Science.gov

Sample records for dysmetria experimental evidence

  1. Ataxia, dysmetria, tremor. Cerebellar diseases.

    PubMed

    Kornegay, J N

    1991-09-01

    Diseases affecting the cerebellum typically cause ataxia, coupled with dysmetria and tremor. Dysmetria is a condition in which there is improper measuring of distance in muscular acts; hypermetria is overreaching (overstepping) and hypometria is underreaching (understepping). Tremor refers to an involuntary, rhythmic, oscillatory movement of a body part. The tremor of cerebellar disease typically is exaggerated by goal-oriented movements (intention tremor). Cerebellar lesions also often cause loss of the menace response, despite the presence of normal vision. The anatomic basis for this phenomenon is obscure. The principal disease affecting the cerebellum in cats is cerebellar hypoplasia due to in utero infection with the panleukopenia virus. This disease will be discussed here. Neurologic signs of cerebellar involvement also may be seen in association with those diseases that affect the CNS multifocally. In these cats, there may be additional signs indicating involvement of other anatomic areas or the cerebellar deficits may occur alone (see discussion of multifocal diseases in Multiple Neurologic Deficits: Inflammatory Diseases [page 426] and Multiple Neurologic Deficits: Noninfectious Diseases [page 440]). PMID:1802262

  2. Communicating Uncertain Experimental Evidence

    ERIC Educational Resources Information Center

    Davis, Alexander L.; Fischhoff, Baruch

    2014-01-01

    Four experiments examined when laypeople attribute unexpected experimental outcomes to error, in foresight and in hindsight, along with their judgments of whether the data should be published. Participants read vignettes describing hypothetical experiments, along with the result of the initial observation, considered as either a possibility…

  3. Sexually antagonistic genes: experimental evidence.

    PubMed

    Rice, W R

    1992-06-01

    When selection differs between the sexes, a mutation beneficial to one sex may be harmful to the other (sexually antagonistic). Because the sexes share a common gene pool, selection in one sex can interfere with the other's adaptive evolution. Theory predicts that sexually antagonistic mutations should accumulate in tight linkage with a new sex-determining gene, even when the harm to benefit ratio is high. Genetic markers and artificial selection were used to make a pair of autosomal genes segregate like a new pair of sex-determining genes in a Drosophila melanogaster model system. A 29-generation study provides experimental evidence that sexually antagonistic genes may be common in nature and will accumulate in response to a new sex-determining gene. PMID:1604317

  4. Experimental evidence of the compressibility of arteries.

    PubMed

    Yosibash, Zohar; Manor, Itay; Gilad, Ilan; Willentz, Udi

    2014-11-01

    A definitive answer to the question whether artery walls are incompressible is to our opinion not yet categorically provided. Experimental-based evidence on the level of compressibility in artery walls is not easily achieved because of the difficulties associated with the measurement of very small differences in volumes under physiological pressure in these biological tissues. Past experiments aimed at addressing the question considered different species, different arteries, the experimental devices were not accurate enough and a statistical analysis of the results was missing. A precise experimental device together with a thorough testing protocol, a careful selection of arteries and a statistical analysis is presented for a definitive evaluation of the artery wall compressibility. We provide experimental evidence that in saphenous and femoral porcine arteries under physiological pressure range a relative compressibility of 2-6% is observed. The pre-assumption of incompressibility in many phenomenological constitutive models of artery walls should probably be re-evaluated.

  5. Experimental evidence of quantum randomness incomputability

    SciTech Connect

    Calude, Cristian S.; Dinneen, Michael J.; Dumitrescu, Monica; Svozil, Karl

    2010-08-15

    In contrast with software-generated randomness (called pseudo-randomness), quantum randomness can be proven incomputable; that is, it is not exactly reproducible by any algorithm. We provide experimental evidence of incomputability--an asymptotic property--of quantum randomness by performing finite tests of randomness inspired by algorithmic information theory.

  6. Experimental evidence for Abraham pressure of light

    NASA Astrophysics Data System (ADS)

    Zhang, Li; She, Weilong; Peng, Nan; Leonhardt, Ulf

    2015-05-01

    The question of how much momentum light carries in media has been debated for over a century. Two rivalling theories, one from 1908 by Hermann Minkowski and the other from 1909 by Max Abraham, predict the exact opposite when light enters an optical material: a pulling force in Minkowski's case and a pushing force in Abraham's. Most experimental tests have agreed with Minkowski's theory, but here we report the first quantitative experimental evidence for Abraham's pushing pressure of light. Our results matter in optofluidics and optomechanics, and wherever light exerts mechanical pressure.

  7. Experimental Evidence on Iterated Reasoning in Games

    PubMed Central

    Grehl, Sascha; Tutić, Andreas

    2015-01-01

    We present experimental evidence on two forms of iterated reasoning in games, i.e. backward induction and interactive knowledge. Besides reliable estimates of the cognitive skills of the subjects, our design allows us to disentangle two possible explanations for the observed limits in performed iterated reasoning: Restrictions in subjects’ cognitive abilities and their beliefs concerning the rationality of co-players. In comparison to previous literature, our estimates regarding subjects’ skills in iterated reasoning are quite pessimistic. Also, we find that beliefs concerning the rationality of co-players are completely irrelevant in explaining the observed limited amount of iterated reasoning in the dirty faces game. In addition, it is demonstrated that skills in backward induction are a solid predictor for skills in iterated knowledge, which points to some generalized ability of the subjects in iterated reasoning. PMID:26312486

  8. Saccadic dysmetria is similar in patients with a lateral medullary lesion and in monkeys with a lesion of the deep cerebellar nucleus.

    PubMed

    Straube, A; Helmchen, C; Robinson, F; Fuchs, A; Büttner, U

    1994-01-01

    Some of the clinical hallmarks of lateral medullary infarction--Wallenberg's syndrome--are saccadic dysmetria, smooth pursuit deficit, and lateropulsion of the body. Similar movement disorders are seen in monkeys after local unilateral injection of GABAergic drugs in the caudal fastigial nucleus of monkeys. These include an ipsilateral saccadic hypermetria and a contralateral saccadic hypometria as well as cogwheel smooth pursuit eye movements toward the contralateral side and an ipsiversive lateropulsion of the body. It was previously suggested that the lateral medullary infarction causes a lesion of climbing fibers to the cerebellum. This lack of climbing fiber input increases the activity of ipsilateral Purkinje cells, which consequently provide too much inhibition of the deep cerebellar nuclei.

  9. Experimental evidence of electromagnetic pollution of ionosphere

    NASA Astrophysics Data System (ADS)

    Pronenko, Vira; Korepanov, Valery; Dudkin, Denis

    multiple low orbiting satellites have confirmed a significant increase in their intensity over the populated areas of Europe and Asia. Recently, there are many experimental evidences of the existence of power line harmonic radiation (PLHR) in the ionosphere. Their spectra consist of succession of 50 (60) Hz harmonics which is accompanied by a set of lines separated by 50 (60) or 100 (120) Hz - the central frequency of which is shifted to high frequency. These lines cover rather wide band - according to the available experimental data, their central frequencies are observed from ~1.5 - 3 kHz up to 15 kHz, and recently the main mains frequencies are also observed. The examples of power line harmonic radiation, which were detected by “Sich-1M”, “Chibis-M” and “Demeter” satellites, have been presented and discussed. The available experimental data, as well as theoretical estimations, allow us with a high degree of certainty to say that the permanent satellite monitoring of the ionospheric and magnetospheric anthropogenic EM perturbations is necessary for: a) objective assessment and prediction of the space weather conditions; b) evaluation of the daily or seasonal changes in the level of energy consumption; c) construction of a map for estimation of near space EM pollution. This study is partially supported by SSAU contract N 4-03/13.

  10. Experimental Evidence of Chaos from Memristors

    NASA Astrophysics Data System (ADS)

    Gambuzza, Lucia Valentina; Fortuna, Luigi; Frasca, Mattia; Gale, Ella

    Until now, most memristor-based chaotic circuits proposed in the literature are based on mathematical models which assume ideal characteristics such as piecewise-linear or cubic nonlinearities. The idea, illustrated here and originating from the experimental approach for device characterization, is to realize a chaotic system exploiting the nonlinearity of only one memristor with a very simple experimental set-up using feedback. In this way, a simple circuit is obtained and chaos is experimentally observed and is confirmed by the calculation of the largest Lyapunov exponent. Numerical results using the Strukov model support the existence of robust chaos in our circuit. To our knowledge, this is the first experimental demonstration of chaos in a real memristor circuit and suggests that memristors are well placed for hardware encryption.

  11. Natural compounds as anticancer agents: Experimental evidence

    PubMed Central

    Wang, Jiao; Jiang, Yang-Fu

    2012-01-01

    Cancer prevention research has drawn much attention worldwide. It is believed that some types of cancer can be prevented by following a healthy life style. Cancer chemoprevention by either natural or synthetic agents is a promising route towards lowering cancer incidence. In recent years, the concept of cancer chemoprevention has evolved greatly. Experimental studies in animal models demonstrate that the reversal or suppression of premalignant lesions by chemopreventive agents is achievable. Natural occurring agents such as dietary phytochemicals, tea polyphenols and resveratrol show chemopreventive activity in animal models. Moreover, clinical trials for testing the safety and efficacy of a variety of natural agents in preventing or treating human malignancy have been ongoing. Here, we summarize experimental data on the chemopreventive or tumor suppressive effects of several natural compounds including curcumin, (-)-epigallocatechin-3-gallate, resveratrol, indole-3-carbinol, and vitamin D. PMID:24520533

  12. Experimental evidence of MHD surface waves

    SciTech Connect

    Amagishi, Y.

    1986-12-01

    MND surface waves of m = -1 (poloidal mode number of left-hand rotation) compressional Alfven waves in a cylindrical finite-..beta.. plasma have been observed for the first time to propagate together with shear Alfven waves. These modes also show a distinctive feature of the dispersion merging with that of shear Alfven waves at the center of a plasma column when a limiting frequency below the ion cyclotron frequencey is reached. The experimental results confirm a recent prediction concerning surface-wave properties of the first radial eigenmode of a nonaxisymmetric compressional wave in a plasma surrounded by an insulating boundary.

  13. Experimental Evidence for Mixed Reality States

    NASA Astrophysics Data System (ADS)

    Gintautas, Vadas; Hubler, Alfred

    2008-03-01

    We present experimental data on the limiting behavior of an inter-reality system: a virtual pendulum with a bi-directional instantaneous coupling to its real-world counterpart [Gintautas & Hubler, Phys.Rev.E 75, 057201 (2007)]. The data show that if the physical parameters of the simplified virtual system are close to the parameters of the real system, there is a phase transition from an uncorrelated dual reality state to a mixed reality state in which the motion of the two pendulums is highly correlated. As virtual systems better approximate real ones, even weak couplings in inter-reality systems may induce sudden transitions to mixed reality states. This phenomenon may be typical for systems with instantaneous coupling and was recently featured on the tip sheet of the American Physical Society [http://www.aps.org/about/tipsheets/tip68.cfm ]. We show that mixed reality states in physical systems are related to out-of- body experiences of humans in 3D-video feedback systems [H. H. Ehrsson, The Experimental Induction of Out-of-Body Experiences. Science 317, 1048 (2007)].

  14. Experimental evidence of condensation-driven airflow

    NASA Astrophysics Data System (ADS)

    Bunyard, P.; Hodnett, M.; Poveda, G.; Burgos Salcedo, J. D.; Peña, C.

    2015-10-01

    The dominant "convection" model of atmospheric circulation is based on the premise that hot air expands and rises, to be replaced by colder air, thereby creating horizontal surface winds. A recent theory put forward by Makarieva and Gorshkov (2007, 2013) maintains that the primary motive force of atmospheric circulation derives from the intense condensation and sharp pressure reduction that is associated with regions where a high rate of evapotranspiration from natural closed-canopy forests provides the "fuel" for cloud formation. The net result of the "biotic pump" theory is that moist air flows from ocean to land, drawn in by the pressure changes associated with a high rate of condensation. To test the physics underpinning the biotic pump theory, namely that condensation of water vapour, at a sufficiently high rate, results in an uni-directional airflow, a 5 m tall experimental apparatus was designed and built, in which a 20 m3 body of atmospheric air is enclosed inside an annular 14 m long space (a "square donut") around which it can circulate freely, allowing for rotary air flows. One vertical side of the apparatus contains some 17 m of copper refrigeration coils, which cause condensation. The apparatus contains a series of sensors measuring temperature, humidity and barometric pressure every five seconds, and air flow every second. The laws of Newtonian physics are used in calculating the rate of condensation inside the apparatus. The results of more than one hundred experiments show a highly significant correlation, with r2 > 0.9, of airflow and the rate of condensation. The rotary air flows created appear to be consistent both in direction and velocity with the biotic pump hypothesis, the critical factor being the rate change in the partial pressure of water vapour in the enclosed body of atmospheric air. Air density changes, in terms of kinetic energy, are found to be orders of magnitude smaller than the kinetic energy of partial pressure change. The

  15. Reconciling Experimental and Quasi-Experimental Evidence on the Impact of Full-Day Kindergarten

    ERIC Educational Resources Information Center

    Gibbs, Chloe

    2013-01-01

    This paper addresses the question of how to interpret evidence on the impact of full-day kindergarten resulting from different study designs, and provides guidance on how this evidence taken in tandem may inform the design and implementation of full-day kindergarten policies. Incorporating both experimental and quasi-experimental estimates on…

  16. Experimental evidence for lattice effects in high temperature superconductors

    SciTech Connect

    Billinge, S.J.L.; Kwei, G.H.; Thompson, J.D.

    1994-01-18

    We present an overview of the experimental evidence for a role of the lattice in the mechanism of high temperature superconductivity. It appears unlikely that a solely conventional electron-phonon interaction produces the pairing. However, there is ample evidence of strong electron and spin to lattice coupling and observations of a response of the lattice to the electronic state. We draw attention to the importance of the local structure in discussions of lattice effects in high-{Tc} superconductivity.

  17. Experimental evidence of vibrational resonance in a multistable system

    NASA Astrophysics Data System (ADS)

    Chizhevsky, V. N.

    2014-06-01

    Experimental evidence of vibrational resonance in a multistable vertical-cavity surface-emitting laser (VCSEL) is reported. The VCSEL is characterized by a coexistence of four polarization states and driven by low-frequency (LF) and high-frequency (HF) periodic signals. In these conditions a series of resonances on the low frequency depending on the HF amplitude is observed. The location of resonances in a parameter space (dc current, amplitude of HF signal) is experimentally studied. For a fixed value of the dc current an evolution of the resonance curves with an increase of the LF amplitude is experimentally investigated.

  18. Single-Subject Experimental Design for Evidence-Based Practice

    ERIC Educational Resources Information Center

    Byiers, Breanne J.; Reichle, Joe; Symons, Frank J.

    2012-01-01

    Purpose: Single-subject experimental designs (SSEDs) represent an important tool in the development and implementation of evidence-based practice in communication sciences and disorders. The purpose of this article is to review the strategies and tactics of SSEDs and their application in speech-language pathology research. Method: The authors…

  19. Experimental evidence of contagious yawning in budgerigars (Melopsittacus undulatus).

    PubMed

    Gallup, Andrew C; Swartwood, Lexington; Militello, Janine; Sackett, Serena

    2015-09-01

    Experimental evidence of contagious yawning has only been documented in four mammalian species. Here, we report the results from two separate experimental studies designed to investigate the presence of contagious yawning in a social parrot, the budgerigar (Melopsittacus undulatus). In Study 1, birds were paired in adjacent cages with and without visual barriers, and the temporal association of yawning was assessed between visual conditions. In Study 2, the same birds were exposed to video stimuli of both conspecific yawns and control behavior, and yawning frequency was compared between conditions. Results from both studies demonstrate that yawning is contagious. To date, this is the first experimental evidence of contagious yawning in a non-mammalian species. We propose that future research could use budgerigars to explore questions related to basic forms of empathic processing. PMID:26012708

  20. Experimental evidence of contagious yawning in budgerigars (Melopsittacus undulatus).

    PubMed

    Gallup, Andrew C; Swartwood, Lexington; Militello, Janine; Sackett, Serena

    2015-09-01

    Experimental evidence of contagious yawning has only been documented in four mammalian species. Here, we report the results from two separate experimental studies designed to investigate the presence of contagious yawning in a social parrot, the budgerigar (Melopsittacus undulatus). In Study 1, birds were paired in adjacent cages with and without visual barriers, and the temporal association of yawning was assessed between visual conditions. In Study 2, the same birds were exposed to video stimuli of both conspecific yawns and control behavior, and yawning frequency was compared between conditions. Results from both studies demonstrate that yawning is contagious. To date, this is the first experimental evidence of contagious yawning in a non-mammalian species. We propose that future research could use budgerigars to explore questions related to basic forms of empathic processing.

  1. Direct Experimental Evidence of Nonequilibrium Energy Sharing in Dissipative Collisions

    NASA Astrophysics Data System (ADS)

    Casini, G.; Maurenzig, P. R.; Olmi, A.; Bini, M.; Calamai, S.; Meucci, F.; Pasquali, G.; Poggi, G.; Stefanini, A. A.; Gobbi, A.; Hildenbrand, K. D.

    1997-02-01

    Primary and secondary masses of heavy reaction products have been deduced from kinematics and energy-time-of-flight measurements, respectively, for the direct and reverse collisions of 100Mo with 120Sn at 14.1A MeV. Direct experimental evidence of the correlation of energy sharing with net mass transfer and model-independent results on the evolution of the average excitation from equal-energy to equal-temperature partition are presented.

  2. Experimental evidence of hyperbolic heat conduction in processed meat

    SciTech Connect

    Mitra, K.; Kumar, S.; Vedavarz, A.; Moallemi, M.K.

    1995-08-01

    The objective of this paper is to present experimental evidence of the wave nature of heat propagation in processed meat and to demonstrate that the hyperbolic heat conduction model is an accurate representation, on a macroscopic level, of the heat conduction process in such biological material. The value of the characteristic thermal time of a specific material, processed bologna meat, is determined experimentally. As a part of the work different thermophysical properties are also measured. The measured temperature distributions in the samples are compared with the Fourier results and significant deviation between the two is observed, especially during the initial stages of the transient conduction process. The measured values are found to match the theoretical non-Fourier hyperbolic predictions very well. The superposition of waves occurring inside the meat sample due to the hyperbolic nature of heat conduction is also proved experimentally. 14 refs., 7 figs., 2 tabs.

  3. Chemicals and cancer in humans: first evidence in experimental animals.

    PubMed Central

    Huff, J

    1993-01-01

    Certain human diseases have been traced to exposure to environmental and occupational chemicals. In many instances the first evidence of potential adverse effects came from experimental studies and were subsequently discovered in humans. Associations of human cancers, as a diverse group of diseases, and chemicals have been made since the middle 1700s. Since then, nearly 100 chemicals, mixtures of chemicals, or exposure circumstances are now recognized as being or strongly implicated as being carcinogenic to humans. Of the less than 1000 agents evaluated adequately for carcinogenicity in laboratory animals, a varying spectrum of data from studies on humans are available for only about 20-25%. So far, more than 60 agents are linked unequivocally as causing cancer in humans, and another 50 or so are strongly suspected of being carcinogenic to humans. Not all of these have been or can be evaluated in animals because some are industrial processes or "occupations," some are environmental and cultural risk factors, and some are mixtures of agents. For those that can be studied experimentally, the qualitative concordance between humans and animals approaches unity, and in every case there is at least one common organ site of cancer in both species. The evidence of carcinogenicity in experimental animals preceded that observed in humans for nearly 30 agents and is the subject of this paper. PMID:8354167

  4. Experimental evidence for herbivore limitation of the treeline.

    PubMed

    Speed, James D M; Austrheim, Gunnar; Hester, Alison J; Mysterud, Atle

    2010-11-01

    The treeline ecotone divides forest from open alpine or arctic vegetation states. Treelines are generally perceived to be temperature limited. The role of herbivores in limiting the treeline is more controversial, as experimental evidence from relevant large scales is lacking. Here we quantify the impact of different experimentally controlled herbivore densities on the recruitment and survival of birch Betula pubescens tortuosa along an altitudinal gradient in the mountains of southern Norway. After eight years of summer grazing in large-scale enclosures at densities of 0, 25, and 80 sheep/km2, birch recruited within the whole altitudinal range of ungrazed enclosures, but recruitment was rarer in enclosures with low-density sheep and was largely limited to within the treeline in enclosures with high-density sheep. In contrast, the distribution of saplings (birch older than the experiment) did not differ between grazing treatments, suggesting that grazing sheep primarily limit the establishment of new tree recruits rather than decrease the survival of existing individuals. This study provides direct experimental evidence that herbivores can limit the treeline below its potential at the landscape scale and even at low herbivore densities in this climatic zone. Land use changes should thus be considered in addition to climatic changes as potential drivers of ecotone shifts. PMID:21141202

  5. Sleep Duration and Cardiovascular Disease Risk: Epidemiologic and Experimental Evidence.

    PubMed

    Covassin, Naima; Singh, Prachi

    2016-03-01

    Inadequate sleep is increasingly pervasive, and the impact on health remains to be fully understood. The cardiovascular consequences alone appear to be substantial. This review summarizes epidemiologic evidence regarding the association between extremes of sleep duration and the prevalence and incidence of cardiovascular diseases. The adverse effects of experimental sleep loss on physiological functions are discussed, along with cardiovascular risk factors that may underlie the association with increased morbidity and mortality. Current data support the concept that inadequate sleep duration confers heightened cardiovascular risk. Thus implementation of preventative strategies may reduce the potential disease burden associated with this high-risk behavior. PMID:26972035

  6. Dichlorvos carcinogenicity: an assessment of the weight of experimental evidence.

    PubMed

    Mennear, J H

    1994-12-01

    After 30 years of experience with human exposure to dichlorvos (DDVP) in the home, workplace, and sickroom, the U.S. EPA has published its intent to revoke the food additive registration of this cholinesterase-inhibiting insecticide. The basis for the Agency action is the result of the National Toxicology Program (NTP) toxicology and carcinogenesis study of DDVP in rats and mice (NTP Technical Report No. 342, September 1989). In those experiments the NTP considered the result in the female mouse portion of the study to afford unequivocal evidence of carcinogenicity. The NTP considered the interpretations of the male and female rat and the male mouse studies to be less than clear. Despite the NTP interpretation, the EPA considers the male rat data (increased incidence of mononuclear cell leukemia) to be sufficient to warrant the regulatory change. The purpose of this report is to summarize a review of the interpretation of the NTP data and to assess the predictive validity of the results relative to potential human health impact. Critical review of experimental data indicates that the evidence for a carcinogenic effect of DDVP in animals is equivocal. Further, DDVP possess no in vivo mutagenic activity in mammalian assay systems and it bears no significant structural similarity to known carcinogens. Therefore, a weight-of-the-evidence analysis leads to the conclusion that DDVP poses neither mutagenic nor carcinogenic risks to humans exposed under normal conditions of use of foreseeable conditions of misuse. PMID:7724838

  7. Experimental evidence for compositional syntax in bird calls

    PubMed Central

    Suzuki, Toshitaka N.; Wheatcroft, David; Griesser, Michael

    2016-01-01

    Human language can express limitless meanings from a finite set of words based on combinatorial rules (i.e., compositional syntax). Although animal vocalizations may be comprised of different basic elements (notes), it remains unknown whether compositional syntax has also evolved in animals. Here we report the first experimental evidence for compositional syntax in a wild animal species, the Japanese great tit (Parus minor). Tits have over ten different notes in their vocal repertoire and use them either solely or in combination with other notes. Experiments reveal that receivers extract different meanings from ‘ABC' (scan for danger) and ‘D' notes (approach the caller), and a compound meaning from ‘ABC–D' combinations. However, receivers rarely scan and approach when note ordering is artificially reversed (‘D–ABC'). Thus, compositional syntax is not unique to human language but may have evolved independently in animals as one of the basic mechanisms of information transmission. PMID:26954097

  8. Experimental evidence for compositional syntax in bird calls.

    PubMed

    Suzuki, Toshitaka N; Wheatcroft, David; Griesser, Michael

    2016-01-01

    Human language can express limitless meanings from a finite set of words based on combinatorial rules (i.e., compositional syntax). Although animal vocalizations may be comprised of different basic elements (notes), it remains unknown whether compositional syntax has also evolved in animals. Here we report the first experimental evidence for compositional syntax in a wild animal species, the Japanese great tit (Parus minor). Tits have over ten different notes in their vocal repertoire and use them either solely or in combination with other notes. Experiments reveal that receivers extract different meanings from 'ABC' (scan for danger) and 'D' notes (approach the caller), and a compound meaning from 'ABC-D' combinations. However, receivers rarely scan and approach when note ordering is artificially reversed ('D-ABC'). Thus, compositional syntax is not unique to human language but may have evolved independently in animals as one of the basic mechanisms of information transmission. PMID:26954097

  9. Experimental evidence of pollination in marine flowers by invertebrate fauna

    PubMed Central

    van Tussenbroek, Brigitta I.; Villamil, Nora; Márquez-Guzmán, Judith; Wong, Ricardo; Monroy-Velázquez, L. Verónica; Solis-Weiss, Vivianne

    2016-01-01

    Pollen transport by water-flow (hydrophily) is a typical, and almost exclusive, adaptation of plants to life in the marine environment. It is thought that, unlike terrestrial environments, animals are not involved in pollination in the sea. The male flowers of the tropical marine angiosperm Thalassia testudinum open-up and release pollen in mucilage at night when invertebrate fauna is active. Here we present experimental evidence that, in the absence of water-flow, these invertebrates visit the flowers, carry and transfer mucilage mass with embedded pollen from the male flowers to the stigmas of the female flowers. Pollen tubes are formed on the stigmas, indicating that pollination is successful. Thus, T. testudinum has mixed abiotic–biotic pollination. We propose a zoobenthophilous pollination syndrome (pollen transfer in the benthic zone by invertebrate animals) which shares many characteristics with hydrophily, but flowers are expected to open-up during the night. PMID:27680661

  10. Experimental evidence of competitive release in sympatric carnivores.

    PubMed

    Trewby, Iain D; Wilson, Gavin J; Delahay, Richard J; Walker, Neil; Young, Richard; Davison, John; Cheeseman, Chris; Robertson, Pete A; Gorman, Martyn L; McDonald, Robbie A

    2008-04-23

    Changes in the relative abundance of sympatric carnivores can have far-reaching ecological consequences, including the precipitation of trophic cascades and species declines. While such observations are compelling, experimental evaluations of interactions among carnivores remain scarce and are both logistically and ethically challenging. Carnivores are nonetheless a particular focus of management practices owing to their roles as predators of livestock and as vectors and reservoirs of zoonotic diseases. Here, we provide evidence from a replicated and controlled experiment that culling Eurasian badgers Meles meles for disease control was associated with increases in red fox Vulpes vulpes densities of 1.6-2.3 foxes km-2. This unique experiment demonstrates the importance of intraguild relations in determining species abundance and of assessing the wider consequences of intervention in predator populations. PMID:18089523

  11. Experimental evidence for action imitation in killer whales (Orcinus orca).

    PubMed

    Abramson, José Z; Hernández-Lloreda, Victoria; Call, Josep; Colmenares, Fernando

    2013-01-01

    Comparative experimental studies of imitative learning have focused mainly on primates and birds. However, cetaceans are promising candidates to display imitative learning as they have evolved in socioecological settings that have selected for large brains, complex sociality, and coordinated predatory tactics. Here we tested imitative learning in killer whales, Orcinus orca. We used a 'do-as-other-does' paradigm in which 3 subjects witnessed a conspecific demonstrator's performance that included 15 familiar and 4 novel behaviours. The three subjects (1) learned the copy command signal 'Do that' very quickly, that is, 20 trials on average; (2) copied 100 % of the demonstrator's familiar and novel actions; (3) achieved full matches in the first attempt for 8-13 familiar behaviours (out of 15) and for the 2 novel behaviours (out of 2) in one subject; and (4) took no longer than 8 trials to accurately copy any familiar behaviour, and no longer than 16 trials to copy any novel behaviour. This study provides experimental evidence for body imitation, including production imitation, in killer whales that is comparable to that observed in dolphins tested under similar conditions. These findings suggest that imitative learning may underpin some of the group-specific traditions reported in killer whales in the field.

  12. Female Rose Bitterling Prefer MHC-Dissimilar Males: Experimental Evidence

    PubMed Central

    Reichard, Martin; Spence, Rowena; Bryjová, Anna; Bryja, Josef; Smith, Carl

    2012-01-01

    The role of genetic benefits in female mate choice remains a controversial aspect of sexual selection theory. In contrast to “good allele” models of sexual selection, “compatible allele” models of mate choice predict that females prefer mates with alleles complementary to their own rather than conferring additive effects. While correlative results suggest complementary genetic effects to be plausible, direct experimental evidence is scarce. A previous study on the Chinese rose bitterling (Rhodeus ocellatus) demonstrated a positive correlation between female mate choice, offspring growth and survival, and the functional dissimilarity between the Major Histocompatibility Complex (MHC) alleles of males and females. Here we directly tested whether females used cues associated with MHC genes to select genetically compatible males in an experimental framework. By sequentially pairing females with MHC similar and dissimilar males, based on a priori known MHC profiles, we showed that females discriminated between similar and dissimilar males and deposited significantly more eggs with MHC dissimilar males. Notably, the degree of dissimilarity was an important factor for female decision to mate, possibly indicating a potential threshold value of dissimilarity for decision making, or of an indirect effect of the MHC. PMID:22815816

  13. Experimental evidence of hepatitis A virus infection in pigs.

    PubMed

    Song, Young-Jo; Park, Woo-Jung; Park, Byung-Joo; Kwak, Sang-Woo; Kim, Yong-Hyeon; Lee, Joong-Bok; Park, Seung-Yong; Song, Chang-Seon; Lee, Sang-Won; Seo, Kun-Ho; Kang, Young-Sun; Park, Choi-Kyu; Song, Jae-Young; Choi, In-Soo

    2016-04-01

    Hepatitis A virus (HAV) is the leading cause of acute viral hepatitis worldwide, with HAV infection being restricted to humans and nonhuman primates. In this study, HAV infection status was serologically determined in domestic pigs and experimental infections of HAV were attempted to verify HAV infectivity in pigs. Antibodies specific to HAV or HAV-like agents were detected in 3.5% of serum samples collected from pigs in swine farms. When the pigs were infected intravenously with 2 × 10(5) 50% tissue culture infectious dose (TCID50 ) of HAV, shedding of the virus in feces, viremia, and seroconversion were detected. In pigs orally infected with the same quantity of HAV, viral shedding was detected only in feces. HAV genomic RNA was detected in the liver and bile of intravenously infected pigs, but only in the bile of orally infected pigs. In further experiments, pigs were intravenously infected with 6 × 10(5) TCID50 of HAV. Shedding of HAV in feces, along with viremia and seroconversion, were confirmed in infected pigs but not in sentinel pigs. HAV genomic RNA was detected in the liver, bile, spleen, lymph node, and kidney of the infected pigs. HAV antigenomic RNA was detected in the spleen of one HAV-infected pig, suggesting HAV replication in splenic cells. Infiltration of inflammatory cells was observed in the livers of infected pigs but not in controls. This is the first experimental evidence to demonstrate that human HAV strains can infect pigs.

  14. Experimental evidence that sperm maturation drives protandry in an ectotherm.

    PubMed

    Breedveld, Merel C; Fitze, Patrick S

    2016-09-01

    Protandry, i.e., the earlier arrival to breeding areas of males than females, has attracted a lot of scientific attention. However, evidence for the evolutionary hypotheses of protandry is surprisingly scarce. Here, we experimentally manipulate the time of emergence from hibernation of males, relative to females, in the common lizard, Zootoca vivipara. We test whether the timing of emergence affects sperm maturation and mating success, to disentangle among proposed selective advantages of protandry. Our results experimentally demonstrate that the timing of emergence affects the date of sperm presence. Moreover, the degree of protandry affected whether males had sperm upon their first encounter with females, but it did not affect the probability of copulating. Mating occurred independent of male fertility and mating during infertility was least common in early emerging males. Early emergence from hibernation by males, relative to females, thus increases the male's chance of fertilising eggs and later emergence from hibernation by females reduces the female's probability of mating with infertile males. These results point to direct reproductive benefits of protandry in males and females, where earlier emergence is predicted to increase the male's opportunities to inseminate mates, and later emergence reduces the female's probability of copulating with infertile males. This suggests that protandry evolved due to the time required for sperm maturation after emergence from hibernation. PMID:27259749

  15. The mechanics of intermediate and deep focus earthquakes: experimental evidences

    NASA Astrophysics Data System (ADS)

    Schubnel, A.; Hilairet, N.; Ferrand, T. P.; Incel, S.; Labrousse, L.; Renner, J.; Gasc, J.; Wang, Y.; Green, H. W., II

    2015-12-01

    At least part of the subducting slab seismic activity could be triggered by phase transformations and mineral reactions. However, the way mineral reactions can modify the deformation regime of deep rocks, from ductile to brittle (embrittlement) is still poorly understood and remains one of the outstanding unsolved problems of geophysics and rock mechanics. Here, we provide experimental evidence that, under differential stress at high pressure and temperature conditions (3-5GPa/800-1000°C), shear fractures nucleate and propagate at the onset of the olivine -> spinel transition in the Mg2GeO4 analogue system. The propagation of these fractures is sufficiently rapid to radiate energy in the form of intense acoustic emissions (AEs). Using a similar set-up, a second set of experiments demonstrates that glaucophane and lawsonite mixtures, two of the principal mineral water carriers in the subducted oceanic crust, undergo dynamic fracture instabilities when deformed within the eclogite field (3GPa/400-800°C). This time, AEs are observed due respectively to the glaucophane breakdown into jadeite and talc under low temperature and lawsonite dehydration under higher temperature. Finally, deformation experiments performed on partially serpentinized peridotites at 2-4GPa, 500-700°C, demonstrate that 5% serpentine in sufficient to trigger dehydration embrittlement of the peridotite body. In this case, low serpentine contents may favor initiation of mechanical failure of the olivine "load bearing" network. In all these three cases, various post-mortem microstructural observations techniques (SEM, TEM, Raman, Microprobe, X-ray tomography) reveals that samples deformed under stress almost systematically present high presure (HP) faulting, to the contrary of samples transformed under isostatic conditions. In addition, AEs correspond to acoustic waves radiated by dynamic HP transformational faulting and follow the Gutenberg-Richter law over sometimes more than 4 orders of moment

  16. Origin of Aphyric Phonolitic Magmas: Natural Evidences and Experimental Constraints

    NASA Astrophysics Data System (ADS)

    Masotta, M.; Freda, C.; Gaeta, M.

    2010-12-01

    Large explosive phonolitic eruptions are commonly characterised by aphyric juvenile eruptive products. Taking into account the low density contrast among phonolitic composition and settling phases (i.e., feldspar and leucite), the almost complete lack of crystals in these differentiated compositions rises the question of which process could produce such an efficient crystal-melt separation. Seeking for an answer, we have investigated crystallization in presence of a thermal gradient as a possible mechanism for crystal-melt separation, considering both chemical and physical effects acting on a variably crystallized system. Using a natural tephri-phonolitic composition as starting material (M.te Aguzzo scoria cone, Sabatini Volcanic District, Central Italy), we have reproduced thermal gradient-driven crystallization in order to simulate the crystallization process in a thermally zoned magma chamber. Crystallization degree (paragenesis made of clinopyroxene±feldspars±leucite) as well as melt composition varies along the thermal gradient. In particular, melt composition ranges from the tephri-phonolitic starting composition at the bottom of the charge (hottest and aphyric zone) to phonolitic at the top (cooler and heterogeneously-crystallised zone). Backscattered images of experimental products clearly evidence: i) the aphyric tephri-phonolitic melt region at the bottom of the charge; ii) a drop-shaped crystal clustering in the middle zone; and iii) large aphyric belt and pockets (up to 100 µm wide) of phonolitic melt, with large deformed-shaped sanidine occurring at their margin, at the charge top region. The latter two features, resulting from solid-melt displacements, suggest that the segregation of phonolitic melt can be related to crystal sinking and compaction. On the other hand, the compositional variability of the melt along the thermal gradient is directly related to the crystallization degree, indicating that chemical diffusion and thermal migration have

  17. Semantics guide infants' vowel learning: Computational and experimental evidence.

    PubMed

    Ter Schure, S M M; Junge, C M M; Boersma, P P G

    2016-05-01

    In their first year, infants' perceptual abilities zoom in on only those speech sound contrasts that are relevant for their language. Infants' lexicons do not yet contain sufficient minimal pairs to explain this phonetic categorization process. Therefore, researchers suggested a bottom-up learning mechanism: infants create categories aligned with the frequency distributions of sounds in their input. Recent evidence shows that this bottom-up mechanism may be complemented by the semantic context in which speech sounds occur, such as simultaneously present objects. To test this hypothesis, we investigated whether discrimination of a non-native vowel contrast improves when sounds from the contrast were paired consistently or randomly with two distinct visually presented objects, while the distribution of speech tokens suggested a single broad category. This was assessed in two ways: computationally, namely in a neural network simulation, and experimentally, namely in a group of 8-month-old infants. The neural network, trained with a large set of sound-meaning pairs, revealed that two categories emerge only if sounds are consistently paired with objects. A group of 49 real 8-month-old infants did not immediately show sensitivity to the pairing condition; a later test at 18 months with some of the same infants, however, showed that this sensitivity at 8 months interacted with their vocabulary size at 18 months. This interaction can be explained by the idea that infants with larger future vocabularies are more positively influenced by consistent training (and/or more negatively influenced by inconsistent training) than infants with smaller future vocabularies. This suggests that consistent pairing with distinct visual objects can help infants to discriminate speech sounds even when the auditory information does not signal a distinction. Together our results give computational as well as experimental support for the idea that semantic context plays a role in disambiguating

  18. Insulin Resistance and Environmental Pollutants: Experimental Evidence and Future Perspectives

    PubMed Central

    Vanparys, Caroline; Van Gaal, Luc F.; Jorens, Philippe G.; Covaci, Adrian; Blust, Ronny

    2013-01-01

    Background: The metabolic disruptor hypothesis postulates that environmental pollutants may be risk factors for metabolic diseases. Because insulin resistance is involved in most metabolic diseases and current health care prevention programs predominantly target insulin resistance or risk factors thereof, a critical analysis of the role of pollutants in insulin resistance might be important for future management of metabolic diseases. Objectives: We aimed to critically review the available information linking pollutant exposure to insulin resistance and to open the discussion on future perspectives for metabolic disruptor identification and prioritization strategies. Methods: We searched PubMed and Web of Science for experimental studies reporting on linkages between environmental pollutants and insulin resistance and identified a total of 23 studies as the prime literature. Discussion: Recent studies specifically designed to investigate the effect of pollutants on insulin sensitivity show a potential causation of insulin resistance. Based on these studies, a summary of viable test systems and end points can be composed, allowing insight into what is missing and what is needed to create a standardized insulin resistance toxicity testing strategy. Conclusions: It is clear that current research predominantly relies on top-down identification of insulin resistance–inducing metabolic disruptors and that the development of dedicated in vitro or ex vivo screens to allow animal sparing and time- and cost-effective bottom-up screening is a major future research need. Citation: Hectors TL, Vanparys C, Van Gaal LF, Jorens PG, Covaci A, Blust R. 2013. Insulin resistance and environmental pollutants: experimental evidence and future perspectives. Environ Health Perspect 121:1273–1281; http://dx.doi.org/10.1289/ehp.1307082 PMID:24058052

  19. Decompression to altitude: assumptions, experimental evidence, and future directions.

    PubMed

    Foster, Philip P; Butler, Bruce D

    2009-02-01

    Although differences exist, hypobaric and hyperbaric exposures share common physiological, biochemical, and clinical features, and their comparison may provide further insight into the mechanisms of decompression stress. Although altitude decompression illness (DCI) has been experienced by high-altitude Air Force pilots and is common in ground-based experiments simulating decompression profiles of extravehicular activities (EVAs) or astronauts' space walks, no case has been reported during actual EVAs in the non-weight-bearing microgravity environment of orbital space missions. We are uncertain whether gravity influences decompression outcomes via nitrogen tissue washout or via alterations related to skeletal muscle activity. However, robust experimental evidence demonstrated the role of skeletal muscle exercise, activities, and/or movement in bubble formation and DCI occurrence. Dualism of effects of exercise, positive or negative, on bubble formation and DCI is a striking feature in hypobaric exposure. Therefore, the discussion and the structure of this review are centered on those highlighted unresolved topics about the relationship between muscle activity, decompression, and microgravity. This article also provides, in the context of altitude decompression, an overview of the role of denitrogenation, metabolic gases, gas micronuclei, stabilization of bubbles, biochemical pathways activated by bubbles, nitric oxide, oxygen, anthropometric or physiological variables, Doppler-detectable bubbles, and potential arterialization of bubbles. These findings and uncertainties will produce further physiological challenges to solve in order to line up for the programmed human return to the Moon, the preparation for human exploration of Mars, and the EVAs implementation in a non-zero gravity environment.

  20. Experimental evidence that wildflower strips increase pollinator visits to crops

    PubMed Central

    Feltham, Hannah; Park, Kirsty; Minderman, Jeroen; Goulson, Dave

    2015-01-01

    Wild bees provide a free and potentially diverse ecosystem service to farmers growing pollination-dependent crops. While many crops benefit from insect pollination, soft fruit crops, including strawberries are highly dependent on this ecosystem service to produce viable fruit. However, as a result of intensive farming practices and declining pollinator populations, farmers are increasingly turning to commercially reared bees to ensure that crops are adequately pollinated throughout the season. Wildflower strips are a commonly used measure aimed at the conservation of wild pollinators. It has been suggested that commercial crops may also benefit from the presence of noncrop flowers; however, the efficacy and economic benefits of sowing flower strips for crops remain relatively unstudied. In a study system that utilizes both wild and commercial pollinators, we test whether wildflower strips increase the number of visits to adjacent commercial strawberry crops by pollinating insects. We quantified this by experimentally sowing wildflower strips approximately 20 meters away from the crop and recording the number of pollinator visits to crops with, and without, flower strips. Between June and August 2013, we walked 292 crop transects at six farms in Scotland, recording a total of 2826 pollinators. On average, the frequency of pollinator visits was 25% higher for crops with adjacent flower strips compared to those without, with a combination of wild and commercial bumblebees (Bombus spp.) accounting for 67% of all pollinators observed. This effect was independent of other confounding effects, such as the number of flowers on the crop, date, and temperature. Synthesis and applications. This study provides evidence that soft fruit farmers can increase the number of pollinators that visit their crops by sowing inexpensive flower seed mixes nearby. By investing in this management option, farmers have the potential to increase and sustain pollinator populations over time

  1. Self-Organization of Blood Pressure Regulation: Experimental Evidence

    PubMed Central

    Fortrat, Jacques-Olivier; Levrard, Thibaud; Courcinous, Sandrine; Victor, Jacques

    2016-01-01

    Blood pressure regulation is a prime example of homeostatic regulation. However, some characteristics of the cardiovascular system better match a non-linear self-organized system than a homeostatic one. To determine whether blood pressure regulation is self-organized, we repeated the seminal demonstration of self-organized control of movement, but applied it to the cardiovascular system. We looked for two distinctive features peculiar to self-organization: non-equilibrium phase transitions and hysteresis in their occurrence when the system is challenged. We challenged the cardiovascular system by means of slow, 20-min Tilt-Up and Tilt-Down tilt table tests in random order. We continuously determined the phase between oscillations at the breathing frequency of Total Peripheral Resistances and Heart Rate Variability by means of cross-spectral analysis. We looked for a significant phase drift during these procedures, which signed a non-equilibrium phase transition. We determined at which head-up tilt angle it occurred. We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis. We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05). Our study shows experimental evidence of self-organized short-term blood pressure regulation. It provides new insights into blood pressure regulation and its related disorders. PMID:27065880

  2. Experimental evidence that wildflower strips increase pollinator visits to crops.

    PubMed

    Feltham, Hannah; Park, Kirsty; Minderman, Jeroen; Goulson, Dave

    2015-08-01

    Wild bees provide a free and potentially diverse ecosystem service to farmers growing pollination-dependent crops. While many crops benefit from insect pollination, soft fruit crops, including strawberries are highly dependent on this ecosystem service to produce viable fruit. However, as a result of intensive farming practices and declining pollinator populations, farmers are increasingly turning to commercially reared bees to ensure that crops are adequately pollinated throughout the season. Wildflower strips are a commonly used measure aimed at the conservation of wild pollinators. It has been suggested that commercial crops may also benefit from the presence of noncrop flowers; however, the efficacy and economic benefits of sowing flower strips for crops remain relatively unstudied. In a study system that utilizes both wild and commercial pollinators, we test whether wildflower strips increase the number of visits to adjacent commercial strawberry crops by pollinating insects. We quantified this by experimentally sowing wildflower strips approximately 20 meters away from the crop and recording the number of pollinator visits to crops with, and without, flower strips. Between June and August 2013, we walked 292 crop transects at six farms in Scotland, recording a total of 2826 pollinators. On average, the frequency of pollinator visits was 25% higher for crops with adjacent flower strips compared to those without, with a combination of wild and commercial bumblebees (Bombus spp.) accounting for 67% of all pollinators observed. This effect was independent of other confounding effects, such as the number of flowers on the crop, date, and temperature. Synthesis and applications. This study provides evidence that soft fruit farmers can increase the number of pollinators that visit their crops by sowing inexpensive flower seed mixes nearby. By investing in this management option, farmers have the potential to increase and sustain pollinator populations over time

  3. Auger Recombination in Indium Gallium Nitride: Experimental Evidence

    NASA Astrophysics Data System (ADS)

    Krames, Michael

    2010-03-01

    Progress in InGaN-based light-emitting diode (LED) technology has resulted in white-light emitters with efficiencies far exceeding those of conventional light sources such as tungsten-filament-based incandescence and mercury-vapor based fluorescence. Indeed, by now efficacies exceeding 150 lumens per Watt for InGaN-based phosphor-converted white LEDs are claimed, which represent a 90% energy savings compared to the conventional incandescent (i.e., ``light bulb'') solution. However, these high performance levels are obtained under conditions of very low forward current-density for the InGaN LED and do not represent true operating conditions (nor cost-effective utilization) for the device. In order to reduce the cost (and thus increase market penetration of) solid-state lighting, more lumens per unit of semiconductor area are required which in practice necessitates higher drive current densities. Unfortunately, at these higher driver current densities, the internal quantum efficiency of InGaN-based LEDs is observed to decrease significantly. In the fall of 2007, researchers at the Advanced Laboratories of Philips Lumileds were the first to propose Auger recombination as the root-cause mechanism in InGaN which was behind this ``efficiency droop'' [1]. They further proposed to circumvent the problem by employing InGaN-based active region designs that maintain low carrier density, and demonstrated an LED device design that reaches a maximum quantum efficiency above 200 A/cm2, compared to ˜1-10 A/cm^2 for typical multiple-quantum-well heterostructures [2]. In this talk we will review the experimental evidence for Auger recombination in InGaN, beginning with the early work from 2007 and then considering additional work from more recent efforts to better understand the details behind this loss mechanism. [4pt] [1] Y. C. Shen, G. O. M"uller, S. Watanabe, N. F. Gardner, A. Munkholm, and M. R. Krames, ``Auger recombination in InGaN measured by photoluminescence'', Appl. Phys

  4. Plant-induced weathering of a basaltic rock: experimental evidence

    NASA Astrophysics Data System (ADS)

    Hinsinger, Philippe; Fernandes Barros, Omar Neto; Benedetti, Marc F.; Noack, Yves; Callot, Gabriel

    2001-01-01

    The active role of higher plants in the weathering of silicate minerals and rocks is still a question for debate. The present work aimed at providing experimental evidence of the important role of a range of crop plants in such processes. In order to quantitatively assess the possible effect of these diverse plant species on the weathering of a basaltic rock, two laboratory experiments were carried out at room temperature. These compared the amounts of elements released from basalt when leached with a dilute salt solution in the presence or absence of crop plants grown for up to 36 days. For Si, Ca, Mg, and Na, plants resulted in an increase in the release rate by a factor ranging from 1 to 5 in most cases. Ca and Na seemed to be preferentially released relative to other elements, suggesting that plagioclase dissolved faster than the other constituents of the studied basalt. Negligible amounts of Fe were released in the absence of plants as a consequence of the neutral pH and atmospheric pO 2 that were maintained in the leaching solution. However, the amounts of Fe released from basalt in the presence of plants were up to 100- to 500-fold larger than in the absence of plants, for banana and maize. The kinetics of dissolution of basalt in the absence of plants showed a constantly decreasing release rate over the whole duration of the experiment (36 days). No steady state value was reached both in the absence and presence of banana plants. However, in the latter case, the rates remained at a high initial level over a longer period of time (up to 15 days) before starting to decrease. For Fe, the maximum rate of release was reached beyond 4 days and this rate remained high up to 22 days of growth of banana. The possible mechanisms responsible for this enhanced release of elements from basalt in the presence of plants are discussed. Although these mechanisms need to be elucidated, the present results clearly show that higher plants can considerably affect the kinetics

  5. Bilateral oligopoly in pollution permit markets: experimental evidence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We experimentally investigate behavior in a bilateral oligopoly using a supply function equilibria model (Klemper and Meyer 1989; Hendricks and McAfee 2010; Malueg and Yates 2009). We focus on the role that market size and the degree of firm heterogeneity have on the market equilibrium. Our results ...

  6. Experimental evidence of antiphase population dynamics in lasers

    SciTech Connect

    Cabrera, Eduardo; Calderon, Oscar G.; Guerra, J.M.

    2005-10-15

    We report a direct experimental observation of antiphase oscillations in population dynamics in lasers. We show that these population oscillations are intrinsically related to the well-known antiphase polarization dynamics, i.e., the antiphase oscillations of two orthogonal polarization laser field states. We have used a class B Nd:YAG (yttrium aluminum garnet) laser.

  7. CB7-: Experimental and Theoretical Evidence Against Hypercoordinated Planar Carbon

    SciTech Connect

    Wang, Leiming; Huang, Wei; Averkiev, Boris B.; Boldyrev, Alexander I.; Wang, Lai S.

    2007-06-11

    The B82– cluster was previously shown to possess a planar molecular wheel structure with a heptacoordinated boron. Substitution of one B– by C in B82– is expected to yield a closed shell CB7– molecular wheel, which has been produced experimentally in a cluster beam and probed by photoelectron spectroscopy. Ab initio calculations show that the CB7– cluster possesses an extremely stable planar C2v structure, in which the C atom substitutes a B– atom at the edge of the B82– molecular wheel, whereas the D7h structure with a heptacoordinated C is a high-lying isomer 63.2 kcal/mol (CCSD(T)/6-311+G(2df)//CCSD(T)/6-311+G*) above the global minimum. The combined experimental and ab initio study demonstrates that a heptacoordinated planar carbon in CB7– is extremely unfavorable and is not a viable candidate for experimental realization of hypercoordinated planar carbon molecules.

  8. Experimental Evidence for Phonemic Contrasts in a Nonhuman Vocal System.

    PubMed

    Engesser, Sabrina; Crane, Jodie M S; Savage, James L; Russell, Andrew F; Townsend, Simon W

    2015-06-01

    The ability to generate new meaning by rearranging combinations of meaningless sounds is a fundamental component of language. Although animal vocalizations often comprise combinations of meaningless acoustic elements, evidence that rearranging such combinations generates functionally distinct meaning is lacking. Here, we provide evidence for this basic ability in calls of the chestnut-crowned babbler (Pomatostomus ruficeps), a highly cooperative bird of the Australian arid zone. Using acoustic analyses, natural observations, and a series of controlled playback experiments, we demonstrate that this species uses the same acoustic elements (A and B) in different arrangements (AB or BAB) to create two functionally distinct vocalizations. Specifically, the addition or omission of a contextually meaningless acoustic element at a single position generates a phoneme-like contrast that is sufficient to distinguish the meaning between the two calls. Our results indicate that the capacity to rearrange meaningless sounds in order to create new signals occurs outside of humans. We suggest that phonemic contrasts represent a rudimentary form of phoneme structure and a potential early step towards the generative phonemic system of human language. PMID:26121619

  9. Experimental Evidence for Phonemic Contrasts in a Nonhuman Vocal System

    PubMed Central

    Savage, James L.; Russell, Andrew F.; Townsend, Simon W.

    2015-01-01

    The ability to generate new meaning by rearranging combinations of meaningless sounds is a fundamental component of language. Although animal vocalizations often comprise combinations of meaningless acoustic elements, evidence that rearranging such combinations generates functionally distinct meaning is lacking. Here, we provide evidence for this basic ability in calls of the chestnut-crowned babbler (Pomatostomus ruficeps), a highly cooperative bird of the Australian arid zone. Using acoustic analyses, natural observations, and a series of controlled playback experiments, we demonstrate that this species uses the same acoustic elements (A and B) in different arrangements (AB or BAB) to create two functionally distinct vocalizations. Specifically, the addition or omission of a contextually meaningless acoustic element at a single position generates a phoneme-like contrast that is sufficient to distinguish the meaning between the two calls. Our results indicate that the capacity to rearrange meaningless sounds in order to create new signals occurs outside of humans. We suggest that phonemic contrasts represent a rudimentary form of phoneme structure and a potential early step towards the generative phonemic system of human language. PMID:26121619

  10. The fungal colonisation of rock-art caves: experimental evidence

    NASA Astrophysics Data System (ADS)

    Jurado, Valme; Fernandez-Cortes, Angel; Cuezva, Soledad; Laiz, Leonila; Cañaveras, Juan Carlos; Sanchez-Moral, Sergio; Saiz-Jimenez, Cesareo

    2009-09-01

    The conservation of rock-art paintings in European caves is a matter of increasing interest. This derives from the bacterial colonisation of Altamira Cave, Spain and the recent fungal outbreak of Lascaux Cave, France—both included in the UNESCO World Heritage List. Here, we show direct evidence of a fungal colonisation of rock tablets in a testing system exposed in Altamira Cave. After 2 months, the tablets, previously sterilised, were heavily colonised by fungi and bacteria. Most fungi isolated were labelled as entomopathogens, while the bacteria were those regularly identified in the cave. Rock colonisation was probably promoted by the dissolved organic carbon supplied with the dripping and condensation waters and favoured by the displacement of aerosols towards the interior of the cave, which contributed to the dissemination of microorganisms. The role of arthropods in the dispersal of spores may also help in understanding fungal colonisation. This study evidences the fragility of rock-art caves and demonstrates that microorganisms can easily colonise bare rocks and materials introduced into the cavity.

  11. Strategic sophistication of individuals and teams. Experimental evidence

    PubMed Central

    Sutter, Matthias; Czermak, Simon; Feri, Francesco

    2013-01-01

    Many important decisions require strategic sophistication. We examine experimentally whether teams act more strategically than individuals. We let individuals and teams make choices in simple games, and also elicit first- and second-order beliefs. We find that teams play the Nash equilibrium strategy significantly more often, and their choices are more often a best response to stated first order beliefs. Distributional preferences make equilibrium play less likely. Using a mixture model, the estimated probability to play strategically is 62% for teams, but only 40% for individuals. A model of noisy introspection reveals that teams differ from individuals in higher order beliefs. PMID:24926100

  12. Experimental evidence of a chaotic region in a neural pacemaker

    NASA Astrophysics Data System (ADS)

    Gu, Hua-Guang; Jia, Bing; Chen, Guan-Rong

    2013-03-01

    In this Letter, we report the finding of period-adding scenarios with chaos in firing patterns, observed in biological experiments on a neural pacemaker, with fixed extra-cellular potassium concentration at different levels and taken extra-cellular calcium concentration as the bifurcation parameter. The experimental bifurcations in the two-dimensional parameter space demonstrate the existence of a chaotic region interwoven with the periodic region thereby forming a period-adding sequence with chaos. The behavior of the pacemaker in this region is qualitatively similar to that of the Hindmarsh-Rose neuron model in a well-known comb-shaped chaotic region in two-dimensional parameter spaces.

  13. Strategic sophistication of individuals and teams. Experimental evidence.

    PubMed

    Sutter, Matthias; Czermak, Simon; Feri, Francesco

    2013-11-01

    Many important decisions require strategic sophistication. We examine experimentally whether teams act more strategically than individuals. We let individuals and teams make choices in simple games, and also elicit first- and second-order beliefs. We find that teams play the Nash equilibrium strategy significantly more often, and their choices are more often a best response to stated first order beliefs. Distributional preferences make equilibrium play less likely. Using a mixture model, the estimated probability to play strategically is 62% for teams, but only 40% for individuals. A model of noisy introspection reveals that teams differ from individuals in higher order beliefs. PMID:24926100

  14. INSTITUTIONS AND BEHAVIOR: EXPERIMENTAL EVIDENCE ON THE EFFECTS OF DEMOCRACY

    PubMed Central

    Bó, Pedro Dal; Foster, Andrew; Putterman, Louis

    2013-01-01

    A novel experiment is used to show that the effect of a policy on the level of cooperation is greater when it is chosen democratically by the subjects than when it is exogenously imposed. In contrast to the previous literature, our experimental design allows us to control for selection effects (e.g. those who choose the policy may be affected differently by it). Our finding implies that democratic institutions may affect behavior directly in addition to having effects through the choice of policies. Our findings have implications for the generalizability of the results of randomized policy interventions. PMID:25076785

  15. Experimental evidence of warm electron populations in magnetron sputtering plasmas

    SciTech Connect

    Sahu, B. B. Han, Jeon G.; Kim, Hye R.; Ishikawa, K.; Hori, M.

    2015-01-21

    This work report on the results obtained using the Langmuir probe (LP) measurements in high-power dc magnetron sputtering discharges. Data show clear evidence of two electron components, such as warm and bulk electrons, in the sputtering plasma in a magnetic trap. We have also used optical emission spectroscopy diagnostic method along with LP to investigate the plasma production. Data show that there is a presence of low-frequency oscillations in the 2–3 MHz range, which are expected to be generated by high-frequency waves. Analysis also suggests that the warm electrons, in the plasmas, can be formed due to the collisionless Landau damping of the bulk electrons.

  16. Predicting the Unpredictable: 75 Years of Experimental Evidence

    NASA Astrophysics Data System (ADS)

    Radin, Dean I.

    2011-11-01

    From time immemorial, people have reported foreknowledge of future events. To determine whether such experiences are best understood via conventional explanations, or whether a retrocausal phenomenon might be involved in some instances, researchers have conducted hundreds of controlled laboratory experiments over the past 75 years. These studies fall into four general classes, and each class has generated repeatable evidence consistent with retrocausation. The statistical results for a class of forced-choice studies is associated with odds against chance of about 1024; for a class of free-response studies, odds about 1020; for psychophysiological-based studies, odds about 1017; and for implicit decision studies, odds about 1010. Effect sizes observed in the latter three classes are nearly identical, indicating replication of similar underlying effects. These effects are also in close agreement with the average effect size across 25,000 conventional social psychology experiments conducted over the last century, suggesting that retrocausal phenomena may not be especially unique, at least not in terms of the magnitude of effect. Bayesian analyses of the most recent classes of experiments confirm that the evidence is strongly in favor of a genuine effect, with Bayes Factors ranging from 13,669 to 1 for implicit decision experiments, to 2.9×1013 to 1 for psychophysiological designs. For the two most recent classes of studies examining retrocausal effects via unconscious physiological or behavioral measures, 85 of 101 studies (84%) reported by 25 different laboratories from the United States, Italy, Spain, Holland, Austria, Sweden, England, Scotland, Iran, Japan, and Australia, have produced results in the direction predicted by a retrocausal effect (odds against chance = 1.3×1012, via a sign test). Assessment of the methodologies used in these studies has not identified plausible conventional alternatives for the observed outcomes, suggesting the existence of a

  17. Multiple Openings and Competitiveness of Forward Markets: Experimental Evidence

    PubMed Central

    Ferreira, José Luis; Kujal, Praveen; Rassenti, Stephen

    2016-01-01

    We test the competition enhancing effect of selling forward in experimental Cournot duopoly and quadropoly with multiple forward markets. We find that two forward periods yields competitive outcomes and that the results are very close to the predicted theoretical results for quantity setting duopolies and quadropolies. Our experiments lend strong support to the hypothesis that forward markets are competition enhancing. We then test a new market that allows for endogenously determined indefinitely many forward periods that only close when sellers coordinate on selling a zero amount in a forward market. We find that the outcomes under an endogenous close rule are also very competitive. These results hold for both duopolies and quadropolies. PMID:27442516

  18. GEOMORPHOLOGY. Experimental evidence for hillslope control of landscape scale.

    PubMed

    Sweeney, K E; Roering, J J; Ellis, C

    2015-07-01

    Landscape evolution theory suggests that climate sets the scale of landscape dissection by modulating the competition between diffusive processes that sculpt convex hillslopes and advective processes that carve concave valleys. However, the link between the relative dominance of hillslope and valley transport processes and landscape scale is difficult to demonstrate in natural landscapes due to the episodic nature of erosion. Here, we report results from laboratory experiments combining diffusive and advective processes in an eroding landscape. We demonstrate that rainsplash-driven disturbances in our experiments are a robust proxy for hillslope transport, such that increasing hillslope transport efficiency decreases drainage density. Our experimental results demonstrate how the coupling of climate-driven hillslope- and valley-forming processes, such as bioturbation and runoff, dictates the scale of eroding landscapes.

  19. GEOMORPHOLOGY. Experimental evidence for hillslope control of landscape scale.

    PubMed

    Sweeney, K E; Roering, J J; Ellis, C

    2015-07-01

    Landscape evolution theory suggests that climate sets the scale of landscape dissection by modulating the competition between diffusive processes that sculpt convex hillslopes and advective processes that carve concave valleys. However, the link between the relative dominance of hillslope and valley transport processes and landscape scale is difficult to demonstrate in natural landscapes due to the episodic nature of erosion. Here, we report results from laboratory experiments combining diffusive and advective processes in an eroding landscape. We demonstrate that rainsplash-driven disturbances in our experiments are a robust proxy for hillslope transport, such that increasing hillslope transport efficiency decreases drainage density. Our experimental results demonstrate how the coupling of climate-driven hillslope- and valley-forming processes, such as bioturbation and runoff, dictates the scale of eroding landscapes. PMID:26138970

  20. NEW EXPERIMENTAL EVIDENCES ABOUT THE FORMATION AND CONSUMPTION OF KETOHYDROPEROXIDES

    PubMed Central

    Battin-Leclerc, Frédérique; Herbinet, Olivier; Glaude, Pierre-Alexandre; Fournet, René; Zhou, Zhongyue; Deng, Liulin; Guo, Huijun; Xie, Mingfeng; Qi, Fei

    2013-01-01

    The formation of hydroperoxides postulated in all the kinetic models for the low temperature oxidation of alkanes have been experimentally proved thanks to a new type of apparatus associating a quartz jet-stirred reactor through a molecular-beam sampling system to a reflectron time-of-flight mass spectrometer combined with tunable synchrotron vacuum ultraviolet photoionization. This apparatus has been used to investigate the low-temperature oxidation of n-butane and has allowed demonstrating the formation of different types of alkylhydroperoxides, namely methylhydroperoxide, ethylhydroperoxide and butylhydroperoxide, and of C4 alkylhydroperoxides including a carbonyl function (ketohydroperoxides). In addition, the formation of products deriving from these ketohydroperoxides, such as C4 molecules including either two carbonyl groups or one carbonyl and one alcohol functions, has been observed. Simulations using a detailed kinetic model have been performed to support some of the assumptions made in this work. PMID:23700382

  1. Experimental evidence for the thermophilicity of ancestral life

    PubMed Central

    Akanuma, Satoshi; Nakajima, Yoshiki; Yokobori, Shin-ichi; Kimura, Mitsuo; Nemoto, Naoki; Mase, Tomoko; Miyazono, Ken-ichi; Tanokura, Masaru; Yamagishi, Akihiko

    2013-01-01

    Theoretical studies have focused on the environmental temperature of the universal common ancestor of life with conflicting conclusions. Here we provide experimental support for the existence of a thermophilic universal common ancestor. We present the thermal stabilities and catalytic efficiencies of nucleoside diphosphate kinases (NDK), designed using the information contained in predictive phylogenetic trees, that seem to represent the last common ancestors of Archaea and of Bacteria. These enzymes display extreme thermal stabilities, suggesting thermophilic ancestries for Archaea and Bacteria. The results are robust to the uncertainties associated with the sequence predictions and to the tree topologies used to infer the ancestral sequences. Moreover, mutagenesis experiments suggest that the universal ancestor also possessed a very thermostable NDK. Because, as we show, the stability of an NDK is directly related to the environmental temperature of its host organism, our results indicate that the last common ancestor of extant life was a thermophile that flourished at a very high temperature. PMID:23776221

  2. Experimental evidence of bark beetle adaptation to a fungal symbiont.

    PubMed

    Bracewell, Ryan R; Six, Diana L

    2015-11-01

    The importance of symbiotic microbes to insects cannot be overstated; however, we have a poor understanding of the evolutionary processes that shape most insect-microbe interactions. Many bark beetle (Coleoptera: Curculionidae, Scolytinae) species are involved in what have been described as obligate mutualisms with symbiotic fungi. Beetles benefit through supplementing their nutrient-poor diet with fungi and the fungi benefit through gaining transportation to resources. However, only a few beetle-fungal symbioses have been experimentally manipulated to test whether the relationship is obligate. Furthermore, none have tested for adaptation of beetles to their specific symbionts, one of the requirements for coevolution. We experimentally manipulated the western pine beetle-fungus symbiosis to determine whether the beetle is obligately dependent upon fungi and to test for fine-scale adaptation of the beetle to one of its symbiotic fungi, Entomocorticium sp. B. We reared beetles from a single population with either a natal isolate of E. sp. B (isolated from the same population from which the beetles originated), a non-natal isolate (a genetically divergent isolate from a geographically distant beetle population), or with no fungi. We found that fungi were crucial for the successful development of western pine beetles. We also found no significant difference in the effects of the natal and non-natal isolate on beetle fitness parameters. However, brood adult beetles failed to incorporate the non-natal fungus into their fungal transport structure (mycangium) indicating adaption by the beetle to particular genotypes of symbiotic fungi. Our results suggest that beetle-fungus mutualisms and symbiont fidelity may be maintained via an undescribed recognition mechanism of the beetles for particular symbionts that may promote particular associations through time.

  3. Implicit negotiation beliefs and performance: experimental and longitudinal evidence.

    PubMed

    Kray, Laura J; Haselhuhn, Michael P

    2007-07-01

    The authors argue that implicit negotiation beliefs, which speak to the expected malleability of negotiating ability, affect performance in dyadic negotiations. They expected negotiators who believe negotiating attributes are malleable (incremental theorists) to outperform negotiators who believe negotiating attributes are fixed (entity theorists). In Study 1, they gathered evidence of convergent and discriminant validity for the implicit negotiation belief construct. In Study 2, they examined the impact of implicit beliefs on the achievement goals that negotiators pursue. In Study 3, they explored the causal role of implicit beliefs on negotiation performance by manipulating negotiators' implicit beliefs within dyads. They also identified perceived ability as a moderator of the link between implicit negotiation beliefs and performance. In Study 4, they measured negotiators' beliefs in a classroom setting and examined how these beliefs affected negotiation performance and overall performance in the course 15 weeks later. Across all performance measures, incremental theorists outperformed entity theorists. Consistent with the authors' hypotheses, incremental theorists captured more of the bargaining surplus and were more integrative than their entity theorist counterparts, suggesting implicit theories are important determinants of how negotiators perform. Implications and future directions are discussed.

  4. [Adolescent cannabis consumption and schizophrenia: epidemiological and experimental evidences].

    PubMed

    Parolaro, Daniela

    2010-01-01

    Marijuana is consistently the most widely used illicit drug among teenagers and most users first experiment it in adolescence. Adolescence is a critical period between childhood and adulthood, including not only reproductive maturation, but also cognitive, emotional and social maturation. In this period adolescent brain is still in transition differing anatomically and neurochemically from the adult's one. The endocannabinoid system is an important determinant for cerebral maturation, therefore its strong stimulation by the delta-9- tetrahydrocannabinol, that acts through the endocannabinoid system, might lead to subtle but lasting neurobiological changes that can affect adult brain functions and behaviour. We summarize the more recent researches investigating the relationships between adolescent exposure to cannabinoids and increased risk for psychotic disease such as schizophrenia, as highlighted by both human and animal studies. Epidemiological evidence suggests that cannabis use is a risk factor for schizophrenia, and an exacerbation of symptoms and worsening of the schizophrenic prognosis may occur in individuals with a predisposition for schizophrenia. The characteristic of adolescent brain probably makes it more vulnerable to cannabis effect producing psychotic like symptoms and possibly cause schizophrenia.

  5. Experimental evidence of a delta-shock in nonlinear chromatography

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2010-01-01

    We report about a new type of composition front in nonlinear chromatography that is called delta-shock, which has to be added to the family of classical transitions, i.e. simple waves, shocks and semi-shocks. Recently, the occurrence of delta-shocks in the case of mixed competitive-cooperative isotherms of the following type n{sub i} = H{sub i}c{sub i}/1 = K{sub 1}c{sub 1} + K{sub 2}c{sub 2} (i = 1,2), (with H{sub 2} > H{sub 1}, where components 1 and 2 have anti-Langmuir and Langmuir adsorption behavior, respectively) was predicted theoretically and their behavior was analyzed in the frame of the equilibrium theory of chromatography. The delta-shock can be viewed as a growing traveling spike superimposed to the discontinuity separating the initial and the feed state, which propagates along the column at constant speed and constant rate of growth. In this work we complement these findings from an experimental point of view. The binary system consisting of phenetole (component 1) and 4-tert-butylphenol (component 2) in methanol-water (about 2:1, v/v) on a Zorbax 300StableBond-C18 column from Agilent has been shown, through a series of overloaded pulse experiments and of frontal analysis experiments with the pure compounds, to be subject to the competitive-cooperative isotherm of the type above, up to rather large concentrations. This system does exhibit adelta-shock when the operating conditions are chosen according to theory, namely when phenetole initially saturating the column is displaced by 4-tert-butylphenol, both at high concentrations (the minimum concentrations exhibiting a fully developed delta-shock in this series of experiments were c{sub 1} = 20 g/L and c{sub 2} = 75 g/L). The propagation of the delta-shock matches the theoretical predictions in terms of both the effect of concentration and the effect of column length. This is the first experimental observation ever of adelta-shock in chromatography. It is noteworthy that the proof of the occurrence of

  6. [Is it possible a bioethics based on the experimental evidence?].

    PubMed

    Pastor, Luis Miguel

    2013-01-01

    For years there are different types of criticism about principialist bioethics. One alternative that has been proposed is to introduce empirical evidence within the bioethical discourse to make it less formal, less theoretical and closer to reality. In this paper we analyze first in synthetic form diverse alternative proposals to make an empirical bioethics. Some of them are strongly naturalistic while others aim to provide empirical data only for correct or improve bioethical work. Most of them are not shown in favor of maintaining a complete separation between facts and values, between what is and what ought to be. With different nuances these proposals of moderate naturalism make ethical judgments depend normative social opinion resulting into a certain social naturalism. Against these proposals we think to make a bioethics in that relates the empirical facts with ethical duties, we must rediscover empirical reality of human action. Only from it and, in particular, from the activity of discernment that makes practical reason, when judged on the object of his action, it is possible to integrate the mere descriptive facts with ethical judgments of character prescriptive. In conclusion we think that it is not possible to perform bioethics a mode of empirical science, as this would be contrary to natural reason, leading to a sort of scientific reductionism. At the same time we believe that empirical data are important in the development of bioethics and to enhance and improve the innate ability of human reason to discern good. From this discernment could develop a bioethics from the perspective of ethical agents themselves, avoiding the extremes of an excessive normative rationalism, accepting empirical data and not falling into a simple pragmatism.

  7. [Is it possible a bioethics based on the experimental evidence?].

    PubMed

    Pastor, Luis Miguel

    2013-01-01

    For years there are different types of criticism about principialist bioethics. One alternative that has been proposed is to introduce empirical evidence within the bioethical discourse to make it less formal, less theoretical and closer to reality. In this paper we analyze first in synthetic form diverse alternative proposals to make an empirical bioethics. Some of them are strongly naturalistic while others aim to provide empirical data only for correct or improve bioethical work. Most of them are not shown in favor of maintaining a complete separation between facts and values, between what is and what ought to be. With different nuances these proposals of moderate naturalism make ethical judgments depend normative social opinion resulting into a certain social naturalism. Against these proposals we think to make a bioethics in that relates the empirical facts with ethical duties, we must rediscover empirical reality of human action. Only from it and, in particular, from the activity of discernment that makes practical reason, when judged on the object of his action, it is possible to integrate the mere descriptive facts with ethical judgments of character prescriptive. In conclusion we think that it is not possible to perform bioethics a mode of empirical science, as this would be contrary to natural reason, leading to a sort of scientific reductionism. At the same time we believe that empirical data are important in the development of bioethics and to enhance and improve the innate ability of human reason to discern good. From this discernment could develop a bioethics from the perspective of ethical agents themselves, avoiding the extremes of an excessive normative rationalism, accepting empirical data and not falling into a simple pragmatism. PMID:24206254

  8. Feedback loop process for controlling inertial cavitation: experimental evidence

    NASA Astrophysics Data System (ADS)

    Inserra, Claude; Sabraoui, Abbas; Reslan, Lina; Bera, Jean-Christophe; Gilles, Bruno; Mestas, Jean-Louis

    2011-09-01

    Applications involving cavitation mechanisms, such as sonoporation, are irreproducible in the case of a fixed-intensity sonication, due to the non-stationary behavior of cavitation. We then propose to work at a fixed-cavitation level instead of under fixed-intensity sonication conditions. For this purpose a regulated cavitation generator has been developed in a stationary wave field configuration, which allows regulation of the cavitation level during sonication by modulating the applied acoustic intensity with a feedback loop based on acoustic cavitation measurements. The cavitation level indicator was quantified by the broadband spectrum noise level relative to inertial cavitation events. This generated inertial cavitation was characterized by both acoustic and chemical measurements, quantifying hydroxyl radicals produced by water sonolysis. While the cavitation level is obtained with a 40% standard deviation for fixed applied acoustic intensities in the range [0.01 3.44] W/cm2, the regulated generator reproduces the cavitation level with a standard deviation of 3%. The results show that the hydroxyl radical production is better correlated with the cavitation level setting than with the applied acoustic intensity, highlighting the fact that broadband noise is a good indicator of inertial cavitation, with greatest interest for cavitation monitoring. In summary, the regulated device generates a cavitation level that is reproducible, repeatable and stable in time. This system produces reproducible effects that allow consideration of biological applications such as sonoporation to be independent of the experimental ultrasound device, as confirmed by transfection efficiency and cell cytotoxicity studies. Thus, this feedback loop process presents interesting perspectives for monitoring and controlling in-vivo cavitation.

  9. Experimental evidence for filter-feeding by the hydrothermal vent mussel, Bathymodiolus thermophilus

    NASA Astrophysics Data System (ADS)

    Page, H. M.; Fiala-Medioni, A.; Fisher, C. R.; Childress, J. J.

    1991-12-01

    We provide experimental evidence, using a high-pressure recirculating aquarium and radiolabeled bacteria, that the hydrothermal vent mussel. Bathymodiolus thermophilus, can clear and assimilate particulate organic matter. Our results support previous evidence that this mussel can filter-feed on particulate organic matter to supplement nutrients provided by endosymbiotic chemoautotrophic bacteria.

  10. Experimental Evidence for LENR in a Polarized Pd/D Lattice

    NASA Astrophysics Data System (ADS)

    Szpak, S.

    2005-03-01

    Experimental evidence in support of claims that excess enthalpy production in a polarized Pd/D lattice is of a nuclear origin is questioned on various grounds, eg marginal intensity and difficulty in reproducing. Here, evidence is presented that is 100% reproducible and of sufficient intensity to be well outside of experimental errors. In addition to the thermal behavior, the nuclear manifestations include: X-ray emission; tritium production; and, when an operating cell is placed in an external electric field, fusion to create heavier metals such as Ca, Al, Mg, and Zn.

  11. Experimental evidence of explosive synchronization in mercury beating-heart oscillators

    NASA Astrophysics Data System (ADS)

    Kumar, Pawan; Verma, Dinesh Kumar; Parmananda, P.; Boccaletti, S.

    2015-06-01

    We report experimental evidence of explosive synchronization in coupled chemo-mechanical systems, namely in mercury beating-heart (MBH) oscillators. Connecting four MBH oscillators in a star network configuration and setting natural frequencies of each oscillator in proportion to the number of its links, a gradual increase of the coupling strength results in an abrupt and irreversible (first-order-like) transition from the system's unordered to ordered phase. On its turn, such a transition indicates the emergence of a bistable regime wherein coexisting states can be experimentally revealed. Finally, we prove how such a regime allows an experimental implementation of magneticlike states of synchronization, by the use of an external signal.

  12. Electric field driven fractal growth in polymer electrolyte composites: Experimental evidence of theoretical simulations

    NASA Astrophysics Data System (ADS)

    Dawar, Anit; Chandra, Amita

    2012-11-01

    The influence of electric field on the diffusion limited aggregation has been observed experimentally. The observation provides experimental confirmation of the theoretical model proposed by Zhi-Jie Tan et al. [Phys. Lett. A 268 (2000) 112]. Most strikingly, a transition from a disordered ramified pattern to an ordered pattern (chain-like growth) has been observed. The growth is governed by diffusion, convection and migration in an electric field which give rise to the different patterns. This Letter can also be considered as an experimental evidence of computer simulated fractal growth given by Huang and Hibbert [Physica A 233 (1996) 888].

  13. Experimental evidence of the decrease of kinetic energy of hadrons in passing through atomic nuclei

    NASA Technical Reports Server (NTRS)

    Strugalski, Z.

    1985-01-01

    Hadrons with kinetic energies higher than the pion production threshold lose their kinetic energies monotonically in traversing atomic nuclei, due to the strong interactions in nuclear matter. This phenomenon is a crude analogy to the energy loss of charged particles in their passage through materials. Experimental evidence is presented.

  14. The Development of Experimentation and Evidence Evaluation Skills at Preschool Age

    ERIC Educational Resources Information Center

    Piekny, Jeanette; Grube, Dietmar; Maehler, Claudia

    2014-01-01

    Researchers taking a domain-general approach to the development of scientific reasoning long thought that the ability to engage in scientific reasoning did not develop until adolescence. However, more recent studies have shown that preschool children already have a basic ability to evaluate evidence and a basic understanding of experimentation.…

  15. Thermal compensation in GaPO4 beam resonators: experimental evidence for length extensional mode.

    PubMed

    Sthal, Fabrice; Bigler, Emmanuel; Bourquin, Roger

    2007-01-01

    Temperature effects in gallium orthophosphate (GaPO4) vibrating beams are reported. In addition to the well-known, thickness-shear AT-cut, temperature-compensated cuts exist in GaPO4 for length extensional modes. Experimental evidence of a temperature-compensated cut in GaPO4 rectangular beam resonator vibrating in length extension is given. PMID:17225814

  16. Experimental evidence of the superfocusing effect for axially channeled MeV protons

    NASA Astrophysics Data System (ADS)

    Motapothula, M.; Petrović, S.; Nešković, N.; Breese, M. B. H.

    2016-08-01

    Sub-Ångström focusing of megaelectronvolt (MeV) ions within axial channels was predicted over 10 years ago, but evidence proved elusive. We present experimental angular distributions of axially channeled MeV protons in a 55-nm-thick (001) silicon membrane through which multiple scattering is negligible. Fine angular structure is in excellent agreement with Monte Carlo simulations based on three interaction potentials, providing indirect evidence of the existence of the superfocusing effect with flux enhancement of around 800 within a focused beam width of ˜20 pm .

  17. Relevance of the glutathione system in temporal lobe epilepsy: evidence in human and experimental models.

    PubMed

    Cárdenas-Rodríguez, Noemí; Coballase-Urrutia, Elvia; Pérez-Cruz, Claudia; Montesinos-Correa, Hortencia; Rivera-Espinosa, Liliana; Sampieri, Aristides; Carmona-Aparicio, Liliana

    2014-01-01

    Oxidative stress, which is a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with diseases that are systemic as well as diseases that affect the central nervous system. Epilepsy is a chronic neurological disorder, and temporal lobe epilepsy represents an estimated 40% of all epilepsy cases. Currently, evidence from human and experimental models supports the involvement of oxidative stress during seizures and in the epileptogenesis process. Hence, the aim of this review was to provide information that facilitates the processing of this evidence and investigate the therapeutic impact of the biochemical status for this specific pathology.

  18. Role of Oxidative Stress in Refractory Epilepsy: Evidence in Patients and Experimental Models

    PubMed Central

    Cardenas-Rodriguez, Noemi; Huerta-Gertrudis, Bernardino; Rivera-Espinosa, Liliana; Montesinos-Correa, Hortencia; Bandala, Cindy; Carmona-Aparicio, Liliana; Coballase-Urrutia, Elvia

    2013-01-01

    Oxidative stress, a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with systemic diseases, and diseases affecting the central nervous system. Epilepsy is a chronic neurological disorder with refractoriness to drug therapy at about 30%. Currently, experimental evidence supports the involvement of oxidative stress in seizures, in the process of their generation, and in the mechanisms associated with refractoriness to drug therapy. Hence, the aim of this review is to present information in order to facilitate the handling of this evidence and determine the therapeutic impact of the biochemical status for this pathology. PMID:23344052

  19. Island of Rare Earth Nuclei with Tetrahedral and Octahedral Symmetries: Possible Experimental Evidence

    SciTech Connect

    Dudek, J.; Dubray, N.; Pangon, V.; Dobaczewski, J.; Olbratowski, P.; Schunck, N.

    2006-08-18

    Calculations using realistic mean-field methods suggest the existence of nuclear shapes with tetrahedral T{sub d} and/or octahedral O{sub h} symmetries sometimes at only a few hundreds of keV above the ground states in some rare earth nuclei around {sup 156}Gd and {sup 160}Yb. The underlying single-particle spectra manifest exotic fourfold rather than Kramers's twofold degeneracies. The associated shell gaps are very strong, leading to a new form of shape coexistence in many rare earth nuclei. We present possible experimental evidence of the new symmetries based on the published experimental results--although an unambiguous confirmation will require dedicated experiments.

  20. Experimental evidence of wave chaos from a double slit experiment with water surface waves.

    PubMed

    Tang, Yunfei; Shen, Yifeng; Yang, Jiong; Liu, Xiaohan; Zi, Jian; Li, Baowen

    2008-10-01

    In this paper, we report experimental evidence of wave chaos using the double slit water surface wave experiment. We demonstrate that classical dynamics of a domain manifests itself in the interference patterns after the diffraction behind the double slit. For a domain whose classical dynamics is integrable clear interference fringes can be observed behind the double slits; for a domain whose classical dynamics is chaotic, however, interference fringes can totally disappear. Our experimental results clearly demonstrate that the centuries-old double slit experiment can render an excellent tool to observe the manifestations of wave chaos.

  1. Experimental Evidence of the Origin of Nanophase Separation in Low Hole-Doped Colossal Magnetoresistant Manganites.

    PubMed

    Cortés-Gil, Raquel; Ruiz-González, M Luisa; González-Merchante, Daniel; Alonso, José M; Hernando, Antonio; Trasobares, Susana; Vallet-Regí, María; Rojo, Juan M; González-Calbet, José M

    2016-01-13

    While being key to understanding their intriguing physical properties, the origin of nanophase separation in manganites and other strongly correlated materials is still unclear. Here, experimental evidence is offered for the origin of the controverted phase separation mechanism in the representative La1-xCaxMnO3 system. For low hole densities, direct evidence of Mn(4+) holes localization around Ca(2+) ions is experimentally provided by means of aberration-corrected scanning transmission electron microscopy combined with electron energy loss spectroscopy. These localized holes give rise to the segregated nanoclusters, within which double exchange hopping between Mn(3+) and Mn(4+) remains restricted, accounting for the insulating character of perovskites with low hole density. This localization is explained in terms of a simple model in which Mn(4+) holes are bound to substitutional divalent Ca(2+) ions.

  2. Experimental evidence that potassium is a substantial radioactive heat source in planetary cores.

    PubMed

    Murthy, V Rama; van Westrenen, Wim; Fei, Yingwei

    2003-05-01

    The hypothesis that (40)K may be a significant radioactive heat source in the Earth's core was proposed on theoretical grounds over three decades ago, but experiments have provided only ambiguous and contradictory evidence for the solubility of potassium in iron-rich alloys. The existence of such radioactive heat in the core would have important implications for our understanding of the thermal evolution of the Earth and global processes such as the generation of the geomagnetic field, the core-mantle boundary heat flux and the time of formation of the inner core. Here we provide experimental evidence to show that the ambiguous results obtained from earlier experiments are probably due to previously unrecognized experimental and analytical difficulties. The high-pressure, high-temperature data presented here show conclusively that potassium enters iron sulphide melts in a strongly temperature-dependent fashion and that (40)K can serve as a substantial heat source in the cores of the Earth and Mars.

  3. The Development of Experimentation and Evidence Evaluation Skills at Preschool Age

    NASA Astrophysics Data System (ADS)

    Piekny, Jeanette; Grube, Dietmar; Maehler, Claudia

    2014-01-01

    Researchers taking a domain-general approach to the development of scientific reasoning long thought that the ability to engage in scientific reasoning did not develop until adolescence. However, more recent studies have shown that preschool children already have a basic ability to evaluate evidence and a basic understanding of experimentation. Data providing insights into when exactly in the preschool years significant gains in these abilities occur are scarce. Drawing on a sample of 138 preschool children, this longitudinal study therefore examined how children's ability to evaluate evidence and their understanding of experimentation develop between the ages of four and six. Findings showed that the ability to evaluate evidence was already well developed at age four and increased steadily and significantly over time as long as the pattern of covariation was perfect. In the case of imperfect covariation, the proportion of correct answers was low over the period of observation, but showed a significant increase between the ages of four and five. If the data did not allow relationship between variables to be inferred, the proportion of correct answers was low, with a significant increase between the ages of five and six. The children's understanding of experimentation increased significantly between the ages of five and six. The implications of these findings for age-appropriate science programs in preschool are discussed.

  4. Experimental evidence for inherent Lévy search behaviour in foraging animals

    PubMed Central

    Kölzsch, Andrea; Alzate, Adriana; Bartumeus, Frederic; de Jager, Monique; Weerman, Ellen J.; Hengeveld, Geerten M.; Naguib, Marc; Nolet, Bart A.; van de Koppel, Johan

    2015-01-01

    Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment. PMID:25904671

  5. Theoretical and experimental evidences of medium range atmospheric transport processes of polycyclic musk fragrances.

    PubMed

    Villa, Sara; Vighi, Marco; Finizio, Antonio

    2014-05-15

    This study investigates some aspects of the environmental fate of galaxolide (HHCB) and tonalide (AHTN) musk fragrances, paying particular attention to the phenomenon of atmospheric transport of these substances. The problem was addressed theoretically and experimentally. Firstly, the application of a multimedia model allowed the analysis of their potential atmospheric transport. The obtained results argued in favor of a possible phenomenon of medium range atmospheric transport for both substances. These theoretical findings were supported by the experimental results, which showed their presence both in the fresh fallen snow and in water samples taken from the Frodolfo, a glacial stream that originates from the Forni Glacier (Alps, Northern Italy). Furthermore, the analysis of the air back-trajectories highlighted the prevalence of air masses of local origins that reached the sampling area passing through a densely anthropized area of Northern Italy. Finally, the experimental results discussed here gave evidences of accumulation of these two compounds in the glacier.

  6. Experimental evidence for inherent Lévy search behaviour in foraging animals.

    PubMed

    Kölzsch, Andrea; Alzate, Adriana; Bartumeus, Frederic; de Jager, Monique; Weerman, Ellen J; Hengeveld, Geerten M; Naguib, Marc; Nolet, Bart A; van de Koppel, Johan

    2015-05-22

    Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment.

  7. Experimental evidence for inherent Lévy search behaviour in foraging animals.

    PubMed

    Kölzsch, Andrea; Alzate, Adriana; Bartumeus, Frederic; de Jager, Monique; Weerman, Ellen J; Hengeveld, Geerten M; Naguib, Marc; Nolet, Bart A; van de Koppel, Johan

    2015-05-22

    Recently, Lévy walks have been put forward as a new paradigm for animal search and many cases have been made for its presence in nature. However, it remains debated whether Lévy walks are an inherent behavioural strategy or emerge from the animal reacting to its habitat. Here, we demonstrate signatures of Lévy behaviour in the search movement of mud snails (Hydrobia ulvae) based on a novel, direct assessment of movement properties in an experimental set-up using different food distributions. Our experimental data uncovered clusters of small movement steps alternating with long moves independent of food encounter and landscape complexity. Moreover, size distributions of these clusters followed truncated power laws. These two findings are characteristic signatures of mechanisms underlying inherent Lévy-like movement. Thus, our study provides clear experimental evidence that such multi-scale movement is an inherent behaviour rather than resulting from the animal interacting with its environment. PMID:25904671

  8. Estimation of postmortem interval in real cases based on experimentally obtained entomological evidence.

    PubMed

    Arnaldos, M I; García, M D; Romera, E; Presa, J J; Luna, A

    2005-04-20

    Using the entomological evidence obtained in several forensic cases analyzed in our laboratory for comparison, we evaluated the results of an experimental study carried out in a semiurban setting to determine the structure of the sarcosaprophagous fauna from a Mediterranean region of SE Spain. In all, 18 orders of arthropods were collected. The summarized experimental results refer to the most important taxa for estimating the postmortem interval. Thus, the seasonal character of certain Diptera species, such as Phaenicia sericata, Calliphora vicina, Chrysomya albiceps and Musca domestica, is cited. Among the Coleoptera, the role of Dermestidae as a necrophagous species, and of Staphylinidae and Histeridae as necrophilous, or Cleridae, Tenebrionidae and Nitidulidae as omnivorous, as well as their appearance on the corpse, is described. Among the Hymenoptera, Formicidae were as the most abundant group, acting as omnivores and not apparently related to any particular decomposition stage. The real cases are discussed using data from the literature and the experimentally obtained results. In every case, the most relevant factors for estimating PMI are briefly discussed, mentioning, when possible, the relation with the experimental results. We confirm the significance of the experimental results because they seem to be applicable to actual forensic cases, the details of which enlarge our very little knowledge on the subject in the Iberian Peninsula. The importance of regional faunistic studies of the sarcosaprophagous arthropod community, the results of which may be applied to forensic practice, is mentioned.

  9. Experimental evidence for the acceleration of thermal electrons by ion cyclotron waves in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Norris, A. J.; Sojka, J. J.; Wrenn, G. L.; Johnson, J. F. E.; Cornilleau-Wehrlin, N.; Perraut, S.; Roux, A.

    1983-01-01

    Experimental evidence is presented for the acceleration of thermal electrons by large amplitude ion cyclotron waves (ICWs). The wave power in the ULF range near the helium gyrofrequency is compared with the distribution function of low energy electrons measured by GEOS satellite instruments. This comparison shows that electrons are accelerated near the geomagnetic equator along field lines, at times when the ICW energy is large and the cold plasma density is below a threshold value. It is suggested that these accelerated electrons can account for the ELF emissions, modulated at the ICW frequency, observed by Wehrlin (1981). A very efficient acceleration of thermal electrons along field lines results from other ULF events having frequencies close to the proton gyrofrequency. Evidence for this lies in the fact that medium energy protons having large temperature anisotropies in the 100-500 eV range are responsible for the ICW wave generation.

  10. Relevance of the Glutathione System in Temporal Lobe Epilepsy: Evidence in Human and Experimental Models

    PubMed Central

    Cárdenas-Rodríguez, Noemí; Coballase-Urrutia, Elvia; Pérez-Cruz, Claudia; Montesinos-Correa, Hortencia; Rivera-Espinosa, Liliana; Sampieri, Aristides; Carmona-Aparicio, Liliana

    2014-01-01

    Oxidative stress, which is a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with diseases that are systemic as well as diseases that affect the central nervous system. Epilepsy is a chronic neurological disorder, and temporal lobe epilepsy represents an estimated 40% of all epilepsy cases. Currently, evidence from human and experimental models supports the involvement of oxidative stress during seizures and in the epileptogenesis process. Hence, the aim of this review was to provide information that facilitates the processing of this evidence and investigate the therapeutic impact of the biochemical status for this specific pathology. PMID:25538816

  11. Theoretical and Experimental Evidence of Hydrogen Migration rather than Isomerization in the Acetylene Dication

    NASA Astrophysics Data System (ADS)

    Liekhus-Schmaltz, Chelsea; Li, Zheng; Petrovic, Vladimir; Martinez, Todd; Bucksbaum, Phil; AMO75113 Collaboration

    2016-05-01

    Theoretical calculations and experimental results in the acetylene dication have long agreed that isomerization after x-ray excitation occurs in the first singlet state, where the carbon-carbon bond lives long enough for isomerization to complete. These same calculations predict that a large barrier to isomerization exists that would cause isomerization to occur in about a picosecond, while there is some evidence for ultrafast isomerization in under 100 fs. However, new ab initio calculations of the acetylene dication reveal that ultrafast isomerization after x-ray excitation is unlikely. In this talk, we present evidence that signatures of hydrogen migration observed in recent time resolved LCLS data are mostly due to hydrogen migration in an excited state which dissociates too quickly for isomerization to complete. This material is based upon work supported by the National Science Foundation under Grant No. PHY-0649578.

  12. Additional experimental evidence for a solar influence on nuclear decay rates

    NASA Astrophysics Data System (ADS)

    Jenkins, Jere H.; Herminghuysen, Kevin R.; Blue, Thomas E.; Fischbach, Ephraim; Javorsek, Daniel; Kauffman, Andrew C.; Mundy, Daniel W.; Sturrock, Peter A.; Talnagi, Joseph W.

    2012-09-01

    Additional experimental evidence is presented in support of the recent hypothesis that a possible solar influence could explain fluctuations observed in the measured decay rates of some isotopes. These data were obtained during routine weekly calibrations of an instrument used for radiological safety at The Ohio State University Research Reactor using 36Cl. The detector system used was based on a Geiger-Müller gas detector, which is a robust detector system with very low susceptibility to environmental changes. A clear annual variation is evident in the data, with a maximum relative count rate observed in January/February, and a minimum relative count rate observed in July/August, for seven successive years from July 2005 to June 2011. This annual variation is not likely to have arisen from changes in the detector surroundings, as we show here.

  13. Permanent dissipative structures in water: the matrix of life? Experimental evidences and their quantum origin.

    PubMed

    Elia, V; Germano, R; Napoli, E

    2015-01-01

    This paper presents a short review of the evidence - both experimental and theoretical - of the formation of dissipative structures in liquid water induced by three kinds of physical perturbations having a low energy content: extremely diluted solution (EDS), iteratively filtered water (IFW), and iteratively nafionated water (INW). Particular attention is devoted to the very recent discovery that such structures are tremendously persistent even in the solid phase: large ponderal quantities of supramolecular aggregates of water (with each nucleus hundreds of nanometers in size) have been observed - at ambient pressure and temperature - using easily-reproducible experimental methods. The nature of these dissipative structures is analyzed and explained in terms of the thermodynamics of far-from-equilibrium systems and irreversible processes, showing their spontaneous quantum origin. Are these kinds of structures the matrix itself of life?.

  14. Experimental evidence of deterministic coherence resonance in coupled chaotic systems with frequency mismatch

    NASA Astrophysics Data System (ADS)

    García-Vellisca, M. A.; Pisarchik, A. N.; Jaimes-Reátegui, R.

    2016-07-01

    We present the experimental evidence of deterministic coherence resonance in unidirectionally coupled two and three Rössler electronic oscillators with mismatch between their natural frequencies. The regularity in both the amplitude and the phase of chaotic fluctuations is experimentally proven by the analyses of normalized standard deviations of the peak amplitude and interpeak interval and Lyapunov exponents. The resonant chaos suppression appears when the coupling strength is increased and the oscillators are in phase synchronization. In two coupled oscillators, the coherence enhancement is associated with negative third and fourth Lyapunov exponents, while the largest first and second exponents remain positive. Distinctly, in three oscillators coupled in a ring, all exponents become negative, giving rise to periodicity. Numerical simulations are in good agreement with the experiments.

  15. Experimental evidence of high-frequency complete elastic bandgap in pillar-based phononic slabs

    SciTech Connect

    Pourabolghasem, Reza; Mohammadi, Saeed; Eftekhar, Ali A.; Adibi, Ali; Khelif, Abdelkrim

    2014-12-08

    We present strong experimental evidence for the existence of a complete phononic bandgap, for Lamb waves, in the high frequency regime (i.e., 800 MHz) for a pillar-based phononic crystal (PnC) membrane with a triangular lattice of gold pillars on top. The membrane is composed of an aluminum nitride film stacked on thin molybdenum and silicon layers. Experimental characterization shows a large attenuation of at least 20 dB in the three major crystallographic directions of the PnC lattice in the frequency range of 760 MHz–820 MHz, which is in agreement with our finite element simulations of the PnC bandgap. The results of experiments are analyzed and the physics behind the attenuation in different spectral windows is explained methodically by assessing the type of Bloch modes and the in-plane symmetry of the displacement profile.

  16. Computer modelling and experimental evidence for two steady states in the photosynthetic Calvin cycle.

    PubMed

    Poolman, M G; Olçer, H; Lloyd, J C; Raines, C A; Fell, D A

    2001-05-01

    We present observations of photosynthetic carbon dioxide assimilation, and leaf starch content from genetically modified tobacco (Nicotiana tabacum) plants in which the activity of the Calvin cycle enzyme, sedoheptulose-1,7-bisphosphatase, is reduced by an antisense construct. The measurements were made on leaves of varying ages and used to calculate the flux control coefficients of sedoheptulose-1,7-bisphosphatase over photosynthetic assimilation and starch synthesis. These calculations suggest that control coefficients for both are negative in young leaves, and positive in mature leaves. This behaviour is compared to control coefficients obtained from a detailed computer model of the Calvin cycle. The comparison demonstrates that the experimental observations are consistent with bistable behaviour exhibited by the model, and provides the first experimental evidence that such behaviour in the Calvin cycle occurs in vivo as well as in silico.

  17. Poverty, inequality, and increased consumption of high calorie food: Experimental evidence for a causal link.

    PubMed

    Bratanova, Boyka; Loughnan, Steve; Klein, Olivier; Claassen, Almudena; Wood, Robert

    2016-05-01

    Rising obesity represents a serious, global problem. It is now well established that obesity is associated with poverty and wealth inequality, suggesting that these factors may promote caloric intake. Whereas previous work has examined these links from an epidemiological perspective, the current paper examined them experimentally. In Study 1 we found that people experimentally induced to view themselves as poor (v. wealthy) exhibited increased calorie intake. In Study 2, participants who believed that they were poorer or wealthier than their interaction partners exhibited higher levels of anxiety compared to those in an equal partners condition; this anxiety in turn led to increased calorie consumption for people who had a strong need to belong. The findings provide causal evidence for the poverty-intake and inequality-intake links. Further, we identify social anxiety and a strong need to belong as important social psychological factors linking inequality to increased calorie intake. PMID:26809142

  18. Experimental evidence and model explanation for cell population characteristics modification when applying sequential photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Sabino, L. G.; de Negreiros, L. M. V.; Vollet-Filho, J. D.; Ferreira, J.; Tirapelli, D. P. C.; Novais, P. C.; Tirapelli, L. F.; Kurachi, C.; Bagnato, V. S.

    2011-03-01

    We present experimental evidence of the existence of cell variability in terms of threshold light dose for Hep G2 (liver cancer cells) cultured. Using a theoretical model to describe the effects caused by successive photodynamic therapy (PDT) sessions, and based on the consequences of a partial response we introduce the threshold dose distribution concept within a tumor. The experimental model consists in a stack of flasks, and simulates subsequent layers of a tissue exposed to PDT application. The result indicates that cells from the same culture could respond in different ways to similar PDT induced-damages. Moreover, the consequence is a partial killing of the cells submitted to PDT, and the death fraction decreased at each in vitro PDT session. To demonstrate the occurrence of cell population modification as a response to PDT, we constructed a simple theoretical model and assumed that the threshold dose distribution for a cell population of a tumor is represented by a modified Gaussian distribution.

  19. Poverty, inequality, and increased consumption of high calorie food: Experimental evidence for a causal link.

    PubMed

    Bratanova, Boyka; Loughnan, Steve; Klein, Olivier; Claassen, Almudena; Wood, Robert

    2016-05-01

    Rising obesity represents a serious, global problem. It is now well established that obesity is associated with poverty and wealth inequality, suggesting that these factors may promote caloric intake. Whereas previous work has examined these links from an epidemiological perspective, the current paper examined them experimentally. In Study 1 we found that people experimentally induced to view themselves as poor (v. wealthy) exhibited increased calorie intake. In Study 2, participants who believed that they were poorer or wealthier than their interaction partners exhibited higher levels of anxiety compared to those in an equal partners condition; this anxiety in turn led to increased calorie consumption for people who had a strong need to belong. The findings provide causal evidence for the poverty-intake and inequality-intake links. Further, we identify social anxiety and a strong need to belong as important social psychological factors linking inequality to increased calorie intake.

  20. Experimental evidence of a symbiosis between red-cockaded woodpeckers and fungi.

    PubMed

    Jusino, Michelle A; Lindner, Daniel L; Banik, Mark T; Rose, Kevin R; Walters, Jeffrey R

    2016-03-30

    Primary cavity excavators, such as woodpeckers, are ecosystem engineers in many systems. Associations between cavity excavators and fungi have long been hypothesized to facilitate cavity excavation, but these relationships have not been experimentally verified. Fungi may help excavators by softening wood, while excavators may facilitate fungal dispersal. Here we demonstrate that excavators facilitate fungal dispersal and thus we report the first experimental evidence of a symbiosis between fungi and a cavity excavator, the red-cockaded woodpecker (RCW,Picoides borealis). Swab samples of birds showed that RCWs carry fungal communities similar to those found in their completed excavations. A 26-month field experiment using human-made aseptically drilled excavations in live trees, half of which were inaccessible to RCWs, demonstrated that RCWs directly alter fungal colonization and community composition. Experimental excavations that were accessible to RCWs contained fungal communities similar to natural RCW excavations, whereas inaccessible experimental excavations contained significantly different fungal communities. Our work demonstrates a complex symbiosis between cavity excavators and communities of fungi, with implications for forest ecology, wildlife management, and conservation. PMID:27009222

  1. The treatment of dissociative identity disorder with cognitive analytic therapy: experimental evidence of sudden gains.

    PubMed

    Kellett, Stephen

    2005-01-01

    The central aim of this study was to assess the effectiveness of cognitive analytic therapy (CAT) with a patient presenting with DID. The methodology employed an A/B single case experimental design with six-months continuous follow-up in seven experimental measures. A and B represent the assessment of seven dissociative experimental variables under two conditions: baseline (A) and treatment (B). Treatment consisted of 24 sessions of CAT with four follow-up sessions, which is standard within the CAT model for personality disorder patients. A battery of measures of general psychological functioning was also completed at assessment, termination, and follow-up. During treatment the intensity of a range of dissociative symptoms was observed to be reduced, with sudden gains evident due to specific CAT interventions in specific dissociative symptoms. The long-term effectiveness of the intervention was established by the illustration of either continued stability or continued improvement in experimental variables across the follow-up period. Analysis of the general measures illustrates clinically significant change across a variety of robust psychometric measures. The study illustrates the utility of single-case approaches with dissociative disorders and the potential for utilizing CAT generally with such presentations.

  2. Delayed school start times and adolescent sleep: A systematic review of the experimental evidence.

    PubMed

    Minges, Karl E; Redeker, Nancy S

    2016-08-01

    Many schools have instituted later morning start times to improve sleep, academic, and other outcomes in response to the mismatch between youth circadian rhythms and early morning start times. However, there has been no systematic synthesis of the evidence on the effects of this practice. To examine the impact of delayed school start time on students' sleep, health, and academic outcomes, electronic databases were systematically searched and data were extracted using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Six studies satisfied selection criteria and used pre-post, no control (n = 3), randomized controlled trial (n = 2), and quasi-experimental (n = 1) designs. School start times were delayed 25-60 min, and correspondingly, total sleep time increased from 25 to 77 min per weeknight. Some studies revealed reduced daytime sleepiness, depression, caffeine use, tardiness to class, and trouble staying awake. Overall, the evidence supports recent non-experimental study findings and calls for policy that advocates for delayed school start time to improve sleep. This presents a potential long-term solution to chronic sleep restriction during adolescence. However, there is a need for rigorous randomized study designs and reporting of consistent outcomes, including objective sleep measures and consistent measures of health and academic performance.

  3. Experimental evidence for a liquid-liquid crossover in deeply cooled confined water.

    PubMed

    Cupane, Antonio; Fomina, Margarita; Piazza, Irina; Peters, Judith; Schirò, Giorgio

    2014-11-21

    In this work we investigate, by means of elastic neutron scattering, the pressure dependence of mean square displacements (MSD) of hydrogen atoms of deeply cooled water confined in the pores of a three-dimensional disordered SiO2 xerogel; experiments have been performed at 250 and 210 K from atmospheric pressure to 1200 bar. The "pressure anomaly" of supercooled water (i.e., a mean square displacement increase with increasing pressure) is observed in our sample at both temperatures; however, contrary to previous simulation results and to the experimental trend observed in bulk water, the pressure effect is smaller at lower (210 K) than at higher (250 K) temperature. Elastic neutron scattering results are complemented by differential scanning calorimetry data that put in evidence, besides the glass transition at about 170 K, a first-order-like endothermic transition occurring at about 230 K that, in view of the neutron scattering results, can be attributed to a liquid-liquid crossover. Our results give experimental evidence for the presence, in deeply cooled confined water, of a crossover occurring at about 230 K (at ambient pressure) from a liquid phase predominant at 210 K to another liquid phase predominant at 250 K; therefore, they are fully consistent with the liquid-liquid transition hypothesis.

  4. Direct experimental evidence for quadruplex–quadruplex interaction within the human ILPR

    PubMed Central

    Schonhoft, Joseph D.; Bajracharya, Rabindra; Dhakal, Soma; Yu, Zhongbo; Mao, Hanbin; Basu, Soumitra

    2009-01-01

    Here we report the analysis of dual G-quadruplexes formed in the four repeats of the consensus sequence from the insulin-linked polymorphic region (ACAGGGGTGTGGGG; ILPRn=4). Mobilities of ILPRn=4 in nondenaturing gel and circular dichroism (CD) studies confirmed the formation of two intramolecular G-quadruplexes in the sequence. Both CD and single molecule studies using optical tweezers showed that the two quadruplexes in the ILPRn=4 most likely adopt a hybrid G-quadruplex structure that was entirely different from the mixture of parallel and antiparallel conformers previously observed in the single G-quadruplex forming sequence (ILPRn=2). These results indicate that the structural knowledge of a single G-quadruplex cannot be automatically extrapolated to predict the conformation of multiple quadruplexes in tandem. Furthermore, mechanical pulling of the ILPRn=4 at the single molecule level suggests that the two quadruplexes are unfolded cooperatively, perhaps due to a quadruplex–quadruplex interaction (QQI) between them. Additional evidence for the QQI was provided by DMS footprinting on the ILPRn=4 that identified specific guanines only protected in the presence of a neighboring G-quadruplex. There have been very few experimental reports on multiple G-quadruplex-forming sequences and this report provides direct experimental evidence for the existence of a QQI between two contiguous G-quadruplexes in the ILPR. PMID:19324891

  5. Experimental evidence for drought induced alternative stable states of soil moisture

    NASA Astrophysics Data System (ADS)

    Robinson, David. A.; Jones, Scott B.; Lebron, Inma; Reinsch, Sabine; Domínguez, María T.; Smith, Andrew R.; Jones, Davey L.; Marshall, Miles R.; Emmett, Bridget A.

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction.

  6. Experimental evidence for drought induced alternative stable states of soil moisture

    PubMed Central

    Robinson, David. A.; Jones, Scott B.; Lebron, Inma; Reinsch, Sabine; Domínguez, María T.; Smith, Andrew R.; Jones, Davey L.; Marshall, Miles R.; Emmett, Bridget A.

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction. PMID:26804897

  7. Experimental evidence for drought induced alternative stable states of soil moisture.

    PubMed

    Robinson, David A; Jones, Scott B; Lebron, Inma; Reinsch, Sabine; Domínguez, María T; Smith, Andrew R; Jones, Davey L; Marshall, Miles R; Emmett, Bridget A

    2016-01-01

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction. PMID:26804897

  8. Experimental evidence for drought induced alternative stable states of soil moisture.

    PubMed

    Robinson, David A; Jones, Scott B; Lebron, Inma; Reinsch, Sabine; Domínguez, María T; Smith, Andrew R; Jones, Davey L; Marshall, Miles R; Emmett, Bridget A

    2016-01-25

    Ecosystems may exhibit alternative stable states (ASS) in response to environmental change. Modelling and observational data broadly support the theory of ASS, however evidence from manipulation experiments supporting this theory is limited. Here, we provide long-term manipulation and observation data supporting the existence of drought induced alternative stable soil moisture states (irreversible soil wetting) in upland Atlantic heath, dominated by Calluna vulgaris (L.) Hull. Manipulated repeated moderate summer drought, and intense natural summer drought both lowered resilience resulting in shifts in soil moisture dynamics. The repeated moderate summer drought decreased winter soil moisture retention by ~10%. However, intense summer drought, superimposed on the experiment, that began in 2003 and peaked in 2005 caused an unexpected erosion of resilience and a shift to an ASS; both for the experimental drought manipulation and control plots, impairing the soil from rewetting in winter. Measurements outside plots, with vegetation removal, showed no evidence of moisture shifts. Further independent evidence supports our findings from historical soil moisture monitoring at a long-term upland hydrological observatory. The results herald the need for a new paradigm regarding our understanding of soil structure, hydraulics and climate interaction.

  9. Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change

    PubMed Central

    Bestion, Elvire; Teyssier, Aimeric; Richard, Murielle; Clobert, Jean; Cote, Julien

    2015-01-01

    Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates. PMID:26501958

  10. Experimental evidence of super-resolution better than λ/105 with positive refraction

    NASA Astrophysics Data System (ADS)

    Miñano, Juan C.; Sánchez-Dehesa, José; González, Juan C.; Benítez, P.; Grabovičkić, D.; Carbonell, Jorge; Ahmadpanahi, H.

    2014-03-01

    Super-resolution (SR) systems surpassing the Abbe diffraction limit have been theoretically and experimentally demonstrated using a number of different approaches and technologies: using materials with a negative refractive index, utilizing optical super-oscillation, using a resonant metalens, etc. However, recently it has been proved theoretically that in the Maxwell fish-eye lens (MFE), a device made of positive refractive index materials, the same phenomenon takes place. Moreover, using a simpler device equivalent to the MFE called the spherical geodesic waveguide (SGW), an SR of up to λ/3000 was simulated in COMSOL. Until now, only one piece of experimental evidence of SR with positive refraction has been reported (up to λ/5) for an MFE prototype working at microwave frequencies. Here, experimental results are presented for an SGW prototype showing an SR of up to λ/105. The SGW prototype consists of two concentric metallic spheres with an air space in between and two coaxial ports acting as an emitter and a receiver. The prototype has been analyzed in the range 1 GHz to 1.3 GHz.

  11. Direct experimental evidence for a multiparticle-hole ground state configuration of deformed 33Mg

    NASA Astrophysics Data System (ADS)

    Datta, Ushasi; Rahaman, A.; Aumann, T.; Beceiro-Novo, S.; Boretzky, K.; Caesar, C.; Carlson, B. V.; Catford, W. N.; Chakraborty, S.; Chartier, M.; Cortina-Gil, D.; de Angelis, G.; Diaz Fernandez, P.; Emling, H.; Ershova, O.; Fraile, L. M.; Geissel, H.; Gonzalez-Diaz, D.; Jonson, B.; Johansson, H.; Kalantar-Nayestanaki, N.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Langer, C.; Le Bleis, T.; Leifels, Y.; Marganiec, J.; Münzenberg, G.; Najafi, M. A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Plag, R.; Reifarth, R.; Ricciardi, V.; Rossi, D.; Scheit, H.; Scheidenberger, C.; Simon, H.; Taylor, J. T.; Togano, Y.; Typel, S.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Winfield, J. S.; Yakorev, D.; Zoric, M.

    2016-09-01

    The first direct experimental evidence of a multiparticle-hole ground state configuration of the neutron-rich 33Mg isotope has been obtained via intermediate energy (400 A MeV) Coulomb dissociation measurement. The major part ˜(70 ±13 )% of the cross section is observed to populate the excited states of 32Mg after the Coulomb breakup of 33Mg. The shapes of the differential Coulomb dissociation cross sections in coincidence with different core excited states favor that the valence neutron occupies both the s1 /2 and p3 /2 orbitals. These experimental findings suggest a significant reduction and merging of s d -p f shell gaps at N ˜20 and 28. The ground state configuration of 33Mg is predominantly a combination of 32Mg(3.0 ,3.5 MeV ;2-,1-) ⨂νs1/2 , 32Mg(2.5 MeV ;2+) ⨂νp3/2 , and 32Mg(0 ;0+) ⨂νp3/2 . The experimentally obtained quantitative spectroscopic information for the valence neutron occupation of the s and p orbitals, coupled with different core states, is in agreement with Monte Carlo shell model (MCSM) calculation using 3 MeV as the shell gap at N =20 .

  12. Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change.

    PubMed

    Bestion, Elvire; Teyssier, Aimeric; Richard, Murielle; Clobert, Jean; Cote, Julien

    2015-10-01

    Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates.

  13. Experimental and CFD evidence of multiple solutions in a naturally ventilated building.

    PubMed

    Heiselberg, P; Li, Y; Andersen, A; Bjerre, M; Chen, Z

    2004-02-01

    This paper considers the existence of multiple solutions to natural ventilation of a simple one-zone building, driven by combined thermal and opposing wind forces. The present analysis is an extension of an earlier analytical study of natural ventilation in a fully mixed building, and includes the effect of thermal stratification. Both computational and experimental investigations were carried out in parallel with an analytical investigation. When flow is dominated by thermal buoyancy, it was found experimentally that there is thermal stratification. When the flow is wind-dominated, the room is fully mixed. Results from all three methods have shown that the hysteresis phenomena exist. Under certain conditions, two different stable steady-state solutions are found to exist by all three methods for the same set of parameters. As shown by both the computational fluid dynamics (CFD) and experimental results, one of the solutions can shift to another when there is a sufficient perturbation. These results have probably provided the strongest evidence so far for the conclusion that multiple states exist in natural ventilation of simple buildings. Different initial conditions in the CFD simulations led to different solutions, suggesting that caution must be taken when adopting the commonly used 'zero initialization'.

  14. The Scientific Consensus on Climate Change as a Gateway Belief: Experimental Evidence

    PubMed Central

    van der Linden, Sander L.; Leiserowitz, Anthony A.; Feinberg, Geoffrey D.; Maibach, Edward W.

    2015-01-01

    There is currently widespread public misunderstanding about the degree of scientific consensus on human-caused climate change, both in the US as well as internationally. Moreover, previous research has identified important associations between public perceptions of the scientific consensus, belief in climate change and support for climate policy. This paper extends this line of research by advancing and providing experimental evidence for a “gateway belief model” (GBM). Using national data (N = 1104) from a consensus-message experiment, we find that increasing public perceptions of the scientific consensus is significantly and causally associated with an increase in the belief that climate change is happening, human-caused and a worrisome threat. In turn, changes in these key beliefs are predictive of increased support for public action. In short, we find that perceived scientific agreement is an important gateway belief, ultimately influencing public responses to climate change. PMID:25714347

  15. Behavioural evidence of magnetoreception in dolphins: detection of experimental magnetic fields

    NASA Astrophysics Data System (ADS)

    Kremers, Dorothee; López Marulanda, Juliana; Hausberger, Martine; Lemasson, Alban

    2014-09-01

    Magnetoreception, meaning the perception of magnetic fields, is supposed to play an important role for orientation/navigation in some terrestrial and aquatic species. Although some spatial observations of free-ranging cetaceans' migration routes and stranding sites led to the assumption that cetaceans may be sensitive to the geomagnetic field, experimental evidence is lacking. Here, we tested the spontaneous response of six captive bottlenose dolphins to the presentation of two magnetized and demagnetized controlled devices while they were swimming freely. Dolphins approached the device with shorter latency when it contained a strongly magnetized neodymium block compared to a control demagnetized block that was identical in form and density and therefore undistinguishable with echolocation. We conclude that dolphins are able to discriminate the two stimuli on the basis of their magnetic properties, a prerequisite for magnetoreception-based navigation.

  16. Behavioural evidence of magnetoreception in dolphins: detection of experimental magnetic fields.

    PubMed

    Kremers, Dorothee; López Marulanda, Juliana; Hausberger, Martine; Lemasson, Alban

    2014-11-01

    Magnetoreception, meaning the perception of magnetic fields, is supposed to play an important role for orientation/navigation in some terrestrial and aquatic species. Although some spatial observations of free-ranging cetaceans' migration routes and stranding sites led to the assumption that cetaceans may be sensitive to the geomagnetic field, experimental evidence is lacking. Here, we tested the spontaneous response of six captive bottlenose dolphins to the presentation of two magnetized and demagnetized controlled devices while they were swimming freely. Dolphins approached the device with shorter latency when it contained a strongly magnetized neodymium block compared to a control demagnetized block that was identical in form and density and therefore undistinguishable with echolocation. We conclude that dolphins are able to discriminate the two stimuli on the basis of their magnetic properties, a prerequisite for magnetoreception-based navigation.

  17. Behavioural evidence of magnetoreception in dolphins: detection of experimental magnetic fields

    NASA Astrophysics Data System (ADS)

    Kremers, Dorothee; López Marulanda, Juliana; Hausberger, Martine; Lemasson, Alban

    2014-11-01

    Magnetoreception, meaning the perception of magnetic fields, is supposed to play an important role for orientation/navigation in some terrestrial and aquatic species. Although some spatial observations of free-ranging cetaceans' migration routes and stranding sites led to the assumption that cetaceans may be sensitive to the geomagnetic field, experimental evidence is lacking. Here, we tested the spontaneous response of six captive bottlenose dolphins to the presentation of two magnetized and demagnetized controlled devices while they were swimming freely. Dolphins approached the device with shorter latency when it contained a strongly magnetized neodymium block compared to a control demagnetized block that was identical in form and density and therefore undistinguishable with echolocation. We conclude that dolphins are able to discriminate the two stimuli on the basis of their magnetic properties, a prerequisite for magnetoreception-based navigation.

  18. Universal limiting shape of worn profile under multiple-mode fretting conditions: theory and experimental evidence

    PubMed Central

    Dmitriev, Andrey I.; Voll, Lars B.; Psakhie, Sergey G.; Popov, Valentin L.

    2016-01-01

    We consider multiple-mode fretting wear in a frictional contact of elastic bodies subjected to a small-amplitude oscillation, which may include in-plane and out-of-plane translation, torsion and tilting (“periodic rolling”). While the detailed kinetics of wear depends on the particular loading history and wear mechanism, the final worn shape, under some additional conditions, occurs to be universal for all types and loading and wear mechanisms. This universal form is determined solely by the radius of the permanent stick region and the maximum indentation depth during the loading cycle. We provide experimental evidence for the correctness of the theoretically predicted limiting shape. The existence of the universal limiting shape can be used for designing joints which are resistant to fretting wear. PMID:26979092

  19. The scientific consensus on climate change as a gateway belief: experimental evidence.

    PubMed

    van der Linden, Sander L; Leiserowitz, Anthony A; Feinberg, Geoffrey D; Maibach, Edward W

    2015-01-01

    There is currently widespread public misunderstanding about the degree of scientific consensus on human-caused climate change, both in the US as well as internationally. Moreover, previous research has identified important associations between public perceptions of the scientific consensus, belief in climate change and support for climate policy. This paper extends this line of research by advancing and providing experimental evidence for a "gateway belief model" (GBM). Using national data (N = 1104) from a consensus-message experiment, we find that increasing public perceptions of the scientific consensus is significantly and causally associated with an increase in the belief that climate change is happening, human-caused and a worrisome threat. In turn, changes in these key beliefs are predictive of increased support for public action. In short, we find that perceived scientific agreement is an important gateway belief, ultimately influencing public responses to climate change.

  20. Definitive experimental evidence for two-band superconductivity in MgB2.

    PubMed

    Tsuda, S; Yokoya, T; Takano, Y; Kito, H; Matsushita, A; Yin, F; Itoh, J; Harima, H; Shin, S

    2003-09-19

    The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. The results show that superconducting gaps with values of 5.5 and 2.2 meV open on the sigma band and the pi band, respectively, but both the gaps close at the bulk transition temperature, providing a definitive experimental evidence for the two-band superconductivity with strong interband pairing interaction in MgB2. The experiments validate the role of k-dependent electron-phonon coupling as the origin of multiple-gap superconductivity as well as the high transition temperature of MgB2.

  1. Hypertension and Dementia: Epidemiological and Experimental Evidence Revealing a Detrimental Relationship.

    PubMed

    Perrotta, Marialuisa; Lembo, Giuseppe; Carnevale, Daniela

    2016-01-01

    Hypertension and dementia represent two major public health challenges worldwide, notably in the elderly population. Although these two conditions have classically been recognized as two distinct diseases, mounting epidemiological, clinical and experimental evidence suggest that hypertension and dementia are strictly intertwined. Here, we briefly report how hypertension profoundly affects brain homeostasis, both at the structural and functional level. Chronic high blood pressure modifies the cerebral vasculature, increasing the risk of Aβ clearance impairment. The latter, excluding genetic etiologies, is considered one of the main causes of Aβ deposition in the brain. Studies have shown that hypertension induces cerebral arterial stiffening and microvascular dysfunction, thus contributing to dementia pathophysiology. This review examines the existing and the updated literature which has attempted to explain and clarify the relationship between hypertension and dementia at the pathophysiological level. PMID:27005613

  2. Behavioural evidence of magnetoreception in dolphins: detection of experimental magnetic fields.

    PubMed

    Kremers, Dorothee; López Marulanda, Juliana; Hausberger, Martine; Lemasson, Alban

    2014-11-01

    Magnetoreception, meaning the perception of magnetic fields, is supposed to play an important role for orientation/navigation in some terrestrial and aquatic species. Although some spatial observations of free-ranging cetaceans' migration routes and stranding sites led to the assumption that cetaceans may be sensitive to the geomagnetic field, experimental evidence is lacking. Here, we tested the spontaneous response of six captive bottlenose dolphins to the presentation of two magnetized and demagnetized controlled devices while they were swimming freely. Dolphins approached the device with shorter latency when it contained a strongly magnetized neodymium block compared to a control demagnetized block that was identical in form and density and therefore undistinguishable with echolocation. We conclude that dolphins are able to discriminate the two stimuli on the basis of their magnetic properties, a prerequisite for magnetoreception-based navigation. PMID:25267469

  3. Experimental evidence for alleviating nociceptive hypersensitivity by single application of capsaicin.

    PubMed

    Ma, Xiao-Li; Zhang, Fang-Xiong; Dong, Fei; Bao, Lan; Zhang, Xu

    2015-04-22

    The single application of high-concentration of capsaicin has been used as an analgesic therapy of persistent pain. However, its effectiveness and underlying mechanisms remain to be further evaluated with experimental approaches. The present study provided evidence showing that the single application of capsaicin dose-dependently alleviated nociceptive hypersensitivity, and reduced the action potential firing in small-diameter neurons of the dorsal root ganglia (DRG) in rats and mice. Pre-treatment with capsaicin reduced formalin-induced acute nocifensive behavior after a brief hyperalgesia in rats and mice. The inhibitory effects of capsaicin were calcium-dependent, and mediated by the capsaicin receptor (transient receptor potential vanilloid type-1). We further found that capsaicin exerted inhibitory effects on the persistent nociceptive hypersensitivity induced by peripheral inflammation and nerve injury. Thus, these results support the long-lasting and inhibitory effects of topical capsaicin on persistent pain, and the clinic use of capsaicin as a pain therapy.

  4. The scientific consensus on climate change as a gateway belief: experimental evidence.

    PubMed

    van der Linden, Sander L; Leiserowitz, Anthony A; Feinberg, Geoffrey D; Maibach, Edward W

    2015-01-01

    There is currently widespread public misunderstanding about the degree of scientific consensus on human-caused climate change, both in the US as well as internationally. Moreover, previous research has identified important associations between public perceptions of the scientific consensus, belief in climate change and support for climate policy. This paper extends this line of research by advancing and providing experimental evidence for a "gateway belief model" (GBM). Using national data (N = 1104) from a consensus-message experiment, we find that increasing public perceptions of the scientific consensus is significantly and causally associated with an increase in the belief that climate change is happening, human-caused and a worrisome threat. In turn, changes in these key beliefs are predictive of increased support for public action. In short, we find that perceived scientific agreement is an important gateway belief, ultimately influencing public responses to climate change. PMID:25714347

  5. First experimental evidence of the feasibility of multi-color magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Rahmer, J.; Halkola, A.; Gleich, B.; Schmale, I.; Borgert, J.

    2015-03-01

    Magnetic particle imaging is a new approach to visualizing magnetic nanoparticles. It is capable of 3D real-time in vivo imaging of particles injected into the blood stream and is a candidate for medical imaging applications. To date, only one particle type has been imaged at a time, however, the ability to separate signals acquired simultaneously from different particle types or from particles in different environments would substantially increase the scope of the method. Different colors could be assigned to different signal sources to allow for visualization in a single image. Successful signal separation has been reported in spectroscopic experiments, but it was unclear how well separation would work in conjunction with spatial encoding in an imaging experiment. This work presents experimental evidence of the separability of signals from different particle types and aggregation states (fluid versus powder) using a ‘multi-color’ reconstruction approach. Several mechanisms are discussed that may form the basis for successful signal separation.

  6. Universal limiting shape of worn profile under multiple-mode fretting conditions: theory and experimental evidence

    NASA Astrophysics Data System (ADS)

    Dmitriev, Andrey I.; Voll, Lars B.; Psakhie, Sergey G.; Popov, Valentin L.

    2016-03-01

    We consider multiple-mode fretting wear in a frictional contact of elastic bodies subjected to a small-amplitude oscillation, which may include in-plane and out-of-plane translation, torsion and tilting (“periodic rolling”). While the detailed kinetics of wear depends on the particular loading history and wear mechanism, the final worn shape, under some additional conditions, occurs to be universal for all types and loading and wear mechanisms. This universal form is determined solely by the radius of the permanent stick region and the maximum indentation depth during the loading cycle. We provide experimental evidence for the correctness of the theoretically predicted limiting shape. The existence of the universal limiting shape can be used for designing joints which are resistant to fretting wear.

  7. Speciation in caves: experimental evidence that permanent darkness promotes reproductive isolation.

    PubMed

    Riesch, Rüdiger; Plath, Martin; Schlupp, Ingo

    2011-12-23

    Divergent selection through biotic factors like predation or parasitism can promote reproductive isolation even in the absence of geographical barriers. On the other hand, evidence for a role of adaptation to abiotic factors during ecological speciation in animals is scant. In particular, the role played by perpetual darkness in establishing reproductive isolation in cave animals (troglobites) remains elusive. We focused on two reproductively isolated ecotypes (surface- and cave-dwelling) of the widespread livebearer Poecilia mexicana, and raised offspring of wild-caught females to sexual maturity in a 12-month common-garden experiment. Fish were reared in light or darkness combined with high- or low-food conditions. Females, but not males, of the surface ecotype suffered from almost complete reproductive failure in darkness, especially in the low-food treatment. Furthermore, surface fish suffered from a significantly higher rate of spontaneous, stress-related infection with bacterial columnaris disease. This experimental evidence for strong selection by permanent darkness on non-adapted surface-dwelling animals adds depth to our understanding of the selective forces establishing and maintaining reproductive isolation in cave faunas.

  8. Experimental evidence that sexual conflict influences the opportunity, form and intensity of sexual selection.

    PubMed

    Hall, Matthew D; Bussière, Luc F; Hunt, John; Brooks, Robert

    2008-09-01

    Sexual interactions are often rife with conflict. Conflict between members of the same sex over opportunities to mate has long been understood to effect evolution via sexual selection. Although conflict between males and females is now understood to be widespread, such conflict is seldom considered in the same light as a general agent of sexual selection. Any interaction between males or females that generates variation in fitness, whether due to conflict, competition or mate choice, can potentially influence sexual selection acting on a range of male traits. Here we seek to address a lack of direct experimental evidence for how sexual conflict influences sexual selection more broadly. We manipulate a major source of sexual conflict in the black field cricket, Teleogryllus commodus, and quantify the resulting changes in the nature of sexual selection using formal selection analysis to statistically compare multivariate fitness surfaces. In T. commodus, sexual conflict occurs over the attachment time of an external spermatophore. By experimentally manipulating the ability of males and females to influence spermatophore attachment, we found that sexual conflict significantly influences the opportunity, form, and intensity of sexual selection on male courtship call and body size. When males were able to harass females, the opportunity for selection was smaller, the form of selection changed, and sexual selection was weaker. We discuss the broader evolutionary implications of these findings, including the contributions of sexual conflict to fluctuating sexual selection and the maintenance of additive genetic variation.

  9. Experimental evidence and molecular modeling of the interaction between hRSV-NS1 and quercetin.

    PubMed

    Gomes, Deriane Elias; Caruso, Ícaro Putinhon; de Araujo, Gabriela Campos; de Lourenço, Isabella Otenio; de Melo, Fernando Alves; Cornélio, Marinônio Lopes; Fossey, Marcelo Andrés; de Souza, Fátima Pereira

    2016-04-01

    Human Respiratory Syncytial Virus is one of the major causes of acute respiratory infections in children, causing bronchiolitis and pneumonia. Non-Structural Protein 1 (NS1) is involved in immune system evasion, a process that contributes to the success of hRSV replication. This protein can act by inhibiting or neutralizing several steps of interferon pathway, as well as by silencing the hRSV ribonucleoproteic complex. There is evidence that quercetin can reduce the infection and/or replication of several viruses, including RSV. The aims of this study include the expression and purification of the NS1 protein besides experimental and computational assays of the NS1-quercetin interaction. CD analysis showed that NS1 secondary structure composition is 30% alpha-helix, 21% beta-sheet, 23% turn and 26% random coils. The melting temperature obtained through DSC analysis was around 56°C. FRET analysis showed a distance of approximately 19Å between the NS1 and quercetin. Fluorescence titration results showed that the dissociation constant of the NS1-quercetin interaction was around 10(-6)M. In thermodynamic analysis, the enthalpy and entropy balanced forces indicated that the NS1-quercetin interaction presented both hydrophobic and electrostatic contributions. The computational results from the molecular modeling for NS1 structure and molecular docking regarding its interaction with quercetin corroborate the experimental data.

  10. Experimental evidence for melt partitioning between olivine and orthopyroxene in partially molten harzburgite

    NASA Astrophysics Data System (ADS)

    Miller, Kevin J.; Zhu, Wen-lu; Montési, Laurent G. J.; Gaetani, Glenn A.; Le Roux, Véronique; Xiao, Xianghui

    2016-08-01

    Observations of dunite channels in ophiolites and uranium series disequilibria in mid-ocean ridge basalt suggest that melt transport in the upper mantle beneath mid-ocean ridges is strongly channelized. We present experimental evidence that spatial variations in mineralogy can also focus melt on the grain scale. This lithologic melt partitioning, which results from differences in the interfacial energies associated with olivine-melt and orthopyroxene-melt boundaries, may complement other melt focusing mechanisms in the upper mantle such as mechanical shear and pyroxene dissolution. We document here lithologic melt partitioning in olivine-/orthopyroxene-basaltic melt samples containing nominal olivine to orthopyroxene ratio of 3 to 2 and melt fractions of 0.02 to 0.20. Experimental samples were imaged using synchrotron-based X-ray microcomputed tomography at a resolution of 700 nm per voxel. By analyzing the local melt fraction distributions associated with olivine and orthopyroxene grains in each sample, we found that the melt partitioning coefficient, i.e., the ratio of melt fraction around olivine to that around orthopyroxene grains, varies between 1.1 and 1.6. The permeability and electrical conductivity of our digital samples were estimated using numerical models and compared to those of samples containing only olivine and basaltic melt. Our results suggest that lithologic melt partitioning and preferential localization of melt around olivine grains might play a role in melt focusing, potentially enhancing average melt ascent velocities.

  11. Experimental evidence validating the computational inference of functional associations from gene fusion events: a critical survey.

    PubMed

    Promponas, Vasilis J; Ouzounis, Christos A; Iliopoulos, Ioannis

    2014-05-01

    More than a decade ago, a number of methods were proposed for the inference of protein interactions, using whole-genome information from gene clusters, gene fusions and phylogenetic profiles. This structural and evolutionary view of entire genomes has provided a valuable approach for the functional characterization of proteins, especially those without sequence similarity to proteins of known function. Furthermore, this view has raised the real possibility to detect functional associations of genes and their corresponding proteins for any entire genome sequence. Yet, despite these exciting developments, there have been relatively few cases of real use of these methods outside the computational biology field, as reflected from citation analysis. These methods have the potential to be used in high-throughput experimental settings in functional genomics and proteomics to validate results with very high accuracy and good coverage. In this critical survey, we provide a comprehensive overview of 30 most prominent examples of single pairwise protein interaction cases in small-scale studies, where protein interactions have either been detected by gene fusion or yielded additional, corroborating evidence from biochemical observations. Our conclusion is that with the derivation of a validated gold-standard corpus and better data integration with big experiments, gene fusion detection can truly become a valuable tool for large-scale experimental biology.

  12. Role of Chronic Inflammation in Myopia Progression: Clinical Evidence and Experimental Validation.

    PubMed

    Lin, Hui-Ju; Wei, Chang-Ching; Chang, Ching-Yao; Chen, Ter-Hsin; Hsu, Yu-An; Hsieh, Yi-Ching; Chen, Hsuan-Ju; Wan, Lei

    2016-08-01

    Prevention and treatment of myopia is an important public problem worldwide. We found a higher incidence of myopia among patients with inflammatory diseases such as type 1 diabetes mellitus (7.9%), uveitis (3.7%), or systemic lupus erythematosus (3.5%) compared to those without inflammatory diseases (p<0.001) using data from children (<18years old) in the National Health Insurance Research database. We then examined the inhibition of myopia by atropine in Syrian hamsters with monocular form deprivation (MFD), an experimental myopia model. We found atropine downregulated inflammation in MFD eyes. The expression levels of c-Fos, nuclear factor κB (NFκB), interleukin (IL)-6, and tumor necrosis factor (TNF)-α were upregulated in myopic eyes and downregulated upon treatment with atropine. The relationship between the inflammatory response and myopia was investigated by treating MFD hamsters with the immunosuppressive agent cyclosporine A (CSA) or the inflammatory stimulators lipopolysaccharide (LPS) or peptidoglycan (PGN). Myopia progression was slowed by CSA application but was enhanced by LPS and PGN administration. The levels of c-Fos, NF-κB, IL-6, and TNF-α were upregulated in LPS- and PGN-treated eyes and downregulated by CSA treatment. These findings provide clinical and experimental evidence that inflammation plays a crucial role in the development of myopia. PMID:27470424

  13. Experimental evidence validating the computational inference of functional associations from gene fusion events: a critical survey

    PubMed Central

    Promponas, Vasilis J.; Ouzounis, Christos A.; Iliopoulos, Ioannis

    2014-01-01

    More than a decade ago, a number of methods were proposed for the inference of protein interactions, using whole-genome information from gene clusters, gene fusions and phylogenetic profiles. This structural and evolutionary view of entire genomes has provided a valuable approach for the functional characterization of proteins, especially those without sequence similarity to proteins of known function. Furthermore, this view has raised the real possibility to detect functional associations of genes and their corresponding proteins for any entire genome sequence. Yet, despite these exciting developments, there have been relatively few cases of real use of these methods outside the computational biology field, as reflected from citation analysis. These methods have the potential to be used in high-throughput experimental settings in functional genomics and proteomics to validate results with very high accuracy and good coverage. In this critical survey, we provide a comprehensive overview of 30 most prominent examples of single pairwise protein interaction cases in small-scale studies, where protein interactions have either been detected by gene fusion or yielded additional, corroborating evidence from biochemical observations. Our conclusion is that with the derivation of a validated gold-standard corpus and better data integration with big experiments, gene fusion detection can truly become a valuable tool for large-scale experimental biology. PMID:23220349

  14. Evidence of low dimensional chaos in renal blood flow control in genetic and experimental hypertension

    NASA Astrophysics Data System (ADS)

    Yip, K.-P.; Marsh, D. J.; Holstein-Rathlou, N.-H.

    1995-01-01

    We applied a surrogate data technique to test for nonlinear structure in spontaneous fluctuations of hydrostatic pressure in renal tubules of hypertensive rats. Tubular pressure oscillates at 0.03-0.05 Hz in animals with normal blood pressure, but the fluctuations become irregular with chronic hypertension. Using time series from rats with hypertension we produced surrogate data sets to test whether they represent linearly correlated noise or ‘static’ nonlinear transforms of a linear stochastic process. The correlation dimension and the forecasting error were used as discriminating statistics to compare surrogate with experimental data. The results show that the original experimental time series can be distinguished from both linearly and static nonlinearly correlated noise, indicating that the nonlinear behavior is due to the intrinsic dynamics of the system. Together with other evidence this strongly suggests that a low dimensional chaotic attractor governs renal hemodynamics in hypertension. This appears to be the first demonstration of a transition to chaotic dynamics in an integrated physiological control system occurring in association with a pathological condition.

  15. Experimental evidence of transport of pesticides through field soils - a review

    SciTech Connect

    Flury, M.

    1996-01-01

    Much information is available in the literature about pesticide transport through soils at the field scale. The purpose of this study is to review the literature with a focus on pesticide leaching to groundwater. The literature was compiled and discussed with respect to different factors that influence pesticide leaching. Pesticide leaching below the root zone has been demonstrated in sandy as well as in loamy soils. Particularly in loamy soils, there is evidence that even strongly adsorbing chemicals can move along preferential flow pathways and that the travel times of pesticides are comparable to those of conservative solutes. The amounts of pesticides leached below the root zone by worst case rainfall events depend on the chemical properties and can reach up to 5% of the applied mass. When there is no heavy rainfall shortly following application of chemicals, the mass annually leached below the root zone is in the range of <0.1 to 1%, occasionally it can reach up to 4%. Although a direct comparison cannot be made, the mass lost by leaching seems generally to be smaller than that lost by runoff, depending of course on the slope of the fields. Several factors that affect pesticide leaching, such as surface preparation, soil structure, soil water content, type of irrigation, pesticide formulation, time of application and rainfall events, are discussed with support of experimental evidence. While some factors showed inconsistent effects, others show promise in controlling leaching mechanisms. These latter factors include initial water content, surface preparation, and time of pesticide application. Based on the reviewed literature recommendations were made for future research activities. 172 refs., 1 fig., 7 tabs.

  16. Biparental incubation-scheduling: no experimental evidence for major energetic constraints

    PubMed Central

    Cresswell, Will; Rutten, Anne L.; Valcu, Mihai; Kempenaers, Bart

    2015-01-01

    Incubation is energetically demanding, but it is debated whether these demands constrain incubation-scheduling (i.e., the length, constancy, and timing of incubation bouts) in cases where both parents incubate. Using 2 methods, we experimentally reduced the energetic demands of incubation in the semipalmated sandpiper, a biparental shorebird breeding in the harsh conditions of the high Arctic. First, we decreased the demands of incubation for 1 parent only by exchanging 1 of the 4 eggs for an artificial egg that heated up when the focal bird incubated. Second, we reanalyzed the data from the only published experimental study that has explicitly tested energetic constraints on incubation-scheduling in a biparentally incubating species (Cresswell et al. 2003). In this experiment, the energetic demands of incubation were decreased for both parents by insulating the nest cup. We expected that the treated birds, in both experiments, would change the length of their incubation bouts, if biparental incubation-scheduling is energetically constrained. However, we found no evidence that heating or insulation of the nest affected the length of incubation bouts: the combined effect of both experiments was an increase in bout length of 3.6min (95% CI: −33 to 40), which is equivalent to a 0.5% increase in the length of the average incubation bout. These results demonstrate that the observed biparental incubation-scheduling in semipalmated sandpipers is not primarily driven by energetic constraints and therefore by the state of the incubating bird, implying that we still do not understand the factors driving biparental incubation-scheduling. PMID:25713473

  17. Photorespiratory Bypasses Lead to Increased Growth in Arabidopsis thaliana: Are Predictions Consistent with Experimental Evidence?

    PubMed Central

    Basler, Georg; Küken, Anika; Fernie, Alisdair R.; Nikoloski, Zoran

    2016-01-01

    Arguably, the biggest challenge of modern plant systems biology lies in predicting the performance of plant species, and crops in particular, upon different intracellular and external perturbations. Recently, an increased growth of Arabidopsis thaliana plants was achieved by introducing two different photorespiratory bypasses via metabolic engineering. Here, we investigate the extent to which these findings match the predictions from constraint-based modeling. To determine the effect of the employed metabolic network model on the predictions, we perform a comparative analysis involving three state-of-the-art metabolic reconstructions of A. thaliana. In addition, we investigate three scenarios with respect to experimental findings on the ratios of the carboxylation and oxygenation reactions of Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO). We demonstrate that the condition-dependent growth phenotypes of one of the engineered bypasses can be qualitatively reproduced by each reconstruction, particularly upon considering the additional constraints with respect to the ratio of fluxes for the RuBisCO reactions. Moreover, our results lend support for the hypothesis of a reduced photorespiration in the engineered plants, and indicate that specific changes in CO2 exchange as well as in the proxies for co-factor turnover are associated with the predicted growth increase in the engineered plants. We discuss our findings with respect to the structure of the used models, the modeling approaches taken, and the available experimental evidence. Our study sets the ground for investigating other strategies for increase of plant biomass by insertion of synthetic reactions. PMID:27092301

  18. Cardiovascular autonomic dysfunction in primary ovarian insufficiency: clinical and experimental evidence

    PubMed Central

    Goldmeier, Silvia; De Angelis, Kátia; Rabello Casali, Karina; Vilodre, César; Consolim-Colombo, Fernanda; Belló Klein, Adriane; Plentz, Rodrigo; Spritzer, PoliMara; Irigoyen, Maria-Cláudia

    2014-01-01

    Objective: Women with primary ovarian insufficiency (POI) present an increased risk for cardiovascular disease. In this study we tested the hypothesis that POI in women under hormone therapy (HT) are associated with vascular vasodilatation attenuation and cardiovascular autonomic dysfunction and these impairments are related to changes in systemic antioxidant enzymes. Furthermore, the possibility that ovarian hormone deprivation can induce such changes and that HT cannot reverse all of those impairments was examined in an experimental model of POI. Methods: Fifteen control and 17 patients with primary ovarian insufficiency receiving HT were included in the study. To test the systemic and cardiac consequences of ovarian hormone deprivation, ovariectomy was induced in young female rats that were submitted or not to HT. Spectral analysis of RR interval and blood pressure signals were performed and oxidative stress parameters were determined. Results: POI women under HT have increased mean arterial pressure (94±10 vs. 86±5 mmHg) despite normal endothelial and autonomic modulation of vasculature. Additionally, they presented impaired baroreflex sensitivity (3.9±1.38 vs. 7.15±3.62 ms/mmHg) and reduced heart rate variability (2310±1173 vs. 3754±1921 ms2). Similar results obtained in ovariectomized female rats were accompanied by an increased lipoperoxidation (7433±1010 vs. 6180±289 cps/mg protein) and decreased antioxidant enzymes in cardiac tissue. As it was observed in women, the HT in animals did not restore hemodynamic and autonomic dysfunctions. Conclusion: These data provide clinical and experimental evidence that long term HT may not restore all cardiovascular risk factors associated with ovarian hormone deprivation. PMID:24349626

  19. Bisphenol A and Reproductive Health: Update of Experimental and Human Evidence, 2007–2013

    PubMed Central

    Peretz, Jackye; Vrooman, Lisa; Ricke, William A.; Hunt, Patricia A.; Ehrlich, Shelley; Hauser, Russ; Padmanabhan, Vasantha; Taylor, Hugh S.; Swan, Shanna H.; VandeVoort, Catherine A.

    2014-01-01

    health: update of experimental and human evidence, 2007–2013. Environ Health Perspect 122:775–786; http://dx.doi.org/10.1289/ehp.1307728 PMID:24896072

  20. Fluorine as a hydrogen-bond acceptor: experimental evidence and computational calculations.

    PubMed

    Dalvit, Claudio; Invernizzi, Christian; Vulpetti, Anna

    2014-08-25

    Hydrogen-bonding interactions play an important role in many chemical and biological systems. Fluorine acting as a hydrogen-bond acceptor in intermolecular and intramolecular interactions has been the subject of many controversial discussions and there are different opinions about it. Recently, we have proposed a correlation between the propensity of fluorine to be involved in hydrogen bonds and its (19)F NMR chemical shift. We now provide additional experimental and computational evidence for this correlation. The strength of hydrogen-bond complexes involving the fluorine moieties CH2F, CHF2, and CF3 was measured and characterized in simple systems by using established and novel NMR methods and compared to the known hydrogen-bond complex formed between acetophenone and p-fluorophenol. Implications of these results for (19)F NMR screening are analyzed in detail. Computed values of the molecular electrostatic potential at the different fluorine atoms and the analysis of the electron density topology at bond critical points correlate well with the NMR results.

  1. Experimental evidence that microbial activity lowers the albedo of glacier surfaces: the cryoconite casserole experiment.

    NASA Astrophysics Data System (ADS)

    Musilova, M.; Tranter, M.; Takeuchi, N.; Anesio, A. M.

    2014-12-01

    Darkened glacier and ice sheet surfaces have lower albedos, absorb more solar radiation and consequently melt more rapidly. The increase in glacier surface darkening is an important positive feedback to warming global temperatures, leading to ever growing world-wide ice mass loss. Most studies focus primarily on glacial albedo darkening caused by the physical properties of snow and ice surfaces, and the deposition of dark impurities on glaciers. To date, however, the important effects of biological activity have not been included in most albedo reduction models. This study provides the first experimental evidence that microbial activity can significantly decrease the albedo of glacier surfaces. An original laboratory experiment, the cryoconite casserole, was designed to test the microbial darkening of glacier surface debris (cryoconite) under simulated Greenlandic summer conditions. It was found that minor fertilisation of the cryoconite (at nutrient concentrations typical of glacial ice melt) stimulated extensive microbial activity. Microbes intensified their organic carbon fixation and even mined phosphorous out of the glacier surface sediment. Furthermore, the microbial organic carbon production, accumulation and transformation caused the glacial debris to darken further by 17.3% reflectivity (albedo analogue). These experiments are consistent with the hypothesis that enhanced fertilisation by anthropogenic inputs results in substantial amounts of organic carbon fixation, debris darkening and ultimately to a considerable decrease in the ice albedo of glacier surfaces on global scales. The sizeable amounts of microbially produced glacier surface organic matter and nutrients can thus be a vital source of bioavailable nutrients for subglacial and downstream environments.

  2. Experimental evidence of spatial memory and home range affinity in White-tailed Deer (Odocoileus virginianus)

    USGS Publications Warehouse

    Nelson, Michael E.

    2015-01-01

    The role of spatial memory in the movement of animals through landscapes remains elusive. To examine spatial memory and home range affinity of White-tailed Deer (Odocoileus virginianus) in northeastern Minnesota during 1995–2007, I translocated 17 adult does with known home ranges to unfamiliar sites and radio-tracked them after their release. Twelve does wearing transmitting radio-collars returned to their home ranges. Death and collar expiration precluded determination of whether the remaining five does would have returned to home ranges. Three of five does wearing global positioning system collars traveled throughout hundreds of square kilometres, circling, backtracking, and returning to release sites, while two others exhibited directional movement for tens of kilometres. Four does that survived to parturition stopped traveling and moved at hourly rates similar to those of control does during the first three weeks of the typical fawn-rearing period, but continued traveling later. Their aberrant extensive travel before and after interruption by parturition suggests that they recognized they were in unfamiliar areas, demonstrating both their capacity and propensity to search for and occupy the familiar space of their individual home ranges. Their successful return to home ranges provided experimental evidence of spatial memory and further elucidated its pervasive role in White-tailed Deer spatial ecology.

  3. Evidence for tempo-specific timing in music using a web-based experimental setup.

    PubMed

    Honing, Henkjan

    2006-06-01

    Perceptual invariance has been studied and found in several domains of cognition, including those of speech, motor behavior, and object motion. It has also been the topic of several studies in music perception. However, the existing perceptual studies present rather inconclusive evidence with regard to the perceptual invariance of expressive timing under tempo transformation in music performance. The current study used a novel experimental methodology that took advantage of new technologies, such as an online Internet setup, high-quality audio, and state-of-the-art tempo-transformation techniques. The results show that listeners could detect which was the original performance when asked to compare 2 recordings, 1 of which was tempo-transformed to make both similar in overall tempo. This result is taken as support for the tempo-specific timing hypothesis--which predicts that a tempo-transformed performance will sound less natural than an original performance--and as counterevidence for the relationally invariant timing hypothesis, which predicts that a tempo-transformed performance will sound equally natural.

  4. The fishermen were right: experimental evidence for tributary refuge hypothesis during floods.

    PubMed

    Koizumi, Itsuro; Kanazawa, Yukiyo; Tanaka, Yuuki

    2013-05-01

    Fishermen often anecdotally report an unexpected increase of fish caught in small tributary streams during floods, presumably due to refuge-seeking behavior from the main stem. From a population perspective, this implies the significance of refuge habitats and connectivity for population viability against natural disturbances. Despite the plausibility, however, surprisingly few studies have examined the tributary refuge hypothesis, mainly due to the difficulty in field survey during floods. Here, we made use of a large-scale controlled flood to assess whether fishes move into tributaries during flooding in the main stem. A planned water release from the Satsunai River Dam located on Hokkaido Island in Japan rapidly increased the main stem discharge by more than 20-fold. Before, during, and after flooding censuses in four tributaries provided evidence of the refuge-seeking behavior of fishes from the main stem. For example, more than 10 Dolly Varden char, a salmonid fish, were caught in a tributary during the flood, even though almost no individuals were captured before or after the flood. The fish responded immediately to the flooding, suggesting the need for studies during disturbances. In addition, the likelihood of refuge movements varied among tributaries, suggesting the importance of local environmental differences between tributary and the main stem habitats. This is the first study to experimentally confirm the tributary refuge hypothesis, and underscores the roles of habitat diversity and connectivity during disturbances, even though some habitats are not used during normal conditions.

  5. Experimental Evidence for an Eco-Evolutionary Coupling between Local Adaptation and Intraspecific Competition.

    PubMed

    Siepielski, Adam M; Nemirov, Alex; Cattivera, Matthew; Nickerson, Avery

    2016-04-01

    Determining how adaptive evolution can be coupled to ecological processes is key for developing a more integrative understanding of the demographic factors that regulate populations. Intraspecific competition is an especially important ecological process because it generates negative density dependence in demographic rates. Although ecological factors are most often investigated to determine the strength of density dependence, evolutionary processes such as local adaptation could also feed back to shape variation in the strength of density dependence among populations. Using an experimental approach with damselflies, a predaceous aquatic insect, we find evidence that both density-dependent intraspecific competition and local adaptation can reduce per capita growth rates. In some cases, the effects of local adaptation on reducing per capita growth rates exceeded the ecological competitive effects of a doubling of density. However, we also found that these ecological and evolutionary properties of populations are coupled, and we offer two interpretations of the causes underlying this pattern: (1) the strength of density-dependent competition depends on the extent of local adaptation, or (2) the extent of local adaptation is shaped by the strength of density-dependent competition. Regardless of the underlying causal pathway, these results show how eco-evolutionary dynamics can affect a key demographic process regulating populations.

  6. Infectivity of DWV associated to flower pollen: experimental evidence of a horizontal transmission route.

    PubMed

    Mazzei, Maurizio; Carrozza, Maria Luisa; Luisi, Elena; Forzan, Mario; Giusti, Matteo; Sagona, Simona; Tolari, Francesco; Felicioli, Antonio

    2014-01-01

    Deformed wing virus (DWV) is a honeybee pathogen whose presence is generally associated with infestation of the colony by the mite Varroa destructor, leading to the onset of infections responsible for the collapse of the bee colony. DWV contaminates bee products such as royal jelly, bee-bread and honey stored within the infected hive. Outside the hive, DWV has been found in pollen loads collected directly from infected as well as uninfected forager bees. It has been shown that the introduction of virus-contaminated pollen into a DWV-free hive results in the production of virus-contaminated food, whose role in the development of infected bees from virus-free eggs has been experimentally demonstrated. The aim of this study was twofold: (i) to ascertain the presence of DWV on pollen collected directly from flowers visited by honeybees and then quantify the viral load and (ii) determine whether the virus associated with pollen is infective. The results of our investigation provide evidence that DWV is present on pollen sampled directly from visited flowers and that, following injection in individuals belonging to the pollinator species Apis mellifera, it is able to establish an active infection, as indicated by the presence of replicating virus in the head of the injected bees. We also provide the first indication that the pollinator species Osmia cornuta is susceptible to DWV infection.

  7. Infectivity of DWV associated to flower pollen: experimental evidence of a horizontal transmission route.

    PubMed

    Mazzei, Maurizio; Carrozza, Maria Luisa; Luisi, Elena; Forzan, Mario; Giusti, Matteo; Sagona, Simona; Tolari, Francesco; Felicioli, Antonio

    2014-01-01

    Deformed wing virus (DWV) is a honeybee pathogen whose presence is generally associated with infestation of the colony by the mite Varroa destructor, leading to the onset of infections responsible for the collapse of the bee colony. DWV contaminates bee products such as royal jelly, bee-bread and honey stored within the infected hive. Outside the hive, DWV has been found in pollen loads collected directly from infected as well as uninfected forager bees. It has been shown that the introduction of virus-contaminated pollen into a DWV-free hive results in the production of virus-contaminated food, whose role in the development of infected bees from virus-free eggs has been experimentally demonstrated. The aim of this study was twofold: (i) to ascertain the presence of DWV on pollen collected directly from flowers visited by honeybees and then quantify the viral load and (ii) determine whether the virus associated with pollen is infective. The results of our investigation provide evidence that DWV is present on pollen sampled directly from visited flowers and that, following injection in individuals belonging to the pollinator species Apis mellifera, it is able to establish an active infection, as indicated by the presence of replicating virus in the head of the injected bees. We also provide the first indication that the pollinator species Osmia cornuta is susceptible to DWV infection. PMID:25419704

  8. Experimental evidence for paternal effects on offspring growth rate in Arctic charr (Salvelinus alpinus)

    PubMed Central

    Eilertsen, Eirik Mack; Bårdsen, Bård-Jørgen; Liljedal, Ståle; Rudolfsen, Geir; Folstad, Ivar

    2008-01-01

    Sexual selection theory predicts that females should choose males that signal viability and quality. However, few studies have found fitness benefits among females mating with highly ornamented males. Here, we use Arctic charr (Salvelinus alpinus), a teleost fish with no parental care, to investigate whether females could gain fitness benefits by mating with highly ornamented and large-sized males. Carotenoid-based coloration signalled by males during spawning is believed to be an indicator of good genes for this species. Paternal effects on offspring size (body length and dry body mass) were examined experimentally by crossing eggs and sperm in vitro from 12 females and 24 males in a split-brood design and raising larvae to 30 days past hatching. We clearly demonstrated that there was a relationship between offspring size and paternal coloration. However, a negative interaction between paternal length and coloration was evident for offspring length, indicating that positive effects of paternal coloration were only present for smaller males. Thus, the red spawning coloration of the male Arctic charr seems to be an indicator of good genes, but the effect of paternal coloration on offspring length, an indicator of ‘offspring quality’, is size dependent. PMID:18782751

  9. Self-deception as self-signalling: a model and experimental evidence.

    PubMed

    Mijović-Prelec, Danica; Prelec, Drazen

    2010-01-27

    Self-deception has long been the subject of speculation and controversy in psychology, evolutionary biology and philosophy. According to an influential 'deflationary' view, the concept is an over-interpretation of what is in reality an instance of motivationally biased judgement. The opposite view takes the interpersonal deception analogy seriously, and holds that some part of the self actively manipulates information so as to mislead the other part. Building on an earlier self-signalling model of Bodner and Prelec, we present a game-theoretic model of self-deception. We propose that two distinct mechanisms collaborate to produce overt expressions of belief: a mechanism responsible for action selection (including verbal statements) and an interpretive mechanism that draws inferences from actions and generates emotional responses consistent with the inferences. The model distinguishes between two modes of self-deception, depending on whether the self-deceived individual regards his own statements as fully credible. The paper concludes with a new experimental study showing that self-deceptive judgements can be reliably and repeatedly elicited with financial incentives in a categorization task, and that the degree of self-deception varies with incentives. The study also finds evidence of the two forms of self-deception. The psychological benefits of self-deception, as measured by confidence, peak at moderate levels.

  10. Experimental evidence for the formation of liquid saline water on Mars

    PubMed Central

    Fischer, Erik; Martínez, Germán M; Elliott, Harvey M; Rennó, Nilton O

    2014-01-01

    Evidence for deliquescence of perchlorate salts has been discovered in the Martian polar region while possible brine flows have been observed in the equatorial region. This appears to contradict the idea that bulk deliquescence is too slow to occur during the short periods of the Martian diurnal cycle during which conditions are favorable for it. We conduct laboratory experiments to study the formation of liquid brines at Mars environmental conditions. We find that when water vapor is the only source of water, bulk deliquescence of perchlorates is not rapid enough to occur during the short periods of the day during which the temperature is above the salts' eutectic value, and the humidity is above the salts' deliquescence value. However, when the salts are in contact with water ice, liquid brine forms in minutes, indicating that aqueous solutions could form temporarily where salts and ice coexist on the Martian surface and in the shallow subsurface. Key Points The formation of brines at Martian conditions was studied experimentally Bulk deliquescence from water vapor is too slow to occur diurnally on Mars Brines form in minutes when salts are placed in direct contact with ice PMID:25821267

  11. Experimental evidence of massive-scale emotional contagion through social networks.

    PubMed

    Kramer, Adam D I; Guillory, Jamie E; Hancock, Jeffrey T

    2014-06-17

    Emotional states can be transferred to others via emotional contagion, leading people to experience the same emotions without their awareness. Emotional contagion is well established in laboratory experiments, with people transferring positive and negative emotions to others. Data from a large real-world social network, collected over a 20-y period suggests that longer-lasting moods (e.g., depression, happiness) can be transferred through networks [Fowler JH, Christakis NA (2008) BMJ 337:a2338], although the results are controversial. In an experiment with people who use Facebook, we test whether emotional contagion occurs outside of in-person interaction between individuals by reducing the amount of emotional content in the News Feed. When positive expressions were reduced, people produced fewer positive posts and more negative posts; when negative expressions were reduced, the opposite pattern occurred. These results indicate that emotions expressed by others on Facebook influence our own emotions, constituting experimental evidence for massive-scale contagion via social networks. This work also suggests that, in contrast to prevailing assumptions, in-person interaction and nonverbal cues are not strictly necessary for emotional contagion, and that the observation of others' positive experiences constitutes a positive experience for people. PMID:24889601

  12. Experimental evidence of massive-scale emotional contagion through social networks

    PubMed Central

    Kramer, Adam D. I.; Guillory, Jamie E.; Hancock, Jeffrey T.

    2014-01-01

    Emotional states can be transferred to others via emotional contagion, leading people to experience the same emotions without their awareness. Emotional contagion is well established in laboratory experiments, with people transferring positive and negative emotions to others. Data from a large real-world social network, collected over a 20-y period suggests that longer-lasting moods (e.g., depression, happiness) can be transferred through networks [Fowler JH, Christakis NA (2008) BMJ 337:a2338], although the results are controversial. In an experiment with people who use Facebook, we test whether emotional contagion occurs outside of in-person interaction between individuals by reducing the amount of emotional content in the News Feed. When positive expressions were reduced, people produced fewer positive posts and more negative posts; when negative expressions were reduced, the opposite pattern occurred. These results indicate that emotions expressed by others on Facebook influence our own emotions, constituting experimental evidence for massive-scale contagion via social networks. This work also suggests that, in contrast to prevailing assumptions, in-person interaction and nonverbal cues are not strictly necessary for emotional contagion, and that the observation of others’ positive experiences constitutes a positive experience for people. PMID:24889601

  13. Smectite clays in Mars soil - Evidence for their presence and role in Viking biology experimental results

    NASA Technical Reports Server (NTRS)

    Banin, A.; Rishpon, J.

    1979-01-01

    Evidence for the presence of smectite clays in Martian soils is reviewed and results of experiments with certain active clays simulating the Viking biology experiments are reported. Analyses of Martian soil composition by means of X-ray fluorescence spectrometry and dust storm spectroscopy and Martian geological history strongly suggest the presence of a mixture of weathered ferro-silicate minerals, mainly nontronite and montmorillonite, accompanied by soluble sulphate salts, as major constituents. Samples of montmorillonite and nontronite incubated with (C-14)-formate or the radioactive nutrient medium solution used in the Viking Labeled Release experiment, were found to produce patterns of release of radioactive gas very similar to those observed in the Viking experiments, indicating the iron-catalyzed decomposition of formate as the reaction responsible for the Viking results. The experimental results of Hubbard (1979) simulating the results of the Viking Pyrolytic Release experiment using iron montmorillonites are pointed out, and it is concluded that many of the results of the Viking biology experiments can be explained in terms of the surface activity of smectite clays in catalysis and adsorption.

  14. Life in varying environments: experimental evidence for delayed effects of juvenile environment on adult life history.

    PubMed

    Helle, Heikki; Koskela, Esa; Mappes, Tapio

    2012-05-01

    1. The effects of environment experienced during early development on phenotype as an adult has started to gain vast amounts of interest in various taxa. Some evidence on long-term effects of juvenile environment is available, but replicated experimental studies in wild animals are still lacking. 2. Here we report the first replicated experiment in wild mammals which examines the long-term effects of juvenile and adult environments on individual fitness (reproduction, survival and health). The early development of bank vole (Myodes glareolus) individuals took place in either food-supplemented or un-supplemented outdoor enclosures. After the summer, adult individuals were reciprocally changed to either a similar or opposite resource environment to overwinter. 3. Adult environment had an overriding effect on reproductive success of females so that females overwintering in food-supplemented enclosures had a higher probability of breeding and advanced the initiation of breeding. However, the characteristics of their litters were determined by juvenile environment: females initially grown in food-supplemented conditions subsequently produced larger litters with bigger pups and a male-biased sex ratio. 4. In males, individuals growing in un-supplemented conditions had the highest survival irrespective of adult environment during winter, whereas in females, neither the juvenile nor adult environments affected their survival significantly. The physiological condition of voles in spring, as determined by haematological parameters, was also differentially affected by juvenile (plasma proteins and male testosterone) and adult (haematocrit) environments. 5. Our results suggest that (i) life-history trajectories of voles are not strictly specialized to a certain environment and (ii) the plastic life-history responses to present conditions can actually be caused by delayed effects of the juvenile environment. More generally, the results are important for understanding

  15. Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature.

    PubMed

    Safonova, E V; Mitrofanov, Yu P; Konchakov, R A; Yu Vinogradov, A; Kobelev, N P; Khonik, V A

    2016-06-01

    The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to [Formula: see text] near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2-3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals. PMID:27143564

  16. Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature

    NASA Astrophysics Data System (ADS)

    Safonova, E. V.; Mitrofanov, Yu P.; Konchakov, R. A.; Vinogradov, A. Yu; Kobelev, N. P.; Khonik, V. A.

    2016-06-01

    The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to -1.5% near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2-3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals.

  17. Experimental evidence that RNA recombination occurs in the Japanese encephalitis virus

    SciTech Connect

    Chuang, C.-K.; Chen, W.-J.

    2009-11-25

    Due to the lack of a proofreading function and error-repairing ability of genomic RNA, accumulated mutations are known to be a force driving viral evolution in the genus Flavivirus, including the Japanese encephalitis (JE) virus. Based on sequencing data, RNA recombination was recently postulated to be another factor associated with genomic variations in these viruses. We herein provide experimental evidence to demonstrate the occurrence of RNA recombination in the JE virus using two local pure clones (T1P1-S1 and CJN-S1) respectively derived from the local strains, T1P1 and CJN. Based on results from a restriction fragment length polymorphism (RFLP) assay on the C/preM junction comprising a fragment of 868 nucleotides (nt 10-877), the recombinant progeny virus was primarily formed in BHK-21 cells that had been co-infected with the two clones used in this study. Nine of 20 recombinant forms of the JE virus had a crossover in the nt 123-323 region. Sequencing data derived from these recombinants revealed that no nucleotide deletion or insertion occurred in this region favoring crossovers, indicating that precisely, not aberrantly, homologous recombination was involved. With site-directed mutagenesis, three stem-loop secondary structures were destabilized and re-stabilized in sequence, leading to changes in the frequency of recombination. This suggests that the conformation, not the free energy, of the secondary structure is important in modulating RNA recombination of the virus. It was concluded that because RNA recombination generates genetic diversity in the JE virus, this must be considered particularly in studies of viral evolution, epidemiology, and possible vaccine safety.

  18. Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature

    NASA Astrophysics Data System (ADS)

    Safonova, E. V.; Mitrofanov, Yu P.; Konchakov, R. A.; Vinogradov, A. Yu; Kobelev, N. P.; Khonik, V. A.

    2016-06-01

    The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to -1.5% near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2–3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals.

  19. Experimental evidence for thermal generation of interstitials in a metallic crystal near the melting temperature.

    PubMed

    Safonova, E V; Mitrofanov, Yu P; Konchakov, R A; Yu Vinogradov, A; Kobelev, N P; Khonik, V A

    2016-06-01

    The only intrinsic point defects of simple crystalline metals known from solid state physics are vacancies and interstitials. It is widely believed that while vacancies play a major role in crystal properties and their concentration reaches relatively big values near the melting temperature T m, interstitials essentially do not occur in thermodynamic equilibrium and their influence on properties is minor. Here, taking aluminum single crystals as an example, we present compelling experimental evidence for rapid thermoactivated growth of interstitial concentration upon approaching T m. Using high precision measurements of the shear modulus we found a diaelastic effect of up to [Formula: see text] near T m. It is argued that this effect is mostly due to the generation of dumbbell (split) interstitials. The interstitial concentration c i rapidly increases upon approaching T m and becomes only 2-3 times smaller than that of vacancies just below T m. The reason for this c i -increase is conditioned by a decrease of the Gibbs free energy with temperature, which in turn originates from the high formation entropy of dumbbell interstitials and a decrease of their formation enthalpy at high c i . Special molecular dynamic simulation confirmed all basic aspects of the proposed interpretation. The results obtained (i) demonstrate the significance of interstitial concentration near T m that could lead to the revaluation of vacancy concentration at high temperatures, (ii) suggest that dumbbell interstitials play a major role in the melting mechanism of monatomic metallic crystals and (iii) support a new avenue for in-depth understanding of glassy metals.

  20. Scientific Reasoning in Early and Middle Childhood: The Development of Domain-General Evidence Evaluation, Experimentation, and Hypothesis Generation Skills

    ERIC Educational Resources Information Center

    Piekny, Jeanette; Maehler, Claudia

    2013-01-01

    According to Klahr's (2000, 2005; Klahr & Dunbar, 1988) Scientific Discovery as Dual Search model, inquiry processes require three cognitive components: hypothesis generation, experimentation, and evidence evaluation. The aim of the present study was to investigate (a) when the ability to evaluate perfect covariation, imperfect…

  1. Experimental evidence for asymmetric mate preference and aggression: behavioral interactions in a woodrat (Neotoma) hybrid zone

    PubMed Central

    2013-01-01

    Background Female mate preferences may be under strong selection in zones of contact between closely related species because of greater variation in available mates and the potential costs of hybridization. We studied female mate preferences experimentally in a zone of secondary contact between Desert and Bryant’s Woodrat (Neotoma lepida and N. bryanti) in the southern foothills of the Sierra Nevada of California. We tested female preference for conspecific versus heterospecific males in paired choice trials in which females could interact freely with males, but males could not interact directly with each other. We compared preferences of females from both allopatric and sympatric sites. Results We did not find evidence of the process of reinforcement as assortative preferences were not stronger in sympatry than in allopatry. Mate preferences, however, were asymmetric, with N. lepida females mating preferentially with conspecifics and N. bryanti females showing no preference by species. Sympatric females were less likely to mate than allopatric females, due in part to an increase in aggressive interactions. However, even in the absence of aggression, courtship led to mating less often in sympatric females, suggesting they were choosier or had lower sexual motivation than allopatric females. Conclusions Patterns of mate choice in this woodrat system appear to be strongly impacted by body size and aggressive behavior. In particular, females of the smaller-bodied species rarely interact with the relatively large heterospecific males. In contrast females of the larger-bodied species accept the relatively small heterospecific males. For sympatric animals, rates of aggression were markedly higher than for allopatric animals and reduced affiliative and reproductive behavior in our trials. Sympatric animals are larger and more aggressive, traits that are likely under strong ecological selection across the sharp resource gradient that characterizes the contact zone

  2. On the early emergence of reverse transcription: theoretical basis and experimental evidence

    NASA Technical Reports Server (NTRS)

    Lazcano, A.; Valverde, V.; Hernandez, G.; Gariglio, P.; Fox, G. E.; Oro, J.

    1992-01-01

    Reverse transcriptase (RT) was first discovered as an essential catalyst in the biological cycle of retroviruses. However, in the past years evidence has accumulated showing that RTs are involved in a surprisingly large number of RNA-mediated transpositional events that include both viral and nonviral genetic entities. Although it is probable that some RT-bearing genetic elements like the different types of AIDS viruses and the mammalian LINE family have arisen in recent geological times, the possibility that reverse transcription first took place in the early Archean is supported by (1) the hypothesis that RNA preceded DNA as cellular genetic material; (2) the existence of homologous regions of the subunit tau of the E. coli DNA polymerase III with the simian immunodeficiency virus RT, the hepatitis B virus RT, and the beta' subunit of the E. coli RNA polymerase (McHenry et al. 1988); (3) the presence of several conserved motifs, including a 14-amino-acid segment that consists of an Asp-Asp pair flanked by hydrophobic amino acids, which are found in all RTs and in most cellular and viral RNA polymerases. However, whether extant RTs descend from the primitive polymerase involved in the RNA-to-DNA transition remains unproven. Substrate specificity of the AMV and HIV-1 RTs can be modified in the presence of Mn2+, a cation which allows them to add ribonucleotides to an oligo (dG) primer in a template-dependent reaction. This change in specificity is comparable to that observed under similar conditions in other nucleic acid polymerases. This experimentally induced change in RT substrate specificity may explain previous observations on the misincorporation of ribonucleotides by the Maloney murine sarcoma virus RT in the minus and plus DNA of this retrovirus (Chen and Temin 1980). Our results also suggest that HIV-infected macrophages and T-cell cells may contain mixed polynucleotides containing both ribo- and deoxyribonucleotides. The evolutionary significance of these

  3. Pursuing Quality Evidence: Applying Single-Subject Quality Indicators to Non-Experimental Qualitative Educational Research

    ERIC Educational Resources Information Center

    Stodden, Robert A.; Yamamoto, Kathryn K.; Folk, Eric; Kong, Eran; Otsuji, Derek N.

    2013-01-01

    The need for quality evidence in support of strategies used while working with persons with autism and intellectual disability (ID) has been long been recognized by researchers and practitioners. The authors reviewed and applied a number of evidence-based indicators, developed through the "What Works Clearinghouse" (WWC), to the conduct…

  4. Chemopreventive properties of 3,3'-diindolylmethane in breast cancer: evidence from experimental and human studies.

    PubMed

    Thomson, Cynthia A; Ho, Emily; Strom, Meghan B

    2016-07-01

    Diet is a modifiable factor associated with the risk of several cancers, with convincing evidence showing a link between diet and breast cancer. The role of bioactive compounds of food origin, including those found in cruciferous vegetables, is an active area of research in cancer chemoprevention. This review focuses on 3,3'-diindolylmethane (DIM), the major bioactive indole in crucifers. Research of the cancer-preventive activity of DIM has yielded basic mechanistic, animal, and human trial data. Further, this body of evidence is largely supported by observational studies. Bioactive DIM has demonstrated chemopreventive activity in all stages of breast cancer carcinogenesis. This review describes current evidence related to the metabolism and mechanisms of DIM involved in the prevention of breast cancer. Importantly, this review also focuses on current evidence from human observational and intervention trials that have contributed to a greater understanding of exposure estimates that will inform recommendations for DIM intake. PMID:27261275

  5. Experimental Evidence Linking Elevated CO2, Rhizosphere C/N Stoichiometry and Microbial Efficiency

    NASA Astrophysics Data System (ADS)

    Carrillo, Y.; Dijkstra, F. A.; Pendall, E.; LeCain, D. R.; Morgan, J.

    2012-12-01

    expected to be more efficient in their C use. Decreasing the C/N ratio of roots decreased SOM respiration and increased the efficiency of SOM-consuming microbes. Direct N additions had a similar but stronger effect. Increased C efficiency with greater nutrient availability is consistent with theoretical expectations of C utilization under nutrient limitation. Notably, the response of C use to N treatments occurred only under eCO2 conditions. This functional contrast was supported by differential responses of microbial PLFA profiles to N treatments under CO2 treatments. Together, these results suggest that the eCO2 environment was more conducive to N limitation, via changes in microbial community structure and function. Our results provide direct experimental evidence of plant-mediated alteration of decomposer C efficiency due to changes in atmospheric CO2 and N availability from both plant and soil sources. An increase in SOM-consuming microbes efficiency in an eCO2 world is likely to have important ecosystem-level implications as it could enhance the amount of C that remains in soil relative to the amount released to the atmosphere. The interactive effects of CO2 and N treatments suggest that microbial efficiency will be more sensitive to changes in nutrient status under the future eCO2 atmosphere.

  6. Counter-intuitive experimental evidence on the initiation of radical crack in ceramic thin films at the atomic scale

    SciTech Connect

    Zhuang, Chunqiang Li, Zhipeng; Lin, Songsheng

    2015-10-15

    The basic issue related to radial crack in ceramic thin films has received considerable attention due to the fact that the radial crack plays an important role in evaluating the toughness properties of ceramic materials. In this work, an atomic-scale new experimental evidence is clearly presented to reveal the counter-intuitive initiation, the nucleation and the propagation mechanism of the radial crack in Al-Cr-N ceramic thin films.

  7. Counter-intuitive experimental evidence on the initiation of radical crack in ceramic thin films at the atomic scale

    NASA Astrophysics Data System (ADS)

    Zhuang, Chunqiang; Li, Zhipeng; Lin, Songsheng

    2015-10-01

    The basic issue related to radial crack in ceramic thin films has received considerable attention due to the fact that the radial crack plays an important role in evaluating the toughness properties of ceramic materials. In this work, an atomic-scale new experimental evidence is clearly presented to reveal the counter-intuitive initiation, the nucleation and the propagation mechanism of the radial crack in Al-Cr-N ceramic thin films.

  8. Long-Term Effects of Teacher Performance Pay: Experimental Evidence from India

    ERIC Educational Resources Information Center

    Muralidharan, Karthik

    2012-01-01

    While the idea of teacher performance-pay is increasingly making its way into policy, the evidence on the effectiveness of such programs is both limited and mixed. The central questions in the literature on teacher performance pay to date have been whether teacher performance pay based on test scores can improve student achievement, and whether…

  9. Teacher Incentives in Developing Countries: Experimental Evidence from India. Working Paper 2008-13

    ERIC Educational Resources Information Center

    Muralidharan, Karthik; Sundararaman, Venkatesh

    2008-01-01

    Performance pay for teachers is frequently suggested as a way of improving educational outcomes in schools, but the empirical evidence to date on its effectiveness is limited and mixed. We present results from a randomized evaluation of a teacher incentive program implemented across a representative sample of government-run rural primary schools…

  10. Evidence for Tempo-Specific Timing in Music Using a Web-Based Experimental Setup

    ERIC Educational Resources Information Center

    Honing, Henkjan

    2006-01-01

    Perceptual invariance has been studied and found in several domains of cognition, including those of speech, motor behavior, and object motion. It has also been the topic of several studies in music perception. However, the existing perceptual studies present rather inconclusive evidence with regard to the perceptual invariance of expressive…

  11. Teacher Performance Pay: Experimental Evidence from India. NBER Working Paper No. 15323

    ERIC Educational Resources Information Center

    Muralidharan, Karthik; Sundararaman, Venkatesh

    2009-01-01

    Performance pay for teachers is frequently suggested as a way of improving education outcomes in schools, but the theoretical predictions regarding its effectiveness are ambiguous and the empirical evidence to date is limited and mixed. We present results from a randomized evaluation of a teacher incentive program implemented across a large…

  12. Persistence of Learning Gains from Computer Assisted Learning: Experimental Evidence from China

    ERIC Educational Resources Information Center

    Mo, D.; Zhang, L.; Wang, J.; Huang, W.; Shi, Y.; Boswell, M.; Rozelle, S.

    2015-01-01

    Computer assisted learning (CAL) programs have been shown to be effective in improving educational outcomes. However, the existing studies on CAL have almost all been conducted over a short period of time. There is very little evidence on how the impact evolves over time. In response, we conducted a clustered randomized experiment involving 2741…

  13. The price elasticity of demand for heroin: Matched longitudinal and experimental evidence.

    PubMed

    Olmstead, Todd A; Alessi, Sheila M; Kline, Brendan; Pacula, Rosalie Liccardo; Petry, Nancy M

    2015-05-01

    This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately -0.80. PMID:25702687

  14. The price elasticity of demand for heroin: matched longitudinal and experimental evidence#

    PubMed Central

    Olmstead, Todd A.; Alessi, Sheila M.; Kline, Brendan; Pacula, Rosalie Liccardo; Petry, Nancy M.

    2015-01-01

    This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally-induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately −0.80. PMID:25702687

  15. Impacts of children with troubles on working poor families: mixed-method and experimental evidence.

    PubMed

    Bernheimer, Lucinda P; Weisner, Thomas S; Lowe, Edward D

    2003-12-01

    Mixed-method and experimental data on working poor families and children with troubles participating in the New Hope anti-poverty experimental initiative in Milwaukee are described. Sixty percent of these families had at least one child who had significant problems (learning, school achievement and/or behavior, home behavior, retardation, other disabilities). Control group families with children who had troubles had more difficulties in sustaining their family routine than did New Hope experimental families. In the context of the many other challenges these parents face, adaptation to children with troubles does not stand out as sharply compared to middle-class European American families. There is less family adaptation specifically due to, or in response to, the troubled child, and more adaptation to the struggles of making ends meet.

  16. Qualitative experimental evidences for the thermal wave mechanisms of temperature oscillations in living tissues

    NASA Astrophysics Data System (ADS)

    Liu, Jing; Ren, Zepei; Wang, Cuncheng; Sun, Xingguo

    1996-12-01

    To make it possible for the thermal wave theory on temperature oscillation (TO) effects in living tissues to be founded on the substantial experimental basis, a series of typical decisive experiments in vivo as well as in artificially simulating constructions were carried out. Conclusions obtained including some other scholars’ animal experimental results all greatly support the thermal wave viewpoint qualitatively. A few experimental facts used not to be easily understood from the classical viewpoint are also well reinterpreted. The revealing on the thermal wave mechanisms of TO in living tissues is a brand new discovery and deep insight into this important thermophysiological phenomenon. It may possibly promote new investigations on the corresponding topics in the field of bioheat transfer science.

  17. The price elasticity of demand for heroin: Matched longitudinal and experimental evidence.

    PubMed

    Olmstead, Todd A; Alessi, Sheila M; Kline, Brendan; Pacula, Rosalie Liccardo; Petry, Nancy M

    2015-05-01

    This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately -0.80.

  18. Psychoneuroimmunology: an interpretation of experimental and case study evidence towards a paradigm for predictable results.

    PubMed

    Kalt, H W

    2000-07-01

    This paper surveys a number of key experiments and case studies relating to psychoneuroimmunology. It finds that most techniques to influence or even direct the immune system via the mind fall into a series of theoretical categories called passive, active and targeted effects. By examining the results of experiments and studies in the light of these categories a number of important conclusions are drawn. These conclusions explain differences in experimental results, describe those variables that appear to be central to obtaining results, and describe in detail where experimentation should be concentrated to further knowledge of psychoneuroimmunology.

  19. Income Mobility Breeds Tolerance for Income Inequality: Cross-National and Experimental Evidence.

    PubMed

    Shariff, Azim F; Wiwad, Dylan; Aknin, Lara B

    2016-05-01

    American politicians often justify income inequality by referencing the opportunities people have to move between economic stations. Though past research has shown associations between income mobility and resistance to wealth redistribution policies, no experimental work has tested whether perceptions of mobility influence tolerance for inequality. In this article, we present a cross-national comparison showing that income mobility is associated with tolerance for inequality and experimental work demonstrating that perceptions of higher mobility directly affect attitudes toward inequality. We find support for both the prospect of upward mobility and the view that peoples' economic station is the product of their own efforts, as mediating mechanisms.

  20. Experimental evidence of skyrmion-like configurations in bilayer nanodisks with perpendicular magnetic anisotropy

    SciTech Connect

    Stebliy, Maxim E. Kolesnikov, Alexander G.; Davydenko, Alexander V.; Ognev, Alexey V.; Samardak, Alexander S.; Chebotkevich, Ludmila A.

    2015-05-07

    Formation and existence of magnetic skyrmion-like configurations in bilayer nanodisks (Ta(3 nm)/[Co(0.37 nm)/Ni(0.58 nm)]{sub 10}){sub 2} with perpendicular magnetic anisotropy are shown experimentally at room temperature. Magnetization reversal through the skyrmion state is studied using magnetic hysteresis measurements. An evolution of skyrmion configurations in the nanodisk structure is analyzed. Experimental methods and micromagnetic simulations help to understand the magnetization reversal processes occurring through the stable skyrmion-like configurations. Formation of the intermediate C-states during magnetization reversal is demonstrated. The skyrmion number for all possible spin configurations is calculated.

  1. Verb Form Indicates Discourse Segment Type in Biological Research Papers: Experimental Evidence

    ERIC Educational Resources Information Center

    de Waard, Anita; Maat, Henk Pander

    2012-01-01

    Corpus studies suggest that verb tense is a differentiating feature between, on the one hand, text pertaining to experimental results (involving methods and results) and on the other hand, text pertaining to more abstract concepts (i.e. regarding background knowledge in a field, hypotheses, problems or claims). In this paper, we describe a user…

  2. Experimental evidence for the accumulation of egg pigment in the brain cavities of Xenopus tadpoles.

    PubMed

    Kordylewski, L

    1983-07-01

    The origin and fate of darkly pigmented clusters of cells that float freely in the brain cavities of the tadpoles of Xenopus laevis have been experimentally investigated. The results point to the conclusion that the clusters are the sites of egg pigment accumulation, which remain within the brain cavities or at its walls until metamorphosis.

  3. Experimental Evidence for Dynamic Social Impact: The Emergence of Subcultures in Electronic Groups.

    ERIC Educational Resources Information Center

    Latane, Bibb; Bourgeois, Martin J.

    1996-01-01

    Presents results of experimental tests of Dynamic Social Impact Theory (DSIT) in which participants engaged in discussions over electronic mail. Finds support for the emergence of four group phenomena predicted by DSIT. Shows how, rewarded for being in the majority, individuals' choices resulted in the emergence of four forms of group level…

  4. Teacher Pay for Performance: Experimental Evidence from the Project on Incentives in Teaching (POINT)

    ERIC Educational Resources Information Center

    Springer, Matthew G.; Ballou, Dale; Hamilton, Laura; Le, Vi-Nhuan; Lockwood, J. R.; McCaffrey, Daniel F.; Pepper, Matthew; Stecher, Brian M.

    2011-01-01

    This paper presents the results of a rigorous experiment examining the impact of pay for performance on student achievement and instructional practice. This study, conducted by the National Center on Performance Incentives in partnership with the RAND Corporation examines an experimental pay for performance program administered via a randomized…

  5. Mimicking Aphasic Semantic Errors in Normal Speech Production: Evidence from a Novel Experimental Paradigm

    ERIC Educational Resources Information Center

    Hodgson, Catherine; Lambon Ralph, Matthew A.

    2008-01-01

    Semantic errors are commonly found in semantic dementia (SD) and some forms of stroke aphasia and provide insights into semantic processing and speech production. Low error rates are found in standard picture naming tasks in normal controls. In order to increase error rates and thus provide an experimental model of aphasic performance, this study…

  6. The Effects of Television Advertising on Children. Report No. 2: Second Year Experimental Evidence. Final Report.

    ERIC Educational Resources Information Center

    Atkin, Charles K.

    This report, the second in a series of six reports on television advertising and children, presents the results from a series of experimental studies designed to test children's intentional and incidental learning from television commercials. A total of 400 elementary school students of varying socioeconomic status participated in the study, with…

  7. Interferometric identification of very near objects by using Fourier analysis: experimental evidence

    NASA Astrophysics Data System (ADS)

    Castañeda, Román; Giraldo, Javier; Arenas, Germán

    2000-09-01

    Experimental results are shown to confirm the interferometric resolution method reported in Ref. 1 [R. Castañeda, J. Giraldo, G. Arenas, On the use of Fourier analysis for the interferometric identification of very near objects, Opt. Commun. 174 (2000) 335-345]. Very near Young's slit pairs coherently illuminated can be resolved by applying this method.

  8. Evidence That Counts: 12 Teacher-Led Randomised Controlled Trials and Other Styles of Experimental Research

    ERIC Educational Resources Information Center

    Churches, Richard; McAleavy, Tony

    2016-01-01

    This publication contains 12 (A3 open-out) poster-style reports of teacher experimental research. The style of presentation parallels the type of preliminary reporting common at academic conferences and postgraduate events. At the same time, it aims to act as a form of short primer to introduce teachers to the basic options that there are when…

  9. Experimental Evaluations of Elementary Science Programs: A Best-Evidence Synthesis

    ERIC Educational Resources Information Center

    Slavin, Robert E.; Lake, Cynthia; Hanley, Pam; Thurston, Allen

    2014-01-01

    This article presents a systematic review of research on the achievement outcomes of all types of approaches to teaching science in elementary schools. Study inclusion criteria included use of randomized or matched control groups, a study duration of at least 4 weeks, and use of achievement measures independent of the experimental treatment. A…

  10. Oxytocin and Major Depressive Disorder: Experimental and Clinical Evidence for Links to Aetiology and Possible Treatment

    PubMed Central

    Slattery, David A.; Neumann, Inga D.

    2010-01-01

    Affective disorders represent the most common psychiatric diseases, with substantial co-morbidity existing between major depressive disorders (MDD) and anxiety disorders. The lack of truly novel acting compounds has led to non-monoaminergic based research and hypotheses in recent years. The large number of brain neuropeptides, characterized by discrete synthesis sites and multiple receptors, represent likely research candidates for novel therapeutic targets. The present review summarises the available preclinical and human evidence regarding the neuropeptide, oxytocin, and its implications in the aetiology and treatment of MDD. While the evidence is not conclusive at present additional studies are warranted to determine whether OXT may be of therapeutic benefit in subsets of MDD patients such as those with comorbid anxiety symptoms and low levels of social attachment. PMID:27713275

  11. Gluconeogenesis in the ruminant fetus: evaluation of conflicting evidence from radiotracer and other experimental techniques

    SciTech Connect

    Prior, R.L.

    1982-01-01

    Conflicting evidence exists as to whether the gluconeogenetic process is active in the late gestation fetal lamb. In vitro evidence based on measurements of enzyme activity and substrate flux into glucose indicates that the capacity for gluconeogenesis exists in fetal liver. The in vivo conversion of (/sup 14/C)lactate and (/sup 14/C)alanine into glucose in the lamb fetus has been demonstrated. Lactate and alanine account for 49 and 2.3% of the fetal glucose pool, respectively. Although gluconeogenesis can occur in the fetal lamb, alterations in net rates of umbilical uptake of glucose or lactate, fetal blood glucose concentrations, fetal or maternal glucose replacement rates, or maternal nutrition may alter the observed rates of fetal gluconeogenesis.

  12. Genetic susceptibility to retinopathy of prematurity: the evidence from clinical and experimental animal studies.

    PubMed

    Holmström, Gerd; van Wijngaarden, Peter; Coster, Douglas J; Williams, Keryn A

    2007-12-01

    Despite advances in management and treatment, retinopathy of prematurity remains a major cause of childhood blindness. Evidence for a genetic basis for susceptibility to retinopathy of prematurity is examined, including the influences of sex, ethnicity, and ocular pigmentation. The role of polymorphisms is explored in the genes for vascular endothelial growth factor and insulin-like growth factor-1, and of mutations in the Norrie disease gene. Insights into the genetic basis of retinopathy of prematurity provided by the animal model of oxygen induced retinopathy are examined. Evidence for a genetic component for susceptibility to retinopathy of prematurity is strong, although the molecular identity of the gene or genes involved remains uncertain. PMID:18024814

  13. Experimental evidence in support of Joule heating associated with geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Devries, L. L.

    1971-01-01

    High resolution accelerometer measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is the primary source of energy for atmospheric heating associated with geomagnetic activity. This conclusion is supported by the following observational evidence: (1) There is an atmospheric response in the auroral zone which is nearly simulataneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) The maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) There is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur. An analysis of atmospheric response time to this heat shows time delays are apparently independent of altitude but are strongly dependent upon geomagnetic latitude.

  14. Oxytocin and Major Depressive Disorder: Experimental and Clinical Evidence for Links to Aetiology and Possible Treatment

    PubMed Central

    Slattery, David A.; Neumann, Inga D.

    2010-01-01

    Affective disorders represent the most common psychiatric diseases, with substantial co-morbidity existing between major depressive disorders (MDD) and anxiety disorders. The lack of truly novel acting compounds has led to non-monoaminergic based research and hypotheses in recent years. The large number of brain neuropeptides, characterized by discrete synthesis sites and multiple receptors, represent likely research candidates for novel therapeutic targets. The present review summarises the available preclinical and human evidence regarding the neuropeptide, oxytocin, and its implications in the aetiology and treatment of MDD. While the evidence is not conclusive at present additional studies are warranted to determine whether OXT may be of therapeutic benefit in subsets of MDD patients such as those with comorbid anxiety symptoms and low levels of social attachment.

  15. Work toward experimental evidence of hard x-ray photoionization in highly charged krypton.

    SciTech Connect

    Silver, E.; Gillaspy, J.D.; Gokhale, P.; Kanter, E.P.; Brickhouse, N.S.; Dunford, R.W.; Kirby, K.; Lin, T.; McDonald, J.; Schneider, D.; Seifert, S.; Young, L.

    2011-06-01

    Ions of almost any charge state can be produced through electron-impact ionization. Here we describe our first experiments designed to photoionize these highly charged ions with hard x-rays by pairing an electron and photon beam. A spectral line at 12.7(1) keV with an intensity corroborated by theory may be the first evidence of hard x-ray photoionization of a highly charged ion.

  16. Experimental evidence of resonant tunneling via localized DQW states in an asymmetric triple barrier structure

    NASA Astrophysics Data System (ADS)

    Velásquez, Rober

    2003-04-01

    In this work we report on field-induced features appearing in the tunneling current traces of a biased asymmetric triple barrier resonant tunneling device in the presence of an in-plane magnetic field. A theoretical model that satisfactorily explains the origin of these features is discussed. The reported data evidences the localized nature of the quantum states in thin layer asymmetric double-quantum-well structures.

  17. Work Towards Experimental Evidence Of Hard X-Ray Photoionization In Highly Charged Krypton

    SciTech Connect

    Silver, E.; Brickhouse, N. S.; Kirby, K.; Lin, T.; Gillaspy, J. D.; Gokhale, P.; Kanter, E. P.; Dunford, R. W.; Seifert, S.; Young, L.; McDonald, J.; Schneider, D.

    2011-06-01

    Ions of almost any charge state can be produced through electron-impact ionization. Here we describe our first experiments designed to photoionize these highly charged ions with hard x-rays by pairing an electron and photon beam. A spectral line at 12.7(1) keV with an intensity corroborated by theory may be the first evidence of hard x-ray photoionization of a highly charged ion.

  18. Memories affect mood: evidence from covert experimental assignment to positive, neutral, and negative memory recall.

    PubMed

    Gillihan, Seth J; Kessler, Jennifer; Farah, Martha J

    2007-06-01

    Memory recall has been proposed as a common and effective mood regulation strategy. Although several studies have presented results suggesting that recalling valenced memories affects subsequent mood, their designs allow for alternative interpretations of the observed effects. Two such alternatives include the reverse effect (mood effects on memory due to non-experimental assignment to memory recall condition) and demand characteristics of the experiment. We used covert experimental assignment to memory condition, asking subjects (N=314; 56% female) to recall memories that were primarily positive, neutral, or negative. Results showed the expected effect on mood (p<.002), with reported mood worst in the negative memory condition, better in the neutral condition, and best in the positive condition. These results suggest that valenced memory recall does indeed exert an effect on mood, and may do so even without the individual's awareness.

  19. Theoretical and experimental evidence of non-symmetric doubly localized rogue waves

    PubMed Central

    He, Jingsong; Guo, Lijuan; Zhang, Yongshuai; Chabchoub, Amin

    2014-01-01

    We present determinant expressions for vector rogue wave (RW) solutions of the Manakov system, a two-component coupled nonlinear Schrödinger (NLS) equation. As a special case, we generate a family of exact and non-symmetric RW solutions of the NLS equation up to third order, localized in both space and time. The derived non-symmetric doubly localized second-order solution is generated experimentally in a water wave flume for deep-water conditions. Experimental results, confirming the characteristic non-symmetric pattern of the solution, are in very good agreement with theory as well as with numerical simulations, based on the modified NLS equation, known to model accurately the dynamics of weakly nonlinear wave packets in deep water. PMID:25383023

  20. Experimental Evidence of Weak Excluded Volume Effects for Nanochannel Confined DNA

    NASA Astrophysics Data System (ADS)

    Gupta, Damini; Miller, Jeremy J.; Muralidhar, Abhiram; Mahshid, Sara; Reisner, Walter; Dorfman, Kevin D.

    In the classical de Gennes picture of weak polymer nanochannel confinement, the polymer contour is envisioned as divided into a series of isometric blobs. Strong excluded volume interactions are present both within a blob and between blobs. In contrast, for semiflexible polymers like DNA, excluded volume interactions are of borderline strength within a blob but appreciable between blobs, giving rise to a chain description consisting of a string of anisometric blobs. We present experimental validation of this subtle effect of excluded volume for DNA nanochannel confinement by performing measurements of variance in chain extension of T4 DNA molecules as a function of effective nanochannel size (305-453 nm). Additionally, we show an approach to systematically reduce the effect of molecular weight dispersity of DNA samples, a typical experimental artifact, by combining confinement spectroscopy with simulations.

  1. Experimental evidence of Xe incorporation in Schottky defects in UO{sub 2}

    SciTech Connect

    Bès, René; Martin, Philippe Vathonne, Emerson; Delorme, Rémy; Sabathier, Catherine; Freyss, Michel; Bertolus, Marjorie; Glatzel, Pieter

    2015-03-16

    We report here the direct experimental observation of the preferential xenon incorporation site in uranium dioxide and analyse how its incorporation evolves with the annealing temperature. We show that High Energy Resolution Fluorescence Detection X-ray Absorption Near Edge Structure in combination with first-principles calculations enable a precise determination of the Xe incorporation site. Our finding provides important insight for the understanding and modeling of noble gases behavior in nuclear oxide fuel.

  2. Recent experimental evidence for the Los Alamos proton storage ring beam instability

    SciTech Connect

    Plum, M.A.; Fitzgerald, D.H.; Johnson, D.

    1997-09-01

    The peak intensity of the PSR is limited by a fast transverse instability. In 1996 the authors started a project to upgrade the PSR to 200 {mu}A at 30 Hz, which requires operation above the instability threshold achieved with the present rf system. The authors have, therefore, resumed their experimental program to understand and control the instability. In this paper they will present their latest data.

  3. Colloid-induced kidney injury: experimental evidence may help to understand mechanisms.

    PubMed

    Schortgen, Frédérique; Brochard, Laurent

    2009-01-01

    Fluid resuscitation is widely used, and many patients are therefore exposed to plasma volume expanders. Among these, colloids, particularly hydroxyethyl starches, have been shown in recent experiments and clinical studies to induce acute kidney injury. The mechanisms of colloid-induced acute kidney injury remain incompletely elucidated. The risks associated with colloid osmotic pressure elevation in vivo and the high incidence of osmotic nephrosis lesions in experimental models and clinical studies indicate that hydroxyethyl starches can no longer be considered safe.

  4. Infiltration on sloping surfaces: Laboratory experimental evidence and implications for infiltration modeling

    NASA Astrophysics Data System (ADS)

    Morbidelli, Renato; Saltalippi, Carla; Flammini, Alessia; Cifrodelli, Marco; Corradini, Corrado; Govindaraju, Rao S.

    2015-04-01

    Infiltration on sloping surfaces occupies an important role in our understanding of surface and subsurface hydrology. Previous studies have provided conflicting results about the role of slope on infiltration. Here, our main objective is to highlight, by well-controlled experiments, the slope role in the absence of the conflicting contributions generated by other physical processes observed in previous studies under natural or laboratory conditions. The experimental program was designed to resolve some of the confounding factors such as lower impermeable boundary condition, range of rainfall rates relative to soil saturated hydraulic conductivity, surface sealing, and erosion of top soil. The experimental apparatus consists of a box containing a natural bare soil with slope angle γ chosen between 0° and 10°, two sensors of surface and deep flow, one probe for moisture content and an artificial rainfall generator. The primary experimental results suggest that under steady conditions and rainfall rate, r, greater than saturated hydraulic conductivity, Ks, the deep flow, Qd, decreases with increasing slope angle, γ, up to a value leading to Qd(γ = 1°)/Qd(γ = 10°) equal to ≈4 which is in contrast with the results provided in a few earlier papers. Furthermore, in sloping bare soils surface runoff is produced even for r < Ks. Finally, we discuss the link between Qd(γ) and the shear stress at the soil surface as a guideline in the determination of an effective saturated hydraulic conductivity to be incorporated in the existing horizontal infiltration models.

  5. Investigation of a model vertical motion liquid damper: comparing numerical simulation and experimental evidence

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Chris; Tabatabai, Habib; Buechel, Craig

    2005-05-01

    Tuned Liquid Dampers (TLD) are used to limit horizontal vibrations in structures, and offer practical alternatives to Tuned Mass Dampers (TMD). However, to our knowledge, liquid damping systems have not been developed to reduce vertical vibrations. In this work, we develop a model for a Vertical Motion Liquid Damper (VMLD), idealized as a discrete, two degree of freedom system. One degree of freedom represents the 'target' structure that is to be damped, and the other represents the approximate, one-dimensional motion of a liquid in a U-shaped tube. Internal losses due to the fluid oscillation serve to limit and control motions of the target structure. The U-shaped tube has a flexible joint such that one vertical portion and the horizontal portion of the tube remain fixed, and the remaining vertical portion of the tube is affixed to the vibrating structure, allowing the liquid to become excited. The equations of motion are derived using Lagrange's Equations, and are integrated using Runge-Kutta algorithms that are available in Matlab. An experimental model was built in the laboratory, consisting of a mass attached to the end of a cantilevered beam (corresponding to the target structure), and a U-tube made from PVC pipe. The various damping and stiffness parameters of the system were calibrated independently based on experimental data. Measured data from the experimental model show reasonable agreement with numerical simulations.

  6. Experimental evidence of icosahedral and decahedral packing in one-dimensional nanostructures.

    PubMed

    Velázquez-Salazar, J Jesús; Esparza, Rodrigo; Mejía-Rosales, Sergio Javier; Estrada-Salas, Rubén; Ponce, Arturo; Deepak, Francis Leonard; Castro-Guerrero, Carlos; José-Yacamán, Miguel

    2011-08-23

    The packing of spheres is a subject that has drawn the attention of mathematicians and philosophers for centuries and that currently attracts the interest of the scientific community in several fields. At the nanoscale, the packing of atoms affects the chemical and structural properties of the material and, hence, its potential applications. This report describes the experimental formation of 5-fold nanostructures by the packing of interpenetrated icosahedral and decahedral units. These nanowires, formed by the reaction of a mixture of metal salts (Au and Ag) in the presence of oleylamine, are obtained when the chemical composition is specifically Ag/Au = 3:1. The experimental images of the icosahedral nanowires have a high likelihood with simulated electron micrographs of structures formed by two or three Boerdijk-Coxeter-Bernal helices roped on a single structure, whereas for the decahedral wires, simulations using a model of adjacent decahedra match the experimental structures. To our knowledge, this is the first report of the synthesis of nanowires formed by the packing of structures with 5-fold symmetry. These icosahedral nanowire structures are similar to those of quasicrystals, which can only be formed if at least two atomic species are present and in which icosahedral and decahedral packing has been found for bulk crystals.

  7. Experimental evidence for strong stabilizing forces at high functional diversity of aquatic microbial communities.

    PubMed

    Carrara, Francesco; Giometto, Andrea; Seymour, Mathew; Rinaldo, Andrea; Altermatt, Florian

    2015-05-01

    Unveiling the mechanisms that promote coexistence in biological communities is a fundamental problem in ecology. Stable coexistence of many species is commonly observed in natural communities. Most of these natural communities, however, are composed of species from multiple trophic and functional groups, while theory and experiments on coexistence have been focusing on functionally similar species. Here, we investigated how functional diversity affects the stability of species coexistence and productivity in multispecies communities by characterizing experimentally all pairwise species interactions in a pool of 11 species of eukaryotes (10 protists and one rotifer) belonging to three different functional groups. Species within the same functional group showed stronger competitive interactions compared to among-functional group interactions. This often led to competitive exclusion between species that had higher functional relatedness, but only at low levels of species richness. Communities with higher functional diversity resulted in increased species coexistence and community biomass production. Our experimental findings and the results of a stochastic model tailored to the experimental interaction matrix suggest the emergence of strong stabilizing forces when species from different functional groups interact in a homogeneous environment. By combining theoretical analysis with experiments we could also disentangle the relationship between species richness and functional diversity, showing that functional diversity per se is a crucial driver of productivity and stability in multispecies community.

  8. Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers.

    PubMed

    Braudrick, Christian A; Dietrich, William E; Leverich, Glen T; Sklar, Leonard S

    2009-10-01

    Meandering rivers are common on Earth and other planetary surfaces, yet the conditions necessary to maintain meandering channels are unclear. As a consequence, self-maintaining meandering channels with cutoffs have not been reproduced in the laboratory. Such experimental channels are needed to explore mechanisms controlling migration rate, sinuosity, floodplain formation, and planform morphodynamics and to test theories for wavelength and bend propagation. Here we report an experiment in which meandering with near-constant width was maintained during repeated cutoff and regeneration of meander bends. We found that elevated bank strength (provided by alfalfa sprouts) relative to the cohesionless bed material and the blocking of troughs (chutes) in the lee of point bars via suspended sediment deposition were the necessary ingredients to successful meandering. Varying flood discharge was not necessary. Scaling analysis shows that the experimental meander migration was fast compared to most natural channels. This high migration rate caused nearly all of the bedload sediment to exchange laterally, such that bar growth was primarily dependent on bank sediment supplied from upstream lateral migration. The high migration rate may have contributed to the relatively low sinuosity of 1.19, and this suggests that to obtain much higher sinuosity experiments at this scale may have to be conducted for several years. Although patience is required to evolve them, these experimental channels offer the opportunity to explore several fundamental issues about river morphodynamics. Our results also suggest that sand supply may be an essential control in restoring self-maintaining, actively shifting gravel-bedded meanders.

  9. Experimental evidence for the role of accessory phases in magma genesis

    NASA Astrophysics Data System (ADS)

    Green, T. H.

    1981-07-01

    Recent experimental studies have established petrogenetic models based on melting processes involving major phases. The possible residual character of trace-element-enriched accessory phases is not considered for temperatures well above the solidus in these models. In contrast, geochemists, applying trace element data to independently test the experimentally-based models, have concluded that residual (or fractionating) accessory phases may have an essential role in controlling the trace element (especially REE) distributions in magmas. Some recent experimental work provides data on the stability of potentially significant accessories such as sphene, rutile, apatite, zoisite and mica in basaltic compositions at elevated P and T. Sphene is stable to 1000°C with 60% melting of a hydrous tholeiite at 15 kbar. At higher pressure, rutile is the only Ti-rich accessory phase, and is present to at least 1000°C and high degrees of melting. Published REE data on sphene and rutile suggest that these phases may be important in controlling REE distribution in some magmas. For example, island are high-Mg, low-Ca-Ti tholeiites with low REE abundances and U-shaped patterns (Hickey and Frey, 1979) may reflect the role of sphene. In addition to rutile, similar close-packed Ti-rich accessory phases such as priderite, perovskite, crichtonite and loveringite may occur in mantle-derived magmas. These phases readily accommodate the REE but their possible role needs experimental confirmation. Apatite is recorded in hawaiite (1.16% P 2O s) with 2% H 2O added at 5-6 kbar and 1050°C within 30°C of the liquidus, but at present no other experimental data are available on its high P, T stability, although thermodynamic calculations indicate that F may increase its stability markedly. Apatite is well known in high-pressure inclusions and as a phenocryst phase in rocks of the alkaline and calc-alkaline series. Ilmenite is known as a near-liquidus phase in some mafic magmas at ˜5-10 kbar, but

  10. Theoretical approaches and experimental evidence for liquid-vapor phase transitions in nuclei

    SciTech Connect

    Moretto, L.G.; Elliott, J.B.; Phair, L.; Wozniak, G.J.; Mader, C.M.; Chappars, A.

    2001-01-01

    The leptodermous approximation is applied to nuclear systems for T > 0. The introduction of surface corrections leads to anomalous caloric curves and to negative heat capacities in the liquid-gas coexistence region. Clusterization in the vapor is described by associating surface energy to clusters according to Fisher's formula. The three-dimensional Ising model, a leptodermous system par excellence, does obey rigorously Fisher's scaling up to the critical point. Multifragmentation data from several experiments including the ISiS and EOS Collaborations, as well as compound nucleus fragment emission at much lower energy follow the same scaling, thus providing the strongest evidence yet of liquid-vapor coexistence.

  11. Experimental Evidence for a Light and Broad Scalar Resonance in D+ --> π-π+π+ Decay

    NASA Astrophysics Data System (ADS)

    Aitala, E. M.; Amato, S.; Anjos, J. C.; Appel, J. A.; Ashery, D.; Banerjee, S.; Bediaga, I.; Blaylock, G.; Bracker, S. B.; Burchat, P. R.; Burnstein, R. A.; Carter, T.; Carvalho, H. S.; Copty, N. K.; Cremaldi, L. M.; Darling, C.; Denisenko, K.; Devmal, S.; Fernandez, A.; Fox, G. F.; Gagnon, P.; Gobel, C.; Gounder, K.; Halling, A. M.; Herrera, G.; Hurvits, G.; James, C.; Kasper, P. A.; Kwan, S.; Langs, D. C.; Leslie, J.; Lundberg, B.; Magnin, J.; Massafferri, A.; Maytal-Beck, S.; Meadows, B.; de Mello Neto, J. R.; Mihalcea, D.; Milburn, R. H.; de Miranda, J. M.; Napier, A.; Nguyen, A.; D'Oliveira, A. B.; O'Shaughnessy, K.; Peng, K. C.; Perera, L. P.; Purohit, M. V.; Quinn, B.; Radeztsky, S.; Rafatian, A.; Reay, N. W.; Reidy, J. J.; Dos Reis, A. C.; Rubin, H. A.; Sanders, D. A.; Santha, A. K.; Santoro, A. F.; Schwartz, A. J.; Sheaff, M.; Sidwell, R. A.; Slaughter, A. J.; Sokoloff, M. D.; Solano, J.; Stanton, N. R.; Stefanski, R. J.; Stenson, K.; Summers, D. J.; Takach, S.; Thorne, K.; Tripathi, A. K.; Watanabe, S.; Weiss-Babai, R.; Wiener, J.; Witchey, N.; Wolin, E.; Yang, S. M.; Yi, D.; Yoshida, S.; Zaliznyak, R.; Zhang, C.

    2001-01-01

    From a sample of 1172+/-61 D+-->π-π+π+ decays, we find γ\\(D+-->π- π+π+\\)/γ\\(D+-->K-π+π+\\) = 0.0311+/-0.0018+0.0016-0.0026. Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478+24-23+/-17 MeV/c2 and width 324+42-40+/-21 MeV/c2 accounts for approximately half of all decays.

  12. The impact of product information and trials on demand for smokeless tobacco and cigarettes: Evidence from experimental auctions

    PubMed Central

    Rousu, Matthew C.; O'Connor, Richard; Thrasher, James F; June, Kristie; Bansal-Travers, Maansi; Pitcavage, James

    2014-01-01

    Introduction Epidemiological and toxicological evidence suggests lower risk of smokeless tobacco (ST) products compared to cigarettes. Less is known, however, about consumer perceptions and use of novel forms of ST, including snus and dissolvable tobacco. Methods In this study, we conducted in-person experimental auctions in Buffalo, NY, Columbia, SC, and Selinsgrove, PA with 571 smokers to test the impact of information and product trials on smokers’ preferences. Auctions were conducted between November 2010-November 2011. Results We found no evidence of an impact of product trials on demand in our auctions. Anti-ST information increased demand for cigarettes when presented alone, but when presented with Pro-ST information it decreased demand for cigarettes. It did not decrease demand for ST products. Anti-smoking information increased demand for ST products, but did not affect cigarette demand. Conclusions These findings suggest that credible and effective communications about tobacco harm reduction should reinforce the negative effects of smoking. PMID:24321456

  13. Experimental Evidence for the Population-Dynamic Mechanisms Underlying Extinction Cascades of Carnivores.

    PubMed

    Sanders, Dirk; Kehoe, Rachel; van Veen, F J Frank

    2015-12-01

    Species extinction rates due to human activities are high, and initial extinctions can trigger cascades of secondary extinctions, leading to further erosion of biodiversity. A potential major mechanism for secondary extinction cascades is provided by the long-standing theory that the diversity of consumer species is maintained due to the positive indirect effects that these species have on each other by reducing competition among their respective resource species. This means that the loss of one carnivore species could lead to competitive exclusion at the prey trophic level, leading to extinctions of further carnivore species. Evidence for these effects is difficult to obtain due to many confounding factors in natural systems, but extinction cascades that could be due to this mechanism have been demonstrated in simplified laboratory microcosms. We established complex insect food webs in replicated field mesocosms and found that the overharvesting of one parasitoid wasp species caused increased extinction rates of other parasitoid species, compared to controls, but only when we manipulated the spatial distribution of herbivore species such that the potential for interspecific competition at this level was high. This provides clear evidence for horizontal extinction cascades at high trophic levels due to the proposed mechanism. Our results demonstrate that the loss of carnivores can have widespread effects on other species at the same trophic level due to indirect population-dynamic effects that are rarely considered in this context. PMID:26585283

  14. Understanding Counterfactuality: A Review of Experimental Evidence for the Dual Meaning of Counterfactuals

    PubMed Central

    Nieuwland, Mante S.

    2016-01-01

    Abstract Cognitive and linguistic theories of counterfactual language comprehension assume that counterfactuals convey a dual meaning. Subjunctive‐counterfactual conditionals (e.g., ‘If Tom had studied hard, he would have passed the test’) express a supposition while implying the factual state of affairs (Tom has not studied hard and failed). The question of how counterfactual dual meaning plays out during language processing is currently gaining interest in psycholinguistics. Whereas numerous studies using offline measures of language processing consistently support counterfactual dual meaning, evidence coming from online studies is less conclusive. Here, we review the available studies that examine online counterfactual language comprehension through behavioural measurement (self‐paced reading times, eye‐tracking) and neuroimaging (electroencephalography, functional magnetic resonance imaging). While we argue that these studies do not offer direct evidence for the online computation of counterfactual dual meaning, they provide valuable information about the way counterfactual meaning unfolds in time and influences successive information processing. Further advances in research on counterfactual comprehension require more specific predictions about how counterfactual dual meaning impacts incremental sentence processing. PMID:27512408

  15. Experimental evidence for convergent evolution of maternal care heuristics in industrialized and small-scale populations.

    PubMed

    Kushnick, Geoff; Hanowell, Ben; Kim, Jun-Hong; Langstieh, Banrida; Magnano, Vittorio; Oláh, Katalin

    2015-06-01

    Maternal care decision rules should evolve responsiveness to factors impinging on the fitness pay-offs of care. Because the caretaking environments common in industrialized and small-scale societies vary in predictable ways, we hypothesize that heuristics guiding maternal behaviour will also differ between these two types of populations. We used a factorial vignette experiment to elicit third-party judgements about likely caretaking decisions of a hypothetical mother and her child when various fitness-relevant factors (maternal age and access to resources, and offspring age, sex and quality) were varied systematically in seven populations-three industrialized and four small-scale. Despite considerable variation in responses, we found that three of five main effects, and the two severity effects, exhibited statistically significant industrialized/ small-scale population differences. All differences could be explained as adaptive solutions to industrialized versus small-scale caretaking environments. Further, we found gradients in the relationship between the population-specific estimates and national-level socio-economic indicators, further implicating important aspects of the variation in industrialized and small-scale caretaking environments in shaping heuristics. Although there is mounting evidence for a genetic component to human maternal behaviour, there is no current evidence for interpopulation variation in candidate genes. We nonetheless suggest that heuristics guiding maternal behaviour in diverse societies emerge via convergent evolution in response to similar selective pressures. PMID:26543577

  16. Effects of Bisphenol A on ion channels: Experimental evidence and molecular mechanisms.

    PubMed

    Soriano, Sergi; Ripoll, Cristina; Alonso-Magdalena, Paloma; Fuentes, Esther; Quesada, Ivan; Nadal, Angel; Martinez-Pinna, Juan

    2016-07-01

    Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) produced in huge quantities in the manufacture of polycarbonate plastics and epoxy resins. It is present in most humans in developed countries, acting as a xenoestrogen and it is considered an environmental risk factor associated to several diseases. Among the whole array of identified mechanisms by which BPA can interfere with physiological processes in living organisms, changes on ion channel activity is one of the most poorly understood. There is still little evidence about BPA regulation of ion channel expression and function. However, this information is key to understand how BPA disrupts excitable and non-excitable cells, including neurons, endocrine cells and muscle cells. This report is the result of a comprehensive literature review on the effects of BPA on ion channels. We conclude that there is evidence to say that these important molecules may be key end-points for EDCs acting as xenoestrogens. However, more research on channel-mediated BPA effects is needed. Particularly, mechanistic studies to unravel the pathophysiological actions of BPA on ion channels at environmentally relevant doses. PMID:26930576

  17. Experimental Evidence for the Population-Dynamic Mechanisms Underlying Extinction Cascades of Carnivores.

    PubMed

    Sanders, Dirk; Kehoe, Rachel; van Veen, F J Frank

    2015-12-01

    Species extinction rates due to human activities are high, and initial extinctions can trigger cascades of secondary extinctions, leading to further erosion of biodiversity. A potential major mechanism for secondary extinction cascades is provided by the long-standing theory that the diversity of consumer species is maintained due to the positive indirect effects that these species have on each other by reducing competition among their respective resource species. This means that the loss of one carnivore species could lead to competitive exclusion at the prey trophic level, leading to extinctions of further carnivore species. Evidence for these effects is difficult to obtain due to many confounding factors in natural systems, but extinction cascades that could be due to this mechanism have been demonstrated in simplified laboratory microcosms. We established complex insect food webs in replicated field mesocosms and found that the overharvesting of one parasitoid wasp species caused increased extinction rates of other parasitoid species, compared to controls, but only when we manipulated the spatial distribution of herbivore species such that the potential for interspecific competition at this level was high. This provides clear evidence for horizontal extinction cascades at high trophic levels due to the proposed mechanism. Our results demonstrate that the loss of carnivores can have widespread effects on other species at the same trophic level due to indirect population-dynamic effects that are rarely considered in this context.

  18. Experimental evidence for the formation of divalent ytterbium in the photodarkening process of Yb-doped fiber lasers.

    PubMed

    Rydberg, S; Engholm, M

    2013-03-25

    In this work we present experimental evidence that the valence instability of the ytterbium ion play a key role for the observed photodarkening mechanism in Yb-doped fiber lasers. Luminescence and excitation spectroscopy performed on UV irradiated Yb/Al doped silica glass preforms and near-infrared diode pumped photodarkened fibers show a concentration increase of Yb(2+) ions. A concentration decrease in Yb(3+) could also be observed for the UV irradiated preform. The findings contribute to an increased understanding of the kinetic processes related to photodarkening in Yb-doped high power fiber lasers.

  19. Renin-angiotensin system as a potential therapeutic target in stroke and retinopathy: experimental and clinical evidence.

    PubMed

    Fouda, Abdelrahman Y; Artham, Sandeep; El-Remessy, Azza B; Fagan, Susan C

    2016-02-01

    As our knowledge expands, it is now clear that the renin-angiotensin (Ang) system (RAS) mediates functions other than regulating blood pressure (BP). The RAS plays a central role in the pathophysiology of different neurovascular unit disorders including stroke and retinopathy. Moreover, the beneficial actions of RAS modulation in brain and retina have been documented in experimental research, but not yet exploited clinically. The RAS is a complex system with distinct yet interconnected components. Understanding the different RAS components and their functions under brain and retinal pathological conditions is crucial to reap their benefits. The aim of the present review is to provide an experimental and clinical update on the role of RAS in the pathophysiology and treatment of stroke and retinopathy. Combining the evidence from both these disorders allows a unique opportunity to move both fields forward.

  20. Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers

    PubMed Central

    Braudrick, Christian A.; Dietrich, William E.; Leverich, Glen T.; Sklar, Leonard S.

    2009-01-01

    Meandering rivers are common on Earth and other planetary surfaces, yet the conditions necessary to maintain meandering channels are unclear. As a consequence, self-maintaining meandering channels with cutoffs have not been reproduced in the laboratory. Such experimental channels are needed to explore mechanisms controlling migration rate, sinuosity, floodplain formation, and planform morphodynamics and to test theories for wavelength and bend propagation. Here we report an experiment in which meandering with near-constant width was maintained during repeated cutoff and regeneration of meander bends. We found that elevated bank strength (provided by alfalfa sprouts) relative to the cohesionless bed material and the blocking of troughs (chutes) in the lee of point bars via suspended sediment deposition were the necessary ingredients to successful meandering. Varying flood discharge was not necessary. Scaling analysis shows that the experimental meander migration was fast compared to most natural channels. This high migration rate caused nearly all of the bedload sediment to exchange laterally, such that bar growth was primarily dependent on bank sediment supplied from upstream lateral migration. The high migration rate may have contributed to the relatively low sinuosity of 1.19, and this suggests that to obtain much higher sinuosity experiments at this scale may have to be conducted for several years. Although patience is required to evolve them, these experimental channels offer the opportunity to explore several fundamental issues about river morphodynamics. Our results also suggest that sand supply may be an essential control in restoring self-maintaining, actively shifting gravel-bedded meanders. PMID:19805077

  1. Time-lag in extinction dynamics in experimental populations: evidence for a genetic Allee effect?

    PubMed Central

    Vercken, Elodie; Vincent, Flora; Mailleret, Ludovic; Ris, Nicolas; Tabone, Elisabeth; Fauvergue, Xavier; Gurney, William

    2013-01-01

    1. Propagule pressure, i.e. the number of individuals introduced, is thought to be a major predictor of the establishment success of introduced populations in the field. Its influence in laboratory experimental systems has however been questioned. In fact, other factors involved in long-term population persistence, like habitat size, were usually found to explain most of the dynamics of experimental populations. 2. To better understand the respective influence of short- and long-term factors and their potential interaction on extinction dynamics in experimental systems, we investigated the influence of propagule pressure, habitat size and genetic background on the early dynamics of laboratory-based populations of a hymenopteran parasitoid. 3. The amount of demographic variance differed between establishment and persistence phase and was influenced by habitat size and genetic background (geographic strain), but independent of propagule pressure. In contrast, the probability of extinction within five generations depended on the genetic background and on the interaction between propagule pressure and habitat size. Vulnerability to extinction in small size habitats was increased when populations were founded with a small number of individuals, but this effect was delayed until the third to fifth generations. 4. These results indicate that demographic stochasticity is influential during population establishment, but is not affected by the genetic variability of propagules. On the other hand, extinction might be influenced by a genetic Allee effect triggered by the combination of low propagule pressure and genetic drift. Finally, we documented consistent differences between genetic backgrounds in both deterministic and stochastic population dynamics patterns, with major consequences on extinction risk and ultimately population establishment. PMID:23398653

  2. Time-lag in extinction dynamics in experimental populations: evidence for a genetic Allee effect?

    PubMed

    Vercken, Elodie; Vincent, Flora; Mailleret, Ludovic; Ris, Nicolas; Tabone, Elisabeth; Fauvergue, Xavier

    2013-05-01

    1. Propagule pressure, i.e. the number of individuals introduced, is thought to be a major predictor of the establishment success of introduced populations in the field. Its influence in laboratory experimental systems has however been questioned. In fact, other factors involved in long-term population persistence, like habitat size, were usually found to explain most of the dynamics of experimental populations. 2. To better understand the respective influence of short- and long-term factors and their potential interaction on extinction dynamics in experimental systems, we investigated the influence of propagule pressure, habitat size and genetic background on the early dynamics of laboratory-based populations of a hymenopteran parasitoid. 3. The amount of demographic variance differed between establishment and persistence phase and was influenced by habitat size and genetic background (geographic strain), but independent of propagule pressure. In contrast, the probability of extinction within five generations depended on the genetic background and on the interaction between propagule pressure and habitat size. Vulnerability to extinction in small size habitats was increased when populations were founded with a small number of individuals, but this effect was delayed until the third to fifth generations. 4. These results indicate that demographic stochasticity is influential during population establishment, but is not affected by the genetic variability of propagules. On the other hand, extinction might be influenced by a genetic Allee effect triggered by the combination of low propagule pressure and genetic drift. Finally, we documented consistent differences between genetic backgrounds in both deterministic and stochastic population dynamics patterns, with major consequences on extinction risk and ultimately population establishment.

  3. Experimental evidence for the conditions necessary to sustain meandering in coarse-bedded rivers.

    PubMed

    Braudrick, Christian A; Dietrich, William E; Leverich, Glen T; Sklar, Leonard S

    2009-10-01

    Meandering rivers are common on Earth and other planetary surfaces, yet the conditions necessary to maintain meandering channels are unclear. As a consequence, self-maintaining meandering channels with cutoffs have not been reproduced in the laboratory. Such experimental channels are needed to explore mechanisms controlling migration rate, sinuosity, floodplain formation, and planform morphodynamics and to test theories for wavelength and bend propagation. Here we report an experiment in which meandering with near-constant width was maintained during repeated cutoff and regeneration of meander bends. We found that elevated bank strength (provided by alfalfa sprouts) relative to the cohesionless bed material and the blocking of troughs (chutes) in the lee of point bars via suspended sediment deposition were the necessary ingredients to successful meandering. Varying flood discharge was not necessary. Scaling analysis shows that the experimental meander migration was fast compared to most natural channels. This high migration rate caused nearly all of the bedload sediment to exchange laterally, such that bar growth was primarily dependent on bank sediment supplied from upstream lateral migration. The high migration rate may have contributed to the relatively low sinuosity of 1.19, and this suggests that to obtain much higher sinuosity experiments at this scale may have to be conducted for several years. Although patience is required to evolve them, these experimental channels offer the opportunity to explore several fundamental issues about river morphodynamics. Our results also suggest that sand supply may be an essential control in restoring self-maintaining, actively shifting gravel-bedded meanders. PMID:19805077

  4. Experimental evidence for improved neuroimaging interpretation using three-dimensional graphic models.

    PubMed

    Ruisoto, Pablo; Juanes, Juan Antonio; Contador, Israel; Mayoral, Paula; Prats-Galino, Alberto

    2012-01-01

    Three-dimensional (3D) or volumetric visualization is a useful resource for learning about the anatomy of the human brain. However, the effectiveness of 3D spatial visualization has not yet been assessed systematically. This report analyzes whether 3D volumetric visualization helps learners to identify and locate subcortical structures more precisely than classical cross-sectional images based on a two dimensional (2D) approach. Eighty participants were assigned to each experimental condition: 2D cross-sectional visualization vs. 3D volumetric visualization. Both groups were matched for age, gender, visual-spatial ability, and previous knowledge of neuroanatomy. Accuracy in identifying brain structures, execution time, and level of confidence in the response were taken as outcome measures. Moreover, interactive effects between the experimental conditions (2D vs. 3D) and factors such as level of competence (novice vs. expert), image modality (morphological and functional), and difficulty of the structures were analyzed. The percentage of correct answers (hit rate) and level of confidence in responses were significantly higher in the 3D visualization condition than in the 2D. In addition, the response time was significantly lower for the 3D visualization condition in comparison with the 2D. The interaction between the experimental condition (2D vs. 3D) and difficulty was significant, and the 3D condition facilitated the location of difficult images more than the 2D condition. 3D volumetric visualization helps to identify brain structures such as the hippocampus and amygdala, more accurately and rapidly than conventional 2D visualization. This paper discusses the implications of these results with regards to the learning process involved in neuroimaging interpretation.

  5. Experimentally enforced monogamy: inadvertent selection, inbreeding, or evidence for sexually antagonistic coevolution?

    PubMed

    Rice, William R; Holland, Brett

    2005-03-01

    There has been recent criticism of experiments that applied enforced monogamous mating to species with a long history of promiscuity. These experiments indicated that the newly introduced monogamy reversed sexually antagonistic coevolution and caused males to evolve to be less harmful to their mates and females to evolve reduced resistance to harm from males. Several authors have proposed alternative interpretations of these experimental results based on qualitative analysis. If well-founded, these criticisms would invalidate an important part of the empirical foundation for sexually antagonistic coevolution between the sexes. Although these criticisms have a reasonable basis in principle, we find that after quantitative evaluation that they are not supported.

  6. Experimental evidence of self-limited growth of nanocrystals in glass.

    PubMed

    Bhattacharyya, Somnath; Bocker, Christian; Heil, Tobias; Jinschek, Jörg R; Höche, Thomas; Rüssel, Christian; Kohl, Helmut

    2009-06-01

    Growth of nanocrystals precipitated in glasses with specific compositions can be effectively limited by diffusion barriers forming around crystallites. For the first time, we do experimentally prove this concept of self-limited growth on the nanoscale for a SiO(2)/Al(2)O(3)/Na(2)O/K(2)O/BaF(2) glass in which BaF(2) nanocrystals are formed. As shown by advanced analytical transmission electron microscopy techniques, the growth of these BaF(2) crystals, having great potential for photonic applications, is inherently limited by the formation of a ca. 1 nm wide SiO(2) shell.

  7. Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

    SciTech Connect

    Laczkowski, P.; Rojas-Sánchez, J.-C.

    2014-04-07

    We report an experimental study of a gold-tungsten alloy (7 at. % W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity, and small induced damping, this AuW alloy may find applications in the nearest future.

  8. Experimental evidences of a large extrinsic spin Hall effect in AuW alloy

    NASA Astrophysics Data System (ADS)

    Laczkowski, P.; Rojas-Sánchez, J.-C.; Savero-Torres, W.; Jaffrès, H.; Reyren, N.; Deranlot, C.; Notin, L.; Beigné, C.; Marty, A.; Attané, J.-P.; Vila, L.; George, J.-M.; Fert, A.

    2014-04-01

    We report an experimental study of a gold-tungsten alloy (7 at. % W concentration in Au host) displaying remarkable properties for spintronics applications using both magneto-transport in lateral spin valve devices and spin-pumping with inverse spin Hall effect experiments. A very large spin Hall angle of about 10% is consistently found using both techniques with the reliable spin diffusion length of 2 nm estimated by the spin sink experiments in the lateral spin valves. With its chemical stability, high resistivity, and small induced damping, this AuW alloy may find applications in the nearest future.

  9. Evidence for a new force in dissipative system derived from Boltzmann equation: Consequence for the mechanics of the material point, experimental evidences and possible applications

    NASA Astrophysics Data System (ADS)

    Evesque, Pierre

    2013-06-01

    A 1d Boltzmann equation is introduced to describe the speed distribution function in granular gas system with local collision dissipation. It leads to introduce a new term, equivalent to an acceleration This term was always assumed to be 0, but it is not zero in general, even when the system is steady (i.e. when local mean flow equals 0). This shows that the flow (+ boundary) exerts a force on any extra steady particle (or plane) that drives it to the center. This result is analyzed, compared and interpreted using the Lagrangian & Eulerian view points of the mechanics; it demonstrates that classic view point of hydrodynamics does not hold anymore. The paper investigates different cases and gives experimental evidences of the features: it explains while local speed distribution f(v,r) of granular gas in a box subjected to vibration is non symmetric in the direction of vibration, while the system is stationary (mean local speed equals 0). Papers giving local experimental or simulated distributions are quoted, where two local pressures P± = Σv>0,orv<0 (mv2) in +Ox and -Ox direction are different. It implies also introducing two local temperatures T± in the ±Ox vibration direction. These points are confirmed using 2d and 3d granular gas simulation. It should apply likely to get deeper understanding of different effects as the "granular Leidenfrost effect", the stoppage of vibrated-hourglass, some turbulent flow, and the granular-Maxwell-demon.

  10. Experimental evidence that keeping eggs dry is a mechanism for the antimicrobial effects of avian incubation

    NASA Astrophysics Data System (ADS)

    D'Alba, Liliana; Oborn, Allison; Shawkey, Matthew D.

    2010-12-01

    Avian incubation dramatically reduces the abundance and diversity of microbial assemblages on eggshells, and this effect has been hypothesized as an adaptive explanation for partial incubation, the bouts of incubation that some birds perform during the egg-laying period. However, the mechanisms for these antimicrobial effects are largely unknown. In this study, we hypothesized that microbial inhibition is partly achieved through removal of liquid water, which generally enhances microbial growth, from eggshells, and experimentally tested this hypothesis in two ways. First, we placed the first- and second-laid eggs of tree swallow ( Tachycineta bicolor) clutches in unincubated holding nests with either ambient or increased water on eggshells. Second, we added water to eggshells in naturally partially incubated nests. We compared microbial growth on shells during a 5-day experimental period and found that, as predicted, both unincubated groups had higher microbial growth than naturally partially incubated controls, and that only in the absence of incubation did wetted eggs have higher microbial growth than unwetted eggs. Thus, we have shown that water increases microbial growth on eggshells and that incubation nullifies these effects, suggesting that removal of water from egg surfaces is one proximate mechanism for the antimicrobial effects of incubation.

  11. In situ and experimental evidence for acidic weathering of rocks and soils on Mars

    NASA Astrophysics Data System (ADS)

    Hurowitz, J. A.; McLennan, S. M.; Tosca, N. J.; Arvidson, R. E.; Michalski, J. R.; Ming, D. W.; Schröder, C.; Squyres, S. W.

    2006-01-01

    Experimental data for alteration of synthetic Martian basalts at pH = 0-1 indicate that chemical fractionations at low pH are vastly different from those observed during terrestrial weathering. Rock surface analyses from Gusev crater are well described by the relationships apparent from low-pH experimental alteration data. A model for rock surface alteration is developed, which indicates that a leached alteration zone is present on rock surfaces at Gusev. This zone is not chemically fractionated to a large degree from the underlying rock interior, indicating that the rock surface alteration process has occurred at low water to rock ratio. The geochemistry of natural rock surfaces analyzed by APXS is consistent with a mixture between adhering soil/dust and the leached alteration zone. The chemistry of rock surfaces analyzed after brushing with the RAT is largely representative of the leached alteration zone. The chemistry of rock surfaces analyzed after grinding with the RAT is largely representative of the interior of the rock, relatively unaffected by the alteration process occurring at the rock surface. Elemental measurements from the Spirit, Opportunity, Pathfinder, and Viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low-pH, low water to rock ratio alteration relationships developed for Gusev rocks. Soils are affected principally by mobility of Fe and Mg, consistent with alteration of olivine-bearing basalt and subsequent precipitation of Fe- and Mg-bearing secondary minerals as the primary control on soil geochemistry.

  12. Experimental evidence that livestock grazing intensity affects the activity of a generalist predator

    NASA Astrophysics Data System (ADS)

    Villar, Nacho; Lambin, Xavier; Evans, Darren; Pakeman, Robin; Redpath, Steve

    2013-05-01

    Grazing by domestic ungulates has substantial impacts on ecosystem structure and composition. In grasslands of the northern hemisphere, livestock grazing limits populations of small mammals, which are a main food source for a variety of vertebrate predators. However, no experimental studies have described the impact of livestock grazing on vertebrate predators. We experimentally manipulated sheep and cattle grazing intensity in the Scottish uplands to test its impact on a relatively abundant small mammal, the field vole (Microtus agrestis), and its archetypal generalist predator, the red fox (Vulpes vulpes). We demonstrate that ungulate grazing had a strong consistent negative impact on both vole densities and indices of fox activity. Ungulate grazing did not substantially affect the relationship between fox activity and vole densities. However, the data suggested that, as grazing intensity increased i) fox activity indices tended to be higher when vole densities were low, and ii) the relationship between fox activity and vole density was weaker. All these patterns are surprising given the relative small scale of our experiment compared to large red fox territories in upland habitats of Britain, and suggest that domestic grazing intensity causes a strong response in the activity of generalist predators important for their conservation in grassland ecosystems.

  13. Experimental evidence of population differences in reproductive investment conditional on environmental stochasticity.

    PubMed

    Gauthey, Zoé; Panserat, Stéphane; Elosegi, Arturo; Herman, Alexandre; Tentelier, Cédric; Labonne, Jacques

    2016-01-15

    Environmental stochasticity is expected to shape life histories of species, wherein organisms subjected to strong environmental variation should display adaptive response by being able to tune their reproductive investment. For riverine ecosystems, climate models forecast an increase in the frequency and intensity of extreme events such as floods and droughts. The speed and the mechanisms by which organisms may adapt their reproductive investment are therefore of primary importance to understand how species will cope with such radical environmental changes. In the present study, we sampled spawners from two different populations of wild brown trout, originating from two environments with contrasting levels of flow stochasticity. We placed them in sympatry within an experimental channel during reproductive season. In one modality, water flow was maintained constant, whereas in another modality, water flow was highly variable. Reproductive investment of all individuals was monitored using weight and energetic plasma metabolite variation throughout the reproductive season. Only the populations originating from the most variable environment showed a plastic response to experimental manipulation of water flow, the females being able to reduce their weight variation (from 19.2% to 13.1%) and metabolites variations (from 84.2% to 18.6% for triglycerides for instance) under variable flow conditions. These results imply that mechanisms to cope with environmental stochasticity can differ between populations of the same species, where some populations can be plastic whereas other cannot.

  14. Theoretical and experimental evidence for the post-cotunnite phase transition in zirconia at high pressure

    NASA Astrophysics Data System (ADS)

    Nishio-Hamane, Daisuke; Dekura, Haruhiko; Seto, Yusuke; Yagi, Takehiko

    2015-05-01

    A post-cotunnite phase transition in zirconia (ZrO2) at high pressure was investigated by synchrotron X-ray diffraction measurements and ab initio calculations based on density functional theory. This study successfully demonstrated a cotunnite- to Fe2P-type phase transition. Static enthalpy difference (Δ H) calculations predicted the appearance of the Fe2P phase at 124 GPa (LDA) and 143 GPa (GGA), and experimental trials demonstrated the coexistence of the Fe2P and cotunnite phases at 175 GPa after heating to 3,000 K. Both phases were quenchable to ambient conditions. The volume of the Fe2P phase was slightly less (~Δ 0.6 %) than that of the cotunnite phase over the experimental pressure range, indicating that the Fe2P phase is the higher pressure phase. The coexistence of both phases in this study may be attributed to the slow kinetics of the phase transition resulting from the close structural relationship of the two phases. An Fe2P-type structural model can be derived by applying a simple operation to the cotunnite-type structure, consisting of a 1/2 shift of several zirconium arrangements parallel to the b-axis of the cotunnite-type unit cell. It is concluded that the high-pressure cotunnite-to-Fe2P phase transition may be a common trend in many dioxides.

  15. Theoretical and experimental evidence of level repulsion states and evanescent modes in sonic crystal stubbed waveguides

    NASA Astrophysics Data System (ADS)

    Romero-García, V.; Vasseur, J. O.; Garcia-Raffi, L. M.; Hladky-Hennion, A. C.

    2012-02-01

    The complex band structures calculated using the extended plane wave expansion (EPWE) reveal the presence of evanescent modes in periodic systems, never predicted by the classical \\omega(\\vec {k}) methods, providing novel interpretations of several phenomena as well as a complete picture of the system. In this work, we theoretically and experimentally observe that in the ranges of frequencies where a deaf band is traditionally predicted, an evanescent mode with excitable symmetry appears, changing drastically the interpretation of the transmission properties. On the other hand, the simplicity of the sonic crystals in which only the longitudinal polarization can be excited is used to interpret, without loss of generality, the level repulsion between symmetric and antisymmetric bands in sonic crystals as the presence of an evanescent mode connecting both repelled bands. These evanescent modes, obtained using EPWE, explain both the attenuation produced in this range of frequencies and the transfer of symmetry from one band to the other in good agreement with both experimental results and multiple scattering predictions. Thus, the evanescent properties of the periodic system have been revealed to be necessary for the design of new acoustic and electromagnetic applications based on periodicity.

  16. Selective Cooperation in the Supermarket : Field Experimental Evidence for Indirect Reciprocity.

    PubMed

    Lange, Florian; Eggert, Frank

    2015-12-01

    Numerous laboratory experiments suggest that mechanisms of indirect reciprocity might account for human cooperation. However, conclusive field data supporting the predictions of indirect reciprocity in everyday life situations is still scarce. Here, we attempt to compensate for this lack by examining the determinants of cooperative behavior in a German supermarket. Our methods were as follows: Confederates of the experimenter lined up at the checkout, apparently to buy a single item. As an act of cooperation, the waiting person in front (the potential helper) could allow the confederate to go ahead. By this means, the potential helper could take a cost (additional waiting time) by providing the confederate with a benefit (saved waiting time). We recorded the potential helpers' behavior and the number of items they purchased as a quantitative measure proportional to the confederate's benefit. Moreover, in a field experimental design, we varied the confederates' image by manipulating the item they purchased (beer vs. water). As predicted, the more waiting time they could save, the more likely the confederates were to receive cooperation. This relationship was moderated by the confederates' image. Cost-to-benefit ratios were required to be more favorable for beer-purchasing individuals to receive cooperation. Our results demonstrate that everyday human cooperation can be studied unobtrusively in the field and that cooperation among strangers is selective in a way that is consistent with current models of indirect reciprocity.

  17. In situ experimental evidence of phosphorus limitation on algal growth in a lake ecosystem.

    PubMed

    An, Kwang-Guk; Park, Seok Soon

    2002-01-01

    This paper presents the results of in situ Nutrient Stimulation Experiments (NSEs) demonstrating that phosphorus was the primary nutrient controlling algal growth in the Taechung Reservoir, Korea. Algal response in most treatments with only nitrogen added was less than or the same as in the controls, whereas the growth in treatments enriched with phosphorus increased by as much as fivefold. Phosphorus limitation was consistent over the experimental period when bioassay experiments were conducted, but the magnitude of growth response to phosphorus enrichments varied with the season. Algal yield in P-treatments was maximum when thermal stratification was strong and total dissolved phosphorus (TDP) was near the level of depletion. Regression analyses of NSEs showed that in situ algal response in P treatments, measured as log-transformed CHLf:CHLi ratios, declined (R2 = 0.995, p < 0.001) with ambient concentrations of log-transformed TDP. Also, algal response in the P treatments showed a first-order linear fit (R2 = 0.961, p < 0.001) with log-transformed DIN (dissolved inorganic nitrogen):TDP ratios. These outcomes indicate that the magnitude of in situ algal response increased with lower levels of P and higher dissolved N:P ratios in the ambient lake water. Our experimental approach employing NSEs suggests that abatement of phosphorus from the watershed seems to be an efficient management strategy to control the eutrophication of this system.

  18. Experimental Evidence for Polybaric Intracrustal Differentiation of Primitive Arc Basalt beneath St. Vincent, Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Blundy, Jon; Melekhova, Lena; Robertson, Richard

    2014-05-01

    We present experimental phase equilibria for a primitive, high-Mg basalt from St. Vincent, Lesser Antilles. Experimental details were presented in Melekhova et al (Nature Geosci, 2013); the objective here is to compare experimental phase compositions to those of erupted lavas and cumulates from St. Vincent. Starting material with 4.5 wt% H2O is multiply-saturated with a lherzolite assemblage at 1.3 GPa and 1180 ° C, consistent with mantle wedge derivation. Experimental glasses from our study, in addition to those of Pichavant et al (GCA, 2002) and Pichavant & Macdonald (CMP 2007) on a similar high-Mg basalt, encompass a compositional range from high-magnesian basalt to dacite, with a systematic dependence on H2O content, temperature and pressure. We are able to match the glasses from individual experiments to different lava types, so as to constrain the differentiation depths at which these magmas could be generated from a high-Mg parent, as follows: Composition wt% H2OP (GPa) T (° C) High-Mg basalt 3.9-4.8 1.45-1.751180-1200 Low-Mg basalt 2.3-4.5 1.0-1.3 1065-1150 High alumina basalt 3.0-4.5 0.4 1050-1080 Basaltic andesite 0.6-4.5 0.7-1.0 1050-1130 Andesite 0.6 1.0 1060-1080 The fact that St. Vincent andesites (and some basaltic andesites) appear to derive from a low-H2O (0.6 wt%) parent suggest that they are products of partial melting of older, high-Mg gabbroic rocks, as 0.6 wt% H2O is approximately the amount that can be stored in amphibole-bearing gabbros. The higher H2O contents of parents for the other lava compositions is consistent with derivation by crystallization of basalts with H2O contents that accord with those of olivine-hosted melt inclusions from St. Vincent (Bouvier et al, J Petrol, 2008). The generation of evolved melts both by basalt crystallization and gabbro melting is consistent with the hot zone concept of Annen et al (J Petrol, 2006) wherein repeated intrusion of mantle-derived basalt simultaneously crystallize by cooling and melt

  19. The role of butyrate, a histone deacetylase inhibitor in diabetes mellitus: experimental evidence for therapeutic intervention.

    PubMed

    Khan, Sabbir; Jena, Gopabandhu

    2015-01-01

    The contribution of epigenetic mechanisms in diabetes mellitus (DM), β-cell reprogramming and its complications is an emerging concept. Recent evidence suggests that there is a link between DM and histone deacetylases (HDACs), because HDAC inhibitors promote β-cell differentiation, proliferation, function and improve insulin resistance. Moreover, gut microbes and diet-derived products can alter the host epigenome. Furthermore, butyrate and butyrate-producing microbes are decreased in DM. Butyrate is a short-chain fatty acid produced from the fermentation of dietary fibers by microbiota and has been proven as an HDAC inhibitor. The present review provides a pragmatic interpretation of chromatin-dependent and independent complex signaling/mechanisms of butyrate for the treatment of Type 1 and Type 2 DM, with an emphasis on the promising strategies for its drugability and therapeutic implication.

  20. Experimental evidence of vocal recognition in young and adult black-legged kittiwakes

    USGS Publications Warehouse

    Mulard, Hervé; Aubin, T.; White, J.F.; Hatch, Shyla A.; Danchin, E.

    2008-01-01

    Individual recognition is required in most social interactions, and its presence has been confirmed in many species. In birds, vocal cues appear to be a major component of recognition. Curiously, vocal recognition seems absent or limited in some highly social species such as the black-legged kittiwake, Rissa tridactyla. Using playback experiments, we found that kittiwake chicks recognized their parents vocally, this capacity being detectable as early as 20 days after hatching, the youngest age tested. Mates also recognized each other's long calls. Some birds reacted to their partner's voice when only a part of the long call was played back. Nevertheless, only about a third of the tested birds reacted to their mate's or parents' call and we were unable to detect recognition among neighbours. We discuss the low reactivity of kittiwakes in relation to their cliff-nesting habit and compare our results with evidence of vocal recognition in other larids. ?? 2008 The Association for the Study of Animal Behaviour.

  1. The Role of Inferences in Sequential Bargaining with One-Sided Incomplete Information: Some Experimental Evidence.

    PubMed

    Srivastava, Joydeep

    2001-05-01

    Two experiments tested a sequential bargaining model with one-sided incomplete information and time discounting. The findings suggest that although the comparative statics of the normative model are somewhat descriptive of the qualitative features of the data, bargainers do not conform to the signaling process that underlies bargaining models with incomplete information. Rather than assess and refine a probabilistic assessment of the private information based on the informed bargainer's behavior, uninformed bargainers infer their opponents' competitiveness. Further, bargainers are unable to use cost of delay in the strategic manner dictated by the equilibrium solution. The evidence suggests that although bargaining behavior is primarily determined by situational constraints, bargainers attribute their opponents' behavior to personal disposition, such as their level of competitiveness. Copyright 2001 Academic Press. PMID:11341821

  2. Camera perspective bias in videotaped confessions: experimental evidence of its perceptual basis.

    PubMed

    Ratcliff, Jennifer J; Lassiter, G Daniel; Schmidt, Heather C; Snyder, Celeste J

    2006-12-01

    The camera perspective from which a criminal confession is videotaped influences later assessments of its voluntariness and the suspect's guilt. Previous research has suggested that this camera perspective bias is rooted in perceptual rather than conceptual processes, but these data are strictly correlational. In 3 experiments, the authors directly manipulated perceptual processing to provide stronger evidence of its mediational role. Prior to viewing a videotape of a simulated confession, participants were shown a photograph of the confessor's apparent victim. Participants in a perceptual interference condition were instructed to visualize the image of the victim in their minds while viewing the videotape; participants in a conceptual interference condition were instructed instead to rehearse an 8-digit number. Because mental imagery and actual perception draw on the same available resources, the authors anticipated that the former, but not the latter, interference task would disrupt the camera perspective bias, if indeed it were perceptually mediated. Results supported this conclusion.

  3. Rapid communication: experimental evidence that juvenile pelagic jacks (Carangidae) respond behaviorally to DMSP.

    PubMed

    Debose, Jennifer L; Nevitt, Gabrielle A; Dittman, Andrew H

    2010-03-01

    Dimethylsulfoniopropionate (DMSP) is produced by marine algae and released during foraging activity by zooplankton and fish. Pelagic fishes depend on patchily distributed foraging opportunities, and DMSP may be an important signaling molecule for these events. We have previously shown that the abundance of carangid jacks is positively associated with elevated DMSP levels over coral reefs in the Gulf of Mexico, suggesting that these fishes may use spatial and temporal variation in DMSP to locate foraging opportunities. Here, we extend this work by demonstrating that juveniles of two species of pelagic jack, crevalle jack, Caranx hippos, and bluefin trevally, C. melampygus, detect and respond to DMSP in a flow-through tank in the laboratory. Juveniles of these species showed elevated swimming activity in response to ecologically relevant concentrations of DMSP (10(-9) M). These results provide further evidence that this chemical may serve as a chemosensory cue for carangid species.

  4. Resveratrol, from experimental data to nutritional evidence: the emergence of a new food ingredient.

    PubMed

    Raederstorff, Daniel; Kunz, Iris; Schwager, Joseph

    2013-07-01

    The polyphenol resveratrol is found notably in grapes and in a variety of medicinal plants. Recently, resveratrol has been suggested to have cardioprotective effects and to improve metabolic health by mimicking the effects of calorie restriction. Numerous animal and in vitro studies suggest that resveratrol could improve cardiovascular and metabolic health in humans. In view of this compelling preclinical evidence, several human studies investigating the effects of resveratrol on vascular and metabolic health have been initiated. Collectively, the animal, human epidemiological, and first human intervention studies support a role of resveratrol in vascular and metabolic health. This has led to the introduction of the first supplement and food products containing resveratrol and its emergence as a promising new health ingredient. Thus, supplementation with resveratrol may be included in nutritional and lifestyle programs aiming to reduce the risk of vascular and obesity-related problems.

  5. Evidence of experimental postcyclic transmission of Bothriocephalus acheilognathi in bonytail chub (Gila elegans)

    USGS Publications Warehouse

    Hansen, S.P.; Choudhury, A.; Cole, R.A.

    2007-01-01

    We examined the role that predation of infected conspecific fish and postcyclic transmission might play in the life cycle of the Asian fish tapeworm, Bothriocephalus acheilognathi (Cestoda: Pseudophyllidea) Yamaguti, 1934. Young-of-the-year (YOY) bonytail chub (Gila elegans) were exposed to copepods infected with B. acheilognathi and subsequently fed to subadult bonytail chub. Within 1 wk after consumption of the YOY chub, subadults were necropsied and found infected with gravid and nongravid tapeworms. This study provides evidence that postcyclic transfer of B. acheilognathi can occur. Postcyclic transmission may be an important life history trait of B. acheilognathi that merits consideration when studying the impact and distribution of this invasive and potentially pathogenic tapeworm. ?? American Society of Parasitologists 2007.

  6. Camera perspective bias in videotaped confessions: experimental evidence of its perceptual basis.

    PubMed

    Ratcliff, Jennifer J; Lassiter, G Daniel; Schmidt, Heather C; Snyder, Celeste J

    2006-12-01

    The camera perspective from which a criminal confession is videotaped influences later assessments of its voluntariness and the suspect's guilt. Previous research has suggested that this camera perspective bias is rooted in perceptual rather than conceptual processes, but these data are strictly correlational. In 3 experiments, the authors directly manipulated perceptual processing to provide stronger evidence of its mediational role. Prior to viewing a videotape of a simulated confession, participants were shown a photograph of the confessor's apparent victim. Participants in a perceptual interference condition were instructed to visualize the image of the victim in their minds while viewing the videotape; participants in a conceptual interference condition were instructed instead to rehearse an 8-digit number. Because mental imagery and actual perception draw on the same available resources, the authors anticipated that the former, but not the latter, interference task would disrupt the camera perspective bias, if indeed it were perceptually mediated. Results supported this conclusion. PMID:17154769

  7. Thioredoxin System Regulation in the Central Nervous System: Experimental Models and Clinical Evidence

    PubMed Central

    Silva-Adaya, Daniela; Gonsebatt, María E.; Guevara, Jorge

    2014-01-01

    The reactive oxygen species produced continuously during oxidative metabolism are generated at very high rates in the brain. Therefore, defending against oxidative stress is an essential task within the brain. An important cellular system against oxidative stress is the thioredoxin system (TS). TS is composed of thioredoxin, thioredoxin reductase, and NADPH. This review focuses on the evidence gathered in recent investigations into the central nervous system, specifically the different brain regions in which the TS is expressed. Furthermore, we address the conditions that modulate the thioredoxin system in both, animal models and the postmortem brains of human patients associated with the most common neurodegenerative disorders, in which the thioredoxin system could play an important part. PMID:24723994

  8. Experimental evidence for the effect of habitat loss on the dynamics of migratory networks.

    PubMed

    Betini, Gustavo S; Fitzpatrick, Mark J; Norris, D Ryan

    2015-06-01

    Migratory animals present a unique challenge for understanding the consequences of habitat loss on population dynamics because individuals are typically distributed over a series of interconnected breeding and non-breeding sites (termed migratory network). Using replicated breeding and non-breeding populations of Drosophila melanogaster and a mathematical model, we investigated three hypotheses to explain how habitat loss influenced the dynamics of populations in networks with different degrees of connectivity between breeding and non-breeding seasons. We found that habitat loss increased the degree of connectivity in the network and influenced population size at sites that were not directly connected to the site where habitat loss occurred. However, connected networks only buffered global population declines at high levels of habitat loss. Our results demonstrate why knowledge of the patterns of connectivity across a species range is critical for predicting the effects of environmental change and provide empirical evidence for why connected migratory networks are commonly found in nature.

  9. Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys.

    PubMed

    De Vos, Alta; O'Riain, M Justin

    2010-02-23

    Many animals respond to predation risk by forming groups. Evolutionary explanations for group formation in previously ungrouped, but loosely associated prey have typically evoked the selfish herd hypothesis. However, despite over 600 studies across a diverse array of taxa, the critical assumptions of this hypothesis have remained collectively untested, owing to several confounding problems in real predator-prey systems. To solve this, we manipulated the domains of danger of Cape fur seal (Arctocephalus pusillus pusillus) decoys to provide evidence that a selfish reduction in a seals' domain of danger results in a proportional reduction in its predation risk from ambush shark attacks. This behaviour confers a survival advantage to individual seals within a group and explains the evolution of selfish herds in a prey species. These findings empirically elevate Hamilton's selfish herd hypothesis to more than a 'theoretical curiosity'.

  10. Sharks shape the geometry of a selfish seal herd: experimental evidence from seal decoys

    PubMed Central

    De Vos, Alta; O'Riain, M. Justin

    2010-01-01

    Many animals respond to predation risk by forming groups. Evolutionary explanations for group formation in previously ungrouped, but loosely associated prey have typically evoked the selfish herd hypothesis. However, despite over 600 studies across a diverse array of taxa, the critical assumptions of this hypothesis have remained collectively untested, owing to several confounding problems in real predator–prey systems. To solve this, we manipulated the domains of danger of Cape fur seal (Arctocephalus pusillus pusillus) decoys to provide evidence that a selfish reduction in a seals' domain of danger results in a proportional reduction in its predation risk from ambush shark attacks. This behaviour confers a survival advantage to individual seals within a group and explains the evolution of selfish herds in a prey species. These findings empirically elevate Hamilton's selfish herd hypothesis to more than a ‘theoretical curiosity’. PMID:19793737

  11. The Impact of Smoking Bans on Smoking and Consumer Behavior: Quasi-Experimental Evidence from Switzerland.

    PubMed

    Boes, Stefan; Marti, Joachim; Maclean, Johanna Catherine

    2015-11-01

    In this paper, we exploit the progressive implementation of smoking bans in public venues at the state level in Switzerland to evaluate both the direct effects on smoking and the potential unintended consequences of these legislations on consumer behaviors as measured by visiting restaurants/bars and discos ('going out'). Our results indicate that public venue smoking bans in Switzerland reduce smoking rates, but the findings do not emerge until 1 year following the ban. This pattern of results is consistent with delays in ban enforcement on the part of business owners, difficulties in changing addictive behaviors such as smoking, and/or learning on the part of smokers. We find evidence that smoking bans influence going-out behavior and there is substantial heterogeneity across venue and consumer characteristics.

  12. The emotional and attitudinal consequences of religious hypocrisy: experimental evidence using a cognitive dissonance paradigm.

    PubMed

    Yousaf, Omar; Gobet, Fernand

    2013-01-01

    We explored the emotional and attitudinal consequences of personal attitude-behavior discrepancies using a religious version of the hypocrisy paradigm. We induced cognitive dissonance in participants (n = 206) by making them feel hypocritical for advocating certain religious behaviors that they had not recently engaged in to their own satisfaction. In Experiment 1, this resulted in higher levels of self-reported guilt and shame compared to the control condition. Experiment 2 further showed that a religious self-affirmation task eliminated the guilt and shame. In Experiment 3, participants boosted their religious attitudes as a result of dissonance, and both religious and non-religious self-affirmation tasks eliminated this effect. The findings provide evidence that dissonance induced through religious hypocrisy can result in guilt and shame as well as an attitude bolstering effect, as opposed to the attitude reconciliation effect that is prevalent in previous dissonance research.

  13. Experimental Evidence of melt-brake at seismic rates in sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Kuo, L.; Suppe, J.; Song, S.; Song, Y.; Yeh, E.; Dong, J.; Wang, C.; Yang, C.

    2011-12-01

    Frictional melts generated along seismic faults theoretically may act either as a lubricant or as a viscous brake. Present geological and geophysical evidence supports melt-lubrication, which is also in good agreement with extreme strength weakening in laboratory frictional experiments. On the contrary, the strengthening behavior of viscous melts at seismic rates is not well reported, especially in sedimentary rocks. Here we provide laboratory evidence of progressive increase in frictional resistance on sandstone at a slip rate of 1.3 m/s with melt generation. The produced melt/pseudotachylyte is observed with Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and is in-situ analyzed with X-ray diffraction analysis (XRD) and Transmission X-ray Microscopy (TXM) in synchrotron radiation. These analytical results show that the formation of pseudotachylyte is composed of pulverized quartz grains suspending in amorphous melts from thermally decomposed clay minerals. The observation of TXM also indicates that the shapes of quartz grains in the slip zone vary from rounded in the central area to angular on the rim. In-situ microstructures and high frictional resistance of sandstones in experiments indicate that the dominant strengthening mechanism is possibly controlled by viscous melts with suspending quartz grains. The melt rheology at high slip rates is not well understood, but the frictional behavior of melt with nano-sized quartz grains appears to be rheopetic instead of melt lubrication and/or powder lubrication. Thus, it suggests that the first-time rupture of sedimentary faults is not lubricated by melts during earthquake; in contrast melts from thermally decomposed clay minerals with suspending quartz grains produced by faulting may be an important process for the dynamic strengthening of faults.

  14. EXPERIMENTAL EVIDENCE FOR WATER FORMATION VIA OZONE HYDROGENATION ON DUST GRAINS AT 10 K

    SciTech Connect

    Mokrane, H.; Chaabouni, H.; Accolla, M.; Congiu, E.; Dulieu, F.; Chehrouri, M.; Lemaire, J. L.

    2009-11-10

    The formation of water molecules from the reaction between ozone (O{sub 3}) and D-atoms is studied experimentally for the first time. Ozone is deposited on non-porous amorphous solid water ice (H{sub 2}O), and D-atoms are then sent onto the sample held at 10 K. HDO molecules are detected during the desorption of the whole substrate where isotope mixing takes place, indicating that water synthesis has occurred. The efficiency of water formation via hydrogenation of ozone is of the same order of magnitude as that found for reactions involving O-atoms or O{sub 2} molecules and exhibits no apparent activation barrier. These experiments validate the assumption made by models using ozone as one of the precursors of water formation via solid-state chemistry on interstellar dust grains.

  15. Electric Dipole Aggregates in Very Dilute Polar Liquids:. Theory and Experimental Evidence

    NASA Astrophysics Data System (ADS)

    Yinnon, Tamar A.; Yinnon, Carmi A.

    We show that rotational excited aggregates with an electric dipole moment may be created in polar liquids. Under proper storage conditions, the life times of the aggregates are very long, e.g., days and even years. In solutions, the aggregates are composed of solvent molecules only or a combination of these and solute particles. The process steps leading to the formation of the aggregates are: (1) vigorous succussing the liquid or its solution; (2) adding nonsuccussed liquid; (3) repetition of step (1) and (2). In solutions, formation of the aggregates requires that these steps are repeated until the concentration is reduced below a solvent and solute specific molarity, which under room temperature and pressure conditions, typically, is of the order of 10-4 M or below. The characteristics of liquids containing aggregates with an electric dipole, theoretically derived in this paper, conform to the experimentally observed ones, reported in the literature.

  16. Experimental evidence for shallow, slow-moving landslides activated by a decrease in ground temperature

    NASA Astrophysics Data System (ADS)

    Shibasaki, Tatsuya; Matsuura, Sumio; Okamoto, Takashi

    2016-07-01

    In order to understand the trigger mechanism of slow-moving landslides occurring in the early cold season from late autumn to winter, we investigated the effect of temperature on the shear strength of slip surface soils. Displacement-controlled and shear stress-controlled box shear experiments were performed on undisturbed slip zone soils under residual strength conditions. Test results conducted at temperatures from 9 to 25°C showed remarkable shear strength reductions with decreasing temperature. Creep-like slow shear displacements were induced by a decrease in temperature. These temperature-dependent shear behaviors are attributed to the rheological properties of hydrous smectite that dominantly compose the soil material along the failure surface. Our experimental results imply that ground temperature conditions influence slope instability, especially for shallow landslides occurring in smectite-bearing rock areas.

  17. Adolescents' implicit theories predict desire for vengeance after peer conflicts: correlational and experimental evidence.

    PubMed

    Yeager, David S; Trzesniewski, Kali H; Tirri, Kirsi; Nokelainen, Petri; Dweck, Carol S

    2011-07-01

    Why do some adolescents respond to interpersonal conflicts vengefully, whereas others seek more positive solutions? Three studies investigated the role of implicit theories of personality in predicting violent or vengeful responses to peer conflicts among adolescents in Grades 9 and 10. They showed that a greater belief that traits are fixed (an entity theory) predicted a stronger desire for revenge after a variety of recalled peer conflicts (Study 1) and after a hypothetical conflict that specifically involved bullying (Study 2). Study 3 experimentally induced a belief in the potential for change (an incremental theory), which resulted in a reduced desire to seek revenge. This effect was mediated by changes in bad-person attributions about the perpetrators, feelings of shame and hatred, and the belief that vengeful ideation is an effective emotion-regulation strategy. Together, the findings illuminate the social-cognitive processes underlying reactions to conflict and suggest potential avenues for reducing violent retaliation in adolescents. PMID:21604865

  18. Adolescents' implicit theories predict desire for vengeance after peer conflicts: correlational and experimental evidence.

    PubMed

    Yeager, David S; Trzesniewski, Kali H; Tirri, Kirsi; Nokelainen, Petri; Dweck, Carol S

    2011-07-01

    Why do some adolescents respond to interpersonal conflicts vengefully, whereas others seek more positive solutions? Three studies investigated the role of implicit theories of personality in predicting violent or vengeful responses to peer conflicts among adolescents in Grades 9 and 10. They showed that a greater belief that traits are fixed (an entity theory) predicted a stronger desire for revenge after a variety of recalled peer conflicts (Study 1) and after a hypothetical conflict that specifically involved bullying (Study 2). Study 3 experimentally induced a belief in the potential for change (an incremental theory), which resulted in a reduced desire to seek revenge. This effect was mediated by changes in bad-person attributions about the perpetrators, feelings of shame and hatred, and the belief that vengeful ideation is an effective emotion-regulation strategy. Together, the findings illuminate the social-cognitive processes underlying reactions to conflict and suggest potential avenues for reducing violent retaliation in adolescents.

  19. Thermodynamic analysis of turbulent combustion in a spark ignition engine. Experimental evidence

    NASA Technical Reports Server (NTRS)

    Beretta, G. P.; Rashidi, M.; Keck, J. C.

    1980-01-01

    A method independent of physical modeling assumptions is presented to analyze high speed flame photography and cylinder pressure measurements from a transparent piston spark ignition research engine. The method involves defining characteristic quantities of the phenomena of flame propagation and combustion, and estimating their values from the experimental information. Using only the pressure information, the mass fraction curves are examined. An empirical burning law is presented which simulates such curves. Statistical data for the characteristics delay and burning angles which show that cycle to cycle fractional variations are of the same order of magnitude for both angles are discussed. The enflamed and burnt mass fractions are compared as are the rates of entrainment and burning.

  20. Molecular dynamics prediction and experimental evidence for density of normal and metastable liquid zirconium

    NASA Astrophysics Data System (ADS)

    Wang, H. P.; Yang, S. J.; Hu, L.; Wei, B.

    2016-06-01

    The density of normal and metastable undercooled liquid zirconium was predicted by performing molecular dynamics calculation with a system consisting of 4000 atoms and measured by electrostatic levitation experiments. The results show that the density increases linearly with the descending of temperature, including a maximum undercooling of 928 K. The density is 6.00 g cm-3 at the melting temperature, which agrees well with the experimental result of 6.06 g cm-3. Furthermore, the atomic number is increased to 32,000 on the basis of 4000 atoms and there appears only 0.02% difference. Besides, the pair distribution function was applied to display the atomic structure, which indicates the liquid structure change occurs at the first neighbor distance.

  1. Modulation of MnSOD in Cancer:Epidemiological and Experimental Evidence

    PubMed Central

    Kim, Aekyong

    2010-01-01

    Since it was first observed in late 1970s that human cancers often had decreased manganese superoxide dismutase (MnSOD) protein expression and activity, extensive studies have been conducted to verify the association between MnSOD and cancer. Significance of MnSOD as a primary mitochondrial antioxidant enzyme is unquestionable; results from in vitro, in vivo and epidemiological studies are in harmony. On the contrary, studies regarding roles of MnSOD in cancer often report conflicting results. Although putative mechanisms have been proposed to explain how MnSOD regulates cellular proliferation, these mechanisms are not capitulated in epidemiological studies. This review discusses most recent epidemiological and experimental studies that examined the association between MnSOD and cancer, and describes emerging hypotheses of MnSOD as a mitochondrial redox regulatory enzyme and of how altered mitochondrial redox may affect physiology of normal as well as cancer cells. PMID:24278510

  2. Unintended effects of poverty programmes on childbearing in less developed countries: experimental evidence from Latin America.

    PubMed

    Stecklov, Guy; Winters, Paul; Todd, Jessica; Regalia, Ferdinando

    2007-07-01

    Because conditional cash transfer (CCT) programmes (which make payments to poor households, conditional on their behaviour) potentially affect both household resource levels and parental preferences for quality vs. quantity of children, they may have unintended consequences for fertility. We use panel data from experimental CCT programmes in three Latin American countries to assess the unintended impact of these programmes on childbearing. Our findings, based on difference-in-difference models, show that the programme in Honduras, which inadvertently created large incentives for childbearing, may have raised fertility by between 2 and 4 percentage points. The CCT programmes in the two other countries, Mexico and Nicaragua, did not have the same unintended incentives for childbearing, and in these countries we found no net impact on fertility. Subsequent analysis examined several potential mechanisms by which fertility in Honduras may have been raised but was not able to identify a primary mechanism with the available data. PMID:17558882

  3. Passive Facebook usage undermines affective well-being: Experimental and longitudinal evidence.

    PubMed

    Verduyn, Philippe; Lee, David Seungjae; Park, Jiyoung; Shablack, Holly; Orvell, Ariana; Bayer, Joseph; Ybarra, Oscar; Jonides, John; Kross, Ethan

    2015-04-01

    Prior research indicates that Facebook usage predicts declines in subjective well-being over time. How does this come about? We examined this issue in 2 studies using experimental and field methods. In Study 1, cueing people in the laboratory to use Facebook passively (rather than actively) led to declines in affective well-being over time. Study 2 replicated these findings in the field using experience-sampling techniques. It also demonstrated how passive Facebook usage leads to declines in affective well-being: by increasing envy. Critically, the relationship between passive Facebook usage and changes in affective well-being remained significant when controlling for active Facebook use, non-Facebook online social network usage, and direct social interactions, highlighting the specificity of this result. These findings demonstrate that passive Facebook usage undermines affective well-being.

  4. Experimental evidence that GNA and TNA were not sequential polymers in the prebiotic evolution of RNA.

    PubMed

    Yang, Ying-Wei; Zhang, Su; McCullum, Elizabeth O; Chaput, John C

    2007-09-01

    Systematic investigation into the chemical etiology of ribose has led to the discovery of glycerol nucleic acid (GNA) and threose nucleic acid (TNA) as possible progenitor candidates of RNA in the origins of life. Coupled with their chemical simplicity, polymers for both systems are capable of forming stable Watson-Crick antiparallel duplex structures with themselves and RNA, thereby providing a mechanism for the transfer of genetic information between successive genetic systems. Investigation into whether both polymers arose independently or descended from a common evolutionary pathway would provide additional constraints on models that describe the emergence of a hypothetical RNA world. Here we show by thermal denaturation that complementary GNA and TNA mixed sequence polymers are unable, even after prolonged incubation times, to adopt stable helical structures by intersystem cross-pairing. This experimental observation suggests that GNA and TNA, whose structures derive from one another, were not consecutive polymers in the same evolutionary pathway to RNA. PMID:17828568

  5. Balloon folding affects the symmetry of stent deployment: experimental and computational evidence.

    PubMed

    Narracott, Andrew J; Lawford, Patricia V; Gunn, Julian P G; Hose, D Rodney

    2007-01-01

    The level of restenosis following coronary artery stenting may be related to the deployed stent geometry. This study investigated the influence of two balloon folding patterns (;C' and ;S' shaped) on stent deployment. In vitro stent expansion showed ;S' shape folding produced more uniform expansion than ;C' shape folding. A numerical contact model (NCM) was developed to study the detail of load transfer between balloon and stent. Finite element analysis of the Palmaz-Schatz 204C stent provided a composite non-linear material model for the NCM. Agreement between the predicted final stent geometry and experimental results was strongly dependent on the frictional coefficient between the stent and balloon. We conclude that non-uniform contact may contribute to the asymmetry of deployed stents reported clinically.

  6. Experimental evidence for chick discrimination without recognition in a brood parasite host

    PubMed Central

    Grim, Tomáš

    2006-01-01

    Recognition is considered a critical basis for discriminatory behaviours in animals. Theoretically, recognition and discrimination of parasitic chicks are not predicted to evolve in hosts of brood parasitic birds that evict nest-mates. Yet, an earlier study showed that host reed warblers (Acrocephalus scirpaceus) of an evicting parasite, the common cuckoo (Cuculus canorus), can avoid the costs of prolonged care for unrelated young by deserting the cuckoo chick before it fledges. Desertion was not based on specific recognition of the parasite because hosts accept any chick cross-fostered into their nests. Thus, the mechanism of this adaptive host response remains enigmatic. Here, I show experimentally that the cue triggering this ‘discrimination without recognition’ behaviour is the duration of parental care. Neither the intensity of brood care nor the presence of a single-chick in the nest could explain desertions. Hosts responded similarly to foreign chicks, whether heterospecific or experimental conspecifics. The proposed mechanism of discrimination strikingly differs from those found in other parasite–host systems because hosts do not need an internal recognition template of the parasite's appearance to effectively discriminate. Thus, host defences against parasitic chicks may be based upon mechanisms qualitatively different from those operating against parasitic eggs. I also demonstrate that this discriminatory mechanism is non-costly in terms of recognition errors. Comparative data strongly suggest that parasites cannot counter-evolve any adaptation to mitigate effects of this host defence. These findings have crucial implications for the process and end-result of host–parasite arms races and our understanding of the cognitive basis of discriminatory mechanisms in general. PMID:17164201

  7. Absence of magnetic isotope fractionation for Hg during dark biological processes: experimental evidence and theoretical considerations

    NASA Astrophysics Data System (ADS)

    Kritee, K.; Barkay, T.; Blum, J. D.

    2008-12-01

    The complex biogeochemistry and toxicity of Hg compounds warrants the search for new strategies that could be used to decipher the relative importance of its multiple abiotic and microbial transformations in ecosystems. In this regard, the emerging mercury isotope systematics is showing tremendous potential. We have studied the extent of fractionation of Hg stable isotopes during 1) degradation of MMHg and 2) Hg(II) reduction by multiple Hg(II) reducing strains, and irrespective of the extent of mass dependent fractionation (MDF) we did not observe any mass independent fractionation (MIF) of Hg isotopes. On the other hand, photo-chemical degradation of MMHg and reduction of Hg(II) cause a very high extent of MIF (Bergquist and Blum, 2007). Because there are many more unexamined microbial processes that influence Hg cycling in addition to the microbial transformations examined experimentally, and because some of these (e.g., oxidative degradation of MMHg) are not amenable to pure culture studies, a crucial question facing Hg biogeochemists is "Can microbial/biological processes cause MIF or are MIF signatures unique to photo- chemical transformations?" Based on the high spin orbit coupling in Hg compounds, the low likelihood of suppression of spin orbit coupling during dark biological processes, and the nature of known enzyme-Hg and microbe-Hg interactions, we suggest that the nuclear spin dependent MIF is unlikely to occur during dark biological processes. Because of the important implications of the absence of MIF during biological processes on Hg isotope systematics, we will also discuss experimental strategies that could be used to confirm this suggestion (Kritee et al., 2008). Bergquist B. A. and Blum J. D. (2007) Mass-dependent and mass-independent fractionation of Hg isotopes by photo-reduction in aquatic systems. Science 318(5849), 417-420. Kritee K., Barkay T., and Blum J. D. (2008) Mass dependent mercury stable isotope fractionation during microbial

  8. Isostaticity and Controlled Force Transmission in the Cytoskeleton: A Model Awaiting Experimental Evidence

    PubMed Central

    Blumenfeld, Raphael

    2006-01-01

    A new model is proposed for force transmission through the cytoskeleton (CSK). A general discussion is first presented on the physical principles that underlie the modeling of this phenomenon. Some fundamental problems of conventional models—continuous and discrete—are examined. It is argued that mediation of focused forces is essential for good control over intracellular mechanical signals. The difficulties of conventional continuous models in describing such mediation are traced to a fundamental assumption rather than to their being continuous. Relevant advantages and disadvantages of continuous and discrete modeling are discussed. It is concluded that favoring discrete models is based on two misconceptions, which are clarified. The model proposed here is based on the idea that focused propagation of mechanical stimuli in frameworks over large distances (compared to the mesh size) can only occur when considerable regions of the CSK are isostatic. The concept of isostaticity is explained and a recently developed continuous isostaticity theory is briefly reviewed. The model enjoys several advantages: it leads to good control over force mediation; it explains nonuniform stresses and action at a distance; it is continuous, making it possible to model force propagation over long distances; and it enables prediction of individual force paths. To be isostatic, or nearly so, CSK networks must possess specific structural characteristics, and these are quantified. Finally, several experimental observations are interpreted using the new model and implications are discussed. It is also suggested that this approach may give insight into the dynamics of reorganization of the CSK. Many of the results are amenable to experimental measurements, providing a testing ground for the proposed picture, and generic experiments are suggested. PMID:16912215

  9. In-Situ and Experimental Evidence for Acidic Weathering of Rocks and Soils on Mars

    NASA Technical Reports Server (NTRS)

    Hurowitz, J. A.; McLennan, S. M.; Tosca, N. J.; Arvidson, R. E.; Michalski, J. R.; Ming, D.; Schroeder, C.; Squyres, S. W.

    2006-01-01

    Experimental data for alteration of synthetic Martian basalts at pH=0-1 indicate that chemical fractionations at low pH are vastly different from those observed during terrestrial weathering. Rock analyses from Gusev crater are well described by the relationships apparent from low pH experimental alteration data. A model for rock surface alteration is developed which indicates that a leached alteration zone is present on rock surfaces at Gusev. This zone is not chemically fractionated to a large degree from the underlying rock interior, indicating that the rock surface alteration process has occurred at low fluid-to-rock ratio. The geochemistry of natural rock surfaces analyzed by APXS is consistent with a mixture between adhering soil/dust and the leached alteration zone. The chemistry of rock surfaces analyzed after brushing with the RAT is largely representative of the leached alteration zone. The chemistry of rock surfaces analyzed after grinding with the RAT is largely representative of the interior of the rock, relatively unaffected by the alteration process occurring at the rock surface. Elemental measurements from the Spirit, Opportunity, Pathfinder and Viking 1 landing sites indicate that soil chemistry from widely separated locations is consistent with the low-pH, low fluid to rock ratio alteration relationships developed for Gusev rocks. Soils are affected principally by mobility of FeO and MgO, consistent with alteration of olivine-bearing basalt and subsequent precipitation of FeO and MgO bearing secondary minerals as the primary control on soil geochemistry.

  10. Experimental evidence for chick discrimination without recognition in a brood parasite host.

    PubMed

    Grim, Tomás

    2007-02-01

    Recognition is considered a critical basis for discriminatory behaviours in animals. Theoretically, recognition and discrimination of parasitic chicks are not predicted to evolve in hosts of brood parasitic birds that evict nest-mates. Yet, an earlier study showed that host reed warblers (Acrocephalus scirpaceus) of an evicting parasite, the common cuckoo (Cuculus canorus), can avoid the costs of prolonged care for unrelated young by deserting the cuckoo chick before it fledges. Desertion was not based on specific recognition of the parasite because hosts accept any chick cross-fostered into their nests. Thus, the mechanism of this adaptive host response remains enigmatic. Here, I show experimentally that the cue triggering this 'discrimination without recognition' behaviour is the duration of parental care. Neither the intensity of brood care nor the presence of a single-chick in the nest could explain desertions. Hosts responded similarly to foreign chicks, whether heterospecific or experimental conspecifics. The proposed mechanism of discrimination strikingly differs from those found in other parasite-host systems because hosts do not need an internal recognition template of the parasite's appearance to effectively discriminate. Thus, host defences against parasitic chicks may be based upon mechanisms qualitatively different from those operating against parasitic eggs. I also demonstrate that this discriminatory mechanism is non-costly in terms of recognition errors. Comparative data strongly suggest that parasites cannot counter-evolve any adaptation to mitigate effects of this host defence. These findings have crucial implications for the process and end-result of host-parasite arms races and our understanding of the cognitive basis of discriminatory mechanisms in general.

  11. Experimental evidence of statistical ensemble behavior in bed load sediment transport

    NASA Astrophysics Data System (ADS)

    Fathel, Siobhan L.; Furbish, David Jon; Schmeeckle, Mark W.

    2015-11-01

    A high-resolution data set obtained from high-speed imaging of coarse sand particles transported as bed load allows us to confidently describe the forms and qualities of the ensemble distributions of particle velocities, accelerations, hop distances, and traveltimes. Autocorrelation functions of frame-averaged values (and the decay of these functions) support the idea that the forms of these distributions become time invariant within the 5 s imaging interval. Distributions of streamwise and cross-stream particle velocities are exponential, consistent with previous experiments and theory. Importantly, streamwise particle velocities possess a "light" tail, where the largest velocities are limited by near-bed fluid velocities. Distributions of streamwise and cross-stream particle accelerations are Laplace in form and are centered on zero, consistent with equilibrium transport conditions. The majority of particle hops, measured start to stop, involve short displacements, and streamwise hop distances possess a Weibull distribution. In contrast to previous work, the distribution of traveltimes is exponential, consistent with a fixed temporal disentrainment rate. The Weibull distribution of hop distances is consistent with a decreasing spatial disentrainment rate and is related to the exponential distribution of traveltimes. By taking into account the effects of experimental censorship associated with a finite sampling window, the relationship between streamwise hop distances and traveltimes, Lx˜Tpα, likely involves an exponent of α ˜ 2. These experimental results—an exponential distribution of traveltimes Tp and a Weibull distribution of hop distances Lx with shape parameter k < 1—are consistent with a nonlinear relationship between these quantities with α > 1.

  12. Experimental evidence for the basal generation place of the short-latency transient-evoked otoacoustic emissions.

    PubMed

    Moleti, A; Sisto, R; Lucertini, M

    2014-05-01

    Time-frequency analysis of the transient-evoked otoacoustic emission response was performed on a population of subjects affected by sensory-neural hearing loss characterized by a sharp audiometric profile, caused by firearm noise exposure (42 ears), and on a control population of normal-hearing subjects (84 ears). Time-frequency filtering permitted a careful evaluation of the relation between the audiometric profile and the spectral shape of the long- and short-latency otoacoustic components. Both filtered spectra closely follow the shape of the audiometric profile, with a frequency shift between them. The typical frequency shift was evaluated by averaging the otoacoustic spectra and the audiograms among groups of ears with the same cutoff frequency. Assuming that the otoacoustic emission source function depends on the local effectiveness of the cochlear amplifier, this experimental evidence suggests that the short-latency response is generated at a cochlear place displaced towards the base by about 0.5-1 mm with respect to the generation place of the long-latency component. The analysis of the control group demonstrates that, below 4 kHz, the observed effect is not dependent on the data acquisition and analysis procedure. These results confirm previous theoretical estimates and independent experimental evidence based on the measured latency difference between the two components. PMID:24815267

  13. The Role of Uric Acid in Kidney Fibrosis: Experimental Evidences for the Causal Relationship

    PubMed Central

    Kim, Il Young; Lee, Dong Won; Kwak, Ihm Soo

    2014-01-01

    Hyperuricemia is a common finding in chronic kidney disease due to decreased uric acid clearance. The role of uric acid as a risk factor for chronic kidney disease has been largely debated, and recent studies suggested a role of uric acid in the causation and progression of kidney fibrosis, a final common pathway in chronic kidney disease. Uric acid and xanthine oxidase may contribute to kidney fibrosis mainly by inducing inflammation, endothelial dysfunction, oxidative stress, and activation of the renin-angiotensin system. Besides, hyperuricemia induces alterations in renal hemodynamics via afferent arteriolopathy and contributes to the onset and progression of kidney fibrosis. Xanthine oxidase inhibitors may prevent kidney damage via lowering uric acid and/or inhibiting xanthine oxidase. However, there is still no sufficient evidence from interventional clinical researches supporting the causal relationship between uric acid and kidney fibrosis. The effect and role of xanthine oxidase inhibitors in preventing kidney fibrosis and chronic kidney disease progression must be further explored by performing future large scale clinical trials. PMID:24877124

  14. Experimental Evidence of an Eco-evolutionary Feedback during Adaptive Divergence.

    PubMed

    Matthews, Blake; Aebischer, Thierry; Sullam, Karen E; Lundsgaard-Hansen, Bänz; Seehausen, Ole

    2016-02-22

    Differences in how organisms modify their environment can evolve rapidly and might influence adaptive population divergence. In a common garden experiment in aquatic mesocosms, we found that adult stickleback from a recently diverged pair of lake and stream populations had contrasting effects on ecosystem metrics. These modifications were caused by both genetic and plastic differences between populations and were sometimes comparable in magnitude to those caused by the presence/absence of stickleback. Lake and stream fish differentially affected the biomass of zooplankton and phytoplankton, the concentration of phosphorus, and the abundance of several prey (e.g., copepods) and non-prey (e.g., cyanobacteria) species. The adult-mediated effects on mesocosm ecosystems influenced the survival and growth of a subsequent generation of juvenile stickleback reared in the same mesocosms. The prior presence of adults decreased the overall growth rate of juveniles, and the prior presence of stream adults lowered overall juvenile survival. Among the survivors, lake juveniles grew faster than co-occurring stream juveniles, except in mesocosm ecosystems previously modified by adult lake fish that were reared on plankton. Overall, our results provide evidence for reciprocal interactions between ecosystem dynamics and evolutionary change (i.e., eco-evolutionary feedbacks) in the early stages of adaptive population divergence. PMID:26804555

  15. Experimental evidence for the functional relevance of anion-π interactions

    NASA Astrophysics Data System (ADS)

    Dawson, Ryan E.; Hennig, Andreas; Weimann, Dominik P.; Emery, Daniel; Ravikumar, Velayutham; Montenegro, Javier; Takeuchi, Toshihide; Gabutti, Sandro; Mayor, Marcel; Mareda, Jiri; Schalley, Christoph A.; Matile, Stefan

    2010-07-01

    Attractive in theory and confirmed to exist, anion-π interactions have never really been seen at work. To catch them in action, we prepared a collection of monomeric, cyclic and rod-shaped naphthalenediimide transporters. Their ability to exert anion-π interactions was demonstrated by electrospray tandem mass spectrometry in combination with theoretical calculations. To relate this structural evidence to transport activity in bilayer membranes, affinity and selectivity sequences were recorded. π-acidification and active-site decrowding increased binding, transport and chloride > bromide > iodide selectivity, and supramolecular organization inverted acetate > nitrate to nitrate > acetate selectivity. We conclude that anion-π interactions on monomeric surfaces are ideal for chloride recognition, whereas their supramolecular enhancement by π,π-interactions appears perfect to target nitrate. Chloride transporters are relevant to treat channelopathies, and nitrate sensors to monitor cellular signaling and cardiovascular diseases. A big impact on organocatalysis can be expected from the stabilization of anionic transition states on chiral π-acidic surfaces.

  16. The Function of Gas Vesicles in Halophilic Archaeaand Bacteria: Theories and Experimental Evidence

    PubMed Central

    Oren, Aharon

    2012-01-01

    A few extremely halophilic Archaea (Halobacterium salinarum, Haloquadratum walsbyi, Haloferax mediterranei, Halorubrum vacuolatum, Halogeometricum borinquense, Haloplanus spp.) possess gas vesicles that bestow buoyancy on the cells. Gas vesicles are also produced by the anaerobic endospore-forming halophilic Bacteria Sporohalobacter lortetii and Orenia sivashensis. We have extensive information on the properties of gas vesicles in Hbt. salinarum and Hfx. mediterranei and the regulation of their formation. Different functions were suggested for gas vesicle synthesis: buoying cells towards oxygen-rich surface layers in hypersaline water bodies to prevent oxygen limitation, reaching higher light intensities for the light-driven proton pump bacteriorhodopsin, positioning the cells optimally for light absorption, light shielding, reducing the cytoplasmic volume leading to a higher surface-area-to-volume ratio (for the Archaea) and dispersal of endospores (for the anaerobic spore-forming Bacteria). Except for Hqr. walsbyi which abounds in saltern crystallizer brines, gas-vacuolate halophiles are not among the dominant life forms in hypersaline environments. There only has been little research on gas vesicles in natural communities of halophilic microorganisms, and the few existing studies failed to provide clear evidence for their possible function. This paper summarizes the current status of the different theories why gas vesicles may provide a selective advantage to some halophilic microorganisms. PMID:25371329

  17. Experimental evidence for phase separation in hydrogen-helium mixtures at Jovian planet conditions

    NASA Astrophysics Data System (ADS)

    Collins, G. W.; Brygoo, S.; Millot, M.; Rygg, J. R.; Celliers, P. M.; Eggert, J.; Boehly, T. R.; Jeanloz, R.; Loubeyre, P.

    2015-11-01

    Whether or not H-He mixtures phase separate in Jovian planets is important to our understanding of the structure and evolution of Jupiter and Saturn. Also integral to such planet models, as well as mechanisms for H-He phase separation, are the insulating-to-conducting and the molecular-to-atomic-hydrogen transitions in the H-He mixture. Coupling static and dynamic compression techniques has allowed us to make the first thermodynamic and transport measurements of H-He mixtures at deep Jovian planet conditions. These data provide evidence that the H-He fluid demixes at the high pressures and temperatures expected to exist deep inside Saturn and Jupiter. This phase separation may result in the differentiation of heavier helium clusters, leading to helium rain in the deep interior of Saturn and perhaps even in a significant outer layer of Jupiter. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory in part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344.

  18. Experimental evidence of pharmacological management of anchorage in Orthodontics: A systematic review

    PubMed Central

    Fernández-González, Felipe José; Cañigral, Aránzazu; Balbontín-Ayala, Felipe; Gonzalo-Orden, José Manuel; de Carlos, Felix; Cobo, Teresa; Fernández-Vázquez, Jose Pedro; Sánchez-Lasheras, Fernando; Vega, José Antonio

    2015-01-01

    Introduction: Orthodontic anchorage is one of the most challenging aspects of Orthodontics. Preventing undesired movement of teeth could result in safer and less complicated orthodontic treatment. Recently, several reviews have been published about the effects of different molecules on bone physiology and the clinical side effects in Orthodontics. However, the effects of local application of these substances on the rate of orthodontic tooth movement have not been assessed. Objectives: The aim of this research was to analyze the scientific evidence published in the literature about the effects of different molecules on orthodontic anchorage. Methods: The literature was systematically reviewed using PubMed/Medline, Scopus and Cochrane databases from 2000 up to July 31st, 2014. Articles were independently selected by two different researchers based on previously established inclusion and exclusion criteria, with a concordance Kappa index of 0.86. The methodological quality of the reviewed papers was performed. Results: Search strategy identified 270 articles. Twenty-five of them were selected after application of inclusion/exclusion criteria, and only 11 qualified for final analysis. Molecules involved in orthodontic anchorage were divided into three main groups: osteoprotegerin (OPG), bisphosphonates (BPs) and other molecules (OMs). Conclusions: Different drugs are able to alter the bone remodeling cycle, influencing osteoclast function and, therefore, tooth movement. Thus, they could be used in order to provide maximal anchorage while preventing undesired movements. OPG was found the most effective molecule in blocking the action of osteoclasts, thereby reducing undesired movements. PMID:26560822

  19. Glycerol Is a Suberin Monomer. New Experimental Evidence for an Old Hypothesis1

    PubMed Central

    Moire, Laurence; Schmutz, Alain; Buchala, Antony; Yan, Bin; Stark, Ruth E.; Ryser, Ulrich

    1999-01-01

    The monomer composition of the esterified part of suberin can be determined using gas chromatography-mass spectroscopy technology and is accordingly believed to be well known. However, evidence was presented recently indicating that the suberin of green cotton (Gossypium hirsutum cv Green Lint) fibers contains substantial amounts of esterified glycerol. This observation is confirmed in the present report by a sodium dodecyl sulfate extraction of membrane lipids and by a developmental study, demonstrating the correlated accumulation of glycerol and established suberin monomers. Corresponding amounts of glycerol also occur in the suberin of the periderm of cotton stems and potato (Solanum tuberosum) tubers. A periderm preparation of wound-healing potato tuber storage parenchyma was further purified by different treatments. As the purification proceeded, the concentration of glycerol increased at about the same rate as that of α,ω-alkanedioic acids, the most diagnostic suberin monomers. Therefore, it is proposed that glycerol is a monomer of suberins in general and can cross-link aliphatic and aromatic suberin domains, corresponding to the electron-translucent and electron-opaque suberin lamellae, respectively. This proposal is consistent with the reported dimensions of the electron-translucent suberin lamellae. PMID:10069853

  20. Experimental evidence for an intraspecific Janzen-Connell effect mediated by soil biota.

    PubMed

    Liu, Xubing; Etienne, Rampal S; Liang, Minxia; Wang, Yongfan; Yu, Shixiao

    2015-03-01

    The negative effect of soil pathogens on seedling survival varies considerably among conspecific individuals, but the underlying mechanisms are largely unknown. For variation between heterospecifics, a common explanation is the Janzen-Connell effect: negative density dependence in survival due to specialized pathogens aggregating on common hosts. We test whether an intraspecific Janzen-Connell effect exists, i.e., whether the survival chances of one population's seedlings surrounded by a different conspecific population increase with genetic difference, spatial distance, and trait dissimilarity between them. In a shade-house experiment, we grew seedlings of five populations of each of two subtropical tree species (Castanopsis fissa and Canarium album) for which we measured genetic distance using intersimple sequence repeat (ISSR) analysis and eight common traits/characters, and we treated them with soil material or soil biota filtrate collected from different populations. We found that the relative survival rate increased with increasing dissimilarity measured by spatial distance, genetic distance, and trait differences between the seedling and the population around which the soil was collected. This effect disappeared after soil sterilization. Our results provide evidence that genetic variation, trait similarity, and spatial distance can explain intraspecific variation in plant-soil biotic interactions and suggest that limiting similarity also occurs at the intraspecific level. PMID:26236863

  1. Is there chaos in the brain? II. Experimental evidence and related models.

    PubMed

    Korn, Henri; Faure, Philippe

    2003-09-01

    The search for chaotic patterns has occupied numerous investigators in neuroscience, as in many other fields of science. Their results and main conclusions are reviewed in the light of the most recent criteria that need to be satisfied since the first descriptions of the surrogate strategy. The methods used in each of these studies have almost invariably combined the analysis of experimental data with simulations using formal models, often based on modified Huxley and Hodgkin equations and/or of the Hindmarsh and Rose models of bursting neurons. Due to technical limitations, the results of these simulations have prevailed over experimental ones in studies on the nonlinear properties of large cortical networks and higher brain functions. Yet, and although a convincing proof of chaos (as defined mathematically) has only been obtained at the level of axons, of single and coupled cells, convergent results can be interpreted as compatible with the notion that signals in the brain are distributed according to chaotic patterns at all levels of its various forms of hierarchy. This chronological account of the main landmarks of nonlinear neurosciences follows an earlier publication [Faure, Korn, C. R. Acad. Sci. Paris, Ser. III 324 (2001) 773-793] that was focused on the basic concepts of nonlinear dynamics and methods of investigations which allow chaotic processes to be distinguished from stochastic ones and on the rationale for envisioning their control using external perturbations. Here we present the data and main arguments that support the existence of chaos at all levels from the simplest to the most complex forms of organization of the nervous system. We first provide a short mathematical description of the models of excitable cells and of the different modes of firing of bursting neurons (Section 1). The deterministic behavior reported in giant axons (principally squid), in pacemaker cells, in isolated or in paired neurons of Invertebrates acting as coupled

  2. Formation of Quartz-Carbonate Veins: Evidence From Experimental Supercritical Carbon Dioxide-Brine-Rock System

    NASA Astrophysics Data System (ADS)

    Janecky, D. R.; Kaszuba, J. P.

    2003-12-01

    Quartz-carbonate veins are common in a variety of moderate temperature hydrothermal systems and ore deposits. Associated fluid inclusions have a wide range of compositions, including liquid carbon dioxide fillings. Examination of chemical and physical conditions which result precipitation of quartz and carbonate in veins raises several key questions about multiphase fluid processes and reaction rates. We have been experimentally investigating physical-chemical reaction processes of mixed brine-carbon dioxide fluids for the shallow crust. Synthetic arkose (microcline + oligoclase + quartz + biotite) plus argillaceous shale were reacted with 5.5 molal NaCl brine. The system was held at 200 C and 200 bars for 32 days to approach steady state, then injected with carbon dioxide and allowed to react for an additional 45 days. In a parallel experiment, the system was allowed to react for 77 days without injection of carbon dioxide. Trace ions initially absent from NaCl brine appeared in solution at mM (K, Ca, and silica) to uM (Mg, Al, Fe and Mn) quantities, reflecting reaction of brine with rock. Without carbon dioxide injection, the silica concentration (2.4 mM) was stable below calculated quartz solubility (3.9 mM). Injection of carbon dioxide resulted in decreased pH and increased silica concentration to a level near calculated chalcedony solubility (5.4 mM). Dissolution of silicate minerals is apparently coupled to the acidity, and concomitant inhibition of the precipitation of quartz (and other silicates). A significant increase in concentration of trace metals is consistent with in-situ pH decrease and increased carbon dioxide dissolved in brine. Multi-phase fluid reaction relationships between supercritical carbon dioxide and brine-rock systems allow formation of carbonate vein precipitates in substantial quantities. Brine and continued rock reactions provide a substantial reservoir for Ca, Mg and Fe components. A separate carbon dioxide liquid allows

  3. Regulation of Sclerostin Production in Human Male Osteocytes by Androgens: Experimental and Clinical Evidence.

    PubMed

    Di Nisio, Andrea; De Toni, Luca; Speltra, Elena; Rocca, Maria Santa; Taglialavoro, Giuseppe; Ferlin, Alberto; Foresta, Carlo

    2015-12-01

    In this study we aimed to elucidate a possible role of T in the regulation of sclerostin, a glycoprotein secreted by osteocytes known to regulate bone mass. To this end, we evaluated the effect of T stimulation on sclerostin production and gene expression in human cultured osteocytes. In addition, we evaluated serum sclerostin levels in a cohort of 20 hypogonadal male patients, compared with 20 age-matched eugonadal controls. Stimulation with DHT decreased sclerostin expression in cultured osteocytes in a time- and dose-dependent manner. Confirming a direct androgen receptor-mediated effect on sclerostin production, flutamide coincubation and silencing of androgen receptor gene in osteocytes abolished the DHT effects. In addition, hypogonadal patients showed higher serum sclerostin levels with respect to controls (145.87 ± 50.83 pg/mL vs 84.02 ± 32.15 pg/mL; P < .001) and in both probands and controls, serum T levels were negatively correlated with sclerostin (R = -0.664, P = 0.007, and R = -0.447, P = .045, respectively). Finally, multiple stepwise regression analysis showed that T represented the only independent predictor of sclerostin levels. In conclusion, by showing a direct correlation between T and sclerostin, both in vivo and in vitro, this study adds further support to the emerging clinical and experimental studies focusing on sclerostin as a therapeutic target for osteoporosis treatment.

  4. Circadian rhythms of liver physiology and disease: experimental and clinical evidence.

    PubMed

    Tahara, Yu; Shibata, Shigenobu

    2016-04-01

    The circadian clock system consists of a central clock located in the suprachiasmatic nucleus in the hypothalamus and peripheral clocks in peripheral tissues. Peripheral clocks in the liver have fundamental roles in maintaining liver homeostasis, including the regulation of energy metabolism and the expression of enzymes controlling the absorption and metabolism of xenobiotics. Over the past two decades, research has investigated the molecular mechanisms linking circadian clock genes with the regulation of hepatic physiological functions, using global clock-gene-knockout mice, or mice with liver-specific knockout of clock genes or clock-controlled genes. Clock dysfunction accelerates the development of liver diseases such as fatty liver diseases, cirrhosis, hepatitis and liver cancer, and these disorders also disrupt clock function. Food is an important regulator of circadian clocks in peripheral tissues. Thus, controlling the timing of food consumption and food composition, a concept known as chrononutrition, is one area of active research to aid recovery from many physiological dysfunctions. In this Review, we focus on the molecular mechanisms of hepatic circadian gene regulation and the relationships between hepatic circadian clock systems and liver physiology and disease. We concentrate on experimental data obtained from cell or mice and rat models and discuss how these findings translate into clinical research, and we highlight the latest developments in chrononutritional studies.

  5. Experimental evidence of large changes in terrestrial chlorine cycling following altered tree species composition.

    PubMed

    Montelius, Malin; Thiry, Yves; Marang, Laura; Ranger, Jacques; Cornelis, Jean-Thomas; Svensson, Teresia; Bastviken, David

    2015-04-21

    Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chloride (Cl(-)) levels. Despite the widespread abundance of Clorg and the common ability of microorganisms to produce Clorg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl(-) and Clorg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl(-) and Clorg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl(-) and Clorg over the experiment period, and showed a 10 and 4 times higher Cl(-) and Clorg storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher storage of Cl(-) and Clorg in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.

  6. Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils

    NASA Astrophysics Data System (ADS)

    Colleary, Caitlin; Dolocan, Andrei; Gardner, James; Singh, Suresh; Wuttke, Michael; Rabenstein, Renate; Habersetzer, Jörg; Schaal, Stephan; Feseha, Mulugeta; Clemens, Matthew; Jacobs, Bonnie F.; Currano, Ellen D.; Jacobs, Louis L.; Lyng Sylvestersen, Rene; Gabbott, Sarah E.; Vinther, Jakob

    2015-10-01

    In living organisms, color patterns, behavior, and ecology are closely linked. Thus, detection of fossil pigments may permit inferences about important aspects of ancient animal ecology and evolution. Melanin-bearing melanosomes were suggested to preserve as organic residues in exceptionally preserved fossils, retaining distinct morphology that is associated with aspects of original color patterns. Nevertheless, these oblong and spherical structures have also been identified as fossilized bacteria. To date, chemical studies have not directly considered the effects of diagenesis on melanin preservation, and how this may influence its identification. Here we use time-of-flight secondary ion mass spectrometry to identify and chemically characterize melanin in a diverse sample of previously unstudied extant and fossil taxa, including fossils with notably different diagenetic histories and geologic ages. We document signatures consistent with melanin preservation in fossils ranging from feathers, to mammals, to amphibians. Using principal component analyses, we characterize putative mixtures of eumelanin and phaeomelanin in both fossil and extant samples. Surprisingly, both extant and fossil amphibians generally exhibit melanosomes with a mixed eumelanin/phaeomelanin composition rather than pure eumelanin, as assumed previously. We argue that experimental maturation of modern melanin samples replicates diagenetic chemical alteration of melanin observed in fossils. This refutes the hypothesis that such fossil microbodies could be bacteria, and demonstrates that melanin is widely responsible for the organic soft tissue outlines in vertebrates found at exceptional fossil localities, thus allowing for the reconstruction of certain aspects of original pigment patterns.

  7. Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils.

    PubMed

    Colleary, Caitlin; Dolocan, Andrei; Gardner, James; Singh, Suresh; Wuttke, Michael; Rabenstein, Renate; Habersetzer, Jörg; Schaal, Stephan; Feseha, Mulugeta; Clemens, Matthew; Jacobs, Bonnie F; Currano, Ellen D; Jacobs, Louis L; Sylvestersen, Rene Lyng; Gabbott, Sarah E; Vinther, Jakob

    2015-10-13

    In living organisms, color patterns, behavior, and ecology are closely linked. Thus, detection of fossil pigments may permit inferences about important aspects of ancient animal ecology and evolution. Melanin-bearing melanosomes were suggested to preserve as organic residues in exceptionally preserved fossils, retaining distinct morphology that is associated with aspects of original color patterns. Nevertheless, these oblong and spherical structures have also been identified as fossilized bacteria. To date, chemical studies have not directly considered the effects of diagenesis on melanin preservation, and how this may influence its identification. Here we use time-of-flight secondary ion mass spectrometry to identify and chemically characterize melanin in a diverse sample of previously unstudied extant and fossil taxa, including fossils with notably different diagenetic histories and geologic ages. We document signatures consistent with melanin preservation in fossils ranging from feathers, to mammals, to amphibians. Using principal component analyses, we characterize putative mixtures of eumelanin and phaeomelanin in both fossil and extant samples. Surprisingly, both extant and fossil amphibians generally exhibit melanosomes with a mixed eumelanin/phaeomelanin composition rather than pure eumelanin, as assumed previously. We argue that experimental maturation of modern melanin samples replicates diagenetic chemical alteration of melanin observed in fossils. This refutes the hypothesis that such fossil microbodies could be bacteria, and demonstrates that melanin is widely responsible for the organic soft tissue outlines in vertebrates found at exceptional fossil localities, thus allowing for the reconstruction of certain aspects of original pigment patterns.

  8. Experimental evidence of dust-induced shaping of surface dissolved organic matter in the oligotrophic ocean

    NASA Astrophysics Data System (ADS)

    Pulido-Villena, Elvira; Djaoudi, Kahina; Barani, Aude; Charrière, Bruno; Delmont, Anne; Hélias-Nunige, Sandra; Marc, Tedetti; Wambeke France, Van

    2016-04-01

    Recent research has shown that dust deposition may impact the functioning of the microbial loop. On one hand, it enhances bacterial mineralization of dissolved organic matter (DOM), and so may limit the carbon export. On the other hand, the interaction between heterotrophic bacteria and DOM in the surface ocean can increase the residence time of DOM, promoting its export and sequestration in the deep ocean. The main goal of this study was to experimentally assess whether the bacterial response to dust deposition is prone to have an effect on the residence time of the DOM pool by modifying its bioavailability. The bacterial degradation of DOM was followed on dust-amended and control treatments during long-term incubations. Dissolved organic carbon concentration decreased by 9 μmol L-1 over the course of the experiment in both control and dust-enriched conditions, with no significant differences between treatments. However, significant differences in DOM optical properties appeared at the latest stage of the incubations suggesting an accumulation of DOM of high molecular weight in the dust-amended treatment. At the end of the incubations, the remaining water was filtered and re-used as a new culture medium for a bacterial natural assemblage. Bacterial abundance and production was lower in the treatment previously submitted to dust enrichment, suggesting a decrease in DOM lability after a dust deposition event. These preliminary results point to a new link between dust and ocean carbon cycle through the modification of the residence time of the DOM pool.

  9. Experimental evidence for modifying the current physical model for ice accretion on aircraft surfaces

    NASA Technical Reports Server (NTRS)

    Olsen, W.; Walker, E.

    1986-01-01

    Closeup movies, still photographs, and other experimental data suggest that the current physical model for ice accretion needs significant modification. At aircraft airspeeds there was no flow of liquid over the surface of the ice after a short initial flow, even at barely subfreezing temperatures. Instead, there were very large stationary drops on the ice surface that lose water from their bottoms by freezing and replenish their liquid by catching the microscopic cloud droplets. This observation disagrees with the existing physical model, which assumes there is a thin liquid film continuously flowing over the ice surface. With no such flow, the freezing-fraction concept of the model fails when a mass balance is performed on the surface water. Rime ice does, as the model predicts, form when the air temperature is low enough to cause the cloud droplets to freeze almost immediately on impact. However, the characteristic shapes of horn-glaze ice or rime ice are primarily caused by the ice shape affecting the airflow locally and consequently the droplet catch and the resulting ice shape. Ice roughness greatly increases the heat transfer coefficient, stops the movement of drops along the surface, and may also affect the airflow initially and thereby the droplet catch. At high subreezing temperatures the initial flow and shedding of surface drops have a large effect on the ice shape. At the incipient freezing limit, no ice forms.

  10. Experimental Evidence of Classical Conditioning and Microscopic Engrams in an Electroconductive Material

    PubMed Central

    Karbowski, Lukasz M.; Persinger, Michael A.

    2016-01-01

    Synthetic experimental substrates are indispensable tools which can allow researchers to model biological processes non-invasively in three-dimensional space. In this study, we investigated the capacities of an electroconductive material whose properties converge upon those of the brain. An electrically conductive material composed of carbohydrates, proteins, fats, ions, water, and trace amounts of other organic compounds and minerals was classically conditioned as inferred by electrophysiological measurements. Spectral densities evoked during the display of a conditioned stimulus (CS) probe were strongly congruent with those displayed during the conditioned-unconditioned stimulus pairing (CS-UCS). The neutral stimulus consisted of the pulsed light from a LED. The unconditioned stimulus was an alternating current. Interstimulus intervals >130 ms did not result in conditioned responses. Microscopic analysis of the chemically-fixed substratum revealed 10–200 μm wide ‘vessel structures’ within samples exposed to a stimulus. Greater complexity (increased fractal dimensions) was clearly discernable by light microscopy for stained sections of fixed samples that had been conditioned compared to various controls. The denser pixels indicated greater concentration of stain and increased canalization. Implications for learning and memory formation are discussed. PMID:27764215

  11. Social learning solves the problem of narrow-peaked search landscapes: experimental evidence in humans

    PubMed Central

    Acerbi, Alberto; Tennie, Claudio

    2016-01-01

    The extensive use of social learning is considered a major reason for the ecological success of humans. Theoretical considerations, models and experiments have explored the evolutionary basis of social learning, showing the conditions under which learning from others is more adaptive than individual learning. Here we present an extension of a previous experimental set-up, in which individuals go on simulated ‘hunts’ and their success depends on the features of a ‘virtual arrowhead’ they design. Individuals can modify their arrowhead either by individual trial and error or by copying others. We study how, in a multimodal adaptive landscape, the smoothness of the peaks influences learning. We compare narrow peaks, in which solutions close to optima do not provide useful feedback to individuals, to wide peaks, where smooth landscapes allow an effective hill-climbing individual learning strategy. We show that individual learning is more difficult in narrow-peaked landscapes, but that social learners perform almost equally well in both narrow- and wide-peaked search spaces. There was a weak trend for more copying in the narrow than wide condition, although as in previous experiments social information was generally underutilized. Our results highlight the importance of tasks’ design space when studying the adaptiveness of high-fidelity social learning. PMID:27703687

  12. Impact of bisphenol a on the cardiovascular system - epidemiological and experimental evidence and molecular mechanisms.

    PubMed

    Gao, Xiaoqian; Wang, Hong-Sheng

    2014-08-15

    Bisphenol A (BPA) is a ubiquitous plasticizing agent used in the manufacturing of polycarbonate plastics and epoxy resins. There is well-documented and broad human exposure to BPA. The potential risk that BPA poses to the human health has attracted much attention from regulatory agencies and the general public, and has been extensively studied. An emerging and rapidly growing area in the study of BPA's toxicity is its impact on the cardiovascular (CV) system. Recent epidemiological studies have shown that higher urinary BPA concentration in humans is associated with various types of CV diseases, including angina, hypertension, heart attack and coronary and peripheral arterial disease. Experimental studies have demonstrated that acute BPA exposure promotes the development of arrhythmias in female rodent hearts. Chronic exposure to BPA has been shown to result in cardiac remodeling, atherosclerosis, and altered blood pressure in rodents. The underlying mechanisms may involve alteration of cardiac Ca2+ handling, ion channel inhibition/activation, oxidative stress, and genome/transcriptome modifications. In this review, we discuss these recent findings that point to the potential CV toxicity of BPA, and highlight the knowledge gaps in this growing research area.

  13. Laying date, incubation and egg breakage as determinants of bacterial load on bird eggshells: experimental evidence.

    PubMed

    Soler, Juan José; Ruiz-Rodríguez, Magdalena; Martín-Vivaldi, Manuel; Peralta-Sánchez, Juan Manuel; Ruiz-Castellano, Cristina; Tomás, Gustavo

    2015-09-01

    Exploring factors guiding interactions of bacterial communities with animals has become of primary importance for ecologists and evolutionary biologists during the last years because of their likely central role in the evolution of animal life history traits. We explored the association between laying date and eggshell bacterial load (mesophilic bacteria, Enterobacteriaceae, Staphylococci, and Enterococci) in natural and artificial magpie (Pica pica) nests containing fresh commercial quail (Coturnix coturnix) eggs. We manipulated hygiene conditions by spilling egg contents on magpie and artificial nests and explored experimental effects during the breeding season. Egg breakage is a common outcome of brood parasitism by great spotted cuckoos (Clamator glandarius) on the nests of magpie, one of its main hosts. We found that the treatment increased eggshell bacterial load in artificial nests, but not in magpie nests with incubating females, which suggests that parental activity prevents the proliferation of bacteria on the eggshells in relation to egg breakage. Moreover, laying date was positively related to eggshell bacterial load in active magpie nests, but negatively in artificial nests. The results suggest that variation in parental characteristics of magpies rather than climatic variation during the breeding season explained the detected positive association. Because the eggshell bacterial load is a proxy of hatching success, the detected positive association between eggshell bacterial loads and laying date in natural, but not in artificial nests, suggests that the generalized negative association between laying date and avian breeding success can be, at least partially, explained by differential bacterial effects.

  14. Benefit of multiple trait selection to increase reproductive traits: experimental evidence from golden hamsters.

    PubMed

    Satoh, M; Nishida, A; van Arendonk, J A; van der Lende, T

    1997-12-01

    Fifteen generations of selection were conducted to study responses for litter size at birth (LSB), weight at weaning of standardized litter (LWW), and individual body weight at 8 wk of age (BW8) using golden hamsters as an experimental model for pigs. The experiment involved three lines: selection on an aggregate breeding value of LSB, LWW, and BW8 (line W); selection on an aggregate breeding value of LSB and LWW (line R); and a randomly selected control (line C). Selection in W and R was based on breeding values from a multiple trait animal model. Restricted maximum likelihood with an animal model was used to estimate genetic parameters and genetic trends. Heritability estimates for LSB, LWW, and BW8 were .10, .47, and .52, respectively, and genetic correlations between traits were all positive. The mean estimated breeding value (EBV) for LSB in generation 15 was +2.2 pups in W and R. The mean EBV for LWW in generation 15 was +318 g for W and +174 g for R, and for BW8 means were +64 g and +24 g, respectively. Average inbreeding at generation 16 was 13.4, 19.5, and 8.0% for W, R, and C, respectively. Including BW8 in the selection criterion reduced inbreeding and had a beneficial effect on selection responses in LSB, LWW, and BW8.

  15. Yes, it turns: experimental evidence of pearl rotation during its formation.

    PubMed

    Gueguen, Yannick; Czorlich, Yann; Mastail, Max; Le Tohic, Bruno; Defay, Didier; Lyonnard, Pierre; Marigliano, Damien; Gauthier, Jean-Pierre; Bari, Hubert; Lo, Cedrik; Chabrier, Sébastien; Le Moullac, Gilles

    2015-07-01

    Cultured pearls are human creations formed by inserting a nucleus and a small piece of mantle tissue into a living shelled mollusc, usually a pearl oyster. Although many pearl observations intuitively suggest a possible rotation of the nucleated pearl inside the oyster, no experimental demonstration of such a movement has ever been done. This can be explained by the difficulty of observation of such a phenomenon in the tissues of a living animal. To investigate this question of pearl rotation, a magnetometer system was specifically engineered to register magnetic field variations with magnetic sensors from movements of a magnetic nucleus inserted in the pearl oyster. We demonstrated that a continuous movement of the nucleus inside the oyster starts after a minimum of 40 days post-grafting and continues until the pearl harvest. We measured a mean angular speed of 1.27° min(-1) calculated for four different oysters. Rotation variability was observed among oysters and may be correlated to pearl shape and defects. Nature's ability to generate so amazingly complex structures like a pearl has delivered one of its secrets. PMID:26587271

  16. Experimental evidence of photoinduced vortex crossing in current carrying superconducting strips

    NASA Astrophysics Data System (ADS)

    Casaburi, A.; Heath, R. M.; Ejrnaes, M.; Nappi, C.; Cristiano, R.; Hadfield, R. H.

    2015-12-01

    We report an experimental investigation that shows how magnetic vortices are generated and cross a current carrying superconducting strip when illuminated by a bright (˜MeV) and fast (<500 ps duration) infrared light pulse. The work has been carried out using a strike-and-probe electro-optic technique on a device consisting of a parallel superconducting strip configuration, with wide spacing between the strips to allow the interaction of the photons with a single strip. We find that photons hitting one strip induce a collective current redistribution in the parallel strips, which we can quantitatively account for in the framework of the London model by including the effect of generated and trapped magnetic vortices in the superconducting loops formed by the two adjacent slots. The amount of trapped vorticity and its dependence on increasing current density flowing in the illuminated strip is in good agreement with the photon-assisted unbinding of vortex-antivortex pairs. This work allows us to gain a deeper understanding of the interaction between photons and current carrying superconducting strips.

  17. Experimental evidence for American bullfrog (Lithobates catesbeianus) susceptibility to chytrid fungus (Batrachochytrium dendrobatidis).

    PubMed

    Gervasi, Stephanie S; Urbina, Jenny; Hua, Jessica; Chestnut, Tara; A Relyea, Rick; R Blaustein, Andrew

    2013-06-01

    The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), has been associated with global amphibian population declines and extinctions. American bullfrogs (Lithobates catesbeianus) are widely reported to be a tolerant host and a carrier of Bd that spreads the pathogen to less tolerant hosts. Here, we examined whether bullfrogs raised from eggs to metamorphosis in outdoor mesocosms were susceptible to Bd. We experimentally exposed metamorphic juveniles to Bd in the laboratory and compared mortality rates of pathogen-exposed animals to controls (non-exposed) in two separate experiments; one using a Bd strain isolated from a Western toad and another using a strain isolated from an American bullfrog. We wanted to examine whether metamorphic bullfrogs were susceptible to either of these strains. We show that bullfrogs were susceptible to one strain of Bd and not the other. In both experiments, infection load detected in the skin decreased over time, suggesting that metamorphic bullfrogs from some populations may be inefficient long-term carriers of Bd. PMID:23539129

  18. Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils

    PubMed Central

    Colleary, Caitlin; Dolocan, Andrei; Gardner, James; Singh, Suresh; Wuttke, Michael; Rabenstein, Renate; Habersetzer, Jörg; Schaal, Stephan; Feseha, Mulugeta; Clemens, Matthew; Jacobs, Bonnie F.; Currano, Ellen D.; Jacobs, Louis L.; Sylvestersen, Rene Lyng; Gabbott, Sarah E.; Vinther, Jakob

    2015-01-01

    In living organisms, color patterns, behavior, and ecology are closely linked. Thus, detection of fossil pigments may permit inferences about important aspects of ancient animal ecology and evolution. Melanin-bearing melanosomes were suggested to preserve as organic residues in exceptionally preserved fossils, retaining distinct morphology that is associated with aspects of original color patterns. Nevertheless, these oblong and spherical structures have also been identified as fossilized bacteria. To date, chemical studies have not directly considered the effects of diagenesis on melanin preservation, and how this may influence its identification. Here we use time-of-flight secondary ion mass spectrometry to identify and chemically characterize melanin in a diverse sample of previously unstudied extant and fossil taxa, including fossils with notably different diagenetic histories and geologic ages. We document signatures consistent with melanin preservation in fossils ranging from feathers, to mammals, to amphibians. Using principal component analyses, we characterize putative mixtures of eumelanin and phaeomelanin in both fossil and extant samples. Surprisingly, both extant and fossil amphibians generally exhibit melanosomes with a mixed eumelanin/phaeomelanin composition rather than pure eumelanin, as assumed previously. We argue that experimental maturation of modern melanin samples replicates diagenetic chemical alteration of melanin observed in fossils. This refutes the hypothesis that such fossil microbodies could be bacteria, and demonstrates that melanin is widely responsible for the organic soft tissue outlines in vertebrates found at exceptional fossil localities, thus allowing for the reconstruction of certain aspects of original pigment patterns. PMID:26417094

  19. Overconfidence in wargames: experimental evidence on expectations, aggression, gender and testosterone.

    PubMed

    Johnson, Dominic D P; McDermott, Rose; Barrett, Emily S; Cowden, Jonathan; Wrangham, Richard; McIntyre, Matthew H; Peter Rosen, Stephen

    2006-10-01

    Overconfidence has long been noted by historians and political scientists as a major cause of war. However, the origins of such overconfidence, and sources of variation, remain poorly understood. Mounting empirical studies now show that mentally healthy people tend to exhibit psychological biases that encourage optimism, collectively known as 'positive illusions'. Positive illusions are thought to have been adaptive in our evolutionary past because they served to cope with adversity, harden resolve, or bluff opponents. Today, however, positive illusions may contribute to costly conflicts and wars. Testosterone has been proposed as a proximate mediator of positive illusions, given its role in promoting dominance and challenge behaviour, particularly in men. To date, no studies have attempted to link overconfidence, decisions about war, gender, and testosterone. Here we report that, in experimental wargames: (i) people are overconfident about their expectations of success; (ii) those who are more overconfident are more likely to attack; (iii) overconfidence and attacks are more pronounced among males than females; and (iv) testosterone is related to expectations of success, but not within gender, so its influence on overconfidence cannot be distinguished from any other gender specific factor. Overall, these results constitute the first empirical support of recent theoretical work linking overconfidence and war.

  20. Overconfidence in wargames: experimental evidence on expectations, aggression, gender and testosterone

    PubMed Central

    Johnson, Dominic D.P; McDermott, Rose; Barrett, Emily S; Cowden, Jonathan; Wrangham, Richard; McIntyre, Matthew H; Peter Rosen, Stephen

    2006-01-01

    Summary Overconfidence has long been noted by historians and political scientists as a major cause of war. However, the origins of such overconfidence, and sources of variation, remain poorly understood. Mounting empirical studies now show that mentally healthy people tend to exhibit psychological biases that encourage optimism, collectively known as ‘positive illusions’. Positive illusions are thought to have been adaptive in our evolutionary past because they served to cope with adversity, harden resolve, or bluff opponents. Today, however, positive illusions may contribute to costly conflicts and wars. Testosterone has been proposed as a proximate mediator of positive illusions, given its role in promoting dominance and challenge behaviour, particularly in men. To date, no studies have attempted to link overconfidence, decisions about war, gender, and testosterone. Here we report that, in experimental wargames: (i) people are overconfident about their expectations of success; (ii) those who are more overconfident are more likely to attack; (iii) overconfidence and attacks are more pronounced among males than females; and (iv) testosterone is related to expectations of success, but not within gender, so its influence on overconfidence cannot be distinguished from any other gender specific factor. Overall, these results constitute the first empirical support of recent theoretical work linking overconfidence and war. PMID:16959643

  1. No evidence of complementary water use along a plant species richness gradient in temperate experimental grasslands.

    PubMed

    Bachmann, Dörte; Gockele, Annette; Ravenek, Janneke M; Roscher, Christiane; Strecker, Tanja; Weigelt, Alexandra; Buchmann, Nina

    2015-01-01

    Niche complementarity in resource use has been proposed as a key mechanism to explain the positive effects of increasing plant species richness on ecosystem processes, in particular on primary productivity. Since hardly any information is available for niche complementarity in water use, we tested the effects of plant diversity on spatial and temporal complementarity in water uptake in experimental grasslands by using stable water isotopes. We hypothesized that water uptake from deeper soil depths increases in more diverse compared to low diverse plant species mixtures. We labeled soil water in 8 cm (with 18O) and 28 cm depth (with ²H) three times during the 2011 growing season in 40 temperate grassland communities of varying species richness (2, 4, 8 and 16 species) and functional group number and composition (legumes, grasses, tall herbs, small herbs). Stable isotope analyses of xylem and soil water allowed identifying the preferential depth of water uptake. Higher enrichment in 18O of xylem water than in ²H suggested that the main water uptake was in the upper soil layer. Furthermore, our results revealed no differences in root water uptake among communities with different species richness, different number of functional groups or with time. Thus, our results do not support the hypothesis of increased complementarity in water use in more diverse than in less diverse communities of temperate grassland species.

  2. Behavioral response to contamination risk information in a spatially explicit groundwater environment: Experimental evidence

    NASA Astrophysics Data System (ADS)

    Li, Jingyuan; Michael, Holly A.; Duke, Joshua M.; Messer, Kent D.; Suter, Jordan F.

    2014-08-01

    This paper assesses the effectiveness of aquifer monitoring information in achieving more sustainable use of a groundwater resource in the absence of management policy. Groundwater user behavior in the face of an irreversible contamination threat is studied by applying methods of experimental economics to scenarios that combine a physics-based, spatially explicit, numerical groundwater model with different representations of information about an aquifer and its risk of contamination. The results suggest that the threat of catastrophic contamination affects pumping decisions: pumping is significantly reduced in experiments where contamination is possible compared to those where pumping cost is the only factor discouraging groundwater use. The level of information about the state of the aquifer also affects extraction behavior. Pumping rates differ when information that synthesizes data on aquifer conditions (a "risk gauge") is provided, despite invariant underlying economic incentives, and this result does not depend on whether the risk information is location-specific or from a whole aquifer perspective. Interestingly, users increase pumping when the risk gauge signals good aquifer status compared to a no-gauge treatment. When the gauge suggests impending contamination, however, pumping declines significantly, resulting in a lower probability of contamination. The study suggests that providing relatively simple aquifer condition guidance derived from monitoring data can lead to more sustainable use of groundwater resources.

  3. Experimental evidence that competition and habitat use shape the individual fitness surface.

    PubMed

    Calsbeek, R

    2009-01-01

    A key prediction made by theories of density-dependent competition is that resource overlap should increase the intensity of competition. By extension, we can predict that competition should lead to density-dependent natural selection. I studied natural selection on limb length and body size in a total of seven populations of Anolis sagrei over 3 years in the Bahamas. Experimental manipulations of population density on small off-shore cays revealed that the strength of natural selection on body size increased with density, suggesting that density-dependent intraspecific competition drives natural selection. At low density, reduced competition revealed significant selection on limb length driven by changes in perch diameter, indicating that selection favoured a match between morphology and habitat. The role habitat played in shaping selection was further illuminated by inter-annual changes in vegetation structure stemming from variation in precipitation among years. Thus, changes in both the intensity of competition across spatial replicates, and in resource availability through time, revealed changes in the targets of natural selection. Results provide empirical support for the long-standing hypothesis that density-dependent natural selection shapes the fitness surface of Greater Antilles anoles.

  4. Pushing the limit: experimental evidence of climate effects on plant range distributions.

    PubMed

    Pfeifer-Meister, Laurel; Bridgham, Scott D; Little, Chelsea J; Reynolds, Lorien L; Goklany, Maya E; Johnson, Bart R

    2013-10-01

    Whether species will be extirpated in their current geographic ranges due to rapidly changing climate, and if so, whether they can avoid extinction by shifting their distributions are pressing questions for biodiversity conservation. However, forecasts of climate change impacts on species' geographic distributions rarely incorporate a demographic understanding of species' responses to climate. Because many biotic and abiotic factors at multiple scales control species' range limits, experimentation is essential to establish underlying mechanisms. We used a manipulative climate change experiment embedded within a natural climate gradient to examine demographic responses of 12 prairie species with northern range limits within the Pacific Northwest, USA. During the first year, warming decreased recruitment of species even at the coolest edge of their current ranges, but this effect disappeared when they were moved poleward beyond their current ranges. This response was largely driven by differences in germination rates. Other vital rates responded in unique and sometimes opposing ways (survivorship vs. fitness) to species' current ranges and climate change, and were mediated by indirect effects of climate on competition and nutrient availability. Our results demonstrate the importance of using regional-scale climate manipulations and the need for longer-term experiments on the demographic responses that control species' distributions.

  5. Experimental evidence for beneficial effects of projected climate change on hibernating amphibians.

    PubMed

    Üveges, Bálint; Mahr, Katharina; Szederkényi, Márk; Bókony, Veronika; Hoi, Herbert; Hettyey, Attila

    2016-05-27

    Amphibians are the most threatened vertebrates today, experiencing worldwide declines. In recent years considerable effort was invested in exposing the causes of these declines. Climate change has been identified as such a cause; however, the expectable effects of predicted milder, shorter winters on hibernation success of temperate-zone Amphibians have remained controversial, mainly due to a lack of controlled experimental studies. Here we present a laboratory experiment, testing the effects of simulated climate change on hibernating juvenile common toads (Bufo bufo). We simulated hibernation conditions by exposing toadlets to current (1.5 °C) or elevated (4.5 °C) hibernation temperatures in combination with current (91 days) or shortened (61 days) hibernation length. We found that a shorter winter and milder hibernation temperature increased survival of toads during hibernation. Furthermore, the increase in temperature and shortening of the cold period had a synergistic positive effect on body mass change during hibernation. Consequently, while climate change may pose severe challenges for amphibians of the temperate zone during their activity period, the negative effects may be dampened by shorter and milder winters experienced during hibernation.

  6. Experimental evidence of beam-foil plasma creation during ion-solid interaction

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Nandi, Tapan

    2016-08-01

    Charge state evolution of the energetic projectile ions during the passage through thin carbon foils has been revisited using the X-ray spectroscopy technique. Contributions from the bulk and the solid surface in the charge changing processes have been segregated by measuring the charge state distribution of the projectile ions in the bulk of the target during the ion-solid interaction. Interestingly, the charge state distribution measured in the bulk exhibits Lorentzian profile in contrast to the well-known Gaussian structure observed using the electromagnetic methods and the theoretical predictions. The occurrence of such behavior is a direct consequence of the imbalance between charge changing processes, which has been seen in various cases of the laboratory plasma. It suggests that the ion-solid collisions constitute high-density, localized plasma in the bulk of the solid target, called the beam-foil plasma. This condensed beam-foil plasma is similar to the high-density solar and stellar plasma which may have practical implementations in various fields, in particular, plasma physics and nuclear astrophysics. The present work suggests further modification in the theoretical charge state distribution calculations by incorporating the plasma coupling effects during the ion-solid interactions. Moreover, the multi-electron capture from the target exit surface has been confirmed through comparison between experimentally measured and theoretically predicted values of the mean charge state of the projectile ions.

  7. Experimental evidence for beneficial effects of projected climate change on hibernating amphibians

    PubMed Central

    Üveges, Bálint; Mahr, Katharina; Szederkényi, Márk; Bókony, Veronika; Hoi, Herbert; Hettyey, Attila

    2016-01-01

    Amphibians are the most threatened vertebrates today, experiencing worldwide declines. In recent years considerable effort was invested in exposing the causes of these declines. Climate change has been identified as such a cause; however, the expectable effects of predicted milder, shorter winters on hibernation success of temperate-zone Amphibians have remained controversial, mainly due to a lack of controlled experimental studies. Here we present a laboratory experiment, testing the effects of simulated climate change on hibernating juvenile common toads (Bufo bufo). We simulated hibernation conditions by exposing toadlets to current (1.5 °C) or elevated (4.5 °C) hibernation temperatures in combination with current (91 days) or shortened (61 days) hibernation length. We found that a shorter winter and milder hibernation temperature increased survival of toads during hibernation. Furthermore, the increase in temperature and shortening of the cold period had a synergistic positive effect on body mass change during hibernation. Consequently, while climate change may pose severe challenges for amphibians of the temperate zone during their activity period, the negative effects may be dampened by shorter and milder winters experienced during hibernation. PMID:27229882

  8. First experimental evidence for female mate choice in a nocturnal primate.

    PubMed

    Craul, Mathias; Zimmermann, Elke; Radespiel, Ute

    2004-10-01

    Female mate choice can be hypothesised in most nocturnal primates, since females show a higher investment in their offspring than males. The aim of this experimental study was to investigate if female grey mouse lemurs perform mate choice and whether age, relatedness (to the male), or male advertisement call activity systematically influence their decisions. A two-way mate choice design was developed in which females could choose between two males. Mate choice was deduced from the time spent in proximity to the males and from mating behaviour. During oestrus 12 of 17 females participated actively in the experiment and all of them showed either a significant spatial (n = 11) or behavioural (n = 1) preference for one male. In four cases copulations were observed. The influence of age on female mate choice was not statistically significant. In the cases with copulations, however, females mostly preferred the older male. This might indicate a preference for older age as an indicator of experience, fitness, and/or status. The influence of relatedness on female mate choice could not be definitely clarified. However, results imply a mechanism of kin recognition on the basis of familiarity. In the majority of choices, females preferred the male with higher trill call activity. Since trill call activity correlates with the relative dominance status of males, these results suggest an importance of the male dominance status for female mate choice in grey mouse lemurs. Altogether our findings indicate that females use a complex of different cues to choose their mates. PMID:15241637

  9. Experimental evidence for climatically controlled changes between lateral erosion and incision of actively uplifting folds

    NASA Astrophysics Data System (ADS)

    Bufe, Aaron; Paola, Chris; Burbank, Douglas; Thompson, Jessica

    2016-04-01

    The understanding of the incision and lateral erosion of rivers provides key data for the interpretation of landscapes as recorders of climatic and tectonic processes. We present results from six physical experiments on the erosion of a simple growing fold by antecedent streams. By varying uplift rates, sediment flux, and the width of alluvial fans upstream of the uplift, we produced a range of morphologies from narrow canyons through the fold to erosion of the entire uplift. The fraction of the uplift that was beveled by the river can be predicted by a dimensionless parameter linking the mobility of channels (strongly dependent on the sediment flux) and the rock-uplift rate. We apply these findings to a series of active folds in the foreland of the Tian Shan in NW China. Whereas the folds are incised today, they preserve uplifted, kilometer-wide beveled platforms. In the light of the experimental results, lateral migration rates required to explain such extensive beveling are similar to the lateral mobility of alluvial streams in areas much wetter than the presently arid northwestern Tarim Basin and suggest that major changes in water and sediment influxes are the probable cause of switches between lateral erosion and incision of active uplifts in the foreland of the Tian Shan. This finding is supported by the clustering of ages of fluvial terrace and alluvial fan deposition in that region.

  10. First Direct Experimental Evidence of Loss Cone Scattering of Energetic Electrons by Plasmaspheric Hiss

    NASA Astrophysics Data System (ADS)

    Breneman, A. W.; Halford, A.; Millan, R. M.; Wygant, J. R.; Cattell, C. A.; Woodger, L. A.; Hospodarsky, G. B.; Fennell, J.; Sample, J. G.; Kletzing, C.; Kurth, W. S.; Ukhorskiy, A. Y.; Goldstein, J.; Bonnell, J. W.

    2014-12-01

    A number of physical mechanisms have been identified as potentially important for causing Van Allen radiation belt electron loss. Over 40 years ago it was suggested that loss caused by electron interaction with an electromagnetic plasma wave called plasmaspheric hiss dominates electron loss in the outer portion of the radiation belt that overlaps with a high density region called the plasmasphere. Motivated by the difficulty of observing this loss process with particle detectors on satellites, the Balloon Array for Radiation Belt Relativistic Electron Losses (BARREL) campaign was designed to observe bremsstrahlung x-rays generated by electrons colliding with atmospheric neutrals after removal from the radiation belts. By comparison of x-ray counts to magnetically conjugate plasmaspheric hiss observed on the Van Allen Probes we provide the first direct experimental verification that hiss removes electrons from the radiation belts. X-ray counts and hiss amplitude show similar variation on timescales ranging from minutes to hours. A surprising result is that 1-20 min period fluctuations of x-rays and hiss are coherent on scales comparable to the size of the plasmasphere, far exceeding the few km scale on which wave-particle interactions operate, and establishing that the loss process has global effects on the radiation belts.

  11. Experimental evidence for American bullfrog (Lithobates catesbeianus) susceptibility to chytrid fungus (Batrachochytrium dendrobatidis).

    PubMed

    Gervasi, Stephanie S; Urbina, Jenny; Hua, Jessica; Chestnut, Tara; A Relyea, Rick; R Blaustein, Andrew

    2013-06-01

    The emerging fungal pathogen, Batrachochytrium dendrobatidis (Bd), has been associated with global amphibian population declines and extinctions. American bullfrogs (Lithobates catesbeianus) are widely reported to be a tolerant host and a carrier of Bd that spreads the pathogen to less tolerant hosts. Here, we examined whether bullfrogs raised from eggs to metamorphosis in outdoor mesocosms were susceptible to Bd. We experimentally exposed metamorphic juveniles to Bd in the laboratory and compared mortality rates of pathogen-exposed animals to controls (non-exposed) in two separate experiments; one using a Bd strain isolated from a Western toad and another using a strain isolated from an American bullfrog. We wanted to examine whether metamorphic bullfrogs were susceptible to either of these strains. We show that bullfrogs were susceptible to one strain of Bd and not the other. In both experiments, infection load detected in the skin decreased over time, suggesting that metamorphic bullfrogs from some populations may be inefficient long-term carriers of Bd.

  12. Experimental evidence for beneficial effects of projected climate change on hibernating amphibians.

    PubMed

    Üveges, Bálint; Mahr, Katharina; Szederkényi, Márk; Bókony, Veronika; Hoi, Herbert; Hettyey, Attila

    2016-01-01

    Amphibians are the most threatened vertebrates today, experiencing worldwide declines. In recent years considerable effort was invested in exposing the causes of these declines. Climate change has been identified as such a cause; however, the expectable effects of predicted milder, shorter winters on hibernation success of temperate-zone Amphibians have remained controversial, mainly due to a lack of controlled experimental studies. Here we present a laboratory experiment, testing the effects of simulated climate change on hibernating juvenile common toads (Bufo bufo). We simulated hibernation conditions by exposing toadlets to current (1.5 °C) or elevated (4.5 °C) hibernation temperatures in combination with current (91 days) or shortened (61 days) hibernation length. We found that a shorter winter and milder hibernation temperature increased survival of toads during hibernation. Furthermore, the increase in temperature and shortening of the cold period had a synergistic positive effect on body mass change during hibernation. Consequently, while climate change may pose severe challenges for amphibians of the temperate zone during their activity period, the negative effects may be dampened by shorter and milder winters experienced during hibernation. PMID:27229882

  13. Experimental evidence for both progressive and simultaneous shear during quasistatic compression of a bulk metallic glass

    NASA Astrophysics Data System (ADS)

    Wright, Wendelin J.; Liu, Yun; Gu, Xiaojun; Van Ness, Katherine D.; Robare, Steven L.; Liu, Xin; Antonaglia, James; LeBlanc, Michael; Uhl, Jonathan T.; Hufnagel, Todd C.; Dahmen, Karin A.

    2016-02-01

    Two distinct types of slip events occur during serrated plastic flow of bulk metallic glasses. These events are distinguished not only by their size but also by distinct stress drop rate profiles. Small stress drop serrations have fluctuating stress drop rates (with maximum stress drop rates ranging from 0.3-1 GPa/s), indicating progressive or intermittent propagation of a shear band. The large stress drop serrations are characterized by sharply peaked stress drop rate profiles (with maximum stress drop rates of 1-100 GPa/s). The propagation of a large slip is preceded by a slowly rising stress drop rate that is presumably due to the percolation of slipping weak spots prior to the initiation of shear over the entire shear plane. The onset of the rapid shear event is accompanied by a burst of acoustic emission. These large slips correspond to simultaneous shear with uniform sliding as confirmed by direct high-speed imaging and image correlation. Both small and large slip events occur throughout plastic deformation. The significant differences between these two types require that they be carefully distinguished in both modeling and experimental efforts.

  14. Exploring the costs and benefits of social information use: an appraisal of current experimental evidence

    PubMed Central

    Rieucau, Guillaume; Giraldeau, Luc-Alain

    2011-01-01

    Research on social learning has focused traditionally on whether animals possess the cognitive ability to learn novel motor patterns from tutors. More recently, social learning has included the use of others as sources of inadvertent social information. This type of social learning seems more taxonomically widespread and its use can more readily be approached as an economic decision. Social sampling information, however, can be tricky to use and calls for a more lucid appraisal of its costs. In this four-part review, we address these costs. Firstly, we address the possibility that only a fraction of group members are actually providing social information at any one time. Secondly, we review experimental research which shows that animals are circumspect about social information use. Thirdly, we consider the cases where social information can lead to incorrect decisions and finally, we review studies investigating the effect of social information quality. We address the possibility that using social information or not is not a binary decision and present results of a study showing that nutmeg mannikins combine both sources of information, a condition that can lead to the establishment of informational cascades. We discuss the importance of empirically investigating the economics of social information use. PMID:21357217

  15. A spotlight on liquefaction: evidence from clinical settings and experimental models in tuberculosis.

    PubMed

    Cardona, Pere-Joan

    2011-01-01

    Liquefaction is one of the most intriguing aspects of human tuberculosis. It is a major cause of the transition from the infection to active disease (tuberculosis, TB) as well as the transmission of M. tuberculosis to other persons. This paper reviews the natural history of liquefaction in humans from a pathological and radiological point of view and discusses how the experimental models available can be used to address the topic of liquefaction and cavity formation. Different concepts that have been related to liquefaction, from the influence of immune response to mechanical factors, are reviewed. Synchronic necrosis or apoptosis of infected macrophages in a close area, together with an ineffective fibrosis, appears to be clue in this process, in which macrophages, the immune response, and bacillary load interact usually in a particular scenario: the upper lobes of the lung. The summary would be that even if being a stochastic effect, liquefaction would result if the organization of the intragranulomatous necrosis (by means of fibrosis) would be disturbed.

  16. Optical manipulation of complex molecular systems by high density green photons: experimental and theoretical evidence

    NASA Astrophysics Data System (ADS)

    Comorosan, Sorin; Polosan, Silviu; Popescu, Irinel; Stamatin, Ioan; Ionescu, Elena; Avramescu, Sorin; Cristian Cune, Liviu; Apostol, Marian

    2013-05-01

    The recent revolution in modern optical techniques revealed that light interaction with matter generates a force, known as optical force, which produces material properties known in physics as optical matter. The basic technique of the domain uses forces exerted by a strongly focused beam of light to trap small objects and subsequently to manipulate their local structures. The purpose of this paper is to develop an alternative approach, using irradiations with high-density-green-photons, which induce electric dipoles by polarization effects. The materials used for the experiments were long carbon chains which represent the framework of biological macromolecules. The physical techniques used to reveal the locally induced molecular arrangements were: dynamic viscosity, zeta potential, chemiluminescence, liquid chromatography; mass spectrometry, and Raman and infrared spectroscopy. The principal result of our experiments was the detection of different molecular arrangements within the mixture of alkane chains, generated by our optical manipulations. This induced "optical matter" displayed two material properties: antioxidant effects and large molecular aggregation effects. In order to bring the experimental results in relation with theory, we developed a physical model and the interacting force between polarizable bodies was computed. By numerical calculations stable structures for N = 6 and N = 8 particles were obtained.

  17. Yes, it turns: experimental evidence of pearl rotation during its formation

    PubMed Central

    Gueguen, Yannick; Czorlich, Yann; Mastail, Max; Le Tohic, Bruno; Defay, Didier; Lyonnard, Pierre; Marigliano, Damien; Gauthier, Jean-Pierre; Bari, Hubert; Lo, Cedrik; Chabrier, Sébastien; Le Moullac, Gilles

    2015-01-01

    Cultured pearls are human creations formed by inserting a nucleus and a small piece of mantle tissue into a living shelled mollusc, usually a pearl oyster. Although many pearl observations intuitively suggest a possible rotation of the nucleated pearl inside the oyster, no experimental demonstration of such a movement has ever been done. This can be explained by the difficulty of observation of such a phenomenon in the tissues of a living animal. To investigate this question of pearl rotation, a magnetometer system was specifically engineered to register magnetic field variations with magnetic sensors from movements of a magnetic nucleus inserted in the pearl oyster. We demonstrated that a continuous movement of the nucleus inside the oyster starts after a minimum of 40 days post-grafting and continues until the pearl harvest. We measured a mean angular speed of 1.27° min−1 calculated for four different oysters. Rotation variability was observed among oysters and may be correlated to pearl shape and defects. Nature's ability to generate so amazingly complex structures like a pearl has delivered one of its secrets. PMID:26587271

  18. Evidence of apoptotic cell death after experimental traumatic brain injury in the rat.

    PubMed Central

    Rink, A.; Fung, K. M.; Trojanowski, J. Q.; Lee, V. M.; Neugebauer, E.; McIntosh, T. K.

    1995-01-01

    Apoptosis plays an important role in many developmental and pathological processes of the central nervous system. However, the role of apoptosis in traumatic brain injury has not been determined. Using the terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end labeling (TUNEL) method, we detected many cells with extensive DNA fragmentation in different regions of the brains of rats subjected to experimental traumatic brain injury. Two types of TUNEL-positive cells were demonstrated by light and electron microscopy, including type I cells that displayed morphological features of necrotic cell death and type II cells that displayed morphological features of classic apoptotic cell death. TUNEL-positive cells were detectable for up to 72 hours after the initial injury. Gel electrophoresis of DNA extracted from affected areas of the injured brain containing both type I and II cells revealed only internucleosomal fragmentation at 185-bp intervals, a feature originally described in apoptotic cell death. These data suggest that apoptosis, in addition to necrotic cell death, occurs after traumatic brain injury, and that internucleosomal fragmentation of DNA may be associated with certain types of necrotic cell death. Images Figure 1 Figure 2 Figure 4 PMID:7495282

  19. Experimental Evidence Shows the Importance of Behavioural Plasticity and Body Size under Competition in Waterfowl

    PubMed Central

    Zhang, Yong; Prins, Herbert H. T.; Versluijs, Martijn; Wessels, Rick; Cao, Lei; de Boer, Willem Frederik

    2016-01-01

    When differently sized species feed on the same resources, interference competition may occur, which may negatively affect their food intake rate. It is expected that competition between species also alters behaviour and feeding patch selection. To assess these changes in behaviour and patch selection, we applied an experimental approach using captive birds of three differently sized Anatidae species: wigeon (Anas penelope) (~600 g), swan goose (Anser cygnoides) (~2700 g) and bean goose (Anser fabalis) (~3200 g). We quantified the functional response for each species and then recorded their behaviour and patch selection with and without potential competitors, using different species combinations. Our results showed that all three species acquired the highest nitrogen intake at relatively tall swards (6, 9 cm) when foraging in single species flocks in the functional response experiment. Goose species were offered foraging patches differing in sward height with and without competitors, and we tested for the effect of competition on foraging behaviour. The mean percentage of time spent feeding and being vigilant did not change under competition for all species. However, all species utilized strategies that increased their peck rate on patches across different sward heights, resulting in the same instantaneous and nitrogen intake rate. Our results suggest that variation in peck rate over different swards height permits Anatidae herbivores to compensate for the loss of intake under competition, illustrating the importance of behavioural plasticity in heterogeneous environments when competing with other species for resources. PMID:27727315

  20. Experimental evidence of impacts of an invasive parakeet on foraging behavior of native birds

    PubMed Central

    2014-01-01

    Resource competition is one potential behavioral mechanism by which invasive species can impact native species, but detecting this competition can be difficult due to the interactions that variable environmental conditions can have on species behavior. This is particularly the case in urban habitats where the disturbed environment can alter natural behavior from that in undisturbed habitats. The rose-ringed parakeet (Psittacula krameri), is an increasingly common invasive species, predominantly associated with large urban centers. Using an experimental approach, we tested the behavioral responses of native garden birds in response to the presence of a rose-ringed parakeet versus the presence of a similarly sized and dominant native bird, the great spotted woodpecker (Dendrocopos major). Parakeet presence significantly reduced feeding rates and increased vigilance among native birds compared with our control treatments. Of visits made by native birds in the presence of a parakeet, feeding was more likely to occur in sites within the parakeet range compared with sites outside, suggesting some habituation of native birds has occurred following prior exposure to parakeets but overall foraging behavior is still disrupted. The results of our study suggest that nonnative species can have complex and subtle impacts on native fauna and show that a nonnative competitor can impact native species simply through their presence near resources. PMID:24822022

  1. Sorption/desorption kinetics of contaminants on mobile particles: Modeling and experimental evidence

    NASA Astrophysics Data System (ADS)

    Bold, Steffen; Kraft, Siegfried; Grathwohl, Peter; Liedl, Rudolf

    2003-12-01

    In this study the impact of sorption/desorption kinetics between organic contaminants and mobile particles suspended in subsurface water is analyzed. TCE migration through a granular activated carbon column is investigated at different transport velocities with lignite and activated carbon particles as mobile carriers. The measured breakthrough characteristics of TCE can be reproduced by a reactive transport model simulating sorption/desorption kinetics applying an intraparticle diffusion approach for mobile particles and the packed bed of granular activated carbon. Model predictions are based on independently measured physicochemical parameters, i.e., no calibration of TCE sorption/desorption is required. The close matches of experimental data to predicted data validate the exclusively process-based model assumptions and indicate that this approach has large predictive capabilities. Extending these findings, a sensitivity study is presented in order to specify under which conditions sorption/desorption of contaminants in mobile particles has to be modeled as a kinetic process. It is found that sorption/desorption kinetics are of major importance for Damköhler numbers between 0.01 and 100.

  2. Evidence of gating in hundred nanometer diameter pores: an experimental and theoretical study

    SciTech Connect

    Letant, S E; Schaldach, C M; Johnson, M R; Sawvel, A; Bourcier, W L; Wilson, W D

    2006-01-11

    We report on the observation of an unexpected gating mechanism at the 100 nm scale on track-etched polycarbonate membranes. Transport measurements of methyl viologen performed by absorption spectroscopy under various pH conditions demonstrated that perfect gating was achieved for 100 nm diameter pores at pH 2, while the positively charged molecular ions moved through the membrane according to diffusion laws at pH 5. An oppositely charged molecular ion, naphthalene disulfonate, in the same membrane, showed the opposite trend: diffusion of the negative ion at pH 2 and perfect gating at pH 5. The influence of parameters such as ionic strength and membrane surface coating were also investigated. A theoretical study of the system shows that at this larger length scale the magnitude of the electric field in the vicinity of the pores is too small to account for the experimental observations, rather, it is the surface trapping of the mobile ion (Cl{sup -} or Na{sup +}) which gives rise to the gating phenomena. This surprising effect might have potential applications for high-throughput separation of large molecules and bio-organisms.

  3. Experimental evidence for a cost of resistance to the fungal pathogen, Batrachochytrium dendrobatidis, for the palmate newt, Lissotriton helveticus

    PubMed Central

    2013-01-01

    Background Batrachochytrium dendrobatidis (Bd), the causative agent of chytridiomycosis, is decimating amphibians worldwide. Unsurprisingly, the majority of studies have therefore concentrated on documenting morbidity and mortality of susceptible species and projecting population consequences as a consequence of this emerging infectious disease. Currently, there is a paucity of studies investigating the sub-lethal costs of Bd in apparently asymptomatic species, particularly in controlled experimental conditions. Here we report the consequences of a single dose of B. dendrobatidis zoospores on captive adult palmate newts (Lissotriton helveticus) for morphological and behavioural traits that associate with reproductive success. Results A single exposure to ~2000 zoospores induced a subclinical Bd infection. One week after inoculation 84% of newts tested positive for Bd, and of those, 98% had apparently lost the infection by the day 30. However, exposed newts suffered significant mass loss compared with control newts, and those experimental newts removing higher levels of Bd lost most mass. We found no evidence to suggest that three secondary sexual characteristics (areas of dorsal crest and rear foot webbing, and length of tail filament) were reduced between experimental versus control newts; in fact, rear foot webbing was 26% more expansive at the end of the experiment in exposed newts. Finally, compared with unexposed controls, exposure to Bd was associated with a 50% earlier initiation of the non-reproductive terrestrial phase. Conclusions Our results suggest that Bd has measureable, but sub-lethal effects, on adult palmate newts, at least under the laboratory conditions presented. We conclude that the effects reported are most likely to be mediated through the initiation of costly immune responses and/or tissue repair mechanisms. Although we found no evidence of hastened secondary sexual trait regression, through reducing individual body condition and potentially

  4. Experimental Evidence for Weathering and Martian Sulfate Formation Under Extremely Cold Weather-Limited Environments

    NASA Technical Reports Server (NTRS)

    Niles, Paul B.; Golden, D. C.; Michalski, J.

    2013-01-01

    High resolution photography and spectroscopy of the martian surface (MOC, HiRISE) from orbit has revolutionized our view of Mars with one of the most important discoveries being wide-spread layered sedimentary deposits associated with sulfate minerals across the low to mid latitude regions of Mars [1, 2]. The mechanism for sulfate formation on Mars has been frequently attributed to playa-like evaporative environments under prolonged warm conditions [3]. However, there are several problems with the presence of prolonged surface temperatures on Mars above 273 K during the Noachian including the faint young Sun [4] and the presence of suitable greenhouse gases [5]. The geomorphic evidence for early warm conditions may instead be explained by periodic episodes of warming rather than long term prolonged warm temperatures [6]. An alternate view of the ancient martian climate contends that prolonged warm temperatures were never present and that the atmosphere and climate has been similar to modern conditions throughout most of its history [6]. This view is more consistent with the climate models, but has had a difficult time explaining the sedimentary history of Mars and in particular the presence of sulfate minerals. We suggest here that mixtures of atmospheric aerosols, ice, and dust have the potential for creating small films of cryo-concentrated acidic solutions that may represent an important unexamined environment for understanding weathering processes on Mars [7, 8]. This study seeks to test whether sulfate formation may be possible at temperatures well below 0 C in water limited environments removing the need for prolonged warm periods to form sulfates on early Mars.

  5. Short Lag Times for Invasive Tropical Plants: Evidence from Experimental Plantings in Hawai'i

    PubMed Central

    Daehler, Curtis C.

    2009-01-01

    Background The lag time of an invasion is the delay between arrival of an introduced species and its successful spread in a new area. To date, most estimates of lag times for plants have been indirect or anecdotal, and these estimates suggest that plant invasions are often characterized by lag times of 50 years or more. No general estimates are available of lag times for tropical plant invasions. Historical plantings and documentation were used to directly estimate lag times for tropical plant invasions in Hawai'i. Methodology/Principal Findings Historical planting records for the Lyon Arboretum dating back to 1920 were examined to identify plants that have since become invasive pests in the Hawaiian Islands. Annual reports describing escape from plantings were then used to determine the lag times between initial plantings and earliest recorded spread of the successful invaders. Among 23 species that eventually became invasive pests, the average lag time between introduction and first evidence of spread was 14 years for woody plants and 5 years for herbaceous plants. Conclusions/Significance These direct estimates of lag times are as much as an order of magnitude shorter than previous, indirect estimates, which were mainly based on temperate plants. Tropical invaders may have much shorter lag times than temperate species. A lack of direct and deliberate observations may have also inflated many previous lag time estimates. Although there have been documented cases of long lag times due to delayed arrival of a mutualist or environmental changes over time, this study suggests that most successful invasions are likely to begin shortly after arrival of the plant in a suitable habitat, at least in tropical environments. Short lag times suggest that controlled field trials may be a practical element of risk assessment for plant introductions. PMID:19223966

  6. Natural and experimental evidence of past seismic faulting from Clay-Clast Aggregates occurrence

    NASA Astrophysics Data System (ADS)

    Boutareaud, S.

    2009-04-01

    S. Boutareaud (1), A.M. Boullier (2,3), M. Andreani (4), D.G. Calugaru (5), P. Beck (6), S.R. Song (7,3), T. Shimamoto (8) Spherical aggregates named Clay-Clast Aggregates (CCAs) have been reported from recent investigations on both retrieved clay-bearing fault gouges from shallow depth seismogenic faults and rotary-shear experiments conducted on clay-bearing gouge at seismic slip-rates. We have conducted additional high velocity rotary-shear experiments and low velocity double-shear experiments. From these two types of friction experiments, we demonstrate that a critical temperature depending on dynamic P-T conditions is needed for the formation of CCAs. This temperature corresponds to the transition of water from liquid to vapor or to critical, that induces gouge pore fluid expansion and therefore a thermal pressurization of the fault. We compared natural CCAs obtained by the Taiwan Chelungpu fault Drilling Program (TCDP) from a gouge layer recognized as the last slip surface of the Mw 7.6 1999 Chi-Chi earthquake, and CCAs obtained from our high velocity experiments. EDX-SEM element mapping, SEM and TEM observations show strong similar characteristics of the two types of CCAs with a concentric well-organized fabric of the cortex, and reveals that their development may result from the combination of electrostatic and capillary forces in a critical reactive medium during the dynamic slip-weakening. The formation of CCAs appears to be related to the shearing of a clay-rich granular material that expands and become fluidized. Accordingly, the occurrence of CCAs in natural clay-rich fault gouges constitutes new unequivocal textural evidence for shallow depth thermal pressurization and consequently for past seismic faulting.

  7. Racemic R,S-venlafaxine hydrochloride-DNA interaction: Experimental and computational evidence

    NASA Astrophysics Data System (ADS)

    Shahabadi, Nahid; Hadidi, Saba; Ghasemian, Zeinab; Taherpour, Avat(Arman)

    2015-06-01

    The interaction of racemic R,S-venlafaxine hydrochloride (rac-VEN) drug with calf thymus deoxyribonucleic acid (ct-DNA) was studied using various physico-chemical techniques and molecular docking at simulated physiological conditions (pH = 7.4). The fluorescence study shows that ct-DNA interacted with rac-VEN and quenched its intrinsic fluorescence in a static quenching process. These results are further supported by UV-Vis spectra. The binding constant of rac-VEN with ct-DNA (0.57 × 104) obtained from the spectroscopic techniques, which is more in keeping with the groove binding with DNA. Furthermore, the competition experiment using Hoechst33258 indicated that rac-VEN may bind to ct-DNA by a minor groove binding mode. In addition, iodide quenching effect on the fluorescence of rac-VEN before and after the interaction with ct-DNA is another evidence to groove binding. The thermodynamic parameters are calculated by van't Hoff equation, which demonstrated that hydrogen bonds and van der Waals interactions played major roles in the binding reaction. Molecular simulation studies carried out by using the AutoDock4 and Spartan10 programs. From the best docking map, we found that R and S-isomers fit in the A6T7T8/T19A18A17 region in minor groove of B-DNA. Finally, these results indicated that the docking of S-VEN-B-DNA is more stable than R-VEN-B-DNA.

  8. Experimental evidence for limited vocal recognition in a wild primate: implications for the social complexity hypothesis

    PubMed Central

    Bergman, Thore J.

    2010-01-01

    Although monitoring social information is a key aspect of the social complexity hypothesis, surprisingly little work has compared social knowledge across different species of wild animals. In the present study, I use playback experiments to test for individual recognition in wild male geladas (Theropithecus gelada) to compare with published accounts of social knowledge in chacma baboons (Papio ursinus). Geladas and baboons are closely related primates living in socially complex groups that differ dramatically in group size—geladas routinely associate with more than 10 times the number of conspecifics than do baboons. Using grunts from non-rival males to simulate approaches, I examined the strength of a subject male's response when the ‘approach’ was from the direction of (i) non-rival males (control), or (ii) rival males (a more salient stimulus if playback grunts are not recognized by the subject). I compared responses separately based on the degree of social overlap between the caller and the subject. Responses indicate that male geladas, unlike baboons, do not use vocalizations to recognize all of the individuals they regularly encounter. This represents, to my knowledge, the first documented evidence of ‘missing’ social knowledge in a natural primate population. The sharp distinction between baboons and geladas suggests that geladas are either unable or unmotivated to keep track of the individual identity of other males in their multi-level society—even males with whom they have a large degree of social overlap. Thus, these results are consistent with the central assumption of the social complexity hypothesis that social cognition is costly. PMID:20462901

  9. Parents influence asymmetric sibling competition: experimental evidence with partially dependent young.

    PubMed

    Smiseth, Per T; Ward, Richard J S; Moore, Allen J

    2007-12-01

    evidence of asymmetric sibling competition when parents were absent and offspring obtained resources solely by self-feeding. PMID:18229851

  10. Lexical plasticity in early bilinguals does not alter phoneme categories: II. Experimental evidence.

    PubMed

    Sebastián-Gallés, Núria; Vera-Constán, Fátima; Larsson, Johan P; Costa, Albert; Deco, Gustavo

    2009-12-01

    When listening to modified speech, either naturally or artificially altered, the human perceptual system rapidly adapts to it. There is some debate about the nature of the mechanisms underlying this adaptation. Although some authors propose that listeners modify their prelexical representations, others assume changes at the lexical level. Recently, Larsson, Vera, Sebastian-Galles, and Deco [Lexical plasticity in early bilinguals does not alter phoneme categories: I. Neurodynamical modelling. Journal of Cognitive Neuroscience, 20, 76-94, 2008] proposed a biologically plausible computational model to account for some existing data, one which successfully modeled how long-term exposure to a dialect triggers the creation of new lexical entries. One specific prediction of the model was that prelexical (phoneme) representations should not be affected by dialectal exposure (as long as the listener is exposed to both standard and dialectal pronunciations). Here we present a series of experiments testing the predictions of the model. Native listeners of Catalan, with extended exposure to Spanish-accented Catalan, were tested on different auditory lexical decision tasks and phoneme discrimination tasks. Behavioral and electrophysiological recordings were obtained. The results supported the predictions of our model. On the one hand, both error rates and N400 measurements indicated the existence of alternative lexical entries for dialectal varieties. On the other hand, no evidence of alterations at the phoneme level, either in the behavioral discrimination task or in the electrophysiological measurement (MMN), could be detected. The results of the present study are compared with those obtained in short-term laboratory exposures in an attempt to provide an integrative account.

  11. Experimental evidence for healing during stick-slip at the bases of ice streams

    NASA Astrophysics Data System (ADS)

    Zoet, Lucas K.; Iverson, Neal R.

    2016-04-01

    The Whillians Ice Stream has twice daily stick-slip events of ca. 50 cm with a maximum inter-event time of ca. 60,000 s. In order for stick-slip phenomena to occur under rate and state friction, two conditions need to be met: 1) A rate-weakening material at the interface, so that a nucleated slip perturbance can be propagated and 2) a material capable of healing (i.e., becoming stronger) when stationary, so that stress can be recharged during hold periods between ruptures. Although rate weakening has been experimentally demonstrated for some basal tills, experimental data relevant to glacier slip that bear on healing have been absent. Without an understanding of the healing mechanisms active at the beds of ice streams, models of the mechanics of ice stream stick-slip or ice stream shut-down will be inadequately informed. We investigated healing mechanisms with slide-hold-slide experiments, a technique common in rock mechanics, using two different ring shear apparatuses. In one set of experiments till alone was sheared, while in another set ice at its melting temperature was slid over till. These two kinds of experiments allowed for the isolation of mechanisms active at ice-till interface from those within the till. In all experiments sliding velocity was ca. 345 m/yr, and effective stress was ca. 150 kPa. Once steady-state sliding friction, μss, was attained, sliding was stopped and the materials were held in stationary contact for a given duration. When sliding was reinitiated, slip resistance initially rose above the previous μss value to a peak friction, μpeak, before returning to μss. The difference between μss and μpeak, Δμ, was then calculated. For each subsequent hold, the duration of stationary contact was increased logarithmically (100, 1,000, 10,000 and 100,000 s) until the maximum hold duration was attained. From the relationship between hold time and Δμ, a healing rate was calculated. Results from both sets of experiment indicate that

  12. Experimental evidence of early costs of reproduction in conspecific viviparous and oviparous lizards.

    PubMed

    Bleu, J; Heulin, B; Haussy, C; Meylan, S; Massot, M

    2012-07-01

    Reproduction entails costs, and disentangling the relative importance of each stage of the reproductive cycle may be important to assess the costs and benefits of different reproductive strategies. We studied the early costs of reproduction in oviparous and viviparous lizard females of the bimodal reproductive species Zootoca vivipara. Egg retention time in oviparous females is approximately one-third of the time in viviparous females. We compared the vitellogenesis and egg retention stages that are common to both reproductive modes. Precisely, we monitored the thermoregulatory behaviour, the weight gain and the immunocompetence of the females. Moreover, we injected an antigen in half of the females (immune challenge) to study the trade-offs between reproductive mode and immune performance and between different components of the immune system. Finally, we experimentally induced parturition in viviparous females at the time of egg laying in oviparous females. Oviparous and viviparous females did not show strong differences in response to the immune challenge. However, viviparous females spent more time thermoregulating while partially hidden and gained more weight than oviparous females. The greater weight gain indicates that the initial period of egg retention is less costly for viviparous than for oviparous females or that viviparous females are able to save and accumulate energy at this period. This energy may be used by viviparous females to cope with the subsequent costs of the last two-third of the gestation. Such an ability to compensate the higher costs of a longer egg retention period may account for the frequent evolution of viviparity in squamate reptiles.

  13. Experimental evidence for enhanced top-down control of freshwater macrophytes with nutrient enrichment.

    PubMed

    Bakker, Elisabeth S; Nolet, Bart A

    2014-11-01

    The abundance of primary producers is controlled by bottom-up and top-down forces. Despite the fact that there is consensus that the abundance of freshwater macrophytes is strongly influenced by the availability of resources for plant growth, the importance of top-down control by vertebrate consumers is debated, because field studies yield contrasting results. We hypothesized that these bottom-up and top-down forces may interact, and that consumer impact on macrophyte abundance depends on the nutrient status of the water body. To test this hypothesis, experimental ponds with submerged vegetation containing a mixture of species were subjected to a fertilization treatment and we introduced consumers (mallard ducks, for 8 days) on half of the ponds in a full factorial design. Over the whole 66-day experiment fertilized ponds became dominated by Elodea nuttallii and ponds without extra nutrients by Chara globularis. Nutrient addition significantly increased plant N and P concentrations. There was a strong interactive effect of duck presence and pond nutrient status: macrophyte biomass was reduced (by 50%) after the presence of the ducks on fertilized ponds, but not in the unfertilized ponds. We conclude that nutrient availability interacts with top-down control of submerged vegetation. This may be explained by higher plant palatability at higher nutrient levels, either by a higher plant nutrient concentration or by a shift towards dominance of more palatable plant species, resulting in higher consumer pressure. Including nutrient availability may offer a framework to explain part of the contrasting field observations of consumer control of macrophyte abundance. PMID:25194349

  14. Experimental infection of mice with hamster parvovirus: evidence for interspecies transmission of mouse parvovirus 3.

    PubMed

    Christie, Rachel D; Marcus, Emily C; Wagner, April M; Besselsen, David G

    2010-04-01

    Hamster parvovirus (HaPV) was isolated 2 decades ago from hamsters with clinical signs similar to those induced in hamsters experimentally infected with other rodent parvoviruses. Genetically, HaPV is most closely related to mouse parvovirus (MPV), which induces subclinical infection in mice. A novel MPV strain, MPV3, was detected recently in naturally infected mice, and genomic sequence analysis indicates that MPV3 is almost identical to HaPV. The goal of the present studies was to examine the infectivity of HaPV in mice. Neonatal and weanling mice of several mouse strains were inoculated with HaPV. Tissues, excretions, and sera were harvested at 1, 2, 4, and 8 wk after inoculation and evaluated by quantitative PCR and serologic assays specific for HaPV. Quantitative PCR detected viral DNA quantities that greatly exceeded the quantity of virus in inocula in multiple tissues of infected mice. Seroconversion to both nonstructural and structural viral proteins was detected in most immunocompetent mice 2 or more weeks after inoculation with HaPV. In neonatal SCID mice, viral transcripts were detected in lymphoid tissues by RT-PCR and viral DNA was detected in feces by quantitative PCR at 8 wk after inoculation. No clinical signs, gross, or histologic lesions were observed. These findings are similar to those observed in mice infected with MPV. These data support the hypothesis that HaPV and MPV3 are likely variants of the same viral species, for which the mouse is the natural rodent host with rare interspecies transmission to the hamster.

  15. Experimental evidence that dispersal drives ant community assembly in human-altered ecosystems.

    PubMed

    King, Joshua R; Tschinkel, Walter R

    2016-01-01

    A key shortcoming in our understanding of exotic species' success is that it is not known how post-introduction dispersal contributes to the success of exotic species and the reassembly of invaded communities. Exotic and native species face poorly understood competition-colonization trade-offs in heterogeneous landscapes of natural and anthropogenic habitats. We conducted three experiments that tested how ant queen behavior during dispersal affects community composition. Using experimental plots, we tested whether (1) different types of habitat disturbance and (2) different sizes of habitat disturbance affected the abundance of newly mated queens landing in the plots. The three most abundant species captured were the exotic fire ant Solenopsis invicta, and the native species Brachymyrmex depilis, and S. pergandei, respectively. When queens were considered collectively, more queens landed in plowed, sand-added, and roadside plots than in control or mow plots, in other words, in the more heavily disturbed plots. We also tested (3) the effect of habitat manipulations on the survival of newly mated fire ant queens (Solenopsis invicta). Soil disturbance (tilling), lack of shade, and removal (poisoning) of the ant community resulted in the greatest fire ant colony survivorship. Collectively, experiments revealed that both exotic and native newly mated ant queens select open, human-altered ecosystems for founding new colonies. The selection of such habitats by fire ant queens leads to their successful colony founding and ultimately to their dominance in those habitats. Selection of disturbed habitats is therefore advantageous for exotic species but is an ecological trap for native species because they do not often succeed in founding colonies in these habitats.

  16. Experimental Evidence of Biological Interactions among Different Isolates of Trypanosoma cruzi from the Chaco Region

    PubMed Central

    Ragone, Paula G.; Pérez Brandán, Cecilia; Monje Rumi, Mercedes; Tomasini, Nicolás; Lauthier, Juan J.; Cimino, Rubén O.; Uncos, Alejandro; Ramos, Federico; Alberti D´Amato, Anahí M.; Basombrío, Miguel A.; Diosque, Patricio

    2015-01-01

    Many infectious diseases arise from co-infections or re-infections with more than one genotype of the same pathogen. These mixed infections could alter host fitness, the severity of symptoms, success in pathogen transmission and the epidemiology of the disease. Trypanosoma cruzi, the etiological agent of Chagas disease, exhibits a high biological variability often correlated with its genetic diversity. Here, we developed an experimental approach in order to evaluate biological interaction between three T. cruzi isolates belonging to different Discrete Typing Units (DTUs TcIII, TcV and TcVI). These isolates were obtained from a restricted geographical area in the Chaco Region. Different mixed infections involving combinations of two isolates (TcIII + TcV, TcIII + TcVI and TcV + TcVI) were studied in a mouse model. The parameters evaluated were number of parasites circulating in peripheral blood, histopathology and genetic characterization of each DTU in different tissues by DNA hybridization probes. We found a predominance of TcVI isolate in blood and tissues respect to TcIII and TcV; and a decrease of the inflammatory response in heart when the damage of mice infected with TcVI and TcIII + TcVI mixture were compared. In addition, simultaneous presence of two isolates in the same tissue was not detected. Our results show that biological interactions between isolates with different biological behaviors lead to changes in their biological properties. The occurrence of interactions among different genotypes of T. cruzi observed in our mouse model suggests that these phenomena could also occur in natural cycles in the Chaco Region. PMID:25789617

  17. Experimental evidence that dispersal drives ant community assembly in human-altered ecosystems.

    PubMed

    King, Joshua R; Tschinkel, Walter R

    2016-01-01

    A key shortcoming in our understanding of exotic species' success is that it is not known how post-introduction dispersal contributes to the success of exotic species and the reassembly of invaded communities. Exotic and native species face poorly understood competition-colonization trade-offs in heterogeneous landscapes of natural and anthropogenic habitats. We conducted three experiments that tested how ant queen behavior during dispersal affects community composition. Using experimental plots, we tested whether (1) different types of habitat disturbance and (2) different sizes of habitat disturbance affected the abundance of newly mated queens landing in the plots. The three most abundant species captured were the exotic fire ant Solenopsis invicta, and the native species Brachymyrmex depilis, and S. pergandei, respectively. When queens were considered collectively, more queens landed in plowed, sand-added, and roadside plots than in control or mow plots, in other words, in the more heavily disturbed plots. We also tested (3) the effect of habitat manipulations on the survival of newly mated fire ant queens (Solenopsis invicta). Soil disturbance (tilling), lack of shade, and removal (poisoning) of the ant community resulted in the greatest fire ant colony survivorship. Collectively, experiments revealed that both exotic and native newly mated ant queens select open, human-altered ecosystems for founding new colonies. The selection of such habitats by fire ant queens leads to their successful colony founding and ultimately to their dominance in those habitats. Selection of disturbed habitats is therefore advantageous for exotic species but is an ecological trap for native species because they do not often succeed in founding colonies in these habitats. PMID:27008792

  18. Fossil bryophytes as recorders of ancient CO2 levels: Experimental evidence and a Cretaceous case study

    NASA Astrophysics Data System (ADS)

    Fletcher, Benjamin J.; Beerling, David J.; Brentnall, Stuart J.; Royer, Dana L.

    2005-09-01

    Biological and geochemical CO2 proxies provide critical constraints on understanding the role of atmospheric CO2 in driving climate change during Earth history. As no single existing CO2 proxy is without its limitations, there is a clear need for new approaches to reconstructing past CO2 concentrations. Here we develop a new pre-Quaternary CO2 proxy based on the stable carbon isotope composition (δ13C) of astomatous land plants. In a series of CO2-controlled laboratory experiments, we show that the carbon isotope discrimination (Δ13C) of a range of bryophyte (liverwort and moss) species increases with atmospheric CO2 across the range 375 to 6000 ppm. Separate experiments establish that variations in growth temperature, water content and substrate type have minor impacts on the Δ13C of liverworts but not mosses, indicating the greater potential of liverworts to faithfully record past variations in CO2. A mechanistic model for calculating past CO2 concentrations from bryophyte Δ13C (White et al., 1994) is extended and calibrated using our experimental results. The potential for fossil liverworts to record past CO2 changes is investigated by analyzing the δ13C of specimens collected from Alexander Island, Antarctica dating to the "greenhouse" world of the mid-Cretaceous. Our analysis and isotopic model yield mid-Cretaceous CO2 concentrations of 1000-1400 ppm, in general agreement with independent proxy data and long-term carbon cycle models. The exceptionally long evolutionary history of bryophytes offers the possibility of reconstructing CO2 concentrations back to the mid-Ordovician, pre-dating all currently used quantitative CO2 proxies.

  19. Experimental evidence for enhanced top-down control of freshwater macrophytes with nutrient enrichment.

    PubMed

    Bakker, Elisabeth S; Nolet, Bart A

    2014-11-01

    The abundance of primary producers is controlled by bottom-up and top-down forces. Despite the fact that there is consensus that the abundance of freshwater macrophytes is strongly influenced by the availability of resources for plant growth, the importance of top-down control by vertebrate consumers is debated, because field studies yield contrasting results. We hypothesized that these bottom-up and top-down forces may interact, and that consumer impact on macrophyte abundance depends on the nutrient status of the water body. To test this hypothesis, experimental ponds with submerged vegetation containing a mixture of species were subjected to a fertilization treatment and we introduced consumers (mallard ducks, for 8 days) on half of the ponds in a full factorial design. Over the whole 66-day experiment fertilized ponds became dominated by Elodea nuttallii and ponds without extra nutrients by Chara globularis. Nutrient addition significantly increased plant N and P concentrations. There was a strong interactive effect of duck presence and pond nutrient status: macrophyte biomass was reduced (by 50%) after the presence of the ducks on fertilized ponds, but not in the unfertilized ponds. We conclude that nutrient availability interacts with top-down control of submerged vegetation. This may be explained by higher plant palatability at higher nutrient levels, either by a higher plant nutrient concentration or by a shift towards dominance of more palatable plant species, resulting in higher consumer pressure. Including nutrient availability may offer a framework to explain part of the contrasting field observations of consumer control of macrophyte abundance.

  20. Thiol groups controls on arsenite binding by organic matter: new experimental and modeling evidence.

    PubMed

    Catrouillet, Charlotte; Davranche, Mélanie; Dia, Aline; Bouhnik-Le Coz, Martine; Pédrot, Mathieu; Marsac, Rémi; Gruau, Gérard

    2015-12-15

    Although it has been suggested that several mechanisms can describe the direct binding of As(III) to organic matter (OM), more recently, the thiol functional group of humic acid (HA) was shown to be an important potential binding site for As(III). Isotherm experiments on As(III) sorption to HAs, that have either been grafted with thiol or not, were thus conducted to investigate the preferential As(III) binding sites. There was a low level of binding of As(III) to HA, which was strongly dependent on the abundance of the thiols. Experimental datasets were used to develop a new model (the modified PHREEQC-Model VI), which defines HA as a group of discrete carboxylic, phenolic and thiol sites. Protonation/deprotonation constants were determined for each group of sites (pKA=4.28±0.03; ΔpKA=2.13±0.10; pKB=7.11±0.26; ΔpKB=3.52±0.49; pKS=5.82±0.052; ΔpKS=6.12±0.12 for the carboxylic, phenolic and thiols sites, respectively) from HAs that were either grafted with thiol or not. The pKS value corresponds to that of single thiol-containing organic ligands. Two binding models were tested: the Mono model, which considered that As(III) is bound to the HA thiol site as monodentate complexes, and the Tri model, which considered that As(III) is bound as tridentate complexes. A simulation of the available literature datasets was used to validate the Mono model, with logKMS=2.91±0.04, i.e. the monodentate hypothesis. This study highlighted the importance of thiol groups in OM reactivity and, notably, determined the As(III) concentration bound to OM (considering that Fe is lacking or at least negligible) and was used to develop a model that is able to determine the As(III) concentrations bound to OM. PMID:26348657

  1. Intrapopulation Variability Shaping Isotope Discrimination and Turnover: Experimental Evidence in Arctic Foxes

    PubMed Central

    Lecomte, Nicolas; Ahlstrøm, Øystein; Ehrich, Dorothée; Fuglei, Eva; Ims, Rolf A.; Yoccoz, Nigel G.

    2011-01-01

    Background Tissue-specific stable isotope signatures can provide insights into the trophic ecology of consumers and their roles in food webs. Two parameters are central for making valid inferences based on stable isotopes, isotopic discrimination (difference in isotopic ratio between consumer and its diet) and turnover time (renewal process of molecules in a given tissue usually measured when half of the tissue composition has changed). We investigated simultaneously the effects of age, sex, and diet types on the variation of discrimination and half-life in nitrogen and carbon stable isotopes (δ15N and δ13C, respectively) in five tissues (blood cells, plasma, muscle, liver, nail, and hair) of a top predator, the arctic fox Vulpes lagopus. Methodology/Principal Findings We fed 40 farmed foxes (equal numbers of adults and yearlings of both sexes) with diet capturing the range of resources used by their wild counterparts. We found that, for a single species, six tissues, and three diet types, the range of discrimination values can be almost as large as what is known at the scale of the whole mammalian or avian class. Discrimination varied depending on sex, age, tissue, and diet types, ranging from 0.3‰ to 5.3‰ (mean  = 2.6‰) for δ15N and from 0.2‰ to 2.9‰ (mean  = 0.9‰) for δ13C. We also found an impact of population structure on δ15N half-life in blood cells. Varying across individuals, δ15N half-life in plasma (6 to 10 days) was also shorter than for δ13C (14 to 22 days), though δ15N and δ13C half-lives are usually considered as equal. Conclusion/Significance Overall, our multi-factorial experiment revealed that at least six levels of isotopic variations could co-occur in the same population. Our experimental analysis provides a framework for quantifying multiple sources of variation in isotopic discrimination and half-life that needs to be taken into account when designing and analysing ecological field studies. PMID:21731715

  2. Experimental evidence for intraplate deformation controlled by netlike plastic-flow in central-eastern Asia

    NASA Astrophysics Data System (ADS)

    Wang, Sheng-zu; Li, Jian-guo; Zhou, Yong-sheng

    2007-12-01

    The experimental results of brittle/ductile two-layer analogue models verify that intraplate tectonic deformation in central-eastern Asia is controlled mainly by the netlike plastic-flow (NPF) occurring in the lower lithosphere, including the lower crust and lithospheric mantle. The ductile lower layer in the model, corresponding to the lower lithosphere in the natural prototype, is made of a mixture of gum rosin and turpentine oil and the brittle upper one, to the upper crust, is formed by the consolidation of talc-powder slurry. The NPF hypothesis for continental dynamics can be regarded as a combination and development of two kinds of seemingly mutually exclusive ones, which are based on the theories of slip-line field and viscous (plastic) flow, respectively. In contrast to "homogeneous" viscous (plastic) flow considered usually in fluid mechanics and rheology, NPF is a viscous (plastic) flow accompanied with shear strain localization, forming plastic-flow network in the flow field. Plastic-flow network, being composed of two families of plastic-flow belts intersecting each other with their initial conjugate angles (i.e. the included angles facing the compression direction) equal to 90°, is similar to but different from the traditional slip-line network, which is assumed as a critical state of yield in elastoplastic medium. The experiments show that there are several NPF-controlled tectonic network systems to be developed in the models and two of them correspond to those in central-eastern Asia, which have the Himalayan and Taiwan arcs as their driving boundaries, respectively. The existence of "stable blocks" in the ductile lower layer has promoted some types of tectonic deformation, including the formation of large-scale compressional basins, corresponding to the Tarim, Ordos, Sichuan basins, etc., the development of compression-shear tectonic zones between some of these basins, corresponding to those shown by the Tianshan and Altay mountain ranges, and the

  3. Experimental Evidence of Momentum Transport Induced by an Up-Down Asymmetric Magnetic Equilibrium in Toroidal Plasmas

    SciTech Connect

    Camenen, Y.; Peeters, A. G.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Szepesi, G.; Bortolon, A.; Duval, B. P.; Federspiel, L.; Karpushov, A. N.; Piras, F.; Sauter, O.

    2010-09-24

    The first experimental evidence of parallel momentum transport generated by the up-down asymmetry of a toroidal plasma is reported. The experiments, conducted in the Tokamak a Configuration Variable, were motivated by the recent theoretical discovery of ion-scale turbulent momentum transport induced by an up-down asymmetry in the magnetic equilibrium. The toroidal rotation gradient is observed to depend on the asymmetry in the outer part of the plasma leading to a variation of the central rotation by a factor of 1.5-2. The direction of the effect and its magnitude are in agreement with theoretical predictions for the eight possible combinations of plasma asymmetry, current, and magnetic field.

  4. The effects of prosocial video games on prosocial behaviors: international evidence from correlational, longitudinal, and experimental studies.

    PubMed

    Gentile, Douglas A; Anderson, Craig A; Yukawa, Shintaro; Ihori, Nobuko; Saleem, Muniba; Ming, Lim Kam; Shibuya, Akiko; Liau, Albert K; Khoo, Angeline; Bushman, Brad J; Rowell Huesmann, L; Sakamoto, Akira

    2009-06-01

    Although dozens of studies have documented a relationship between violent video games and aggressive behaviors, very little attention has been paid to potential effects of prosocial games. Theoretically, games in which game characters help and support each other in nonviolent ways should increase both short-term and long-term prosocial behaviors. We report three studies conducted in three countries with three age groups to test this hypothesis. In the correlational study, Singaporean middle-school students who played more prosocial games behaved more prosocially. In the two longitudinal samples of Japanese children and adolescents, prosocial game play predicted later increases in prosocial behavior. In the experimental study, U.S. undergraduates randomly assigned to play prosocial games behaved more prosocially toward another student. These similar results across different methodologies, ages, and cultures provide robust evidence of a prosocial game content effect, and they provide support for the General Learning Model.

  5. Experimental evidence of the spatial coherence moiré and the filtering of classes of radiator pairs.

    PubMed

    Castaneda, Roman; Usuga-Castaneda, Mario; Herrera-Ramírez, Jorge

    2007-08-01

    Evidence of the physical existence of the spatial coherence moiré is obtained by confronting numerical results with experimental results of spatially partial interference. Although it was performed for two particular cases, the results reveal a general behavior of the optical fields in any state of spatial coherence. Moreover, the study of the spatial coherence moiré deals with a new type of filtering, named filtering of classes of radiator pairs, which allows changing the power spectrum at the observation plane by modulating the complex degree of spatial coherence, without altering the power distribution at the aperture plane or introducing conventional spatial filters. This new procedure can optimize some technological applications of actual interest, as the beam shaping for instance.

  6. Extrapolation of the evidence on teratogenicity of chemicals between humans and experimental animals: chemicals other than drugs

    SciTech Connect

    Hemminki, K.; Vineis, P.

    1985-01-01

    Epidemiologic literature regarding the possible association between malformations and 23 exposures or occupations other than pharmaceutical products, was analysed. The qualitative level of scientific evidence was classified into four categories: high (ethanol, methylmercury, PCBs, laboratory work), limited (anesthetic gases, carbon monoxide), low (hexachlorophene, LSD, nitrous oxide, smelter work, tobacco), and inadequate (all other exposures). Human data for exposures belonging to categories high and limited were quantitatively compared to results of animal teratogenicity tests of the relevant chemicals. Ethanol, methylmercury, and PCBs have caused malformations in experimental animals, and the effective doses have ranged from 0.2 to 8.0 times the effective human doses. Ethanol and PCBs caused similar types of lesions in some animal species as have been observed in humans. 60 references.

  7. Experimental evidence for growth advantage and metabolic shift stimulated by photophosphorylation of proteorhodopsin expressed in Escherichia coli at anaerobic condition.

    PubMed

    Wang, Ying; Li, Yan; Xu, Tuan; Shi, Zhenyu; Wu, Qiong

    2015-05-01

    Since solar light energy is the source of all renewable biological energy, the direct usage of light energy by bacterial cell factory has been a very attractive concept, especially using light energy to promote anaerobic fermentation growth and even recycle low-energy carbon source when energy is the limiting factor. Proteorhodopsin(PR), a light-driven proton pump proven to couple with ATP synthesis when expressed heterogeneously, is an interesting and simple option to enable light usage in engineered strains. However, although it was reported to influence fermentation in some cases, heterogeneous proteorhodopsin expression was never shown to support growth advantage or cause metabolic shift by photophosphorylation so far. Hereby, we presented the first experimental evidence that heterogeneously expressed proteorhodopsin can provide growth advantage and cause ATP-dependent metabolism shift of acetate and lactate changes in Escherichia coli at anaerobic condition. Those discoveries suggest further application potential of PR in anaerobic fermentation where energy is a limiting factor.

  8. The Effects of Prosocial Video Games on Prosocial Behaviors: International Evidence from Correlational, Longitudinal, and Experimental Studies

    PubMed Central

    Gentile, Douglas A.; Anderson, Craig A.; Yukawa, Shintaro; Ihori, Nobuko; Saleem, Muniba; Ming, Lim Kam; Shibuya, Akiko; Liau, Albert K.; Khoo, Angeline; Bushman, Brad J.; Huesmann, L. Rowell; Sakamoto, Akira

    2009-01-01

    Although dozens of studies have documented a relation between violent video games and aggressive behaviors, very little attention has been paid to potential effects of prosocial games. Theoretically, games in which game characters help and support each other in nonviolent ways should increase both short-term and long-term prosocial behaviors. We report three studies conducted in three countries with three age groups to test this hypothesis. In the correlational study, Singaporean middle-school students who played more prosocial games behaved more prosocially. In the two longitudinal samples of Japanese children and adolescents, prosocial game play predicted later increases in prosocial behavior. In the experimental study, U.S. undergraduates randomly assigned to play prosocial games behaved more prosocially toward another student. These similar results across different methodologies, ages, and cultures provide robust evidence a prosocial game content effect, and provide support for the General Learning Model. PMID:19321812

  9. The effects of prosocial video games on prosocial behaviors: international evidence from correlational, longitudinal, and experimental studies.

    PubMed

    Gentile, Douglas A; Anderson, Craig A; Yukawa, Shintaro; Ihori, Nobuko; Saleem, Muniba; Ming, Lim Kam; Shibuya, Akiko; Liau, Albert K; Khoo, Angeline; Bushman, Brad J; Rowell Huesmann, L; Sakamoto, Akira

    2009-06-01

    Although dozens of studies have documented a relationship between violent video games and aggressive behaviors, very little attention has been paid to potential effects of prosocial games. Theoretically, games in which game characters help and support each other in nonviolent ways should increase both short-term and long-term prosocial behaviors. We report three studies conducted in three countries with three age groups to test this hypothesis. In the correlational study, Singaporean middle-school students who played more prosocial games behaved more prosocially. In the two longitudinal samples of Japanese children and adolescents, prosocial game play predicted later increases in prosocial behavior. In the experimental study, U.S. undergraduates randomly assigned to play prosocial games behaved more prosocially toward another student. These similar results across different methodologies, ages, and cultures provide robust evidence of a prosocial game content effect, and they provide support for the General Learning Model. PMID:19321812

  10. Modulation of Antioxidant Enzymatic Activities by Certain Antiepileptic Drugs (Valproic Acid, Oxcarbazepine, and Topiramate): Evidence in Humans and Experimental Models

    PubMed Central

    Cárdenas-Rodríguez, Noemí; Coballase-Urrutia, Elvia; Rivera-Espinosa, Liliana; Romero-Toledo, Arantxa; Sampieri, Aristides III; Ortega-Cuellar, Daniel; Montesinos-Correa, Hortencia; Floriano-Sánchez, Esaú; Carmona-Aparicio, Liliana

    2013-01-01

    It is estimated that at least 100 million people worldwide will suffer from epilepsy at some point in their lives. This neurological disorder induces brain death due to the excessive liberation of glutamate, which activates the postsynaptic N-methyl-D-aspartic acid (NMDA) receptors, which in turn cause the reuptake of intracellular calcium (excitotoxicity). This excitotoxicity elicits a series of events leading to nitric oxide synthase (NOS) activation and the generation of reactive oxygen species (ROS). Several studies in experimental models and in humans have demonstrated that certain antiepileptic drugs (AEDs) exhibit antioxidant effects by modulating the activity of various enzymes associated with this type of stress. Considering the above-mentioned data, we aimed to compile evidence elucidating how AEDs such as valproic acid (VPA), oxcarbazepine (OXC), and topiramate (TPM) modulate oxidative stress. PMID:24454986

  11. Modulation of antioxidant enzymatic activities by certain antiepileptic drugs (valproic acid, oxcarbazepine, and topiramate): evidence in humans and experimental models.

    PubMed

    Cárdenas-Rodríguez, Noemí; Coballase-Urrutia, Elvia; Rivera-Espinosa, Liliana; Romero-Toledo, Arantxa; Sampieri, Aristides; Ortega-Cuellar, Daniel; Montesinos-Correa, Hortencia; Floriano-Sánchez, Esaú; Carmona-Aparicio, Liliana

    2013-01-01

    It is estimated that at least 100 million people worldwide will suffer from epilepsy at some point in their lives. This neurological disorder induces brain death due to the excessive liberation of glutamate, which activates the postsynaptic N-methyl-D-aspartic acid (NMDA) receptors, which in turn cause the reuptake of intracellular calcium (excitotoxicity). This excitotoxicity elicits a series of events leading to nitric oxide synthase (NOS) activation and the generation of reactive oxygen species (ROS). Several studies in experimental models and in humans have demonstrated that certain antiepileptic drugs (AEDs) exhibit antioxidant effects by modulating the activity of various enzymes associated with this type of stress. Considering the above-mentioned data, we aimed to compile evidence elucidating how AEDs such as valproic acid (VPA), oxcarbazepine (OXC), and topiramate (TPM) modulate oxidative stress.

  12. The role of barrier membranes for guided bone regeneration and restoration of large bone defects: current experimental and clinical evidence

    PubMed Central

    2012-01-01

    Treatment of large bone defects represents a great challenge in orthopedic and craniomaxillofacial surgery. Although there are several methods for bone reconstruction, they all have specific indications and limitations. The concept of using barrier membranes for restoration of bone defects has been developed in an effort to simplify their treatment by offering a sinlge-staged procedure. Research on this field of bone regeneration is ongoing, with evidence being mainly attained from preclinical studies. The purpose of this review is to summarize the current experimental and clinical evidence on the use of barrier membranes for restoration of bone defects in maxillofacial and orthopedic surgery. Although there are a few promising preliminary human studies, before clinical applications can be recommended, future research should aim to establish the 'ideal' barrier membrane and delineate the need for additional bone grafting materials aiming to 'mimic' or even accelerate the normal process of bone formation. Reproducible results and long-term observations with barrier membranes in animal studies, and particularly in large animal models, are required as well as well-designed clinical studies to evaluate their safety, efficacy and cost-effectiveness. PMID:22834465

  13. Reanalysis and experimental evidence indicate that the earliest trace fossil of a winged insect was a surface-skimming neopteran.

    PubMed

    Marden, James H

    2013-01-01

    A recent description and analysis of an imprint fossil from the Carboniferous concluded that it was made by a mayfly landing in sediment at the edge of water. Here, I reanalyze that trace fossil and supply experimental evidence regarding wing traces and behavior. The thorax of the trace maker lacked structures characteristic of mayflies, but closely matches a modern neopteran insect family (Taeniopterygidae, Plecoptera) little changed from Early Permian fossils. Edges of the folded wings of live Taeniopteryx leave marks on sediment closely matching marks in the trace fossil. Faint marks lateral to and beyond the reach of meso- and metathoracic legs match the location where wings of surface-skimming Taeniopteryx stoneflies lightly touch the sediment when these insects skim onto wet ground at shorelines. Dimensions of the thorax of the trace indicate relatively weak flight ability compared to fossils from the Early Permian, making doubtful the hypothesis that the trace maker was flight capable. Ultimately, this fossil best fits a scenario in which a neopteran insect skimmed across the surface of water, then folded its wings. Surface skimming as a precursor to the evolution of flight in insects is supported by this fossil evidence of skimming behavior in a Carboniferous insect.

  14. Experimental evidence for the effects of chronic anthropogenic noise on abundance of Greater Sage-Grouse at leks.

    PubMed

    Blickley, Jessica L; Blackwood, Diane; Patricelli, Gail L

    2012-06-01

    Increasing evidence suggests that chronic noise from human activities negatively affects wild animals, but most studies have failed to separate the effects of chronic noise from confounding factors, such as habitat fragmentation. We played back recorded continuous and intermittent anthropogenic sounds associated with natural gas drilling and roads at leks of Greater Sage-Grouse (Centrocercus urophasianus). For 3 breeding seasons, we monitored sage grouse abundance at leks with and without noise. Peak male attendance (i.e., abundance) at leks experimentally treated with noise from natural gas drilling and roads decreased 29% and 73%, respectively, relative to paired controls. Decreases in abundance at leks treated with noise occurred in the first year of the study and continued throughout the experiment. Noise playback did not have a cumulative effect over time on peak male attendance. There was limited evidence for an effect of noise playback on peak female attendance at leks or male attendance the year after the experiment ended. Our results suggest that sage-grouse avoid leks with anthropogenic noise and that intermittent noise has a greater effect on attendance than continuous noise. Our results highlight the threat of anthropogenic noise to population viability for this and other sensitive species.

  15. Cash transfers, maternal depression and emotional well-being: Quasi-experimental evidence from India's Janani Suraksha Yojana programme.

    PubMed

    Powell-Jackson, Timothy; Pereira, Shreya K; Dutt, Varun; Tougher, Sarah; Haldar, Kaveri; Kumar, Paresh

    2016-08-01

    Maternal depression is an important public health concern. We investigated whether a national-scale initiative that provides cash transfers to women giving birth in government health facilities, the Janani Suraksha Yojana (JSY), reduced maternal depression in India's largest state, Uttar Pradesh. Using primary data on 1695 women collected in early 2015, our quasi-experimental design exploited the fact that some women did not receive the JSY cash due to administrative problems in its disbursement - reasons that are unlikely to be correlated with determinants of maternal depression. We found that receipt of the cash was associated with an 8.5% reduction in the continuous measure of maternal depression and a 36% reduction in moderate depression. There was no evidence of an association with measures of emotional well-being, namely happiness and worry. The results suggest that the JSY had a clinically meaningful effect in reducing the burden of maternal depression, possibly by lessening the financial strain of delivery care. They contribute to the evidence that financial incentive schemes may have public health benefits beyond improving uptake of targeted health services. PMID:27387651

  16. Proprotein convertase subtilisin kexin type 9 and high-density lipoprotein metabolism: experimental animal models and clinical evidence.

    PubMed

    Ferri, Nicola; Corsini, Alberto; Macchi, Chiara; Magni, Paolo; Ruscica, Massimiliano

    2016-07-01

    Proprotein convertase subtilisin kexin type 9 (PCSK9) belongs to the proprotein convertase family. Several studies have demonstrated its involvement in the regulation of low-density lipoprotein (LDL) cholesterol levels by inducing the degradation of the LDL receptor (LDLR). However, experimental, epidemiologic, and pharmacologic data provide important evidence on the role of PCSK9 also on high-density lipoproteins (HDLs). In mice, PCSK9 regulates the HDL cholesterol (HDL-C) levels by the degradation of hepatic LDLR, thus inhibiting the uptake of apolipoprotein (Apo)E-containing HDLs. Several epidemiologic and genetic studies reported positive relationship between PCSK9 and HDL-C levels, likely by reducing the uptake of the ApoE-containing HDL particles. PCSK9 enhances also the degradation of LDLR's closest family members, ApoE receptor 2, very low-density lipoprotein receptor, and LDLR-related protein 1. This feature provides a molecular mechanism by which PCSK9 may affect HDL metabolism. Experimental studies demonstrated that PCSK9 directly interacts with HDL by modulating PCSK9 self-assembly and its binding to the LDLR. Finally, the inhibition of PCSK9 by means of monoclonal antibodies directed to PCSK9 (ie, evolocumab and alirocumab) determines an increase of HDL-C fraction by 7% and 4.2%, respectively. Thus, the understanding of the role of PCSK9 on HDL metabolism needs to be elucidated with a particular focus on the effect of PCSK9 on HDL-mediated reverse cholesterol transport. PMID:26548330

  17. Experimental evidence and 43 years of monitoring data show that food limits reproduction in a food-caching passerine.

    PubMed

    Derbyshire, Rachael; Strickland, Dan; Norris, D Ryan

    2015-11-01

    Several species of birds and mammals overcome periods of scarcity by caching food, but for the vast majority of species, it is virtually unknown whether they are food limited during these periods. The Gray Jay (Perisoreus canadensis) is a boreal-resident, food-caching passerine that breeds in late winter when fresh food is scarce. Using a two-year experiment and 43 years of monitoring data, we examined the food limitation hypothesis in a population of Gray Jays in Algonquin Park, Ontario, Canada, that has declined by over 50% in the last three decades. Breeding pairs that were experimentally food supplemented during the pre-breeding period laid eggs earlier in the season and had larger brood sizes than non-supplemented controls. From the long-term data, we found strong evidence that pairs that were regularly supplemented by the public (park visitors) tended to lay eggs earlier and have larger clutches and brood sizes compared to pairs that were not supplemented. Nestling body condition (mass controlled for body size) was not influenced by either experimental or public food supplementation. Our results support the hypothesis that Gray Jays are food limited during their late-winter breeding period and suggest that warmer fall temperatures, which have been hypothesized to lead to cache spoilage, may have a significant impact on reproductive success in this declining population. Moreover, our results contribute to understanding how public feeding can influence the fitness of wild animals. PMID:27070019

  18. Direct, experimental evidence of the Fermi surface in YBa sub 2 Cu sub 3 O sub 7-x

    SciTech Connect

    Haghighi, H.; Kaiser, J.H.; Rayner, S.L.; West, R.N. ); Liu, J.Z.; Shelton, R. ); Howell, R.H.; Sterne, P.A.; Solal, F.; Fluss, M.J. )

    1991-04-29

    We report new measurements of the electron-positron momentum spectra of YBa{sub 2}Cu{sub 3}O{sub 7-x} performed with ultra-high statistical precision. These data differ from previous results in two significant respects: They show the D{sub 2} symmetry appropriate for untwinned crystals and, more importantly, they show unmistakable, statistically significant, discontinuities that are evidence of a major Fermi surface section. These results provide a partial answer to a question of special significance to the study of high temperature superconductors i.e. the distribution of the electrons in the material, the electronic structure. Special consideration has been given both experimentally and theoretically to the existence and shape of a Fermi surface in the materials and to the superconducting gap. There are only three experimental techniques that can provide details of the electronic structure at useful resolutions. They are angular correlation of positron annihilation radiation, ACAR, angle resolved photo emission, PE, and de Haas van Alphen measurements. 11 refs., 4 figs.

  19. OA01.25.The first direct experimental evidence correlating ayurveda based tridosha prakriti, with western constitutional psychology somatotypes

    PubMed Central

    Metri, Kashinath G; Bhargav, Hemant; Ramarao, Nagendra Hongasandra; Rizzo-Sierra; Basavakatti, Ramakrishna R

    2012-01-01

    Purpose: Ayurveda is one of the most ancient systems of medical health care. The basic principles, diagnosis of the diseases and their treatment are based on individual prakriti (constitutional type). Ayurveda further classifies the prakriti of an individual on the basis of a set of psychosomatic attributes of personality, depending on whether this individual belongs to Vata, Pitta, or Kapha prakriti, or any combination of them (Patwardhan et al., 2005). The appropriate prakriti assessment is done by several means including questionnaires (Rastogi, 2012; Shilpa and Venkatesha-Murthy, 2011). We aimed to obtain experimental evidence correlating Ayurveda based tridosha-prakriti with western constitutional psychology somatotypes (Rizzo-Sierra, 2011). Method: We employed our Tridosha-prakriti questionnaire (Ramakrishna and Nagendra, 2012), and compared its results with a set of body composition parameters: Height, body weight, body mass index (BMI), muscle mass, fat mass, and fat percentage in normal healthy volunteers (25 males and 25 females, mean age was 26 (± 4) and 25 (± 6) years respectively). Moreover, two-tailed Pearson's correlations were investigated to match the extreme prakriti types with the western constitutional psychology somatotypes, through the mentioned body composition measures. Result: Significant negative correlations were observed between the percentage of Vata attributes as per the questionnaire in the individuals and their BMI, body weight and fat mass respectively (p<0.05). Similarly, there was a significant positive correlation between the percentage of Pitta attributes with the height, body weight, and muscle mass respectively. Also, a significant positive correlation was observed between the percentage of Kapha attributes with fat mass and fat percentage, along with a negative correlation with height. Conclusion: We provide evidence-linking Ayurveda to modern constitutional psychology. In this way, a concept such as prakriti is suggested

  20. Experimental evidence for UNC-6 (netrin) axon guidance by stochastic fluctuations of intracellular UNC-40 (DCC) outgrowth activity

    PubMed Central

    Kulkarni, Gauri; Xu, Zhennan; Mohamed, Ahmed M.; Li, Haichang; Tang, Xia; Limerick, Gerard; Wadsworth, William G.

    2013-01-01

    Summary How the direction of axon guidance is determined is not understood. In Caenorhabditis elegans the UNC-40 (DCC) receptor mediates a response to the UNC-6 (netrin) guidance cue that directs HSN axon development. UNC-40 becomes asymmetrically localized within the HSN neuron to the site of axon outgrowth. Here we provide experimental evidence that the direction of guidance can be explained by the stochastic fluctuations of UNC-40 asymmetric outgrowth activity. We find that the UNC-5 (UNC5) receptor and the cytoskeletal binding protein UNC-53 (NAV2) regulate the induction of UNC-40 localization by UNC-6. If UNC-40 localization is induced without UNC-6 by using an unc-53 mutation, the direction of UNC-40 localization undergoes random fluctuations. Random walk models describe the path made by a succession of randomly directed movement. This model was experimentally tested using mutations that affect Wnt/PCP signaling. These mutations inhibit UNC-40 localization in the anterior and posterior directions. As the axon forms in Wnt/PCP mutants, the direction of UNC-40 localization randomly fluctuates; it can localize in either the anterior, posterior, or ventral direction. Consistent with a biased random walk, over time the axon will develop ventrally in response to UNC-6, even though at a discrete time UNC-40 localization and outgrowth can be observed anterior or posterior. Also, axon formation is slower in the mutants than in wild-type animals. This is also consistent with a random walk since this model predicts that the mean square displacement (msd) will increase only linearly with time, whereas the msd increases quadratically with time for straight-line motion. PMID:24337114

  1. Induction and inhibition of diapause by the same photoperiod: experimental evidence for a "double circadian oscillator clock".

    PubMed

    Spieth, Hubert R; Xue, Fangsen; Strau, Katharina

    2004-12-01

    On the southern Iberian Peninsula, the seasonal life history of the large white butterfly, Pieris brassicae, comprises 2 different photoperiodically induced developmental arrests: a hibernation diapause at photophases < 11 h and an estivation diapause at photophases > 14 h. At intermediate photophases (12 h to 13 h), the butterfly responds with a nondiapause. Combined with the experimental setup to determine photosensitivity in insects, the different photoperiodic responses at long-, intermediate-, and short-night conditions were examined to gain more insight into the time measurement mechanism in P. brassicae. The study reveals evidence for a "double circadian oscillator clock" mechanism that is based on 2 submechanisms, a "short-night determining system" and a separate "long-night determining system." This conclusion was drawn from the facts that an LD 9:15 long-night induces a hibernation diapause but inhibits an estivation diapause and, conversely, that an LD 16:8 short-night inhibits a hibernation diapause but induces an estivation diapause. This opposite effect of the same photoperiod supports the argument for the existence of 2 independent targets for light-dark cycles, interpreted as 2 antagonistic time measurement systems. The existence and independence of 2 systems was further shown by differences in long-night versus short-night responses regarding photosensitivity, temperature dependence, and heritable factors. The long-night measurement system is most effective in the 5th larval stage, is highly affected by temperature, and is easy to manipulate by selective inbreeding. The short-night measurement system is most effective in the 4th larval stage, is largely temperature compensated, and is not affected by experimental manipulation of the longnight measurement system.

  2. Assessing the impact of human trampling on vegetation: a systematic review and meta-analysis of experimental evidence

    PubMed Central

    Stewart, Gavin B.

    2014-01-01

    Vegetation trampling resulting from recreation can adversely impact natural habitats, leading to the loss of vegetation and the degradation of plant communities. A considerable primary literature exists on this topic, therefore it is important to assess whether this accumulated evidence can be used to reach general conclusions concerning vegetation vulnerability to inform conservation management decisions. Experimental trampling studies on a global scale were retrieved using a systematic review methodology and synthesised using random effects meta-analysis. The relationships between vegetation recovery and each of initial vegetation resistance, trampling intensity, time for recovery, Raunkiaer life-form (perennating bud position), and habitat were tested using random effects multiple meta-regressions and subgroup analyses. The systematic search yielded 304 studies; of these, nine reported relevant randomized controlled experiments, providing 188 vegetation recovery effect sizes for analysis. The synthesis indicated there was significant heterogeneity in the impact of trampling on vegetation recovery. This was related to resistance and recovery time, and the interactions of these variables with Raunkiaer life-form, but was not strongly dependent on the intensity of the trampling experienced. The available evidence suggests that vegetation dominated by hemicryptophytes and geophytes recovers from trampling to a greater extent than vegetation dominated by other life-forms. Variation in effect within the chamaephyte, hemicryptophyte and geophyte life-form sub-groups was also explained by the initial resistance of vegetation to trampling, but not by trampling intensity. Intrinsic properties of plant communities appear to be the most important factors determining the response of vegetation to trampling disturbance. Specifically, the dominant Raunkiaer life-form of a plant community accounts for more variation in the resilience of communities to trampling than the

  3. Assessing the impact of human trampling on vegetation: a systematic review and meta-analysis of experimental evidence.

    PubMed

    Pescott, Oliver L; Stewart, Gavin B

    2014-01-01

    Vegetation trampling resulting from recreation can adversely impact natural habitats, leading to the loss of vegetation and the degradation of plant communities. A considerable primary literature exists on this topic, therefore it is important to assess whether this accumulated evidence can be used to reach general conclusions concerning vegetation vulnerability to inform conservation management decisions. Experimental trampling studies on a global scale were retrieved using a systematic review methodology and synthesised using random effects meta-analysis. The relationships between vegetation recovery and each of initial vegetation resistance, trampling intensity, time for recovery, Raunkiaer life-form (perennating bud position), and habitat were tested using random effects multiple meta-regressions and subgroup analyses. The systematic search yielded 304 studies; of these, nine reported relevant randomized controlled experiments, providing 188 vegetation recovery effect sizes for analysis. The synthesis indicated there was significant heterogeneity in the impact of trampling on vegetation recovery. This was related to resistance and recovery time, and the interactions of these variables with Raunkiaer life-form, but was not strongly dependent on the intensity of the trampling experienced. The available evidence suggests that vegetation dominated by hemicryptophytes and geophytes recovers from trampling to a greater extent than vegetation dominated by other life-forms. Variation in effect within the chamaephyte, hemicryptophyte and geophyte life-form sub-groups was also explained by the initial resistance of vegetation to trampling, but not by trampling intensity. Intrinsic properties of plant communities appear to be the most important factors determining the response of vegetation to trampling disturbance. Specifically, the dominant Raunkiaer life-form of a plant community accounts for more variation in the resilience of communities to trampling than the

  4. Experimental evidence for the formation of CoFe2C phase with colossal magnetocrystalline-anisotropy

    SciTech Connect

    El-Gendy, AA; Bertino, M; Clifford, D; Qian, MC; Khanna, SN; Carpenter, EE

    2015-05-25

    Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe2C) of nanoparticles. Structural characterization of the CoFe2C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, TB, of 790K for particles with a domain size as small as 5 +/- 1 nm. The particles have magnetocrystalline anisotropy of 4.662 +/- 10 6 J/m(3), which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe2C nanoparticles have huge potential for enhanced magnetic data storage devices. (C) 2015 AIP Publishing LLC.

  5. Experimental evidence for the formation of CoFe{sub 2}C phase with colossal magnetocrystalline-anisotropy

    SciTech Connect

    El-Gendy, Ahmed A. E-mail: ecarpenter2@vcu.edu; Bertino, Massimo; Qian, Meichun; Khanna, Shiv N. E-mail: ecarpenter2@vcu.edu; Clifford, Dustin; Carpenter, Everett E. E-mail: ecarpenter2@vcu.edu

    2015-05-25

    Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe{sub 2}C) of nanoparticles. Structural characterization of the CoFe{sub 2}C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, T{sub B}, of 790 K for particles with a domain size as small as 5 ± 1 nm. The particles have magnetocrystalline anisotropy of 4.6 ± 2 × 10{sup 6 }J/m{sup 3}, which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe{sub 2}C nanoparticles have huge potential for enhanced magnetic data storage devices.

  6. Experimental Inoculation of Artibeus jamaicensis Bats with Dengue Virus Serotypes 1 or 4 Showed No Evidence of Sustained Replication

    PubMed Central

    Cabrera-Romo, Salomé; Recio-Tótoro, Benito; Alcalá, Ana C.; Lanz, Humberto; del Ángel, Rosa María; Sánchez-Cordero, Victor; Rodríguez-Moreno, Ángel; Ludert, Juan E.

    2014-01-01

    Dengue is the most important mosquito-borne viral disease to humans. Bats are potential reservoirs for flaviviruses, including dengue virus (DENV). In this work, Artibeus jamaicensis bats were inoculated with two serotypes of DENV using different routes. For experimental inoculations (EI) 1 and 2, bats were inoculated subcutaneously or intraperitoneally with DENV-4; for EI-3 bats were inoculated intraperitoneally with DENV-1. Mock inoculated bats were kept as controls. In EI-4, bats were bitten by Aedes aegypti mosquitoes infected with DENV-1 or 4. Reverse transcription-polymerase chain reaction assays in plasma and spleen tissue collected from Day 1 to Days 9–17 after inoculation failed to reveal the presence of viral RNA in any of the samples. No evidence of circulating NS1 or specific anti-DENV IgG was detected in the plasma of the inoculated bats. These results indicate that A. jamaicensis bats are incapable of sustaining dengue virus replication and are unlikely to act as reservoirs for this virus. PMID:25311698

  7. On the psychology of cooperation in humans and other primates: combining the natural history and experimental evidence of prosociality.

    PubMed

    Jaeggi, Adrian V; Burkart, Judith M; Van Schaik, Carel P

    2010-09-12

    In any given species, cooperation involves prosocial acts that usually return a fitness benefit to the actor. These acts are produced by a set of psychological rules, which will be similar in related species if they have a similar natural history of cooperation. Prosocial acts can be (i) reactive, i.e. in response to specific stimuli, or (ii) proactive, i.e. occur in the absence of such stimuli. We propose that reactive prosocial acts reflect sensitivity to (i) signals or signs of need and (ii) the presence and size of an audience, as modified by (iii) social distance to the partner or partners. We examine the evidence for these elements in humans and other animals, especially non-human primates, based on the natural history of cooperation, quantified in the context of food sharing, and various experimental paradigms. The comparison suggests that humans share with their closest living relatives reactive responses to signals of need, but differ in sensitivity to signs of need and cues of being watched, as well as in the presence of proactive prosociality. We discuss ultimate explanations for these derived features, in particular the adoption of cooperative breeding as well as concern for reputation and costly signalling during human evolution.

  8. Evidence of intra-hepatic vascular proliferation remodeling early after cure in experimental schistosomiasis mansoni: an immunohistochemical descriptive study.

    PubMed

    Abdel Fattah, Nashwa S; Ahmed, Naglaa S

    2012-01-01

    Experimental studies have demonstrated the occurrence of angiogenesis, blood vessels formation from pre-existing vessels, in the initial phase of bilharzial granuloma formation and during fibrosis progression in chronic hepatic schistosomiasis. Paradoxically, a recent work demonstrated an occurrence of angiogenesis during fibrosis regression months after curative treatment. Studies regarding the in situ kinetics of blood vessels in the phase of granuloma resolution and liver tissue healing early after treatment are lacking. The current work compared the kinetics of blood vessels by immunohistochemical staining using CD34, vascular endothelial growth factor (VEGF) and actin in the livers of normal control mice, Schistosoma mansoni infected mice and mice 2 weeks after curative treatment. The present study demonstrated a process of angiogenesis remodeling in the liver in the curative phase of hepatic schistosomiasis during the stage of granuloma resolution. Such finding raises the evidence of the importance and potential beneficial effect of vascular proliferation in the process of healing and restoration of liver tissue functions. Thus, blocking of angiogenesis may not represent the appropriate therapeutic target for the early treatment of schistosomal liver fibrosis.

  9. Experimental evidence for the physiological role of bacterial luciferase in the protection of cells against oxidative stress.

    PubMed

    Szpilewska, Hanna; Czyz, Agata; Wegrzyn, Grzegorz

    2003-11-01

    The origin and function of bioluminescence was considered a problematic question of the Charles Darwin theory. Early evolution of bacterial luminescence and its current physiological importance seem to be especially mysterious. Recently, it was proposed that stimulation of DNA repair may be a physiological role for production of light by bacterial cells. On the other hand, it was also proposed that primary role of luminescent systems could be detoxification of the deleterious oxygen derivatives. Although some previous results might suggest that this hypothesis can be correct, until now experimental evidence for such a mechanism operating in bacterial cells and having physiological importance was generally lacking. Here we demonstrate that in the presence of various oxidants (hydrogen peroxide, cumene hydroperoxide, t-butyl hydroperoxide, and ferrous ions) at certain concentrations in the culture medium, growth of Vibrio harveyi mutants luxA and luxB, but not of the mutant luxD, is severely impaired relative to wild-type bacteria. This deleterious effect of oxidants on the mutants luxA and luxB could be significantly reduced by addition of the antioxidants A-TEMPO or 40H-TEMPO. We conclude that bacterial luciferase may indeed play a physiological role in the protection of cells against oxidative stress.

  10. A Direct Experimental Evidence For the New Thermodynamic Boundary in the Supercritical State: Implications for Earth and Planetary Sciences.

    NASA Astrophysics Data System (ADS)

    Bolmatov, D.

    2015-12-01

    While scientists have a good theoretical understanding of the heat capacity of both solids and gases, a general theory of the heat capacity of liquids has always remained elusive. Apart from being an awkward hole in our knowledge, heat capacity - the amount of heat needed to change a substance's temperature by a certain amount - is a relevant quantity that it would be nice to be able to predict. I will introduce a phonon-based approach to liquids and supercritical fluids to describe its thermodynamics in terms of sound propagation. I will show that the internal liquid energy has a transverse sound propagation gaps and explain their evolution with temperature variations on the P-T diagram. I will explain how this theoretical framework covers the Debye theory of solids, the phonon theory of liquids, and thermodynamic limits such as the Delong-Petit and the ideal gas thermodynamic limits. As a results, the experimental evidence for the new thermodynamic boundary in the supercritical state (the Frenkel line) on the P-T phase diagram will be demonstrated. Then, I will report on inelastic X-ray scattering experiments combined with the molecular dynamics simulations on deeply supercritical Ar. The presented results unveil the mechanism and regimes of sound propagation in the liquid matter and provide compelling evidence for the adiabatic-to-isothermal longitudinal sound propagation transition. As a result, a universal link will be demonstrated between the positive sound dispersion (PSD) phenomenon and the origin of transverse sound propagation revealing the viscous-to-elastic crossover in compressed liquids. Both can be considered as a universal fingerprint of the dynamic response of a liquid. They can be used then for a signal detection and analysis of a dynamic response in deep water and other fluids which is relevant for describing the thermodynamics of gas giants. The consequences of this finding will be discussed, including a physically justified way to demarcate the

  11. Experimental evidence of cut-wire-induced enhanced transmission of transverse-electric fields through sub-wavelength slits in a thin metallic screen

    NASA Astrophysics Data System (ADS)

    di Gennaro, Emiliano; Gallina, Ilaria; Andreone, Antonello; Castaldi, Giuseppe; Galdi, Vincenzo

    2010-12-01

    Recent numerical studies have demonstrated the possibility of achieving substantial enhancements in the transmission of transverse-electric-polarized electromagnetic fields through subwavelength slits in a thin metallic screen by placing single or paired metallic cut-wire arrays at a close distance from the screen. In this Letter, we report on the first experimental evidence of such extraordinary transmission phenomena, via microwave (X/Ku-band) measurements on printed-circuit-board prototypes. Experimental results agree very well with full-wave numerical predictions, and indicate an intrinsic robustness of the enhanced transmission phenomena with respect to fabrication tolerances and experimental imperfections.

  12. Deciphering The Speed of Link: Experimental Evidence of a Rapid Increase in Soil Respiration Following the Onset of Photosynthesis

    NASA Astrophysics Data System (ADS)

    Kayler, Z. E.; Keitel, C.; Jansen, K.; Gessler, A.

    2011-12-01

    The degree of coupling between aboveground assimilation and transport with below-ground metabolism is an indicator of ecosystem nutrient cycling and energy turnover in the rhizosphere as well as having a large impact on their long-term storage capacity in the soil. Understanding how and when assimilates arrive below-ground for mineralization is necessary to predict how nutrient and energy cycles might be altered by current and future changes in climate, species distribution and land use. Currently, there are two proposed mechanisms that describe the link between assimilation and below-ground respiration via the phloem: 1) the transport of assimilates basipetally according to the Münch theory, and 2) pressure-concentration waves. The transport of assimilates through the phloem by mechanism 1 is often quantified through isotopic labeling studies. Thus, the time between isotopic labeling in the canopy and when the labeled carbon is respired from the rhizoshpere characterizes the degree of coupling between aboveground and below-ground metabolism. The timing between the uptake and below-ground respiration of the labeled carbon is termed the "speed of link". Based on statistical approaches, recent studies have reported a speed of link on the order of one day or less in mature forests, which is too fast for phloem transport by molecular diffusion or classical sink-source dynamics. These studies often cite mechanism 2 to support their conclusions despite the lack of experimental evidence. In this presentation, we report results from experiments designed to observe the mechanisms behind the speed of link of Douglas-fir saplings. We kept the plants for several days (0,1 and 6 days) in the dark to create a large carbon source-sink gradient with the intention of inducing a strong pressure-concentration wave. Following the no light treatment, in a controlled growth chamber, we introduced labelled CO2 prior to exposing the plant to light. Upon exposing the plants to light, the

  13. Relative importance of temperature and other factors in determining geographic boundaries of seaweeds: Experimental and phenological evidence

    NASA Astrophysics Data System (ADS)

    Breeman, A. M.

    1988-06-01

    Experimentally determined ranges of thermal tolerance and requirements for completion of the life history of some 60 seaweed species from the North Atlantic Ocean were compared with annual temperature regimes at their geographic boundaries. In all but a few species, thermal responses accounted for the location of boundaries. Distribution was restricted by: (a) lethal effects of high or low temperatures preventing survival of the hardiest life history stage (often microthalli), (b) temperature requirements for completion of the life history operating on any one process (i.e. [sexual] reproduction, formation of macrothalli or blades), (c) temperature requirements for the increase of population size (through growth or the formation of asexual propagules). Optimum growth/reproduction temperatures or lethal limits of the non-hardiest stage (often macrothalli) were irrelevant in explaining distribution. In some species, ecotypic differentiation in thermal responses over the distribution range influenced the location of geographic boundaries, but in many other species no such ecotypic differences were evident. Specific daylength requirements affected the location of boundaries only when interacting with temperature. The following types of thermal responses could be recognised, resulting in characteristic distribution patterns: (A) Species endemic to the (warm) temperate eastern Atlantic had narrow survival ranges (between ca 5 and ca 25°C) preventing occurrence in NE America. In species with isomorphic life histories without very specific temperature requirements for reproduction, northern and southern boundaries in Eur/Africa are set by lethal limits. Species with heteromorphic life histories often required high and/or low temperatures to induce reproduction in one or both life history phases which further restricted distribution. (B) Species endemic to the tropical western Atlantic also had narrow survival ranges (between ca 10 and ca 35°C). Northern boundaries are

  14. Experimental evidence of direct contact formation for the current transport in silver thick film metallized silicon emitters

    NASA Astrophysics Data System (ADS)

    Cabrera, Enrique; Olibet, Sara; Glatz-Reichenbach, Joachim; Kopecek, Radovan; Reinke, Daniel; Schubert, Gunnar

    2011-12-01

    Great advances have been achieved in the development of silver pastes. The use of smaller silver particles, higher silver content, and, thus, less glass frit allow modern silver pastes to contact high resistive emitters without the necessity of a selective emitter or subsequent plating. To identify the microscopic key reasons behind the improvement of silver paste, it is essential to understand the current transport mechanism from the silicon emitter into the bulk of the silver finger. Two current transport theories predominate: i) The current flows through the Ag crystallites grown into the Si emitter, which are separated by a thin glass layer or possibly in direct contact with the silver finger. ii) The current is transported by means of multistep tunneling into the silver finger across nano-Ag colloids in the glass layer, which are formed at optimal firing conditions; the formation of Ag crystallites into the Si surface is synonymous with over-firing. In this study, we contact Si solar cell emitters with different silver pastes on textured and flat silicon surfaces. A sequential selective silver-glass etching process is employed to expose and isolate the different contact components for current transport. The surface configurations after the etching sequences are observed with scanning electron microscopy. Liquid conductive silver is then applied to each sample and the contact resistivity is measured to determine the dominant microscopic conduction path system. We observe glass-free emitter areas at the tops of the pyramidal-textured Si that lead to the formation of direct contacts between the Ag crystallites grown into the Si emitter and the bulk of the silver finger. We present experimental evidence that the major current flow into the silver finger is through these direct contacts.

  15. Adaptation of an evidence-based intervention to promote colorectal cancer screening: a quasi-experimental study

    PubMed Central

    2014-01-01

    Background To accelerate the translation of research findings into practice for underserved populations, we investigated the adaptation of an evidence-based intervention (EBI), designed to increase colorectal cancer (CRC) screening in one limited English-proficient (LEP) population (Chinese), for another LEP group (Vietnamese) with overlapping cultural and health beliefs. Methods Guided by Diffusion of Innovations Theory, we adapted the EBI to achieve greater reach. Core elements of the adapted intervention included: small media (a DVD and pamphlet) translated into Vietnamese from Chinese; medical assistants distributing the small media instead of a health educator; and presentations on CRC screening to the medical assistants. A quasi-experimental study examined CRC screening adherence among eligible Vietnamese patients at the intervention and control clinics, before and after the 24-month intervention. The proportion of the adherence was assessed using generalized linear mixed models that account for clustering under primary care providers and also within-patient correlation between baseline and follow up. Results Our study included two cross-sectional samples: 1,016 at baseline (604 in the intervention clinic and 412 in the control clinic) and 1,260 post-intervention (746 in the intervention and 514 in the control clinic), including appreciable overlaps between the two time points. Pre-post change in CRC screening over time, expressed as an odds ratio (OR) of CRC screening adherence by time, showed a marginally-significant greater increase in CRC screening adherence at the intervention clinic compared to the control clinic (the ratio of the two ORs = 1.42; 95% CI 0.95, 2.15). In the sample of patients who were non-adherent to CRC screening at baseline, compared to the control clinic, the intervention clinic had marginally-significant greater increase in FOBT (adjusted OR = 1.77; 95% CI 0.98, 3.18) and a statistically-significantly greater increase in CRC

  16. Evidence Evaluation: Measure "Z" Corresponds to Human Utility Judgments Better than Measure "L" and Optimal-Experimental-Design Models

    ERIC Educational Resources Information Center

    Rusconi, Patrice; Marelli, Marco; D'Addario, Marco; Russo, Selena; Cherubini, Paolo

    2014-01-01

    Evidence evaluation is a crucial process in many human activities, spanning from medical diagnosis to impression formation. The present experiments investigated which, if any, normative model best conforms to people's intuition about the value of the obtained evidence. Psychologists, epistemologists, and philosophers of science have proposed…

  17. Metal-free α-Amination of Secondary Amines: Computational and Experimental Evidence for Azaquinone Methide and Azomethine Ylide Intermediates

    PubMed Central

    Dieckmann, Arne; Richers, Matthew T.; Platonova, Alena Yu.; Zhang, Chen; Seidel, Daniel; Houk, K. N.

    2013-01-01

    We have performed a combined computational and experimental study to elucidate the mechanism of a metal-free α-amination of secondary amines. Calculations predicted azaquinone methides and azomethine ylides as the reactive intermediates and showed that iminium ions are unlikely to participate in these transformations. These results were confirmed by experimental deuterium labeling studies and the successful trapping of the postulated azomethine ylide and azaquinone methide intermediates. In addition, computed barrier heights for the rate-limiting step correlate qualitatively with experimental findings. PMID:23517448

  18. Theoretical evidence for inconsistencies in experimental bubble nucleation rates of propane/CO2 and R22/CO2 mixtures

    NASA Astrophysics Data System (ADS)

    Němec, Tomáš

    2015-12-01

    A binary formulation of the classical nucleation theory (CNT) is developed for homogeneous bubble nucleation in systems composed of a liquid solvent and a dissolved gas. The CNT predictions coincide with experimental nucleation data from the literature for diethylether/N2 and isobutane/CO2 mixtures, while several inconsistencies are identified for propane/CO2 and R22/CO2 experimental datasets.

  19. Experimental evidence that an asteroid impact led to the extinction of many species 65 million years ago

    SciTech Connect

    Alvarez, L.W.

    1982-09-01

    The development of the theory that the mass extinction of the dinosaurs at the Cretaceous-Tertiary boundary was caused by an asteroid impact is reviewed. The personnel involved, the objections to the theory, and the evidence refuting those objections are presented chronologically. (ACR)

  20. Quasi-Experimental Evidence of Peer Effects in First-Year Economics Courses at a Chinese University

    ERIC Educational Resources Information Center

    Chen, Qihui; Tian, Guoqiang; Okediji, Tade O.

    2014-01-01

    The authors of this article implement a quasi-experimental strategy to estimate peer effects in economic education by exploiting the institutional setting in a large public university in China, where roommates are randomly assigned conditional on a student's major and province of origin. They found significant impacts of peer academic…

  1. Experimental Evidence of the Superiority of the Prevalence Model of Conceptual Change over the Classical Models and Repetition

    ERIC Educational Resources Information Center

    Potvin, Patrice; Sauriol, Érik; Riopel, Martin

    2015-01-01

    This quasi-experimental study investigated the effects on 558 grades five and six students of three different teaching conditions: the "classical" model of conceptual change (for which cognitive conflict is considered as a precondition to the transformation of knowledge), the "prevalence" model of conceptual change (in which…

  2. Experimental evidence of impingement induced strains at the interface and the periphery of an embedded acetabular cup implant.

    PubMed

    Arndt, Christoph; Voigt, Christian; Steinke, Hanno; Salis-Soglio, Georg V; Scholz, Roger

    2012-01-01

    After total hip arthroplasty, impingement of implant components may occur during every-day patient activities causing increased shear stresses at the acetabular implant-bone interface. In the literature, impingement related lever-out moments were noted for a number of acetabular components. But there is little information about pelvic load transfer. The aim of the current study was to measure the three-dimensional strain distribution at the macrostructured hemispherical interface and in the periphery of a standard acetabular press-fit cup in an experimental implant-bone substitute model. An experimental setup was developed to simulate impingement loading via a lever arm representing the femoral component and the lower limb. In one experimental setup 12 strain gauges were embedded at predefined positions in the periphery of the acetabular cup implant inside a tray, using polyurethane composite resin as a bone substitute material. By incremental rotation of the implant tray in steps of 10 and 30 deg, respectively, the strains were measured at evenly distributed positions. With the described method 288 genuine strain values were measured in the periphery of an embedded acetabular cup implant in one experimental setup. In two additional setups the strains were evaluated at different distances from the implant interface. Both in radial and meridional interface directions strain magnitudes reach their peak near the rim of the cup below the impingement site. Values of equatorial strains vary near zero and reach their peaks near the rim of the cup on either side and in some distance from the impingement site. Interestingly, the maximum of averaged radial strains does not occur, as expected, close to the interface but at an interface offset of 5.6 mm. With the described experimental setup it is now possible to measure and display the three-dimensional strain distribution in the interface and the periphery of an embedded acetabular cup implant. The current study provides the

  3. Experimental Evidence of Backward Raman Scattering Driven Cooperatively by Two Picosecond Laser Pulses Propagating Side by Side

    NASA Astrophysics Data System (ADS)

    Rousseaux, C.; Glize, K.; Baton, S. D.; Lancia, L.; Bénisti, D.; Gremillet, L.

    2016-07-01

    This Letter investigates experimentally the backward stimulated Raman scattering (SRS) of two copropagating, 1-μ m wavelength, 1.5-ps duration laser pulses focused side by side, but not simultaneously, in a preformed underdense plasma. When the two lasers do not interact, one of the pulses (so-called strong) yields a large SRS reflectivity, while the other weak pulse is essentially ineffective as regards SRS. By contrast, the weak pulse shows significant SRS activity if it is launched in the plasma slightly after the strong one, and for time delays as large as about 15 ps. For crossed polarizations and a lateral distance of 80 - 90 μ m , the time delay has to be larger than 3-4 ps for the weak pulse to be active, while it has just to be positive when the polarizations are parallel. The experimental results are discussed with the help of large-scale particle-in-cell simulations.

  4. When Genomics Is Not Enough: Experimental Evidence for a Decrease in LINE-1 Activity During the Evolution of Australian Marsupials.

    PubMed

    Gallus, Susanne; Lammers, Fritjof; Nilsson, Maria Anna

    2016-01-01

    The autonomous transposable element LINE-1 is a highly abundant element that makes up between 15% and 20% of therian mammal genomes. Since their origin before the divergence of marsupials and placental mammals, LINE-1 elements have contributed actively to the genome landscape. A previous in silico screen of the Tasmanian devil genome revealed a lack of functional coding LINE-1 sequences. In this study we present the results of an in vitro analysis from a partial LINE-1 reverse transcriptase coding sequence in five marsupial species. Our experimental screen supports the in silico findings of the genome-wide degradation of LINE-1 sequences in the Tasmanian devil, and identifies a high frequency of degraded LINE-1 sequences in other Australian marsupials. The comparison between the experimentally obtained LINE-1 sequences and reference genome assemblies suggests that conclusions from in silico analyses of retrotransposition activity can be influenced by incomplete genome assemblies from short reads. PMID:27389686

  5. When Genomics Is Not Enough: Experimental Evidence for a Decrease in LINE-1 Activity During the Evolution of Australian Marsupials

    PubMed Central

    Gallus, Susanne; Lammers, Fritjof

    2016-01-01

    The autonomous transposable element LINE-1 is a highly abundant element that makes up between 15% and 20% of therian mammal genomes. Since their origin before the divergence of marsupials and placental mammals, LINE-1 elements have contributed actively to the genome landscape. A previous in silico screen of the Tasmanian devil genome revealed a lack of functional coding LINE-1 sequences. In this study we present the results of an in vitro analysis from a partial LINE-1 reverse transcriptase coding sequence in five marsupial species. Our experimental screen supports the in silico findings of the genome-wide degradation of LINE-1 sequences in the Tasmanian devil, and identifies a high frequency of degraded LINE-1 sequences in other Australian marsupials. The comparison between the experimentally obtained LINE-1 sequences and reference genome assemblies suggests that conclusions from in silico analyses of retrotransposition activity can be influenced by incomplete genome assemblies from short reads. PMID:27389686

  6. Silica-rich lavas in the oceanic crust: experimental evidence for fractional crystallization under low water activity

    NASA Astrophysics Data System (ADS)

    Erdmann, Martin; Koepke, Jürgen

    2016-10-01

    We experimentally investigated phase relations and phase compositions as well as the influence of water activity ( aH2O) and redox conditions on the equilibrium crystallization path within an oceanic dacitic potassium-depleted system at shallow pressure (200 MPa). Moreover, we measured the partitioning of trace elements between melt and plagioclase via secondary ion mass spectrometry for a highly evolved experiment (SiO2 = 74.6 wt%). As starting material, we used a dacitic glass dredged at the Pacific-Antarctic Rise. Phase assemblages in natural high-silica systems reported from different locations of fast-spreading oceanic crust could be experimentally reproduced only in a relatively small range of temperature and melt-water content ( T ~950 °C; melt H2O < 1.5 wt%) at redox conditions slightly below the quartz-fayalite-magnetite buffer. The relatively low water content is remarkable, because distinct hydrothermal influence is generally regarded as key for producing silica-rich rocks in an oceanic environment. However, our conclusion is also supported by mineral and melt chemistry of natural evolved rocks; these rocks are only congruent to the composition of those experimental phases that are produced under low aH2O. Low FeO contents under water-saturated conditions and the characteristic enrichment of Al2O3 in high aH2O experiments, in particular, contradict natural observations, while experiments with low aH2O match the natural trend. Moreover, the observation that highly evolved experimental melts remain H2O-poor while they are relatively enriched in chlorine implies a decoupling between these two volatiles during crustal contamination.

  7. Experimental evidence of E × B plasma rotation in a 2.45 GHz hydrogen discharge

    SciTech Connect

    Cortázar, O. D.; Tarvainen, O.; Koivisto, H.

    2015-12-15

    An experimental observation of a rotating plasma structure in a 2.45 GHz microwave-driven hydrogen discharge is reported. The rotation is presumably produced by E × B drift. The formation of the rotating plasma structure is sensitive to the strength of the off-resonance static magnetic field. The rotation frequency is on the order of 10 kHz and is affected by the neutral gas pressure and applied microwave power.

  8. Favorable results from the use of herbal and plant products in inflammatory bowel disease: evidence from experimental animal studies

    PubMed Central

    Triantafillidis, John K.; Triantafyllidi, Aikaterini; Vagianos, Constantinos; Papalois, Apostolos

    2016-01-01

    The use of herbal therapy for inflammatory bowel disease is increasing worldwide. The aim of this study was to review the available literature on the efficacy of herbal therapy in experimental colitis. All relevant studies published in Medline and Embase up to June 2015 have been reviewed. The results of bowel histology and serum parameters have been recorded. A satisfactory number of published experimental studies, and a quite large one of both herbal and plant products tested in different studies have been reported. The results showed that in the majority of the studies, herbal therapy reduced the inflammatory activity of experimental colitis and diminished the levels of many inflammatory indices, including serum cytokines and indices of oxidative stress. The most promising plant and herbal products were tormentil extracts, wormwoodherb, Aloe vera, germinated barley foodstuff, curcumin, Boswellia serrata, Panax notoginseng, Ixeris dentata, green tea, Cordia dichotoma, Plantago lanceolata, Iridoidglycosides, and mastic gum. Herbal therapies exert their therapeutic benefit via various mechanisms, including immune regulation, anti-oxidant activity, inhibition of leukotriene B4 and nuclear factor-κB, and antiplatelet activity. Large, double-blind clinical studies assessing these natural substances should be urgently conducted. PMID:27366027

  9. Favorable results from the use of herbal and plant products in inflammatory bowel disease: evidence from experimental animal studies.

    PubMed

    Triantafillidis, John K; Triantafyllidi, Aikaterini; Vagianos, Constantinos; Papalois, Apostolos

    2016-01-01

    The use of herbal therapy for inflammatory bowel disease is increasing worldwide. The aim of this study was to review the available literature on the efficacy of herbal therapy in experimental colitis. All relevant studies published in Medline and Embase up to June 2015 have been reviewed. The results of bowel histology and serum parameters have been recorded. A satisfactory number of published experimental studies, and a quite large one of both herbal and plant products tested in different studies have been reported. The results showed that in the majority of the studies, herbal therapy reduced the inflammatory activity of experimental colitis and diminished the levels of many inflammatory indices, including serum cytokines and indices of oxidative stress. The most promising plant and herbal products were tormentil extracts, wormwoodherb, Aloe vera, germinated barley foodstuff, curcumin, Boswellia serrata, Panax notoginseng, Ixeris dentata, green tea, Cordia dichotoma, Plantago lanceolata, Iridoidglycosides, and mastic gum. Herbal therapies exert their therapeutic benefit via various mechanisms, including immune regulation, anti-oxidant activity, inhibition of leukotriene B4 and nuclear factor-κB, and antiplatelet activity. Large, double-blind clinical studies assessing these natural substances should be urgently conducted. PMID:27366027

  10. Favorable results from the use of herbal and plant products in inflammatory bowel disease: evidence from experimental animal studies.

    PubMed

    Triantafillidis, John K; Triantafyllidi, Aikaterini; Vagianos, Constantinos; Papalois, Apostolos

    2016-01-01

    The use of herbal therapy for inflammatory bowel disease is increasing worldwide. The aim of this study was to review the available literature on the efficacy of herbal therapy in experimental colitis. All relevant studies published in Medline and Embase up to June 2015 have been reviewed. The results of bowel histology and serum parameters have been recorded. A satisfactory number of published experimental studies, and a quite large one of both herbal and plant products tested in different studies have been reported. The results showed that in the majority of the studies, herbal therapy reduced the inflammatory activity of experimental colitis and diminished the levels of many inflammatory indices, including serum cytokines and indices of oxidative stress. The most promising plant and herbal products were tormentil extracts, wormwoodherb, Aloe vera, germinated barley foodstuff, curcumin, Boswellia serrata, Panax notoginseng, Ixeris dentata, green tea, Cordia dichotoma, Plantago lanceolata, Iridoidglycosides, and mastic gum. Herbal therapies exert their therapeutic benefit via various mechanisms, including immune regulation, anti-oxidant activity, inhibition of leukotriene B4 and nuclear factor-κB, and antiplatelet activity. Large, double-blind clinical studies assessing these natural substances should be urgently conducted.

  11. Direct Experimental Evidence for Atomic Tunneling of Europium in Crystalline Eu8GaGe30

    SciTech Connect

    Hermann, R. P.; Keppens, Veerle; Bonville, Pierre; Nolas, G. S.; Grandjean, F.; Long, G. J.; Christen, Hans M; Chakoumakos, Bryan C; Sales, Brian C; Mandrus, David

    2006-01-01

    Moessbauer-effect and microwave absorption experimental evidence unambiguously demonstrates the presence of slow, {approx}450 MHz, tunneling of magnetic europium between four equivalent sites in Eu{sub 8}Ga{sub 16}Ge{sub 30}, a stoichiometric clathrate. Remarkably, six of the eight europium atoms, or 11% of the constituents in this solid, tunnel between these four sites separated by 0.55 {angstrom}. The off centering of the atoms or ions in crystalline clathrates appears to be a promising route for producing Rabi oscillators in solid-state materials.

  12. Experimental evidence of an incomplete thermalization of the energy in an x-ray microcalorimeter with a TaAu absorber.

    PubMed

    Perinati, E; Barbera, M; Varisco, S; Silver, E; Beeman, J; Pigot, C

    2008-05-01

    We have conducted an experimental test at our XACT facility using an x-ray microcalorimeter with TaAu absorber and neutron transmutation doped germanium thermal sensor. The test was aimed at measuring the percentage of energy effectively thermalized after absorption of x-ray photons in superconducting tantalum. Moreover, in general, possible formation of long living quasiparticles implies that by using a superconducting absorber, a fraction of the deposited energy could not be thermalized on the useful time scale of the thermal sensor. To investigate this scenario, we exploited an absorber made of gold, where no energy trapping is expected, with a small piece of superconducting tantalum attached on top. We obtained evidence that the thermalization of photons absorbed in tantalum is delayed by energy trapping from quasiparticles. We compare the experimental results with numerical simulations and derive a value for the intrinsic lifetime of quasiparticles. PMID:18513077

  13. Circum-crater variability of deposits from discrete, laterally and vertically migrating volcanic explosions: Experimental evidence and field implications

    NASA Astrophysics Data System (ADS)

    Graettinger, A. H.; Valentine, G. A.; Sonder, I.

    2015-12-01

    Circumferential variation in sorting, thickness, granulometry, and componentry of tephra ring deposits can result from instabilities in the eruptive jet and interactions with the confining crater. Jet instabilities result in fingers of high particle concentrations that form deposits radiating away from a crater, referred to as rays. Two major types of rayed deposits are described from subsurface explosion experiments: (1) symmetrical rayed deposits with an axisymmetric ejecta blanket, which result from vertically directed eruptive jets and (2) zones of rays that extend out from sectors of a crater, with an asymmetrical proximal ejecta skirt, that result from inclined jets. Variations within each group are also associated with variations in the explosion depth relative to the energy of the explosion. Although the surface morphology of rays is likely to be lost in natural tephra rings due to overlapping deposits of numerous explosions, rayed deposits are expected to be preserved in cross section as lenses of relatively coarse and poorly sorted material compared to surrounding deposits. Asymmetrical deposits of inclined jets are anticipated to be particularly distinctive. The experimental facies associations indicate that these deposits would be easily distinguished, given sufficient exposure, from other heterogeneities caused by wind influence, collapse of the crater rim, or the influence of topography on density currents. These experimental results can also be used to further the discussion of deposits from inclined jets from other explosion scenarios, such as Vulcanian blasts and hydrothermal explosions. The experimental rayed deposits described here indicate that the classic interpretation of clast concentration zones in tephra ring deposits must be reevaluated.

  14. A review of experimental evidences that could warn of possible dangers of alcohol consumption by pregnant mothers.

    PubMed

    Chaudhuri, J D

    2000-12-01

    Most of the features of fetal alcohol syndrome (FAS) have been replicated in experimental models. They provide an insight into the effects of alcohol on the developing embryo, however, satisfactory explanations for these effects are still not available. Certain maternal characteristics of children with FAS have been identified. However, it is not absolute as at times the most unlikely women are susceptible to problems of maternal alcoholism. The levels of awareness of FAS among the general public and health workers are inadequate. Measures need to be taken to remedy this condition.

  15. Experimental Evidence Supported by Simulations of a Very High H{sub 2} Diffusion in Metal Organic Framework Materials

    SciTech Connect

    Salles, F.; Maurin, G.; Jobic, H.; Koza, M. M.; Llewellyn, P. L.; Devic, T.; Serre, C.; Ferey, G.

    2008-06-20

    Quasielastic neutron scattering measurements are combined with molecular dynamics simulations to extract the self-diffusion coefficient of hydrogen in the metal organic frameworks MIL-47(V) and MIL-53(Cr). We find that the diffusivity of hydrogen at low loading is about 2 orders of magnitude higher than in zeolites. Such a high mobility has never been experimentally observed before in any nanoporous materials, although it was predicted in carbon nanotubes. Either 1D or 3D diffusion mechanisms are elucidated depending on the chemical features of the MIL framework.

  16. Experimental Evidence of Short Light Pulse Amplification Using Strong-Coupling Stimulated Brillouin Scattering in the Pump Depletion Regime

    SciTech Connect

    Lancia, L.; Antici, P.; Marques, J.-R.; Nakatsutsumi, M.; Mancic, A.; Audebert, P.; Fuchs, J.; Riconda, C.; Weber, S.; Tikhonchuk, V. T.; Hueller, S.; Heron, A.

    2010-01-15

    The energy transfer from a long (3.5 ps) pump pulse to a short (400 fs) seed pulse due to stimulated Brillouin backscattering in the strong-coupling regime is investigated. The two pulses, both at the same wavelength of 1.057 {mu}m are quasicounterpropagating in a preformed underdense plasma. Relative amplification factors for the seed pulse of up to 32 are obtained. The maximum obtained amplified energy is 60 mJ. Simulations are in agreement with the experimental results and suggest paths for further improvement of the amplification scheme.

  17. Experimental evidence concerning the different behavior of energy and exergy performance indicators of refrigeration systems in transient regimes

    NASA Astrophysics Data System (ADS)

    Vasilescu, Elena Eugenia; Feidt, Michel; Boussehain, Rahal; Dobrovicescu, Alexandru

    2016-01-01

    This article presents the results obtained from an energy-exergy analysis of a vapor compression refrigeration system during induced transient regimes. Using experimental data, exergy destruction as a function of time under the influence of some factors that perturb the stationary regime, such as deactivation of piston, variation of mass flow rate and initial temperature of cooled fluid, and diminution of the compressor rotation speed, was calculated. Under the perturbation, an antagonistic increase in the coefficient of performance and a decrease in exergy efficiency were noted.

  18. Accumulation and transport of microbial-size particles in a pressure protected model burn unit: CFD simulations and experimental evidence

    PubMed Central

    2011-01-01

    Background Controlling airborne contamination is of major importance in burn units because of the high susceptibility of burned patients to infections and the unique environmental conditions that can accentuate the infection risk. In particular the required elevated temperatures in the patient room can create thermal convection flows which can transport airborne contaminates throughout the unit. In order to estimate this risk and optimize the design of an intensive care room intended to host severely burned patients, we have relied on a computational fluid dynamic methodology (CFD). Methods The study was carried out in 4 steps: i) patient room design, ii) CFD simulations of patient room design to model air flows throughout the patient room, adjacent anterooms and the corridor, iii) construction of a prototype room and subsequent experimental studies to characterize its performance iv) qualitative comparison of the tendencies between CFD prediction and experimental results. The Electricité De France (EDF) open-source software Code_Saturne® (http://www.code-saturne.org) was used and CFD simulations were conducted with an hexahedral mesh containing about 300 000 computational cells. The computational domain included the treatment room and two anterooms including equipment, staff and patient. Experiments with inert aerosol particles followed by time-resolved particle counting were conducted in the prototype room for comparison with the CFD observations. Results We found that thermal convection can create contaminated zones near the ceiling of the room, which can subsequently lead to contaminate transfer in adjacent rooms. Experimental confirmation of these phenomena agreed well with CFD predictions and showed that particles greater than one micron (i.e. bacterial or fungal spore sizes) can be influenced by these thermally induced flows. When the temperature difference between rooms was 7°C, a significant contamination transfer was observed to enter into the positive

  19. Experimental evidence of short light pulse amplification using strong-coupling stimulated brillouin scattering in the pump depletion regime.

    PubMed

    Lancia, L; Marquès, J-R; Nakatsutsumi, M; Riconda, C; Weber, S; Hüller, S; Mancić, A; Antici, P; Tikhonchuk, V T; Héron, A; Audebert, P; Fuchs, J

    2010-01-15

    The energy transfer from a long (3.5 ps) pump pulse to a short (400 fs) seed pulse due to stimulated Brillouin backscattering in the strong-coupling regime is investigated. The two pulses, both at the same wavelength of 1.057 microm are quasicounterpropagating in a preformed underdense plasma. Relative amplification factors for the seed pulse of up to 32 are obtained. The maximum obtained amplified energy is 60 mJ. Simulations are in agreement with the experimental results and suggest paths for further improvement of the amplification scheme. PMID:20366602

  20. Experimental evidence of dynamical propagation for solitary waves in ultra slow stochastic non-local Kerr medium.

    PubMed

    Louis, H; Tlidi, M; Louvergneaux, E

    2016-07-11

    We perform a statistical analysis of the optical solitary wave propagation in an ultra-slow stochastic non-local focusing Kerr medium such as liquid crystals. Our experimental results show that the localized beam trajectory presents a dynamical random walk whose beam position versus the propagation distance z depicts two different kind of evolutions A power law is found for the beam position standard deviation during the first stage of propagation. It obeys approximately z3/2 up to ten times the power threshold for solitary wave generation. PMID:27410886

  1. Experimental evidence of dynamical propagation for solitary waves in ultra slow stochastic non-local Kerr medium.

    PubMed

    Louis, H; Tlidi, M; Louvergneaux, E

    2016-07-11

    We perform a statistical analysis of the optical solitary wave propagation in an ultra-slow stochastic non-local focusing Kerr medium such as liquid crystals. Our experimental results show that the localized beam trajectory presents a dynamical random walk whose beam position versus the propagation distance z depicts two different kind of evolutions A power law is found for the beam position standard deviation during the first stage of propagation. It obeys approximately z3/2 up to ten times the power threshold for solitary wave generation. PMID:27410887

  2. Honest sexual signaling in turtles: experimental evidence of a trade-off between immune response and coloration in red-eared sliders Trachemys scripta elegans

    NASA Astrophysics Data System (ADS)

    Ibáñez, Alejandro; Polo-Cavia, Nuria; López, Pilar; Martín, José

    2014-10-01

    Sexual signals can be evolutionarily stable if they are honest and condition dependent or costly to the signaler. One possible cost is the existence of a trade-off between maintaining the immune system and the elaboration of ornaments. This hypothesis has been experimentally tested in some groups of animals but not in others such as turtles. We experimentally challenged the immune system of female red-eared sliders Trachemys scripta elegans, with a bacterial antigen (lipopolysaccharide (LPS)) without pathogenic effects to explore whether the immune activation affected visual colorful ornaments of the head. The LPS injection altered the reflectance patterns of color ornaments. In comparison to the control animals, the yellow chin stripes of injected animals exhibited (1) reduced brightness, (2) lower long wavelength (>470 nm) reflectance, and (3) lower values for carotenoid chroma. The postorbital patches of injected individuals also showed reduced very long wavelength (>570 nm) reflectance but did not change in carotenoid chroma. Thus, experimental turtles showed darker and less "yellowish" chin stripes and less "reddish" postorbital patches at the end of the experiment, whereas control turtles did not change their coloration. This is the first experimental evidence supporting the existence of a trade-off between the immune system and the expression of visual ornaments in turtles. We suggest that this trade-off may allow turtles to honestly signal individual quality via characteristics of coloration, which may have an important role in intersexual selection processes.

  3. Honest sexual signaling in turtles: experimental evidence of a trade-off between immune response and coloration in red-eared sliders Trachemys scripta elegans.

    PubMed

    Ibáñez, Alejandro; Polo-Cavia, Nuria; López, Pilar; Martín, José

    2014-10-01

    Sexual signals can be evolutionarily stable if they are honest and condition dependent or costly to the signaler. One possible cost is the existence of a trade-off between maintaining the immune system and the elaboration of ornaments. This hypothesis has been experimentally tested in some groups of animals but not in others such as turtles. We experimentally challenged the immune system of female red-eared sliders Trachemys scripta elegans, with a bacterial antigen (lipopolysaccharide (LPS)) without pathogenic effects to explore whether the immune activation affected visual colorful ornaments of the head. The LPS injection altered the reflectance patterns of color ornaments. In comparison to the control animals, the yellow chin stripes of injected animals exhibited (1) reduced brightness, (2) lower long wavelength (>470 nm) reflectance, and (3) lower values for carotenoid chroma. The postorbital patches of injected individuals also showed reduced very long wavelength (>570 nm) reflectance but did not change in carotenoid chroma. Thus, experimental turtles showed darker and less "yellowish" chin stripes and less "reddish" postorbital patches at the end of the experiment, whereas control turtles did not change their coloration. This is the first experimental evidence supporting the existence of a trade-off between the immune system and the expression of visual ornaments in turtles. We suggest that this trade-off may allow turtles to honestly signal individual quality via characteristics of coloration, which may have an important role in intersexual selection processes.

  4. First Experimental Evidence for the Diverse Requirements of Excimer vs Hole Stabilization in π-Stacked Assemblies.

    PubMed

    Reilly, Neil; Ivanov, Maxim; Uhler, Brandon; Talipov, Marat; Rathore, Rajendra; Reid, Scott A

    2016-08-01

    Exciton formation and charge separation and transport are key dynamical events in a variety of functional polymeric materials and biological systems, including DNA. Beyond the necessary cofacial approach of a pair of aromatic molecules at van der Waals contact, the extent of overlap and necessary geometrical reorganization for optimal stabilization of an excimer vs dimer cation radical remain unresolved. Here, we compare experimentally the dynamics of excimer formation (via emission) and charge stabilization (via threshold ionization) of a novel covalently linked, cofacially stacked fluorene dimer (F2) with the unlinked van der Waals dimer of fluorene, that is, (F)2. Although the measured ionization potentials are identical, the excimeric state is stabilized by up to ∼30 kJ/mol in covalently linked F2. Supported by theory, this work demonstrates for the first time experimentally that optimal stabilization of an excimer requires a perfect sandwich-like geometry with maximal overlap, whereas hole stabilization in π-stacked aggregates is less geometrically restrictive. PMID:27447947

  5. Experimental evidence of intermittent chaos in a glow discharge plasma without external forcing and its numerical modelling

    SciTech Connect

    Ghosh, S. Kumar Shaw, Pankaj; Sekar Iyengar, A. N.; Janaki, M. S.; Saha, Debajyoti; Michael Wharton, Alpha

    2014-03-15

    Intermittent chaos was observed in a glow discharge plasma as the system evolved from regular type of relaxation oscillations (of larger amplitude) to an irregular type of oscillations (of smaller amplitude) as the discharge voltage was increased. Floating potential fluctuations were analyzed by different statistical and spectral methods. Features like a gradual change in the normal variance of the interpeak time intervals, a dip in the skewness, and a hump in the kurtosis with variation in the control parameter have been seen, which are strongly indicative of intermittent behavior in the system. Detailed analysis also suggests that the intrinsic noise level in the experiment increases with the increasing discharge voltage. An attempt has been made to model the experimental observations by a second order nonlinear ordinary differential equation derived from the fluid equations for an unmagnetized plasma. Though the experiment had no external forcing, it was conjectured that the intrinsic noise in the experiment could be playing a vital role in the dynamics of the system. Hence, a constant bias and noise as forcing terms were included in the model. Results from the theoretical model are in close qualitative agreement with the experimental results.

  6. Non-standard coupled extensional and bending bias tests for planar pantographic lattices. Part II: comparison with experimental evidence

    NASA Astrophysics Data System (ADS)

    Turco, Emilio; Barcz, Katarzyna; Rizzi, Nicola Luigi

    2016-10-01

    In dell'Isola et al. (Zeitschrift für Angewandte Math und Physik 66(6):3473-3498, 2015, Proc R Soc Lond A Math Phys Eng Sci 472(2185):1-23, 2016) pantographic sheets are proposed as a basic constituent for a novel metamaterial. In Part I, see Turco et al. (Zeitschrift für Angewandte Math und Physik, doi: 10.1007/s00033-016-0713-4, 2016), two different numerical models are applied in order to design an experimental setup aimed to prove the effectiveness of introduced concept. The aim of this paper is to prove that the Hencky-type model introduced for planar pantographic sheets allows for the correct prediction, in a large range of imposed displacements, of the experimental measurements concerning specimens undergoing coupled bending and extensional deformations. The four-parameter numerical model introduced is shown to have a large range of applicability: Indeed without changing the values of the material parameters previously attributed in simple extensional tests to a specific specimen by a best-fit procedure, it is possible to forecast its behavior in all the considered type of imposed deformations. The measurements performed include the determination of reactive forces exerted by used hard devices, and the numerical modeling is able to predict very carefully quantitatively and qualitatively also this complex aspect of phenomenology, where previously attempted models seem to have failed.

  7. Non-linear infrared spectroscopy of the water bending mode: Direct experimental evidence of hydration shell reorganization?

    PubMed Central

    Chuntonov, Lev; Kumar, Revati

    2014-01-01

    The structure and dynamics of liquid water are further studied by investigating the bend vibrational mode of HDO/D2O and pure H2O via two-dimensional infrared spectroscopy (2D-IR) and linear absorption. The experimental findings and theoretical calculations support a picture in which the HDO bend is localized and the H2O bend is delocalized. The HDO and H2O bends present a loss of the frequency-frequency correlation in subpicosecond time scale. While the loss of correlation for the H2O bend is likely to be associated with the vibrational dynamics of a delocalized transition, the loss of the correlation in the localized HDO bend appears to arise from the fluctuations/rearrangements of the local environment. Interestingly, analysis of the HDO 2D-IR spectra shows the presence of multiple overlapping inhomogeneous distributions of frequencies that interchange in a few picoseconds. Theoretical calculations allow us to propose an atomistic model of the observed vibrational dynamics in which the different in homogeneous distributions and their interchange are assigned to water molecules with different hydrogen-bond states undergoing chemical exchange. The frequency shifts as well as the concentration of the water molecules with single and double hydrogen-bonds as donors derived from the theory are in good agreement with our experimental findings. PMID:24871901

  8. Gut reaction by heartless shrimps: experimental evidence for the role of the gut in generating circulation before cardiac ontogeny.

    PubMed

    Spicer, John I

    2006-12-22

    Before the appearance of a functional heart in many invertebrate species, the assumption was that general body movements provide circulatory function. Consequently, I investigated the frequency of gut movements in the brine shrimp, Artemia franciscana, immediately post-hatch to the point when a functional heart appeared. Prior to cardiac ontogeny, movements of internal musculature and gut provided pre-cardiac circulatory currents with the rate of gut movements increasing when swimming limbs were impeded. There was also some evidence that gut movements were responsive to low oxygen, indicating a possible regulatory function for the gut in early circulation. Overall, this suggests that general body movements are not always adequate to provide internal circulation in small, heartless individuals. PMID:17148293

  9. Developmental programming of the metabolic syndrome by maternal nutritional imbalance: how strong is the evidence from experimental models in mammals?

    PubMed Central

    Armitage, James A; Khan, Imran Y; Taylor, Paul D; Nathanielsz, Peter W; Poston, Lucilla

    2004-01-01

    The incidence of the metabolic syndrome, a cluster of abnormalities focusing on insulin resistance and associated with high risk for cardiovascular disease and diabetes, is reaching epidemic proportions. Prevalent in both developed and developing countries, the metabolic syndrome has largely been attributed to altered dietary and lifestyle factors that favour the development of central obesity. However, population-based studies have suggested that predisposition to the metabolic syndrome may be acquired very early in development through inappropriate fetal or neonatal nutrition. Further evidence for developmental programming of the metabolic syndrome has now been suggested by animal studies in which the fetal environment has been manipulated through altered maternal dietary intake or modification of uterine artery blood flow. This review examines these studies and assesses whether the metabolic syndrome can be reliably induced by the interventions made. The validity of the different species, diets, feeding regimes and end-point measures used is also discussed. PMID:15459241

  10. Mental Practice Combined with Motor Rehabilitation to Treat Upper Limb Hemiparesis of Post-Stroke Patients: Clinical and Experimental Evidence.

    PubMed

    Machado, Sergio; Lattari, Eduardo; Paes, Flávia; Rocha, Nuno B F; Nardi, Antonio E; Arias-Carrión, Oscar; Mura, Gioia; Yuan, Ti-Fei; Carta, Mauro G; Campos, Carlos

    2016-01-01

    Stroke is one of the major causes of disability in the world. Due to the extended lifetime of the world's population, the number of people affected by stroke has increased substantially over the last years. Stroke may lead to sensorimotor deficits, usually causing hemiplegia or hemiparesia. In order to reduce motor deficits and accelerate functional recovery, MP combined with motor rehabilitation was introduced to the rehabilitation process of post-stroke patients. Evidence has shown that MP combining with motor rehabilitation based on activities of daily living was more effective than conventional motor rehabilitation used per se. This combination proved very useful and effective, with significant results in improvement of motor deficits in post-stroke patients. However, further studies must be conducted to determine specific parameters, such as type of imagery, frequency or duration. PMID:27346996

  11. Experimental evidence of false-positive Comet test results due to TiO2 particle--assay interactions.

    PubMed

    Rajapakse, Katarina; Drobne, Damjana; Kastelec, Damijana; Marinsek-Logar, Romana

    2013-08-01

    We have studied the genotoxicity of TiO2 particles with a Comet assay on a unicellular organism, Tetrahymena thermophila. Exposure to bulk- or nano-TiO2 of free cells, cells embedded in gel or nuclei embedded in gel, all resulted in a positive Comet assay result but this outcome could not be confirmed by cytotoxicity measures such as lipid peroxidation, elevated reactive oxygen species or cell membrane composition. Published reports state that in the absence of cytotoxicity, nano- and bulk-TiO2 genotoxicity do not occur directly, and a possible explanation of our Comet assay results is that they are false positives resulting from post festum exposure interactions between particles and DNA. We suggest that before Comet assay is used for nanoparticle genotoxicity testing, evidence for the possibility of post festum exposure interactions should be considered. The acellular Comet test described in this report can be used for this purpose.

  12. Mental Practice Combined with Motor Rehabilitation to Treat Upper Limb Hemiparesis of Post-Stroke Patients: Clinical and Experimental Evidence.

    PubMed

    Machado, Sergio; Lattari, Eduardo; Paes, Flávia; Rocha, Nuno B F; Nardi, Antonio E; Arias-Carrión, Oscar; Mura, Gioia; Yuan, Ti-Fei; Carta, Mauro G; Campos, Carlos

    2016-01-01

    Stroke is one of the major causes of disability in the world. Due to the extended lifetime of the world's population, the number of people affected by stroke has increased substantially over the last years. Stroke may lead to sensorimotor deficits, usually causing hemiplegia or hemiparesia. In order to reduce motor deficits and accelerate functional recovery, MP combined with motor rehabilitation was introduced to the rehabilitation process of post-stroke patients. Evidence has shown that MP combining with motor rehabilitation based on activities of daily living was more effective than conventional motor rehabilitation used per se. This combination proved very useful and effective, with significant results in improvement of motor deficits in post-stroke patients. However, further studies must be conducted to determine specific parameters, such as type of imagery, frequency or duration.

  13. Mental Practice Combined with Motor Rehabilitation to Treat Upper Limb Hemiparesis of Post-Stroke Patients: Clinical and Experimental Evidence

    PubMed Central

    Machado, Sergio; Lattari, Eduardo; Paes, Flávia; Rocha, Nuno B.F.; Nardi, Antonio E.; Arias-Carrión, Oscar; Mura, Gioia; Yuan, Ti-Fei; Carta, Mauro G.; Campos, Carlos

    2016-01-01

    Stroke is one of the major causes of disability in the world. Due to the extended lifetime of the world's population, the number of people affected by stroke has increased substantially over the last years. Stroke may lead to sensorimotor deficits, usually causing hemiplegia or hemiparesia. In order to reduce motor deficits and accelerate functional recovery, MP combined with motor rehabilitation was introduced to the rehabilitation process of post-stroke patients. Evidence has shown that MP combining with motor rehabilitation based on activities of daily living was more effective than conventional motor rehabilitation used per se. This combination proved very useful and effective, with significant results in improvement of motor deficits in post-stroke patients. However, further studies must be conducted to determine specific parameters, such as type of imagery, frequency or duration. PMID:27346996

  14. Effects of Exercise on Physical and Mental Health, and Cognitive and Brain Functions in Schizophrenia: Clinical and Experimental Evidence.

    PubMed

    Rimes, Ridson Rosa; de Souza Moura, Antonio Marcos; Lamego, Murilo Khede; de Sá Filho, Alberto Souza; Manochio, João; Paes, Flávia; Carta, Mauro Giovanni; Mura, Gioia; Wegner, Mirko; Budde, Henning; Ferreira Rocha, Nuno Barbosa; Rocha, Joana; Tavares, João Manuel R S; Arias-Carrión, Oscar; Nardi, Antonio Egidio; Yuan, Ti-Fei; Machado, Sergio

    2015-01-01

    Exercise promotes several health benefits, such as cardiovascular, musculoskeletal and cardiorespiratory improvements. It is believed that the practice of exercise in individuals with psychiatric disorders, e.g. schizophrenia, can cause significant changes. Schizophrenic patients have problematic lifestyle habits compared with general population; this may cause a high mortality rate, mainly caused by cardiovascular and metabolic diseases. Thus, the aim of this study is to investigate changes in physical and mental health, cognitive and brain functioning due to the practice of exercise in patients with schizophrenia. Although still little is known about the benefits of exercise on mental health, cognitive and brain functioning of schizophrenic patients, exercise training has been shown to be a beneficial intervention in the control and reduction of disease severity. Type of training, form of execution, duration and intensity need to be better studied as the effects on physical and mental health, cognition and brain activity depend exclusively of interconnected factors, such as the combination of exercise and medication. However, one should understand that exercise is not only an effective nondrug alternative, but also acts as a supporting linking up interventions to promote improvements in process performance optimization. In general, the positive effects on mental health, cognition and brain activity as a result of an exercise program are quite evident. Few studies have been published correlating effects of exercise in patients with schizophrenia, but there is increasing evidence that positive and negative symptoms can be improved. Therefore, it is important that further studies be undertaken to expand the knowledge of physical exercise on mental health in people with schizophrenia, as well as its dose-response and the most effective type of exercise. PMID:26556069

  15. Effects of Exercise on Physical and Mental Health, and Cognitive and Brain Functions in Schizophrenia: Clinical and Experimental Evidence.

    PubMed

    Rimes, Ridson Rosa; de Souza Moura, Antonio Marcos; Lamego, Murilo Khede; de Sá Filho, Alberto Souza; Manochio, João; Paes, Flávia; Carta, Mauro Giovanni; Mura, Gioia; Wegner, Mirko; Budde, Henning; Ferreira Rocha, Nuno Barbosa; Rocha, Joana; Tavares, João Manuel R S; Arias-Carrión, Oscar; Nardi, Antonio Egidio; Yuan, Ti-Fei; Machado, Sergio

    2015-01-01

    Exercise promotes several health benefits, such as cardiovascular, musculoskeletal and cardiorespiratory improvements. It is believed that the practice of exercise in individuals with psychiatric disorders, e.g. schizophrenia, can cause significant changes. Schizophrenic patients have problematic lifestyle habits compared with general population; this may cause a high mortality rate, mainly caused by cardiovascular and metabolic diseases. Thus, the aim of this study is to investigate changes in physical and mental health, cognitive and brain functioning due to the practice of exercise in patients with schizophrenia. Although still little is known about the benefits of exercise on mental health, cognitive and brain functioning of schizophrenic patients, exercise training has been shown to be a beneficial intervention in the control and reduction of disease severity. Type of training, form of execution, duration and intensity need to be better studied as the effects on physical and mental health, cognition and brain activity depend exclusively of interconnected factors, such as the combination of exercise and medication. However, one should understand that exercise is not only an effective nondrug alternative, but also acts as a supporting linking up interventions to promote improvements in process performance optimization. In general, the positive effects on mental health, cognition and brain activity as a result of an exercise program are quite evident. Few studies have been published correlating effects of exercise in patients with schizophrenia, but there is increasing evidence that positive and negative symptoms can be improved. Therefore, it is important that further studies be undertaken to expand the knowledge of physical exercise on mental health in people with schizophrenia, as well as its dose-response and the most effective type of exercise.

  16. Experimental evidence of bulk chemistry constraint on SiO2 solubility in clinopyroxene at high-pressure conditions

    NASA Astrophysics Data System (ADS)

    Kawasaki, Toshisuke; Osanai, Yasuhito

    2015-06-01

    We have experimentally confirmed that the solubility of SiO2 in clinopyroxene at ultrahigh-pressure metamorphic conditions is buffered by coesite and kyanite. The present findings were derived from high-pressure experiments on metapelite glass, powdered andesite and eclogite glass under anhydrous conditions. The metapelite glass and powdered andesite were recrystallised in boron nitride capsules at 8 GPa and 1100-1500 °C. The eclogite glass was heated in an AuPd capsule, both ends of which were welded, at 3 GPa and 1000 °C. Clinopyroxene nucleated from metapelite glass, the bulk composition of which is saturated in both SiO2 and Al2SiO5 components plotting within the Jd (Na,K)(Al,Cr)(Si,Ti)2O6-Qtz (Si,Ti)O2-Grt M3(Al,Cr)2(Si,Ti)3O12-Als (Al,Cr)2(Si,Ti)O5 tetrahedron (M = Fe, Mn, Mg, Ni, Zn, Ca), coexists with garnet, coesite and kyanite. The average excess silica content of the clinopyroxene ranges from 23.4 to 35.4 mol%. In contrast, an andesite experiment saturated in SiO2 but undersaturated in Al2SiO5 within the Jd-Qtz-Aug M(Si,Ti)O3-Grt tetrahedron produced clinopyroxene, garnet and coesite but no kyanite. The average excess silica in the clinopyroxene was 9.7-15.5 mol%, which is comparable to previous experimental data. Experiment on the eclogite glass with similar composition to andesite yielded clinopyroxene, garnet and coesite. An average excess silica content in clinopyroxene counts 6.4 mol%, which is much lower than that obtained from the andesite. The SiO2 content of clinopyroxene coexisting with garnet, coesite and kyanite is much higher than that of clinopyroxene coexisting with garnet and coesite without kyanite. Although the temperature dependence is unclear, the SiO2 solubility increases with pressure and Fe/(Fe+Mg). Clinopyroxene forms the solid solution series Jd-Es □0.5M0.5Al(Si,Ti)2O6 and Aug-Es, rather than Jd-Ts MAl2(Si,Ti)O6 and Es-Ts joins. Our experimental data suggest the probable existence of octahedral Si which may accompany the M2

  17. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  18. Experimental evidence of excited electron number density and temperature effects on electron-phonon coupling in gold films

    SciTech Connect

    Giri, Ashutosh; Gaskins, John T.; Foley, Brian M.; Cheaito, Ramez; Hopkins, Patrick E.

    2015-01-28

    The electronic transport properties of metals with weak electron-phonon coupling can be influenced by non-thermal electrons. Relaxation processes involving non-thermal electrons competing with the thermalized electron system have led to inconsistencies in the understanding of how electrons scatter and relax with the less energetic lattice. Recent theoretical and computational works have shown that the rate of energy relaxation with the metallic lattice will change depending on the thermalization state of the electrons. Even though 20 years of experimental works have focused on understanding and isolating these electronic relaxation mechanisms with short pulsed irradiation, discrepancies between these existing works have not clearly answered the fundamental question of the competing effects between non-thermal and thermal electrons losing energy to the lattice. In this work, we demonstrate the ability to measure the electron relaxation for varying degrees of both electron-electron and electron-phonon thermalization. This series of measurements of electronic relaxation over a predicted effective electron temperature range up to ∼3500 K and minimum lattice temperatures of 77 K validate recent computational and theoretical works that theorize how a nonequilibrium distribution of electrons transfers energy to the lattice. Utilizing this wide temperature range during pump-probe measurements of electron-phonon relaxation, we explain discrepancies in the past two decades of literature of electronic relaxation rates. We experimentally demonstrate that the electron-phonon coupling factor in gold increases with increasing lattice temperature and laser fluences. Specifically, we show that at low laser fluences corresponding to small electron perturbations, energy relaxation between electrons and phonons is mainly governed by non-thermal electrons, while at higher laser fluences, non-thermal electron scattering with the lattice is less influential on the energy relaxation

  19. Experimental evidence of biomineralisation for three benthic foraminiferal species under different redox conditions: implications for paleo-redox proxies interpretation

    NASA Astrophysics Data System (ADS)

    Nardelli, Maria Pia; Barras, Christine; Metzger, Edouard; Filipsson, Helena; Jorissen, Frans; Geslin, Emmanuelle

    2014-05-01

    Foraminifera are among the most used group of organisms for paleoceanographic and paleoenvironmental reconstructions thanks to their ability to fossilize and the preservation potential in marine sediments. Calibrations of foraminiferal-based proxies are therefore of crucial importance for precise reconstructions together with uncertainty estimates of paleoenvironments; experimental approaches are increasingly used to deepen the understanding of biological and ecological aspects of biomineralization that can influence shell geochemistry. Some of the most important and still unanswered questions are: under which circumstances can foraminiferal biomineralization take place? Can their shells record different oxygenation levels and redox fronts migrations at the sediment-water interface? The hypothesis of their ability to biomineralise even in absence of oxygen was investigated in an experimental study. Calcein-labeled specimens of three benthic foraminiferal species, Ammonia tepida, Bulimina marginata and Cassidulina laevigata were introduced in different sediment layers of reconstituted cores (up to 10 cm depth). The sediment layers were separated by 100 µm mesh-size nets preventing specimen migrations. We could therefore evaluate the ability of the species to calcify at different redox fronts in the sediment. The results show that all species were able to calcify within 2 months in hypoxic. Two of them (Ammonia tepida and Bulimina marginata) are also able to calcify in completely anoxic conditions. The result suggests that foraminifera could register in their calcareous shells the migration of redox fronts associated to bottom-water oxygen depletions and anoxic events. With the help of microanalytical tools it will potentially be possible to reconstruct past oxygen levels with much higher accuracy and precision and to obtain proxies of completely anoxic conditions.

  20. How communication changes when we cannot mime the world: Experimental evidence for the effect of iconicity on combinatoriality.

    PubMed

    Roberts, Gareth; Lewandowski, Jirka; Galantucci, Bruno

    2015-08-01

    Communication systems are exposed to two different pressures: a pressure for transmission efficiency, such that messages are simple to produce and perceive, and a pressure for referential efficiency, such that messages are easy to understand with their intended meaning. A solution to the first pressure is combinatoriality--the recombination of a few basic meaningless forms to express an infinite number of meanings. A solution to the second is iconicity--the use of forms that resemble what they refer to. These two solutions appear to be incompatible with each other, as iconic forms are ill-suited for use as meaningless combinatorial units. Furthermore, in the early stages of a communication system, when basic referential forms are in the process of being established, the pressure for referential efficiency is likely to be particularly strong, which may lead it to trump the pressure for transmission efficiency. This means that, where iconicity is available as a strategy, it is likely to impede the emergence of combinatoriality. Although this hypothesis seems consistent with some observations of natural language, it was unclear until recently how it could be soundly tested. This has changed thanks to the development of a line of research, known as Experimental Semiotics, in which participants construct novel communication systems in the laboratory using an unfamiliar medium. We conducted an Experimental Semiotic study in which we manipulated the opportunity for iconicity by varying the kind of referents to be communicated, while keeping the communication medium constant. We then measured the combinatoriality and transmission efficiency of the communication systems. We found that, where iconicity was available, it provided scaffolding for the construction of communication systems and was overwhelmingly adopted. Where it was not available, however, the resulting communication systems were more combinatorial and their forms more efficient to produce. This study enriches

  1. Expression of TLR4 protein is reduced in chronic renal failure: evidence from an experimental model of nephron reduction.

    PubMed

    Kacsó, Ina Maria; Borza, Gabriel Mircea; Ciuce, Cătălin C; Bîrsan, Andrei; Apostu, Raluca Cristina; Dindelegan, George Călin; Bondor, Cosmina Ioana; Potra, Alina Ramona; Netea, Mihai G; Cătoi, Cornel

    2015-01-01

    Toll-like receptor 4 (TLR4) signaling is involved in various acute and chronic renal lesions and contributes to inflammation and fibrosis in several organs; the latter are important determinants to the progression of chronic kidney disease (CKD). We aimed to assess TLR4 expression in progressive CKD and relate it to severity of kidney damage, using an experimental nephron reduction model. Male Wistar rats were subjected to subtotal nephrectomy using the ligation technique, after 12 weeks of observation, serum creatinine and proteinuria were determined, animals were sacrificed, glomerulosclerosis and interstitial scarring were quantified histologically, and TLR4 expression was assessed by immunohistochemistry. Sham-operated rats served as controls. Case animals had significantly higher creatinine, proteinuria, glomerulosclerosis and tubulointerstitial involvement. TLR4 expression was prominent in proximal tubes, less staining was observed on infiltrating inflammatory cells. Percentage of TLR4-positive tubes was reduced in the subtotal nephrectomy animals, when compared to controls (0.67±0.09 versus 0.79±0.07, p=0.003). Percentage of TLR4-positive tubes correlated inversely to markers of kidney damage: to proteinuria (r=-0.55, p=0.02), serum creatinine (r=-0.53, p=0.01); percentage of glomeruli with glomerulosclerosis (r=-0.54, p=0.01) and tubulointerstitial score (r=-0.36, p=0.01). As TLR4 staining appears in tubular casts only in nephrectomy animals, shedding from damaged tubular cells is a very likely explanation for the reduced TLR4 expression in the kidneys of subjects with experimental nephron reduction.

  2. Molecular concept and experimental evidence of H2O, CH4 and CO2 adsorption on organic material

    NASA Astrophysics Data System (ADS)

    Gensterblum, Yves; Krooss, Bernhard; Busch, Andreas

    2014-05-01

    Unconventional gas, such as shale gas or coalbed methane offers an attractive low-carbon solution and furthermore provides possibilities for CO2-storage and coevally for enhanced gas recovery. In order to better understand gas and water interaction with organic matter (coal) of different maturity we developed a molecular concept with experimental and literature support for sorption of these fluids on organic material over the entire range of thermal maturity. With increasing burial depth and temperature CO2 and CH4 are the main volatiles released when organic material matures (cf. coalification). While most CO2 is generally dissolved in formation water and transported away from the coal, most CH4 (coalbed methane, CBM) remains adsorbed to the coal pore structure and is produced as unconventional gas. We present here the experimental basis and a conceptual model and to explain CO2 and CH4 sorption in the presence of water on coal with varying coal maturity (from lignite to anthracite). Adsorption experiments have been performed on different maturity coals at various temperatures, pressures up to 20 MPa and under dry and moist conditions. With increasing coal maturity we find for both gases a linear sorption capacity trend for moisture-equilibrated and a more parabolic trend for dry coal samples. When investigating the difference in CH4 and CO2 sorption capacity on coal of different maturity as a function of moisture content we infer that oxygen containing functional groups account for the selective sorption properties of gases and water to coals. Additionally restrictions in translational and vibrational movements of the sorbed gas molecules induced by adsorbed water molecules cause differences in the presence of water.

  3. Experimental and Computational Evidence for the Reduction Mechanisms of Aromatic N-oxides by Aqueous Fe(II)-Tiron Complex.

    PubMed

    Chen, Yiling; Dong, Hao; Zhang, Huichun

    2016-01-01

    A combined experimental-theoretical approach was taken to elucidate the reduction mechanisms of five representative aromatic N-oxides (ANOs) by Fe(II)-tiron complex and to identify the rate-limiting step. Based on the possible types of complexes formed with the reductant, three groups of ANOs were studied: type I refers to those forming 5-membered ring complexes through the N and O atoms on the side chain; type II refers to those forming 6-membered ring complexes through the N-oxide O atom and the O atom on the side chain; and type III refers to complexation through the N-oxide O atom only. Density functional theory calculations suggested that the elementary reactions, including protonation, N-O bond cleavage, and the second electron transfer processes, are barrierless, indicating that the first electron transfer is rate-limiting. Consistent with the theoretical results, the experimental solvent isotope effect, KIEH, for the reduction of quinoline N-oxide (a type III ANO) was obtained to be 1.072 ± 0.025, suggesting protonation was not involved in the rate-limiting step. The measured nitrogen kinetic isotope effect, KIEN, for the reduction of pyridine N-oxide (a type III ANO) (1.022 ± 0.006) is in good agreement with the calculated KIEN for its first electron transfer (1.011-1.028), confirming that the first electron transfer is rate-limiting. Electrochemical cell experiments demonstrated that the electron transfer process can be facilitated significantly by type I complexation with FeL2(6-) (1:2 Fe(II)-tiron complex), to some extent by type II complexation with free Fe(II), but not by weak type III complexation.

  4. How communication changes when we cannot mime the world: Experimental evidence for the effect of iconicity on combinatoriality.

    PubMed

    Roberts, Gareth; Lewandowski, Jirka; Galantucci, Bruno

    2015-08-01

    Communication systems are exposed to two different pressures: a pressure for transmission efficiency, such that messages are simple to produce and perceive, and a pressure for referential efficiency, such that messages are easy to understand with their intended meaning. A solution to the first pressure is combinatoriality--the recombination of a few basic meaningless forms to express an infinite number of meanings. A solution to the second is iconicity--the use of forms that resemble what they refer to. These two solutions appear to be incompatible with each other, as iconic forms are ill-suited for use as meaningless combinatorial units. Furthermore, in the early stages of a communication system, when basic referential forms are in the process of being established, the pressure for referential efficiency is likely to be particularly strong, which may lead it to trump the pressure for transmission efficiency. This means that, where iconicity is available as a strategy, it is likely to impede the emergence of combinatoriality. Although this hypothesis seems consistent with some observations of natural language, it was unclear until recently how it could be soundly tested. This has changed thanks to the development of a line of research, known as Experimental Semiotics, in which participants construct novel communication systems in the laboratory using an unfamiliar medium. We conducted an Experimental Semiotic study in which we manipulated the opportunity for iconicity by varying the kind of referents to be communicated, while keeping the communication medium constant. We then measured the combinatoriality and transmission efficiency of the communication systems. We found that, where iconicity was available, it provided scaffolding for the construction of communication systems and was overwhelmingly adopted. Where it was not available, however, the resulting communication systems were more combinatorial and their forms more efficient to produce. This study enriches

  5. A strenuous experimental journey searching for spectroscopic evidence of a bridging nickel–iron–hydride in [NiFe] hydrogenase

    PubMed Central

    Wang, Hongxin; Yoda, Yoshitaka; Ogata, Hideaki; Tanaka, Yoshihito; Lubitz, Wolfgang

    2015-01-01

    Direct spectroscopic evidence for a hydride bridge in the Ni–R form of [NiFe] hydrogenase has been obtained using iron-specific nuclear resonance vibrational spectroscopy (NRVS). The Ni–H–Fe wag mode at 675 cm−1 is the first spectroscopic evidence for a bridging hydride in Ni–R as well as the first iron-hydride-related NRVS feature observed for a biological system. Although density function theory (DFT) calculation assisted the determination of the Ni–R structure, it did not predict the Ni–H–Fe wag mode at ∼675 cm−1 before NRVS. Instead, the observed Ni–H–Fe mode provided a critical reference for the DFT calculations. While the overall science about Ni–R is presented and discussed elsewhere, this article focuses on the long and strenuous experimental journey to search for and experimentally identify the Ni–H–Fe wag mode in a Ni–R sample. As a methodology, the results presented here will go beyond Ni–R and hydrogenase research and will also be of interest to other scientists who use synchrotron radiation for measuring dilute samples or weak spectroscopic features. PMID:26524296

  6. Cross-cultural similarities and differences in person-body reasoning: experimental evidence from the United Kingdom and Brazilian Amazon.

    PubMed

    Cohen, Emma; Burdett, Emily; Knight, Nicola; Barrett, Justin

    2011-01-01

    We report the results of a cross-cultural investigation of person-body reasoning in the United Kingdom and northern Brazilian Amazon (Marajó Island). The study provides evidence that directly bears upon divergent theoretical claims in cognitive psychology and anthropology, respectively, on the cognitive origins and cross-cultural incidence of mind-body dualism. In a novel reasoning task, we found that participants across the two sample populations parsed a wide range of capacities similarly in terms of the capacities' perceived anchoring to bodily function. Patterns of reasoning concerning the respective roles of physical and biological properties in sustaining various capacities did vary between sample populations, however. Further, the data challenge prior ad-hoc categorizations in the empirical literature on the developmental origins of and cognitive constraints on psycho-physical reasoning (e.g., in afterlife concepts). We suggest cross-culturally validated categories of "Body Dependent" and "Body Independent" items for future developmental and cross-cultural research in this emerging area. PMID:21884221

  7. The impact of positive affect on health cognitions and behaviours: a meta-analysis of the experimental evidence.

    PubMed

    Cameron, David S; Bertenshaw, Emma J; Sheeran, Paschal

    2015-01-01

    Several reviews suggest that positive affect is associated with improved longevity, fewer physical symptoms, and biological indicators of good health. It is possible that positive affect could influence these outcomes by promoting healthful cognitions and behaviours. The present review identified conceptual pathways from positive affect to health cognitions and behaviour, and used random effects meta-analysis to quantify the impact of positive affect inductions (versus neutral affect conditions) on these outcomes. Literature searches located 54 independent tests that could be included in the review. Across all studies, the findings revealed no reliable effects on intentions (d+ = -.12, 95% CI = -.32 to .08, k = 15) or behaviour (d+ = .15, 95% CI = -.03 to .33, k = 23). There were four reliable effects involving specific cognitions and behaviours, but little clear evidence for generalised benefits or adverse effects of positive emotions on health-related cognitions or actions. Conclusions must be cautious given the paucity of tests available for analysis. The review offers suggestions about research designs that might profitably be deployed in future studies, and calls for additional tests of the impact of discrete positive emotions on health cognitions and behaviour. PMID:27028049

  8. Experimental evidence that adult antipredator behaviour is heritable and not influenced by behavioural copying in a wild bird.

    PubMed

    Bize, Pierre; Diaz, Claris; Lindström, Jan

    2012-04-01

    Knowledge of the relative importance of genetics and behavioural copying is crucial to appraise the evolvability of behavioural consistencies. Yet, genetic and non-genetic factors are often deeply intertwined, and experiments are required to address this issue. We investigated the sources of variation of adult antipredator behaviour in the Alpine swift (Apus melba) by making use of long-term behavioural observations on parents and cross-fostered offspring. By applying an 'animal model' approach to observational data, we show that antipredator behaviour of adult Alpine swifts was significantly repeatable over lifetime (r = 0.273) and heritable (h(2) = 0.146). Regression models also show that antipredator behaviours differed between colonies and sexes (females were more tame), and varied with the hour and year of capture. By applying a parent-offspring regression approach to 59 offspring that were exchanged as eggs or hatchlings between pairs of nests, we demonstrate that offspring behaved like their biological parents rather than like their foster parents when they were adults themselves. Those findings provide strong evidence that antipredator behaviour of adult Alpine swifts is shaped by genetics and/or pre-hatching maternal effects taking place at conception but not by behavioural copying.

  9. Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz

    PubMed Central

    Pignatelli, Isabella; Kumar, Aditya; Field, Kevin G.; Wang, Bu; Yu, Yingtian; Le Pape, Yann; Bauchy, Mathieu; Sant, Gaurav

    2016-01-01

    Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar+-ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows little change in dissolution rate - although its density noted to reduce by ≈9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral’s atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. The outcomes have major implications on the durability of concrete structural elements formed with calcite or quartz bearing aggregates in nuclear power plants. PMID:26822012

  10. Experimental Evidence Shows Salubrinal, an eIF2α Dephosphorylation Inhibitor, Reduces Xenotoxicant-Induced Cellular Damage

    PubMed Central

    Matsuoka, Masato; Komoike, Yuta

    2015-01-01

    Accumulating evidence indicates that endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) are involved in the pathogenesis of not only the protein misfolding disorders such as certain neurodegenerative and metabolic diseases, but also in the cytotoxicity of environmental pollutants, industrial chemicals, and drugs. Thus, the modulation of ER stress signaling pathways is an important issue for protection against cellular damage induced by xenotoxicants. The substance salubrinal has been shown to prevent dephosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α). The phosphorylation of eIF2α appears to be cytoprotective during ER stress, because inhibition of the translation initiation activity of eIF2α reduces global protein synthesis. In addition, the expression of activating transcription factor 4 (ATF4), a transcription factor that induces the expression of UPR target genes, is up-regulated through alternative translation. This review shows that salubrinal can protect cells from the damage induced by a wide range of xenotoxicants, including environmental pollutants and drugs. The canonical and other possible mechanisms of cytoprotection by salubrinal from xenotoxicant-induced ER stress are also discussed. PMID:26193263

  11. Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz

    NASA Astrophysics Data System (ADS)

    Pignatelli, Isabella; Kumar, Aditya; Field, Kevin G.; Wang, Bu; Yu, Yingtian; Le Pape, Yann; Bauchy, Mathieu; Sant, Gaurav

    2016-01-01

    Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar+-ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows little change in dissolution rate - although its density noted to reduce by ≈9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral’s atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. The outcomes have major implications on the durability of concrete structural elements formed with calcite or quartz bearing aggregates in nuclear power plants.

  12. Experimental Evidence Shows Salubrinal, an eIF2α Dephosphorylation Inhibitor, Reduces Xenotoxicant-Induced Cellular Damage.

    PubMed

    Matsuoka, Masato; Komoike, Yuta

    2015-01-01

    Accumulating evidence indicates that endoplasmic reticulum (ER) stress and the subsequent unfolded protein response (UPR) are involved in the pathogenesis of not only the protein misfolding disorders such as certain neurodegenerative and metabolic diseases, but also in the cytotoxicity of environmental pollutants, industrial chemicals, and drugs. Thus, the modulation of ER stress signaling pathways is an important issue for protection against cellular damage induced by xenotoxicants. The substance salubrinal has been shown to prevent dephosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2α). The phosphorylation of eIF2α appears to be cytoprotective during ER stress, because inhibition of the translation initiation activity of eIF2α reduces global protein synthesis. In addition, the expression of activating transcription factor 4 (ATF4), a transcription factor that induces the expression of UPR target genes, is up-regulated through alternative translation. This review shows that salubrinal can protect cells from the damage induced by a wide range of xenotoxicants, including environmental pollutants and drugs. The canonical and other possible mechanisms of cytoprotection by salubrinal from xenotoxicant-induced ER stress are also discussed. PMID:26193263

  13. Experimental Evidence of Threat-Sensitive Collective Avoidance Responses in a Large Wild-Caught Herring School

    PubMed Central

    Rieucau, Guillaume; Boswell, Kevin M.; De Robertis, Alex; Macaulay, Gavin J.; Handegard, Nils Olav

    2014-01-01

    Aggregation is commonly thought to improve animals' security. Within aquatic ecosystems, group-living prey can learn about immediate threats using cues perceived directly from predators, or from collective behaviours, for example, by reacting to the escape behaviours of companions. Combining cues from different modalities may improve the accuracy of prey antipredatory decisions. In this study, we explored the sensory modalities that mediate collective antipredatory responses of herring (Clupea harengus) when in a large school (approximately 60 000 individuals). By conducting a simulated predator encounter experiment in a semi-controlled environment (a sea cage), we tested the hypothesis that the collective responses of herring are threat-sensitive. We investigated whether cues from potential threats obtained visually or from the perception of water displacement, used independently or in an additive way, affected the strength of the collective avoidance reactions. We modified the sensory nature of the simulated threat by exposing the herring to 4 predator models differing in shape and transparency. The collective vertical avoidance response was observed and quantified using active acoustics. The combination of sensory cues elicited the strongest avoidance reactions, suggesting that collective antipredator responses in herring are mediated by the sensory modalities involved during threat detection in an additive fashion. Thus, this study provides evidence for magnitude-graded threat responses in a large school of wild-caught herring which is consistent with the “threat-sensitive hypothesis”. PMID:24489778

  14. Experimental and geochemical evidence for derivation of the El Capitan Granite, California, by partial melting of hydrous gabbroic lower crust

    USGS Publications Warehouse

    Ratajeski, K.; Sisson, T.W.; Glazner, A.F.

    2005-01-01

    Partial melting of mafic intrusions recently emplaced into the lower crust can produce voluminous silicic magmas with isotopic ratios similar to their mafic sources. Low-temperature (825 and 850??C) partial melts synthesized at 700 MPa in biotite-hornblende gabbros from the central Sierra Nevada batholith (Sisson et al. in Contrib Mineral Petrol 148:635-661, 2005) have major-element and modeled trace-element (REE, Rb, Ba, Sr, Th, U) compositions matching those of the Cretaceous El Capitan Granite, a prominent granite and silicic granodiorite pluton in the central part of the Sierra Nevada batholith (Yosemite, CA, USA) locally mingled with coeval, isotopically similar quartz diorite through gabbro intrusions (Ratajeski et al. in Geol Soc Am Bull 113:1486-1502, 2001). These results are evidence that the El Capitan Granite, and perhaps similar intrusions in the Sierra Nevada batholith with lithospheric-mantle-like isotopic values, were extracted from LILE-enriched, hydrous (hornblende-bearing) gabbroic rocks in the Sierran lower crust. Granitic partial melts derived by this process may also be silicic end members for mixing events leading to large-volume intermediate composition Sierran plutons such as the Cretaceous Lamarck Granodiorite. Voluminous gabbroic residues of partial melting may be lost to the mantle by their conversion to garnet-pyroxene assemblages during batholithic magmatic crustal thickening. ?? Springer-Verlag 2005.

  15. Experimental evidence of threat-sensitive collective avoidance responses in a large wild-caught herring school.

    PubMed

    Rieucau, Guillaume; Boswell, Kevin M; De Robertis, Alex; Macaulay, Gavin J; Handegard, Nils Olav

    2014-01-01

    Aggregation is commonly thought to improve animals' security. Within aquatic ecosystems, group-living prey can learn about immediate threats using cues perceived directly from predators, or from collective behaviours, for example, by reacting to the escape behaviours of companions. Combining cues from different modalities may improve the accuracy of prey antipredatory decisions. In this study, we explored the sensory modalities that mediate collective antipredatory responses of herring (Clupea harengus) when in a large school (approximately 60,000 individuals). By conducting a simulated predator encounter experiment in a semi-controlled environment (a sea cage), we tested the hypothesis that the collective responses of herring are threat-sensitive. We investigated whether cues from potential threats obtained visually or from the perception of water displacement, used independently or in an additive way, affected the strength of the collective avoidance reactions. We modified the sensory nature of the simulated threat by exposing the herring to 4 predator models differing in shape and transparency. The collective vertical avoidance response was observed and quantified using active acoustics. The combination of sensory cues elicited the strongest avoidance reactions, suggesting that collective antipredator responses in herring are mediated by the sensory modalities involved during threat detection in an additive fashion. Thus, this study provides evidence for magnitude-graded threat responses in a large school of wild-caught herring which is consistent with the "threat-sensitive hypothesis".

  16. Communities of different plant diversity respond similarly to drought stress: experimental evidence from field non-weeded and greenhouse conditions

    NASA Astrophysics Data System (ADS)

    Lanta, Vojtěch; Doležal, Jiří; Zemková, Lenka; Lepš, Jan

    2012-06-01

    Accelerating rate of species loss has prompted researchers to study the role of species diversity in processes that control ecosystem functioning. Although negative impact of species loss has been documented, the evidence concerning its impact on ecosystem stability is still limited. Here, we studied the effects of declining species and functional diversity on plant community responses to drought in the field (open to weed colonization) and greenhouse conditions. Both species and functional diversity positively affected the average yields of field communities. However, this pattern was similar in both drought-stressed and control plots. No effect of diversity on community resistance, biomass recovery after drought and resilience was found because drought reduced biomass production similarly at each level of diversity by approximately 30 %. The use of dissimilarity (characterized by Euclidean distance) revealed higher variation under changing environments (drought-stressed vs. control) in more diverse communities compared to less species-rich assemblages. In the greenhouse experiment, the effect of species diversity affected community resistance, indicating that more diverse communities suffered more from drought than species-poor ones. We conclude that our study did not support the insurance hypothesis (stability properties of a community should increase with species richness) because species diversity had an equivocal effect on ecosystem resistance and resilience in an environment held under non-weeded practice, regardless of the positive relationship between sown species diversity and community biomass production. More species-rich communities were less resistant against drought-stressed conditions than species-poor ones grown in greenhouse conditions.

  17. Direct Experimental Evidence for Differing Reactivity Alterations of Minerals following Irradiation: The Case of Calcite and Quartz.

    PubMed

    Pignatelli, Isabella; Kumar, Aditya; Field, Kevin G; Wang, Bu; Yu, Yingtian; Le Pape, Yann; Bauchy, Mathieu; Sant, Gaurav

    2016-01-01

    Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar(+)-ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%, and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. Calcite however, shows little change in dissolution rate - although its density noted to reduce by ≈9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral's atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. The outcomes have major implications on the durability of concrete structural elements formed with calcite or quartz bearing aggregates in nuclear power plants. PMID:26822012

  18. Strong dependence of rain-induced lidar depolarization on the illumination angle: experimental evidence and geometrical-optics interpretation.

    PubMed

    Roy, G; Bissonnette, L R

    2001-09-20

    Backscatter and depolarization lidar measurements from clouds and precipitation are reported as functions of the elevation angle of the pointing lidar direction. We recorded the data by scanning the lidar beam (Nd:YAG) at a constant angular speed of ~3.5 degrees /s while operating at a repetition rate of 10 Hz. We show that in rain there is an evident and at times spectacular dependence on the elevation angle. That dependence appears to be sensitive to raindrop size. We have developed a three-dimensional polarization-dependent ray-tracing algorithm to calculate the backscatter and the depolarization ratio by large nonspherical droplets. We have applied it to raindrop shapes derived from existing static and dynamic (oscillating) models. We show that many of the observed complex backscatter and depolarization features can be interpreted to a good extent by geometrical optics. These results suggest that there is a definite need for more extensive calculations of the scattering phase matrix elements for large deformed raindrops as functions of the direction of illumination. Obvious applications are retrieval of information on the liquid-solid phase of precipitation and on the size and the vibration state of raindrops. PMID:18360518

  19. Direct experimental evidence for differing reactivity alterations of minerals following irradiation. The case of calcite and quartz

    DOE PAGESBeta

    Pignatelli, Isabella; Kumar, Aditya; Field, Kevin G.; Wang, Bu; Yu, Yingtian; Le Pape, Yann; Bauchy, Mathieu; Sant, Gaurav

    2016-01-29

    Concrete, used in the construction of nuclear power plants (NPPs), may be exposed to radiation emanating from the reactor core. Until recently, concrete has been assumed immune to radiation exposure. Direct evidence acquired on Ar+ -ion irradiated calcite and quartz indicates, on the contrary, that, such minerals, which constitute aggregates in concrete, may be significantly altered by irradiation. More specifically, while quartz undergoes disordering of its atomic structure resulting in a near complete lack of periodicity, calcite only experiences random rotations, and distortions of its carbonate groups. As a result, irradiated quartz shows a reduction in density of around 15%,more » and an increase in chemical reactivity, described by its dissolution rate, similar to a glassy silica. However, calcite shows little change in dissolution rate - although its density noted to reduce by 9%. These differences are correlated with the nature of bonds in these minerals, i.e., being dominantly ionic or covalent, and the rigidity of the mineral's atomic network that is characterized by the number of topological constraints (nc) that are imposed on the atoms in the network. Our outcomes have major implications on the durability of concrete structural elements formed with calcitic or quartzitic aggregates in nuclear power plants.« less

  20. Strong dependence of rain-induced lidar depolarization on the illumination angle: experimental evidence and geometrical-optics interpretation.

    PubMed

    Roy, G; Bissonnette, L R

    2001-09-20

    Backscatter and depolarization lidar measurements from clouds and precipitation are reported as functions of the elevation angle of the pointing lidar direction. We recorded the data by scanning the lidar beam (Nd:YAG) at a constant angular speed of ~3.5 degrees /s while operating at a repetition rate of 10 Hz. We show that in rain there is an evident and at times spectacular dependence on the elevation angle. That dependence appears to be sensitive to raindrop size. We have developed a three-dimensional polarization-dependent ray-tracing algorithm to calculate the backscatter and the depolarization ratio by large nonspherical droplets. We have applied it to raindrop shapes derived from existing static and dynamic (oscillating) models. We show that many of the observed complex backscatter and depolarization features can be interpreted to a good extent by geometrical optics. These results suggest that there is a definite need for more extensive calculations of the scattering phase matrix elements for large deformed raindrops as functions of the direction of illumination. Obvious applications are retrieval of information on the liquid-solid phase of precipitation and on the size and the vibration state of raindrops.

  1. Experimental Evidence for Fast Lithium Diffusion and Isotope Fractionation in Water-bearing Rhyolitic Melts at Magmatic Conditions

    NASA Astrophysics Data System (ADS)

    Cichy, S. B.; Till, C. B.; Roggensack, K.; Hervig, R. L.; Clarke, A. B.

    2015-12-01

    The aim of this work is to extend the existing database of experimentally-determined lithium diffusion coefficients to more natural cases of water-bearing melts at the pressure-temperature range of the upper crust. In particular, we are investigating Li intra-melt and melt-vapor diffusion and Li isotope fractionation, which have the potential to record short-lived magmatic processes (seconds to hours) in the shallow crust, especially during decompression-induced magma degassing. Hydrated intra-melt Li diffusion-couple experiments on Los Posos rhyolite glass [1] were performed in a piston cylinder at 300 MPa and 1050 °C. The polished interfaces between the diffusion couples were marked by addition of Pt powder for post-run detection. Secondary ion mass spectrometry analyses indicate that lithium diffuses extremely fast in the presence of water. Re-equilibration of a hydrated ~2.5 mm long diffusion-couple experiment was observed during the heating period from room temperature to the final temperature of 1050 °C at a rate of ~32 °C/min. Fractionation of ~40‰ δ7Li was also detected in this zero-time experiment. The 0.5h and 3h runs show progressively higher degrees of re-equilibration, while the isotope fractionation becomes imperceptible. Li contamination was observed in some experiments when flakes filed off Pt tubing were used to mark the diffusion couple boundary, while the use of high purity Pt powder produced better results and allowed easier detection of the diffusion-couple boundary. The preliminary lithium isotope fractionation results (δ7Li vs. distance) support findings from [2] that 6Li diffuses substantially faster than 7Li. Further experimental sets are in progress, including lower run temperatures (e.g. 900 °C), faster heating procedure (~100 °C/min), shorter run durations and the extension to mafic systems. [1] Stanton (1990) Ph.D. thesis, Arizona State Univ., [2] Richter et al. (2003) GCA 67, 3905-3923.

  2. Influences of Electromagnetic Energy on Bio-Energy Transport through Protein Molecules in Living Systems and Its Experimental Evidence.

    PubMed

    Pang, Xiaofeng; Chen, Shude; Wang, Xianghui; Zhong, Lisheng

    2016-07-25

    The influences of electromagnetic fields (EMFs) on bio-energy transport and its mechanism of changes are investigated through analytic and numerical simulation and experimentation. Bio-energy transport along protein molecules is performed by soliton movement caused by the dipole-dipole electric interactions between neighboring amino acid residues. As such, EMFs can affect the structure of protein molecules and change the properties of the bio-energy transported in living systems. This mechanism of biological effect from EMFs involves the amino acid residues in protein molecules. To study and reveal this mechanism, we simulated numerically the features of the movement of solitons along protein molecules with both a single chain and with three channels by using the Runge-Kutta method and Pang's soliton model under the action of EMFs with the strengths of 25,500, 51,000, 76,500, and 102,000 V/m in the single-chain protein, as well as 17,000, 25,500, and 34,000 V/m in the three-chain protein, respectively. Results indicate that electric fields (EFs) depress the binding energy of the soliton, decrease its amplitude, and change its wave form. Also, the soliton disperses at 102,000 V/m in a single-chain protein and at 25,500 and 34,000 V/m in three-chain proteins. These findings signify that the influence of EMFs on the bio-energy transport cannot be neglected; however, these variations depend on both the strength and the direction of the EF in the EMF. This direction influences the biological effects of EMF, which decrease with increases in the angle between the direction of the EF and that of the dipole moment of amino acid residues; however, randomness at the macroscopic level remains. Lastly, we experimentally confirm the existence of a soliton and the validity of our conclusion by using the infrared spectra of absorption of the collagens, which is activated by another type of EF. Thus, we can affirm that both the described mechanism and the corresponding theory are

  3. 3D relationships between sills and their feeders: evidence from the Golden Valley Sill Complex (Karoo Basin) and experimental modelling

    NASA Astrophysics Data System (ADS)

    Galerne, Christophe Y.; Galland, Olivier; Neumann, Else-Ragnhild; Planke, Sverre

    2013-04-01

    Saucer shaped sills are tabular intrusions observed worldwide on volcanic margins and in sedimentary basins (e.g., offshore Norway, Karoo Basin). Although they are common, their feeding mechanisms are still poorly known mainly because the relationships between sills and their feeders are (1) rarely exposed, and (2) difficult to image on seismic data. The present study address sill emplacement mechanisms through an integrated approach: i) we use field observations and geochemistry in order to assess the three-dimensional relationships between sills and their potential feeders (dykes or sills) in the well-exposed Golden Valley Sill Complex (GVSC), Karoo Basin, South Africa; ii) the results were then compared with scaled laboratory experiments of saucer-shaped sill emplacement. Field observations in the GVSC show that sills present some physical contacts between them, suggesting sill-feeding-sill relationships. Systematic chemical analyses, however, show that their compositions were different, implying that these sills were not connected when they were emplaced. There are, however, close associations between one elliptical sill (the GVS) and a small dyke (d4): the dyke crops out underneath the southern tip of the sill, is parallel and superimposed on the long axis of the GVS sill, and they both exhibit identical geochemical compositions. Such relationships suggest that GVS is fed by d4 and that the linear shape of the dyke may have controlled the elliptical development of the GVS. To test this hypothesis, we present results of experimental modelling of sill emplacement, in which we vary the shape of the feeder. In the experiment with a punctual feeder (E1), the sill develops a sub-circular geometry, whereas in the experiment with a linear feeder (E2), the sill develops an elliptical geometry. The geometrical relationships between the sill and its feeder in E2 show that the elliptical shape of the sill is controlled by the linear shape and the length of the linear

  4. Influences of Electromagnetic Energy on Bio-Energy Transport through Protein Molecules in Living Systems and Its Experimental Evidence.

    PubMed

    Pang, Xiaofeng; Chen, Shude; Wang, Xianghui; Zhong, Lisheng

    2016-01-01

    The influences of electromagnetic fields (EMFs) on bio-energy transport and its mechanism of changes are investigated through analytic and numerical simulation and experimentation. Bio-energy transport along protein molecules is performed by soliton movement caused by the dipole-dipole electric interactions between neighboring amino acid residues. As such, EMFs can affect the structure of protein molecules and change the properties of the bio-energy transported in living systems. This mechanism of biological effect from EMFs involves the amino acid residues in protein molecules. To study and reveal this mechanism, we simulated numerically the features of the movement of solitons along protein molecules with both a single chain and with three channels by using the Runge-Kutta method and Pang's soliton model under the action of EMFs with the strengths of 25,500, 51,000, 76,500, and 102,000 V/m in the single-chain protein, as well as 17,000, 25,500, and 34,000 V/m in the three-chain protein, respectively. Results indicate that electric fields (EFs) depress the binding energy of the soliton, decrease its amplitude, and change its wave form. Also, the soliton disperses at 102,000 V/m in a single-chain protein and at 25,500 and 34,000 V/m in three-chain proteins. These findings signify that the influence of EMFs on the bio-energy transport cannot be neglected; however, these variations depend on both the strength and the direction of the EF in the EMF. This direction influences the biological effects of EMF, which decrease with increases in the angle between the direction of the EF and that of the dipole moment of amino acid residues; however, randomness at the macroscopic level remains. Lastly, we experimentally confirm the existence of a soliton and the validity of our conclusion by using the infrared spectra of absorption of the collagens, which is activated by another type of EF. Thus, we can affirm that both the described mechanism and the corresponding theory are

  5. Influences of Electromagnetic Energy on Bio-Energy Transport through Protein Molecules in Living Systems and Its Experimental Evidence

    PubMed Central

    Pang, Xiaofeng; Chen, Shude; Wang, Xianghui; Zhong, Lisheng

    2016-01-01

    The influences of electromagnetic fields (EMFs) on bio-energy transport and its mechanism of changes are investigated through analytic and numerical simulation and experimentation. Bio-energy transport along protein molecules is performed by soliton movement caused by the dipole–dipole electric interactions between neighboring amino acid residues. As such, EMFs can affect the structure of protein molecules and change the properties of the bio-energy transported in living systems. This mechanism of biological effect from EMFs involves the amino acid residues in protein molecules. To study and reveal this mechanism, we simulated numerically the features of the movement of solitons along protein molecules with both a single chain and with three channels by using the Runge–Kutta method and Pang’s soliton model under the action of EMFs with the strengths of 25,500, 51,000, 76,500, and 102,000 V/m in the single-chain protein, as well as 17,000, 25,500, and 34,000 V/m in the three-chain protein, respectively. Results indicate that electric fields (EFs) depress the binding energy of the soliton, decrease its amplitude, and change its wave form. Also, the soliton disperses at 102,000 V/m in a single-chain protein and at 25,500 and 34,000 V/m in three-chain proteins. These findings signify that the influence of EMFs on the bio-energy transport cannot be neglected; however, these variations depend on both the strength and the direction of the EF in the EMF. This direction influences the biological effects of EMF, which decrease with increases in the angle between the direction of the EF and that of the dipole moment of amino acid residues; however, randomness at the macroscopic level remains. Lastly, we experimentally confirm the existence of a soliton and the validity of our conclusion by using the infrared spectra of absorption of the collagens, which is activated by another type of EF. Thus, we can affirm that both the described mechanism and the corresponding theory

  6. Experimental Identification of Actinobacillus pleuropneumoniae Strains L20 and JL03 Heptosyltransferases, Evidence for a New Heptosyltransferase Signature Sequence

    PubMed Central

    Merino, Susana; Knirel, Yuriy A.; Regué, Miguel; Tomás, Juan M.

    2013-01-01

    We experimentally identified the activities of six predicted heptosyltransferases in Actinobacillus pleuropneumoniae genome serotype 5b strain L20 and serotype 3 strain JL03. The initial identification was based on a bioinformatic analysis of the amino acid similarity between these putative heptosyltrasferases with others of known function from enteric bacteria and Aeromonas. The putative functions of all the Actinobacillus pleuropneumoniae heptosyltrasferases were determined by using surrogate LPS acceptor molecules from well-defined A. hydrophyla AH-3 and A. salmonicida A450 mutants. Our results show that heptosyltransferases APL_0981 and APJL_1001 are responsible for the transfer of the terminal outer core D-glycero-D-manno-heptose (D,D-Hep) residue although they are not currently included in the CAZY glycosyltransferase 9 family. The WahF heptosyltransferase group signature sequence [S(T/S)(GA)XXH] differs from the heptosyltransferases consensus signature sequence [D(TS)(GA)XXH], because of the substitution of D261 for S261, being unique. PMID:23383222

  7. Temporal separation between CO2 assimilation and growth? Experimental and theoretical evidence from the desiccation-tolerant moss Syntrichia ruralis.

    PubMed

    Royles, Jessica; Ogée, Jérôme; Wingate, Lisa; Hodgson, Dominic A; Convey, Peter; Griffiths, Howard

    2013-03-01

    The extent of an external water layer around moss tissue influences CO(2) assimilation. Experiments on the desiccation-tolerant moss Syntrichia ruralis assessed the real-time dependence of the carbon and oxygen isotopic compositions of CO(2) and H(2)O in terms of moss water status and integrated isotope signals in cellulose. As external (capillary) water, and then mesophyll water, evaporated from moss tissue, assimilation rate, relative water content and the stable isotope composition of tissue water (δ(18)O(TW)), and the CO(2) and H(2)O fluxes, were analysed. After drying, carbon (δ(13)C(C)) and oxygen (δ(18)O(C)) cellulose compositions were determined. During desiccation, assimilation and (13)CO(2) discrimination increased to a maximum and then declined; δ(18)O(TW) increased progressively by 8‰, indicative of evaporative isotopic enrichment. Experimental and meteorological data were combined to predict tissue hydration dynamics over one growing season. Nonsteady-state model predictions of δ(18)O(TW) were consistent with instantaneous measurements. δ(13)C(C) values suggest that net assimilation occurs at 25% of maximum relative water content, while δ(18)O(C) data suggests that cellulose is synthesized during much higher relative water content conditions. This implies that carbon assimilation and cellulose synthesis (growth) may be temporally separated, with carbon reserves possibly contributing to desiccation tolerance and resumption of metabolism upon rehydration.

  8. Keep logging in! Experimental evidence showing the relation of affiliation needs to the idea of online social networking.

    PubMed

    Lee, Chun-Chia; Chiou, Wen-Bin

    2013-06-01

    As social networking sites (SNS) increasingly provide social connections that meet the need for affiliation, people are developing symbiotic relationships with these sites. Drawing on the notion that people motivated by affiliation may increase their attention to sources that provide social connections, we conducted a lab experiment to explore whether priming affiliation needs would prompt the idea of online social networking. Participants were randomly assigned to one of three between-subjects conditions (affiliation arousal, social exclusion, control) in which we employed the scrambled-sentence paradigm to manipulate affiliation motivations. Each experimental condition was followed by a modified Stroop task (a color naming task) to test reaction times to SNS and non-SNS terms (including general terms and brand names). People who were primed to think about a topic typically showed slowed reaction times for naming the color of related words (i.e., Stroop interference), as those words become more interesting and accessible. Confirming our hypothesis, participants took longer to name the font color of SNS-related words than that of matched general words when affiliation motivation was evoked. Moreover, priming with affiliation motivation created more Stroop interference for SNS brand names rather than for other global brand names. These results suggest that the idea of online social networking seems to have become deeply rooted in human social practices. PMID:23427848

  9. Experimental evidence of the synergistic effects of warming and invasive algae on a temperate reef-builder coral

    PubMed Central

    Kersting, Diego K; Cebrian, Emma; Casado, Clara; Teixidó, Núria; Garrabou, Joaquim; Linares, Cristina

    2015-01-01

    In the current global climate change scenario, stressors overlap in space and time, and knowledge on the effects of their interaction is highly needed to understand and predict the response and resilience of organisms. Corals, among many other benthic organisms, are affected by an increasing number of global change-related stressors including warming and invasive species. In this study, the cumulative effects between warming and invasive algae were experimentally assessed on the temperate reef-builder coral Cladocora caespitosa. We first investigated the potential local adaptation to thermal stress in two distant populations subjected to contrasting thermal and necrosis histories. No significant differences were found between populations. Colonies from both populations suffered no necrosis after long-term exposure to temperatures up to 29 °C. Second, we tested the effects of the interaction of both warming and the presence of invasive algae. The combined exposure triggered critical synergistic effects on photosynthetic efficiency and tissue necrosis. At the end of the experiment, over 90% of the colonies subjected to warming and invasive algae showed signs of necrosis. The results are of particular concern when considering the predicted increase of extreme climatic events and the spread of invasive species in the Mediterranean and other seas in the future. PMID:26692424

  10. Experimental evidence of the synergistic effects of warming and invasive algae on a temperate reef-builder coral.

    PubMed

    Kersting, Diego K; Cebrian, Emma; Casado, Clara; Teixidó, Núria; Garrabou, Joaquim; Linares, Cristina

    2015-12-22

    In the current global climate change scenario, stressors overlap in space and time, and knowledge on the effects of their interaction is highly needed to understand and predict the response and resilience of organisms. Corals, among many other benthic organisms, are affected by an increasing number of global change-related stressors including warming and invasive species. In this study, the cumulative effects between warming and invasive algae were experimentally assessed on the temperate reef-builder coral Cladocora caespitosa. We first investigated the potential local adaptation to thermal stress in two distant populations subjected to contrasting thermal and necrosis histories. No significant differences were found between populations. Colonies from both populations suffered no necrosis after long-term exposure to temperatures up to 29 °C. Second, we tested the effects of the interaction of both warming and the presence of invasive algae. The combined exposure triggered critical synergistic effects on photosynthetic efficiency and tissue necrosis. At the end of the experiment, over 90% of the colonies subjected to warming and invasive algae showed signs of necrosis. The results are of particular concern when considering the predicted increase of extreme climatic events and the spread of invasive species in the Mediterranean and other seas in the future.

  11. Experimental evidence for spring and autumn windows for the detection of geobotanical anomalies through the remote sensing of overlying vegetation

    NASA Technical Reports Server (NTRS)

    Labovitz, M. L.; Masuoka, E. J.; Bell, R.; Nelson, R. F.; Larsen, C. A.; Hooker, L. K.; Troensegaard, K. W.

    1985-01-01

    It is pointed out that in many regions of the world, vegetation is the predominant factor influencing variation in reflected energy in the 0.4-2.5 micron region of the spectrum. Studies have, therefore, been conducted regarding the utility of remote sensing for detecting changes in vegetation which could be related to the presence of mineralization. The present paper provides primarily a report on the results of the second year of a multiyear study of geobotanical-remote-sensing relationships as developed over areas of sulfide mineralization. The field study has a strong experimental design basis. It is proceeded by first delineating the boundaries of a large geographic region which satisfied a set of previously enumerated field-site criteria. Within this region, carefully selected pairs of mineralized and nonmineralized test sites were examined over the growing season. The experiment is to provide information about the spectral and temporal resolutions required for remote-sensing-geobotanical exploration. The obtained results are evaluated.

  12. BMI is not related to altruism, fairness, trust or reciprocity: Experimental evidence from the field and the lab.

    PubMed

    Brañas-Garza, Pablo; Espín, Antonio M; Lenkei, Balint

    2016-03-15

    Over the past few decades obesity has become one of the largest public policy concerns among the adult population in the developed world. Obesity and overweight are hypothesized to affect individuals' sociability through a number of channels, including discrimination and low self-esteem. However, whether these effects translate into differential behavioural patterns in social interactions remains unknown. In two large-scale economic experiments, we explore the relationship between Body Mass Index (BMI) and social behaviour, using three paradigmatic economic games: the dictator, ultimatum, and trust games. Our first experiment employs a representative sample of a Spanish city's population (N=753), while the second employs a sample of university students from the same city (N=618). Measures of altruism, fairness/equality, trust and reciprocity are obtained from participants' experimental decisions. Using a variety of regression specifications and control variables, our results suggest that BMI does not exert an effect on any of these social preferences. Some implications of these findings are discussed. PMID:26780149

  13. A novel pathway for the biosynthesis of heme in Archaea: genome-based bioinformatic predictions and experimental evidence.

    PubMed

    Storbeck, Sonja; Rolfes, Sarah; Raux-Deery, Evelyne; Warren, Martin J; Jahn, Dieter; Layer, Gunhild

    2010-12-13

    Heme is an essential prosthetic group for many proteins involved in fundamental biological processes in all three domains of life. In Eukaryota and Bacteria heme is formed via a conserved and well-studied biosynthetic pathway. Surprisingly, in Archaea heme biosynthesis proceeds via an alternative route which is poorly understood. In order to formulate a working hypothesis for this novel pathway, we searched 59 completely sequenced archaeal genomes for the presence of gene clusters consisting of established heme biosynthetic genes and colocalized conserved candidate genes. Within the majority of archaeal genomes it was possible to identify such heme biosynthesis gene clusters. From this analysis we have been able to identify several novel heme biosynthesis genes that are restricted to archaea. Intriguingly, several of the encoded proteins display similarity to enzymes involved in heme d(1) biosynthesis. To initiate an experimental verification of our proposals two Methanosarcina barkeri proteins predicted to catalyze the initial steps of archaeal heme biosynthesis were recombinantly produced, purified, and their predicted enzymatic functions verified.

  14. Physical Health Effects of the Housing Boom: Quasi-Experimental Evidence From the Health and Retirement Study

    PubMed Central

    Hamoudi, Amar

    2013-01-01

    Objectives. We examined the impact of the dramatic increases in housing prices in the United States in the 1990s and early 2000s on physical health outcomes among a representative sample of middle-aged and older Americans. Methods. Using a quasi-experimental design, we exploited geographic and time variation in housing prices using third-party valuation estimates of median single-family detached houses from 1988 to 2007 in each of 2400 zip codes combined with Health and Retirement Study data from 1992 to 2006 to test the impact of housing appreciation on physical health outcomes. Results. Respondents living in communities in which home values appreciated more rapidly had fewer functional limitations, performed better on interviewer-administered physical tasks, and had smaller waist circumference. Conclusions. Our results indicate that increases in housing wealth were associated with better health outcomes for homeowners in late middle age and older. The recent sharp decline in housing values for this group may likewise be expected to have important implications for health and should be examined as data become available. PMID:23597343

  15. Impediment of basilar membrane motion reduces overload protection but not threshold sensitivity: evidence from clinical and experimental hydrops.

    PubMed

    Braun, M

    1996-08-01

    The mechanical function of the basilar membrane (BM) in the mammalian cochlea has been newly debated after the discovery of frequency selectivity of single hair cells. Decisive information on this matter can be expected from hydropic ears, since hydrops presumably alters cochlear mechanics by (1) impeding BM motion and (2) uncoupling outer hair cell (OHC) stereocilia from the tectorial membrane (TM). Therefore hearing in Menière's disease (MD) was examined analysing data on epidemiology of MD types and audiogram types, 2f thresholds, over-recruitment, loudness intolerance, and otoacoustic emissions. Further, hearing in experimental hydrops (XH) was examined analysing data on: morphological changes on TM and OHCs in relation to hydrops duration; morphological and electrophysiological changes upon acoustic overstimulation. The results were unequivocal on two points: (1) co-occurrence of hydrops and normal hearing thresholds can appear both in MD and XH, (2) co-occurrence of non-hearing-loss hydrops and loudness hypersensitivity is typical both in MD and XH. The conclusion is that BM motion apparently is no necessary element in the chain of cochlear sound transmission but obviously is an auxiliary element for overload protection through resonant absorption. The results are further indicative of audiometric methods for an early detection of incipient MD. PMID:8844181

  16. Experimental evidence for the immediate impact of fertilization and irrigation upon the plant and invertebrate communities of mountain grasslands

    PubMed Central

    Andrey, Aline; Humbert, Jean-Yves; Pernollet, Claire; Arlettaz, Raphaël

    2014-01-01

    The response of montane and subalpine hay meadow plant and arthropod communities to the application of liquid manure and aerial irrigation – two novel, rapidly spreading management practices – remains poorly understood, which hampers the formulation of best practice management recommendations for both hay production and biodiversity preservation. In these nutrient-poor mountain grasslands, a moderate management regime could enhance overall conditions for biodiversity. This study experimentally assessed, at the site scale, among low-input montane and subalpine meadows, the short-term effects (1 year) of a moderate intensification (slurry fertilization: 26.7–53.3 kg N·ha−1·year−1; irrigation with sprinklers: 20 mm·week−1; singly or combined together) on plant species richness, vegetation structure, hay production, and arthropod abundance and biomass in the inner European Alps (Valais, SW Switzerland). Results show that (1) montane and subalpine hay meadow ecological communities respond very rapidly to an intensification of management practices; (2) on a short-term basis, a moderate intensification of very low-input hay meadows has positive effects on plant species richness, vegetation structure, hay production, and arthropod abundance and biomass; (3) vegetation structure is likely to be the key factor limiting arthropod abundance and biomass. Our ongoing experiments will in the longer term identify which level of management intensity achieves an optimal balance between biodiversity and hay production. PMID:25360290

  17. Heavy rainfall increases nestling mortality of an Arctic top predator: experimental evidence and long-term trend in peregrine falcons.

    PubMed

    Anctil, Alexandre; Franke, Alastair; Bêty, Joël

    2014-03-01

    Although animal population dynamics have often been correlated with fluctuations in precipitation, causal relationships have rarely been demonstrated in wild birds. We combined nest observations with a field experiment to investigate the direct effect of rainfall on survival of peregrine falcon (Falco peregrinus) nestlings in the Canadian Arctic. We then used historical data to evaluate if recent changes in the precipitation regime could explain the long-term decline of falcon annual productivity. Rainfall directly caused more than one-third of the recorded nestling mortalities. Juveniles were especially affected by heavy rainstorms (≥8 mm/day). Nestlings sheltered from rainfall by a nest box had significantly higher survival rates. We found that the increase in the frequency of heavy rain over the last three decades is likely an important factor explaining the recent decline in falcon nestling survival rates, and hence the decrease in annual breeding productivity of the population. Our study is among the first experimental demonstrations of the direct link between rainfall and survival in wild birds, and clearly indicates that top arctic predators can be significantly impacted by changes in precipitation regime.

  18. Tarantulas do not shoot silk from their legs: experimental evidence in four species of New World tarantulas.

    PubMed

    Pérez-Miles, Fernando; Ortíz-Villatoro, David

    2012-05-15

    Theraphosid tarantulas, like all other spiders, secrete silk from spigots on the abdominal spinnerets. A few years ago, it was proposed that the large tarantula Aphonopelma seemanni could extrude silk from specialized spigots on the tarsi to help adhesion to vertical surfaces. This suggestion was later questioned because silk was not observed after the spinnerets had been sealed. Recently, experiments with the tarantula Grammostola rosea again suggested tarsal silk secretion. All observations of the supposed tarsal silk were made in spiders with functional spinnerets, thus contamination with silk coming from the spinnerets could not be excluded. Recent morphological arguments also questioned putative tarsal spigots and proposed that they are actually contact chemoreceptors. We here test the supposed tarsal silk secretion in Aphonopelma seemanni, Avicularia avicularia, Brachypelma vagans and Grammostola mollicoma using similar experimental conditions as the previous authors, but with sealed spinnerets. Our results clearly demonstrate that when spinnerets are sealed, tarantulas do not show any tarsal silk secretion. We reinterpret those putative tarsal spigots and discuss possible evolutionary implications of these findings. PMID:22539742

  19. Plant-soil interactions in salt marsh environments: Experimental evidence from electrical resistivity tomography in the Venice Lagoon

    NASA Astrophysics Data System (ADS)

    Boaga, Jacopo; D'Alpaos, Andrea; Cassiani, Giorgio; Marani, Marco; Putti, Mario

    2014-09-01

    The role of root water uptake in regulating soil water saturation in salt marshes is controversial. Modeling studies suggest that soil aeration is improved by transpiration, with implications for the distribution of vegetation species and of the associated topographic features controlling the hydraulic regime of the marshland and eventually its survival. Marsh vegetation plays a key role in the preservation of such critical environment, which represents unique marker for climatic change and impact studies. However, the direct quantification of space-time aeration patterns has remained elusive, in part, because of the limitations posed by high salinity to conventional observation techniques such as time or frequency domain reflectometry. Here we show that time-lapse microscale electrical resistivity tomography, coupled with tensiometric observations, allows the identification of variably saturated zones and the characterization of space-time soil moisture dynamics in a salt marsh in the Venice Lagoon (Italy). This is the first quantitative observational experiment which confirms that periodically flooded plants are capable of producing a persistently aerated layer below the flooded surface when transpiration proceeds at a sufficiently high rate. The experimental results are compared against previously published model predictions.

  20. Field and experimental evidence for coseismic ruptures along shallow creeping faults in forearc sediments of the Crotone Basin, South Italy

    NASA Astrophysics Data System (ADS)

    Balsamo, Fabrizio; Aldega, Luca; De Paola, Nicola; Faoro, Igor; Storti, Fabrizio

    2014-05-01

    Large seismic slip occurring along shallow creeping faults in tectonically active areas represents an unsolved paradox, which is largely due to our poor understanding of the mechanics governing creeping faults, and to the lack of documented geological evidence showing how coseismic rupturing overprints creep in near-surface conditions. In this contribution we integrate field, petrophysical, mineralogical and friction data to characterize the signature of coseismic ruptures propagating along shallow creeping faults affecting unconsolidated forearc sediments of the seismically active Crotone Basin, in South Italy. Field observations of fault zones show widespread foliated cataclasites in fault cores, locally overprinted by sharp slip surfaces decorated by thin (0.5-1.5 cm) black gouge layers. Compared to foliated cataclasites, black gouges have much lower grain size, porosity and permeability, which may have facilitated slip weakening by thermal fluid pressurization. Moreover, black gouges are characterized by distinct mineralogical assemblages compatible with high temperatures (180-200°C) due to frictional heating during seismic slip. Foliated cataclasites and black gouges were also produced by laboratory friction experiments performed on host sediments at sub-seismic (≤ 0.1 m/s) and seismic (1 m/s) slip rates, respectively. Black gouges display low friction coefficients (0.3) and velocity-weakening behaviours, as opposed to high friction coefficients (0.65) and velocity-strengthening behaviours shown by the foliated cataclasites. Our results show that narrow black gouges developed within foliated cataclasites represent a potential diagnostic marker for episodic seismic activity in shallow creeping faults. These findings can help understanding the time-space partitioning between aseismic and seismic slip of faults at shallow crustal levels, impacting on seismic hazard evaluation of subduction zones and forearc regions affected by destructive earthquakes and

  1. Fluorescent proteins function as a prey attractant: experimental evidence from the hydromedusa Olindias formosus and other marine organisms

    PubMed Central

    Haddock, Steven H. D.; Dunn, Casey W.

    2015-01-01

    ABSTRACT Although proteins in the green fluorescent protein family (GFPs) have been discovered in a wide array of taxa, their ecological functions in these organisms remain unclear. Many hypothesized roles are related to modifying bioluminescence spectra or modulating the light regime for algal symbionts, but these do not explain the presence of GFPs in animals that are non-luminous and non-symbiotic. Other hypothesized functions are unrelated to the visual signals themselves, including stress responses and antioxidant roles, but these cannot explain the localization of fluorescence in particular structures on the animals. Here we tested the hypothesis that fluorescence might serve to attract prey. In laboratory experiments, the predator was the hydromedusa Olindias formosus (previously known as O. formosa), which has fluorescent and pigmented patches on the tips of its tentacles. The prey, juvenile rockfishes in the genus Sebastes, were significantly more attracted (P<1×10−5) to the medusa's tentacles under lighting conditions where fluorescence was excited and tentacle tips were visible above the background. The fish did not respond significantly when treatments did not include fluorescent structures or took place under yellow or white lights, which did not generate fluorescence visible above the ambient light. Furthermore, underwater observations of the behavior of fishes when presented with a brightly illuminated point showed a strong attraction to this visual stimulus. In situ observations also provided evidence for fluorescent lures as supernormal stimuli in several other marine animals, including the siphonophore Rhizophysa eysenhardti. Our results support the idea that fluorescent structures can serve as prey attractants, thus providing a potential function for GFPs and other fluorescent proteins in a diverse range of organisms. PMID:26231627

  2. Standardised (plain) cigarette packaging increases attention to both text-based and graphical health warnings: experimental evidence

    PubMed Central

    Shankleman, M.; Sykes, C.; Mandeville, K.L.; Di Costa, S.; Yarrow, K.

    2015-01-01

    Objective To investigate whether standardised cigarette packaging increases the time spent looking at health warnings, regardless of the format of those warnings. Study design A factorial (two pack styles x three warning types) within-subject experiment, with participants randomised to different orders of conditions, completed at a university in London, UK. Methods Mock-ups of cigarette packets were presented to participants with their branded portion in either standardised (plain) or manufacturer-designed (branded) format. Health warnings were present on all packets, representing all three types currently in use in the UK: black & white text, colour text, or colour images with accompanying text. Gaze position was recorded using a specialised eye tracker, providing the main outcome measure, which was the mean proportion of a five-second viewing period spent gazing at the warning-label region of the packet. Results An opportunity sample of 30 (six male, mean age = 23) young adults met the following inclusion criteria: 1) not currently a smoker; 2) <100 lifetime cigarettes smoked; 3) gaze position successfully tracked for > 50% viewing time. These participants spent a greater proportion of the available time gazing at the warning-label region when the branded section of the pack was standardised (following current Australian guidelines) rather than containing the manufacturer's preferred design (mean difference in proportions = 0.078, 95% confidence interval 0.049 to 0.106, p < 0.001). There was no evidence that this effect varied based on the type of warning label (black & white text vs. colour text vs. colour image & text; interaction p = 0.295). Conclusions During incidental viewing of cigarette packets, young adult never-smokers are likely to spend more time looking at health warnings if manufacturers are compelled to use standardised packaging, regardless of the warning design. PMID:25542740

  3. Experimental evidence for the effect of small wind turbine proximity and operation on bird and bat activity.

    PubMed

    Minderman, Jeroen; Pendlebury, Chris J; Pearce-Higgins, James W; Park, Kirsty J

    2012-01-01

    The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6-18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0-5 m), bat activity (measured as the probability of a bat "pass" per hour) decreases from 84% (71-91%) to 28% (11-54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20-25 m) from operating turbines (activity decreases from 80% (65-89%) to 59% (32-81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat. PMID:22859969

  4. Experimental Evidence for the Effect of Small Wind Turbine Proximity and Operation on Bird and Bat Activity

    PubMed Central

    Minderman, Jeroen; Pendlebury, Chris J.; Pearce-Higgins, James W.; Park, Kirsty J.

    2012-01-01

    The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6–18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0–5 m), bat activity (measured as the probability of a bat “pass” per hour) decreases from 84% (71–91%) to 28% (11–54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20–25 m) from operating turbines (activity decreases from 80% (65–89%) to 59% (32–81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat. PMID:22859969

  5. Experimental evidence for the effect of small wind turbine proximity and operation on bird and bat activity.

    PubMed

    Minderman, Jeroen; Pendlebury, Chris J; Pearce-Higgins, James W; Park, Kirsty J

    2012-01-01

    The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6-18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0-5 m), bat activity (measured as the probability of a bat "pass" per hour) decreases from 84% (71-91%) to 28% (11-54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20-25 m) from operating turbines (activity decreases from 80% (65-89%) to 59% (32-81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat.

  6. Experimental and observational evidence reveals that predators in natural environments do not regulate their prey: They are passengers, not drivers

    NASA Astrophysics Data System (ADS)

    White, T. C. R.

    2013-11-01

    Among both ecologists and the wider community there is a tacit assumption that predators regulate populations of their prey. But there is evidence from a wide taxonomic and geographic range of studies that predators that are adapted to co-evolved prey generally do not regulate their prey. This is because predators either cannot reproduce as fast as their prey and/or are inefficient hunters unable to catch enough prey to sustain maximum reproduction. The greater capacity of herbivores to breed successfully is, however, normally restricted by a lack of enough food of sufficient quality to support reproduction. But whenever this shortage is alleviated by a large pulse of food, herbivores increase their numbers to outbreak levels. Their predators are unable to contain this increase, but their numbers, too, surge in response to this increase in food. Eventually both their populations will crash once the food supply runs out, first for the herbivores and then for the predators. Then an “over-run” of predators will further depress the already declining prey population, appearing to be controlling its abundance. This latter phenomenon has led many ecologists to conclude that predators are regulating the numbers of their prey. However, it is the same process that is revealed during outbreaks that limits populations of both predator and prey in “normal” times, although this is usually not readily apparent. Nevertheless, as all the diverse cases discussed here attest, the abundance of predators and their co-evolved prey are both limited by their food: the predators are passengers, not drivers.

  7. Effect of phytoplankton community composition and cell size on absorption properties in eutrophic shallow lakes: field and experimental evidence.

    PubMed

    Zhang, Yunlin; Yin, Yan; Wang, Mingzhu; Liu, Xiaohan

    2012-05-21

    We investigated phytoplankton absorption properties of Lake Taihu, in the spring and summer of 2005 and 2006, and for 17 days studied laboratory cultures of Scenedesmus obliquus (chlorophyta) and Microcystis aeruginosa (cyanophyta) to determine the effect of phytoplankton community composition and cell size on the absorption properties. There were significant seasonal differences in phytoplankton community composition and absorption coefficients. In spring, the phytoplankton community was dominated by chlorophyta with large cells, whereas in summer was dominated by cyanophyta with small cells. Phytoplankton absorption coefficients increased significantly from spring to summer, with the increase in chlorophyll a (Chla) concentration. In addition, Chla-specific absorption coefficients increased with the phytoplankton community succession from chlorophyta to cyanophyta. In culture, the cells density of S. obliquus was generally lower than that of M. aeruginosa, and Chla concentrations of S. obliquus were significantly higher than those of M. aeruginosa. Correspondingly, the Chla-specific absorption coefficients of S. obliquus were significantly lower than those of M. aeruginosa. Significant exponential correlations were found between absorption and Chla-specific absorption coefficients and Chla concentration for S. obliquus and M. aeruginosa. In addition, we developed a model to predict absorption and Chla-specific absorption coefficients using Chla concentration and cell size when data from two species was grouped together. Field and experimental results both showed that the Chla-specific absorption coefficients of cyanophyta were significantly higher than those of chlorophyta. The variability in specific absorption can attributed to phytoplankton community composition, cell size and pigment composition. As phytoplankton community composition changed significantly with season in the lake, and as variation in the cell sizes and accessory pigments of the phytoplankton

  8. Infiltration-soil moisture redistribution under natural conditions: experimental evidence as a guideline for realizing simulation models

    NASA Astrophysics Data System (ADS)

    Morbidelli, R.; Corradini, C.; Saltalippi, C.; Flammini, A.; Rossi, E.

    2011-06-01

    The evolution in time, t, of the experimental soil moisture vertical profile under natural conditions is investigated in order to address the corresponding simulation modelling. The measurements were conducted in a plot with a bare silty loam soil. The soil water content, θ, was continuously monitored at different depths, z, using a Time Domain Reflectometry (TDR) system. For each profile four buriable three-rod waveguides were inserted horizontally at different depths (5, 15, 25 and 35 cm). In addition, we used sensors of air temperature and relative humidity, wind speed, solar radiation, evaporation and rain as supports for the application of selected simulation models, as well as for the detection of elements leading to their improvement. The results indicate that, under natural conditions, very different trends of the θ(z,t) function can be observed in the given fine-textured soil, where the formation of a sealing layer over the parent soil requires an adjustment of the simulation modelling commonly used for hydrological applications. In particular, because of the considerable variations in the shape of the moisture content vertical profile as a function of time, a generalization of the existing models should incorporate a representation of the variability in time of the saturated hydraulic conductivity of the uppermost soil. This conclusion is supported by the fact that the observed shape of θ(z) can be appropriately reproduced by adopting this approach, however the observed rainfall rate and the occurrence of freeze-thaw cycles with high soil moisture contents have to be explicitly incorporated.

  9. Infiltration-soil moisture redistribution under natural conditions: experimental evidence as a guideline for realizing simulation models

    NASA Astrophysics Data System (ADS)

    Morbidelli, R.; Corradini, C.; Saltalippi, C.; Flammini, A.; Rossi, E.

    2011-09-01

    The evolution in time, t, of the experimental soil moisture vertical profile under natural conditions is investigated in order to address the corresponding simulation modelling. The measurements were conducted in a plot with a bare silty loam soil. The soil water content, θ, was continuously monitored at different depths, z, using a Time Domain Reflectometry (TDR) system. Four buriable three-rod waveguides were inserted horizontally at different depths (5, 15, 25 and 35 cm). In addition, we used sensors of air temperature and relative humidity, wind speed, solar radiation, evaporation and rain as supports for the application of selected simulation models, as well as for the detection of elements leading to their improvement. The results indicate that, under natural conditions, very different trends of the θ(z, t) function can be observed in the given fine-textured soil, where the formation of a sealing layer over the parent soil requires an adjustment of the simulation modelling commonly used for hydrological applications. In particular, because of the considerable variations in the shape of the moisture content vertical profile as a function of time, a generalization of the existing models should incorporate a first approximation of the variability in time of the saturated hydraulic conductivity, K1s, of the uppermost soil. This conclusion is supported by the fact that the observed shape of θ(z, t) can be appropriately reproduced by adopting the proposed approach with K1s kept constant during each rainfall event but considered variable from event to event, however the observed rainfall rate and the occurrence of freeze-thaw cycles with high soil moisture contents have to be explicitly incorporated in a functional form for K1s(t).

  10. Experimental and numerical evidences of the observation of the Biot slow wave thanks to its electrokinetic conversion

    NASA Astrophysics Data System (ADS)

    Bordes, C.; Garambois, S.; Brito, D.; Dietrich, M.; Holzhauer, J.

    2013-12-01

    As originally described by Biot in 1956, seismic propagation in fluid-filled porous media should include two longitudinal contributions: the fast and slow P waves, the latest being commonly referred to as the ';Biot slow wave'. This seismic wave has been seldom observed in natural rocks at laboratory frequencies due to its low amplitude properties and has never been recognized at seismic frequencies due to its diffusive properties. In porous media, a part of seismic energy may also be converted into electromagnetic fields by a coupling phenomenon of electrokinetic nature: the so-called seismoelectric effect. Most seismoelectric studies focus on the observation of co-seismic or depth-converted electric fields generated by the propagation of fast P-waves, mainly to detect or to image new physico-chemical contrasts. Based on Pride's theory (1994), numerical modeling of seismo-electromagnetic wave propagation suggests that the observation of the Biot slow wave could be boosted by its electrokinetic conversion, i.e. that it would be easier to record the electric fields accompanying Biot slow waves generated by a mechanical source rather than the seismic fields. In order to confirm these numerical predictions, we designed a specific laboratory experiment involving a silica sand tank excited by using a homemade pneumatic seismic source. The investigated frequency range [0.5-5kHz] contains the Biot (transition) frequency separating the diffusive from the propagation regimes of the slow wave. Numerical seismoelectromagnetic experiments were also performed at this scale to compute the seismoelectric response in homogeneous and partially saturated sand with this acquisition configuration. The comparison of these experimental data to numerical results provides new perspectives for the detection, study and potential use of the Biot slow wave.

  11. Role of peroxisome proliferator-activated receptors alpha and gamma in gastric ulcer: An overview of experimental evidences.

    PubMed

    Saha, Lekha

    2015-11-01

    Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. Three subtypes, PPARα, PPARβ/δ, and PPARγ, have been identified so far. PPARα is expressed in the liver, kidney, small intestine, heart, and muscle, where it activates the fatty acid catabolism and control lipoprotein assembly in response to long-chain unsaturated fatty acids, eicosanoids, and hypolipidemic drugs (e.g., fenofibrate). PPARβ/δ is more broadly expressed and is implicated in fatty acid oxidation, keratinocyte differentiation, wound healing, and macrophage response to very low density lipoprotein metabolism. This isoform has been implicated in transcriptional-repression functions and has been shown to repress the activity of PPARα or PPARγ target genes. PPARγ1 and γ2 are generated from a single-gene peroxisome proliferator-activated receptors gamma by differential promoter usage and alternative splicing. PPARγ1 is expressed in colon, immune system (e.g., monocytes and macrophages), and other tissues where it participates in the modulation of inflammation, cell proliferation, and differentiation. PPARs regulate gene expression through distinct mechanisms: Ligand-dependent transactivation, ligand-independent repression, and ligand-dependent transrepression. Studies in animals have demonstrated the gastric antisecretory activity of PPARα agonists like ciprofibrate, bezafibrate and clofibrate. Study by Pathak et al also demonstrated the effect of PPARα agonist, bezafibrate, on gastric secretion and gastric cytoprotection in various gastric ulcer models in rats. The majority of the experimental studies is on pioglitazone and rosiglitazone, which are PPARγ activators. In all the studies, both the PPARγ activators showed protection against the gastric ulcer and also accelerate the ulcer healing in gastric ulcer model in rats. Therefore, PPARα and PPARγ may be a target for gastric ulcer therapy

  12. Role of peroxisome proliferator-activated receptors alpha and gamma in gastric ulcer: An overview of experimental evidences

    PubMed Central

    Saha, Lekha

    2015-01-01

    Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. Three subtypes, PPARα, PPARβ/δ, and PPARγ, have been identified so far. PPARα is expressed in the liver, kidney, small intestine, heart, and muscle, where it activates the fatty acid catabolism and control lipoprotein assembly in response to long-chain unsaturated fatty acids, eicosanoids, and hypolipidemic drugs (e.g., fenofibrate). PPARβ/δ is more broadly expressed and is implicated in fatty acid oxidation, keratinocyte differentiation, wound healing, and macrophage response to very low density lipoprotein metabolism. This isoform has been implicated in transcriptional-repression functions and has been shown to repress the activity of PPARα or PPARγ target genes. PPARγ1 and γ2 are generated from a single-gene peroxisome proliferator-activated receptors gamma by differential promoter usage and alternative splicing. PPARγ1 is expressed in colon, immune system (e.g., monocytes and macrophages), and other tissues where it participates in the modulation of inflammation, cell proliferation, and differentiation. PPARs regulate gene expression through distinct mechanisms: Ligand-dependent transactivation, ligand-independent repression, and ligand-dependent transrepression. Studies in animals have demonstrated the gastric antisecretory activity of PPARα agonists like ciprofibrate, bezafibrate and clofibrate. Study by Pathak et al also demonstrated the effect of PPARα agonist, bezafibrate, on gastric secretion and gastric cytoprotection in various gastric ulcer models in rats. The majority of the experimental studies is on pioglitazone and rosiglitazone, which are PPARγ activators. In all the studies, both the PPARγ activators showed protection against the gastric ulcer and also accelerate the ulcer healing in gastric ulcer model in rats. Therefore, PPARα and PPARγ may be a target for gastric ulcer therapy

  13. Experimental evidence of nitrogen control on pCO(2) in phosphorus-enriched humic and clear coastal lagoon waters.

    PubMed

    Peixoto, Roberta B; Marotta, Humberto; Enrich-Prast, Alex

    2013-01-01

    Natural and human-induced controls on carbon dioxide (CO(2)) in tropical waters may be very dynamic (over time and among or within ecosystems) considering the potential role of warmer temperatures intensifying metabolic responses and playing a direct role on the balance between photosynthesis and respiration. The high magnitude of biological processes at low latitudes following eutrophication by nitrogen (N) and phosphorus (P) inputs into coastal lagoons waters may be a relevant component of the carbon cycle, showing controls on partial pressure of CO(2) (pCO(2)) that are still poorly understood. Here we assessed the strength of N control on pCO(2) in P-enriched humic and clear coastal lagoons waters, using four experimental treatments in microcosms: control (no additional nutrients) and three levels of N additions coupled to P enrichments. In humic coastal lagoons waters, a persistent CO(2) supersaturation was reported in controls and all nutrient-enriched treatments, ranging from 24- to 4-fold the atmospheric equilibrium value. However, both humic and clear coastal lagoons waters only showed significant decreases in pCO(2) in relation to the controlled microcosms in the two treatments with higher N addition levels. Additionally, clear coastal lagoons water microcosms showed a shift from CO(2) sources to CO(2) sinks, in relation to the atmosphere. Only in the two more N-enriched treatments did pCO(2) substantially decrease, from 650 µatm in controls and less N-enriched treatments to 10 µatm in more N-enriched microcosms. Humic substrates and N inputs can modulate pCO(2) even in P-enriched coastal lagoons waters, thereby being important drivers on CO(2) outgassing from inland waters.

  14. Experimental evidence of nitrogen control on pCO2 in phosphorus-enriched humic and clear coastal lagoon waters

    PubMed Central

    Peixoto, Roberta B.; Marotta, Humberto; Enrich-Prast, Alex

    2013-01-01

    Natural and human-induced controls on carbon dioxide (CO2) in tropical waters may be very dynamic (over time and among or within ecosystems) considering the potential role of warmer temperatures intensifying metabolic responses and playing a direct role on the balance between photosynthesis and respiration. The high magnitude of biological processes at low latitudes following eutrophication by nitrogen (N) and phosphorus (P) inputs into coastal lagoons waters may be a relevant component of the carbon cycle, showing controls on partial pressure of CO2 (pCO2) that are still poorly understood. Here we assessed the strength of N control on pCO2 in P-enriched humic and clear coastal lagoons waters, using four experimental treatments in microcosms: control (no additional nutrients) and three levels of N additions coupled to P enrichments. In humic coastal lagoons waters, a persistent CO2 supersaturation was reported in controls and all nutrient-enriched treatments, ranging from 24- to 4-fold the atmospheric equilibrium value. However, both humic and clear coastal lagoons waters only showed significant decreases in pCO2 in relation to the controlled microcosms in the two treatments with higher N addition levels. Additionally, clear coastal lagoons water microcosms showed a shift from CO2 sources to CO2 sinks, in relation to the atmosphere. Only in the two more N-enriched treatments did pCO2 substantially decrease, from 650 µatm in controls and less N-enriched treatments to 10 µatm in more N-enriched microcosms. Humic substrates and N inputs can modulate pCO2 even in P-enriched coastal lagoons waters, thereby being important drivers on CO2 outgassing from inland waters. PMID:23390422

  15. Field and experimental evidence of a new caiman trypanosome species closely phylogenetically related to fish trypanosomes and transmitted by leeches

    PubMed Central

    Fermino, Bruno R.; Paiva, Fernando; Soares, Priscilla; Tavares, Luiz Eduardo R.; Viola, Laerte B.; Ferreira, Robson C.; Botero-Arias, Robinson; de-Paula, Cátia D.; Campaner, Marta; Takata, Carmen S.A.; Teixeira, Marta M.G.; Camargo, Erney P.

    2015-01-01

    Trypanosoma terena and Trypanosoma ralphi are known species of the South American crocodilians Caiman crocodilus, Caiman yacare and Melanosuchus niger and are phylogenetically related to the tsetse-transmitted Trypanosoma grayi of the African Crocodylus niloticus. These trypanosomes form the Crocodilian clade of the terrestrial clade of the genus Trypanosoma. A PCR-survey for trypanosomes in caiman blood samples and in leeches taken from caimans revealed unknown trypanosome diversity and frequent mixed infections. Phylogenies based on SSU (small subunit) of rRNA and gGAPDH (glycosomal Glyceraldehyde Phosphate Dehydrogenase) gene sequences revealed a new trypanosome species clustering with T. terena and T. ralphi in the crocodilian clade and an additional new species nesting in the distant Aquatic clade of trypanosomes, which is herein named Trypanosoma clandestinus n. sp. This new species was found in Caiman yacare, Caiman crocodilus and M. niger from the Pantanal and Amazonian biomes in Brazil. Large numbers of dividing epimastigotes and unique thin and long trypomastigotes were found in the guts of leeches (Haementeria sp.) removed from the mouths of caimans. The trypanosomes recovered from the leeches had sequences identical to those of T. clandestinus of caiman blood samples. Experimental infestation of young caimans (Caiman yacare) with infected leeches resulted in long-lasting T. clandestinus infections that permitted us to delineate its life cycle. In contrast to T. terena, T. ralphi and T. grayi, which are detectable by hemoculturing, microscopy and standard PCR of caiman blood, T. clandestinus passes undetected by these methods due to very low parasitemia and could be detected solely by the more sensitive nested PCR method. T. clandestinus n. sp. is the first crocodilian trypanosome known to be transmitted by leeches and positioned in the aquatic clade closest to fish trypanosomes. Our data show that caimans can host trypanosomes of the aquatic or

  16. Experimental evidence for the interplay of exogenous and endogenous factors on the movement ecology of a migrating songbird.

    PubMed

    Cohen, Emily B; Moore, Frank R; Fischer, Richard A

    2012-01-01

    Movement patterns during songbird migration remain poorly understood despite their expected fitness consequences in terms of survival, energetic condition and timing of migration that will carry over to subsequent phases of the annual cycle. We took an experimental approach to test hypotheses regarding the influence of habitat, energetic condition, time of season and sex on the hour-by-hour, local movement decisions of a songbird during spring stopover. To simulate arrival of nocturnal migrants at unfamiliar stopover sites, we translocated and continuously tracked migratory red-eyed vireos (Vireo olivaceus) throughout spring stopover with and without energetic reserves that were released in two replicates of three forested habitat types. Migrants moved the most upon release, during which time they selected habitat characterized by greater food abundance and higher foraging attack rates. Presumably under pressure to replenish fuel stores necessary to continue migration in a timely fashion, migrants released in poorer energetic condition moved faster and further than migrants in better condition and the same pattern was true for migrants released late in spring relative to those released earlier. However, a migrant's energetic condition had less influence on their behavior when they were in poor quality habitat. Movement did not differ between sexes. Our study illustrates the importance of quickly finding suitable habitat at each stopover site, especially for energetically constrained migrants later in the season. If an initial period prior to foraging were necessary at each stop along a migrant's journey, non-foraging periods would cumulatively result in a significant energetic and time cost to migration. However, we suggest behavior during stopover is not solely a function of underlying resource distributions but is a complex response to a combination of endogenous and exogenous factors.

  17. Initial experimental evidence of self-collimation of TNSA proton beam in a stack of conducting foils

    NASA Astrophysics Data System (ADS)

    Ni, Pavel

    2013-10-01

    Phenomena consistent with self-collimation (or weak self-focusing) of laser target-normal-sheath-accelerated (TNSA) protons was experimentally observed for the first time, in a specially engineered structure (``lens'') consisting of a stack of 300 thin aluminum foils separated by 50 μm vacuum gaps. The experiments were carried out in a ``passive environment,'' i.e. no external fields applied, neutralization plasma or injection of secondary charged particles was imposed. Experiments were performed at the petawatt ``PHELIX'' laser user facility (E = 100 J, Δt = 400 fs, λ = 1062 nm) at the ``Helmholtzzentrum für Schwerionenforschung-GSI'' in Darmstadt, Germany. The observed rms beam spot reduction depends inversely on energy, with a focusing degree decreasing monotonically from 2 at 5.4 MeV to 1.5 MeV at 18.7 MeV. The physics inside the lens is complex, resulting in a number of different mechanisms that can potentially affect the particle dynamics within the structure. We present a plausible simple interpretation of the experiment in which the combination of magnetic self-pinch forces generated by the beam current together with the simultaneous reduction of the repulsive electrostatic forces due to the foils are the dominant mechanisms responsible for the observed focusing/collimation. This focusing technique could be applied to a wide variety of space-charge dominated proton and heavy ion beams and impact fields and applications, such as HEDP science, inertial confinement fusion in both fast ignition and heavy ion fusion approaches, compact laser-driven injectors for a LINAC or synchrotron, medical therapy, materials processing, etc.

  18. Experimental evidence for the interplay of exogenous and endogenous factors on the movement ecology of a migrating songbird.

    PubMed

    Cohen, Emily B; Moore, Frank R; Fischer, Richard A

    2012-01-01

    Movement patterns during songbird migration remain poorly understood despite their expected fitness consequences in terms of survival, energetic condition and timing of migration that will carry over to subsequent phases of the annual cycle. We took an experimental approach to test hypotheses regarding the influence of habitat, energetic condition, time of season and sex on the hour-by-hour, local movement decisions of a songbird during spring stopover. To simulate arrival of nocturnal migrants at unfamiliar stopover sites, we translocated and continuously tracked migratory red-eyed vireos (Vireo olivaceus) throughout spring stopover with and without energetic reserves that were released in two replicates of three forested habitat types. Migrants moved the most upon release, during which time they selected habitat characterized by greater food abundance and higher foraging attack rates. Presumably under pressure to replenish fuel stores necessary to continue migration in a timely fashion, migrants released in poorer energetic condition moved faster and further than migrants in better condition and the same pattern was true for migrants released late in spring relative to those released earlier. However, a migrant's energetic condition had less influence on their behavior when they were in poor quality habitat. Movement did not differ between sexes. Our study illustrates the importance of quickly finding suitable habitat at each stopover site, especially for energetically constrained migrants later in the season. If an initial period prior to foraging were necessary at each stop along a migrant's journey, non-foraging periods would cumulatively result in a significant energetic and time cost to migration. However, we suggest behavior during stopover is not solely a function of underlying resource distributions but is a complex response to a combination of endogenous and exogenous factors. PMID:22844528

  19. Experimental evidence of edge intrinsic momentum source driven by kinetic ion loss and edge radial electric fields in tokamaks

    NASA Astrophysics Data System (ADS)

    Boedo, J. A.; deGrassie, J. S.; Grierson, B.; Stoltzfus-Dueck, T.; Battaglia, D. J.; Rudakov, D. L.; Belli, E. A.; Groebner, R. J.; Hollmann, E.; Lasnier, C.; Solomon, W. M.; Unterberg, E. A.; Watkins, J.

    2016-09-01

    Bulk ion toroidal velocity profiles, V| | D + , peaking at 40-60 km/s are observed with Mach probes in a narrow edge region of DIII-D discharges without external momentum input. This intrinsic rotation can be well reproduced by a first principle, collisionless kinetic loss model of thermal ion loss that predicts the existence of a loss-cone distribution in velocity space resulting in a co-Ip directed velocity. We consider two kinetic models, one of which includes turbulence-enhanced momentum transport, as well as the Pfirsch-Schluter (P-S) fluid mechanism. We measure a fine structure of the boundary radial electric field, Er, insofar ignored, featuring large (10-20 kV/m) positive peaks in the scrape off layer (SOL) at, or slightly inside, the last closed flux surface of these low power L- and H-mode discharges in DIII-D. The Er structure significantly affects the ion-loss model, extended to account for a non-uniform electric field. We also find that V| | D + is reduced when the magnetic topology is changed from lower single null to upper single null. The kinetic ion loss model containing turbulence-enhanced momentum transport can explain the reduction, as we find that the potential fluctuations decay with radius, while we need to invoke a topology-enhanced collisionality on the simpler kinetic model. The P-S mechanism fails to reproduce the damping. We show a clear correlation between the near core V| | C 6 + velocity and the peak edge V| | D + in discharges with no external torque, further supporting the hypothesis that ion loss is the source for intrinsic torque in the present tokamaks. However, we also show that when external torque is injected in the core, it can complete with, and eventually overwhelm, the edge source, thus determining the near SOL flows. Finally, we show some additional evidence that the ion/electron distribution in the SOL is non-Maxwellian.

  20. Charge Transport in 4 nm Molecular Wires with Interrupted Conjugation: Combined Experimental and Computational Evidence for Thermally Assisted Polaron Tunneling.

    PubMed

    Taherinia, Davood; Smith, Christopher E; Ghosh, Soumen; Odoh, Samuel O; Balhorn, Luke; Gagliardi, Laura; Cramer, Christopher J; Frisbie, C Daniel

    2016-04-26

    We report the synthesis, transport measurements, and electronic structure of conjugation-broken oligophenyleneimine (CB-OPI 6) molecular wires with lengths of ∼4 nm. The wires were grown from Au surfaces using stepwise aryl imine condensation reactions between 1,4-diaminobenzene and terephthalaldehyde (1,4-benzenedicarbaldehyde). Saturated spacers (conjugation breakers) were introduced into the molecular backbone by replacing the aromatic diamine with trans-1,4-diaminocyclohexane at specific steps during the growth processes. FT-IR and ellipsometry were used to follow the imination reactions on Au surfaces. Surface coverages (∼4 molecules/nm(2)) and electronic structures of the wires were determined by cyclic voltammetry and UV-vis spectroscopy, respectively. The current-voltage (I-V) characteristics of the wires were acquired using conducting probe atomic force microscopy (CP-AFM) in which an Au-coated AFM probe was brought into contact with the wires to form metal-molecule-metal junctions with contact areas of ∼50 nm(2). The low bias resistance increased with the number of saturated spacers, but was not sensitive to the position of the spacer within the wire. Temperature dependent measurements of resistance were consistent with a localized charge (polaron) hopping mechanism in all of the wires. Activation energies were in the range of 0.18-0.26 eV (4.2-6.0 kcal/mol) with the highest belonging to the fully conjugated OPI 6 wire and the lowest to the CB3,5-OPI 6 wire (the wire with two saturated spacers). For the two other wires with a single conjugation breaker, CB3-OPI 6 and CB5-OPI 6, activation energies of 0.20 eV (4.6 kcal/mol) and 0.21 eV (4.8 kcal/mol) were found, respectively. Computational studies using density functional theory confirmed the polaronic nature of charge carriers but predicted that the semiclassical activation energy of hopping should be higher for CB-OPI molecular wires than for the OPI 6 wire. To reconcile the experimental and

  1. Experimental growth of åkermanite reaction rims between wollastonite and monticellite: evidence for volume diffusion control

    NASA Astrophysics Data System (ADS)

    Joachim, Bastian; Gardés, Emmanuel; Abart, Rainer; Heinrich, Wilhelm

    2011-03-01

    Growth rates of monomineralic, polycrystalline åkermanite (Ca2MgSi2O7) rims produced by solid-state reactions between monticellite (CaMgSiO4) and wollastonite (CaSiO3) single crystals were determined at 0.5 GPa dry argon pressure, 1,000-1,200°C and 5 min to 60 h, using an internally heated pressure vessel. Inert Pt-markers, initially placed at the monticellite-wollastonite interface, indicate symmetrical growth into both directions. This and mass balance considerations demonstrate that rim growth is controlled by transport of MgO. At 1,200°C and run durations between 5 min and 60 h, rim growth follows a parabolic rate law with rim widths ranging from 0.4 to 16.3 μm indicating diffusion-controlled rim growth. The effective bulk diffusion coefficient D_{{eff,MgO}}^{{Ak}} is calculated to 10-15.8±0.1 m2 s-1. Between 1,000°C and 1,200°C, the effective bulk diffusion coefficient follows an Arrhenius law with E a = 204 ± 18 kJ/mol and D 0 = 10-8.6±1.6 m2 s-1. Åkermanite grains display a palisade texture with elongation perpendicular to the reaction interface. At 1,200°C, average grain widths measured normal to elongation, increase with the square root of time and range from 0.4 to 5.4 μm leading to a successive decrease in the grain boundary area fraction, which, however, does not affect D_{{eff,MgO}}^{{Ak}} to a detectible extent. This implies that grain boundary diffusion only accounts for a minor fraction of the overall chemical mass transfer, and rim growth is essentially controlled by volume diffusion. This is corroborated by the agreement between our estimates of the effective MgO bulk diffusion coefficient and experimentally determined volume diffusion data for Mg and O in åkermanite from the literature. There is sharp contrast to the MgO-SiO2 binary system, where grain boundary diffusion controls rim growth.

  2. Charge Transport in 4 nm Molecular Wires with Interrupted Conjugation: Combined Experimental and Computational Evidence for Thermally Assisted Polaron Tunneling.

    PubMed

    Taherinia, Davood; Smith, Christopher E; Ghosh, Soumen; Odoh, Samuel O; Balhorn, Luke; Gagliardi, Laura; Cramer, Christopher J; Frisbie, C Daniel

    2016-04-26

    We report the synthesis, transport measurements, and electronic structure of conjugation-broken oligophenyleneimine (CB-OPI 6) molecular wires with lengths of ∼4 nm. The wires were grown from Au surfaces using stepwise aryl imine condensation reactions between 1,4-diaminobenzene and terephthalaldehyde (1,4-benzenedicarbaldehyde). Saturated spacers (conjugation breakers) were introduced into the molecular backbone by replacing the aromatic diamine with trans-1,4-diaminocyclohexane at specific steps during the growth processes. FT-IR and ellipsometry were used to follow the imination reactions on Au surfaces. Surface coverages (∼4 molecules/nm(2)) and electronic structures of the wires were determined by cyclic voltammetry and UV-vis spectroscopy, respectively. The current-voltage (I-V) characteristics of the wires were acquired using conducting probe atomic force microscopy (CP-AFM) in which an Au-coated AFM probe was brought into contact with the wires to form metal-molecule-metal junctions with contact areas of ∼50 nm(2). The low bias resistance increased with the number of saturated spacers, but was not sensitive to the position of the spacer within the wire. Temperature dependent measurements of resistance were consistent with a localized charge (polaron) hopping mechanism in all of the wires. Activation energies were in the range of 0.18-0.26 eV (4.2-6.0 kcal/mol) with the highest belonging to the fully conjugated OPI 6 wire and the lowest to the CB3,5-OPI 6 wire (the wire with two saturated spacers). For the two other wires with a single conjugation breaker, CB3-OPI 6 and CB5-OPI 6, activation energies of 0.20 eV (4.6 kcal/mol) and 0.21 eV (4.8 kcal/mol) were found, respectively. Computational studies using density functional theory confirmed the polaronic nature of charge carriers but predicted that the semiclassical activation energy of hopping should be higher for CB-OPI molecular wires than for the OPI 6 wire. To reconcile the experimental and

  3. Long-term geochemical evolution of the near field repository: insights from reactive transport modelling and experimental evidences.

    PubMed

    Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M; Villar, María V; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

    2008-12-12

    The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral

  4. Long-term geochemical evolution of the near field repository: insights from reactive transport modelling and experimental evidences.

    PubMed

    Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M; Villar, María V; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

    2008-12-12

    The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral

  5. Vertical linear feeder to elliptical igneous saucer-shaped sills: evidences from structural observations, geochemistry and experimental modeling

    NASA Astrophysics Data System (ADS)

    Galerne, C. Y.; Galland, O.; Neumann, E. R.; Planke, S.

    2009-12-01

    The structural relationships between sills and their feeders are poorly documented because they are rarely observed in the field and difficult to image on seismic data. For instance, it is unclear whether sills are fed by pipes, dikes or other sills. Nevertheless, the geometrical relationships between sills and their feeders provide first-order constraints on magma emplacement mechanisms. Here, we investigate the structural and geochemical relationships between sills and potential feeder dikes in a remarkably well-preserved and exposed sill complex, the Golden Valley Sill Complex (GVSC), Karoo Basin, South Africa. The GVSC consists of five major saucer-shaped sills and six dikes. The Golden Valley sill itself is an elliptical saucer, with a N-S trend. A one meter thick dike (D4) crops out underneath the southern tip of the Golden Valley sill. The strike of this dike is parallel to the long axis of the Golden Valley sill. Detailed sampling and geochemical analyses of the GVSC show that each sill and dike exhibits a specific geochemical signature. The Golden Valley sill and its underlying dike D4 have identical signatures. Although there is no clear structural evidence, the consistent geometrical and geochemical relationships between the Golden Valley sill and the D4 dike suggest that this vertical linear structure is the feeder of the overlying saucer-shaped sill. In order to investigate the relationships between sills and feeders, we resorted to scaled laboratory experiments. The experiments consisted of a low-viscosity vegetable oil representing magma and a cohesive fine-grained silica flour representing brittle rocks. We placed a horizontal weak layer into the silica flour, just above the top of the inlet, to simulate strata. Such a weak layer controlled the formation of horizontal sill that subsequently turned into a transgressive sheet leading to the formation of a saucer geometry. We ran experiments with varying inlet shapes: 1) a point inlet representing a

  6. Long-term geochemical evolution of the near field repository: Insights from reactive transport modelling and experimental evidences

    NASA Astrophysics Data System (ADS)

    Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M.; Villar, María V.; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

    2008-12-01

    The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral

  7. A Review of Evidence for High Life Coefficients on Propeller and Rotor Blades Under Static Thrust Conditions with Some New Experimental Results

    NASA Technical Reports Server (NTRS)

    Talbot, Peter D.; Meyer, Mark; Branum, Lonnie; Burks, John S. (Technical Monitor)

    1994-01-01

    Interest has increased recently in the thrust-producing capability of rotors at very high collective pitch angles. An early reference noted this behaviour in rotors and offered alternative models for section lift characteristics to explain it. The same phenomenon was coincidentally noted and used in a propeller code, resulting in very good correlation with static thrust data. The proposed paper will present experimental data demonstrating the pronounced persistence of thrust for propellers at increasing collective pitch angles. Comparisons with blade element/momentum theory will be made. These results are expected to point to the need to define (ultimately to explain) aerodynamic lift and drag behaviour in a rotating environment. Experimental measurements made by the U.S. Army Aeroflightdynamics Directorate at the Ames Research Center have shown that locally measured normal force coefficients along the span of a highly twisted rotor blade continue to increase at high values of collective pitch. In some cases these coefficients exceed expected values for the same type of airfoil tested under two dimensional conditions. To date no one to the authors' knowledge has defined the variation of C(n) with pitch for very high angles (to 45 deg) in a rotating environment and for a blade of reasonably high aspect ratio; however, total propeller thrust measurements support the idea that stalling does not occur in the same way as on a wing. This paper will present experimental data in the form of surface pressure distributions as well as flow visualization (microtufts) to explore the aerodynamic behavior of the rotating airfoil at high values of blade incidence. This paper also reviews experimental evidence and infers some high lift coefficient behavior from it. Comparisons between predicted thrust, utilizing modified airfoil characteristics and a blade element model, and measured thrust for both rotors and propellers that cover the extremes of collective pitch are shown and

  8. Flow and transport at the hillslope scale: New experimental evidence from whole-hillslope irrigation and excavations

    NASA Astrophysics Data System (ADS)

    Graham, C. B.; McDonnell, J. J.; Woods, R.

    2007-12-01

    Lateral subsurface flowpaths and flow velocities are poorly quantified. The controls on subsurface flow characteristics are needed for better modeling of nutrient and contaminant transport and flood prediction. We present results from a whole-hillslope investigation designed to characterize unsaturated zone subsurface flow paths and velocities. Specifically, we address the questions: What are flow velocities of lateral subsurface flow at the soil bedrock interface? What controls flowpath location and extent? We performed two irrigation experiments on a 6m (parallel to stream) by 8m (upslope) section of hillslope at the Woods and Rowe Maimai experimental hillslope on the South Island of New Zealand. Lateral flow on this hillslope is monitored at an exposed trench face. In the first experiment water with a dye was pumped into a pit excavated to bedrock 8 meters upslope the hillslope base until steady state conditions were reached at the trench face. Flowpath locations were then identified by excavating soil in 0.2-0.3 m slices upslope from the trench. A Bromide solution was injected every 0.4-0.6 m to determine flow velocities. The second experiment was identical except that water was applied on the soil surface as a line 4 m upslope of the trench. Once the hillslope was cleared of soil, the irrigation experiment was repeated on the exposed bedrock. A very high resolution DEM (grid spacing = 5mm) of bedrock topography was constructed using a Trimble laser scanner. The dominant subsurface flow paths were continuous and predominantly at the soil bedrock interface, less than 0.1 m above the bedrock in both experiments. In the pit experiment unbroken flow paths along the entire 8m excavated hillslope were observed. In the second experiment water applied to the soil surface moved via subvertical cracks through the soil profile for <1.5m and then traveled laterally along the bedrock interface. The bedrock topography proved to be the dominant control on flowpath locations

  9. Nutrition, weight gain and eating behavior in pregnancy: a review of experimental evidence for long-term effects on the risk of obesity in offspring.

    PubMed

    Sen, Sarbattama; Carpenter, Arielle H; Hochstadt, Jessica; Huddleston, Juli Y; Kustanovich, Vladimir; Reynolds, Ashley A; Roberts, Susan

    2012-08-20

    Obesity has reached near epidemic proportions in the developed world. As reproductive age women are a part of this trend, the effect of maternal obesity on the developing fetus must be investigated. In this review, we evaluated the experimental evidence relating maternal nutritional status and eating behavior before and during pregnancy on the risk of obesity in the offspring. The studies were compiled and selected based on their methodologies, study design and relevance. The analyzed studies were compiled to quantify, if possible, the relationship between maternal and offspring weight. Descriptive and observational studies were also included if they were seminal in the field. Based on the current data, maternal obesity is a critical factor exacerbating multigenerational obesity. Mechanistic studies, mainly in animals, have identified potential areas for intervention which might limit transmission of adverse risk factors for obesity from mothers to infants during pregnancy.

  10. Multiple intra-tube junctions in the inner tube of peapod-derived double walled carbon nanotubes: theoretical study and experimental evidence.

    PubMed

    Xu, Ziwei; Li, Hui; Fujisawa, Kazunori; Kim, Yoong Ahm; Endo, Morinobu; Ding, Feng

    2012-01-01

    The coalescence process of fullerenes in the hollow core of single walled carbon nanotubes is systematically explored by the kinetic Monte Carlo method. Two elongation (or growth) modes via the coalescence (i) between an inner tube and fullerenes and (ii) between neighboring inner tubes are identified. It is found that the coalescence of two inner tubes mostly creates a very stable intra-tube junction which is composed of multiple pentagon-heptagon pairs. As a consequence, the study predicts that the inner tube of peapod derived double walled carbon nanotubes (DWNTs) must contain many intra-tube junctions. Careful high resolution transmission electron microscopy observation on peapod-grown DWNT sample provides experimental evidence of the presence of the junctions.

  11. Enhancing the gene-environment interaction framework through a quasi-experimental research design: evidence from differential responses to September 11.

    PubMed

    Fletcher, Jason M

    2014-01-01

    This article uses a gene-environment interaction framework to examine the differential responses to an objective external stressor based on genetic variation in the production of depressive symptoms. This article advances the literature by utilizing a quasi-experimental environmental exposure design, as well as a regression discontinuity design, to control for seasonal trends, which limit the potential for gene-environment correlation and allow stronger causal claims. Replications are attempted for two prominent genes (5-HTT and MAOA), and three additional genes are explored (DRD2, DRD4, and DAT1). This article provides evidence of a main effect of 9/11 on reports of feelings of sadness and fails to replicate a common finding of interaction using 5-HTT but does show support for interaction with MAOA in men. It also provides new evidence that variation in the DRD4 gene modifies an individual's response to the exposure, with individuals with no 7-repeats found to have a muted response.

  12. Enhancing the gene-environment interaction framework through a quasi-experimental research design: evidence from differential responses to September 11.

    PubMed

    Fletcher, Jason M

    2014-01-01

    This article uses a gene-environment interaction framework to examine the differential responses to an objective external stressor based on genetic variation in the production of depressive symptoms. This article advances the literature by utilizing a quasi-experimental environmental exposure design, as well as a regression discontinuity design, to control for seasonal trends, which limit the potential for gene-environment correlation and allow stronger causal claims. Replications are attempted for two prominent genes (5-HTT and MAOA), and three additional genes are explored (DRD2, DRD4, and DAT1). This article provides evidence of a main effect of 9/11 on reports of feelings of sadness and fails to replicate a common finding of interaction using 5-HTT but does show support for interaction with MAOA in men. It also provides new evidence that variation in the DRD4 gene modifies an individual's response to the exposure, with individuals with no 7-repeats found to have a muted response. PMID:24784984

  13. In vivo evidence for CD4+ and CD8+ suppressor T cells in vaccination-induced suppression of murine experimental autoimmune thyroiditis

    SciTech Connect

    Flynn, J.C.; Kong, Y.C. )

    1991-09-01

    In several experimental autoimmune diseases, including experimental autoimmune thyroiditis (EAT), vaccination with attenuated autoantigen-specific T cells has provided protection against subsequent induction of disease. However, the mechanism(s) of vaccination-induced suppression remains to be clarified. Since the authors have previously shown that suppression generated by pretreatment with mouse thyroglobulin (MTg) or thyroid-stimulating hormone in EAT is mediated by CD4+, not CD8+, suppressor T cells, they examined the role of T cell subsets in vaccination-induced suppression of EAT. Mice were vaccinated with irradiated, MTg-primed, and MTg-activated spleen cells and then challenged. Pretreatment with these cells suppressed EAT induced by immunization with MTg and adjuvant, but not by adoptive transfer of thyroiditogenic cells, suggesting a mechanism of afferent suppression. The activation of suppressor mechanisms did not require CD8+ cells, since mice depleted of CD8+ cells before vaccination showed reduced EAT comparable to control vaccinated mice. Furthermore, depletion of either the CD4+ or the CD8+ subset after vaccination did not significantly abrogate suppression. However, suppression was eliminated by the depletion of both CD4+ and CD8+ cells in vaccinated mice. These results provide evidence for the cooperative effects of CD4+ and CD8+ T cells in vaccination-induced suppression of EAT.

  14. Experimental evidence for kinetic effects on B/Ca in synthetic calcite: Implications for potential B(OH)4- and B(OH)3 incorporation

    NASA Astrophysics Data System (ADS)

    Uchikawa, Joji; Penman, Donald E.; Zachos, James C.; Zeebe, Richard E.

    2015-02-01

    The boron to calcium ratio (B/Ca) in biogenic CaCO3 is being increasingly utilized as a proxy for past ocean carbonate chemistry. However, B/Ca of cultured and core-top foraminifers show dependence on multiple physicochemical seawater properties and only a few of those have been inorganically tested for their impacts. Accordingly, our understanding of the controls on foraminiferal B/Ca and thus how to interpret B/Ca in fossil shells is incomplete. To gain a clearer understanding of the B incorporation mechanism, we performed inorganic calcite precipitation experiments using a pH-stat system. As previously reported, we confirm that B/Ca in calcite increases with both fluid pH and total B concentration (denoted as [BT], where [BT] = [B(OH)3] + [B(OH)4-]). We provide the first evidence that B/Ca also increases with the concentration of total dissolved inorganic carbon (DIC) and calcium ion. With the exception of the [BT] experiments, these chemical manipulations were accompanied by an increase in calcite saturation, and accordingly precipitation rate (denoted as R). But when pH and [Ca2+] were jointly varied at a fixed saturation level to maintain relatively constant R at different pH and [Ca2+] combinations, B/Ca was insensitive to both pH and [Ca2+] changes. These experimental results unequivocally suggest kinetic effects related to R on B/Ca. Furthermore, with a suite of chemical manipulations we found that the B/Ca variability is explicable by just R and the [BT]/[DIC] ratio in the parent fluids. This observation was particularly robust for relatively rapidly precipitated samples, whereas for relatively slowly precipitated samples, it was somewhat ambiguous whether the [BT]/[DIC] or [B(OH)4-]/[HCO3-] ratio provides a better fit to the experimental data. Nonetheless, our experimental results can be considered as indirect evidence for incorporation of both B(OH)4- and B(OH)3 into calcite. We propose a simple mathematical expression to describe the mode of B

  15. Experimental evidence of coherent transport

    PubMed Central

    Flores-Olmedo, E.; Martínez-Argüello, A. M.; Martínez-Mares, M.; Báez, G.; Franco-Villafañe, J. A.; Méndez-Sánchez, R. A.

    2016-01-01

    Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations. PMID:27121226

  16. Experimental evidence of coherent transport.

    PubMed

    Flores-Olmedo, E; Martínez-Argüello, A M; Martínez-Mares, M; Báez, G; Franco-Villafañe, J A; Méndez-Sánchez, R A

    2016-04-28

    Coherent transport phenomena are difficult to observe due to several sources of decoherence. For instance, in the electronic transport through quantum devices the thermal smearing and dephasing, the latter induced by inelastic scattering by phonons or impurities, destroy phase coherence. In other wave systems, the temperature and dephasing may not destroy the coherence and can then be used to observe the underlying wave behaviour of the coherent phenomena. Here, we observe coherent transmission of mechanical waves through a two-dimensional elastic Sinai billiard with two waveguides. The flexural-wave transmission, performed by non-contact means, shows the quantization when a new mode becomes open. These measurements agree with the theoretical predictions of the simplest model highlighting the universal character of the transmission fluctuations.

  17. Improving implementation of evidence-based practice in mental health service delivery: protocol for a cluster randomised quasi-experimental investigation of staff-focused values interventions

    PubMed Central

    2013-01-01

    Background There is growing acceptance that optimal service provision for individuals with severe and recurrent mental illness requires a complementary focus on medical recovery (i.e., symptom management and general functioning) and personal recovery (i.e., having a ‘life worth living’). Despite significant research attention and policy-level support, the translation of this vision of healthcare into changed workplace practice continues to elude. Over the past decade, evidence-based training interventions that seek to enhance the knowledge, attitudes, and skills of staff working in the mental health field have been implemented as a primary redress strategy. However, a large body of multi-disciplinary research indicates disappointing rates of training transfer. There is an absence of empirical research that investigates the importance of worker-motivation in the uptake of desired workplace change initiatives. ‘Autonomy’ is acknowledged as important to human effectiveness and as a correlate of workplace variables like productivity, and wellbeing. To our knowledge, there have been no studies that investigate purposeful and structured use of values-based interventions to facilitate increased autonomy as a means of promoting enhanced implementation of workplace change. Methods This study involves 200 mental health workers across 22 worksites within five community-managed organisations in three Australian states. It involves cluster-randomisation of participants within organisation, by work site, to the experimental (values) condition, or the control (implementation). Both conditions receive two days of training focusing on an evidence-based framework of mental health service delivery. The experimental group receives a third day of values-focused intervention and 12 months of values-focused coaching. Well-validated self-report measures are used to explore variables related to values concordance, autonomy, and self-reported implementation success. Audits of work

  18. Experimental evidence for the evolution of indirect genetic effects: changes in the interaction effect coefficient, psi (Psi), due to sexual selection.

    PubMed

    Chenoweth, Stephen F; Rundle, Howard D; Blows, Mark W

    2010-06-01

    Indirect genetics effects (IGEs)--when the genotype of one individual affects the phenotypic expression of a trait in another--may alter evolutionary trajectories beyond that predicted by standard quantitative genetic theory as a consequence of genotypic evolution of the social environment. For IGEs to occur, the trait of interest must respond to one or more indicator traits in interacting conspecifics. In quantitative genetic models of IGEs, these responses (reaction norms) are termed interaction effect coefficients and are represented by the parameter psi (Psi). The extent to which Psi exhibits genetic variation within a population, and may therefore itself evolve, is unknown. Using an experimental evolution approach, we provide evidence for a genetic basis to the phenotypic response caused by IGEs on sexual display traits in Drosophila serrata. We show that evolution of the response is affected by sexual but not natural selection when flies adapt to a novel environment. Our results indicate a further mechanism by which IGEs can alter evolutionary trajectories--the evolution of interaction effects themselves.

  19. New Insights into the Negative Thermal Expansion: Direct Experimental Evidence for the "Guitar-String" Effect in Cubic ScF3.

    PubMed

    Hu, Lei; Chen, Jun; Sanson, Andrea; Wu, Hui; Guglieri Rodriguez, Clara; Olivi, Luca; Ren, Yang; Fan, Longlong; Deng, Jinxia; Xing, Xianran

    2016-07-13

    The understanding of the negative thermal expansion (NTE) mechanism remains challenging but critical for the development of NTE materials. This study sheds light on NTE of ScF3, one of the most outstanding materials with NTE. The local dynamics of ScF3 has been investigated by a combined analysis of synchrotron-based X-ray total scattering, extended X-ray absorption fine structure, and neutron powder diffraction. Very interestingly, we observe that (i) the Sc-F nearest-neighbor distance strongly expands with increasing temperature, while the Sc-Sc next-nearest-neighbor distance contracts, (ii) the thermal ellipsoids of relative vibrations between Sc-F nearest-neighbors are highly elongated in the direction perpendicular to the Sc-F bond, indicating that the Sc-F bond is much softer to bend than to stretch, and (iii) there is mainly dynamically transverse motion of fluorine atoms, rather than static shifts. These results are direct experimental evidence for the NTE mechanism, in which the rigid unit is not necessary for the occurrence of NTE, and the key role is played by the transverse thermal vibrations of fluorine atoms through the "guitar-string" effect. PMID:27336200

  20. New Insights into the Negative Thermal Expansion: Direct Experimental Evidence for the "Guitar-String" Effect in Cubic ScF3.

    PubMed

    Hu, Lei; Chen, Jun; Sanson, Andrea; Wu, Hui; Guglieri Rodriguez, Clara; Olivi, Luca; Ren, Yang; Fan, Longlong; Deng, Jinxia; Xing, Xianran

    2016-07-13

    The understanding of the negative thermal expansion (NTE) mechanism remains challenging but critical for the development of NTE materials. This study sheds light on NTE of ScF3, one of the most outstanding materials with NTE. The local dynamics of ScF3 has been investigated by a combined analysis of synchrotron-based X-ray total scattering, extended X-ray absorption fine structure, and neutron powder diffraction. Very interestingly, we observe that (i) the Sc-F nearest-neighbor distance strongly expands with increasing temperature, while the Sc-Sc next-nearest-neighbor distance contracts, (ii) the thermal ellipsoids of relative vibrations between Sc-F nearest-neighbors are highly elongated in the direction perpendicular to the Sc-F bond, indicating that the Sc-F bond is much softer to bend than to stretch, and (iii) there is mainly dynamically transverse motion of fluorine atoms, rather than static shifts. These results are direct experimental evidence for the NTE mechanism, in which the rigid unit is not necessary for the occurrence of NTE, and the key role is played by the transverse thermal vibrations of fluorine atoms through the "guitar-string" effect.