivine particles are produced, and that the chemical reaction is fast. The chemical weathering of 7 km3 olivine would be needed on a yearly basis in order to compensate the human CO2 emissions. This seems very much. It is, however, of the same order of magnitude as the volume of fossil fuels (in oil equivalents ~10 km3) that are burnt annually. Olivine is readily available at the Earth' surface on all continents, and past mining efforts show that such volume of 7 km3 is exceeded by existing mines; e.g. the Bingham Canyon open pit mine in Utah has an excavated volume of 25 km3. Hydrocarbons, on the other hand, are commonly retrieved with great efforts, from great depths, and often at remote locations. The annual spreading of large amounts of olivine (and/or serpentinite) in high-energy shelf seas where coarse sand and gravel can be transported, will counteract human CO2 production by fossil fuel burning and ocean acidification against a price well below that of other methods. For

  18. Speciation of volatile organic compound emissions for regional air quality modeling of particulate matter and ozone

    NASA Astrophysics Data System (ADS)

    Makar, P. A.; Moran, M. D.; Scholtz, M. T.; Taylor, A.

    2003-01-01

    mixtures, and that separate treatment for these groups may be required in future air quality model simulations. The post-processing model used here overestimates the organic particle formation relative to measurements, lacks the complexity of a regional air quality model, and is not intended as an alternative to the latter. Results from the post-processing model do, however, provide guidance for the treatment of organic gases and particles in future air quality modeling work. Future air quality model simulations should attempt to speciate primary particulate organic compounds and include more detailed organic compound classes. Future emissions profile measurements should speciate gaseous high-molecular-mass organic compounds and primary organics emitted in particulate form (primary particle emissions are only available as a total particulate mass in currently available emissions data).

  19. Mechanisms of speciation and faunal enrichment in Atlantic parrotfishes.

    PubMed

    Robertson, D Ross; Karg, Frances; Leao de Moura, Rodrigo; Victor, Benjamin C; Bernardi, Giacomo

    2006-09-01

    Relationships based on mtDNA and nDNA sequences were used to assess effects of two major geographic barriers (the >30 myo Atlantic ocean and the approximately 11 myo Amazon-Orinoco outflow) on speciation among Atlantic parrotfishes (Sparisoma and Nicholsina). Allopatric distributions of sister taxa implicate isolating actions of both barriers in all recent speciation in these fishes, with no clear indications that any speciation resulted from other mechanisms. Molecular clock estimates of the timing of lineage splits indicate that both barriers acted by limiting dispersal well after they formed, although the Amazon barrier also may have been a vicariance agent. Fluctuations in sealevel, climate, and ocean-current dynamics over the past approximately 10 my likely produced marked variation in the effectiveness of both barriers, but particularly the Amazon barrier, allowing intermittent dispersal leading to establishment and allopatric speciation. A dynamic Amazon barrier represents a major engine of West Atlantic faunal enrichment that has repeatedly facilitated bidirectional dispersal, allopatric speciation, and remixing of the Caribbean and Brazilian faunas.

  20. Song evolution, speciation, and vocal learning in passerine birds.

    PubMed

    Mason, Nicholas A; Burns, Kevin J; Tobias, Joseph A; Claramunt, Santiago; Seddon, Nathalie; Derryberry, Elizabeth P

    2017-03-01

    Phenotypic divergence can promote reproductive isolation and speciation, suggesting a possible link between rates of phenotypic evolution and the tempo of speciation at multiple evolutionary scales. To date, most macroevolutionary studies of diversification have focused on morphological traits, whereas behavioral traits─including vocal signals─are rarely considered. Thus, although behavioral traits often mediate mate choice and gene flow, we have a limited understanding of how behavioral evolution contributes to diversification. Furthermore, the developmental mode by which behavioral traits are acquired may affect rates of behavioral evolution, although this hypothesis is seldom tested in a phylogenetic framework. Here, we examine evidence for rate shifts in vocal evolution and speciation across two major radiations of codistributed passerines: one oscine clade with learned songs (Thraupidae) and one suboscine clade with innate songs (Furnariidae). We find that evolutionary bursts in rates of speciation and song evolution are coincident in both thraupids and furnariids. Further, overall rates of vocal evolution are higher among taxa with learned rather than innate songs. Taken together, these findings suggest an association between macroevolutionary bursts in speciation and vocal evolution, and that the tempo of behavioral evolution can be influenced by variation in developmental modes among lineages.

  1. Speciation with gene flow on Lord Howe Island

    PubMed Central

    Papadopulos, Alexander S. T.; Baker, William J.; Crayn, Darren; Butlin, Roger K.; Kynast, Ralf G.; Hutton, Ian; Savolainen, Vincent

    2011-01-01

    Understanding the processes underlying the origin of species is a fundamental goal of biology. It is widely accepted that speciation requires an interruption of gene flow between populations: ongoing gene exchange is considered a major hindrance to population divergence and, ultimately, to the evolution of new species. Where a geographic barrier to reproductive isolation is lacking, a biological mechanism for speciation is required to counterbalance the homogenizing effect of gene flow. Speciation with initially strong gene flow is thought to be extremely rare, and few convincing empirical examples have been published. However, using phylogenetic, karyological, and ecological data for the flora of a minute oceanic island (Lord Howe Island, LHI), we demonstrate that speciation with gene flow may, in fact, be frequent in some instances and could account for one in five of the endemic plant species of LHI. We present 11 potential instances of species divergence with gene flow, including an in situ radiation of five species of Coprosma (Rubiaceae, the coffee family). These results, together with the speciation of Howea palms on LHI, challenge current views on the origin of species diversity. PMID:21730151

  2. Extreme changes to gene expression associated with homoploid hybrid speciation.

    PubMed

    Hegarty, Matthew J; Barker, Gary L; Brennan, Adrian C; Edwards, Keith J; Abbott, Richard J; Hiscock, Simon J

    2009-03-01

    Hybridization is an important cause of abrupt speciation. Hybrid speciation without a change in ploidy (homoploid hybrid speciation) is well-established in plants but has also been reported in animals and fungi. A notable example of recent homoploid hybrid speciation is Senecio squalidus (Oxford ragwort), which originated in the UK in the 18th Century following introduction of hybrid material from a hybrid zone between S. chrysanthemifolius and S. aethnensis on Mount Etna, Sicily. To investigate genetic divergence between these taxa, we used complementary DNA microarrays to compare patterns of floral gene expression. These analyses revealed major differences in gene expression between the parent species and wild and resynthesized S. squalidus. Comparisons of gene expression between S. aethnensis, S. chrysanthemifolius and natural S. squalidus identified genes potentially involved in local environmental adaptation. The analysis also revealed non-additive patterns of gene expression in the hybrid relative to its progenitors. These expression changes were more dramatic and widespread in resynthesized hybrids than in natural S. squalidus, suggesting that a unique expression pattern may have been fixed during the allopatric divergence of British S. squalidus. We speculate that hybridization-induced gene-expression change may provide an immediate source of novel phenotypic variation upon which selection can act to facilitate homoploid hybrid speciation in plants.

  3. On the origin of species by sympatric speciation

    NASA Astrophysics Data System (ADS)

    Dieckmann, Ulf; Doebeli, Michael

    1999-07-01

    Understanding speciation is a fundamental biological problem. It is believed that many species originated through allopatric divergence, where new species arise from geographically isolated populations of the same ancestral species. In contrast, the possibility of sympatric speciation (in which new species arise without geographical isolation) has often been dismissed, partly because of theoretical difficulties,. Most previous models analysing sympatric speciation concentrated on particular aspects of the problem while neglecting others. Here we present a model that integrates a novel combination of different features and show that sympatric speciation is a likely outcome of competition for resources. We use multilocus genetics to describe sexual reproduction in an individual-based model, and we consider the evolution of assortative mating (where individuals mate preferentially with like individuals) depending either on an ecological character affecting resource use or on a selectively neutral marker trait. In both cases, evolution of assortative mating often leads to reproductive isolation between ecologically diverging subpopulations. When assortative mating depends on a marker trait, and is therefore not directly linked to resource competition, speciation occurs when genetic drift breaks the linkage equilibrium between the marker and the ecological trait. Our theory conforms well with mounting empirical evidence for the sympatric origin of many species.

  4. Genomics of Rapid Incipient Speciation in Sympatric Threespine Stickleback.

    PubMed

    Marques, David A; Lucek, Kay; Meier, Joana I; Mwaiko, Salome; Wagner, Catherine E; Excoffier, Laurent; Seehausen, Ole

    2016-02-01

    Ecological speciation is the process by which reproductively isolated populations emerge as a consequence of divergent natural or ecologically-mediated sexual selection. Most genomic studies of ecological speciation have investigated allopatric populations, making it difficult to infer reproductive isolation. The few studies on sympatric ecotypes have focused on advanced stages of the speciation process after thousands of generations of divergence. As a consequence, we still do not know what genomic signatures of the early onset of ecological speciation look like. Here, we examined genomic differentiation among migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. Importantly, these ecotypes started diverging less than 150 years ago. We obtained 34,756 SNPs with restriction-site associated DNA sequencing and identified genomic islands of differentiation using a Hidden Markov Model approach. Consistent with incipient ecological speciation, we found significant genomic differentiation between ecotypes both in sympatry and parapatry. Of 19 islands of differentiation resisting gene flow in sympatry, all were also differentiated in parapatry and were thus likely driven by divergent selection among habitats. These islands clustered in quantitative trait loci controlling divergent traits among the ecotypes, many of them concentrated in one region with low to intermediate recombination. Our findings suggest that adaptive genomic differentiation at many genetic loci can arise and persist in sympatry at the very early stage of ecotype divergence, and that the genomic architecture of adaptation may facilitate this.

  5. Bromine speciation in hydrous haplogranitic melts up to 7 GPa

    NASA Astrophysics Data System (ADS)

    Cochain, B.; de Grouchy, C.; Crepisson, C.; Kantor, I.; Irifune, T.; Sanloup, C.

    2013-12-01

    Halogens are minor volatiles in the Earth's mantle and crust, but they have significant and specific influences on magmatic and degassing processes. They also provide insights about subsurface magma movement and eruption likelihood in subduction-related volcanism. Their speciation in silicate melts affects volatile exsolution, rheology, and the thermodynamic properties of the melts but still remains relatively unknown. A few studies have explored halogen speciation at room conditions, i.e. in glasses but no firm conclusion has yet been reached. Furthermore, halogen speciation remains unexplored at high pressures and temperatures. In this work we investigate the speciation of Br in subduction-related melt (hydrous haplogranite melt) up to 1200°C and 7 GPa using X-ray absorption spectroscopy (XANES and EXAFS) at the Br K-edge. High P-T conditions were generated by the Paris-Edinburgh press. The use of nanocrystalline diamond capsules enabled us to avoid glitches in the EXAFS spectra. The results provide valuable information on Br speciation and its evolution with pressure. It gives insights into solubility mechanisms for halogens in magmas at depth and on their degassing from the melt. In addition, we were able to identify quench effects on the atomic environment of Br by comparison of high P-T in-situ spectra and ex-situ spectra recorded on quenched samples.

  6. Pleistocene phylogeographic effects on avian populations and the speciation process.

    PubMed Central

    Avise, J C; Walker, D

    1998-01-01

    Pleistocene biogeographic events have traditionally been ascribed a major role in promoting speciations and in sculpting the present-day diversity and distributions of vertebrate taxa. However, this paradigm has recently come under challenge from a review of interspecific mtDNA genetic distances in birds: most sister-species separations dated to the Pliocene. Here we summarize the literature on intraspecific mtDNA phylogeographic patterns in birds and reinterpret the molecular evidence bearing on Pleistocene influences. At least 37 of the 63 avian species surveyed (59%) are sundered into recognizable phylogeographic units, and 28 of these separations (76%) trace to the Pleistocene. Furthermore, use of phylogroup separation times within species as minimum estimates of 'speciation durations' also indicates that many protracted speciations, considered individually, probably extended through time from Pliocene origins to Pleistocene completions. When avian speciation is viewed properly as an extended temporal process rather than as a point event, Pleistocene conditions appear to have played an active role both in initiating major phylogeographic separations within species, and in completing speciations that had been inaugurated earlier. Whether the Pleistocene was exceptional in these regards compared with other geological times remains to be determined. PMID:9569664

  7. Genomics of Rapid Incipient Speciation in Sympatric Threespine Stickleback

    PubMed Central

    Marques, David A.; Lucek, Kay; Meier, Joana I.; Mwaiko, Salome; Wagner, Catherine E.; Excoffier, Laurent; Seehausen, Ole

    2016-01-01

    Ecological speciation is the process by which reproductively isolated populations emerge as a consequence of divergent natural or ecologically-mediated sexual selection. Most genomic studies of ecological speciation have investigated allopatric populations, making it difficult to infer reproductive isolation. The few studies on sympatric ecotypes have focused on advanced stages of the speciation process after thousands of generations of divergence. As a consequence, we still do not know what genomic signatures of the early onset of ecological speciation look like. Here, we examined genomic differentiation among migratory lake and resident stream ecotypes of threespine stickleback reproducing in sympatry in one stream, and in parapatry in another stream. Importantly, these ecotypes started diverging less than 150 years ago. We obtained 34,756 SNPs with restriction-site associated DNA sequencing and identified genomic islands of differentiation using a Hidden Markov Model approach. Consistent with incipient ecological speciation, we found significant genomic differentiation between ecotypes both in sympatry and parapatry. Of 19 islands of differentiation resisting gene flow in sympatry, all were also differentiated in parapatry and were thus likely driven by divergent selection among habitats. These islands clustered in quantitative trait loci controlling divergent traits among the ecotypes, many of them concentrated in one region with low to intermediate recombination. Our findings suggest that adaptive genomic differentiation at many genetic loci can arise and persist in sympatry at the very early stage of ecotype divergence, and that the genomic architecture of adaptation may facilitate this. PMID:26925837

  8. Reproductive character displacement and speciation in periodical cicadas, with description of new species, 13-year Magicicada neotredecem.

    PubMed

    Marshall, D C; Cooley, J R

    2000-08-01

    Acoustic mate-attracting signals of related sympatric, synchronic species are always distinguishable, but those of related allopatric species sometimes are not, thus suggesting that such signals may evolve to "reinforce" premating species isolation when similar species become sympatric. This hypothesis predicts divergences restricted to regions of sympatry in partially overlapping species, but such "reproductive character displacement" has rarely been confirmed. We report such a case in the acoustic signals of a previously unrecognized 13-year periodical cicada species, Magicicada neotredecim, described here as a new species (see Appendix). Where M. neotredecim overlaps M. tredecim in the central United States, the dominant male call pitch (frequency) of M. neotredecim increases from approximately 1.4 kHz to 1.7 kHz, whereas that of M. tredecim remains comparatively stable. The average preferences of female M. neotredecim for call pitch show a similar geographic pattern, changing with the call pitch of conspecific males. Magicicada neotredecim differs from 13-year M. tredecim in abdomen coloration, mitochondrial DNA, and call pitch, but is not consistently distinguishable from 17-year M. septendecim; thus, like other Magicicada species, M. neotredecim appears most closely related to a geographically adjacent counterpart with the alternative life cycle. Speciation in Magicicada may be facilitated by life-cycle changes that create temporal isolation, and reinforcement could play a role by fostering divergence in premating signals prior to speciation. We present two theories of Magicicada speciation by life-cycle evolution: "nurse-brood facilitation" and "life-cycle canalization."

  9. A speciation gene for left-right reversal in snails results in anti-predator adaptation.

    PubMed

    Hoso, Masaki; Kameda, Yuichi; Wu, Shu-Ping; Asami, Takahiro; Kato, Makoto; Hori, Michio

    2010-01-01

    How speciation genes can spread in a population is poorly understood. In land snails, a single gene for left-right reversal could be responsible for instant speciation, because dextral and sinistral snails have difficulty in mating. However, the traditional two-locus speciation model predicts that a mating disadvantage for the reversal should counteract this speciation. In this study, we show that specialized snake predation of the dextral majority drives prey speciation by reversal. Our experiments demonstrate that sinistral Satsuma snails (Stylommatophora: Camaenidae) survive predation by Pareas iwasakii (Colubroidea: Pareatidae). Worldwide biogeography reveals that stylommatophoran snail speciation by reversal has been accelerated in the range of pareatid snakes, especially in snails that gain stronger anti-snake defense and reproductive isolation from dextrals by sinistrality. Molecular phylogeny of Satsuma snails further provides intriguing evidence of repetitive speciation under snake predation. Our study demonstrates that a speciation gene can be fixed in populations by positive pleiotropic effects on survival.

  10. Neptunium redox speciation at the illite surface

    NASA Astrophysics Data System (ADS)

    Marsac, Rémi; Banik, Nidhu lal; Lützenkirchen, Johannes; Marquardt, Christian Michael; Dardenne, Kathy; Schild, Dieter; Rothe, Joerg; Diascorn, Alexandre; Kupcik, Tomas; Schäfer, Thorsten; Geckeis, Horst

    2015-03-01

    Neptunium (Np(V)) sorption onto a purified illite is investigated as a function of pH (3-10) and [NpVO2+]tot(3 × 10-8-3 × 10-4 M) in 0.1 M NaCl under Ar atmosphere. After about one week reaction time, only insignificant variation of Np sorption is observed and the establishment of reaction equilibrium can be assumed. Surprisingly, solid-liquid distribution ratios (Rd) are clearly higher than those measured for Np(V) sorption onto illite under aerobic conditions. The observation that Rd increases with decreasing pe (pe = -log ae-) suggests partial reduction to Np(IV), although measured redox potentials (pe values) at a first glance suggest the predominance of Np(V). Reduction to Np(IV) at the illite surface could indeed be confirmed by X-ray absorption near-edge spectroscopy (XANES). Np speciation in presence of the purified Na-illite under given conditions is consistently described by applying the 2 sites protolysis non-electrostatic surface complexation and cation exchange model. Measured pe data are taken to calculate Np redox state and surface complexation constants for Np(IV) are derived by applying a data fitting procedure. Constants are very consistent with results obtained by applying an existing linear free energy relationship (LFER). Taking Np(IV) surface complexation constants into account shifts the calculated Np(V)/Np(IV) redox borderline in presence of illite surfaces by 3-5 pe units (0.2-0.3 V) towards redox neutral conditions. Our study suggests that Np(V) reduction in presence of a sorbing mineral phase is thermodynamically favored.

  11. Arsenic speciation and reactivity in poultry litter

    USGS Publications Warehouse

    Arai, Y.; Lanzirotti, A.; Sutton, S.; Davis, J.A.; Sparks, D.L.

    2003-01-01

    Recent U.S. government action to lower the maximum concentration levels (MCL) of total arsenic (As) (10 ppb) in drinking water has raised serious concerns about the agricultural use of As-containing biosolids such as poultry litter (PL). In this study, solid-state chemical speciation, desorbability, and total levels of As in PL and long-term amended soils were investigated using novel synchrotronbased probing techniques (microfocused (??) synchrotron X-ray fluorescence (SXRF) and ??-X-ray absorption near-edge structure (XANES) spectroscopies) coupled with chemical digestion and batch experiments. The total As levels in the PL were as high as ???50 mg kg-1, and As(II/III and V) was always concentrated in abundant needle-shaped microscopic particles (???20/ ??m x 850 ??m) associated with Ca, Cu, and Fe and to a lesser extent with S, CI, and Zn. Postedge XANES features of litter particles are dissimilar to those of the organo-As(V) compound in poultry feed (i.e., roxarsone), suggesting possible degradation/transformation of roxarsone in the litter and/or in poultry digestive tracts. The extent of As desorption from the litter increased with increasing time and pH from 4.5 to 7, but at most 15% of the total As was released after 5 d at pH 7, indicating the presence of insoluble phases and/or strongly retained soluble compounds. No significant As accumulation (< 15 mg kg-1) was found in long-term PL-a mended agricultural surface soils. This suggests that As in the PL may have undergone surface and subsurface transport processes. Our research results raise concerns about long-term PL amendment effects on As contamination in surrounding soilwater environments.

  12. Aluminium (Al) fractionation and speciation; getting closer to describing the factors influencing Al(3+) in water impacted by acid mine drainage.

    PubMed

    Chamier, Jessica; Wicht, Merrill; Cyster, Lilburne; Ndindi, Nosintu P

    2015-07-01

    Acid mine drainage (AMD) severely impacts the water chemistry of a receiving resource, changing the occurrence, speciation and toxicity of metals such as Aluminium (Al). The toxicity of Al is determined by its speciation represented by the labile monomer Al fraction or Al(3+). The purpose of the study was to combine fractionation and Visual MINTEQ speciation to calculate the effect of AMD altered water chemistry on Al speciation and Al(3+) concentration. Water in rivers impacted by AMD presented with monomeric Al (Almon) concentrations between 0.35 and 15.37mgL(-)(1) which existed almost exclusively in the toxic labile form (98%). For the reference site, Almon was less than 2% (10μgL(-1)), suggesting significantly lower Al toxicity. Principal component analysis plots illustrated that labile Al was directly related to the total Al and iron concentrations and strongly influenced by parameters such as pH, electrical conductivity, sulphate and dissolved organic carbon. Visual MINTEQ modelling was used to determine the primary Al species distribution. The dominant form of Al in AMD impacted water was AlSO4(+), which increased proportionally with the sulphate and Al(3+) concentration. Heavily impacted areas, presented with an average of 1mgmL(-)(1) Al(3+), which poses a potential human health risk. A novel centrifugal ultrafiltration method was investigated as an alternative to determining Almon to simplify the speciation of Al. Monomeric and centrifugal ultrafiltrated (<10kD) Al fractions were significantly similar (p=0.74), suggesting that ultrafiltration may present a time, energy and cost saving alternative to organic extraction of Almon.

  13. Inference of Gene Flow in the Process of Speciation: An Efficient Maximum-Likelihood Method for the Isolation-with-Initial-Migration Model

    PubMed Central

    Costa, Rui J.; Wilkinson-Herbots, Hilde

    2017-01-01

    The isolation-with-migration (IM) model is commonly used to make inferences about gene flow during speciation, using polymorphism data. However, it has been reported that the parameter estimates obtained by fitting the IM model are very sensitive to the model’s assumptions—including the assumption of constant gene flow until the present. This article is concerned with the isolation-with-initial-migration (IIM) model, which drops precisely this assumption. In the IIM model, one ancestral population divides into two descendant subpopulations, between which there is an initial period of gene flow and a subsequent period of isolation. We derive a very fast method of fitting an extended version of the IIM model, which also allows for asymmetric gene flow and unequal population sizes. This is a maximum-likelihood method, applicable to data on the number of segregating sites between pairs of DNA sequences from a large number of independent loci. In addition to obtaining parameter estimates, our method can also be used, by means of likelihood-ratio tests, to distinguish between alternative models representing the following divergence scenarios: (a) divergence with potentially asymmetric gene flow until the present, (b) divergence with potentially asymmetric gene flow until some point in the past and in isolation since then, and (c) divergence in complete isolation. We illustrate the procedure on pairs of Drosophila sequences from ∼30,000 loci. The computing time needed to fit the most complex version of the model to this data set is only a couple of minutes. The R code to fit the IIM model can be found in the supplementary files of this article. PMID:28193727

  14. Rapid acceleration of plant speciation during the Anthropocene.

    PubMed

    Thomas, Chris D

    2015-08-01

    Speciation rates need to be considered when estimating human impacts on the numbers of species on Earth, given that past mass extinctions have been followed by the accelerated origination of new taxa. Here, I suggest that the Anthropocene is already exhibiting a greatly accelerated plant speciation rate due to agriculture, horticulture, and the human-mediated transport of species, followed by hybridisation. For example, more new plant species have come into existence in Europe over the past three centuries than have been documented as becoming extinct over the same period, even though most new hybrid-origin species are likely to remain undetected. Current speciation rates are unusually high and they could be higher than during or after previous mass extinctions.

  15. Dispersal, Genetic Differentiation and Speciation in Estuarine Organisms

    NASA Astrophysics Data System (ADS)

    Bilton, D. T.; Paula, J.; Bishop, J. D. D.

    2002-12-01

    For some of their occupants, estuaries represent spatially discrete habitats, isolated from each other by barriers to dispersal or physiological tolerance. We present contrasting strategies for the retention or export of larvae from their estuary of origin, and consider the implications these have on population structure and divergence. Reported patterns of genetic differentiation and inferred gene flow in estuarine taxa (principally animals) are reviewed, and difficulties in the interpretation of existing genetic data discussed. Species concepts and models of speciation relevant to estuaries are outlined, and patterns of speciation of estuarine taxa reviewed. It is concluded that estuarine environments tend to restrict gene flow and impose distinct selective regimes, generating physiologically adapted populations divergent from their marine counterparts, and the potential for in situ speciation in complete or partial isolation. The resulting taxa may represent sibling or cryptic species groups of truly estuarine origin, rather than simply estuarine populations of marine eurytopes.

  16. The relationship of selenium tolerance and speciation in Lecythidaceae species.

    PubMed

    Németh, Anikó; García Reyes, Juan Francisco; Kosáry, Judit; Dernovics, Mihály

    2013-12-01

    Comparative study of selenium (Se) speciation in hyperaccumulator plants offers an interesting challenge from the analytical point of view. In our study the application of a sophisticated sample clean-up procedure and the combination of elemental and molecular mass spectrometric methods led to the identification of several new selenocompounds. The difference between the Se speciation of the primary accumulator Lecythis minor and the secondary accumulator Bertholletia excelsa confirmed the current opinion that the speciation pattern in hyperaccumulator plants is principally related to the mechanism of accumulation and not to taxonomy. The most abundant new selenocompounds were found to be the derivatives of selenohomocysteine (SeHCy) and selenomethionine (SeMet), including fatty acid metabolism related compounds. A series of SeHCy derived species containing multiple Se atoms (>2) was also detected and their structures were validated by the synthesis of their S-Se analogues.

  17. Computer simulations of sympatric speciation in a simple food web

    NASA Astrophysics Data System (ADS)

    Luz-Burgoa, K.; Dell, Tony; de Oliveira, S. Moss

    2005-07-01

    Galapagos finches, have motivated much theoretical research aimed at understanding the processes associated with the formation of the species. Inspired by them, in this paper we investigate the process of sympatric speciation in a simple food web model. For that we modify the individual-based Penna model that has been widely used to study aging as well as other evolutionary processes. Initially, our web consists of a primary food source and a single herbivore species that feeds on this resource. Subsequently we introduce a predator that feeds on the herbivore. In both instances we manipulate directly a basal resource distribution and monitor the changes in the populations. Sympatric speciation is obtained for the top species in both cases, and our results suggest that the speciation velocity depends on how far up, in the food chain, the focus population is feeding. Simulations are done with three different sexual imprintinglike mechanisms, in order to discuss adaptation by natural selection.

  18. Plutonium Speciation in Support of Oxidative-Leaching Demonstration Test

    SciTech Connect

    Sinkov, Sergey I.

    2007-10-31

    Bechtel National, Inc. (BNI) is evaluating the plutonium speciation in caustic solutions that reasonably represent the process streams from the oxidative-leaching demonstration test. Battelle—Pacific Northwest Division (PNWD) was contracted to develop a spectrophotometric method to measure plutonium speciation at submicromolar (< 10-6 M) concentrations in alkaline solutions in the presence of chromate and carbonate. Data obtained from the testing will be used to identify the oxidation state of Pu(IV), Pu(V), and Pu(VI) species, which potentially could exist in caustic leachates. Work was initially conducted under contract number 24590-101-TSA-W000-00004 satisfying the needs defined in Appendix C of the Research and Technology Plan TSS A-219 to evaluate the speciation of chromium, plutonium, and manganese before and after oxidative leaching. In February 2007, the contract mechanism was switched to Pacific Northwest National Laboratory (PNNL) Operating Contract MOA: 24590-QL-HC9-WA49-00001.

  19. Patterns of plant speciation in the Cape floristic region.

    PubMed

    van der Niet, Timotheüs; Johnson, Steven D

    2009-04-01

    Plant species have accumulated in the Cape region of southern Africa to a much greater degree than in areas of equivalent size in the rest of the subcontinent. Although this could be a consequence simply of lower extinction rates in the Cape, most researchers have invoked high rates of ecological speciation, driven by unique aspects of the Cape environment, as the primary explanation for this richness. To assess these ideas, we analyzed the frequencies of ecological shifts among 188 sister species pairs obtained from molecular phylogenies of eight Cape clades. Ecological shifts were evident in 80% of sister species pairs, with general habitat, pollinator, and fire-survival strategy shifts being especially frequent. Contrary to an established idea that shifts in soil type are frequently associated with speciation of Cape taxa, these shifts were relatively rare, occurring in just 17% of species pairs. More cases of sister species divergence are accompanied solely by floral than by vegetative diversification, suggesting an important role for pollinator-driven speciation. In an analysis of two large orchid genera that have radiated in both the Cape and the rest of southern Africa, the frequency of ecological shifts (general habitat, soil type, altitude and flowering time), did not differ between sister species pairs in the Cape region and those outside it. Despite suggestions that Cape plants tend to have small range sizes and show fine-scale patterns of speciation, range size did not differ significantly between species in the Cape and those outside it. We conclude that ecological speciation is likely to have been important for radiation of the Cape flora, but there is no evidence as yet for special "Cape" patterns of ecological speciation.

  20. Sexual selection and speciation in mammals, butterflies and spiders.

    PubMed Central

    Gage, Matthew J G; Parker, Geoffrey A; Nylin, Soren; Wiklund, Christer

    2002-01-01

    Recently refined evolutionary theories propose that sexual selection and reproductive conflict could be drivers of speciation. Male and female reproductive optima invariably differ because the potential reproductive rate of males almost always exceeds that of females: females are selected to maximize mate 'quality', while males can increase fitness through mate 'quantity'. A dynamic, sexually selected conflict therefore exists in which 'competitive' males are selected to override the preference tactics evolved by 'choosy' females. The wide variation across taxa in mating systems therefore generates variance in the outcome of intrasexual conflict and the strength of sexual selection: monandry constrains reproductive heterozygosity and allows female choice to select and maintain particular (preferred) genes; polyandry promotes reproductive heterozygosity and will more likely override female choice. Two different theories predict how sexual selection might influence speciation. Traditional ideas indicate that increased sexual selection (and hence conflict) generates a greater diversity of male reproductive strategies to be counteracted by female mate preferences, thus providing elevated potentials for speciation as more evolutionary avenues of male-female interaction are created. A less intuitively obvious theory proposes that increased sexual selection and conflict constrains speciation by reducing the opportunities for female mate choice under polyandry. We use a comparative approach to test these theories by investigating whether two general measures of sexual selection and the potential for sexual conflict have influenced speciation. Sexual size dimorphism (across 480 mammalian genera, 105 butterfly genera and 148 spider genera) and degree of polyandry (measured as relative testes size in mammals (72 genera) and mating frequency in female butterflies (54 genera)) showed no associations with the variance in speciosity. Our results therefore show that speciation

  1. SPECIATE 4.4: The Bridge Between Emissions Characterization and Modeling

    EPA Science Inventory

    SPECIATE is the U.S. Environmental Protection Agency’s (EPA) repository of volatile organic gas and particulate matter (PM) speciation profiles of air pollution sources. Some of the many uses of these source profiles include: (1) creating speciated emissions inventories for...

  2. Examination of Arsenic Speciation in Sulfidic Solutions Using X-ray Absorption Spectroscopy

    EPA Science Inventory

    The chemical speciation of arsenic in sulfidic waters is complicated by the existence of thioarsenic species. The purpose of this research was to use advanced spectroscopy techniques along with speciation modeling and chromatography to elucidate the chemical speciation of As in ...

  3. XANES Identification of Plutonium Speciation in RFETS Samples

    SciTech Connect

    LoPresti, V.; Conradson, S.D.; Clark, D.L.

    2009-06-03

    Using primarily X-ray absorption near edge spectroscopy (XANES) with standards run in tandem with samples, probable plutonium speciation was determined for 13 samples from contaminated soil, acid-splash or fire-deposition building interior surfaces, or asphalt pads from the Rocky Flats Environmental Technology Site (RFETS). Save for extreme oxidizing situations, all other samples were found to be of Pu(IV) speciation, supporting the supposition that such contamination is less likely to show mobility off site. EXAFS analysis conducted on two of the 13 samples supported the validity of the XANES features employed as determinants of the plutonium valence.

  4. Hybrid speciation and independent evolution in lineages of alpine butterflies.

    PubMed

    Nice, Chris C; Gompert, Zachariah; Fordyce, James A; Forister, Matthew L; Lucas, Lauren K; Buerkle, C Alex

    2013-04-01

    The power of hybridization between species to generate variation and fuel adaptation is poorly understood despite long-standing interest. There is, however, increasing evidence that hybridization often generates biodiversity, including via hybrid speciation. We tested the hypothesis of hybrid speciation in butterflies occupying extreme, high-altitude habitats in four mountain ranges in western North America with an explicit, probabilistic model, and genome-wide DNA sequence data. Using this approach, in concert with ecological experiments and observations and morphological data, we document three lineages of hybrid origin. These lineages have different genome admixture proportions and distinctive trait combinations that suggest unique and independent evolutionary histories.

  5. [Speciation and its mechanisms: conceptual background and recent advances].

    PubMed

    Colley, Eduardo; Fischer, Marta Luciane

    2013-10-01

    This paper presents a historical approach on general concepts of speciation and its mechanisms, from the primordial ideas to the most recent theories that seek to elucidate the origin of biodiversity. It is common knowledge that speciation is a controversial and complex issue that encompasses virtually all the lines of research of biology, in addition to geology and paleontology. The main objective of the paper is to clarify the theoretical concepts on the origin of the animal species, in the chronological order in which they became established throughout the whole of the development of evolutionary biology as a science.

  6. Sympatric speciation: compliance with phenotype diversification from a single genotype.

    PubMed Central

    Kaneko, K; Yomo, T

    2000-01-01

    A novel mechanism for sympatric speciation that takes into account complex bioprocesses within each individual organism is proposed. According to dynamical systems theory, organisms with identical genotypes can possess differentiated physiological states and may coexist 'symbiotically' through appropriate mutual interaction. With mutations, the phenotypically differentiated organisms gradually come to possess distinct genotypes while maintaining their symbiotic relationship. This symbiotic speciation is robust against sexual recombination, because offspring of mixed parentage with intermediate genotypes are less fit than their parents. This leads to sterility of the hybrid. Accordingly, a basis for mating preference also arises. PMID:11133025

  7. Alternative fuels

    NASA Technical Reports Server (NTRS)

    Grobman, J. S.; Butze, H. F.; Friedman, R.; Antoine, A. C.; Reynolds, T. W.

    1977-01-01

    Potential problems related to the use of alternative aviation turbine fuels are discussed and both ongoing and required research into these fuels is described. This discussion is limited to aviation turbine fuels composed of liquid hydrocarbons. The advantages and disadvantages of the various solutions to the problems are summarized. The first solution is to continue to develop the necessary technology at the refinery to produce specification jet fuels regardless of the crude source. The second solution is to minimize energy consumption at the refinery and keep fuel costs down by relaxing specifications.

  8. Fast pulsed excitation wiggler or undulator

    DOEpatents

    van Steenbergen, Arie

    1990-01-01

    A fast pulsed excitation, electromagnetic undulator or wiggler, employing geometrically alternating substacks of thin laminations of ferromagnetic material, together with a single turn current loop excitation of the composite assembly, of such shape and configuration that intense, spatially alternating, magnetic fields are generated; for use as a pulsed mode undulator or wiggler radiator, for use in a Free Electron Laser (FEL) type radiation source or, for use in an Inverse Free Electron Laser (IFEL) charged particle accelerator.

  9. Fast dynamic processes of solar radiation

    SciTech Connect

    Tomson, Teolan

    2010-02-15

    This paper studies dynamic processes of fast-alternating solar radiation which are assessed by alternation of clouds. Most attention is devoted to clouds of type Cumulus Humilis, identified through visual recognition and/or a specially constructed automatic sensor. One second sampling period was used. Recorded data series were analyzed with regard to duration of illuminated 'windows' between shadows, their stochastic intervals, fronts and the magnitude of increments of solar irradiance. (author)

  10. 75 FR 38821 - Agency Information Collection Activities: Application-Alternative Inspection Services (SENTRI...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-06

    ... Information Collection Activities: Application-- Alternative Inspection Services (SENTRI Application and FAST... Application (CBP Form 823S) and the FAST Commercial Driver Application (CBP Form 823F). This request for...: Application--Alternative Inspection Services including the SENTRI Application and the FAST Commercial...

  11. Transformation of heavy metal speciation during sludge drying: mechanistic insights

    SciTech Connect

    Weng, Huanxin; Ma, Xue-Wen; Fu, Feng-Xia; Zhang, Jin-Jun; Liu, Zan; Tian, Li-Xun; Liu, Chongxuan

    2014-01-30

    Speciation can fundamentally affect on the stability and toxicity of heavy metals in sludge from wastewater treatment plants. This research investigated the speciation of heavy metals in sludge from both municipal and industrial sources, and metal speciation change as a result of drying process to reduce sludge volume. The changes in sludge properties including sludge moisture content, temperature, density, and electrical conductivity were also monitored to provide insights into the mechanisms causing the change in heavy metal speciation. The results show that the drying process generally stabilized the Cr, Cu, Cd and Pb in sludge by transforming acid-soluble, reducible and oxidizable species into structurally stable forms. Such transformation and stabilization occurred regardless of the sludge source and type, and were primarily caused by the changes in sludge properties associated with decomposition of organic matter and sulfide. The results enhanced our understanding of the geochemical behavior of heavy metals in municipal sludge, and are useful for designing a treatment system for environment-friendly disposal of sludge.

  12. Speciation of Iberian diving beetles in Pleistocene refugia (Coleoptera, Dytiscidae).

    PubMed

    Ribera, Ignacio; Vogler, Alfried P

    2004-01-01

    The Mediterranean basin is an area of high diversity and endemicity, but the age and origin of its fauna are still largely unknown. Here we use species-level phylogenies based on approximately 1300 base pairs of the genes 16S rRNA and cytochrome oxidase I to establish the relationships of 27 of the 34 endemic Iberian species of diving beetles in the family Dytiscidae, and to investigate their level of divergence. Using a molecular clock approach, 18-19 of these species were estimated to be of Pleistocene origin, with four to six of them from the Late Pleistocene ( approximately 100 000 years). A second, lower speciation frequency peak was assigned to Late Miocene or Early Pliocene. Analysis of the distributional ranges showed that endemic species placed in the tip nodes of the trees are significantly more likely to be allopatric with their sisters than endemic species at lower node levels. Allopatric sister species are also significantly younger than sympatric clades, in agreement with an allopatric mode of speciation and limited subsequent range movement. These results strongly suggest that for some taxa Iberian populations were isolated during the Pleistocene long enough to speciate, and apparently did not expand their ranges to recolonize areas north of the Pyrenees. This is in contradiction to observations from fossil beetles in areas further north, which document large range movements associated with the Pleistocene glacial cycles hypothesized to suppress population isolation and allopatric speciation.

  13. Plant evolution: pulses of extinction and speciation in gymnosperm diversity.

    PubMed

    Davis, Charles C; Schaefer, Hanno

    2011-12-20

    Living gymnosperms represent the survivors of ancient seed plant lineages whose fossil record reaches back 270 million years. Two recent studies find that recent pulses of extinction and speciation have shaped today's gymnosperm diversity, contradicting the widespread assumption that gymnosperms have remained largely unchanged for tens of millions of years.

  14. Latitude, elevational climatic zonation and speciation in New World vertebrates

    PubMed Central

    Cadena, Carlos Daniel; Kozak, Kenneth H.; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M.; Bowie, Rauri C. K.; Carnaval, Ana C.; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E.; Sanders, Nathan J.; Schneider, Christopher J.; VanDerWal, Jeremy; Zamudio, Kelly R.; Graham, Catherine H.

    2012-01-01

    Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions. PMID:21632626

  15. Latitude, elevational climatic zonation and speciation in New World vertebrates.

    PubMed

    Cadena, Carlos Daniel; Kozak, Kenneth H; Gómez, Juan Pablo; Parra, Juan Luis; McCain, Christy M; Bowie, Rauri C K; Carnaval, Ana C; Moritz, Craig; Rahbek, Carsten; Roberts, Trina E; Sanders, Nathan J; Schneider, Christopher J; VanDerWal, Jeremy; Zamudio, Kelly R; Graham, Catherine H

    2012-01-07

    Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions.

  16. Microscale characterization of sulfur speciation in lake sediments.

    PubMed

    Zeng, Teng; Arnold, William A; Toner, Brandy M

    2013-02-05

    Prairie pothole lakes (PPLs) are naturally sulfur-enriched wetlands in the glaciated prairie region of North America. High sulfate levels and dynamic hydrogeochemistry in combination render PPLs a unique environment to explore the speciation of sedimentary sulfur (S). The goals of this research were to define and quantify the solid-phase S pools in PPL sediments and track seasonal dynamics of S speciation. A quantitative X-ray microprobe method was developed based on S 1s X-ray absorption near-edge structure (XANES) spectroscopy and multienergy X-ray fluorescence mapping. Three S pools-pyritic S, reduced organic S (organic mono- and disulfide), and oxidized S (inorganic sulfate, ester sulfate, and sulfonate)-were identified in PPL sediments. No significant seasonal variation was evident for total S, but S speciation showed a seasonal response. During the spring-summer transition, the reduced organic S decreased from 55 to 15 mol %, with a concomitant rise in the oxidized S. During the summer-fall transition, the trend reversed and the reduced organic S grew to 75 mol % at the expense of the oxidized S. The pyritic S, on the other hand, remained relatively constant (∼22 mol %) over time. The seasonal changes in S speciation have strong potential to force the cycling of elements such as mercury in prairie wetlands.

  17. Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography.

    PubMed

    Mittelbach, Gary G; Schemske, Douglas W; Cornell, Howard V; Allen, Andrew P; Brown, Jonathan M; Bush, Mark B; Harrison, Susan P; Hurlbert, Allen H; Knowlton, Nancy; Lessios, Harilaos A; McCain, Christy M; McCune, Amy R; McDade, Lucinda A; McPeek, Mark A; Near, Thomas J; Price, Trevor D; Ricklefs, Robert E; Roy, Kaustuv; Sax, Dov F; Schluter, Dolph; Sobel, James M; Turelli, Michael

    2007-04-01

    A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.

  18. Cytonuclear incompatibility contributes to the early stages of speciation.

    PubMed

    Barnard-Kubow, Karen B; So, Nina; Galloway, Laura F

    2016-12-01

    Genetic incompatibility is a hallmark of speciation. Cytonuclear incompatibilities are proposed to be among the first genetic barriers to arise during speciation. Accordingly, reproductive isolation (RI) within species should be heavily influenced by interactions between the organelle and nuclear genomes. However, there are few clear examples of cytonuclear incompatibility within a species. Here, we show substantial postzygotic RI in first-generation hybrids between differentiated populations of an herbaceous plant (up to 92% reduction in fitness). RI was primarily due to germination and survival, with moderate RI for pollen viability. RI for survival was asymmetric and caused by cytonuclear incompatibility, with the strength of incompatibility linearly related to chloroplast genetic distance. This cytonuclear incompatibility may be the result of a rapidly evolving plastid genome. Substantial asymmetric RI was also found for germination, but was not associated with cytonuclear incompatibility, indicating endosperm or maternal-zygote incompatibilities. These results demonstrate that cytonuclear incompatibility contributes to RI within species, suggesting that initial rates of speciation could be influenced by rates of organelle evolution. However, other genetic incompatibilities are equally important, indicating that even at early stages, speciation can be a complex process involving multiple genes and incompatibilities.

  19. Model inadequacy and mistaken inferences of trait-dependent speciation.

    PubMed

    Rabosky, Daniel L; Goldberg, Emma E

    2015-03-01

    Species richness varies widely across the tree of life, and there is great interest in identifying ecological, geographic, and other factors that affect rates of species proliferation. Recent methods for explicitly modeling the relationships among character states, speciation rates, and extinction rates on phylogenetic trees- BiSSE, QuaSSE, GeoSSE, and related models-have been widely used to test hypotheses about character state-dependent diversification rates. Here, we document the disconcerting ease with which neutral traits are inferred to have statistically significant associations with speciation rate. We first demonstrate this unfortunate effect for a known model assumption violation: shifts in speciation rate associated with a character not included in the model. We further show that for many empirical phylogenies, characters simulated in the absence of state-dependent diversification exhibit an even higher Type I error rate, indicating that the method is susceptible to additional, unknown model inadequacies. For traits that evolve slowly, the root cause appears to be a statistical framework that does not require replicated shifts in character state and diversification. However, spurious associations between character state and speciation rate arise even for traits that lack phylogenetic signal, suggesting that phylogenetic pseudoreplication alone cannot fully explain the problem. The surprising severity of this phenomenon suggests that many trait-diversification relationships reported in the literature may not be real. More generally, we highlight the need for diagnosing and understanding the consequences of model inadequacy in phylogenetic comparative methods.

  20. Metacommunity speciation models and their implications for diversification theory.

    PubMed

    Hubert, Nicolas; Calcagno, Vincent; Etienne, Rampal S; Mouquet, Nicolas

    2015-08-01

    The emergence of new frameworks combining evolutionary and ecological dynamics in communities opens new perspectives on the study of speciation. By acknowledging the relative contribution of local and regional dynamics in shaping the complexity of ecological communities, metacommunity theory sheds a new light on the mechanisms underlying the emergence of species. Three integrative frameworks have been proposed, involving neutral dynamics, niche theory, and life history trade-offs respectively. Here, we review these frameworks of metacommunity theory to emphasise that: (1) studies on speciation and community ecology have converged towards similar general principles by acknowledging the central role of dispersal in metacommunities dynamics, (2) considering the conditions of emergence and maintenance of new species in communities has given rise to new models of speciation embedded in the metacommunity theory, (3) studies of diversification have shifted from relating phylogenetic patterns to landscapes spatial and ecological characteristics towards integrative approaches that explicitly consider speciation in a mechanistic ecological framework. We highlight several challenges, in particular the need for a better integration of the eco-evolutionary consequences of dispersal and the need to increase our understanding on the relative rates of evolutionary and ecological changes in communities.

  1. Speciation of volatile organic compounds from poultry production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The air consent agreement between EPA and large animal feeding operations (AFO) is designed to determine at what level compounds are being emitted from these facilities. However, the methodology used for quantifying total non-methane hydrocarbons and speciation of volatile organic compounds (VOC) n...

  2. Speciation And Bioavailability Of Zinc In Amended Sediments

    EPA Science Inventory

    The speciation and bioavailability of zinc (Zn) in smelter-contaminated sediments was investigated as a function of phosphate (apatite) and organic amendment loading rate. Zinc species identified in preamendment sediment were zinc hydroxide-like phases, sphalerite, and zinc sorbe...

  3. Lead Speciation And Bioavailability In Apatite-Amended Sediments

    EPA Science Inventory

    The in situ sequestration of lead (Pb) in sediment with a phosphate amendment was investigated by Pb speciation and bioavailability. Sediment Pb in preamendment samples was identified as galena (PbS) with trace amounts of absorbed Pb. Sediment exposed to atmospheric conditions ...

  4. The secondary contact phase of allopatric speciation in Darwin's finches

    PubMed Central

    Grant, Peter R.; Grant, B. Rosemary

    2009-01-01

    Speciation, the process by which two species form from one, involves the development of reproductive isolation of two divergent lineages. Here, we report the establishment and persistence of a reproductively isolated population of Darwin's finches on the small Galápagos Island of Daphne Major in the secondary contact phase of speciation. In 1981, an immigrant medium ground finch (Geospiza fortis) arrived on the island. It was unusually large, especially in beak width, sang an unusual song, and carried some Geospiza scandens alleles. We followed the fate of this individual and its descendants for seven generations over a period of 28 years. In the fourth generation, after a severe drought, the lineage was reduced to a single brother and sister, who bred with each other. From then on this lineage, inheriting unusual song, morphology, and a uniquely homozygous marker allele, was reproductively isolated, because their own descendants bred with each other and with no other member of the resident G. fortis population. These observations agree with some expectations of an ecological theory of speciation in that a barrier to interbreeding arises as a correlated effect of adaptive divergence in morphology. However, the important, culturally transmitted, song component of the barrier appears to have arisen by chance through an initial imperfect copying of local song by the immigrant. The study reveals additional stochastic elements of speciation, in which divergence is initiated in allopatry; immigration to a new area of a single male hybrid and initial breeding with a rare hybrid female. PMID:19918081

  5. Transformation of heavy metal speciation during sludge drying: mechanistic insights.

    PubMed

    Weng, Huan-Xin; Ma, Xue-Wen; Fu, Feng-Xia; Zhang, Jin-Jun; Liu, Zan; Tian, Li-Xun; Liu, Chongxuan

    2014-01-30

    Speciation can fundamentally affect on the stability and toxicity of heavy metals in sludge from wastewater treatment plants. This research investigated the speciation of heavy metals in sludge from both municipal and industrial sources, and metal speciation change as a result of drying process to reduce sludge volume. The changes in sludge properties including sludge moisture content, temperature, density, and electrical conductivity were also monitored to provide insights into the mechanisms causing the change in heavy metal speciation. The results show that the drying process generally stabilized Cr, Cu, Cd, and Pb in sludge by transforming acid-soluble, reducible, and oxidizable species into structurally stable forms. Such transformation and stabilization occurred regardless of the sludge source and type, and were primarily caused by the changes in sludge properties associated with decomposition of organic matter and sulfide. The results enhanced our understanding of the geochemical behavior of heavy metals in municipal sludge, and are useful for designing a treatment system for environment-friendly disposal of sludge.

  6. Capillary electrophoresis application in metal speciation and complexation characterization

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Capillary electrophoresis is amenable to the separation of metal ionic species and the characterization of metal-ligand interactions. This book chapter reviews and discusses three representative case studies in applications of CE technology in speciation and reactions of metal with organic molecules...

  7. PM 2.5 ORGANIC SPECIATION INTERCOMPARISON RESULTS

    EPA Science Inventory

    This abstract describes a poster on results to a laboratory intercomparison of organic aerosol speciation analysis to be presented at the 2006 International Aerosol Conference sponsored by the American Association for Aerosol Research in St. Paul, Minnesota on September 10-15. T...

  8. LINKING WATERFOWL WITH CONTAMINANT SPECIATION IN RIPARIAN SOILS

    EPA Science Inventory

    This report summarizes the results of Mine Waste Technology Program (MWTP) Activity III, Project 38, Linking Waterfowl with Contaminant Speciation in Riparian Soils, implemented and funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U...

  9. Chiral speciation of selenoamino acids in biological samples.

    PubMed

    Chen, Beibei; He, Man; Zhong, Cheng; Hu, Bin

    2014-10-10

    In this paper, the "state of the art" of chiral speciation of selenoamino acids (SeAAs) in biological samples is critically reviewed. The significance and the features of such studies are highlighted. A special focus lies on chiral speciation of SeAAs by hyphenation techniques in which a chiral separation method (such as gas chromatography (GC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE)) is on-line coupled with an elemental specific detector, especially inductively coupled plasma mass spectrometry (ICP-MS). The advances in the development and application of hyphenation techniques in chiral speciation of SeAAs in biological samples are summarized and a perspective for future developments including sophisticated and innovative applications is discussed. Overall, HPLC-ICP-MS is more applicable than GC/CE-ICP-MS for chiral speciation of SeAAs. In the future, more novel chiral HPLC methods with high enantio-resolution, low cost and robustness, and their more applications in real biological samples analysis are expected.

  10. FINE PARTICULATE MATTER (PM) AND ORGANIC SPECIATION OF FIREPLACE EMISSIONS

    EPA Science Inventory

    This paper presents a summary of fireplace particle size and organic speciation data gathered to date in an on-going project. Tests are being conducted in a residential wood combustion (RWC) laboratory on three factory-built fireplaces. RWC wood smoke particles <10?m (PM10) con...

  11. Reconstructing the history of selection during homoploid hybrid speciation.

    PubMed

    Karrenberg, Sophie; Lexer, Christian; Rieseberg, Loren H

    2007-06-01

    This study aims to identify selection pressures during the historical process of homoploid hybrid speciation in three Helianthus (sunflower) hybrid species. If selection against intrinsic genetic incompatibilities (fertility selection) or for important morphological/ecological traits (phenotypic selection) were important in hybrid speciation, we would expect this selection to have influenced the parentage of molecular markers or chromosomal segments in the hybrid species' genomes. To infer past selection, we compared the parentage of molecular markers in high-density maps of the three hybrid species with predicted marker parentage from an analysis of fertility selection in artificial hybrids and from the directions of quantitative trait loci effects with respect to the phenotypes of the hybrid species. Multiple logistic regression models were consistent with both fertility and phenotypic selection in all three species. To further investigate traits under selection, we used a permutation test to determine whether marker parentage predicted from groups of functionally related traits differed from neutral expectations. Our results suggest that trait groups associated with ecological divergence were under selection during hybrid speciation. This study presents a new method to test for selection and supports earlier claims that fertility selection and phenotypic selection on ecologically relevant traits have operated simultaneously during sunflower hybrid speciation.

  12. Comparative tests of the role of dewlap size in Anolis lizard speciation.

    PubMed

    Ingram, Travis; Harrison, Alexis; Mahler, D Luke; Castañeda, María Del Rosario; Glor, Richard E; Herrel, Anthony; Stuart, Yoel E; Losos, Jonathan B

    2016-12-28

    Phenotypic traits may be linked to speciation in two distinct ways: character values may influence the rate of speciation or diversification in the trait may be associated with speciation events. Traits involved in signal transmission, such as the dewlap of Anolis lizards, are often involved in the speciation process. The dewlap is an important visual signal with roles in species recognition and sexual selection, and dewlaps vary among species in relative size as well as colour and pattern. We compile a dataset of relative dewlap size digitized from photographs of 184 anole species from across the genus' geographical range. We use phylogenetic comparative methods to test two hypotheses: that larger dewlaps are associated with higher speciation rates, and that relative dewlap area diversifies according to a speciational model of evolution. We find no evidence of trait-dependent speciation, indicating that larger signals do not enhance any role the dewlap has in promoting speciation. Instead, we find a signal of mixed speciational and gradual trait evolution, with a particularly strong signal of speciational change in the dewlaps of mainland lineages. This indicates that dewlap size diversifies in association with the speciation process, suggesting that divergent selection may play a role in the macroevolution of this signalling trait.

  13. Enhanced Model for Fast Ignition

    SciTech Connect

    Mason, Rodney J.

    2010-10-12

    Laser Fusion is a prime candidate for alternate energy production, capable of serving a major portion of the nation's energy needs, once fusion fuel can be readily ignited. Fast Ignition may well speed achievement of this goal, by reducing net demands on laser pulse energy and timing precision. However, Fast Ignition has presented a major challenge to modeling. This project has enhanced the computer code ePLAS for the simulation of the many specialized phenomena, which arise with Fast Ignition. The improved code has helped researchers to understand better the consequences of laser absorption, energy transport, and laser target hydrodynamics. ePLAS uses efficient implicit methods to acquire solutions for the electromagnetic fields that govern the accelerations of electrons and ions in targets. In many cases, the code implements fluid modeling for these components. These combined features, "implicitness and fluid modeling," can greatly facilitate calculations, permitting the rapid scoping and evaluation of experiments. ePLAS can be used on PCs, Macs and Linux machines, providing researchers and students with rapid results. This project has improved the treatment of electromagnetics, hydrodynamics, and atomic physics in the code. It has simplified output graphics, and provided new input that avoids the need for source code access by users. The improved code can now aid university, business and national laboratory users in pursuit of an early path to success with Fast Ignition.

  14. Fast-food consumption, diet quality, and neighborhood exposure to fast food: the multi-ethnic study of atherosclerosis.

    PubMed

    Moore, Latetia V; Diez Roux, Ana V; Nettleton, Jennifer A; Jacobs, David R; Franco, Manuel

    2009-07-01

    The authors examined associations among fast-food consumption, diet, and neighborhood fast-food exposure by using 2000-2002 Multi-Ethnic Study of Atherosclerosis data. US participants (n = 5,633; aged 45-84 years) reported usual fast-food consumption (never, <1 time/week, or > or =1 times/week) and consumption near home (yes/no). Healthy diet was defined as scoring in the top quintile of the Alternate Healthy Eating Index or bottom quintile of a Western-type dietary pattern. Neighborhood fast-food exposure was measured by densities of fast-food outlets, participant report, and informant report. Separate logistic regression models were used to examine associations of fast-food consumption and diet; fast-food exposure and consumption near home; and fast-food exposure and diet adjusted for site, age, sex, race/ethnicity, education, and income. Those never eating fast food had a 2-3-times higher odds of having a healthy diet versus those eating fast food > or =1 times/week, depending on the dietary measure. For every standard deviation increase in fast-food exposure, the odds of consuming fast food near home increased 11%-61% and the odds of a healthy diet decreased 3%-17%, depending on the model. Results show that fast-food consumption and neighborhood fast-food exposure are associated with poorer diet. Interventions that reduce exposure to fast food and/or promote individual behavior change may be helpful.

  15. Host shift and speciation in a coral-feeding nudibranch

    PubMed Central

    Faucci, Anuschka; Toonen, Robert J; Hadfield, Michael G

    2006-01-01

    While the role of host preference in ecological speciation has been investigated extensively in terrestrial systems, very little is known in marine environments. Host preference combined with mate choice on the preferred host can lead to population subdivision and adaptation leading to host shifts. We use a phylogenetic approach based on two mitochondrial genetic markers to disentangle the taxonomic status and to investigate the role of host specificity in the speciation of the nudibranch genus Phestilla (Gastropoda, Opisthobranchia) from Guam, Palau and Hawaii. Species of the genus Phestilla complete their life cycle almost entirely on their specific host coral (species of Porites, Goniopora and Tubastrea). They reproduce on their host coral and their planktonic larvae require a host-specific chemical cue to metamorphose and settle onto their host. The phylogenetic trees of the combined cytochrome oxidase I and ribosomal 16S gene sequences clarify the relationship among species of Phestilla identifying most of the nominal species as monophyletic clades. We found a possible case of host shift from Porites to Goniopora and Tubastrea in sympatric Phestilla spp. This represents one of the first documented cases of host shift as a mechanism underlying speciation in a marine invertebrate. Furthermore, we found highly divergent clades within Phestilla sp. 1 and Phestilla minor (8.1–11.1%), suggesting cryptic speciation. The presence of a strong phylogenetic signal for the coral host confirms that the tight link between species of Phestilla and their host coral probably played an important role in speciation within this genus. PMID:17134995

  16. Alternative Splice in Alternative Lice.

    PubMed

    Tovar-Corona, Jaime M; Castillo-Morales, Atahualpa; Chen, Lu; Olds, Brett P; Clark, John M; Reynolds, Stuart E; Pittendrigh, Barry R; Feil, Edward J; Urrutia, Araxi O

    2015-10-01

    Genomic and transcriptomics analyses have revealed human head and body lice to be almost genetically identical; although con-specific, they nevertheless occupy distinct ecological niches and have differing feeding patterns. Most importantly, while head lice are not known to be vector competent, body lice can transmit three serious bacterial diseases; epidemictyphus, trench fever, and relapsing fever. In order to gain insights into the molecular bases for these differences, we analyzed alternative splicing (AS) using next-generation sequencing data for one strain of head lice and one strain of body lice. We identified a total of 3,598 AS events which were head or body lice specific. Exon skipping AS events were overrepresented among both head and body lice, whereas intron retention events were underrepresented in both. However, both the enrichment of exon skipping and the underrepresentation of intron retention are significantly stronger in body lice compared with head lice. Genes containing body louse-specific AS events were found to be significantly enriched for functions associated with development of the nervous system, salivary gland, trachea, and ovarian follicle cells, as well as regulation of transcription. In contrast, no functional categories were overrepresented among genes with head louse-specific AS events. Together, our results constitute the first evidence for transcript pool differences in head and body lice, providing insights into molecular adaptations that enabled human lice to adapt to clothing, and representing a powerful illustration of the pivotal role AS can play in functional adaptation.

  17. Alternative Splice in Alternative Lice

    PubMed Central

    Tovar-Corona, Jaime M.; Castillo-Morales, Atahualpa; Chen, Lu; Olds, Brett P.; Clark, John M.; Reynolds, Stuart E.; Pittendrigh, Barry R.; Feil, Edward J.; Urrutia, Araxi O.

    2015-01-01

    Genomic and transcriptomics analyses have revealed human head and body lice to be almost genetically identical; although con-specific, they nevertheless occupy distinct ecological niches and have differing feeding patterns. Most importantly, while head lice are not known to be vector competent, body lice can transmit three serious bacterial diseases; epidemictyphus, trench fever, and relapsing fever. In order to gain insights into the molecular bases for these differences, we analyzed alternative splicing (AS) using next-generation sequencing data for one strain of head lice and one strain of body lice. We identified a total of 3,598 AS events which were head or body lice specific. Exon skipping AS events were overrepresented among both head and body lice, whereas intron retention events were underrepresented in both. However, both the enrichment of exon skipping and the underrepresentation of intron retention are significantly stronger in body lice compared with head lice. Genes containing body louse-specific AS events were found to be significantly enriched for functions associated with development of the nervous system, salivary gland, trachea, and ovarian follicle cells, as well as regulation of transcription. In contrast, no functional categories were overrepresented among genes with head louse-specific AS events. Together, our results constitute the first evidence for transcript pool differences in head and body lice, providing insights into molecular adaptations that enabled human lice to adapt to clothing, and representing a powerful illustration of the pivotal role AS can play in functional adaptation. PMID:26169943

  18. Is fast food addictive?

    PubMed

    Garber, Andrea K; Lustig, Robert H

    2011-09-01

    Studies of food addiction have focused on highly palatable foods. While fast food falls squarely into that category, it has several other attributes that may increase its salience. This review examines whether the nutrients present in fast food, the characteristics of fast food consumers or the presentation and packaging of fast food may encourage substance dependence, as defined by the American Psychiatric Association. The majority of fast food meals are accompanied by a soda, which increases the sugar content 10-fold. Sugar addiction, including tolerance and withdrawal, has been demonstrated in rodents but not humans. Caffeine is a "model" substance of dependence; coffee drinks are driving the recent increase in fast food sales. Limited evidence suggests that the high fat and salt content of fast food may increase addictive potential. Fast food restaurants cluster in poorer neighborhoods and obese adults eat more fast food than those who are normal weight. Obesity is characterized by resistance to insulin, leptin and other hormonal signals that would normally control appetite and limit reward. Neuroimaging studies in obese subjects provide evidence of altered reward and tolerance. Once obese, many individuals meet criteria for psychological dependence. Stress and dieting may sensitize an individual to reward. Finally, fast food advertisements, restaurants and menus all provide environmental cues that may trigger addictive overeating. While the concept of fast food addiction remains to be proven, these findings support the role of fast food as a potentially addictive substance that is most likely to create dependence in vulnerable populations.

  19. Transcriptome, genetic editing, and microRNA divergence substantiate sympatric speciation of blind mole rat, Spalax.

    PubMed

    Li, Kexin; Wang, Liuyang; Knisbacher, Binyamin A; Xu, Qinqin; Levanon, Erez Y; Wang, Huihua; Frenkel-Morgenstern, Milana; Tagore, Satabdi; Fang, Xiaodong; Bazak, Lily; Buchumenski, Ilana; Zhao, Yang; Lövy, Matěj; Li, Xiangfeng; Han, Lijuan; Frenkel, Zeev; Beiles, Avigdor; Cao, Yi Bin; Wang, Zhen Long; Nevo, Eviatar

    2016-07-05

    Incipient sympatric speciation in blind mole rat, Spalax galili, in Israel, caused by sharp ecological divergence of abutting chalk-basalt ecologies, has been proposed previously based on mitochondrial and whole-genome nuclear DNA. Here, we present new evidence, including transcriptome, DNA editing, microRNA, and codon usage, substantiating earlier evidence for adaptive divergence in the abutting chalk and basalt populations. Genetic divergence, based on the previous and new evidence, is ongoing despite restricted gene flow between the two populations. The principal component analysis, neighbor-joining tree, and genetic structure analysis of the transcriptome clearly show the clustered divergent two mole rat populations. Gene-expression level analysis indicates that the population transcriptome divergence is displayed not only by soil divergence but also by sex. Gene ontology enrichment of the differentially expressed genes from the two abutting soil populations highlights reproductive isolation. Alternative splicing variation of the two abutting soil populations displays two distinct splicing patterns. L-shaped FST distribution indicates that the two populations have undergone divergence with gene flow. Transcriptome divergent genes highlight neurogenetics and nutrition characterizing the chalk population, and energetics, metabolism, musculature, and sensory perception characterizing the abutting basalt population. Remarkably, microRNAs also display divergence between the two populations. The GC content is significantly higher in chalk than in basalt, and stress-response genes mostly prefer nonoptimal codons. The multiple lines of evidence of ecological-genomic and genetic divergence highlight that natural selection overrules the gene flow between the two abutting populations, substantiating the sharp ecological chalk-basalt divergence driving sympatric speciation.

  20. Transcriptome, genetic editing, and microRNA divergence substantiate sympatric speciation of blind mole rat, Spalax

    PubMed Central

    Li, Kexin; Wang, Liuyang; Knisbacher, Binyamin A.; Xu, Qinqin; Levanon, Erez Y.; Wang, Huihua; Frenkel-Morgenstern, Milana; Tagore, Satabdi; Fang, Xiaodong; Bazak, Lily; Buchumenski, Ilana; Zhao, Yang; Lövy, Matěj; Li, Xiangfeng; Han, Lijuan; Frenkel, Zeev; Beiles, Avigdor; Cao, Yi Bin; Wang, Zhen Long; Nevo, Eviatar

    2016-01-01

    Incipient sympatric speciation in blind mole rat, Spalax galili, in Israel, caused by sharp ecological divergence of abutting chalk–basalt ecologies, has been proposed previously based on mitochondrial and whole-genome nuclear DNA. Here, we present new evidence, including transcriptome, DNA editing, microRNA, and codon usage, substantiating earlier evidence for adaptive divergence in the abutting chalk and basalt populations. Genetic divergence, based on the previous and new evidence, is ongoing despite restricted gene flow between the two populations. The principal component analysis, neighbor-joining tree, and genetic structure analysis of the transcriptome clearly show the clustered divergent two mole rat populations. Gene-expression level analysis indicates that the population transcriptome divergence is displayed not only by soil divergence but also by sex. Gene ontology enrichment of the differentially expressed genes from the two abutting soil populations highlights reproductive isolation. Alternative splicing variation of the two abutting soil populations displays two distinct splicing patterns. L-shaped FST distribution indicates that the two populations have undergone divergence with gene flow. Transcriptome divergent genes highlight neurogenetics and nutrition characterizing the chalk population, and energetics, metabolism, musculature, and sensory perception characterizing the abutting basalt population. Remarkably, microRNAs also display divergence between the two populations. The GC content is significantly higher in chalk than in basalt, and stress-response genes mostly prefer nonoptimal codons. The multiple lines of evidence of ecological–genomic and genetic divergence highlight that natural selection overrules the gene flow between the two abutting populations, substantiating the sharp ecological chalk–basalt divergence driving sympatric speciation. PMID:27339131

  1. Refractive index fiber sensor based on Brillouin fast light

    NASA Astrophysics Data System (ADS)

    Chen, Jiali; Gan, Jiulin; Zhang, Zhishen; Yang, Tong; Deng, Huaqiu; Yang, Zhongmin

    2014-01-01

    A new type of refractive index fiber sensor was invented by combining the evanescent-field scattering sensing mechanism with the Brillouin fast light scheme. Superluminal light was realized using Brillouin lasing oscillation in a fiber ring cavity. The refractive index of the solution around the microfiber within the cavity is related to the group velocity of the fast light. This fast light refractive index sensor offers an alternative for high-accuracy sensing applications.

  2. Looking for an Alternative.

    ERIC Educational Resources Information Center

    Kennedy, Jack

    1999-01-01

    Argues that high school newspapers might do well to create stronger ties with alternative weeklies. Discusses issues of niche marketing, alternative content, and alternative presentation. Notes that high school papers could learn a lot from alternative newspapers. (SR)

  3. Integrative Physiology of Fasting.

    PubMed

    Secor, Stephen M; Carey, Hannah V

    2016-03-15

    Extended bouts of fasting are ingrained in the ecology of many organisms, characterizing aspects of reproduction, development, hibernation, estivation, migration, and infrequent feeding habits. The challenge of long fasting episodes is the need to maintain physiological homeostasis while relying solely on endogenous resources. To meet that challenge, animals utilize an integrated repertoire of behavioral, physiological, and biochemical responses that reduce metabolic rates, maintain tissue structure and function, and thus enhance survival. We have synthesized in this review the integrative physiological, morphological, and biochemical responses, and their stages, that characterize natural fasting bouts. Underlying the capacity to survive extended fasts are behaviors and mechanisms that reduce metabolic expenditure and shift the dependency to lipid utilization. Hormonal regulation and immune capacity are altered by fasting; hormones that trigger digestion, elevate metabolism, and support immune performance become depressed, whereas hormones that enhance the utilization of endogenous substrates are elevated. The negative energy budget that accompanies fasting leads to the loss of body mass as fat stores are depleted and tissues undergo atrophy (i.e., loss of mass). Absolute rates of body mass loss scale allometrically among vertebrates. Tissues and organs vary in the degree of atrophy and downregulation of function, depending on the degree to which they are used during the fast. Fasting affects the population dynamics and activities of the gut microbiota, an interplay that impacts the host's fasting biology. Fasting-induced gene expression programs underlie the broad spectrum of integrated physiological mechanisms responsible for an animal's ability to survive long episodes of natural fasting.

  4. Non-chromatographic mercury speciation and determination in wine by new core-shell ion-imprinted sorbents.

    PubMed

    Dakova, Ivanka; Yordanova, Tanya; Karadjova, Irina

    2012-09-15

    In this study new Hg(II) core-shell imprinted sorbents (Hg(II)-IIPs) were prepared and tested for speciation and determination of Hg in wine. The silica gel, chemically modified with 3-(trimethoxysilyl)propyl methacrylate (TSPM) was used as supporting material. The Hg(II)-imprinted polymer layer was grafted by copolymerization of methacrylic acid and trimethylolpropane trimethacrylate in the presence of Hg(II) complexes with two different chelating agents: 1-pyrrolidinedithiocarboxylic acid (P(PDC-Hg)/SiG) and 1-(2-thiazolylazo)-2-naphthol (P(TAN-Hg)/SiG). High selectivity and fast kinetics of processes of sorption and desorption for Hg(II) were found by using P(PDC-Hg)/SiG. Recovery experiments performed for selective determination of inorganic mercury in wines showed that the interfering organic matrix did not influence the extraction efficiency. Column solid phase extraction scheme was developed for the determination and speciation of Hg in wines. The limit of detection (LOD) achieved for inorganic mercury determination in wine samples is 0.02 μg L(-1) (3σ), measured by CV AAS. The relative standard deviation varied in the range 6-11% at 0.05-2 μg L(-1) Hg levels. The sorbents showed high mechanical and chemical stability and extraction efficiency has not changed after more than 50 sorption/desorption cycles.

  5. Speciation of mercury compounds by differential atomization - atomic absorption spectroscopy

    SciTech Connect

    Robinson, J.W.; Skelly, E.M.

    1982-01-01

    This paper describes the dual stage atomization technique which allows speciation of several mercury-containing compounds in aqueous solution and in biological fluids. The technique holds great promise for further speciation studies. Accurate temperature control, expecially at temperatures less than 200/sup 0/C, is needed to separate the extremely volatile mercury halides and simple organomercurials from each other. Studies with mercury salts and EDTA, L-cysteine and dithioxamide demonstrate that this technique may be used to study the extent of complex formation. Investigations of biological fluids indicate that there is a single predominant form of mercury in sweat and a single predominant form of mercury in urine. The mercury compound in urine is more volatile than that in sweat. Both quantitative and qualitative analyses are possible with this technique.

  6. Optimisation of the storage of natural freshwaters before organotin speciation.

    PubMed

    Bancon-Montigny, C; Lespes, G; Potin-Gautier, M

    2001-01-01

    The speciation of organotin compounds is essential due to the species-dependent toxicity, especially in natural waters. Precautions have to be taken during sampling and storage of waters in order to prevent degradations and losses. Experimental design methodology has been used to study the conditions of stability of organotins after water sampling in rivers. The modelling of results allows the determination of optimal conditions of preservation. After acidification at pH = 4 with nitric acid, the storage in polyethylene containers at 4 degrees C in the dark is suitable to preserve the most degradable trisubstituted (butyl- and phenyl-) species over 1 month. These conditions of sampling and storage are applied to two different freshwaters. The rate of species decomposition appears to be only dependent on the water nature, whatever the organotin concentrations in the sample. Speciation could be so preserved between 1 and 3 months.

  7. Hybridization Reveals the Evolving Genomic Architecture of Speciation

    PubMed Central

    Kronforst, Marcus R.; Hansen, Matthew E.B.; Crawford, Nicholas G.; Gallant, Jason R.; Zhang, Wei; Kulathinal, Rob J.; Kapan, Durrell D.; Mullen, Sean P.

    2014-01-01

    SUMMARY The rate at which genomes diverge during speciation is unknown, as are the physical dynamics of the process. Here, we compare full genome sequences of 32 butterflies, representing five species from a hybridizing Heliconius butterfly community, to examine genome-wide patterns of introgression and infer how divergence evolves during the speciation process. Our analyses reveal that initial divergence is restricted to a small fraction of the genome, largely clustered around known wing-patterning genes. Over time, divergence evolves rapidly, due primarily to the origin of new divergent regions. Furthermore, divergent genomic regions display signatures of both selection and adaptive introgression, demonstrating the link between microevolutionary processes acting within species and the origin of species across macroevolutionary timescales. Our results provide a uniquely comprehensive portrait of the evolving species boundary due to the role that hybridization plays in reducing the background accumulation of divergence at neutral sites. PMID:24183670

  8. Speciation of uranium in compartments of living cells.

    PubMed

    Geipel, Gerhard; Viehweger, Katrin

    2015-06-01

    Depleted uranium used as ammunition corrodes in the environment forming mineral phases and then dissolved uranium species like uranium carbonates (Schimmack et al., in Radiat Environ Biophys 46:221-227, 2007) and hydroxides. These hydroxide species were contacted with plant cells (canola). After 24 h contact time the cells were fractionated and the uranium speciation in the fraction was determined by time resolved laser-induced fluorescence spectroscopy at room temperature as well at 150 K. It could be shown that the uranium speciation in the fractions is different to that in the nutrient solution. Comparison of the emission bands with literature data allows assignment of the uranium binding forms.

  9. Speciation of Fe in ambient aerosol and cloudwater

    SciTech Connect

    Siefert, Ronald Lyn

    1996-08-15

    Atmospheric iron (Fe) is thought to play an important role in cloudwater chemistry (e.g., S(IV) oxidation, oxidant production, etc.), and is also an important source of Fe to certain regions of the worlds oceans where Fe is believed to be a rate-limiting nutrient for primary productivity. This thesis focuses on understanding the chemistry, speciation and abundance of Fe in cloudwater and aerosol in the troposphere, through observations of Fe speciation in the cloudwater and aerosol samples collected over the continental United States and the Arabian Sea. Different chemical species of atmospheric Fe were measured in aerosol and cloudwater samples to help assess the role of Fe in cloudwater chemistry.

  10. Cooperative breeding in oscine passerines: does sociality inhibit speciation?

    PubMed Central

    Cockburn, Andrew

    2003-01-01

    Cooperative breeding in birds is much more prevalent than has been previously realized, occurring in 18.5% of oscine passerines known to have biparental care, and is the predominant social system of some ancient oscine clades. Cooperation is distributed unevenly in clades that contain both cooperative and pair breeders, and is usually confined to a few related genera in which it can be ubiquitous. Cooperative clades are species poor compared with pair-breeding clades, because pair breeders evolve migratory habits, speciate on oceanic islands and are more likely to have distributions spread across more than one biogeographic region. These differences reflect the increased capacity for colonization by pair breeders because their young disperse. Thus cooperative breeding has macroevolutionary consequences by restricting rates of speciation and macroecological implications by influencing the assembly of island and migrant faunas. PMID:14613606

  11. Metal accumulation by stream bryophytes, related to chemical speciation.

    PubMed

    Tipping, E; Vincent, C D; Lawlor, A J; Lofts, S

    2008-12-01

    Metal accumulation by aquatic bryophytes was investigated using data for headwater streams of differing chemistry. The Windermere Humic Aqueous Model (WHAM) was applied to calculate chemical speciation, including competitive proton and metal interactions with external binding sites on the plants. The speciation modelling approach gives smaller deviations between observed and predicted bryophyte contents of Cu, Zn, Cd and Pb than regressions based on total filtered metal concentrations. If all four metals, and Ni, are considered together, the WHAM predictions are superior at the 1% level. Optimised constants for bryophyte binding by the trace metals are similar to those for humic substances and simple carboxylate ligands. Bryophyte contents of Na, Mg and Ca are approximately explained by binding at external sites, while most of the K is intracellular. Oxide phases account for some of the Al, and most of the Mn, Fe and Co.

  12. Speciation of uranium(VI) sorption complexes on montmorillonite

    SciTech Connect

    Chisholm-Brause, C.J.; Morris, D.E.; Richard, R.E.

    1992-05-01

    Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

  13. SUBSURFACE MOBILE PLUTONIUM SPECIATION: SAMPLING ARTIFACTS FOR GROUNDWATER COLLOIDS

    SciTech Connect

    Kaplan, D.; Buesseler, K.

    2010-06-29

    A recent review found several conflicting conclusions regarding colloid-facilitated transport of radionuclides in groundwater and noted that colloids can both facilitate and retard transport. Given these contrasting conclusions and the profound implications even trace concentrations of plutonium (Pu) have on the calculated risk posed to human health, it is important that the methodology used to sample groundwater colloids be free of artifacts. The objective of this study was: (1) to conduct a field study and measure Pu speciation, ({sup 239}Pu and {sup 240}Pu for reduced-Pu{sub aq}, oxidized-Pu{sub aq}, reduced-Pu{sub colloid}, and oxidized-Pu{sub colloid}), in a Savannah River Site (SRS) aquifer along a pH gradient in F-Area, (2) to determine the impact of pumping rate on Pu concentration, Pu speciation, and Pu isotopic ratios, (3) determine the impact of delayed sample processing (as opposed to processing directly from the well).

  14. The frequency of polyploid speciation in vascular plants

    PubMed Central

    Wood, Troy E.; Takebayashi, Naoki; Barker, Michael S.; Mayrose, Itay; Greenspoon, Philip B.; Rieseberg, Loren H.

    2009-01-01

    Since its discovery in 1907, polyploidy has been recognized as an important phenomenon in vascular plants, and several lines of evidence indicate that most, if not all, plant species ultimately have a polyploid ancestry. However, previous estimates of the frequency of polyploid speciation suggest that the formation and establishment of neopolyploid species is rare. By combining information from the botanical community's vast cytogenetic and phylogenetic databases, we establish that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase. These frequency estimates are higher by a factor of four than earlier estimates and lead to a standing incidence of polyploid species within genera of 35% (n = 1,506). Despite this high incidence, we find no direct evidence that polyploid lines, once established, enjoy greater net species diversification. Thus, the widespread occurrence of polyploid taxa appears to result from the substantial contribution of polyploidy to cladogenesis, but not from subsequent increases in diversification rates of polyploid lines. PMID:19667210

  15. Plutonium speciation in water from Mono Lake, California

    USGS Publications Warehouse

    Cleveland, J.M.; Rees, T.F.; Nash, K.L.

    1983-01-01

    The solubility of plutonium in Mono Lake water is enhanced by the presence of large concentrations of indigenous carbonate ions and moderate concentrations of fluoride ions. In spite of the complex chemical composition of this water, only a few ions govern the behavior of plutonium, as demonstrated by the fact that it was possible to duplicate plutonium speciation in a synthetic water containing only the principal components of Mono Lake water.

  16. Plutonium speciation in water from Mono Lake, California

    SciTech Connect

    Cleveland, J.M.; Rees, T.F.; Nash, K.L.

    1983-12-23

    The solubility of plutonium in Mono Lake water is enhanced by the presence of large concentrations of indigenous carbonate ions and moderate concentrations of fluoride ions. In spite of the complex chemical composition of this water, only a few ions govern the behavior of plutonium, as demonstrated by the fact that it was possible to duplicate plutonium speciation in a synthetic water containing only the principal components of Mono Lake water.

  17. Pu speciation in actual and simulated aged wastes

    SciTech Connect

    Lezama-pacheco, Juan S; Conradson, Steven D

    2008-01-01

    X-ray Absorption Fine Structure Spectroscopy (XAFS) at the Pu L{sub II/III} edge was used to determine the speciation of this element in (1) Hanford Z-9 Pu crib samples, (2) deteriorated waste resins from a chloride process ion-exchange purification line, and (3) the sediments from two Waste Isolation Pilot Plant Liter Scale simulant brine systems. The Pu speciation in all of these samples except one is within the range previously displayed by PuO{sub 2+x-2y}(OH){sub y}{center_dot}zH{sub 2}O compounds, which is expected based on the putative thermodynamic stability of this system for Pu equilibrated with excess H{sub 2}O and O{sub 2} under environmental conditions. The primary exception was a near neutral brine experiment that displayed evidence for partial substitution of the normal O-based ligands with Cl{sup -} and a concomitant expansion of the Pu-Pu distance relative to the much more highly ordered Pu near neighbor shell in PuO{sub 2}. However, although the Pu speciation was not necessarily unusual, the Pu chemistry identified via the history of these samples did exhibit unexpected patterns, the most significant of which may be that the presence of the Pu(V)-oxo species may decrease rather than increase the overall solubility of these compounds. Several additional aspects of the Pu speciation have also not been previously observed in laboratory-based samples. The molecular environmental chemistry of Pu is therefore likely to be more complicated than would be predicted based solely on the behavior of PuO{sub 2} under laboratory conditions.

  18. The Sphere Anemometer - A Fast Alternative to Cup Anemometry

    NASA Astrophysics Data System (ADS)

    Heißelmann, Hendrik; Hölling, Michael; Peinke, Joachim

    The main problem of cup anemometry is the different response time for increasing and decreasing wind velocities due to its moment of inertia. This results in an overestimation of wind speed under turbulent wind conditions, the so-called over-speeding. Additionally, routine calibrations are necessary due to the wear of bearings. Motivated by these problems the sphere anemometer, a new simple and robust sensor for wind velocity measurements without moving parts, was developed at the University of Oldenburg. In contrast to other known thrust-based sensors, the sphere anemometer uses the light pointer principle to detect the deflection of a bending tube caused by the drag force acting on a sphere mounted at its top. This technique allows the simultaneous determination of wind speed and direction via a two-dimensional position sensitive detector.

  19. Results from Tests of the Fast Alternative Cryogenic Experiment Testbed

    NASA Technical Reports Server (NTRS)

    Nash, A.

    1999-01-01

    To address the gap in manifest opportunities for low temperature microgravity payloads that has accompanied the start of the build era for the International Space Station (ISS), development of a new facility compatible with one or more carriers in the baseline shuttle manifest has been undertaken.

  20. Hybrid speciation in angiosperms: parental divergence drives ploidy

    PubMed Central

    Paun, Ovidiu; Forest, Félix; Fay, Michael F.; Chase, Mark W.

    2010-01-01

    Summary Hybridization and polyploidy are now hypothesized to have regularly stimulated speciation in angiosperms, but individual or combined involvement of these two processes seems to involve significant differences in pathways of formation, establishment and evolutionary consequences of resulting lineages. We evaluate here the classical cytological hypothesis that ploidy in hybrid speciation is governed by the extent of chromosomal rearrangements among parental species. Within a phylogenetic framework, we calculate genetic divergence indices for 50 parental species pairs and use these indices as surrogates for the overall degree of genomic divergence (i.e. as proxy for assessments of dissimilarity of the parental chromosomes). The results confirm that genomic differentiation between progenitor taxa influences the likelihood of diploid (homoploid) versus polyploid hybrid speciation because genetic divergence between parents of polyploids is found to be significantly greater than in the case of homoploid hybrid species. We argue that this asymmetric relationship may be reinforced immediately after hybrid formation, during stabilization and establishment. Underlying mechanisms potentially producing this pattern are discussed. PMID:19220761

  1. Speciation Progress: A Case Study on the Bushcricket Poecilimon veluchianus

    PubMed Central

    Eweleit, Lucienne; Reinhold, Klaus; Sauer, Jan

    2015-01-01

    Different mechanisms such as selection or genetic drift permitted e.g. by geographical isolation can lead to differentiation of populations and could cause subsequent speciation. The two subspecies of Poecilimon veluchianus, a bushcricket endemic to central Greece, show a parapatric distribution and are partially reproductively isolated. Therefore, P. veluchianus is suitable to investigate an ongoing speciation process. We based our analysis on sequences of the internal transcribed spacer (ITS) and the mitochondrial control region (CR). The population genetic analysis based on the nuclear marker ITS revealed a barrier to gene flow within the range of Poecilimon veluchianus, which corresponds well to the described subspecies. In contrast to the results based on the nuclear ITS marker, the mitochondrial CR marker does not clearly support the separation into two subspecies with restricted gene flow and a clear contact zone. Furthermore, we could identify isolation by distance (IBD) as one important mechanism responsible for the observed genetic structure (based on the ITS marker). The population genetic analysis based on the nuclear marker ITS also suggests the existence of hybrids in the wild. Furthermore, the simultaneous lack of strong prezygotic barriers and the presence of postzygotic mating barriers, observed in previous laboratory experiments, suggest that a secondary contact after an allopatric phase is more likely than parapatric speciation. PMID:26436732

  2. Tree of Life Reveals Clock-Like Speciation and Diversification

    PubMed Central

    Hedges, S. Blair; Marin, Julie; Suleski, Michael; Paymer, Madeline; Kumar, Sudhir

    2015-01-01

    Genomic data are rapidly resolving the tree of living species calibrated to time, the timetree of life, which will provide a framework for research in diverse fields of science. Previous analyses of taxonomically restricted timetrees have found a decline in the rate of diversification in many groups of organisms, often attributed to ecological interactions among species. Here, we have synthesized a global timetree of life from 2,274 studies representing 50,632 species and examined the pattern and rate of diversification as well as the timing of speciation. We found that species diversity has been mostly expanding overall and in many smaller groups of species, and that the rate of diversification in eukaryotes has been mostly constant. We also identified, and avoided, potential biases that may have influenced previous analyses of diversification including low levels of taxon sampling, small clade size, and the inclusion of stem branches in clade analyses. We found consistency in time-to-speciation among plants and animals, ∼2 My, as measured by intervals of crown and stem species times. Together, this clock-like change at different levels suggests that speciation and diversification are processes dominated by random events and that adaptive change is largely a separate process. PMID:25739733

  3. Selenium speciation in framboidal and euhedral pyrites in shales.

    PubMed

    Matamoros-Veloza, Adriana; Peacock, Caroline L; Benning, Liane G

    2014-08-19

    The release of Se from shales is poorly understood because its occurrence, distribution, and speciation in the various components of shale are unknown. To address this gap we combined bulk characterization, sequential extractions, and spatially resolved μ-focus spectroscopic analyses and investigated the occurrence and distribution of Se and other associated elements (Fe, As, Cr, Ni, and Zn) and determined the Se speciation at the μ-scale in typical, low bulk Se containing shales. Our results revealed Se primarily correlated with the pyrite fraction with exact Se speciation highly dependent on pyrite morphology. In euhedral pyrites, we found Se(-II) substitutes for S in the mineral structure. However, we also demonstrate that Se is associated with framboidal pyrite grains as a discrete, independent FeSex phase. The presence of this FeSex species has major implications for Se release, because FeSex species oxidize much faster than Se substituted in the euhedral pyrite lattice. Thus, such an FeSex species will enhance and control the dynamics of Se weathering and release into the aqueous environment.

  4. Learning about modes of speciation by computational approaches.

    PubMed

    Becquet, Céline; Przeworski, Molly

    2009-10-01

    How often do the early stages of speciation occur in the presence of gene flow? To address this enduring question, a number of recent papers have used computational approaches, estimating parameters of simple divergence models from multilocus polymorphism data collected in closely related species. Applications to a variety of species have yielded extensive evidence for migration, with the results interpreted as supporting the widespread occurrence of parapatric speciation. Here, we conduct a simulation study to assess the reliability of such inferences, using a program that we recently developed MCMC estimation of the isolation-migration model allowing for recombination (MIMAR) as well as the program isolation-migration (IM) of Hey and Nielsen (2004). We find that when one of many assumptions of the isolation-migration model is violated, the methods tend to yield biased estimates of the parameters, potentially lending spurious support for allopatric or parapatric divergence. More generally, our results highlight the difficulty in drawing inferences about modes of speciation from the existing computational approaches alone.

  5. Arsenic speciation in freshwater snails and its life cycle variation.

    PubMed

    Lai, Vivian W-M; Kanaki, Katerina; Pergantis, Spiros A; Cullen, William R; Reimer, Kenneth J

    2012-03-01

    Terrestrial snails are consumed by humans occasionally and they are an important food source for many creatures including fish and birds. Little is known about arsenic speciation in these gastropods, let alone life cycle variations. Here we report on the arsenic speciation in freshwater snails from Pender Island and Vancouver Island, B.C., Canada, which was determined on methanol/water extracts (43-59% extraction efficiency) by using high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and HPLC-electrospray tandem mass spectrometry. The tetramethylarsonium ion, oxo-arsenosugars and thio-arsenosugars are the main arsenic species encountered. Arsenobetaine, which is commonly found in the marine environment, is minor. Live bearing snails Viviparidae sp. from Pender Island were maintained in aquaria and the arsenic speciation in the unborn, newly born, and adult animals was monitored. Oxo-arsenosugars predominate in the adults, whereas thio-arsenosugars seem to predominate in juveniles, suggesting that these arsenicals are snail metabolites.

  6. Mercury speciation in seafood using isotope dilution analysis: a review.

    PubMed

    Clémens, Stéphanie; Monperrus, Mathilde; Donard, Olivier F X; Amouroux, David; Guérin, Thierry

    2012-01-30

    Mercury is a toxic compound that can contaminate humans through food and especially via fish consumption. Mercury's toxicity depends on the species, with methylmercury being the most hazardous form for humans. Hg speciation analysis has been and remains a widely studied subject because of the potential difficulty of preserving the initial distribution of mercury species in the analysed sample. Accordingly, many analytical methods have been developed and most of them incur significant loss and/or cross-species transformations during sample preparation. Therefore, to monitor and correct artefact formations, quantification by isotope dilution is increasingly used and provides significant added value for analytical quality assurance and quality control. This review presents and discusses the two different modes of application of isotope dilution analysis for elemental speciation (i.e. species-unspecific isotope dilution analysis and species-specific isotope dilution analysis) and the different quantification techniques (i.e. classical and multiple spike isotope dilution analyses). Isotope tracers are thus used at different stages of sample preparation to determine the extent of inter-species transformations and correct such analytical artefacts. Finally, a synthesis of the principal methods used for mercury speciation in seafood using isotope dilution analysis is presented.

  7. Chromosome variation, genomics, speciation and evolution in Sceloporus lizards.

    PubMed

    Hall, W P

    2009-01-01

    The clade of the North American lizard genus Sceloporus and its relatives comprising the subfamily Phrynosomatinae (Iguanidae) includes perhaps 150 evolutionary lineages. The work reviewed here begins with the discovery of the concentration of Robertsonian chromosomal variability in Sceloporus more than 40 years ago and cytogenetic and genomic evidence of remarkable chromosomal variation within the S. grammicus complex associated with narrow zones of hybridization between different chromosomal races. These discoveries led to hypotheses about hybrid zones involving negative heterosis, possible modes of chromosomal speciation, and the potential roles of such speciation in phylogenesis. The radiation of Sceloporus has now been studied by many different workers extending and mapping the geographic distribution of cytogenetic and genomic variation to understand the biology of the chromosomal variation and to establish the phyletic relationships of the various lineages. The result is a robust phylogeny and a large and still growing database of genic, cytogenetic and other biological parameters. These materials provide a rich series of natural experiments to support both synthetic-comparative and analytical studies of the roles of chromosomal variation, hybrid zones and modes of speciation in phylogenesis and evolutionary success.

  8. The 'shape' of phylogenies under simple random speciation models

    NASA Astrophysics Data System (ADS)

    Steel, Mike; McKenzie, Andy

    We describe some discrete structural properties of evolutionary trees generated under simple null models of speciation, such as the Yule model. These models have been used as priors in Bayesian approaches to phylogenetic analysis, and also to test hypotheses concerning the speciation process. Here we describe new results for four properties of trees generated under such models. Firstly, for a rooted tree generated by the Yule model we describe the probability distribution on the depth (number of edges from the root) of the most recent common ancestor of a random subset of k species. Secondly, for trees generated under the Yule and uniform models, we describe the induced distribution they generate on the number Cn of cherries in the tree, where a cherry is a pair of leaves each of which is adjacent to a common ancestor. Next we show that, for trees generated under the Yule model, the approximate position of the root can be estimated from the associated unrooted tree, even for trees with a large number of leaves. Finally, we analyse a biologically-motivated extension of the Yule model and describe its distribution on tree shapes when speciation occurs in rapid bursts.

  9. Recent advances in arsenic bioavailability, transport, and speciation in rice.

    PubMed

    Wang, Xin; Peng, Bo; Tan, Changyin; Ma, Lena; Rathinasabapathi, Bala

    2015-04-01

    Widespread arsenic (As) contamination in paddy rice (Oryza sativa) from both geologic and anthropogenic origins is an increasing concern globally. Substantial efforts have been made to elucidate As transformation and uptake processes in rhizosphere and metabolism in rice plant, which provides an essential foundation for the development of mitigation strategies. However, a range of crucial mechanisms from As mobilization in rhizosphere to transport to grains remain poorly understood. To provide new insight into the underlying mechanisms of As accumulation in rice, a range of new perspectives on As bioavailability, transport pathways, and in situ speciation are reviewed here. Specifically, the prominent effects of water regime, Fe plaque, and biochar on As mobilization in rice rhizosphere are discussed critically. An updated understanding of arsenite (AsIII) and methylated As transport from root to vascular bundle and grain is integrated and discussed in detail. Special attention is given to As speciation and distribution in rice grain with potential coping strategies being provided and discussed. Future research priorities are also identified. The new insight into As bioavailability, transport and speciation in rice would lead to a better understanding of As contamination in rice. They would also provide useful strategies from agronomic measures to genetic engineering for more effective restriction of As transport and accumulation in food chain.

  10. Artificial life and speciation, a case study: heterochromatin and speciation in the Microtus savii Group (Rodentia-Arvicolinae).

    PubMed

    Cordelli, Alessandro; Cerrai, Paola; Galleni, Lodovico

    2003-01-01

    Artificial life is a tool which is used for simulation of peculiar cases of evolutionary events. The main characteristic of artificial life is that with this technique it is possible to simulate for a high number of generations the evolution of a population of individuals. Each individual is characterised by a small number of parameters, but each individual has its own evolutive story. So far it is possible to simulate the evolution of a population of some thousands specimens, for a high number of generations. The realistic aspect of the simulation is that each specimen is taken individually. In our opinion this instrument is very useful to simulate the evolution of the hybrids barrier during speciation. For this reason it is applied to a peculiar case of speciation, that of the Savi pine vole (Microtus savii) whose experimental data were recently investigated.

  11. ISSUES IN SIMULATING ELEMENTAL MERCURY AIR/WATER EXCHANGE AND AQUEOUS MONOMETHYLMERCURY SPECIATION

    EPA Science Inventory

    This presentation focuses on two areas relevant to assessing the global fate and bioavailability of mercury: elemental mercury air/water exchange and aqueous environmental monomethylmercury speciation.

  12. Revisiting the particular role of host shifts in initiating insect speciation.

    PubMed

    Forbes, Andrew A; Devine, Sara N; Hippee, Alaine C; Tvedte, Eric S; Ward, Anna K G; Widmayer, Heather A; Wilson, Caleb J

    2017-01-04

    The notion that shifts to new hosts can initiate insect speciation is more than 150 years old, yet widespread conflation with paradigms of sympatric speciation has led to confusion about how much support exists for this hypothesis. Here, we review 85 insect systems and evaluate the relationship between host shifting, reproductive isolation, and speciation. We sort insects into five categories: (1) systems in which a host shift has initiated speciation; (2) systems in which a host shift has made a contribution to speciation; (3) systems in which a host shift has caused the evolution of new reproductive isolating barriers; (4) systems with host-associated genetic differences; and (5) systems with no evidence of host-associated genetic differences. We find host-associated genetic structure in 65 systems, 43 of which show that host shifts have resulted in the evolution of new reproductive barriers. Twenty-six of the latter also support a role for host shifts in speciation, including eight studies that definitively support the hypothesis that a host shift has initiated speciation. While this review is agnostic as to the fraction of all insect speciation events to which host shifts have contributed, it clarifies that host shifts absolutely can and do initiate speciation.

  13. A complex speciation-richness relationship in a simple neutral model.

    PubMed

    Desjardins-Proulx, Philippe; Gravel, Dominique

    2012-08-01

    Speciation is the "elephant in the room" of community ecology. As the ultimate source of biodiversity, its integration in ecology's theoretical corpus is necessary to understand community assembly. Yet, speciation is often completely ignored or stripped of its spatial dimension. Recent approaches based on network theory have allowed ecologists to effectively model complex landscapes. In this study, we use this framework to model allopatric and parapatric speciation in networks of communities. We focus on the relationship between speciation, richness, and the spatial structure of communities. We find a strong opposition between speciation and local richness, with speciation being more common in isolated communities and local richness being higher in more connected communities. Unlike previous models, we also find a transition to a positive relationship between speciation and local richness when dispersal is low and the number of communities is small. We use several measures of centrality to characterize the effect of network structure on diversity. The degree, the simplest measure of centrality, is the best predictor of local richness and speciation, although it loses some of its predictive power as connectivity grows. Our framework shows how a simple neutral model can be combined with network theory to reveal complex relationships between speciation, richness, and the spatial organization of populations.

  14. Mercury Speciation by X-ray Absorption Fine Structure Spectroscopy and Sequential Chemical Extractions: A Comparison of Speciation Methods

    USGS Publications Warehouse

    Kim, C.S.; Bloom, N.S.; Rytuba, J.J.; Brown, Gordon E.

    2003-01-01

    Determining the chemical speciation of mercury in contaminated mining and industrial environments is essential for predicting its solubility, transport behavior, and potential bioavailability as well as for designing effective remediation strategies. In this study, two techniques for determining Hg speciation-X-ray absorption fine structure (XAFS) spectroscopy and sequential chemical extractions (SCE)-are independently applied to a set of samples with Hg concentrations ranging from 132 to 7539 mg/kg to determine if the two techniques provide comparable Hg speciation results. Generally, the proportions of insoluble HgS (cinnabar, metacinnabar) and HgSe identified by XAFS correlate well with the proportion of Hg removed in the aqua regia extraction demonstrated to remove HgS and HgSe. Statistically significant (> 10%) differences are observed however in samples containing more soluble Hg-containing phases (HgCl2, HgO, Hg3S2O 4). Such differences may be related to matrix, particle size, or crystallinity effects, which could affect the apparent solubility of Hg phases present. In more highly concentrated samples, microscopy techniques can help characterize the Hg-bearing species in complex multiphase natural samples.

  15. Conservation as an alternative energy source

    NASA Technical Reports Server (NTRS)

    Allen, D. E.

    1978-01-01

    A speech is given outlining the energy situation in the United States. It is warned that the existing energy situation cannot prevail and the time is fast running out for continued growth or even maintenance of present levels. Energy conservation measures are given as an aid to decrease U.S. energy consumption, which would allow more time to develop alternative sources of energy.

  16. Fast wave current drive

    SciTech Connect

    Goree, J.; Ono, M.; Colestock, P.; Horton, R.; McNeill, D.; Park, H.

    1985-07-01

    Fast wave current drive is demonstrated in the Princeton ACT-I toroidal device. The fast Alfven wave, in the range of high ion-cyclotron harmonics, produced 40 A of current from 1 kW of rf power coupled into the plasma by fast wave loop antenna. This wave excites a steady current by damping on the energetic tail of the electron distribution function in the same way as lower-hybrid current drive, except that fast wave current drive is appropriate for higher plasma densities.

  17. fast-matmul

    SciTech Connect

    Grey Ballard, Austin Benson

    2014-11-26

    This software provides implementations of fast matrix multiplication algorithms. These algorithms perform fewer floating point operations than the classical cubic algorithm. The software uses code generation to automatically implement the fast algorithms based on high-level descriptions. The code serves two general purposes. The first is to demonstrate that these fast algorithms can out-perform vendor matrix multiplication algorithms for modest problem sizes on a single machine. The second is to rapidly prototype many variations of fast matrix multiplication algorithms to encourage future research in this area. The implementations target sequential and shared memory parallel execution.

  18. Including the spatial variability of metal speciation in the effect factor in life cycle impact assessment: Limits of the equilibrium partitioning method.

    PubMed

    Tromson, Clara; Bulle, Cécile; Deschênes, Louise

    2017-03-01

    In life cycle assessment (LCA), the potential terrestrial ecotoxicity effect of metals, calculated as the effect factor (EF), is usually extrapolated from aquatic ecotoxicological data using the equilibrium partitioning method (EqP) as it is more readily available than terrestrial data. However, when following the AMI recommendations (i.e. with at least enough species that represents three different phyla), there are not enough terrestrial data for which soil properties or metal speciation during ecotoxicological testing are specified to account for the influence of soil property variations on metal speciation when using this approach. Alternatively, the TBLM (Terrestrial Biotic Ligand Model) has been used to determine an EF that accounts for speciation, but is not available for metals; hence it cannot be consistently applied to metals in an LCA context. This paper proposes an approach to include metal speciation by regionalizing the EqP method for Cu, Ni and Zn with a geochemical speciation model (the Windermere Humic Aqueous Model 7.0), for 5213 soils selected from the Harmonized World Soil Database. Results obtained by this approach (EF(EqP)regionalized) are compared to the EFs calculated with the conventional EqP method, to the EFs based on available terrestrial data and to the EFs calculated with the TBLM (EF(TBLM)regionalized) when available. The spatial variability contribution of the EF to the overall spatial variability of the characterization factor (CF) has been analyzed. It was found that the EFs(EqP)regionalized show a significant spatial variability. The EFs calculated with the two non-regionalized methods (EqP and terrestrial data) fall within the range of the EFs(EqP)regionalized. The EFs(TBLM)regionalized cover a larger range of values than the EFs(EqP)regionalized but the two methods are not correlated. This paper highlights the importance of including speciation into the terrestrial EF and shows that using the regionalized EqP approach is not an

  19. Alternative Route Graphs in Road Networks

    NASA Astrophysics Data System (ADS)

    Bader, Roland; Dees, Jonathan; Geisberger, Robert; Sanders, Peter

    Every human likes choices. But today's fast route planning algorithms usually compute just a single route between source and target. There are beginnings to compute alternative routes, but there is a gap between the intuition of humans what makes a good alternative and mathematical definitions needed for grasping these concepts algorithmically. In this paper we make several steps towards closing this gap: Based on the concept of an alternative graph that can compactly encode many alternatives, we define and motivate several attributes quantifying the quality of the alternative graph. We show that it is already NP-hard to optimize a simple objective function combining two of these attributes and therefore turn to heuristics. The combination of the refined penalty based iterative shortest path routine and the previously proposed Plateau heuristics yields best results. A user study confirms these results.

  20. Fast protein folding kinetics

    PubMed Central

    Gelman, Hannah; Gruebele, Martin

    2014-01-01

    Fast folding proteins have been a major focus of computational and experimental study because they are accessible to both techniques: they are small and fast enough to be reasonably simulated with current computational power, but have dynamics slow enough to be observed with specially developed experimental techniques. This coupled study of fast folding proteins has provided insight into the mechanisms which allow some proteins to find their native conformation well less than 1 ms and has uncovered examples of theoretically predicted phenomena such as downhill folding. The study of fast folders also informs our understanding of even “slow” folding processes: fast folders are small, relatively simple protein domains and the principles that govern their folding also govern the folding of more complex systems. This review summarizes the major theoretical and experimental techniques used to study fast folding proteins and provides an overview of the major findings of fast folding research. Finally, we examine the themes that have emerged from studying fast folders and briefly summarize their application to protein folding in general as well as some work that is left to do. PMID:24641816

  1. Fast and effective?

    PubMed

    Trueland, Jennifer

    2013-12-18

    The 5.2 diet involves two days of fasting each week. It is being promoted as the key to sustained weight loss, as well as wider health benefits, despite the lack of evidence on the long-term effects. Nurses need to support patients who wish to try intermittent fasting.

  2. fastKDE

    SciTech Connect

    O'Brien, Travis A.; Kashinath, Karthik

    2015-05-22

    This software implements the fast, self-consistent probability density estimation described by O'Brien et al. (2014, doi: ). It uses a non-uniform fast Fourier transform technique to reduce the computational cost of an objective and self-consistent kernel density estimation method.

  3. Fast optical pyrometry

    NASA Technical Reports Server (NTRS)

    Cezairliyan, Ared

    1988-01-01

    Design and operation of accurate millisecond and microsecond resolution optical pyrometers developed at the National Bureau of Standards during the last two decades are described. Results of tests are presented and estimates of uncertainties in temperature measurements are given. Calibration methods are discussed and examples of applications of fast pyrometry are given. Ongoing research in developing fast multiwavelength and spatial scanning pyrometers are summarized.

  4. Approaches to Alternative Assessment.

    ERIC Educational Resources Information Center

    Hamayan, Else V.

    1995-01-01

    Examines the major characteristics of nontraditional or alternative assessment in language learning, the uses of alternative assessment procedures, and different types of alternative assessment. An annotated bibliography discusses eight important works in the field. (75 references) (MDM)

  5. Selenium speciation influences bioaccumulation in Limnodynastes peronii tadpoles.

    PubMed

    Lanctôt, C M; Melvin, S D; Cresswell, T

    2017-03-12

    Despite being essential for animal health and fitness, Se has a relatively narrow range between deficiency and toxicity, and excess Se can cause a variety of adverse effects in aquatic organisms. Amphibians are particularly vulnerable to contaminants during larval aquatic life stage, because they can accumulate toxic ions through various routes including skin, gills, lungs and digestive tract. Few attempts have been made to understand the tissue-specific accumulation of trace elements, including the impacts of chemical speciation in developing amphibian larvae. We used radiolabelled (75)Se to explore the biokinetics and tissue distributions of the two dominant forms occurring in surface waters, selenite (SeIV) and selenate (SeVI). Tadpoles of the native Australian frog Limnodynastes peronii were exposed to Se in both forms, and live-animal gamma spectroscopy was used to track accumulation and retention over time. Tissue biodistributions were also quantified at the end of the uptake and depuration phases. Results showed the bioconcentration of SeIV to be 3 times greater compared to SeVI, but rates of elimination were similar for both forms. This suggests a change of Se speciation within the organism prior to excretion. Depuration kinetics were best described by a one-phase exponential decay model, and tadpoles retained approximately 19% of the accumulated Se after 12 days of depuration in clean water. Selenium bioaccumulation was greatest in digestive and excretory organs, as well as the eye, which may directly relate to previously reported Se-induced impairments. Results demonstrate how the use of radiotracing techniques can significantly improve our understanding of trace element toxicokinetics and tissue distributions in developing amphibians. From an environmental monitoring perspective, the findings highlight the importance of considering chemical speciation as this could influence the accuracy of risk assessment.

  6. Models of selection, isolation, and gene flow in speciation.

    PubMed

    Hart, Michael W

    2014-10-01

    Many marine ecologists aspire to use genetic data to understand how selection and demographic history shape the evolution of diverging populations as they become reproductively isolated species. I propose combining two types of genetic analysis focused on this key early stage of the speciation process to identify the selective agents directly responsible for population divergence. Isolation-with-migration (IM) models can be used to characterize reproductive isolation between populations (low gene flow), while codon models can be used to characterize selection for population differences at the molecular level (especially positive selection for high rates of amino acid substitution). Accessible transcriptome sequencing methods can generate the large quantities of data needed for both types of analysis. I highlight recent examples (including our work on fertilization genes in sea stars) in which this confluence of interest, models, and data has led to taxonomically broad advances in understanding marine speciation at the molecular level. I also highlight new models that incorporate both demography and selection: simulations based on these theoretical advances suggest that polymorphisms shared among individuals (a key source of information in IM models) may lead to false-positive evidence of selection (in codon models), especially during the early stages of population divergence and speciation that are most in need of study. The false-positive problem may be resolved through a combination of model improvements plus experiments that document the phenotypic and fitness effects of specific polymorphisms for which codon models and IM models indicate selection and reproductive isolation (such as genes that mediate sperm-egg compatibility at fertilization).

  7. Mass spectrometic study of speciation in aluminium-fluoroquinolone solutions.

    PubMed

    Cvijovic, Mirjana; Di Marco, Valerio; Traldi, Pietro; Stankov, Milena J; Djurdjevic, Predrag

    2012-01-01

    Fluoroquinolones (FQLs) are synthetic antibacterial agents containing a 4-oxo-1,4-dihydroquinoline skeleton. When concomintantly administered with other drugs which may contain metal ions, particularly Al(3+) (antacids, phosphate binders, vaccines etc) they may form metal-drug complexes. Pharmacokinetic studies showed that aluminium-quinolone interactions lead to reduced bio- availability and altered activity of the drug with possible development of the toxic effects of aluminum ion. Reliable speciation in Al(3+) - quinolone systems at micromolar concentration level is needed to better understand pharmaco- and toxicokinetics of the FQLs in the presence of Al. In this work, the speciation in solutions containing Al(3+) and FQL family members (fleroxacin, moxifloxacin and ciprofloxacin) was studied by electrospray mass spectrometry (ESI-MS), ESI-MS/MS, and laser desorption ionization (LDI) MS. The dominating species identified in all the three Al(3+)-FQL solutions, at ca 30-50 µmol L(-1) total Al concentration and 2:1 to 1:3 metal-to-ligand ratio in the pH range 3.0- 6.0, were the ions related to the complexes AlL(2+), AlL(2)(+) and AlL(3)(0) (L = ligand in the monodeprotonated form). Mixed protonated and hydroxo complexes were also formed at lower and higher pH values respectively and, as expected, dimeric and polymeric species were not observed in ESI spectra. LDI measurements confirmed the existence of the mononuclear complexes found by ESI, and indicated the formation of polymeric species. The ion [2Al(3+) +5(-)](+) was identified with all three FQLs. This ionic species most probably arises from Al(2)L(2) by clustering with free ligand anions. Comparison of literature potentiometric data with mass spectral data indicated good agreement between speciation schemes. The obtained results suggest the presence of strong interaction between FQLs and Al(3+) which may be important in affecting absorption of these drugs in the gastrointestinal tract.

  8. Divergent selection drives genetic differentiation in an R2R3-MYB transcription factor that contributes to incipient speciation in Mimulus aurantiacus.

    PubMed

    Streisfeld, Matthew A; Young, Wambui N; Sobel, James M

    2013-03-01

    Identifying the molecular genetic basis of traits contributing to speciation is of crucial importance for understanding the ecological and evolutionary mechanisms that generate biodiversity. Despite several examples describing putative "speciation genes," it is often uncertain to what extent these genetic changes have contributed to gene flow reductions in nature. Therefore, considerable interest lies in characterizing the molecular basis of traits that actively confer reproductive isolation during the early stages of speciation, as these loci can be attributed directly to the process of divergence. In Southern California, two ecotypes of Mimulus aurantiacus are parapatric and differ primarily in flower color, with an anthocyanic, red-flowered morph in the west and an anthocyanin-lacking, yellow-flowered morph in the east. Evidence suggests that the genetic changes responsible for this shift in flower color have been essential for divergence and have become fixed in natural populations of each ecotype due to almost complete differences in pollinator preference. In this study, we demonstrate that a cis-regulatory mutation in an R2R3-MYB transcription factor results in differential regulation of enzymes in the anthocyanin biosynthetic pathway and is the major contributor to differences in floral pigmentation. In addition, molecular population genetic data show that, despite gene flow at neutral loci, divergent selection has driven the fixation of alternate alleles at this gene between ecotypes. Therefore, by identifying the genetic basis underlying ecologically based divergent selection in flower color between these ecotypes, we have revealed the ecological and functional mechanisms involved in the evolution of pre-mating isolation at the early stages of incipient speciation.

  9. EFFECTS OF PH AND COMPETING ANIONS ON THE SOLUTION SPECIATION OF ARSENIC BY ION EXCHANGE RESINS

    EPA Science Inventory

    Anion-exchange resins (AER) are used to differentiate As(V) and As(III) by retaining As(V) and allowing As(III) to pass through. AERs allow rapid speciation of As in the field which precludes the effects sample preservation on As speciation. Aqueous environmental samples contai...

  10. SPECIATION OF ORGANICS IN WATER WITH RAMAN SPECTROSCOPY: UTILITY OF IONIC STRENGTH VARIATION

    EPA Science Inventory

    We have developed and are applying an experimental and mathematical method for describing the micro-speciation of complex organic contaminants in aqueous media. For our case, micro-speciation can be defined as qualitative and quantitative identification of all discrete forms of ...

  11. GEOCHEM-EZ: a chemical speciation program with greater power and flexibility

    Technology Transfer Automated Retrieval System (TEKTRAN)

    GEOCHEM –EZ is a multi-functional chemical speciation program, which was designed to replace the existing GEOCHEM-PC, a program that can only be used on DOS consoles. Chemical speciation programs, such as GEOCHEM (Sposito and Mattigod, 1980) and GEOCHEM-PC (Parker et al., 1995), have been excellent ...

  12. A STUDY OF GAS-PHASE MERCURY SPECIATION USING DETAILED CHEMICAL KINETICS

    EPA Science Inventory

    Mercury (Hg) speciation in combustion-generated flue gas is modeled using a detailed chemical mechanism consisting of 60 reactions and 21 species. This speciation model accounts for chlorination and oxidation of key flue-gas components, including elemental mercury. Results indica...

  13. Recent Developments in the Speciation and Determination of Mercury Using Various Analytical Techniques

    PubMed Central

    Suvarapu, Lakshmi Narayana; Baek, Sung-Ok

    2015-01-01

    This paper reviews the speciation and determination of mercury by various analytical techniques such as atomic absorption spectrometry, voltammetry, inductively coupled plasma techniques, spectrophotometry, spectrofluorometry, high performance liquid chromatography, and gas chromatography. Approximately 126 research papers on the speciation and determination of mercury by various analytical techniques published in international journals since 2013 are reviewed. PMID:26236539

  14. Speciation is associated with changing ornamentation rather than stronger sexual selection.

    PubMed

    Gomes, Ana Cristina R; Sorenson, Michael D; Cardoso, Gonçalo C

    2016-12-01

    Although sexual ornamentation mediates reproductive isolation, comparative evidence does not support the hypothesis that stronger sexual selection promotes speciation. Prior analyses have neglected the possibility that decreases in ornamentation may also promote speciation, such that both increases and decreases in the strength of sexual selection and associated changes in ornamentation promote speciation. To test this hypothesis, we studied color ornamentation in one of the largest and fastest avian radiations, the estrildid finches. We show that more ornamented lineages do not speciate more, even though they tend to have faster rates of ornamental evolution, whereas changes in ornamentation (i.e., increases or decreases) are associated with speciation. This indicates that divergence in sexually selected ornamentation, rather than stronger sexual selection, promotes or is otherwise associated with speciation. We also show that gregariousness and investment in reproduction are related to the elaboration of some ornamental traits, suggesting ecological influences on speciation mediated by ornamentation. We conclude that past work focusing specifically on the strength of sexual selection may have greatly underestimated the importance of sexual ornamentation for speciation.

  15. EPA’s SPECIATE 4.4 Database - Development and Uses

    EPA Science Inventory

    SPECIATE is the EPA's repository of TOG, PM, and Other Gases speciation profiles of air pollution sources. It includes weight fractions of both organic species and PM and provides data in consistent units. Species include metals, ions, elements, and organic and inorganic compound...

  16. Speciated organic VOC and PM emissions from peat burns

    EPA Pesticide Factsheets

    Supporting information Tables S3 and S4 list emission factors in g/kg of speciated volatile and particulate organic compounds emitted from peat burning. Peat samples were acquired from Alligator River (AR) and Pocosin Lakes (PL) National Wildlife Refuges. This dataset is associated with the following publication:George , I., R. Black, J. Walker , C. Geron , J. Aurell , M. Hays , W. Preston, and B. Gullett. Volatile and semivolatile organic compounds in laboratory peat fire emissions. ATMOSPHERIC ENVIRONMENT. Elsevier Science Ltd, New York, NY, USA, 132: 163-170, (2016).

  17. Biotoxicity of mercury as influenced by mercury(II) speciation.

    PubMed

    Farrell, R E; Germida, J J; Huang, P M

    1990-10-01

    Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and Hg

  18. Colonization and speciation of cave animals in the Philippines

    NASA Astrophysics Data System (ADS)

    Husana, D.; Yamamuro, M.; Kase, T.

    2012-12-01

    Island-like situation of caves resulted to species isolation while organism's phenotypic plasticity allows the animal to cope with the cave's environment. These conditions eventually lead to organism's speciation through genetic differentiation. Combined morphological and molecular analyses provided insights on the speciation events and colonization of the subterranean ecosystem. Morphological analysis of hypogean species, known as troglobite, and its epigean congeners showed the interesting differences in their characters. Troglobite exhibited cave adaptations such as degenerated eyesight, enlargement or elongation of ambulatory organs, loss of pigmentation and development of other useful organs that favors their survival in the dark cave environment. Molecular clock estimation based on the substitution rate of 0.88% per million years established for 16S rRNA for the grapsid crab genus Sesarma suggested that the troglobitic Sundathelphusa species colonized the cave habitat in Samar Island in the late Miocene epoch and started to diverge from its epigean ancestor ca. 5.92 mya. Interestingly, the five species of the genus Sundathelphusa from Bohol Island comprising of both hypogean and epigean species (S. cavernicola, S. sottoae, S. vediniki, S. urichi and S. boex) occupy a single clade with divergence time from its sister clade ca. 2.58 mya. This phenomenon suggests two possible interpretations of the existence of Bohol species: (1) they belong to a single species with regular genetic flow from their surface relative and that their character differences can be best interpreted as ecophenotypic, or, (2) the speciation event was very rapid and quite recent. Mitochondrial DNA sequences of 430 base pairs of the large subunit rRNA (16S rRNA) revealed the phylogenetic relationships of the genus Sundathelphusa suggesting a multiple colonizations of caves. The speciation events coincided with the timing of the eustatic sea level fluctuation and geologic changes in the

  19. Fe, Ni and Zn speciation, in airborne particulate matter

    NASA Astrophysics Data System (ADS)

    Thiodjio Sendja, Bridinette; Aquilanti, Giuliana; Vassura, Ivano; Giorgetti, Marco

    2016-05-01

    The study of elemental speciation in atmospheric particulate matter is important for the assessment of the source of the particle as well for the evaluation of its toxicity. XANES data at Fe, Ni, and Zn K-edges are recorded on a sample of urban dust (from the Rimini area of Emilia Romagna region, Italy) deposited on a filter and on the NIST standard reference material 1648. Using linear combination fitting we give an indication of the chemical species of the three metals present in the samples.

  20. Identification of Trace Metal Speciation in Environment Using Z-Contrast Imaging

    SciTech Connect

    S. Utsunomiya

    2005-01-11

    A major challenge to understanding the fate of contaminants in environment is the direct identification of trace concentrations (ppm to ppb) at the sub-micron scale. In order to efficiently characterize the trace metals in various environmental and geological samples, we have utilized high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with conventional TEM techniques. In general, the image contrast observed in the HAADF-STEM is correlated to the atomic mass: heavier elements contribute to a brighter contrast. Additionally, the contrast in HAADF-STEM is characteristically independent of focus, because the image is formed by incoherent scattering. Remarkable results obtained using the advanced TEM technique are shown as an example. (1) Fine- and ultra-fine particles with heavy metals in urban aerosols from various locations were examined to investigate metal concentrations and speciation. The trace element speciation: Pb, As, Sb, La, Ce, Sr, Zn, Cr, Se, Sn, Y, Zr, Au, Ag and U have been characterized. We have identified nanocrystals of uraninite encapsulated in carbonaceous matter ({approx} 50 nm). The ''carbon-caged'' nanocrystals of uraninite are protected from the immediate oxidation that would lead to increased mobility of uranium in the environment. Still, the presence of uranium in the very fine-fraction (PM{sub 2.5}) of atmospheric particulates provides another pathway for radiation exposure [1]. (2) A direct, near atomic-scale characterization of Pb is demonstrated in zircon (3.3-4.4 Ga). Two forms of Pb have been identified: Pb concentrated at {approx}3 atom% as a nanoscale patch in zircon structure, and Pb concentrated within the amorphous domain created by fission fragment damage. The first result suggests that the Pb atoms directly substitute for Zr{sup 4+} in the zircon structure, and the latter observation demonstrates that Pb diffusion can occur through amorphous regions created by radiation damage, although

  1. Non-refractory PM1 in SE Asia: Chemically speciated aerosol fluxes and concentrations above contrasting land-uses in SE Asia.

    NASA Astrophysics Data System (ADS)

    Phillips, Gavin; Farmer, Delphine; di Marco, Chiara; Misztal, Pawel; Sueper, Donna; Kimmel, Joel; Jimenez, Jose; Fowler, David; Nemitz, Eiko

    2010-05-01

    aerosol components formed through fast chemistry below the measurement height would appear as an upward flux, and the direct flux measurement therefore provides an alternative approach to probing BSOA formation mechanisms. In particular, through the calculation of mass spectra in terms of flux and deposition velocity those masses and aerosol fragments can be identified that show similar behaviour. In addition, the contribution of the various chemical species (e.g. nitrate, sulphate, OA sub-types) to the total mass flux will be elucidated.

  2. Minimal effects of latitude on present-day speciation rates in New World birds.

    PubMed

    Rabosky, Daniel L; Title, Pascal O; Huang, Huateng

    2015-06-22

    The tropics contain far greater numbers of species than temperate regions, suggesting that rates of species formation might differ systematically between tropical and non-tropical areas. We tested this hypothesis by reconstructing the history of speciation in New World (NW) land birds using BAMM, a Bayesian framework for modelling complex evolutionary dynamics on phylogenetic trees. We estimated marginal distributions of present-day speciation rates for each of 2571 species of birds. The present-day rate of speciation varies approximately 30-fold across NW birds, but there is no difference in the rate distributions for tropical and temperate taxa. Using macroevolutionary cohort analysis, we demonstrate that clades with high tropical membership do not produce species more rapidly than temperate clades. For nearly any value of present-day speciation rate, there are far more species in the tropics than the temperate zone. Any effects of latitude on speciation rate are marginal in comparison to the dramatic variation in rates among clades.

  3. Miniaturized preconcentration methods based on liquid-liquid extraction and their application in inorganic ultratrace analysis and speciation: A review

    NASA Astrophysics Data System (ADS)

    Pena-Pereira, Francisco; Lavilla, Isela; Bendicho, Carlos

    2009-01-01

    Liquid-liquid extraction (LLE) is widely used as a pre-treatment technique for separation and preconcentration of both organic and inorganic analytes from aqueous samples. Nevertheless, it has several drawbacks, such as emulsion formation or the use of large volumes of solvents, which makes LLE expensive and labour intensive. Therefore, miniaturization of conventional liquid-liquid extraction is needed. The search for alternatives to the conventional LLE using negligible volumes of extractant and the minimum number of steps has driven the development of three new miniaturized methodologies, i.e. single-drop microextraction (SDME), hollow fibre liquid-phase microextraction (HF-LPME) and dispersive liquid-liquid microextraction (DLLME). The aim of this paper is to provide an overview of these novel preconcentration approaches and their potential use in analytical labs involved in inorganic (ultra)trace analysis and speciation. Relevant applications to the determination of metal ions, metalloids, organometals and non-metals are included.

  4. In-situ speciation of Ni and Zn in freshwaters: comparison between DGT measurements and speciation models.

    PubMed

    Zhang, Hao

    2004-03-01

    The technique of DGT (diffusive gradients in thin films) was used for the first time to measure in situ the distribution of Zn and Ni between inorganic species and complexes with fulvic and humic acids in natural waters. With DGT, metals are bound to a resin embedded in a layer of hydrogel after diffusive transport through an adjacent layer of hydrogel. The metal concentrations in the waters can be quantified using simple diffusion equations. By using devices with hydrogels of different pore size, large and small complex species were discriminated. Inorganic species diffuse freely through all gels, but larger organic complexes with fulvic and humic acids diffuse less freely through more restricted gels (gels with smaller pore size). Systematic differences between DGT devices containing gels of different pore size were obtained. Their calibration for the diffusion of fulvic and humic complexes allowed calculation of the concentrations of labile inorganic (Zn, 34.6 +/- 2.5 nM; Ni, 23.5 +/- 0.9 nM) and labile organic (Zn, 43.1 +/- 2.9 nM; Ni, 11.2 +/- 0.7 nM) complexes. The concentration of Zn measured by anodic stripping voltammetry in samples returned to the laboratory lay between the DGT-measured inorganic concentration and the total dissolved concentration, consistent with partial measurement of organic complexes of Zn. The speciation model WHAM successfully predicted the species distribution of Ni, Zn, and Cu, provided that competitive binding by Fe(III) was considered. Using the speciation models WHAM and ECOSAT, free ion activities of Zn and Ni were calculated from (1) the total inorganic species measured by DGT and (2) the total dissolved species and dissolved organic carbon. The calculations confirmed the good model predictions of metal-humic binding but highlighted problems with default databases used for the speciation of inorganic components.

  5. Reusable fast opening switch

    DOEpatents

    Van Devender, J.P.; Emin, D.

    1983-12-21

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  6. Reusable fast opening switch

    DOEpatents

    Van Devender, John P.; Emin, David

    1986-01-01

    A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

  7. FAST Construction Progress

    NASA Astrophysics Data System (ADS)

    Nan, R. D.; Zhang, H. Y.; Zhang, Y.; Yang, L.; Cai, W. J.; Liu, N.; Xie, J. T.; Zhang, S. X.

    2016-11-01

    The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is a Chinese mega-science project to build the largest single dish radio telescope in the world. A unique karst depression in Guizhou province has been selected as the site to build an active reflector radio telescope with a diameter of 500 m and three outstanding aspects, which enables FAST to have a large sky coverage and the ability of observing astronomical targets with a high precision. Chinese Academy of Sciences and Guizhou province are in charge of FAST construction. The first light of the telescope was expected on September 25, 2016.

  8. Ecological factors influencing tetraploid speciation in snow buttercups (Ranunculus Adoneus): niche differentiation and tetraploid establishment.

    PubMed

    Baack, Eric J; Stanton, Maureen L

    2005-09-01

    Chromosome doubling plays an important role in generating new species of flowering plants. However, reproductive incompatibilities between newly formed tetraploid plants and their diploid progenitors are expected to create a significant barrier to the persistence and establishment of neopolyploid populations. Ecological differentiation can reduce this barrier via prezygotic isolation arising from spatial separation. Alternatively, superior viability or fecundity of neotetraploid plants might compensate for the reproductive cost of incompatible pollen from diploid neighbors. The performance of plants of both cytotypes can be assessed in their respective habitats through reciprocal transplants, although such experiments have not been used previously in the study of tetraploid speciation. We used a series of seed and seedling transplant experiments to assess ecological differentiation and competitive ability during early establishment phases for tetraploid and diploid forms of the snow buttercup (Ranunculus adoneus). At two sites, seeds from diploids and tetraploids had similar germination probabilities. Tetraploid snow buttercup seedlings had a significant growth advantage in a controlled environment chamber experiment. However, in the field diploid and tetraploid buttercup seedlings did not differ consistently in survival or growth, nor did the two cytotypes show reciprocal advantages in performance, as expected if ecological differentiation has occurred. At the seed and seedling stages, neither niche differentiation nor tetraploid competitive superiority appears sufficient to explain neotetraploid success in the presence of their diploid progenitors.

  9. A sensitive flow-based procedure for spectrophotometric speciation analysis of inorganic bromine in waters.

    PubMed

    Rocha, Diogo L; Machado, Marcos C; Melchert, Wanessa R

    2014-11-01

    A flow-based system with solenoid micro-pumps and long path-length spectrophotometry for bromate and bromide determination in drinking water is proposed. The method is based on the formation of an unstable dye from the reaction between bromate, 2-(5-dibromo-2-pyridylazo)-5-(diethylamino)phenol (5-Br-PADAP) and thiocyanate ions. A multivariate optimization was carried out. A linear response was observed between 5.0 and 100 µg L(-1) BrO3(-) and the detection limit was estimated as 2.0 µg L(-1) (99.7% confidence level). The coefficient of variation (n=20) and sampling rate were estimated as 1.0% and 40 determinations per hour, respectively. Reagent consumption was estimated as 0.17 µg of 5-Br-PADAP and 230 μg of NaSCN per measurement, generating 6.0 mL of waste. Bromide determination was carried out after UV-assisted conversion with K2S2O8 using 300 µL of sample within the range 20-400 µg L(-1) Br(-). The generated bromate was then determined by the proposed flow system. The results for tap and commercial mineral water samples agreed with those obtained with the reference procedure at the 95% confidence level. The proposed procedure is therefore a sensitive, environmentally friendly and reliable alternative for inorganic bromine speciation.

  10. All About Alternatives

    ERIC Educational Resources Information Center

    Barr, Robert D.; And Others

    1972-01-01

    A primer on alternative schools. Described are existing programs in different areas, philosophy of the alternative schools, funding, student behavior, community relations, accountability, State regulations, management, and the environment of the alternative school. A list of sources of additional information on alternative schools is included.…

  11. Rapid biological speciation driven by tectonic evolution in New Zealand

    NASA Astrophysics Data System (ADS)

    Craw, Dave; Upton, Phaedra; Burridge, Christopher P.; Wallis, Graham P.; Waters, Jonathan M.

    2016-02-01

    Collisions between tectonic plates lead to the rise of new mountain ranges that can separate biological populations and ultimately result in new species. However, the identification of links between tectonic mountain-building and biological speciation is confounded by environmental and ecological factors. Thus, there are surprisingly few well-documented examples of direct tectonic controls on terrestrial biological speciation. Here we present examples from New Zealand, where the rapid evolution of 18 species of freshwater fishes has resulted from parallel tectonic landscape evolution. We use numerical models to reconstruct changes in the deep crustal structure and surface drainage catchments of the southern island of New Zealand over the past 25 million years. We show that the island and mountain topography evolved in six principal tectonic zones, which have distinct drainage catchments that separated fish populations. We use new and existing phylogenetic analyses of freshwater fish populations, based on over 1,000 specimens from more than 400 localities, to show that fish genomes can retain evidence of this tectonic landscape development, with a clear correlation between geologic age and extent of DNA sequence divergence. We conclude that landscape evolution has controlled on-going biological diversification over the past 25 million years.

  12. Timing and rate of speciation in Agave (Agavaceae).

    PubMed

    Good-Avila, Sara V; Souza, Valeria; Gaut, Brandon S; Eguiarte, Luis E

    2006-06-13

    The Agave (Agavaceae) are keystone species of semiarid to arid regions where the geographic center of origin is Mexico but whose populations spread from the southwestern U.S. through Central America, the Caribbean, and into northern South America. Our analyses indicate that Agave is a young genus, between 7.8 and 10.1 million years old, and yet it harbors the most species of any genera in the family. Of the eight genera in the family, Agave is paraphyletic with respect to three of them, and these four genera are often grouped into a genus termed Agave sensu lato, which harbors 208 of the 293 recognized species in the Agavaceae. In this article, we examine the phylogenetic limits of Agave sensu lato and present analyses elucidating the origin and rate of speciation in the group. These analyses lead to some new insights into the phylogenetic limits of Agave, indicate an estimated age of the family between 20 and 26 million years and an age of the Agave sensu lato of speciation were significantly elevated between 8 and 6 million years ago and then again between 3 and 2.5 million years ago. We discuss the potential for both monocarpy and the evolution of a generalist pollination system, largely dependent on nectarivorous bat species, as possible driving factors in the radiation of the group.

  13. Incipient speciation driven by hypertrophied lips in Midas cichlid fishes?

    PubMed

    Machado-Schiaffino, Gonzalo; Kautt, Andreas F; Torres-Dowdall, Julian; Baumgarten, Lukas; Henning, Frederico; Meyer, Axel

    2017-01-30

    Sympatric speciation has been debated in evolutionary biology for decades. Although it has gained in acceptance recently, still only a handful of empirical examples are seen as valid (e.g. crater lake cichlids). In this study, we disentangle the role of hypertrophied lips in the repeated adaptive radiations of Nicaraguan crater lake cichlid fish. We assessed the role of disruptive selection and assortative mating during the early stages of divergence and found a functional trade-off in feeding behaviour between thick- and thin-lipped ecotypes, suggesting that this trait is a target of disruptive selection. Thick-lipped fish perform better on nonevasive prey at the cost of a poorer performance on evasive prey. Using enclosures in the wild, we found that thick-lipped fish perform significantly better in rocky than in sandy habitats. We found almost no mixed pairs during two breeding seasons and hence significant assortative mating. Genetic differentiation between ecotypes seems to be related to the time since colonization, being subtle in L. Masaya (1600 generations ago) and absent in the younger L. Apoyeque (<600 generations ago). Genome-wide differentiation between ecotypes was higher in the old source lakes than in the young crater lakes. Our results suggest that hypertrophied lips might be promoting incipient sympatric speciation through divergent selection (ecological divergence in feeding performance) and nonrandom mating (assortative mating) in the young Nicaraguan crater lakes. Nonetheless, further manipulative experiments are needed in order to confirm the role of hypertrophied lips as the main cue for assortative mating.

  14. Astatine standard redox potentials and speciation in acidic medium.

    PubMed

    Champion, J; Alliot, C; Renault, E; Mokili, B M; Chérel, M; Galland, N; Montavon, G

    2010-01-14

    A combined experimental and theoretical approach is used to define astatine (At) speciation in acidic aqueous solution and to answer the two main questions raised from literature data: does At(0) exist in aqueous solution and what is the chemical form of At(+III), if it exists. The experimental approach considers that a given species is characterized by its distribution coefficient (D) experimentally determined in a biphasic system. The change in speciation arising from a change in experimental conditions is observed by a change in D value. The theoretical approach involves quasi-relativistic quantum chemistry calculations. The results show that At at the oxidation state 0 cannot exist in aqueous solution. The three oxidation states present in the range of water stability are At(-I), At(+I), and At(+III) and exist as At(-), At(+), and AtO(+), respectively, in the 1-2 pH range. The standard redox potentials of the At(+)/At(-) and AtO(+)/At(+) couples have been determined, the respective values being 0.36 +/- 0.01 and 0.74 +/- 0.01 V vs NHE.

  15. Parallel speciation in Astyanax cave fish (Teleostei) in Northern Mexico.

    PubMed

    Strecker, Ulrike; Hausdorf, Bernhard; Wilkens, Horst

    2012-01-01

    We investigated differentiation processes in the Neotropical fish Astyanax that represents a model system for examining adaptation to caves, including regressive evolution. In particular, we analyzed microsatellite and mitochondrial data of seven cave and seven surface populations from Mexico to test whether the evolution of the cave fish represents a case of parallel evolution. Our data revealed that Astyanax invaded northern Mexico across the Trans-Mexican Volcanic Belt at least three times and that populations of all three invasions adapted to subterranean habitats. Significant differentiation was found between the cave and surface populations. We did not observe gene flow between the strongly eye and pigment reduced old cave populations (Sabinos, Tinaja, Pachon) and the surface fish, even when syntopically occurring like in Yerbaniz cave. Little gene flow, if any, was found between cave populations, which are variable in eye and pigmentation (Micos, Chica, Caballo Moro caves), and surface fish. This suggests that the variability is due to their more recent origin rather than to hybridization. Finally, admixture of the young Chica cave fish population with nuclear markers from older cave fish demonstrates that gene flow between populations that independently colonized caves occurs. Thus, all criteria of parallel speciation are fulfilled. Moreover, the microsatellite data provide evidence that two co-occurring groups with small sunken eyes and externally visible eyes, respectively, differentiated within the partly lightened Caballo Moro karst window cave and might represent an example for incipient sympatric speciation.

  16. Evaluation of mercury speciation by EPA (Draft) Method 29

    SciTech Connect

    Laudal, D.L.; Heidt, M.K.; Nott, B.

    1995-11-01

    The 1990 Clean Air Act Amendments require that the U.S. Environmental protection Agency (EPA) assess the health risks associated with mercury emissions. Also, the law requires a separate assessment of health risks posed by the emission of 189 tract chemicals (including mercury) for electric utility steam-generating units. In order to conduct a meaningful assessment of health and environmental effects, we must have, among other things, a reliable and accurate method to measure mercury emissions. In addition, the rate of mercury deposition and the type of control strategies used may depend upon the type of mercury emitted (i.e., whether it is in the oxidized or elemental form). It has been speculated that EPA (Draft) Method 29 can speciate mercury by selective absorption; however, this claim has yet to be proven. The Electric Power Research Institute (EPRI) and the U.S. Department of Energy (DOE) have contracted with the Energy & Environmental Research Center (EERC) at University of North Dakota to evaluate EPA (Draft) Method 29 at the pilot-scale level. The objective of the work is to determine whether EPA (Draft) Method 29 can reliably quantify and speciate mercury in the flue gas from coal-fired boilers.

  17. Technetium Inventory, Distribution, and Speciation in Hanford Tanks

    SciTech Connect

    Serne, R. Jeffrey; Rapko, Brian M.; Pegg, Ian L.

    2014-11-13

    The purpose of this report is three fold: 1) assemble the available information regarding Tc inventory, distribution between phases, and speciation in Hanford’s 177 storage tanks into a single, detailed, comprehensive assessment; 2) discuss the fate (distribution/speciation) of Tc once retrieved from the storage tanks and processed into final waste forms; and 3) discuss/document in less detail the available data on the inventory of Tc in other “pools” such as the vadose zone below inactive cribs and trenches, below single-shell tanks (SSTs) that have leaked, and in the groundwater below the Hanford Site. This report was revised in September 2014 to add detail and correct inaccuracies in Section 5.0 on the fate of technetium (Tc) recycle from the off-gas systems downstream of the low-activity waste (LAW) melters back to the melters, based on several reports that were not found in the original literature search on the topic. The newly provided reports, from experts active in the Hanford Tank Waste Treatment and Immobilization Plant (WTP) glass studies, the Vitreous State Laboratory at The Catholic University of America (VSL) melter and off-gas system demonstrations and overall WTP systems analysis, were not originally found on electronic databases commonly searched. The major revisions to Section 5.0 also required changes to Section 7.0 (Summary and Conclusions) and this executive summary.

  18. Arsenic leachability and speciation in cement immobilized water treatment sludge.

    PubMed

    Jing, Chuanyong; Liu, Suqin; Meng, Xiaoguang

    2005-06-01

    Arsenic leachability and speciation in cement immobilized water treatment sludge were investigated with leaching tests and X-ray absorption near edge structure (XANES) spectroscopy. The As leachability in the sludge determined with the toxicity characteristic leaching procedure (TCLP) and the waste extraction test (WET) was 283 and 7490 microgl(-1), respectively. Extractions with a lower liquid to solid ratio, under anaerobic conditions, and using citric acid buffer solution dramatically increased the leachate As concentration. XANES results showed that the As(III) composition was reduced from 51.1% of the total As content in the sludge to 16.3% in the cement treated sample with 28 days of cure. When the cement treated sample was cured for two years, the As(III) composition was decreased to 7.4%. The cement treatment reduced the As leachability. The leachate As(III) and total As concentrations were of the same order of magnitude in the samples cured for 28 days as for 2yr. However, consistently lower concentrations were detected in samples with longer cure time. The results of this study improve our understanding of arsenic speciation and leachability in the cement matrix after long cure times.

  19. Recent speciation between sympatric Tanganyikan cichlid colour morphs.

    PubMed

    Wagner, Catherine E; McCune, Amy R; Lovette, Irby J

    2012-07-01

    Lake Tanganyika, Africa's oldest lake, harbours an impressive diversity of cichlid fishes. Although diversification in its radiating groups is thought to have been initially rapid, cichlids from Lake Tanganyika show little evidence for ongoing speciation. In contrast, examples of recent divergence among sympatric colour morphs are well known in haplochromine cichlids from Lakes Malawi and Victoria. Here, we report genetic evidence for recent divergence between two sympatric Tanganyikan cichlid colour morphs. These Petrochromis morphs share mitochondrial haplotypes, yet microsatellite loci reveal that their sympatric populations form distinct genetic groups. Nuclear divergence between the two morphs is equivalent to that which arises geographically within one of the morphs over short distances and is substantially smaller than that among other sympatric species in this genus. These patterns suggest that these morphs diverged only recently, yet that barriers to gene flow exist which prevent extensive admixture despite their sympatric distribution. The morphs studied here provide an unusual example of active diversification in Lake Tanganyika's generally ancient cichlid fauna and enable comparisons of speciation processes between Lake Tanganyika and other African lakes.

  20. Speciation, formation, stability and analytical challenges of human arsenic metabolites

    PubMed Central

    Yehiayan, Lucy; Pattabiraman, Mahesh; Kavallieratos, Konstantinos; Wang, Xiaotang; Boise, Lawrence H.

    2012-01-01

    Human arsenic metabolism produces a number of species with varying toxicities; the presence of some has been identified while the existence of others has been postulated through indirect evidence. Speciation methods for the analysis of arsenite (AsIII), monomethylarsonous acid (MMAIII), dimethylarsinous acid (DMAIII), arsenate (AsV), monomethylarsonic acid (MMAV), dimethylarsinic acid (DMAV), arsino-glutathione (As(GS)3), monomethylarsino-glutathione (MMA(GS)2) and dimethylarsino-glutathione (DMA(GS)) were developed in this study through the use of cation exchange and reverse phase chromatography in a complementary manner. Electrospray ionization mass spectrometry (ESI-MS) was used for molecular identification of the arsenicals while inductively coupled plasma mass spectrometry (ICP-MS) was employed for quantitation purposes. Validation of the developed methods against each other for the quantitation of trivalent and pentavalent arsenicals was performed. The effect of reduced glutathione (GSH) concentration on the formation of arsenic-glutathione (As-GSH) complexes was studied. In the presence of glutathione, the occurrence of chromatographic artifacts on the cation exchange column was observed. The stability of trivalent arsenicals and As-GSH complexes was studied at various pH conditions. The results shed light on the importance of sample preparation, storage and proper choice of analytical column for the accurate identification of the As species. Reinvestigation of some of the previously reported As speciation studies of glutathione-rich biological samples needs to be performed for the verification of occurrence of As-GSH complexes and DMAIII. PMID:23495261

  1. Timing and rate of speciation in Agave (Agavaceae)

    PubMed Central

    Good-Avila, Sara V.; Souza, Valeria; Gaut, Brandon S.; Eguiarte, Luis E.

    2006-01-01

    The Agave (Agavaceae) are keystone species of semiarid to arid regions where the geographic center of origin is Mexico but whose populations spread from the southwestern U.S. through Central America, the Caribbean, and into northern South America. Our analyses indicate that Agave is a young genus, between 7.8 and 10.1 million years old, and yet it harbors the most species of any genera in the family. Of the eight genera in the family, Agave is paraphyletic with respect to three of them, and these four genera are often grouped into a genus termed Agave sensu lato, which harbors 208 of the 293 recognized species in the Agavaceae. In this article, we examine the phylogenetic limits of Agave sensu lato and present analyses elucidating the origin and rate of speciation in the group. These analyses lead to some new insights into the phylogenetic limits of Agave, indicate an estimated age of the family between 20 and 26 million years and an age of the Agave sensu lato of ≤10 million years. Furthermore, we estimate a high mean per-lineage rate of diversification for the genus and find that rates of speciation were significantly elevated between 8 and 6 million years ago and then again between 3 and 2.5 million years ago. We discuss the potential for both monocarpy and the evolution of a generalist pollination system, largely dependent on nectarivorous bat species, as possible driving factors in the radiation of the group. PMID:16757559

  2. Allopatric speciation within a cryptic species complex of Australasian octopuses.

    PubMed

    Amor, Michael D; Norman, Mark D; Cameron, Hayley E; Strugnell, Jan M

    2014-01-01

    Despite extensive revisions over recent decades, the taxonomy of benthic octopuses (Family Octopodidae) remains in a considerable flux. Among groups of unresolved status is a species complex of morphologically similar shallow-water octopods from subtropical Australasia, including: Allopatric populations of Octopus tetricus on the eastern and western coasts of Australia, of which the Western Australian form is speculated to be a distinct or sub-species; and Octopus gibbsi from New Zealand, a proposed synonym of Australian forms. This study employed a combination of molecular and morphological techniques to resolve the taxonomic status of the 'tetricus complex'. Phylogenetic analyses (based on five mitochondrial genes: 12S rRNA, 16S rRNA, COI, COIII and Cytb) and Generalised Mixed Yule Coalescent (GMYC) analysis (based on COI, COIII and Cytb) distinguished eastern and Western Australian O. tetricus as distinct species, while O. gibbsi was found to be synonymous with the east Australian form (BS = >97, PP = 1; GMYC p = 0.01). Discrete morphological differences in mature male octopuses (based on sixteen morphological traits) provided further evidence of cryptic speciation between east (including New Zealand) and west coast populations; although females proved less useful in morphological distinction among members of the tetricus complex. In addition, phylogenetic analyses suggested populations of octopuses currently treated under the name Octopus vulgaris are paraphyletic; providing evidence of cryptic speciation among global populations of O. vulgaris, the most commercially valuable octopus species worldwide.

  3. Speciation and bioavailability of zinc in amended sediments

    SciTech Connect

    Williams, Aaron G.B.; Scheckel, Kirk G.; McDermott, Gregory; Gratson, David; Neptune, Dean; Ryan, James A.

    2011-12-09

    The speciation and bioavailability of zinc (Zn) in smelter-contaminated sediments were investigated as a function of phosphate (apatite) and organic amendment loading rate. Zinc species identified in preamendment sediment were zinc hydroxide-like phases, sphalerite, and zinc sorbed to an iron oxide via X-ray adsorption near edge structure (XANES) spectroscopy. Four months after adding the amendments to the contaminated sediment, hopeite, a Zn phosphate mineral, was identified indicating phosphate was binding and sequestering available Zn and Zn pore water concentrations were decreased at levels of 90% or more. Laboratory experiments indicate organic amendments exhibit a limited effect and may hinder sequestration of pore water Zn when mixed with apatite. The acute toxicity of the sediment Zn was evaluated with Hyalella azteca, and bioaccumulation of Zn with Lumbriculus variegates. The survivability of H. azteca increased as a function of phosphate (apatite) loading rate. In contaminated sediment without apatite, no specimens of H. azteca survived. The bioaccumulation of Zn in L. variegates also followed a trend of decreased bioaccumulation with increased phosphate loading in the contaminated sediment. The research supports an association between Zn speciation and bioavailability.

  4. Speciation in Thaparocleidus (Monogenea: Dactylogyridae) Parasitizing Asian Pangasiid Catfishes

    PubMed Central

    Šimková, Andrea; Serbielle, Celine; Vanhove, Maarten P. M.; Morand, Serge

    2013-01-01

    The phylogeny of monogeneans of the genus Thaparocleidus that parasitize the gills of Pangasiidae in Borneo and Sumatra was inferred from molecular data to investigate parasite speciation. The phylogeny of the Pangasiidae was also reconstructed in order to investigate host-parasite coevolutionary history. The monophyly of Thaparocleidus parasitizing Pangasiidae was confirmed. Low intraspecies molecular variability was observed in three Thaparocleidus species collected from geographically distant localities. However, a high intraspecies molecular variability was observed in two Thaparocleidus species suggesting that these species represent a complex of species highly similar in morphology. Distance-based and tree-based methods revealed a significant global fit between parasite and host phylogenies. Parasite duplication (i.e., intrahost speciation) was recognized as the most common event in Thaparocleidus, while the numbers of cospeciation and host switches were lower and similar to each other. When collapsing nodes correspond to duplication cases, our results suggest host switches in the Thaparocleidus-Pangasiidae system precluding congruence between host and parasite trees. We found that the morphometric variability of the parasite attachment organ is not linked to phylogeny, suggesting that the attachment organ is under adaptive constraint. We showed that haptor morphometry is linked to host specificity, whereby nonspecific parasites display higher morphometric variability than specialists. PMID:24350263

  5. Selenium speciation from food source to metabolites: a critical review.

    PubMed

    Dumont, Emmie; Vanhaecke, Frank; Cornelis, Rita

    2006-08-01

    Especially in the last decade, a vast number of papers on Se and its role in health issues have been published. This review gives a brief, critical overview of the main analytical findings reported in these papers. Of particular interest is the Se content in different food sources worldwide and the extent to which their consumption is reflected in the Se content of human tissues and body fluids. Several food sources, both natural (Brazil nuts, garlic, Brassica juncea) and Se-enriched (yeast-based supplements), are discussed as to origin, characteristics, Se metabolism and impact of their consumption on the human body. The continuous development of new and improvement of existing analytical techniques has provided different powerful tools to unravel the Se species and their function. An up-to-date literature study on Se speciation analysis is given, illustrating how analytical chemistry in its different facets aids in the identification of Se compounds and provides insight into the complete metabolic pathway of Se throughout the human body. This review includes a detailed image of the current state-of-the-art of Se speciation analysis in these food sources and in human tissues and body fluids.

  6. Effects of dispersal plasticity on population divergence and speciation

    PubMed Central

    Arendt, J D

    2015-01-01

    Phenotypic plasticity is thought to have a role in driving population establishment, local adaptation and speciation. However, dispersal plasticity has been underappreciated in this literature. Plasticity in the decision to disperse is taxonomically widespread and I provide examples for insects, molluscs, polychaetes, vertebrates and flowering plants. Theoretical work is limited but indicates an interaction between dispersal distance and plasticity in the decision to disperse. When dispersal is confined to adjacent patches, dispersal plasticity may enhance local adaptation over unconditional (non-plastic) dispersal. However, when dispersal distances are greater, plasticity in dispersal decisions strongly reduces the potential for local adaptation and population divergence. Upon dispersal, settlement may be random, biased but genetically determined, or biased but plastically determined. Theory shows that biased settlement of either type increases population divergence over random settlement. One model suggests that plasticity further enhances chances of speciation. However, there are many strategies for deciding on where to settle such as a best-of-N strategy, sequential sampling with a threshold for acceptance or matching with natal habitat. To date, these strategies do not seem to have been compared within a single model. Although we are just beginning to explore evolutionary effects of dispersal plasticity, it clearly has the potential to enhance as well as inhibit population divergence. Additional work should pay particular attention to dispersal distance and the strategy used to decide on where to settle. PMID:25806544

  7. Thiolated eggshell membranes sorb and speciate inorganic selenium.

    PubMed

    Yang, Ting; Chen, Ming-Li; Hu, Xian-Wei; Wang, Zhao-Wen; Wang, Jian-Hua; Dasgupta, Purnendu K

    2011-01-07

    Eggshell membranes (ESMs) provide a unique, disulfide bond-rich surface. Thioglycolate reduction was used to generate thiol (-SH) groups on the ESM surface by S-S bond cleavage. The thiol-bearing ESMs (TESMs) were characterized by scanning electron microscopy and Raman spectroscopy. The fibrous network structure of the ESM is retained in the TESMs. TESMs adsorb both Se(IV) and Se(VI) but by different mechanisms: Se(VI) is retained reversibly, possibly via ionic interactions, while Se(IV) is reduced to Se(0) and deposited. We thus demonstrate speciation of selenium species, by using samples (a) as such and after prior oxidation to Se(VI), (b) preconcentration on a TESM microcolumn, (c) elution by 0.5 M HNO(3) that only elutes Se(VI) and (d) detection by graphite furnace atomic absorption spectrometry (GFAAS). The Se(IV) amount is determined by difference. For a 1.0 mL sample, the enrichment factor was 17.2, the S/N = 3 detection limit was 0.06 μg L(-1) and the precision was 3.3% at 0.50 μg L(-1). The linear range was 0.25-2.50 μg L(-1). The procedure was validated by analyzing selenium in certified reference materials of human hair (GBW 09101) and rice (GBW 10010). We further demonstrate utility by speciation of inorganic selenium in a series of water samples.

  8. Ecogeographic isolation and speciation in the genus Mimulus.

    PubMed

    Sobel, James M

    2014-11-01

    Despite a long history of examining the geographic context of speciation, differences in geographic range have rarely been considered a legitimate isolating mechanism. This likely results from the complex relationship between historical and ecological processes in determining the spatial distribution of species. Ecogeographic isolation is the proportion of geographic isolation that results from genetically based ecological differences between taxa and should therefore be measured as an isolating mechanism under the biological species concept. In this study, species distribution modeling was used to evaluate the potential ranges of 12 recently diverged pairs of species in the genus Mimulus. Variation in the distribution models showed that these species differ significantly in the niches they occupy. These differences result in substantial ecogeographic isolation, with an average strength of 0.67, revealing that, on average, Mimulus species exhibit only 33% overlap in the extent of suitable habitat with their closest relatives. Because prezygotic barriers act early in the life cycle of organisms, this strong barrier has the potential to contribute greatly to the total isolation experienced between diverging species. Therefore, ecogeographic isolation appears to play an important role in Mimulus, and estimating the strength of this barrier is essential to our general understanding of speciation.

  9. Arsenic speciation in marine fish and shellfish from American Samoa.

    PubMed

    Peshut, Peter J; Morrison, R John; Brooks, Barbara A

    2008-03-01

    We speciated arsenic compounds in marine fish and shellfish from two islands of the United States Territory of American Samoa in the South Pacific, and found that inorganic arsenic occurred as a minor fraction. The proportion of inorganic arsenic was generally far below the levels of prevailing assumptions typically used in human health risk assessments when only total arsenic is analysed. Fish and shellfish were collected from Tutuila and Ofu between May 2001 and March 2002 (n=383 individual specimens, with 117 composites); sites were selected based on habitat type and were representative of those frequented by local fishers. These islands have moderately developed reef fish fisheries among artisanal fishers, are far removed from any industrial or mining sources of arsenic, and presented an opportunity to study arsenic variations in marine biota from un-impacted environments. Target species were from various trophic levels and are among those frequently harvested for human consumption. We found evidence that arsenic concentrated in some marine species, but did not tend to follow classic trophic patterns for biomagnification or bioaccumulation. For the majority of samples, inorganic arsenic was less than 0.5% of total arsenic, with only a few samples in the range of 1-5%, the latter being mollusks which are recognized to have unusually high arsenic levels in general. This work supports the importance of speciation analysis for arsenic, because of the ubiquitous occurrence of arsenic in the environment, and its variable toxicity depending on chemical form.

  10. Trace metal speciation and bioavailability in anaerobic digestion: A review.

    PubMed

    Thanh, Pham Minh; Ketheesan, Balachandran; Yan, Zhou; Stuckey, David

    2016-01-01

    Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se; compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups; determine what factors influence metal sulfide dissolution; investigate whether chelating agents can increase trace metal bioavailability; develop and adapt specialized analytical techniques, and; determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).

  11. SPECIATION IN MAMMALS AND THE GENETIC SPECIES CONCEPT

    PubMed Central

    Baker, Robert J.; Bradley, Robert D.

    2009-01-01

    We define a genetic species as a group of genetically compatible interbreeding natural populations that is genetically isolated from other such groups. This focus on genetic isolation rather than reproductive isolation distinguishes the Genetic Species Concept from the Biological Species Concept. Recognition of species that are genetically isolated (but not reproductively isolated) results in an enhanced understanding of biodiversity and the nature of speciation as well as speciation-based issues and evolution of mammals. We review criteria and methods for recognizing species of mammals and explore a theoretical scenario, the Bateson–Dobzhansky–Muller (BDM) model, for understanding and predicting genetic diversity and speciation in mammals. If the BDM model is operating in mammals, then genetically defined phylogroups would be predicted to occur within species defined by morphology, and phylogroups experiencing stabilizing selection will evolve genetic isolation without concomitant morphological diversification. Such species will be undetectable using classical skin and skull morphology (Morphological Species Concept). Using cytochrome-b data from sister species of mammals recognized by classical morphological studies, we estimated the number of phylogroups that exist within mammalian species and hypothesize that there will be >2,000 currently unrecognized species of mammals. Such an underestimation significantly affects conclusions on the nature of speciation in mammals, barriers associated with evolution of genetic isolation, estimates of biodiversity, design of conservation initiatives, zoonoses, and so on. A paradigm shift relative to this and other speciation-based issues will be needed. Data that will be effective in detecting these “morphologically cryptic genetic species” are genetic, especially DNA-sequence data. Application of the Genetic Species Concept uses genetic data from mitochondrial and nuclear genomes to identify species and species

  12. FAST joins Breakthrough programme

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2016-11-01

    The 180m Five-hundred-meter Aperture Spherical radio Telescope (FAST) - the world's largest single-aperture radio receiver - has become part of the Breakthrough Listen programme, which launched in July 2015 to look for intelligent life beyond Earth.

  13. Pneumococcal Disease Fast Facts

    MedlinePlus

    ... Home About Pneumococcal Types of Infection Risk Factors & Transmission Symptoms & Complications Diagnosis & Treatment Prevention Photos Fast Facts Pneumococcal Vaccination For Clinicians Streptococcus pneumoniae Transmission Clinical Features Risk Factors Diagnosis & Management Prevention For ...

  14. Calorie count - Fast food

    MedlinePlus

    ... count - fast food FOOD ITEM SERVING SIZE CALORIES Breakfast Foods Dunkin Donuts Egg White Veggie Wrap 1 ... Cheese Biscuit Sandwich 1 sandwich 510 BK Ultimate Breakfast Platter 1 platter 1190 McDonalds Fruit 'n Yogurt ...

  15. Discovery with FAST

    NASA Astrophysics Data System (ADS)

    Wilkinson, P.

    2016-02-01

    FAST offers "transformational" performance well-suited to finding new phenomena - one of which might be polarised spectral transients. But discoveries will only be made if "the system" provides its users with the necessary opportunities. In addition to designing in as much observational flexibility as possible, FAST should be operated with a philosophy which maximises its "human bandwidth". This band includes the astronomers of tomorrow - many of whom not have yet started school or even been born.

  16. 75 FR 58417 - Agency Information Collection Activities: Application-Alternative Inspection Services (SENTRI...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-24

    ...-- Alternative Inspection Services (SENTRI Application and FAST Commercial Driver Application) AGENCY: U.S... Form 823S) and the FAST Commercial Driver Application (CBP Form 823F). This is a proposed extension of... Inspection Services including the SENTRI application and the FAST Commercial Driver Application. OMB...

  17. Ecological niche partitioning between Anopheles gambiae molecular forms in Cameroon: the ecological side of speciation

    PubMed Central

    Simard, Frédéric; Ayala, Diego; Kamdem, Guy Colince; Pombi, Marco; Etouna, Joachim; Ose, Kenji; Fotsing, Jean-Marie; Fontenille, Didier; Besansky, Nora J; Costantini, Carlo

    2009-01-01

    Background Speciation among members of the Anopheles gambiae complex is thought to be promoted by disruptive selection and ecological divergence acting on sets of adaptation genes protected from recombination by polymorphic paracentric chromosomal inversions. However, shared chromosomal polymorphisms between the M and S molecular forms of An. gambiae and insufficient information about their relationship with ecological divergence challenge this view. We used Geographic Information Systems, Ecological Niche Factor Analysis, and Bayesian multilocus genetic clustering to explore the nature and extent of ecological and chromosomal differentiation of M and S across all the biogeographic domains of Cameroon in Central Africa, in order to understand the role of chromosomal arrangements in ecological specialisation within and among molecular forms. Results Species distribution modelling with presence-only data revealed differences in the ecological niche of both molecular forms and the sibling species, An. arabiensis. The fundamental environmental envelope of the two molecular forms, however, overlapped to a large extent in the rainforest, where they occurred in sympatry. The S form had the greatest niche breadth of all three taxa, whereas An. arabiensis and the M form had the smallest niche overlap. Correspondence analysis of M and S karyotypes confirmed that molecular forms shared similar combinations of chromosomal inversion arrangements in response to the eco-climatic gradient defining the main biogeographic domains occurring across Cameroon. Savanna karyotypes of M and S, however, segregated along the smaller-scale environmental gradient defined by the second ordination axis. Population structure analysis identified three chromosomal clusters, each containing a mixture of M and S specimens. In both M and S, alternative karyotypes were segregating in contrasted environments, in agreement with a strong ecological adaptive value of chromosomal inversions. Conclusion Our

  18. Geographic variation in animal colour polymorphisms and its role in speciation.

    PubMed

    McLean, Claire A; Stuart-Fox, Devi

    2014-11-01

    Polymorphic species, in which multiple variants coexist within a population, are often used as model systems in evolutionary biology. Recent research has been dominated by the hypothesis that polymorphism can be a precursor to speciation. To date, the majority of research regarding polymorphism and speciation has focused on whether polymorphism is maintained within a population or whether morphs within populations may diverge to form separate species (sympatric speciation); however, the geographical context of speciation in polymorphic systems is likely to be both diverse and complex. In this review, we draw attention to the geographic variation in morph composition and frequencies that characterises many, if not most polymorphic species. Recent theoretical and empirical developments suggest that such variation in the number, type and frequency of morphs present among populations can increase the probability of speciation. Thus, the geographical context of a polymorphism requires a greater research focus. Here, we review the prevalence, causes and evolutionary consequences of geographic variation in polymorphism in colour-polymorphic animal species. The prevalence and nature of geographic variation in polymorphism suggests that polymorphism may be a precursor to and facilitate speciation more commonly than appreciated previously. We argue that a better understanding of the processes generating geographic variation in polymorphism is vital to understanding how polymorphism can promote speciation.

  19. Reticulate Speciation and Barriers to Introgression in the Anopheles gambiae Species Complex.

    PubMed

    Crawford, Jacob E; Riehle, Michelle M; Guelbeogo, Wamdaogo M; Gneme, Awa; Sagnon, N'Fale; Vernick, Kenneth D; Nielsen, Rasmus; Lazzaro, Brian P

    2015-11-28

    Speciation as a process remains a central focus of evolutionary biology, but our understanding of the genomic architecture and prevalence of speciation in the face of gene flow remains incomplete. The Anopheles gambiae species complex of malaria mosquitoes is a radiation of ecologically diverse taxa. This complex is well-suited for testing for evidence of a speciation continuum and genomic barriers to introgression because its members exhibit partially overlapping geographic distributions as well as varying levels of divergence and reproductive isolation. We sequenced 20 genomes from wild A. gambiae s.s., Anopheles coluzzii, Anopheles arabiensis, and compared these with 12 genomes from the "GOUNDRY" subgroup of A. gambiae s.l. Amidst a backdrop of strong reproductive isolation, we find strong evidence for a speciation continuum with introgression of autosomal chromosomal regions among species and subgroups. The X chromosome, however, is strongly differentiated among all taxa, pointing to a disproportionately large effect of X chromosome genes in driving speciation among anophelines. Strikingly, we find that autosomal introgression has occurred from contemporary hybridization between A. gambiae and A. arabiensis despite strong divergence (∼5× higher than autosomal divergence) and isolation on the X chromosome. In addition to the X, we find strong evidence that lowly recombining autosomal regions, especially pericentromeric regions, serve as barriers to introgression secondarily to the X. We show that speciation with gene flow results in genomic mosaicism of divergence and introgression. Such a reticulate gene pool connecting vector taxa across the speciation continuum has important implications for malaria control efforts.

  20. Density-dependent speciation alters the structure and dynamics of neutral communities.

    PubMed

    Wang, Shaopeng; Chen, Anping; Pacala, Stephen W; Fang, Jingyun

    2015-05-07

    The neutral theory of biodiversity (NTB) provides an individual-based modeling framework to study eco-evolutionary dynamics. Previous NTB models usually assumed the same per capita rate of speciation across lineages. However, population dynamics may induce macroevolutionary feedbacks that can result in variable per capita speciation rates across lineages. In this paper, with analytical and simulation approaches, we explore how different scenarios of density-dependent speciation may impact the diversity and phylogenetic patterns of neutral communities, and compare the results to predictions of the original NTB model with an invariant speciation rate. Our results show that positive per capita speciation rate-abundance relationships could result in higher species richness and evenness, enhanced stability (evidenced by higher post-disturbance recovery rates and lower temporal variability in species diversity), and higher imbalance in phylogenetic trees. The opposite patterns are predicted when per capita speciation rates decrease with abundance. Particularly, strong negative speciation rate-abundance relationships can generate a positive correlation between phylogenetic age and abundance, which has been observed in Panamanian tree species. Our findings demonstrate the importance of eco-evolutionary feedbacks for understanding long-term diversity and phylogenetic patterns in ecological communities.

  1. A comparative analysis of island floras challenges taxonomy-based biogeographical models of speciation.

    PubMed

    Igea, Javier; Bogarín, Diego; Papadopulos, Alexander S T; Savolainen, Vincent

    2015-02-01

    Speciation on islands, and particularly the divergence of species in situ, has long been debated. Here, we present one of the first, complete assessments of the geographic modes of speciation for the flora of a small oceanic island. Cocos Island (Costa Rica) is pristine; it is located 550 km off the Pacific coast of Central America. It harbors 189 native plant species, 33 of which are endemic. Using phylogenetic data from insular and mainland congeneric species, we show that all of the endemic species are derived from independent colonization events rather than in situ speciation. This is in sharp contrast to the results of a study carried out in a comparable system, Lord Howe Island (Australia), where as much as 8.2% of the plant species were the product of sympatric speciation. Differences in physiography and age between the islands may be responsible for the contrasting patterns of speciation observed. Importantly, comparing phylogenetic assessments of the modes of speciation with taxonomy-based measures shows that widely used island biogeography approaches overestimate rates of in situ speciation.

  2. Assessment of co-contaminant effects on uranium and thorium speciation in freshwater using geochemical modelling.

    PubMed

    Lofts, Stephen; Fevrier, Laureline; Horemans, Nele; Gilbin, Rodolphe; Bruggeman, Christophe; Vandenhove, Hildegarde

    2015-11-01

    Speciation modelling of uranium (as uranyl) and thorium, in four freshwaters impacted by mining activities, was used to evaluate (i) the influence of the co-contaminants present on the predicted speciation, and (ii) the influence of using nine different model/database combinations on the predictions. Generally, co-contaminants were found to have no significant effects on speciation, with the exception of Fe(III) in one system, where formation of hydrous ferric oxide and adsorption of uranyl to its surface impacted the predicted speciation. Model and database choice on the other hand clearly influenced speciation prediction. Complexes with dissolved organic matter, which could be simulated by three of the nine model/database combinations, were predicted to be important in a slightly acidic, soft water. Model prediction of uranyl and thorium speciation needs to take account of database comprehensiveness and cohesiveness, including the capability of the model and database to simulate interactions with dissolved organic matter. Measurement of speciation in natural waters is needed to provide data that may be used to assess and improve model capabilities and to better constrain the type of predictive modelling work presented here.

  3. Sorption and speciation of selenium in boreal forest soil.

    PubMed

    Söderlund, Mervi; Virkanen, Juhani; Holgersson, Stellan; Lehto, Jukka

    2016-11-01

    Sorption and speciation of selenium in the initial chemical forms of selenite and selenate were investigated in batch experiments on humus and mineral soil samples taken from a 4-m deep boreal forest soil excavator pit on Olkiluoto Island, on the Baltic Sea coast in southwestern Finland. The HPLC-ICP-MS technique was used to monitor any possible transformations in the selenium liquid phase speciation and to determine the concentrations of selenite and selenate in the samples for calculation of the mass distribution coefficient, Kd, for both species. Both SeO3(2-) and SeO4(2-) proved to be resistant forms in the prevailing soil conditions and no changes in selenium liquid phase speciation were seen in the sorption experiments in spite of variations in the initial selenium species, incubation time or conditions, pH, temperature or microbial activity. Selenite sorption on the mineral soil increased with time in aerobic conditions whilst the opposite trend was seen for the anaerobic soil samples. Selenite retention correlated with the contents of organic matter and weakly crystalline oxides of aluminum and iron, solution pH and the specific surface area. Selenate exhibited poorer sorption on soil than selenite and on average the Kd values were 27-times lower. Mineral soil was more efficient in retaining selenite and selenate than humus, implicating the possible importance of weakly crystalline aluminum and iron oxides for the retention of oxyanions in Olkiluoto soil. Sterilization of the soil samples decreased the retention of selenite, thus implying some involvement of soil microbes in the sorption processes or a change in sample composition, but it produced no effect for selenate. There was no sorption of selenite by quartz, potassium feldspar, hornblende or muscovite. Biotite showed the best retentive properties for selenite in the model soil solution at about pH 8, followed by hematite, plagioclase and chlorite. The Kd values for these minerals were 18, 14, 8 and 7

  4. Speciational history of North American Haemorhous finches (Aves: Fringillidae) inferred from multilocus data.

    PubMed

    Smith, Brian Tilston; Bryson, Robert W; Chua, Vivien; Africa, Lia; Klicka, John

    2013-03-01

    We investigated species relationships and timing of speciation in North American Haemorhous finches by using a mitochondrial phylogeographic approach combined with a multilocus species tree reconstruction. Haemorhous purpureus and H. cassinii were strongly supported as sister taxa, and H. mexicanus was sister to H. purpureus+H. cassinii. Our divergence times indicated that diversification within Haemorhous occurred progressively from the Late Miocene into the Pleistocene. Our inferred pattern of speciation demonstrates the complexity of the origins of North American birds, and provides additional evidence that a single cause for speciation in closely related North American birds, such as Late Pleistocene glacial-interglacial cycles, is unlikely.

  5. Fast wave current drive

    NASA Astrophysics Data System (ADS)

    Goree, J.; Ono, M.; Colestock, P.; Horton, R.; McNeill, D.; Park, H.

    1985-07-01

    Experiments on the fast wave in the range of high ion cyclotron harmonics in the ACT-1 device show that current drive is possible with the fast wave just as it is for the lower hybrid wave, except that it is suitable for higher plasma densities. A 140° loop antenna launched the high ion cyclotron harmonic fast wave [ω/Ω=O(10)] into a He+ plasma with ne≂4×1012 cm-3 and B=4.5 kG. Probe and magnetic loop diagnostics and FIR laser scattering confirmed the presence of the fast wave, and the Rogowski loop indicated that the circulating plasma current increased by up to 40A with 1 kW of coupled power, which is comparable to lower hybrid current drive in the same device with the same unidirectional fast electron beam used as the target for the rf. A phased antenna array would be used for FWCD in a tokamak without the E-beam.

  6. Genomic Speciation and Adaptation in Aquilegia (2011 JGI User Meeting)

    SciTech Connect

    Hodges, Scott

    2011-03-23

    The U.S. Department of Energy Joint Genome Institute (JGI) invited scientists interested in the application of genomics to bioenergy and environmental issues, as well as all current and prospective users and collaborators, to attend the annual DOE JGI Genomics of Energy & Environment Meeting held March 22-24, 2011 in Walnut Creek, Calif. The emphasis of this meeting was on the genomics of renewable energy strategies, carbon cycling, environmental gene discovery, and engineering of fuel-producing organisms. The meeting features presentations by leading scientists advancing these topics. Scott Hodges of the University of California, Santa Barbara gives a presentation on "Genomic Speciation and Adaptation in Aquilegia" at the 6th annual Genomics of Energy & Environment Meeting on March 23, 2011

  7. Plutonium, americium, and neptunium speciation in selected groundwaters

    USGS Publications Warehouse

    Cleveland, J.M.; Rees, T.F.; Nash, K.L.

    1985-01-01

    Speciation was determined at 25 and 90 degree C in four groundwaters from diverse sources: the Sparta aquifer in Louisiana, near the Vacherie salt dome; Mansfield No. 2 well in the Palo Duro Basin, Texas; the Stripa mine in Sweden; and the Waste Isolation Pilot Plant in New Mexico. Neptunium generally was soluble in all waters and was present exclusively as Np(V) and Np(VI), regardless of initial oxidation state. The results indicated that plutonium and neptunium solubilities were determined by the oxidation-reduction properties of the waters, i. e. , their abilities to convert these elements to soluble oxidation states. This was not the case for americium, however; Am(IV) was not detected, and the solubility of this element was determined entirely by the chemical properties of Am(III).

  8. Mercury speciation in fluorescent lamps by thermal release analysis

    SciTech Connect

    Raposo, Claudio; Windmoeller, Claudia Carvalhinho; Durao Junior, Walter Alves

    2003-07-01

    In this work, mercury speciation in phosphorus powder matrices and soda lime glass waste from new and spent fluorescent lamp wastes has been studied by thermo-desorption/atomic absorption spectrometry (TDAAS), X-ray diffraction (XRD), cold vapor-atomic absorption (CV-AAS) and atomic emission spectrometry/inductively coupled plasma (ICP/AES). TDAAS results show the presence of oxidized forms of mercury, i.e., Hg{sup 1+} and Hg{sup 2+}, especially in wastes with high mercury concentration. Such forms are mobile, and therefore represent a potential hazard waste material. Glass TD profiles of spent fluorescent lamps suggested the presence of mercury strongly linked to the matrix, which desorbs only at high temperatures.

  9. Mercury speciation in fluorescent lamps by thermal release analysis.

    PubMed

    Raposo, Cláudio; Windmöller, Cláudia Carvalhinho; Durão, Walter Alves

    2003-01-01

    In this work, mercury speciation in phosphorus powder matrices and soda lime glass waste from new and spent fluorescent lamp wastes has been studied by thermo-desorption/atomic absorption spectrometry (TDAAS), X-ray diffraction (XRD), cold vapor-atomic absorption (CV-AAS) and atomic emission spectrometry/inductively coupled plasma (ICP/AES). TDAAS results show the presence of oxidized forms of mercury, i.e., Hg(1+) and Hg(2+), especially in wastes with high mercury concentration. Such forms are mobile, and therefore represent a potential hazard waste material. Glass TD profiles of spent fluorescent lamps suggested the presence of mercury strongly linked to the matrix, which desorbs only at high temperatures.

  10. Speciation and intrasubspecific variation of Bornean orangutans, Pongo pygmaeus pygmaeus.

    PubMed

    Warren, K S; Verschoor, E J; Langenhuijzen, S; Heriyanto; Swan, R A; Vigilant, L; Heeney, J L

    2001-04-01

    Mitochondrial DNA control region sequences of orangutans (Pongo pygmaeus) from six different populations on the island of Borneo were determined and analyzed for evidence of regional diversity and were compared separately with orangutans from the island of Sumatra. Within the Bornean population, four distinct subpopulations were identified. Furthermore, the results of this study revealed marked divergence, supportive evidence of speciation between Sumatran and Bornean orangutans. This study demonstrates that, as an entire population, Bornean orangutans have not experienced a serious genetic bottleneck, which has been suggested as the cause of low diversity in humans and east African chimpanzees. Based on these new data, it is estimated that Bornean and Sumatran orangutans diverged approximately 1.1 MYA and that the four distinct Bornean populations diverged 860,000 years ago. These findings have important implications for management, breeding, and reintroduction practices in orangutan conservation efforts.

  11. Speciation of nanoscale objects by nanoparticle imprinted matrices

    NASA Astrophysics Data System (ADS)

    Hitrik, Maria; Pisman, Yamit; Wittstock, Gunther; Mandler, Daniel

    2016-07-01

    The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and separation based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochemical detection using the concept of ``nanoparticles imprinted matrices'' (NAIM). Negatively charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The selective matrix is formed by the adsorption of either oleic acid (OA) or poly(acrylic acid) (PAA) on the non-occupied areas. The AuNPs are removed by electrooxidation to form complementary voids. These voids are able to recognize the AuNPs selectively based on their size. Furthermore, the selectivity could be improved by adsorbing an additional layer of 1-hexadecylamine, which deepened the voids. Interestingly, silver nanoparticles (AgNPs) were also recognized if their size matched those of the template AuNPs. The steps in assembling the NAIMs and the reuptake of the nanoparticles were characterized carefully. The prospects for the analytical use of NAIMs, which are simple, of small dimension, cost-efficient and portable, are in the sensing and separation of nanoobjects.The toxicity of nanoparticles is not only a function of the constituting material but depends largely on their size, shape and stabilizing shell. Hence, the speciation of nanoscale objects, namely, their detection and separation based on the different species, similarly to heavy metals, is of outmost importance. Here we demonstrate the speciation of gold nanoparticles (AuNPs) and their electrochemical detection using the concept of ``nanoparticles imprinted matrices'' (NAIM). Negatively charged AuNPs are adsorbed as templates on a conducting surface previously modified with polyethylenimine (PEI). The

  12. Biotoxicity of mercury as influenced by mercury(II) speciation.

    PubMed Central

    Farrell, R E; Germida, J J; Huang, P M

    1990-01-01

    Integration of physicochemical procedures for studying mercury(II) speciation with microbiological procedures for studying the effects of mercury on bacterial growth allows evaluation of ionic factors (e.g., pH and ligand species and concentration) which affect biotoxicity. A Pseudomonas fluorescens strain capable of methylating inorganic Hg(II) was isolated from sediment samples collected at Buffalo Pound Lake in Saskatchewan, Canada. The effect of pH and ligand species on the toxic response (i.e., 50% inhibitory concentration [IC50]) of the P. fluorescens isolated to mercury were determined and related to the aqueous speciation of Hg(II). It was determined that the toxicities of different mercury salts were influenced by the nature of the co-ion. At a given pH level, mercuric acetate and mercuric nitrate yielded essentially the same IC50s; mercuric chloride, on the other hand, always produced lower IC50s. For each Hg salt, toxicity was greatest at pH 6.0 and decreased significantly (P = 0.05) at pH 7.0. Increasing the pH to 8.0 had no effect on the toxicity of mercuric acetate or mercuric nitrate but significantly (P = 0.05) reduced the toxicity of mercuric chloride. The aqueous speciation of Hg(II) in the synthetic growth medium M-IIY (a minimal salts medium amended to contain 0.1% yeast extract and 0.1% glycerol) was calculated by using the computer program GEOCHEM-PC with a modified data base. Results of the speciation calculations indicated that complexes of Hg(II) with histidine [Hg(H-HIS)HIS+ and Hg(H-HIS)2(2+)], chloride (HgCl+, HgCl2(0), HgClOH0, and HgCl3-), phosphate (HgHPO4(0), ammonia (HgNH3(2+), glycine [Hg(GLY)+], alanine [Hg(ALA)+], and hydroxyl ion (HgOH+) were the Hg species primarily responsible for toxicity in the M-IIY medium. The toxicity of mercuric nitrate at pH 8.0 was unaffected by the addition of citrate, enhanced by the addition of chloride, and reduced by the addition of cysteine. In the chloride-amended system, HgCl+, HgCl2(0), and Hg

  13. Dissolution, speciation, and reaction of acetaldehyde in cold sulfuric acid

    NASA Astrophysics Data System (ADS)

    Michelsen, Rebecca R.; Ashbourn, Samantha F. M.; Iraci, Laura T.

    2004-12-01

    The uptake of gas-phase acetaldehyde [CH3CHO, ethanal] by aqueous sulfuric acid solutions was studied under upper tropospheric/lower stratospheric (UT/LS) conditions. The solubility of acetaldehyde was found to be low, between 2 × 102 M atm-1 and 1.5 × 105 M atm-1 under the ranges of temperature (211-241 K) and acid composition (39-76 weight percent, wt%, H2SO4) studied. Under most conditions, acetaldehyde showed simple solubility behavior when exposed to sulfuric acid. Under moderately acidic conditions (usually 47 wt% H2SO4), evidence of reaction was observed. Enhancement of uptake at long times was occasionally detected in conjunction with reaction. The source of these behaviors and the effect of acetaldehyde speciation on solubility are discussed. Implications for the uptake of oxygenated organic compounds by tropospheric aerosols are considered.

  14. Genomic Speciation and Adaptation in Aquilegia (2011 JGI User Meeting)

    ScienceCinema

    Hodges, Scott [University of California, Santa Barbara

    2016-07-12

    The U.S. Department of Energy Joint Genome Institute (JGI) invited scientists interested in the application of genomics to bioenergy and environmental issues, as well as all current and prospective users and collaborators, to attend the annual DOE JGI Genomics of Energy & Environment Meeting held March 22-24, 2011 in Walnut Creek, Calif. The emphasis of this meeting was on the genomics of renewable energy strategies, carbon cycling, environmental gene discovery, and engineering of fuel-producing organisms. The meeting features presentations by leading scientists advancing these topics. Scott Hodges of the University of California, Santa Barbara gives a presentation on "Genomic Speciation and Adaptation in Aquilegia" at the 6th annual Genomics of Energy & Environment Meeting on March 23, 2011

  15. Speciation and recovery of chromium from chromite ore processing residues.

    PubMed

    Sreeram, K J; Ramasami, T

    2001-10-01

    The processing of chromite ore is associated with the generation of large quantities of solid wastes containing chromium, which have been disposed of as landfill for many years. The mobilization and operational speciation of chromium contained in soils contaminated with metal salts are important in terms of the environment. Several methods have been employed for the extraction and recovery of solid wastes. Chromium contained in contaminated soils and solid wastes can be categorized as exchangeable, oxidizable, carbonate-bound, reducible and residual. The results from this study indicate a need for efficient leaching methodologies in chromite ore processing plants to decrease the non-detrital fractions of chromium in the residue. Aggressive methodologies are required to recover chromium from the detrital fractions. The potential benefits of employing sodium peroxide for the complete recovery of chromium from chromite residue have been demonstrated, and the need to ensure the safety of the process has been emphasized.

  16. Intercomparison of analytical methods for arsenic speciation in human urine.

    PubMed Central

    Crecelius, E; Yager, J

    1997-01-01

    An intercomparison exercise was conducted for the quantification of arsenic species in spiked human urine. The primary objective of the exercise was to determine the variance among laboratories in the analysis of arsenic species such as inorganic As (As+3 and As+5), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Laboratories that participated had previous experience with arsenic speciation analysis. The results of this interlaboratory comparison are encouraging. There is relatively good agreement on the concentrations of these arsenic species in urine at concentrations that are relevant to research on the metabolism of arsenic in humans and other mammals. Both the accuracy and precision are relatively poor for arsenic concentrations of less than about 5 micrograms/l. PMID:9288500

  17. Alternative and Integrative Medicine

    MedlinePlus

    ... Alternative & Integrative Medicine Clinical Trials GBM AGILE TTFields – Optune™ Brain Tumor Treatment Locations Treatment Side Effects & their ... Alternative & Integrative Medicine Clinical Trials GBM AGILE TTFields – Optune™ Brain Tumor Treatment Locations Treatment Side Effects & their ...

  18. Alternative Refractive Surgery Procedures

    MedlinePlus

    ... LASIK Alternative Refractive Surgery Procedures Laser Surgery Recovery Alternative Refractive Surgery Procedures Dec. 12, 2015 Today's refractive ... that releases controlled amounts of radio frequency (RF) energy, instead of a laser, to apply heat to ...

  19. Technetium Inventory, Distribution, and Speciation in Hanford Tanks

    SciTech Connect

    Serne, R. Jeffrey; Rapko, Brian M.

    2014-05-02

    The purpose of this report is three fold: 1) assemble the available information regarding technetium (Tc) inventory, distribution between phases, and speciation in Hanford’s 177 storage tanks into a single, detailed, comprehensive assessment; 2) discuss the fate (distribution/speciation) of Tc once retrieved from the storage tanks and processed into a final waste form; and 3) discuss/document in less detail the available data on the inventory of Tc in other "pools" such as the vadose zone below inactive cribs and trenches, below single-shell tanks (SSTs) that have leaked, and in the groundwater below the Hanford Site. A thorough understanding of the inventory for mobile contaminants is key to any performance or risk assessment for Hanford Site facilities because potential groundwater and river contamination levels are proportional to the amount of contaminants disposed at the Hanford Site. Because the majority of the total 99Tc produced at Hanford (~32,600 Ci) is currently stored in Hanford’s 177 tanks (~26,500 Ci), there is a critical need for knowledge of the fate of this 99Tc as it is removed from the tanks and processed into a final solid waste form. Current flow sheets for the Hanford Waste Treatment and Immobilization Plant process show most of the 99Tc will be immobilized as low-activity waste glass that will remain on the Hanford Site and disposed at the Integrated Disposal Facility (IDF); only a small fraction will be shipped to a geologic repository with the immobilized high-level waste. Past performance assessment studies, which focused on groundwater protection, have shown that 99Tc would be the primary dose contributor to the IDF performance.

  20. Chromium speciation in coal and biomass co-combustion products.

    PubMed

    Stam, Arthur F; Meij, Ruud; Te Winkel, Henk; Eijk, Ronald J van; Huggins, Frank E; Brem, Gerrit

    2011-03-15

    Chromium speciation is vital for the toxicity of products resulting from co-combustion of coal and biomass. Therefore, understanding of formation processes has been studied using a combination of X-ray absorption fine structure (XAFS) spectroscopy and thermodynamic equilibrium calculations. The influence of cofiring on Cr speciation is very dependent on the type of fuel. Cr(VI) contents in the investigated fly ash samples from coal and cofiring average around 7% of the total chromium. An exception is cofiring 7-28% wood for which ashes exhibited Cr(VI) concentrations of 12-16% of the total chromium. Measurements are in line with thermodynamic predictions: RE factors of Cr around 1 are in line with volatile Cr only above 1400 °C; lower Cr(VI) concentrations with lower oxygen content and Cr(III) dissolved in aluminosilicate glass. Stability of Cr(VI) below 700 °C does not correlate with Cr(VI) concentrations found in the combustion products. It is indicated that Cr(VI) formation is a high-temperature process dependent on Cr evaporation (mode of occurrence in fuel, promoted by organic association), oxidation (local oxygen content), and formation of solid chromates (promoted by presence of free lime (CaO) in the ash). CaCrO(4)(s) is a probable chemical form but, given different leachable fractions (varying from 25 to 100%), different forms of Cr(VI) must be present. Clay-bound Cr is likely to dissolve in the aluminosilicate glass phase during melting of the clay.

  1. Field Deployable Method for Arsenic Speciation in Water

    PubMed Central

    Voice, Thomas C.; Flores del Pino, Lisveth V.; Havezov, Ivan; Long, David T.

    2010-01-01

    Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance. The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 µg/L, were analyzed. Arsenic recoveries ranged from 78–112 % and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 µg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in

  2. Speciation with gene flow in equids despite extensive chromosomal plasticity

    PubMed Central

    Jónsson, Hákon; Seguin-Orlando, Andaine; Ginolhac, Aurélien; Petersen, Lillian; Fumagalli, Matteo; Albrechtsen, Anders; Petersen, Bent; Vilstrup, Julia T.; Lear, Teri; Myka, Jennifer Leigh; Lundquist, Judith; Miller, Donald C.; Alfarhan, Ahmed H.; Alquraishi, Saleh A.; Al-Rasheid, Khaled A. S.; Stagegaard, Julia; Strauss, Günter; Bertelsen, Mads Frost; Antczak, Douglas F.; Bailey, Ernest; Nielsen, Rasmus; Willerslev, Eske; Orlando, Ludovic

    2014-01-01

    Horses, asses, and zebras belong to a single genus, Equus, which emerged 4.0–4.5 Mya. Although the equine fossil record represents a textbook example of evolution, the succession of events that gave rise to the diversity of species existing today remains unclear. Here we present six genomes from each living species of asses and zebras. This completes the set of genomes available for all extant species in the genus, which was hitherto represented only by the horse and the domestic donkey. In addition, we used a museum specimen to characterize the genome of the quagga zebra, which was driven to extinction in the early 1900s. We scan the genomes for lineage-specific adaptations and identify 48 genes that have evolved under positive selection and are involved in olfaction, immune response, development, locomotion, and behavior. Our extensive genome dataset reveals a highly dynamic demographic history with synchronous expansions and collapses on different continents during the last 400 ky after major climatic events. We show that the earliest speciation occurred with gene flow in Northern America, and that the ancestor of present-day asses and zebras dispersed into the Old World 2.1–3.4 Mya. Strikingly, we also find evidence for gene flow involving three contemporary equine species despite chromosomal numbers varying from 16 pairs to 31 pairs. These findings challenge the claim that the accumulation of chromosomal rearrangements drive complete reproductive isolation, and promote equids as a fundamental model for understanding the interplay between chromosomal structure, gene flow, and, ultimately, speciation. PMID:25453089

  3. Speciation and bioavailability of lead in complementary medicines.

    PubMed

    Bolan, S; Naidu, R; Kunhikrishnan, A; Seshadri, B; Ok, Y S; Palanisami, T; Dong, M; Clark, I

    2016-01-01

    Complementary medicines have associated risks which include toxic heavy metal(loid) and pesticide contamination. The objective of this study was to examine the speciation and bioavailability of lead (Pb) in selected complementary medicines. Six herbal and six ayurvedic medicines were analysed for: (i) total heavy metal(loid) contents including arsenic (As), cadmium (Cd), Pb and mercury (Hg); (ii) speciation of Pb using sequential fractionation and extended x-ray absorption fine structure (EXAFS) techniques; and (iii) bioavailability of Pb using a physiologically-based in vitro extraction test (PBET). The daily intake of Pb through the uptake of these medicines was compared with the safety guidelines for Pb. The results indicated that generally ayurvedic medicines contained higher levels of heavy metal(loid)s than herbal medicines with the amount of Pb much higher than the other metal(loid)s. Sequential fractionation indicated that while organic-bound Pb species dominated the herbal medicines, inorganic-bound Pb species dominated the ayurvedic medicines. EXAFS data indicated the presence of various Pb species in ayurvedic medicines. This implies that Pb is derived from plant uptake and inorganic mineral input in herbal and ayurvedic medicines, respectively. Bioavailability of Pb was higher in ayurvedic than herbal medicines, indicating that Pb added as a mineral therapeutic input is more bioavailable than that derived from plant uptake. There was a positive relationship between soluble Pb fraction and bioavailability indicating that solubility is an important factor controlling bioavailability. The daily intake values for Pb as estimated by total and bioavailable metal(loid) contents are likely to exceed the safe threshold level in certain ayurvedic medicines. This research demonstrated that Pb toxicity is likely to result from the regular intake of these medicines which requires further investigation.

  4. Choice matters: incipient speciation in Gyrodactylus corydori (Monogenoidea: Gyrodactylidae).

    PubMed

    Bueno-Silva, Marlus; Boeger, Walter A; Pie, Marcio R

    2011-05-01

    We investigated how Gyrodactylus corydoriBueno-Silva and Boeger, 2009 exploits two sympatric host species, Corydoras paleatus (Jenyns, 1842) and Corydoras ehrhardti Steindachner, 1910. Specimens of G. corydori were collected from the Piraquara and Miringuava Rivers, State of Paraná, Brazil, between 2005 and 2006. A total of 167 parasites was measured from both host species. Nine morphometric features of the haptoral sclerites were measured and analyzed by discriminant analysis, cluster analysis and multivariate analysis of variance. A fragment of the mitochondrial cytochrome oxidase I gene (COI) (∼740 bp) and the rDNA internal transcribed spacers (ITS) (∼1200 bp) of G. corydori were sequenced. Bayesian and parsimony analyses of COI recognized two genetically structured clades of G. corydori, which corresponded closely with the two species of Corydoras. Twenty-eight haplotypes were detected (18 were exclusive to C. ehrhardti and seven were exclusive to C. paleatus). The same general pattern between parasites and host species was observed in the morphometric analyses. Nevertheless, poor correlation of genetic and morphometric variation strongly supports the plastic nature of the morphological variation of haptoral sclerites. The existence of two clades with limited gene flow would suggest that G. corydori already represents two cryptic species. However, the morphometric and molecular data showed that there is insufficient evidence to support two valid species. The low COI (0.1-6.2%) and ITS (0.09-3.5%) divergence within G. corydori suggest a recent separation of the lineages between distinct host species (less than 1 million years). As the hypothesis of secondary contact of the parasite demographic history was rejected, our results point to the possibility of sympatric incipient ongoing speciation of G. corydori to form distinct parasite lineages adapted to C. ehrhardti and C. paleatus. This may be a common event within the Gyrodactylidae, adding a yet

  5. A novel colorimetric method for field arsenic speciation analysis.

    PubMed

    Hu, Shan; Lu, Jinsuo; Jing, Chuanyong

    2012-01-01

    Accurate on-site determination of arsenic (As) concentration as well as its speciation presents a great environmental challenge especially to developing countries. To meet the need of routine field monitoring, we developed a rapid colorimetric method with a wide dynamic detection range and high precision. The novel application of KMnO4 and CH4N2S as effective As(III) oxidant and As(V) reductant, respectively, in the formation of molybdenum blue complexes enabled the differentiation of As(III) and As(V). The detection limit of the method was 8 microg/L with a linear range (R2 = 0.998) of four orders of magnitude in total As concentrations. The As speciation in groundwater samples determined with the colorimetric method in the field were consistent with the results using the high performance liquid chromatography atomic fluorescence spectrometry, as evidenced by a linear correlation in paired analysis with a slope of 0.9990-0.9997 (p < 0.0001, n = 28). The recovery of 96%-116% for total As, 85%-122% for As(III), and 88%-127% for As(V) were achieved for groundwater samples with a total As concentration range 100-800 microg/L. The colorimetric result showed that 3.61 g/L As(III) existed as the only As species in a real industrial wastewater, which was in good agreement with the HPLC-AFS result of 3.56 g/L As(III). No interference with the color development was observed in the presence of sulfate, phosphate, silicate, humic acid, and heavy metals from complex water matrix. This accurate, sensitive, and easy-to-use method is especially suitable for field As determination.

  6. Genomic Divergence during Speciation Driven by Adaptation to Altitude

    PubMed Central

    Chapman, Mark A.; Hiscock, Simon J.; Filatov, Dmitry A.

    2013-01-01

    Even though Darwin’s “On the Origin of Species” implied selection being the main driver of species formation, the role of natural selection in speciation remains poorly understood. In particular, it remains unclear how selection at a few genes can lead to genomewide divergence and the formation of distinct species. We used a particularly attractive clear-cut case of recent plant ecological speciation to investigate the demography and genomic bases of species formation driven by adaptation to contrasting conditions. High-altitude Senecio aethnensis and low-altitude S. chrysanthemifolius live at the extremes of a mountain slope on Mt. Etna, Sicily, and form a hybrid zone at intermediate altitudes but remain morphologically distinct. Genetic differentiation of these species was analyzed at the DNA polymorphism and gene expression levels by high-throughput sequencing of transcriptomes from multiple individuals. Out of ∼18,000 genes analyzed, only a small number (90) displayed differential expression between the two species. These genes showed significantly elevated species differentiation (FST and Dxy), consistent with diversifying selection acting on these genes. Genomewide genetic differentiation of the species is surprisingly low (FST = 0.19), while ∼200 genes showed significantly higher (false discovery rate < 1%; mean outlier FST > 0.6) interspecific differentiation and evidence for local adaptation. Diversifying selection at only a handful of loci may be enough for the formation and maintenance of taxonomically well-defined species, despite ongoing gene flow. This provides an explanation of why many closely related species (in plants, in particular) remain phenotypically and ecologically distinct despite ongoing hybridization, a question that has long puzzled naturalists and geneticists alike. PMID:24077768

  7. Explosive speciation in the New World Dendroica warblers

    PubMed Central

    Lovette, I. J.; Bermingham, E.

    1999-01-01

    The 27 species of Dendroica wood-warblers represent North America's most spectacular avian adaptive radiation. Dendroica species exhibit high levels of local sympatry and differ in plumage and song, but the group contrasts with other well-known avian adaptive radiations such as the Hawaiian honeycreepers and Galapagos finches in that Dendroica species have differentiated modestly in morphometric traits related to foraging. Instead, sympatric Dendroica tend to partition resources behaviourally and they have become a widely cited example of competitive exclusion. We explored the temporal structure of Dendroica diversification via a phylogeny based on 3639 nucleotides of protein-coding mitochondrial DNA (mtDNA). The taxa sampled included 60 individuals representing 24 Dendroica species and a variety of other paruline warbler and outgroup species. Mitochondrial divergences among Dendroica species were generally large (mean pairwise interspecific distances, 10.0%) and many species were rooted in a basal polytomy. The prevalence of long terminal branches indicates that these species have evolved efficient isolating mechanisms that have prevented mtDNA introgression despite the many opportunities for hybridization resulting from local sympatry. Comparisons with a null model of random bifurcation–extinction demonstrate that cladogenesis in Dendroica has been clustered non-randomly with respect to time, with a significant burst of speciation occurring early in the history of the genus, possibly as long ago as the Late Miocene or Early Pliocene periods. Although this non-random clustering of speciation is consistent with the pattern expected of an adaptive radiation, the age of the Dendroica radiation suggests it is an 'ancient species flock' in which most extant species represent lineages that have long been evolutionarily independent.

  8. Field Deployable Method for Arsenic Speciation in Water.

    PubMed

    Voice, Thomas C; Flores Del Pino, Lisveth V; Havezov, Ivan; Long, David T

    2011-01-01

    Contamination of drinking water supplies by arsenic is a world-wide problem. Total arsenic measurements are commonly used to investigate and regulate arsenic in water, but it is well understood that arsenic occurs in several chemical forms, and these exhibit different toxicities. It is problematic to use laboratory-based speciation techniques to assess exposure as it has been suggested that the distribution of species is not stable during transport in some types of samples. A method was developed in this study for the on-site speciation of the most toxic dissolved arsenic species: As (III), As (V), monomethylarsonic acid (MMA) and dimethylarsenic acid (DMA). Development criteria included ease of use under field conditions, applicable at levels of concern for drinking water, and analytical performance.The approach is based on selective retention of arsenic species on specific ion-exchange chromatography cartridges followed by selective elution and quantification using graphite furnace atomic absorption spectroscopy. Water samples can be delivered to a set of three cartridges using either syringes or peristaltic pumps. Species distribution is stable at this point, and the cartridges can be transported to the laboratory for elution and quantitative analysis. A set of ten replicate spiked samples of each compound, having concentrations between 1 and 60 µg/L, were analyzed. Arsenic recoveries ranged from 78-112 % and relative standard deviations were generally below 10%. Resolution between species was shown to be outstanding, with the only limitation being that the capacity for As (V) was limited to approximately 50 µg/L. This could be easily remedied by changes in either cartridge design, or the extraction procedure. Recoveries were similar for two spiked hard groundwater samples indicating that dissolved minerals are not likely to be problematic. These results suggest that this methodology can be use for analysis of the four primary arsenic species of concern in

  9. Shoreside Alternative Energy Evaluation

    DTIC Science & Technology

    2002-09-01

    in November 2000 titled, Shoreside Alternative Energy Evaluation. This study of alternative energies focused on usage of natural gas, and included...energy sources such as costs, benefits, and logistic availability. This study of alternative energies focused on usage of natural gas and included...resources in this area. Recognizing Air Station Cape Cod as a leader in utilizing alternative energies , the Research and Development Center established

  10. Selenium Speciation and Management in Wet FGD Systems

    SciTech Connect

    Searcy, K; Richardson, M; Blythe, G; Wallschlaeger, D; Chu, P; Dene, C

    2012-02-29

    This report discusses results from bench- and pilot-scale simulation tests conducted to determine the factors that impact selenium speciation and phase partitioning in wet FGD systems. The selenium chemistry in wet FGD systems is highly complex and not completely understood, thus extrapolation and scale-up of these results may be uncertain. Control of operating parameters and application of scrubber additives have successfully demonstrated the avoidance or decrease of selenite oxidation at the bench and pilot scale. Ongoing efforts to improve sample handling methods for selenium speciation measurements are also discussed. Bench-scale scrubber tests explored the impacts of oxidation air rate, trace metals, scrubber additives, and natural limestone on selenium speciation in synthetic and field-generated full-scale FGD liquors. The presence and concentration of redox-active chemical species as well as the oxidation air rate contribute to the oxidation-reduction potential (ORP) conditions in FGD scrubbers. Selenite oxidation to the undesirable selenate form increases with increasing ORP conditions, and decreases with decreasing ORP conditions. Solid-phase manganese [Mn(IV)] appeared to be the significant metal impacting the oxidation of selenite to selenate. Scrubber additives were tested for their ability to inhibit selenite oxidation. Although dibasic acid and other scrubber additives showed promise in early clear liquor (sodium based and without calcium solids) bench-scale tests, these additives did not show strong inhibition of selenite oxidation in tests with higher manganese concentrations and with slurries from full-scale wet FGD systems. In bench-tests with field liquors, addition of ferric chloride at a 250:1 iron-to-selenium mass ratio sorbed all incoming selenite to the solid phase, although addition of ferric salts had no impact on native selenate that already existed in the field slurry liquor sample. As ORP increases, selenite may oxidize to selenate more

  11. Alternatives for Education Manual.

    ERIC Educational Resources Information Center

    Alternatives for Education, San Pedro, CA.

    A directory of alternative schools and a list of books and reprints about alternative education are presented. The alternative schools listed are almost all on the West Coast and include both day and boarding schools at the primary and secondary level. The name and address of each school is given along with supplementary material about its…

  12. Chicano Alternative Education.

    ERIC Educational Resources Information Center

    Galicia, H. Homero; Almaguer, Clementina

    Alternative schooling is challenging some basic notions of curriculum, operation, and structure of traditional schools; it is not challenging the basic concept of schooling. Chicano alternative education, an elusive concept, lacks a precise definition. Chicano alternative schools reflect a vast diversity in structure, focus, and goals. The Chicano…

  13. Assessment "Honest Alternatives".

    ERIC Educational Resources Information Center

    Mandel, Susan Glazer

    1995-01-01

    Addresses the challenge of finding or creating alternatives to tests and traditional grading systems. Reflects on and describes the experience of creating an assessment tool and cautions against choosing alternatives that merely camouflage the grades. Encourages educators to find authentic alternatives to describe children's growth. (BAC)

  14. A Fast Hermite Transform.

    PubMed

    Leibon, Gregory; Rockmore, Daniel N; Park, Wooram; Taintor, Robert; Chirikjian, Gregory S

    2008-12-17

    We present algorithms for fast and stable approximation of the Hermite transform of a compactly supported function on the real line, attainable via an application of a fast algebraic algorithm for computing sums associated with a three-term relation. Trade-offs between approximation in bandlimit (in the Hermite sense) and size of the support region are addressed. Numerical experiments are presented that show the feasibility and utility of our approach. Generalizations to any family of orthogonal polynomials are outlined. Applications to various problems in tomographic reconstruction, including the determination of protein structure, are discussed.

  15. Status and Prospects of the Fast Ignition Inertial Fusion Concept

    SciTech Connect

    Key, M H

    2006-11-15

    Fast ignition is an alternate concept in inertial confinement fusion, which has the potential for easier ignition and greater energy multiplication. If realized it could improve the prospects for inertial fusion energy. It poses stimulating challenges in science and technology and the research is approaching a key stage in which the feasibility of fast ignition will be determined. This review covers the concepts, the state of the science and technology, the near term prospects and the challenges and risks involved in demonstrating high gain fast ignition.

  16. FastBit Reference Manual

    SciTech Connect

    Wu, Kesheng

    2007-08-02

    An index in a database system is a data structure that utilizes redundant information about the base data to speed up common searching and retrieval operations. Most commonly used indexes are variants of B-trees, such as B+-tree and B*-tree. FastBit implements a set of alternative indexes call compressed bitmap indexes. Compared with B-tree variants, these indexes provide very efficient searching and retrieval operations by sacrificing the efficiency of updating the indexes after the modification of an individual record. In addition to the well-known strengths of bitmap indexes, FastBit has a special strength stemming from the bitmap compression scheme used. The compression method is called the Word-Aligned Hybrid (WAH) code. It reduces the bitmap indexes to reasonable sizes and at the same time allows very efficient bitwise logical operations directly on the compressed bitmaps. Compared with the well-known compression methods such as LZ77 and Byte-aligned Bitmap code (BBC), WAH sacrifices some space efficiency for a significant improvement in operational efficiency. Since the bitwise logical operations are the most important operations needed to answer queries, using WAH compression has been shown to answer queries significantly faster than using other compression schemes. Theoretical analyses showed that WAH compressed bitmap indexes are optimal for one-dimensional range queries. Only the most efficient indexing schemes such as B+-tree and B*-tree have this optimality property. However, bitmap indexes are superior because they can efficiently answer multi-dimensional range queries by combining the answers to one-dimensional queries.

  17. Results of Hg speciation testing on tanks 30, 32, and 37 surface samples

    SciTech Connect

    Bannochie, C. J.

    2015-11-11

    The Savannah River National Laboratory (SRNL) was tasked with preparing and shipping samples for Hg speciation by Eurofins Frontier Global Sciences, Inc. in Seattle, WA on behalf of the Savannah River Remediation (SRR) Mercury Task Team.

  18. Genomic islands of divergence are not affected by geography of speciation in sunflowers.

    PubMed

    Renaut, S; Grassa, C J; Yeaman, S; Moyers, B T; Lai, Z; Kane, N C; Bowers, J E; Burke, J M; Rieseberg, L H

    2013-01-01

    Genomic studies of speciation often report the presence of highly differentiated genomic regions interspersed within a milieu of weakly diverged loci. The formation of these speciation islands is generally attributed to reduced inter-population gene flow near loci under divergent selection, but few studies have critically evaluated this hypothesis. Here, we report on transcriptome scans among four recently diverged pairs of sunflower (Helianthus) species that vary in the geographical context of speciation. We find that genetic divergence is lower in sympatric and parapatric comparisons, consistent with a role for gene flow in eroding neutral differences. However, genomic islands of divergence are numerous and small in all comparisons, and contrary to expectations, island number and size are not significantly affected by levels of interspecific gene flow. Rather, island formation is strongly associated with reduced recombination rates. Overall, our results indicate that the functional architecture of genomes plays a larger role in shaping genomic divergence than does the geography of speciation.

  19. Colour pattern as a single trait driving speciation in Hypoplectrus coral reef fishes?

    PubMed Central

    Puebla, Oscar; Bermingham, Eldredge; Guichard, Frédéric; Whiteman, Elizabeth

    2007-01-01

    Theory shows that speciation in the presence of gene flow occurs only under narrow conditions. One of the most favourable scenarios for speciation with gene flow is established when a single trait is both under disruptive natural selection and used to cue assortative mating. Here, we demonstrate the potential for a single trait, colour pattern, to drive incipient speciation in the genus Hypoplectrus (Serranidae), coral reef fishes known for their striking colour polymorphism. We provide data demonstrating that sympatric Hypoplectrus colour morphs mate assortatively and are genetically distinct. Furthermore, we identify ecological conditions conducive to disruptive selection on colour pattern by presenting behavioural evidence of aggressive mimicry, whereby predatory Hypoplectrus colour morphs mimic the colour patterns of non-predatory reef fish species to increase their success approaching and attacking prey. We propose that colour-based assortative mating, combined with disruptive selection on colour pattern, is driving speciation in Hypoplectrus coral reef fishes. PMID:17360287

  20. Mercury speciation comparison. Brooks applied laboratories and eurofins frontier global sciences

    SciTech Connect

    Bannochie, C. J.; Wilmarth, W. R.

    2016-12-16

    The Savannah River National Laboratory (SRNL) was tasked with preparing and shipping samples for Hg speciation by Eurofins Frontier Global Sciences (FGS), Inc. in Bothell, WA on behalf of the Savannah River Remediation (SRR) Mercury Program Team.

  1. 250 years of hybridization between two biennial herb species without speciation.

    PubMed

    Matthews, Andrew; Emelianova, Katie; Hatimy, Abubakar A; Chester, Michael; Pellicer, Jaume; Ahmad, Khawaja Shafique; Guignard, Maité S; Rouhan, Germinal; Soltis, Douglas E; Soltis, Pamela S; Leitch, Ilia J; Leitch, Andrew R; Mavrodiev, Evgeny V; Buggs, Richard J A

    2015-07-17

    Hybridization between plant species can generate novel morphological diversity and lead to speciation at homoploid or polyploid levels. Hybrids between biennial herbs Tragopogon pratensis and T. porrifolius have been studied in experimental and natural populations for over 250 years. Here we examine their current status in natural populations in southeast England. All hybrids found were diploid; they tended to grow taller and with more buds than their parental species; many showed partial fertility; a few showed evidence of backcrossing. However, we found no evidence to suggest that the hybrids are establishing as a new species, nor can we find literature documenting speciation of these hybrids elsewhere. This lack of speciation despite at least 250 years of hybridization contrasts with the fact that both parental species have formed new allopolyploid species through hybridization with another diploid, T. dubius. Understanding why hybrids often do not speciate, despite repeated opportunities, would enhance our understanding of both the evolutionary process and risk assessments of invasive species.

  2. Tempo and mode of speciation in Holacanthus angelfishes based on RADseq markers.

    PubMed

    Tariel, Juliette; Longo, Gary C; Bernardi, Giacomo

    2016-05-01

    In this study we estimated the timing of speciation events in a group of angelfishes using 1186 RADseq markers corresponding to 94,880 base pairs. The genus Holacanthus comprises seven species, including two clades of Panama trans-Isthmian geminates, which diverged approximately 3-3.5Mya. These clades diversified within the Tropical Eastern Pacific (TEP, three species) and Tropical Western Atlantic (TWA, two species) which our data suggest to have occurred within the past 1.5My in both ocean basins, but may have proceeded via different mechanisms. In the TEP, speciation is likely to have followed a peripatric pathway, while in the TWA, sister species are currently partially sympatric, thus raising the possibility of sympatric speciation. This study highlights the use of RADseq markers for estimating both divergence times and modes of speciation at a 1-3My timescale.

  3. Multielemental speciation analysis by advanced hyphenated technique - HPLC/ICP-MS: A review.

    PubMed

    Marcinkowska, Monika; Barałkiewicz, Danuta

    2016-12-01

    Speciation analysis has become an invaluable tool in human health risk assessment, environmental monitoring or food quality control. Another step is to develop reliable multielemental speciation methodologies, to reduce costs, waste and time needed for the analysis. Separation and detection of species of several elements in a single analytical run can be accomplished by high performance liquid chromatography hyphenated to inductively coupled plasma mass spectrometry (HPLC/ICP-MS). Our review assembles articles concerning multielemental speciation determination of: As, Se, Cr, Sb, I, Br, Pb, Hg, V, Mo, Te, Tl, Cd and W in environmental, biological, food and clinical samples analyzed with HPLC/ICP-MS. It addresses the procedures in terms of following issues: sample collection and pretreatment, selection of optimal conditions for elements species separation by HPLC and determination using ICP-MS as well as metrological approach. The presented work is the first review article concerning multielemental speciation analysis by advanced hyphenated technique HPLC/ICP-MS.

  4. Speciation in peripheral populations: effects of drift load and mating systems.

    PubMed

    Rettelbach, A; Servedio, M R; Hermisson, J

    2016-05-01

    Speciation in peripheral populations has long been considered one of the most plausible scenarios for speciation with gene flow. In this study, however we identify two additional problems of peripatric speciation, as compared to the parapatric case, that may impede the completion of the speciation process for most parameter regions. First, with (predominantly) unidirectional gene flow, there is no selection pressure to evolve assortative mating on the continent. We discuss the implications of this for different mating schemes. Second, genetic load can build up in small populations. This can lead to extinction of the peripheral species, or generate selection pressure for lower assortative mating to avoid inbreeding. In this case, either a stable equilibrium with intermediate assortment evolves or there is cycling between phases of hybridization and phases of complete isolation.

  5. Synchrotron Speciation Of Silver And Zinc Oxide Nanoparticles Aged In A Kaolin Suspension

    EPA Science Inventory

    Assessments of the environmental fate and mobility of nanoparticles must consider the behavior of nanoparticles in relevant environmental systems that may result in speciation changes over time. Environmental conditions may act on nanoparticles to change their size, shape, and s...

  6. Colour pattern as a single trait driving speciation in Hypoplectrus coral reef fishes?

    PubMed

    Puebla, Oscar; Bermingham, Eldredge; Guichard, Frédéric; Whiteman, Elizabeth

    2007-05-22

    Theory shows that speciation in the presence of gene flow occurs only under narrow conditions. One of the most favourable scenarios for speciation with gene flow is established when a single trait is both under disruptive natural selection and used to cue assortative mating. Here, we demonstrate the potential for a single trait, colour pattern, to drive incipient speciation in the genus Hypoplectrus (Serranidae), coral reef fishes known for their striking colour polymorphism. We provide data demonstrating that sympatric Hypoplectrus colour morphs mate assortatively and are genetically distinct. Furthermore, we identify ecological conditions conducive to disruptive selection on colour pattern by presenting behavioural evidence of aggressive mimicry, whereby predatory Hypoplectrus colour morphs mimic the colour patterns of non-predatory reef fish species to increase their success approaching and attacking prey. We propose that colour-based assortative mating, combined with disruptive selection on colour pattern, is driving speciation in Hypoplectrus coral reef fishes.

  7. Biodiesel and Cold Temperature Effects on Speciated Mobile Source Air Toxics from Modern Diesel Trucks

    EPA Science Inventory

    Speciated volatile organic compounds (VOCs) with a particular focus on mobile source air toxics (MSATs) were measured in diesel exhaust from three heavy-duty trucks equipped with modern aftertreatment technologies. Emissions testing was conducted on a temperature controlled chass...

  8. Biodiesel and Cold Temperature Effect on Speciated Mobile Source Air Toxics from Modern Diesel Trucks

    EPA Science Inventory

    Speciated volatile organic compounds (VOCs) with a particular focus on mobile source air toxics (MSATs) were measured in diesel exhaust from three heavy-duty trucks equipped with modern aftertreatment technologies. Emissions testing was conducted on a temperature controlled chass...

  9. Something's Fishy in Paxton Lake: A Case on Speciation in Sticklebacks.

    ERIC Educational Resources Information Center

    Sharp, Joan

    2002-01-01

    Introduces a case study on speciation and evolutionary mechanisms. Teaches science process skills as well as natural selection, biological species concepts, basic genetic terminology, and classification. Includes teaching notes and classroom management strategies. (Contains 14 references.) (YDS)

  10. A potential relationship between molybdenum speciation and its isotopic signature in sedimentary records: New insights from old shales

    NASA Astrophysics Data System (ADS)

    Chappaz, A.; Reinhard, C.

    2015-12-01

    Molybdenum has emerged as a powerful paleo-indicator of sulfidic conditions in studies of the evolution of Earth's early oxygenation, either by examining patterns of Mo enrichment and/or the δ98Mo isotopic signature in sedimentary records. However, the processes leading to Mo incorporation in sulfidic sediments are still unknown, limiting its use as a proxy. The Mount McRae Shale, deposited ~2.5 billion years ago (Ga) in the Hamersley Basin, Western Australia, provides a unique opportunity to examine Earth surface conditions during the Archean just prior to the Great Oxidation Event, and an important example of the deep time application of Mo geochemistry. Trace element [1] and iron speciation [2] data measured in the upper shale interval indicate deposition under euxinic conditions and significant aqueous transport of redox-sensitive trace elements. δ98Mo measured in the upper euxinic interval of the Mt. McRae Shale ranges from 0.99 to 1.86 ‰ [3]. These heavy δ98Mo values have been attributed to the effects of oxidative weathering and adsorption of Mo to oxide mineral surfaces. To further explore the implications of these data and to identify possible mechanisms controlling Mo burial, we analyzed samples from the upper euxinic shale using XANES and EXAFS. First, our data suggest an association between Mo and organic matter implying that metamorphic processes have not altered this interval. Perhaps more surprisingly, we find a strong relationship between Mo speciation and δ98Mo isotopic signature (r2 = 0.90). We suggest an alternative mechanism for explaining the Mo isotope systematics of the upper Mt. McRae Shale involving Mo reduction. If correct, our results add new interpretive texture to sedimentary Mo isotope records and imply a primary role for speciation in the Mo isotope composition of sulfidic marine environments. [1] Anbar et al., 2007. Science 317, 1903-1906 [2] Reinhard et al. 2009. Science 326, 713-716 [3] Duan et al. 2010. GCA 74, 6655-6668

  11. Living at the edge: biogeographic patterns of habitat segregation conform to speciation by niche expansion in Anopheles gambiae

    PubMed Central

    Costantini, Carlo; Ayala, Diego; Guelbeogo, Wamdaogo M; Pombi, Marco; Some, Corentin Y; Bassole, Imael HN; Ose, Kenji; Fotsing, Jean-Marie; Sagnon, N'Falé; Fontenille, Didier; Besansky, Nora J; Simard, Frédéric

    2009-01-01

    Background Ongoing lineage splitting within the African malaria mosquito Anopheles gambiae is compatible with ecological speciation, the evolution of reproductive isolation by divergent natural selection acting on two populations exploiting alternative resources. Divergence between two molecular forms (M and S) identified by fixed differences in rDNA, and characterized by marked, although incomplete, reproductive isolation is occurring in West and Central Africa. To elucidate the role that ecology and geography play in speciation, we carried out a countrywide analysis of An. gambiae M and S habitat requirements, and that of their chromosomal variants, across Burkina Faso. Results Maps of relative abundance by geostatistical interpolators produced a distinct pattern of distribution: the M-form dominated in the northernmost arid zones, the S-form in the more humid southern regions. Maps of habitat suitability, quantified by Ecological Niche Factor Analysis based on 15 eco-geographical variables revealed less contrast among forms. M was peculiar as it occurred proportionally more in habitat of marginal quality. Measures of ecological niche breadth and overlap confirmed the mismatch between the fundamental and realized patterns of habitat occupation: forms segregated more than expected from the extent of divergence of their environmental envelope – a signature of niche expansion. Classification of chromosomal arm 2R karyotypes by multilocus genetic clustering identified two clusters loosely corresponding to molecular forms, with 'mismatches' representing admixed individuals due to shared ancestral polymorphism and/or residual hybridization. In multivariate ordination space, these karyotypes plotted in habitat of more marginal quality compared to non-admixed, 'typical', karyotypes. The distribution of 'typical' karyotypes along the main eco-climatic gradient followed a consistent pattern within and between forms, indicating an adaptive role of inversions at this

  12. Speciation on Oceanic Islands: Rapid Adaptive Divergence vs. Cryptic Speciation in a Guadalupe Island Songbird (Aves: Junco)

    PubMed Central

    Aleixandre, Pau; Hernández Montoya, Julio; Milá, Borja

    2013-01-01

    The evolutionary divergence of island populations, and in particular the tempo and relative importance of neutral and selective factors, is of central interest to the study of speciation. The rate of phenotypic evolution upon island colonization can vary greatly among taxa, and cases of convergent evolution can further confound the inference of correct evolutionary histories. Given the potential lability of phenotypic characters, molecular dating of insular lineages analyzed in a phylogenetic framework provides a critical tool to test hypotheses of phenotypic divergence since colonization. The Guadalupe junco is the only insular form of the polymorphic dark-eyed junco (Junco hyemalis), and shares eye and plumage color with continental morphs, yet presents an enlarged bill and reduced body size. Here we use variation in mtDNA sequence, morphological traits and song variables to test whether the Guadalupe junco evolved rapidly following a recent colonization by a mainland form of the dark-eyed junco, or instead represents a well-differentiated “cryptic” lineage adapted to the insular environment through long-term isolation, with plumage coloration a result of evolutionary convergence. We found high mtDNA divergence of the island lineage with respect to both continental J. hyemalis and J. phaeonotus, representing a history of isolation of about 600,000 years. The island lineage was also significantly differentiated in morphological and male song variables. Moreover, and contrary to predictions regarding diversity loss on small oceanic islands, we document relatively high levels of both haplotypic and song-unit diversity on Guadalupe Island despite long-term isolation in a very small geographic area. In contrast to prevailing taxonomy, the Guadalupe junco is an old, well-differentiated evolutionary lineage, whose similarity to mainland juncos in plumage and eye color is due to evolutionary convergence. Our findings confirm the role of remote islands in driving

  13. Speciation on oceanic islands: rapid adaptive divergence vs. cryptic speciation in a Guadalupe Island songbird (Aves: Junco).

    PubMed

    Aleixandre, Pau; Hernández Montoya, Julio; Milá, Borja

    2013-01-01

    The evolutionary divergence of island populations, and in particular the tempo and relative importance of neutral and selective factors, is of central interest to the study of speciation. The rate of phenotypic evolution upon island colonization can vary greatly among taxa, and cases of convergent evolution can further confound the inference of correct evolutionary histories. Given the potential lability of phenotypic characters, molecular dating of insular lineages analyzed in a phylogenetic framework provides a critical tool to test hypotheses of phenotypic divergence since colonization. The Guadalupe junco is the only insular form of the polymorphic dark-eyed junco (Junco hyemalis), and shares eye and plumage color with continental morphs, yet presents an enlarged bill and reduced body size. Here we use variation in mtDNA sequence, morphological traits and song variables to test whether the Guadalupe junco evolved rapidly following a recent colonization by a mainland form of the dark-eyed junco, or instead represents a well-differentiated "cryptic" lineage adapted to the insular environment through long-term isolation, with plumage coloration a result of evolutionary convergence. We found high mtDNA divergence of the island lineage with respect to both continental J. hyemalis and J. phaeonotus, representing a history of isolation of about 600,000 years. The island lineage was also significantly differentiated in morphological and male song variables. Moreover, and contrary to predictions regarding diversity loss on small oceanic islands, we document relatively high levels of both haplotypic and song-unit diversity on Guadalupe Island despite long-term isolation in a very small geographic area. In contrast to prevailing taxonomy, the Guadalupe junco is an old, well-differentiated evolutionary lineage, whose similarity to mainland juncos in plumage and eye color is due to evolutionary convergence. Our findings confirm the role of remote islands in driving

  14. Fast ForWord.

    ERIC Educational Resources Information Center

    Education Commission of the States, Denver, CO.

    This paper provides an overview of Fast ForWord, a CD-ROM and Internet-based training program for children (pre-K to grade 8) with language and reading problems that helps children rapidly build oral language comprehension and other critical skills necessary for learning to read or becoming a better reader. With the help of computers, speech…

  15. The Integral Fast Reactor

    SciTech Connect

    Till, C.E.; Chang, Y.I. ); Lineberry, M.J. )

    1990-01-01

    Argonne National Laboratory, since 1984, has been developing the Integral Fast Reactor (IFR). This paper will describe the way in which this new reactor concept came about; the technical, public acceptance, and environmental issues that are addressed by the IFR; the technical progress that has been made; and our expectations for this program in the near term. 5 refs., 3 figs.

  16. Integral Fast Reactor concept

    SciTech Connect

    Till, C.E.; Chang, Y.I.

    1986-01-01

    The Integral Fast Reactor (IFR) is an innovative LMR concept, being developed at Argonne National Laboratory, that fully exploits the inherent properties of liquid metal cooling and metallic fuel to achieve breakthroughs in economics and inherent safety. This paper describes key features and potential advantages of the IFR concept, technology development status, fuel cycle economics potential, and future development path.

  17. A microchannel confocal examination of arsenic speciation and distribution in Bufo americanus

    NASA Astrophysics Data System (ADS)

    Nearing, Michelle M.; Koch, Iris; Gordon, Robert A.; Reimer, Kenneth J.

    2016-05-01

    We have used confocal methods to examine the distribution and speciation of arsenic within amphibian tissue (Bufo americanus) from a contaminated mine site. The use of new microchannel technology permits a confocal, and energy-independent, examination of a given voxel within the amphibian tissue without the need for sectioning. We observe differences in arsenic concentration and speciation depending on tissue type, with the Eberth- Katschenko layer in particular containing Mn, Fe, Cu and Zn in addition to Ca and pentavalent arsenic.

  18. A statistical model for bacterial speciation triggered by lateral gene transfer

    NASA Astrophysics Data System (ADS)

    Sidhu, Sunjeet; Peng, Wequin

    2006-03-01

    The process of bacterial speciation has been a major unresolved issue in the study of bacterial evolution. It has been proposed that lateral gene transfer and homologous recombination play critical and complementary roles in speciation. We introduce a statistical model, of a population, for the evolution under lateral gene transfer and local homologous recombination. We examine the evolutionary dynamics and its dependence on various evolutionary operators. J. G. Lawrence, Theor. Popul. Biol. 61, 449(2002).

  19. The geography and ecology of plant speciation: range overlap and niche divergence in sister species.

    PubMed

    Anacker, Brian L; Strauss, Sharon Y

    2014-03-07

    A goal of evolutionary biology is to understand the roles of geography and ecology in speciation. The recent shared ancestry of sister species can leave a major imprint on their geographical and ecological attributes, possibly revealing processes involved in speciation. We examined how ecological similarity, range overlap and range asymmetry are related to time since divergence of 71 sister species pairs in the California Floristic Province (CFP). We found that plants exhibit strikingly different age-range correlation patterns from those found for animals; the latter broadly support allopatric speciation as the primary mode of speciation. By contrast, plant sisters in the CFP were sympatric in 80% of cases and range sizes of sisters differed by a mean of 10-fold. Range overlap and range asymmetry were greatest in younger sisters. These results suggest that speciation mechanisms broadly grouped under 'budding' speciation, in which a larger ranged progenitor gives rise to a smaller ranged derivative species, are probably common. The ecological and reproductive similarity of sisters was significantly greater than that of sister-non-sister congeners for every trait assessed. However, shifts in at least one trait were present in 93% of the sister pairs; habitat and soil shifts were especially common. Ecological divergence did not increase with range overlap contrary to expectations under character displacement in sympatry. Our results suggest that vicariant speciation is more ubiquitous in animals than plants, perhaps owing to the sensitivity of plants to fine-scale environmental heterogeneity. Despite high levels of range overlap, ecological shifts in the process of budding speciation may result in low rates of fine-scale spatial co-occurrence. These results have implications for ecological studies of trait evolution and community assembly; despite high levels of sympatry, sister taxa and potentially other close relatives, may be missing from local communities.

  20. The geography and ecology of plant speciation: range overlap and niche divergence in sister species

    PubMed Central

    Anacker, Brian L.; Strauss, Sharon Y.

    2014-01-01

    A goal of evolutionary biology is to understand the roles of geography and ecology in speciation. The recent shared ancestry of sister species can leave a major imprint on their geographical and ecological attributes, possibly revealing processes involved in speciation. We examined how ecological similarity, range overlap and range asymmetry are related to time since divergence of 71 sister species pairs in the California Floristic Province (CFP). We found that plants exhibit strikingly different age-range correlation patterns from those found for animals; the latter broadly support allopatric speciation as the primary mode of speciation. By contrast, plant sisters in the CFP were sympatric in 80% of cases and range sizes of sisters differed by a mean of 10-fold. Range overlap and range asymmetry were greatest in younger sisters. These results suggest that speciation mechanisms broadly grouped under ‘budding’ speciation, in which a larger ranged progenitor gives rise to a smaller ranged derivative species, are probably common. The ecological and reproductive similarity of sisters was significantly greater than that of sister–non-sister congeners for every trait assessed. However, shifts in at least one trait were present in 93% of the sister pairs; habitat and soil shifts were especially common. Ecological divergence did not increase with range overlap contrary to expectations under character displacement in sympatry. Our results suggest that vicariant speciation is more ubiquitous in animals than plants, perhaps owing to the sensitivity of plants to fine-scale environmental heterogeneity. Despite high levels of range overlap, ecological shifts in the process of budding speciation may result in low rates of fine-scale spatial co-occurrence. These results have implications for ecological studies of trait evolution and community assembly; despite high levels of sympatry, sister taxa and potentially other close relatives, may be missing from local communities

  1. Phosphorus Speciation of Forest-soil Organic Surface Layers using P K-edge XANES Spectroscopy

    SciTech Connect

    J Prietzel; J Thieme; D Paterson

    2011-12-31

    The phosphorus (P) speciation of organic surface layers from two adjacent German forest soils with different degree of water-logging (Stagnosol, Rheic Histosol) was analyzed by P K-edge XANES and subsequent Linear Combination Fitting. In both soils, {approx}70% of the P was inorganic phosphate and {approx}30% organic phosphate; reduced P forms such as phosphonate were absent. The increased degree of water-logging in the Histosol compared to the Stagnosol did not affect P speciation.

  2. Fasting or caloric restriction for Healthy Aging

    PubMed Central

    Anton, Stephen; Leeuwenburgh, Christiaan

    2014-01-01

    Aging is associated with a host of biological changes that contribute to a progressive decline in cognitive and physical function, ultimately leading to a loss of independence, and increased risk of mortality. To date, prolonged caloric restriction (i.e., a reduction in caloric intake without malnutrition) is the only non-genetic intervention that has consistently been found to extend both mean and maximal life span across a variety of species. Most individuals have difficulty sustaining prolonged caloric restriction, which has led to a search for alternative approaches that can produce similar to benefits as caloric restriction. A growing body of evidence indicates that fasting periods and intermittent fasting regimens in particular can trigger similar biological pathways as caloric restriction. For this reason, there is increasing scientific interest in further exploring the biological and metabolic effects of intermittent fasting periods, as well as whether long-term compliance may be improved by this type of dietary approach. This special will highlight the latest scientific findings related to the effects of both caloric restriction and intermittent fasting across various species including yeast, fruit flies, worms, rodents, primates, and humans. A specific emphasis is placed on translational research with findings from basic bench to bedside reviewed and practical clinical implications discussed. PMID:23639403

  3. Interaction between Digestive Strategy and Niche Specialization Predicts Speciation Rates across Herbivorous Mammals.

    PubMed

    Tran, Lucy A P

    2016-04-01

    Biotic and abiotic factors often are treated as mutually exclusive drivers of diversification processes. In this framework, ecological specialists are expected to have higher speciation rates than generalists if abiotic factors are the primary controls on species diversity but lower rates if biotic interactions are more important. Speciation rate is therefore predicted to positively correlate with ecological specialization in the purely abiotic model but negatively correlate in the biotic model. In this study, I show that the positive relationship between ecological specialization and speciation expected from the purely abiotic model is recovered only when a species-specific trait, digestive strategy, is modeled in the terrestrial, herbivorous mammals (Mammalia). This result suggests a more nuanced model in which the response of specialized lineages to abiotic factors is dependent on a biological trait. I also demonstrate that the effect of digestive strategy on the ecological specialization-speciation rate relationship is not due to a difference in either the degree of ecological specialization or the speciation rate between foregut- and hindgut-fermenting mammals. Together, these findings suggest that a biological trait, alongside historical abiotic events, played an important role in shaping mammal speciation at long temporal and large geographic scales.

  4. Mercury speciation in floodplain soils and sediments along a contaminated river transect

    SciTech Connect

    Wallschlaeger, D.; Desai, M.V.M.; Spengler, M.; Wilken, R.D.

    1998-09-01

    A novel mercury-specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg-contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesting low availability. However, distinct differences between Hg speciation in the floodplain soils and sediments were also discovered. Mercury deposited in the floodplains shows speciation patterns that indicate stronger fixation compared with Hg in the sediments. This difference is attributed to the association of Hg with larger quantities of OM, which presumably also has higher molecular weight (MW). By comparison, Hg in the sediments was distributed among weaker binding forms, which are more likely to liberate Hg. Particularly, sediments showed a total lack of sulfidic binding forms for Hg. Pronounced geographical trends were detected in the Hg speciation along the river transect, with a general downstream shift from weaker to stronger binding forms, probably due to increased association with OM. These studies indicate that Hg speciation in riverine ecosystems is dynamic and reflects the chemical mechanisms underlying (bio) geochemical processes like distribution and transport.

  5. Genome sequencing reveals fine scale diversification and reticulation history during speciation in Sus

    PubMed Central

    2013-01-01

    Background Elucidating the process of speciation requires an in-depth understanding of the evolutionary history of the species in question. Studies that rely upon a limited number of genetic loci do not always reveal actual evolutionary history, and often confuse inferences related to phylogeny and speciation. Whole-genome data, however, can overcome this issue by providing a nearly unbiased window into the patterns and processes of speciation. In order to reveal the complexity of the speciation process, we sequenced and analyzed the genomes of 10 wild pigs, representing morphologically or geographically well-defined species and subspecies of the genus Sus from insular and mainland Southeast Asia, and one African common warthog. Results Our data highlight the importance of past cyclical climatic fluctuations in facilitating the dispersal and isolation of populations, thus leading to the diversification of suids in one of the most species-rich regions of the world. Moreover, admixture analyses revealed extensive, intra- and inter-specific gene-flow that explains previous conflicting results obtained from a limited number of loci. We show that these multiple episodes of gene-flow resulted from both natural and human-mediated dispersal. Conclusions Our results demonstrate the importance of past climatic fluctuations and human mediated translocations in driving and complicating the process of speciation in island Southeast Asia. This case study demonstrates that genomics is a powerful tool to decipher the evolutionary history of a genus, and reveals the complexity of the process of speciation. PMID:24070215

  6. Phylogenetic test of speciation by host shift in leaf cone moths (Caloptilia) feeding on maples (Acer).

    PubMed

    Nakadai, Ryosuke; Kawakita, Atsushi

    2016-07-01

    The traditional explanation for the exceptional diversity of herbivorous insects emphasizes host shift as the major driver of speciation. However, phylogenetic studies have often demonstrated widespread host plant conservatism by insect herbivores, calling into question the prevalence of speciation by host shift to distantly related plants. A limitation of previous phylogenetic studies is that host plants were defined at the family or genus level; thus, it was unclear whether host shifts predominate at a finer taxonomic scale. The lack of a statistical approach to test the hypothesis of host-shift-driven speciation also hindered studies at the species level. Here, we analyze the radiation of leaf cone moths (Caloptilia) associated with maples (Acer) using a newly developed, phylogeny-based method that tests the role of host shift in speciation. This method has the advantage of not requiring complete taxon sampling from an entire radiation. Based on 254 host plant records for 14 Caloptilia species collected at 73 sites in Japan, we show that major dietary changes are more concentrated toward the root of the phylogeny, with host shift playing a minor role in recent speciation. We suggest that there may be other roles for host shift in promoting herbivorous insect diversification rather than facilitating speciation per se.

  7. Persistence of within-species lineages: a neglected control of speciation rates.

    PubMed

    Dynesius, Mats; Jansson, Roland

    2014-04-01

    We present a framework distinguishing three principal controls of speciation rate: rate of splitting, level of persistence, and length of speciation duration. We contend that discussions on diversification become clearer in the light of this framework, because speciation rate variation could be attributed to any of these controls. In particular, we claim that the role of persistence of within-species lineages in controlling speciation rates has been greatly underappreciated. More emphasis on the persistence control would change expectations of the role of several biological traits and environmental factors, because they may drive speciation rate in one direction through the persistence control and in the opposite direction through the other two controls. Traits and environments have been little studied regarding their influence on speciation rate through the persistence control, with climatic fluctuations being a relatively well-studied exception. Considering the recent advances in genomic and phylogenetic analysis, we think that the time is ripe for applying the framework in empirical research. Variation among clades and areas (and thus among traits and environments) in the importance of the three rate controls could be addressed for example by dating splitting events, detecting within-species lineages, and scanning genomes for evidence of divergent selection.

  8. Adaptive divergence with gene flow in incipient speciation of Miscanthus floridulus/sinensis complex (Poaceae).

    PubMed

    Huang, Chao-Li; Ho, Chuan-Wen; Chiang, Yu-Chung; Shigemoto, Yasumasa; Hsu, Tsai-Wen; Hwang, Chi-Chuan; Ge, Xue-Jun; Chen, Charles; Wu, Tai-Han; Chou, Chang-Hung; Huang, Hao-Jen; Gojobori, Takashi; Osada, Naoki; Chiang, Tzen-Yuh

    2014-12-01

    Young incipient species provide ideal materials for untangling the process of ecological speciation in the presence of gene flow. The Miscanthus floridulus/sinensis complex exhibits diverse phenotypic and ecological differences despite recent divergence (approximately 1.59 million years ago). To elucidate the process of genetic differentiation during early stages of ecological speciation, we analyzed genomic divergence in the Miscanthus complex using 72 randomly selected genes from a newly assembled transcriptome. In this study, rampant gene flow was detected between species, estimated as M = 3.36 × 10(-9) to 1.20 × 10(-6) , resulting in contradicting phylogenies across loci. Nevertheless, beast analyses revealed the species identity and the effects of extrinsic cohesive forces that counteracted the non-stop introgression. As expected, early in speciation with gene flow, only 3-13 loci were highly diverged; two to five outliers (approximately 2.78-6.94% of the genome) were characterized by strong linkage disequilibrium, and asymmetrically distributed among ecotypes, indicating footprints of diversifying selection. In conclusion, ecological speciation of incipient species of Miscanthus probably followed the parapatric model, whereas allopatric speciation cannot be completely ruled out, especially between the geographically isolated northern and southern M. sinensis, for which no significant gene flow across oceanic barriers was detected. Divergence between local ecotypes in early-stage speciation began at a few genomic regions under the influence of natural selection and divergence hitchhiking that overcame gene flow.

  9. A test of whether rates of speciation were unusually high during the Cambrian radiation.

    PubMed

    Lieberman, B S

    2001-08-22

    The Cambrian radiation represents an interval when nearly 20 animal phyla appear in the fossil record in a short geological time span; however, whether this radiation also represents a period of extremely rapid speciation remains unclear. Here, a stochastic framework is used to test the null hypothesis that diversity changes in one of the dominant Early Cambrian groups, the olenelloid trilobites, could be produced by tempos of speciation known to have operated during later time periods. Two continuous-time models, the Yule model and the birth and death process model, and one discrete-time model, the Bienaymé-Galton-Watson branching process model, were used. No statistical evidence for uniquely high rates of speciation during the radiation in these trilobites was found when the continuous-time models were used with low or moderate extinction rates, the rates typically associated with the Cambrian radiation, although the p values are fairly low or, in one case, significant when high extinction rates were used. However, rates of speciation were higher than the average Phanerozoic rates of speciation. The discrete-time model produced equivocal results: either rates were unusually high or the model is inapplicable during the Cambrian radiation. This suggests that there was nothing unique about evolutionary processes relating to the tempo of speciation during the Cambrian radiation.

  10. Is Speciation Accompanied by Rapid Evolution? Insights from Comparing Reproductive and Nonreproductive Transcriptomes in Drosophila

    PubMed Central

    Jagadeeshan, Santosh; Haerty, Wilfried; Singh, Rama S.

    2011-01-01

    The tempo and mode of evolutionary change during speciation have remained contentious until recently. While much of the evidence claiming speciation is an abrupt and rapid process comes from fossil data, recent molecular phylogenetics show that the background of gradual evolution is often broken by accelerated rates of molecular evolution during speciation. However, what kinds of genes affect or are affected by speciation remains unexplored. Our analysis of 4843 protein-coding genes in five species of the Drosophila melanogaster subgroup shows that while ~70% of genes follow clock-like evolution, between 17–19.67% of loci show signatures of accelerated rates of evolution in recently formed species. These genes show 2-3-fold higher rates of substitution in recently diverged species compared to older species. This fraction of loci affects a diverse range of functions. Only a small proportion of reproductive genes experience speciation-related accelerated changes but many sex-and -reproduction related genes show an interesting pattern of persistent rapid evolution suggesting that sex-and-reproduction related genes are under constant selective pressures. The identification of loci associated with accelerated evolution allows us to address the mechanisms of rapid evolution and speciation, which in our study appears to be a combination of both selection and rapid demographical changes. PMID:21869936

  11. Hybridization masks speciation in the evolutionary history of the Galápagos marine iguana.

    PubMed

    MacLeod, Amy; Rodríguez, Ariel; Vences, Miguel; Orozco-terWengel, Pablo; García, Carolina; Trillmich, Fritz; Gentile, Gabriele; Caccone, Adalgisa; Quezada, Galo; Steinfartz, Sebastian

    2015-06-22

    The effects of the direct interaction between hybridization and speciation-two major contrasting evolutionary processes--are poorly understood. We present here the evolutionary history of the Galápagos marine iguana (Amblyrhynchus cristatus) and reveal a case of incipient within--island speciation, which is paralleled by between-island hybridization. In-depth genome-wide analyses suggest that Amblyrhynchus diverged from its sister group, the Galápagos land iguanas, around 4.5 million years ago (Ma), but divergence among extant populations is exceedingly young (less than 50,000 years). Despite Amblyrhynchus appearing as a single long-branch species phylogenetically, we find strong population structure between islands, and one case of incipient speciation of sister lineages within the same island--ostensibly initiated by volcanic events. Hybridization between both lineages is exceedingly rare, yet frequent hybridization with migrants from nearby islands is evident. The contemporary snapshot provided by highly variable markers indicates that speciation events may have occurred throughout the evolutionary history of marine iguanas, though these events are not visible in the deeper phylogenetic trees. We hypothesize that the observed interplay of speciation and hybridization might be a mechanism by which local adaptations, generated by incipient speciation, can be absorbed into a common gene pool, thereby enhancing the evolutionary potential of the species as a whole.

  12. Aircraft emissions, plume chemistry, and alternative fuels: results from the APEX, AAFEX, and MDW-2009 campaigns

    NASA Astrophysics Data System (ADS)

    Wood, E. C.; Herndon, S. C.; Timko, M.; Yu, Z.; Miake-Lye, R. C.; Lee, B. H.; Santoni, G.; Munger, J. W.; Wofsy, S.; Anderson, B.; Knighton, W. B.

    2009-12-01

    We describe observations of aircraft emissions from the APEX, JETS-APEX2, APEX3, MDW-2009 and AAFEX campaigns. Direct emissions of HOx precursors are important for understanding exhaust plume chemistry due to their role in determining HOx concentrations. Nitrous acid (HONO) and formaldehyde are crucial HOx precursors and thus drivers of plume chemistry. At idle power, aircraft engine exhaust is unique among fossil fuel combustion sources due to the speciation of both NOx and VOCs. The impacts of emissions of HOx precursors on plume chemistry at low power are demonstrated with empirical observations of rapid NO to NO2 conversion, indicative of rapid HOx chemistry. The impacts of alternative fuels (derived from biomass, coal, and natural gas) on emissions of NOx, CO, and speciated VOCs are discussed.

  13. Feelings of Preparedness among Alternatively Certified Teachers: What Is the Role of Program Features?

    ERIC Educational Resources Information Center

    Kee, Ayana N.

    2012-01-01

    In the United States, about one third of new teachers being hired are drawn from alternative certification programs. One way to address controversy about the differences among the training experiences of teachers in traditional certification programs, fast-track alternative programs, and residency alternative programs is to examine teacher reports…

  14. Fabrication techniques for very fast diffractive lenses

    NASA Technical Reports Server (NTRS)

    Tai, Anthony M.; Marron, Joseph C.

    1993-01-01

    Aspheric lenses with arbitrary phase functions can be fabricated on thin light weight substrates via the binary optics fabrication technique. However, it is difficult and costly to fabricate a fast lens (f/number less than 1) for use as the shorter wavelengths. The pitch of the masks and the alignment accuracy must be very fine. For a large lens, the space-bandwidth product of the element can also become impractically large. In this paper, two alternate approaches for the fabrication of fast aspheric diffractive lenses are described. The first approach fabricates the diffractive lens interferometrically, utilizing a spherical wavefront to provide the optical power of the lens and a computer generated hologram to create the aspheric components. The second approach fabricates the aspheric diffractive lens in the form if a higher order kinoform which trades groove profile fidelity for coarser feature size. The design and implementation issues for these two fabrication techniques are discussed.

  15. Parallel speciation or long-distance dispersal? Lessons from seaweeds (Fucus) in the Baltic Sea.

    PubMed

    Pereyra, R T; Huenchuñir, C; Johansson, D; Forslund, H; Kautsky, L; Jonsson, P R; Johannesson, K

    2013-08-01

    Parallel evolution has been invoked as a forceful mechanism of ecotype and species formation in many animal taxa. However, parallelism may be difficult to separate from recently monophyletically diverged species that are likely to show complex genetic relationships as a result of considerable shared ancestral variation and secondary hybridization in local areas. Thus, species' degrees of reproductive isolation, barriers to dispersal and, in particular, limited capacities for long-distance dispersal will affect demographical structures underlying mechanisms of divergent evolution. Here, we used nine microsatellite DNA markers to study intra- and interspecific genetic diversity of two recently diverged species of brown macroalgae, Fucus radicans (L. Bergström & L. Kautsky) and F. vesiculosus (Linnaeus), in the Baltic Sea. We further performed biophysical modelling to identify likely connectivity patterns influencing the species' genetic structures. For each species, we found intraspecific contrasting patterns of clonality incidence and population structure. In addition, strong genetic differentiation between the two species within each locality supported the existence of two distinct evolutionary lineages (FST  = 0.15-0.41). However, overall genetic clustering analyses across both species' populations revealed that all populations from one region (Estonia) were more genetically similar to each other than to their own taxon from the other two regions (Sweden and Finland). Our data support a hypothesis of parallel speciation. Alternatively, Estonia may be the ancestral source of both species, but is presently isolated by oceanographic barriers to dispersal. Thus, a limited gene flow in combination with genetic drift could have shaped the seemingly parallel structure.

  16. Speciation on a conveyor belt: sequential colonization of the hawaiian islands by Orsonwelles spiders (Araneae, Linyphiidae).

    PubMed

    Hormiga, Gustavo; Arnedo, Miquel; Gillespie, Rosemary G

    2003-02-01

    Spiders of the recently described linyphiid genus Orsonwelles (Araneae, Linyphiidae) are one of the most conspicuous groups of terrestrial arthropods of Hawaiian native forests. There are 13 known Orsonwelles species, and all are single- island endemics. This radiation provides an excellent example of insular gigantism. We reconstructed the cladistic relationships of Orsonwelles species using a combination of morphological and molecular characters (both mitochondrial and nuclear sequences) within a parsimony framework. We explored and quantified the contribution of different character partitions and their sensitivity to changes in the traditional parameters (gap, transition, and transversion costs). The character data show a strong phylogenetic signal, robust to parameter changes. The monophyly of the genus Orsonwelles is strongly supported. The parsimony analysis of all character evidence combined recovered a clade with of all the non-Kauai Orsonwelles species; the species from Kauai form a paraphyletic assemblage with respect to the latter former clade. The biogeographic pattern of the Hawaiian Orsonwelles species is consistent with colonization by island progression, but alternative explanations for our data exist. Although the geographic origin of the radiation remains unknown, it appears that the ancestral colonizing species arrived first on Kauai (or an older island). The ambiguity in the area cladogram (i.e., post-Oahu colonization) is not derived from conflicting or unresolved phylogenetic signal among Orsonwelles species but rather from the number of taxa on the youngest islands. Speciation in Orsonwelles occurred more often within islands (8 of the 12 cladogenic events) than between islands. A molecular clock was rejected for the sequence data. Divergence times were estimated by using the nonparametric rate smoothing method of Sanderson (1997, Mol. Biol. Evol. 14:1218-1231) and the available geological data for calibration. The results suggest that the

  17. Compositional dependence of sulfur speciation in Terrestrial and Martian magmas

    NASA Astrophysics Data System (ADS)

    Nash, William; Wood, Bernard; Smythe, Duane

    2016-04-01

    The capacity of magmas to transport sulfur from mantle to crust strongly influences a planet's surface chemistry. Sulfur is perhaps exceptional among the elements in the diversity of it's chemical speciation, exhibiting four redox species at geologically relevant conditions: sulfide (2-), elemental sulfur (0), sulfite (4+) and sulphate (6+). Furthermore, the solubility of sulfur in a magma (and hence the magma's capacity for delivering mantle-derived sulfur to the crust) depends critically on it's oxidation state. Our aim with this experimental study was to quantitatively determine the chemical speciation of sulfur within several common magmas, as a function of oxygen fugacity (fO2). We have performed a series of experiments on six sulfur-bearing silicate melts, which together represent a broad range of naturally occurring compositions: two putative Martian basalts, two terrestrial MORBs (one primitive, one evolved), an andesite, and a dacite. These melts were equilibrated together (at one-atmosphere pressure, 1300°C) with various CO-CO2-SO2 gas mixtures, which imposed a range of fO2s. This range spanned -2 to +1.6 log units (relative to the Quartz-Fayalite-Magnetite or QFM buffer), and the step-size was 0.25 log units. The quenched glasses were analyzed by X-ray Absorption Spectroscopy (specifically XANES) at the Diamond synchrotron (UK), and the spectra obtained were used to determine the species of sulfur present in each glass. The chemical composition of each glass (including their sulfur contents) was characterized by electron-probe microanalysis. Despite the generally low concentrations of sulfur in our glasses (never exceeding 0.24 wt%), we have clearly resolved the crossover between reduced (S2-) and oxidized (S6+) species for three of our basalts. The other three melts yielded more noisy XANES spectra, and as a result their redox crossovers are visible, but less clearly resolved. For every melt composition, the redox crossover is a continuous (though

  18. The inorganic speciation of tin(II) in aqueous solution

    NASA Astrophysics Data System (ADS)

    Cigala, Rosalia Maria; Crea, Francesco; De Stefano, Concetta; Lando, Gabriele; Milea, Demetrio; Sammartano, Silvio

    2012-06-01

    This paper reports new voltammetric measurements on the interactions between tin(II) and the most important natural inorganic ligands, OH-, Cl-, F-, CO32-, SO42- and PO43-. For a better understanding of tin(II) speciation, an analysis is also given of prior data on the same systems from the literature. The formation constants were determined at t = 25 °C in different ionic media and at different ionic strengths, specifically the following: Sn(OH)q (0.1 ⩽ I/mol L-1 ⩽ 1.0 in NaNO3), SnClr and Sn(OH)Cl (0.1 ⩽ I/mol L-1 ⩽ 2.3 in Na(NO3, Cl)), Sn(SO4)r (0.1 ⩽ I/mol L-1 ⩽ 1.6 in Na(NO3, SO4)), SnHqCO3 and SnHqPO4 (0.15 ⩽ I/mol L-1 ⩽ 1.0 in NaNO3), where the subscripts r and q represent the stoichiometric coefficients. Concerning the SnFr species, reliable literature values were considered (0.15 ⩽ I/mol L-1 ⩽ 1.0 in NaClO4). Fifteen voltammetric measurements were performed in synthetic seawater; the total seawater binding ability was evaluated by a model in which synthetic seawater is expressed as a single salt, BA. The formation of species between tin(II) and the anion of the marine salt (A) was also proposed, and the corresponding stability constants at different salinities (5 ⩽ S ⩽ 50) were reported. In addition, studies on the solubility of Sn(OH)2(s) were carried out using voltammetry and light scattering measurements. The "extra-stability" of the mixed species with respect to the parent species was evaluated, in particular for Sn(OH)Cl and the corresponding species involving the anion of the marine salt (A). The dependence of the formation constants on ionic strength was analysed using extended Debye-Hückel and Specific ion Interaction Theory (SIT) type equations. Tin(II) speciation was also evaluated in different natural fluid conditions, where, in all cases, carbonate complexation was predominant, hampering the formation of hydrolytic species throughout the investigated pH range. Moreover, some formation enthalpy changes were calculated

  19. Radiogenic metabolism: an alternative cellular energy source.

    PubMed

    Benford, M S

    2001-01-01

    The concept of 'healing energy' is commonly used in complementary and alternative medicine; however, efforts to define this concept using contemporary scientific theory, and measure it using modern scientific methods, have been limited to date. Recent experimental testing by Benford et al. observed a uniform, substantial, and consistent decrease in gamma radiation during alternative healing sessions, thus supporting a new energy-balance paradigm hypothesizing ionizing radiation as an alternative cellular energy source. This hypothesis extends the known elements of radiogenic metabolism to potentially explain a number of presumably biopositive energy-related phenomena, including fasting and radiation hormesis, as well as to demystify unexplained anomalies such as idiopathic thermogenesis, halos and auras, and incorruptibility of human corpses.

  20. Speciation or Irruption: The Significance of the Darwin Finches.

    ERIC Educational Resources Information Center

    Harper, G. H.

    1980-01-01

    Uses the irruption theory in explaining the occurrence of the Darwin finches in the Galapagos Islands as an example of how alternative theories can be presented in an educational setting. Advocates the comparison of alternative theories to encourage creative thinking and a critical attitude. (CS)