Science.gov

Sample records for lead time bias

  1. The effect of lead time bias on severity of illness scoring, mortality prediction and standardised mortality ratio in intensive care--a pilot study.

    PubMed

    Tunnell, R D; Millar, B W; Smith, G B

    1998-11-01

    The effect of lead time bias on severity of illness scoring, mortality prediction and standardised mortality ratios was examined in a pilot study of 76 intensive care (ICU) patients using APACHE II, APACHE III and SAPS II scoring systems. The inclusion of data collected in the period prior to ICU admission increased severity of illness scores and estimated risk of hospital mortality significantly for all three scoring systems (p < 0.01) by up to 14 points and 42.7% (APACHE II), 50 points and 26.3% (APACHE III) and 23 points and 33.4% (SAPS II), respectively. Standardised mortality ratios fell from 0.99 to 0.79 (APACHE II), 0.96 to 0.84 (APACHE III) and 0.75 to 0.64 (SAPS II), but these changes failed to reach statistical significance. Lead time bias had most effect in medical patients and on emergency admissions, and least effect in patients admitted from the operating theatre. These trends suggest that mortality ratios may not necessarily reflect intensive care unit performance and indicate that a larger study of the effect of lead time bias, case mix, pre-ICU care or post-ICU management on standardised mortality ratios is indicated. PMID:10023272

  2. SEASAT altimeter timing bias estimation

    NASA Astrophysics Data System (ADS)

    Marsh, J. G.; Williamson, R. G.

    1982-04-01

    The calibration of the altimeter observation time tags to the millisecond level of accuracy is fundamental to the processing of the data. Initial analyses of the SEASAT altimeter data indicated the presence of a time calibration bias which produced altimeter measurement errors in excess of a meter. A technique has been developed for the solution of the time tag bias based upon the analysis of sea surface height discrepancies at ground track intersections. This technique has permitted very good separation of the dominant once per revolution ephemeris error, which amounts to about 1.5 m rms, from the timing error signature. Furthermore, the technique does not depend upon the availability of precise geoid data. The application of this technique to a global set of SEASAT altimeter data covering the time period of July 28-August 9, 1978, has resulted in a value of -81.0±2 ms for the time tag bias. This value agrees to within 2.9 ms of the value derived at the University of Texas from a similar analysis of the altimeter data. Furthermore, these values corroborate the revised value of -79.4 ms derived at NASA/Wallops Flight Center and the Johns Hopkins University/Applied Physics Lab from a reexamination of the internal instrument time delays. The modeling of oceanic tides and the orbit computations are the major error sources in these analyses.

  3. Cognitive Reflection, Decision Biases, and Response Times

    PubMed Central

    Alós-Ferrer, Carlos; Garagnani, Michele; Hügelschäfer, Sabine

    2016-01-01

    We present novel evidence on response times and personality traits in standard questions from the decision-making literature where responses are relatively slow (medians around half a minute or above). To this end, we measured response times in a number of incentivized, framed items (decisions from description) including the Cognitive Reflection Test, two additional questions following the same logic, and a number of classic questions used to study decision biases in probability judgments (base-rate neglect, the conjunction fallacy, and the ratio bias). All questions create a conflict between an intuitive process and more deliberative thinking. For each item, we then created a non-conflict version by either making the intuitive impulse correct (resulting in an alignment question), shutting it down (creating a neutral question), or making it dominant (creating a heuristic question). For CRT questions, the differences in response times are as predicted by dual-process theories, with alignment and heuristic variants leading to faster responses and neutral questions to slower responses than the original, conflict questions. For decision biases (where responses are slower), evidence is mixed. To explore the possible influence of personality factors on both choices and response times, we used standard personality scales including the Rational-Experiential Inventory and the Big Five, and used them as controls in regression analysis. PMID:27713710

  4. Challenges of guarantee-time bias.

    PubMed

    Giobbie-Hurder, Anita; Gelber, Richard D; Regan, Meredith M

    2013-08-10

    The potential for guarantee-time bias (GTB), also known as immortal time bias, exists whenever an analysis that is timed from enrollment or random assignment, such as disease-free or overall survival, is compared across groups defined by a classifying event occurring sometime during follow-up. The types of events associated with GTB are varied and may include the occurrence of objective disease response, onset of toxicity, or seroconversion. However, comparative analyses using these types of events as predictors are different from analyses using baseline characteristics that are specified completely before the occurrence of any outcome event. Recognizing the potential for GTB is not always straightforward, and it can be challenging to know when GTB is influencing the results of an analysis. This article defines GTB, provides examples of GTB from several published articles, and discusses three analytic techniques that can be used to remove the bias: conditional landmark analysis, extended Cox model, and inverse probability weighting. The strengths and limitations of each technique are presented. As an example, we explore the effect of bisphosphonate use on disease-free survival (DFS) using data from the BIG (Breast International Group) 1-98 randomized clinical trial. An analysis using a naive approach showed substantial benefit for patients who received bisphosphonate therapy. In contrast, analyses using the three methods known to remove GTB showed no statistical evidence of a reduction in risk of a DFS event with bisphosphonate therapy.

  5. Timing in multitasking: memory contamination and time pressure bias.

    PubMed

    Moon, Jungaa; Anderson, John R

    2013-01-01

    There can be systematic biases in time estimation when it is performed in complex multitasking situations. In this paper we focus on the mechanisms that cause participants to tend to respond too quickly and underestimate a target interval (250-400 ms) in a complex, real-time task. We hypothesized that two factors are responsible for the too-early bias: (1) Memory contamination from an even shorter time interval in the task, and (2) time pressure to take appropriate actions in time. In a simpler experiment that was focused on just these two factors, we found a strong too-early bias when participants estimated the target interval in alternation with a shorter interval and when they had little time to perform the task. The too-early bias was absent when they estimated the target interval in isolation without contamination and time pressure. A strong too-late bias occurred when the target interval alternated with a longer interval and there was no time pressure to respond. The effects were captured by incorporating the timing model of Taatgen and van Rijn (2011) into the ACT-R model for the Space Fortress task (Bothell, 2010). The results show that to properly understand time estimation in a dynamic task one needs to model the multiple influences that are occurring from the surrounding context.

  6. Intergroup time bias and racialized social relations.

    PubMed

    Vala, Jorge; Pereira, Cícero Roberto; Oliveira Lima, Marcus Eugênio; Leyens, Jacques-Philippe

    2012-04-01

    Within the framework of intergroup relations, the authors analyzed the time people spent evaluating ingroup and outgroup members. They hypothesized that White participants take longer to evaluate White targets than Black targets. In four experiments, White participants were slower to form impressions of White than of Black people; that is, they showed an intergroup time bias (ITB). In Study 1 (N = 60), the ITB correlated with implicit prejudice and homogeneity. Study 2 (N = 60) showed that the ITB was independent of the type of trait in question (nonstereotypical vs. stereotypical). Study 3 (N = 100) demonstrated that ITB correlates with racism measured 3 months beforehand, is independent of motivation to control prejudice, and is not an epiphenomenon of homogeneity. In Study 4 (N = 40) participants not only showed the ITB in a racialized social context but also displayed it following a minimal group manipulation.

  7. Racial-ethnic biases, time pressure, and medical decisions.

    PubMed

    Stepanikova, Irena

    2012-09-01

    This study examined two types of potential sources of racial-ethnic disparities in medical care: implicit biases and time pressure. Eighty-one family physicians and general internists responded to a case vignette describing a patient with chest pain. Time pressure was manipulated experimentally. Under high time pressure, but not under low time pressure, implicit biases regarding blacks and Hispanics led to a less serious diagnosis. In addition, implicit biases regarding blacks led to a lower likelihood of a referral to specialist when physicians were under high time pressure. The results suggest that when physicians face stress, their implicit biases may shape medical decisions in ways that disadvantage minority patients.

  8. Biased predecisional processing of leading and nonleading alternatives.

    PubMed

    Blanchard, Simon J; Carlson, Kurt A; Meloy, Margaret G

    2014-03-01

    When people obtain information about choice alternatives in a set one attribute at a time, they rapidly identify a leading alternative. Although previous research has established that people then distort incoming information, it is unclear whether distortion occurs through favoring of the leading alternative, disfavoring of the trailing alternative, or both. Prior examinations have not explored the predecisional treatment of the nonleading alternative (or alternatives) because they conceptualized distortion as a singular construct in binary choice and measured it using a relative item comparing the evaluation of both alternatives simultaneously. In this article, we introduce a measure of distortion at the level of the alternative, which allows for measuring whether predecisional distortion favors or disfavors every alternative being considered in choice sets of various sizes. We report that both proleader and antitrailer distortion occur and that the use of antitrailer processing differs between binary choices and multiple-options choices. PMID:24403397

  9. Leading time domain seismic precursors

    NASA Astrophysics Data System (ADS)

    Boucouvalas, A. C.; Gkasios, M.; Keskebes, A.; Tselikas, N. T.

    2014-08-01

    The problem of predicting the occurrence of earthquakes is threefold. On one hand it is necessary to predict the date and magnitude of an earthquake, and on the other hand the location of the epicenter. In this work after a brief review of the state of earthquake prediction research, we report on a new leading time precursor for determining time onset of earthquake occurrence. We report the linking between earthquakes of the past with those which happen in the future via Fibonacci, Dual and Lucas numbers (FDL) numbers. We demonstrate it here with two example seed earthquakes at least 100 years old. Using this leading indicator method we can predict significant earthquake events >6.5R, with good accuracy approximately +- 1 day somewhere in the world. From a single seed we produce at least 100 trials simultaneously of which 50% are correct to +- 1day. The indicator is based on Fibonacci, Dual and Lucas numbers (FDL). This result hints that the log periodic FDL numbers are at the root of the understanding of the earthquake mechanism. The theory is based on the assumption that each occurred earthquake discontinuity can be thought of as a generating source of FDL time series. (The mechanism could well be linked to planetary orbits). When future dates are derived from clustering and convergence from previous strong earthquake dates at an FDL time distance, then we have a high probability for an earthquake to occur on that date. We set up a real time system which generates FDL time series from each previous significant earthquake (>7R) and we produce a year to year calendar of high probability earthquake dates. We have tested this over a number of years with considerable success. We have applied this technique for strong (>7R) earthquakes across the globe as well as on a restricted region such as the Greek geographic region where the magnitude is small (>4R-6.5R). In both cases the success of the method is impressive. It is our belief that supplementing this method with

  10. Alleviating bias leads to accurate and personalized recommendation

    NASA Astrophysics Data System (ADS)

    Qiu, Tian; Wang, Tian-Tian; Zhang, Zi-Ke; Zhong, Li-Xin; Chen, Guang

    2013-11-01

    Recommendation bias towards objects has been found to have an impact on personalized recommendation, since objects present heterogeneous characteristics in some network-based recommender systems. In this article, based on a biased heat conduction recommendation algorithm (BHC) which considers the heterogeneity of the target objects, we propose a heterogeneous heat conduction algorithm (HHC), by further taking the heterogeneity of the source objects into account. Tested on three real datasets, the Netflix, RYM and MovieLens, the HHC algorithm is found to present better recommendation in both the accuracy and diversity than two benchmark algorithms, i.e., the original BHC and a hybrid algorithm of heat conduction and mass diffusion (HHM), while not requiring any other accessorial information or parameter. Moreover, the HHC algorithm also elevates the recommendation accuracy on cold objects, referring to the so-called cold-start problem. Eigenvalue analyses show that, the HHC algorithm effectively alleviates the recommendation bias towards objects with different level of popularity, which is beneficial to solving the accuracy-diversity dilemma.

  11. Ocean acoustic tomography - Travel time biases

    NASA Technical Reports Server (NTRS)

    Spiesberger, J. L.

    1985-01-01

    The travel times of acoustic rays traced through a climatological sound-speed profile are compared with travel times computed through the same profile containing an eddy field. The accuracy of linearizing the relations between the travel time difference and the sound-speed deviation at long ranges is assessed using calculations made for two different eddy fields measured in the eastern Atlantic. Significant nonlinearities are found in some cases, and the relationships of the values of these nonlinearities to the range between source and receiver, to the anomaly size associated with the eddies, and to the positions of the eddies are studied. An analytical model of the nonlinearities is discussed.

  12. Racial-Ethnic Biases, Time Pressure, and Medical Decisions

    ERIC Educational Resources Information Center

    Stepanikova, Irena

    2012-01-01

    This study examined two types of potential sources of racial-ethnic disparities in medical care: implicit biases and time pressure. Eighty-one family physicians and general internists responded to a case vignette describing a patient with chest pain. Time pressure was manipulated experimentally. Under high time pressure, but not under low time…

  13. Leading in times of trauma.

    PubMed

    Dutton, Jane E; Frost, Peter J; Worline, Monica C; Lilius, Jacoba M; Kanov, Jason M

    2002-01-01

    An employee is diagnosed with cancer or loses a family member unexpectedly. An earthquake destroys an entire section of a city, leaving hundreds dead, injured, or homeless. At time like these, managerial handbooks fail us. After all, leaders can't eliminate personal suffering, nor can they ask employees who are dealing with these crises to check their emotions at the door. But compassionate leadership can facilitate personal as well as organizational healing. Based on research the authors have conducted at the University of Michigan and the University of British Columbia's CompassionLab, this article describes what leaders can do to foster organizational compassion in times of trauma. They recount real-world examples, including a story of personal tragedy at Newsweek, natural disasters that affected Macy's and Malden Mills, and the events of September 11, 2001. During times of collective pain and confusion, compassionate leaders take some form of public action, however small, that is intended to ease people's pain and inspire others to act. By openly demonstrating their own humanity, executives can unleash a compassionate response throughout the whole company, increasing bonds among employees and attachments to the organization. The authors say compassionate leaders uniformly provide two things: a "context for meaning"--creating an environment in which people can freely express and discuss how they feel--and a "context for action"--creating an environment in which those who experience or witness pain can find ways to alleviate their own and others' suffering. A leader's competence in demonstrating and fostering compassion is vital, the authors conclude, to nourishing the very humanity that can make people--and organizations--great. PMID:12964467

  14. Leading in times of trauma.

    PubMed

    Dutton, Jane E; Frost, Peter J; Worline, Monica C; Lilius, Jacoba M; Kanov, Jason M

    2002-01-01

    An employee is diagnosed with cancer or loses a family member unexpectedly. An earthquake destroys an entire section of a city, leaving hundreds dead, injured, or homeless. At time like these, managerial handbooks fail us. After all, leaders can't eliminate personal suffering, nor can they ask employees who are dealing with these crises to check their emotions at the door. But compassionate leadership can facilitate personal as well as organizational healing. Based on research the authors have conducted at the University of Michigan and the University of British Columbia's CompassionLab, this article describes what leaders can do to foster organizational compassion in times of trauma. They recount real-world examples, including a story of personal tragedy at Newsweek, natural disasters that affected Macy's and Malden Mills, and the events of September 11, 2001. During times of collective pain and confusion, compassionate leaders take some form of public action, however small, that is intended to ease people's pain and inspire others to act. By openly demonstrating their own humanity, executives can unleash a compassionate response throughout the whole company, increasing bonds among employees and attachments to the organization. The authors say compassionate leaders uniformly provide two things: a "context for meaning"--creating an environment in which people can freely express and discuss how they feel--and a "context for action"--creating an environment in which those who experience or witness pain can find ways to alleviate their own and others' suffering. A leader's competence in demonstrating and fostering compassion is vital, the authors conclude, to nourishing the very humanity that can make people--and organizations--great.

  15. Directionality Time - New Analytical Treatment of Directionally Biased, Crawling Motility

    NASA Astrophysics Data System (ADS)

    Tang, Jay; Loosley, Alexander

    Insights on crucial biological functions often emerge from measuring how animal cells crawl on surfaces, particularly in response to gradients of external cues that cause directionally biased motion. Most existing metrics commonly used to characterize directional migration, such as straightness index (or chemotactic index), persistence time, and turning angle distribution, tend to be sensitive to relatively large errors at short sampling times. In contrast, we recently introduced a new metric, called directionality time, to define the onset time by which a seemingly random motion becomes directionally biased (O'Brien et al., J Leukocyte Biol, 2014, 95:993-1004 Loosley et al., PLOS ONE, 2015, 10.1371). Directionality time is obtained by fitting the mean squared displacement as a function of time interval, in log-log coordinates, to a fit function based on biased and persistent random walk processes. We show that the fit function is approximately model invariant and is applicable to a variety of directionally biased motions. Simulations are performed to show the robustness of the directionality time model and its decoupling from measurement errors. Finally, we demonstrate as an example how to usefully apply the directionality time fit to trajectories of chemotactic neutrophils.

  16. Time-course of attention biases in social phobia.

    PubMed

    Schofield, Casey A; Inhoff, Albrecht W; Coles, Meredith E

    2013-10-01

    Theoretical models of social phobia implicate preferential attention to social threat in the maintenance of anxiety symptoms, though there has been limited work characterizing the nature of these biases over time. The current study utilized eye-movement data to examine the time-course of visual attention over 1500ms trials of a probe detection task. Nineteen participants with a primary diagnosis of social phobia based on DSM-IV criteria and 20 non-clinical controls completed this task with angry, fearful, and happy face trials. Overt visual attention to the emotional and neutral faces was measured in 50ms segments across the trial. Over time, participants with social phobia attend less to emotional faces and specifically less to happy faces compared to controls. Further, attention to emotional relative to neutral expressions did not vary notably by emotion for participants with social phobia, but control participants showed a pattern after 1000ms in which over time they preferentially attended to happy expressions and avoided negative expressions. Findings highlight the importance of considering attention biases to positive stimuli as well as the pattern of attention between groups. These results suggest that attention "bias" in social phobia may be driven by a relative lack of the biases seen in non-anxious participants.

  17. Finale furioso: referee-biased injury times and their effects on home advantage in football.

    PubMed

    Riedl, Dennis; Strauss, Bernd; Heuer, Andreas; Rubner, Oliver

    2015-01-01

    The role of referees has become a central issue in the investigation of home advantage. The main aim of this study was a thorough examination of the referee bias concerning injury time in football, which is currently seen as an important example for the assertion that referees contribute to home advantage. First, we use archival data from the German Bundesliga (seasons 2000/2001-2010/2011) to confirm the existence of an asymmetry in the allocation of injury time. We show this asymmetry to be a bias by ruling out hitherto remaining alternative explanations (effect = 18 s, P < 0.001, R2(adj) = 0.05). Second, we identify a further referee bias, stating that referees systematically accord more injury time when one team leads in the game compared to a draw (effect = 21 s, P = 0.004, R2(adj) = 0.06). Third, the quantitative benefit of home or away teams in goals and points due to these biases is assessed. Overall, referee decisions on injury time indeed reveal biases, but they do not contribute to the home advantage, that is, there is no significant effect on goals scored by the teams. The qualitative findings (a new bias on injury time) as well as the quantitative findings (no overall effect) shed new light on the role of referees for home advantage.

  18. Timing discriminator using leading-edge extrapolation

    DOEpatents

    Gottschalk, B.

    1981-07-30

    A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting is described. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

  19. Timing discriminator using leading-edge extrapolation

    DOEpatents

    Gottschalk, Bernard

    1983-01-01

    A discriminator circuit to recover timing information from slow-rising pulses by means of an output trailing edge, a fixed time after the starting corner of the input pulse, which is nearly independent of risetime and threshold setting. This apparatus comprises means for comparing pulses with a threshold voltage; a capacitor to be charged at a certain rate when the input signal is one-third threshold voltage, and at a lower rate when the input signal is two-thirds threshold voltage; current-generating means for charging the capacitor; means for comparing voltage capacitor with a bias voltage; a flip-flop to be set when the input pulse reaches threshold voltage and reset when capacitor voltage reaches the bias voltage; and a clamping means for discharging the capacitor when the input signal returns below one-third threshold voltage.

  20. Current through a multilead nanojunction in response to an arbitrary time-dependent bias

    NASA Astrophysics Data System (ADS)

    Ridley, Michael; MacKinnon, Angus; Kantorovich, Lev

    2015-03-01

    We apply the nonequilibrium Green's function formalism to the problem of a multiterminal nanojunction subject to an arbitrary time-dependent bias. In particular, we show that taking a generic one-particle system Hamiltonian within the wide-band-limit approximation, it is possible to obtain a closed analytical expression for the current in each lead. Our formula reduces to the well-known result of Jauho et al. [Phys. Rev. B 50, 5528 (1994), 10.1103/PhysRevB.50.5528] in the limit where the switch-on time is taken to the remote past, and to the result of Tuovinen et al. [Phys. Rev. B 89, 085131 (2014), 10.1103/PhysRevB.89.085131] when the bias is maintained at a constant value after the switch-on. As we use a partition-free approach, our formula contains both the long-time current and transient effects due to the sudden switch-on of the bias. Numerical calculations performed for the simple case of a single-level quantum dot coupled to two leads are performed for a sinusoidally varying bias. At certain frequencies of the driving bias, we observe "ringing" oscillations of the current, whose dependence on the dot level, level width, oscillation amplitude, and temperature is also investigated.

  1. Time scale bias in erosion rates of glaciated landscapes

    PubMed Central

    Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P.; Fischer, Woodward W.; Avouac, Jean-Philippe

    2016-01-01

    Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time. PMID:27713925

  2. Habitual reading biases in the allocation of study time.

    PubMed

    Ariel, Robert; Al-Harthy, Ibrahim S; Was, Christopher A; Dunlosky, John

    2011-10-01

    Item order can bias learners' study decisions and undermine the use of more effective allocation strategies, such as allocating study time to items in one's region of proximal learning. In two experiments, we evaluated whether the influence of item order on study decisions reflects habitual responding based on a reading bias. We manipulated the order in which relatively easy, moderately difficult, and difficult items were presented from left to right on a computer screen and examined selection preference as a function of item order and item difficulty. Experiment 1a was conducted with native Arabic readers and in Arabic, and Experiment 1b was conducted with native English readers and in English. Students from both cultures prioritized items for study in the reading order of their native language: Arabic readers selected items for study in a right-to-left fashion, whereas English readers largely selected items from left to right. In Experiment 2, native English readers completed the same task as participants in Experiment 1b, but for some participants, lines of text were rotated upside down to encourage them to read from right to left. Participants who read upside-down text were more likely to first select items on the right side of an array than were participants who studied right-side-up text. These results indicate that reading habits can bias learners' study decisions and can undermine agenda-based regulation.

  3. Condition bias of hunter-shot ring-necked ducks exposed to lead

    USGS Publications Warehouse

    McCracken, K.G.; Afton, A.D.; Peters, M.S.

    2000-01-01

    We evaluated the condition bias hypothesis for ring-necked ducks (Aythya collaris) exposed to lead by testing the null hypothesis that ducks shot by hunters do not differ in physiological condition from those collected randomly from the same location. After adjusting for structural body size and log(e) concentration of blood lead, we found that overall body condition differed significantly between collection types and age classes, and marginally between sexes. Ingesta-free body mass of ring-necked ducks sampled randomly averaged 8.8% greater than those shot over decoys, and 99% of this difference was accounted for by lipid reserves. Ingesta, ash, and protein did not differ between collection types; however, after-hatching-year (AHY) birds had 5.1% more ash and 4.8% more protein than did hatching-year (HY) birds. The only sex difference was that males had 4.1% more protein than did females. Ingesta-free body mass, lipids, and protein were negatively related to concentration of blood lead. Collection type-by-concentration of blood lead and age-by-sex-by-concentration of blood lead interactions were not significant. To the extent that lead pellets persist as a cause of disease or mortality, waterfowl biologists should account for lead exposure as a possible source of condition bias when estimating population parameters and modeling survival of ring-necked ducks and other waterfowl species prone to ingest lead. These findings further underscore the problem that ingested lead shotgun pellets pose for waterfowl.

  4. Recombination of haplotypes leads to biased estimates of admixture proportions in human populations

    SciTech Connect

    Chakraborty, R.; Smouse, P.E.

    1988-05-01

    A population formed by genetic admixture of two or more source populations may exhibit considerable linkage disequilibrium between genetic loci. In the presence of recombination, this linkage disequilibrium declines with time, a fact that is often ignored when considering haplotypes of closely linked systems (e.g., Gm serum group (gamma globulins), HLA and, more recently, restriction fragment length polymorphisms). Recombination alters haplotype frequencies over time, and the haplotype-derived measures of admixture proportions from haplotype frequencies in generations following the admixture event become progressively more biased. The direction and extent of this bias can be predicted only when the history of admixture is known. Numerical illustration suggests that this bias is problematic whenever rt > 0.05, where r is the recombination rate between linked loci and t is the time (in generations) that has elapsed since the admixture extent. In general, even the haplotype frequencies defined by multiple restriction fragment length polymorphisms should be used with caution for admixture analysis. When recombination rates or the time since admixture are not precisely known, it is advantageous to consider each restriction fragment length polymorphism site separately for admixture analysis.

  5. Response time of a normal-metal/superconductor hybrid system under a step-like pulse bias

    NASA Astrophysics Data System (ADS)

    Xing, Yanxia; Sun, Qing-Feng; Wang, Jian

    2007-03-01

    The response of a quantum dot coupled with one normal lead and a superconductor lead driven by a step-like pulse bias VL is studied using the nonequilibrium Green’s function method. In the linear pulse bias regime, the responses of the upward and downward biases are symmetric. In this regime, the turn-on time and turn-off time are much slower than those of the normal system due to the Andreev reflection. On the other hand, for the large pulse bias VL , the instantaneous current exhibits oscillatory behaviors with the frequency ℏΩ=qVL . The turn-on/off times are in (or shorter than) the scale of 1/VL , so they are faster for the larger bias VL . In addition, the responses for the upward and downward biases are asymmetric at large VL . The turn-on time is larger than the turn-off time, but the relaxation time depends only on the coupling strength Γ and it is much smaller than the turn-on/off times for the large bias VL . [The turn-on/off time describes how fast a device can turn on/off a current, which is also named rise/fall time in M. Plihal , Phys. Rev. B 61, R13341 (2000), while the relaxation time was referred to how fast the device can go to a new steady state after a bias is abruptly switched on. It is also named saturation time in A. Schiller and S. Hershfield, Phys. Rev. B 62, R16271 (2000).

  6. Odors Bias Time Perception in Visual and Auditory Modalities

    PubMed Central

    Yue, Zhenzhu; Gao, Tianyu; Chen, Lihan; Wu, Jiashuang

    2016-01-01

    Previous studies have shown that emotional states alter our perception of time. However, attention, which is modulated by a number of factors, such as emotional events, also influences time perception. To exclude potential attentional effects associated with emotional events, various types of odors (inducing different levels of emotional arousal) were used to explore whether olfactory events modulated time perception differently in visual and auditory modalities. Participants were shown either a visual dot or heard a continuous tone for 1000 or 4000 ms while they were exposed to odors of jasmine, lavender, or garlic. Participants then reproduced the temporal durations of the preceding visual or auditory stimuli by pressing the spacebar twice. Their reproduced durations were compared to those in the control condition (without odor). The results showed that participants produced significantly longer time intervals in the lavender condition than in the jasmine or garlic conditions. The overall influence of odor on time perception was equivalent for both visual and auditory modalities. The analysis of the interaction effect showed that participants produced longer durations than the actual duration in the short interval condition, but they produced shorter durations in the long interval condition. The effect sizes were larger for the auditory modality than those for the visual modality. Moreover, by comparing performance across the initial and the final blocks of the experiment, we found odor adaptation effects were mainly manifested as longer reproductions for the short time interval later in the adaptation phase, and there was a larger effect size in the auditory modality. In summary, the present results indicate that odors imposed differential impacts on reproduced time durations, and they were constrained by different sensory modalities, valence of the emotional events, and target durations. Biases in time perception could be accounted for by a framework of

  7. Odors Bias Time Perception in Visual and Auditory Modalities.

    PubMed

    Yue, Zhenzhu; Gao, Tianyu; Chen, Lihan; Wu, Jiashuang

    2016-01-01

    Previous studies have shown that emotional states alter our perception of time. However, attention, which is modulated by a number of factors, such as emotional events, also influences time perception. To exclude potential attentional effects associated with emotional events, various types of odors (inducing different levels of emotional arousal) were used to explore whether olfactory events modulated time perception differently in visual and auditory modalities. Participants were shown either a visual dot or heard a continuous tone for 1000 or 4000 ms while they were exposed to odors of jasmine, lavender, or garlic. Participants then reproduced the temporal durations of the preceding visual or auditory stimuli by pressing the spacebar twice. Their reproduced durations were compared to those in the control condition (without odor). The results showed that participants produced significantly longer time intervals in the lavender condition than in the jasmine or garlic conditions. The overall influence of odor on time perception was equivalent for both visual and auditory modalities. The analysis of the interaction effect showed that participants produced longer durations than the actual duration in the short interval condition, but they produced shorter durations in the long interval condition. The effect sizes were larger for the auditory modality than those for the visual modality. Moreover, by comparing performance across the initial and the final blocks of the experiment, we found odor adaptation effects were mainly manifested as longer reproductions for the short time interval later in the adaptation phase, and there was a larger effect size in the auditory modality. In summary, the present results indicate that odors imposed differential impacts on reproduced time durations, and they were constrained by different sensory modalities, valence of the emotional events, and target durations. Biases in time perception could be accounted for by a framework of

  8. History effects in visual search for monsters: search times, choice biases, and liking.

    PubMed

    Chetverikov, Andrey; Kristjansson, Árni

    2015-02-01

    Repeating targets and distractors on consecutive visual search trials facilitates search performance, whereas switching targets and distractors harms search. In addition, search repetition leads to biases in free choice tasks, in that previously attended targets are more likely to be chosen than distractors. Another line of research has shown that attended items receive high liking ratings, whereas ignored distractors are rated negatively. Potential relations between the three effects are unclear, however. Here we simultaneously measured repetition benefits and switching costs for search times, choice biases, and liking ratings in color singleton visual search for "monster" shapes. We showed that if expectations from search repetition are violated, targets are liked to be less attended than otherwise. Choice biases were, on the other hand, affected by distractor repetition, but not by target/distractor switches. Target repetition speeded search times but had little influence on choice or liking. Our findings suggest that choice biases reflect distractor inhibition, and liking reflects the conflict associated with attending to previously inhibited stimuli, while speeded search follows both target and distractor repetition. Our results support the newly proposed affective-feedback-of-hypothesis-testing account of cognition, and additionally, shed new light on the priming of visual search.

  9. Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup; Denning, Emil Vosmar; Jepsen, Peter Uhd

    2016-06-01

    The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR), and linearity of detection have been characterized. Moreover, the performance of a photomultiplier tube (PMT) and an avalanche photodiode (APD) as photodetector in the ABCD have been compared. We have observed nonlinear behavior of PMT detector, which leads to artificial gain factor in TDS spectroscopy. The APD turns out to have superior linearity and three times higher dynamic compared to the PMT.

  10. Incorrect representation of uncertainty in the modeling of growth leads to biased estimates of future biomass.

    PubMed

    Valle, Denis

    2011-06-01

    Biomass is a fundamental measure in the natural sciences, and numerous models have been developed to forecast timber and fishery yields, forest carbon content, and other environmental services that depend on biomass estimates. We derive general results that reveal how dynamic models that simulate growth as an increase in a linear measure of size (e.g., diameter, length, height) result in biased estimates of future mean biomass when uncertainty in growth is misrepresented. Our case study shows how models of tree growth that predict the same mean diameter increment, but with alternative representations of growth uncertainty, result in almost a threefold difference in the projections of future mean tree biomass after a 20-yr simulation. These results have important implications concerning our ability to accurately predict future biomass and all the related environmental services (e.g., forest carbon content, timber and fishery yields). If the objective is to predict future biomass, we strongly recommend that: (1) ecological modelers should choose a growth model based on a variable more linearly related to biomass (e.g., tree basal area instead of tree diameter for forest models); (2) if field measurements preclude the use of variables other than the linear measure of size, both the mean and other statistical moments (e.g., covariances) should be carefully modeled; (3) careful assessment be done on models that aggregate similar individuals (i.e., cohort models) to see if neglecting autocorrelated growth from individuals leads to biased estimates of future mean biomass.

  11. Time to End the Bias towards Inclusive Education?

    ERIC Educational Resources Information Center

    Runswick-Cole, Katherine

    2011-01-01

    The UK coalition Government's call to end the "bias" towards inclusion represents a shift in "policy speak" as the new administration attempts to re-narrate special education by putting forward a "reasonable and sensible" solution to the "problem of inclusion". However, implicit in the call is the assumption that there has, in fact, been a "bias…

  12. Time and Causation in Discourse: Temporal Proximity, Implicit Causality, and Re-mention Biases.

    PubMed

    Dery, Jeruen E; Bittner, Dagmar

    2016-08-01

    Using referential processing in discourse featuring implicit causality verbs as a test case, we demonstrate how a discourse's causal and temporal dimensions interact. We show that referential processing is affected by multiple discourse biases, and that these biases do not have uniform effects. In three discourse continuation experiments, we show that the bias to re-mention a particular referent in discourse involving implicit causality verbs is not only affected by the verb's implicit causality bias, but also by the discourse's temporal structure, which at times, can even override the implicit causality bias. Our results add to the growing number of studies that show how various discourse dimensions interact in discourse processing.

  13. Reducing bias and analyzing variability in the time-left procedure.

    PubMed

    Trujano, R Emmanuel; Orduña, Vladimir

    2015-04-01

    The time-left procedure was designed to evaluate the psychophysical function for time. Although previous results indicated a linear relationship, it is not clear what role the observed bias toward the time-left option plays in this procedure and there are no reports of how variability changes with predicted indifference. The purposes of this experiment were to reduce bias experimentally, and to contrast the difference limen (a measure of variability around indifference) with predictions from scalar expectancy theory (linear timing) and behavioral economic model (logarithmic timing). A control group of 6 rats performed the original time-left procedure with C=60 s and S=5, 10,…, 50, 55 s, whereas a no-bias group of 6 rats performed the same conditions in a modified time-left procedure in which only a single response per choice trial was allowed. Results showed that bias was reduced for the no-bias group, observed indifference grew linearly with predicted indifference for both groups, and difference limen and Weber ratios decreased as expected indifference increased for the control group, which is consistent with linear timing, whereas for the no-bias group they remained constant, consistent with logarithmic timing. Therefore, the time-left procedure generates results consistent with logarithmic perceived time once bias is experimentally reduced.

  14. Reducing bias and analyzing variability in the time-left procedure.

    PubMed

    Trujano, R Emmanuel; Orduña, Vladimir

    2015-04-01

    The time-left procedure was designed to evaluate the psychophysical function for time. Although previous results indicated a linear relationship, it is not clear what role the observed bias toward the time-left option plays in this procedure and there are no reports of how variability changes with predicted indifference. The purposes of this experiment were to reduce bias experimentally, and to contrast the difference limen (a measure of variability around indifference) with predictions from scalar expectancy theory (linear timing) and behavioral economic model (logarithmic timing). A control group of 6 rats performed the original time-left procedure with C=60 s and S=5, 10,…, 50, 55 s, whereas a no-bias group of 6 rats performed the same conditions in a modified time-left procedure in which only a single response per choice trial was allowed. Results showed that bias was reduced for the no-bias group, observed indifference grew linearly with predicted indifference for both groups, and difference limen and Weber ratios decreased as expected indifference increased for the control group, which is consistent with linear timing, whereas for the no-bias group they remained constant, consistent with logarithmic timing. Therefore, the time-left procedure generates results consistent with logarithmic perceived time once bias is experimentally reduced. PMID:25659914

  15. Improving Order Lead Time: A Case Study

    ERIC Educational Resources Information Center

    Villarreal, Bernardo; Salido, Lucy

    2009-01-01

    A fundamental challenge of globally competing companies is to increase their level of customer satisfaction, by devising and implementing strategies aimed at providing better price, quality, and service. This paper describes the efforts of a Mexican company to achieve this goal, and in particular, with the need to decrease order lead time…

  16. Comparison of Statistical Approaches for Dealing With Immortal Time Bias in Drug Effectiveness Studies.

    PubMed

    Karim, Mohammad Ehsanul; Gustafson, Paul; Petkau, John; Tremlett, Helen

    2016-08-15

    In time-to-event analyses of observational studies of drug effectiveness, incorrect handling of the period between cohort entry and first treatment exposure during follow-up may result in immortal time bias. This bias can be eliminated by acknowledging a change in treatment exposure status with time-dependent analyses, such as fitting a time-dependent Cox model. The prescription time-distribution matching (PTDM) method has been proposed as a simpler approach for controlling immortal time bias. Using simulation studies and theoretical quantification of bias, we compared the performance of the PTDM approach with that of the time-dependent Cox model in the presence of immortal time. Both assessments revealed that the PTDM approach did not adequately address immortal time bias. Based on our simulation results, another recently proposed observational data analysis technique, the sequential Cox approach, was found to be more useful than the PTDM approach (Cox: bias = -0.002, mean squared error = 0.025; PTDM: bias = -1.411, mean squared error = 2.011). We applied these approaches to investigate the association of β-interferon treatment with delaying disability progression in a multiple sclerosis cohort in British Columbia, Canada (Long-Term Benefits and Adverse Effects of Beta-Interferon for Multiple Sclerosis (BeAMS) Study, 1995-2008). PMID:27455963

  17. The Politics of Affirmation Theory: When Group-Affirmation Leads to Greater Ingroup Bias.

    PubMed

    Ehrlich, Gaven A; Gramzow, Richard H

    2015-08-01

    It has been well established in the literature that affirming the individual self reduces the tendency to exhibit group-favoring biases. The limited research examining group-affirmation and bias, however, is inconclusive. We argue that group-affirmation can exacerbate group-serving biases in certain contexts, and in the current set of studies, we document this phenomenon directly. Unlike self-affirmation, group-affirmation led to greater ingroup-favoring evaluative judgments among political partisans (Experiment 1). This increase in evaluative bias following group-affirmation was moderated by political party identification and was not found among those who affirmed a non-political ingroup (Experiment 2). In addition, the mechanism underlying these findings is explored and interpreted within the theoretical frameworks of self-categorization theory and the multiple self-aspects model (Experiments 2 and 3). The broader implications of our findings for the understanding of social identity and affirmation theory are discussed. PMID:26070859

  18. The Politics of Affirmation Theory: When Group-Affirmation Leads to Greater Ingroup Bias.

    PubMed

    Ehrlich, Gaven A; Gramzow, Richard H

    2015-08-01

    It has been well established in the literature that affirming the individual self reduces the tendency to exhibit group-favoring biases. The limited research examining group-affirmation and bias, however, is inconclusive. We argue that group-affirmation can exacerbate group-serving biases in certain contexts, and in the current set of studies, we document this phenomenon directly. Unlike self-affirmation, group-affirmation led to greater ingroup-favoring evaluative judgments among political partisans (Experiment 1). This increase in evaluative bias following group-affirmation was moderated by political party identification and was not found among those who affirmed a non-political ingroup (Experiment 2). In addition, the mechanism underlying these findings is explored and interpreted within the theoretical frameworks of self-categorization theory and the multiple self-aspects model (Experiments 2 and 3). The broader implications of our findings for the understanding of social identity and affirmation theory are discussed.

  19. Naturally Biased? In Search for Reaction Time Evidence for a Natural Number Bias in Adults

    ERIC Educational Resources Information Center

    Vamvakoussi, Xenia; Van Dooren, Wim; Verschaffel, Lieven

    2012-01-01

    A major source of errors in rational number tasks is the inappropriate application of natural number rules. We hypothesized that this is an instance of intuitive reasoning and thus can persist in adults, even when they respond correctly. This was tested by means of a reaction time method, relying on a dual process perspective that differentiates…

  20. Lax decision criteria lead to negativity bias: evidence from the emotional stroop task.

    PubMed

    Liu, Guofang; Xin, Ziqiang; Lin, Chongde

    2014-06-01

    Negativity bias means that negative information is usually given more emphasis than comparable positive information. Under signal detection theory, recent research found that people more frequently and incorrectly identify negative task-related words as having been presented originally than positive words, even when they were not presented. That is, people have lax decision criteria for negative words. However, the response biases for task-unrelated negative words and for emotionally important words are still unclear. This study investigated response bias for these two kinds of words. Study 1 examined the response bias for task-unrelated negative words using an emotional Stroop task. Proportions of correct recognition to negative and positive words were assessed by non-parametric signal detection analysis. Participants have lower (i.e., more lax) decision criteria for task-unrelated negative words than for positive words. Study 2 supported and expanded this result by investigating participants' response bias for highly emotional words. Participants have lower decision criteria for highly emotional words than for less emotional words. Finally, possible evolutionary sources of the response bias were discussed. PMID:25074310

  1. Lax decision criteria lead to negativity bias: evidence from the emotional stroop task.

    PubMed

    Liu, Guofang; Xin, Ziqiang; Lin, Chongde

    2014-06-01

    Negativity bias means that negative information is usually given more emphasis than comparable positive information. Under signal detection theory, recent research found that people more frequently and incorrectly identify negative task-related words as having been presented originally than positive words, even when they were not presented. That is, people have lax decision criteria for negative words. However, the response biases for task-unrelated negative words and for emotionally important words are still unclear. This study investigated response bias for these two kinds of words. Study 1 examined the response bias for task-unrelated negative words using an emotional Stroop task. Proportions of correct recognition to negative and positive words were assessed by non-parametric signal detection analysis. Participants have lower (i.e., more lax) decision criteria for task-unrelated negative words than for positive words. Study 2 supported and expanded this result by investigating participants' response bias for highly emotional words. Participants have lower decision criteria for highly emotional words than for less emotional words. Finally, possible evolutionary sources of the response bias were discussed.

  2. Phase Shift of a Coplanar Waveguide by Bias Voltage on Thick Lead Zirconate Titanate Film at Microwave Frequency

    NASA Astrophysics Data System (ADS)

    Shibata, Kouji; Iijima, Takashi; Masuda, Yoichiro

    2008-09-01

    A coplanar waveguide was fabricated by depositing a 1-µm-thick Au film on a multilayer dielectric, consisting of a 2-µm-thick lead zirconate titanate (PZT) film over an Al2O3 substrate, through etching. Following this, the reflection constant, transmission constant, and phase variation were measured for this transmission line as bias voltage was varied from 30 to 50 V. As a result, it was confirmed that the phase variation becomes about 15° at a 50 V bias at a frequency of 10 GHz. We then confirmed the basic input-output characteristics of this type of structure in the microwave band. Finally, the relative permittivity of a PZT thick film as a coplanar waveguide was estimated using the measurement results of relative permittivity according to the split cavity resonator method, and phase variation under the condition in which a bias voltage was applied.

  3. Understanding and Avoiding Immortal-Time Bias in Gastrointestinal Observational Research.

    PubMed

    Targownik, Laura E; Suissa, Samy

    2015-12-01

    Pharmacoepidemiologic analyses, in which observational data is interrogated to evaluate relationships between patterns of drug use and both beneficial and adverse outcomes, are being increasingly used in the study of inflammatory bowel disease. However, the results of many of these analyses may be corrupted by the presence of immortal person-time bias, an analytic error which can result in an overestimation of the benefits of medical therapy. In this report, we will describe immortal person-time bias, explain the mechanism through which it confers a false benefit, and guide the reader in how to identify this source of bias in the medical literature.

  4. Possible bias in tree-ring time series due to mortality

    SciTech Connect

    Lucier, A A; Warnick, W L; Hyink, D M

    1989-07-01

    This article discusses the possible bias in tree-ring time series studies extending from the year of sample collection to a prepollution period. The authors hypothesizes that normal mortality (i.e., mortality not associated with sudden disturbance) can cause reduced tree ring widths in years preceding actual tree death and produce a bias toward smaller and more variable ring widths at the end of the tree-ring time series.

  5. Timing group delay and differential code bias corrections for BeiDou positioning

    NASA Astrophysics Data System (ADS)

    Guo, Fei; Zhang, Xiaohong; Wang, Jinling

    2015-05-01

    This article first clearly figures out the relationship between parameters of timing group delay (TGD) and differential code bias (DCB) for BDS, and demonstrates the equivalence of TGD and DCB correction models combining theory with practice. The TGD/DCB correction models have been extended to various occasions for BDS positioning, and such models have been evaluated by real triple-frequency datasets. To test the effectiveness of broadcast TGDs in the navigation message and DCBs provided by the Multi-GNSS Experiment (MGEX), both standard point positioning (SPP) and precise point positioning (PPP) tests are carried out for BDS signals with different schemes. Furthermore, the influence of differential code biases on BDS positioning estimates such as coordinates, receiver clock biases, tropospheric delays and carrier phase ambiguities is investigated comprehensively. Comparative analysis show that the unmodeled differential code biases degrade the performance of BDS SPP by a factor of two or more, whereas the estimates of PPP are subject to varying degrees of influences. For SPP, the accuracy of dual-frequency combinations is slightly worse than that of single-frequency, and they are much more sensitive to the differential code biases, particularly for the B2B3 combination. For PPP, the uncorrected differential code biases are mostly absorbed into the receiver clock bias and carrier phase ambiguities and thus resulting in a much longer convergence time. Even though the influence of the differential code biases could be mitigated over time and comparable positioning accuracy could be achieved after convergence, it is suggested to properly handle with the differential code biases since it is vital for PPP convergence and integer ambiguity resolution.

  6. Sex Ratio Bias Leads to the Evolution of Sex Role Reversal in Honey Locust Beetles.

    PubMed

    Fritzsche, Karoline; Booksmythe, Isobel; Arnqvist, Göran

    2016-09-26

    The reversal of conventional sex roles was enigmatic to Darwin, who suggested that it may evolve when sex ratios are female biased [1]. Here we present direct evidence confirming Darwin's hypothesis. We investigated mating system evolution in a sex-role-reversed beetle (Megabruchidius dorsalis) using experimental evolution under manipulated sex ratios and food regimes. In female-biased populations, where reproductive competition among females was intensified, females evolved to be more attractive and the sex roles became more reversed. Interestingly, female-specific mating behavior evolved more rapidly than male-specific mating behavior. We show that sexual selection due to reproductive competition can be strong in females and can target much the same traits as in males of species with conventional mating systems. Our study highlights two central points: the role of ecology in directing sexual selection and the role that females play in mating system evolution. PMID:27593373

  7. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation.

    PubMed

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-09-18

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  8. Agonistic aptamer to the insulin receptor leads to biased signaling and functional selectivity through allosteric modulation

    PubMed Central

    Yunn, Na-Oh; Koh, Ara; Han, Seungmin; Lim, Jong Hun; Park, Sehoon; Lee, Jiyoun; Kim, Eui; Jang, Sung Key; Berggren, Per-Olof; Ryu, Sung Ho

    2015-01-01

    Due to their high affinity and specificity, aptamers have been widely used as effective inhibitors in clinical applications. However, the ability to activate protein function through aptamer-protein interaction has not been well-elucidated. To investigate their potential as target-specific agonists, we used SELEX to generate aptamers to the insulin receptor (IR) and identified an agonistic aptamer named IR-A48 that specifically binds to IR, but not to IGF-1 receptor. Despite its capacity to stimulate IR autophosphorylation, similar to insulin, we found that IR-A48 not only binds to an allosteric site distinct from the insulin binding site, but also preferentially induces Y1150 phosphorylation in the IR kinase domain. Moreover, Y1150-biased phosphorylation induced by IR-A48 selectively activates specific signaling pathways downstream of IR. In contrast to insulin-mediated activation of IR, IR-A48 binding has little effect on the MAPK pathway and proliferation of cancer cells. Instead, AKT S473 phosphorylation is highly stimulated by IR-A48, resulting in increased glucose uptake both in vitro and in vivo. Here, we present IR-A48 as a biased agonist able to selectively induce the metabolic activity of IR through allosteric binding. Furthermore, our study also suggests that aptamers can be a promising tool for developing artificial biased agonists to targeted receptors. PMID:26245346

  9. Biasing the pacemaker in the behavioral theory of timing.

    PubMed

    Bizo, L A; White, K G

    1995-09-01

    In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.

  10. Biasing the pacemaker in the behavioral theory of timing

    PubMed Central

    Bizo, Lewis A.; White, K. Geoffrey

    1995-01-01

    In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate. PMID:16812769

  11. Biased differential relay with digital real time integration

    NASA Astrophysics Data System (ADS)

    Hijazi, M. E. A.; Basak, A.

    1993-05-01

    A new algorithm has been developed for a single phase relay. This can be used for the protection of both single phase and three phase transformers. This paper presents a new scheme using the real time integration technique to determine the differential current caused by either magnetizing inrush current or an internal fault. The proposed relay has been simulated for continuous monitoring of the behavior of the differential current wave form, through the peak value of each current cycle and digital integration of that cycle. The trip of the relay depends on any changes in the area under the differential current wave form. The magnetizing inrush current waveform has less area under its curve than the fault current wave form which contains a sinusoidal wave and a transient dc component. This phenomenon has been used to block the operation of the relay on ``not true'' fault current seen as differential current.

  12. Calculation of the current response in a nanojunction for an arbitrary time-dependent bias: application to the molecular wire

    NASA Astrophysics Data System (ADS)

    Ridley, Michael; MacKinnon, Angus; Kantorovich, Lev

    2016-03-01

    Recently [Phys. Rev. B 91, 125433 (2015)] we derived a general formula for the time-dependent quantum electron current through a molecular junction subject to an arbitrary time-dependent bias within the Wide Band Limit Approximation (WBLA) and assuming a single particle Hamiltonian. Here we present an efficient numerical scheme for calculating the current and particle number. Using the Padé expansion of the Fermi function, it is shown that all frequency integrals occurring in the general formula for the current can be removed analytically. When the bias in the reservoirs is assumed to be sinusoidal it is possible to manipulate the general formula into a form containing only summations over special functions. To illustrate the method, we consider electron transport through a one-dimensional molecular wire coupled to two leads subject to out-of-phase biases. We also investigate finite size effects in the current response and particle number that result from the switch-on of this bias.

  13. Bias Corrections for Regional Estimates of the Time-averaged Geomagnetic Field

    NASA Astrophysics Data System (ADS)

    Constable, C.; Johnson, C. L.

    2009-05-01

    We assess two sources of bias in the time-averaged geomagnetic field (TAF) and paleosecular variation (PSV): inadequate temporal sampling, and the use of unit vectors in deriving temporal averages of the regional geomagnetic field. For the first temporal sampling question we use statistical resampling of existing data sets to minimize and correct for bias arising from uneven temporal sampling in studies of the time- averaged geomagnetic field (TAF) and its paleosecular variation (PSV). The techniques are illustrated using data derived from Hawaiian lava flows for 0-5~Ma: directional observations are an updated version of a previously published compilation of paleomagnetic directional data centered on ± 20° latitude by Lawrence et al./(2006); intensity data are drawn from Tauxe & Yamazaki, (2007). We conclude that poor temporal sampling can produce biased estimates of TAF and PSV, and resampling to appropriate statistical distribution of ages reduces this bias. We suggest that similar resampling should be attempted as a bias correction for all regional paleomagnetic data to be used in TAF and PSV modeling. The second potential source of bias is the use of directional data in place of full vector data to estimate the average field. This is investigated for the full vector subset of the updated Hawaiian data set. Lawrence, K.P., C.G. Constable, and C.L. Johnson, 2006, Geochem. Geophys. Geosyst., 7, Q07007, DOI 10.1029/2005GC001181. Tauxe, L., & Yamazkai, 2007, Treatise on Geophysics,5, Geomagnetism, Elsevier, Amsterdam, Chapter 13,p509

  14. Neural correlates of belief-bias reasoning under time pressure: a near-infrared spectroscopy study.

    PubMed

    Tsujii, Takeo; Watanabe, Shigeru

    2010-04-15

    The dual-process theory of reasoning explained the belief-bias effect, the tendency for human reasoning to be erroneously biased when logical conclusions are incongruent with belief about the world, by proposing a belief-based fast heuristic system and a logic-based slow analytic system. Although the claims were supported by behavioral findings that the belief-bias effect was enhanced when subjects were not given sufficient time for reasoning, the neural correlates were still unknown. The present study therefore examined the relationship between the time-pressure effect and activity in the inferior frontal cortex (IFC) during belief-bias reasoning using near-infrared spectroscopy (NIRS). Forty-eight subjects performed congruent and incongruent reasoning tasks, involving long-span (20 s) and short-span trials (10 s). Behavioral analysis found that only incongruent reasoning performance was impaired by the time-pressure of short-span trials. NIRS analysis found that the time-pressure decreased right IFC activity during incongruent trials. Correlation analysis showed that subjects with enhanced right IFC activity could perform better in incongruent trials, while subjects for whom the right IFC activity was impaired by the time-pressure could not maintain better reasoning performance. These findings suggest that the right IFC may be responsible for the time-pressure effect in conflicting reasoning processes. When the right IFC activity was impaired in the short-span trials in which subjects were not given sufficient time for reasoning, the subjects may rely on the fast heuristic system, which result in belief-bias responses. We therefore offer the first demonstration of neural correlates of time-pressure effect on the IFC activity in belief-bias reasoning.

  15. Time Course of Attentional Bias in Anxiety: Emotion and Gender Specificity

    PubMed Central

    Sass, Sarah M.; Heller, Wendy; Stewart, Jennifer L.; Silton, Rebecca Levin; Edgar, J. Christopher; Fisher, Joscelyn E.; Miller, Gregory A.

    2011-01-01

    Anxiety is characterized by cognitive biases, including attentional bias to emotional (especially threatening) stimuli. Accounts differ on the time course of attention to threat, but the literature generally confounds emotional valence and arousal and overlooks gender effects, both addressed in the present study. Nonpatients high in self-reported anxious apprehension, anxious arousal, or neither completed an emotion-word Stroop task during ERP recording. Hypotheses differentiated time course of preferential attention to emotional stimuli. Individuals high in anxious apprehension and anxious arousal showed distinct early ERP evidence of preferential processing of emotionally arousing stimuli along with some evidence for gender differences in processing. Healthy controls showed gender differences at both early and later processing stages. The conjunction of valence, arousal, and gender is critical in the time course of attentional bias. PMID:19863758

  16. Mind-set and close relationships: when bias leads to (In)accurate predictions.

    PubMed

    Gagné, F M; Lydon, J E

    2001-07-01

    The authors investigated whether mind-set influences the accuracy of relationship predictions. Because people are more biased in their information processing when thinking about implementing an important goal, relationship predictions made in an implemental mind-set were expected to be less accurate than those made in a more impartial deliberative mind-set. In Study 1, open-ended thoughts of students about to leave for university were coded for mind-set. In Study 2, mind-set about a major life goal was assessed using a self-report measure. In Study 3, mind-set was experimentally manipulated. Overall, mind-set interacted with forecasts to predict relationship survival. Forecasts were more accurate in a deliberative mind-set than in an implemental mind-set. This effect was more pronounced for long-term than for short-term relationship survival. Finally, deliberatives were not pessimistic; implementals were unduly optimistic.

  17. Inhomogeneities in bias-corrected precipitation time-series over Russia

    NASA Astrophysics Data System (ADS)

    Shabanov, Pavel

    2016-04-01

    Inhomogeneities in climate time series of bias-corrected precipitation over Russia are analyzed. During XX century in the USSR there was several changes in precipitation measurement procedures, which caused inhomogeneities in precipitation time-series. Two precipitation datasets are under investigation: the original one (without correction procedures and wetting correction), and the other - undergone the bias-correction procedure following the full empirical correction model of precipitation gauge data (The Voeikov Main Geophysical Observatory monthly datasets; Golubev, 2000; Bogdanova, 2008). Three homogeneity tests were applied for annual sums to detect the breaks: the standard normal homogeneity test (Alexandersson, 1986), the Buishand range test (Buishand, 1982) and the Pettitt test (Pettitt, 1979). The artifact inhomogeneities were detected not only in original dataset, where it was expected, especially after 1966, when the precipitation collecting method was modified, but also in bias-corrected time series. Most of breaks appear in 1950-s, when new gauges with Tretyakov wind shield were installed all over the observation hydrometeorological network of the USSR. Although all basic systematic measurement errors of precipitation gauges were excluded from bias-corrected dataset, homogeneity tests detect breaks. After 1966-1967, when wetting correction usage was started and the number of measurements was increased from 2 to 4 per day, and near 1986, when the number of measurements decreased from 4 to 2 per day, homogeneity tests also show biases. In the early 1970-s there were also changes in wind speed measurement procedure, which could cause breaks in corrected precipitation datasets (full model uses wind speed as a parameter). The percent of determined breaks (5% significant level), detected at least by two tests, is near 50% for original dataset and near 30% for bias-corrected dataset. So, even bias-corrected precipitation dataset over Russia should be checked

  18. Recurrent positive selection and heterogeneous codon usage bias events leading to coexistence of divergent pigeon circoviruses.

    PubMed

    Liao, Pei-Chun; Wang, Kung-Kai; Tsai, Shinn-Shyong; Liu, Hung-Jen; Huang, Bing-Hong; Chuang, Kuo-Pin

    2015-08-01

    The capsid genes from 14 pigeon circovirus (PiCV) sequences, collected from Taiwan between 2009 and 2010, were sequenced and compared with 14 PiCV capsid gene sequences from GenBank. Based on pairwise comparison, PiCV strains from Taiwan shared 73.9-100% nucleotide identity and 72-100% amino acid identity with those of the 14 reported PiCV sequences. Phylogenetic analyses revealed that Taiwanese PiCV isolates can be grouped into two clades: clade 1 comprising isolates from Belgium, Australia, USA, Italy and China, and clade 2 showing close relation to isolates from Germany and France. Recurrent positive selection was detected in clade 1 PiCV lineages, which may contribute to the diversification of predominant PiCV sequences in Taiwan. Further observations suggest that synonymous codon usage variations between PiCV clade 1 and clade 2 may reflect the adaptive divergence on translation efficiency of capsid genes in infectious hosts. Variation in selective pressures acting on the evolutionary divergence and codon usage bias of both clades explains the regional coexistence of virus sequences congeners prevented from competitive exclusion within an island such as Taiwan. Our genotyping results also provide insight into the aetiological agents of PiCV outbreak in Taiwan and we present a comparative analysis of the central coding region of PiCV genome. From the sequence comparison results of 28 PiCVs which differs in regard to the geographical origin and columbid species, we identified conserved regions within the capsid gene that are likely to be suitable for primer selection and vaccine development.

  19. Time-Lag Bias in Trials of Pediatric Antidepressants: A Systematic Review and Meta-Analysis

    ERIC Educational Resources Information Center

    Reyes, Magdalena M.; Panza, Kaitlyn E.; Martin, Andres; Bloch, Michael H.

    2011-01-01

    Objective: To determine whether there is evidence of a time-lag bias in the publication of pediatric antidepressant trials. Method: We conducted a meta-analysis of published and unpublished randomized placebo-controlled trials of serotonin reuptake inhibitors (SRIs) in subjects less than 18 years of age with major depressive disorder. Our main…

  20. Exploring the influential factors in incident clearance time: Disentangling causation from self-selection bias.

    PubMed

    Ding, Chuan; Ma, Xiaolei; Wang, Yinhai; Wang, Yunpeng

    2015-12-01

    Understanding the relationships between influential factors and incident clearance time is crucial to make effective countermeasures for incident management agencies. Although there have been a certain number of achievements on incident clearance time modeling, limited effort is made to investigate the relative role of incident response time and its self-selection in influencing the clearance time. To fill this gap, this study uses the endogenous switching model to explore the influential factors in incident clearance time, and aims to disentangle causation from self-selection bias caused by response process. Under the joint two-stage model framework, the binary probit model and switching regression model are formulated for both incident response time and clearance time, respectively. Based on the freeway incident data collected in Washington State, full information maximum likelihood (FIML) method is utilized to estimate the endogenous switching model parameters. Significant factors affecting incident response time and clearance time can be identified, including incident, temporal, geographical, environmental, traffic and operational attributes. The estimate results reveal the influential effects of incident, temporal, geographical, environmental, traffic and operational factors on incident response time and clearance time. In addition, the causality of incident response time itself and its self-selection correction on incident clearance time are found to be indispensable. These findings suggest that the causal effect of response time on incident clearance time will be overestimated if the self-selection bias is not considered.

  1. Exploring the influential factors in incident clearance time: Disentangling causation from self-selection bias.

    PubMed

    Ding, Chuan; Ma, Xiaolei; Wang, Yinhai; Wang, Yunpeng

    2015-12-01

    Understanding the relationships between influential factors and incident clearance time is crucial to make effective countermeasures for incident management agencies. Although there have been a certain number of achievements on incident clearance time modeling, limited effort is made to investigate the relative role of incident response time and its self-selection in influencing the clearance time. To fill this gap, this study uses the endogenous switching model to explore the influential factors in incident clearance time, and aims to disentangle causation from self-selection bias caused by response process. Under the joint two-stage model framework, the binary probit model and switching regression model are formulated for both incident response time and clearance time, respectively. Based on the freeway incident data collected in Washington State, full information maximum likelihood (FIML) method is utilized to estimate the endogenous switching model parameters. Significant factors affecting incident response time and clearance time can be identified, including incident, temporal, geographical, environmental, traffic and operational attributes. The estimate results reveal the influential effects of incident, temporal, geographical, environmental, traffic and operational factors on incident response time and clearance time. In addition, the causality of incident response time itself and its self-selection correction on incident clearance time are found to be indispensable. These findings suggest that the causal effect of response time on incident clearance time will be overestimated if the self-selection bias is not considered. PMID:26373988

  2. Stationary Probability and First-Passage Time of Biased Random Walk

    NASA Astrophysics Data System (ADS)

    Li, Jing-Wen; Tang, Shen-Li; Xu, Xin-Ping

    2016-09-01

    In this paper, we consider the stationary probability and first-passage time of biased random walk on 1D chain, where at each step the walker moves to the left and right with probabilities p and q respectively (0 ⩽ p, q ⩽ 1, p + q = 1). We derive exact analytical results for the stationary probability and first-passage time as a function of p and q for the first time. Our results suggest that the first-passage time shows a double power-law F ˜ (N - 1)γ, where the exponent γ = 2 for N < |p - q|-1 and γ = 1 for N > |p - q|-1. Our study sheds useful insights into the biased random-walk process. Supported by the National Natural Science Foundation of China under Grant No. 11205110, Shanghai Key Laboratory of Intelligent Information Processing (IIPL-2011-009), and Innovative Training Program for College Students under Grant No. 2015xj070

  3. Time-Lag Bias in Trials of Pediatric Antidepressants: A Systematic Review and Meta-Analysis

    PubMed Central

    Reyes, Magdalena M.; Panza, Kaitlyn E.; Martin, Andrés; Bloch, Michael H.

    2013-01-01

    Objective To determine if there is evidence of a time-lag bias in the publication of pediatric antidepressant trials. Method We conducted a meta-analysis of published and unpublished randomized, placebo-controlled trials of serotonin reuptake inhibitors (SRIs) in subjects less than 18 years old with major depressive disorder. Our main outcomes were (1) time to publication of positive versus negative trials, and (2) proportion of treatment responders in trials with standard (< 3 years after study completion) versus delayed publication. Results We identified 15 randomized, placebo-controlled trials of SRIs for pediatric depression. Trials with negative findings had a significantly longer time to publication (median years ± standard deviation = 4.2 ±1.9) than trials with positive findings (2.2 ±0.9; log-rank χ2 = 4.35, p = 0.037). The estimated efficacy in trials with standard publication time (number needed to treat = 7, 95% CI: 5 – 11) was significantly greater than those with delayed publication (17, 95% CI: 9 – ∞; χ2 = 4.98, p = 0.025). The inflation-adjusted impact factor of journals for published trials with positive (15.33 ±11.01) and negative results (7.54 ±7.90) did not statistically differ (t = 1.4, df = 10, p = 0.17). Conclusions Despite a small number of trials of SRIs for pediatric antidepressants we found a significant evidence of time-lag bias in the publication of findings. This time-lag bias altered the perceived efficacy of pediatric antidepressants in the medical literature. Time-lag bias is not unique to child psychiatry and reflects a larger problem in scientific publishing. PMID:21156271

  4. Observational selection biases in time-delay strong lensing and their impact on cosmography

    NASA Astrophysics Data System (ADS)

    Collett, Thomas E.; Cunnington, Steven D.

    2016-11-01

    Inferring cosmological parameters from time-delay strong lenses requires a significant investment of telescope time; it is therefore tempting to focus on the systems with the brightest sources, the highest image multiplicities and the widest image separations. We investigate if this selection bias can influence the properties of the lenses studied and the cosmological parameters inferred. Using an ellipsoidal power-law deflector population, we build a sample of double- and quadruple-image systems. Assuming reasonable thresholds on image separation and flux, based on current lens monitoring campaigns, we find that the typical density profile slopes of monitorable lenses are significantly shallower than the input ensemble. From a sample of quads, we find that this selection function can introduce a 3.5 per cent bias on the inferred time-delay distances if the properties of the input ensemble are (incorrectly) used as priors on the lens model. This bias remains at the 2.4 per cent level when high-resolution imaging of the quasar host is used to precisely infer the properties of individual lenses. We also investigate if the lines of sight for monitorable strong lenses are biased. The expectation value for the line-of-sight convergence is increased by 0.009 (0.004) for quads (doubles) implying a 0.9 per cent (0.4 per cent) bias on H0. We therefore conclude that whilst the properties of typical quasar lenses and their lines of sight do deviate from the global population, the total magnitude of this effect is likely to be a subdominant effect for current analyses, but has the potential to be a major systematic for samples of ˜25 or more lenses.

  5. Selection bias in dynamically measured supermassive black hole samples: consequences for pulsar timing arrays

    NASA Astrophysics Data System (ADS)

    Sesana, Alberto; Shankar, Francesco; Bernardi, Mariangela; Sheth, Ravi K.

    2016-11-01

    Supermassive black hole -- host galaxy relations are key to the computation of the expected gravitational wave background (GWB) in the pulsar timing array (PTA) frequency band. It has been recently pointed out that standard relations adopted in GWB computations are in fact biased-high. We show that when this selection bias is taken into account, the expected GWB in the PTA band is a factor of about three smaller than previously estimated. Compared to other scaling relations recently published in the literature, the median amplitude of the signal at $f=1$yr$^{-1}$ drops from $1.3\\times10^{-15}$ to $4\\times10^{-16}$. Although this solves any potential tension between theoretical predictions and recent PTA limits without invoking other dynamical effects (such as stalling, eccentricity or strong coupling with the galactic environment), it also makes the GWB detection more challenging.

  6. In Darwinian evolution, feedback from natural selection leads to biased mutations.

    PubMed

    Caporale, Lynn Helena; Doyle, John

    2013-12-01

    Natural selection provides feedback through which information about the environment and its recurring challenges is captured, inherited, and accumulated within genomes in the form of variations that contribute to survival. The variation upon which natural selection acts is generally described as "random." Yet evidence has been mounting for decades, from such phenomena as mutation hotspots, horizontal gene transfer, and highly mutable repetitive sequences, that variation is far from the simplifying idealization of random processes as white (uniform in space and time and independent of the environment or context).  This paper focuses on what is known about the generation and control of mutational variation, emphasizing that it is not uniform across the genome or in time, not unstructured with respect to survival, and is neither memoryless nor independent of the (also far from white) environment. We suggest that, as opposed to frequentist methods, Bayesian analysis could capture the evolution of nonuniform probabilities of distinct classes of mutation, and argue not only that the locations, styles, and timing of real mutations are not correctly modeled as generated by a white noise random process, but that such a process would be inconsistent with evolutionary theory.

  7. Born at the Wrong Time: Selection Bias in the NHL Draft

    PubMed Central

    Deaner, Robert O.; Lowen, Aaron; Cobley, Stephen

    2013-01-01

    Relative age effects (RAEs) occur when those who are relatively older for their age group are more likely to succeed. RAEs occur reliably in some educational and athletic contexts, yet the causal mechanisms remain unclear. Here we provide the first direct test of one mechanism, selection bias, which can be defined as evaluators granting fewer opportunities to relatively younger individuals than is warranted by their latent ability. Because RAEs are well-established in hockey, we analyzed National Hockey League (NHL) drafts from 1980 to 2006. Compared to those born in the first quarter (i.e., January–March), those born in the third and fourth quarters were drafted more than 40 slots later than their productivity warranted, and they were roughly twice as likely to reach career benchmarks, such as 400 games played or 200 points scored. This selection bias in drafting did not decrease over time, apparently continues to occur, and reduces the playing opportunities of relatively younger players. This bias is remarkable because it is exhibited by professional decision makers evaluating adults in a context where RAEs have been widely publicized. Thus, selection bias based on relative age may be pervasive. PMID:23460902

  8. Uniform-acceptance force-bias Monte Carlo method with time scale to study solid-state diffusion

    NASA Astrophysics Data System (ADS)

    Mees, Maarten J.; Pourtois, Geoffrey; Neyts, Erik C.; Thijsse, Barend J.; Stesmans, André

    2012-04-01

    Monte Carlo (MC) methods have a long-standing history as partners of molecular dynamics (MD) to simulate the evolution of materials at the atomic scale. Among these techniques, the uniform-acceptance force-bias Monte Carlo (UFMC) method [G. Dereli, Mol. Simul.10.1080/08927029208022490 8, 351 (1992)] has recently attracted attention [M. Timonova , Phys. Rev. BPRBMDO1098-012110.1103/PhysRevB.81.144107 81, 144107 (2010)] thanks to its apparent capacity of being able to simulate physical processes in a reduced number of iterations compared to classical MD methods. The origin of this efficiency remains, however, unclear. In this work we derive a UFMC method starting from basic thermodynamic principles, which leads to an intuitive and unambiguous formalism. The approach includes a statistically relevant time step per Monte Carlo iteration, showing a significant speed-up compared to MD simulations. This time-stamped force-bias Monte Carlo (tfMC) formalism is tested on both simple one-dimensional and three-dimensional systems. Both test-cases give excellent results in agreement with analytical solutions and literature reports. The inclusion of a time scale, the simplicity of the method, and the enhancement of the time step compared to classical MD methods make this method very appealing for studying the dynamics of many-particle systems.

  9. Adaptively biased molecular dynamics: An umbrella sampling method with a time-dependent potential

    NASA Astrophysics Data System (ADS)

    Babin, Volodymyr; Karpusenka, Vadzim; Moradi, Mahmoud; Roland, Christopher; Sagui, Celeste

    We discuss an adaptively biased molecular dynamics (ABMD) method for the computation of a free energy surface for a set of reaction coordinates. The ABMD method belongs to the general category of umbrella sampling methods with an evolving biasing potential. It is characterized by a small number of control parameters and an O(t) numerical cost with simulation time t. The method naturally allows for extensions based on multiple walkers and replica exchange mechanism. The workings of the method are illustrated with a number of examples, including sugar puckering, and free energy landscapes for polymethionine and polyproline peptides, and for a short β-turn peptide. ABMD has been implemented into the latest version (Case et al., AMBER 10; University of California: San Francisco, 2008) of the AMBER software package and is freely available to the simulation community.

  10. Taphonomic trade-offs in tropical marine death assemblages: Differential time averaging, shell loss, and probable bias in siliciclastic vs. carbonate facies

    NASA Astrophysics Data System (ADS)

    Kidwell, Susan M.; Best, Mairi M. R.; Kaufman, Darrell S.

    2005-09-01

    Radiocarbon-calibrated amino-acid racemization ages of individually dated bivalve mollusk shells from Caribbean reef, nonreefal carbonate, and siliciclastic sediments in Panama indicate that siliciclastic sands and muds contain significantly older shells (median 375 yr, range up to ˜5400 yr) than nearby carbonate seafloors (median 72 yr, range up to ˜2900 yr; maximum shell ages differ significantly at p < 0.02 using extreme-value statistics). The implied difference in shell loss rates is contrary to physicochemical expectations but is consistent with observed differences in shell condition (greater bioerosion and dissolution in carbonates). Higher rates of shell loss in carbonate sediments should lead to greater compositional bias in surviving skeletal material, resulting in taphonomic trade-offs: less time averaging but probably higher taxonomic bias in pure carbonate sediments, and lower bias but greater time averaging in siliciclastic sediments from humid-weathered accretionary arc terrains, which are a widespread setting of tropical sedimentation.

  11. Real-time video compression using entropy-biased ANN codebooks

    NASA Astrophysics Data System (ADS)

    Ahalt, Stanley C.; Fowler, James E.

    1994-03-01

    We describe hardware that has been built to compress video in real time using full-search vector quantization (VQ). This architecture implements a differential-vector-quantization (DVQ) algorithm which features entropy-biased codebooks designed using an artificial neural network. A special-purpose digital associative memory, the VAMPIRE chip, performs the VQ processing. We describe the DVQ algorithm, its adaptations for sampled NTSC composite- color video, and details of its hardware implementation. We conclude by presenting results drawn from real-time operation of the DVQ hardware.

  12. Stationary Probability and First-Passage Time of Biased Random Walk

    NASA Astrophysics Data System (ADS)

    Li, Jing-Wen; Tang, Shen-Li; Xu, Xin-Ping

    2016-09-01

    In this paper, we consider the stationary probability and first-passage time of biased random walk on 1D chain, where at each step the walker moves to the left and right with probabilities p and q respectively (0 ⩽ p, q ⩽ 1, p + q = 1). We derive exact analytical results for the stationary probability and first-passage time as a function of p and q for the first time. Our results suggest that the first-passage time shows a double power-law F ∼ (N ‑ 1)γ, where the exponent γ = 2 for N < |p ‑ q|‑1 and γ = 1 for N > |p ‑ q|‑1. Our study sheds useful insights into the biased random-walk process. Supported by the National Natural Science Foundation of China under Grant No. 11205110, Shanghai Key Laboratory of Intelligent Information Processing (IIPL-2011-009), and Innovative Training Program for College Students under Grant No. 2015xj070

  13. Cooperative adsorption behavior of phosphopeptides on TiO2 leads to biased enrichment, detection and quantification.

    PubMed

    Eriksson, A I K; Edwards, K; Agmo Hernández, V

    2015-01-01

    The adsorption behavior of phosphopeptides onto TiO2 surfaces was studied using the quartz crystal microbalance with dissipation monitoring (QCM-D) as the main experimental technique. The main focus is the characterization of the emergence of positive cooperativity under conditions where the peptides have a positively charged C-term. It is shown that when carrying no net charge, small water-soluble peptides as a rule develop positive cooperativity. The impact of the adsorption mechanism on the outcome of TiO2 based enrichment methods was investigated with the help of matrix assisted laser desorption-ionization mass spectrometry (MALDI-MS). The data presented illustrate how the phosphopeptide profile in the enriched material may deviate from that in the native sample, as cooperative phosphopeptides are overrepresented in the former. Furthermore, commonly employed washing and elution solutions may facilitate preferential release of certain peptides, leading to further bias in the recovered sample. Taken together, the results of the present study demonstrate that thorough understanding of the mechanisms behind the adsorption of phosphopeptides on the enrichment material is necessary in order to develop reliable qualitative and quantitative methods for phosphoproteomics.

  14. Negativity bias of the self across time: an event-related potentials study.

    PubMed

    Luo, Yangmei; Huang, Xiting; Chen, Youguo; Jackson, Todd; Wei, Dongtao

    2010-05-14

    To investigate the neural basis of self-evaluation across time as a function of emotional valence, event-related potentials were recorded among participants instructed to make self-reference judgments when evaluating their past, present and future selves. Results showed that, when evaluating present and past selves, negative words elicited a more positive ERP deflection in the time window between 650ms and 800ms (LPC) relative to positive words. However, when evaluating the future selves, there was no significant difference on the amplitude of the LPC evoked by negative versus positive words. Findings provided evidence for the effect of emotional valence on the self across time at a neurophysiological level and identified the time course of negative bias in the temporal self. More specifically, people were inclined to be relatively less negative and optimistic about their future self but had mixed emotions about past and present selves.

  15. Finite-time position and velocity estimation adapted to noisy biased acceleration measurements from periodic motion

    NASA Astrophysics Data System (ADS)

    Estrada, Antonio; Efimov, Denis; Perruquetti, Wilfrid

    2016-09-01

    The present work focuses on the problem of velocity and position estimation. A solution is presented for a class of oscillating systems in which position, velocity and acceleration are zero mean signals. The proposed scheme considers that the dynamic model of the system is unknown. Only noisy acceleration measurements, that may be contaminated by zero mean noise and constant bias, are considered to be available. The proposal uses the periodic nature of the signals obtaining finite-time estimations while tackling integration drift accumulation.

  16. A System for Continuous Hydrological Ensemble Forecasting (SCHEF) to lead times of 9 days

    NASA Astrophysics Data System (ADS)

    Bennett, James C.; Robertson, David E.; Shrestha, Durga Lal; Wang, Q. J.; Enever, David; Hapuarachchi, Prasantha; Tuteja, Narendra K.

    2014-11-01

    This study describes a System for Continuous Hydrological Ensemble Forecasting (SCHEF) designed to forecast streamflows to lead times of 9 days. SCHEF is intended to support optimal management of water resources for consumptive and environmental purposes and ultimately to support the management of impending floods. Deterministic rainfall forecasts from the ACCESS-G numerical weather prediction (NWP) model are post-processed using a Bayesian joint probability model to correct biases and quantify uncertainty. Realistic temporal and spatial characteristics are instilled in the rainfall forecast ensemble with the Schaake shuffle. The ensemble rainfall forecasts are then used as inputs to the GR4H hydrological model to produce streamflow forecasts. A hydrological error correction is applied to ensure forecasts transit smoothly from recent streamflow observations. SCHEF forecasts streamflows skilfully for a range of hydrological and climate conditions. Skill is particularly evident in forecasts of streamflows at lead times of 1-6 days. Forecasts perform best in temperate perennially flowing rivers, while forecasts are poorest in intermittently flowing rivers. The poor streamflow forecasts in intermittent rivers are primarily the result of poor rainfall forecasts, rather than an inadequate representation of hydrological processes. Forecast uncertainty becomes more reliably quantified at longer lead times; however there is considerable scope for improving the reliability of streamflow forecasts at all lead times. Additionally, we show that the choice of forecast time-step can influence forecast accuracy: forecasts generated at a 1-h time-step tend to be more accurate than at longer time-steps (e.g. 1-day). This is largely because at shorter time-steps the hydrological error correction is able to correct streamflow forecasts with more recent information, rather than the ability of GR4H to simulate hydrological processes better at shorter time-steps. SCHEF will form the

  17. Symmetrically biased T/R switches for NMR and MRI with microsecond dead time.

    PubMed

    Brunner, David O; Furrer, Lukas; Weiger, Markus; Baumberger, Werner; Schmid, Thomas; Reber, Jonas; Dietrich, Benjamin E; Wilm, Bertram J; Froidevaux, Romain; Pruessmann, Klaas P

    2016-02-01

    For direct NMR detection and imaging of compounds with very short coherence life times the dead time between radio-frequency (RF) pulse and reception of the free induction decay (FID) is a major limiting factor. It is typically dominated by the transient and recovery times of currently available transmit-receive (T/R) switches and amplification chains. A novel PIN diode-based T/R switch topology is introduced allowing for fast switching by high bias transient currents but nevertheless producing a very low video leakage signal and insertion loss (0.5dB). The low transient spike level in conjunction with the high isolation (75dB) prevent saturation of the preamplifier entirely which consequently does not require time for recovery. Switching between transmission and reception is demonstrated within less than 1μs in bench tests as well as in acquisitions of FIDs and zero echo time (ZTE) images with bandwidths up to 500kHz at 7T. Thereby the 2kW switch exhibited a rise-time of 350ns (10-99%) producing however a total video leakage of below 20mV peak-to-peak and less than -89dBm in-band. The achieved switching time renders the RF pulse itself the dominant contribution to the dead time in which a coherence cannot be observed, thus making pulsed NMR experiments almost time-optimal even for compounds with very short signal life times. PMID:26796113

  18. Symmetrically biased T/R switches for NMR and MRI with microsecond dead time

    NASA Astrophysics Data System (ADS)

    Brunner, David O.; Furrer, Lukas; Weiger, Markus; Baumberger, Werner; Schmid, Thomas; Reber, Jonas; Dietrich, Benjamin E.; Wilm, Bertram J.; Froidevaux, Romain; Pruessmann, Klaas P.

    2016-02-01

    For direct NMR detection and imaging of compounds with very short coherence life times the dead time between radio-frequency (RF) pulse and reception of the free induction decay (FID) is a major limiting factor. It is typically dominated by the transient and recovery times of currently available transmit-receive (T/R) switches and amplification chains. A novel PIN diode-based T/R switch topology is introduced allowing for fast switching by high bias transient currents but nevertheless producing a very low video leakage signal and insertion loss (0.5 dB). The low transient spike level in conjunction with the high isolation (75 dB) prevent saturation of the preamplifier entirely which consequently does not require time for recovery. Switching between transmission and reception is demonstrated within less than 1 μs in bench tests as well as in acquisitions of FIDs and zero echo time (ZTE) images with bandwidths up to 500 kHz at 7 T. Thereby the 2 kW switch exhibited a rise-time of 350 ns (10-99%) producing however a total video leakage of below 20 mV peak-to-peak and less than -89 dBm in-band. The achieved switching time renders the RF pulse itself the dominant contribution to the dead time in which a coherence cannot be observed, thus making pulsed NMR experiments almost time-optimal even for compounds with very short signal life times.

  19. Symmetrically biased T/R switches for NMR and MRI with microsecond dead time.

    PubMed

    Brunner, David O; Furrer, Lukas; Weiger, Markus; Baumberger, Werner; Schmid, Thomas; Reber, Jonas; Dietrich, Benjamin E; Wilm, Bertram J; Froidevaux, Romain; Pruessmann, Klaas P

    2016-02-01

    For direct NMR detection and imaging of compounds with very short coherence life times the dead time between radio-frequency (RF) pulse and reception of the free induction decay (FID) is a major limiting factor. It is typically dominated by the transient and recovery times of currently available transmit-receive (T/R) switches and amplification chains. A novel PIN diode-based T/R switch topology is introduced allowing for fast switching by high bias transient currents but nevertheless producing a very low video leakage signal and insertion loss (0.5dB). The low transient spike level in conjunction with the high isolation (75dB) prevent saturation of the preamplifier entirely which consequently does not require time for recovery. Switching between transmission and reception is demonstrated within less than 1μs in bench tests as well as in acquisitions of FIDs and zero echo time (ZTE) images with bandwidths up to 500kHz at 7T. Thereby the 2kW switch exhibited a rise-time of 350ns (10-99%) producing however a total video leakage of below 20mV peak-to-peak and less than -89dBm in-band. The achieved switching time renders the RF pulse itself the dominant contribution to the dead time in which a coherence cannot be observed, thus making pulsed NMR experiments almost time-optimal even for compounds with very short signal life times.

  20. Resonance and decay phenomena lead to quantum mechanical time asymmetry

    NASA Astrophysics Data System (ADS)

    Bohm, A.; Bui, H. V.

    2013-04-01

    The states (Schrödinger picture) and observables (Heisenberg picture) in the standard quantum theory evolve symmetrically in time, given by the unitary group with time extending over -∞ < t < +∞. This time evolution is a mathematical consequence of the Hilbert space boundary condition for the dynamical differential equations. However, this unitary group evolution violates causality. Moreover, it does not solve an old puzzle of Wigner: How does one describe excited states of atoms which decay exponentially, and how is their lifetime τ related to the Lorentzian width Γ? These question can be answered if one replaces the Hilbert space boundary condition by new, Hardy space boundary conditions. These Hardy space boundary conditions allow for a distinction between states (prepared by a preparation apparatus) and observables (detected by a registration apparatus). The new Hardy space quantum theory is time asymmetric, i.e, the time evolution is given by the semigroup with t0 <= t < +∞, which predicts a finite "beginning of time" t0, where t0 is the ensemble of time at which each individual system has been prepared. The Hardy space axiom also leads to the new prediction: the width Γ and the lifetime τ are exactly related by τ = hslash/Γ.

  1. Investigating bias in the application of curve fitting programs to atmospheric time series

    NASA Astrophysics Data System (ADS)

    Pickers, P. A.; Manning, A. C.

    2014-07-01

    The decomposition of an atmospheric time series into its constituent parts is an essential tool for identifying and isolating variations of interest from a data set, and is widely used to obtain information about sources, sinks and trends in climatically important gases. Such procedures involve fitting appropriate mathematical functions to the data, however, it has been demonstrated that the application of such curve fitting procedures can introduce bias, and thus influence the scientific interpretation of the data sets. We investigate the potential for bias associated with the application of three curve fitting programs, known as HPspline, CCGCRV and STL, using CO2, CH4 and O3 data from three atmospheric monitoring field stations. These three curve fitting programs are widely used within the greenhouse gas measurement community to analyse atmospheric time series, but have not previously been compared extensively. The programs were rigorously tested for their ability to accurately represent the salient features of atmospheric time series, their ability to cope with outliers and gaps in the data, and for sensitivity to the values used for the input parameters needed for each program. We find that the programs can produce significantly different curve fits, and these curve fits can be dependent on the input parameters selected. There are notable differences between the results produced by the three programs for many of the decomposed components of the time series, such as the representation of seasonal cycle characteristics and the long-term growth rate. The programs also vary significantly in their response to gaps and outliers in the time series. Overall, we found that none of the three programs were superior, and that each program had its strengths and weaknesses. Thus, we provide a list of recommendations on the appropriate use of these three curve fitting programs for certain types of data sets, and for certain types of analyses and applications. In addition, we

  2. Investigating bias in the application of curve fitting programs to atmospheric time series

    NASA Astrophysics Data System (ADS)

    Pickers, P. A.; Manning, A. C.

    2015-03-01

    The decomposition of an atmospheric time series into its constituent parts is an essential tool for identifying and isolating variations of interest from a data set, and is widely used to obtain information about sources, sinks and trends in climatically important gases. Such procedures involve fitting appropriate mathematical functions to the data. However, it has been demonstrated that the application of such curve fitting procedures can introduce bias, and thus influence the scientific interpretation of the data sets. We investigate the potential for bias associated with the application of three curve fitting programs, known as HPspline, CCGCRV and STL, using multi-year records of CO2, CH4 and O3 data from three atmospheric monitoring field stations. These three curve fitting programs are widely used within the greenhouse gas measurement community to analyse atmospheric time series, but have not previously been compared extensively. The programs were rigorously tested for their ability to accurately represent the salient features of atmospheric time series, their ability to cope with outliers and gaps in the data, and for sensitivity to the values used for the input parameters needed for each program. We find that the programs can produce significantly different curve fits, and these curve fits can be dependent on the input parameters selected. There are notable differences between the results produced by the three programs for many of the decomposed components of the time series, such as the representation of seasonal cycle characteristics and the long-term (multi-year) growth rate. The programs also vary significantly in their response to gaps and outliers in the time series. Overall, we found that none of the three programs were superior, and that each program had its strengths and weaknesses. Thus, we provide a list of recommendations on the appropriate use of these three curve fitting programs for certain types of data sets, and for certain types of

  3. The SDT Model of Belief Bias: Complexity, Time, and Cognitive Ability Mediate the Effects of Believability

    ERIC Educational Resources Information Center

    Trippas, Dries; Handley, Simon J.; Verde, Michael F.

    2013-01-01

    When people evaluate conclusions, they are often influenced by prior beliefs. Prevalent theories claim that "belief bias" affects the quality of syllogistic reasoning. However, recent work by Dube, Rotello, and Heit (2010) has suggested that belief bias may be a simple response bias. In Experiment 1, receiver operating characteristic…

  4. Psychometric properties of reaction time based experimental paradigms measuring anxiety-related information-processing biases in children.

    PubMed

    Brown, H M; Eley, T C; Broeren, S; Macleod, C; Rinck, M; Hadwin, J A; Lester, K J

    2014-01-01

    Theoretical frameworks highlight the importance of threat-related information-processing biases for understanding the emergence of anxiety in childhood. The psychometric properties of several tasks measuring these biases and their associations with anxiety were examined in an unselected sample of 9-year-old children (N=155). In each task, threat bias was assessed using bias scores reflecting task performance on threat versus non-threat conditions. Reliability was assessed using split-half and test-retest correlations of mean reaction times (RTs), accuracy and bias indices. Convergence between measures was also examined. Mean RTs showed substantial split-half and test-retest correlations. Bias score reliability coefficients were near zero and non-significant, suggesting poor reliability in children of this age. Additionally, associations between bias scores and anxiety were weak and inconsistent and performance between tasks showed little convergence. Bias scores from RT based paradigms in the current study lacked adequate psychometric properties for measuring individual differences in anxiety-related information-processing in children.

  5. Time-scale bias in evidence for anthropogenic acceleration of soil erosion and floodplain accretion

    NASA Astrophysics Data System (ADS)

    Willenbring, J. K.; Hoffmann, T.; Sadler, P.; Kaplan, J. O.; Chiverrell, R. C.; Erkens, G.; von Blanckenburg, F.

    2014-12-01

    The claim that humans modify the landscape more dramatically than any previous geological agent has impacts for river restoration, conservation and models of both nutrient- and carbon-cycling. This view of extreme sediment mobilization driven by human activities is largely based on data, which unfortunately are measured over discrepant timescales that can introduce bias. Comparing denudation rates discerned from cosmogenic nuclides as 'baseline' or 'natural' rates with continent-scale sediment export rates over modern timescales reveals that most cosmogenic nuclide-based erosion rates are faster than human-impacted rates of sediment yield [1]. One explanation for relatively low recent continental sediment yields is that the eroded sediment may be accumulating and stored for an uncertain duration in swelling floodplains and deltas. We present a global compilation of Holocene floodplain accumulation rates. Rates measured over the last ~100 years are faster than those averaged over ~1000 years, which in turn are faster than those for the last ~10000 years. Floodplain sediment accumulation measurements, however, are taken at discreet cores or bank exposures, and this introduces both temporal and spatial bias. Vertical accumulation rates are calculated by dividing thickness of sediment by the time-span of accumulation for discrete packages of sediment. Thus, time integrates from the present to a past datum provided by 14C measurements for buried organics (or other chronological tools). We argue that the pattern of rate increase in sedimentation over time is related to infilling behavior of all floodplains and not specifically tied to the supply of (anthropogenic) sediment. The apparent acceleration in sedimentation rates appears globally synchronous over 8000-year timescales, despite diachronous human and land use histories. Moreover, some rate acceleration pre-dates significant human land use. When the effect/bias of averaging time is accounted for, recent accumulation

  6. Methodological issues in current practice may lead to bias in the development of biomarker combinations for predicting acute kidney injury

    PubMed Central

    Meisner, Allison; Kerr, Kathleen F.; Thiessen-Philbrook, Heather; Coca, Steven G.; Parikh, Chirag R.

    2015-01-01

    Individual biomarkers of renal injury are only modestly predictive of acute kidney injury (AKI). Using multiple biomarkers has the potential to improve predictive capacity. In this systematic review, statistical methods of articles developing biomarker combinations to predict acute kidney injury were assessed. We identified and described three potential sources of bias (resubstitution bias, model selection bias and bias due to center differences) that may compromise the development of biomarker combinations. Fifteen studies reported developing kidney injury biomarker combinations for the prediction of AKI after cardiac surgery (8 articles), in the intensive care unit (4 articles) or other settings (3 articles). All studies were susceptible to at least one source of bias and did not account for or acknowledge the bias. Inadequate reporting often hindered our assessment of the articles. We then evaluated, when possible (7 articles), the performance of published biomarker combinations in the TRIBE-AKI cardiac surgery cohort. Predictive performance was markedly attenuated in six out of seven cases. Thus, deficiencies in analysis and reporting are avoidable and care should be taken to provide accurate estimates of risk prediction model performance. Hence, rigorous design, analysis and reporting of biomarker combination studies are essential to realizing the promise of biomarkers in clinical practice. PMID:26398494

  7. Sensitivity bias in the mass-radius distribution from transit timing variations and radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Steffen, Jason H.

    2016-04-01

    Motivated by recent discussions, both in private and in the literature, we use a Monte Carlo simulation of planetary systems to investigate sources of bias in determining the mass-radius distribution of exoplanets for the two primary techniques used to measure planetary masses - radial velocities (RVs) and transit timing variations (TTVs). We assert that mass measurements derived from these two methods are comparably reliable - as the physics underlying their respective signals is well understood. Nevertheless, their sensitivity to planet mass varies with the properties of the planets themselves. We find that for a given planet size, the RV method tends to find planets with higher mass while the sensitivity of TTVs is more uniform. This `sensitivity bias' implies that a complete census of TTV systems is likely to yield a more robust estimate of the mass-radius distribution provided there are not important physical differences between planets near and far from mean-motion resonance. We discuss differences in the sensitivity of the two methods with orbital period and system architecture, which may compound the discrepancies between them (e.g. short-period planets detectable by RVs may be more dense due to atmospheric loss). We advocate for continued mass measurements using both approaches as a means both to measure the masses of more planets and to identify potential differences in planet structure that may result from their dynamical and environmental histories.

  8. A Perceptual Pathway to Bias: Interracial Exposure Reduces Abrupt Shifts in Real-Time Race Perception That Predict Mixed-Race Bias.

    PubMed

    Freeman, Jonathan B; Pauker, Kristin; Sanchez, Diana T

    2016-04-01

    In two national samples, we examined the influence of interracial exposure in one's local environment on the dynamic process underlying race perception and its evaluative consequences. Using a mouse-tracking paradigm, we found in Study 1 that White individuals with low interracial exposure exhibited a unique effect of abrupt, unstable White-Black category shifting during real-time perception of mixed-race faces, consistent with predictions from a neural-dynamic model of social categorization and computational simulations. In Study 2, this shifting effect was replicated and shown to predict a trust bias against mixed-race individuals and to mediate the effect of low interracial exposure on that trust bias. Taken together, the findings demonstrate that interracial exposure shapes the dynamics through which racial categories activate and resolve during real-time perceptions, and these initial perceptual dynamics, in turn, may help drive evaluative biases against mixed-race individuals. Thus, lower-level perceptual aspects of encounters with racial ambiguity may serve as a foundation for mixed-race prejudice. PMID:26976082

  9. Observation Impacts for Longer Forecast Lead-Times

    NASA Astrophysics Data System (ADS)

    Mahajan, R.; Gelaro, R.; Todling, R.

    2013-12-01

    Observation impact on forecasts evaluated using adjoint-based techniques (e.g. Langland and Baker, 2004) are limited by the validity of the assumptions underlying the forecasting model adjoint. Most applications of this approach have focused on deriving observation impacts on short-range forecasts (e.g. 24-hour) in part to stay well within linearization assumptions. The most widely used measure of observation impact relies on the availability of the analysis for verifying the forecasts. As pointed out by Gelaro et al. (2007), and more recently by Todling (2013), this introduces undesirable correlations in the measure that are likely to affect the resulting assessment of the observing system. Stappers and Barkmeijer (2012) introduced a technique that, in principle, allows extending the validity of tangent linear and corresponding adjoint models to longer lead-times, thereby reducing the correlations in the measures used for observation impact assessments. The methodology provides the means to better represent linearized models by making use of Gaussian quadrature relations to handle various underlying non-linear model trajectories. The formulation is exact for particular bi-linear dynamics; it corresponds to an approximation for general-type nonlinearities and must be tested for large atmospheric models. The present work investigates the approach of Stappers and Barkmeijer (2012)in the context of NASA's Goddard Earth Observing System Version 5 (GEOS-5) atmospheric data assimilation system (ADAS). The goal is to calculate observation impacts in the GEOS-5 ADAS for forecast lead-times of at least 48 hours in order to reduce the potential for undesirable correlations that occur at shorter forecast lead times. References [1]Langland, R. H., and N. L. Baker, 2004: Estimation of observation impact using the NRL atmospheric variational data assimilation adjoint system. Tellus, 56A, 189-201. [2] Gelaro, R., Y. Zhu, and R. M. Errico, 2007: Examination of various

  10. Time perception and depressive realism: judgment type, psychophysical functions and bias.

    PubMed

    Kornbrot, Diana E; Msetfi, Rachel M; Grimwood, Melvyn J

    2013-01-01

    The effect of mild depression on time estimation and production was investigated. Participants made both magnitude estimation and magnitude production judgments for five time intervals (specified in seconds) from 3 sec to 65 sec. The parameters of the best fitting psychophysical function (power law exponent, intercept, and threshold) were determined individually for each participant in every condition. There were no significant effects of mood (high BDI, low BDI) or judgment (estimation, production) on the mean exponent, n = .98, 95% confidence interval (.96-1.04) or on the threshold. However, the intercept showed a 'depressive realism' effect, where high BDI participants had a smaller deviation from accuracy and a smaller difference between estimation and judgment than low BDI participants. Accuracy bias was assessed using three measures of accuracy: difference, defined as psychological time minus physical time, ratio, defined as psychological time divided by physical time, and a new logarithmic accuracy measure defined as ln (ratio). The ln (ratio) measure was shown to have approximately normal residuals when subjected to a mixed ANOVA with mood as a between groups explanatory factor and judgment and time category as repeated measures explanatory factors. The residuals of the other two accuracy measures flagrantly violated normality. The mixed ANOVAs of accuracy also showed a strong depressive realism effect, just like the intercepts of the psychophysical functions. There was also a strong negative correlation between estimation and production judgments. Taken together these findings support a clock model of time estimation, combined with additional cognitive mechanisms to account for the depressive realism effect. The findings also suggest strong methodological recommendations.

  11. Lead

    MedlinePlus

    ... Lead Share Facebook Twitter Google+ Pinterest Contact Us Lead Poisoning is Preventable If your home was built before ... of the RRP rule. Read more . Learn about Lead Poisoning Prevention Week . Report Uncertified Contractors and Environmental Violations ...

  12. Do Young and Old Preschoolers Exhibit Response Bias Due to Different Mechanisms? Investigating Children's Response Time

    ERIC Educational Resources Information Center

    Okanda, Mako; Itakura, Shoji

    2011-01-01

    Previous studies have suggested that younger preschoolers exhibit a yes bias due to underdeveloped cognitive abilities, whereas older preschoolers exhibit a response bias due to other factors. To test this hypothesis, we investigated the response latency to yes-no questions pertaining to familiar and unfamiliar objects in 3- to 6-year-olds. The…

  13. Lead

    MedlinePlus

    ... obvious symptoms, it frequently goes unrecognized. CDC’s Childhood Lead Poisoning Prevention Program is committed to the Healthy People ... Lead Levels Information for Parents Tips for preventing lead poisoning About Us Overview of CDC’s Childhood Lead Poisoning ...

  14. Confirmation bias leads to overestimation of losses of woody plant foliage to insect herbivores in tropical regions.

    PubMed

    Kozlov, Mikhail V; Zverev, Vitali; Zvereva, Elena L

    2014-01-01

    Confirmation bias, i.e., the tendency of humans to seek out evidence in a manner that confirms their hypotheses, is almost overlooked in ecological studies. For decades, insect herbivory was commonly accepted to be highest in tropical regions. By comparing the data collected blindly (when the observer was not aware of the research hypothesis being tested) with the results of non-blind studies (when the observer knew what results could be expected), we tested the hypothesis that the records made in the tropics could have overestimated community-wide losses of plant foliage to insects due to the confirmation bias. The average loss of leaf area of woody plants to defoliating insects in Brazil, when measured by a blind method (1.11%), was significantly lower than the loss measured in non-blind studies, both original (5.14%) and published (6.37%). We attribute the overestimation of the community-wide losses of plant foliage to insects in non-blind studies to the unconsciously preconceived selection of study species with higher-than-average levels of herbivory. Based on our findings, we urge for caution in obtaining community-wide characteristics from the results of multiple single-species studies. Our data suggest that we may need to revise the paradigm of the highest level of background insect herbivory in the tropical regions. More generally, we argue that more attention should be paid by ecologists to the problem of biases occurring at the pre-publication phases of the scientific research and, consequently, to the development and the wide application of methods that avoid biases occurring due to unconscious psychological processes.

  15. Mean SST bias and variability at inter-annual and decadal time-scales in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Polo, Irene; Villamayor, Julian; Rodriguez-Fonseca, Belen; Mohino, Elsa; Losada, Teresa

    2016-04-01

    Analysis of model systematic errors in Sea Surface Temperature (SST) has generally focused on local processes and particular basins. Mean warm bias over the south subtropical upwelling systems in coupled models are largely studied and local cloud cover, alongshore winds and ocean stratification are pointed out as the responsible processes. Mean errors have impacts on the variability but this is less understood. In this study we try to understand the relation between mean global SST biases and how models perform the variability at different time-scales. To this end, we calculate the SST variability modes for 18 models in the preindustrial control CMIP5 experiment. We first analyse the seasonality of those modes and the inter-model differences. Associated parameters are confronted with the mean SST bias variability among models, thus we conclude how realistic models simulate the variability depending on the mean SST bias. Preliminary results suggest that models with cooler (warmer) that average SST mean bias over the southern hemisphere reproduce better (worse) the Inter-Decadal Pacific variability. Similar mean bias pattern has an effect on the skill for reproducing Pacific El Nino and Atlantic Nino modes. Finally an inter-model SST bias variability mode is found relating errors over the southern upwelling systems with cloud cover around 60S and equatorial precipitation shift. This mode is able to summarize some features in relation with inter-decadal to inter-annual variability in CMIP5 models and thus represents a potential tool to understand the wider picture in relation to SST biases and future projections.

  16. Circuital characterisation of space-charge motion with a time-varying applied bias.

    PubMed

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-01-01

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes. PMID:26133999

  17. Circuital characterisation of space-charge motion with a time-varying applied bias

    PubMed Central

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-01-01

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes. PMID:26133999

  18. Circuital characterisation of space-charge motion with a time-varying applied bias.

    PubMed

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-07-02

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes.

  19. Circuital characterisation of space-charge motion with a time-varying applied bias

    NASA Astrophysics Data System (ADS)

    Kim, Chul; Moon, Eun-Yi; Hwang, Jungho; Hong, Hiki

    2015-07-01

    Understanding the behaviour of space-charge between two electrodes is important for a number of applications. The Shockley-Ramo theorem and equivalent circuit models are useful for this; however, fundamental questions of the microscopic nature of the space-charge remain, including the meaning of capacitance and its evolution into a bulk property. Here we show that the microscopic details of the space-charge in terms of resistance and capacitance evolve in a parallel topology to give the macroscopic behaviour via a charge-based circuit or electric-field-based circuit. We describe two approaches to this problem, both of which are based on energy conservation: the energy-to-current transformation rule, and an energy-equivalence-based definition of capacitance. We identify a significant capacitive current due to the rate of change of the capacitance. Further analysis shows that Shockley-Ramo theorem does not apply with a time-varying applied bias, and an additional electric-field-based current is identified to describe the resulting motion of the space-charge. Our results and approach provide a facile platform for a comprehensive understanding of the behaviour of space-charge between electrodes.

  20. Sexual difference in juvenile-hormone titer in workers leads to sex-biased soldier differentiation in termites.

    PubMed

    Toga, Kouhei; Hanmoto, Shutaro; Suzuki, Ryutaro; Watanabe, Dai; Miura, Toru; Maekawa, Kiyoto

    2016-04-01

    In termites, the soldier caste, with its specialized defensive morphology, is one of the most important characteristics for sociality. Most of the basal termite species have both male and female soldiers, and the soldier sex ratio is almost equal or only slightly biased. However, in the apical lineages (especially family Termitidae), there are many species that have soldiers with strongly biased sex ratio. Generally in termites, since high juvenile hormone (JH) titer is required for soldier differentiation from a worker via a presoldier stage, it was hypothesized that the biased soldier-sex ratio was caused by differences in JH sensitivity and/or JH titer between male and female workers. Therefore, we focused on the presoldier differentiation and the worker JH titer in species with only male soldiers (Nasutitermes takasagoensis) and with both male and female soldiers (Reticulitermes speratus) in natural conditions. In the former species, there are four types of workers; male minor, male medium, female medium and female major workers, and presoldiers differentiate from male minor workers. First, we tried to artificially induce presoldiers from male and female workers. In N. takasagoensis, the presoldier differentiation rate and mortality was significantly higher in male minor workers. Morphological analyses showed that both male and female induced presoldiers possessed normal soldier-specific morphologies. It was suggested that female workers, from which soldiers do not differentiate under natural conditions, also maintained the physiological and developmental potential for soldier differentiation. In R. speratus, however, no differences were observed in solder differentiation rate and mortality between male and female workers. Second, the JH titers of each sex/type of workers were quantified by high performance liquid chromatography-mass spectrometry in two different seasons (April and December). The results showed that, in N. takasagoensis, JH titer in male minor

  1. Sexual difference in juvenile-hormone titer in workers leads to sex-biased soldier differentiation in termites.

    PubMed

    Toga, Kouhei; Hanmoto, Shutaro; Suzuki, Ryutaro; Watanabe, Dai; Miura, Toru; Maekawa, Kiyoto

    2016-04-01

    In termites, the soldier caste, with its specialized defensive morphology, is one of the most important characteristics for sociality. Most of the basal termite species have both male and female soldiers, and the soldier sex ratio is almost equal or only slightly biased. However, in the apical lineages (especially family Termitidae), there are many species that have soldiers with strongly biased sex ratio. Generally in termites, since high juvenile hormone (JH) titer is required for soldier differentiation from a worker via a presoldier stage, it was hypothesized that the biased soldier-sex ratio was caused by differences in JH sensitivity and/or JH titer between male and female workers. Therefore, we focused on the presoldier differentiation and the worker JH titer in species with only male soldiers (Nasutitermes takasagoensis) and with both male and female soldiers (Reticulitermes speratus) in natural conditions. In the former species, there are four types of workers; male minor, male medium, female medium and female major workers, and presoldiers differentiate from male minor workers. First, we tried to artificially induce presoldiers from male and female workers. In N. takasagoensis, the presoldier differentiation rate and mortality was significantly higher in male minor workers. Morphological analyses showed that both male and female induced presoldiers possessed normal soldier-specific morphologies. It was suggested that female workers, from which soldiers do not differentiate under natural conditions, also maintained the physiological and developmental potential for soldier differentiation. In R. speratus, however, no differences were observed in solder differentiation rate and mortality between male and female workers. Second, the JH titers of each sex/type of workers were quantified by high performance liquid chromatography-mass spectrometry in two different seasons (April and December). The results showed that, in N. takasagoensis, JH titer in male minor

  2. Real time tests for long lead-time forecasting of the magnetic field vectors within CMEs

    NASA Astrophysics Data System (ADS)

    Savani, Neel; Vourlidas, Angelos; Pulkkinen, Antti; Wold, Alexandra M.

    2016-07-01

    The direction of magnetic vectors within coronal mass ejections, CMEs, has significant importance for forecasting terrestrial behavior. We have developed a technique to estimate the time-varying magnetic field at Earth for periods within CMEs (Savani et al 2015, 2016). This technique reduces the complex dynamics in order to create a reliable prediction methodology to operate everyday under robust conditions. In this presentation, we focus on the results and skill scores of the forecasting technique calculated from 40 historical CME events from the pre-STEREO mission. Since these results provided substantial improvements in the long lead-time Kp index forecasts, we have now begun testing under real-time conditions. We will also show the preliminary results of our methodology under these real-time conditions within the CCMC hosted at NASA Goddard Space Flight Center.

  3. Non Linear Optimization Applied to Angle-Of Satellite Based Geo-Localization for Biased and Time-Drifting Sensors

    NASA Astrophysics Data System (ADS)

    Levy, Daniel; Roos, Jason; Robinson, Jace; Carpenter, William; Martin, Richard; Taylor, Clark; Sugrue, Joseph; Terzuoli, Andrew

    2016-06-01

    Multiple sensors are used in a variety of geolocation systems. Many use Time Difference of Arrival (TDOA) or Received Signal Strength (RSS) measurements to estimate the most likely location of a signal. When an object does not emit an RF signal, Angle of Arrival (AOA) measurements using optical or infrared frequencies become more feasible than TDOA or RSS measurements. AOA measurements can be created from any sensor platform with any sort of optical sensor, location and attitude knowledge to track passive objects. Previous work has created a non-linear optimization (NLO) method for calculating the most likely estimate from AOA measurements. Two new modifications to the NLO algorithm are created and shown to correct AOA measurement errors by estimating the inherent bias and time-drift in the Inertial Measurement Unit (IMU) of the AOA sensing platform. One method corrects the sensor bias in post processing while treating the NLO method as a module. The other method directly corrects the sensor bias within the NLO algorithm by incorporating the bias parameters as a state vector in the estimation process. These two methods are analyzed using various Monte-Carlo simulations to check the general performance of the two modifications in comparison to the original NLO algorithm.

  4. Real-time Sub-cm Differential Orbit Determination of two Low-Earth Orbiters with GPS Bias Fixing

    NASA Technical Reports Server (NTRS)

    Wu, Sien-Chong; Bar-Sever, Yoaz E.

    2006-01-01

    An effective technique for real-time differential orbit determination with GPS bias fixing is formulated. With this technique, only real-time GPS orbits and clocks are needed (available from the NASA Global Differential GPS System with 10-20 cm accuracy). The onboard, realtime orbital states of user satellites (few meters in accuracy) are used for orbit initialization and integration. An extended Kalman filter is constructed for the estimation of the differential orbit between the two satellites as well as a reference orbit, together with their associating dynamics parameters. Due to close proximity of the two satellites and of similar body shapes, the differential dynamics are highly common and can be tightly constrained which, in turn, strengthens the orbit estimation. Without explicit differencing of GPS data, double-differenced phase biases are formed by a transformation matrix. Integer-valued fixing of these biases are then performed which greatly strengthens the orbit estimation. A 9-day demonstration between GRACE orbits with baselines of approx.200 km indicates that approx.80% of the double-differenced phase biases can successfully be fixed and the differential orbit can be determined to approx.7 mm as compared to the results of onboard K-band ranging.

  5. Statistical modelling of forecast errors for multiple lead-times and a system of reservoirs

    NASA Astrophysics Data System (ADS)

    Engeland, Kolbjorn; Steinsland, Ingelin; Kolberg, Sjur

    2010-05-01

    Water resources management, e.g. operation of reservoirs, is amongst others based on forecasts of inflow provided by a precipitation-runoff model. The forecasted inflow is normally given as one value, even though it is an uncertain value. There is a growing interest to account for uncertain information in decision support systems, e.g. how to operate a hydropower reservoir to maximize the gain. One challenge is to develop decision support systems that can use uncertain information. The contribution from the hydrological modeler is to derive a forecast distribution (from which uncertainty intervals can be computed) for the inflow predictions. In this study we constructed a statistical model for the forecast errors for daily inflow into a system of four hydropower reservoirs in Ulla-Førre in Western Norway. A distributed hydrological model was applied to generate the inflow forecasts using weather forecasts provided by ECM for lead-times up to 10 days. The precipitation forecasts were corrected for systematic bias. A statistical model based on auto-regressive innovations for Box-Cox-transformed observations and forecasts was constructed for the forecast errors. The parameters of the statistical model were conditioned on climate and the internal snow state in the hydrological model. The model was evaluated according to the reliability of the forecast distribution, the width of the forecast distribution, and efficiency of the median forecast for the 10 lead times and the four catchments. The interpretation of the results had to be done carefully since the inflow data have a large uncertainty.

  6. Real-Time PPP Based on the Coupling Estimation of Clock Bias and Orbit Error with Broadcast Ephemeris

    PubMed Central

    Pan, Shuguo; Chen, Weirong; Jin, Xiaodong; Shi, Xiaofei; He, Fan

    2015-01-01

    Satellite orbit error and clock bias are the keys to precise point positioning (PPP). The traditional PPP algorithm requires precise satellite products based on worldwide permanent reference stations. Such an algorithm requires considerable work and hardly achieves real-time performance. However, real-time positioning service will be the dominant mode in the future. IGS is providing such an operational service (RTS) and there are also commercial systems like Trimble RTX in operation. On the basis of the regional Continuous Operational Reference System (CORS), a real-time PPP algorithm is proposed to apply the coupling estimation of clock bias and orbit error. The projection of orbit error onto the satellite-receiver range has the same effects on positioning accuracy with clock bias. Therefore, in satellite clock estimation, part of the orbit error can be absorbed by the clock bias and the effects of residual orbit error on positioning accuracy can be weakened by the evenly distributed satellite geometry. In consideration of the simple structure of pseudorange equations and the high precision of carrier-phase equations, the clock bias estimation method coupled with orbit error is also improved. Rovers obtain PPP results by receiving broadcast ephemeris and real-time satellite clock bias coupled with orbit error. By applying the proposed algorithm, the precise orbit products provided by GNSS analysis centers are rendered no longer necessary. On the basis of previous theoretical analysis, a real-time PPP system was developed. Some experiments were then designed to verify this algorithm. Experimental results show that the newly proposed approach performs better than the traditional PPP based on International GNSS Service (IGS) real-time products. The positioning accuracies of the rovers inside and outside the network are improved by 38.8% and 36.1%, respectively. The PPP convergence speeds are improved by up to 61.4% and 65.9%. The new approach can change the

  7. Real-Time PPP Based on the Coupling Estimation of Clock Bias and Orbit Error with Broadcast Ephemeris.

    PubMed

    Pan, Shuguo; Chen, Weirong; Jin, Xiaodong; Shi, Xiaofei; He, Fan

    2015-07-22

    Satellite orbit error and clock bias are the keys to precise point positioning (PPP). The traditional PPP algorithm requires precise satellite products based on worldwide permanent reference stations. Such an algorithm requires considerable work and hardly achieves real-time performance. However, real-time positioning service will be the dominant mode in the future. IGS is providing such an operational service (RTS) and there are also commercial systems like Trimble RTX in operation. On the basis of the regional Continuous Operational Reference System (CORS), a real-time PPP algorithm is proposed to apply the coupling estimation of clock bias and orbit error. The projection of orbit error onto the satellite-receiver range has the same effects on positioning accuracy with clock bias. Therefore, in satellite clock estimation, part of the orbit error can be absorbed by the clock bias and the effects of residual orbit error on positioning accuracy can be weakened by the evenly distributed satellite geometry. In consideration of the simple structure of pseudorange equations and the high precision of carrier-phase equations, the clock bias estimation method coupled with orbit error is also improved. Rovers obtain PPP results by receiving broadcast ephemeris and real-time satellite clock bias coupled with orbit error. By applying the proposed algorithm, the precise orbit products provided by GNSS analysis centers are rendered no longer necessary. On the basis of previous theoretical analysis, a real-time PPP system was developed. Some experiments were then designed to verify this algorithm. Experimental results show that the newly proposed approach performs better than the traditional PPP based on International GNSS Service (IGS) real-time products. The positioning accuracies of the rovers inside and outside the network are improved by 38.8% and 36.1%, respectively. The PPP convergence speeds are improved by up to 61.4% and 65.9%. The new approach can change the

  8. Lens galaxies in the Illustris simulation: power-law models and the bias of the Hubble constant from time delays

    NASA Astrophysics Data System (ADS)

    Xu, Dandan; Sluse, Dominique; Schneider, Peter; Springel, Volker; Vogelsberger, Mark; Nelson, Dylan; Hernquist, Lars

    2016-02-01

    A power-law density model, i.e. ρ (r) ∝ r^{-γ ^' }}, has been commonly employed in strong gravitational lensing studies, including the so-called time-delay technique used to infer the Hubble constant H0. However, since the radial scale at which strong lensing features are formed corresponds to the transition from the dominance of baryonic matter to dark matter, there is no known reason why galaxies should follow a power law in density. The assumption of a power law artificially breaks the mass-sheet degeneracy, a well-known invariance transformation in gravitational lensing which affects the product of Hubble constant and time delay and can therefore cause a bias in the determination of H0 from the time-delay technique. In this paper, we use the Illustris hydrodynamical simulations to estimate the amplitude of this bias, and to understand how it is related to observational properties of galaxies. Investigating a large sample of Illustris galaxies that have velocity dispersion σSIE ≥ 160 km s-1 at redshifts below z = 1, we find that the bias on H0 introduced by the power-law assumption can reach 20-50 per cent, with a scatter of 10-30 per cent (rms). However, we find that by selecting galaxies with an inferred power-law model slope close to isothermal, it is possible to reduce the bias on H0 to ≲ 5 per cent and the scatter to ≲ 10 per cent. This could potentially be used to form less biased statistical samples for H0 measurements in the upcoming large survey era.

  9. Non-random temporary emigration and the robust design: Conditions for bias at the end of a time series: Section VIII

    USGS Publications Warehouse

    Langtimm, Catherine A.

    2008-01-01

    Knowing the extent and magnitude of the potential bias can help in making decisions as to what time frame provides the best estimates or the most reliable opportunity to model and test hypotheses about factors affecting survival probability. To assess bias, truncating the capture histories to shorter time frames and reanalyzing the data to compare time-specific estimates may help identify spurious effects. Running simulations that mimic the parameter values and movement conditions in the real situation can provide estimates of standardized bias that can be used to identify those annual estimates that are biased to the point where the 95% confidence intervals are inadequate in describing the uncertainty of the estimates.

  10. Real Time Corrosion Monitoring in Lead and Lead-Bismuth Systems

    SciTech Connect

    James F. Stubbins; Alan Bolind; Ziang Chen

    2010-02-25

    The objective of this research program is to develop a real-time, in situ corrosion monitoring technique for flowing liquid Pb and eutectic PbBi (LBE) systems in a temperature range of 400 to 650 C. These conditions are relevant to future liquid metal cooled fast reactor operating parameters. THis program was aligned with the Gen IV Reactor initiative to develp technologies to support the design and opertion of a Pb or LBE-cooled fast reactor. The ability to monitor corrosion for protection of structural components is a high priority issue for the safe and prolonged operation of advanced liquid metal fast reactor systems. In those systems, protective oxide layers are intentionally formed and maintained to limit corrosion rates during operation. This program developed a real time, in situ corrosion monitoring tecnique using impedance spectroscopy (IS) technology.

  11. Leading the Charge for Real-Time Data

    ERIC Educational Resources Information Center

    Aarons, Dakarai I.

    2009-01-01

    Well before the idea of using data to manage schools gained prominence on the national stage, Oklahoma's Western Heights school district had made the ideal of real-time, data-driven decisionmaking a reality. Back in 2001, Superintendent Joe Kitchens was already being spotlighted for his focus on creating a longitudinal-data system that would give…

  12. Real-time DC-dynamic biasing method for switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators.

    PubMed

    Small, Joshua; Fruehling, Adam; Garg, Anurag; Liu, Xiaoguang; Peroulis, Dimitrios

    2014-01-01

    Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement. PMID:25145811

  13. Real-time DC-dynamic biasing method for switching time improvement in severely underdamped fringing-field electrostatic MEMS actuators.

    PubMed

    Small, Joshua; Fruehling, Adam; Garg, Anurag; Liu, Xiaoguang; Peroulis, Dimitrios

    2014-01-01

    Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement.

  14. Real-Time DC-dynamic Biasing Method for Switching Time Improvement in Severely Underdamped Fringing-field Electrostatic MEMS Actuators

    PubMed Central

    Small, Joshua; Fruehling, Adam; Garg, Anurag; Liu, Xiaoguang; Peroulis, Dimitrios

    2014-01-01

    Mechanically underdamped electrostatic fringing-field MEMS actuators are well known for their fast switching operation in response to a unit step input bias voltage. However, the tradeoff for the improved switching performance is a relatively long settling time to reach each gap height in response to various applied voltages. Transient applied bias waveforms are employed to facilitate reduced switching times for electrostatic fringing-field MEMS actuators with high mechanical quality factors. Removing the underlying substrate of the fringing-field actuator creates the low mechanical damping environment necessary to effectively test the concept. The removal of the underlying substrate also a has substantial improvement on the reliability performance of the device in regards to failure due to stiction. Although DC-dynamic biasing is useful in improving settling time, the required slew rates for typical MEMS devices may place aggressive requirements on the charge pumps for fully-integrated on-chip designs. Additionally, there may be challenges integrating the substrate removal step into the back-end-of-line commercial CMOS processing steps. Experimental validation of fabricated actuators demonstrates an improvement of 50x in switching time when compared to conventional step biasing results. Compared to theoretical calculations, the experimental results are in good agreement. PMID:25145811

  15. Attentional bias in injection phobia: overt components, time course, and relation to behavior.

    PubMed

    Armstrong, Thomas; Hemminger, Adam; Olatunji, Bunmi O

    2013-06-01

    Blood-injection-injury (BII) phobia is an anxiety disorder that can cause serious health consequences by interfering with medical treatment. Although attentional bias for threat appears to be a core feature of many anxiety disorders and a potential target of treatment, very little is known about attentional bias in BII phobia. In the present study, eye movements were recorded in individuals high and low in injection fear (HIF, LIF) during 18-s exposures to stimulus arrays containing injection, attack, appetitive, and neutral images. Evidence for attentional vigilance was mixed, as HIF individuals oriented to injection images more often than LIF individuals, but did not orient to injection images more often than other emotional images. In contrast, evidence of attentional avoidance was highly robust. HIF individuals rapidly disengaged from injection images on initial viewing and viewed these images less overall compared to other image types, a pattern not observed in the LIF group. Furthermore, attentional avoidance of injection threat was found to uniquely predict behavioral avoidance on an injection behavioral avoidance task (BAT), and group differences on the BAT were mediated by group differences in attentional avoidance. The implications of these findings for further delineating the nature and function of attentional biases in BII phobia are discussed. PMID:23523867

  16. Attentional bias between modalities: effect on the internal clock, memory, and decision stages used in animal time discrimination.

    PubMed

    Meck, W H

    1984-01-01

    Both the presentation of unbalanced stimulus probabilities and the insertion of a predictive cue prior to the signal on each trial apparently induces a strong bias to use a particular stimulus modality in order to select a temporal criterion and response rule. This attentional bias toward one modality is apparently independent of the modality of the stimulus being timed and is strongly influenced by stimulus probabilities or prior warning cues. These techniques may be useful to control trial-by-trial sequential effects that influence a subject's perceptual and response biases when signals from more than one modality are used in duration discrimination tasks. Cross-procedural generality of the effects of attentional bias was observed. An asymmetrical modality effect on the latency to begin timing was observed with both the temporal bisection and the peak procedure. The latency to begin timing light signals, but not the latency to begin timing sound signals, was increased when the signal modality was unexpected. This asymmetrical effect was explained with the assumption that sound signals close the mode switch automatically, but that light signals close the mode switch only if attention is directed to the light. The time required to switch attention is reflected in a reduction of the number of pulses from the pacemaker that enter the accumulator. One positive aspect of this work is the demonstration that procedures similar to those used to study human cognition can be used with animal subjects with similar results. Perhaps these similarities will stimulate animal research on the physiological basis of various cognitive capacities. Animal subjects would be preferred for such physiological experimentation if it were established that they possessed some of the cognitive processes described by investigators of human information processing. One of the negative aspects of this work is that only one combination of modalities was used and variables such as stimulus intensity

  17. Mitochondrial DNA as a non-invasive biomarker: Accurate quantification using real time quantitative PCR without co-amplification of pseudogenes and dilution bias

    SciTech Connect

    Malik, Afshan N.; Shahni, Rojeen; Rodriguez-de-Ledesma, Ana; Laftah, Abas; Cunningham, Phil

    2011-08-19

    Highlights: {yields} Mitochondrial dysfunction is central to many diseases of oxidative stress. {yields} 95% of the mitochondrial genome is duplicated in the nuclear genome. {yields} Dilution of untreated genomic DNA leads to dilution bias. {yields} Unique primers and template pretreatment are needed to accurately measure mitochondrial DNA content. -- Abstract: Circulating mitochondrial DNA (MtDNA) is a potential non-invasive biomarker of cellular mitochondrial dysfunction, the latter known to be central to a wide range of human diseases. Changes in MtDNA are usually determined by quantification of MtDNA relative to nuclear DNA (Mt/N) using real time quantitative PCR. We propose that the methodology for measuring Mt/N needs to be improved and we have identified that current methods have at least one of the following three problems: (1) As much of the mitochondrial genome is duplicated in the nuclear genome, many commonly used MtDNA primers co-amplify homologous pseudogenes found in the nuclear genome; (2) use of regions from genes such as {beta}-actin and 18S rRNA which are repetitive and/or highly variable for qPCR of the nuclear genome leads to errors; and (3) the size difference of mitochondrial and nuclear genomes cause a 'dilution bias' when template DNA is diluted. We describe a PCR-based method using unique regions in the human mitochondrial genome not duplicated in the nuclear genome; unique single copy region in the nuclear genome and template treatment to remove dilution bias, to accurately quantify MtDNA from human samples.

  18. A Flight-Calibrated Methodology for Determination of Cassini Thruster On-Times for Reaction Wheel Biases

    NASA Technical Reports Server (NTRS)

    Sarani, Sam

    2010-01-01

    The Cassini spacecraft, the largest and most complex interplanetary spacecraft ever built, continues to undertake unique scientific observations of planet Saturn, Titan, Enceladus, and other moons of the ring world. In order to maintain a stable attitude during the course of its mission, this three-axis stabilized spacecraft uses two different control systems: the Reaction Control System (or RCS) and the Reaction Wheel Assembly (RWA) control system. In the course of its mission, Cassini performs numerous reaction wheel momentum biases (or unloads) using its reaction control thrusters. The use of the RCS thrusters often imparts undesired velocity changes (delta Vs) on the spacecraft and it is crucial for Cassini navigation and attitude control teams to be able to, quickly but accurately, predict the hydrazine usage and delta V vector in Earth Mean Equatorial (J2000) inertial coordinates for reaction wheel bias events, without actually having to spend time and resources simulating the event in a dynamic or hardware-in-the-loop simulation environments. The flight-calibrated methodology described in this paper, and the ground software developed thereof, are designed to provide the RCS thruster on-times, with acceptable accuracy and without any form of dynamic simulation, for reaction wheel biases, along with the hydrazine usage and the delta V in EME-2000 inertial frame.

  19. Adult brains don't fully overcome biases that lead to incorrect performance during cognitive development: an fMRI study in young adults completing a Piaget-like task.

    PubMed

    Leroux, Gaëlle; Spiess, Jeanne; Zago, Laure; Rossi, Sandrine; Lubin, Amélie; Turbelin, Marie-Renée; Mazoyer, Bernard; Tzourio-Mazoyer, Nathalie; Houdé, Olivier; Joliot, Marc

    2009-03-01

    A current issue in developmental science is that greater continuity in cognition between children and adults may exist than is usually appreciated in Piaget-like (stages or 'staircase') models. This phenomenon has been demonstrated at the behavioural level, but never at the brain level. Here we show with functional magnetic resonance imaging (fMRI), for the first time, that adult brains do not fully overcome the biases of childhood. More specifically, the aim of this fMRI study was to evaluate whether the perceptual bias that leads to incorrect performance during cognitive development in a Piaget-like task is still a bias in the adult brain and hence requires an executive network to overcome it. Here, we compared two numerical-judgment tasks, one being a Piaget-like task with number-length interference (called 'INT') and the other being a control task with number-length covariation ('COV'). We also used a colour-detection task to control for stimuli numerosity, spatial distribution, and frequency. Our behavioural results confirmed that INT remains a difficult task for young adults. Indeed, response times were significantly higher in INT than in COV. Moreover, we observed that only in INT did response times increase linearly as a function of the number of items. The fMRI results indicate that the brain network common to INT and COV shows a large rightward functional asymmetry, emphasizing the visuospatial nature of these two tasks. When INT was compared with COV, activations were found within a right frontal network, including the pre-supplementary motor area, the anterior cingulate cortex, and the middle frontal gyrus, which probably reflect detection of the number/length conflict and inhibition of the 'length-equals-number' response strategy. Finally, activations related to visuospatial and quantitative processing, enhanced or specifically recruited in the Piaget-like task, were found in bilateral posterior areas.

  20. Effect of dc bias and hydrostatic pressure on the ferroelectric-antiferroelectric phase transformation in a tin modified lead zirconate titanate ceramic.

    SciTech Connect

    Grubbs, Robert K.; DiAntonio, Christopher Brian; Yang, Pin; Roesler, Alexander William; Montgomery, Stephen Tedford; Moore, Roger Howard

    2010-06-01

    Phase transformation between the ferroelectric (FE) and the antiferroelectric (AFE) phases in tin modified lead zirconate titanate (PSZT) ceramics can be influenced by pressure and electric field. Increasing the pressure has the tendency to favor the AFE phase while electric field favors the FE phase. In this study, these phase transformations are studied as functions of external pressure, temperature, and dc bias. The shifting of transformation temperature and the relative phase stability between FE and AFE with respect to these external parameters will be presented. Results will be compared to a pressure-induced depoling behavior (or FE-to-AFE phase transformation) for the PSZT ceramic. Fundamental issues relates to the relative phase stability will be discussed from the perspective of lattice dynamics theory.

  1. Time differences in the formation of meteorites as determined from the ratio of lead-207 to lead-206

    USGS Publications Warehouse

    Tatsumoto, M.; Knight, R.J.; Allegre, C.J.

    1973-01-01

    Measurements of the lead isotopic composition and the uranium, thorium, and lead concentrations in meteorites were made in order to obtain more precise radiometric ages of these members of the solar system. The newly determined value of the lead isotopic composition of Canyon Diablo troilite is as follows: 206Pb/204Pb = 9.307, 207Pb/204Pb = 10.294, and 208Pb/204Pb = 29.476. The leads of Angra dos Reis, Sioux County, and Nuevo Laredo achondrites are very radiogenic, the 206Pb/204Pb values are about 200, and the uranium-thorium-lead systems are nearly concordant. The ages of the meteorites as calculated from a single-stage 207Pb/206Pb isochron based on the newly determined primordial lead value and the newly reported 235U and 238U decay constants, are 4.528 ?? 10 9 years for Sioux County and Nuevo Laredo and 4.555 ?? 10 9 years for Angra dos Reis. When calculated with the uranium decay constants used by Patterson, these ages are 4.593 ?? 109 years and 4.620 ?? 109 years, respectively, and are therefore 40 to 70 ?? 106 years older than the 4.55 ?? 109 years age Patterson reported. The age difference of 27 ?? 106 years between Angra dos Reis and the other two meteorites is compatible with the difference between the initial 87Sr/86Sr ratio of Angra dos Reis and that of seven basaltic achondrites observed by Papanastassiou and Wasserburg. The time difference is also comparable to that determined by 129I-129Xe chronology. The ages of ordinary chondrites (H5 and L6) range from 4.52 to 4.57 ?? 109 years, and, here too, time differences in the formation of the parent bodies or later metamorphic events are indicated. Carbonaceous chondrites (C2 and C3) appear to contain younger lead components.

  2. Cognitive Bias in Systems Verification

    NASA Technical Reports Server (NTRS)

    Larson, Steve

    2012-01-01

    Working definition of cognitive bias: Patterns by which information is sought and interpreted that can lead to systematic errors in decisions. Cognitive bias is used in diverse fields: Economics, Politics, Intelligence, Marketing, to name a few. Attempts to ground cognitive science in physical characteristics of the cognitive apparatus exceed our knowledge. Studies based on correlations; strict cause and effect is difficult to pinpoint. Effects cited in the paper and discussed here have been replicated many times over, and appear sound. Many biases have been described, but it is still unclear whether they are all distinct. There may only be a handful of fundamental biases, which manifest in various ways. Bias can effect system verification in many ways . Overconfidence -> Questionable decisions to deploy. Availability -> Inability to conceive critical tests. Representativeness -> Overinterpretation of results. Positive Test Strategies -> Confirmation bias. Debiasing at individual level very difficult. The potential effect of bias on the verification process can be managed, but not eliminated. Worth considering at key points in the process.

  3. A Flight-Calibrated Methodology for Determination of Cassini Thruster On-Times for Reaction Wheel Biases

    NASA Technical Reports Server (NTRS)

    Sarani, Siamak

    2010-01-01

    This paper describes a methodology for accurate and flight-calibrated determination of the on-times of the Cassini spacecraft Reaction Control System (RCS) thrusters, without any form of dynamic simulation, for the reaction wheel biases. The hydrazine usage and the delta V vector in body frame are also computed from the respective thruster on-times. The Cassini spacecraft, the largest and most complex interplanetary spacecraft ever built, continues to undertake ambitious and unique scientific observations of planet Saturn, Titan, Enceladus, and other moons of Saturn. In order to maintain a stable attitude during the course of its mission, this three-axis stabilized spacecraft uses two different control systems: the RCS and the reaction wheel assembly control system. The RCS is used to execute a commanded spacecraft slew, to maintain three-axis attitude control, control spacecraft's attitude while performing science observations with coarse pointing requirements, e.g. during targeted low-altitude Titan and Enceladus flybys, bias the momentum of reaction wheels, and to perform RCS-based orbit trim maneuvers. The use of RCS often imparts undesired delta V on the spacecraft. The Cassini navigation team requires accurate predictions of the delta V in spacecraft coordinates and inertial frame resulting from slews using RCS thrusters and more importantly from reaction wheel bias events. It is crucial for the Cassini spacecraft attitude control and navigation teams to be able to, quickly but accurately, predict the hydrazine usage and delta V for various reaction wheel bias events without actually having to spend time and resources simulating the event in flight software-based dynamic simulation or hardware-in-the-loop simulation environments. The methodology described in this paper, and the ground software developed thereof, are designed to provide just that. This methodology assumes a priori knowledge of thrust magnitudes and thruster pulse rise and tail-off time

  4. Mitochondrial DNA as a non-invasive biomarker: accurate quantification using real time quantitative PCR without co-amplification of pseudogenes and dilution bias.

    PubMed

    Malik, Afshan N; Shahni, Rojeen; Rodriguez-de-Ledesma, Ana; Laftah, Abas; Cunningham, Phil

    2011-08-19

    Circulating mitochondrial DNA (MtDNA) is a potential non-invasive biomarker of cellular mitochondrial dysfunction, the latter known to be central to a wide range of human diseases. Changes in MtDNA are usually determined by quantification of MtDNA relative to nuclear DNA (Mt/N) using real time quantitative PCR. We propose that the methodology for measuring Mt/N needs to be improved and we have identified that current methods have at least one of the following three problems: (1) As much of the mitochondrial genome is duplicated in the nuclear genome, many commonly used MtDNA primers co-amplify homologous pseudogenes found in the nuclear genome; (2) use of regions from genes such as β-actin and 18S rRNA which are repetitive and/or highly variable for qPCR of the nuclear genome leads to errors; and (3) the size difference of mitochondrial and nuclear genomes cause a "dilution bias" when template DNA is diluted. We describe a PCR-based method using unique regions in the human mitochondrial genome not duplicated in the nuclear genome; unique single copy region in the nuclear genome and template treatment to remove dilution bias, to accurately quantify MtDNA from human samples.

  5. The Influence of Referee Bias on Extra Time in Elite Soccer Matches.

    PubMed

    Lago-Peñas, Carlos; Gómez-López, Maite

    2016-04-01

    Referees have discretion over the addition of extra time at the end of the soccer game to compensate for lost time due to unusual stoppages. This study assesses if referees favor big teams by shortening close games where the big team is ahead and lengthening close games where the big team is behind. The sample comprises all 380 matches in the Spanish La Liga during the 2014-2015 season. The dependent variable was the extra time the referee decides to add to the second half. The independent variables were the score difference, opponent team's level of play, yellow cards, red cards, player substitutions, average attendance, and fouls committed. Linear regression analysis suggested that the greater the score difference between teams, the less extra time was added by the referee. However, in close games, referees tended to add more time for a higher level team when they were behind and add less time when they were ahead. Red cards and the number of fouls committed increased the extra time.

  6. It's about Time: Leading School Reform in an Era of Time Scarcity.

    ERIC Educational Resources Information Center

    Bruno, James E.

    Research about the American experience with school reform has underscored time as the major obstacle to change. This book presents a psychosocial perspective of time and the problems it presents for teachers and administrators in an era of time scarcity. Specifically, it explores the effects of five major concepts (time investment portfolios,…

  7. Odour-tracking capability of a silkmoth driving a mobile robot with turning bias and time delay.

    PubMed

    Ando, N; Emoto, S; Kanzaki, R

    2013-03-01

    The reconstruction of mechanisms behind odour-tracking behaviours of animals is expected to enable the development of biomimetic robots capable of adaptive behaviour and effectively locating odour sources. However, because the behavioural mechanisms of animals have not been extensively studied, their behavioural capabilities cannot be verified. In this study, we have employed a mobile robot driven by a genuine insect (insect-controlled robot) to evaluate the behavioural capabilities of a biological system implemented in an artificial system. We used a male silkmoth as the 'driver' and investigated its behavioural capabilities to imposed perturbations during odour tracking. When we manipulated the robot to induce the turning bias, it located the odour source by compensatory turning of the on-board moth. Shifting of the orientation paths to the odour plume boundaries and decreased orientation ability caused by covering the visual field suggested that the moth steered with bilateral olfaction and vision to overcome the bias. An evaluation of the time delays of the moth and robot movements suggested an acceptable range for sensory-motor processing when the insect system was directly applied to artificial systems. Further evaluations of the insect-controlled robot will provide a 'blueprint' for biomimetic robots and strongly promote the field of biomimetics. PMID:23385386

  8. Odour-tracking capability of a silkmoth driving a mobile robot with turning bias and time delay.

    PubMed

    Ando, N; Emoto, S; Kanzaki, R

    2013-03-01

    The reconstruction of mechanisms behind odour-tracking behaviours of animals is expected to enable the development of biomimetic robots capable of adaptive behaviour and effectively locating odour sources. However, because the behavioural mechanisms of animals have not been extensively studied, their behavioural capabilities cannot be verified. In this study, we have employed a mobile robot driven by a genuine insect (insect-controlled robot) to evaluate the behavioural capabilities of a biological system implemented in an artificial system. We used a male silkmoth as the 'driver' and investigated its behavioural capabilities to imposed perturbations during odour tracking. When we manipulated the robot to induce the turning bias, it located the odour source by compensatory turning of the on-board moth. Shifting of the orientation paths to the odour plume boundaries and decreased orientation ability caused by covering the visual field suggested that the moth steered with bilateral olfaction and vision to overcome the bias. An evaluation of the time delays of the moth and robot movements suggested an acceptable range for sensory-motor processing when the insect system was directly applied to artificial systems. Further evaluations of the insect-controlled robot will provide a 'blueprint' for biomimetic robots and strongly promote the field of biomimetics.

  9. Nonlinear relationships can lead to bias in biomass calculations and drift-foraging models when using summaries of invertebrate drift data

    USGS Publications Warehouse

    Dodrill, Michael J.; Yackulic, Charles B.

    2016-01-01

    Drift-foraging models offer a mechanistic description of how fish feed in flowing water and the application of drift-foraging bioenergetics models to answer both applied and theoretical questions in aquatic ecology is growing. These models typically include nonlinear descriptions of ecological processes and as a result may be sensitive to how model inputs are summarized because of a mathematical property of nonlinear equations known as Jensen’s inequality. In particular, we show that the way in which continuous size distributions of invertebrate prey are represented within foraging models can lead to biases within the modeling process. We begin by illustrating how different equations common to drift-foraging models are sensitive to invertebrate inputs. We then use two case studies to show how different representations of invertebrate prey can influence predictions of energy intake and lifetime growth. Greater emphasis should be placed on accurate characterizations of invertebrate drift, acknowledging that inferences from drift-foraging models may be influenced by how invertebrate prey are represented.

  10. ChIP bias as a function of cross-linking time.

    PubMed

    Baranello, Laura; Kouzine, Fedor; Sanford, Suzanne; Levens, David

    2016-05-01

    The chromatin immunoprecipitation (ChIP) assay is widely used to capture interactions between chromatin and regulatory proteins in vivo. Formaldehyde cross-linking of DNA and proteins is a critical step required to trap their interactions inside the cells before immunoprecipitation and analysis. Yet insufficient attention has been given to variables that might give rise to artifacts in this procedure, such as the duration of cross-linking. We analyzed the dependence of the ChIP signal on the duration of formaldehyde cross-linking time for two proteins: DNA topoisomerase 1 (Top1) that is functionally associated with the double helix in vivo, especially with active chromatin, and green fluorescent protein (GFP) that has no known bona fide interactions with DNA. With short time of formaldehyde fixation, only Top1 immunoprecipation efficiently recovered DNA from active promoters, whereas prolonged fixation augmented non-specific recovery of GFP dramatizing the need to optimize ChIP protocols to minimize the time of cross-linking, especially for abundant nuclear proteins. Thus, ChIP is a powerful approach to study the localization of protein on the genome when care is taken to manage potential artifacts. PMID:26685864

  11. Temporal position priming: memory traces of recent experience bias the allocation of attention in time.

    PubMed

    Yashar, Amit; Lamy, Dominique

    2013-10-01

    Explicit expectations can guide attention toward the time at which an upcoming target is likely to appear. However, in real-life situations, explicit preknowledge of upcoming events' temporal occurrence is rarely provided. We investigated whether implicit memory traces can guide attention in time, as they guide attention to recently attended features and locations (priming of pop-out and priming of location; V. Maljkovic & K. Nakayama, 1994, Priming of pop-out: I. Role of features, Memory & Cognition, Vol. 22, pp. 657-672; V. Maljkovic & K. Nakayama, 1996, Priming of pop-out: II. The role of position, Perception & Psychophysics, Vol. 58, pp. 977-991). Using a rapid serial visual presentation task, we show a temporal position priming (TPP) effect by which search performance is speeded when the target temporal position within the visual stream happens to repeat on consecutive trials. We show that such repetition priming is one of the mechanisms that underlie the much-studied sequential effect of the foreperiod. We further demonstrate that the learned association that gives rise to TPP does not require the selection or execution of a motor response and that it affects perceptual stages of visual processing. The relations between these findings and existing accounts of the sequential effect as well as with other intertrial priming effects in visual search are discussed.

  12. Quantification Bias Caused by Plasmid DNA Conformation in Quantitative Real-Time PCR Assay

    PubMed Central

    Lin, Chih-Hui; Chen, Yu-Chieh; Pan, Tzu-Ming

    2011-01-01

    Quantitative real-time PCR (qPCR) is the gold standard for the quantification of specific nucleic acid sequences. However, a serious concern has been revealed in a recent report: supercoiled plasmid standards cause significant over-estimation in qPCR quantification. In this study, we investigated the effect of plasmid DNA conformation on the quantification of DNA and the efficiency of qPCR. Our results suggest that plasmid DNA conformation has significant impact on the accuracy of absolute quantification by qPCR. DNA standard curves shifted significantly among plasmid standards with different DNA conformations. Moreover, the choice of DNA measurement method and plasmid DNA conformation may also contribute to the measurement error of DNA standard curves. Due to the multiple effects of plasmid DNA conformation on the accuracy of qPCR, efforts should be made to assure the highest consistency of plasmid standards for qPCR. Thus, we suggest that the conformation, preparation, quantification, purification, handling, and storage of standard plasmid DNA should be described and defined in the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) to assure the reproducibility and accuracy of qPCR absolute quantification. PMID:22194997

  13. Are Secondary School Students Still Hampered by the Natural Number Bias? A Reaction Time Study on Fraction Comparison Tasks

    ERIC Educational Resources Information Center

    Van Hoof, Jo; Lijnen, Tristan; Verschaffel, Lieven; Van Dooren, Wim

    2013-01-01

    Rational numbers and particularly fractions are difficult for students. It is often claimed that the "natural number bias" underlies erroneous reasoning about rational numbers. This cross-sectional study investigated the natural number bias in first and fifth year secondary school students. Relying on dual process theory assumptions that…

  14. Effective use of general circulation model outputs for forecasting monthly rainfalls to long lead times

    NASA Astrophysics Data System (ADS)

    Hawthorne, Sandra; Wang, Q. J.; Schepen, Andrew; Robertson, David

    2013-09-01

    Long lead rainfall forecasts are highly valuable for planning and management of water resources and agriculture. In this study, we establish multiple statistical calibration and bridging models that use general circulation model (GCM) outputs as predictors to produce monthly rainfall forecasts for Australia with lead times up to 8 months. The statistical calibration models make use of raw forecasts of rainfall from a coupled GCM, and the statistical bridging models make use of sea surface temperature (SST) forecasts of the GCM. The forecasts from the multiple models are merged through Bayesian model averaging to take advantage of the strengths of individual models. The skill of monthly rainfall forecasts is generally low. Compared to forecasting seasonal rainfall totals, it is more challenging to forecast monthly rainfall. However, there are regions and months for which forecasts are skillful. In particular, there are months of the year for which forecasts can be skillfully made at long lead times. This is most evident for the period of November and December. Using GCM forecasts of SST through bridging clearly improves monthly rainfall forecasts. For lead time 0, the improvement is particularly evident for February to March, July and October to December. For longer lead times, the benefit of bridging is more apparent. As lead time increases, bridging is able to maintain forecast skill much better than when only calibration is applied.

  15. Temperature trend biases

    NASA Astrophysics Data System (ADS)

    Venema, Victor; Lindau, Ralf

    2016-04-01

    In an accompanying talk we show that well-homogenized national dataset warm more than temperatures from global collections averaged over the region of common coverage. In this poster we want to present auxiliary work about possible biases in the raw observations and on how well relative statistical homogenization can remove trend biases. There are several possible causes of cooling biases, which have not been studied much. Siting could be an important factor. Urban stations tend to move away from the centre to better locations. Many stations started inside of urban areas and are nowadays more outside. Even for villages the temperature difference between the centre and edge can be 0.5°C. When a city station moves to an airport, which often happened around WWII, this takes the station (largely) out of the urban heat island. During the 20th century the Stevenson screen was established as the dominant thermometer screen. This screen protected the thermometer much better against radiation than earlier designs. Deficits of earlier measurement methods have artificially warmed the temperatures in the 19th century. Newer studies suggest we may have underestimated the size of this bias. Currently we are in a transition to Automatic Weather Stations. The net global effect of this transition is not clear at this moment. Irrigation on average decreases the 2m-temperature by about 1 degree centigrade. At the same time, irrigation has increased significantly during the last century. People preferentially live in irrigated areas and weather stations serve agriculture. Thus it is possible that there is a higher likelihood that weather stations are erected in irrigated areas than elsewhere. In this case irrigation could lead to a spurious cooling trend. In the Parallel Observations Science Team of the International Surface Temperature Initiative (ISTI-POST) we are studying influence of the introduction of Stevenson screens and Automatic Weather Stations using parallel measurements

  16. Time Course of Visual Attention in Infant Categorization of Cats versus Dogs: Evidence for a Head Bias as Revealed through Eye Tracking

    ERIC Educational Resources Information Center

    Quinn, Paul C.; Doran, Matthew M.; Reiss, Jason E.; Hoffman, James E.

    2009-01-01

    Previous looking time studies have shown that infants use the heads of cat and dog images to form category representations for these animal classes. The present research used an eye-tracking procedure to determine the time course of attention to the head and whether it reflects a preexisting bias or online learning. Six- to 7-month-olds were…

  17. Attentional bias toward low-intensity stimuli: an explanation for the intensity dissociation between reaction time and temporal order judgment?

    PubMed

    Jaśkowski, P; Verleger, R

    2000-09-01

    If two stimuli need different times to be processed, this difference should in principle be reflected both by response times (RT) and by judgments of their temporal order (TOJ). However, several dissociations have been reported between RT and TOJ, e.g., RT is more affected than TOJ when stimulus intensity decreases. One account for these dissociations is to assume differences in the allocation of attention induced by the two tasks. To test this hypothesis, different distributions of attention were induced in the present study between two stimulus positions (above and below fixation). Only bright stimuli appeared in one position and either bright or dim stimuli in the other. In the two RT experiments, participants had to respond to every stimulus appearing in one of the two positions. Reaction times to bright stimuli were faster when they appeared in the position where dim stimuli were likely to occur. This finding suggests that the allocation of attention was adapted to the asymmetrical arrangement of stimuli, not suggested by explicit instruction. In the two TOJ experiments, the temporal order of stimuli appearing in the two positions had to be judged. Although bright stimuli appearing at the bright-and-dim location were judged to be earlier, this effect was small and insignificant. Further, the intensity dissociation between RT and TOJ was insensitive to random vs blockwise presentations of intensities, therefore was not modified by attentional preferences. Thus, asymmetrical arrangement of stimuli has an impact on the allocation of attention, but only in the RT task. Therefore dissociations between TOJ and response times cannot be accounted for by an attentional bias in the TOJ task but probably by different use of temporal information in the two tasks.

  18. Optimising seasonal streamflow forecast lead time for operational decision making in Australia

    NASA Astrophysics Data System (ADS)

    Schepen, Andrew; Zhao, Tongtiegang; Wang, Q. J.; Zhou, Senlin; Feikema, Paul

    2016-10-01

    Statistical seasonal forecasts of 3-month streamflow totals are released in Australia by the Bureau of Meteorology and updated on a monthly basis. The forecasts are often released in the second week of the forecast period, due to the onerous forecast production process. The current service relies on models built using data for complete calendar months, meaning the forecast production process cannot begin until the first day of the forecast period. Somehow, the bureau needs to transition to a service that provides forecasts before the beginning of the forecast period; timelier forecast release will become critical as sub-seasonal (monthly) forecasts are developed. Increasing the forecast lead time to one month ahead is not considered a viable option for Australian catchments that typically lack any predictability associated with snowmelt. The bureau's forecasts are built around Bayesian joint probability models that have antecedent streamflow, rainfall and climate indices as predictors. In this study, we adapt the modelling approach so that forecasts have any number of days of lead time. Daily streamflow and sea surface temperatures are used to develop predictors based on 28-day sliding windows. Forecasts are produced for 23 forecast locations with 0-14- and 21-day lead time. The forecasts are assessed in terms of continuous ranked probability score (CRPS) skill score and reliability metrics. CRPS skill scores, on average, reduce monotonically with increase in days of lead time, although both positive and negative differences are observed. Considering only skilful forecast locations, CRPS skill scores at 7-day lead time are reduced on average by 4 percentage points, with differences largely contained within +5 to -15 percentage points. A flexible forecasting system that allows for any number of days of lead time could benefit Australian seasonal streamflow forecast users by allowing more time for forecasts to be disseminated, comprehended and made use of prior to

  19. Time-averaged fluxes of lead and fallout radionuclides to sediments in Florida Bay

    USGS Publications Warehouse

    Robbins, J.A.; Holmes, C.; Halley, R.; Bothner, M.; Shinn, E.; Graney, J.; Keeler, G.; TenBrink, M.; Orlandini, K.A.; Rudnick, D.

    2000-01-01

    Recent, unmixed sediments from mud banks of central Florida Bay were dated using 210Pb/226Ra, and chronologies were verified by comparing sediment lead temporal records with Pb/Ca ratios in annual layers of coral (Montastrea annularis) located on the ocean side of the Florida Keys. Dates of sediment lead peaks (1978 ?? 2) accord with prior observations of a 6 year lag between the occurrence of maximum atmospheric lead in 1972 and peak coral lead in 1978. Smaller lags of 1-2 years occur between the maximum atmospheric radionuclide fallout and peaks in sediment temporal records of 137Cs and Pu. Such lags are consequences of system time averaging (STA) in which atmospherically delivered particle-associated constituents accumulate and mix in a (sedimentary?) reservoir before transferring to permanent sediments and coral. STA model calculations, using time-dependent atmospheric inputs, produced optimized profiles in excellent accord with measured sediment 137Cs, Pu, lead, and coral lead distributions. Derived residence times of these particle tracers (16 ?? 1, 15.7 ?? 0.7, 19 ?? 3, and 16 ?? 2 years, respectively) are comparable despite differences in sampling locations, in accumulating media, and in element loading histories and geochemical properties. For a 16 year weighted mean residence time, STA generates the observed 6 year lead peak lag. Evidently, significant levels of nondegradable, particle-associated contaminants can persist in Florida Bay for many decades following elimination of external inputs. Present results, in combination with STA model analysis of previously reported radionuclide profiles, suggest that decade-scale time averaging may occur widely in recent coastal marine sedimentary environments. Copyright 2000 by the American Geophysical Union.

  20. The influence of time on lead toxicity and bioaccumulation determined by the OECD earthworm toxicity test.

    PubMed

    Davies, Nicola A; Hodson, Mark E; Black, Stuart

    2003-01-01

    Internationally agreed standard protocols for assessing chemical toxicity of contaminants in soil to worms assume that the test soil does not need to equilibrate with the chemical to be tested prior to the addition of the test organisms and that the chemical will exert any toxic effect upon the test organism within 28 days. Three experiments were carried out to investigate these assumptions. The first experiment was a standard toxicity test where lead nitrate was added to a soil in solution to give a range of concentrations. The mortality of the worms and the concentration of lead in the survivors were determined. The LC50s for 14 and 28 days were 5311 and 5395 microgPb g(-1)soil respectively. The second experiment was a timed lead accumulation study with worms cultivated in soil containing either 3000 or 5000 microgPb g(-1)soil. The concentration of lead in the worms was determined at various sampling times. Uptake at both concentrations was linear with time. Worms in the 5000 microg g(-1) soil accumulated lead at a faster rate (3.16 microg Pb g(-1)tissue day(-1)) than those in the 3000 microg g(-1) soil (2.21 microg Pb g(-1)tissue day(-1)). The third experiment was a timed experiment with worms cultivated in soil containing 7000 microgPb g(-1)soil. Soil and lead nitrate solution were mixed and stored at 20 degrees C. Worms were added at various times over a 35-day period. The time to death increased from 23 h, when worms were added directly after the lead was added to the soil, to 67 h when worms were added after the soil had equilibrated with the lead for 35 days. In artificially Pb-amended soils the worms accumulate Pb over the duration of their exposure to the Pb. Thus time limited toxicity tests may be terminated before worm body load has reached a toxic level. This could result in under-estimates of the toxicity of Pb to worms. As the equilibration time of artificially amended Pb-bearing soils increases the bioavailability of Pb decreases. Thus addition of

  1. Use of Six Sigma Methodology to Reduce Appointment Lead-Time in Obstetrics Outpatient Department.

    PubMed

    Ortiz Barrios, Miguel A; Felizzola Jiménez, Heriberto

    2016-10-01

    This paper focuses on the issue of longer appointment lead-time in the obstetrics outpatient department of a maternal-child hospital in Colombia. Because of extended appointment lead-time, women with high-risk pregnancy could develop severe complications in their health status and put their babies at risk. This problem was detected through a project selection process explained in this article and to solve it, Six Sigma methodology has been used. First, the process was defined through a SIPOC diagram to identify its input and output variables. Second, six sigma performance indicators were calculated to establish the process baseline. Then, a fishbone diagram was used to determine the possible causes of the problem. These causes were validated with the aid of correlation analysis and other statistical tools. Later, improvement strategies were designed to reduce appointment lead-time in this department. Project results evidenced that average appointment lead-time reduced from 6,89 days to 4,08 days and the deviation standard dropped from 1,57 days to 1,24 days. In this way, the hospital will serve pregnant women faster, which represents a risk reduction of perinatal and maternal mortality. PMID:27580729

  2. Use of Six Sigma Methodology to Reduce Appointment Lead-Time in Obstetrics Outpatient Department.

    PubMed

    Ortiz Barrios, Miguel A; Felizzola Jiménez, Heriberto

    2016-10-01

    This paper focuses on the issue of longer appointment lead-time in the obstetrics outpatient department of a maternal-child hospital in Colombia. Because of extended appointment lead-time, women with high-risk pregnancy could develop severe complications in their health status and put their babies at risk. This problem was detected through a project selection process explained in this article and to solve it, Six Sigma methodology has been used. First, the process was defined through a SIPOC diagram to identify its input and output variables. Second, six sigma performance indicators were calculated to establish the process baseline. Then, a fishbone diagram was used to determine the possible causes of the problem. These causes were validated with the aid of correlation analysis and other statistical tools. Later, improvement strategies were designed to reduce appointment lead-time in this department. Project results evidenced that average appointment lead-time reduced from 6,89 days to 4,08 days and the deviation standard dropped from 1,57 days to 1,24 days. In this way, the hospital will serve pregnant women faster, which represents a risk reduction of perinatal and maternal mortality.

  3. A New Model for Real-Time Regional Vertical Total Electron Content and Differential Code Bias Estimation Using IGS Real-Time Service (IGS-RTS) Products

    NASA Astrophysics Data System (ADS)

    Abdelazeem, Mohamed; Çelik, Rahmi N.; El-Rabbany, Ahmed

    2016-04-01

    The international global navigation satellite system (GNSS) real-time service (IGS-RTS) products have been used extensively for real-time precise point positioning and ionosphere modeling applications. In this study, we develop a regional model for real-time vertical total electron content (RT-VTEC) and differential code bias (RT-DCB) estimation over Europe using the IGS-RTS satellite orbit and clock products. The developed model has a spatial and temporal resolution of 1°×1° and 15 minutes, respectively. GPS observations from a regional network consisting of 60 IGS and EUREF reference stations are processed in the zero-difference mode using the Bernese-5.2 software package in order to extract the geometry-free linear combination of the smoothed code observations. The spherical harmonic expansion function is used to model the VTEC, the receiver and the satellite DCBs. To validate the proposed model, the RT-VTEC values are computed and compared with the final IGS-global ionospheric map (IGS-GIM) counterparts in three successive days under high solar activity including one of an extreme geomagnetic activity. The real-time satellite DCBs are also estimated and compared with the IGS-GIM counterparts. Moreover, the real-time receiver DCB for six IGS stations are obtained and compared with the IGS-GIM counterparts. The examined stations are located in different latitudes with different receiver types. The findings reveal that the estimated RT-VTEC values show agreement with the IGS-GIM counterparts with root mean-square-errors (RMSEs) values less than 2 TEC units. In addition, RMSEs of both the satellites and receivers DCBs are less than 0.85 ns and 0.65 ns, respectively in comparison with the IGS-GIM.

  4. Understanding selection bias, time-lags and measurement bias in secondary data sources: Putting the Encyclopedia of Associations database in broader context.

    PubMed

    Bevan, Shaun; Baumgartner, Frank R; Johnson, Erik W; McCarthy, John D

    2013-11-01

    Secondary data gathered for purposes other than research play an important role in the social sciences. A recent data release has made an important source of publicly available data on associational interests, the Encyclopedia of Associations (EA), readily accessible to scholars (www.policyagendas.org). In this paper we introduce these new data and systematically investigate issues of lag between events and subsequent reporting in the EA, as these have important but under-appreciated effects on time-series statistical models. We further analyze the accuracy and coverage of the database in numerous ways. Our study serves as a guide to potential users of this database, but we also reflect upon a number of issues that should concern all researchers who use secondary data such as newspaper records, IRS reports and FBI Uniform Crime Reports. PMID:24090865

  5. Understanding selection bias, time-lags and measurement bias in secondary data sources: Putting the Encyclopedia of Associations database in broader context.

    PubMed

    Bevan, Shaun; Baumgartner, Frank R; Johnson, Erik W; McCarthy, John D

    2013-11-01

    Secondary data gathered for purposes other than research play an important role in the social sciences. A recent data release has made an important source of publicly available data on associational interests, the Encyclopedia of Associations (EA), readily accessible to scholars (www.policyagendas.org). In this paper we introduce these new data and systematically investigate issues of lag between events and subsequent reporting in the EA, as these have important but under-appreciated effects on time-series statistical models. We further analyze the accuracy and coverage of the database in numerous ways. Our study serves as a guide to potential users of this database, but we also reflect upon a number of issues that should concern all researchers who use secondary data such as newspaper records, IRS reports and FBI Uniform Crime Reports.

  6. Experimentally Increased Codon Bias in the Drosophila Adh Gene Leads to an Increase in Larval, But Not Adult, Alcohol Dehydrogenase Activity

    PubMed Central

    Hense, Winfried; Anderson, Nathan; Hutter, Stephan; Stephan, Wolfgang; Parsch, John; Carlini, David B.

    2010-01-01

    Although most amino acids can be encoded by more than one codon, the synonymous codons are not used with equal frequency. This phenomenon is known as codon bias and appears to be a universal feature of genomes. The translational selection hypothesis posits that the use of optimal codons, which match the most abundant species of isoaccepting tRNAs, results in increased translational efficiency and accuracy. Previous work demonstrated that the experimental reduction of codon bias in the Drosophila alcohol dehydrogenase (Adh) gene led to a significant decrease in ADH protein expression. In this study we performed the converse experiment: we replaced seven suboptimal leucine codons that occur naturally in the Drosophila melanogaster Adh gene with the optimal codon. We then compared the in vivo ADH activities imparted by the wild-type and mutant alleles. The introduction of optimal leucine codons led to an increase in ADH activity in third-instar larvae. In adult flies, however, the introduction of optimal codons led to a decrease in ADH activity. There is no evidence that other selectively constrained features of the Adh gene, or its rate of transcription, were altered by the synonymous replacements. These results are consistent with translational selection for codon bias being stronger in the larval stage and suggest that there may be a selective conflict over optimal codon usage between different developmental stages. PMID:19966063

  7. Experimentally increased codon bias in the Drosophila Adh gene leads to an increase in larval, but not adult, alcohol dehydrogenase activity.

    PubMed

    Hense, Winfried; Anderson, Nathan; Hutter, Stephan; Stephan, Wolfgang; Parsch, John; Carlini, David B

    2010-02-01

    Although most amino acids can be encoded by more than one codon, the synonymous codons are not used with equal frequency. This phenomenon is known as codon bias and appears to be a universal feature of genomes. The translational selection hypothesis posits that the use of optimal codons, which match the most abundant species of isoaccepting tRNAs, results in increased translational efficiency and accuracy. Previous work demonstrated that the experimental reduction of codon bias in the Drosophila alcohol dehydrogenase (Adh) gene led to a significant decrease in ADH protein expression. In this study we performed the converse experiment: we replaced seven suboptimal leucine codons that occur naturally in the Drosophila melanogaster Adh gene with the optimal codon. We then compared the in vivo ADH activities imparted by the wild-type and mutant alleles. The introduction of optimal leucine codons led to an increase in ADH activity in third-instar larvae. In adult flies, however, the introduction of optimal codons led to a decrease in ADH activity. There is no evidence that other selectively constrained features of the Adh gene, or its rate of transcription, were altered by the synonymous replacements. These results are consistent with translational selection for codon bias being stronger in the larval stage and suggest that there may be a selective conflict over optimal codon usage between different developmental stages.

  8. Electrophysiological evidence of the time course of attentional bias in non-patients reporting symptoms of depression with and without co-occurring anxiety

    PubMed Central

    Sass, Sarah M.; Heller, Wendy; Fisher, Joscelyn E.; Silton, Rebecca L.; Stewart, Jennifer L.; Crocker, Laura D.; Edgar, J. Christopher; Mimnaugh, Katherine J.; Miller, Gregory A.

    2014-01-01

    Anxiety is characterized by attentional biases to threat, but findings are inconsistent for depression. To address this inconsistency, the present study systematically assessed the role of co-occurring anxiety in attentional bias in depression. In addition, the role of emotional valence, arousal, and gender was explored. Ninety-two non-patients completed the Penn State Worry Questionnaire (Meyer et al., 1990; Molina and Borkovec, 1994) and portions of the Mood and Anxiety Symptom Questionnaire (Watson et al., 1995a,1995b). Individuals reporting high levels of depression and low levels of anxiety (depression only), high levels of depression and anxiety (combined), or low levels of both (control) completed an emotion-word Stroop task during event-related brain potential recording. Pleasant and unpleasant words were matched on emotional arousal level. An attentional bias was not evident in the depression-only group. Women in the combined group had larger N200 amplitude for pleasant than unpleasant stimuli, and the combined group as a whole had larger right-lateralized P300 amplitude for pleasant than unpleasant stimuli, consistent with an early and later attentional bias that is specific to unpleasant valence in the combined group. Men in the control group had larger N200 amplitude for pleasant than unpleasant stimuli, consistent with an early attentional bias that is specific to pleasant valence. The present study indicates that the nature and time course of attention prompted by emotional valence and not arousal differentiates depression with and without anxiety, with some evidence of gender moderating early effects. Overall, results suggest that co-occurring anxiety is more important than previously acknowledged in demonstrating evidence of attentional biases in depression. PMID:24782804

  9. A seller-buyer supply chain model with exponential distribution lead time

    NASA Astrophysics Data System (ADS)

    Bahri, Mehrab; Tarokh, Mohammad Jafar

    2012-08-01

    Supply chain is an accepted way of remaining in the competition in today's rapidly changing market. This paper presents a coordinated seller-buyer supply chain model in two stages, which is called Joint Economic Lot Sizing (JELS) in literature. The delivery activities in the supply chain consist of a single raw material. We assume that the delivery lead time is stochastic and follows an exponential distribution. Also, the shortage during the lead time is permitted and completely back-ordered for the buyer. With these assumptions, the annual cost function of JELS is minimized. At the end, a numerical example is presented to show that the integrated approach considerably improves the costs in comparison with the independent decisions by seller and buyer.

  10. Verification of short lead time forecast models: applied to Kp and Dst forecasting

    NASA Astrophysics Data System (ADS)

    Wintoft, Peter; Wik, Magnus

    2016-04-01

    In the ongoing EU/H2020 project PROGRESS models that predicts Kp, Dst, and AE from L1 solar wind data will be used as inputs to radiation belt models. The possible lead times from L1 measurements are shorter (10s of minutes to hours) than the typical duration of the physical phenomena that should be forecast. Under these circumstances several metrics fail to single out trivial cases, such as persistence. In this work we explore metrics and approaches for short lead time forecasts. We apply these to current Kp and Dst forecast models. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637302.

  11. Enhancing Nursing Staffing Forecasting With Safety Stock Over Lead Time Modeling.

    PubMed

    McNair, Douglas S

    2015-01-01

    In balancing competing priorities, it is essential that nursing staffing provide enough nurses to safely and effectively care for the patients. Mathematical models to predict optimal "safety stocks" have been routine in supply chain management for many years but have up to now not been applied in nursing workforce management. There are various aspects that exhibit similarities between the 2 disciplines, such as an evolving demand forecast according to acuity and the fact that provisioning "stock" to meet demand in a future period has nonzero variable lead time. Under assumptions about the forecasts (eg, the demand process is well fit as an autoregressive process) and about the labor supply process (≥1 shifts' lead time), we show that safety stock over lead time for such systems is effectively equivalent to the corresponding well-studied problem for systems with stationary demand bounds and base stock policies. Hence, we can apply existing models from supply chain analytics to find the optimal safety levels of nurse staffing. We use a case study with real data to demonstrate that there are significant benefits from the inclusion of the forecast process when determining the optimal safety stocks. PMID:26340239

  12. Enhancing Nursing Staffing Forecasting With Safety Stock Over Lead Time Modeling.

    PubMed

    McNair, Douglas S

    2015-01-01

    In balancing competing priorities, it is essential that nursing staffing provide enough nurses to safely and effectively care for the patients. Mathematical models to predict optimal "safety stocks" have been routine in supply chain management for many years but have up to now not been applied in nursing workforce management. There are various aspects that exhibit similarities between the 2 disciplines, such as an evolving demand forecast according to acuity and the fact that provisioning "stock" to meet demand in a future period has nonzero variable lead time. Under assumptions about the forecasts (eg, the demand process is well fit as an autoregressive process) and about the labor supply process (≥1 shifts' lead time), we show that safety stock over lead time for such systems is effectively equivalent to the corresponding well-studied problem for systems with stationary demand bounds and base stock policies. Hence, we can apply existing models from supply chain analytics to find the optimal safety levels of nurse staffing. We use a case study with real data to demonstrate that there are significant benefits from the inclusion of the forecast process when determining the optimal safety stocks.

  13. Analog filtering methods improve leading edge timing performance of multiplexed SiPMs

    NASA Astrophysics Data System (ADS)

    Bieniosek, M. F.; Cates, J. W.; Grant, A. M.; Levin, C. S.

    2016-08-01

    Multiplexing many SiPMs to a single readout channel is an attractive option to reduce the readout complexity of high performance time of flight (TOF) PET systems. However, the additional dark counts and shaping from each SiPM cause significant baseline fluctuations in the output waveform, degrading timing measurements using a leading edge threshold. This work proposes the use of a simple analog filtering network to reduce the baseline fluctuations in highly multiplexed SiPM readouts. With 16 SiPMs multiplexed, the FWHM coincident timing resolution for single 3~\\text{mm}× 3~\\text{mm}× 20 mm LYSO crystals was improved from 401  ±  4 ps without filtering to 248  ±  5 ps with filtering. With 4 SiPMs multiplexed, using an array of 3~\\text{mm}× 3~\\text{mm}× 20 mm LFS crystals the mean time resolution was improved from 436  ±  6 ps to 249  ±  2 ps. Position information was acquired with a novel binary positioning network. All experiments were performed at room temperature with no active temperature regulation. These results show a promising technique for the construction of high performance multiplexed TOF PET readout systems using analog leading edge timing pickoff.

  14. Analog filtering methods improve leading edge timing performance of multiplexed SiPMs.

    PubMed

    Bieniosek, M F; Cates, J W; Grant, A M; Levin, C S

    2016-08-21

    Multiplexing many SiPMs to a single readout channel is an attractive option to reduce the readout complexity of high performance time of flight (TOF) PET systems. However, the additional dark counts and shaping from each SiPM cause significant baseline fluctuations in the output waveform, degrading timing measurements using a leading edge threshold. This work proposes the use of a simple analog filtering network to reduce the baseline fluctuations in highly multiplexed SiPM readouts. With 16 SiPMs multiplexed, the FWHM coincident timing resolution for single [Formula: see text] mm LYSO crystals was improved from 401  ±  4 ps without filtering to 248  ±  5 ps with filtering. With 4 SiPMs multiplexed, using an array of [Formula: see text] mm LFS crystals the mean time resolution was improved from 436  ±  6 ps to 249  ±  2 ps. Position information was acquired with a novel binary positioning network. All experiments were performed at room temperature with no active temperature regulation. These results show a promising technique for the construction of high performance multiplexed TOF PET readout systems using analog leading edge timing pickoff.

  15. Reversing Stimulus Timing in Visual Conditioning Leads to Memories with Opposite Valence in Drosophila

    PubMed Central

    Vogt, Katrin; Yarali, Ayse; Tanimoto, Hiromu

    2015-01-01

    Animals need to associate different environmental stimuli with each other regardless of whether they temporally overlap or not. Drosophila melanogaster displays olfactory trace conditioning, where an odor is followed by electric shock reinforcement after a temporal gap, leading to conditioned odor avoidance. Reversing the stimulus timing in olfactory conditioning results in the reversal of memory valence such that an odor that follows shock is later on approached (i.e. relief conditioning). Here, we explored the effects of stimulus timing on memory in another sensory modality, using a visual conditioning paradigm. We found that flies form visual memories of opposite valence depending on stimulus timing and can associate a visual stimulus with reinforcement despite being presented with a temporal gap. These results suggest that associative memories with non-overlapping stimuli and the effect of stimulus timing on memory valence are shared across sensory modalities. PMID:26430885

  16. Size speed bias or size arrival effect-How judgments of vehicles' approach speed and time to arrival are influenced by the vehicles' size.

    PubMed

    Petzoldt, Tibor

    2016-10-01

    Crashes at railway level crossings are a key problem for railway operations. It has been suggested that a potential explanation for such crashes might lie in a so-called size speed bias, which describes the phenomenon that observers underestimate the speed of larger objects, such as aircraft or trains. While there is some evidence that this size speed bias indeed exists, it is somewhat at odds with another well researched phenomenon, the size arrival effect. When asked to judge the time it takes an approaching object to arrive at a predefined position (time to arrival, TTA), observers tend to provide lower estimates for larger objects. In that case, road users' crossing decisions when confronted with larger vehicles should be rather conservative, which has been confirmed in multiple studies on gap acceptance. The aim of the experiment reported in this paper was to clarify the relationship between size speed bias and size arrival effect. Employing a relative judgment task, both speed and TTA estimates were assessed for virtual depictions of a train and a truck, using a car as a reference to compare against. The results confirmed the size speed bias for the speed judgments, with both train and truck being perceived as travelling slower than the car. A comparable bias was also present in the TTA estimates for the truck. In contrast, no size arrival effect could be found for the train or the truck, neither in the speed nor the TTA judgments. This finding is inconsistent with the fact that crossing behaviour when confronted with larger vehicles appears to be consistently more conservative. This discrepancy might be interpreted as an indication that factors other than perceived speed or TTA play an important role for the differences in gap acceptance between different types of vehicles.

  17. Size speed bias or size arrival effect-How judgments of vehicles' approach speed and time to arrival are influenced by the vehicles' size.

    PubMed

    Petzoldt, Tibor

    2016-10-01

    Crashes at railway level crossings are a key problem for railway operations. It has been suggested that a potential explanation for such crashes might lie in a so-called size speed bias, which describes the phenomenon that observers underestimate the speed of larger objects, such as aircraft or trains. While there is some evidence that this size speed bias indeed exists, it is somewhat at odds with another well researched phenomenon, the size arrival effect. When asked to judge the time it takes an approaching object to arrive at a predefined position (time to arrival, TTA), observers tend to provide lower estimates for larger objects. In that case, road users' crossing decisions when confronted with larger vehicles should be rather conservative, which has been confirmed in multiple studies on gap acceptance. The aim of the experiment reported in this paper was to clarify the relationship between size speed bias and size arrival effect. Employing a relative judgment task, both speed and TTA estimates were assessed for virtual depictions of a train and a truck, using a car as a reference to compare against. The results confirmed the size speed bias for the speed judgments, with both train and truck being perceived as travelling slower than the car. A comparable bias was also present in the TTA estimates for the truck. In contrast, no size arrival effect could be found for the train or the truck, neither in the speed nor the TTA judgments. This finding is inconsistent with the fact that crossing behaviour when confronted with larger vehicles appears to be consistently more conservative. This discrepancy might be interpreted as an indication that factors other than perceived speed or TTA play an important role for the differences in gap acceptance between different types of vehicles. PMID:27428866

  18. Directional selection for flowering time leads to adaptive evolution in Raphanus raphanistrum (Wild radish).

    PubMed

    Ashworth, Michael B; Walsh, Michael J; Flower, Ken C; Vila-Aiub, Martin M; Powles, Stephen B

    2016-04-01

    Herbicides have been the primary tool for controlling large populations of yield depleting weeds from agro-ecosystems, resulting in the evolution of widespread herbicide resistance. In response, nonherbicidal techniques have been developed which intercept weed seeds at harvest before they enter the soil seed bank. However, the efficiency of these techniques allows an intense selection for any trait that enables weeds to evade collection, with early-flowering ecotypes considered likely to result in early seed shedding. Using a field-collected wild radish population, five recurrent generations were selected for early maturity and three generations for late maturity. Phenology associated with flowering time and growth traits were measured. Our results demonstrate the adaptive capacity of wild radish to halve its time to flowering following five generations of early-flowering selection. Early-maturing phenotypes had reduced height and biomass at maturity, leading to less competitive, more prostrate growth forms. Following three generations of late-flowering selection, wild radish doubled its time to flowering time leading to increased biomass and flowering height at maturity. This study demonstrates the potential for the rapid evolution in growth traits in response to highly effective seed collection techniques that imposed a selection on weed populations within agro-ecosystems at harvest. PMID:27099626

  19. Directional selection for flowering time leads to adaptive evolution in Raphanus raphanistrum (Wild radish).

    PubMed

    Ashworth, Michael B; Walsh, Michael J; Flower, Ken C; Vila-Aiub, Martin M; Powles, Stephen B

    2016-04-01

    Herbicides have been the primary tool for controlling large populations of yield depleting weeds from agro-ecosystems, resulting in the evolution of widespread herbicide resistance. In response, nonherbicidal techniques have been developed which intercept weed seeds at harvest before they enter the soil seed bank. However, the efficiency of these techniques allows an intense selection for any trait that enables weeds to evade collection, with early-flowering ecotypes considered likely to result in early seed shedding. Using a field-collected wild radish population, five recurrent generations were selected for early maturity and three generations for late maturity. Phenology associated with flowering time and growth traits were measured. Our results demonstrate the adaptive capacity of wild radish to halve its time to flowering following five generations of early-flowering selection. Early-maturing phenotypes had reduced height and biomass at maturity, leading to less competitive, more prostrate growth forms. Following three generations of late-flowering selection, wild radish doubled its time to flowering time leading to increased biomass and flowering height at maturity. This study demonstrates the potential for the rapid evolution in growth traits in response to highly effective seed collection techniques that imposed a selection on weed populations within agro-ecosystems at harvest.

  20. Real-time Assay of Toxic Lead in In Vivo Living Plant Tissue.

    PubMed

    Ly, Suwyoung; Kim, Nack Joo; Youn, Minsang; Kim, Yongwook; Sung, Yeolmin; Kim, Dohoon; Chung, Tackhyun

    2013-12-31

    A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL(-1)-20 mgL(-1) with preconcentration time of 100, 200, and 400 sec at the concentration of mgL(-1), μgL(-1), and ngL(-1), respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 μgL(-1) under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL(-1) (2.6 × 10(-8) M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses. PMID:24578800

  1. Real-time Assay of Toxic Lead in In Vivo Living Plant Tissue.

    PubMed

    Ly, Suwyoung; Kim, Nack Joo; Youn, Minsang; Kim, Yongwook; Sung, Yeolmin; Kim, Dohoon; Chung, Tackhyun

    2013-12-31

    A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL(-1)-20 mgL(-1) with preconcentration time of 100, 200, and 400 sec at the concentration of mgL(-1), μgL(-1), and ngL(-1), respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 μgL(-1) under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL(-1) (2.6 × 10(-8) M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses.

  2. Real-time Assay of Toxic Lead in In Vivo Living Plant Tissue

    PubMed Central

    Kim, Nack Joo; Youn, Minsang; Kim, Yongwook; Sung, Yeolmin; Kim, Dohoon

    2013-01-01

    A method of detecting lead was developed using square wave anodic stripping voltammetry (SWASV) with DNA-carbon nanotube paste electrode (CNTPE). The results indicated a sensitive oxidation peak current of lead on the DNA-CNTPE. The curves were obtained within a concentration range of 50 ngL−1-20 mgL−1 with preconcentration time of 100, 200, and 400 sec at the concentration of mgL−1, μgL−1, and ngL−1, respectively. The observed relative standard deviation was 0.101% (n = 12) in the lead concentration of 30.0 μgL−1 under optimum conditions. The low detection limit (S/N) was pegged at 8 ngL−1 (2.6 × 10−8 M). Results showed that the developed method can be used in real-time assay in vivo without requiring any pretreatment and pharmaceutical samples, and food samples, as well as other materials requiring water source contamination analyses. PMID:24578800

  3. Ultrafast strong-field photoelectron emission from biased metal surfaces: exact solution to time-dependent Schrödinger Equation

    PubMed Central

    Zhang, Peng; Lau, Y. Y.

    2016-01-01

    Laser-driven ultrafast electron emission offers the possibility of manipulation and control of coherent electron motion in ultrashort spatiotemporal scales. Here, an analytical solution is constructed for the highly nonlinear electron emission from a dc biased metal surface illuminated by a single frequency laser, by solving the time-dependent Schrödinger equation exactly. The solution is valid for arbitrary combinations of dc electric field, laser electric field, laser frequency, metal work function and Fermi level. Various emission mechanisms, such as multiphoton absorption or emission, optical or dc field emission, are all included in this single formulation. The transition between different emission processes is analyzed in detail. The time-dependent emission current reveals that intense current modulation may be possible even with a low intensity laser, by merely increasing the applied dc bias. The results provide insights into the electron pulse generation and manipulation for many novel applications based on ultrafast laser-induced electron emission. PMID:26818710

  4. Growth differences and competition between Listeria monocytogenes strains determine their predominance on ham slices and lead to bias during selective enrichment with the ISO protocol.

    PubMed

    Zilelidou, Evangelia; Manthou, Evanthia; Skandamis, Panagiotis

    2016-10-17

    Listeria monocytogenes strains are widespread in the environment where they live well mixed, often resulting in multiple strains contaminating a single food sample. The occurrence of different strains in the same food might trigger strain competition, contributing to uneven growth of strains in food and to bias during selective procedures. We tested the growth of seven L. monocytogenes strains (C5, 6179, ScottA, PL24, PL25, PL26, PL27) on ham slices and on nutrient-rich agar at 10°C, singly and in combinations. Strains were made resistant to different antibiotics for their selective enumeration. In addition, growth of single strains (axenic culture) and competition between strains in xenic cultures of two strains was evaluated in enrichment broth and on selective agar. According to ISO 11290-1:1996/Amd 1:2004 standard protocol for detection of L. monocytogenes, two enrichment steps both followed by streaking on ALOA were performed. Strain cultures were directly added in the enrichment broth or used to inoculate minced beef and sliced hams which were then mixed with enrichment broth. 180-360 colonies were used to determine the relative percentage of each strain recovered on plates per enrichment step. The data showed a significant impact of co-cultivation on the growth of six out of seven strains on ham and a bias towards certain strains during selective enrichment. Competition was manifested by: (i) cessation of growth for the outcompeted strain when the dominant strain reached stationary phase, (ii) reduction of growth rates or (iii) total suppression of growth (both on ham and in enrichment broth or ALOA). Outgrowth of strains by their competitors on ALOA resulted in limited to no recovery, with the outcompeting strain accounting for up to 100% of the total recovered colonies. The observed bias was associated with the enrichment conditions (i.e. food type added to the enrichment broth) and the strain-combination. The outcome of growth competition on food or

  5. Time-dependent propensity score and collider-stratification bias: an example of beta2-agonist use and the risk of coronary heart disease.

    PubMed

    Sanni Ali, M; Groenwold, Rolf H H; Pestman, Wiebe R; Belitser, Svetlana V; Hoes, Arno W; de Boer, A; Klungel, Olaf H

    2013-04-01

    Stratification and conditioning on time-varying cofounders which are also intermediates can induce collider-stratification bias and adjust-away the (indirect) effect of exposure. Similar bias could be expected when one conditions on time-dependent PS. We explored collider-stratification and confounding bias due to conditioning or stratifying on time-dependent PS using a clinical example on the effect of inhaled short- and long-acting beta2-agonist use (SABA and LABA, respectively) on coronary heart disease (CHD). In an electronic general practice database we selected a cohort of patients with an indication for SABA and/or LABA use and ascertained potential confounders and SABA/LABA use per three month intervals. Hazard ratios (HR) were estimated using PS stratification as well as covariate adjustment and compared with those of Marginal Structural Models (MSMs) in both SABA and LABA use separately. In MSMs, censoring was accounted for by including inverse probability of censoring weights.The crude HR of CHD was 0.90 [95 % CI: 0.63, 1.28] and 1.55 [95 % CI: 1.06, 2.62] in SABA and LABA users respectively. When PS stratification, covariate adjustment using PS, and MSMs were used, the HRs were 1.09 [95 % CI: 0.74, 1.61], 1.07 [95 % CI: 0.72, 1.60], and 0.86 [95 % CI: 0.55, 1.34] for SABA, and 1.09 [95 % CI: 0.74, 1.62], 1.13 [95 % CI: 0.76, 1.67], 0.77 [95 % CI: 0.45, 1.33] for LABA, respectively. Results were similar for different PS methods, but higher than those of MSMs. When treatment and confounders vary during follow-up, conditioning or stratification on time-dependent PS could induce substantial collider-stratification or confounding bias; hence, other methods such as MSMs are recommended.

  6. A new order splitting model with stochastic lead times for deterioration items

    NASA Astrophysics Data System (ADS)

    Sazvar, Zeinab; Akbari Jokar, Mohammad Reza; Baboli, Armand

    2014-09-01

    In unreliable supply environments, the strategy of pooling lead time risks by splitting replenishment orders among multiple suppliers simultaneously is an attractive sourcing policy that has captured the attention of academic researchers and corporate managers alike. While various assumptions are considered in the models developed, researchers tend to overlook an important inventory category in order splitting models: deteriorating items. In this paper, we study an order splitting policy for a retailer that sells a deteriorating product. The inventory system is modelled as a continuous review system (s, Q) under stochastic lead time. Demand rate per unit time is assumed to be constant over an infinite planning horizon and shortages are backordered completely. We develop two inventory models. In the first model, it is assumed that all the requirements are supplied by only one source, whereas in the second, two suppliers are available. We use sensitivity analysis to determine the situations in which each sourcing policy is the most economic. We then study a real case from the European pharmaceutical industry to demonstrate the applicability and effectiveness of the proposed models. Finally, more promising directions are suggested for future research.

  7. Real-time estimation of lead-acid battery parameters: A dynamic data-driven approach

    NASA Astrophysics Data System (ADS)

    Li, Yue; Shen, Zheng; Ray, Asok; Rahn, Christopher D.

    2014-12-01

    This short paper presents a recently reported dynamic data-driven method, Symbolic Dynamic Filtering (SDF), for real-time estimation of the state-of-health (SOH) and state-of-charge (SOC) in lead-acid batteries, as an alternative to model-based analysis techniques. In particular, SOC estimation relies on a k-NN regression algorithm while SOH estimation is obtained from the divergence between extracted features. The results show that the proposed data-driven method successfully distinguishes battery voltage responses under different SOC and SOH situations.

  8. Short-Term Memory for Space and Time Flexibly Recruit Complementary Sensory-Biased Frontal Lobe Attention Networks.

    PubMed

    Michalka, Samantha W; Kong, Lingqiang; Rosen, Maya L; Shinn-Cunningham, Barbara G; Somers, David C

    2015-08-19

    The frontal lobes control wide-ranging cognitive functions; however, functional subdivisions of human frontal cortex are only coarsely mapped. Here, functional magnetic resonance imaging reveals two distinct visual-biased attention regions in lateral frontal cortex, superior precentral sulcus (sPCS) and inferior precentral sulcus (iPCS), anatomically interdigitated with two auditory-biased attention regions, transverse gyrus intersecting precentral sulcus (tgPCS) and caudal inferior frontal sulcus (cIFS). Intrinsic functional connectivity analysis demonstrates that sPCS and iPCS fall within a broad visual-attention network, while tgPCS and cIFS fall within a broad auditory-attention network. Interestingly, we observe that spatial and temporal short-term memory (STM), respectively, recruit visual and auditory attention networks in the frontal lobe, independent of sensory modality. These findings not only demonstrate that both sensory modality and information domain influence frontal lobe functional organization, they also demonstrate that spatial processing co-localizes with visual processing and that temporal processing co-localizes with auditory processing in lateral frontal cortex.

  9. How NOAA/DSCOVR Will Perform during Extreme Space Weather and Why Lead Time Exceeds Expectations

    NASA Astrophysics Data System (ADS)

    Biesecker, D. A.

    2014-12-01

    The NOAA/DSCOVR satellite is expected to launch in January, 2015 and replace the NASA/ACE satellite as the L1 Sentinel in early Summer, 2015. Having relied on ACE to provide critical warnings of geomagnetic storms since 1998, it is important for the space weather community to understand how DSCOVR will perform relative to ACE in real-time operations. The WIND/SWE instrument is sufficiently similar to the DSCOVR Faraday Cup that it can be used as a proxy for DSCOVR, with some caveats. We compare the ACE/SWEPAM and WIND/SWE observations for all geomagnetic storm events meeting the criteria of severe or extreme. We also examine time periods where ACE data were compromised by solar energetic particles. We find that DSCOVR will provide a more robust data stream than was provided by ACE during solar cycle 23. We will briefly address the magnetometer, supra-thermal particle measurements, and relativistic proton measurements provided by ACE, of which only the magnetometer is retained on DSCOVR. We also demonstrate that lead time for geomagnetic storm notifications to customers far exceeds the L1 to Earth delay time.

  10. Clover root exudate produces male-biased sex ratios and accelerates male metamorphic timing in wood frogs.

    PubMed

    Lambert, Max R

    2015-12-01

    In amphibians, abnormal metamorph sex ratios and sexual development have almost exclusively been considered in response to synthetic compounds like pesticides or pharmaceuticals. However, endocrine-active plant chemicals (i.e. phytoestrogens) are commonly found in agricultural and urban waterways hosting frog populations with deviant sexual development. Yet the effects of these compounds on amphibian development remain predominantly unexplored. Legumes, like clover, are common in agricultural fields and urban yards and exude phytoestrogen mixtures from their roots. These root exudates serve important ecological functions and may also be a source of phytoestrogens in waterways. I show that clover root exudate produces male-biased sex ratios and accelerates male metamorphosis relative to females in low and intermediate doses of root exudate. My results indicate that root exudates are a potential source of contaminants impacting vertebrate development and that humans may be cultivating sexual abnormalities in wildlife by actively managing certain plant species.

  11. Clover root exudate produces male-biased sex ratios and accelerates male metamorphic timing in wood frogs.

    PubMed

    Lambert, Max R

    2015-12-01

    In amphibians, abnormal metamorph sex ratios and sexual development have almost exclusively been considered in response to synthetic compounds like pesticides or pharmaceuticals. However, endocrine-active plant chemicals (i.e. phytoestrogens) are commonly found in agricultural and urban waterways hosting frog populations with deviant sexual development. Yet the effects of these compounds on amphibian development remain predominantly unexplored. Legumes, like clover, are common in agricultural fields and urban yards and exude phytoestrogen mixtures from their roots. These root exudates serve important ecological functions and may also be a source of phytoestrogens in waterways. I show that clover root exudate produces male-biased sex ratios and accelerates male metamorphosis relative to females in low and intermediate doses of root exudate. My results indicate that root exudates are a potential source of contaminants impacting vertebrate development and that humans may be cultivating sexual abnormalities in wildlife by actively managing certain plant species. PMID:27019728

  12. Clover root exudate produces male-biased sex ratios and accelerates male metamorphic timing in wood frogs

    PubMed Central

    Lambert, Max R.

    2015-01-01

    In amphibians, abnormal metamorph sex ratios and sexual development have almost exclusively been considered in response to synthetic compounds like pesticides or pharmaceuticals. However, endocrine-active plant chemicals (i.e. phytoestrogens) are commonly found in agricultural and urban waterways hosting frog populations with deviant sexual development. Yet the effects of these compounds on amphibian development remain predominantly unexplored. Legumes, like clover, are common in agricultural fields and urban yards and exude phytoestrogen mixtures from their roots. These root exudates serve important ecological functions and may also be a source of phytoestrogens in waterways. I show that clover root exudate produces male-biased sex ratios and accelerates male metamorphosis relative to females in low and intermediate doses of root exudate. My results indicate that root exudates are a potential source of contaminants impacting vertebrate development and that humans may be cultivating sexual abnormalities in wildlife by actively managing certain plant species. PMID:27019728

  13. Long lead-time flood forecasting using data-driven modeling approaches

    NASA Astrophysics Data System (ADS)

    Bhatia, N.; He, J.; Srivastav, R. K.

    2014-12-01

    In spite of numerous structure measures being taken for floods, accurate flood forecasting is essential to condense the damages in hazardous areas considerably. The need of producing more accurate flow forecasts motivates the researchers to develop advanced innovative methods. In this study, it is proposed to develop a hybrid neural network model to exploit the strengths of artificial neural networks (ANNs). The proposed model has two components: i.) Dual - ANN model developed using river flows; and ii.) Multiple Linear Regression (MLR) model trained on meteorological data (Rainfall and Snow on ground). Potential model inputs that best represent the process of river basin were selected in stepwise manner by identifying input-output relationship using a linear approach, Partial Correlation Input Selection (PCIS) combined with Akaike Information Criterion (AIC) technique. The presented hybrid model was compared with three conventional methods: i) Feed-forward artificial neural network (FF-ANN) using daily river flows; ii) FF-ANN applied on decomposed river flows (low flow, rising limb and falling limb of hydrograph); and iii) Recursive method for daily river flows with lead-time of 7 days. The applicability of the presented model is illustrated through daily river flow data of Bow River, Canada. Data from 1912 to 1976 were used to train the models while data from 1977 to 2006 were used to validate the models. The results of the study indicate that the proposed model is robust enough to capture the non-linear nature of hydrograph and proves to be highly promising to forecast peak flows (extreme values) well in advance (higher lead time).

  14. Introduction to Unconscious Bias

    NASA Astrophysics Data System (ADS)

    Schmelz, Joan T.

    2010-05-01

    We all have biases, and we are (for the most part) unaware of them. In general, men and women BOTH unconsciously devalue the contributions of women. This can have a detrimental effect on grant proposals, job applications, and performance reviews. Sociology is way ahead of astronomy in these studies. When evaluating identical application packages, male and female University psychology professors preferred 2:1 to hire "Brian” over "Karen” as an assistant professor. When evaluating a more experienced record (at the point of promotion to tenure), reservations were expressed four times more often when the name was female. This unconscious bias has a repeated negative effect on Karen's career. This talk will introduce the concept of unconscious bias and also give recommendations on how to address it using an example for a faculty search committee. The process of eliminating unconscious bias begins with awareness, then moves to policy and practice, and ends with accountability.

  15. BOOK REVIEW: Great Physicists - The Life and Times of Leading Physicists from Galileo to Hawking

    NASA Astrophysics Data System (ADS)

    Cropper, William H.

    2002-11-01

    The author, a former American chemistry professor, has organized his book into nine parts with 29 chapters, covering, in a fairly historical sequence and systemtic conceptual progression, all fundamentals of today's physics: i.e., mechanics, thermodynamics, electromagnetism, statistical mechanics, relativity, quantum mechanics, nuclear physics, particle physics, astronomy-astrophysics-cosmology. Obviously, the 20th century (when about 90% of professional physicists of all time worked) assumes with five topics the dominant role in this enterprise. For each topic, a small number (ranging from one to eight) of leading personalities is selected and the biographies of these 29 physicists, including two women (Marie Curie and Lise Meitner), are presented in some detail together with their achievements in the particular topic. Important relevant contributions of other scholars to each topic are also discussed. In addition, Cropper provides each of the topics with a short 'historical synopsis' justifying his selection of key persons. One may argue that concentrating on leading physicists constitutes an old-fashioned approach to displaying the history and contents of fundamental topics in physics. However, the mixture of biographies and explanation of leading contributions given here will certainly serve for a larger public, not just professional physicists and scientists, as a guide through the exciting development of physical ideas and discoveries. In general, the presentation of the material is quite satisfactory (with only few slips, e.g., in the Meitner story, where the author follows too closely a new biography) and gives the essence of the great advances in physics since the 15th century. One notices perhaps the limitation of the author in cases where no biography in English is available - this would also explain the omission of some of the main contributors to atomic and particle physics, such as Arnold Sommerfeld and Hideki Yukawa, or that French or Russian readers

  16. Inattentional Deafness: Visual Load Leads to Time-Specific Suppression of Auditory Evoked Responses

    PubMed Central

    Molloy, Katharine; Griffiths, Timothy D.; Lavie, Nilli

    2015-01-01

    Due to capacity limits on perception, conditions of high perceptual load lead to reduced processing of unattended stimuli (Lavie et al., 2014). Accumulating work demonstrates the effects of visual perceptual load on visual cortex responses, but the effects on auditory processing remain poorly understood. Here we establish the neural mechanisms underlying “inattentional deafness”—the failure to perceive auditory stimuli under high visual perceptual load. Participants performed a visual search task of low (target dissimilar to nontarget items) or high (target similar to nontarget items) load. On a random subset (50%) of trials, irrelevant tones were presented concurrently with the visual stimuli. Brain activity was recorded with magnetoencephalography, and time-locked responses to the visual search array and to the incidental presence of unattended tones were assessed. High, compared to low, perceptual load led to increased early visual evoked responses (within 100 ms from onset). This was accompanied by reduced early (∼100 ms from tone onset) auditory evoked activity in superior temporal sulcus and posterior middle temporal gyrus. A later suppression of the P3 “awareness” response to the tones was also observed under high load. A behavioral experiment revealed reduced tone detection sensitivity under high visual load, indicating that the reduction in neural responses was indeed associated with reduced awareness of the sounds. These findings support a neural account of shared audiovisual resources, which, when depleted under load, leads to failures of sensory perception and awareness. SIGNIFICANCE STATEMENT The present work clarifies the neural underpinning of inattentional deafness under high visual load. The findings of near-simultaneous load effects on both visual and auditory evoked responses suggest shared audiovisual processing capacity. Temporary depletion of shared capacity in perceptually demanding visual tasks leads to a momentary reduction in

  17. Estimating Attitude, Trajectory, and Gyro Biases in an Extended Kalman Filter using Earth Magnetic Field Data from the Rossi X-Ray Timing Explorer

    NASA Technical Reports Server (NTRS)

    Deutschmann, Julie; Bar-Itzhack, Itzhack

    1997-01-01

    Traditionally satellite attitude and trajectory have been estimated with completely separate systems, using different measurement data. The estimation of both trajectory and attitude for low earth orbit satellites has been successfully demonstrated in ground software using magnetometer and gyroscope data. Since the earth's magnetic field is a function of time and position, and since time is known quite precisely, the differences between the computed and measured magnetic field components, as measured by the magnetometers throughout the entire spacecraft orbit, are a function of both the spacecraft trajectory and attitude errors. Therefore, these errors can be used to estimate both trajectory and attitude. This work further tests the single augmented Extended Kalman Filter (EKF) which simultaneously and autonomously estimates spacecraft trajectory and attitude with data from the Rossi X-Ray Timing Explorer (RXTE) magnetometer and gyro-measured body rates. In addition, gyro biases are added to the state and the filter's ability to estimate them is presented.

  18. Time trends in burdens of cadmium, lead, and mercury in the population of northern Sweden

    SciTech Connect

    Wennberg, Maria . E-mail: miawennberg@skehus19.ac; Lundh, Thomas; Bergdahl, Ingvar A.; Hallmans, Goeran; Jansson, Jan-Hakan; Stegmayr, Birgitta; Custodio, Hipolito M.; Skerfving, Staffan

    2006-03-15

    The time trends of exposure to heavy metals are not adequately known. This is a worldwide problem with regard to the basis for preventive actions and evaluation of their effects. This study addresses time trends for the three toxic elements cadmium (Cd), mercury (Hg), and lead (Pb). Concentrations in erythrocytes (Ery) were determined in a subsample of the population-based MONICA surveys from 1990, 1994, and 1999 in a total of 600 men and women aged 25-74 years. The study took place in the two northernmost counties in Sweden. To assess the effect of changes in the environment, adjustments were made for life-style factors that are determinants of exposure. Annual decreases of 5-6% were seen for Ery-Pb levels (adjusted for age and changes in alcohol intake) and Ery-Hg levels (adjusted for age and changes in fish intake). Ery-Cd levels (adjusted for age) showed a similar significant decrease in smoking men. It is concluded that for Pb and maybe also Hg the actions against pollution during recent decades have caused a rapid decrease of exposure; for Hg the decreased use of dental amalgam may also have had an influence. For Cd, the decline in Ery-Cd was seen only in smokers, indicating that Cd exposure from tobacco has decreased, while other environmental sources of Cd have not changed significantly. To further improve the health status in Sweden, it is important to decrease the pollution of Cd, and actions against smoking in the community are important.

  19. Crack azimuths on Europa: time sequence in the southern leading face

    NASA Astrophysics Data System (ADS)

    Sarid, Alyssa Rose; Greenberg, Richard; Hoppa, Gregory V.; Geissler, Paul; Preblich, Brandon

    2004-03-01

    The formation sequence of prominent ridges and other tectonic lineaments on the southern portion of the leading hemisphere of Europa is determined from cross-cutting relationships. These selected features formed fairly recently relative to most of the surface; older lineaments no longer retain clear evidence of cross-cutting. If we assume that this sequence represents the order of formation of cracks that underlie each lineament, and that the orientation of each crack was determined by tidal stress whose azimuth varies monotonically counter-clockwise with time, the azimuth must have rotated more than 740°, which would correspond to the change in tidal stress over two periods of nonsynchronous rotation (relative to the direction of Jupiter). However, that interpretation is not necessarily compelling, because the observed orientations of cross-cutting lineaments are not densely spaced over these cycles; in fact, the sequence would fit nearly as well into an arbitrary model with rotation in the opposite sense from that predicted by theory. This tectonic record may have formed over many more rotational cycles, such that typically only a few cracks form per cycle, which would be consistent with evidence from considerations of cycloidal crack patterns. Sets of cracks that cluster near certain azimuth orientations appear to be parts of globe-encircling lineament systems and may result from other effects, perhaps polar wander that occurred rapidly relative to nonsynchronous rotation.

  20. Assessment of realistic nowcasting lead-times based on predictability analysis of Mediterranean Heavy Precipitation Events

    NASA Astrophysics Data System (ADS)

    Bech, Joan; Berenguer, Marc

    2014-05-01

    Operational quantitative precipitation forecasts (QPF) are provided routinely by weather services or hydrological authorities, particularly those responsible for densely populated regions of small catchments, such as those typically found in Mediterranean areas prone to flash-floods. Specific rainfall values are used as thresholds for issuing warning levels considering different time frameworks (mid-range, short-range, 24h, 1h, etc.), for example 100 mm in 24h or 60 mm in 1h. There is a clear need to determine how feasible is a specific rainfall value for a given lead-time, in particular for very short range forecasts or nowcasts typically obtained from weather radar observations (Pierce et al 2012). In this study we assess which specific nowcast lead-times can be provided for a number of heavy precipitation events (HPE) that affected Catalonia (NE Spain). The nowcasting system we employed generates QPFs through the extrapolation of rainfall fields observed with weather radar following a Lagrangian approach developed and tested successfully in previous studies (Berenguer et al. 2005, 2011).Then QPFs up to 3h are compared with two quality controlled observational data sets: weather radar quantitative precipitation estimates (QPE) and raingauge data. Several high-impact weather HPE were selected including the 7 September 2005 Llobregat Delta river tornado outbreak (Bech et al. 2007) or the 2 November 2008 supercell tornadic thunderstorms (Bech et al. 2011) both producing, among other effects, local flash floods. In these two events there were torrential rainfall rates (30' amounts exceeding 38.2 and 12.3 mm respectively) and 24h accumulation values above 100 mm. A number of verification scores are used to characterize the evolution of precipitation forecast quality with time, which typically presents a decreasing trend but showing an strong dependence on the selected rainfall threshold and integration period. For example considering correlation factors, 30

  1. Laterality and flight: concurrent tests of side-bias and optimality in flying tree swallows.

    PubMed

    Mandel, James T; Ratcliffe, John M; Cerasale, David J; Winkler, David W

    2008-01-01

    Behavioural side-bias occurs in many vertebrates, including birds as a result of hemispheric specialization and can be advantageous by improving response times to sudden stimuli and efficiency in multi-tasking. However, behavioural side-bias can lead to morphological asymmetries resulting in reduced performance for specific activities. For flying animals, wing asymmetry is particularly costly and it is unclear if behavioural side-biases will be expressed in flight; the benefits of quick response time afforded by side-biases must be balanced against the costs of less efficient flight due to the morphological asymmetry side-biases may incur. Thus, competing constraints could lead to context-dependent expression or suppression of side-bias in flight. In repeated flight trials through an outdoor tunnel with obstacles, tree swallows (Tachycineta bicolor) preferred larger openings, but we did not detect either individual or population-level side-biases. Thus, while observed behavioural side-biases during substrate-foraging and copulation are common in birds, we did not see such side-bias expressed in obstacle avoidance behaviour in flight. This finding highlights the importance of behavioural context for investigations of side-bias and hemispheric laterality and suggests both proximate and ultimate trade-offs between species-specific cognitive ecology and flight biomechanics.

  2. Increasing streamflow forecast lead time for snowmelt-driven catchment based on large-scale climate patterns

    NASA Astrophysics Data System (ADS)

    Kalra, Ajay; Ahmad, Sajjad; Nayak, Anurag

    2013-03-01

    This study focuses on improving the spring-summer streamflow forecast lead time using large scale climate patterns. An artificial intelligence type data-driven model, Support Vector Machine (SVM), was developed incorporating oceanic-atmospheric oscillations to increase the forecast lead time. The application of SVM model is tested on three unimpaired gages in the North Platte River Basin. Seasonal averages of oceanic-atmospheric indices for the period of 1940-2007 are used to generate spring-summer streamflow volumes with 3-, 6- and 9-month lead times. The results reveal a strong association between coupled indices compared to their individual effects. The best streamflow estimates are obtained at 6-month compared to 3-month and 9-month lead times. The proposed modeling technique is expected to provide useful information to water managers and help in better managing the water resources and the operation of water systems.

  3. Achieving Forecasts in the Thermosphere and Ionosphere with Lead Times of a Few Days

    NASA Astrophysics Data System (ADS)

    Mannucci, A. J.; Meng, X.; Verkhoglyadova, O. P.; Tsurutani, B.; Manchester, W.; Sharma, S.

    2015-12-01

    Forecasting space weather requires the development of first-principles-based models for the coupled Sun-Earth System. To achieve lead times of a few days for disturbances in planetary thermospheres and ionospheres, models of the solar wind propagating through the heliosphere are required. An active research community has achieved a suite of models that describe conditions within, and coupling between, the solar wind, the Earth's magnetosphere and the ionosphere. At least one version of each model in the suite is available for broad community use and investigation. While these models represent an important step towards the goal of achieving accurate space weather forecasts, it is recognized that certain physical processes are not represented in these models, with unknown impact on the forecasts. We suggest an approach towards improved space weather forecasts that emphasizes model evaluation techniques, providing detailed information on how the physical processes represented in the models affect forecasts based on those models. Such detailed information permits the models to be used for investigating science questions, and permits observations to be the basis for improving the models and increasing scientific understanding. In this talk, we present upper atmosphere forecasting results using community models of the coupled Sun-Earth system. We describe our approach to analyzing the physics of ionospheric storms as represented in the Global Ionosphere Thermosphere Model developed at the University of Michigan. Such analysis involves both an approach to model diagnostics and the use of a comprehensive set of observations. We compare forecast results for high-speed solar wind stream storms and storms initiated by solar coronal mass ejections. First-principle and empirically based approaches to coupling between the solar wind and ionosphere are compared. These comparisons provide insight into the strengths and limitations, and areas for future improvement, of first

  4. Analyses of evolutionary dynamics in viruses are hindered by a time-dependent bias in rate estimates

    PubMed Central

    Duchêne, Sebastián; Holmes, Edward C.; Ho, Simon Y. W.

    2014-01-01

    Time-scales of viral evolution and emergence have been studied widely, but are often poorly understood. Molecular analyses of viral evolutionary time-scales generally rely on estimates of rates of nucleotide substitution, which vary by several orders of magnitude depending on the timeframe of measurement. We analysed data from all major groups of viruses and found a strong negative relationship between estimates of nucleotide substitution rate and evolutionary timescale. Strikingly, this relationship was upheld both within and among diverse groups of viruses. A detailed case study of primate lentiviruses revealed that the combined effects of sequence saturation and purifying selection can explain this time-dependent pattern of rate variation. Therefore, our analyses show that studies of evolutionary time-scales in viruses require a reconsideration of substitution rates as a dynamic, rather than as a static, feature of molecular evolution. Improved modelling of viral evolutionary rates has the potential to change our understanding of virus origins. PMID:24850916

  5. [Lead exposure in the ceramic tile industry: time trends and current exposure levels].

    PubMed

    Candela, S; Ferri, F; Olmi, M

    1998-01-01

    There is a high density of industries for the production of ceramic tiles in the District of Scandiano (province of Reggio Emilia, Emilia Romagna region). In this area, since the beginning of 1970s, the time trend of Pb exposure in ceramic tile plants has been evaluated by means of biological monitoring (BM) data collected at the Service of Prevention and Safety in the Work Environment and its associated Toxicology Laboratory. From these data, a clear decreasing time trend of exposure levels is documented, the reduction being more evident during the seventies and in 1985-88. During the seventies BM was introduced systematically in all ceramic tile plants with the determination of delta-aminolevulinic acid in urine (ALA-U). As a consequence of the BM programme, hygienic measures for the abatement of pollution inside the plants were implemented, and a reduction, from 20.6% to 2%, of ALA-U values exceeding 10 mg/l, was observed. In 1985, the determination of lead in blood (PbB) replaced that of ALA-U in the BM programmes and highlighted the persistence of high level of exposure to Pb, which could not be outlined by means of ALA-U because of its lower sensitivity. PbB levels were 36.1 micrograms/100 ml and 25.7 micrograms/100 ml in male and female workers, respectively. These results required the implementation, within the plants, of additional hygienic measures and a significant reduction of PbB was obtained in the following three years. In 1988 PbB levels were 26.0 +/- 10.7 and 21.6 +/- 10.3 micrograms/100 ml in male and female workers, respectively. In 1993-95 Pb levels were obtained from 1328 male and 771 female workers of 56 plants, accounting for about 40% of the total number of workers in the ceramic industry, in the zones of Sassuolo and Scandiano. Exposure levels are not different from those observed in the preceding years, with PbB levels of 25.3 +/- 11.1 and 19.1 +/- 9.2 micrograms/100 ml in male and female workers, respectively.

  6. The efficacy of protoporphyrin as a predictive biomarker for lead exposure in canvasback ducks: effect of sample storage time

    USGS Publications Warehouse

    Franson, J.C.; Hohman, W.L.; Moore, J.L.; Smith, M.R.

    1996-01-01

    We used 363 blood samples collected from wild canvasback ducks (Aythya valisineria) at Catahoula Lake, Louisiana, U.S.A. to evaluate the effect of sample storage time on the efficacy of erythrocytic protoporphyrin as an indicator of lead exposure. The protoporphyrin concentration of each sample was determined by hematofluorometry within 5 min of blood collection and after refrigeration at 4 °C for 24 and 48 h. All samples were analyzed for lead by atomic absorption spectrophotometry. Based on a blood lead concentration of ≥0.2 ppm wet weight as positive evidence for lead exposure, the protoporphyrin technique resulted in overall error rates of 29%, 20%, and 19% and false negative error rates of 47%, 29% and 25% when hematofluorometric determinations were made on blood at 5 min, 24 h, and 48 h, respectively. False positive error rates were less than 10% for all three measurement times. The accuracy of the 24-h erythrocytic protoporphyrin classification of blood samples as positive or negative for lead exposure was significantly greater than the 5-min classification, but no improvement in accuracy was gained when samples were tested at 48 h. The false negative errors were probably due, at least in part, to the lag time between lead exposure and the increase of blood protoporphyrin concentrations. False negatives resulted in an underestimation of the true number of canvasbacks exposed to lead, indicating that hematofluorometry provides a conservative estimate of lead exposure.

  7. Bias in Dynamic Monte Carlo Alpha Calculations

    SciTech Connect

    Sweezy, Jeremy Ed; Nolen, Steven Douglas; Adams, Terry R.; Trahan, Travis John

    2015-02-06

    A 1/N bias in the estimate of the neutron time-constant (commonly denoted as α) has been seen in dynamic neutronic calculations performed with MCATK. In this paper we show that the bias is most likely caused by taking the logarithm of a stochastic quantity. We also investigate the known bias due to the particle population control method used in MCATK. We conclude that this bias due to the particle population control method is negligible compared to other sources of bias.

  8. Lead Slowing-Down Spectrometry Time Spectral Analysis for Spent Fuel Assay: FY12 Status Report

    SciTech Connect

    Kulisek, Jonathan A.; Anderson, Kevin K.; Casella, Andrew M.; Siciliano, Edward R.; Warren, Glen A.

    2012-09-28

    Executive Summary Developing a method for the accurate, direct, and independent assay of the fissile isotopes in bulk materials (such as used fuel) from next-generation domestic nuclear fuel cycles is a goal of the Office of Nuclear Energy, Fuel Cycle R&D, Material Protection and Control Technology (MPACT) Campaign. To meet this goal, MPACT supports a multi-institutional collaboration, of which PNNL is a part, to study the feasibility of Lead Slowing Down Spectroscopy (LSDS). This technique is an active nondestructive assay method that has the potential to provide independent, direct measurement of Pu and U isotopic masses in used fuel with an uncertainty considerably lower than the approximately 10% typical of today’s confirmatory methods. This document is a progress report for FY2012 PNNL analysis and algorithm development. Progress made by PNNL in FY2012 continues to indicate the promise of LSDS analysis and algorithms applied to used fuel assemblies. PNNL further refined the semi-empirical model developed in FY2011 based on singular value decomposition (SVD) to numerically account for the effects of self-shielding. The average uncertainty in the Pu mass across the NGSI-64 fuel assemblies was shown to be less than 3% using only six calibration assemblies with a 2% uncertainty in the isotopic masses. When calibrated against the six NGSI-64 fuel assemblies, the algorithm was able to determine the total Pu mass within <2% uncertainty for the 27 diversion cases also developed under NGSI. Two purely empirical algorithms were developed that do not require the use of Pu isotopic fission chambers. The semi-empirical and purely empirical algorithms were successfully tested using MCNPX simulations as well applied to experimental data measured by RPI using their LSDS. The algorithms were able to describe the 235U masses of the RPI measurements with an average uncertainty of 2.3%. Analyses were conducted that provided valuable insight with regard to design requirements (e

  9. Reducing bias in survival under non-random temporary emigration

    USGS Publications Warehouse

    Peñaloza, Claudia L.; Kendall, William L.; Langtimm, Catherine Ann

    2014-01-01

    Despite intensive monitoring, temporary emigration from the sampling area can induce bias severe enough for managers to discard life-history parameter estimates toward the terminus of the times series (terminal bias). Under random temporary emigration unbiased parameters can be estimated with CJS models. However, unmodeled Markovian temporary emigration causes bias in parameter estimates and an unobservable state is required to model this type of emigration. The robust design is most flexible when modeling temporary emigration, and partial solutions to mitigate bias have been identified, nonetheless there are conditions were terminal bias prevails. Long-lived species with high adult survival and highly variable non-random temporary emigration present terminal bias in survival estimates, despite being modeled with the robust design and suggested constraints. Because this bias is due to uncertainty about the fate of individuals that are undetected toward the end of the time series, solutions should involve using additional information on survival status or location of these individuals at that time. Using simulation, we evaluated the performance of models that jointly analyze robust design data and an additional source of ancillary data (predictive covariate on temporary emigration, telemetry, dead recovery, or auxiliary resightings) in reducing terminal bias in survival estimates. The auxiliary resighting and predictive covariate models reduced terminal bias the most. Additional telemetry data was effective at reducing terminal bias only when individuals were tracked for a minimum of two years. High adult survival of long-lived species made the joint model with recovery data ineffective at reducing terminal bias because of small-sample bias. The naïve constraint model (last and penultimate temporary emigration parameters made equal), was the least efficient, though still able to reduce terminal bias when compared to an unconstrained model. Joint analysis of several

  10. Biased Allostery.

    PubMed

    Edelstein, Stuart J; Changeux, Jean-Pierre

    2016-09-01

    G-protein-coupled receptors (GPCRs) constitute a large group of integral membrane proteins that transduce extracellular signals from a wide range of agonists into targeted intracellular responses. Although the responses can vary depending on the category of G-proteins activated by a particular receptor, responses were also found to be triggered by interactions of the receptor with β-arrestins. It was subsequently discovered that for the same receptor molecule (e.g., the β-adrenergic receptor), some agonists have a propensity to specifically favor responses by G-proteins, others by β-arrestins, as has now been extensively studied. This feature of the GPCR system is known as biased agonism and is subject to various interpretations, including agonist-induced conformational change versus selective stabilization of preexisting active conformations. Here, we explore a complete allosteric framework for biased agonism based on alternative preexisting conformations that bind more strongly, but nonexclusively, either G-proteins or β-arrestins. The framework incorporates reciprocal effects among all interacting molecules. As a result, G-proteins and β-arrestins are in steric competition for binding to the cytoplasmic surface of either the G-protein-favoring or β-arrestin-favoring GPCR conformation. Moreover, through linkage relations, the strength of the interactions of G-proteins or β-arrestins with the corresponding active conformation potentiates the apparent affinity for the agonist, effectively equating these two proteins to allosteric modulators. The balance between response alternatives can also be influenced by the physiological concentrations of either G-proteins or β-arrestins, as well as by phosphorylation or interactions with positive or negative allosteric modulators. The nature of the interactions in the simulations presented suggests novel experimental tests to distinguish more fully among alternative mechanisms. PMID:27602718

  11. Extended Time on Academic Assignments: Does Increased Time Lead to Improved Performance for Children with Attention-Deficit/Hyperactivity Disorder?

    ERIC Educational Resources Information Center

    Pariseau, Meaghan E.; Fabiano, Gregory A.; Massetti, Greta M.; Hart, Katie C.; Pelham, William E., Jr.

    2010-01-01

    Researchers examined the impact of an extended time accommodation on appropriate classroom behavior and rate of work completion for 33 children with attention-deficit/hyperactivity disorder (ADHD). Participants received standard (30 min) or extended (45 min) time to complete seatwork in a within-subject, crossover design study. Appropriate…

  12. Potential for bias and low precision in molecular divergence time estimation of the Canopy of Life: an example from aquatic bird families

    PubMed Central

    van Tuinen, Marcel; Torres, Christopher R.

    2015-01-01

    Uncertainty in divergence time estimation is frequently studied from many angles but rarely from the perspective of phylogenetic node age. If appropriate molecular models and fossil priors are used, a multi-locus, partitioned analysis is expected to equally minimize error in accuracy and precision across all nodes of a given phylogeny. In contrast, if available models fail to completely account for rate heterogeneity, substitution saturation and incompleteness of the fossil record, uncertainty in divergence time estimation may increase with node age. While many studies have stressed this concern with regard to deep nodes in the Tree of Life, the inference that molecular divergence time estimation of shallow nodes is less sensitive to erroneous model choice has not been tested explicitly in a Bayesian framework. Because of available divergence time estimation methods that permit fossil priors across any phylogenetic node and the present increase in efficient, cheap collection of species-level genomic data, insight is needed into the performance of divergence time estimation of shallow (<10 MY) nodes. Here, we performed multiple sensitivity analyses in a multi-locus data set of aquatic birds with six fossil constraints. Comparison across divergence time analyses that varied taxon and locus sampling, number and position of fossil constraint and shape of prior distribution showed various insights. Deviation from node ages obtained from a reference analysis was generally highest for the shallowest nodes but determined more by temporal placement than number of fossil constraints. Calibration with only the shallowest nodes significantly underestimated the aquatic bird fossil record, indicating the presence of saturation. Although joint calibration with all six priors yielded ages most consistent with the fossil record, ages of shallow nodes were overestimated. This bias was found in both mtDNA and nDNA regions. Thus, divergence time estimation of shallow nodes may suffer

  13. Sequential biases in accumulating evidence

    PubMed Central

    Huggins, Richard; Dogo, Samson Henry

    2015-01-01

    Whilst it is common in clinical trials to use the results of tests at one phase to decide whether to continue to the next phase and to subsequently design the next phase, we show that this can lead to biased results in evidence synthesis. Two new kinds of bias associated with accumulating evidence, termed ‘sequential decision bias’ and ‘sequential design bias’, are identified. Both kinds of bias are the result of making decisions on the usefulness of a new study, or its design, based on the previous studies. Sequential decision bias is determined by the correlation between the value of the current estimated effect and the probability of conducting an additional study. Sequential design bias arises from using the estimated value instead of the clinically relevant value of an effect in sample size calculations. We considered both the fixed‐effect and the random‐effects models of meta‐analysis and demonstrated analytically and by simulations that in both settings the problems due to sequential biases are apparent. According to our simulations, the sequential biases increase with increased heterogeneity. Minimisation of sequential biases arises as a new and important research area necessary for successful evidence‐based approaches to the development of science. © 2015 The Authors. Research Synthesis Methods Published by John Wiley & Sons Ltd. PMID:26626562

  14. Simulation of blast-induced, early-time intracranial wave physics leading to traumatic brain injury.

    SciTech Connect

    Taylor, Paul Allen; Ford, Corey C.

    2008-04-01

    U.S. soldiers are surviving blast and impacts due to effective body armor, trauma evacuation and care. Blast injuries are the leading cause of traumatic brain injury (TBI) in military personnel returning from combat. Understanding of Primary Blast Injury may be needed to develop better means of blast mitigation strategies. The objective of this paper is to investigate the effects of blast direction and strength on the resulting mechanical stress and wave energy distributions generated in the brain.

  15. Ensemble forecasts of monthly catchment rainfall out to long lead times by post-processing coupled general circulation model output

    NASA Astrophysics Data System (ADS)

    Schepen, Andrew; Wang, Q. J.

    2014-11-01

    Monthly streamflow forecasts with long lead time are being sought by water managers in Australia. In this study, we take a first step towards a monthly streamflow modelling approach by harnessing a coupled ocean-atmosphere general circulation model (CGCM) to produce monthly rainfall forecasts for three catchments across Australia. Bayesian methodologies are employed to produce forecasts based on CGCM raw rainfall forecasts and also CGCM sea surface temperature forecasts. The Schaake Shuffle is used to connect forecast ensemble members of individual months to form ensemble monthly time series forecasts. Monthly forecasts and three-monthly forecasts of rainfall are assessed for lead times of 0-6 months, based on leave-one-year-out cross-validation for 1980-2010. The approach is shown to produce well-calibrated ensemble forecasts that source skill from both the atmospheric and ocean modules of the CGCM. Although skill is generally low, moderate skill scores are observed in some catchments for lead times of up to 6 months. In months and catchments where there is limited skill, the forecasts revert to climatology. Thus the forecasts developed can be considered suitable for continuously forecasting time series of streamflow to long lead times, when coupled with a suitable monthly hydrological model.

  16. Influence of SST biases on future climate change projections

    SciTech Connect

    Ashfaq, Moetasim; Skinner, Chris B; Cherkauer, Keith

    2010-01-01

    We use a quantile-based bias correction technique and a multi-member ensemble of the atmospheric component of NCAR CCSM3 (CAM3) simulations to investigate the influence of sea surface temperature (SST) biases on future climate change projections. The simulations, which cover 1977 1999 in the historical period and 2077 2099 in the future (A1B) period, use the CCSM3-generated SSTs as prescribed boundary conditions. Bias correction is applied to the monthly time-series of SSTs so that the simulated changes in SST mean and variability are preserved. Our comparison of CAM3 simulations with and without SST correction shows that the SST biases affect the precipitation distribution in CAM3 over many regions by introducing errors in atmospheric moisture content and upper-level (lower-level) divergence (convergence). Also, bias correction leads to significantly different precipitation and surface temperature changes over many oceanic and terrestrial regions (predominantly in the tropics) in response to the future anthropogenic increases in greenhouse forcing. The differences in the precipitation response from SST bias correction occur both in the mean and the percent change, and are independent of the ocean atmosphere coupling. Many of these differences are comparable to or larger than the spread of future precipitation changes across the CMIP3 ensemble. Such biases can affect the simulated terrestrial feedbacks and thermohaline circulations in coupled climate model integrations through changes in the hydrological cycle and ocean salinity. Moreover, biases in CCSM3-generated SSTs are generally similar to the biases in CMIP3 ensemble mean SSTs, suggesting that other GCMs may display a similar sensitivity of projected climate change to SST errors. These results help to quantify the influence of climate model biases on the simulated climate change, and therefore should inform the effort to further develop approaches for reliable climate change projection.

  17. Time-lapse imaging of neural development: Zebrafish lead the way into the fourth dimension

    PubMed Central

    Rieger, Sandra; Wang, Fang; Sagasti, Alvaro

    2011-01-01

    Time-lapse imaging is often the only way to appreciate fully the many dynamic cell movements critical to neural development. Zebrafish possess many advantages that make them the best vertebrate model organism for live imaging of dynamic development events. This review will discuss technical considerations of time-lapse imaging experiments in zebrafish, describe selected examples of imaging studies in zebrafish that revealed new features or principles of neural development, and consider the promise and challenges of future time-lapse studies of neural development in zebrafish embryos and adults. PMID:21305690

  18. Matching times of leading and following suggest cooperation through direct reciprocity during V-formation flight in ibis

    PubMed Central

    Voelkl, Bernhard; Portugal, Steven J.; Unsöld, Markus; Usherwood, James R.; Wilson, Alan M.; Fritz, Johannes

    2015-01-01

    One conspicuous feature of several larger bird species is their annual migration in V-shaped or echelon formation. When birds are flying in these formations, energy savings can be achieved by using the aerodynamic up-wash produced by the preceding bird. As the leading bird in a formation cannot profit from this up-wash, a social dilemma arises around the question of who is going to fly in front? To investigate how this dilemma is solved, we studied the flight behavior of a flock of juvenile Northern bald ibis (Geronticus eremita) during a human-guided autumn migration. We could show that the amount of time a bird is leading a formation is strongly correlated with the time it can itself profit from flying in the wake of another bird. On the dyadic level, birds match the time they spend in the wake of each other by frequent pairwise switches of the leading position. Taken together, these results suggest that bald ibis cooperate by directly taking turns in leading a formation. On the proximate level, we propose that it is mainly the high number of iterations and the immediacy of reciprocation opportunities that favor direct reciprocation. Finally, we found evidence that the animals' propensity to reciprocate in leading has a substantial influence on the size and cohesion of the flight formations. PMID:25646487

  19. Biased Brownian dynamics for rate constant calculation.

    PubMed

    Zou, G; Skeel, R D; Subramaniam, S

    2000-08-01

    An enhanced sampling method-biased Brownian dynamics-is developed for the calculation of diffusion-limited biomolecular association reaction rates with high energy or entropy barriers. Biased Brownian dynamics introduces a biasing force in addition to the electrostatic force between the reactants, and it associates a probability weight with each trajectory. A simulation loses weight when movement is along the biasing force and gains weight when movement is against the biasing force. The sampling of trajectories is then biased, but the sampling is unbiased when the trajectory outcomes are multiplied by their weights. With a suitable choice of the biasing force, more reacted trajectories are sampled. As a consequence, the variance of the estimate is reduced. In our test case, biased Brownian dynamics gives a sevenfold improvement in central processing unit (CPU) time with the choice of a simple centripetal biasing force.

  20. Biased Brownian dynamics for rate constant calculation.

    PubMed

    Zou, G; Skeel, R D; Subramaniam, S

    2000-08-01

    An enhanced sampling method-biased Brownian dynamics-is developed for the calculation of diffusion-limited biomolecular association reaction rates with high energy or entropy barriers. Biased Brownian dynamics introduces a biasing force in addition to the electrostatic force between the reactants, and it associates a probability weight with each trajectory. A simulation loses weight when movement is along the biasing force and gains weight when movement is against the biasing force. The sampling of trajectories is then biased, but the sampling is unbiased when the trajectory outcomes are multiplied by their weights. With a suitable choice of the biasing force, more reacted trajectories are sampled. As a consequence, the variance of the estimate is reduced. In our test case, biased Brownian dynamics gives a sevenfold improvement in central processing unit (CPU) time with the choice of a simple centripetal biasing force. PMID:10919998

  1. Revisiting the question: Does high-latitude solar activity lead low-latitude solar activity in time phase?

    SciTech Connect

    Kong, D. F.; Qu, Z. N.; Guo, Q. L.

    2014-05-01

    Cross-correlation analysis and wavelet transform methods are used to investigate whether high-latitude solar activity leads low-latitude solar activity in time phase or not, using the data of the Carte Synoptique solar filaments archive from 1919 March to 1989 December. From the cross-correlation analysis, high-latitude solar filaments have a time lead of 12 Carrington solar rotations with respect to low-latitude ones. Both the cross-wavelet transform and wavelet coherence indicate that high-latitude solar filaments lead low-latitude ones in time phase. Furthermore, low-latitude solar activity is better correlated with high-latitude solar activity of the previous cycle than with that of the following cycle, which is statistically significant. Thus, the present study confirms that high-latitude solar activity in the polar regions is indeed better correlated with the low-latitude solar activity of the following cycle than with that of the previous cycle, namely, leading in time phase.

  2. [Influence of Reaction Time on Titanate Nanomaterials and Its Adsorptioi Capability for Lead in Aqueous Solutions].

    PubMed

    Fan, Gong-duan; Chen, Li-ru; Lin, Ru-jing; Lin, Qian; Su, Zhao-yue; Lin, Xiu-yong

    2016-02-15

    Titanate nanomaterials (TNs) were synthesized via a simple hydrothermal method using TiO2 (ST-01) and NaOH as the raw materials, and presented different morphologies by adjusting the reaction time. The physico-chemical properties of the as-prepared TNs, such as morphology, structure, surface area, and chemical composition were characterized by XRD, SEM and BET. The adsorption capability and rules of Pb(II) in aqueous solutions were tested in the static system. The results showed that the TNs prepared with 12-72 h reaction time were pure monoclinic phase titanate and their specific surface areas were in the range from 243.05 m2 x g(-1) to 286.20 m2 x g(-1). TNs with reaction time between 12-36 h mainly showed sheet structure, and those with reaction time higher than 48 h showed linear structure. The adsorption capacity of Pb(II) by TNs-12, TNs-24, TNs-36, TNs-48, TNs-60 and TNs-72 was 479.40, 504.12, 482.00, 388.10, 364.60 and 399.00 mg x g(-1), respectively. The sheet TNs had a better adsorption capacity than the linear TNs. TNs-24 had the highest adsorbing capacity. The adsorption kinetics of Pb(II) by TNs-24 followed the pseudo-second-order model, and the equilibrium data was best fitted with the Langmuir isotherm model. The equilibrium adsorption time of TNs-24 was 120 min, and the adsorption was an exothermic process, with a high adsorption capacity at low temperature or room temperature; the optimal adsorption pH was 5.0. When pH was 1.0, the desorption rate of TNs-24 could reach 99.00%, and the removal efficiency of Pb(II) by regenerated TNs was still more than 97% after six times of usage. Therefore, TNs could efficiently remove Pb(II) in aqueous solutions, and the optimal reaction time should be controlled to 12-24 h. When Cd(II) or Ni(II) existed in the solution, the equilibrium adsorption capacity and removal rate of TNs-24 were decreased. The adsorption mechanism was mainly ion-exchanged between Pb(II) and H+/Na+ in TNs.

  3. [Influence of Reaction Time on Titanate Nanomaterials and Its Adsorptioi Capability for Lead in Aqueous Solutions].

    PubMed

    Fan, Gong-duan; Chen, Li-ru; Lin, Ru-jing; Lin, Qian; Su, Zhao-yue; Lin, Xiu-yong

    2016-02-15

    Titanate nanomaterials (TNs) were synthesized via a simple hydrothermal method using TiO2 (ST-01) and NaOH as the raw materials, and presented different morphologies by adjusting the reaction time. The physico-chemical properties of the as-prepared TNs, such as morphology, structure, surface area, and chemical composition were characterized by XRD, SEM and BET. The adsorption capability and rules of Pb(II) in aqueous solutions were tested in the static system. The results showed that the TNs prepared with 12-72 h reaction time were pure monoclinic phase titanate and their specific surface areas were in the range from 243.05 m2 x g(-1) to 286.20 m2 x g(-1). TNs with reaction time between 12-36 h mainly showed sheet structure, and those with reaction time higher than 48 h showed linear structure. The adsorption capacity of Pb(II) by TNs-12, TNs-24, TNs-36, TNs-48, TNs-60 and TNs-72 was 479.40, 504.12, 482.00, 388.10, 364.60 and 399.00 mg x g(-1), respectively. The sheet TNs had a better adsorption capacity than the linear TNs. TNs-24 had the highest adsorbing capacity. The adsorption kinetics of Pb(II) by TNs-24 followed the pseudo-second-order model, and the equilibrium data was best fitted with the Langmuir isotherm model. The equilibrium adsorption time of TNs-24 was 120 min, and the adsorption was an exothermic process, with a high adsorption capacity at low temperature or room temperature; the optimal adsorption pH was 5.0. When pH was 1.0, the desorption rate of TNs-24 could reach 99.00%, and the removal efficiency of Pb(II) by regenerated TNs was still more than 97% after six times of usage. Therefore, TNs could efficiently remove Pb(II) in aqueous solutions, and the optimal reaction time should be controlled to 12-24 h. When Cd(II) or Ni(II) existed in the solution, the equilibrium adsorption capacity and removal rate of TNs-24 were decreased. The adsorption mechanism was mainly ion-exchanged between Pb(II) and H+/Na+ in TNs. PMID:27363159

  4. Action and Perception Are Temporally Coupled by a Common Mechanism That Leads to a Timing Misperception

    PubMed Central

    Astefanoaei, Corina; Daye, Pierre M.; FitzGibbon, Edmond J.; Creanga, Dorina-Emilia; Rufa, Alessandra; Optican, Lance M.

    2015-01-01

    We move our eyes to explore the world, but visual areas determining where to look next (action) are different from those determining what we are seeing (perception). Whether, or how, action and perception are temporally coordinated is not known. The preparation time course of an action (e.g., a saccade) has been widely studied with the gap/overlap paradigm with temporal asynchronies (TA) between peripheral target onset and fixation point offset (gap, synchronous, or overlap). However, whether the subjects perceive the gap or overlap, and when they perceive it, has not been studied. We adapted the gap/overlap paradigm to study the temporal coupling of action and perception. Human subjects made saccades to targets with different TAs with respect to fixation point offset and reported whether they perceived the stimuli as separated by a gap or overlapped in time. Both saccadic and perceptual report reaction times changed in the same way as a function of TA. The TA dependencies of the time change for action and perception were very similar, suggesting a common neural substrate. Unexpectedly, in the perceptual task, subjects misperceived lights overlapping by less than ∼100 ms as separated in time (overlap seen as gap). We present an attention-perception model with a map of prominence in the superior colliculus that modulates the stimulus signal's effectiveness in the action and perception pathways. This common source of modulation determines how competition between stimuli is resolved, causes the TA dependence of action and perception to be the same, and causes the misperception. PMID:25632126

  5. Cascading time evolution of dissipative structures leading to unique crystalline textures

    PubMed Central

    Hashimoto, Takeji; Murase, Hiroki

    2015-01-01

    This article reports unique pattern formation processes and mechanisms via crystallization of materials under external flow fields as one of the general problems of open nonequilibrium phenomena in statistical physics. The external fields effectively reduce step-by-step the exceedingly large free energy barriers associated with the reduction of the enormously large entropy necessary for crystallization into unique crystalline textures in the absence of the fields. The cascading reduction of the free energy barrier was discovered to be achieved as a consequence of a cascading evolution of a series of dissipative structures. Moreover, this cascading pattern evolution obeys the Ginzburg–Landau law. It first evolves a series of large-length-scale amorphous precursors driven by liquid–liquid phase separation under a relatively low bulk stress and then small-length-scale structures driven by a large local stress concentrated on the heterogeneous amorphous precursors, eventually leading to the formation of unique crystalline textures which cannot be developed free from the external fields. Here the multi-length-scale heterogeneous structures developed in the amorphous precursors play a dominant role in the triggering of the crystallization in the local regions subjected to a large stress concentration even under a relatively small applied bulk stress. PMID:25610628

  6. The neuroscience of in-group bias.

    PubMed

    Molenberghs, Pascal

    2013-09-01

    Racism and in-group favoritism is prevalent in our society and has been studied in Social Psychology for a long time. Recently it has become possible to investigate the neural mechanisms that underlie these in-group biases, and hence this review will give an overview of recent developments on the topic. Rather than relying on a single brain region or network, it seems that subtle changes in neural activation across the brain, depending on the modalities involved, underlie how we divide the world into 'us' versus 'them'. These insights have important implications for our understanding of how in-group biases develop and could potentially lead to new insights on how to reduce them.

  7. Simulation of blast-induced early-time intracranial wave physics leading to traumatic brain injury.

    PubMed

    Taylor, Paul A; Ford, Corey C

    2009-06-01

    The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm3 voxels) five material model of the human head was created by segmentation of color cryosections from the Visible Human Female data set. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior, and lateral directions. Three-dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric stress within the first 2 ms of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 ms time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early-time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI. PMID:19449961

  8. How do geological sampling biases affect studies of morphological evolution in deep time? A case study of pterosaur (Reptilia: Archosauria) disparity.

    PubMed

    Butler, Richard J; Brusatte, Stephen L; Andres, Brian; Benson, Roger B J

    2012-01-01

    A fundamental contribution of paleobiology to macroevolutionary theory has been the illumination of deep time patterns of diversification. However, recent work has suggested that taxonomic diversity counts taken from the fossil record may be strongly biased by uneven spatiotemporal sampling. Although morphological diversity (disparity) is also frequently used to examine evolutionary radiations, no empirical work has yet addressed how disparity might be affected by uneven fossil record sampling. Here, we use pterosaurs (Mesozoic flying reptiles) as an exemplar group to address this problem. We calculate multiple disparity metrics based upon a comprehensive anatomical dataset including a novel phylogenetic correction for missing data, statistically compare these metrics to four geological sampling proxies, and use multiple regression modeling to assess the importance of uneven sampling and exceptional fossil deposits (Lagerstätten). We find that range-based disparity metrics are strongly affected by uneven fossil record sampling, and should therefore be interpreted cautiously. The robustness of variance-based metrics to sample size and geological sampling suggests that they can be more confidently interpreted as reflecting true biological signals. In addition, our results highlight the problem of high levels of missing data for disparity analyses, indicating a pressing need for more theoretical and empirical work.

  9. Lead Slowing-Down Spectrometry Time Spectral Analysis for Spent Fuel Assay: FY11 Status Report

    SciTech Connect

    Kulisek, Jonathan A.; Anderson, Kevin K.; Bowyer, Sonya M.; Casella, Andrew M.; Gesh, Christopher J.; Warren, Glen A.

    2011-09-30

    Developing a method for the accurate, direct, and independent assay of the fissile isotopes in bulk materials (such as used fuel) from next-generation domestic nuclear fuel cycles is a goal of the Office of Nuclear Energy, Fuel Cycle R&D, Material Protection and Control Technology (MPACT) Campaign. To meet this goal, MPACT supports a multi-institutional collaboration, of which PNNL is a part, to study the feasibility of Lead Slowing Down Spectroscopy (LSDS). This technique is an active nondestructive assay method that has the potential to provide independent, direct measurement of Pu and U isotopic masses in used fuel with an uncertainty considerably lower than the approximately 10% typical of today's confirmatory assay methods. This document is a progress report for FY2011 PNNL analysis and algorithm development. Progress made by PNNL in FY2011 continues to indicate the promise of LSDS analysis and algorithms applied to used fuel. PNNL developed an empirical model based on calibration of the LSDS to responses generated from well-characterized used fuel. The empirical model, which accounts for self-shielding effects using empirical basis vectors calculated from the singular value decomposition (SVD) of a matrix containing the true self-shielding functions of the used fuel assembly models. The potential for the direct and independent assay of the sum of the masses of 239Pu and 241Pu to within approximately 3% over a wide used fuel parameter space was demonstrated. Also, in FY2011, PNNL continued to develop an analytical model. Such efforts included the addition of six more non-fissile absorbers in the analytical shielding function and the non-uniformity of the neutron flux across the LSDS assay chamber. A hybrid analytical-empirical approach was developed to determine the mass of total Pu (sum of the masses of 239Pu, 240Pu, and 241Pu), which is an important quantity in safeguards. Results using this hybrid method were of approximately the same accuracy as the pure

  10. Dilaton-derived quintessence scenario leading naturally to the late-time acceleration of the Universe

    NASA Astrophysics Data System (ADS)

    Bean, R.; Magueijo, J.

    2001-09-01

    Quintessence scenarios provide a simple explanation for the observed acceleration of the Universe. Yet, explaining why acceleration did not start a long time ago remains a challenge. The idea that the transition from radiation to matter domination played a dynamical role in triggering acceleration has been put forward in various guises. We propose a simple dilaton-derived quintessence model in which temporary vacuum domination is naturally triggered by the radiation to matter transition. In this model Einstein's gravity is preserved but quintessence couples non-minimally to the cold dark matter, but not to ``visible'' matter. Such couplings have been attributed to the dilaton in the low-energy limit of string theory beyond tree level. We also show how a cosmological constant in the string frame translates into a quintessence-type of potential in the atomic frame.

  11. Effects of rest time on discharge response and equivalent circuit model for a lead-acid battery

    NASA Astrophysics Data System (ADS)

    Devarakonda, Lalitha; Hu, Tingshu

    2015-05-01

    This work carries out a detailed investigation on the effects of rest time on the discharge response and the parameters of the Thevenin's equivalent circuit model for a lead acid battery. Traditional methods for battery modeling require a long rest time before a discharging test so that a steady state is reached for the open circuit voltage. In a recent work, we developed an algebraic method for parameter identification of circuit models for batteries by applying discharging tests after variable and possibly very short rest time. This new method opens a door to the understanding of the effects of rest time on battery behavior, which may be used for better simulation, analysis and design of battery powered systems for improved battery efficiency and state of health. As we used the new method to extract circuit parameters after different rest times, we observed some unexpected results on the relationship between the rest time and circuit parameters. The initial voltages on the capacitors can be negative and becomes more negative as the rest time is increased. We also observed that the time constants increase with rest time. Relationships between rest time and other parameters are also reported in this paper.

  12. Robust design of (s, S) inventory policy parameters in supply chains with demand and lead time uncertainties

    NASA Astrophysics Data System (ADS)

    Karimi Movahed, Kamran; Zhang, Zhi-Hai

    2015-09-01

    Demand and lead time uncertainties have significant effects on supply chain behaviour. In this paper, we present a single-product three-level multi-period supply chain with uncertain demands and lead times by using robust techniques to study the managerial insights of the supply chain inventory system under uncertainty. We formulate this problem as a robust mixed-integer linear program with minimised expected cost and total cost variation to determine the optimal (s, S) values of the inventory parameters. Several numerical studies are performed to investigate the supply chain behaviour. Useful guidelines for the design of a robust supply chain are also provided. Results show that the order variance and the expected cost in a supply chain significantly increase when the manufacturer's review period is an integer ratio of the distributor's and the retailer's review periods.

  13. Open source and healthcare in Europe - time to put leading edge ideas into practice.

    PubMed

    Murray, Peter J; Wright, Graham; Karopka, Thomas; Betts, Helen; Orel, Andrej

    2009-01-01

    Free/Libre and Open Source Software (FLOSS) is a process of software development, a method of licensing and a philosophy. Although FLOSS plays a significant role in several market areas, the impact in the health care arena is still limited. FLOSS is promoted as one of the most effective means for overcoming fragmentation in the health care sector and providing a basis for more efficient, timely and cost effective health care provision. The 2008 European Federation for Medical Informatics (EFMI) Special Topic Conference (STC) explored a range of current and future issues related to FLOSS in healthcare (FLOSS-HC). In particular, there was a focus on health records, ubiquitous computing, knowledge sharing, and current and future applications. Discussions resulted in a list of main barriers and challenges for use of FLOSS-HC. Based on the outputs of this event, the 2004 Open Steps events and subsequent workshops at OSEHC2009 and Med-e-Tel 2009, a four-step strategy has been proposed for FLOSS-HC: 1) a FLOSS-HC inventory; 2) a FLOSS-HC collaboration platform, use case database and knowledge base; 3) a worldwide FLOSS-HC network; and 4) FLOSS-HC dissemination activities. The workshop will further refine this strategy and elaborate avenues for FLOSS-HC from scientific, business and end-user perspectives. To gain acceptance by different stakeholders in the health care industry, different activities have to be conducted in collaboration. The workshop will focus on the scientific challenges in developing methodologies and criteria to support FLOSS-HC in becoming a viable alternative to commercial and proprietary software development and deployment.

  14. Estimate of overdiagnosis of breast cancer due to mammography after adjustment for lead time. A service screening study in Italy

    PubMed Central

    Paci, Eugenio; Miccinesi, Guido; Puliti, Donella; Baldazzi, Paola; De Lisi, Vincenzo; Falcini, Fabio; Cirilli, Claudia; Ferretti, Stefano; Mangone, Lucia; Finarelli, Alba Carola; Rosso, Stefano; Segnan, Nereo; Stracci, Fabrizio; Traina, Adele; Tumino, Rosario; Zorzi, Manuel

    2006-01-01

    Introduction Excess of incidence rates is the expected consequence of service screening. The aim of this paper is to estimate the quota attributable to overdiagnosis in the breast cancer screening programmes in Northern and Central Italy. Methods All patients with breast cancer diagnosed between 50 and 74 years who were resident in screening areas in the six years before and five years after the start of the screening programme were included. We calculated a corrected-for-lead-time number of observed cases for each calendar year. The number of observed incident cases was reduced by the number of screen-detected cases in that year and incremented by the estimated number of screen-detected cases that would have arisen clinically in that year. Results In total we included 13,519 and 13,999 breast cancer cases diagnosed in the pre-screening and screening years, respectively. In total, the excess ratio of observed to predicted in situ and invasive cases was 36.2%. After correction for lead time the excess ratio was 4.6% (95% confidence interval 2 to 7%) and for invasive cases only it was 3.2% (95% confidence interval 1 to 6%). Conclusion The remaining excess of cancers after individual correction for lead time was lower than 5%. PMID:17147789

  15. Lead-time reduction utilizing lean tools applied to healthcare: the inpatient pharmacy at a local hospital.

    PubMed

    Al-Araidah, Omar; Momani, Amer; Khasawneh, Mohammad; Momani, Mohammed

    2010-01-01

    The healthcare arena, much like the manufacturing industry, benefits from many aspects of the Toyota lean principles. Lean thinking contributes to reducing or eliminating nonvalue-added time, money, and energy in healthcare. In this paper, we apply selected principles of lean management aiming at reducing the wasted time associated with drug dispensing at an inpatient pharmacy at a local hospital. Thorough investigation of the drug dispensing process revealed unnecessary complexities that contribute to delays in delivering medications to patients. We utilize DMAIC (Define, Measure, Analyze, Improve, Control) and 5S (Sort, Set-in-order, Shine, Standardize, Sustain) principles to identify and reduce wastes that contribute to increasing the lead-time in healthcare operations at the pharmacy understudy. The results obtained from the study revealed potential savings of > 45% in the drug dispensing cycle time. PMID:20151593

  16. Lead-time reduction utilizing lean tools applied to healthcare: the inpatient pharmacy at a local hospital.

    PubMed

    Al-Araidah, Omar; Momani, Amer; Khasawneh, Mohammad; Momani, Mohammed

    2010-01-01

    The healthcare arena, much like the manufacturing industry, benefits from many aspects of the Toyota lean principles. Lean thinking contributes to reducing or eliminating nonvalue-added time, money, and energy in healthcare. In this paper, we apply selected principles of lean management aiming at reducing the wasted time associated with drug dispensing at an inpatient pharmacy at a local hospital. Thorough investigation of the drug dispensing process revealed unnecessary complexities that contribute to delays in delivering medications to patients. We utilize DMAIC (Define, Measure, Analyze, Improve, Control) and 5S (Sort, Set-in-order, Shine, Standardize, Sustain) principles to identify and reduce wastes that contribute to increasing the lead-time in healthcare operations at the pharmacy understudy. The results obtained from the study revealed potential savings of > 45% in the drug dispensing cycle time.

  17. [Bias and confounding: pharmacoepidemiological study using administrative database].

    PubMed

    Nojiri, Shuko

    2015-01-01

    The provision of health care frequently creates digitalized data such as hospital-based electronic data, medication prescription records, and claims data collectively termed "administrative database research". The data source and analytical opportunities for study create risks that can lead to misinterpretation or bias the results. This review serves as an introduction to the concept of bias and confounding to help researchers conduct methodologically sound pharmacoepidemiologic research projects using administrative databases. Beyond general considerations for observational study, there are several unique issues related to database research that should be addressed. The risks of uninterpretable or biased results can be minimized by: providing a robust description of the data tables used; focusing on why and how they were created; measuring and reporting the accuracy of diagnostic and procedural codes used; and properly accounting for any time-dependent nature of variables. The hallmark of good research is rigorously careful analysis and interpretation. The promise for value of real world evidence using databases in medical decision making must be balanced against concerns related to observational inherited limitations for bias and confounding. Researchers should aim to avoid bias in the design of a study, adjust for confounding, and discuss the effects of residual bias on the results. PMID:26028416

  18. Bias correction of satellite precipitation products for flood forecasting application at the Upper Mahanadi River Basin in Eastern India

    NASA Astrophysics Data System (ADS)

    Beria, H.; Nanda, T., Sr.; Chatterjee, C.

    2015-12-01

    High resolution satellite precipitation products such as Tropical Rainfall Measuring Mission (TRMM), Climate Forecast System Reanalysis (CFSR), European Centre for Medium-Range Weather Forecasts (ECMWF), etc., offer a promising alternative to flood forecasting in data scarce regions. At the current state-of-art, these products cannot be used in the raw form for flood forecasting, even at smaller lead times. In the current study, these precipitation products are bias corrected using statistical techniques, such as additive and multiplicative bias corrections, and wavelet multi-resolution analysis (MRA) with India Meteorological Department (IMD) gridded precipitation product,obtained from gauge-based rainfall estimates. Neural network based rainfall-runoff modeling using these bias corrected products provide encouraging results for flood forecasting upto 48 hours lead time. We will present various statistical and graphical interpretations of catchment response to high rainfall events using both the raw and bias corrected precipitation products at different lead times.

  19. Real-Time 12-Lead High-Frequency QRS Electrocardiography for Enhanced Detection of Myocardial Ischemia and Coronary Artery Disease

    NASA Technical Reports Server (NTRS)

    Schlegel, Todd T.; Kulecz, Walter B.; DePalma, Jude L.; Feiveson, Alan H.; Wilson, John S.; Rahman, M. Atiar; Bungo, Michael W.

    2004-01-01

    Several studies have shown that diminution of the high-frequency (HF; 150-250 Hz) components present within the central portion of the QRS complex of an electrocardiogram (ECG) is a more sensitive indicator for the presence of myocardial ischemia than are changes in the ST segments of the conventional low-frequency ECG. However, until now, no device has been capable of displaying, in real time on a beat-to-beat basis, changes in these HF QRS ECG components in a continuously monitored patient. Although several software programs have been designed to acquire the HF components over the entire QRS interval, such programs have involved laborious off-line calculations and postprocessing, limiting their clinical utility. We describe a personal computer-based ECG software program developed recently at the National Aeronautics and Space Administration (NASA) that acquires, analyzes, and displays HF QRS components in each of the 12 conventional ECG leads in real time. The system also updates these signals and their related derived parameters in real time on a beat-to-beat basis for any chosen monitoring period and simultaneously displays the diagnostic information from the conventional (low-frequency) 12-lead ECG. The real-time NASA HF QRS ECG software is being evaluated currently in multiple clinical settings in North America. We describe its potential usefulness in the diagnosis of myocardial ischemia and coronary artery disease.

  20. Neonatal anoxia leads to time dependent progression of mitochondrial linked apoptosis in rat cortex and associated long term sensorimotor deficits.

    PubMed

    Samaiya, Puneet K; Narayan, Gopeshwar; Kumar, Ashok; Krishnamurthy, Sairam

    2016-08-01

    Neonatal anoxia arises due to oxygen deprivation at the time of birth and results in life long neurodevelopmental deficits and sometimes may lead to death. The present study investigated the time dependent cortical mitochondrial dysfunction linked apoptosis and related sensorimotor deficits in neonates. Neonates after 30h to birth (P2) were subjected to anoxia of two episodes (10min in each) at a time interval of 24h by passing 100% N2 into an enclosed chamber as confirmed by pulse oximetry. Sensorimotor activities like reflex latency and hanging latency were carried out 24h after last anoxic episode i.e. from P4 (day-1) and continued up to P10 (day-7). Mitochondrial dysfunction after anoxia was evident by the decrease in respiration states, respiratory control ratio (RCR), antioxidant enzyme activity but an increase in oxidative stress and lipid peroxidation and alteration in mitochondrial membrane potential (MMP) at different time points (30min, 24h and day-7). A change in expression of Bcl-2 family proteins and opening of mitochondrial transition pore (mPTP) in terms of mitochondrial swelling was observed resulting in release of cytochrome-C which further activated intrinsic (mitochondrial) pathway of apoptosis through increased expression of caspase-9/3 as confirmed by flow cytometry. In conclusion, anoxia injury leads to progressive activation of mitochondrial events leading to increase in apoptotic cell death following secondary pathological insult. Therefore, strategies in limiting mitochondrial-linked apoptosis during the secondary insult input process may be useful in treatment of long term sensorimotor deficits following anoxia. PMID:27184438

  1. Correcting for systematic biases in GCM simulations in the frequency domain

    NASA Astrophysics Data System (ADS)

    Nguyen, Ha; Mehrotra, Rajeshwar; Sharma, Ashish

    2016-07-01

    Bias correction is considered as a critical post-processing step to remove systematic errors and improve the quality of General Circulation Model (GCM) simulations before their use in climate change impact assessment applications. A majority of the bias correction approaches correct for biases either at a single time scale or at multiple pre-specified time scales. An inappropriate or insufficient selection of time scales may lead to improper or sub-optimal bias corrected outputs, especially when persistence attributes across a range of scales are of interest. In this paper, we present a new bias correction approach that works in the frequency space and is independent of specific time scales. The approach is named as frequency-based bias correction (FBC). The usefulness of the approach is demonstrated by applying it to the monthly rainfall simulations of MIROC5 GCM over Australia and comparing the results with two other approaches, namely, empirical quantile mapping and recursive nesting bias correction, in cross validation. The comparison is based on the reproduction of various observed distribution and persistence attributes. Cross-validation results indicate that the proposed approach shows similar performance in terms of reproducing the first- and second-order moments of observed precipitation time series, however, outperforms with regard to persistence attributes. The approach shows high potential for use in downscaling and other climate change impact assessment studies, especially for the planning and design of hydrologic systems that are sensitive to the characterisation of persistence in the hydrologic time series.

  2. The application of EOQ and lead time crashing cost models in material with limited life time (Case study: CN-235 Aircraft at PT Dirgantara Indonesia)

    NASA Astrophysics Data System (ADS)

    Agustina Hidayat, Yosi; Ria Kasanah, Aprilia; Yudhistira, Titah

    2016-02-01

    PT. Dirgantara Indonesia, one of State Owned Enterprises engaging in the aerospace industry, targets to control 30% of world market for light and medium sized aircraft. One type of the aircrafts produced by PT. DI every year is CN-235. Currently, the cost of material procurement reaches 50% of the total cost of production. Material has a variety of characteristics, one of which is having a lifetime. The demand characteristic of the material with expiration for the CN-235 aircraft is deterministic. PT DI does not have any scientific background for its procurement of raw material policy. In addition, there are two methods of transportation used for delivering materials, i.e. by land and air. Each method has different lead time. Inventory policies used in this research are deterministic and probabilistic. Both deterministic and probabilistic single and multi-item inventory policies have order quantity, time to order, reorder point, and lead time as decision variables. The performance indicator for this research is total inventory cost. Inventory policy using the single item EOQ and considering expiration factor inventory results in a reduction in total costs up to 69.58% and multi item results in a decrease in total costs amounted to 71.16%. Inventory policy proposal using the model of a single item by considering expiration factor and lead time crashing cost results in a decrease in total costs amounted to 71.5% and multi item results in a decrease in total costs amounted to 71.62%. Subsequently, wasted expired materials, with the proposed models have been successfully decreased to 95%.

  3. delta-biased Josephson tunnel junctions

    SciTech Connect

    Monaco, R.; Mygind, J.; Koshelets, V. P.; Dmitriev, P.

    2010-02-01

    The behavior of a long Josephson tunnel junction drastically depends on the distribution of the dc bias current. We investigate the case in which the bias current is fed in the central point of a one-dimensional junction. Such junction configuration has been recently used to detect the persistent currents circulating in a superconducting loop. Analytical and numerical results indicate that the presence of fractional vortices leads to remarkable differences from the conventional case of uniformly distributed dc bias current. The theoretical findings are supported by detailed measurements on a number of delta-biased samples having different electrical and geometrical parameters.

  4. Accuracy of sea level predictions with lead time of one week: a comparison between Prognocean and MyOcean

    NASA Astrophysics Data System (ADS)

    Swierczynska, Malgorzata; Mizinski, Bartlomiej; Niedzielski, Tomasz

    2015-04-01

    There exist several systems which produce sea level forecasts in real time, with lead times ranging from hours to two weeks in the future. One of the recently developed solutions is Prognocean, the system that has been built and implemented at the University of Wroclaw, Poland. Its main feature is that it uses simple time series models to predict sea level anomaly maps, and does it for lead times ranging from 1 to 14 days with daily update. The empirical data-based models are fitted in real time both to individual grids (polynomial-harmonic model, polynomial-harmonic model combined with autoregressive model, polynomial-harmonic model combined with threshold autoregressive model) and to numerous grids forming a spatial latitude x longitude window of 3˚ x 5˚ (polynomial-harmonic model combined with multivariate autoregressive model). Although their simplicity, the approaches have already been shown to produce sea level anomaly predictions of reasonable accuracy. However, none of the analyses targeted at the comparative study which would present the skills of the Prognocean system against a background of the performance of other systems that use physically-based models. This study aims to fill this gap by comparing Prognocean-based predictions for one week into the future with the corresponding prognoses calculated by MyOcean. The reader is provided with the objectively-calculated set of statistics, presented as maps, which describes prediction errors (mean absolute error, root mean square error, index of agreement) and prediction skills (prediction efficiency, coefficient of determination) of the two systems. The exercise enables to compare the skills of the approaches, and the gridwise comparison allows one to identify areas of superior performance of each system.

  5. Divertor bias experiments

    NASA Astrophysics Data System (ADS)

    Staebler, G. M.

    1994-06-01

    Electrical biasing of the divertor target plates has recently been implemented on several tokamaks. The results of these experiments to date will be reviewed in this paper. The bias electrode configuration is unique in each experiment. The effects of biasing on the scrape-off layer (SOL) plasma also differ. By comparing results between machines, and using theoretical models, an understanding of the basic physics of biasing begins to emerge. Divertor biasing has been demonstrated to have a strong influence on the particle and energy transport within the SOL. The ability to externally control the SOL plasma with biasing has promising applications to future tokamak reactors.

  6. Measurement of Receptor Signaling Bias.

    PubMed

    Kenakin, Terry

    2016-01-01

    G protein-coupled receptors (GPCRs) are often pleiotropically linked to numerous cellular signaling mechanisms in cells, and it is now known that many agonists differentially activate some signaling pathways at the expense of others. The mechanism for this effect is the stabilization of different active receptor states by different agonists, and it leads to varying qualities of efficacy for different agonists. Agonist bias is a powerful mechanism to amplify beneficial signals and diminish harmful signals, and thus improve the overall profile of agonist ligands. This unit describes a method to quantify agonist bias with a scale that enables medicinal chemists to amplify or reduce these effects in new molecules. The method is based on the Black/Leff operational model and yields a statistical estimate of the confidence for bias measurements. © 2016 by John Wiley & Sons, Inc. PMID:27636109

  7. Mississippi Valley-type lead-zinc deposits through geological time: Implications from recent age-dating research

    USGS Publications Warehouse

    Leach, D.L.; Bradley, D.; Lewchuk, Michael T.; Symons, David T. A.; De Marsily, G.; Brannon, J.

    2001-01-01

    Remarkable advances in age dating Mississippi Valley-type (MVT) lead-zinc deposits provide a new opportunity to understand how and where these deposits form in the Earth's crust. These dates are summarized and examined in a framework of global tectonics, paleogeography, fluid migration, and paleoclimate. Nineteen districts have been dated by paleomagnetic and/or radiometric methods. Of the districts that have both paleomagnetic and radiometric dates, only the Pine Point and East Tennessee districts have significant disagreements. This broad agreement between paleomagnetic and radiometric dates provides added confidence in the dating techniques used. The new dates confirm the direct connection between the genesis of MVT lead-zinc ores with global-scale tectonic events. The dates show that MVT deposits formed mainly during large contractional tectonic events at restricted times in the history of the Earth. Only the deposits in the Lennard Shelf of Australia and Nanisivik in Canada have dates that correspond to extensional tectonic events. The most important period for MVT genesis was the Devonian to Permian time, which corresponds to a series of intense tectonic events during the assimilation of Pangea. The second most important period for MVT genesis was Cretaceous to Tertiary time when microplate assimilation affected the western margin of North America and Africa-Eurasia. There is a notable paucity of MVT lead-zinc ore formation following the breakup of Rodinia and Pangea. Of the five MVT deposits hosted in Proterozoic rocks, only the Nanisivik deposit has been dated as Proterozoic. The contrast in abundance between SEDEX and MVT lead-zinc deposits in the Proterozoic questions the frequently suggested notion that the two types of ores share similar genetic paths. The ages of MVT deposits, when viewed with respect to the orogenic cycle in the adjacent orogen suggest that no single hydrologic model can be universally applied to the migration of the ore fluids

  8. Mississippi Valley-type lead-zinc deposits through geological time: implications from recent age-dating research

    NASA Astrophysics Data System (ADS)

    Leach, David L.; Bradley, Dwight; Lewchuk, Michael T.; Symons, David T.; de Marsily, Ghislain; Brannon, Joyce

    2001-12-01

    Remarkable advances in age dating Mississippi Valley-type (MVT) lead-zinc deposits provide a new opportunity to understand how and where these deposits form in the Earth's crust. These dates are summarized and examined in a framework of global tectonics, paleogeography, fluid migration, and paleoclimate. Nineteen districts have been dated by paleomagnetic and/or radiometric methods. Of the districts that have both paleomagnetic and radiometric dates, only the Pine Point and East Tennessee districts have significant disagreements. This broad agreement between paleomagnetic and radiometric dates provides added confidence in the dating techniques used. The new dates confirm the direct connection between the genesis of MVT lead-zinc ores with global-scale tectonic events. The dates show that MVT deposits formed mainly during large contractional tectonic events at restricted times in the history of the Earth. Only the deposits in the Lennard Shelf of Australia and Nanisivik in Canada have dates that correspond to extensional tectonic events. The most important period for MVT genesis was the Devonian to Permian time, which corresponds to a series of intense tectonic events during the assimilation of Pangea. The second most important period for MVT genesis was Cretaceous to Tertiary time when microplate assimilation affected the western margin of North America and Africa-Eurasia. There is a notable paucity of MVT lead-zinc ore formation following the breakup of Rodinia and Pangea. Of the five MVT deposits hosted in Proterozoic rocks, only the Nanisivik deposit has been dated as Proterozoic. The contrast in abundance between SEDEX and MVT lead-zinc deposits in the Proterozoic questions the frequently suggested notion that the two types of ores share similar genetic paths. The ages of MVT deposits, when viewed with respect to the orogenic cycle in the adjacent orogen suggest that no single hydrologic model can be universally applied to the migration of the ore fluids

  9. Chlorine doping reduces electron-hole recombination in lead iodide perovskites: time-domain ab initio analysis.

    PubMed

    Liu, Jin; Prezhdo, Oleg V

    2015-11-19

    Rapid development in lead halide perovskites has led to solution-processable thin film solar cells with power conversion efficiencies close to 20%. Nonradiative electron-hole recombination within perovskites has been identified as the main pathway of energy losses, competing with charge transport and limiting the efficiency. Using nonadiabatic (NA) molecular dynamics, combined with time-domain density functional theory, we show that nonradiative recombination happens faster than radiative recombination and long-range charge transfer to an acceptor material. Doping of lead iodide perovskites with chlorine atoms reduces charge recombination. On the one hand, chlorines decrease the NA coupling because they contribute little to the wave functions of the valence and conduction band edges. On the other hand, chlorines shorten coherence time because they are lighter than iodines and introduce high-frequency modes. Both factors favor longer excited-state lifetimes. The simulation shows good agreement with the available experimental data and contributes to the comprehensive understanding of electronic and vibrational dynamics in perovskites. The generated insights into design of higher-efficiency solar cells range from fundamental scientific principles, such as the role of electron-vibrational coupling and quantum coherence, to practical guidelines, such as specific suggestions for chemical doping. PMID:26505613

  10. Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: bias introduced by strong concentration gradients within the plume.

    PubMed

    Zeru, Allelign; Schäfer, Gerhard

    2005-12-01

    When only few monitoring wells are available to assess the extent and level of groundwater contamination, inversion of concentration breakthrough curves acquired during an integral pumping test can be used as an alternative quantification method. The idea is to use concentration-time series recorded during integral pumping tests through an inversion technique to estimate contaminant mass fluxes crossing a control plane. In this paper, we examine how a longitudinal concentration gradient along a contaminant plume length scale affects the estimated inversed-concentration distribution and its associated mass flux. The analytically inversed-concentration distribution at the imaginary control plane (ICP) is compared to a numerically generated concentration distribution, treating the latter one as a "real contaminant plume" characterized by the presence of a longitudinal concentration gradient. It is found that the analytically inversed-concentration can lead to overestimation or underestimation of concentration distribution values depending on the transport time period and dispersivity values. At lower dispersivity values, with shorter transport time periods, the analytically inversed-concentration distribution overestimates the "real" concentration distribution. A better fit of the estimated concentration distribution to the "real" one is observed when the transport time period increases, i.e. when the advective front has already crossed the ICP. However, for higher dispersivity values, underestimation of the real concentration distribution is observed. Deviation of the inversed-concentration distribution from the "real" one is assessed for a site-specific concentration gradient term. A concentration gradient adjusted contaminant mass flux is thus formulated to evaluate groundwater contamination levels at a given time period through an ICP. This concentration gradient ratio can indicate whether the ICP is well positioned to evaluate accurately contaminant mass fluxes

  11. Demonstrating the Correspondence Bias

    ERIC Educational Resources Information Center

    Howell, Jennifer L.; Shepperd, James A.

    2011-01-01

    Among the best-known and most robust biases in person perception is the correspondence bias--the tendency for people to make dispositional, rather than situational, attributions for an actor's behavior. The correspondence bias appears in virtually every social psychology textbook and in many introductory psychology textbooks, yet the authors'…

  12. Bias in Grading

    ERIC Educational Resources Information Center

    Malouff, John

    2008-01-01

    Bias in grading can be conscious or unconscious. The author describes different types of bias, such as those based on student attractiveness or performance in prior courses, and a variety of methods of reducing bias, including keeping students anonymous during grading and using detailed criteria for subjective grading.

  13. Real-time measurement and control of particle-number density and size of the detonation products of lead azide

    NASA Astrophysics Data System (ADS)

    Tzuk, Y.; Ben-Porat, T.; Bar, I.; Rosenwaks, S.

    1994-07-01

    Time-resolved measurement and modeling of the number density and size of lead particles produced following the detonation of Lead Azide (LA) are presented. Particles expanding freely into vacuum through a supersonic nozzle or interacting with a barrier placed above the LA sample are monitored via attenuation of laser beams at 0.67, 1.3 and 10.6 µm. The attenuation depends on the conditions of expansion, but is always much more pronounced at 0.67 µm and 1.3 µm. From the ratio between the attenuations at 0.67 µm and 10.6 µm, the radius and number density of the particles are calculated applying Beer's law and Mie's theory. It is found that 20 90 µs following the detonation the attenuation at 32 36 mm above the LA sample is due to particles with radii of ≈0.9, ≈0.7 and ≈0.1 µm for free expansion into vacuum through the nozzle or near the barrier, respectively. Also, the expansion through the nozzle results in a transparent medium above the nozzle exit for the first few µs following the detonation. The effect of the nozzle is attributed to the fact that the velocity of the expanding detonation products is supersonic, which leads to compression and heating in the throat region, in contrast to the more familiar phenomenon of cooling at subsonic velocities. The dynamics of particles expanding under the different conditions and the mechanism of size reduction and elimination of particles is discussed.

  14. Estimation of attitude sensor timetag biases

    NASA Technical Reports Server (NTRS)

    Sedlak, J.

    1995-01-01

    This paper presents an extended Kalman filter for estimating attitude sensor timing errors. Spacecraft attitude is determined by finding the mean rotation from a set of reference vectors in inertial space to the corresponding observed vectors in the body frame. Any timing errors in the observations can lead to attitude errors if either the spacecraft is rotating or the reference vectors themselves vary with time. The state vector here consists of the attitude quaternion, timetag biases, and, optionally, gyro drift rate biases. The filter models the timetags as random walk processes: their expectation values propagate as constants and white noise contributes to their covariance. Thus, this filter is applicable to cases where the true timing errors are constant or slowly varying. The observability of the state vector is studied first through an examination of the algebraic observability condition and then through several examples with simulated star tracker timing errors. The examples use both simulated and actual flight data from the Extreme Ultraviolet Explorer (EUVE). The flight data come from times when EUVE had a constant rotation rate, while the simulated data feature large angle attitude maneuvers. The tests include cases with timetag errors on one or two sensors, both constant and time-varying, and with and without gyro bias errors. Due to EUVE's sensor geometry, the observability of the state vector is severely limited when the spacecraft rotation rate is constant. In the absence of attitude maneuvers, the state elements are highly correlated, and the state estimate is unreliable. The estimates are particularly sensitive to filter mistuning in this case. The EUVE geometry, though, is a degenerate case having coplanar sensors and rotation vector. Observability is much improved and the filter performs well when the rate is either varying or noncoplanar with the sensors, as during a slew. Even with bad geometry and constant rates, if gyro biases are

  15. Queries for Bias Testing

    NASA Technical Reports Server (NTRS)

    Gordon, Diana F.

    1992-01-01

    Selecting a good bias prior to concept learning can be difficult. Therefore, dynamic bias adjustment is becoming increasingly popular. Current dynamic bias adjustment systems, however, are limited in their ability to identify erroneous assumptions about the relationship between the bias and the target concept. Without proper diagnosis, it is difficult to identify and then remedy faulty assumptions. We have developed an approach that makes these assumptions explicit, actively tests them with queries to an oracle, and adjusts the bias based on the test results.

  16. New Trends in Magnetic Exchange Bias

    NASA Astrophysics Data System (ADS)

    Mougin, Alexandra; Mangin, Stéphane; Bobo, Jean-Francois; Loidl, Alois

    2005-05-01

    of the constituant layers. The spirit of this topical issue is, for the first time, to gather and survey recent and original developments, both experimental and theoretical, which bring new insights into the physics of exchange bias. It has been planned in relation with an international workshop exclusively devoted to exchange bias, namely IWEBMN’04 (International Workshop on Exchange Bias in Magnetic Nanostructures) that took place in Anglet, in the south west of France, from 16th to 18th September 2004. The conference gathered worldwide researchers in the area, both experimentalists and theoreticians. Several research paths are particularly active in the field of magnetic exchange coupling. The conference, as well as this topical issue, which was also open to contributions from scientists not participating in the conference, has been organized according to the following principles: 1. Epitaxial systems: Since the essential behavior of exchange bias critically depends on the atomic-level chemical and spin structure at the interface between the ferromagnetic and antiferromagnetic components, epitaxial AF/F systems in which the quality of the interface and the crystalline coherence are optimized and well known are ideal candidates for a better understanding of the underlying physics of exchange bias. The dependence of exchange bias on the spin configurations at the interfaces can be accomplished by selecting different crystallographic orientations. The role of interface roughness can also be understood from thin-film systems by changing the growth parameters, and correlations between the interface structure and exchange bias can be made, as reported in this issue. 2. Out-of-plane magnetized systems: While much important work has been devoted to the study of structures with in-plane magnetization, little has been done on the study of exchange bias and exchange coupling in samples with out-of-plane magnetization. Some systems can exhibit either in-plane or out

  17. The Impact of Weather Forecasts of Various Lead Times on Snowmaking Decisions Made for the 2010 Vancouver Olympic Winter Games

    NASA Astrophysics Data System (ADS)

    Doyle, Chris

    2014-01-01

    The Vancouver 2010 Winter Olympics were held from 12 to 28 February 2010, and the Paralympic events followed 2 weeks later. During the Games, the weather posed a grave threat to the viability of one venue and created significant complications for the event schedule at others. Forecasts of weather with lead times ranging from minutes to days helped organizers minimize disruptions to sporting events and helped ensure all medal events were successfully completed. Of comparable importance, however, were the scenarios and forecasts of probable weather for the winter in advance of the Games. Forecasts of mild conditions at the time of the Games helped the Games' organizers mitigate what would have been very serious potential consequences for at least one venue. Snowmaking was one strategy employed well in advance of the Games to prepare for the expected conditions. This short study will focus on how operational decisions were made by the Games' organizers on the basis of both climatological and snowmaking forecasts during the pre-Games winter. An attempt will be made to quantify, economically, the value of some of the snowmaking forecasts made for the Games' operators. The results obtained indicate that although the economic value of the snowmaking forecast was difficult to determine, the Games' organizers valued the forecast information greatly. This suggests that further development of probabilistic forecasts for applications like pre-Games snowmaking would be worthwhile.

  18. Decomposing bias in different types of simple decisions.

    PubMed

    White, Corey N; Poldrack, Russell A

    2014-03-01

    The ability to adjust bias, or preference for an option, allows for great behavioral flexibility. Decision bias is also important for understanding cognition as it can provide useful information about underlying cognitive processes. Previous work suggests that bias can be adjusted in 2 primary ways: by adjusting how the stimulus under consideration is processed, or by adjusting how the response is prepared. The present study explored the experimental, behavioral, and theoretical distinctions between these biases. Different bias manipulations were employed in parallel across perceptual and memory-based decisions to assess the generality of the 2 biases. This is the 1st study to directly test whether conceptually similar bias instructions can induce dissociable bias effects across different decision tasks. The results show that stimulus and response biases can be separately induced in both tasks, suggesting that the biases generalize across different types of decisions. When analyzing behavioral data, the 2 biases can be differentiated by focusing on the time course of bias effects and/or by fitting choice reaction time models to the data. These findings have strong theoretical implications about how observed bias relates to underlying cognitive processes and how it should be used when testing cognitive theories. Guidelines are presented to help researchers identify how to induce the biases experimentally, how to dissociate them in the behavioral data, and how to quantify them using drift diffusion models. Because decision bias is pervasive across many domains of cognitive science, these guidelines can be useful for future work exploring decision bias and choice preferences.

  19. [Appositional rate of incisor dentin and hematic calcium level in rats. Application of time marking method using lead acetate].

    PubMed

    Matsumoto, S

    1990-12-01

    Matsumoto et al. have reported that the remineralization of rat incisor dentin following administration of various drugs depends upon the hematic calcium (hCa) level in parathyroidectomized (PTX) rats. It is known that injected lead according to a time marking method deposits at the mineralizing front in hard tissues. In the present study, we observed the alteration of the mineralizing front of the incisor dentin and examined the dependency of the dentin remineralization on the hCa level in PTX rats given 1,25 (OH)2D3. Male Wistar rats (7-8 weeks old) were used. They were fed a synthetic diet containing 0.3% Ca or 0.02% Ca (Ca-deficient) from 3 days before PTX. In order to mark the time in the incisor dentin, lead acetate was injected at 3 day intervals. Exp. I: A group of rats fed a diet containing 0.3% Ca was given a single injection (400 ng/kg) of 1,25 (OH)2D3 on the 9th day after PTX. Exp. II: four groups of rats were given daily injections of various doses (vehicle, 25, 50 and 100 ng/kg) of 1,25 (OH)2D3 from the 11th day after PTX for 13 days. The distance between the two lead-lines observed in the histological sections of the incisor was measured as an indicator of the appositional rate of dentin. In rats given a diet containing Ca below 0.3%, the hCa level was about 5 mg/dl after PTX. Mineralization of the incisor dentin was suppressed markedly, and a hematoxylin unstained zone was observed in the histological sections, indicating that the mineralizing front had been stagnant. In Exp I, a high dosage of 1,25 (OH)2D3 raised the hCa level to over 8 mg/dl within 12 hours; formation of a new mineralizing front and remineralization of the dentin were observed. In Exp. II, daily injections of 1.25 (OH)2D3 raised the hCa levels gradually and dose dependently. The hCa levels in groups of rats given 50 and 100 ng/kg of 1,25 (OH)2D3 were over 8 and 10 mg/dl respectively after the 6th day from the beginning of the drug administrations. The distance between the two lead

  20. TYPE Ia SUPERNOVA DISTANCE MODULUS BIAS AND DISPERSION FROM K-CORRECTION ERRORS: A DIRECT MEASUREMENT USING LIGHT CURVE FITS TO OBSERVED SPECTRAL TIME SERIES

    SciTech Connect

    Saunders, C.; Aldering, G.; Aragon, C.; Bailey, S.; Childress, M.; Fakhouri, H. K.; Kim, A. G.; Antilogus, P.; Bongard, S.; Canto, A.; Cellier-Holzem, F.; Guy, J.; Baltay, C.; Buton, C.; Chotard, N.; Copin, Y.; Gangler, E.; and others

    2015-02-10

    We estimate systematic errors due to K-corrections in standard photometric analyses of high-redshift Type Ia supernovae. Errors due to K-correction occur when the spectral template model underlying the light curve fitter poorly represents the actual supernova spectral energy distribution, meaning that the distance modulus cannot be recovered accurately. In order to quantify this effect, synthetic photometry is performed on artificially redshifted spectrophotometric data from 119 low-redshift supernovae from the Nearby Supernova Factory, and the resulting light curves are fit with a conventional light curve fitter. We measure the variation in the standardized magnitude that would be fit for a given supernova if located at a range of redshifts and observed with various filter sets corresponding to current and future supernova surveys. We find significant variation in the measurements of the same supernovae placed at different redshifts regardless of filters used, which causes dispersion greater than ∼0.05 mag for measurements of photometry using the Sloan-like filters and a bias that corresponds to a 0.03 shift in w when applied to an outside data set. To test the result of a shift in supernova population or environment at higher redshifts, we repeat our calculations with the addition of a reweighting of the supernovae as a function of redshift and find that this strongly affects the results and would have repercussions for cosmology. We discuss possible methods to reduce the contribution of the K-correction bias and uncertainty.

  1. Interpretation biases in paranoia.

    PubMed

    Savulich, George; Freeman, Daniel; Shergill, Sukhi; Yiend, Jenny

    2015-01-01

    Information in the environment is frequently ambiguous in meaning. Emotional ambiguity, such as the stare of a stranger, or the scream of a child, encompasses possible good or bad emotional consequences. Those with elevated vulnerability to affective disorders tend to interpret such material more negatively than those without, a phenomenon known as "negative interpretation bias." In this study we examined the relationship between vulnerability to psychosis, measured by trait paranoia, and interpretation bias. One set of material permitted broadly positive/negative (valenced) interpretations, while another allowed more or less paranoid interpretations, allowing us to also investigate the content specificity of interpretation biases associated with paranoia. Regression analyses (n=70) revealed that trait paranoia, trait anxiety, and cognitive inflexibility predicted paranoid interpretation bias, whereas trait anxiety and cognitive inflexibility predicted negative interpretation bias. In a group comparison those with high levels of trait paranoia were negatively biased in their interpretations of ambiguous information relative to those with low trait paranoia, and this effect was most pronounced for material directly related to paranoid concerns. Together these data suggest that a negative interpretation bias occurs in those with elevated vulnerability to paranoia, and that this bias may be strongest for material matching paranoid beliefs. We conclude that content-specific biases may be important in the cause and maintenance of paranoid symptoms.

  2. Real time analysis of lead-containing atmospheric particles in Beijing during springtime by single particle aerosol mass spectrometry.

    PubMed

    Ma, Li; Li, Mei; Huang, Zhengxu; Li, Lei; Gao, Wei; Nian, Huiqing; Zou, Lilin; Fu, Zhong; Gao, Jian; Chai, Fahe; Zhou, Zhen

    2016-07-01

    Using a single particle aerosol mass spectrometer (SPAMS), the chemical composition and size distributions of lead (Pb)-containing particles with diameter from 0.1 μm to 2.0 μm in Beijing were analyzed in the spring of 2011 during clear, hazy, and dusty days. Based on mass spectral features of particles, cluster analysis was applied to Pb-containing particles, and six major classes were acquired consisting of K-rich, carboneous, Fe-rich, dust, Pb-rich, and Cl-rich particles. Pb-containing particles accounted for 4.2-5.3%, 21.8-22.7%, and 3.2% of total particle number during clear, hazy and dusty days, respectively. K-rich particles are a major contribution to Pb-containing particles, varying from 30.8% to 82.1% of total number of Pb-containing particles, lowest during dusty days and highest during hazy days. The results reflect that the chemical composition and amount of Pb-containing particles has been affected by meteorological conditions as well as the emissions of natural and anthropogenic sources. K-rich particles and carbonaceous particles could be mainly assigned to the emissions of coal combustion. Other classes of Pb-containing particles may be associated with metallurgical processes, coal combustion, dust, and waste incineration etc. In addition, Pb-containing particles during dusty days were first time studied by SPAMS. This method could provide a powerful tool for monitoring and controlling of Pb pollution in real time.

  3. Time-Spectral Analysis Methods for Spent Fuel Assay Using Lead Slowing-Down Spectroscopy of Spent Fuel

    SciTech Connect

    Smith, Leon E.; Anderson, Kevin K.; Ressler, Jennifer J.; Shaver, Mark W.

    2010-08-08

    Nondestructive techniques for measuring the mass of fissile isotopes in spent nuclear fuel is a considerable challenge in the safeguarding of nuclear fuel cycles. A nondestructive assay technology that could provide direct measurement of fissile mass, particularly for the plutonium (Pu) isotopes, and improve upon the uncertainty of today’s confirmatory methods is needed. Lead slowing-down spectroscopy (LSDS) has been studied for the spent fuel application previously, but the nonlinear effects of assembly self shielding (of the interrogating neutron population) have led to discouraging assay accuracy for realistic pressurized water reactor fuels. In this paper, we describe the development of time-spectral analysis algorithms for LSDS intended to overcome these self-shielding effects. The algorithm incorporates the tabulated energy-dependent cross sections from key fissile and absorbing isotopes, but leaves their mass as free variables. Multi-parameter regression analysis is then used to directly calculate not only the mass of fissile isotopes in the fuel assembly (e.g., Pu-239, U-235, and Pu-241), but also the mass of key absorbing isotopes such as Pu-240 and U-238. Modeling-based assay results using a first-order self-shielding relationship indicate that LSDS has the potential to directly measure fissile isotopes with less than 5% average relative error, over a wide fuel burnup range. Shortcomings in the first-order self-shielding model and methods to improve the formulation are described.

  4. Quantifying Biogenic Bias in Screening Libraries

    PubMed Central

    Hert, Jérôme; Irwin, John J.; Laggner, Christian; Keiser, Michael J.; Shoichet, Brian K.

    2009-01-01

    In lead discovery, libraries of 106 molecules are screened for biological activity. Given the over 1060 drug-like molecules thought possible, such screens might never succeed. That they do, even occasionally, implies a biased selection of library molecules. Here a method is developed to quantify the bias in screening libraries towards biogenic molecules. With this approach, we consider what is missing from screening libraries and how they can be optimized. PMID:19483698

  5. Biases in southern hemisphere climate trends induced by coarsely specifying the temporal resolution of stratospheric ozone

    NASA Astrophysics Data System (ADS)

    Neely, R. R.; Marsh, D. R.; Smith, K. L.; Davis, S. M.; Polvani, L. M.

    2014-12-01

    Global climate models that do not include interactive middle atmosphere chemistry, such as most of those contributing to the Coupled Model Intercomparison Project Phase 5, typically specify stratospheric ozone using monthly mean, zonal mean values and linearly interpolate to the time resolution of the model. We show that this method leads to significant biases in the simulated climate of the southern hemisphere (SH) over the late twentieth century. Previous studies have attributed similar biases in simulated SH climate change to the effect of the spatial smoothing of the specified ozone, i.e., to using zonal mean concentrations. We here show that the bias in climate trends due to undersampling of the rapid temporal changes in ozone during the seasonal evolution of the Antarctic ozone hole is considerable and reaches all the way into the troposphere. Our results suggest that the bias can be substantially reduced by specifying daily ozone concentrations.

  6. Political bias is tenacious.

    PubMed

    Ditto, Peter H; Wojcik, Sean P; Chen, Eric Evan; Grady, Rebecca Hofstein; Ringel, Megan M

    2015-01-01

    Duarte et al. are right to worry about political bias in social psychology but they underestimate the ease of correcting it. Both liberals and conservatives show partisan bias that often worsens with cognitive sophistication. More non-liberals in social psychology is unlikely to speed our convergence upon the truth, although it may broaden the questions we ask and the data we collect.

  7. Investigating Test Bias.

    ERIC Educational Resources Information Center

    Hoepfner, Ralph; Strickland, Guy P.

    This study investigates the question of test bias to develop an index of the appropriateness of a test to a particular socioeconomic or racial-ethnic group. Bias is defined as an item by race interaction in an analysis-of-variance design. The sample of 172 third graders at two integrated schools in a large California school district, included 26…

  8. Sampler bias -- Phase 1

    SciTech Connect

    Blanchard, R.J.

    1995-03-07

    This documents Phase 1 determinations on sampler induced bias for four sampler types used in tank characterization. Each sampler, grab sampler or bottle-on-a-string, auger sampler, sludge sampler and universal sampler, is briefly discussed and their physical limits noted. Phase 2 of this document will define additional testing and analysis to further define Sampler Bias.

  9. Exploration and comparison of the pre-impact lead time of active and passive falls based on inertial sensors.

    PubMed

    Liang, Ding; Ivanov, Kamen; Li, Huiqi; Ning, Yunkun; Zhang, Qi; Wang, Lei; Zhao, Guoru

    2014-01-01

    Research on falls in elderly people has a great social significance because of the rapidly growing of the aging population. The pre-impact lead time of fall (PLT) is an important part of the human fall theory. PLT is the longest time for a person who is going to fall to take action in order to prevent the fall or to reduce bodily injuries from the fall impact. However, there is no clear definition of PLT so far. There is also no comparative study for active and passive falls. In this study, we proposed a theoretical definition of the PLT, based on a new method of fall event division. We also compared the differences of PLT and the related angles between active and passive falls. Eight healthy adult subjects were arranged to perform three kinds of activities of daily living (sitting, walking and lying), and two kinds fall activities (active and passive) in three directions (forward, backward and lateral fall). Nine inertial sensor modules were used to measure the body segmental kinematic characteristics of each subject in our experimental activities. In this paper, a fall event was suggested to divide into three or four phases and then the critical phase could be divided into three periods (pre-impact, impact, and post-impact). Two fall models were developed for active and passive falls using acceleration data. The average value of PLT for active falls is about 514 ± 112 ms and it is smaller than the value for passive falls, which is 731 ± 104 ms. The longest PLTs were measured on the chest or waist instead of other locations, such as the thigh and shank. The PLTs of the three kinds of fall activities were slightly different, but there was a significant difference between two fall modes. The PLT showed the correlation to the body angle at the start of PLT, but it was uncorrelated at the end of PLT. The angles at the start of PLT had slight variations (<10 degrees) from the steady standing state except in passive forward falls (max 16 degrees) due to the self

  10. Self regulating body bias generator

    NASA Technical Reports Server (NTRS)

    Hass, Kenneth (Inventor)

    2004-01-01

    The back bias voltage on a functional circuit is controlled through a closed loop process. A delay element receives a clock pulse and produces a delay output. The delay element is advantageously constructed of the same materials as the functional circuit so that the aging and degradation of the delay element parallels the degradation of the functional circuit. As the delay element degrades, the transistor switching time increases, increasing the time delay of the delay output. An AND gate compares a clock pulse to an output pulse of the delay element, the AND output forming a control pulse. A duty cycle of the control pulse is determined by the delay time between the clock pulse and the delay element output. The control pulse is received at the input of a charge pump. The charge pump produces a back bias voltage which is then applied to the delay element and to the functional circuit. If the time delay produced by the delay element exceeds the optimal delay, the duty cycle of the control pulse is shortened, and the back bias voltage is lowered, thereby increasing the switching speed of the transistors in the delay element and reducing the time delay. If the throughput of the delay element is too fast, the duty cycle of the control pulse is lengthened, raising the back bias voltage produced by the charge pump. This, in turn, lowers the switching speed of the transistors in both the delay element and the functional circuit. The slower switching speed in the delay element increases time delay. In this manner, the switching speed of the delay element, and of the functional circuit, is maintained at a constant level over the life of the circuit.

  11. Integrated bias removal in passive radar systems

    NASA Astrophysics Data System (ADS)

    Subramaniam, M.; Punithakumar, K.; McDonald, M.; Kirubarajan, T.

    2008-04-01

    A passive coherent location (PCL) system exploits the ambient FM radio or television signals from powerful local transmitters, which makes it ideal for covert tracking. In a passive radar system, also known as PCL system, a variety of measurements can be used to estimate target states such as direction of arrival (DOA), time difference of arrival (TDOA) or Doppler shift. Noise and the precision of DOA estimation are main issues in a PCL system and methods such as conventional beam forming (CBF) algorithm, algebraic constant modulus algorithm (ACMA) are widely analyzed in literature to address them. In practical systems, although it is necessary to reduce the directional ambiguities, the placement of receivers closed to each other results in larger bias in the estimation of DOA of signals, especially when the targets move off bore-sight. This phenomenon leads to degradation in the performance of the tracking algorithm. In this paper, we present a method for removing the bias in DOA to alleviate the aforementioned problem. The simulation results are presented to show the effectiveness of the proposed algorithm with an example of tracking airborne targets.

  12. Political Bias and Nonpolitical News: A Content Analysis of an Armenian and Iranian Earthquake in the "New York Times" and the "Washington Post."

    ERIC Educational Resources Information Center

    Keshishian, Flora

    1997-01-01

    Examines coverage in two leading United States newspapers of earthquakes in Armenia and Iran. Finds that the newspapers' reportage was more sympathetic (both in the amount and language of coverage) toward Armenia/Soviet Union with whom the United States had friendly relations, than to the earthquake in Iran, a country on unfriendly terms with the…

  13. Biased predecision processing.

    PubMed

    Brownstein, Aaron L

    2003-07-01

    Decision makers conduct biased predecision processing when they restructure their mental representation of the decision environment to favor one alternative before making their choice. The question of whether biased predecision processing occurs has been controversial since L. Festinger (1957) maintained that it does not occur. The author reviews relevant research in sections on theories of cognitive dissonance, decision conflict, choice certainty, action control, action phases, dominance structuring, differentiation and consolidation, constructive processing, motivated reasoning, and groupthink. Some studies did not find evidence of biased predecision processing, but many did. In the Discussion section, the moderators are summarized and used to assess the theories. PMID:12848220

  14. Investigating the mechanisms of seasonal ENSO phase locking bias in the ACCESS coupled model

    NASA Astrophysics Data System (ADS)

    Rashid, Harun A.; Hirst, Anthony C.

    2016-02-01

    The mechanisms of coupled model bias in seasonal ENSO phase locking are investigated using versions 1.0 and 1.3 of the CSIRO-BOM ACCESS coupled model (hereafter, ACCESS1.0 and ACCESS1.3, respectively). The two ACCESS coupled models are mostly similar in construction except for some differences, the most notable of which are in the cloud and land surface schemes used in the models. ACCESS1.0 simulates a realistic seasonal phase locking, with the ENSO variability peaking in December as in observations. On the other hand, the simulated ENSO variability in ACCESS1.3 peaks in March, a bias shown to be shared by many other CMIP5 models. To explore the mechanisms of this model bias, we contrast the atmosphere-ocean feedbacks associated with ENSO in both ACCESS model simulations and also compare the key feedbacks with those in other CMIP5 models. We find evidence that the ENSO phase locking bias in ACCESS1.3 is primarily caused by incorrect simulations of the shortwave feedback and the thermocline feedback in this model. The bias in the shortwave feedback is brought about by unrealistic SST-cloud interactions leading to a positive cloud feedback bias that is largest around March, in contrast to the strongest negative cloud feedback found in ACCESS1.0 simulations and observations at that time. The positive cloud feedback bias in ACCESS1.3 is the result of a dominant role played by the low-level clouds in its modeled SST-cloud interactions in the tropical eastern Pacific. Two factors appear to contribute to the dominance of low-level clouds in ACCESS1.3: the occurrence of a stronger mean descending motion bias and, to a lesser extent, a larger mean SST cold bias during March-April in ACCESS1.3 than in ACCESS1.0. A similar association is found between the positive cloud feedback bias and the biases in spring-time mean descending motion and SST for a group of CMIP5 models that show a seasonal phase locking bias similar to ACCESS1.3. Significant differences are also found

  15. Officiating bias: the effect of foul differential on foul calls in NCAA basketball.

    PubMed

    Anderson, Kyle J; Pierce, David A

    2009-05-01

    In this study, we examined the pattern of foul calls exhibited during 365 NCAA basketball games during the 2004-2005 season. Results of the analysis indicate that officials are more likely to call fouls on the team with the fewest fouls, making it likely that the number of fouls will tend to even out during the game. This increased probability increases as the foul differential increases. In addition, there is a significant bias towards officials calling more fouls on the visiting team, and a bias towards foul calls on the team that is leading. The result is that the probability of the next foul being called on the visiting team can reach as high as 0.70. Finally, the implications of this officiating bias are explored, including the fact that basketball teams have an incentive to play more aggressively, leading to more physical play over time.

  16. Adaptive Variable Bias Magnetic Bearing Control

    NASA Technical Reports Server (NTRS)

    Johnson, Dexter; Brown, Gerald V.; Inman, Daniel J.

    1998-01-01

    Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. With the existence of the bias current, even in no load conditions, there is always some power consumption. In aerospace applications, power consumption becomes an important concern. In response to this concern, an alternative magnetic bearing control method, called Adaptive Variable Bias Control (AVBC), has been developed and its performance examined. The AVBC operates primarily as a proportional-derivative controller with a relatively slow, bias current dependent, time-varying gain. The AVBC is shown to reduce electrical power loss, be nominally stable, and provide control performance similar to conventional bias control. Analytical, computer simulation, and experimental results are presented in this paper.

  17. Effect of pH, empty bed contact time and hydraulic loading rate on lead removal by granular activated carbon columns

    SciTech Connect

    Reed, B.E.; Jamil, M.; Thomas, B.

    1996-07-01

    Batch and column studies were performed to determine the effect of pH, empty bed contact time (EBCT), and hydraulic loading rate (HLR) on lead removal by granular activated carbon (GAC) columns. Lead removal increased with increasing pH, and for the majority of the adsorbate:adsorbent ratios investigated, was 100% as pHs < pH{sub prec}. Column pH was extremely important to lead removal in GAC columns. A simple acid-base regeneration procedure was found to be effective in desorbing/resolubilizing the carbon-bound lead and raising the pH for the subsequent treatment run. Regeneration efficiencies were often less than 100%, but column performance was not adversely affected. For 1 mg/L lead, the optimum EBCT was between 6 and 7 minutes, Whereas for 10 mg/L lead it was less than 10 minutes. The effect of HLR (4.9 and 9.8 m/hr) on column performance was minimal for 1 mg/L lead, whereas at 10 mg/L lead column removal was slightly better at the higher HLR. Carbon usage rates were higher than those observed for wastewaters containing organic contaminants, especially at 10 mg/L lead. However, given the relatively simple regeneration scheme, the applicability of GAC columns for metal-bearing wastewaters appears to be technically feasible. 8 refs., 7 figs., 3 tabs.

  18. Elimination of the gate and drain bias stresses in I-V characteristics of WSe2 FETs by using dual channel pulse measurement

    NASA Astrophysics Data System (ADS)

    Park, Jun-Mo; Cho, In-Tak; Kang, Won-Mook; Park, Byung-Gook; Lee, Jong-Ho

    2016-08-01

    Intrinsic transfer and output characteristics of WSe2 field effect transistors are obtained by adopting the dual channel pulsed I-V measurement. Due to the DC gate bias stress during the measurement, a large hysteresis is observed and increased with increasing the sweeping range of the gate bias in the transfer curves. In addition, as a drain bias increases, the drain bias stress during the measurement induces the threshold voltage shift. The output curves measured by a DC method are significantly affected by the drain bias sweeping direction and the previous measurement, which leads to a large error in the analysis. By using the dual channel pulsed I-V measurement with a short turn-on time (10-4 s), a long turn-off time (1 s), and a base voltage (gate and drain bias during turn-off time) of 0 V, hysteretic behaviors caused by the gate bias stress and threshold voltage shift due to the drain bias stress in transfer curves are eliminated. The effect of the drain bias sweeping direction and the previous measurement in output curves are also eliminated, and the output curves show a typical field effect behavior. The intrinsic characteristics of WSe2 field effect transistors show negligible hysteresis and remarkably enhanced mobility (˜200 cm2/V s), and higher current drive capability compared to those of DC measurements.

  19. Estimating Bias Error Distributions

    NASA Technical Reports Server (NTRS)

    Liu, Tian-Shu; Finley, Tom D.

    2001-01-01

    This paper formulates the general methodology for estimating the bias error distribution of a device in a measuring domain from less accurate measurements when a minimal number of standard values (typically two values) are available. A new perspective is that the bias error distribution can be found as a solution of an intrinsic functional equation in a domain. Based on this theory, the scaling- and translation-based methods for determining the bias error distribution arc developed. These methods are virtually applicable to any device as long as the bias error distribution of the device can be sufficiently described by a power series (a polynomial) or a Fourier series in a domain. These methods have been validated through computational simulations and laboratory calibration experiments for a number of different devices.

  20. Political bias is tenacious.

    PubMed

    Ditto, Peter H; Wojcik, Sean P; Chen, Eric Evan; Grady, Rebecca Hofstein; Ringel, Megan M

    2015-01-01

    Duarte et al. are right to worry about political bias in social psychology but they underestimate the ease of correcting it. Both liberals and conservatives show partisan bias that often worsens with cognitive sophistication. More non-liberals in social psychology is unlikely to speed our convergence upon the truth, although it may broaden the questions we ask and the data we collect. PMID:26786070

  1. Eye Movements while Reading Biased Homographs: Effects of Prior Encounter and Biasing Context on Reducing the Subordinate Bias Effect

    PubMed Central

    Leinenger, Mallorie; Rayner, Keith

    2013-01-01

    Readers experience processing difficulties when reading biased homographs preceded by subordinate-biasing contexts. Attempts to overcome this processing deficit have often failed to reduce the subordinate bias effect (SBE). In the present studies, we examined the processing of biased homographs preceded by single-sentence, subordinate-biasing contexts, and varied whether this preceding context contained a prior instance of the homograph or a control word/phrase. Having previously encountered the homograph earlier in the sentence reduced the SBE for the subsequent encounter, while simply instantiating the subordinate meaning produced processing difficulty. We compared these reductions in reading times to differences in processing time between dominant-biased repeated and non-repeated conditions in order to verify that the reductions observed in the subordinate cases did not simply reflect a general repetition benefit. Our results indicate that a strong, subordinate-biasing context can interact during lexical access to overcome the activation from meaning frequency and reduce the SBE during reading. PMID:24073328

  2. Composition strand asymmetries in prokaryotic genomes: mutational bias and biased gene orientation.

    PubMed

    Lopez, P; Philippe, H

    2001-03-01

    Most prokaryotic genomes display strand compositional asymmetries, but the reasons for these biases remain unclear. When the distribution of gene orientation is biased, as it often is, this may induce a bias in composition, as codon frequencies are not identical. We show here that this effect can be estimated and removed, and that the residual base skews are the highest at third base codon positions and lower at first and second positions. This strongly suggests that compositional asymmetries result from 1) a replication-related mutational bias that is filtered through selective pressure and/or from 2) an uneven distribution of gene orientation. In most cases, the mutational bias alters the codon usage and amino acid frequencies of the leading and the lagging strand. However, these features are not ubiquitous amongst prokaryotes, and the biological reasons for them remain to be found.

  3. Over-fitting Time Series Models of Air Pollution Health Effects: Smoothing Tends to Bias Non-Null Associations Towards the Null.

    EPA Science Inventory

    Background: Simulation studies have previously demonstrated that time-series analyses using smoothing splines correctly model null health-air pollution associations. Methods: We repeatedly simulated season, meteorology and air quality for the metropolitan area of Atlanta from cyc...

  4. Inequities in the freedom to lead a flourishing and healthy life: time for a progressive social protections framework

    PubMed Central

    Carey, Gemma

    2014-01-01

    Evidence now shows that the key drivers of poor health are social factors, such as education, employment, housing and urban environments. Variations in these social factors—or the conditions in which we live our lives—have lead to a growth in health inequalities within and between countries. One of the key challenges facing those concerned with health equity is how to effect change across the broad policy areas that impact these social PMID:25279385

  5. LEAD STUDIES

    PubMed Central

    Aub, Joseph C.; Reznikoff, Paul; Smith, Dorothea E.

    1924-01-01

    It appears, from the investigations in other laboratories, that the anemia observed in cases of lead poisoning is due to destruction of blood rather than to diminished production of blood. The method of poisoning cells in vitro with lead was adopted in order to study this phenomenon, and distinct effects were thereby obtained, even when only 0.001 mg. of lead is added to approximately 5 billion washed red corpuscles. In order to obtain optimum results the usual dosage employed was ten times this or 0.01 mg. per 5 billion cells. The following changes were observed in cells so treated. 1. Such a marked increase in the resistance to hypotonic salt solution develops that complete hemolysis does not occur until the cells are exposed to a saline solution of 0.05 per cent. Untreated cells are completely hemolyzed in 0.25 or 0.225 per cent saline. 2. This reaction is quantitative and varies with the concentration of lead used. Under the conditions of our experiments this phenomenon seems to be unique. The effects of arsenic are very slight in comparison. 3. While from this reaction it may be concluded that lead increases cellular resistance, it also appears that it shortens the life of blood cells. This may be demonstrated by the much more rapid appearance of hemolysis than normal when the cells are merely allowed to stand in Ringer solution of any dilution. 4. In rabbits with acute lead poisoning these same phenomena may be noted in vivo. 5. Both phenomena may be changed in vitro by varying the time and temperature of the reaction and the concentration of lead, as Fici has already pointed out. 6. If normal cells stand in Ringer solution for 6 hours something diffuses into the solution which largely reduces the action of lead. After repeated washing these cells react with lead in the usual manner. 7. Small amounts of serum react with lead and eliminate its effects. Red blood cells, treated with a mixture of lead and blood serum, show normal hemolysis in hypotonic salt

  6. Ocean-atmosphere processes driving Indian summer monsoon biases in CFSv2 hindcasts

    NASA Astrophysics Data System (ADS)

    Narapusetty, Balachandrudu; Murtugudde, Raghu; Wang, Hui; Kumar, Arun

    2016-09-01

    This paper analyzes the role of the Indian Ocean (IO) and the atmosphere biases in generating and sustaining large-scale precipitation biases over Central India (CI) during the Indian summer monsoon (ISM) in the climate forecast system version 2 (CFSv2) hindcasts that are produced by initializing the system each month from January 1982 to March 2011. The CFSv2 hindcasts are characterized by a systematic dry monsoon bias over CI that deteriorate with forecast lead-times and coexist with a wet bias in the tropical IO suggesting a large-scale interplay between coupled ocean-atmosphere and land biases. The biases evolving from spring-initialized forecasts are analyzed in detail to understand the evolution of summer biases. The northward migration of the Inter Tropical Convergence Zone (ITCZ) that typically crosses the equator in the IO sector during April in nature is delayed in the hindcasts when the forecast system is initialized in early spring. Our analyses show that the delay in the ITCZ coexists with wind and SST biases and the associated processes project onto the seasonal evolution of the coupled ocean-atmosphere features. This delay in conjunction with the SST and the wind biases during late spring and early summer contributes to excessive precipitation over the ocean and leading to a deficit in rainfall over CI throughout the summer. Attribution of bias to a specific component in a coupled forecast system is particularly challenging as seemingly independent biases from one component affect the other components or are affected by their feedbacks. In the spring-initialized forecasts, the buildup of deeper thermocline in association with warmer SSTs due to the enhanced Ekman pumping in the southwest IO inhibits the otherwise typical northward propagation of ITCZ in the month of April. Beyond this deficiency in the forecasts, two key ocean-atmosphere coupled mechanisms are identified; one in the Arabian Sea, where a positive windstress curl bias in conjunction

  7. Comment on "Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume" by Allelign Zeru and Gerhard Schäfer.

    PubMed

    Bayer-Raich, Martí; Jarsjö, Jerker; Teutsch, Georg

    2007-03-20

    We consider the results of a recent paper in this journal [Zeru, A. and Schäfer, G., 2005. Analysis of groundwater contamination using concentration-time series recorded during an integral pumping test: Bias introduced by strong concentration gradients within the plume. Journal of Contaminant Hydrology 81 (2005) 106-124], which addresses the field-scale characterisation of contaminant plumes in groundwater. There, it is concluded that contaminant concentration gradients can bias Integral Pumping Test (IPT) interpretations considerably, in particular if IPTs are conducted in advective fronts of contaminant plumes. We discuss implications of this setting and also argue that the longitudinal and transverse dispersivities used in the examples of Zeru and Schäfer (2005) of up to 30 m and 3 m, respectively, are generally very high for the here relevant capture zone scale (<20 m). However, regardless of both longitudinal and transverse concentration gradients, we further show through a counter-example that IPT results are unbiased as long as the concentration attenuation along the flow direction is linear over the capture zone extent.

  8. Immunotherapy prolongs the serum CEA-TPA-CA15.3 lead time at the metastatic progression in endocrine-dependent breast cancer patients: a retrospective longitudinal study.

    PubMed

    Nicolini, A; Carpi, A; Ferrari, P; Rossi, G

    2008-05-01

    In metastatic breast cancer tumour markers' increase predicts, by a few months (lead time) disease progression. In breast cancer patients with endocrine dependent metastatic disease, we reported a prolonged clinical benefit and overall survival when first line conventional antiestrogen hormone therapy was started at the lead time and also when an immunotherapy schedule was added to the same conventional hormone treatment. Thirty-two of these last patients were considered (group a). In 27 (group b) of these 32 patients who progressed during first line salvage hormone plus immunotherapy the lead time at the progression of metastatic disease during therapy was compared with that at the onset of metastases when the same patients were without treatment and with that of a control group (group c) who did not receive immunotherapy. At disease progression, CEA-TPA-CA15.3 sensitivity was 92.5% in the group b (studied patients) and 88.5% in the group c (controls). At the progression in the group b, CEA-TPA-CA15.3 lead time (m+/-sd, months) was significantly longer than in group c (12.1+/-12.9 vs 2.4+/-4.0) (P=0.000). Besides, in group b the lead time was significantly longer at the progression than at the metastatic onset (P=0.003) while in the group c the difference was near to significance (P=0.05). The CEA-TPA-CA15.3 tumour marker panel accurately predicted metastatic disease progression and immunotherapy significantly prolonged the CEA-TPA-CA15.3 lead time. This can be used for anticipating salvage treatment in these patients.

  9. Where Will LEAD Lead?

    ERIC Educational Resources Information Center

    Wildman, Louis

    After setting forth eight assumptions concerning the education of educational administrators, findings about the Leadership in Educational Administration Development (LEAD) program are discussed. The analysis is based on the first-year applications, telephone conversations with staff at a majority of the project sites, and additional material…

  10. LEADING WITH LEADING INDICATORS

    SciTech Connect

    PREVETTE, S.S.

    2005-01-27

    This paper documents Fluor Hanford's use of Leading Indicators, management leadership, and statistical methodology in order to improve safe performance of work. By applying these methods, Fluor Hanford achieved a significant reduction in injury rates in 2003 and 2004, and the improvement continues today. The integration of data, leadership, and teamwork pays off with improved safety performance and credibility with the customer. The use of Statistical Process Control, Pareto Charts, and Systems Thinking and their effect on management decisions and employee involvement are discussed. Included are practical examples of choosing leading indicators. A statistically based color coded dashboard presentation system methodology is provided. These tools, management theories and methods, coupled with involved leadership and employee efforts, directly led to significant improvements in worker safety and health, and environmental protection and restoration at one of the nation's largest nuclear cleanup sites.

  11. Detecting Gender Bias through Test Item Analysis

    ERIC Educational Resources Information Center

    Gonzalez-Espada, Wilson J.

    2009-01-01

    Many physical science and physics instructors might not be trained in pedagogically appropriate test construction methods. This could lead to test items that do not measure what they are intended to measure. A subgroup of these items might show bias against some groups of students. This paper describes how the author became aware of potentially…

  12. A rich fossil record yields calibrated phylogeny for Acanthaceae (Lamiales) and evidence for marked biases in timing and directionality of intercontinental disjunctions.

    PubMed

    Tripp, Erin A; McDade, Lucinda A

    2014-09-01

    More than a decade of phylogenetic research has yielded a well-sampled, strongly supported hypothesis of relationships within the large ( > 4000 species) plant family Acanthaceae. This hypothesis points to intriguing biogeographic patterns and asymmetries in sister clade diversity but, absent a time-calibrated estimate for this evolutionary history, these patterns have remained unexplored. Here, we reconstruct divergence times within Acanthaceae using fossils as calibration points and experimenting with both fossil selection and effects of invoking a maximum age prior related to the origin of Eudicots. Contrary to earlier reports of a paucity of fossils of Lamiales (an order of ∼ 23,000 species that includes Acanthaceae) and to the expectation that a largely herbaceous to soft-wooded and tropical lineage would have few fossils, we recovered 51 reports of fossil Acanthaceae. Rigorous evaluation of these for accurate identification, quality of age assessment and utility in dating yielded eight fossils judged to merit inclusion in analyses. With nearly 10 kb of DNA sequence data, we used two sets of fossils as constraints to reconstruct divergence times. We demonstrate differences in age estimates depending on fossil selection and that enforcement of maximum age priors substantially alters estimated clade ages, especially in analyses that utilize a smaller rather than larger set of fossils. Our results suggest that long-distance dispersal events explain present-day distributions better than do Gondwanan or northern land bridge hypotheses. This biogeographical conclusion is for the most part robust to alternative calibration schemes. Our data support a minimum of 13 Old World (OW) to New World (NW) dispersal events but, intriguingly, only one in the reverse direction. Eleven of these 13 were among Acanthaceae s.s., which comprises > 90% of species diversity in the family. Remarkably, if minimum age estimates approximate true history, these 11 events occurred within

  13. Effect of bias in ferroelectric-antiferroelectric relaxation

    NASA Astrophysics Data System (ADS)

    Geday, M. A.; Medialdea, D. P.; Cerrolaza, B.; Bennis, N.; Quintana, X.; Otón, J. M.

    2009-06-01

    The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC) is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity of the AFLC, magnitude of the data pulse, and bias voltage. The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the dynamic response of the AFLC device and reduce the reset time of the waveform. In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth pattern and speed and present an extension of the previously model on order to explain the results.

  14. Optimization of Angular-Momentum Biases of Reaction Wheels

    NASA Technical Reports Server (NTRS)

    Lee, Clifford; Lee, Allan

    2008-01-01

    RBOT [RWA Bias Optimization Tool (wherein RWA signifies Reaction Wheel Assembly )] is a computer program designed for computing angular momentum biases for reaction wheels used for providing spacecraft pointing in various directions as required for scientific observations. RBOT is currently deployed to support the Cassini mission to prevent operation of reaction wheels at unsafely high speeds while minimizing time in undesirable low-speed range, where elasto-hydrodynamic lubrication films in bearings become ineffective, leading to premature bearing failure. The problem is formulated as a constrained optimization problem in which maximum wheel speed limit is a hard constraint and a cost functional that increases as speed decreases below a low-speed threshold. The optimization problem is solved using a parametric search routine known as the Nelder-Mead simplex algorithm. To increase computational efficiency for extended operation involving large quantity of data, the algorithm is designed to (1) use large time increments during intervals when spacecraft attitudes or rates of rotation are nearly stationary, (2) use sinusoidal-approximation sampling to model repeated long periods of Earth-point rolling maneuvers to reduce computational loads, and (3) utilize an efficient equation to obtain wheel-rate profiles as functions of initial wheel biases based on conservation of angular momentum (in an inertial frame) using pre-computed terms.

  15. Halo velocity bias

    NASA Astrophysics Data System (ADS)

    Biagetti, Matteo; Desjacques, Vincent; Kehagias, Alex; Riotto, Antonio

    2014-11-01

    It has been recently shown that any halo velocity bias present in the initial conditions does not decay to unity, in agreement with predictions from peak theory. However, this is at odds with the standard formalism based on the coupled-fluids approximation for the coevolution of dark matter and halos. Starting from conservation laws in phase space, we discuss why the fluid momentum conservation equation for the biased tracers needs to be modified in accordance with the change advocated in Baldauf et al. Our findings indicate that a correct description of the halo properties should properly take into account peak constraints when starting from the Vlasov-Boltzmann equation.

  16. Statistical framework for estimating GNSS bias

    NASA Astrophysics Data System (ADS)

    Vierinen, Juha; Coster, Anthea J.; Rideout, William C.; Erickson, Philip J.; Norberg, Johannes

    2016-03-01

    We present a statistical framework for estimating global navigation satellite system (GNSS) non-ionospheric differential time delay bias. The biases are estimated by examining differences of measured line-integrated electron densities (total electron content: TEC) that are scaled to equivalent vertical integrated densities. The spatiotemporal variability, instrumentation-dependent errors, and errors due to inaccurate ionospheric altitude profile assumptions are modeled as structure functions. These structure functions determine how the TEC differences are weighted in the linear least-squares minimization procedure, which is used to produce the bias estimates. A method for automatic detection and removal of outlier measurements that do not fit into a model of receiver bias is also described. The same statistical framework can be used for a single receiver station, but it also scales to a large global network of receivers. In addition to the Global Positioning System (GPS), the method is also applicable to other dual-frequency GNSS systems, such as GLONASS (Globalnaya Navigazionnaya Sputnikovaya Sistema). The use of the framework is demonstrated in practice through several examples. A specific implementation of the methods presented here is used to compute GPS receiver biases for measurements in the MIT Haystack Madrigal distributed database system. Results of the new algorithm are compared with the current MIT Haystack Observatory MAPGPS (MIT Automated Processing of GPS) bias determination algorithm. The new method is found to produce estimates of receiver bias that have reduced day-to-day variability and more consistent coincident vertical TEC values.

  17. Girl child and gender bias.

    PubMed

    Chowdhry, D P

    1995-01-01

    This article identifies gender bias against female children and youth in India. Gender bias is based on centuries-old religious beliefs and sayings from ancient times. Discrimination is reflected in denial or ignorance of female children's educational, health, nutrition, and recreational needs. Female infanticide and selective abortion of female fetuses are other forms of discrimination. The task of eliminating or reducing gender bias will involve legal, developmental, political, and administrative measures. Public awareness needs to be created. There is a need to reorient the education and health systems and to advocate for gender equality. The government of India set the following goals for the 1990s: to protect the survival of the girl child and practice safe motherhood; to develop the girl child in general; and to protect vulnerable girl children in different circumstances and in special groups. The Health Authorities should monitor the laws carefully to assure marriage after the minimum age, ban sex determination of the fetus, and monitor the health and nutrition of pre-school girls and nursing and pregnant mothers. Mothers need to be encouraged to breast feed, and to breast feed equally between genders. Every village and slum area needs a mini health center. Maternal mortality must decline. Primary health centers and hospitals need more women's wards. Education must be universally accessible. Enrollments should be increased by educating rural tribal and slum parents, reducing distances between home and school, making curriculum more relevant to girls, creating more female teachers, and providing facilities and incentives for meeting the needs of girl students. Supplementary income could be provided to families for sending girls to school. Recreational activities must be free of gender bias. Dowry, sati, and devdasi systems should be banned.

  18. Effect of a real-time tele-transmission system of 12-lead electrocardiogram on the first-aid for athletes with ST-elevation myocardial infarction.

    PubMed

    Zhang, Huan; Song, Donghan; An, Lina

    2016-05-01

    To study the effect of a real-time tele-transmission system of 12-lead electrocardiogram on door-to-balloon time in athletes with ST-elevation myocardial infarction. A total of 60 athletes with chest pain diagnosed as ST-elevation myocardial infarction (STEMI) from our hospital were randomly divided into group A (n=35) and group B (n=25), the patients in group A transmitted the real-time tele-transmission system of 12-lead electrocardiogram to the chest pain center before arriving in hospital, however, the patients in group B not. The median door-to-balloon time was significant shorter in-group A than group B (38min vs 94 min, p<0.01) and the ratio of door-to-balloon time below 90 min was remarkable higher in-group A (94.2% vs 60%, p<0.01). The rate of catheter laboratory occupied was 5.7% in-group A and 40% in group B respectively (p=0.001). There was no statistically difference in mortality between the two groups (5.7% vs 4%, p>0.05). The median length of stay was significant reduced in-group A (5 days vs 7 days, p<0.01). Real-time tele-transmission system of 12 lead electrocardiogram is beneficial to the pre-hospital diagnosis of STEMI. PMID:27383498

  19. Separating response-execution bias from decision bias: arguments for an additional parameter in Ratcliff's diffusion model.

    PubMed

    Voss, Andreas; Voss, Jochen; Klauer, Karl Christoph

    2010-11-01

    Diffusion model data analysis permits the disentangling of different processes underlying the effects of experimental manipulations. Estimates can be provided for the speed of information accumulation, for the amount of information used to draw conclusions, and for a decision bias. One parameter describes the duration of non-decisional processes including the duration of motor-response execution. In the default diffusion model, it is implicitly assumed that both responses are executed with the same speed. In some applications of the diffusion model, this assumption will be violated. This will lead to biased parameter estimates. Consequently, we suggest accounting explicitly for differences in the speed of response execution for both responses. Results from a simulation study illustrate that parameter estimates from the default model are biased if the speed of response execution differs between responses. A second simulation study shows that large trial numbers (N>1,000) are needed to detect whether differences in response-execution times are based on different execution times.

  20. Landauer Approach to Time-Dependent Transport

    NASA Astrophysics Data System (ADS)

    Chen, L. Y.; Nash, P. L.

    Based upon the nonequilibrium Green's function formalism, we present a time-dependent Landauer approach to transport through a mesoscopic system under an ac bias voltage. The system is modeled as an elastic scatterer coupled to large electron reservoirs through perfect conducting wires (leads). The chemical potentials of the reservoirs are driven apart by the bias and, consequently, current flows through the leads from one reservoir to another. We examine the nonequilibrium statistical processes of electrons in the leads. The electronic waves are quantized on the basis of orthonormal wave packets moving along the leads, scattered by the scatterer, and coupled to the reservoirs. The time for an electron to traverse the leads between the source and the drain reservoirs plus the phase delay time caused by the scatterer is found to be the relevant time scale in the time-dependent transport. The frequency dependence of the admittance is fully investigated.

  1. Nonequilibrium Keldysh formalism for interacting leads—Application to quantum dot transport driven by spin bias

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Jalil, M. B. A.; Tan, Seng Ghee

    2012-06-01

    The conductance through a mesoscopic system of interacting electrons coupled to two adjacent leads is conventionally derived via the Keldysh nonequilibrium Green's function technique, in the limit of noninteracting leads [Y. Meir, N.S. Wingreen, Phys. Rev. Lett. 68 (1992) 2512]. We extend the standard formalism to cater for a quantum dot system with Coulombic interactions between the quantum dot and the leads. The general current expression is obtained by considering the equation of motion of the time-ordered Green's function of the system. The nonequilibrium effects of the interacting leads are then incorporated by determining the contour-ordered Green's function over the Keldysh loop and applying Langreth's theorem. The dot-lead interactions significantly increase the height of the Kondo peaks in density of states of the quantum dot. This translates into two Kondo peaks in the spin differential conductance when the magnitude of the spin bias equals that of the Zeeman splitting. There also exists a plateau in the charge differential conductance due to the combined effect of spin bias and the Zeeman splitting. The low-bias conductance plateau with sharp edges is also a characteristic of the Kondo effect. The conductance plateau disappears for the case of asymmetric dot-lead interaction.

  2. Own Variety Bias

    PubMed Central

    García, Andrea Ariza

    2015-01-01

    In a language identification task, native Belgian French and native Swiss French speakers identified French from France as their own variety. However, Canadian French was not subject to this bias. Canadian and French listeners didn’t claim a different variety as their own.

  3. Biased to Learn Language

    ERIC Educational Resources Information Center

    Sebastian-Galles, Nuria

    2007-01-01

    Some recent publications that explore the foundations of early language development are reviewed in this article. The review adopts the pivotal idea that infants' advancements are helped by the existence of different types of biases. The infant's discovery of the phonological properties of the language of the environment, as well as their learning…

  4. Optically biased laser gyro

    SciTech Connect

    Anderson, D.Z.; Chow, W.W.; Scully, M.O.; Sanders, V.E.

    1980-10-01

    We describe a four-mode ring laser that exhibits none of the mode-locking characteristics that plague laser gyros. This laser is characterized by a bias that changes sign with a change in the direction of rotation and prevents the counterpropagating modes from locking. A theoretical analysis explaining the experimental results is outlined.

  5. Own Variety Bias.

    PubMed

    Sloos, Marjoleine; García, Andrea Ariza

    2015-10-01

    In a language identification task, native Belgian French and native Swiss French speakers identified French from France as their own variety. However, Canadian French was not subject to this bias. Canadian and French listeners didn't claim a different variety as their own. PMID:27648211

  6. Are Providers More Likely to Contribute to Healthcare Disparities Under High Levels of Cognitive Load? How Features of the Healthcare Setting May Lead to Biases in Medical Decision Making

    PubMed Central

    Burgess, Diana J.

    2014-01-01

    Systematic reviews of healthcare disparities suggest that clinicians’ diagnostic and therapeutic decision making varies by clinically irrelevant characteristics, such as patient race, and that this variation may contribute to healthcare disparities. However, there is little understanding of the particular features of the healthcare setting under which clinicians are most likely to be inappropriately influenced by these characteristics. This study delineates several hypotheses to stimulate future research in this area. It is posited that healthcare settings in which providers experience high levels of cognitive load will increase the likelihood of racial disparities via 2 pathways. First, providers who experience higher levels of cognitive load are hypothesized to make poorer medical decisions and provide poorer care for all patients, due to lower levels of controlled processing (H1). Second, under greater levels of cognitive load, it is hypothesized that healthcare providers’ medical decisions and interpersonal behaviors will be more likely to be influenced by racial stereotypes, leading to poorer processes and outcomes of care for racial minority patients (H2). It is further hypothesized that certain characteristics of healthcare settings will result in higher levels of cognitive load experienced by providers (H3). Finally, it is hypothesized that minority patients will be disproportionately likely to be treated in healthcare settings in which providers experience greater levels of cognitive load (H4a), which will result in racial disparities due to lower levels of controlled processing by providers (H4b) and the influence of racial stereotypes (H4c).The study concludes with implications for research and practice that flow from this framework. PMID:19726783

  7. Delayed self-regulation and time-dependent chemical drive leads to novel states in epigenetic landscapes.

    PubMed

    Mitra, Mithun K; Taylor, Paul R; Hutchison, Chris J; McLeish, T C B; Chakrabarti, Buddhapriya

    2014-11-01

    The epigenetic pathway of a cell as it differentiates from a stem cell state to a mature lineage-committed one has been historically understood in terms of Waddington's landscape, consisting of hills and valleys. The smooth top and valley-strewn bottom of the hill represent their undifferentiated and differentiated states, respectively. Although mathematical ideas rooted in nonlinear dynamics and bifurcation theory have been used to quantify this picture, the importance of time delays arising from multistep chemical reactions or cellular shape transformations have been ignored so far. We argue that this feature is crucial in understanding cell differentiation and explore the role of time delay in a model of a single-gene regulatory circuit. We show that the interplay of time-dependent drive and delay introduces a new regime where the system shows sustained oscillations between the two admissible steady states. We interpret these results in the light of recent perplexing experiments on inducing the pluripotent state in mouse somatic cells. We also comment on how such an oscillatory state can provide a framework for understanding more general feedback circuits in cell development. PMID:25165605

  8. Delayed self-regulation and time-dependent chemical drive leads to novel states in epigenetic landscapes

    PubMed Central

    Mitra, Mithun K.; Taylor, Paul R.; Hutchison, Chris J.; McLeish, T. C. B.; Chakrabarti, Buddhapriya

    2014-01-01

    The epigenetic pathway of a cell as it differentiates from a stem cell state to a mature lineage-committed one has been historically understood in terms of Waddington's landscape, consisting of hills and valleys. The smooth top and valley-strewn bottom of the hill represent their undifferentiated and differentiated states, respectively. Although mathematical ideas rooted in nonlinear dynamics and bifurcation theory have been used to quantify this picture, the importance of time delays arising from multistep chemical reactions or cellular shape transformations have been ignored so far. We argue that this feature is crucial in understanding cell differentiation and explore the role of time delay in a model of a single-gene regulatory circuit. We show that the interplay of time-dependent drive and delay introduces a new regime where the system shows sustained oscillations between the two admissible steady states. We interpret these results in the light of recent perplexing experiments on inducing the pluripotent state in mouse somatic cells. We also comment on how such an oscillatory state can provide a framework for understanding more general feedback circuits in cell development. PMID:25165605

  9. Delayed self-regulation and time-dependent chemical drive leads to novel states in epigenetic landscapes.

    PubMed

    Mitra, Mithun K; Taylor, Paul R; Hutchison, Chris J; McLeish, T C B; Chakrabarti, Buddhapriya

    2014-11-01

    The epigenetic pathway of a cell as it differentiates from a stem cell state to a mature lineage-committed one has been historically understood in terms of Waddington's landscape, consisting of hills and valleys. The smooth top and valley-strewn bottom of the hill represent their undifferentiated and differentiated states, respectively. Although mathematical ideas rooted in nonlinear dynamics and bifurcation theory have been used to quantify this picture, the importance of time delays arising from multistep chemical reactions or cellular shape transformations have been ignored so far. We argue that this feature is crucial in understanding cell differentiation and explore the role of time delay in a model of a single-gene regulatory circuit. We show that the interplay of time-dependent drive and delay introduces a new regime where the system shows sustained oscillations between the two admissible steady states. We interpret these results in the light of recent perplexing experiments on inducing the pluripotent state in mouse somatic cells. We also comment on how such an oscillatory state can provide a framework for understanding more general feedback circuits in cell development.

  10. Modeling and simulation of blast-induced, early-time intracranial wave physics leading to traumatic brain injury.

    SciTech Connect

    Ford, Corey C.; Taylor, Paul Allen

    2008-02-01

    The objective of this modeling and simulation study was to establish the role of stress wave interactions in the genesis of traumatic brain injury (TBI) from exposure to explosive blast. A high resolution (1 mm{sup 3} voxels), 5 material model of the human head was created by segmentation of color cryosections from the Visible Human Female dataset. Tissue material properties were assigned from literature values. The model was inserted into the shock physics wave code, CTH, and subjected to a simulated blast wave of 1.3 MPa (13 bars) peak pressure from anterior, posterior and lateral directions. Three dimensional plots of maximum pressure, volumetric tension, and deviatoric (shear) stress demonstrated significant differences related to the incident blast geometry. In particular, the calculations revealed focal brain regions of elevated pressure and deviatoric (shear) stress within the first 2 milliseconds of blast exposure. Calculated maximum levels of 15 KPa deviatoric, 3.3 MPa pressure, and 0.8 MPa volumetric tension were observed before the onset of significant head accelerations. Over a 2 msec time course, the head model moved only 1 mm in response to the blast loading. Doubling the blast strength changed the resulting intracranial stress magnitudes but not their distribution. We conclude that stress localization, due to early time wave interactions, may contribute to the development of multifocal axonal injury underlying TBI. We propose that a contribution to traumatic brain injury from blast exposure, and most likely blunt impact, can occur on a time scale shorter than previous model predictions and before the onset of linear or rotational accelerations traditionally associated with the development of TBI.

  11. Charge amplifier with bias compensation

    DOEpatents

    Johnson, Gary W.

    2002-01-01

    An ion beam uniformity monitor for very low beam currents using a high-sensitivity charge amplifier with bias compensation. The ion beam monitor is used to assess the uniformity of a raster-scanned ion beam, such as used in an ion implanter, and utilizes four Faraday cups placed in the geometric corners of the target area. Current from each cup is integrated with respect to time, thus measuring accumulated dose, or charge, in Coulombs. By comparing the dose at each corner, a qualitative assessment of ion beam uniformity is made possible. With knowledge of the relative area of the Faraday cups, the ion flux and areal dose can also be obtained.

  12. Bias in Estimation of Hippocampal Atrophy using Deformation-Based Morphometry Arises from Asymmetric Global Normalization: An Illustration in ADNI 3 Tesla MRI Data

    PubMed Central

    Yushkevich, Paul A.; Avants, Brian B.; Das, Sandhitsu R.; Pluta, John; Altinay, Murat; Craige, Caryne

    2009-01-01

    Measurement of brain change due to neurodegenerative disease and treatment is one of the fundamental tasks of neuroimaging. Deformation-based morphometry (DBM) has been long recognized as an effective and sensitive tool for estimating the change in the volume of brain regions over time. This paper demonstrates that a straightforward application of DBM to estimate the change in the volume of the hippocampus can result in substantial bias, i.e., an overestimation of the rate of change in hippocampal volume. In ADNI data, this bias is manifested as a non-zero intercept of the regression line fitted to the 6 and 12 month rates of hippocampal atrophy. The bias is further confirmed by applying DBM to repeat scans of subjects acquired on the same day. This bias appears to be the result of asymmetry in the interpolation of baseline and followup images during longitudinal image registration. Correcting this asymmetry leads to bias-free atrophy estimation. PMID:20005963

  13. Observational Results of Diurnal Variation in Quiet Time Inner Plasmasphere Equatorial Noise Leading to Post-Midnight Ion Loss

    NASA Astrophysics Data System (ADS)

    Sarno-Smith, L. K.; Liemohn, M. W.; Skoug, R. M.; Morley, S.; Breneman, A. W.; Larsen, B.; Reeves, G. D.; Wygant, J. R.; Kletzing, C.; Hospodarsky, G. B.; Moldwin, M.; Katus, R. M.; Zou, S.

    2015-12-01

    After the discovery of the plasmaspheric post-midnight 1-10 eV ion loss between L =2 and L =3, we have expanded upon these results and connected the observed ion loss with changes in plasma wave activity. Using the Van Allen Probes Helium, Oxygen, Proton, and Electron (HOPE) and the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instruments, we observed that diurnal variation in EMFISIS equatorial noise measurements was consistent with HOPE H+ thermal ion measurement variations. Through statistical studies and case studies, we present how enhanced dayside equatorial noise heats via cyclotron resonance to form the 1-10 eV ion population of the inner plasmasphere during quiet time.

  14. Time is no healer: increasing restoration age does not lead to improved benthic invertebrate communities in restored river reaches.

    PubMed

    Leps, Moritz; Sundermann, Andrea; Tonkin, Jonathan D; Lorenz, Armin W; Haase, Peter

    2016-07-01

    Evidence for successful restoration of riverine communities is scarce, particularly for benthic invertebrates. Among the multitude of reasons discussed so far for the lack of observed effects is too short of a time span between implementation and monitoring. Yet, studies that explicitly focus on the importance of restoration age are rare. We present a comprehensive study based on 44 river restoration projects in Germany, focusing on standardized benthic invertebrate sampling. A broad gradient ranging from 1 to 25years in restoration age was available. In contrast to clear improvements in habitat heterogeneity, benthic community responses to restoration were inconsistent when compared to control sections. Taxon richness increased in response to restoration, but abundance, diversity and various assessment metrics did not respond clearly. Restoration age was a poor predictor of community composition and community change, as no significant linear responses could be detected using 34 metrics. Moreover, only 5 out of 34 tested metrics showed non-linear shifts at restoration ages of 2 to 3years. This might be interpreted as an indication of a post-restoration disturbance followed by a re-establishment of pre-restoration conditions. BIO-ENV analysis and fourth-corner modeling underlined the low importance of restoration age, but revealed high importance of catchment-scale characteristics (e.g., ecoregion, catchment size and land use) in controlling community composition and community change. Overall, a lack of time for community development did not appear to be the ultimate reason for impaired benthic invertebrate communities. Instead, catchment-scale characteristics override the effectiveness of restoration. To enhance the ecological success of future river restoration projects, we recommend improving water quality conditions and catchment-scale processes (e.g., connectivity and hydrodynamics) in addition to restoring local habitat structure. PMID:27046138

  15. Time is no healer: increasing restoration age does not lead to improved benthic invertebrate communities in restored river reaches.

    PubMed

    Leps, Moritz; Sundermann, Andrea; Tonkin, Jonathan D; Lorenz, Armin W; Haase, Peter

    2016-07-01

    Evidence for successful restoration of riverine communities is scarce, particularly for benthic invertebrates. Among the multitude of reasons discussed so far for the lack of observed effects is too short of a time span between implementation and monitoring. Yet, studies that explicitly focus on the importance of restoration age are rare. We present a comprehensive study based on 44 river restoration projects in Germany, focusing on standardized benthic invertebrate sampling. A broad gradient ranging from 1 to 25years in restoration age was available. In contrast to clear improvements in habitat heterogeneity, benthic community responses to restoration were inconsistent when compared to control sections. Taxon richness increased in response to restoration, but abundance, diversity and various assessment metrics did not respond clearly. Restoration age was a poor predictor of community composition and community change, as no significant linear responses could be detected using 34 metrics. Moreover, only 5 out of 34 tested metrics showed non-linear shifts at restoration ages of 2 to 3years. This might be interpreted as an indication of a post-restoration disturbance followed by a re-establishment of pre-restoration conditions. BIO-ENV analysis and fourth-corner modeling underlined the low importance of restoration age, but revealed high importance of catchment-scale characteristics (e.g., ecoregion, catchment size and land use) in controlling community composition and community change. Overall, a lack of time for community development did not appear to be the ultimate reason for impaired benthic invertebrate communities. Instead, catchment-scale characteristics override the effectiveness of restoration. To enhance the ecological success of future river restoration projects, we recommend improving water quality conditions and catchment-scale processes (e.g., connectivity and hydrodynamics) in addition to restoring local habitat structure.

  16. Thinking in Black and White: Conscious thought increases racially biased judgments through biased face memory.

    PubMed

    Strick, Madelijn; Stoeckart, Peter F; Dijksterhuis, Ap

    2015-11-01

    It is a common research finding that conscious thought helps people to avoid racial discrimination. These three experiments, however, illustrate that conscious thought may increase biased face memory, which leads to increased judgment bias (i.e., preferring White to Black individuals). In Experiments 1 and 2, university students formed impressions of Black and White housemate candidates. They judged the candidates either immediately (immediate decision condition), thought about their judgments for a few minutes (conscious thought condition), or performed an unrelated task for a few minutes (unconscious thought condition). Conscious thinkers and immediate decision-makers showed a stronger face memory bias than unconscious thinkers, and this mediated increased judgment bias, although not all results were significant. Experiment 3 used a new, different paradigm and showed that a Black male was remembered as darker after a period of conscious thought than after a period of unconscious thought. Implications for racial prejudice are discussed. PMID:26164254

  17. Thinking in Black and White: Conscious thought increases racially biased judgments through biased face memory.

    PubMed

    Strick, Madelijn; Stoeckart, Peter F; Dijksterhuis, Ap

    2015-11-01

    It is a common research finding that conscious thought helps people to avoid racial discrimination. These three experiments, however, illustrate that conscious thought may increase biased face memory, which leads to increased judgment bias (i.e., preferring White to Black individuals). In Experiments 1 and 2, university students formed impressions of Black and White housemate candidates. They judged the candidates either immediately (immediate decision condition), thought about their judgments for a few minutes (conscious thought condition), or performed an unrelated task for a few minutes (unconscious thought condition). Conscious thinkers and immediate decision-makers showed a stronger face memory bias than unconscious thinkers, and this mediated increased judgment bias, although not all results were significant. Experiment 3 used a new, different paradigm and showed that a Black male was remembered as darker after a period of conscious thought than after a period of unconscious thought. Implications for racial prejudice are discussed.

  18. Lead and the Romans

    ERIC Educational Resources Information Center

    Reddy, Aravind; Braun, Charles L.

    2010-01-01

    Lead poisoning has been a problem since early history and continues into modern times. An appealing characteristic of lead is that many lead salts are sweet. In the absence of cane and beet sugars, early Romans used "sugar of lead" (lead acetate) to sweeten desserts, fruits, and sour wine. People most at risk would have been those who consumed the…

  19. Taphonomic bias in pollen and spore record: a review

    SciTech Connect

    Fisk, L.H.

    1986-05-01

    The high dispersibility and ease of pollen and spore transport have led researchers to conclude erroneously that fossil pollen and spore floras are relatively complete and record unbiased representations of the regional vegetation extant at the time of sediment deposition. That such conclusions are unjustified is obvious when the authors remember that polynomorphs are merely organic sedimentary particles and undergo hydraulic sorting not unlike clastic sedimentary particles. Prior to deposition in the fossil record, pollen and spores can be hydraulically sorted by size, shape, and weight, subtly biasing relative frequencies in fossil assemblages. Sorting during transport results in palynofloras whose composition is environmentally dependent. Therefore, depositional environment is an important consideration to make correct inferences on the source vegetation. Sediment particle size of original rock samples may contain important information on the probability of a taphonomically biased pollen and spore assemblage. In addition, a reasonable test of hydraulic sorting is the distribution of pollen grain sizes and shapes in each assemblage. Any assemblage containing a wide spectrum of grain sizes and shapes has obviously not undergone significant sorting. If unrecognized, taphonomic bias can lead to paleoecologic, paleoclimatic, and even biostratigraphic misinterpretations.

  20. Lead Poisoning

    MedlinePlus

    ... Experiments Stories Lessons Topics Games Activities Lessons MENU Lead Poisoning Kids Homepage Topics Pollution Lead Poisoning What is ... you can avoid contact with it! Sources of Lead Poisoning HOUSE PAINTS: Before1950, lead-based paint was used ...

  1. Lead Test

    MedlinePlus

    ... to determine lead sources, educating family members about lead poisoning , and instituting follow-up testing to monitor the ... high levels of lead, see the article on Lead Poisoning . The Occupational Safety and Health Administration (OSHA) has ...

  2. Lead Poisoning

    MedlinePlus

    Lead Poisoning What is it and who is affected? Lead is a highly toxic substance, exposure to which ... and children can suffer from the effects of lead poisoning, but childhood lead poisoning is much more frequent. ...

  3. A new method of adjusting spatial and temporal biases for selected climate variables.

    NASA Astrophysics Data System (ADS)

    Grillakis, Manolis; Koutroulis, Aristeidis; Tsanis, Ioannis

    2016-04-01

    Climate models is a valuable source of data for climate change impact studies. Often, the climate model data cannot be used in their native form due to the presence of biases. The lack of an appropriate adjustment of climate forcings may even lead to unrealistic model results. Many methodologies of bias adjustment have been developed and can be found in the literature dealing with the temporal biases in the time-series. Their main task is to adjust the temporal statistical properties of climate simulations for a single point value to resemble those of observations in a common climate period. However, they do not adjust or retain the spatial patterns of the data with respect to the observational datasets. In cases where impact models are sensitive to the spatial distribution of the variables, the adjustment of the spatial patterns is equally or more important to the adjustment of the temporal statistics. Examples of such impact models are cyclone tracking schemes or coastal flooding models that consider the spatial structure of wind and/or atmospheric pressure data. Here we develop a method to deal with this type of biases in space, along with the temporal biases. The methodology considers correction in the entire spectrum of CDF data and then redistribution of the data in time, to adjust the spatial consistency against observations. The methodology is tested on surface pressure and wind data derived from selected global climate models.

  4. Cosmology of biased discrete symmetry breaking

    NASA Technical Reports Server (NTRS)

    Gelmini, Graciela B.; Gleiser, Marcelo; Kolb, Edward W.

    1988-01-01

    The cosmological consequences of spontaneous breaking of an approximate discrete symmetry are studied. The breaking leads to formation of proto-domains of false and true vacuum separated by domain walls of thickness determined by the mass scale of the model. The cosmological evolution of the walls is extremely sensitive to the magnitude of the biasing; several scenarios are possible, depending on the interplay between the surface tension on the walls and the volume pressure from the biasing. Walls may disappear almost immediately after they form, or may live long enough to dominate the energy density of the Universe and cause power-law inflation. Limits are obtained on the biasing that characterizes each possible scenario.

  5. Recursive bias estimation for high dimensional smoothers

    SciTech Connect

    Hengartner, Nicolas W; Matzner-lober, Eric; Cornillon, Pierre - Andre

    2008-01-01

    In multivariate nonparametric analysis, sparseness of the covariates also called curse of dimensionality, forces one to use large smoothing parameters. This leads to biased smoothers. Instead of focusing on optimally selecting the smoothing parameter, we fix it to some reasonably large value to ensure an over-smoothing of the data. The resulting smoother has a small variance but a substantial bias. In this paper, we propose to iteratively correct the bias initial estimator by an estimate of the latter obtained by smoothing the residuals. We examine in detail the convergence of the iterated procedure for classical smoothers and relate our procedure to L{sub 2}-Boosting. We apply our method to simulated and real data and show that our method compares favorably with existing procedures.

  6. Identification of new leishmanicidal peptide lead structures by automated real-time monitoring of changes in intracellular ATP.

    PubMed Central

    Luque-Ortega, J Román; Saugar, José M; Chiva, Cristina; Andreu, David; Rivas, Luis

    2003-01-01

    Leishmanicidal drugs interacting stoichiometrically with parasite plasma membrane lipids, thus promoting permeability, have raised significant expectations for Leishmania chemotherapy due to their nil or very low induction of resistance. Inherent in this process is a decrease in intracellular ATP, either wasted by ionic pumps to restore membrane potential or directly leaked through larger membrane lesions caused by the drug. We have adapted a luminescence method for fast automated real-time monitoring of this process, using Leishmania donovani promastigotes transfected with a cytoplasmic luciferase form, previously tested for anti-mitochondrial drugs. The system was first assayed against a set of well-known membrane-active drugs [amphotericin B, nystatin, cecropin A-melittin peptide CA(1-8)M(1-18)], plus two ionophoric polyethers (narasin and salinomycin) not previously tested on Leishmania, then used to screen seven new cecropin A-melittin hybrid peptides. All membrane-active compounds showed a good correlation between inhibition of luminescence and leishmanicidal activity. Induction of membrane permeability was demonstrated by dissipation of membrane potential, SYTOX trade mark Green influx and membrane damage assessed by electron microscopy, except for the polyethers, where ATP decrease was due to inhibition of its mitochondrial synthesis. Five of the test peptides showed an ED50 around 1 microM on promastigotes. These peptides, with equal or better activity than 26-residue-long CA(1-8)M(1-18), are the shortest leishmanicidal peptides described so far, and validate our luminescence assay as a fast and cheap screening tool for membrane-active compounds. PMID:12864731

  7. Assessment of risk of bias in translational science

    PubMed Central

    2013-01-01

    Risk of bias in translational medicine may take one of three forms: A. a systematic error of methodology as it pertains to measurement or sampling (e.g., selection bias), B. a systematic defect of design that leads to estimates of experimental and control groups, and of effect sizes that substantially deviate from true values (e.g., information bias), and C. a systematic distortion of the analytical process, which results in a misrepresentation of the data with consequential errors of inference (e.g., inferential bias). Risk of bias can seriously adulterate the internal and the external validity of a clinical study, and, unless it is identified and systematically evaluated, can seriously hamper the process of comparative effectiveness and efficacy research and analysis for practice. The Cochrane Group and the Agency for Healthcare Research and Quality have independently developed instruments for assessing the meta-construct of risk of bias. The present article begins to discuss this dialectic. PMID:23927081

  8. Cognitive neuroscience. Unlearning implicit social biases during sleep.

    PubMed

    Hu, Xiaoqing; Antony, James W; Creery, Jessica D; Vargas, Iliana M; Bodenhausen, Galen V; Paller, Ken A

    2015-05-29

    Although people may endorse egalitarianism and tolerance, social biases can remain operative and drive harmful actions in an unconscious manner. Here, we investigated training to reduce implicit racial and gender bias. Forty participants processed counterstereotype information paired with one sound for each type of bias. Biases were reduced immediately after training. During subsequent slow-wave sleep, one sound was unobtrusively presented to each participant, repeatedly, to reactivate one type of training. Corresponding bias reductions were fortified in comparison with the social bias not externally reactivated during sleep. This advantage remained 1 week later, the magnitude of which was associated with time in slow-wave and rapid-eye-movement sleep after training. We conclude that memory reactivation during sleep enhances counterstereotype training and that maintaining a bias reduction is sleep-dependent. PMID:26023137

  9. Assessment of bias for MRI diffusion tensor imaging using SIMEX.

    PubMed

    Lauzon, Carolyn B; Asman, Andrew J; Crainiceanu, Ciprian; Caffo, Brian C; Landman, Bennett A

    2011-01-01

    Diffusion Tensor Imaging (DTI) is a Magnetic Resonance Imaging method for measuring water diffusion in vivo. One powerful DTI contrast is fractional anisotropy (FA). FA reflects the strength of water's diffusion directional preference and is a primary metric for neuronal fiber tracking. As with other DTI contrasts, FA measurements are obscured by the well established presence of bias. DTI bias has been challenging to assess because it is a multivariable problem including SNR, six tensor parameters, and the DTI collection and processing method used. SIMEX is a modem statistical technique that estimates bias by tracking measurement error as a function of added noise. Here, we use SIMEX to assess bias in FA measurements and show the method provides; i) accurate FA bias estimates, ii) representation of FA bias that is data set specific and accessible to non-statisticians, and iii) a first time possibility for incorporation of bias into DTI data analysis. PMID:21995019

  10. HESS Opinions "Should we apply bias correction to global and regional climate model data?"

    NASA Astrophysics Data System (ADS)

    Ehret, U.; Zehe, E.; Wulfmeyer, V.; Warrach-Sagi, K.; Liebert, J.

    2012-04-01

    Despite considerable progress in recent years, output of both Global and Regional Circulation Models is still afflicted with biases to a degree that precludes its direct use, especially in climate change impact studies. This is well known, and to overcome this problem bias correction (BC), i.e. the correction of model output towards observations in a post processing step for its subsequent application in climate change impact studies has now become a standard procedure. In this paper we argue that bias correction, which has a considerable influence on the results of impact studies, is not a valid procedure in the way it is currently used: it impairs the advantages of Circulation Models which are based on established physical laws by altering spatiotemporal field consistency, relations among variables and by violating conservation principles. Bias correction largely neglects feedback mechanisms and it is unclear whether bias correction methods are time-invariant under climate change conditions. Applying bias correction increases agreement of Climate Model output with observations in hind casts and hence narrows the uncertainty range of simulations and predictions without, however, providing a satisfactory physical justification. This is in most cases not transparent to the end user. We argue that this masks rather than reduces uncertainty, which may lead to avoidable forejudging of end users and decision makers. We present here a brief overview of state-of-the-art bias correction methods, discuss the related assumptions and implications, draw conclusions on the validity of bias correction and propose ways to cope with biased output of Circulation Models in the short term and how to reduce the bias in the long term. The most promising strategy for improved future Global and Regional Circulation Model simulations is the increase in model resolution to the convection-permitting scale in combination with ensemble predictions based on sophisticated approaches for

  11. Dynamics of Pulsed Chlorine Plasmas with and without Substrate RF-Bias

    NASA Astrophysics Data System (ADS)

    Donnelly, Vincent M.

    2000-10-01

    Pulsed plasmas can significantly decrease plasma-process-induced damage and reduce unwanted etch profile anomalies. In electronegative plasmas (e.g. chlorine), these benefits are often attributed to the build-up of negative ions (e.g. Cl-) in the OFF time, and the charge reduction that occurs when these negative ions reach the wafer. A reduction of the period-averaged electron temperature (Te) and impingement of low-energy positive ions are also thought to be important in reducing charge build-up and damage. We report results of a study of a chlorine, inductively-coupled pulsed plasma operated with and without a continuous radio frequency (rf) bias applied to the wafer stage. Without stage bias, Te decays rapidly in the OFF period, as does electron density (ne) on a somewhat longer time scale. The decay in ne is accompanied by a buildup in Cl-. The plasma dynamics in the presence of rf bias power are nearly the same as with no bias in the first 20 us of the OFF period. Then, however, after reaching a minimum of 0.5 eV, Te starts to increase rapidly and reaches values even higher than the steady state ON time values. Since ne is still quite high when Te goes through the minimum, the sheath near the wafer does not collapse and negative ions do not reach the wafer. In a previous study in a similar reactor, damage to thin gate oxide layers during aluminum etching was reduced while operating with a pulsed source and a continuous bias. This implies that the decreased damage cannot be attributed to a reduction of charging of the wafer by negative ions. We further show that increasing the duration of the OFF time or increasing the bias power leads to the transition of the plasma into a reactive ion etching (RIE) mode, when the decaying positive ion density reaches the level sustained by the stage power.

  12. Assessing Bias in Search Engines.

    ERIC Educational Resources Information Center

    Mowshowitz, Abbe; Kawaguchi, Akira

    2002-01-01

    Addresses the measurement of bias in search engines on the Web, defining bias as the balance and representation of items in a collection retrieved from a database for a set of queries. Assesses bias by measuring the deviation from the ideal of the distribution produced by a particular search engine. (Author/LRW)

  13. Negativity bias and basic values.

    PubMed

    Schwartz, Shalom H

    2014-06-01

    Basic values explain more variance in political attitudes and preferences than other personality and sociodemographic variables. The values most relevant to the political domain are those likely to reflect the degree of negativity bias. Value conflicts that represent negativity bias clarify differences between what worries conservatives and liberals and suggest that relations between ideology and negativity bias are linear. PMID:24970450

  14. Stray comment about AIDS leads to job bias trial.

    PubMed

    1999-03-01

    A supervisor's comment that an employee's poor work attitude could be attributed to his AIDS diagnosis or medications led to a lawsuit for discrimination. The suit was filed by [name removed], who claims he was fired from his job at New York publisher, [name removed] Inc., because he has AIDS. [Name removed] disclosed his diagnosis when his supervisor, [name removed], inquired about his frequent absences. [Name removed] reportedly responded that the medical condition "could cost the company a lot of money"; however, an affidavit presented at the trial showed that the company's insurance premiums would not increase because of [name removed]'s condition. [Name removed] fired [name removed] allegedly after learning that [name removed] was in contact with a competitor about possible employment opportunities. U.S. District Judge Robert L. Carter, finding that the issue turned on the credibility of both the ex-employee and the supervisor, refused to grant summary judgment to the employer in such a close situation.

  15. Exploring the Links Between Biases in Regional Climate Models and their Representation of Synoptic Circulation Types in the European Alps

    NASA Astrophysics Data System (ADS)

    Addor, N.; Rohrer, M.; Furrer, R.; Seibert, J.

    2014-12-01

    Climate model simulations can show large departures from observations. These biases are often subtracted and then forgotten, or post-processed for impact modeling using pragmatic methods that typically do not account for the origins of the biases. Yet, enhancing our understanding of the reasons behind these biases is essential for the improvement of climate models and for the design of more robust bias-correction techniques. We pursue these objectives by exploring the links between biases at different spatial scales. We quantify biases at the regional scale in an alpine area (Switzerland) and explore whether they are influenced by the misrepresentation of the frequency, temperature and precipitation of circulation types (CTs) at the synoptic scale. Our analysis relies on simulations from 14 regional climate models (RCMs) forced by general circulation models and produced for the ENSEMBLES project. For each model, we characterized the daily synoptic situation over 1960-2099 by using a CT classification based on a hierarchical cluster analysis of principal components. The classification relies on sea level pressure fields within an area representative of the European Alps. We find significant biases in the CT frequency for 1980-2001 and that some of them lead to biases in temperature and precipitation reported in RCM comparison studies. For instance, in winter, models overestimate both the frequency and precipitation intensity of westerly situations, which carry moist air from the Atlantic Ocean and are responsible for most of the rainfall. We propose this as a main driver for the generalized overestimation of precipitation in winter, which is one of the most concerning biases affecting simulations in our area, as it leads to unrealistic estimates of snow accumulation. A general consequence is that CT-based downscaling methods that do not account for biases in CT frequency will generate biased outputs. Overall, we show that decomposing RCM time series using CTs

  16. Leading Learning in Our Times

    ERIC Educational Resources Information Center

    Trilling, Bernie

    2010-01-01

    Important tools that schools need to support a 21st century approach to teaching and learning include the usual suspects: the Internet, pen and paper, cell phones, educational games, tests and quizzes, good teachers, caring communities, educational funding, and loving parents. All of these items and more contribute to a 21st century education, but…

  17. Lead Toxicity

    MedlinePlus

    ... homes. • Most people, especially children, who suffer from lead poisoning are exposed through lead-contaminated household dust or ... and six if they are at risk of lead poisoning (see: ). Who can I call to get more ...

  18. Characterization of organic gunshot residues in lead-free ammunition using a new sample collection device for liquid chromatography-quadrupole time-of-flight mass spectrometry.

    PubMed

    Benito, Sandra; Abrego, Zuriñe; Sánchez, Alicia; Unceta, Nora; Goicolea, M Aranzazu; Barrio, Ramón J

    2015-01-01

    The identification of characteristic organic gunshot residues (OGSR) provides conclusive evidence in the elucidation of elemental profiles when lead-free ammunition is fired. OGSR also prevents false negatives. Toward this aim, a quick and efficient method based on liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF) was developed to detect and identify 18 gunpowder additives in gunshot residues (GSR). The unequivocal identification of target analytes was assured by using MS/MS mode. Swabs were compared with home-modified tape lift supports covered with a PTFE layer to determine the better sampling technique. The modified tape lift provided better extraction recoveries and enabled the analysis of inorganic and organic GSR simultaneously. The developed method was applied to the analysis of GSR from four different lead-free ammunitions. Diphenylamine and its nitrated degradation products and centralites were identified in all samples, providing strong evidence of GSR.

  19. On System-Dependent Sources of Uncertainty and Bias in Ultrasonic Quantitative Shear-Wave Imaging.

    PubMed

    Deng, Yufeng; Rouze, Ned C; Palmeri, Mark L; Nightingale, Kathryn R

    2016-03-01

    Ultrasonic quantitative shear-wave imaging methods have been developed over the last decade to estimate tissue elasticity by measuring the speed of propagating shear waves following acoustic radiation force excitation. This work discusses eight sources of uncertainty and bias arising from ultrasound system-dependent parameters in ultrasound shear-wave speed (SWS) measurements. Each of the eight sources of error is discussed in the context of a linear, isotropic, elastic, homogeneous medium, combining previously reported analyses with Field II simulations, full-wave 2-D acoustic propagation simulations, and experimental studies. Errors arising from both spatial and temporal sources lead to errors in SWS measurements. Arrival time estimation noise, speckle bias, hardware fluctuations, and phase aberration cause uncertainties (variance) in SWS measurements, while pulse repetition frequency (PRF) and beamforming errors, as well as coupling medium sound speed mismatch, cause biases in SWS measurements (accuracy errors). Calibration of the sources of bias is an important step in the development of shear-wave imaging systems. In a well-calibrated system, where the sources of bias are minimized, and averaging over a region of interest (ROI) is employed to reduce the sources of uncertainty, an SWS error can be expected. PMID:26886980

  20. Identifying ligand-specific signalling within biased responses: focus on δ opioid receptor ligands

    PubMed Central

    Charfi, I; Audet, N; Bagheri Tudashki, H; Pineyro, G

    2015-01-01

    Opioids activate GPCRs to produce powerful analgesic actions but at the same time induce side effects and generate tolerance, which restrict their clinical use. Reducing this undesired response profile has remained a major goal of opioid research and the notion of ‘biased agonism’ is raising increasing interest as a means of separating therapeutic responses from unwanted side effects. However, to fully exploit this opportunity, it is necessary to confidently identify biased signals and evaluate which type of bias may support analgesia and which may lead to undesired effects. The development of new computational tools has made it possible to quantify ligand-dependent signalling and discriminate this component from confounders that may also yield biased responses. Here, we analyse different approaches to identify and quantify ligand-dependent bias and review different types of confounders. Focus is on δ opioid receptor ligands, which are currently viewed as promising agents for chronic pain management. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2 PMID:24665881

  1. Sampling biases in CMIP5 decadal forecasts

    NASA Astrophysics Data System (ADS)

    Choudhury, Dipayan; Sharma, Ashish; Sen Gupta, Alexander; Mehrotra, Rajeshwar; Sivakumar, Bellie

    2016-04-01

    Recent studies examining the fidelity of decadal hindcast experiments from phase 5 of the Coupled Model Intercomparison Project have highlighted the need for larger ensembles of forecasts, compared to the initial five yearly spaced initializations, to help correct for model biases (drift). This study quantifies differences in the two drift estimates in sea surface temperature (SST) and SST anomaly (SSTA) predictions, between experiments initialized every 5 years and those initialized every year. The effect of the recommended mean drift correction, on the two sets of predictions, is also analyzed. Our results indicate that differences between the SST drift estimates are largest over the tropical Pacific. Moreover, this difference is large for Niño 3.4 and almost negligible for the global average SSTA. Drift correction as per the mean drift from the 5 year case leads to spurious peaks in the drift-corrected Niño 3.4 (and the tropical Pacific) and sporadic improvements in skill. This problem with Niño 3.4 stems from an aliasing that occurs during the drift calculation that results from a combination of the timing of major El Niño events in relation to the initialization dates. The study recommends accounting for such sampling effects while considering any subset of the full data set.

  2. Opportunistic biases: Their origins, effects, and an integrated solution.

    PubMed

    DeCoster, Jamie; Sparks, Erin A; Sparks, Jordan C; Sparks, Glenn G; Sparks, Cheri W

    2015-09-01

    Researchers commonly explore their data in multiple ways before deciding which analyses they will include in the final versions of their papers. While this improves the chances of researchers finding publishable results, it introduces an "opportunistic bias," such that the reported relations are stronger or otherwise more supportive of the researcher's theories than they would be without the exploratory process. The magnitudes of opportunistic biases can often be stronger than those of the effects being investigated, leading to invalid conclusions and a lack of clarity in research results. Authors typically do not report their exploratory procedures, so opportunistic biases are very difficult to detect just by reading the final version of a research report. In this article, we explain how a number of accepted research practices can lead to opportunistic biases, discuss the prevalence of these practices in psychology, consider the different effects that opportunistic biases have on psychological science, evaluate the strategies that methodologists have proposed to prevent or correct for the effects of these biases, and introduce an integrated solution to reduce the prevalence and influence of opportunistic biases. The recent prominence of articles discussing questionable research practices both in scientific journals and in the public media underscores the importance of understanding how opportunistic biases are created and how we might undo their effects. PMID:26348333

  3. Increased or Reversed? The Effect of Surprise on Hindsight Bias Depends on the Hindsight Component

    ERIC Educational Resources Information Center

    Nestler, Steffen; Egloff, Boris

    2009-01-01

    Two diverging hypotheses concerning the influence of surprising events on hindsight effects have been proposed: Although some authors believe that surprising events lead to a reversal of hindsight bias, others have proposed that surprise increases hindsight bias. Drawing on the separate-components view of the hindsight bias (which argues that…

  4. Summertime central U.S. warm bias examined in the short-term hindcasts

    NASA Astrophysics Data System (ADS)

    Ma, H. Y.; Klein, S. A.; Xie, S.; Lo, M. H.; Zhang, Y.

    2014-12-01

    In this study, we evaluate the central U.S. summertime surface warm temperature bias seen in many climate models. The main focus is to identify the role of cloud, radiation, and precipitation processes in contributing to the temperature biases. We use short-term hindcast approach and look at the growth of the error as a function of hindcast lead time. Our results of Community Earth System Model compared to data from U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site and other available observations indicate that the lack of soil moisture due to insufficient precipitation in the model is likely the primary source contribution to surface energy and temperature biases. Other processes that may lead to the warm biases are also explored. (http://portal.nersc.gov/project/capt/CAUSES/) (This study is funded by the RGCM and ASR programs of the U.S. Department of Energy as part of the Cloud-Associated Parameterizations Testbed. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-658004)

  5. Lead Poisoning

    MedlinePlus

    ... can be found in all parts of our environment. Much of it comes from human activities such as mining and manufacturing. Lead used to be in paint; older houses may still have lead paint. You could be exposed to lead by Eating food or drinking water that contains lead. Water pipes in older homes ...

  6. Lead poisoning

    SciTech Connect

    Rekus, J.F.

    1992-08-01

    Construction workers who weld, cut or blast structural steel coated with lead-based paint are at significant risk of lead poisoning. Although technology to control these exposures may not have existed when the lead standard was promulgated, it is available today. Employers who do not take steps to protect their employees from lead exposure may be cited and fined severely for their failure.

  7. Researching Sex Bias in the Classroom.

    ERIC Educational Resources Information Center

    Donlan, Dan

    This paper outlines five methods of research on sex bias in the classroom: one-time survey, one class/one treatment, two class/two treatment, one class/random assignment to treatment, and analysis of differentiated effect. It shows how each method could be used in attempting to measure the effect of a unit on Norma Klein's "Mom, the Wolfman and…

  8. Origin of lead in eight Central European peat bogs determined from isotope ratios, strengths, and operation times of regional pollution sources.

    PubMed

    Novák, Martin; Emmanuel, Simon; Vile, Melanie A; Erel, Yigal; Véron, Alain; Paces, Tomás; Wieder, R Kelman; Vanecek, Mirko; Stepánová, Markéta; Brízová, Eva; Hovorka, Jan

    2003-02-01

    Lead originating from coal burning, gasoline burning, and ore smelting was identified in 210Pb-dated profiles through eight peat bogs distributed over an area of 60,000 km2. The Sphagnum-dominated bogs were located mainly in mountainous regions of the Czech Republic bordering with Germany, Austria, and Poland. Basal peat 14C-dated at 11,000 years BP had a relatively high 206Pb/207Pb ratio (1.193). Peat deposited around 1800 AD had a lower 206Pb/207Pb ratio of 1.168-1.178, indicating that environmental lead in Central Europe had been largely affected by human activity (smelting) even before the beginning of the Industrial Revolution. Five of the sites exhibited a nearly constant 206Pb/207Pb ratio (1.175) throughout the 19th century, resembling the "anthropogenic baseline" described in Northern Europe (1.17). At all sites, the 206Pb/207Pb ratio of peat decreased at least until 1980; at four sites, a reversal to more radiogenic values (higher 206Pb/207Pb), typical of easing pollution, was observed in the following decade (1980-1990). A time series of annual outputs for 14 different mining districts dispersing lead into the environment has been constructed for the past 200 years. The production of Ag-Pb, coal, and leaded gasoline peaked in 1900, 1980, and 1980, respectively. In contrast to other European countries, no peak in annual Pb accumulation rates was found in 1900, the year of maximum ore smelting. The highest annual Pb accumulation rates in peat were consistent with the highest Pb emission rates from coal-fired power plants and traffic (1980). Although maximum coal and gasoline production coincided in time, their isotope ratios were unique. The mean measured 206Pb/207Pb ratios of local coal, ores, and gasoline were 1.19, 1.16, and 1.11, respectively. A considerable proportion of coal emissions, relative to gasoline emisions, was responsible for the higher 206Pb/207Pb ratios in the recent atmosphere (1.15) compared to Western Europe (1.10). As in West European

  9. Attentional Bias towards Positive Emotion Predicts Stress Resilience.

    PubMed

    Thoern, Hanna A; Grueschow, Marcus; Ehlert, Ulrike; Ruff, Christian C; Kleim, Birgit

    2016-01-01

    There is extensive evidence for an association between an attentional bias towards emotionally negative stimuli and vulnerability to stress-related psychopathology. Less is known about whether selective attention towards emotionally positive stimuli relates to mental health and stress resilience. The current study used a modified Dot Probe task to investigate if individual differences in attentional biases towards either happy or angry emotional stimuli, or an interaction between these biases, are related to self-reported trait stress resilience. In a nonclinical sample (N = 43), we indexed attentional biases as individual differences in reaction time for stimuli preceded by either happy or angry (compared to neutral) face stimuli. Participants with greater attentional bias towards happy faces (but not angry faces) reported higher trait resilience. However, an attentional bias towards angry stimuli moderated this effect: The attentional bias towards happy faces was only predictive for resilience in those individuals who also endorsed an attentional bias towards angry stimuli. An attentional bias towards positive emotional stimuli may thus be a protective factor contributing to stress resilience, specifically in those individuals who also endorse an attentional bias towards negative emotional stimuli. Our findings therefore suggest a novel target for prevention and treatment interventions addressing stress-related psychopathology. PMID:27008475

  10. Attentional Bias towards Positive Emotion Predicts Stress Resilience.

    PubMed

    Thoern, Hanna A; Grueschow, Marcus; Ehlert, Ulrike; Ruff, Christian C; Kleim, Birgit

    2016-01-01

    There is extensive evidence for an association between an attentional bias towards emotionally negative stimuli and vulnerability to stress-related psychopathology. Less is known about whether selective attention towards emotionally positive stimuli relates to mental health and stress resilience. The current study used a modified Dot Probe task to investigate if individual differences in attentional biases towards either happy or angry emotional stimuli, or an interaction between these biases, are related to self-reported trait stress resilience. In a nonclinical sample (N = 43), we indexed attentional biases as individual differences in reaction time for stimuli preceded by either happy or angry (compared to neutral) face stimuli. Participants with greater attentional bias towards happy faces (but not angry faces) reported higher trait resilience. However, an attentional bias towards angry stimuli moderated this effect: The attentional bias towards happy faces was only predictive for resilience in those individuals who also endorsed an attentional bias towards angry stimuli. An attentional bias towards positive emotional stimuli may thus be a protective factor contributing to stress resilience, specifically in those individuals who also endorse an attentional bias towards negative emotional stimuli. Our findings therefore suggest a novel target for prevention and treatment interventions addressing stress-related psychopathology.

  11. Attentional Bias towards Positive Emotion Predicts Stress Resilience

    PubMed Central

    Ehlert, Ulrike; Ruff, Christian C.; Kleim, Birgit

    2016-01-01

    There is extensive evidence for an association between an attentional bias towards emotionally negative stimuli and vulnerability to stress-related psychopathology. Less is known about whether selective attention towards emotionally positive stimuli relates to mental health and stress resilience. The current study used a modified Dot Probe task to investigate if individual differences in attentional biases towards either happy or angry emotional stimuli, or an interaction between these biases, are related to self-reported trait stress resilience. In a nonclinical sample (N = 43), we indexed attentional biases as individual differences in reaction time for stimuli preceded by either happy or angry (compared to neutral) face stimuli. Participants with greater attentional bias towards happy faces (but not angry faces) reported higher trait resilience. However, an attentional bias towards angry stimuli moderated this effect: The attentional bias towards happy faces was only predictive for resilience in those individuals who also endorsed an attentional bias towards angry stimuli. An attentional bias towards positive emotional stimuli may thus be a protective factor contributing to stress resilience, specifically in those individuals who also endorse an attentional bias towards negative emotional stimuli. Our findings therefore suggest a novel target for prevention and treatment interventions addressing stress-related psychopathology. PMID:27008475

  12. Concurrent bias correction in hemodynamic data assimilation.

    PubMed

    Hu, Zhenghui; Liu, Huafeng; Shi, Pengcheng

    2012-10-01

    Low-frequency drift in fMRI datasets can be caused by various sources and are generally not of interest in a conventional task-based fMRI experiment. This feature complicates the assimilation approach that is always under specific assumption on statistics of system uncertainties. In this paper, we present a novel approach to the assimilation of nonlinear hemodynamic system with stochastic biased noise. By treating the drift variation as a random-walk process, the assimilation problem was translated into the identification of a nonlinear system in the presence of time-varying bias. We developed a bias aware unscented Kalman estimator to efficiently handle this problem. In this framework, the estimates of bias-free states and drift are separately carried out in two parallel filters, the optimal estimates of the system states then are corrected from bias-free states with drift estimates. The approach can simultaneously deal with the fMRI responses and drift in an assimilation cycle in an on-line fashion. It makes no assumptions of the structure and statistics of the drift, thereby is particularly suited for fMRI imaging where the formulation of real drift remains difficult to acquire. Experiments with synthetic data and real fMRI data are performed to demonstrate feasibility of our approach and to explore its potential advantages over classic polynomial approach. Moreover, we include the comparison of the variability of observables from the scanner and of normalized signal used in assimilation procedure in Appendix.

  13. Lead neurotoxicity and socioeconomic status: conceptual and analytical issues.

    PubMed

    Bellinger, David C

    2008-09-01

    Socioeconomic status (SES) is usually considered to be a potential confounder of the association between lead exposure and children's neurodevelopment, but experimental and epidemiological data suggest that SES might also modify lead neurotoxicity. The basis of this effect modification is uncertain, but might include differences among SES strata in co-exposures to other neurotoxicants, genetic susceptibilities, environmental enrichment, and stress. The role of SES in the causal nexus is likely to include other dimensions, however. It conveys information about lead exposure opportunities as well as about predictors of child outcome that are correlated with but causally independent of lead. Failure to distinguish these aspects of SES will lead to an underestimate of lead's contribution, and might even result in attributing to SES health effects that should be attributed to lead. Conventional models, which treat SES and SES-related factors solely as potential confounders, do not capture the possibility that a child's early lead exposure alters the behaviors that the child elicits from others. Failure to model lead's contribution to such time-varying covariates will also tend to bias estimates of lead neurotoxicity toward the null. On a trans-generational level, low SES might be a proxy for vulnerability to lead. To estimate the burden of lead-associated neurotoxicity on a population level, we need to apply analytical approaches that model a child's development and its context as a complex system of interdependent relationships that change over time.

  14. Growth rates and interface shapes in germanium and lead tin telluride observed in-situ, real-time in vertical Bridgman furnaces

    NASA Technical Reports Server (NTRS)

    Barber, P. G.; Berry, R. F.; Debnam, W. J.; Fripp, A. L.; Woodell, G.; Simchick, R. T.

    1995-01-01

    Using the advanced technology developed to visualize the melt-solid interface in low Prandtl number materials, crystal growth rates and interface shapes have been measured in germanium and lead tin telluride semiconductors grown in vertical Bridgman furnaces. The experimental importance of using in-situ, real time observations to determine interface shapes, to measure crystal growth rates, and to improve furnace and ampoule designs is demonstrated. The interface shapes observed in-situ, in real-time were verified by quenching and mechanically induced interface demarcation, and they were also confirmed using machined models to ascertain the absence of geometric distortions. Interface shapes depended upon the interface position in the furnace insulation zone, varied with the nature of the crystal being grown, and were dependent on the extent of transition zones at the ends of the ampoule. Actual growth rates varied significantly from the constant translation rate in response to the thermophysical properties of the crystal and its melt and the thermal conditions existing in the furnace at the interface. In the elemental semiconductor germanium the observed rates of crystal growth exceeded the imposed translation rate, but in the compound semiconductor lead tin telluride the observed rates of growth were less than the translation rate. Finally, the extent of ampoule thermal loading influenced the interface positions, the shapes, and the growth rates.

  15. Developing the Bias Blind Spot: Increasing Skepticism towards Others.

    PubMed

    Elashi, Fadwa B; Mills, Candice M

    2015-01-01

    Two experiments with eighty-eight 7- to 10-year-olds examined the bias blind spot in children. Both younger and older children rated themselves as less likely than a specific other (Experiment 1) or an average child (Experiment 2) to commit various biases. These self-other differences were also more extreme for biased behaviors than for other behaviors. At times, older children demonstrated stronger self-other differences than younger children, which seemed primarily driven by older children's judgments about bias in others. These findings suggest that, although the bias blind spot exists as soon as children recognize other-committed biases, what changes over development is how skeptical children are towards others. PMID:26523603

  16. Micromagnetic modeling of overlaid exchange-biased giant magnetoresistance head

    NASA Astrophysics Data System (ADS)

    Zheng, Yuankai; You, Dan; Wu, Yihong

    2002-05-01

    Overlaid exchange-biased structures for giant magnetoresistance head have been proposed and investigated. A home-developed three-dimensional micromagnetic modeling tool has been used to simulate synthetic antiferromagnetic spin valves of this type of biased structure with dimensions of 100 nm in width and 80 nm in height. Simulation results showed that, with a properly chosen antiferromagnetic material and structure, the exchange-biasing field could be made sufficient to suppress the noise without severely reducing the sensitivity. The sensitivity of overlaid exchange-biased spin valves is 1.73 times that of the abutted hard biased ones. Microtrack profiles showed that side reading effect could be suppressed effectively with an effective exchange-biasing field over 600 Oe.

  17. Developing the Bias Blind Spot: Increasing Skepticism towards Others

    PubMed Central

    2015-01-01

    Two experiments with eighty-eight 7- to 10-year-olds examined the bias blind spot in children. Both younger and older children rated themselves as less likely than a specific other (Experiment 1) or an average child (Experiment 2) to commit various biases. These self-other differences were also more extreme for biased behaviors than for other behaviors. At times, older children demonstrated stronger self-other differences than younger children, which seemed primarily driven by older children’s judgments about bias in others. These findings suggest that, although the bias blind spot exists as soon as children recognize other-committed biases, what changes over development is how skeptical children are towards others. PMID:26523603

  18. Bias correcting precipitation forecasts to improve the skill of seasonal streamflow forecasts

    NASA Astrophysics Data System (ADS)

    Crochemore, Louise; Ramos, Maria-Helena; Pappenberger, Florian

    2016-09-01

    Meteorological centres make sustained efforts to provide seasonal forecasts that are increasingly skilful, which has the potential to benefit streamflow forecasting. Seasonal streamflow forecasts can help to take anticipatory measures for a range of applications, such as water supply or hydropower reservoir operation and drought risk management. This study assesses the skill of seasonal precipitation and streamflow forecasts in France to provide insights into the way bias correcting precipitation forecasts can improve the skill of streamflow forecasts at extended lead times. We apply eight variants of bias correction approaches to the precipitation forecasts prior to generating the streamflow forecasts. The approaches are based on the linear scaling and the distribution mapping methods. A daily hydrological model is applied at the catchment scale to transform precipitation into streamflow. We then evaluate the skill of raw (without bias correction) and bias-corrected precipitation and streamflow ensemble forecasts in 16 catchments in France. The skill of the ensemble forecasts is assessed in reliability, sharpness, accuracy and overall performance. A reference prediction system, based on historical observed precipitation and catchment initial conditions at the time of forecast (i.e. ESP method) is used as benchmark in the computation of the skill. The results show that, in most catchments, raw seasonal precipitation and streamflow forecasts are often more skilful than the conventional ESP method in terms of sharpness. However, they are not significantly better in terms of reliability. Forecast skill is generally improved when applying bias correction. Two bias correction methods show the best performance for the studied catchments, each method being more successful in improving specific attributes of the forecasts: the simple linear scaling of monthly values contributes mainly to increasing forecast sharpness and accuracy, while the empirical distribution mapping

  19. The intentionality bias and schizotypy.

    PubMed

    Moore, J W; Pope, A

    2014-01-01

    The "intentionality bias" refers to our automatic tendency to judge other people's actions to be intentional. In this experiment we extended research on this effect in two key ways. First, we developed a novel nonlinguistic task for assessing the intentionality bias. This task used video stimuli of ambiguous movements. Second, we investigated the relationship between the strength of this bias and schizotypy (schizophrenia-like symptoms in healthy individuals). Our results showed that the intentionality bias was replicated for the video stimuli and also that this bias is stronger in those individuals scoring higher on the schizotypy rating scales. Overall these findings lend further support for the existence of the intentionality bias. We also discuss the possible relevance of these findings for our understanding of certain symptoms of schizophrenic illness.

  20. Bias voltage control of magnetic phase transitions in graphene nanojunctions.

    PubMed

    Luo, Kaikai; Sheng, Weidong

    2015-08-28

    The magnetic state of a spintronic device is usually controlled by magnetic contacts or a transverse electric field generated by side gates. In this work, we consider a graphene nanojunction in the presence of a bias voltage that leads to magnetic phase transitions in the system. Combining the non-equilibrium Green’s function with the Hubbard model, our self consistent calculation reveals that an increasing bias voltage induces consecutive transitions among antiferromagnetic and ferromagnetic states. It is further shown that the graphene nanojunction is turned off in the antiferromagnetic state when the bias voltage is low and can then be switched on to the ferromagnetic state by a high bias voltage. We therefore demonstrate that the magnetic state of the graphene system can be controlled by the bias voltage without resorting to any transverse gates.

  1. Recall bias in exposed subjects following a toxic exposure incident

    SciTech Connect

    Hopwood, D.G.; Guidotti, T.L.

    1988-05-01

    Attempts to reconstruct health effects following toxic exposure incidents may be subject to bias from distorted or incomplete recollection. The authors examined recall in 22 of 31 subjects exposed to fumes from ruptured drums containing nitric acid during a U.S. Environmental Protection Agency-supervised hazardous waste site clean up operation in August 1983. Exposed subjects were interviewed by emergency room staff immediately after the episode and the next morning by telephone by a public health epidemiologists. Six months later, the subjects were again interviewed by telephone and asked to report the symptoms they had experienced during the incident. For each respondent, symptoms recalled at 6 mo were compared to symptoms reported at the time. They found a low level of agreement compared to that expected by chance, associated with significant nonrandom differences in the distribution of responses consistently favoring selective recall on the later interview. They conclude that allowing time to elapse before obtaining data on individual symptoms following exposure may lead to a significant bias in response.

  2. Occupational Cohort Time Scales

    PubMed Central

    Roth, H. Daniel

    2015-01-01

    Purpose: This study explores how highly correlated time variables (occupational cohort time scales) contribute to confounding and ambiguity of interpretation. Methods: Occupational cohort time scales were identified and organized through simple equations of three time scales (relational triads) and the connections between these triads (time scale web). The behavior of the time scales was examined when constraints were imposed on variable ranges and interrelationships. Results: Constraints on a time scale in a triad create high correlations between the other two time scales. These correlations combine with the connections between relational triads to produce association paths. High correlation between time scales leads to ambiguity of interpretation. Conclusions: Understanding the properties of occupational cohort time scales, their relational triads, and the time scale web is helpful in understanding the origins of otherwise obscure confounding bias and ambiguity of interpretation. PMID:25647318

  3. Lead poisoning.

    PubMed Central

    Landrigan, P J; Todd, A C

    1994-01-01

    Lead poisoning is the most common disease of environmental origin in the United States today. Adult lead poisoning results primarily from exposure by inhalation in the workplace. Pediatric lead poisoning results principally from the ingestion of lead from environmental media, including paint chips, dust, soil, drinking water, ceramics, and medications. Lead is toxic to many organ systems, among them developing erythrocytes, the kidneys, and the nervous system. Lead-induced toxicity to the central nervous system causes delayed development, diminished intelligence, and altered behavior. In young children, this effect has been demonstrated convincingly to occur at blood lead levels between 10 and 20 micrograms per dl. The Centers for Disease Control and Prevention has recommended that a blood lead level of 10 micrograms per dl or higher be considered evidence of increased lead absorption, and the National Academy of Sciences has concurred in that recommendation. Unresolved issues in need of further study include the frequency of screening young children for lead, the question of whether women should be offered screening for lead before conceiving a pregnancy, the role of x-ray fluorescence analysis in assessing lead in bone, and the appropriate legislative response of the United States government to lead-based paint abatement. PMID:7941534

  4. Skill improvement of seasonal Arctic sea ice forecasts using bias-correction and ensemble calibration

    NASA Astrophysics Data System (ADS)

    Krikken, Folmer; Hazeleger, Wilco; Vlot, Willem; Schmeits, Maurice; Guemas, Virginie

    2016-04-01

    We explore the standard error and skill of dynamical seasonal sea ice forecasts of the Arctic using different bias-correction and ensemble calibration methods. The latter is often used in weather forecasting, but so far has not been applied to Arctic sea ice forecasts. We use seasonal predictions of Arctic sea ice of a 5-member ensemble forecast using the fully coupled GCM EC-Earth, with model initial states obtained by nudging towards ORAS4 and ERA-Interim. The raw model forecasts contain large biases in total sea ice area, especially during the summer months. This is mainly caused by a difference in average seasonal cycle between EC-Earth and observations, which translates directly into the forecasts yielding large biases. Further errors are introduced by the differences in long term trend between the observed sea ice, and the uninitialised EC-earth simulation. We find that extended logistic regression (ELR) and heteroscedastic extended logistic regression (HELR) both prove viable ensemble calibration methods, and improve the forecasts substantially compared to standard bias correction techniques. No clear distinction between ELR and HELR is found. Forecasts starting in May have higher skill (CRPSS > 0 up to 5 months lead time) than forecasts starting in August (2-3 months) and November (2-3 months), with trend-corrected climatology as reference. Analysis of regional skill in the Arctic shows distinct differences, where mainly the Arctic ocean and the Kara and Barents sea prove to be one of the more predictable regions with skilful forecasts starting in May up to 5-6 months lead time. Again, forecasts starting in August and November show much lower regional skill. Overall, it is still difficult to beat relative simple statistical forecasts, but by using ELR and HELR we are getting reasonably close to skilful seasonal forecasts up to 12 months lead time. These results show there is large potential, and need, for using ensemble calibration in seasonal forecasts of

  5. New Trends in Magnetic Exchange Bias

    NASA Astrophysics Data System (ADS)

    Mougin, Alexandra; Mangin, Stéphane; Bobo, Jean-Francois; Loidl, Alois

    2005-05-01

    of the constituant layers. The spirit of this topical issue is, for the first time, to gather and survey recent and original developments, both experimental and theoretical, which bring new insights into the physics of exchange bias. It has been planned in relation with an international workshop exclusively devoted to exchange bias, namely IWEBMN’04 (International Workshop on Exchange Bias in Magnetic Nanostructures) that took place in Anglet, in the south west of France, from 16th to 18th September 2004. The conference gathered worldwide researchers in the area, both experimentalists and theoreticians. Several research paths are particularly active in the field of magnetic exchange coupling. The conference, as well as this topical issue, which was also open to contributions from scientists not participating in the conference, has been organized according to the following principles: 1. Epitaxial systems: Since the essential behavior of exchange bias critically depends on the atomic-level chemical and spin structure at the interface between the ferromagnetic and antiferromagnetic components, epitaxial AF/F systems in which the quality of the interface and the crystalline coherence are optimized and well known are ideal candidates for a better understanding of the underlying physics of exchange bias. The dependence of exchange bias on the spin configurations at the interfaces can be accomplished by selecting different crystallographic orientations. The role of interface roughness can also be understood from thin-film systems by changing the growth parameters, and correlations between the interface structure and exchange bias can be made, as reported in this issue. 2. Out-of-plane magnetized systems: While much important work has been devoted to the study of structures with in-plane magnetization, little has been done on the study of exchange bias and exchange coupling in samples with out-of-plane magnetization. Some systems can exhibit either in-plane or out

  6. Lead poisoning

    MedlinePlus

    ... lead is still found in some modern faucets. Soil contaminated by decades of car exhaust or years ... house paint scrapings. Lead is more common in soil near highways and houses. Hobbies involving soldering, stained ...

  7. Quantum Error Correction with Biased Noise

    NASA Astrophysics Data System (ADS)

    Brooks, Peter

    Quantum computing offers powerful new techniques for speeding up the calculation of many classically intractable problems. Quantum algorithms can allow for the efficient simulation of physical systems, with applications to basic research, chemical modeling, and drug discovery; other algorithms have important implications for cryptography and internet security. At the same time, building a quantum computer is a daunting task, requiring the coherent manipulation of systems with many quantum degrees of freedom while preventing environmental noise from interacting too strongly with the system. Fortunately, we know that, under reasonable assumptions, we can use the techniques of quantum error correction and fault tolerance to achieve an arbitrary reduction in the noise level. In this thesis, we look at how additional information about the structure of noise, or "noise bias," can improve or alter the performance of techniques in quantum error correction and fault tolerance. In Chapter 2, we explore the possibility of designing certain quantum gates to be extremely robust with respect to errors in their operation. This naturally leads to structured noise where certain gates can be implemented in a protected manner, allowing the user to focus their protection on the noisier unprotected operations. In Chapter 3, we examine how to tailor error-correcting codes and fault-tolerant quantum circuits in the presence of dephasing biased noise, where dephasing errors are far more common than bit-flip errors. By using an appropriately asymmetric code, we demonstrate the ability to improve the amount of error reduction and decrease the physical resources required for error correction. In Chapter 4, we analyze a variety of protocols for distilling magic states, which enable universal quantum computation, in the presence of faulty Clifford operations. Here again there is a hierarchy of noise levels, with a fixed error rate for faulty gates, and a second rate for errors in the distilled

  8. Sex bias in paediatric autoimmune disease - Not just about sex hormones?

    PubMed

    Chiaroni-Clarke, Rachel C; Munro, Jane E; Ellis, Justine A

    2016-05-01

    Autoimmune diseases affect up to 10% of the world's population, and approximately 80% of those affected are female. The majority of autoimmune diseases occur more commonly in females, although some are more frequent in males, while others show no bias by sex. The mechanisms leading to sex biased disease prevalence are not well understood. However, for adult-onset autoimmune disease, at least some of the cause is usually ascribed to sex hormones. This is because levels of sex hormones are one of the most obvious physiological differences between adult males and females, and their impact on immune system function is well recognised. While for paediatric-onset autoimmune diseases a sex bias is not as common, there are several such diseases for which one sex predominates. For example, the oligoarticular subtype of juvenile idiopathic arthritis (JIA) occurs in approximately three times more girls than boys, with a peak age of onset well before the onset of puberty, and at a time when levels of androgen and oestrogen are low and not strikingly different between the sexes. Here, we review potential explanations for autoimmune disease sex bias with a particular focus on paediatric autoimmune disease, and biological mechanisms outside of sex hormone differences.

  9. From daily to sub-daily time steps - Creating a high temporal and spatial resolution climate reference data set for hydrological modeling and bias-correction of RCM data

    NASA Astrophysics Data System (ADS)

    Willkofer, Florian; Wood, Raul R.; Schmid, Josef; von Trentini, Fabian; Ludwig, Ralf

    2016-04-01

    The ClimEx project (Climate change and hydrological extreme events - risks and perspectives for water management in Bavaria and Québec) focuses on the effects of climate change on hydro-meteorological extreme events and their implications for water management in Bavaria and Québec. It builds on the conjoint analysis of a large ensemble of the CRCM5, driven by 50 members of the CanESM2, and the latest information provided through the CORDEX-initiative, to better assess the influence of natural climate variability and climatic change on the dynamics of extreme events. A critical point in the entire project is the preparation of a meteorological reference dataset with the required temporal (1-6h) and spatial (500m) resolution to be able to better evaluate hydrological extreme events in mesoscale river basins. For Bavaria a first reference data set (daily, 1km) used for bias-correction of RCM data was created by combining raster based data (E-OBS [1], HYRAS [2], MARS [3]) and interpolated station data using the meteorological interpolation schemes of the hydrological model WaSiM [4]. Apart from the coarse temporal and spatial resolution, this mosaic of different data sources is considered rather inconsistent and hence, not applicable for modeling of hydrological extreme events. Thus, the objective is to create a dataset with hourly data of temperature, precipitation, radiation, relative humidity and wind speed, which is then used for bias-correction of the RCM data being used as driver for hydrological modeling in the river basins. Therefore, daily data is disaggregated to hourly time steps using the 'Method of fragments' approach [5], based on available training stations. The disaggregation chooses fragments of daily values from observed hourly datasets, based on similarities in magnitude and behavior of previous and subsequent events. The choice of a certain reference station (hourly data, provision of fragments) for disaggregating daily station data (application

  10. Bone lead, hypertension, and lead nephropathy

    SciTech Connect

    Wedeen, R.P.

    1988-06-01

    There is considerable clinical evidence that excessive lead absorption causes renal failure with hypertension and predisposes individuals to hypertension even in the absence of detectable renal failure. Recent analyses of transiliac bone biopsies indicate that unsuspected elevated bone leads may reflect the cause (or contributing cause) of end-stage renal disease in 5% of the European dialysis population. In these patients, bone lead levels were four times higher than in unexposed cadavers (6 micrograms/g wet weight) and approximated levels found in lead workers (30 micrograms/g). At present, the most reliable index of the body lead burden is the CaNa2 EDTA lead mobilization test. In vivo tibial X-ray-induced X-ray fluorescence (XRF) is a more practical noninvasive technique for assessing bone lead, which should find widespread application as a diagnostic tool and for epidemiologic studies.

  11. Contamination effects on fixed-bias Langmuir probes

    SciTech Connect

    Steigies, C. T.; Barjatya, A.

    2012-11-15

    Langmuir probes are standard instruments for plasma density measurements on many sounding rockets. These probes can be operated in swept-bias as well as in fixed-bias modes. In swept-bias Langmuir probes, contamination effects are frequently visible as a hysteresis between consecutive up and down voltage ramps. This hysteresis, if not corrected, leads to poorly determined plasma densities and temperatures. With a properly chosen sweep function, the contamination parameters can be determined from the measurements and correct plasma parameters can then be determined. In this paper, we study the contamination effects on fixed-bias Langmuir probes, where no hysteresis type effect is seen in the data. Even though the contamination is not evident from the measurements, it does affect the plasma density fluctuation spectrum as measured by the fixed-bias Langmuir probe. We model the contamination as a simple resistor-capacitor circuit between the probe surface and the plasma. We find that measurements of small scale plasma fluctuations (meter to sub-meter scale) along a rocket trajectory are not affected, but the measured amplitude of large scale plasma density variation (tens of meters or larger) is attenuated. From the model calculations, we determine amplitude and cross-over frequency of the contamination effect on fixed-bias probes for different contamination parameters. The model results also show that a fixed bias probe operating in the ion-saturation region is affected less by contamination as compared to a fixed bias probe operating in the electron saturation region.

  12. Contamination effects on fixed-bias Langmuir probes.

    PubMed

    Steigies, C T; Barjatya, A

    2012-11-01

    Langmuir probes are standard instruments for plasma density measurements on many sounding rockets. These probes can be operated in swept-bias as well as in fixed-bias modes. In swept-bias Langmuir probes, contamination effects are frequently visible as a hysteresis between consecutive up and down voltage ramps. This hysteresis, if not corrected, leads to poorly determined plasma densities and temperatures. With a properly chosen sweep function, the contamination parameters can be determined from the measurements and correct plasma parameters can then be determined. In this paper, we study the contamination effects on fixed-bias Langmuir probes, where no hysteresis type effect is seen in the data. Even though the contamination is not evident from the measurements, it does affect the plasma density fluctuation spectrum as measured by the fixed-bias Langmuir probe. We model the contamination as a simple resistor-capacitor circuit between the probe surface and the plasma. We find that measurements of small scale plasma fluctuations (meter to sub-meter scale) along a rocket trajectory are not affected, but the measured amplitude of large scale plasma density variation (tens of meters or larger) is attenuated. From the model calculations, we determine amplitude and cross-over frequency of the contamination effect on fixed-bias probes for different contamination parameters. The model results also show that a fixed bias probe operating in the ion-saturation region is affected less by contamination as compared to a fixed bias probe operating in the electron saturation region.

  13. Real time and in situ determination of lead in road sediments using a man-portable laser-induced breakdown spectroscopy analyzer.

    PubMed

    Cuñat, J; Fortes, F J; Laserna, J J

    2009-02-01

    In situ, real time levels of lead in road sediments have been measured using a man-portable laser-induced breakdown spectroscopy analyzer. The instrument consists of a backpack and a probe housing a Q-switched Nd:YAG laser head delivering 50 mJ per pulse at 1064 nm. Plasma emission was collected and transmitted via fiber optic to a compact cross Czerny-Turner spectrometer equipped with a linear CCD array allocated in the backpack together with a personal computer. The limit of detection (LOD) for lead and the precision measured in the laboratory were 190 microg g(-1) (calculated by the 3 sigma method) and 9% R.S.D. (relative standard deviation), respectively. During the field campaign, averaged Pb concentration in the sediments were ranging from 480 microg g(-1) to 660 microg g(-1) depending on the inspected area, i.e. the entrance, the central part and the exit of the tunnel. These results were compared with those obtained with flame-atomic absorption spectrometry (flame-AAS). The relative error, expressed as [100(LIBS result-flame AAS result)/(LIBS result)], was approximately 14%.

  14. Is there gender bias in nursing research?

    PubMed

    Polit, Denise F; Beck, Cheryl Tatano

    2008-10-01

    Using data from a consecutive sample of 259 studies published in four leading nursing research journals in 2005-2006, we examined whether nurse researchers favor females as study participants. On average, 75.3% of study participants were female, and 38% of studies had all-female samples. The bias favoring female participants was statistically significant and persistent. The bias was observed regardless of funding source, methodological features, and other participant and researcher characteristics, with one exception: studies that had male investigators had more sex-balanced samples. When designing studies, nurse researchers need to pay close attention to who will benefit from their research and to whether they are leaving out a specific group about which there is a gap in knowledge. PMID:18324681

  15. Quantitative Bias Analysis in Regulatory Settings.

    PubMed

    Lash, Timothy L; Fox, Matthew P; Cooney, Darryl; Lu, Yun; Forshee, Richard A

    2016-07-01

    Nonrandomized studies are essential in the postmarket activities of the US Food and Drug Administration, which, however, must often act on the basis of imperfect data. Systematic errors can lead to inaccurate inferences, so it is critical to develop analytic methods that quantify uncertainty and bias and ensure that these methods are implemented when needed. "Quantitative bias analysis" is an overarching term for methods that estimate quantitatively the direction, magnitude, and uncertainty associated with systematic errors influencing measures of associations. The Food and Drug Administration sponsored a collaborative project to develop tools to better quantify the uncertainties associated with postmarket surveillance studies used in regulatory decision making. We have described the rationale, progress, and future directions of this project. PMID:27196652

  16. Tunable electronic properties of silicon nanowires under strain and electric bias

    SciTech Connect

    Nduwimana, Alexis; Wang, Xiao-Qian

    2014-07-15

    The electronic structure characteristics of silicon nanowires under strain and electric bias are studied using first-principles density functional theory. The unique wire-like structure leads to distinct spatial distribution of carriers, which can be tailored by applying tensile and compressive strains, as well as by an electric bias. Our results indicate that the combined effect of strain and electric bias leads to tunable electronic structures that can be used for piezo-electric devices.

  17. Classifying sex biased congenital anomalies

    SciTech Connect

    Lubinsky, M.S.

    1997-03-31

    The reasons for sex biases in congenital anomalies that arise before structural or hormonal dimorphisms are established has long been unclear. A review of such disorders shows that patterning and tissue anomalies are female biased, and structural findings are more common in males. This suggests different gender dependent susceptibilities to developmental disturbances, with female vulnerabilities focused on early blastogenesis/determination, while males are more likely to involve later organogenesis/morphogenesis. A dual origin for some anomalies explains paradoxical reductions of sex biases with greater severity (i.e., multiple rather than single malformations), presumably as more severe events increase the involvement of an otherwise minor process with opposite biases to those of the primary mechanism. The cause for these sex differences is unknown, but early dimorphisms, such as differences in growth or presence of H-Y antigen, may be responsible. This model provides a useful rationale for understanding and classifying sex-biased congenital anomalies. 42 refs., 7 tabs.

  18. Incorporating circulation statistics in bias correction of GCM ensembles: hydrological application for the Rhine basin

    NASA Astrophysics Data System (ADS)

    Photiadou, Christiana; van den Hurk, Bart; van Delden, Aarnout; Weerts, Albrecht

    2016-01-01

    An adapted statistical bias correction method is introduced to incorporate circulation-dependence of the model precipitation bias, and its influence on estimated discharges for the Rhine basin is analyzed for a historical period. The bias correction method is tailored to time scales relevant to flooding events in the basin. Large-scale circulation patterns (CPs) are obtained through Maximum Covariance Analysis using reanalysis sea level pressure and high-resolution precipitation observations. A bias correction using these CPs is applied to winter and summer separately, acknowledging the seasonal variability of the circulation regimes in North Europe and their correlation with regional precipitation rates over the Rhine basin. Two different climate model ensemble outputs are explored: ESSENCE and CMIP5. The results of the CP-method are then compared to observations and uncorrected model outputs. Results from a simple bias correction based on a delta factor (NoCP-method) are also used for comparison. For both summer and winter, the CP-method offers a statistically significant improvement of precipitation statistics for subsets of data dominated by particular circulation regimes, demonstrating the circulation-dependence of the precipitation bias. Uncorrected, CP and NoCP corrected model outputs were used as forcing to a hydrological model to simulate river discharges. The CP-method leads to a larger improvement in simulated discharge in the Alpine area in winter than in summer due to a stronger dependence of Rhine precipitation on atmospheric circulation in winter. However, the NoCP-method, in comparison to the CP-method, improves the discharge estimations over the entire Rhine basin.

  19. Lead in petrol. The isotopic lead experiment

    SciTech Connect

    Facchetti, S. )

    1989-10-01

    Many studies were dedicated to the evaluation of the impact of automotive lead on the environment and to the assessment of its absorption in the human population. They can be subdivided into two groups, those based on changes of air and blood lead concentrations and those based on changes of air and blood lead isotopic compositions. According to various authors, 50-66% of the lead added to petrol is mobilized in the atmosphere, while most of the remainder adheres to the walls of the exhaust system from which it is expelled by mechanical and thermal shocks in the forms of easily sedimented particles. The fraction directly emitted by engine exhaust fumes is found in the form of fine particles, which can be transferred a long way from the emitting sources. However important the contribution of petrol lead to the total airborne lead may be, our knowledge does not permit a straightforward calculation of the percentage of petrol lead in total blood lead, which of course can also originate from other sources (e.g., industrial, natural). To evaluate this percentage in 1973, the idea of the Isotopic Lead Experiment (ILE project) was conceived to label, on a regional scale, petrol with a nonradioactive lead of an isotopic composition sufficiently different from that of background lead and sufficiently stable in time. This Account summarizes the main results obtained by the ILE project.

  20. The potential for social contextual and group biases in team decision-making: biases, conditions and psychological mechanisms.

    PubMed

    Jones, P E; Roelofsma, P H

    2000-08-01

    This paper provides a critical review of social contextual and group biases that are relevant to team decision-making in command and control situations. Motivated by the insufficient level of attention this area has received, the purpose of the paper is to provide an insight into the potential that these types of biases have to affect the decision-making of such teams. The biases considered are: false consensus, groupthink, group polarization and group escalation of commitment. For each bias the following four questions are addressed. What is the descriptive nature of the bias? What factors induce the bias? What psychological mechanisms underlie the bias? What is the relevance of the bias to command and control teams? The analysis suggests that these biases have a strong potential to affect team decisions. Consistent with the nature of team decision-making in command and control situations, all of the biases considered tend to be associated with those decisions that are important or novel and are promoted by time pressure and high levels of uncertainty. A concept unifying these biases is that of the shared mental model, but whereas false consensus emanates from social projection tendencies, the rest emanate from social influence factors. The authors also discuss the 'tricky' distinction between teams and groups and propose a revised definition for command and control team. Finally, the authors emphasize the need for future empirical research in this area to pay additional attention to the social side of cognition and the potential that social biases have to affect team decision-making.

  1. The effect of window size and lead time on pre-impact fall detection accuracy using support vector machine analysis of waist mounted inertial sensor data.

    PubMed

    Aziz, Omar; Russell, Colin M; Park, Edward J; Robinovitch, Stephen N

    2014-01-01

    Falls are a major cause of death and morbidity in older adults. In recent years many researchers have examined the role of wearable inertial sensors (accelerometers and/or gyroscopes) to automatically detect falls. The primary goal of such fall monitors is to alert care providers of the fall event, who can then commence earlier treatment. Although such fall detection systems may reduce time until the arrival of medical assistance, they cannot help to prevent or reduce the severity of traumatic injury caused by the fall. In the current study, we extend the application of wearable inertial sensors beyond post-impact fall detection, by developing and evaluating the accuracy of a sensor system for detecting falls prior to the fall impact. We used support vector machine (SVM) analysis to classify 7 fall and 8 non-fall events. In particular, we focused on the effect of data window size and lead time on the accuracy of our pre-impact fall detection system using signals from a single waist sensor. We found that our system was able to detect fall events at between 0.0625-0.1875 s prior to the impact with at least 95% sensitivity and at least 90% specificity for window sizes between 0.125-1 s.

  2. Error covariance calculation for forecast bias estimation in hydrologic data assimilation

    NASA Astrophysics Data System (ADS)

    Pauwels, Valentijn R. N.; De Lannoy, Gabriëlle J. M.

    2015-12-01

    To date, an outstanding issue in hydrologic data assimilation is a proper way of dealing with forecast bias. A frequently used method to bypass this problem is to rescale the observations to the model climatology. While this approach improves the variability in the modeled soil wetness and discharge, it is not designed to correct the results for any bias. Alternatively, attempts have been made towards incorporating dynamic bias estimates into the assimilation algorithm. Persistent bias models are most often used to propagate the bias estimate, where the a priori forecast bias error covariance is calculated as a constant fraction of the unbiased a priori state error covariance. The latter approach is a simplification to the explicit propagation of the bias error covariance. The objective of this paper is to examine to which extent the choice for the propagation of the bias estimate and its error covariance influence the filter performance. An Observation System Simulation Experiment (OSSE) has been performed, in which ground water storage observations are assimilated into a biased conceptual hydrologic model. The magnitudes of the forecast bias and state error covariances are calibrated by optimizing the innovation statistics of groundwater storage. The obtained bias propagation models are found to be identical to persistent bias models. After calibration, both approaches for the estimation of the forecast bias error covariance lead to similar results, with a realistic attribution of error variances to the bias and state estimate, and significant reductions of the bias in both the estimates of groundwater storage and discharge. Overall, the results in this paper justify the use of the traditional approach for online bias estimation with a persistent bias model and a simplified forecast bias error covariance estimation.

  3. Agitated Honeybees Exhibit Pessimistic Cognitive Biases

    PubMed Central

    Bateson, Melissa; Desire, Suzanne; Gartside, Sarah E.; Wright, Geraldine A.

    2011-01-01

    Summary Whether animals experience human-like emotions is controversial and of immense societal concern [1–3]. Because animals cannot provide subjective reports of how they feel, emotional state can only be inferred using physiological, cognitive, and behavioral measures [4–8]. In humans, negative feelings are reliably correlated with pessimistic cognitive biases, defined as the increased expectation of bad outcomes [9–11]. Recently, mammals [12–16] and birds [17–20] with poor welfare have also been found to display pessimistic-like decision making, but cognitive biases have not thus far been explored in invertebrates. Here, we ask whether honeybees display a pessimistic cognitive bias when they are subjected to an anxiety-like state induced by vigorous shaking designed to simulate a predatory attack. We show for the first time that agitated bees are more likely to classify ambiguous stimuli as predicting punishment. Shaken bees also have lower levels of hemolymph dopamine, octopamine, and serotonin. In demonstrating state-dependent modulation of categorization in bees, and thereby a cognitive component of emotion, we show that the bees' response to a negatively valenced event has more in common with that of vertebrates than previously thought. This finding reinforces the use of cognitive bias as a measure of negative emotional states across species and suggests that honeybees could be regarded as exhibiting emotions. Video Abstract PMID:21636277

  4. Leading Democratically

    ERIC Educational Resources Information Center

    Brookfield, Stephen

    2010-01-01

    Democracy is the most venerated of American ideas, the one for which wars are fought and people die. So most people would probably agree that leaders should be able to lead well in a democratic society. Yet, genuinely democratic leadership is a relative rarity. Leading democratically means viewing leadership as a function or process, rather than…

  5. Observational biases for transiting planets

    NASA Astrophysics Data System (ADS)

    Kipping, David M.; Sandford, Emily

    2016-09-01

    Observational biases distort our view of nature, such that the patterns we see within a surveyed population of interest are often unrepresentative of the truth we seek. Transiting planets currently represent the most informative data set on the ensemble properties of exoplanets within 1 AU of their star. However, the transit method is inherently biased due to both geometric and detection-driven effects. In this work, we derive the overall observational biases affecting the most basic transit parameters from first principles. By assuming a trapezoidal transit and using conditional probability, we infer the expected distribution of these terms both as a joint distribution and in a marginalized form. These general analytic results provide a baseline against which to compare trends predicted by mission-tailored injection/recovery simulations and offer a simple way to correct for observational bias. Our results explain why the observed population of transiting planets displays a non-uniform impact parameter distribution, with a bias towards near-equatorial geometries. We also find that the geometric bias towards observed planets transiting near periastron is attenuated by the longer durations which occur near apoastron. Finally, we predict that the observational bias with respect to ratio-of-radii is super-quadratic, scaling as (RP/R⋆)5/2, driven by an enhanced geometric transit probability and modestly longer durations.

  6. Measurement of the $B^-$ lifetime using a simulation free approach for trigger bias correction

    SciTech Connect

    Aaltonen, T.; Adelman, J.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A.; Antos, J.; Apollinari, G.; Appel, J.; Apresyan, A.; /Purdue U. /Waseda U.

    2010-04-01

    The collection of a large number of B hadron decays to hadronic final states at the CDF II detector is possible due to the presence of a trigger that selects events based on track impact parameters. However, the nature of the selection requirements of the trigger introduces a large bias in the observed proper decay time distribution. A lifetime measurement must correct for this bias and the conventional approach has been to use a Monte Carlo simulation. The leading sources of systematic uncertainty in the conventional approach are due to differences between the data and the Monte Carlo simulation. In this paper they present an analytic method for bias correction without using simulation, thereby removing any uncertainty between data and simulation. This method is presented in the form of a measurement of the lifetime of the B{sup -} using the mode B{sup -} {yields} D{sup 0}{pi}{sup -}. The B{sup -} lifetime is measured as {tau}{sub B{sup -}} = 1.663 {+-} 0.023 {+-} 0.015 ps, where the first uncertainty is statistical and the second systematic. This new method results in a smaller systematic uncertainty in comparison to methods that use simulation to correct for the trigger bias.

  7. Publication bias in dermatology systematic reviews and meta-analyses.

    PubMed

    Atakpo, Paul; Vassar, Matt

    2016-05-01

    Systematic reviews and meta-analyses in dermatology provide high-level evidence for clinicians and policy makers that influence clinical decision making and treatment guidelines. One methodological problem with systematic reviews is the under representation of unpublished studies. This problem is due in part to publication bias. Omission of statistically non-significant data from meta-analyses may result in overestimation of treatment effect sizes which may lead to clinical consequences. Our goal was to assess whether systematic reviewers in dermatology evaluate and report publication bias. Further, we wanted to conduct our own evaluation of publication bias on meta-analyses that failed to do so. Our study considered systematic reviews and meta-analyses from ten dermatology journals from 2006 to 2016. A PubMed search was conducted, and all full-text articles that met our inclusion criteria were retrieved and coded by the primary author. 293 articles were included in our analysis. Additionally, we formally evaluated publication bias in meta-analyses that failed to do so using trim and fill and cumulative meta-analysis by precision methods. Publication bias was mentioned in 107 articles (36.5%) and was formally evaluated in 64 articles (21.8%). Visual inspection of a funnel plot was the most common method of evaluating publication bias. Publication bias was present in 45 articles (15.3%), not present in 57 articles (19.5%) and not determined in 191 articles (65.2%). Using the trim and fill method, 7 meta-analyses (33.33%) showed evidence of publication bias. Although the trim and fill method only found evidence of publication bias in 7 meta-analyses, the cumulative meta-analysis by precision method found evidence of publication bias in 15 meta-analyses (71.4%). Many of the reviews in our study did not mention or evaluate publication bias. Further, of the 42 articles that stated following PRISMA reporting guidelines, 19 (45.2%) evaluated for publication bias. In

  8. Thermal and bias cycling stabilizes planar silicon devices

    NASA Technical Reports Server (NTRS)

    Harris, R. E.; Meinhard, J. E.

    1967-01-01

    Terminal burn-in or baking step time in the processing of planar silicon devices is extended to reduce their inversion tendencies. The collector-base junction of the device is also cyclically biased during the burn-in.

  9. Left face matching bias: right hemisphere dominance or scanning habits?

    PubMed

    Megreya, Ahmed M; Havard, Catriona

    2011-01-01

    A large body of work report a leftward bias in face processing. However, it is not clear whether this leftward bias purely reflects the dominance of the right hemisphere or is influenced by scanning habits developed by reading directions. Here, we report two experiments examining how well native readers of right to left Arabic scripts (Egyptians) could match (for identity) a target face that appeared with a companion to a line-up of 10 faces. There was a significant advantage for matching faces that appeared on the left. However, Experiment 2 found that the magnitude of this left face matching bias was almost three times weaker than the magnitude of the leftward bias shown by native readers of left to right English scripts (British). Accordingly, we suggest that the right hemisphere dominance for face processing underlies the leftward face perception bias, but with the interaction of scanning habits.

  10. Directional Bias and Pheromone for Discovery and Coverage on Networks

    SciTech Connect

    Fink, Glenn A.; Berenhaut, Kenneth S.; Oehmen, Christopher S.

    2012-09-11

    Natural multi-agent systems often rely on “correlated random walks” (random walks that are biased toward a current heading) to distribute their agents over a space (e.g., for foraging, search, etc.). Our contribution involves creation of a new movement and pheromone model that applies the concept of heading bias in random walks to a multi-agent, digital-ants system designed for cyber-security monitoring. We examine the relative performance effects of both pheromone and heading bias on speed of discovery of a target and search-area coverage in a two-dimensional network layout. We found that heading bias was unexpectedly helpful in reducing search time and that it was more influential than pheromone for improving coverage. We conclude that while pheromone is very important for rapid discovery, heading bias can also greatly improve both performance metrics.

  11. The source of the truth bias: Heuristic processing?

    PubMed

    Street, Chris N H; Masip, Jaume

    2015-06-01

    People believe others are telling the truth more often than they actually are; this is called the truth bias. Surprisingly, when a speaker is judged at multiple points across their statement the truth bias declines. Previous claims argue this is evidence of a shift from (biased) heuristic processing to (reasoned) analytical processing. In four experiments we contrast the heuristic-analytic model (HAM) with alternative accounts. In Experiment 1, the decrease in truth responding was not the result of speakers appearing more deceptive, but was instead attributable to the rater's processing style. Yet contrary to HAMs, across three experiments we found the decline in bias was not related to the amount of processing time available (Experiments 1-3) or the communication channel (Experiment 2). In Experiment 4 we found support for a new account: that the bias reflects whether raters perceive the statement to be internally consistent.

  12. The source of the truth bias: Heuristic processing?

    PubMed

    Street, Chris N H; Masip, Jaume

    2015-06-01

    People believe others are telling the truth more often than they actually are; this is called the truth bias. Surprisingly, when a speaker is judged at multiple points across their statement the truth bias declines. Previous claims argue this is evidence of a shift from (biased) heuristic processing to (reasoned) analytical processing. In four experiments we contrast the heuristic-analytic model (HAM) with alternative accounts. In Experiment 1, the decrease in truth responding was not the result of speakers appearing more deceptive, but was instead attributable to the rater's processing style. Yet contrary to HAMs, across three experiments we found the decline in bias was not related to the amount of processing time available (Experiments 1-3) or the communication channel (Experiment 2). In Experiment 4 we found support for a new account: that the bias reflects whether raters perceive the statement to be internally consistent. PMID:25707774

  13. Single-Receiver GPS Phase Bias Resolution

    NASA Technical Reports Server (NTRS)

    Bertiger, William I.; Haines, Bruce J.; Weiss, Jan P.; Harvey, Nathaniel E.

    2010-01-01

    Existing software has been modified to yield the benefits of integer fixed double-differenced GPS-phased ambiguities when processing data from a single GPS receiver with no access to any other GPS receiver data. When the double-differenced combination of phase biases can be fixed reliably, a significant improvement in solution accuracy is obtained. This innovation uses a large global set of GPS receivers (40 to 80 receivers) to solve for the GPS satellite orbits and clocks (along with any other parameters). In this process, integer ambiguities are fixed and information on the ambiguity constraints is saved. For each GPS transmitter/receiver pair, the process saves the arc start and stop times, the wide-lane average value for the arc, the standard deviation of the wide lane, and the dual-frequency phase bias after bias fixing for the arc. The second step of the process uses the orbit and clock information, the bias information from the global solution, and only data from the single receiver to resolve double-differenced phase combinations. It is called "resolved" instead of "fixed" because constraints are introduced into the problem with a finite data weight to better account for possible errors. A receiver in orbit has much shorter continuous passes of data than a receiver fixed to the Earth. The method has parameters to account for this. In particular, differences in drifting wide-lane values must be handled differently. The first step of the process is automated, using two JPL software sets, Longarc and Gipsy-Oasis. The resulting orbit/clock and bias information files are posted on anonymous ftp for use by any licensed Gipsy-Oasis user. The second step is implemented in the Gipsy-Oasis executable, gd2p.pl, which automates the entire process, including fetching the information from anonymous ftp

  14. Bias correcting precipitation forecasts for extended-range skilful seasonal streamflow predictions

    NASA Astrophysics Data System (ADS)

    Crochemore, Louise; Ramos, Maria-Helena; Pappenberger, Florian

    2016-04-01

    Meteorological centres make sustained efforts to provide seasonal forecasts that are increasingly skilful, which has the potential to also benefit streamflow forecasting. Seasonal streamflow forecasts can help to take anticipatory measures for a range of applications, such as water supply or hydropower reservoir operation and drought risk management. This study assesses the skill of seasonal precipitation and streamflow forecasts in France in order to provide insights into the way bias correcting seasonal precipitation forecasts can contribute to maintain skill of seasonal flow predictions at extended lead times. First, we evaluate the skill of raw (i.e., without bias correction) seasonal precipitation ensemble forecasts for streamflow forecasting in sixteen French catchments. A lumped daily hydrological model is applied at the catchment scale to transform precipitation into streamflow. A reference prediction system based on historic observed precipitation and watershed initial conditions at the time of forecast (i.e., ESP method) is used as benchmark. In a second step, we apply eight variants of bias correction approaches to the precipitation forecasts prior to generating the flow forecasts. The approaches were based on the linear scaling and the distribution mapping methods. The skill of the ensemble forecasts is assessed in reliability, sharpness, accuracy, and overall performance. The results show that, in most catchments, raw seasonal precipitation and streamflow forecasts are often more skilful than the conventional ESP method in terms of sharpness. However, reliability is an attribute that is not significantly improved. Forecast skill is generally improved when applying bias correction. Two bias correction methods showed the best performance for the studied catchments, with, however, each method being more successful in improving specific attributes of forecast quality: the simple linear scaling of monthly values contributed mainly to increase forecast

  15. The intentionality bias in schizophrenia.

    PubMed

    Peyroux, Elodie; Strickland, Brent; Tapiero, Isabelle; Franck, Nicolas

    2014-11-30

    The tendency to over-interpret events of daily life as resulting from voluntary or intentional actions is one of the key aspects of schizophrenia with persecutory delusions. Here, we ask whether this characteristic may emerge from the abnormal activity of a basic cognitive process found in healthy adults and children: the intentionality bias, which refers to the implicit and automatic inclination to interpret human actions as intentional (Rosset, 2008, Cognition 108, 771-780). In our experiment, patients with schizophrenia and healthy controls were shown sentences describing human actions in various linguistic contexts, and were asked to indicate whether the action was intentional or not. The results indicated that people with schizophrenia exhibited a striking bias to over attribute intentionality regardless of linguistic context, contrary to healthy controls who did not exhibit such a general intentionality bias. Moreover, this study provides some insight into the cognitive mechanisms underlying this bias: an inability to inhibit the automatic attribution of intentionality.

  16. Magnetic bearings with zero bias

    NASA Technical Reports Server (NTRS)

    Brown, Gerald V.; Grodsinsky, Carlos M.

    1991-01-01

    A magnetic bearing operating without a bias field has supported a shaft rotating at speeds up to 12,000 rpm with the usual four power supplies and with only two. A magnetic bearing is commonly operated with a bias current equal to half of the maximum current allowable in its coils. This linearizes the relation between net force and control current and improves the force slewing rate and hence the band width. The steady bias current dissipates power, even when no force is required from the bearing. The power wasted is equal to two-thirds of the power at maximum force output. Examined here is the zero bias idea. The advantages and disadvantages are noted.

  17. Inequities in the freedom to lead a flourishing and healthy life: time for a progressive social protections framework : Comment on "Inequities in the freedom to lead a flourishing and healthy life: issues for healthy public policy".

    PubMed

    Carey, Gemma

    2014-09-01

    Evidence now shows that the key drivers of poor health are social factors, such as education, employment, housing and urban environments. Variations in these social factors-or the conditions in which we live our lives-have lead to a growth in health inequalities within and between countries. One of the key challenges facing those concerned with health equity is how to effect change across the broad policy areas that impact these social. PMID:25279385

  18. Inequities in the freedom to lead a flourishing and healthy life: time for a progressive social protections framework : Comment on "Inequities in the freedom to lead a flourishing and healthy life: issues for healthy public policy".

    PubMed

    Carey, Gemma

    2014-09-01

    Evidence now shows that the key drivers of poor health are social factors, such as education, employment, housing and urban environments. Variations in these social factors-or the conditions in which we live our lives-have lead to a growth in health inequalities within and between countries. One of the key challenges facing those concerned with health equity is how to effect change across the broad policy areas that impact these social.

  19. Active current gating in electrically biased conical nanopores

    NASA Astrophysics Data System (ADS)

    Bearden, Samuel; Simpanen, Erik; Zhang, Guigen

    2015-05-01

    We observed that the ionic current through a gold/silicon nitride (Si3N4) nanopore could be modulated and gated by electrically biasing the gold layer. Rather than employing chemical modification to alter device behavior, we achieved control of conductance directly by electrically biasing the gold portion of the nanopore. By stepping through a range of bias potentials under a constant trans-pore electric field, we observed a gating phenomenon in the trans-pore current response in a variety of solutions including potassium chloride (KCl), sodium chloride (NaCl), and potassium iodide (KI). A computational model with a conical nanopore was developed to examine the effect of the Gouy-Chapman-Stern electrical double layer along with nanopore geometry, work function potentials, and applied electrical bias on the ionic current. The numerical results indicated that the observed modulation and gating behavior was due to dynamic reorganization of the electrical double layer in response to changes in the electrical bias. Specifically, in the conducting state, the nanopore conductance (both numerical and experimental) is linearly proportional to the applied bias due to accumulation of charge in the diffuse layer. The gating effect occurs due to the asymmetric charge distribution in the fluid induced by the distribution of potentials at the nanopore surface. Time dependent changes in current due to restructuring of the electrical double layer occur when the electrostatic bias is instantaneously changed. The nanopore device demonstrates direct external control over nanopore behavior via modulation of the electrical double layer by electrostatic biasing.

  20. Quantifying ligand bias at seven-transmembrane receptors.

    PubMed

    Rajagopal, Sudarshan; Ahn, Seungkirl; Rominger, David H; Gowen-MacDonald, William; Lam, Christopher M; Dewire, Scott M; Violin, Jonathan D; Lefkowitz, Robert J

    2011-09-01

    Seven transmembrane receptors (7TMRs), commonly referred to as G protein-coupled receptors, form a large part of the "druggable" genome. 7TMRs can signal through parallel pathways simultaneously, such as through heterotrimeric G proteins from different families, or, as more recently appreciated, through the multifunctional adapters, β-arrestins. Biased agonists, which signal with different efficacies to a receptor's multiple downstream pathways, are useful tools for deconvoluting this signaling complexity. These compounds may also be of therapeutic use because they have distinct functional and therapeutic profiles from "balanced agonists." Although some methods have been proposed to identify biased ligands, no comparison of these methods applied to the same set of data has been performed. Therefore, at this time, there are no generally accepted methods to quantify the relative bias of different ligands, making studies of biased signaling difficult. Here, we use complementary computational approaches for the quantification of ligand bias and demonstrate their application to two well known drug targets, the β2 adrenergic and angiotensin II type 1A receptors. The strategy outlined here allows a quantification of ligand bias and the identification of weakly biased compounds. This general method should aid in deciphering complex signaling pathways and may be useful for the development of novel biased therapeutic ligands as drugs.

  1. Estimation and correction of model bias in the NASA/GMAO GEOS5 data assimilation system: Sequential implementation

    NASA Astrophysics Data System (ADS)

    Zhang, Banglin; Tallapragada, Vijay; Weng, Fuzhong; Sippel, Jason; Ma, Zaizhong

    2016-06-01

    This study presents a simplified multivariate bias correction scheme that is sequentially implemented in the GEOS5 data assimilation system and compared against a control experiment without model bias correction. The results show considerable improvement in terms of the mean biases of rawinsonde observation-minus-background (OmB) residuals for observed water vapor, wind and temperature variables. The time series spectral analysis shows whitening of bias-corrected OmB residuals, and mean biases for rawinsonde observation-minus-analysis (OmA) are also improved. Some wind and temperature biases in the control experiment near the equatorial tropopause nearly vanish from the bias-corrected experiment. Despite the analysis improvement, the bias correction scheme has only a moderate impact on forecast skill. Significant interaction is also found among quality-control, satellite observation bias correction, and background bias correction, and the latter positively impacts satellite bias correction.

  2. Integrated Bypass Battery for ReverseBias Protection

    NASA Technical Reports Server (NTRS)

    Landis, Geoffrey A,

    2002-01-01

    When a single solar cell of a series-connect string is placed in shadow, the entire array current is forced through that cell in reverse bias. Reverse bias current can lead to "hot-spot" heating, where the power produced by the unshadowed cells is dissipated as heat in the shadowed cell. Since occasional shadows are unavoidable in most applications, most solar arrays include shadow protection to prevent damage. In current practice, shadow protection is done with a "bypass diode" on each cell, to shunt the reverse bias current if a cell is shadowed. A new method of reverse bias protection is to use an Integral thin-film battery to provide voltage in the case of a shadowed cell. In this case, the shadowed cell continues to provide voltage during the transient shadow.

  3. Bias and robustness of uncertainty components estimates in transient climate projections

    NASA Astrophysics Data System (ADS)

    Hingray, Benoit; Blanchet, Juliette; Jean-Philippe, Vidal

    2016-04-01

    A critical issue in climate change studies is the estimation of uncertainties in projections along with the contribution of the different uncertainty sources, including scenario uncertainty, the different components of model uncertainty and internal variability. Quantifying the different uncertainty sources faces actually different problems. For instance and for the sake of simplicity, an estimate of model uncertainty is classically obtained from the empirical variance of the climate responses obtained for the different modeling chains. These estimates are however biased. Another difficulty arises from the limited number of members that are classically available for most modeling chains. In this case, the climate response of one given chain and the effect of its internal variability may be actually difficult if not impossible to separate. The estimate of scenario uncertainty, model uncertainty and internal variability components are thus likely to be not really robust. We explore the importance of the bias and the robustness of the estimates for two classical Analysis of Variance (ANOVA) approaches: a Single Time approach (STANOVA), based on the only data available for the considered projection lead time and a time series based approach (QEANOVA), which assumes quasi-ergodicity of climate outputs over the whole available climate simulation period (Hingray and Saïd, 2014). We explore both issues for a simple but classical configuration where uncertainties in projections are composed of two single sources: model uncertainty and internal climate variability. The bias in model uncertainty estimates is explored from theoretical expressions of unbiased estimators developed for both ANOVA approaches. The robustness of uncertainty estimates is explored for multiple synthetic ensembles of time series projections generated with MonteCarlo simulations. For both ANOVA approaches, when the empirical variance of climate responses is used to estimate model uncertainty, the bias

  4. Bias and design in software specifications

    NASA Technical Reports Server (NTRS)

    Straub, Pablo A.; Zelkowitz, Marvin V.

    1990-01-01

    Implementation bias in a specification is an arbitrary constraint in the solution space. Presented here is a model of bias in software specifications. Bias is defined in terms of the specification process and a classification of the attributes of the software product. Our definition of bias provides insight into both the origin and the consequences of bias. It also shows that bias is relative and essentially unavoidable. Finally, we describe current work on defining a measure of bias, formalizing our model, and relating bias to software defects.

  5. Bias and spread in EVT performance tests.

    NASA Technical Reports Server (NTRS)

    Smith, J. G.

    1971-01-01

    Performance tests (error probability measurements) of communications systems characterized by low bit rates and high reliability requirements frequently utilize classical extreme value theory (EVT) to avoid the excessive test times encountered with bit error rate (BER) tests. If the underlying noise is Gaussian or perturbed Gaussian, the EVT error estimates have either excessive bias or excessive variance if an insufficient number of test samples is used. EVT is examined to explain the cause of this bias and spread. Experimental verification is made by testing a known Gaussian source, and procedures that minimize these effects are described. It seems apparent that even under the best of conditions the EVT test results are not particularly better than those of BER tests.

  6. Human language reveals a universal positivity bias

    PubMed Central

    Dodds, Peter Sheridan; Clark, Eric M.; Desu, Suma; Frank, Morgan R.; Reagan, Andrew J.; Williams, Jake Ryland; Mitchell, Lewis; Harris, Kameron Decker; Kloumann, Isabel M.; Bagrow, James P.; Megerdoomian, Karine; McMahon, Matthew T.; Tivnan, Brian F.; Danforth, Christopher M.

    2015-01-01

    Using human evaluation of 100,000 words spread across 24 corpora in 10 languages diverse in origin and culture, we present evidence of a deep imprint of human sociality in language, observing that (i) the words of natural human language possess a universal positivity bias, (ii) the estimated emotional content of words is consistent between languages under translation, and (iii) this positivity bias is strongly independent of frequency of word use. Alongside these general regularities, we describe interlanguage variations in the emotional spectrum of languages that allow us to rank corpora. We also show how our word evaluations can be used to construct physical-like instruments for both real-time and offline measurement of the emotional content of large-scale texts. PMID:25675475

  7. Ecotoxicology: Lead

    USGS Publications Warehouse

    Scheuhammer, A.M.; Beyer, W.N.; Schmitt, C.J.; Jorgensen, Sven Erik; Fath, Brian D.

    2008-01-01

    Lead (Pb) is a naturally occurring metallic element; trace concentrations are found in all environmental media and in all living things. However, certain human activities, especially base metal mining and smelting; combustion of leaded gasoline; the use of Pb in hunting, target shooting, and recreational angling; the use of Pb-based paints; and the uncontrolled disposal of Pb-containing products such as old vehicle batteries and electronic devices have resulted in increased environmental levels of Pb, and have created risks for Pb exposure and toxicity in invertebrates, fish, and wildlife in some ecosystems.

  8. Effects of Low Level Lead Exposure on Associative Learning and Memory in the Rat: Influences of Sex and Developmental Timing Of Exposure

    PubMed Central

    Anderson, D.W.; Mettil, W.; Schneider, J.S.

    2016-01-01

    Lead (Pb) exposure during development impairs a variety of cognitive, behavioral and neurochemical processes resulting in deficits in learning, memory, attention, impulsivity and executive function. Numerous studies have attempted to model this effect of Pb in rodents, with the majority of studies focusing on hippocampus-associated spatial learning and memory processes. Using a different paradigm, trace fear conditioning, a process requiring coordinated integration of both the medial prefrontal cortex and the hippocampus, we have assessed the effects of Pb exposure on associative learning and memory. The present study examined both female and male Long Evans rats exposed to three environmentally relevant levels of Pb (150 ppm, 375 ppm and 750 ppm) during different developmental periods: perinatal (PERI; gestation – postnatal day 21), early postnatal (EPN; postnatal days 1–21) and late postnatal (LPN; postnatal days 1–55). Testing began at postnatal day 55 and consisted of a single day of acquisition training, and three post training time points (1, 2 and 10 days) to assess memory consolidation and recall. All animals, regardless of sex, developmental window or level of Pb-exposure, successfully acquired conditioned-unconditioned stimulus association during training. However, there were significant effects of Pb-exposure on consolidation and memory recall at days 1–10 post training. In females, EPN and LPN exposure to 150 ppm Pb (but not PERI exposure) significantly impaired recall. In contrast, only PERI 150 ppm and 750 ppm-exposed males had significant recall deficits. These data suggest a complex interaction between sex, developmental window of exposure and Pb-exposure level on consolidation and recall of associative memories. PMID:26812500

  9. Effects of low level lead exposure on associative learning and memory in the rat: Influences of sex and developmental timing of exposure.

    PubMed

    Anderson, D W; Mettil, W; Schneider, J S

    2016-03-30

    Lead (Pb) exposure during development impairs a variety of cognitive, behavioral and neurochemical processes resulting in deficits in learning, memory, attention, impulsivity and executive function. Numerous studies have attempted to model this effect of Pb in rodents, with the majority of studies focusing on hippocampus-associated spatial learning and memory processes. Using a different paradigm, trace fear conditioning, a process requiring coordinated integration of both the medial prefrontal cortex and the hippocampus, we have assessed the effects of Pb exposure on associative learning and memory. The present study examined both female and male long evans rats exposed to three environmentally relevant levels of Pb (150 ppm, 375 ppm and 750 ppm) during different developmental periods: perinatal (PERI; gestation-postnatal day 21), early postnatal (EPN; postnatal days 1-21) and late postnatal (LPN; postnatal days 1-55). Testing began at postnatal day 55 and consisted of a single day of acquisition training, and three post training time points (1, 2 and 10 days) to assess memory consolidation and recall. All animals, regardless of sex, developmental window or level of Pb-exposure, successfully acquired conditioned-unconditioned stimulus association during training. However, there were significant effects of Pb-exposure on consolidation and memory recall at days 1-10 post training. In females, EPN and LPN exposure to 150 ppm Pb (but not PERI exposure) significantly impaired recall. In contrast, only PERI 150 ppm and 750 ppm-exposed males had significant recall deficits. These data suggest a complex interaction between sex, developmental window of exposure and Pb-exposure level on consolidation and recall of associative memories.

  10. Cognitive Biases Questionnaire for Psychosis

    PubMed Central

    Peters, Emmanuelle R.

    2014-01-01

    Objective: The Cognitive Biases Questionnaire for psychosis (CBQp) was developed to capture 5 cognitive distortions (jumping to conclusions, intentionalising, catastrophising, emotional reasoning, and dichotomous thinking), which are considered important for the pathogenesis of psychosis. Vignettes were adapted from the Cognitive Style Test (CST),1 relating to “Anomalous Perceptions” and “Threatening Events” themes. Method: Scale structure, reliability, and validity were investigated in a psychosis group, and CBQp scores were compared with those of depressed and healthy control samples. Results: The CBQp showed good internal consistency and test-retest reliability. The 5 biases were not independent, with a 2-related factor scale providing the best fit. This structure suggests that the CBQp assesses a general thinking bias rather than distinct cognitive errors, while Anomalous Perception and Threatening Events theme scores can be used separately. Total CBQp scores showed good convergent validity with the CST, but individual biases were not related to existing tasks purporting to assess similar reasoning biases. Psychotic and depressed populations scored higher than healthy controls, and symptomatic psychosis patients scored higher than their nonsymptomatic counterparts, with modest relationships between CBQp scores and symptom severity once emotional disorders were partialled out. Anomalous Perception theme and Intentionalising bias scores showed some specificity to psychosis. Conclusions: Overall, the CBQp has good psychometric properties, although it is likely that it measures a different construct to existing tasks, tentatively suggested to represent a bias of interpretation rather than reasoning, judgment or decision-making processes. It is a potentially useful tool in both research and clinical arenas. PMID:23413104

  11. Sensitivity of hydrologic simulations to bias corrected driving parameters

    NASA Astrophysics Data System (ADS)

    Papadimitriou, Lamprini; Grillakis, Manolis; Koutroulis, Aristeidis; Tsanis, Ioannis

    2016-04-01

    Climate model outputs feature systematic errors and biases that render them unsuitable for direct use by the impact models. To deal with this issue many bias correction techniques have been developed to adjust the modelled variables against observations. For the most common applications adjustment concerns only precipitation and temperature whilst for others all the driving parameters (including radiation, wind speed, humidity, air pressure) are bias adjusted. Bias adjusting only part of the variables required as biophysical model input could affect the physical consistency among input variables and is poorly studied. It is important to determine and quantify the effect that bias adjusting each climate variable has on the impact model's simulation and identify parameters that could be treated as raw outputs for specific model applications. In this work, the sensitivity of climate simulations to bias adjusted driving parameters is tested by conducting a series of model runs, for which the impact model JULES is forced with: i) not bias corrected input variables, ii) all bias corrected input variables, iii-viii) all input variables bias corrected except for: iii) precipitation, iv) temperature, v) radiation, vi) specific humidity, vii) air pressure and viii) wind speed. This set of runs is conducted for three climate models of different equilibrium climate sensitivity: GFDL-ESM2M, MIROC-ESM-CHEM and IPSL-CM5A-LR. The baseline for the comparison of the experimental runs is a JULES run forced with the WFDEI dataset, the dataset that was used as the observational dataset for adjusting biases. The comparative analysis is performed using the time period 1981-2010 and focusing on output variables of the hydrological cycle (runoff, evapotranspiration, soil moisture).

  12. Biased selection within the social health insurance market in Colombia.

    PubMed

    Castano, Ramon; Zambrano, Andres

    2006-12-01

    Reducing the impact of insurance market failures with regulations such as community-rated premiums, standardized benefit packages and open enrolment, yield limited effect because they create room for selection bias. The Colombian social health insurance system started a market approach in 1993 expecting to improve performance of preexisting monopolistic insurance funds by exposing them to competition by new entrants. This paper tests the hypothesis that market failures would lead to biased selection favoring new entrants. Two household surveys are analyzed using Self-Reported Health Status and the presence of chronic conditions as prospective indicators of individual risk. Biased selection is found to take place, leading to adverse selection among incumbents, and favorable selection among new entrants. This pattern is absent in 1997 but is evident in 2003. Given that the two incumbents analyzed are public organizations, the fiscal implications of the findings in terms of government bailouts, are analyzed. PMID:16516333

  13. Improved analysis of bias in Monte Carlo criticality safety

    NASA Astrophysics Data System (ADS)

    Haley, Thomas C.

    2000-08-01

    Criticality safety, the prevention of nuclear chain reactions, depends on Monte Carlo computer codes for most commercial applications. One major shortcoming of these codes is the limited accuracy of the atomic and nuclear data files they depend on. In order to apply a code and its data files to a given criticality safety problem, the code must first be benchmarked against similar problems for which the answer is known. The difference between a code prediction and the known solution is termed the "bias" of the code. Traditional calculations of the bias for application to commercial criticality problems are generally full of assumptions and lead to large uncertainties which must be conservatively factored into the bias as statistical tolerances. Recent trends in storing commercial nuclear fuel---narrowed regulatory margins of safety, degradation of neutron absorbers, the desire to use higher enrichment fuel, etc.---push the envelope of criticality safety. They make it desirable to minimize uncertainty in the bias to accommodate these changes, and they make it vital to understand what assumptions are safe to make under what conditions. A set of improved procedures is proposed for (1) developing multivariate regression bias models, and (2) applying multivariate regression bias models. These improved procedures lead to more accurate estimates of the bias and much smaller uncertainties about this estimate, while also generally providing more conservative results. The drawback is that the procedures are not trivial and are highly labor intensive to implement. The payback in savings in margin to criticality and conservatism for calculations near regulatory and safety limits may be worth this cost. To develop these procedures, a bias model using the statistical technique of weighted least squares multivariate regression is developed in detail. Problems that can occur from a weak statistical analysis are highlighted, and a solid statistical method for developing the bias

  14. Tetraethyl lead

    Integrated Risk Information System (IRIS)

    Tetraethyl lead ; CASRN 78 - 00 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Ef

  15. Attentional bias in adults with cannabis use disorders

    PubMed Central

    Vujanovic, Anka A.; Wardle, Margaret C.; Liu, Shijing; Dias, Nadeeka R.; Lane, Scott D.

    2016-01-01

    ABSTRACT There has been modest examination of attentional bias in individuals with cannabis use disorders. Clinical implications of this work are directly relevant to better informing extant evidence-based treatment for substance use disorders (e.g., relapse prevention) and/or developing novel interventions. The overarching aim of this investigation was to examine a novel attentional bias task in adults with cannabis use disorders. Participants were comprised of 25 adults (8 women: M age = 31, SD = 6.8; range = 22–45) with cannabis use disorders (n = 12) and controls (n = 13) without any current (past month) psychopathology. Relative to controls, adults with cannabis use disorders had greater attentional bias scores. These differences were present only at the 125-ms probe time, where the cannabis use disorders group showed greater attentional bias to cannabis cues than the control group (adjusted p = .001, cannabis use disorders mean = 59.9, control mean = −24.8, Cohen's d-effect size for 125 ms = 1.03). The cannabis use disorders group also reported significantly greater perceived stress and post-task stress scores than the control group, but stress was not related to attentional bias. This study informs understanding of the influence of cannabis cues on visual detection and reaction time under different cue-target onset times, as attentional bias was most prevalent under time pressure to detect the probe. PMID:26566718

  16. Bias neglect: a blind spot in the evaluation of scientific results.

    PubMed

    Strickland, Brent; Mercier, Hugo

    2014-01-01

    Experimenter bias occurs when scientists' hypotheses influence their results, even if involuntarily. Meta-analyses have suggested that in some domains, such as psychology, up to a third of the studies could be unreliable due to such biases. A series of experiments demonstrates that while people are aware of the possibility that scientists can be more biased when the conclusions of their experiments fit their initial hypotheses, they robustly fail to appreciate that they should also be more sceptical of such results. This is true even when participants read descriptions of studies that have been shown to be biased. Moreover, participants take other sources of bias-such as financial incentives-into account, showing that this bias neglect may be specific to theory-driven hypothesis testing. In combination with a common style of scientific reporting, bias neglect could lead the public to accept premature conclusions.

  17. Diamond nucleation under bias conditions

    SciTech Connect

    Stoeckel, R.; Stammler, M.; Janischowsky, K.; Ley, L.; Albrecht, M.; Strunk, H.P.

    1998-01-01

    The so-called bias pretreatment allows the growth of heteroepitaxial diamond films by plasma chemical vapor deposition on silicon (100) surfaces. We present plan-view and cross-sectional transmission electron micrographs of the substrate surface at different phases of the bias pretreatment. These observations are augmented by measurements of the etch rates of Si, SiC, and different carbon modifications under plasma conditions and the size distribution of oriented diamond crystals grown after bias pretreatment. Based on these results a new model for diamond nucleation under bias conditions is proposed. First, a closed layer of nearly epitaxially oriented cubic SiC with a thickness of about 10 nm is formed. Subplantation of carbon into this SiC layer causes a supersaturation with carbon and results in the subcutaneous formation of epitaxially oriented nucleation centers in the SiC layer. Etching of the SiC during the bias pretreatment as well as during diamond growth brings these nucleation centers to the sample surface and causes the growth of diamonds epitaxially oriented on the Si/SiC substrate. {copyright} {ital 1998 American Institute of Physics.}

  18. Biased signaling at chemokine receptors.

    PubMed

    Corbisier, Jenny; Galès, Céline; Huszagh, Alexandre; Parmentier, Marc; Springael, Jean-Yves

    2015-04-10

    The ability of G protein-coupled receptors (GPCRs) to activate selective signaling pathways according to the conformation stabilized by bound ligands (signaling bias) is a challenging concept in the GPCR field. Signaling bias has been documented for several GPCRs, including chemokine receptors. However, most of these studies examined the global signaling bias between G protein- and arrestin-dependent pathways, leaving unaddressed the potential bias between particular G protein subtypes. Here, we investigated the coupling selectivity of chemokine receptors CCR2, CCR5, and CCR7 in response to various ligands with G protein subtypes by using bioluminescence resonance energy transfer biosensors monitoring directly the activation of G proteins. We also compared data obtained with the G protein biosensors with those obtained with other functional readouts, such as β-arrestin-2 recruitment, cAMP accumulation, and calcium mobilization assays. We showed that the binding of chemokines to CCR2, CCR5, and CCR7 activated the three Gαi subtypes (Gαi1, Gαi2, and Gαi3) and the two Gαo isoforms (Gαoa and Gαob) with potencies that generally correlate to their binding affinities. In addition, we showed that the binding of chemokines to CCR5 and CCR2 also activated Gα12, but not Gα13. For each receptor, we showed that the relative potency of various agonist chemokines was not identical in all assays, supporting the notion that signaling bias exists at chemokine receptors.

  19. Commissioning and Initial LHC Run-2 operation of the ATLAS minimum bias trigger scintillators

    NASA Astrophysics Data System (ADS)

    Hoffmann, M.

    2016-07-01

    The Minimum Bias Trigger Scintillators (MBTS) are sub-detectors in ATLAS delivering the primary trigger for selecting events from low luminosity proton-proton, lead-lead and lead-proton collisions with the smallest possible bias. The MBTS have undergone a complete replacement before LHC Run-2 and several improvements have been implemented in the layout. Since 2014 the MBTS have been commissioned with cosmic rays and first LHC Run-2 beam splash events. We summarise the outcome of the commissioning.

  20. Locally Biased Galaxy Formation and Large-Scale Structure

    NASA Astrophysics Data System (ADS)

    Narayanan, Vijay K.; Berlind, Andreas A.; Weinberg, David H.

    2000-01-01

    We examine the influence of the morphology-density relation and a wide range of simple models for biased galaxy formation on statistical measures of large-scale structure. We contrast the behavior of local biasing models, in which the efficiency of galaxy formation is determined by the density, geometry, or velocity dispersion of the local mass distribution, with that of nonlocal biasing models, in which galaxy formation is modulated coherently over scales larger than the galaxy correlation length. If morphological segregation of galaxies is governed by a local morphology-density relation, then the correlation function of E/S0 galaxies should be steeper and stronger than that of spiral galaxies on small scales, as observed, while on large scales the E/S0 and spiral galaxies should have correlation functions with the same shape but different amplitudes. Similarly, all of our local bias models produce scale-independent amplification of the correlation function and power spectrum in the linear and mildly nonlinear regimes; only a nonlocal biasing mechanism can alter the shape of the power spectrum on large scales. Moments of the biased galaxy distribution retain the hierarchical pattern of the mass moments, but biasing alters the values and scale dependence of the hierarchical amplitudes S3 and S4. Pair-weighted moments of the galaxy velocity distribution are sensitive to the details of the bias prescription even if galaxies have the same local velocity distribution as the underlying dark matter. The nonlinearity of the relation between galaxy density and mass density depends on the biasing prescription and the smoothing scale, and the scatter in this relation is a useful diagnostic of the physical parameters that determine the bias. While the assumption that galaxy formation is governed by local physics leads to some important simplifications on large scales, even local biasing is a multifaceted phenomenon whose impact cannot be described by a single parameter or

  1. The association between negative attention biases and symptoms of depression in a community sample of adolescents

    PubMed Central

    Murphy, Susannah E.; Lau, Jennifer Y.F.

    2015-01-01

    Adolescence is a vulnerable time for the onset of depression. Recent evidence from adult studies suggests not only that negative attention biases are correlated with symptoms of depression, but that reducing negative attention biases through training can in turn reduce symptomology. The role and plasticity of attention biases in adolescent depression, however, remains unclear. This study examines the association between symptoms of depression and attention biases, and whether such biases are modifiable, in a community sample of adolescents. We report data from 105 adolescents aged 13–17 who completed a dot-probe measure of attention bias before and after a single session of visual search-based cognitive bias modification training. This is the first study to find a significant association between negative attention biases and increased symptoms of depression in a community sample of adolescents. Contrary to expectations, we were unable to manipulate attention biases using a previously successful cognitive bias modification task. There were no significant effects of the training on positive affect and only modest effects of the training, identified in post-hoc analyses, were observed on negative affect. Our data replicate those from the adult literature, which suggest that adolescent depression is a disorder associated with negative attention biases, although we were unable to modify attention biases in our study. We identify numerous parameters of our methodology which may explain these null training effects, and which could be addressed in future cognitive bias modification studies of adolescent depression. PMID:26539335

  2. Time?

    NASA Astrophysics Data System (ADS)

    Amoroso, Richard L.

    2013-09-01

    The concept of time in the `clockwork' Newtonian world was irrelevant; and has generally been ignored until recently by several generations of physicists since the implementation of quantum mechanics. We will set aside the utility of time as a property relating to physical calculations of events relating to a metrics line element or as an aspect of the transformation of a particles motion/interaction in a coordinate system or in relation to thermodynamics etc., i.e. we will discard all the usual uses of time as a concept used to circularly define physical parameters in terms of other physical parameters; concentrating instead on time as an aspect of the fundamental cosmic topology of our virtual reality especially as it inseparably relates to the nature and role of the observer in natural science.

  3. Adaptive Control in the Presence of Simultaneous Sensor Bias and Actuator Failures

    NASA Technical Reports Server (NTRS)

    Joshi, Suresh M.

    2012-01-01

    The problem of simultaneously accommodating unknown sensor biases and unknown actuator failures in uncertain systems is considered in a direct model reference adaptive control (MRAC) setting for state tracking using state feedback. Sensor biases and actuator faults may be present at the outset or may occur at unknown instants of time during operation. A modified MRAC law is proposed, which combines sensor bias estimation with control gain adaptation for accommodation of sensor biases and actuator failures. This control law is shown to provide signal boundedness in the resulting system. For the case when an external asymptotically stable sensor bias estimator is available, an MRAC law is developed to accomplish asymptotic state tracking and signal boundedness. For a special case wherein biases are only present in the rate measurements and bias-free position measurements are available, an MRAC law is developed using a model-independent bias estimator, and is shown to provide asymptotic state tracking with signal boundedness.

  4. Pursuing Peace--"Enlisting Students in the Battle against Bias"

    ERIC Educational Resources Information Center

    Bradley, Elizabeth H.

    2007-01-01

    In communities all over the United States, issues of mistrust, anger, harassment, and bias often accompany the task of cultures learning to live together, and Lewiston, Maine, is no exception. Lewiston High School has recognized the potential conflict and addressed it in a forthright manner. The students have helped lead the way. This article…

  5. Heuristic-biased stochastic sampling

    SciTech Connect

    Bresina, J.L.

    1996-12-31

    This paper presents a search technique for scheduling problems, called Heuristic-Biased Stochastic Sampling (HBSS). The underlying assumption behind the HBSS approach is that strictly adhering to a search heuristic often does not yield the best solution and, therefore, exploration off the heuristic path can prove fruitful. Within the HBSS approach, the balance between heuristic adherence and exploration can be controlled according to the confidence one has in the heuristic. By varying this balance, encoded as a bias function, the HBSS approach encompasses a family of search algorithms of which greedy search and completely random search are extreme members. We present empirical results from an application of HBSS to the realworld problem of observation scheduling. These results show that with the proper bias function, it can be easy to outperform greedy search.

  6. Anchoring bias in online voting

    NASA Astrophysics Data System (ADS)

    Yang, Zimo; Zhang, Zi-Ke; Zhou, Tao

    2012-12-01

    Voting online with explicit ratings could largely reflect people's preferences and objects' qualities, but ratings are always irrational, because they may be affected by many unpredictable factors like mood, weather and other people's votes. By analyzing two real systems, this paper reveals a systematic bias embedding in the individual decision-making processes, namely people tend to give a low rating after a low rating, as well as a high rating following a high rating. This so-called anchoring bias is validated via extensive comparisons with null models, and numerically speaking, the extent of bias decays with voting interval in a logarithmic form. Our findings could be applied in the design of recommender systems and considered as important complementary materials to previous knowledge about anchoring effects on financial trades, performance judgments, auctions, and so on.

  7. Unpacking the Evidence of Gender Bias

    ERIC Educational Resources Information Center

    Fulmer, Connie L.

    2010-01-01

    The purpose of this study was to investigate gender bias in pre-service principals using the Gender-Leader Implicit Association Test. Analyses of student-learning narratives revealed how students made sense of gender bias (biased or not-biased) and how each reacted to evidence (surprised or not-surprised). Two implications were: (1) the need for…

  8. Measurement Bias Detection through Factor Analysis

    ERIC Educational Resources Information Center

    Barendse, M. T.; Oort, F. J.; Werner, C. S.; Ligtvoet, R.; Schermelleh-Engel, K.

    2012-01-01

    Measurement bias is defined as a violation of measurement invariance, which can be investigated through multigroup factor analysis (MGFA), by testing across-group differences in intercepts (uniform bias) and factor loadings (nonuniform bias). Restricted factor analysis (RFA) can also be used to detect measurement bias. To also enable nonuniform…

  9. A Reconsideration of Bias in the News.

    ERIC Educational Resources Information Center

    Stevenson, Robert L.; Greene, Mark T.

    This paper discusses three conceptual problems--point of view, unit of bias, and behavioral response--with using content analysis to study news bias. The paper shows that the point of view of the content analyst is not appropriate if one wants to see how news consumers define and react to bias, that the unit of bias should be the specific instance…

  10. Collection Development and the Psychology of Bias

    ERIC Educational Resources Information Center

    Quinn, Brian

    2012-01-01

    The library literature addressing the role of bias in collection development emphasizes a philosophical approach. It is based on the notion that bias can be controlled by the conscious act of believing in certain values and adhering to a code of ethics. It largely ignores the psychological research on bias, which suggests that bias is a more…

  11. The Truth and Bias Model of Judgment

    ERIC Educational Resources Information Center

    West, Tessa V.; Kenny, David A.

    2011-01-01

    We present a new model for the general study of how the truth and biases affect human judgment. In the truth and bias model, judgments about the world are pulled by 2 primary forces, the truth force and the bias force, and these 2 forces are interrelated. The truth and bias model differentiates force and value, where the force is the strength of…

  12. Without Bias: A Guidebook for Nondiscriminatory Communication.

    ERIC Educational Resources Information Center

    Pickens, Judy E., Ed.; And Others

    This guidebook discusses ways to eliminate various types of discrimination from business communications. Separately authored chapters discuss eliminating racial and ethnic bias; eliminating sexual bias; achieving communication sensitive about handicaps of disabled persons; eliminating bias from visual media; eliminating bias from meetings,…

  13. The Threshold of Embedded M Collider Bias and Confounding Bias

    ERIC Educational Resources Information Center

    Kelcey, Benjamin; Carlisle, Joanne

    2011-01-01

    Of particular import to this study, is collider bias originating from stratification on retreatment variables forming an embedded M or bowtie structural design. That is, rather than assume an M structural design which suggests that "X" is a collider but not a confounder, the authors adopt what they consider to be a more reasonable position and…

  14. Rapid recollection of foresight judgments increases hindsight bias in a memory design.

    PubMed

    Calvillo, Dustin P

    2013-05-01

    One component of hindsight bias is memory distortion. This component is measured with a memory design, in which individuals answer questions, learn the correct answers, and recall their original answers. Hindsight bias occurs when participants' recollections are closer to the correct answers than their original judgments actually were. The present study used a memory design to examine the relationship between response time in recalling original answers and the magnitude of hindsight bias. In Experiment 1, participants' response times were negatively correlated with a hindsight bias index. In Experiment 2, half of the participants were instructed to recall their original judgments quickly and the other participants were instructed to take time to recall their judgments. The hindsight bias index was greater among rapidly responding participants than among delayed responding participants. These results, in conjunction with other findings, support a separate components view of hindsight bias. The memory distortion component of hindsight bias appears to occur quickly, and unbiased responding requires time for processing. This finding relates the memory distortion component of hindsight bias to other cognitive biases, such as the belief bias in syllogistic reasoning. The relationship of this hindsight bias component to dual-process models of cognition is discussed, and several avenues for additional research are suggested.

  15. Solar array/spacecraft biasing

    NASA Technical Reports Server (NTRS)

    Fitzgerald, D. J.

    1981-01-01

    Biasing techniques and their application to the control of spacecraft potential is discussed. Normally when a spacecraft is operated with ion thrusters, the spacecraft will be 10-20 volts negative of the surrounding plasma. This will affect scientific measurements and will allow ions from the charge-exchange plasma to bombard the spacecraft surfaces with a few tens of volts of energy. This condition may not be tolerable. A proper bias system is described that can bring the spacecraft to or near the potential of the surrounding plasma.

  16. Contamination effects on fixed-bias Langmuir probes.

    PubMed

    Steigies, C T; Barjatya, A

    2012-11-01

    Langmuir probes are standard instruments for plasma density measurements on many sounding rockets. These probes can be operated in swept-bias as well as in fixed-bias modes. In swept-bias Langmuir probes, contamination effects are frequently visible as a hysteresis between consecutive up and down voltage ramps. This hysteresis, if not corrected, leads to poorly determined plasma densities and temperatures. With a properly chosen sweep function, the contamination parameters can be determined from the measurements and correct plasma parameters can then be determined. In this paper, we study the contamination effects on fixed-bias Langmuir probes, where no hysteresis type effect is seen in the data. Even though the contamination is not evident from the measurements, it does affect the plasma density fluctuation spectrum as measured by the fixed-bias Langmuir probe. We model the contamination as a simple resistor-capacitor circuit between the probe surface and the plasma. We find that measurements of small scale plasma fluctuations (meter to sub-meter scale) along a rocket trajectory are not affected, but the measured amplitude of large scale plasma density variation (tens of meters or larger) is attenuated. From the model calculations, we determine amplitude and cross-over frequency of the contamination effect on fixed-bias probes for different contamination parameters. The model results also show that a fixed bias probe operating in the ion-saturation region is affected less by contamination as compared to a fixed bias probe operating in the electron saturation region. PMID:23206057

  17. [Biochemical parameters of blood and morpho-functional state of the liver of experimental animals by the actions of lead sulfide nanoparticles in different time study].

    PubMed

    Omel'chuk, S T; Aleksiĭchuk, V D; Sokurenko, L M

    2014-01-01

    Biochemical studies revealed that alanine aminotransferase levels changing first during short action (30 injections) of lead sulfide nanoparticles of size 10 and 30 nm, and the ionic form of a 400 nm lead while the growth of both enzymes (aspartate aminotransferase and alanine aminotransferase) activity during long-term exposure (60 injections) is the same intensity. It it confirmed by the value of de Ritis coefficient, which is statistically the same as control. Morphological studies also confirm these data--degenerative changes of hepatocytes, reactive changes of the stroma and vascular responses were detected. It is shown that the severity of metabolic and morphological damages in the liver increased with prolonging the duration of lead nanoparticles intake.

  18. Sampling Biases in MODIS and SeaWiFS Ocean Chlorophyll Data

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Casey, Nancy W.

    2007-01-01

    Although modem ocean color sensors, such as MODIS and SeaWiFS are often considered global missions, in reality it takes many days, even months, to sample the ocean surface enough to provide complete global coverage. The irregular temporal sampling of ocean color sensors can produce biases in monthly and annual mean chlorophyll estimates. We quantified the biases due to sampling using data assimilation to create a "truth field", which we then sub-sampled using the observational patterns of MODIS and SeaWiFS. Monthly and annual mean chlorophyll estimates from these sub-sampled, incomplete daily fields were constructed and compared to monthly and annual means from the complete daily fields of the assimilation model, at a spatial resolution of 1.25deg longitude by 0.67deg latitude. The results showed that global annual mean biases were positive, reaching nearly 8% (MODIS) and >5% (SeaWiFS). For perspective the maximum interannual variability in the SeaWiFS chlorophyll record was about 3%. Annual mean sampling biases were low (<3%) in the midlatitudes (between -40deg and 40deg). Low interannual variability in the global annual mean sampling biases suggested that global scale trend analyses were valid. High latitude biases were much higher than the global annual means, up to 20% as a basin annual mean, and over 80% in some months. This was the result of the high solar zenith angle exclusion in the processing algorithms. Only data where the solar angle is <75deg are permitted, in contrast to the assimilation which samples regularly over the entire area and month. High solar zenith angles do not facilitate phytoplankton photosynthesis and consequently low chlorophyll concentrations occurring here are missed by the data sets. Ocean color sensors selectively sample in locations and times of favorable phytoplankton growth, producing overestimates of chlorophyll. The biases derived from lack of sampling in the high latitudes varied monthly, leading to artifacts in the apparent

  19. HESS Opinions "Should we apply bias correction to global and regional climate model data?"

    NASA Astrophysics Data System (ADS)

    Ehret, U.; Zehe, E.; Wulfmeyer, V.; Warrach-Sagi, K.; Liebert, J.

    2012-09-01

    Despite considerable progress in recent years, output of both global and regional circulation models is still afflicted with biases to a degree that precludes its direct use, especially in climate change impact studies. This is well known, and to overcome this problem, bias correction (BC; i.e. the correction of model output towards observations in a post-processing step) has now become a standard procedure in climate change impact studies. In this paper we argue that BC is currently often used in an invalid way: it is added to the GCM/RCM model chain without sufficient proof that the consistency of the latter (i.e. the agreement between model dynamics/model output and our judgement) as well as the generality of its applicability increases. BC methods often impair the advantages of circulation models by altering spatiotemporal field consistency, relations among variables and by violating conservation principles. Currently used BC methods largely neglect feedback mechanisms, and it is unclear whether they are time-invariant under climate change conditions. Applying BC increases agreement of climate model output with observations in hindcasts and hence narrows the uncertainty range of simulations and predictions without, however, providing a satisfactory physical justification. This is in most cases not transparent to the end user. We argue that this hides rather than reduces uncertainty, which may lead to avoidable forejudging of end users and decision makers. We present here a brief overview of state-of-the-art bias correction methods, discuss the related assumptions and implications, draw conclusions on the validity of bias correction and propose ways to cope with biased output of circulation models in the short term and how to reduce the bias in the long term. The most promising strategy for improved future global and regional circulation model simulations is the increase in model resolution to the convection-permitting scale in combination with ensemble

  20. Correcting for numerator/denominator bias when assessing changing inequalities in occupational class mortality, Australia 1981 -2002.

    PubMed Central

    Williams, Gail M.; Najman, Jake M.; Clavarino, Alexandra

    2006-01-01

    OBJECTIVE: Comparisons of the changing patterns of inequalities in occupational mortality provide one way to monitor the achievement of equity goals. However, previous comparisons have not corrected for numerator/denominator bias, which is a consequence of the different ways in which occupational details are recorded on death certificates and on census forms. The objective of this study was to measure the impact of this bias on mortality rates and ratios over time. METHODS: Using data provided by the Australian Bureau of Statistics, we examined the evidence for bias over the period 1981 -2002, and used imputation methods to adjust for this bias. We compared unadjusted with imputed rates of mortality for manual/non-manual workers. FINDINGS: Unadjusted data indicate increasing inequality in the age-adjusted rates of mortality for manual/non-manual workers during 1981 -2002. Imputed data suggest that there have been modest fluctuations in the ratios of mortality for manual/non-manual workers during this time, but with evidence that inequalities have increased only in recent years and are now at historic highs. CONCLUSION: We found that imputation for missing data leads to changes in estimates of inequalities related to social class in mortality for some years but not for others. Occupational class comparisons should be imputed or otherwise adjusted for missing data on census or death certificates. PMID:16583078

  1. Attributional Bias and Course Evaluations.

    ERIC Educational Resources Information Center

    Gigliotti, Richard J.; Buchtel, Foster S.

    1990-01-01

    How self-serving bias affects evaluations of college courses was tested for 691 students by comparing a model predicting that evaluations reflect actual grades with a model predicting that evaluations reflect confirmation or disconfirmation of expectations. Results support course evaluation validity by indicating a minimal effect of self-serving…

  2. Attentional bias in math anxiety.

    PubMed

    Rubinsten, Orly; Eidlin, Hili; Wohl, Hadas; Akibli, Orly

    2015-01-01

    Cognitive theory from the field of general anxiety suggests that the tendency to display attentional bias toward negative information results in anxiety. Accordingly, the current study aims to investigate whether attentional bias is involved in math anxiety (MA) as well (i.e., a persistent negative reaction to math). Twenty seven participants (14 with high levels of MA and 13 with low levels of MA) were presented with a novel computerized numerical version of the well established dot probe task. One of six types of prime stimuli, either math related or typically neutral, was presented on one side of a computer screen. The prime was preceded by a probe (either one or two asterisks) that appeared in either the prime or the opposite location. Participants had to discriminate probe identity (one or two asterisks). Math anxious individuals reacted faster when the probe was at the location of the numerical related stimuli. This suggests the existence of attentional bias in MA. That is, for math anxious individuals, the cognitive system selectively favored the processing of emotionally negative information (i.e., math related words). These findings suggest that attentional bias is linked to unduly intense MA symptoms.

  3. Combating Anti-Muslim Bias

    ERIC Educational Resources Information Center

    Shah, Nirvi

    2011-01-01

    America's 2.5 million Muslims make up less than 1% of the U.S. population, according to the Pew Research Center. Many Muslim students face discrimination and some cases have warranted investigation by the U.S. Department of Education's Office of Civil Rights. Muslim groups have reported widespread bias as well. For many Muslim…

  4. Stereotype Formation: Biased by Association

    ERIC Educational Resources Information Center

    Le Pelley, Mike E.; Reimers, Stian J.; Calvini, Guglielmo; Spears, Russell; Beesley, Tom; Murphy, Robin A.

    2010-01-01

    We propose that biases in attitude and stereotype formation might arise as a result of learned differences in the extent to which social groups have previously been predictive of behavioral or physical properties. Experiments 1 and 2 demonstrate that differences in the experienced predictiveness of groups with respect to evaluatively neutral…

  5. Attentional bias in math anxiety.

    PubMed

    Rubinsten, Orly; Eidlin, Hili; Wohl, Hadas; Akibli, Orly

    2015-01-01

    Cognitive theory from the field of general anxiety suggests that the tendency to display attentional bias toward negative information results in anxiety. Accordingly, the current study aims to investigate whether attentional bias is involved in math anxiety (MA) as well (i.e., a persistent negative reaction to math). Twenty seven participants (14 with high levels of MA and 13 with low levels of MA) were presented with a novel computerized numerical version of the well established dot probe task. One of six types of prime stimuli, either math related or typically neutral, was presented on one side of a computer screen. The prime was preceded by a probe (either one or two asterisks) that appeared in either the prime or the opposite location. Participants had to discriminate probe identity (one or two asterisks). Math anxious individuals reacted faster when the probe was at the location of the numerical related stimuli. This suggests the existence of attentional bias in MA. That is, for math anxious individuals, the cognitive system selectively favored the processing of emotionally negative information (i.e., math related words). These findings suggest that attentional bias is linked to unduly intense MA symptoms. PMID:26528208

  6. Key Words in Instruction. Bias

    ERIC Educational Resources Information Center

    Callison, Daniel

    2005-01-01

    Two challenging criteria for judging information involve bias and authority. In both cases, judgments may not be clearly possible. In both cases, there may be degrees or levels of acceptability. For students to gain experience and to demonstrate skills in making judgments, they need opportunities to consider a wide spectrum of resources under a…

  7. Attentional bias in math anxiety

    PubMed Central

    Rubinsten, Orly; Eidlin, Hili; Wohl, Hadas; Akibli, Orly

    2015-01-01

    Cognitive theory from the field of general anxiety suggests that the tendency to display attentional bias toward negative information results in anxiety. Accordingly, the current study aims to investigate whether attentional bias is involved in math anxiety (MA) as well (i.e., a persistent negative reaction to math). Twenty seven participants (14 with high levels of MA and 13 with low levels of MA) were presented with a novel computerized numerical version of the well established dot probe task. One of six types of prime stimuli, either math related or typically neutral, was presented on one side of a computer screen. The prime was preceded by a probe (either one or two asterisks) that appeared in either the prime or the opposite location. Participants had to discriminate probe identity (one or two asterisks). Math anxious individuals reacted faster when the probe was at the location of the numerical related stimuli. This suggests the existence of attentional bias in MA. That is, for math anxious individuals, the cognitive system selectively favored the processing of emotionally negative information (i.e., math related words). These findings suggest that attentional bias is linked to unduly intense MA symptoms. PMID:26528208

  8. Comparing halo bias from abundance and clustering

    NASA Astrophysics Data System (ADS)

    Hoffmann, K.; Bel, J.; Gaztañaga, E.

    2015-06-01

    We model the abundance of haloes in the ˜(3 Gpc h-1)3 volume of the MICE Grand Challenge simulation by fitting the universal mass function with an improved Jackknife error covariance estimator that matches theory predictions. We present unifying relations between different fitting models and new predictions for linear (b1) and non-linear (c2 and c3) halo clustering bias. Different mass function fits show strong variations in their performance when including the low mass range (Mh ≲ 3 × 1012 M⊙ h-1) in the analysis. Together with fits from the literature, we find an overall variation in the amplitudes of around 10 per cent in the low mass and up to 50 per cent in the high mass (galaxy cluster) range (Mh > 1014 M⊙ h-1). These variations propagate into a 10 per cent change in b1 predictions and a 50 per cent change in c2 or c3. Despite these strong variations, we find universal relations between b1 and c2 or c3 for which we provide simple fits. Excluding low-mass haloes, different models fitted with reasonable goodness in this analysis, show per cent level agreement in their b1 predictions, but are systematically 5-10 per cent lower than the bias directly measured with two-point halo-mass clustering. This result confirms previous findings derived from smaller volumes (and smaller masses). Inaccuracies in the bias predictions lead to 5-10 per cent errors in growth measurements. They also affect any halo occupation distribution fitting or (cluster) mass calibration from clustering measurements.

  9. Biased Signaling of Protease-Activated Receptors

    PubMed Central

    Zhao, Peishen; Metcalf, Matthew; Bunnett, Nigel W.

    2014-01-01

    In addition to their role in protein degradation and digestion, proteases can also function as hormone-like signaling molecules that regulate vital patho-physiological processes, including inflammation, hemostasis, pain, and repair mechanisms. Certain proteases can signal to cells by cleaving protease-activated receptors (PARs), a family of four G protein-coupled receptors. PARs are expressed by almost all cell types, control important physiological and disease-relevant processes, and are an emerging therapeutic target for major diseases. Most information about PAR activation and function derives from studies of a few proteases, for example thrombin in the case of PAR1, PAR3, and PAR4, and trypsin in the case of PAR2 and PAR4. These proteases cleave PARs at established sites with the extracellular N-terminal domains, and expose tethered ligands that stabilize conformations of the cleaved receptors that activate the canonical pathways of G protein- and/or β-arrestin-dependent signaling. However, a growing number of proteases have been identified that cleave PARs at divergent sites to activate distinct patterns of receptor signaling and trafficking. The capacity of these proteases to trigger distinct signaling pathways is referred to as biased signaling, and can lead to unique patho-physiological outcomes. Given that a different repertoire of proteases are activated in various patho-physiological conditions that may activate PARs by different mechanisms, signaling bias may account for the divergent actions of proteases and PARs. Moreover, therapies that target disease-relevant biased signaling pathways may be more effective and selective approaches for the treatment of protease- and PAR-driven diseases. Thus, rather than mediating the actions of a few proteases, PARs may integrate the biological actions of a wide spectrum of proteases in different patho-physiological conditions. PMID:24860547

  10. A Smart Move in Tough Times: How SREB States Can Strengthen Adult Learning and the Work Force. Challenge to Lead Series

    ERIC Educational Resources Information Center

    Lord, Joan M.; Blackmon, Trudy; Chaloux, Bruce; Weaver, Chris; Street, Sue

    2010-01-01

    This report, part of the "Challenge to Lead" education goals series, examines the impact of an undereducated work force and calls for making adult learning programs a priority across the SREB (Southern Regional Education Board) region especially during the current recession. "A Smart Move" tracks declining enrollment in adult learning programs in…

  11. Sedimentation Time Measurements of Soil Particles by Light Scattering and Determination of Chromium, Lead, and Iron in Soil Samples via ICP

    ERIC Educational Resources Information Center

    Todebush, Patricia Metthe; Geiger, Franz M.

    2005-01-01

    The study of soil samples, using light scattering and Inductively Coupled Plasma spectrometry (ICP) to determine colloid sedimentation rates and the quantity of chromium, lead, and iron in the sample is described. It shows the physical and chemical behavior of solid components in soil, and how such pollutant binding colloid surfaces directly…

  12. Clinical Judgmental Biases: The Moderating Roles of Counselor Cognitive Complexity and Counselor Client Preferences.

    ERIC Educational Resources Information Center

    Spengler, Paul M.; Strohmer, Douglas C.

    1994-01-01

    Study of 119 counseling psychologists revealed that counselor individual differences in cognitive complexity, but not preferences for client problems, moderated cognitive processes that lead to bias in clinical judgment. Counseling psychologists with lower cognitive complexity were more likely to form biased clinical judgments than were those with…

  13. Publication Bias in Studies of an Applied Behavior-Analytic Intervention: An Initial Analysis

    ERIC Educational Resources Information Center

    Sham, Elyssa; Smith, Tristram

    2014-01-01

    Publication bias arises when studies with favorable results are more likely to be reported than are studies with null findings. If this bias occurs in studies with single-subject experimental designs (SSEDs) on applied behavior-analytic (ABA) interventions, it could lead to exaggerated estimates of intervention effects. Therefore, we conducted an…

  14. Camera Perspective Bias in Videotaped Confessions: Evidence that Visual Attention Is a Mediator

    ERIC Educational Resources Information Center

    Ware, Lezlee J.; Lassiter, G. Daniel; Patterson, Stephen M.; Ransom, Michael R.

    2008-01-01

    Several experiments have demonstrated a "camera perspective bias" in evaluations of videotaped confessions: videotapes with the camera focused on the suspect lead to judgments of greater voluntariness than alternative presentation formats. The present research investigated potential mediators of this bias. Using eye tracking to measure visual…

  15. Implicit Bias and First Name Stereotypes: What Are the Implications for Online Instruction?

    ERIC Educational Resources Information Center

    Conaway, Wendy; Bethune, Sonja

    2015-01-01

    The online classroom is perceived as being a non-threatening, unbiased, safe environment due to the lack of visual cues that normally trigger hidden attitudes and biases. However, it is possible that stereotypical student names often trigger implicit bias in instructors leading to group expectations that can often manifest in a variety of ways…

  16. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    PubMed

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application.

  17. Hysteresis, Stability, and Ion Migration in Lead Halide Perovskite Photovoltaics.

    PubMed

    Miyano, Kenjiro; Yanagida, Masatoshi; Tripathi, Neeti; Shirai, Yasuhiro

    2016-06-16

    Ion migration has been suspected as the origin of various irreproducible and unstable properties, most notably the hysteresis, of lead halide perovskite photovoltaic (PV) cells since the early stage of the research. Although many evidence of ionic movement have been presented both numerically and experimentally, a coherent and quantitative picture that accounts for the observed irreproducible phenomena is still lacking. At the same time, however, it has been noticed that in certain types of PV cells, the hysteresis is absent or at least within the measurement reproducibility. We have previously shown that the electronic properties of hysteresis-free cells are well represented in terms of the conventional inorganic semiconductors. The reproducibility of these measurements was confirmed typically within tens of minutes under the biasing field of -1 V to +1.5 V. In order to probe the effect of ionic motion in the hysteresis-free cells, we extended the time scale and the biasing rage in the electronic measurements, from which we conclude the following: (1) From various evidence, it appears that ion migration is inevitable. However, it does not cause detrimental effects to the PV operation. (2) We propose, based on the quantitative characterization, that the degradation is more likely due to the chemical change at the interfaces between the carrier selective layers and perovskite rather than the compositional change of the lead iodide perovskite bulk. Together, they give much hope in the use of the lead iodide perovskite in the use of actual application. PMID:27227427

  18. Hybrid nonlinearity supported by nonconventionally biased photorefractive crystals

    NASA Astrophysics Data System (ADS)

    Zhang, P.; Liu, S.; Lou, C.; Gao, Y.; Zhao, J.; Xu, J.; Chen, Z.

    2009-06-01

    We theoretically and experimentally demonstrate that a nonconventionally biased photorefractive crystal can support hybrid nonlinearity, i.e., coexistence of self-focusing and self-defocusing nonlinearities under an identical bias condition. It is revealed that the nonlinearity experienced by a one-dimensional (stripe) beam can be switched between self-focusing and self-defocusing solely by changing the beam orientation. For a two-dimensional beam, the hybrid nonlinearity leads to unusual nonlinear beam dynamics with enhanced anisotropy and nonlocality.

  19. Accelerated evolution of morph-biased genes in pea aphids.

    PubMed

    Purandare, Swapna R; Bickel, Ryan D; Jaquiery, Julie; Rispe, Claude; Brisson, Jennifer A

    2014-08-01

    Phenotypic plasticity, the production of alternative phenotypes (or morphs) from the same genotype due to environmental factors, results in some genes being expressed in a morph-biased manner. Theoretically, these morph-biased genes experience relaxed selection, the consequence of which is the buildup of slightly deleterious mutations at these genes. Over time, this is expected to result in increased protein divergence at these genes between species and a signature of relaxed purifying selection within species. Here we test these theoretical expectations using morph-biased genes in the pea aphid, a species that produces multiple morphs via polyphenism. We find that morph-biased genes exhibit faster rates of evolution (in terms of dN/dS) relative to unbiased genes and that divergence generally increases with increasing morph bias. Further, genes with expression biased toward rarer morphs (sexual females and males) show faster rates of evolution than genes expressed in the more common morph (asexual females), demonstrating that the amount of time a gene spends being expressed in a morph is associated with its rate of evolution. And finally, we show that genes expressed in the rarer morphs experience decreased purifying selection relative to unbiased genes, suggesting that it is a relaxation of purifying selection that contributes to their faster rates of evolution. Our results provide an important empirical look at the impact of phenotypic plasticity on gene evolution.

  20. Causes, consequences, and kin bias of human group fissions.

    PubMed

    Walker, Robert S; Hill, Kim R

    2014-12-01

    Fissions of human communities are monumental occasions with consequences for cultural and genetic variation and divergence through time by means of serial founder effects. An ethnographic review shows that most human group fissions are fueled primarily by internal political conflict and secondarily by resource scarcity. As found for other social animals, human fissions lead to subgroups that have higher levels of relatedness as compared with the original community because of kin-biased assortment known as the lineal effect. Fission processes that increase the average relatedness of subgroups are important because relatedness governs how strongly kin/group selection favors social behaviors such as warfare, peacekeeping, and other forms of collection action. However, random individual assortment is not an appropriate null model for evaluating lineage assortment because nuclear families and extended households are expected to remain together, which in and of itself forces higher relatedness in smaller subgroups. We develop a lineage assortment index where low values represent subgroups with coefficients of relatedness near those expected if nuclear and extended households had chosen to associate into random groupings. Two fissions of Ache villages (Paraguay) are examples of this type of fission with a low lineage assortment index not significantly different from zero as evaluated with controlled simulations. On the other extreme, a lineage assortment index near unity represents a lineal fission that maximizes the relatedness of subgroups such as the perfect split of a lineage into sublineages. A fission of Piaroa (Venezuela) fits this scenario. While previous discussions of fission have emphasized similarities among human studies and even other social mammals, we highlight the full range of potential kin bias in the formation of new communities.

  1. Causes, consequences, and kin bias of human group fissions.

    PubMed

    Walker, Robert S; Hill, Kim R

    2014-12-01

    Fissions of human communities are monumental occasions with consequences for cultural and genetic variation and divergence through time by means of serial founder effects. An ethnographic review shows that most human group fissions are fueled primarily by internal political conflict and secondarily by resource scarcity. As found for other social animals, human fissions lead to subgroups that have higher levels of relatedness as compared with the original community because of kin-biased assortment known as the lineal effect. Fission processes that increase the average relatedness of subgroups are important because relatedness governs how strongly kin/group selection favors social behaviors such as warfare, peacekeeping, and other forms of collection action. However, random individual assortment is not an appropriate null model for evaluating lineage assortment because nuclear families and extended households are expected to remain together, which in and of itself forces higher relatedness in smaller subgroups. We develop a lineage assortment index where low values represent subgroups with coefficients of relatedness near those expected if nuclear and extended households had chosen to associate into random groupings. Two fissions of Ache villages (Paraguay) are examples of this type of fission with a low lineage assortment index not significantly different from zero as evaluated with controlled simulations. On the other extreme, a lineage assortment index near unity represents a lineal fission that maximizes the relatedness of subgroups such as the perfect split of a lineage into sublineages. A fission of Piaroa (Venezuela) fits this scenario. While previous discussions of fission have emphasized similarities among human studies and even other social mammals, we highlight the full range of potential kin bias in the formation of new communities. PMID:25056829

  2. Flow of active suspensions and biased swimming

    NASA Astrophysics Data System (ADS)

    Rafai, Salima; Peyla, Philippe; Garcia, Xabel; Kitenbergs, Guntars; Garcia, Michaël; LIPhy Team

    2012-11-01

    It is a challenge to understand the hydrodynamics associated with individual or collective motion of microswimmers through their fluid-mediated interactions in order for instance to manipulate the cells efficiently for some applications purposes. The motion of these micro-organisms can be often affected by the presence of gradients leading to a biased random walk (chemotaxis in the presence of chemicals, gyrotaxis in a gravity field, phototaxis under light exposure). In this study, we present our experimental results concerning the coupling of a Poiseuille flow with the biased random walk of Chlamydomonas Reinhardtii, a green unicellular micro-alga. This is done by illuminating the microswimmer suspension while flowing in a microchannel device. We show that one can obtain a spontaneous and reversible migration and separation of the microalgae suspension from the rest of the suspending medium under illumination and then dynamically control the concentration of the suspension with light. We present a simple model that accounts for the observed phenomenon. We thank the ANR MOSICOB and MICMACSWIM.

  3. Bayesian ROC curve estimation under verification bias.

    PubMed

    Gu, Jiezhun; Ghosal, Subhashis; Kleiner, David E

    2014-12-20

    Receiver operating characteristic (ROC) curve has been widely used in medical science for its ability to measure the accuracy of diagnostic tests under the gold standard. However, in a complicated medical practice, a gold standard test can be invasive, expensive, and its result may not always be available for all the subjects under study. Thus, a gold standard test is implemented only when it is necessary and possible. This leads to the so-called 'verification bias', meaning that subjects with verified disease status (also called label) are not selected in a completely random fashion. In this paper, we propose a new Bayesian approach for estimating an ROC curve based on continuous data following the popular semiparametric binormal model in the presence of verification bias. By using a rank-based likelihood, and following Gibbs sampling techniques, we compute the posterior distribution of the binormal parameters intercept and slope, as well as the area under the curve by imputing the missing labels within Markov Chain Monte-Carlo iterations. Consistency of the resulting posterior under mild conditions is also established. We compare the new method with other comparable methods and conclude that our estimator performs well in terms of accuracy. PMID:25269427

  4. Weight functions for biases in atomic frequency standards.

    PubMed

    Shirley, Jon H

    2010-03-01

    Many perturbations that affect atomic frequency standards vary during the period of measurement. To include this time variation, we introduce 3 time-dependent weight functions built from the solution of the unperturbed equations of motion of a 2-level system. The integral of the time-dependent part of a perturbation with a weight function gives the associated first-order change in transition probability. Biases are then found easily. The same weight function may be used for different perturbations, thus unifying the derivation of their associated biases. We give several examples of the use of weight functions.

  5. Intergroup relationships do not reduce racial bias in empathic neural responses to pain.

    PubMed

    Contreras-Huerta, Luis Sebastian; Hielscher, Emily; Sherwell, Chase S; Rens, Natalie; Cunnington, Ross

    2014-11-01

    Perceiving the pain of others activates similar neural structures to those involved in the direct experience of pain, including sensory and affective-motivational areas. Empathic responses can be modulated by race, such that stronger neural activation is elicited by the perception of pain in people of the same race compared with another race. In the present study, we aimed to identify when racial bias occurs in the time course of neural empathic responses to pain. We also investigated whether group affiliation could modulate the race effect. Using the minimal group paradigm, we assigned participants to one of two mixed-race teams. We examined event-related potentials from participants when viewing members of their own and the other team receiving painful or non-painful touch. We identified a significant racial bias in early ERP components at N1 over frontal electrodes, where Painful stimuli elicited a greater negative shift relative to Non-Painful stimuli in response to own race faces only. A long latency empathic response was also found at P3, where there was significant differentiation between Painful and Non-Painful stimuli regardless of Race or Group. There was no evidence that empathy-related brain activity was modulated by minimal group manipulation. These results support a model of empathy for pain that consists of early, automatic bias towards own-race empathic responses and a later top-down cognitive evaluation that does not differentiate between races and may ultimately lead to unbiased behaviour. PMID:25281885

  6. Potential unsatisfiability of cyclic constraints on stochastic biological networks biases selection towards hierarchical architectures

    PubMed Central

    Smith, Cameron; Pechuan, Ximo; Puzio, Raymond S.; Biro, Daniel; Bergman, Aviv

    2015-01-01

    Constraints placed upon the phenotypes of organisms result from their interactions with the environment. Over evolutionary time scales, these constraints feed back onto smaller molecular subnetworks comprising the organism. The evolution of biological networks is studied by considering a network of a few nodes embedded in a larger context. Taking into account this fact that any network under study is actually embedded in a larger context, we define network architecture, not on the basis of physical interactions alone, but rather as a specification of the manner in which constraints are placed upon the states of its nodes. We show that such network architectures possessing cycles in their topology, in contrast to those that do not, may be subjected to unsatisfiable constraints. This may be a significant factor leading to selection biased against those network architectures where such inconsistent constraints are more likely to arise. We proceed to quantify the likelihood of inconsistency arising as a function of network architecture finding that, in the absence of sampling bias over the space of possible constraints and for a given network size, networks with a larger number of cycles are more likely to have unsatisfiable constraints placed upon them. Our results identify a constraint that, at least in isolation, would contribute to a bias in the evolutionary process towards more hierarchical -modular versus completely connected network architectures. Together, these results highlight the context dependence of the functionality of biological networks. PMID:26040595

  7. Sensitivity of NCEP GFS Forecast of Hurricane Sandy to Model Biases

    NASA Astrophysics Data System (ADS)

    Yang, F.

    2014-12-01

    Hurricane Sandy was the most destructive hurricane of the 2012 Atlantic hurricane season. It developed from a tropical depression on October 22 and became a Category three storm at its peak intensity on October 25. Early on October 29 Sandy became a post-tropical cyclone with hurricane-force winds and made landfall along the New Jersey seashores. While all NWP models correctly predicted that the storm will strike the New Jersey Seashore within 72 hours of its landfall, most models struggled to predict its path at longer forecast lead times. The United States GFS (Global Forecast Systems) predicted a northeast instead of northwest path from the forecast cycles before October 25 and a path biased toward the north from the cycles before October 27. This study investigates the impact of GFS biases in environmental flow and surface forcing on the predicted Sandy storm path and intensity. A set of sensitivity experiments were carried out to explore the cause of forecast biases. In particular, the sensitivity of forecasts to model resolution and different physics parameterization options were examined.

  8. Characterization of Multicrystalline Silicon Modules with System Bias Voltage Applied in Damp Heat

    SciTech Connect

    Hacke, P.; Kempe, M.; Terwilliger, K.; Glick, S.; Call, N.; Johnston, S.; Kurtz, S.

    2011-07-01

    As it is considered economically favorable to serially connect modules to build arrays with high system voltage, it is necessary to explore potential long-term degradation mechanisms the modules may incur under such electrical potential. We performed accelerated lifetime testing of multicrystalline silicon PV modules in 85 degrees C/ 85% relative humidity and 45 degrees C/ 30% relative humidity while placing the active layer in either positive or negative 600 V bias with respect to the grounded module frame. Negative bias applied to the active layer in some cases leads to more rapid and catastrophic module power degradation. This is associated with significant shunting of individual cells as indicated by electroluminescence, thermal imaging, and I-V curves. Mass spectroscopy results support ion migration as one of the causes. Electrolytic corrosion is seen occurring with the silicon nitride antireflective coating and silver gridlines, and there is ionic transport of metallization at the encapsulant interface observed with damp heat and applied bias. Leakage current and module degradation is found to be highly dependent upon the module construction, with factors such as encapsulant and front glass resistivity affecting performance. Measured leakage currents range from about the same seen in published reports of modules deployed in Florida (USA) and is accelerated to up to 100 times higher in the environmental chamber testing.

  9. Can pollution bias peatland paleoclimate reconstruction?

    NASA Astrophysics Data System (ADS)

    Payne, Richard J.; Mitchell, Edward A. D.; Nguyen-Viet, Hung; Gilbert, Daniel

    2012-09-01

    Peatland testate amoebae are widely used to reconstruct paleohydrological/climatic changes, but many species are also known to respond to pollutants. Peatlands around the world have been exposed to anthropogenic and intermittent natural pollution through the late Holocene. This raises the question: can pollution lead to changes in the testate amoeba paleoecological record that could be erroneously interpreted as a climatic change? To address this issue we applied testate amoeba transfer functions to the results of experiments adding pollutants (N, P, S, Pb, O3) to peatlands and similar ecosystems. We found a significant effect in only one case, an experiment in which N and P were added, suggesting that pollution-induced biases are limited. However, we caution researchers to be aware of this possibility when interpreting paleoecological records. Studies characterising the paleoecological response to pollution allow pollution impacts to be tracked and distinguished from climate change.

  10. Social Categorization on Perception Bias in the Practice of Microteaching

    NASA Astrophysics Data System (ADS)

    Hong, Jon-Chao; Hwang, Ming-Yueh; Lu, Chow-Chin; Tsai, Chi-Ruei

    2016-01-01

    Microteaching has gained considerable attention for its effectiveness in rapid and contextual training in professional development programs. However, the interpretive quality of the teaching demonstration and peer feedback may influence individuals' attribution and self-correction, leading to ineffective learning. In this study, a microteaching workshop in a professional development program for 78 elementary school science teachers was investigated. The results showed that the effectiveness of microteaching was negatively affected by participants' perception bias due to social categorization. Moreover, it was indicated that the participants' perception of the in-group and out-group, classified by the degree of the individuals' science knowledge, fostered social categorization. Participants tended to experience perception conflicts caused by their inability to see personal faults, and a typical perception bias of "seeing one's own strengths and seeing others' shortcomings" was more frequently recognized in the out-group. These results converge to highlight the importance of social categorization in perception bias relevant to microteaching.

  11. Conservative Tests under Satisficing Models of Publication Bias.

    PubMed

    McCrary, Justin; Christensen, Garret; Fanelli, Daniele

    2016-01-01

    Publication bias leads consumers of research to observe a selected sample of statistical estimates calculated by producers of research. We calculate critical values for statistical significance that could help to adjust after the fact for the distortions created by this selection effect, assuming that the only source of publication bias is file drawer bias. These adjusted critical values are easy to calculate and differ from unadjusted critical values by approximately 50%-rather than rejecting a null hypothesis when the t-ratio exceeds 2, the analysis suggests rejecting a null hypothesis when the t-ratio exceeds 3. Samples of published social science research indicate that on average, across research fields, approximately 30% of published t-statistics fall between the standard and adjusted cutoffs. PMID:26901834

  12. [Implications of publication bias on guideline development and appraisal].

    PubMed

    Kopp, Ina B

    2011-01-01

    The issue of selective publishing of research results is gaining more and more scientific, public and political awareness. For guideline authors, in particular, it leads to uncertainty about the interpretability of the methodological quality and clinical relevance of the available evidence and the risk of bias where their conclusions and thus guideline recommendations are concerned. The actual impact of publication bias on guideline contents appears to be low if a systematic and methodically sound approach is followed in the process of guideline development. However, the quality of the evidence on this topic is poor. Different strategies to deal with publication bias have been proposed for authors of systematic reviews but they are of limited use for guideline authors. The goal must therefore be to implement appropriate measures in order to avoid the problem ex ante. The first step would be the systematic registration of study results in publicly accessible registers.

  13. Conservative Tests under Satisficing Models of Publication Bias

    PubMed Central

    McCrary, Justin; Christensen, Garret; Fanelli, Daniele

    2016-01-01

    Publication bias leads consumers of research to observe a selected sample of statistical estimates calculated by producers of research. We calculate critical values for statistical significance that could help to adjust after the fact for the distortions created by this selection effect, assuming that the only source of publication bias is file drawer bias. These adjusted critical values are easy to calculate and differ from unadjusted critical values by approximately 50%—rather than rejecting a null hypothesis when the t-ratio exceeds 2, the analysis suggests rejecting a null hypothesis when the t-ratio exceeds 3. Samples of published social science research indicate that on average, across research fields, approximately 30% of published t-statistics fall between the standard and adjusted cutoffs. PMID:26901834

  14. Mapping Species Distributions with MAXENT Using a Geographically Biased Sample of Presence Data: A Performance Assessment of Methods for Correcting Sampling Bias

    PubMed Central

    Fourcade, Yoan; Engler, Jan O.; Rödder, Dennis; Secondi, Jean

    2014-01-01

    MAXENT is now a common species distribution modeling (SDM) tool used by conservation practitioners for predicting the distribution of a species from a set of records and environmental predictors. However, datasets of species occurrence used to train the model are often biased in the geographical space because of unequal sampling effort across the study area. This bias may be a source of strong inaccuracy in the resulting model and could lead to incorrect predictions. Although a number of sampling bias correction methods have been proposed, there is no consensual guideline to account for it. We compared here the performance of five methods of bias correction on three datasets of species occurrence: one “virtual” derived from a land cover map, and two actual datasets for a turtle (Chrysemys picta) and a salamander (Plethodon cylindraceus). We subjected these datasets to four types of sampling biases corresponding to potential types of empirical biases. We applied five correction methods to the biased samples and compared the outputs of distribution models to unbiased datasets to assess the overall correction performance of each method. The results revealed that the ability of methods to correct the initial sampling bias varied greatly depending on bias type, bias intensity and species. However, the simple systematic sampling of records consistently ranked among the best performing across the range of conditions tested, whereas other methods performed more poorly in most cases. The strong effect of initial conditions on correction performance highlights the need for further research to develop a step-by-step guideline to account for sampling bias. However, this method seems to be the most efficient in correcting sampling bias and should be advised in most cases. PMID:24818607

  15. Variable-bias coin tossing

    NASA Astrophysics Data System (ADS)

    Colbeck, Roger; Kent, Adrian

    2006-03-01

    Alice is a charismatic quantum cryptographer who believes her parties are unmissable; Bob is a (relatively) glamorous string theorist who believes he is an indispensable guest. To prevent possibly traumatic collisions of self-perception and reality, their social code requires that decisions about invitation or acceptance be made via a cryptographically secure variable-bias coin toss (VBCT). This generates a shared random bit by the toss of a coin whose bias is secretly chosen, within a stipulated range, by one of the parties; the other party learns only the random bit. Thus one party can secretly influence the outcome, while both can save face by blaming any negative decisions on bad luck. We describe here some cryptographic VBCT protocols whose security is guaranteed by quantum theory and the impossibility of superluminal signaling, setting our results in the context of a general discussion of secure two-party computation. We also briefly discuss other cryptographic applications of VBCT.

  16. Belief bias and relational reasoning.

    PubMed

    Roberts, Maxwell J; Sykes, Elizabeth D A

    2003-01-01

    When people evaluate categorical syllogisms, they tend to reject unbelievable conclusions and accept believable ones irrespective of their validity. Typically, this effect is particularly marked for invalid conclusions that are possible, but do not necessarily follow, given the premises. However, smaller believability effects can also be detected for other types of conclusion. Three experiments are reported here, in which an attempt was made to determine whether belief bias effects can manifest themselves on the relational inference task. Subjects evaluated the validity of conclusions such as William the Conqueror was king after the Pyramids were built (temporal task) or Manchester is north of Bournemouth (spatial task) with respect to their premises. All of the major findings for equivalent categorical syllogism tasks were replicated. However, the overall size of the main effect of believability appears to be related to task presentation, a phenomenon not previously identified for categorical syllogisms and which current theories of belief bias have difficulty explaining.

  17. Casuistry and social category bias.

    PubMed

    Norton, Michael I; Vandello, Joseph A; Darley, John M

    2004-12-01

    This research explored cases where people are drawn to make judgments between individuals based on questionable criteria, in particular those individuals' social group memberships. We suggest that individuals engage in casuistry to mask biased decision making, by recruiting more acceptable criteria to justify such decisions. We present 6 studies that demonstrate how casuistry licenses people to judge on the basis of social category information but appear unbiased--to both others and themselves--while doing so. In 2 domains (employment and college admissions decisions), with 2 social categories (gender and race), and with 2 motivations (favoring an in-group or out-group), the present studies explored how participants justify decisions biased by social category information by arbitrarily inflating the relative value of their preferred candidates' qualifications over those of competitors.

  18. Generalization of the FRAM's Bias

    SciTech Connect

    Duc T. Vo

    2005-10-01

    The Fixed-Energy Response-Function Analysis with Multiple Efficiency (FRAM) code was developed at Los Alamos National Laboratory to measure the gamma-ray spectrometry of the isotopic composition of plutonium, uranium, and other actinides. Its reported uncertainties of the results come from the propagation of the statistics in the peak areas only. No systematic error components are included in the reported uncertainties. We have done several studies and found that the FRAM's statistical precision can be reasonably represented by its reported uncertainties. The FRAM's biases or systematic uncertainties can come from a variety of sources and can be difficult to determine. We carefully examined the FRAM analytical results of the archival plutonium data and of the data specifically acquired for this isotopic uncertainty analysis project and found the relationship between the bias and other parameters. We worked out the equations representing the biases of the measured isotopes from each measurement using the internal parameters in the spectrum such as peak resolution and shape, region of analysis, and burnup (for plutonium) or enrichment (for uranium).

  19. Response bias in plaintiffs' histories.

    PubMed

    Lees-Haley, P R; Williams, C W; Zasler, N D; Marguilies, S; English, L T; Stevens, K B

    1997-11-01

    This study investigated response bias in self-reported history of factors relevant to the assessment of traumatic brain injury, toxic brain injury and related emotional distress. Response bias refers to systematic error in self-report data. A total of 446 subjects (comprising 131 litigating and 315 non-litigating adults from five locations in the United States) completed a symptom questionnaire. Data were obtained from university faculty and students, from patients in clinics specializing in physiatry neurology, and family medicine, and from plaintiffs undergoing forensic neuropsychological evaluations. Comparisons were made for litigant and non litigant ratings of their past and current cognitive and emotional functioning, including life in general, ability to concentrate, memory, depression, anxiety, alcohol, drugs, ability to work or attend school, irritability, headaches, confusion, self-esteem, and fatigue. Although there is no basis for hypothesizing plaintiffs to be healthier than the general population, plaintiffs rated their pre-injury functioning superior to non-plaintiffs. These findings suggest that response biases need to be taken into account by forensic examiners when relying on litigants' self-reports of pre-injury status.

  20. Editorial Bias in Crowd-Sourced Political Information

    PubMed Central

    2015-01-01

    The Internet has dramatically expanded citizens’ access to and ability to engage with political information. On many websites, any user can contribute and edit “crowd-sourced” information about important political figures. One of the most prominent examples of crowd-sourced information on the Internet is Wikipedia, a free and open encyclopedia created and edited entirely by users, and one of the world’s most accessed websites. While previous studies of crowd-sourced information platforms have found them to be accurate, few have considered biases in what kinds of information are included. We report the results of four randomized field experiments that sought to explore what biases exist in the political articles of this collaborative website. By randomly assigning factually true but either positive or negative and cited or uncited information to the Wikipedia pages of U.S. senators, we uncover substantial evidence of an editorial bias toward positivity on Wikipedia: Negative facts are 36% more likely to be removed by Wikipedia editors than positive facts within 12 hours and 29% more likely within 3 days. Although citations substantially increase an edit’s survival time, the editorial bias toward positivity is not eliminated by inclusion of a citation. We replicate this study on the Wikipedia pages of deceased as well as recently retired but living senators and find no evidence of an editorial bias in either. Our results demonstrate that crowd-sourced information is subject to an editorial bias that favors the politically active. PMID:26331611

  1. Shape measurement biases from underfitting and ellipticity gradients

    SciTech Connect

    Bernstein, Gary M.

    2010-08-21

    With this study, precision weak gravitational lensing experiments require measurements of galaxy shapes accurate to <1 part in 1000. We investigate measurement biases, noted by Voigt and Bridle (2009) and Melchior et al. (2009), that are common to shape measurement methodologies that rely upon fitting elliptical-isophote galaxy models to observed data. The first bias arises when the true galaxy shapes do not match the models being fit. We show that this "underfitting bias" is due, at root, to these methods' attempts to use information at high spatial frequencies that has been destroyed by the convolution with the point-spread function (PSF) and/or by sampling. We propose a new shape-measurement technique that is explicitly confined to observable regions of k-space. A second bias arises for galaxies whose ellipticity varies with radius. For most shape-measurement methods, such galaxies are subject to "ellipticity gradient bias". We show how to reduce such biases by factors of 20–100 within the new shape-measurement method. The resulting shear estimator has multiplicative errors < 1 part in 103 for high-S/N images, even for highly asymmetric galaxies. Without any training or recalibration, the new method obtains Q = 3000 in the GREAT08 Challenge of blind shear reconstruction on low-noise galaxies, several times better than any previous method.

  2. Editorial Bias in Crowd-Sourced Political Information.

    PubMed

    Kalla, Joshua L; Aronow, Peter M

    2015-01-01

    The Internet has dramatically expanded citizens' access to and ability to engage with political information. On many websites, any user can contribute and edit "crowd-sourced" information about important political figures. One of the most prominent examples of crowd-sourced information on the Internet is Wikipedia, a free and open encyclopedia created and edited entirely by users, and one of the world's most accessed websites. While previous studies of crowd-sourced information platforms have found them to be accurate, few have considered biases in what kinds of information are included. We report the results of four randomized field experiments that sought to explore what biases exist in the political articles of this collaborative website. By randomly assigning factually true but either positive or negative and cited or uncited information to the Wikipedia pages of U.S. senators, we uncover substantial evidence of an editorial bias toward positivity on Wikipedia: Negative facts are 36% more likely to be removed by Wikipedia editors than positive facts within 12 hours and 29% more likely within 3 days. Although citations substantially increase an edit's survival time, the editorial bias toward positivity is not eliminated by inclusion of a citation. We replicate this study on the Wikipedia pages of deceased as well as recently retired but living senators and find no evidence of an editorial bias in either. Our results demonstrate that crowd-sourced information is subject to an editorial bias that favors the politically active.

  3. Shape measurement biases from underfitting and ellipticity gradients

    DOE PAGES

    Bernstein, Gary M.

    2010-08-21

    With this study, precision weak gravitational lensing experiments require measurements of galaxy shapes accurate to <1 part in 1000. We investigate measurement biases, noted by Voigt and Bridle (2009) and Melchior et al. (2009), that are common to shape measurement methodologies that rely upon fitting elliptical-isophote galaxy models to observed data. The first bias arises when the true galaxy shapes do not match the models being fit. We show that this "underfitting bias" is due, at root, to these methods' attempts to use information at high spatial frequencies that has been destroyed by the convolution with the point-spread function (PSF)more » and/or by sampling. We propose a new shape-measurement technique that is explicitly confined to observable regions of k-space. A second bias arises for galaxies whose ellipticity varies with radius. For most shape-measurement methods, such galaxies are subject to "ellipticity gradient bias". We show how to reduce such biases by factors of 20–100 within the new shape-measurement method. The resulting shear estimator has multiplicative errors < 1 part in 103 for high-S/N images, even for highly asymmetric galaxies. Without any training or recalibration, the new method obtains Q = 3000 in the GREAT08 Challenge of blind shear reconstruction on low-noise galaxies, several times better than any previous method.« less

  4. Spatial bias in field-estimated unsaturated hydraulic properties

    NASA Astrophysics Data System (ADS)

    Holt, Robert M.; Wilson, John L.; Glass, Robert J.

    2002-12-01

    We use a Monte Carlo approach to explore the potential impact of observation and inversion model errors on the spatial statistics of field-estimated unsaturated hydraulic properties. For this analysis we simulate tension infiltrometer measurements in a series of idealized realities, each consisting of spatially correlated random property fields. We consider only simple measurement errors that can be easily modeled. We show that estimated hydraulic properties are strongly biased by small, simple observation and inversion model errors. This bias can lead to order-of-magnitude errors in spatial statistics and artificial cross correlation between measured properties. The magnitude of bias varies with the true mean of the property field, the type of error considered, and the type of spatial statistic. We find no unique indicators of bias as property values may appear reasonable and spatial statistics may look realistic. Our results suggest new concerns for geostatisticians, stochastic modelers, and unsaturated zone practitioners who are unaware of the potential impact of spatial bias in field-estimated properties.

  5. Biased learning affects mate choice in a butterfly

    PubMed Central

    Westerman, Erica L.; Hodgins-Davis, Andrea; Dinwiddie, April; Monteiro, Antónia

    2012-01-01

    Early acquisition of mate preferences or mate-preference learning is associated with signal diversity and speciation in a wide variety of animal species. However, the diversity of mechanisms of mate-preference learning across taxa remains poorly understood. Using the butterfly Bicyclus anynana we uncover a mechanism that can lead to directional sexual selection via mate-preference learning: a bias in learning enhanced ornamentation, which is independent of preexisting mating biases. Naïve females mated preferentially with wild-type males over males with enhanced wing ornamentation, but females briefly exposed to enhanced males mated significantly more often with enhanced males. In contrast, females exposed to males with reduced wing ornamentation did not learn to prefer drab males. Thus, we observe both a learned change of a preexisting mating bias, and a bias in ability to learn enhanced male ornaments over reduced ornaments. Our findings demonstrate that females are able to change their preferences in response to a single social event, and suggest a role for biased learning in the evolution of visual sexual ornamentation. PMID:22689980

  6. Upper visual field distractors preferentially bias attention to the left.

    PubMed

    Thomas, Nicole A; Castine, Benjamin R; Loetscher, Tobias; Nicholls, Michael E R

    2015-03-01

    Pseudoneglect is influenced by vertical visual field stimulation, such that attentional biases are stronger for upper space distractors. Leftward biases result from right hemisphere visuospatial processing, and may be accentuated by additional right hemisphere activation during upper space distraction. Three experiments examined potential explanations for this finding. Experiment 1 controlled for perceptual grouping and leftward biases remained stronger in upper space. Experiment 2 used peripheral distractors to eliminate two further potential explanations: centre-of-mass and framing effects. Eye tracking was included to compare overt and covert attention. Findings supported the occurrence of a stronger leftward attentional bias during upper space distraction. Distractors were rarely fixated, suggesting covert attentional mechanisms are preferentially drawn toward upper space distractors. Experiment 3 employed a cueing paradigm that purposefully directed attention away from centre to determine whether pseudoneglect was influenced by overt attentional orienting. Results indicated that when attention was overtly directed away from centre, the strength of pseudoneglect did not differ based on visual field. It is concluded that covert attention toward upper space distractors recruits additional right hemisphere activation, leading existing leftward biases to be accentuated.

  7. An SIS model for cultural trait transmission with conformity bias.

    PubMed

    Walters, Caroline E; Kendal, Jeremy R

    2013-12-01

    Epidemiological models have been applied to human health-related behaviors that are affected by social interaction. Typically these models have not considered conformity bias, that is, the exaggerated propensity to adopt commonly observed behaviors or opinions, or content biases, where the content of the learned trait affects the probability of adoption. Here we consider an interaction of these two effects, presenting an SIS-type model for the spread and persistence of a behavior which is transmitted via social learning. Uptake is controlled by a nonlinear dependence on the proportion of individuals demonstrating the behavior in a population. Three equilibrium solutions are found, their linear stability is analyzed and the results are compared with a model for unbiased social learning. Our analysis focuses on the effects of the strength of conformity bias and the effects of content biases which alter a conformity threshold frequency of the behavior, above which there is an exaggerated propensity for adoption. The strength of the conformity bias is found to qualitatively alter the predictions regarding whether the trait becomes endemic within the population and the proportion of individuals who display the trait when it is endemic. As the conformity strength increases, the number of feasible equilibrium solutions increases from two to three, leading to a situation where the stable equilibrium attained is dependent upon the initial state. Varying the conformity threshold frequency directionally alters the behavior invasion threshold. Finally we discuss the possible application of this model to binge drinking behavior.

  8. Strain-mediated multiferroic control of spontaneous exchange bias in Ni-NiO heterostructures

    NASA Astrophysics Data System (ADS)

    Domann, John P.; Sun, Wei-Yang; Schelhas, Laura T.; Carman, Greg P.

    2016-10-01

    This paper presents the measurement of strain-mediated multiferroic control of spontaneous exchange bias (SEB) in magnetostrictive nickel/nickel oxide (Ni/NiO) bilayers on ferroelectric lead magnesium niobate-lead titanate (PMN-PT). Electric field control of a positive to negative exchange bias shift was measured, with an overall shift of 40.5 Oe, corresponding to a 325% change. Observed changes in coercivity are also reported and provide insight into the role of competing anisotropies in these structures. The findings in this paper provide evidence that magnetoelastic anisotropy can be utilized to control spontaneous exchange bias (SEB). This control of SEB is accomplished by modifying a bulk anisotropy (magnetoelasticity) that adjusts the mobility of interfacial anti-ferromagnetic spins and, therefore, the magnitude of the exchange bias. The demonstrated magnetoelastic control of exchange bias provides a useful tool in the creation of future magnetoelectric devices.

  9. The Probability Distribution for a Biased Spinner

    ERIC Educational Resources Information Center

    Foster, Colin

    2012-01-01

    This article advocates biased spinners as an engaging context for statistics students. Calculating the probability of a biased spinner landing on a particular side makes valuable connections between probability and other areas of mathematics. (Contains 2 figures and 1 table.)

  10. The Nonverbal Transmission of Intergroup Bias: A Model of Bias Contagion with Implications for Social Policy

    PubMed Central

    Weisbuch, Max; Pauker, Kristin

    2013-01-01

    Social and policy interventions over the last half-century have achieved laudable reductions in blatant discrimination. Yet members of devalued social groups continue to face subtle discrimination. In this article, we argue that decades of anti-discrimination interventions have failed to eliminate intergroup bias because such bias is contagious. We present a model of bias contagion in which intergroup bias is subtly communicated through nonverbal behavior. Exposure to such nonverbal bias “infects” observers with intergroup bias. The model we present details two means by which nonverbal bias can be expressed—either as a veridical index of intergroup bias or as a symptom of worry about appearing biased. Exposure to this nonverbal bias can increase perceivers’ own intergroup biases through processes of implicit learning, informational influence, and normative influence. We identify critical moderators that may interfere with these processes and consequently propose several social and educational interventions based on these moderators. PMID:23997812

  11. Maintenance of motility bias during cyanobacterial phototaxis.

    PubMed

    Chau, Rosanna Man Wah; Ursell, Tristan; Wang, Shuo; Huang, Kerwyn Casey; Bhaya, Devaki

    2015-04-01

    Signal transduction in bacteria is complex, ranging across scales from molecular signal detectors and effectors to cellular and community responses to stimuli. The unicellular, photosynthetic cyanobacterium Synechocystis sp. PCC6803 transduces a light stimulus into directional movement known as phototaxis. This response occurs via a biased random walk toward or away from a directional light source, which is sensed by intracellular photoreceptors and mediated by Type IV pili. It is unknown how quickly cells can respond to changes in the presence or directionality of light, or how photoreceptors affect single-cell motility behavior. In this study, we use time-lapse microscopy coupled with quantitative single-cell tracking to investigate the timescale of the cellular response to various light conditions and to characterize the contribution of the photoreceptor TaxD1 (PixJ1) to phototaxis. We first demonstrate that a community of cells exhibits both spatial and population heterogeneity in its phototactic response. We then show that individual cells respond within minutes to changes in light conditions, and that movement directionality is conferred only by the current light directionality, rather than by a long-term memory of previous conditions. Our measurements indicate that motility bias likely results from the polarization of pilus activity, yielding variable levels of movement in different directions. Experiments with a photoreceptor (taxD1) mutant suggest a supplementary role of TaxD1 in enhancing movement directionality, in addition to its previously identified role in promoting positive phototaxis. Motivated by the behavior of the taxD1 mutant, we demonstrate using a reaction-diffusion model that diffusion anisotropy is sufficient to produce the observed changes in the pattern of collective motility. Taken together, our results establish that single-cell tracking can be used to determine the factors that affect motility bias, which can then be coupled with

  12. Lead toxicity: a review

    PubMed Central

    Ara, Anjum; Usmani, Jawed Ahmad

    2015-01-01

    Lead toxicity is an important environmental disease and its effects on the human body are devastating. There is almost no function in the human body which is not affected by lead toxicity. Though in countries like US and Canada the use of lead has been controlled up to a certain extent, it is still used vehemently in the developing countries. This is primarily because lead bears unique physical and chemical properties that make it suitable for a large number of applications for which humans have exploited its benefits from historical times and thus it has become a common environmental pollutant. Lead is highly persistent in the environment and because of its continuous use its levels rise in almost every country, posing serious threats. This article reviews the works listed in the literature with recent updates regarding the toxicity of lead. Focus is also on toxic effects of lead on the renal, reproductive and nervous system. Finally the techniques available for treating lead toxicity are presented with some recent updates. PMID:27486361

  13. Simulated Climate Sensitivity Uncertainty: Control Climate Bias vs. Perturbed Physics

    NASA Astrophysics Data System (ADS)

    Dommenget, D.

    2013-12-01

    In this talk I address the relationship between climate model biases in the control climate and the simulated climate sensitivity. On the basis of a globally resolved energy balance (GREB) model a number of perturbed physics ensembles are discussed. It is illustrated that the uncertainties in the simulated climate sensitivity can be conceptually split into two parts: a direct effect of the perturbed physics on the climate sensitivity independent of the control mean climate and an indirect effect of the perturbed physics by changing the control mean climate, which in turn changes the climate sensitivity, as the climate sensitivity itself is depending on the control climate. It is shown that the two effects are opposing each other. Biases in the control climate are negatively correlated with the climate sensitivity (colder climates have large sensitivities) and perturbed physics are in average positively correlated with the climate sensitivity (perturbed parameters that lead to warmer control climates lead to larger climate sensitivities). In the GREB model the biases in the control climate are more important effect for the regional climate sensitivity uncertainties, but on the global mean climate sensitivity both, the biases in the control climate and the perturbed physics are equally important.

  14. Gender Bias: Recent Research and Interventions.

    ERIC Educational Resources Information Center

    New Jersey Research Bulletin, 1996

    1996-01-01

    This annotated bibliography lists 14 publications about recent research on gender bias and interventions to reduce gender bias in schools. The bibliography is divided into two sections: current research and intervention. The first includes descriptions of studies examining the following topics: gender bias in U.S. schools and its effects;…

  15. Outcome-Reporting Bias in Education Research

    ERIC Educational Resources Information Center

    Pigott, Therese D.; Valentine, Jeffrey C.; Polanin, Joshua R.; Williams, Ryan T.; Canada, Dericka D.

    2013-01-01

    Outcome-reporting bias occurs when primary studies do not include information about all outcomes measured in a study. When studies omit findings on important measures, efforts to synthesize the research using systematic review techniques will be biased and interpretations of individual studies will be incomplete. Outcome-reporting bias has been…

  16. Attentional Bias for Exercise-Related Images

    ERIC Educational Resources Information Center

    Berry, Tanya R.; Spence, John C.; Stolp, Sean M.

    2011-01-01

    This research examined attentional bias toward exercise-related images using a visual probe task. It was hypothesized that more-active participants would display attentional bias toward the exercise-related images. The results showed that men displayed attentional bias for the exercise images. There was a significant interaction of activity level…

  17. Using Newspapers to Study Media Bias.

    ERIC Educational Resources Information Center

    Kirman, Joseph M.

    1992-01-01

    Suggests that students can learn to recognize media bias by studying media reports of current events or historical topics. Describes a study unit using media coverage of the second anniversary of the Palestinian uprising against Israel. Discusses lesson objectives, planning, defining bias teaching procedures, and criteria for determining bias. (DK)

  18. Culturally Biased Assumptions in Counseling Psychology

    ERIC Educational Resources Information Center

    Pedersen, Paul B.

    2003-01-01

    Eight clusters of culturally biased assumptions are identified for further discussion from Leong and Ponterotto's (2003) article. The presence of cultural bias demonstrates that cultural bias is so robust and pervasive that is permeates the profession of counseling psychology, even including those articles that effectively attack cultural bias…

  19. Industry leading satellite based GNSS (Global Navigation Satellite System) positioning and monitoring solutions with real-time CORS (Continuously Operating Reference Station) networks

    NASA Astrophysics Data System (ADS)

    Janousek, Martin

    2010-05-01

    Real-Time CORS (Continuously Operating Reference Station Networks) today are typically GNSS networks for positioning and monitoring purposes. Real-Time networks can consist of a few stations for a local network up to nation- or continental wide networks with several hundred CORS stations. Such networks use wide area modeling of GNSS error sources including ionospheric, tropospheric and satellite orbit correction parameters to produce highest precision and efficiency method of positioning using GNSS. In 1998 Trimble Navigation Ltd. introduced a method of surveying with a non-physical or computed base station, called VRS (Virtual Reference Station). It is the most widely supported method of producing a network solution for precise carrier phase positioning in the industry. Surveying historically required one base as the fixed point of reference, and one or multiple rovers using that point of reference to compute their location by processing a vector result, either in real-time or in a postprocessed sense. Real-time survey is often referred to as RTK, short for real-time kinematic, and as the name suggests the results are in real time and you can move. The power of VRS is in the ability to compute a real-time wide-area solution to the factors that cause single base methods to degrade with distance. Namely, ionospheric and tropospheric modeling, and satellite orbit corrections. This is achieved by the reference network of CORS. A wide scattering of CORS across a state, typically 50-70km in mid-latitudes, creates a ground based sampling which significantly reduces the distance dependent errors that accumulate in the single base-rover relationship described early. Furthermore, GNSS networks can be used for real-time monitoring purposes at various distance range. Trimble Integrity Manager software provides a suite of motion engines designed to detect and quantify any movement in a range of scales from slow, creeping movement like subsidence, through sudden events such as

  20. An alternative method for determining GPS receiver phase biases

    NASA Astrophysics Data System (ADS)

    Kersten, Tobias; Schön, Steffen

    2015-04-01

    Precise Point Positioning (PPP) is used in a broad variety of applications to determine very economically high precision parameters for positioning, navigation and timing. In comparison to traditional differential approaches, PPP with undifferenced phase measurements is highly attractive, since the effort on the user side can be reduced to minimum, e.g. due to an unnecessary reference station. The quality of obtained position solutions is comparable to those obtained from a differential approach. One of the most important limiting factor is the long integration time to determine (float) ambiguities. Furthermore, it is critical to consider adequately all occurring error sources. In this context, receiver phase biases are one of the limiting factors and very complex to model. At least they are highly correlated with the ambiguities during the estimation process, (Laurichesse et al. 2009). This contribution presents an alternative method to estimate carrier phase biases of different GPS/GNSS receivers and signals w.r.t. a reference receiver. Receiver phase biases are estimated on a zero baseline and in combination with a very stable and precise clock (H-Maser) using single differences. The presented method will be discussed in detail. This includes a critical look to the estimability of bias values for several GPS/GNSS receivers as well as a discussion on the stability and universality of these bias values. Finally relative phase biases are quantified and it will be discussed how GPS/GNSS observation equations have to be extended, to take these bias values correctly into account. References: Laurichesse D., Mercier F., Berthias J.P., Broca P., Cerri L. (2009): Integer ambiguity resolution on undifferenced GPS phase measurements and its application to PPP and satellite precise orbit determination, In: NAVIGATION, Journal of the Institute of Navigation, Volume 56, Number 2, pages: 135 - 149

  1. Removing the ISW-lensing bias from the local-form primordial non-Gaussianity estimation

    SciTech Connect

    Kim, Jaiseung; Komatsu, Eiichiro; Rotti, Aditya E-mail: aditya@iucaa.ernet.in

    2013-04-01

    The Integrated Sachs-Wolfe (ISW) effect produces a secondary temperature aniso\\-tropy of the cosmic microwave background (CMB), as CMB photons travel through time-varying potentials along the line-of-sight. The main contribution comes from redshifts z∼<2, where dark energy leads to a decay of potentials. As the same photons are gravitationally lensed by these decaying potentials, there exists a high degree of correlation between the ISW effect and CMB lensing, leading to a non-zero three-point correlation (bispectrum) of the observed temperature anisotropy. This ISW-lensing bispectrum, whose shape resembles that of the so-called ''local-form'' primordial bispectrum parametrized by f{sub NL}, is known to be the largest contamination of f{sub NL}. In order to avoid a spurious detection of primordial non-Gaussianity, we need to remove the ISW-lensing bias. In this work, we investigate three debiasing methods: (I) subtraction of an expected, ensemble average of the ISW-lensing bispectrum; (II) subtraction of a measured ISW-lensing bispectrum; and (III) direct subtraction of an estimated ISW signal from an observed temperature map. One may use an estimation of the ISW map from external non-CMB data or that from the CMB data themselves. As the methods II and III are based on fewer assumptions about the nature of dark energy, they are preferred over the method I. While the methods I and II yield unbiased estimates of f{sub NL} with comparable error bars, the method III yields a biased result when the underlying primordial f{sub NL} is non-zero and the ISW map is estimated from a lensing potential reconstructed from the observed temperature map. One of the sources of the bias is a lensing reconstruction noise bias which is independent of f{sub NL} and can be calculated precisely, but other f{sub NL}-dependent terms are difficult to compute reliably. We thus conclude that the method II is the best, model-independent way to remove the ISW-lensing bias of f{sub NL

  2. Sex-biased transcriptome evolution in Drosophila.

    PubMed

    Assis, Raquel; Zhou, Qi; Bachtrog, Doris

    2012-01-01

    Sex-biased genes are thought to drive phenotypic differences between males and females. The recent availability of high-throughput gene expression data for many related species has led to a burst of investigations into the genomic and evolutionary properties of sex-biased genes. In Drosophila, a number of studies have found that X chromosomes are deficient in male-biased genes (demasculinized) and enriched for female-biased genes (feminized) and that male-biased genes evolve faster than female-biased genes. However, studies have yielded vastly different conclusions regarding the numbers of sex-biased genes and forces shaping their evolution. Here, we use RNA-seq data from multiple tissues of Drosophila melanogaster and D. pseudoobscura, a species with a recently evolved X chromosome, to explore the evolution of sex-biased genes in Drosophila. First, we compare several independent metrics for classifying sex-biased genes and find that the overlap of genes identified by different metrics is small, particularly for female-biased genes. Second, we investigate genome-wide expression patterns and uncover evidence of demasculinization and feminization of both ancestral and new X chromosomes, demonstrating that gene content on sex chromosomes evolves rapidly. Third, we examine the evolutionary rates of sex-biased genes and show that male-biased genes evolve much faster than female-biased genes, which evolve at similar rates to unbiased genes. Analysis of gene expression among tissues reveals that this trend may be partially due to pleiotropic effects of female-biased genes, which limits their evolutionary potential. Thus, our findings illustrate the importance of accurately identifying sex-biased genes and provide insight into their evolutionary dynamics in Drosophila.

  3. Selection bias in evaluating of influenza vaccine effectiveness: a lesson from an observational study of elderly nursing home residents.

    PubMed

    Fukushima, Wakaba; Hayashi, Yoshimitsu; Mizuno, Yaichi; Suzuki, Kanzo; Kase, Tetsuo; Ohfuji, Satoko; Fujieda, Megumi; Maeda, Akiko; Hirota, Yoshio

    2008-11-25

    Selection bias is of critical concern in the study of influenza vaccine effectiveness when using an observational study design. This bias is attributable to the inherently different characteristics between vaccinees and non-vaccinees. The differences, which are related both to vaccination and signs of clinical disease as an outcome, may lead to erroneous estimation of the effectiveness. In this report, we describe how selection bias among elderly nursing home residents may lead to a spurious interpretation of the protective effect of influenza vaccine. Our results should be a lesson in the importance of regarding selection bias when assessing influenza vaccine effectiveness.

  4. Interoception and symptom reporting: disentangling accuracy and bias.

    PubMed

    Petersen, Sibylle; Van Staeyen, Ken; Vögele, Claus; von Leupoldt, Andreas; Van den Bergh, Omer

    2015-01-01

    Anxiety and anxiety sensitivity are positively related to accuracy in the perception of bodily sensations. At the same time, research consistently reports that these traits are positively related to bias, resulting in the report of more and more intense symptoms that poorly correspond with physiological dysfunction. The aim of this study was to test the relationship of accuracy and bias in interoception. Furthermore, we tested the impact of individual differences in negative affect and symptom report in daily life on interoceptive accuracy and bias. Individuals higher in symptom report in daily life and negative affect were marginally more accurate in an interoceptive classification task in which participants were asked to identify different respiratory stimuli (inducing breathing effort) as belonging to a high or low intensity category. At the same time, bias in overestimating intensity of stimuli was significantly increased in participants higher in symptom report and negative affect, but only for more ambiguous stimuli. Results illustrate that interoceptive accuracy and bias need to be considered independently to understand their interaction with psychological factors and to disentangle (mis)perception of bodily sensations from liberal or conservative perceptual decision strategies.

  5. Interoception and symptom reporting: disentangling accuracy and bias

    PubMed Central

    Petersen, Sibylle; Van Staeyen, Ken; Vögele, Claus; von Leupoldt, Andreas; Van den Bergh, Omer

    2015-01-01

    Anxiety and anxiety sensitivity are positively related to accuracy in the perception of bodily sensations. At the same time, research consistently reports that these traits are positively related to bias, resulting in the report of more and more intense symptoms that poorly correspond with physiological dysfunction. The aim of this study was to test the relationship of accuracy and bias in interoception. Furthermore, we tested the impact of individual differences in negative affect and symptom report in daily life on interoceptive accuracy and bias. Individuals higher in symptom report in daily life and negative affect were marginally more accurate in an interoceptive classification task in which participants were asked to identify different respiratory stimuli (inducing breathing effort) as belonging to a high or low intensity category. At the same time, bias in overestimating intensity of stimuli was significantly increased in participants higher in symptom report and negative affect, but only for more ambiguous stimuli. Results illustrate that interoceptive accuracy and bias need to be considered independently to understand their interaction with psychological factors and to disentangle (mis)perception of bodily sensations from liberal or conservative perceptual decision strategies. PMID:26089810

  6. Bias of apparent tracer ages in heterogeneous environments.

    PubMed

    McCallum, James L; Cook, Peter G; Simmons, Craig T; Werner, Adrian D

    2014-01-01

    The interpretation of apparent ages often assumes that a water sample is composed of a single age. In heterogeneous aquifers, apparent ages estimated with environmental tracer methods do not reflect mean water ages because of the mixing of waters from many flow paths with different ages. This is due to nonlinear variations in atmospheric concentrations of the tracer with time resulting in biases of mixed concentrations used to determine apparent ages. The bias of these methods is rarely reported and has not been systematically evaluated in heterogeneous settings. We simulate residence time distributions (RTDs) and environmental tracers CFCs, SF6 , (85) Kr, and (39) Ar in synthetic heterogeneous confined aquifers and compare apparent ages to mean ages. Heterogeneity was simulated as both K-field variance (σ(2) ) and structure. We demonstrate that an increase in heterogeneity (increase in σ(2) or structure) results in an increase in the width of the RTD. In low heterogeneity cases, widths were generally on the order of 10 years and biases generally less than 10%. In high heterogeneity cases, widths can reach 100 s of years and biases can reach up to 100%. In cases where the temporal variations of atmospheric concentration of individual tracers vary, different patterns of bias are observed for the same mean age. We show that CFC-12 and CFC-113 ages may be used to correct for the mean age if analytical errors are small. PMID:23550995

  7. Effects of time, soil organic matter, and iron oxides on the relative retention and redistribution of lead, cadmium, and copper on soils.

    PubMed

    Diagboya, Paul N; Olu-Owolabi, Bamidele I; Adebowale, Kayode O

    2015-07-01

    In order to predict the bioavailability of toxic metals in soils undergoing degradation of organic matter (OM) and iron oxides (IOs), it is vital to understand the roles of these soil components in relation to metal retention and redistribution with time. In this present work, batch competitive sorptions of Pb(II), Cu(II), and Cd(II) were investigated between 1 and 90 days. Results showed that competition affected Cd(II) sorption more than Cu(II) and Pb(II). The sorption followed the trend Pb(II) > > Cu(II) > Cd(II), irrespective of aging, and this high preference for Pb(II) ions in soils reduced with time. Removal of OM led to reduction in distribution coefficient (K d) values of ≈33% for all cations within the first day. However, K d increased nearly 100% after 7 days and over 1000% after 90-day period. The enhanced K d values indicated that sorptions occurred on the long run on surfaces which were masked by OM. Removal of IO caused selective increases in the K d values, but this was dependent on the dominant soil constituent(s) in the absence of IO. The K d values of the IO-degraded samples nearly remained constant irrespective of aging indicating that sorptions on soil components other than the IO are nearly instantaneous while iron oxides played greater role than other constituents with time. Hence, in the soils studied, organic matter content determines the immediate relative metal retention while iron oxides determine the redistribution of metals with time.

  8. Relationship between lead mining and blood lead levels in children.

    PubMed

    Murgueytio, A M; Evans, R G; Sterling, D A; Clardy, S A; Shadel, B N; Clements, B W

    1998-01-01

    The authors studied blood lead levels of 226 randomly selected children, aged 6-92 mo, who lived in either a lead-mining area or a nonmining area, and 69 controls. The authors sought to determine to what extent mining activities contributed to blood lead levels in the children. The mean blood lead levels in the study and control groups were 6.52 microg/dl and 3.43 microg/dl, respectively. The corresponding proportions of children with elevated blood lead levels were 17% and 3%. Soil and dust lead levels were up to 10 times higher in the study than the control group. Elevated blood lead levels appeared to result from exposure to both lead-mining waste and lead-based paint. Mining waste was the cause of the higher prevalence of elevated blood lead levels in these children. PMID:9886161

  9. Observer bias: an interaction of temperament traits with biases in the semantic perception of lexical material.

    PubMed

    Trofimova, Ira

    2014-01-01

    The lexical approach is a method in differential psychology that uses people's estimations of verbal descriptors of human behavior in order to derive the structure of human individuality. The validity of the assumptions of this method about the objectivity of people's estimations is rarely questioned. Meanwhile the social nature of language and the presence of emotionality biases in cognition are well-recognized in psychology. A question remains, however, as to whether such an emotionality-capacities bias is strong enough to affect semantic perception of verbal material. For the lexical approach to be valid as a method of scientific investigations, such biases should not exist in semantic perception of the verbal material that is used by this approach. This article reports on two studies investigating differences between groups contrasted by 12 temperament traits (i.e. by energetic and other capacities, as well as emotionality) in the semantic perception of very general verbal material. Both studies contrasted the groups by a variety of capacities: endurance, lability and emotionality separately in physical, social-verbal and mental aspects of activities. Hypotheses of "background emotionality" and a "projection through capacities" were supported. Non-evaluative criteria for categorization (related to complexity, organization, stability and probability of occurrence of objects) followed the polarity of evaluative criteria, and did not show independence from this polarity. Participants with stronger physical or social endurance gave significantly more positive ratings to a variety of concepts, and participants with faster physical tempo gave more positive ratings to timing-related concepts. The results suggest that people's estimations of lexical material related to human behavior have emotionality, language- and dynamical capacities-related biases and therefore are unreliable. This questions the validity of the lexical approach as a method for the objective study

  10. Observer Bias: An Interaction of Temperament Traits with Biases in the Semantic Perception of Lexical Material

    PubMed Central

    Trofimova, Ira

    2014-01-01

    The lexical approach is a method in differential psychology that uses people's estimations of verbal descriptors of human behavior in order to derive the structure of human individuality. The validity of the assumptions of this method about the objectivity of people's estimations is rarely questioned. Meanwhile the social nature of language and the presence of emotionality biases in cognition are well-recognized in psychology. A question remains, however, as to whether such an emotionality-capacities bias is strong enough to affect semantic perception of verbal material. For the lexical approach to be valid as a method of scientific investigations, such biases should not exist in semantic perception of the verbal material that is used by this approach. This article reports on two studies investigating differences between groups contrasted by 12 temperament traits (i.e. by energetic and other capacities, as well as emotionality) in the semantic perception of very general verbal material. Both studies contrasted the groups by a variety of capacities: endurance, lability and emotionality separately in physical, social-verbal and mental aspects of activities. Hypotheses of “background emotionality” and a “projection through capacities” were supported. Non-evaluative criteria for categorization (related to complexity, organization, stability and probability of occurrence of objects) followed the polarity of evaluative criteria, and did not show independence from this polarity. Participants with stronger physical or social endurance gave significantly more positive ratings to a variety of concepts, and participants with faster physical tempo gave more positive ratings to timing-related concepts. The results suggest that people's estimations of lexical material related to human behavior have emotionality, language- and dynamical capacities-related biases and therefore are unreliable. This questions the validity of the lexical approach as a method for the objective

  11. Challenges in bias correcting climate change simulations

    NASA Astrophysics Data System (ADS)

    Maraun, Douglas; Shepherd, Ted; Zappa, Giuseppe; Gutierrez, Jose; Widmann, Martin; Hagemann, Stefan; Richter, Ingo; Soares, Pedro; Mearns, Linda

    2016-04-01

    Biases in climate model simulations - if these are directly used as input for impact models - will introduce further biases in subsequent impact simulations. In response to this issue, so-called bias correction methods have been developed to post-process climate model output. These methods are now widely used and a crucial component in the generation of high resolution climate change projections. Bias correction is conceptually similar to model output statistics, which has been successfully used for several decades in numerical weather prediction. Yet in climate science, some authors outrightly dismiss any form of bias correction. Starting from this seeming contradiction, we highlight differences between the two contexts and infer consequences and limitations for the applicability of bias correction to climate change projections. We first show that cross validation approaches successfully used to evaluate weather forecasts are fundamentally insufficient to evaluate climate change bias correction. We further demonstrate that different types of model mismatches with observations require different solutions, and some may not sensibly be mitigated. In particular we consider the influence of large-scale circulation biases, biases in the persistence of weather regimes, and regional biases caused by an insufficient representation of the flow-topography interaction. We conclude with a list of recommendations and suggestions for future research to reduce, to post-process, and to cope with climate model biases.

  12. Numeracy and framing bias in epilepsy.

    PubMed

    Choi, Hyunmi; Wong, John B; Mendiratta, Anil; Heiman, Gary A; Hamberger, Marla J

    2011-01-01

    Patients with epilepsy are frequently confronted with complex treatment decisions. Communicating treatment risks is often difficult because patients may have difficulty with basic statistical concepts (i.e., low numeracy) or might misconceive the statistical information based on the way information is presented, a phenomenon known as "framing bias." We assessed numeracy and framing bias in 95 adults with chronic epilepsy and explored cognitive correlates of framing bias. Compared with normal controls, patients with epilepsy had significantly poorer performance on the Numeracy scale (P=0.02), despite a higher level of education than normal controls (P<0.001). Compared with patients with higher numeracy, patients with lower numeracy were significantly more likely to exhibit framing bias. Abstract problem solving performance correlated with the degree of framing bias (r=0.631, P<0.0001), suggesting a relationship between aspects of executive functioning and framing bias. Poor numeracy and susceptibility framing bias place patients with epilepsy at risk for uninformed decisions.

  13. Ion acceleration in a helicon source due to the self-bias effect

    NASA Astrophysics Data System (ADS)

    Wiebold, Matt; Sung, Yung-Ta; Scharer, John E.

    2012-05-01

    Time-averaged plasma potential differences up to 165 V over several hundred Debye lengths are observed in low pressure (pn < 1 mTorr) expanding argon plasmas in the Madison Helicon eXperiment (MadHeX). The potential gradient leads to ion acceleration greater than that predicted by ambipolar expansion, exceeding Ei ≈ 7 kTe in some cases. RF power up to 500 W at 13.56 MHz is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field, adjustable up to 1 kG. A retarding potential analyzer (RPA) measures the ion energy distribution function (IEDF) and a swept emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in density as RF power is increased. In the capacitive (E) mode, large fluctuations of the plasma potential (Vp -p≳140V, Vp-p/Vp¯≈150%) exist at the RF frequency and its harmonics. The more mobile electrons can easily respond to RF-timescale gradients in the plasma potential whereas the inertially constrained ions cannot, leading to an initial flux imbalance and formation of a self-bias voltage between the source and expansion chambers. In the capacitive mode, the ion acceleration is not well described by an ambipolar relation, while in the inductive and helicon modes the ion acceleration more closely follows an ambipolar relation. The scaling of the potential gradient with the argon flow rate and RF power are investigated, with the largest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees with that predicted for RF self-bias at a wall. Rapid fluctuations in the plasma potential result in a time-dependent axial electron flux that acts to "neutralize" the accelerated ion population, resulting in a zero net time-averaged current through the acceleration region when an

  14. Ion acceleration in a helicon source due to the self-bias effect

    SciTech Connect

    Wiebold, Matt; Sung, Yung-Ta; Scharer, John E.

    2012-05-15

    Time-averaged plasma potential differences up to 165 V over several hundred Debye lengths are observed in low pressure (p{sub n} < 1 mTorr) expanding argon plasmas in the Madison Helicon eXperiment (MadHeX). The potential gradient leads to ion acceleration greater than that predicted by ambipolar expansion, exceeding E{sub i} Almost-Equal-To 7 kT{sub e} in some cases. RF power up to 500 W at 13.56 MHz is supplied to a half-turn, double-helix antenna in the presence of a nozzle magnetic field, adjustable up to 1 kG. A retarding potential analyzer (RPA) measures the ion energy distribution function (IEDF) and a swept emissive probe measures the plasma potential. Single and double probes measure the electron density and temperature. Two distinct mode hops, the capacitive-inductive (E-H) and inductive-helicon (H-W) transitions, are identified by jumps in density as RF power is increased. In the capacitive (E) mode, large fluctuations of the plasma potential (V{sub p-p} Greater-Than-Or-Equivalent-To 140V, V{sub p-p}/V{sub p} Almost-Equal-To 150%) exist at the RF frequency and its harmonics. The more mobile electrons can easily respond to RF-timescale gradients in the plasma potential whereas the inertially constrained ions cannot, leading to an initial flux imbalance and formation of a self-bias voltage between the source and expansion chambers. In the capacitive mode, the ion acceleration is not well described by an ambipolar relation, while in the inductive and helicon modes the ion acceleration more closely follows an ambipolar relation. The scaling of the potential gradient with the argon flow rate and RF power are investigated, with the largest potential gradients observed for the lowest flow rates in the capacitive mode. The magnitude of the self-bias voltage agrees with that predicted for RF self-bias at a wall. Rapid fluctuations in the plasma potential result in a time-dependent axial electron flux that acts to 'neutralize' the accelerated ion population

  15. Real-Time, Label-Free, All-Electrical Detection of Salmonella typhimurium Using Lead Zirconate Titanate/Gold-Coated Glass Cantilevers at any Relative Humidity

    PubMed Central

    Zhu, Qing; Shih, Wan Y.; Shih, Wei-Heng

    2007-01-01

    We have examined non-insulated PZT/gold-coated glass cantilevers for real-time, label-free detection of Salmonella t. by partial dipping at any relative humidity. The PZT/gold-coated glass cantilevers were consisted of a 0.127 mm thick PZT layer about 0.8 mm long, 2 mm wide bonded to a 0.15 mm thick gold-coated glass layer with a 3.0 mm long gold-coated glass tip for detection. We showed that by placing the water level at the nodal point, about 0.8 mm from the free end of the gold-glass tip, there was a 1-hr window in which the resonance frequency was stable despite the water level change by evaporation at 20% relative humidity or higher. By dipping the cantilevers to their nodal point, we were able to do real-time, label-free detection without background resonance frequency corrections at any relative humidity. The partially dipped PZT/gold-coated glass cantilever exhibited mass detection sensitivity, Δm/Δf = −5×10−11g/Hz, and a detection concentration sensitivity, 5×103 cells/ml in 2 ml of liquid, which was about two orders of magnitude lower than that of a 5 MHz QCM. It was also about two orders of magnitude lower than the infection dosage and one order of magnitude lower that the detection limit of a commercial Raptor sensor. PMID:22872784

  16. Real-Time, Label-Free, All-Electrical Detection of Salmonella typhimurium Using Lead Zirconate Titanate/Gold-Coated Glass Cantilevers at any Relative Humidity.

    PubMed

    Zhu, Qing; Shih, Wan Y; Shih, Wei-Heng

    2007-08-01

    We have examined non-insulated PZT/gold-coated glass cantilevers for real-time, label-free detection of Salmonella t. by partial dipping at any relative humidity. The PZT/gold-coated glass cantilevers were consisted of a 0.127 mm thick PZT layer about 0.8 mm long, 2 mm wide bonded to a 0.15 mm thick gold-coated glass layer with a 3.0 mm long gold-coated glass tip for detection. We showed that by placing the water level at the nodal point, about 0.8 mm from the free end of the gold-glass tip, there was a 1-hr window in which the resonance frequency was stable despite the water level change by evaporation at 20% relative humidity or higher. By dipping the cantilevers to their nodal point, we were able to do real-time, label-free detection without background resonance frequency corrections at any relative humidity. The partially dipped PZT/gold-coated glass cantilever exhibited mass detection sensitivity, Δm/Δf = -5×10(-11)g/Hz, and a detection concentration sensitivity, 5×10(3) cells/ml in 2 ml of liquid, which was about two orders of magnitude lower than that of a 5 MHz QCM. It was also about two orders of magnitude lower than the infection dosage and one order of magnitude lower that the detection limit of a commercial Raptor sensor.

  17. Identifying the sources and timing of ancient and medieval atmospheric lead pollution in England using a peat profile from Lindow bog, Manchester.

    PubMed

    Le Roux, Gaël; Weiss, Dominik; Grattan, John; Givelet, Nicolas; Krachler, Michael; Cheburkin, Andriy; Rausch, Nicole; Kober, Bernd; Shotyk, William

    2004-05-01

    A peat core from Lindow bog near Manchester, England, was precisely cut into 2 cm slices to provide a high-resolution reconstruction of atmospheric Pb deposition. Radiocarbon and (210)Pb age dates show that the peat core represents the period ca. 2000 BC to AD 1800. Eleven radiocarbon age dates of bulk peat samples reveal a linear age-depth relationship with an average temporal resolution of 18.5 years per cm, or 37 years per sample. Using the Pb/Ti ratio to calculate the rates of anthropogenic, atmospheric Pb deposition, the profile reveals Pb contamination first appearing in peat samples dating from ca. 900 BC which clearly pre-date Roman mining activities. Using TIMS, MC-ICP-MS, and SF-ICP-MS to measure the isotopic composition of Pb, the (208)Pb/(206)Pb and (206)Pb/(207)Pb data indicate that English ores were the predominant sources during the pre-Roman, Roman, and Medieval Periods. The study shows that detailed studies of peat profiles from ombrotrophic bogs, using appropriate preparatory and analytical methods, can provide new insight into the timing, intensity, and predominant sources of atmospheric Pb contamination, even in samples dating from ancient times.

  18. Identifying the sources and timing of ancient and medieval atmospheric lead pollution in England using a peat profile from Lindow bog, Manchester.

    PubMed

    Le Roux, Gaël; Weiss, Dominik; Grattan, John; Givelet, Nicolas; Krachler, Michael; Cheburkin, Andriy; Rausch, Nicole; Kober, Bernd; Shotyk, William

    2004-05-01

    A peat core from Lindow bog near Manchester, England, was precisely cut into 2 cm slices to provide a high-resolution reconstruction of atmospheric Pb deposition. Radiocarbon and (210)Pb age dates show that the peat core represents the period ca. 2000 BC to AD 1800. Eleven radiocarbon age dates of bulk peat samples reveal a linear age-depth relationship with an average temporal resolution of 18.5 years per cm, or 37 years per sample. Using the Pb/Ti ratio to calculate the rates of anthropogenic, atmospheric Pb deposition, the profile reveals Pb contamination first appearing in peat samples dating from ca. 900 BC which clearly pre-date Roman mining activities. Using TIMS, MC-ICP-MS, and SF-ICP-MS to measure the isotopic composition of Pb, the (208)Pb/(206)Pb and (206)Pb/(207)Pb data indicate that English ores were the predominant sources during the pre-Roman, Roman, and Medieval Periods. The study shows that detailed studies of peat profiles from ombrotrophic bogs, using appropriate preparatory and analytical methods, can provide new insight into the timing, intensity, and predominant sources of atmospheric Pb contamination, even in samples dating from ancient times. PMID:15152320

  19. The mixed impact of medical school on medical students’ implicit and explicit weight bias

    PubMed Central

    Puhl, Rebecca M.; Burke, Sara E.; Hardeman, Rachel; Dovidio, John F.; Nelson, David B.; Przedworski, Julia; Burgess, Diana J.; Perry, Sylvia; Yeazel, Mark W.; van Ryn, Michelle

    2016-01-01

    Background Healthcare trainees demonstrate implicit (automatic, unconscious) and explicit (conscious) bias against people from stigmatized and marginalized social groups, which can negatively influence communication and decision-making. Medical schools are well positioned to intervene and reduce bias in new physicians. Objective To assess medical school factors that influence change in implicit and explicit bias against individuals from one stigmatized group, people with obesity. Design Prospective cohort study of medical students enrolled at 49 US medical schools randomly selected from all US medical schools within strata of public/private schools and region. Participants 1,795 medical students surveyed at the beginning of their 1st year and end of their 4th year. Measurement Web-based surveys included measures of weight bias, and medical school experiences and climate. We compared bias change to changes in the general public over the same time period. We used linear mixed models to assess the impact of curriculum, contact with people who have obesity, and faculty role-modeling on weight bias change. Results Increased implicit and explicit biases were associated with less positive contact with patients who have obesity and more exposure to faculty role-modeling of discriminatory behavior or negative comments about patients with obesity. Increased implicit bias was associated with training in how to deal with difficult patients. On average, implicit weight bias decreased and explicit bias increased during medical school, over a period of time where implicit weight bias in the general public increased and explicit bias remained stable. Conclusion Medical schools may reduce students’ weight biases by increasing positive contact between students and patients with obesity, eliminating unprofessional role-modeling by faculty and residents, and altering curricula focused on treating difficult patients. PMID:26383070

  20. Uncertainty and bias in contrast concentration measurements using spoiled gradient echo pulse sequences.

    PubMed

    Schabel, Matthias C; Parker, Dennis L

    2008-05-01

    Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a widely used technique for assessing tissue physiology. Spoiled gradient echo (SPGR) pulse sequences are one of the most common methods for acquisition of DCE-MRI data, providing high temporal and spatial resolution with strong T(1)-weighting. Conversion of SPGR signal to concentration is briefly reviewed, and a new closed-form expression for concentration measurement uncertainty for finite signal-to-noise ratio (SNR) and baseline scan time is derived. This result is applicable to arbitrary concentration-dependent relaxation rate and is valid over the same domain as the theoretical SPGR signal equation. Expressions for the lower and upper bounds on measurable concentration are also derived. The existence of a concentration- and tissue-dependent optimal flip angle that minimizes concentration uncertainty is demonstrated and it is shown that, for clinically relevant pulse sequence parameters, this optimal flip angle is significantly larger than the corresponding Ernst angle. Analysis of three pulse sequences from the DCE-MRI literature shows that optimization of flip angle using the methods discussed here leads to potential improvements of 10-1166% in effective SNR over the 0.5-5.0 mM concentration range with minimal or no loss of measurement accuracy down to 0.1 mM. In vivo data from three study patients provide further support for our theoretical expression for concentration measurement uncertainty, with predicted and experimental estimates agreeing to within +/- 30%. Equations for concentration bias resulting from biases in flip angle and from pre-contrast relaxation time and contrast relaxivity (both longitudinal and transverse) are also derived in closed-form. The resulting equations show the potential for significant contributions to bias in concentration measurement arising from even relatively small mis-specification of flip angle and/or pre-contrast longitudinal relaxation time, particularly