Science.gov

Sample records for export-led growth hypothesis

  1. Temperature spans for growth: Hypothesis and discussion

    SciTech Connect

    Wiegel, J. )

    1990-01-01

    In recent years the upper and lower temperature limits for growth of pure cultures of microorganisms have been extended at least to 110C and [minus]14C, respectively. There are no organisms which grow at both 0C and 100C and, therefore, organisms are grouped according to their ranges of growth temperatures. Thus, the questions of importance are: (1) What is the widest temperature range (temperature span) over which a single organism can grow and (2) How much can one alter the temperature spans of an organism The concept of cryptic thermophiles' is used to explain some of the published data on the latter question. A wider temperature range can be very important for organisms in various ways, since it makes an organism more versatile with regard to changes in the environment. Also, it enables the organism to utilize a wider range of ecological niches. Some aerobic and anaerobic extreme thermophiles will grow within a span of more than 40C. Furthermore, such organisms are regarded suitable for biotechnological applications as well. The following hypothesis is presented and discussed: these organisms have two sets of key enzymes, and their synthesis is regulated by temperature. Such organisms are capable of growing in two different ranges, such as the mesophilic and thermophilic ranges. The hypothesis is based on the fact that these bacteria exhibit broken Arrhenius plots, and is illustrated with 'temperature tolerant extreme thermophiles' as the major example. However, the hypothesis is not restricted to this group, but it also applicable to the 'temperature tolerant thermophiles and mesophiles'.

  2. General hypothesis governing the growth of single-crystal nanowires

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2010-06-01

    The growth and growth rates of single-crystal nanowires by vapor phase mechanisms have been studied. A hypothesis has been proposed, which lays down foundation for the nanowire growth. It redefines the basic concepts of droplets from seeds and describes the fundamental basis of the adhesive properties of droplets. A set of droplet characteristics has been defined, a model in the framework of the hypothesis has been developed, and theoretical calculations have been performed. Experiments have also been carried out. Close correspondences between the theoretical and the experimental results lend support for the hypothesis and the model. Additional experimental evidences quantify the validity of the hypothesis. The calculated results resolve conflicts and controversies. They address the roles of catalysts in the growth of single-crystal nanowires. They shed light on the basic differences in the growth of thin and thick nanowires. They elucidate possible relationship between eutectic temperature and activation energy in the vapor-liquid-solid growth. They provide ground rules that govern the relative supplies of constituent vapor species for the growth of compound semiconductor nanowires. They explain how the same alloyed droplet (e.g., Au/Ga) is activated differently under the influence of different nonmetal elements of different nanowires (for example, As of GaAs, P of GaP, and N of GaN). They demonstrate, for example, that the nanowire growth may be achieved by means that creates thermodynamic imbalance and nanopores inside the seeds at temperatures far below the seed's melting temperature. Alloying in the vapor-solid-liquid mechanism is one such means where growth of even thick nanowires (radius of rD≥50 nm) is possible at temperatures far below the eutectic temperature. The hypothesis, is called the simple, novel, and malleable (SNM) hypothesis. This hypothesis, together with the model, appears to have solved the basic origin of the nanowire growth. It

  3. Isotopic Resonance Hypothesis: Experimental Verification by Escherichia coli Growth Measurements

    NASA Astrophysics Data System (ADS)

    Xie, Xueshu; Zubarev, Roman A.

    2015-03-01

    Isotopic composition of reactants affects the rates of chemical and biochemical reactions. As a rule, enrichment of heavy stable isotopes leads to progressively slower reactions. But the recent isotopic resonance hypothesis suggests that the dependence of the reaction rate upon the enrichment degree is not monotonous. Instead, at some ``resonance'' isotopic compositions, the kinetics increases, while at ``off-resonance'' compositions the same reactions progress slower. To test the predictions of this hypothesis for the elements C, H, N and O, we designed a precise (standard error +/-0.05%) experiment that measures the parameters of bacterial growth in minimal media with varying isotopic composition. A number of predicted resonance conditions were tested, with significant enhancements in kinetics discovered at these conditions. The combined statistics extremely strongly supports the validity of the isotopic resonance phenomenon (p << 10-15). This phenomenon has numerous implications for the origin of life studies and astrobiology, and possible applications in agriculture, biotechnology, medicine, chemistry and other areas.

  4. Isotopic Resonance Hypothesis: Experimental Verification by Escherichia coli Growth Measurements

    PubMed Central

    Zubarev, Roman A.

    2015-01-01

    Isotopic composition of reactants affects the rates of chemical and biochemical reactions. As a rule, enrichment of heavy stable isotopes leads to progressively slower reactions. But the recent isotopic resonance hypothesis suggests that the dependence of the reaction rate upon the enrichment degree is not monotonous. Instead, at some “resonance” isotopic compositions, the kinetics increases, while at “off-resonance” compositions the same reactions progress slower. To test the predictions of this hypothesis for the elements C, H, N and O, we designed a precise (standard error ±0.05%) experiment that measures the parameters of bacterial growth in minimal media with varying isotopic composition. A number of predicted resonance conditions were tested, with significant enhancements in kinetics discovered at these conditions. The combined statistics extremely strongly supports the validity of the isotopic resonance phenomenon (p ≪ 10−15). This phenomenon has numerous implications for the origin of life studies and astrobiology, and possible applications in agriculture, biotechnology, medicine, chemistry and other areas. PMID:25782666

  5. Competitiveness and economic growth: a test of Schumpeter's hypothesis.

    PubMed

    Yang, Bijou; Lester, David

    2003-12-01

    A study of 36 nations indicated that measures of economic growth for the period 1980-1995 were not predicted by scores of national samples in the mid-1980s on a measure of competitiveness. PMID:14723427

  6. Does the Slow-Growth, High-Mortality Hypothesis Apply Below Ground?

    PubMed

    Hourston, James E; Bennett, Alison E; Johnson, Scott N; Gange, Alan C

    2016-01-01

    Belowground tri-trophic study systems present a challenging environment in which to study plant-herbivore-natural enemy interactions. For this reason, belowground examples are rarely available for testing general ecological theories. To redress this imbalance, we present, for the first time, data on a belowground tri-trophic system to test the slow growth, high mortality hypothesis. We investigated whether the differing performance of entomopathogenic nematodes (EPNs) in controlling the common pest black vine weevil Otiorhynchus sulcatus could be linked to differently resistant cultivars of the red raspberry Rubus idaeus. The O. sulcatus larvae recovered from R. idaeus plants showed significantly slower growth and higher mortality on the Glen Rosa cultivar, relative to the more commercially favored Glen Ample cultivar creating a convenient system for testing this hypothesis. Heterorhabditis megidis was found to be less effective at controlling O. sulcatus than Steinernema kraussei, but conformed to the hypothesis. However, S. kraussei maintained high levels of O. sulcatus mortality regardless of how larval growth was influenced by R. idaeus cultivar. We link this to direct effects that S. kraussei had on reducing O. sulcatus larval mass, indicating potential sub-lethal effects of S. kraussei, which the slow-growth, high-mortality hypothesis does not account for. Possible origins of these sub-lethal effects of EPN infection and how they may impact on a hypothesis designed and tested with aboveground predator and parasitoid systems are discussed.

  7. Does the Slow-Growth, High-Mortality Hypothesis Apply Below Ground?

    PubMed Central

    Bennett, Alison E.; Johnson, Scott N.; Gange, Alan C.

    2016-01-01

    Belowground tri-trophic study systems present a challenging environment in which to study plant-herbivore-natural enemy interactions. For this reason, belowground examples are rarely available for testing general ecological theories. To redress this imbalance, we present, for the first time, data on a belowground tri-trophic system to test the slow growth, high mortality hypothesis. We investigated whether the differing performance of entomopathogenic nematodes (EPNs) in controlling the common pest black vine weevil Otiorhynchus sulcatus could be linked to differently resistant cultivars of the red raspberry Rubus idaeus. The O. sulcatus larvae recovered from R. idaeus plants showed significantly slower growth and higher mortality on the Glen Rosa cultivar, relative to the more commercially favored Glen Ample cultivar creating a convenient system for testing this hypothesis. Heterorhabditis megidis was found to be less effective at controlling O. sulcatus than Steinernema kraussei, but conformed to the hypothesis. However, S. kraussei maintained high levels of O. sulcatus mortality regardless of how larval growth was influenced by R. idaeus cultivar. We link this to direct effects that S. kraussei had on reducing O. sulcatus larval mass, indicating potential sub-lethal effects of S. kraussei, which the slow-growth, high-mortality hypothesis does not account for. Possible origins of these sub-lethal effects of EPN infection and how they may impact on a hypothesis designed and tested with aboveground predator and parasitoid systems are discussed. PMID:27571368

  8. Patterns of fluctuating asymmetry in developing primary feathers: a test of the compensational growth hypothesis

    PubMed Central

    Aparicio, J. M.

    1998-01-01

    The study of asymmetry ontogeny may reveal the mechanisms controlling the development of bilaterally symmetrical characters and the causes of asymmetry. In birds, flight feather asymmetries appear to increase at the beginning of growth and decrease at the end of their development. It has been proposed that such a pattern could be proximately caused by a developmental mechanism of compensational growth between the left and right wings, which should act to restore trait symmetry at the end of growth. In this study, I tested the hypothesis of the existence of a mechanism of compensational growth by performing an experiment, which consisted of provoking small asymmetries in the seventh primary feathers of house sparrows (Passer domesticus) by inducing the two feathers (one each side) to moult two days apart. On each side, the feathers grew in a similar way, independently of the growth of the other side. Feather length asymmetries were shortened with the advance of growth. However, the differences in time of growth persisted throughout development. These results do not support the existence of a mechanism of compensational growth. Primary feathers' asymmetries could decrease at the end of growth because the growth of the two feathers follows a programmed trajectory, which tends towards a certain maximum potential size.

  9. Testing the growth-differentiation balance hypothesis: dynamic responses of willows to nutrient availability.

    PubMed

    Glynn, Carolyn; Herms, Daniel A; Orians, Colin M; Hansen, Robert C; Larsson, Stig

    2007-01-01

    Here, the growth-differentiation balance hypothesis (GDBH) was tested by quantifying temporal variation in the relative growth rate (RGR), net assimilation rate (NAR), and phenylpropanoid concentrations of two willow species (Salix sericea and Salix eriocephala) across five fertility levels. Initially, RGR increased and total phenylpropanoids declined (although every individual phenolic did not) as fertility increased, but NAR was unaffected. Subsequently, NAR and phenylpropanoids declined in the low fertility treatment, generating a quadratic response of secondary metabolism across the nutrient gradient. As above- and below-ground growth rates equilibrated, NAR and phenylpropanoids increased in the low fertility treatment, re-establishing a negative linear effect of fertility on secondary metabolism. A transient quadratic response of secondary metabolism is predicted when GDBH is integrated with models of optimal phenotypic plasticity, occurring when low NAR imposes carbon constraints on secondary metabolism in low nutrient environments. Once plants acclimate to nutrient limitation, the equilibrium allocation state is predicted to be a negative correlation between growth and secondary metabolism. Although both willow species generally responded according to GDBH, the complexity observed suggests that prediction of the effects of nutrient availability on secondary metabolism (and other plastic responses) in specific cases requires a priori knowledge of the physiological status of the plant and soil nutrient availability.

  10. Testing the growth-differentiation balance hypothesis: dynamic responses of willows to nutrient availability.

    PubMed

    Glynn, Carolyn; Herms, Daniel A; Orians, Colin M; Hansen, Robert C; Larsson, Stig

    2007-01-01

    Here, the growth-differentiation balance hypothesis (GDBH) was tested by quantifying temporal variation in the relative growth rate (RGR), net assimilation rate (NAR), and phenylpropanoid concentrations of two willow species (Salix sericea and Salix eriocephala) across five fertility levels. Initially, RGR increased and total phenylpropanoids declined (although every individual phenolic did not) as fertility increased, but NAR was unaffected. Subsequently, NAR and phenylpropanoids declined in the low fertility treatment, generating a quadratic response of secondary metabolism across the nutrient gradient. As above- and below-ground growth rates equilibrated, NAR and phenylpropanoids increased in the low fertility treatment, re-establishing a negative linear effect of fertility on secondary metabolism. A transient quadratic response of secondary metabolism is predicted when GDBH is integrated with models of optimal phenotypic plasticity, occurring when low NAR imposes carbon constraints on secondary metabolism in low nutrient environments. Once plants acclimate to nutrient limitation, the equilibrium allocation state is predicted to be a negative correlation between growth and secondary metabolism. Although both willow species generally responded according to GDBH, the complexity observed suggests that prediction of the effects of nutrient availability on secondary metabolism (and other plastic responses) in specific cases requires a priori knowledge of the physiological status of the plant and soil nutrient availability. PMID:17725548

  11. Testing a growth efficiency hypothesis with continental-scale phenological variations of common and cloned plants.

    PubMed

    Liang, Liang; Schwartz, Mark D

    2014-10-01

    Variation in the timing of plant phenology caused by phenotypic plasticity is a sensitive measure of how organisms respond to weather and climate variability. Although continental-scale gradients in climate and consequential patterns in plant phenology are well recognized, the contribution of underlying genotypic difference to the geography of phenology is less well understood. We hypothesize that different temperate plant genotypes require varying amount of heat energy for resuming annual growth and reproduction as a result of adaptation and other ecological and evolutionary processes along climatic gradients. In particular, at least for some species, the growing degree days (GDD) needed to trigger the same spring phenology events (e.g., budburst and flower bloom) may be less for individuals originated from colder climates than those from warmer climates. This variable intrinsic heat energy requirement in plants can be characterized by the term growth efficiency and is quantitatively reflected in the timing of phenophases-earlier timing indicates higher efficiency (i.e., less heat energy needed to trigger phenophase transitions) and vice versa compared to a standard reference (i.e., either a uniform climate or a uniform genotype). In this study, we tested our hypothesis by comparing variations of budburst and bloom timing of two widely documented plants from the USA National Phenology Network (i.e., red maple-Acer rubrum and forsythia-Forsythia spp.) with cloned indicator plants (lilac-Syringa x chinensis 'Red Rothomagensis') at multiple eastern US sites. Our results indicate that across the accumulated temperature gradient, the two non-clonal plants showed significantly more gradual changes than the cloned plants, manifested by earlier phenology in colder climates and later phenology in warmer climates relative to the baseline clone phenological response. This finding provides initial evidence supporting the growth efficiency hypothesis, and suggests more work is

  12. Continental collision zones are primary sites for net continental crust growth — A testable hypothesis

    NASA Astrophysics Data System (ADS)

    Niu, Yaoling; Zhao, Zhidan; Zhu, Di-Cheng; Mo, Xuanxue

    2013-12-01

    The significance of the continental crust (CC) on which we live is self-evident. However, our knowledge remains limited on its origin, its way and rate of growth, and how it has acquired the "andesitic" composition from mantle derived magmas. Compared to rocks formed from mantle derived magmas in all geological environments, volcanic arc rocks associated with seafloor subduction share some common features with the CC; both are relatively depleted in "fluid-insoluble" elements (e.g., Nb, Ta and Ti), but enriched in "fluid-soluble" elements (e.g., U, K and Pb). These chemical characteristics are referred to as the "arc-like signature", and point to a possible link between subduction-zone magmatism and CC formation, thus leading to the "island arc" model widely accepted for the origin of the CC over the past 45 years. However, this "island-arc" model has many difficulties: e.g., (1) the bulk arc crust (AC) is basaltic whereas the bulk CC is andesitic; (2) the AC has variably large Sr excess whereas the CC is weakly Sr deficient; and (3) AC production is mass-balanced by subduction erosion and sediment recycling, thus contributing no net mass to the CC growth, at least in the Phanerozoic. Our recent and ongoing studies on granitoid rocks (both volcanic and intrusive) formed in response to the India-Asia continental collision (~ 55 ± 10 Ma) show remarkable compositional similarity to the bulk CC with the typical "arc-like signature". Also, these syncollisional granitoid rocks exhibit strong mantle isotopic signatures, meaning that they were recently derived from a mantle source. The petrology and geochemistry of these syncollisional granitoid rocks are most consistent with an origin via partial melting of the upper ocean crust (i.e., last fragments of underthrusting ocean crust upon collision) under amphibolite facies conditions, adding net mantle-derived materials to form juvenile CC mass. This leads to the logical and testable hypothesis that continental collision

  13. Testing the junk-food hypothesis on marine birds: Effects of prey type on growth and development

    USGS Publications Warehouse

    Romano, Marc D.; Piatt, J.F.; Roby, D.D.

    2006-01-01

    The junk-food hypothesis attributes declines in productivity of marine birds and mammals to changes in the species of prey they consume and corresponding differences in nutritional quality of those prey. To test this hypothesis nestling Black-legged Kittiwakes (Rissa tridactyla) and Tufted Puffins (Fratercula cirrhata) were raised in captivity under controlled conditions to determine whether the type and quality of fish consumed by young seabirds constrains their growth and development. Some nestlings were fed rations of Capelin (Mallotus villosus), Herring (Clupea pallasi) or Sand Lance (Ammodytes hexapterus) and their growth was compared with nestlings raised on equal biomass rations of Walleye Pollock (Theragra chalcograma). Nestlings fed rations of herring, sand lance, or capelin experienced higher growth increments than nestlings fed pollock. The energy density of forage fish fed to nestlings had a marked effect on growth increments and could be expected to have an effect on pre- and post-fledging survival of nestlings in the wild. These results provide empirical support for the junk-food hypothesis.

  14. Growth-Related Neural Reorganization and the Autism Phenotype: A Test of the Hypothesis that Altered Brain Growth Leads to Altered Connectivity

    ERIC Educational Resources Information Center

    Lewis, John D.; Elman, Jeffrey L.

    2008-01-01

    Theoretical considerations, and findings from computational modeling, comparative neuroanatomy and developmental neuroscience, motivate the hypothesis that a deviant brain growth trajectory will lead to deviant patterns of change in cortico-cortical connectivity. Differences in brain size during development will alter the relative cost and…

  15. Growth-related neural reorganization and the autism phenotype: a test of the hypothesis that altered brain growth leads to altered connectivity.

    PubMed

    Lewis, John D; Elman, Jeffrey L

    2008-01-01

    Theoretical considerations, and findings from computational modeling, comparative neuroanatomy and developmental neuroscience, motivate the hypothesis that a deviant brain growth trajectory will lead to deviant patterns of change in cortico-cortical connectivity. Differences in brain size during development will alter the relative cost and effectiveness of short- and long-distance connections, and should thus impact the growth and retention of connections. Reduced brain size should favor long-distance connectivity; brain overgrowth should favor short-distance connectivity; and inconsistent deviations from the normal growth trajectory - as occurs in autism - should result in potentially disruptive changes to established patterns of functional and physical connectivity during development. To explore this hypothesis, neural networks which modeled inter-hemispheric interaction were grown at the rate of either typically developing children or children with autism. The influence of the length of the inter-hemispheric connections was analyzed at multiple developmental time-points. The networks that modeled autistic growth were less affected by removal of the inter-hemispheric connections than those that modeled normal growth - indicating a reduced reliance on long-distance connections - for short response times, and this difference increased substantially at approximately 24 simulated months of age. The performance of the networks showed a corresponding decline during development. And direct analysis of the connection weights showed a parallel reduction in connectivity. These modeling results support the hypothesis that the deviant growth trajectory in autism spectrum disorders may lead to a disruption of established patterns of functional connectivity during development, with potentially negative behavioral consequences, and a subsequent reduction in physical connectivity. The results are discussed in relation to the growing body of evidence of reduced functional and

  16. Growth-limiting proteins in maize coleoptiles and the auxin-brassinosteroid hypothesis of mesocotyl elongation.

    PubMed

    Kutschera, Ulrich; Wang, Zhi-Yong

    2016-01-01

    The shoot of grass coleoptiles consists of the mesocotyl, the node, and the coleoptile (with enclosed primary leaf). Since the 1930s, it is known that auxin (indole-3-acetic acid, IAA), produced in the tip of the coleoptile, is the central regulator of turgor-driven organ growth. Fifty years ago, it was discovered that antibiotics that suppress protein biosynthesis, such as cycloheximide, inhibit auxin (IAA)-induced cell elongation in excised sections of coleoptiles and stems. Based on such inhibitor studies, the concept of "growth-limiting proteins (GLPs)" emerged that was subsequently elaborated and modified. Here, we summarize the history of this idea with reference to IAA-mediated shoot elongation in maize (Zea mays) seedlings and recent studies on the molecular mechanism underlying auxin action in Arabidopsis thaliana. In addition, the analysis of light-induced inhibition of shoot elongation in intact corn seedlings is discussed. We propose a concept to account for the GLP-mediated epidermal wall-loosening process in coleoptile segments and present a more general model of growth regulation in intact maize seedlings. Quantitative proteomic and genomic studies led to a refinement of the classic "GLP concept" to explain phytohormone-mediated cell elongation at the molecular level (i.e., the recently proposed theory of a "central growth regulation network," CGRN). Novel data show that mesocotyl elongation not only depends on auxin but also on brassinosteroids (BRs). However, the biochemical key processes that regulate the IAA/BR-mediated loosening of the expansion-limiting epidermal wall(s) have not yet been elucidated. PMID:25772679

  17. Growth-limiting proteins in maize coleoptiles and the auxin-brassinosteroid hypothesis of mesocotyl elongation.

    PubMed

    Kutschera, Ulrich; Wang, Zhi-Yong

    2016-01-01

    The shoot of grass coleoptiles consists of the mesocotyl, the node, and the coleoptile (with enclosed primary leaf). Since the 1930s, it is known that auxin (indole-3-acetic acid, IAA), produced in the tip of the coleoptile, is the central regulator of turgor-driven organ growth. Fifty years ago, it was discovered that antibiotics that suppress protein biosynthesis, such as cycloheximide, inhibit auxin (IAA)-induced cell elongation in excised sections of coleoptiles and stems. Based on such inhibitor studies, the concept of "growth-limiting proteins (GLPs)" emerged that was subsequently elaborated and modified. Here, we summarize the history of this idea with reference to IAA-mediated shoot elongation in maize (Zea mays) seedlings and recent studies on the molecular mechanism underlying auxin action in Arabidopsis thaliana. In addition, the analysis of light-induced inhibition of shoot elongation in intact corn seedlings is discussed. We propose a concept to account for the GLP-mediated epidermal wall-loosening process in coleoptile segments and present a more general model of growth regulation in intact maize seedlings. Quantitative proteomic and genomic studies led to a refinement of the classic "GLP concept" to explain phytohormone-mediated cell elongation at the molecular level (i.e., the recently proposed theory of a "central growth regulation network," CGRN). Novel data show that mesocotyl elongation not only depends on auxin but also on brassinosteroids (BRs). However, the biochemical key processes that regulate the IAA/BR-mediated loosening of the expansion-limiting epidermal wall(s) have not yet been elucidated.

  18. Biorhythms, deciduous enamel thickness, and primary bone growth: a test of the Havers-Halberg Oscillation hypothesis.

    PubMed

    Mahoney, Patrick; Miszkiewicz, Justyna J; Pitfield, Rosie; Schlecht, Stephen H; Deter, Chris; Guatelli-Steinberg, Debbie

    2016-06-01

    Across mammalian species, the periodicity with which enamel layers form (Retzius periodicity) in permanent teeth corresponds with average body mass and the pace of life history. According to the Havers-Halberg Oscillation hypothesis (HHO), Retzius periodicity (RP) is a manifestation of a biorhythm that is also expressed in lamellar bone. Potentially, these links provide a basis for investigating aspects of a species' biology from fossilized teeth. Here, we tested intra-specific predictions of this hypothesis on skeletal samples of human juveniles. We measured daily enamel growth increments to calculate RP in deciduous molars (n = 25). Correlations were sought between RP, molar average and relative enamel thickness (AET, RET), and the average amount of primary bone growth (n = 7) in humeri of age-matched juveniles. Results show a previously undescribed relationship between RP and enamel thickness. Reduced major axis regression reveals RP is significantly and positively correlated with AET and RET, and scales isometrically. The direction of the correlation was opposite to HHO predictions as currently understood for human adults. Juveniles with higher RPs and thicker enamel had increased primary bone formation, which suggests a coordinating biorhythm. However, the direction of the correspondence was, again, opposite to predictions. Next, we compared RP from deciduous molars with new data for permanent molars, and with previously published values. The lowermost RP of 4 and 5 days in deciduous enamel extends below the lowermost RP of 6 days in permanent enamel. A lowered range of RP values in deciduous enamel implies that the underlying biorhythm might change with age. Our results develop the intra-specific HHO hypothesis.

  19. Novel Therapy to Treat Corneal Epithelial Defects: A Hypothesis with Growth Hormone

    PubMed Central

    Wirostko, Barbara; Rafii, MaryJane; Sullivan, David A.; Morelli, Julia; Ding, Juan

    2015-01-01

    Impaired corneal wound healing that occurs with ocular surface disease, trauma, systemic disease, or surgical intervention can lead to persistent corneal epithelial defects (PCED), which result in corneal scarring, ulceration, opacification, corneal neovascularization, and, ultimately, visual compromise and vision loss. The current standard of care can include lubricants, ointments, bandage lenses, amniotic membranes, autologous serum eye drops, and corneal transplants. Various inherent problems exist with application and administration of these treatments, which often may not result in a completely healed surface. A topically applicable compound capable of promoting corneal epithelial cell proliferation and/or migration would be ideal to accelerate healing. We hypothesize that human growth hormone (HGH) is such a compound. In a recent study, HGH was shown to activate signal transducer and activators of transcription-5 (STAT5) signaling and promote corneal wound healing by enhancing corneal epithelial migration in a co-culture system of corneal epithelial cells and fibroblasts. These effects require an intact communication between corneal epithelia and fibroblasts. Further, HGH promotes corneal wound healing in a rabbit debridement model, thus demonstrating the effectiveness of HGH in vivo as well. In conclusion, HGH may represent an exciting and effective topical therapeutic to promote corneal wound healing. PMID:26045234

  20. Novel Therapy to Treat Corneal Epithelial Defects: A Hypothesis with Growth Hormone.

    PubMed

    Wirostko, Barbara; Rafii, MaryJane; Sullivan, David A; Morelli, Julia; Ding, Juan

    2015-07-01

    Impaired corneal wound healing that occurs with ocular surface disease, trauma, systemic disease, or surgical intervention can lead to persistent corneal epithelial defects (PCED), which result in corneal scarring, ulceration, opacification, corneal neovascularization, and, ultimately, visual compromise and vision loss. The current standard of care can include lubricants, ointments, bandage lenses, amniotic membranes, autologous serum eye drops, and corneal transplants. Various inherent problems exist with application and administration of these treatments, which often may not result in a completely healed surface. A topically applicable compound capable of promoting corneal epithelial cell proliferation and/or migration would be ideal to accelerate healing. We hypothesize that human growth hormone (HGH) is such a compound. In a recent study, HGH was shown to activate signal transducer and activators of transcription-5 (STAT5) signaling and promote corneal wound healing by enhancing corneal epithelial migration in a co-culture system of corneal epithelial cells and fibroblasts. These effects require an intact communication between corneal epithelia and fibroblasts. Further, HGH promotes corneal wound healing in a rabbit debridement model, thus demonstrating the effectiveness of HGH in vivo as well. In conclusion, HGH may represent an exciting and effective topical therapeutic to promote corneal wound healing.

  1. Energetic constraint of non-monotonic mass change during offspring growth: a general hypothesis and application of a new tool.

    PubMed

    Arnold, Jennifer M; Nisbet, Ian C T; Oswald, Stephen A

    2016-03-01

    Post-natal growth is an important life-history trait and can be a sensitive indicator of ecological stress. For over 50 years, monotonic (never-decreasing) growth has been viewed as the predominant trajectory of post-natal mass change in most animal species, notably among birds. However, prevailing analytical approaches and energetic constraints may limit detection of non-monotonic (or multiphasic), determinate growth patterns, such as mass recession in birds (weight loss prior to fledging, preceded by overshooting adult mass), which is currently believed to be restricted to few taxa. Energetic surplus and shortfall are widespread conditions that can directly influence the degree of mass overshooting and recession. Thus, we hypothesize that in many species, prevailing energetic constraints force mass change away from a fundamental non-monotonic trajectory to instead follow a monotonic curve. We observed highly non-monotonic, mass change trajectories (overshooting adult mass by up to almost 20%) among common tern Sterna hirundo chicks, a well-studied species long-established as growing monotonically. We quantified the prevalence and magnitude of non-monotonic mass change prior to fledging for 313 common tern chicks that successfully fledged from two discrete populations in multiple years. We used a new approach for analysing non-monotonic curves to examine differences in mass change trajectories between populations under contrasting abiotic (freshwater vs. saltwater) and biotic stresses (low rates of food provisioning). Some degree of mass recession occurred in 73% of all study chicks. Overshooting adult mass followed by extensive mass recession was most prevalent at our freshwater colony, being detected among 34-38% of chicks annually. Non-monotonic trajectories were less marked in populations experiencing ecological stress and among lower quality individuals. Chicks that were provisioned at higher rates were more likely to both overshoot adult mass and experience

  2. Biomechanical spinal growth modulation and progressive adolescent scoliosis – a test of the 'vicious cycle' pathogenetic hypothesis: Summary of an electronic focus group debate of the IBSE

    PubMed Central

    Stokes, Ian AF; Burwell, R Geoffrey; Dangerfield, Peter H

    2006-01-01

    There is no generally accepted scientific theory for the causes of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this debate was written by Dr Ian A Stokes. It evaluates the hypothesis that in progressive scoliosis vertebral body wedging during adolescent growth results from asymmetric muscular loading in a "vicious cycle" (vicious cycle hypothesis of pathogenesis) by affecting vertebral body growth plates (endplate physes). A frontal plane mathematical simulation tested whether the calculated loading asymmetry created by muscles in a scoliotic spine could explain the observed rate of scoliosis increase by measuring the vertebral growth modulation by altered compression. The model deals only with vertebral (not disc) wedging. It assumes that a pre-existing scoliosis curve initiates the mechanically-modulated alteration of vertebral body growth that in turn causes worsening of the scoliosis, while everything else is anatomically and physiologically 'normal' The results provide quantitative data consistent with the vicious cycle hypothesis. Dr Stokes' biomechanical research engenders controversy. A new speculative concept is proposed of vertebral symphyseal dysplasia with implications for Dr Stokes' research and the etiology of AIS. What is not controversial is the need to test this hypothesis using additional factors in his current model and in three-dimensional quantitative models that incorporate intervertebral discs and simulate thoracic as well as lumbar scoliosis. The growth modulation process in the vertebral body can be viewed as one type of the biologic phenomenon of mechanotransduction. In certain connective tissues this involves the effects of mechanical

  3. Did debris-covered glaciers serve as pleistocene refugia for plants? A new hypothesis derived from observations of recent plant growth on glacier surfaces

    USGS Publications Warehouse

    Fickert, T.; Friend, D.; Gruninger, F.; Molnia, B.; Richter, M.

    2007-01-01

    This study proposes a new hypothesis: Debris-covered glaciers served as Pleistocene biological refugia. This is based on detailed studies of vascular plant growth on six debris-mantled glaciers, literally around the world, as well as many casual observations also across the globe. We find that such glaciers are quite common and are distributed globally. Using Carbon Glacier, Mount Rainier, U.S.A., as a type locality and case study, we show aspects of the floristic and structural diversity as well as spatial patterns of plant growth on the glacier surface. Migration strategies, root characteristics, and origin and dispersal strategies for vascular plant species are documented. Also reported are special microclimatic conditions in these areas allowing for this remarkable plant ecology. We find that alpine taxa can grow considerably below their usual altitudinal niche due to the cooler subsurface soil temperatures found on glacial debris with ice underneath, and that may have significantly altered the spatial distribution of such flora during full glacial conditions. This in turn creates previously undocumented areas from which alpine, and perhaps arctic, plant species reestablished in post-glacial time. This hypothesis is complementary to both the nunatak hypothesis and tabula rasa theory and possibly helps solve the ongoing controversy between them. ?? 2007 Regents of the University of Colorado.

  4. Beyond the functional matrix hypothesis: a network null model of human skull growth for the formation of bone articulations.

    PubMed

    Esteve-Altava, Borja; Rasskin-Gutman, Diego

    2014-09-01

    Craniofacial sutures and synchondroses form the boundaries among bones in the human skull, providing functional, developmental and evolutionary information. Bone articulations in the skull arise due to interactions between genetic regulatory mechanisms and epigenetic factors such as functional matrices (soft tissues and cranial cavities), which mediate bone growth. These matrices are largely acknowledged for their influence on shaping the bones of the skull; however, it is not fully understood to what extent functional matrices mediate the formation of bone articulations. Aiming to identify whether or not functional matrices are key developmental factors guiding the formation of bone articulations, we have built a network null model of the skull that simulates unconstrained bone growth. This null model predicts bone articulations that arise due to a process of bone growth that is uniform in rate, direction and timing. By comparing predicted articulations with the actual bone articulations of the human skull, we have identified which boundaries specifically need the presence of functional matrices for their formation. We show that functional matrices are necessary to connect facial bones, whereas an unconstrained bone growth is sufficient to connect non-facial bones. This finding challenges the role of the brain in the formation of boundaries between bones in the braincase without neglecting its effect on skull shape. Ultimately, our null model suggests where to look for modified developmental mechanisms promoting changes in bone growth patterns that could affect the development and evolution of the head skeleton.

  5. Beyond the functional matrix hypothesis: a network null model of human skull growth for the formation of bone articulations

    PubMed Central

    Esteve-Altava, Borja; Rasskin-Gutman, Diego

    2014-01-01

    Craniofacial sutures and synchondroses form the boundaries among bones in the human skull, providing functional, developmental and evolutionary information. Bone articulations in the skull arise due to interactions between genetic regulatory mechanisms and epigenetic factors such as functional matrices (soft tissues and cranial cavities), which mediate bone growth. These matrices are largely acknowledged for their influence on shaping the bones of the skull; however, it is not fully understood to what extent functional matrices mediate the formation of bone articulations. Aiming to identify whether or not functional matrices are key developmental factors guiding the formation of bone articulations, we have built a network null model of the skull that simulates unconstrained bone growth. This null model predicts bone articulations that arise due to a process of bone growth that is uniform in rate, direction and timing. By comparing predicted articulations with the actual bone articulations of the human skull, we have identified which boundaries specifically need the presence of functional matrices for their formation. We show that functional matrices are necessary to connect facial bones, whereas an unconstrained bone growth is sufficient to connect non-facial bones. This finding challenges the role of the brain in the formation of boundaries between bones in the braincase without neglecting its effect on skull shape. Ultimately, our null model suggests where to look for modified developmental mechanisms promoting changes in bone growth patterns that could affect the development and evolution of the head skeleton. PMID:24975579

  6. Palatability to a generalist herbivore, defence and growth of invasive and native Senecio species: testing the evolution of increased competitive ability hypothesis.

    PubMed

    Caño, L; Escarré, J; Vrieling, K; Sans, F X

    2009-02-01

    This paper tests the prediction that introduced plants may become successful invaders because they experience evolutionary changes in growth and defence in their new range [evolution of increased competitive ability hypothesis (EICA)]. Interspecific and intraspecific binary feeding choices were offered to the snail Helix aspersa. The choices were between: (1) plants of the invasive Senecio inaequidens and Senecio pterophorus derived from populations in the introduced range (Europe) and plants of three indigenous species (Senecio jacobea, Senecio vulgaris and Senecio malacitanus) from populations in Europe; (2) plants of the invasive S. inaequidens and S. pterophorus from populations in the introduced range (Europe) and from populations in the native range (South Africa). We did not find a clear pattern of preference for indigenous or alien species of Senecio. However, we found that European invasive populations of S. inaequidens and S. pterophorus were less palatable than South African native populations. Moreover, in contrast to the predictions of the EICA hypothesis, the invasive genotypes of both species also showed a higher total concentration of pyrrolizidine alkaloids, and in the case of S. inaequidens we also found higher growth than in native genotypes. Our results are discussed with respect to the refinement of the EICA hypothesis that takes into account the difference between specialist and generalist herbivores and between qualitative and quantitative defences. We conclude that invasive populations of S. inaequidens and S. pterophorus are less palatable than native populations, suggesting that genetic differentiation associated with founding may occur and contribute to the plants' invasion success by selecting the best-defended genotypes in the introduced range.

  7. The early origins hypothesis with an emphasis on growth rate in the first year of life and asthma: a prospective study in Chile

    PubMed Central

    Rona, R; Smeeton, N; Bustos, P; Amigo, H; Diaz, P

    2005-01-01

    Background: There is uncertainty about the impact of the programming hypothesis in terms of nutritional status at birth, rate of growth in the first year of life, length of gestation, breast feeding, and episodes of illness on asthma. An analysis was therefore carried out to test this hypothesis. Methods: Data were collected on 1232 children born between 1974 and 1978 in a semi-rural area of Chile. Measurements at birth and growth in the first year of life were obtained from a birth registry and clinical notes. Information on asthma was collected using the European Community Respiratory Health Survey questionnaire. Sensitisation to eight allergens and bronchial hyperresponsiveness (BHR) to methacholine were determined. All other information was obtained using a questionnaire. Polytomous logistic analyses were carried out to explore the association of factors at birth and during the first year of life with asthma symptoms, atopy, and BHR. Results: Weight and length gain in the first year were positively associated with wheeze (odds ratio (OR) 1.004, 95% CI 1.001 to 1.007 and OR 1.11, 95% CI 0.98 to 1.25, respectively). A higher body mass index (BMI) at birth was protective in subjects reporting both wheeze and waking with breathlessness (OR 0.54, 95% CI 0.35 to 0.84). Length rate in tertiles divided by length at birth in tertiles was related to asthma symptoms (OR 1.68, 95% CI 1.19 to 2.37). Most other assessments were not associated with asthma. Conclusion: These results show promising but inconclusive evidence that a rapid rate of growth in length, especially in newborn infants of low length, might be involved in the aetiology of asthma. PMID:15994261

  8. Hypothesis: Neuroendocrine Mechanisms (Hypothalamus–Growth Hormone–STAT5 Axis) Contribute to Sex Bias in Pulmonary Hypertension

    PubMed Central

    Sehgal, Pravin B; Yang, Yang-Ming; Miller, Edmund J

    2015-01-01

    Pulmonary hypertension (PH) is a disease with high morbidity and mortality. The prevalence of idiopathic pulmonary arterial hypertension (IPAH) and hereditary pulmonary arterial hypertension (HPAH) is approximately two- to four-fold higher in women than in men. Paradoxically, there is an opposite male bias in typical rodent models of PH (chronic hypoxia or monocrotaline); in these models, administration of estrogenic compounds (for example, estradiol-17β [E2]) is protective. Further complexities are observed in humans ingesting anorexigens (female bias) and in rodent models, such as after hypoxia plus SU5416/Sugen (little sex bias) or involving serotonin transporter overexpression or dexfenfluramine administration (female bias). These complexities in sex bias in PH remain incompletely understood. We recently discovered that conditional deletion of signal transducer and activator of transcription 5a/b (STAT5a/b) in vascular smooth muscle cells abrogated the male bias in PH in hypoxic mice and that late-stage obliterative lesions in patients of both sexes with IPAH and HPAH showed reduced STAT5a/b, reduced Tyr-P-STAT5 and reduced B-cell lymphoma 6 protein (BCL6). In trying to understand the significance of these observations, we realized that there existed a well-characterized E2-sensitive central neuroendocrine mechanism of sex bias, studied over the last 40 years, that, at its peripheral end, culminated in species-specific male (“pulsatile”) versus female (“more continuous”) temporal patterns of circulating growth hormone (GH) levels leading to male versus female patterned activation of STAT5a/b in peripheral tissues and thus sex-biased expression of hundreds of genes. In this report, we consider the contribution of this neuroendocrine mechanism (hypothalamus-GH-STAT5) in the generation of sex bias in different PH situations. PMID:26252185

  9. Physiopathological hypothesis of cellulite.

    PubMed

    de Godoy, José Maria Pereira; de Godoy, Maria de Fátima Guerreiro

    2009-08-31

    A series of questions are asked concerning this condition including as regards to its name, the consensus about the histopathological findings, physiological hypothesis and treatment of the disease. We established a hypothesis for cellulite and confirmed that the clinical response is compatible with this hypothesis. Hence this novel approach brings a modern physiological concept with physiopathologic basis and clinical proof of the hypothesis. We emphasize that the choice of patient, correct diagnosis of cellulite and the technique employed are fundamental to success.

  10. Ecosystem Succession and Nutrient Retention: A Hypothesis

    ERIC Educational Resources Information Center

    Vitousek, Peter M.; Reiners, William A.

    1975-01-01

    A hypothesis is presented for the regulation of elemental losses from terrestrial ecosystems. Losses of elements are controlled by the net increment of biomass growth and the elemental composition of this net increment. According to this hypothesis, loss rates are highest in early succession and in steady state ecosystems. (Author/EB)

  11. Physiopathological Hypothesis of Cellulite

    PubMed Central

    de Godoy, José Maria Pereira; de Godoy, Maria de Fátima Guerreiro

    2009-01-01

    A series of questions are asked concerning this condition including as regards to its name, the consensus about the histopathological findings, physiological hypothesis and treatment of the disease. We established a hypothesis for cellulite and confirmed that the clinical response is compatible with this hypothesis. Hence this novel approach brings a modern physiological concept with physiopathologic basis and clinical proof of the hypothesis. We emphasize that the choice of patient, correct diagnosis of cellulite and the technique employed are fundamental to success. PMID:19756187

  12. Life Origination Hydrate Hypothesis (LOH-Hypothesis)

    PubMed Central

    Ostrovskii, Victor; Kadyshevich, Elena

    2012-01-01

    The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis), according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides), DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their “thermodynamic front” guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor. PMID:25382120

  13. Life Origination Hydrate Hypothesis (LOH-Hypothesis).

    PubMed

    Ostrovskii, Victor; Kadyshevich, Elena

    2012-01-01

    The paper develops the Life Origination Hydrate Hypothesis (LOH-hypothesis), according to which living-matter simplest elements (LMSEs, which are N-bases, riboses, nucleosides, nucleotides), DNA- and RNA-like molecules, amino-acids, and proto-cells repeatedly originated on the basis of thermodynamically controlled, natural, and inevitable processes governed by universal physical and chemical laws from CH4, niters, and phosphates under the Earth's surface or seabed within the crystal cavities of the honeycomb methane-hydrate structure at low temperatures; the chemical processes passed slowly through all successive chemical steps in the direction that is determined by a gradual decrease in the Gibbs free energy of reacting systems. The hypothesis formulation method is based on the thermodynamic directedness of natural movement and consists ofan attempt to mentally backtrack on the progression of nature and thus reveal principal milestones alongits route. The changes in Gibbs free energy are estimated for different steps of the living-matter origination process; special attention is paid to the processes of proto-cell formation. Just the occurrence of the gas-hydrate periodic honeycomb matrix filled with LMSEs almost completely in its final state accounts for size limitation in the DNA functional groups and the nonrandom location of N-bases in the DNA chains. The slowness of the low-temperature chemical transformations and their "thermodynamic front" guide the gross process of living matter origination and its successive steps. It is shown that the hypothesis is thermodynamically justified and testable and that many observed natural phenomena count in its favor. PMID:25382120

  14. Hypothesis analysis methods, hypothesis analysis devices, and articles of manufacture

    DOEpatents

    Sanfilippo, Antonio P.; Cowell, Andrew J.; Gregory, Michelle L.; Baddeley, Robert L.; Paulson, Patrick R.; Tratz, Stephen C.; Hohimer, Ryan E.

    2012-03-20

    Hypothesis analysis methods, hypothesis analysis devices, and articles of manufacture are described according to some aspects. In one aspect, a hypothesis analysis method includes providing a hypothesis, providing an indicator which at least one of supports and refutes the hypothesis, using the indicator, associating evidence with the hypothesis, weighting the association of the evidence with the hypothesis, and using the weighting, providing information regarding the accuracy of the hypothesis.

  15. Hypothesis: the reversal of the relation between economic growth and health progress in Sweden in the nineteenth and twentieth centuries was caused by electrification.

    PubMed

    Milham, Samuel

    2014-01-01

    The expected decline of health indicators with economic recessions and improvement with economic growth in the nineteenth century Sweden was reversed in the twentieth century, giving the counterintuitive pattern of higher mortality and lower life expectancy in economic expansions and improvement of these indices in recessions. The change or "tipping point" occurred at the end of the nineteenth century or early in the twentieth century when electrification was introduced into Sweden. All 5 of the reversals of annual industrial electric energy use in the US between 1912 and 1970 were accompanied by recessions with lowered GDP, increased unemployment, decreased mortality and increased life expectancy. The health indices were not related to residential electricity use. The mortality improvement between 1931 and 1932 by state in the US strongly favored urban areas over rural areas. Rural unemployment by state in 1930 was significantly positively correlated with residential electrification percentage by state in 1930. The health effects of economic change are mediated by electrical exposure.

  16. Metabolic hypothesis for human altriciality

    PubMed Central

    Dunsworth, Holly M.; Warrener, Anna G.; Deacon, Terrence; Ellison, Peter T.; Pontzer, Herman

    2012-01-01

    The classic anthropological hypothesis known as the “obstetrical dilemma” is a well-known explanation for human altriciality, a condition that has significant implications for human social and behavioral evolution. The hypothesis holds that antagonistic selection for a large neonatal brain and a narrow, bipedal-adapted birth canal poses a problem for childbirth; the hominin “solution” is to truncate gestation, resulting in an altricial neonate. This explanation for human altriciality based on pelvic constraints persists despite data linking human life history to that of other species. Here, we present evidence that challenges the importance of pelvic morphology and mechanics in the evolution of human gestation and altriciality. Instead, our analyses suggest that limits to maternal metabolism are the primary constraints on human gestation length and fetal growth. Although pelvic remodeling and encephalization during hominin evolution contributed to the present parturitional difficulty, there is little evidence that pelvic constraints have altered the timing of birth. PMID:22932870

  17. Hypothesis: the reversal of the relation between economic growth and health progress in Sweden in the nineteenth and twentieth centuries was caused by electrification.

    PubMed

    Milham, Samuel

    2014-01-01

    The expected decline of health indicators with economic recessions and improvement with economic growth in the nineteenth century Sweden was reversed in the twentieth century, giving the counterintuitive pattern of higher mortality and lower life expectancy in economic expansions and improvement of these indices in recessions. The change or "tipping point" occurred at the end of the nineteenth century or early in the twentieth century when electrification was introduced into Sweden. All 5 of the reversals of annual industrial electric energy use in the US between 1912 and 1970 were accompanied by recessions with lowered GDP, increased unemployment, decreased mortality and increased life expectancy. The health indices were not related to residential electricity use. The mortality improvement between 1931 and 1932 by state in the US strongly favored urban areas over rural areas. Rural unemployment by state in 1930 was significantly positively correlated with residential electrification percentage by state in 1930. The health effects of economic change are mediated by electrical exposure. PMID:23803154

  18. Developmental regulation of the effects of fibroblast growth factor-2 and 1-octanol on neuronogenesis: implications for a hypothesis relating to mitogen-antimitogen opposition

    NASA Technical Reports Server (NTRS)

    Goto, T.; Takahashi, T.; Miyama, S.; Nowakowski, R. S.; Bhide, P. G.; Caviness, V. S. Jr

    2002-01-01

    Neocortical neurons arise from a pseudostratified ventricular epithelium (PVE) that lies within the ventricular zone (VZ) at the margins of the embryonic cerebral ventricles. We examined the effects of fibroblast growth factor-2 (FGF-2) and 1-octanol on cell output behavior of the PVE in explants of the embryonic mouse cerebral wall. FGF-2 is mitogenic and 1-octanol antimitogenic in the PVE. Whereas all postmitotic cells migrate out of the VZ in vivo, in the explants some postmitotic cells remain within the VZ. We refer to these cells as the indeterminate or I fraction, because they neither exit from the VZ nor reenter S phase as part of the proliferative (P) fraction. They are considered to be either in an extremely prolonged G(1) phase, unable to pass the G(1)/S transition, or in the G(0) state. The I fate choice is modulated by both FGF-2 and 1-octanol. FGF-2 decreased the I fraction and increased the P fraction. In contrast, 1-octanol increased the I fraction and nearly eliminated the P fraction. The effects of FGF-2 and 1-octanol were developmentally regulated, in that they were observed in the developmentally advanced lateral region of the cerebral wall but not in the medial region. Copyright 2002 Wiley-Liss, Inc.

  19. Analysis of the relationship between economic growth and industrial pollution in Zaozhuang, China-based on the hypothesis of the environmental Kuznets curve.

    PubMed

    Liu, Xiao-Hui; Wang, Wei-Liang; Lu, Shao-Yong; Wang, Yu-Fan; Ren, Zongming

    2016-08-01

    In Zaozhuang, economic development affects the discharge amount of industrial wastewater, chemical oxygen demand (COD), and ammonia nitrogen (NH3-N). To reveal the trend of water environmental quality related to the economy in Zaozhuang, this paper simulated the relationships between industrial wastewater discharge, COD, NH3-N load, and gross domestic product (GDP) per capita for Zaozhuang (2002-2012) using environmental Kuznets curve (EKC) models. The results showed that the added value of industrial GDP, the per capita GDP, and wastewater emission had average annual growth rates of 16.62, 16.19, and 17.89 %, respectively, from 2002 to 2012, while COD and NH3-N emission in 2012, compared with 2002, showed average annual decreases of 10.70 and 31.12 %, respectively. The export of EKC models revealed that industrial wastewater discharge had a typical inverted-U-shaped relationship with per capita GDP. However, both COD and NH3-N showed the binding curve of the left side of the "U" curve and left side U-shaped curve. The economy in Zaozhuang had been at the "fast-growing" stage, with low environmental pollution according to the industrial pollution level. In recent years, Zaozhuang has abated these heavy-pollution industries emphatically, so pollutants have been greatly reduced. Thus, Zaozhuang industrial wastewater treatment has been quite effective, with water quality improved significantly. The EKC models provided scientific evidence for estimating industrial wastewater discharge, COD, and NH3-N load as well as their changeable trends for Zaozhuang from an economic perspective.

  20. A Molecular–Structure Hypothesis

    PubMed Central

    Boeyens, Jan C. A.

    2010-01-01

    The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation. PMID:21151437

  1. The dysconnection hypothesis (2016).

    PubMed

    Friston, Karl; Brown, Harriet R; Siemerkus, Jakob; Stephan, Klaas E

    2016-10-01

    Twenty years have passed since the dysconnection hypothesis was first proposed (Friston and Frith, 1995; Weinberger, 1993). In that time, neuroscience has witnessed tremendous advances: we now live in a world of non-invasive neuroanatomy, computational neuroimaging and the Bayesian brain. The genomics era has come and gone. Connectomics and large-scale neuroinformatics initiatives are emerging everywhere. So where is the dysconnection hypothesis now? This article considers how the notion of schizophrenia as a dysconnection syndrome has developed - and how it has been enriched by recent advances in clinical neuroscience. In particular, we examine the dysconnection hypothesis in the context of (i) theoretical neurobiology and computational psychiatry; (ii) the empirical insights afforded by neuroimaging and associated connectomics - and (iii) how bottom-up (molecular biology and genetics) and top-down (systems biology) perspectives are converging on the mechanisms and nature of dysconnections in schizophrenia. PMID:27450778

  2. The gender similarities hypothesis.

    PubMed

    Hyde, Janet Shibley

    2005-09-01

    The differences model, which argues that males and females are vastly different psychologically, dominates the popular media. Here, the author advances a very different view, the gender similarities hypothesis, which holds that males and females are similar on most, but not all, psychological variables. Results from a review of 46 meta-analyses support the gender similarities hypothesis. Gender differences can vary substantially in magnitude at different ages and depend on the context in which measurement occurs. Overinflated claims of gender differences carry substantial costs in areas such as the workplace and relationships. PMID:16173891

  3. The gender similarities hypothesis.

    PubMed

    Hyde, Janet Shibley

    2005-09-01

    The differences model, which argues that males and females are vastly different psychologically, dominates the popular media. Here, the author advances a very different view, the gender similarities hypothesis, which holds that males and females are similar on most, but not all, psychological variables. Results from a review of 46 meta-analyses support the gender similarities hypothesis. Gender differences can vary substantially in magnitude at different ages and depend on the context in which measurement occurs. Overinflated claims of gender differences carry substantial costs in areas such as the workplace and relationships.

  4. The Keystone Pathogen Hypothesis

    PubMed Central

    Hajishengallis, George; Darveau, Richard P.; Curtis, Michael A.

    2012-01-01

    Recent studies have highlighted the importance of the human microbiome in host health and disease. However, for the most part the mechanisms by which the microbiome mediates disease, or protection from it, remain poorly understood. The “keystone pathogen” hypothesis holds that certain low-abundance microbial pathogens can orchestrate inflammatory disease by remodelling a normally benign microbiota into a dysbiotic one. In this Opinion, we critically assess the available literature in support of this hypothesis, which may provide a novel conceptual basis for the development of targeted diagnostic and treatment modalities for complex dysbiotic diseases. PMID:22941505

  5. The Qualitative Similarity Hypothesis

    ERIC Educational Resources Information Center

    Paul, Peter V.; Lee, Chongmin

    2010-01-01

    Evidence is presented for the qualitative similarity hypothesis (QSH) with respect to children and adolescents who are d/Deaf or hard of hearing. The primary focus is on the development of English language and literacy skills, and some information is provided on the acquisition of English as a second language. The QSH is briefly discussed within…

  6. The interactive brain hypothesis

    PubMed Central

    Di Paolo, Ezequiel; De Jaegher, Hanne

    2012-01-01

    Enactive approaches foreground the role of interpersonal interaction in explanations of social understanding. This motivates, in combination with a recent interest in neuroscientific studies involving actual interactions, the question of how interactive processes relate to neural mechanisms involved in social understanding. We introduce the Interactive Brain Hypothesis (IBH) in order to help map the spectrum of possible relations between social interaction and neural processes. The hypothesis states that interactive experience and skills play enabling roles in both the development and current function of social brain mechanisms, even in cases where social understanding happens in the absence of immediate interaction. We examine the plausibility of this hypothesis against developmental and neurobiological evidence and contrast it with the widespread assumption that mindreading is crucial to all social cognition. We describe the elements of social interaction that bear most directly on this hypothesis and discuss the empirical possibilities open to social neuroscience. We propose that the link between coordination dynamics and social understanding can be best grasped by studying transitions between states of coordination. These transitions form part of the self-organization of interaction processes that characterize the dynamics of social engagement. The patterns and synergies of this self-organization help explain how individuals understand each other. Various possibilities for role-taking emerge during interaction, determining a spectrum of participation. This view contrasts sharply with the observational stance that has guided research in social neuroscience until recently. We also introduce the concept of readiness to interact to describe the practices and dispositions that are summoned in situations of social significance (even if not interactive). This latter idea links interactive factors to more classical observational scenarios. PMID:22701412

  7. Mesoamerican cosmovision: an hypothesis.

    NASA Astrophysics Data System (ADS)

    Franch, J. A.

    In the present conference the author explains a new hypothesis to interpret the cosmogonic vision of the people and the cultures from the Mesoamerican area during the precolumbian period. The hypothesis at issue consists in irregular octahedrical form, or as two pyramids jointed by the base in such a manner that the celestial pyramid has thirteen heavens in the form of platforms in such a way that the zenith is the seventh platform; on the contrary, the infraworld pyramid has nine platforms. The sequence of the heavens comes to an end in the number 13 heaven, or the West side of the world, that is to say the Omeyocan or the Tamoanchan, whereas the ninth infraworld is the Apochcalocan. This is the point of the intercommunication between the celestial world and the infraworld, the place of Death and Birth. In order to develop that hypothesis the author has a great number of ethnographic testimonies taken from Totonacs, Tzotziles, Mayas and, along with this, from Southamerican areas, as it is the case of the Kogi, of Colombia. The author has also considered the evidence that proceeds from the ancient codices as well as numerous samples of sculptures and reliefs, especially from the Aztec culture.

  8. Serotonergic hypothesis of sleepwalking.

    PubMed

    Juszczak, Grzegorz R; Swiergiel, Artur H

    2005-01-01

    Despite widespread prevalence of sleepwalking, its etiology and pathophysiology are not well understood. However, there is some evidence that sleepwalking can be precipitated by sleep-disordered breathing. A hypothesis is proposed that serotonergic system may be a link between sleep-disordered breathing and sleepwalking. Serotonergic neurons meet basic requirements for such a role because they are activated by hypercapnia, provide a tonic excitatory drive that gates afferent inputs to motoneurons, and the activity of serotonergic neurons can be dissociated from the level of arousal. This paper discusses also drug-induced somnambulism and co-occurrence of sleepwalking and other disorders such as migraine and febrile illness.

  9. Hypothesis: neoplasms in myotonic dystrophy

    PubMed Central

    Hilbert, James E.; Martens, William; Thornton, Charles A.; Moxley, Richard T.; Greene, Mark H.

    2011-01-01

    Tumorigenesis is a multi-step process due to an accumulation of genetic mutations in multiple genes in diverse pathways which ultimately lead to loss of control over cell growth. It is well known that inheritance of rare germline mutations in genes involved in tumorigenesis pathways confer high lifetime risk of neoplasia in affected individuals. Furthermore, a substantial number of multiple malformation syndromes include cancer susceptibility in their phenotype. Studies of the mechanisms underlying these inherited syndromes have added to the understanding of both normal development and the pathophysiology of carcinogenesis. Myotonic dystrophy (DM) represents a group of autosomal dominant, multisystemic diseases that share the clinical features of myotonia, muscle weakness, and early-onset cataracts. Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) result from unstable nucleotide repeat expansions in their respective genes. There have been multiple reports of tumors in individuals with DM, most commonly benign calcifying cutaneous tumors known as pilomatricomas. We provide a summary of the tumors reported in DM and a hypothesis for a possible mechanism of tumorigenesis. We hope to stimulate further study into the potential role of DM genes in tumorigenesis, and help define DM pathogenesis, and facilitate developing novel treatment modalities. PMID:19642006

  10. Is the Aluminum Hypothesis Dead?

    PubMed Central

    2014-01-01

    The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed with concern by some of the public. This review article discusses reasons that mainstream science has largely abandoned the Aluminum Hypothesis and explores a possible reason for some in the general public continuing to view aluminum with mistrust. PMID:24806729

  11. Is the Aluminum Hypothesis dead?

    PubMed

    Lidsky, Theodore I

    2014-05-01

    The Aluminum Hypothesis, the idea that aluminum exposure is involved in the etiology of Alzheimer disease, dates back to a 1965 demonstration that aluminum causes neurofibrillary tangles in the brains of rabbits. Initially the focus of intensive research, the Aluminum Hypothesis has gradually been abandoned by most researchers. Yet, despite this current indifference, the Aluminum Hypothesis continues to attract the attention of a small group of scientists and aluminum continues to be viewed with concern by some of the public. This review article discusses reasons that mainstream science has largely abandoned the Aluminum Hypothesis and explores a possible reason for some in the general public continuing to view aluminum with mistrust.

  12. Threshold Hypothesis: Fact or Artifact?

    ERIC Educational Resources Information Center

    Karwowski, Maciej; Gralewski, Jacek

    2013-01-01

    The threshold hypothesis (TH) assumes the existence of complex relations between creative abilities and intelligence: linear associations below 120 points of IQ and weaker or lack of associations above the threshold. However, diverse results have been obtained over the last six decades--some confirmed the hypothesis and some rejected it. In this…

  13. A new hypothesis of drug refractory epilepsy: neural network hypothesis.

    PubMed

    Fang, Min; Xi, Zhi-Qin; Wu, Yuan; Wang, Xue-Feng

    2011-06-01

    Drug refractory is an important clinical problem in epilepsy, affecting a substantial number of patients globally. Mechanisms underlying drug refractory need to be understood to develop rational therapies. Current two prevailing theories on drug refractory epilepsy (DRE) include the target hypothesis and the transporter hypothesis. However, those hypotheses could not be adequate to explain the mechanisms of all the DRE. Thus, we propose another possible mechanism of DRE, which is neural network hypothesis. It is hypothesized that seizure-induced alterations of brain plasticity including axonal sprouting, synaptic reorganization, neurogenesis and gliosis could contribute to the formation of abnormal neural network, which has not only avoided the inhibitory effect of endogenous antiepileptic system but also prevented the traditional antiepileptic drugs from entering their targets, eventually leading to DRE. We will illustrate this hypothesis at molecular and structural level based on our recent studies and other related researches.

  14. Evaluating the Stage Learning Hypothesis.

    ERIC Educational Resources Information Center

    Thomas, Hoben

    1980-01-01

    A procedure for evaluating the Genevan stage learning hypothesis is illustrated by analyzing Inhelder, Sinclair, and Bovet's guided learning experiments (in "Learning and the Development of Cognition." Cambridge: Harvard University Press, 1974). (Author/MP)

  15. The GAIA Hypothesis and Chaos in Daisyworld.

    NASA Astrophysics Data System (ADS)

    Flynn, Cathal Michael

    1993-01-01

    To correctly model the climate it is necessary to include the effects of the biosphere. The Gaia hypothesis claims that the earth's living matter, air, oceans, and land form a complex system which has the capacity to regulate the earth's climate. A model developed by Lovelock and Watson to demonstrate the Gaia hypothesis is explained and the results of their work are reviewed. Only steady state behavior is observed in the Daisyworld model. The work of Zeng et al. on the presence of chaos in Daisyworld is reviewed as an introduction to our own work. The presence of oscillatory and even chaotic behavior in this Daisyworld model brings into question the Gaia hypothesis. We develop a model of two-dimensional crystal growth called Crystalworld. The Crystalworld model is similar to the Daisyworld model in that there is a coupling between the growing entities and their environment via temperature. The results of this model are similar to that of the Daisyworld model. We present the results of another modified model of Daisyworld which we developed. This modified model takes into account the finite response time of the daisies to changes in the planet's climatic conditions. With a generation time introduced into the model equations, while retaining the differential equation format, it is found that the system can show oscillatory and chaotic behavior. These results show that any climate-biosphere model must contain a time delay and that such a time delay leads to behavior which contradicts the Gaia hypothesis. In order to determine the effects of introducing more species we develop a model with two species of daisies and a parasite species. For this Parasite-Daisyworld model steady state, periodic and chaotic behavior is found. A comparison between the results of this model and that of Zeng et al. is made. The results of the Parasite-Daisyworld model show that increasing the number of species does not lead to increased regulation. This contradicts the Gaia hypothesis and

  16. Testicular descent: a hypothesis and review of current controversies.

    PubMed

    Husmann, Douglas A

    2009-06-01

    Descent of the testis into the scrotum occurs by a complex multifactorial process involving the normal development of the testis, the hormonal actions of insulin like growth factor 3, testosterone, a intact hypothalamic pituitary testicular axis, the patent processus vaginalis, gubernacular outgrowth and regression and intraabdominal pressure. The paper reviews the key components of testicular descent, the current hypothesis on how testicular descent occurs and the controversies surrounding this hypothesis.

  17. An experimental test of Darwin's naturalization hypothesis.

    PubMed

    Jiang, Lin; Tan, Jiaqi; Pu, Zhichao

    2010-04-01

    One of the oldest ideas in invasion biology, known as Darwin's naturalization hypothesis, suggests that introduced species are more successful in communities in which their close relatives are absent. We conducted the first experimental test of this hypothesis in laboratory bacterial communities varying in phylogenetic relatedness between resident and invading species with and without a protist bacterivore. As predicted, invasion success increased with phylogenetic distance between the invading and the resident bacterial species in both the presence and the absence of protistan bacterivory. The frequency of successful invader establishment was best explained by average phylogenetic distance between the invader and all resident species, possibly indicating limitation by the availability of the unexploited niche (i.e., organic substances in the medium capable of supporting the invader growth); invader abundance was best explained by phylogenetic distance between the invader and its nearest resident relative, possibly indicating limitation by the availability of the unexploited optimal niche (i.e., the subset of organic substances supporting the best invader growth). These results were largely driven by one resident bacterium (a subspecies of Serratia marcescens) posting the strongest resistance to the alien bacterium (another subspecies of S. marcescens). Overall, our findings support phylogenetic relatedness as a useful predictor of species invasion success.

  18. Counselor Hypothesis-Testing Strategies.

    ERIC Educational Resources Information Center

    Strohmer, Douglas C.; Newman, Lisa J.

    1983-01-01

    Reports two experiments relevant to the questioning strategies counselors use in testing their hypotheses about clients. Results supported the idea that counselors are able to take a tentative hypothesis about a client and test its accuracy against additional independent, unbiased observations of the client. (LLL)

  19. On the Weyl curvature hypothesis

    SciTech Connect

    Stoica, Ovidiu Cristinel

    2013-11-15

    The Weyl curvature hypothesis of Penrose attempts to explain the high homogeneity and isotropy, and the very low entropy of the early universe, by conjecturing the vanishing of the Weyl tensor at the Big-Bang singularity. In previous papers it has been proposed an equivalent form of Einstein’s equation, which extends it and remains valid at an important class of singularities (including in particular the Schwarzschild, FLRW, and isotropic singularities). Here it is shown that if the Big-Bang singularity is from this class, it also satisfies the Weyl curvature hypothesis. As an application, we study a very general example of cosmological models, which generalizes the FLRW model by dropping the isotropy and homogeneity constraints. This model also generalizes isotropic singularities, and a class of singularities occurring in Bianchi cosmologies. We show that the Big-Bang singularity of this model is of the type under consideration, and satisfies therefore the Weyl curvature hypothesis. -- Highlights: •The singularities we introduce are described by finite geometric/physical objects. •Our singularities have smooth Riemann and Weyl curvatures. •We show they satisfy Penrose’s Weyl curvature hypothesis (Weyl=0 at singularities). •Examples: FLRW, isotropic singularities, an extension of Schwarzschild’s metric. •Example: a large class of singularities which may be anisotropic and inhomogeneous.

  20. Argument as Hypothesis-Testing.

    ERIC Educational Resources Information Center

    Zarefsky, David

    The argumentative perspective enables rhetoric to function in a manner analagous to science or analytic philosophy, yielding reliable knowledge about nonempirical topics, which other methods cannot address. In short, argumentation is the equivalent of hypothesis-testing. Forensics should offer laboratory experience in developing this perspective…

  1. Gender and the hygiene hypothesis.

    PubMed

    Clough, Sharyn

    2011-02-01

    The hygiene hypothesis offers an explanation for the correlation, well-established in the industrialized nations of North and West, between increased hygiene and sanitation, and increased rates of asthma and allergies. Recent studies have added to the scope of the hypothesis, showing a link between decreased exposure to certain bacteria and parasitic worms, and increased rates of depression and intestinal auto-immune disorders, respectively. What remains less often discussed in the research on these links is that women have higher rates than men of asthma and allergies, as well as many auto-immune disorders, and also depression. The current paper introduces a feminist understanding of gender socialization to the epidemiological and immunological picture. That standards of cleanliness are generally higher for girls than boys, especially under the age of five when children are more likely to be under close adult supervision, is a robust phenomenon in industrialized nations, and some research points to a cross-cultural pattern. I conclude that, insofar as the hygiene hypothesis successfully identifies standards of hygiene and sanitation as mediators of immune health, then attention to the relevant patterns of gender socialization is important. The review also makes clear that adding a feminist analysis of gender socialization to the hygiene hypothesis helps explain variation in morbidity rates not addressed by other sources and responds to a number of outstanding puzzles in current research. Alternative explanations for the sex differences in the relevant morbidity rates are also discussed (e.g., the effects of estrogens). Finally, new sources of evidence for the hygiene hypothesis are suggested in the form of cross-cultural and other natural experiments. PMID:21195519

  2. Climate induced temperature effects on growth performance, fecundity and recruitment in marine fish: developing a hypothesis for cause and effect relationships in Atlantic cod ( Gadus morhua) and common eelpout ( Zoarces viviparus)

    NASA Astrophysics Data System (ADS)

    Pörtner, H. O.; Berdal, B.; Blust, R.; Brix, O.; Colosimo, A.; De Wachter, B.; Giuliani, A.; Johansen, T.; Fischer, T.; Knust, R.; Lannig, G.; Naevdal, G.; Nedenes, A.; Nyhammer, G.; Sartoris, F. J.; Serendero, I.; Sirabella, P.; Thorkildsen, S.; Zakhartsev, M.

    2001-12-01

    Effects of global warming on animal distribution and performance become visible in many marine ecosystems. The present study was designed to develop a concept for a cause and effect understanding with respect to temperature changes and to explain ecological findings based on physiological processes. The concept is based on a wide comparison of invertebrate and fish species with a special focus on recent data obtained in two model species of fish. These fish species are both characterized by northern and southern distribution limits in the North Atlantic: eelpout ( Zoarces viviparus), as a typical non-migrating inhabitant of the coastal zone and the cod ( Gadus morhua), as a typical inhabitant of the continental shelf with a high importance for fisheries. Mathematical modelling demonstrates a clear significant correlation between climate induced temperature fluctuations and the recruitment of cod stocks. Growth performance in cod is optimal at temperatures close to 10°C, regardless of the population investigated in a latitudinal cline. However, temperature specific growth rates decrease at higher latitudes. Also, fecundity is less in White Sea than in North and Baltic Sea cod or eelpout populations. These findings suggest that a cold-induced shift in energy budget occurs which is unfavorable for growth performance and fecundity. Thermal tolerance limits shift depending on latitude and are characterized by oxygen limitation at both low or high temperatures. Oxygen supply to tissues is optimized at low temperature by a shift in hemoglobin isoforms and oxygen binding properties to lower affinities and higher unloading potential. Protective stimulation of heat shock protein synthesis was not observed. According to a recent model of thermal tolerance the downward shift of tolerance limits during cold adaptation is associated with rising mitochondrial densities and, thus, aerobic capacity and performance in the cold, especially in eurythermal species. At the same time

  3. Growth

    NASA Astrophysics Data System (ADS)

    Waag, Andreas

    This chapter is devoted to the growth of ZnO. It starts with various techniques to grow bulk samples and presents in some detail the growth of epitaxial layers by metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD). The last section is devoted to the growth of nanorods. Some properties of the resulting samples are also presented. If a comparison between GaN and ZnO is made, very often the huge variety of different growth techniques available to fabricate ZnO is said to be an advantage of this material system. Indeed, growth techniques range from low cost wet chemical growth at almost room temperature to high quality MOCVD growth at temperatures above 1, 000∘C. In most cases, there is a very strong tendency of c-axis oriented growth, with a much higher growth rate in c-direction as compared to other crystal directions. This often leads to columnar structures, even at relatively low temperatures. However, it is, in general, not straight forward to fabricate smooth ZnO thin films with flat surfaces. Another advantage of a potential ZnO technology is said to be the possibility to grow thin films homoepitaxially on ZnO substrates. ZnO substrates are mostly fabricated by vapor phase transport (VPT) or hydrothermal growth. These techniques are enabling high volume manufacturing at reasonable cost, at least in principle. The availability of homoepitaxial substrates should be beneficial to the development of ZnO technology and devices and is in contrast to the situation of GaN. However, even though a number of companies are developing ZnO substrates, only recently good quality substrates have been demonstrated. However, these substrates are not yet widely available. Still, the situation concerning ZnO substrates seems to be far from low-cost, high-volume production. The fabrication of dense, single crystal thin films is, in general, surprisingly difficult, even when ZnO is grown on a ZnO substrate. However

  4. Advances in uterine leiomyoma research: the progesterone hypothesis.

    PubMed

    Rein, M S

    2000-10-01

    Uterine leiomyomas are monoclonal tumors. However, the factors involved in their initiation and growth remain poorly understood. The neoplastic transformation of myometrium to leiomyoma likely involves somatic mutations of normal myometrium and the complex interactions of sex steroids and local growth factors. Traditionally, estrogen has been considered the major promoter of myoma growth. The purpose of this review is to highlight the biochemical, histologic, and clinical evidence that supports an equally important role for progesterone in the growth of uterine myomas. Biochemical studies suggest that progesterone, progestins, and the progesterone receptor modulate myoma mitotic activity. A hypothesis to explain the pathogenesis of myomas is presented.

  5. Temperature-driven plasticity in growth cessation and dormancy development in deciduous woody plants: a working hypothesis suggesting how molecular and cellular function is affected by temperature during dormancy induction.

    PubMed

    Tanino, Karen K; Kalcsits, Lee; Silim, Salim; Kendall, Edward; Gray, Gordon R

    2010-05-01

    The role of temperature during dormancy development is being reconsidered as more research emerges demonstrating that temperature can significantly influence growth cessation and dormancy development in woody plants. However, there are seemingly contradictory responses to warm and low temperature in the literature. This research/review paper aims to address this contradiction. The impact of temperature was examined in four poplar clones and two dogwood ecotypes with contrasting dormancy induction patterns. Under short day (SD) conditions, warm night temperature (WT) strongly accelerated timing of growth cessation leading to greater dormancy development and cold hardiness in poplar hybrids. In contrast, under long day (LD) conditions, low night temperature (LT) can completely bypass the short photoperiod requirement in northern but not southern dogwood ecotypes. These findings are in fact consistent with the literature in which both coniferous and deciduous woody plant species' growth cessation, bud set or dormancy induction are accelerated by temperature. The contradictions are addressed when photoperiod and ecotypes are taken into account in which the combination of either SD/WT (northern and southern ecotypes) or LD/LT (northern ecotypes only) are separated. Photoperiod insensitive types are driven to growth cessation by LT. Also consistent is the importance of night temperature in regulating these warm and cool temperature responses. However, the physiological basis for these temperature effects remain unclear. Changes in water content, binding and mobility are factors known to be associated with dormancy induction in woody plants. These were measured using non-destructive magnetic resonance micro-imaging (MRMI) in specific regions within lateral buds of poplar under SD/WT dormancing inducing conditions. Under SD/WT, dormancy was associated with restrictions in inter- or intracellular water movement between plant cells that reduces water mobility during dormancy

  6. Beyond the Black Queen Hypothesis.

    PubMed

    Mas, Alix; Jamshidi, Shahrad; Lagadeuc, Yvan; Eveillard, Damien; Vandenkoornhuyse, Philippe

    2016-09-01

    The Black Queen Hypothesis, recently proposed to explain an evolution of dependency based on gene loss, is gaining ground. This paper focuses on how the evolution of dependency transforms interactions and the community. Using agent-based modeling we suggest that species specializing in the consumption of a common good escape competition and therefore favor coexistence. This evolutionary trajectory could open the way for novel long-lasting interactions and a need to revisit the classically accepted assembly rules. Such evolutionary events also reshape the structure and dynamics of communities, depending on the spatial heterogeneity of the common good production. Let Black be the new black! PMID:26953598

  7. Antiaging therapy: a prospective hypothesis.

    PubMed

    Shahidi Bonjar, Mohammad Rashid; Shahidi Bonjar, Leyla

    2015-01-01

    This hypothesis proposes a new prospective approach to slow the aging process in older humans. The hypothesis could lead to developing new treatments for age-related illnesses and help humans to live longer. This hypothesis has no previous documentation in scientific media and has no protocol. Scientists have presented evidence that systemic aging is influenced by peculiar molecules in the blood. Researchers at Albert Einstein College of Medicine, New York, and Harvard University in Cambridge discovered elevated titer of aging-related molecules (ARMs) in blood, which trigger cascade of aging process in mice; they also indicated that the process can be reduced or even reversed. By inhibiting the production of ARMs, they could reduce age-related cognitive and physical declines. The present hypothesis offers a new approach to translate these findings into medical treatment: extracorporeal adjustment of ARMs would lead to slower rates of aging. A prospective "antiaging blood filtration column" (AABFC) is a nanotechnological device that would fulfill the central role in this approach. An AABFC would set a near-youth homeostatic titer of ARMs in the blood. In this regard, the AABFC immobilizes ARMs from the blood while blood passes through the column. The AABFC harbors antibodies against ARMs. ARM antibodies would be conjugated irreversibly to ARMs on contact surfaces of the reaction platforms inside the AABFC till near-youth homeostasis is attained. The treatment is performed with the aid of a blood-circulating pump. Similar to a renal dialysis machine, blood would circulate from the body to the AABFC and from there back to the body in a closed circuit until ARMs were sufficiently depleted from the blood. The optimal application criteria, such as human age for implementation, frequency of treatments, dosage, ideal homeostasis, and similar concerns, should be revealed by appropriate investigations. If AABFC technology undergoes practical evaluations and gains approval

  8. In search of the hypothesis.

    PubMed Central

    Kaufman, J S; Cooper, R S

    1995-01-01

    Epidemiologic studies of racial differences sorely lack sound and explicit hypotheses. Race is a social convention, not a biological concept. Its careless use in epidemiology demonstrates a failure to generate appropriate hypotheses to study its role in health. Studies of hypertension in blacks illustrate the point. Two underlying pitfalls plague hypothesis generation: directionality involving the null and alternative hypotheses and circularity, where efforts to understand social factors have the effect of emphasizing racial differences. The proper prescription is to identify explicitly the hypotheses of interest, including their origins and implication. Images p662-a p665-a PMID:8570813

  9. [HYPOTHESIS OF FORMATION DURING THE EVOLUTION OF MECHANISM OF SENESCENCE].

    PubMed

    Makrushin, A V

    2015-01-01

    A hypothesis is in the evolution origin of the mechanism of senescence--is consequence of growth of individual integrity and thus loss ability to asexual reproduction. Evolutionary precursor of senescence mechanism was probably morphogenetic adaptation of potentially immortal precambrian Metazoa with which they adapted to the changing environment. PMID:26390606

  10. North Pacific High: an hypothesis

    NASA Astrophysics Data System (ADS)

    Kenyon, Kern E.

    An hypothesis is offered for the cause and maintenance of the North Pacific High (NPH). Over a broad but well defined open ocean area, in the mid-latitude North Pacific, the ocean heats the atmosphere from below, and outside the boundaries of the heat source the ocean cools the air at the sea surface. Vertical thermal convection in the air over the heat source brings down relatively cool dry air, producing a horizontal contrast mainly in relative humidity inside and outside the heat source region. Consequently relatively high density air is produced over the heat source, and if the temperature is approximately constant, then the barometric pressure will be high over the heat source as well. Being unstable, due to a horizontal pressure gradient, the high density air will try to move radially outward from the heat source, and the Coriolis force will bend the outward flow into a clockwise circulation around the center of high pressure. The heat source is provided by a broad northeastward warm surface current, previously described, that crosses mid-latitudes on the eastern side of the North Pacific at all times of the year. Given the known characteristics of the warm current, the heat source mechanism can explain the observed seasonal variations of the NPH also. A more complete substantiation (or refutation) of the general hypothesis for the origin of the NPH must await the accumulation of additional oceanic and atmospheric data.

  11. Ecology: Darwin's naturalization hypothesis challenged.

    PubMed

    Duncan, Richard P; Williams, Peter A

    2002-06-01

    Naturalized plants can have a significant ecological and economic impact, yet they comprise only a fraction ot the plant species introduced by humans. Darwin proposed that introduced plant species will be less likely to establish a self-sustaining wild population in places with congeneric native species because the introduced plants have to compete with their close relatives, or are more likely to be attacked by native herbivores or pathogens, a theory known as Darwin's naturalization hypothesis. Here we analyze a complete list of seed-plant species that have been introduced to New Zealand and find that those with congeneric relatives are significantly more, not less, likely to naturalize--perhaps because they share with their native relatives traits that pre-adapt them to their new environment.

  12. A maximum hypothesis of transpiration

    NASA Astrophysics Data System (ADS)

    Wang, Jingfeng; Bras, Rafael L.; Lerdau, Manuel; Salvucci, Guido D.

    2007-09-01

    We hypothesize that the system of liquid water in leaf tissues and the water vapor in the atmosphere tends to evolve towards a potential equilibrium as quickly as possible by maximization of the transpiration rate. We make two assumptions in formulating the transpiration rate: (1) stomatal aperture is directly controlled by guard cell turgor (or leaf water potential); (2) CO2 flux can be used as a nonparametric equivalent of stomatal conductance for a given stomatal function (not necessarily optimal in terms of the water use efficiency for photosynthesis). Transpiration is then expressed as a function of leaf temperature, CO2 flux (as a surrogate of stomatal conductance), and sensible heat flux characterizing the transport mechanism at a given level of radiative energy input. Maximization of transpiration constrained by the energy balance equation leads to vanishing derivatives of transpiration with respect to leaf temperature and CO2 flux. We have obtained observational evidence in support of the proposed hypothesis.

  13. The selection-arena hypothesis.

    PubMed

    Stearns, S C

    1987-01-01

    The selection arena hypothesis offers one answer to a puzzling question. Why do some organisms produce many more fertilized zygotes than are actually reared to hatching, birth, or release-then neglect, discard, resorb, or eat some of them, or allow them to eat each other? It makes four assumptions: (1) zygotes are cheap; (2) after conception the investment of parental time, energy, or risk into offspring continues; (3) offspring vary in fitness; (4) variation in offspring fitness can be identified by the mother at an early stage of the life cycle. If these assumptions hold, then one general prediction follows: the parent should overproduce zygotes, identify those with lower expected fitness, then either kill and reabsorb them, let them be eaten by sibs, or simply stop feeding them in order to invest in more promising offspring. The explanation appears to apply to a wide range of phenomena whose common cause had not previously been appreciated. These include: (1) polyovulation in some bats, tenrecs, the plains viscacha, and the pronghorn antelope; (2) cases of recurrent, consecutive, spontaneous abortions in humans; (3) some cases of surplus flower production and fruit abortion; (4) sex-ratio adjustment in red deer, mice, and coypus; (5) some types of cannibalism, including possible cases in mice, sharks, and wasps. Some cases that might be explained by the selection arena hypothesis are also plausibly explained by other causes, including bet-hedging reproductive investment in the face of unpredictable food supplies, and inter-specific or inter-familial aggression as an alternative to parent-offspring or sib-sib cannibalism. PMID:2961604

  14. The Over-Pruning Hypothesis of Autism

    ERIC Educational Resources Information Center

    Thomas, Michael S. C.; Davis, Rachael; Karmiloff-Smith, Annette; Knowland, Victoria C. P.; Charman, Tony

    2016-01-01

    This article outlines the "over-pruning hypothesis" of autism. The hypothesis originates in a neurocomputational model of the regressive sub-type (Thomas, Knowland & Karmiloff-Smith, 2011a, 2011b). Here we develop a more general version of the over-pruning hypothesis to address heterogeneity in the timing of manifestation of ASD,…

  15. Multijurisdictional economies, the Tiebout Hypothesis, and sorting

    PubMed Central

    Wooders, Myrna H.

    1999-01-01

    The Tiebout Hypothesis asserts that, when it is efficient to have multiple jurisdictions providing local public goods, then competition between jurisdictions for residents will lead to a near-optimal outcome. Research from cooperative game theory both provides a foundation for the hypothesis and extends the hypothesis to diverse situations where small groups of participants are effective. PMID:10485868

  16. The venom optimization hypothesis revisited.

    PubMed

    Morgenstern, David; King, Glenn F

    2013-03-01

    Animal venoms are complex chemical mixtures that typically contain hundreds of proteins and non-proteinaceous compounds, resulting in a potent weapon for prey immobilization and predator deterrence. However, because venoms are protein-rich, they come with a high metabolic price tag. The metabolic cost of venom is sufficiently high to result in secondary loss of venom whenever its use becomes non-essential to survival of the animal. The high metabolic cost of venom leads to the prediction that venomous animals may have evolved strategies for minimizing venom expenditure. Indeed, various behaviors have been identified that appear consistent with frugality of venom use. This has led to formulation of the "venom optimization hypothesis" (Wigger et al. (2002) Toxicon 40, 749-752), also known as "venom metering", which postulates that venom is metabolically expensive and therefore used frugally through behavioral control. Here, we review the available data concerning economy of venom use by animals with either ancient or more recently evolved venom systems. We conclude that the convergent nature of the evidence in multiple taxa strongly suggests the existence of evolutionary pressures favoring frugal use of venom. However, there remains an unresolved dichotomy between this economy of venom use and the lavish biochemical complexity of venom, which includes a high degree of functional redundancy. We discuss the evidence for biochemical optimization of venom as a means of resolving this conundrum.

  17. Alien abduction: a medical hypothesis.

    PubMed

    Forrest, David V

    2008-01-01

    In response to a new psychological study of persons who believe they have been abducted by space aliens that found that sleep paralysis, a history of being hypnotized, and preoccupation with the paranormal and extraterrestrial were predisposing experiences, I noted that many of the frequently reported particulars of the abduction experience bear more than a passing resemblance to medical-surgical procedures and propose that experience with these may also be contributory. There is the altered state of consciousness, uniformly colored figures with prominent eyes, in a high-tech room under a round bright saucerlike object; there is nakedness, pain and a loss of control while the body's boundaries are being probed; and yet the figures are thought benevolent. No medical-surgical history was apparently taken in the above mentioned study, but psychological laboratory work evaluated false memory formation. I discuss problems in assessing intraoperative awareness and ways in which the medical hypothesis could be elaborated and tested. If physicians are causing this syndrome in a percentage of patients, we should know about it; and persons who feel they have been abducted should be encouraged to inform their surgeons and anesthesiologists without challenging their beliefs.

  18. The oxidative hypothesis of senescence.

    PubMed

    Gilca, M; Stoian, I; Atanasiu, V; Virgolici, B

    2007-01-01

    The oxidative hypothesis of senescence, since its origin in 1956, has garnered significant evidence and growing support among scientists for the notion that free radicals play an important role in ageing, either as "damaging" molecules or as signaling molecules. Age-increasing oxidative injuries induced by free radicals, higher susceptibility to oxidative stress in short-lived organisms, genetic manipulations that alter both oxidative resistance and longevity and the anti-ageing effect of caloric restriction and intermittent fasting are a few examples of accepted scientific facts that support the oxidative theory of senescence. Though not completely understood due to the complex "network" of redox regulatory systems, the implication of oxidative stress in the ageing process is now well documented. Moreover, it is compatible with other current ageing theories (e.g, those implicating the mitochondrial damage/mitochondrial-lysosomal axis, stress-induced premature senescence, biological "garbage" accumulation, etc). This review is intended to summarize and critically discuss the redox mechanisms involved during the ageing process: sources of oxidant agents in ageing (mitochondrial -electron transport chain, nitric oxide synthase reaction- and non-mitochondrial- Fenton reaction, microsomal cytochrome P450 enzymes, peroxisomal beta -oxidation and respiratory burst of phagocytic cells), antioxidant changes in ageing (enzymatic- superoxide dismutase, glutathione-reductase, glutathion peroxidase, catalase- and non-enzymatic glutathione, ascorbate, urate, bilirubine, melatonin, tocopherols, carotenoids, ubiquinol), alteration of oxidative damage repairing mechanisms and the role of free radicals as signaling molecules in ageing.

  19. Segmentation and the pairing hypothesis.

    PubMed

    Bragason, Orn

    2004-09-30

    The effect of stimulus contiguity and response contingency on responding in chain schedules was examined in two experiments. In Experiment 1, four pigeons were trained on two simple three-link chain schedules that alternated within sessions. Initial links were correlated with a variable-interval 30s schedule, and middle and terminal links were correlated with interdependent variable-interval 30s variable-interval 30s schedules. The combined duration of the interdependent schedules summed to 60s. The two chains differed with respect to signaling of the schedule components: a two-stimulus chain had one stimulus paired with the initial link and one stimulus paired with both the middle and the terminal link, while a three-stimulus chain had a different stimulus paired with the each of the three links. The results showed that the two-stimulus chain maintained lower initial-link responding than the three-stimulus chain. In Experiment 2, four pigeons were exposed to three separate conditions, the two- and three-stimulus chains of Experiment 1 and a three-stimulus chain that had a 3s delay to terminal-link entry from the middle-link response that produced it. The two-stimulus chain maintained lower initial-link responding than the three-stimulus chain, as in Experiment 1, and a similar initial-link responding was maintained by the two-stimulus chain and the three-stimulus chain with the delay contingency. The results demonstrate that a stimulus noncontiguous with food can maintain responding that is sometimes greater than a stimulus contiguous with food, depending on the response contingency for terminal-link entry. The results are contrary to the pairing hypothesis of conditioned reinforcement.

  20. Testing the geometric clutch hypothesis.

    PubMed

    Lindemann, Charles B

    2004-12-01

    The Geometric Clutch hypothesis is based on the premise that transverse forces (t-forces) acting on the outer doublets of the eukaryotic axoneme coordinate the action of the dynein motors to produce flagellar and ciliary beating. T-forces result from tension and compression on the outer doublets when a bend is present on the flagellum or cilium. The t-force acts to pry the doublets apart in an active bend, and push the doublets together when the flagellum is passively bent and thus could engage and disengage the dynein motors. Computed simulations of this working mechanism have reproduced the beating pattern of simple cilia and flagella, and of mammalian sperm. Cilia-like beating, with a clearly defined effective and recovery stroke, can be generated using one uniformly applied switching algorithm. When the mechanical properties and dimensions appropriate to a specific flagellum are incorporated into the model the same algorithm can simulate a sea urchin or bull sperm-like beat. The computed model reproduces many of the observed behaviors of real flagella and cilia. The model can duplicate the results of outer arm extraction experiments in cilia and predicted two types of arrest behavior that were verified experimentally in bull sperm. It also successfully predicted the experimentally determined nexin elasticity. Calculations based on live and reactivated sea urchin and bull sperm yielded a value of 0.5 nN/microm for the t-force at the switch-point. This is a force sufficient to overcome the shearing force generated by all the dyneins on one micron of outer doublet. A t-force of this magnitude should produce substantial distortion of the axoneme at the switch-point, especially in spoke or spoke-head deficient motile flagella. This concrete and verifiable prediction is within the grasp of recent advances in imaging technology, specifically cryoelectron microscopy and atomic force microscopy. PMID:15567522

  1. Infantile amnesia: a neurogenic hypothesis.

    PubMed

    Josselyn, Sheena A; Frankland, Paul W

    2012-08-16

    In the late 19th Century, Sigmund Freud described the phenomenon in which people are unable to recall events from early childhood as infantile amnesia. Although universally observed, infantile amnesia is a paradox; adults have surprisingly few memories of early childhood despite the seemingly exuberant learning capacity of young children. How can these findings be reconciled? The mechanisms underlying this form of amnesia are the subject of much debate. Psychological/cognitive theories assert that the ability to maintain detailed, declarative-like memories in the long term correlates with the development of language, theory of mind, and/or sense of "self." However, the finding that experimental animals also show infantile amnesia suggests that this phenomenon cannot be explained fully in purely human terms. Biological explanations of infantile amnesia suggest that protracted postnatal development of key brain regions important for memory interferes with stable long-term memory storage, yet they do not clearly specify which particular aspects of brain maturation are causally related to infantile amnesia. Here, we propose a hypothesis of infantile amnesia that focuses on one specific aspect of postnatal brain development--the continued addition of new neurons to the hippocampus. Infants (humans, nonhuman primates, and rodents) exhibit high levels of hippocampal neurogenesis and an inability to form lasting memories. Interestingly, the decline of postnatal neurogenesis levels corresponds to the emergence of the ability to form stable long-term memory. We propose that high neurogenesis levels negatively regulate the ability to form enduring memories, most likely by replacing synaptic connections in preexisting hippocampal memory circuits.

  2. The viral hypothesis in parkinsonism.

    PubMed

    Elizan, T S; Casals, J

    1983-01-01

    The most crucial unanswered question in Parkinson's disease is its fundamental cause. Since Carlsson's original suggestion that dopamine may be a transmitter in the central nervous system involved in the control of motor function and that it may be involved in the Parkinsonian syndrome (Carlsson, 1959), and the now-classic paper by Ehringer and Hornykiewicz (1960) which definitively showed the significant reduction of dopamine concentration in the neostriatum of cases of idiopathic Parkinson and postencephalitic parkinsonism, the vast amount of work on the subject has focused on the biochemical and pharmacologic correlates of this dopaminergic system failure involving particularly the nigrostriatal pathways. The concept of a specific neurotransmitter deficiency associated with a specific neurological syndrome potentially amenable to replacement therapy, has appropriately generated a considerable degree of clinical and research interest for over 20 years, but, with few exceptions, there has been hardly any focused or concerted research effort on looking at direct causal factors or primary initiating events in this disease process. As in Alzheimer's disease, another of the degenerative diseases of the brain of unknown origin with a specific biochemical substrate, any etiologic hypothesis for Parkinson's disease--whether a virus, an age-related immune system dysfunction, a genetic factor, a "trophic" substance, or a toxin--would have to explain the selective involvement of specific transmitter-defined neuronal pathways, the non-specificity of the brain lesions that define the disease, and the clinical involvement of a sizeable segment of the aging population. Of the several plausible hypotheses mentioned earlier, which are not necessarily mutually exclusive, we would like to critically consider the possibility of a viral cause. PMID:6583315

  3. Fungiculture or Termite Husbandry? The Ruminant Hypothesis.

    PubMed

    Nobre, Tânia; Aanen, Duur K

    2012-01-01

    We present a new perspective for the role of Termitomyces fungi in the mutualism with fungus-growing termites. According to the predominant view, this mutualism is as an example of agriculture with termites as farmers of a domesticated fungus crop, which is used for degradation of plant-material and production of fungal biomass. However, a detailed study of the literature indicates that the termites might as well be envisioned as domesticates of the fungus. According to the "ruminant hypothesis" proposed here, termite workers, by consuming asexual fruiting bodies not only harvest asexual spores, but also lignocellulolytic enzymes, which they mix with foraged plant material and enzymes of termite and possibly bacterial origin. This mixture is the building material of the fungus garden and facilitates efficient degradation of plant material. The fungus garden thus functions as an external rumen for termites and primarily the fungi themselves benefit from their own, and gut-derived, lignocellulolytic enzymes, using the termites to efficiently mix these with their growth substrate. Only secondarily the termites benefit, when they consume the degraded, nitrogen-enriched plant-fungus mixture a second time. We propose that the details of substrate use, and the degree of complementarity and redundancy among enzymes in food processing, determine selection of horizontally transmitted fungal symbionts at the start of a colony: by testing spores on a specific, mechanically and enzymatically pre-treated growth substrate, the termite host has the opportunity to select specific fungal symbionts. Potentially, the gut-microbiota thus influence host-fungus specificity, and the selection of specific fungal strains at the start of a new colony. We argue that we need to expand the current bipartite insect-biased view of the mutualism of fungus-growing termites and include the possible role of bacteria and the benefit for the fungi to fully understand the division of labor among

  4. Hypothesis generation in signaling networks.

    PubMed

    Ruths, Derek A; Nakhleh, Luay; Iyengar, M Sriram; Reddy, Shrikanth A G; Ram, Prahlad T

    2006-11-01

    Biological signaling networks comprise the chemical processes by which cells detect and respond to changes in their environment. Such networks have been implicated in the regulation of important cellular activities, including cellular reproduction, mobility, and death. Though technological and scientific advances have facilitated the rapid accumulation of information about signaling networks, utilizing these massive information resources has become infeasible except through computational methods and computer-based tools. To date, visualization and simulation tools have received significant emphasis. In this paper, we present a graph-theoretic formalization of biological signaling network models that are in wide but informal use, and formulate two problems on the graph: the Constrained Downstream and Minimum Knockout Problems. Solutions to these problems yield qualitative tools for generating hypotheses about the networks, which can then be experimentally tested in a laboratory setting. Using established graph algorithms, we provide a solution to the Constrained Downstream Problem. We also show that the Minimum Knockout Problem is NP-Hard, propose a heuristic, and assess its performance. In tests on the Epidermal Growth Factor Receptor (EGFR) network, we find that our heuristic reports the correct solution to the problem in seconds. Source code for the implementations of both solutions is available from the authors upon request.

  5. Vascular gene expression: a hypothesis

    PubMed Central

    Martínez-Navarro, Angélica C.; Galván-Gordillo, Santiago V.; Xoconostle-Cázares, Beatriz; Ruiz-Medrano, Roberto

    2013-01-01

    The phloem is the conduit through which photoassimilates are distributed from autotrophic to heterotrophic tissues and is involved in the distribution of signaling molecules that coordinate plant growth and responses to the environment. Phloem function depends on the coordinate expression of a large array of genes. We have previously identified conserved motifs in upstream regions of the Arabidopsis genes, encoding the homologs of pumpkin phloem sap mRNAs, displaying expression in vascular tissues. This tissue-specific expression in Arabidopsis is predicted by the overrepresentation of GA/CT-rich motifs in gene promoters. In this work we have searched for common motifs in upstream regions of the homologous genes from plants considered to possess a “primitive” vascular tissue (a lycophyte), as well as from others that lack a true vascular tissue (a bryophyte), and finally from chlorophytes. Both lycophyte and bryophyte display motifs similar to those found in Arabidopsis with a significantly low E-value, while the chlorophytes showed either a different conserved motif or no conserved motif at all. These results suggest that these same genes are expressed coordinately in non-vascular plants; this coordinate expression may have been one of the prerequisites for the development of conducting tissues in plants. We have also analyzed the phylogeny of conserved proteins that may be involved in phloem function and development. The presence of CmPP16, APL, FT, and YDA in chlorophytes suggests the recruitment of ancient regulatory networks for the development of the vascular tissue during evolution while OPS is a novel protein specific to vascular plants. PMID:23882276

  6. Testing the gravitational instability hypothesis?

    NASA Technical Reports Server (NTRS)

    Babul, Arif; Weinberg, David H.; Dekel, Avishai; Ostriker, Jeremiah P.

    1994-01-01

    We challenge a widely accepted assumption of observational cosmology: that successful reconstruction of observed galaxy density fields from measured galaxy velocity fields (or vice versa), using the methods of gravitational instability theory, implies that the observed large-scale structures and large-scale flows were produced by the action of gravity. This assumption is false, in that there exist nongravitational theories that pass the reconstruction tests and gravitational theories with certain forms of biased galaxy formation that fail them. Gravitational instability theory predicts specific correlations between large-scale velocity and mass density fields, but the same correlations arise in any model where (a) structures in the galaxy distribution grow from homogeneous initial conditions in a way that satisfies the continuity equation, and (b) the present-day velocity field is irrotational and proportional to the time-averaged velocity field. We demonstrate these assertions using analytical arguments and N-body simulations. If large-scale structure is formed by gravitational instability, then the ratio of the galaxy density contrast to the divergence of the velocity field yields an estimate of the density parameter Omega (or, more generally, an estimate of beta identically equal to Omega(exp 0.6)/b, where b is an assumed constant of proportionality between galaxy and mass density fluctuations. In nongravitational scenarios, the values of Omega or beta estimated in this way may fail to represent the true cosmological values. However, even if nongravitational forces initiate and shape the growth of structure, gravitationally induced accelerations can dominate the velocity field at late times, long after the action of any nongravitational impulses. The estimated beta approaches the true value in such cases, and in our numerical simulations the estimated beta values are reasonably accurate for both gravitational and nongravitational models. Reconstruction tests

  7. The Input Hypothesis: An Inside Look.

    ERIC Educational Resources Information Center

    Higgs, Theodore V.

    1985-01-01

    Summarizes and discusses Krashen's "input hypothesis" as presented in his "Principles and Practice in Second Language Acquisition." Suggests that the input hypothesis fails to account convincingly for arrested second language acquisition in an acquisition-rich environment and that it is not directly applicable to U.S. high school and university…

  8. A Model of the Relative Income Hypothesis

    ERIC Educational Resources Information Center

    Sanders, Shane

    2010-01-01

    James Duesenberry's (1949) relative income hypothesis holds substantial empirical credibility, as well as a rich set of implications. Although present in the pages of leading economics journals, the hypothesis has become all but foreign to the blackboards of economics classrooms. To help reintegrate the concept into the undergraduate economics…

  9. The Interaction Hypothesis: A Literature Review

    ERIC Educational Resources Information Center

    Tran, Thu Hoang

    2009-01-01

    This paper will examine the interaction hypothesis (IH) in second language acquisition (SLA). To begin with a short discussion of the confusing terms in SLA such as theory, model, hypothesis, and construct will be done so as to help readers easily understand theories in the field of SLA and related concepts. Next, what the IH is, and who proposed…

  10. Statistics and Hypothesis Testing in Biology.

    ERIC Educational Resources Information Center

    Maret, Timothy J.; Ziemba, Robert E.

    1997-01-01

    Suggests that early in their education students be taught to use basic statistical tests as rigorous methods of comparing experimental results with scientific hypotheses. Stresses that students learn how to use statistical tests in hypothesis-testing by applying them in actual hypothesis-testing situations. To illustrate, uses questions such as…

  11. Three Strategies for Elaborating the Cultivation Hypothesis.

    ERIC Educational Resources Information Center

    Potter, W. James

    1988-01-01

    Uses three strategies (dividing cultivation into component subprocesses, testing for an intervening variable, and contingent relationships) for elaborating the cultivation hypothesis. Finds evidence that cultivation effects do exist but that dividing the socialization process does not increase the predictive power of the cultivation hypothesis.…

  12. Current Status of the Molecular Clock Hypothesis

    ERIC Educational Resources Information Center

    Hermann, Gilbert

    2003-01-01

    Molecular genetics is a rapidly changing field with new developments almost from day to day. One interesting hypothesis that has come from everyone's ability to sequence proteins and/or genes is that of the molecular clock. This hypothesis postulates that homologous sequences of DNA and thus macro molecules evolve at a constant and invariable rate…

  13. Investigation of the Frohlich hypothesis with high intensity terahertz radiation

    NASA Astrophysics Data System (ADS)

    Weightman, Peter

    2014-03-01

    This article provides an update to recent reviews of the Frohlich hypothesis that biological organisation is facilitated by the creation of coherent excited states driven by a flow of free energy provided by metabolic processes and mediated by molecular motions in the terahertz range. Sources of intense terahertz radiation have the potential to test this hypothesis since if it is true the growth and development of sensitive systems such as stem cells should be influenced by irradiation with intense terahertz radiation. A brief survey of recent work shows that it is not yet possible to make an assessment of the validity of the Frohlich hypothesis. Under some conditions a variety of cell types respond to irradiation with intense THz radiation in ways that involve changes in the activity of their DNA. In other experiments very intense and prolonged THz radiation has no measureable effect on the behavior of very sensitive systems such as stem cells. The wide variation in experimental conditions makes it impossible to draw any conclusions as to characteristics of THz radiation that will induce a response in living cells. It is possible that in environments suitable for their maintenance and growth cells are capable of compensating for any effects caused by exposure to THz radiation up to some currently unknown level of THz peak power.

  14. The arsenic exposure hypothesis for Alzheimer disease.

    PubMed

    Gong, Gordon; OʼBryant, Sid E

    2010-01-01

    Prior research has shown that arsenic exposure induces changes that coincide with most of the developmental, biochemical, pathologic, and clinical features of Alzheimer disease (AD) and associated disorders. On the basis of this literature, we propose the Arsenic Exposure Hypothesis for AD that is inclusive of and cooperative with the existing hypotheses. Arsenic toxicity induces hyperphosphorylation of protein tau and overtranscription of the amyloid precursor protein, which are involved in the formation of neurofibrillary tangles and brain amyloid plaques, consistent with the amyloid hypothesis of AD. Arsenic exposure has been associated with cardiovascular diseases and associated risk factors, which is in agreement with the vascular hypothesis of AD. Arsenic exposure invokes brain inflammatory responses, which resonates with the inflammatory hypotheses of AD. Arsenic exposure has been linked to reduced memory and intellectual abilities in children and adolescents, which provides a biologic basis for the developmental origin of health and disease hypothesis for AD. Arsenic and its metabolites generate free radicals causing oxidative stress and neuronal death, which fits the existing oxidative stress hypothesis. Taken together, the arsenic exposure hypothesis for AD provides a parsimonious testable hypothesis for the development and progression of this devastating disease at least for some subsets of individuals.

  15. Knowledge dimensions in hypothesis test problems

    NASA Astrophysics Data System (ADS)

    Krishnan, Saras; Idris, Noraini

    2012-05-01

    The reformation in statistics education over the past two decades has predominantly shifted the focus of statistical teaching and learning from procedural understanding to conceptual understanding. The emphasis of procedural understanding is on the formulas and calculation procedures. Meanwhile, conceptual understanding emphasizes students knowing why they are using a particular formula or executing a specific procedure. In addition, the Revised Bloom's Taxonomy offers a twodimensional framework to describe learning objectives comprising of the six revised cognition levels of original Bloom's taxonomy and four knowledge dimensions. Depending on the level of complexities, the four knowledge dimensions essentially distinguish basic understanding from the more connected understanding. This study identifiesthe factual, procedural and conceptual knowledgedimensions in hypothesis test problems. Hypothesis test being an important tool in making inferences about a population from sample informationis taught in many introductory statistics courses. However, researchers find that students in these courses still have difficulty in understanding the underlying concepts of hypothesis test. Past studies also show that even though students can perform the hypothesis testing procedure, they may not understand the rationale of executing these steps or know how to apply them in novel contexts. Besides knowing the procedural steps in conducting a hypothesis test, students must have fundamental statistical knowledge and deep understanding of the underlying inferential concepts such as sampling distribution and central limit theorem. By identifying the knowledge dimensions of hypothesis test problems in this study, suitable instructional and assessment strategies can be developed in future to enhance students' learning of hypothesis test as a valuable inferential tool.

  16. Hypothesis-free? No such thing

    SciTech Connect

    Wiley, H. S.

    2008-06-01

    Finding meaningful relationships in complex datasets requires starting with the appropriate data. A hypothesis usually takes the form of a mechanistic relationship between a specific cause and a consequent effect, and this will almost always depend on experimental context. There are some circumstances when data must be gathered in the absence of context or hypothesis to characterize a system, but it is unrealistic to expect such preliminary studies to lead to significant biological insights. For this, you need a hypothesis. Systems biology might be the future of biology, but we still need hypotheses to take us where we want to go.

  17. Killing Me Softly: The Fetal Origins Hypothesis*

    PubMed Central

    Almond, Douglas

    2013-01-01

    In the epidemiological literature, the fetal origins hypothesis associated with David J. Barker posits that chronic, degenerative conditions of adult health, including heart disease and type 2 diabetes, may be triggered by circumstance decades earlier, in utero nutrition in particular. Economists have expanded on this hypothesis, investigating a broader range of fetal shocks and circumstances and have found a wealth of later-life impacts on outcomes including test scores, educational attainment, and income, along with health. In the process, they have provided some of the most credible observational evidence in support of the hypothesis. The magnitude of the impacts is generally large. Thus, the fetal origins hypothesis has not only survived contact with economics, but has flourished. PMID:25152565

  18. Putting Down the Discovery Learning Hypothesis

    ERIC Educational Resources Information Center

    Chambers, David W.

    1971-01-01

    The author analyzes some of the conceptual problems which have prevented a direct test of the discovery learning hypothesis, provides an operational definition of discovery learning, and proposes an improved experimental paradigm. Appended are 38 references. (AA)

  19. Energy-squeeze model: further tests of the hypothesis

    SciTech Connect

    Santini, D.J.; Belak, F.J.

    1985-01-01

    In order to extend the time period for statistical tests of the validity of the energy-squeeze model, Shaw's data on the Value of Commodity Output since 1869 is used in conjunction with Historical Statistics of the US and an updated version of the data base compiled for the original paper. Use of Shaw's data for the period 1890 to 1933 allows the examination of the consistency of success of the hypothesis over almost a century. Measures of changes of the consumer's share of expenditures devoted to energy are used as predictors of changes in real Gross National Product (GNP) per capita, unemployment, and durable goods output (or purchases). The theory that a change in the rate of growth of the money supply determines economic activity is also tested. Comparison of the results for the two theories shows that they work about equally well under the tests used here. A ''cumulative pressure'' hypothesis asserting that it takes two years of cumulative energy-share or monetary-growth-rate changes to cause consumers to react strongly is found to be quite successful. The correlation of two-year energy-share and monetary-growth-rate shifts is found to be highest during depressions, suggesting that depression-inducing energy and monetary problems are fundamentally linked. 14 refs., 3 tabs.

  20. Asynchronous hatching and food limitation: a test of Lack's hypothesis

    USGS Publications Warehouse

    Skagen, Susan Knight

    1988-01-01

    Lack’s (1954, 1968) hypothesis that asynchronous hatching of altricial birds is an adaptive response to unpredictable food shortages during the breeding season was examined in the highly granivorous Zebra Finch (Poephila guttata). I compared growth and survival of nestlings in asynchronous and artificially created synchronous brood reared under food-limited and food-abundant conditions in an aviary. I also examined the role of parental experience on survival and growth of nestlings. There was no differential mortality of Zebra Finch nestlings due to either asynchrony or food abundance. Young in abundant food treatments grew more rapidly, however, than those in food restricted treatments. Heaviest Zebra Finch nestlings in a brood grew more quickly than their lightest siblings when food was limited, supporting Lack’s hypothesis. Further, differential survival of light and heavy siblings occurred when food was abundant, suggesting that asynchronous hatching can be maladaptive under some ecological conditions. Nestlings reared by inexperienced parents suffered greater mortality and slower growth when food was abundant than nestlings raised by experienced parents. Prefledging mass was correlated with size at adulthood.

  1. Aromatic herbs in Corsican blue tit nests: The 'Potpourri' hypothesis

    NASA Astrophysics Data System (ADS)

    Lambrechts, Marcel M.; Dos Santos, Anabelle

    2000-05-01

    This study reports that Corsican blue tit ( Parus caeruleus ogliastrae) nests contain between one to five aromatic herb species between the onset of egg laying till the chicks' finished growth 13 d after hatching. An herb removal experiment during the chick stage shows that blue tits bring fresh aromatic material 1-5 d after herb removal. Nests with a series of distinct odour classes easily perceived by humans have never been reported in birds. A new 'Potpourri' hypothesis is proposed that may explain the functional significance of this behaviour.

  2. Does the dopamine hypothesis explain schizophrenia?

    PubMed

    Lau, Chi-Ieong; Wang, Han-Cheng; Hsu, Jung-Lung; Liu, Mu-En

    2013-01-01

    The dopamine hypothesis has been the cornerstone in the research and clinical practice of schizophrenia. With the initial emphasis on the role of excessive dopamine, the hypothesis has evolved to a concept of combining prefrontal hypodopaminergia and striatal hyperdopaminergia, and subsequently to the present aberrant salience hypothesis. This article provides a brief overview of the development and evidence of the dopamine hypothesis. It will argue that the current model of aberrant salience explains psychosis in schizophrenia and provides a plausible linkage between the pharmacological and cognitive aspects of the disease. Despite the privileged role of dopamine hypothesis in psychosis, its pathophysiological rather than etiological basis, its limitations in defining symptoms other than psychosis, as well as the evidence of other neurotransmitters such as glutamate and adenosine, prompt us to a wider perspective of the disease. Finally, dopamine does explain the pathophysiology of schizophrenia, but not necessarily the cause per se. Rather, dopamine acts as the common final pathway of a wide variety of predisposing factors, either environmental, genetic, or both, that lead to the disease. Other neurotransmitters, such as glutamate and adenosine, may also collaborate with dopamine to give rise to the entire picture of schizophrenia. PMID:23843581

  3. Multiple hypothesis tracking for the cyber domain

    NASA Astrophysics Data System (ADS)

    Schwoegler, Stefan; Blackman, Sam; Holsopple, Jared; Hirsch, Michael J.

    2011-09-01

    This paper discusses how methods used for conventional multiple hypothesis tracking (MHT) can be extended to domain-agnostic tracking of entities from non-kinematic constraints such as those imposed by cyber attacks in a potentially dense false alarm background. MHT is widely recognized as the premier method to avoid corrupting tracks with spurious data in the kinematic domain but it has not been extensively applied to other problem domains. The traditional approach is to tightly couple track maintenance (prediction, gating, filtering, probabilistic pruning, and target confirmation) with hypothesis management (clustering, incompatibility maintenance, hypothesis formation, and Nassociation pruning). However, by separating the domain specific track maintenance portion from the domain agnostic hypothesis management piece, we can begin to apply the wealth of knowledge gained from ground and air tracking solutions to the cyber (and other) domains. These realizations led to the creation of Raytheon's Multiple Hypothesis Extensible Tracking Architecture (MHETA). In this paper, we showcase MHETA for the cyber domain, plugging in a well established method, CUBRC's INFormation Engine for Real-time Decision making, (INFERD), for the association portion of the MHT. The result is a CyberMHT. We demonstrate the power of MHETA-INFERD using simulated data. Using metrics from both the tracking and cyber domains, we show that while no tracker is perfect, by applying MHETA-INFERD, advanced nonkinematic tracks can be captured in an automated way, perform better than non-MHT approaches, and decrease analyst response time to cyber threats.

  4. Pasture succession in the Neotropics: extending the nucleation hypothesis into a matrix discontinuity hypothesis.

    PubMed

    Peterson, Chris J; Dosch, Jerald J; Carson, Walter P

    2014-08-01

    The nucleation hypothesis appears to explain widespread patterns of succession in tropical pastures, specifically the tendency for isolated trees to promote woody species recruitment. Still, the nucleation hypothesis has usually been tested explicitly for only short durations and in some cases isolated trees fail to promote woody recruitment. Moreover, at times, nucleation occurs in other key habitat patches. Thus, we propose an extension, the matrix discontinuity hypothesis: woody colonization will occur in focal patches that function to mitigate the herbaceous vegetation effects, thus providing safe sites or regeneration niches. We tested predictions of the classical nucleation hypothesis, the matrix discontinuity hypothesis, and a distance from forest edge hypothesis, in five abandoned pastures in Costa Rica, across the first 11 years of succession. Our findings confirmed the matrix discontinuity hypothesis: specifically, rotting logs and steep slopes significantly enhanced woody colonization. Surprisingly, isolated trees did not consistently significantly enhance recruitment; only larger trees did so. Finally, woody recruitment consistently decreased with distance from forest. Our results as well as results from others suggest that the nucleation hypothesis needs to be broadened beyond its historical focus on isolated trees or patches; the matrix discontinuity hypothesis focuses attention on a suite of key patch types or microsites that promote woody species recruitment. We argue that any habitat discontinuities that ameliorate the inhibition by dense graminoid layers will be foci for recruitment. Such patches could easily be manipulated to speed the transition of pastures to closed canopy forests. PMID:24972697

  5. Pasture succession in the Neotropics: extending the nucleation hypothesis into a matrix discontinuity hypothesis.

    PubMed

    Peterson, Chris J; Dosch, Jerald J; Carson, Walter P

    2014-08-01

    The nucleation hypothesis appears to explain widespread patterns of succession in tropical pastures, specifically the tendency for isolated trees to promote woody species recruitment. Still, the nucleation hypothesis has usually been tested explicitly for only short durations and in some cases isolated trees fail to promote woody recruitment. Moreover, at times, nucleation occurs in other key habitat patches. Thus, we propose an extension, the matrix discontinuity hypothesis: woody colonization will occur in focal patches that function to mitigate the herbaceous vegetation effects, thus providing safe sites or regeneration niches. We tested predictions of the classical nucleation hypothesis, the matrix discontinuity hypothesis, and a distance from forest edge hypothesis, in five abandoned pastures in Costa Rica, across the first 11 years of succession. Our findings confirmed the matrix discontinuity hypothesis: specifically, rotting logs and steep slopes significantly enhanced woody colonization. Surprisingly, isolated trees did not consistently significantly enhance recruitment; only larger trees did so. Finally, woody recruitment consistently decreased with distance from forest. Our results as well as results from others suggest that the nucleation hypothesis needs to be broadened beyond its historical focus on isolated trees or patches; the matrix discontinuity hypothesis focuses attention on a suite of key patch types or microsites that promote woody species recruitment. We argue that any habitat discontinuities that ameliorate the inhibition by dense graminoid layers will be foci for recruitment. Such patches could easily be manipulated to speed the transition of pastures to closed canopy forests.

  6. The over-pruning hypothesis of autism.

    PubMed

    Thomas, Michael S C; Davis, Rachael; Karmiloff-Smith, Annette; Knowland, Victoria C P; Charman, Tony

    2016-03-01

    This article outlines the over-pruning hypothesis of autism. The hypothesis originates in a neurocomputational model of the regressive sub-type (Thomas, Knowland & Karmiloff-Smith, 2011a, 2011b). Here we develop a more general version of the over-pruning hypothesis to address heterogeneity in the timing of manifestation of ASD, including new computer simulations which reconcile the different observed developmental trajectories (early onset, late onset, regression) via a single underlying atypical mechanism; and which show how unaffected siblings of individuals with ASD may differ from controls either by inheriting a milder version of the pathological mechanism or by co-inheriting the risk factors without the pathological mechanism. The proposed atypical mechanism involves overly aggressive synaptic pruning in infancy and early childhood, an exaggeration of a normal phase of brain development. We show how the hypothesis generates novel predictions that differ from existing theories of ASD including that (1) the first few months of development in ASD will be indistinguishable from typical, and (2) the earliest atypicalities in ASD will be sensory and motor rather than social. Both predictions gain cautious support from emerging longitudinal studies of infants at-risk of ASD. We review evidence consistent with the over-pruning hypothesis, its relation to other current theories (including C. Frith's under-pruning proposal; C. Frith, 2003, 2004), as well as inconsistent data and current limitations. The hypothesis situates causal accounts of ASD within a framework of protective and risk factors (Newschaffer et al., 2012); clarifies different versions of the broader autism phenotype (i.e. the implication of observed similarities between individuals with autism and their family members); and integrates data from multiple disciplines, including behavioural studies, neuroscience studies, genetics, and intervention studies. PMID:25845529

  7. An excitatory synapse hypothesis of depression

    PubMed Central

    Thompson, Scott M.; Kallarackal, Angy J.; Kvarta, Mark D.; Van Dyke, Adam M.; LeGates, Tara A.; Cai, Xiang

    2015-01-01

    Depression is a common cause of mortality and morbidity, but the biological bases of the deficits in emotional and cognitive processing remain incompletely understood. Current antidepressant therapies are effective in only some patients and act slowly. We propose an excitatory synapse hypothesis of depression in which chronic stress and genetic susceptibility cause changes in the strength of subsets of glutamatergic synapses at multiple locations, including the prefrontal cortex, hippocampus and nucleus accumbens, leading to a dysfunction of cortico-mesolimbic reward circuitry that underlies many of the symptoms of depression. This hypothesis accounts for current depression treatments and suggests an updated framework for the development of better therapeutic compounds. PMID:25887240

  8. Migraine: the platelet hypothesis after 10 years.

    PubMed

    Hanington, E

    1989-01-01

    The proposal that migraine is a blood disorder and caused by a primary abnormality of platelet behaviour was first put forward in 1978. This paper outlines the basis on which the proposal was made and the way in which the platelet hypothesis can account for the many facets of the disorder. It also reports further studies of platelet composition and function which have been undertaken by a large number of independent workers during the past ten years. The results of their investigations provide strong additional support for the platelet hypothesis in migraine.

  9. Hypothesis Formation and Testing in Clinical Judgment.

    ERIC Educational Resources Information Center

    Strohmer, Douglas C.; And Others

    1983-01-01

    Examined the influence of cognitive complexity and client observation on the quality of clinical hypotheses counselors develop and the number of questions generated to test them. Results showed no effect of these variables on hypothesis quality; but a significant interaction between client observations on the number of questions developed. (LLL)

  10. The Hypothesis of Incommensurability and Multicultural Education

    ERIC Educational Resources Information Center

    McDonough, Tim

    2009-01-01

    This article describes the logical and rhetorical grounds for a multicultural pedagogy that teaches students the knowledge and skills needed to interact creatively in the public realm betwixt and between cultures. I begin by discussing the notion of incommensurability. I contend that this hypothesis was intended to perform a particular rhetorical…

  11. In Defense of Chi's Ontological Incompatibility Hypothesis

    ERIC Educational Resources Information Center

    Slotta, James D.

    2011-01-01

    This article responds to an article by A. Gupta, D. Hammer, and E. F. Redish (2010) that asserts that M. T. H. Chi's (1992, 2005) hypothesis of an "ontological commitment" in conceptual development is fundamentally flawed. In this article, I argue that Chi's theoretical perspective is still very much intact and that the critique offered by Gupta…

  12. Diagnostic Hypothesis Generation and Human Judgment

    ERIC Educational Resources Information Center

    Thomas, Rick P.; Dougherty, Michael R.; Sprenger, Amber M.; Harbison, J. Isaiah

    2008-01-01

    Diagnostic hypothesis-generation processes are ubiquitous in human reasoning. For example, clinicians generate disease hypotheses to explain symptoms and help guide treatment, auditors generate hypotheses for identifying sources of accounting errors, and laypeople generate hypotheses to explain patterns of information (i.e., data) in the…

  13. Hypothesis on the nature of atmospheric UFOs

    NASA Astrophysics Data System (ADS)

    Mukharev, L. A.

    1991-08-01

    A hypothesis is developed according to which the atmospheric UFO phenomenon has an electromagnetic nature. It is suggested that an atmospheric UFO is an agglomeration of charged atmospheric dust within which there exists a slowly damped electromagnetic field. This field is considered to be the source of the observed optical effects and the motive force of the UFO.

  14. Forty Years Later: Updating the Fossilization Hypothesis

    ERIC Educational Resources Information Center

    Han, ZhaoHong

    2013-01-01

    A founding concept in second language acquisition (SLA) research, fossilization has been fundamental to understanding second language (L2) development. The Fossilization Hypothesis, introduced in Selinker's seminal text (1972), has thus been one of the most influential theories, guiding a significant bulk of SLA research for four decades; 2012…

  15. A Developmental Study of the Infrahumanization Hypothesis

    ERIC Educational Resources Information Center

    Martin, John; Bennett, Mark; Murray, Wayne S.

    2008-01-01

    Intergroup attitudes in children were examined based on Leyen's "infrahumanization hypothesis". This suggests that some uniquely human emotions, such as shame and guilt (secondary emotions), are reserved for the in-group, whilst other emotions that are not uniquely human and shared with animals, such as anger and pleasure (primary emotions), are…

  16. Sleep memory processing: the sequential hypothesis

    PubMed Central

    Giuditta, Antonio

    2014-01-01

    According to the sequential hypothesis (SH) memories acquired during wakefulness are processed during sleep in two serial steps respectively occurring during slow wave sleep (SWS) and rapid eye movement (REM) sleep. During SWS memories to be retained are distinguished from irrelevant or competing traces that undergo downgrading or elimination. Processed memories are stored again during REM sleep which integrates them with preexisting memories. The hypothesis received support from a wealth of EEG, behavioral, and biochemical analyses of trained rats. Further evidence was provided by independent studies of human subjects. SH basic premises, data, and interpretations have been compared with corresponding viewpoints of the synaptic homeostatic hypothesis (SHY). Their similarities and differences are presented and discussed within the framework of sleep processing operations. SHY’s emphasis on synaptic renormalization during SWS is acknowledged to underline a key sleep effect, but this cannot marginalize sleep’s main role in selecting memories to be retained from downgrading traces, and in their integration with preexisting memories. In addition, SHY’s synaptic renormalization raises an unsolved dilemma that clashes with the accepted memory storage mechanism exclusively based on modifications of synaptic strength. This difficulty may be bypassed by the assumption that SWS-processed memories are stored again by REM sleep in brain subnuclear quantum particles. Storing of memories in quantum particles may also occur in other vigilance states. Hints are provided on ways to subject the quantum hypothesis to experimental tests. PMID:25565985

  17. Vacuum counterexamples to the cosmic censorship hypothesis

    SciTech Connect

    Miller, B.D.

    1981-07-01

    In cylindrically symmetric vacuum spacetimes it is possible to specify nonsingular initial conditions such that timelike singularities will (necessarily) evolve from these conditions. Examples are given; the spacetimes are somewhat analogous to one of the spherically symmetric counterexamples to the cosmic censorship hypothesis.

  18. A new hypothesis on HIV cure

    PubMed Central

    Hladik, Florian

    2015-01-01

    In this opinion article, I provide the rationale for my hypothesis that nucleoside reverse transcriptase inhibitors (NRTIs) may prevent human immunodeficiency virus (HIV) cure by promoting the survival of cells with integrated provirus. If correct, we may be closer to a cure than we realize. PMID:26380071

  19. The Marathon Group Hypothesis: An Unanswered Question

    ERIC Educational Resources Information Center

    Marks, Stephen E.; And Others

    1973-01-01

    The authors of this article contend that the Guinan and Foulds study was inadequately designed and executed, and the results indicate little of the "usefulness" of the test, much less illuminate the important hypothesis central to the investigation. Specific suggestions for further research in marathon group evaluation are made. (Author)

  20. Television Exposure Measures and the Cultivation Hypothesis.

    ERIC Educational Resources Information Center

    Potter, W. James; Chang, Ik Chin

    1990-01-01

    Describes study of students in grades 8 through 12 that was conducted to determine the degree to which television messages influence a person's construction of reality (the cultivation hypothesis). Research methodology that tests the effects of television exposure is examined with emphasis on the importance of demographic control variables. (38…

  1. Perceived Reality and the Cultivation Hypothesis.

    ERIC Educational Resources Information Center

    Potter, W. James

    1986-01-01

    Tested cultivation hypothesis by studying relationships between amount of television viewing by high school students and college students and their estimates of chances of victimization and causes of death. Stepwise multiple regression analyses were performed to determine importance of perceived reality, demographic, and televison viewing measures…

  2. Trouble for the most attractive channel hypothesis

    NASA Astrophysics Data System (ADS)

    Holdom, B.; Roux, F. S.

    1999-01-01

    We show that the next-to-leading corrections to the kernel of the gap equation can be large and of opposite sign to the lowest order kernel, in the presence of a gauge boson mass. This calls into question the reliability of the most attractive channel hypothesis.

  3. Einstein's Revolutionary Light-Quantum Hypothesis

    NASA Astrophysics Data System (ADS)

    Stuewer, Roger H.

    2005-05-01

    The paper in which Albert Einstein proposed his light-quantum hypothesis was the only one of his great papers of 1905 that he himself termed ``revolutionary.'' Contrary to widespread belief, Einstein did not propose his light-quantum hypothesis ``to explain the photoelectric effect.'' Instead, he based his argument for light quanta on the statistical interpretation of the second law of thermodynamics, with the photoelectric effect being only one of three phenomena that he offered as possible experimental support for it. I will discuss Einstein's light-quantum hypothesis of 1905 and his introduction of the wave-particle duality in 1909 and then turn to the reception of his work on light quanta by his contemporaries. We will examine the reasons that prominent physicists advanced to reject Einstein's light-quantum hypothesis in succeeding years. Those physicists included Robert A. Millikan, even though he provided convincing experimental proof of the validity of Einstein's equation of the photoelectric effect in 1915. The turning point came after Arthur Holly Compton discovered the Compton effect in late 1922, but even then Compton's discovery was contested both on experimental and on theoretical grounds. Niels Bohr, in particular, had never accepted the reality of light quanta and now, in 1924, proposed a theory, the Bohr-Kramers-Slater theory, which assumed that energy and momentum were conserved only statistically in microscopic interactions. Only after that theory was disproved experimentally in 1925 was Einstein's revolutionary light-quantum hypothesis generally accepted by physicists---a full two decades after Einstein had proposed it.

  4. Cortical Neural Computation by Discrete Results Hypothesis

    PubMed Central

    Castejon, Carlos; Nuñez, Angel

    2016-01-01

    One of the most challenging problems we face in neuroscience is to understand how the cortex performs computations. There is increasing evidence that the power of the cortical processing is produced by populations of neurons forming dynamic neuronal ensembles. Theoretical proposals and multineuronal experimental studies have revealed that ensembles of neurons can form emergent functional units. However, how these ensembles are implicated in cortical computations is still a mystery. Although cell ensembles have been associated with brain rhythms, the functional interaction remains largely unclear. It is still unknown how spatially distributed neuronal activity can be temporally integrated to contribute to cortical computations. A theoretical explanation integrating spatial and temporal aspects of cortical processing is still lacking. In this Hypothesis and Theory article, we propose a new functional theoretical framework to explain the computational roles of these ensembles in cortical processing. We suggest that complex neural computations underlying cortical processing could be temporally discrete and that sensory information would need to be quantized to be computed by the cerebral cortex. Accordingly, we propose that cortical processing is produced by the computation of discrete spatio-temporal functional units that we have called “Discrete Results” (Discrete Results Hypothesis). This hypothesis represents a novel functional mechanism by which information processing is computed in the cortex. Furthermore, we propose that precise dynamic sequences of “Discrete Results” is the mechanism used by the cortex to extract, code, memorize and transmit neural information. The novel “Discrete Results” concept has the ability to match the spatial and temporal aspects of cortical processing. We discuss the possible neural underpinnings of these functional computational units and describe the empirical evidence supporting our hypothesis. We propose that fast

  5. Examination of the auxin hypothesis of phytomelatonin action in classical auxin assay systems in maize.

    PubMed

    Kim, Minjae; Seo, Hyesu; Park, Chanwoo; Park, Woong June

    2016-01-15

    Melatonin has been found in a wide range of plant groups. Its physiological roles have been suggested to be diverse in stress protection and plant growth regulation. An attractive hypothesis is that phytomelatonin acts as an auxin to regulate plant development. However, the auxin hypothesis is controversial, since both supporting and contradictory evidence has been reported. We systematically investigated whether melatonin fulfilled the definition for auxin in maize (Zea mays). Melatonin did not affect coleoptile elongation, root growth or ACC synthase gene expression, contrary to 10(-5)M IAA in our assay system. The auxin hypothesis of phytomelatonin action is not supported in maize, because melatonin appeared inactive in all of the auxin activity tests. On the other hand, melatonin was active in the protection of maize growth against salt stress, suggesting its importance in another context. PMID:26681269

  6. Roger Sperry and his chemoaffinity hypothesis.

    PubMed

    Meyer, R L

    1998-10-01

    In the early 1940s, Roger Sperry performed a series of insightful experiments on the visual system of lower vertebrates that led him to draw two important conclusions: When optic fibers were severed, the regenerating fibers grew back to their original loci in the midbrain tectum to re-establish a topographical set of connections; and the re-establishment of these orderly connections underlay the orderly behavior of the animal. From these conclusions, he inferred that each optic fiber and each tectal neuron possessed cytochemical labels that uniquely denoted their neuronal type and position and that optic fibers could utilize these labels to selectively navigate to their matching target cell. This inference was subsequently formulated into a general explanation of how neurons form ordered interconnections during development and became known as the chemoaffinity hypothesis. The origins of this hypothesis, the controversies that surrounded it for several decades and its eventual acceptance, are discussed in this article. PMID:9845045

  7. A hypothesis for delayed dynamic earthquake triggering

    USGS Publications Warehouse

    Parsons, T.

    2005-01-01

    It's uncertain whether more near-field earthquakes are triggered by static or dynamic stress changes. This ratio matters because static earthquake interactions are increasingly incorporated into probabilistic forecasts. Recent studies were unable to demonstrate all predictions from the static-stress-change hypothesis, particularly seismicity rate reductions. However, current dynamic stress change hypotheses do not explain delayed earthquake triggering and Omori's law. Here I show numerically that if seismic waves can alter some frictional contacts in neighboring fault zones, then dynamic triggering might cause delayed triggering and an Omori-law response. The hypothesis depends on faults following a rate/state friction law, and on seismic waves changing the mean critical slip distance (Dc) at nucleation zones.

  8. Exploring heterogeneous market hypothesis using realized volatility

    NASA Astrophysics Data System (ADS)

    Chin, Wen Cheong; Isa, Zaidi; Mohd Nor, Abu Hassan Shaari

    2013-04-01

    This study investigates the heterogeneous market hypothesis using high frequency data. The cascaded heterogeneous trading activities with different time durations are modelled by the heterogeneous autoregressive framework. The empirical study indicated the presence of long memory behaviour and predictability elements in the financial time series which supported heterogeneous market hypothesis. Besides the common sum-of-square intraday realized volatility, we also advocated two power variation realized volatilities in forecast evaluation and risk measurement in order to overcome the possible abrupt jumps during the credit crisis. Finally, the empirical results are used in determining the market risk using the value-at-risk approach. The findings of this study have implications for informationally market efficiency analysis, portfolio strategies and risk managements.

  9. Geochemical confirmation of the lunar magmasphere hypothesis

    NASA Technical Reports Server (NTRS)

    Warren, P. H.

    1985-01-01

    The lunar magmasphere (or magma ocean) hypothesis was originally conceived to account for the enrichment of cumulus plagioclase (Al and Ca) in the main (highlands) portion of the crust. The great age of the highlands, and the complementary pattern of Eu anomalies between the highlands and the younger mare basalts, helped convince most specialists that the magmasphere hypothesis is correct. Doubts persist, however, particularly among physicists concerned about heat sources. It was shown in 1976 that a plot of Na/Ca vs. Mg/Fe for pristine highlands cumulates manifests a profound bimodality: One group, the Mg-rich rocks, plots along a normal igneous trend of inverse correlation between Na/Ca and Mg/Fe; the other group, the ferroan anorthosites (FAN), features low Na/Ca and low Mg/Fe. Only the FAN group can be plausibly linked to plag. flotation over the magmasphere.

  10. Hypothesis: microtubules, a key to Alzheimer disease.

    PubMed Central

    Matsuyama, S S; Jarvik, L F

    1989-01-01

    Alzheimer disease (AD) is a clinicopathologic syndrome of unknown etiology with numerous abnormalities in neuronal and nonneuronal cells. A review of the literature suggests that a common basic intracellular defect may underlie many of the reported abnormalities. We hypothesize impairment of the microtubule (MT) system as one explanation for the pathogenesis of AD. Evidence in support of the hypothesis includes the following: MTs are ubiquitous and vital cell components, unequally distributed, with the highest concentration in the brain; various abnormalities, including the key neuropathologic lesions, can be explained by impairments of the MT system; and experiments utilizing pharmacologic agents known to disrupt MTs have reproduced certain abnormalities observed in AD. The hypothesis provides a framework for systematic investigations of MTs at the cellular and molecular levels as well as the basis for in vivo diagnostic tests for AD. PMID:2813384

  11. Roger Sperry and his chemoaffinity hypothesis.

    PubMed

    Meyer, R L

    1998-10-01

    In the early 1940s, Roger Sperry performed a series of insightful experiments on the visual system of lower vertebrates that led him to draw two important conclusions: When optic fibers were severed, the regenerating fibers grew back to their original loci in the midbrain tectum to re-establish a topographical set of connections; and the re-establishment of these orderly connections underlay the orderly behavior of the animal. From these conclusions, he inferred that each optic fiber and each tectal neuron possessed cytochemical labels that uniquely denoted their neuronal type and position and that optic fibers could utilize these labels to selectively navigate to their matching target cell. This inference was subsequently formulated into a general explanation of how neurons form ordered interconnections during development and became known as the chemoaffinity hypothesis. The origins of this hypothesis, the controversies that surrounded it for several decades and its eventual acceptance, are discussed in this article.

  12. Tests of the Giant Impact Hypothesis

    NASA Technical Reports Server (NTRS)

    Jones, J. H.

    1998-01-01

    The giant impact hypothesis has gained popularity as a means of explaining a volatile-depleted Moon that still has a chemical affinity to the Earth. As Taylor's Axiom decrees, the best models of lunar origin are testable, but this is difficult with the giant impact model. The energy associated with the impact would be sufficient to totally melt and partially vaporize the Earth. And this means that there should he no geological vestige of Barber times. Accordingly, it is important to devise tests that may be used to evaluate the giant impact hypothesis. Three such tests are discussed here. None of these is supportive of the giant impact model, but neither do they disprove it.

  13. The Neural Rejuvenation Hypothesis of Cocaine Addiction

    PubMed Central

    Dong, Yan; Nestler, Eric J.

    2014-01-01

    A leading hypothesis guiding current molecular and cellular research of drug addiction conceptualizes key aspects of addiction as a form of memory, in which common neuroplasticity mechanisms that mediate normal learning and memory processes are “hijacked” by exposure to drugs of abuse to produce pathologic addiction-related memories. Such addiction-related memories are particularly robust and long-lasting and once formed, less amenable to updating. Here, we propose the Neural Rejuvenation Hypothesis of Cocaine Addiction: that repeated exposure to drugs of abuse induces some plasticity mechanisms that are normally associated with brain development within the brain’s reward circuitry, which mediate the highly efficient and unusually stable memory abnormalities that characterize addiction. PMID:24958329

  14. Kelvin on an old, celebrated hypothesis

    NASA Astrophysics Data System (ADS)

    Harrison, Edward

    1986-07-01

    Lord Kelvin in 1901 tested an ``old and celebrated hypothesis'' that if we could see far enough into space the whole sky would be occupied with stellar disks all of perhaps the same brightness as the Sun. Kelvin was the first to solve quantitatively and correctly the riddle of a dark night sky, a riddle that had been previously solved qualitatively by Edgar Allan Poe, and is now known as Olbers' paradox.

  15. Sea otter health: challenging a pet hypothesis

    USGS Publications Warehouse

    Lafferty, Kevin D.

    2015-01-01

    A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission.

  16. Moon origin - The impact-trigger hypothesis

    NASA Technical Reports Server (NTRS)

    Hartmann, William K.

    1986-01-01

    Arguments in favor of the impact-trigger model of lunar origin are presented. Lunar properties favoring this hypothesis include: (1) lunar iron and volatile deficiency; (2) angular momentum of the earth-moon system; and (3) similar O isotopes, bulk iron contents, and densities of earth's mantle and the moon. It is shown that the intense early bombardment averaged during earth's formation was several billion times the present meteoritic mass flux, consistent with a giant impact.

  17. Sea otter health: Challenging a pet hypothesis

    PubMed Central

    Lafferty, Kevin D.

    2015-01-01

    A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission. PMID:26155464

  18. An impact hypothesis for Venus argon anomalies

    NASA Astrophysics Data System (ADS)

    Kaula, W. M.; Newman, W. I.

    1997-03-01

    The Ar-36+38 argon-excess anomally of Venus has been hypothesized to have its origin in the impact of an outer solar system body of about 100-km diameter. A critical evaluation is made of this hypothesis and its competitors; it is judged that its status must for the time being remain one of 'Sherlock Holmes' type, in that something so improbable must be accepted when all alternatives are eliminated.

  19. Sea otter health: Challenging a pet hypothesis.

    PubMed

    Lafferty, Kevin D

    2015-12-01

    A recent series of studies on tagged sea otters (Enhydra lutris nereis) challenges the hypothesis that sea otters are sentinels of a dirty ocean, in particular, that pet cats are the main source of exposure to Toxoplasma gondii in central California. Counter to expectations, sea otters from unpopulated stretches of coastline are less healthy and more exposed to parasites than city-associated otters. Ironically, now it seems that spillover from wildlife, not pets, dominates spatial patterns of disease transmission. PMID:26155464

  20. Testing the single-state dominance hypothesis

    SciTech Connect

    Álvarez-Rodríguez, R.; Moreno, O.; Moya de Guerra, E.; Sarriguren, P.; Šimkovic, F.; Faessler, A.

    2013-12-30

    We present a theoretical analysis of the single-state dominance hypothesis for the two-neutrino double-beta decay process. The theoretical framework is a proton-neutron QRPA based on a deformed Hartree-Fock mean field with BCS pairing correlations. We focus on the decays of {sup 100}Mo, {sup 116}Cd and {sup 128}Te. We do not find clear evidences for single-state dominance within the present approach.

  1. The spline probability hypothesis density filter

    NASA Astrophysics Data System (ADS)

    Sithiravel, Rajiv; Tharmarasa, Ratnasingham; McDonald, Mike; Pelletier, Michel; Kirubarajan, Thiagalingam

    2012-06-01

    The Probability Hypothesis Density Filter (PHD) is a multitarget tracker for recursively estimating the number of targets and their state vectors from a set of observations. The PHD filter is capable of working well in scenarios with false alarms and missed detections. Two distinct PHD filter implementations are available in the literature: the Sequential Monte Carlo Probability Hypothesis Density (SMC-PHD) and the Gaussian Mixture Probability Hypothesis Density (GM-PHD) filters. The SMC-PHD filter uses particles to provide target state estimates, which can lead to a high computational load, whereas the GM-PHD filter does not use particles, but restricts to linear Gaussian mixture models. The SMC-PHD filter technique provides only weighted samples at discrete points in the state space instead of a continuous estimate of the probability density function of the system state and thus suffers from the well-known degeneracy problem. This paper proposes a B-Spline based Probability Hypothesis Density (S-PHD) filter, which has the capability to model any arbitrary probability density function. The resulting algorithm can handle linear, non-linear, Gaussian, and non-Gaussian models and the S-PHD filter can also provide continuous estimates of the probability density function of the system state. In addition, by moving the knots dynamically, the S-PHD filter ensures that the splines cover only the region where the probability of the system state is significant, hence the high efficiency of the S-PHD filter is maintained at all times. Also, unlike the SMC-PHD filter, the S-PHD filter is immune to the degeneracy problem due to its continuous nature. The S-PHD filter derivations and simulations are provided in this paper.

  2. Paleoindian demography and the extraterrestrial impact hypothesis

    PubMed Central

    Buchanan, Briggs; Collard, Mark; Edinborough, Kevan

    2008-01-01

    Recently it has been suggested that one or more large extraterrestrial (ET) objects struck northern North America 12,900 ± 100 calendar years before present (calBP) [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 104: 16016–16021]. This impact is claimed to have triggered the Younger Dryas major cooling event and resulted in the extinction of the North American megafauna. The impact is also claimed to have caused major cultural changes and population decline among the Paleoindians. Here, we report a study in which ≈1,500 radiocarbon dates from archaeological sites in Canada and the United States were used to test the hypothesis that the ET resulted in population decline among the Paleoindians. Following recent studies [e.g., Gamble C, Davies W, Pettitt P, Hazelwood L, Richards M (2005) Camb Archaeol J 15:193–223), the summed probability distribution of the calibrated dates was used to identify probable changes in human population size between 15,000 and 9,000 calBP. Subsequently, potential biases were evaluated by modeling and spatial analysis of the dated occupations. The results of the analyses were not consistent with the predictions of extraterrestrial impact hypothesis. No evidence of a population decline among the Paleoindians at 12,900 ± 100 calBP was found. Thus, minimally, the study suggests the extraterrestrial impact hypothesis should be amended. PMID:18697936

  3. The Nebular Hypothesis - A False Paradigm Misleading Scientists

    NASA Astrophysics Data System (ADS)

    Myers, L. S.

    2005-05-01

    ignored in the belief this comparatively small volume is insignificant relative to Earth's total mass and gravity. This misconception led to outdated gravitational constants and trajectories for "slingshotted" space missions that approached Earth closer than anticipated because the daily increase in mass increases Earth's gravitational pull. Today's philosophy assumes comets, meteoroids, asteroids and planets are different types of objects because of their varied sizes and appearances, but when all solar bodies are arranged by size they form a continuum from irregular meteoroids (remnants of comets) to spherical asteroids and planets. When meteoroids reach diameters of 500-600 kilometers, they become spherical-the critical threshold at which gravity can focus total molecular weight of any body omnidirectionally onto its exact center to initiate compressive heating and melting of originally cold rock core, producing magma, H2O and other gases. The Accreation concept assumes all solar bodies are different-sized objects of the same species, each having reached its present size and chemical composition by amalgamation and accretion. Each is at a different stage of growth but destined to become larger until it reaches the size of another sun (star). This is universal planetary growth controlled by gravity, but initiated by the trajectory imparted at its supernova birth and chance capture by some larger body elsewhere in the Universe. Like the paradigm shift from geocentrism to heliocentrism sparked by Copernicus in 1543, the time has come for a new paradigm to put scientific research on a more productive course toward TRUTH. The new concept of Accreation (creation by accretion) is offered as a replacement for the now defunct nebular hypothesis.

  4. Telomeres and longevity: testing an evolutionary hypothesis.

    PubMed

    Haussmann, Mark F; Mauck, Robert A

    2008-01-01

    Identifying mechanisms that underlie variation in adult survivorship provide insight into the evolution of life history strategies and phenotypic variation in longevity. There is accumulating evidence that shortening telomeres, the protective caps at the ends of chromosomes, play an important role in individual variation in longevity. Given that telomeres generally shorten with age, it was surprising to find that in a population of a long-lived seabird, Leach's storm petrel, telomeres appear to lengthen with age. This unique finding suggested that the longest lived individuals are able to elongate telomeres, an interpretation we call the "elongation hypothesis." Alternatively, the "selection hypothesis" states that the longest lived individuals start with the longest telomeres and variation in telomere length decreases with age due to the selective disappearance of individuals with short telomeres. In the same population in which evidence supporting both hypotheses was uncovered, we tested mutually exclusive predictions from the elongation and selection hypotheses by measuring telomere length with the telomere restriction fragment assay in hatchling and old, adult storm petrels. As previously found, adult birds had longer telomeres on average compared with hatchlings. We also found that 3 hatchlings had mean telomere lengths exceeding that of the most extreme old bird, old birds on average had longer initial telomere lengths than hatchlings, and the variance in mean telomere length was significantly greater for hatchlings than for old birds, all predicted by the selection hypothesis. Perhaps more surprisingly, the oldest adults also show little or no accumulation of short telomeres over time, a pattern unknown in other species. Long telomeres are thought to provide a buffer against cellular senescence and be generally indicative of genome stability and overall cell health. In storm petrels, because the progressive accumulation of short telomeres appears negligible

  5. Consumer Health Information Seeking as Hypothesis Testing

    PubMed Central

    Keselman, Alla; Browne, Allen C.; Kaufman, David R.

    2008-01-01

    Objective Despite the proliferation of consumer health sites, lay individuals often experience difficulty finding health information online. The present study attempts to understand users' information seeking difficulties by drawing on a hypothesis testing explanatory framework. It also addresses the role of user competencies and their interaction with internet resources. Design Twenty participants were interviewed about their understanding of a hypothetical scenario about a family member suffering from stable angina and then searched MedlinePlus® consumer health information portal for information on the problem presented in the scenario. Participants' understanding of heart disease was analyzed via semantic analysis. Thematic coding was used to describe information seeking trajectories in terms of three key strategies: verification of the primary hypothesis, narrowing search within the general hypothesis area and bottom-up search. Results Compared to an expert model, participants' understanding of heart disease involved different key concepts, which were also differently grouped and defined. This understanding provided the framework for search-guiding hypotheses and results interpretation. Incorrect or imprecise domain knowledge led individuals to search for information on irrelevant sites, often seeking out data to confirm their incorrect initial hypotheses. Online search skills enhanced search efficiency, but did not eliminate these difficulties. Conclusions Regardless of their web experience and general search skills, lay individuals may experience difficulty with health information searches. These difficulties may be related to formulating and evaluating hypotheses that are rooted in their domain knowledge. Informatics can provide support at the levels of health information portals, individual websites, and consumer education tools. PMID:18436912

  6. Updating the Lamellar Hypothesis of Hippocampal Organization

    PubMed Central

    Sloviter, Robert S.; Lømo, Terje

    2012-01-01

    Andersen et al. (1971) proposed that excitatory activity in the entorhinal cortex propagates topographically to the dentate gyrus, and on through a “trisynaptic circuit” lying within transverse hippocampal “slices” or “lamellae.” In this way, a relatively simple structure might mediate complex functions in a manner analogous to the way independent piano keys can produce a nearly infinite variety of unique outputs. The lamellar hypothesis derives primary support from the “lamellar” distribution of dentate granule cell axons (the mossy fibers), which innervate dentate hilar neurons and area CA3 pyramidal cells and interneurons within the confines of a thin transverse hippocampal segment. Following the initial formulation of the lamellar hypothesis, anatomical studies revealed that unlike granule cells, hilar mossy cells, CA3 pyramidal cells, and Layer II entorhinal cells all form axonal projections that are more divergent along the longitudinal axis than the clearly “lamellar” mossy fiber pathway. The existence of pathways with “translamellar” distribution patterns has been interpreted, incorrectly in our view, as justifying outright rejection of the lamellar hypothesis (Amaral and Witter, 1989). We suggest that the functional implications of longitudinally projecting axons depend not on whether they exist, but on what they do. The observation that focal granule cell layer discharges normally inhibit, rather than excite, distant granule cells suggests that longitudinal axons in the dentate gyrus may mediate “lateral” inhibition and define lamellar function, rather than undermine it. In this review, we attempt a reconsideration of the evidence that most directly impacts the physiological concept of hippocampal lamellar organization. PMID:23233836

  7. Buffet hypothesis for microbial nutrition at the rhizosphere.

    PubMed

    López-Guerrero, Martha G; Ormeño-Orrillo, Ernesto; Rosenblueth, Mónica; Martinez-Romero, Julio; Martïnez-Romero, Esperanza

    2013-01-01

    An emphasis is made on the diversity of nutrients that rhizosphere bacteria may encounter derived from roots, soil, decaying organic matter, seeds, or the microbial community. This nutrient diversity may be considered analogous to a buffet and is contrasting to the hypothesis of oligotrophy at the rhizosphere. Different rhizosphere bacteria may have preferences for some substrates and this would allow a complex community to be established at the rhizosphere. To profit from diverse nutrients, root-associated bacteria should have large degrading capabilities and many transporters (seemingly inducible) that may be encoded in a significant proportion of the large genomes that root-associated bacteria have. Rhizosphere microbes may have a tendency to evolve toward generalists. We propose that many genes with unknown function may encode enzymes that participate in degrading diverse rhizosphere substrates. Knowledge of bacterial genes required for nutrition at the rhizosphere will help to make better use of bacteria as plant-growth promoters in agriculture.

  8. Migraine pathogenesis: the neural hypothesis reexamined.

    PubMed

    Blau, J N

    1984-05-01

    The hypothesis that migraine is a primary neurological disturbance with secondary vascular manifestations is tested by analysing the five phases of migraine attacks and the eight groups of recognised precipitating factors. Accessory evidence from cerebral blood flow and EEG recordings taken during attacks is also considered. The evidence supports the concept that the sensory cortex and hypothalamus could be initiating sites for migraine attacks, and indicates that a neurological mechanism, suggested by Liveing and Gowers 100 years ago, remains viable and needs to be considered in future research.

  9. Learning-Related Changes in Adolescents' Neural Networks during Hypothesis-Generating and Hypothesis-Understanding Training

    ERIC Educational Resources Information Center

    Lee, Jun-Ki; Kwon, Yongju

    2012-01-01

    Fourteen science high school students participated in this study, which investigated neural-network plasticity associated with hypothesis-generating and hypothesis-understanding in learning. The students were divided into two groups and participated in either hypothesis-generating or hypothesis-understanding type learning programs, which were…

  10. Learning-Related Changes in Adolescents' Neural Networks During Hypothesis-Generating and Hypothesis-Understanding Training

    NASA Astrophysics Data System (ADS)

    Lee, Jun-Ki; Kwon, Yongju

    2010-11-01

    Fourteen science high school students participated in this study, which investigated neural-network plasticity associated with hypothesis-generating and hypothesis-understanding in learning. The students were divided into two groups and participated in either hypothesis-generating or hypothesis-understanding type learning programs, which were composed of 12 topics taught over a 12-week period. To measure change in student competence and brain networks, a paper & pencil test and an fMRI scanning session were administered before and after the training programs. Unlike the hypothesis-understanding group, a before and after training comparison for the hypothesis-generating group showed significantly strong changes in hypothesis explanation quotients and functional brain connectivity associated with hypothesis-generating. However, for the hypothesis-understanding group, the brain network related to hypothesis-understanding significantly strengthened, not from hypothesis-generating type learning, but from hypothesis-understanding type learning. These findings suggest that for hypothesis-generating and hypothesis-understanding there are at least two specialized brain network systems or processes at work in the brain. Furthermore, hypothesis-generating competence could be developed by appropriate training programs such as teaching by way of active hypothesis generation rather than present passive expository teaching practices.

  11. Temperature and competition between bull trout and brook trout: A test of the elevation refuge hypothesis.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We tested the elevation refuge hypothesis that colder water temperatures impart a competitive advantage to bull trout Salvelinus confluentus and thus account for increased biotic resistance to invasion and displacement by brook trout S. fontinalis in headwater streams. Growth, survival, and behavio...

  12. Parenting as a Dynamic Process: A Test of the Resource Dilution Hypothesis

    ERIC Educational Resources Information Center

    Strohschein, Lisa; Gauthier, Anne H.; Campbell, Rachel; Kleparchuk, Clayton

    2008-01-01

    In this paper, we tested the resource dilution hypothesis, which posits that, because parenting resources are finite, the addition of a new sibling depletes parenting resources for other children in the household. We estimated growth curve models on the self-reported parenting practices of mothers using four waves of data collected biennially…

  13. The mitonuclear compatibility hypothesis of sexual selection

    PubMed Central

    Hill, Geoffrey E.; Johnson, James D.

    2013-01-01

    Why females assess ornaments when choosing mates remains a central question in evolutionary biology. We hypothesize that the imperative for a choosing female to find a mate with nuclear oxidative phosphorylation (OXPHOS) genes that are compatible with her mitochondrial OXPHOS genes drives the evolution of ornaments. Indicator traits are proposed to signal the efficiency of OXPHOS function thus enabling females to select mates with nuclear genes that are compatible with maternal mitochondrial genes in the formation of OXPHOS complexes. Species-typical pattern of ornamentation is proposed to serve as a marker of mitochondrial type ensuring that females assess prospective mates with a shared mitochondrial background. The mitonuclear compatibility hypothesis predicts that the production of ornaments will be closely linked to OXPHOS pathways, and that sexual selection for compatible mates will be strongest when genes for nuclear components of OXPHOS complexes are Z-linked. The implications of this hypothesis are that sexual selection may serve as a driver for the evolution of more efficient cellular respiration. PMID:23945683

  14. Einstein's Revolutionary Light--Quantum Hypothesis

    NASA Astrophysics Data System (ADS)

    Stuewer, R. H.

    2006-03-01

    Albert Einstein's light-quantum paper was the only one of his great papers of 1905 that he himself called ``very revolutionary''. I sketch his arguments for light quanta, his analysis of the photoelectric effect, and his introduction of the wave-particle duality into physics in 1909. I show that Robert Andrews Millikan, in common with almost all physicists at the time, rejected Einstein's light-quantum hypothesis as an interpretation of his photoelectric-effect experiments of 1915. I then trace the complex experimental and theoretical route that Arthur Holly Compton followed between 1916 and 1922 that led to his discovery of the Compton effect, a discovery that Peter Debye also made virtually simultaneously and independently. Compton's discovery, however, was challenged on experimental grounds by William Duane and on theoretical grounds by Niels Bohr in the Bohr--Kramers--Slater theory of 1924, and only after that theory was disproved experimentally the following year by Walther Bothe and Hans Geiger in Berlin and by Compton and Alfred W. Simon in Chicago was Einstein's light-quantum hypothesis generally accepted by physicists.

  15. Advent of Continents: A New Hypothesis

    NASA Astrophysics Data System (ADS)

    Tamura, Yoshihiko; Sato, Takeshi; Fujiwara, Toshiya; Kodaira, Shuichi; Nichols, Alexander

    2016-09-01

    The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10–20 km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian arc are underlain by crust ~35 km thick. Interestingly, andesite magmas dominate eruptive products from the former volcanoes and mostly basaltic lavas erupt from the latter. According to the hypothesis presented here, rising mantle diapirs stall near the base of the oceanic crust at depths controlled by the thickness of the overlying crust. Where the crust is thin, melting occurs at relatively low pressures in the mantle wedge producing andesitic magmas. Where the crust is thick, melting pressures are higher and only basaltic magmas tend to be produced. The implications of this hypothesis are: (1) the rate of continental crust accumulation, which is andesitic in composition, would have been greatest soon after subduction initiated on Earth, when most crust was thin; and (2) most andesite magmas erupted on continental crust could be recycled from “primary” andesite originally produced in oceanic arcs.

  16. A default Bayesian hypothesis test for mediation.

    PubMed

    Nuijten, Michèle B; Wetzels, Ruud; Matzke, Dora; Dolan, Conor V; Wagenmakers, Eric-Jan

    2015-03-01

    In order to quantify the relationship between multiple variables, researchers often carry out a mediation analysis. In such an analysis, a mediator (e.g., knowledge of a healthy diet) transmits the effect from an independent variable (e.g., classroom instruction on a healthy diet) to a dependent variable (e.g., consumption of fruits and vegetables). Almost all mediation analyses in psychology use frequentist estimation and hypothesis-testing techniques. A recent exception is Yuan and MacKinnon (Psychological Methods, 14, 301-322, 2009), who outlined a Bayesian parameter estimation procedure for mediation analysis. Here we complete the Bayesian alternative to frequentist mediation analysis by specifying a default Bayesian hypothesis test based on the Jeffreys-Zellner-Siow approach. We further extend this default Bayesian test by allowing a comparison to directional or one-sided alternatives, using Markov chain Monte Carlo techniques implemented in JAGS. All Bayesian tests are implemented in the R package BayesMed (Nuijten, Wetzels, Matzke, Dolan, & Wagenmakers, 2014).

  17. Inoculation Stress Hypothesis of Environmental Enrichment

    PubMed Central

    Crofton, Elizabeth J.; Zhang, Yafang; Green, Thomas A.

    2014-01-01

    One hallmark of psychiatric conditions is the vast continuum of individual differences in susceptibility vs. resilience resulting from the interaction of genetic and environmental factors. The environmental enrichment paradigm is an animal model that is useful for studying a range of psychiatric conditions, including protective phenotypes in addiction and depression models. The major question is how environmental enrichment, a non-drug and non-surgical manipulation, can produce such robust individual differences in such a wide range of behaviors. This paper draws from a variety of published sources to outline a coherent hypothesis of inoculation stress as a factor producing the protective enrichment phenotypes. The basic tenet suggests that chronic mild stress from living in a complex environment and interacting non-aggressively with conspecifics can inoculate enriched rats against subsequent stressors and/or drugs of abuse. This paper reviews the enrichment phenotypes, mulls the fundamental nature of environmental enrichment vs. isolation, discusses the most appropriate control for environmental enrichment, and challenges the idea that cortisol/corticosterone equals stress. The intent of the inoculation stress hypothesis of environmental enrichment is to provide a scaffold with which to build testable hypotheses for the elucidation of the molecular mechanisms underlying these protective phenotypes and thus provide new therapeutic targets to treat psychiatric/neurological conditions. PMID:25449533

  18. The mitonuclear compatibility hypothesis of sexual selection.

    PubMed

    Hill, Geoffrey E; Johnson, James D

    2013-10-01

    Why females assess ornaments when choosing mates remains a central question in evolutionary biology. We hypothesize that the imperative for a choosing female to find a mate with nuclear oxidative phosphorylation (OXPHOS) genes that are compatible with her mitochondrial OXPHOS genes drives the evolution of ornaments. Indicator traits are proposed to signal the efficiency of OXPHOS function thus enabling females to select mates with nuclear genes that are compatible with maternal mitochondrial genes in the formation of OXPHOS complexes. Species-typical pattern of ornamentation is proposed to serve as a marker of mitochondrial type ensuring that females assess prospective mates with a shared mitochondrial background. The mitonuclear compatibility hypothesis predicts that the production of ornaments will be closely linked to OXPHOS pathways, and that sexual selection for compatible mates will be strongest when genes for nuclear components of OXPHOS complexes are Z-linked. The implications of this hypothesis are that sexual selection may serve as a driver for the evolution of more efficient cellular respiration. PMID:23945683

  19. Inoculation stress hypothesis of environmental enrichment.

    PubMed

    Crofton, Elizabeth J; Zhang, Yafang; Green, Thomas A

    2015-02-01

    One hallmark of psychiatric conditions is the vast continuum of individual differences in susceptibility vs. resilience resulting from the interaction of genetic and environmental factors. The environmental enrichment paradigm is an animal model that is useful for studying a range of psychiatric conditions, including protective phenotypes in addiction and depression models. The major question is how environmental enrichment, a non-drug and non-surgical manipulation, can produce such robust individual differences in such a wide range of behaviors. This paper draws from a variety of published sources to outline a coherent hypothesis of inoculation stress as a factor producing the protective enrichment phenotypes. The basic tenet suggests that chronic mild stress from living in a complex environment and interacting non-aggressively with conspecifics can inoculate enriched rats against subsequent stressors and/or drugs of abuse. This paper reviews the enrichment phenotypes, mulls the fundamental nature of environmental enrichment vs. isolation, discusses the most appropriate control for environmental enrichment, and challenges the idea that cortisol/corticosterone equals stress. The intent of the inoculation stress hypothesis of environmental enrichment is to provide a scaffold with which to build testable hypotheses for the elucidation of the molecular mechanisms underlying these protective phenotypes and thus provide new therapeutic targets to treat psychiatric/neurological conditions.

  20. Investigations into the hypothesis of transgenic cannabis.

    PubMed

    Cascini, Fidelia

    2012-05-01

    The unusual concentration of cannabinoids recently found in marijuana samples submitted to the forensic laboratory for chemical analysis prompted an investigation into whether genetic modifications have been made to the DNA of Cannabis sativa L. to increase its potency. Traditional methods for the detection of genetically modified organisms (GMO) were used to analyze herbal cannabis preparations. Our analyses support the hypothesis that marijuana samples submitted to forensic laboratories and characterized by an abnormal level of Δ(9)-THC are the product of breeding selection rather than of transgenic modifications. Further, this research has shown a risk of false positive results associated with the poor quality of the seized samples and probably due to the contamination by other transgenic vegetable products. On the other hand, based on these data, a conclusive distinction between the hypothesis of GMO plant contamination and the other of genetic modification of cannabis cannot be made requiring further studies on comparative chemical and genetic analyses to find out an explanation for the recently detected increased potency of cannabis. PMID:22211569

  1. The Malaria-High Blood Pressure Hypothesis

    PubMed Central

    Smeeth, Liam; Cruickshank, J. Kennedy; Scott, J. Anthony G.

    2016-01-01

    Rationale: Several studies have demonstrated links between infectious diseases and cardiovascular conditions. Malaria and hypertension are widespread in many low- and middle-income countries, but the possible link between them has not been considered. Objective: In this article, we outline the basis for a possible link between malaria and hypertension and discuss how the hypothesis could be confirmed or refuted. Methods and Results: We reviewed published literature on factors associated with hypertension and checked whether any of these were also associated with malaria. We then considered various study designs that could be used to test the hypothesis. Malaria causes low birth weight, malnutrition, and inflammation, all of which are associated with hypertension in high-income countries. The hypothetical link between malaria and hypertension can be tested through the use of ecological, cohort, or Mendelian randomization studies, each of which poses specific challenges. Conclusions: Confirmation of the existence of a causative link with malaria would be a paradigm shift in efforts to prevent and control hypertension and would stimulate wider research on the links between infectious and noncommunicable disease. PMID:27151400

  2. Advent of Continents: A New Hypothesis

    PubMed Central

    Tamura, Yoshihiko; Sato, Takeshi; Fujiwara, Toshiya; Kodaira, Shuichi; Nichols, Alexander

    2016-01-01

    The straightforward but unexpected relationship presented here relates crustal thickness to magma type in the Izu-Ogasawara (Bonin) and Aleutian oceanic arcs. Volcanoes along the southern segment of the Izu-Ogasawara arc and the western Aleutian arc (west of Adak) are underlain by thin crust (10–20 km). In contrast those along the northern segment of the Izu-Ogasawara arc and eastern Aleutian arc are underlain by crust ~35 km thick. Interestingly, andesite magmas dominate eruptive products from the former volcanoes and mostly basaltic lavas erupt from the latter. According to the hypothesis presented here, rising mantle diapirs stall near the base of the oceanic crust at depths controlled by the thickness of the overlying crust. Where the crust is thin, melting occurs at relatively low pressures in the mantle wedge producing andesitic magmas. Where the crust is thick, melting pressures are higher and only basaltic magmas tend to be produced. The implications of this hypothesis are: (1) the rate of continental crust accumulation, which is andesitic in composition, would have been greatest soon after subduction initiated on Earth, when most crust was thin; and (2) most andesite magmas erupted on continental crust could be recycled from “primary” andesite originally produced in oceanic arcs. PMID:27669662

  3. Investigations into the hypothesis of transgenic cannabis.

    PubMed

    Cascini, Fidelia

    2012-05-01

    The unusual concentration of cannabinoids recently found in marijuana samples submitted to the forensic laboratory for chemical analysis prompted an investigation into whether genetic modifications have been made to the DNA of Cannabis sativa L. to increase its potency. Traditional methods for the detection of genetically modified organisms (GMO) were used to analyze herbal cannabis preparations. Our analyses support the hypothesis that marijuana samples submitted to forensic laboratories and characterized by an abnormal level of Δ(9)-THC are the product of breeding selection rather than of transgenic modifications. Further, this research has shown a risk of false positive results associated with the poor quality of the seized samples and probably due to the contamination by other transgenic vegetable products. On the other hand, based on these data, a conclusive distinction between the hypothesis of GMO plant contamination and the other of genetic modification of cannabis cannot be made requiring further studies on comparative chemical and genetic analyses to find out an explanation for the recently detected increased potency of cannabis.

  4. The Younger Dryas impact hypothesis: A requiem

    NASA Astrophysics Data System (ADS)

    Pinter, Nicholas; Scott, Andrew C.; Daulton, Tyrone L.; Podoll, Andrew; Koeberl, Christian; Anderson, R. Scott; Ishman, Scott E.

    2011-06-01

    The Younger Dryas (YD) impact hypothesis is a recent theory that suggests that a cometary or meteoritic body or bodies hit and/or exploded over North America 12,900 years ago, causing the YD climate episode, extinction of Pleistocene megafauna, demise of the Clovis archeological culture, and a range of other effects. Since gaining widespread attention in 2007, substantial research has focused on testing the 12 main signatures presented as evidence of a catastrophic extraterrestrial event 12,900 years ago. Here we present a review of the impact hypothesis, including its evolution and current variants, and of efforts to test and corroborate the hypothesis. The physical evidence interpreted as signatures of an impact event can be separated into two groups. The first group consists of evidence that has been largely rejected by the scientific community and is no longer in widespread discussion, including: particle tracks in archeological chert; magnetic nodules in Pleistocene bones; impact origin of the Carolina Bays; and elevated concentrations of radioactivity, iridium, and fullerenes enriched in 3He. The second group consists of evidence that has been active in recent research and discussions: carbon spheres and elongates, magnetic grains and magnetic spherules, byproducts of catastrophic wildfire, and nanodiamonds. Over time, however, these signatures have also seen contrary evidence rather than support. Recent studies have shown that carbon spheres and elongates do not represent extraterrestrial carbon nor impact-induced megafires, but are indistinguishable from fungal sclerotia and arthropod fecal material that are a small but common component of many terrestrial deposits. Magnetic grains and spherules are heterogeneously distributed in sediments, but reported measurements of unique peaks in concentrations at the YD onset have yet to be reproduced. The magnetic grains are certainly just iron-rich detrital grains, whereas reported YD magnetic spherules are

  5. The Criticality Hypothesis in Neural Systems

    NASA Astrophysics Data System (ADS)

    Karimipanah, Yahya

    There is mounting evidence that neural networks of the cerebral cortex exhibit scale invariant dynamics. At the larger scale, fMRI recordings have shown evidence for spatiotemporal long range correlations. On the other hand, at the smaller scales this scale invariance is marked by the power law distribution of the size and duration of spontaneous bursts of activity, which are referred as neuronal avalanches. The existence of such avalanches has been confirmed by several studies in vitro and in vivo, among different species and across multiple scales, from spatial scale of MEG and EEG down to single cell resolution. This prevalent scale free nature of cortical activity suggests the hypothesis that the cortex resides at a critical state between two phases of order (short-lasting activity) and disorder (long-lasting activity). In addition, it has been shown, both theoretically and experimentally, that being at criticality brings about certain functional advantages for information processing. However, despite the plenty of evidence and plausibility of the neural criticality hypothesis, still very little is known on how the brain may leverage such criticality to facilitate neural coding. Moreover, the emergent functions that may arise from critical dynamics is poorly understood. In the first part of this thesis, we review several pieces of evidence for the neural criticality hypothesis at different scales, as well as some of the most popular theories of self-organized criticality (SOC). Thereafter, we will focus on the most prominent evidence from small scales, namely neuronal avalanches. We will explore the effect of adaptation and how it can maintain scale free dynamics even at the presence of external stimuli. Using calcium imaging we also experimentally demonstrate the existence of scale free activity at the cellular resolution in vivo. Moreover, by exploring the subsampling issue in neural data, we will find some fundamental constraints of the conventional methods

  6. The hexagon hypothesis: Six disruptive scenarios.

    PubMed

    Burtles, Jim

    2015-01-01

    This paper aims to bring a simple but effective and comprehensive approach to the development, delivery and monitoring of business continuity solutions. To ensure that the arguments and principles apply across the board, the paper sticks to basic underlying concepts rather than sophisticated interpretations. First, the paper explores what exactly people are defending themselves against. Secondly, the paper looks at how defences should be set up. Disruptive events tend to unfold in phases, each of which invites a particular style of protection, ranging from risk management through to business continuity to insurance cover. Their impact upon any business operation will fall into one of six basic scenarios. The hexagon hypothesis suggests that everyone should be prepared to deal with each of these six disruptive scenarios and it provides them with a useful benchmark for business continuity.

  7. A neuroplastic deafferentation hypothesis for bipolar disorder

    PubMed Central

    Rogers, Jonathan; Mirams, Jamie; Patel, Rashmi

    2015-01-01

    Bipolar disorder, characterised by extreme cyclical variations in mood between depression and mania, is a common, debilitating and sometimes fatal psychiatric condition with an unclear aetiology. In this paper we propose a hypothesis for the development of bipolar disorder through which neuroplastic changes in response to an index depressive episode leads to the amplification of subthreshold pleasurable stimuli that then drive conversion into a manic state. This ‘pleasure deafferentation hypothesis’ is reached through a discussion of the neuroscientific basis of deafferentation at the level of the neuron and its role in the development of various neurological and psychiatric phenomena before a case for deafferentation as applied to bipolar disorder is justified and its implications discussed. PMID:26459976

  8. Bayesian hypothesis testing for key comparisons

    NASA Astrophysics Data System (ADS)

    Wübbeler, Gerd; Bodnar, Olha; Elster, Clemens

    2016-08-01

    Unilateral degrees of equivalence are the key result in the analysis of key comparison data and they are used to approve, or disapprove, calibration and measurement capabilities of the participating laboratories. To this end, it is checked whether a degree of equivalence differs significantly from zero. Proceeding in such a way can be viewed as carrying out a classical hypothesis test. We develop a Bayesian counterpart to this approach which has the advantage that it can include prior assessment of the corresponding Consultative Committee about the calibration and measurement capabilities of the participating laboratories. Simple expressions are derived and their implementation is provided in terms of MATLAB® and R programs. The novel procedure is illustrated by its application to two recent key comparisons CCL-K1 and CCM.FF-K4.1.2011.

  9. Origin of the moon - The collision hypothesis

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.

    1987-01-01

    Theoretical models of lunar origin involving one or more collisions between the earth and other large sun-orbiting bodies are examined in a critical review. Ten basic propositions of the collision hypothesis (CH) are listed; observational data on mass and angular momentum, bulk chemistry, volatile depletion, trace elements, primordial high temperatures, and orbital evolution are summarized; and the basic tenets of alternative models (fission, capture, and coformation) are reviewed. Consideration is given to the thermodynamics of large impacts, rheological and dynamical problems, numerical simulations based on the CH, disk evolution models, and the chemical implications of the CH. It is concluded that the sound arguments and evidence supporting the CH are not (yet) sufficient to rule out other hypotheses.

  10. The hexagon hypothesis: Six disruptive scenarios.

    PubMed

    Burtles, Jim

    2015-01-01

    This paper aims to bring a simple but effective and comprehensive approach to the development, delivery and monitoring of business continuity solutions. To ensure that the arguments and principles apply across the board, the paper sticks to basic underlying concepts rather than sophisticated interpretations. First, the paper explores what exactly people are defending themselves against. Secondly, the paper looks at how defences should be set up. Disruptive events tend to unfold in phases, each of which invites a particular style of protection, ranging from risk management through to business continuity to insurance cover. Their impact upon any business operation will fall into one of six basic scenarios. The hexagon hypothesis suggests that everyone should be prepared to deal with each of these six disruptive scenarios and it provides them with a useful benchmark for business continuity. PMID:26420396

  11. Testing Darwin's naturalization hypothesis in the Azores.

    PubMed

    Schaefer, Hanno; Hardy, Olivier J; Silva, Luís; Barraclough, Timothy G; Savolainen, Vincent

    2011-04-01

    Invasive species are a threat for ecosystems worldwide, especially oceanic islands. Predicting the invasive potential of introduced species remains difficult, and only a few studies have found traits correlated to invasiveness. We produced a molecular phylogenetic dataset and an ecological trait database for the entire Azorean flora and find that the phylogenetic nearest neighbour distance (PNND), a measure of evolutionary relatedness, is significantly correlated with invasiveness. We show that introduced plant species are more likely to become invasive in the absence of closely related species in the native flora of the Azores, verifying Darwin's 'naturalization hypothesis'. In addition, we find that some ecological traits (especially life form and seed size) also have predictive power on invasive success in the Azores. Therefore, we suggest a combination of PNND with ecological trait values as a universal predictor of invasiveness that takes into account characteristics of both introduced species and receiving ecosystem.

  12. A Reassessment of the Mars Ocean Hypothesis

    NASA Technical Reports Server (NTRS)

    Parker, T. J.

    2004-01-01

    Initial work on the identification and mapping of potential ancient shorelines on Mars was based on Viking Orbiter image data (Parker et al., 1987, 1989, 1993). The Viking Orbiters were designed to locate landing site for the two landers and were not specifically intended to map the entire planet. Fortunately, they mapped the entire planet. Unfortunately, they did so at an average resolution of greater than 200m/pixel. Higher resolution images, even mosaics of interesting regions, are available, but relatively sparse. Mapping of shorelines on Earth requires both high-resolution aerial photos or satellite images and good topographic information. Three significant sources of additional data from missions subsequent to Viking are useful for reassessing the ocean hypothesis. These are: MGS MOC images; MGS MOLA topography; Odyssey THEMIS IR and VIS images; and MER surface geology at Meridiani and Gusev. Okay, my mistake: Four.

  13. A critical examination of the bioplasma hypothesis.

    PubMed

    Quickenden, T I; Tilbury, R N

    1986-01-01

    The hypothesis of Zon (Physiol. Chem. and Physics 11, 501-506 (1979); 12, 357-364 (1980] that regions of semiconduction within living organisms may exhibit plasma behaviour is shown to be most unlikely. Although charge carrier concentrations may be acceptable, calculated Debye lengths are shown to be only marginally acceptable and calculated plasma frequencies are not sufficiently high to ensure that charge carrier motions are governed by electrical and magnetic forces rather than hydrodynamic considerations. For the latter reason, conventional semiconductors do not exhibit plasma behaviour except close to absolute zero and if they are free from impurities and lattice disorder. The experimental evidences presented for the existence of biological plasma (bioplasma) from the areas of Kirlian photography, mitogenetic radiation, acupuncture and studies of biological fields, are largely explainable in conventional terms without invoking the existence of biological plasma. PMID:3809263

  14. Large numbers hypothesis. II - Electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Adams, P. J.

    1983-01-01

    This paper develops the theory of electromagnetic radiation in the units covariant formalism incorporating Dirac's large numbers hypothesis (LNH). A direct field-to-particle technique is used to obtain the photon propagation equation which explicitly involves the photon replication rate. This replication rate is fixed uniquely by requiring that the form of a free-photon distribution function be preserved, as required by the 2.7 K cosmic radiation. One finds that with this particular photon replication rate the units covariant formalism developed in Paper I actually predicts that the ratio of photon number to proton number in the universe varies as t to the 1/4, precisely in accord with LNH. The cosmological red-shift law is also derived and it is shown to differ considerably from the standard form of (nu)(R) - const.

  15. Multiple model cardinalized probability hypothesis density filter

    NASA Astrophysics Data System (ADS)

    Georgescu, Ramona; Willett, Peter

    2011-09-01

    The Probability Hypothesis Density (PHD) filter propagates the first-moment approximation to the multi-target Bayesian posterior distribution while the Cardinalized PHD (CPHD) filter propagates both the posterior likelihood of (an unlabeled) target state and the posterior probability mass function of the number of targets. Extensions of the PHD filter to the multiple model (MM) framework have been published and were implemented either with a Sequential Monte Carlo or a Gaussian Mixture approach. In this work, we introduce the multiple model version of the more elaborate CPHD filter. We present the derivation of the prediction and update steps of the MMCPHD particularized for the case of two target motion models and proceed to show that in the case of a single model, the new MMCPHD equations reduce to the original CPHD equations.

  16. Ecological Hypothesis of Dentin and Root Caries.

    PubMed

    Takahashi, Nobuhiro; Nyvad, Bente

    2016-01-01

    Recent advances regarding the caries process indicate that ecological phenomena induced by bacterial acid production tilt the de- and remineralization balance of the dental hard tissues towards demineralization through bacterial acid-induced adaptation and selection within the microbiota - from the dynamic stability stage to the aciduric stage via the acidogenic stage [Takahashi and Nyvad, 2008]. Dentin and root caries can also be partly explained by this hypothesis; however, the fact that these tissues contain a considerable amount of organic material suggests that protein degradation is involved in caries formation. In this review, we compiled relevant histological, biochemical, and microbiological information about dentin/root caries and refined the hypothesis by adding degradation of the organic matrix (the proteolytic stage) to the abovementioned stages. Bacterial acidification not only induces demineralization and exposure of the organic matrix in dentin/root surfaces but also activation of dentin-embedded and salivary matrix metalloproteinases and cathepsins. These phenomena initiate degradation of the demineralized organic matrix in dentin/root surfaces. While a bacterial involvement has never been confirmed in the initial degradation of organic material, the detection of proteolytic/amino acid-degrading bacteria and bacterial metabolites in dentin and root caries suggests a bacterial digestion and metabolism of partly degraded matrix. Moreover, bacterial metabolites might induce pulpitis as an inflammatory/immunomodulatory factor. Root and dentin surfaces are always at risk of becoming demineralized in the oral cavity, and exposed organic materials can be degraded by host-derived proteases contained in saliva and dentin itself. New approaches to the prevention and treatment of root/dentin caries are required. PMID:27458979

  17. Limb apraxia and the "affordance competition hypothesis".

    PubMed

    Rounis, Elisabeth; Humphreys, Glyn

    2015-01-01

    Limb apraxia, a disorder of higher order motor control, has long been a challenge for clinical assessment and understanding (Leiguarda and Marsden, 2000). The deficits originally described in limb apraxia (Liepmann, 1920) have been classified by the nature of the errors made by the patients leading to, namely, ideational and ideomotor apraxia. The dual stream hypothesis (Goodale and Milner, 1992) has been used to explain these categories: ideational apraxia is thought to relate to a deficit in the concept of a movement (coded in the ventral stream). Patients have difficulty using objects, sequencing actions to interact with them or pantomiming their use. Ideomotor apraxia, on the other hand, is thought to arise from problems in the accurate implementation of movements within the dorsal stream. One of the limitations on understanding apraxia is the failure by the clinical literature to draw on knowledge of the factors determining actions in the environment. Here we emphasize the role of affordance. There is much recent work indicating that our responses to stimuli are strongly influenced by the actions that the objects "afford", based on their physical properties and the intentions of the actor (e.g., Tucker and Ellis, 1998). The concept of affordance, originally suggested by Gibson (1979) has been incorporated in a recent model of interactive behavior that draws from findings in non-human primates, namely the "affordance competition hypothesis" (Cisek, 2007). This postulates that interactive behavior arises by a process of competition between possible actions elicited by the environment. In this paper we argue that "affordance competition" may play a role in apraxia. We review evidence that at least some aspects of apraxia may reflect an abnormal sensitivity to competition when multiple affordances are present (Riddoch et al., 1998) and/or a poor ability to exert cognitive control over this competition when it occurs. This framework suggests a new way of

  18. DIOXINS AND ENDOMETRIOSIS: A PLAUSIBLE HYPOTHESIS

    EPA Science Inventory

    A potential connection exists between the increasing prevalence of endometriosis and exposure to organochlorine chemicals. There is evidence that dioxin (2,3,7,8-TCDD) can increase the incidence and severity of the disease in monkeys and can promote the growth or survival of end...

  19. Revisiting the environmental Kuznets curve hypothesis in a tourism development context.

    PubMed

    de Vita, Glauco; Katircioglu, Salih; Altinay, Levent; Fethi, Sami; Mercan, Mehmet

    2015-11-01

    This study investigates empirically an extended version of the Environmental Kuznets Curve model that controls for tourism development. We find that international tourist arrivals into Turkey alongside income, squared income and energy consumption, cointegrate with CO2 emissions. Tourist arrivals, growth, and energy consumption exert a positive and significant impact on CO2 emissions in the long-run. Our results provide empirical support to EKC hypothesis showing that at exponential levels of growth, CO2 emissions decline. The findings suggest that despite the environmental degradation stemming from tourism development, policies aimed at environmental protection should not be pursued at the expense of tourism-led growth. PMID:26081781

  20. Revisiting the environmental Kuznets curve hypothesis in a tourism development context.

    PubMed

    de Vita, Glauco; Katircioglu, Salih; Altinay, Levent; Fethi, Sami; Mercan, Mehmet

    2015-11-01

    This study investigates empirically an extended version of the Environmental Kuznets Curve model that controls for tourism development. We find that international tourist arrivals into Turkey alongside income, squared income and energy consumption, cointegrate with CO2 emissions. Tourist arrivals, growth, and energy consumption exert a positive and significant impact on CO2 emissions in the long-run. Our results provide empirical support to EKC hypothesis showing that at exponential levels of growth, CO2 emissions decline. The findings suggest that despite the environmental degradation stemming from tourism development, policies aimed at environmental protection should not be pursued at the expense of tourism-led growth.

  1. A Test of the Salience Hypothesis of Dream Recall

    ERIC Educational Resources Information Center

    Cohen, David B.; MacNeilage, Peter F.

    1974-01-01

    A test was made of the hypothesis that dream salience (subjective impact of the generated dream) would be greater for frequent than infrequent dream recallers. Analysis of the verbal reports confirmed the hypothesis. (Author)

  2. Mars' Oceanus Borealis, Ancient Glaciers, and the MEGAOUTFLO Hypothesis

    NASA Technical Reports Server (NTRS)

    Baker, V. R.; Strom, R. G.; Dohm, J. M.; Gulick, V. C.; Kargel, J. S.; Komatsu, G.; Ori, G. G.; Rice, J. W., Jr.

    2000-01-01

    Recent results from Global Surveyor corroborate the hypothesis that episodes of outburst flooding produced ponded water and climate change on Mars. This hypothesis colligates diverse facts concerning the Martian landscape and its history into a unified genetic system.

  3. Hypothesis of demodicidosis rosacea flushing etiopathogenesis.

    PubMed

    Robledo, Mary Ann; Orduz, Mariana

    2015-04-01

    Most of the patients with erythematotelangiectatic rosacea are characterized by flushing, oedema and telangiectasia. The etiopathogenesis of the flushing in rosacea patients is unknown. Clinically the flushing in rosacea is similar to the "Asian flushing syndrome". Most Asians have an overactive alcohol dehydrogenase (ADH) that tends to break down alcohol into acetaldehyde faster. People with "Asians flushing syndrome" have a genetic disorder with the Aldehyde Dehydrogenase 2(∗)2 (ALDH2(∗)2) allele. This is the reason why they do not metabolize very well the acetaldehyde that comes from the alcohol, which means that acetaldehyde takes much longer to clear from their blood. ALDH2 enzyme is primarily responsible for oxidation of acetaldehyde derived from ethanol metabolism, as well as oxidation of various other endogenous and exogenous aldehydes. Acetaldehyde produces the vasodilatation in the "Asian flushing syndrome". The antibodies against the GroEl chaperonin protein, a 62-kDa heat shock protein were found in the Bacillus oleronius isolated from Demodex mites, in rosacea patients. The GroEl chaperonin protein is a protein that plays a key role in normal folding of ALDH2. If the GroEl chaperonin antibodies found in patients with rosacea, cross react with the human GroEl chaperonin protein, they will not fold normally the ALDH2, and then the enzyme will not metabolize the acetaldehyde. Many of the patients with rosacea have a concomitant infection with Helicobacter pylori in their stomach. The H.pylori produces high amounts of acetaldehyde, which comes from their metabolism of ethanol or carbohydrates. As a result, high amounts of acetaldehyde will circulate for longer time in the blood, until the liver CYP2E1(p450) enzyme system finally metabilizes the acetaldehyde, during that period of time the patients will experience a flushing as well as the people with the "Asian flushing syndrome" suffer when they drink ethanol. To prove the hypothesis it is necessary

  4. Hypothesis of demodicidosis rosacea flushing etiopathogenesis.

    PubMed

    Robledo, Mary Ann; Orduz, Mariana

    2015-04-01

    Most of the patients with erythematotelangiectatic rosacea are characterized by flushing, oedema and telangiectasia. The etiopathogenesis of the flushing in rosacea patients is unknown. Clinically the flushing in rosacea is similar to the "Asian flushing syndrome". Most Asians have an overactive alcohol dehydrogenase (ADH) that tends to break down alcohol into acetaldehyde faster. People with "Asians flushing syndrome" have a genetic disorder with the Aldehyde Dehydrogenase 2(∗)2 (ALDH2(∗)2) allele. This is the reason why they do not metabolize very well the acetaldehyde that comes from the alcohol, which means that acetaldehyde takes much longer to clear from their blood. ALDH2 enzyme is primarily responsible for oxidation of acetaldehyde derived from ethanol metabolism, as well as oxidation of various other endogenous and exogenous aldehydes. Acetaldehyde produces the vasodilatation in the "Asian flushing syndrome". The antibodies against the GroEl chaperonin protein, a 62-kDa heat shock protein were found in the Bacillus oleronius isolated from Demodex mites, in rosacea patients. The GroEl chaperonin protein is a protein that plays a key role in normal folding of ALDH2. If the GroEl chaperonin antibodies found in patients with rosacea, cross react with the human GroEl chaperonin protein, they will not fold normally the ALDH2, and then the enzyme will not metabolize the acetaldehyde. Many of the patients with rosacea have a concomitant infection with Helicobacter pylori in their stomach. The H.pylori produces high amounts of acetaldehyde, which comes from their metabolism of ethanol or carbohydrates. As a result, high amounts of acetaldehyde will circulate for longer time in the blood, until the liver CYP2E1(p450) enzyme system finally metabilizes the acetaldehyde, during that period of time the patients will experience a flushing as well as the people with the "Asian flushing syndrome" suffer when they drink ethanol. To prove the hypothesis it is necessary

  5. Vocational Hypothesis Testing in Career Decision-Making.

    ERIC Educational Resources Information Center

    Blustein, David L.; Strohmer, Douglas C.

    1987-01-01

    Examined vocational hypothesis testing by applying Snyder's hypothesis-testing research paradigm to a vocational task in two experiments. Subjects (N=106) were asked to evaluate the appropriateness of a specific occupation for themselves. Subjects tended to exhibit confirmatory hypothesis-testing strategies when relevant occupations were…

  6. In Defense of the Play-Creativity Hypothesis

    ERIC Educational Resources Information Center

    Silverman, Irwin W.

    2016-01-01

    The hypothesis that pretend play facilitates the creative thought process in children has received a great deal of attention. In a literature review, Lillard et al. (2013, p. 8) concluded that the evidence for this hypothesis was "not convincing." This article focuses on experimental and training studies that have tested this hypothesis.…

  7. Mental deterioration at epilepsy onset: a hypothesis.

    PubMed

    Meinardi, H; Aldenkamp, A P; Nunes, B

    1992-01-01

    In this study, we hypothesized a type of mental deterioration in epilepsy, characterized as a discontinued, cascading process, i.e. a sudden mental decline in a limited time interval, immediately after the onset of the seizures. The posttraumatic epilepsy model (PTE) may appear to be exceptionally useful in avoiding one of the major methodological obstacles for testing this hypothesis, i.e. the unavailability of test results obtained with the same battery of tests prior to and directly after the onset of the seizures. We propose a multicentre study in which a large group of patients are assessed, after recovering from the direct aftermath of head injury, but before the onset of PTE. This baseline provides an opportunity for longitudinal follow-up. Full recovery from head injury before the onset of PTE is to be expected in the mild and moderate groups of closed head injury patients. In this category, approximately 2000 head injured patients have to be assessed to obtain a reasonable group of approximately 100-200 PTE patients. This group will be followed during the critical period of 2-3 years after the onset of epilepsy. PMID:1414549

  8. The social brain hypothesis of schizophrenia

    PubMed Central

    BURNS, JONATHAN

    2006-01-01

    The social brain hypothesis is a useful heuristic for understanding schizophrenia. It focuses attention on the core Bleulerian concept of autistic alienation and is consistent with well-replicated findings of social brain dysfunction in schizophrenia as well as contemporary theories of human cognitive and brain evolution. The contributions of Heidegger, Merleau-Ponty and Wittgenstein allow us to arrive at a new "philosophy of interpersonal relatedness", which better reflects the "embodied mind" and signifies the end of Cartesian dualistic thinking. In this paper I review the evolution, development and neurobiology of the social brain - the anatomical and functional substrate for adaptive social behaviour and cognition. Functional imaging identifies fronto-temporal and fronto-parietal cortical networks as comprising the social brain, while the discovery of "mirror neurons" provides an understanding of social cognition at a cellular level. Patients with schizophrenia display abnormalities in a wide range of social cognition tasks such as emotion recognition, theory of mind and affective responsiveness. Furthermore, recent research indicates that schizophrenia is a disorder of functional and structural connectivity of social brain networks. These findings lend support to the claim that schizophrenia represents a costly by-product of social brain evolution in Homo sapiens. Individuals with this disorder find themselves seriously disadvantaged in the social arena and vulnerable to the stresses of their complex social environments. This state of "disembodiment" and interpersonal alienation is the core phenomenon of schizophrenia and the root cause of intolerable suffering in the lives of those affected. PMID:16946939

  9. Bayesian Hypothesis Testing for Planet Finding

    NASA Astrophysics Data System (ADS)

    Braems, I.; Kasdin, N. J.

    2003-12-01

    One of the most important performance metrics of any space planet finding system is integration time. The time needed to make a positive detection of an extrasolar planet determines the number of systems we can observe for the life of the mission and the stability requirements of the spacecraft and optical control systems. Most astronomical detection approaches rely on fairly simple signal-to-noise calculations and a threshold determined by the ability of the human eye to extract the planet image from the background (usually a signal-to-noise ratio of five). In this paper we present an alternative approach to detection using Bayesian hypothesis testing. This optimal approach provides a quantitative measure of the probability of detection under various conditions and integration times (such as known or unknown background levels) and under different prior assumptions. We also show how the technique allows for a much higher probability of detection for shorter integration times than the previous photometric approaches. We gratefully acknowledge the support of the Jet Propulsion Laboratory of the National Aeronautics and Space Administration for this work and Institut National de Recherche en Informatique et Automatique (INRIA) for its support of Ms. Braems.

  10. [Serotonin hypothesis and pulmonary artery hypertension].

    PubMed

    Kloza, Monika; Baranowska-Kuczko, Marta; Pędzińska-Betiuk, Anna; Jackowski, Konrad; Kozłowska, Hanna

    2014-06-06

    Pulmonary arterial hypertension (PAH) is a progressive, complex disease leading to the right ventricular failure and premature death. PAH is characterized by increased pulmonary arterial pressure, increased vascular resistance, pulmonary vascular remodeling and endothelial dysfunction. Pathomechanism of this disease is still unknown. It has been suggested, that endothelial dysfunction is caused by unbalance between vasodilators and vasoconstrictors e.g. serotonin (5-HT). Previously, serotonin hypothesis was linked to the anorexigens, derivatives of fenfluramine, which are serotonin transporter (SERT) substrates. Nowadays, it has been proved that all elements of serotonergic system within pulmonary circulation participate in the developement of PAH. The tryptophan hydroxylase 1 (Tph-1) catalyses synthesis of 5-HT from tryptophan in the pulmonary arterial endothelial cells. 5-HT mediates contraction of pulmonary vessels via 5-HT1B and 5-HT2A receptors. 5-HT is also transported into pulmonary arterial smooth muscle cells via SERT and through activation of reactive oxygen species and Rho-kinase may contribute to contraction or/and, via stimulation of transcription factors, lead to proliferation and remodelling. There is also increasing number of evidence about functional interaction between 5-HT1B receptor and SERT in modulation of vasoconstriction and proliferation in pulmonary arteries. This review discusses the role of 5-HT in the development of PAH and highlights possible therapeutic targets within serotonergic system.

  11. Hypothesis exploration with visualization of variance

    PubMed Central

    2014-01-01

    Background The Consortium for Neuropsychiatric Phenomics (CNP) at UCLA was an investigation into the biological bases of traits such as memory and response inhibition phenotypes—to explore whether they are linked to syndromes including ADHD, Bipolar disorder, and Schizophrenia. An aim of the consortium was in moving from traditional categorical approaches for psychiatric syndromes towards more quantitative approaches based on large-scale analysis of the space of human variation. It represented an application of phenomics—wide-scale, systematic study of phenotypes—to neuropsychiatry research. Results This paper reports on a system for exploration of hypotheses in data obtained from the LA2K, LA3C, and LA5C studies in CNP. ViVA is a system for exploratory data analysis using novel mathematical models and methods for visualization of variance. An example of these methods is called VISOVA, a combination of visualization and analysis of variance, with the flavor of exploration associated with ANOVA in biomedical hypothesis generation. It permits visual identification of phenotype profiles—patterns of values across phenotypes—that characterize groups. Visualization enables screening and refinement of hypotheses about variance structure of sets of phenotypes. Conclusions The ViVA system was designed for exploration of neuropsychiatric hypotheses by interdisciplinary teams. Automated visualization in ViVA supports ‘natural selection’ on a pool of hypotheses, and permits deeper understanding of the statistical architecture of the data. Large-scale perspective of this kind could lead to better neuropsychiatric diagnostics. PMID:25097666

  12. A Matched Filter Hypothesis for Cognitive Control

    PubMed Central

    Thompson-Schill, Sharon L.

    2013-01-01

    The prefrontal cortex exerts top-down influences on several aspects of higher-order cognition by functioning as a filtering mechanism that biases bottom-up sensory information toward a response that is optimal in context. However, research also indicates that not all aspects of complex cognition benefit from prefrontal regulation. Here we review and synthesize this research with an emphasis on the domains of learning and creative cognition, and outline how the appropriate level of cognitive control in a given situation can vary depending on the organism's goals and the characteristics of the given task. We offer a Matched Filter Hypothesis for cognitive control, which proposes that the optimal level of cognitive control is task-dependent, with high levels of cognitive control best suited to tasks that are explicit, rule-based, verbal or abstract, and can be accomplished given the capacity limits of working memory and with low levels of cognitive control best suited to tasks that are implicit, reward-based, non-verbal or intuitive, and which can be accomplished irrespective of working memory limitations. Our approach promotes a view of cognitive control as a tool adapted to a subset of common challenges, rather than an all-purpose optimization system suited to every problem the organism might encounter. PMID:24200920

  13. Handedness in man: The energy availability hypothesis.

    PubMed

    Chan, Yoo Kuen; Loh, Pui San

    2016-09-01

    More than 90% of the human species are right handed. Although outwardly our body appears symmetrical, a 50/50% lateralization in handedness never occurs. Neither have we seen more than 50% left handedness in any subset of the human population. By 12-15weeks of intrauterine life, as many as 6 times more fetuses are noted by ultrasound studies to be sucking on their right thumbs. Distinct difference in oxygenation leading to dissimilar energy availability between right and left subclavian arteries in place by week 9 of life may hold the clue to the lateralization of hand function and eventually, the same in the brain. We know there is a higher incidence of left handedness in males, twins, premature babies and those born to mothers who smoke. They may represent a subset with less distinct difference in oxygenation between the 2 subclavian arteries during the fetal stage. This hypothesis if correct not only closes the gap in understanding human handedness and lateralization but also opens a vista for new research to focus on in utero tissue energy availability and its impact on outcome in life. PMID:27515214

  14. The social brain hypothesis of schizophrenia.

    PubMed

    Burns, Jonathan

    2006-06-01

    The social brain hypothesis is a useful heuristic for understanding schizophrenia. It focuses attention on the core Bleulerian concept of autistic alienation and is consistent with well-replicated findings of social brain dysfunction in schizophrenia as well as contemporary theories of human cognitive and brain evolution. The contributions of Heidegger, Merleau-Ponty and Wittgenstein allow us to arrive at a new "philosophy of interpersonal relatedness", which better reflects the "embodied mind" and signifies the end of Cartesian dualistic thinking. In this paper I review the evolution, development and neurobiology of the social brain - the anatomical and functional substrate for adaptive social behaviour and cognition. Functional imaging identifies fronto-temporal and fronto-parietal cortical networks as comprising the social brain, while the discovery of "mirror neurons" provides an understanding of social cognition at a cellular level. Patients with schizophrenia display abnormalities in a wide range of social cognition tasks such as emotion recognition, theory of mind and affective responsiveness. Furthermore, recent research indicates that schizophrenia is a disorder of functional and structural connectivity of social brain networks. These findings lend support to the claim that schizophrenia represents a costly by-product of social brain evolution in Homo sapiens. Individuals with this disorder find themselves seriously disadvantaged in the social arena and vulnerable to the stresses of their complex social environments. This state of "disembodiment" and interpersonal alienation is the core phenomenon of schizophrenia and the root cause of intolerable suffering in the lives of those affected.

  15. Transpiration: A Test of Optimality Hypothesis

    NASA Astrophysics Data System (ADS)

    Wang, J.; Bras, R. L.; Lerdau, M.; Salvucci, G. D.; Wofsy, S.

    2003-12-01

    The argument is that the fundamental mechanisms behind bare soil evaporation are also responsible for plant transpiration except that stomata affect the exchange of water vapor between the evaporating surface and the atmosphere. It is hypothesized that the system of liquid water in leaf tissues and the water vapor in the atmosphere tries to evolve towards a potential equilibrium as quickly as possible by maximizing transpiration. In the proposed theory, CO2 flux is used as a non-parametric equivalent of stomatal conductance as CO2 and water vapor diffuse in and out of leaves through the same path. It is further assumed that stomatal aperture is directly controlled by guard cell turgor (or leaf water potential). Transpiration is formulated as a function of leaf temperature, leaf water potential/stomatal conductance (or CO2 flux as the surrogate), and sensible heat flux (characterizing transport mechanism) at a given level of radiative energy input. Optimization of transpiration constrained by the energy balance equation leads to vanishing derivatives of transpiration with respect to leaf temperature and CO2 flux. Effect of vapor pressure deficit on transpiration is also investigated. Preliminary tests using field experimental measurements lead to encouraging evidence in support of the hypothesis. It is found that transpiration is fairly insensitive to atmospheric humidity as suggested by several earlier studies.

  16. [GADV]-protein world hypothesis on the origin of life.

    PubMed

    Ikehara, Kenji

    2014-12-01

    RNA world hypothesis is widely accepted still now, as an idea by which the origin of life might be explained. But, there are many weak points in the hypothesis. In contrast, I have proposed a more reasonable [GADV]-protein world hypothesis or GADV hypothesis, suggesting that life originated from the protein world, which was formed by pseudo-replication of [GADV]-proteins. In this communication, I will discuss about the origin of life from the point of view of the GADV hypothesis.

  17. [GADV]-Protein World Hypothesis on the Origin of Life

    NASA Astrophysics Data System (ADS)

    Ikehara, Kenji

    2014-12-01

    RNA world hypothesis is widely accepted still now, as an idea by which the origin of life might be explained. But, there are many weak points in the hypothesis. In contrast, I have proposed a more reasonable [GADV]-protein world hypothesis or GADV hypothesis, suggesting that life originated from the protein world, which was formed by pseudo-replication of [GADV]-proteins. In this communication, I will discuss about the origin of life from the point of view of the GADV hypothesis.

  18. The oxidative damage initiation hypothesis for meiosis.

    PubMed

    Hörandl, Elvira; Hadacek, Franz

    2013-12-01

    The maintenance of sexual reproduction in eukaryotes is still a major enigma in evolutionary biology. Meiosis represents the only common feature of sex in all eukaryotic kingdoms, and thus, we regard it a key issue for discussing its function. Almost all asexuality modes maintain meiosis either in a modified form or as an alternative pathway, and facultatively apomictic plants increase frequencies of sexuality relative to apomixis after abiotic stress. On the physiological level, abiotic stress causes oxidative stress. We hypothesize that repair of oxidative damage on nuclear DNA could be a major driving force in the evolution of meiosis. We present a hypothetical model for the possible redox chemistry that underlies the binding of the meiosis-specific protein Spo11 to DNA. During prophase of meiosis I, oxidized sites at the DNA molecule are being targeted by the catalytic tyrosine moieties of Spo11 protein, which acts like an antioxidant reducing the oxidized target. The oxidized tyrosine residues, tyrosyl radicals, attack the phosphodiester bonds of the DNA backbone causing DNA double strand breaks that can be repaired by various mechanisms. Polyploidy in apomictic plants could mitigate oxidative DNA damage and decrease Spo11 activation. Our hypothesis may contribute to explaining various enigmatic phenomena: first, DSB formation outnumbers crossovers and, thus, effective recombination events by far because the target of meiosis may be the removal of oxidative lesions; second, it offers an argument for why expression of sexuality is responsive to stress in many eukaryotes; and third, repair of oxidative DNA damage turns meiosis into an essential characteristic of eukaryotic reproduction.

  19. The oxidative damage initiation hypothesis for meiosis.

    PubMed

    Hörandl, Elvira; Hadacek, Franz

    2013-12-01

    The maintenance of sexual reproduction in eukaryotes is still a major enigma in evolutionary biology. Meiosis represents the only common feature of sex in all eukaryotic kingdoms, and thus, we regard it a key issue for discussing its function. Almost all asexuality modes maintain meiosis either in a modified form or as an alternative pathway, and facultatively apomictic plants increase frequencies of sexuality relative to apomixis after abiotic stress. On the physiological level, abiotic stress causes oxidative stress. We hypothesize that repair of oxidative damage on nuclear DNA could be a major driving force in the evolution of meiosis. We present a hypothetical model for the possible redox chemistry that underlies the binding of the meiosis-specific protein Spo11 to DNA. During prophase of meiosis I, oxidized sites at the DNA molecule are being targeted by the catalytic tyrosine moieties of Spo11 protein, which acts like an antioxidant reducing the oxidized target. The oxidized tyrosine residues, tyrosyl radicals, attack the phosphodiester bonds of the DNA backbone causing DNA double strand breaks that can be repaired by various mechanisms. Polyploidy in apomictic plants could mitigate oxidative DNA damage and decrease Spo11 activation. Our hypothesis may contribute to explaining various enigmatic phenomena: first, DSB formation outnumbers crossovers and, thus, effective recombination events by far because the target of meiosis may be the removal of oxidative lesions; second, it offers an argument for why expression of sexuality is responsive to stress in many eukaryotes; and third, repair of oxidative DNA damage turns meiosis into an essential characteristic of eukaryotic reproduction. PMID:23995700

  20. Attempting to Unravel the Australian Megatsunami Hypothesis

    NASA Astrophysics Data System (ADS)

    Goff, J. R.

    2008-12-01

    Nearly two decades of information report apparent megatsunamis along the SE coast of Australia and yet these interpretations are still highly controversial. This work has proven to be particularly influential in guiding more recent megatsunami researchers, and yet it has never been critically evaluated in the light of recent advances in tsunami research. Much of the controversy hinges upon the nature of the original observations, event chronologies, and source identification. The most recent incarnation of the megatsunami hypothesis is indicative of the controversy. A supposed impact crater to the SW of New Zealand is linked with abandoned Maori settlements, Maori legends, and high elevation beach sand deposits in New Zealand, and apparent megatsunami evidence in eastern Australia and on Lord Howe Island. A date of around AD1500 is proposed. There are two key issues here. First, is there currently any evidence for contemporaneous trans Tasman palaeotsunamis (or megatsunamis) in the Holocene? Second, how reliable is the evidence? The first issue was addressed by comparing Holocene events from the Australian and New Zealand palaeotsunami databases. Up to five possible contemporaneous events were identified, but at the same time flaws in the underpinning data were highlighted. To start with, there is no consistent approach to the interpretation of chronological information comprising the databases. A consistent recalibration of all available radiocarbon data was carried out for both databases. This was based upon information contained in the relevant original papers. No clusters of radiocarbon ages were found for apparent megatsunami deposits along the SE coast of Australia. Clusters were found however, in New Zealand for inferred local and regional events. Next, the nature and extent of physical evidence used to determine tsunami emplacement were found to be highly variable. A preliminary reassessment of the physical evidence casts doubt upon the interpretation of

  1. The Zinc Dyshomeostasis Hypothesis of Alzheimer's Disease

    PubMed Central

    Craddock, Travis J. A.; Tuszynski, Jack A.; Chopra, Deepak; Casey, Noel; Goldstein, Lee E.; Hameroff, Stuart R.; Tanzi, Rudolph E.

    2012-01-01

    Alzheimer's disease (AD) is the most common form of dementia in the elderly. Hallmark AD neuropathology includes extracellular amyloid plaques composed largely of the amyloid-β protein (Aβ), intracellular neurofibrillary tangles (NFTs) composed of hyper-phosphorylated microtubule-associated protein tau (MAP-tau), and microtubule destabilization. Early-onset autosomal dominant AD genes are associated with excessive Aβ accumulation, however cognitive impairment best correlates with NFTs and disrupted microtubules. The mechanisms linking Aβ and NFT pathologies in AD are unknown. Here, we propose that sequestration of zinc by Aβ-amyloid deposits (Aβ oligomers and plaques) not only drives Aβ aggregation, but also disrupts zinc homeostasis in zinc-enriched brain regions important for memory and vulnerable to AD pathology, resulting in intra-neuronal zinc levels, which are either too low, or excessively high. To evaluate this hypothesis, we 1) used molecular modeling of zinc binding to the microtubule component protein tubulin, identifying specific, high-affinity zinc binding sites that influence side-to-side tubulin interaction, the sensitive link in microtubule polymerization and stability. We also 2) performed kinetic modeling showing zinc distribution in extra-neuronal Aβ deposits can reduce intra-neuronal zinc binding to microtubules, destabilizing microtubules. Finally, we 3) used metallomic imaging mass spectrometry (MIMS) to show anatomically-localized and age-dependent zinc dyshomeostasis in specific brain regions of Tg2576 transgenic, mice, a model for AD. We found excess zinc in brain regions associated with memory processing and NFT pathology. Overall, we present a theoretical framework and support for a new theory of AD linking extra-neuronal Aβ amyloid to intra-neuronal NFTs and cognitive dysfunction. The connection, we propose, is based on β-amyloid-induced alterations in zinc ion concentration inside neurons affecting stability of polymerized

  2. Fungiculture or Termite Husbandry? The Ruminant Hypothesi

    PubMed Central

    Nobre, Tânia; Aanen, Duur K.

    2012-01-01

    We present a new perspective for the role of Termitomyces fungi in the mutualism with fungus-growing termites. According to the predominant view, this mutualism is as an example of agriculture with termites as farmers of a domesticated fungus crop, which is used for degradation of plant-material and production of fungal biomass. However, a detailed study of the literature indicates that the termites might as well be envisioned as domesticates of the fungus. According to the “ruminant hypothesis” proposed here, termite workers, by consuming asexual fruiting bodies not only harvest asexual spores, but also lignocellulolytic enzymes, which they mix with foraged plant material and enzymes of termite and possibly bacterial origin. This mixture is the building material of the fungus garden and facilitates efficient degradation of plant material. The fungus garden thus functions as an external rumen for termites and primarily the fungi themselves benefit from their own, and gut-derived, lignocellulolytic enzymes, using the termites to efficiently mix these with their growth substrate. Only secondarily the termites benefit, when they consume the degraded, nitrogen-enriched plant-fungus mixture a second time. We propose that the details of substrate use, and the degree of complementarity and redundancy among enzymes in food processing, determine selection of horizontally transmitted fungal symbionts at the start of a colony: by testing spores on a specific, mechanically and enzymatically pre-treated growth substrate, the termite host has the opportunity to select specific fungal symbionts. Potentially, the gut-microbiota thus influence host-fungus specificity, and the selection of specific fungal strains at the start of a new colony. We argue that we need to expand the current bipartite insect-biased view of the mutualism of fungus-growing termites and include the possible role of bacteria and the benefit for the fungi to fully understand the division of labor among

  3. Modelling wind turbine wakes using the turbulent entrainment hypothesis

    NASA Astrophysics Data System (ADS)

    Luzzatto-Fegiz, Paolo

    2015-11-01

    Simple models for turbine wakes have been used extensively in the wind energy community, both as independent tools, as well as to complement more refined and computationally-intensive techniques. Jensen (1983; see also Katić et al. 1986) developed a model assuming that the wake radius grows linearly with distance x, approximating the velocity deficit with a top-hat profile. While this model has been widely implemented in the wind energy community, recently Bastankhah & Porté-Agel (2014) showed that it does not conserve momentum. They proposed a momentum-conserving theory, which assumed a Gaussian velocity deficit and retained the linear-spreading assumption, significantly improving agreement with experiments and LES. While the linear spreading assumption facilitates conceptual modeling, it requires empirical estimates of the spreading rate, and does not readily enable generalizations to other turbine designs. Furthermore, field measurements show sub-linear wake growth with x in the far-wake, consistently with results from fundamental turbulence studies. We develop a model by relying on a simple and general turbulence parameterization, namely the entrainment hypothesis, which has been used extensively in other areas of geophysical fluid dynamics. Without assuming similarity, we derive an analytical solution for a circular turbine wake, which predicts a far-wake radius increasing with x 1 / 3, and is consistent with field measurements and fundamental turbulence studies. Finally, we discuss developments accounting for effects of stratification, as well as generalizations to other turbine designs.

  4. Does hunting regulate cougar populations? A test of the compensatory mortality hypothesis.

    PubMed

    Cooley, Hilary S; Wielgus, Robert B; Koehler, Gary M; Robinson, Hugh S; Maletzke, Benjamin T

    2009-10-01

    Many wildlife species are managed based on the compensatory mortality hypothesis, which predicts that harvest mortality (especially adult male mortality) will trigger density-dependent responses in reproduction, survival, and population growth caused via reduced competition for resources. We tested the compensatory mortality hypothesis on two cougar (Puma concolor) populations in Washington, USA (one heavily hunted and one lightly hunted). We estimated population growth, density, survival, and reproduction to determine the effects of hunting on cougar population demography based on data collected from 2002 to 2007. In the heavily hunted population, the total hunting mortality rate (mean +/- SD) was 0.24 +/- 0.05 (0.35 +/- 0.08 for males, 0.16 +/- 0.05 for females). In the lightly hunted population, the total hunting mortality rate was 0.11 +/- 0.04 (0.16 +/- 0.06 for males, 0.07 +/- 0.05 for females). The compensatory mortality hypothesis predicts that higher mortality will result in higher maternity, kitten survival, reproductive success, and lower natural mortality. We found no differences in rates of maternity or natural mortality between study areas, and kitten survival was lower in the heavily hunted population. We rejected the compensatory mortality hypothesis because vital rates did not compensate for hunting mortality. Heavy harvest corresponded with increased immigration, reduced kitten survival, reduced female population growth, and a younger overall age structure. Light harvest corresponded with increased emigration, higher kitten survival, increased female population growth, and an older overall age structure. Managers should not assume the existence of compensatory mortality when developing harvest prescriptions for cougars.

  5. Sex, Sport, IGF-1 and the Community Effect in Height Hypothesis

    PubMed Central

    Bogin, Barry; Hermanussen, Michael; Blum, Werner F.; Aßmann, Christian

    2015-01-01

    We test the hypothesis that differences in social status between groups of people within a population may induce variation in insulin-like growth factor-1(IGF-1) levels and, by extension, growth in height. This is called the community effect in height hypothesis. The relationship between IGF-1, assessed via finger-prick dried blood spot, and elite level sport competition outcomes were analysed for a sample of 116 undergraduate men and women. There was a statistically significant difference between winners and losers of a competition. Winners, as a group, had higher average pre-game and post-game IGF-1 levels than losers. We proposed this type of difference as a proxy for social dominance. We found no evidence that winners increased in IGF-1 levels over losers or that members of the same team were more similar in IGF-1 levels than they were to players from other teams. These findings provide limited support toward the community effect in height hypothesis. The findings are discussed in relation to the action of the growth hormone/IGF-1 axis as a transducer of multiple bio-social influences into a coherent signal which allows the growing human to adjust and adapt to local ecological conditions. PMID:25946190

  6. Sex, Sport, IGF-1 and the Community Effect in Height Hypothesis.

    PubMed

    Bogin, Barry; Hermanussen, Michael; Blum, Werner F; Aßmann, Christian

    2015-05-04

    We test the hypothesis that differences in social status between groups of people within a population may induce variation in insulin-like growth factor-1(IGF-1) levels and, by extension, growth in height. This is called the community effect in height hypothesis. The relationship between IGF-1, assessed via finger-prick dried blood spot, and elite level sport competition outcomes were analysed for a sample of 116 undergraduate men and women. There was a statistically significant difference between winners and losers of a competition. Winners, as a group, had higher average pre-game and post-game IGF-1 levels than losers. We proposed this type of difference as a proxy for social dominance. We found no evidence that winners increased in IGF-1 levels over losers or that members of the same team were more similar in IGF-1 levels than they were to players from other teams. These findings provide limited support toward the community effect in height hypothesis. The findings are discussed in relation to the action of the growth hormone/IGF-1 axis as a transducer of multiple bio-social influences into a coherent signal which allows the growing human to adjust and adapt to local ecological conditions.

  7. Constructal approach to cell membranes transport: Amending the ‘Norton-Simon’ hypothesis for cancer treatment

    PubMed Central

    Lucia, Umberto; Ponzetto, Antonio; Deisboeck, Thomas S.

    2016-01-01

    To investigate biosystems, we propose a new thermodynamic concept that analyses ion, mass and energy flows across the cell membrane. This paradigm-shifting approach has a wide applicability to medically relevant topics including advancing cancer treatment. To support this claim, we revisit ‘Norton-Simon’ and evolving it from an already important anti-cancer hypothesis to a thermodynamic theorem in medicine. We confirm that an increase in proliferation and a reduction in apoptosis trigger a maximum of ATP consumption by the tumor cell. Moreover, we find that positive, membrane-crossing ions lead to a decrease in the energy used by the tumor, supporting the notion of their growth inhibitory effect while negative ions apparently increase the cancer’s consumption of energy hence reflecting a growth promoting impact. Our results not only represent a thermodynamic proof of the original Norton-Simon hypothesis but, more concretely, they also advance the clinically intriguing and experimentally testable, diagnostic hypothesis that observing an increase in negative ions inside a cell in vitro, and inside a diseased tissue in vivo, may indicate growth or recurrence of a tumor. We conclude with providing theoretical evidence that applying electromagnetic field therapy early on in the treatment cycle may maximize its anti-cancer efficacy. PMID:26822208

  8. The Younger Dryas impact hypothesis: a critical review

    NASA Astrophysics Data System (ADS)

    van Hoesel, Annelies; Hoek, Wim Z.; Pennock, Gillian M.; Drury, Martyn R.

    2014-01-01

    The Younger Dryas impact hypothesis suggests that multiple extraterrestrial airbursts or impacts resulted in the Younger Dryas cooling, extensive wildfires, megafaunal extinctions and changes in human population. After the hypothesis was first published in 2007, it gained much criticism, as the evidence presented was either not indicative of an extraterrestrial impact or not reproducible by other groups. Only three years after the hypothesis had been presented, a requiem paper was published. Despite this, the controversy continues. New evidence, both in favour and against the hypothesis, continues to be published.

  9. Streamlined islands and the English Channel megaflood hypothesis

    NASA Astrophysics Data System (ADS)

    Collier, J. S.; Oggioni, F.; Gupta, S.; García-Moreno, D.; Trentesaux, A.; De Batist, M.

    2015-12-01

    Recognising ice-age catastrophic megafloods is important because they had significant impact on large-scale drainage evolution and patterns of water and sediment movement to the oceans, and likely induced very rapid, short-term effects on climate. It has been previously proposed that a drainage system on the floor of the English Channel was initiated by catastrophic flooding in the Pleistocene but this suggestion has remained controversial. Here we examine this hypothesis through an analysis of key landform features. We use a new compilation of multi- and single-beam bathymetry together with sub-bottom profiler data to establish the internal structure, planform geometry and hence origin of a set of 36 mid-channel islands. Whilst there is evidence of modern-day surficial sediment processes, the majority of the islands can be clearly demonstrated to be formed of bedrock, and are hence erosional remnants rather than depositional features. The islands display classic lemniscate or tear-drop outlines, with elongated tips pointing downstream, typical of streamlined islands formed during high-magnitude water flow. The length-to-width ratio for the entire island population is 3.4 ± 1.3 and the degree-of-elongation or k-value is 3.7 ± 1.4. These values are comparable to streamlined islands in other proven Pleistocene catastrophic flood terrains and are distinctly different to values found in modern-day rivers. The island geometries show a correlation with bedrock type: with those carved from Upper Cretaceous chalk having larger length-to-width ratios (3.2 ± 1.3) than those carved into more mixed Paleogene terrigenous sandstones, siltstones and mudstones (3.0 ± 1.5). We attribute these differences to the former rock unit having a lower skin friction which allowed longer island growth to achieve minimum drag. The Paleogene islands, although less numerous than the Chalk islands, also assume more perfect lemniscate shapes. These lithologies therefore reached island

  10. Lava Flows Cooling: The initial hypothesis

    NASA Astrophysics Data System (ADS)

    Cordonnier, B.; Self, S.; Manga, M.

    2013-12-01

    Many cooling models of lava have one precondition: an instantaneous-thick layer emplacement with a spatially uniform temperature, often as high as the effusion temperature. The cooling is then mostly controlled by conduction and is a function of the thermal parameters and dimensions of the lava flow (most important being thickness). However, many lavas, especially pahoehoe and compound lavas, are not directly emplaced with an established lava thickness but, rather, inflate from their core or result from piling-up of several layers, respectively. In both cases, this leads initially to thin fast-cooling lavas in which the final emplacement temperature may differ strongly from the initial temperature of the liquid lava feeding the flow. Here we investigate both the behavior of inflating flows and superposition layering of lava. With a modified Peclet Number (Pe), where the velocity has been replaced by the inflation rate, we identify the conditions where lavas lose the most of their thermal energy before the final thickness is reached. For a given growth rate, inflating flows are hotter than those that grow through superposition. In the latter case, temperature depends not only with Pe, but also on the discrete lava-layer thickness. A clear quantification of the energy loss during these processes has been established and demonstrates the impact of each of them on the temperature of emplacement. Apart from this simple point, our study raises the question of lava-flow morphology. The two processes described, despite having opposite thermal effects, may be coupled during a single eruptive event. When a lava reaches its emplacement temperature and stops, then the pressing material uphill starts to bifurcate, turn around or superpose the previously emplaced layer. Our Peclet number could be again modified to consider the traditional emplacement condition of a Graetz number of 300. Beyond this point, the inflating process turns into a superposing process and the conditions

  11. The cometary breakup hypothesis re-examined - A reply

    NASA Astrophysics Data System (ADS)

    Clube, S. V. M.; Napier, W. M.

    1987-04-01

    It is shown that the giant comet breakup hypothesis has a clear basis in astronomical fact and, contrary to LaViolette's claims, is consistent with the available geochemical evidence. The importance of further trace element studies in polar ice for testing this hypothesis is, however, emphasized.

  12. About the structure of cellulose: debating the Lindman hypothesis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The hypothesis advanced in this issue of Cellulose, that the solubility or insolubility characteristics of cellulose are significantly based upon amphiphilic and hydrophobic molecular interactions, is bound to shake the roots of (some of) our textbook wisdom. The hypothesis is based on the considera...

  13. Teaching Hypothesis Testing by Debunking a Demonstration of Telepathy.

    ERIC Educational Resources Information Center

    Bates, John A.

    1991-01-01

    Discusses a lesson designed to demonstrate hypothesis testing to introductory college psychology students. Explains that a psychology instructor demonstrated apparent psychic abilities to students. Reports that students attempted to explain the instructor's demonstrations through hypothesis testing and revision. Provides instructions on performing…

  14. Token Women: An Empirical Test of Kanter's Hypothesis

    ERIC Educational Resources Information Center

    Spangler, Eve; And Others

    1978-01-01

    This study compared female students in a male-dominated law school with female students in a law school where the percentage of women was higher in order to test the hypothesis that the minority-to-minority ratio is a significant determinant of minority member achievement. Results were found to support the hypothesis. (Author/BC)

  15. Assess the Critical Period Hypothesis in Second Language Acquisition

    ERIC Educational Resources Information Center

    Du, Lihong

    2010-01-01

    The Critical Period Hypothesis aims to investigate the reason for significant difference between first language acquisition and second language acquisition. Over the past few decades, researchers carried out a series of studies to test the validity of the hypothesis. Although there were certain limitations in these studies, most of their results…

  16. Making Knowledge Delivery Failsafe: Adding Step Zero in Hypothesis Testing

    ERIC Educational Resources Information Center

    Pan, Xia; Zhou, Qiang

    2010-01-01

    Knowledge of statistical analysis is increasingly important for professionals in modern business. For example, hypothesis testing is one of the critical topics for quality managers and team workers in Six Sigma training programs. Delivering the knowledge of hypothesis testing effectively can be an important step for the incapable learners or…

  17. The Importance of Teaching Power in Statistical Hypothesis Testing

    ERIC Educational Resources Information Center

    Olinsky, Alan; Schumacher, Phyllis; Quinn, John

    2012-01-01

    In this paper, we discuss the importance of teaching power considerations in statistical hypothesis testing. Statistical power analysis determines the ability of a study to detect a meaningful effect size, where the effect size is the difference between the hypothesized value of the population parameter under the null hypothesis and the true value…

  18. An Exercise for Illustrating the Logic of Hypothesis Testing

    ERIC Educational Resources Information Center

    Lawton, Leigh

    2009-01-01

    Hypothesis testing is one of the more difficult concepts for students to master in a basic, undergraduate statistics course. Students often are puzzled as to why statisticians simply don't calculate the probability that a hypothesis is true. This article presents an exercise that forces students to lay out on their own a procedure for testing a…

  19. Longitudinal Dimensionality of Adolescent Psychopathology: Testing the Differentiation Hypothesis

    ERIC Educational Resources Information Center

    Sterba, Sonya K.; Copeland, William; Egger, Helen L.; Costello, E. Jane; Erkanli, Alaattin; Angold, Adrian

    2010-01-01

    Background: The differentiation hypothesis posits that the underlying liability distribution for psychopathology is of low dimensionality in young children, inflating diagnostic comorbidity rates, but increases in dimensionality with age as latent syndromes become less correlated. This hypothesis has not been adequately tested with longitudinal…

  20. The planet beyond the plume hypothesis

    NASA Astrophysics Data System (ADS)

    Smith, Alan D.; Lewis, Charles

    1999-12-01

    Acceptance of the theory of plate tectonics was accompanied by the rise of the mantle plume/hotspot concept which has come to dominate geodynamics from its use both as an explanation for the origin of intraplate volcanism and as a reference frame for plate motions. However, even with a large degree of flexibility permitted in plume composition, temperature, size, and depth of origin, adoption of any limited number of hotspots means the plume model cannot account for all occurrences of the type of volcanism it was devised to explain. While scientific protocol would normally demand that an alternative explanation be sought, there have been few challenges to "plume theory" on account of a series of intricate controls set up by the plume model which makes plumes seem to be an essential feature of the Earth. The hotspot frame acts not only as a reference but also controls plate tectonics. Accommodating plumes relegates mantle convection to a weak, sluggish effect such that basal drag appears as a minor, resisting force, with plates having to move themselves by boundary forces and continents having to be rifted by plumes. Correspondingly, the geochemical evolution of the mantle is controlled by the requirement to isolate subducted crust into plume sources which limits potential buffers on the composition of the MORB-source to plume- or lower mantle material. Crustal growth and Precambrian tectonics are controlled by interpretations of greenstone belts as oceanic plateaus generated by plumes. Challenges to any aspect of the plume model are thus liable to be dismissed unless a counter explanation is offered across the geodynamic spectrum influenced by "plume theory". Nonetheless, an alternative synthesis can be made based on longstanding petrological evidence for derivation of intraplate volcanism from volatile-bearing sources (wetspots) in conjunction with concepts dismissed for being incompatible or superfluous to "plume theory". In the alternative Earth, the sources for

  1. Is sex advantageous in adverse environments? A test of the abandon-ship hypothesis.

    PubMed

    Griffiths, Joshua G; Bonser, Stephen P

    2013-12-01

    Understanding the evolution and maintenance of sexual reproduction remains a long-standing challenge in evolutionary biology. Stress often induces sexual reproduction in facultatively sexual species (those species capable of both sexual and asexual reproduction). The abandon-ship hypothesis predicts higher allocation to sex under stress to allow low-fitness individuals to recombine their genotype, potentially increasing offspring fitness. However, effective tests of the abandon-ship hypothesis, particularly in multicellular organisms, are lacking. Here we test the abandon-ship hypothesis, using cyanogenic and acyanogenic defense phenotypes of the short-lived perennial herb Trifolium repens. Cyanogenesis provides an effective defense against herbivores and is under relatively simple genetic control (plants dominant for cyanogenesis at two alleles express the defended phenotype). Thus, maladapted individuals can acquire adaptive defense alleles for their offspring in a single episode of sexual reproduction. Plants were grown under high- and low-herbivory treatments (plants were exposed to herbivorous snails) and a control treatment (no herbivory). Herbivores reduced growth and fitness in all treated plants, but herbivory induced higher sexual allocation only in maladapted (acyanogenic) individuals. Overall, our results support the abandon-ship hypothesis. PMID:24231534

  2. Role of stable isotopes in life--testing isotopic resonance hypothesis.

    PubMed

    Zubarev, Roman A

    2011-04-01

    Stable isotopes of most important biological elements, such as C, H, N and O, affect living organisms. In rapidly growing species, deuterium and to a lesser extent other heavy isotopes reduce the growth rate. At least for deuterium it is known that its depletion also negatively impacts the speed of biological processes. As a rule, living organisms "resist" changes in their isotopic environment, preferring natural isotopic abundances. This preference could be due to evolutionary optimization; an additional effect could be due to the presence of the "isotopic resonance". The isotopic resonance phenomenon has been linked to the choice of earliest amino acids, and thus affected the evolution of genetic code. To test the isotopic resonance hypothesis, literature data were analyzed against quantitative and qualitative predictions of the hypothesis. Four studies provided five independent datasets, each in very good quantitative agreement with the predictions. Thus, the isotopic resonance hypothesis is no longer simply plausible; it can now be deemed likely. Additional testing is needed, however, before full acceptance of this hypothesis.

  3. Is sex advantageous in adverse environments? A test of the abandon-ship hypothesis.

    PubMed

    Griffiths, Joshua G; Bonser, Stephen P

    2013-12-01

    Understanding the evolution and maintenance of sexual reproduction remains a long-standing challenge in evolutionary biology. Stress often induces sexual reproduction in facultatively sexual species (those species capable of both sexual and asexual reproduction). The abandon-ship hypothesis predicts higher allocation to sex under stress to allow low-fitness individuals to recombine their genotype, potentially increasing offspring fitness. However, effective tests of the abandon-ship hypothesis, particularly in multicellular organisms, are lacking. Here we test the abandon-ship hypothesis, using cyanogenic and acyanogenic defense phenotypes of the short-lived perennial herb Trifolium repens. Cyanogenesis provides an effective defense against herbivores and is under relatively simple genetic control (plants dominant for cyanogenesis at two alleles express the defended phenotype). Thus, maladapted individuals can acquire adaptive defense alleles for their offspring in a single episode of sexual reproduction. Plants were grown under high- and low-herbivory treatments (plants were exposed to herbivorous snails) and a control treatment (no herbivory). Herbivores reduced growth and fitness in all treated plants, but herbivory induced higher sexual allocation only in maladapted (acyanogenic) individuals. Overall, our results support the abandon-ship hypothesis.

  4. Extracorporeal shockwave therapy promotes chondrogenesis in cartilage tissue engineering: A hypothesis based on previous evidence.

    PubMed

    Ji, Qiaodan; He, Chengqi

    2016-06-01

    The dearth of intrinsic regenerative capacity of articular cartilage makes it a challenge to deal with the cartilage defects. Among all the recommended clinical options, cartilage tissue engineering (CTE) which is highlighted of dominant features and less drawbacks for functional cartilage restoration, has been emphasized recently. Shock waves, a mode of therapeutic mechanical forces, utilized in extracorporeal shockwave therapy (ESWT), is hypothesized to enhance proliferation, chondrogenic differentiation, and cartilage extracellular matrix production of target cells seeded on bioactive scaffolds. The hypothesis is firstly based on cellular mechanotransduction by which cells convent the shockwave mechanical signals into biochemical responses via integrins, iron channels, cytoskeletal filaments, growth factor receptors and nuclei. Secondly, by modulating gene expression and up-regulating the release of various growth factors which are of vital importance in three-dimensional cartilage culture environment, ESWT holds a promising potential to favor the cell sources (e.g. chondrocytes and stem cells) to mimic the optimal functional cartilage. In all, on the basis of cellular mechanotransduction and previous evidence, the hypothesis is developed to support the beneficial effects of ESWT on chondrogenesis in CTE. If this hypothesis is confirmed, shockwaves may allow a better success in combination with other stimulating factors for cartilage repair. There is a paucity of studies investigating the assistant role of shockwave stimulation in CTE. Further research is required to elucidate the mechanisms, and explore effectiveness and appropriate protocols of this novel stimulative factor in cartilage tissue engineering.

  5. Extracorporeal shockwave therapy promotes chondrogenesis in cartilage tissue engineering: A hypothesis based on previous evidence.

    PubMed

    Ji, Qiaodan; He, Chengqi

    2016-06-01

    The dearth of intrinsic regenerative capacity of articular cartilage makes it a challenge to deal with the cartilage defects. Among all the recommended clinical options, cartilage tissue engineering (CTE) which is highlighted of dominant features and less drawbacks for functional cartilage restoration, has been emphasized recently. Shock waves, a mode of therapeutic mechanical forces, utilized in extracorporeal shockwave therapy (ESWT), is hypothesized to enhance proliferation, chondrogenic differentiation, and cartilage extracellular matrix production of target cells seeded on bioactive scaffolds. The hypothesis is firstly based on cellular mechanotransduction by which cells convent the shockwave mechanical signals into biochemical responses via integrins, iron channels, cytoskeletal filaments, growth factor receptors and nuclei. Secondly, by modulating gene expression and up-regulating the release of various growth factors which are of vital importance in three-dimensional cartilage culture environment, ESWT holds a promising potential to favor the cell sources (e.g. chondrocytes and stem cells) to mimic the optimal functional cartilage. In all, on the basis of cellular mechanotransduction and previous evidence, the hypothesis is developed to support the beneficial effects of ESWT on chondrogenesis in CTE. If this hypothesis is confirmed, shockwaves may allow a better success in combination with other stimulating factors for cartilage repair. There is a paucity of studies investigating the assistant role of shockwave stimulation in CTE. Further research is required to elucidate the mechanisms, and explore effectiveness and appropriate protocols of this novel stimulative factor in cartilage tissue engineering. PMID:27142133

  6. The linear hypothesis - an idea whose time has passed

    SciTech Connect

    Tschaeche, A.N.

    1995-12-31

    The linear no-threshold hypothesis is the basis for radiation protection standards in the United States. In the words of the National Council on Radiation Protection and Measurements (NCRP), the hypothesis is: {open_quotes}In the interest of estimating effects in humans conservatively, it is not unreasonable to follow the assumption of a linear relationship between dose and effect in the low dose regions for which direct observational data are not available.{close_quotes} The International Commission on Radiological Protection (ICRP) stated the hypothesis in a slightly different manner: {open_quotes}One such basic assumption ... is that ... there is ... a linear relationship without threshold between dose and the probability of an effect. The hypothesis was necessary 50 yr ago when it was first enunciated because the dose-effect curve for ionizing radiation for effects in humans was not known. The ICRP and NCRP needed a model to extrapolate high-dose effects to low-dose effects. So the linear no-threshold hypothesis was born. Certain details of the history of the development and use of the linear hypothesis are presented. In particular, use of the hypothesis by the U.S. regulatory agencies is examined. Over time, the sense of the hypothesis has been corrupted. The corruption of the hypothesis into the current paradigm of {open_quote}a little radiation, no matter how small, can and will harm you{close_quotes} is presented. The reasons the corruption occurred are proposed. The effects of the corruption are enumerated, specifically, the use of the corruption by the antinuclear forces in the United States and some of the huge costs to U.S. taxpayers due to the corruption. An alternative basis for radiation protection standards to assure public safety, based on the weight of scientific evidence on radiation health effects, is proposed.

  7. A physical-space approach for the probability hypothesis density and cardinalized probability hypothesis density filters

    NASA Astrophysics Data System (ADS)

    Erdinc, Ozgur; Willett, Peter; Bar-Shalom, Yaakov

    2006-05-01

    The probability hypothesis density (PHD) filter, an automatically track-managed multi-target tracker, is attracting increasing but cautious attention. Its derivation is elegant and mathematical, and thus of course many engineers fear it; perhaps that is currently limiting the number of researchers working on the subject. In this paper, we explore a physical-space approach - a bin model - which leads us to arrive the same filter equations as the PHD. Unlike the original derivation of the PHD filter, the concepts used are the familiar ones of conditional probability. The original PHD suffers from a "target-death" problem in which even a single missed detection can lead to the apparent disappearance of a target. To obviate this, PHD originator Mahler has recently developed a new "cardinalized" version of PHD (CPHD). We are able to extend our physical-space derivation to the CPHD case as well. We stress that the original derivations are mathematically correct, and need no embellishment from us; our contribution here is to offer an alternative derivation, one that we find appealing.

  8. Biostatistics Series Module 2: Overview of Hypothesis Testing.

    PubMed

    Hazra, Avijit; Gogtay, Nithya

    2016-01-01

    Hypothesis testing (or statistical inference) is one of the major applications of biostatistics. Much of medical research begins with a research question that can be framed as a hypothesis. Inferential statistics begins with a null hypothesis that reflects the conservative position of no change or no difference in comparison to baseline or between groups. Usually, the researcher has reason to believe that there is some effect or some difference which is the alternative hypothesis. The researcher therefore proceeds to study samples and measure outcomes in the hope of generating evidence strong enough for the statistician to be able to reject the null hypothesis. The concept of the P value is almost universally used in hypothesis testing. It denotes the probability of obtaining by chance a result at least as extreme as that observed, even when the null hypothesis is true and no real difference exists. Usually, if P is < 0.05 the null hypothesis is rejected and sample results are deemed statistically significant. With the increasing availability of computers and access to specialized statistical software, the drudgery involved in statistical calculations is now a thing of the past, once the learning curve of the software has been traversed. The life sciences researcher is therefore free to devote oneself to optimally designing the study, carefully selecting the hypothesis tests to be applied, and taking care in conducting the study well. Unfortunately, selecting the right test seems difficult initially. Thinking of the research hypothesis as addressing one of five generic research questions helps in selection of the right hypothesis test. In addition, it is important to be clear about the nature of the variables (e.g., numerical vs. categorical; parametric vs. nonparametric) and the number of groups or data sets being compared (e.g., two or more than two) at a time. The same research question may be explored by more than one type of hypothesis test. While this may be

  9. Vehicle Detection Based on Probability Hypothesis Density Filter

    PubMed Central

    Zhang, Feihu; Knoll, Alois

    2016-01-01

    In the past decade, the developments of vehicle detection have been significantly improved. By utilizing cameras, vehicles can be detected in the Regions of Interest (ROI) in complex environments. However, vision techniques often suffer from false positives and limited field of view. In this paper, a LiDAR based vehicle detection approach is proposed by using the Probability Hypothesis Density (PHD) filter. The proposed approach consists of two phases: the hypothesis generation phase to detect potential objects and the hypothesis verification phase to classify objects. The performance of the proposed approach is evaluated in complex scenarios, compared with the state-of-the-art. PMID:27070621

  10. Vehicle Detection Based on Probability Hypothesis Density Filter.

    PubMed

    Zhang, Feihu; Knoll, Alois

    2016-01-01

    In the past decade, the developments of vehicle detection have been significantly improved. By utilizing cameras, vehicles can be detected in the Regions of Interest (ROI) in complex environments. However, vision techniques often suffer from false positives and limited field of view. In this paper, a LiDAR based vehicle detection approach is proposed by using the Probability Hypothesis Density (PHD) filter. The proposed approach consists of two phases: the hypothesis generation phase to detect potential objects and the hypothesis verification phase to classify objects. The performance of the proposed approach is evaluated in complex scenarios, compared with the state-of-the-art. PMID:27070621

  11. Biostatistics Series Module 2: Overview of Hypothesis Testing

    PubMed Central

    Hazra, Avijit; Gogtay, Nithya

    2016-01-01

    Hypothesis testing (or statistical inference) is one of the major applications of biostatistics. Much of medical research begins with a research question that can be framed as a hypothesis. Inferential statistics begins with a null hypothesis that reflects the conservative position of no change or no difference in comparison to baseline or between groups. Usually, the researcher has reason to believe that there is some effect or some difference which is the alternative hypothesis. The researcher therefore proceeds to study samples and measure outcomes in the hope of generating evidence strong enough for the statistician to be able to reject the null hypothesis. The concept of the P value is almost universally used in hypothesis testing. It denotes the probability of obtaining by chance a result at least as extreme as that observed, even when the null hypothesis is true and no real difference exists. Usually, if P is < 0.05 the null hypothesis is rejected and sample results are deemed statistically significant. With the increasing availability of computers and access to specialized statistical software, the drudgery involved in statistical calculations is now a thing of the past, once the learning curve of the software has been traversed. The life sciences researcher is therefore free to devote oneself to optimally designing the study, carefully selecting the hypothesis tests to be applied, and taking care in conducting the study well. Unfortunately, selecting the right test seems difficult initially. Thinking of the research hypothesis as addressing one of five generic research questions helps in selection of the right hypothesis test. In addition, it is important to be clear about the nature of the variables (e.g., numerical vs. categorical; parametric vs. nonparametric) and the number of groups or data sets being compared (e.g., two or more than two) at a time. The same research question may be explored by more than one type of hypothesis test. While this may be

  12. Biostatistics Series Module 2: Overview of Hypothesis Testing.

    PubMed

    Hazra, Avijit; Gogtay, Nithya

    2016-01-01

    Hypothesis testing (or statistical inference) is one of the major applications of biostatistics. Much of medical research begins with a research question that can be framed as a hypothesis. Inferential statistics begins with a null hypothesis that reflects the conservative position of no change or no difference in comparison to baseline or between groups. Usually, the researcher has reason to believe that there is some effect or some difference which is the alternative hypothesis. The researcher therefore proceeds to study samples and measure outcomes in the hope of generating evidence strong enough for the statistician to be able to reject the null hypothesis. The concept of the P value is almost universally used in hypothesis testing. It denotes the probability of obtaining by chance a result at least as extreme as that observed, even when the null hypothesis is true and no real difference exists. Usually, if P is < 0.05 the null hypothesis is rejected and sample results are deemed statistically significant. With the increasing availability of computers and access to specialized statistical software, the drudgery involved in statistical calculations is now a thing of the past, once the learning curve of the software has been traversed. The life sciences researcher is therefore free to devote oneself to optimally designing the study, carefully selecting the hypothesis tests to be applied, and taking care in conducting the study well. Unfortunately, selecting the right test seems difficult initially. Thinking of the research hypothesis as addressing one of five generic research questions helps in selection of the right hypothesis test. In addition, it is important to be clear about the nature of the variables (e.g., numerical vs. categorical; parametric vs. nonparametric) and the number of groups or data sets being compared (e.g., two or more than two) at a time. The same research question may be explored by more than one type of hypothesis test. While this may be

  13. Investigating the environmental Kuznets curve hypothesis: the role of tourism and ecological footprint.

    PubMed

    Ozturk, Ilhan; Al-Mulali, Usama; Saboori, Behnaz

    2016-01-01

    The main objective of this study is to examine the environmental Kuznets curve (EKC) hypothesis by utilizing the ecological footprint as an environment indicator and GDP from tourism as the economic indicator. To achieve this goal, an environmental degradation model is established during the period of 1988-2008 for 144 countries. The results from the time series generalized method of moments (GMM) and the system panel GMM revealed that the number of countries that have a negative relationship between the ecological footprint and its determinants (GDP growth from tourism, energy consumption, trade openness, and urbanization) is more existent in the upper middle- and high-income countries. Moreover, the EKC hypothesis is more present in the upper middle- and high-income countries than the other income countries. From the outcome of this research, a number of policy recommendations were provided for the investigated countries. PMID:26408117

  14. Investigating the environmental Kuznets curve hypothesis: the role of tourism and ecological footprint.

    PubMed

    Ozturk, Ilhan; Al-Mulali, Usama; Saboori, Behnaz

    2016-01-01

    The main objective of this study is to examine the environmental Kuznets curve (EKC) hypothesis by utilizing the ecological footprint as an environment indicator and GDP from tourism as the economic indicator. To achieve this goal, an environmental degradation model is established during the period of 1988-2008 for 144 countries. The results from the time series generalized method of moments (GMM) and the system panel GMM revealed that the number of countries that have a negative relationship between the ecological footprint and its determinants (GDP growth from tourism, energy consumption, trade openness, and urbanization) is more existent in the upper middle- and high-income countries. Moreover, the EKC hypothesis is more present in the upper middle- and high-income countries than the other income countries. From the outcome of this research, a number of policy recommendations were provided for the investigated countries.

  15. Growth hormone and growth?

    PubMed

    Harvey, Steve

    2013-09-01

    Pituitary GH is obligatory for normal growth in mammals, but the importance of pituitary GH in avian growth is less certain. In birds, pituitary GH is biologically active and has growth promoting actions in the tibia-test bioassay. Its importance in normal growth is indicated by the growth suppression following the surgical removal of the pituitary gland or after the immunoneutralization of endogenous pituitary GH. The partial restoration of growth in some studies with GH-treated hypophysectomized birds also suggests GH dependency in avian growth, as does the dwarfism that occurs in some strains with GHR dysfunctions. Circulating GH concentrations are also correlated with body weight gain, being high in young, rapidly growing birds and low in slower growing older birds. Nevertheless, despite these observations, there is an extensive literature that concludes pituitary GH is not important in avian growth. This is based on numerous studies with hypophysectomized and intact birds that show only slight, transitory or absent growth responses to exogenous GH-treatment. Moreover, while circulating GH levels correlate with weight gain in young birds, this may merely reflect changes in the control of pituitary GH secretion during aging, as numerous studies involving experimental alterations in growth rate fail to show positive correlations between plasma GH concentrations and the alterations in growth rate. Furthermore, growth is known to occur in the absence of pituitary GH, as most embryonic development occurs prior to the ontogenetic appearance of pituitary somatotrophs and the appearance of GH in embryonic circulation. Early embryonic growth is also independent of the endocrine actions of pituitary GH, since removal of the presumptive pituitary gland does not impair early growth. Embryonic growth does, however, occur in the presence of extrapituitary GH, which is produced by most tissues and has autocrine or paracrine roles that locally promote growth and development

  16. Modelling the growth of feather crystals

    SciTech Connect

    Wood, H.J.; Hunt, J.D.; Evans, P.V.

    1997-02-01

    An existing numerical model of dendritic growth has been adapted to model the growth of twinned columnar dendrites (feather crystals) in a binary aluminium alloy, Examination of the effect of dendrite tip angle on growth has led to an hypothesis regarding the stability of a pointed tip morphology in these crystals.

  17. Alzheimer's disease: the amyloid hypothesis and the Inverse Warburg effect.

    PubMed

    Demetrius, Lloyd A; Magistretti, Pierre J; Pellerin, Luc

    2014-01-01

    Epidemiological and biochemical studies show that the sporadic forms of Alzheimer's disease (AD) are characterized by the following hallmarks: (a) An exponential increase with age; (b) Selective neuronal vulnerability; (c) Inverse cancer comorbidity. The present article appeals to these hallmarks to evaluate and contrast two competing models of AD: the amyloid hypothesis (a neuron-centric mechanism) and the Inverse Warburg hypothesis (a neuron-astrocytic mechanism). We show that these three hallmarks of AD conflict with the amyloid hypothesis, but are consistent with the Inverse Warburg hypothesis, a bioenergetic model which postulates that AD is the result of a cascade of three events-mitochondrial dysregulation, metabolic reprogramming (the Inverse Warburg effect), and natural selection. We also provide an explanation for the failures of the clinical trials based on amyloid immunization, and we propose a new class of therapeutic strategies consistent with the neuroenergetic selection model. PMID:25642192

  18. Alzheimer's disease: the amyloid hypothesis and the Inverse Warburg effect

    PubMed Central

    Demetrius, Lloyd A.; Magistretti, Pierre J.; Pellerin, Luc

    2014-01-01

    Epidemiological and biochemical studies show that the sporadic forms of Alzheimer's disease (AD) are characterized by the following hallmarks: (a) An exponential increase with age; (b) Selective neuronal vulnerability; (c) Inverse cancer comorbidity. The present article appeals to these hallmarks to evaluate and contrast two competing models of AD: the amyloid hypothesis (a neuron-centric mechanism) and the Inverse Warburg hypothesis (a neuron-astrocytic mechanism). We show that these three hallmarks of AD conflict with the amyloid hypothesis, but are consistent with the Inverse Warburg hypothesis, a bioenergetic model which postulates that AD is the result of a cascade of three events—mitochondrial dysregulation, metabolic reprogramming (the Inverse Warburg effect), and natural selection. We also provide an explanation for the failures of the clinical trials based on amyloid immunization, and we propose a new class of therapeutic strategies consistent with the neuroenergetic selection model. PMID:25642192

  19. Hypothesis Testing Using the Films of the Three Stooges

    ERIC Educational Resources Information Center

    Gardner, Robert; Davidson, Robert

    2010-01-01

    The use of The Three Stooges' films as a source of data in an introductory statistics class is described. The Stooges' films are separated into three populations. Using these populations, students may conduct hypothesis tests with data they collect.

  20. Autism: demise of the innate social orienting hypothesis.

    PubMed

    Johnson, Mark H

    2014-01-01

    Some have suggested that autism may be caused by poor orienting to social stimuli in early infancy, compounded by the resulting failures to learn from, and about, other humans. Recent results contradict this hypothesis, suggesting a need to rethink.

  1. Null but not void: considerations for hypothesis testing.

    PubMed

    Shaw, Pamela A; Proschan, Michael A

    2013-01-30

    Standard statistical theory teaches us that once the null and alternative hypotheses have been defined for a parameter, the choice of the statistical test is clear. Standard theory does not teach us how to choose the null or alternative hypothesis appropriate to the scientific question of interest. Neither does it tell us that in some cases, depending on which alternatives are realistic, we may want to define our null hypothesis differently. Problems in statistical practice are frequently not as pristinely summarized as the classic theory in our textbooks. In this article, we present examples in statistical hypothesis testing in which seemingly simple choices are in fact rich with nuance that, when given full consideration, make the choice of the right hypothesis test much less straightforward. Published 2012. This article is a US Government work and is in the public domain in the USA. PMID:22807023

  2. Using the Gaia Hypothesis to Synthesize an Introductory Biology Course.

    ERIC Educational Resources Information Center

    Baker, Gail A.

    1993-01-01

    The Gaia Hypothesis emphasizes the interactions and feedback mechanisms between the living and nonliving process that take place on Earth. Employing this concept in instruction can emphasize the interdisciplinary nature of science and give a planetary perspective of biology. (PR)

  3. The Hygiene Hypothesis and Its Inconvenient Truths about Helminth Infections.

    PubMed

    Briggs, Neima; Weatherhead, Jill; Sastry, K Jagannadha; Hotez, Peter J

    2016-09-01

    Current iterations of the hygiene hypothesis suggest an adaptive role for helminth parasites in shaping the proper maturation of the immune system. However, aspects of this hypothesis are based on assumptions that may not fully account for realities about human helminth infections. Such realities include evidence of causal associations between helminth infections and asthma or inflammatory bowel disease as well as the fact that helminth infections remain widespread in the United States, especially among populations at greatest risk for inflammatory and autoimmune diseases.

  4. On the 'fast electron hypothesis' for stellar flares

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1990-01-01

    It is pointed out that Gurzadyan's (1988) fast-electron hypothesis for stellar flares encounters certain difficulties. The origin of the fast electrons is obscure. Negative flares and predicted ratios of X-ray to optical fluxes are not necessarily a proof of the fast-electron hypothesis. When the electrons thermalize, they will yield X-ray fluxes which are orders of magnitude too large to be consistent with observations.

  5. Testing the null hypothesis: the forgotten legacy of Karl Popper?

    PubMed

    Wilkinson, Mick

    2013-01-01

    Testing of the null hypothesis is a fundamental aspect of the scientific method and has its basis in the falsification theory of Karl Popper. Null hypothesis testing makes use of deductive reasoning to ensure that the truth of conclusions is irrefutable. In contrast, attempting to demonstrate the new facts on the basis of testing the experimental or research hypothesis makes use of inductive reasoning and is prone to the problem of the Uniformity of Nature assumption described by David Hume in the eighteenth century. Despite this issue and the well documented solution provided by Popper's falsification theory, the majority of publications are still written such that they suggest the research hypothesis is being tested. This is contrary to accepted scientific convention and possibly highlights a poor understanding of the application of conventional significance-based data analysis approaches. Our work should remain driven by conjecture and attempted falsification such that it is always the null hypothesis that is tested. The write up of our studies should make it clear that we are indeed testing the null hypothesis and conforming to the established and accepted philosophical conventions of the scientific method.

  6. The progene hypothesis: the nucleoprotein world and how life began.

    PubMed

    Altstein, Anatoly D

    2015-01-01

    In this article, I review the results of studies on the origin of life distinct from the popular RNA world hypothesis. The alternate scenario postulates the origin of the first bimolecular genetic system (a polynucleotide gene and a polypeptide processive polymerase) with simultaneous replication and translation and includes the following key features: 1. The bimolecular genetic system emerges not from mononucleotides and monoamino acids, but from progenes, namely, trinucleotides aminoacylated on 3'-end by a non-random amino acid (NpNpNp ~ pX ~ Aa, where N--deoxyribo- or ribonucleoside, p--phosphate, X--a bifunctional agent, for example ribose, Aa--amino acid, ~ macroerge bond). Progenes are used as substrates for simultaneous synthesis of a polynucleotide and a polypeptide. Growth of the system is controlled by the growing polypeptide, and the bimolecular genetic system emerges as an extremely rare event. The first living being (virus-like organism protoviroid, Protoviroidum primum) arises and reproduces in prebiotic liposome-like structures using progenes. A population of protoviroids possessing the genetic system evolves in accordance with the Darwinian principle. Early evolution from protoviroid world to protocell world is shortly described. 2. The progene forming mechanism (NpNp + Np ~ pX ~ Aa) makes it possible to explain the emergence of the prebiotic physicochemical group genetic code, as well as the selection of organic compounds for the future genetic system from the racemic environment. 3. The protoviroid is reproduced on a progene basis via replicative transcription-translation (RTT, the first molecular genetic process) that is similar to its modern counterparts. Nothing is required for the emergence and reproduction of the protoviroid except for progenes and conditions for their formation. 4. The general scheme of early evolution is as follows: prebiotic world → protoviroid (nucleoprotein) world → protocell (DNA-RNA-protein) world → LUCA

  7. Applying the light: nutrient hypothesis to stream periphyton

    SciTech Connect

    Fanta, S.E.; Hill, Walter; Smith, Timothy B.; Roberts, Brian J

    2010-01-01

    The light:nutrient hypothesis (LNH) states that algal nutrient content is determined by the balance of light and dissolved nutrients available to algae during growth. Light and phosphorus gradients in both laboratory and natural streams were used to examine the relevance of the LNH to stream periphyton. Controlled gradients of light (12-426 mol photons m{sup -2} s{sup -1}) and dissolved reactive phosphorus (DRP, 3-344 {mu}g L{sup -1}) were applied experimentally to large flow-through laboratory streams, and natural variability in canopy cover and discharge from a wastewater treatment facility created gradients of light (0.4-35 mol photons m{sup -2} day{sup -1}) and DRP (10-1766 {mu}g L{sup -1}) in a natural stream. Periphyton phosphorus content was strongly influenced by the light and DRP gradients, ranging from 1.8 to 10.7 {mu}g mg AFDM{sup -1} in the laboratory streams and from 2.3 to 36.9 {mu}g mg AFDM{sup -1} in the natural stream. Phosphorus content decreased with increasing light and increased with increasing water column phosphorus. The simultaneous effects of light and phosphorus were consistent with the LNH that the balance between light and nutrients determines algal nutrient content. In experiments in the laboratory streams, periphyton phosphorus increased hyperbolically with increasing DRP. Uptake then began leveling off around 50 {mu}g L{sup -1}. The relationship between periphyton phosphorus and the light: phosphorus ratio was highly nonlinear in both the laboratory and natural streams, with phosphorus content declining sharply with initial increases in the light: phosphorus ratio, then leveling off at higher values of the ratio. Although light and DRP both affected periphyton phosphorus content, the effects of DRP were much stronger than those of light in both the laboratory and natural streams. DRP explained substantially more of the overall variability in periphyton phosphorus than did light, and light effects were evident only at lower phosphorus

  8. The progene hypothesis: the nucleoprotein world and how life began.

    PubMed

    Altstein, Anatoly D

    2015-11-26

    In this article, I review the results of studies on the origin of life distinct from the popular RNA world hypothesis. The alternate scenario postulates the origin of the first bimolecular genetic system (a polynucleotide gene and a polypeptide processive polymerase) with simultaneous replication and translation and includes the following key features: 1. The bimolecular genetic system emerges not from mononucleotides and monoamino acids, but from progenes, namely, trinucleotides aminoacylated on 3'-end by a non-random amino acid (NpNpNp ~ pX ~ Aa, where N--deoxyribo- or ribonucleoside, p--phosphate, X--a bifunctional agent, for example ribose, Aa--amino acid, ~ macroerge bond). Progenes are used as substrates for simultaneous synthesis of a polynucleotide and a polypeptide. Growth of the system is controlled by the growing polypeptide, and the bimolecular genetic system emerges as an extremely rare event. The first living being (virus-like organism protoviroid, Protoviroidum primum) arises and reproduces in prebiotic liposome-like structures using progenes. A population of protoviroids possessing the genetic system evolves in accordance with the Darwinian principle. Early evolution from protoviroid world to protocell world is shortly described. 2. The progene forming mechanism (NpNp + Np ~ pX ~ Aa) makes it possible to explain the emergence of the prebiotic physicochemical group genetic code, as well as the selection of organic compounds for the future genetic system from the racemic environment. 3. The protoviroid is reproduced on a progene basis via replicative transcription-translation (RTT, the first molecular genetic process) that is similar to its modern counterparts. Nothing is required for the emergence and reproduction of the protoviroid except for progenes and conditions for their formation. 4. The general scheme of early evolution is as follows: prebiotic world → protoviroid (nucleoprotein) world → protocell (DNA-RNA-protein) world → LUCA

  9. General hypothesis and shell model for the synthesis of semiconductor nanotubes, including carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2010-09-01

    Semiconductor nanotubes, including carbon nanotubes, have vast potential for new technology development. The fundamental physics and growth kinetics of these nanotubes are still obscured. Various models developed to elucidate the growth suffer from limited applicability. An in-depth investigation of the fundamentals of nanotube growth has, therefore, been carried out. For this investigation, various features of nanotube growth, and the role of the foreign element catalytic agent (FECA) in this growth, have been considered. Observed growth anomalies have been analyzed. Based on this analysis, a new shell model and a general hypothesis have been proposed for the growth. The essential element of the shell model is the seed generated from segregation during growth. The seed structure has been defined, and the formation of droplet from this seed has been described. A modified definition of the droplet exhibiting adhesive properties has also been presented. Various characteristics of the droplet, required for alignment and organization of atoms into tubular forms, have been discussed. Employing the shell model, plausible scenarios for the formation of carbon nanotubes, and the variation in the characteristics of these carbon nanotubes have been articulated. The experimental evidences, for example, for the formation of shell around a core, dipole characteristics of the seed, and the existence of nanopores in the seed, have been presented. They appear to justify the validity of the proposed model. The diversities of nanotube characteristics, fundamentals underlying the creation of bamboo-shaped carbon nanotubes, and the impurity generation on the surface of carbon nanotubes have been elucidated. The catalytic action of FECA on growth has been quantified. The applicability of the proposed model to the nanotube growth by a variety of mechanisms has been elaborated. These mechanisms include the vapor-liquid-solid mechanism, the oxide-assisted growth mechanism, the self

  10. Dopamine and reward: the anhedonia hypothesis 30 years on.

    PubMed

    Wise, Roy A

    2008-10-01

    The anhedonia hypothesis--that brain dopamine plays a critical role in the subjective pleasure associated with positive rewards--was intended to draw the attention of psychiatrists to the growing evidence that dopamine plays a critical role in the objective reinforcement and incentive motivation associated with food and water, brain stimulation reward, and psychomotor stimulant and opiate reward. The hypothesis called to attention the apparent paradox that neuroleptics, drugs used to treat a condition involving anhedonia (schizophrenia), attenuated in laboratory animals the positive reinforcement that we normally associate with pleasure. The hypothesis held only brief interest for psychiatrists, who pointed out that the animal studies reflected acute actions of neuroleptics whereas the treatment of schizophrenia appears to result from neuroadaptations to chronic neuroleptic administration, and that it is the positive symptoms of schizophrenia that neuroleptics alleviate, rather than the negative symptoms that include anhedonia. Perhaps for these reasons, the hypothesis has had minimal impact in the psychiatric literature. Despite its limited heuristic value for the understanding of schizophrenia, however, the anhedonia hypothesis has had major impact on biological theories of reinforcement, motivation, and addiction. Brain dopamine plays a very important role in reinforcement of response habits, conditioned preferences, and synaptic plasticity in cellular models of learning and memory. The notion that dopamine plays a dominant role in reinforcement is fundamental to the psychomotor stimulant theory of addiction, to most neuroadaptation theories of addiction, and to current theories of conditioned reinforcement and reward prediction. Properly understood, it is also fundamental to recent theories of incentive motivation.

  11. Reassessing the Amyloid Cascade Hypothesis of Alzheimer’s Disease

    PubMed Central

    Pimplikar, Sanjay W.

    2009-01-01

    Since its inception, the amyloid cascade hypothesis has dominated the field of Alzheimer’s disease (AD) research and has provided the intellectual framework for therapeutic intervention. Although the details of the hypothesis continue to evolve, its core principle has remained essentially unaltered. It posits that the amyloid-β peptides, derived from amyloid precursor protein (APP), are the root cause of AD. Substantial genetic and biochemical data support this view, and yet a number of findings also run contrary to its tenets. The presence of familial AD mutations in APP and presenilins, demonstration of Aβ toxicity, and studies in mouse models of AD all support the hypothesis, whereas the presence of Aβ plaques in normal individuals, the uncertain nature of the pathogenic Aβ species, and repeated disappointments with Aβ-centered therapeutic trials are inconsistent with the hypothesis. The current state of knowledge does not prove nor disprove the amyloid hypothesis, but rather points to the need for its reassessment. A view that Aβ is one of the factors, as opposed to the factor, that causes AD is more consistent with the present knowledge, and is more likely to promote comprehensive and effective therapeutic strategies. PMID:19124085

  12. An experimental test of the transmission-virulence trade-off hypothesis in a plant virus.

    PubMed

    Doumayrou, Juliette; Avellan, Astrid; Froissart, Rémy; Michalakis, Yannis

    2013-02-01

    The transmission-virulence trade-off hypothesis is one of the few adaptive explanations of virulence evolution, and assumes that there is an overall positive correlation between parasite transmission and virulence. The shape of the transmission-virulence relationship predicts whether virulence should evolve toward either a maximum or to an intermediate optimum. A positive correlation between each of these traits and within-host growth is often suggested to underlie the relationship between virulence and transmission. There are few experimental tests of this hypothesis; this study reports on the first empirical test on a plant pathogen. We infected Brassica rapa plants with nine natural isolates of Cauliflower mosaic virus and then estimated three traits: transmission, virulence, and within-host viral accumulation. As predicted by the trade-off hypothesis, we observed a positive correlation between transmission and virulence, suggestive of the existence of an intermediate optimum. We discovered the unexpected existence of two groups of within-host accumulation, differing by at least an order of magnitude. When accumulation groups were not accounted for, within-host accumulation was correlated neither to virulence nor transmission, although our results suggest that within each group these correlations exist.

  13. Stress relief may promote the evolution of greater phenotypic plasticity in exotic invasive species: a hypothesis

    PubMed Central

    Huang, Qiao Q; Pan, Xiao Y; Fan, Zhi W; Peng, Shao L

    2015-01-01

    Invasion ecologists have often found that exotic invaders evolve to be more plastic than conspecific populations from their native range. However, an open question is why some exotic invaders can even evolve to be more plastic given that there may be costs to being plastic. Investigation into the benefits and costs of plasticity suggests that stress may constrain the expression of plasticity (thereby reducing the benefits of plasticity) and exacerbate the costs of plasticity (although this possibility might not be generally applicable). Therefore, evolution of adaptive plasticity is more likely to be constrained in stressful environments. Upon introduction to a new range, exotic species may experience more favorable growth conditions (e.g., because of release from natural enemies). Therefore, we hypothesize that any factors mitigating stress in the introduced range may promote exotic invaders to evolve increased adaptive plasticity by reducing the costs and increasing the benefits of plasticity. Empirical evidence is largely consistent with this hypothesis. This hypothesis contributes to our understanding of why invasive species are often found to be more competitive in a subset of environments. Tests of this hypothesis may not only help us understand what caused increased plasticity in some exotic invaders, but could also tell us if costs (unless very small) are more likely to inhibit the evolution of adaptive plasticity in stressful environments in general. PMID:25859323

  14. Celtic Sea linear sediment ridges: a basis for testing the tidal hypothesis

    NASA Astrophysics Data System (ADS)

    Scourse, James; Ward, Sophie

    2015-04-01

    The linear sediment ridges (LSR) of the Celtic Sea constitute the largest examples of their bedform type on Earth. Published sedimentological and seismic stratigraphic interpretation, supported by simulated bed stress vectors derived from numerical palaeotidal models suggests, that the LSR are moribund tidally remobilised sediments representing the transgressive systems tract. Recently this interpretation has been challenged by the hypothesis that these ridges may be subglacial bedforms linked to extension of the Last Glacial Maximum Irish Sea Ice Stream to the shelf break. We address the tidal hypothesis using data from a new palaeotidal simulation of the Celtic shelf to test predictions of ridge axis orientations deriving from dynamical theory. Theoretically ridge axes should evolve at a set offset to the tidal ellipse rotation. As the palaeotidal simulations generate tidal ellipses for each timestep, the ridge axis orientations and their evolution through time can be therefore be predicted. These predictions provide a basis for comparison with observations of ridge orientations from multi-beam swath bathymetry. If consistent with the observed axes of ridge growth and degradation this will provide support for the tidal hypothesis.

  15. An experimental test of the transmission-virulence trade-off hypothesis in a plant virus.

    PubMed

    Doumayrou, Juliette; Avellan, Astrid; Froissart, Rémy; Michalakis, Yannis

    2013-02-01

    The transmission-virulence trade-off hypothesis is one of the few adaptive explanations of virulence evolution, and assumes that there is an overall positive correlation between parasite transmission and virulence. The shape of the transmission-virulence relationship predicts whether virulence should evolve toward either a maximum or to an intermediate optimum. A positive correlation between each of these traits and within-host growth is often suggested to underlie the relationship between virulence and transmission. There are few experimental tests of this hypothesis; this study reports on the first empirical test on a plant pathogen. We infected Brassica rapa plants with nine natural isolates of Cauliflower mosaic virus and then estimated three traits: transmission, virulence, and within-host viral accumulation. As predicted by the trade-off hypothesis, we observed a positive correlation between transmission and virulence, suggestive of the existence of an intermediate optimum. We discovered the unexpected existence of two groups of within-host accumulation, differing by at least an order of magnitude. When accumulation groups were not accounted for, within-host accumulation was correlated neither to virulence nor transmission, although our results suggest that within each group these correlations exist. PMID:23356619

  16. Evaluation of Darwin's fecundity advantage hypothesis in Parthenium beetle, Zygogramma bicolorata.

    PubMed

    Omkar; Afaq, Uzma

    2013-08-01

    In the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), variation in body size exists between and within the sexes. The females are larger than the males. Darwin (1874) proposed the fecundity advantage hypothesis, i.e. large sized female produce more progeny, with subsequent studies supporting as well as refuting the hypothesis. Thus, in order to evaluate whether this hypothesis stands in Z. bicolorata we performed experiments to investigate the role of body size in influencing: (i) assortative mating, (ii) reproductive attributes, and (iii) growth, development and survival of offspring. It is the first attempt in this beetle. We found that size influenced assortative mating, reproductive output and offspring fitness. Larger males and females were preferred as mates over smaller ones. The pairs having larger adults as mates had higher fecundity while the egg viability was influenced by the male size only. The offspring of larger parents had fast development and higher survival indicating thereby possible better nutrient allotment by the female and supply of accessory gland proteins by the male in addition to better quality of genes. PMID:24006336

  17. Evaluation of Darwin's fecundity advantage hypothesis in Parthenium beetle, Zygogramma bicolorata.

    PubMed

    Omkar; Afaq, Uzma

    2013-08-01

    In the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), variation in body size exists between and within the sexes. The females are larger than the males. Darwin (1874) proposed the fecundity advantage hypothesis, i.e. large sized female produce more progeny, with subsequent studies supporting as well as refuting the hypothesis. Thus, in order to evaluate whether this hypothesis stands in Z. bicolorata we performed experiments to investigate the role of body size in influencing: (i) assortative mating, (ii) reproductive attributes, and (iii) growth, development and survival of offspring. It is the first attempt in this beetle. We found that size influenced assortative mating, reproductive output and offspring fitness. Larger males and females were preferred as mates over smaller ones. The pairs having larger adults as mates had higher fecundity while the egg viability was influenced by the male size only. The offspring of larger parents had fast development and higher survival indicating thereby possible better nutrient allotment by the female and supply of accessory gland proteins by the male in addition to better quality of genes.

  18. Multiple fault condition recognition of gearbox with sequential hypothesis test

    NASA Astrophysics Data System (ADS)

    Chen, Hanxin; Shang, Yunfei; Sun, Kui

    2013-11-01

    A novel method for the fault condition recognition in which the recognition system interrogates a propagation channel adaptively and intelligently by using the available data is proposed based on sequential hypothesis testing. The waveform of the data in the propagation channel for the fault condition recognition is designed with the kurtosis of the measured data in time domain. The sequential hypothesis testing framework is proposed when hard decisions are made with adequate confidence. The distinguished characteristic of the channel recognition is that it operates in a closed loop and makes constant optimization in response to its changing understanding of the channel. The fault condition recognition of the gearbox is to update the multiple target hypothesis/class based on the measured data, customize waveform as the class probabilities changes, and make conclusion when the sufficient understanding of the propagation channel is achieved.

  19. The concept possession hypothesis of self-consciousness.

    PubMed

    Savanah, Stephane

    2012-06-01

    This paper presents the hypothesis that concept possession is sufficient and necessary for self-consciousness. If this is true it provides a yardstick for gauging the validity of different research paradigms in which claims for self-consciousness in animals or human infants are made: a convincing demonstration of concept possession in a research subject, such as a display of inferential reasoning, may be taken as conclusive evidence of self-consciousness. Intuitively, there appears to be a correlation between intelligence in animals (which presupposes concept possession) and the existence of self-consciousness. I present three discussions to support the hypothesis: an analogy between perception and conception, where both are self-specifying; an argument that any web of concepts will always include the self-concept; and a fresh interpretation of Bermũdez (1998) showing how his theory of non-conceptual content provides strong support for the concept possession hypothesis.

  20. On Using Taylor's Hypothesis for Three-Dimensional Mixing Layers

    NASA Technical Reports Server (NTRS)

    LeBoeuf, Richard L.; Mehta, Rabindra D.

    1995-01-01

    In the present study, errors in using Taylor's hypothesis to transform measurements obtained in a temporal (or phase) frame onto a spatial one were evaluated. For the first time, phase-averaged ('real') spanwise and streamwise vorticity data measured on a three-dimensional grid were compared directly to those obtained using Taylor's hypothesis. The results show that even the qualitative features of the spanwise and streamwise vorticity distributions given by the two techniques can be very different. This is particularly true in the region of the spanwise roller pairing. The phase-averaged spanwise and streamwise peak vorticity levels given by Taylor's hypothesis are typically lower (by up to 40%) compared to the real measurements.

  1. Local equilibrium hypothesis and Taylor’s dissipation law

    NASA Astrophysics Data System (ADS)

    Goto, Susumu; Vassilicos, J. C.

    2016-04-01

    To qualitatively investigate the validity of Kolmogorov local equilibrium hypothesis and the Taylor dissipation law, we conduct direct numerical simulations of the three-dimensional turbulent Kolmogorov flow. Since strong scale-by-scale (i.e. Richardson-type) energy cascade events occur quasi-periodically, the kinetic energy of the turbulence and its dissipation rate evolve quasi-periodically too. In this unsteady turbulence driven by a steady force, instantaneous values of the dissipation rate obey the scaling recently discovered in wind tunnel experiments (Vassilicos 2015 Ann. Rev. Fluid Mech. 47 95-114) instead of the Taylor dissipation law. The Taylor dissipation law does not hold because the local equilibrium hypothesis does not hold in a relatively low wave-number range. The breakdown of this hypothesis is caused by the finite time needed for the energy at such large scales to reach the dissipative scale by the scale-by-scale energy cascade.

  2. Deep and beautiful. The reward prediction error hypothesis of dopamine.

    PubMed

    Colombo, Matteo

    2014-03-01

    According to the reward-prediction error hypothesis (RPEH) of dopamine, the phasic activity of dopaminergic neurons in the midbrain signals a discrepancy between the predicted and currently experienced reward of a particular event. It can be claimed that this hypothesis is deep, elegant and beautiful, representing one of the largest successes of computational neuroscience. This paper examines this claim, making two contributions to existing literature. First, it draws a comprehensive historical account of the main steps that led to the formulation and subsequent success of the RPEH. Second, in light of this historical account, it explains in which sense the RPEH is explanatory and under which conditions it can be justifiably deemed deeper than the incentive salience hypothesis of dopamine, which is arguably the most prominent contemporary alternative to the RPEH. PMID:24252364

  3. Extraversion and the EEG: II. A test of Gale's hypothesis.

    PubMed

    O'Gorman, J G; Mallise, L R

    1984-09-01

    The study sought to test A. Gale's hypothesis that only under moderately arousing conditions will introverts be shown to differ from extraverts in EEG defined arousal. Alpha activity was recorded for 45 subjects under each of six conditions, and extravert and introvert groups formed on the basis of subject's score on the E scale of the Eysenck Personality Questionnaire (EPQ). Contrary to the hypothesis, extraverts showed more prestimulus alpha activity than introverts under all conditions except opening and closing eyes on instruction where the reverse was the case. It is argued that the failure to confirm the hypothesis is not due to faults in design or execution of the study, and that future research may profit more from ignoring interactions of the sort demonstrated. PMID:6518221

  4. Alzheimer's Disease and the Amyloid Cascade Hypothesis: A Critical Review

    PubMed Central

    Reitz, Christiane

    2012-01-01

    Since 1992, the amyloid cascade hypothesis has played the prominent role in explaining the etiology and pathogenesis of Alzheimer's disease (AD). It proposes that the deposition of β-amyloid (Aβ) is the initial pathological event in AD leading to the formation of senile plaques (SPs) and then to neurofibrillary tangles (NFTs), neuronal cell death, and ultimately dementia. While there is substantial evidence supporting the hypothesis, there are also limitations: (1) SP and NFT may develop independently, and (2) SPs and NFTs may be the products rather than the causes of neurodegeneration in AD. In addition, randomized clinical trials that tested drugs or antibodies targeting components of the amyloid pathway have been inconclusive. This paper provides a critical overview of the evidence for and against the amyloid cascade hypothesis in AD and provides suggestions for future directions. PMID:22506132

  5. Deep and beautiful. The reward prediction error hypothesis of dopamine.

    PubMed

    Colombo, Matteo

    2014-03-01

    According to the reward-prediction error hypothesis (RPEH) of dopamine, the phasic activity of dopaminergic neurons in the midbrain signals a discrepancy between the predicted and currently experienced reward of a particular event. It can be claimed that this hypothesis is deep, elegant and beautiful, representing one of the largest successes of computational neuroscience. This paper examines this claim, making two contributions to existing literature. First, it draws a comprehensive historical account of the main steps that led to the formulation and subsequent success of the RPEH. Second, in light of this historical account, it explains in which sense the RPEH is explanatory and under which conditions it can be justifiably deemed deeper than the incentive salience hypothesis of dopamine, which is arguably the most prominent contemporary alternative to the RPEH.

  6. RPD-based Hypothesis Reasoning for Cyber Situation Awareness

    NASA Astrophysics Data System (ADS)

    Yen, John; McNeese, Michael; Mullen, Tracy; Hall, David; Fan, Xiaocong; Liu, Peng

    Intelligence workers such as analysts, commanders, and soldiers often need a hypothesis reasoning framework to gain improved situation awareness of the highly dynamic cyber space. The development of such a framework requires the integration of interdisciplinary techniques, including supports for distributed cognition (human-in-the-loop hypothesis generation), supports for team collaboration (identification of information for hypothesis evaluation), and supports for resource-constrained information collection (hypotheses competing for information collection resources). We here describe a cognitively-inspired framework that is built upon Klein’s recognition-primed decision model and integrates the three components of Endsley’s situation awareness model. The framework naturally connects the logic world of tools for cyber situation awareness with the mental world of human analysts, enabling the perception, comprehension, and prediction of cyber situations for better prevention, survival, and response to cyber attacks by adapting missions at the operational, tactical, and strategic levels.

  7. Unicorns do exist: a tutorial on "proving" the null hypothesis.

    PubMed

    Streiner, David L

    2003-12-01

    Introductory statistics classes teach us that we can never prove the null hypothesis; all we can do is reject or fail to reject it. However, there are times when it is necessary to try to prove the nonexistence of a difference between groups. This most often happens within the context of comparing a new treatment against an established one and showing that the new intervention is not inferior to the standard. This article first outlines the logic of "noninferiority" testing by differentiating between the null hypothesis (that which we are trying to nullify) and the "nill" hypothesis (there is no difference), reversing the role of the null and alternate hypotheses, and defining an interval within which groups are said to be equivalent. We then work through an example and show how to calculate sample sizes for noninferiority studies. PMID:14733457

  8. Lay understanding of genetics: a test of a hypothesis.

    PubMed Central

    Richards, M; Ponder, M

    1996-01-01

    There have been growing calls for more education in genetics for the public and in schools. However, studies of the public, school children, and those who have received genetic counselling show that understanding of scientific genetics is very limited. A hypothesis to explain this limited understanding is proposed and tested. It is argued that there is a widespread lay knowledge of inheritance which conflicts in a number of aspects with scientific explanations and which impedes the assimilation of the latter. It is suggested that this lay knowledge is derived from concepts of the social relationships of kinship. Concepts of kinship ties are sustained by everyday social activities and relationships which may make them resistant to change. A prediction which follows from the hypothesis that the lay understanding of genetics is derived from concepts of family and kinship relationships is that closeness in genetic terms will be determined by the closeness of the family ties of social relationship and social obligation. While the proportion of genes shared with parents, children, and sibs is, on average, the same, kin relationships and obligations are much stronger between parents and children than between sibs. The hypothesis was tested in a questionnaire study of two samples of adult women (n = 64 and n = 113) and one of social science students (n = 73). In all three groups a higher proportion of subjects gave the correct response for the proportion of shared genes with a father and child than with a sister, uncle, or grandmother. In the cases of sisters and uncle (and grandmother), there was a consistent tendency to underestimate the degree of genetic connection as predicted by the hypothesis. Answers to other questions are consistent with the hypothesis. The fundamental implications of the hypothesis for genetic education in the clinic and classroom are outlined. PMID:9004138

  9. Recent sediment studies refute Glen Canyon Dam hypothesis

    USGS Publications Warehouse

    Rubin, David M.; Topping, David J.; Schmidt, John C.; Hazel, Joe; Kaplinski, Matt; Melis, Theodore S.

    2002-01-01

    Recent studies of sedimentology hydrology, and geomorphology indicate that releases from Glen Canyon Dam are continuing to erode sandbars and beaches in the Colorado River in Grand Canyon National Park, despite attempts to restore these resources. The current strategy for dam operations is based on the hypothesis that sand supplied by tributaries of the Colorado River downstream from the dam will accumulate in the channel during normal dam operations and remain available for restoration floods. Recent work has shown that this hypothesis is false, and that tributary sand inputs are exported downstream rapidly typically within weeks or months under the current flow regime.

  10. The Hygiene Hypothesis and Its Inconvenient Truths about Helminth Infections.

    PubMed

    Briggs, Neima; Weatherhead, Jill; Sastry, K Jagannadha; Hotez, Peter J

    2016-09-01

    Current iterations of the hygiene hypothesis suggest an adaptive role for helminth parasites in shaping the proper maturation of the immune system. However, aspects of this hypothesis are based on assumptions that may not fully account for realities about human helminth infections. Such realities include evidence of causal associations between helminth infections and asthma or inflammatory bowel disease as well as the fact that helminth infections remain widespread in the United States, especially among populations at greatest risk for inflammatory and autoimmune diseases. PMID:27632204

  11. Paleomagnetic test of the Emperor fracture zone hypothesis

    SciTech Connect

    Gordon, R.G.

    1982-11-01

    Late Cretaceous paleomagnetic data from the Pacific plate were used to test Farrar and Dixon's (1981) hypothesis that approx.1700 km of strike-slip accumulated during the early Tertiary along the Emperor fracture zone system, and 8000 km long NW-SE trending features, which consists mainly of the Emperor trough, the Gardner seamounts, and the Line Islands. The data strongly disagree with this hypothesis; instead the data are consistent with no motion having occurred between seafloor east of the Emperor fracture zone and seafloor west of the Emperor fracture zone.

  12. The Savant Hypothesis: is autism a signal-processing problem?

    PubMed

    Fabricius, Thomas

    2010-08-01

    Autism is being investigated through many different approaches. This paper suggests the genetic, perceptual, cognitive, and histological findings ultimately manifest themselves as variations of the same signal-processing problem of defective compression. The Savant Hypothesis is formulated from first principles of both mathematical signal-processing and primary neuroscience to reflect the failure of compression. The Savant Hypothesis is applied to the problem of autism in a surprisingly straightforward application. The enigma of the autistic savant becomes intuitive when observed from this approach.

  13. The equilibrium-point hypothesis--past, present and future.

    PubMed

    Feldman, Anatol G; Levin, Mindy F

    2009-01-01

    This chapter is a brief account of fundamentals of the equilibrium-point hypothesis or more adequately called the threshold control theory (TCT). It also compares the TCT with other approaches to motor control. The basic notions of the TCT are reviewed with a major focus on solutions to the problems of multi-muscle and multi-degrees of freedom redundancy. The TCT incorporates cognitive aspects by explaining how neurons recognize that internal (neural) and external (environmental) events match each other. These aspects as well as how motor learning occurs are subjects of further development of the TCT hypothesis. PMID:19227529

  14. Tunguska, 1908: the gas pouch and soil fluidization hypothesis

    NASA Astrophysics Data System (ADS)

    Nistor, I.

    2012-01-01

    The Siberian taiga explosion of 30 June 1908 remains one of the great mysteries of the 20th century: millions of trees put down over an area of 2200 km2 without trace of a crater or meteorite fragments. Hundred years of failed searches have followed, resulting in as many flawed hypothesis which could not offer satisfactory explanations: meteorite, comet, UFO, etc. In the author's opinion, the cause is that the energy the explorers looked for was simply not there! The author's hypothesis is that a meteoroid encountered a gas pouch in the atmosphere, producing a devastating explosion, its effects being amplified by soil fluidization.

  15. The Effectiveness of the Comprehension Hypothesis: A Review on the Current Research on Incidental Vocabulary Acquisition

    ERIC Educational Resources Information Center

    Ponniah, Joseph

    2011-01-01

    The Comprehension Hypothesis (CH) is the most powerful hypothesis in the field of Second Language Acquisition despite the presence of the rivals the skill-building hypothesis, the output hypothesis, and the interaction hypothesis. The competing hypotheses state that consciously learned linguistic knowledge is a necessary step for the development…

  16. Toxic Alexandrium blooms in the western Gulf of Maine: The plume advection hypothesis revisited

    USGS Publications Warehouse

    Anderson, D.M.; Keafer, B.A.; Geyer, W.R.; Signell, R.P.; Loder, T.C.

    2005-01-01

    The plume advection hypothesis links blooms of the toxic dinoflagellate Alexandrium fundyense in the western Gulf of Maine (GOM) to a buoyant plume derived from river outflows. This hypothesis was examined with cruise and moored-instrument observations in 1993 when levels of paralytic shellfish poisoning (PSP) toxins were high, and in 1994 when toxicity was low. A coupled physical-biological model simulated hydrography and A. fundyense distributions. Initial A. fundyense populations were restricted to low-salinity nearshore waters near Casco Bay, but also occurred in higher salinity waters along the plume boundary. This suggests two sources of cells - those from shallow-water cyst populations and those transported to shore from offshore blooms in the eastern segment of the Maine coastal current (EMCC). Observations confirm the role of the plume in A. fundyense transport and growth. Downwelling-favorable winds in 1993 transported the plume and its cells rapidly alongshore, enhancing toxicity and propagating PSP to the south. In 1994, sustained upwelling moved the plume offshore, resulting in low toxicity in intertidal shellfish. A. fundyense blooms were likely nutrient limited, leading to low growth rates and moderate cell abundances. These observations and mechanisms were reproduced by coupled physical-biological model simulations. The plume advection hypothesis provides a viable explanation for outbreaks of PSP in the western GOM, but should be refined to include two sources for cells that populate the plume and two major pathways for transport: one within the low-salinity plume and another where A. fundyense cells originating in the EMCC are transported along the outer boundary of the plume front with the western segment of the Maine coastal current.

  17. Interpersonal Attraction in Relation to the Loss-Gain Hypothesis.

    ERIC Educational Resources Information Center

    Sharma, Vandana; Kaur, Inderjeet

    1996-01-01

    Maintains that a loss-gain hypothesis (a negative impression gives way to a positive one) is a more powerful indicator and incentive for future friendship than an opposite sequence (positive to negative). Both of these, however, were eclipsed by a positive-positive interaction as a determinant of interpersonal attraction. (MJP)

  18. Animal Models for Testing the DOHaD Hypothesis

    EPA Science Inventory

    Since the seminal work in human populations by David Barker and colleagues, several species of animals have been used in the laboratory to test the Developmental Origins of Health and Disease (DOHaD) hypothesis. Rats, mice, guinea pigs, sheep, pigs and non-human primates have bee...

  19. A Life-Course Perspective on the "Gateway Hypothesis"

    ERIC Educational Resources Information Center

    Van Gundy, Karen; Rebellon, Cesar J.

    2010-01-01

    Drawing on stress and life-course perspectives and using panel data from 1,286 south Florida young adults, we assess three critical questions regarding the role of marijuana in the "gateway hypothesis." First, does teen marijuana use independently (causally) affect subsequent use of more dangerous substances? Second, if so, does that effect apply…

  20. Rational Variability in Children's Causal Inferences: The Sampling Hypothesis

    ERIC Educational Resources Information Center

    Denison, Stephanie; Bonawitz, Elizabeth; Gopnik, Alison; Griffiths, Thomas L.

    2013-01-01

    We present a proposal--"The Sampling Hypothesis"--suggesting that the variability in young children's responses may be part of a rational strategy for inductive inference. In particular, we argue that young learners may be randomly sampling from the set of possible hypotheses that explain the observed data, producing different hypotheses with…

  1. Acquisition in Context: The Discourse Domain Hypothesis of Interlanguage Variation.

    ERIC Educational Resources Information Center

    Whyte, Shona

    This study tested a refined version of the discourse domain hypothesis, which defines the discourse domain as a topic area in which second language learners demonstrate extensive, current, and important knowledge, including both cognitive and affective dimensions. The study tested the results of previous studies, which showed that learners show…

  2. Hypothesis, Prediction, and Conclusion: Using Nature of Science Terminology Correctly

    ERIC Educational Resources Information Center

    Eastwell, Peter

    2012-01-01

    This paper defines the terms "hypothesis," "prediction," and "conclusion" and shows how to use the terms correctly in scientific investigations in both the school and science education research contexts. The scientific method, or hypothetico-deductive (HD) approach, is described and it is argued that an understanding of the scientific method,…

  3. An Hypothesis of the Pathogenesis of Curb in Horses

    PubMed Central

    Rooney, J. R.

    1981-01-01

    An hypothesis on the pathogenesis of curb in horses is considered in the light of conformation, work and the appropriate mechanics. Prevention consists of graded work until the planter tarsal ligament has strengthened sufficiently to withstand maximum normal forces. PMID:7343069

  4. The Antieconomy Hypothesis (Part 3): Toward a Solution

    ERIC Educational Resources Information Center

    Vanderburg, Willem H.

    2009-01-01

    Parts 1 and 2 explore the hypothesis that the application of mainstream economics has led to economies becoming uneconomic, which is as close as a social science can get to experimentally disproving its theories. One of the primary reasons for this failure is traced to the characteristics of the knowledge infrastructures of contemporary societies,…

  5. A Double-Deficit Hypothesis for Developmental Reading Disorders.

    ERIC Educational Resources Information Center

    Bowers, Patricia Greig; Wolff, Maryanne

    Two longitudinal studies examined a "double deficit" hypothesis of reading disorders that contends that along with a core phonological deficit, slow speed of lexical access disrupts the efficient formation of orthographic representations and their quick retrieval. In the first study, 38 children from 6 classrooms in a predominantly white, middle…

  6. Samara Dispersal in Boxelder: An Exercise in Hypothesis Testing.

    ERIC Educational Resources Information Center

    Minorsky, Peter V.; Willing, R. Paul

    1999-01-01

    Presents a fun, inexpensive, and pedagogically useful laboratory exercise that involves indoor studies of the dispersal properties of the winged fruits (samaras) of boxelder trees. Engages students in the process of hypothesis testing, experimental design, and data analysis as well as introducing students to important concepts related to…

  7. Social Skills Deficits in Learning Disabilities: The Psychiatric Comorbidity Hypothesis.

    ERIC Educational Resources Information Center

    San Miguel, Stephanie K.; And Others

    1996-01-01

    This article explores the hypothesis that social skill deficits among children with learning disabilities are associated with high rates of undetected psychiatric diagnoses. The maladaptive social skills patterns of children with specific subtypes of learning disabilities appear to mimic the symptom patterns of children with attention deficit…

  8. Developmental Psychology and the Biophilia Hypothesis: Children's Affiliation with Nature.

    ERIC Educational Resources Information Center

    Kahn, Peter H., Jr.

    1997-01-01

    Reviews literature on biophilia hypothesis that children have fundamental, genetically based propensity to affiliate with other living organisms. Identifies three concerns: (1) genetic basis of biophilia; (2) existence of seemingly negative affiliations with nature; and (3) quality of supporting evidence. Presents structural-developmental approach…

  9. Societal Complexity and Familial Complexity: Evidence for the Curvilinear Hypothesis

    ERIC Educational Resources Information Center

    Blumberg, Rae Lesser; Winch, Robert F.

    1972-01-01

    The hypothesis is supported that the most extended, complex familial systems should be found among societies in an intermediate range of societal complexity, particularly among settled agricultural peoples. Among the simple hunting-gathering groups and in modern industrial states is found the nuclear family system: small, independent, nonextended…

  10. The Aspect Hypothesis: Development of Morphology and Appropriateness of Use

    ERIC Educational Resources Information Center

    Comajoan, Llorenc

    2006-01-01

    According to the aspect hypothesis (Andersen & Shirai, 1996; Bardovi-Harlig, 2000), perfective morphology emerges before imperfective morphology, it is first used in telic predicates (achievements and accomplishments) and it later extends to atelic predicates (activities and states). The opposite development is hypothesized for imperfective…

  11. The data aggregation problem in quantum hypothesis testing

    NASA Astrophysics Data System (ADS)

    Cialdi, Simone; Paris, Matteo G. A.

    2015-01-01

    We discuss the implications of quantum-classical Yule-Simpson effect for quantum hypothesis testing in the presence of noise, and provide an experimental demonstration of its occurrence in the problem of discriminating which polarization quantum measurement has been actually performed by a detector box designed to measure linear polarization of single-photon states along a fixed but unknown direction.

  12. Examination of the Eyberg Child Behavior Inventory Discrepancy Hypothesis

    ERIC Educational Resources Information Center

    Butler, Ashley M.; Brestan, Elizabeth V.; Eyberg, Sheila M.

    2008-01-01

    This study examined the Eyberg Child Behavior Inventory (ECBI) "discrepancy hypothesis", which asserts that a discrepancy in score elevations on the ECBI Intensity and Problem Scales is related to problematic parenting styles. The Intensity Scale measures the frequency of child disruptive behavior, and the Problem Scale measures parent perception…

  13. The "Discouraged-Business-Major" Hypothesis: Policy Implications

    ERIC Educational Resources Information Center

    Marangos, John

    2012-01-01

    This paper uses a relatively large dataset of the stated academic major preferences of economics majors at a relatively large, not highly selective, public university in the USA to identify the "discouraged-business-majors" (DBMs). The DBM hypothesis addresses the phenomenon where students who are screened out of the business curriculum often…

  14. Evaluation of an Interactive Tutorial for Teaching Hypothesis Testing Concepts

    ERIC Educational Resources Information Center

    Aberson, Christopher L.; Berger, Dale E.; Healy, Michael R.; Romero, Victoria L.

    2003-01-01

    In this article, we describe and evaluate a Web-based interactive tutorial used to present hypothesis testing concepts. The tutorial includes multiple-choice questions with feedback, an interactive applet that allows students to draw samples and evaluate null hypotheses, and follow-up questions suitable for grading. Students either used the…

  15. The Vascular Depression Hypothesis: Mechanisms Linking Vascular Disease with Depression

    PubMed Central

    Taylor, Warren D.; Aizenstein, Howard J.; Alexopoulos, George S.

    2013-01-01

    The ‘Vascular Depression’ hypothesis posits that cerebrovascular disease may predispose, precipitate, or perpetuate some geriatric depressive syndromes. This hypothesis stimulated much research that has improved our understanding of the complex relationships between late-life depression (LLD), vascular risk factors, and cognition. Succinctly, there are well-established relationships between late-life depression, vascular risk factors, and cerebral hyperintensities, the radiological hallmark of vascular depression. Cognitive dysfunction is common in late-life depression, particularly executive dysfunction, a finding predictive of poor antidepressant response. Over time, progression of hyperintensities and cognitive deficits predicts a poor course of depression and may reflect underlying worsening of vascular disease. This work laid the foundation for examining the mechanisms by which vascular disease influences brain circuits and influences the development and course of depression. We review data testing the vascular depression hypothesis with a focus on identifying potential underlying vascular mechanisms. We propose a disconnection hypothesis, wherein focal vascular damage and white matter lesion location is a crucial factor influencing neural connectivity that contributes to clinical symptomatology. We also propose inflammatory and hypoperfusion hypotheses, concepts that link underlying vascular processes with adverse effects on brain function that influence the development of depression. Testing such hypotheses will not only inform the relationship between vascular disease and depression but also provide guidance on the potential repurposing of pharmacological agents that may improve late-life depression outcomes. PMID:23439482

  16. Cultural evolution and prosociality: Widening the hypothesis space.

    PubMed

    Huebner, Bryce; Sarkissian, Hagop

    2016-01-01

    Norenzayan et al. suggest that Big Gods can be replaced by Big Governments. We examine forms of social and self-monitoring and ritual practice that emerged in Classical China, heterarchical societies like those that emerged in pre-Columbian Mesoamerica, and the contemporary Zapatista movement of Chiapas, and we recommend widening the hypothesis space to include these alternative forms of social organization.

  17. Explorations in Statistics: Hypothesis Tests and P Values

    ERIC Educational Resources Information Center

    Curran-Everett, Douglas

    2009-01-01

    Learning about statistics is a lot like learning about science: the learning is more meaningful if you can actively explore. This second installment of "Explorations in Statistics" delves into test statistics and P values, two concepts fundamental to the test of a scientific null hypothesis. The essence of a test statistic is that it compares what…

  18. Planned Hypothesis Tests Are Not Necessarily Exempt from Multiplicity Adjustment

    ERIC Educational Resources Information Center

    Frane, Andrew V.

    2015-01-01

    Scientific research often involves testing more than one hypothesis at a time, which can inflate the probability that a Type I error (false discovery) will occur. To prevent this Type I error inflation, adjustments can be made to the testing procedure that compensate for the number of tests. Yet many researchers believe that such adjustments are…

  19. The Declarative/Procedural Model and the Shallow Structure Hypothesis

    ERIC Educational Resources Information Center

    Ullman, Michael T.

    2006-01-01

    Clahsen and Felser (CF) have written a beautiful and important paper. I applaud their integrative empirical approach, and believe that their theoretical account is largely correct, if not in some of its specific claims, at least in its broader assumptions. CF directly compare their shallow structure hypothesis (SSH) with a model that my colleagues…

  20. Stereotype Measurement and the "Kernel of Truth" Hypothesis.

    ERIC Educational Resources Information Center

    Gordon, Randall A.

    1989-01-01

    Describes a stereotype measurement suitable for classroom demonstration. Illustrates C. McCauley and C. L. Stitt's diagnostic ratio measure and examines the validity of the "kernel of truth" hypothesis. Uses this as a starting point for class discussion. Reports results and gives suggestions for discussion of related concepts. (Author/NL)

  1. The Eigenstate Thermalization Hypothesis in 1D Anyon Chains

    NASA Astrophysics Data System (ADS)

    Burnell, Fiona; Chandran, Anushya; Schulz, Marc

    For ergodic systems with Hilbert spaces satisfying a local product structure, the eigenstate thermalization hypothesis (ETH) is relatively well-established. Using exact diagonalization studies, we investigate whether quantum spin chains based on SU(2)_k anyon theories, which do not admit a Hilbert space with an exactly local product structure, also satisfy ETH, and which observables exhibit this behaviour.

  2. The "One-Shot" Hypothesis for Context Storage

    ERIC Educational Resources Information Center

    Malmberg, Kenneth J.; Shiffrin, Richard M.

    2005-01-01

    In 3 experiments motivated by the implicit memory literature, the authors investigated the effects of different strengthening operations on the list strength effect (LSE) for explicit free recall, an effect posited by R. M. Shiffrin, R. Ratcliff, and S. E. Clark (1990) to be due to context cuing. According to the one-shot hypothesis, a fixed…

  3. Four Centuries of the Geocentric Axial Dipole Hypothesis

    NASA Astrophysics Data System (ADS)

    Tauxe, L.; Kent, D. V.

    2004-12-01

    William Gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis. The GAD hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude. For decades there have been calls for permanent non-dipole contributions to the time averaged field. Recently, these have demanded large contributions of the axial octupole, which, if valid, would call into question the general utility of the GAD hypothesis. In the process of geological recording of the geomagnetic field, ``Earth filters'' distort the directions. Many processes, for example, sedimentary inclination error and random tilting lead to a net shallowing of the observed direction. Therefore inclinations that are shallower than expected from GAD can be explained by recording biases, northward transport, or non-dipole geomagnetic fields. Using paleomagnetic data from the last five million years from well constrained lava flow data allows the construction of a statistical geomagnetic field model. Such a model can predict not only the average expected direction for a given latitude, but also the shape of the distribution of directions produced by secular variation. This allows us to differentiate among the possible explanations for shallow bias. We find no compelling reason to abandon the geocentric dipole hypothesis that has served us well for four centuries.

  4. THE BARKER HYPOTHESIS: IMPLICATIONS FOR FUTURE DIRECTIONS IN TOXICOLOGY RESEARCH

    EPA Science Inventory

    This review covers the past year’s papers germane to the Barker hypothesis. While much of the literature has centered on maternal and developmental nutrition, new findings have emerged on the ability of toxic exposures during development to impact fetal/developmental programming....

  5. Bimodal Bilingualism and the Frequency-Lag Hypothesis

    ERIC Educational Resources Information Center

    Emmorey, Karen; Petrich, Jennifer A. F.; Gollan, Tamar H.

    2013-01-01

    The frequency-lag hypothesis proposes that bilinguals have slowed lexical retrieval relative to monolinguals and in their nondominant language relative to their dominant language, particularly for low-frequency words. These effects arise because bilinguals divide their language use between 2 languages and use their nondominant language less…

  6. Learner Output, Hypothesis Testing, and Internalizing Linguistic Knowledge.

    ERIC Educational Resources Information Center

    Shehadeh, Ali

    2003-01-01

    Investigates how output can be a process by which second language (L2) learners test out hypotheses about the L2 and the extent to which learner hypothesis testing attempts that result in non-target like (NTL) output are challenged by interlocutors. A picture-descriptions task was used to collect data from eight native- and eight…

  7. Random Effects Structure for Confirmatory Hypothesis Testing: Keep It Maximal

    ERIC Educational Resources Information Center

    Barr, Dale J.; Levy, Roger; Scheepers, Christoph; Tily, Harry J.

    2013-01-01

    Linear mixed-effects models (LMEMs) have become increasingly prominent in psycholinguistics and related areas. However, many researchers do not seem to appreciate how random effects structures affect the generalizability of an analysis. Here, we argue that researchers using LMEMs for confirmatory hypothesis testing should minimally adhere to the…

  8. The Evolving Context of the Fundamental Difference Hypothesis

    ERIC Educational Resources Information Center

    Bley-Vroman, Robert

    2009-01-01

    Foreign language learning contrasts with native language development in two key respects: It is unreliable and it is nonconvergent. At the same time, it is clear that foreign languages are languages. The fundamental difference hypothesis (FDH) was introduced as a way to account for the general characteristics of foreign language learning. The FDH…

  9. Bayesian Approaches to Imputation, Hypothesis Testing, and Parameter Estimation

    ERIC Educational Resources Information Center

    Ross, Steven J.; Mackey, Beth

    2015-01-01

    This chapter introduces three applications of Bayesian inference to common and novel issues in second language research. After a review of the critiques of conventional hypothesis testing, our focus centers on ways Bayesian inference can be used for dealing with missing data, for testing theory-driven substantive hypotheses without a default null…

  10. Socially explosive minds: the triple imbalance hypothesis of reactive aggression.

    PubMed

    van Honk, Jack; Harmon-Jones, Eddie; Morgan, Barak E; Schutter, Dennis J L G

    2010-02-01

    The psychobiological basis of reactive aggression, a condition characterized by uncontrolled outbursts of socially violent behavior, is unclear. Nonetheless, several theoretical models have been proposed that may have complementary views about the psychobiological mechanisms involved. In this review, we attempt to unite these models and theorize further on the basis of recent data from psychological and neuroscientific research to propose a comprehensive neuro-evolutionary framework: The Triple Imbalance Hypothesis (TIH) of reactive aggression. According to this model, reactive aggression is essentially subcortically motivated by an imbalance in the levels of the steroid hormones cortisol and testosterone (Subcortical Imbalance Hypothesis). This imbalance not only sets a primal predisposition for social aggression, but also down-regulates cortical-subcortical communication (Cortical-Subcortical Imbalance Hypothesis), hence diminishing control by cortical regions that regulate socially aggressive inclinations. However, these bottom-up hormonally mediated imbalances can drive both instrumental and reactive social aggression. The TIH suggests that reactive aggression is differentiated from proactive aggression by low brain serotonergic function and that reactive aggression is associated with left-sided frontal brain asymmetry (Cortical Imbalance Hypothesis), especially observed when the individual is socially threatened or provoked. This triple biobehavioral imbalance mirrors an evolutionary relapse into violently aggressive motivational drives that are adaptive among many reptilian and mammalian species, but may have become socially maladaptive in modern humans. PMID:20433613

  11. Multiple-hypothesis multiple-model line tracking

    NASA Astrophysics Data System (ADS)

    Pace, Donald W.; Owen, Mark W.; Cox, Henry

    2000-07-01

    Passive sonar signal processing generally includes tracking of narrowband and/or broadband signature components observed on a Lofargram or on a Bearing-Time-Record (BTR) display. Fielded line tracking approaches to date have been recursive and single-hypthesis-oriented Kalman- or alpha-beta filters, with no mechanism for considering tracking alternatives beyond the most recent scan of measurements. While adaptivity is often built into the filter to handle changing track dynamics, these approaches are still extensions of single target tracking solutions to multiple target tracking environment. This paper describes an application of multiple-hypothesis, multiple target tracking technology to the sonar line tracking problem. A Multiple Hypothesis Line Tracker (MHLT) is developed which retains the recursive minimum-mean-square-error tracking behavior of a Kalman Filter in a maximum-a-posteriori delayed-decision multiple hypothesis context. Multiple line track filter states are developed and maintained using the interacting multiple model (IMM) state representation. Further, the data association and assignment problem is enhanced by considering line attribute information (line bandwidth and SNR) in addition to beam/bearing and frequency fit. MHLT results on real sonar data are presented to demonstrate the benefits of the multiple hypothesis approach. The utility of the system in cluttered environments and particularly in crossing line situations is shown.

  12. New symbiotic hypothesis on the origin of eukaryotic flagella

    NASA Astrophysics Data System (ADS)

    Li, Jing Yan; Wu, Chuan Fen

    2005-07-01

    The origin of eukaryotic flagella has long been a mystery. Here we review the possibility that flagella sprouted evolutionarily from the eukaryotic cell proper seems very unlikely because it is hard to imagine what function and benefit in natural selection the flagella would have provided to the cells when they first emerged as simple buds. Lynn Margulis’ 1970 spirochete hypothesis, though popular still, has never been confirmed. Moreover, the absence of tubulin and axonemal dynein in the spirochetes and the incapability of the bacterial and eukaryotic membranes’ making a continuum now suggest that the hypothesis is outdated. Tubulin genes were recently identified in a new bacteria division, verrucomicrobia, and microtubules have also been found in one of these species, epixenosomes, the defensive ectosymbionts. On the basis of these data, we propose a new symbiotic hypothesis: that the mid-ancestor of eukaryotic cells obtained epixenosomelike verrucomicrobia as defensive ectosymbionts and the ectosymbionts later became endosymbiotic. They still, however, protruded from the surface of their host to play their role. Later, many genes were lost or incorporated into the host genome. Finally, the genome, the bacterial membrane, and the endosymbiotic vesicle membrane were totally lost, and fingerlike protrusions with microtubules formed. As the cells grew larger, the defensive function of the protrusions eventually weakened and then vanished. Some of the protrusions took on a new role in cell movement, which led them to evolve into flagella. The key step in this process was that the dynein obtained from the host evolved into axonemal dyneins, attaching onto the microtubules and forming motile axonemes. Our hypothesis is unproven, but it offers a possible explanation that is consistent with current scientific thought. We hope that our ideas will stimulate additional studies on the origin of eukaryotic flagella and on investigations of verrucomicrobia. Whether such

  13. Dopamine and Reward: The Anhedonia Hypothesis 30 years on

    PubMed Central

    Wise, Roy A.

    2011-01-01

    The anhedonia hypothesis – that brain dopamine plays a critical role in the subjective pleasure associated with positive rewards – was intended to draw the attention of psychiatrists to the growing evidence that dopamine plays a critical role in the objective reinforcement and incentive motivation associated with food and water, brain stimulation reward, and psychomotor stimulant and opiate reward. The hypothesis called to attention the apparent paradox that neuroleptics, drugs used to treat a condition involving anhedonia (schizophrenia), attenuated in laboratory animals the positive reinforcement that we normally associate with pleasure. The hypothesis held only brief interest for psychiatrists, who pointed out that the animal studies reflected acute actions of neuroleptics whereas the treatment of schizophrenia appears to result from neuroadaptations to chronic neuroleptic administration, and that it is the positive symptoms of schizophrenia that neuroleptics alleviate, rather than the negative symptoms that include anhedonia. Perhaps for these reasons, the hypothesis has had minimal impact in the psychiatric literature. Despite its limited heuristic value for the understanding of schizophrenia, however, the anhedonia hypothesis has had major impact on biological theories of reinforcement, motivation, and addiction. Brain dopamine plays a very important role in reinforcement of response habits, conditioned preferences, and synaptic plasticity in cellular models of learning and memory. The notion that dopamine plays a dominant role in reinforcement is fundamental to the psychomotor stimulant theory of addiction, to most neuroadaptation theories of addiction, and to current theories of conditioned reinforcement and reward prediction. Properly understood, it is also fundamental to recent theories of incentive motivation. PMID:19073424

  14. A critique of statistical hypothesis testing in clinical research

    PubMed Central

    Raha, Somik

    2011-01-01

    Many have documented the difficulty of using the current paradigm of Randomized Controlled Trials (RCTs) to test and validate the effectiveness of alternative medical systems such as Ayurveda. This paper critiques the applicability of RCTs for all clinical knowledge-seeking endeavors, of which Ayurveda research is a part. This is done by examining statistical hypothesis testing, the underlying foundation of RCTs, from a practical and philosophical perspective. In the philosophical critique, the two main worldviews of probability are that of the Bayesian and the frequentist. The frequentist worldview is a special case of the Bayesian worldview requiring the unrealistic assumptions of knowing nothing about the universe and believing that all observations are unrelated to each other. Many have claimed that the first belief is necessary for science, and this claim is debunked by comparing variations in learning with different prior beliefs. Moving beyond the Bayesian and frequentist worldviews, the notion of hypothesis testing itself is challenged on the grounds that a hypothesis is an unclear distinction, and assigning a probability on an unclear distinction is an exercise that does not lead to clarity of action. This critique is of the theory itself and not any particular application of statistical hypothesis testing. A decision-making frame is proposed as a way of both addressing this critique and transcending ideological debates on probability. An example of a Bayesian decision-making approach is shown as an alternative to statistical hypothesis testing, utilizing data from a past clinical trial that studied the effect of Aspirin on heart attacks in a sample population of doctors. As a big reason for the prevalence of RCTs in academia is legislation requiring it, the ethics of legislating the use of statistical methods for clinical research is also examined. PMID:22022152

  15. A critique of statistical hypothesis testing in clinical research.

    PubMed

    Raha, Somik

    2011-07-01

    Many have documented the difficulty of using the current paradigm of Randomized Controlled Trials (RCTs) to test and validate the effectiveness of alternative medical systems such as Ayurveda. This paper critiques the applicability of RCTs for all clinical knowledge-seeking endeavors, of which Ayurveda research is a part. This is done by examining statistical hypothesis testing, the underlying foundation of RCTs, from a practical and philosophical perspective. In the philosophical critique, the two main worldviews of probability are that of the Bayesian and the frequentist. The frequentist worldview is a special case of the Bayesian worldview requiring the unrealistic assumptions of knowing nothing about the universe and believing that all observations are unrelated to each other. Many have claimed that the first belief is necessary for science, and this claim is debunked by comparing variations in learning with different prior beliefs. Moving beyond the Bayesian and frequentist worldviews, the notion of hypothesis testing itself is challenged on the grounds that a hypothesis is an unclear distinction, and assigning a probability on an unclear distinction is an exercise that does not lead to clarity of action. This critique is of the theory itself and not any particular application of statistical hypothesis testing. A decision-making frame is proposed as a way of both addressing this critique and transcending ideological debates on probability. An example of a Bayesian decision-making approach is shown as an alternative to statistical hypothesis testing, utilizing data from a past clinical trial that studied the effect of Aspirin on heart attacks in a sample population of doctors. As a big reason for the prevalence of RCTs in academia is legislation requiring it, the ethics of legislating the use of statistical methods for clinical research is also examined.

  16. New symbiotic hypothesis on the origin of eukaryotic flagella.

    PubMed

    Li, Jing Yan; Wu, Chuan Fen

    2005-07-01

    The origin of eukaryotic flagella has long been a mystery. Here we review the possibility that flagella sprouted evolutionarily from the eukaryotic cell proper seems very unlikely because it is hard to imagine what function and benefit in natural selection the flagella would have provided to the cells when they first emerged as simple buds. Lynn Margulis' 1970 spirochete hypothesis, though popular still, has never been confirmed. Moreover, the absence of tubulin and axonemal dynein in the spirochetes and the incapability of the bacterial and eukaryotic membranes' making a continuum now suggest that the hypothesis is outdated. Tubulin genes were recently identified in a new bacteria division, verrucomicrobia, and microtubules have also been found in one of these species, epixenosomes, the defensive ectosymbionts. On the basis of these data, we propose a new symbiotic hypothesis: that the mid-ancestor of eukaryotic cells obtained epixenosomelike verrucomicrobia as defensive ectosymbionts and the ectosymbionts later became endosymbiotic. They still, however, protruded from the surface of their host to play their role. Later, many genes were lost or incorporated into the host genome. Finally, the genome, the bacterial membrane, and the endosymbiotic vesicle membrane were totally lost, and fingerlike protrusions with microtubules formed. As the cells grew larger, the defensive function of the protrusions eventually weakened and then vanished. Some of the protrusions took on a new role in cell movement, which led them to evolve into flagella. The key step in this process was that the dynein obtained from the host evolved into axonemal dyneins, attaching onto the microtubules and forming motile axonemes. Our hypothesis is unproven, but it offers a possible explanation that is consistent with current scientific thought. We hope that our ideas will stimulate additional studies on the origin of eukaryotic flagella and on investigations of verrucomicrobia. Whether such

  17. Distinguishing between the Partial-Mapping Preparation Hypothesis and the Failure-to-Engage Hypothesis of Residual Switch Costs

    ERIC Educational Resources Information Center

    Lindsen, Job P.; de Jong, Ritske

    2010-01-01

    Lien, Ruthruff, Remington, & Johnston (2005) reported residual switch cost differences between stimulus-response (S-R) pairs and proposed the partial-mapping preparation (PMP) hypothesis, which states that advance preparation will typically be limited to a subset of S-R pairs because of structural capacity limitations, to account for these…

  18. Growth Disorders

    MedlinePlus

    ... gland problem or disease. The pituitary gland makes growth hormone, which stimulates the growth of bone and other ... of it may be very short. Treatment with growth hormone can stimulate growth. People can also have too ...

  19. Radiation hormesis: the demise of a legitimate hypothesis.

    PubMed

    Calabrese, E J; Baldwin, L A

    2000-01-01

    This paper examines the underlying factors that contributed to the marginalization of radiation hormesis in the early and middle decades of the 20th century. The most critical factor affecting the demise of radiation hormesis was a lack of agreement over how to define the concept of hormesis and quantitatively describe its dose-response features. If radiation hormesis had been defined as a modest overcompensation to a disruption in homeostasis as would have been consistent with the prevailing notion in the area of chemical hormesis, this would have provided the theoretical and practical means to blunt subsequent legitimate criticism of this hypothesis. A second critical factor undermining the radiation hormesis hypothesis was the generally total lack of recognition by radiation scientists of the concept of chemical hormesis which was markedly more advanced, substantiated and generalized than in the radiation domain. The third factor was that major scientific criticism of low dose stimulatory responses was galvanized at the time that the National Research Council (NRC) was organizing a national research agenda on radiation and the hormetic hypothesis was generally excluded from the future planned research opportunities. Furthermore, the criticisms of the leading scientists of the 1930s which undermined the concept of radiation hormesis were limited in scope and highly flawed and then perpetuated over the decades by other 'prestigious' experts who appeared to simply accept the earlier reports. This setting was then linked to a growing fear of radiation as a cause of birth defects, mutation and cancer, factors all reinforced by later concerns over the atomic bomb. Strongly supportive findings on hormetic effects in the 1940s by Soviet scientists were either generally not available to US scientists or disregarded as part of the Cold War mindset without adequate analysis. Finally, a massive, but poorly designed, US Department of Agriculture experiment in the late 1940s

  20. A Hypothesis-Driven Approach to Site Investigation

    NASA Astrophysics Data System (ADS)

    Nowak, W.

    2008-12-01

    Variability of subsurface formations and the scarcity of data lead to the notion of aquifer parameters as geostatistical random variables. Given an information need and limited resources for field campaigns, site investigation is often put into the context of optimal design. In optimal design, the types, numbers and positions of samples are optimized under case-specific objectives to meet the information needs. Past studies feature optimal data worth (balancing maximum financial profit in an engineering task versus the cost of additional sampling), or aim at a minimum prediction uncertainty of stochastic models for a prescribed investigation budget. Recent studies also account for other sources of uncertainty outside the hydrogeological range, such as uncertain toxicity, ingestion and behavioral parameters of the affected population when predicting the human health risk from groundwater contaminations. The current study looks at optimal site investigation from a new angle. Answering a yes/no question under uncertainty directly requires recasting the original question as a hypothesis test. Otherwise, false confidence in the resulting answer would be pretended. A straightforward example is whether a recent contaminant spill will cause contaminant concentrations in excess of a legal limit at a nearby drinking water well. This question can only be answered down to a specified chance of error, i.e., based on the significance level used in hypothesis tests. Optimal design is placed into the hypothesis-driven context by using the chance of providing a false yes/no answer as new criterion to be minimized. Different configurations apply for one-sided and two-sided hypothesis tests. If a false answer entails financial liability, the hypothesis-driven context can be re-cast in the context of data worth. The remaining difference is that failure is a hard constraint in the data worth context versus a monetary punishment term in the hypothesis-driven context. The basic principle

  1. Intergenerational transmission of homeownership in Europe: revisiting the socialisation hypothesis.

    PubMed

    Lersch, Philipp M; Luijkx, Ruud

    2015-01-01

    Socialisation towards homeownership during childhood has been proposed as one transmission channel of homeownership across generations in previous literature, but tests of this socialisation hypothesis are scarce. This study presents the yet most rigorous test of the socialisation hypothesis using retrospective life-history data (SHARELIFE, N=19,567 individuals) from 13 European countries. Event history and panel regression models are applied. Results show that socialisation in homeownership positively affects the hazard rates of entering homeownership for the first time and the probability to be a homeowner throughout individuals' lives net of other parental background variables and material transfers. We find a socialisation effect across divergent (but not all) examined countries. Further sensitivity analyses using a placebo test and a hypothetical confounder support the conclusion that being socialised in homeownership during childhood increases the chances of becoming and being a homeowner in later life.

  2. Question 2: relation of panspermia-hypothesis to astrobiology.

    PubMed

    Zagorski, Zbigniew Pawel

    2007-10-01

    In the answer to major questions of astrobiology and chirality, the panspermia-hypothesis is often discussed as the only proposal of transportation of life to the Earth. On the basis of the known presence of ionizing radiation in the space, assumed on the level calculated by Clark (Orig Life Evol Biosph 31:185-197, 2001), the hypothesis is rejected as the explanation of origins of life on Earth. In fact, comparatively low doses of radiation sterilize irreversibly all biological material. Sufficiently long sojourn in space of objects containing prebiotic chemical blocks also does not contribute to the origins of life on Earth, because of elimination of homochirality, if any, and of radiation induced reactions of dehydrogenation, decarboxylation and deamination of chemical compounds closing with complete decomposition of organics, leaving elementary nano-carbon and/or minerals like calcium carbonate.

  3. A molecular phylogenetic hypothesis for the manakins (Aves: Pipridae).

    PubMed

    McKay, Bailey D; Barker, F Keith; Mays, Herman L; Doucet, Stéphanie M; Hill, Geoffrey E

    2010-05-01

    Phylogenetic relationships among the 14 manakin genera were inferred from DNA sequence data obtained from both mitochondrial and nuclear DNA loci. Phylogenetic analysis resulted in a well-supported hypothesis that corroborates a sister relationship between tyrant-manakins and the "core" manakins (Antilophia, Chiroxiphia, Corapipo, Dixiphia, Heterocercus, Ilicura, Lepidothrix, Manacus, Masius, Machaeropterus, Pipra, and Xenopipo). Our data strongly support these core manakin genera as a monophyletic group. Consistent with previous work, we find two major clades within the core manakins, although the placement of the genus Xenopipo with regards to these two clades is ambiguous. Generic relationships within these clades are generally well resolved. Although we find some concordance between our study and a previous manakin phylogeny based on syringeal characters, we note several fundamental differences between the phylogenies. Thus, we offer a new phylogenetic hypothesis for Pipridae. PMID:20188842

  4. Cooperation and human cognition: the Vygotskian intelligence hypothesis.

    PubMed

    Moll, Henrike; Tomasello, Michael

    2007-04-29

    Nicholas Humphrey's social intelligence hypothesis proposed that the major engine of primate cognitive evolution was social competition. Lev Vygotsky also emphasized the social dimension of intelligence, but he focused on human primates and cultural things such as collaboration, communication and teaching. A reasonable proposal is that primate cognition in general was driven mainly by social competition, but beyond that the unique aspects of human cognition were driven by, or even constituted by, social cooperation. In the present paper, we provide evidence for this Vygotskian intelligence hypothesis by comparing the social-cognitive skills of great apes with those of young human children in several domains of activity involving cooperation and communication with others. We argue, finally, that regular participation in cooperative, cultural interactions during ontogeny leads children to construct uniquely powerful forms of perspectival cognitive representation. PMID:17296598

  5. Hypothesis testing in students: Sequences, stages, and instructional strategies

    NASA Astrophysics Data System (ADS)

    Moshman, David; Thompson, Pat A.

    Six sequences in the development of hypothesis-testing conceptions are proposed, involving (a) interpretation of the hypothesis; (b) the distinction between using theories and testing theories; (c) the consideration of multiple possibilities; (d) the relation of theory and data; (e) the nature of verification and falsification; and (f) the relation of truth and falsity. An alternative account is then provided involving three global stages: concrete operations, formal operations, and a postformal metaconstructivestage. Relative advantages and difficulties of the stage and sequence conceptualizations are discussed. Finally, three families of teaching strategy are distinguished, which emphasize, respectively: (a) social transmission of knowledge; (b) carefully sequenced empirical experience by the student; and (c) self-regulated cognitive activity of the student. It is argued on the basis of Piaget's theory that the last of these plays a crucial role in the construction of such logical reasoning strategies as those involved in testing hypotheses.

  6. Why is muscularity sexy? Tests of the fitness indicator hypothesis.

    PubMed

    Frederick, David A; Haselton, Martie G

    2007-08-01

    Evolutionary scientists propose that exaggerated secondary sexual characteristics are cues of genes that increase offspring viability or reproductive success. In six studies the hypothesis that muscularity is one such cue is tested. As predicted, women rate muscular men as sexier, more physically dominant and volatile, and less committed to their mates than nonmuscular men. Consistent with the inverted-U hypothesis of masculine traits, men with moderate muscularity are rated most attractive. Consistent with past research on fitness cues, across two measures, women indicate that their most recent short-term sex partners were more muscular than their other sex partners (ds = .36, .47). Across three studies, when controlling for other characteristics (e.g., body fat), muscular men rate their bodies as sexier to women (partial rs = .49-.62) and report more lifetime sex partners (partial rs = .20-.27), short-term partners (partial rs = .25-.28), and more affairs with mated women (partial r = .28).

  7. A phenotypic null hypothesis for the genetics of personality.

    PubMed

    Turkheimer, Eric; Pettersson, Erik; Horn, Erin E

    2014-01-01

    We review the genetically informed literature on the genetics of personality. Over the past century, quantitative genetic studies, using identical and fraternal twins, have demonstrated that differences in human personality are substantially heritable. We focus on more contemporary questions to which that basic observation has led. We examine whether differences in the heritability of personality are replicable across different traits, samples, and studies; how the heritability of personality relates to its reliability; and how behavior genetics can be employed in studies of validity, and we discuss the stability of personality in genetic and environmental variance. The appropriate null hypothesis in behavior genetics is not that genetic or environmental influence on personality is zero. Instead, we offer a phenotypic null hypothesis, which states that genetic variance is not an independent mechanism of individual differences in personality but rather a reflection of processes that are best conceptualized at the phenotypic level. PMID:24050184

  8. Cognitive style, cortical stimulation, and the conversion hypothesis

    PubMed Central

    Kraemer, David J. M.; Hamilton, Roy H.; Messing, Samuel B.; DeSantis, Jennifer H.; Thompson-Schill, Sharon L.

    2014-01-01

    What does it mean to have a “verbal cognitive style?” We adopt the view that a cognitive style represents a cognitive strategy, and we posit the conversion hypothesis – the notion that individuals with a proclivity for the verbal cognitive style tend to code nonverbal information into the verbal domain. Here we used repetitive transcranial magnetic stimulation (rTMS) to disrupt this hypothesized verbal conversion strategy. Following our previous research implicating left supramarginal gyrus (SMG) in the verbal cognitive style, we used an fMRI paradigm to localize left SMG activity for each subject, then these functional peaks became rTMS targets. Left SMG stimulation impaired performance during a task requiring conversion from pictures to verbal labels. The magnitude of this effect was predicted by individuals’ level of verbal cognitive style, supporting the hypothesized role of left SMG in the verbal labeling strategy, and more generally supporting the conversion hypothesis for cognitive styles. PMID:24523687

  9. Microbial biofilms and wound healing: an ecological hypothesis.

    PubMed

    Krom, Bastiaan P; Oskam, Jacques

    2014-05-19

    Man has lived together with microbes for so long that we have become completely dependent on their presence. Most microbes reside in biofilms; structured communities encased in a protective matrix of biopolymers. Under healthy conditions, the microbial biofilm is in balance with itself (endo-balance) and with the host (exo-balance). Integrity of the skin is an important immunological function. Wounds go through a well-orchestrated series of healing steps. However, if for some reason healing times are extended, serious problems related to infection and homeostasis can develop. Based on recent advances in biofilm research and microbiological identification we discuss two hypotheses describing the role of microbial biofilms in chronic wound biology. The first hypothesis describes microbial biofilms as the cause of extended healing times. The second hypothesis is based on the host as cause of extended healing times and basically treats microbial biofilms as a logical consequence of failure to re-build the integrity of the skin.

  10. Neuromuscular deficits after peripheral joint injury: a neurophysiological hypothesis.

    PubMed

    Ward, Sarah; Pearce, Alan J; Pietrosimone, Brian; Bennell, Kim; Clark, Ross; Bryant, Adam L

    2015-03-01

    In addition to biomechanical disturbances, peripheral joint injuries (PJIs) can also result in chronic neuromuscular alterations due in part to loss of mechanoreceptor-mediated afferent feedback. An emerging perspective is that PJI should be viewed as a neurophysiological dysfunction, not simply a local injury. Neurophysiological and neuroimaging studies have provided some evidence for central nervous system (CNS) reorganization at both the cortical and spinal levels after PJI. The novel hypothesis proposed is that CNS reorganization is the underlying mechanism for persisting neuromuscular deficits after injury, particularly muscle weakness. There is a lack of direct evidence to support this hypothesis, but future studies utilizing force-matching tasks with superimposed transcranial magnetic stimulation may be help clarify this notion.

  11. Distinguishability in EIT using a hypothesis-testing model

    NASA Astrophysics Data System (ADS)

    Adler, Andy; Gaggero, Pascal; Maimaitijiang, Yasheng

    2010-04-01

    In this paper we propose a novel formulation for the distinguishability of conductivity targets in electrical impedance tomography (EIT). It is formulated in terms of a classic hypothesis test to make it directly applicable to experimental configurations. We test to distinguish conductivity distributions σ2 from σ1, from which EIT measurements are obtained with added white Gaussian noise with covariance Σn. In order to distinguish the distributions, we must reject the null hypothesis , which has a probability based on the z-score: . This result shows that distinguishability is a product of the impedance change amplitude, the measurement strategy and the inverse of the noise amplitude. This approach is used to explore different current stimulation strategies.

  12. Neural networks supporting switching, hypothesis testing, and rule application.

    PubMed

    Liu, Zhiya; Braunlich, Kurt; Wehe, Hillary S; Seger, Carol A

    2015-10-01

    We identified dynamic changes in recruitment of neural connectivity networks across three phases of a flexible rule learning and set-shifting task similar to the Wisconsin Card Sort Task: switching, rule learning via hypothesis testing, and rule application. During fMRI scanning, subjects viewed pairs of stimuli that differed across four dimensions (letter, color, size, screen location), chose one stimulus, and received feedback. Subjects were informed that the correct choice was determined by a simple unidimensional rule, for example "choose the blue letter". Once each rule had been learned and correctly applied for 4-7 trials, subjects were cued via either negative feedback or visual cues to switch to learning a new rule. Task performance was divided into three phases: Switching (first trial after receiving the switch cue), hypothesis testing (subsequent trials through the last error trial), and rule application (correct responding after the rule was learned). We used both univariate analysis to characterize activity occurring within specific regions of the brain, and a multivariate method, constrained principal component analysis for fMRI (fMRI-CPCA), to investigate how distributed regions coordinate to subserve different processes. As hypothesized, switching was subserved by a limbic network including the ventral striatum, thalamus, and parahippocampal gyrus, in conjunction with cortical salience network regions including the anterior cingulate and frontoinsular cortex. Activity in the ventral striatum was associated with switching regardless of how switching was cued; visually cued shifts were associated with additional visual cortical activity. After switching, as subjects moved into the hypothesis testing phase, a broad fronto-parietal-striatal network (associated with the cognitive control, dorsal attention, and salience networks) increased in activity. This network was sensitive to rule learning speed, with greater extended activity for the slowest

  13. A hypothesis-assessment model of categorical argument strength.

    PubMed

    McDonald, J; Samuels, M; Rispoli, J

    1996-05-01

    According to the proposed hypothesis-assessment model, the strength of inductive categorical arguments, such as {All Robins Have Substance X therefore All Birds Have Substance X}, is determined by the same factors that affect hypothesis plausibility in the everyday social milieu. The premises of such arguments are viewed as evidence and the conclusion is viewed as a hypothesis. Specifically, the proposed model predicts that the perceived strength of general-conclusion categorical arguments will be a function of (a) the number of premises that instantiate the conclusion; (b) the scope of the conclusion; and (c) the number of accessed alternatives to the conclusion. In Experiment 1, one group rated the strength of individual arguments and another constructed superordinate hypotheses in response to the premise information alone. Most of the variance in perceived argument strength was accounted for by the proposed predictors, R = .94. Experiment 2 employed a new set of arguments and included an additional forced-choice condition in which subjects had to choose the stronger of two arguments. Again, the correlation between predictors and argument strength was high, R = .91, and, all significant forced-choice preferences except one were correctly predicted by the model. The one unpredicted preference suggests the need to include conclusion accessibility as a fourth factor. Also, on a subset of the forced-choice pairs in which no significant preference was observed, two distinct patterns of responding were detected-one predicted and the other unanticipated. Some strengths and limitations of the proposed hypothesis-assessment model are discussed in light of these results. PMID:8681511

  14. Human Cancers Express a Mutator Phenotype: Hypothesis, Origin, and Consequences

    PubMed Central

    Loeb, Lawrence A.

    2016-01-01

    The mutator phenotype hypothesis was postulated more than 40 years ago. It was based on the multiple enzymatic steps required to precisely replicate the 6 billion bases in the human genome each time a normal cell divides. A reduction in this accuracy during tumor progression could be responsible for the striking heterogeneity of malignant cells within a tumor and for the rapidity by which cancers become resistant to therapy. PMID:27197248

  15. The micron stroke hypothesis of Alzheimer's disease and dementia.

    PubMed

    Orehek, Allen J

    2012-05-01

    Alzheimer's disease as currently described in the medical literature is often more a description of dementia rather than a specific disease. In over a century of scientific work there has been no proven theory as to the precise pathogenesis of Alzheimer's disease and dementia. As there is no efficient treatment for patients with Alzheimer's disease, prevention or attenuation of the disease is of substantial value. An intricate collection of hypotheses, studies, research, and experience has made it complicated for one to completely understand this disease. The purpose of this hypothesis is to illustrate new concepts and work to link those concepts to the present understanding of an obscure disease. The search for a single unifying hypothesis on the etiology of Alzheimer's disease has been elusive. Many hypotheses associated to Alzheimer's disease have not survived their testing to become theory. Suggested here is that the elusive nature of etiology of dementia is not from one cause, but rather the causes are numerous. Medical terminology used freely for decades is rarely evaluated in the light of a new hypothesis. At the foundation of this work is the suggestion of a new medical term: Micron Strokes. The Micron Stroke Hypothesis of Alzheimer's Disease and Dementia include primary and secondary factors. The primary factors can be briefly described as baseline brain tissue, atrial fibrillation, hypercoaguable state, LDL, carotid artery stenosis, tobacco exposure, hypertension diabetes mellitus, and the presence of systemic inflammation. Dozens of secondary factors contribute to the development of dementia. Most dementia is caused by nine primary categories of factors as they interact to cause micron strokes to the brain.

  16. Strongly trapped points and the cosmic censorship hypothesis

    SciTech Connect

    Krolak, A.

    1987-04-15

    It is shown that singularities predicted by one of the theorems of Hawking cannot be naked. This result supports the validity of the cosmic censorship hypothesis put forward by Penrose. The condition that only singularities predicted by Hawking's singularity theorem occur in space-time is shown to be related to the condition that all singularities in space-time should be of Tipler's strong-curvature type.

  17. Spatial expression of the genome: the signal hypothesis at forty.

    PubMed

    Matlin, Karl S

    2011-05-01

    The signal hypothesis, formulated by Günter Blobel and David Sabatini in 1971, and elaborated by Blobel and his colleagues between 1975 and 1980, fundamentally expanded our view of cells by introducing the concept of topogenic signals. Cells were no longer just morphological entities with compartmentalized biochemical functions; they were now active participants in the creation and perpetuation of their own form and identity, the decoders of linear genetic information into three dimensions. PMID:21487438

  18. Cultural evolution and prosociality: Widening the hypothesis space.

    PubMed

    Huebner, Bryce; Sarkissian, Hagop

    2016-01-01

    Norenzayan et al. suggest that Big Gods can be replaced by Big Governments. We examine forms of social and self-monitoring and ritual practice that emerged in Classical China, heterarchical societies like those that emerged in pre-Columbian Mesoamerica, and the contemporary Zapatista movement of Chiapas, and we recommend widening the hypothesis space to include these alternative forms of social organization. PMID:26948732

  19. Growth outcome: nutritionist perspective.

    PubMed

    Agostoni, Carlo; Fattore, Giovanni

    2013-01-01

    Increasing evidence points to a fundamental role of early nutrition on rates of growth and development, and later health. We may identify three major fields of scientific interest and clinical application. (1) In developing countries poor growth is associated with greater risk of morbidity and mortality from infectious diseases, mainly lower respiratory infections and diarrhea. In these settings, failure to promote compensatory growth may have negative short-term consequences, and the nutritionist's task is the primary prevention of nutrient deficiencies to promote the full expression of the individual genetic potential, while allowing for recovery of early secondary functional deficiencies. (2) A second challenge for nutritionists is represented by the approach to growth impairments in rare disorders, ranging from congenital disorders to chronic infections. Most disorders are favorably influenced by improved nutritional status and better growth, and patients may satisfactorily reach adolescence, pubertal and reproductive age, up to ageing. Even for the less positive conditions, an improvement in the quality of life for families is in any case a rewarding aim. (3) A third challenge is represented by the definition of the role of nutrition on growth in physiological conditions for all individuals. Concern has been raised about the potential adverse long-term consequences of accelerated child growth rates, possibly resulting in a predisposition to develop non-communicable chronic diseases in the adult age. Accordingly, this hypothesis might explain the benefits of breastfeeding in terms of slower early growth, and the fetal origins hypothesis in terms of adverse postnatal catch-up growth in infants born small. Therefore, growth as viewed by a pediatric nutritionist perspective is a complex matter, ranging from the early stages of intrauterine development up to adult ages and ageing processes. Cost/benefit analyses of interventions on growth such as cost per DALYs

  20. The nephridial hypothesis of the gill slit origin.

    PubMed

    Ezhova, Olga V; Malakhov, Vladimir V

    2015-12-01

    Metameric gill slits are mysterious structures, unique for Chordata and Hemichordata, and also, perhaps, for the extinct Cambrian Calcichordata. There is a discussed hypothesis of the gill slits origin from the metameric nephridia. According to the hypothesis, the hypothetical metameric deuterostome ancestor had in each segment a pair of coelomoducts and a pair of intestinal pockets. In the anterior segments, the coelomoducts have fused with the intestinal pockets. As a result, each nephridium opened both into the gut and into the environment. Then the dissepiments and funnels reduced in all segments except the collar one. Thus, in recent enteropneusts, only the first pair of gill slits keeps the ancestral arrangement communicating at the same time with the gut, with the environment, and with the coelom of the preceding (collar) segment. In the anterior part of the branchio-genital trunk region of enteropneusts, the metameric intestinal pockets remained, as well as the metameric coelomoducts functioning as the ducts of the metameric gonads, i.e., as the gonoducts. The consequence of the hypothesis is that the metameric gill pores originate from the metameric excreting pores, and the metameric branchial sacs originate from the metameric endodermal pockets of the gut fused with the coelomoducts. The metameric gill slits by themselves correspond with metameric openings connecting the gut with metameric intestinal pockets. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 647-652, 2015. © 2015 Wiley Periodicals, Inc. PMID:26227807

  1. Mood-as-input hypothesis and perseverative psychopathologies.

    PubMed

    Meeten, Frances; Davey, Graham C L

    2011-12-01

    Mood-as-input hypothesis is a theory of task perseveration that has been applied to the understanding of perseveration across psychopathologies such as pathological worrying, compulsive checking, depressive rumination, and chronic pain. We review 10 years of published evidence from laboratory-based analogue studies and describe their relevance for perseveration in clinical populations. In particular, mood-as-input hypothesis predicts that perseveration at a task will be influenced by interactions between the individual's stop rules for the task and their concurrent mood, and that the valency of an individual's concurrent mood is used as information about whether the stop rule-defined goals for the task have been met. The majority of the published research is consistent with this hypothesis, and we provide evidence that clinical populations possess characteristics that would facilitate perseveration through mood-as-input processes. We argue that mood-as-input research on clinical populations is long overdue because (1) it has potential as a transdiagnostic mechanism helping to explain the development of perseveration and its comorbidity across a range of different psychopathologies, (2) it is potentially applicable to any psychopathology where perseveration is a defining feature of the symptoms, and (3) it has treatment implications for dealing with clinical perseveration. PMID:21963671

  2. Considerations for multiple hypothesis correlation on tactical platforms

    NASA Astrophysics Data System (ADS)

    Thomas, Alan M.; Turpen, James E.

    2013-05-01

    Tactical platforms benefit greatly from the fusion of tracks from multiple sources in terms of increased situation awareness. As a necessary precursor to this track fusion, track-to-track association, or correlation, must first be performed. The related measurement-to-track fusion problem has been well studied with multiple hypothesis tracking and multiple frame assignment methods showing the most success. The track-to-track problem differs from this one in that measurements themselves are not available but rather track state update reports from the measuring sensors. Multiple hypothesis, multiple frame correlation systems have previously been considered; however, their practical implementation under the constraints imposed by tactical platforms is daunting. The situation is further exacerbated by the inconvenient nature of reports from legacy sensor systems on bandwidth- limited communications networks. In this paper, consideration is given to the special difficulties encountered when attempting the correlation of tracks from legacy sensors on tactical aircraft. Those difficulties include the following: covariance information from reporting sensors is frequently absent or incomplete; system latencies can create temporal uncertainty in data; and computational processing is severely limited by hardware and architecture. Moreover, consideration is given to practical solutions for dealing with these problems in a multiple hypothesis correlator.

  3. Parallelism Effects and Verb Activation: The Sustained Reactivation Hypothesis

    PubMed Central

    Shapiro, Lewis P.; Love, Tracy

    2010-01-01

    This study investigated the processes underlying parallelism by evaluating the activation of a parallel element (i.e., a verb) throughout and-coordinated sentences. Four points were tested: (1) approximately 1,600ms after the verb in the first conjunct (PP1), (2) immediately following the conjunction (PP2), (3) approximately 1,100ms after the conjunction (PP3), (4) at the end of the second conjunct (PP4). The results revealed no activation at PP1, suggesting activation related to the initial presentation had decayed by this point; however, activation was observed at PP2, PP3, and PP4, suggesting the conjunction elicits reactivation that is sustained throughout the second conjunct. These findings support a specific hypothesis about parallelism, the sustained reactivation hypothesis. This hypothesis claims that, in conjoined structures, a cue that is associated with parallelism elicits the reactivation of material from the first conjunct and that this activation is sustained until integration with the second conjunct can be completed. PMID:19774464

  4. Mary Lyon and the hypothesis of random X chromosome inactivation.

    PubMed

    Harper, Peter S

    2011-08-01

    The 50th anniversary of Mary Lyon's 1961 Nature paper, proposing random inactivation in early embryonic life of one of the two X chromosomes in the cells of mammalian females, provides an opportunity to remember and celebrate the work of those involved. While the hypothesis was initially put forward by Lyon based on findings in the mouse, it was founded on earlier studies, notably the work of Susumu Ohno; it was also suggested independently by Beutler and colleagues using experimental evidence from a human X-linked disorder, glucose-6-phosphate dehydrogenase deficiency, and has proved to be of as great importance for human and medical genetics as it has for general mammalian genetics. Alongside the hypothesis itself, previous cytological studies of mouse and human chromosomes, and the observations on X-linked mutants in both species deserve recognition for their essential role in underpinning the hypothesis of random X-inactivation, while subsequent research on the X-inactivation centre and the molecular mechanisms underlying the inactivation process represent some of the most outstanding contributions to human and wider mammalian genetics over the past 50 years.

  5. The tagging and capture hypothesis from synapse to memory.

    PubMed

    Viola, Haydée; Ballarini, Fabricio; Martínez, María Cecilia; Moncada, Diego

    2014-01-01

    The synaptic tagging and capture theory (STC) was postulated by Frey and Morris in 1997 and provided a strong framework to explain how to achieve synaptic specificity and persistence of electrophysiological-induced plasticity changes. Ten years later, the same argument was applied on learning and memory models to explain the formation of long-term memories, resulting in the behavioral tagging hypothesis (BT). These hypotheses are able to explain how a weak event that induces transient changes in the brain can establish long-lasting phenomena through a tagging and capture process. In this framework, it was postulated that the weak event sets a tag that captures plasticity-related proteins/products (PRPs) synthesized by an independent strong event. The tagging and capture processes exhibit symmetry, and therefore, PRPs can be captured if they are synthesized either before or after the setting of the tag. In summary, the hypothesis provides a wide framework that gives a solid explanation of how lasting changes occur and how the interaction between different events leads to promotion, reinforcement, or impairment of such changes. In this chapter, we will summarize the postulates of STC hypothesis, the common features between synaptic plasticity and memory, as well as a detailed compilation of the findings supporting the existence of BT process. At the end, we pose some questions related to BT mechanism and LTM formation, which probably will be answered in the near future.

  6. An Analysis of the Matching Hypothesis in Networks.

    PubMed

    Jia, Tao; Spivey, Robert F; Szymanski, Boleslaw; Korniss, Gyorgy

    2015-01-01

    The matching hypothesis in social psychology claims that people are more likely to form a committed relationship with someone equally attractive. Previous works on stochastic models of human mate choice process indicate that patterns supporting the matching hypothesis could occur even when similarity is not the primary consideration in seeking partners. Yet, most if not all of these works concentrate on fully-connected systems. Here we extend the analysis to networks. Our results indicate that the correlation of the couple's attractiveness grows monotonically with the increased average degree and decreased degree diversity of the network. This correlation is lower in sparse networks than in fully-connected systems, because in the former less attractive individuals who find partners are likely to be coupled with ones who are more attractive than them. The chance of failing to be matched decreases exponentially with both the attractiveness and the degree. The matching hypothesis may not hold when the degree-attractiveness correlation is present, which can give rise to negative attractiveness correlation. Finally, we find that the ratio between the number of matched couples and the size of the maximum matching varies non-monotonically with the average degree of the network. Our results reveal the role of network topology in the process of human mate choice and bring insights into future investigations of different matching processes in networks. PMID:26083728

  7. Motor Synergies and the Equilibrium-Point Hypothesis

    PubMed Central

    Latash, Mark L.

    2010-01-01

    The article offers a way to unite three recent developments in the field of motor control and coordination: (1) The notion of synergies is introduced based on the principle of motor abundance; (2) The uncontrolled manifold hypothesis is described as offering a computational framework to identify and quantify synergies; and (3) The equilibrium-point hypothesis is described for a single muscle, single joint, and multi-joint systems. Merging these concepts into a single coherent scheme requires focusing on control variables rather than performance variables. The principle of minimal final action is formulated as the guiding principle within the referent configuration hypothesis. Motor actions are associated with setting two types of variables by a controller, those that ultimately define average performance patterns and those that define associated synergies. Predictions of the suggested scheme are reviewed, such as the phenomenon of anticipatory synergy adjustments, quick actions without changes in synergies, atypical synergies, and changes in synergies with practice. A few models are briefly reviewed. PMID:20702893

  8. Geometric and Topological Invariants of the Hypothesis Space

    NASA Astrophysics Data System (ADS)

    Rodríguez, Carlos C.

    2011-03-01

    The form and shape of a hypothesis space imposes natural objective constraints to any inferential process. This contribution summarizes what is currently known and the mathematics that are thought to be needed for new developments in this area. For example, it is well known that the quality of best possible estimators deteriorates with increasing volume, dimension and curvature of the hypothesis space. It is also known that regular statistical parametric models are finite dimensional Riemannian manifolds admitting a family of dual affine connections. Fisher information is the metric induced on the hypothesis space by the Hellinger distance. Nonparametric models are infinite dimensional manifolds. Global negative curvature implies asymptotic inadmissibility of uniform priors. When there is uncertainty about the model and the prior, entropic methods are more robust than standard Bayesian inference. The presence of some types of singularities allow the existence of faster than normal estimators …, etc. The large number of fundamental statistical concepts with geometric and topological content suggest to try to look at Riemannian Geometry, Algebraic Geometry, K-theory, Algebraic Topology, Knot-theory and other branches of current mathematics, not as empty esoteric abstractions but as allies for statistical inference.

  9. An Analysis of the Matching Hypothesis in Networks

    PubMed Central

    Jia, Tao; Spivey, Robert F.; Szymanski, Boleslaw; Korniss, Gyorgy

    2015-01-01

    The matching hypothesis in social psychology claims that people are more likely to form a committed relationship with someone equally attractive. Previous works on stochastic models of human mate choice process indicate that patterns supporting the matching hypothesis could occur even when similarity is not the primary consideration in seeking partners. Yet, most if not all of these works concentrate on fully-connected systems. Here we extend the analysis to networks. Our results indicate that the correlation of the couple’s attractiveness grows monotonically with the increased average degree and decreased degree diversity of the network. This correlation is lower in sparse networks than in fully-connected systems, because in the former less attractive individuals who find partners are likely to be coupled with ones who are more attractive than them. The chance of failing to be matched decreases exponentially with both the attractiveness and the degree. The matching hypothesis may not hold when the degree-attractiveness correlation is present, which can give rise to negative attractiveness correlation. Finally, we find that the ratio between the number of matched couples and the size of the maximum matching varies non-monotonically with the average degree of the network. Our results reveal the role of network topology in the process of human mate choice and bring insights into future investigations of different matching processes in networks. PMID:26083728

  10. The nephridial hypothesis of the gill slit origin.

    PubMed

    Ezhova, Olga V; Malakhov, Vladimir V

    2015-12-01

    Metameric gill slits are mysterious structures, unique for Chordata and Hemichordata, and also, perhaps, for the extinct Cambrian Calcichordata. There is a discussed hypothesis of the gill slits origin from the metameric nephridia. According to the hypothesis, the hypothetical metameric deuterostome ancestor had in each segment a pair of coelomoducts and a pair of intestinal pockets. In the anterior segments, the coelomoducts have fused with the intestinal pockets. As a result, each nephridium opened both into the gut and into the environment. Then the dissepiments and funnels reduced in all segments except the collar one. Thus, in recent enteropneusts, only the first pair of gill slits keeps the ancestral arrangement communicating at the same time with the gut, with the environment, and with the coelom of the preceding (collar) segment. In the anterior part of the branchio-genital trunk region of enteropneusts, the metameric intestinal pockets remained, as well as the metameric coelomoducts functioning as the ducts of the metameric gonads, i.e., as the gonoducts. The consequence of the hypothesis is that the metameric gill pores originate from the metameric excreting pores, and the metameric branchial sacs originate from the metameric endodermal pockets of the gut fused with the coelomoducts. The metameric gill slits by themselves correspond with metameric openings connecting the gut with metameric intestinal pockets. J. Exp. Zool. (Mol. Dev. Evol.) 324B: 647-652, 2015. © 2015 Wiley Periodicals, Inc.

  11. Language control in bilinguals: The adaptive control hypothesis

    PubMed Central

    Abutalebi, Jubin

    2013-01-01

    Speech comprehension and production are governed by control processes. We explore their nature and dynamics in bilingual speakers with a focus on speech production. Prior research indicates that individuals increase cognitive control in order to achieve a desired goal. In the adaptive control hypothesis we propose a stronger hypothesis: Language control processes themselves adapt to the recurrent demands placed on them by the interactional context. Adapting a control process means changing a parameter or parameters about the way it works (its neural capacity or efficiency) or the way it works in concert, or in cascade, with other control processes (e.g., its connectedness). We distinguish eight control processes (goal maintenance, conflict monitoring, interference suppression, salient cue detection, selective response inhibition, task disengagement, task engagement, opportunistic planning). We consider the demands on these processes imposed by three interactional contexts (single language, dual language, and dense code-switching). We predict adaptive changes in the neural regions and circuits associated with specific control processes. A dual-language context, for example, is predicted to lead to the adaptation of a circuit mediating a cascade of control processes that circumvents a control dilemma. Effective test of the adaptive control hypothesis requires behavioural and neuroimaging work that assesses language control in a range of tasks within the same individual. PMID:25077013

  12. Testing competing forms of the Milankovitch hypothesis: A multivariate approach

    NASA Astrophysics Data System (ADS)

    Kaufmann, Robert K.; Juselius, Katarina

    2016-02-01

    We test competing forms of the Milankovitch hypothesis by estimating the coefficients and diagnostic statistics for a cointegrated vector autoregressive model that includes 10 climate variables and four exogenous variables for solar insolation. The estimates are consistent with the physical mechanisms postulated to drive glacial cycles. They show that the climate variables are driven partly by solar insolation, determining the timing and magnitude of glaciations and terminations, and partly by internal feedback dynamics, pushing the climate variables away from equilibrium. We argue that the latter is consistent with a weak form of the Milankovitch hypothesis and that it should be restated as follows: internal climate dynamics impose perturbations on glacial cycles that are driven by solar insolation. Our results show that these perturbations are likely caused by slow adjustment between land ice volume and solar insolation. The estimated adjustment dynamics show that solar insolation affects an array of climate variables other than ice volume, each at a unique rate. This implies that previous efforts to test the strong form of the Milankovitch hypothesis by examining the relationship between solar insolation and a single climate variable are likely to suffer from omitted variable bias.

  13. A hypothesis on the biological origins and social evolution of music and dance.

    PubMed

    Wang, Tianyan

    2015-01-01

    The origins of music and musical emotions is still an enigma, here I propose a comprehensive hypothesis on the origins and evolution of music, dance, and speech from a biological and sociological perspective. I suggest that every pitch interval between neighboring notes in music represents corresponding movement pattern through interpreting the Doppler effect of sound, which not only provides a possible explanation for the transposition invariance of music, but also integrates music and dance into a common form-rhythmic movements. Accordingly, investigating the origins of music poses the question: why do humans appreciate rhythmic movements? I suggest that human appreciation of rhythmic movements and rhythmic events developed from the natural selection of organisms adapting to the internal and external rhythmic environments. The perception and production of, as well as synchronization with external and internal rhythms are so vital for an organism's survival and reproduction, that animals have a rhythm-related reward and emotion (RRRE) system. The RRRE system enables the appreciation of rhythmic movements and events, and is integral to the origination of music, dance and speech. The first type of rewards and emotions (rhythm-related rewards and emotions, RRREs) are evoked by music and dance, and have biological and social functions, which in turn, promote the evolution of music, dance and speech. These functions also evoke a second type of rewards and emotions, which I name society-related rewards and emotions (SRREs). The neural circuits of RRREs and SRREs develop in species formation and personal growth, with congenital and acquired characteristics, respectively, namely music is the combination of nature and culture. This hypothesis provides probable selection pressures and outlines the evolution of music, dance, and speech. The links between the Doppler effect and the RRREs and SRREs can be empirically tested, making the current hypothesis scientifically

  14. Testing the joint effects hypothesis of elemental defense using Spodoptera exigua.

    PubMed

    Cheruiyot, Dorothy J; Boyd, Robert S; Moar, William

    2015-02-01

    Metal hyperaccumulation may be an elemental defense, in which high concentrations of a metal in plant tissues decrease herbivore survival or growth rate. The Joint Effects Hypothesis suggests that a combination of metals, or a combination of a metal with an organic compound, may have an enhanced defensive effect. The enhancement may be additive or synergistic: in either case the concentration of a particular metal necessary to provide a defensive benefit for the plant is lowered. We tested the Joint Effects Hypothesis using Spodoptera exigua (beet armyworm) neonates fed artificial diets. Metal + metal experiments utilized diets amended with metal pairs, using four metals commonly hyperaccumulated by plants (Co, Cu, Ni, and Zn). We also conducted metal + organic compound experiments, pairing each metal with nicotine, mustard seed powder, or tannic acid. We tested for joint effects using both lethal (LC20 levels) and sublethal concentrations (10-25 % reduced larval weight) of the chemicals tested. For all experiments, either additive or synergistic effects were found. Of the metal + metal pairs tested, three (Co + Cu, Cu + Zn, and Ni + Zn) were synergistic in lethal concentration tests and only Co + Cu was synergistic in sublethal tests. For metal + organic combination lethal tests, synergism occurred for all combinations except for Co or Ni + nicotine, Ni + mustard seed powder, and Zn + nicotine. For sublethal tests, Zn + all three organic chemicals, Co + mustard seed powder or tannic acid, and Cu + nicotine, were synergistic. These results support the Joint Effects Hypothesis, suggesting that metals combined with other metals or organic compounds may be more effective against herbivores than individual metals. PMID:25712748

  15. A hypothesis on the biological origins and social evolution of music and dance.

    PubMed

    Wang, Tianyan

    2015-01-01

    The origins of music and musical emotions is still an enigma, here I propose a comprehensive hypothesis on the origins and evolution of music, dance, and speech from a biological and sociological perspective. I suggest that every pitch interval between neighboring notes in music represents corresponding movement pattern through interpreting the Doppler effect of sound, which not only provides a possible explanation for the transposition invariance of music, but also integrates music and dance into a common form-rhythmic movements. Accordingly, investigating the origins of music poses the question: why do humans appreciate rhythmic movements? I suggest that human appreciation of rhythmic movements and rhythmic events developed from the natural selection of organisms adapting to the internal and external rhythmic environments. The perception and production of, as well as synchronization with external and internal rhythms are so vital for an organism's survival and reproduction, that animals have a rhythm-related reward and emotion (RRRE) system. The RRRE system enables the appreciation of rhythmic movements and events, and is integral to the origination of music, dance and speech. The first type of rewards and emotions (rhythm-related rewards and emotions, RRREs) are evoked by music and dance, and have biological and social functions, which in turn, promote the evolution of music, dance and speech. These functions also evoke a second type of rewards and emotions, which I name society-related rewards and emotions (SRREs). The neural circuits of RRREs and SRREs develop in species formation and personal growth, with congenital and acquired characteristics, respectively, namely music is the combination of nature and culture. This hypothesis provides probable selection pressures and outlines the evolution of music, dance, and speech. The links between the Doppler effect and the RRREs and SRREs can be empirically tested, making the current hypothesis scientifically

  16. A hypothesis on the biological origins and social evolution of music and dance

    PubMed Central

    Wang, Tianyan

    2015-01-01

    The origins of music and musical emotions is still an enigma, here I propose a comprehensive hypothesis on the origins and evolution of music, dance, and speech from a biological and sociological perspective. I suggest that every pitch interval between neighboring notes in music represents corresponding movement pattern through interpreting the Doppler effect of sound, which not only provides a possible explanation for the transposition invariance of music, but also integrates music and dance into a common form—rhythmic movements. Accordingly, investigating the origins of music poses the question: why do humans appreciate rhythmic movements? I suggest that human appreciation of rhythmic movements and rhythmic events developed from the natural selection of organisms adapting to the internal and external rhythmic environments. The perception and production of, as well as synchronization with external and internal rhythms are so vital for an organism's survival and reproduction, that animals have a rhythm-related reward and emotion (RRRE) system. The RRRE system enables the appreciation of rhythmic movements and events, and is integral to the origination of music, dance and speech. The first type of rewards and emotions (rhythm-related rewards and emotions, RRREs) are evoked by music and dance, and have biological and social functions, which in turn, promote the evolution of music, dance and speech. These functions also evoke a second type of rewards and emotions, which I name society-related rewards and emotions (SRREs). The neural circuits of RRREs and SRREs develop in species formation and personal growth, with congenital and acquired characteristics, respectively, namely music is the combination of nature and culture. This hypothesis provides probable selection pressures and outlines the evolution of music, dance, and speech. The links between the Doppler effect and the RRREs and SRREs can be empirically tested, making the current hypothesis scientifically

  17. Entrepreneurship, Information, and Growth

    PubMed Central

    Bunten, Devin; Weiler, Stephan; Weiler, Stephan; Zahran, Sammy

    2016-01-01

    We examine the contribution to economic growth of entrepreneurial “marketplace information” within a regional endogenous growth framework. Entrepreneurs are posited to provide an input to economic growth through the information revealed by their successes and failures. We empirically identify this information source with the regional variation in establishment births and deaths, which create geographic information asymmetries that influence subsequent entrepreneurial activity and economic growth. We find that local establishment birth and death rates are significantly and positively correlated with subsequent entrepreneurship for US counties. To account for the potential endogeneity caused by forward-looking entrepreneurs, we utilize instruments based on historic mining activity. We find that the information spillover component of local establishment birth and death rates have significant positive effects on subsequent entrepreneurship and employment growth for US counties and metropolitan areas. With the help of these intruments, we show that establishment births have a positive and significant effect on future employment growth within all counties, and that in line with the information hypothesis, local establishment death rates have a similar positive effect within metropolitan counties. PMID:27516625

  18. A Critique of One-Tailed Hypothesis Test Procedures in Business and Economics Statistics Textbooks.

    ERIC Educational Resources Information Center

    Liu, Tung; Stone, Courtenay C.

    1999-01-01

    Surveys introductory business and economics statistics textbooks and finds that they differ over the best way to explain one-tailed hypothesis tests: the simple null-hypothesis approach or the composite null-hypothesis approach. Argues that the composite null-hypothesis approach contains methodological shortcomings that make it more difficult for…

  19. Endogamy and suicide: An observation-based hypothesis.

    PubMed

    Jollant, F; Macdonald, C

    2015-11-01

    Suicide is a complex and multifactorial behavior, which is likely the result of distinct pathways in different individuals or groups. Endogamy has been associated with numerous diseases, including behavioral disorders. Here, we discuss the hypothesis of endogamy as one mechanism facilitating high rates of suicide in some small and isolated groups of people across the world. To support our hypothesis, we describe four geographically and culturally distinct populations (the Aguarunas of Peru, the Vaqueiros of Spain, the Baruyas of New Guinea, and the Palawans of the Philippines), which present the following characteristics: (1) a high level of isolation and endogamy; (2) very high rates of suicide restricted to one group with (3) adjacent groups of similar origin and culture displaying low rates of suicide. Within these four distinct populations, endogamy could act in one isolated group as the amplifier of both selected genetic risk alleles and microcultural values (e.g. suicide as an acceptable solution), beyond cultural and genetic traits shared by the whole population (and therefore found in all groups). Genetic and microcultural risk factors are transmitted through close kinship and imitation/modeling, and could interact to increase the frequency of vulnerable individuals leading, in turn, to heightened rates of suicide. Culture could sometimes additionally act by generating stressful conditions for some individuals (e.g. lower social status and maltreatment). In contrast to endogamy, suicide motives (notably interpersonal conflicts) and mental disorders appear to be universal risk factors. More investigation of this endogamy hypothesis is necessary, which could represent a singular case of gene-culture co-transmission and shed light on particular conditions of suicide genesis.

  20. Etiology of inflammatory bowel disease: A unified hypothesis

    PubMed Central

    Qin, Xiaofa

    2012-01-01

    Inflammatory bowel disease (IBD), including both ulcerative colitis (UC) and Crohn’s disease (CD), emerged and dramatically increased for about a century. Despite extensive research, its cause remains regarded as unknown. About a decade ago, a series of findings made me suspect that saccharin may be a key causative factor for IBD, through its inhibition on gut bacteria and the resultant impaired inactivation of digestive proteases and over digestion of the mucus layer and gut barrier (the Bacteria-Protease-Mucus-Barrier hypothesis). It explained many puzzles in IBD such as its emergence and temporal changes in last century. Recently I further found evidence suggesting sucralose may be also linked to IBD through a similar mechanism as saccharin and have contributed to the recent worldwide increase of IBD. This new hypothesis suggests that UC and CD are just two symptoms of the same morbidity, rather than two different diseases. They are both caused by a weakening in gut barrier and only differ in that UC is mainly due to increased infiltration of gut bacteria and the resultant recruitment of neutrophils and formation of crypt abscess, while CD is mainly due to increased infiltration of antigens and particles from gut lumen and the resultant recruitment of macrophages and formation of granulomas. It explained the delayed appearance but accelerated increase of CD over UC and many other phenomena. This paper aims to provide a detailed description of a unified hypothesis regarding the etiology of IBD, including the cause and mechanism of IBD, as well as the relationship between UC and CD. PMID:22553395

  1. How organisms do the right thing: The attractor hypothesis

    USGS Publications Warehouse

    Emlen, J.M.; Freeman, D.C.; Mills, A.; Graham, J.H.

    1998-01-01

    Neo-Darwinian theory is highly successful at explaining the emergence of adaptive traits over successive generations. However, there are reasons to doubt its efficacy in explaining the observed, impressively detailed adaptive responses of organisms to day-to-day changes in their surroundings. Also, the theory lacks a clear mechanism to account for both plasticity and canalization. In effect, there is a growing sentiment that the neo-Darwinian paradigm is incomplete, that something more than genetic structure, mutation, genetic drift, and the action of natural selection is required to explain organismal behavior. In this paper we extend the view of organisms as complex self-organizing entities by arguing that basic physical laws, coupled with the acquisitive nature of organisms, makes adaptation all but tautological. That is, much adaptation is an unavoidable emergent property of organisms' complexity and, to some a significant degree, occurs quite independently of genomic changes wrought by natural selection. For reasons that will become obvious, we refer to this assertion as the attractor hypothesis. The arguments also clarify the concept of "adaptation." Adaptation across generations, by natural selection, equates to the (game theoretic) maximization of fitness (the success with which one individual produces more individuals), while self-organizing based adaptation, within generations, equates to energetic efficiency and the matching of intake and biosynthesis to need. Finally, we discuss implications of the attractor hypothesis for a wide variety of genetical and physiological phenomena, including genetic architecture, directed mutation, genetic imprinting, paramutation, hormesis, plasticity, optimality theory, genotype-phenotype linkage and puncuated equilibrium, and present suggestions for tests of the hypothesis. ?? 1998 American Institute of Physics.

  2. Endogamy and suicide: An observation-based hypothesis.

    PubMed

    Jollant, F; Macdonald, C

    2015-11-01

    Suicide is a complex and multifactorial behavior, which is likely the result of distinct pathways in different individuals or groups. Endogamy has been associated with numerous diseases, including behavioral disorders. Here, we discuss the hypothesis of endogamy as one mechanism facilitating high rates of suicide in some small and isolated groups of people across the world. To support our hypothesis, we describe four geographically and culturally distinct populations (the Aguarunas of Peru, the Vaqueiros of Spain, the Baruyas of New Guinea, and the Palawans of the Philippines), which present the following characteristics: (1) a high level of isolation and endogamy; (2) very high rates of suicide restricted to one group with (3) adjacent groups of similar origin and culture displaying low rates of suicide. Within these four distinct populations, endogamy could act in one isolated group as the amplifier of both selected genetic risk alleles and microcultural values (e.g. suicide as an acceptable solution), beyond cultural and genetic traits shared by the whole population (and therefore found in all groups). Genetic and microcultural risk factors are transmitted through close kinship and imitation/modeling, and could interact to increase the frequency of vulnerable individuals leading, in turn, to heightened rates of suicide. Culture could sometimes additionally act by generating stressful conditions for some individuals (e.g. lower social status and maltreatment). In contrast to endogamy, suicide motives (notably interpersonal conflicts) and mental disorders appear to be universal risk factors. More investigation of this endogamy hypothesis is necessary, which could represent a singular case of gene-culture co-transmission and shed light on particular conditions of suicide genesis. PMID:26206761

  3. [Examination of the hypothesis 'the factors and mechanisms of superiority'].

    PubMed

    Sierra-Fitzgerald, O; Quevedo-Caicedo, J; López-Calderón, M G

    INTRODUCTION. The hypothesis of Geschwind and Galaburda suggests that specific cognitive superiority arises as a result of an alteration in development of the nervous system. In this article we review the co existence of superiority and inferiority . PATIENTS AND METHODS. A study was made of six children aged between 6 and 8 years old at the Instituto de Belles Artes Antonio Maria Valencia in Cali,Columbia with an educational level between second and third grade at a primary school and of medium low socio economic status. The children were considered to have superior musical ability by music experts, which is the way in which the concept of superiority was to be tested. The concept of inferiority was tested by neuropsychological tests = 1.5 DE below normal for the same age. We estimated the perinatal neurological risk in each case. Subsequently the children s general intelligence and specific cognitive abilities were evaluated. In the first case the WISC R and MSCA were used. The neuropsychological profiles were obtained by broad evaluation using a verbal fluency test, a test using counters, Boston vocabulary test, the Wechster memory scale, sequential verbal memory test, super imposed figures test, Piaget Head battery, Rey Osterrieth complex figure and the Wisconsin card classification test. The RESULTS showed slight/moderate deficits in practical construction ability and mild defects of memory and concept abilities. In general the results supported the hypothesis tested. The mechanisms of superiority proposed in the classical hypothesis mainly involve the contralateral hemisphere: in this study the ipsilateral mechanism was more important.

  4. Early injury of the neonatal lung contributes to premature lung aging: a hypothesis.

    PubMed

    Meiners, Silke; Hilgendorff, Anne

    2016-12-01

    Chronic lung disease of the newborn, also known as bronchopulmonary dysplasia (BPD), is the most common chronic lung disease in early infancy and results in an increased risk for long-lasting pulmonary impairment in the adult. BPD develops upon injury of the immature lung by oxygen toxicity, mechanical ventilation, and infections which trigger sustained inflammatory immune responses and extensive remodeling of the extracellular matrix together with dysregulated growth factor signaling. Histopathologically, BPD is characterized by impaired alveolarization, disrupted vascular development, and saccular wall fibrosis. Here, we explore the hypothesis that development of BPD involves disturbance of conserved pathways of molecular aging that may contribute to premature aging of the lung and an increased susceptibility to chronic lung diseases in adulthood. PMID:27406259

  5. Autumn leaf colouration: a new hypothesis involving plant-ant mutualism via aphids

    NASA Astrophysics Data System (ADS)

    Yamazaki, Kazuo

    2008-07-01

    Several recent hypotheses on the adaptive significance of autumn leaf colours have focused on specialist aphids. However, these hypotheses have overlooked several factors: the preferential investment by healthy vigorous trees in growth rather than defence against herbivores, variation among aphid species in their responses to bright autumn leaves and plant defences and the occurrence of tritrophic interactions in tree crowns. I incorporate these factors into a hypothesis that autumn leaf colours signal tree quality to myrmecophilous specialist aphids, with the aphids, in turn, attracting aphid-tending ants during the following spring, and the ants defending the trees from other aphids and herbivores. Therefore, bright autumn leaves may have adaptive significance, attracting myrmecophilous specialist aphids and their attending ants and, thus, reducing herbivory and competition among aphids.

  6. Hypothesis: Hemolytic Transfusion Reactions Represent an Alternative Type of Anaphylaxis

    PubMed Central

    Hod, Eldad A.; Sokol, Set A.; Zimring, James C.; Spitalnik, Steven L.

    2009-01-01

    Classical anaphylaxis is the most severe, and potentially fatal, type of allergic reaction, manifested by hypotension, bronchoconstriction, and vascular permeability. Similarly, a hemolytic transfusion reaction (HTR) is the most feared consequence of blood transfusion. Evidence for the existence of an alternative, IgG-mediated pathway of anaphylaxis may be relevant for explaining the pathophysiology of IgG-mediated-HTRs. The purpose of this review is to summarize the evidence for this alternative pathway of anaphylaxis and to present the hypothesis that an IgG-mediated HTR is one example of this type of anaphylaxis. PMID:18830382

  7. Insights in Hypothesis Testing and Making Decisions in Biomedical Research

    PubMed Central

    Sacha, Varin; Panagiotakos, Demosthenes B.

    2016-01-01

    It is a fact that p values are commonly used for inference in biomedical and other social fields of research. Unfortunately, the role of p value is very often misused and misinterpreted; that is why it has been recommended the use of resampling methods, like the bootstrap method, to calculate the confidence interval, which provides more robust results for inference than does p value. In this review a discussion is made about the use of p values through hypothesis testing and its alternatives using resampling methods to develop confidence intervals of the tested statistic or effect measure. PMID:27733868

  8. Robust operative diagnosis as problem solving in a hypothesis space

    NASA Technical Reports Server (NTRS)

    Abbott, Kathy H.

    1988-01-01

    This paper describes an approach that formulates diagnosis of physical systems in operation as problem solving in a hypothesis space. Such a formulation increases robustness by: (1) incremental hypotheses construction via dynamic inputs, (2) reasoning at a higher level of abstraction to construct hypotheses, and (3) partitioning the space by grouping fault hypotheses according to the type of physical system representation and problem solving techniques used in their construction. It was implemented for a turbofan engine and hydraulic subsystem. Evaluation of the implementation on eight actual aircraft accident cases involving engine faults provided very promising results.

  9. One-Shot Classical-Quantum Capacity and Hypothesis Testing

    NASA Astrophysics Data System (ADS)

    Wang, Ligong; Renner, Renato

    2012-05-01

    The one-shot classical capacity of a quantum channel quantifies the amount of classical information that can be transmitted through a single use of the channel such that the error probability is below a certain threshold. In this work, we show that this capacity is well approximated by a relative-entropy-type measure defined via hypothesis testing. Combined with a quantum version of Stein’s lemma, our results give a conceptually simple proof of the well-known Holevo-Schumacher-Westmoreland theorem for the capacity of memoryless channels. More generally, we obtain tight capacity formulas for arbitrary (not necessarily memoryless) channels.

  10. Complement Propriety and Conspiracy in Nanomedicine: Perspective and a Hypothesis.

    PubMed

    Moghimi, Seyed Moein

    2016-04-01

    The complement system is the first line of body's defense against intruders and it acts as a functional bridge between innate and adaptive arms of the immune system. This commentary examines the key roles of complement activation in response to nanomedicine administration, including nucleic acid complexes. These comprise beneficial (eg, adjuvanticity) as well as adverse effects (eg, infusion-related reactions). Pigs (and sheep) are often used as predictive models of nanomedicine-mediated infusion-related reactions in humans. The validity of these models in relation to human responses is questioned, and an alternative hypothesis is presented. PMID:26720796

  11. The biofield hypothesis: its biophysical basis and role in medicine.

    PubMed

    Rubik, Beverly

    2002-12-01

    This paper provides a scientific foundation for the biofield: the complex, extremely weak electromagnetic field of the organism hypothesized to involve electromagnetic bioinformation for regulating homeodynamics. The biofield is a useful construct consistent with bioelectromagnetics and the physics of nonlinear, dynamical, nonequilibrium living systems. It offers a unifying hypothesis to explain the interaction of objects or fields with the organism, and is especially useful toward understanding the scientific basis of energy medicine, including acupuncture, biofield therapies, bioelectromagnetic therapies, and homeopathy. The rapid signal propagation of electromagnetic fields comprising the biofield as well as its holistic properties may account for the rapid, holistic effects of certain alternative and complementary medical interventions.

  12. Human Cancers Express a Mutator Phenotype: Hypothesis, Origin, and Consequences.

    PubMed

    Loeb, Lawrence A

    2016-04-15

    The mutator phenotype hypothesis was postulated more than 40 years ago. It was based on the multiple enzymatic steps required to precisely replicate the 6 billion bases in the human genome each time a normal cell divides. A reduction in this accuracy during tumor progression could be responsible for the striking heterogeneity of malignant cells within a tumor and for the rapidity by which cancers become resistant to therapy. Cancer Res; 76(8); 2057-9. ©2016 AACRSee related article by Loeb et al. Cancer Res. 1974;34:2311-21.

  13. A multi-hypothesis tracker for clicking whales.

    PubMed

    Baggenstoss, Paul M

    2015-05-01

    This paper describes a tracker specially designed to track clicking beaked whales using widely spaced bottom-mounted hydrophones, although it can be adapted to different species and sensors. The input to the tracker is a sequence of static localization solutions obtained using time difference of arrival information at widely spaced hydrophones. To effectively handle input localizations with high ambiguity, the tracker is based on multi-hypothesis tracker concepts, so it considers all potential association hypotheses and keeps a large number of potential tracks in memory. The method is demonstrated on actual data and shown to successfully track multiple beaked whales at depth.

  14. Yawning, fatigue, and cortisol: expanding the Thompson Cortisol Hypothesis.

    PubMed

    Thompson, Simon B N

    2014-10-01

    Yawning and its involvement in neurological disorders has become the new scientific conundrum. Cortisol levels are known to rise during stress and fatigue; yawning may occur when we are under stress or tired. However, the link between yawning, fatigue, and cortisol has not been fully understood. Expansion of the Thompson Cortisol Hypothesis proposes that the stress hormone, cortisol, is responsible for yawning and fatigue especially in people with incomplete innervation such as multiple sclerosis. This informs our understanding of the functional importance of the brain stem region of the brain in regulating stress and fatigue.

  15. Inclination flattening and the geocentric axial dipole hypothesis [rapid communication

    NASA Astrophysics Data System (ADS)

    Tauxe, Lisa

    2005-05-01

    William Gilbert first articulated what has come to be known as the geocentric axial dipole hypothesis. The GAD hypothesis is the principle on which paleogeographic reconstructions rely to constrain paleolatitude. For decades, there have been calls for permanent non-dipole contributions to the time-averaged field. Recently, these have demanded large contributions of the axial octupole, which, if valid, would call into question the general utility of the GAD hypothesis. In the process of geological recording of the geomagnetic field, "Earth filters" distort the directions. Many processes, for example, sedimentary inclination flattening and random tilting, can lead to a net shallowing of the observed direction. Therefore, inclinations that are shallower than expected from GAD can be explained by recording biases, northward transport, or non-dipole geomagnetic fields. Using paleomagnetic data from the last 5 million years from well-constrained lava flow data allows the construction of a statistical geomagnetic field model. Such a model can predict not only the average expected direction for a given latitude, but also the shape of the distribution of directions produced by secular variation. The elongation of predicted directions varies as a function of latitude (from significantly elongate in the up/down direction at the equator to circularly symmetric at the poles). Sedimentary inclination flattening also works in a predictable manner producing elongations that are stretched side to side and the degree of flattening depending on the inclination of the applied field and a "flattening factor" f. The twin tools of the predicted elongation/inclination relationship characteristic of the geomagnetic field for the past 5 million years and the distortion of the directions predicted from sedimentary inclination flattening allows us to find the flattening factor that yields corrected directions with an elongation and average inclination consistent with the statistical field

  16. The regression hypothesis: communicative continuum vs. parametrically defined grammars.

    PubMed

    Schnitzer, M L

    1995-02-01

    Proposals concerning the regression hypothesis in aphasia presented in Grodzinsky (1990) and Schnitzer (1989, 1990) are compared. It is argued that Grodzinsky's model, which is syndrome-based, is observationally inadequate, and thus fails to lend aphasiological support to a neurophysiologically realized central language system along the lines of Chomsky's Theory of Principles and Parameters. Schnitzer's approach rejects the notion of mental grammars and interprets aphasic regression microgenetically, along the lines of Givón's continuum. It is argued that this approach has the potential to become truly explanatory. PMID:7728515

  17. Yawning, fatigue, and cortisol: expanding the Thompson Cortisol Hypothesis.

    PubMed

    Thompson, Simon B N

    2014-10-01

    Yawning and its involvement in neurological disorders has become the new scientific conundrum. Cortisol levels are known to rise during stress and fatigue; yawning may occur when we are under stress or tired. However, the link between yawning, fatigue, and cortisol has not been fully understood. Expansion of the Thompson Cortisol Hypothesis proposes that the stress hormone, cortisol, is responsible for yawning and fatigue especially in people with incomplete innervation such as multiple sclerosis. This informs our understanding of the functional importance of the brain stem region of the brain in regulating stress and fatigue. PMID:25169036

  18. HLA-sharing, recurrent spontaneous abortion, and the genetic hypothesis

    SciTech Connect

    Hedrick, P.W.

    1988-05-01

    A number of studies indicates that there is a high sharing of HLA antigens in couples having recurrent spontaneous abortions. The genetic hypothesis to explain this phenomenon suggests that this fetal loss results from homozygosity of recessive lethal or deleterius alleles in gametic disequilibrium with HLA antigens. Theory predicting the lethality rate is derived when antigens are shared at one, two or three loci, given the disequilibrium is absolute. In addition, the effects of partial disequilibrium, inbreeding, and segregation distortion on the lethal proportion are examined.

  19. Evaluation of the endogenous glucocorticoid hypothesis of denervation atrophy

    NASA Technical Reports Server (NTRS)

    Konagaya, Masaaki; Konagaya, Yoko; Max, Stephen R.

    1988-01-01

    The effects are studied of the oral administration of RU38486, a potent selective glucocorticoid antagonist, on muscle weight, non-collagen protein content, and selected enzyme activities (choline acetyltransferase, glucose 6-phosphate dehydrogenase, and glutamine synthetase) following denervation of rat skeletal muscle. Neither decreases in muscle weight, protein content, and choline acetyltransferase activity, nor increases in the activities of glucose 6-phosphate dehydrogernase and glutamine synthetase were affected by RU38486. These data do not support the hypothesis that denervation atrophy results from enhanced sensitivity of muscle to endogenous glucocorticoids.

  20. Mouth Growths

    MedlinePlus

    ... Dry Mouth Mouth Growths Mouth Sores and Inflammation Toothache Malocclusion Teeth Grinding Recurrent Aphthous Stomatitis Growths can ... Dry Mouth Mouth Growths Mouth Sores and Inflammation Toothache Malocclusion Teeth Grinding Recurrent Aphthous Stomatitis NOTE: This ...

  1. The plant stress hypothesis and variable responses by blue grama grass (Bouteloua gracilis) to water, mineral nitrogen, and insect herbivory.

    PubMed

    Joern, Anthony; Mole, Simon

    2005-09-01

    Acting simultaneously or sequentially, plants encounter multiple stresses from combined abiotic and biotic factors that result in decreased growth and internal reallocation of resources. The plant stress hypothesis predicts that environmental stresses on plants decrease plant resistance to insect herbivory by altering biochemical source-sink relationships and foliar chemistry, leading to more palatable food. Such changes in the nutritional landscape for insects may facilitate insect population outbreaks during periods of moderate stress on host plants. We examined the plant stress hypothesis with field experiments in continental grassland (USA) using the C4 grass Bouteloua gracilis. Water, nitrogen fertilizer, and herbivory from the grass-feeding grasshopper Ageneotettix deorum were manipulated. Combined stresses from water and mineral-N in the soil decreased plant growth and altered foliar percent total N (TN) and percent total nonstructural carbohydrate (TNC) concentrations in an additive fashion. Grasshopper herbivory affected final biomass only in dry years; plants compensated for tissue loss when rainfall was abundant. Foliar TN and TNC concentrations were dynamic with respect to variable climatic conditions and treatment combinations, showing significant interactions. Grasshopper herbivory had its greatest impact on TN or TNC in dry years, interacting with other forms of stress. Herbivory as a single factor had strong effects on TNC in years with normal precipitation, but not in a dry year. Performance (developmental rate and survival) by the grasshoppers Phoetaliotes nebrascensis and A. deorum were not greatly affected by plant stress in a manner consistent with the plant stress hypothesis.

  2. Analyzing Quasi-Experiments: Some Implications of Assuming Continuous Growth Models.

    ERIC Educational Resources Information Center

    Blumberg, Carol Joyce; Porter, Andrew C.

    1983-01-01

    The general class of continuous growth models are described and examples representative of growth models suggested for various types of academic and/or physical growth are given. The fan spread hypothesis is discussed in relationship to natural growth models, as well as differential linear growth. (PN)

  3. The apparency hypothesis applied to a local pharmacopoeia in the Brazilian northeast

    PubMed Central

    2014-01-01

    Background Data from an ethnobotanical study were analyzed to see if they were in agreement with the biochemical basis of the apparency hypothesis based on an analysis of a pharmacopeia in a rural community adjacent to the Araripe National Forest (Floresta Nacional do Araripe - FLONA) in northeastern Brazil. The apparency hypothesis considers two groups of plants, apparent and non-apparent, that are characterized by conspicuity for herbivores (humans) and their chemical defenses. Methods This study involved 153 interviewees and used semi-structured interviews. The plants were grouped by habit and lignification to evaluate the behavior of these categories in terms of ethnospecies richness, use value and practical and commercial importance. Information about sites for collecting medicinal plants was also obtained. The salience of the ethnospecies was calculated. G-tests were used to test for differences in ethnospecies richness among collection sites and the Kruskal-Wallis test to identify differences in the use values of plants depending on habit and lignifications (e.g. plants were classes as woody or non-woody, the first group comprising trees, shrubs, and lignified climbers (vines) and the latter group comprising herbs and non-lignified climbers). Spearman’s correlation test was performed to relate salience to use value and these two factors with the commercial value of the plants. Results A total of 222 medicinal plants were cited. Herbaceous and woody plants exhibited the highest ethnospecies richness, the non-woody and herbaceous plants had the most practical value (current use), and anthropogenic areas were the main sources of woody and non-woody medicinal plants; herbs and trees were equally versatile in treating diseases and did not differ with regard to use value. Trees were highlighted as the most commercially important growth habit. Conclusions From the perspective of its biochemical fundamentals, the apparency hypothesis does not have predictive

  4. Empirical tests of the Chicago model and the Easterlin hypothesis: a case study of Japan.

    PubMed

    Ohbuchi, H

    1982-05-01

    The objective of this discussion is to test the applicability of economic theory of fertility with special reference to postwar Japan and to find a clue for forecasting the future trend of fertility. The theories examined are the "Chicago model" and the "Easterlin hypothesis." The major conclusion common among the leading economic theories of fertility, which have their origin with Gary S. Becker (1960, 1965) and Richard A. Easterlin (1966), is the positive income effect, i.e., that the relationship between income and fertility is positive despite the evidence that higher income families have fewer children and that fertility has declined with economic development. To bridge the gap between theory and fact is the primary purpose of the economic theory of fertility, and each offers a different interpretation for it. The point of the Chicago model, particularly of the household decision making model of the "new home economics," is the mechanism that a positive effect of husband's income growth on fertility is offset by a negative price effect caused by the opportunity cost of wife's time. While the opportunity cost of wife's time is independent of the female wage rate for an unemployed wife, it is directly associated with the wage rate for a gainfully employed wife. Thus, the fertility response to female wages occurs only among families with an employed wife. The primary concern of empirical efforts to test the Chicago model has been with the determination of income and price elasticities. An attempt is made to test the relevance of the Chicago model and the Easterlin hypothesis in explaning the fertility movement in postwar Japan. In case of the Chicago model, the statistical results appeared fairly successful but did not match with the theory. The effect on fertility of a rise in women's real wage (and, therefore in the opportunity cost of mother's time) and of a rise in labor force participation rate of married women of childbearing age in recent years could not

  5. The history and reception of Charles Darwin's hypothesis of pangenesis.

    PubMed

    Holterhoff, Kate

    2014-01-01

    This paper explores Charles Darwin's hypothesis of pangenesis through a popular and professional reception history. First published in The Variation of Animals and Plants under Domestication (1868), pangenesis stated that inheritance can be explained by sub-cellular "gemmules" which aggregated in the sexual organs during intercourse. Pangenesis thereby accounted for the seemingly arbitrary absence and presence of traits in offspring while also clarifying some botanical and invertebrates' limb regeneration abilities. I argue that critics largely interpreted Variation as an extension of On the Origin of Species by Means of Natural Selection (1859), while pangenesis was an extension of natural selection. Contrary to claims that pangenesis was divorced from natural selection by its reliance on the inheritance of acquired characters, pangenesis's mid nineteenth-century reception suggests that Darwin's hypothesis responded directly to selection's critics. Using Variation's several editions, periodical reviews, and personal correspondence I assess pangenesis popularly, professionally, and biographically to better understand Variation's impact on 1860s and 70s British evolutionism and inheritance. PMID:24570302

  6. Marine radionuclide transfer factors in chordates and a phylogenetic hypothesis.

    PubMed

    Jeffree, Ross A; Oberhaensli, Francois; Teyssie, Jean-Louis

    2013-12-01

    Previous radiotracer experiments that compared multi-elemental whole organism: water transfer factors among chondrichthyan and teleost fishes, including an ICRP reference flatfish Psetta maxima, demonstrated distinctive contrasts in their bioaccumulation characteristics, with generally elevated bioaccumulation in chondrichthyans. These results supported a hypothesis that phylogenetic divergence may influence marine radionuclide transfer factors. This notion has been further evaluated in an amphioxus species Branchiostoma lanceolatum, sub-phylum Cephalochordata. This taxon diverged about 800 MYBP from a common ancestor of the teleosts and the chondrichthyans, which in turn diverged from each other around 500 MYBP. Our experimental results indicate that amphioxus is indeed more divergent in its multi-elemental bioaccumulation patterns from teleosts and chondrichthyans than they are from each other, consistent with our hypothesis. The experimental comparisons with the ICRP reference flatfish P. maxima also revealed an unexpectedly enhanced capacity in amphioxus to accumulate all eight tested trace elements from seawater, and for some by more than two orders of magnitude. These results have practical applications for the strategic selection of marine biota for further radioecological investigations to better guarantee the radiological protection of marine biodiversity. Such seemingly anomalous results for understudied biota like amphioxus and chondrichthyans suggest that more effort in marine radioecology be directed to assessing the bioaccumulatory capacities of other phylogenetic groups that have received less attention so far, particularly those that are phylogenetically more remote from commonly investigated taxa and those nominated as ICRP marine reference organisms.

  7. Marine radionuclide transfer factors in chordates and a phylogenetic hypothesis.

    PubMed

    Jeffree, Ross A; Oberhaensli, Francois; Teyssie, Jean-Louis

    2013-12-01

    Previous radiotracer experiments that compared multi-elemental whole organism: water transfer factors among chondrichthyan and teleost fishes, including an ICRP reference flatfish Psetta maxima, demonstrated distinctive contrasts in their bioaccumulation characteristics, with generally elevated bioaccumulation in chondrichthyans. These results supported a hypothesis that phylogenetic divergence may influence marine radionuclide transfer factors. This notion has been further evaluated in an amphioxus species Branchiostoma lanceolatum, sub-phylum Cephalochordata. This taxon diverged about 800 MYBP from a common ancestor of the teleosts and the chondrichthyans, which in turn diverged from each other around 500 MYBP. Our experimental results indicate that amphioxus is indeed more divergent in its multi-elemental bioaccumulation patterns from teleosts and chondrichthyans than they are from each other, consistent with our hypothesis. The experimental comparisons with the ICRP reference flatfish P. maxima also revealed an unexpectedly enhanced capacity in amphioxus to accumulate all eight tested trace elements from seawater, and for some by more than two orders of magnitude. These results have practical applications for the strategic selection of marine biota for further radioecological investigations to better guarantee the radiological protection of marine biodiversity. Such seemingly anomalous results for understudied biota like amphioxus and chondrichthyans suggest that more effort in marine radioecology be directed to assessing the bioaccumulatory capacities of other phylogenetic groups that have received less attention so far, particularly those that are phylogenetically more remote from commonly investigated taxa and those nominated as ICRP marine reference organisms. PMID:22800799

  8. Pornography actresses: an assessment of the damaged goods hypothesis.

    PubMed

    Griffith, James D; Mitchell, Sharon; Hart, Christian L; Adams, Lea T; Gu, Lucy L

    2013-01-01

    The damaged goods hypothesis posits that female performers in the adult entertainment industry have higher rates of childhood sexual abuse (CSA), psychological problems, and drug use compared to the typical woman. The present study compared the self-reports of 177 porn actresses to a sample of women matched on age, ethnicity, and marital status. Comparisons were conducted on sexual behaviors and attitudes, self-esteem, quality of life, and drug use. Porn actresses were more likely to identify as bisexual, first had sex at an earlier age, had more sexual partners, were more concerned about contracting a sexually transmitted disease (STD), and enjoyed sex more than the matched sample, although there were no differences in incidence of CSA. In terms of psychological characteristics, porn actresses had higher levels of self-esteem, positive feelings, social support, sexual satisfaction, and spirituality compared to the matched group. Last, female performers were more likely to have ever used 10 different types of drugs compared to the comparison group. A discriminant function analysis was able to correctly classify 83% of the participants concerning whether they were a porn actress or member of the matched sample. These findings did not provide support for the damaged goods hypothesis. PMID:23167939

  9. The history and reception of Charles Darwin's hypothesis of pangenesis.

    PubMed

    Holterhoff, Kate

    2014-01-01

    This paper explores Charles Darwin's hypothesis of pangenesis through a popular and professional reception history. First published in The Variation of Animals and Plants under Domestication (1868), pangenesis stated that inheritance can be explained by sub-cellular "gemmules" which aggregated in the sexual organs during intercourse. Pangenesis thereby accounted for the seemingly arbitrary absence and presence of traits in offspring while also clarifying some botanical and invertebrates' limb regeneration abilities. I argue that critics largely interpreted Variation as an extension of On the Origin of Species by Means of Natural Selection (1859), while pangenesis was an extension of natural selection. Contrary to claims that pangenesis was divorced from natural selection by its reliance on the inheritance of acquired characters, pangenesis's mid nineteenth-century reception suggests that Darwin's hypothesis responded directly to selection's critics. Using Variation's several editions, periodical reviews, and personal correspondence I assess pangenesis popularly, professionally, and biographically to better understand Variation's impact on 1860s and 70s British evolutionism and inheritance.

  10. Fungal communities as an experimental approach to Darwin's naturalization hypothesis.

    PubMed

    Morales, María Camila; Verdejo, Valentina; Orlando, Julieta; Carú, Margarita

    2016-01-01

    Darwin's naturalization hypothesis suggests that the success of an invasive species will be lower when colonizing communities are formed by phylogenetically related rather than unrelated species due to increased competition. Although microbial invasions are involved in both natural and anthropogenic processes, factors affecting the success of microbial invaders are unknown. A biological invasion assay was designed using Trichoderma cf. harzianum as the invader and two types of recipient communities assembled in microcosm assays: communities phylogenetically related to the invader, and communities phylogenetically unrelated to it. Both types of communities were invaded by T. cf. harzianum, and the success of colonization was monitored by qPCR; its effect on the genetic structure of recipient fungal communities was then assessed by DGGE profiles. T. cf. harzianum established itself in both communities, reaching 1000-10,000 times higher copy numbers in the non-related communities. However, invader establishment does not affect the structure of the invaded communities. These results suggest that the composition of recipient communities and their phylogenetic relationship to the invader affect the success of colonization by T. cf. harzianum. While this approach represents a very simplified assay, these microcosms enable an experimental test of Darwin's hypothesis in order to understand the biological invasion process in microbial communities. PMID:26506029

  11. A HYPOTHESIS FOR THE COLOR DIVERSITY OF THE KUIPER BELT

    SciTech Connect

    Brown, M. E.; Fraser, W. C.; Schaller, E. L.

    2011-10-01

    We propose a chemical and dynamical process to explain the surface colors of the Kuiper belt. In our hypothesis, the initial bulk compositions of the bodies themselves can be quite diverse-as is seen in comets-but the early surface compositions are set by volatile evaporation after the objects are formed. Strong gradients in surface composition, coupled with UV and particle irradiation, lead to the surface colors that are seen today. The objects formed in the inner part of the primordial belt retain only H{sub 2}O and CO{sub 2} as the major ice species on their surfaces. Irradiation of these species plausibly results in the dark neutrally colored centaurs and Kuiper belt objects (KBOs). Object formed further in the disk retain CH{sub 3}OH, which has been shown to lead to brighter redder surfaces after irradiation, as seen in the brighter redder centaurs and KBOs. Objects formed at the current location of the cold classical Kuiper belt uniquely retain NH{sub 3}, which has been shown to affect irradiation chemistry and could plausibly lead to the unique colors of these objects. We propose observational and experimental tests of this hypothesis.

  12. Testing the depth-differentiation hypothesis in a deepwater octocoral.

    PubMed

    Quattrini, Andrea M; Baums, Iliana B; Shank, Timothy M; Morrison, Cheryl L; Cordes, Erik E

    2015-05-22

    The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200-1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations.

  13. The szilard hypothesis on the nature of aging revisited.

    PubMed

    Zetterberg, Henrik; Båth, Magnus; Zetterberg, Madeleine; Bernhardt, Peter; Hammarsten, Ola

    2009-05-01

    This year marks the 50th anniversary of a nearly forgotten hypothesis on aging by Leo Szilard, best known for his pioneering work in nuclear physics, his participation in the Manhattan Project during World War II, his opposition to the nuclear arms race in the postwar era, and his pioneering ideas in biology. Given a specific set of assumptions, Szilard hypothesized that the major reason for the phenomenon of aging was aging hits, e.g., by ionizing radiation, to the gene-bearing chromosomes and presented a mathematical target-hit model enabling the calculation of the average and maximum life span of a species, as well as the influence of increased exposure to DNA-damaging factors on life expectancy. While many new findings have cast doubt on the specific features of the model, this was the first serious effort to posit accumulated genetic damage as a cause of senescence. Here, we review Szilard's assumptions in the light of current knowledge on aging and reassess his mathematical model in an attempt to reach a conclusion on the relevance of Szilard's aging hypothesis today.

  14. Antiracism and the level of health services: a sociomedical hypothesis.

    PubMed

    Schatzkin, A; Cooper, R; Green, L

    1984-04-01

    Little attention has been paid to the validity of the "reverse discrimination" position that antiracist initiatives in the health sector would be associated with reduced services for whites. This paper advances the sociomedical hypothesis that antiracism leads to an increase in the level of health services and opportunities available to both minority and white populations.FOUR TYPES OF US HEALTH CARE UTILIZATION AND TRAINING DATA ARE EXPLORED: annual rates of discharge from short-stay hospitals, percent of population seeing a physician during the year, rates of hypertension treatment and control, and admissions to the first-year class of US medical schools. These data are examined according to race for years prior and subsequent to the upsurge of antiracist activity that characterized the Civil Rights Movement era.From the early or mid-1960s to the mid- or late 1970s, hospital discharges, physician visits, and hypertension treatment and control for minorities and whites increased substantially. Generally these increases were proportionally greater for minorities. Although the percentage of increase in minority medical school admissions was necessarily accompanied by a decline in percentage of admissions of whites, the absolute number of whites admitted rose substantially as overall class size grew.These data do not support the "reverse discrimination" notion of one racial group benefiting at the expense of another. The data are consistent with the hypothesis that antiracist efforts in the health sector lead to an expansion of services and opportunities for minority and majority populations.

  15. Testing the depth-differentiation hypothesis in a deepwater octocoral.

    PubMed

    Quattrini, Andrea M; Baums, Iliana B; Shank, Timothy M; Morrison, Cheryl L; Cordes, Erik E

    2015-05-22

    The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200-1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations. PMID:25904664

  16. The Szilard Hypothesis on the Nature of Aging Revisited

    PubMed Central

    Zetterberg, Henrik; Båth, Magnus; Zetterberg, Madeleine; Bernhardt, Peter; Hammarsten, Ola

    2009-01-01

    This year marks the 50th anniversary of a nearly forgotten hypothesis on aging by Leo Szilard, best known for his pioneering work in nuclear physics, his participation in the Manhattan Project during World War II, his opposition to the nuclear arms race in the postwar era, and his pioneering ideas in biology. Given a specific set of assumptions, Szilard hypothesized that the major reason for the phenomenon of aging was aging hits, e.g., by ionizing radiation, to the gene-bearing chromosomes and presented a mathematical target-hit model enabling the calculation of the average and maximum life span of a species, as well as the influence of increased exposure to DNA-damaging factors on life expectancy. While many new findings have cast doubt on the specific features of the model, this was the first serious effort to posit accumulated genetic damage as a cause of senescence. Here, we review Szilard's assumptions in the light of current knowledge on aging and reassess his mathematical model in an attempt to reach a conclusion on the relevance of Szilard's aging hypothesis today. PMID:19403867

  17. Partner choice, relationship satisfaction, and oral contraception: the congruency hypothesis.

    PubMed

    Roberts, S Craig; Little, Anthony C; Burriss, Robert P; Cobey, Kelly D; Klapilová, Kateřina; Havlíček, Jan; Jones, Benedict C; DeBruine, Lisa; Petrie, Marion

    2014-07-01

    Hormonal fluctuation across the menstrual cycle explains temporal variation in women's judgment of the attractiveness of members of the opposite sex. Use of hormonal contraceptives could therefore influence both initial partner choice and, if contraceptive use subsequently changes, intrapair dynamics. Associations between hormonal contraceptive use and relationship satisfaction may thus be best understood by considering whether current use is congruent with use when relationships formed, rather than by considering current use alone. In the study reported here, we tested this congruency hypothesis in a survey of 365 couples. Controlling for potential confounds (including relationship duration, age, parenthood, and income), we found that congruency in current and previous hormonal contraceptive use, but not current use alone, predicted women's sexual satisfaction with their partners. Congruency was not associated with women's nonsexual satisfaction or with the satisfaction of their male partners. Our results provide empirical support for the congruency hypothesis and suggest that women's sexual satisfaction is influenced by changes in partner preference associated with change in hormonal contraceptive use.

  18. Machine learning and data mining: strategies for hypothesis generation.

    PubMed

    Oquendo, M A; Baca-Garcia, E; Artés-Rodríguez, A; Perez-Cruz, F; Galfalvy, H C; Blasco-Fontecilla, H; Madigan, D; Duan, N

    2012-10-01

    Strategies for generating knowledge in medicine have included observation of associations in clinical or research settings and more recently, development of pathophysiological models based on molecular biology. Although critically important, they limit hypothesis generation to an incremental pace. Machine learning and data mining are alternative approaches to identifying new vistas to pursue, as is already evident in the literature. In concert with these analytic strategies, novel approaches to data collection can enhance the hypothesis pipeline as well. In data farming, data are obtained in an 'organic' way, in the sense that it is entered by patients themselves and available for harvesting. In contrast, in evidence farming (EF), it is the provider who enters medical data about individual patients. EF differs from regular electronic medical record systems because frontline providers can use it to learn from their own past experience. In addition to the possibility of generating large databases with farming approaches, it is likely that we can further harness the power of large data sets collected using either farming or more standard techniques through implementation of data-mining and machine-learning strategies. Exploiting large databases to develop new hypotheses regarding neurobiological and genetic underpinnings of psychiatric illness is useful in itself, but also affords the opportunity to identify novel mechanisms to be targeted in drug discovery and development.

  19. [Hygienic hypothesis in immunopathogenesis of inflammatory bowel disease].

    PubMed

    Gonciarz, Maciej; Szkudłapski, Dawid; Mularczyk, Aldona; Smagacz, Justyna

    2016-06-01

    Over three last decades, it has been noticed that morbidity of immunology-dependent illnesses, like asthma, inflammatory bowel disease or atopic dermatitis, apparently increased. That is the reason to focus on searching and exploring new ideas which could explain etiopathology of those diseases. In etiopathology the role of environmental factors is particularly emphasized. Research indicated the inverse relationship between the frequency of infectious and/ or parasites and autoimmune diseases. It was a leading subject of many studies what allowed to create a hypothesis which explains the phenomenon. The most original and innovative idea, named hygenic hypothesis, was proposed in the late 80s of the last century. Avoiding or limiting the contact with common bacteria and parasites in well-and very well-developed countries probably caused depletion of immune memory which resulted in the hypersensitive response after exposure to general factors. Nowadays, autoimmunological diseases make really serious problem for medical care in the United States of America and Western European countries, ranking just behind cardiovascular diseases, cancer and metabolic sicknesses. PMID:27403907

  20. Romanticism and schizophrenia. Second part: The intimacy hypothesis.

    PubMed

    López-Ibor, Juan J; López-Ibor, María I

    2014-01-01

    In the first part of this article we have analyzed the evidence supporting the recency hypothesis of schizophrenia and also what we can call the intimate nature of the disease. In this part we highlight the role of certain cultural aspects that have been ignored up to now, aspects that are associated with deep changes in the Weltanschauung and systems of beliefs on human nature brought up by the late Modernism, specifically by Romanticism. The description of the main characteristics of Romanticism, starting with the “discovery of intimacy”, leads to the conclusion that the characteristic alteration of subjectivity and ipseity of the disease appears to be a vulnerability factor when somebody has to face the new challenges raise Romanticism. The consideration of Hölderlin’s literary achievements and the deep psychological drama prevailing in them, makes explicit how the late modern human being finds in Romanticism the source of creativity and personal development but also the threat of his or her own destruction. Finally we link our hypothesis with recent genetic perspectives that consider sets of diseases associated to the same gene or genes (diseasome). In any case the process of associating the traits of Late Modernism and Romanticism with the core features of schizophrenia allows to consider the amalgamation of insanity with society, both at a general level an in what concerns individual patients, paving the way for novel therapeutic strategies.

  1. Is the Amyloid Hypothesis of Alzheimer's disease therapeutically relevant?

    PubMed Central

    Teich, Andrew F.; Arancio, Ottavio

    2013-01-01

    The conventional view of AD (Alzheimer's disease) is that much of the pathology is driven by an increased load of β-amyloid in the brain of AD patients (the ‘Amyloid Hypothesis’). Yet, many therapeutic strategies based on lowering β-amyloid have so far failed in clinical trials. This failure of β-amyloid-lowering agents has caused many to question the Amyloid Hypothesis itself. However, AD is likely to be a complex disease driven by multiple factors. In addition, it is increasingly clear that β-amyloid processing involves many enzymes and signalling pathways that play a role in a diverse array of cellular processes. Thus the clinical failure of β-amyloid-lowering agents does not mean that the hypothesis itself is incorrect; it may simply mean that manipulating β-amyloid directly is an unrealistic strategy for therapeutic intervention, given the complex role of β-amyloid in neuronal physiology. Another possible problem may be that toxic β-amyloid levels have already caused irreversible damage to downstream cellular pathways by the time dementia sets in. We argue in the present review that a more direct (and possibly simpler) approach to AD therapeutics is to rescue synaptic dysfunction directly, by focusing on the mechanisms by which elevated levels of β-amyloid disrupt synaptic physiology. PMID:22891628

  2. A multi-pathway hypothesis for human visual fear signaling

    PubMed Central

    Silverstein, David N.; Ingvar, Martin

    2015-01-01

    A hypothesis is proposed for five visual fear signaling pathways in humans, based on an analysis of anatomical connectivity from primate studies and human functional connectvity and tractography from brain imaging studies. Earlier work has identified possible subcortical and cortical fear pathways known as the “low road” and “high road,” which arrive at the amygdala independently. In addition to a subcortical pathway, we propose four cortical signaling pathways in humans along the visual ventral stream. All four of these traverse through the LGN to the visual cortex (VC) and branching off at the inferior temporal area, with one projection directly to the amygdala; another traversing the orbitofrontal cortex; and two others passing through the parietal and then prefrontal cortex, one excitatory pathway via the ventral-medial area and one regulatory pathway via the ventral-lateral area. These pathways have progressively longer propagation latencies and may have progressively evolved with brain development to take advantage of higher-level processing. Using the anatomical path lengths and latency estimates for each of these five pathways, predictions are made for the relative processing times at selective ROIs and arrival at the amygdala, based on the presentation of a fear-relevant visual stimulus. Partial verification of the temporal dynamics of this hypothesis might be accomplished using experimental MEG analysis. Possible experimental protocols are suggested. PMID:26379513

  3. Evidence against a hypothesis of vestibular efferent function

    NASA Technical Reports Server (NTRS)

    Cochran, S. L.

    1994-01-01

    Efferent stimulation and nicotinic agonists can either decrease or increase the frequency of occurrence of EPSPs recorded from VIIIth nerve afferents in the frog. It has been hypothesized that the distribution of hair cell resting membrane potentials overlaps the equilibrium potential dictated by the nicotinic-gated channels on the hair cells. Nicotinic mediated increases in EPSP frequency would then be due to depolarization of hair cells that were more hyperpolarized at rest, while decreases in EPSP frequency would be due to hyperpolarization of hair cells more depolarized at rest. In order to test this hypothesis, while recording from afferents which showed an increase in EPSP frequency due to bath application of the nicotinic agonist DMPP (1,1-dimethyl-4-phenylpiperizinium iodide), hair cells were depolarized with 10 mM K+ in the bath, and then the effects of DMPP on EPSP frequency were assessed. In this situation, DMPP still increased EPSP frequency, suggesting that the equilibrium potential for the nicotinic-gated channel was much more positive than the resting potentials of the hair cells. An alternative hypothesis then seems likely, that the nicotinic receptors on hair cells are able to activate different iontophores that result in either hair cell depolarization or hyperpolarization, dependent upon which iontophore predominates in the hair cells innervating a particular afferent.

  4. Pornography actresses: an assessment of the damaged goods hypothesis.

    PubMed

    Griffith, James D; Mitchell, Sharon; Hart, Christian L; Adams, Lea T; Gu, Lucy L

    2013-01-01

    The damaged goods hypothesis posits that female performers in the adult entertainment industry have higher rates of childhood sexual abuse (CSA), psychological problems, and drug use compared to the typical woman. The present study compared the self-reports of 177 porn actresses to a sample of women matched on age, ethnicity, and marital status. Comparisons were conducted on sexual behaviors and attitudes, self-esteem, quality of life, and drug use. Porn actresses were more likely to identify as bisexual, first had sex at an earlier age, had more sexual partners, were more concerned about contracting a sexually transmitted disease (STD), and enjoyed sex more than the matched sample, although there were no differences in incidence of CSA. In terms of psychological characteristics, porn actresses had higher levels of self-esteem, positive feelings, social support, sexual satisfaction, and spirituality compared to the matched group. Last, female performers were more likely to have ever used 10 different types of drugs compared to the comparison group. A discriminant function analysis was able to correctly classify 83% of the participants concerning whether they were a porn actress or member of the matched sample. These findings did not provide support for the damaged goods hypothesis.

  5. HYPOTHESIS TESTING FOR HIGH-DIMENSIONAL SPARSE BINARY REGRESSION

    PubMed Central

    Mukherjee, Rajarshi; Pillai, Natesh S.; Lin, Xihong

    2015-01-01

    In this paper, we study the detection boundary for minimax hypothesis testing in the context of high-dimensional, sparse binary regression models. Motivated by genetic sequencing association studies for rare variant effects, we investigate the complexity of the hypothesis testing problem when the design matrix is sparse. We observe a new phenomenon in the behavior of detection boundary which does not occur in the case of Gaussian linear regression. We derive the detection boundary as a function of two components: a design matrix sparsity index and signal strength, each of which is a function of the sparsity of the alternative. For any alternative, if the design matrix sparsity index is too high, any test is asymptotically powerless irrespective of the magnitude of signal strength. For binary design matrices with the sparsity index that is not too high, our results are parallel to those in the Gaussian case. In this context, we derive detection boundaries for both dense and sparse regimes. For the dense regime, we show that the generalized likelihood ratio is rate optimal; for the sparse regime, we propose an extended Higher Criticism Test and show it is rate optimal and sharp. We illustrate the finite sample properties of the theoretical results using simulation studies. PMID:26246645

  6. Dopamine dysfunction in borderline personality disorder: a hypothesis.

    PubMed

    Friedel, Robert O

    2004-06-01

    Research on the biological basis of borderline personality disorder (BPD) has focused primarily on the serotonin model of impulsive aggression. However, there is evidence that dopamine (DA) dysfunction may also be associated with BPD. Pertinent research and review articles, identified by Medline searches of relevant topics, books, references from bibliographies, and conference proceedings from 1975 to 2003, were reviewed. Evidence of DA dysfunction in BPD derives from the efficacy of traditional and atypical antipsychotic agents in BPD, and from provocative challenges with amphetamine and methylphenidate of subjects with the disorder. In addition, human and animal studies indicate that DA activity plays an important role in emotion information processing, impulse control, and cognition. The results of this review suggest that DA dysfunction is associated with three dimensions of BPD, that is, emotional dysregulation, impulsivity, and cognitive-perceptual impairment. The main limitation of this hypothesis is that the evidence reviewed is circumstantial. There is no study that directly demonstrates DA dysfunction in BPD. In addition, the therapeutic effects of antipsychotic agents observed in BPD may be mediated by non-DA mechanisms of action. If the stated hypothesis is correct, DA dysfunction in BPD may result from genetic, developmental, or environmental factors directly affecting specific DA pathways. Alternatively, DA dysfunction in BPD may be a compensatory response to alterations in the primary neural systems that control emotion, impulse control, and cognition, and that are mediated by the brain's main neurotransmitters, glutamate, and GABA, or in one or more other neuromodulatory pathways such as serotonin, acetylcholine, and norepinephrine.

  7. Fungal communities as an experimental approach to Darwin's naturalization hypothesis.

    PubMed

    Morales, María Camila; Verdejo, Valentina; Orlando, Julieta; Carú, Margarita

    2016-01-01

    Darwin's naturalization hypothesis suggests that the success of an invasive species will be lower when colonizing communities are formed by phylogenetically related rather than unrelated species due to increased competition. Although microbial invasions are involved in both natural and anthropogenic processes, factors affecting the success of microbial invaders are unknown. A biological invasion assay was designed using Trichoderma cf. harzianum as the invader and two types of recipient communities assembled in microcosm assays: communities phylogenetically related to the invader, and communities phylogenetically unrelated to it. Both types of communities were invaded by T. cf. harzianum, and the success of colonization was monitored by qPCR; its effect on the genetic structure of recipient fungal communities was then assessed by DGGE profiles. T. cf. harzianum established itself in both communities, reaching 1000-10,000 times higher copy numbers in the non-related communities. However, invader establishment does not affect the structure of the invaded communities. These results suggest that the composition of recipient communities and their phylogenetic relationship to the invader affect the success of colonization by T. cf. harzianum. While this approach represents a very simplified assay, these microcosms enable an experimental test of Darwin's hypothesis in order to understand the biological invasion process in microbial communities.

  8. More than genes: the advanced fetal programming hypothesis.

    PubMed

    Hocher, Berthold

    2014-10-01

    Many lines of data, initial epidemiologic studies as well as subsequent extensive experimental studies, indicate that early-life events play a powerful role in influencing later suceptibility to certain chronic diseases. Such events might be over- or undernutrition, exposure to environmental toxins, but also changes in hormones, in particular stress hormones. Typically, those events are triggered by the environmental challenges of the mother. However, recent studies have shown that paternal environmental or nutritional factors affect the phenotype of the offspring as well. The maternal and paternal environmental factors act on the phenotype of the offspring via epigenetic modification of its genome. The advanced fetal programming hypothesis proposes an additional non-environmentally driven mechanism: maternal and also paternal genes may influence the maturating sperm, the oocyte, and later the embryo/fetus, leading to their epigenetic alteration. Thus, the observed phenotype of the offspring may be altered by maternal/paternal genes independent of the fetal genome. Meanwhile, several independent association studies in humans dealing with metabolic and neurological traits also suggest that maternal genes might affect the offspring phenotype independent of the transmission of that particular gene to the offspring. Considering the implications of this hypothesis, some conclusions drawn from transgenic or knockout animal models and based on the causality between a genetic alteration and a phenotype, need to be challenged. Possible implications for the development, diagnostic and therapy of human genetic diseases have to be investigated.

  9. Seat belt usage rates: a test of Peltzman's hypothesis.

    PubMed

    McCarthy, P S

    1986-10-01

    Despite the universally accepted belief that the use of seat belts would have a significant impact upon the number of vehicular fatalities, current evidence indicates that relatively few drivers employ their seat belts. Various hypotheses have been offered to explain this phenomenon, many of which conclude that a driver's decision to use a seat belt is independent of the risk experienced in his trip making. This paper develops an economic model which focuses upon the relationship between driver use of seat belts and the travel conditions under which trips are made. Using data obtained from a national survey of households, a binary logit model is developed to test the hypothesis that seat belt usage is influenced by the level of risk experienced in one's trip making. The estimation results were consistent with the underlying hypothesis that individuals travelling in more risky environments are more likely to use their seat belts. The econometric results are then employed to examine various policy issues, including the predicted use of seat belts for population sub-groups, driver response to the introduction of a small urban car, and the impact upon the probability of a fatality resulting from vehicle fleet downsizing. PMID:3768132

  10. Testing the depth-differentiation hypothesis in a deepwater octocoral

    PubMed Central

    Quattrini, Andrea M.; Baums, Iliana B.; Shank, Timothy M.; Morrison, Cheryl L.; Cordes, Erik E.

    2015-01-01

    The depth-differentiation hypothesis proposes that the bathyal region is a source of genetic diversity and an area where there is a high rate of species formation. Genetic differentiation should thus occur over relatively small vertical distances, particularly along the upper continental slope (200–1000 m) where oceanography varies greatly over small differences in depth. To test whether genetic differentiation within deepwater octocorals is greater over vertical rather than geographical distances, Callogorgia delta was targeted. This species commonly occurs throughout the northern Gulf of Mexico at depths ranging from 400 to 900 m. We found significant genetic differentiation (FST = 0.042) across seven sites spanning 400 km of distance and 400 m of depth. A pattern of isolation by depth emerged, but geographical distance between sites may further limit gene flow. Water mass boundaries may serve to isolate populations across depth; however, adaptive divergence with depth is also a possible scenario. Microsatellite markers also revealed significant genetic differentiation (FST = 0.434) between C. delta and a closely related species, Callogorgia americana, demonstrating the utility of microsatellites in species delimitation of octocorals. Results provided support for the depth-differentiation hypothesis, strengthening the notion that factors covarying with depth serve as isolation mechanisms in deep-sea populations. PMID:25904664

  11. The community conditioning hypothesis and its application to environmental toxicology

    SciTech Connect

    Matthews, R.A.; Landis, W.G.; Matthews, G.B.

    1996-04-01

    In this paper the authors present the community conditions hypothesis, ecological communities retain information bout events in their history. This hypothesis, which was derived from the concept of nonequilibrium community ecology, was developed as a framework for understanding the persistence of dose-related responses in multispecies toxicity tests. The authors present data from three standardized aquatic microcosm (SAM) toxicity tests using the water-soluble fractions from turbine fuels (Jet-A, JP-4, and JP-8). In all three tests, the toxicants depressed the Daphnia populations for several weeks, which resulted in algal blooms in the dosed microcosms due to lower predation rates. These effects were short-lived, and by the second and third months of the experiments, the Daphnia populations appeared to have recovered. However, multivariate analysis of the data released dose/response differences that reappeared during the later part of the tests, often due to differences in other consumers (rotifers, ostracods, ciliates), or algae that are not normally consumed (filamentous green algae and bluegreen algae). The findings are consistent with ecological theories that describe communities as the unique production of their etiologies. The implications of this to environmental toxicology are that almost all environmental events leave lasting effects, whether or not they have observed them.

  12. Testing for Marshall-Lerner hypothesis: A panel approach

    NASA Astrophysics Data System (ADS)

    Azizan, Nur Najwa; Sek, Siok Kun

    2014-12-01

    The relationship between real exchange rate and trade balances are documented in many theories. One of the theories is the so-called Marshall-Lerner condition. In this study, we seek to test for the validity of Marshall-Lerner hypothesis, i.e. to reveal if the depreciation of real exchange rate leads to the improvement in trade balances. We focus our study in ASEAN-5 countries and their main trade partners of U.S., Japan and China. The dynamic panel data of pooled mean group (PMG) approach is used to detect the Marshall-Lerner hypothesis among ASEAN-5, between ASEAN-5 and U.S., between ASEAN-5 and Japan and between ASEAN-5 and China respectively. The estimation is based on the autoregressive Distributed Lag or ARDL model for the period of 1970-2012. The paper concludes that Marshal Lerner theory does not hold in bilateral trades in four groups of countries. The trade balances of ASEAN5 are mainly determined by the domestic income level and foreign production cost.

  13. Limitations of methods to test density-dependent fecundity hypothesis.

    PubMed

    Beja, Pedro; Palma, Luis

    2008-03-01

    1. Two main hypotheses are usually invoked to explain density dependence in fecundity: the habitat heterogeneity hypothesis (HHH) and the individual adjustment hypothesis (IAH). Although simple methods have been proposed to discriminate between the two hypotheses, their adequacy was tested for only a limited set of real and model populations. 2. In a computer simulation study based on a stochastic territory-based approach, Ferrer, Newton & Casado (2006, Journal of Animal Ecology, 75, 111-117) argued that a strong negative relationship between mean fecundity and its skewness in stable or increasing populations provides critical support for HHH, as this relationship should be lacking under IAH. A negative relationship between mean fecundity and its coefficient of variation (CV) was predicted under both hypotheses, although with a lower slope under IAH. 3. We used a comparable simulation approach, with model populations parameterized from an increasing Bonelli's eagle Hieraaetus fasciatus population (1992-2006), to show that both HHH and IAH can produce indistinguishable relationships between mean fecundity and both its CV and its skewness. 4. Strong negative correlations between the mean and both its CV and its skewness can emerge as statistical artifacts under biologically plausible assumptions, and so they may be largely inadequate to infer mechanisms underlying density dependence in demographic parameters. PMID:18254920

  14. A hypothesis for the 2007 dengue outbreak in Singapore.

    PubMed

    Massad, E; Coutinho, F A B; Ma, S; Burattini, M N

    2010-07-01

    A previous mathematical model explaining dengue in Singapore predicted a reasonable outbreak of about 6500 cases for 2006 and a very mild outbreak with about 2000 cases for 2007. However, only 3051 cases were reported in 2006 while more than 7800 were reported in the first 44 weeks of 2007. We hypothesized that the combination of haze with other local sources of particulate matter had a significant impact on mosquito life expectancy, significantly increasing their mortality rate. To test the hypothesis a mathematical model based on the reproduction number of dengue fever and aimed at comparing the impact of several possible alternative control strategies was proposed. This model also aimed at contributing to the understanding of the causes of dengue resurgence in Singapore in the last decade. The model's simulation demonstrated that an increase in mosquito mortality in 2006 and either a reduction in mortality or an increase in the carrying capacity of mosquitoes in 2007 explained the patterned observed in Singapore. Based on the model's simulation we concluded that the fewer than expected number of dengue cases in Singapore in 2006 was caused by an increase in mosquito mortality due to the disproportionate haze affecting the country that year and that particularly favourable environmental conditions in 2007 propitiated mosquitoes with a lower mortality rate, which explains the greater than expected number of dengue cases in 2007. Whether our hypothesis is plausible or not should be debated further.

  15. Romanticism and schizophrenia. Second part: The intimacy hypothesis.

    PubMed

    López-Ibor, Juan J; López-Ibor, María I

    2014-01-01

    In the first part of this article we have analyzed the evidence supporting the recency hypothesis of schizophrenia and also what we can call the intimate nature of the disease. In this part we highlight the role of certain cultural aspects that have been ignored up to now, aspects that are associated with deep changes in the Weltanschauung and systems of beliefs on human nature brought up by the late Modernism, specifically by Romanticism. The description of the main characteristics of Romanticism, starting with the “discovery of intimacy”, leads to the conclusion that the characteristic alteration of subjectivity and ipseity of the disease appears to be a vulnerability factor when somebody has to face the new challenges raise Romanticism. The consideration of Hölderlin’s literary achievements and the deep psychological drama prevailing in them, makes explicit how the late modern human being finds in Romanticism the source of creativity and personal development but also the threat of his or her own destruction. Finally we link our hypothesis with recent genetic perspectives that consider sets of diseases associated to the same gene or genes (diseasome). In any case the process of associating the traits of Late Modernism and Romanticism with the core features of schizophrenia allows to consider the amalgamation of insanity with society, both at a general level an in what concerns individual patients, paving the way for novel therapeutic strategies. PMID:25179093

  16. Apomorphine and the dopamine hypothesis of schizophrenia: a dilemma?

    PubMed Central

    Dépatie, L; Lal, S

    2001-01-01

    The dopamine (DA) hypothesis of schizophrenia implicates an enhancement of DA function in the pathophysiology of the disorder, at least in the genesis of positive symptoms. Accordingly, apomorphine, a directly acting DA receptor agonist, should display psychotomimetic properties. A review of the literature shows little or no evidence that apomorphine, in doses that stimulate postsynaptic DA receptors, induces psychosis in non-schizophrenic subjects or a relapse or exacerbation of psychotic symptoms in patients with schizophrenia. After a detailed review of the literature reporting psychotogenic effects of apomorphine in patients with Parkinson's disease, an interpretation of these data is difficult, in part because of several confounding factors, such as the concomitant use of drugs known to induce psychosis and the advanced state of the progressive neurological disorder. In the context of the DA hypothesis of schizophrenia, the limited ability of apomorphine to induce psychosis, in contrast to indirectly acting DA agonists that increase synaptic DA, may be explained by the relatively weak affinity of apomorphine for the D3 receptor compared with DA. Alternatively, enhancement of DA function, though necessary, may be insufficient by itself to induce psychosis. PMID:11394190

  17. Diversification, biotic interchange, and the universal trade-off hypothesis.

    PubMed

    Tilman, David

    2011-09-01

    Competition theory predicts that multispecies coexistence requires that species have traits that fall on the same interspecific trade-off surface. Fossil records for mollusks, mammals, trees, and other taxa show that with rare exception, ecologically similar species have coexisted for a million years or more after interchange between formerly isolated realms. This coexistence suggests the possibility, termed the universal trade-off hypothesis, that ecologically similar species of different realms have been bound to the same interspecific trade-off surface despite millions of years of independent evolution. Such persistence fails to support the biogeographic superiority hypothesis, which posits that genetic drift, recombination, mutation, and selection would cause taxa of one realm to gain superiority over those of another realm during long periods of isolation. Analysis of the lengths of time that species have persisted once in contact suggests that the trade-off surfaces of realms differed by <0.1% at the time of interchange. This implies that macroevolutionary patterns of differentiation and speciation within and between realms were more likely the movement of traits on a common trade-off surface rather than directional selection achieved without compensatory trade-offs and costs. The existence of transrealm trade-offs, should further work support this possibility, has deep implications for ecology and evolution.

  18. Darwinian evolution does not rule out the gaia hypothesis.

    PubMed

    Sugimoto, Takeshi

    2002-10-21

    This study explores so-called Darwinian Daisyworlds mathematically rigorously in detail. The original Daisyworld was introduced by Watson & Lovelock (1983) to demonstrate how two species of daisies regulate the global temperature of their planet through competition among these species against the rising solar luminosity, i.e. the Gaia hypothesis. Its variants are Darwinian Daisyworlds in which daisies can adapt themselves to the local temperature. Robertson & Robinson (1998) insist their Darwinian daisies lose the ability for temperature regulation on the basis of their spreadsheet simulations. Lenton & Lovelock (2000) point out that the constraints on adaptation recovers Darwinian daisies' ability of temperature regulation on the basis of their Euler-code simulations. The present study shows there exist the exact and closed-form solutions to these two Daisyworlds. The results contradict the former studies: Robertson and Robinson's daisies do regulate the global temperature even longer than non-adaptive daisies; Lenton and Lovelock's daisies are less adaptive than Robertson and Robinson's daisies because of the constraints on adaptation; the introduction of weak adaptability drives species into a dead end of evolution. Thus, the present results confirm that the Gaia hypothesis and Darwinian evolution can coexist. PMID:12384048

  19. Cardiac torsion and electromagnetic fields: the cardiac bioinformation hypothesis.

    PubMed

    Burleson, Katharine O; Schwartz, Gary E

    2005-01-01

    Although in physiology the heart is often referred to as a simple piston pump, there are in fact two additional features that are integral to cardiac physiology and function. First, the heart as it contracts in systole, also rotates and produces torsion due to the structure of the myocardium. Second, the heart produces a significant electromagnetic field with each contraction due to the coordinated depolarization of myocytes producing a current flow. Unlike the electrocardiogram, the magnetic field is not limited to volume conduction and extends outside the body. The therapeutic potential for interaction of this cardioelectromagnetic field both within and outside the body is largely unexplored. It is our hypothesis that the heart functions as a generator of bioinformation that is central to normative functioning of body. The source of this bioinformation is based on: (1) vortex blood flow in the left ventricle; (2) a cardiac electromagnetic field and both; (3) heart sounds; and (4) pulse pressure which produce frequency and amplitude information. Thus, there is a multidimensional role for the heart in physiology and biopsychosocial dynamics. Recognition of these cardiac properties may result in significant implications for new therapies for cardiovascular disease based on increasing cardiac energy efficiency (coherence) and bioinformation from the cardioelectromagnetic field. Research studies to test this hypothesis are suggested.

  20. An Alternative Hypothesis for How Microgravity Improves Macromolecular Crystal Quality

    NASA Technical Reports Server (NTRS)

    Pusey, Marc

    2003-01-01

    There is a substantial body of experimental evidence, from this and other laboratories, that strongly suggests that for many proteins crystal nucleation and growth is by addition of associated species that are preformed by reversible concentration-driven self association processes in the bulk solution. We have developed a self-association model for the crystal nucleation and growth of the protein chicken egg lysozyme. The model accounts for the obtained crystal symmetry, explains the observed surface structures, and shows the importance of the symmetry obtained by self-association in solution to the process as a whole. This model also offers a possible mechanism for fluid flow effects on the growth process and how microgravity may affect it. While a single lysozyme molecule is relatively small an octamer in the 43 helix configuration (the proposed average sized growth unit) would have a M.W. approx. 115,000 and dimensions of 5.6 x 5.6 x 7.6 nm. Direct AFM measurements of growth unit incorporation indicate that units as wide as 11.2 nm and as long as 11.4 nm (a 24-mer) commonly attach to the crystal. AFM results from Weichmann et al. (Ultramicroscopy 86, 159-166, 2001) suggest that associated species of up to 40-mers in size add to the (101) faces. These measurements reflect the sizes of units that both added and desorbed from the crystal surface. The larger and less isotropic the associated species the more likely that it will be oriented to some degree in a flowing boundary layer, even at the low flow velocities measured about macromolecule crystals. On Earth, concentration gradient driven flow will maintain a high interfacial concentration, i.e., a high level (essentially that of the bulk solution) of solute association at the interface and higher growth rate. Higher growth rates mean an increased probability that misaligned growth units are trapped by subsequent growth layers before they can be desorbed and try again, or that the desorbing species is more likely

  1. Testing the activitystat hypothesis: a randomised controlled trial protocol

    PubMed Central

    2012-01-01

    Background The activitystat hypothesis proposes that when physical activity or energy expenditure is increased or decreased in one domain, there will be a compensatory change in another domain to maintain an overall, stable level of physical activity or energy expenditure. To date, there has been no experimental study primarily designed to test the activitystat hypothesis in adults. The aim of this trial is to determine the effect of two different imposed exercise loads on total daily energy expenditure and physical activity levels. Methods This study will be a randomised, multi-arm, parallel controlled trial. Insufficiently active adults (as determined by the Active Australia survey) aged 18–60 years old will be recruited for this study (n=146). Participants must also satisfy the Sports Medicine Australia Pre-Exercise Screening System and must weigh less than 150 kg. Participants will be randomly assigned to one of three groups using a computer-generated allocation sequence. Participants in the Moderate exercise group will receive an additional 150 minutes of moderate to vigorous physical activity per week for six weeks, and those in the Extensive exercise group will receive an additional 300 minutes of moderate to vigorous physical activity per week for six weeks. Exercise targets will be accumulated through both group and individual exercise sessions monitored by heart rate telemetry. Control participants will not be given any instructions regarding lifestyle. The primary outcome measures are activity energy expenditure (doubly labeled water) and physical activity (accelerometry). Secondary measures will include resting metabolic rate via indirect calorimetry, use of time, maximal oxygen consumption and several anthropometric and physiological measures. Outcome measures will be conducted at baseline (zero weeks), mid- and end-intervention (three and six weeks) with three (12 weeks) and six month (24 week) follow-up. All assessors will be blinded to group

  2. Kinetics of Prion Growth

    PubMed Central

    Pöschel, Thorsten; Brilliantov, Nikolai V.; Frömmel, Cornelius

    2003-01-01

    We study the kinetics of prion fibril growth, described by the nucleated polymerization model analytically and by means of numerical experiments. The elementary processes of prion fibril formation lead us to a set of differential equations for the number of fibrils, their total mass, and the number of prion monomers. In difference to previous studies we analyze this set by explicitly taking into account the time-dependence of the prion monomer concentration. The theoretical results agree with experimental data, whereas the generally accepted hypothesis of constant monomer concentration leads to a fibril growth behavior which is not in agreement with experiments. The obtained size distribution of the prion fibril aggregates is shifted significantly toward shorter lengths as compared to earlier results, which leads to a enhanced infectivity of the prion material. Finally, we study the effect of filtering of the inoculated material on the incubation time of the disease. PMID:14645042

  3. A network approach in analysis of the matching hypothesis

    NASA Astrophysics Data System (ADS)

    Jia, Tao; Spivey, Robert; Korniss, Gyorgy; Szymanski, Boleslaw

    2014-03-01

    The matching hypothesis in social psychology claimed that people are more likely to form a committed relationship with someone who is equally attractive. This phenomenon can be well interpreted by the principle of homophily that people are apt to get in touch with others similar to them. Yet, social experiments indicate that people in general tend to prefer more attractive individuals regardless of their own attractiveness. Here study the stochastic matching process for different underlying networks and different attractiveness distributions. We showed that the correlation of attractiveness within couples could purely due to the limited number of acquaintance each person has and such correlation decreases as the network becomes more sparse. We also analyzed the effect of the degree distribution and the attractiveness on the number of individuals that can not find their partners. This work is supported by ARL NS-CTA, ARO, and ONR.

  4. An aboral-dorsalization hypothesis for chordate origin.

    PubMed

    Satoh, Nori

    2008-11-01

    Chordates originated from a common ancestor(s) shared with two other deuterostome groups, echinoderms and hemichordates, by creating a novel type of tadpole-like larva, which was characterized by a dorsal hollow neural tube and notochord. Recent molecular phylogeny supports the notion that echinoderms and hemichordates form a clade named the Ambulacraria and that, among the chordates, cephalochordates are more basal than urochordates and vertebrates. An aboral-dorsalization hypothesis is proposed to explain how the tadpole-type larva evolved. Embryological comparison of cephalochordates with nonchordate deuterostomes suggests that, because of limited space on the oral side of the ancestral embryo, morphogenesis to form the neural tube and notochord occurred on the aboral side of the embryo. Namely, the dorsalization of the aboral side of the ancestral embryo may have been a key developmental event that led to the formation of the basic chordate body plan.

  5. The source dilemma hypothesis: Perceptual uncertainty contributes to musical emotion.

    PubMed

    Bonin, Tanor L; Trainor, Laurel J; Belyk, Michel; Andrews, Paul W

    2016-09-01

    Music can evoke powerful emotions in listeners. Here we provide the first empirical evidence that the principles of auditory scene analysis and evolutionary theories of emotion are critical to a comprehensive theory of musical emotion. We interpret these data in light of a theoretical framework termed "the source dilemma hypothesis," which predicts that uncertainty in the number, identity or location of sound objects elicits unpleasant emotions by presenting the auditory system with an incoherent percept, thereby motivating listeners to resolve the auditory ambiguity. We describe two experiments in which source location and timbre were manipulated to change uncertainty in the auditory scene. In both experiments, listeners rated tonal and atonal melodies with congruent auditory scene cues as more pleasant than melodies with incongruent auditory scene cues. These data suggest that music's emotive capacity relies in part on the perceptual uncertainty it produces regarding the auditory scene.

  6. Macular pigment and the edge hypothesis of flicker photometry.

    PubMed

    Bone, Richard A; Landrum, John T; Gibert, Jorge C

    2004-12-01

    Heterochromatic flicker photometry is commonly used to measure macular pigment optical density (MPOD) in the human retina. It has been proposed, and accepted by many, that the MPOD so measured represents the value at a retinal location corresponding to the edge of the flickering, circular stimulus. We have investigated this proposal by using a series of annular stimuli to determine the MPOD distribution in the central 1.5 degrees of the retina for both eyes of 10 subjects. The MPOD obtained using a 1.5 degrees circular stimulus matched the MPOD distribution at a retinal eccentricity that was always less than the stimulus radius, and averaged, for the 10 subjects, 51% of the stimulus radius. Similar results were obtained using a 1 degrees stimulus. Thus the edge hypothesis is inconsistent with our data. We suggest that involuntary eye movements may be responsible for an apparent edge effect.

  7. Prefrontal Cortical Opioids and Dysregulated Motivation: A Network Hypothesis.

    PubMed

    Baldo, Brian A

    2016-06-01

    Loss of inhibitory control over appetitively motivated behavior occurs in multiple psychiatric disorders, including drug abuse, behavioral addictions, and eating disorders with binge features. In this opinion article, novel actions of μ-opioid peptides in the prefrontal cortex (PFC) that could contribute to inhibitory control deficits will be discussed. Evidence has accrued to suggest that excessive intra-PFC μ-opioid receptor (μ-OR) signaling alters the PFC response to excitatory drive, resulting in supernormal and incoherent recruitment of multiple PFC output pathways. Affected pathways include functionally opposed PFC→hypothalamus 'appetitive driver' and PFC→striatum 'appetitive limiter' projections. This network perturbation engenders disorganized, impulsive appetitive responses. Evidence supporting this hypothesis from human imaging and animal studies will be discussed, and combinatorial drug treatments targeting μ-ORs and specific PFC subcortical targets will be explored. PMID:27233653

  8. An Algorithm for Testing the Efficient Market Hypothesis

    PubMed Central

    Boboc, Ioana-Andreea; Dinică, Mihai-Cristian

    2013-01-01

    The objective of this research is to examine the efficiency of EUR/USD market through the application of a trading system. The system uses a genetic algorithm based on technical analysis indicators such as Exponential Moving Average (EMA), Moving Average Convergence Divergence (MACD), Relative Strength Index (RSI) and Filter that gives buying and selling recommendations to investors. The algorithm optimizes the strategies by dynamically searching for parameters that improve profitability in the training period. The best sets of rules are then applied on the testing period. The results show inconsistency in finding a set of trading rules that performs well in both periods. Strategies that achieve very good returns in the training period show difficulty in returning positive results in the testing period, this being consistent with the efficient market hypothesis (EMH). PMID:24205148

  9. Deconvolution from wave front sensing using the frozen flow hypothesis.

    PubMed

    Jefferies, Stuart M; Hart, Michael

    2011-01-31

    Deconvolution from wave front sensing (DWFS) is an image-reconstruction technique for compensating the image degradation due to atmospheric turbulence. DWFS requires the simultaneous recording of high cadence short-exposure images and wave-front sensor (WFS) data. A deconvolution algorithm is then used to estimate both the target object and the wave front phases from the images, subject to constraints imposed by the WFS data and a model of the optical system. Here we show that by capturing the inherent temporal correlations present in the consecutive wave fronts, using the frozen flow hypothesis (FFH) during the modeling, high-quality object estimates may be recovered in much worse conditions than when the correlations are ignored.

  10. Cognitive impairment in Parkinson's disease: the dual syndrome hypothesis.

    PubMed

    Kehagia, Angie A; Barker, Roger A; Robbins, Trevor W

    2013-01-01

    Research into the heterogeneous nature of cognitive impairment documented in patients with Parkinson's disease (PD) has focused on disentangling deficits that vary between individuals, evolve and respond differentially to pharmacological treatments, and relate differentially to PD dementia (PDD). We summarise studies conducted in our laboratory over the last 2 decades, outlining the incremental development of our hypotheses, the starting point for which is our early work on executive deficits mirroring fronto-striatal dysfunction. We present subsequent findings linking these deficits to a model of dopaminergic function that conforms to an inverted curvilinear function. We review studies that investigated the range of dopamine-independent attentional and visuospatial memory deficits seen in PD, demonstrating that abnormalities in these domains more accurately predict PDD. We conclude with an exposition of the dual syndrome hypothesis, which distinguishes between dopaminergically mediated fronto-striatal executive impairments and a dementia syndrome with distinctive prodromal visuospatial deficits in which cholinergic treatments offer some clinical benefits.

  11. A shrinkage probability hypothesis density filter for multitarget tracking

    NASA Astrophysics Data System (ADS)

    Tong, Huisi; Zhang, Hao; Meng, Huadong; Wang, Xiqin

    2011-12-01

    In radar systems, tracking targets in low signal-to-noise ratio (SNR) environments is a very important task. There are some algorithms designed for multitarget tracking. Their performances, however, are not satisfactory in low SNR environments. Track-before-detect (TBD) algorithms have been developed as a class of improved methods for tracking in low SNR environments. However, multitarget TBD is still an open issue. In this article, multitarget TBD measurements are modeled, and a highly efficient filter in the framework of finite set statistics (FISST) is designed. Then, the probability hypothesis density (PHD) filter is applied to multitarget TBD. Indeed, to solve the problem of the target and noise not being separated correctly when the SNR is low, a shrinkage-PHD filter is derived, and the optimal parameter for shrinkage operation is obtained by certain optimization procedures. Through simulation results, it is shown that our method can track targets with high accuracy by taking advantage of shrinkage operations.

  12. Inflammation and the Two-Hit Hypothesis of Schizophrenia

    PubMed Central

    Feigenson, Keith A.; Kusnecov, Alex W.; Silverstein, Steven M.

    2014-01-01

    The high societal and individual cost of schizophrenia necessitates finding better, more effective treatment, diagnosis, and prevention strategies. One of the obstacles in this endeavor is the diverse set of etiologies that comprises schizophrenia. A substantial body of evidence has grown over the last few decades to suggest that schizophrenia is a heterogeneous syndrome with overlapping symptoms and etiologies. At the same time, an increasing number of clinical, epidemiological, and experimental studies have shown links between schizophrenia and inflammatory conditions. In this review, we analyze the literature on inflammation and schizophrenia, with a particular focus on comorbidity, biomarkers, and environmental insults. We then identify several mechanisms by which inflammation could influence the development of schizophrenia via the two-hit hypothesis. Lastly, we note the relevance of these findings to clinical applications in the diagnosis, prevention, and treatment of schizophrenia. PMID:24247023

  13. Neurobiological hypothesis of color appearance and hue perception

    PubMed Central

    Schmidt, Brian P.; Neitz, Maureen; Neitz, Jay

    2014-01-01

    DeValois and DeValois (1993) showed that to explain hue appearance, S-cone signals have to be combined with M vs. L opponent signals in two different ways to produce red-green and yellow-blue axes respectively. Recently, it has been shown that color appearance is normal for individuals with genetic mutations that block S-cone input to blue-on ganglion cells. This is inconsistent with the DeValois hypothesis in which S-opponent konio-geniculate signals are combined with L−M signals at a 3rd processing stage in cortex. Instead, here we show that color appearance, including individual differences never explained before, are predicted by a model in which S-cone signals are combined with L vs. M signals in the outer retina. PMID:24695170

  14. Image feature localization by multiple hypothesis testing of Gabor features.

    PubMed

    Ilonen, Jarmo; Kamarainen, Joni-Kristian; Paalanen, Pekka; Hamouz, Miroslav; Kittler, Josef; Kälviäinen, Heikki

    2008-03-01

    Several novel and particularly successful object and object category detection and recognition methods based on image features, local descriptions of object appearance, have recently been proposed. The methods are based on a localization of image features and a spatial constellation search over the localized features. The accuracy and reliability of the methods depend on the success of both tasks: image feature localization and spatial constellation model search. In this paper, we present an improved algorithm for image feature localization. The method is based on complex-valued multi resolution Gabor features and their ranking using multiple hypothesis testing. The algorithm provides very accurate local image features over arbitrary scale and rotation. We discuss in detail issues such as selection of filter parameters, confidence measure, and the magnitude versus complex representation, and show on a large test sample how these influence the performance. The versatility and accuracy of the method is demonstrated on two profoundly different challenging problems (faces and license plates).

  15. Emotions in reading: disgust, empathy and the contextual learning hypothesis.

    PubMed

    Silva, Catarina; Montant, Marie; Ponz, Aurelie; Ziegler, Johannes C

    2012-11-01

    Emotion effects in reading have typically been investigated by manipulating words' emotional valence and arousal in lexical decision. The standard finding is that valence and arousal can have both facilitatory and inhibitory effects, which is hard to reconcile with current theories of emotion processing in reading. Here, we contrasted these theories with the contextual-learning hypothesis, according to which, sensitivity to a specific emotion - disgust in the present study - rather than valence or arousal affects lexical decision performance. Participants were divided into two groups (high versus low disgust sensitivity). Results showed that participants with high disgust sensitivity showed an inhibitory effect, whereas participants with low-disgust sensitivity showed a facilitatory effect. Individual differences in lexical decision performance were predicted by disgust sensitivity but not valence, arousal, or general emotion sensitivity. These findings highlight the need to focus on individual differences both in studies and theories of emotion processing in reading.

  16. An algorithm for testing the efficient market hypothesis.

    PubMed

    Boboc, Ioana-Andreea; Dinică, Mihai-Cristian

    2013-01-01

    The objective of this research is to examine the efficiency of EUR/USD market through the application of a trading system. The system uses a genetic algorithm based on technical analysis indicators such as Exponential Moving Average (EMA), Moving Average Convergence Divergence (MACD), Relative Strength Index (RSI) and Filter that gives buying and selling recommendations to investors. The algorithm optimizes the strategies by dynamically searching for parameters that improve profitability in the training period. The best sets of rules are then applied on the testing period. The results show inconsistency in finding a set of trading rules that performs well in both periods. Strategies that achieve very good returns in the training period show difficulty in returning positive results in the testing period, this being consistent with the efficient market hypothesis (EMH).

  17. Cognitive Impairment in Parkinson's Disease: The Dual Syndrome Hypothesis

    PubMed Central

    Kehagia, Angie A.; Barker, Roger A.; Robbins, Trevor W.

    2012-01-01

    Research into the heterogeneous nature of cognitive impairment documented in patients with Parkinson's disease (PD) has focused on disentangling deficits that vary between individuals, evolve and respond differentially to pharmacological treatments, and relate differentially to PD dementia (PDD). We summarise studies conducted in our laboratory over the last 2 decades, outlining the incremental development of our hypotheses, the starting point for which is our early work on executive deficits mirroring fronto-striatal dysfunction. We present subsequent findings linking these deficits to a model of dopaminergic function that conforms to an inverted curvilinear function. We review studies that investigated the range of dopamine-independent attentional and visuospatial memory deficits seen in PD, demonstrating that abnormalities in these domains more accurately predict PDD. We conclude with an exposition of the dual syndrome hypothesis, which distinguishes between dopaminergically mediated fronto-striatal executive impairments and a dementia syndrome with distinctive prodromal visuospatial deficits in which cholinergic treatments offer some clinical benefits. PMID:23038420

  18. Brain evolution and human neuropsychology: the inferential brain hypothesis.

    PubMed

    Koscik, Timothy R; Tranel, Daniel

    2012-05-01

    Collaboration between human neuropsychology and comparative neuroscience has generated invaluable contributions to our understanding of human brain evolution and function. Further cross-talk between these disciplines has the potential to continue to revolutionize these fields. Modern neuroimaging methods could be applied in a comparative context, yielding exciting new data with the potential of providing insight into brain evolution. Conversely, incorporating an evolutionary base into the theoretical perspectives from which we approach human neuropsychology could lead to novel hypotheses and testable predictions. In the spirit of these objectives, we present here a new theoretical proposal, the Inferential Brain Hypothesis, whereby the human brain is thought to be characterized by a shift from perceptual processing to inferential computation, particularly within the social realm. This shift is believed to be a driving force for the evolution of the large human cortex. (JINS, 2012, 18, 394-401).

  19. The synaptic plasticity and memory hypothesis: encoding, storage and persistence

    PubMed Central

    Takeuchi, Tomonori; Duszkiewicz, Adrian J.; Morris, Richard G. M.

    2014-01-01

    The synaptic plasticity and memory hypothesis asserts that activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the encoding and trace storage of the type of memory mediated by the brain area in which it is observed. Criteria for establishing the necessity and sufficiency of such plasticity in mediating trace storage have been identified and are here reviewed in relation to new work using some of the diverse techniques of contemporary neuroscience. Evidence derived using optical imaging, molecular-genetic and optogenetic techniques in conjunction with appropriate behavioural analyses continues to offer support for the idea that changing the strength of connections between neurons is one of the major mechanisms by which engrams are stored in the brain. PMID:24298167

  20. Porcine Reproductive and Respiratory Syndrome Virus: Origin Hypothesis

    PubMed Central

    2003-01-01

    Porcine reproductive and respiratory syndrome is a serious swine disease that appeared suddenly in the midwestern United States and central Europe approximately 14 years ago; the disease has now spread worldwide. In North America and Europe, the syndrome is caused by two genotypes of porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus whose genomes diverge by approximately 40%. My hypothesis, which explains the origin and evolution of the two distinct PRRSV genotypes, is that a mutant of a closely related arterivirus of mice (lactate dehydrogenase-elevating virus) infected wild boars in central Europe. These wild boars functioned as intermediate hosts and spread the virus to North Carolina in imported, infected European wild boars in 1912; the virus then evolved independently on the two continents in the prevalent wild hog populations for approximately 70 years until independently entering the domestic pig population. PMID:12967485

  1. Infectious Diseases Are Analogous With Cancer. Hypothesis And Implications

    PubMed Central

    Benharroch, Daniel; Osyntsov, Lidia

    2012-01-01

    We propose to disclose first degree analogous features between cancer and infectious diseases and to find out whether these similarities are superficial and negligible, due to the use of the same bodily pathways by the two categories of disease or if they represent significantly parallel characteristics. We have found several primary analogous features, predominantly regarding pathways of spread, but to some extent also concerning the interaction with the immune system. Some of the implications to our hypothesis are probably available in the recent literature, at the experimental or clinical levels. For example endostatin, an angiogenic inhibitor has been used to prevent promotion of metastasis in cancer and to reduce granulomas formation in schistosomiasis. An ECFR antagonist employed to restrain bronchial vessels proliferation in pseudomonas infection, has also been used for the treatment of lung cancer. PMID:22408684

  2. The source dilemma hypothesis: Perceptual uncertainty contributes to musical emotion.

    PubMed

    Bonin, Tanor L; Trainor, Laurel J; Belyk, Michel; Andrews, Paul W

    2016-09-01

    Music can evoke powerful emotions in listeners. Here we provide the first empirical evidence that the principles of auditory scene analysis and evolutionary theories of emotion are critical to a comprehensive theory of musical emotion. We interpret these data in light of a theoretical framework termed "the source dilemma hypothesis," which predicts that uncertainty in the number, identity or location of sound objects elicits unpleasant emotions by presenting the auditory system with an incoherent percept, thereby motivating listeners to resolve the auditory ambiguity. We describe two experiments in which source location and timbre were manipulated to change uncertainty in the auditory scene. In both experiments, listeners rated tonal and atonal melodies with congruent auditory scene cues as more pleasant than melodies with incongruent auditory scene cues. These data suggest that music's emotive capacity relies in part on the perceptual uncertainty it produces regarding the auditory scene. PMID:27318599

  3. Brain Evolution and Human Neuropsychology: The Inferential Brain Hypothesis

    PubMed Central

    Koscik, Timothy R.; Tranel, Daniel

    2013-01-01

    Collaboration between human neuropsychology and comparative neuroscience has generated invaluable contributions to our understanding of human brain evolution and function. Further cross-talk between these disciplines has the potential to continue to revolutionize these fields. Modern neuroimaging methods could be applied in a comparative context, yielding exciting new data with the potential of providing insight into brain evolution. Conversely, incorporating an evolutionary base into the theoretical perspectives from which we approach human neuropsychology could lead to novel hypotheses and testable predictions. In the spirit of these objectives, we present here a new theoretical proposal, the Inferential Brain Hypothesis, whereby the human brain is thought to be characterized by a shift from perceptual processing to inferential computation, particularly within the social realm. This shift is believed to be a driving force for the evolution of the large human cortex. PMID:22459075

  4. Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere.

    PubMed

    Chalmers, Benjamin A; Xing, Hui; Houston, Sevan; Clark, Charlotte; Ghassabian, Sussan; Kuo, Andy; Cao, Benjamin; Reitsma, Andrea; Murray, Cody-Ellen P; Stok, Jeanette E; Boyle, Glen M; Pierce, Carly J; Littler, Stuart W; Winkler, David A; Bernhardt, Paul V; Pasay, Cielo; De Voss, James J; McCarthy, James; Parsons, Peter G; Walter, Gimme H; Smith, Maree T; Cooper, Helen M; Nilsson, Susan K; Tsanaktsidis, John; Savage, G Paul; Williams, Craig M

    2016-03-01

    Pharmaceutical and agrochemical discovery programs are under considerable pressure to meet increasing global demand and thus require constant innovation. Classical hydrocarbon scaffolds have long assisted in bringing new molecules to the market place, but an obvious omission is that of the Platonic solid cubane. Eaton, however, suggested that this molecule has the potential to act as a benzene bioisostere. Herein, we report the validation of Eaton's hypothesis with cubane derivatives of five molecules that are used clinically or as agrochemicals. Two cubane analogues showed increased bioactivity compared to their benzene counterparts whereas two further analogues displayed equal bioactivity, and the fifth one demonstrated only partial efficacy. Ramifications from this study are best realized by reflecting on the number of bioactive molecules that contain a benzene ring. Substitution with the cubane scaffold where possible could revitalize these systems, and thus expedite much needed lead candidate identification.

  5. [New hypothesis on the replication of centrioles and basal bodies].

    PubMed

    Mignot, J P

    1996-12-01

    Certain morphological data, obtained in studies of the ultrastructure of centrioles and basal bodies in cells of metazoa and protists, lead us to think that the cartwheel represents of the most appropriate organization for a self-reproducing and transmissible centriolar organizer. Centrioles and basal bodies might then not be simply the centres of replication of those organizers, but also reservoirs containing several superposed centriolar organizers, which are released depending on the requirements of the cell. As an isolated cartwheel is extremely unlikely to be detected, either in conventional electron microscopy or in immunocytochemistry, it is thus the reservoir which has so far been under consideration. Such a hypothesis would permit the explanation that biogenesis de novo and biogenesis in proximity to preexisting organelles may differ only in terms of the number of morphogenetic units involved.

  6. Southwest U. S. -East Antarctic (SWEAT) connection: A hypothesis

    SciTech Connect

    Moores, E.M. )

    1991-05-01

    A hypothesis for a late Precambrian fit of western North America with the Australia-Antarctic shield region permits the extension of many features through Antarctica and into other parts of Gondwana. Specifically, the Grenville orogen may extend around the coast of East Antarctica into India and Australia. The Wopmay orogen of northwest Canada may extend through eastern Australia into Antarctica and thence beneath the ice to connect with the Yavapai-Mazatzal orogens of the southwestern US. The ophiolitic belt of the latter may extend into East Antarctica. Counterparts of the Precambrian-Paleozoic sedimentary rocks along the US Cordilleran miogeocline may be present in the Transantarctic Mountains. Orogenic belt boundaries provide useful piercing points for Precambrian continental reconstructions. The model implies that Gondwana and Laurentia rifted away from each other on one margin and collided some 300 m.y. later on their opposite margins to from the Appalachians.

  7. The synaptic plasticity and memory hypothesis: encoding, storage and persistence.

    PubMed

    Takeuchi, Tomonori; Duszkiewicz, Adrian J; Morris, Richard G M

    2014-01-01

    The synaptic plasticity and memory hypothesis asserts that activity-dependent synaptic plasticity is induced at appropriate synapses during memory formation and is both necessary and sufficient for the encoding and trace storage of the type of memory mediated by the brain area in which it is observed. Criteria for establishing the necessity and sufficiency of such plasticity in mediating trace storage have been identified and are here reviewed in relation to new work using some of the diverse techniques of contemporary neuroscience. Evidence derived using optical imaging, molecular-genetic and optogenetic techniques in conjunction with appropriate behavioural analyses continues to offer support for the idea that changing the strength of connections between neurons is one of the major mechanisms by which engrams are stored in the brain.

  8. Dengue haemorrhagic fever integral hypothesis: confirming observations, 1987-2007.

    PubMed

    Guzman, Maria G; Kouri, Gustavo

    2008-06-01

    In 1987, Kouri et al. published in Transactions their integral hypothesis to explain the development of dengue haemorrhagic fever (DHF) epidemics (Kouri, G.P., Guzmán, M.G., Bravo, J.R., 1987. Why dengue haemorrhagic fever in Cuba? 2. An integral analysis. Trans. R. Soc. Trop. Med. Hyg. 81, 821-823). Based on observations carried out during the 1981 Cuban DHF epidemic, the authors integrated in one model the most advanced knowledge at that time. Observations in the last 20 years confirm the importance of this multifactorial and unifying view of the problem, where the interaction between the host, the virus and the vector in an epidemiological and ecosystem setting might determine DHF as a final outcome. Investigations on the interaction among host, virus and mosquito with an ecosystemic view are needed.

  9. Birth order and fratricide: an evaluation of Sulloway's hypothesis.

    PubMed

    Marleau, Jacques D

    2005-01-01

    Sulloway (1996) suggested that older siblings were more likely to be fratricidal than younger ones. Our data, based on 113 case studies found in the psychiatric, psychological and criminological literature since 1959, confirms his hypothesis. In 72 out of the 92 cases (78%) where age could be determined, the aggressor was older than the victim. The same held true even when the age of aggressor, sex of aggressor and victim, presence or not of a blood tie, and presence of one or more victims are taken into account. Surprisingly, most of the aggressors in our sample were under the age of 18 years. Also, first-borns were more often the aggressor than the victim. This result seems to confirm the Adlerian theory of dethronement. Some suggestions and hypotheses are advanced for future research to improve our understanding of this phenomenon.

  10. The amyloid cascade hypothesis has misled the pharmaceutical industry.

    PubMed

    2011-08-01

    The pharmaceutical industry has invested a great deal of time and finance in the development of therapeutics targeting amyloid generation, signalling and plaque stability. This has been based on the amyloid cascade hypothesis which states that abnormal amyloid precursor protein processing and the formation of amyloid plaques is the central process in the development of the symptoms of Alzheimer's disease. However, most clinical trials in this area have been disappointing; therefore the attendees of the Models of Dementia: the Good, the Bad and the Future meeting were given the opportunity to openly debate the proposal 'the amyloid cascade has misled the pharmaceutical industry', with the main contributions from Professor John Hardy and Professor John Mayer. The present article is a representation of the debate. PMID:21787324

  11. Structural evidence for the rare tautomer hypothesis of spontaneous mutagenesis

    SciTech Connect

    Wang, Weina; Hellinga, Homme W.; Beese, Lorena S.

    2012-05-10

    Even though high-fidelity polymerases copy DNA with remarkable accuracy, some base-pair mismatches are incorporated at low frequency, leading to spontaneous mutagenesis. Using high-resolution X-ray crystallographic analysis of a DNA polymerase that catalyzes replication in crystals, we observe that a C {center_dot} A mismatch can mimic the shape of cognate base pairs at the site of incorporation. This shape mimicry enables the mismatch to evade the error detection mechanisms of the polymerase, which would normally either prevent mismatch incorporation or promote its nucleolytic excision. Movement of a single proton on one of the mismatched bases alters the hydrogen-bonding pattern such that a base pair forms with an overall shape that is virtually indistinguishable from a canonical, Watson-Crick base pair in double-stranded DNA. These observations provide structural evidence for the rare tautomer hypothesis of spontaneous mutagenesis, a long-standing concept that has been difficult to demonstrate directly.

  12. An especial skill: Support for a learned parameters hypothesis.

    PubMed

    Breslin, Gavin; Hodges, Nicola J; Kennedy, Rodney; Hanlon, Michael; Williams, A Mark

    2010-05-01

    We tested the 'learned parameters' hypothesis as an explanation of the 'especial skill effect'. Outcome attainment and movement kinematics were recorded for 10 expert and 10 novice players performing basketball free-throw shots at five distances (11-19 ft) with a regular and heavy weight basketball. As predicted, experts performed better than expected relative to the regression equation at the 15 ft, free-throw line with the regular basketball, supporting the 'especial skill effect'. This effect was not present for the experts when shooting with the heavy ball. Novices did not show an advantage at the free-throw line when performing with either ball. Although the outcome attainment scores support the 'learned parameters' hypotheses, kinematic analysis failed to identify differences in the movement pattern for the especial skill, suggesting that these skills (i.e., shooting at different distances) are not governed by separate motor programs.

  13. On the equipotential surface hypothesis of lunar maria floors

    NASA Astrophysics Data System (ADS)

    Arkani-Hamed, Jafar; Konopliv, A. S.; Sjogren, W. L.

    1999-03-01

    The equipotential surface hypothesis suggests that lunar maria floors lie on a surface parallel to the selenoid. This is examined using the spherical harmonic representations of the Clementine topography and Lunar Prospector gravity data. It is demonstrated that the floors of both circular and noncircular maria significantly deviate from an equipotential surface. Deeper circular maria and the deeper part of the noncircular Mare Tranquillitatis have been subsided under larger mass loads in the crust. We calculate the mass beneath the maria to be in excess to the mass required for isostatic compensation of the topography at 60 km depth. A global map of this excess mass shows that the noncircular maria are isostatically compensated, unlike the circular maria. The map also reveals seven new sizable mascons: the three largest are associated with Mendel-Rydberg, Mare Humboldtianum, and Mare Moscoviense.

  14. Mefloquine use, psychosis, and violence: a retinoid toxicity hypothesis.

    PubMed

    Mawson, Anthony

    2013-07-15

    Mefloquine use has been linked to severe gastrointestinal and neuropsychiatric adverse effects, including cognitive disturbances, anxiety, depression, psychosis, and violence. The adverse effects of the drug are thought to result from the secondary consequences of hepatocellular injury; in fact, mefloquine is known to cause a transient, anicteric chemical hepatitis. However, the mechanism of mefloquine-associated liver damage and the associated neuropsychiatric and behavioral effects of the drug are not well understood. Mefloquine and other 8-amino-quinolines are the only antimalarial drugs that target the liver-stage malaria parasites, which selectively absorb vitamin A from the host. Vitamin A is also stored mainly in the liver, in potentially poisonous concentrations. These observations suggest that both the therapeutic effectiveness of mefloquine and its adverse effects are related to the ability of the 8-aminoquinolines to alter the metabolism of retinoids (vitamin A and its congeners). Several lines of evidence support the hypothesis that mefloquine neurotoxicity and other adverse effects reflect an endogenous form of hypervitaminosis A due to a process involving: mefloquine-induced dehydrogenase inhibition; the accumulation of retinoids in the liver; retinoid-induced hepatocellular damage; the spillage of stored retinoids into the circulation; and the transport of these compounds to the gut and brain in toxic concentrations. The retinoid hypothesis could be tested clinically by comparing cases of mefloquine toxicity and untreated controls in terms of retinoid profiles (retinol, retinyl esters, percent retinyl esters, and retinoic acid). Subject to such tests, retinoid profiling could provide an indicator for assessing mefloquine-associated adverse effects.

  15. Seeing via Miniature Eye Movements: A Dynamic Hypothesis for Vision

    PubMed Central

    Ahissar, Ehud; Arieli, Amos

    2012-01-01

    During natural viewing, the eyes are never still. Even during fixation, miniature movements of the eyes move the retinal image across tens of foveal photoreceptors. Most theories of vision implicitly assume that the visual system ignores these movements and somehow overcomes the resulting smearing. However, evidence has accumulated to indicate that fixational eye movements cannot be ignored by the visual system if fine spatial details are to be resolved. We argue that the only way the visual system can achieve its high resolution given its fixational movements is by seeing via these movements. Seeing via eye movements also eliminates the instability of the image, which would be induced by them otherwise. Here we present a hypothesis for vision, in which coarse details are spatially encoded in gaze-related coordinates, and fine spatial details are temporally encoded in relative retinal coordinates. The temporal encoding presented here achieves its highest resolution by encoding along the elongated axes of simple-cell receptive fields and not across these axes as suggested by spatial models of vision. According to our hypothesis, fine details of shape are encoded by inter-receptor temporal phases, texture by instantaneous intra-burst rates of individual receptors, and motion by inter-burst temporal frequencies. We further describe the ability of the visual system to readout the encoded information and recode it internally. We show how reading out of retinal signals can be facilitated by neuronal phase-locked loops (NPLLs), which lock to the retinal jitter; this locking enables recoding of motion information and temporal framing of shape and texture processing. A possible implementation of this locking-and-recoding process by specific thalamocortical loops is suggested. Overall it is suggested that high-acuity vision is based primarily on temporal mechanisms of the sort presented here and low-acuity vision is based primarily on spatial mechanisms. PMID:23162458

  16. Distinguishing genuine from spurious causes: a coherence hypothesis.

    PubMed

    Lien, Y; Cheng, P W

    2000-03-01

    Two opposing views have been proposed to explain how people distinguish genuine causes from spurious ones: the power view and the covariational view. This paper notes two phenomena that challenge both views. First, even when 1) there is no innate specific causal knowledge about a regularity (so that the power view does not apply) and 2) covariation cannot be computed while controlling for alternative causes (so that the covariation view should not apply), people are still able to systematically judge whether a regularity is causal. Second, when an alternative cause explains the effect, a spurious cause is judged to be spurious with greater confidence than otherwise (in both cases, no causal mechanism underlies the spurious cause). To fill the gap left by the traditional views, this paper proposes a new integration of these views. According to the coherence hypothesis, although a genuine cause and a spurious one may both covary with an effect in a way that does not imply causality at some level of abstraction, the categories to which these candidate causes belong covary with the effect differently at a more abstract level: one covariation implies causality; the other does not. Given this superordinate knowledge, the causal judgments of a reasoner who seeks to explain as much as possible with as few causal rules as possible will exhibit the properties that challenge the traditional views. Two experiments tested and supported the coherence hypothesis. Both experiments involved candidate causes that covary with an effect without implying causality at some level, manipulating whether covariation that implies causality has been acquired at a more abstract level. The experiments differed on whether an alternative cause explains the effect. PMID:10716875

  17. Lynn White Jr. and the greening-of-religion hypothesis.

    PubMed

    Taylor, Bron; Van Wieren, Gretel; Zaleha, Bernard Daley

    2016-10-01

    Lynn White Jr.'s "The Historical Roots of Our Ecologic Crisis," which was published in Science in 1967, has played a critical role in precipitating interdisciplinary environmental studies. Although White advances a multifaceted argument, most respondents focus on his claim that the Judeo-Christian tradition, especially Christianity, has promoted anthropocentric attitudes and environmentally destructive behaviors. Decades later, some scholars argue contrarily that Christianity in particular and the world's predominant religions in general are becoming more environmentally friendly, known as the greening-of-religion hypothesis. To test these claims, we conducted a comprehensive review of over 700 articles-historical, qualitative, and quantitative-that are pertinent to them. Although definitive conclusions are difficult, we identified many themes and dynamics that hinder environmental understanding and mobilization, including conservative theological orientations and beliefs about the role of divine agency in preventing or promoting natural events, whether the religion is an Abrahamic tradition or originated in Asia. On balance, we found the thrust of White's thesis is supported, whereas the greening-of-religion hypothesis is not. We also found that indigenous traditions often foster proenvironmental perceptions. This finding suggests that indigenous traditions may be more likely to be proenvironmental than other religious systems and that some nature-based cosmologies and value systems function similarly. Although we conclude White's thesis and subsequent claims are largely born out, additional research is needed to better understand under what circumstances and communication strategies religious or other individuals and groups may be more effectively mobilized to respond to contemporary environmental challenges.

  18. The origin of ovarian carcinomas: a unifying hypothesis.

    PubMed

    Auersperg, Nelly

    2011-01-01

    It is currently a controversial issue whether epithelial ovarian cancers arise in the ovarian surface epithelium (OSE) or the fimbrial epithelium of the oviduct. The hypothesis presented here aims to reconcile these 2 views and provides a possible explanation for 2 questions arising: first, why tumors originating in the fimbriae and OSE, which are parts of different organs, express common features; second, why these epithelia are prone to neoplastic transformation whereas the remaining oviduct and the extraovarian mesothelium are not. We hypothesize that these questions relate to the common origin of the OSE and fimbriae in that region of the embryonic coelomic epithelium, which will eventually link the extraovarian mesothelium to the epithelium of the oviductal ampulla. OSE and fimbriae become separated during embryonic development but, like other transitional, interepithelial junctions in adults, this region might remain incompletely committed and thus prone to neoplastic progression. To define differentiation at the OSE-tubal junction, salpingo-oophorectomy specimens were stained immunohistochemically for mesenchymal differentiation markers of OSE and for epithelial markers and Pax8, characterizing oviductal fimbriae and ampullae. OSE and ampullae were distinctly different, but there was no sharp boundary between OSE and fimbriae. Rather, both mesenchymal and epithelial markers overlapped, and Pax8 and fimbrial epithelial markers diminished distally, near the OSE. The results support the hypothesis that the OSE and fimbriae are parts of a transitional epithelium of common origin rather than 2 independent sources of ovarian cancer, and suggest that their immature, incompletely determined phenotype contributes to their propensity to neoplastic transformation. PMID:21131839

  19. Harmony as Ideology: Questioning the Diversity-Stability Hypothesis.

    PubMed

    Nikisianis, Nikos; Stamou, Georgios P

    2016-03-01

    The representation of a complex but stable, self-regulated and, finally, harmonious nature penetrates the whole history of Ecology, thus contradicting the core of the Darwinian evolution. Originated in the pre-Darwinian Natural History, this representation defined theoretically the various schools of early ecology and, in the context of the cybernetic synthesis of the 1950s, it assumed a typical mathematical form on account of α positive correlation between species diversity and community stability. After 1960, these two aforementioned concepts and their positive correlation were proposed as environmental management tools, in the face of the ecological crisis arising at the time. In the early 1970s, and particularly after May's evolutionary arguments, the consensus around this positive correlation collapsed for a while, only to be promptly restored for the purpose of attaching an ecological value on biodiversity. In this paper, we explore the history of the diversity-stability hypothesis and we review the successive terms that have been used to express community stability. We argue that this hypothesis has been motivated by the nodal ideological presuppositions of order and harmony and that the scientific developments in this field largely correspond to external social pressures. We conclude that the conflict about the diversity-stability relationship is in fact an ideological debate, referring mostly to the way we see nature and society rather than to an autonomous scientific question. From this point of view, we may understand why Ecology's concepts and perceptions may decline and return again and again, forming a pluralistic scientific history. PMID:26563140

  20. Lynn White Jr. and the greening-of-religion hypothesis.

    PubMed

    Taylor, Bron; Van Wieren, Gretel; Zaleha, Bernard Daley

    2016-10-01

    Lynn White Jr.'s "The Historical Roots of Our Ecologic Crisis," which was published in Science in 1967, has played a critical role in precipitating interdisciplinary environmental studies. Although White advances a multifaceted argument, most respondents focus on his claim that the Judeo-Christian tradition, especially Christianity, has promoted anthropocentric attitudes and environmentally destructive behaviors. Decades later, some scholars argue contrarily that Christianity in particular and the world's predominant religions in general are becoming more environmentally friendly, known as the greening-of-religion hypothesis. To test these claims, we conducted a comprehensive review of over 700 articles-historical, qualitative, and quantitative-that are pertinent to them. Although definitive conclusions are difficult, we identified many themes and dynamics that hinder environmental understanding and mobilization, including conservative theological orientations and beliefs about the role of divine agency in preventing or promoting natural events, whether the religion is an Abrahamic tradition or originated in Asia. On balance, we found the thrust of White's thesis is supported, whereas the greening-of-religion hypothesis is not. We also found that indigenous traditions often foster proenvironmental perceptions. This finding suggests that indigenous traditions may be more likely to be proenvironmental than other religious systems and that some nature-based cosmologies and value systems function similarly. Although we conclude White's thesis and subsequent claims are largely born out, additional research is needed to better understand under what circumstances and communication strategies religious or other individuals and groups may be more effectively mobilized to respond to contemporary environmental challenges. PMID:27604414

  1. A Hypothesis for the Color Bimodality of Jupiter Trojans

    NASA Astrophysics Data System (ADS)

    Wong, Ian; Brown, Michael E.

    2016-10-01

    One of the most enigmatic and hitherto unexplained properties of Jupiter Trojans is their bimodal color distribution. This bimodality is indicative of two sub-populations within the Trojans, which have distinct size distributions. In this paper, we present a simple, plausible hypothesis for the origin and evolution of the two Trojan color sub-populations. In the framework of dynamical instability models of early solar system evolution, which suggest a common primordial progenitor population for both Trojans and Kuiper Belt objects, we use observational constraints to assert that the color bimodalities evident in both minor body populations developed within the primordial population prior to the onset of instability. We show that, beginning with an initial composition of rock and ices, location-dependent volatile loss through sublimation in this primordial population could have led to sharp changes in the surface composition with heliocentric distance. We propose that the depletion or retention of H2S ice on the surface of these objects was the key factor in creating an initial color bimodality. Objects that retained H2S on their surfaces developed characteristically redder colors upon irradiation than those that did not. After the bodies from the primordial population were scattered and emplaced into their current positions, they preserved this primordial color bimodality to the present day. We explore predictions of the volatile loss model—in particular, the effect of collisions within the Trojan population on the size distributions of the two sub-populations—and propose further experimental and observational tests of our hypothesis.

  2. Evolution of Motor Control: From Reflexes and Motor Programs to the Equilibrium-Point Hypothesis

    PubMed Central

    Latash, Mark L.

    2009-01-01

    This brief review analyzes the evolution of motor control theories along two lines that emphasize active (motor programs) and reactive (reflexes) features of voluntary movements. It suggests that the only contemporary hypothesis that integrates both approaches in a fruitful way is the equilibrium-point hypothesis. Physical, physiological, and behavioral foundations of the EP-hypothesis are considered as well as relations between the EP-hypothesis and the recent developments of the notion of motor synergies. The paper ends with a brief review of the criticisms of the EP-hypothesis and challenges that the hypothesis faces at this time. PMID:19823595

  3. Revisiting the Dedifferentiation Hypothesis with Longitudinal Multi-Cohort Data

    ERIC Educational Resources Information Center

    de Frias, Cindy M.; Lovden, Martin; Lindenberger, Ulman; Nilsson, Lars-Goran

    2007-01-01

    The present longitudinal multi-cohort study examines whether interindividual variability in cognitive performance and change increases in old age, and whether associations among developments of different cognitive functions increase with adult age. Multivariate multiple-group latent growth modeling was applied to data from narrow cohorts separated…

  4. The sequential megafaunal collapse hypothesis: Testing with existing data

    NASA Astrophysics Data System (ADS)

    DeMaster, Douglas P.; Trites, Andrew W.; Clapham, Phillip; Mizroch, Sally; Wade, Paul; Small, Robert J.; Hoef, Jay Ver

    2006-02-01

    Springer et al. [Springer, A.M., Estes, J.A., van Vliet, G.B., Williams, T.M., Doak, D.F., Danner, E.M., Forney, K.A., Pfister, B., 2003. Sequential megafaunal collapse in the North Pacific Ocean: an ongoing legacy of industrial whaling? Proceedings of the National Academy of Sciences 100 (21), 12,223-12,228] hypothesized that great whales were an important prey resource for killer whales, and that the removal of fin and sperm whales by commercial whaling in the region of the Bering Sea/Aleutian Islands (BSAI) in the late 1960s and 1970s led to cascading trophic interactions that caused the sequential decline of populations of harbor seal, northern fur seal, Steller sea lion and northern sea otter. This hypothesis, referred to as the Sequential Megafaunal Collapse (SMC), has stirred considerable interest because of its implication for ecosystem-based management. The SMC has the following assumptions: (1) fin whales and sperm whales were important as prey species in the Bering Sea; (2) the biomass of all large whale species (i.e., North Pacific right, fin, humpback, gray, sperm, minke and bowhead whales) was in decline in the Bering Sea in the 1960s and early 1970s; and (3) pinniped declines in the 1970s and 1980s were sequential. We concluded that the available data are not consistent with the first two assumptions of the SMC. Statistical tests of the timing of the declines do not support the assumption that pinniped declines were sequential. We propose two alternative hypotheses for the declines that are more consistent with the available data. While it is plausible, from energetic arguments, for predation by killer whales to have been an important factor in the declines of one or more of the three populations of pinnipeds and the sea otter population in the BSAI region over the last 30 years, we hypothesize that the declines in pinniped populations in the BSAI can best be understood by invoking a multiple factor hypothesis that includes both bottom-up forcing (as

  5. Trade-Offs in Relative Limb Length among Peruvian Children: Extending the Thrifty Phenotype Hypothesis to Limb Proportions

    PubMed Central

    Pomeroy, Emma; Stock, Jay T.; Stanojevic, Sanja; Miranda, J. Jaime; Cole, Tim J.; Wells, Jonathan C. K.

    2012-01-01

    Background and Methods Both the concept of ‘brain-sparing’ growth and associations between relative lower limb length, childhood environment and adult disease risk are well established. Furthermore, tibia length is suggested to be particularly plastic under conditions of environmental stress. The mechanisms responsible are uncertain, but three hypotheses may be relevant. The ‘thrifty phenotype’ assumes that some components of growth are selectively sacrificed to preserve more critical outcomes, like the brain. The ‘distal blood flow’ hypothesis assumes that blood nutrients decline with distance from the heart, and hence may affect limbs in relation to basic body geometry. Temperature adaptation predicts a gradient of decreased size along the limbs reflecting decreasing tissue temperature/blood flow. We examined these questions by comparing the size of body segments among Peruvian children born and raised in differentially stressful environments. In a cross-sectional sample of children aged 6 months to 14 years (n = 447) we measured head circumference, head-trunk height, total upper and lower limb lengths, and zeugopod (ulna and tibia) and autopod (hand and foot) lengths. Results Highland children (exposed to greater stress) had significantly shorter limbs and zeugopod and autopod elements than lowland children, while differences in head-trunk height were smaller. Zeugopod elements appeared most sensitive to environmental conditions, as they were relatively shorter among highland children than their respective autopod elements. Discussion The results suggest that functional traits (hand, foot, and head) may be partially protected at the expense of the tibia and ulna. The results do not fit the predictions of the distal blood flow and temperature adaptation models as explanations for relative limb segment growth under stress conditions. Rather, our data support the extension of the thrifty phenotype hypothesis to limb growth, and suggest that certain

  6. Problems with the Younger Dryas Boundary (YDB) Impact Hypothesis

    NASA Astrophysics Data System (ADS)

    Boslough, M.

    2009-12-01

    One breakthrough of 20th-century Earth science was the recognition of impacts as an important geologic process. The most obvious result is a crater. There are more than 170 confirmed terrestrial impact structures with a non-uniform spatial distribution suggesting more to be found. Many have been erased by tectonics and erosion. Deep water impacts do not form craters, and craters in ice sheets disappear when the ice melts. There is growing speculation that such hidden impacts have caused frequent major environmental events of the Holocene, but this is inconsistent with the astronomically-constrained population of Earth-crossing asteroids. Impacts can have consequences much more significant than excavation of a crater. The K/T boundary mass extinction is attributed to the environmental effects of a major impact, and some researchers argue that other extinctions, abrupt climate changes, and even civilization collapses have resulted from impacts. Nuclear winter models suggest that 2-km diameter asteroids exceed a "global catastrophe threshold" by injecting sufficient dust into the stratosphere to cause short-term climate changes, but would not necessarily collapse most natural ecosystems or cause mass extinctions. Globally-catastrophic impacts recur on timescales of about one million years. The 1994 collision of Comet Shoemaker-Levy 9 with Jupiter led us recognize the significance of terrestrial airbursts caused by objects exploding violently in Earth’s atmosphere. We have invoked airbursts to explain rare forms of non-volcanic glasses and melts by using high-resolution computational models to improve our understanding of atmospheric explosions, and have suggested that multiple airbursts from fragmented impactors could be responsible for regional effects. Our models have been cited in support of the widely-publicized YDB impact hypothesis. Proponents claim that a broken comet exploded over North America, with some fragments cratering the Laurentide Ice Sheet. They

  7. Introducing the refined gravity hypothesis of extreme sexual size dimorphism

    PubMed Central

    2010-01-01

    Background Explanations for the evolution of female-biased, extreme Sexual Size Dimorphism (SSD), which has puzzled researchers since Darwin, are still controversial. Here we propose an extension of the Gravity Hypothesis (i.e., the GH, which postulates a climbing advantage for small males) that in conjunction with the fecundity hypothesis appears to have the most general power to explain the evolution of SSD in spiders so far. In this "Bridging GH" we propose that bridging locomotion (i.e., walking upside-down under own-made silk bridges) may be behind the evolution of extreme SSD. A biomechanical model shows that there is a physical constraint for large spiders to bridge. This should lead to a trade-off between other traits and dispersal in which bridging would favor smaller sizes and other selective forces (e.g. fecundity selection in females) would favor larger sizes. If bridging allows faster dispersal, small males would have a selective advantage by enjoying more mating opportunities. We predicted that both large males and females would show a lower propensity to bridge, and that SSD would be negatively correlated with sexual dimorphism in bridging propensity. To test these hypotheses we experimentally induced bridging in males and females of 13 species of spiders belonging to the two clades in which bridging locomotion has evolved independently and in which most of the cases of extreme SSD in spiders are found. Results We found that 1) as the degree of SSD increased and females became larger, females tended to bridge less relative to males, and that 2) smaller males and females show a higher propensity to bridge. Conclusions Physical constraints make bridging inefficient for large spiders. Thus, in species where bridging is a very common mode of locomotion, small males, by being more efficient at bridging, will be competitively superior and enjoy more mating opportunities. This "Bridging GH" helps to solve the controversial question of what keeps males small

  8. The Maximum Disk Hypothesis and 2-D Spiral Galaxy Models

    NASA Astrophysics Data System (ADS)

    Palunas, P.; Williams, T. B.

    1995-12-01

    We present an analysis of two-dimensional \\ha\\ velocity fields and I-band surface photometry for spiral galaxies taken from the southern sky Fabry-Perot Tully-Fisher survey (Schommer et al., 1993, AJ 105, 97). We construct axi-symmetric maximum disk mass models for 75 galaxies and examine in detail the deviations from axi-symmetry in the surface brightness and kinematics for a subsample of these galaxies. The luminosity profiles and rotation curves are derived using consistent centers, position angles, and inclinations. The disk and bulge are deconvolved by fitting an exponential disk and a series expansion of Gaussians for the bulge directly to the I-band images. This helps constrain the deconvolution by exploiting geometric information as well as the distinct disk and bulge radial profiles. The final disk model is the surface brightness profile of the bulge-subtracted image. The photometric model is fitted to the rotation curve assuming a maximum disk and constant M/L's for the disk and bulge components. The overall structure of the photometric models reproduces the structure in the rotation curves in the majority of galaxies spanning a large range of morphologies and rotation widths from 120 \\kms\\ to 680 \\kms. The median I-band M/L in solar units is 2.8, consistent with normal stellar populations. These results make the disk-halo conspiracy even more puzzling. The degree to which spiral galaxy mass models can reproduce small-scale structure in rotation curves is often used as evidence to support or refute the maximum disk hypothesis. However, single-slit rotation curves sample the velocity distribution only along the major axis, and photometric profiles for inclined galaxies are also sampled most heavily near the major axis. The small-scale structure can be due to local perturbations, such as spiral arms and spiral-arm streaming motions, rather than variations in the global mass distribution. We test this hypothesis by analysing azimuthal correlations in

  9. Climate Model Tests of the Early Anthropogenic Hypothesis

    NASA Astrophysics Data System (ADS)

    Vavrus, S.; Kutzbach, J.; Philippon, G.

    2008-12-01

    We test the hypothesis that greenhouse gas emissions produced by the combination of early and recent human activities, augmented by additional rises in greenhouse gases through ocean feedbacks, have kept the climate warmer than its natural level and offset an incipient glaciation. We use four different configurations of NCAR's Community Climate System Model to investigate the natural climate that should exist today if CO2 and CH4 concentrations had fallen to their average levels reached during previous interglaciations. The model simulations consist of three using a coupled atmosphere-slab ocean configuration---fixed land cover at moderate (T42) and high (T85) model resolution and interactive vegetation composition at T42 resolution--and one employing a coupled atmosphere-dynamical ocean configuration and fixed land cover at T42 resolution. With greenhouse gas concentrations lowered to their estimated natural levels, global mean temperature falls by 2.5-3.0 K in all four experiments. Of the total global cooling with fixed land cover and moderate model resolution, 38% (62%) is attributable to early agricultural activities (industrialization), while early agriculture accounts for approximately half of the expanded permanent snow cover area. The greenhouse cooling triggers widespread glacial inception in the Northern Hemisphere, where permanent snow cover expands by at least 80% and even more with the addition of enhanced model processes: 130% with the dynamical ocean, 150% with high (T85) model resolution, and 200% with vegetation feedbacks included. The regional pattern of incipient glaciation is strongly influenced by atmospheric and circulation changes, sea ice feedbacks, and model resolution. The simulation with a dynamical ocean produces a decrease in vertically integrated global ocean temperature of 1.25 K, a 20% weakening of the Atlantic meridional overturning cell, and an expansion of sea ice and reduced upwelling in the Southern Ocean. Viewed from the

  10. The sequential hypothesis of the function of sleep.

    PubMed

    Giuditta, A; Ambrosini, M V; Montagnese, P; Mandile, P; Cotugno, M; Grassi Zucconi, G; Vescia, S

    1995-01-01

    In addition to modulatory roles concerning bodily functions, sleep is assumed to play a main processing role with regard to newly acquired neural information. Elaboration of memory traces acquired during the waking period is assumed to require two sequential steps taking place during slow wave sleep (SWS) and eventually during paradoxical sleep (PS). This view is suggested by several considerations, not the least of which concerns the natural sequence of appearance of SWS and PS in the adult animal. While the involvement of PS in memory processing is well documented, the involvement of SWS is supported by the results of baseline and post-trial EEG analyses carried out in rats trained for a two-way active avoidance task or a spatial habituation task. Together with control analyses, these data indicate that the marked increase in the average duration of post-trial SWS episodes does not reflect the outcome of non-specific contingent factors, such as sleep loss or stress, but is related to memory processing events. Several considerations have furthermore led to the proposal that, during SWS, after a preliminary selection step, the first processing operation consists in the weakening of non-adaptative memory traces. The remaining memory traces would then be stored again under a better configuration during the ensuing PS episode. This view is in agreement with several relevant features of sleep, including the EEG waveforms prevailing during SWS and PS, as well as the ontogenetic sequence of appearance of SWS and PS. Some theoretical considerations on the role of sleep are also in agreement with the sequential hypothesis. More recent data indicate that the learning capacity of rats is correlated with several baseline EEG features of sleep and wakefulness. They include the average duration of PS episodes and of SWS episodes followed by wakefulness (longer in fast learning rats), and the waking EEG power spectrum of fast learning rats whose output is more balanced in the

  11. Laws of valley growth

    NASA Astrophysics Data System (ADS)

    Yi, Robert; Seybold, Hansjoerg; Rothman, Daniel

    2014-05-01

    River networks incised by re-emerging groundwater flow provide a model framework for studying channelization. The underlying physical equations are well-defined and thus analytical predictions can be obtained and tested in the field. Theory of growth in such channel systems was first formed by Dunne in the early 1980s. A small bulge in the sidewall of a stream leads to the focusing of the ground water flow, and thus to a larger flux of water resulting in a higher erosion rate in this direction. In time such small perturbations grow into newly formed channels, but how they do so is unclear. To probe this problem, we begin by relating the advancement of the tip to the discharge into the spring. If a stream advances at a rate v ~ qη, where q is the discharge of water into the tip, theory of growth in a diffusive field predicts that η has to be smaller than 1 to obtain ramified networks. We test this hypothesis by measuring erosion rates in a field site of groundwater driven channels on the Florida Panhandle. Our network reconstruction yields tip growth rates, which we can directly compare to observational rates obtained from collected cosmogenic 10Be data. This allows us to both verify the existence of a discharge-erosion relation, as well as better characterize growth and competition in the channelization process.

  12. Milk-borne relaxin and the lactocrine hypothesis for maternal programming of neonatal tissues.

    PubMed

    Bagnell, Carol A; Steinetz, Bernard G; Bartol, Frank F

    2009-04-01

    The fact that all newborn mammals drink milk extends the time frame of maternal influence on development into neonatal life. While the nutritional and immunological benefits of milk are clear, the role of milk as a conduit for bioactive factors with the potential to affect neonatal development is less well defined. Porcine and canine milk contain immunoreactive relaxin (RLX) that is transmitted into the circulation of nursing offspring. In the pig, a window of opportunity for transmission of milk-borne RLX is open at birth and remains so for about the first 3 days of neonatal life. Recent studies have shown that pro RLX is the major form of RLX in milk and that milk-borne porcine pro RLX is biologically active. Moreover, RLX receptor (RXFP1) expression is detectable in the porcine female reproductive tract and other somatic tissues at birth. The lactocrine hypothesis for maternal programming of neonatal development was proposed as a mechanism whereby RLX, a prototypical milk-borne growth factor in the pig, is delivered to nursing offspring, where it can affect development of RXFP1-positive target tissues. Data indicating that treatment of newborn gilts with RLX increased estrogen receptor-alpha expression in the uterus and cervix by postnatal day 2 support a role for RLX in lactocrine programming of the female reproductive tract. Effects of RLX on Wnt/beta-catenin expression in neonatal porcine cardiac tissue support a role for RLX in developmental programming of nonreproductive target tissues as well. Ongoing studies will test the lactocrine hypothesis for maternal programming of development by RLX and related milk-borne factors.

  13. Step-by-step description of a computationally efficient version of multiple hypothesis tracking

    NASA Astrophysics Data System (ADS)

    Werthmann, John R.

    1992-08-01

    Under the recently completed Covert Air Combat Definition Study, a form of multiple hypothesis tracking, known as structured branching (SB/MHT), was developed and tested by Hughes Radar Systems Group. SB/MHT offers significant computational savings compared to other approaches, enabling it to maintain a great number of hypothesized tracks, initiated in high false alarm environments without overwhelming current generation tactical processors. Under the recently initiated Advanced Tracking Algorithms Program, the SB/MHT algorithm will be further developed and hosted on a tactical airborne processor to demonstrate realtime performance. This paper walks through the algorithm sequence of operations in order to give the reader an intuitive understanding of SB/MHT. The paper begins with a description of the basic idea of MHT algorithms; i.e., to carry hypotheses when there is doubt about which tracks to associate with new observations. The primary differences between SB/MHT and `classical' MHT are briefly discussed. Each operation in the SB/MHT block diagram is explained by stepping through the operations that would take place given an assumed set of tracks, and a set of observations to be processed. Operations to be discussed include: observation filtering and prediction, gate formation and observation-to-track association, track branching and initiation, initial track scoring and pruning, track clustering, hypothesis generation and scoring, and finally, global track scoring and pruning. Methods for controlling track-file growth and its resultant computational load are also discussed. Although high level in terms of the amount of detail covered, this description should provide the reader with a good understanding of the fundamental characteristics of a streamlined MHT algorithm envisioned to operate in real time on a current generation airborne tactical processor.

  14. Personal Hypothesis Testing: The Role of Consistency and Self-Schema.

    ERIC Educational Resources Information Center

    Strohmer, Douglas C.; And Others

    1988-01-01

    Studied how individuals test hypotheses about themselves. Examined extent to which Snyder's bias toward confirmation persists when negative or nonconsistent personal hypothesis is tested. Found negativity or positivity did not affect hypothesis testing directly, though hypothesis consistency did. Found cognitive schematic variable (vulnerability…

  15. Counselor Hypothesis Testing Strategies: The Role of Initial Impressions and Self-Schema.

    ERIC Educational Resources Information Center

    Strohmer, Douglas C.; Chiodo, Anthony L.

    1984-01-01

    Presents two experiments concerning confirmatory bias in the way counselors collect data to test their hypotheses. Counselors were asked either to develop their own clinical hypothesis or were given a hypothesis to test. Confirmatory bias in hypothesis testing was not supported in either experiment. (JAC)

  16. The Double-Deficit Hypothesis: A Comprehensive Analysis of the Evidence

    ERIC Educational Resources Information Center

    Vukovic, Rose K.; Siegel, Linda S.

    2006-01-01

    The double-deficit hypothesis of developmental dyslexia proposes that deficits in phonological processing and naming speed represent independent sources of dysfunction in dyslexia. The present article is a review of the evidence for the double-deficit hypothesis, including a discussion of recent findings related to the hypothesis. Studies in this…

  17. The Feminization of School Hypothesis Called into Question among Junior and High School Students

    ERIC Educational Resources Information Center

    Verniers, Catherine; Martinot, Delphine; Dompnier, Benoît

    2016-01-01

    Background: The feminization of school hypothesis suggests that boys underachieve in school compared to girls because school rewards feminine characteristics that are at odds with boys' masculine features. Aims: The feminization of school hypothesis lacks empirical evidence. The aim of this study was to test this hypothesis by examining the extent…

  18. The Cognitive Mediation Hypothesis Revisited: An Empirical Response to Methodological and Theoretical Criticism.

    ERIC Educational Resources Information Center

    Romero, Anna A.; And Others

    1996-01-01

    In order to address criticisms raised against the cognitive mediation hypothesis, three experiments were conducted to develop a more direct test of the hypothesis. Taken together, the three experiments provide converging support for the cognitive mediation hypothesis, reconfirming the central role of cognition in the persuasion process.…

  19. Growth Hormone

    MedlinePlus

    ... the dose of glucose. Growth hormone stimulates the production of insulin-like growth factor-1 (IGF-1) . ... regular intervals for years afterward to monitor GH production and to detect tumor recurrence. Other blood tests ...

  20. Eyelid Growths

    MedlinePlus

    ... a microscope). The growth is usually removed surgically. Did You Know... A growth on the eyelid that ... respond to initial treatments. Resources In This Article Did You Know 1 Did You Know... Figure 1 ...

  1. The GABAergic Deficit Hypothesis of Major Depressive Disorder

    PubMed Central

    Luscher, Bernhard; Shen, Qiuying; Sahir, Nadia

    2012-01-01

    Increasing evidence points to an association between major depressive disorders (MDDs) and diverse types of GABAergic deficits. Here we summarize clinical and preclinical evidence supporting a central and causal role of GABAergic deficits in the etiology of depressive disorders. Studies of depressed patients indicate that MDDs are accompanied by reduced brain concentration of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) as well as alterations in the subunit composition of the principal receptors (GABAA receptors) mediating GABAergic inhibition. In addition, there is abundant evidence that GABA plays a prominent role in the brain control of stress, the most important vulnerability factor in mood disorders. Furthermore, preclinical evidence suggests that currently used antidepressant drugs designed to alter monoaminergic transmission as well as non-pharmacologic therapies may ultimately act to counteract GABAergic deficits. In particular, GABAergic transmission plays an important role in the control of hippocampal neurogenesis and neural maturation, which are now established as cellular substrates of most if not all antidepressant therapies. Lastly, comparatively modest deficits in GABAergic transmission in GABAA-receptor-deficient mice are sufficient to cause behavioral, cognitive, neuroanatomical, and neuroendocrine phenotypes as well as antidepressant drug response characteristics expected of an animal model of MDD. The GABAergic hypothesis of MDD suggests that alterations in GABAergic transmission represent fundamentally important aspects of the etiological sequelae of major depressive disorders that are reversed by monoaminergic antidepressant drug action. PMID:21079608

  2. Anosognosia as motivated unawareness: the 'defence' hypothesis revisited.

    PubMed

    Turnbull, Oliver H; Fotopoulou, Aikaterini; Solms, Mark

    2014-12-01

    Anosognosia for hemiplegia has seen a century of almost continuous research, yet a definitive understanding of its mechanism remains elusive. Essentially, anosognosic patients hold quasi-delusional beliefs about their paralysed limbs, in spite of all the contrary evidence, repeated questioning, and logical argument. We review a range of findings suggesting that emotion and motivation play an important role in anosognosia. We conclude that anosognosia involves (amongst other things) a process of psychological defence. This conclusion stems from a wide variety of clinical and experimental investigations, including data on implicit awareness of deficit, fluctuations in awareness over time, and dramatic effects upon awareness of psychological interventions such as psychotherapy, reframing of the emotional consequences of the paralysis, and first versus third person perspectival manipulations. In addition, we review and refute the (eight) arguments historically raised against the 'defence' hypothesis, including the claim that a defence-based account cannot explain the lateralised nature of the disorder. We argue that damage to a well-established right-lateralised emotion regulation system, with links to psychological processes that appear to underpin allocentric spatial cognition, plays a key role in anosognosia (at least in some patients). We conclude with a discussion of implications for clinical practice. PMID:25481464

  3. Human sinus arrhythmia: inconsistencies of a teleological hypothesis.

    PubMed

    Tzeng, Y C; Sin, P Y W; Galletly, D C

    2009-01-01

    Respiratory sinus arrhythmia (RSA) may serve an inherent function in optimizing pulmonary gas exchange efficiency via clustering and scattering of heart beats during the inspiratory and expiratory phases of the respiratory cycle. This study sought to determine whether physiological levels of RSA, enhanced by slow paced breathing, caused more heart beats to cluster in inspiration. In 12 human subjects, we analyzed the histogram distribution of heart beats throughout the respiratory cycle during paced breathing at 12, 9, and 6 breaths/min (br/min). The inspiratory period-to-respiratory period ratio was fixed at approximately 0.5. RSA and its relationship with respiration was characterized in the phase domain by average cubic-spline interpolation of electrocardiographic R wave-to-R wave interval fluctuations throughout all respiratory cycles. Although 6 br/min breathing was associated with a significant increase in RSA amplitude (P < 0.01), we observed no significant increase in the proportion of heart beats in inspiration (P = 0.34). Contrary to assumptions in the literature, we observed no significant clustering of heart beats even with high levels of RSA enhanced by slow breathing. The results of this study do not support the hypothesis that RSA optimizes pulmonary gas exchange efficiency via clustering of heart beats in inspiration.

  4. The iron hypothesis: Basic research meets environmental policy

    NASA Astrophysics Data System (ADS)

    Chisholm, Sallie W.

    1995-07-01

    In October 1993, an interdisciplinary group of scientists spread 445 kg of iron over a 64 km2 patch of surface ocean in the eastern equatorial Pacific. They monitored the patch for 9 days, comparing its biology and chemistry to the unfertilized surrounding waters. They found that the phytoplankton (microscopic plants which comprise the base of the food web in the oceans) were three times more productive in the patch than outside it. In other words, the cells were photosynthesizing—i.e., converting CO2 to organic carbon—at a significantly enhanced rate. The group concluded that iron was the limiting factor in this ecosystem, solving one of the more perplexing puzzles in biological oceanography in recent years. This event marked not only the first unenclosed ocean ecosystem experiment, but also the climax to a complex and fascinating evolution of ideas in biological oceanography. The climax was bittersweet, however, as John Martin, the designer of the experiment and originator of the hypothesis, died shortly before the expedition.

  5. Dehydration influences mood and cognition: a plausible hypothesis?

    PubMed

    Benton, David

    2011-05-01

    The hypothesis was considered that a low fluid intake disrupts cognition and mood. Most research has been carried out on young fit adults, who typically have exercised, often in heat. The results of these studies are inconsistent, preventing any conclusion. Even if the findings had been consistent, confounding variables such as fatigue and increased temperature make it unwise to extrapolate these findings. Thus in young adults there is little evidence that under normal living conditions dehydration disrupts cognition, although this may simply reflect a lack of relevant evidence. There remains the possibility that particular populations are at high risk of dehydration. It is known that renal function declines in many older individuals and thirst mechanisms become less effective. Although there are a few reports that more dehydrated older adults perform cognitive tasks less well, the body of information is limited and there have been little attempt to improve functioning by increasing hydration status. Although children are another potentially vulnerable group that have also been subject to little study, they are the group that has produced the only consistent findings in this area. Four intervention studies have found improved performance in children aged 7 to 9 years. In these studies children, eating and drinking as normal, have been tested on occasions when they have and not have consumed a drink. After a drink both memory and attention have been found to be improved.

  6. Cognitive load hypothesis of item-method directed forgetting.

    PubMed

    Lee, Yuh-Shiow

    2012-01-01

    This study examined the effect of the processing demands of to-be-remembered (TBR) words on item-method directed forgetting. Experiment 1 found that a standard memory group remembered fewer to-be-forgotten (TBF) words than a naming group, in which participants simply named the TBR words during the study phase, even though both groups were equally instructed to forget the TBF words. Experiment 2 manipulated the number of TBR words in the study list, keeping the number of TBF words constant, and found that TBF word forgetting was more difficult in the few TBR words condition than the more TBR words condition. The same pattern was found in the result of Experiment 3 when a cued recall test, instead of a free recall test, was used. In all the experiments, participants were asked to recall the TBF words before the TBR words. These findings are consistent with the cognitive load hypothesis that it is easier to forget when there are fewer cognitive resources available during encoding. PMID:22372566

  7. An epigenetic hypothesis for the genomic memory of pain

    PubMed Central

    Alvarado, Sebastian; Tajerian, Maral; Suderman, Matthew; Machnes, Ziv; Pierfelice, Stephanie; Millecamps, Magali; Stone, Laura S.; Szyf, Moshe

    2015-01-01

    Chronic pain is accompanied with long-term sensory, affective and cognitive disturbances. What are the mechanisms that mediate the long-term consequences of painful experiences and embed them in the genome? We hypothesize that alterations in DNA methylation, an enzymatic covalent modification of cytosine bases in DNA, serve as a “genomic” memory of pain in the adult cortex. DNA methylation is an epigenetic mechanism for long-term regulation of gene expression. Neuronal plasticity at the neuroanatomical, functional, morphological, physiological and molecular levels has been demonstrated throughout the neuroaxis in response to persistent pain, including in the adult prefrontal cortex (PFC). We have previously reported widespread changes in gene expression and DNA methylation in the PFC many months following peripheral nerve injury. In support of this hypothesis, we show here that up-regulation of a gene involved with synaptic function, Synaptotagmin II (syt2), in the PFC in a chronic pain model is associated with long-term changes in DNA methylation. The challenges of understanding the contributions of epigenetic mechanisms such as DNA methylation within the PFC to pain chronicity and their therapeutic implications are discussed. PMID:25852480

  8. Upper and lower neural tube defects: an alternate hypothesis.

    PubMed Central

    Garabedian, B H; Fraser, F C

    1993-01-01

    It has been suggested that neural tube defects (NTDs) of the upper type (anencephaly, encephalocele, and thoracic spina bifida) may have a pathogenesis different from those of the lower type (lumbosacral spina bifida), since recurrent cases within a sibship were said always to be concordant with respect to NTD type. Also, spontaneous abortion, additional malformation, and recurrence rate were observed to be higher in the upper group, and there was an excess of females in upper NTD probands. To test this hypothesis, we measured the above variables in upper and lower NTDs in a sample from Quebec. We found less than full concordance (50%) of NTD type in 18 sib pairs. Recurrence rate was not significantly lower in the lower NTD group (5.6 v 5.8%). The other variables were in general agreement with previous studies, inconsistent findings possibly attributable to different NTD population incidences. These findings can be accounted for if upper and lower NTDs share a similar pathogenesis and the embryo is more susceptible during early than late neural tube formation. PMID:8230161

  9. [Evolutionary process unveiled by the maximum genetic diversity hypothesis].

    PubMed

    Huang, Yi-Min; Xia, Meng-Ying; Huang, Shi

    2013-05-01

    As two major popular theories to explain evolutionary facts, the neutral theory and Neo-Darwinism, despite their proven virtues in certain areas, still fail to offer comprehensive explanations to such fundamental evolutionary phenomena as the genetic equidistance result, abundant overlap sites, increase in complexity over time, incomplete understanding of genetic diversity, and inconsistencies with fossil and archaeological records. Maximum genetic diversity hypothesis (MGD), however, constructs a more complete evolutionary genetics theory that incorporates all of the proven virtues of existing theories and adds to them the novel concept of a maximum or optimum limit on genetic distance or diversity. It has yet to meet a contradiction and explained for the first time the half-century old Genetic Equidistance phenomenon as well as most other major evolutionary facts. It provides practical and quantitative ways of studying complexity. Molecular interpretation using MGD-based methods reveal novel insights on the origins of humans and other primates that are consistent with fossil evidence and common sense, and reestablished the important role of China in the evolution of humans. MGD theory has also uncovered an important genetic mechanism in the construction of complex traits and the pathogenesis of complex diseases. We here made a series of sequence comparisons among yeasts, fishes and primates to illustrate the concept of limit on genetic distance. The idea of limit or optimum is in line with the yin-yang paradigm in the traditional Chinese view of the universal creative law in nature.

  10. Hypothesis: origin of life in deep-reaching tectonic faults.

    PubMed

    Schreiber, Ulrich; Locker-Grütjen, Oliver; Mayer, Christian

    2012-02-01

    The worldwide discussion on the origin of life encounters difficulties when it comes to estimate the conditions of the early earth and to define plausible environments for the development of the first complex organic molecules. Until now, the role of the earth's crust has been more or less ignored. In our opinion, deep-reaching open, interconnected tectonic fault systems may provide possible reaction habitats ranging from nano- to centimetre and even larger dimensions for the formation of prebiotic molecules. In addition to the presence of all necessary raw materials including phosphate, as well as variable pressure and temperature conditions, we suggest that supercritical CO2 as a nonpolar solvent could have played an important role. A hypothetical model for the origin of life is proposed which will be used to design crucial experiments for the model's verification. Because all proposed processes could still occur in tectonic faults at the present time, it may be possible to detect and analyse the formation of prebiotic molecules in order to assess the validity of the proposed hypothesis.

  11. Updates on the antinociceptive mechanism hypothesis of botulinum toxin A.

    PubMed

    Aoki, K Roger; Francis, Joseph

    2011-11-01

    Botulinum toxin A has been traditionally viewed as a motor nerve specific treatment. However, clinical uses for botulinum toxin A have continued to expand, with increased use in conditions implicating sensory pain nerve dysfunction. Chronic pain is associated with excess pain fiber activity. When the site of this excess activity resides in the peripheral portion of the pain pathway, a condition of peripheral sensitization can establish. During this state, excess pain signaling reaches the central nervous system, which can then lead to a condition of central sensitization, manifesting as the symptoms associated with chronic pain (i.e. burning, electric pain, lowered pain threshold to normal stimuli, etc). Experimentally, botulinum toxin type A has been shown to reduce neuropeptides and neurotransmitter release from treated cells or nerve endings and to attenuate nociception in both neuropathic and non-neuropathic pain models. This review summarizes the literature to update the hypothesis for the mechanism by which botulinum toxin type A can modulate chronic pain. PMID:21999893

  12. Network beyond IDO in psychiatric disorders: revisiting neurodegeneration hypothesis.

    PubMed

    Myint, Aye-Mu; Kim, Yong-Ku

    2014-01-01

    The involvement of immune system activation in the pathophysiology of certain psychiatric disorders is well documented. Inflammatory molecules such as pro-inflammatory cytokines could enhance the activity of the indoleamine 2,3-dioxygenase (IDO) enzyme which is the first rate-limiting enzyme of the tryptophan degradation pathway, the kynurenine pathway. The increased tryptophan degradation could induce serotonin depletion and depressive mood. On the other hand, the downstream metabolites from this pathway, such as 3-hydroxykynurenine, quinolinic acid and kynurenic acid, are neuroactive metabolites which can modulate several neurotransmissions, such as glutamatergic, GABAergic, dopaminergic and noradrenergic neurotransmissions, which in turn induce changes in neuronal-glial network and neuropsychiatric consequences. In this issue, we have revised the previous 'neurodegeneration hypothesis,' which explained the involvement of cytokines and IDO pathway interaction in depression, with a further extended view related to the network beyond IDO, the network between immune molecules, tryptophan metabolites and different neurotransmitters, in depression and other major psychiatric disorders such as schizophrenia, bipolar disorder and childhood psychiatric disorders.

  13. Cumulative risk hypothesis: Predicting and preventing child maltreatment recidivism.

    PubMed

    Solomon, David; Åsberg, Kia; Peer, Samuel; Prince, Gwendolyn

    2016-08-01

    Although Child Protective Services (CPS) and other child welfare agencies aim to prevent further maltreatment in cases of child abuse and neglect, recidivism is common. Having a better understanding of recidivism predictors could aid in preventing additional instances of maltreatment. A previous study identified two CPS interventions that predicted recidivism: psychotherapy for the parent, which was related to a reduced risk of recidivism, and temporary removal of the child from the parent's custody, which was related to an increased recidivism risk. However, counter to expectations, this previous study did not identify any other specific risk factors related to maltreatment recidivism. For the current study, it was hypothesized that (a) cumulative risk (i.e., the total number of risk factors) would significantly predict maltreatment recidivism above and beyond intervention variables in a sample of CPS case files and that (b) therapy for the parent would be related to a reduced likelihood of recidivism. Because it was believed that the relation between temporary removal of a child from the parent's custody and maltreatment recidivism is explained by cumulative risk, the study also hypothesized that that the relation between temporary removal of the child from the parent's custody and recidivism would be mediated by cumulative risk. After performing a hierarchical logistic regression analysis, the first two hypotheses were supported, and an additional predictor, psychotherapy for the child, also was related to reduced chances of recidivism. However, Hypothesis 3 was not supported, as risk did not significantly mediate the relation between temporary removal and recidivism.

  14. The Marley hypothesis: denial of racism reflects ignorance of history.

    PubMed

    Nelson, Jessica C; Adams, Glenn; Salter, Phia S

    2013-02-01

    This study used a signal detection paradigm to explore the Marley hypothesis--that group differences in perception of racism reflect dominant-group denial of and ignorance about the extent of past racism. White American students from a midwestern university and Black American students from two historically Black universities completed surveys about their historical knowledge and perception of racism. Relative to Black participants, White participants perceived less racism in both isolated incidents and systemic manifestations of racism. They also performed worse on a measure of historical knowledge (i.e., they did not discriminate historical fact from fiction), and this group difference in historical knowledge mediated the differences in perception of racism. Racial identity relevance moderated group differences in perception of systemic manifestations of racism (but not isolated incidents), such that group differences were stronger among participants who scored higher on a measure of racial identity relevance. The results help illuminate the importance of epistemologies of ignorance: cultural-psychological tools that afford denial of and inaction about injustice.

  15. Curvilinear shapes and the snake detection hypothesis: An ERP study.

    PubMed

    Van Strien, Jan W; Christiaans, Gerwin; Franken, Ingmar H A; Huijding, Jorg

    2016-02-01

    Consistent with the snake detection hypothesis, previous ERP studies have established a larger early posterior negativity (EPN) in response to pictures depicting snakes than to pictures depicting other creatures. Here, we examined to what extent the curvilinear shape of the snake's body drives the larger EPN. To this end, we employed pictures of threatening and nonthreatening species with or without typical curvature. Participants watched a random rapid serial visual presentation of snake, worm, spider, and beetle pictures. The EPN was scored as the mean activity (225-300 ms after picture onset) at occipital and parieto-occipital electrodes. Across electrodes, the EPN was significantly larger for snake pictures than for spider, worm, and beetle pictures, and for spider and worm pictures than for beetle pictures. The results suggest that curvilinear body shapes may partly drive the enhanced EPN. However, the unique cortical response to snakes is not fully explained by this mechanism, and is most probably also determined by other threat-relevant cues. PMID:26481589

  16. Rejection of the C-7 Diffuse Interstellar Band Hypothesis

    NASA Astrophysics Data System (ADS)

    McCall, B. J.; Thorburn, J.; Hobbs, L. M.; Oka, T.; York, D. G.

    2001-09-01

    Using the new high-resolution (~8 km s-1) echelle spectrograph on the 3.5 m telescope at the Apache Point Observatory, we have begun a high-sensitivity survey of the diffuse interstellar bands (DIBs) in a large sample of reddened stars. Now that we are 2 years into this long-term survey, our sample includes over 20 reddened stars that show at least one of the DIBs that had been suggested to be caused by C-7, based on the gas-phase measurement of the C-7 spectrum by J. P. Maier's group. The high-quality astronomical data from this larger sample of stars, along with the spectroscopic constants from the new laboratory work recently reported by Maier's group, have enabled us to examine more carefully the agreement between C-7 and the DIBs. We find that none of the C-7 bands match the DIBs in wavelength or expected profile. One of the DIBs (λ5748) attributed to C-7 is actually a stellar line. The two strongest DIBs attributed to C-7 (λ6270 and λ4964) are not correlated in strength, so they cannot share the same carrier. On the whole, we find no evidence supporting the hypothesis that C-7 is a carrier of the DIBs.

  17. A spectral analysis of the periodicity hypothesis in cratering records

    NASA Astrophysics Data System (ADS)

    Yabushita, Shin

    2004-11-01

    Analysis is made of cratering records, whereby not only the crater ages, but also the sizes can be naturally taken into account. The method adopted is the periodogram analysis first discussed by Lomb. From the crater data based on Grieve's compilation, a period can be derived when a statistical weight of a crater is taken proportional to the size or when a weight proportional to the impact energy is adopted. The period so derived is 37.5 million years. A similar analysis based on Napier's list of craters yields almost the same result. To estimate the significance of the derived period, Monte Carlo experiments have been carried out. It turns out that the probability of occurrence of the derived period due to chance on the null hypothesis of a random distribution of crater ages lies between 0.02 +/- 0.004 and 0.10 +/- 0.009 depending on the data set adopted. The result shows that the level of significance obtained here is higher than in earlier investigations where large craters (with D > 30 km) only are taken into account. A brief discussion is made of the implication of the derived period for the estimates of the Galactic mass density by Stothers and by Hipparcos data analysis.

  18. An Integrated Hypothesis on the Domestication of Bactris gasipaes

    PubMed Central

    Dufour, Dominique; van Zonneveld, Maarten; Escobar Salamanca, Andrés Felipe; Giraldo Toro, Andrés; Rivera, Andrés; Salazar Duque, Hector; Suárez Baron, Harold; Gallego, Gerardo; Scheldeman, Xavier; Gonzalez Mejia, Alonso

    2015-01-01

    Peach palm (Bactris gasipaes Kunth) has had a central place in the livelihoods of people in the Americas since pre-Columbian times, notably for its edible fruits and multi-purpose wood. The botanical taxon includes both domesticated and wild varieties. Domesticated var gasipaes is believed to derive from one or more of the three wild types of var. chichagui identified today, although the exact dynamics and location of the domestication are still uncertain. Drawing on a combination of molecular and phenotypic diversity data, modeling of past climate suitability and existing literature, we present an integrated hypothesis about peach palm’s domestication. We support a single initial domestication event in south western Amazonia, giving rise to var. chichagui type 3, the putative incipient domesticate. We argue that subsequent dispersal by humans across western Amazonia, and possibly into Central America allowed for secondary domestication events through hybridization with resident wild populations, and differential human selection pressures, resulting in the diversity of present-day landraces. The high phenotypic diversity in the Ecuadorian and northern Peruvian Amazon suggest that human selection of different traits was particularly intense there. While acknowledging the need for further data collection, we believe that our results contribute new insights and tools to understand domestication and dispersal patterns of this important native staple, as well as to plan for its conservation. PMID:26658881

  19. The adaptive bleaching hypothesis: experimental tests of critical assumptions.

    PubMed

    Kinzie, R A; Takayama, M; Santos, S R; Coffroth, M A

    2001-02-01

    Coral bleaching, the loss of color due to loss of symbiotic zooxanthellae or their pigment, appears to be increasing in intensity and geographic extent, perhaps related to increasing sea surface temperatures. The adaptive bleaching hypothesis (ABH) posits that when environmental circumstances change, the loss of one or more kinds of zooxanthellae is rapidly, sometimes unnoticeably, followed by formation of a new symbiotic consortium with different zooxanthellae that are more suited to the new conditions in the host's habitat. Fundamental assumptions of the ABH include (1) different types of zooxanthellae respond differently to environmental conditions, specifically temperature, and (2) bleached adults can secondarily acquire zooxanthellae from the environment. We present simple tests of these assumptions and show that (1) genetically different strains of zooxanthellae exhibit different responses to elevated temperature, (2) bleached adult hosts can acquire algal symbionts with an apparently dose-dependent relationship between the concentration of zooxanthellae and the rate of establishment of the symbiosis, (3) and finally, bleached adult hosts can acquire symbionts from the water column.

  20. Patterns of coral bleaching: Modeling the adaptive bleaching hypothesis

    USGS Publications Warehouse

    Ware, J.R.; Fautin, D.G.; Buddemeier, R.W.

    1996-01-01

    Bleaching - the loss of symbiotic dinoflagellates (zooxanthellae) from animals normally possessing them - can be induced by a variety of stresses, of which temperature has received the most attention. Bleaching is generally considered detrimental, but Buddemeier and Fautin have proposed that bleaching is also adaptive, providing an opportunity for recombining hosts with alternative algal types to form symbioses that might be better adapted to altered circumstances. Our mathematical model of this "adaptive bleaching hypothesis" provides insight into how animal-algae symbioses might react under various circumstances. It emulates many aspects of the coral bleaching phenomenon including: corals bleaching in response to a temperature only slightly greater than their average local maximum temperature; background bleaching; bleaching events being followed by bleaching of lesser magnitude in the subsequent one to several years; higher thermal tolerance of corals subject to environmental variability compared with those living under more constant conditions; patchiness in bleaching; and bleaching at temperatures that had not previously resulted in bleaching. ?? 1996 Elsevier Science B.V. All rights reserved.