Science.gov

Sample records for hashi syedain explains

  1. The Mayer Hashi Large-Scale Program to Increase Use of Long-Acting Reversible Contraceptives and Permanent Methods in Bangladesh: Explaining the Disappointing Results. An Outcome and Process Evaluation

    PubMed Central

    Rahman, Mizanur; Haider, M Moinuddin; Curtis, Sian L; Lance, Peter M

    2016-01-01

    ABSTRACT Background: Bangladesh has achieved a low total fertility rate of 2.3. Two-thirds of currently married women of reproductive age (CMWRA) want to limit fertility, and many women achieve their desired fertility before age 30. The incidence of unintended pregnancy and pregnancy termination is high, however. Long-acting reversible contraceptives (LARCs), consisting of the intrauterine device and implant, and permanent methods (PM), including female sterilization and vasectomy, offer several advantages in this situation, but only 8% of CMWRA or 13% of method users use these methods. Program: The Mayer Hashi (MH) program (2009–2013) aimed to improve access to and the quality of LARC/PM services in 21 of the 64 districts in Bangladesh. It was grounded in the SEED (supply–enabling environment–demand) Programming Model. Supply improvements addressed provider knowledge and skills, system strengthening, and logistics. Creating an enabling environment involved holding workshops with local and community leaders, including religious leaders, to encourage them to help promote demand for LARCs and PMs and overcome cultural barriers. Demand promotion encompassed training of providers in counseling, distribution of behavior change communication materials in the community and in facilities, and community mobilization. Methods: We selected 6 MH program districts and 3 nonprogram districts to evaluate the program. We used a before–after and intervention–comparison design to measure the changes in key contraceptive behavior outcomes, and we used a difference-in-differences (DID) specification with comparison to the nonprogram districts to capture the impact of the program. In addition to the outcome evaluation, we considered intermediate indicators that measured the processes through which the interventions were expected to affect the use of LARCs and PMs. Results: The use of LARCs/PMs among CMWRA increased between 2010 and 2013 in both program (from 5.3% to 7.5%) and

  2. Explaining cloud chamber tracks

    SciTech Connect

    Broyles, A.A.

    1992-06-16

    The operation of many detection devices is usually explained in terms of the ionization tracks produced by particles despite the fact that the corresponding incident wave functions extended over the entire sensitive regions of the detectors. The mechanisms by which the wave function appears to collapse to a track is analyzed here.

  3. Explaining the Interpretive Mind.

    ERIC Educational Resources Information Center

    Brockmeier, Jens

    1996-01-01

    Examines two prominent positions in the epistemological foundations of psychology--Piaget's causal explanatory claims and Vygotsky's interpretive understanding; contends that they need to be placed in their wider philosophical contexts. Argues that the danger of causally explaining cultural practices through which human beings construct and…

  4. Explaining wartime rape.

    PubMed

    Gottschall, Jonathan

    2004-05-01

    In the years since the first reports of mass rapes in the Yugoslavian wars of secession and the genocidal massacres in Rwanda, feminist activists and scholars, human rights organizations, journalists, and social scientists have dedicated unprecedented efforts to document, explain, and seek solutions for the phenomenon of wartime rape. While contributors to this literature agree on much, there is no consensus on causal factors. This paper provides a brief overview of the literature on wartime rape in historical and ethnographical societies and a critical analysis of the four leading explanations for its root causes: the feminist theory, the cultural pathology theory, the strategic rape theory, and the biosocial theory. The paper concludes that the biosocial theory is the only one capable of bringing all the phenomena associated with wartime rape into a single explanatory context. PMID:15326538

  5. Explaining moral religions.

    PubMed

    Baumard, Nicolas; Boyer, Pascal

    2013-06-01

    Moralizing religions, unlike religions with morally indifferent gods or spirits, appeared only recently in some (but not all) large-scale human societies. A crucial feature of these new religions is their emphasis on proportionality (between deeds and supernatural rewards, between sins and penance, and in the formulation of the Golden Rule, according to which one should treat others as one would like others to treat oneself). Cognitive science models that account for many properties of religion can be extended to these religions. Recent models of evolved dispositions for fairness in cooperation suggest that proportionality-based morality is highly intuitive to human beings. The cultural success of moralizing movements, secular or religious, could be explained based on proportionality. PMID:23664451

  6. Jupiter's Gossamer Rings Explained.

    NASA Astrophysics Data System (ADS)

    Hamilton, D. P.

    2003-05-01

    Over the past several years, Galileo measurements and groundbased imaging have drastically improved our knowledge of Jupiter's faint ring system. We now recognize that the ring consists of four components: a main ring 7000km wide, whose inner edge blossoms into a vertically-extended halo, and a pair of more tenuous Gossamer rings, one associated with each of the small moons Thebe and Amalthea. When viewed edge on, the Gossamer rings appear as diaphanous disks whose thicknesses agree with the vertical excursions of the inclined satellites from the equatorial plane. In addition, the brightness of each Gossamer ring drops off sharply outside the satellite orbits. These correlations allowed Burns etal (1999, Science, 284, 1146) to argue convincingly that the satellites act as sources of the dusty ring material. In addition, since most material is seen inside the orbits of the source satellites, an inwardly-acting dissipative force such as Poynting-Robertson drag is implicated. The most serious problem with this simple and elegant picture is that it is unable to explain the existence of a faint swath of material that extends half a jovian radius outward from Thebe. A key constraint is that this material has the same thickness as the rest of the Thebe ring. In this work, we identify the mechanism responsible for the outward extension: it is a shadow resonance, first investigated by Horanyi and Burns (1991, JGR, 96, 19283). When a dust grain enters Jupiter's shadow, photoelectric processes shut down and the grain's electric charge becomes more negative. The electromagnetic forces associated with the varying charge cause periodic oscillations in the orbital eccentricity and semimajor axis as the orbital pericenter precesses. This results in a ring which spreads both inward and outward of its source satellite while preserving its vertical thickness - just as is observed for the Thebe ring. Predictions of the model are: i) gaps of micron-sized material interior to Thebe and

  7. Your Radiologist Explains CT Colonography

    MedlinePlus Videos and Cool Tools

    ... About this Site RadiologyInfo.org is produced by: Image/Video Gallery Your Radiologist Explains CT Colonography (Virtual ... to allow for inflation with air while CT images are being taken. If you’re scheduled for ...

  8. Your Radiologist Explains Nuclear Medicine

    MedlinePlus Videos and Cool Tools

    ... by: Image/Video Gallery Your Radiologist Explains Nuclear Medicine Transcript Welcome to Radiology Info dot org Hello! ... d like to talk to you about nuclear medicine. Nuclear medicine offers the potential to identify disease ...

  9. Explaining Errors in Children's Questions

    ERIC Educational Resources Information Center

    Rowland, Caroline F.

    2007-01-01

    The ability to explain the occurrence of errors in children's speech is an essential component of successful theories of language acquisition. The present study tested some generativist and constructivist predictions about error on the questions produced by ten English-learning children between 2 and 5 years of age. The analyses demonstrated that,…

  10. Can Marxism Explain America's Racism?

    ERIC Educational Resources Information Center

    Willhelm, Sidney M.

    1980-01-01

    The Marxist interpretation of the Black experience in America has always had difficulty explaining various noneconomic aspects of racism. A perspective is needed that can blend racism as a variable in relationship with economic variables. To reach this perspective, the labor process within capitalism must be more fully understood. (Author/GC)

  11. Explaining the gender wealth gap.

    PubMed

    Ruel, Erin; Hauser, Robert M

    2013-08-01

    To assess and explain the United States' gender wealth gap, we use the Wisconsin Longitudinal Study to examine wealth accumulated by a single cohort over 50 years by gender, by marital status, and limited to the respondents who are their family's best financial reporters. We find large gender wealth gaps between currently married men and women, and between never-married men and women. The never-married accumulate less wealth than the currently married, and there is a marital disruption cost to wealth accumulation. The status-attainment model shows the most power in explaining gender wealth gaps between these groups explaining about one-third to one-half of the gap, followed by the human-capital explanation. In other words, a lifetime of lower earnings for women translates into greatly reduced wealth accumulation. After controlling for the full model, we find that a gender wealth gap remains between married men and women that we speculate may be related to gender differences in investment strategies and selection effects. PMID:23264038

  12. Explaining mirror-touch synesthesia.

    PubMed

    Ward, Jamie; Banissy, Michael J

    2015-01-01

    Mirror-touch synesthesia (MTS) is the conscious experience of tactile sensations induced by seeing someone else touched. This paper considers two different, although not mutually exclusive, theoretical explanations and, in the final section, considers the relation between MTS and other forms of synesthesia and also other kinds of vicarious perception (e.g., contagious yawning). The Threshold Theory explains MTS in terms of hyper-activity within a mirror system for touch and/or pain. This offers a good account for some of the evidence (e.g., from fMRI) but fails to explain the whole pattern (e.g., structural brain differences outside of this system; performance on some tests of social cognition). The Self-Other Theory explains MTS in terms of disturbances in the ability to distinguish the self from others. This can be construed in terms of over-extension of the bodily self in to others, or as difficulties in the control of body-based self-other representations. In this account, MTS is a symptom of a broader cognitive profile. We suggest this meets the criteria for synesthesia, despite the proximal causal mechanisms remaining largely unknown, and that the tendency to localize vicarious sensory experiences distinguishes it from other kinds of seemingly related phenomena (e.g., non-localized affective responses to observing pain). PMID:25893437

  13. Towards Explaining the Water Siphon

    NASA Astrophysics Data System (ADS)

    Jumper, William D.; Stanchev, Boris

    2014-11-01

    Many high school and introductory college physics courses cover topics in fluidics through the Bernoulli and Poiseuille equations, and consequently one might think that siphons should present an excellent opportunity to engage students in various laboratory measurement exercises incorporating these fascinating devices. However, the flow rates (or average exit velocities) of simple water siphons have not been sufficiently explained,1 nor has an associated analytical model been developed demonstrating sufficient experimental correspondence to allow physics instructors to bring closure between theoretical concepts and laboratory experiences. We present such an explanation and analytical model for the flow rates of simple water tube siphons. Further, we report measurements that show the model gives good correspondence to flow rates of siphons over a wide range of tube lengths, inner diameters, and water heights (hydrostatic head), and for which the Reynolds numbers range from 102 to 105.

  14. Dark antiatoms can explain DAMA

    NASA Astrophysics Data System (ADS)

    Wallemacq, Quentin; Cudell, Jean-René

    2015-02-01

    We show that the existence of a sub-dominant form of dark matter, made of dark "antiatoms" of mass m~ 1 TeV and size dot a0~ 3 fm, can explain the results of direct detection experiments, with a positive signal in DAMA/NaI and DAMA/LIBRA and no signal in other experiments. The signal comes from the binding of the dark antiatoms to thallium, a dopant in DAMA, and is not present for the constituent atoms of other experiments. The dark antiatoms are made of two particles oppositely charged under a dark U(1) symmetry and can bind to terrestrial atoms because of a kinetic mixing between the photon and the massless dark photon, such that the dark particles acquire an electric millicharge ~ ± 5.10-4e. This millicharge enables them to bind to high-Z atoms via radiative capture, after they thermalize in terrestrial matter through elastic collisions.

  15. What explains consciousness? Or…What consciousness explains?

    PubMed

    Dulany, Donelson E

    2014-01-01

    In this invited commentary I focus on the topic addressed in three papers: De Sousa's (2013[1617]) Toward an Integrative Theory of Consciousness, a monograph with Parts 1 & 2, as well as commentaries by Pereira (2013a[59]) and Hirstein (2013[42]). All three are impressively scholarly and can stand-and shout-on their own. But theory of consciousness? My aim is to slice that topic into the two fundamentally different kinds of theories of consciousness, say what appears to be an ideology, out of behaviourism into cognitivism, now also influencing the quest for an "explanation of consciousness" in cognitive neuroscience. I will then say what can be expected given what we know of the complexity of brain structure, the richness of a conscious "vocabulary", and current technological limits of brain imaging. This will then turn to the strategy for examining "what consciousness explains"-metatheory, theories, mappings, and a methodology of competitive support, a methodology especially important where there are competing commitments. There are also increasingly common identifications of methodological bias in, along with failures to replicate, studies reporting unconscious controls in decision, social priming-as there have been in perception, learning, problem solving, etc. The literature critique has provided evidence taken as reducing, and in some cases eliminating, a role for conscious controls-a position consistent with that ideology out of behaviourism into cognitivism. It is an ideological position that fails to recognize the fundamental distinction between theoretical and metaphysical assertions. PMID:24891796

  16. Explain bioinformatics to your grandmother!

    PubMed

    Bernard, Virginie; Michaut, Magali

    2013-10-01

    What are you working on? You have certainly been asked that question many times, whether it be at a Saturday night party, during a discussion with your neighbors, or at a family gathering. Communicating with a lay audience about scientific subjects and making them attractive is a difficult task. But difficult or not, you will have to do it for many years, not only with your family and friends, but also with your colleagues and collaborators. So, better learn now! Although not usually taught, the ability to explain your work to others is an essential skill in science, where communication plays a key role. Using some examples of the French Regional Student Group activities, we discuss here (i) why it is important to have such communication skills, (ii) how you can get involved in these activities by using existing resources or working with people who have previous experience, and (iii) what you get out of this amazing experience. We aim to motivate you and provide you with tips and ideas to get involved in promoting scientific activities while getting all the benefits. PMID:24204239

  17. Dark antiatoms can explain DAMA

    SciTech Connect

    Wallemacq, Quentin; Cudell, Jean-René E-mail: jr.cudell@ulg.ac.be

    2015-02-01

    We show that the existence of a sub-dominant form of dark matter, made of dark ''antiatoms'' of mass m∼ 1 TeV and size a-dot {sub 0}∼ 3 fm, can explain the results of direct detection experiments, with a positive signal in DAMA/NaI and DAMA/LIBRA and no signal in other experiments. The signal comes from the binding of the dark antiatoms to thallium, a dopant in DAMA, and is not present for the constituent atoms of other experiments. The dark antiatoms are made of two particles oppositely charged under a dark U(1) symmetry and can bind to terrestrial atoms because of a kinetic mixing between the photon and the massless dark photon, such that the dark particles acquire an electric millicharge ∼ ± 5.10{sup −4}e. This millicharge enables them to bind to high-Z atoms via radiative capture, after they thermalize in terrestrial matter through elastic collisions.

  18. Topology Explains Why Automobile Sunshades Fold Oddly

    ERIC Educational Resources Information Center

    Feist, Curtis; Naimi, Ramin

    2009-01-01

    Automobile sunshades always fold into an "odd" number of loops. The explanation why involves elementary topology (braid theory and linking number, both explained in detail here with definitions and examples), and an elementary fact from algebra about symmetric group.

  19. Explained variation for recurrent event data.

    PubMed

    Alotaibi, Refah; Fiaccone, Rosemeire; Henderson, Robin; Stare, Janez

    2015-07-01

    Although there are many suggested measures of explained variation for single-event survival data, there has been little attention to explained variation for recurrent event data. We describe an existing rank-based measure and we investigate a new statistic based on observed and expected event count processes. Both methods can be used for all models. Adjustments for missing data are proposed and demonstrated through simulation to be effective. We compare the population values of the two statistics and illustrate their use in comparing an array of non-nested models for data on recurrent episodes of infant diarrhoea. PMID:25899247

  20. Mining and Explaining Relationships in Wikipedia

    NASA Astrophysics Data System (ADS)

    Zhang, Xinpeng; Asano, Yasuhito; Yoshikawa, Masatoshi

    Mining and explaining relationships between concepts are challenging tasks in the field of knowledge search. We propose a new approach for the tasks using disjoint paths formed by links in Wikipedia. Disjoint paths are easy to understand and do not contain redundant information. To achieve this approach, we propose a naive method, as well as a generalized flow based method, and a technique for mining more disjoint paths using the generalized flow based method. We also apply the approach to classification of relationships. Our experiments reveal that the generalized flow based method can mine many disjoint paths important for understanding a relationship, and the classification is effective for explaining relationships.

  1. How Employees Remain Happy: Explaining a Paradox

    ERIC Educational Resources Information Center

    Hutton, Dorothy M.; Atkinson, Barbara; Judd, Priya; Darling, Julie; Tran, Linh; Cummins, Robert A.

    2004-01-01

    This paper draws on subjective quality of life theory to explain findings from three studies of quality of work life. The studies were conducted with 346 regional process workers, metropolitan employment officers and nurses. The results support the adoption of the theory of homeostasis as an explanation for findings on subjective wellbeing at work…

  2. Explaining Autism: Its Discursive and Neuroanatomical Characteristics.

    ERIC Educational Resources Information Center

    Oller, John W., Jr.; Rascon, Dana

    This paper reviews the existing empirical research on autism in the context of the semiotic theories of Charles S. Peirce. His ideas of the generalized logic of relations are seen as explaining the unusual associations (or lack thereof) in autism. Concepts of "indices" or signs singling out distinct objects, and "adinity" or the number of distinct…

  3. Explaining High Abilities of Nobel Laureates

    ERIC Educational Resources Information Center

    Shavinina, Larisa

    2004-01-01

    Although the Nobel Prize is associated with a rare, superior degree of intellectually creative achievement, high abilities of Nobel laureates are far from well explained. This paper argues that Nobel laureates' high abilities are determined in part by their extracognitive abilities, that is, specific feelings, preferences, beliefs and intuitive…

  4. Do changes in connectivity explain desertification?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Desertification, broad-scale land degradation in drylands, is a major environmental hazard facing inhabitants of the world’s deserts as well as an important component of global change. There is no unifying framework that simply and effectively explains different forms of desertification. Here we arg...

  5. Evidence and Proof: Explaining Vector Relationships.

    ERIC Educational Resources Information Center

    Doerr, Helen M.

    This paper addresses a central issue in secondary school geometry, namely the role of proof. In an integrated mathematics and science curriculum, the role of proof as a process of conjecturing, explaining, and justifying within a small-group setting is analyzed. Particular attention is given to the students' use of empirical evidence and algebraic…

  6. Heavy fermion behavior explained by bosons

    NASA Technical Reports Server (NTRS)

    Kallio, A.; Poykko, S.; Apaja, V.

    1995-01-01

    Conventional heavy fermion (HF) theories require existence of massive fermions. We show that heavy fermion phenomena can also be simply explained by existence of bosons with moderate mass but temperature dependent concentration below the formation temperature T(sub B), which in turn is close to room temperature. The bosons B(++) are proposed to be in chemical equilibrium with a system of holes h(+): B(++) = h(+) + h(+). This equilibrium is governed by a boson breaking function f(T), which determines the decreasing boson density and the increasing fermion density with increasing temperature. Since HF-compounds are hybridized from minimum two elements, we assume in addition existence of another fermion component h(sub s)(+) with temperature independent density. This spectator component is thought to be the main agent in binding the bosons in analogy with electronic or muonic molecules. Using a linear boson breaking function we can explain temperature dependence of the giant linear specific heat coefficient gamma(T) coming essentially from bosons. The maxima in resistivity, Hall coefficient, and susceptibility are explained by boson localization effects due to the Wigner crystallization. The antiferromagnetic transitions in turn are explained by similar localization of the pairing fermion system when their density n(sub h)(T(sub FL)) becomes lower than n(sub WC), the critical density of Wigner crystallization. The model applies irrespective whether a compound is superconducting or not. The same model explains the occurrence of low temperature antiferromagnetism also in high-T(sub c) superconductors. The double transition in UPt3 is proposed to be due to the transition of the pairing fermion liquid from spin polarized to unpolarized state.

  7. Children's Theories and the Drive to Explain

    NASA Astrophysics Data System (ADS)

    Schwitzgebel, Eric

    Debate has been growing in developmental psychology over how much the cognitive development of children is like theory change in science. Useful debate on this topic requires a clear understanding of what it would be for a child to have a theory. I argue that existing accounts of theories within philosophy of science and developmental psychology either are less precise than is ideal for the task or cannot capture everyday theorizing of the sort that children, if they theorize, must do. I then propose an account of theories that ties theories and explanation very closely together, treating theories primarily as products of a drive to explain. I clarify some of the positions people have taken regarding the theory theory of development, and I conclude by proposing that psychologists interested in the ''theory theory'' look for patterns of affect and arousal in development that would accompany the existence of a drive to explain.

  8. Explaining Underrepresentation: A Theory of Precluded Interest

    PubMed Central

    Plaut, Victoria C.

    2010-01-01

    What processes best explain women’s underrepresentation in science, math, and engineering fields in the U.S.? Do they also explain men’s underrepresentation in the humanities? Two survey studies across two U.S. West Coast universities (N = 62; N = 614) addressed these questions in the context of two fields: one male-dominated (computer science) and the other female-dominated (English). Among a set of social predictors—including perceived similarity to the people in the field, social identity threats, and expectations of success—the best mediator of women’s lower interest in computer science and men’s lower interest in English was perceived similarity. Thus, changing students’ social perceptions of how they relate to those in the field may help to diversify academic fields. PMID:20930923

  9. ExplainHoudini: Making Houdini Inference Transparent

    NASA Astrophysics Data System (ADS)

    Lahiri, Shuvendu K.; Vanegue, Julien

    Houdini is a simple yet scalable technique for annotation inference for modular contract checking. The input to Houdini is a set of candidate annotations, and the output is a consistent subset of these candidates. Since this technique is most useful as an annotation assistant for user-guided refinement of annotations, understanding the reason for the removal of annotations is crucial for a user to refine the set of annotations, and classify false errors easily. This is especially true for applying Houdini to large legacy modules with thousands of procedures and deep call chains. In this work we present a method ExplainHoudini that explains the reason why a given candidate was removed, purely in terms of the existing candidates. We have implemented this algorithm and provide preliminary experience of applying it on large modules.

  10. Dissipative dark matter explains rotation curves

    NASA Astrophysics Data System (ADS)

    Foot, R.

    2015-06-01

    Dissipative dark matter, where dark matter particles interact with a massless (or very light) boson, is studied. Such dark matter can arise in simple hidden sector gauge models, including those featuring an unbroken U (1 )' gauge symmetry, leading to a dark photon. Previous work has shown that such models can not only explain the large scale structure and cosmic microwave background, but potentially also dark matter phenomena on small scales, such as the inferred cored structure of dark matter halos. In this picture, dark matter halos of disk galaxies not only cool via dissipative interactions but are also heated via ordinary supernovae (facilitated by an assumed photon-dark photon kinetic mixing interaction). This interaction between the dark matter halo and ordinary baryons, a very special feature of these types of models, plays a critical role in governing the physical properties of the dark matter halo. Here, we further study the implications of this type of dissipative dark matter for disk galaxies. Building on earlier work, we develop a simple formalism which aims to describe the effects of dissipative dark matter in a fairly model independent way. This formalism is then applied to generic disk galaxies. We also consider specific examples, including NGC 1560 and a sample of dwarf galaxies from the LITTLE THINGS survey. We find that dissipative dark matter, as developed here, does a fairly good job accounting for the rotation curves of the galaxies considered. Not only does dissipative dark matter explain the linear rise of the rotational velocity of dwarf galaxies at small radii, but it can also explain the observed wiggles in rotation curves which are known to be correlated with corresponding features in the disk gas distribution.

  11. Deglaciation explains bat extinction in the Caribbean

    PubMed Central

    Dávalos, Liliana M; Russell, Amy L

    2012-01-01

    Ecological factors such as changing climate on land and interspecific competition have been debated as possible causes of postglacial Caribbean extinction. These hypotheses, however, have not been tested against a null model of climate-driven postglacial area loss. Here, we use a new Quaternary mammal database and deep-sea bathymetry to estimate species–area relationships (SARs) at present and during the Last Glacial Maximum (LGM) for bats of the Caribbean, and to model species loss as a function of area loss from rising sea level. Island area was a significant predictor of species richness in the Bahamas, Greater Antilles, and Lesser Antilles at all time periods, except for the Lesser Antilles during the LGM. Parameters of LGM and current SARs were similar in the Bahamas and Greater Antilles, but not the Lesser Antilles, which had fewer estimated species during the LGM than expected given their size. Estimated postglacial species losses in the Bahamas and Greater Antilles were largely explained by inferred area loss from rising sea level in the Holocene. However, there were more species in the Bahamas at present, and fewer species in the smaller Greater Antilles, than expected given island size and the end-Pleistocene/early Holocene SARs. Poor fossil sampling and ecological factors may explain these departures from the null. Our analyses illustrate the importance of changes in area in explaining patterns of species richness through time and emphasize the role of the SAR as a null hypothesis in explorations of the impact of novel ecological interactions on extinction. PMID:23301171

  12. Life-Saving Space Technology Explained

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Dr. Harry Whelan, a pediatric Neurologist at the Medical Hospital of Wisconsin in Milwaukee and professor of Neurology at the Medical College of Wisconsin, explains the operation of light-emitting diodes (LEDs) developed for use in space plant growth experiments and now adapted for use in photodynamic therapy, a technique in which light from the LEDs activates light-sensitive, tumor-treating drugs. The technique has been used in at least two surgeries on brain tumors. The LED project was one of several NASA exhibits at AirVenture 2000 sponsored by the Experimental Aircraft Association in Oshkosh, WI.

  13. Does information theory explain biological evolution?

    NASA Astrophysics Data System (ADS)

    Battail, G.

    1997-11-01

    It is suggested that Dawkins' model of evolution needs error-correction coding in the genome replication process. Nested coding is moreover assumed. Consequences of these hypotheses are drawn using fundamental results of information theory. Genome replication is dealt with independently of phenotype encoding, which pertains to semantics. The proposed hypotheses enable explaining facts of genetics and evolution, including the existence of redundant DNA (the introns), the observed correlation between the rate of mutations on the one hand, the genome length and the redundancy rate on the other hand, the discreteness of species and the trend of eukaryotes evolution towards complexity.

  14. Can predictive coding explain repetition suppression?

    PubMed

    Grotheer, Mareike; Kovács, Gyula

    2016-07-01

    While in earlier work various local or bottom-up neural mechanisms were proposed to give rise to repetition suppression (RS), current theories suggest that top-down processes play a role in determining the repetition related reduction of the neural responses. In the current review we summarise those results, which support the role of these top-down processes, concentrating on the Bayesian models of predictive coding (PC). Such models assume that RS is related to the statistical probabilities of prior stimulus occurrences and to the future predictability of these stimuli. Here we review the current results that support or argue against this explanation. We point out that the heterogeneity of experimental manipulations that are thought to reflect predictive processes are likely to measure different processing steps, making their direct comparison difficult. In addition we emphasize the importance of identifying these sub-processes and clarifying their role in explaining RS. Finally, we propose a two-stage model for explaining the relationships of repetition and expectation phenomena in the human cortex. PMID:26861559

  15. Mach bands explained by response normalization.

    PubMed

    Kingdom, Frederick A A

    2014-01-01

    Mach bands are the illusory dark and bright bars seen at the foot and knee of a luminance trapezoid. First demonstrated by Ernst Mach in the latter part of the 19th century, Mach bands are a test bed not only for models of brightness illusions but of spatial vision in general. Up until 50 years ago the dominant explanation of Mach Bands was that they were caused by lateral inhibition among retinal neurons. More recently, the dominant idea has been that Mach bands are a consequence of a visual process that generates a sparse, binary description of the image in terms of "edges" and "bars". Another recent explanation is that Mach bands result from learned expectations about the pattern of light typically found on sharply curved surfaces. In keeping with recent multi-scale filtering accounts of brightness illusions as well as current physiology, I show however that Mach bands are most simply explained by response normalization, whereby the gains of early visual channels are adjusted on a local basis to make their responses more equal. I show that a simple one-dimensional model of response normalization explains the range of conditions under which Mach bands occur, and as importantly, the conditions under which they do not occur. PMID:25408643

  16. EXPLAINING THE ASSOCIATION BETWEEN INCARCERATION AND DIVORCE*

    PubMed Central

    Siennick, Sonja E.; Stewart, Eric A.; Staff, Jeremy

    2014-01-01

    Recent studies have suggested that incarceration dramatically increases the odds of divorce, but we know little about the mechanisms that explain the association. This study uses prospective longitudinal data from a subset of married young adults in the National Longitudinal Study of Adolescent Health (N = 1,919) to examine whether incarceration is associated with divorce indirectly via low marital love, economic strain, relationship violence, and extramarital sex. The findings confirmed that incarcerations occurring during, but not before, a marriage were associated with an increased hazard of divorce. Incarcerations occurring during marriage also were associated with less marital love, more relationship violence, more economic strain, and greater odds of extramarital sex. Above-average levels of economic strain were visible among respondents observed preincarceration, but only respondents observed postincarceration showed less marital love, more relationship violence, and higher odds of extramarital sex than did respondents who were not incarcerated during marriage. These relationship problems explained approximately 40 percent of the association between incarceration and marital dissolution. These findings are consistent with theoretical predictions that a spouse’s incarceration alters the rewards and costs of the marriage and the relative attractiveness of alternative partners. PMID:25598544

  17. Mach bands explained by response normalization

    PubMed Central

    Kingdom, Frederick A. A.

    2014-01-01

    Mach bands are the illusory dark and bright bars seen at the foot and knee of a luminance trapezoid. First demonstrated by Ernst Mach in the latter part of the 19th century, Mach bands are a test bed not only for models of brightness illusions but of spatial vision in general. Up until 50 years ago the dominant explanation of Mach Bands was that they were caused by lateral inhibition among retinal neurons. More recently, the dominant idea has been that Mach bands are a consequence of a visual process that generates a sparse, binary description of the image in terms of “edges” and “bars”. Another recent explanation is that Mach bands result from learned expectations about the pattern of light typically found on sharply curved surfaces. In keeping with recent multi-scale filtering accounts of brightness illusions as well as current physiology, I show however that Mach bands are most simply explained by response normalization, whereby the gains of early visual channels are adjusted on a local basis to make their responses more equal. I show that a simple one-dimensional model of response normalization explains the range of conditions under which Mach bands occur, and as importantly, the conditions under which they do not occur. PMID:25408643

  18. Dark Matter and Dark Energy Explained

    NASA Astrophysics Data System (ADS)

    Aisenberg, Sol

    2006-03-01

    The standard model of the universe has many mysteries and defects requiring the use of large fudge factors such as Dark Matter and Dark Energy. We will show that Dark Matter is needed when we try to extend Newton's law of gravity (based upon observations in our solar system) to galactic distances. Dark Matter was introduced to explain the observed flat velocity rotation curves of the outer parts of spiral galaxies, as observed by Vera. Rubin. Much earlier, the (under appreciated) Fritz Zwicky introduced the need for large amounts of missing invisible matter to explain the surprising observed motion of groups of remote galaxies. In our hypothesis, the modification of Newton's laws by the addition of a linear term to the gravitational constant that increases with distance will eliminate the need for dark matter. Our hypothesis is different from the MOND theory of Milgrom, which depends upon acceleration. The Red shift observations by Hubble as a function of distance, and interpreted as ``apparent Doppler effect'' led to the unproven belief that the universe is expanding, and thus to the Big Bang. In turn the apparent acceleration of the expansion required the introduction of Dark Energy. Actually there are three additional components of the red shift that are solely due to gravity and distance and can be larger than the Doppler contribution.

  19. Developmental systems theory: what does it explain, and how does it explain it?

    PubMed

    Griffiths, Paul E; Tabery, James

    2013-01-01

    We examine developmental systems theory (DST) with two questions in mind: What does DST explain? How does DST explain it? To answer these questions, we start by reviewing major contributions to the origins of DST: the introduction of the idea of a "developmental system", the idea of probabilistic epigenesis, the attention to the role of information in the developmental system, and finally the explicit identification of a DST. We then consider what DST is not, contrasting it with two approaches that have been foils for DST: behavioral genetics and nativist cognitive psychology. Third, we distill out two core concepts that have defined DSTthroughout its history: epigenesis and developmental dynamics. Finally, we turn to how DST explains, arguing that it explains by elucidating mechanisms. PMID:23834002

  20. Bell Test experiments explained without entanglement

    NASA Astrophysics Data System (ADS)

    Boyd, Jeffrey

    2011-04-01

    by Jeffrey H. Boyd. Jeffreyhboyd@gmail.com. John Bell proposed a test of what was called "local realism." However that is a different view of reality than we hold. Bell incorrectly assumed the validity of wave particle dualism. According to our model waves are independent of particles; wave interference precedes the emission of a particle. This results in two conclusions. First the proposed inequalities that apply to "local realism" in Bell's theorem do not apply to this model. The alleged mathematics of "local realism" is therefore wrong. Second, we can explain the Bell Test experimental results (such as the experiments done at Innsbruck) without any need for entanglement, non-locality, or particle superposition.

  1. Explaining math: gesturing lightens the load.

    PubMed

    Goldin-Meadow, S; Nusbaum, H; Kelly, S D; Wagner, S

    2001-11-01

    Why is it that people cannot keep their hands still when they talk? One reason may be that gesturing actually lightens cognitive load while a person is thinking of what to say. We asked adults and children to remember a list of letters or words while explaining how they solved a math problem. Both groups remembered significantly more items when they gestured during their math explanations than when they did not gesture. Gesturing appeared to save the speakers' cognitive resources on the explanation task, permitting the speakers to allocate more resources to the memory task. It is widely accepted that gesturing reflects a speaker's cognitive state, but our observations suggest that, by reducing cognitive load, gesturing may also play a role in shaping that state. PMID:11760141

  2. Weaker dental enamel explains dental decay.

    PubMed

    Vieira, Alexandre R; Gibson, Carolyn W; Deeley, Kathleen; Xue, Hui; Li, Yong

    2015-01-01

    Dental caries continues to be the most prevalent bacteria-mediated non-contagious disease of humankind. Dental professionals assert the disease can be explained by poor oral hygiene and a diet rich in sugars but this does not account for caries free individuals exposed to the same risk factors. In order to test the hypothesis that amount of amelogenin during enamel development can influence caries susceptibility, we generated multiple strains of mice with varying levels of available amelogenin during dental development. Mechanical tests showed that dental enamel developed with less amelogenin is "weaker" while the dental enamel of animals over-expressing amelogenin appears to be more resistant to acid dissolution. PMID:25885796

  3. Explaining Today's Physics Through History and Biography

    NASA Astrophysics Data System (ADS)

    Lindley, David

    2014-03-01

    Quantum computers, string theory, holographic universes - to the general audience, today's physics can be as mystifying as it is fascinating. But modern ideas evolved from an earlier phase of physics - Newtonian mechanics, simple cause and effect - that is in principle easier for the non-expert to grasp. I have found that writing about physics from a historical and biographical perspective is an effective way to convey modern thinking by explaining where it comes from - it is a way of carrying the reader from concepts that make intuitive sense to ideas that seem, on first encounter, utterly bizarre. Smuggling explanations into stories satisfies the reader's desire for narrative - bearing in mind that narrative can include the evolution of ideas as well as tales about intriguing and original people.

  4. Explaining the gender difference in nightmare frequency.

    PubMed

    Schredl, Michael

    2014-01-01

    A recent meta-analysis showed a robust gender difference in nightmare frequency of medium effect size in adolescents and young adults: Women tend to report nightmares more frequently than men. The present study, carried out in an unselected student sample, indicates that 2 factors mediate the gender difference in nightmare frequency: neuroticism and overall dream recall frequency. The effect of neuroticism on the gender difference and the finding that the gender difference in nightmare frequency emerges at an age of about 10 years suggest that gender-specific socialization processes may play an important role in explaining the gender differences in nightmare frequency in adolescents and young to middle-aged adults. This idea is supported by the previous finding that nightmare frequency is related to sex role orientation. However, longitudinal studies are necessary to validate these hypotheses. PMID:24934011

  5. Macromolecular crowding explains overflow metabolism in cells

    PubMed Central

    Vazquez, Alexei; Oltvai, Zoltán N.

    2016-01-01

    Overflow metabolism is a metabolic phenotype of cells characterized by mixed oxidative phosphorylation (OxPhos) and fermentative glycolysis in the presence of oxygen. Recently, it was proposed that a combination of a protein allocation constraint and a higher proteome fraction cost of energy generation by OxPhos relative to fermentation form the basis of overflow metabolism in the bacterium, Escherichia coli. However, we argue that the existence of a maximum or optimal macromolecular density is another essential requirement. Here we re-evaluate our previous theory of overflow metabolism based on molecular crowding following the proteomic fractions formulation. We show that molecular crowding is a key factor in explaining the switch from OxPhos to overflow metabolism. PMID:27484619

  6. Transitioning from Idiopathic to Explainable Autoimmune Hepatitis.

    PubMed

    Czaja, Albert J

    2015-10-01

    Autoimmune hepatitis lacks an identifiable cause, and its diagnosis requires the exclusion of etiologically defined diseases that resemble it. Insights into its pathogenesis are moving autoimmune hepatitis from an idiopathic to explainable disease, and the goal of this review is to describe the insights that are hastening this transition. Two types of autoimmune hepatitis are justified by serological markers, but they also have distinctive genetic associations (DRB1 and DQB1 genes) and autoantigens. DRB1 alleles are the principal susceptibility factors in white adults, and a six amino acid sequence encoded in the antigen-binding groove of class II molecules of the major histocompatibility complex can influence the selection of autoantigens. Polymorphisms, including variants of SH2B3 and CARD10 genes, may affect immune reactivity and disease severity. The cytochrome mono-oxygenase, CYP2D6, is the autoantigen associated with type 2 autoimmune hepatitis, and it shares homologies with multiple viruses that might promote self-intolerance by molecular mimicry. Chemokines, especially CXCL9 and CXCL10, orchestrate the migration of effector cells to sites of injury and are associated with disease severity. Cells of the innate and adaptive immune responses promote tissue damage, and possible deficiencies in the number and function of regulatory T cells may facilitate the injurious process. Receptor-mediated apoptosis is the principal mechanism of hepatocyte loss, and cell-mediated and antibody-dependent mechanisms of cytotoxicity also contribute. Insights that explain autoimmune hepatitis will allow triggering exogenous antigens to be characterized, risk management to be improved, prognostic indices to be refined, and site-specific therapeutic interventions to emerge. PMID:25999246

  7. Explaining Polarization Reversals in STEREO Wave Data

    NASA Technical Reports Server (NTRS)

    Breneman, A.; Cattell, C.; Wygant, J.; Kersten, K.; Wilson, L, B., III; Dai, L.; Colpitts, C.; Kellogg, P. J.; Goetz, K.; Paradise, A.

    2012-01-01

    Recently Breneman et al. reported observations of large amplitude lightning and transmitter whistler mode waves from two STEREO passes through the inner radiation belt (L<2). Hodograms of the electric field in the plane transverse to the magnetic field showed that the transmitter waves underwent periodic polarization reversals. Specifically, their polarization would cycle through a pattern of right-hand to linear to left-hand polarization at a rate of roughly 200 Hz. The lightning whistlers were observed to be left-hand polarized at frequencies greater than the lower hybrid frequency and less than the transmitter frequency (21.4 kHz) and right-hand polarized otherwise. Only righthand polarized waves in the inner radiation belt should exist in the frequency range of the whistler mode and these reversals were not explained in the previous paper. We show, with a combination of observations and simulated wave superposition, that these polarization reversals are due to the beating of an incident electromagnetic whistler mode wave at 21.4 kHz and linearly polarized, symmetric lower hybrid sidebands Doppler-shifted from the incident wave by +/-200 Hz. The existence of the lower hybrid waves is consistent with the parametric decay mechanism of Lee and Kuo whereby an incident whistler mode wave decays into symmetric, short wavelength lower hybrid waves and a purely growing (zero-frequency) mode. Like the lower hybrid waves, the purely growing mode is Doppler-shifted by 200 Hz as observed on STEREO. This decay mechanism in the upper ionosphere has been previously reported at equatorial latitudes and is thought to have a direct connection with explosive spread F enhancements. As such it may represent another dissipation mechanism of VLF wave energy in the ionosphere and may help to explain a deficit of observed lightning and transmitter energy in the inner radiation belts as reported by Starks et al.

  8. Explaining evolution via constrained persistent perfect phylogeny

    PubMed Central

    2014-01-01

    Background The perfect phylogeny is an often used model in phylogenetics since it provides an efficient basic procedure for representing the evolution of genomic binary characters in several frameworks, such as for example in haplotype inference. The model, which is conceptually the simplest, is based on the infinite sites assumption, that is no character can mutate more than once in the whole tree. A main open problem regarding the model is finding generalizations that retain the computational tractability of the original model but are more flexible in modeling biological data when the infinite site assumption is violated because of e.g. back mutations. A special case of back mutations that has been considered in the study of the evolution of protein domains (where a domain is acquired and then lost) is persistency, that is the fact that a character is allowed to return back to the ancestral state. In this model characters can be gained and lost at most once. In this paper we consider the computational problem of explaining binary data by the Persistent Perfect Phylogeny model (referred as PPP) and for this purpose we investigate the problem of reconstructing an evolution where some constraints are imposed on the paths of the tree. Results We define a natural generalization of the PPP problem obtained by requiring that for some pairs (character, species), neither the species nor any of its ancestors can have the character. In other words, some characters cannot be persistent for some species. This new problem is called Constrained PPP (CPPP). Based on a graph formulation of the CPPP problem, we are able to provide a polynomial time solution for the CPPP problem for matrices whose conflict graph has no edges. Using this result, we develop a parameterized algorithm for solving the CPPP problem where the parameter is the number of characters. Conclusions A preliminary experimental analysis shows that the constrained persistent perfect phylogeny model allows to

  9. Ocean currents help explain population genetic structure

    PubMed Central

    White, Crow; Selkoe, Kimberly A.; Watson, James; Siegel, David A.; Zacherl, Danielle C.; Toonen, Robert J.

    2010-01-01

    Management and conservation can be greatly informed by considering explicitly how environmental factors influence population genetic structure. Using simulated larval dispersal estimates based on ocean current observations, we demonstrate how explicit consideration of frequency of exchange of larvae among sites via ocean advection can fundamentally change the interpretation of empirical population genetic structuring as compared with conventional spatial genetic analyses. Both frequency of larval exchange and empirical genetic difference were uncorrelated with Euclidean distance between sites. When transformed into relative oceanographic distances and integrated into a genetic isolation-by-distance framework, however, the frequency of larval exchange explained nearly 50 per cent of the variance in empirical genetic differences among sites over scales of tens of kilometres. Explanatory power was strongest when we considered effects of multiple generations of larval dispersal via intermediary locations on the long-term probability of exchange between sites. Our results uncover meaningful spatial patterning to population genetic structuring that corresponds with ocean circulation. This study advances our ability to interpret population structure from complex genetic data characteristic of high gene flow species, validates recent advances in oceanographic approaches for assessing larval dispersal and represents a novel approach to characterize population connectivity at small spatial scales germane to conservation and fisheries management. PMID:20133354

  10. Explaining numeracy development in weak performing kindergartners.

    PubMed

    Toll, Sylke W M; Van Luit, Johannes E H

    2014-08-01

    Gaining better insight into precursors of early numeracy in young children is important, especially in those with inadequate numeracy skills. Therefore, in the current study, visual and verbal working memory, non-symbolic and symbolic comparison skills, and specific math-related language were used to explain early numeracy performance and development of weak performing children throughout kindergarten. The early numeracy ability of both weak performers and typical performers was measured at four time points during 2 years of kindergarten to compare growth rates. Results show a significant faster development of early numeracy in the weak performers. The development of weak performers' numeracy was influenced by verbal working memory, symbolic comparison skills, and math language, whereas only math language was positively related to the slope of typical performers' numeracy. In the weak performers, visual working memory, non-symbolic comparison skills, and math language showed an effect on the initial early numeracy level of these children. The intercept of the typical performers was predicted by five covariates, all except non-symbolic comparison. PMID:24786672

  11. Explaining the Cambrian "Explosion" of Animals

    NASA Astrophysics Data System (ADS)

    Marshall, Charles R.

    2006-05-01

    The Cambrian "explosion" is a unique episode in Earth history, when essentially all the animal phyla first appear in the fossil record. A variety of environmental, developmental (genetic), and ecological explanations for this complex and somewhat protracted event are reviewed, with a focus on how well each explains the observed increases in disparity and diversity, the time of onset of the radiation, its duration, and its uniqueness. The increase in disparity (the origin of the phyla) and diversity are best understood as being the result of the interplay of the combinatorial bilaterian developmental system and the increase in the number of needs the first bilaterians had to meet as complex ecological interactions developed. The time of onset is constrained by the evolution of the environment, whereas its duration appears to be controlled primarily by rates of developmental innovation. The uniqueness of the event is either due to ensuing developmental limitation, to ecological saturation, or simply to the exhaustion of ecologically viable morphologies that could be produced by the nascent bilaterian developmental system.

  12. Can Thermal Nonequilibrium Explain Coronal Loops?

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.; Karpen, Judy T.; Antiochos, Spiro K.

    2010-01-01

    Any successful model of coronal loops must explain a number of observed properties. For warm (approx. 1 MK) loops, these include: 1. excess density, 2. flat temperature profile, 3. super-hydrostatic scale height, 4. unstructured intensity profile, and 5. 1000-5000 s lifetime. We examine whether thermal nonequilibrium can reproduce the observations by performing hydrodynamic simulations based on steady coronal heating that decreases exponentially with height. We consider both monolithic and multi-stranded loops. The simulations successfully reproduce certain aspects of the observations, including the excess density, but each of them fails in at least one critical way. -Xonolithic models have far too much intensity structure, while multi-strand models are either too structured or too long-lived. Storms of nanoflares remain the only viable explanation for warm loops that has been proposed so far. Our results appear to rule out the widespread existence of heating that is both highly concentrated low in the corona and steady or quasi-steady (slowly varying or impulsive with a rapid cadence). Active regions would have a very different appearance if the dominant heating mechanism had these properties. Thermal nonequilibrium may nonetheless play an important role in prominences and catastrophic cooling e(veen.gts..,coronal rain) that occupy a small fraction of the coronal volume. However, apparent inconsistencies between the models and observations of cooling events have yet to be understood.

  13. CAN THERMAL NONEQUILIBRIUM EXPLAIN CORONAL LOOPS?

    SciTech Connect

    Klimchuk, James A.; Karpen, Judy T.; Antiochos, Spiro K.

    2010-05-10

    Any successful model of coronal loops must explain a number of observed properties. For warm ({approx}1 MK) loops, these include (1) excess density, (2) flat temperature profile, (3) super-hydrostatic scale height, (4) unstructured intensity profile, and (5) 1000-5000 s lifetime. We examine whether thermal nonequilibrium can reproduce the observations by performing hydrodynamic simulations based on steady coronal heating that decreases exponentially with height. We consider both monolithic and multi-stranded loops. The simulations successfully reproduce certain aspects of the observations, including the excess density, but each of them fails in at least one critical way. Monolithic models have far too much intensity structure, while multi-strand models are either too structured or too long-lived. Our results appear to rule out the widespread existence of heating that is both highly concentrated low in the corona and steady or quasi-steady (slowly varying or impulsive with a rapid cadence). Active regions would have a very different appearance if the dominant heating mechanism had these properties. Thermal nonequilibrium may nonetheless play an important role in prominences and catastrophic cooling events (e.g., coronal rain) that occupy a small fraction of the coronal volume. However, apparent inconsistencies between the models and observations of cooling events have yet to be understood.

  14. Birdsong dialect patterns explained using magnetic domains

    NASA Astrophysics Data System (ADS)

    Burridge, James; Kenney, Steven

    2016-06-01

    The songs and calls of many bird species, like human speech, form distinct regional dialects. We suggest that the process of dialect formation is analogous to the physical process of magnetic domain formation. We take the coastal breeding grounds of the Puget Sound white crowned sparrow as an example. Previous field studies suggest that birds of this species learn multiple songs early in life, and when establishing a territory for the first time, retain one of these dialects in order to match the majority of their neighbors. We introduce a simple lattice model of the process, showing that this matching behavior can produce single dialect domains provided the death rate of adult birds is sufficiently low. We relate death rate to thermodynamic temperature in magnetic materials, and calculate the critical death rate by analogy with the Ising model. Using parameters consistent with the known behavior of these birds we show that coastal dialect domain shapes may be explained by viewing them as low-temperature "stripe states."

  15. Birdsong dialect patterns explained using magnetic domains.

    PubMed

    Burridge, James; Kenney, Steven

    2016-06-01

    The songs and calls of many bird species, like human speech, form distinct regional dialects. We suggest that the process of dialect formation is analogous to the physical process of magnetic domain formation. We take the coastal breeding grounds of the Puget Sound white crowned sparrow as an example. Previous field studies suggest that birds of this species learn multiple songs early in life, and when establishing a territory for the first time, retain one of these dialects in order to match the majority of their neighbors. We introduce a simple lattice model of the process, showing that this matching behavior can produce single dialect domains provided the death rate of adult birds is sufficiently low. We relate death rate to thermodynamic temperature in magnetic materials, and calculate the critical death rate by analogy with the Ising model. Using parameters consistent with the known behavior of these birds we show that coastal dialect domain shapes may be explained by viewing them as low-temperature "stripe states." PMID:27415293

  16. Punishments and Prizes for Explaining Global Warming

    NASA Astrophysics Data System (ADS)

    Somerville, R. C.

    2006-12-01

    Some few gifted scientists, the late Carl Sagan being an iconic example, are superbly skilled at communicating science clearly and compellingly to non-scientists. Most scientists, however, have serious shortcomings as communicators. The common failings include being verbose, addicted to jargon, caveat- obsessed and focused on details. In addition, it is far easier for a scientist to scoff at the scientific illiteracy of modern society than to work at understanding the viewpoints and concerns of journalists, policymakers and the public. Obstacles await even those scientists with the desire and the talent to communicate science well. Peer pressure and career disincentives can act as powerful deterrents, discouraging especially younger scientists from spending time on non-traditional activities. Scientists often lack mentors and role models to help them develop skills in science communication. Journalists also face real difficulties in getting science stories approved by editors and other gatekeepers. Climate change science brings its own problems in communication. The science itself is unusually wide- ranging and complex. The contentious policies and politics of dealing with global warming are difficult to disentangle from the science. Misinformation and disinformation about climate change are widespread. Intimidation and censorship of scientists by some employers is a serious problem. Polls show that global warming ranks low on the public's list of important issues. Despite all the obstacles, communicating climate change science well is critically important today. It is an art that can be learned and that brings its own rewards and satisfactions. Academic institutions and research funding agencies increasingly value outreach by scientists, and they provide resources to facilitate it. Society needs scientists who can clearly and authoritatively explain the science of global warming and its implications, while remaining objective and policy-neutral. This need will

  17. CAN PLANETARY INSTABILITY EXPLAIN THE KEPLER DICHOTOMY?

    SciTech Connect

    Johansen, Anders; Davies, Melvyn B.; Church, Ross P.; Holmelin, Viktor

    2012-10-10

    The planet candidates discovered by the Kepler mission provide a rich sample to constrain the architectures and relative inclinations of planetary systems within approximately 0.5 AU of their host stars. We use the triple-transit systems from the Kepler 16 months data as templates for physical triple-planet systems and perform synthetic transit observations, varying the internal inclination variation of the orbits. We find that all the Kepler triple-transit and double-transit systems can be produced from the triple-planet templates, given a low mutual inclination of around 5 Degree-Sign . Our analysis shows that the Kepler data contain a population of planets larger than four Earth radii in single-transit systems that cannot arise from the triple-planet templates. We explore the hypothesis that high-mass counterparts of the triple-transit systems underwent dynamical instability to produce a population of massive double-planet systems of moderately high mutual inclination. We perform N-body simulations of mass-boosted triple-planet systems and observe how the systems heat up and lose planets by planet-planet collisions, and less frequently by ejections or collisions with the star, yielding transits in agreement with the large planets in the Kepler single-transit systems. The resulting population of massive double-planet systems nevertheless cannot explain the additional excess of low-mass planets among the observed single-transit systems and the lack of gas-giant planets in double-transit and triple-transit systems. Planetary instability of systems of triple gas-giant planets can be behind part of the dichotomy between systems hosting one or more small planets and those hosting a single giant planet. The main part of the dichotomy, however, is more likely to have arisen already during planet formation when the formation, migration, or scattering of a massive planet, triggered above a threshold metallicity, suppressed the formation of other planets in sub-AU orbits.

  18. Modeling factors explaining physicians’ satisfaction with competence

    PubMed Central

    Lepnurm, Rein; Dobson, Roy Thomas; Peña-Sánchez, Juan-Nicolás; Nesdole, Robert

    2015-01-01

    Recognition explained 60.2% of the variation in Satisfaction with Competence, controlling for years in practice, self-reported health and duties of physicians. Conclusion: Satisfaction with Competence could be affected by excessive accumulation of duties, concerns about quality, efficiency, access, excessive distress, inadequate coping abilities, personal satisfaction with life as a physician, challenges in managing practices and persistent inequities among physicians. PMID:27092256

  19. Explaining the Paleoproterozoic Rise of O2

    NASA Astrophysics Data System (ADS)

    Anbar, A. D.; Rye, R.; Kaufman, A. J.

    2001-12-01

    The Paleoproterozoic rise of atmospheric O2 is not understood. Geochemical evidence indicates pO2 \\leq 5 x 10-4 atm before ~ 2.2 Ga and >= 0.03 atm by 2.0 Ga [1]. Most models of this rapid oxygenation account for the timing in an ad hoc manner. In contrast, we suggest oxygenation was driven by rising solar luminosity, a hypothesis consistent with emerging geochemical evidence. Solar luminosity was { ~} 80 % of present value 2.75 Ga. Climate models indicate that pCO2 > 0.2 atm was required before 2.75 Ga if CO2 alone accounted for greenhouse enhancement that averted global glaciation [2]. Paleosols reveal pCO2 <= 10-1.4 atm between 2.75 and 2.2 Ga [3]. This constraint may extend earlier [4]. Given insufficient CO2, CH4 likely helped maintain surface temperature. pCH4 > 10-4 atm would have been adequate 2.75 Ga; Methanogens could sustain this level as long as pO2 was negligible [5]. Atmospheric CH4 and O2 are incompatible. If CH4 was a critical greenhouse gas, increases in pO2 caused global cooling. Temperature and photosynthetic O2 production are probably positively correlated between 273 and 300 K. Combined, these effects constituted a negative feedback on pO2: Excess O2 production cooled the surface, decreasing O2 production until pCH4 was restored. Methanogenesis was decoupled from this feedback as the bulk of Archean methanogens presumably lived in the deep ocean, insulated from surface temperature. Hence, the CH4 greenhouse acted as a cap on pO2 in the Archean. This cap would have eased as rising solar luminosity permitted "titration" of CH4 by increased O2 production; pO2 increased slowly as pCH4 decreased. This feedback suppressed pO2 until solar luminosity allowed the CO2-H2O greenhouse to maintain equable temperatures without appreciable CH4. This threshold was crossed { ~} 2.5 to 2.0 Ga [2], explaining Paleoproterozoic oxygenation. As Earth approached the threshold the CH4 buffer shrank and the likelihood of the feedback being temporarily overwhelmed by

  20. Learning from Explaining: Does It Matter if Mom Is Listening?

    ERIC Educational Resources Information Center

    Rittle-Johnson, B.; Saylor, M.; Swygert, K.E.

    2008-01-01

    The goal of the current study was to examine whether explaining to another person improves learning and transfer. In the study, 4- and 5-year-olds (N=54) solved multiple classification problems, received accuracy feedback, and were prompted to explain the correct solutions to their moms, to explain the correct solutions to themselves, or to repeat…

  1. Explaining and Communicating Science Using Student-Created Blended Media

    ERIC Educational Resources Information Center

    Hoban, Garry; Nielsen, Wendy; Shepherd, Alyce

    2013-01-01

    Students engage with science content when they are asked to explain and communicate their knowledge to others. In particular, encouraging students to create various digital media forms such as videos, podcasts, vodcasts, screencasts, digital stories and animations to explain science is usually engaging, especially if they have ownership of the…

  2. Explainable expert systems: A research program in information processing

    NASA Technical Reports Server (NTRS)

    Paris, Cecile L.

    1993-01-01

    Our work in Explainable Expert Systems (EES) had two goals: to extend and enhance the range of explanations that expert systems can offer, and to ease their maintenance and evolution. As suggested in our proposal, these goals are complementary because they place similar demands on the underlying architecture of the expert system: they both require the knowledge contained in a system to be explicitly represented, in a high-level declarative language and in a modular fashion. With these two goals in mind, the Explainable Expert Systems (EES) framework was designed to remedy limitations to explainability and evolvability that stem from related fundamental flaws in the underlying architecture of current expert systems.

  3. Case-based reasoning to explain medical model exceptions.

    PubMed

    Schmidt, Rainer; Vorobieva, Olga

    2008-01-01

    In medicine many exceptions occur. In medical practise and in knowledge-based systems too, it is necessary to consider them and to deal with them appropriately. In medical studies and in research exceptions shall be explained. We present a system that helps to explain cases that do not fit into a theoretical hypothesis. Our starting points are situations where neither a well-developed theory nor reliable knowledge nor a proper case base is available. So, instead of reliable theoretical knowledge and intelligent experience, we have just some theoretical hypothesis and a set of measurements. In this paper, we propose to combine CBR with a statistical model. We use CBR to explain those cases that do not fit the model. The case base has to be set up incrementally, it contains the exceptional cases, and their explanations are the solutions, which can be used to help to explain further exceptional cases. PMID:18487741

  4. Using Plant Functional Traits to Explain Diversity–Productivity Relationships

    PubMed Central

    Roscher, Christiane; Schumacher, Jens; Gubsch, Marlén; Lipowsky, Annett; Weigelt, Alexandra; Buchmann, Nina; Schmid, Bernhard; Schulze, Ernst-Detlef

    2012-01-01

    Background The different hypotheses proposed to explain positive species richness–productivity relationships, i.e. selection effect and complementarity effect, imply that plant functional characteristics are at the core of a mechanistic understanding of biodiversity effects. Methodology/Principal Findings We used two community-wide measures of plant functional composition, (1) community-weighted means of trait values (CWM) and (2) functional trait diversity based on Rao’s quadratic diversity (FDQ) to predict biomass production and measures of biodiversity effects in experimental grasslands (Jena Experiment) with different species richness (2, 4, 8, 16 and 60) and different functional group number and composition (1 to 4; legumes, grasses, small herbs, tall herbs) four years after establishment. Functional trait composition had a larger predictive power for community biomass and measures of biodiversitity effects (40–82% of explained variation) than species richness per se (<1–13% of explained variation). CWM explained a larger amount of variation in community biomass (80%) and net biodiversity effects (70%) than FDQ (36 and 38% of explained variation respectively). FDQ explained similar proportions of variation in complementarity effects (24%, positive relationship) and selection effects (28%, negative relationship) as CWM (27% of explained variation for both complementarity and selection effects), but for all response variables the combination of CWM and FDQ led to significant model improvement compared to a separate consideration of different components of functional trait composition. Effects of FDQ were mainly attributable to diversity in nutrient acquisition and life-history strategies. The large spectrum of traits contributing to positive effects of CWM on biomass production and net biodiversity effects indicated that effects of dominant species were associated with different trait combinations. Conclusions/Significance Our results suggest that the

  5. Explaining patterns in the ratification of global environmental treaties

    NASA Technical Reports Server (NTRS)

    Cook, David W.

    1991-01-01

    A study was made of the ratification behavior of 160 countries with respect to 38 global environmental treaties. The study identifies and explains patterns in the ratification of treaties, providing two means of assessing the likelihood that any given country will support global environmental treaties. National ratification totals reveal a pattern of high ratification by countries in Western Europe, North America, Japan, Australia, and New Zealand. A country's standing within the range of high to low ratification rates can be explained by the statistical model developed in the study. This research allows one to identify countries likely to support global environmental treaties.

  6. Explaining the motherhood wage penalty during the early occupational career.

    PubMed

    Staff, Jeremy; Mortimer, Jeylan T

    2012-02-01

    Prior research shows that mothers earn lower hourly wages than women without children, and that this maternal wage penalty cannot be fully explained by differences between mothers and other women in work experience and job characteristics. This research examines whether the residual motherhood wage penalty results from differences between mothers and other women in the accumulation of work interruptions and breaks in schooling. Using longitudinal data for 486 women followed from ages 19 to 31 in the Minnesota Youth Development Study, we find that accumulated months not in the labor force and not enrolled in school explain the residual pay gap between mothers and other women. PMID:22037996

  7. Explaining Learning: From Analysis to Paralysis to Hippocampus

    ERIC Educational Resources Information Center

    Clark, John

    2005-01-01

    This paper seeks to explain learning by examining five theories of learning--conceptual analysis, behavioural, constructivist, computational and connectionist. The first two are found wanting and rejected. Piaget's constructivist theory offers a general explanatory framework (assimilation and accommodation) but fails to provide an adequate account…

  8. A Quest to Explain the Extreme Realism in Newbery Books

    ERIC Educational Resources Information Center

    Miguez, Betsy Bryan; Goetting, Denise

    2006-01-01

    The quest to explain the extreme realism found in some Newbery Award books led the authors to discover that there is no unified view of childhood affecting children's literature today. While some adults feel that children must be protected against the evil surrounding them, others feel that they must be prepared to face the world in which they…

  9. The Effect of Self-Explaining on Robust Learning

    ERIC Educational Resources Information Center

    Hausmann, Robert G. M.; VanLehn, Kurt

    2010-01-01

    Self-explaining is a domain-independent learning strategy that generally leads to a robust understanding of the domain material. However, there are two potential explanations for its effectiveness. First, self-explanation generates additional "content" that does not exist in the instructional materials. Second, when compared to comprehension,…

  10. Understanding Electrochemistry Concepts Using the Predict-Observe-Explain Strategy

    ERIC Educational Resources Information Center

    Karamustafaoglu, Sevilay; Mamlok-Naaman, Rachel

    2015-01-01

    The current study deals with freshman students who study at the Department of Science at the Faculty of Education. The aim of the study was to investigate the effect of teaching electrochemistry concepts using Predict-Observe-Explain (POE) strategy. The study was quasi-experimental design using 20 students each in the experimental group (EG) and…

  11. Teacher Styles in Questioning and Explaining. Technical Report No. 39.

    ERIC Educational Resources Information Center

    Moore, Carol Ann

    The primary purpose of this study was to identify and describe individual differences in teaching style (i.e., teachers' patterns of questioning and explaining) in a standardized teaching situation. The secondary purpose was to explore relationships between teaching behavior and other teacher characteristics: teaching experience; sex and selected…

  12. Gender Differences in Explaining Grades Using Structural Equation Modeling

    ERIC Educational Resources Information Center

    Ruban, Lilia M.; McCoach, D. Betsy

    2005-01-01

    This study examined the differential impacts of SAT scores and high school rank, college academic level, motivational variables, and self-regulatory variables in explaining variance in the academic achievement of male and female collegians using structural equation modeling and multiple groups analyses. Significantly, in light of earlier research,…

  13. Visualisation and Reasoning in Explaining the Phases of the Moon

    ERIC Educational Resources Information Center

    Subramaniam, K.; Padalkar, Shamin

    2009-01-01

    In this study, we examine how subjects set up, transform, and reason with models that they establish on the basis of known facts as they seek to explain a familiar everyday phenomenon--the phases of the moon. An interview schedule was designed to elicit subjects' reasoning, and in the case where explanations were mistaken, to induce a change in…

  14. Explaining Common Variance Shared by Early Numeracy and Literacy

    ERIC Educational Resources Information Center

    Davidse, N. J.; De Jong, M. T.; Bus, A. G.

    2014-01-01

    How can it be explained that early literacy and numeracy share variance? We specifically tested whether the correlation between four early literacy skills (rhyming, letter knowledge, emergent writing, and orthographic knowledge) and simple sums (non-symbolic and story condition) reduced after taking into account preschool attention control,…

  15. Learning to apply models of materials while explaining their properties

    NASA Astrophysics Data System (ADS)

    Karpin, Tiia; Juuti, Kalle; Lavonen, Jari

    2014-09-01

    Background:Applying structural models is important to chemistry education at the upper secondary level, but it is considered one of the most difficult topics to learn. Purpose:This study analyses to what extent in designed lessons students learned to apply structural models in explaining the properties and behaviours of various materials. Sample:An experimental group is 27 Finnish upper secondary school students and control group included 18 students from the same school. Design and methods:In quasi-experimental setting, students were guided through predict, observe, explain activities in four practical work situations. It was intended that the structural models would encourage students to learn how to identify and apply appropriate models when predicting and explaining situations. The lessons, organised over a one-week period, began with a teacher's demonstration and continued with student experiments in which they described the properties and behaviours of six household products representing three different materials. Results:Most students in the experimental group learned to apply the models correctly, as demonstrated by post-test scores that were significantly higher than pre-test scores. The control group showed no significant difference between pre- and post-test scores. Conclusions:The findings indicate that the intervention where students engage in predict, observe, explain activities while several materials and models are confronted at the same time, had a positive effect on learning outcomes.

  16. Explaining Recent Army and Navy Minority Recruiting Trends. Research Brief

    ERIC Educational Resources Information Center

    Steinberg, Paul

    2009-01-01

    Between 2000 and 2007, the representation of blacks among high-quality Army recruits declined, while in the Navy, black representation remained stable; the representation of Hispanics among high-quality recruits in both the Army and Navy grew during this period. RAND researchers identified factors that explain these recruiting trends and found…

  17. Explaining the Effects of Communities of Pastoral Care for Students

    ERIC Educational Resources Information Center

    Murphy, Joseph; Holste, Linda

    2016-01-01

    This article explains how communities of pastoral care work. It presents an empirically forged theory in action. We examined theoretical and empirical work across the targeted area of personalization for students. We also completed what Hallinger (2012) refers to as "exhaustive review" of the field of school improvement writ large. We…

  18. Children's Understanding of Substances, Part 2: Explaining Chemical Change.

    ERIC Educational Resources Information Center

    Johnson, Philip

    2002-01-01

    Focuses on the idea of chemical change and reports data from a study exploring the development of the concept of substance in children aged 11-14. Examines the use of the idea of elements, compounds, and bonding between atoms to explain chemical change and the intersection of these ideas with "basic" particle ideas. (Contains 21 references.)…

  19. Learning to Apply Models of Materials While Explaining Their Properties

    ERIC Educational Resources Information Center

    Karpin, Tiia; Juuti, Kalle; Lavonen, Jari

    2014-01-01

    Background: Applying structural models is important to chemistry education at the upper secondary level, but it is considered one of the most difficult topics to learn. Purpose: This study analyses to what extent in designed lessons students learned to apply structural models in explaining the properties and behaviours of various materials.…

  20. The Role of Secondary Education in Explaining Competitiveness

    ERIC Educational Resources Information Center

    Baumann, Chris; Winzar, Hume

    2016-01-01

    The literature establishes that education drives economic performance, but the extent that education is associated with a country's competitiveness is empirically untested. Our study analyses Programme for International Student Assessment (PISA) data from 63 countries to ascertain education's role in explaining the competitiveness of a country.…

  1. Students Explaining Science—Assessment of Science Communication Competence

    NASA Astrophysics Data System (ADS)

    Kulgemeyer, Christoph; Schecker, Horst

    2013-12-01

    Science communication competence (SCC) is an important educational goal in the school science curricula of several countries. However, there is a lack of research about the structure and the assessment of SCC. This paper specifies the theoretical framework of SCC by a competence model. We developed a qualitative assessment method for SCC that is based on an expert-novice dialog: an older student (explainer, expert) explains a physics phenomenon to a younger peer (addressee, novice) in a controlled test setting. The explanations are video-recorded and analysed by qualitative content analysis. The method was applied in a study with 46 secondary school students as explainers. Our aims were (a) to evaluate whether our model covers the relevant features of SCC, (b) to validate the assessment method and (c) to find characteristics of addressee-adequate explanations. A performance index was calculated to quantify the explainers' levels of competence on an ordinal scale. We present qualitative and quantitative evidence that the index is adequate for assessment purposes. It correlates with results from a written SCC test and a perspective taking test (convergent validity). Addressee-adequate explanations can be characterized by use of graphical representations and deliberate switches between scientific and everyday language.

  2. Explaining the Socio-Economic Status School Completion Gap

    ERIC Educational Resources Information Center

    Polidano, Cain; Hanel, Barbara; Buddelmeyer, Hielke

    2013-01-01

    Relatively low rates of school completion among students from low socio-economic backgrounds is a key driver of intergenerational inequality. Linking data from the Programme for International Student Assessment with data from the Longitudinal Survey of Australian Youth, we use a decomposition framework to explain the gap in school completion rates…

  3. Using Culture to Explain Behavior: An Integrative Cultural Approach

    ERIC Educational Resources Information Center

    Shepherd, Hana R.; Stephens, Nicole M.

    2010-01-01

    While savings rates among low-income families vary greatly, a 2008 National Poverty Center report finds that over 40 percent of low-income families fail to save any money. For decades policy makers and social scientists have sought to explain this phenomenon. Even after accounting for the fact that low-income families have less money to save, why…

  4. Economic Models to Explain School Board Expenditures in Ontario.

    ERIC Educational Resources Information Center

    Lawton, Stephen B.

    1985-01-01

    Explains variations in per pupil expenditures among school boards in Ontario, Canada, using the "median voter model," which compares consumer behavior with government funding actions. With an inequitable tax price an important policy variable, the school grant program needs redesigning to achieve equity without sacrificing efficiency. Includes 21…

  5. Analysis and Assessment of Students' Competency to Explain Geographical Processes

    ERIC Educational Resources Information Center

    Dulama, Maria-Eliza; Alexandru, Diana-Elena

    2010-01-01

    In this study we seek to analyse the ability of students to explain, exemplify and outline geographical processes, as well as to assess their competencies by using an evaluation grid. Therefore, we tested two types of hypotheses. The first one regards the fact that it becomes more difficult for students to represent a previously learned…

  6. Does a Corresponding Set of Variables for Explaining Voluntary Organizational Turnover Transfer to Explaining Voluntary Occupational Turnover?

    ERIC Educational Resources Information Center

    Blau, Gary

    2007-01-01

    This study proposed and tested corresponding sets of variables for explaining voluntary organizational versus occupational turnover for a sample of medical technologists. This study is believed to be the first test of the Rhodes and Doering (1983) occupational change model using occupational turnover data. Results showed that corresponding job…

  7. A developmental hypothesis to explain the multicentricity of breast cancer.

    PubMed

    Sharpe, C R

    1998-07-14

    In this article the author proposes that the multicentricity of breast cancer might be explained by a developmental hypothesis. Genetic alterations ("hits") occurring in epithelial stem cells during the development of the breast may be transmitted to populations of daughter cells during growth. As a result, areas of the breast may be predisposed to malignant transformation with the occurrence of further genetic hits. Areas with the same predisposition should be anatomically connected, and earlier hits during breast development should result in larger areas of predisposition. The multicentricity of breast cancer would be explained if multiple lesions--monoclonal for the predisposing genetic hit and polyclonal for subsequent hits--developed within a predisposed area. Multiple lesions arising from the spread of disease by extension would be expected to share many genetic hits. The author discusses the implications that further evidence supporting the developmental hypothesis would have for the prevention and treatment of breast cancer. PMID:9679488

  8. A developmental hypothesis to explain the multicentricity of breast cancer

    PubMed Central

    Sharpe, C R

    1998-01-01

    In this article the author proposes that the multicentricity of breast cancer might be explained by a developmental hypothesis. Genetic alterations ("hits") occurring in epithelial stem cells during the development of the breast may be transmitted to populations of daughter cells during growth. As a result, areas of the breast may be predisposed to malignant transformation with the occurrence of further genetic hits. Areas with the same predisposition should be anatomically connected, and earlier hits during breast development should result in larger areas of predisposition. The multicentricity of breast cancer would be explained if multiple lesions--monoclonal for the predisposing genetic hit and polyclonal for subsequent hits--developed within a predisposed area. Multiple lesions arising from the spread of disease by extension would be expected to share many genetic hits. The author discusses the implications that further evidence supporting the developmental hypothesis would have for the prevention and treatment of breast cancer. PMID:9679488

  9. Explaining dehumanization among children: the interspecies model of prejudice.

    PubMed

    Costello, Kimberly; Hodson, Gordon

    2014-03-01

    Although many theoretical approaches have emerged to explain prejudices expressed by children, none incorporate outgroup dehumanization, a key predictor of prejudice among adults. According to the Interspecies Model of Prejudice, beliefs in the human-animal divide facilitate outgroup prejudice through fostering animalistic dehumanization (Costello & Hodson, 2010). In the present investigation, White children attributed Black children fewer 'uniquely human' characteristics, representing the first systematic evidence of racial dehumanization among children (Studies 1 and 2). In Study 2, path analyses supported the Interspecies Model of Prejudice: children's human-animal divide beliefs predicted greater racial prejudice, an effect explained by heightened racial dehumanization. Similar patterns emerged among parents. Furthermore, parent Social Dominance Orientation predicted child prejudice indirectly through children's endorsement of a hierarchical human-animal divide and subsequent dehumanizing tendencies. Encouragingly, children's human-animal divide perceptions were malleable to an experimental prime highlighting animal-human similarity. Implications for prejudice interventions are considered. PMID:23083220

  10. Mechanical vulnerability explains size-dependent mortality of reef corals

    PubMed Central

    Madin, Joshua S; Baird, Andrew H; Dornelas, Maria; Connolly, Sean R

    2014-01-01

    Understanding life history and demographic variation among species within communities is a central ecological goal. Mortality schedules are especially important in ecosystems where disturbance plays a major role in structuring communities, such as coral reefs. Here, we test whether a trait-based, mechanistic model of mechanical vulnerability in corals can explain mortality schedules. Specifically, we ask whether species that become increasingly vulnerable to hydrodynamic dislodgment as they grow have bathtub-shaped mortality curves, whereas species that remain mechanically stable have decreasing mortality rates with size, as predicted by classical life history theory for reef corals. We find that size-dependent mortality is highly consistent between species with the same growth form and that the shape of size-dependent mortality for each growth form can be explained by mechanical vulnerability. Our findings highlight the feasibility of predicting assemblage-scale mortality patterns on coral reefs with trait-based approaches. PMID:24894390

  11. Private nurses and playboy bunnies: explaining permissible sex discrimination.

    PubMed

    Yuracko, Kimberly A

    2004-01-01

    Discrimination on the basis of sex in employment is illegal--usually. In cases in which employers contend that sex-based hiring is necessary to protect the privacy interests of their customer, however, and in cases in which employers contend that sex-based hiring is necessary to provide a particular type of sexual titillation for their customers, courts sometimes do allow employers to discriminate. Courts say that they allow sex discrimination in employment when it is necessary to preserve the "essence of the business." This Article shows, however, that there is no plausible conception of business "essence" that can explain and make sense of the existing case law. The Article therefore looks beyond the courts' rhetoric to explain and defend why courts distinguish in the ways they do between permissible and impermissible sex discrimination in employment. PMID:15046068

  12. Explaining large-scale patterns of vertebrate diversity

    PubMed Central

    Wiens, John J.

    2015-01-01

    The major clades of vertebrates differ dramatically in their current species richness, from 2 to more than 32 000 species each, but the causes of this variation remain poorly understood. For example, a previous study noted that vertebrate clades differ in their diversification rates, but did not explain why they differ. Using a time-calibrated phylogeny and phylogenetic comparative methods, I show that most variation in diversification rates among 12 major vertebrate clades has a simple ecological explanation: predominantly terrestrial clades (i.e. birds, mammals, and lizards and snakes) have higher net diversification rates than predominantly aquatic clades (i.e. amphibians, crocodilians, turtles and all fish clades). These differences in diversification rates are then strongly related to patterns of species richness. Habitat may be more important than other potential explanations for richness patterns in vertebrates (such as climate and metabolic rates) and may also help explain patterns of species richness in many other groups of organisms. PMID:26202428

  13. Imitation explains the propagation, not the stability of animal culture

    PubMed Central

    Claidière, Nicolas; Sperber, Dan

    2010-01-01

    For acquired behaviour to count as cultural, two conditions must be met: it must propagate in a social group, and it must remain stable across generations in the process of propagation. It is commonly assumed that imitation is the mechanism that explains both the spread of animal culture and its stability. We review the literature on transmission chain studies in chimpanzees (Pan troglodytes) and other animals, and we use a formal model to argue that imitation, which may well play a major role in the propagation of animal culture, cannot be considered faithful enough to explain its stability. We consider the contribution that other psychological and ecological factors might make to the stability of animal culture observed in the wild. PMID:19889707

  14. Climate variation explains a third of global crop yield variability

    PubMed Central

    Ray, Deepak K.; Gerber, James S.; MacDonald, Graham K.; West, Paul C.

    2015-01-01

    Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32–39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability. PMID:25609225

  15. Computing measures of explained variation for logistic regression models.

    PubMed

    Mittlböck, M; Schemper, M

    1999-01-01

    The proportion of explained variation (R2) is frequently used in the general linear model but in logistic regression no standard definition of R2 exists. We present a SAS macro which calculates two R2-measures based on Pearson and on deviance residuals for logistic regression. Also, adjusted versions for both measures are given, which should prevent the inflation of R2 in small samples. PMID:10195643

  16. Explaining Racial Disparities in Infant Health in Brazil

    PubMed Central

    Nyarko, Kwame A.; Lopez-Camelo, Jorge; Castilla, Eduardo E.

    2013-01-01

    Objectives. We sought to quantify how socioeconomic, health care, demographic, and geographic effects explain racial disparities in low birth weight (LBW) and preterm birth (PTB) rates in Brazil. Methods. We employed a sample of 8949 infants born between 1995 and 2009 in 15 cities and 7 provinces in Brazil. We focused on disparities in LBW (< 2500 g) and PTB (< 37 gestational weeks) prevalence between infants of African ancestry alone or African mixed with other ancestries, and European ancestry alone. We used a decomposition model to quantify the contributions of conceptually relevant factors to these disparities. Results. The model explained 45% to 94% of LBW and 64% to 94% of PTB disparities between the African ancestry groups and European ancestry. Differences in prenatal care use and geographic location were the most important contributors, followed by socioeconomic differences. The model explained the majority of the disparities for mixed African ancestry and part of the disparity for African ancestry alone. Conclusions. Public policies to improve children’s health should target prenatal care and geographic location differences to reduce health disparities between infants of African and European ancestries in Brazil. PMID:23409894

  17. Weather explains high annual variation in butterfly dispersal.

    PubMed

    Kuussaari, Mikko; Rytteri, Susu; Heikkinen, Risto K; Heliölä, Janne; von Bagh, Peter

    2016-07-27

    Weather conditions fundamentally affect the activity of short-lived insects. Annual variation in weather is therefore likely to be an important determinant of their between-year variation in dispersal, but conclusive empirical studies are lacking. We studied whether the annual variation of dispersal can be explained by the flight season's weather conditions in a Clouded Apollo (Parnassius mnemosyne) metapopulation. This metapopulation was monitored using the mark-release-recapture method for 12 years. Dispersal was quantified for each monitoring year using three complementary measures: emigration rate (fraction of individuals moving between habitat patches), average residence time in the natal patch, and average distance moved. There was much variation both in dispersal and average weather conditions among the years. Weather variables significantly affected the three measures of dispersal and together with adjusting variables explained 79-91% of the variation observed in dispersal. Different weather variables became selected in the models explaining variation in three dispersal measures apparently because of the notable intercorrelations. In general, dispersal rate increased with increasing temperature, solar radiation, proportion of especially warm days, and butterfly density, and decreased with increasing cloudiness, rainfall, and wind speed. These results help to understand and model annually varying dispersal dynamics of species affected by global warming. PMID:27440662

  18. Explaining formation of Astronomical Jets using Dynamic Universe Model

    NASA Astrophysics Data System (ADS)

    Naga Parameswara Gupta, Satyavarapu

    2016-07-01

    Astronomical jets are observed from the centres of many Galaxies including our own Milkyway. The formation of such jet is explained using SITA simulations of Dynamic Universe Model. For this purpose the path traced by a test neutron is calculated and depicted using a set up of one densemass of the mass equivalent to mass of Galaxy center, 90 stars with similar masses of stars near Galaxy center, mass equivalents of 23 Globular Cluster groups, 16 Milkyway parts, Andromeda and Triangulum Galaxies at appropriate distances. Five different kinds of theoretical simulations gave positive results The path travelled by this test neutron was found to be an astronomical jet emerging from Galaxy center. This is another result from Dynamic Universe Model. It solves new problems like a. Variable Mass Rocket Trajectory Problem b. Explaining Very long baseline interferometry (VLBI) observations c. Astronomical jets observed from Milkyway Center d. Prediction of Blue shifted Galaxies e. Explaining Pioneer Anomaly f. Prediction of New Horizons satellite trajectory etc. Dynamic Universe Model never reduces to General relativity on any condition. It uses a different type of mathematics based on Newtonian physics. This mathematics used here is simple and straightforward. As there are no differential equations present in Dynamic Universe Model, the set of equations give single solution in x y z Cartesian coordinates for every point mass for every time step

  19. Earthquake lubrication and healing explained by amorphous nanosilica

    NASA Astrophysics Data System (ADS)

    Rowe, C. D.; Lamothe, K. G.; Rempe, M.; Andrews, M.; Mitchell, T. M.; Di Toro, G.; White, J. C.

    2015-12-01

    Earthquake slip and rupture propagation require fault strength to decrease during slip. Extreme shear weakening observed in laboratory friction experiments on silica-rich rocks has been explained by the formation of a hydrated amorphous 'silica gel' on the slip surface, but the mode of formation and deformation behavior of this material are not known. In addition, the wear material displays time-dependent strengthening on timescales of hours to days. We performed shearing experiments on chert rocks and analyzed the wear material formed at a range of slip rates from 10-4 - 10-1 m/s. We show by transmission electron microscopy (TEM) and X-ray diffraction that silica lubrication is the result of the formation of amorphous nanopowder rather than a gel. The nanopowder has distinct structure and properties when compared to commercially available amorphous silica nanoparticles, which result from the degree and distribution of hydration and the style of bond strain within particles (observed by Raman spectroscopy and FTIR). The lubrication effect is due to intra-particle plasticity, even at low temperature and interparticle lubrication caused by trapping of water layers between hydrated surfaces. The hours to days timescale of healing may be explained by the natural time-dependent sintering between the hydrated surfaces of the nanopowder. Formation of amorphous silica nanopowders during slip can explain the general characteristics of earthquake ruptures, including the timescales of coseismic weakening and post-seismic healing.

  20. Genetic Pleiotropy Explains Associations between Musical Auditory Discrimination and Intelligence

    PubMed Central

    Mosing, Miriam A.; Pedersen, Nancy L.; Madison, Guy; Ullén, Fredrik

    2014-01-01

    Musical aptitude is commonly measured using tasks that involve discrimination of different types of musical auditory stimuli. Performance on such different discrimination tasks correlates positively with each other and with intelligence. However, no study to date has explored these associations using a genetically informative sample to estimate underlying genetic and environmental influences. In the present study, a large sample of Swedish twins (N = 10,500) was used to investigate the genetic architecture of the associations between intelligence and performance on three musical auditory discrimination tasks (rhythm, melody and pitch). Phenotypic correlations between the tasks ranged between 0.23 and 0.42 (Pearson r values). Genetic modelling showed that the covariation between the variables could be explained by shared genetic influences. Neither shared, nor non-shared environment had a significant effect on the associations. Good fit was obtained with a two-factor model where one underlying shared genetic factor explained all the covariation between the musical discrimination tasks and IQ, and a second genetic factor explained variance exclusively shared among the discrimination tasks. The results suggest that positive correlations among musical aptitudes result from both genes with broad effects on cognition, and genes with potentially more specific influences on auditory functions. PMID:25419664

  1. Explaining the Early Development and Health of Teen Mothers’ Children*

    PubMed Central

    Mollborn, Stefanie; Dennis, Jeff A.

    2013-01-01

    The transmission of social disadvantage from teenage mothers to their children is well established, but when and why do these disparities emerge in the early life course? Using nationally representative data from the Early Childhood Longitudinal Study-Birth Cohort, this study investigated the relationship between teen childbearing and children’s cognition, behavior, and health from infancy through preschool. Developmental disparities between teenage mothers’ children and others were largely nonexistent at 9 months but accumulated with age. Having a teenage mother predicted compromised development across several domains by age 4½. Our conceptual model expected preexisting disadvantage, ongoing resource disadvantage, and compromised parenting quality to explain the association between teen childbearing and child outcomes. Preexisting social disadvantage accounted for much of this relationship. Financial, social, and material resources in the child’s household partially or fully explained each of the remaining significant relationships between teenage childbearing and child outcomes. Parenting quality explained a smaller proportion of these relationships than did resources, and these factors’ influences were largely independent. Because children of teenage mothers with a modest set of resources were not predicted to have compromised development, resources provided in early childhood may have the potential to reduce developmental disparities for teenage mothers’ children. PMID:23630407

  2. Predator mimicry, not conspicuousness, explains the efficacy of butterfly eyespots

    PubMed Central

    De Bona, Sebastiano; Valkonen, Janne K.; López-Sepulcre, Andrés; Mappes, Johanna

    2015-01-01

    Large conspicuous eyespots on butterfly wings have been shown to deter predators. This has been traditionally explained by mimicry of vertebrate eyes, but recently the classic eye-mimicry hypothesis has been challenged. It is proposed that the conspicuousness of the eyespot, not mimicry, is what causes aversion due to sensory biases, neophobia or sensory overloads. We conducted an experiment to directly test whether the eye-mimicry or the conspicuousness hypothesis better explain eyespot efficacy. We used great tits (Parus major) as model predator, and tested their reaction towards animated images on a computer display. Birds were tested against images of butterflies without eyespots, with natural-looking eyespots, and manipulated spots with the same contrast but reduced resemblance to an eye, as well as images of predators (owls) with and without eyes. We found that mimetic eyespots were as effective as true eyes of owls and more efficient in eliciting an aversive response than modified, less mimetic but equally contrasting eyespots. We conclude that the eye-mimicry hypothesis explains our results better than the conspicuousness hypothesis and is thus likely to be an important mechanism behind the evolution of butterfly eyespots. PMID:25854889

  3. Predator mimicry, not conspicuousness, explains the efficacy of butterfly eyespots.

    PubMed

    De Bona, Sebastiano; Valkonen, Janne K; López-Sepulcre, Andrés; Mappes, Johanna

    2015-05-01

    Large conspicuous eyespots on butterfly wings have been shown to deter predators. This has been traditionally explained by mimicry of vertebrate eyes, but recently the classic eye-mimicry hypothesis has been challenged. It is proposed that the conspicuousness of the eyespot, not mimicry, is what causes aversion due to sensory biases, neophobia or sensory overloads. We conducted an experiment to directly test whether the eye-mimicry or the conspicuousness hypothesis better explain eyespot efficacy. We used great tits (Parus major) as model predator, and tested their reaction towards animated images on a computer display. Birds were tested against images of butterflies without eyespots, with natural-looking eyespots, and manipulated spots with the same contrast but reduced resemblance to an eye, as well as images of predators (owls) with and without eyes. We found that mimetic eyespots were as effective as true eyes of owls and more efficient in eliciting an aversive response than modified, less mimetic but equally contrasting eyespots. We conclude that the eye-mimicry hypothesis explains our results better than the conspicuousness hypothesis and is thus likely to be an important mechanism behind the evolution of butterfly eyespots. PMID:25854889

  4. Explaining ecological clusters of maternal depression in South Western Sydney

    PubMed Central

    2014-01-01

    Background The aim of the qualitative study reported here was to: 1) explain the observed clustering of postnatal depressive symptoms in South Western Sydney; and 2) identify group-level mechanisms that would add to our understanding of the social determinants of maternal depression. Methods Critical realism provided the methodological underpinning for the study. The setting was four local government areas in South Western Sydney, Australia. Child and Family practitioners and mothers in naturally occurring mothers groups were interviewed. Results Using an open coding approach to maximise emergence of patterns and relationships we have identified seven theoretical concepts that might explain the observed spatial clustering of maternal depression. The theoretical concepts identified were: Community-level social networks; Social Capital and Social Cohesion; "Depressed community"; Access to services at the group level; Ethnic segregation and diversity; Supportive social policy; and Big business. Conclusions We postulate that these regional structural, economic, social and cultural mechanisms partially explain the pattern of maternal depression observed in families and communities within South Western Sydney. We further observe that powerful global economic and political forces are having an impact on the local situation. The challenge for policy and practice is to support mothers and their families within this adverse regional and global-economic context. PMID:24460690

  5. Explaining Racial Disparities in Infant Health in Brazil

    PubMed Central

    Nyarko, Kwame A.; Lopez-Camelo, Jorge; Castilla, Eduardo E.

    2015-01-01

    Objectives. We sought to quantify how socioeconomic, health care, demographic, and geographic effects explain racial disparities in low birth weight (LBW) and preterm birth (PTB) rates in Brazil. Methods. We employed a sample of 8949 infants born between 1995 and 2009 in 15 cities and 7 provinces in Brazil. We focused on disparities in LBW (< 2500 g) and PTB (< 37 gestational weeks) prevalence between infants of African ancestry alone or African mixed with other ancestries, and European ancestry alone. We used a decomposition model to quantify the contributions of conceptually relevant factors to these disparities. Results. The model explained 45% to 94% of LBW and 64% to 94% of PTB disparities between the African ancestry groups and European ancestry. Differences in prenatal care use and geographic location were the most important contributors, followed by socioeconomic differences. The model explained the majority of the disparities for mixed African ancestry and part of the disparity for African ancestry alone. Conclusions. Public policies to improve children’s health should target prenatal care and geographic location differences to reduce health disparities between infants of African and European ancestries in Brazil. PMID:26313046

  6. Does cultural integration explain a mental health advantage for adolescents?

    PubMed Central

    Bhui, Kamaldeep S; Lenguerrand, Erik; Maynard, Maria J; Stansfeld, Stephen A; Harding, Seeromanie

    2012-01-01

    Background A mental health advantage has been observed among adolescents in urban areas. This prospective study tests whether cultural integration measured by cross-cultural friendships explains a mental health advantage for adolescents. Methods A prospective cohort of adolescents was recruited from 51 secondary schools in 10 London boroughs. Cultural identity was assessed by friendship choices within and across ethnic groups. Cultural integration is one of four categories of cultural identity. Using gender-specific linear-mixed models we tested whether cultural integration explained a mental health advantage, and whether gender and age were influential. Demographic and other relevant factors, such as ethnic group, socio-economic status, family structure, parenting styles and perceived racism were also measured and entered into the models. Mental health was measured by the Strengths and Difficulties Questionnaire as a ‘total difficulties score’ and by classification as a ‘probable clinical case’. Results A total of 6643 pupils in first and second years of secondary school (ages 11–13 years) took part in the baseline survey (2003/04) and 4785 took part in the follow-up survey in 2005–06. Overall mental health improved with age, more so in male rather than female students. Cultural integration (friendships with own and other ethnic groups) was associated with the lowest levels of mental health problems especially among male students. This effect was sustained irrespective of age, ethnicity and other potential explanatory variables. There was a mental health advantage among specific ethnic groups: Black Caribbean and Black African male students (Nigerian/Ghanaian origin) and female Indian students. This was not fully explained by cultural integration, although cultural integration was independently associated with better mental health. Conclusions Cultural integration was associated with better mental health, independent of the mental health advantage

  7. Psychological Factors Explaining the Referral Behavior of Iranian Family Physicians

    PubMed Central

    Mohaghegh, Bahram; Seyedin, Hesam; Rashidian, Arash; Ravaghi, Hamid; Khalesi, Nader; Kazemeini, Hossein

    2014-01-01

    Background: The recently developed policy of the family practice program in rural regions of Iran faced some challenges such as inefficient referral system. The health insurance organizations (purchaser) and health policy makers are concerned about the high rate of patient referrals from family physicians to specialists due to imposing unnecessary services and costs. Objectives: This study examined utility of the theory of planned behavior to explain intention of Iranian family physicians to reduce referral rate of patients with respiratory diseases to medical specialist. Patients and Methods: An exploratory cross-sectional study, employing a correlational design directed by the theory of planned behavior was conducted. A questionnaire was developed based on an eliciting study and review of literature. One hundred and seventy-four family physicians working at primary care centers in two provinces of Iran completed the questionnaire (response rate of 86%). Results: The finding revealed that intention of family physicians to reduce referral rate of patients to specialists was significantly related to two theory-based variables of subjective norms (r = 0.38, P < 0.001) and perceived behavioral control (r = 0.43, P < 0.001), and not to attitudes. A stepwise regression entering direct measures of the theory variables explained 35% of the variance on the intention, with perceived behavioral control being the strongest predictor. Adding background variables to the model achieved further 5% by variables of practice size and past referral rate behavior. Conclusions: The results indicated that psychological variables of the theory of planned behavior could explain a noticeable proportion of variance in family physician's intention to decrease the rate of referring patients with respiratory diseases to medical specialists. The intention is primarily influenced by normative and control considerations. These findings contribute to a better understanding of referral decisions by

  8. Traits underpinning desiccation resistance explain distribution patterns of terrestrial isopods.

    PubMed

    Dias, André T C; Krab, Eveline J; Mariën, Janine; Zimmer, Martin; Cornelissen, Johannes H C; Ellers, Jacintha; Wardle, David A; Berg, Matty P

    2013-07-01

    Predicted changes in soil water availability regimes with climate and land-use change will impact the community of functionally important soil organisms, such as macro-detritivores. Identifying and quantifying the functional traits that underlie interspecific differences in desiccation resistance will enhance our ability to predict both macro-detritivore community responses to changing water regimes and the consequences of the associated species shifts for organic matter turnover. Using path analysis, we tested (1) how interspecific differences in desiccation resistance among 22 northwestern European terrestrial isopod species could be explained by three underlying traits measured under standard laboratory conditions, namely, body ventral surface area, water loss rate and fatal water loss; (2) whether these relationships were robust to contrasting experimental conditions and to the phylogenetic relatedness effects being excluded; (3) whether desiccation resistance and hypothesized underlying traits could explain species distribution patterns in relation to site water availability. Water loss rate and (secondarily) fatal water loss together explained 90% of the interspecific variation in desiccation resistance. Our path model indicated that body surface area affects desiccation resistance only indirectly via changes in water loss rate. Our results also show that soil moisture determines isopod species distributions by filtering them according to traits underpinning desiccation resistance. These findings reveal that it is possible to use functional traits measured under standard conditions to predict soil biota responses to water availability in the field over broad spatial scales. Taken together, our results demonstrate an increasing need to generate mechanistic models to predict the effect of global changes on functionally important organisms. PMID:23224790

  9. Explaining cross-country variation in cigarette consumption

    PubMed Central

    Srinivas, Kolluru; Rao, Bhanoji

    2009-01-01

    This short paper uses cross-country data on per capita cigarette consumption and selected socio-economic variables to explain inter-country differentials in consumption. It is found that the proportion of the aged in the total population and higher literacy among women have relatively greater and positive impact on cigarette consumption. Even after controlling for the effect of the two variables, a country's industrialized status has a positive impact on consumption. It would thus seem that aging and economic, and social developments are pro-cigarette consumption. PMID:19133163

  10. A third alternative to explain recent observations: Future deceleration

    NASA Astrophysics Data System (ADS)

    Chakraborty, Subenoy; Pan, Supriya; Saha, Subhajit

    2014-11-01

    In the present work we discuss a third alternative to explain the latest observational data concerning the accelerating Universe and its different stages. The particle creation mechanism in the framework of non-equilibrium thermodynamics is considered as a basic cosmic mechanism acting on the flat FRW geometry. By assuming that the gravitationally induced particle production occurs under "adiabatic" conditions, the deceleration parameter is expressed in terms of the particle creation rate which is chosen as a truncated power series of the Hubble parameter. The model shows the evolution of the Universe starting from inflation to the present late time acceleration and it also predicts future decelerating stage.

  11. Decaying dark matter can explain the e{sup {+-}} excesses

    SciTech Connect

    Nardi, Enrico; Sannino, Francesco; Strumia, Alessandro E-mail: astrumia@mail.df.unipi.it

    2009-01-15

    PAMELA and ATIC recently reported excesses in e{sup {+-}} cosmic rays. Since the interpretation in terms of DM annihilations was found to be not easily compatible with constraints from photon observations, we consider the DM decay hypothesis and find that it can explain the e{sup {+-}} excesses compatibly with all constraints, and can be tested by dedicated HESS observations of the Galactic Ridge. ATIC data indicate a DM mass of about 2 TeV: this mass naturally implies the observed DM abundance relative to ordinary matter if DM is a quasi-stable composite particle with a baryon-like matter asymmetry. Technicolor naturally yields these type of candidates.

  12. Explaining human uniqueness: genome interactions with environment, behaviour and culture

    PubMed Central

    Varki, Ajit; Geschwind, Daniel H.; Eichler, Evan E.

    2009-01-01

    What makes us human? Specialists in each discipline respond through the lens of their own expertise. In fact, ‘anthropogeny’ (explaining the origin of humans) requires a transdisciplinary approach that eschews such barriers. Here we take a genomic and genetic perspective towards molecular variation, explore systems analysis of gene expression and discuss an organ-systems approach. Rejecting any ‘genes versus environment’ dichotomy, we then consider genome interactions with environment, behaviour and culture, finally speculating that aspects of human uniqueness arose because of a primate evolutionary trend towards increasing and irreversible dependence on learned behaviours and culture — perhaps relaxing allowable thresholds for large-scale genomic diversity. PMID:18802414

  13. Crystal Structure Anisotropy Explains Anomalous Elastic Properties of Metal Nanorods

    NASA Astrophysics Data System (ADS)

    Goupalov, Serguei

    2014-03-01

    It is demonstrated that the frequency of the extensional vibrational mode of a nanorod made of an elastically anisotropic crystalline material deviates widely from the predictions of the theories based on the analysis of the long-wavelength limit. The dispersion relation for the fundamental extensional mode of a gold rod grown in the [ 100 ] direction is calculated and found to be in an excellent agreement with experimental data obtained from the transient optical absorption measurements on gold nanorods.[1] This explains an anomaly in the elastic properties of nanorods which was previously attributed to a 26% decrease in Young's modulus for nanorods compared to its bulk value.

  14. Explaining and overcoming barriers to climate change adaptation

    NASA Astrophysics Data System (ADS)

    Eisenack, Klaus; Moser, Susanne C.; Hoffmann, Esther; Klein, Richard J. T.; Oberlack, Christoph; Pechan, Anna; Rotter, Maja; Termeer, Catrien J. A. M.

    2014-10-01

    The concept of barriers is increasingly used to describe the obstacles that hinder the planning and implementation of climate change adaptation. The growing literature on barriers to adaptation reveals not only commonly reported barriers, but also conflicting evidence, and few explanations of why barriers exist and change. There is thus a need for research that focuses on the interdependencies between barriers and considers the dynamic ways in which barriers develop and persist. Such research, which would be actor-centred and comparative, would help to explain barriers to adaptation and provide insights into how to overcome them.

  15. Can model-free reinforcement learning explain deontological moral judgments?

    PubMed

    Ayars, Alisabeth

    2016-05-01

    Dual-systems frameworks propose that moral judgments are derived from both an immediate emotional response, and controlled/rational cognition. Recently Cushman (2013) proposed a new dual-system theory based on model-free and model-based reinforcement learning. Model-free learning attaches values to actions based on their history of reward and punishment, and explains some deontological, non-utilitarian judgments. Model-based learning involves the construction of a causal model of the world and allows for far-sighted planning; this form of learning fits well with utilitarian considerations that seek to maximize certain kinds of outcomes. I present three concerns regarding the use of model-free reinforcement learning to explain deontological moral judgment. First, many actions that humans find aversive from model-free learning are not judged to be morally wrong. Moral judgment must require something in addition to model-free learning. Second, there is a dearth of evidence for central predictions of the reinforcement account-e.g., that people with different reinforcement histories will, all else equal, make different moral judgments. Finally, to account for the effect of intention within the framework requires certain assumptions which lack support. These challenges are reasonable foci for future empirical/theoretical work on the model-free/model-based framework. PMID:26918742

  16. Explaining fruit and vegetable intake using a consumer marketing tool.

    PubMed

    Della, Lindsay J; Dejoy, David M; Lance, Charles E

    2009-10-01

    In response to calls to reinvent the 5 A Day fruit and vegetable campaign, this study assesses the utility of VALS, a consumer-based audience segmentation tool that divides the U.S. population into groups leading similar lifestyles. The study examines whether the impact of theory of planned behavior (TPB) constructs varies across VALS groups in a cross-sectional sample of 1,588 U.S. adults. In a multigroup structural equation model, the VALS audience group variable moderated latent TPB relationships. Attitudes, subjective norms, and perceived behavioral control explained 57% to 70% of the variation in intention to eat fruit and vegetables across 5 different VALS groups. Perceived behavioral control and intention also predicted self-reported consumption behavior (R2 = 20% to 71% across VALS groups). Bivariate z tests were calculated to determine statistical differences in parameter estimates across groups. Nine of the bivariate z tests were statistically significant (p < or = .04), with standardized coefficients ranging from .05 to .70. These findings confirm the efficacy of using the TPB to explain variation in fruit and vegetable consumption as well as the validity of using a consumer-based algorithm to segment audiences for fruit and vegetable consumption messaging. PMID:19158253

  17. Can Chunk Size Differences Explain Developmental Changes in Lexical Learning?

    PubMed

    Smalle, Eleonore H M; Bogaerts, Louisa; Simonis, Morgane; Duyck, Wouter; Page, Michael P A; Edwards, Martin G; Szmalec, Arnaud

    2015-01-01

    In three experiments, we investigated Hebb repetition learning (HRL) differences between children and adults, as a function of the type of item (lexical vs. sub-lexical) and the level of item-overlap between sequences. In a first experiment, it was shown that when non-repeating and repeating (Hebb) sequences of words were all permutations of the same words, HRL was slower than when the sequences shared no words. This item-overlap effect was observed in both children and adults. In a second experiment, we used syllable sequences and we observed reduced HRL due to item-overlap only in children. The findings are explained within a chunking account of the HRL effect on the basis of which we hypothesize that children, compared with adults, chunk syllable sequences in smaller units. By hypothesis, small chunks are more prone to interference from anagram representations included in the filler sequences, potentially explaining the item-overlap effect in children. This hypothesis was tested in a third experiment with adults where we experimentally manipulated the chunk size by embedding pauses in the syllable sequences. Interestingly, we showed that imposing a small chunk size caused adults to show the same behavioral effects as those observed in children. Departing from the analogy between verbal HRL and lexical development, the results are discussed in light of the less-is-more hypothesis of age-related differences in language acquisition. PMID:26779065

  18. Can Chunk Size Differences Explain Developmental Changes in Lexical Learning?

    PubMed Central

    Smalle, Eleonore H. M.; Bogaerts, Louisa; Simonis, Morgane; Duyck, Wouter; Page, Michael P. A.; Edwards, Martin G.; Szmalec, Arnaud

    2016-01-01

    In three experiments, we investigated Hebb repetition learning (HRL) differences between children and adults, as a function of the type of item (lexical vs. sub-lexical) and the level of item-overlap between sequences. In a first experiment, it was shown that when non-repeating and repeating (Hebb) sequences of words were all permutations of the same words, HRL was slower than when the sequences shared no words. This item-overlap effect was observed in both children and adults. In a second experiment, we used syllable sequences and we observed reduced HRL due to item-overlap only in children. The findings are explained within a chunking account of the HRL effect on the basis of which we hypothesize that children, compared with adults, chunk syllable sequences in smaller units. By hypothesis, small chunks are more prone to interference from anagram representations included in the filler sequences, potentially explaining the item-overlap effect in children. This hypothesis was tested in a third experiment with adults where we experimentally manipulated the chunk size by embedding pauses in the syllable sequences. Interestingly, we showed that imposing a small chunk size caused adults to show the same behavioral effects as those observed in children. Departing from the analogy between verbal HRL and lexical development, the results are discussed in light of the less-is-more hypothesis of age-related differences in language acquisition. PMID:26779065

  19. Dynamical models explaining social balance and evolution of cooperation.

    PubMed

    Traag, Vincent Antonio; Van Dooren, Paul; De Leenheer, Patrick

    2013-01-01

    Social networks with positive and negative links often split into two antagonistic factions. Examples of such a split abound: revolutionaries versus an old regime, Republicans versus Democrats, Axis versus Allies during the second world war, or the Western versus the Eastern bloc during the Cold War. Although this structure, known as social balance, is well understood, it is not clear how such factions emerge. An earlier model could explain the formation of such factions if reputations were assumed to be symmetric. We show this is not the case for non-symmetric reputations, and propose an alternative model which (almost) always leads to social balance, thereby explaining the tendency of social networks to split into two factions. In addition, the alternative model may lead to cooperation when faced with defectors, contrary to the earlier model. The difference between the two models may be understood in terms of the underlying gossiping mechanism: whereas the earlier model assumed that an individual adjusts his opinion about somebody by gossiping about that person with everybody in the network, we assume instead that the individual gossips with that person about everybody. It turns out that the alternative model is able to lead to cooperative behaviour, unlike the previous model. PMID:23634204

  20. Explaining the footsteps, belly dancer, Wenceslas, and kickback illusions.

    PubMed

    Howe, Piers D L; Thompson, Peter G; Anstis, Stuart M; Sagreiya, Hersh; Livingstone, Margaret S

    2006-01-01

    The footsteps illusion (FI) demonstrates that an object's background can have a profound effect on the object's perceived speed. This illusion consists of a yellow bar and a blue bar that move over a black-and-white, striped background. Although the bars move at a constant rate, they appear to repeatedly accelerate and decelerate in antiphase with each other. Previously, this illusion has been explained in terms of the variations in contrast at the leading and trailing edges of the bars that occur as the bars traverse the striped background. Here, we show that this explanation is inadequate and instead propose that for each bar, the bar's leading edge, trailing edge, lateral edges, and the surrounding background edges all contribute to the bar's perceived speed and that the degree to which each edge contributes to the motion percept is determined by that edge's contrast. We show that this theory can explain all the data on the FI as well as the belly dancer and Wenceslas illusions. We conclude by presenting a new illusion, the kickback illusion, which, although geometrically similar to the FI, is mediated by a different mechanism, namely, reverse phi motion. PMID:17209742

  1. Reinforcement Learning Explains Conditional Cooperation and Its Moody Cousin.

    PubMed

    Ezaki, Takahiro; Horita, Yutaka; Takezawa, Masanori; Masuda, Naoki

    2016-07-01

    Direct reciprocity, or repeated interaction, is a main mechanism to sustain cooperation under social dilemmas involving two individuals. For larger groups and networks, which are probably more relevant to understanding and engineering our society, experiments employing repeated multiplayer social dilemma games have suggested that humans often show conditional cooperation behavior and its moody variant. Mechanisms underlying these behaviors largely remain unclear. Here we provide a proximate account for this behavior by showing that individuals adopting a type of reinforcement learning, called aspiration learning, phenomenologically behave as conditional cooperator. By definition, individuals are satisfied if and only if the obtained payoff is larger than a fixed aspiration level. They reinforce actions that have resulted in satisfactory outcomes and anti-reinforce those yielding unsatisfactory outcomes. The results obtained in the present study are general in that they explain extant experimental results obtained for both so-called moody and non-moody conditional cooperation, prisoner's dilemma and public goods games, and well-mixed groups and networks. Different from the previous theory, individuals are assumed to have no access to information about what other individuals are doing such that they cannot explicitly use conditional cooperation rules. In this sense, myopic aspiration learning in which the unconditional propensity of cooperation is modulated in every discrete time step explains conditional behavior of humans. Aspiration learners showing (moody) conditional cooperation obeyed a noisy GRIM-like strategy. This is different from the Pavlov, a reinforcement learning strategy promoting mutual cooperation in two-player situations. PMID:27438888

  2. Plate-wide stress relaxation explains European Palaeocene basin inversions.

    PubMed

    Nielsen, Søren B; Thomsen, Erik; Hansen, David L; Clausen, Ole R

    2005-05-12

    During Late Cretaceous and Cenozoic times, many Palaeozoic and Mesozoic rifts and basin structures in the interior of the European continent underwent several phases of inversion (the process of shortening a previously extensional basin). The main phases occurred during the Late Cretaceous and Middle Palaeocene, and have been previously explained by pulses of compression, mainly from the Alpine orogen. Here we show that the main phases differed both in structural style and cause. The Cretaceous phase was characterized by narrow uplift zones, reverse activation of faults, crustal shortening, and the formation of asymmetric marginal troughs. In contrast, the Middle Palaeocene phase was characterized by dome-like uplift of a wider area with only mild fault movements, and formation of more distal and shallow marginal troughs. A simple flexural model explains how domal, secondary inversion follows inevitably from primary, convergence-related inversion on relaxation of the in-plane tectonic stress. The onset of relaxation inversions was plate-wide and simultaneous, and may have been triggered by stress changes caused by elevation of the North Atlantic lithosphere by the Iceland plume or the drop in the north-south convergence rate between Africa and Europe. PMID:15889089

  3. Reinforcement Learning Explains Conditional Cooperation and Its Moody Cousin

    PubMed Central

    Ezaki, Takahiro; Horita, Yutaka; Masuda, Naoki

    2016-01-01

    Direct reciprocity, or repeated interaction, is a main mechanism to sustain cooperation under social dilemmas involving two individuals. For larger groups and networks, which are probably more relevant to understanding and engineering our society, experiments employing repeated multiplayer social dilemma games have suggested that humans often show conditional cooperation behavior and its moody variant. Mechanisms underlying these behaviors largely remain unclear. Here we provide a proximate account for this behavior by showing that individuals adopting a type of reinforcement learning, called aspiration learning, phenomenologically behave as conditional cooperator. By definition, individuals are satisfied if and only if the obtained payoff is larger than a fixed aspiration level. They reinforce actions that have resulted in satisfactory outcomes and anti-reinforce those yielding unsatisfactory outcomes. The results obtained in the present study are general in that they explain extant experimental results obtained for both so-called moody and non-moody conditional cooperation, prisoner’s dilemma and public goods games, and well-mixed groups and networks. Different from the previous theory, individuals are assumed to have no access to information about what other individuals are doing such that they cannot explicitly use conditional cooperation rules. In this sense, myopic aspiration learning in which the unconditional propensity of cooperation is modulated in every discrete time step explains conditional behavior of humans. Aspiration learners showing (moody) conditional cooperation obeyed a noisy GRIM-like strategy. This is different from the Pavlov, a reinforcement learning strategy promoting mutual cooperation in two-player situations. PMID:27438888

  4. Mackay icosahedron explaining orientation relationship of dispersoids in aluminium alloys.

    PubMed

    Muggerud, Astrid Marie F; Li, Yanjun; Holmestad, Randi; Andersen, Sigmund J

    2014-10-01

    The orientation relations (ORs) of the cubic icosahedral quasicrystal approximant phase α-Al(Fe,Mn)Si have been studied after low temperature annealing of a 3xxx wrought aluminium alloy by transmission electron microscopy. From diffraction studies it was verified that the most commonly observed OR for the α-Al(Fe,Mn)Si dispersoids is [1\\bar 11]α // [1\\bar 11]Al, (5\\bar 2\\bar 7)α // (011)Al. This orientation could be explained by assuming that the internal Mackay icosahedron (MI) in the α-phase has a fixed orientation in relation to Al, similar to that of the icosahedral quasi-crystals existing in this alloy system. It is shown that mirroring of the normal-to-high-symmetry icosahedral directions of the MI explains the alternative orientations, which are therefore likely to be caused by twinning of the fixed MI. Only one exception was found, which was related to the Bergman icosahedron internal to the T-phase of the Al-Mg-Zn system. PMID:25274523

  5. Scent marking in sifaka: no one function explains it all.

    PubMed

    Lewis, Rebecca J

    2006-06-01

    Various hypotheses to explain possible functions of scent-marking have been put forth and basically fall into five categories: territorial demarcation, ownership of resources, mate attraction, noncombative fighting, and self-advertisement. Verreaux's sifaka (Propithecus verreauxi verreauxi), like many prosimians, use scent-marking as one form of communication. The goal of this study was to determine the function of scent-marking in sifaka. All-occurrence of scent-marks, scent-mark context, and scent-mark style were collected on 23 sifaka in the Kirindy Forest of western Madagascar for 7 months (September 2001-March 2002). Scent-mark rates were collected using continuous focal animal sampling from November 2000-March 2002. Home range data were collected using monthly censuses and instantaneous focal sampling throughout the 17 months. Scent-marking behavior was exhibited almost exclusively by adults. Scent-mark rates were not related to the number of resident adult males, number of resident adult females, rank, or group size. The majority of scent-marks occurred in the perimeter of the home range; however, less than a quarter of the home range was used by only a single group. Sifaka did not preferentially mark food trees, mark during the mating season, or mark during intergroup encounters. The results from this study indicate that none of the five hypothesized functions best explains all scent-marking in Verreaux's sifaka. Rather, scent-marking may serve different functions for different individuals. PMID:16715510

  6. Male reproductive strategy explains spatiotemporal segregation in brown bears

    PubMed Central

    Steyaert, Sam MJG; Kindberg, Jonas; Swenson, Jon E; Zedrosser, Andreas

    2013-01-01

    1. Spatiotemporal segregation is often explained by the risk for offspring predation or by differences in physiology, predation risk vulnerability or competitive abilities related to size dimorphism. 2. Most large carnivores are size dimorphic and offspring predation is often intraspecific and related to nonparental infanticide (NPI). NPI can be a foraging strategy, a strategy to reduce competition, or a male reproductive strategy. Spatiotemporal segregation is widespread among large carnivores, but its nature remains poorly understood. 3. We evaluated three hypotheses to explain spatiotemporal segregation in the brown bear, a size-dimorphic large carnivore in which NPI is common; the ‘NPI – foraging/competition hypothesis', i.e. NPI as a foraging strategy or a strategy to reduce competition, the ‘NPI – sexual selection hypothesis’, i.e. infanticide as a male reproductive strategy and the ‘body size hypothesis’, i.e. body-size-related differences in physiology, predation risk vulnerability or competitive ability causes spatiotemporal segregation. To test these hypotheses, we quantified spatiotemporal segregation among adult males, lone adult females and females with cubs-of-the-year, based on GPS-relocation data (2006–2010) and resource selection functions in a Scandinavian population. 4. We found that spatiotemporal segregation was strongest between females with cubs-of-the-year and adult males during the mating season. During the mating season, females with cubs-of-the-year selected their resources, in contrast to adult males, in less rugged landscapes in relative close proximity to certain human-related variables, and in more open habitat types. After the mating season, females with cubs-of-the-year markedly shifted their resource selection towards a pattern more similar to that of their conspecifics. No strong spatiotemporal segregation was apparent between females with cubs-of-the-year and conspecifics during the mating and the postmating

  7. Carbonatite ring-complexes explained by caldera-style volcanism

    PubMed Central

    Andersson, Magnus; Malehmir, Alireza; Troll, Valentin R.; Dehghannejad, Mahdieh; Juhlin, Christopher; Ask, Maria

    2013-01-01

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alnö carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at ~3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas. PMID:23591904

  8. Can Personality Type Explain Heterogeneity in Probability Distortions?

    PubMed Central

    Capra, C. Monica; Jiang, Bing; Engelmann, Jan B.; Berns, Gregory S.

    2014-01-01

    There are two regularities we have learned from experimental studies of choice under risk. The first is that the majority of people weigh objective probabilities non-linearly. The second regularity, although less commonly acknowledged, is that there is a large amount of heterogeneity in how people distort probabilities. Despite of this, little effort has been made to identify the source of heterogeneity. In this paper, we explore the possibility that personality type is linked to probability distortions. Using validated psychological questionnaires, we clustered participants into distinct personality types: motivated, impulsive, and affective. We found that the motivated viewed gambling more attractive, whereas the impulsive were the most capable of discriminating non-extreme probabilities. Our results suggest that the observed heterogeneity in probability distortions may be explained by personality profiles, which can be elicited though standard psychological questionnaires. PMID:24639891

  9. Explaining How to Play Real-Time Strategy Games

    NASA Astrophysics Data System (ADS)

    Metoyer, Ronald; Stumpf, Simone; Neumann, Christoph; Dodge, Jonathan; Cao, Jill; Schnabel, Aaron

    Real-time strategy games share many aspects with real situations in domains such as battle planning, air traffic control, and emergency response team management which makes them appealing test-beds for Artificial Intelligence (AI) and machine learning. End user annotations could help to provide supplemental information for learning algorithms, especially when training data is sparse. This paper presents a formative study to uncover how experienced users explain game play in real-time strategy games. We report the results of our analysis of explanations and discuss their characteristics that could support the design of systems for use by experienced real-time strategy game users in specifying or annotating strategy-oriented behavior.

  10. Heterogeneity explains features of “anomalous” thermodynamics and statistics

    PubMed Central

    Gheorghiu, Stefan; Coppens, Marc-Olivier

    2004-01-01

    Phenomena characterized by power-law probability distributions abound in nature and the applied sciences. We show that many of these power laws are well described by the Student, or t, distribution, and we discuss the origin of this universality based on three examples (Brownian motion, Knudsen diffusion in rough pores, and bubbly multiphase flow). These case studies are representative for a large class of systems with heterogeneous features, examples of which can be found from Earth sciences to astrophysics, and even in the social sciences. We show that common forms of polydispersity, such as polydispersity arising naturally as a result of aggregation–fragmentation phenomena, typically lie at the basis of the observed scaling. We conclude that complicated arguments based on long-range correlations or nonergodicity are often incorrect or misleading in explaining many naturally observed power laws and, in particular, those described by the Student distribution. PMID:15514018

  11. Can Nomenclature for the Body be Explained by Embodiment Theories?

    PubMed

    Majid, Asifa; van Staden, Miriam

    2015-10-01

    According to widespread opinion, the meaning of body part terms is determined by salient discontinuities in the visual image; such that hands, feet, arms, and legs, are natural parts. If so, one would expect these parts to have distinct names which correspond in meaning across languages. To test this proposal, we compared three unrelated languages-Dutch, Japanese, and Indonesian-and found both naming systems and boundaries of even basic body part terms display variation across languages. Bottom-up cues alone cannot explain natural language semantic systems; there simply is not a one-to-one mapping of the body semantic system to the body structural description. Although body parts are flexibly construed across languages, body parts semantics are, nevertheless, constrained by non-linguistic representations in the body structural description, suggesting these are necessary, although not sufficient, in accounting for aspects of the body lexicon. PMID:26466949

  12. Microeconomic principles explain an optimal genome size in bacteria.

    PubMed

    Ranea, Juan A G; Grant, Alastair; Thornton, Janet M; Orengo, Christine A

    2005-01-01

    Bacteria can clearly enhance their survival by expanding their genetic repertoire. However, the tight packing of the bacterial genome and the fact that the most evolved species do not necessarily have the biggest genomes suggest there are other evolutionary factors limiting their genome expansion. To clarify these restrictions on size, we studied those protein families contributing most significantly to bacterial-genome complexity. We found that all bacteria apply the same basic and ancestral 'molecular technology' to optimize their reproductive efficiency. The same microeconomics principles that define the optimum size in a factory can also explain the existence of a statistical optimum in bacterial genome size. This optimum is reached when the bacterial genome obtains the maximum metabolic complexity (revenue) for minimal regulatory genes (logistic cost). PMID:15680509

  13. Exploring and Explaining Friction with the Prandtl-Tomlinson Model.

    PubMed

    Schwarz, Udo D; Hölscher, Hendrik

    2016-01-26

    The Prandtl-Tomlinson model of friction, first introduced in 1928 as a "conceptual model" for a single-atom contact, consists of a point mass that is dragged over a sinusoidal potential by a spring. After decades of virtual oblivion, it has recently found impressive validation for contacts comprising tens or even hundreds of atoms. To date, the Prandtl-Tomlinson model enjoys widespread popularity as depicting arguably the most insightful mechanical analogue to atomic-scale effects occurring at sliding interfaces. In this issue of ACS Nano, Pawlak et al. demonstrate the model's applicability to a true single-atom contact, thereby illustrating that simple mechanical representations can indeed go a long way toward explaining interactions at atomically defined interfaces. PMID:26765866

  14. Models explaining motor vehicle death rates in the United States.

    PubMed

    Zlatoper, T J

    1989-04-01

    This paper is a selective survey of models explaining motor vehicle death rates in the United States. First, it reviews Peltzman's 1975 study of the effect of automobile safety regulation and critiques of the study. Then it summarizes several subsequent statistical studies of highway fatalities. The surveyed studies are typically regression analyses of the impact of various factors on motor vehicle deaths. They are categorized in this paper according to which of three types of data they utilized: time-series; cross-sectional; or pooled time-series, cross-sectional. This paper notes what can be inferred collectively from the surveyed studies regarding the impacts of various factors on highway fatalities. It also discusses certain shortcomings of the studies in general along with possible remedies, and makes recommendations regarding future research. Tabular summaries of the statistical studies surveyed in this paper are included in the Appendix. PMID:2785390

  15. [To explain is to narrate. How to visualize scientific data].

    PubMed

    Hawtin, Nigel

    2014-01-01

    When you try to appeal a vast ranging audience, as it occurs at the New Scientist that addresses scientists as well as the general public, your scientific visual explainer must be succinct, clear, accurate and easily understandable. In order to reach this goal, your message should provide only the main data, the ones that allow you to balance information and clarity: information should be put into context and all the extra details should be cut down. It is very important, then, to know well both your audience and the subject you are going to describe, as graphic masters of the past, like William Playfair and Charles Minard, have taught us. Moreover, you should try to engage your reader connecting the storytelling power of words and the driving force of the graphics: colours, visual elements, typography. To be effective, in fact, an infographic should not only be truthful and functional, but also elegant, having style and legibility. PMID:25072540

  16. Explaining Society: An Expanded Toolbox for Social Scientists

    PubMed Central

    Bell, David C.; Atkinson-Schnell, Jodie L.; DiBacco, Aron E.

    2012-01-01

    We propose for social scientists a theoretical toolbox containing a set of motivations that neurobiologists have recently validated. We show how these motivations can be used to create a theory of society recognizably similar to existing stable societies (sustainable, self-reproducing, and largely peaceful). Using this toolbox, we describe society in terms of three institutions: economy (a source of sustainability), government (peace), and the family (reproducibility). Conducting a thought experiment in three parts, we begin with a simple theory with only two motivations. We then create successive theories that systematically add motivations, showing that each element in the toolbox makes its own contribution to explain the workings of a stable society and that the family has a critical role in this process. PMID:23082093

  17. Muon-Induced Neutrons Do Not Explain the DAMA Data

    NASA Astrophysics Data System (ADS)

    Klinger, J.; Kudryavtsev, V. A.

    2015-04-01

    We present an accurate model of the muon-induced background in the DAMA/LIBRA experiment. Our work challenges proposed mechanisms which seek to explain the observed DAMA signal modulation with muon-induced backgrounds. Muon generation and transport are performed using the MUSIC /MUSUN code, and subsequent interactions in the vicinity of the DAMA detector cavern are simulated with Geant4. We estimate the total muon-induced neutron flux in the detector cavern to be Φnν=1.0 ×10-9 cm-2 s-1 . We predict 3.49 ×10-5 counts /day /kg /keV , which accounts for less than 0.3% of the DAMA signal modulation amplitude.

  18. "Developmental capture" of the state: explaining Thailand's universal coverage policy.

    PubMed

    Harris, Joseph

    2015-02-01

    The notion of "regulatory capture" is typically used to describe the takeover of state agencies by outside interest groups that seek to weaken regulation and advance the agendas of interest groups through control over state policy levers. This concept can be contrasted with that of "developmental capture" of state agencies by networks of reformist bureaucrats within the state who seek to promote inclusive state social and developmental policies of benefit to the broader populace. Building on work that has pointed to instances in which state bureaucrats act autonomously from societal and political pressures, this article argues that existing explanations are insufficient for explaining Thailand's universal health care policy. It points to the critical role played by a network of bureaucrats within the state who strategically mobilized resources in the bureaucracy, political parties, civil society, and international organizations to institutionalize universal health care in the face of broader professional dissent, political uncertainty, and international pressure. PMID:25480847

  19. Explaining exercise behavior and satisfaction with social exchange theory.

    PubMed

    Unger, J; Johnson, C A

    1995-10-01

    This study tested the hypothesis that the variables specified by social exchange theory (perceived rewards of exercising, perceived costs of exercising, social and tangible investments, and available alternative activities) are associated with exercise behavior and satisfaction. 190 health club members completed a questionnaire assessing attitudes toward exercise, exercise behavior, and demographic information. Exercise frequency and satisfaction were regressed on the social exchange theory variables and demographic covariates. Exercise satisfaction, the number of investments in exercise, and the number of available alternative activities were significantly related to exercise frequency, and the number of perceived rewards of exercise and the number of investments were significantly related to exercise satisfaction. These results suggest that social exchange theory is useful for explaining exercise behavior. PMID:8570365

  20. Ecology and multilevel selection explain aggression in spider colonies.

    PubMed

    Biernaskie, Jay M; Foster, Kevin R

    2016-08-01

    Progress in sociobiology continues to be hindered by abstract debates over methodology and the relative importance of within-group vs. between-group selection. We need concrete biological examples to ground discussions in empirical data. Recent work argued that the levels of aggression in social spider colonies are explained by group-level adaptation. Here, we examine this conclusion using models that incorporate ecological detail while remaining consistent with kin- and multilevel selection frameworks. We show that although levels of aggression are driven, in part, by between-group selection, incorporating universal within-group competition provides a striking fit to the data that is inconsistent with pure group-level adaptation. Instead, our analyses suggest that aggression is favoured primarily as a selfish strategy to compete for resources, despite causing lower group foraging efficiency or higher risk of group extinction. We argue that sociobiology will benefit from a pluralistic approach and stronger links between ecologically informed models and data. PMID:27264438

  1. Explaining social discrimination: racism in Brazil and xenophobia in Spain.

    PubMed

    Camino, Leoncio; Álvaro, José Luis; Torres, Ana Raquel R; Garrido, Alicia; Morais, Thiago; Barbosa, Juliana

    2013-01-01

    The present study investigates the arguments used by university students in order to explain social differences between social minorities and majorities. In Brazil, the issues investigated refer to White and Black people. In Spain, the reference is to native Spaniards and Moroccan immigrants. The participants were 144 Brazilians and 93 Spaniards, who answered a questionnaire composed of socio-demographic variables and one open question about the causes of social inequalities between Black and White people in Brazil and between autochthonous Spaniards and Moroccan Immigrants. A model is proposed to integrate the four discursive classes found using ALCESTE software. In Brazil, the strongest argument is based on the historical roots of the exploitation of Black people. In Spain, cultural differences are the main explanation for social inequalities. PMID:24230936

  2. Muon-Induced Neutrons Do Not Explain the DAMA Data.

    PubMed

    Klinger, J; Kudryavtsev, V A

    2015-04-17

    We present an accurate model of the muon-induced background in the DAMA/LIBRA experiment. Our work challenges proposed mechanisms which seek to explain the observed DAMA signal modulation with muon-induced backgrounds. Muon generation and transport are performed using the MUSIC/MUSUN code, and subsequent interactions in the vicinity of the DAMA detector cavern are simulated with Geant4. We estimate the total muon-induced neutron flux in the detector cavern to be Φ(n)(ν)=1.0 × 10(-9)  cm(-2) s(-1). We predict 3.49 × 10(-5)  counts/day/kg/keV, which accounts for less than 0.3% of the DAMA signal modulation amplitude. PMID:25933303

  3. Carbonatite ring-complexes explained by caldera-style volcanism.

    PubMed

    Andersson, Magnus; Malehmir, Alireza; Troll, Valentin R; Dehghannejad, Mahdieh; Juhlin, Christopher; Ask, Maria

    2013-01-01

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alnö carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at ~3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas. PMID:23591904

  4. The role of authority power in explaining procedural fairness effects.

    PubMed

    van Dijke, Marius; De Cremer, David; Mayer, David M

    2010-05-01

    Building on fairness heuristic theory, fairness theory, and trust development models, we argue that unfairly enacted procedures decrease followers' trust in the authority particularly when authorities have high power over their followers. Moreover, we expected trust to mediate procedural fairness effects on followers' attitudes (authorities' legitimacy and charisma attributed to authorities) and organizational citizenship behavior. Procedural fairness effects on these variables, as mediated by trust, should therefore also be stronger when authority power is high. The results of a single- and multisource field study and a laboratory experiment supported these predictions. These studies support the role of authority power as a theoretically and practically relevant moderator of procedural fairness effects and show that its effectiveness is explained through trust in authorities. PMID:20476828

  5. Social inheritance can explain the structure of animal social networks.

    PubMed

    Ilany, Amiyaal; Akçay, Erol

    2016-01-01

    The social network structure of animal populations has major implications for survival, reproductive success, sexual selection and pathogen transmission of individuals. But as of yet, no general theory of social network structure exists that can explain the diversity of social networks observed in nature, and serve as a null model for detecting species and population-specific factors. Here we propose a simple and generally applicable model of social network structure. We consider the emergence of network structure as a result of social inheritance, in which newborns are likely to bond with maternal contacts, and via forming bonds randomly. We compare model output with data from several species, showing that it can generate networks with properties such as those observed in real social systems. Our model demonstrates that important observed properties of social networks, including heritability of network position or assortative associations, can be understood as consequences of social inheritance. PMID:27352101

  6. Real world ocean rogue waves explained without the modulational instability

    PubMed Central

    Fedele, Francesco; Brennan, Joseph; Ponce de León, Sonia; Dudley, John; Dias, Frédéric

    2016-01-01

    Since the 1990s, the modulational instability has commonly been used to explain the occurrence of rogue waves that appear from nowhere in the open ocean. However, the importance of this instability in the context of ocean waves is not well established. This mechanism has been successfully studied in laboratory experiments and in mathematical studies, but there is no consensus on what actually takes place in the ocean. In this work, we question the oceanic relevance of this paradigm. In particular, we analyze several sets of field data in various European locations with various tools, and find that the main generation mechanism for rogue waves is the constructive interference of elementary waves enhanced by second-order bound nonlinearities and not the modulational instability. This implies that rogue waves are likely to be rare occurrences of weakly nonlinear random seas. PMID:27323897

  7. Social inheritance can explain the structure of animal social networks

    PubMed Central

    Ilany, Amiyaal; Akçay, Erol

    2016-01-01

    The social network structure of animal populations has major implications for survival, reproductive success, sexual selection and pathogen transmission of individuals. But as of yet, no general theory of social network structure exists that can explain the diversity of social networks observed in nature, and serve as a null model for detecting species and population-specific factors. Here we propose a simple and generally applicable model of social network structure. We consider the emergence of network structure as a result of social inheritance, in which newborns are likely to bond with maternal contacts, and via forming bonds randomly. We compare model output with data from several species, showing that it can generate networks with properties such as those observed in real social systems. Our model demonstrates that important observed properties of social networks, including heritability of network position or assortative associations, can be understood as consequences of social inheritance. PMID:27352101

  8. Explanations in knowledge systems - Design for Explainable Expert Systems

    NASA Technical Reports Server (NTRS)

    Swartout, William; Paris, Cecile; Moore, Johanna

    1991-01-01

    The Explainable Expert Systems framework (EES), in which the focus is on capturing those design aspects that are important for producing good explanations, including justifications of the system's actions, explications of general problem-solving strategies, and descriptions of the system's terminology, is discussed. EES was developed as part of the Strategic Computing Initiative of DARPA. Both the general principles from which the system was derived and how the system was derived from those principles can be represented in EES. The Program Enhancement Advisor, which is the main prototype on which the explanation work has been developed and tested, is presented. PEA is an advice system that helps users improve their Common Lisp programs by recommending transformations that enhance the user's code. How EES produces better explanations is shown.

  9. Quantitative experiments to explain the change of seasons

    NASA Astrophysics Data System (ADS)

    Testa, Italo; Busarello, Gianni; Puddu, Emanuella; Leccia, Silvio; Merluzzi, Paola; Colantonio, Arturo; Moretti, Maria Ida; Galano, Silvia; Zappia, Alessandro

    2015-03-01

    The science education literature shows that students have difficulty understanding what causes the seasons. Incorrect explanations are often due to a lack of knowledge about the physical mechanisms underlying this phenomenon. To address this, we present a module in which the students engage in quantitative measurements with a photovoltaic panel to explain changes to the sunray flow on Earth’s surface over the year. The activities also provide examples of energy transfers between the incoming radiation and the environment to introduce basic features of Earth’s climate. The module was evaluated with 45 secondary school students (aged 17-18) and a pre-/post-test research design. Analysis of students’ learning outcomes supports the effectiveness of the proposed activities.

  10. Lymphangiogenesis may explain adrenal selectivity in lung cancer metastases.

    PubMed

    Onuigbo, Wilson I B

    2010-08-01

    The 'seed and soil' hypothesis of organ selectivity in cancer metastasis dated back to the 1870s. A century later, a review of significant selectivity data revealed that the adrenals featured in 11 of 12 classes of it, thus promoting these two organs for research. Fortunately, two discoveries have also occurred, namely, (a) that cancer stimulates lymph vessel formation, i.e., lymphangiogenesis, and (b) that lymph and blood vessels are differentially stainable. Accordingly, these interesting ideas should be exploited with a hypothesis. Therefore, it is proposed that, at autopsy in lung cancer cases, the tissues between the primary lung tumor and the adrenal secondary should be meticulously serially sectioned and disjunctively stained because they must reveal what naturally occurs in this zone during life. It is predicted that this maneuver will identify lymphangiogenesis as the phenomenon responsible for the age-old puzzle of adrenal selectivity. Indeed, it may explain other puzzles such as intracranial lymphatic connectivity. PMID:20303219

  11. Trophic network models explain instability of Early Triassic terrestrial communities

    PubMed Central

    Roopnarine, Peter D; Angielczyk, Kenneth D; Wang, Steve C; Hertog, Rachel

    2007-01-01

    Studies of the end-Permian mass extinction have emphasized potential abiotic causes and their direct biotic effects. Less attention has been devoted to secondary extinctions resulting from ecological crises and the effect of community structure on such extinctions. Here we use a trophic network model that combines topological and dynamic approaches to simulate disruptions of primary productivity in palaeocommunities. We apply the model to Permian and Triassic communities of the Karoo Basin, South Africa, and show that while Permian communities bear no evidence of being especially susceptible to extinction, Early Triassic communities appear to have been inherently less stable. Much of the instability results from the faster post-extinction diversification of amphibian guilds relative to amniotes. The resulting communities differed fundamentally in structure from their Permian predecessors. Additionally, our results imply that changing community structures over time may explain long-term trends like declining rates of Phanerozoic background extinction PMID:17609191

  12. Aerobic scope explains individual variation in feeding capacity

    PubMed Central

    Auer, Sonya K.; Salin, Karine; Anderson, Graeme J.; Metcalfe, Neil B.

    2015-01-01

    Links between metabolism and components of fitness such as growth, reproduction and survival can depend on food availability. A high standard metabolic rate (SMR; baseline energy expenditure) or aerobic scope (AS; the difference between an individual's maximum and SMR) is often beneficial when food is abundant or easily accessible but can be less important or even disadvantageous when food levels decline. While the mechanisms underlying these context-dependent associations are not well understood, they suggest that individuals with a higher SMR or AS are better able to take advantage of high food abundance. Here we show that juvenile brown trout (Salmo trutta) with a higher AS were able to consume more food per day relative to individuals with a lower AS. These results help explain why a high aerobic capacity can improve performance measures such as growth rate at high but not low levels of food availability. PMID:26556902

  13. EARTHSHINE ON A YOUNG MOON: EXPLAINING THE LUNAR FARSIDE HIGHLANDS

    SciTech Connect

    Roy, Arpita; Wright, Jason T.; Sigurðsson, Steinn

    2014-06-20

    The lunar farside highlands problem refers to the curious and unexplained fact that the farside lunar crust is thicker, on average, than the nearside crust. Here we recognize the crucial influence of Earthshine, and propose that it naturally explains this hemispheric dichotomy. Since the accreting Moon rapidly achieved synchronous rotation, a surface and atmospheric thermal gradient was imposed by the proximity of the hot, post-giant impact Earth. This gradient guided condensation of atmospheric and accreting material, preferentially depositing crust-forming refractories on the cooler farside, resulting in a primordial bulk chemical inhomogeneity that seeded the crustal asymmetry. Our model provides a causal solution to the lunar highlands problem: the thermal gradient created by Earthshine produced the chemical gradient responsible for the crust thickness dichotomy that defines the lunar highlands.

  14. Aerobic scope explains individual variation in feeding capacity.

    PubMed

    Auer, Sonya K; Salin, Karine; Anderson, Graeme J; Metcalfe, Neil B

    2015-11-01

    Links between metabolism and components of fitness such as growth, reproduction and survival can depend on food availability. A high standard metabolic rate (SMR; baseline energy expenditure) or aerobic scope (AS; the difference between an individual's maximum and SMR) is often beneficial when food is abundant or easily accessible but can be less important or even disadvantageous when food levels decline. While the mechanisms underlying these context-dependent associations are not well understood, they suggest that individuals with a higher SMR or AS are better able to take advantage of high food abundance. Here we show that juvenile brown trout (Salmo trutta) with a higher AS were able to consume more food per day relative to individuals with a lower AS. These results help explain why a high aerobic capacity can improve performance measures such as growth rate at high but not low levels of food availability. PMID:26556902

  15. Explaining prompts children to privilege inductively rich properties.

    PubMed

    Walker, Caren M; Lombrozo, Tania; Legare, Cristine H; Gopnik, Alison

    2014-11-01

    Four experiments with preschool-aged children test the hypothesis that engaging in explanation promotes inductive reasoning on the basis of shared causal properties as opposed to salient (but superficial) perceptual properties. In Experiments 1a and 1b, 3- to 5-year-old children prompted to explain during a causal learning task were more likely to override a tendency to generalize according to perceptual similarity and instead extend an internal feature to an object that shared a causal property. Experiment 2 replicated this effect of explanation in a case of label extension (i.e., categorization). Experiment 3 demonstrated that explanation improves memory for clusters of causally relevant (non-perceptual) features, but impairs memory for superficial (perceptual) features, providing evidence that effects of explanation are selective in scope and apply to memory as well as inference. In sum, our data support the proposal that engaging in explanation influences children's reasoning by privileging inductively rich, causal properties. PMID:25128793

  16. Coordinated hydrolysis explains the mechanical behavior of kinesin.

    PubMed Central

    Peskin, C S; Oster, G

    1995-01-01

    The two-headed motor protein kinesin hydrolyzes nucleotide to move unidirectionally along its microtubule track at speeds up to 1000 nm/s (Saxton et al., 1988) and develops forces in excess of 5 pN (Hunt et al., 1994; Svoboda et al., 1994a). Individual kinesin molecules have been studied recently in vitro, and their behavior has been characterized in terms of force-velocity curves and variance measurements (Svoboda and Block, 1994a; Svoboda et al., 1994b). We present a model for force generation in kinesin in which the ATP hydrolysis reactions are coordinated with the relative positions of the two heads. The model explains the experimental data and permits us to study the relative roles of Brownian motion and elastic deformation in the motor mechanism of kinesin. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:7787069

  17. Jumping Jupiter Can Explain Mercury’s Orbit

    NASA Astrophysics Data System (ADS)

    Roig, Fernando; Nesvorný, David; DeSouza, Sandro Ricardo

    2016-04-01

    The orbit of Mercury has large values of eccentricity and inclination that cannot be easily explained if this planet formed on a circular and coplanar orbit. Here, we study the evolution of Mercury’s orbit during the instability related to the migration of the giant planets in the framework of the jumping-Jupiter model. We found that some instability models are able to produce the correct values of Mercury’s eccentricity and inclination, provided that relativistic effects are included in the precession of Mercury’s perihelion. The orbital excitation is driven by the fast change of the normal oscillation modes of the system corresponding to the perihelion precession of Jupiter (for the eccentricity) and the nodal regression of Uranus (for the inclination).

  18. Real world ocean rogue waves explained without the modulational instability.

    PubMed

    Fedele, Francesco; Brennan, Joseph; Ponce de León, Sonia; Dudley, John; Dias, Frédéric

    2016-01-01

    Since the 1990s, the modulational instability has commonly been used to explain the occurrence of rogue waves that appear from nowhere in the open ocean. However, the importance of this instability in the context of ocean waves is not well established. This mechanism has been successfully studied in laboratory experiments and in mathematical studies, but there is no consensus on what actually takes place in the ocean. In this work, we question the oceanic relevance of this paradigm. In particular, we analyze several sets of field data in various European locations with various tools, and find that the main generation mechanism for rogue waves is the constructive interference of elementary waves enhanced by second-order bound nonlinearities and not the modulational instability. This implies that rogue waves are likely to be rare occurrences of weakly nonlinear random seas. PMID:27323897

  19. Using Literature-Based Discovery to Explain Adverse Drug Effects.

    PubMed

    Hristovski, Dimitar; Kastrin, Andrej; Dinevski, Dejan; Burgun, Anita; Žiberna, Lovro; Rindflesch, Thomas C

    2016-08-01

    We report on our research in using literature-based discovery (LBD) to provide pharmacological and/or pharmacogenomic explanations for reported adverse drug effects. The goal of LBD is to generate novel and potentially useful hypotheses by analyzing the scientific literature and optionally some additional resources. Our assumption is that drugs have effects on some genes or proteins and that these genes or proteins are associated with the observed adverse effects. Therefore, by using LBD we try to find genes or proteins that link the drugs with the reported adverse effects. These genes or proteins can be used to provide insight into the processes causing the adverse effects. Initial results show that our method has the potential to assist in explaining reported adverse drug effects. PMID:27318993

  20. Classic reaction kinetics can explain complex patterns of antibiotic action

    PubMed Central

    zur Wiesch, P. Abel; Abel, S.; Gkotzis, S.; Ocampo, P.; Engelstädter, J.; Hinkley, T.; Magnus, C.; Waldor, M. K.; Udekwu, K.; Cohen, T.

    2015-01-01

    Finding optimal dosing strategies for treating bacterial infections is extremely difficult, and improving therapy requires costly and time-intensive experiments. To date, an incomplete mechanistic understanding of drug effects has limited our ability to make accurate quantitative predictions of drug-mediated bacterial killing and impeded the rational design of antibiotic treatment strategies. Three poorly understood phenomena complicate predictions of antibiotic activity: post-antibiotic growth suppression, density-dependent antibiotic effects, and persister cell formation. Here, we show that chemical binding kinetics alone are sufficient to explain these three phenomena, using single cell data and time-kill curves of Escherichia coli and Vibrio cholerae exposed to a variety of antibiotics in combination with a theoretical model that links chemical reaction kinetics to bacterial population biology. Our model reproduces existing observations, has a high predictive power across different experimental setups (R2= 0.86), and makes several testable predictions, which we verified in new experiments and by analysing published data from a clinical trial on tuberculosis therapy. While a variety of biological mechanisms have previously been invoked to explain post-antibiotic growth suppression, density-dependent antibiotic effects, and especially persister cell formation, our findings reveal that a simple model which considers only binding kinetics provides a parsimonious and unifying explanation for these three complex, phenotypically distinct behaviours. Current antibiotic and other chemotherapeutic regimens are often based on trial-and-error or expert opinion. Our ‘chemical reaction kinetics’-based approach may inform new strategies, that are based on rational design. PMID:25972005

  1. Strange history: the fall of Rome explained in Hereditas.

    PubMed

    Bengtsson, Bengt O

    2014-12-01

    In 1921 Hereditas published an article on the fall of Rome written by the famous classical scholar Martin P:son Nilsson. Why was a paper on this unexpected topic printed in the newly founded journal? To Nilsson, the demise of the Roman Empire was explained by the "bastardization" occurring between "races" from different parts of the realm. Offspring from mixed couples were of a less stable "type" than their parents, due to the breaking up by recombination of the original hereditary dispositions, which led to a general loss of competence to rule and govern. Thus, the "hardness" of human genes, together with their recombination, was - according to Nilsson - the main cause of the fall of Rome. Nilsson's argument is not particularly convincingly presented. Human "races" are taken to have the same genetic structure as inbred crop strains, and Nilsson believes in a metaphysical unity between the individual and the race to which it belongs. However, in my view, Martin P:son Nilsson and his friend Herman Nilsson-Ehle had wider aims with the article than to explain a historical event. The article can be read as indicating strong support from the classical human sciences to the ambitious new science of genetics. Support is also transferred from genetics to the conservative worldview, where the immutability and inflexibility of the Mendelian genes are used to strengthen the wish for greater stability in politics and life. The strange article in Hereditas can, thus, be read as an early instance in the - still ongoing - tug-of-war between the conservative and the liberal ideological poles over how genetic results best are socially interpreted. PMID:25588300

  2. Social processes explaining the benefits of Al-Anon participation.

    PubMed

    Timko, Christine; Halvorson, Max; Kong, Calvin; Moos, Rudolf H

    2015-12-01

    This study examined social processes of support, goal direction, provision of role models, and involvement in rewarding activities to explain benefits of participating in Al-Anon, a 12-step mutual-help program for people concerned about another person's substance use. Newcomers to Al-Anon were studied at baseline and 6 months later, at which time they were identified as having either sustained attendance or dropped out. Among both newcomers and established Al-Anon members ("old-timers"), we also used number of Al-Anon meetings attended during follow-up to indicate extent of participation. Social processes significantly mediated newcomers' sustained attendance status versus dropped out and outcomes of Al-Anon in the areas of life context (e.g., better quality of life, better able to handle problems due to the drinker), improved positive symptoms (e.g., higher self-esteem, more hopeful), and decreased negative symptoms (e.g., less abuse, less depressed). Social processes also significantly mediated newcomers' number of meetings attended and outcomes. However, among old-timers, Al-Anon attendance was not associated with outcomes, so the potential mediating role of social processes could not be examined, but social processes were associated with outcomes. Findings add to the growing body of work identifying mechanisms by which 12-step groups are effective, by showing that bonding, goal direction, and access to peers in recovery and rewarding pursuits help to explain associations between sustained Al-Anon participation among newcomers and improvements on key concerns of Al-Anon attendees. Al-Anon is free of charge and widely available, making it a potentially cost-effective public health resource for help alleviating negative consequences of concern about another's addiction. PMID:26727006

  3. Classic reaction kinetics can explain complex patterns of antibiotic action.

    PubMed

    Abel Zur Wiesch, Pia; Abel, Sören; Gkotzis, Spyridon; Ocampo, Paolo; Engelstädter, Jan; Hinkley, Trevor; Magnus, Carsten; Waldor, Matthew K; Udekwu, Klas; Cohen, Ted

    2015-05-13

    Finding optimal dosing strategies for treating bacterial infections is extremely difficult, and improving therapy requires costly and time-intensive experiments. To date, an incomplete mechanistic understanding of drug effects has limited our ability to make accurate quantitative predictions of drug-mediated bacterial killing and impeded the rational design of antibiotic treatment strategies. Three poorly understood phenomena complicate predictions of antibiotic activity: post-antibiotic growth suppression, density-dependent antibiotic effects, and persister cell formation. We show that chemical binding kinetics alone are sufficient to explain these three phenomena, using single-cell data and time-kill curves of Escherichia coli and Vibrio cholerae exposed to a variety of antibiotics in combination with a theoretical model that links chemical reaction kinetics to bacterial population biology. Our model reproduces existing observations, has a high predictive power across different experimental setups (R(2) = 0.86), and makes several testable predictions, which we verified in new experiments and by analyzing published data from a clinical trial on tuberculosis therapy. Although a variety of biological mechanisms have previously been invoked to explain post-antibiotic growth suppression, density-dependent antibiotic effects, and especially persister cell formation, our findings reveal that a simple model that considers only binding kinetics provides a parsimonious and unifying explanation for these three complex, phenotypically distinct behaviours. Current antibiotic and other chemotherapeutic regimens are often based on trial and error or expert opinion. Our "chemical reaction kinetics"-based approach may inform new strategies, which are based on rational design. PMID:25972005

  4. Social Processes Explaining the Benefits of Al-Anon Participation

    PubMed Central

    Timko, Christine; Halvorson, Max; Kong, Calvin; Moos, Rudolf H

    2015-01-01

    This study examined social processes of support, goal direction, provision of role models, and involvement in rewarding activities to explain benefits of participating in Al-Anon, a 12-step mutual-help program for people concerned about another person’s substance use. Newcomers to Al-Anon were studied at baseline and 6 months later, when they were identified as having sustained attendance or dropped out. Among newcomers, and among established Al-Anon members (“oldtimers”), we also used number of Al-Anon meetings attended during follow-up to indicate extent of participation. Social processes significantly mediated between newcomers’ attendance status as sustained (versus dropped out) and outcomes of Al-Anon in the domains of life context (e.g., better quality of life, better able to handle problems due to the drinker), improved positive symptoms (more self-esteem, more hopeful), and decreased negative symptoms (e.g., less abuse, less depressed). Social processes also significantly mediated between newcomers’ number of meetings and outcomes. However, among oldtimers, Al-Anon attendance was not associated with outcomes, so the potential mediating role of social processes could not be examined, but social processes were associated with outcomes. Findings add to the growing body of work identifying mechanisms by which 12-step groups are effective, by showing that bonding, goal direction, and access to peers in recovery and rewarding pursuits help to explain associations between sustained Al-Anon participation among newcomers and improvements on key concerns of Al-Anon attendees. Al-Anon is free of charge and widely available, making it a potentially cost-effective public health resource in helping to alleviate negative consequences of concern about another’s addiction. PMID:26727006

  5. Why Cosmic Fine-Tuning Needs to BE Explained

    NASA Astrophysics Data System (ADS)

    Manson, Neil Alan

    Discoveries in modern physics and Big Bang cosmology indicate that if either the initial conditions of the universe or the physical laws governing its development had differed even slightly, life could never have developed. It is for this reason that the universe is said to be ``fine-tuned'' for life. I argue that cosmic fine-tuning, which some want to dismiss as the way things just happen to be, in fact needs to be explained. In Chapter One I provide an overview of the evidence that the universe is fine-tuned for life. In Chapter Two I present a set of sufficient conditions for a fact's needing to be explained. The conditions are that the fact is improbable and that a ``tidy'' explanation of it is available. A tidy explanation of a fact is considerably less improbable than that fact and makes the obtaining of that fact considerably less improbable. Chapters Three, Four, and Five are devoted to showing that cosmic Chapter Three I argue that the universe's being finely tuned for life can meaningfully be considered improbable. In Chapter Four I claim that there is at least one tidy explanation of cosmic fine-tuning: that the universe was created by some sort of extramundane designer. In Chapters Four and Five I respond to three objections. The first is that the design hypothesis is ad hoc. The second is that we have no reason to believe a supernatural designer would prefer life-permitting cosmoi to other possible cosmoi and that our tendency to believe otherwise is the result of anthropocentrism. The third is that the design hypothesis never buys us an explanatory advantage.

  6. Explaining the Kuiper Belt with a Jumping Planet

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    A feature of the Kuiper Belt known as the kernel has yet to be adequately explained by solar system formation models. In a recent study, a theorist at the Southwest Research Institute proposes a new explanation for how Neptune arrived at its current orbit and how this planets migration in the early years of the solar system might have created the kernel.Orbital JumpThe kernel is a concentration of orbits within the Kuiper Belt that all have semimajor axes of roughly a 44 AU, low eccentricities, and low inclinations. How this collection of objects formed and why they exist where they do is difficult to explain with current models, however. Kernel objects arent in resonance with any of the larger bodies, so why are they concentrated at that specific distance? In this study, David Nesvorn proposes that the kernel resulted from Neptunes outward migration through the solar system.In the currently favored model of our solar systems formation, the outermost gas giant planets formed closer to the Sun and then migrated out to their current locations. Nesvorn ran a series of simulations of this migration to test the theory that a discontinuity in Neptunes movement outward i.e., a sudden jump in the planets orbital distance could explain the presence of the Kuiper Belts kernel.Results from a previous study, in which the authors evolved the four gas giant planets plus a fifth giant planet (blue) initially on an orbit between Saturn and Uranus. At 18.3 Myr, a close encounter with the fifth planet causes Neptunes orbit (pink) to jump outwards by ~0.4 AU, and the fifth planet is then ejected from the solar system by Jupiter. [Nesvorn 2015]Resonant PopulationNesvorn was successful in finding a model that reproduced the kernel, as well as other observed features of the solar system today. In his model, Neptune began its journey closer to the Sun, at a distance of roughly 24 AU, and it migrated fairly rapidly outward to about 28 AU. As it traveled, it swept up bodies in the outer

  7. Simple settlement decisions explain common dispersal patterns in territorial species.

    PubMed

    Gilroy, James J; Lockwood, Julie L

    2016-09-01

    Dispersal is one of the least-understood aspects of animal behaviour. For example, little is known of the mechanisms that determine how individuals express different dispersal behaviours in response to different circumstances. Uncovering these mechanisms is important for our understanding of spatial population dynamics. Using agent-based simulations, we examine how simple decision rules generate individual-level dispersal plasticity, and how this can influence population-scale dispersal dynamics. We model a territorial, monogamous population inhabiting a completely homogeneous environment. Dispersal variability therefore emerges solely as a result of between-individual interactions (competition, settlement, reproduction), which are governed by simple decision-making algorithms. We show that complex dispersal dynamics, including sex biases and strong density dependence, emerge naturally from simple rule-based behaviours. Dispersal is particularly sensitive to the inclusion of mate availability as a criterion for settlement: if neither sex evaluates mate availability, dispersal distances tend to decline at low densities, leading to a strong Allee effect from reduced pairing success. If one sex evaluates mate availability (females), Allee effects are largely avoided, but female-biased dispersal generates increasingly male-biased adult sex ratios at low densities. Sex biases are eliminated if both sexes evaluate mate availability, but population growth rates tend to be reduced due to survival costs and reduced pairing success. Our models suggest that simple decision mechanisms can explain several dynamic patterns that are commonly observed among territorial species. Importantly, these patterns emerge in the absence of environmental heterogeneity or between-individual variation in dispersal phenotypes, two conditions that are often invoked to explain dispersal heterogeneity in nature. This has implications for studies seeking to examine the causes of dispersal

  8. Explaining employment relationships with social exchange and job embeddedness.

    PubMed

    Hom, Peter W; Tsui, Anne S; Wu, Joshua B; Lee, Thomas W; Zhang, Ann Yan; Fu, Ping Ping; Li, Lan

    2009-03-01

    The research reported in this article clarifies how employee-organization relationships (EORs) work. Specifically, the authors tested whether social exchange and job embeddedness mediate how mutual-investment (whereby employers offer high inducements to employees for their high contributions) and over-investment (high inducements without corresponding high expected contributions) EOR approaches, which are based on Tsui, Pearce, Porter, and Tripoli's (1997) framework, affect quit propensity and organizational commitment. Two studies evaluated these intervening mechanisms. Study 1 surveyed 953 Chinese managers attending part-time master of business administration (MBA) programs in China, whereas Study 2 collected cross-sectional and longitudinal data from 526 Chinese middle managers in 41 firms. Standard and multilevel causal modeling techniques affirmed that social exchange and job embeddedness translate EOR influence. A second multilevel test using lagged outcome measures further established that job embeddedness mediates long-term EOR effects over 18 months. These findings corroborate prevailing views that social exchange explains how mutual- and over-investment EORs motivate greater workforce commitment and loyalty. This study enriches EOR perspectives by identifying job embeddedness as another mediator that is more enduring than social exchange. PMID:19271791

  9. Explaining the distribution of breeding and dispersal syndromes in conifers

    PubMed Central

    Leslie, Andrew B.; Beaulieu, Jeremy M.; Crane, Peter R.; Donoghue, Michael J.

    2013-01-01

    The evolution of plants exhibiting different sexes, or dioecy, is correlated with a number of ecological and life-history traits such as woody growth form and animal-dispersed seeds, but the underlying causes of these associations are unclear. Previous work in seed plants has suggested that the evolution of fleshy cones or seeds may favour dioecy. In this study, we use a well-sampled molecular phylogeny of conifers to show that although dioecy and fleshiness strongly co-occur at the species level, this relationship has not resulted from numerous separate origins of this trait combination or from differential rates of diversification. Instead, we suggest that two character combinations—the ancestral dry-monoecious condition and the derived fleshy-dioecious condition—have persisted in conifers longer than other combinations over evolutionary time. The persistence of these trait combinations appears to reflect differences in the rate of successful transition into and out of these character states over time, as well as the geographical restriction of species with rare combinations and their consequent vulnerability to extinction. In general, we argue that such persistence explanations should be considered alongside ‘key innovation’ hypotheses in explaining the phylogenetic distribution of traits. PMID:24026822

  10. Can mathematics explain the evolution of human language?

    PubMed Central

    2011-01-01

    Investigation into the sequence structure of the genetic code by means of an informatic approach is a real success story. The features of human language are also the object of investigation within the realm of formal language theories. They focus on the common rules of a universal grammar that lies behind all languages and determine generation of syntactic structures. This universal grammar is a depiction of material reality, i.e., the hidden logical order of things and its relations determined by natural laws. Therefore mathematics is viewed not only as an appropriate tool to investigate human language and genetic code structures through computer science-based formal language theory but is itself a depiction of material reality. This confusion between language as a scientific tool to describe observations/experiences within cognitive constructed models and formal language as a direct depiction of material reality occurs not only in current approaches but was the central focus of the philosophy of science debate in the twentieth century, with rather unexpected results. This article recalls these results and their implications for more recent mathematical approaches that also attempt to explain the evolution of human language. PMID:22046452

  11. Fatal attraction: Explaining Russia's sensitive nuclear transfers to Iran

    NASA Astrophysics Data System (ADS)

    Kuchinsky, Leah R.

    This paper explores Russia's sensitive nuclear assistance to Iran in an effort to determine why a supplier state might proliferate against its own apparent security interests. The goal is to help readers understand the supply-side dynamics of nuclear proliferation. Through careful reconstruction of the historical narrative, using open source data, this study tests the plausibility of a "fatalistic calculus" explanation, identified by Stephen Sestanovich as a possible driver for Russia's behavior. According to the hypothesis, Russia has cooperated with Iran as a way both to stay in the good graces of a neighbor that is suspected of developing nuclear weapons and to win short-term influence and profits. The paper also examines the role of other factors advanced in the existing supply-side literature, such as economic motives identified by physicist and nonproliferation scholar David Albright. The findings show that bureaucratic, economic and fatalistic factors have each played a role in motivating Russia's cooperation with Iran, with their relative importance shifting over time. Fatalism begets a strategy of Russian "minimaxing," in the lexicon of Russia scholar Robert Freedman, wherein Russia attempts to minimize damage to its relationship with the U.S. while maximizing influence in Iran via nuclear cooperation. Fatalism, as actualized by minimaxing, best explains Russia's behavior after former Russian president Vladmir Putin came to power, when the bureaucratic and economic arguments become less cogent.

  12. Behavioral pathways explaining oral health disparity in children.

    PubMed

    Gao, X-L; Hsu, C-Y S; Xu, Y C; Loh, T; Koh, D; Hwarng, H B

    2010-09-01

    Policymakers' understanding of and ability to reduce health disparities are pivotal for health promotion worldwide. This study aimed to verify the behavioral pathways leading to oral health disparities. Oral examinations were conducted for 1782 randomly selected preschoolers (3-6 yrs), and 1576 (88.4%) participants were followed up after 12 months. Parents were surveyed on their knowledge (K), attitude (A), and practices (P) regarding their children's oral health homecare (infant feeding, diet, and oral hygiene) and dental attendance. Structural equation modeling substantiated the links between specific KAs and corresponding practices, while generic KA did not affect practices. KAP pathways partly explained the ethnic and socio-economic disparities in oral health. Deprivation had a direct effect (not mediated by KA) on dental attendance, but not on oral health homecare. Ethnicity directly influenced oral health homecare practices, but not dental attendance. These behavioral pathways, furthering our understanding of health disparity, may have practical implications for health promotion and policy-making. PMID:20554887

  13. Causal Inference and Explaining Away in a Spiking Network

    PubMed Central

    Moreno-Bote, Rubén; Drugowitsch, Jan

    2015-01-01

    While the brain uses spiking neurons for communication, theoretical research on brain computations has mostly focused on non-spiking networks. The nature of spike-based algorithms that achieve complex computations, such as object probabilistic inference, is largely unknown. Here we demonstrate that a family of high-dimensional quadratic optimization problems with non-negativity constraints can be solved exactly and efficiently by a network of spiking neurons. The network naturally imposes the non-negativity of causal contributions that is fundamental to causal inference, and uses simple operations, such as linear synapses with realistic time constants, and neural spike generation and reset non-linearities. The network infers the set of most likely causes from an observation using explaining away, which is dynamically implemented by spike-based, tuned inhibition. The algorithm performs remarkably well even when the network intrinsically generates variable spike trains, the timing of spikes is scrambled by external sources of noise, or the network is mistuned. This type of network might underlie tasks such as odor identification and classification. PMID:26621426

  14. Galaxies on FIRE: Stellar Feedback Explains Inefficient Star Formation

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.

    2014-06-01

    Many of the most fundamental unsolved questions in star and galaxy formation revolve around star formation and "feedback" from both massive stars and accretion onto super-massive black holes. I'll present new simulations which attempt to realistically model the diverse physics of the interstellar medium, star formation, and feedback from stellar radiation pressure, supernovae, stellar winds, and photo-ionization. These mechanisms lead to 'self-regulated' galaxy and star formation, in which global correlations such as the Schmidt-Kennicutt law and the global inefficiency of star formation -- the stellar mass function -- emerge naturally. Within galaxies, feedback regulates the structure of the interstellar medium, and many observed properties of the ISM, star formation, and galaxies can be understood as a fundamental consequence of super-sonic turbulence in a rapidly cooling, self-gravitating medium. But feedback also produces galactic super-winds that can dramatically alter the cosmological evolution of galaxies, their behavior in galaxy mergers, and structure of the inter-galactic medium: these winds depend non-linearly on multiple feedback mechanisms in a way that explains why they have been so difficult to model in previous "sub-grid" approaches.

  15. Failed supernovae explain the compact remnant mass function

    SciTech Connect

    Kochanek, C. S.

    2014-04-10

    One explanation for the absence of higher mass red supergiants (16.5 M {sub ☉} ≲ M ≲ 25 M {sub ☉}) as the progenitors of Type IIP supernovae (SNe) is that they die in failed SNe creating black holes. Simulations show that such failed SNe still eject their hydrogen envelopes in a weak transient, leaving a black hole with the mass of the star's helium core (5-8 M {sub ☉}). Here we show that this naturally explains the typical masses of observed black holes and the gap between neutron star and black hole masses without any fine-tuning of stellar mass loss, binary mass transfer, or the SN mechanism, beyond having it fail in a mass range where many progenitor models have density structures that make the explosions more likely to fail. There is no difficulty including this ∼20% population of failed SNe in any accounting of SN types over the progenitor mass function. And, other than patience, there is no observational barrier to either detecting these black hole formation events or limiting their rates to be well below this prediction.

  16. Static stress triggering explains the empirical aftershock distance decay

    NASA Astrophysics Data System (ADS)

    Hainzl, Sebastian; Moradpour, Javad; Davidsen, Jörn

    2014-12-01

    The shape of the spatial aftershock decay is sensitive to the triggering mechanism and thus particularly useful for discriminating between static and dynamic stress triggering. For California seismicity, it has been recently recognized that its form is more complicated than typically assumed consisting of three different regimes with transitions at the scale of the rupture length and the thickness of the crust. The intermediate distance range is characterized by a relative small decay exponent of 1.35 previously declared to relate to dynamic stress triggering. We perform comprehensive simulations of a simple clock-advance model, in which the number of aftershocks is just proportional to the Coulomb-stress change, to test whether the empirical result can be explained by static stress triggering. Similarly to the observations, the results show three scaling regimes. For simulations adapted to the depths and focal mechanisms observed in California, we find a remarkable agreement with the observation over the whole distance range for a fault distribution with fractal dimension of 1.8, which is shown to be in good agreement with an independent analysis of California seismicity.

  17. Can mathematics explain the evolution of human language?

    PubMed

    Witzany, Guenther

    2011-09-01

    Investigation into the sequence structure of the genetic code by means of an informatic approach is a real success story. The features of human language are also the object of investigation within the realm of formal language theories. They focus on the common rules of a universal grammar that lies behind all languages and determine generation of syntactic structures. This universal grammar is a depiction of material reality, i.e., the hidden logical order of things and its relations determined by natural laws. Therefore mathematics is viewed not only as an appropriate tool to investigate human language and genetic code structures through computer science-based formal language theory but is itself a depiction of material reality. This confusion between language as a scientific tool to describe observations/experiences within cognitive constructed models and formal language as a direct depiction of material reality occurs not only in current approaches but was the central focus of the philosophy of science debate in the twentieth century, with rather unexpected results. This article recalls these results and their implications for more recent mathematical approaches that also attempt to explain the evolution of human language. PMID:22046452

  18. Two phenomenological constants explain similarity laws in stably stratified turbulence.

    PubMed

    Katul, Gabriel G; Porporato, Amilcare; Shah, Stimit; Bou-Zeid, Elie

    2014-02-01

    In stably stratified turbulent flows, the mixing efficiency associated with eddy diffusivity for heat, or equivalently the turbulent Prandtl number (Pr(t)), is fraught with complex dynamics originating from the scalewise interplay between shear generation of turbulence and its dissipation by density gradients. A large corpus of data and numerical simulations agree on a near-universal relation between Pr(t) and the Richardson number (R(i)), which encodes the relative importance of buoyancy dissipation to mechanical production of turbulent kinetic energy. The Pr(t)-R(i) relation is shown to be derivable solely from the cospectral budgets for momentum and heat fluxes if a Rotta-like return to isotropy closure for the pressure-strain effects and Kolmogorov's theory for turbulent cascade are invoked. The ratio of the Kolmogorov to the Kolmogorov-Obukhov-Corrsin phenomenological constants, and a constant associated with isotropization of the production whose value (= 3/5) has been predicted from Rapid Distortion Theory, explain all the macroscopic nonlinearities. PMID:25353571

  19. Nonlinear Bayesian cue integration explains the dynamics of vocal learning

    NASA Astrophysics Data System (ADS)

    Zhou, Baohua; Sober, Samuel; Nemenman, Ilya

    The acoustics of vocal production in songbirds is tightly regulated during both development and adulthood as birds progressively refine their song using sensory feedback to match an acoustic target. Here, we perturb this sensory feedback using headphones to shift the pitch (fundamental frequency) of song. When the pitch is shifted upwards (downwards), birds eventually learn to compensate and sing lower (higher), bringing the experienced pitch closer to the target. Paradoxically, the speed and amplitude of this motor learning decrease with increases in the introduced error size, so that birds respond rapidly to a small sensory perturbation, while seemingly never correcting a much bigger one. Similar results are observed broadly across the animal kingdom, and they do not derive from a limited plasticity of the adult brain since birds can compensate for a large error as long as the error is imposed gradually. We develop a mathematical model based on nonlinear Bayesian integration of two sensory modalities (one perturbed and the other not) that quantitatively explains all of these observations. The model makes predictions about the structure of the probability distribution of the pitches sung by birds during the pitch shift experiments, which we confirm using experimental data. This work was supported in part by James S. McDonnell Foundation Grant # 220020321, NSF Grant # IOS/1208126, NSF Grant # IOS/1456912 and NIH Grants # R01NS084844.

  20. Relative resource abundance explains butterfly biodiversity in island communities

    PubMed Central

    Yamamoto, Naoaki; Yokoyama, Jun; Kawata, Masakado

    2007-01-01

    Ecologists have long been intrigued by the factors that control the pattern of biodiversity, i.e., the distribution and abundance of species. Previous studies have demonstrated that coexisting species partition their resources and/or that the compositional similarity between communities is determined by environmental factors, lending support to the niche-assembly model. However, no attempt has been made to test whether the relative amount of resources that reflects relative niche space controls relative species abundance in communities. Here, we demonstrate that the relative abundance of butterfly species in island communities is significantly related to the relative biomasses of their host plants but not to the geographic distance between communities. In the studied communities, the biomass of particular host plant species positively affected the abundance of the butterfly species that used them, and consequently, influenced the relative abundance of the butterfly communities. This indicated that the niche space of butterflies (i.e., the amount of resources) strongly influences butterfly biodiversity patterns. We present this field evidence of the niche-apportionment model that propose that the relative amount of niche space explains the pattern of the relative abundance of the species in communities. PMID:17553963

  1. Drastic growth effect may explain sympatric cannibalistic polymorphism.

    PubMed

    Wakano, Joe Yuichiro

    2004-01-01

    Cannibalistic polyphenism is observed in many fishes and amphibians. In the case of amphibian larvae, cannibal morph and typical morph coexist. Benefits and costs of the cannibal morph have been studied empirically but the mechanism of the maintenance of polymorphism is not well known. Here, we construct a game model of typical and cannibal morph strategies to obtain the condition of stable coexistence. Generally, once an individual succeeds in cannibalism, it grows very quickly, which facilitates the next cannibalism. In a model without this 'drastic growth effect', stable coexistence cannot occur. To represent drastic growth effect, it is assumed that cannibal/typical morph stage is followed by giant/normal stage. A cannibal morph that performs cannibalism in the first stage can become a 'giant' in the next stage. This model allows stable coexistence of cannibal and typical morphs. The condition for coexistence is that payoff of a giant is two times larger than normal individuals. As long as direct consumption of victim's body is considered as reward for successful cannibalism, coexistence cannot be explained. When the reward is considered as social standing of being outstanding size in a population, sympatric cannibalistic polymorphism is possible, without regard to the initial size variation or resource shortage. PMID:14637056

  2. Explaining Self and Vicarious Reactance: A Process Model Approach.

    PubMed

    Sittenthaler, Sandra; Jonas, Eva; Traut-Mattausch, Eva

    2016-04-01

    Research shows that people experience a motivational state of agitation known as reactance when they perceive restrictions to their freedoms. However, research has yet to show whether people experience reactance if they merely observe the restriction of another person's freedom. In Study 1, we activated realistic vicarious reactance in the laboratory. In Study 2, we compared people's responses with their own and others' restrictions and found the same levels of experienced reactance and behavioral intentions as well as aggressive tendencies. We did, however, find differences in physiological arousal: Physiological arousal increased quickly after participants imagined their own freedom being restricted, but arousal in response to imagining a friend's freedom being threatened was weaker and delayed. In line with the physiological data, Study 3's results showed that self-restrictions aroused more emotional thoughts than vicarious restrictions, which induced more cognitive responses. Furthermore, in Study 4a, a cognitive task affected only the cognitive process behind vicarious reactance. In contrast, in Study 4b, an emotional task affected self-reactance but not vicarious reactance. We propose a process model explaining the emotional and cognitive processes of self- and vicarious reactance. PMID:26984012

  3. Oriented attachment explains cobalt ferrite nanoparticle growth in bioinspired syntheses.

    PubMed

    Wolff, Annalena; Hetaba, Walid; Wißbrock, Marco; Löffler, Stefan; Mill, Nadine; Eckstädt, Katrin; Dreyer, Axel; Ennen, Inga; Sewald, Norbert; Schattschneider, Peter; Hütten, Andreas

    2014-01-01

    Oriented attachment has created a great debate about the description of crystal growth throughout the last decade. This aggregation-based model has successfully described biomineralization processes as well as forms of inorganic crystal growth, which could not be explained by classical crystal growth theory. Understanding the nanoparticle growth is essential since physical properties, such as the magnetic behavior, are highly dependent on the microstructure, morphology and composition of the inorganic crystals. In this work, the underlying nanoparticle growth of cobalt ferrite nanoparticles in a bioinspired synthesis was studied. Bioinspired syntheses have sparked great interest in recent years due to their ability to influence and alter inorganic crystal growth and therefore tailor properties of nanoparticles. In this synthesis, a short synthetic version of the protein MMS6, involved in nanoparticle formation within magnetotactic bacteria, was used to alter the growth of cobalt ferrite. We demonstrate that the bioinspired nanoparticle growth can be described by the oriented attachment model. The intermediate stages proposed in the theoretical model, including primary-building-block-like substructures as well as mesocrystal-like structures, were observed in HRTEM measurements. These structures display regions of substantial orientation and possess the same shape and size as the resulting discs. An increase in orientation with time was observed in electron diffraction measurements. The change of particle diameter with time agrees with the recently proposed kinetic model for oriented attachment. PMID:24605288

  4. CRISPR adaptation biases explain preference for acquisition of foreign DNA

    PubMed Central

    Yosef, Ido; Auster, Oren; Manor, Miriam; Amitai, Gil; Edgar, Rotem; Qimron, Udi; Sorek, Rotem

    2015-01-01

    In the process of CRISPR adaptation, short pieces of DNA (“spacers”) are acquired from foreign elements and integrated into the CRISPR array. It so far remained a mystery how spacers are preferentially acquired from the foreign DNA while the self chromosome is avoided. Here we show that spacer acquisition is replication-dependent, and that DNA breaks formed at stalled replication forks promote spacer acquisition. Chromosomal hotspots of spacer acquisition were confined by Chi sites, which are sequence octamers highly enriched on the bacterial chromosome, suggesting that these sites limit spacer acquisition from self DNA. We further show that the avoidance of “self” is mediated by the RecBCD dsDNA break repair complex. Our results suggest that in E. coli, acquisition of new spacers depends on RecBCD-mediated processing of dsDNA breaks occurring primarily at replication forks, and that the preference for foreign DNA is achieved through the higher density of Chi sites on the self chromosome, in combination with the higher number of forks on the foreign DNA. This model explains the strong preference to acquire spacers from both high copy plasmids and phages. PMID:25874675

  5. Cortical thinning explains changes in sleep slow waves during adulthood.

    PubMed

    Dubé, Jonathan; Lafortune, Marjolaine; Bedetti, Christophe; Bouchard, Maude; Gagnon, Jean François; Doyon, Julien; Evans, Alan C; Lina, Jean-Marc; Carrier, Julie

    2015-05-20

    Sleep slow waves (SWs) change considerably throughout normal aging. In humans, SWs are generated and propagate on a structural backbone of highly interconnected cortical regions that form most of the default mode network, such as the insula, cingulate cortices, temporal lobe, parietal lobe, and medial frontal lobe. Regions in this network undergo cortical thinning and breakdown in structural and functional connectivity over the course of normal aging. In this study, we investigated how changes in cortical thickness (CT), a measure of gray matter integrity, are involved in modifications of sleep SWs during adulthood in humans. Thirty young (mean age = 23.49 years; SD = 2.79) and 33 older (mean age = 60.35 years; SD = 5.71) healthy subjects underwent a nocturnal polysomnography and T1 MRI. We show that, when controlling for age, higher SW density (nb/min of nonrapid eye movement sleep) was associated with higher CT in cortical regions involved in SW generation surrounding the lateral fissure (insula, superior temporal, parietal, middle frontal), whereas higher SW amplitude was associated with higher CT in middle frontal, medial prefrontal, and medial posterior regions. Mediation analyses demonstrated that thinning in a network of cortical regions involved in SW generation and propagation, but also in cognitive functions, explained the age-related decrease in SW density and amplitude. Altogether, our results suggest that microstructural degradation of specific cortical regions compromise SW generation and propagation in older subjects, critically contributing to age-related changes in SW oscillations. PMID:25995467

  6. Optimization of biomass composition explains microbial growth-stoichiometry relationships

    USGS Publications Warehouse

    Franklin, O.; Hall, E.K.; Kaiser, C.; Battin, T.J.; Richter, A.

    2011-01-01

    Integrating microbial physiology and biomass stoichiometry opens far-reaching possibilities for linking microbial dynamics to ecosystem processes. For example, the growth-rate hypothesis (GRH) predicts positive correlations among growth rate, RNA content, and biomass phosphorus (P) content. Such relationships have been used to infer patterns of microbial activity, resource availability, and nutrient recycling in ecosystems. However, for microorganisms it is unclear under which resource conditions the GRH applies. We developed a model to test whether the response of microbial biomass stoichiometry to variable resource stoichiometry can be explained by a trade-off among cellular components that maximizes growth. The results show mechanistically why the GRH is valid under P limitation but not under N limitation. We also show why variability of growth rate-biomass stoichiometry relationships is lower under P limitation than under N or C limitation. These theoretical results are supported by experimental data on macromolecular composition (RNA, DNA, and protein) and biomass stoichiometry from two different bacteria. In addition, compared to a model with strictly homeostatic biomass, the optimization mechanism we suggest results in increased microbial N and P mineralization during organic-matter decomposition. Therefore, this mechanism may also have important implications for our understanding of nutrient cycling in ecosystems.

  7. Explaining History. Hippolyte Taine's Philosophy of Historical Science

    NASA Astrophysics Data System (ADS)

    Müller, Philipp

    Historians of European historiography have often characterized Hippolyte Taine (1828-1893) as an adherent of the positivist school of thought, typical for the development of a scientific culture in Western Europe that differed from its German counterpart.1 In accordance with that view, Wilhelm Dilthey grouped him together with other scholars like John Stuart Mill and Herbert Spencer against who Dilthey tried to develop his conception of the human sciences based on the notion of "verstehen" (see Dilthey [1924] 1957, 139ff.). Dilthey understood Taine as proposing to analyze the human mind by identifying its individual components and then explaining their meaning by laws of their relation. He argued that such an approach might be adequate for the natural sciences, but neglected the fact that an analysis of the mind had to start from a given psychological connection that was prior to any definition of particular phenomena. From Dilthey's point of view, applying Taine's theory to historical studies only made them look more objective while actually Taine was unaware of just following the prevailing convictions of his time (idem, 191f.).

  8. Nature designs tough collagen: Explaining the nanostructure of collagen fibrils

    PubMed Central

    Buehler, Markus J.

    2006-01-01

    Collagen is a protein material with superior mechanical properties. It consists of collagen fibrils composed of a staggered array of ultra-long tropocollagen (TC) molecules. Theoretical and molecular modeling suggests that this natural design of collagen fibrils maximizes the strength and provides large energy dissipation during deformation, thus creating a tough and robust material. We find that the mechanics of collagen fibrils can be understood quantitatively in terms of two critical molecular length scales χS and χR that characterize when (i) deformation changes from homogeneous intermolecular shear to propagation of slip pulses and when (ii) covalent bonds within TC molecules begin to fracture, leading to brittle-like failure. The ratio χS/χR indicates which mechanism dominates deformation. Our modeling rigorously links the chemical properties of individual TC molecules to the macroscopic mechanical response of fibrils. The results help to explain why collagen fibers found in nature consist of TC molecules with lengths in the proximity of 300 nm and advance the understanding how collagen diseases that change intermolecular adhesion properties influence mechanical properties. PMID:16895989

  9. Social sampling explains apparent biases in judgments of social environments.

    PubMed

    Galesic, Mirta; Olsson, Henrik; Rieskamp, Jörg

    2012-12-01

    How people assess their social environments plays a central role in how they evaluate their life circumstances. Using a large probabilistic national sample, we investigated how accurately people estimate characteristics of the general population. For most characteristics, people seemed to underestimate the quality of others' lives and showed apparent self-enhancement, but for some characteristics, they seemed to overestimate the quality of others' lives and showed apparent self-depreciation. In addition, people who were worse off appeared to enhance their social position more than those who were better off. We demonstrated that these effects can be explained by a simple social-sampling model. According to the model, people infer how others are doing by sampling from their own immediate social environments. Interplay of these sampling processes and the specific structure of social environments leads to the apparent biases. The model predicts the empirical results better than alternative accounts and highlights the importance of considering environmental structure when studying human cognition. PMID:23104680

  10. [Ticagrelor in acute coronary syndrome. Explaining the inexplicable].

    PubMed

    Criniti, Juan Martín; Izcovich, Ariel; Popoff, Federico; Ruiz, Juan Ignacio; Catalano, Hugo N

    2014-01-01

    The PLATO study evaluated the efficacy of adding ticagrelor, instead of clopidogrel, to aspirin in patients with acute coronary syndrome, which showed surprisingly positive results making the drug acceptable to regulatory agencies and specialty societies worldwide. Notwithstanding the aforementioned success, contradictory information supplied by critical analysis was submitted by the sponsor. The controversial findings revealed several aspects that are difficult to explain, threatening the veracity of the study's conclusions. Mortality rate pattern, excessive benefit not comparable to prior studies, unexplained loss of follow-up development and inconsistency in findings in accordance with the country, the type of events arbitrator and monitoring committee are some of the most questionable issues. Dubious reaction to this trial is based on the fact that the information could not be found in published articles. This complex situation poses a challenge to the critical analysis of the text and raises questions as to how far the conflicts of financial interest influenced the development of the study, the communication of its results and probably, acceptance of the drug for commercial use. PMID:24918677

  11. Global patterns in endemism explained by past climatic change.

    PubMed

    Jansson, Roland

    2003-03-22

    I propose that global patterns in numbers of range-restricted endemic species are caused by variation in the amplitude of climatic change occurring on time-scales of 10-100 thousand years (Milankovitch oscillations). The smaller the climatic shifts, the more probable it is that palaeoendemics survive and that diverging gene pools persist without going extinct or merging, favouring the evolution of neoendemics. Using the change in mean annual temperature since the last glacial maximum, estimated from global circulation models, I show that the higher the temperature change in an area, the fewer endemic species of mammals, birds, reptiles, amphibians and vascular plants it harbours. This relationship was robust to variation in area (for areas greater than 10(4) km2), latitudinal position, extent of former glaciation and whether or not areas are oceanic islands. Past climatic change was a better predictor of endemism than annual temperature range in all phylads except amphibians, suggesting that Rapoport's rule (i.e. species range sizes increase with latitude) is best explained by the increase in the amplitude of climatic oscillations towards the poles. Globally, endemic-rich areas are predicted to warm less in response to greenhouse-gas emissions, but the predicted warming would cause many habitats to disappear regionally, leading to species extinctions. PMID:12769457

  12. Explaining the electroweak scale and stabilizing moduli in M theory

    SciTech Connect

    Acharya, Bobby S.; Bobkov, Konstantin; Kane, Gordon L.; Kumar, Piyush; Shao Jing

    2007-12-15

    In a recent paper [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).] it was shown that in fluxless M theory vacua with at least two hidden sectors undergoing strong gauge dynamics and a particular form of the Kaehler potential, all moduli are stabilized by the effective potential and a stable hierarchy is generated, consistent with standard gauge unification. This paper explains the results of [B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006).] in more detail and generalizes them, finding an essentially unique de Sitter vacuum under reasonable conditions. One of the main phenomenological consequences is a prediction which emerges from this entire class of vacua: namely, gaugino masses are significantly suppressed relative to the gravitino mass. We also present evidence that, for those vacua in which the vacuum energy is small, the gravitino mass, which sets all the superpartner masses, is automatically in the TeV-100 TeV range.

  13. Explaining trends and variability in coastal relative sea level

    NASA Astrophysics Data System (ADS)

    Frederikse, Thomas; Riva, Riccardo

    2016-04-01

    Comprehensive understanding of trends and variability in coastal mean sea level is vital for protecting shores under a changing climate. To understand the behavior of coastal relative sea level (RSL), it is crucial to identify all relevant processes. We combine data from various geophysical models and observations to determine whether the trends and decadal variability observed in relative sea level at tide gauges can be explained by the sum of all known contributors. A key contributor to RSL is vertical land motion, which is caused by glacial isostatic adjustment (GIA), solid earth response to surface loading, tectonics, and local effects. We explicitly model low-frequency loading effects to correct GPS records, which leads to a more consistent trend than only using GIA models. Secondly, we create sea level fingerprints based on estimates of ice melt and changes in land hydrology, which provide the RSL contribution due to large-scale mass transport. Since coastal areas are often located on shallow continental shelves, steric effects will generally be small, and a large fraction of the decadal sea level variability will have a remote steric origin. Therefore, we determine a relation between coastal sea level and deep sea steric variability. For the period 1950-2012, we find that for many locations, including the European coast, the observed and modeled RSL time series agree well on decadal and secular scales.

  14. Explaining weapons proliferation: Going beyond the security dilemma

    SciTech Connect

    Rattray, G.J.

    1994-07-01

    Most analyses addressing the subject of why states choose to proliferate focus on external motivations, particularly the security dilemma, facing a country`s leaders. This paper concludes that, other factors, such as prestige, regime type and stability, and economic status, can have impact in determining proliferation outcomes. In the case of Newly Independent States of the former Soviet Union (NIS), the domestic problems generated by internal conflicts, arms remaining from the Cold War, excess defense industrial capacity, economic difficulties and the breakdown of central authority resulting in a loss of border control and corruption have all made the NIS an extremely fertile ground for weapons proliferation. A more positive `rollback` situation has emerged in Latin America where both Argentina and Brazil have seemingly decided to forgo the acquisition of nuclear weapons and ballistic missiles. The US must understand the `strategic personality` of each potential proliferation. Not all state behavior can be explained in terms of the security dilemma. One must also keep in mind the complexity of possible motivations. Economic and technological assistance and cooperative efforts at institution-building hold great potential to combating proliferation.

  15. What is believed is what is explained (sometimes)

    SciTech Connect

    Li, Renwei; Pereira, L.M.

    1996-12-31

    This paper presents a formal and computational methodology for incorporation of new knowledge into knowledge bases about actions and changes. We employ Gelfond and Lifschitz action description language A to describe domains of actions. The knowledge bases on domains of actions are defined and obtained by a new translation from domain descriptions in A into abductive normal logic programs, where a time dimension is incorporated. The knowledge bases are shown to be both sound and complete with respect to their domain descriptions. In particular, we propose a possible causes approach (PCA) to belief update based on the slogan: What is believed is what is explained. A possible cause of new knowledge consists of abduced occurrences of actions and value propositions about the initial state of the domain of actions, that would allow to derive the new knowledge. We show how to compute possible causes with abductive logic programming, and present some techniques to improve search efficiency. We use examples to compare our possible causes approach with Ginsberg`s possible worlds approach (PWA) and Winslett`s possible models approach (PMA).

  16. Incorporating coping into an expectancy framework for explaining drinking behaviour.

    PubMed

    Hasking, Penelope A; Oei, Tian P S

    2008-01-01

    Expectancy Theory has offered much in the way of understanding alcohol use and abuse, and has contributed greatly to prevention and treatment initiatives. However although many cognitive-behavioural treatment approaches are based on expectancy constructs, such as outcome expectancies and self-efficacy, high relapse rates imply that expectancy theory may be too narrow in scope, and that additional variables need to be examined if a comprehensive understanding of drinking behaviour, and better treatment outcomes, are to be achieved. We suggest that the coping strategies an individual employs present one such set of variables that have largely been neglected from an expectancy framework. Although coping skills training is routinely used in prevention and treatment of alcohol problems, coping research has suffered from a poor theoretical framework. In this paper we review the existing research relating expectancies, self-efficacy and coping to drinking behaviour and propose a model which explains both social and dependent drinking, by incorporating coping into an expectancy theory framework. We also outline research and clinical implications of the proposed model. PMID:19630702

  17. Hypotheses to explain the origin of species in Amazonia.

    PubMed

    Haffer, J

    2008-11-01

    The main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different factors, as follow: (1) Changes in the distribution of land and sea or in the landscape due to tectonic movements or sea level fluctuations (Paleogeography hypothesis), (2) the barrier effect of Amazonian rivers (River hypothesis), (3) a combination of the barrier effect of broad rivers and vegetational changes in northern and southern Amazonia (River-refuge hypothesis), (4) the isolation of humid rainforest blocks near areas of surface relief in the periphery of Amazonia separated by dry forests, savannas and other intermediate vegetation types during dry climatic periods of the Tertiary and Quaternary (Refuge hypothesis), (5) changes in canopy-density due to climatic reversals (Canopy-density hypothesis) (6) the isolation and speciation of animal populations in small montane habitat pockets around Amazonia due to climatic fluctuations without major vegetational changes (Museum hypothesis), (7) competitive species interactions and local species isolations in peripheral regions of Amazonia due to invasion and counterinvasion during cold/warm periods of the Pleistocene (Disturbance-vicariance hypothesis) and (8) parapatric speciation across steep environmental gradients without separation of the respective populations (Gradient hypothesis). Several of these hypotheses probably are relevant to a different degree for the speciation processes in different faunal groups or during different geological periods. The basic paleogeography model refers mainly to faunal differentiation during the Tertiary and in combination with the Refuge hypothesis. Milankovitch cycles leading to global main hypotheses proposed to explain barrier formation separating populations and causing the differentiation of species in Amazonia during the course of geological history are based on different

  18. A Self-Consistent Model to Explain Shallow Volcanic Tremor

    NASA Astrophysics Data System (ADS)

    Girona, T.; Caudron, C.; Costa Rodriguez, F.; Taisne, B.

    2015-12-01

    Volcanic tremor sourced at shallow depths (~ hundreds of meters) is one of the most characteristic seismic signals recorded at active volcanoes and yet to be fully understood. It typically appears preceding many impending volcanic eruptions. However, the origin of this seismic signal remains unclear, which limits our understanding of the sub-surface processes during volcanic unrest. In this study, we propose that the shallow volcanic tremor emerges from pressure oscillations occurring beneath volcanic craters as consequence of continuous degassing. To test this hypothesis, we have coupled a new three-dimensional two-phase flow agent-based model that simulates the bubble dynamics in a magma conduit, a lumped-parameter model for the evolution of the gas pressure beneath the crater, and a lumped-parameter model to simulate the permeable transfer of volcanic gases to the atmosphere. Our numerical experiments reveal that pressure oscillations beneath volcanic craters can explain the main features of shallow volcanic tremor, namely, the direct correlation with gas emissions, the increase of amplitude of the ground vibrations when an eruption approaches, the broadband character of the dominant frequencies (in the range ~ 0.5 - 5 Hz), the frequency gliding towards higher values when the volcanic activity increases, and the power law distribution in the very high-frequency range of the spectra (from the dominant peaks till ~ 10 - 15 Hz). Our model also predicts that the exponent of the power law of the frequency spectra changes systematically with the physical parameters that are thought to vary during the onset of an unrest episode.

  19. Can physics help to explain embryonic development? An overview.

    PubMed

    Fleury, V

    2013-10-01

    Recent technical advances including digital imaging and particle image velocimetry can be used to extract the full range of embryonic movements that constitute the instantaneous 'morphogenetic fields' of a developing animal. The final shape of the animal results from the sum over time (integral) of the movements that make up the velocity fields of all the tissue constituents. In vivo microscopy can be used to capture the details of vertebrate development at the earliest embryonic stages. The movements thus observed can be quantitatively compared to physical models that provide velocity fields based on simple hypotheses about the nature of living matter (a visco-elastic gel). This approach has cast new light on the interpretation of embryonic movement, folding, and organisation. It has established that several major discontinuities in development are simple physical changes in boundary conditions. In other words, with no change in biology, the physical consequences of collisions between folds largely explain the morphogenesis of the major structures (such as the head). Other discontinuities result from changes in physical conditions, such as bifurcations (changes in physical behaviour beyond specific yield points). For instance, beyond a certain level of stress, a tissue folds, without any new gene being involved. An understanding of the physical features of movement provides insights into the levers that drive evolution; the origin of animals is seen more clearly when viewed under the light of the fundamental physical laws (Newton's principle, action-reaction law, changes in symmetry breaking scale). This article describes the genesis of a vertebrate embryo from the shapeless stage (round mass of tissue) to the development of a small, elongated, bilaterally symmetric structure containing vertebral precursors, hip and shoulder enlarges, and a head. PMID:24029587

  20. The Amazon River reversal explained by tectonic and surface processes

    NASA Astrophysics Data System (ADS)

    Sacek, V.

    2014-12-01

    The drainage pattern in Amazonia was expressively modified during the mountain building of central and northern Andes. In Early Miocene, the fluvial systems in western Amazonia flowed to the foreland basins and northward to the Caribbean. By Late Miocene the drainage reversal occurred and formed the transcontinental Amazon River, connecting the Andes and the equatorial Atlantic margin. This event is recorded in the stratigraphic evolution of the Foz do Amazonas Basin by the onset of Andean-derived sedimentation. Additionally, an abrupt increase in sedimentation rate after the reversal occurred in the Foz do Amazonas Basin. Based on three-dimensional numerical models that couple surface processes, flexural isostasy and crustal thickening due to orogeny, I concluded that the Miocene drainage reversal can be explained by the flexural and surface processes response to the Andes formation with no need to invoke dynamic topography induced by mantle convection, as previously proposed. I observed that the instant of drainage reversal is directly linked to the rate of crustal thickening in the orogeny, the rate of erosion and, mainly, the efficiency of sediment transport. Moreover, the numerical experiments were able to predict the increase in sedimentation rate in the Amazon fan after the drainage reversal of the Amazon River as observed in the Late Miocene-Pliocene sedimentary record. However, the present numerical model fails to fully reproduce the evolution of the Pebas system, a megawetland in western Amazonia that preceded the drainage reversal. Therefore, further investigation is necessary to evaluate the mechanisms that generated and sustained the Pebas system.

  1. To Explain Copernicus: The Islamic Scientific and Religious Contexts

    NASA Astrophysics Data System (ADS)

    Ragep, F. Jamil

    No one seriously disputes the novelty of Copernicus's monumental decision to put the Earth in motion or its importance for the development of modern science. But that decision can appear quite different when viewed from the perspective of a modern scientist versus that of a contextualist historian. In his recent book To Explain the World, Prof. Weinberg places great store on what he calls aesthetic criteria for understanding Copernicus's choice. The historical record, however, is rather ambiguous on the matter, and if anything supports the view that Copernicus came to his aesthetic justifications (such as the beautiful ordering of the planets) after first reaching his heliocentric theory. So if not aesthetics, what did lead him to go against a two-millenium tradition that placed the Earth firmly in the center of the Cosmos? There are no doubt many factors; one of the most intriguing suggestions, well-argued by Noel Swerdlow, is that Copernicus was led to heliocentrism by his rather conservative desire to restore uniform, circular motion to the heavens and remove the irregularities of Ptolemaic astronomy. Swerdlow has also asserted that this has much to do with Islamic predecessors who were attempting to do the same thing, only within a geocentric framework. In this presentation, I will briefly summarize this Islamic scientific context and then explore the religious beliefs that led not only to the questioning of Ptolemaic scientific authority, including his alleged lack of observational diligence, but also ancient philosophical authority, the latter opening up possibilities for alternative cosmologies, at least one of which included the Earth's motion. Finally, evidence will be presented that connects these Islamic contexts with Copernicus's theories and justifications.

  2. Second-Chance Signal Transduction Explains Cooperative Flagellar Switching

    PubMed Central

    Zot, Henry G.; Hasbun, Javier E.; Van Minh, Nguyen

    2012-01-01

    The reversal of flagellar motion (switching) results from the interaction between a switch complex of the flagellar rotor and a torque-generating stationary unit, or stator (motor unit). To explain the steeply cooperative ligand-induced switching, present models propose allosteric interactions between subunits of the rotor, but do not address the possibility of a reaction that stimulates a bidirectional motor unit to reverse direction of torque. During flagellar motion, the binding of a ligand-bound switch complex at the dwell site could excite a motor unit. The probability that another switch complex of the rotor, moving according to steady-state rotation, will reach the same dwell site before that motor unit returns to ground state will be determined by the independent decay rate of the excited-state motor unit. Here, we derive an analytical expression for the energy coupling between a switch complex and a motor unit of the stator complex of a flagellum, and demonstrate that this model accounts for the cooperative switching response without the need for allosteric interactions. The analytical result can be reproduced by simulation when (1) the motion of the rotor delivers a subsequent ligand-bound switch to the excited motor unit, thereby providing the excited motor unit with a second chance to remain excited, and (2) the outputs from multiple independent motor units are constrained to a single all-or-none event. In this proposed model, a motor unit and switch complex represent the components of a mathematically defined signal transduction mechanism in which energy coupling is driven by steady-state and is regulated by stochastic ligand binding. Mathematical derivation of the model shows the analytical function to be a general form of the Hill equation (Hill AV (1910) The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves. J Physiol 40: iv–vii). PMID:22844429

  3. Is Titan's shape explained by its meteorology and carbon cycle?

    NASA Astrophysics Data System (ADS)

    Choukroun, M.; Sotin, C.

    2012-04-01

    Titan, Saturn's largest satellite, is unique in the Solar System: it is the only satellite bearing a dense atmosphere and it is the only place besides Earth with stable liquid bodies at its surface. In addition complex organics are produced in its atmosphere by the photolysis of methane, the second most abundant atmospheric molecule that irreversibly produces ethane and other more complex carbon bearing molecules. The Cassini/Huygens mission has revealed that the difference between its equatorial and polar radii is several hundred meters larger than that expected from its spin rate, and that it is in hydrostatic equilibrium. Global circulation models predict a large meridional circulation with upwelling at the summer hemisphere and downwelling at the winter pole where ethane can condense and fall at the surface. Lakes and Mare have been observed at the poles only (Stofan et al., Nature, 2007). Ethane has been spectroscopically identified in one of the lakes (Brown et al., Nature, 2008). The present study investigates the subsidence associated with ethane rain at the poles. As suggested by laboratory experiments, ethane flows very easily in a porous crust made of either pure water ice or methane clathrates. Loading of the lithosphere by liquid hydrocarbons induces a tendency of the polar terrains to subside relative to the lower latitudes terrains. In addition, laboratory experiments suggest that ethane substitutes to methane in a methane clathrate crust. The present study estimates the kinetics of this transformation. It suggests that such a transformation would occur on timescales much smaller than geological timescales. To explain a value of 270 m of the subsidence as determined by the radar instrument onboard the Cassini spacecraft (Zebker et al., Science, 2009), our study predicts that the percolation of ethane liquid in the polar crust should have operated during the last 300 - 1,200 Myr. This number is in agreement with the isotopic age of the atmospheric

  4. Parsimonious snow model explains reindeer population dynamics and ranging behavior

    NASA Astrophysics Data System (ADS)

    Kohler, J.; Aanes, R.; Hansen, B. B.; Loe, L.; Severinsen, T.; Stien, A.

    2008-12-01

    Winter snow is a key factor affecting polar ecosystems. One example is the strong negative correlation of winter precipitation with fluctuations in population in some high-arctic animal populations. Ice layers within and at the base of the snowpack have particularly deleterious effects on such populations. Svalbard reindeer have small home ranges and are vulnerable to local "locked pasture" events due to ground-ice formation. When pastures are locked, reindeer are faced with the decision of staying, living off a diminishing fat store, or trying to escape beyond the unknown spatial borders of the ice. Both strategies may inhibit reproduction and increase mortality, leading to population declines. Here we assess the impact of winter snow and ice on the population dynamics of an isolated herd of Svalbard reindeer near Ny-Ålesund, monitored annually since 1978, with a retrospective analysis of the winter snowpack. Because there are no long-term observational records of snow or snow properties, such as ice layers, we must recourse to snowpack modeling. A parsimonious model of snow and ground-ice thickness is driven with daily temperature and precipitation data collected at a nearby weather station. The model uses the degree-day concept and has three adjustable parameters which are tuned to correlate model snow and ground-ice thicknesses to the limited observations available: April snow accumulation measurements on two local glaciers, and a limited number of ground-ice observations made in recent years. Parameter values used are comparable to those reported elsewhere. We find that modeled mean winter ground-ice thickness explains a significant percentage of the observed variance in reindeer population growth rate. Adding other explanatory parameters, such as modeled mean winter snowpack thickness or previous years' population size does not significanly improve the relation. Furthermore, positioning data from a small subset of reindeer show that model icing events are

  5. Nanoscale Structure Of Organic Matter Explain Its Recalcitrance To Degradation

    NASA Astrophysics Data System (ADS)

    Spagnol, M.; Salati, S.; Papa, G.; Tambone, F.; Adani, F.

    2009-04-01

    Recalcitrance can be defined as the natural resistance of organic matter (OM) to microbial and enzymatic deconstruction (Himmel et al., 2007). The nature of OM recalcitrance remained not completely understood and more studies need above all to elucidate the role of the chemical topography of the OM at nanometer scale. Hydrolytic enzymes responsible of OM degradation have a molecular weight of 20-25 kD, corresponding to a size of about 4 nm, hardly penetrate into micropores (i.e. the pore having a diameter < 2 nm) and small mesopores (i.e. pores having a diameter 2 < 50 nm) of OM structures, so that their activities are confined only to a portion of the total surface (Zimmerman et al., 2004; Chesson, 1997; Adani et al., 2006). As consequence of that the characterization of the organic matter at nano-scale became interesting in view to explain OM recalcitrance. The aim of this work was to asses the effect of the nano-scale structure of OM versus its recalcitrance. The evolution of organic matter of organic matrices was studied in two systems: plant residue-soil system and simulated landfill system. Plant residues were incubated in soil for one year and recalcitrant fraction, i.e. humic acid, was isolated and studied. Laboratory simulated landfill considered organic fraction of municipal solid waste sampled at different stages of evolution from a full scale plant and incubated under anaerobic condition for one year. In addition the nano-scale structure of fossilized OM (leonardite, chair coal and graphite) was detected as used as model of recalcitrant OM. Nano-scale structures were detected by using meso and microporosity detection. In particular microporosity was determined by adsorption method using CO2 at 273 K and Non Local Density Functional Theory (NLDFT) method was applied to measure the CO2 adsorption isotherms. On the other hand mesoporosity was detected by using N2 adsorption method at 77 K. The BET (Brunauer-Emmett-Teller) equation and the BJH (Barret

  6. Thai visitors’ expectations and experiences of explainer interaction within a science museum context

    PubMed Central

    Chen, Ganigar; Sonchaeng, Pichai; Wilkinson, Clare; Willey, Neil; Bultitude, Karen

    2015-01-01

    In Western literature, there is evidence that museum explainers offer significant potential for enhancing visitors’ learning through influencing their knowledge, content, action, behaviour and attitudes. However, little research has focused on the role of explainers in other cultural contexts. This study explored interactions between visitors and museum explainers within the setting of Thailand. Two questionnaires were distributed to 600 visitors and 41 museum explainers. The results demonstrated both potential similarities and differences with Western contexts. Explainers appeared to prefer didactic approaches, focussing on factual knowledge rather than encouraging deep learning. Two-way communication, however, appeared to be enhanced by the use of a ‘pseudo-sibling relationship’ by explainers. Traditional Thai social reserve was reduced through such approaches, with visitors taking on active learning roles. These findings have implications for training museum explainers in non-Western cultures, as well as museum communication practice more generally. PMID:24751689

  7. Explaining happiness.

    PubMed

    Easterlin, Richard A

    2003-09-16

    What do social survey data tell us about the determinants of happiness? First, that the psychologists' setpoint model is questionable. Life events in the nonpecuniary domain, such as marriage, divorce, and serious disability, have a lasting effect on happiness, and do not simply deflect the average person temporarily above or below a setpoint given by genetics and personality. Second, mainstream economists' inference that in the pecuniary domain "more is better," based on revealed preference theory, is problematic. An increase in income, and thus in the goods at one's disposal, does not bring with it a lasting increase in happiness because of the negative effect on utility of hedonic adaptation and social comparison. A better theory of happiness builds on the evidence that adaptation and social comparison affect utility less in the nonpecuniary than pecuniary domains. Because individuals fail to anticipate the extent to which adaptation and social comparison undermine expected utility in the pecuniary domain, they allocate an excessive amount of time to pecuniary goals, and shortchange nonpecuniary ends such as family life and health, reducing their happiness. There is need to devise policies that will yield better-informed individual preferences, and thereby increase individual and societal well-being. PMID:12958207

  8. Religion explained

    NASA Astrophysics Data System (ADS)

    Crease, Robert P.

    2009-08-01

    When Physics World carried out a readers' survey to mark its 20th anniversary in October 2008, in the main the editors took a light-hearted approach. They asked readers to answer nine multiple-choice questions on matters such as who inspired them to do physics, whether they mind being unpopular at parties, and what was the top physics discovery of the previous 20 years. A summary of the results appeared last year on the physicsworld.com blog (22 December 2008).

  9. Speaker Credibility in Persuasive Business Communication: A Model which Explains Gender Differences.

    ERIC Educational Resources Information Center

    Kenton, Sherron B.

    1989-01-01

    Expands Carl Hovland's Yale Communication Model to include dimensions which explain gender differences in speaker credibility in persuasive business communication, with support from the gender literature. (MS)

  10. Development and Assessment of Self-explaining Skills in College Chemistry Instruction

    NASA Astrophysics Data System (ADS)

    Villalta-Cerdas, Adrian

    The prevalent trend in chemistry instruction relies on what has been described as the classroom game. In this model, students take a passive role and the instructor does all the explaining (thinking), and learning is trivialized to knowing the correct answers (memorizing) and being able to produce them when prompted (regurgitating). The generation of explanations is central to scientific and technological development. In the process of figuring out explanations, the generation of inferences relies on the application of skills associated with scientific behaviors (e.g., analytical reasoning and critical thinking). The process of explanation generation causes a deeper analysis and revision of the scientific models, thus impacting the conceptual understanding of such models. Although the process of generating authentic explanations is closer to the experience of doing science, this process is seldom replicated in science instruction. Self-explaining refers to the generation of inferences about causal connections between objects and events. In science, this may be summarized as making sense of how and why actual or hypothetical phenomena take place. Research findings in educational psychology show that implementing activities that elicit self-explaining improves learning in general and specifically enhances authentic learning in the sciences. Research also suggests that self-explaining influences many aspects of cognition, including acquisition of problem-solving skills and conceptual understanding. Although the evidence that links self-explaining and learning is substantial, most of the research has been conducted in experimental settings. The purpose of this work was to advance knowledge in this area by investigating the effect of different self-explaining tasks on self-explaining behavior and the effect of engaging in different levels of self-explaining on learning chemistry concepts. Unlike most of the research in the field, this work did not focus on advancing

  11. Development and Assessment of Self-explaining Skills in College Chemistry Instruction

    NASA Astrophysics Data System (ADS)

    Villalta-Cerdas, Adrian

    The prevalent trend in chemistry instruction relies on what has been described as the classroom game. In this model, students take a passive role and the instructor does all the explaining (thinking), and learning is trivialized to knowing the correct answers (memorizing) and being able to produce them when prompted (regurgitating). The generation of explanations is central to scientific and technological development. In the process of figuring out explanations, the generation of inferences relies on the application of skills associated with scientific behaviors (e.g., analytical reasoning and critical thinking). The process of explanation generation causes a deeper analysis and revision of the scientific models, thus impacting the conceptual understanding of such models. Although the process of generating authentic explanations is closer to the experience of doing science, this process is seldom replicated in science instruction. Self-explaining refers to the generation of inferences about causal connections between objects and events. In science, this may be summarized as making sense of how and why actual or hypothetical phenomena take place. Research findings in educational psychology show that implementing activities that elicit self-explaining improves learning in general and specifically enhances authentic learning in the sciences. Research also suggests that self-explaining influences many aspects of cognition, including acquisition of problem-solving skills and conceptual understanding. Although the evidence that links self-explaining and learning is substantial, most of the research has been conducted in experimental settings. The purpose of this work was to advance knowledge in this area by investigating the effect of different self-explaining tasks on self-explaining behavior and the effect of engaging in different levels of self-explaining on learning chemistry concepts. Unlike most of the research in the field, this work did not focus on advancing

  12. Preschoolers Selectively Infer History When Explaining Outcomes: Evidence from Explanations of Ownership, Liking, and Use

    ERIC Educational Resources Information Center

    Nancekivell, Shaylene E.; Friedman, Ori

    2014-01-01

    Two experiments provide evidence that preschoolers selectively infer history when explaining outcomes and infer past events that could have plausibly happened. In Experiment 1, thirty-three 3-year-olds and thirty-six 4-year-olds explained why a character owns or likes certain objects. In Experiment 2, thirty-four 4-year-olds and thirty-six…

  13. Content-Free Computer Supports for Self-Explaining: Modifiable Typing Interface and Prompting

    ERIC Educational Resources Information Center

    Chou, Chih-Yueh; Liang, Hung-Ta

    2009-01-01

    Self-explaining, which asks students to generate explanations while reading a text, is a self-constructive activity and is helpful for students' learning. Studies have revealed that prompts by a human tutor promote students' self-explanations. However, most studies on self-explaining focus on spoken self-explanations. This study investigates the…

  14. When The Right Answer is a Question. Students as Explainers at the Exploratorium.

    ERIC Educational Resources Information Center

    Klages, Ellen; And Others

    Students who work at the Exploratorium in San Francisco, California learn about science by explaining to the visitors from all over the world how the museum's exhibits work. The students are teen-agers who also come from all over the world to be "Explainers" for the Exploratorium. They go through a training period to learn the basics of how the…

  15. The Role of Perspective Taking in How Children Connect Reference Frames When Explaining Astronomical Phenomena

    ERIC Educational Resources Information Center

    Plummer, Julia D.; Bower, Corinne A.; Liben, Lynn S.

    2016-01-01

    This study investigates the role of perspective-taking skills in how children explain spatially complex astronomical phenomena. Explaining many astronomical phenomena, especially those studied in elementary and middle school, requires shifting between an Earth-based description of the phenomena and a space-based reference frame. We studied 7- to…

  16. Explaining Local Authority Choices on Public Hospital Provision in the 1930s: A Public Policy Hypothesis

    PubMed Central

    Neville, Julia

    2012-01-01

    This article summarises the findings of recent work on local authority public hospital services in England and Wales in the inter-war years and identifies the lack of a robust hypothesis to explain the variations found, particularly one that would explain the actions of county councils as well as county boroughs. Using public policy techniques on a group of local authorities in the far South West it proposes that variations can be explained by an understanding of the deep core beliefs of councillors, their previous experience of ‘commissioner’ and ‘provider’ roles, and the availability or otherwise of a dedicated policy entrepreneur to promote change. PMID:23752983

  17. Explaining local authority choices on public hospital provision in the 1930s: a public policy hypothesis.

    PubMed

    Neville, Julia

    2012-01-01

    This article summarises the findings of recent work on local authority public hospital services in England and Wales in the inter-war years and identifies the lack of a robust hypothesis to explain the variations found, particularly one that would explain the actions of county councils as well as county boroughs. Using public policy techniques on a group of local authorities in the far South West it proposes that variations can be explained by an understanding of the deep core beliefs of councillors, their previous experience of 'commissioner' and 'provider' roles, and the availability or otherwise of a dedicated policy entrepreneur to promote change. PMID:23752983

  18. Artist: Ken Hodges Composite image explaining Objective and Motivation for Galileo Probe Heat Loads:

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Artist: Ken Hodges Composite image explaining Objective and Motivation for Galileo Probe Heat Loads: Galileo Probe descending into Jupiters Atmosphere shows heat shield separation with parachute deployed. (Ref. JPL P-19180)

  19. A neutral theory with environmental stochasticity explains static and dynamic properties of ecological communities.

    PubMed

    Kalyuzhny, Michael; Kadmon, Ronen; Shnerb, Nadav M

    2015-06-01

    Understanding the forces shaping ecological communities is crucial to basic science and conservation. Neutral theory has made considerable progress in explaining static properties of communities, like species abundance distributions (SADs), with a simple and generic model, but was criticised for making unrealistic predictions of fundamental dynamic patterns and for being sensitive to interspecific differences in fitness. Here, we show that a generalised neutral theory incorporating environmental stochasticity may resolve these limitations. We apply the theory to real data (the tropical forest of Barro Colorado Island) and demonstrate that it much better explains the properties of short-term population fluctuations and the decay of compositional similarity with time, while retaining the ability to explain SADs. Furthermore, the predictions are considerably more robust to interspecific fitness differences. Our results suggest that this integration of niches and stochasticity may serve as a minimalistic framework explaining fundamental static and dynamic characteristics of ecological communities. PMID:25903067

  20. An Historical Analysis to Explain the Evolution of Advertising Agency Services

    ERIC Educational Resources Information Center

    Miracle, Gordon E.

    1977-01-01

    Traces the evolution of services that advertising agencies perform and identifies major factors that are responsible for this evolution. The purpose is to explain or predict changes and to demonstrate "systems thinking." (MB)

  1. Explainers' development of science-learner identities through participation in a community of practice

    NASA Astrophysics Data System (ADS)

    Richardson, Anne E.

    The urgent environmental issues of today require science-literate adults to engage in business and political decisions to create solutions. Despite the need, few adults have the knowledge and skills of science literacy. This doctoral dissertation is an analytical case study examining the science-learner identity development of Exploratorium Field Trip Explainers. Located in San Francisco, CA, the Exploratorium is a museum of science, art, and human perception dedicated to nurturing curiosity and exploration. Data collected included semi-structured interviews with sixteen former Field Trip Explainers, participant observation of the current Field Trip Explainer Program, and review of relevant documentation. Data analysis employed constant comparative analysis, guided by the communities of practice theoretical framework (Wenger, 1998) and the National Research Council's (2009) Six Strands of Science Learning. Findings of this research indicate that Exploratorium Field Trip Explainers participate in a community of practice made up of a diverse group of people that values curiosity and openness to multiple ways of learning. Many participants entered the Field Trip Explainer Program with an understanding of science learning as a rigid process reserved for a select group of people; through participation in the Field Trip Explainer community of practice, participants developed an understanding of science learning as accessible and a part of everyday life. The findings of this case study have implications for research, theory, and practice in informal adult science learning, access of non-dominant groups to science learning, and adult workplace learning in communities of practice.

  2. LIFE HISTORY. Age-related mortality explains life history strategies of tropical and temperate songbirds.

    PubMed

    Martin, Thomas E

    2015-08-28

    Life history theory attempts to explain why species differ in offspring number and quality, growth rate, and parental effort. I show that unappreciated interactions of these traits in response to age-related mortality risk challenge traditional perspectives and explain life history evolution in songbirds. Counter to a long-standing paradigm, tropical songbirds grow at similar overall rates to temperate species but grow wings relatively faster. These growth tactics are favored by predation risk, both in and after leaving the nest, and are facilitated by greater provisioning of individual offspring by parents. Increased provisioning of individual offspring depends on partitioning effort among fewer young because of constraints on effort from adult and nest mortality. These growth and provisioning responses to mortality risk finally explain the conundrum of small clutch sizes of tropical birds. PMID:26315435

  3. Too early to explain all experimental data with a single model.

    PubMed

    Gielen, C C

    2000-01-01

    The target article by Prilutsky gives an excellent overview of the predictions of the Crowninshield and Brand model and about the relevant literature about muscle coordination. However, we do not agree with the claim that the Crowninshield and Brand model can explain the coordination between one-joint and two-joint muscles. In this commentary we will make three claims: (a) The Crowninshield and Brand model cannot explain all aspects of muscle coordination, (b) there is good experimental evidence that different constraints and models may be necessary to explain muscle coordination in different motor tasks, and (c) the reason for the lack of quantitative fits between predictions about muscle force and experimental data is that it is hard to measure muscle force in man. As a compromise one has to rely on EMG activity as a measure of muscle force. Because of the complex relationship between EMG and muscle force, a quantitative test of models is difficult. PMID:10675810

  4. Time delay and noise explaining the behaviour of the cell growth in fermentation process

    SciTech Connect

    Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md

    2015-02-03

    This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.

  5. Time delay and noise explaining the behaviour of the cell growth in fermentation process

    NASA Astrophysics Data System (ADS)

    Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md

    2015-02-01

    This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.

  6. Can theories of visual representation help to explain asymmetries in amygdala function?

    PubMed Central

    McMenamin, Brenton W.; Marsolek, Chad J.

    2012-01-01

    Emotional processing differs between the left and right hemispheres of the brain, and functional differences have been reported more specifically between the left amygdala and right amygdala, subcortical structures heavily implicated in emotional processing. However, the empirical pattern of amygdalar asymmetries is inconsistent with extant theories of emotional asymmetries. Here we review this discrepancy, and we hypothesize that hemispheric differences in visual object processing help to explain the previously reported functional differences between the left and right amygdalae. The implication that perceptual factors play a large role in determining amygdalar asymmetries may help to explain amygdalar dysfunction in the development and maintenance of post-traumatic stress disorder. PMID:23239022

  7. STS-45 MS and PLC Sullivan explains camera usage on OV-104's aft flight deck

    NASA Technical Reports Server (NTRS)

    1992-01-01

    STS-45 Mission Specialist (MS) and Payload Commander (PLC) Kathryn D. Sullivan, holding communications kit assembly unit and 70mm HASSELBLAD camera, explains camera usage and Earth observation procedures during a television downlink to the ground. Sullivan is on the aft flight deck of Atlantis, Orbiter Vehicle (OV) 104. Behind Sullivan are the onorbit station control panels with the payload station control panels at her left. The STS-45 crew put together a brief video 'tour' program to explain some of their inflight operations.

  8. Explaining Cross-Country Differences in Attitudes towards Immigration in the EU-15

    ERIC Educational Resources Information Center

    Malchow-Moller, Nikolaj; Munch, Jakob Roland; Schroll, Sanne; Skaksen, Jan Rose

    2009-01-01

    In this paper, we use data from the first two rounds of the European Social Survey to analyze the extent to which differences in average attitudes towards immigration across the EU-15 countries may be explained by differences in socioeconomic characteristics and individually perceived consequences of immigration, using an extension of a…

  9. Toward Explaining the Transformative Power of Talk about, around, and for Writing

    ERIC Educational Resources Information Center

    Godbee, Beth

    2012-01-01

    This article provides an initial approach for capturing moments of talk about, around, and for writing to explain why writing groups and writing conferences are so often considered "transformative" for the people involved. After describing the widespread and yet disparate transformations so often attributed to collaborative writing talk, I…

  10. Can Intertrial Effects of Features and Dimensions Be Explained by a Single Theory?

    ERIC Educational Resources Information Center

    Becker, Stefanie I.

    2008-01-01

    This study investigated feature- and dimension-based intertrial effects in visual search for a pop-out target. The 2 prominent theories explaining intertrial effects, priming of pop-out and dimension weighting, both assume that repeating the target from the previous trial facilitates attention shifts to the target, whereas changing the target…

  11. Explaining Helping Behavior in a Cooperative Learning Classroom Setting Using Attribution Theory

    ERIC Educational Resources Information Center

    Ahles, Paula M.; Contento, Jann M.

    2006-01-01

    This recently completed study examined whether attribution theory can explain helping behavior in an interdependent classroom environment that utilized a cooperative-learning model. The study focused on student participants enrolled in 6 community college communication classes taught by the same instructor. Three levels of cooperative-learning…

  12. Explaining the Ordinary Magic of Stable African Multilingualism in the Vaal Triangle Region in South Africa

    ERIC Educational Resources Information Center

    Coetzee-Van Rooy, Susan

    2014-01-01

    The academic and public debates about language maintenance and language shift in the post-1994 South Africa distract attention from the more productive and important endeavour of explaining the nature of the multilingualism observed among users of African languages in urban contexts. An explanation for this phenomenon is offered here, based on…

  13. Colleges Have Done a Bad Job of Explaining Affirmative Action to Students, Critics Say.

    ERIC Educational Resources Information Center

    Collison, Michele N-K

    1992-01-01

    Admissions offices of colleges trying to increase undergraduate student diversity are being criticized for failing to explain their affirmative action policies to prospective students and their parents, resulting in a backlash against affirmative action as white students fear reverse discrimination. (DB)

  14. Explaining Metaphors in High-Functioning Autism Spectrum Disorder Children: A Brief Report

    ERIC Educational Resources Information Center

    Melogno, Sergio; D'Ardia, Caterina; Pinto, Maria Antonietta; Levi, Gabriel

    2012-01-01

    This study investigated metaphor comprehension in a group of 24 Italian high-functioning ASD children (mean age: 8.5 y.). Children were administered a test that was composed of "sensorial metaphors", which are understood by normally developing preschoolers, that the children had to verbally explain. Two normally developing control groups, which…

  15. Can Spectro-Temporal Complexity Explain the Autistic Pattern of Performance on Auditory Tasks?

    ERIC Educational Resources Information Center

    Samson, Fabienne; Mottron, Laurent; Jemel, Boutheina; Belin, Pascal; Ciocca, Valter

    2006-01-01

    To test the hypothesis that level of neural complexity explain the relative level of performance and brain activity in autistic individuals, available behavioural, ERP and imaging findings related to the perception of increasingly complex auditory material under various processing tasks in autism were reviewed. Tasks involving simple material…

  16. Explaining and Forecasting Job Satisfaction: The Contribution of Occupational Profiling. Working Paper.

    ERIC Educational Resources Information Center

    Rose, Michael

    The contribution of occupational profiling to explaining and forecasting job satisfaction were analyzed by using data on job satisfaction for 33,249 workers from waves 1-7 of the British Household Panel Survey. Overall job satisfaction gradients were defined for major and minor groups of occupations in the United Kingdom's Standard Occupational…

  17. Why Teach Abroad: Two American Teachers Explain Their Motivations and Experiences Teaching in Bulgaria

    ERIC Educational Resources Information Center

    Potash, Betsy; Potash, Brett

    2011-01-01

    A Fulbright poster on the bulletin board, a Search Associates flier in the mailbox, a rumor of something different--everyone has heard about teaching abroad. But is it worth filling out all that paperwork, installing Skype on the family's computers, and learning a new language? In this article, two American teachers explain their motivations and…

  18. Causal Discourse and the Teaching of History. How Do Teachers Explain Historical Causality?

    ERIC Educational Resources Information Center

    Montanero, Manuel; Lucero, Manuel

    2011-01-01

    In this paper we aim to describe how secondary school teachers explain multicausal historical events. To that end, we recorded and analyzed seven classes on "The discovery and colonization of America". The results show that secondary school teachers do not simply deal with history as a catalog of actions, characters and dates. On the contrary,…

  19. Beyond Socioeconomics: Explaining Ethnic Group Differences in Parenting through Cultural and Immigration Processes

    ERIC Educational Resources Information Center

    Chao, Ruth; Kanatsu, Akira

    2008-01-01

    This study examined both socioeconomic and cultural factors in explaining ethnic differences in monitoring, behavioral control, and warmth--part of a series of coordinated studies presented in this special issue. Socioeconomic variables included mother's and father's educational levels, employment status, home ownership, number of siblings in the…

  20. Explaining Career Decision-Making Self-Efficacy: Personality, Cognitions, and Cultural Mistrust

    ERIC Educational Resources Information Center

    Bullock-Yowell, Emily; Andrews, Lindsay; Buzzetta, Mary E.

    2011-01-01

    The authors explore the hypothesis that career decision-making self-efficacy could be affected by negative career thoughts, Big Five personality factors, and cultural mistrust in a sample of African American and Caucasian college students. Findings demonstrated that negative career thinking, openness, and conscientiousness explained a significant…

  1. The Role of Family Obligations and School Adjustment in Explaining the Immigrant Paradox

    ERIC Educational Resources Information Center

    van Geel, Mitch; Vedder, Paul

    2011-01-01

    This study examined the role of family obligations and school adjustment in explaining immigrant adolescents' adaptation. Despite a relatively low socio-economic status, immigrant adolescents have been found to have a pattern of adaptation superior to that of national adolescents. Immigrant adolescents' strong sense of family obligations and…

  2. Explaining the Effectiveness of the Contrast Culture Method for Managing Interpersonal Interactions across Cultures

    ERIC Educational Resources Information Center

    Hiratsuka, Hiroyoshi; Suzuki, Hanako; Pusina, Alexis

    2016-01-01

    One of the current challenges in the field of intercultural education comes from the limited availability of training efficacy studies. The present study focused on explaining the effectiveness of the Contrast Culture Method (CCM) as an intercultural education method for managing interpersonal interactions across cultures between graduate…

  3. Explaining fruit and vegetable consumption: the theory of planned behaviour and misconception of personal intake levels.

    PubMed

    Bogers, R P; Brug, J; van Assema, P; Dagnelie, P C

    2004-04-01

    The influence of individuals' misconceptions in assessing fruit and vegetable consumption on the ability of the theory of planned behaviour to explain variance in the consumption of these foods was studied. Dutch women (mean age 41, n=159) completed a questionnaire assessing the theory's constructs with regard to the daily consumption of at least two pieces of fruit and 200 gram of vegetables. Consumption was assessed using a self-rated measure and more objectively with a food-frequency questionnaire. Both measures were combined to classify participants according to the accuracy of their self-assessed intake levels ('realists' vs. 'overestimators'). The model explained variation in objective fruit and vegetable intake much better among realists (R2 = 45% for fruits and 39% for vegetables) than among overestimators (R2 = 18% and 5%, respectively). Perceived behavioural control was the strongest predictor of intentions and behaviour. When plasma vitamin C and carotenoid concentrations were used as objective indicators for fruit and vegetable intake, the explanatory value of the model was lower, but again more variance was explained among realists than among overestimators. We conclude that awareness of personal behaviour should be taken into account when applying the theory of planned behaviour to explain dietary behaviours as well as to design health education interventions. PMID:15010180

  4. Explaining the Gap in Charter and Traditional Public School Teacher Turnover Rates

    ERIC Educational Resources Information Center

    Stuit, David A.; Smith, Thomas M.

    2012-01-01

    This study uses national survey data to examine why charter school teachers are more likely to turnover than their traditional public school counterparts. We test whether the turnover gap is explained by different distributions of factors that are empirically and theoretically linked to turnover risk. We find that the turnover rate of charter…

  5. How do Turkish High School Graduates Use the Wave Theory of Light to Explain Optics Phenomena?

    ERIC Educational Resources Information Center

    Sengoren, S. K.

    2010-01-01

    This research was intended to investigate whether Turkish students who had graduated from high school used the wave theory of light properly in explaining optical phenomena. The survey method was used in this research. The data, which were collected from 175 first year university students in Turkey, were analysed quantitatively and qualitatively.…

  6. Run-D.M.C.: A Mnemonic Aid for Explaining Mass Transfer in Electrochemical Systems

    ERIC Educational Resources Information Center

    Miles, Deon T.

    2013-01-01

    Electrochemistry is a significant area of analytical chemistry encompassing electrical measurements of chemical systems. The applications associated with electrochemistry appear in many aspects of everyday life: explaining how batteries work, how the human nervous system functions, and how metal corrosion occurs. The most common electrochemical…

  7. Semantic Language as a Mechanism Explaining the Association between ADHD Symptoms and Reading and Mathematics Underachievement

    ERIC Educational Resources Information Center

    Gremillion, Monica L.; Martel, Michelle M.

    2012-01-01

    ADHD is associated with academic underachievement, but it remains unclear what mechanism accounts for this association. Semantic language is an underexplored mechanism that provides a developmental explanation for this association. The present study will examine whether semantic language deficits explain the association between ADHD and reading…

  8. Teachers' Use of Curriculum to Support Students in Writing Scientific Arguments to Explain Phenomena

    ERIC Educational Resources Information Center

    McNeill, Katherine L.

    2009-01-01

    The role of the teacher is essential for students' successful engagement in scientific inquiry practices. This study focuses on teachers' use of an 8-week chemistry curriculum that explicitly supports students in one particular inquiry practice, the construction of scientific arguments to explain phenomena in which students justify their claims…

  9. Disentangling vegetation diversity from climate-energy and habitat heterogeneity for explaining animal geographic patterns.

    PubMed

    Jiménez-Alfaro, Borja; Chytrý, Milan; Mucina, Ladislav; Grace, James B; Rejmánek, Marcel

    2016-03-01

    Broad-scale animal diversity patterns have been traditionally explained by hypotheses focused on climate-energy and habitat heterogeneity, without considering the direct influence of vegetation structure and composition. However, integrating these factors when considering plant-animal correlates still poses a major challenge because plant communities are controlled by abiotic factors that may, at the same time, influence animal distributions. By testing whether the number and variation of plant community types in Europe explain country-level diversity in six animal groups, we propose a conceptual framework in which vegetation diversity represents a bridge between abiotic factors and animal diversity. We show that vegetation diversity explains variation in animal richness not accounted for by altitudinal range or potential evapotranspiration, being the best predictor for butterflies, beetles, and amphibians. Moreover, the dissimilarity of plant community types explains the highest proportion of variation in animal assemblages across the studied regions, an effect that outperforms the effect of climate and their shared contribution with pure spatial variation. Our results at the country level suggest that vegetation diversity, as estimated from broad-scale classifications of plant communities, may contribute to our understanding of animal richness and may be disentangled, at least to a degree, from climate-energy and abiotic habitat heterogeneity. PMID:26900451

  10. Explaining pathological changes in axonal excitability through dynamical analysis of conductance-based models

    NASA Astrophysics Data System (ADS)

    Coggan, Jay S.; Ocker, Gabriel K.; Sejnowski, Terrence J.; Prescott, Steven A.

    2011-10-01

    Neurons rely on action potentials, or spikes, to relay information. Pathological changes in spike generation likely contribute to certain enigmatic features of neurological disease, like paroxysmal attacks of pain and muscle spasm. Paroxysmal symptoms are characterized by abrupt onset and short duration, and are associated with abnormal spiking although the exact pathophysiology remains unclear. To help decipher the biophysical basis for 'paroxysmal' spiking, we replicated afterdischarge (i.e. continued spiking after a brief stimulus) in a minimal conductance-based axon model. We then applied nonlinear dynamical analysis to explain the dynamical basis for initiation and termination of afterdischarge. A perturbation could abruptly switch the system between two (quasi-)stable attractor states: rest and repetitive spiking. This bistability was a consequence of slow positive feedback mediated by persistent inward current. Initiation of afterdischarge was explained by activation of the persistent inward current forcing the system to cross a saddle point that separates the basins of attraction associated with each attractor. Termination of afterdischarge was explained by the attractor associated with repetitive spiking being destroyed. This occurred when ultra-slow negative feedback, such as intracellular sodium accumulation, caused the saddle point and stable limit cycle to collide; in that regard, the active attractor is not truly stable when the slowest dynamics are taken into account. The model also explains other features of paroxysmal symptoms, including temporal summation and refractoriness.

  11. Explaining Voter Behavior toward Local School Expenditures: The Impact of Public Attitudes.

    ERIC Educational Resources Information Center

    Brokaw, Alan J.; And Others

    1990-01-01

    Two logic models are presented to explain voter turnout and voter choice for a referendum considering a millage increase to finance a new high school building. The models incorporate attitudinal, demographic, and economic variables. This approach suggests that interested parties (like school officials) can influence referendum outcomes. Includes…

  12. Explaining Student Success and Failure in a Distance Teaching System: A Multi-variate Approach.

    ERIC Educational Resources Information Center

    Woodley, Alan

    A multivariate model to explain student success and failure at the Open University of the United Kingdom is outlined. The model is based on the results of an evaluation study that explored the suitability of this teaching system for young people under 21 years old. Twenty-three characteristics were designated as social and psychological problems,…

  13. What explains the rural-urban gap in infant mortality: household or community characteristics?

    PubMed

    Van de Poel, Ellen; O'Donnell, Owen; Van Doorslaer, Eddy

    2009-11-01

    The rural-urban gap in infant mortality rates is explained by using a new decomposition method that permits identification of the contribution of unobserved heterogeneity at the household and the community level. Using Demographic and Health Survey data for six Francophone countries in Central and West sub-Saharan Africa, we find that differences in the distributions of factors that determine mortality--not differences in their effects--explain almost the entire gap. Higher infant mortality rates in rural areas mainly derive from the rural disadvantage in household characteristics, both observed and unobserved, which explain two-thirds of the gap. Among the observed characteristics, environmental factors--a safe source of drinking water, electricity, and quality of housing materials--are the most important contributors. Community characteristics explain less than one-quarter of the gap, with about two-thirds of this coming from community unobserved heterogeneity and one-third from the existence of a health facility within the community. The effect of disadvantageous environmental conditions--such as limited electricity and water supply--derives both from a lack of community-level infrastructure and from the inability of some households to exploit it when available. Policy needs to operate at both the community and household levels to correct such deficiencies. PMID:20084831

  14. Explaining the Gender Gap in Help to Parents: The Importance of Employment

    ERIC Educational Resources Information Center

    Sarkisian, Natalia; Gerstel, Naomi

    2004-01-01

    Although it is well established that adult daughters spend more time giving assistance to their parents than do sons, the sources of this gender gap are not well understood. This paper asks: To what extent can this gap be explained by structural variation, especially the different rates of employment and kinds of jobs that women and men tend to…

  15. The Maldistribution Thesis of Poverty: How Much of Rural Southern Poverty Can It Explain?

    ERIC Educational Resources Information Center

    Thomas, George

    The Maldistribution Thesis (whether a maldistribution in skilled manpower, accumulated wealth, and their implied production of income, goods, and services is demonstrable and the extent to which the thesis explains poverty) is at least in part testable by the amount that redressing old imbalances contributes to the increased income, improved life…

  16. Explaining the Rise in Educational Gradients in Mortality. NBER Working Paper No. 15678

    ERIC Educational Resources Information Center

    Cutler, David M.; Lange, Fabian; Meara, Ellen; Richards, Seth; Ruhm, Christopher J.

    2010-01-01

    The long-standing inverse relationship between education and mortality strengthened substantially later in the 20th century. This paper examines the reasons for this increase. We show that behavioral risk factors are not of primary importance. Smoking has declined more for the better educated, but not enough to explain the trend. Obesity has risen…

  17. MA-9 ASTRONAUT GORDON COOPER EXPLAINS CAMERA TO BACKUP PILOT ALAN SHEPARD

    NASA Technical Reports Server (NTRS)

    1963-01-01

    Astronaut L. Gordon Cooper explains the 16MM handheld spacecraft camera to his back-up pilot Astronaut Alan Shepard. The camera designed by J. R. Hereford, McDonnell Aircraft Corp., will be used by Cooper during the MA-9 mission.

  18. The Role of Goal Orientations and Goal Structures in Explaining Classroom Social and Affective Characteristics

    ERIC Educational Resources Information Center

    Polychroni, Fotini; Hatzichristou, Chryse; Sideridis, Georgios

    2012-01-01

    Examining motivational variables may prove to be particularly fruitful towards our understanding of classroom processes, student behaviors and school outcomes. The present study examined the role of personal and contextual goals (goals and goal structures) towards explaining social relationships (peer, teacher-student and home-school). 1493 fifth…

  19. Explaining the Difference between PISA 2009 Reading Scores in Finland and Estonia

    ERIC Educational Resources Information Center

    Mikk, Jaan

    2015-01-01

    The aim of the study was to explain the difference between the Programme for International Student Assessment (PISA) 2009 reading results for Finland and Estonia using characteristics of teaching and learning, and characteristics of the overall development of these countries. PISA data were collected via a reading test and student questionnaires…

  20. The Positive Illusory Bias: Does It Explain Self-Evaluations in College Students with ADHD?

    ERIC Educational Resources Information Center

    Prevatt, Frances; Proctor, Briley; Best, Lori; Baker, Leigh; Van Walker, Jerry; Taylor, Nicki Wright

    2012-01-01

    Objective: To evaluate whether the positive illusory bias explains the self-evaluations of driving and work behaviors in college students with ADHD. Method: A total of 103 students with ADHD were compared to a sample of 94 students without ADHD. Both groups completed self-reports of their specific driving and work behaviors and then rated their…

  1. Metaphors Used by Some Engineering Academics in Australia for Understanding and Explaining Sustainability

    ERIC Educational Resources Information Center

    Carew, Anna L.; Mitchell, Cynthia A.

    2006-01-01

    Metaphors can be powerful teaching and learning tools which may help us to understand novel, complex or abstract concepts using familiar language and thought structures. Academics routinely use metaphors in their university teaching to explain new or difficult ideas to students. In this article the authors argue that tertiary teachers' metaphors…

  2. Funeral Benefits in Public Higher Education Institutions: How Do They Explain Employees' Perception of Equity?

    ERIC Educational Resources Information Center

    Komba, Aneth Anselmo

    2016-01-01

    The study examined the government and three campuses of a higher public education institution's funeral policies with a view to determining how these policies explain employees' equity perception. Three research questions guided the study: (1) what does the government's funeral policy say about the burial of government employees and their…

  3. Explaining the Increase in Publication Productivity among Academic Staff: A Generational Perspective

    ERIC Educational Resources Information Center

    Kyvik, Svein; Aksnes, Dag W.

    2015-01-01

    In Norwegian research universities, a large individual increase has taken place in scientific and scholarly publishing over the last 30 years. The purpose of this article is to explain the reasons for this growth in a generational perspective. We put forward six hypotheses that can be illuminated by cross-sectional data drawn from five surveys to…

  4. Changes in variance explained by top SNP windows over generations for three traits in broiler chicken

    PubMed Central

    Fragomeni, Breno de Oliveira; Misztal, Ignacy; Lourenco, Daniela Lino; Aguilar, Ignacio; Okimoto, Ronald; Muir, William M.

    2014-01-01

    The purpose of this study was to determine if the set of genomic regions inferred as accounting for the majority of genetic variation in quantitative traits remain stable over multiple generations of selection. The data set contained phenotypes for five generations of broiler chicken for body weight, breast meat, and leg score. The population consisted of 294,632 animals over five generations and also included genotypes of 41,036 single nucleotide polymorphism (SNP) for 4,866 animals, after quality control. The SNP effects were calculated by a GWAS type analysis using single step genomic BLUP approach for generations 1–3, 2–4, 3–5, and 1–5. Variances were calculated for windows of 20 SNP. The top ten windows for each trait that explained the largest fraction of the genetic variance across generations were examined. Across generations, the top 10 windows explained more than 0.5% but less than 1% of the total variance. Also, the pattern of the windows was not consistent across generations. The windows that explained the greatest variance changed greatly among the combinations of generations, with a few exceptions. In many cases, a window identified as top for one combination, explained less than 0.1% for the other combinations. We conclude that identification of top SNP windows for a population may have little predictive power for genetic selection in the following generations for the traits here evaluated. PMID:25324857

  5. Microwave-Mediated Synthesis of Lophine: Developing a Mechanism to Explain a Product

    ERIC Educational Resources Information Center

    Crouch, R. David; Howard, Jessica L.; Zile, Jennifer L.; Barker, Kathryn H.

    2006-01-01

    The microwave-mediated preparation of lophine (2,4,5-triphenylimidazole) is described. This experiment allows for an introduction to the emerging technology of microwave-assisted organic synthesis while providing an opportunity for students to employ the principles of carbonyl chemistry in devising a mechanism to explain the formation of the…

  6. No Place to Escape: Explaining the Cultural Revolution to American Students

    ERIC Educational Resources Information Center

    Jiang, Ji-li

    2012-01-01

    In this article the author reflects on her visits to American schools to talk about the experiences she describes in "Red Scarf Girl." In her book, she explains picture by picture, story after story how she and her family lived in darkness, how they were brainwashed, and about the concentration of power in China. She stresses that American kids…

  7. Learning in Virtual Worlds: Using Communities of Practice to Explain How People Learn from Play

    ERIC Educational Resources Information Center

    Oliver, Martin; Carr, Diane

    2009-01-01

    Although there is interest in the educational potential of online multiplayer games and virtual worlds, there is still little evidence to explain specifically what and how people learn from these environments. This paper addresses this issue by exploring the experiences of couples that play "World of Warcraft" together. Learning outcomes were…

  8. Understanding Middle School Students' Difficulties in Explaining Density Differences from a Language Perspective

    ERIC Educational Resources Information Center

    Seah, Lay Hoon; Clarke, David; Hart, Christina

    2015-01-01

    This study examines how a class of Grade 7 students employed linguistic resources to explain density differences. Drawing from the same data-set as a previous study by, we take a language perspective to investigate the challenges students face in learning the concept of density. Our study thus complements previous research on learning about…

  9. Facilitating High School Students' Use of Multiple Representations to Describe and Explain Simple Chemical Reactions

    ERIC Educational Resources Information Center

    Chandrasegaran, A. L.; Treagust, David F.; Mocerino, Mauro

    2011-01-01

    This study involved the evaluation of the efficacy of a planned instructional program to facilitate understanding of the macroscopic, submicroscopic and symbolic representational systems when describing and explaining chemical reactions by sixty-five Grade 9 students in a Singapore secondary school. A two-tier multiple-choice diagnostic instrument…

  10. Does Mother's IQ Explain the Association between Birth Weight and Cognitive Ability in Childhood?

    ERIC Educational Resources Information Center

    Deary, Ian J.; Der, Geoff; Shenkin, Susan D.

    2005-01-01

    There is a significant association between birth weight and cognitive test scores in childhood, even among individuals born at term and with normal birth weight. The association is not explained by the child's social background. Here we examine whether mother's cognitive ability accounts for the birth weight-cognitive ability association. We…

  11. Explaining Self-Harm: Youth Cybertalk and Marginalized Sexualities and Genders

    ERIC Educational Resources Information Center

    McDermott, Elizabeth; Roen, Katrina; Piela, Anna

    2015-01-01

    This study investigates self-harm among young lesbian, gay, bisexual, and trans (LGBT) people. Using qualitative virtual methods, we examined online forums to explore young LGBT people's cybertalk about emotional distress and self-harming. We investigated how youth explained the relationship between self-harm and sexuality and gender. We found…

  12. Explaining Changing Suicide Rates in Norway 1948-2004: The Role of Social Integration

    ERIC Educational Resources Information Center

    Barstad, Anders

    2008-01-01

    Using Norway 1948-2004 as a case, I test whether changes in variables related to social integration can explain changes in suicide rates. The method is the Box-Jenkins approach to time-series analysis. Different aspects of family integration contribute significantly to the explanation of Norwegian suicide rates in this period. The estimated effect…

  13. A Model of How Different Biology Experts Explain Molecular and Cellular Mechanisms

    ERIC Educational Resources Information Center

    Trujillo, Caleb M.; Anderson, Trevor R.; Pelaez, Nancy J.

    2015-01-01

    Constructing explanations is an essential skill for all science learners. The goal of this project was to model the key components of expert explanation of molecular and cellular mechanisms. As such, we asked: What is an appropriate model of the components of explanation used by biology experts to explain molecular and cellular mechanisms? Do…

  14. Children Learning to Explain Daily Celestial Motion: Understanding Astronomy across Moving Frames of Reference

    ERIC Educational Resources Information Center

    Plummer, Julia D.; Wasko, Kyle D.; Slagle, Cynthia

    2011-01-01

    This study investigated elementary students' explanations for the daily patterns of apparent motion of the Sun, Moon, and stars. Third-grade students were chosen for this study because this age level is at the lower end of when many US standards documents suggest students should learn to use the Earth's rotation to explain daily celestial motion.…

  15. Semantic language as a mechanism explaining the association between ADHD symptoms and reading and mathematics underachievement.

    PubMed

    Gremillion, Monica L; Martel, Michelle M

    2012-11-01

    ADHD is associated with academic underachievement, but it remains unclear what mechanism accounts for this association. Semantic language is an underexplored mechanism that provides a developmental explanation for this association. The present study will examine whether semantic language deficits explain the association between ADHD and reading and mathematics underachievement, taking into account alternative explanations for associations, including verbal working memory (WM) impairments, as well as specificity of effects to inattentive and hyperactive-impulsive ADHD symptom domains. Participants in this cross-sectional study were 546 children (54 % male) ages six to twelve (M = 9.77, SD = 1.49). ADHD symptoms were measured via maternal and teacher report during structured interviews and on standardized rating forms. Children completed standardized semantic language, verbal WM, and academic testing. Semantic language fully mediated the ADHD-reading achievement association and partially mediated the ADHD-mathematics achievement association. Verbal WM also partially mediated the ADHD-mathematics association but did not mediate the ADHD-reading achievement association. Results generalized across inattentive and hyperactive-impulsive ADHD symptom domains. Semantic language explained the association between ADHD and reading underachievement and partially explained the association between ADHD and mathematics underachievement. Together, language impairment and WM fully explained the association between ADHD and reading underachievement, in line with developmental models suggesting that language and WM conjointly influence the development of attention and subsequent academic achievement. This work has implication for the development of tailored interventions for academic underachievement in children with ADHD. PMID:22661106

  16. Analysing How Scientists Explain Their Research: A Rubric for Measuring the Effectiveness of Scientific Explanations

    ERIC Educational Resources Information Center

    Sevian, Hannah; Gonsalves, Lisa

    2008-01-01

    The present article presents a rubric we developed for assessing the quality of scientific explanations by science graduate students. The rubric was developed from a qualitative analysis of science graduate students' abilities to explain their own research to an audience of non-scientists. Our intention is that use of the rubric to characterise…

  17. Combining Self-Explaining with Computer Architecture Diagrams to Enhance the Learning of Assembly Language Programming

    ERIC Educational Resources Information Center

    Hung, Y.-C.

    2012-01-01

    This paper investigates the impact of combining self explaining (SE) with computer architecture diagrams to help novice students learn assembly language programming. Pre- and post-test scores for the experimental and control groups were compared and subjected to covariance (ANCOVA) statistical analysis. Results indicate that the SE-plus-diagram…

  18. Why Science? Members of PSR Editorial Board Explain What Drew Them to Science

    ERIC Educational Resources Information Center

    Primary Science Review, 2006

    2006-01-01

    Members of "Primary Science Review" Editorial Board explain what drew them to science. Alan Peacock, "PSR" Editor, emphasises the need to preserve children's sense of wonderment about the world. Robert Collins, a science educator in the Faculty of Education, University of Strathclyde, thinks people are "secret science superstars" and reminds one…

  19. Applying a Predict-Observe-Explain Sequence in Teaching of Buoyant Force

    ERIC Educational Resources Information Center

    Radovanovic, Jelena; Slisko, Josip

    2013-01-01

    An active learning sequence based on the predict-observe-explain teaching strategy is applied to a lesson on buoyant force. The results obtained clearly justify the use of this teaching method and suggest devising a series of activities to enable more effective removal of students' commonly held alternative conceptions regarding floating and…

  20. Explaining the Intention to Use Technology among University Students: A Structural Equation Modeling Approach

    ERIC Educational Resources Information Center

    Teo, Timothy; Zhou, Mingming

    2014-01-01

    The aim of this study is to examine the factors that an influence higher education students' intention to use technology. Using an extended technology acceptance model as a research framework, a sample of 314 university students were surveyed on their responses to seven constructs hypothesized to explain their intention to use technology.…

  1. Explaining Inference on a Population of Independent Agents Using Bayesian Networks

    ERIC Educational Resources Information Center

    Sutovsky, Peter

    2013-01-01

    The main goal of this research is to design, implement, and evaluate a novel explanation method, the hierarchical explanation method (HEM), for explaining Bayesian network (BN) inference when the network is modeling a population of conditionally independent agents, each of which is modeled as a subnetwork. For example, consider disease-outbreak…

  2. What We Don't Understand, We Explain to Each Other

    ERIC Educational Resources Information Center

    Pines, David

    2015-01-01

    "What we don't understand, we explain to each other" was Robert Oppenheimer's 1948 description of theoretical physics as a profession. Because the phrase connects research, teaching, and learning, it seemed the right approach for the talk I gave to the AAPT [American Association of Physics Teachers] on receiving the 2013 J.D. Jackson…

  3. Disentangling vegetation diversity from climate–energy and habitat heterogeneity for explaining animal geographic patterns

    USGS Publications Warehouse

    Jimenez-Alfaro, Borja; Chytry, Milan; Mucina, Ladislav; Grace, James B.; Rejmanek, Marcel

    2016-01-01

    Broad-scale animal diversity patterns have been traditionally explained by hypotheses focused on climate–energy and habitat heterogeneity, without considering the direct influence of vegetation structure and composition. However, integrating these factors when considering plant–animal correlates still poses a major challenge because plant communities are controlled by abiotic factors that may, at the same time, influence animal distributions. By testing whether the number and variation of plant community types in Europe explain country-level diversity in six animal groups, we propose a conceptual framework in which vegetation diversity represents a bridge between abiotic factors and animal diversity. We show that vegetation diversity explains variation in animal richness not accounted for by altitudinal range or potential evapotranspiration, being the best predictor for butterflies, beetles, and amphibians. Moreover, the dissimilarity of plant community types explains the highest proportion of variation in animal assemblages across the studied regions, an effect that outperforms the effect of climate and their shared contribution with pure spatial variation. Our results at the country level suggest that vegetation diversity, as estimated from broad-scale classifications of plant communities, may contribute to our understanding of animal richness and may be disentangled, at least to a degree, from climate–energy and abiotic habitat heterogeneity.

  4. Teachers' Ability to Identify and Explain Students' Actions in Near and Far Figural Pattern Generalization Tasks

    ERIC Educational Resources Information Center

    El Mouhayar, Rabih Raif; Jurdak, Murad Eid

    2013-01-01

    The purpose of this paper is to explore middle school in-service mathematics teachers' ability (1) to identify and explain students' actions in pattern generalization and (2) to account for the variation in teachers' explanations of students' actions in terms of task and teachers' factors. Two questionnaires were developed: (1) a questionnaire to…

  5. Relevance of Student and Contextual School Variables in Explaining a Student's Severity of Violence Experienced

    ERIC Educational Resources Information Center

    Mooij, Ton

    2015-01-01

    Teachers conceptualise and interpret violent behaviour of secondary students in different ways. They also differ in their estimates of the relevance of student and contextual school variables when explaining the severity of violence experienced by students. Research can assist here by explicating the role of different types of contextual school…

  6. Explaining Parents' School Involvement: The Role of Ethnicity and Gender in the Netherlands

    ERIC Educational Resources Information Center

    Fleischmann, Fenella; de Haas, Annabel

    2016-01-01

    Ethnic minority parents are often less involved with their children's schooling, and this may hamper their children's academic success, thus contributing to ethnic educational inequality. The authors aim to explain differences in parental involvement, using nationally representative survey data from the Netherlands of parents of primary…

  7. The Utility of the UTAUT Model in Explaining Mobile Learning Adoption in Higher Education in Guyana

    ERIC Educational Resources Information Center

    Thomas, Troy Devon; Singh, Lenandlar; Gaffar, Kemuel

    2013-01-01

    In this paper, we compare the utility of modified versions of the unified theory of acceptance and use of technology (UTAUT) model in explaining mobile learning adoption in higher education in a developing country and evaluate the size and direction of the impacts of the UTAUT factors on behavioural intention to adopt mobile learning in higher…

  8. Bullying Explains Only Part of LGBTQ-Heterosexual Risk Disparities: Implications for Policy and Practice

    ERIC Educational Resources Information Center

    Robinson, Joseph P.; Espelage, Dorothy L.

    2012-01-01

    Students who identify as lesbian, gay, bisexual, transgender, and questioning (LGBTQ) experience higher rates of victimization by bullying than do their heterosexual-identified peers. In this article, we investigate the extent to which this difference in rates of victimization can explain LGBTQ youths' greater rates of suicidal ideation, suicide…

  9. Does Human Capital Theory Explain the Value of Higher Education? A South African Case Study

    ERIC Educational Resources Information Center

    van der Merwe, Alex

    2010-01-01

    A perennial debate in the economics of education is whether human capital or screening/signalling theories best explain the value of schooling and hence the private demand for, in particular, higher education. Human capital theory proposes that formal training such as that offered by higher education institutions improves the productive capacity…

  10. How Can We Explain Poverty? Case Study of Dee Reveals the Complexities

    ERIC Educational Resources Information Center

    Seccombe, Karen

    2011-01-01

    Many theories have been offered to explain why people are impoverished. This article by Karen Seccombe uses the case study of "Dee," a newly single mother, to explore four of the most common: individualism, social structuralism, the culture of poverty, and fatalism. She concludes that poverty is a highly complex phenomenon, and it is likely that…

  11. Cognitive Abilities Explaining Age-Related Changes in Time Perception of Short and Long Durations

    ERIC Educational Resources Information Center

    Zelanti, Pierre S.; Droit-Volet, Sylvie

    2011-01-01

    The current study investigated how the development of cognitive abilities explains the age-related changes in temporal judgment over short and long duration ranges from 0.5 to 30 s. Children (5- and 9-year-olds) as well as adults were given a temporal bisection task with four different duration ranges: a duration range shorter than 1 s, two…

  12. Science and Technology Pre-Service Teachers' Tendencies to Explain Vitality

    ERIC Educational Resources Information Center

    Ozdemir, Oguz

    2012-01-01

    The present study was carried out to determine the Science and Technology pre-service teachers' tendencies to explain vitality in a university located in Southeast Anatolia of Turkey in 2010-2011 academic year. The data were collected through the administration of a questionnaire developed by the researcher to 1st and 4th year Science and…

  13. Explaining Girls' Advantage in Kindergarten Literacy Learning: Do Classroom Behaviors Make a Difference?

    ERIC Educational Resources Information Center

    Ready, Douglas D.; LoGerfo, Laura F.; Burkam, David T.; Lee, Valerie E.

    2005-01-01

    This study investigated gender differences in kindergarteners' literacy skills, specifically, whether differences in children's classroom behaviors explained females' early learning advantage. Data included information on 16,883 kindergartners (8,701 boys and 8,182 girls) from the Early Childhood Longitudinal Study, Kindergarten Cohort of…

  14. Inference to the Best Explanation (IBE) versus Explaining for the Best Inference (EBI)

    ERIC Educational Resources Information Center

    Wilkenfeld, Daniel A.; Lombrozo, Tania

    2015-01-01

    In pedagogical contexts and in everyday life, we often come to believe something because it would best explain the data. What is it about the explanatory endeavor that makes it essential to everyday learning and to scientific progress? There are at least two plausible answers. On one view, there is something special about having true…

  15. A Socio-Psychophysiological Model for Explaining the Causal Effects of Social Reinforcement Systems.

    ERIC Educational Resources Information Center

    Brown, Edward K.

    The expanded socio-psychophysiological model (SPPM) appears to provide a meaningful paradigm for explaining the psycho-psysiological effects of Social Reinforcement Systems (SRS). This model may be used to assist individuals, and the society, to become more aware of the effects that social practices have on the immediate and long-term actions of…

  16. Explaining rigid dieting in normal-weight women: the key role of body image inflexibility.

    PubMed

    Ferreira, Cláudia; Trindade, Inês A; Martinho, Ana

    2016-03-01

    Restrictive dieting is an increasing behavior presented by women in modern societies, independently of their weight. There are several known factors that motivate diet, namely a sense of dissatisfaction with one's body and unfavorable social comparisons based on physical appearance. However, dieting seems to have a paradoxical effect and has been considered a risk factor for weight gain and obesity in women and for maladaptive eating. Nevertheless, the study of the emotional regulation processes that explain the adoption of inflexible and rigid eating behaviors still remains little explored. In this line, the present study aims to explore why normal-weight women engage in highly rigid and inflexible diets. We hypothesize that body and weight dissatisfaction and unfavorable social comparisons based on physical appearance explain the adoption of inflexible eating rules, through the mechanisms of body image inflexibility. The current study comprised 508 normal-weight female college students. Path analyses were conducted to explore the study's hypotheses. Results revealed that the model explained 43 % of inflexible eating and revealed excellent fit indices. Furthermore, the unwillingness to experience unwanted events related to body image (body image inflexibility) mediated the impact of body dissatisfaction and unfavorable social comparisons on the adoption of inflexible eating rules. This study highlights the relevance of body image inflexibility to explain rigid eating attitudes, and it seems to be an important avenue for the development of interventions focusing on the promotion of adaptive attitudes towards body image and eating in young women. PMID:25753131

  17. Learning Behaviours, Attention and Anxiety in Caribbean Children: Beyond the 'Usual Suspects' in Explaining Academic Performance.

    ERIC Educational Resources Information Center

    Durbrow, Eric H.; Schaefer, Barbara A.; Jimerson, Shane R.

    2000-01-01

    Contributions of learning behaviors; anxiety; attention problems; cognitive ability; and home background to academic performance was investigated in Caribbean village children (N=61). It was determined that anxiety, attention, and learning-related behaviors explained 32-35% of variance in academic scores. Results suggest that academic performance…

  18. The Efficacy of the Theory of Reasoned Action to Explain Gambling Behavior in College Students

    ERIC Educational Resources Information Center

    Thrasher, Robert G.; Andrew, Damon P. S.; Mahony, Daniel F.

    2007-01-01

    Shaffer and Hall (1997) have estimated college student gambling to be three times as high as their adult counterparts. Despite a considerable amount of research on gambling, researchers have struggled to develop a universal theory that explains gambling behavior. This study explored the potential of Ajzen and Fishbein's (1980) Theory of Reasoned…

  19. Deep supervised, but not unsupervised, models may explain IT cortical representation.

    PubMed

    Khaligh-Razavi, Seyed-Mahdi; Kriegeskorte, Nikolaus

    2014-11-01

    Inferior temporal (IT) cortex in human and nonhuman primates serves visual object recognition. Computational object-vision models, although continually improving, do not yet reach human performance. It is unclear to what extent the internal representations of computational models can explain the IT representation. Here we investigate a wide range of computational model representations (37 in total), testing their categorization performance and their ability to account for the IT representational geometry. The models include well-known neuroscientific object-recognition models (e.g. HMAX, VisNet) along with several models from computer vision (e.g. SIFT, GIST, self-similarity features, and a deep convolutional neural network). We compared the representational dissimilarity matrices (RDMs) of the model representations with the RDMs obtained from human IT (measured with fMRI) and monkey IT (measured with cell recording) for the same set of stimuli (not used in training the models). Better performing models were more similar to IT in that they showed greater clustering of representational patterns by category. In addition, better performing models also more strongly resembled IT in terms of their within-category representational dissimilarities. Representational geometries were significantly correlated between IT and many of the models. However, the categorical clustering observed in IT was largely unexplained by the unsupervised models. The deep convolutional network, which was trained by supervision with over a million category-labeled images, reached the highest categorization performance and also best explained IT, although it did not fully explain the IT data. Combining the features of this model with appropriate weights and adding linear combinations that maximize the margin between animate and inanimate objects and between faces and other objects yielded a representation that fully explained our IT data. Overall, our results suggest that explaining IT requires

  20. Variation in Plant Traits Explains Global Biogeographic Variation in the Abundance of Major Forest Functional Types

    NASA Astrophysics Data System (ADS)

    Wang, Y.

    2015-12-01

    Contrasting leaf types (needle vs. broadleaf) with different lifespans (annual vs. perennial) represent different adaptive strategies of plants under different environmental conditions. Previous studies explained adaptive advantages of different strategies using empirical models but cannot adequately explain the co-dominance of multiple plant functional types (PFTs) as observed in many parts of the world. Here we used a process-based model to explore whether observed inter- and intra-PFT variation in key plant traits can explain global biogeographic variation in co-dominance of major forest functional types. Using a parameter screening method, we identified the four most important plant traits for simulating annual net primary production (NPP) using the Australian Community Atmosphere-Biosphere-Land Exchange model (CABLE). Using ensemble CABLE simulations, we estimated the fraction of global land cover attributed to each PFT by comparing the simulated NPP for all three PFTs at each land point, globally. Our results were consistent with land area cover fractions of major forest types estimated from remote sensing data products; i.e., evergreen needle-leaf forests dominate in boreal regions, evergreen broadleaf forests dominate in tropical regions, and deciduous broadleaf forests are distributed widely across a broad range of environmental conditions. More importantly our approach successfully explained a paradox that has puzzled ecologists for over a century: why evergreen leaf types dominate in both boreal and tropical regions. We conclude that variation in and co-variation between key plant traits can explain significant fractions of global biogeographic variation of three major forest types, and should be taken into account when simulating global vegetation dynamics.

  1. Brief Report: Cognitive Control Helps Explain Comorbidity Between Alcohol Use Disorder and Internalizing Disorders

    PubMed Central

    Ellingson, Jarrod M; Richmond-Rakerd, Leah S; Slutske, Wendy S

    2015-01-01

    Objective: Alcohol use and internalizing problems frequently co-occur. Cognitive control has been implicated in their etiology, but no studies have tested whether this construct helps explain the co-occurrence of these disorders. Method: A total of 1,313 undergraduate students completed assessments of cognitive control, negative emotionality, and symptoms of alcohol use disorder (AUD), depression, and generalized anxiety disorder. Structural equation models examined the extent to which overlap between AUD and internalizing problems was explained by variance specific to cognitive control and negative emotionality, as well as variance shared by both constructs. Results: Symptoms of AUD and internalizing disorders were modestly correlated (depression: r = .16; anxiety: r = .14). Variance specific to cognitive control explained a significant proportion of the correlation between AUD and both depression and generalized anxiety (depression: 19%; generalized anxiety: 18%), as did variance common to cognitive control and negative emotionality (depression: 24%; generalized anxiety: 31%). Consistent with previous work, variance specific to negative emotionality also explained a large and statistically significant proportion of the correlation between AUD and internalizing disorder symptoms. Of note, the residualized correlation for AUD symptom endorsement with both depression and generalized anxiety problems was not statistically significant after accounting for both cognitive control and negative emotionality. Conclusions: This study provides new evidence that cognitive control may help explain the overlap between AUD and internalizing disorders while further supporting the contribution of negative emotionality to this overlap. Results have implications for intervention efforts aimed at reducing comorbid alcohol use disorder and internalizing disorders, as well as general psychopathology. PMID:25486397

  2. Deep Supervised, but Not Unsupervised, Models May Explain IT Cortical Representation

    PubMed Central

    Khaligh-Razavi, Seyed-Mahdi; Kriegeskorte, Nikolaus

    2014-01-01

    Inferior temporal (IT) cortex in human and nonhuman primates serves visual object recognition. Computational object-vision models, although continually improving, do not yet reach human performance. It is unclear to what extent the internal representations of computational models can explain the IT representation. Here we investigate a wide range of computational model representations (37 in total), testing their categorization performance and their ability to account for the IT representational geometry. The models include well-known neuroscientific object-recognition models (e.g. HMAX, VisNet) along with several models from computer vision (e.g. SIFT, GIST, self-similarity features, and a deep convolutional neural network). We compared the representational dissimilarity matrices (RDMs) of the model representations with the RDMs obtained from human IT (measured with fMRI) and monkey IT (measured with cell recording) for the same set of stimuli (not used in training the models). Better performing models were more similar to IT in that they showed greater clustering of representational patterns by category. In addition, better performing models also more strongly resembled IT in terms of their within-category representational dissimilarities. Representational geometries were significantly correlated between IT and many of the models. However, the categorical clustering observed in IT was largely unexplained by the unsupervised models. The deep convolutional network, which was trained by supervision with over a million category-labeled images, reached the highest categorization performance and also best explained IT, although it did not fully explain the IT data. Combining the features of this model with appropriate weights and adding linear combinations that maximize the margin between animate and inanimate objects and between faces and other objects yielded a representation that fully explained our IT data. Overall, our results suggest that explaining IT requires

  3. Explaining variation in gun control policy advocacy tactics among local organizations.

    PubMed

    Zakocs, Ronda C; Earp, Jo Anne L

    2003-06-01

    The goal of this study was to determine how well four organizational characteristics (structure, resources, motivation, or political capacity) explained local organizations' use of a variety of advocacy tactics aimed at promoting state gun control laws. In 1998, 679 local organizations were identified as potentially active on state gun control issues; a questionnaire was mailed to each group's leader. Seventy-nine percent (n = 538) responded to the survey, with 81% (n = 207) of eligible organizations completing questionnaires. The four organizational characteristics explained approximately half the variation in local groups' use of a wide range of advocacy tactics. Organizations with stronger motivation to address the gun control issue and greater political capacity engaged in more diverse gun control advocacy tactics; the authors found organizational structure and resources unlikely to be related. Leaders of advocacy organizations should consider ways to encourage members' motivations on the issue while fostering greater capacity for political action. PMID:19731501

  4. Can genetically based clines in plant defence explain greater herbivory at higher latitudes?

    PubMed

    Anstett, Daniel N; Ahern, Jeffrey R; Glinos, Julia; Nawar, Nabanita; Salminen, Juha-Pekka; Johnson, Marc T J

    2015-12-01

    Greater plant defence is predicted to evolve at lower latitudes in response to increased herbivore pressure. However, recent studies question the generality of this pattern. In this study, we tested for genetically based latitudinal clines in resistance to herbivores and underlying defence traits of Oenothera biennis. We grew plants from 137 populations from across the entire native range of O. biennis. Populations from lower latitudes showed greater resistance to multiple specialist and generalist herbivores. These patterns were associated with an increase in total phenolics at lower latitudes. A significant proportion of the phenolics were driven by the concentrations of two major ellagitannins, which exhibited opposing latitudinal clines. Our analyses suggest that these findings are unlikely to be explained by local adaptation of herbivore populations or genetic variation in phenology. Rather greater herbivory at high latitudes can be explained by latitudinal clines in the evolution of plant defences. PMID:26482702

  5. Using theories of delusion formation to explain abnormal beliefs in Body Dysmorphic Disorder (BDD).

    PubMed

    Rossell, Susan L; Labuschagne, Izelle; Dunai, Judy; Kyrios, Michael; Castle, David J

    2014-03-30

    Body Dysmorphic Disorder (BDD) is characterised by overvalued or delusional beliefs of 'imagined ugliness'. Delusional beliefs have been explained by a number of cognitive theories, including faulty perceptions, biases in attention, and corruption of semantic memory. Atypical aesthetics may also influence beliefs in BDD. In fourteen BDD patients, compared to controls (n=14), we examined these theories of beliefs in a cognitive test battery consisting of perceptual organisation and visual affect perception tasks, a Stroop task using body words, a sentence verification task, a fluency task, and an attractiveness task. BDD patients performed similar to controls on tasks measuring information (bias) processing and aesthetics. However, BDD showed abnormal abilities on semantic processing involving sentence verification and category fluency. There was only a trend finding of impaired performance on perceptual processing tasks in BDD. The findings suggest that the delusional beliefs in BDD may be explained by impaired semantic processing. PMID:24412353

  6. Explaining spatial variability in mean annual runoff in the conterminous United States

    USGS Publications Warehouse

    Wolock, D.M.; McCabe, G.J.

    1999-01-01

    The hydrologic concepts needed in a water-balance model to estimate the spatial variation in mean annual runoff for the 344 climate divisions in the conterminous United States (U.S.) were determined. The concepts that were evaluated were the climatic supply of water (precipitation), climatic demand for water (potential evapotranspiration), seasonality in supply and demand, and soil-moisture-storage capacity. Most (91%) of the spatial variability in mean annual runoff for the climate divisions in the conterminous U.S. was explained by the spatial variability of mean annual precipitation minus mean annual potential evapotranspiration. When soil-moisture-storage capacity and seasonality in supply and demand were added to the water balance, the explained variance in mean annual runoff increased slightly, and the error in estimated mean annual runoff decreased significantly. Adding soil-moisture-storage capacity and seasonality in supply and demand provided the most improvement in areas where seasonal supply and demand are out of phase.

  7. A nematomorph parasite explains variation in terrestrial subsidies to trout streams in Japan

    USGS Publications Warehouse

    Sato, Takuya; Watanabe, Katsutoshi; Tokuchi, Naoko; Kamauchi, Hiromitsu; Harada, Yasushi; Lafferty, Kevin D.

    2011-01-01

    Nematomorph parasites alter the behavior of their orthopteran hosts, driving them to water and creating a source of food for stream salmonids. We investigated whether nematomorphs could explain variation in terrestrial subsidies across several streams. In nine study streams, orthopterans comprise much of the stomach contents of trout (46 +/- 31% on average). Total mass of ingested prey per trout biomass positively correlated with the mass of orthopterans ingested, suggesting that the orthopterans enhanced absolute mass of prey consumption by the trout population. The orthopterans ingested per trout biomass positively correlated with the abundance of nematomorphs in the stream, but not with the abundance of camel crickets (the dominant hosts) around the streams. Streams in conifer plantations had fewer nematomorphs than streams in natural deciduous forests. These results provide the first quantitative evidence that a manipulative parasite can explain variation in the allochthonous energy flow through and across ecosystems.

  8. Morphologies in Solvent-Annealed Clotrimazole Thin Films Explained by Hansen-Solubility Parameters

    PubMed Central

    2014-01-01

    The induction of different crystal morphologies is of crucial importance for many applications. In this work, the preparation of various crystal morphologies within clotrimazole films on glass substrates is demonstrated. Amorphous clotrimazole thin films were transformed via vapor annealing into crystalline structures; highly monodisperse/multidisperse crystallites, spherulite, or dendritic structures were obtained as the solvent was exchanged. X-ray diffraction experiments reveal that the same polymorph is present for all samples but with varying texture. The achieved morphologies are explained in terms of Hansen-solubility parameters and vapor pressures; thus, the different morphologies and crystal orientations can be explained by solvent—solid interaction strengths within the thin film samples. PMID:24624042

  9. A Bayesian observer model constrained by efficient coding can explain 'anti-Bayesian' percepts.

    PubMed

    Wei, Xue-Xin; Stocker, Alan A

    2015-10-01

    Bayesian observer models provide a principled account of the fact that our perception of the world rarely matches physical reality. The standard explanation is that our percepts are biased toward our prior beliefs. However, reported psychophysical data suggest that this view may be simplistic. We propose a new model formulation based on efficient coding that is fully specified for any given natural stimulus distribution. The model makes two new and seemingly anti-Bayesian predictions. First, it predicts that perception is often biased away from an observer's prior beliefs. Second, it predicts that stimulus uncertainty differentially affects perceptual bias depending on whether the uncertainty is induced by internal or external noise. We found that both model predictions match reported perceptual biases in perceived visual orientation and spatial frequency, and were able to explain data that have not been explained before. The model is general and should prove applicable to other perceptual variables and tasks. PMID:26343249

  10. Enriched Pt-Re-Os isotope systematics in plume lavas explained by metasomatic sulfides.

    PubMed

    Luguet, Ambre; Graham Pearson, D; Nowell, Geoff M; Dreher, Scott T; Coggon, Judith A; Spetsius, Zdislav V; Parman, Stephen W

    2008-01-25

    To explain the elevated osmium isotope (186Os-187Os) signatures in oceanic basalts, the possibility of material flux from the metallic core into the crust has been invoked. This hypothesis conflicts with theoretical constraints on Earth's thermal and dynamic history. To test the veracity and uniqueness of elevated 186Os-187Os in tracing core-mantle exchange, we present highly siderophile element analyses of pyroxenites, eclogites plus their sulfides, and new 186Os/188Os measurements on pyroxenites and platinum-rich alloys. Modeling shows that involvement in the mantle source of either bulk pyroxenite or, more likely, metasomatic sulfides derived from either pyroxenite or peridotite melts can explain the 186Os-187Os signatures of oceanic basalts. This removes the requirement for core-mantle exchange and provides an effective mechanism for generating Os isotope diversity in basalt source regions. PMID:18218894

  11. Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspot.

    PubMed

    Sunday, Jennifer M; Pecl, Gretta T; Frusher, Stewart; Hobday, Alistair J; Hill, Nicole; Holbrook, Neil J; Edgar, Graham J; Stuart-Smith, Rick; Barrett, Neville; Wernberg, Thomas; Watson, Reg A; Smale, Dan A; Fulton, Elizabeth A; Slawinski, Dirk; Feng, Ming; Radford, Ben T; Thompson, Peter A; Bates, Amanda E

    2015-09-01

    Species' ranges are shifting globally in response to climate warming, with substantial variability among taxa, even within regions. Relationships between range dynamics and intrinsic species traits may be particularly apparent in the ocean, where temperature more directly shapes species' distributions. Here, we test for a role of species traits and climate velocity in driving range extensions in the ocean-warming hotspot of southeast Australia. Climate velocity explained some variation in range shifts, however, including species traits more than doubled the variation explained. Swimming ability, omnivory and latitudinal range size all had positive relationships with range extension rate, supporting hypotheses that increased dispersal capacity and ecological generalism promote extensions. We find independent support for the hypothesis that species with narrow latitudinal ranges are limited by factors other than climate. Our findings suggest that small-ranging species are in double jeopardy, with limited ability to escape warming and greater intrinsic vulnerability to stochastic disturbances. PMID:26189556

  12. Metacommunity process rather than continental tectonic history better explains geographically structured phylogenies in legumes.

    PubMed Central

    Lavin, Matt; Schrire, Brian P; Lewis, Gwilym; Pennington, R Toby; Delgado-Salinas, Alfonso; Thulin, Mats; Hughes, Colin E; Matos, Angela Beyra; Wojciechowski, Martin F

    2004-01-01

    Penalized likelihood estimated ages of both densely sampled intracontinental and sparsely sampled transcontinental crown clades in the legume family show a mostly Quaternary to Neogene age distribution. The mode ages of the intracontinental crown clades range from 4-6 Myr ago, whereas those of the transcontinental crown clades range from 8-16 Myr ago. Both of these young age estimates are detected despite methodological approaches that bias results toward older ages. Hypotheses that resort to vicariance or continental history to explain continental disjunct distributions are dismissed because they require mostly Palaeogene and older tectonic events. An alternative explanation centring on dispersal that may well explain the geographical as well as the ecological phylogenetic structure of legume phylogenies is Hubbell's unified neutral theory of biodiversity and biogeography. This is the only dispersalist theory that encompasses evolutionary time and makes predictions about phylogenetic structure. PMID:15519969

  13. Does the standard hot-big-bang model explain the primordial abundances of helium and deuterium

    SciTech Connect

    Rana, N.C.

    1982-01-18

    It is shown that according to the standard hot-big-bang nucleosynthesis calculations, no single value of the ratio eta of baryon to the photon number density can explain the right abundances of both /sup 4/He and /sup 2/D. A slight neutrino degeneracy, however, provides a testable solution for eta which is in conformity with the current estimate of the baryonic component of the density parameter (..cap omega../sub N/)/sub 0/ of the Universe.

  14. The role of local food availability in explaining obesity risk among young school-aged children.

    PubMed

    Lee, Helen

    2012-04-01

    In recent years, research and public policy attention has increasingly focused on understanding whether modifiable aspects of the local food environment - the types and composition of food outlets families have proximate access to - are drivers of and potential solutions to the problem of childhood obesity in the United States. Given that much of the earlier published research has documented greater concentrations of fast-food outlets alongside limited access to large grocery stores in neighborhoods with higher shares of racial/ethnic minority groups and residents living in poverty, differences in retail food contexts may indeed exacerbate notable child obesity disparities along socioeconomic and racial/ethnic lines. This paper examines whether the lack of access to more healthy food retailers and/or the greater availability of "unhealthy" food purveyors in residential neighborhoods explains children's risk of excessive weight gain, and whether differential food availability explains obesity disparities. I do so by analyzing a national survey of U.S. children followed over elementary school (Early Childhood Longitudinal Study - Kindergarten Cohort) who are linked to detailed, longitudinal food availability measures from a comprehensive business establishment database (the National Establishment Time Series). I find that children who live in residentially poor and minority neighborhoods are indeed more likely to have greater access to fast-food outlets and convenience stores. However, these neighborhoods also have greater access to other food establishments that have not been linked to increased obesity risk, including large-scale grocery stores. When examined in a multi-level modeling framework, differential exposure to food outlets does not independently explain weight gain over time in this sample of elementary school-aged children. Variation in residential food outlet availability also does not explain socioeconomic and racial/ethnic differences. It may thus be

  15. A simple model explaining super-resolution in absolute optical instruments

    NASA Astrophysics Data System (ADS)

    Leonhardt, Ulf; Sahebdivan, Sahar; Kogan, Alex; Tyc, Tomáš

    2015-05-01

    We develop a simple, one-dimensional model for super-resolution in absolute optical instruments that is able to describe the interplay between sources and detectors. Our model explains the subwavelength sensitivity of a point detector to a point source reported in previous computer simulations and experiments (Miñano 2011 New J. Phys.13 125009; Miñano 2014 New J. Phys.16 033015).

  16. When apperceptive agnosia is explained by a deficit of primary visual processing.

    PubMed

    Serino, Andrea; Cecere, Roberto; Dundon, Neil; Bertini, Caterina; Sanchez-Castaneda, Cristina; Làdavas, Elisabetta

    2014-03-01

    Visual agnosia is a deficit in shape perception, affecting figure, object, face and letter recognition. Agnosia is usually attributed to lesions to high-order modules of the visual system, which combine visual cues to represent the shape of objects. However, most of previously reported agnosia cases presented visual field (VF) defects and poor primary visual processing. The present case-study aims to verify whether form agnosia could be explained by a deficit in basic visual functions, rather that by a deficit in high-order shape recognition. Patient SDV suffered a bilateral lesion of the occipital cortex due to anoxia. When tested, he could navigate, interact with others, and was autonomous in daily life activities. However, he could not recognize objects from drawings and figures, read or recognize familiar faces. He was able to recognize objects by touch and people from their voice. Assessments of visual functions showed blindness at the centre of the VF, up to almost 5°, bilaterally, with better stimulus detection in the periphery. Colour and motion perception was preserved. Psychophysical experiments showed that SDV's visual recognition deficits were not explained by poor spatial acuity or by the crowding effect. Rather a severe deficit in line orientation processing might be a key mechanism explaining SDV's agnosia. Line orientation processing is a basic function of primary visual cortex neurons, necessary for detecting "edges" of visual stimuli to build up a "primal sketch" for object recognition. We propose, therefore, that some forms of visual agnosia may be explained by deficits in basic visual functions due to widespread lesions of the primary visual areas, affecting primary levels of visual processing. PMID:24607265

  17. Does the Standard Hot-Big-Bang Model Explain the Primordial Abundances of Helium and Deuterium?

    NASA Astrophysics Data System (ADS)

    Rana, N. C.

    1982-01-01

    It is shown that according to the standard hot-big-bang nucleosynthesis calculations, no single value of the ratio η of baryon to photon number density can explain the right abundances of both 4He and 2D. A slight neutrino degeneracy, however, provides a testable solution for η which is in conformity with the current estimate of the baryonic component of the density parameter (ΩN)0 of the Universe.

  18. INL Director Explains How the National Labs Are Assisting With Japan's Nuclear Crisis

    ScienceCinema

    Grossenbacher, John

    2013-05-28

    Idaho National Laboratory's Director John Grossenbacher discusses the types of nuclear expertise and capabilities that exist within the U.S. Department of Energy's national labs to assist with the Japan nuclear crisis. He also explains how the labs will provide long-term research that will uncover lessons learned from the Fukushima nuclear plants. For more information about INL's nuclear energy research, visit http://www.facebook.com/idahonationallaboratory.

  19. INL Director Explains How the National Labs Are Assisting With Japan's Nuclear Crisis

    SciTech Connect

    Grossenbacher, John

    2011-01-01

    Idaho National Laboratory's Director John Grossenbacher discusses the types of nuclear expertise and capabilities that exist within the U.S. Department of Energy's national labs to assist with the Japan nuclear crisis. He also explains how the labs will provide long-term research that will uncover lessons learned from the Fukushima nuclear plants. For more information about INL's nuclear energy research, visit http://www.facebook.com/idahonationallaboratory.

  20. Measurement confounding affects the extent to which verbal IQ explains social gradients in mortality

    PubMed Central

    Chapman, Benjamin; Fiscella, Kevin; Duberstein, Paul; Kawachi, Ichiro; Muennig, Peter

    2016-01-01

    Background IQ is thought to explain social gradients in mortality. IQ scores are based roughly equally on Verbal IQ (VIQ) and Performance IQ tests. VIQ tests, however, are suspected to confound true verbal ability with socioeconomic status (SES), raising the possibility that associations between SES and IQ scores might be overestimated. We examined, first, whether two of the most common types of VIQ tests exhibited differential item functioning (DIF) favouring persons of higher SES and/or majority race/ethnicity. Second, we assessed what impact, if any, this had on estimates of the extent to which VIQ explains social gradients in mortality. Methods Data from the General Social Survey-National Death Index cohort, a US population representative dataset, was used. Item response theory models queried social-factor DIF on the Thorndike Verbal Intelligence Scale and Wechsler Adult Intelligence Scales, Revised Similarities test. Cox models examined mortality associations among SES and VIQ scores corrected and uncorrected for DIF. Results When uncorrected for DIF, VIQ was correlated with income, education, occupational prestige and race, with correlation coefficients ranging between |0.12| and |0.43|. After correcting for DIF, correlations ranged from |0.06| to |0.16|. Uncorrected VIQ scores explained 11–40% of the Relative Index of Inequalities in mortality for social factors, while DIF-corrected scores explained 2–29%. Conclusions Two of the common forms of VIQ tests appear confound verbal intelligence with SES. Since these tests appear in most IQ batteries, circumspection may be warranted in estimating the amount of social inequalities in mortality attributable to IQ. PMID:24729404

  1. Explaining sex differences in chronic musculoskeletal pain in a general population.

    PubMed

    Wijnhoven, Hanneke A H; de Vet, Henrica C W; Picavet, H Susan J

    2006-09-01

    Many studies report a female predominance in the prevalence of chronic musculoskeletal pain (CMP) but the mechanisms explaining these sex differences are poorly understood. Data from a random postal questionnaire survey in the Dutch general population were used to examine whether sex differences in the prevalences of CMP are due to sex differences in the distribution of known potential risk factors for CMP (exposure model) and/or to the different importance of risk factors for CMP (i.e. show different strength of association) in men and women (vulnerability model). In the present analyses, 909 men and 1178 women aged 25-65 were included. CMP was defined as pain lasting longer than 3 months and was assessed for 10 anatomical locations (neck, shoulder, higher back, elbow, wrist/hand, lower back, hip, knee, ankle, foot). Sex differences in CMP could not be explained by a different distribution of age, educational level, smoking status, overweight, physical activity, and pain catastrophizing. Having no paid job was associated with CMP, explaining part of the sex differences, but its role seems complex. Risk factors with a sex-specific association were: overweight (all pain locations) and older age (lower extremities)--both having only an effect among women--and pain catastrophizing (upper extremities), which was stronger associated with CMP among men than among women. In conclusion, sex differences in prevalence of CMP may partly be explained by sex differences in vulnerability to risk factors for CMP. Future research towards sex-specific identification of risk factors for CMP is warranted. Eventually this may lead to sex-specific prevention and management of CMP. PMID:16716517

  2. Medical educators' social acts of explaining passing underperformance in students: a qualitative study.

    PubMed

    Monrouxe, Lynn V; Rees, Charlotte E; Lewis, Natalie J; Cleland, Jennifer A

    2011-05-01

    Passing underperformance in students is ubiquitous across health and social care educators and is intimately related to the subsequent welfare of patients: underperforming students may become underperforming practitioners. This paper aims to examine how medical educators construct passing underperformance through an analysis of their social act of explaining such behaviours in peer-group settings. Ten focus groups were conducted with 70 medical educators across two UK schools with different curricular/assessment styles (England, Scotland). A qualitative content analysis of how educators explained their behaviours of passing underperformance was undertaken using the psychological concepts of proximality and distalness according to: (1) Malle's F.Ex. coding framework for behavioural explanations, and (2) participants' use of pronouns. 149 explanations of passing underperformance were identified: 72 for participants' own behaviour, 77 for others' behaviour. When explaining their own behaviour, participants used the proximal pronoun I 37% (n = 27) of the time and the distancing pronouns we/you 51% (n = 37) of the time. More Causal History of Reasons (38%; n = 27) and Enabling Factors (29%; n = 21) than Reasons (33%; n = 24) were cited. A similar pattern was found for explaining others' behaviour. Thus, medical educators used linguistic form, explanation mode and informational content within peer-group discussions to distance themselves from intentionality for their action of passing underperformance and highlighted desirable characteristics of themselves and medical educators in general. Faculty development programmes should develop assessors' awareness of how implicit factors within their talk can legitimise a culture of passing underperformance and explore the steps for cultural change. PMID:21063770

  3. An alternative classical force of gravitation in order to explain the velocity curve of spiral galaxies

    NASA Astrophysics Data System (ADS)

    Guiot, E.

    2015-03-01

    The purpose of this work is to investigate an alternative to modified Newtonian dynamics (MOND), in order to explain the rotation curve of galaxies without dark matter hypothesis, and with respect for classical physics. Our hypothesis is that the force of gravitation, in the case of large distances and under certain conditions, possesses a tangential component. We show that the force of gravitation we obtain is compatible with observational data, such as "flat" curve of rotation and the conic trajectories of the stars.

  4. Optimisation explains global leaf trait patterns and plant adaptations to global change (Invited)

    NASA Astrophysics Data System (ADS)

    Dewar, R. C.; McMurtrie, R. E.

    2009-12-01

    Measured values of four key leaf traits (leaf area per unit mass, nitrogen concentration, photosynthetic rate and leaf lifespan) co-vary globally according to relationships that hold across all the world’s terrestrial plants. The same leaf traits respond consistently to altered environmental conditions (e.g. light intensity, carbon dioxide concentration and nitrogen supply). Explaining observed global leaf trait patterns and leaf responses to environmental change is a prerequisite to understanding and predicting vegetation responses to global change more generally across a range of time scales. Recently [1] we have shown, using a simple model of plant carbon-nitrogen economy, that all of these leaf trait patterns and responses are consistent with an optimisation hypothesis that cumulative carbon export from leaves over their lifespan is maximised. Various closely-related optimisation hypotheses also explain other plant adaptations to environmental change, such as stomatal responses and altered patterns of growth allocation [2]. Incorporating plant optimisation into large scale vegetation-atmosphere models would ensure they are consistent with global leaf trait relationships, and would improve predictions of vegetation responses to global change. The challenge, both scientific and operational, is to do this consistently over a wide range of time scales. This talk will review our recent work using plant optimisation models [1,2] and highlight the potential of Maximum Entropy Production as a unifying optimisation principle for plant and ecosystem function across different time scales [3]. [1] McMurtrie RE, Dewar RC. 2009. Global variation of leaf traits explained from an hypothesis of optimal plant function. Manuscript in preparation. [2] Dewar RC, Franklin O, Makela A, McMurtrie RE, Valentine HT. 2009. Optimal function explains forest responses to global change. BioScience 59:127-139. [3] Dewar RC. 2009. Maximum entropy production and plants. Submitted to Phil

  5. Canonical Cortical Circuit Model Explains Rivalry, Intermittent Rivalry, and Rivalry Memory.

    PubMed

    Vattikuti, Shashaank; Thangaraj, Phyllis; Xie, Hua W; Gotts, Stephen J; Martin, Alex; Chow, Carson C

    2016-05-01

    It has been shown that the same canonical cortical circuit model with mutual inhibition and a fatigue process can explain perceptual rivalry and other neurophysiological responses to a range of static stimuli. However, it has been proposed that this model cannot explain responses to dynamic inputs such as found in intermittent rivalry and rivalry memory, where maintenance of a percept when the stimulus is absent is required. This challenges the universality of the basic canonical cortical circuit. Here, we show that by including an overlooked realistic small nonspecific background neural activity, the same basic model can reproduce intermittent rivalry and rivalry memory without compromising static rivalry and other cortical phenomena. The background activity induces a mutual-inhibition mechanism for short-term memory, which is robust to noise and where fine-tuning of recurrent excitation or inclusion of sub-threshold currents or synaptic facilitation is unnecessary. We prove existence conditions for the mechanism and show that it can explain experimental results from the quartet apparent motion illusion, which is a prototypical intermittent rivalry stimulus. PMID:27138214

  6. The challenges of choosing and explaining a phenomenon in epidemiological research on the "Hispanic Paradox".

    PubMed

    Valles, Sean A

    2016-04-01

    According to public health data, the US Hispanic population is far healthier than would be expected for a population with low socioeconomic status. Ever since Kyriakos Markides and Jeannine Coreil highlighted this in a seminal 1986 article, public health researchers have sought to explain the so-called "Hispanic paradox." Several candidate explanations have been offered over the years, but the debate goes on. This article offers a philosophical analysis that clarifies how two sets of obstacles make it particularly difficult to explain the Hispanic paradox. First, different research projects define the Hispanic paradox phenomenon in substantially different ways. Moreover, using Bas van Fraassen's pragmatic theory of explanation and Sean Valles's extension of it with the concept of "phenomenon choice," it also becomes clear that there are also multiple ways of explaining each individual definition of the phenomenon. A second set of philosophical and methodological challenges arises during any attempt to study "Hispanic" phenomena, with one key challenge being that the "Hispanic" panethnic concept was intentionally made vague as it was developed and popularized during the 1960s-1970s. After comparing this case with similar cases in the philosophical literature, the article concludes with observations on what makes this problem unique, particularly its ethical features. PMID:26754488

  7. Explaining body composition by some covariate factors among the elderly Bengalee Hindu women of Calcutta, India.

    PubMed

    Ghosh, A; Das Chaudhuri, A B

    2005-01-01

    Understanding the changes in body composition with passage of time and factors associated with them will help to improve our knowledge and understanding about these processes and could guide in the prevention of functional limitations and formulation of better health care among the elderly. The present cross-sectional work was under taken to study the effect of age, menopause, age at first conception, educational level and physical activity in explaining body composition among 200 elderly (55 years and above) Bengalee Hindu women of Calcutta, India. Body composition measures namely percentage of body fat (PBF), fat mass index (FMI), and fat free mass index (FFMI) were calculated from skinfolds thickness using standard equations. Multiple regression analyses of body composition variables by covariate factors revealed that Age, age of onset of menopause, age at first conception, educational level and frequency of walking cumulative explains 35%, 28% and 21% of PBF, FMI and FFMI respectively. Present study revealed that beside age, both biosocial (age of onset of menopause, age at first conception, education level) and physical activity as measured by brisk walking have significant contribution in explaining body composition among elderly females. Significant negative impact of physical activity on PBF, FMI and positive impact on FFMI in the present study were also evident. Therefore, brisk walking could be useful to increase body's fat free mass. PMID:16395512

  8. An instructional design process based on expert knowledge for teaching students how mechanisms are explained.

    PubMed

    Trujillo, Caleb M; Anderson, Trevor R; Pelaez, Nancy J

    2016-06-01

    In biology and physiology courses, students face many difficulties when learning to explain mechanisms, a topic that is demanding due to the immense complexity and abstract nature of molecular and cellular mechanisms. To overcome these difficulties, we asked the following question: how does an instructor transform their understanding of biological mechanisms and other difficult-to-learn topics so that students can comprehend them? To address this question, we first reviewed a model of the components used by biologists to explain molecular and cellular mechanisms: the MACH model, with the components of methods (M), analogies (A), context (C), and how (H). Next, instructional materials were developed and the teaching activities were piloted with a physical MACH model. Students who used the MACH model to guide their explanations of mechanisms exhibited both improvements and some new difficulties. Third, a series of design-based research cycles was applied to bring the activities with an improved physical MACH model into biology and biochemistry courses. Finally, a useful rubric was developed to address prevalent student difficulties. Here, we present, for physiology and biology instructors, the knowledge and resources for explaining molecular and cellular mechanisms in undergraduate courses with an instructional design process aimed at realizing pedagogical content knowledge for teaching. Our four-stage process could be adapted to advance instruction with a range of models in the life sciences. PMID:27231262

  9. Explaining and Forecasting Interannual Variability in the Flow of the Nile River

    NASA Astrophysics Data System (ADS)

    Eltahir, E. A.; Siam, M.

    2013-12-01

    The natural interannual variability in the flow of Nile River had a significant impact on the ancient civilizations and cultures that flourished on the banks of the river. Here, we analyze extensive data sets collected during the 20th century and define four modes of natural variability in the flow of Nile River, identifying a new significant potential for improving predictability of floods and droughts. Previous studies have identified a significant teleconnection between the Nile flow and the Eastern Pacific Ocean. El Niño-Southern Oscillation (ENSO) explains about 25% of the interannual variability in the Nile flow. Here, we identify, for the first time, a region in the southern Indian Ocean with similarly strong teleconnection to the Nile flow. Sea Surface Temperature (SST) in the region (60oE-90oE and 25oS-35oS) explains 28% of the interannual variability in the Nile flow. During those years with anomalous SST conditions in both Oceans, we estimate that indices of the SSTs in the Pacific and Indian Oceans can collectively explain up to 84% of the interannual variability in the flow of Nile. Building on these findings, we use classical Bayesian theorem to develop a new hybrid forecasting algorithm that predicts the Nile flow based on indices of the SST in the Eastern Pacific and Southern Indian Oceans.

  10. Explaining and forecasting interannual variability in the flow of the Nile River

    NASA Astrophysics Data System (ADS)

    Siam, M. S.; Eltahir, E. A. B.

    2014-05-01

    The natural interannual variability in the flow of Nile River had a significant impact on the ancient civilizations and cultures that flourished on the banks of the river. This is evident from stories in the Bible and Koran, and from the numerous Nilometers discovered near ancient temples. Here, we analyze extensive data sets collected during the 20th century and define four modes of natural variability in the flow of Nile River, identifying a new significant potential for improving predictability of floods and droughts. Previous studies have identified a significant teleconnection between the Nile flow and the Eastern Pacific Ocean. El Niño-Southern Oscillation (ENSO) explains about 25% of the interannual variability in the Nile flow. Here, we identify, for the first time, a region in the southern Indian Ocean with similarly strong teleconnection to the Nile flow. Sea Surface Temperature (SST) in the region (50-80° E and 25-35° S) explains 28% of the interannual variability in the Nile flow. During those years with anomalous SST conditions in both Oceans, we estimate that indices of the SSTs in the Pacific and Indian Oceans can collectively explain up to 84% of the interannual variability in the flow of Nile. Building on these findings, we use classical Bayesian theorem to develop a new hybrid forecasting algorithm that predicts the Nile flow based on global models predictions of indices of the SST in the Eastern Pacific and Southern Indian Oceans.

  11. Handgrip strength deficits best explain limitations in performing bimanual activities after stroke

    PubMed Central

    Basílio, Marluce Lopes; de Faria-Fortini, Iza; Polese, Janaine Cunha; Scianni, Aline A.; Faria, Christina DCM; Teixeira-Salmela, Luci Fuscaldi

    2016-01-01

    [Purpose] To evaluate the relationships between residual strength deficits (RSD) of the upper limb muscles and the performance in bimanual activities and to determine which muscular group would best explain the performance in bimanual activities of chronic stroke individuals. [Subjects and Methods] Strength measures of handgrip, wrist extensor, elbow flexor/extensor, and shoulder flexor muscles of 107 subjects were obtained and expressed as RSD. The performance in bimanual activities was assessed by the ABILHAND questionnaire. [Results] The correlations between the RSD of handgrip and wrist extensor muscles with the ABILHAND scores were negative and moderate, whereas those with the elbow flexor/extensor and shoulder flexor muscles were negative and low. Regression analysis showed that the RSD of handgrip and wrist extensor muscles explained 38% of the variance in the ABILHAND scores. Handgrip RSD alone explained 33% of the variance. [Conclusion] The RSD of the upper limb muscles were negatively associated with the performance in bimanual activities and the RSD of handgrip muscles were the most relevant variable. It is possible that stroke subjects would benefit from interventions aiming at improving handgrip strength, when the goal is to increase the performance in bimanual activities. PMID:27190447

  12. A local realistic model of quantum information systems explaining the four Bell states

    NASA Astrophysics Data System (ADS)

    Boyd, Jeffrey

    Can quantum computers and other information systems (like cryptography) be explained by local realism? The overwhelming consensus is NO. Thirty years of Bell test experiments proved Einstein, Podolsky and Rosen (EPR) wrong. Unknown to most physicists a new form of local realism has arisen, drastically different than EPR. The Theory of Elementary Waves (TEW) proposes that two entangled particles are both following the same elementary bi-ray. The same Bell test experiments that invalidate EPR, validate TEW. What is an elementary bi-ray? In TEW waves and particles usually travel in opposite directions. In entanglement experiments the picture is more complex. A bi-ray consists of two coaxial elementary rays, moving in opposite directions. Such bi-rays can explain all four Bell states on the basis of this peculiar form of local realism. Bell theory would classify TEW as ``nonlocal,'' even though it is local and realistic. The word ``nonlocal'' needs to be discarded, since ``elementary bi-ray'' is a more accurate and fertile descriptor of the same phenomena. TEW explains entanglement swapping heralding entanglement between distant spinning electrons in NV cavities, or trapped ions. The question is: So what? Would anything in quantum information science change if TEW were true? We think not.

  13. Evolutionary patterns and physicochemical properties explain macroinvertebrate sensitivity to heavy metals.

    PubMed

    Malaj, Egina; Guénard, Guillaume; Schäfer, Ralf B; von der Ohe, Peter C

    2016-06-01

    Ecological risk assessment depends strongly on species sensitivity data. Typically, sensitivity data are based on laboratory toxicity bioassays, which for practical constraints cannot be exhaustively performed for all species and chemicals available. Bilinear models integrating phylogenetic information of species and physicochemical properties of compounds allow to predict species sensitivity to chemicals. Combining the molecular information (DNA sequences) of 31 invertebrate species with the physicochemical properties of six bivalent metals, we built bilinear models that explained 70-80% of the variability in species sensitivity to heavy metals. Phylogeny was the most important component of the bilinear models, as it explained the major part of the explained variance (> 40%). Predicted values from bilinear modeling were in agreement with experimental values (> 50%); therefore, this approach is a good starting point to build statistical models which can potentially predict heavy metal toxicity for untested invertebrate species based on empirical values for similar species. Despite their good performance, development of the presented bilinear models would benefit from improved phylogenetic and toxicological datasets. Our analysis is an example for linking evolutionary biology with applied ecotoxicology. Its future applications may encompass other stress factors or traits influencing the survival of aquatic organisms in polluted environments. PMID:27509762

  14. A Local, Self-Organizing Reaction-Diffusion Model Can Explain Somite Patterning in Embryos.

    PubMed

    Cotterell, James; Robert-Moreno, Alexandre; Sharpe, James

    2015-10-28

    During somitogenesis in embryos, a posteriorly moving differentiation front arrests the oscillations of "segmentation clock" genes, leaving behind a frozen, periodic pattern of expression stripes. Both mathematical theories and experimental observations have invoked a "clock and wavefront" model to explain this phenomenon, in which long-range molecular gradients control the movement of the front and therefore the placement of the stripes in the embryo. Here, we develop a fundamentally different model-a progressive oscillatory reaction-diffusion (PORD) system driven by short-range interactions. In this model, posterior movement of the front is a local, emergent phenomenon that, in contrast to the clock and wavefront model, is not controlled by global positional information. The PORD model explains important features of somitogenesis, such as size regulation, that previous reaction-diffusion models could not explain. Moreover, the PORD and clock and wavefront models make different predictions about the results of FGF-inhibition and tissue-cutting experiments, and we demonstrate that the results of these experiments favor the PORD model. PMID:27136055

  15. A Model of How Different Biology Experts Explain Molecular and Cellular Mechanisms

    PubMed Central

    Trujillo, Caleb M.; Anderson, Trevor R.; Pelaez, Nancy J.

    2015-01-01

    Constructing explanations is an essential skill for all science learners. The goal of this project was to model the key components of expert explanation of molecular and cellular mechanisms. As such, we asked: What is an appropriate model of the components of explanation used by biology experts to explain molecular and cellular mechanisms? Do explanations made by experts from different biology subdisciplines at a university support the validity of this model? Guided by the modeling framework of R. S. Justi and J. K. Gilbert, the validity of an initial model was tested by asking seven biologists to explain a molecular mechanism of their choice. Data were collected from interviews, artifacts, and drawings, and then subjected to thematic analysis. We found that biologists explained the specific activities and organization of entities of the mechanism. In addition, they contextualized explanations according to their biological and social significance; integrated explanations with methods, instruments, and measurements; and used analogies and narrated stories. The derived methods, analogies, context, and how themes informed the development of our final MACH model of mechanistic explanations. Future research will test the potential of the MACH model as a guiding framework for instruction to enhance the quality of student explanations. PMID:25999313

  16. Canonical Cortical Circuit Model Explains Rivalry, Intermittent Rivalry, and Rivalry Memory

    PubMed Central

    Vattikuti, Shashaank; Xie, Hua W.; Gotts, Stephen J.; Martin, Alex; Chow, Carson C.

    2016-01-01

    It has been shown that the same canonical cortical circuit model with mutual inhibition and a fatigue process can explain perceptual rivalry and other neurophysiological responses to a range of static stimuli. However, it has been proposed that this model cannot explain responses to dynamic inputs such as found in intermittent rivalry and rivalry memory, where maintenance of a percept when the stimulus is absent is required. This challenges the universality of the basic canonical cortical circuit. Here, we show that by including an overlooked realistic small nonspecific background neural activity, the same basic model can reproduce intermittent rivalry and rivalry memory without compromising static rivalry and other cortical phenomena. The background activity induces a mutual-inhibition mechanism for short-term memory, which is robust to noise and where fine-tuning of recurrent excitation or inclusion of sub-threshold currents or synaptic facilitation is unnecessary. We prove existence conditions for the mechanism and show that it can explain experimental results from the quartet apparent motion illusion, which is a prototypical intermittent rivalry stimulus. PMID:27138214

  17. Order in ectoparasite communities of marine fish is explained by epidemiological processes.

    PubMed

    Morand, S; Rohde, K; Hayward, C

    2002-01-01

    Two kinds of community structure referred to, nestedness and bimodal distribution, have been observed or were searched for in parasite communities. We investigate here the relation between these two kinds of organisation, using marine fishes as a model, in order to show that parasite population dynamics may parsimoniously explain the patterns of ectoparasite species distribution and abundance. Thirty six assemblages of metazoan ectoparasites on the gills and heads of marine fish showed the following patterns: a positive relationship between abundance and the variance of abundance; a positive relationship between abundance and prevalence of infection; a bimodal pattern of the frequency distribution of prevalence of infection; nestedness as indicated by Atmar and Patterson's thermodynamic measure (a mean of 7.9 degrees C); a unimodal distribution of prevalence in parasite assemblages with a temperature lower than the mean, and a bimodal distribution in assemblages with a temperature higher than the mean. We conclude that patterns are the result of characteristics of the parasite species themselves and that interspecific competition is not necessary to explain them. We emphasize that a holistic approach, taking all evidence jointly into account, is necessary to explain patterns of community structure. Ectoparasite assemblages of marine fish are among the animal groups that have been most thoroughly examined using many different methods, and all evidence supports the view that these animals live under non-equilibrium conditions, in largely non-saturated niche space in which interspecific competition occurs but is of little evolutionary importance. PMID:12396216

  18. Lower hamstring extensibility in men compared to women is explained by differences in stretch tolerance

    PubMed Central

    2014-01-01

    Background This study examined whether passive hamstring tissue stiffness and/or stretch tolerance explain the relationship between sex and hamstring extensibility. Methods Ninety healthy participants, 45 men and 45 women (mean ± SD; age 24.6 ± 5.9 years, height 1.72 ± 0.09 m, weight 74.6 ± 14.1 kg) volunteered for this study. The instrumented straight leg raise was used to determine hamstring extensibility and allow measurement of stiffness and stretch tolerance (visual analog pain score, VAS). Results Hamstring extensibility was 9.9° greater in women compared to men (p = 0.003). VAS scores were 16 mm lower in women (p = 0.001). Maximal stiffness (maximal applied torque) was not different between men and women (p = 0.42). Passive stiffness (slope from 20-50° hip flexion) was 0.09 Nm.°-1 lower in women (p = 0.025). For women, linear and stepwise regression showed that no predictor variables were associated with hamstring extensibility (adjusted r2 = -0.03, p = 0.61). For men, 44% of the variance in hamstring extensibility was explained by VAS and maximal applied torque (adjusted r2 = 0.44, p < 0.001), with 41% of the model accounted for by the relationship between higher VAS scores and lower extensibility (standardized β coefficient = -0.64, p < 0.001). Conclusions The results of this study suggest that stretch tolerance and not passive stiffness explains hamstring extensibility, but this relationship is only manifest in men. PMID:25000977

  19. Explaining Spatial Variation in the Recording Effort of Citizen Science Data across Multiple Taxa.

    PubMed

    Mair, Louise; Ruete, Alejandro

    2016-01-01

    The collation of citizen science data in open-access biodiversity databases makes temporally and spatially extensive species' observation data available to a wide range of users. Such data are an invaluable resource but contain inherent limitations, such as sampling bias in favour of recorder distribution, lack of survey effort assessment, and lack of coverage of the distribution of all organisms. Any technical assessment, monitoring program or scientific research applying citizen science data should therefore include an evaluation of the uncertainty of its results. We use 'ignorance' scores, i.e. spatially explicit indices of sampling bias across a study region, to further understand spatial patterns of observation behaviour for 13 reference taxonomic groups. The data is based on voluntary observations made in Sweden between 2000 and 2014. We compared the effect of six geographical variables (elevation, steepness, population density, log population density, road density and footpath density) on the ignorance scores of each group. We found substantial variation among taxonomic groups in the relative importance of different geographic variables for explaining ignorance scores. In general, road access and logged population density were consistently important variables explaining bias in sampling effort, indicating that access at a landscape-scale facilitates voluntary reporting by citizen scientists. Also, small increases in population density can produce a substantial reduction in ignorance score. However the between-taxa variation in the importance of geographic variables for explaining ignorance scores demonstrated that different taxa suffer from different spatial biases. We suggest that conservationists and researchers should use ignorance scores to acknowledge uncertainty in their analyses and conclusions, because they may simultaneously include many correlated variables that are difficult to disentangle. PMID:26820846

  20. Microbial Diversity Indexes Can Explain Soil Carbon Dynamics as a Function of Carbon Source

    PubMed Central

    Maron, Pierre-Alain; Menasseri-Aubry, Safya; Sarr, Amadou; Lévêque, Jean; Mathieu, Olivier; Jolivet, Claudy; Leterme, Philippe; Viaud, Valérie

    2016-01-01

    Mathematical models do not explicitly represent the influence of soil microbial diversity on soil organic carbon (SOC) dynamics despite recent evidence of relationships between them. The objective of the present study was to statistically investigate relationships between bacterial and fungal diversity indexes (richness, evenness, Shannon index, inverse Simpson index) and decomposition of different pools of soil organic carbon by measuring dynamics of CO2 emissions under controlled conditions. To this end, 20 soils from two different land uses (cropland and grassland) were incubated with or without incorporation of 13C-labelled wheat-straw residue. 13C-labelling allowed us to study residue mineralisation, basal respiration and the priming effect independently. An innovative data-mining approach was applied, based on generalized additive models and a predictive criterion. Results showed that microbial diversity indexes can be good covariates to integrate in SOC dynamics models, depending on the C source and the processes considered (native soil organic carbon vs. fresh wheat residue). Specifically, microbial diversity indexes were good candidates to help explain mineralisation of native soil organic carbon, while priming effect processes seemed to be explained much more by microbial composition, and no microbial diversity indexes were found associated with residue mineralisation. Investigation of relationships between diversity and mineralisation showed that higher diversity, as measured by the microbial diversity indexes, seemed to be related to decreased CO2 emissions in the control soil. We suggest that this relationship can be explained by an increase in carbon yield assimilation as microbial diversity increases. Thus, the parameter for carbon yield assimilation in mathematical models could be calculated as a function of microbial diversity indexes. Nonetheless, given limitations of the methods used, these observations should be considered with caution and

  1. Explaining the decline in coronary heart disease mortality in Turkey between 1995 and 2008

    PubMed Central

    2013-01-01

    Background Coronary heart disease (CHD) mortality rates have been decreasing in Turkey since the early 1990s. Our study aimed to determine how much of the CHD mortality decrease in Turkey between 1995 and 2008 could be attributed to temporal trends in major risk factors and how much to advances in medical and surgical treatments. Methods The validated IMPACT CHD mortality model was used to combine and analyse data on uptake and effectiveness of CHD treatments and risk factor trends in Turkey in adults aged 35–84 years between 1995 and 2008. Data sources were identified, searched and appraised on population, mortality and major CHD risk factors for adults those aged 35–84 years. Official statistics, electronic databases, national registers, surveys and published trials were screened from 1995 onwards. Results Between 1995 and 2008, coronary heart disease mortality rates in Turkey decreased by 34% in men and 28% in women 35 years and over. This resulted in 35,720 fewer deaths in 2008. Approximately 47% of this mortality decrease was attributed to treatments in individuals (including approximately 16% to secondary prevention, 3% angina treatments, 9% to heart failure treatments, 5% to initial treatments of acute myocardial infarction, and 5% to hypertension treatments) and approximately 42% was attributable to population risk factor reductions (notably blood pressure 29%; smoking 27%; and cholesterol 1%). Adverse trends were seen for obesity and diabetes (potentially increasing mortality by approximately 11% and 14% respectively). The model explained almost 90% of the mortality fall. Conclusion Reduction in major cardiovascular risk factors explained approximately 42% and improvements in medical and surgical treatments explained some 47% of the CHD mortality fall. These findings emphasize the complimentary value of primary prevention and evidence-based medical treatments in controlling coronary heart disease. PMID:24308515

  2. Testing the Effectiveness of Environmental Variables to Explain European Terrestrial Vertebrate Species Richness across Biogeographical Scales.

    PubMed

    Mouchet, Maud; Levers, Christian; Zupan, Laure; Kuemmerle, Tobias; Plutzar, Christoph; Erb, Karlheinz; Lavorel, Sandra; Thuiller, Wilfried; Haberl, Helmut

    2015-01-01

    We compared the effectiveness of environmental variables, and in particular of land-use indicators, to explain species richness patterns across taxonomic groups and biogeographical scales (i.e. overall pan-Europe and ecoregions within pan-Europe). Using boosted regression trees that handle non-linear relationships, we compared the relative influence (as a measure of effectiveness) of environmental variables related to climate, landscape (or habitat heterogeneity), land-use intensity or energy availability to explain European vertebrate species richness (birds, amphibians, and mammals) at the continental and ecoregion scales. We found that dominant land cover and actual evapotranspiration that relate to energy availability were the main correlates of vertebrate species richness over Europe. At the ecoregion scale, we identified four distinct groups of ecoregions where species richness was essentially associated to (i) seasonality of temperature, (ii) actual evapotranspiration and/or mean annual temperature, (iii) seasonality of precipitation, actual evapotranspiration and land cover) and (iv) and an even combination of the environmental variables. This typology of ecoregions remained valid for total vertebrate richness and the three vertebrate groups taken separately. Despite the overwhelming influence of land cover and actual evapotranspiration to explain vertebrate species richness patterns at European scale, the ranking of the main correlates of species richness varied between regions. Interestingly, landscape and land-use indicators did not stand out at the continental scale but their influence greatly increased in southern ecoregions, revealing the long-lasting human footprint on land-use-land-cover changes. Our study provides one of the first multi-scale descriptions of the variability in the ranking of correlates across several taxa. PMID:26161981

  3. Microbial Diversity Indexes Can Explain Soil Carbon Dynamics as a Function of Carbon Source.

    PubMed

    Louis, Benjamin P; Maron, Pierre-Alain; Menasseri-Aubry, Safya; Sarr, Amadou; Lévêque, Jean; Mathieu, Olivier; Jolivet, Claudy; Leterme, Philippe; Viaud, Valérie

    2016-01-01

    Mathematical models do not explicitly represent the influence of soil microbial diversity on soil organic carbon (SOC) dynamics despite recent evidence of relationships between them. The objective of the present study was to statistically investigate relationships between bacterial and fungal diversity indexes (richness, evenness, Shannon index, inverse Simpson index) and decomposition of different pools of soil organic carbon by measuring dynamics of CO2 emissions under controlled conditions. To this end, 20 soils from two different land uses (cropland and grassland) were incubated with or without incorporation of 13C-labelled wheat-straw residue. 13C-labelling allowed us to study residue mineralisation, basal respiration and the priming effect independently. An innovative data-mining approach was applied, based on generalized additive models and a predictive criterion. Results showed that microbial diversity indexes can be good covariates to integrate in SOC dynamics models, depending on the C source and the processes considered (native soil organic carbon vs. fresh wheat residue). Specifically, microbial diversity indexes were good candidates to help explain mineralisation of native soil organic carbon, while priming effect processes seemed to be explained much more by microbial composition, and no microbial diversity indexes were found associated with residue mineralisation. Investigation of relationships between diversity and mineralisation showed that higher diversity, as measured by the microbial diversity indexes, seemed to be related to decreased CO2 emissions in the control soil. We suggest that this relationship can be explained by an increase in carbon yield assimilation as microbial diversity increases. Thus, the parameter for carbon yield assimilation in mathematical models could be calculated as a function of microbial diversity indexes. Nonetheless, given limitations of the methods used, these observations should be considered with caution and

  4. Testing the Effectiveness of Environmental Variables to Explain European Terrestrial Vertebrate Species Richness across Biogeographical Scales

    PubMed Central

    Mouchet, Maud; Levers, Christian; Zupan, Laure; Kuemmerle, Tobias; Plutzar, Christoph; Erb, Karlheinz; Lavorel, Sandra; Thuiller, Wilfried; Haberl, Helmut

    2015-01-01

    We compared the effectiveness of environmental variables, and in particular of land-use indicators, to explain species richness patterns across taxonomic groups and biogeographical scales (i.e. overall pan-Europe and ecoregions within pan-Europe). Using boosted regression trees that handle non-linear relationships, we compared the relative influence (as a measure of effectiveness) of environmental variables related to climate, landscape (or habitat heterogeneity), land-use intensity or energy availability to explain European vertebrate species richness (birds, amphibians, and mammals) at the continental and ecoregion scales. We found that dominant land cover and actual evapotranspiration that relate to energy availability were the main correlates of vertebrate species richness over Europe. At the ecoregion scale, we identified four distinct groups of ecoregions where species richness was essentially associated to (i) seasonality of temperature, (ii) actual evapotranspiration and/or mean annual temperature, (iii) seasonality of precipitation, actual evapotranspiration and land cover) and (iv) and an even combination of the environmental variables. This typology of ecoregions remained valid for total vertebrate richness and the three vertebrate groups taken separately. Despite the overwhelming influence of land cover and actual evapotranspiration to explain vertebrate species richness patterns at European scale, the ranking of the main correlates of species richness varied between regions. Interestingly, landscape and land-use indicators did not stand out at the continental scale but their influence greatly increased in southern ecoregions, revealing the long-lasting human footprint on land-use–land-cover changes. Our study provides one of the first multi-scale descriptions of the variability in the ranking of correlates across several taxa. PMID:26161981

  5. Mechanisms of classical crystal growth theory explain quartz and silicate dissolution behavior

    PubMed Central

    Dove, Patricia M.; Han, Nizhou; De Yoreo, James J.

    2005-01-01

    The central control of mineral weathering rates on biogeochemical systems has motivated studies of dissolution for more than 50 years. A complete physical picture that explains widely observed variations in dissolution behavior is lacking, and some data show apparent serious inconsistencies that cannot be explained by the largely empirical kinetic “laws.” Here, we show that mineral dissolution can, in fact, be understood through the same mechanistic theory of nucleation developed for mineral growth. In principle, this theory should describe dissolution but has never been tested. By generalizing nucleation rate equations to include dissolution, we arrive at a model that predicts how quartz dissolution processes change with undersaturation from step retreat, to defect-driven and homogeneous etch pit formation. This finding reveals that the “salt effect,” recognized almost 100 years ago, arises from a crossover in dominant nucleation mechanism to greatly increase step density. The theory also explains the dissolution kinetics of major weathering aluminosilicates, kaolinite and K-feldspar. In doing so, it provides a sensible origin of discrepancies reported for the dependence of kaolinite dissolution and growth rates on saturation state by invoking a temperature-activated transition in the nucleation process. Although dissolution by nucleation processes was previously unknown for oxides or silicates, our mechanism-based findings are consistent with recent observations of dissolution (i.e., demineralization) in biological minerals. Nucleation theory may be the missing link to unifying mineral growth and dissolution into a mechanistic and quantitative framework across the continuum of driving force. PMID:16230632

  6. Explaining Spatial Variation in the Recording Effort of Citizen Science Data across Multiple Taxa

    PubMed Central

    Mair, Louise; Ruete, Alejandro

    2016-01-01

    The collation of citizen science data in open-access biodiversity databases makes temporally and spatially extensive species’ observation data available to a wide range of users. Such data are an invaluable resource but contain inherent limitations, such as sampling bias in favour of recorder distribution, lack of survey effort assessment, and lack of coverage of the distribution of all organisms. Any technical assessment, monitoring program or scientific research applying citizen science data should therefore include an evaluation of the uncertainty of its results. We use ‘ignorance’ scores, i.e. spatially explicit indices of sampling bias across a study region, to further understand spatial patterns of observation behaviour for 13 reference taxonomic groups. The data is based on voluntary observations made in Sweden between 2000 and 2014. We compared the effect of six geographical variables (elevation, steepness, population density, log population density, road density and footpath density) on the ignorance scores of each group. We found substantial variation among taxonomic groups in the relative importance of different geographic variables for explaining ignorance scores. In general, road access and logged population density were consistently important variables explaining bias in sampling effort, indicating that access at a landscape-scale facilitates voluntary reporting by citizen scientists. Also, small increases in population density can produce a substantial reduction in ignorance score. However the between-taxa variation in the importance of geographic variables for explaining ignorance scores demonstrated that different taxa suffer from different spatial biases. We suggest that conservationists and researchers should use ignorance scores to acknowledge uncertainty in their analyses and conclusions, because they may simultaneously include many correlated variables that are difficult to disentangle. PMID:26820846

  7. Is the association between irritable bowel syndrome and abuse explained by neuroticism? A population based study

    PubMed Central

    Talley, N; Boyce, P; Jones, M

    1998-01-01

    Background—In outpatients and the community, an association between abuse (particularly sexual abuse) and irritable bowel syndrome (IBS) has been observed, but whether there is a causal link continues to be disputed. 
Aims—To test the hypothesis that psychological factors explain the apparent association between abuse and IBS. 
Methods—A sample of residents of Penrith (a Sydney suburb sociodemographically similar to the Australian population) selected randomly from the electoral rolls (that by law include the entire population of age 18 years and above) was mailed a validated self report questionnaire. Measured were gastrointestinal (GI) symptoms including the Rome criteria for IBS, abuse (including the standardised Drossman questions), neuroticism (Eysenck Personality Questionnaire), and psychological morbidity (General Health Questionnaire). 
Results—The response rate was 64% (n=730); 12% fulfilled the Rome criteria for IBS. Overall abuse in childhood (odds ratio (OR)=2.02, 95% confidence interval (CI) 1.29 to 3.15) but not adulthood (OR=1.39, 95% CI 0.88 to 2.19) was associazted with IBS univariately. Neuroticism and psychological morbidity were also univariately associated with abuse in childhood, abuse in adulthood, and IBS, respectively. However, by logistic regression, abuse in childhood was not associated with IBS after controlling for age, gender, and psychological factors (OR=1.34, 95% CI 0.83to 2.17). The results were not altered by restricting the analyses to more severe forms of abuse, and were not explained by interactions between abuse and psychological variables. 
Conclusion—There is an association between abuse and IBS in the community, but this may be explained in part by other psychological factors. Based on a path analysis, we postulate that abuse may induce the expression of neuroticism that in turn leads to IBS. 

 Keywords: epidemiology; irritable bowel syndrome; abuse; neuroticism PMID:9505885

  8. Multiple associated variants increase the heritability explained for plasma lipids and coronary artery disease

    PubMed Central

    Tada, Hayato; Won, Hong-Hee; Melander, Olle; Yang, Jian; Peloso, Gina M; Kathiresan, Sekar

    2015-01-01

    Background Plasma lipid levels as well as coronary artery disease (CAD) have been shown to be highly heritable with estimates ranging from 40%–60%. However, top variants detected by large-scale genome-wide association studies (GWAS) explain only a fraction of the total variance in plasma lipid phenotypes and CAD. Methods and Results We performed a conditional and joint association analysis using summary-level statistics from two large GWAS meta-analyses: (1) the Global Lipids Genetics Consortium (GLGC) study, and (2) the Coronary ARtery DIsease Genome-wide Replication and Meta-analysis (CARDIoGRAM) study. There were 100,184 individuals from 46 GLGC studies for plasma lipids, and 22,233 cases and 64,762 controls from 14 studies for CAD. We detected a number of loci where multiple independent SNPs were associated with lipid traits within a locus (12 out of 33 loci for high-density lipoprotein cholesterol [HDL-C], 10 of 35 loci for low-density lipoprotein cholesterol [LDL-C], 13 of 44 loci for total cholesterol [TC], and 8 of 28 loci for triglycerides [TG]), reaching genome-wide significance (P<5×10−8), nearly doubling the heritability explained by GWAS (3.6% to 7.6% for HDL-C, 5.0% to 8.8% for LDL-C, 5.5% to 8.8% for TC, and 5.7% to 8.5% for TG). Multiple SNPs were also associated with CAD (3 of 15 loci, 9.6% to 11.4% of increased heritability). Conclusion These results demonstrate that a portion of the missing heritability for lipid traits and CAD can be explained by multiple variants at each locus. PMID:25170055

  9. When Family History Matters: The Importance of Lineage Analyses and Fate Maps for Explaining Animal Development.

    PubMed

    Klein, Steven L; Moody, Sally A

    2016-01-01

    Initial interest in understanding how the fertilized egg becomes a multicellular animal suggested two possible answers: either the embryo came from preformed components or it arose through epigenetic processes. Extensive research during the past few decades has identified aspects of development that depend on preformed elements, such as cytoplasmic components and a cell's lineage; it also has identified aspects that depend on epigenetic processes, such as cell interactions and morphogen gradients. These advances have depended on understanding embryonic cell lineage and cell fate. This essay explains how lineage analysis and fate mapping have contributed to our current understanding of embryonic development. PMID:26969974

  10. SO(10) GUT models and their present success in explaining mass and mixing data

    SciTech Connect

    Carl H. Albright

    2002-12-13

    Some features of SO(10) GUT models are reviewed, and a number of such models in the literature are compared. While some have been eliminated by recent neutrino data, others are presently successful in explaining the quark and lepton mass and mixing data. A short description of one very predictive model is given which illustrates some of the features discussed. Future tests of the models are pointed out including one which contrasts sharply with those models based on an L{sub e}-L{sub {mu}}-L{sub {tau}} type symmetry.

  11. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates.

    PubMed

    Song, Z Q; Ni, Y; Peng, L M; Liang, H Y; He, L H

    2016-01-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites. PMID:27029955

  12. Using hegemonic masculinity to explain gay male attraction to muscular and athletic men.

    PubMed

    Lanzieri, Nicholas; Hildebrandt, Tom

    2011-01-01

    This article reviews relevant research on male homosexual attraction. Utilizing masculinity as its theoretical frame, the authors use childhood experiences with both fathers and peers, the gay community's inculcation of heteronormative ideologies, and the gay media's adherence to masculine prototypes, to provide causal explanations for the appeal of muscular, lean, and athletic physiques. While the authors acknowledge that not all individuals within the gay community look toward muscularity and athleticism as the primary components of attractiveness, it nonetheless remains important to examine the theoretical perspectives that may explain the appeal of this specific aesthetic. PMID:21294030

  13. Transcript Abundance Explains mRNA Mobility Data in Arabidopsis thaliana.

    PubMed

    Calderwood, Alexander; Kopriva, Stanislav; Morris, Richard J

    2016-03-01

    Recently, a large population of mRNA was shown to be able to travel between plant organs via sieve elements as a putative long-distance signaling molecule. However, a mechanistic basis by which transcripts are selected for transport has not yet been identified. Here, we show that experimental mRNA mobility data in Arabidopsis can be explained by transcript abundance and half-life. This suggests that the majority of identified mobile transcripts can be accounted for by non-sequence-specific movement of mRNA from companion cells into sieve elements. PMID:26952566

  14. A Little Knowledge of Ground Motion: Explaining 3-D Physics-Based Modeling to Engineers

    NASA Astrophysics Data System (ADS)

    Porter, K.

    2014-12-01

    Users of earthquake planning scenarios require the ground-motion map to be credible enough to justify costly planning efforts, but not all ground-motion maps are right for all uses. There are two common ways to create a map of ground motion for a hypothetical earthquake. One approach is to map the median shaking estimated by empirical attenuation relationships. The other uses 3-D physics-based modeling, in which one analyzes a mathematical model of the earth's crust near the fault rupture and calculates the generation and propagation of seismic waves from source to ground surface by first principles. The two approaches produce different-looking maps. The more-familiar median maps smooth out variability and correlation. Using them in a planning scenario can lead to a systematic underestimation of damage and loss, and could leave a community underprepared for realistic shaking. The 3-D maps show variability, including some very high values that can disconcert non-scientists. So when the USGS Science Application for Risk Reduction's (SAFRR) Haywired scenario project selected 3-D maps, it was necessary to explain to scenario users—especially engineers who often use median maps—the differences, advantages, and disadvantages of the two approaches. We used authority, empirical evidence, and theory to support our choice. We prefaced our explanation with SAFRR's policy of using the best available earth science, and cited the credentials of the maps' developers and the reputation of the journal in which they published the maps. We cited recorded examples from past earthquakes of extreme ground motions that are like those in the scenario map. We explained the maps on theoretical grounds as well, explaining well established causes of variability: directivity, basin effects, and source parameters. The largest mapped motions relate to potentially unfamiliar extreme-value theory, so we used analogies to human longevity and the average age of the oldest person in samples of

  15. Money Earlier or Later? Simple Heuristics Explain Intertemporal Choices Better than Delay Discounting1

    PubMed Central

    Marzilli Ericson, Keith M.; White, John Myles; Laibson, David; Cohen, Jonathan D.

    2015-01-01

    Heuristic models have been proposed for many domains of choice. We compare heuristic models of intertemporal choice, which can account for many of the known intertemporal choice anomalies, to discounting models. We conduct an out-of-sample, cross-validated comparison of intertemporal choice models. Heuristic models outperform traditional utility discounting models, including models of exponential and hyperbolic discounting. The best performing models predict choices by using a weighted average of absolute differences and relative (percentage) differences of the attributes of the goods in a choice set. We conclude that heuristic models explain time-money tradeoff choices in experiments better than utility discounting models. PMID:25911124

  16. Into the looking glass: Broadening models to explain the spectrum of sensory and affective vicarious experiences.

    PubMed

    Giummarra, Melita J; Fitzgibbon, Bernadette M

    2015-01-01

    Ward and Bannisy's proposed conceptual framework-Threshold Theory and Self-Other Theory-for mirror touch synesthesia are welcomed as an explanation of mechanisms giving rise to innocuous vicarious phenomena. Herein we propose that these vicarious, or synesthetic, experiences should be considered along a spectrum of experiences, from innocuous through to noxious or threatening sensations. In particular, we would like to see these theories considered within a broader framework to explain the multitude of vicarious experiences that seem to share fundamental neurophysiological and trait characteristics. PMID:25998034

  17. Can Self-Control Explain Avoiding Free Money? Evidence from Interest-Free Student Loans.

    PubMed

    Cadena, Brian C; Keys, Benjamin J

    2013-10-01

    This paper uses insights from behavioral economics to explain a particularly surprising borrowing phenomenon: One in six undergraduate students offered interest-free loans turn them down. Models of impulse control predict that students may optimally reject subsidized loans to avoid excessive consumption during school. Using the National Postsecondary Student Aid Study (NPSAS), we investigate students' take-up decisions and identify a group of students for whom the loans create an especially tempting liquidity increase. Students who would receive the loan in cash are significantly more likely to turn it down, suggesting that consumers choose to limit their liquidity in economically meaningful situations. PMID:24839312

  18. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

    NASA Astrophysics Data System (ADS)

    Song, Z. Q.; Ni, Y.; Peng, L. M.; Liang, H. Y.; He, L. H.

    2016-03-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites.

  19. Using patient and general practice characteristics to explain variations in cervical smear uptake rates.

    PubMed Central

    Majeed, F. A.; Cook, D. G.; Anderson, H. R.; Hilton, S.; Bunn, S.; Stones, C.

    1994-01-01

    OBJECTIVES--To produce practice and patient variables for general practices from census and family health services authority data, and to determine the importance of these variables in explaining variation in cervical smear uptake rates between practices. DESIGN--Population based study examining variations in cervical smear uptake rates among 126 general practices using routine data. SETTING--Merton, Sutton, and Wandsworth Family Health Services Authority, which covers parts of inner and outer London. MAIN OUTCOME MEASURE--Percentage of women aged 25-64 years registered with a general practitioner who had undergone a cervical smear test during the five and a half years preceding 31 March 1992. RESULTS--Cervical smear uptake rates varied from 16.5% to 94.1%. The estimated percentage of practice population from ethnic minority groups correlated negatively with uptake rates (r = -0.42), as did variables associated with social deprivation such as overcrowding (r = -0.42), not owning a car (r = -0.41), and unemployment (r = -0.40). Percentage of practice population under 5 years of age correlated positively with uptake rate (r = 0.42). Rates were higher in practices with a female partner than in those without (66.6% v 49.1%; difference 17.5% (95% confidence interval 10.5% to 24.5%)), and in computerised than in non-computerised practices (64.5% v 50.5%; 14.0% (6.4% to 21.6%)). Rates were higher in larger practices. In a stepwise multiple regression model that explained 52% of variation, five factors were significant predictors of uptake rates: presence of a female partner; children under 5; overcrowding; number of women aged 35-44 as percentage of all women aged 25-64; change of address in past year. CONCLUSIONS--Over half of variation in cervical smear uptake rates can be explained by patient and practice variables derived from census and family health services authority data; these variables may have a role in explaining variations in performance of general practices

  20. Interface failure modes explain non-monotonic size-dependent mechanical properties in bioinspired nanolaminates

    PubMed Central

    Song, Z. Q.; Ni, Y.; Peng, L. M.; Liang, H. Y.; He, L. H.

    2016-01-01

    Bioinspired discontinuous nanolaminate design becomes an efficient way to mitigate the strength-ductility tradeoff in brittle materials via arresting the crack at the interface followed by controllable interface failure. The analytical solution and numerical simulation based on the nonlinear shear-lag model indicates that propagation of the interface failure can be unstable or stable when the interfacial shear stress between laminae is uniform or highly localized, respectively. A dimensionless key parameter defined by the ratio of two characteristic lengths governs the transition between the two interface-failure modes, which can explain the non-monotonic size-dependent mechanical properties observed in various laminate composites. PMID:27029955

  1. Governance and performance: the performance of Dutch hospitals explained by governance characteristics.

    PubMed

    Blank, Jos L T; van Hulst, Bart Laurents

    2011-10-01

    This paper describes the efficiency of Dutch hospitals using the Data Envelopment Analysis (DEA) method with bootstrapping. In particular, the analysis focuses on accounting for cost inefficiency measures on the part of hospital corporate governance. We use bootstrap techniques, as introduced by Simar and Wilson (J. Econom. 136(1):31-64, 2007), in order to obtain more efficient estimates of the effects of governance on the efficiency. The results show that part of the cost efficiency can be explained with governance. In particular we find that a higher remuneration of the board as well as a higher remuneration of the supervisory board does not implicate better performance. PMID:20703757

  2. Transcript Abundance Explains mRNA Mobility Data in Arabidopsis thaliana[OPEN

    PubMed Central

    Calderwood, Alexander

    2016-01-01

    Recently, a large population of mRNA was shown to be able to travel between plant organs via sieve elements as a putative long-distance signaling molecule. However, a mechanistic basis by which transcripts are selected for transport has not yet been identified. Here, we show that experimental mRNA mobility data in Arabidopsis can be explained by transcript abundance and half-life. This suggests that the majority of identified mobile transcripts can be accounted for by non-sequence-specific movement of mRNA from companion cells into sieve elements. PMID:26952566

  3. Can a microscopic stochastic model explain the emergence of pain cycles in patients?

    NASA Astrophysics Data System (ADS)

    Di Patti, Francesca; Fanelli, Duccio

    2009-01-01

    A stochastic model is introduced here to investigate the molecular mechanisms which trigger the perception of pain. The action of analgesic drug compounds is discussed in a dynamical context, where the competition with inactive species is explicitly accounted for. Finite size effects inevitably perturb the mean-field dynamics: oscillations in the amount of bound receptors are spontaneously manifested, driven by the noise which is intrinsic to the system under scrutiny. These effects are investigated both numerically, via stochastic simulations, and analytically, through a large size expansion. The claim that our findings could provide a consistent interpretative framework for explaining the emergence of cyclic behaviors in response to analgesic treatments is substantiated.

  4. Can Self-Control Explain Avoiding Free Money? Evidence from Interest-Free Student Loans*

    PubMed Central

    Cadena, Brian C.; Keys, Benjamin J.

    2014-01-01

    This paper uses insights from behavioral economics to explain a particularly surprising borrowing phenomenon: One in six undergraduate students offered interest-free loans turn them down. Models of impulse control predict that students may optimally reject subsidized loans to avoid excessive consumption during school. Using the National Postsecondary Student Aid Study (NPSAS), we investigate students’ take-up decisions and identify a group of students for whom the loans create an especially tempting liquidity increase. Students who would receive the loan in cash are significantly more likely to turn it down, suggesting that consumers choose to limit their liquidity in economically meaningful situations. PMID:24839312

  5. Behavioral factors explaining the low risk for cervical carcinoma in Utah Mormon women.

    PubMed

    Gardner, J W; Sanborn, J S; Slattery, M L

    1995-03-01

    We used data from a population-based case-control study conducted in Utah from 1984 to 1987 to determine whether the low incidence of cervical carcinoma in Mormon women can be explained by adherence to their religious teachings, which proscribe smoking and extramarital sexual relations. Mormon women had substantially lower risk for cervical carcinoma than non-Mormons [odds ratio (OR) = 0.39; 95% confidence interval (CI) = 0.28-0.54]; this low risk was confined to those who attended church frequently. The protective effect disappeared after controlling for differences in age, sexual behavior, and smoking (OR = 1.22; 95% CI = 0.80-1.87). PMID:7742409

  6. A General Model of Negative Frequency Dependent Selection Explains Global Patterns of Human ABO Polymorphism.

    PubMed

    Villanea, Fernando A; Safi, Kristin N; Busch, Jeremiah W

    2015-01-01

    The ABO locus in humans is characterized by elevated heterozygosity and very similar allele frequencies among populations scattered across the globe. Using knowledge of ABO protein function, we generated a simple model of asymmetric negative frequency dependent selection and genetic drift to explain the maintenance of ABO polymorphism and its loss in human populations. In our models, regardless of the strength of selection, models with large effective population sizes result in ABO allele frequencies that closely match those observed in most continental populations. Populations must be moderately small to fall out of equilibrium and lose either the A or B allele (N(e) ≤ 50) and much smaller (N(e) ≤ 25) for the complete loss of diversity, which nearly always involved the fixation of the O allele. A pattern of low heterozygosity at the ABO locus where loss of polymorphism occurs in our model is consistent with small populations, such as Native American populations. This study provides a general evolutionary model to explain the observed global patterns of polymorphism at the ABO locus and the pattern of allele loss in small populations. Moreover, these results inform the range of population sizes associated with the recent human colonization of the Americas. PMID:25946124

  7. Can motor imagery and hypnotic susceptibility explain Conversion Disorder with motor symptoms?

    PubMed

    Srzich, Alexander J; Byblow, Winston D; Stinear, James W; Cirillo, John; Anson, J Greg

    2016-08-01

    Marked distortions in sense of agency can be induced by hypnosis in susceptible individuals, including alterations in subjective awareness of movement initiation and control. These distortions, with associated disability, are similar to those experienced with Conversion Disorder (CD), an observation that has led to the hypothesis that hypnosis and CD share causal mechanisms. The purpose of this review is to explore the relationships among motor imagery (MI), hypnotic susceptibility, and CD, then to propose how MI ability may contribute to hypnotic responding and CD. Studies employing subjective assessments of mental imagery have found little association between imagery abilities and hypnotic susceptibility. A positive association between imagery abilities and hypnotic susceptibility becomes apparent when objective measures of imagery ability are employed. A candidate mechanism to explain motor responses during hypnosis is kinaesthetic MI, which engages a strategy that involves proprioception or the "feel" of movement when no movement occurs. Motor suppression imagery (MSI), a strategy involving inhibition of movement, may provide an alternate objective measurable phenomenon that underlies both hypnotic susceptibility and CD. Evidence to date supports the idea that there may be a positive association between kinaesthetic MI ability and hypnotic susceptibility. Additional evidence supports a positive association between hypnotic susceptibility and CD. Disturbances in kinaesthetic MI performance in CD patients indicate that MI mechanisms may also underlie CD symptoms. Further investigation of the above relationships is warranted to explain these phenomena, and establish theoretical explanations underlying sense of agency. PMID:27346334

  8. Analysis of trans-Neptunian objects and a proposed theory to explain their origin

    NASA Astrophysics Data System (ADS)

    Brown, Robert B.; Firth, Jordan A.

    2016-02-01

    Current theories cannot explain how trans-Neptunian objects (TNOs) either formed in situ or how ultrawide trans-Neptunian binaries (TNBs) exist if they were formed closer to the Sun and were later dispersed during Neptune's migration. Furthermore, no theory can adequately explain the documented clustering of ω near 0° for TNOs with a > 150 au. Here, we show that not only is ω clustered for the nine long-period TNOs (LPTNOs) with a > 200 au, but Ω is also grouped almost as closely. Neither of these orbital elements is randomly distributed for any collection of TNOs investigated, including those that are not in resonance with Neptune, those with q > 30 au, q > 44 au, and LPTNOs. Every frequency distribution of ω and Ω indicates that many TNOs were recently affected by Neptune. Based on this study, we propose that TNOs were inside Neptune's orbit in the last few Myr. The TNOs then migrated outwards in a relatively short time period. Ultrawide TNBs never came close to Neptune during this migration, allowing these fragile pairs to remain intact. However, many other TNOs were perturbed as they passed Neptune, resulting in the distribution of orbital elements we see today for all TNOs, including those in the Kuiper belt and the LPTNOs.

  9. Mitochondrial Dysfunction may explain symptom variation in Phelan-McDermid Syndrome

    PubMed Central

    Frye, Richard E.; Cox, Devin; Slattery, John; Tippett, Marie; Kahler, Stephen; Granpeesheh, Doreen; Damle, Shirish; Legido, Agustin; Goldenthal, Michael J.

    2016-01-01

    Phelan-McDermid Syndrome (PMS), which is defined by a deletion within 22q13, demonstrates significant phenotypic variation. Given that six mitochondrial genes are located within 22q13, including complex I and IV genes, we hypothesize that mitochondrial complex activity abnormalities may explain phenotypic variation in PMS symptoms. Complex I, II, II + III and IV activity was measured in 51 PMS participants. Caretakers completed questionnaires and provided genetic information through the PMS foundation registry. Complex activity was abnormal in 59% of PMS participants. Abnormalities were found in complex I and IV but not complex II + III and II activity, consistent with disruption of genes within the 22q13 region. However, complex activity abnormalities were not related to specific gene deletions suggesting a “neighboring effect” of regional deletions on adjacent gene expression. A specific combination of symptoms (autism spectrum disorder, developmental regression, failure-to-thrive, exercise intolerance/fatigue) was associated with complex activity abnormalities. 64% of 106 individuals in the PMS foundation registry who did not have complex activity measured also endorsed this pattern of symptoms. These data suggest that mitochondrial abnormalities, specifically abnormalities in complex I and IV activity, may explain some phenotypic variation in PMS individuals. These results point to novel pathophysiology mechanisms and treatment targets for PMS patients. PMID:26822410

  10. Brain hemodynamic activity during viewing and re-viewing of comedy movies explained by experienced humor.

    PubMed

    Jääskeläinen, Iiro P; Pajula, Juha; Tohka, Jussi; Lee, Hsin-Ju; Kuo, Wen-Jui; Lin, Fa-Hsuan

    2016-01-01

    Humor is crucial in human social interactions. To study the underlying neural processes, three comedy clips were shown twice to 20 volunteers during functional magnetic resonance imaging (fMRI). Inter-subject similarities in humor ratings, obtained immediately after fMRI, explained inter-subject correlation of hemodynamic activity in right frontal pole and in a number of other brain regions. General linear model analysis also indicated activity in right frontal pole, as well as in additional cortical areas and subcortically in striatum, explained by humorousness. The association of the right frontal pole with experienced humorousness is a novel finding, which might be related to humor unfolding over longer time scales in the movie clips. Specifically, frontal pole has been shown to exhibit longer temporal receptive windows than, e.g., sensory areas, which might have enabled processing of humor in the clips based on holding information and reinterpreting that in light of new information several (even tens of) seconds later. As another novel finding, medial and lateral prefrontal areas, frontal pole, posterior-inferior temporal areas, posterior parietal areas, posterior cingulate, striatal structures and amygdala showed reduced activity upon re-viewing of the clips, suggesting involvement in processing of humor related to novelty of the comedic events. PMID:27323928

  11. Territoriality and Conflict Avoidance Explain Asociality (Solitariness) of the Endosymbiotic Pea Crab Tunicotheres moseri.

    PubMed

    Ambrosio, Louis J; Baeza, J Antonio

    2016-01-01

    Host monopolization theory predicts symbiotic organisms inhabiting morphologically simple, relatively small and scarce hosts to live solitarily as a result of territorial behaviors. We tested this prediction with Tunicotheres moseri, an endosymbiotic crab dwelling in the atrial chamber of the morphologically simple, small, and relatively scarce ascidian Styela plicata. As predicted, natural populations of T. moseri inhabit ascidian hosts solitarily with greater frequency than expected by chance alone. Furthermore, laboratory experiments demonstrated that intruder crabs take significantly longer to colonize previously infected compared to uninfected hosts, indicating as expected, that resident crabs exhibit monopolization behaviors. While territoriality does occur, agonistic behaviors employed by T. moseri do not mirror the overt behaviors commonly reported for other territorial crustaceans. Documented double and triple cohabitations in the field coupled with laboratory observations demonstrating the almost invariable success of intruder crabs colonizing occupied hosts, suggest that territoriality is ineffective in completely explaining the solitary social habit of this species. Additional experiments showed that T. moseri juveniles and adults, when searching for ascidians use chemical cues to avoid hosts occupied by conspecifics. This conspecific avoidance behavior reported herein is a novel strategy most likely employed to preemptively resolve costly territorial conflicts. In general, this study supports predictions central to host monopolization theory, but also implies that alternative behavioral strategies (i.e., conflict avoidance) may be more important than originally thought in explaining the host use pattern of symbiotic organisms. PMID:26910474

  12. Territoriality and Conflict Avoidance Explain Asociality (Solitariness) of the Endosymbiotic Pea Crab Tunicotheres moseri

    PubMed Central

    Ambrosio, Louis J.; Baeza, J. Antonio

    2016-01-01

    Host monopolization theory predicts symbiotic organisms inhabiting morphologically simple, relatively small and scarce hosts to live solitarily as a result of territorial behaviors. We tested this prediction with Tunicotheres moseri, an endosymbiotic crab dwelling in the atrial chamber of the morphologically simple, small, and relatively scarce ascidian Styela plicata. As predicted, natural populations of T. moseri inhabit ascidian hosts solitarily with greater frequency than expected by chance alone. Furthermore, laboratory experiments demonstrated that intruder crabs take significantly longer to colonize previously infected compared to uninfected hosts, indicating as expected, that resident crabs exhibit monopolization behaviors. While territoriality does occur, agonistic behaviors employed by T. moseri do not mirror the overt behaviors commonly reported for other territorial crustaceans. Documented double and triple cohabitations in the field coupled with laboratory observations demonstrating the almost invariable success of intruder crabs colonizing occupied hosts, suggest that territoriality is ineffective in completely explaining the solitary social habit of this species. Additional experiments showed that T. moseri juveniles and adults, when searching for ascidians use chemical cues to avoid hosts occupied by conspecifics. This conspecific avoidance behavior reported herein is a novel strategy most likely employed to preemptively resolve costly territorial conflicts. In general, this study supports predictions central to host monopolization theory, but also implies that alternative behavioral strategies (i.e., conflict avoidance) may be more important than originally thought in explaining the host use pattern of symbiotic organisms. PMID:26910474

  13. Contamination cannot explain the lack of large-scale power in the cosmic microwave background radiation

    SciTech Connect

    Bunn, Emory F.; Bourdon, Austin

    2008-12-15

    Several anomalies appear to be present in the large-angle cosmic microwave background (CMB) anisotropy maps of the Wilkinson Microwave Anisotropy Probe. One of these is a lack of large-scale power. Because the data otherwise match standard models extremely well, it is natural to consider perturbations of the standard model as possible explanations. We show that, as long as the source of the perturbation is statistically independent of the source of the primary CMB anisotropy, no such model can explain this large-scale power deficit. On the contrary, any such perturbation always reduces the probability of obtaining any given low value of large-scale power. We rigorously prove this result when the lack of large-scale power is quantified with a quadratic statistic, such as the quadrupole moment. When a statistic based on the integrated square of the correlation function is used instead, we present strong numerical evidence in support of the result. The result applies to models in which the geometry of spacetime is perturbed (e.g., an ellipsoidal universe) as well as explanations involving local contaminants, undiagnosed foregrounds, or systematic errors. Because the large-scale power deficit is arguably the most significant of the observed anomalies, explanations that worsen this discrepancy should be regarded with great skepticism, even if they help in explaining other anomalies such as multipole alignments.

  14. High Poisson's ratio of Earth's inner core explained by carbon alloying

    NASA Astrophysics Data System (ADS)

    Prescher, C.; Dubrovinsky, L.; Bykova, E.; Kupenko, I.; Glazyrin, K.; Kantor, A.; McCammon, C.; Mookherjee, M.; Nakajima, Y.; Miyajima, N.; Sinmyo, R.; Cerantola, V.; Dubrovinskaia, N.; Prakapenka, V.; Rüffer, R.; Chumakov, A.; Hanfland, M.

    2015-03-01

    Geochemical, cosmochemical, geophysical, and mineral physics data suggest that iron (or iron-nickel alloy) is the main component of the Earth’s core. The inconsistency between the density of pure iron at pressure and temperature conditions of the Earth’s core and seismological observations can be explained by the presence of light elements. However, the low shear wave velocity and high Poisson’s ratio of the Earth’s core remain enigmatic. Here we experimentally investigate the effect of carbon on the elastic properties of iron at high pressures and temperatures and report a high-pressure orthorhombic phase of iron carbide, Fe7C3. We determined the crystal structure of the material at ambient conditions and investigated its stability and behaviour at pressures up to 205 GPa and temperatures above 3,700 K using single-crystal and powder X-ray diffraction, Mössbauer spectroscopy, and nuclear inelastic scattering. Estimated shear wave and compressional wave velocities show that Fe7C3 exhibits a lower shear wave velocity than pure iron and a Poisson’s ratio similar to that of the Earth’s inner core. We suggest that carbon alloying significantly modifies the properties of iron at extreme conditions to approach the elastic behaviour of rubber. Thus, the presence of carbon may explain the anomalous elastic properties of the Earth’s core.

  15. Selection against Heteroplasmy Explains the Evolution of Uniparental Inheritance of Mitochondria

    PubMed Central

    Christie, Joshua R.; Schaerf, Timothy M.; Beekman, Madeleine

    2015-01-01

    Why are mitochondria almost always inherited from one parent during sexual reproduction? Current explanations for this evolutionary mystery include conflict avoidance between the nuclear and mitochondrial genomes, clearing of deleterious mutations, and optimization of mitochondrial-nuclear coadaptation. Mathematical models, however, fail to show that uniparental inheritance can replace biparental inheritance under any existing hypothesis. Recent empirical evidence indicates that mixing two different but normal mitochondrial haplotypes within a cell (heteroplasmy) can cause cell and organism dysfunction. Using a mathematical model, we test if selection against heteroplasmy can lead to the evolution of uniparental inheritance. When we assume selection against heteroplasmy and mutations are neither advantageous nor deleterious (neutral mutations), uniparental inheritance replaces biparental inheritance for all tested parameter values. When heteroplasmy involves mutations that are advantageous or deleterious (non-neutral mutations), uniparental inheritance can still replace biparental inheritance. We show that uniparental inheritance can evolve with or without pre-existing mating types. Finally, we show that selection against heteroplasmy can explain why some organisms deviate from strict uniparental inheritance. Thus, we suggest that selection against heteroplasmy explains the evolution of uniparental inheritance. PMID:25880558

  16. Functional traits help to explain half-century long shifts in pollinator distributions

    PubMed Central

    Aguirre-Gutiérrez, Jesús; Kissling, W. Daniel; Carvalheiro, Luísa G.; WallisDeVries, Michiel F.; Franzén, Markus; Biesmeijer, Jacobus C.

    2016-01-01

    Changes in climate and land use can have important impacts on biodiversity. Species respond to such environmental modifications by adapting to new conditions or by shifting their geographic distributions towards more suitable areas. The latter might be constrained by species’ functional traits that influence their ability to move, reproduce or establish. Here, we show that functional traits related to dispersal, reproduction, habitat use and diet have influenced how three pollinator groups (bees, butterflies and hoverflies) responded to changes in climate and land-use in the Netherlands since 1950. Across the three pollinator groups, we found pronounced areal range expansions (>53%) and modelled range shifts towards the north (all taxa: 17–22 km), west (bees: 14 km) and east (butterflies: 11 km). The importance of specific functional traits for explaining distributional changes varied among pollinator groups. Larval diet preferences (i.e. carnivorous vs. herbivorous/detritivorous and nitrogen values of host plants, respectively) were important for hoverflies and butterflies, adult body size for hoverflies, and flight period length for all groups. Moreover, interactions among multiple traits were important to explain species’ geographic range shifts, suggesting that taxon-specific multi-trait analyses are needed to predict how global change will affect biodiversity and ecosystem services. PMID:27079784

  17. Individual-area relationship best explains goose species density in wetlands.

    PubMed

    Zhang, Yong; Jia, Qiang; Prins, Herbert H T; Cao, Lei; de Boer, Willem Fred

    2015-01-01

    Explaining and predicting animal distributions is one of the fundamental objectives in ecology and conservation biology. Animal habitat selection can be regulated by top-down and bottom-up processes, and is mediated by species interactions. Species varying in body size respond differently to top-down and bottom-up determinants, and hence understanding these allometric responses to those determinants is important for conservation. In this study, using two differently sized goose species wintering in the Yangtze floodplain, we tested the predictions derived from three different hypotheses (individual-area relationship, food resource and disturbance hypothesis) to explain the spatial and temporal variation in densities of two goose species. Using Generalized Linear Mixed Models with a Markov Chain Monte Carlo technique, we demonstrated that goose density was positive correlated with patch area size, suggesting that the individual area-relationship best predicts differences in goose densities. Moreover, the other predictions, related to food availability and disturbance, were not significant. Buffalo grazing probably facilitated greater white-fronted geese, as the number of buffalos was positively correlated to the density of this species. We concluded that patch area size is the most important factor determining the density of goose species in our study area. Patch area size is directly determined by water levels in the Yangtze floodplain, and hence modifying the hydrological regimes can enlarge the capacity of these wetlands for migratory birds. PMID:25996502

  18. The Right Ventricle Explains Sex Differences in Survival in Idiopathic Pulmonary Arterial Hypertension

    PubMed Central

    Jacobs, Wouter; van de Veerdonk, Mariëlle C.; Trip, Pia; de Man, Frances; Heymans, Martijn W.; Marcus, Johannes T.; Kawut, Steven M.; Bogaard, Harm-Jan; Boonstra, Anco

    2014-01-01

    Background: Male sex is an independent predictor of worse survival in pulmonary arterial hypertension (PAH). This finding might be explained by more severe pulmonary vascular disease, worse right ventricular (RV) function, or different response to therapy. The aim of this study was to investigate the underlying cause of sex differences in survival in patients treated for PAH. Methods: This was a retrospective cohort study of 101 patients with PAH (82 idiopathic, 15 heritable, four anorexigen associated) who were diagnosed at VU University Medical Centre between February 1999 and January 2011 and underwent right-sided heart catheterization and cardiac MRI to assess RV function. Change in pulmonary vascular resistance (PVR) was taken as a measure of treatment response in the pulmonary vasculature, whereas change in RV ejection fraction (RVEF) was used to assess RV response to therapy. Results: PVR and RVEF were comparable between men and women at baseline; however, male patients had a worse transplant-free survival compared with female patients (P = .002). Although male and female patients showed a similar reduction in PVR after 1 year, RVEF improved in female patients, whereas it deteriorated in male patients. In a mediator analysis, after correcting for confounders, 39.0% of the difference in transplant-free survival between men and women was mediated through changes in RVEF after initiating PAH medical therapies. Conclusions: This study suggests that differences in RVEF response with initiation of medical therapy in idiopathic PAH explain a significant portion of the worse survival seen in men. PMID:24306900

  19. Personality and problem-solving performance explain competitive ability in the wild

    PubMed Central

    Cole, Ella F.; Quinn, John L.

    2012-01-01

    Competitive ability is a major determinant of fitness, but why individuals vary so much in their competitiveness remains only partially understood. One increasingly prevalent view is that realized competitive ability varies because it represents alternative strategies that arise because of the costs associated with competitiveness. Here we use a population of great tits (Parus major) to explore whether individual differences in competitive ability when foraging can be explained by two traits that have previously been linked to alternative behavioural strategies: the personality trait ‘exploration behaviour’ and a simple cognitive trait, ‘innovative problem-solving performance’. We assayed these traits under standardized conditions in captivity and then measured competitive ability at feeders with restricted access in the wild. Competitive ability was repeatable within individual males across days and correlated positively with exploration behaviour, representing the first such demonstration of a link between a personality trait and both competitive ability and food intake in the wild. Competitive ability was also simultaneously negatively correlated with problem-solving performance; individuals who were poor competitors were good at problem-solving. Rather than being the result of variation in ‘individual quality’, our results support the hypothesis that individual variation in competitive ability can be explained by alternative behavioural strategies. PMID:21937498

  20. A model explaining synchronization of neuron bioelectric frequency under weak alternating low frequency magnetic field

    NASA Astrophysics Data System (ADS)

    del Moral, A.; Azanza, María J.

    2015-03-01

    A biomagnetic-electrical model is presented that explains rather well the experimentally observed synchronization of the bioelectric potential firing rate ("frequency"), f, of single unit neurons of Helix aspersa mollusc under the application of extremely low frequency (ELF) weak alternating (AC) magnetic fields (MF). The proposed model incorporates to our widely experimentally tested model of superdiamagnetism (SD) and Ca2+ Coulomb explosion (CE) from lipid (LP) bilayer membrane (SD-CE model), the electrical quadrupolar long range interaction between the bilayer LP membranes of synchronized neuron pairs, not considered before. The quadrupolar interaction is capable of explaining well the observed synchronization. Actual extension of our SD-CE-model shows that the neuron firing frequency field, B, dependence becomes not modified, but the bioelectric frequency is decreased and its spontaneous temperature, T, dependence is modified. A comparison of the model with synchronization experimental results of pair of neurons under weak (B0 ≅0.2-15 mT) AC-MF of frequency fM=50 Hz is reported. From the deduced size of synchronized LP clusters under B, is suggested the formation of small neuron networks via the membrane lipid correlation.

  1. AMEND: A Model Explaining Neutrino masses and Dark matter testable at the LHC and MEG

    NASA Astrophysics Data System (ADS)

    Farzan, Yasaman; Pascoli, Silvia; Schmidt, Michael A.

    2010-10-01

    Despite being very successful in explaining the wide range of precision experimental results obtained so far, the Standard Model (SM) of elementary particles fails to address two of the greatest observations of the recent decades: tiny but nonzero neutrino masses and the well-known problem of missing mass in the Universe. Typically the new models beyond the SM explain only one of these observations. Instead, in the present article, we take the view that they both point towards the same new extension of the Standard Model. The new particles introduced are responsible simultaneously for neutrino masses and for the dark matter of the Universe. The stability of dark matter and the smallness of neutrino masses are guaranteed by a U(1) global symmetry, broken to a remnant {mathbb{Z}_2} . The canonical seesaw mechanism is forbidden and neutrino masses emerge at the loop level being further suppressed by the small explicit breaking of the U(1) symmetry. The new particles and interactions are invoked at the electroweak scale and lead to rich phenomenology in colliders, in lepton flavour violating rare decays and in direct and indirect dark matter searches, making the model testable in the coming future.

  2. Causal trait theories: a new form of person knowledge that explains egocentric pattern projection.

    PubMed

    Critcher, Clayton R; Dunning, David; Rom, Sarah C

    2015-03-01

    Representations of the self and others include not only piecemeal traits but also causal trait theories-explanations for why a person's standing on 1 trait causes or is caused by standings on other traits (Studies 1a-1c). These causal theories help resolve the puzzle of egocentric pattern projection-the tendency for people to assume that traits correlate in the population in the same way they align in the self. Causal trait theories-created to explain trait co-occurrence in a single person-are exported to guide one's implicit personality theories about people in general (Study 2). Pattern projection was found to be largely egocentric (i.e., more strong guided by self- than by social perceptions) for 2 reasons. First, causal trait theories are more numerous for the self. When participants were prompted to generate causal trait theories about someone else, they pattern projected more from that person (Study 3). Second, causal trait theories about the self are more likely to draw on behavioral information from multiple contexts instead of merely seeking to explain why 2 traits co-occur in a single context. Causal trait theories based on trait-relevant behaviors from different contexts, instead of trait co-occurrence within a single context, produce more pattern projection (Study 4). Implications for self and social cognition are discussed. PMID:25643223

  3. Sexual dimorphism in venom chemistry in Tetragnatha spiders is not easily explained by adult niche differences.

    PubMed

    Binford, Greta J; Gillespie, Rosemary G; Maddison, Wayne P

    2016-05-01

    Spider venom composition typically differs between sexes. This pattern is anecdotally thought to reflect differences in adult feeding biology. We used a phylogenetic approach to compare intersexual venom dimorphism between species that differ in adult niche dimorphism. Male and female venoms were compared within and between related species of Hawaiian Tetragnatha, a mainland congener, and outgroups. In some species of Hawaiian Tetragnatha adult females spin orb-webs and adult males capture prey while wandering, while in other species both males and females capture prey by wandering. We predicted that, if venom sexual dimorphism is primarily explained by differences in adult feeding biology, species in which both sexes forage by wandering would have monomorphic venoms or venoms with reduced dimorphism relative to species with different adult feeding biology. However, we found striking sexual dimorphism in venoms of both wandering and orb-weaving Tetragnatha species with males having high molecular weight components in their venoms that were absent in females, and a reduced concentration of low molecular weight components relative to females. Intersexual differences in venom composition within Tetragnatha were significantly larger than in non-Tetragnatha species. Diet composition was not different between sexes. This striking venom dimorphism is not easily explained by differences in feeding ecology or behavior. Rather, we hypothesize that the dimorphism reflects male-specific components that play a role in mating biology possibly in sexual stimulation, nuptial gifts and/or mate recognition. PMID:26908290

  4. Can selection on nest size from nest predation explain the latitudinal gradient in clutch size?

    USGS Publications Warehouse

    Biancucci, L.; Martin, T.E.

    2010-01-01

    1. Latitudinal variation in clutch sizes of birds is a well described, but poorly understood pattern. Many hypotheses have been proposed, but few have been experimentally tested, and none have been universally accepted by researchers. 2. The nest size hypothesis posits that higher nest predation in the tropics favours selection for smaller nests and thereby constrains clutch size by shrinking available space for eggs and/or nestlings in the nest. We tested this hypothesis with an experiment in a tropical forest and a comparative study between temperate and tropical field sites. 3. Specifically, we tested if: (i) predation increased with nest size; (ii) tropical birds had smaller nests controlled for body size; and (iii) clutch size was explained by nest size controlled for body size. 4. Experimental swapping of nests of different sizes showed that nest predation increased with nest size in the tropical site. Moreover, nest predation rates were higher in species with larger nests in both sites. However, nest size, corrected for body mass and phylogeny, did not differ between sites and was not related to clutch size between sites. 5. Hence, nest predation can exert selection on nest size as predicted by the hypothesis. Nest size increased with adult body mass, such that adult size might indirectly influence reproductive success through effects on nest size and nest predation risk. Ultimately, however, selection from nest predation on nest size does not explain the smaller clutch sizes typical of the tropics.

  5. Explaining the t - t¯ asymmetry with a light axigluon

    DOE PAGESBeta

    Marques Tavares, Gustavo; Schmaltz, Martin

    2011-09-12

    We propose an axigluon with mass between 400 and 450 GeV and flavor-universal couplings to quarks to explain the Tevatron t -t¯ forward-backward asymmetry. The model predicts a small negative asymmetry for t - t¯ pairs with invariant mass below 450 GeV and a large positive asymmetry above 450 GeV. The asymmetry arises from interference between s-channel gluon and axigluon diagrams and requires a relatively weakly coupled axigluon (ga=gqcd/3). Axigluon-gluon interference does not contribute to the t - t¯ cross section. New contributions to the cross section arise only at fourth order in the axigluon coupling and are very smallmore » for a sufficiently broad axigluon. Dijet measurements do not significantly constrain the axigluon couplings. We propose several possible UV completions of the phenomenological axigluon which explain the required small couplings and large width. Such UV completions necessarily contain new colored fermions or scalars below the axigluon mass and predict multijet events with large cross sections at the Tevatron and LHC.« less

  6. Changes in materials properties explain the effects of humidity on gecko adhesion.

    PubMed

    Puthoff, Jonathan B; Prowse, Michael S; Wilkinson, Matt; Autumn, Kellar

    2010-11-01

    Geckos owe their remarkable stickiness to millions of dry setae on their toes, and the mechanism of adhesion in gecko setae has been the topic of scientific scrutiny for over two centuries. Previously, we demonstrated that van der Waals forces are sufficient for strong adhesion and friction in gecko setae, and that water-based capillary adhesion is not required. However, recent studies demonstrated that adhesion increases with relative humidity (RH) and proposed that surface hydration and capillary water bridge formation is important or even necessary. In this study, we confirmed a significant effect of RH on gecko adhesion, but rejected the capillary adhesion hypothesis. While contact forces of isolated tokay gecko setal arrays increased with humidity, the increase was similar on hydrophobic and hydrophilic surfaces, inconsistent with a capillary mechanism. Contact forces increased with RH even at high shear rates, where capillary bridge formation is too slow to affect adhesion. How then can a humidity-related increase in adhesion and friction be explained? The effect of RH on the mechanical properties of setal β-keratin has escaped consideration until now. We discovered that an increase in RH softens setae and increases viscoelastic damping, which increases adhesion. Changes in setal materials properties, not capillary forces, fully explain humidity-enhanced adhesion, and van der Waals forces remain the only empirically supported mechanism of adhesion in geckos. PMID:20952618

  7. Explained and unexplained tissue loss in corals from the Tropical Eastern Pacific.

    PubMed

    Rodríguez-Villalobos, Jenny Carolina; Work, Thierry Martin; Calderon-Aguilera, Luis Eduardo; Reyes-Bonilla, Héctor; Hernández, Luis

    2015-10-16

    Coral reefs rival rainforest in biodiversity, but are declining in part because of disease. Tissue loss lesions, a manifestation of disease, are present in dominant Pocillopora along the Pacific coast of Mexico. We characterized tissue loss in 7 species of Pocillopora from 9 locations (44 sites) spanning southern to northern Mexico. Corals were identified to species, and tissue loss lesions were photographed and classified as those explainable by predation and those that were unexplained. A focal predation study was done concurrently at 3 locations to confirm origin of explained lesions. Of 1054 cases of tissue loss in 7 species of corals, 84% were associated with predation (fish, snails, or seastar) and the remainder were unexplained. Types of tissue loss were not related to coral density; however there was significant geographic heterogeneity in type of lesion; one site in particular (Cabo Pulmo) had the highest prevalence of predator-induced tissue loss (mainly pufferfish predation). Crown-of-thorns starfish, pufferfish, and snails were the most common predators and preferred P. verrucosa, P. meandrina, and P. capitata, respectively. Of the 9 locations, 4 had unexplained tissue loss with prevalence ranging from 1 to 3% with no species predilection. Unexplained tissue loss was similar to white syndrome (WS) in morphology, indicating additional study is necessary to clarify the cause(s) of the lesions and the potential impacts to dominant corals along the Pacific coast of Mexico. PMID:26480915

  8. Declines in the Lethality of Suicide Attempts Explain the Decline in Suicide Deaths in Australia

    PubMed Central

    Spittal, Matthew J.; Pirkis, Jane; Miller, Matthew; Studdert, David M.

    2012-01-01

    Background To investigate the epidemiology of a steep decrease in the incidence of suicide deaths in Australia. Methods National data on suicide deaths and deliberate self-harm for the period 1994–2007 were obtained from the Australian Institute of Health and Welfare. We calculated attempt and death rates for five major methods and the lethality of these methods. Negative binomial regression was used to estimate the size and significance of method-specific time-trends in attempts and lethality. Results Hanging, motor vehicle exhaust and firearms were the most lethal methods, and together accounted for 72% of all deaths. The lethality of motor vehicle exhaust attempts decreased sharply (RR = 0.94 per year, 95% CI 0.93–0.95) while the motor vehicle exhaust attempt rate changed little; this combination of motor vehicle exhaust trends explained nearly half of the overall decline in suicide deaths. Hanging lethality also decreased sharply (RR = 0.96 per year, 95% CI 0.956–0.965) but large increases in hanging attempts negated the effect on death rates. Firearm lethality changed little while attempts decreased. Conclusion Declines in the lethality of suicide attempts–especially attempts by motor vehicle exhaust and hanging–explain the remarkable decline in deaths by suicide in Australia since 1997. PMID:22957084

  9. Explaining the differences in income-related health inequalities across European countries.

    PubMed

    van Doorslaer, Eddy; Koolman, Xander

    2004-07-01

    This paper provides new evidence on the sources of differences in the degree of income-related inequalities in self-assessed health in 13 European Union member states. It goes beyond earlier work by measuring health using an interval regression approach to compute concentration indices and by decomposing inequality into its determining factors. New and more comparable data were used, taken from the 1996 wave of the European Community Household Panel. Significant inequalities in health (utility) favouring the higher income groups emerge in all countries, but are particularly high in Portugal and - to a lesser extent - in the UK and in Denmark. By contrast, relatively low health inequality is observed in the Netherlands and Germany, and also in Italy, Belgium, Spain Austria and Ireland. There is a positive correlation with income inequality per se but the relationship is weaker than in previous research. Health inequality is not merely a reflection of income inequality. A decomposition analysis shows that the (partial) income elasticities of the explanatory variables are generally more important than their unequal distribution by income in explaining the cross-country differences in income-related health inequality. Especially the relative health and income position of non-working Europeans like the retired and disabled explains a great deal of 'excess inequality'. We also find a substantial contribution of regional health disparities to socio-economic inequalities, primarily in the Southern European countries. PMID:15259042

  10. Reduced methane growth rate explained by decreased Northern Hemisphere microbial sources.

    PubMed

    Kai, Fuu Ming; Tyler, Stanley C; Randerson, James T; Blake, Donald R

    2011-08-11

    Atmospheric methane (CH(4)) increased through much of the twentieth century, but this trend gradually weakened until a stable state was temporarily reached around the turn of the millennium, after which levels increased once more. The reasons for the slowdown are incompletely understood, with past work identifying changes in fossil fuel, wetland and agricultural sources and hydroxyl (OH) sinks as important causal factors. Here we show that the late-twentieth-century changes in the CH(4) growth rates are best explained by reduced microbial sources in the Northern Hemisphere. Our results, based on synchronous time series of atmospheric CH(4) mixing and (13)C/(12)C ratios and a two-box atmospheric model, indicate that the evolution of the mixing ratio requires no significant change in Southern Hemisphere sources between 1984 and 2005. Observed changes in the interhemispheric difference of (13)C effectively exclude reduced fossil fuel emissions as the primary cause of the slowdown. The (13)C observations are consistent with long-term reductions in agricultural emissions or another microbial source within the Northern Hemisphere. Approximately half (51 ± 18%) of the decrease in Northern Hemisphere CH(4) emissions can be explained by reduced emissions from rice agriculture in Asia over the past three decades associated with increases in fertilizer application and reductions in water use. PMID:21833086

  11. Ability of matrix models to explain the past and predict the future of plant populations.

    USGS Publications Warehouse

    McEachern, Kathryn; Crone, Elizabeth E.; Ellis, Martha M.; Morris, William F.; Stanley, Amanda; Bell, Timothy; Bierzychudek, Paulette; Ehrlen, Johan; Kaye, Thomas N.; Knight, Tiffany M.; Lesica, Peter; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Ticktin, Tamara; Valverde, Teresa; Williams, Jennifer I.; Doak, Daniel F.; Ganesan, Rengaian; Thorpe, Andrea S.; Menges, Eric S.

    2013-01-01

    Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage-based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts' 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data-collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk-averse decisions than to expect precise forecasts from models.

  12. The role of perspective taking in how children connect reference frames when explaining astronomical phenomena

    NASA Astrophysics Data System (ADS)

    Plummer, Julia D.; Bower, Corinne A.; Liben, Lynn S.

    2016-02-01

    This study investigates the role of perspective-taking skills in how children explain spatially complex astronomical phenomena. Explaining many astronomical phenomena, especially those studied in elementary and middle school, requires shifting between an Earth-based description of the phenomena and a space-based reference frame. We studied 7- to 9-year-old children (N = 15) to (a) develop a method for capturing how children make connections between reference frames and to (b) explore connections between perspective-taking skill and the nature of children's explanations. Children's explanations for the apparent motion of the Sun and stars and for seasonal changes in constellations were coded for accuracy of explanation, connection between frames of reference, and use of gesture. Children with higher spatial perspective-taking skills made more explicit connections between reference frames and used certain gesture-types more frequently, although this pattern was evident for only some phenomena. Findings suggest that children - particularly those with lower perspective-taking skills - may need additional support in learning to explicitly connect reference frames in astronomy. Understanding spatial thinking among children who successfully made explicit connections between reference frames in their explanations could be a starting point for future instruction in this domain.

  13. CAN A LONG NANOFLARE STORM EXPLAIN THE OBSERVED EMISSION MEASURE DISTRIBUTIONS IN ACTIVE REGION CORES?

    SciTech Connect

    Mulu-Moore, Fana M.; Winebarger, Amy R.; Warren, Harry P.

    2011-11-20

    All theories that attempt to explain the heating of the high-temperature plasma observed in the solar corona are based on short bursts of energy. The intensities and velocities measured in the cores of quiescent active regions, however, can be steady over many hours of observation. One heating scenario that has been proposed to reconcile such observations with impulsive heating models is the 'long nanoflare storm', where short-duration heating events occur infrequently on many sub-resolution strands; the emission of the strands is then averaged together to explain the observed steady structures. In this Letter, we examine the emission measure distribution predicted for such a long nanoflare storm by modeling an arcade of strands in an active region core. Comparisons of the computed emission measure distributions with recent observations indicate that the long nanoflare storm scenario implies greater than five times more 1 MK emission than is actually observed for all plausible combinations of loop lengths, heating rates, and abundances. We conjecture that if the plasma had 'super coronal' abundances, the model may be able to match the observations at low temperatures.

  14. Explaining age differences in women's emotional well-being: The role of subjective experiences of aging.

    PubMed

    Barrett, Anne E; Toothman, Erica L

    2016-01-01

    Our study examines explanations for the "paradox" of older women's better emotional well-being compared with younger women. We consider the role of subjective experiences of aging in a society that devalues older women. Using a sample of women (n = 872) from the National Survey of Midlife Development in the United States (1995-1996 and 2004-2006), we examine the role of five components of the subjective experience of aging in explaining older women's better emotional well-being compared with younger women: age identity, conceptions of the timing of middle age, aging attitudes, aging anxieties, and self-assessed physiological changes. We find that, compared with women 50-54 years old, those 35-39 years old report lower positive affect, and those 25-49 report higher negative affect. These patterns are partially explained by younger women's greater anxiety about declines in health and attractiveness and older women's more youthful identities. Our study underscores the value of considering the implications of our ageist and sexist society for women's emotional well-being across adulthood. PMID:27029460

  15. Explaining the power-law distribution of human mobility through transportation modality decomposition.

    PubMed

    Zhao, Kai; Musolesi, Mirco; Hui, Pan; Rao, Weixiong; Tarkoma, Sasu

    2015-01-01

    Human mobility has been empirically observed to exhibit Lévy flight characteristics and behaviour with power-law distributed jump size. The fundamental mechanisms behind this behaviour has not yet been fully explained. In this paper, we propose to explain the Lévy walk behaviour observed in human mobility patterns by decomposing them into different classes according to the different transportation modes, such as Walk/Run, Bike, Train/Subway or Car/Taxi/Bus. Our analysis is based on two real-life GPS datasets containing approximately 10 and 20 million GPS samples with transportation mode information. We show that human mobility can be modelled as a mixture of different transportation modes, and that these single movement patterns can be approximated by a lognormal distribution rather than a power-law distribution. Then, we demonstrate that the mixture of the decomposed lognormal flight distributions associated with each modality is a power-law distribution, providing an explanation to the emergence of Lévy Walk patterns that characterize human mobility patterns. PMID:25779306

  16. Explaining topic prevalence in answers to open-ended survey questions about climate change

    NASA Astrophysics Data System (ADS)

    Tvinnereim, Endre; Fløttum, Kjersti

    2015-08-01

    Citizens’ opinions are crucial for action on climate change, but are, owing to the complexity of the issue, diverse and potentially unformed. We contribute to the understanding of public views on climate change and to knowledge needed by decision-makers by using a new approach to analyse answers to the open survey question `what comes to mind when you hear the words `climate change’?’. We apply automated text analysis, specifically structural topic modelling, which induces distinct topics based on the relative frequencies of the words used in 2,115 responses. From these data, originating from the new, nationally representative Norwegian Citizen Panel, four distinct topics emerge: Weather/Ice, Future/Impact, Money/Consumption and Attribution. We find that Norwegians emphasize societal aspects of climate change more than do respondents in previous US and UK studies. Furthermore, variables that explain variation in closed questions, such as gender and education, yield different and surprising results when employed to explain variation in what respondents emphasize. Finally, the sharp distinction between scepticism and acceptance of conventional climate science, often seen in previous studies, blurs in many textual responses as scepticism frequently turns into ambivalence.

  17. Do severity measures explain differences in length of hospital stay? The case of hip fracture.

    PubMed Central

    Shwartz, M; Iezzoni, L I; Ash, A S; Mackiernan, Y D

    1996-01-01

    OBJECTIVE: To examine whether judgments about hospital length of stay (LOS) vary depending on the measure used to adjust for severity differences. DATA SOURCES/STUDY SETTING: Data on admissions to 80 hospitals nationwide in the 1992 MedisGroups Comparative Database. STUDY DESIGN: For each of 14 severity measures, LOS was regressed on patient age/sex, DRG, and severity score. Regressions were performed on trimmed and untrimmed data. R-squared was used to evaluate model performance. For each severity measure for each hospital, we calculated the expected LOS and the z-score, a measure of the deviation of observed from expected LOS. We ranked hospitals by z-scores. DATA EXTRACTION: All patients admitted for initial surgical repair of a hip fracture, defined by DRG, diagnosis, and procedure codes. PRINCIPAL FINDINGS: The 5,664 patients had a mean (s.d.) LOS of 11.9 (8.9) days. Cross-validated R-squared values from the multivariable regressions (trimmed data) ranged from 0.041 (Comorbidity Index) to 0.165 (APR-DRGs). Using untrimmed data, observed average LOS for hospitals ranged from 7.6 to 23.9 days. The 14 severity measures showed excellent agreement in ranking hospitals based on z-scores. No severity measure explained the differences between hospitals with the shortest and longest LOS. CONCLUSIONS: Hospitals differed widely in their mean LOS for hip fracture patients, and severity adjustment did little to explain these differences. PMID:8885854

  18. Explaining Vegetable Consumption among Young Adults: An Application of the Theory of Planned Behaviour

    PubMed Central

    Menozzi, Davide; Sogari, Giovanni; Mora, Cristina

    2015-01-01

    Although fruit and vegetable consumption is highly recommended for a healthy and balanced daily diet, several European countries do not meet these recommendations. In Italy, only 45% of young people are consuming at least one portion of vegetables per day. Therefore, this paper aims to understand the main determinants of vegetables consumption among young adults to suggest possible intervention strategies. A cross-sectional study was conducted on a samples of Italian students (n = 751), using the theory of planned behaviour (TPB) as a conceptual framework. A structural equation model (SEM) was developed to test the TPB predictors for vegetable consumption, and the role of background factors (socio-demographic and personal characteristics) in improving the TPB model’s explaining power. Overall, 81% and 68%, respectively, of intentions and behaviour variance is explained by the TPB model. Socio-demographic and personal characteristics were found to influence intentions and behaviour indirectly by their effects on the theory’s more proximal determinants. Interventions should be targeted to improve perceived behavioural control (PBC), attitudes and subjective norms that significantly affect intentions. Tailored interventions for male students, enrolled in courses other than food science, and doing less physical activity may have a larger effect on behavioural change. PMID:26378570

  19. Explaining Vegetable Consumption among Young Adults: An Application of the Theory of Planned Behaviour.

    PubMed

    Menozzi, Davide; Sogari, Giovanni; Mora, Cristina

    2015-09-01

    Although fruit and vegetable consumption is highly recommended for a healthy and balanced daily diet, several European countries do not meet these recommendations. In Italy, only 45% of young people are consuming at least one portion of vegetables per day. Therefore, this paper aims to understand the main determinants of vegetables consumption among young adults to suggest possible intervention strategies. A cross-sectional study was conducted on a samples of Italian students (n = 751), using the theory of planned behaviour (TPB) as a conceptual framework. A structural equation model (SEM) was developed to test the TPB predictors for vegetable consumption, and the role of background factors (socio-demographic and personal characteristics) in improving the TPB model's explaining power. Overall, 81% and 68%, respectively, of intentions and behaviour variance is explained by the TPB model. Socio-demographic and personal characteristics were found to influence intentions and behaviour indirectly by their effects on the theory's more proximal determinants. Interventions should be targeted to improve perceived behavioural control (PBC), attitudes and subjective norms that significantly affect intentions. Tailored interventions for male students, enrolled in courses other than food science, and doing less physical activity may have a larger effect on behavioural change. PMID:26378570

  20. Explaining Spatial Variability in Wellbore Impairment Risk for Pennsylvania Oil and Gas Wells, 2000-2014

    NASA Astrophysics Data System (ADS)

    Santoro, R.; Ingraffea, A. R.

    2015-12-01

    Previous modeling (ingraffea et al. PNAS, 2014) indicated roughly two-times higher cumulative risk for wellbore impairment in unconventional wells, relative to conventional wells, and large spatial variation in risk for oil and gas wells drilled in the state of Pennsylvania. Impairment risk for wells in the northeast portion of the state were found to be 8.5-times greater than that of wells drilled in the rest of the state. Here, we set out to explain this apparent regional variability through Boosted Regression Tree (BRT) analysis of geographic, developmental, and general well attributes. We find that regional variability is largely driven by the nature of the development, i.e. whether conventional or unconventional development is dominant. Oil and natural gas market prices and total well depths present as major influences in wellbore impairment, with moderate influences from well densities and geologic factors. The figure depicts influence paths for predictors of impairments for the state (top left), SW region (top right), unconventional/NE region (bottom left) and conventional/NW region (bottom right) models. Influences are scaled to reflect percent contributions in explaining variability in the model.

  1. Distributions and averages of electron density parameters: Explaining the effects of gradient corrections

    NASA Astrophysics Data System (ADS)

    Zupan, Ales; Burke, Kieron; Ernzerhof, Matthias; Perdew, John P.

    1997-06-01

    We analyze the electron densities n(r) of atoms, molecules, solids, and surfaces. The distributions of values of the Seitz radius rs=(3/4πn)1/3 and the reduced density gradient s=|∇n|/(2(3π2)1/3n4/3) in an electron density indicate which ranges of these variables are significant for physical processes. We also define energy-weighted averages of these variables, and , from which local spin density (LSD) and generalized gradient approximation (GGA) exchange-correlation energies may be estimated. The changes in these averages upon rearrangement of the nuclei (atomization of molecules or solids, stretching of bond lengths or lattice parameters, change of crystal structure, etc.) are used to explain why GGA corrects LSD in the way it does. A thermodynamic-like inequality (essentially d/>d/2) determines whether the gradient corrections drive a process forward. We use this analysis to explain why gradient corrections usually stretch bonds (but not for example H-H bonds), reduce atomization and surface energies, and raise energy barriers to formation at transition states.

  2. A simple microstructure return model explaining microstructure noise and Epps effects

    NASA Astrophysics Data System (ADS)

    Saichev, A.; Sornette, D.

    2014-01-01

    We present a novel simple microstructure model of financial returns that combines (i) the well-known ARFIMA process applied to tick-by-tick returns, (ii) the bid-ask bounce effect, (iii) the fat tail structure of the distribution of returns and (iv) the non-Poissonian statistics of inter-trade intervals. This model allows us to explain both qualitatively and quantitatively important stylized facts observed in the statistics of both microstructure and macrostructure returns, including the short-ranged correlation of returns, the long-ranged correlations of absolute returns, the microstructure noise and Epps effects. According to the microstructure noise effect, volatility is a decreasing function of the time-scale used to estimate it. The Epps effect states that cross correlations between asset returns are increasing functions of the time-scale at which the returns are estimated. The microstructure noise is explained as the result of the negative return correlations inherent in the definition of the bid-ask bounce component (ii). In the presence of a genuine correlation between the returns of two assets, the Epps effect is due to an average statistical overlap of the momentum of the returns of the two assets defined over a finite time-scale in the presence of the long memory process (i).

  3. Explaining Alcohol Use and Suicide Risk: A Moderated Mediation Model Involving Insomnia Symptoms and Gender

    PubMed Central

    Nadorff, Michael R.; Salem, Taban; Winer, E. Samuel; Lamis, Dorian A.; Nazem, Sarra; Berman, Mitchell E.

    2014-01-01

    Study Objectives: The purpose of the study was to examine whether insomnia symptoms and nightmares mediated the relation between alcohol use and suicide risk. Further, we examined whether this mediation was moderated by gender. Design: The study consisted of questionnaires administered online examining insomnia symptoms, nightmares, alcohol use, and suicide risk. Setting: University. Patients or Participants: 375 undergraduate students at a large, public university in the southeastern United States. Interventions: N/A. Measurements and Results: Results indicated that insomnia symptoms significantly mediated the relation between alcohol use and suicide risk; however, this mediation was moderated by gender. For women, there was both a direct effect of alcohol use on suicide risk as well as an indirect effect of alcohol use through insomnia symptoms increasing suicide risk. For men, there was no direct effect of alcohol use on suicide risk, but there was a significant indirect effect of alcohol use increasing suicide risk through insomnia symptoms. Nightmares were not related to alcohol use, and the association between nightmares and suicide risk was found to be independent of alcohol use Conclusions: Insomnia symptoms are an important factor in explaining the mechanism by which alcohol use increases suicide risk. Citation: Nadorff MR, Salem T, Winer ES, Lamis DA, Nazem S, Berman ME. Explaining alcohol use and suicide risk: a moderated mediation model involving insomnia symptoms and gender. J Clin Sleep Med 2014;10(12):1317-1323. PMID:25325605

  4. Rectilinear Edge Selectivity Is Insufficient to Explain the Category Selectivity of the Parahippocampal Place Area.

    PubMed

    Bryan, Peter B; Julian, Joshua B; Epstein, Russell A

    2016-01-01

    The parahippocampal place area (PPA) is one of several brain regions that respond more strongly to scenes than to non-scene items such as objects and faces. The mechanism underlying this scene-preferential response remains unclear. One possibility is that the PPA is tuned to low-level stimulus features that are found more often in scenes than in less-preferred stimuli. Supporting this view, Nasr et al. (2014) recently observed that some of the stimuli that are known to strongly activate the PPA contain a large number of rectilinear edges. They further demonstrated that PPA response is modulated by rectilinearity for a range of non-scene images. Motivated by these results, we tested whether rectilinearity suffices to explain PPA selectivity for scenes. In the first experiment, we replicated the previous finding of modulation by rectilinearity in the PPA for arrays of 2-d shapes. However, two further experiments failed to find a rectilinearity effect for faces or scenes: high-rectilinearity faces and scenes did not activate the PPA any more strongly than low-rectilinearity faces and scenes. Moreover, the categorical advantage for scenes vs. faces was maintained in the PPA and two other scene-selective regions-the retrosplenial complex (RSC) and occipital place area (OPA)-when rectilinearity was matched between stimulus sets. We conclude that selectivity for scenes in the PPA cannot be explained by a preference for low-level rectilinear edges. PMID:27064591

  5. Robust efficiency and actuator saturation explain healthy heart rate control and variability

    PubMed Central

    Li, Na; Cruz, Jerry; Chien, Chenghao Simon; Sojoudi, Somayeh; Recht, Benjamin; Stone, David; Csete, Marie; Bahmiller, Daniel; Doyle, John C.

    2014-01-01

    The correlation of healthy states with heart rate variability (HRV) using time series analyses is well documented. Whereas these studies note the accepted proximal role of autonomic nervous system balance in HRV patterns, the responsible deeper physiological, clinically relevant mechanisms have not been fully explained. Using mathematical tools from control theory, we combine mechanistic models of basic physiology with experimental exercise data from healthy human subjects to explain causal relationships among states of stress vs. health, HR control, and HRV, and more importantly, the physiologic requirements and constraints underlying these relationships. Nonlinear dynamics play an important explanatory role––most fundamentally in the actuator saturations arising from unavoidable tradeoffs in robust homeostasis and metabolic efficiency. These results are grounded in domain-specific mechanisms, tradeoffs, and constraints, but they also illustrate important, universal properties of complex systems. We show that the study of complex biological phenomena like HRV requires a framework which facilitates inclusion of diverse domain specifics (e.g., due to physiology, evolution, and measurement technology) in addition to general theories of efficiency, robustness, feedback, dynamics, and supporting mathematical tools. PMID:25092335

  6. Functional traits help to explain half-century long shifts in pollinator distributions.

    PubMed

    Aguirre-Gutiérrez, Jesús; Kissling, W Daniel; Carvalheiro, Luísa G; WallisDeVries, Michiel F; Franzén, Markus; Biesmeijer, Jacobus C

    2016-01-01

    Changes in climate and land use can have important impacts on biodiversity. Species respond to such environmental modifications by adapting to new conditions or by shifting their geographic distributions towards more suitable areas. The latter might be constrained by species' functional traits that influence their ability to move, reproduce or establish. Here, we show that functional traits related to dispersal, reproduction, habitat use and diet have influenced how three pollinator groups (bees, butterflies and hoverflies) responded to changes in climate and land-use in the Netherlands since 1950. Across the three pollinator groups, we found pronounced areal range expansions (>53%) and modelled range shifts towards the north (all taxa: 17-22 km), west (bees: 14 km) and east (butterflies: 11 km). The importance of specific functional traits for explaining distributional changes varied among pollinator groups. Larval diet preferences (i.e. carnivorous vs. herbivorous/detritivorous and nitrogen values of host plants, respectively) were important for hoverflies and butterflies, adult body size for hoverflies, and flight period length for all groups. Moreover, interactions among multiple traits were important to explain species' geographic range shifts, suggesting that taxon-specific multi-trait analyses are needed to predict how global change will affect biodiversity and ecosystem services. PMID:27079784

  7. Folding of the anterior cingulate cortex partially explains inhibitory control during childhood: a longitudinal study.

    PubMed

    Borst, G; Cachia, A; Vidal, J; Simon, G; Fischer, C; Pineau, A; Poirel, N; Mangin, J-F; Houdé, O

    2014-07-01

    Difficulties in cognitive control including inhibitory control (IC) are related to the pathophysiology of several psychiatric conditions. In healthy subjects, IC efficiency in childhood is a strong predictor of academic and professional successes later in life. The dorsal anterior cingulate cortex (ACC) is one of the core structures responsible for IC. Although quantitative structural characteristics of the ACC contribute to IC efficiency, the qualitative structural brain characteristics contributing to IC development are less-understood. Using anatomical magnetic resonance imaging, we investigated whether the ACC sulcal pattern at age 5, a stable qualitative characteristic of the brain determined in utero, explains IC at age 9. 18 children performed Stroop tasks at age 5 and age 9. Children with asymmetrical ACC sulcal patterns (n=7) had better IC efficiency at age 5 and age 9 than children with symmetrical ACC sulcal patterns (n=11). The ACC sulcal patterns appear to affect specifically IC efficiency given that the ACC sulcal patterns had no effect on verbal working memory. Our study provides the first evidence that the ACC sulcal pattern - a qualitative structural characteristic of the brain not affected by maturation and learning after birth - partially explains IC efficiency during childhood. PMID:24642370

  8. An expanded sequence context model broadly explains variability in polymorphism levels across the human genome.

    PubMed

    Aggarwala, Varun; Voight, Benjamin F

    2016-04-01

    The rate of single-nucleotide polymorphism varies substantially across the human genome and fundamentally influences evolution and incidence of genetic disease. Previous studies have only considered the immediately flanking nucleotides around a polymorphic site-the site's trinucleotide sequence context-to study polymorphism levels across the genome. Moreover, the impact of larger sequence contexts has not been fully clarified, even though context substantially influences rates of polymorphism. Using a new statistical framework and data from the 1000 Genomes Project, we demonstrate that a heptanucleotide context explains >81% of variability in substitution probabilities, highlighting new mutation-promoting motifs at ApT dinucleotide, CAAT and TACG sequences. Our approach also identifies previously undocumented variability in C-to-T substitutions at CpG sites, which is not immediately explained by differential methylation intensity. Using our model, we present informative substitution intolerance scores for genes and a new intolerance score for amino acids, and we demonstrate clinical use of the model in neuropsychiatric diseases. PMID:26878723

  9. Transcriptional regulation is insufficient to explain substrate-induced flux changes in Bacillus subtilis

    PubMed Central

    Chubukov, Victor; Uhr, Markus; Le Chat, Ludovic; Kleijn, Roelco J; Jules, Matthieu; Link, Hannes; Aymerich, Stephane; Stelling, Jörg; Sauer, Uwe

    2013-01-01

    One of the key ways in which microbes are thought to regulate their metabolism is by modulating the availability of enzymes through transcriptional regulation. However, the limited success of efforts to manipulate metabolic fluxes by rewiring the transcriptional network has cast doubt on the idea that transcript abundance controls metabolic fluxes. In this study, we investigate control of metabolic flux in the model bacterium Bacillus subtilis by quantifying fluxes, transcripts, and metabolites in eight metabolic states enforced by different environmental conditions. We find that most enzymes whose flux switches between on and off states, such as those involved in substrate uptake, exhibit large corresponding transcriptional changes. However, for the majority of enzymes in central metabolism, enzyme concentrations were insufficient to explain the observed fluxes—only for a number of reactions in the tricarboxylic acid cycle were enzyme changes approximately proportional to flux changes. Surprisingly, substrate changes revealed by metabolomics were also insufficient to explain observed fluxes, leaving a large role for allosteric regulation and enzyme modification in the control of metabolic fluxes. PMID:24281055

  10. Testing the efficacy of the theory of planned behavior to explain strength training in older adults.

    PubMed

    Dean, Rachel N; Farrell, Jocelyn M; Kelley, Mary Lou; Taylor, M Jane; Rhodes, Ryan E

    2007-01-01

    The purpose of this study was to use the constructs of the theory of planned behavior (TPB) to gain a better understanding of the factors influencing older adults' participation in strength training. Two hundred men and women age 55 years and older were purposely sampled from seniors' centers in Ontario Canada. Participants completed a TPB questionnaire and reported their current physical activity participation. It was hypothesized that perceived behavioral control followed by attitude would be the strongest determinants of strength-training intentions and that intention would be the strongest determinant of strength-training behavior. Regression analyses revealed that subjective norm and perceived behavioral control explained 42% of the variance in intention and intention explained 40% of the variance in behavior. Gender and current strength-training participation did not significantly moderate the relationship between the TPB variables. The results suggest that interventions targeting subjective norm and perceived control might be helpful in promoting strength-training behavior among older adults. PMID:17387225

  11. Individualistic sensitivities and exposure to climate change explain variation in species' distribution and abundance changes.

    PubMed

    Palmer, Georgina; Hill, Jane K; Brereton, Tom M; Brooks, David R; Chapman, Jason W; Fox, Richard; Oliver, Tom H; Thomas, Chris D

    2015-10-01

    The responses of animals and plants to recent climate change vary greatly from species to species, but attempts to understand this variation have met with limited success. This has led to concerns that predictions of responses are inherently uncertain because of the complexity of interacting drivers and biotic interactions. However, we show for an exemplar group of 155 Lepidoptera species that about 60% of the variation among species in their abundance trends over the past four decades can be explained by species-specific exposure and sensitivity to climate change. Distribution changes were less well predicted, but nonetheless, up to 53% of the variation was explained. We found that species vary in their overall sensitivity to climate and respond to different components of the climate despite ostensibly experiencing the same climate changes. Hence, species have undergone different levels of population "forcing" (exposure), driving variation among species in their national-scale abundance and distribution trends. We conclude that variation in species' responses to recent climate change may be more predictable than previously recognized. PMID:26601276

  12. Individualistic sensitivities and exposure to climate change explain variation in species’ distribution and abundance changes

    PubMed Central

    Palmer, Georgina; Hill, Jane K.; Brereton, Tom M.; Brooks, David R.; Chapman, Jason W.; Fox, Richard; Oliver, Tom H.; Thomas, Chris D.

    2015-01-01

    The responses of animals and plants to recent climate change vary greatly from species to species, but attempts to understand this variation have met with limited success. This has led to concerns that predictions of responses are inherently uncertain because of the complexity of interacting drivers and biotic interactions. However, we show for an exemplar group of 155 Lepidoptera species that about 60% of the variation among species in their abundance trends over the past four decades can be explained by species-specific exposure and sensitivity to climate change. Distribution changes were less well predicted, but nonetheless, up to 53% of the variation was explained. We found that species vary in their overall sensitivity to climate and respond to different components of the climate despite ostensibly experiencing the same climate changes. Hence, species have undergone different levels of population “forcing” (exposure), driving variation among species in their national-scale abundance and distribution trends. We conclude that variation in species’ responses to recent climate change may be more predictable than previously recognized. PMID:26601276

  13. Micro-halocline enabled nutrient recycling may explain extreme Azolla event in the Eocene Arctic Ocean.

    PubMed

    van Kempen, Monique M L; Smolders, Alfons J P; Lamers, Leon P M; Roelofs, Jan G M

    2012-01-01

    In order to understand the physicochemical mechanisms that could explain the massive growth of Azolla arctica in the Eocene Arctic Ocean, we carried out a laboratory experiment in which we studied the interacting effects of rain and wind on the development of salinity stratification, both in the presence and in the absence of a dense Azolla cover. Additionally, we carried out a mesocosm experiment to get a better understanding of the nutrient cycling within and beneath a dense Azolla cover in both freshwater and brackish water environments. Here we show that Azolla is able to create a windproof, small-scale salinity gradient in brackish waters, which allows for efficient recycling of nutrients. We suggest that this mechanism ensures the maintenance of a large standing biomass in which additional input of nutrients ultimately result in a further expansion of an Azolla cover. As such, it may not only explain the extent of the Azolla event during the Eocene, but also the absence of intact vegetative Azolla remains and the relatively low burial efficiency of organic carbon during this interval. PMID:23166833

  14. A tethered delivery mechanism explains the catalytic action of a microtubule polymerase

    PubMed Central

    Ayaz, Pelin; Munyoki, Sarah; Geyer, Elisabeth A; Piedra, Felipe-Andrés; Vu, Emily S; Bromberg, Raquel; Otwinowski, Zbyszek; Grishin, Nick V; Brautigam, Chad A; Rice, Luke M

    2014-01-01

    Stu2p/XMAP215 proteins are essential microtubule polymerases that use multiple αβ-tubulin-interacting TOG domains to bind microtubule plus ends and catalyze fast microtubule growth. We report here the structure of the TOG2 domain from Stu2p bound to yeast αβ-tubulin. Like TOG1, TOG2 binds selectively to a fully ‘curved’ conformation of αβ-tubulin, incompatible with a microtubule lattice. We also show that TOG1-TOG2 binds non-cooperatively to two αβ-tubulins. Preferential interactions between TOGs and fully curved αβ-tubulin that cannot exist elsewhere in the microtubule explain how these polymerases localize to the extreme microtubule end. We propose that these polymerases promote elongation because their linked TOG domains concentrate unpolymerized αβ-tubulin near curved subunits already bound at the microtubule end. This tethering model can explain catalyst-like behavior and also predicts that the polymerase action changes the configuration of the microtubule end. DOI: http://dx.doi.org/10.7554/eLife.03069.001 PMID:25097237

  15. Circuitry to explain how the relative number of L and M cones shapes color experience

    PubMed Central

    Schmidt, Brian P.; Touch, Phanith; Neitz, Maureen; Neitz, Jay

    2016-01-01

    The wavelength of light that appears unique yellow is surprisingly consistent across people even though the ratio of middle (M) to long (L) wavelength sensitive cones is strikingly variable. This observation has been explained by normalization to the mean spectral distribution of our shared environment. Our purpose was to reconcile the nearly perfect alignment of everyone's unique yellow through a normalization process with the striking variability in unique green, which varies by as much as 60 nm between individuals. The spectral location of unique green was measured in a group of volunteers whose cone ratios were estimated with a technique that combined genetics and flicker photometric electroretinograms. In contrast to unique yellow, unique green was highly dependent upon relative cone numerosity. We hypothesized that the difference in neural architecture of the blue-yellow and red-green opponent systems in the presence of a normalization process creates the surprising dependence of unique green on cone ratio. We then compared the predictions of different theories of color vision processing that incorporate L and M cone ratio and a normalization process. The results of this analysis reveal that—contrary to prevailing notions--postretinal contributions may not be required to explain the phenomena of unique hues. PMID:27366885

  16. Does Individualism Help Explain Differences in Employers' Stigmatizing Attitudes Toward Disability Across Chinese and American Cities?

    PubMed Central

    Rao, Deepa; Horton, Randall A.; Tsang, Hector W.H.; Shi, Kan; Corrigan, Patrick W.

    2011-01-01

    Purpose Stigmatizing attitudes toward people with disabilities can jeopardize such individuals' well-being and recovery through denial of employment and community isolation. By shaping social norms that define group membership, the construct of individualism may partially explain differences in stigmatizing attitudes across cultures. Further, widespread globalization has brought intensely individualistic social practices to certain segments of non-Western cultures. This paper examines whether the construct of individualism can help to explain cross-cultural differences in stigmatizing attitudes observed between American and Chinese employers. Design Employers (N = 879) from Beijing, Hong Kong, and Chicago provided information on their attitudes toward hiring people with disabilities, and Path Analyses were conducted to examine potential mediating relationships. Results Path analyses indicated that vertical individualism, along with perceived responsibility for acquiring a condition, partially mediated the relationship between culture and employers' negative attitudes about job candidates with disabilities. Conclusion These results suggested that greater espousal of competitive and individualist values may drive stigmatizing attitudes across cultures. PMID:21171794

  17. Examining Pre-Service Teachers' Use of Atomic Models in Explaining Subsequent Ionisation Energy Values

    NASA Astrophysics Data System (ADS)

    Wheeldon, Ruth

    2012-06-01

    Chemistry students' explanations of ionisation energy phenomena often involve a number of non-scientific or inappropriate ideas being used to form causality arguments. Research has attributed this to many science teachers using these ideas themselves (Tan and Taber, in J Chem Educ 86(5):623-629, 2009). This research extends this work by considering which atomic models are used in pre-service teachers' explanations and how that relates to the causality ideas expressed. Thirty-one pre-service teachers were interviewed. Each was asked to describe and explain four different atomic representations (Rutherford, Electron cloud micrograph, Bohr and Schrödinger types) in as much detail as they could. They also provided an explanation for the subsequent ionisation energy values for an oxygen atom and identified which representations were helpful in explaining the values. Significantly, when pre-service teachers only used Bohr type representations, they did not use repelling electron ideas in their explanations. However, arguments that were based on electron-electron repulsion used features from Schrödinger type atoms. These findings suggest that many pre-service teachers need to develop their atomic modelling skills so that they select and use models more expertly and that subsequent ionisation explanations offer a context in which to explore different atomic models' limitations and their deployment as explanatory resources.

  18. Polarization in Raman spectroscopy helps explain bone brittleness in genetic mouse models

    NASA Astrophysics Data System (ADS)

    Makowski, Alexander J.; Pence, Isaac J.; Uppuganti, Sasidhar; Zein-Sabatto, Ahbid; Huszagh, Meredith C.; Mahadevan-Jansen, Anita; Nyman, Jeffry S.

    2014-11-01

    Raman spectroscopy (RS) has been extensively used to characterize bone composition. However, the link between bone biomechanics and RS measures is not well established. Here, we leveraged the sensitivity of RS polarization to organization, thereby assessing whether RS can explain differences in bone toughness in genetic mouse models for which traditional RS peak ratios are not informative. In the selected mutant mice-activating transcription factor 4 (ATF4) or matrix metalloproteinase 9 (MMP9) knock-outs-toughness is reduced but differences in bone strength do not exist between knock-out and corresponding wild-type controls. To incorporate differences in the RS of bone occurring at peak shoulders, a multivariate approach was used. Full spectrum principal components analysis of two paired, orthogonal bone orientations (relative to laser polarization) improved genotype classification and correlation to bone toughness when compared to traditional peak ratios. When applied to femurs from wild-type mice at 8 and 20 weeks of age, the principal components of orthogonal bone orientations improved age classification but not the explanation of the maturation-related increase in strength. Overall, increasing polarization information by collecting spectra from two bone orientations improves the ability of multivariate RS to explain variance in bone toughness, likely due to polarization sensitivity to organizational changes in both mineral and collagen.

  19. Explaining neural signals in human visual cortex with an associative learning model.

    PubMed

    Jiang, Jiefeng; Schmajuk, Nestor; Egner, Tobias

    2012-08-01

    "Predictive coding" models posit a key role for associative learning in visual cognition, viewing perceptual inference as a process of matching (learned) top-down predictions (or expectations) against bottom-up sensory evidence. At the neural level, these models propose that each region along the visual processing hierarchy entails one set of processing units encoding predictions of bottom-up input, and another set computing mismatches (prediction error or surprise) between predictions and evidence. This contrasts with traditional views of visual neurons operating purely as bottom-up feature detectors. In support of the predictive coding hypothesis, a recent human neuroimaging study (Egner, Monti, & Summerfield, 2010) showed that neural population responses to expected and unexpected face and house stimuli in the "fusiform face area" (FFA) could be well-described as a summation of hypothetical face-expectation and -surprise signals, but not by feature detector responses. Here, we used computer simulations to test whether these imaging data could be formally explained within the broader framework of a mathematical neural network model of associative learning (Schmajuk, Gray, & Lam, 1996). Results show that FFA responses could be fit very closely by model variables coding for conditional predictions (and their violations) of stimuli that unconditionally activate the FFA. These data document that neural population signals in the ventral visual stream that deviate from classic feature detection responses can formally be explained by associative prediction and surprise signals. PMID:22845706

  20. EXPLAINING THE GAP IN ANTENATAL CARE SERVICE UTILIZATION BETWEEN YOUNGER AND OLDER MOTHERS IN GHANA.

    PubMed

    Boamah, Sheila A; Amoyaw, Jonathan; Luginaah, Isaac

    2016-05-01

    Over two-thirds of pregnant women (69%) have at least one antenatal care (ANC) coverage contact in sub-Saharan Africa. However, to achieve the full life-saving potential that ANC promises for women and babies, a nuanced understanding of age-specific gaps in utilization of ANC services is required. Using the 2008 Ghana Demographic and Health Survey of 1456 individuals, this study examined the disparities in the use of ANC services between younger and older mothers by applying four counterfactual decomposition techniques. The results show that cross-group differences in the explanatory variables largely account for the differentials in ANC service utilization between younger and older mothers. Birth order (parity) accounts for the largest share of the contribution to the overall explained gap in ANC utilization between the younger and older mothers, suggesting that ANC differentials between the two groups are probably due to biosocial factors. To a lesser extent, wealth status of the two groups also contributes to the overall explained gap in ANC service utilization. The policy implications of these findings are that in order to bridge the ANC service utilization gap between the two groups, policymakers must systematically address gaps in cross-group differences in the explanatory variables in order to increase the utilization of ANC to attain the minimum recommendation of four visits as per World Health Organization guidelines. PMID:26160032

  1. Genetic surfing, not allopatric divergence, explains spatial sorting of mitochondrial haplotypes in venomous coralsnakes.

    PubMed

    Streicher, Jeffrey W; McEntee, Jay P; Drzich, Laura C; Card, Daren C; Schield, Drew R; Smart, Utpal; Parkinson, Christopher L; Jezkova, Tereza; Smith, Eric N; Castoe, Todd A

    2016-07-01

    Strong spatial sorting of genetic variation in contiguous populations is often explained by local adaptation or secondary contact following allopatric divergence. A third explanation, spatial sorting by stochastic effects of range expansion, has been considered less often though theoretical models suggest it should be widespread, if ephemeral. In a study designed to delimit species within a clade of venomous coralsnakes, we identified an unusual pattern within the Texas coral snake (Micrurus tener): strong spatial sorting of divergent mitochondrial (mtDNA) lineages over a portion of its range, but weak sorting of these lineages elsewhere. We tested three alternative hypotheses to explain this pattern-local adaptation, secondary contact following allopatric divergence, and range expansion. Collectively, near panmixia of nuclear DNA, the signal of range expansion associated sampling drift, expansion origins in the Gulf Coast of Mexico, and species distribution modeling suggest that the spatial sorting of divergent mtDNA lineages within M. tener has resulted from genetic surfing of standing mtDNA variation-not local adaptation or allopatric divergence. Our findings highlight the potential for the stochastic effects of recent range expansion to mislead estimations of population divergence made from mtDNA, which may be exacerbated in systems with low vagility, ancestral mtDNA polymorphism, and male-biased dispersal. PMID:27251954

  2. In kittiwakes food availability partially explains the seasonal decline in humoral immunocompetence

    USGS Publications Warehouse

    Gasparini, J.; Roulin, A.; Gill, V.A.; Hatch, Shyla A.; Boulinier, T.

    2006-01-01

    1. The immune system plays an important role in fitness, and interindividual variation in immunocompetence is due to several factors including food supply. 2. Seasonal variation in food resources may therefore explain why immunocompetence in bird nestlings usually declines throughout the breeding season, with chicks born early in the season receiving more food than chicks born later, and thereby possibly developing a more potent immune system. Although there are studies supporting this hypothesis, none has been experimental. 3. We performed an experiment in the kittiwake Rissa tridactyla by manipulating the food supply of pairs that were left to produce a first brood, and of pairs that were induced to produce a late replacement brood. 4. If food supply mediates, at least partially, seasonal variations in chick immunocompetence, non-food-supplemented chicks would show a stronger seasonal decline in immunocompetence than food-supplemented chicks. 5. Food supplementation improved humoral immunocompetence (the production of immunoglobulins Y), but not T-cell immunocompetence (phytohaemagglutinin, PHA response). T-cell immunocompetence of food-supplemented and non-food- supplemented chicks decreased through the season but to a similar extent, whereas the humoral immunocompetence of non-food-supplemented chicks decreased more strongly than that of food-supplemented chicks. 6. Our results suggest that the seasonal decline in humoral immunocompetence can be explained, at least partly, by variations in food supply throughout the breeding season. ?? 2006 British Ecological Society.

  3. Brain hemodynamic activity during viewing and re-viewing of comedy movies explained by experienced humor

    PubMed Central

    Jääskeläinen, Iiro P.; Pajula, Juha; Tohka, Jussi; Lee, Hsin-Ju; Kuo, Wen-Jui; Lin, Fa-Hsuan

    2016-01-01

    Humor is crucial in human social interactions. To study the underlying neural processes, three comedy clips were shown twice to 20 volunteers during functional magnetic resonance imaging (fMRI). Inter-subject similarities in humor ratings, obtained immediately after fMRI, explained inter-subject correlation of hemodynamic activity in right frontal pole and in a number of other brain regions. General linear model analysis also indicated activity in right frontal pole, as well as in additional cortical areas and subcortically in striatum, explained by humorousness. The association of the right frontal pole with experienced humorousness is a novel finding, which might be related to humor unfolding over longer time scales in the movie clips. Specifically, frontal pole has been shown to exhibit longer temporal receptive windows than, e.g., sensory areas, which might have enabled processing of humor in the clips based on holding information and reinterpreting that in light of new information several (even tens of) seconds later. As another novel finding, medial and lateral prefrontal areas, frontal pole, posterior-inferior temporal areas, posterior parietal areas, posterior cingulate, striatal structures and amygdala showed reduced activity upon re-viewing of the clips, suggesting involvement in processing of humor related to novelty of the comedic events. PMID:27323928

  4. Rectilinear Edge Selectivity Is Insufficient to Explain the Category Selectivity of the Parahippocampal Place Area

    PubMed Central

    Bryan, Peter B.; Julian, Joshua B.; Epstein, Russell A.

    2016-01-01

    The parahippocampal place area (PPA) is one of several brain regions that respond more strongly to scenes than to non-scene items such as objects and faces. The mechanism underlying this scene-preferential response remains unclear. One possibility is that the PPA is tuned to low-level stimulus features that are found more often in scenes than in less-preferred stimuli. Supporting this view, Nasr et al. (2014) recently observed that some of the stimuli that are known to strongly activate the PPA contain a large number of rectilinear edges. They further demonstrated that PPA response is modulated by rectilinearity for a range of non-scene images. Motivated by these results, we tested whether rectilinearity suffices to explain PPA selectivity for scenes. In the first experiment, we replicated the previous finding of modulation by rectilinearity in the PPA for arrays of 2-d shapes. However, two further experiments failed to find a rectilinearity effect for faces or scenes: high-rectilinearity faces and scenes did not activate the PPA any more strongly than low-rectilinearity faces and scenes. Moreover, the categorical advantage for scenes vs. faces was maintained in the PPA and two other scene-selective regions—the retrosplenial complex (RSC) and occipital place area (OPA)—when rectilinearity was matched between stimulus sets. We conclude that selectivity for scenes in the PPA cannot be explained by a preference for low-level rectilinear edges. PMID:27064591

  5. Polarization in Raman spectroscopy helps explain bone brittleness in genetic mouse models

    PubMed Central

    Makowski, Alexander J.; Pence, Isaac J.; Uppuganti, Sasidhar; Zein-Sabatto, Ahbid; Huszagh, Meredith C.; Mahadevan-Jansen, Anita; Nyman, Jeffry S.

    2014-01-01

    Abstract. Raman spectroscopy (RS) has been extensively used to characterize bone composition. However, the link between bone biomechanics and RS measures is not well established. Here, we leveraged the sensitivity of RS polarization to organization, thereby assessing whether RS can explain differences in bone toughness in genetic mouse models for which traditional RS peak ratios are not informative. In the selected mutant mice—activating transcription factor 4 (ATF4) or matrix metalloproteinase 9 (MMP9) knock-outs—toughness is reduced but differences in bone strength do not exist between knock-out and corresponding wild-type controls. To incorporate differences in the RS of bone occurring at peak shoulders, a multivariate approach was used. Full spectrum principal components analysis of two paired, orthogonal bone orientations (relative to laser polarization) improved genotype classification and correlation to bone toughness when compared to traditional peak ratios. When applied to femurs from wild-type mice at 8 and 20 weeks of age, the principal components of orthogonal bone orientations improved age classification but not the explanation of the maturation-related increase in strength. Overall, increasing polarization information by collecting spectra from two bone orientations improves the ability of multivariate RS to explain variance in bone toughness, likely due to polarization sensitivity to organizational changes in both mineral and collagen. PMID:25402627

  6. Neglected role of fungal community composition in explaining variation in wood decay rates.

    PubMed

    Van der Wal, A; Ottosson, E; De Boer, W

    2015-01-01

    Decomposition of wood is an important component of global carbon cycling. Most wood decomposition models are based on tree characteristics and environmental conditions; however, they do not include community dynamics of fungi that are the major wood decomposers. We examined the factors explaining variation in sapwood decay in oak tree stumps two and five years after cutting. Wood moisture content was significantly correlated with sapwood decay in younger stumps, whereas ITS-based composition and species richness of the fungal community were the best predictors for mass loss in the older stumps. Co-occurrence analysis showed that, in freshly cut trees and in younger stumps, fungal communities were nonrandomly structured, whereas fungal communities in old stumps could not be separated from a randomly assembled community. These results indicate that the most important factors explaining variation in wood decay rates can change over time and that the strength of competitive interactions between fungi in decaying tree stumps may level off with increased wood decay. Our field analysis further suggests that ascomycetes may have a prominent role in wood decay, but their wood-degrading abilities need to be further tested under controlled conditions. The next challenging step will be to integrate fungal community assembly processes in wood decay models to improve carbon sequestration estimates of forests. PMID:26236897

  7. Predator-prey dynamics stabilised by nonlinearity explain oscillations in dust-forming plasmas

    NASA Astrophysics Data System (ADS)

    Ross, A. E.; McKenzie, D. R.

    2016-04-01

    Dust-forming plasmas are ionised gases that generate particles from a precursor. In nature, dust-forming plasmas are found in flames, the interstellar medium and comet tails. In the laboratory, they are valuable in generating nanoparticles for medicine and electronics. Dust-forming plasmas exhibit a bizarre, even puzzling behaviour in which they oscillate with timescales of seconds to minutes. Here we show how the problem of understanding these oscillations may be cast as a predator-prey problem, with electrons as prey and particles as predators. The addition of a nonlinear loss term to the classic Lotka-Volterra equations used for describing the predator-prey problem in ecology not only stabilises the oscillations in the solutions for the populations of electrons and particles in the plasma but also explains the behaviour in more detail. The model explains the relative phase difference of the two populations, the way in which the frequency of the oscillations varies with the concentration of the precursor gas, and the oscillations of the light emission, determined by the populations of both species. Our results demonstrate the value of adopting an approach to a complex physical science problem that has been found successful in ecology, where complexity is always present.

  8. Predator-prey dynamics stabilised by nonlinearity explain oscillations in dust-forming plasmas.

    PubMed

    Ross, A E; McKenzie, D R

    2016-01-01

    Dust-forming plasmas are ionised gases that generate particles from a precursor. In nature, dust-forming plasmas are found in flames, the interstellar medium and comet tails. In the laboratory, they are valuable in generating nanoparticles for medicine and electronics. Dust-forming plasmas exhibit a bizarre, even puzzling behaviour in which they oscillate with timescales of seconds to minutes. Here we show how the problem of understanding these oscillations may be cast as a predator-prey problem, with electrons as prey and particles as predators. The addition of a nonlinear loss term to the classic Lotka-Volterra equations used for describing the predator-prey problem in ecology not only stabilises the oscillations in the solutions for the populations of electrons and particles in the plasma but also explains the behaviour in more detail. The model explains the relative phase difference of the two populations, the way in which the frequency of the oscillations varies with the concentration of the precursor gas, and the oscillations of the light emission, determined by the populations of both species. Our results demonstrate the value of adopting an approach to a complex physical science problem that has been found successful in ecology, where complexity is always present. PMID:27046237

  9. Predator-prey dynamics stabilised by nonlinearity explain oscillations in dust-forming plasmas

    PubMed Central

    Ross, A. E.; McKenzie, D. R.

    2016-01-01

    Dust-forming plasmas are ionised gases that generate particles from a precursor. In nature, dust-forming plasmas are found in flames, the interstellar medium and comet tails. In the laboratory, they are valuable in generating nanoparticles for medicine and electronics. Dust-forming plasmas exhibit a bizarre, even puzzling behaviour in which they oscillate with timescales of seconds to minutes. Here we show how the problem of understanding these oscillations may be cast as a predator-prey problem, with electrons as prey and particles as predators. The addition of a nonlinear loss term to the classic Lotka-Volterra equations used for describing the predator-prey problem in ecology not only stabilises the oscillations in the solutions for the populations of electrons and particles in the plasma but also explains the behaviour in more detail. The model explains the relative phase difference of the two populations, the way in which the frequency of the oscillations varies with the concentration of the precursor gas, and the oscillations of the light emission, determined by the populations of both species. Our results demonstrate the value of adopting an approach to a complex physical science problem that has been found successful in ecology, where complexity is always present. PMID:27046237

  10. Phytoplankton succession explains size-partitioning of new production following upwelling-induced blooms

    NASA Astrophysics Data System (ADS)

    Van Oostende, N.; Dunne, J. P.; Fawcett, S. E.; Ward, B. B.

    2015-08-01

    Large and chain-forming diatoms typically dominate the phytoplankton biomass after initiation of coastal upwelling. The ability of these diatoms to accelerate and maintain elevated nitrate uptake rates has been proposed to explain the dominance of diatoms over all other phytoplankton groups. Moreover, the observed delay in biomass accumulation following nitrate supply after initiation of upwelling events has been hypothesised to result from changes in the diatom community structure or from physiological acclimation. To investigate these mechanisms, we used both numerical modelling and experimental incubations that reproduced the characteristic succession from small to large species in phytoplankton community composition and size structure. Using the Tracers Of Phytoplankton with Allometric Zooplankton (TOPAZ) ecosystem model as a framework, we find that variations in functional group-specific traits must be taken into account, through adjustments of group-dependent maximum production rates (PCmax, s- 1), in order to accurately reproduce the observed patterns and timescales of size-partitioned new production in a non-steady state environment. Representation of neither nutrient acclimation, nor diatom diversity in the model was necessary as long as lower than theoretical maximum production rates were implemented. We conclude that this physiological feature, PCmax, is critical in representing the early, relatively higher specific nitrate uptake rate of large diatoms, and explains the differential success of small and large phytoplankton communities in response to nitrate supply during upwelling.

  11. Understanding Middle School Students' Difficulties in Explaining Density Differences from a Language Perspective

    NASA Astrophysics Data System (ADS)

    Seah, Lay Hoon; Clarke, David; Hart, Christina

    2015-09-01

    This study examines how a class of Grade 7 students employed linguistic resources to explain density differences. Drawing from the same data-set as a previous study by, we take a language perspective to investigate the challenges students face in learning the concept of density. Our study thus complements previous research on learning about density which has mostly focussed on the conceptual challenges. The data consist of transcripts of lessons on density and students' written assignments. Using selected analytical categories from the Systemic Functional Linguistics framework, we first examined students' use of linguistic resources in their written reports of a practical activity. We then compared the language employed by the students with the instructional language, identifying possible links. Our analysis identified specific aspects of language that the students need to appropriate in order to express an understanding of density that aligns with a scientific perspective. The findings from this study illuminate ways by which teachers could assist students in overcoming the linguistic challenges in explaining density differences, which complement those made by existing studies that focus on conceptual challenges.

  12. Alignment of Quasar Polarizations on Large Scales Explained by Warped Cosmic Strings

    NASA Astrophysics Data System (ADS)

    Slagter, Reinoud Jan

    The recently discovered alignment of quasar polarizations on very large scales could possibly explained by considering cosmic strings on a warped five dimensional spacetime. Compact objects, such as cosmic strings, could have tremendous mass in the bulk, while their warped manifestations in the brane can be consistent with general relativity in 4D. The self-gravitating cosmic string induces gravitational wavelike disturbances which could have effects felt on the brane, i.e., the massive effective 4D modes (Kaluza-Klein modes) of the perturbative 5D graviton. This effect is amplified by the time dependent part of the warp factor. Due to this warp factor, disturbances don't fade away during the expansion of the universe. From a non-linear perturbation analysis it is found that the effective Einstein 4D equations on an axially symmetric spacetime, contain a "back-reaction" term on the righthand side caused by the projected 5D Weyl tensor and can act as a dark energy term. The propagation equations to first order for the metric components and scalar-gauge fields contain $\\varphi$-dependent terms, so the approximate wave solutions are no longer axially symmetric. The disturbances, amplified by the warp factor, can possess extremal values for fixed polar angles. This could explain the two preferred polarization vectors mod $(\\varphi, 90^o)$.

  13. Explaining the t - t¯ asymmetry with a light axigluon

    SciTech Connect

    Marques Tavares, Gustavo; Schmaltz, Martin

    2011-09-12

    We propose an axigluon with mass between 400 and 450 GeV and flavor-universal couplings to quarks to explain the Tevatron t -t¯ forward-backward asymmetry. The model predicts a small negative asymmetry for t - t¯ pairs with invariant mass below 450 GeV and a large positive asymmetry above 450 GeV. The asymmetry arises from interference between s-channel gluon and axigluon diagrams and requires a relatively weakly coupled axigluon (ga=gqcd/3). Axigluon-gluon interference does not contribute to the t - t¯ cross section. New contributions to the cross section arise only at fourth order in the axigluon coupling and are very small for a sufficiently broad axigluon. Dijet measurements do not significantly constrain the axigluon couplings. We propose several possible UV completions of the phenomenological axigluon which explain the required small couplings and large width. Such UV completions necessarily contain new colored fermions or scalars below the axigluon mass and predict multijet events with large cross sections at the Tevatron and LHC.

  14. General Relativity Explains the Shnoll Effect and Makes Possible Forecasting Earthquakes and Weather Cataclysms

    NASA Astrophysics Data System (ADS)

    Rabounski, Dmitri; Borissova, Larissa

    2014-03-01

    The Shnoll effect is manifested in the fine structure of the noise registered in stable processes, wherein as the magnitude of signal and the average noise remain unchanged. It is periodic fluctuation of the fine structure of the noise according to the cosmic cycles connected with stars, the Sun, and the Moon. The Shnoll effect is explained herein according to General Relativity, as the twin/entangled synchronization states of the observer's reference frame. The states are repeated while the observer travels, in common with the Earth, through the cosmic grid of the geodesic synchronization paths that connect his local reference frame with the reference frames of the other cosmic bodies. These synchronization periods are expected to be existing in the noise of natural processes of any type (physics, biology, social, etc.) and such artificial processes as the random number generation by a computer software. These periods match with the periods of the Shnoll effect. The theory gives not only to explain the Shnoll effect, but also allows forecasting the fluctuations in the stock exchange market, the fluctuations of weather, earthquakes, and other cataclysms.

  15. Adaptive Use of Information during Growth Can Explain Long-Term Effects of Early Life Experiences.

    PubMed

    English, Sinead; Fawcett, Tim W; Higginson, Andrew D; Trimmer, Pete C; Uller, Tobias

    2016-05-01

    Development is a continuous process during which individuals gain information about their environment and adjust their phenotype accordingly. In many natural systems, individuals are particularly sensitive to early life experiences, even in the absence of later constraints on plasticity. Recent models have highlighted how the adaptive use of information can explain age-dependent plasticity. These models assume that information gain and phenotypic adjustments either cannot occur simultaneously or are completely independent. This assumption is not valid in the context of growth, where finding food results both in a size increase and learning about food availability. Here, we describe a simple model of growth to provide proof of principle that long-term effects of early life experiences can arise through the coupled dynamics of information acquisition and phenotypic change in the absence of direct constraints on plasticity. The increase in reproductive value from gaining information and sensitivity of behavior to experiences declines across development. Early life experiences have long-term impacts on age of maturity, yet-due to compensatory changes in behavior-our model predicts no substantial effects on reproductive success. We discuss how the evolution of sensitive windows can be explained by experiences having short-term effects on informational and phenotypic states, which generate long-term effects on life-history decisions. PMID:27104994

  16. Relation between rainfall intensity and savanna tree abundance explained by water use strategies.

    PubMed

    Xu, Xiangtao; Medvigy, David; Rodriguez-Iturbe, Ignacio

    2015-10-20

    Tree abundance in tropical savannas exhibits large and unexplained spatial variability. Here, we propose that differentiated tree and grass water use strategies can explain the observed negative relation between maximum tree abundance and rainfall intensity (defined as the characteristic rainfall depth on rainy days), and we present a biophysical tree-grass competition model to test this idea. The model is founded on a premise that has been well established in empirical studies, namely, that the relative growth rate of grasses is much higher compared with trees in wet conditions but that grasses are more susceptible to water stress and lose biomass more quickly in dry conditions. The model is coupled with a stochastic rainfall generator and then calibrated and tested using field observations from several African savanna sites. We show that the observed negative relation between maximum tree abundance and rainfall intensity can be explained only when differentiated water use strategies are accounted for. Numerical experiments reveal that this effect is more significant than the effect of root niche separation. Our results emphasize the importance of vegetation physiology in determining the responses of tree abundance to climate variations in tropical savannas and suggest that projected increases in rainfall intensity may lead to an increase in grass in this biome. PMID:26438847

  17. Explained and unexplained tissue loss in corals from the Tropical Eastern Pacific

    USGS Publications Warehouse

    Rodriguez-Villalobos, Jenny Carolina; Work, Thierry M.; Calderon-Aguilera, Luis Eduardo; Reyes-Bonilla, Hector; Hernández, Luis

    2015-01-01

    Coral reefs rival rainforest in biodiversity, but are declining in part because of disease. Tissue loss lesions, a manifestation of disease, are present in dominant Pocillopora along the Pacific coast of Mexico. We characterized tissue loss in 7 species of Pocillopora from 9 locations (44 sites) spanning southern to northern Mexico. Corals were identified to species, and tissue loss lesions were photographed and classified as those explainable by predation and those that were unexplained. A focal predation study was done concurrently at 3 locations to confirm origin of explained lesions. Of 1054 cases of tissue loss in 7 species of corals, 84% were associated with predation (fish, snails, or seastar) and the remainder were unexplained. Types of tissue loss were not related to coral density; however there was significant geographic heterogeneity in type of lesion; one site in particular (Cabo Pulmo) had the highest prevalence of predator-induced tissue loss (mainly pufferfish predation). Crown-of-thorns starfish, pufferfish, and snails were the most common predators and preferred P. verrucosa, P. meandrina, and P. capitata, respectively. Of the 9 locations, 4 had unexplained tissue loss with prevalence ranging from 1 to 3% with no species predilection. Unexplained tissue loss was similar to white syndrome (WS) in morphology, indicating additional study is necessary to clarify the cause(s) of the lesions and the potential impacts to dominant corals along the Pacific coast of Mexico.

  18. Extensive heterosis in growth of yeast hybrids is explained by a combination of genetic models

    PubMed Central

    Shapira, R; Levy, T; Shaked, S; Fridman, E; David, L

    2014-01-01

    Heterosis, also known as hybrid vigor, is the superior performance of a heterozygous hybrid relative to its homozygous parents. Despite the scientific curiosity of this phenotypic phenomenon and its significance for food production in agriculture, its genetic basis is insufficiently understood. Studying heterosis in yeast can potentially yield insights into its genetic basis, can allow one to test the different hypotheses that have been proposed to explain the phenomenon and allows better understanding of how to take advantage of this phenomenon to enhance food production. We therefore crossed 16 parental yeast strains to form 120 yeast hybrids, and measured their growth rates under five environmental conditions. A considerable amount of dominant genetic variation was found in growth performance, and heterosis was measured in 35% of the hybrid–condition combinations. Despite previous reports of correlations between heterosis and measures of sequence divergence between parents, we detected no such relationship. We used several analyses to examine which genetic model might explain heterosis. We found that dominance complementation of recessive alleles, overdominant interactions within loci and epistatic interactions among loci each contribute to heterosis. We concluded that in yeast heterosis is a complex phenotype created by the combined contribution of different genetic interactions. PMID:24690755

  19. Mineral disequilibrium in lavas explained by convective self-mixing in open magma chambers.

    PubMed

    Couch, S; Sparks, R S; Carroll, M R

    2001-06-28

    Characteristic features of many porphyritic andesite and dacite lavas are that they are rich in crystals and display a range of disequilibrium features, including reversely zoned crystals, resorption surfaces, wide ranges of mineral compositions and minerals which are not in equilibrium with the surrounding rock matrix. These features are often interpreted as evidence of the mixing of magmas of contrasting composition, temperature and origin. Here, however, we propose that such features can also be caused by convection within a magma body with a single composition, that is heated from below and cooled from above. We describe petrological observations of andesite lava erupted at the Soufrière Hills volcano, Montserrat, which indicate a heating event and the intermingling of crystals that have very different thermal histories. We present experimental data on a representative groundmass composition of this lava, which indicate that it is difficult to explain the calcic compositions of plagioclase overgrowth rims and microphenocrysts unless parts of the magma were at temperatures much higher than the inferred average temperature. The concept of convective self-mixing allows us to explain the occurrence of compositions of minerals that apparently cannot coexist under equilibrium conditions. PMID:11429601

  20. Co-regulation of metabolic genes is better explained by flux coupling than by network distance.

    PubMed

    Notebaart, Richard A; Teusink, Bas; Siezen, Roland J; Papp, Balázs

    2008-01-01

    To what extent can modes of gene regulation be explained by systems-level properties of metabolic networks? Prior studies on co-regulation of metabolic genes have mainly focused on graph-theoretical features of metabolic networks and demonstrated a decreasing level of co-expression with increasing network distance, a naïve, but widely used, topological index. Others have suggested that static graph representations can poorly capture dynamic functional associations, e.g., in the form of dependence of metabolic fluxes across genes in the network. Here, we systematically tested the relative importance of metabolic flux coupling and network position on gene co-regulation, using a genome-scale metabolic model of Escherichia coli. After validating the computational method with empirical data on flux correlations, we confirm that genes coupled by their enzymatic fluxes not only show similar expression patterns, but also share transcriptional regulators and frequently reside in the same operon. In contrast, we demonstrate that network distance per se has relatively minor influence on gene co-regulation. Moreover, the type of flux coupling can explain refined properties of the regulatory network that are ignored by simple graph-theoretical indices. Our results underline the importance of studying functional states of cellular networks to define physiologically relevant associations between genes and should stimulate future developments of novel functional genomic tools. PMID:18225949

  1. A model ensemble for explaining the seasonal cycle of globally averaged atmospheric carbon dioxide concentration

    NASA Astrophysics Data System (ADS)

    Alexandrov, Georgii; Eliseev, Alexey

    2015-04-01

    The seasonal cycle of the globally averaged atmospheric carbon dioxide concentrations results from the seasonal changes in the gas exchange between the atmosphere and other carbon pools. Terrestrial pools are the most important. Boreal and temperate ecosystems provide a sink for carbon dioxide only during the warm period of the year, and, therefore, the summertime reduction in the atmospheric carbon dioxide concentration is usually explained by the seasonal changes in the magnitude of terrestrial carbon sink. Although this explanation seems almost obvious, it is surprisingly difficult to support it by calculations of the seasonal changes in the strength of the sink provided by boreal and temperate ecosystems. The traditional conceptual framework for modelling net ecosystem exchange (NEE) leads to the estimates of the NEE seasonal cycle amplitude which are too low for explaining the amplitude of the seasonal cycle of the atmospheric carbon dioxide concentration. To propose a more suitable conceptual framework we develop a model ensemble that consists of nine structurally different models and covers various approaches to modelling gross primary production and heterotrophic respiration, including the effects of light saturation, limited light use efficiency, limited water use efficiency, substrate limitation and microbiological priming. The use of model ensembles is a well recognized methodology for evaluating structural uncertainty of model-based predictions. In this study we use this methodology for exploratory modelling analysis - that is, to identify the mechanisms that cause the observed amplitude of the seasonal cycle of the atmospheric carbon dioxide concentration and its slow but steady growth.

  2. A chemical mechanism to explain matrix effects in multi-collector ICP-MS

    NASA Astrophysics Data System (ADS)

    Mueller, B.

    2012-12-01

    A chemical mechanism is presented to explain many of the matrix effects observed in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). It suggests that breakdown products of the ion exchange resins used to remove sample matrix co-elute with samples and subsequently contaminates the uptake tubing and nebulizer of the ICP-MS. The sample path then contains stationary ligands and acts as a mini-column causing memory or carry-over that lead to the observed matrix effects. The minicolumn mechanism is used to explain: variations in sensitivity between samples and standards, variations in sensitivity on the addition of inorganic or organic matrix, changes in mass bias on the addition of matrix elements or column matrix, the coupling of sensitivity changes with mass bias changes, light isotope backgrounds, changes in mass bias with changes in analyte concentration, the poor reproducibility of the matrix effects, the reduction of mass bias with increasing matrix load and variations in mass bias across isotopes of the same element.

  3. Selective Pressures Explain Differences in Flower Color among Gentiana lutea Populations

    PubMed Central

    Domínguez, Paula; Guitián, Javier A.; Guitián, Pablo; Guitián, José M.

    2015-01-01

    Flower color variation among plant populations might reflect adaptation to local conditions such as the interacting animal community. In the northwest Iberian Peninsula, flower color of Gentiana lutea varies longitudinally among populations, ranging from orange to yellow. We explored whether flower color is locally adapted and the role of pollinators and seed predators as agents of selection by analyzing the influence of flower color on (i) pollinator visitation rate and (ii) escape from seed predation and (iii) by testing whether differences in pollinator communities correlate with flower color variation across populations. Finally, (iv) we investigated whether variation in selective pressures explains flower color variation among 12 G. lutea populations. Flower color influenced pollinator visits and differences in flower color among populations were related to variation in pollinator communities. Selective pressures on flower color vary among populations and explain part of flower color differences among populations of G. lutea. We conclude that flower color in G. lutea is locally adapted and that pollinators play a role in this adaptation. PMID:26172378

  4. A Particle Model Explaining Mass and Relativity in a Physical Way

    NASA Astrophysics Data System (ADS)

    Giese, Albrecht

    Physicists' understanding of relativity and the way it is handled is up to present days dominated by the interpretation of Albert Einstein, who related relativity to specific properties of space and time. The principal alternative to Einstein's interpretation is based on a concept proposed by Hendrik A. Lorentz, which uses knowledge of classical physics alone to explain relativistic phenomena. In this paper, we will show that on the one hand the Lorentz-based interpretation provides a simpler mathematical way of arriving at the known results for both Special and General Relativity. On the other hand, it is able to solve problems which have remained open to this day. Furthermore, a particle model will be presented, based on Lorentzian relativity and the quantum mechanical concept of Louis de Broglie, which explains the origin of mass without the use of the Higgs mechanism. It is based on the finiteness of the speed of light and provides classical results for particle properties which are currently only accessible through quantum mechanics.

  5. The lost Gemeinschaft: how people working with the elderly explain loneliness.

    PubMed

    Schirmer, Werner; Michailakis, Dimitris

    2015-04-01

    We conducted a qualitative interview study with people of different professions working with lonely elderly people. The rationale of the study was to examine how these respondents explain loneliness among the elderly. The present article focuses on the social explanations, i.e. explanations that identify causes of loneliness in the structure of modern society. We found that many of the social explanations given are aspects of a more encompassing and general pattern underlying all the reasoning about loneliness among the elderly. This pattern is the expression of two contrasting images of society which the classical sociologist Ferdinand Tönnies termed Gemeinschaft (community) and Gesellschaft (society). The former refers to traditional or small-size rural communities characterized by high degrees of social cohesion, integration, solidarity, proximity and familiarity, whereas the latter refers to functional differentiation, distance, individualization, exchanged-based social relations and anonymity. Loneliness among the elderly is explained by the lack of Gemeinschaft and its characteristics in contemporary society. This explanatory pattern goes hand in hand with a critical view of contemporary society and a nostalgic yearning for the lost communities of past societies, where inhabitants find their staked-out place and sense of belonging, and thus loneliness hardly seems to occur. We summarized this view under the label the "lost Gemeinschaft". PMID:25841724

  6. Explaining health care utilization for panic attacks using cusp catastrophe modeling.

    PubMed

    Katerndahl, David

    2008-10-01

    Despite increased health care utilization, patients with panic disorder continue to report unmet needs. The objective was to compare the fit of linear and Cusp Catastrophe Modeling in explaining changes in utilization of emergency, general and mental health settings, and self-treatments for panic symptoms. This community-based study surveyed 97 subjects with panic attacks drawn from a sample of randomly-selected adults from randomly-selected households. The stressor (splitting) variable used was Phobic Anxiety while predisposing variables included Family Health Care Utilization, Perceived Life Threat and Need For Treatment, and Treatment Experience. Outcomes consisted of the number of sites and self-treatments used for panic symptoms when first seeking care and during the 2 months prior to survey. Use of mental health sites and self-treatments demonstrated superior modeling with cusp catastrophe approaches using treatment experience as the predisposing variable, accounting for 47% and 38% of variances respectively, improving the fit by over 20% compared to the best linear models in both cases. Cusp catastrophe modeling accounted for more variance than all linear models when describing use of mental health settings and self-treatments. Cusp catastrophe may explain bimodal distributions in behavior, delays in behavior change, and sudden shifts in behavior in stressful situations. PMID:18765074

  7. Individual-Area Relationship Best Explains Goose Species Density in Wetlands

    PubMed Central

    Prins, Herbert H. T.; Cao, Lei; de Boer, Willem Fred

    2015-01-01

    Explaining and predicting animal distributions is one of the fundamental objectives in ecology and conservation biology. Animal habitat selection can be regulated by top-down and bottom-up processes, and is mediated by species interactions. Species varying in body size respond differently to top-down and bottom-up determinants, and hence understanding these allometric responses to those determinants is important for conservation. In this study, using two differently sized goose species wintering in the Yangtze floodplain, we tested the predictions derived from three different hypotheses (individual-area relationship, food resource and disturbance hypothesis) to explain the spatial and temporal variation in densities of two goose species. Using Generalized Linear Mixed Models with a Markov Chain Monte Carlo technique, we demonstrated that goose density was positive correlated with patch area size, suggesting that the individual area-relationship best predicts differences in goose densities. Moreover, the other predictions, related to food availability and disturbance, were not significant. Buffalo grazing probably facilitated greater white-fronted geese, as the number of buffalos was positively correlated to the density of this species. We concluded that patch area size is the most important factor determining the density of goose species in our study area. Patch area size is directly determined by water levels in the Yangtze floodplain, and hence modifying the hydrological regimes can enlarge the capacity of these wetlands for migratory birds. PMID:25996502

  8. Horizon-scale Lepton Acceleration in Jets: Explaining the Compact Radio Emission in M87

    NASA Astrophysics Data System (ADS)

    Broderick, Avery E.; Tchekhovskoy, Alexander

    2015-08-01

    It has now become clear that the radio jet in the giant elliptical galaxy M87 must turn on very close to the black hole. This implies the efficient acceleration of leptons within the jet at scales much smaller than feasible by the typical dissipative events usually invoked to explain jet synchrotron emission. Here we show that the stagnation surface, the separatrix between material that falls back into the black hole and material that is accelerated outward forming the jet, is a natural site of pair formation and particle acceleration. This occurs via an inverse Compton pair catastrophe driven by unscreened electric fields within the charge-starved region about the stagnation surface and substantially amplified by a post-gap cascade. For typical estimates of the jet properties in M87, we find excellent quantitive agreement between the predicted relativistic lepton densities and those required by recent high-frequency radio observations of M87. This mechanism fails to adequately fill a putative jet from Sagittarius A* with relativistic leptons, which may explain the lack of an obvious radio jet in the Galactic center. Finally, this process implies a relationship between the kinetic jet power and the gamma-ray luminosity of blazars, produced during the post-gap cascade.

  9. Explaining the power-law distribution of human mobility through transportation modality decomposition

    NASA Astrophysics Data System (ADS)

    Zhao, Kai; Musolesi, Mirco; Hui, Pan; Rao, Weixiong; Tarkoma, Sasu

    2015-03-01

    Human mobility has been empirically observed to exhibit Lévy flight characteristics and behaviour with power-law distributed jump size. The fundamental mechanisms behind this behaviour has not yet been fully explained. In this paper, we propose to explain the Lévy walk behaviour observed in human mobility patterns by decomposing them into different classes according to the different transportation modes, such as Walk/Run, Bike, Train/Subway or Car/Taxi/Bus. Our analysis is based on two real-life GPS datasets containing approximately 10 and 20 million GPS samples with transportation mode information. We show that human mobility can be modelled as a mixture of different transportation modes, and that these single movement patterns can be approximated by a lognormal distribution rather than a power-law distribution. Then, we demonstrate that the mixture of the decomposed lognormal flight distributions associated with each modality is a power-law distribution, providing an explanation to the emergence of Lévy Walk patterns that characterize human mobility patterns.

  10. Temperature limitation may explain the containment of the trophozoites in the cornea during Acanthamoeba castellanii keratitis.

    PubMed

    Nielsen, Mattias Kiel; Nielsen, Kim; Hjortdal, Jesper; Sørensen, Uffe B Skov

    2014-12-01

    Acanthamoeba keratitis is a serious sight-threatening disease. The relatively low temperature of the cornea may explain why amoebic infections usually are localized in this tissue and rarely spread to other parts of the eye. In this study, the growth rate of the amoeba Acanthamoeba castellanii was examined at different temperatures. The aim was to establish the optimal growth temperature for A. castellanii and to examine the growth within the vicinity of the core body temperature. The growth rates of four clinical and two environmental strains of A. castellanii were estimated at different temperatures, and temperature limitations for the trophozoite stage was established. Movements influenced by temperature gradients were monitored for two clinical strains of A. castellanii. The highest growth rate for each of the six amoebic strains tested was found to be close to 32 °C. The growth of the trophozoites of all examined strains was greatly reduced or completely halted at temperatures above 36 °C and encysted at the elevated temperature. Thus, the optimal growth temperature for the four strains of A. castellanii is close to the surface temperature of the human cornea, while the higher body core-temperature induced encysting of the amoebae. This may explain why most amoebic eye infections are confined to the cornea. PMID:25204727

  11. Plant traits explain landscape-scale variation in C stocks and soil microbial communities

    NASA Astrophysics Data System (ADS)

    de Vries, F. T.; Manning, P.; Bardgett, R. D.

    2012-04-01

    In recent years, plant traits have been found to relate to ecosystem processes such as rates of nitrogen mineralisation and decomposition, but also to the composition of the soil microbial community. Most evidence for these patterns, however, comes from relatively small-scale, within-field studies, and relationships are often based on data derived from plants grown in monoculture. It is not clear, therefore, if these same patterns can be observed at landscape or regional scales where such relationships might be overwhelmed by the effects of abiotic factors, including soil physical and chemical properties and climate. Here, we sampled 180 grasslands across England to assess the importance of plant traits, expressed as community-weighted means (CWM), for determining soil carbon stocks and microbial communities, on top of abiotic factors such as climate and soil properties, such as texture and pH. We fitted statistical models to data detailing the climate, soil properties, vegetation, carbon (C) and nitrogen (N) stocks, and microbial communities (assessed using PLFAs) of this wide range of grassland types. We found that total soil C and N stocks were explained by a combination of abiotic factors, whereas for the separate pools plant traits appeared to be important: the active C fraction (>250 μm) decreased with a greater CWM of the plant trait specific leaf area (SLA), and the stable pool of physically and biochemically protected C (0.45-50 µm) increased with greater CWM leaf N content. Plant traits were also explained variation in soil microbial community composition across these grasslands, and in particular the fungal-to-bacterial biomass ratio decreased with increasing CWM leaf N content. In a subset of 22 grasslands in the Yorkshire Dales, we found that N leaching in the field increased with greater leaf N content, and that retention of added N was greater with increasing fungal abundance, because of greater immobilisation in microbial biomass. Collectively

  12. Apparent enrichment of organically bound tritium in rivers explained by the heritage of our past.

    PubMed

    Eyrolle-Boyer, Frédérique; Boyer, Patrick; Claval, David; Charmasson, Sabine; Cossonnet, Catherine

    2014-10-01

    The global inventory of naturally produced tritium (3H) is estimated at 2.65 kg, whereas more than 600 kg have been released during atmospheric nuclear tests (NCRP, 1979; UNSCEAR, 2000) constituting the main source of artificial tritium throughout the Anthropocene. The behaviour of this radioactive isotope in the environment has been widely studied since the 1950s, both through laboratory experiments and, more recently, through field observations (e.g., Cline, 1953; Kirchmann et al., 1979; Daillant et al., 2004; McCubbin et al., 2001; Kim et al., 2012). In its "free" forms, [i.e. 3H gas or 3H hydride (HT); methyl 3H gas (CH3T); tritiated H2O or 3H-oxide (HTO); and Tissue Free Water 3H (TFWT)], tritium closely follows the water cycle. However, 3H bound with organic compounds, mainly during the basic stages of photosynthesis or through weak hydrogen links, is less exchangeable with water, which explains its persistence in the carbon cycle as re underlined recently by Baglan et al. (2013), Jean-Batiste and Fourré (2013), Kim et al. (2013a,b). In this paper, we demonstrate that terrestrial biomass pools, historically contaminated by global atmospheric fallout from nuclear testing, have constituted a significant delayed source of organically bound tritium (OBT) for aquatic systems, resulting in an apparent enrichment of OBT as compared to HTO. This finding helps to explain concentration factors (tritium concentration in biota/concentration in water) greater than 1 observed in areas that are not directly affected by industrial radioactive wastes, and thus sheds light on the controversies regarding tritium 'bioaccumulation'. Such apparent enrichment of OBT is expected to be more pronounced in the Northern Hemisphere where fallout was most significant, depending on the nature and biodegradability of terrestrial biomass at the regional scale. We further believe that OBT transfers from the continent to oceans have been sufficient to affect tritium concentrations in

  13. Explaining the discrepancy between intentions and actions: the case of hypothetical bias in contingent valuation.

    PubMed

    Ajzen, Icek; Brown, Thomas C; Carvajal, Franklin

    2004-09-01

    An experiment was designed to account for intention-behavior discrepancies by applying the theory of planned behavior to contingent valuation. College students (N = 160) voted in hypothetical and real payment referenda to contribute $8 to a scholarship fund. Overestimates of willingness to pay in the hypothetical referendum could not be attributed to moderately favorable latent dispositions. Instead, this hypothetical bias was explained by activation of more favorable beliefs and attitudes in the context of a hypothetical rather than a real referendum. A corrective entreaty was found to eliminate this bias by bringing beliefs, attitudes, and intentions in line with those in the real payment situation. As a result, the theory of planned behavior produced more accurate prediction of real payment when participants were exposed to the corrective entreaty. PMID:15359015

  14. Two cellular hypotheses explaining the initiation of ketamine's antidepressant actions: Direct inhibition and disinhibition.

    PubMed

    Miller, Oliver H; Moran, Jacqueline T; Hall, Benjamin J

    2016-01-01

    A single, low dose of ketamine evokes antidepressant actions in depressed patients and in patients with treatment-resistant depression (TRD). Unlike classic antidepressants, which regulate monoamine neurotransmitter systems, ketamine is an antagonist of the N-methyl-D-aspartate (NMDA) family of glutamate receptors. The effectiveness of NMDAR antagonists in TRD unveils a new set of targets for therapeutic intervention in major depressive disorder (MDD) and TRD. However, a better understanding of the cellular mechanisms underlying these effects is required for guiding future therapeutic strategies, in order to minimize side effects and prolong duration of efficacy. Here we review the evidence for and against two hypotheses that have been proposed to explain how NMDAR antagonism initiates protein synthesis and increases excitatory synaptic drive in corticolimbic brain regions, either through selective antagonism of inhibitory interneurons and cortical disinhibition, or by direct inhibition of cortical pyramidal neurons. This article is part of the Special Issue entitled 'Synaptopathy--from Biology to Therapy'. PMID:26211972

  15. Explaining distortions in utility elicitation through the rank-dependent model for risky choices.

    PubMed

    Wakker, P; Stiggelbout, A

    1995-01-01

    The standard-gamble (SG) method has been accepted as the "gold standard" for the elicitation of utility when risk or uncertainty is involved in decisions, and thus for the measurement of utility in medical decisions. It is based on the assumptions of expected-utility theory. Unfortunately, there is now abundant evidence that expected utility is not empirically valid, and that the SG method overestimates risk aversion and the utilities of impaired health states. This paper shows how rank-dependent utility theory, a newly developed theory in decision science, can explain the main violations of expected utility. Thus it provides a means for correcting the SG method and for improving the assessments of quality-adjusted life years for medical decisions in which there is uncertainty about outcomes. PMID:7783579

  16. A Longitudinal Multilevel Study of Individual Characteristics and Classroom Norms in Explaining Bullying Behaviors.

    PubMed

    Sentse, Miranda; Veenstra, René; Kiuru, Noona; Salmivalli, Christina

    2015-07-01

    This three-wave longitudinal study was set out to examine the interplay between individual characteristics (social standing in the classroom) and descriptive and injunctive classroom norms (behavior and attitudes, respectively) in explaining subsequent bullying behavior, defined as initiating, assisting, or reinforcing bullying. The target sample contained fourth- to sixth-grade students (n = 2,051) who attended the control schools in the Finnish evaluation of the KiVa antibullying program. Random slope multilevel analyses revealed that, over time, higher popularity or rejection, or lower acceptance were associated with increases in bullying behaviors, especially in classrooms with a high descriptive bullying norm. In contrast, the injunctive norm did not moderate the associations between social standing and engagement in bullying, except for children high on popularity. Theoretical and practical implications of the results are discussed. PMID:25370007

  17. Probabilistic Model of Onset Detection Explains Paradoxes in Human Time Perception

    PubMed Central

    Nikolov, Stanislav; Rahnev, Dobromir A.; Lau, Hakwan C.

    2010-01-01

    A very basic computational model is proposed to explain two puzzling findings in the time perception literature. First, spontaneous motor actions are preceded by up to 1–2 s of preparatory activity (Kornhuber and Deecke, 1965). Yet, subjects are only consciously aware of about a quarter of a second of motor preparation (Libet et al., 1983). Why are they not aware of the early part of preparation? Second, psychophysical findings (Spence et al., 2001) support the principle of attention prior entry (Titchener, 1908), which states that attended stimuli are perceived faster than unattended stimuli. However, electrophysiological studies reported no or little corresponding temporal difference between the neural signals for attended and unattended stimuli (McDonald et al., 2005; Vibell et al., 2007). We suggest that the key to understanding these puzzling findings is to think of onset detection in probabilistic terms. The two apparently paradoxical phenomena are naturally predicted by our signal detection theoretic model. PMID:21833206

  18. Can the pattern of foraminiferal intratest trace element variations be explained by Ca dilution during biomineralization?

    NASA Astrophysics Data System (ADS)

    Hathorne, Ed

    2010-05-01

    Recently Hathorne et al. (2009) documented large intratest trace element (TE) variations in planktonic foraminifera from a single sediment trap sample that could not be explained by variations in water column properties. The laser ablation ICP-MS depth profiles of trace elements through the test walls revealed strong positive correlations between Li, Mg, Mn and Ba resulting from the mixing of a lower TE outer calcite with a higher TE inner calcite. In contrast Sr/Ca ratios remained relatively constant throughout the test wall. These intratest TE variations likely result from biomineralization processes and therefore should be explained by any valid biomineralization model. However, changes in calcite precipitation rate, crystal structure, or the chemical composition of the internal calcification reservoir could not, by themselves, fully account for the pattern of cation intratest variability. Here I expand on this work and investigate if a model of coral biomineralization by Sinclair and Risk (2006) can be adapted to explain the pattern of intratest TE variability in foraminifera. It is clear that the low Mg calcite secreting foraminifera must reduce the Mg/Ca ratio of the calcifying solution by at least a factor of 10 (e.g. Hathorne et al., 2009) and it has been suggested this is achieved by active removal of Mg from the calcification reservoir, although the actual mechanisms remain debatable (e.g. Bentov and Erez, 2006). However, a recent study of the calcification of a low Mg calcite species in the laboratory found a large shortcoming in the amount of Ca potentially provided by seawater transported to the site of calcification in vacuoles compared to a conservative estimate of the amount required to form the new calcite wall (de Nooijer et al., 2009a). This suggests active Ca transport to the site of calcification is required to provide sufficient Ca. If Ca specific, this Ca addition would effectively dilute the TE content (including Mg) of the calcification

  19. Can neutrino-induced photon production explain the low energy excess in MiniBooNE?

    NASA Astrophysics Data System (ADS)

    Zhang, Xilin; Serot, Brian D.

    2013-02-01

    This report summarizes our study of Neutral Current (NC)-induced photon production in MiniBooNE, as motivated by the low energy excess in this experiment [A.A. Aquilar-Arevalo et al., MiniBooNE Collaboration, Phys. Rev. Lett. 98 (2007) 231801; A.A. Aquilar-Arevalo et al., MiniBooNE Collaboration, Phys. Rev. Lett. 103 (2009) 111801]. It was proposed that NC photon production with two anomalous photon-Z boson-vector meson couplings might explain the excess. However, our computed event numbers in both neutrino and antineutrino runs are consistent with the previous MiniBooNE estimate that is based on their pion production measurement. Various nuclear effects discussed in our previous works, including nucleon Fermi motion, Pauli blocking, and the Δ resonance broadening in the nucleus, are taken into account. Uncertainty due to the two anomalous terms and nuclear effects are studied in a conservative way.

  20. Explaining the Behavioral Intention towards BI Implementation in Public Administrations - A Principal-Agent Theory Approach

    NASA Astrophysics Data System (ADS)

    Becker, Jörg; Bergener, Philipp; Lis, Łukasz; Niehaves, Björn

    Business Intelligence (BI) is an established instrument to support public administrations in their management tasks by increasing their information level. BI is of special interest in the context of introducing accrual accounting in public administrations as this affects the information level of different stakeholders, leading to a possible decrease for municipal councils. The principal-agent theory can help to explain different behavioral intentions of the stakeholders concerning the introduction of BI. We employ a single qualitative case study to analyze these behavioral intentions. It shows that the introduction of accrual accounting did decrease the information level of the municipal council making the principal-agent problems possible. Furthermore, it shows that BI might be a solution for this problem. Therefore, council members show the behavioral intention to support the BI implementation while administration staff members rather resist it. Based on these finding, we discuss implications for practice and future research.

  1. Explaining Extremity in Evaluation of Group Members: Meta-Analytic Tests of Three Theories.

    PubMed

    Bettencourt, B Ann; Manning, Mark; Molix, Lisa; Schlegel, Rebecca; Eidelman, Scott; Biernat, Monica

    2016-02-01

    A meta-analysis that included more than 1,100 effect sizes tested the predictions of three theoretical perspectives that explain evaluative extremity in social judgment: complexity-extremity theory, subjective group dynamics model, and expectancy-violation theory. The work seeks to understand the ways in which group-based information interacts with person-based information to influence extremity in evaluations. Together, these three theories point to the valence of person-based information, group membership of the evaluated targets relative to the evaluator, status of the evaluators' ingroup, norm consistency of the person-based information, and incongruency of person-based information with stereotype-based expectations as moderators. Considerable support, but some limiting conditions, were found for each theoretical perspective. Implications of the results are discussed. PMID:25770087

  2. Explaining equity gains in child survival in Bangladesh: scale, speed, and selectivity in health and development.

    PubMed

    Adams, Alayne M; Rabbani, Atonu; Ahmed, Shamim; Mahmood, Shehrin Shaila; Al-Sabir, Ahmed; Rashid, Sabina F; Evans, Timothy G

    2013-12-14

    By disaggregating gains in child health in Bangladesh over the past several decades, significant improvements in gender and socioeconomic inequities have been revealed. With the use of a social determinants of health approach, key features of the country's development experience can be identified that help explain its unexpected health trajectory. The systematic equity orientation of health and socioeconomic development in Bangladesh, and the implementation attributes of scale, speed, and selectivity, have been important drivers of health improvement. Despite this impressive pro-equity trajectory, there remain significant residual inequities in survival of girls and lower wealth quintiles as well as a host of new health and development challenges such as urbanisation, chronic disease, and climate change. Further progress in sustaining and enhancing equity-oriented achievements in health hinges on stronger governance and longer-term systems thinking regarding how to effectively promote inclusive and equitable development within and beyond the health system. PMID:24268604

  3. Children's skepticism: developmental and individual differences in children's ability to detect and explain distorted claims.

    PubMed

    Mills, Candice M; Elashi, Fadwa B

    2014-08-01

    The current study examined some key developmental and individual differences in how elementary school-aged children evaluate sources of information. A sample of 130 children ages 6 to 9 years participated in a task designed to measure children's understanding of ways that claims can be distorted (i.e., biased decisions, skewed self-reports, and misleading persuasive claims). Children also completed several individual difference measures, including a brief intelligence task and an advanced social cognition measure (interpretive theory of mind). Overall, older children were less trusting and better than younger children at explaining the reasons to doubt sources that might provide distorted claims. Crucially, the results also suggest that beyond age, both general intelligence and advanced social cognitive skills play roles in children's ability to understand when and why they must doubt sources of distortion. PMID:24727295

  4. 750 GeV diphoton excess explained by a resonant sneutrino in R -parity violating supersymmetry

    NASA Astrophysics Data System (ADS)

    Allanach, B. C.; Dev, P. S. Bhupal; Renner, S. A.; Sakurai, Kazuki

    2016-06-01

    We explain the recent excess seen by ATLAS and CMS experiments at around 750 GeV in the diphoton invariant mass as a narrow-width sneutrino decaying to diphotons via a stau loop in R -parity violating supersymmetry. The stau mass is predicted to be somewhere between half the resonant sneutrino mass and half the sneutrino mass plus 14 GeV. The scenario also predicts further signal channels at an invariant mass of 750 GeV, the most promising being into dijets and W W . We also predict a left-handed charged slepton decaying into W Z and W γ at a mass 750-754 GeV.

  5. Explaining trends in addictive behaviour policy--the role of policy coherence.

    PubMed

    Adam, Christian; Raschzok, Andreas

    2014-05-01

    This article analyses addictive behaviour policy regimes - focusing on illegal drugs and gambling - in 19 countries over a period of 50 years. It compares how these countries have combined rules on the consumption and possession of cannabis and on the participation in sports betting with sanctions for violations of these rules. While theories of policy convergence can explain dominant trends in the way the combination of these policy instruments have changed, they cannot account for all of the empirical variation observed. Turning to Portugal, a case which deviates in both illegal drug and gambling policy from the expected trend, we show that explanations of policy change improve substantially when taking the concept of policy coherence into account. Specifically, we argue that changes of the policy status quo are facilitated when policy entrepreneurs succeed in shaping a perception of policy incoherence. In turn, when relevant actors are able to maintain a perception of policy coherence, the policy status quo is stabilized. PMID:24726776

  6. Qualitative Dynamical Modelling Can Formally Explain Mesoderm Specification and Predict Novel Developmental Phenotypes.

    PubMed

    Mbodj, Abibatou; Gustafson, E Hilary; Ciglar, Lucia; Junion, Guillaume; Gonzalez, Aitor; Girardot, Charles; Perrin, Laurent; Furlong, Eileen E M; Thieffry, Denis

    2016-09-01

    Given the complexity of developmental networks, it is often difficult to predict the effect of genetic perturbations, even within coding genes. Regulatory factors generally have pleiotropic effects, exhibit partially redundant roles, and regulate highly interconnected pathways with ample cross-talk. Here, we delineate a logical model encompassing 48 components and 82 regulatory interactions involved in mesoderm specification during Drosophila development, thereby providing a formal integration of all available genetic information from the literature. The four main tissues derived from mesoderm correspond to alternative stable states. We demonstrate that the model can predict known mutant phenotypes and use it to systematically predict the effects of over 300 new, often non-intuitive, loss- and gain-of-function mutations, and combinations thereof. We further validated several novel predictions experimentally, thereby demonstrating the robustness of model. Logical modelling can thus contribute to formally explain and predict regulatory outcomes underlying cell fate decisions. PMID:27599298

  7. Can Professional Environments in Schools Promote Teacher Development? Explaining Heterogeneity in Returns to Teaching Experience

    PubMed Central

    Kraft, Matthew A.; Papay, John P.

    2014-01-01

    Although wide variation in teacher effectiveness is well established, much less is known about differences in teacher improvement over time. We document that average returns to teaching experience mask large variation across individual teachers and across groups of teachers working in different schools. We examine the role of school context in explaining these differences using a measure of the professional environment constructed from teachers responses to state-wide surveys. Our analyses show that teachers working in more supportive professional environments improve their effectiveness more over time than teachers working in less supportive contexts. On average, teachers working in schools at the 75th percentile of professional environment ratings improved 38% more than teachers in schools at the 25th percentile after 10 years. PMID:25866426

  8. Sensory interactions between six common aroma vectors explain four main red wine aroma nuances.

    PubMed

    Ferreira, Vicente; Sáenz-Navajas, María-Pilar; Campo, Eva; Herrero, Paula; de la Fuente, Arancha; Fernández-Zurbano, Purificación

    2016-05-15

    This work aims at assessing the aromatic sensory dimensions linked to 6 common wine aroma vectors (N, norisoprenoids; A, branched acids; F, enolones; E, branched ethyl esters; L, fusel alcohols, M, wood compounds) varying in their natural range of occurrence. Wine models were built by adding the vectors at two levels (fractional factorial design 2(VI)) to a de-aromatised aged red wine. Twenty other different models were evaluated by descriptive analysis. Red, black and dried fruits and woody notes were satisfactorily reproduced. Individual vectors explained just 15% of the sensory space, mostly dependent on perceptual interactions. N influences dried and black fruits and suppresses red fruits. A suppresses black fruits and enhances red and dried fruits. F exerts a major role on red fruits. E suppresses dried fruits and modulates black fruits. L is revealed as a strong suppressor of red fruits and particularly of woody notes. PMID:26775994

  9. Large-scale magnetic fields can explain the baryon asymmetry of the Universe

    NASA Astrophysics Data System (ADS)

    Fujita, Tomohiro; Kamada, Kohei

    2016-04-01

    Helical hypermagnetic fields in the primordial Universe can produce the observed amount of baryon asymmetry through the chiral anomaly without any ingredients beyond the standard model of particle physics. While they generate no B -L asymmetry, the generated baryon asymmetry survives the spharelon washout effect, because the generating process remains active until the electroweak phase transition. Solving the Boltzmann equation numerically and finding an attractor solution, we show that the baryon asymmetry of our Universe can be explained, if the present large-scale magnetic fields indicated by the blazar observations have a negative helicity and existed in the early Universe before the electroweak phase transition. We also derive the upper bound on the strength of the helical magnetic field, which is tighter than the cosmic microwave background constraint, to avoid the overproduction of baryon asymmetry.

  10. Explaining Gender Differences in Caries: A Multifactorial Approach to a Multifactorial Disease

    PubMed Central

    Ferraro, Maria; Vieira, Alexandre R.

    2010-01-01

    Many studies have demonstrated that caries rates are higher in women than in men. This review attempts to provide an explanation for this trend by examining each factor which contributes to caries and how the factor differs in men and women. Evidence has been provided to demonstrate that caries risk factors for women include a different salivary composition and flow rate, hormonal fluctuations, dietary habits, genetic variations, and particular social roles among their family. Systemic diseases that have been found to be associated with caries have also been found to have an association with the female gender. An extended exposure to the oral cavity or a more cariogenic oral microflora has not been proven to contribute to higher caries in women. Further research in these areas could be done in the future to explain their contribution, or lack thereof, to a higher caries rate in women. PMID:20339488

  11. It was meant to happen: explaining cultural variations in fate attributions.

    PubMed

    Norenzayan, Ara; Lee, Albert

    2010-05-01

    People often perceive important and improbable life outcomes as "meant to happen," that is, predetermined and inevitable. In 4 studies, we constructed diverse measures of such fate attributions and examined the cultural correlates of this attributional tendency, focusing on ethnic culture and religious affiliation differences. Independently of ethnic culture, Christians were found to endorse fate attributions more than did the nonreligious; and independently of religious affiliation, East Asian Canadians attributed events to fate more than did European Canadians. Consistent with theoretical predictions, the religious affiliation difference was mediated by belief in God, whereas the ethnic cultural difference was mediated by a measure of causal complexity, although not by a measure of acculturation. Experimentally inducing thoughts of causal complexity in one domain increased fate attributions in unrelated domains. These results point to 2 independent psychological sources of fate attributions which also explain observed cultural differences in this tendency. PMID:20438219

  12. Phylogenetic niche conservatism explains an inverse latitudinal diversity gradient in freshwater arthropods.

    PubMed

    Morinière, Jérôme; Van Dam, Matthew H; Hawlitschek, Oliver; Bergsten, Johannes; Michat, Mariano C; Hendrich, Lars; Ribera, Ignacio; Toussaint, Emmanuel F A; Balke, Michael

    2016-01-01

    The underlying mechanisms responsible for the general increase in species richness from temperate regions to the tropics remain equivocal. Many hypotheses have been proposed to explain this astonishing pattern but additional empirical studies are needed to shed light on the drivers at work. Here we reconstruct the evolutionary history of the cosmopolitan diving beetle subfamily Colymbetinae, the majority of which are found in the Northern hemisphere, hence exhibiting an inversed latitudinal diversity gradient. We reconstructed a dated phylogeny using 12 genes, to investigate the biogeographical history and diversification dynamics in the Colymbetinae. We aimed to identify the role that phylogenetic niche conservatism plays in the inversed diversification pattern seen in this group. Our results suggest that Colymbetinae originated in temperate climates, which supports the hypothesis that their distribution is the result of an ancestral adaptation to temperate environmental conditions rather than tropical origins, and that temperate niche conservatism can generate and/or maintain inverse latitudinal diversity gradients. PMID:27215956

  13. Radiative forcing by coastal anthropogenic emissions explains observed 20th century Southeast Pacific cooling

    NASA Astrophysics Data System (ADS)

    Spak, S.; Saide, P. E.; Mena, M.; Carmichael, G. R.

    2014-12-01

    The coastal Southeast Pacific cooled by 0.25K from 1979-2006, a period when the nearby Andes warmed by 0.25K. While correlated with atmospheric teleconnections, the magnitude and causes of observed cooling and changes in regional cloud cover have not been explained quantitatively. Here we show that inadvertent cloud modification by anthropogenic emissions from Chile and Peru has increased cloud brightness and lifetime throughout the region's extensive stratocumulus, resulting in net shortwave surface climate forcing and boundary layer cooling consistent with the vertical profile of observed cooling. The extensive stratocumulus observed in the region throughout the satellite era are more widespread and brighter than pre-industrial conditions. Results underscore the need to consider potentially large local and global climatic impacts when setting air quality and greenhouse gas policies in regions with extensive warm boundary layer cloud regimes.

  14. Attachment at (not to) work: applying attachment theory to explain individual behavior in organizations.

    PubMed

    Richards, David A; Schat, Aaron C H

    2011-01-01

    In this article, we report the results of 2 studies that were conducted to investigate whether adult attachment theory explains employee behavior at work. In the first study, we examined the structure of a measure of adult attachment and its relations with measures of trait affectivity and the Big Five. In the second study, we examined the relations between dimensions of attachment and emotion regulation behaviors, turnover intentions, and supervisory reports of counterproductive work behavior and organizational citizenship behavior. Results showed that anxiety and avoidance represent 2 higher order dimensions of attachment that predicted these criteria (except for counterproductive work behavior) after controlling for individual difference variables and organizational commitment. The implications of these results for the study of attachment at work are discussed. PMID:20718531

  15. Differentiation without Distancing. Explaining Bi-Polarization of Opinions without Negative Influence

    PubMed Central

    Mäs, Michael; Flache, Andreas

    2013-01-01

    Explanations of opinion bi-polarization hinge on the assumption of negative influence, individuals’ striving to amplify differences to disliked others. However, empirical evidence for negative influence is inconclusive, which motivated us to search for an alternative explanation. Here, we demonstrate that bi-polarization can be explained without negative influence, drawing on theories that emphasize the communication of arguments as central mechanism of influence. Due to homophily, actors interact mainly with others whose arguments will intensify existing tendencies for or against the issue at stake. We develop an agent-based model of this theory and compare its implications to those of existing social-influence models, deriving testable hypotheses about the conditions of bi-polarization. Hypotheses were tested with a group-discussion experiment (N = 96). Results demonstrate that argument exchange can entail bi-polarization even when there is no negative influence. PMID:24312164

  16. Social cognitive impairment and autism: what are we trying to explain?

    PubMed Central

    Leekam, Susan

    2016-01-01

    Early psychological theories of autism explained the clinical features of this condition in terms of perceptual and sensory processing impairments. The arrival of domain-specific social cognitive theories changed this focus, postulating a ‘primary’ and specific psychological impairment of social cognition. Across the years, evidence has been growing in support of social cognitive and social attention explanations in autism. However, there has also been evidence for general non-social cognitive impairments in representational understanding, attention allocation and sensory processing. Here, I review recent findings and consider the case for the specificity and primacy of the social cognitive impairment, proposing that we should focus more explicitly on clinically valid features for insights on the integration of ‘social’ and ‘non-social’ cognition. PMID:26644600

  17. Can Charge Exchange Explain Anomalous Soft X-Ray Emission in the Cygnus Loop?

    NASA Astrophysics Data System (ADS)

    Cumbee, R. S.; Henley, D. B.; Stancil, P. C.; Shelton, R. L.; Nolte, J. L.; Wu, Y.; Schultz, D. R.

    2014-06-01

    Recent X-ray studies have shown that supernova shock models are unable to satisfactorily explain X-ray emission in the rim of the Cygnus Loop. In an attempt to account for this "anomalously" enhanced X-ray flux, we fit the region with a model including theoretical charge exchange (CX) data along with shock and background X-ray models. The model includes the CX collisions of O8 +, O7 +, N7 +, N6 +, C6 +, and C5 + with H with an energy of 1 keV u-1 (438 km s-1). The observations reveal a strong emission feature near 0.7 keV that cannot fully be accounted for by a shock model, nor the current CX data. Inclusion of CX, specifically O7 + + H, does provide for a statistically significant improvement over a pure shock model.

  18. Does the situational couple violence- intimate terrorism typology explain cohabitors' high risk of intimate partner violence?

    PubMed

    Brownridge, Douglas A

    2010-07-01

    This study examines M. P. Johnson's assertion that violence in marital unions is more likely to be intimate terrorism (IT) and violence in cohabiting unions is more likely to be situational couple violence (SCV). Having overcome limitations of the data on which Johnson based his assertion, the results show that cohabiting and married victims of violence are equally likely to report experiencing SCV and IT. Moreover, cohabitors have higher odds of experiencing SCV and IT compared to their counterparts living in a marital union. These marital status differences are explained by selection and relationship factors theorized to account for them. Although the SCV- IT typology does appear to shed light on gender differences, the results of this study suggest that, where relevant, researchers using this typology should not neglect risk factors derived from theories for understanding intimate partner violence (IPV). PMID:19729674

  19. A nonadaptive scenario explaining the genetic predisposition to obesity: the "predation release" hypothesis.

    PubMed

    Speakman, John R

    2007-07-01

    The "thrifty gene hypothesis" suggests we evolved genes for efficient food collection and fat deposition to survive periods of famine and that now that food is continuously available, these genes are disadvantageous because they make us obese in preparation for a famine that never comes. However, famines are relatively infrequent modern phenomena that involve insufficient mortality for thrifty genes to propagate. I suggest here that early hominids would have been subjected to stabilizing selection for body fatness, with obesity selected against by the risk of predation. Around two million years ago predation was removed as a significant factor by the development of social behavior, weapons, and fire. The absence of predation led to a change in the population distribution of body fatness due to random mutations and drift. Because this novel hypothesis involves random drift, rather than directed selection, it explains why, even in Western society, most people are not obese. PMID:17618852

  20. Unravelling gossamer with boxing gloves: problems in explaining the decline in smoking.

    PubMed Central

    Chapman, S

    1993-01-01

    For about three decades countries such as Australia, Great Britain, and the United States have been turning up the heat on tobacco advertising. Encouraging, sometimes dramatic falls in consumption have followed. On any given day in 1993 smokers in such countries are exposed to a welter of news, information, persuasion, and policies designed to turn them off smoking. For a long time explanations and evaluations of the effects of these policies and interventions have been tied to oversimplified causal models when the reality is rather more messy and complicated. Four factors largely explain the reluctance of researchers to move beyond these models: the reductionist tradition of science; the explanatory privileging of recent events and factors; pragmatic concern for policy "tractable" factors; and the relation of funding to the evaluative process. Broader research approaches to understanding changes in complex behaviours such as smoking are required--for example, qualitative methods. Images p431-a p432-a PMID:8374457

  1. The influence of categories on perception: Explaining the perceptual magnet effect as optimal statistical inference

    PubMed Central

    Feldman, Naomi H.; Griffiths, Thomas L.; Morgan, James L.

    2009-01-01

    A variety of studies have demonstrated that organizing stimuli into categories can affect the way the stimuli are perceived. We explore the influence of categories on perception through one such phenomenon, the perceptual magnet effect, in which discriminability between vowels is reduced near prototypical vowel sounds. We present a Bayesian model to explain why this reduced discriminability might occur: it arises as a consequence of optimally solving the statistical problem of perception in noise. In the optimal solution to this problem, listeners’ perception is biased toward phonetic category means because they use knowledge of these categories to guide their inferences about speakers’ target productions. Simulations show that model predictions closely correspond to previously published human data, and novel experimental results provide evidence for the predicted link between perceptual warping and noise. The model unifies several previous accounts of the perceptual magnet effect and provides a framework for exploring categorical effects in other domains. PMID:19839683

  2. Ontology-Driven Hypothesis Generation to Explain Anomalous Patient Responses to Treatment

    NASA Astrophysics Data System (ADS)

    Moss, Laura; Sleeman, Derek; Sim, Malcolm; Booth, Malcolm; Daniel, Malcolm; Donaldson, Lyndsay; Gilhooly, Charlotte; Hughes, Martin; Kinsella, John

    Within the medical domain there are clear expectations as to how a patient should respond to treatments administered. When these responses are not observed it can be challenging for clinicians to understand the anomalous responses. The work reported here describes a tool which can detect anomalous patient responses to treatment and further suggest hypotheses to explain the anomaly. In order to develop this tool, we have undertaken a study to determine how Intensive Care Unit (ICU) clinicians identify anomalous patient responses; we then asked further clinicians to provide potential explanations for such anomalies. The high level reasoning deployed by the clinicians has been captured and generalised to form the procedural component of the ontology-driven tool. An evaluation has shown that the tool successfully reproduced the clinician’s hypotheses in the majority of cases. Finally, the paper concludes by describing planned extensions to this work.

  3. Recent physical connections may explain weak genetic structure in western Alaskan chum salmon (Oncorhynchus keta) populations.

    PubMed

    Garvin, Michael R; Kondzela, Christine M; Martin, Patrick C; Finney, Bruce; Guyon, Jeffrey; Templin, William D; Decovich, Nick; Gilk-Baumer, Sara; Gharrett, Anthony J

    2013-07-01

    Low genetic divergence at neutral loci among populations is often the result of high levels of contemporary gene flow. Western Alaskan summer-run chum salmon (Oncorhynchus keta) populations demonstrate weak genetic structure, but invoking contemporary gene flow as the basis for the low divergence is problematic because salmon home to their natal streams and some of the populations are thousands of kilometers apart. We used genotypes from microsatellite and single nucleotide polymorphism loci to investigate alternative explanations for the current genetic structure of chum salmon populations from western Alaska. We also estimated current levels of gene flow among Kuskokwim River populations. Our results suggest that weak genetic structure is best explained by physical connections that occurred after the Holocene Thermal Maximum among the Yukon, Kuskokwim, and Nushagak drainages that allowed gene flow to occur among now distant populations. PMID:23919176

  4. Phylogenetic niche conservatism explains an inverse latitudinal diversity gradient in freshwater arthropods

    NASA Astrophysics Data System (ADS)

    Morinière, Jérôme; van Dam, Matthew H.; Hawlitschek, Oliver; Bergsten, Johannes; Michat, Mariano C.; Hendrich, Lars; Ribera, Ignacio; Toussaint, Emmanuel F. A.; Balke, Michael

    2016-05-01

    The underlying mechanisms responsible for the general increase in species richness from temperate regions to the tropics remain equivocal. Many hypotheses have been proposed to explain this astonishing pattern but additional empirical studies are needed to shed light on the drivers at work. Here we reconstruct the evolutionary history of the cosmopolitan diving beetle subfamily Colymbetinae, the majority of which are found in the Northern hemisphere, hence exhibiting an inversed latitudinal diversity gradient. We reconstructed a dated phylogeny using 12 genes, to investigate the biogeographical history and diversification dynamics in the Colymbetinae. We aimed to identify the role that phylogenetic niche conservatism plays in the inversed diversification pattern seen in this group. Our results suggest that Colymbetinae originated in temperate climates, which supports the hypothesis that their distribution is the result of an ancestral adaptation to temperate environmental conditions rather than tropical origins, and that temperate niche conservatism can generate and/or maintain inverse latitudinal diversity gradients.

  5. A novel theory to explain species diversity in landscapes: positive frequency dependence and habitat suitability.

    PubMed Central

    Molofsky, Jane; Bever, James D

    2002-01-01

    Theories to explain the diversity of species have required that individual species occupy unique niches and/or vary in their response to environmental factors. Positive interactions within a species, although common in communities, have not been thought to maintain species diversity because in non-spatial models the more abundant species always outcompetes the rarer species. Here, we show, using a stochastic spatial model, that positive intraspecific interactions such as those caused by positive frequency dependence and/or priority effects, can maintain species diversity if interactions between individuals are primarily local and the habitat contains areas that cannot be colonized by any species, such as boulders or other physical obstructions. When intraspecific interactions are primarily neutral, species diversity will eventually erode to a single species. When the landscape is homogeneous (i.e. does not contain areas that cannot be colonized by any species), the presence of strong intraspecific interactions will not maintain diversity. PMID:12495479

  6. A Comparative Perspective on Intermarriage: Explaining Differences Among National-Origin Groups in the United States

    PubMed Central

    KALMIJN, MATTHIJS; VAN TUBERGEN, FRANK

    2010-01-01

    Little is known about the validity of group-level theories of ethnic intermarriage despite the fact that such theories are often invoked in explaining why certain ethnic groups are “closed,” whereas others are relatively “open.” We develop a comparative perspective by analyzing the marriage choices of 94 national-origin groups in the United States, using pooled data from the Current Population Surveys, 1994–2006, and multilevel models in which individual and contextual determinants of intermarriage are included simultaneously. Our analyses show large differences in endogamy across groups. After taking compositional effects into account, we find that both structural and cultural group-level factors have significant effects on endogamy. Cultural explanations (which focus on the role of norms and preferences) play a more important role than structural explanations (which focus on meeting and mating opportunities). Our results reinforce the common but untested interpretation of endogamy in terms of group boundaries. PMID:20608106

  7. Theory of Planned Behavior Explains Gender Difference in Fruit and Vegetable Consumption

    PubMed Central

    Emanuel, Amber S.; McCully, Scout N.; Gallagher, Kristel M.; Updegraff, John A.

    2012-01-01

    A gender difference in fruit and vegetable intake (FVI) is widely documented, but not well understood. Using data from the National Cancer Institute’s Food Attitudes and Behavior Survey, we assessed the extent to which gender differences in FVI are attributable to gender differences in constructs from the Theory of Planned Behavior (TPB). Females reported more favorable attitudes and greater perceived behavior control regarding FVI than males, and these beliefs mediated the observed gender difference. Males reported greater perceived norms for FVI, but norms did not predict FVI. Gender did not moderate the influence of TPB constructs on FVI. Thus, TPB constructs substantially explained the gender difference. Interventions targeted toward adult males may benefit by promoting favorable attitudes and perceived behavioral control over FVI. PMID:22898607

  8. EXPLAINING THE Sr AND Ba SCATTER IN EXTREMELY METAL-POOR STARS

    SciTech Connect

    Aoki, W.; Suda, T.; Boyd, R. N.; Kajino, T.; Famiano, M. A. E-mail: takuma.suda@nao.ac.jp E-mail: kajino@nao.ac.jp

    2013-03-20

    Compilations of abundances of strontium and barium in extremely metal-poor stars show that an apparent cutoff is observed for [Sr/Ba] at [Fe/H] < -3.6 and large fluctuations for [Fe/H] > -3.6 with a clear upper bound depending on metallicity. We study the factors that place upper limits on the logarithmic ratio [Sr/Ba]. A model is developed in which the collapses of type II supernovae are found to reproduce many of the features seen in the data. This model is consistent with galactic chemical evolution constraints of light-element enrichment in metal-poor stars. Effects of turbulence in an explosive site have also been simulated, and are found to be important in explaining the large scatter observed in the [Sr/Ba] data.

  9. Leaf development and demography explain photosynthetic seasonality in Amazon evergreen forests

    USGS Publications Warehouse

    Wu, Jin; Albert, Lauren; Lopes, Aline; Restrepo-Coupe, Natalia; Hayek, Matthew; Wiedemann, Kenia T.; Guan, Kaiyu; Stark, Scott C.; Christoffersen, Bradley; Prohaska, Neill; Tavares, Julia V.; Marostica, Suelen; Kobayashi, Hideki; Ferreira, Maurocio L.; Campos, Kleber Silva; da Silva, Rodrigo; Brando, Paulo M.; Dye, Dennis G.; Huxman, Travis E.; Huete, Alfredo; Nelson, Bruce; Saleska, Scott

    2016-01-01

    In evergreen tropical forests, the extent, magnitude, and controls on photosynthetic seasonality are poorly resolved and inadequately represented in Earth system models. Combining camera observations with ecosystem carbon dioxide fluxes at forests across rainfall gradients in Amazônia, we show that aggregate canopy phenology, not seasonality of climate drivers, is the primary cause of photosynthetic seasonality in these forests. Specifically, synchronization of new leaf growth with dry season litterfall shifts canopy composition toward younger, more light-use efficient leaves, explaining large seasonal increases (~27%) in ecosystem photosynthesis. Coordinated leaf development and demography thus reconcile seemingly disparate observations at different scales and indicate that accounting for leaf-level phenology is critical for accurately simulating ecosystem-scale responses to climate change.

  10. Explaining the Geographical Variation of HIV Among Injection Drug Users in the United States

    PubMed Central

    Ciccarone, D.; Bourgois, P.

    2005-01-01

    Distinct physical and chemical types of street heroin exist worldwide, but their impact on behavior and disease acquisition is not well understood or documented. This article presents a hypothesis to explain the unequal diffusion of HIV among injection drug users in the United States by examining the distribution and use of one type of heroin—“Mexican black tar.” Drawing on ethnographic, clinical, epidemiological, and laboratory data, we suggest that the chemical properties of black tar heroin promote the following safer injection practices: (1) the rinsing of syringes with water to prevent clogging; (2) the heating of cookers to promote dissolution; and (3) a rapid transition from venous injection to subcutaneous or intramuscular injections. PMID:14677781

  11. Parental genetic effects in a cavefish adaptive behavior explain disparity between nuclear and mitochondrial DNA.

    PubMed

    Yoshizawa, Masato; Ashida, Go; Jeffery, William R

    2012-09-01

    Epigenetic parental genetic effects are important in many biological processes but their roles in the evolution of adaptive traits and their consequences in naturally evolving populations remain to be addressed. By comparing two divergent blind cave-dwelling cavefish populations with a sighted surface-dwelling population (surface fish) of the teleost Astyanax mexicanus, we report here that convergences in vibration attraction behavior (VAB), the lateral line sensory receptors underlying this behavior, and the feeding benefits of this behavior are controlled by parental genetic effects, either maternal or paternal inheritance. From behavioral studies and mathematical evolutionary simulations, we further demonstrate that disparity in nuclear and mitochondrial DNA in one of these cavefish populations that has hybridized with surface fish can be explained by paternal inheritance of VAB. The results suggest that parental genetic effects in adaptive behaviors may be important factors in biasing mitochondrial DNA inheritance in natural populations that are subject to introgression. PMID:22946818

  12. The Role of Forcing and Internal Dynamics in explaining the 'Medieval Climate Anomaly'

    NASA Technical Reports Server (NTRS)

    Goossee, Hugues; Crespin, Elisabeth; Dubinkina, Svetlana; Loutre, Marie-France; Mann, Michael E.; Renssen, Hans; Shindell, Drew

    2012-01-01

    Proxy reconstructions suggest that peak global temperature during the past warm interval known as the Medieval Climate Anomaly (MCA, roughly 950-1250 AD) has been exceeded only during the most recent decades. To better understand the origin of this warm period, we use model simulations constrained by data assimilation establishing the spatial pattern of temperature changes that is most consistent with forcing estimates, model physics and the empirical information contained in paleoclimate proxy records. These numerical experiments demonstrate that the reconstructed spatial temperature pattern of the MCA can be explained by a simple thermodynamical response of the climate system to relatively weak changes in radiative forcing combined with a modification of the atmospheric circulation, displaying some similarities with the positive phase of the so-called Arctic Oscillation, and with northward shifts in the position of the Gulf Stream and Kuroshio currents. The mechanisms underlying the MCA are thus quite different from anthropogenic mechanisms responsible for modern global warming.

  13. Leaf development and demography explain photosynthetic seasonality in Amazon evergreen forests.

    PubMed

    Wu, Jin; Albert, Loren P; Lopes, Aline P; Restrepo-Coupe, Natalia; Hayek, Matthew; Wiedemann, Kenia T; Guan, Kaiyu; Stark, Scott C; Christoffersen, Bradley; Prohaska, Neill; Tavares, Julia V; Marostica, Suelen; Kobayashi, Hideki; Ferreira, Mauricio L; Campos, Kleber Silva; da Silva, Rodrigo; Brando, Paulo M; Dye, Dennis G; Huxman, Travis E; Huete, Alfredo R; Nelson, Bruce W; Saleska, Scott R

    2016-02-26

    In evergreen tropical forests, the extent, magnitude, and controls on photosynthetic seasonality are poorly resolved and inadequately represented in Earth system models. Combining camera observations with ecosystem carbon dioxide fluxes at forests across rainfall gradients in Amazônia, we show that aggregate canopy phenology, not seasonality of climate drivers, is the primary cause of photosynthetic seasonality in these forests. Specifically, synchronization of new leaf growth with dry season litterfall shifts canopy composition toward younger, more light-use efficient leaves, explaining large seasonal increases (~27%) in ecosystem photosynthesis. Coordinated leaf development and demography thus reconcile seemingly disparate observations at different scales and indicate that accounting for leaf-level phenology is critical for accurately simulating ecosystem-scale responses to climate change. PMID:26917771

  14. What We Don't Understand, We Explain to Each Other

    NASA Astrophysics Data System (ADS)

    Pines, David

    2015-12-01

    "What we don't understand, we explain to each other" was Robert Oppenheimer's 1948 description of theoretical physics as a profession. Because the phrase connects research, teaching, and learning, it seemed the right approach for the talk I gave to the AAPT on receiving the 2013 J.D. Jackson Award for Excellence in Graduate Teaching, on which the present article is based. In what follows I describe how my experiences as a student, researcher, and teacher combined to shape the way I learn and teach physics, from my own courses to inventing and editing Frontiers in Physics, reshaping Reviews of Modern Physics, and experimenting with different approaches to communicating key concepts in physics.

  15. Radiatively driven winds for different power law spectra. [for explaining narrow and broad quasar absorption lines

    NASA Technical Reports Server (NTRS)

    Beltrametti, M.

    1980-01-01

    The analytic solutions for radiatively driven winds are given for the case in which the winds are driven by absorption of line and continuum radiation. The wind solutions are analytically estimated for different parameters of the central source and for different power law spectra. For flat spectra, three sonic points can exist; it is shown, however, that only one of these sonic points is physically realistic. Parameters of the central source are given which generate winds of further interest for explaining the narrow and broad absorption lines in quasars. For the quasar model presented here, winds which could give rise to the narrow absorption lines are generated by central sources with parameters which are not realistic for quasars.

  16. Colonisation and competition dynamics can explain incomplete sterilisation parasitism in ant-plant symbioses.

    PubMed

    Tarnita, Corina E; Palmer, Todd M; Pringle, Robert M

    2014-10-01

    Sterilisation of parasites prevents host reproduction, thereby diverting host resources to their own benefit. Previous theory predicts that parasites should evolve maximum virulence, yet hosts are often incompletely sterilised. Whereas prior attempts to resolve this paradox have sought evolutionary explanations, we present theory and experiments showing that incomplete sterilisation can arise from ecologically driven fluctuations in parasite load. The African ant-plant Acacia drepanolobium reproduced more when occupied by small colonies of the sterilising symbiont Crematogaster nigriceps. In nature, small colonies result from interference competition between ant colonies; these territorial conflicts thus provide intermittent windows of opportunity for host reproduction. Our mean-field model shows that numerical insufficiency of parasites can produce partial sterilisation of host populations, creating the appearance of reduced virulence even if ants have evolved to sterilise completely. This general framework helps explain both the apparent ubiquity of partial sterilisation parasitism and the ability of these symbiotic associations to persist. PMID:25109706

  17. Response of microbial decomposition to spin-up explains CMIP5 soil carbon range until 2100

    NASA Astrophysics Data System (ADS)

    Exbrayat, J.-F.; Pitman, A. J.; Abramowitz, G.

    2014-05-01

    Soil carbon storage simulated by the Coupled Model Intercomparison Project (CMIP5) models varies 6-fold for the present day. We show that this range already exists at the beginning of the historical simulations and demonstrate that it is mostly an artifact of the representation of microbial decomposition and its response during the spin-up procedure used by the models. The 6-fold range in soil carbon, once established, is maintained through the present and to 2100 almost unchanged even under a strong business-as-usual emissions scenario. By highlighting the role of the response of decomposition to spin-up in explaining why current CMIP5 soil carbon stores vary widely, we identify the need to better constrain the outcome of this procedure as a means to reduce uncertainty in transient simulations.

  18. Can settlement in natal-like habitat explain maladaptive habitat selection?

    PubMed Central

    Piper, Walter H.; Palmer, Michael W.; Banfield, Nathan; Meyer, Michael W.

    2013-01-01

    The study of habitat selection has long been influenced by the ideal free model, which maintains that young adults settle in habitat according to its inherent quality and the density of conspecifics within it. The model has gained support in recent years from the finding that conspecifics produce cues inadvertently that help prebreeders locate good habitat. Yet abundant evidence shows that animals often fail to occupy habitats that ecologists have identified as those of highest quality, leading to the conclusion that young animals settle on breeding spaces by means not widely understood. Here, we report that a phenomenon virtually unknown in nature, natal habitat preference induction (NHPI), is a strong predictor of territory settlement in both male and female common loons (Gavia immer). NHPI causes young animals to settle on natal-like breeding spaces, but not necessarily those that maximize reproductive success. If widespread, NHPI might explain apparently maladaptive habitat settlement. PMID:23804619

  19. Can self-ordering scalar fields explain the BICEP2 B-mode signal?

    SciTech Connect

    Durrer, Ruth; Figueroa, Daniel G.; Kunz, Martin E-mail: daniel.figueroa@unige.ch

    2014-08-01

    We show that self-ordering scalar fields (SOSF), i.e. non-topological cosmic defects arising after a global phase transition, cannot explain the B-mode signal recently announced by BICEP2. We compute the full C{sub ℓ}{sup B} angular power spectrum of B-modes due to vector and tensor perturbations of SOSF, modeled in the large N limit of a spontaneously broken global O(N) symmetry. We conclude that the low ℓ multipoles detected by BICEP2 cannot be due mainly to SOSF, since they have the wrong spectrum at low multipoles. As a byproduct we derive the first cosmological constraints on this model, showing that the BICEP2 B-mode polarization data admits at most a 2-3% contribution from SOSF in the temperature anisotropies, similar to (but somewhat tighter than) the recently studied case of cosmic strings.

  20. Explaining seasonal fluctuations of measles in Niger using nighttime lights imagery.

    PubMed

    Bharti, N; Tatem, A J; Ferrari, M J; Grais, R F; Djibo, A; Grenfell, B T

    2011-12-01

    Measles epidemics in West Africa cause a significant proportion of vaccine-preventable childhood mortality. Epidemics are strongly seasonal, but the drivers of these fluctuations are poorly understood, which limits the predictability of outbreaks and the dynamic response to immunization. We show that measles seasonality can be explained by spatiotemporal changes in population density, which we measure by quantifying anthropogenic light from satellite imagery. We find that measles transmission and population density are highly correlated for three cities in Niger. With dynamic epidemic models, we demonstrate that measures of population density are essential for predicting epidemic progression at the city level and improving intervention strategies. In addition to epidemiological applications, the ability to measure fine-scale changes in population density has implications for public health, crisis management, and economic development. PMID:22158822