WorldWideScience

Sample records for term time variability

  1. Sort Term Time-Variability of Galactic High Energy Gamma-Ray Sources

    Science.gov (United States)

    Bertsch, D. L.; Hunter, S. D.; Thompson, D. J.; Bloom, S. D.; Wallace, P. M.

    1997-12-01

    Studies of the EGRET high-energy galactic gamma-ray sources have been undertaken in order to examine the possibility of other classes besides the established pulsars. The question is whether the time variability of unidentified sources is characteristically different from that of the pulsars. A secondary issue is that if there is a separate class, what is the nature of the sources and their emission mechanisms? At least one object of a distinctly different class has been established with the gamma-ray source 2CG 135+01, believed to be associated with the radio flaring Be star system LSI 61 303. Another candidate class is AGN, over 50 of which have been seen in gamma-rays and which are known to be variable in gamma rays on a timescale of days and longer. In the absence of better spatial resolution time variability is a key in making additional identifications and classifications. To do this, flux histories have been studied down to one-day timescales. The results are compared with those of the known classes.

  2. Long commuting time, extensive overtime, and sympathodominant state assessed in terms of short-term heart rate variability among male white-collar workers in the Tokyo megalopolis.

    Science.gov (United States)

    Kageyama, T; Nishikido, N; Kobayashi, T; Kurokawa, Y; Kaneko, T; Kabuto, M

    1998-07-01

    To investigate the possible effects of long commuting time and extensive overtime on daytime cardiac autonomic activity, the short-term heart rate variability (HRV) both at supine rest and at standing rest of 223 male white-collar workers in the Tokyo Megalopolis was examined. Workers with a one-way commute of 90 min or more exhibited decreased vagal activity at supine rest and increased sympathetic activity regardless of posture, and those doing overtime of 60 h/month or more exhibited decreased vagal activity and increased sympathetic activity at standing rest. These findings suggest that chronic stress or fatigue resulting from long commuting time or extensive overtime caused these individuals to be in a sympathodominant state. Although these shifts in autonomic activities are not direct indicators of disease, it can be hypothesized that they can induce cardiovascular abnormalities or dysfunctions related to the onset of heart disease. Assessment of the daily and weekly variations in HRV as a function of daily life activities (such as working, commuting, sleeping, and exercising) among workers in Asia-Pacific urban areas might be one way of studying the possible effects of long commuting time, and extensive overtime, on health.

  3. Variable camshaft timing system

    Energy Technology Data Exchange (ETDEWEB)

    Butterfield, R.P.; Smith, F.R.

    1989-09-05

    This patent describes an improvement in a variable camshaft timing system for an internal combustion engine having intake and exhaust valves and a camshaft for each of the intake and exhaust valves, an intake sprocket and an exhaust sprocket keyed to their respective camshaft, only one of the camshafts being directly driven by an engine crankshaft, and a timing chain engaging both sprockets. The improvement comprising a single bracket carrying at least one idler sprocket engaging the timing chain, the bracket being mounted for movement to alter the timing relationship between the intake and exhaust sprockets.

  4. Long Term Time Variability of Cosmic Rays and Possible Relevance to the Development of Life on Earth

    Science.gov (United States)

    Erlykin, A. D.; Wolfendale, A. W.

    2010-07-01

    An analysis is made of the manner in which the cosmic ray intensity at Earth has varied over its existence and its possible relevance to both the origin and the evolution of life. Much of the analysis relates to the `high energy’ cosmic rays ( E > 1014 eV; =0.1 PeV) and their variability due to the changing proximity of the solar system to supernova remnants which are generally believed to be responsible for most cosmic rays up to PeV energies. It is pointed out that, on a statistical basis, there will have been considerable variations in the likely 100 My between the Earth’s biosphere reaching reasonable stability and the onset of very elementary life. Interestingly, there is the increasingly strong possibility that PeV cosmic rays are responsible for the initiation of terrestrial lightning strokes and the possibility arises of considerable increases in the frequency of lightnings and thereby the formation of some of the complex molecules which are the `building blocks of life’. Attention is also given to the well known generation of the oxides of nitrogen by lightning strokes which are poisonous to animal life but helpful to plant growth; here, too, the violent swings of cosmic ray intensities may have had relevance to evolutionary changes. A particular variant of the cosmic ray acceleration model, put forward by us, predicts an increase in lightning rate in the past and this has been sought in Korean historical records. Finally, the time dependence of the overall cosmic ray intensity, which manifests itself mainly at sub-10 GeV energies, has been examined. The relevance of cosmic rays to the `global electrical circuit’ points to the importance of this concept.

  5. Distinguishing Inter-annual Phenological Variability from Long-term Change in the Great Basin Using a new Method of Time-Series Modeling

    Science.gov (United States)

    Bradley, B.; Jacob, R.; Hermance, J.; Mustard, J.

    2004-12-01

    Semi-arid vegetation communities are affected over time by a host of factors, including climate change, inter-annual climate variability, changes in hydrologic cycle, and land use-land cover change. Because vegetation exhibits inter-annual variability, it is important to determine characteristic inter-annual responses of semi-arid vegetation communities to distinguish variability from change. We explore the phenologies of five major ecosystem types located in central and northern Nevada: dry desert shrub, sagebrush steppe, annual grassland, pinyon-juniper woodland, and montane perennial grassland. By identifying the phenological characteristics of these major Great Basin land cover classes, we constrain the range of expected inter-annual and decadal variability. Time series of known vegetation types are analyzed by applying a new methodology to characterize inter-annual vegetation phenology using time series of 1 km Normalized Difference Vegetation Index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR) from 1990-2001. We characterize vegetation community response on both inter-annual and decadal time scales using a curve-fit algorithm that is flexible enough to address change over time without being influenced by error caused by sensor drift, clouds, snow, or missing data. Our methodology uses least mean squares to fit weekly and biweekly NDVI data simultaneously to a low-order baseline polynomial, which models both long-term change and mean inter-annual periodicity, and a high order annual polynomial, which allows for flexible phenologies between years. Long-term sensor drift is accounted for by removing a fit to mean NDVI from non-vegetated surfaces salt flats in Nevada and Utah prior to analysis. Anomalously low data caused by clouds or snow are removed by identifying the standard deviation of the curve-fit during the stable fall months and removing all points within one standard deviation of zero (all negative values are also excluded). Missing

  6. Long term time variability of cosmic rays and possible relevance to the development of life on Earth

    OpenAIRE

    Erlykin, A. D.; Wolfendale, A. W.

    2010-01-01

    An analysis is made of the manner in which the cosmic ray intensity at Earth has varied over its existence and its possible relevance to both the origin and the evolution of life. Much of the analysis relates to the 'high energy' cosmic rays ($E>10^{14}eV;=0.1PeV$) and their variability due to the changing proximity of the solar system to supernova remnants which are generally believed to be responsible for most cosmic rays up to PeV energies. It is pointed out that, on a statistical basis, t...

  7. Examination of the Relation between Academic Procrastination and Time Management Skills of Undergraduate Students in Terms of Some Variables

    Science.gov (United States)

    Ocak, Gürbüz; Boyraz, Serkan

    2016-01-01

    Academic procrastination is seen to be quite common among undergraduates and time management is thought to be one of the possible reasons of it. Two surveys, academic procrastination and time management, were given to 332 undergraduate students in this correlational research. Students' academic procrastination is explained through frequencies and…

  8. Magnetized String Cosmology in Anisotropic Bianchi-II Space-time with Variable Cosmological Term

    Science.gov (United States)

    Jotania, Kanti; Yadav, Padminin; Faruqi, S. A.

    2011-05-01

    The present study deals with a spatially homogeneous and anisotropic Bianchi-II cosmological models representing massive strings by applying the variation law for generalized Hubble's parameter that yields a constant value of deceleration parameter. We find that the constant value of deceleration parameter is reasonable for the present day universe. The variation law for Hubble's parameter generates two types of solutions for the average scale factor, one is of power-law type and other is of the exponential form. Using these two forms, Einstein's field equations are solved separately that correspond to expanding singular and non-singular models of the universe respectively. The energy-momentum tensor for such string as formulated by Letelier (Phys. Rev. D 28:2414, 1983) is used to construct massive string cosmological models for which we assume that the expansion ( θ) in the model is proportional to the component σ11 of the shear tensor σji. This condition leads to A=( BC) m , where A, B and C are the metric coefficients and m is proportionality constant. Our models are in accelerating phase which is consistent to the recent observations. The cosmological constant Λ is found to be a decreasing function of time and it approaches a small positive value at present epoch which is in good agreement by the results from recent supernovae observations. Some physical and geometric behaviour of the models are also discussed.

  9. Time as a dynamical variable

    Science.gov (United States)

    Thron, Christopher

    2017-01-01

    Since the time of Galileo, the equations of physics have expressed dynamical variables such as particle position or electromagnetic field strength as functions of time. In this paper, we argue that this assumption reflects observational bias, and that there are many good reasons for viewing time also as a dynamical variable. We hypothesize that the spacetime universe is an outcome of a process, rather than a process unfolding in time. This new viewpoint gives rise to a physical interpretation of the wavefunction as a complex vibrational amplitude in a non-spacetime independent variable. It resolves quantum mechanical paradoxes involving wavefunction entanglement, and gives a much simpler solution to the problem of wavefunction collapse than the many-worlds interpretation. The Born rule is also shown to be a natural consequence. We also show that small deviations from conventional quantum probabilities are predicted.

  10. Additive measures of travel time variability

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2011-01-01

    This paper derives a measure of travel time variability for travellers equipped with scheduling preferences defined in terms of time-varying utility rates, and who choose departure time optimally. The corresponding value of travel time variability is a constant that depends only on preference...... parameters. The measure is unique in being additive with respect to independent parts of a trip. It has the variance of travel time as a special case. Extension is provided to the case of travellers who use a scheduled service with fixed headway....

  11. The CARIACO Ocean Time-Series: two decades of oceanographic observations to understand linkages between biogeochemistry, ecology, and long-term environmental variability.

    Science.gov (United States)

    Lorenzoni, L.; Muller-Karger, F. E.; Rueda-Roa, D. T.; Thunell, R.; Scranton, M. I.; Taylor, G. T.; benitez-Nelson, C. R.; Montes, E.; Astor, Y. M.; Rojas, J.

    2016-02-01

    The CARIACO Ocean Time-Series project, located in the Cariaco Basin off the coast of Venezuela, seeks to understand relationships between hydrography, primary production, community composition, microbial activity, particle fluxes, and element cycling in the water column, and how variations in these processes are preserved in sediments accumulating in this anoxic basin. CARIACO uses autonomous and shipboard measurements to understand ecological and biogeochemical changes and how these relate to regional and global climatic/ocean variability. CARIACO is a model for national ocean observing programs in Central/South America, and has been developed as a community facility platform with open access to all data (http://imars.marine.usf.edu/cariaco). Research resulting from this program has contributed to knowledge about the decomposition and cycling of particles, the biological pump, and to our understanding of the ecology and oceanography of oxygen minimum zones. Despite this basin being anoxic below 250m, remineralization rates of organic matter are comparable to those in well oxygenated waters. A dynamic microbial community significantly influences carbon and nutrient biogeochemical cycling throughout the water column. Since 1995, declining particulate organic carbon fluxes have been measured throughout the water column using sediment traps, likely in response to declining Chl-a concentrations and smaller phytoplankton which have replaced the larger taxa over the past decade. This community shift appears to be caused by regional changes in the physical regime. CARIACO also recorded marked long-term changes in surface and deep DIC in response to a combination of factors including surface water warming. The observations of CARIACO highlight the importance of a sustained, holistic approach to studying biodiversity, ecology and the marine carbon cycle to predict potential impacts of climate change on the ocean's ecosystem services and carbon sequestration efficiency.

  12. Climate-driven variability in lake and wetland distribution across the Prairie Pothole Region: From modern observations to long-term reconstructions with space-for-time substitution

    Science.gov (United States)

    Liu, Ganming; Schwartz, Franklin W.

    2012-08-01

    This study was designed (1) to explore the links between climate variability and the population dynamics of closed-basin surface water bodies of the Prairie Pothole Region (PPR) in North America, and (2) to test the validity of space-for-time (SFT) substitution approach for the analysis of hydrologic systems. Observational results from 1981 to 2000 show that the climate with respect to annual residual moisture (ɛ, i.e., precipitation minus potential evaporation or evapotranspiration) of the PPR changed across space (over 0.6 m) and time (over 0.3 m in central North Dakota), causing spatiotemporal variability in water areas and water body numbers. Spatial analysis of a suite of surface water complexes along a spatial ɛ gradient in the Missouri Coteau shows that a four parameter Boltzmann function quantitatively describes how the number of water bodies (N) varied as a function of 5-year average annualɛ (R2 = 0.76). Temporal analysis of monthly N data (1931-2005) reconstructed by a hydrologic model also demonstrates that values of temporally varying N were highly correlated with ɛand yielded a nearly identical Boltzmann function. This result confirms the validity of SFT substitution and suggests that detailed modern spatial data can be used to interpret hydrologic system behaviors under past or future climate conditions. This study also has important regional-scale implications for water resources management by providing a complete picture of the spatiotemporal water body distribution across the entire PPR and the potential for rapidly converting climate predictions into surface water assessments.

  13. Short-term and long-term variability of standard deviation scores for size in children.

    Science.gov (United States)

    Sheehy, A; Gasser, T; Largo, R; Molinari, L

    2002-01-01

    To quantify long-term and short-term variability in the standard deviation scores (SDS's) for six skeletal size variables and body mass index (BMI) in children and to compare average values of these quantities for boys with those of girls and to make comparisons across variables. The analysis is based on measurements made regularly for 120 boys and 112 girls from 1 month until 20 years for seven variables (standing height, sitting height, leg height, arm length, biiliac width, bihumeral width and BMI) as part of the first Zurich longitudinal growth study. Variation in these scores due to variablity in the timing of the pubertal spurt (PS) is separated out by rescaling the age axis on an individual basis and comparing children with the same developmental age rather than the same chronological age. For a given child, the relationship between the value of its SDS and age is modelled as the sum of an arbitrary (child dependent) smooth function plus an error term. The long-term variability for that child is defined to be the mean square of the departures of this smooth function from its mean level while the short-term variability is defined to be the variance of the error term. Girls' SDS scores have significantly more long-term variability than those of boys, while there is no significant difference between the sexes for short-term variability. Bihumeral width, BMI and sitting height have significantly more long-term variation than the other variables. Bihumeral width and BMI have the largest short-term variability and standing height has the smallest. Correlations between long-term variability and adult size and timing and intensity of the PS were small. A useful way of assessing long-term and short-term variability of SDS's, which is widely applicable has been described and applied to data relating to the growth of children. The results of this analysis are intriguing. Why is the underlying growth process of girls more variable than that of boys? Differences across

  14. Large scale variability, long-term trends and extreme events in total ozone over the northern mid-latitudes based on satellite time series

    Science.gov (United States)

    Rieder, H. E.; Staehelin, J.; Maeder, J. A.; Ribatet, M.; Davison, A. C.

    2009-04-01

    Various generations of satellites (e.g. TOMS, GOME, OMI) made spatial datasets of column ozone available to the scientific community. This study has a special focus on column ozone over the northern mid-latitudes. Tools from geostatistics and extreme value theory are applied to analyze variability, long-term trends and frequency distributions of extreme events in total ozone. In a recent case study (Rieder et al., 2009) new tools from extreme value theory (Coles, 2001; Ribatet, 2007) have been applied to the world's longest total ozone record from Arosa, Switzerland (e.g. Staehelin 1998a,b), in order to describe extreme events in low and high total ozone. Within the current study this analysis is extended to satellite datasets for the northern mid-latitudes. Further special emphasis is given on patterns and spatial correlations and the influence of changes in atmospheric dynamics (e.g. tropospheric and lower stratospheric pressure systems) on column ozone. References: Coles, S.: An Introduction to Statistical Modeling of Extreme Values, Springer Series in Statistics, ISBN:1852334592, Springer, Berlin, 2001. Ribatet, M.: POT: Modelling peaks over a threshold, R News, 7, 34-36, 2007. Rieder, H.E., Staehelin, J., Maeder, J.A., Ribatet, M., Stübi, R., Weihs, P., Holawe, F., Peter, T., and Davison, A.C.: From ozone mini holes and mini highs towards extreme value theory: New insights from extreme events and non stationarity, submitted to J. Geophys. Res., 2009. Staehelin, J., Kegel, R., and Harris, N. R.: Trend analysis of the homogenized total ozone series of Arosa (Switzerland), 1929-1996, J. Geophys. Res., 103(D7), 8389-8400, doi:10.1029/97JD03650, 1998a. Staehelin, J., Renaud, A., Bader, J., McPeters, R., Viatte, P., Hoegger, B., Bugnion, V., Giroud, M., and Schill, H.: Total ozone series at Arosa (Switzerland): Homogenization and data comparison, J. Geophys. Res., 103(D5), 5827-5842, doi:10.1029/97JD02402, 1998b.

  15. Short-Term Variability in Enceladus' Plume

    Science.gov (United States)

    Spitale, Joseph N.; Hurford, Terry; Rhoden, Alyssa R.

    2017-10-01

    The density of solids in Enceladus' south-polar plume at altitudes above about 50 km has been observed to vary by a factor of three between Enceladus' periapse and apoapse. This variability of the combined plume on the orbital time scale supports a relation between tidal stress and combined eruptive activity, and contains information about how the fractures fail in an averaged sense, but local variability is still not understood.Here we report on a sequence of three Cassini images showing a single collimated jet transitioning from dormant to active during a period of a few minutes. In the first image, the jet is not visible; in the subsequent images, it is seen increasing to heights of order 100 km. Prior estimates of particle velocities have been based on observing the vertical brightness profiles of steady-state eruptions. The non-steady-state jet observations discussed here provide a different way of measuring velocities, as the rate of change in density at each altitude can be estimated (using appropriate photometric assumptions). Moreover, the timing and location of the eruption contain information about the failure mechanism leading to an eruption at this particular time and place.Other jets may also be observed activating at this time, but the detections are less certain.

  16. Long-term Periodicities of Cataclysmic Variables with Synoptic Surveys

    Science.gov (United States)

    Yang, Michael Ting-Chang; Chou, Yi; Ngeow, Chow-Choong; Hu, Chin-Ping; Su, Yi-Hao; Prince, Thomas A.; Kulkarni, Shrinivas R.; Levitan, David; Laher, Russ; Surace, Jason; Drake, Andrew J.; Djorgovski, Stanislav G.; Mahabal, Ashish A.; Graham, Matthew J.; Donalek, Ciro

    2017-09-01

    A systematic study on the long-term periodicities of known Galactic cataclysmic variables (CVs) was conducted. Among 1580 known CVs, 344 sources were matched and extracted from the Palomar Transient Factory (PTF) data repository. The PTF light curves were combined with the Catalina Real-Time Transient Survey (CRTS) light curves and analyzed. Ten targets were found to exhibit long-term periodic variability, which is not frequently observed in the CV systems. These long-term variations are possibly caused by various mechanisms, such as the precession of the accretion disk, hierarchical triple star system, magnetic field change of the companion star, and other possible mechanisms. We discuss the possible mechanisms in this study. If the long-term period is less than several tens of days, the disk precession period scenario is favored. However, the hierarchical triple star system or the variations in magnetic field strengths are most likely the predominant mechanisms for longer periods.

  17. Travel time variability and rational inattention

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Jiang, Gege

    2017-01-01

    This paper sets up a rational inattention model for the choice of departure time for a traveler facing random travel time. The traveler chooses how much information to acquire about the travel time out-come before choosing departure time. This reduces the cost of travel time variability compared...

  18. Evolution of Long Term Variability in Solar Analogs

    Science.gov (United States)

    Egeland, Ricky; Soon, Willie; Baliunas, Sallie; Hall, Jeffrey C.; Henry, Gregory W.

    2017-10-01

    Earth is the only planet known to harbor life, therefore we may speculate on how the nature of the Sun-Earth interaction is relevant to life on Earth, and how the behavior of other stars may influence the development of life on their planetary systems. We study the long-term variability of a sample of five solar analog stars using composite chromospheric activity records up to 50 years in length and synoptic visible-band photometry about 20 years long. This sample covers a large range of stellar ages which we use to represent the evolution in activity for solar mass stars. We find that young, fast rotators have an amplitude of variability many times that of the solar cycle, while old, slow rotators have very little variability. We discuss the possible impacts of this variability on young Earth and exoplanet climates.

  19. The cost of travel time variability

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2016-01-01

    This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...

  20. Travel time variability and airport accessibility

    NARCIS (Netherlands)

    Koster, P.R.; Kroes, E.P.; Verhoef, E.T.

    2011-01-01

    We analyze the cost of access travel time variability for air travelers. Reliable access to airports is important since the cost of missing a flight is likely to be high. First, the determinants of the preferred arrival times at airports are analyzed. Second, the willingness to pay (WTP) for

  1. Local short-term variability in solar irradiance

    Directory of Open Access Journals (Sweden)

    G. M. Lohmann

    2016-05-01

    Full Text Available Characterizing spatiotemporal irradiance variability is important for the successful grid integration of increasing numbers of photovoltaic (PV power systems. Using 1 Hz data recorded by as many as 99 pyranometers during the HD(CP2 Observational Prototype Experiment (HOPE, we analyze field variability of clear-sky index k* (i.e., irradiance normalized to clear-sky conditions and sub-minute k* increments (i.e., changes over specified intervals of time for distances between tens of meters and about 10 km. By means of a simple classification scheme based on k* statistics, we identify overcast, clear, and mixed sky conditions, and demonstrate that the last of these is the most potentially problematic in terms of short-term PV power fluctuations. Under mixed conditions, the probability of relatively strong k* increments of ±0.5 is approximately twice as high compared to increment statistics computed without conditioning by sky type. Additionally, spatial autocorrelation structures of k* increment fields differ considerably between sky types. While the profiles for overcast and clear skies mostly resemble the predictions of a simple model published by Hoff and Perez (2012, this is not the case for mixed conditions. As a proxy for the smoothing effects of distributed PV, we finally show that spatial averaging mitigates variability in k* less effectively than variability in k* increments, for a spatial sensor density of 2 km−2.

  2. Ubiquitous time variability of integrated stellar populations

    Science.gov (United States)

    Conroy, Charlie; van Dokkum, Pieter G.; Choi, Jieun

    2015-11-01

    Long-period variable stars arise in the final stages of the asymptotic giant branch phase of stellar evolution. They have periods of up to about 1,000 days and amplitudes that can exceed a factor of three in the I-band flux. These stars pulsate predominantly in their fundamental mode, which is a function of mass and radius, and so the pulsation periods are sensitive to the age of the underlying stellar population. The overall number of long-period variables in a population is directly related to their lifetimes, which is difficult to predict from first principles because of uncertainties associated with stellar mass-loss and convective mixing. The time variability of these stars has not previously been taken into account when modelling the spectral energy distributions of galaxies. Here we construct time-dependent stellar population models that include the effects of long-period variable stars, and report the ubiquitous detection of this expected ‘pixel shimmer’ in the massive metal-rich galaxy M87. The pixel light curves display a variety of behaviours. The observed variation of 0.1 to 1 per cent is very well matched to the predictions of our models. The data provide a strong constraint on the properties of variable stars in an old and metal-rich stellar population, and we infer that the lifetime of long-period variables in M87 is shorter by approximately 30 per cent compared to predictions from the latest stellar evolution models.

  3. Short-term optical variability of high-redshift QSO's

    OpenAIRE

    Bachev, R.; Strigachev, A.; Semkov, E.

    2004-01-01

    This paper presents results of a search for short-term variability in the optical band of selected high-luminosity, high-redshift radio-quiet quasars. Each quasar has been monitored typically for 2 - 4 hours with a time resolution of 2 - 5 minutes and a photometric accuracy of about 0.01 - 0.02 mag. Due to the significant redshift (z>2), the covered wavelength range falls into the UV region (typically 1500 - 2500A). We found no statistical evidence for any continuum variations larger than 0.0...

  4. Nonflat time-variable dark energy cosmology

    Science.gov (United States)

    Pavlov, Anatoly; Westmoreland, Shawn; Saaidi, Khaled; Ratra, Bharat

    2013-12-01

    We generalize the time-variable dark energy scalar field Φ model (ΦCDM) to nonflat space. We show that even in the space-curvature-dominated epoch the scalar field solution is a time-dependent fixed point or attractor, with scalar field energy density that grows relative to the energy density in spatial curvature. This is the first example of a physically consistent and complete model of dynamical dark energy in a nonflat geometry.

  5. Long-term X-ray Variability of NGC 4945

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Amara; /UC, Davis /SLAC

    2007-08-29

    Though short-term X-ray variability has been studied for the active galaxy NGC 4945, long-term studies promise to contribute to our understanding of the processes involved in accretion onto supermassive black holes. In order to understand the relationship between black hole mass and breaks in the power spectral density (PSD), the long-term X-ray variability of NGC 4945 was studied over the energy range 8-30 keV. Observations occurred over the year 2006 using the Rossi X-ray Timing Explorer. The data was reduced using the package FTOOLS, most notably the scripts Rex and faxbary. Light curves were produced and a PSD was obtained using a Fast Fourier Transform algorithm. Preliminary studies of the light curve show greater X-ray variability at higher frequencies. This result complements previous studies of NGC 4945 by Martin Mueller. However, the PSD produced must go through further study before accurate results can be obtained. A way to account for the window function of the PSD must be found before the behavior at lower frequencies can be studied with accuracy and the relationship between black hole mass and the break in NGC 4945's PSD can be better understood. Further work includes exploration into ways to subtract the window function from the PSD, as well as a closer analysis of the PSD produced by averaging the data into logarithmic bins. The possibility of a better way to bin the data should be considered so that the window function would be minimized.

  6. Long-Term Variability of Surface Albedo and Its Correlation with Climatic Variables over Antarctica

    Directory of Open Access Journals (Sweden)

    Minji Seo

    2016-11-01

    Full Text Available The cryosphere is an essential part of the earth system for understanding climate change. Components of the cryosphere, such as ice sheets and sea ice, are generally decreasing over time. However, previous studies have indicated differing trends between the Antarctic and the Arctic. The South Pole also shows internal differences in trends. These phenomena indicate the importance of continuous observation of the Polar Regions. Albedo is a main indicator for analyzing Antarctic climate change and is an important variable with regard to the radiation budget because it can provide positive feedback on polar warming and is related to net radiation and atmospheric heating in the mainly snow- and ice-covered Antarctic. Therefore, in this study, we analyzed long-term temporal and spatial variability of albedo and investigated the interrelationships between albedo and climatic variables over Antarctica. We used broadband surface albedo data from the Satellite Application Facility on Climate Monitoring and data for several climatic variables such as temperature and Antarctic oscillation index (AAO during the period of 1983 to 2009. Time series analysis and correlation analysis were performed through linear regression using albedo and climatic variables. The results of this research indicated that albedo shows two trends, west trend and an east trend, over Antarctica. Most of the western side of Antarctica showed a negative trend of albedo (about −0.0007 to −0.0015 year−1, but the other side showed a positive trend (about 0.0006 year−1. In addition, albedo and surface temperature had a negative correlation, but this relationship was weaker in west Antarctica than in east Antarctica. The correlation between albedo and AAO revealed different relationships in the two regions; west Antarctica had a negative correlation and east Antarctica showed a positive correlation. In addition, the correlation between albedo and AAO was weaker in the west. This

  7. A Polynomial Term Structure Model with Macroeconomic Variables

    Directory of Open Access Journals (Sweden)

    José Valentim Vicente

    2007-06-01

    Full Text Available Recently, a myriad of factor models including macroeconomic variables have been proposed to analyze the yield curve. We present an alternative factor model where term structure movements are captured by Legendre polynomials mimicking the statistical factor movements identified by Litterman e Scheinkmam (1991. We estimate the model with Brazilian Foreign Exchange Coupon data, adopting a Kalman filter, under two versions: the first uses only latent factors and the second includes macroeconomic variables. We study its ability to predict out-of-sample term structure movements, when compared to a random walk. We also discuss results on the impulse response function of macroeconomic variables.

  8. Microlensing makes lensed quasar time delays significantly time variable

    Science.gov (United States)

    Tie, S. S.; Kochanek, C. S.

    2018-01-01

    The time delays of gravitationally lensed quasars are generally believed to be unique numbers whose measurement is limited only by the quality of the light curves and the models for the contaminating contribution of gravitational microlensing to the light curves. This belief is incorrect - gravitational microlensing also produces changes in the actual time delays on the ∼day(s) light-crossing time-scale of the emission region. This is due to a combination of the inclination of the disc relative to the line of sight and the differential magnification of the temperature fluctuations producing the variability. We demonstrate this both mathematically and with direct calculations using microlensing magnification patterns. Measuring these delay fluctuations can provide a physical scale for microlensing observations, removing the need for priors on either the microlens masses or the component velocities. That time delays in lensed quasars are themselves time variable likely explains why repeated delay measurements of individual lensed quasars appear to vary by more than their estimated uncertainties. This effect is also a new important systematic problem for attempts to use time delays in lensed quasars for cosmology or to detect substructures (satellites) in lens galaxies.

  9. Understanding Storm Time Poynting Flux Variability

    Science.gov (United States)

    Garner, H. M.; Ober, D. M.; Wilson, G. R.

    2012-12-01

    It is known that energy deposited by dayside Earth-directed Poynting flux (S||) is greater during geomagnetic storms; however, S|| spatial and temporal variability are less well understood. Eight years (2000-2008) of data from the WDC for Geomagnetism, Kyoto, were collected to identify thirteen large and five super storms according to specific criteria: "classic" storm structure in which the time interval between sudden storm commencement (SSC) and minimum Dst (Dstmin) was ≤ 24 hours; the main and recovery phases did not experience secondary or tertiary disturbances; large storms where Dst ≤ -93 nT; and, super storms where Dst ≤ -184 nT. Solar wind and magnetospheric data for the 18 storms were collected from the Defense Meteorological Satellite Program (DMSP F-15) and NASA OMNI. For all storms, the data were averaged and plotted to identify S|| variability for the mantle, cusp, polar rain, and central and boundary layer plasma sheet regions during geomagnetic storm time. As known for all storms, while Dst decreased, average S|| peaked, as did Kp. The energy deposited per square-meter by precipitating energetic particles (electrons) did not increase, though average hemispheric power increased by nearly a factor of two for the large and super storms between SSC and Dstmin. For the large storms, average S|| from the central and boundary layer plasma sheet regions (on closed field lines) was enhanced by nearly a factor of two between SSC and Dstmin; for the super storms, enhancement was over a factor of three. Average large storm S|| enhancement from the mantle, cusp, and polar rain regions (on open field lines) was significantly more enhanced by a factor of three between SSC and Dstmin. It was enhanced by a factor of over five for the super storms. For the open field line regions, a large, prolonged secondary peak in S|| was observed for large and super storms during the recovery phase. As suggested by this and prior studies, research is needed to better

  10. Short-term versus long-term heart rate variability in ischemic cardiomyopathy risk stratification

    Directory of Open Access Journals (Sweden)

    Andreas eVoss

    2013-12-01

    Full Text Available In industrialized countries with aging populations, heart failure affects 0.3%-2% of the general population. The investigation of 24h-ECG recordings revealed the potential of nonlinear indices of heart rate variability (HRV for enhanced risk stratification in patients with ischemic heart failure (IHF. However, long-term analyses are time-consuming, expensive and delay the initial diagnosis. The objective of this study was to investigate whether 30min short-term HRV analysis is sufficient for comparable risk stratification in IHF in comparison to 24h-HRV analysis. From 256 IHF patients (221 at low risk (IHFLR and 35 at high risk (IHFHR a 24h beat-to-beat time series b the first 30min segment c the 30min most stationary day segment and d the 30min most stationary night segment were investigated. We calculated linear (time and frequency domain and nonlinear HRV analysis indices. Optimal parameter sets for risk stratification in IHF were determined for 24 hours and for each 30min segment by applying discriminant analysis on significant clinical and non-clinical indices. Long- and short-term HRV indices from frequency domain and particularly from nonlinear dynamics revealed high univariate significances (p

  11. MLTrends: Graphing MEDLINE term usage over time.

    Science.gov (United States)

    Palidwor, Gareth A; Andrade-Navarro, Miguel A

    2010-01-25

    The MEDLINE database of medical literature is routinely used by researchers and doctors to find articles pertaining to their area of interest. Insight into historical changes in research areas may be gained by chronological analysis of the 18 million records currently in the database, however such analysis is generally complex and time consuming. The authors' MLTrends web application graphs term usage in MEDLINE over time, allowing the determination of emergence dates for biomedical terms and historical variations in term usage intensity. MLTrends may be used at: http://www.ogic.ca/mltrends.

  12. Formal Variability of Terms in the Sphere of Network Technologies

    Directory of Open Access Journals (Sweden)

    Roman Viktorovich Deniko

    2015-09-01

    Full Text Available The article addresses the problem of formal variability of terms in the sphere of network terminology in the Russian language. The research is based on data from the Internet communication in the sphere of network technologies. Such formal variability types as graphical, phonemic, word building and complex (graphic and phonetic, morphologic and accentual are discussed in this article. The authors reveal the reasons for graphic variability of foreign origin terms making up the international terminological fund. These reasons cover such aspects as the use of graphics of source language and recipient language; the presence or absence of hyphenation, etc. It is determined that the phonemic variants of terms appear as a result of oral or written borrowings. The existence of such variants is also connected with the stage of their adaptation in the Russian language after borrowing. In this case the variants are related with soft or hard pronunciation of consonants. There are also some cases of phonemic variability on the graphic level. The complex variability is regarded as a part of active processes taking place in the modern Russian language, and these processes involve both native and foreign origin terms. The particular attention is paid to the word-building variants – word-building affixes the variability of which is peculiar of network technologies. The results of the research show that the variability of professional units belonging to the network technologies sublanguage is caused by the active process of borrowing of specialpurpose vocabulary into the Russian language. The process is due to the intensification of intercultural communication in the professional spheres.

  13. Quadratic time dependent Hamiltonians and separation of variables

    Science.gov (United States)

    Anzaldo-Meneses, A.

    2017-06-01

    Time dependent quantum problems defined by quadratic Hamiltonians are solved using canonical transformations. The Green's function is obtained and a comparison with the classical Hamilton-Jacobi method leads to important geometrical insights like exterior differential systems, Monge cones and time dependent Gaussian metrics. The Wei-Norman approach is applied using unitary transformations defined in terms of generators of the associated Lie groups, here the semi-direct product of the Heisenberg group and the symplectic group. A new explicit relation for the unitary transformations is given in terms of a finite product of elementary transformations. The sequential application of adequate sets of unitary transformations leads naturally to a new separation of variables method for time dependent Hamiltonians, which is shown to be related to the Inönü-Wigner contraction of Lie groups. The new method allows also a better understanding of interacting particles or coupled modes and opens an alternative way to analyze topological phases in driven systems.

  14. Viscous cosmological models with a variable cosmological term ...

    African Journals Online (AJOL)

    Einstein's field equations for a Friedmann-Lamaitre Robertson-Walker universe filled with a dissipative fluid with a variable cosmological term L described by full Israel-Stewart theory are considered. General solutions to the field equations for the flat case have been obtained. The solution corresponds to the dust free model ...

  15. Model for expressing leaf photosynthesis in terms of weather variables

    African Journals Online (AJOL)

    A theoretical mathematical model for describing photosynthesis in individual leaves in terms of weather variables is proposed. The model utilizes a series of efficiency parameters, each of which reflect the fraction of potential photosynthetic rate permitted by the different environmental elements. These parameters are useful ...

  16. Simple model for crop photosynthesis in terms of weather variables ...

    African Journals Online (AJOL)

    A theoretical mathematical model for describing crop photosynthetic rate in terms of the weather variables and crop characteristics is proposed. The model utilizes a series of efficiency parameters, each of which reflect the fraction of possible photosynthetic rate permitted by the different weather elements or crop architecture.

  17. Investigating Organizational Alienation Behavior in Terms of Some Variables

    Science.gov (United States)

    Dagli, Abidin; Averbek, Emel

    2017-01-01

    The aim of this study is to detect the perceptions of public primary school teachers regarding organizational alienation behaviors in terms of some variables (gender, marital status and seniority). Survey model was used in this study. The research sample consists of randomly selected 346 teachers from 40 schools in the central district of Mardin,…

  18. Short term climate trend and variability around Woliso, Oromia ...

    African Journals Online (AJOL)

    Based on the meteorological data of Woliso for the last decade (2004-2013), short-term climate variability was assessed. ... dry (low RC <0.6), whereas May and September received big rains with moderate concentration (rainfall coefficient =1.0-1.9) and the summer (JJA) received big rainfall with high concentration (rainfall ...

  19. Long-term spatio-temporal drought variability in Turkey

    Science.gov (United States)

    Dabanlı, İsmail; Mishra, Ashok K.; Şen, Zekai

    2017-09-01

    The spatio-temporal variability of drought is presented by evaluating homogeneously distributed 250 station records from 1931 to 2010 for 80 years' duration in Turkey. The drought analysis is implemented using Standardized Precipitation Index (SPI) in terms of SPI-1, SPI-3, SPI-6, SPI-6AS (SPI-6 April to September) and SPI-12. The principle component analysis (PCA) is applied to SPI time series to identify spatial and temporal drought patterns. SPI time series are classified into two groups (1st group: SPI-1, SPI-3, SPI-6AS; and 2nd group: SPI-6 and SPI-12) according to the similarity in spatial drought patterns. SPI-3 and SPI-12 are selected as representative members of each group for spatio-temporal analysis. A relationship among correlation area (An), correlation coefficient (CC), principle component numbers (Fn) and total variances explained (Vexp) are investigated for identifying four well-defined drought vulnerable homogeneous regions over Turkey mainland. Mean percentages of extreme, severe, and moderate drought areas are calculated as 3.13% (2.81%), 3.75% (4.06%) and 7.19% (7.50%) for SPI-3 (SPI-12) based on 80 years in all drought vulnerable regions. Spectral characteristics of drought are also investigated based on fast Fourier transform (FFT) method. It is observed that while southeastern and western parts of Turkey are more stable due to the highly-correlated variances of spatial patterns; central parts and few pockets in northern areas of Turkey are less stable regions because of the low-correlated variance scores (below 10%). Furthermore, the impact of extreme phases of the ENSO (El Nino/La Nina) on droughts in four drought regions over Turkey is discussed.

  20. Inverse Ising problem in continuous time: A latent variable approach

    Science.gov (United States)

    Donner, Christian; Opper, Manfred

    2017-12-01

    We consider the inverse Ising problem: the inference of network couplings from observed spin trajectories for a model with continuous time Glauber dynamics. By introducing two sets of auxiliary latent random variables we render the likelihood into a form which allows for simple iterative inference algorithms with analytical updates. The variables are (1) Poisson variables to linearize an exponential term which is typical for point process likelihoods and (2) Pólya-Gamma variables, which make the likelihood quadratic in the coupling parameters. Using the augmented likelihood, we derive an expectation-maximization (EM) algorithm to obtain the maximum likelihood estimate of network parameters. Using a third set of latent variables we extend the EM algorithm to sparse couplings via L1 regularization. Finally, we develop an efficient approximate Bayesian inference algorithm using a variational approach. We demonstrate the performance of our algorithms on data simulated from an Ising model. For data which are simulated from a more biologically plausible network with spiking neurons, we show that the Ising model captures well the low order statistics of the data and how the Ising couplings are related to the underlying synaptic structure of the simulated network.

  1. Complexity Variability Assessment of Nonlinear Time-Varying Cardiovascular Control

    Science.gov (United States)

    Valenza, Gaetano; Citi, Luca; Garcia, Ronald G.; Taylor, Jessica Noggle; Toschi, Nicola; Barbieri, Riccardo

    2017-02-01

    The application of complex systems theory to physiology and medicine has provided meaningful information about the nonlinear aspects underlying the dynamics of a wide range of biological processes and their disease-related aberrations. However, no studies have investigated whether meaningful information can be extracted by quantifying second-order moments of time-varying cardiovascular complexity. To this extent, we introduce a novel mathematical framework termed complexity variability, in which the variance of instantaneous Lyapunov spectra estimated over time serves as a reference quantifier. We apply the proposed methodology to four exemplary studies involving disorders which stem from cardiology, neurology and psychiatry: Congestive Heart Failure (CHF), Major Depression Disorder (MDD), Parkinson’s Disease (PD), and Post-Traumatic Stress Disorder (PTSD) patients with insomnia under a yoga training regime. We show that complexity assessments derived from simple time-averaging are not able to discern pathology-related changes in autonomic control, and we demonstrate that between-group differences in measures of complexity variability are consistent across pathologies. Pathological states such as CHF, MDD, and PD are associated with an increased complexity variability when compared to healthy controls, whereas wellbeing derived from yoga in PTSD is associated with lower time-variance of complexity.

  2. Decoupling Shoreline Behavior Over Variable Time and Space Scales

    Science.gov (United States)

    Hapke, C. J.; Plant, N. G.; Henderson, R.; Schwab, W. C.; Nelson, T. R.

    2016-12-01

    A combination of small-scale sediment transport processes and large-scale geologic, oceanographic, and morphologic processes drives shoreline change on time scales ranging from single storm events to decades. The relative importance of storm processes versus geological control on event response and long-term evolution of barrier islands is largely unknown but is important for understanding decadal-scale evolution Here, we investigate the primary controls on shoreline response along Fire Island, NY, a 50-km long barrier island, on timescales that resolve storms and decadal variations over a period of 80 yrs. An empirical orthogonal function (EOF) analysis is applied to a time series of shoreline positions to identify coherent patterns of shoreline variability that can be correlated to oceanographic or geologic framework parameters to help identify the controlling short-term or long-term processes. The analysis shows that storm response and recovery dominates the shoreline behavior on the largest spatial scales in the form of alternating episodes of shoreline retreat and advance that have a length scale of 1 km. The shoreline response to and recovery from Hurricane Sandy is included in this EOF analysis and indicates that this historic storm is not notable or distinguishable from several other large storms of the prior decade. This suggests that Fire Island is historically, and continues to be, resilient to severe storms. A secondary mode of the EOF analysis supports that the framework geology of the barrier island system, represented by known variations in inner shelf bathymetry, sediment availability, beach-shoreface morphology, and long-term rates of shoreline change, controls multi-decadal shoreline evolution. The geologic processes that control the long-term morphodynamics result in the ends of the island responding in opposite phase to the central portion. A third mode reveals an intermediate-scale pattern that persists over both long and short-term time scales

  3. Study on Short-term Variability of Ship Responses in Waves

    DEFF Research Database (Denmark)

    Nielsen, Ulrik Dam; Iseki, Toshio

    2015-01-01

    of the cross-spectra, has not been discussed in detail. Using long stationary time series, the transition of amplitudes and relative phase angles of the cross-spectra has been investigated by iterative analyzes with a few seconds of time shifting. In the results, the short-term variability of the relative...

  4. First-Passage-Time Distribution for Variable-Diffusion Processes

    Science.gov (United States)

    Barney, Liberty; Gunaratne, Gemunu H.

    2017-05-01

    First-passage-time distribution, which presents the likelihood of a stock reaching a pre-specified price at a given time, is useful in establishing the value of financial instruments and in designing trading strategies. First-passage-time distribution for Wiener processes has a single peak, while that for stocks exhibits a notable second peak within a trading day. This feature has only been discussed sporadically—often dismissed as due to insufficient/incorrect data or circumvented by conversion to tick time—and to the best of our knowledge has not been explained in terms of the underlying stochastic process. It was shown previously that intra-day variations in the market can be modeled by a stochastic process containing two variable-diffusion processes (Hua et al. in, Physica A 419:221-233, 2015). We show here that the first-passage-time distribution of this two-stage variable-diffusion model does exhibit a behavior similar to the empirical observation. In addition, we find that an extended model incorporating overnight price fluctuations exhibits intra- and inter-day behavior similar to those of empirical first-passage-time distributions.

  5. Time Resolved Spectroscopy of Cepheid Variable Stars

    Science.gov (United States)

    Hartman, Katherine; Beaton, Rachael L.; SDSS-IV APOGEE-2 Team

    2018-01-01

    Galactic Cepheid variable stars have been used for over a century as standard candles and as the first rung of the cosmic distance ladder, integral to the calculation of the Hubble constant. However, it is challenging to observe Cepheids within the Milky Way Galaxy because of extinction, and there are still uncertainties in the Cepheid period-luminosity relation (or Leavitt Law) that affect these important distance calculations. The Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey has provided spectra for a large sample of Galactic Cepheids, but the standard chemical abundance pipeline (ASPCAP) processing is not well-suited to pulsational variables, preventing us from using them to study metallicity effect in the Leavitt Law with standard processing. Using a standalone version of the ASPCAP pipeline, we present an analysis of individual visit spectra from a test sample of nine APOGEE Cepheids, and we compare its output to the stars’ literature abundance values. Based on the results of this comparison, we will be able to improve the standard analysis and process the entirety of APOGEE’s Cepheid catalogue to improve its abundance measurements. The resulting abundance data will allow us to constrain the effect of metallicity on the Leavitt Law and thus allow for more accurate Cepheid distance measurements for the determination of the Hubble constant.

  6. Long term stability of atomic time scales

    Science.gov (United States)

    Petit, Gérard; Arias, Elisa Felicitas

    2012-08-01

    International Atomic Time TAI gets its stability from some 400 atomic clocks worldwide that generate the free atomic scale EA L and its accuracy from a small number of primary frequency standards (PFS) which frequency measurements are used to steer the EAL frequency. Because TAI is computed in "real - time" (every month) and has operational constraints, it is not optimal and the BIPM computes in deferred time another time scale TT(BIPM), which is based on a weighted average of the evaluations of TAI frequency by the PFS. We show that a point has been reached where the stability of atomic time scales, the accuracy of primary frequency standards, and the capabilities of frequency transfer are approximately at a similar level, in the low 10 - 16 in relative frequency. The goal is now to reach and surpass 1x10 - 16 and the three fields are in various stages of advancement towards this aim. We review the stability and accuracy recently achieved by frequency standards, focusing on primary frequency standards on one hand, and on new secondary realizations e.g. based on optical transitions on the other hand. We study how these performances can translate to the performance of atomic time scales, and the possible implications of the availability of new high - accuracy frequency standards operating on a regular basis. Finally we show how time transfer is trying to keep up with the progresses of frequency standards. Time transfer is presently the limiting factor at short averaging time (e.g. 1 - 2 weeks) but it should not be limiting the long term stability of atomic time scales, which is the main need of many applications in astronomy.

  7. Short time-scale variability in the Faint Sky Variability Survey

    NARCIS (Netherlands)

    Morales-Rueda, L.; Groot, P.J.; Augusteijn, T.; Nelemans, G.A.; Vreeswijk, P.M.; Besselaar, E.J.M. van den

    2006-01-01

    We present the V-band variability analysis of the point sources in the Faint Sky Variability Survey on time-scales from 24 min to tens of days. We find that about one per cent of the point sources down to V = 24 are variables. We discuss the variability-detection probabilities for each field

  8. Implications of Wide-Area Geographic Diversity for Short- Term Variability of Solar Power

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Andrew; Wiser, Ryan

    2010-08-23

    Worldwide interest in the deployment of photovoltaic generation (PV) is rapidly increasing. Operating experience with large PV plants, however, demonstrates that large, rapid changes in the output of PV plants are possible. Early studies of PV grid impacts suggested that short-term variability could be a potential limiting factor in deploying PV. Many of these early studies, however, lacked high-quality data from multiple sites to assess the costs and impacts of increasing PV penetration. As is well known for wind, accounting for the potential for geographic diversity can significantly reduce the magnitude of extreme changes in aggregated PV output, the resources required to accommodate that variability, and the potential costs of managing variability. We use measured 1-min solar insolation for 23 time-synchronized sites in the Southern Great Plains network of the Atmospheric Radiation Measurement program and wind speed data from 10 sites in the same network to characterize the variability of PV with different degrees of geographic diversity and to compare the variability of PV to the variability of similarly sited wind. The relative aggregate variability of PV plants sited in a dense 10 x 10 array with 20 km spacing is six times less than the variability of a single site for variability on time scales less than 15-min. We find in our analysis of wind and PV plants similarly sited in a 5 x 5 grid with 50 km spacing that the variability of PV is only slightly more than the variability of wind on time scales of 5-15 min. Over shorter and longer time scales the level of variability is nearly identical. Finally, we use a simple approximation method to estimate the cost of carrying additional reserves to manage sub-hourly variability. We conclude that the costs of managing the short-term variability of PV are dramatically reduced by geographic diversity and are not substantially different from the costs for managing the short-term variability of similarly sited wind in

  9. Is Reaction Time Variability in ADHD Mainly at Low Frequencies?

    Science.gov (United States)

    Karalunas, Sarah L.; Huang-Pollock, Cynthia L.; Nigg, Joel T.

    2013-01-01

    Background: Intraindividual variability in reaction times (RT variability) has garnered increasing interest as an indicator of cognitive and neurobiological dysfunction in children with attention deficit hyperactivity disorder (ADHD). Recent theory and research has emphasized specific low-frequency patterns of RT variability. However, whether…

  10. Short- and long-term variations in non-linear dynamics of heart rate variability

    DEFF Research Database (Denmark)

    Kanters, J K; Højgaard, M V; Agner, E

    1996-01-01

    variability. METHODS: Twelve healthy subjects were investigated by 3-h ambulatory ECG recordings repeated on 3 separate days. Correlation dimension, non-linear predictability, mean heart rate, and heart rate variability in the time and frequency domains were measured and compared with the results from......OBJECTIVES: The purpose of the study was to investigate the short- and long-term variations in the non-linear dynamics of heart rate variability, and to determine the relationships between conventional time and frequency domain methods and the newer non-linear methods of characterizing heart rate...... corresponding surrogate time series. RESULTS: A small significant amount of non-linear dynamics exists in heart rate variability. Correlation dimensions and non-linear predictability are relatively specific parameters for each individual examined. The correlation dimension is inversely correlated to the heart...

  11. Do nonlinearities play a significant role in short term, beat-to-beat variability?

    Science.gov (United States)

    Choi, H. G.; Mukkamala, R.; Moody, G. B.; Mark, R. G.

    2001-01-01

    Numerous studies of short-term beat-to-beat variability in cardiovascular signals have not resolved the debate about the completeness of linear analysis techniques. This aim of this paper is to evaluate further the role of nonlinearities in short-term, beat-to-beat variability. We compared linear autoregressive moving average (ARMA) and nonlinear neural network (NN) models for predicting instantaneous heart rate (HR) and mean arterial blood pressure (BP) from past HR and BP. To evaluate these models, we used HR and BP time series from the MIMIC database. Experimental results indicate that NN-based nonlinearities do not play a significant role and suggest that ARMA linear analysis techniques provide adequate characterization of the system dynamics responsible for generating short-term, beat-to-beat variability.

  12. Important meteorological variables for statistical long-term air quality prediction in eastern China

    Science.gov (United States)

    Zhang, Libo; Liu, Yongqiang; Zhao, Fengjun

    2017-09-01

    Weather is an important factor for air quality. While there have been increasing attentions to long-term (monthly and seasonal) air pollution such as regional hazes from land-clearing fires during El Niño, the weather-air quality relationships are much less understood at long-term than short-term (daily and weekly) scales. This study is aimed to fill this gap through analyzing correlations between meteorological variables and air quality at various timescales. A regional correlation scale was defined to measure the longest time with significant correlations at a substantial large number of sites. The air quality index (API) and five meteorological variables during 2001-2012 at 40 eastern China sites were used. The results indicate that the API is correlated to precipitation negatively and air temperature positively across eastern China, and to wind, relative humidity and air pressure with spatially varied signs. The major areas with significant correlations vary with meteorological variables. The correlations are significant not only at short-term but also at long-term scales, and the important variables are different between the two types of scales. The concurrent regional correlation scales reach seasonal at p air temperature and relative humidity. Precipitation, which was found to be the most important variable for short-term air quality conditions, and air pressure are not important for long-term air quality. The lagged correlations are much smaller in magnitude than the concurrent correlations and their regional correction scales are at long term only for wind speed and relative humidity. It is concluded that wind speed should be considered as a primary predictor for statistical prediction of long-term air quality in a large region over eastern China. Relative humidity and temperature are also useful predictors but at less significant levels.

  13. Long-term variability of the spring taryn-aufeises

    Directory of Open Access Journals (Sweden)

    V. R. Alekseev

    2016-01-01

    Full Text Available Long-term variability of large taryn-aufeises was studied for several decades in different regions of the USA (Alaska and Russia (Chukotka, Kolyma, Southern Yakutia, Transbaikalia, and Eastern Sayan. Differences between volumes of individual ice massifs and the recorded maximal values change from 2–3 to 95–100%, and they do not depend on sizes of ice fields and their geographical locations. No statistically significant dependence of the aufeis volumes on the atmospheric precipitation amount and the air temperature was revealed in the most of the above areas. However, a general tendency for decreasing of the annual maxima of the ice reserves due to the climate warming was noticed. The long-term variations of the aufeises show existence of cycles of increase and decrease in their maximum sizes with their durations of 3, 7 and 11 years with the 25–30% amplitude of variations relative to the mean long-term values. In the Arctic areas, some of the giant aufeises do not melt completely during the summer and remain for a next winter. The volume of pereletoks (shortterm permafrost varies within the range of 5–25%, averaging 16% of the spring ice reserves. In the southern geocryological zone, a clearly pronounced dependence of activity of the aufeis processes on the snow thickness was found: when the snow depth increased from 70 to 100 cm, volumes of aufeises decreased by a factor of three, and the aufeises disappeared completely under the thickness larger 120 cm. It should be noted that the processes producing the aufeis-forming sources of subsurface water, and the factors of their layered-ice accumulation remain almost unexplored.

  14. Short-term variability in body weight predicts long-term weight gain1

    Science.gov (United States)

    Lowe, Michael R; Feig, Emily H; Winter, Samantha R; Stice, Eric

    2015-01-01

    Background: Body weight in lower animals and humans is highly stable despite a very large flux in energy intake and expenditure over time. Conversely, the existence of higher-than-average variability in weight may indicate a disruption in the mechanisms responsible for homeostatic weight regulation. Objective: In a sample chosen for weight-gain proneness, we evaluated whether weight variability over a 6-mo period predicted subsequent weight change from 6 to 24 mo. Design: A total of 171 nonobese women were recruited to participate in this longitudinal study in which weight was measured 4 times over 24 mo. The initial 3 weights were used to calculate weight variability with the use of a root mean square error approach to assess fluctuations in weight independent of trajectory. Linear regression analysis was used to examine whether weight variability in the initial 6 mo predicted weight change 18 mo later. Results: Greater weight variability significantly predicted amount of weight gained. This result was unchanged after control for baseline body mass index (BMI) and BMI change from baseline to 6 mo and for measures of disinhibition, restrained eating, and dieting. Conclusions: Elevated weight variability in young women may signal the degradation of body weight regulatory systems. In an obesogenic environment this may eventuate in accelerated weight gain, particularly in those with a genetic susceptibility toward overweight. Future research is needed to evaluate the reliability of weight variability as a predictor of future weight gain and the sources of its predictive effect. The trial on which this study is based is registered at clinicaltrials.gov as NCT00456131. PMID:26354535

  15. Photoelectron counting autoguiding system with variable accumulating time and variable corrective value.

    Science.gov (United States)

    Zheng, Yi-Jin

    1990-12-01

    This paper discusses three variants of a photoelectron counting autoguiding system based on half-disc light modulator. The first variant operates with constant accumulating time. The second variant operates with variable accumulating time but constant corrective value, which equals the allowable error of the guiding system. The third variant operates with both variable accumulating time and variable corrective value. Guiding errors and time responses of these three variants are compared. Guiders based on the third variant have been successfully used at the 1.56 m astrometrical telescope and the double-tube 40 cm telescope in Shanghai Observatory. The guiding error measured from the plate is about 0″11.

  16. Anomalous Low States and Long Term Variability in the Black Hole Binary LMC X-3

    Science.gov (United States)

    Smale, Alan P.; Boyd, Patricia T.

    2012-01-01

    Rossi X-my Timing Explorer observations of the black hole binary LMC X-3 reveal an extended very low X-ray state lasting from 2003 December 13 until 2004 March 18, unprecedented both in terms of its low luminosity (>15 times fainter than ever before seen in this source) and long duration (approx 3 times longer than a typical low/hard state excursion). During this event little to no source variability is observed on timescales of approx hours-weeks, and the X-ray spectrum implies an upper limit of 1.2 x 10(exp 35) erg/s, Five years later another extended low state occurs, lasting from 2008 December 11 until 2009 June 17. This event lasts nearly twice as long as the first, and while significant variability is observed, the source remains reliably in the low/hard spectral state for the approx 188 day duration. These episodes share some characteristics with the "anomalous low states" in the neutron star binary Her X-I. The average period and amplitude of the Variability of LMC X-3 have different values between these episodes. We characterize the long-term variability of LMC X-3 before and after the two events using conventional and nonlinear time series analysis methods, and show that, as is the case in Her X-I, the characteristic amplitude of the variability is related to its characteristic timescale. Furthermore, the relation is in the same direction in both systems. This suggests that a similar mechanism gives rise to the long-term variability, which in the case of Her X-I is reliably modeled with a tilted, warped precessing accretion disk.

  17. Genetic analysis of reaction time variability : room for improvement?

    NARCIS (Netherlands)

    Kuntsi, J.; Frazier-Wood, A. C.; Banaschewski, T.; Gill, M.; Miranda, A.; Oades, R. D.; Roeyers, H.; Rothenberger, A.; Steinhausen, H. -C.; van der Meere, J. J.; Faraone, S. V.; Asherson, P.; Rijsdijk, F.

    Background. Increased reaction time variability (RTV) on cognitive tasks requiring a speeded response is characteristic of several psychiatric disorders. In attention deficit hyperactivity disorder (ADHD), the association with RTV is strong phenotypically and genetically, yet high RTV is not a

  18. Variability of Travel Times on New Jersey Highways

    Science.gov (United States)

    2011-06-01

    This report presents the results of a link and path travel time study conducted on selected New Jersey (NJ) highways to produce estimates of the corresponding variability of travel time (VTT) by departure time of the day and days of the week. The tra...

  19. The cost of travel time variability: three measures with properties

    DEFF Research Database (Denmark)

    Engelson, Leonid; Fosgerau, Mogens

    2016-01-01

    This paper explores the relationships between three types of measures of the cost of travel time variability: measures based on scheduling preferences and implicit departure time choice, Bernoulli type measures based on a univariate function of travel time, and mean-dispersion measures. We...

  20. THE TIME DOMAIN SPECTROSCOPIC SURVEY: VARIABLE SELECTION AND ANTICIPATED RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Morganson, Eric; Green, Paul J. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Anderson, Scott F.; Ruan, John J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Eracleous, Michael; Brandt, William Nielsen [Department of Astronomy and Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States); Kelly, Brandon [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106-9530 (United States); Badenes, Carlos [Department of Physics and Astronomy and Pittsburgh Particle Physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara St, Pittsburgh, PA 15260 (United States); Bañados, Eduardo [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 N. Charter St., Madison, WI 53706 (United States); Borissova, Jura [Instituto de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, and Millennium Institute of Astrophysics (MAS), Santiago (Chile); Burgett, William S. [GMTO Corp, Suite 300, 251 S. Lake Ave, Pasadena, CA 91101 (United States); Chambers, Kenneth, E-mail: emorganson@cfa.harvard.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); and others

    2015-06-20

    We present the selection algorithm and anticipated results for the Time Domain Spectroscopic Survey (TDSS). TDSS is an Sloan Digital Sky Survey (SDSS)-IV Extended Baryon Oscillation Spectroscopic Survey (eBOSS) subproject that will provide initial identification spectra of approximately 220,000 luminosity-variable objects (variable stars and active galactic nuclei across 7500 deg{sup 2} selected from a combination of SDSS and multi-epoch Pan-STARRS1 photometry. TDSS will be the largest spectroscopic survey to explicitly target variable objects, avoiding pre-selection on the basis of colors or detailed modeling of specific variability characteristics. Kernel Density Estimate analysis of our target population performed on SDSS Stripe 82 data suggests our target sample will be 95% pure (meaning 95% of objects we select have genuine luminosity variability of a few magnitudes or more). Our final spectroscopic sample will contain roughly 135,000 quasars and 85,000 stellar variables, approximately 4000 of which will be RR Lyrae stars which may be used as outer Milky Way probes. The variability-selected quasar population has a smoother redshift distribution than a color-selected sample, and variability measurements similar to those we develop here may be used to make more uniform quasar samples in large surveys. The stellar variable targets are distributed fairly uniformly across color space, indicating that TDSS will obtain spectra for a wide variety of stellar variables including pulsating variables, stars with significant chromospheric activity, cataclysmic variables, and eclipsing binaries. TDSS will serve as a pathfinder mission to identify and characterize the multitude of variable objects that will be detected photometrically in even larger variability surveys such as Large Synoptic Survey Telescope.

  1. Timing and consequences of early term and late term deliveries.

    Science.gov (United States)

    Parikh, Laura; Singh, Jasbir; Timofeev, Julia; Zahn, Christopher M; Istwan, Niki B; Rhea, Debbie J; Driggers, Rita W

    2014-07-01

    To examine the timing of elective delivery and neonatal intensive care unit (NICU) utilization of electively delivered infants from 2008 to 2011. Analysis included 42,290 women with singleton gestation enrolled in a pregnancy education program, reporting uncomplicated pregnancies with elective labor induction (ELI) (n = 27,677) or scheduled cesarean delivery (SCD) (n = 14,613) at 37.0-41.9 weeks' gestation. Data were grouped by type and week of delivery (37.0-37.9, 38.0-38.9, and 39.0-41.9 weeks). ELI and SCD for each week of delivery from 2008 to 2011 and nursery utilization by delivery week were compared. During the 2008-2011 timeframe, a shift in timing of ELI and SCD toward ≥39.0 weeks was observed. In 2008, 80.9% of ELI occurred at ≥39.0 weeks versus 92.6% in 2011 (p age at elective delivery from 2008 to 2011 and increased NICU utilization for neonates born at <39 weeks' gestation.

  2. Periodicity and stability for variable-time impulsive neural networks.

    Science.gov (United States)

    Li, Hongfei; Li, Chuandong; Huang, Tingwen

    2017-10-01

    The paper considers a general neural networks model with variable-time impulses. It is shown that each solution of the system intersects with every discontinuous surface exactly once via several new well-proposed assumptions. Moreover, based on the comparison principle, this paper shows that neural networks with variable-time impulse can be reduced to the corresponding neural network with fixed-time impulses under well-selected conditions. Meanwhile, the fixed-time impulsive systems can be regarded as the comparison system of the variable-time impulsive neural networks. Furthermore, a series of sufficient criteria are derived to ensure the existence and global exponential stability of periodic solution of variable-time impulsive neural networks, and to illustrate the same stability properties between variable-time impulsive neural networks and the fixed-time ones. The new criteria are established by applying Schaefer's fixed point theorem combined with the use of inequality technique. Finally, a numerical example is presented to show the effectiveness of the proposed results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Long-term time series prediction using OP-ELM.

    Science.gov (United States)

    Grigorievskiy, Alexander; Miche, Yoan; Ventelä, Anne-Mari; Séverin, Eric; Lendasse, Amaury

    2014-03-01

    In this paper, an Optimally Pruned Extreme Learning Machine (OP-ELM) is applied to the problem of long-term time series prediction. Three known strategies for the long-term time series prediction i.e. Recursive, Direct and DirRec are considered in combination with OP-ELM and compared with a baseline linear least squares model and Least-Squares Support Vector Machines (LS-SVM). Among these three strategies DirRec is the most time consuming and its usage with nonlinear models like LS-SVM, where several hyperparameters need to be adjusted, leads to relatively heavy computations. It is shown that OP-ELM, being also a nonlinear model, allows reasonable computational time for the DirRec strategy. In all our experiments, except one, OP-ELM with DirRec strategy outperforms the linear model with any strategy. In contrast to the proposed algorithm, LS-SVM behaves unstably without variable selection. It is also shown that there is no superior strategy for OP-ELM: any of three can be the best. In addition, the prediction accuracy of an ensemble of OP-ELM is studied and it is shown that averaging predictions of the ensemble can improve the accuracy (Mean Square Error) dramatically. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Long-term variability of dust-storms in Iceland

    Science.gov (United States)

    Dagsson-Waldhauserová, Pavla; Ólafsson, Haraldur; Arnalds, Ólafur

    2013-04-01

    Iceland is a volcanic island in the North Atlantic Ocean with maritime climate. In spite of moist climate, large areas are with limited vegetation cover where >40% of Iceland is classified with considerable to very severe erosion and 21% of Iceland are volcanic sandy deserts. Natural emissions from these sources influenced by strong winds affect not only regional air quality in Iceland ("Reykjavik haze") but dust particles are transported over the Atlantic ocean and Arctic Ocean > 1000 km at times. The study places Icelandic dust production area into international perspective, present long term frequency of dust storm events in NE Iceland, and estimate dust aerosol concentrations during reported dust events. Meteorological observations with dust presence codes and related visibility were used to identify the frequency and the long-term changes in dust production in NE Iceland. There were annually 16.4 days on average with reported dust observations on weather stations within the NE erosion area, indicating extreme dust plume activity and erosion within the NE deserts, even though the area is covered with snow during the major part of winter. During the 2000s the highest occurrence of dust events in six decades was reported. We have measured saltation and aeolian transport during dust/volcanic ash storms in Iceland which give some of the most intense wind erosion events ever measured. Icelandic dust affects the ecosystems over much of Iceland and causes regional haze. It is likely to affect the ecosystems of the oceans around Iceland, and it brings dust that lowers the albedo of the Icelandic glaciers, increasing melt-off due to global warming. The study indicates that Icelandic dust is not only a substantial source for regional air pollution, but may be considered to contribute to the Arctic haze phenomena and Arctic air pollution.

  5. Long-term phenology and variability of Southern Africa

    CSIR Research Space (South Africa)

    Steenkamp, K

    2008-11-01

    Full Text Available southern Africa in order to investigate which phenometrics (and their inter-annual variability) distinguish biomes based on functional patterns. A second objective was to quantify the inter-annual variability of phenometrics during a 15-year period (1985...

  6. Timing variability in children with early-treated congenital hypothyroidism

    NARCIS (Netherlands)

    Kooistra, L.; Snijders, T.A.B.; Schellekens, J.M.H.; Kalverboer, A.F.; Geuze, R.H.

    This study reports on central and peripheral determinants of timing variability in self-paced tapping by children with early-treated congenital hypothyroidism (CH). A theoretical model of the timing of repetitive movements developed by Wing and Kristofferson was applied to estimate the central

  7. Pulping Variables, Storage Time and Pitch Deposit | Ogunwusi ...

    African Journals Online (AJOL)

    The effects of pulping variable, wood classification and storage time on pitch deposition during kraft pulping of mixed tropical hardwood species growing in Nigeria were investigated. Storage time has effect on pitch deposition in all the groups. Pulp resin decreased from 0.535% in control experiment to 0.235% after the sixth ...

  8. Predicting travel time variability for cost-benefit analysis

    NARCIS (Netherlands)

    Peer, S.; Koopmans, C.; Verhoef, E.T.

    2010-01-01

    Unreliable travel times cause substantial costs to travelers. Nevertheless, they are not taken into account in many cost-benefit-analyses (CBA), or only in very rough ways. This paper aims at providing simple rules on how variability can be predicted, based on travel time data from Dutch highways.

  9. Intra-Individual Reaction Time Variability in Schizophrenia, Depression and Borderline Personality Disorder

    Science.gov (United States)

    Kaiser, Stefan; Roth, Alexander; Rentrop, Mirjam; Friederich, Hans-Christoph; Bender, Stephan; Weisbrod, Matthias

    2008-01-01

    Intra-individual reaction time variability (IIV) in neuropsychological task performance reflects short term fluctuations in performance. Increased IIV has been reported in patients with schizophrenia and could be related to a deficient neural timing mechanism, but the role of IIV in adult patients with other psychiatric disorders has not been…

  10. Verification of models for ballistic movement time and endpoint variability.

    Science.gov (United States)

    Lin, Ray F; Drury, Colin G

    2013-01-01

    A hand control movement is composed of several ballistic movements. The time required in performing a ballistic movement and its endpoint variability are two important properties in developing movement models. The purpose of this study was to test potential models for predicting these two properties. Twelve participants conducted ballistic movements of specific amplitudes using a drawing tablet. The measured data of movement time and endpoint variability were then used to verify the models. This study was successful with Hoffmann and Gan's movement time model (Hoffmann, 1981; Gan and Hoffmann 1988) predicting more than 90.7% data variance for 84 individual measurements. A new theoretically developed ballistic movement variability model, proved to be better than Howarth, Beggs, and Bowden's (1971) model, predicting on average 84.8% of stopping-variable error and 88.3% of aiming-variable errors. These two validated models will help build solid theoretical movement models and evaluate input devices. This article provides better models for predicting end accuracy and movement time of ballistic movements that are desirable in rapid aiming tasks, such as keying in numbers on a smart phone. The models allow better design of aiming tasks, for example button sizes on mobile phones for different user populations.

  11. The Gaia spectrophotometric standard stars survey - III. Short-term variability monitoring

    Science.gov (United States)

    Marinoni, S.; Pancino, E.; Altavilla, G.; Bellazzini, M.; Galleti, S.; Tessicini, G.; Valentini, G.; Cocozza, G.; Ragaini, S.; Braga, V.; Bragaglia, A.; Federici, L.; Schuster, W. J.; Carrasco, J. M.; Castro, A.; Figueras, F.; Jordi, C.

    2016-11-01

    We present the results of the short-term constancy monitoring of candidate Gaia Spectrophotometric Standard Stars (SPSS). We obtained time series of typically 1.24 h - with sampling periods from 1-3 min to a few hours, depending on the case - to monitor the constancy of our candidate SPSS down to 10 mmag, as required for the calibration of Gaia photometric data. We monitored 162 out of a total of 212 SPSS candidates. The observing campaign started in 2006 and finished in 2015, using 143 observing nights on nine different instruments covering both hemispheres. Using differential photometry techniques, we built light curves with a typical precision of 4 mmag, depending on the data quality. As a result of our constancy assessment, 150 SPSS candidates were validated against short-term variability, and only 12 were rejected because of variability including some widely used flux standards such as BD+174708, SA 105-448, 1740346, and HD 37725.

  12. Examining Computer Gaming Addiction in Terms of Different Variables

    Science.gov (United States)

    Kurt, Adile Askim; Dogan, Ezgi; Erdogmus, Yasemin Kahyaoglu; Emiroglu, Bulent Gursel

    2018-01-01

    The computer gaming addiction is one of the newer concepts that young generations face and can be defined as the excessive and problematic use of computer games leading to social and/or emotional problems. The purpose of this study is to analyse through variables the computer gaming addiction levels of secondary school students. The research was…

  13. Due-Window Assignment Scheduling with Variable Job Processing Times

    Directory of Open Access Journals (Sweden)

    Yu-Bin Wu

    2015-01-01

    Full Text Available We consider a common due-window assignment scheduling problem jobs with variable job processing times on a single machine, where the processing time of a job is a function of its position in a sequence (i.e., learning effect or its starting time (i.e., deteriorating effect. The problem is to determine the optimal due-windows, and the processing sequence simultaneously to minimize a cost function includes earliness, tardiness, the window location, window size, and weighted number of tardy jobs. We prove that the problem can be solved in polynomial time.

  14. Energy decay of a variable-coefficient wave equation with nonlinear time-dependent localized damping

    Directory of Open Access Journals (Sweden)

    Jieqiong Wu

    2015-09-01

    Full Text Available We study the energy decay for the Cauchy problem of the wave equation with nonlinear time-dependent and space-dependent damping. The damping is localized in a bounded domain and near infinity, and the principal part of the wave equation has a variable-coefficient. We apply the multiplier method for variable-coefficient equations, and obtain an energy decay that depends on the property of the coefficient of the damping term.

  15. Numerical Simulations for the Space-Time Variable Order Nonlinear Fractional Wave Equation

    Directory of Open Access Journals (Sweden)

    Nasser Hassan Sweilam

    2013-01-01

    Full Text Available The explicit finite-difference method for solving variable order fractional space-time wave equation with a nonlinear source term is considered. The concept of variable order fractional derivative is considered in the sense of Caputo. The stability analysis and the truncation error of the method are discussed. To demonstrate the effectiveness of the method, some numerical test examples are presented.

  16. Predictor variables for marathon race time in recreational female runners.

    Science.gov (United States)

    Schmid, Wiebke; Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rüst, Christoph Alexander; Rosemann, Thomas; Lepers, Romuald

    2012-06-01

    We intended to determine predictor variables of anthropometry and training for marathon race time in recreational female runners in order to predict marathon race time for future novice female runners. Anthropometric characteristics such as body mass, body height, body mass index, circumferences of limbs, thicknesses of skin-folds and body fat as well as training variables such as volume and speed in running training were related to marathon race time using bi- and multi-variate analysis in 29 female runners. The marathoners completed the marathon distance within 251 (26) min, running at a speed of 10.2 (1.1) km/h. Body mass (r=0.37), body mass index (r=0.46), the circumferences of thigh (r=0.51) and calf (r=0.41), the skin-fold thicknesses of front thigh (r=0.38) and of medial calf (r=0.40), the sum of eight skin-folds (r=0.44) and body fat percentage (r=0.41) were related to marathon race time. For the variables of training, maximal distance ran per week (r=- 0.38), number of running training sessions per week (r=- 0.46) and the speed of the training sessions (r= - 0.60) were related to marathon race time. In the multi-variate analysis, the circumference of calf (P=0.02) and the speed of the training sessions (P=0.0014) were related to marathon race time. Marathon race time might be partially (r(2)=0.50) predicted by the following equation: Race time (min)=184.4 + 5.0 x (circumference calf, cm) -11.9 x (speed in running during training, km/h) for recreational female marathoners. Variables of both anthropometry and training were related to marathon race time in recreational female marathoners and cannot be reduced to one single predictor variable. For practical applications, a low circumference of calf and a high running speed in training are associated with a fast marathon race time in recreational female runners.

  17. Timing of Palliative Care Consultations and Recommendations: Understanding the Variability.

    Science.gov (United States)

    Kozlov, Elissa; Carpenter, Brian D; Thorsten, Michael; Heiland, Mark; Agarwal, Anupam

    2015-11-01

    Palliative care consultation teams (PCCTs) provide care that enhances quality of life. The effectiveness of PCCTs depends, however, on their timely utilization by other providers. The goal of this study was to examine the timing of palliative care consultation requests and responses at a single Veteran Affairs Medical Center. The median interval between admission and consultation request was 5 days (range = 0-73 days). The median interval between consultation request and death was 23 days (range = 0-847 days). In logistic regressions, timing variables were not significant predictors of whether consultation recommendations were made or implemented. There is substantial variability in when patients receive a palliative care consultation. Many patients receive palliative care within the first week of hospitalization and their final month of life. © The Author(s) 2014.

  18. Physical attraction to reliable, low variability nervous systems: Reaction time variability predicts attractiveness.

    Science.gov (United States)

    Butler, Emily E; Saville, Christopher W N; Ward, Robert; Ramsey, Richard

    2017-01-01

    The human face cues a range of important fitness information, which guides mate selection towards desirable others. Given humans' high investment in the central nervous system (CNS), cues to CNS function should be especially important in social selection. We tested if facial attractiveness preferences are sensitive to the reliability of human nervous system function. Several decades of research suggest an operational measure for CNS reliability is reaction time variability, which is measured by standard deviation of reaction times across trials. Across two experiments, we show that low reaction time variability is associated with facial attractiveness. Moreover, variability in performance made a unique contribution to attractiveness judgements above and beyond both physical health and sex-typicality judgements, which have previously been associated with perceptions of attractiveness. In a third experiment, we empirically estimated the distribution of attractiveness preferences expected by chance and show that the size and direction of our results in Experiments 1 and 2 are statistically unlikely without reference to reaction time variability. We conclude that an operating characteristic of the human nervous system, reliability of information processing, is signalled to others through facial appearance. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. North Atlantic warming: patterns of long-term trend and multidecadal variability

    Energy Technology Data Exchange (ETDEWEB)

    Polyakov, Igor V.; Alexeev, Vladimir A.; Zhang, Xiangdong [University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK (United States); Bhatt, Uma S. [University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK (United States); Polyakova, Evgenia I. [Stanford University, Department of Geological and Environmental Studies, Stanford, CA (United States)

    2010-02-15

    Climate fluctuations in the North Atlantic Ocean have wide-spread implications for Europe, Africa, and the Americas. This study assesses the relative contribution of the long-term trend and variability of North Atlantic warming using EOF analysis of deep-ocean and near-surface observations. Our analysis demonstrates that the recent warming over the North Atlantic is linked to both long-term (including anthropogenic and natural) climate change and multidecadal variability (MDV, {proportional_to}50-80 years). Our results suggest a general warming trend of 0.031 {+-} 0.006 C/decade in the upper 2,000 m North Atlantic over the last 80 years of the twentieth century, although during this time there are periods in which short-term trends were strongly amplified by MDV. For example, MDV accounts for {proportional_to}60% of North Atlantic warming since 1970. The single-sign basin-scale pattern of MDV with prolonged periods of warming (cooling) in the upper ocean layer and opposite tendency in the lower layer is evident from observations. This pattern is associated with a slowdown (enhancement) of the North Atlantic thermohaline overturning circulation during negative (positive) MDV phases. In contrast, the long-term trend exhibits warming in tropical and mid-latitude North Atlantic and a pattern of cooling in regions associated with major northward heat transports, consistent with a slowdown of the North Atlantic circulation as evident from observations and confirmed by selected modeling results. This localized cooling has been masked in recent decades by warming during the positive phase of MDV. Finally, since the North Atlantic Ocean plays a crucial role in establishing and regulating the global thermohaline circulation, the multidecadal fluctuations discussed here should be considered when assessing long-term climate change and variability, both in the North Atlantic and at global scales. (orig.)

  20. Increased timing variability in schizophrenia and bipolar disorder.

    Directory of Open Access Journals (Sweden)

    Amanda R Bolbecker

    Full Text Available Theoretical and empirical evidence suggests that impaired time perception and the neural circuitry underlying internal timing mechanisms may contribute to severe psychiatric disorders, including psychotic and mood disorders. The degree to which alterations in temporal perceptions reflect deficits that exist across psychosis-related phenotypes and the extent to which mood symptoms contribute to these deficits is currently unknown. In addition, compared to schizophrenia, where timing deficits have been more extensively investigated, sub-second timing has been studied relatively infrequently in bipolar disorder. The present study compared sub-second duration estimates of schizophrenia (SZ, schizoaffective disorder (SA, non-psychotic bipolar disorder (BDNP, bipolar disorder with psychotic features (BDP, and healthy non-psychiatric controls (HC on a well-established time perception task using sub-second durations. Participants included 66 SZ, 37 BDNP, 34 BDP, 31 SA, and 73 HC who participated in a temporal bisection task that required temporal judgements about auditory durations ranging from 300 to 600 milliseconds. Timing variability was significantly higher in SZ, BDP, and BDNP groups compared to healthy controls. The bisection point did not differ across groups. These findings suggest that both psychotic and mood symptoms may be associated with disruptions in internal timing mechanisms. Yet unexpected findings emerged. Specifically, the BDNP group had significantly increased variability compared to controls, but the SA group did not. In addition, these deficits appeared to exist independent of current symptom status. The absence of between group differences in bisection point suggests that increased variability in the SZ and bipolar disorder groups are due to alterations in perceptual timing in the sub-second range, possibly mediated by the cerebellum, rather than cognitive deficits.

  1. Short-term reproducibility and variability of the pupillographic sleepiness test.

    Science.gov (United States)

    Wilhelm, Barbara; Bittner, Evelyn; Hofmann, Anna; Koerner, Andreas; Peters, Tobias; Lüdtke, Holger; Wilhelm, Helmut

    2015-01-01

    The pupillographic sleepiness test (PST) measures the amplitude of the fluctuations of pupil size in the dark, which reflects the level of central nervous system activation and thus alertness. The aim of this study was to assess the short-term reproducibility and variability of the results obtained with the PST in normal healthy subjects. The PST was measured at 9.00, 11:00, and 13:00 h on three consecutive days in 13 young adults. Subjective sleepiness was assessed with the Stanford Sleepiness Scale (SSS) and with a Visual Analogue Scale (VAS). The intra-class correlation (ICC), a measure of reproducibility and the intra- and inter-individual variability, was calculated. ANOVA analysis of the data revealed no significant differences in the PST measurements for testing day. Time of day and subject did however significantly affect the results with an ICC 73.1%. For the SSS and VAS, the ICC was 38.8% and 45.9%, respectively. The intra- and inter-individual variability in PST results did not differ considerably between time and days. We conclude that recordings of the PST have a good reproducibility and low intra- and inter-individual variability compared to subjective scales of sleepiness or the Multiple Sleep Latency Test. The PST is thus a viable method to measure daytime sleepiness objectively. © 2015 Wiley Periodicals, Inc.

  2. Enceladus Plume Structure and Time Variability: Comparison of Cassini Observations.

    Science.gov (United States)

    Teolis, Ben D; Perry, Mark E; Hansen, Candice J; Waite, J Hunter; Porco, Carolyn C; Spencer, John R; Howett, Carly J A

    2017-09-01

    During three low-altitude (99, 66, 66 km) flybys through the Enceladus plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Science Subsystem (ISS) imaging observations of the plume's icy component have been reported, which constrain the locations and orientations of the numerous gas/grain jets. In the present study, we used these ISS imaging results, together with ultraviolet imaging spectrograph stellar and solar occultation measurements and modeling of the three-dimensional structure of the vapor cloud, to constrain the magnitudes, velocities, and time variability of the plume gas sources from the INMS data. Our results confirm a mixture of both low and high Mach gas emission from Enceladus' surface tiger stripes, with gas accelerated as fast as Mach 10 before escaping the surface. The vapor source fluxes and jet intensities/densities vary dramatically and stochastically, up to a factor 10, both spatially along the tiger stripes and over time between flyby observations. This complex spatial variability and dynamics may result from time-variable tidal stress fields interacting with subsurface fissure geometry and tortuosity beyond detectability, including changing gas pathways to the surface, and fluid flow and boiling in response evolving lithostatic stress conditions. The total plume gas source has 30% uncertainty depending on the contributions assumed for adiabatic and nonadiabatic gas expansion/acceleration to the high Mach emission. The overall vapor plume source rate exhibits stochastic time variability up to a factor ∼5 between observations, reflecting that found in the individual gas sources/jets. Key Words: Cassini at Saturn-Geysers-Enceladus-Gas dynamics-Icy satellites. Astrobiology 17, 926-940.

  3. Long-term successional forest dynamics: species and community responses to climatic variability

    Energy Technology Data Exchange (ETDEWEB)

    Kardol, Paul [ORNL; Todd Jr, Donald E [ORNL; Hanson, Paul J [ORNL; Mulholland, Patrick J [ORNL

    2010-01-01

    Question: Are tree dynamics sensitive to climatic variability, and do tree species differ in their responses to climatic variability? Hence, is vulnerability of forest communities to climatic variability depending on stand composition? Location: Mixed young forest at Walker Branch Watershed near Oak Ridge, East-Tennessee, USA. Methods: Using a long-term data set (1967-2006), we analyzed temporal forest dynamics at the tree and species level, and we analyzed community dynamics for forest stands that different in their initial species composition (i.e., Chestnut Oak, Oak-Hickory, Pine, and Yellow poplar stands). Using summer drought and growing season temperature as defined climate drivers, we evaluated relationships between forest dynamics and climate across levels of organization. Results: Over the 4-decade studied period, forest communities underwent successional change and substantially increased their biomass. Variation in summer drought and growing season temperature contributed to temporal biomass dynamics for some tree species, but not for others. Stand-level responses to climatic variability were shown to be related to responses of specific component species; however, not for Pine stands. Pinus echinata, the dominant species in stands initially identified as Pine stands, decreased over time due to periodical outbreaks of the pine bark beetle (Dendroctonus frontalis). The outbreaks on Walker Branch could not be directly related to climatic conditions. Conclusions: Our results imply that vulnerability of developing forests to predicted climate conditions is stand-type dependent, and hence, is a function of species composition. Autogenic successional processes (or insect outbreaks) were found to prevail over climatic variability in determining long-term forest dynamics for stands dominated by sensitive species, emphasizing the importance of studying interactions between forest succession and climate change.

  4. Long term X-ray variability of Circinus X-1

    Energy Technology Data Exchange (ETDEWEB)

    Saz Parkinson, Pablo

    2003-03-19

    We present an analysis of long term X-ray monitoring observations of Circinus X-1 (Cir X-1) made with four different instruments: Vela 5B, Ariel V ASM, Ginga ASM, and RXTE ASM, over the course of more than 30 years. We use Lomb-Scargle periodograms to search for the {approx}16.5 day orbital period of Cir X-1 in each of these data sets and from this derive a new orbital ephemeris based solely on X-ray measurements, which we compare to the previous ephemerides obtained from radio observations. We also use the Phase Dispersion Minimization (PDM) technique, as well as FFT analysis, to verify the periods obtained from periodograms. We obtain dynamic periodograms (both Lomb-Scargle and PDM) of Cir X-1 during the RXTE era, showing the period evolution of Cir X-1, and also displaying some unexplained discrete jumps in the location of the peak power.

  5. Allocating operating room block time using historical caseload variability.

    Science.gov (United States)

    Hosseini, Narges; Taaffe, Kevin M

    2015-12-01

    Operating room (OR) allocation and planning is one of the most important strategic decisions that OR managers face. The number of ORs that a hospital opens depends on the number of blocks that are allocated to the surgical groups, services, or individual surgeons, combined with the amount of open posting time (i.e., first come, first serve posting) that the hospital wants to provide. By allocating too few ORs, a hospital may turn away surgery demand whereas opening too many ORs could prove to be a costly decision. The traditional method of determining block frequency and size considers the average historical surgery demand for each group. However, given that there are penalties to the system for having too much or too little OR time allocated to a group, demand variability should play a role in determining the real OR requirement. In this paper we present an algorithm that allocates block time based on this demand variability, specifically accounting for both over-utilized time (time used beyond the block) and under-utilized time (time unused within the block). This algorithm provides a solution to the situation in which total caseload demand can be accommodated by the total OR resource set, in other words not in a capacity-constrained situation. We have found this scenario to be common among several regional healthcare providers with large OR suites and excess capacity. This algorithm could be used to adjust existing blocks or to assign new blocks to surgeons that did not previously have a block. We also have studied the effect of turnover time on the number of ORs that needs to be allocated. Numerical experiments based on real data from a large health-care provider indicate the opportunity to achieve over 2,900 hours of OR time savings through improved block allocations.

  6. Respiratory variability in preterm and term infants: Effect of sleep state, position and age.

    Science.gov (United States)

    Elder, Dawn E; Campbell, Angela J; Larsen, Peter D; Galletly, Duncan

    2011-02-15

    The influence of sleep state and position on respiratory variability (RV) was studied in 13 preterm infants (PTIs) and 19 term infants (TIs). Temporally matched epochs of nasal pressure and oxygen saturation (Spo₂) data were extracted from nap polysomnography. Inspiratory onset times (I) were determined, and variability measures of the I-I interval compared in quiet sleep and active sleep, prone and supine and with age. Sleep state influenced respiratory variability (RV) in PTI and TI but Spo₂ only varied with sleep state in PTI (p=0.03). Position had no effect on RV in TI but influenced the standard deviation of ventilatory frequency (SDf) in PTI (p=0.04). Age did not influence RV in PTI but SDf and the coefficient of variation of ventilatory frequency (CVf) decreased in TI from birth to 3 months. These data confirm sleep state as the predominant influence on RV in healthy term and convalescent preterm infants, with horizontal prone positioning having little effect when sleep state is controlled for. Copyright © 2010 Elsevier B.V. All rights reserved.

  7. Long-term sea surface temperature variability in the Aegean Sea

    Directory of Open Access Journals (Sweden)

    Nikolaos Skliris

    2011-12-01

    Full Text Available The inter-annual/decadal scale variability of the Aegean Sea Surface Temperature (SST is investigated by means of long-term series of satellite-derived and in situ data. Monthly mean declouded SST maps are constructed over the 1985–2008 period, based on a re-analysis of AVHRR Oceans Pathfinder optimally interpolated data over the Aegean Sea. Basin-average SST time series are also constructed using the ICOADS in situ data over 1950–2006. Results indicate a small SST decreasing trend until the early nineties, and then a rapid surface warming consistent with the acceleration of the SST rise observed on the global ocean scale. Decadal-scale SST anomalies were found to be negatively correlated with the winter North Atlantic Oscillation (NAO index over the last 60 years suggesting that along with global warming effects on the regional scale, a part of the long-term SST variability in the Aegean Sea is driven by large scale atmospheric natural variability patterns. In particular, the acceleration of surface warming in the Aegean Sea began nearly simultaneously with the NAO index abrupt shift in the mid-nineties from strongly positive values to weakly positive/negative values.

  8. Interpersonal variability in timing strategy and temporal accuracy in rapid interception task with variable time-to-contact.

    Science.gov (United States)

    Ijiri, Tetsuya; Shinya, Masahiro; Nakazawa, Kimitaka

    2015-01-01

    In rapid interceptive actions such as hitting a baseball, cricket ball or tennis ball, ball speed varies between trials, and players have to compensate the time lag by controlling the moment of movement onset and movement duration. Previous studies have found that these two variables can flexibly co-vary and are robustly influenced by target speed (i.e. velocity-coupling effect: faster movement for faster target). However, some studies reported an interpersonal variability in the timing control strategy and the relationship between the strategy and temporal accuracy in rapid interception is unclear. We used a baseball-simulated rapid interceptive task to assess this issue. Under relatively easy time constraints, there was a large interpersonal variability, and participants were distinctively divided into two groups: those who mainly modulated their movement duration and those who mainly controlled their movement onset. When the time constraint became severe, the second strategy shifted to the first strategy in most of the second group participants. In the both cases, being able to mainly control movement onset resulted in higher temporal accuracy. These results suggest that minimising the velocity-coupling effect is an important factor to achieve high temporal accuracy in rapid interception.

  9. Overcoming Long-Term Variability in Local Field Potentials Using an Adaptive Decoder.

    Science.gov (United States)

    Tadipatri, Vijay Aditya; Tewfik, Ahmed H; Pellizzer, Giuseppe; Ashe, James

    2017-02-01

    Long-term variability remains one of the major hurdles in using intracortical recordings like local field potentials for brain computer interfaces (BCI). Practical neural decoders need to overcome time instability of neural signals to estimate subject behavior accurately and faithfully over the long term. This paper presents a novel decoder that 1) characterizes each behavioral task (i.e., different movement directions under different force conditions) with multiple neural patterns and 2) adapts to the long-term variations in neural features by identifying the stable neural patterns. This adaptation can be performed in both an unsupervised and a semisupervised learning framework requiring minimal feedback from the user. To achieve generalization over time, the proposed decoder uses redundant sparse regression models that adapt to day-to-day variations in neural patterns. While this update requires no explicit feedback from the BCI user, any feedback (explicit or derived) to the BCI improves its performance. With this adaptive decoder, we investigated the effects of long-term neural modulation especially when subjects encountered new external forces against movement. The proposed decoder predicted eight hand-movement directions with an accuracy of 95% over two weeks (when there was no external forces); and 85% in later acquisition sessions spanning up to 42 days (when the monkeys countered external field forces). Since the decoder can operate with or without manual intervention, it could alleviate user frustration associated with BCI.

  10. Long-term variability and trends of sea level storminess and extremes in European Seas

    Science.gov (United States)

    Vilibić, Ivica; Šepić, Jadranka

    2010-03-01

    This paper documents the variability and trends of mean storminess and extreme sea level amplitudes at selected long-term operating tide gauge stations located in the European Seas over different frequency bands, seasons and months. Six stations have been chosen for the analyses-Antalya, Ceuta, Rovinj, Newlyn, Wladyslawowo and Lerwick-which possess at least a half-centurial record of hourly or higher frequency sea level data. The data have been carefully inspected for time shifts and drifts in the record. The analyses included the extraction of sea level amplitudes (envelopes) over four frequency bands: super-diurnal frequencies (0-1 days), small-scale synoptic disturbances (1-3 days), large-scale synoptic disturbances (3-10 days) and planetary-scale disturbances (10-100 days). Interannual variability in sea level amplitudes is occasionally found to coincide with some known variability in the atmosphere. For example, the northern European stations have overall positive sea level storminess and extreme trends, which is opposite from the southern stations, confirming a northward shift in atmosphere storm tracks. Redistribution of sea level amplitudes between different seasons and different frequency bands has been observed at some stations in both variability and trends. The latter may be important for the assessment of a region's total hazard risks and vulnerability, as maximum storminess and extremes may or may not coincide with maximum mean sea level.

  11. Long-term optical and radio variability of BL Lacertae

    OpenAIRE

    Guo, Y. C.; S.M. Hu; Xu, C; Liu, C Y; Chen, X; Guo, D. F.; Meng, F.Y.; Xu, M. T.; J. Q. Xu

    2014-01-01

    Well-sampled optical and radio light curves of BL Lacertae in B, V, R, I bands and 4.8, 8.0, 14.5 GHz from 1968 to 2014 were presented in this paper. A possible $1.26 \\pm 0.05$ yr period in optical bands and a $7.50 \\pm 0.15$ yr period in radio bands were detected based on discrete correlation function, structure function as well as Jurkevich method. Correlations among different bands were also analyzed and no reliable time delay was found between optical bands. Very weak correlations were de...

  12. Valuing travel time variability: Characteristics of the travel time distribution on an urban road

    DEFF Research Database (Denmark)

    Fosgerau, Mogens; Fukuda, Daisuke

    2012-01-01

    This paper provides a detailed empirical investigation of the distribution of travel times on an urban road for valuation of travel time variability. Our investigation is premised on the use of a theoretical model with a number of desirable properties. The definition of the value of travel time...... variability depends on certain properties of the distribution of random travel times that require empirical verification. Applying a range of nonparametric statistical techniques to data giving minute-by-minute travel times for a congested urban road over a period of five months, we show that the standardized...... travel time is roughly independent of the time of day as required by the theory. Except for the extreme right tail, a stable distribution seems to fit the data well. The travel time distributions on consecutive links seem to share a common stability parameter such that the travel time distribution...

  13. Long-term Radiation Budget Variability in the Northern Eurasian Region: Assessing the Interaction with Fire

    Science.gov (United States)

    Stackhouse, P. W.; Soja, A. J.; Zhang, T.; Mikovitz, J. C.

    2013-12-01

    In terms of global change, boreal regions are particularly important, because significant warming and change are already evident and significant future warming is predicted. Mean global air temperature has increased by 0.74°C in the last century, and temperatures are predicted to increase by 1.8°C to 4°C by 2090, depending on the Inter-governmental Panel on Climate Change (IPCC) scenario. Some of the greatest temperature increases are currently found in the Northern Eurasian winter and spring, which has led to longer growing seasons, increased potential evapotranspiration and extreme fire weather [Groisman et al., 2007]. In the Siberian Sayan, winter temperatures have already exceeded a 2090 Hadley Centre scenario (HadCM3GGa1) [Soja et al., 2007]. There is evidence of climate-induced change across the circumboreal in terms of increased infestations, alterations in vegetation and increased fire regimes (area burned, fire frequency, severity and number of extreme fire seasons). In this paper, we analyzed long-term surface radiation data sets from the NASA/GEWEX (Global Energy and Water Exchanges) Surface Radiation Budget data products, CERES Surface EBAF and SYN data products and also the available surface radiation measurements in the region. First, we show that during overlap years SRB and CERES data products agree very well in terms of anomalies and we'll use this fact to evaluate 30 years of satellite based estimates of the variability of downwelling SW parameters first corresponding to locations of surface measurements and then for the region as a whole. We also show the observed variability of other SW components such as the net SW and the albedo. Next we assess the variability of the downward and LW fluxes over time and compare these to variability observed in the surface temperature and other meteorological measurements. We assess anomalies on various spatial scales. Finally, we assess the correlation of this variability in specific locations to known fire

  14. Short-Term Variability and Predictors of Urinary Pentachlorophenol Levels in Ohio Preschool Children

    Directory of Open Access Journals (Sweden)

    Marsha Morgan

    2015-01-01

    Full Text Available Pentachlorophenol (PCP is a persistent and ubiquitous environmental contaminant. No published data exist on the temporal variability or important predictors of urinary PCP concentrations in young children. In this further analysis of study data, we have examined the associations between selected sociodemographic or lifestyle factors and urinary PCP concentrations in 115 preschool children over a 48-h period and assessed the 48-hour variability of urinary PCP levels in a subset of 15 children. Monitoring was performed at 115 homes and 16 daycares in Ohio (USA in 2001. Questionnaires/diaries and spot urine samples were collected from each child. The median urinary PCP level was 0.8 ng/mL (range < 0.2–23.8 ng/mL. The intraclass correlation coefficient for urinary PCP was 0.42, which indicates fairly low reliability for a single sample over a 48-h period. In a multiple regression model, age of home and ln(creatinine levels were significant predictors and sampling season, time spent outside, and pet ownership were marginally significant predictors of ln(urinary PCP levels, collectively explaining 29% of the variability of PCP in urine. To adequately assess short-term exposures of children to PCP, several spot urine measurements are likely needed as well as information regarding residence age, seasonality, time spent outdoors, and pet ownership.

  15. Handling Time-dependent Variables: Antibiotics and Antibiotic Resistance.

    Science.gov (United States)

    Munoz-Price, L Silvia; Frencken, Jos F; Tarima, Sergey; Bonten, Marc

    2016-06-15

    Elucidating quantitative associations between antibiotic exposure and antibiotic resistance development is important. In the absence of randomized trials, observational studies are the next best alternative to derive such estimates. Yet, as antibiotics are prescribed for varying time periods, antibiotics constitute time-dependent exposures. Cox regression models are suited for determining such associations. After explaining the concepts of hazard, hazard ratio, and proportional hazards, the effects of treating antibiotic exposure as fixed or time-dependent variables are illustrated and discussed. Wider acceptance of these techniques will improve quantification of the effects of antibiotics on antibiotic resistance development and provide better evidence for guideline recommendations. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

  16. Long-term and ultra long-term blood pressure variability during follow-up and mortality in 14,522 patients with hypertension.

    Science.gov (United States)

    Hastie, Claire E; Jeemon, Panniyammakal; Coleman, Holli; McCallum, Linsay; Patel, Rajan; Dawson, Jesse; Sloan, William; Meredith, Peter; Jones, Gregory C; Muir, Scott; Walters, Matthew; Dominiczak, Anna F; Morrison, David; McInnes, Gordon T; Padmanabhan, Sandosh

    2013-10-01

    Recent evidence indicates that long-term visit-to-visit blood pressure variability (BPV) may be an independent cardiovascular risk predictor. The implication of this variability in hypertension clinical practice is unclear. BPV as average real variability (ARV) was calculated in 14,522 treated patients with hypertension in 4 time frames: year 1 (Y1), years 2 to 5 (Y2-5), years 5 to 10 (Y5-10), and years >10 (Y10+) from first clinic visit. Cox proportional hazards models for cause-specific mortality were used in each time frame separately for long-term BPV, across time frames based on ultra long-term BPV, and within each time frame stratified by mean BP. ARV in systolic blood pressure (SBP), termed ARV(SBP), was higher in Y1 (21.3±11.9 mm Hg) in contrast to Y2-5 (17.7±9.9 mm Hg), Y5-10 (17.4±9.6 mm Hg), and Y10+ (16.8±8.5 mm Hg). In all time frames, ARV(SBP) was higher in women (Pclinical practice may facilitate risk reduction strategies by identifying treated hypertensive individuals at high risk, especially those with BP within the normal range.

  17. Temporal Prediction Errors Affect Short-Term Memory Scanning Response Time.

    Science.gov (United States)

    Limongi, Roberto; Silva, Angélica M

    2016-11-01

    The Sternberg short-term memory scanning task has been used to unveil cognitive operations involved in time perception. Participants produce time intervals during the task, and the researcher explores how task performance affects interval production - where time estimation error is the dependent variable of interest. The perspective of predictive behavior regards time estimation error as a temporal prediction error (PE), an independent variable that controls cognition, behavior, and learning. Based on this perspective, we investigated whether temporal PEs affect short-term memory scanning. Participants performed temporal predictions while they maintained information in memory. Model inference revealed that PEs affected memory scanning response time independently of the memory-set size effect. We discuss the results within the context of formal and mechanistic models of short-term memory scanning and predictive coding, a Bayes-based theory of brain function. We state the hypothesis that our finding could be associated with weak frontostriatal connections and weak striatal activity.

  18. Does tropical forest fragmentation increase long-term variability of butterfly communities?

    Science.gov (United States)

    Leidner, Allison K; Haddad, Nick M; Lovejoy, Thomas E

    2010-03-10

    Habitat fragmentation is a major driver of biodiversity loss. Yet, the overall effects of fragmentation on biodiversity may be obscured by differences in responses among species. These opposing responses to fragmentation may be manifest in higher variability in species richness and abundance (termed hyperdynamism), and in predictable changes in community composition. We tested whether forest fragmentation causes long-term hyperdynamism in butterfly communities, a taxon that naturally displays large variations in species richness and community composition. Using a dataset from an experimentally fragmented landscape in the central Amazon that spanned 11 years, we evaluated the effect of fragmentation on changes in species richness and community composition through time. Overall, adjusted species richness (adjusted for survey duration) did not differ between fragmented forest and intact forest. However, spatial and temporal variation of adjusted species richness was significantly higher in fragmented forests relative to intact forest. This variation was associated with changes in butterfly community composition, specifically lower proportions of understory shade species and higher proportions of edge species in fragmented forest. Analysis of rarefied species richness, estimated using indices of butterfly abundance, showed no differences between fragmented and intact forest plots in spatial or temporal variation. These results do not contradict the results from adjusted species richness, but rather suggest that higher variability in butterfly adjusted species richness may be explained by changes in butterfly abundance. Combined, these results indicate that butterfly communities in fragmented tropical forests are more variable than in intact forest, and that the natural variability of butterflies was not a buffer against the effects of fragmentation on community dynamics.

  19. Does tropical forest fragmentation increase long-term variability of butterfly communities?

    Directory of Open Access Journals (Sweden)

    Allison K Leidner

    Full Text Available Habitat fragmentation is a major driver of biodiversity loss. Yet, the overall effects of fragmentation on biodiversity may be obscured by differences in responses among species. These opposing responses to fragmentation may be manifest in higher variability in species richness and abundance (termed hyperdynamism, and in predictable changes in community composition. We tested whether forest fragmentation causes long-term hyperdynamism in butterfly communities, a taxon that naturally displays large variations in species richness and community composition. Using a dataset from an experimentally fragmented landscape in the central Amazon that spanned 11 years, we evaluated the effect of fragmentation on changes in species richness and community composition through time. Overall, adjusted species richness (adjusted for survey duration did not differ between fragmented forest and intact forest. However, spatial and temporal variation of adjusted species richness was significantly higher in fragmented forests relative to intact forest. This variation was associated with changes in butterfly community composition, specifically lower proportions of understory shade species and higher proportions of edge species in fragmented forest. Analysis of rarefied species richness, estimated using indices of butterfly abundance, showed no differences between fragmented and intact forest plots in spatial or temporal variation. These results do not contradict the results from adjusted species richness, but rather suggest that higher variability in butterfly adjusted species richness may be explained by changes in butterfly abundance. Combined, these results indicate that butterfly communities in fragmented tropical forests are more variable than in intact forest, and that the natural variability of butterflies was not a buffer against the effects of fragmentation on community dynamics.

  20. Short-term spatial and temporal variability in greenhouse gas fluxes in riparian zones.

    Science.gov (United States)

    Vidon, P; Marchese, S; Welsh, M; McMillan, S

    2015-08-01

    Recent research indicates that riparian zones have the potential to contribute significant amounts of greenhouse gases (GHG: N2O, CO2, CH4) to the atmosphere. Yet, the short-term spatial and temporal variability in GHG emission in these systems is poorly understood. Using two transects of three static chambers at two North Carolina agricultural riparian zones (one restored, one unrestored), we show that estimates of the average GHG flux at the site scale can vary by one order of magnitude depending on whether the mean or the median is used as a measure of central tendency. Because the median tends to mute the effect of outlier points (hot spots and hot moments), we propose that both must be reported or that other more advanced spatial averaging techniques (e.g., kriging, area-weighted average) should be used to estimate GHG fluxes at the site scale. Results also indicate that short-term temporal variability in GHG fluxes (a few days) under seemingly constant temperature and hydrological conditions can be as large as spatial variability at the site scale, suggesting that the scientific community should rethink sampling protocols for GHG at the soil-atmosphere interface to include repeated measures over short periods of time at select chambers to estimate GHG emissions in the field. Although recent advances in technology provide tools to address these challenges, their cost is often too high for widespread implementation. Until technology improves, sampling design strategies will need to be carefully considered to balance cost, time, and spatial and temporal representativeness of measurements.

  1. Consequences of mixing assumptions for time-variable travel time distributions

    NARCIS (Netherlands)

    Velde, van der Y.; Heidbüchel, I.; Lyon, S.W.; Nyberg, L.; Rodhe, A.; Bishop, K.; Troch, P.A.

    2015-01-01

    The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare

  2. Changes in heart rate variability are associated with expression of short-term and long-term contextual and cued fear memories.

    Directory of Open Access Journals (Sweden)

    Jun Liu

    Full Text Available Heart physiology is a highly useful indicator for measuring not only physical states, but also emotional changes in animals. Yet changes of heart rate variability during fear conditioning have not been systematically studied in mice. Here, we investigated changes in heart rate and heart rate variability in both short-term and long-term contextual and cued fear conditioning. We found that while fear conditioning could increase heart rate, the most significant change was the reduction in heart rate variability which could be further divided into two distinct stages: a highly rhythmic phase (stage-I and a more variable phase (stage-II. We showed that the time duration of the stage-I rhythmic phase were sensitive enough to reflect the transition from short-term to long-term fear memories. Moreover, it could also detect fear extinction effect during the repeated tone recall. These results suggest that heart rate variability is a valuable physiological indicator for sensitively measuring the consolidation and expression of fear memories in mice.

  3. Energy Storage on the Grid and the Short-term Variability of Wind

    Science.gov (United States)

    Hittinger, Eric Stephen

    Wind generation presents variability on every time scale, which must be accommodated by the electric grid. Limited quantities of wind power can be successfully integrated by the current generation and demand-side response mix but, as deployment of variable resources increases, the resulting variability becomes increasingly difficult and costly to mitigate. In Chapter 2, we model a co-located power generation/energy storage block composed of wind generation, a gas turbine, and fast-ramping energy storage. A scenario analysis identifies system configurations that can generate power with 30% of energy from wind, a variability of less than 0.5% of the desired power level, and an average cost around $70/MWh. While energy storage technologies have existed for decades, fast-ramping grid-level storage is still an immature industry and is experiencing relatively rapid improvements in performance and cost across a variety of technologies. Decreased capital cost, increased power capability, and increased efficiency all would improve the value of an energy storage technology and each has cost implications that vary by application, but there has not yet been an investigation of the marginal rate of technical substitution between storage properties. The analysis in chapter 3 uses engineering-economic models of four emerging fast-ramping energy storage technologies to determine which storage properties have the greatest effect on cost-of-service. We find that capital cost of storage is consistently important, and identify applications for which power/energy limitations are important. In some systems with a large amount of wind power, the costs of wind integration have become significant and market rules have been slowly changing in order to internalize or control the variability of wind generation. Chapter 4 examines several potential market strategies for mitigating the effects of wind variability and estimate the effect that each strategy would have on the operation and

  4. Drivers of interannual variability in CO2 effects on productivity across long-term experiments

    Science.gov (United States)

    Langley, J. A.; Hovenden, M. J.; Leuzinger, S.

    2015-12-01

    Despite three decades of long-term field manipulations, there remains no clear consensus as to what regulates the magnitude of the CO2 stimulation of plant productivity across ecosystems and through time. A large body of work suggests that availability of nutrients or water, the factors that most strongly control NPP in most ecosystems, also control the magnitude of the CO2 effect on NPP. On the other hand, several recent studies have suggested that indirect CO2 effects, mediated through soil moisture savings, may hold importance in explaining results from individual sites. To determine how water availability may drive CO2 stimulation of productivity we collected annual NPP and rainfall data from 12 long-term CO2 studies. We found that the CO2 effect size was not consistently related to interannual variability in NPP under ambient conditions, indicating that the factors controlling interannual variability in NPP do not control the magnitude of CO2 effects on NPP in a consistent manner. Across sites and years, the CO2 effect size was negatively related to the number of rain days during the growing season, indicating that CO2 may have engendered important indirect effects on productivity that were manifested during under drying intervals. While the drivers underlying direct CO2 effect size remain elusive, this analysis suggests that indirect effects may exhibit generality across sites.

  5. Interrupter technique in infancy: Higher airway resistance and lower short-term variability in preterm versus term infants.

    Science.gov (United States)

    Usemann, Jakob; Demann, Désirée; Anagnostopoulou, Pinelopi; Korten, Insa; Gorlanova, Olga; Schulzke, Sven; Frey, Urs; Latzin, Philipp

    2017-10-01

    In preschool children, measurement of airway resistance using interrupter technique (Rint) is feasible to assess the degree of bronchial obstruction. Although some studies measured Rint in infancy, values of Rint and its variability in preterm infants are unknown. In this study, Rint and its variability was measured at infancy and compared between healthy term and preterm infants. High quality Rint measurements in term (n = 50) and preterm (n = 48) infants were obtained at postmenstrual age of 42-50 weeks in two study centers in Switzerland. Intra-measurement variability of Rint in one measurement and inter-measurement variability between two subsequent measurements was assessed by coefficient of variation (CV). Mean Rint in term infants was 4.2 ± (SD; 1.9) kPa · s · L -1 and in preterm infants was 5.6 ± (2.8) kPa · s · L -1 . Mean CV in term infants was 29.6 ± (14.9)% and in preterm infants was 20.2 ± (8.4)%. Rint was significantly lower (95%CI -2.31 to -0.38; P = 0.007) and CV significantly higher (95%CI 4.53-14.3; P preterm infants. There were no differences in mean Rint and mean CV between the first and the second measurement obtained in a subgroup of term (n = 24, 48%) and preterm (n = 22, 45%) infants. Our results suggest that differences in airway mechanics between term and preterm infants can be assessed with the interrupter technique during early infancy. Before clinical application of Rint measurements in this age group, reasons underlying the variability of measurements should be further investigated. © 2017 Wiley Periodicals, Inc.

  6. Electric Vehicle Routing Problem with Charging Time and Variable Travel Time

    OpenAIRE

    Sai Shao; Wei Guan; Bin Ran; Zhengbing He; Jun Bi

    2017-01-01

    An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe op...

  7. Synchronizing time delay systems using variable delay in coupling

    Energy Technology Data Exchange (ETDEWEB)

    Ambika, G., E-mail: g.ambika@iiserpune.ac.in [Indian Institute of Science Education and Research, Pune 411 021 (India); Amritkar, R.E., E-mail: amritkar@prl.res.in [Physical Research Laboratory, Ahmedabad 380 009 (India)

    2011-11-15

    Highlights: > Delay and anticipation in coupling function varies with system dynamics. > Delay or anticipation of the synchronized state is independent of system delay. > Stability analysis developed is quite general. > We demonstrate enhanced security in communication. > Generalized synchronization possible over a wide range of parameter mismatch. - Abstract: We present a mechanism for synchronizing time delay systems using one way coupling with a variable delay in coupling that is reset at finite intervals. We present the analysis of the error dynamics that helps to isolate regions of stability of the synchronized state in the parameter space of interest for single and multiple delays. We supplement this by numerical simulations in a standard time delay system like Mackey Glass system. This method has the advantage that it can be adjusted to be delay or anticipatory in synchronization with a time which is independent of the system delay. We demonstrate the use of this method in communication using the bi channel scheme. We show that since the synchronizing channel carries information from transmitter only at intervals of reset time, it is not susceptible to an easy reconstruction.

  8. Long-Term Optical Spectra Variability of BL Lacertae Object S5 ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy; Volume 32; Issue 1-2. Long-Term Optical Spectra Variability of BL Lacertae Object S5 0716+714. Zhang Hao Jing ... BL Lac object individual: S5 0716+714; optical spectral index variability period; methods: periodogram analysis method, wavelet analysis method.

  9. Long-Term Variability of Surface Albedo and Its Correlation with Climatic Variables over Antarctica

    OpenAIRE

    Minji Seo; Hyun-Cheol Kim; Morang Huh; Jong-Min Yeom; Chang Suk Lee; Kyeong-Sang Lee; Sungwon Choi; Kyung-Soo Han

    2016-01-01

    The cryosphere is an essential part of the earth system for understanding climate change. Components of the cryosphere, such as ice sheets and sea ice, are generally decreasing over time. However, previous studies have indicated differing trends between the Antarctic and the Arctic. The South Pole also shows internal differences in trends. These phenomena indicate the importance of continuous observation of the Polar Regions. Albedo is a main indicator for analyzing Antarctic climate change a...

  10. Long-Term Total Solar Irradiance (TSI) Variability Trends: 1984-2004

    Science.gov (United States)

    Lee, Robert Benjamin, III; Wilson, Robert S.; Thomas, Susan

    2004-01-01

    The incoming total solar irradiance (TSI), typically referred to as the solar constant, is being studied to identify long-term TSI changes, which may trigger global climate changes. The TSI is normalized to the mean earth-sun distance. Studies of spacecraft TSI data sets confirmed the existence of 0.1 %, long-term TSI variability component with a period of 10 years. The component varied directly with solar magnetic activity associated with recent 10-year sunspot cycles. The 0.1 % TSI variability component is clearly present in the spacecraft data sets from the 1984-2004, Earth Radiation Budget Experiment (ERBE) active cavity radiometer (ACR) solar monitor; 1978-1993, Nimbus-7 HF; 1980-1989, Solar Maximum Mission [SMM] ACRIM; 1991-2004, Upper Atmosphere Research Satellite (UARS) ACRIM; 1996-2003, Solar and Heliospheric Observatory (SOHO)/VIRGO, Space Science (ATLAS), 2000-2004, ACRIMSAT; and 2003-2004 SOlar Radiation and Climate Experiment (SORCE) active cavity radiometer (ACR) missions. From October 1984, through March 2004, the ERBS/ERBE solar monitor was used to produce the longest continuous data set of total solar irradiance (TSI) variability measurements. The solar monitor is located on Shuttle Atmospheric Laboratory for Applications and the NASA Earth Radiation Budget Satellite (ERBS). Maximum TSI values occurred during the 1989-1991, and 1998-2002, time frames; while minimum [quiet sun] TSI levels occurred during 1986 and 1996. Recent ERBS measurements indicate that the TSI is decreasing to forecasted, minimum levels by 2006. Using the discontinuous non-operational Nimbus-7, SMM ACRIM, and UARS ACRIM mission TSI data sets, Wilson and Mordvinor (2003) suggested the existence of an additional long-term TSI variability component, 0.05 %, with a period longer than a decade. Analyses of the ERBS/ERBE data set do not support the Wilson and Mordvinor analyses approach because it used the Nimbus-7 data set which exhibited a significant ACR response shift of 0.7 Wm-2

  11. Higher order multi-term time-fractional partial differential equations involving Caputo-Fabrizio derivative

    Directory of Open Access Journals (Sweden)

    Erkinjon Karimov

    2017-10-01

    Full Text Available In this work we discuss higher order multi-term partial differential equation (PDE with the Caputo-Fabrizio fractional derivative in time. Using method of separation of variables, we reduce fractional order partial differential equation to the integer order. We represent explicit solution of formulated problem in particular case by Fourier series.

  12. Efficient conservative ADER schemes based on WENO reconstruction and space-time predictor in primitive variables

    Science.gov (United States)

    Zanotti, Olindo; Dumbser, Michael

    2016-01-01

    We present a new version of conservative ADER-WENO finite volume schemes, in which both the high order spatial reconstruction as well as the time evolution of the reconstruction polynomials in the local space-time predictor stage are performed in primitive variables, rather than in conserved ones. To obtain a conservative method, the underlying finite volume scheme is still written in terms of the cell averages of the conserved quantities. Therefore, our new approach performs the spatial WENO reconstruction twice: the first WENO reconstruction is carried out on the known cell averages of the conservative variables. The WENO polynomials are then used at the cell centers to compute point values of the conserved variables, which are subsequently converted into point values of the primitive variables. This is the only place where the conversion from conservative to primitive variables is needed in the new scheme. Then, a second WENO reconstruction is performed on the point values of the primitive variables to obtain piecewise high order reconstruction polynomials of the primitive variables. The reconstruction polynomials are subsequently evolved in time with a novel space-time finite element predictor that is directly applied to the governing PDE written in primitive form. The resulting space-time polynomials of the primitive variables can then be directly used as input for the numerical fluxes at the cell boundaries in the underlying conservative finite volume scheme. Hence, the number of necessary conversions from the conserved to the primitive variables is reduced to just one single conversion at each cell center. We have verified the validity of the new approach over a wide range of hyperbolic systems, including the classical Euler equations of gas dynamics, the special relativistic hydrodynamics (RHD) and ideal magnetohydrodynamics (RMHD) equations, as well as the Baer-Nunziato model for compressible two-phase flows. In all cases we have noticed that the new ADER

  13. Travel times in the vadose zone: Variability in space and time

    Science.gov (United States)

    Sprenger, Matthias; Seeger, Stefan; Blume, Theresa; Weiler, Markus

    2016-08-01

    Water travel times reflect hydrological processes, yet we know little about how travel times in the unsaturated zone vary with time. Using the soil physical model HYDRUS-1D, we derived time variable travel time distributions for 35 study sites within the Attert catchment in Luxembourg. While all sites experience similar climatic forcing, they differ with regard to soil types (16 Cambisols, 12 Arenosols, and 7 Stagnosols) and the vegetation cover (29 forest and 6 grassland). We estimated site specific water flow and transport parameters by fitting the model simulations to observed soil moisture time series and depth profiles of pore water stable isotopes. With the calibrated model, we tracked the water parcels introduced with each rainfall event over a period of several years. Our results show that the median travel time of water from the soil surface to depths down to 200 cm is mainly driven by the subsequent rainfall amounts. The median time until precipitation is taken up by roots is governed by the seasonality of evapotranspiration rates. The ratio between the amount of water that leaves the soil profile by on the one hand and evaporation and transpiration on the other hand also shows an annual cycle. This time variable response due to climatic forcing is furthermore visible in the multimodal nature of the site specific master transit time distribution representing the flow-averaged probability density for rainwater to become recharge. The spatial variability of travel times is mainly driven by soil texture and structure, with significant longer travel times for the clayey Stagnosols than for the loamy to sandy Cambisols and Arenosols.

  14. The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

    NARCIS (Netherlands)

    Ponsoni, Leandro; Aguiar-Gonzalez, Borja; Ridderinkhof, Herman; Maas, L.R.M.

    This study provides a long-term description of the poleward East Madagascar Current (EMC) in terms of its observed velocities, estimated volume transport, and variability based on both ;2.5 yr of continuous in situ measurements and ;21 yr of satellite altimeter data. An array of five moorings was

  15. The East Madagascar Current: Volume Transport and Variability Based on Long-Term Observations

    NARCIS (Netherlands)

    Ponsoni, L.; Aguiar-González, B.; Ridderinkhof, H.; Maas, L.

    2016-01-01

    This study provides a long-term description of the poleward East Madagascar Current (EMC) in terms of its observed velocities, estimated volume transport, and variability based on both ~2.5 yr of continuous in situ measurements and ~21 yr of satellite altimeter data. An array of five moorings was

  16. Expanding space-time and variable vacuum energy

    Science.gov (United States)

    Parmeggiani, Claudio

    2017-08-01

    The paper describes a cosmological model which contemplates the presence of a vacuum energy varying, very slightly (now), with time. The constant part of the vacuum energy generated, some 6 Gyr ago, a deceleration/acceleration transition of the metric expansion; so now, in an aged Universe, the expansion is inexorably accelerating. The vacuum energy varying part is instead assumed to be eventually responsible of an acceleration/deceleration transition, which occurred about 14 Gyr ago; this transition has a dynamic origin: it is a consequence of the general relativistic Einstein-Friedmann equations. Moreover, the vacuum energy (constant and variable) is here related to the zero-point energy of some quantum fields (scalar, vector, or spinor); these fields are necessarily described in a general relativistic way: their structure depends on the space-time metric, typically non-flat. More precisely, the commutators of the (quantum field) creation/annihilation operators are here assumed to depend on the local value of the space-time metric tensor (and eventually of its curvature); furthermore, these commutators rapidly decrease for high momentum values and they reduce to the standard ones for a flat metric. In this way, the theory is ”gravitationally” regularized; in particular, the zero-point (vacuum) energy density has a well defined value and, for a non static metric, depends on the (cosmic) time. Note that this varying vacuum energy can be negative (Fermi fields) and that a change of its sign typically leads to a minimum for the metric expansion factor (a ”bounce”).

  17. Bovine colostrum supplementation's lack of effect on immune variables during short-term intense exercise in well-trained athletes.

    Science.gov (United States)

    Carol, Arnoud; Witkamp, Renger F; Wichers, Harry J; Mensink, Marco

    2011-04-01

    The purpose of this study was to investigate the potential of bovine colostrum to attenuate postexercise decline in immune function. The authors evaluated the time course of a number of immune variables after short-term intense exercise in 9 male athletes after 10 d of supplementation with either colostrum or skim-milk powder. To increase the stress on the immune system subjects performed a glycogen-depletion trial the evening before the endurance trial (90 min at 50% Wmax). Blood samples were taken before the glycogen-depletion trial, before and after the endurance trial, and the next morning, ~22 hr after cessation of the exercise. Plasma cortisol levels increased over time, reaching the highest level directly after exercise, and were still elevated ~22 hr after exercise compared with baseline values (p exercise and dropped below starting values 22 hr after exercise (time effect p time. A significant time effect was seen for interleukin (IL)-6, IL-10, IL-1-receptor agonist, and C-reactive protein, with levels being higher directly after exercise (p time effect. No differences were seen between colostrum and skim-milk powder in any of the investigated variables. Our results are consistent with the hypothesis that intense exercise affects several variables of the immune system. Colostrum did not alter any of the postexercise immune variables compared with skim-milk powder, suggesting no role for bovine colostrum supplementation in preventing postexercise immune suppression after short-term intense exercise.

  18. Detecting the harmonics of oscillations with time-variable frequencies

    Science.gov (United States)

    Sheppard, L. W.; Stefanovska, A.; McClintock, P. V. E.

    2011-01-01

    A method is introduced for the spectral analysis of complex noisy signals containing several frequency components. It enables components that are independent to be distinguished from the harmonics of nonsinusoidal oscillatory processes of lower frequency. The method is based on mutual information and surrogate testing combined with the wavelet transform, and it is applicable to relatively short time series containing frequencies that are time variable. Where the fundamental frequency and harmonics of a process can be identified, the characteristic shape of the corresponding oscillation can be determined, enabling adaptive filtering to remove other components and nonoscillatory noise from the signal. Thus the total bandwidth of the signal can be correctly partitioned and the power associated with each component then can be quantified more accurately. The method is first demonstrated on numerical examples. It is then used to identify the higher harmonics of oscillations in human skin blood flow, both spontaneous and associated with periodic iontophoresis of a vasodilatory agent. The method should be equally relevant to all situations where signals of comparable complexity are encountered, including applications in astrophysics, engineering, and electrical circuits, as well as in other areas of physiology and biology.

  19. Volume, intensity, and timing of muscle power potentiation are variable.

    Science.gov (United States)

    Chaouachi, Anis; Poulos, Nick; Abed, Fathi; Turki, Olfa; Brughelli, Matt; Chamari, Karim; Drinkwater, Eric J; Behm, David G

    2011-10-01

    Whereas muscle potentiation is consistently demonstrated with evoked contractile properties, the potentiation of functional and physiological measures is inconsistent. The objective was to compare a variety of conditioning stimuli volumes and intensities over a 15-min recovery period. Twelve volleyball players were subjected to conditioning stimuli that included 10 repetitions of half squats with 70% of 1-repetition maximum (RM) (10 × 70), 5 × 70, 5 × 85, 3 × 85, 3 × 90, 1 × 90, and control. Jump height, power, velocity, and force were measured at baseline, 1, 3, 5, 10, and 15 min. Data were analysed with a 2-way repeated measure ANOVA and magnitude-based inferences. The ANOVA indicated significant decreases in jump height, power, and velocity during recovery. This should not be interpreted that no potentiation occurred. Each dependent variable reached a peak at a slightly different time: peak jump height (2.8 ± 2.3 min), mean power (3.6 ± 3.01 min), peak power (2.5 ± 1.8 min), and peak velocity (2.5 ± 1.8 min). Magnitude-based inference revealed that both the 5 × 70 and 3 × 85 protocol elicited changes that exceeded 75% likelihood of exceeding the smallest worthwhile change (SWC) for peak power and velocity. The 10 × 70 and the 5 × 70 had a substantial likelihood of potentiating peak velocity and mean power above the SWC, respectively. Magnitude-based inferences revealed that while no protocol had a substantial likelihood of potentiating the peak vertical jump, the 5 × 70 had the most consistent substantial likelihood of increasing the peak of most dependent variables. We were unable to consistently predict if these peaks occurred at 1, 3, or 5 min poststimulation, though declines after 5 min seems probable.

  20. Long-term trend of climate variables in the upper Dong Nai river basin in Vietnam

    Science.gov (United States)

    Truong, Nguyen Cung Que; Nguyen, Hong Quan; Kondoh, Akihiko

    2015-04-01

    Dong Nai river and Mekong delta downstream are located in and supplied the major water resources to the whole Southern of Vietnam. In the state of continuous changes in water resources due to climate changes, there are several controversy about the potential impact of sediment transport and river flows downstream due to either the cascade hydroelectric power plant system or dam construction in the upper of Mekong delta. Therefore, management and planning for efficient use of Dong Nai river water resource is very important. Furthermore, that it is necessary to consider the hydrological regime change by the effects of climate variable. On the other hand, solving the problems of water shortage in the dry season and flood control in rainy season are also important for issues of water management at Dong Nai river basin. In this study we evaluated changes in two main factors of the water balance equation (both rainfall and evapotranspiration) to assess long-term change in the hydrological regime in the upper area of Dong Nai river basin. This key theme was divided into the following two sub-goals. The first goal was to analyze long term spatial and temporal rainfall trends. The second goal was to analyze the long-term trend of meteorological factors determining evapotranspiration such as air temperature, wind speed, solar radiation and sunshine duration. The results were used to assess their impact to evapotranspiration. The meteorological and hydrological data of the basin for the last 20 years (from 1993 to 2012) were analyzed based on the Empirical Mode Decomposition (EMD) method. The EMD method has been pioneered by Huang et al. (1998) for adaptively representing nonstationary time-series data as sum of zero-mean amplitude modulation-frequency modulation (AM-FM) components by iteratively conducting the sifting process. These components called Intrinsic Mode Functions (IMFs) allow the calculation of a meaningful multi-component instantaneous frequency. The results

  1. Optimizing acceleration-based ethograms: the use of variable-time versus fixed-time segmentation.

    Science.gov (United States)

    Bom, Roeland A; Bouten, Willem; Piersma, Theunis; Oosterbeek, Kees; van Gils, Jan A

    2014-01-01

    Animal-borne accelerometers measure body orientation and movement and can thus be used to classify animal behaviour. To univocally and automatically analyse the large volume of data generated, we need classification models. An important step in the process of classification is the segmentation of acceleration data, i.e. the assignment of the boundaries between different behavioural classes in a time series. So far, analysts have worked with fixed-time segments, but this may weaken the strength of the derived classification models because transitions of behaviour do not necessarily coincide with boundaries of the segments. Here we develop random forest automated supervised classification models either built on variable-time segments generated with a so-called 'change-point model', or on fixed-time segments, and compare for eight behavioural classes the classification performance. The approach makes use of acceleration data measured in eight free-ranging crab plovers Dromas ardeola. Useful classification was achieved by both the variable-time and fixed-time approach for flying (89% vs. 91%, respectively), walking (88% vs. 87%) and body care (68% vs. 72%). By using the variable-time segment approach, significant gains in classification performance were obtained for inactive behaviours (95% vs. 92%) and for two major foraging activities, i.e. handling (84% vs. 77%) and searching (78% vs. 67%). Attacking a prey and pecking were never accurately classified by either method. Acceleration-based behavioural classification can be optimized using a variable-time segmentation approach. After implementing variable-time segments to our sample data, we achieved useful levels of classification performance for almost all behavioural classes. This enables behaviour, including motion, to be set in known spatial contexts, and the measurement of behavioural time-budgets of free-living birds with unprecedented coverage and precision. The methods developed here can be easily adopted in

  2. Assessing variability and long-term trends in burned area by merging multiple satellite fire products

    Directory of Open Access Journals (Sweden)

    L. Giglio

    2010-03-01

    Full Text Available Long term, high quality estimates of burned area are needed for improving both prognostic and diagnostic fire emissions models and for assessing feedbacks between fire and the climate system. We developed global, monthly burned area estimates aggregated to 0.5° spatial resolution for the time period July 1996 through mid-2009 using four satellite data sets. From 2001–2009, our primary data source was 500-m burned area maps produced using Moderate Resolution Imaging Spectroradiometer (MODIS surface reflectance imagery; more than 90% of the global area burned during this time period was mapped in this fashion. During times when the 500-m MODIS data were not available, we used a combination of local regression and regional regression trees developed over periods when burned area and Terra MODIS active fire data were available to indirectly estimate burned area. Cross-calibration with fire observations from the Tropical Rainfall Measuring Mission (TRMM Visible and Infrared Scanner (VIRS and the Along-Track Scanning Radiometer (ATSR allowed the data set to be extended prior to the MODIS era. With our data set we estimated that the global annual area burned for the years 1997–2008 varied between 330 and 431 Mha, with the maximum occurring in 1998. We compared our data set to the recent GFED2, L3JRC, GLOBCARBON, and MODIS MCD45A1 global burned area products and found substantial differences in many regions. Lastly, we assessed the interannual variability and long-term trends in global burned area over the past 13 years. This burned area time series serves as the basis for the third version of the Global Fire Emissions Database (GFED3 estimates of trace gas and aerosol emissions.

  3. Protecting chips against hold time violations due to variability

    CERN Document Server

    Neuberger, Gustavo; Reis, Ricardo

    2013-01-01

    With the development of Very-Deep Sub-Micron technologies, process variability is becoming increasingly important and is a very important issue in the design of complex circuits. Process variability is the statistical variation of process parameters, meaning that these parameters do not have always the same value, but become a random variable, with a given mean value and standard deviation. This effect can lead to several issues in digital circuit design.The logical consequence of this parameter variation is that circuit characteristics, as delay and power, also become random variables. Becaus

  4. Atmospheric Parameter Climatologies from AIRS: Monitoring Short-, and Longer-Term Climate Variabilities and 'Trends'

    Science.gov (United States)

    Molnar, Gyula; Susskind, Joel

    2008-01-01

    The AIRS instrument is currently the best space-based tool to simultaneously monitor the vertical distribution of key climatically important atmospheric parameters as well as surface properties, and has provided high quality data for more than 5 years. AIRS analysis results produced at the GODDARD/DAAC, based on Versions 4 & 5 of the AIRS retrieval algorithm, are currently available for public use. Here, first we present an assessment of interrelationships of anomalies (proxies of climate variability based on 5 full years, since Sept. 2002) of various climate parameters at different spatial scales. We also present AIRS-retrievals-based global, regional and 1x1 degree grid-scale "trend"-analyses of important atmospheric parameters for this 5-year period. Note that here "trend" simply means the linear fit to the anomaly (relative the mean seasonal cycle) time series of various parameters at the above-mentioned spatial scales, and we present these to illustrate the usefulness of continuing AIRS-based climate observations. Preliminary validation efforts, in terms of intercomparisons of interannual variabilities with other available satellite data analysis results, will also be addressed. For example, we show that the outgoing longwave radiation (OLR) interannual spatial variabilities from the available state-of-the-art CERES measurements and from the AIRS computations are in remarkably good agreement. Version 6 of the AIRS retrieval scheme (currently under development) promises to further improve bias agreements for the absolute values by implementing a more accurate radiative transfer model for the OLR computations and by improving surface emissivity retrievals.

  5. Long-term variability of the leading seasonal modes of rainfall in south-eastern Australia

    Directory of Open Access Journals (Sweden)

    Maryam Montazerolghaem

    2016-09-01

    Full Text Available Knowledge of temporal and spatial variability of climate and rainfall can improve agriculture production and can help to manage risks caused by climate variability. Available high-quality monthly rainfall data from the Australian Bureau of Meteorology for 1907–2011 was used to investigate the leading seasonal mode of the long-term rainfall variability over south-eastern and eastern Australia. Spatio-temporal variations of seasonal rainfall and their connection to oceanic-atmospheric predictors were analysed. The links between the first two Principal Components of rainfall of each season with lagged Southern Oscillation Index (SOI, Indian Ocean Dipole (IOD and Southern Annular Mode (SAM were season-dependent. The relationship between these climatic indices changed within both inter-seasonal and decadal time scales. Spring and winter rainfalls were continuously positively correlated with lagged (SOI. However, summer rainfall variations indicated negative correlations with lagged SOI which increase from 1970. The correlations between lagged SOI and autumn variations were weak and change to a stronger relationship from 1990. Correlations between lagged (IOD which varied across all seasons have recently been increasing. Variations in rainfall across all seasons were highly correlated with Southern Annular Mode (SAM with different signs. Overall, the relationship between predictors and seasonal rainfall has changed after 1970. The results of running correlations between leading modes of seasonal rainfall and lagged SOI, SAM, and IOD indices indicates non-stationary in these links. The relationships of climatic indices and leading modes of seasonal rainfall changed since 1970, with stronger evidence in case of IOD. Recent changes in the relationships between climatic indices and rainfall need to be considered in climate prediction systems. The results of this study suggests that improvement in statistical regional rainfall forecast system with fixed

  6. On the time variability of gamma-ray sources

    DEFF Research Database (Denmark)

    F. Torres, Diego; Pessah, Martin Elias; E. Romero, Gustavo

    2001-01-01

    We present a Monte Carlo analysis of the recently introduced variability indices $\\tau$ (Tompkins 1999) and $I$ (Zhang et al. 2000 & Torres et al. 2001) for $\\gamma$-ray sources. We explore different variability criteria and prove that these two indices, despite the very different approaches used...

  7. Prediction of Individual Social-Demographic Role Based on Travel Behavior Variability Using Long-Term GPS Data

    Directory of Open Access Journals (Sweden)

    Lei Zhu

    2017-01-01

    Full Text Available With the development of and advances in smartphones and global positioning system (GPS devices, travelers’ long-term travel behaviors are not impossible to obtain. This study investigates the pattern of individual travel behavior and its correlation with social-demographic features. For different social-demographic groups (e.g., full-time employees and students, the individual travel behavior may have specific temporal-spatial-mobile constraints. The study first extracts the home-based tours, including Home-to-Home and Home-to-Non-Home, from long-term raw GPS data. The travel behavior pattern is then delineated by home-based tour features, such as departure time, destination location entropy, travel time, and driving time ratio. The travel behavior variability describes the variances of travelers’ activity behavior features for an extended period. After that, the variability pattern of an individual’s travel behavior is used for estimating the individual’s social-demographic information, such as social-demographic role, by a supervised learning approach, support vector machine. In this study, a long-term (18-month recorded GPS data set from Puget Sound Regional Council is used. The experiment’s result is very promising. The sensitivity analysis shows that as the number of tours thresholds increases, the variability of most travel behavior features converges, while the prediction performance may not change for the fixed test data.

  8. Time-variable gravity potential components for optical clock comparisons and the definition of international time scales

    Science.gov (United States)

    Voigt, C.; Denker, H.; Timmen, L.

    2016-12-01

    The latest generation of optical atomic clocks is approaching the level of one part in 1018 in terms of frequency stability and uncertainty. For clock comparisons and the definition of international time scales, a relativistic redshift effect of the clock frequencies has to be taken into account at a corresponding uncertainty level of about 0.1 m2 s-2 and 0.01 m in terms of gravity potential and height, respectively. Besides the predominant static part of the gravity potential, temporal variations must be considered in order to avoid systematic frequency shifts. Time-variable gravity potential components induced by tides and non-tidal mass redistributions are investigated with regard to the level of one part in 1018. The magnitudes and dominant time periods of the individual gravity potential contributions are investigated globally and for specific laboratory sites together with the related uncertainty estimates. The basics of the computation methods are presented along with the applied models, data sets and software. Solid Earth tides contribute by far the most dominant signal with a global maximum amplitude of 4.2 m2 s-2 for the potential and a range (maximum-to-minimum) of up to 1.3 and 10.0 m2 s-2 in terms of potential differences between specific laboratories over continental and intercontinental scales, respectively. Amplitudes of the ocean tidal loading potential can amount up to 1.25 m2 s-2, while the range of the potential between specific laboratories is 0.3 and 1.1 m2 s-2 over continental and intercontinental scales, respectively. These are the only two contributors being relevant at a 10-17 level. However, several other time-variable potential effects can particularly affect clock comparisons at the 10-18 level. Besides solid Earth pole tides, these are non-tidal mass redistributions in the atmosphere, the oceans and the continental water storage.

  9. Long-term variability of the thunderstorm and hail potential in Europe

    Science.gov (United States)

    Mohr, Susanna; Kunz, Michael; Speidel, Johannes; Piper, David

    2016-04-01

    Severe thunderstorms and associated hazardous weather events such as hail frequently cause considerable damage to buildings, crops, and automobiles, resulting in large monetary costs in many parts of Europe and the world. To relate single extreme hail events to the historic context and to estimate their return periods and possible trends related to climate change, long-term statistics of hail events are required. Due to the local-scale nature of hail and a lack of suitable observation systems, however, hailstorms are not captured reliably and comprehensively for a long period of time. In view of this fact, different proxies (indirect climate data) obtained from sounding stations and regional climate models can be used to infer the probability and intensity of thunderstorms or hailstorms. In contrast to direct observational data, such proxies are available homogeneously over a long time period. The aim of the study is to investigate the potential for severe thunderstorms and their changes over past decades. Statistical analyses of sounding data show that the convective potential over the past 20 - 30 years has significantly increased over large parts of Central Europe, making severe thunderstorms more likely. A similar picture results from analyses of weather types that are most likely associated with damaging hailstorms. These weather patterns have increased, even if only slightly but nevertheless statistically significantly, in the time period from 1971 to 2000. To improve the diagnostics of hail events in regional climate models, a logistic hail model has been developed by means of a multivariate analysis method. The model is based on a combination of appropriate hail-relevant meteorological parameters. The output of the model is a new index that estimates the potential of the atmosphere for hailstorm development, referred to as potential hail index (PHI). Applied to a high-resolved reanalysis run for Europe driven by NCEP/NCAR1, long-term changes of the PHI for

  10. Reaction time variability and related brain activity in methamphetamine psychosis.

    Science.gov (United States)

    Fassbender, Catherine; Lesh, Tyler A; Ursu, Stefan; Salo, Ruth

    2015-03-01

    This study investigated the dynamics of cognitive control instability in methamphetamine (MA) abuse, as well its relationship to substance-induced psychiatric symptoms and drug use patterns. We used an ex-Gaussian reaction time (RT) distribution to examine intraindividual variability (IIV) and excessively long RTs (tau) in an individual's RT on a Stroop task in 30 currently drug-abstinent (3 months to 2 years) MA abusers compared with 27 nonsubstance-abusing control subjects. All subjects underwent functional magnetic resonance imaging while performing the Stroop task, which allowed us to measure the relationship between IIV and tau to functional brain activity. Elevated IIV in the MA compared with the control group did not reach significance; however, when the MA group was divided into those subjects who had experienced MA-induced psychosis (MAP+) (n = 19) and those who had not (n = 11), the MAP+ group had higher average IIV compared with the other groups (p < .03). In addition, although control subjects displayed a relationship between IIV and conflict-related brain activity in bilateral prefrontal cortex such that increased IIV was associated with increased activity, the MAP+ group displayed this relationship in right prefrontal cortex only, perhaps reflecting elevated vigilance in the MAP+ group. Greater IIV did not correlate with severity of use or months MA abstinent. No group differences emerged in tau values. These results suggest increased cognitive instability in those MA-dependent subjects who had experienced MA-induced psychosis. Copyright © 2015 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  11. Spatial-time variability of particulate material content and its composition: From mesoscale to interannual variability

    Science.gov (United States)

    Dudarev, Oleg; Charkin, Alexander; Semiletov, Igor; Gustafsson, Örjan; Vonk, Jorien; Sánchez-García, Laura

    2010-05-01

    The role of the coastal zone in lateral transport and fate of terrestrial organic carbon in the East Siberian Arctic Shelf (ESAS) has not been well studied to date because most recent activities have focused on onshore geomorphologic and geochemical features, while biogeochemical and sedimentation consequences of coastal erosion and riverine runoff into the sea were not studied sufficiently. Here we present the data obtained on joint Russian-US cruises (NOAA and NSF funded) in 2003, 2004, 2005, and in the International Siberian Shelf Study-2008 (ISSS-2008, supported by the Wallenberg Foundation, FEBRAS, NOAA, and the Russian NSF), which characterized a spatial and interannual variability in distribution of particulate material (PM), and its organic carbon and stable isotopes content. Dynamics and composition of PM were studied twice along the Lena River in summer-fall of 2003. Here, the spatial-time dynamics of PM composition (particulate organic carbon (POC), isotopes and mineralogical composition) is considered in connection with changing river runoff and wind patterns. It has been found that the dominant source of POC into the ESAS is coastal erosion, rather than input from the rivers (Lena, Yana, Indigirka, Kolyma). A sharp PM concentration gradient from "freshened/high PM" to "Pacific/low PM" waters was found across the frontal zone. The position of the frontal zone varies significantly from year to year; this difference is mainly attributed to the difference in atmospheric circulation patterns driving the Arctic Ocean circulation. During storms and surges the PM concentration in a single area was increased by 10 times or more (up to 80-242 mg/l) in 2000 and 2005 compared to the 2003 and 2004 PM concentration.

  12. Short-term variability in particle flux: Storms, blooms and river discharge in a coastal sea

    Science.gov (United States)

    Johannessen, Sophia C.; Macdonald, Robie W.; Wright, Cynthia A.; Spear, David J.

    2017-07-01

    The flux and composition of particles sinking in the surface ocean vary on a wide range of time scales. This variability is a component of underwater weather that is analogous to rain. The rain of particles in the coastal ocean is affected by atmospheric events, such as rainstorms and windstorms; by events on land, such as peaks in river discharge or coastal erosion; and by events within the surface ocean, such as phytoplankton blooms. Here, we use a four-year record of sinking particles collected using sediment traps moored at 50 m depth at two locations in the Strait of Georgia, a coastal sea off the west coast of Canada, to determine the relative importance of short-term events to particle flux. We identify four dominant types of particle-flux events: those associated with 1) summer freshet of the Fraser River, 2) rainstorms, 3) phytoplankton blooms, and 4) a jellyfish bloom. The relative importance of these events differs between the southern Strait, where the Fraser River freshet dominates flux and variability, and the northern Strait, where the effects of phytoplankton blooms, rainstorms and small local rivers are more evident. During 2008-2012, half of each year's total flux accumulated over 10-26% of the year in the southern Strait, mainly during the Fraser River freshet. In the northern Strait half of the annual flux accumulated over 22-36% of the year, distributed among small events during spring to fall. The composition of the sinking particulate matter also varied widely, with organic carbon and biogenic silica ranging over 0.70-5.7% (excluding one event) and 0.4-14%, respectively, in the south, compared with 0.17-22% and 0.31-33% in the north. Windstorms had no immediate effect on particle flux in either basin. A large phytoplankton bloom in April 2011, in the northern Strait contributed 25% of the year's organic carbon at that site and 53% of the biogenic silica. A jellyfish bloom in July 2008 contributed 16% of the year's nitrogen and 12% of the year

  13. Electric Vehicle Routing Problem with Charging Time and Variable Travel Time

    Directory of Open Access Journals (Sweden)

    Sai Shao

    2017-01-01

    Full Text Available An electric vehicle routing problem with charging time and variable travel time is developed to address some operational issues such as range limitation and charging demand. The model is solved by using genetic algorithm to obtain the routes, the vehicle departure time at the depot, and the charging plan. Meanwhile, a dynamic Dijkstra algorithm is applied to find the shortest path between any two adjacent nodes along the routes. To prevent the depletion of all battery power and ensure safe operation in transit, electric vehicles with insufficient battery power can be repeatedly recharged at charging stations. The fluctuations in travel time are implemented to reflect a dynamic traffic environment. In conclusion, a large and realistic case study with a road network in the Beijing urban area is conducted to evaluate the model performance and the solution technology and analyze the results.

  14. Variability in rate of cervical dilation in nulliparous women at term.

    Science.gov (United States)

    Incerti, Maddalena; Locatelli, Anna; Ghidini, Alessandro; Ciriello, Elena; Consonni, Sara; Pezzullo, John C

    2011-03-01

    Cervical dilatation is commonly documented on a partogram indicating the expected rate of progress of labor. Although deviations from such a line can be used to indicate abnormal progress, what constitutes the "normal" rate of cervical dilation is still largely unknown. The objectives of this study were to assess the variability of the rate of cervical dilation in nulliparous women and to determine whether the rate of labor was independent of dilation on admission. We analyzed a cohort of consecutive nulliparous women with spontaneous labor at term and singleton fetuses in cephalic presentation. Exclusion criteria were gestational age less than 37 weeks, induction of labor, or the presence of a uterine scar. Management of labor was standardized using set protocols of care. Active labor was diagnosed as regular contractions every 10 minutes or less, lasting more than 40 seconds, with cervical effacement more than 80 percent and dilation of 2 cm. Vaginal examinations were performed by a dedicated midwife every 2 hours. Amniotomy was performed for slow progress or arrest of dilation over 2 hours. Oxytocin was administered for arrest of cervical dilation for 2 hours with membranes ruptured. Data pertaining to cases ending in cesarean delivery were included up to the time of cesarean section. The study sample comprised 1,119 women at 39.7 ± 1.1 weeks with an average duration of labor of 4.1 ± 2.4 hours. The rate of oxytocin use was 27 percent and of epidural analgesia 5 percent. The rate of oxytocin use was inversely related to cervical dilation on admission. Cesarean delivery was performed in 6 percent of women. Duration of labor at each centimeter of cervical dilation on admission showed a broad distribution (e.g., at 4 cm: median = 5.5, range: 0.8-12.5 hr). The rate of labor progression (expressed as the slope of the dilation-vs-time curve) was approximately 1.5 cm/hr, and it was essentially independent of cervical dilation on admission (r = 0.034, p = 0.267). A

  15. Long term variability of Cygnus X-1. VI. Energy-resolved X-ray variability 1999-2011

    Science.gov (United States)

    Grinberg, V.; Pottschmidt, K.; Böck, M.; Schmid, C.; Nowak, M. A.; Uttley, P.; Tomsick, J. A.; Rodriguez, J.; Hell, N.; Markowitz, A.; Bodaghee, A.; Cadolle Bel, M.; Rothschild, R. E.; Wilms, J.

    2014-05-01

    We present the most extensive analysis of Fourier-based X-ray timing properties of the black hole binary Cygnus X-1 to date, based on 12 years of bi-weekly monitoring with RXTE from 1999 to 2011. Our aim is a comprehensive study of timing behavior across all spectral states, including the elusive transitions and extreme hard and soft states. We discuss the dependence of the timing properties on spectral shape and photon energy, and study correlations between Fourier-frequency dependent coherence and time lags with features in the power spectra. Our main results follow. (a) The fractional rms in the 0.125-256 Hz range in different spectral states shows complex behavior that depends on the energy range considered. It reaches its maximum not in the hard state, but in the soft state in the Comptonized tail above 10 keV. (b) The shape of power spectra in hard and intermediate states and the normalization in the soft state are strongly energy-dependent in the 2.1-15 keV range. This emphasizes the need for an energy-dependent treatment of power spectra and a careful consideration of energy- and mass-scaling when comparing the variability of different source types, e.g., black hole binaries and AGN. PSDs during extremely hard and extremely soft states can be easily confused for energies above ~5 keV in the 0.125-256 Hz range. (c) The coherence between energy bands drops during transitions from the intermediate into the soft state but recovers in the soft state. (d) The time lag spectra in soft and intermediate states show distinct features at frequencies related to the frequencies of the main variability components seen in the power spectra and show the same shift to higher frequencies as the source softens. Our results constitute a template for other sources and for physical models for the origin of the X-ray variability. In particular, we discuss how the timing properties of Cyg X-1 can be used to assess the evolution of variability with spectral shape in other black

  16. Excitation of Earth Rotation Variations "Observed" by Time-Variable Gravity

    Science.gov (United States)

    Chao, Ben F.; Cox, C. M.

    2005-01-01

    Time variable gravity measurements have been made over the past two decades using the space geodetic technique of satellite laser ranging, and more recently by the GRACE satellite mission with improved spatial resolutions. The degree-2 harmonic components of the time-variable gravity contain important information about the Earth s length-of-day and polar motion excitation functions, in a way independent to the traditional "direct" Earth rotation measurements made by, for example, the very-long-baseline interferometry and GPS. In particular, the (degree=2, order= 1) components give the mass term of the polar motion excitation; the (2,O) component, under certain mass conservation conditions, gives the mass term of the length-of-day excitation. Combining these with yet another independent source of angular momentum estimation calculated from global geophysical fluid models (for example the atmospheric angular momentum, in both mass and motion terms), in principle can lead to new insights into the dynamics, particularly the role or the lack thereof of the cores, in the excitation processes of the Earth rotation variations.

  17. Localized spectral analysis of global satellite gravity fields for recovering time-variable mass redistributions

    NARCIS (Netherlands)

    Han, S.C.; Ditmar, P.

    2007-01-01

    A spatiospectral localization method is discussed for processing the global geopotential coefficients from satellite mission data to investigate time-variable gravity. The time-variable mass variation signal usually appears associated with a particular geographical area yielding inherently regional

  18. On the effects of small scale space-time variability of rainfall on basin flood response

    Science.gov (United States)

    Paschalis, Athanasios; Fatichi, Simone; Molnar, Peter; Rimkus, Stefan; Burlando, Paolo

    2014-06-01

    The spatio-temporal variability of rainfall, especially at fine temporal and spatial scales can significantly affect flood generation, leading to a large variability in the flood response and uncertainty in its prediction. In this study we quantify the impact of rainfall spatial and temporal structure on the catchment hydrological response based on a numerical experiment. Rainfall ensembles generated using a state-of-the-art space-time stochastic model are used as input into a distributed process-based hydrological model. The sensitivity of the hydrograph to several structural characteristics of storm rainfall for three soil moisture initial conditions is numerically assessed at the basin outlet of an Alpine catchment in central Switzerland. The results highlight that the flood response is strongly affected by the temporal correlation of rainfall and to a lesser extent by its spatial variability. Initial soil moisture conditions play a paramount role in mediating the response. We identify the underlying mechanistic explanations in terms of runoff generation and connectivity of saturated areas that determine the sensitivity of flood response to the spatio-temporal variability of rainfall. We show that the element that mostly influences both the flood peak and the time of peak occurrence is the clustering of saturated areas in the catchment which leads to local enhanced runoff.

  19. Investigation of Social Studies Teachers' Intended Uses of Social Networks in Terms of Various Variables

    Science.gov (United States)

    Akgün, Ismail Hakan

    2016-01-01

    The aim of this research is to determine Social Studies teacher candidates' intended uses of social networks in terms of various variables. The research was carried out by using screening model of quantitative research methods. In the study, "The Social Network Intended Use Scale" was used as a data collection tool. As a result of the…

  20. Variability of breast density assessment in short-term reimaging with digital mammography

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Won Hwa [Department of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of); Moon, Woo Kyung, E-mail: moonwk@snu.ac.kr [Department of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of); Kim, Sun Mi [Department of Radiology, Seoul National University Bundang Hospital, Gyeonggi-do (Korea, Republic of); Yi, Ann [Department of Radiology, Seoul Metropolitan Government Seoul National University, Boramae Medical Center, Seoul (Korea, Republic of); Chang, Jung Min; Koo, Hye Ryoung; Lee, Su Hyun; Cho, Nariya [Department of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2013-10-01

    Objective: To evaluate the variability of breast density assessments in short-term reimaging with digital mammography. Materials and methods: In 186 women, short term (mean interval, 27.6 days) serial digital mammograms including CC and MLO views were obtained without any treatment. Mammographic density assessments were performed by three blinded radiologists for Breast Imaging Report and Data System (BI-RADS, grades 1–4) and visual percentage density (PD) estimation, and by one radiologist for computer-aided PD estimation. The variability of assessments was analyzed according to the age, breast density, and mammography types by multivariate logistic regression. Results: In BI-RADS assessments, 29% (161 of 558) of breast density categories were assessed differently after short-term reimaging and the mean absolute difference in PD for CC and MLO view was 7.6% and 8.1% for visual assessments, and 7.4% and 6.4% for computer-aided assessments, respectively. Among all computer-aided assessments, 29% (54 of 186) of CC view and 22% (41 of 186) of MLO view assessments had discrepancy over 10% in PD. Younger age (<50), greater breast density (grades 3 and 4), and different mammography types were significantly associated with the variability. Conclusion: Considerable variability in breast density assessments occurred in short-term reimaging with digital mammography, particularly in women with younger age and greater breast density and when examined using different types of mammography.

  1. Investigating Lifelong Learning Dispositions of Students Studying English Language and Literature in Terms of Different Variables

    Science.gov (United States)

    Elaldi, Senel

    2015-01-01

    This study aims to determine lifelong learning dispositions of English Language and Literature students in terms of gender, grade levels, and age variables. Descriptive research design was used. The study group consisted of 402 students studying English Language and Literature at Cumhuriyet University in Sivas, Turkey. Research data were collected…

  2. Metabolic Syndrome and Short-Term Heart Rate Variability in Adults with Intellectual Disabilities

    Science.gov (United States)

    Chang, Yaw-Wen; Lin, Jin-Ding; Chen, Wei-Liang; Yen, Chia-Feng; Loh, Ching-Hui; Fang, Wen-Hui; Wu, Li-Wei

    2012-01-01

    Metabolic syndrome (MetS) increases the risk of cardiovascular events. Heart rate variability (HRV) represents autonomic functioning, and reduced HRV significantly increases cardiovascular mortality. The aims of the present paper are to assess the prevalence of MetS in adults with intellectual disabilities (ID), the difference in short-term HRV…

  3. Variability and long-term change in Australian temperature and precipitation extremes

    Directory of Open Access Journals (Sweden)

    Dörte Jakob

    2016-12-01

    We conclude that in assessing the likelihood of climate hazards, one needs to consider the modulation of climate extremes due to both long-term change and climate variability. Our findings imply that when planning for adaptation, different emphasis needs to be given to changing temperature and precipitation extremes.

  4. Short and long term variability of the interrupter technique under field and standardised conditions in 3-6 year old children

    NARCIS (Netherlands)

    Beelen, RMJ; Smit, HA; van Strien, RT; Koopman, LP; Brussee, JE; Brunekreef, B; Gerritsen, J; Merkus, PJFM

    2003-01-01

    Background: The short and long term variability of the interrupter technique was assessed to determine whether interrupter resistance is a stable individual characteristic over time. The effect of field and standardised measurement conditions on the within-subject variability of the interrupter

  5. Precipitable water trends and variability investigated from homogenized global, long-term, GPS and DORIS datasets

    Science.gov (United States)

    Bock, Olivier; Willis, Pacal; Collilieux, Xavier

    2014-05-01

    High-quality, consistent, global, long-term datasets of zenith tropospheric delay (ZTD) and precipitable water (PW) were produced from Global Positioning System (GPS) and Doppler Orbitography Radiopositioning Integrated by Satellite (DORIS) measurements. The GPS dataset (based on IGS repro1 & trop-new) comprises more than 400 sites over the globe among which 120 sites have more than 15 years of data (1995-2010). The DORIS data comprises 81 sites over the globe with 23 sites having more than 15 years of data. The ZTD data were screened using a two-level screening method. The first level uses post-processing information and applies range checks and outlier checks to ZTD and formal error estimates. It rejects less than 3% of the data. The second screening level detects outliers by comparing GPS and DORIS ZTD data with ECMWF reanalysis (ERA-Interim) data and rejects about 1% of the data. There is good consistency between the screened DORIS and GPS data and the ERA-Interim reanalysis data. However, biases and shifts are evidenced in the DORIS and GPS data which potentially result from instrument changes (e.g. replacement of DORIS Alcatel antennas with Starec antennas). Afterward, the GPS and DORIS PW data were homogenized by applying constant offset corrections based on the median difference with respect to ERA-Interim PW data. Such an offset is applied each time a known station equipment change occurs (based on station log files). Precipitable water vapour trends and variability (seasonal cycle, intra-seasonal and inter-annual variability) from GPS, DORIS and ERA-Interim data are compared at common sites with more than 10 or 15 years of data. Good consistency is found between all three datasets. This work demonstrates the high potential of the GPS and DORIS PW datasets for climate monitoring. These datasets may also be used for the verification of climate model simulations and climate data, e.g. PW measurements from radiosondes and satellites.

  6. Trend Change Detection in NDVI Time Series: Effects of Inter-Annual Variability and Methodology

    Science.gov (United States)

    Forkel, Matthias; Carvalhais, Nuno; Verbesselt, Jan; Mahecha, Miguel D.; Neigh, Christopher S.R.; Reichstein, Markus

    2013-01-01

    Changing trends in ecosystem productivity can be quantified using satellite observations of Normalized Difference Vegetation Index (NDVI). However, the estimation of trends from NDVI time series differs substantially depending on analyzed satellite dataset, the corresponding spatiotemporal resolution, and the applied statistical method. Here we compare the performance of a wide range of trend estimation methods and demonstrate that performance decreases with increasing inter-annual variability in the NDVI time series. Trend slope estimates based on annual aggregated time series or based on a seasonal-trend model show better performances than methods that remove the seasonal cycle of the time series. A breakpoint detection analysis reveals that an overestimation of breakpoints in NDVI trends can result in wrong or even opposite trend estimates. Based on our results, we give practical recommendations for the application of trend methods on long-term NDVI time series. Particularly, we apply and compare different methods on NDVI time series in Alaska, where both greening and browning trends have been previously observed. Here, the multi-method uncertainty of NDVI trends is quantified through the application of the different trend estimation methods. Our results indicate that greening NDVI trends in Alaska are more spatially and temporally prevalent than browning trends. We also show that detected breakpoints in NDVI trends tend to coincide with large fires. Overall, our analyses demonstrate that seasonal trend methods need to be improved against inter-annual variability to quantify changing trends in ecosystem productivity with higher accuracy.

  7. Variability in stratification and flushing times of the Gautami ...

    Indian Academy of Sciences (India)

    stretch of 36 km, at 500×50 m grid spacing using. Differential Global Positioning System (DGPS;. Ceeducer, Australia). The DGPS is a satellite-based. Figure 2. Variability of (a) along channel depth and (b) cross-sectional area at transect locations in the Gautami–. Godavari estuary. The numbers on the top indicate station.

  8. The Effect of Gestational Age at Birth on Post-Term Maturation of Heart Rate Variability

    Science.gov (United States)

    Fyfe, Karinna L.; Yiallourou, Stephanie R.; Wong, Flora Y.; Odoi, Alexsandria; Walker, Adrian M.; Horne, Rosemary S.C.

    2015-01-01

    Study Objective: Preterm birth delays maturation of autonomic cardiovascular control, reflected in reduced heart rate variability (HRV) in preterm compared to term infants at term-equivalent age. It has been suggested that immature cardiovascular control contributes to the increased risk for the sudden infant death syndrome (SIDS) in preterm infants. However, the effects of prone sleeping, the major SIDS risk factor, and of gestational age (GA) at birth on HRV have not been assessed in preterm infants beyond term-equivalent age. Subjects and Methods: Very preterm (n = 21; mean GA 29.4 ± 0.3 weeks), preterm (n = 14; mean GA 33.5 ± 0.3 weeks), and term (n = 17; mean GA 40.1 ± 0.3 weeks) infants were recruited and underwent daytime polysomnography at 2–4 weeks, 2–3 months, and 5–6 months post-term corrected age (CA). Infants slept both supine and prone. HRV was assessed in the low frequency (LF) and high frequency (HF) ranges. Results: There was no effect of prone sleeping on HRV parameters in either preterm group. In term infants LF/HF was significantly elevated in the prone position in AS at 2–4 weeks (P preterm compared to both preterm and term infants at 2–3 months CA. Conclusion: Prone sleeping did not significantly impact on heart rate variability (HRV) in preterm infants. However, reduced maturation of high frequency HRV in very preterm infants resulted in significantly altered sympathovagal balance at 2–3 months corrected age, the age of peak sudden infant death syndrome (SIDS) risk. This may contribute to the increased risk of SIDS in infants born at earlier gestational age. Citation: Fyfe KL, Yiallourou SR, Wong FY, Odoi A, Walker AM, Horne RS. The effect of gestational age at birth on post-term maturation of heart rate variability. SLEEP 2015;38(10):1635–1644. PMID:25902805

  9. Expressing Environment Assumptions and Real-time Requirements for a Distributed Embedded System with Shared Variables

    DEFF Research Database (Denmark)

    Tjell, Simon; Fernandes, João Miguel

    2008-01-01

    In a distributed embedded system, it is often necessary to share variables among its computing nodes to allow the distribution of control algorithms. It is therefore necessary to include a component in each node that provides the service of variable sharing. For that type of component, this paper...... discusses how to create a Colored Petri Nets (CPN) model that formally expresses the following elements in a clearly separated structure: (1) assumptions about the behavior of the environment of the component, (2) real-time requirements for the component, and (3) a possible solution in terms of an algorithm...... for the component. The CPN model can be used to validate the environment assumptions and the requirements. The validation is performed by execution of the model during which traces of events and states are automatically generated and evaluated against the requirements....

  10. Long-term variability of supratidal coastal boulder activation in Brittany (France)

    Science.gov (United States)

    Autret, Ronan; Dodet, Guillaume; Suanez, Serge; Roudaut, Gildas; Fichaut, Bernard

    2018-03-01

    High-energy supratidal coastal boulder deposit (SCBD) dynamics were investigated on Vierge Island and Pors Carn Point, north and south of western Brittany, France, respectively. Morphological changes induced by boulder transport and quarrying were quantified using high-resolution topographic survey data taken between 2012 and 2017. Additional in-situ wave parameters and water levels were also recorded over this period (2014-2017) in order to compute the maximum water levels and assess the relationship between SCBD morphological changes and specific hydrodynamic conditions. During extreme water levels (for maximum water levels exceeding a one in ten year event), SCBDs were broadly reworked (up to 40% of the total volume). During lower intensity events, for which maximum water levels were still very high, morphological changes represented 1% to 5% of the total volume. These morphological and hydrodynamic observations were then used to calibrate a chronology of SCBD activation events based on 70 years of hindcast winter maximum water levels. These long-term time-series showed great interannual variability in SCBD activation but no significant long-term trend. Winter-frequency SCBD activation was better correlated to the WEPA index (r = 0.46) than the NAO index (r = 0.1). Therefore, the WEPA index can be considered to be a more significant climate proxy for assessing storm-related geomorphic changes in the temperate latitudes of the N-E Atlantic basin (36°-52° N), including the Brittany coast. The potential of SCBDs as a morphological storm proxy for macrotidal high-energy rocky coasts is addressed.

  11. Discrimination power of short-term heart rate variability measures for CHF assessment.

    Science.gov (United States)

    Pecchia, Leandro; Melillo, Paolo; Sansone, Mario; Bracale, Marcello

    2011-01-01

    In this study, we investigated the discrimination power of short-term heart rate variability (HRV) for discriminating normal subjects versus chronic heart failure (CHF) patients. We analyzed 1914.40 h of ECG of 83 patients of which 54 are normal and 29 are suffering from CHF with New York Heart Association (NYHA) classification I, II, and III, extracted by public databases. Following guidelines, we performed time and frequency analysis in order to measure HRV features. To assess the discrimination power of HRV features, we designed a classifier based on the classification and regression tree (CART) method, which is a nonparametric statistical technique, strongly effective on nonnormal medical data mining. The best subset of features for subject classification includes square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD), total power, high-frequencies power, and the ratio between low- and high-frequencies power (LF/HF). The classifier we developed achieved sensitivity and specificity values of 79.3 % and 100 %, respectively. Moreover, we demonstrated that it is possible to achieve sensitivity and specificity of 89.7 % and 100 %, respectively, by introducing two nonstandard features ΔAVNN and ΔLF/HF, which account, respectively, for variation over the 24 h of the average of consecutive normal intervals (AVNN) and LF/HF. Our results are comparable with other similar studies, but the method we used is particularly valuable because it allows a fully human-understandable description of classification procedures, in terms of intelligible "if … then …" rules.

  12. Long-Term Variability of Airborne Asian Dust Observed from TOMS

    Science.gov (United States)

    Herman, J. R.; Hsu, N. C.; Seftor, C. J.; Holben, B. N.; Holben, B. N.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Recent studies suggest that airborne Asian dust may not only play an important role in the regional radiation budget, but also influence the air quality over North America through long-range transport. In this paper, we use satellite data to investigate the long-term variability of airborne Asian dust as well as the daily variation of the dust aerosol distribution. By combining the Total Ozone Mapping Spectrometer (TOMS) aerosol index with National Centers for Environmental Prediction (NCEP) wind data, our analysis shows a strong correlation between the generation of dust storms in the region and the passage of springtime weather fronts. This is consistent with earlier studies performed by other researchers. According to both the Nimbus-7 and Earth-Probe TOMS data the Takla Makan desert, the Gobi desert, and the and region of Inner Mongolia are major sources of the eastward-flowing airborne Asian dust. Heavily populated areas in eastern China (e.g., Beijing) are often on the primary path of the dust storms originating in these desert regions. The increasing desertification north of the Beijing region has served to exacerbate problems stemming from these storms. The time series derived from 20 years of TOMS aerosol index data shows the first significant satellite evidence of the atmospheric effect of increasing desertification, indicating that the amount of dust blown eastward has increased strongly during the past few years including the year 2000.

  13. Preterm Infants Exhibit Greater Variability in Cerebrovascular Control than Term Infants

    Science.gov (United States)

    Fyfe, Karinna L.; Odoi, Alexsandria; Yiallourou, Stephanie R.; Wong, Flora Y.; Walker, Adrian M.; Horne, Rosemary S.C.

    2015-01-01

    Study Objectives: Sudden infant death syndrome (SIDS) remains an important cause of infant death, particularly among infants born preterm. Prone sleeping is the major risk factor for SIDS and this has recently been shown to alter cerebrovascular control in term infants. As preterm infants are at greater risk for SIDS than those born at term, we hypothesized that their cerebrovascular control in the prone position would be reduced compared to term infants. Patients or Participants: There were 35 preterm (mean gestation 31.2 ± 0.4 w) and 17 term (mean gestation 40.1 ± 0.3 w) infants. Design: Infants underwent daytime polysomnography at 2–4 w, 2–3 mo, and 5–6 mo postterm age. Infants slept both prone and supine and were presented with cardiovascular challenges in the form of 15° head-up tilts (HUT). Measurements and Results: Cerebral tissue oxygenation index (TOI) was recorded using near-infrared spectroscopy (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and mean arterial pressure (MAP) was recorded using a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands). In the prone position TOI increased following the HUT (P < 0.05), whereas no change was seen in the supine position. The overall pattern of response was similar in both groups, but more variable in preterm than term infants (P < 0.05). Conclusions: Cerebrovascular control differs between the prone and supine positions in preterm infants. Although overall the responses to head-up tilts were similar between term and preterm infants, greater variability of responses in preterm infants suggests persisting immaturity of their cerebrovascular control in the first year of life, which may contribute to their increased risk of sudden infant death syndrome. Citation: Fyfe KL, Odoi A, Yiallourou SR, Wong FY, Walker AM, Horne RS. Preterm infants exhibit greater variability in cerebrovascular control than term infants. SLEEP 2015;38(9):1411–1421. PMID:25669192

  14. Short-term variability in halocarbons in relation to phytoplankton pigments in coastal waters of the central eastern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Roy, R.

    The sampling locations, along the Candolim Time-Series Section (CaTS), in coastal waters of the eastern Arabian Sea, are shown in Fig. 1. Water depth at these stations varied between 6 m (G1) and 28 m (G5) whereas samples at G5 were generally collected from a... times. 6 3. Results The short-term variability of halocarbons and pigments has been presented for CaTS station G5, with a brief on hydrography. However, data from stations G1- G4 have been used to derive statistically significant relationships among...

  15. Long-term changes and variability in rainfall and streamflow in Luvuvhu River Catchment, South Africa

    Directory of Open Access Journals (Sweden)

    John O. Odiyo

    2015-07-01

    Full Text Available We investigated long-term changes and variability in daily rainfall and streamflow in the Luvuvhu River Catchment, South Africa. Changes and variability in rainfall and streamflow impact on available water resources and the allocation of these resources. Daily rainfall data for six stations and daily streamflow data for four stations for the period 1920/1921�2005/2006 were grouped into cycles of 5 and 10 years. Daily means and standard deviations were computed for each cycle. Standard deviation was used to define the rainfall and streamflow variability. Linear regression was used to compute trends in 5- and 10-year average rainfall and streamflow and their standard deviations. Paired two-tailed�t-tests (significance level of 0.05 were carried out to verify the spatial variability of rainfall and streamflow in the study area. Mann�Kendall and linear regression were used to determine trend analyses based on long-term annual rainfall and streamflow data. All but two rainfall stations showed decreasing trends in 5- and 10-year mean rainfall; 10-year mean daily rainfall showed decadal rainfall fluctuations. Contrasting trends were observed in 5- and 10-year mean streamflow, indicating that other factors such as anthropogenic activities and impoundments could be impacting on streamflow. Trend directions identified from Mann-Kendall and linear regression analyses of long-term annual rainfall and streamflow were similar to those identified by linear regression of 5- and 10-year mean daily rainfall. Results of paired two-tailed�t-tests verified the spatial variability of rainfall and streamflow in the study area. We have shown that the variability of rainfall and streamflow has increased in the Luvuvhu River Catchment over the 86-year study period.

  16. Climate Variable is Time-Averaged: Dealing with Uncertainty of Paleoclimatic Record Caused by Smoothening of Noisy Variations

    Science.gov (United States)

    Umemura, K.; Ebina, K.

    2014-12-01

    Climate is the average of weather over some time period and shows characteristic behavior in each time scale. In paleoclimatic research, values of climate variables are measured from proxies that give time series of time-averaged variables. Therefore, understanding the dynamics of time-averaged variable is important to investigate climate variations thorough different time scales. In our recent study, we formulated how stochastic dynamics changes corresponding to averaging time intervals using one dimensional first order stochastic differential equation which contains parametrically controlled terms of deterministic single-well or double-well potential force and random force. The dynamics of time-averaged variable is described by conditional probability density function. In the case of single-well, the function is analytically derived as normal distribution with scaling parameters. In the case of double-well potential, the function is obtained as skew generalized normal distribution function through numerical simulations. The mathematical framework of stochastic dynamics of time-averaged variable is general and applicable to analysis of many kinds of climate time series data. In this study, we apply the above framework to the analysis of proxy data from ice core and discuss about time scaling of the past climate variations. We test several models to infer the optimal model description for the data.

  17. Long-term trends and spatial variability of shallow groundwater temperatures beneath Bratislava

    Science.gov (United States)

    Krcmar, David; Benz, Susanne A.; Bayer, Peter; Blum, Philipp; Stankova, Hana

    2017-04-01

    Shallow groundwater temperatures are closely linked to surface temperatures. In recent years several studies have shown that the effects from atmospheric warming can be observed in rural groundwater temperature measurements. However, urban groundwater temperatures are different. Especially shallow aquifers show temperatures that change with the evolution of a city. Temperatures are locally variable and regionally higher when compared to undisturbed rural environments. For several cities, particularly in cold and temperate climate zones, pronounced subsurface urban heat islands have been reported with groundwater temperatures that are increased by several degrees compared to their rural surrounding. Heat release from basements and other urban infrastructure has been identified as a major heat source, superposing the effects from atmospheric warming. A major challenge still is to distinguish between the anthropogenic urban effects and the influence from climate change. In our study, we focus on the conditions in the city of Bratislava in Slovakia, where productive aquifers are hosted by the sediments in the Danube river valley. At selected wells, long-term groundwater temperature measurements have been recorded since the year 2002. These temperature time series are measured in shallow depth and therefore show substantial seasonal variations. Each temperature time series is compared to satellite-derived land surface temperature trends, and a clear correlation is found that supports the strong coupling between atmospheric, land surface and groundwater temperatures. Additionally, it is now possible to analyze the main differences between these two temperature trends for all selected wells and relate them to location specific cases of urban infrastructure that influence groundwater temperatures but not land surface temperatures.

  18. Time variability of cyclonic geostrophic circulation in the Mediterranean

    Directory of Open Access Journals (Sweden)

    J. A. Guijarro

    2006-01-01

    Full Text Available Interannual variability and trends of the surface geostrophic cyclonic circulation and cyclone frequency in Western and Eastern Mediterranean areas are analyzed, based on a cyclone data base derived from the ERA-40 ECWMF reanalysis (within the MEDEX project tasks, spanning from September/1957 to August/2002. In this 45 years, the cyclonic circulation show a significant decrease in the Western Mediterranean, mostly in winter and spring, and an increase in the Eastern, mainly due to the summer and autumn increase in the frequency of thermal lows.

  19. Short-term temporal variability in fish community structure at two western Mediterranean slope locations

    Science.gov (United States)

    Moranta, Joan; Massutí, Enric; Stefanescu, Constantí; Palmer, Miquel; Morales-Nin, Beatriz

    2008-07-01

    Short-term temporal variability in deep-sea demersal fish assemblages is described for two slope areas characterised by different oceanographic conditions, which are situated north (Balearic sub-basin, BsB) and south (Algerian sub-basin, AsB) of the Balearic Islands (western Mediterranean). A total of 75 hauls were analysed from six bottom trawl surveys carried out in the two sub-basins. At BsB, surveys were designed for sampling different slope habitats during April 1991, December 1991, March 1992 and July 1992: (i) a submarine canyon at a depth of around 450 m, (ii) the upper slope at a depth of 600-650 m, and (iii) the middle slope at a depth of around 1200 m. At AsB, surveys were carried out during October 1996 and May 1998, along a continuous transect on the upper, middle and lower slope. The taxonomic composition, ecological parameters (number of species, abundance and biomass) and biomass spectra of the assemblages, as well as the length frequency distribution of the main species, were compared for different seasons and bathymetric ranges. Forty-four demersal species were captured in BsB and 38 in AsB. Helicolenus dactylopterus and Trachyrinchus scabrus were more abundant in BsB, and Hoplostethus mediterraneus, Galeus melastomus and Centroscymnus coelolepis in AsB. Depth was the determinant factor in all the analyses. Species-specific densities (abundance and biomass) showed significant differences between surveys, depth strata and their interaction in BsB. However, survey and its interaction with depth, were not significant in AsB. We also found significant differences in relation to depth and season for the three ecological parameters tested in BsB, but only significant differences in relation to depth in AsB. Biomass spectra showed large differences in relation to depth but only slight between-survey differences, which mainly occurred in the upper slope. The length frequency distributions of single species presented short-term temporal variations, mainly

  20. Generating k-independent variables in constant time

    DEFF Research Database (Denmark)

    Christiani, Tobias Lybecker; Pagh, Rasmus

    2014-01-01

    The generation of pseudorandom elements over finite fields is fundamental to the time, space and randomness complexity of randomized algorithms and data structures. We consider the problem of generating k-independent random values over a finite field F in a word RAM model equipped with constant...... time addition and multiplication in F, and present the first nontrivial construction of a generator that outputs each value in constant time, not dependent on k. Our generator has period length |F| poly log k and uses k poly (log k) log |F| bits of space, which is optimal up to a poly log k factor. We...

  1. Radiocaesium in grazing sheep. A statistical analysis of variability, survey methodology and long term behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Mehli, H.

    1996-05-01

    Since 1987 sheep grazing in the areas of Norway that received Chernobyl-fallout have been monitored before slaughter. These monitoring data formed the basis for development of a model describing the long term behaviour of radiocesium in unimproved pasture showing that in years with good mushroom abundance 70-80% of the radiocesium concentration in sheep is due to fungi consumption. A study of sampling strategy and variability of radiocesium concentration within flocks was also performed. 55 refs., 31 figs., 15 tabs.

  2. HEART RATE VARIABILITY DURING DAYTIME NAPS IN HEALTHY ADULTS: AUTONOMIC PROFILE AND SHORT-TERM RELIABILITY

    OpenAIRE

    Cellini, Nicola; Whitehurst, Lauren N.; McDevitt, Elizabeth A.; Sara C Mednick

    2015-01-01

    In healthy individuals, a reduction in cardiovascular output and a shift to parasympathetic/vagal dominant activity is observed across nocturnal sleep. This cardiac autonomic profile, often measured by heart rate variability (HRV), has been associated with significant benefits for the cardiovascular system. However, little is known about the autonomic profile during daytime sleep. Here we investigated the autonomic profile and the short-term reliability of HRV during daytime naps in 66 health...

  3. Handling Time-dependent Variables : Antibiotics and Antibiotic Resistance

    NARCIS (Netherlands)

    Munoz-Price, L. Silvia; Frencken, Jos F.; Tarima, Sergey; Bonten, Marc

    2016-01-01

    Elucidating quantitative associations between antibiotic exposure and antibiotic resistance development is important. In the absence of randomized trials, observational studies are the next best alternative to derive such estimates. Yet, as antibiotics are prescribed for varying time periods,

  4. Practical Implementations of Real-Time Heart Rate Variability

    National Research Council Canada - National Science Library

    Sastre, Antonio

    2004-01-01

    ... interventions, but to date it has not been possible to use it in real-time (RT) . Because HRV reflects homeostasis in thermoregulation and blood pressure control, it provides a non-invasive "window" into these processes...

  5. Variable Renewable Energy in Long-Term Planning Models: A Multi-Model Perspective

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Wesley [National Renewable Energy Lab. (NREL), Golden, CO (United States); Frew, Bethany [National Renewable Energy Lab. (NREL), Golden, CO (United States); Mai, Trieu [National Renewable Energy Lab. (NREL), Golden, CO (United States); Sun, Yinong [National Renewable Energy Lab. (NREL), Golden, CO (United States); Bistline, John [Electric Power Research Inst. (EPRI), Knoxville, TN (United States); Blanford, Geoffrey [Electric Power Research Inst. (EPRI), Knoxville, TN (United States); Young, David [Electric Power Research Inst. (EPRI), Knoxville, TN (United States); Marcy, Cara [U.S. Energy Information Administration, Washington, DC (United States); Namovicz, Chris [U.S. Energy Information Administration, Washington, DC (United States); Edelman, Risa [US Environmental Protection Agency (EPA), Washington, DC (United States); Meroney, Bill [US Environmental Protection Agency (EPA), Washington, DC (United States); Sims, Ryan [US Environmental Protection Agency (EPA), Washington, DC (United States); Stenhouse, Jeb [US Environmental Protection Agency (EPA), Washington, DC (United States); Donohoo-Vallett, Paul [Dept. of Energy (DOE), Washington DC (United States)

    2017-11-01

    Long-term capacity expansion models of the U.S. electricity sector have long been used to inform electric sector stakeholders and decision-makers. With the recent surge in variable renewable energy (VRE) generators — primarily wind and solar photovoltaics — the need to appropriately represent VRE generators in these long-term models has increased. VRE generators are especially difficult to represent for a variety of reasons, including their variability, uncertainty, and spatial diversity. This report summarizes the analyses and model experiments that were conducted as part of two workshops on modeling VRE for national-scale capacity expansion models. It discusses the various methods for treating VRE among four modeling teams from the Electric Power Research Institute (EPRI), the U.S. Energy Information Administration (EIA), the U.S. Environmental Protection Agency (EPA), and the National Renewable Energy Laboratory (NREL). The report reviews the findings from the two workshops and emphasizes the areas where there is still need for additional research and development on analysis tools to incorporate VRE into long-term planning and decision-making. This research is intended to inform the energy modeling community on the modeling of variable renewable resources, and is not intended to advocate for or against any particular energy technologies, resources, or policies.

  6. Short-term variability of fish condition and growth in estuarine and shallow coastal areas.

    Science.gov (United States)

    Duarte, Irina A; Vasconcelos, Rita P; França, Susana; Batista, Marisa I; Tanner, Susanne; Cabral, Henrique N; Fonseca, Vanessa F

    2018-03-01

    Short-term variability in condition factor: relative condition factor Kn; biochemical condition: RNA:DNA and protein content; and instantaneous growth rates were determined in estuarine and coastal fish. Dicentrarchus labrax, Solea senegalensis and Pomatoschistus microps were sampled in the Tejo estuary, while Trachurus trachurus was sampled in an adjacent shallow coastal area. Variation of condition indices was more frequent at the week scale (sampling periods with fortnight intervals) than at the daily scale (consecutive days in each sampling period) in all species. Water temperature was correlated with biochemical indices, while salinity showed no effect, evidencing the influence of environmental short-term variation (temperature) on biochemical condition in natural populations. Yet, decreasing individual variability in fish condition was observed along the sampled weeks, resulting in a more homogeneous condition of populations, particularly for T. trachurus likely due to a more stable coastal environment. Biochemical indices proved to be sensitive to short-term environmental variability, despite species-specific responses. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Test-retest variability of multifocal electroretinography in normal volunteers and short-term variability in hydroxychloroquine users

    Directory of Open Access Journals (Sweden)

    Browning DJ

    2014-08-01

    Full Text Available David J Browning,1 Chong Lee2 1Charlotte Eye, Ear, Nose and Throat Associates, 2University of North Carolina – Charlotte, Charlotte, NC, USA Purpose: To determine measurement variability of N1P1 amplitudes and the R1/R2 ratio in normal subjects and hydroxychloroquine users without retinopathy. Design: Retrospective, observational study. Subjects: Normal subjects (n=21 and 44 patients taking hydroxychloroquine (n=44 without retinopathy. Methods: Multifocal electroretinography (mfERG was performed twice in one session in the 21 normal subjects and twice within 1 year in the hydroxychloroquine users, during which time no clinical change in macular status occurred. Main outcome measures: N1P1 amplitudes of rings R1–R5, the R1/R2 ratio, and coefficients of repeatability (COR for these measurements. Results: Values for N1P1 amplitudes in hydroxychloroquine users were reduced compared with normal subjects by the known effect of age, but R1/R2 was not affected by age. The COR for R1–R5 ranged from 43% to 52% for normal subjects and from 43% to 59% for hydroxychloroquine users; for R1/R2 the COR was 29% in normal subjects and 45% in hydroxychloroquine users. Conclusion: mfERG measurements show high test-retest variability, limiting the ability of a single mfERG test to influence a decision to stop hydroxychloroquine; corroborative evidence with a different ancillary test is recommended in a suspicious case. Keywords: multifocal electroretinography, hydroxychloroquine, test-retest variability 

  8. Numerical assessment and optimization of discrete-variable time-frequency quantum key distribution

    Science.gov (United States)

    Rödiger, Jasper; Perlot, Nicolas; Mottola, Roberto; Elschner, Robert; Weinert, Carl-Michael; Benson, Oliver; Freund, Ronald

    2017-05-01

    The discrete-variables (DV) time-frequency (TF) quantum key distribution (QKD) protocol is a BB84-like protocol, which utilizes time and frequency as complementary bases. As orthogonal modulations, pulse position modulation (PPM) and frequency shift keying (FSK) are capable of transmitting several bits per symbol, i.e., per photon. However, unlike traditional binary polarization shift keying, PPM and FSK do not allow perfectly complementary bases. So information is not completely deleted when the wrong-basis filters are applied. Since a general security proof does not yet exist, we numerically assess DV-TF-QKD. We show that the secret key rate increases with a higher number of symbols per basis. Further we identify the optimal pulse relations in the two bases in terms of key rate and resistance against eavesdropping attacks.

  9. Long-Term Trend and Seasonal Variability of Horizontal Visibility in Nigerian Troposphere

    Directory of Open Access Journals (Sweden)

    Mukhtar Balarabe

    2015-10-01

    Full Text Available A study of the long-term variability; trend and characteristics of visibility in four zones of Nigeria was carried out. Visibility and other meteorological data from NOAA-NCDC and aerosol index data over Nigeria during 1984–2013 are analyzed using time series and  simple regression model. There are significant decreasing trends for every region and season during the 30-years period; the fluctuations exhibited nearly similar pattern. The 30-year mean visibilities for the four zones (Sahel; North Central; Southern; and Coastal were 13.8 ± 3.9; 14.3 ± 4.2; 13.6 ± 3.5 and 12.8 ± 3.1 km with decreasing trends at the rates of 0.08; 0.06; 0.02 and 0.02 km/year. In all the zones; visibilities were better in summer while worse in Harmattan (dry season. During summer visibility was best in Sahel and North-central; however; in Harmattan visibility was best in southern and coastal zones. It was best between May and June (17.6; 18.9; 16.6 and 15.1 km with a second peak in September. The 30-year seasonal averages were 16.2 ± 2.1; 16.8 ± 2.4; 15.4 ± 1.8 and 14.0 ± 2.2 km in summer; and 10.2 ± 2.5; 10.9 ± 2.9; 11.0 ± 3.3 and 11.4 ± 3.0 km in Harmattan for the respective zones. Sahel and North Central had the worse visibility reduction during Harmattan compared with Southern and coastal areas. An analysis based on simple regression equation reveals a strong and negative relationship between visibility on one hand; AI; and AOD on the other hand. The analysis also discusses the variability regarding the frequency of occurrence of a dust storm; dust haze; and good visibility over the period of study.

  10. Concentrated Hitting Times of Randomized Search Heuristics with Variable Drift

    DEFF Research Database (Denmark)

    Lehre, Per Kristian; Witt, Carsten

    2014-01-01

    Drift analysis is one of the state-of-the-art techniques for the runtime analysis of randomized search heuristics (RSHs) such as evolutionary algorithms (EAs), simulated annealing etc. The vast majority of existing drift theorems yield bounds on the expected value of the hitting time for a target...

  11. Stability Criteria for Differential Equations with Variable Time Delays

    Science.gov (United States)

    Schley, D.; Shail, R.; Gourley, S. A.

    2002-01-01

    Time delays are an important aspect of mathematical modelling, but often result in highly complicated equations which are difficult to treat analytically. In this paper it is shown how careful application of certain undergraduate tools such as the Method of Steps and the Principle of the Argument can yield significant results. Certain delay…

  12. Public Mode Access And Waiting Time Variability In Maiduguri ...

    African Journals Online (AJOL)

    This work examines public mode access and waiting time variations in Maiduguri Metropolitan Area. Data for the study were sought through a comprehensive field survey using a travel diary questionnaire. A total of 623 households were surveyed in 342 dwelling units. The results indicate that variations in modal access and ...

  13. Start time variability and predictability in railroad train and engine freight and passenger service employees.

    Science.gov (United States)

    2014-04-01

    Start time variability in work schedules is often hypothesized to be a cause of railroad employee fatigue because unpredictable work start times prevent employees from planning sleep and personal activities. This report examines work start time diffe...

  14. Preterm Infants Exhibit Greater Variability in Cerebrovascular Control than Term Infants.

    Science.gov (United States)

    Fyfe, Karinna L; Odoi, Alexsandria; Yiallourou, Stephanie R; Wong, Flora Y; Walker, Adrian M; Horne, Rosemary S C

    2015-09-01

    Sudden infant death syndrome (SIDS) remains an important cause of infant death, particularly among infants born preterm. Prone sleeping is the major risk factor for SIDS and this has recently been shown to alter cerebrovascular control in term infants. As preterm infants are at greater risk for SIDS than those born at term, we hypothesized that their cerebrovascular control in the prone position would be reduced compared to term infants. There were 35 preterm (mean gestation 31.2 ± 0.4 w) and 17 term (mean gestation 40.1 ± 0.3 w) infants. Infants underwent daytime polysomnography at 2-4 w, 2-3 mo, and 5-6 mo postterm age. Infants slept both prone and supine and were presented with cardiovascular challenges in the form of 15° head-up tilts (HUT). Cerebral tissue oxygenation index (TOI) was recorded using near-infrared spectroscopy (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and mean arterial pressure (MAP) was recorded using a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands). In the prone position TOI increased following the HUT (P position. The overall pattern of response was similar in both groups, but more variable in preterm than term infants (P positions in preterm infants. Although overall the responses to head-up tilts were similar between term and preterm infants, greater variability of responses in preterm infants suggests persisting immaturity of their cerebrovascular control in the first year of life, which may contribute to their increased risk of sudden infant death syndrome. © 2015 Associated Professional Sleep Societies, LLC.

  15. Investigation of Pedagogical Formation Certification Program Students’ Attitudes Towards Teaching Profession in Terms Of Some Variables

    Directory of Open Access Journals (Sweden)

    Zeynep DEMİRTAŞ

    2016-01-01

    Full Text Available The aim of the current study is to determine the attitudes of students who have training on pedagogical formation in order to be assigned as a teacher towards teaching profession. Within the scope of this general aim the following question is sought an answer: Do pedagogical formation certification program students’ attitudes towards teaching profession change significantly in terms of (1 gender, (2 level of education (grade or graduation (3 department (studying or graduated, (4 faculty/ high school (studying or graduated variables? The present study has the characteristics of descriptive survey model. The participants include 644 students who take pedagogical formation at 2010- 2011 Academic year Spring term at Sakarya University’s Faculty of Education and who are studying at or graduated from Faculty of Arts and Sciences, Faculty of Fine Arts, Faculty of Theology, School of Physical Education and Sports, Health High School, and School of State Conservatory. Attitude Scale towards Teaching Profession (ASTP, developed by Üstüner (2006, is used as a data collection tool. In order to determine whether total scores obtained from data collection tools differ in terms of variables or not T test, analysis of variance, Mann Whitney U Test and Kruskal Wallis H-test are conducted. According to results, the attitudes of students, taking pedagogical formation, towards teaching profession show significant differences in the sense of faculty/ high school variable and do not show a significant difference with regard to gender and level of education variables. Moreover, attitude scores of students differ in accordance with Faculty of Arts and Sciences and Health High School and do not differ with regards to other departments in other faculties or high schools.

  16. Influence of temperature and precipitation variability on near-term snow trends

    Science.gov (United States)

    Mankin, Justin S.; Diffenbaugh, Noah S.

    2015-08-01

    Snow is a vital resource for a host of natural and human systems. Global warming is projected to drive widespread decreases in snow accumulation by the end of the century, potentially affecting water, food, and energy supplies, seasonal heat extremes, and wildfire risk. However, over the next few decades, when the planning and implementation of current adaptation responses are most relevant, the snow response is more uncertain, largely because of uncertainty in regional and local precipitation trends. We use a large (40-member) single-model ensemble climate model experiment to examine the influence of precipitation variability on the direction and magnitude of near-term Northern Hemisphere snow trends. We find that near-term uncertainty in the sign of regional precipitation change does not cascade into uncertainty in the sign of regional snow accumulation change. Rather, temperature increases drive statistically robust consistency in the sign of future near-term snow accumulation trends, with all regions exhibiting reductions in the fraction of precipitation falling as snow, along with mean decreases in late-season snow accumulation. However, internal variability does create uncertainty in the magnitude of hemispheric and regional snow changes, including uncertainty as large as 33 % of the baseline mean. In addition, within the 40-member ensemble, many mid-latitude grid points exhibit at least one realization with a statistically significant positive trend in net snow accumulation, and at least one realization with a statistically significant negative trend. These results suggest that the direction of near-term snow accumulation change is robust at the regional scale, but that internal variability can influence the magnitude and direction of snow accumulation changes at the local scale, even in areas that exhibit a high signal-to-noise ratio.

  17. An application of fractional differintegration to heart rate variability time series.

    Science.gov (United States)

    García-González, Miguel A; Fernández-Chimeno, Mireya; Capdevila, Lluis; Parrado, Eva; Ramos-Castro, Juan

    2013-07-01

    Fractional differintegration is used as a new tool to characterize heart rate variability time series. This paper proposes and focuses in two indexes (αc and fnQ) derived from the fractional differintegration operator. Both indexes are applied to fractional Gaussian noise (fGn) and actual RR time series in order to test their behavior. In the analysis of monofractal time series, αc is linearly related with the Hurst exponent and the estimation of the exponent by the proposed index has lower variance than by using Detrended Fluctuation Analysis (DFA) or the periodogram. The other index fnQ quantifies how the time series adjust to a monofractal time series. Age, postural changes and paced breathing cause significant changes on fnQ while αc only shows significant changes due to posture. In the analyzed actual HRV time series, αc shows good correlation with the short term scaling exponent obtained by DFA, LF/HF and RMSSD while no correlations have been found for fnQ. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  18. Core-temperature sensor ingestion timing and measurement variability.

    Science.gov (United States)

    Domitrovich, Joseph W; Cuddy, John S; Ruby, Brent C

    2010-01-01

    Telemetric core-temperature monitoring is becoming more widely used as a noninvasive means of monitoring core temperature during athletic events. To determine the effects of sensor ingestion timing on serial measures of core temperature during continuous exercise. Crossover study. Outdoor dirt track at an average ambient temperature of 4.4°C ± 4.1°C and relative humidity of 74.1% ± 11.0%. Seven healthy, active participants (3 men, 4 women; age  =  27.0 ± 7.5 years, height  =  172.9 ± 6.8 cm, body mass  =  67.5 ± 6.1 kg, percentage body fat  =  12.7% ± 6.9%, peak oxygen uptake [Vo(2peak)]  =  54.4 ± 6.9 mL•kg⁻¹•min⁻¹) completed the study. Participants completed a 45-minute exercise trial at approximately 70% Vo(2peak). They consumed core-temperature sensors at 24 hours (P1) and 40 minutes (P2) before exercise. Core temperature was recorded continuously (1-minute intervals) using a wireless data logger worn by the participants. All data were analyzed using a 2-way repeated-measures analysis of variance (trial × time), Pearson product moment correlation, and Bland-Altman plot. Fifteen comparisons were made between P1 and P2. The main effect of time indicated an increase in core temperature compared with the initial temperature. However, we did not find a main effect for trial or a trial × time interaction, indicating no differences in core temperature between the sensors (P1  =  38.3°C ± 0.2°C, P2  =  38.3°C ± 0.4°C). We found no differences in the temperature recordings between the 2 sensors. These results suggest that assumed sensor location (upper or lower gastrointestinal tract) does not appreciably alter the transmission of reliable and repeatable measures of core temperature during continuous running in the cold.

  19. Time-Variable Phenomena in the Jovian System

    Science.gov (United States)

    Belton, Michael J. S. (Editor); West, Robert A. (Editor); Rahe, Jurgen (Editor); Pereyda, Margarita

    1989-01-01

    The current state of knowledge of dynamic processes in the Jovian system is assessed and summaries are provided of both theoretical and observational foundations upon which future research might be based. There are three sections: satellite phenomena and rings; magnetospheric phenomena, Io's torus, and aurorae; and atmospheric phenomena. Each chapter discusses time dependent theoretical framework for understanding and interpreting what is observed; others describe the evidence and nature of observed changes or their absence. A few chapters provide historical perspective and attempt to present a comprehensive synthesis of the current state of knowledge.

  20. Variability of Capillary Refill Time among Physician Measurements.

    Science.gov (United States)

    Sheridan, David C; Baker, Steven D; Kayser, Susan A; Jones, David; Hansen, Matthew L

    2017-11-01

    The assessment of capillary refill time (CRT) is a common physical examination technique. However, despite its importance and its widespread use, there is little standardization, which can lead to inaccurate assessments. In this article, we assessed how different physicians estimate CRT. We hypothesized that when different physicians are presented with the same recordings of CRT, clinicians will, on average, provide different CRT estimates. Using recordings of different fingertip compressions, physicians assessed and documented when capillary refill had returned to normal. Videos were recorded of the fingertips only, with no other identifying markers or subject characteristics provided. Videos were shown at one-quarter speed to allow time for recognition and response to the capillary refill. The primary outcome was physician estimates of CRT for each video recording. An analysis of variance regression revealed significant differences in physician estimates of CRT when examining the same CRT videos from 34 subjects. Further regression analyses reveal the importance of controlling for the physician that is examining the patient when predicting a patient's CRT. Results indicate that some physicians gave, on average, slower CRT estimates, whereas others gave, on average, faster CRT estimates. Objective approaches and innovations in assessment of capillary refill have the potential to increase the diagnostic accuracy of this important clinical examination finding. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. On the stability and convergence of the time-fractional variable order telegraph equation

    Science.gov (United States)

    Atangana, Abdon

    2015-07-01

    In this work, we have generalized the time-fractional telegraph equation using the concept of derivative of fractional variable order. The generalized equation is called time-fractional variable order telegraph equation. This new equation was solved numerically via the Crank-Nicholson scheme. Stability and convergence of the numerical solution were presented in details. Numerical simulations of the approximate solution of the time-fractional variable order telegraph equation were presented for different values of the grid point.

  2. Climate Variability Impacts in the Long Term: Hazelnut Yield in Turkey

    Science.gov (United States)

    An, Nazan; Turp, M. Tufan; Kurnaz, M. Levent

    2017-04-01

    Many studies indicating changes in agricultural productivity due to climate change examine the impact of climate change on crop productivity and do not take into account the impact of climate variability in the long run. We have considered the hazelnut crop, which is the most exported crop of Turkey and we tried to see how the fruit yield has changed based on climate variability in the long term. Correspondingly, we have used the minimum, maximum temperature values, total precipitation, relative humidity, duration of sunshine, growing degree days and other related indices obtained from the regional climate model called RegCM as the climate data for the future period of 2020-2049 and the reference period of 1991-2012. Accordingly, in the study, the effects of climate variability on the production of hazelnut, mostly growing in the eastern part of the Black Sea and the Marmara region were determined and future studies and evaluations were conducted to show that they lead decision makers in terms of product management in Turkey. Acknowledgement: This research has been supported by Bogazici University Research Fund Grant Number 12220.

  3. Long-term Spectral Variability of the Ultraluminous X-Ray Source Holmberg IX X–1

    Science.gov (United States)

    Jithesh, V.; Misra, Ranjeev; Wang, Zhongxiang

    2017-11-01

    We investigate the long-term spectral variability in the ultraluminous X-ray source Holmberg IX X–1. By analyzing the data from 8 Suzaku and 13 XMM-Newton observations conducted between 2001 and 2015, we perform a detailed spectral modeling for all spectra with simple models and complex physical models. We find that the spectra can be well explained by a disk-plus-thermal-Comptonization model. Applying this model, we unveil correlations between the X-ray luminosity ({L}{{X}}) and the spectral parameters. One particular correlation is the statistically significant positive correlation between {L}{{X}} and the photon index (Γ), while at the high luminosities of > 2× {10}40 {erg} {{{s}}}-1, the source becomes marginally hard, which results in a change in the slope of the {{Γ }}{--}{L}{{X}} correlation. Similar variability behavior is observed in the optical depth of the source around {L}{{X}}∼ 2× {10}40 {erg} {{{s}}}-1 as the source becomes more optically thick. We consider the scenario that a corona covers the inner part of the disk, and the correlations can be explained as being driven by the variability of seed photons from the disk input into the corona. On the basis of the disk-corona model, we discuss the physical processes that are possibly indicated by the variability of the spectral parameters. Our analysis reveals the complex variability behavior of Holmberg IX X–1 and the variability mechanism is likely related to the geometry of the X-ray-emitting regions.

  4. Intra-Night Variability of OJ 287 with Long-Term Multiband Optical Monitoring

    Directory of Open Access Journals (Sweden)

    Wei Zeng

    2017-11-01

    Full Text Available We present long-term optical multi-band photometric monitoring of the blazar OJ 287 from 6 March 2010 to 3 April 2016, with high temporal resolution in the V R I -bands. The flux variations and colour-magnitude variations on long and short timescales were investigated to understand the emission mechanisms. In our observation, the major outbursts occurred in January 2016, as predicted by the binary pair of black holes model for OJ 287, with F v a r of 1.3∼2.1%, and variability amplitude (Amp of 5.8∼9.0%. The intra-night variability (IDV durations were from 18.5 to 51.3 min, and the minimal variability timescale was about 4.7 min. The colour-magnitude variation showed a weak positive correlation on the long timescale with Pearson’s r = 0 . 450 , while a negative correlation was found on intra-night timescales. We briefly discuss the possible physical mechanisms that are most likely to be responsible for the observed flux and colour-magnitude correlation variability.

  5. Impact of short-term temperature variability on emergency hospital admissions for schizophrenia stratified by season of birth

    Science.gov (United States)

    Zhao, Desheng; Zhang, Xulai; Xu, Zhiwei; Cheng, Jian; Xie, Mingyu; Zhang, Heng; Wang, Shusi; Li, Kesheng; Yang, Huihui; Wen, Liying; Wang, Xu; Su, Hong

    2017-04-01

    Diurnal temperature range (DTR) and temperature change between neighboring days (TCN) are important meteorological indicators closely associated with global climate change. However, up to date, there have been no studies addressing the impacts of both DTR and TCN on emergency hospital admissions for schizophrenia. We conducted a time-series analysis to assess the relationship between temperature variability and daily schizophrenia onset in Hefei, an inland city in southeast China. Daily meteorological data and emergency hospital admissions for schizophrenia from 2005 to 2014 in Hefei were collected. After stratifying by season of birth, Poisson generalized linear regression combined with distributed lag nonlinear model (DLNM) was used to examine the relationship between temperature variability and schizophrenia, adjusting for long-term trend and seasonality, mean temperature, and relative humidity. Our analysis revealed that extreme temperature variability may increase the risk for schizophrenia onset among patients born in spring, while no such association was found in patients born in summer and autumn. In patients born in spring, the relative risks of extremely high DTR comparing the 95th and 99th percentiles with the reference (50th, 10 °C) at 3-day lag were 1.078 (95 % confidence interval (CI) 1.025-1.135) and 1.159 (95 % CI 1.050-1.279), respectively. For TCN effects, only comparing 99th percentile with reference (50th, 0.7 °C) was significantly associated with emergency hospital admissions for schizophrenia (relative risk (RR) 1.111, 95 % CI 1.002-1.231). This study suggested that exposure to extreme temperature variability in short-term may trigger later days of schizophrenia onset for patients born in spring, which may have important implications for developing intervention strategies to prevent large temperature variability exposure.

  6. On the use of variability time-scales as an early classifier of radio transients and variables

    Science.gov (United States)

    Pietka, M.; Staley, T. D.; Pretorius, M. L.; Fender, R. P.

    2017-11-01

    We have shown previously that a broad correlation between the peak radio luminosity and the variability time-scales, approximately L ∝ τ5, exists for variable synchrotron emitting sources and that different classes of astrophysical sources occupy different regions of luminosity and time-scale space. Based on those results, we investigate whether the most basic information available for a newly discovered radio variable or transient - their rise and/or decline rate - can be used to set initial constraints on the class of events from which they originate. We have analysed a sample of ≈800 synchrotron flares, selected from light curves of ≈90 sources observed at 5-8 GHz, representing a wide range of astrophysical phenomena, from flare stars to supermassive black holes. Selection of outbursts from the noisy radio light curves has been done automatically in order to ensure reproducibility of results. The distribution of rise/decline rates for the selected flares is modelled as a Gaussian probability distribution for each class of object, and further convolved with estimated areal density of that class in order to correct for the strong bias in our sample. We show in this way that comparing the measured variability time-scale of a radio transient/variable of unknown origin can provide an early, albeit approximate, classification of the object, and could form part of a suite of measurements used to provide early categorization of such events. Finally, we also discuss the effect scintillating sources will have on our ability to classify events based on their variability time-scales.

  7. An approach for estimating time-variable rates from geodetic time series

    Science.gov (United States)

    Didova, Olga; Gunter, Brian; Riva, Riccardo; Klees, Roland; Roese-Koerner, Lutz

    2016-11-01

    There has been considerable research in the literature focused on computing and forecasting sea-level changes in terms of constant trends or rates. The Antarctic ice sheet is one of the main contributors to sea-level change with highly uncertain rates of glacial thinning and accumulation. Geodetic observing systems such as the Gravity Recovery and Climate Experiment (GRACE) and the Global Positioning System (GPS) are routinely used to estimate these trends. In an effort to improve the accuracy and reliability of these trends, this study investigates a technique that allows the estimated rates, along with co-estimated seasonal components, to vary in time. For this, state space models are defined and then solved by a Kalman filter (KF). The reliable estimation of noise parameters is one of the main problems encountered when using a KF approach, which is solved by numerically optimizing likelihood. Since the optimization problem is non-convex, it is challenging to find an optimal solution. To address this issue, we limited the parameter search space using classical least-squares adjustment (LSA). In this context, we also tested the usage of inequality constraints by directly verifying whether they are supported by the data. The suggested technique for time-series analysis is expanded to classify and handle time-correlated observational noise within the state space framework. The performance of the method is demonstrated using GRACE and GPS data at the CAS1 station located in East Antarctica and compared to commonly used LSA. The results suggest that the outlined technique allows for more reliable trend estimates, as well as for more physically valuable interpretations, while validating independent observing systems.

  8. Examining the Pre - competition Anxiety Levels of Sportsmen Participating in a Folk Dance Branch in Terms of Some Variables

    Directory of Open Access Journals (Sweden)

    Serkan HACICAFEROĞLU

    2015-08-01

    Full Text Available This study was carried out with in order to determine the pre - competition anxiety levels of sportsmen participating in the Turkish Folk Dance branch in terms of some variables. The population of the study, which was carried out using a general screening model, consisted of 253 sportsmen, partici pated with the local halay dance in the group competition, organized by the Turkish Folk Dance Federation in city of Malatya , and its sampling consisted of 187 sportsmen chosen from the population by a random method. State (instantaneous Anxiety part of t he State - Trait Continuous Anxiety Scale was used in the study. In analyzing the data, frequency, percentage, standard deviation, arithmetic mean, t - test and one - way analysis of variance (ANOVA and Tukey's test were used in the study to find the source of the difference. As the result of the study, it has been determined that the ove rall arithmetic mean of the pre - competition instantaneous anxiety state felt by the sportsmen, statistically was 2. 34. A statistically significant difference was found in the r esearch in terms of pre - competition instantaneous anxiety state of feeling of the sportsmen, depending on the variables of gender, age and folk playing time. Nonetheless, depending on the gender, it was determined in the research, that the sportsmen of 2 0 - 22 and 17 - 19 age groups, in favour of the female athletes and according to the age variable, the sportsmen who played folk dances less than a year according to the dancing time variable, felt more pre - competition instantaneous anxiety compared to the sportsmen of other groups.

  9. Seasonal variability in Arctic temperatures during early Eocene time

    Science.gov (United States)

    Eberle, Jaelyn J.; Fricke, Henry C.; Humphrey, John D.; Hackett, Logan; Newbrey, Michael G.; Hutchison, J. Howard

    2010-08-01

    As a deep time analog for today's rapidly warming Arctic region, early Eocene (52-53 Ma) rock on Ellesmere Island in Canada's High Arctic (˜ 79°N.) preserves evidence of lush swamp forests inhabited by turtles, alligators, primates, tapirs, and hippo-like Coryphodon. Although the rich flora and fauna of the early Eocene Arctic imply warmer, wetter conditions than at present, the quantification of Eocene Arctic climate has been more elusive. By analyzing oxygen isotope ratios of biogenic phosphate from mammal, fish, and turtle fossils from a single locality on central Ellesmere Island, we infer early Eocene Arctic temperatures, including mean annual temperature (MAT) of ˜ 8 °C, mean annual range in temperature of ˜ 16.5-19 °C, warm month mean temperature of 19-20 °C, and cold month mean temperature of 0-3.5 °C. Our seasonal range in temperature is similar to the range in estimated MAT obtained using different proxies. In particular, relatively high estimates of early Eocene Arctic MAT and SST by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether (GDGT) membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine Crenarchaeota fall close to our warm month temperature, suggesting a bias towards summer values. From a paleontologic perspective, our temperature estimates verify that alligators and tortoises, by way of nearest living relative-based climatic inference, are viable paleoclimate proxies for mild, above-freezing year-round temperatures. Although for both of these reptilian groups, past temperature tolerances probably were greater than in living descendants.

  10. Variable speed wind turbine control by discrete-time sliding mode approach.

    Science.gov (United States)

    Torchani, Borhen; Sellami, Anis; Garcia, Germain

    2016-05-01

    The aim of this paper is to propose a new design variable speed wind turbine control by discrete-time sliding mode approach. This methodology is designed for linear saturated system. The saturation constraint is reported on inputs vector. To this end, the back stepping design procedure is followed to construct a suitable sliding manifold that guarantees the attainment of a stabilization control objective. It is well known that the mechanisms are investigated in term of the most proposed assumptions to deal with the damping, shaft stiffness and inertia effect of the gear. The objectives are to synthesize robust controllers that maximize the energy extracted from wind, while reducing mechanical loads and rotor speed tracking combined with an electromagnetic torque. Simulation results of the proposed scheme are presented. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  11. Dynamic sensorimotor planning during long-term sequence learning: the role of variability, response chunking and planning errors.

    Science.gov (United States)

    Verstynen, Timothy; Phillips, Jeff; Braun, Emily; Workman, Brett; Schunn, Christian; Schneider, Walter

    2012-01-01

    Many everyday skills are learned by binding otherwise independent actions into a unified sequence of responses across days or weeks of practice. Here we looked at how the dynamics of action planning and response binding change across such long timescales. Subjects (N = 23) were trained on a bimanual version of the serial reaction time task (32-item sequence) for two weeks (10 days total). Response times and accuracy both showed improvement with time, but appeared to be learned at different rates. Changes in response speed across training were associated with dynamic changes in response time variability, with faster learners expanding their variability during the early training days and then contracting response variability late in training. Using a novel measure of response chunking, we found that individual responses became temporally correlated across trials and asymptoted to set sizes of approximately 7 bound responses at the end of the first week of training. Finally, we used a state-space model of the response planning process to look at how predictive (i.e., response anticipation) and error-corrective (i.e., post-error slowing) processes correlated with learning rates for speed, accuracy and chunking. This analysis yielded non-monotonic association patterns between the state-space model parameters and learning rates, suggesting that different parts of the response planning process are relevant at different stages of long-term learning. These findings highlight the dynamic modulation of response speed, variability, accuracy and chunking as multiple movements become bound together into a larger set of responses during sequence learning.

  12. Dynamic sensorimotor planning during long-term sequence learning: the role of variability, response chunking and planning errors.

    Directory of Open Access Journals (Sweden)

    Timothy Verstynen

    Full Text Available Many everyday skills are learned by binding otherwise independent actions into a unified sequence of responses across days or weeks of practice. Here we looked at how the dynamics of action planning and response binding change across such long timescales. Subjects (N = 23 were trained on a bimanual version of the serial reaction time task (32-item sequence for two weeks (10 days total. Response times and accuracy both showed improvement with time, but appeared to be learned at different rates. Changes in response speed across training were associated with dynamic changes in response time variability, with faster learners expanding their variability during the early training days and then contracting response variability late in training. Using a novel measure of response chunking, we found that individual responses became temporally correlated across trials and asymptoted to set sizes of approximately 7 bound responses at the end of the first week of training. Finally, we used a state-space model of the response planning process to look at how predictive (i.e., response anticipation and error-corrective (i.e., post-error slowing processes correlated with learning rates for speed, accuracy and chunking. This analysis yielded non-monotonic association patterns between the state-space model parameters and learning rates, suggesting that different parts of the response planning process are relevant at different stages of long-term learning. These findings highlight the dynamic modulation of response speed, variability, accuracy and chunking as multiple movements become bound together into a larger set of responses during sequence learning.

  13. Analysis of the short-term overproduction capability of variable speed wind turbines

    DEFF Research Database (Denmark)

    Hansen, Anca Daniela; Altin, Müfit; Margaris, Ioannis D.

    2014-01-01

    Emphasis in this article is on variable speed wind turbines (VSWTs) capability to provide short-term overproduction and better understanding of VSWTs’ mechanical and electrical limits to deliver such support. VSWTs’ short-term overproduction capability is of primary concern for the transmission...... system operators (TSOs) in the process of restoring critical situations during large frequency excursions in power systems with high wind power penetration. This study is conducted on a simplified generic model for VSWTs with full scale power converter (Type IV), which includes several adjustments...... and extensions of the Type IV standard wind turbine model proposed by the IEC Committee in IEC 61400-27-1. This modified standard model is able to account for dynamic features relevant for integrating active power ancillary services in wind power plants, such as frequency support capabilities. The performance...

  14. Space-time LAI variability in Northern Puglia (Italy) from SPOT VGT data.

    Science.gov (United States)

    Balacco, Gabriella; Figorito, Benedetto; Tarantino, Eufemia; Gioia, Andrea; Iacobellis, Vito

    2015-07-01

    The vegetation space-time variability during 1999-2010 in the North of the Apulian region (Southern Italy) was analysed using SPOT VEGETATION (VGT) sensor data. Three bands of VEGETATION (RED, NIR and SWIR) were used to implement the vegetation index named reduced simple ratio (RSR) to derive leaf area index (LAI). The monthly average LAI is an indicator of biomass and canopy cover, while the difference between the annual maximum and minimum LAI is an indicator of annual leaf turnover. The space-time distribution of LAI at the catchment scale was analysed over the examined period to detect the consistency of vegetation dynamics in the study area. A diffuse increase of LAI was observed in the examined years that cannot be directly explained only in terms of increasing water availability. Thus, in order to explain such a general behaviour in terms of climatic factors, the analysis was performed upon stratification of land cover classes, focusing on the most widespread species: forest and wheat. An interesting ascending-descending behaviour was observed in the relationship between inter-annual increments of maximum LAI and rainfall, and in particular, a strong negative correlation was found when the rainfall amount in January and February exceeded a critical threshold of about 100 mm.

  15. Recovering the time-variable gravitational field using satellite gradiometry: requirements and gradiometer concept

    Science.gov (United States)

    Douch, Karim; Müller, Jürgen; Heinzel, Gerhard; Wu, Hu

    2017-04-01

    The successful GRACE mission and its far-reaching benefits have highlighted the interest to continue and extend the mapping of the Earth's time-variable gravitational field with follow-on missions and ideally a higher spatiotemporal resolution. Here, we would like to put forward satellite gravitational gradiometry as an alternative solution to satellite-to-satellite tracking for future missions. Besides the higher sensitivity to smaller scales compared to GRACE-like missions, a gradiometry mission would only require one satellite and would provide a direct estimation of a functional of the gravitational field. GOCE, the only gradiometry mission launched so far, was not sensitive enough to map the time-variable part of the gravity field. However, the unprecedented precision of the state-of-the-art optical metrology system on-board the LISA PATHFINDER satellite has opened the way to more performant space inertial sensors. We will therefore examine whether it is technically possible to go beyond GOCE performances and to quantify to what extent the time-variable gravitational field could be determined. First, we derive the requirements on the knowledge of the attitude and the position of the satellite and on the measured gradients in terms of sensitivity and calibration accuracy for a typical repeat low-orbit. We conclude in particular that a noise level smaller than 0.1 mE/√Hz- is required in the measurement bandwidth [5x10-4 ; 10-2]Hz so as to be sensitive to the time-variable gravity signal. We introduce then the design and characteristics of the new gradiometer concept and give an assessment of its noise budget. Contrary to the GOCE electrostatic gradiometer, the position of the test-mass in the accelerometer is measured here by laser interferometry rather than by a capacitive readout system, which improves the overall measurement chain. Finally, the first results of a performance analysis carried out thanks to an end-to-end simulator are discussed and compared

  16. Variable separation for time fractional advection-dispersion equation with initial and boundary conditions

    Directory of Open Access Journals (Sweden)

    Zhang Sheng

    2016-01-01

    Full Text Available In this paper, variable separation method combined with the properties of Mittag-Leffler function is used to solve a variable-coefficient time fractional advection-dispersion equation with initial and boundary conditions. As a result, a explicit exact solution is obtained. It is shown that the variable separation method can provide a useful mathematical tool for solving the time fractional heat transfer equations.

  17. Constructing Proxy Variables to Measure Adult Learners' Time Management Strategies in LMS

    Science.gov (United States)

    Jo, Il-Hyun; Kim, Dongho; Yoon, Meehyun

    2015-01-01

    This study describes the process of constructing proxy variables from recorded log data within a Learning Management System (LMS), which represents adult learners' time management strategies in an online course. Based on previous research, three variables of total login time, login frequency, and regularity of login interval were selected as…

  18. Evaluation of Online Log Variables That Estimate Learners' Time Management in a Korean Online Learning Context

    Science.gov (United States)

    Jo, Il-Hyun; Park, Yeonjeong; Yoon, Meehyun; Sung, Hanall

    2016-01-01

    The purpose of this study was to identify the relationship between the psychological variables and online behavioral patterns of students, collected through a learning management system (LMS). As the psychological variable, time and study environment management (TSEM), one of the sub-constructs of MSLQ, was chosen to verify a set of time-related…

  19. Measurement of the effect of Isha Yoga on cardiac autonomic nervous system using short-term heart rate variability

    Directory of Open Access Journals (Sweden)

    Krishnan Muralikrishnan

    2012-01-01

    Full Text Available Background: Beneficial effects of Yoga have been postulated to be due to modulation of the autonomic nervous system. Objective: To assess the effect of Isha Yoga practices on cardiovascular autonomic nervous system through short-term heart rate variability (HRV. Design of the Study: Short-term HRV of long-term regular healthy 14 (12 males and 2 females Isha Yoga practitioners was compared with that of age- and gender-matched 14 (12 males and 2 females non-Yoga practitioners. Methods and Materials: ECG Lead II and respiratory movements were recorded in both groups using Polyrite during supine rest for 5 min and controlled deep breathing for 1 minute. Frequency domain analysis [RR interval is the mean of distance between subsequent R wave peaks in ECG], low frequency (LF power, high frequency (HF power, LF normalized units (nu, HF nu, LF/HF ratio] and time domain analysis [Standard Deviation of normal to normal interval (SDNN, square of mean squared difference of successive normal to normal intervals (RMSSD, normal to normal intervals which are differing by 50 ms (NN50, and percentage of NN50 (pNN50] of HRV variables were analyzed for supine rest. Time domain analysis was recorded for deep breathing. Results: Results showed statistically significant differences between Isha Yoga practitioners and controls in both frequency and time domain analyses of HRV indices, with no difference in resting heart rate between the groups. Conclusions: Practitioners of Isha Yoga showed well-balanced beneficial activity of vagal efferents, an overall increased HRV, and sympathovagal balance, compared to non-Yoga practitioners during supine rest and deep breathing.

  20. Measurement of the effect of Isha Yoga on cardiac autonomic nervous system using short-term heart rate variability.

    Science.gov (United States)

    Muralikrishnan, Krishnan; Balakrishnan, Bhavani; Balasubramanian, Kabali; Visnegarawla, Fehmida

    2012-04-01

    Beneficial effects of Yoga have been postulated to be due to modulation of the autonomic nervous system. To assess the effect of Isha Yoga practices on cardiovascular autonomic nervous system through short-term heart rate variability (HRV). Short-term HRV of long-term regular healthy 14 (12 males and 2 females) Isha Yoga practitioners was compared with that of age- and gender-matched 14 (12 males and 2 females) non-Yoga practitioners. ECG Lead II and respiratory movements were recorded in both groups using Polyrite during supine rest for 5 min and controlled deep breathing for 1 minute. Frequency domain analysis [RR interval is the mean of distance between subsequent R wave peaks in ECG], low frequency (LF) power, high frequency (HF) power, LF normalized units (nu), HF nu, LF/HF ratio] and time domain analysis [Standard Deviation of normal to normal interval (SDNN), square of mean squared difference of successive normal to normal intervals (RMSSD), normal to normal intervals which are differing by 50 ms (NN50), and percentage of NN50 (pNN50)] of HRV variables were analyzed for supine rest. Time domain analysis was recorded for deep breathing. Results showed statistically significant differences between Isha Yoga practitioners and controls in both frequency and time domain analyses of HRV indices, with no difference in resting heart rate between the groups. Practitioners of Isha Yoga showed well-balanced beneficial activity of vagal efferents, an overall increased HRV, and sympathovagal balance, compared to non-Yoga practitioners during supine rest and deep breathing.

  1. Extreme values of snow-related variables in Mediterranean regions: trends and long-term forecasting in Sierra Nevada (Spain

    Directory of Open Access Journals (Sweden)

    M. J. Pérez-Palazón

    2015-06-01

    Full Text Available Mountain areas in Mediterranean regions constitute key monitoring points for climate variability and its impacts, but long time datasets are not always available due to the difficult access to high areas, relevant for capturing temperature and precipitation regimes, and the predominance of cloudy remote sensing images during the snow season. Sierra Nevada National Park (South Spain, with altitudes higher than 3500 m a.s.l., is part of the Global Change in Mountain Regions network. Snow occurrence just 40 km from the seaside determines a wide range of biodiversity, a snowmelt fluvial regime, and the associated ecosystem services. This work presents the local trend analysis of weather variables at this area together with additional snow-related variables. For this, long term point and distributed observations from weather stations and remote sensing sources were studied and used as input and calibration datasets of a physically based snow model to derive long term series of mean and maximum daily fraction of snow covered area, annual number of days with snow, annual number of days with precipitation, mean and maximum mean daily snow water equivalent, and snowmelt and evaporation volumes. The joint analysis of weather and snow variables showed a decrease trend in the persistence and extent of the snow cover area. The precipitation regime, rather than the temperature trend, seems to be the most relevant driver on the snow regime forcing in Mediterranean areas. This poses a constraint for rigorous scenario analysis in these regions, since the precipitation pattern is poorly approximated by climatic models in these regions.

  2. Extreme values of snow-related variables in Mediterranean regions: trends and long-term forecasting in Sierra Nevada (Spain)

    Science.gov (United States)

    Pérez-Palazón, M. J.; Pimentel, R.; Herrero, J.; Aguilar, C.; Perales, J. M.; Polo, M. J.

    2015-06-01

    Mountain areas in Mediterranean regions constitute key monitoring points for climate variability and its impacts, but long time datasets are not always available due to the difficult access to high areas, relevant for capturing temperature and precipitation regimes, and the predominance of cloudy remote sensing images during the snow season. Sierra Nevada National Park (South Spain), with altitudes higher than 3500 m a.s.l., is part of the Global Change in Mountain Regions network. Snow occurrence just 40 km from the seaside determines a wide range of biodiversity, a snowmelt fluvial regime, and the associated ecosystem services. This work presents the local trend analysis of weather variables at this area together with additional snow-related variables. For this, long term point and distributed observations from weather stations and remote sensing sources were studied and used as input and calibration datasets of a physically based snow model to derive long term series of mean and maximum daily fraction of snow covered area, annual number of days with snow, annual number of days with precipitation, mean and maximum mean daily snow water equivalent, and snowmelt and evaporation volumes. The joint analysis of weather and snow variables showed a decrease trend in the persistence and extent of the snow cover area. The precipitation regime, rather than the temperature trend, seems to be the most relevant driver on the snow regime forcing in Mediterranean areas. This poses a constraint for rigorous scenario analysis in these regions, since the precipitation pattern is poorly approximated by climatic models in these regions.

  3. Long-term variability in terms of arrival and departure of whitethroat (Sylvia communis and chaffinch (Fringilla coelebs in the South-East of the lake Ladoga

    Directory of Open Access Journals (Sweden)

    Ufimtseva Anna

    2016-10-01

    Full Text Available In the annual cycle of birds several changing physiological states are marked out, and their duration is controlled by endogenous and environmental factors. The change in the annual cycle parameters influences the seasonal differences in the migratory behavior of species as a whole. The results of the analysis of arrival and departure terms of two bird species – long-distance migrant whitethroat (Sylvia communis and short-distance migrant chaffinch (Fringilla coelebs – are presented in this article. The research was based on the materials of the long-term monitoring of migration terms at the Ladoga ornithological station. The results of this research correlate to the studies of birds in the Western Europe. Annual variability of the first and last registration dates of the whitethroat is less pronounced than the dates of short-distance migrant – chaffinch. The both species have a trend to come earlier to the breeding area and to fly away later from this territory. At the same time the displacement of migration dates is significant and more long-lasting for chaffinch. In general, whitethroats stay in the South-East of the lake Ladoga on an average 8 days more, chaffinches – 31 days more (by the results of 40 years observation.

  4. Development and evaluation of a stochastic daily rainfall model with long-term variability

    Directory of Open Access Journals (Sweden)

    A. F. M. K. Chowdhury

    2017-12-01

    Full Text Available The primary objective of this study is to develop a stochastic rainfall generation model that can match not only the short resolution (daily variability but also the longer resolution (monthly to multiyear variability of observed rainfall. This study has developed a Markov chain (MC model, which uses a two-state MC process with two parameters (wet-to-wet and dry-to-dry transition probabilities to simulate rainfall occurrence and a gamma distribution with two parameters (mean and standard deviation of wet day rainfall to simulate wet day rainfall depths. Starting with the traditional MC-gamma model with deterministic parameters, this study has developed and assessed four other variants of the MC-gamma model with different parameterisations. The key finding is that if the parameters of the gamma distribution are randomly sampled each year from fitted distributions rather than fixed parameters with time, the variability of rainfall depths at both short and longer temporal resolutions can be preserved, while the variability of wet periods (i.e. number of wet days and mean length of wet spell can be preserved by decadally varied MC parameters. This is a straightforward enhancement to the traditional simplest MC model and is both objective and parsimonious.

  5. Variable Renewable Energy in Long-Term Planning Models: A Multi-Model Perspective

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Wesley J. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Frew, Bethany A. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Mai, Trieu T. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sun, Yinong [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Bistline, John [Electric Power Research Inst., Palo Alto, CA (United States); Blanford, Geoffrey [Electric Power Research Inst., Palo Alto, CA (United States); Young, David [Electric Power Research Inst., Palo Alto, CA (United States); Marcy, Cara [Energy Information Administration, Washington, DC (United States); Namovicz, Chris [Energy Information Administration, Washington, DC (United States); Edelman, Risa [Environmental Protection Agency, Washington, DC (United States); Meroney, Bill [Environmental Protection Agency; Sims, Ryan [Environmental Protection Agency; Stenhouse, Jeb [Environmental Protection Agency; Donohoo-Vallett, Paul [U.S. Department of Energy

    2017-11-03

    Long-term capacity expansion models of the U.S. electricity sector have long been used to inform electric sector stakeholders and decision makers. With the recent surge in variable renewable energy (VRE) generators - primarily wind and solar photovoltaics - the need to appropriately represent VRE generators in these long-term models has increased. VRE generators are especially difficult to represent for a variety of reasons, including their variability, uncertainty, and spatial diversity. To assess current best practices, share methods and data, and identify future research needs for VRE representation in capacity expansion models, four capacity expansion modeling teams from the Electric Power Research Institute, the U.S. Energy Information Administration, the U.S. Environmental Protection Agency, and the National Renewable Energy Laboratory conducted two workshops of VRE modeling for national-scale capacity expansion models. The workshops covered a wide range of VRE topics, including transmission and VRE resource data, VRE capacity value, dispatch and operational modeling, distributed generation, and temporal and spatial resolution. The objectives of the workshops were both to better understand these topics and to improve the representation of VRE across the suite of models. Given these goals, each team incorporated model updates and performed additional analyses between the first and second workshops. This report summarizes the analyses and model 'experiments' that were conducted as part of these workshops as well as the various methods for treating VRE among the four modeling teams. The report also reviews the findings and learnings from the two workshops. We emphasize the areas where there is still need for additional research and development on analysis tools to incorporate VRE into long-term planning and decision-making.

  6. Comparison of maternal omentin-1 levels and genetic variability between spontaneous term and preterm births.

    Science.gov (United States)

    Šplíchal, Zbyněk; Zlámal, Filip; Máchal, Jan; Lipková, Jolana; Pavlová, Tereza; Hodická, Zuzana; Ventruba, Pavel; Vašků, Anna; Bienertová-Vašků, Julie

    2017-05-14

    To determine maternal omentin-1 levels and genetic variability in the omentin-1 gene in women with spontaneous term and preterm births (PTBs). Maternal serum omentin-1 levels and the role of the omentin-1 Val109Asp (rs2274907) polymorphism were evaluated in 32 women with spontaneous term birth (sTB) and 30 women with spontaneous preterm birth (sPTB) including women with (n = 16) and without (n = 14) preterm premature rupture of membranes (PPROM). Maternal omentin-1 levels were significantly lower in women with sPTBs compared to term births during the hospitalization period (p = .015). However, maternal omentin-1 levels were similar in women with sPTBs with and without PPROM (p = .990). Furthermore, the omentin-1 Val109Asp polymorphism was found to have no significant effect on omentin-1 serum levels. In addition, no significant differences in genotype distributions and allelic frequencies between sTB and sPTB were established. High omentin-1 levels in normal sTBs compared to PTBs without significant differences between cases with and without PPROM suggest that omentin-1 plays a potential role in the pathophysiology of PTB but not in the PPROM mechanism itself.

  7. Determination of a source term for a time fractional diffusion equation with an integral type over-determining condition

    Directory of Open Access Journals (Sweden)

    Timurkhan S. Aleroev

    2013-12-01

    Full Text Available We consider a linear heat equation involving a fractional derivative in time, with a nonlocal boundary condition. We determine a source term independent of the space variable, and the temperature distribution for a problem with an over-determining condition of integral type. We prove the existence and uniqueness of the solution, and its continuous dependence on the data.

  8. Bovine Colostrum Supplementation’s Lack of Effect on Immune Variables During Short-Term Intense Exercise in Well-Trained Athletes

    NARCIS (Netherlands)

    Carol, A.; Witkamp, R.F.; Wichers, H.J.; Mensink, M.R.

    2011-01-01

    The purpose of this study was to investigate the potential of bovine colostrum to attenuate postexercise decline in immune function. The authors evaluated the time course of a number of immune variables after short-term intense exercise in 9 male athletes after 10 d of supplementation with either

  9. Serial Holter ST-segment monitoring after first acute myocardial infarction. Prevalence, variability, and long-term prognostic importance of transient myocardial ischemia

    DEFF Research Database (Denmark)

    Mickley, H; Nielsen, J R; Berning, J

    1998-01-01

    Based on serial Holter monitoring performed 7 times within 3 years after a first acute myocardial infarction, we assessed the prevalence, variability and long-term clinical importance of transient myocardial ischemia (TMI) defined as episodes of ambulatory ST-segment depression. In all, 121...

  10. Separation of Variables and Exactly Soluble Time-Dependent Potentials in Quantum Mechanics

    OpenAIRE

    Efthimiou, Costas John; Spector, Donald

    1993-01-01

    We use separation of variables as a tool to identify and to analyze exactly soluble time-dependent quantum mechanical potentials. By considering the most general possible time-dependent re-definition of the spatial coordinate, as well as general transformations on the wavefunctions, we show that separation of variables applies and exact solubility occurs only in a very restricted class of time-dependent models. We consider the formal structure underlying our findings, and the relationship bet...

  11. Relative influence of age, resting heart rate and sedentary life style in short-term analysis of heart rate variability

    Directory of Open Access Journals (Sweden)

    E.R. Migliaro

    2001-04-01

    Full Text Available In order to assess the relative influence of age, resting heart rate (HR and sedentary life style, heart rate variability (HRV was studied in two different groups. The young group (YG consisted of 9 sedentary subjects aged 15 to 20 years (YG-S and of 9 nonsedentary volunteers (YG-NS also aged 15 to 20. The elderly sedentary group (ESG consisted of 16 sedentary subjects aged 39 to 82 years. HRV was assessed using a short-term procedure (5 min. R-R variability was calculated in the time-domain by means of the root mean square successive differences. Frequency-domain HRV was evaluated by power spectrum analysis considering high frequency and low frequency bands. In the YG the effort tolerance was ranked in a bicycle stress test. HR was similar for both groups while ESG showed a reduced HRV compared with YG. Within each group, HRV displayed a negative correlation with HR. Although YG-NS had better effort tolerance than YG-S, their HR and HRV were not significantly different. We conclude that HRV is reduced with increasing HR or age, regardless of life style. The results obtained in our short-term study agree with others of longer duration by showing that age and HR are the main determinants of HRV. Our results do not support the idea that changes in HRV are related to regular physical activity.

  12. Effect of Exercise Testing on Short-term Heart Rate Variability in Patients with Coronary Heart Disease

    DEFF Research Database (Denmark)

    Niu, Hui-Yan; Zhang, Dai-Fu; Liang, Bo

    2005-01-01

    Objective To study the effect of exercise testing on short term heart rate variability in patients with CHD.Methods In 12 patients with CHD and 12 age-and sex-matched healthy controls, short-term frequency domain analysis was performed at respective stage before, during and after ET.Results It sh......Objective To study the effect of exercise testing on short term heart rate variability in patients with CHD.Methods In 12 patients with CHD and 12 age-and sex-matched healthy controls, short-term frequency domain analysis was performed at respective stage before, during and after ET...

  13. Long and Short Term Variability of the Main Physical Parameters in the Coastal Area of the SE Baltic Proper

    Science.gov (United States)

    Mingelaite, Toma; Rukseniene, Viktorija; Dailidiene, Inga

    2015-04-01

    Keywords: SE Baltic Sea, coastal upwelling, IR Remote Sensing The memory of the ocean and seas of atmospheric forcing events contributes to the long-term climate change. Intensifying climate change processes in the North Atlantic region including Baltic Sea has drawn widespread interest, as a changing water temperature has ecological, economic and social impact in coastal areas of the Europe seas. In this work we analyse long and short term variability of the main physical parameters in the coastal area of the South Eastern Baltic Sea Proper. The analysis of long term variability is based on monitoring data measured in the South Eastern Baltic Sea for the last 50 years. The main focus of the long term variability is changes of hydro meteorological parameters relevant to the observed changes in the climate.The water salinity variations in the Baltic Sea near the Lithuanian coast and in the Curonian Lagoon, a shallow and enclosed sub-basin of the Baltic Sea, were analysed along with the time series of some related hydroclimatic factors. The short term water temperature and salinity variations were analysed with a strong focus on coastal upwelling events. Combining both remote sensing and in situ monitoring data physical parameters such as vertical salinity variations during upwelling events was analysed. The coastal upwelling in the SE Baltic Sea coast, depending on its scale and intensity, may lead to an intrusion of colder and saltier marine waters to the Curonian Lagoon resulting in hydrodynamic changes and pronounced temperature drop extending for 30-40 km further down the Lagoon. The study results show that increasing trends of water level, air and water temperature, and decreasing ice cover duration are related to the changes in meso-scale atmospheric circulation, and more specifically, to the changes in regional and local wind regime climate. That is in a good agreement with the increasing trends in local higher intensity of westerly winds, and with the winter

  14. Visibility graph analysis of very short-term heart rate variability during sleep

    Science.gov (United States)

    Hou, F. Z.; Li, F. W.; Wang, J.; Yan, F. R.

    2016-09-01

    Based on a visibility-graph algorithm, complex networks were constructed from very short-term heart rate variability (HRV) during different sleep stages. Network measurements progressively changed from rapid eye movement (REM) sleep to light sleep and then deep sleep, exhibiting promising ability for sleep assessment. Abnormal activation of the cardiovascular controls with enhanced 'small-world' couplings and altered fractal organization during REM sleep indicates that REM could be a potential risk factor for adverse cardiovascular event, especially in males, older individuals, and people who are overweight. Additionally, an apparent influence of gender, aging, and obesity on sleep was demonstrated in healthy adults, which may be helpful for establishing expected sleep-HRV patterns in different populations.

  15. Validity of the ithlete™ Smart Phone Application for Determining Ultra-Short-Term Heart Rate Variability

    Science.gov (United States)

    Flatt, Andrew A.; Esco, Michael R.

    2013-01-01

    The purpose of this investigation was to cross-validate the ithlete™ heart rate variability smart phone application with an electrocardiograph for determining ultra-short-term root mean square of successive R-R intervals. The root mean square of successive R-R intervals was simultaneously determined via electrocardiograph and ithlete™ at rest in twenty five healthy participants. There were no significant differences between the electrocardiograph and ithlete™ derived root mean square of successive R-R interval values (p > 0.05) and the correlation was near perfect (r = 0.99, p study lays groundwork for future research determining the efficacy of ithlete™ for reflecting athletic training status over a chronic conditioning period. PMID:24511344

  16. Relation of increased short-term variability of QT interval to congenital long-QT syndrome

    DEFF Research Database (Denmark)

    Hinterseer, Martin; Beckmann, Britt-Maria; Thomsen, Morten B

    2009-01-01

    Apart from clinical symptoms the diagnosis and risk stratification in long-QT syndrome (LQTS) is usually based on the surface electrocardiogram. Studies have indicated that not only prolongation of the QT interval but also an increased short-term variability of QT interval (STV(QT)) is a marker...... for a decreased repolarization reserve in patients with drug-induced LQTS. The aims of this study were to determine if STV(QT) (1) is higher in patients with LQTS compared with controls, (2) if this effect is more pronounced in a high-risk LQTS population, and (3) could increase the diagnostic power...... of the surface electrocardiogram in identifying mutation carriers. Forty mutation carriers were compared with age- and gender-matched control subjects in the absence of beta-receptor-blocking agents. Lead II or V(5) RR and QT intervals from 30 consecutive beats were manually measured. STV(QT) was determined from...

  17. The impact of inter-annual variability of annual cycle on long-term memory in long historical temperature records

    Science.gov (United States)

    Deng, Qimin; Fu, Zuntao

    2017-04-01

    Changes in the estimation of long-term correlation induced by inter-annual variability of annual cycle have been investigated by means of detrended fluctuation analysis (DFA). In a consequence of the intrinsic nonlinearity of the climate system, the annual cycle suffers from both amplitude and phase fluctuations. How does this changing annual cycle affect the fluctuation of temperature anomalies? A recently developed adaptive data analysis tool, the Nonlinear Mode Decomposition (NMD), is used to extract and remove time-varying annual cycle. We compared the differences of the long-term correlation calculated by removing different annual cycle, time-varying and stationary. The study was based on long historical temperature records around the North Atlantic Ocean. The traditional climatology annual cycle which lack characteristic of inter-annual fluctuation would lead to: (1) the estimation of Hurst exponent (2) how to choose scaling range and (3) the goodness of fit. Especially removing steady climatology annual cycle would introduce an artificial crossover around one-year period in the DFA curve. The conclusion is verified by generating deterministic time series through Monte Carlo simulations.

  18. Long-term variability of low-mass X-ray binaries

    Directory of Open Access Journals (Sweden)

    Filippova E.

    2014-01-01

    Full Text Available We consider modulations of mass captured by the compact object from the companion star’s stellar wind in Low Mass X-ray Binaries with late type giants. Based on 3D simulations with two different hydrodynamic codes used Lagrangian and Eulerian approaches – the SPH code GADGET and the Eulerian code PLUTO, we conclude that a hydrodynamical interaction of the wind matter within a binary system even without eccentricity results in variability of the mass accretion rate with characteristic time-scales close to the orbital period. Observational appearances of this wind might be similar to that of an accretion disc corona/wind.

  19. On the long-term variability of Jupiter and Saturn zonal winds

    Science.gov (United States)

    Sanchez-Lavega, A.; Garcia-Melendo, E.; Hueso, R.; Barrado-Izagirre, N.; Legarreta, J.; Rojas, J. F.

    2012-12-01

    We present an analysis of the long-term variability of Jupiter and Saturn zonal wind profiles at their upper cloud level as retrieved from cloud motion tracking on images obtained at ground-based observatories and with different spacecraft missions since 1979, encompassing about three Jovian and one Saturn years. We study the sensitivity and variability of the zonal wind profile in both planets to major planetary-scale disturbances and to seasonal forcing. We finally discuss the implications that these results have for current model efforts to explain the global tropospheric circulation in these planets. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support, Grupos Gobierno Vasco IT-464-07 and UPV/EHU UFI11/55. [1] Sánchez-Lavega A., et al., Icarus, 147, 405-420 (2000). [2] García-Melendo E., Sánchez LavegaA., Icarus, 152, 316-330 (2001) [3] Sánchez-Lavega A., et al., Nature, 423, 623-625 (2003). [4] García-Melendo E., et al., Geophysical Research Letters, 37, L22204 (2010).

  20. On the Long-Term Variability of Jupiter's Winds and Brightness as Observed from Hubble

    Science.gov (United States)

    Simon-Miller, Amy A.; Gierasch, Peter J.

    2010-01-01

    Hubble Space Telescope Wide Field Planetary Camera 2 imaging data of Jupiter were combined with wind profiles from Voyager and Cassini data to study long-term variability in Jupiter's winds and cloud brightness. Searches for evidence of wind velocity periodicity yielded a few latitudes with potential variability; the most significant periods were found nearly symmetrically about the equator at 0 deg., 10-12 deg. N, and 14-18 deg. S planetographic latitude. The low to mid-latitude signals have components consistent with the measured stratospheric temperature Quasi-Quadrennial Oscillation (QQO) period of-5 years, while the equatorial signal is approximately seasonal and could be tied to mesoscale wave formation, robustness tests indicate that a constant or continuously varying periodic signal near 4.5 years would appear with high significance in the data periodograms as long as uncertainties or noise in the data are not of greater magnitude. However, the lack of a consistent signal over many latitudes makes it difficult to interpret as a QQO-related change. In addition, further analyses of calibrated 410-nm and 953-nm brightness scans found few corresponding changes in troposphere haze and cloud structure on QQO timescales. However, stratospheric haze reflectance at 255-nm did appear to vary on seasonal timescales, though the data do not have enough temporal coverage or photometric accuracy to be conclusive. Sufficient temporal coverage and spacing, as well as data quality, are critical to this type of search.

  1. Long-Term Variability of Satellite Lake Surface Water Temperatures in the Great Lakes

    Science.gov (United States)

    Gierach, M. M.; Matsumoto, K.; Holt, B.; McKinney, P. J.; Tokos, K.

    2014-12-01

    The Great Lakes are the largest group of freshwater lakes on Earth that approximately 37 million people depend upon for fresh drinking water, food, flood and drought mitigation, and natural resources that support industry, jobs, shipping and tourism. Recent reports have stated (e.g., the National Climate Assessment) that climate change can impact and exacerbate a range of risks to the Great Lakes, including changes in the range and distribution of certain fish species, increased invasive species and harmful algal blooms, declining beach health, and lengthened commercial navigation season. In this study, we will examine the impact of climate change on the Laurentian Great Lakes through investigation of long-term lake surface water temperatures (LSWT). We will use the ATSR Reprocessing for Climate: Lake Surface Water Temperature & Ice Cover (ARC-Lake) product over the period 1995-2012 to investigate individual and interlake variability. Specifically, we will quantify the seasonal amplitude of LSWTs, the first and last appearances of the 4°C isotherm (i.e., an important identifier of the seasonal evolution of the lakes denoting winter and summer stratification), and interpret these quantities in the context of global interannual climate variability such as ENSO.

  2. TIME VARIABLE BROAD-LINE EMISSION IN NGC 4203: EVIDENCE FOR STELLAR CONTRAILS

    Energy Technology Data Exchange (ETDEWEB)

    Devereux, Nick, E-mail: devereux@erau.edu [Department of Physics, Embry-Riddle Aeronautical University, Prescott, AZ 86301 (United States)

    2011-12-10

    Dual epoch spectroscopy of the lenticular galaxy, NGC 4203, obtained with the Hubble Space Telescope has revealed that the double-peaked component of the broad H{alpha} emission line is time variable, increasing by a factor of 2.2 in brightness between 1999 and 2010. Modeling the gas distribution responsible for the double-peaked profiles indicates that a ring is a more appropriate description than a disk and most likely represents the contrail of a red supergiant star that is being tidally disrupted at a distance of {approx}1500 AU from the central black hole. There is also a bright core of broad H{alpha} line emission that is not time variable and identified with a large-scale inflow from an outer radius of {approx}1 pc. If the gas number density is {>=}10{sup 6} cm{sup -3}, as suggested by the absence of similarly broad [O I] and [O III] emission lines, then the steady state inflow rate is {approx} 2 Multiplication-Sign 10{sup -2} M{sub Sun} yr{sup -1}, which exceeds the inflow requirement to explain the X-ray luminosity in terms of radiatively inefficient accretion by a factor of {approx}6. The central active galactic nucleus (AGN) is unable to sustain ionization of the broad-line region; the discrepancy is particularly acute in 2010 when the broad H{alpha} emission line is dominated by the contrail of the infalling supergiant star. However, ram pressure shock ionization produced by the interaction of the infalling supergiant with the ambient interstellar medium may help alleviate the ionizing deficit by generating a mechanical source of ionization supplementing the photoionization provided by the AGN.

  3. Stride-Time Variability and Fall Risk in Persons with Multiple Sclerosis.

    Science.gov (United States)

    Moon, Yaejin; Wajda, Douglas A; Motl, Robert W; Sosnoff, Jacob J

    2015-01-01

    Gait variability is associated with falls in clinical populations. However, gait variability's link to falls in persons with Multiple Sclerosis (PwMS) is not well established. This investigation examined the relationship between stride-time variability, fall risk, and physiological fall risk factors in PwMS. 17 PwMS (62.8 ± 7.4 years) and 17 age-matched controls (62.8 ± 5.9 years) performed the 6-minute walk test. Stride-time was assessed with accelerometers attached to the participants' shanks. Stride-time variability was measured by interstride coefficient of variation (CV) of stride-time. The participant's fall risk was measured by the short form physiological profile assessment (PPA). A Spearman correlation analysis was used to determine the relationship between variables. Increased fall risk was strongly associated with increased stride-time CV in both PwMS (ρ = 0.71, p 0.05). In PwMS, stride-time CV was related to postural sway (ρ = 0.74, p < 0.01) while in the control group, it was related to proprioception (ρ = 0.61, p < 0.01) and postural sway (ρ = 0.78, p < 0.01). Current observations suggest that gait variability is maybe more sensitive marker of fall risk than average gait parameters in PwMS. It was also noted that postural sway may be potentially targeted to modify gait variability in PwMS.

  4. Numerical counting ratemeter with variable time constant and integrated circuits; Ictometre numerique a constante de temps variable a circuits integres

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, J.; Fuan, J. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1967-07-01

    We present here the prototype of a numerical counting ratemeter which is a special version of variable time-constant frequency meter (1). The originality of this work lies in the fact that the change in the time constant is carried out automatically. Since the criterion for this change is the accuracy in the annunciated result, the integration time is varied as a function of the frequency. For the prototype described in this report, the time constant varies from 1 sec to 1 millisec. for frequencies in the range 10 Hz to 10 MHz. This prototype is built entirely of MECL-type integrated circuits from Motorola and is thus contained in two relatively small boxes. (authors) [French] Nous presentons ici le prototype d'un ictometre numerique, celui-ci etant une version speciale d'un frequencemetre a constante de temps variable (1). Le nouvel interet de cette etude est le fait que le changement de la constante de temps se fait automatiquement. Le critere de ce changement etant la precision du resultat a afficher on change alors le temps d'integration en fonction de la frequence. Pour le prototype decrit dans ce rapport la constante de temps varie entre 1 s et 1 ms pour des frequences allant de 10 Hz a 10 MHz. Ce prototype est entierement realise en circuit integre type MECL de Motorola et se presente en consequence dans deux boitiers d'une taille relativement petite. (auteurs)

  5. The time variation in infrared water-vapour bands in Mira variables

    NARCIS (Netherlands)

    Matsuura, M; Yamamura, [No Value; Cami, J; Onaka, T; Murakami, H; Yamamura, I.

    The time variation in the water-vapour bands in oxygen-rich Mira variables has been investigated using multi-epoch ISO/SWS spectra of four Mira variables in the 2.5-4.0 mum region. All four stars show H2O bands in absorption around minimum in the visual light curve. At maximum, H2O emission features

  6. Long-term Variability of H2CO Masers in Star-forming Regions

    Science.gov (United States)

    Andreev, N.; Araya, E. D.; Hoffman, I. M.; Hofner, P.; Kurtz, S.; Linz, H.; Olmi, L.; Lorran-Costa, I.

    2017-10-01

    We present results of a multi-epoch monitoring program on variability of 6 cm formaldehyde (H2CO) masers in the massive star-forming region NGC 7538 IRS 1 from 2008 to 2015, conducted with the Green Bank Telescope, the Westerbork Radio Telescope , and the Very Large Array. We found that the similar variability behaviors of the two formaldehyde maser velocity components in NGC 7538 IRS 1 (which was pointed out by Araya and collaborators in 2007) have continued. The possibility that the variability is caused by changes in the maser amplification path in regions with similar morphology and kinematics is discussed. We also observed 12.2 GHz methanol and 22.2 GHz water masers toward NGC 7538 IRS 1. The brightest maser components of CH3OH and H2O species show a decrease in flux density as a function of time. The brightest H2CO maser component also shows a decrease in flux density and has a similar LSR velocity to the brightest H2O and 12.2 GHz CH3OH masers. The line parameters of radio recombination lines and the 20.17 and 20.97 GHz CH3OH transitions in NGC 7538 IRS 1 are also reported. In addition, we observed five other 6 cm formaldehyde maser regions. We found no evidence of significant variability of the 6 cm masers in these regions with respect to previous observations, the only possible exception being the maser in G29.96-0.02. All six sources were also observed in the {{{H}}}213{CO} isotopologue transition of the 6 cm H2CO line; {{{H}}}213{CO} absorption was detected in five of the sources. Estimated column density ratios [{{{H}}}212{CO}]/[{{{H}}}213{CO}] are reported.

  7. The Performance of Short-Term Heart Rate Variability in the Detection of Congestive Heart Failure.

    Science.gov (United States)

    Lucena, Fausto; Barros, Allan Kardec; Ohnishi, Noboru

    2016-01-01

    Congestive heart failure (CHF) is a cardiac disease associated with the decreasing capacity of the cardiac output. It has been shown that the CHF is the main cause of the cardiac death around the world. Some works proposed to discriminate CHF subjects from healthy subjects using either electrocardiogram (ECG) or heart rate variability (HRV) from long-term recordings. In this work, we propose an alternative framework to discriminate CHF from healthy subjects by using HRV short-term intervals based on 256 RR continuous samples. Our framework uses a matching pursuit algorithm based on Gabor functions. From the selected Gabor functions, we derived a set of features that are inputted into a hybrid framework which uses a genetic algorithm and k-nearest neighbour classifier to select a subset of features that has the best classification performance. The performance of the framework is analyzed using both Fantasia and CHF database from Physionet archives which are, respectively, composed of 40 healthy volunteers and 29 subjects. From a set of nonstandard 16 features, the proposed framework reaches an overall accuracy of 100% with five features. Our results suggest that the application of hybrid frameworks whose classifier algorithms are based on genetic algorithms has outperformed well-known classifier methods.

  8. The Performance of Short-Term Heart Rate Variability in the Detection of Congestive Heart Failure

    Directory of Open Access Journals (Sweden)

    Fausto Lucena

    2016-01-01

    Full Text Available Congestive heart failure (CHF is a cardiac disease associated with the decreasing capacity of the cardiac output. It has been shown that the CHF is the main cause of the cardiac death around the world. Some works proposed to discriminate CHF subjects from healthy subjects using either electrocardiogram (ECG or heart rate variability (HRV from long-term recordings. In this work, we propose an alternative framework to discriminate CHF from healthy subjects by using HRV short-term intervals based on 256 RR continuous samples. Our framework uses a matching pursuit algorithm based on Gabor functions. From the selected Gabor functions, we derived a set of features that are inputted into a hybrid framework which uses a genetic algorithm and k-nearest neighbour classifier to select a subset of features that has the best classification performance. The performance of the framework is analyzed using both Fantasia and CHF database from Physionet archives which are, respectively, composed of 40 healthy volunteers and 29 subjects. From a set of nonstandard 16 features, the proposed framework reaches an overall accuracy of 100% with five features. Our results suggest that the application of hybrid frameworks whose classifier algorithms are based on genetic algorithms has outperformed well-known classifier methods.

  9. The mortality burden of hourly temperature variability in five capital cities, Australia: Time-series and meta-regression analysis.

    Science.gov (United States)

    Cheng, Jian; Xu, Zhiwei; Bambrick, Hilary; Su, Hong; Tong, Shilu; Hu, Wenbiao

    2017-12-01

    Unstable weather, such as intra- and inter-day temperature variability, can impair the health and shorten the survival time of population around the world. Climate change will cause Earth's surface temperature rise, but has unclear effects on temperature variability, making it urgent to understand the characteristics of the burden of temperature variability on mortality, regionally and nationally. This paper aims to quantify the mortality risk of exposure to short-term temperature variability, estimate the resulting death toll and explore how the strength of temperature variability effects will vary as a function of city-level characteristics. Ten-year (2000-2009) time-series data on temperature and mortality were collected for five largest Australia's cities (Sydney, Melbourne, Brisbane, Perth and Adelaide), collectively registering 708,751 deaths in different climates. Short-term temperature variability was captured and represented as the hourly temperature standard deviation within two days. Three-stage analyses were used to assess the burden of temperature variability on mortality. First, we modelled temperature variability-mortality relation and estimated the relative risk of death for each city, using a time-series quasi-Poisson regression model. Second, we used meta-analysis to pool the city-specific estimates, and meta-regression to explore if some city-level factors will modify the population vulnerability to temperature variability. Finally, we calculated the city-specific deaths attributable to temperature variability, and applied such estimates to the whole of Australia as a reflection of the nation-wide death burden associated with temperature variability. We found evidence of significant associations between temperature variability and mortality in all cities assessed. Deaths associated with each 1°C rise in temperature variability elevated by 0.28% (95% confidence interval (CI): 0.05%, 0.52%) in Melbourne to 1.00% (95%CI: 0.52%, 1.48%) in Brisbane

  10. Long-term variability of importance of brain regions in evolving epileptic brain networks

    Science.gov (United States)

    Geier, Christian; Lehnertz, Klaus

    2017-04-01

    We investigate the temporal and spatial variability of the importance of brain regions in evolving epileptic brain networks. We construct these networks from multiday, multichannel electroencephalographic data recorded from 17 epilepsy patients and use centrality indices to assess the importance of brain regions. Time-resolved indications of highest importance fluctuate over time to a greater or lesser extent, however, with some periodic temporal structure that can mostly be attributed to phenomena unrelated to the disease. In contrast, relevant aspects of the epileptic process contribute only marginally. Indications of highest importance also exhibit pronounced alternations between various brain regions that are of relevance for studies aiming at an improved understanding of the epileptic process with graph-theoretical approaches. Nonetheless, these findings may guide new developments for individualized diagnosis, treatment, and control.

  11. Long-term variability of importance of brain regions in evolving epileptic brain networks.

    Science.gov (United States)

    Geier, Christian; Lehnertz, Klaus

    2017-04-01

    We investigate the temporal and spatial variability of the importance of brain regions in evolving epileptic brain networks. We construct these networks from multiday, multichannel electroencephalographic data recorded from 17 epilepsy patients and use centrality indices to assess the importance of brain regions. Time-resolved indications of highest importance fluctuate over time to a greater or lesser extent, however, with some periodic temporal structure that can mostly be attributed to phenomena unrelated to the disease. In contrast, relevant aspects of the epileptic process contribute only marginally. Indications of highest importance also exhibit pronounced alternations between various brain regions that are of relevance for studies aiming at an improved understanding of the epileptic process with graph-theoretical approaches. Nonetheless, these findings may guide new developments for individualized diagnosis, treatment, and control.

  12. Long-term variability of aerosol optical properties and radiative effects in Northern Finland

    Science.gov (United States)

    Lihavainen, Heikki; Hyvärinen, Antti; Asmi, Eija; Hatakka, Juha; Viisanen, Yrjö

    2017-04-01

    We introduce long term dataset of aerosol scattering and absorption properties and combined aerosol optical properties measured in Pallas Atmosphere-Ecosystem Supersite in Norhern Finland. The station is located 170 km north of the Arctic Circle. The station is affected by both pristine Arctic air masses as well as long transported air pollution from northern Europe. We studied the optical properties of aerosols and their radiative effects in continental and marine air masses, including seasonal cycles and long-term trends. The average (median) scattering coefficient, backscattering fraction, absorption coefficient and single scattering albedo at the wavelength of 550 nm were 7.9 (4.4) 1/Mm, 0.13 (0.12), 0.74 (0.35) 1/Mm and 0.92 (0.93), respectively. We observed clear seasonal cycles in these variables, the scattering coefficient having high values during summer and low in fall, and absorption coefficient having high values during winter and low in fall. We found that the high values of the absorption coefficient and low values of the single scattering albedo were related to continental air masses from lower latitudes. These aerosols can induce an additional effect on the surface albedo and melting of snow. We observed the signal of the Arctic haze in marine (northern) air masses during March and April. The haze increased the value of the absorption coefficient by almost 80% and that of the scattering coefficient by about 50% compared with the annual-average values. We did not observe any long-term trend in the scattering coefficient, while our analysis showed a clear decreasing trend in the backscattering fraction and scattering Ångström exponent during winter. We also observed clear relationship with temperature and aerosol scattering coefficient. We will present also how these different features affects to aerosol direct radiative forcing.

  13. Variables predicting change in benign melanocytic nevi undergoing short-term dermoscopic imaging.

    Science.gov (United States)

    Menzies, Scott W; Stevenson, Mary L; Altamura, Davide; Byth, Karen

    2011-06-01

    To determine whether certain patient demographics are associated with poorer specificity for the diagnosis of melanoma in nevi undergoing short-term sequential digital dermoscopic imaging. Retrospective cohort study performed from April 1, 1998, through May 31, 2007. Sydney Melanoma Diagnostic Centre, a tertiary referral institution. A total of 2497 benign melanocytic lesions in 1765 patients undergoing short-term sequential digital dermoscopic imaging during 2.5 to 4.5 months (42.3% male; mean [SD] age, 40 [14] years; age range, 1-86 years). Proportion of changed nevi as a function of age, sex, lesion diameter, and anatomical site. The only variable significantly associated with nevus change was age group (P = .002). When compared with the middle-aged (aged 36-50 years) group, the odds of change were significantly increased in the child and adolescent (aged 0-18 years: odds ratio, 2.60; 95% confidence interval, 1.30-5.22), young adult (aged 19-35 years: 1.50; 1.04-2.17), and elderly (> 65 years old: 2.04; 1.04-3.99) age groups. Within the changed benign lesions, a significant association was observed between histologic subtype and age group (P = .01). The proportion of changed lesions of the banal nevi type decreased and the proportion of the dysplastic nevi type increased with age. In the elderly group, 75.9% of changed lesions were of the dysplastic nevi type compared with 35.7% in the youngest group. A poorer specificity is observed for the diagnosis of melanoma for nevi undergoing short-term sequential digital dermoscopic imaging in children and adolescents (75.7%) and elderly patients (77.9%) compared with other patients (84.6%).

  14. Exploring the Variability of Short-term Precipitation and Hydrological Response of Small Czech Watersheds

    Science.gov (United States)

    Kavka, Petr; Strouhal, Ludek; Weyskrabova, Lenka; Müller, Miloslav; Kozant, Petr

    2017-04-01

    The short-term rainfall temporal distribution is known to have a significant effect on the small watersheds' hydrological response. In Czech Republic there are limited publicly available data on rainfall patterns of short-term precipitation. On one side there are catalogues of very short-term synthetic rainfalls used in urban drainage planning and on the other side hourly distribution of daily totals of rainfalls with long return period for larger catchments analyses. This contribution introduces the preliminary outcomes of a running three years' project, which should bridge this gap and provide such data and methodology to the community of scientists, state administration as well as design planners. Six generalized 6-hours hyetographs with 1 minute resolution were derived from 10 years of radar and gauging stations data. These hyetographs are accompanied with information concerning the region of occurrence as well as their frequency related to the rainfall amount. In the next step these hyetographs are used in a complex sensitivity analysis focused on a rainfall-runoff response of small watersheds. This analysis takes into account the uncertainty related to type of the hydrological model, watershed characteristics and main model routines parameterization. Five models with different methods and structure are considered and each model is applied on 5 characteristic watersheds selected from a classification of 7700 small Czech watersheds. For each combination of model and watershed 30, rainfall scenarios were simulated and other scenarios will be used to address the parameters uncertainty. In the last step the variability of outputs will be assessed in the context of economic impacts on design of landscape water structures or mitigation measures. The research is supported by the grant QJ1520265 of the Czech Ministry of Agriculture, rainfall data were provided by the Czech Hydrometeorological Institute.

  15. The long-term variability of cosmic ray protons in the heliosphere: A modeling approach

    Directory of Open Access Journals (Sweden)

    M.S. Potgieter

    2013-05-01

    Full Text Available Galactic cosmic rays are charged particles created in our galaxy and beyond. They propagate through interstellar space to eventually reach the heliosphere and Earth. Their transport in the heliosphere is subjected to four modulation processes: diffusion, convection, adiabatic energy changes and particle drifts. Time-dependent changes, caused by solar activity which varies from minimum to maximum every ∼11 years, are reflected in cosmic ray observations at and near Earth and along spacecraft trajectories. Using a time-dependent compound numerical model, the time variation of cosmic ray protons in the heliosphere is studied. It is shown that the modeling approach is successful and can be used to study long-term modulation cycles.

  16. Analysis of Modal Travel Time Variability Due to Mesoscale Ocean Structure

    National Research Council Canada - National Science Library

    Smith, Amy

    1997-01-01

    .... First, for an open ocean environment away from strong boundary currents, the effects of randomly phased linear baroclinic Rossby waves on acoustic travel time are shown to produce a variable overall...

  17. The loss of short-term visual representations over time: decay or temporal distinctiveness?

    Science.gov (United States)

    Mercer, Tom

    2014-12-01

    There has been much recent interest in the loss of visual short-term memories over the passage of time. According to decay theory, visual representations are gradually forgotten as time passes, reflecting a slow and steady distortion of the memory trace. However, this is controversial and decay effects can be explained in other ways. The present experiment aimed to reexamine the maintenance and loss of visual information over the short term. Decay and temporal distinctiveness models were tested using a delayed discrimination task, in which participants compared complex and novel objects over unfilled retention intervals of variable length. Experiment 1 found no significant change in the accuracy of visual memory from 2 to 6 s, but the gap separating trials reliably influenced task performance. Experiment 2 found evidence for information loss at a 10-s retention interval, but temporally separating trials restored the fidelity of visual memory, possibly because temporally isolated representations are distinct from older memory traces. In conclusion, visual representations lose accuracy at some point after 6 s, but only within temporally crowded contexts. These findings highlight the importance of temporal distinctiveness within visual short-term memory. PsycINFO Database Record (c) 2014 APA, all rights reserved.

  18. Term Context

    OpenAIRE

    Bancerek Grzegorz

    2015-01-01

    Two construction functors: simple term with a variable and compound term with an operation and argument terms and schemes of term induction are introduced. The degree of construction as a number of used operation symbols is defined. Next, the term context is investigated. An x-context is a term which includes a variable x once only. The compound term is x-context iff the argument terms include an x-context once only. The context induction is shown and used many times. As a key concept, the co...

  19. Term Context

    Directory of Open Access Journals (Sweden)

    Bancerek Grzegorz

    2015-02-01

    Full Text Available Two construction functors: simple term with a variable and compound term with an operation and argument terms and schemes of term induction are introduced. The degree of construction as a number of used operation symbols is defined. Next, the term context is investigated. An x-context is a term which includes a variable x once only. The compound term is x-context iff the argument terms include an x-context once only. The context induction is shown and used many times. As a key concept, the context substitution is introduced. Finally, the translations and endomorphisms are expressed by context substitution.

  20. Effects of reaction time variability and age on brain activity during Stroop task performance.

    Science.gov (United States)

    Tam, Angela; Luedke, Angela C; Walsh, Jeremy J; Fernandez-Ruiz, Juan; Garcia, Angeles

    2015-09-01

    Variability in reaction time during task performance may reflect fluctuations in attention and cause reduced performance in goal-directed tasks, yet it is unclear whether the mechanisms behind this phenomenon change with age. Using fMRI, we tested young and cognitively healthy older adults with the Stroop task to determine whether aging affects the neural mechanisms underlying intra-individual reaction time variability. We found significant between-group differences in BOLD activity modulated by reaction time. In older adults, longer reaction times were associated with greater activity in frontoparietal attentional areas, while in younger adults longer reaction times were associated with greater activity in default mode network areas. Our results suggest that the neural correlates of reaction time variability change with healthy aging, reinforcing the concept of functional plasticity to maintain high cognitive function throughout the lifespan.

  1. Estimating the Impact of Time-Invariant Variables on FDI with Fixed Effects

    DEFF Research Database (Denmark)

    Davies, Ronald B.; Ionascu, Delia Simona; Kristjánsdóttir, Helga

    This paper applies the panel fixed effects with vector decomposition estimator to three FDI datasets to estimate the impact of time-invariant variables on FDI while including fixed effects. We find that the omission of fixed effects significantly biases several of these variables, especially those...... proxying for trade costs and culture. After including fixed effects, we find that many time-invariant variables indicate the importance of vertical FDI. We also find that by eliminating these biases, the differences across datasets largely disappear. Thus, controversies in the literature that are driven...

  2. Exact solutions of time fractional heat-like and wave-like equations with variable coefficients

    Directory of Open Access Journals (Sweden)

    Zhang Sheng

    2016-01-01

    Full Text Available In this paper, a variable-coefficient time fractional heat-like and wave-like equation with initial and boundary conditions is solved by the use of variable separation method and the properties of Mittag-Leffler function. As a result, exact solutions are obtained, from which some known special solutions are recovered. It is shown that the variable separation method can also be used to solve some others time fractional heat-like and wave-like equation in science and engineering.

  3. Solving Time-Fractional Advection-Dispersion Equation by Variable Weights Particle Tracking Method

    Science.gov (United States)

    Cao, Shaohua; Jiang, Jianguo; Wu, Jichun

    2017-09-01

    Particle tracking method is an efficient and reliable method to solve time-fractional advection-dispersion equation, which can describe anomalous transport in heterogeneous porous media. However, this method will lead to severe fluctuation or disappearance of solutions if the concentration value is small. A variable weights method is developed to conquer the shortcoming of particle tracking method. Then, one-dimensional and two-dimensional time-fractional advection-dispersion equations are solved by the variable weights particle tracking method. Compared to traditional particle tracking method, the variable weights version may eliminate the fluctuation and improve the accuracy by orders of magnitude without more computational cost.

  4. Generalized space time autoregressive with exogenous variable model and its application

    Science.gov (United States)

    Astuti, Dewi; Nurani Ruchjana, Budi; Soemartini

    2017-10-01

    In this paper we proposed the Generalized Space Time Autoregressive with variable Exogenous, abbreviated GSTARX as GSTAR development with the addition of exogenous variables. GSTARX not only involves the element of time and location, but also the influence of exogenous variables in the model. GSTARX equation can be written as a linear model, so we can estimate parameters of GSTARX model using Ordinary Least Squares (OLS) method. For our case study, we use GSTARX model with uniform and inverse distance weights to predict an export volume of Crude Palm Oil (CPO) in several locations on the island of Sumatera, where X is the international CPO prices.

  5. Stable isotope fractionation in response to variable fluid residence time distributions

    Science.gov (United States)

    Druhan, J. L.; Maher, K.

    2013-12-01

    Hydrogeochemical processes governing groundwater quantity and quality are often inferred from fluid samples that are the flux-weighted average of a heterogeneous system. This connection has been demonstrated for solutes subject to transport and equilibrium constraints, in which the steady state concentration - discharge relationship is cast in terms of the choice of expression for residence time distribution (Maher, 2011). Here, we examine the extent to which the spatial correlation of the permeability field, which governs the fluid residence time distribution, exerts a principle control on the partitioning of stable isotopes between reactant and product species during heterogeneous reactions in groundwater systems. We demonstrate this relationship using numerical simulations of δ53Cr fractionation due to abiotic CrO42- reduction by Fe2+, implemented in the reactive transport code CrunchFlow. The chemically homogeneous redox reaction generates Cr3+ with an isotope ratio distinct from the reactant pool, and in turn this product species precipitates as a mineral phase Cr(OH)3(s) through a non-fractionating reaction. The corresponding chromate δ53Cr enrichment across a homogeneous domain varies from a maximum value set by the kinetic fractionation factor (αk) at high mean fluid residence times, to a value reaction-limited to transport-limited regimes. For physically heterogeneous flow fields, the transition in isotopic fractionation from a reaction-limited to a transport-limited regime becomes variable, and falls between the upper and lower bounds set by the homogeneous simulations at slow and fast precipitation rates, respectively. Our results show that while minimal variation occurs in the steady-state isotopic profile of the reactant species (δ53Cr of CrO42-), the combined effects of the precipitation rate and the heterogeneous structure of the porous media lead to a wide range in the steady state isotopic composition of the product species (δ53Cr of Cr3

  6. Importance of variable time-step algorithms in spatial kinetics calculations

    Energy Technology Data Exchange (ETDEWEB)

    Aviles, B.N.

    1994-12-31

    The use of spatial kinetics codes in conjunction with advanced thermal-hydraulics codes is becoming more widespread as better methods and faster computers appear. The integrated code packages are being used for routine nuclear power plant design and analysis, including simulations with instrumentation and control systems initiating system perturbations such as rod motion and scrams. As a result, it is important to include a robust variable time-step algorithm that can accurately and efficiently follow widely varying plant neutronic behavior. This paper describes the variable time-step algorithm in SPANDEX and compares the automatic time-step scheme with a more traditional fixed time-step scheme.

  7. Tropical cyclone influence on the long-term variability of Philippine summer monsoon onset

    Science.gov (United States)

    Kubota, Hisayuki; Shirooka, Ryuichi; Matsumoto, Jun; Cayanan, Esperanza O.; Hilario, Flaviana D.

    2017-12-01

    The long-term variability of Philippine summer monsoon onset from 1903 to 2013 was investigated. The onset date is defined by daily rainfall data at eight stations in the northwestern Philippines. Summer monsoons tended to start earlier in May after the mid-1990s. Other early onset periods were found during the 1900s, 1920s, and 1930s, and an interdecadal variability of summer monsoon onset was identified. Independent surface wind data observed by ships in the South China Sea (SCS) revealed prevailing westerly wind in May during the early monsoon onset period. To identify atmospheric structures that trigger Philippine summer monsoon onset, we focused on the year 2013, conducting intensive upper-air observations. Tropical cyclone (TC) Yagi traveled northward in the Philippine Sea (PS) in 2013 and triggered the Philippine monsoon onset by intensifying moist low-level southwesterly wind in the southwestern Philippines and intensifying low-level southerly wind after the monsoon onset in the northwestern Philippines. The influence of TC was analyzed by the probability of the existence of TC in the PS and the SCS since 1951, which was found to be significantly correlated with the Philippine summer monsoon onset date. After the mid-1990s, early monsoon onset was influenced by active TC formation in the PS and the SCS. However, the role of TC activity decreased during the late summer monsoon periods. In general, it was found that TC activity in the PS and the SCS plays a key role in initiating Philippine summer monsoon onset. [Figure not available: see fulltext.

  8. Short-term variability on the surface of (1) Ceres⋆. A changing amount of water ice?

    Science.gov (United States)

    Perna, D.; Kaňuchová, Z.; Ieva, S.; Fornasier, S.; Barucci, M. A.; Lantz, C.; Dotto, E.; Strazzulla, G.

    2015-03-01

    Context. The dwarf planet (1) Ceres - next target of the NASA Dawn mission - is the largest body in the asteroid main belt. Although several observations of this body have been performed so far, the presence of surface water ice is still questioned. Aims: Our goal is to better understand the surface composition of Ceres and to constrain the presence of exposed water ice. Methods: We acquired new visible and near-infrared spectra at the Telescopio Nazionale Galileo (La Palma, Spain), and reanalyzed literature spectra in the 3-μm region. Results: We obtained the first rotationally resolved spectroscopic observations of Ceres at visible wavelengths. Visible spectra taken one month apart at almost the same planetocentric coordinates show a significant slope variation (up to 3%/103Å). A faint absorption centered at 0.67 μm, possibly due to aqueous alteration, is detected in a subset of our spectra. The various explanations in the literature for the 3.06-μm feature can be interpreted as due to a variable amount of surface water ice at different epochs. Conclusions: The remarkable short-term temporal variability of the visible spectral slope and the changing shape of the 3.06-μm band can be hints of different amounts of water ice exposed on the surface of Ceres. This would agree with the recent detection by the Herschel Space Observatory of localized and transient sources of water vapor over this dwarf planet. Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.Appendices are available in electronic form at http://www.aanda.org

  9. Short-Term Spectral Variability in the Binary FS CMa-Type Object MWC 728

    Science.gov (United States)

    Zharikov, S. V.; Miroshnichenko, A. S.

    2017-02-01

    We report the results of a long-term spectroscopic monitoring of the FS CM-type object MWC 728. We found that it is a binary system with a B5 ve (T1,eff = 14000±1000 K) primary and a G8 III (T2,eff ˜ 5000 K) secondary. Absorption lines of the cool star show regular variations with a semi-amplitude of ˜20 km s-1 and a period of 27.5 days. The system mass function is 2.3×10-2 M⊙, and its orbital plane is ˜ 13-15° tilted from the plane of the sky. The hot star has a projected rotational velocity of ˜110 km s-1 which implies a nearly breakup rotation at the equator. We detected strong variations of the Balmer and He I emission-line profiles on timescales from days to years. This points out to a variable stellar wind of the hot star in addition to the presence of a circum-primary gaseous disk. The strength of the absorption-line spectrum along with the optical and near-IR continuum suggest that the hot star contributes ˜60% of the V-band flux, the disk contributes ˜30%, and the cool star ˜10%.The binary system parameters, along with the interstellar extinction, suggest a distance of ˜1 kpc, that the cool star radius (˜8 R⊙) is smaller than its Roche lobe, and that the companions' mass ratio is q ˜0.5. Overall, the observed spectral variability and the presence of a strong IR-excess are in agreement with a model of a close binary system that has undergone a non-conservative mass-transfer.

  10. The Role of Global Hydrologic Processes in Interannual and Long-Term Climate Variability

    Science.gov (United States)

    Robertson, Franklin R.

    1997-01-01

    The earth's climate and its variability is linked inextricably with the presence of water on our planet. El Nino / Southern Oscillation-- the major mode of interannual variability-- is characterized by strong perturbations in oceanic evaporation, tropical rainfall, and radiation. On longer time scales, the major feedback mechanism in CO2-induced global warming is actually that due to increased water vapor holding capacity of the atmosphere. The global hydrologic cycle effects on climate are manifested through influence of cloud and water vapor on energy fluxes at the top of atmosphere and at the surface. Surface moisture anomalies retain the "memory" of past precipitation anomalies and subsequently alter the partitioning of latent and sensible heat fluxes at the surface. At the top of atmosphere, water vapor and cloud perturbations alter the net amount of radiation that the earth's climate system receives. These pervasive linkages between water, radiation, and surface processes present major complexities for observing and modeling climate variations. Major uncertainties in the observations include vertical structure of clouds and water vapor, surface energy balance, and transport of water and heat by wind fields. Modeling climate variability and change on a physical basis requires accurate by simplified submodels of radiation, cloud formation, radiative exchange, surface biophysics, and oceanic energy flux. In the past, we m safely say that being "data poor' has limited our depth of understanding and impeded model validation and improvement. Beginning with pre-EOS data sets, many of these barriers are being removed. EOS platforms with the suite of measurements dedicated to specific science questions are part of our most cost effective path to improved understanding and predictive capability. This talk will highlight some of the major questions confronting global hydrology and the prospects for significant progress afforded by EOS-era measurements.

  11. Predictor variables for a half marathon race time in recreational male runners.

    Science.gov (United States)

    Rüst, Christoph Alexander; Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Lepers, Romuald; Rosemann, Thomas

    2011-01-01

    The aim of this study was to investigate predictor variables of anthropometry, training, and previous experience in order to predict a half marathon race time for future novice recreational male half marathoners. Eighty-four male finishers in the 'Half Marathon Basel' completed the race distance within (mean and standard deviation, SD) 103.9 (16.5) min, running at a speed of 12.7 (1.9) km/h. After multivariate analysis of the anthropometric characteristics, body mass index (r = 0.56), suprailiacal (r = 0.36) and medial calf skin fold (r = 0.53) were related to race time. For the variables of training and previous experience, speed in running of the training sessions (r = -0.54) were associated with race time. After multivariate analysis of both the significant anthropometric and training variables, body mass index (P = 0.0150) and speed in running during training (P = 0.0045) were related to race time. Race time in a half marathon might be partially predicted by the following equation (r(2) = 0.44): Race time (min) = 72.91 + 3.045 * (body mass index, kg/m(2)) -3.884 * (speed in running during training, km/h) for recreational male runners. To conclude, variables of both anthropometry and training were related to half marathon race time in recreational male half marathoners and cannot be reduced to one single predictor variable.

  12. Examining the Level of Internet Addiction of Adolescents in Terms of Various Variables

    Directory of Open Access Journals (Sweden)

    Mehmet Fatih Ayaz

    2016-11-01

    Full Text Available The aim of the research is to examine the internet addiction of adolescents according to their genders, the type of their high-schools and class level, the time interval that they use internet most widely, their internet usage duration and usage purpose. For that, it is studied with 335 high-school students in Elazig city of Turkey in 2015. The internet addiction scale that Young (1998 developed was used to determine internet addiction of adolescents. In the analysis of data, t-test and unilateral variance analysis were used. At the result of analysis, the mean score of that adolescents got by internet addiction scale was determined as . In analysis between variables it was seen that the internet addiction level of Science-High School students was lower compared to Anatolian and Vocational High-School students. It was observed that the more the usage duration increases the more the internet addiction increases. It was determined the students who use internet mostly for games or social media are more addicted. Besides; as statistical, a significant difference wasn’t determined between genders, classes and the variables that internet is mostly used.

  13. Resting heart rate variability is associated with ex-Gaussian metrics of intra-individual reaction time variability.

    Science.gov (United States)

    Spangler, Derek P; Williams, DeWayne P; Speller, Lassiter F; Brooks, Justin R; Thayer, Julian F

    2018-02-02

    The relationships between vagally mediated heart rate variability (vmHRV) and the cognitive mechanisms underlying performance can be elucidated with ex-Gaussian modeling-an approach that quantifies two different forms of intra-individual variability (IIV) in reaction time (RT). To this end, the current study examined relations of resting vmHRV to whole-distribution and ex-Gaussian IIV. Subjects (N = 83) completed a 5-minute baseline while vmHRV (root mean square of successive differences; RMSSD) was measured. Ex-Gaussian (sigma, tau) and whole-distribution (standard deviation) estimates of IIV were derived from reaction times on a Stroop task. Resting vmHRV was found to be inversely related to tau (exponential IIV) but not to sigma (Gaussian IIV) or the whole-distribution standard deviation of RTs. Findings suggest that individuals with high vmHRV can better prevent attentional lapses but not difficulties with motor control. These findings inform the differential relationships of cardiac vagal control to the cognitive processes underlying human performance. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  14. Influence of the sampling period and time resolution on the PM source apportionment: Study based on the high time-resolution data and long-term daily data

    Science.gov (United States)

    Tian, Yingze; Xiao, Zhimei; Wang, Haiting; Peng, Xing; Guan, Liao; Huangfu, Yanqi; Shi, Guoliang; Chen, Kui; Bi, Xiaohui; Feng, Yinchang

    2017-09-01

    When planning short-term and long-term measurement campaigns of particulate matter (PM), parameters such as sampling period, time resolution, sampling number, etc. are vital. To study their influence and to provide suggestion for the sampling plan of PM source apportionment (SA), ambient and synthetic speciated datasets (including a high time-resolution dataset and a long-term daily dataset) were studied. First, aiming at studying the sampling period required to generate representative and reliable results for SA, high time-resolution ambient samples were collected by online instruments in a megacity in China. Datasets with different sampling periods (four months, two months, one month, two weeks and one week) were modeled by the Positive Matrix Factorization (PMF). Compared with four month results, AAEs (percent absolute errors between true and estimated contributions) ranged from 11.2 to 27.2% (two months), 19.8-44.5% (one month), 21.0-45.9% (two weeks) and 23.9-44.6% (one week), indicating that divergence increased with decreasing sampling periods. To systematically evaluate this problem and investigate if the increasing time resolutions in a short period could enhance the modeling performance, synthetic datasets were constructed. Results revealed that a sufficient sampling period is required to ensure stable results; without sufficient sampling period, the contributions cannot be reliably estimated, even if the number of samples is large. Then, to explore the influence of variability absences, long-term daily datasets with various variability absences were apportioned and compared. The summed AAEs were 102.2% (no winter), 73.6% (no weekend), 138.7% (no weekday) and 165.6% (no autumn, winter or weekends). This general increase of AAEs can indicate that uncertainty enhanced with the increase in variability absences. When planning short-term measurement campaigns, except for number of samples, sampling period that involves sufficient source cycles has significant

  15. Spontaneous fluctuations in sensory processing predict within-subject reaction time variability

    Directory of Open Access Journals (Sweden)

    Maria José Ribeiro

    2016-05-01

    Full Text Available When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs and reaction time using two different analyses: 1 time point by time point correlation analyses thereby identifying time windows of interest, and 2 correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis procedure.Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus

  16. Spontaneous Fluctuations in Sensory Processing Predict Within-Subject Reaction Time Variability.

    Science.gov (United States)

    Ribeiro, Maria J; Paiva, Joana S; Castelo-Branco, Miguel

    2016-01-01

    When engaged in a repetitive task our performance fluctuates from trial-to-trial. In particular, inter-trial reaction time variability has been the subject of considerable research. It has been claimed to be a strong biomarker of attention deficits, increases with frontal dysfunction, and predicts age-related cognitive decline. Thus, rather than being just a consequence of noise in the system, it appears to be under the control of a mechanism that breaks down under certain pathological conditions. Although the underlying mechanism is still an open question, consensual hypotheses are emerging regarding the neural correlates of reaction time inter-trial intra-individual variability. Sensory processing, in particular, has been shown to covary with reaction time, yet the spatio-temporal profile of the moment-to-moment variability in sensory processing is still poorly characterized. The goal of this study was to characterize the intra-individual variability in the time course of single-trial visual evoked potentials and its relationship with inter-trial reaction time variability. For this, we chose to take advantage of the high temporal resolution of the electroencephalogram (EEG) acquired while participants were engaged in a 2-choice reaction time task. We studied the link between single trial event-related potentials (ERPs) and reaction time using two different analyses: (1) time point by time point correlation analyses thereby identifying time windows of interest; and (2) correlation analyses between single trial measures of peak latency and amplitude and reaction time. To improve extraction of single trial ERP measures related with activation of the visual cortex, we used an independent component analysis (ICA) procedure. Our ERP analysis revealed a relationship between the N1 visual evoked potential and reaction time. The earliest time point presenting a significant correlation of its respective amplitude with reaction time occurred 175 ms after stimulus onset

  17. Heart rate variability during daytime naps in healthy adults: Autonomic profile and short-term reliability.

    Science.gov (United States)

    Cellini, Nicola; Whitehurst, Lauren N; McDevitt, Elizabeth A; Mednick, Sara C

    2016-04-01

    In healthy individuals, a reduction in cardiovascular output and a shift to parasympathetic/vagal dominant activity is observed across nocturnal sleep. This cardiac autonomic profile, often measured by heart rate variability (HRV), has been associated with significant benefits for the cardiovascular system. However, little is known about the autonomic profile during daytime sleep. Here, we investigated the autonomic profile and short-term reliability of HRV during daytime naps in 66 healthy young adults. Participants took an 80-120 min polysomnographically recorded nap at 1:30 pm. Beat-by-beat RR interval values (RR), high (HF) and low frequency (LF) power, total power (TP), HF normalized units (HF(nu)), and the LF/HF ratio were obtained for 5 min during presleep wakefulness and during nap sleep stages (N2, N3, REM). A subsample of 37 participants took two additional naps with 2 weeks between recordings. We observed lengthening of the RR, higher HF and HF(nu), and lower LF/HF during NREM, compared with REM and wake, and a marked reduction of LF and TP during N3. Intraclass correlation coefficients highlighted a short-term stability of RR and HF ranging across sleep stages between 0.52-0.76 and 0.52-0.80, respectively. Our results suggest that daytime napping in healthy young adults is associated with dynamic changes in the autonomic profile, similar to those seen during nocturnal sleep. Moreover, a reliable intraindividual measure of autonomic cardiac activity can be obtained by just a single daytime nap depending on specific parameters and recording purposes. Nap methodology may be a new and promising tool to explore sleep-dependent, autonomic fluctuations in healthy and at-risk populations. © 2015 Society for Psychophysiological Research.

  18. Investigation of Dependence between Time-zero and Time-dependent Variability in High-k NMOS Transistors

    CERN Document Server

    Hassan, Mohammad Khaled

    2016-01-01

    Bias Temperature Instability (BTI) is a major reliability concern in CMOS technology, especially with High dielectric constant (High-\\k{appa}/HK) metal gate (MG) transistors. In addition, the time independent process induced variation has also increased because of the aggressive scaling down of devices. As a result, the faster devices at the lower threshold voltage distribution tail experience higher stress, leading to additional skewness in the BTI degradation. Since time dependent dielectric breakdown (TDDB) and stress-induced leakage current (SILC) in NMOS devices are correlated to BTI, it is necessary to investigate the effect of time zero variability on all these effects simultaneously. To that effect, we propose a simulation framework to model and analyze the impact of time-zero variability (in particular, random dopant fluctuations) on different aging effects. For small area devices (~1000 nm2) in 30nm technology, we observe significant effect of Random Dopant Fluctuation (RDF) on BTI induced variabili...

  19. Short-term Time Structure of Food-related Emotions

    NARCIS (Netherlands)

    Jager, Gerry

    2016-01-01

    Contemporary emotion theories have come to conceptualize emotions as multicomponent and dynamic phenomena. Central to this dynamical perspective is that emotions are viewed as a series of dynamic and recursive events that unfold over time, rather than single discrete responses. This chapter

  20. The added value of time-variable microgravimetry to the understanding of how volcanoes work

    Science.gov (United States)

    Carbone, Daniele; Poland, Michael; Greco, Filippo; Diament, Michel

    2017-01-01

    During the past few decades, time-variable volcano gravimetry has shown great potential for imaging subsurface processes at active volcanoes (including some processes that might otherwise remain “hidden”), especially when combined with other methods (e.g., ground deformation, seismicity, and gas emissions). By supplying information on changes in the distribution of bulk mass over time, gravimetry can provide information regarding processes such as magma accumulation in void space, gas segregation at shallow depths, and mechanisms driving volcanic uplift and subsidence. Despite its potential, time-variable volcano gravimetry is an underexploited method, not widely adopted by volcano researchers or observatories. The cost of instrumentation and the difficulty in using it under harsh environmental conditions is a significant impediment to the exploitation of gravimetry at many volcanoes. In addition, retrieving useful information from gravity changes in noisy volcanic environments is a major challenge. While these difficulties are not trivial, neither are they insurmountable; indeed, creative efforts in a variety of volcanic settings highlight the value of time-variable gravimetry for understanding hazards as well as revealing fundamental insights into how volcanoes work. Building on previous work, we provide a comprehensive review of time-variable volcano gravimetry, including discussions of instrumentation, modeling and analysis techniques, and case studies that emphasize what can be learned from campaign, continuous, and hybrid gravity observations. We are hopeful that this exploration of time-variable volcano gravimetry will excite more scientists about the potential of the method, spurring further application, development, and innovation.

  1. Within-Session Stability of Short-Term Heart Rate Variability Measurement

    Directory of Open Access Journals (Sweden)

    Cipryan Lukas

    2016-04-01

    Full Text Available The primary aim of this study was to assess the retest stability of the short-term heart rate variability (HRV measurement performed within one session and without the use of any intervention. Additionally, a precise investigation of the possible impact of intrinsic biological variation on HRV reliability was also performed. First, a single test-retest HRV measurement was conducted with 20-30 min apart from one another. Second, the HRV measurement was repeated in ten non-interrupted consecutive intervals. The lowest typical error (CV = 21.1% was found for the square root of the mean squared differences of successive RR intervals (rMSSD and the highest for the low frequency power (PLF (CV = 93.9%. The standardized changes in the mean were trivial to small. The correlation analysis revealed the highest level for ln rMSSD (ICC = 0.87, while ln PLF represented the worst case (ICC = 0.59. The reliability indices for ln rMSSD in 10 consecutive intervals improved (CV = 9.9%; trivial standardized changes in the mean; ICC = 0.96. In conclusion, major differences were found in the reliability level between the HRV indices. The rMSSD demonstrated the highest reliability level. No substantial influence of intrinsic biological variation on the HRV reliability was observed.

  2. Examining of the social problem solving skills in preschool children in terms of different variables

    Directory of Open Access Journals (Sweden)

    Şuheda Bozkurt Yükçü

    2017-09-01

    Full Text Available The purpose of this research is to examine preschool children's social problem solving skills in terms of various variables. The population of the study consisted of parents and their children between the ages four-six years who attend independent kindergartens located in Çankaya county of Ankara during the 2015-2016 academic year. The sample of the study selected by simple random sampling method, consisted of 240 parents and their children between the ages four-six years who attend independent kindergartens located in Çankaya counties of Ankara during the 2015-2016 academic year. In this study conducted by descriptive screenning model, General Information Form and Wally Child Social Problem Solving Detective Game Test were used. Kruskal Wallis-H Test, Independent Groups T Test, One Way Anova were used to analyze of data. According to the results of this study, social problem solving skills of children differ based on child’s age but do not differ based on gender, number of siblings, montly income, parents’s age, educational status and working status. The findings were discussed and interpreted within the scope of the literature.

  3. UV variability in Moscow according to long-term UV measurements and reconstruction model

    Directory of Open Access Journals (Sweden)

    N. Y. Chubarova

    2008-06-01

    Full Text Available Long-term measurements of erythemally weighted UV irradiance (Qer have been analyzed for the 1999–2006 period as well as UV variability according to a reconstruction model since 1968. The estimates of different atmospheric parameters effects, including NO2 content, on Qer have been obtained on seasonal and interannual scales. It has been shown that NO2 content in conditions of large megalopolis provides average Qer decrease of about 1.5–2%. The seasonal variations of the observed UV indices are discussed from the point of view of the impact on health. Using the reconstruction model we showed a distinct growth in Qer since 1980 due to changes in total ozone (+2.5% per decade, effective cloud amount transmission (+2.1% per decade and aerosol loading (+1.1% per decade. However, there is no change in Qer over the longer 1968–2006 period due to significant decrease in effective cloud amount transmission (−11% per decade in 1968–1980.

  4. UV variability in Moscow according to long-term UV measurements and reconstruction model

    Science.gov (United States)

    Chubarova, N. Y.

    2008-06-01

    Long-term measurements of erythemally weighted UV irradiance (Qer) have been analyzed for the 1999-2006 period as well as UV variability according to a reconstruction model since 1968. The estimates of different atmospheric parameters effects, including NO2 content, on Qer have been obtained on seasonal and interannual scales. It has been shown that NO2 content in conditions of large megalopolis provides average Qer decrease of about 1.5-2%. The seasonal variations of the observed UV indices are discussed from the point of view of the impact on health. Using the reconstruction model we showed a distinct growth in Qer since 1980 due to changes in total ozone (+2.5% per decade), effective cloud amount transmission (+2.1% per decade) and aerosol loading (+1.1% per decade). However, there is no change in Qer over the longer 1968-2006 period due to significant decrease in effective cloud amount transmission (-11% per decade) in 1968-1980.

  5. Short-term variability of aragonite saturation state in the central Mid-Atlantic Bight

    Science.gov (United States)

    Xu, Yuan-Yuan; Cai, Wei-Jun; Gao, Yonghui; Wanninkhof, Rik; Salisbury, Joseph; Chen, Baoshan; Reimer, Janet J.; Gonski, Stephen; Hussain, Najid

    2017-05-01

    The uptake of anthropogenic carbon dioxide (CO2) from the atmosphere has resulted in a decrease in seawater aragonite saturation state (Ωarag), which affects the health of carbonate-bearing organisms and the marine ecosystem. A substantial short-term variability of surface water Ωarag, with an increase of up to 0.32, was observed in the central Mid-Atlantic Bight off the Delaware and the Chesapeake Bays over a short period of 10 days in summer 2015. High-frequency underway measurements for temperature, salinity, percentage saturation of dissolved oxygen, oxygen to argon ratio, pH, fCO2, and measurements based on discrete samples for pH, dissolved inorganic carbon, and total alkalinity are used to investigate how physical and biogeochemical processes contribute to the changes of Ωarag. Quantitative analyses show that physical advection and mixing processes are the dominant forces for higher Ωarag in slope waters while biological carbon removal and CO2 degassing contribute to increased Ωarag in shelf waters.

  6. Research on problem solving skills of orienteering athletes in terms of some variables

    Directory of Open Access Journals (Sweden)

    Eroğlu Başak

    2016-01-01

    Full Text Available The aim of this study is to examine the problem solving skills of orienteering athletes in terms of different variables. 157 male and 43 female orienteering athletes, making a total of 200 athletes that joined the 3rd Level of Turkey Championship in 2015 have participated in this study which is in a survey model. The data collection tools were the Problem Solving Inventory and Personal Information Form that were formed by Heppner & Peterson (1982 and adapted into Turkish by Şahin, Şahin & Heppner (1993. In the data analysis, descriptive statics, anova, t test and Tukey test have been utilized. In the line with the findings, it has been determined that the difference between the total mean values (85.55+20.45 that the orienteering athletes got from the problem solving inventory and their age, marital status, sports age, the years of practice in orienteering sports, and the status of being national player is significant (p<0.05. It has been found that male orienteering athletes perform higher evaluating approach compared to the female athletes, and that as the age levels increase, the problem solving skill is affected more positively. Furthermore, it has been determined that the perceptions of the participants that have more experience and sports age in orienteering sports and that do orienteering sports at a national level are more positive in the matter of problem solving skills.

  7. TIMING VARIABILITY OF REACH TRAJECTORIES IN LEFT VERSUS RIGHT HEMISPHERE STROKE

    Science.gov (United States)

    Freitas, Sandra Maria Sbeghen Ferreira; Gera, Geetanjali; Scholz, John Peter

    2011-01-01

    This study investigated trajectory timing variability in right and left stroke survivors and healthy controls when reaching to a centrally located target under a fixed target condition or when the target could suddenly change position after reach onset. Trajectory timing variability was investigated with a novel method based on dynamic programming that identifies the steps required to time warp one trial’s acceleration time series to match that of a reference trial. Greater trajectory timing variability of both hand and joint motions was found for the paretic arm of stroke survivors compared to their non-paretic arm or either arm of controls. Overall, the non-paretic left arm of the LCVA group and the left arm of controls had higher timing variability than the non-paretic right arm of the RCVA group and right arm of controls. The shoulder and elbow joint warping costs were consistent predictors of the hand’s warping cost for both left and right arms only in the LCVA group, whereas the relationship between joint and hand warping costs was relatively weak in control subjects and less consistent across arms in the RCVA group. These results suggest that the left hemisphere may be more involved in trajectory timing, although the results may be confounded by skill differences between the arms in these right hand dominant participants. On the other hand, arm differences did not appear to be related to differences in targeting error. The paretic left arm of the RCVA exhibited greater trajectory timing variability than the paretic right arm of the LCVA group. This difference was highly correlated with the level of impairment of the arms. Generally, the effect of target uncertainty resulted in slightly greater trajectory timing variability for all participants. The results are discussed in light of previous studies of hemispheric differences in the control of reaching, in particular, left hemisphere specialization for temporal control of reaching movements. PMID:21920508

  8. EVALUATING SHORT-TERM CLIMATE VARIABILITY IN THE LATE HOLOCENE OF THE NORTHERN GREAT PLAINS

    Energy Technology Data Exchange (ETDEWEB)

    Joseph H. Hartman

    1999-09-01

    This literature study investigated methods and areas to deduce climate change and climate patterns, looking for short-term cycle phenomena and the means to interpret them. Many groups are actively engaged in intensive climate-related research. Ongoing research might be (overly) simplified into three categories: (1) historic data on weather that can be used for trend analysis and modeling; (2) detailed geological, biological (subfossil), and analytical (geochemical, radiocarbon, etc.) studies covering the last 10,000 years (about since last glaciation); and (3) geological, paleontological, and analytical (geochemical, radiometric, etc.) studies over millions of years. Of importance is our ultimate ability to join these various lines of inquiry into an effective means of interpretation. At this point, the process of integration is fraught with methodological troubles and misconceptions about what each group can contribute. This project has met its goals to the extent that it provided an opportunity to study resource materials and consider options for future effort toward the goal of understanding the natural climate variation that has shaped our current civilization. A further outcome of this project is a proposed methodology based on ''climate sections'' that provides spatial and temporal correlation within a region. The method would integrate cultural and climate data to establish the climate history of a region with increasing accuracy with progressive study and scientific advancement (e. g., better integration of regional and global models). The goal of this project is to better understand natural climatic variations in the recent past (last 5000 years). The information generated by this work is intended to provide better context within which to examine global climate change. The ongoing project will help to establish a basis upon which to interpret late Holocene short-term climate variability as evidenced in various studies in the northern

  9. Mechanisms of the global electric circuit and lightning variability on the ENSO time scale

    Science.gov (United States)

    Mareev, Evgeny; Volodin, Evgeny; Slyunyaev, Nikolay

    2017-04-01

    Many studies of lightning activity on the El Niño-Southern Oscillation (ENSO) time scale show increased activity over tropical land areas during the warm El Niño phase (e.g., Satori et al., 2009; Price, 2009). The mechanisms of this variability—particularly in terms of its role in the global electric circuit (GEC)—are still under debate (e.g., Williams and Mareev, 2014). In this study a general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modelling the GEC variability on the ENSO time scale. The ionospheric potential (IP) and the lightning flash rate are calculated to study regional peculiarities and possible mechanisms of lightning variation. The IP parameterisation is used (Mareev and Volodin, 2014) which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The account of conductivity variation in the IP parameterisation is suggested based on the approach realised in (Slyunyaev et al., 2014). Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. Numerical simulations suggest that the inter-annual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature (SST) in the Pacific Ocean (180W-100W, 5S-5N—El Niño area). The IP maximum corresponds to the SST minimum. This result can be explained taking into account that during El Niño (positive temperature anomaly) precipitations in the equatorial part of the Pacific increase while in other tropic zones including the land areas they decrease. Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. During the El Niño period in the model, the mean aerosol content in the atmosphere decrease, which is caused by the weakening of the winds over Sahara and

  10. Increase of Short-Term Heart Rate Variability Induced by Blood Pressure Measurements during Ambulatory Blood Pressure Monitoring

    Directory of Open Access Journals (Sweden)

    Attila Frigy

    2017-01-01

    Full Text Available Objective. The possible effect of blood pressure measurements per se on heart rate variability (HRV was studied in the setting of concomitant ambulatory blood pressure monitoring (ABPM and Holter ECG monitoring (HM. Methods. In 25 hypertensive patients (14 women and 11 men, mean age: 58.1 years, 24-hour combined ABPM and HM were performed. For every blood pressure measurement, 2-minute ECG segments (before, during, and after measurement were analyzed to obtain time domain parameters of HRV: SDNN and rMSSD. Mean of normal RR intervals (MNN, SDNN/MNN, and rMSSD/MNN were calculated, too. Parameter variations related to blood pressure measurements were analyzed using one-way ANOVA with multiple comparisons. Results. 2281 measurements (1518 during the day and 763 during the night were included in the analysis. Both SDNN and SDNN/MNN had a constant (the same for 24-hour, daytime, and nighttime values and significant change related to blood pressure measurements: an increase during measurements and a decrease after them (p<0.01 for any variation. Conclusion. In the setting of combined ABPM and HM, the blood pressure measurement itself produces an increase in short-term heart rate variability. Clarifying the physiological basis and the possible clinical value of this phenomenon needs further studies.

  11. Stability of Delayed Hopfield Neural Networks with Variable-Time Impulses

    Directory of Open Access Journals (Sweden)

    Yangjun Pei

    2014-01-01

    Full Text Available In this paper the globally exponential stability criteria of delayed Hopfield neural networks with variable-time impulses are established. The proposed criteria can also be applied in Hopfield neural networks with fixed-time impulses. A numerical example is presented to illustrate the effectiveness of our theoretical results.

  12. Cross shelf hydrographic and hydrochemical conditions and their short term variability at the northern Benguela during a normal upwelling season

    Science.gov (United States)

    Mohrholz, Volker; Eggert, Anja; Junker, Tim; Nausch, Günther; Ohde, Thomas; Schmidt, Martin

    2014-11-01

    Cross shelf hydrographic and hydrochemical conditions were investigated during the seasonal maximum of upwelling in the northern Benguela upwelling system. The study combines in situ observations, remotely sensed data and results of a regional 3-dimensional numerical model. In situ observations were recorded along a cross shelf transect off Namibia starting at 20°S 13°E, repeated five times during 16 August 2011 until 19 September 2011. Comparison of wind forcing and sea surface temperatures during the time of the expedition with long-term climatological data as well as the index of intensity of the Benguela upwelling indicates "normal" upwelling conditions in austral winter 2011 in the northern Benguela. Small scale temporal (days) and spatial (km) variability is high during the upwelling season, primarily caused by highly variable wind forcing and dynamics of mesoscale structures like eddies and filaments as found in remotely sensed data. This mesoscale dynamics impact the applicability of a conceptual 2-dimensional circulation model, i.e. a linear succession along the cross-shelf transect. Therefore, an age proxy for surface water was constructed based on oxygen and heat fluxes during the first aging period and on salinity and heat fluxes during the second phase. The application of an age proxy instead of distance to shore successfully validates the succession concept. Furthermore, the investigation of the upwelling strengths by analytical and circulation models verified their dependence on coastal- and curl driven upwelling processes with the onshore dominance of coastal upwelling. In the investigated time period, offshore, curl driven upwelling dominated with a maximum located on the shelf.

  13. Space-time variability of Indonesian rainfall at inter-annual and multi-decadal time scales

    Science.gov (United States)

    Yanto; Rajagopalan, Balaji; Zagona, Edith

    2016-11-01

    We investigated the space-time variability of wet (Nov-Apr) and dry (May-Oct) season rainfall over Indonesia, using monthly gridded rainfall data from the University of East Anglia Climatic Research Unit covering the period 1901-2012. Three complimentary techniques were employed—(1) principal component analysis to identify the dominant modes of variability, (2) wavelet spectral analysis to identify the spectral characteristics of the leading modes and their coherence with large scale climate variables and (3) Bayesian Dynamical Linear Model (BDLM) to quantify the temporal variability of the association between rainfall modes and climate variables. In the dry season when the Inter Tropical Convergence Zone (ITCZ) is to the north of the equator the leading two principal components (PCs) explain close to 50 % of the rainfall. In the wet season the ITCZ moves to the south and the leading PCs explain close to 30 % of the variance. El Niño Southern Oscillation (ENSO) is the driver of the leading modes of rainfall variability during both seasons. We find asymmetry in the teleconnections of ENSO to high and low rainfall years in the dry season. Furthermore, ENSO and the leading PCs of rainfall have spectral coherence in the inter-annual band (2-8 years) over the entire period of record and in the multi-decadal (8-16 years) band in post-1980 years. In addition, during the 1950-1980 period the second mode of variability in both seasons has a strong relationship with Pacific Decadal Oscillation. The association between ENSO and the leading mode of Indonesian rainfall has strengthened in recent decades, more so during dry season. These inter-annual and multi-decadal variability of Indonesian rainfall modulated by Pacific climate drivers has implications for rainfall and hydrologic predictability important for water resources management.

  14. A Time-Series Water Level Forecasting Model Based on Imputation and Variable Selection Method

    Directory of Open Access Journals (Sweden)

    Jun-He Yang

    2017-01-01

    Full Text Available Reservoirs are important for households and impact the national economy. This paper proposed a time-series forecasting model based on estimating a missing value followed by variable selection to forecast the reservoir’s water level. This study collected data from the Taiwan Shimen Reservoir as well as daily atmospheric data from 2008 to 2015. The two datasets are concatenated into an integrated dataset based on ordering of the data as a research dataset. The proposed time-series forecasting model summarily has three foci. First, this study uses five imputation methods to directly delete the missing value. Second, we identified the key variable via factor analysis and then deleted the unimportant variables sequentially via the variable selection method. Finally, the proposed model uses a Random Forest to build the forecasting model of the reservoir’s water level. This was done to compare with the listing method under the forecasting error. These experimental results indicate that the Random Forest forecasting model when applied to variable selection with full variables has better forecasting performance than the listing model. In addition, this experiment shows that the proposed variable selection can help determine five forecast methods used here to improve the forecasting capability.

  15. A Time-Series Water Level Forecasting Model Based on Imputation and Variable Selection Method.

    Science.gov (United States)

    Yang, Jun-He; Cheng, Ching-Hsue; Chan, Chia-Pan

    2017-01-01

    Reservoirs are important for households and impact the national economy. This paper proposed a time-series forecasting model based on estimating a missing value followed by variable selection to forecast the reservoir's water level. This study collected data from the Taiwan Shimen Reservoir as well as daily atmospheric data from 2008 to 2015. The two datasets are concatenated into an integrated dataset based on ordering of the data as a research dataset. The proposed time-series forecasting model summarily has three foci. First, this study uses five imputation methods to directly delete the missing value. Second, we identified the key variable via factor analysis and then deleted the unimportant variables sequentially via the variable selection method. Finally, the proposed model uses a Random Forest to build the forecasting model of the reservoir's water level. This was done to compare with the listing method under the forecasting error. These experimental results indicate that the Random Forest forecasting model when applied to variable selection with full variables has better forecasting performance than the listing model. In addition, this experiment shows that the proposed variable selection can help determine five forecast methods used here to improve the forecasting capability.

  16. Instrumental variable method for time-to-event data using a pseudo-observation approach.

    Science.gov (United States)

    Kjaersgaard, Maiken I S; Parner, Erik T

    2016-06-01

    Observational studies are often in peril of unmeasured confounding. Instrumental variable analysis is a method for controlling for unmeasured confounding. As yet, theory on instrumental variable analysis of censored time-to-event data is scarce. We propose a pseudo-observation approach to instrumental variable analysis of the survival function, the restricted mean, and the cumulative incidence function in competing risks with right-censored data using generalized method of moments estimation. For the purpose of illustrating our proposed method, we study antidepressant exposure in pregnancy and risk of autism spectrum disorder in offspring, and the performance of the method is assessed through simulation studies. © 2015, The International Biometric Society.

  17. Scheduling Jobs with Variable Job Processing Times on Unrelated Parallel Machines

    Directory of Open Access Journals (Sweden)

    Guang-Qian Zhang

    2014-01-01

    Full Text Available m unrelated parallel machines scheduling problems with variable job processing times are considered, where the processing time of a job is a function of its position in a sequence, its starting time, and its resource allocation. The objective is to determine the optimal resource allocation and the optimal schedule to minimize a total cost function that dependents on the total completion (waiting time, the total machine load, the total absolute differences in completion (waiting times on all machines, and total resource cost. If the number of machines is a given constant number, we propose a polynomial time algorithm to solve the problem.

  18. Scheduling jobs with variable job processing times on unrelated parallel machines.

    Science.gov (United States)

    Zhang, Guang-Qian; Wang, Jian-Jun; Liu, Ya-Jing

    2014-01-01

    m unrelated parallel machines scheduling problems with variable job processing times are considered, where the processing time of a job is a function of its position in a sequence, its starting time, and its resource allocation. The objective is to determine the optimal resource allocation and the optimal schedule to minimize a total cost function that dependents on the total completion (waiting) time, the total machine load, the total absolute differences in completion (waiting) times on all machines, and total resource cost. If the number of machines is a given constant number, we propose a polynomial time algorithm to solve the problem.

  19. A Methodology to Infer Crop Yield Response to Climate Variability and Change Using Long-Term Observations

    Directory of Open Access Journals (Sweden)

    Manfred A. Lange

    2013-11-01

    Full Text Available A new methodology to extract crop yield response to climate variability and change from long-term crop yield observations is presented in this study. In contrast to the existing first-difference approach (FDA, the proposed methodology considers that the difference in value between crop yields of two consecutive years reflects necessarily the contributions of climate and management conditions, especially at large spatial scales where both conditions may vary significantly from one year to the next. Our approach was applied to remove the effect of non-climatic factors on crop yield and, hence, to isolate the effect of the observed climate change between 1961 and 2006 on three widely crops grown in three Mediterranean countries—namely wheat, corn and potato—using national-level crop yield observations’ time-series. Obtained results show that the proposed methodology provides us with a ground basis to improve substantially our understanding of crop yield response to climate change at a scale that is relevant to large-scale estimations of agricultural production and to food security analyses; and therefore to reduce uncertainties in estimations of potential climate change effects on agricultural production. Furthermore, a comparison of outputs of our methodology and FDA outputs yielded a difference in terms of maize production in Egypt, for example, that exceeds the production of some neighbouring countries.

  20. 34 CFR 674.32 - Special terms: loans to less than half-time student borrowers.

    Science.gov (United States)

    2010-07-01

    ... 34 Education 3 2010-07-01 2010-07-01 false Special terms: loans to less than half-time student... (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL PERKINS LOAN PROGRAM Terms of Loans § 674.32 Special terms: loans to less than half-time student borrowers. (a) The promissory note...

  1. Time-Frequency Signal Representations Using Interpolations in Joint-Variable Domains

    Science.gov (United States)

    2016-06-14

    nature classification using dynamic time warping ,” IEEE Trans. Aerosp. Electron. Syst., vol. 46, no. 3, pp. 1078–1096, Jul. 2010. [12] S. S. Ram, C...SECURITY CLASSIFICATION OF: Time -frequency (TF) representations are a powerful tool for analyzing Doppler and micro-Doppler signals. These signals are...applied in the instantaneous autocorrelation domain over the time variable, the low-pass filter characteristic underlying linear interpolators lends

  2. Low-Energy Real-Time OS Using Voltage Scheduling Algorithm for Variable Voltage Processors

    OpenAIRE

    Okuma, Takanori; Yasuura, Hiroto

    2001-01-01

    This paper presents a real-time OS based on $ mu $ITRON using proposed voltage scheduling algorithm for variable voltage processors which can vary supply voltage dynamically. The proposed voltage scheduling algorithms assign voltage level for each task dynamically in order to minimize energy consumption under timing constraints. Using the presented real-time OS, running tasks with low supply voltage leads to drastic energy reduction. In addition, the presented voltage scheduling algorithm is ...

  3. Long-term variability and environmental control of the carbon cycle in an oak-dominated temperate forest

    Science.gov (United States)

    Jing Xie; Jiquan Chen; Ge Sun; Housen Chu; Asko Noormets; Zutao Ouyang; Ranjeet John; Shiqiang Wan; Wenbin Guan

    2014-01-01

    Our understanding of the long-term carbon (C) cycle of temperate deciduous forests and its sensitivity to climate variability is limited due to the large temporal dynamics of C fluxes. The goal of the study was to quantify the effects of environmental variables on the C balance in a 70-year-old mixed-oak woodland forest over a 7-year period in northwest Ohio, USA. The...

  4. Discriminant Analysis of Time Series in the Presence of Within-Group Spectral Variability.

    Science.gov (United States)

    Krafty, Robert T

    2016-07-01

    Many studies record replicated time series epochs from different groups with the goal of using frequency domain properties to discriminate between the groups. In many applications, there exists variation in cyclical patterns from time series in the same group. Although a number of frequency domain methods for the discriminant analysis of time series have been explored, there is a dearth of models and methods that account for within-group spectral variability. This article proposes a model for groups of time series in which transfer functions are modeled as stochastic variables that can account for both between-group and within-group differences in spectra that are identified from individual replicates. An ensuing discriminant analysis of stochastic cepstra under this model is developed to obtain parsimonious measures of relative power that optimally separate groups in the presence of within-group spectral variability. The approach possess favorable properties in classifying new observations and can be consistently estimated through a simple discriminant analysis of a finite number of estimated cepstral coefficients. Benefits in accounting for within-group spectral variability are empirically illustrated in a simulation study and through an analysis of gait variability.

  5. Application of Remote Sensing to Assess the Impact of Short Term Climate Variability on Coastal Sedimentation

    Science.gov (United States)

    Moeller, Christopher C.; Gunshor, Mathew M.; Menzel, W. Paul; Huh, Oscar K.; Walker, Nan D.; Rouse, Lawrence J.; Frey, Herbert V. (Technical Monitor)

    2001-01-01

    The University of Wisconsin and Louisiana State University have teamed to study the forcing of winter season cold frontal wind systems on sediment distribution patterns and geomorphology in the Louisiana coastal zone. Wind systems associated with cold fronts have been shown to modify coastal circulation and resuspend sediments along the microtidal Louisiana coast. The assessment includes quantifying the influence of cumulative winter season atmospheric forcing (through surface wind observations) from year to year in response to short term climate variability, such as El Nino events. A correlation between winter cyclone frequency and the strength of El Nino events has been suggested. The atmospheric forcing data are being correlated to geomorphic measurements along western Louisiana's prograding muddy coast. Remote sensing data is being used to map and track sediment distribution patterns for various wind conditions. Transferring a suspended sediment concentration (SSC) algorithm to EOS MODIS observations will enable estimates of SSC in case 2 waters over the global domain. Progress in Year 1 of this study has included data collection and analysis of wind observations for atmospheric forcing characterization, a field activity (TX-2001) to collect in situ water samples with co-incident remote sensing measurements from the NASA ER-2 based MODIS Airborne Simulator (MAS) and the EOS Terra based MODerate resolution Imaging Spectroradiometer (MODIS) instruments, aerial photography and of sediment burial pipe field measurements along the prograding muddy Chenier Plain coast of western Louisiana for documenting coastal change in that dynamic region, and routine collection of MODIS 250 in resolution data for monitoring coastal sediment patterns. The data sets are being used in a process to transfer an SSC estimation algorithm to the MODIS platform. Work is underway on assessing coastal transport for the winter 2000-01 season. Water level data for use in a Geomorphic Impact

  6. Spatial and temporal variability and long-term trends in skew surges globally

    Directory of Open Access Journals (Sweden)

    Robert eMawdsley

    2016-03-01

    Full Text Available Storm surges and the resulting extreme high sea levels are among the most dangerous natural disasters and are responsible for widespread social, economic and environmental consequences. Using a set of 220 tide gauges, this paper investigates the temporal variations in storm surges around the world and the spatial coherence of its variability. We compare results derived from two parameters used to represent storm surge: skew surge and the more traditional, non-tidal residual. We determine the extent of tide-surge interaction, at each study site, and find statistically significant (95% confidence levels of tide-surge interaction at 59% of sites based on tidal level and 81% of sites based on tidal-phase. The tide-surge interaction was strongest in regions of shallow bathymetry such as the North Sea, north Australia and the Malay Peninsula. At most sites the trends in the skew surge time series were similar to those of non-tidal residuals, but where there were large differences in trends, the sites tended to have a large tidal range. Only 13% of sites had a statistically significant trend in skew surge, and of these approximately equal numbers were positive and negative. However, for trends in the non-tidal residual there are significantly more negative trends. We identified 8 regions where there were strong positive correlations in skew surge variability between sites, which meant that a regional index could be created to represent these groups of sites. Despite, strong correlations between some regional skew surge indices, none are significant at the 95% level, however, at the 80% level there was significant positive correlation between the north-west Atlantic - south and the North Sea. Correlations between the regional skew surge indices and climate indices only became significant at the 80% level, where Nińo 4 was positively correlated with the Gulf of Mexico skew surge index and negatively correlated with the east Australia skew surge index

  7. Stride-Time Variability and Fall Risk in Persons with Multiple Sclerosis

    Directory of Open Access Journals (Sweden)

    Yaejin Moon

    2015-01-01

    Full Text Available Gait variability is associated with falls in clinical populations. However, gait variability’s link to falls in persons with Multiple Sclerosis (PwMS is not well established. This investigation examined the relationship between stride-time variability, fall risk, and physiological fall risk factors in PwMS. 17 PwMS (62.8±7.4 years and 17 age-matched controls (62.8±5.9 years performed the 6-minute walk test. Stride-time was assessed with accelerometers attached to the participants’ shanks. Stride-time variability was measured by interstride coefficient of variation (CV of stride-time. The participant’s fall risk was measured by the short form physiological profile assessment (PPA. A Spearman correlation analysis was used to determine the relationship between variables. Increased fall risk was strongly associated with increased stride-time CV in both PwMS (ρ=0.71, p0.05. In PwMS, stride-time CV was related to postural sway (ρ=0.74, p<0.01 while in the control group, it was related to proprioception (ρ=0.61, p<0.01 and postural sway (ρ=0.78, p<0.01. Current observations suggest that gait variability is maybe more sensitive marker of fall risk than average gait parameters in PwMS. It was also noted that postural sway may be potentially targeted to modify gait variability in PwMS.

  8. [Timing of clamping and factors associated with iron stores in full-term newborns].

    Science.gov (United States)

    Oliveira, Fabiana de Cássia Carvalho; Assis, Karine Franklin; Martins, Mariana Campos; Prado, Mara Rúbia Maciel Cardoso do; Ribeiro, Andréia Queiroz; Sant'Ana, Luciana Ferreira da Rocha; Priore, Silvia Eloiza; Franceschini, Sylvia do Carmo Castro

    2014-02-01

    To analyze the impact of timing of clamping and obstetric, biological and socioeconomic factors on the iron stores of full-term newborns. Cross-sectional study between October 2011 and July 2012 in which hematological parameters were evaluated for newborns in Viçosa, MG, Southeastern Brazil. It involved collecting 7 mL of umbilical cord blood from 144 full-term not underweight newborns. The parameters investigated were complete blood count, serum iron, ferritin and C-reactive protein. The time of umbilical cord clamping was measured using a digital timer without interfering in the procedures of childbirth. The birth data were collected from Live Birth Certificates and other information was obtained from the mother through a questionnaire applied in the first month postpartum. Analysis of multiple linear regression was then used to estimate the influence of biological, obstetrics and socioeconomic factors on the ferritin levels at birth. The median ferritin was 130.3 µg/L (n = 129, minimum = 16.4; maximum = 420.5 µg/L), the mean serum iron was 137.9 μg/dL (n = 144, SD = 39.29) and mean hemoglobin was 14.7 g/dL (n = 144, SD = 1.47). The median time of cord clamping was 36 seconds, ranging between 7 and 100. The bivariate analysis detected an association between ferritin levels and color of the child, timing clamping of 60 seconds, type of delivery, the presence of gestational diabetes and per capita family income. In multivariate analysis, the variables per capita income, number of antenatal visits and length at birth accounted for 22.0% of variation in ferritin levels. Iron stores at birth were influenced by biological, obstetric and social characteristics. Tackling anemia should involve creating policies aimed at reducing social inequalities, improving the quality of antenatal care, as well as implementing a criterion of delayed clamping of the umbilical cord within the guidelines of labor.

  9. Modified Pressure-Correction Projection Methods: Open Boundary and Variable Time Stepping

    KAUST Repository

    Bonito, Andrea

    2014-10-31

    © Springer International Publishing Switzerland 2015. In this paper, we design and study two modifications of the first order standard pressure increment projection scheme for the Stokes system. The first scheme improves the existing schemes in the case of open boundary condition by modifying the pressure increment boundary condition, thereby minimizing the pressure boundary layer and recovering the optimal first order decay. The second scheme allows for variable time stepping. It turns out that the straightforward modification to variable time stepping leads to unstable schemes. The proposed scheme is not only stable but also exhibits the optimal first order decay. Numerical computations illustrating the theoretical estimates are provided for both new schemes.

  10. Long-Term Acoustic Real-Time Sensor for Polar Areas (LARA)

    Science.gov (United States)

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Long- term Acoustic Real-Time Sensor for Polar Areas (LARA...13-1-0345 http://www.bioacoustics.us LONG- TERM GOALS With ONR/DURIP funding, we are currently developing the Long- term Acoustic Real-Time...is not possible to update the system clock by GPS, which might drift significantly during long- term deployments and hinder accurate localization of

  11. Electrical Activity in a Time-Delay Four-Variable Neuron Model under Electromagnetic Induction

    Directory of Open Access Journals (Sweden)

    Keming Tang

    2017-11-01

    Full Text Available To investigate the effect of electromagnetic induction on the electrical activity of neuron, the variable for magnetic flow is used to improve Hindmarsh–Rose neuron model. Simultaneously, due to the existence of time-delay when signals are propagated between neurons or even in one neuron, it is important to study the role of time-delay in regulating the electrical activity of the neuron. For this end, a four-variable neuron model is proposed to investigate the effects of electromagnetic induction and time-delay. Simulation results suggest that the proposed neuron model can show multiple modes of electrical activity, which is dependent on the time-delay and external forcing current. It means that suitable discharge mode can be obtained by selecting the time-delay or external forcing current, which could be helpful for further investigation of electromagnetic radiation on biological neuronal system.

  12. Variability of African Farming Systems from Phenological Analysis of NDVI Time Series

    Science.gov (United States)

    Vrieling, Anton; deBeurs, K. M.; Brown, Molly E.

    2011-01-01

    Food security exists when people have access to sufficient, safe and nutritious food at all times to meet their dietary needs. The natural resource base is one of the many factors affecting food security. Its variability and decline creates problems for local food production. In this study we characterize for sub-Saharan Africa vegetation phenology and assess variability and trends of phenological indicators based on NDVI time series from 1982 to 2006. We focus on cumulated NDVI over the season (cumNDVI) which is a proxy for net primary productivity. Results are aggregated at the level of major farming systems, while determining also spatial variability within farming systems. High temporal variability of cumNDVI occurs in semiarid and subhumid regions. The results show a large area of positive cumNDVI trends between Senegal and South Sudan. These correspond to positive CRU rainfall trends found and relate to recovery after the 1980's droughts. We find significant negative cumNDVI trends near the south-coast of West Africa (Guinea coast) and in Tanzania. For each farming system, causes of change and variability are discussed based on available literature (Appendix A). Although food security comprises more than the local natural resource base, our results can perform an input for food security analysis by identifying zones of high variability or downward trends. Farming systems are found to be a useful level of analysis. Diversity and trends found within farming system boundaries underline that farming systems are dynamic.

  13. Radon hazard in shallow groundwaters: Amplification and long term variability induced by rainfall

    Energy Technology Data Exchange (ETDEWEB)

    De Francesco, S., E-mail: stefano.defrancesco@unina2.it [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); Tommasone, F. Pascale [Office of Civil Protection, Meteorology, Climatology and Natural Hazards, Piazza Municipio, 81051 Pietramelara, Caserta (Italy); Cuoco, E.; Verrengia, G. [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); Tedesco, D. [Department of Environmental Sciences, Second University of Naples, Via Vivaldi, 43, 81100 Caserta (Italy); C.N.R. (Italian Council for Research), Institute of Environmental Geology and Geological Engineering, Piazzale Aldo Moro, 00100 Roma (Italy)

    2010-01-15

    {sup 222}Rn concentrations have been determined with a RAD7 radon detector in shallow groundwaters of the Pietramelara Plain, north-western Campania, southern Italy, where pyroclastic deposits, along with recent stream alluvial sediments, come in contact with Mesozoic carbonate reservoirs. The aim of this study has been to study the annual variation of {sup 222}Rn concentration in the shallow groundwaters, scarcely considered in the literature and of obvious relevance for radon hazard evaluation. Our results definitely show that {sup 222}Rn levels are characterized by a clear annual periodicity, strictly related to rainfall and water table levels, with a pronounced difference between the dry and the wet season. In this last case with concentrations increasing up to two orders of magnitude (up to two times the lower threshold given in the Recommendation 2001/928/EURATOM for public waters). In relation to this, experimental field data will be presented to demonstrate that this variability is due to purely hydrological mechanisms, mainly rinse out and discharge that control leaching efficiency. The detected cycle (Radon Hydrological Amplification Cycle, RHAC) has been generalized for the Mediterranean Tyrrhenian climate. The marked and seasonally persistent amplification in {sup 222}Rn levels poses the problem of evaluating the epidemiological risk brought up by this previously not yet reported mechanism. This mechanism, occurring in shallow groundwaters, very likely should strongly influence indoor radon levels via groundwater-soil-building exchange.

  14. A space-time spectral collocation algorithm for the variable order fractional wave equation.

    Science.gov (United States)

    Bhrawy, A H; Doha, E H; Alzaidy, J F; Abdelkawy, M A

    2016-01-01

    The variable order wave equation plays a major role in acoustics, electromagnetics, and fluid dynamics. In this paper, we consider the space-time variable order fractional wave equation with variable coefficients. We propose an effective numerical method for solving the aforementioned problem in a bounded domain. The shifted Jacobi polynomials are used as basis functions, and the variable-order fractional derivative is described in the Caputo sense. The proposed method is a combination of shifted Jacobi-Gauss-Lobatto collocation scheme for the spatial discretization and the shifted Jacobi-Gauss-Radau collocation scheme for temporal discretization. The aforementioned problem is then reduced to a problem consists of a system of easily solvable algebraic equations. Finally, numerical examples are presented to show the effectiveness of the proposed numerical method.

  15. Predictor variables for a half marathon race time in recreational male runners

    Directory of Open Access Journals (Sweden)

    Rüst CA

    2011-08-01

    Full Text Available Christoph Alexander Rüst1, Beat Knechtle1,2, Patrizia Knechtle2, Ursula Barandun1, Romuald Lepers3, Thomas Rosemann11Institute of General Practice and Health Services Research, University of Zurich, Zurich, Switzerland; 2Gesundheitszentrum St Gallen, St Gallen, Switzerland; 3INSERM U887, University of Burgundy, Faculty of Sport Sciences, Dijon, FranceAbstract: The aim of this study was to investigate predictor variables of anthropometry, training, and previous experience in order to predict a half marathon race time for future novice recreational male half marathoners. Eighty-four male finishers in the ‘Half Marathon Basel’ completed the race distance within (mean and standard deviation, SD 103.9 (16.5 min, running at a speed of 12.7 (1.9 km/h. After multivariate analysis of the anthropometric characteristics, body mass index (r = 0.56, suprailiacal (r = 0.36 and medial calf skin fold (r = 0.53 were related to race time. For the variables of training and previous experience, speed in running of the training sessions (r = –0.54 were associated with race time. After multivariate analysis of both the significant anthropometric and training variables, body mass index (P = 0.0150 and speed in running during training (P = 0.0045 were related to race time. Race time in a half marathon might be partially predicted by the following equation (r2 = 0.44: Race time (min = 72.91 + 3.045 * (body mass index, kg/m2 –3.884 * (speed in running during training, km/h for recreational male runners. To conclude, variables of both anthropometry and training were related to half marathon race time in recreational male half marathoners and cannot be reduced to one single predictor variable.Keywords: anthropometry, body fat, skin-folds, training, endurance

  16. Short-term association between personal exposure to noise and heart rate variability: The RECORD MultiSensor Study.

    Science.gov (United States)

    El Aarbaoui, Tarik; Méline, Julie; Brondeel, Ruben; Chaix, Basile

    2017-12-01

    Studies revealed long-term associations between noise exposure and cardiovascular health, but the underlying short-term mechanisms remain uncertain. To explore the concomitant and lagged short-term associations between personal exposure to noise and heart rate variability (HRV) in a real life setting in the Île-de-France region. The RECORD MultiSensor Study collected between July 2014 and June 2015 noise and heart rate data for 75 participants, aged 34-74 years, in their living environments for 7 days using a personal dosimeter and electrocardiography (ECG) sensor on the chest. HRV parameters and noise levels were calculated for 5-min windows. Short-term relationships between noise level and log-transformed HRV parameters were assessed using mixed effects models with a random intercept for participants and a temporal autocorrelation structure, adjusted for heart rate, physical activity (accelerometry), and short-term trends. An increase by one dB(A) of A-weighted equivalent sound pressure level (Leq) was associated with a 0.97% concomitant increase of the Standard deviation of normal to normal intervals (SDNN) (95% CI: 0.92, 1.02), of 2.08% of the Low frequency band power (LF) (95% CI: 1.97, 2.18), of 1.30% of the High frequency band power (HF) (95% CI: 1.17, 1.43), and of 1.16% of the LF/HF ratio (95% CI: 1.10, 1.23). The analysis of lagged exposures to noise adjusted for the concomitant exposure illustrates the dynamic of recovery of the autonomic nervous system. Non-linear associations were documented with all HRV parameters with the exception of HF. Piecewise regression revealed that the association was almost 6 times stronger below than above 65 Leq dB(A) for the SDNN and LF/HF ratio. Personal noise exposure was found to be related to a concomitant increase of the overall HRV, with evidence of imbalance of the autonomic nervous system towards sympathetic activity, a pathway to increased cardiovascular morbidity and mortality. Copyright © 2017 Elsevier Ltd

  17. Development and validation of a prediction model for long-term sickness absence based on occupational health survey variables.

    Science.gov (United States)

    Roelen, Corné; Thorsen, Sannie; Heymans, Martijn; Twisk, Jos; Bültmann, Ute; Bjørner, Jakob

    2018-01-01

    The purpose of this study is to develop and validate a prediction model for identifying employees at increased risk of long-term sickness absence (LTSA), by using variables commonly measured in occupational health surveys. Based on the literature, 15 predictor variables were retrieved from the DAnish National working Environment Survey (DANES) and included in a model predicting incident LTSA (≥4 consecutive weeks) during 1-year follow-up in a sample of 4000 DANES participants. The 15-predictor model was reduced by backward stepwise statistical techniques and then validated in a sample of 2524 DANES participants, not included in the development sample. Identification of employees at increased LTSA risk was investigated by receiver operating characteristic (ROC) analysis; the area-under-the-ROC-curve (AUC) reflected discrimination between employees with and without LTSA during follow-up. The 15-predictor model was reduced to a 9-predictor model including age, gender, education, self-rated health, mental health, prior LTSA, work ability, emotional job demands, and recognition by the management. Discrimination by the 9-predictor model was significant (AUC = 0.68; 95% CI 0.61-0.76), but not practically useful. A prediction model based on occupational health survey variables identified employees with an increased LTSA risk, but should be further developed into a practically useful tool to predict the risk of LTSA in the general working population. Implications for rehabilitation Long-term sickness absence risk predictions would enable healthcare providers to refer high-risk employees to rehabilitation programs aimed at preventing or reducing work disability. A prediction model based on health survey variables discriminates between employees at high and low risk of long-term sickness absence, but discrimination was not practically useful. Health survey variables provide insufficient information to determine long-term sickness absence risk profiles. There is a need for

  18. Seasonal variability of the Red Sea, from GRACE time-variable gravity and altimeter sea surface height measurements

    Science.gov (United States)

    Wahr, John; Smeed, David; Leuliette, Eric; Swenson, Sean

    2014-05-01

    Seasonal variability of sea surface height and mass within the Red Sea, occurs mostly through the exchange of heat with the atmosphere and wind-driven inflow and outflow of water through the strait of Bab el Mandab that opens into the Gulf of Aden to the south. The seasonal effects of precipitation and evaporation, of water exchange through the Suez Canal to the north, and of runoff from the adjacent land, are all small. The flow through the Bab el Mandab involves a net mass transfer into the Red Sea during the winter and a net transfer out during the summer. But that flow has a multi-layer pattern, so that in the summer there is actually an influx of cool water at intermediate (~100 m) depths. Thus, summer water in the southern Red Sea is warmer near the surface due to higher air temperatures, but cooler at intermediate depths (especially in the far south). Summer water in the northern Red Sea experiences warming by air-sea exchange only. The temperature profile affects the water density, which impacts the sea surface height but has no effect on vertically integrated mass. Here, we study this seasonal cycle by combining GRACE time-variable mass estimates, altimeter (Jason-1, Jason-2, and Envisat) measurements of sea surface height, and steric sea surface height contributions derived from depth-dependent, climatological values of temperature and salinity obtained from the World Ocean Atlas. We find good consistency, particularly in the northern Red Sea, between these three data types. Among the general characteristics of our results are: (1) the mass contributions to seasonal SSHT variations are much larger than the steric contributions; (2) the mass signal is largest in winter, consistent with winds pushing water into the Red Sea through the Strait of Bab el Mandab in winter, and out during the summer; and (3) the steric signal is largest in summer, consistent with summer sea surface warming.

  19. Short-term variability of surface heat budget of the east central Arabian Sea during November, 1992

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, B.; Murty, V.S.N.; Rao, L.V.G.

    The analysis of surface meteorological data collected from the east central Arabian Sea during 10-28 November, 1992 revealed considerable variability in the meteorological parameters and heat budget components on both daily and diurnal time scales...

  20. Determining long-term water quality change in the presence of climate variability: Lake Tahoe (U.S.A.)

    National Research Council Canada - National Science Library

    Jassby A.D; Reuter J.E; Goldman C.R

    2003-01-01

    We developed a time series model of Secchi depth for Lake Tahoe incorporating a mechanistic understanding of interannual variability with sufficient simplicity to allow data-based parameter estimation...

  1. Countermovement jump height: gender and sport-specific differences in the force-time variables.

    Science.gov (United States)

    Laffaye, Guillaume; Wagner, Phillip P; Tombleson, Tom I L

    2014-04-01

    The goal of this study was to assess (a) the eccentric rate of force development, the concentric force, and selected time variables on vertical performance during countermovement jump, (b) the existence of gender differences in these variables, and (c) the sport-specific differences. The sample was composed of 189 males and 84 females, all elite athletes involved in college and professional sports (primarily football, basketball, baseball, and volleyball). The subjects performed a series of 6 countermovement jumps on a force plate (500 Hz). Average eccentric rate of force development (ECC-RFD), total time (TIME), eccentric time (ECC-T), Ratio between eccentric and total time (ECC-T:T) and average force (CON-F) were extracted from force-time curves and the vertical jumping performance, measured by impulse momentum. Results show that CON-F (r = 0.57; p height (JH), whereas the time variables are slightly and negatively correlated (r = -0.21-0.23, p sport-specific signatures: volleyball players revealed a temporal-prevailing profile, a weak-force with large ECC-T:T for basketball players and explosive and powerful profiles for football and baseball players.

  2. Observations of entrainment and time variability in the HH 47 jet

    Science.gov (United States)

    Hartigan, Patrick; Morse, Jon A.; Heathcote, Steve; Cecil, Gerald

    1993-01-01

    We present new Fabry-Perot images of the HH 47 jet that show the first clear evidence for entrainment in a jet from a young star. The material in the jet moves faster down the axis of the flow and slower at the edges, similar to viscous flow in a pipe. The higher excitation lines occur along the edges of the jet, as expected if entrainment accelerates and heats the ambient material. We confirm previous observations of multiple bow shocks in this system. Together, time variability and entrainment produce much of the observed shock-excited gas in this object. Our data show that the 'wiggles' along the jet are not caused by jet material tied to a spiraling magnetic field, but instead result from time variability, variable ejection angles, or inhomogeneities in the flow. The gas entrained in the HH 47 jet may be atomic; our results do not provide direct evidence that stellar jets drive molecular outflows.

  3. Real-time energy resources scheduling considering short-term and very short-term wind forecast

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Marco; Sousa, Tiago; Morais, Hugo; Vale, Zita [Polytechnic of Porto (Portugal). GECAD - Knowledge Engineering and Decision Support Research Center

    2012-07-01

    This paper proposes an energy resources management methodology based on three distinct time horizons: day-ahead scheduling, hour-ahead scheduling, and real-time scheduling. In each scheduling process the update of generation and consumption operation and of the storage and electric vehicles storage status are used. Besides the new operation conditions, the most accurate forecast values of wind generation and of consumption using results of short-term and very short-term methods are used. A case study considering a distribution network with intensive use of distributed generation and electric vehicles is presented. (orig.)

  4. Long term variability of the annual hydrological regime and sensitivity to temperature phase shifts in Saxony/Germany

    OpenAIRE

    Renner, M.; Bernhofer, C.

    2011-01-01

    The timing of the seasons strongly effects ecosystems and human activities. Recently, there is increasing evidence of changes in the timing of the seasons, such as earlier spring seasons detected in phenological records, advanced seasonal timing of surface temperature, earlier snow melt or streamflow timing. For water resources management there is a need to quantitatively describe the variability in the timing of hydrological regimes and to understand how climatic changes control the seasonal...

  5. Test of synthetic DNA tracers in a periodic hydrodynamic system for time-variable transit time distribution assessment

    Science.gov (United States)

    Dahlke, H. E.; Wang, C.; McNew, C.; McLaughlin, S.; Lyon, S. W.

    2016-12-01

    Recent research on time-varying transport through hydrologic systems proposed using decomposed over-printed tracer breakthrough curves to directly observe transport through complex flow systems. This method, also known as the PERTH (Periodic Tracer Hierarchy) method requires periodic flow and multiple tracer injections to reveal changes in flow pathways and transport behavior. Time-variable transit time distributions (TTD) estimated from tracer breakthrough curves often vary with the storage state of the system, which in turn is influenced by internal and external variabilities, such as the arrangement of flow pathways and fluctuations in system inputs. Deciphering internal from external variabilities in TTDs might help to advance the use of TTDs for estimating the physical state of a system; however, thus far the finite number of unique conservative tracers available for tracing has limited deeper insights. Synthetic DNA tracers consisting of short strands of synthetic DNA encapsulated by polylactic acid (PLA) microspheres could potentially provide multiple unique tracers with identical transport properties needed to explore time varying transport through hydrologic systems in more detail. An experiment was conducted on the miniLeo hillslope, a 1 m3 sloping lysimeter, within the Biosphere 2 Landscape Evolution Observatory near Tucson, AZ to investigate transit time variability. The goal of the experiment was to 1) test the suitability of using synthetic DNA tracers for estimating TTDs in a hydrologic system and 2) to determine the TTDs of individual tracer pulses under periodic steady-state conditions. Five DNA tracers, consisting of four unique, encapsulated DNA sequences and one free/non-encapsulated DNA sequence, were applied as reference and probe tracers together with deuterium, using the PERTH method. The lysimeter received three 2-hour pulses of rainfall at a rate of 30 mm/hr for 10 days. Initial results show that both the encapsulated and free DNA tracers

  6. Assessment of noise in non-tectonic displacement derived from GRACE time-variable gravity filed

    Science.gov (United States)

    Li, Weiwei; Shen, Yunzhong

    2017-04-01

    Many studies have been focusing on estimating the noises in GNSS monitoring time series. While the noises of GNSS time series after the correction with non-tectonic displacement should be re-estimated. Knowing the noises in the non-tectonic can help to better identify the sources of re-estimated noises. However, there is a lack of knowledge of noises in the non-tectonic displacement. The objective of this work is to assess the noise in the non-tectonic displacement. GRACE time-variable gravity is used to reflect the global mass variation. The GRACE stokes coefficients of the gravity field are used to calculate the non-tectonic surface displacement at any point on the surface. The Atmosphere and Ocean AOD1B de-aliasing model to the GRACE solutions is added because the complete mass variation is requested. The monthly GRACE solutions from CSR, JPL, GFZ and Tongji span from January 2003 to September 2015 are compared. The degree-1 coefficients derived by Swenson et al (2008) are added and also the C20 terms are replaced with those obtained from Satellite Laser Ranging. The P4M6 decorrelation and Fan filter with a radius of 300 km are adopted to reduce the stripe errors. Optimal noise models for the 1054 stations in ITRF2014 are presented. It is found that white noise only take up a small proportion: less than 18% in horizontal and less than 13% in vertical. The dominant models in up and north components are ARMA and flicker, while in east the power law noise shows significance. The local distribution comparison of the optimal noise models among different products is quite similar, which shows that there is little dependence on the different strategies adopted. In addition, the reasons that caused to different distributions of the optimal noise models are also investigated. Meanwhile different filtering methods such as Gaussian filters, Han filters are applied to see whether the noise is related with filters. Keyword: optimal noise model; non-tectonic displacement

  7. NUMERICAL METHODS FOR SOLVING THE MULTI-TERM TIME-FRACTIONAL WAVE-DIFFUSION EQUATION.

    Science.gov (United States)

    Liu, F; Meerschaert, M M; McGough, R J; Zhuang, P; Liu, Q

    2013-03-01

    In this paper, the multi-term time-fractional wave-diffusion equations are considered. The multi-term time fractional derivatives are defined in the Caputo sense, whose orders belong to the intervals [0,1], [1,2), [0,2), [0,3), [2,3) and [2,4), respectively. Some computationally effective numerical methods are proposed for simulating the multi-term time-fractional wave-diffusion equations. The numerical results demonstrate the effectiveness of theoretical analysis. These methods and techniques can also be extended to other kinds of the multi-term fractional time-space models with fractional Laplacian.

  8. Time Series Analysis: A New Methodology for Comparing the Temporal Variability of Air Temperature

    Directory of Open Access Journals (Sweden)

    Piia Post

    2013-01-01

    Full Text Available Temporal variability of three different temperature time series was compared by the use of statistical modeling of time series. The three temperature time series represent the same physical process, but are at different levels of spatial averaging: temperatures from point measurements, from regional Baltan65+, and from global ERA-40 reanalyses. The first order integrated average model IMA(0, 1, 1 is used to compare the temporal variability of the time series. The applied IMA(0, 1, 1 model is divisible into a sum of random walk and white noise component, where the variances for both white noises (one of them serving as a generator of the random walk are computable from the parameters of the fitted model. This approach enables us to compare the models fitted independently to the original and restored series using two new parameters. This operation adds a certain new method to the analysis of nonstationary series.

  9. Development of a variable time-step transient NEW code: SPANDEX

    Energy Technology Data Exchange (ETDEWEB)

    Aviles, B.N. (Knolls Atomic Power Lab., Schenectady, NY (United States))

    1993-01-01

    This paper describes a three-dimensional, variable time-step transient multigroup diffusion theory code, SPANDEX (space-time nodal expansion method). SPANDEX is based on the static nodal expansion method (NEM) code, NODEX (Ref. 1), and employs a nonlinear algorithm and a fifth-order expansion of the transverse-integrated fluxes. The time integration scheme in SPANDEX is a fourth-order implicit generalized Runge-Kutta method (GRK) with on-line error control and variable time-step selection. This Runge-Kutta method has been applied previously to point kinetics and one-dimensional finite difference transient analysis. This paper describes the application of the Runge-Kutta method to three-dimensional reactor transient analysis in a multigroup NEM code.

  10. Tacrolimus trough-level variability predicts long-term allograft survival following kidney transplantation.

    Science.gov (United States)

    O'Regan, John A; Canney, Mark; Connaughton, Dervla M; O'Kelly, Patrick; Williams, Yvonne; Collier, Geraldine; deFreitas, Declan G; O'Seaghdha, Conall M; Conlon, Peter J

    2016-04-01

    The purpose of this study is to investigate tacrolimus trough-level variability from 3 to 12 months following transplantation and its association with allograft survival in renal transplant recipients. In this observational cohort study, tacrolimus trough-level variability was used as the predictor of all-cause allograft failure (defined as return to dialysis) and patient survival (all-cause mortality). In total, 394 transplants were included in the analysis. Sixty-two transplants failed during the study. Tacrolimus trough-level variability across quartile groups were: Q1 median variability 12.5 %, range 4.76-15.71 % (n = 99), Q2 median variability 18.17 %, range 15.74-21.29 % (n = 96), Q3 median variability 24.63 % range 21.42-28.88 % (n = 100), Q4 median variability 36.91 %, range 28.91-81.9 % (n = 99). Higher tacrolimus trough-level variability was associated with inferior allograft survival in univariate models [hazard ratio per quartile increase (HR), 1.46, 95 % CI 1.16-1.83, p value = 0.001] and multivariate models (HR 1.36, 95 % CI 1.05-1.78, p value = 0.019). Higher tacrolimus trough-level variability was not associated with patient survival; univariate model (HR 1.25, 95 % CI 0.90-1.74, p value = 0.17), multivariate model (HR 1.25, 95 % CI 0.86-1.83, p value = 0.23). Inferior renal allograft survival was observed in recipients with higher variability in tacrolimus trough-levels.

  11. Long-term Satellite Observations of Asian Dust Storm: Source, Pathway, and Interannual Variability

    Science.gov (United States)

    Hsu, N. Christina

    2008-01-01

    between Deep Blue retrievals of aerosol optical thickness and those directly from AERONET sunphotometers over desert and semi-desert regions. New Deep Blue products will allow scientists to determine quantitatively the aerosol properties near sources using high spatial resolution measurements from SeaWiFS and MODIS-like instruments. Long-term satellite measurements (1998 - 2007) from SeaWiFS will be utilized to investigate the interannual variability of source, pathway, and dust loading associated with the Asian dust storm outbreaks. In addition, monthly averaged aerosol optical thickness during the springtime from SeaWiFS will also be compared with the MODIS Deep Blue products.

  12. Time series pCO2 at a coastal mooring: Internal consistency, seasonal cycles, and interannual variability

    Science.gov (United States)

    Reimer, Janet J.; Cai, Wei-Jun; Xue, Liang; Vargas, Rodrigo; Noakes, Scott; Hu, Xinping; Signorini, Sergio R.; Mathis, Jeremy T.; Feely, Richard A.; Sutton, Adrienne J.; Sabine, Christopher; Musielewicz, Sylvia; Chen, Baoshan; Wanninkhof, Rik

    2017-08-01

    Marine carbonate system monitoring programs often consist of multiple observational methods that include underway cruise data, moored autonomous time series, and discrete water bottle samples. Monitored parameters include all, or some of the following: partial pressure of CO2 of the water (pCO2w) and air, dissolved inorganic carbon (DIC), total alkalinity (TA), and pH. Any combination of at least two of the aforementioned parameters can be used to calculate the others. In this study at the Gray's Reef (GR) mooring in the South Atlantic Bight (SAB) we: examine the internal consistency of pCO2w from underway cruise, moored autonomous time series, and calculated from bottle samples (DIC-TA pairing); describe the seasonal to interannual pCO2w time series variability and air-sea flux (FCO2), as well as describe the potential sources of pCO2w variability; and determine the source/sink for atmospheric pCO2. Over the 8.5 years of GR mooring time series, mooring-underway and mooring-bottle calculated-pCO2w strongly correlate with r-values > 0.90. pCO2w and FCO2 time series follow seasonal thermal patterns; however, seasonal non-thermal processes, such as terrestrial export, net biological production, and air-sea exchange also influence variability. The linear slope of time series pCO2w increases by 5.2 ± 1.4 μatm y-1 with FCO2 increasing 51-70 mmol m-2 y-1. The net FCO2 sign can switch interannually with the magnitude varying greatly. Non-thermal pCO2w is also increasing over the time series, likely indicating that terrestrial export and net biological processes drive the long term pCO2w increase.

  13. A time series analysis of climate variability and its impacts on food ...

    African Journals Online (AJOL)

    Also, estimation of the impacts of CC on food production was done using an econometric model; where climate variables together with other factors were set to be determinant of food production over time. The co-integrated Vector Auto Regressive and Error Correction Models were employed to empirically analyse the ...

  14. Mind wandering at the fingertips: automatic parsing of subjective states based on response time variability

    Science.gov (United States)

    Bastian, Mikaël; Sackur, Jérôme

    2013-01-01

    Research from the last decade has successfully used two kinds of thought reports in order to assess whether the mind is wandering: random thought-probes and spontaneous reports. However, none of these two methods allows any assessment of the subjective state of the participant between two reports. In this paper, we present a step by step elaboration and testing of a continuous index, based on response time variability within Sustained Attention to Response Tasks (N = 106, for a total of 10 conditions). We first show that increased response time variability predicts mind wandering. We then compute a continuous index of response time variability throughout full experiments and show that the temporal position of a probe relative to the nearest local peak of the continuous index is predictive of mind wandering. This suggests that our index carries information about the subjective state of the subject even when he or she is not probed, and opens the way for on-line tracking of mind wandering. Finally we proceed a step further and infer the internal attentional states on the basis of the variability of response times. To this end we use the Hidden Markov Model framework, which allows us to estimate the durations of on-task and off-task episodes. PMID:24046753

  15. Time-dependent exact solutions for Rosenau-Hyman equations with variable coefficients

    Science.gov (United States)

    Souza, Wescley Luiz de; Silva, Érica de Mello

    2015-03-01

    In this work we study Rosenau-Hyman-like equations that were obtained by imposing the Lie point symmetry algebra of standard KdV to a general K (m, n) equation with variable coefficients. We present time-dependent exact solutions for suited choices of parameters m and n, including the similarity solution related to rarefaction shock wave phenomena.

  16. Simulation of the time-variable gravity field by means of coupled geophysical models

    NARCIS (Netherlands)

    Gruber, T.; Bamber, J.L.; Bierkens, M.F.P.; Dobslaw, H.; Murböck, M.; Thomas, M.; Beek, L.P.H. van; Dam, T. van; Vermeersen, L.L.A.; Visser, P.

    2011-01-01

    Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's

  17. Symmetry Classification and Exact Solutions of a Variable Coefficient Space-Time Fractional Potential Burgers’ Equation

    Directory of Open Access Journals (Sweden)

    Manoj Gaur

    2016-01-01

    Full Text Available We investigate the symmetry properties of a variable coefficient space-time fractional potential Burgers’ equation. Fractional Lie symmetries and corresponding infinitesimal generators are obtained. With the help of the infinitesimal generators, some group invariant solutions are deduced. Further, some exact solutions of fractional potential Burgers’ equation are generated by the invariant subspace method.

  18. Using Derivative Estimates to Describe Intraindividual Variability at Multiple Time Scales

    Science.gov (United States)

    Deboeck, Pascal R.; Montpetit, Mignon A.; Bergeman, C. S.; Boker, Steven M.

    2009-01-01

    The study of intraindividual variability is central to the study of individuals in psychology. Previous research has related the variance observed in repeated measurements (time series) of individuals to traitlike measures that are logically related. Intraindividual measures, such as intraindividual standard deviation or the coefficient of…

  19. Improved theory of time domain reflectometry with variable coaxial cable length for electrical conductivity measurements

    Science.gov (United States)

    Although empirical models have been developed previously, a mechanistic model is needed for estimating electrical conductivity (EC) using time domain reflectometry (TDR) with variable lengths of coaxial cable. The goals of this study are to: (1) derive a mechanistic model based on multisection tra...

  20. Error Analysis of a Fractional Time-Stepping Technique for Incompressible Flows with Variable Density

    KAUST Repository

    Guermond, J.-L.

    2011-01-01

    In this paper we analyze the convergence properties of a new fractional time-stepping technique for the solution of the variable density incompressible Navier-Stokes equations. The main feature of this method is that, contrary to other existing algorithms, the pressure is determined by just solving one Poisson equation per time step. First-order error estimates are proved, and stability of a formally second-order variant of the method is established. © 2011 Society for Industrial and Applied Mathematics.

  1. LONG-TERM VARIABILITY OF BRONCHIAL RESPONSIVENESS TO HISTAMINE IN A RANDOM-POPULATION SAMPLE OF ADULTS

    NARCIS (Netherlands)

    RIJCKEN, B; SCHOUTEN, JP; WEISS, ST; ROSNER, B; DEVRIES, K; VANDERLENDE, R

    1993-01-01

    Long-term variability of bronchial responsiveness has been studied in a random population sample of adults. During a follow-up period of 18 yr, 2,216 subjects contributed 5,012 observations to the analyses. Each subject could have as many as seven observations. Bronchial responsiveness was assessed

  2. Determination of the Footballers' Anger Expression Styles in Terms of Some Variable at Different Universities and High Schools in Turkey

    Science.gov (United States)

    Nas, Kazim

    2016-01-01

    This research aims at revealing whether or not footballers' anger expression styles show an alteration in terms of different variables. The descriptive method which is one of the quantitative research methods was adopted as the research model. Research group consists of 154 footballers who play in 8 teams from 12 teams in fifth-group in the…

  3. A high intrapatient variability in tacrolimus exposure is associated with poor long-term outcome of kidney transplantation

    NARCIS (Netherlands)

    Shuker, N.; Shuker, L.; Rosmalen, J. van; Roodnat, J.I.; Borra, L.C.P.; Weimar, W.; Hesselink, D.A.; Gelder, T. van

    2016-01-01

    Tacrolimus is a critical dose drug with a considerable intrapatient variability (IPV) in its pharmacokinetics. We investigated whether a high IPV in tacrolimus exposure is associated with adverse long-term renal transplantation outcomes. Tacrolimus IPV was calculated from predose concentrations

  4. Examination of Foreign Language Classroom Anxiety and Achievement in Foreign Language in Turkish University Students in Terms of Various Variables

    Science.gov (United States)

    Dogan, Yunus; Tuncer, Murat

    2016-01-01

    This correlational survey study aimed to investigate whether the Turkish prep-class students' foreign language classroom anxiety levels and foreign language achievement significantly differ in terms of such variables as their gender, their experience abroad, perceived level of income and any third language (other than Turkish and English) they…

  5. Essential Oil Variability and Biological Activities of Tetraclinis articulata (Vahl) Mast. Wood According to the Extraction Time.

    Science.gov (United States)

    Djouahri, Abderrahmane; Saka, Boualem; Boudarene, Lynda; Baaliouamer, Aoumeur

    2016-12-01

    In the present work, the hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) kinetics of essential oil (EO) extracted from Tetraclinis articulata (Vahl) Mast. wood was conducted, in order to assess the impact of extraction time and technique on chemical composition and biological activities. Gas chromatography (GC) and GC/mass spectrometry analyses showed significant differences between the extracted EOs, where each family class or component presents a specific kinetic according to extraction time, technique and especially for the major components: camphene, linalool, cedrol, carvacrol and α-acorenol. Furthermore, our findings showed a high variability for both antioxidant and anti-inflammatory activities, where each activity has a specific effect according to extraction time and technique. The highlighted variability reflects the high impact of extraction time and technique on chemical composition and biological activities, which led to conclude that we should select EOs to be investigated carefully depending on extraction time and technique, in order to isolate the bioactive components or to have the best quality of EO in terms of biological activities and preventive effects in food. © 2016 Wiley-VHCA AG, Zurich, Switzerland.

  6. Mean Sea Level Variability and Influence of the North Atlantic Oscillation on Long-Term Trends in the German Bight

    Directory of Open Access Journals (Sweden)

    Jürgen Jensen

    2012-02-01

    Full Text Available Changes in the seasonal cycle of mean sea level (MSL may affect the heights of storm surges and thereby flood risk in coastal areas. This study investigates the intra- and inter-annual variability of monthly MSL and its link to the North Atlantic Oscillation using records from 13 tide gauges located in the German Bight. The amplitudes of the seasonal MSL cycle are not regionally uniform and vary between 20 and 29 cm. Generally, the amplitudes are smaller at the southwestern stations, increasing as one travels to the northeastern part. The amplitudes, as well as the phase of the seasonal cycle, are characterized by a large inter-annual and inter-decadal variability, but no long-term trend could be detected. Nevertheless, in the last two decades annual maximum peaks more frequently occurred in January and February, whereas beforehand an accumulation was detected for the November and December period. These changes in phase in the various sea level time series are consistent with a shift in the annual cycle, which is, however, not significant. The changes are associated with strongly increasing trends in monthly MSL of the winter season (J–M, which are considerably higher compared to the remaining seasons. For the same season, the MSL and North Atlantic Oscillation (NAO indices show strong similarities, resulting in statistically significant correlations (r ~ 0.7. Hence, these changes are linked with changing pressure conditions over the North Atlantic, which lead to a strong phase of positive values in the NAO index between the 1960’s and 1990’s.

  7. Space-time variability of hydrological drought and wetness in Iran using NCEP/NCAR and GPCC datasets

    Directory of Open Access Journals (Sweden)

    T. Raziei

    2010-10-01

    Full Text Available Space-time variability of hydrological drought and wetness over Iran is investigated using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR reanalysis and the Global Precipitation Climatology Centre (GPCC dataset for the common period 1948–2007. The aim is to complement previous studies on the detection of long-term trends in drought/wetness time series and on the applicability of reanalysis data for drought monitoring in Iran. Climate conditions of the area are assessed through the Standardized Precipitation Index (SPI on 24-month time scale, while Principal Component Analysis (PCA and Varimax rotation are used for investigating drought/wetness variability, and drought regionalization, respectively. Singular Spectrum Analysis (SSA is applied to the time series of interest to extract the leading nonlinear components and compare them with linear fittings.

    Differences in drought and wetness area coverage resulting from the two datasets are discussed also in relation to the change occurred in recent years. NCEP/NCAR and GPCC are in good agreement in identifying four sub-regions as principal spatial modes of drought variability. However, the climate variability in each area is not univocally represented by the two datasets: a good agreement is found for south-eastern and north-western regions, while noticeable discrepancies occur for central and Caspian sea regions. A comparison with NCEP Reanalysis II for the period 1979–2007, seems to exclude that the discrepancies are merely due to the introduction of satellite data into the reanalysis assimilation scheme.

  8. The potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum peatlands.

    Science.gov (United States)

    Sullivan, Maura E; Booth, Robert K

    2011-07-01

    Testate amoebae are a group of moisture-sensitive, shell-producing protozoa that have been widely used as indicators of changes in mean water-table depth within oligotrophic peatlands. However, short-term environmental variability (i.e., sub-annual) also probably influences community composition. The objective of this study was to assess the potential influence of short-term environmental variability on the composition of testate amoeba communities in Sphagnum-dominated peatlands. Testate amoebae and environmental conditions, including hourly measurements of relative humidity within the upper centimeter of the peatland surface, were examined throughout the 2008 growing season at 72 microsites within 11 peatlands of Pennsylvania and Wisconsin, USA. Relationships among testate amoeba communities, vegetation, depth to water table, pH, and an index of short-term environmental variability (EVI), were examined using nonmetric multidimensional scaling and correlation analysis. Results suggest that EVI influences testate amoeba communities, with some taxa more abundant under highly variable conditions (e.g., Arcella discoides, Difflugia pulex, and Hyalosphenia subflava) and others more abundant when environmental conditions at the peatland surface were relatively stable (e.g., Archerella flavum and Bullinularia indica). The magnitude of environmental variability experienced at the peatland surface appears to be primarily controlled by vegetation composition and density. In particular, sites with dense Sphagnum cover had lower EVI values than sites with loose-growing Sphagnum or vegetation dominated by vascular plants and/or non-Sphagnum bryophytes. Our results suggest that more environmental information may be inferred from testate amoebae than previously recognized. Knowledge of relationships between testate amoebae and short-term environmental variability should lead to more detailed and refined environmental inferences.

  9. Time–cost tradeoff analysis considering funding variability and time uncertainty

    Directory of Open Access Journals (Sweden)

    Amr Metwally El-kholy

    2013-03-01

    Full Text Available This paper presents a linear programming model for solution of the time–cost tradeoff problem. Although several analytical models have been developed for time–cost optimization (TCO, some of them mainly focused on projects where the contract duration is fixed. The optimization objective is therefore restricted to identify the minimum total cost only. Another group have primarily focused on project duration minimization. The model presented here considers scheduling characteristics that were ignored simultaneously in prior research. In the new formulation, variability of funding and uncertainty of project duration are considered simultaneously. A chance-constrained programming is used to incorporate the variability of funding, which is quantified by the coefficient of variation. The financial feasibility expressed as a stochastic constraint, which transformed into a deterministic equivalent at a pre-specified confidence level. Also, the project duration uncertainty incorporated into the model by applying PERT in scheduling and then the uncertainty is quantified by the coefficient of variation at a pre-specified confidence level. A system of objective function, which is minimizing direct cost and the group of constraints are solved by means of Lindo software. Two examples are conducted to demonstrate the model performance and its contributions. Four scenarios were adopted in solving the example problems to reflect the effect of each of funding variability and time uncertainty on project cost and duration. The results revealed that with 95% confidence level: 10% variability in funding versus neglecting it, would increase direct cost with 20% approximately for a pre-specified project deadline. Also, 10% variability in time versus neglecting it, would increase duration in range from 16.5% to 30% approximately, for a pre-specified direct cost. Also, considering 10% variability in funding and time would increase direct cost with more than 25% for a

  10. Short-term variability and predictors of urinary pentachlorophenol levels in Ohio preschool children

    Science.gov (United States)

    Pentachlorophenol (PCP) is a persistent and ubiquitous environmental contaminant. No published data exist on the temporal variability or important predictors of urinary PCP concentrations in young children. In this further analysis of study data, we have examined the associations...

  11. Time continuum and true long-term ecology: from theory to practice

    National Research Council Canada - National Science Library

    Rull, Valentí

    2014-01-01

    ... scales larger than centuries will not be fully resolved. Palaeoecology can provide the needed time scale for true long-term ecology, but it is limited by the ability to merge ecological and palaeoecological data into continuous time series...

  12. Ensemble X-ray variability of active galactic nuclei at intermediate and long time lags

    OpenAIRE

    Vagnetti, Fausto; Middei, Riccardo

    2016-01-01

    We present a variability analysis for a sample of 2700 active galactic nuclei extracted from the latest release of the XMM-Newton serendipitous source catalogue. The structure function of this sample increases up to rest-frame time lags of about 5 years. Moreover, comparing observations performed by the XMM-Newton and ROSAT satellites, we are able to extend the X-ray structure function to 20 years rest-frame, showing a further increase of variability without any evidence of a plateau. Our res...

  13. Online Synthesis for Operation Execution Time Variability on Digital Microfluidic Biochips

    DEFF Research Database (Denmark)

    Alistar, Mirela; Pop, Paul

    2014-01-01

    have assumed that each biochemical operation in an application is characterized by a worst-case execution time (wcet). However, during the execution of the application, due to variability and randomness in biochemical reactions, operations may finish earlier than their wcets. In this paper we propose...... an online synthesis strategy that re-synthesizes the application at runtime when operations experience variability in their execution time, obtaining thus shorter application execution times. The proposed strategy has been evaluated using several benchmarks.......Several approaches have been proposed for the synthesis of digital microfluidic biochips, which, starting from a biochemical application and a given biochip architecture, determine the allocation, resource binding, scheduling, placement and routing of the operations in the application. Researchers...

  14. Synthesis of Biochemical Applications on Digital Microfluidic Biochips with Operation Execution Time Variability

    DEFF Research Database (Denmark)

    Alistar, Mirela; Pop, Paul

    2015-01-01

    Microfluidic-based biochips are replacing the conventional biochemical analyzers, and are able to integrate all the necessary functions for biochemical analysis. The digital microfluidic biochips are based on the manipulation of liquids not as a continuous flow, but as discrete droplets. Several...... that each biochemical operation in an application is characterized by a worst-case execution time (wcet). However, during the execution of the application, due to variability and randomness in biochemical reactions, operations may finish earlier than their wcetswcets, resulting in unexploited slack...... in the schedule. In this paper, we first propose an online synthesis strategy that re-synthesizes the application at runtime when operations experience variability in their execution time, exploiting thus the slack to obtain shorter application completion times. We also propose a quasi-static synthesis strategy...

  15. Preferences for travel time variability – A study of Danish car drivers

    DEFF Research Database (Denmark)

    Hjorth, Katrine; Rich, Jeppe

    preferences, to exclude non-traders, and to avoid complicated issues related to scheduled public transport services. The survey uses customised Internet questionnaires, containing a series of questions related to the traveller’s most recent morning trip to work, e.g.: • Travel time experienced on this day......Travel time variability (TTV) is a measure of the extent of unpredictability in travel times. It is generally accepted that TTV has a negative effect on travellers’ wellbeing and overall utility of travelling, and valuation of variability is an important issue in transport demand modelling...... and in appraisal of transport and infrastructure projects. The effect of TTV has been analysed in several methodological papers and empirical studies (see, e.g., the review in Carrion and Levinson, 2012). Most methodological research is based on the premise that the value of TTV is closely linked to travellers...

  16. Space-time variability of floods across Germany: Gradual trends, step changes and fluctuations

    Science.gov (United States)

    Merz, Bruno; Vorogushyn, Sergiy; Viet Dung, Nguyen; Schröter, Kai

    2015-04-01

    The space-time variability of flood magnitude and frequency across Germany at the interannual and decadal time scale is analyzed and interpreted. The analyses are based on flood time series of 68 catchments for a joint period of 74 years. The catchments are distributed across Germany and show different flood regimes. Different statistical tests are applied to investigate different types of flood changes: gradual trends, step changes and fluctuations. In addition, changes in the mean behavior and in the variability are studied. A focus is placed on the spatial stability of changes, i.e. answering the question to which extent flood changes are coherent across Germany. The joint analysis of changes for a large number of catchments allows interpreting the causes of the observed changes. For instance, climate-related flood changes are expected to show a different behavior than changes caused by river training or land-use change.

  17. Incorporating geostrophic wind information for improved space–time short-term wind speed forecasting

    KAUST Repository

    Zhu, Xinxin

    2014-09-01

    Accurate short-term wind speed forecasting is needed for the rapid development and efficient operation of wind energy resources. This is, however, a very challenging problem. Although on the large scale, the wind speed is related to atmospheric pressure, temperature, and other meteorological variables, no improvement in forecasting accuracy was found by incorporating air pressure and temperature directly into an advanced space-time statistical forecasting model, the trigonometric direction diurnal (TDD) model. This paper proposes to incorporate the geostrophic wind as a new predictor in the TDD model. The geostrophic wind captures the physical relationship between wind and pressure through the observed approximate balance between the pressure gradient force and the Coriolis acceleration due to the Earth’s rotation. Based on our numerical experiments with data from West Texas, our new method produces more accurate forecasts than does the TDD model using air pressure and temperature for 1to 6-hour-ahead forecasts based on three different evaluation criteria. Furthermore, forecasting errors can be further reduced by using moving average hourly wind speeds to fit the diurnal pattern. For example, our new method obtains between 13.9% and 22.4% overall mean absolute error reduction relative to persistence in 2-hour-ahead forecasts, and between 5.3% and 8.2% reduction relative to the best previous space-time methods in this setting.

  18. Time-consistent calibration of short-term regional wind power ensemble forecasts

    Directory of Open Access Journals (Sweden)

    Stephan Späth

    2015-04-01

    Full Text Available With increasing wind power capacity, accurate uncertainty forecasts get more and more important for grid integration. The uncertainty of forecasts can be quantified by ensemble forecasts. We use ensemble forecasts from the COSMO-DE EPS to generate short-term ensemble forecasts of regionally aggregated wind power. The wind power forecasts are generated by an optimised regional power curve model that is based on minimum score estimation and leads to wind power forecasts with small deterministic errors. Remaining bias and dispersion errors in the wind power forecasts are removed by statistical post-processing (also called calibration with ensemble model output statistics and the temporal rank correlation of the raw ensemble is maintained by ensemble copula coupling. The verification of raw and calibrated ensembles shows both strong improvements by calibration and the benefit of ensuring time consistency with ensemble copula coupling. The improvements are indicated by the multivariate energy score as well as in a proposed univariate verification approach that is based on integrated wind power forecast and measurement trajectories. Slight deficits in time consistency of the forecasts remain because the theoretical assumptions of ensemble copula coupling are not always fulfilled as the COSMO-DE EPS is based on distinguishable ensemble members. The more training days are used for calibration against measurements of regionally aggregated wind power, the lower is the improvement by calibration which contradicts former results for different variables like wind speed.

  19. Formic acid above the Jungfraujoch during 1985–2007: observed variability, seasonality, but no long-term background evolution

    Directory of Open Access Journals (Sweden)

    A. Perrin

    2010-10-01

    Full Text Available This paper reports on daytime total vertical column abundances of formic acid (HCOOH above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m alt.. The columns were derived from the analysis of infrared solar observations regularly performed with high spectral resolution Fourier transform spectrometers during over 1500 days between September 1985 and September 2007. The investigation was based on the spectrometric fitting of five spectral intervals, one encompassing the HCOOH ν6 band Q branch at 1105 cm−1, and four additional ones allowing to optimally account for critical temperature-sensitive or time-evolving interferences by other atmospheric gases, in particular HDO, CCl2F2 and CHClF2. The main results derived from the 22 years long database indicate that the free tropospheric burden of HCOOH above the Jungfraujoch undergoes important short-term daytime variability, diurnal and seasonal modulations, inter-annual anomalies, but no significant long-term background change. A major progress in the remote determination of the atmospheric HCOOH columns reported here has resulted from the adoption of new, improved absolute spectral line intensities for the infrared ν6 band of trans-formic acid, resulting in retrieved free tropospheric loadings being about a factor two smaller than if derived with previous spectroscopic parameters. Implications of this significant change with regard to earlier remote measurements of atmospheric formic acid and comparison with relevant Northern mid-latitude findings, both in situ and remote, will be assessed critically. Sparse HCOOH model predictions will also be evoked and assessed with respect to findings reported here.

  20. Long term variability of the annual hydrological regime and sensitivity to temperature phase shifts in Saxony/Germany

    OpenAIRE

    Renner, M.; Bernhofer, C.

    2011-01-01

    Recently, climatological studies report observational evidence of changes in the timing of the seasons, such as earlier timing of the annual cycle of surface temperature, earlier snow melt and earlier onset of the phenological spring season. Also hydrological studies report earlier timing and changes in monthly streamflows. From a water resources management perspective, there is a need to quantitatively describe the variability in the timing of hydrological regimes and to understand how clima...

  1. Intra-Subject Variability of 5 Km Time Trial Performance Completed by Competitive Trained Runners

    Directory of Open Access Journals (Sweden)

    Fisher James

    2017-06-01

    Full Text Available Time-trials represent an ecologically valid approach to assessment of endurance performance. Such information is useful in the application of testing protocols and estimation of sample sizes required for research/magnitude based inference methods. The present study aimed to investigate the intra-subject variability of 5 km time-trial running performance in trained runners. Six competitive trained male runners (age = 33.8 ± 10.1 years; stature = 1.78 ± 0.01 m; body mass = 69.0 ± 10.4 kg, V. $\\it V^{.}$ O2max = 62.6 ± 11.0 ml·kg·min-1 completed an incremental exercise test to volitional exhaustion followed by 5 x 5 km time-trials (including a familiarisation trial, individually spaced by 48 hours. The time taken to complete each trial, heart rate, rating of perceived exertion and speed were all assessed. Intra-subject absolute standard error of measurement and the coefficient of variance were calculated for time-trial variables in addition to the intra-class correlation coefficient for time taken to complete the time-trial. For the primary measure time, results showed a coefficient of variation score across all participants of 1.5 ± 0.59% with an intra-class correlation coefficient score of 0.990. Heart rate, rating of perceived exertion and speed data showed a variance range between 0.8 and 3.05%. It was concluded that when compared with related research, there was observed low intra-subject variability in trained runners over a 5 km distance. This supports the use of this protocol for 5 km time-trial performance for assessment of nutritional strategies, ergogenic aids or training interventions on endurance running performance.

  2. Modelling the variability of lag times and the first generation times of single cells of E. coli.

    Science.gov (United States)

    Métris, A; Le Marc, Y; Elfwing, A; Ballagi, A; Baranyi, J

    2005-04-15

    A mathematical model combining deterministic and stochastic elements describes the growth and division of single cells. Its deterministic part is based on the model of Baranyi and Roberts [International Journal of Food Microbiology 23 (1994) 277] modelling the gradual adjustment of the cells to a new environment. The stochastic part assumes a random threshold size for the division of a single cell, which accounts for the variability of the individual generation times. Experimental results of the first division times of thousands of single cells using a microscopic flow system could be reproduced with this model, and it has the potential to be used to study the effects of different stress and environmental factors on the distribution of the lag and generation times of individual cells.

  3. Metabolic syndrome and short-term and long-term heart rate variability in elderly free of clinical cardiovascular disease: the PROOF study.

    Science.gov (United States)

    Assoumou, H G Ntougou; Pichot, V; Barthelemy, J C; Dauphinot, V; Celle, S; Gosse, P; Kossovsky, M; Gaspoz, J M; Roche, F

    2010-12-01

    Autonomic nervous system (ANS) activity decrease has been associated with a higher risk of sudden cardiovascular and cerebrovascular disease. Thus, we explored the relationship between ANS control of the cardiovascular system and metabolic syndrome. We analyzed the relationship with both short-term and long-term heart rate variability (HRV) and metabolic syndrome in the cross-sectional PROgnostic indicator OF cardiovascular and cerebrovascular events (PROOF) cohort study of 1,011 elderly subjects recruited amongst the inhabitants of the city of Saint Etienne, France, aged 65.6 ± 0.8 years at the inclusion date. Physical examination included measurements of height, weight, systolic and diastolic blood pressure, waist circumference, and biological parameters. HRV variables were measured over 5-min, nighttime, and 24-h periods using Holter monitoring. After adjustment for current type 2 diabetes, depression, and smoking, we found that metabolic syndrome status, high-density lipoprotein cholesterol (HDL-C), and waist circumference were significantly (p cardiovascular system was more pronounced when evaluated by long-term than short-term HRV recordings, particularly in women.

  4. Teaching long-term science investigations: A matter of talk, text, and time

    Science.gov (United States)

    Bills, Patricia Susan

    Science educators regard long-term investigations as one impactful form of teaching science through inquiry in K-12 classrooms. While we have idealized notions of what this work looks like, we have few, if any, descriptive studies about investigations that engage students in sustained, focused work over a period of time longer than a few days or even weeks. In a policy context that calls for teachers to develop strategies for engaging students in authentic science practices, such as those that can come from long-term science investigations, we would do well to learn from experienced teachers. This study followed three middle school science teachers in a large U. S. urban school district as they conducted long-term investigations. Using discourse analysis and taking a sociocultural perspective, this study documented the classroom talk and interaction of teachers and their students. The study's goals were to describe how teachers engage students in long-term investigations and the ways that classroom interaction involved specific reform-based science practices. Data include field notes and transcripts of audio recordings from 15 observations of three experienced middle school science teachers, three semi-structured interviews with each teacher, curriculum materials, student work, and classroom demographic data. Teachers engaged students in whole group, small group, and one-on-one conversations about several stages of the long-term investigations. Teachers most often discussed two of the eight science practices: 1) planning and carrying out investigations; and 2) obtaining, evaluating, and communicating information. The planning discussions involved conversations about identifying and describing variables, measuring and recording data, and concerns about data collection procedures. Conversations about using and communicating scientific information included talk about formal science writing conventions, and using background information to support all other parts of the

  5. Continuous-variable quantum computing in optical time-frequency modes using quantum memories.

    Science.gov (United States)

    Humphreys, Peter C; Kolthammer, W Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A

    2014-09-26

    We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

  6. Three-Factor Market-Timing Models with Fama and French's Spread Variables

    Directory of Open Access Journals (Sweden)

    Joanna Olbryś

    2010-01-01

    Full Text Available The traditional performance measurement literature has attempted to distinguish security selection, or stock-picking ability, from market-timing, or the ability to predict overall market returns. However, the literature finds that it is not easy to separate ability into such dichotomous categories. Some researchers have developed models that allow the decomposition of manager performance into market-timing and selectivity skills. The main goal of this paper is to present modified versions of classical market-timing models with Fama and French’s spread variables SMB and HML, in the case of Polish equity mutual funds. (original abstract

  7. Almost periodic solutions of impulsive BAM neural networks with variable delays on time scales

    Science.gov (United States)

    Wang, Chao

    2014-08-01

    This paper is concerned with a class of impulsive BAM neural networks with variable delays on time scales. Some sufficient conditions are established to ensure the existence and exponential stability of almost periodic solutions for such class of impulsive BAM neural networks. The results are essentially new when T=R or T=Z. It is the first time that the existence and exponential stability of almost periodic solutions for impulsive BAM neural networks are obtained on time scales. Furthermore, an example and numerical simulations are given to illustrate our effectiveness of the obtained results.

  8. Pursuing Benefit or Avoiding Detriment: Term-Time Job Selection of Sports Major Undergraduates

    Science.gov (United States)

    Wu, Huan-Hung; Chen, Shan-Hua

    2013-01-01

    Higher education expansion accompanied with the tuition rising has resulted in the increasing number of term-time employed students in many countries. Taiwan is no exception to this trend. Thus, there were a few studies to explore the impact of term-time employment on undergraduates. However, very few researchers focus on how undergraduates make…

  9. Genetic and environmental contributions to the associations between intraindividual variability in reaction time and cognitive function.

    Science.gov (United States)

    Finkel, Deborah; Pedersen, Nancy L

    2014-01-01

    Intraindividual variability (IIV) in reaction time has been related to cognitive decline, but questions remain about the nature of this relationship. Mean and range in movement and decision time for simple reaction time were available from 241 individuals aged 51-86 years at the fifth testing wave of the Swedish Adoption/Twin Study of Aging. Cognitive performance on four factors was also available: verbal, spatial, memory, and speed. Analyses indicated that range in reaction time could be used as an indicator of IIV. Heritability estimates were 35% for mean reaction and 20% for range in reaction. Multivariate analysis indicated that the genetic variance on the memory, speed, and spatial factors is shared with genetic variance for mean or range in reaction time. IIV shares significant genetic variance with fluid ability in late adulthood, over and above and genetic variance shared with mean reaction time.

  10. Impact Time Guidance Law Considering Autopilot Dynamics Based on Variable Coefficients Strategy for Maneuvering Target

    Directory of Open Access Journals (Sweden)

    Wei Shang

    2015-01-01

    Full Text Available This paper investigates the terminal guidance problem for the missile intercepting a maneuvering target with impact time constraint. An impact time guidance law based on finite time convergence control theory is developed regarding the target motion as an unknown disturbance. To further improve the performance of the guidance law, an autopilot dynamics which is considered as a first-order lag is taken into consideration. In the proposed method, the coefficients change with the relative distance between missile and target. This variable coefficient strategy ensures that the missile impacts the target at the desired time with little final miss distance. Then it is proved that states of the guidance system converge to sliding mode in finite time under the proposed guidance law. Numerical simulations are presented to demonstrate the effectiveness of the impact time guidance law with autopilot dynamics (ITGAD.

  11. Short-term effects of muscular denervation and fasciotomy on global limb variables during locomotion in the decerebrate cat.

    Science.gov (United States)

    Stahl, Victoria A; Nichols, T Richard

    2011-01-01

    The motor system is capable of preserving the trajectories during locomotion of task level variables such as limb length and limb orientation in the face of paralysis of major muscle groups. This compensation is accomplished by the adjustment of the kinematics of joints other than the one most affected by the paralysis. The conservation of these task level variables could be accomplished quickly by feedback regulation or intrinsic mechanics, or by a longer-term adaptive process. We investigated the immediate effects of denervation of the triceps surae muscles in one limb of stepping, decerebrate cats to determine whether task level variables were preserved by short-term regulatory or intrinsic mechanisms. We further investigated the effects of disruption of the crural fascia in conjunction with denervation of the triceps surae muscles to determine whether the system consisting of multi-articular muscles of the thigh and crural fascia provided some contribution toward the preservation of limb length and orientation. Denervation led to substantial increases in ankle yield during stance, as previously observed, but also to significant decreases in limb length during early stance. Disruption of the crural fascia did not lead to increased ankle yield but, instead, to evidence for decreased propulsion. The results suggest that the preservation of task level variables observed in other studies does not result from online error correction or intrinsic properties of the musculoskeletal system but, by inference, from longer-term neural adaptation. Copyright © 2011 S. Karger AG, Basel.

  12. Hindcasting the Continuum of Dansgaard-Oeschger variability: Mechanisms, Patterns and Timing

    Science.gov (United States)

    Timmermann, A.; Menviel, L.; Friedrich, T.; England, M. H.

    2013-12-01

    Millennial-scale variability associated with Dansgaard-Oeschger (DO) and Heinrich events (HE) is arguably one of the most puzzling climate phenomena ever discovered in paleoclimate archives of the last glacial period. With similar variability occurring during other glacial periods, it is very timely to identify the underlying mechanisms. Here, we set out to elucidate the dynamics of millennial-scale climate variability by conducting a transient global hindcast simulation with a 3-dimensional intermediate complexity Earth system model covering the period 50 ka B.P. to 30 ka B.P. The model is forced by time-varying external boundary conditions (greenhouse gases, orbital forcing, and ice-sheet orography and albedo) and anomalous North Atlantic freshwater fluxes, which capture the effects of Northern Hemisphere ice-sheet calving on millennial timescales. Together these forcings generate a realistic global climate trajectory, as demonstrated by an extensive model/paleo data comparison. Our analysis is consistent with the simple idea that variations in ice-sheet calving and related changes of the Atlantic Meridional Overturning Circulation were the main driver for the continuum of MIS3 DO and HE variability seen in paleorecords across the globe. According to this scenario, timescale and abruptness of millennial-scale variability are primarily determined by the ice-sheet/ice-shelf calving processes, rather than by the thermohaline circulation. Using a number of high-resolution paleo records from other glacial periods we demonstrate that the proposed ice-sheet calving/AMOC response mechanism can universally explain the continuum of millennial-scale glacial variability during the Late Pleistocene.

  13. A long-term study of AGN X-ray variability . Structure function analysis on a ROSAT-XMM quasar sample

    Science.gov (United States)

    Middei, R.; Vagnetti, F.; Bianchi, S.; La Franca, F.; Paolillo, M.; Ursini, F.

    2017-03-01

    Context. Variability in the X-rays is a key ingredient in understanding and unveiling active galactic nuclei (AGN) properties. In this band, flux variations occur on short timescales (hours) as well as on larger timescales. While short timescale variability is often investigated in single source studies, only a few works are able to explore flux variation on very long timescales. Aims: This work aims to provide a statistical analysis of the AGN long term X-ray variability. We study variability on the largest time interval ever investigated for the 0.2-2 keV band, up to approximately 20 yr rest-frame for a sample of 220 sources. Moreover, we study variability for 2700 quasars up to approximatley eight years rest-frame in the same (soft) band. Methods: We built our source sample using the 3XMM serendipitous source catalogue data release 5, and data from ROSAT All Sky Survey Bright and Faint source catalogues. To ensure that we selected AGN only, we used the Sloan Digital Sky Survey quasar catalogues data releases 7 and 12. Combining ROSAT and XMM-Newton observations, we investigated variability using the structure function analysis which describes the amount of variability as a function of the lag between the observations. Results: Our work shows an increase of the structure function up to 20 yr. We find no evidence of a plateau in the structure function on these long timescales. Conclusions: The increase of the structure function at long time lags suggests that variability in the soft X-rays can be influenced by flux variations originated in the accretion disk or that they take place in a region large enough to justify variation on such long timescales.

  14. Intraindividual variability in reaction time before and after neoadjuvant chemotherapy in women diagnosed with breast cancer.

    Science.gov (United States)

    Yao, Christie; Rich, Jill B; Tirona, Kattleya; Bernstein, Lori J

    2017-12-01

    Women treated with chemotherapy for breast cancer experience subtle cognitive deficits. Research has focused on mean performance level, yet recent work suggests that within-person variability in reaction time performance may underlie cognitive symptoms. We examined intraindividual variability (IIV) in women diagnosed with breast cancer and treated with neoadjuvant chemotherapy. Patients (n = 28) were assessed at baseline before chemotherapy (T1), approximately 1 month after chemotherapy but prior to surgery (T2), and after surgery about 9 months post chemotherapy (T3). Healthy women of similar age and education (n = 20) were assessed at comparable time intervals. Using a standardized regression-based approach, we examined changes in mean performance level and IIV (eg, intraindividual standard deviation) on a Stroop task and self-report measures of cognitive function from T1 to T2 and T1 to T3. At T1, women with breast cancer were more variable than controls as task complexity increased. Change scores from T1 to T2 were similar between groups on all Stroop performance measures. From T1 to T3, controls improved more than women with breast cancer. IIV was more sensitive than mean reaction time in capturing group differences. Additional analyses showed increased cognitive symptoms reported by women with breast cancer from T1 to T3. Specifically, change in language symptoms was positively correlated with change in variability. Women with breast cancer declined in attention and inhibitory control relative to pretreatment performance. Future studies should include measures of variability, because they are an important sensitive indicator of change in cognitive function. Copyright © 2016 John Wiley & Sons, Ltd.

  15. The effect of atmospheric variability at intra-seasonal time scale on the SST of the Southwestern Atlantic Continental Shelf

    Science.gov (United States)

    Simionato, Claudia; Clara, Moira Luz; Jaureguizar, Andrés

    2017-04-01

    The Southwestern Atlantic Continental Shelf is characterized by large SST variability which origin remains unknown. In this work, we use blended SST data provided by NOAA CoastWatch Program, which combine the information coming from infrared and microwave sensors to provide daily images of an intermediate spatial resolution (11 km) with a noise floor of less than 0.2 °C. The data base starts at the middle of 2002, when an increase in signal variance is observed due to the fact that the Advanced Microwave Scanning Radiometer became available and as a consequence to its near all-weather coverage. Several years of observations are thus available, and even though the temporal and spatial resolution of these data is intermediate, they are reasonable for observing and characterizing the most significant patterns of SST variability in the (atmospheric) synoptic to intra-seasonal time scales, so as to help on understanding the physical processes which occur in the area and their forcing mechanisms. As we hypothesize that most of the variability in those time scales is wind forced, the study is complemented with the use of atmospheric observations -coming from remote sensing and reanalysis-. To perform the analysis, the long-term trend, inter-annual and seasonal variability are subtracted to the SST data to obtain the signal on intra-seasonal time scales. Then, Principal Components (EOF) analysis is applied to the data and composites of SST and several meteorological variables (wind, sea level pressure, air temperature, OLR, etc.) are computed for the days when the leading modes are active. It is found that the first three modes account for more than 70% of the variance. Modes 1 and 2 seem to be related to atmospheric waves generated in the tropical Pacific. Those waves, through atmospheric teleconnections, affect the SST on the southwestern South Atlantic Continental Shelf very rapidly. The oceanic anomalies exceed 0.7°C and are quite persistent. Mode 2 seems to be

  16. Short-term effect of crural fasciotomy on kinematic variability and propulsion during level locomotion.

    Science.gov (United States)

    Stahl, V A; Nichols, T R

    2014-01-01

    Treadmill locomotion can be characterized by consistent step-to-step kinematics despite the redundant degrees of freedom. The authors investigated the effect of disrupting the crural fascia in decerebrate cats to determine if the crural fascia contributed to kinematic variability and propulsion in the limb. Crural fasciotomy resulted in statistically significant decreases in velocity and acceleration in the joint angles during level walking, before, during, and after paw-off, particularly at the ankle. A further finding was an increase in variance of the limb segment trajectories in the frontal plane. The crural fascia therefore provides force transmission and reduction in kinematic variability to the limb during locomotion.

  17. Does climate variability influence the demography of wild primates? Evidence from long-term life-history data in seven species.

    Science.gov (United States)

    Campos, Fernando A; Morris, William F; Alberts, Susan C; Altmann, Jeanne; Brockman, Diane K; Cords, Marina; Pusey, Anne; Stoinski, Tara S; Strier, Karen B; Fedigan, Linda M

    2017-11-01

    Earth's rapidly changing climate creates a growing need to understand how demographic processes in natural populations are affected by climate variability, particularly among organisms threatened by extinction. Long-term, large-scale, and cross-taxon studies of vital rate variation in relation to climate variability can be particularly valuable because they can reveal environmental drivers that affect multiple species over extensive regions. Few such data exist for animals with slow life histories, particularly in the tropics, where climate variation over large-scale space is asynchronous. As our closest relatives, nonhuman primates are especially valuable as a resource to understand the roles of climate variability and climate change in human evolutionary history. Here, we provide the first comprehensive investigation of vital rate variation in relation to climate variability among wild primates. We ask whether primates are sensitive to global changes that are universal (e.g., higher temperature, large-scale climate oscillations) or whether they are more sensitive to global change effects that are local (e.g., more rain in some places), which would complicate predictions of how primates in general will respond to climate change. To address these questions, we use a database of long-term life-history data for natural populations of seven primate species that have been studied for 29-52 years to investigate associations between vital rate variation, local climate variability, and global climate oscillations. Associations between vital rates and climate variability varied among species and depended on the time windows considered, highlighting the importance of temporal scale in detection of such effects. We found strong climate signals in the fertility rates of three species. However, survival, which has a greater impact on population growth, was little affected by climate variability. Thus, we found evidence for demographic buffering of life histories, but also

  18. Spatial variability of the effect of air pollution on term birth weight: evaluating influential factors using Bayesian hierarchical models.

    Science.gov (United States)

    Li, Lianfa; Laurent, Olivier; Wu, Jun

    2016-02-05

    Epidemiological studies suggest that air pollution is adversely associated with pregnancy outcomes. Such associations may be modified by spatially-varying factors including socio-demographic characteristics, land-use patterns and unaccounted exposures. Yet, few studies have systematically investigated the impact of these factors on spatial variability of the air pollution's effects. This study aimed to examine spatial variability of the effects of air pollution on term birth weight across Census tracts and the influence of tract-level factors on such variability. We obtained over 900,000 birth records from 2001 to 2008 in Los Angeles County, California, USA. Air pollution exposure was modeled at individual level for nitrogen dioxide (NO2) and nitrogen oxides (NOx) using spatiotemporal models. Two-stage Bayesian hierarchical non-linear models were developed to (1) quantify the associations between air pollution exposure and term birth weight within each tract; and (2) examine the socio-demographic, land-use, and exposure-related factors contributing to the between-tract variability of the associations between air pollution and term birth weight. Higher air pollution exposure was associated with lower term birth weight (average posterior effects: -14.7 (95 % CI: -19.8, -9.7) g per 10 ppb increment in NO2 and -6.9 (95 % CI: -12.9, -0.9) g per 10 ppb increment in NOx). The variation of the association across Census tracts was significantly influenced by the tract-level socio-demographic, exposure-related and land-use factors. Our models captured the complex non-linear relationship between these factors and the associations between air pollution and term birth weight: we observed the thresholds from which the influence of the tract-level factors was markedly exacerbated or attenuated. Exacerbating factors might reflect additional exposure to environmental insults or lower socio-economic status with higher vulnerability, whereas attenuating factors might indicate reduced

  19. No effect of short-term amino acid supplementation on variables related to skeletal muscle damage in 100 km ultra-runners - a randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Rosemann Thomas

    2011-04-01

    Full Text Available Abstract Background The purpose of this study was to investigate the effect of short-term supplementation of amino acids before and during a 100 km ultra-marathon on variables of skeletal muscle damage and muscle soreness. We hypothesized that the supplementation of amino acids before and during an ultra-marathon would lead to a reduction in the variables of skeletal muscle damage, a decrease in muscle soreness and an improved performance. Methods Twenty-eight experienced male ultra-runners were divided into two groups, one with amino acid supplementation and the other as a control group. The amino acid group was supplemented a total of 52.5 g of an amino acid concentrate before and during the 100 km ultra-marathon. Pre- and post-race, creatine kinase, urea and myoglobin were determined. At the same time, the athletes were asked for subjective feelings of muscle soreness. Results Race time was not different between the groups when controlled for personal best time in a 100 km ultra-marathon. The increases in creatine kinase, urea and myoglobin were not different in both groups. Subjective feelings of skeletal muscle soreness were not different between the groups. Conclusions We concluded that short-term supplementation of amino acids before and during a 100 km ultra-marathon had no effect on variables of skeletal muscle damage and muscle soreness.

  20. Global-mean surface temperature variability: space-time perspective from rotated EOFs

    Science.gov (United States)

    Chen, Xianyao; Tung, Ka-Kit

    2017-10-01

    The observed global-mean surface temperature (GST) has been warming in the presence of increasing atmospheric concentration of greenhouse gases, but its rise has not been monotonic. Attention has increasingly been focused on the prominent variations about the linear trend in GST, especially on interdecadal and multidecadal time scales. When the sea-surface temperature (SST) and the land- plus-ocean surface temperature (ST) are averaged globally to yield the global-mean SST (GSST) and the GST, respectively, spatial information is lost. Information on both space and time is needed to properly identify the modes of variability on interannual, decadal, interdecadal and multidecadal time scales contributing to the GSST and GST variability. Empirical Orthogonal Function (EOF) analysis is usually employed to extract the space-time modes of climate variability. Here we use the method of pair-wise rotation of the principal components (PCs) to extract the modes in these time-scale bands and obtain global spatial EOFs that correspond closely with regionally defined climate modes. Global averaging these clearly identified global modes allows us to reconstruct GSST and GST, and in the process identify their components. The results are: Pacific contributes to the global mean variation mostly on the interannual time scale through El Nino-Southern Oscillation (ENSO) and its teleconnections, while the Atlantic contributes strongly to the global mean on the multidecadal time scale through the interhemispheric mode called the Atlantic Multidecadal Oscillation (AMO). The Pacific Decadal Oscillation (PDO) has twice as large a variance as the AMO, but its contribution to GST is only 1/10 that of the AMO because of its compensating patterns of cold and warm SST in northwest and northeast Pacific. Its teleconnection pattern, the Pacific/North America (PNA) pattern over land, is also found to be self-cancelling when globally averaged because of its alternating warm and cold centers. The

  1. VizieR Online Data Catalog: Time-series of 9 cataclysmic variables (Papadaki+, 2009)

    Science.gov (United States)

    Papadaki, C.; Boffin, H. M. J.; Stanishev, V.; Boumis, P.; Akras, S.; Sterken, C.

    2009-05-01

    We present time-series photometry of nine cataclysmic variables: EI UMa, V844 Her, V751 Cyg, V516 Cyg, GZ Cnc, TY Psc, V1315 Aql, ASAS J002511+1217.2, V1315 Aql and LN UMa. The observations were conducted at various observatories, covering 170 hours and comprising 7850 data points in total. For the majority of targets we confirm previously reported periodicities and for some of them we give, for the first time through photometry, their underlying spectroscopic orbital period. For those dwarf-nova systems which we observed during both quiescence and outburst, the increase in brightness was accompanied by a decrease in the level of flickering. For the eclipsing system V1315 Aql we have covered 9 eclipses, and obtained a refined orbital ephemeris. We find that, during its long baseline of observations, no change in the orbital period of this system has occurred. V1315 Aql also shows eclipses of variable depth. (22 data files).

  2. Photometric study of selected cataclysmic variables II. Time-series photometry of nine systems.

    Science.gov (United States)

    Papadaki, C.; Boffin, H. M. J.; Stanishev, V.; Boumis, P.; Akras, S.; Sterken, C.

    2009-05-01

    We present time-series photometry of nine cataclysmic variables: EI UMa, V844 Her, V751 Cyg, V516 Cyg, GZ Cnc, TY Psc, V1315 Aql, ASAS J002511+1217.2, V1315 Aql and LN UMa. The observations were conducted at various observatories, covering 170 hours and comprising 7,850 data points in total. For the majority of targets we confirm previously reported periodicities and for some of them we give, for the first time through photometry, their underlying spectroscopic orbital period. For those dwarf-nova systems which we observed during both quiescence and outburst, the increase in brightness was accompanied by a decrease in the level of flickering. For the eclipsing system V1315 Aql we have covered 9 eclipses, and obtained a refined orbital ephemeris. We find that, during this long baseline of observations, no change in the orbital period of this system has occurred. V1315 Aql also shows eclipses of variable depth.

  3. Single-Machine Group Scheduling Problems with Variable Job Processing Times

    Directory of Open Access Journals (Sweden)

    Ping Ji

    2015-01-01

    Full Text Available This paper considers two resource constrained single-machine group scheduling problems. These problems involve variable job processing times (general position-dependent learning effects and deteriorating jobs; that is, the processing time of a job is defined by the function that involves its starting time and position in the group, and groups’ setup time is a positive strictly decreasing continuous function of the amount of consumed resource. Polynomial time algorithms are proposed to optimally solve the makespan minimization problem under the constraint that the total resource consumption does not exceed a given limit and the total resource consumption minimization problem under the constraint that the makespan does not exceed a given limit, respectively.

  4. Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

    Directory of Open Access Journals (Sweden)

    Yeqing Zhang

    2018-02-01

    Full Text Available For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully.

  5. Long-term demography of the Northern Goshawk in a variable environment

    Science.gov (United States)

    Richard T. Reynolds; Jeffrey S. Lambert; Curtis H. Flather; Gary C. White; Benjamin J. Bird; L. Scott Baggett; Carrie Lambert; Shelley Bayard De Bolo

    2017-01-01

    The Nearctic northern goshawk (Accipiter gentilis atricapillis) is a resident of conifer, broadleaf, and mixed forests from the boreal to the southwestern montane regions of North America. We report on a 20-year mark-recapture investigation (1991-2010) of the distribution and density of breeders, temporal and spatial variability in breeding, nestling sex ratios, local...

  6. Influence of short-term blood pressure variability on blood pressure determinations

    NARCIS (Netherlands)

    Bos, W. J.; van Goudoever, J.; van Montfrans, G. A.; Wesseling, K. H.

    1992-01-01

    To evaluate the effect of blood pressure variability on Riva Rocci Korotkoff blood pressure determinations, we studied the intra-arterial pressure during Riva Rocci Korotkoff determinations in 25 patients. In 50 measurements with a cuff deflation rate of 2.5 mm Hg/sec, the systolic intra-arterial

  7. Investigation of Primary School Teachers' Conflict Resolution Skills in Terms of Different Variable

    Science.gov (United States)

    Bayraktar, Hatice Vatansever; Yilmaz, Kamile Özge

    2016-01-01

    In this study, it is aimed to determine the level of conflict resolution skills of primary school teachers and whether they vary by different variables. The study was organised in accordance with the scanning model. The universe of the study consists of primary school teachers working at 14 primary schools, two from each of the seven geographical…

  8. Long-term trend and variability of precipitation in Chhattisgarh State, India

    Science.gov (United States)

    Meshram, Sarita Gajbhiye; Singh, Vijay P.; Meshram, Chandrashekhar

    2017-08-01

    Spatial and temporal precipitation variability in Chhattisgarh State in India was examined by using monthly precipitation data for 102 years (1901-2002) from 16 stations. The homogeneity of precipitation data was evaluated by the double-mass curve approach and the presence of serial correlation by lag-1 autocorrelation coefficient. Linear regression analysis, the conventional Mann-Kendall (MK) test, and Spearman's rho were employed to identify trends and Sen's slope to estimate the slope of trend line. The coefficient of variation (CV) was used to analyze precipitation variability. Spatial interpolation was done by a Kriging process using ArcGIS 9.3. Results of both parametric and non-parametric tests and trend tests showed that at 5 % significance level, annual precipitation exhibited a decreasing trend at all stations except Bilaspur and Dantewada. For both annual and monsoon precipitation, Sen's test showed a decreasing trend for all stations, except Bilaspur and Dantewada. The highest percentage of variability was observed in winter precipitation (88.75 %) and minimum percentage variability in annual series (14.01 %) over the 102-year periods.

  9. Reviewing Personality Compliance Level of Trainee Music Teachers in Terms of Music Genres, and Some Variables

    Science.gov (United States)

    Pirgon, Yuksel

    2014-01-01

    In this study, personality compliance levels are examined according to tonality and tempo variables, which are acquired in consequence of analysis of music genres and pieces to which fine arts faculty, trainee music teachers mostly listen. A total of 31 students participated in the study. Data acquired from Hacettepe Personality Inventory (HPI)…

  10. Evaluation of Metacognitive Competence of Pre-Service Music Teachers in Terms of Some Variables

    Science.gov (United States)

    Hakan, Okay

    2016-01-01

    The purpose of the present research is to define pre-service music teachers' competence in using metacognitive activities in relation to academic achievement, gender, and class grade variables. The work-group consists of 131 pre-service music teachers, who study at Balikesir University Necatibey Faculty of Education, Programme of Music Teaching.…

  11. Long-term streamflow response to climatic variability in the Loess Plateau, China

    Science.gov (United States)

    Shenping Wang; Zhiqiang Zhang; Ge Sun; Steven G. McNulty; Huayong Zhang; Jianlao Li; Manliang Zhang

    2008-01-01

    The Loess Plateau region in northwestern China has experienced severe water resource shortages due to the combined impacts of climate and land use changes and water resource exploitation during the past decades. This study was designed to examine the impacts of climatic variability on streamflow characteristics of a 12-km2 watershed near Tianshui City, Gansu Province...

  12. Examining Decision Making Level of Wrestlers in Terms of Some Variable

    Science.gov (United States)

    Yigit, Sihmehmet; Dalbudak, Ibrahim; Musa, Mihriay; Gürkan, Alper C.; Dalkiliç, Mehmet

    2016-01-01

    The aim of this research is to examine decision making level of wrestlers who joined Turkey inter university wrestling championship, according to variables as wrestlers' sex, age, grade, department, and education type. Study group consists of 34 females and 196 males, totally 230 athletes, who joined Turkey Inter University Wrestling Championship…

  13. Attenuation effect on seasonal basin-scale water storage changes from GRACE time-variable gravity

    OpenAIRE

    Chen, JL; Wilson, CR; Famiglietti, JS; Rodell, M.

    2007-01-01

    In order to effectively recover surface mass or geoid height changes from the gravity recovery and climate experiment (GRACE) time-variable gravity models, spatial smoothing is required to minimize errors from noise. Spatial smoothing, such as Gaussian smoothing, not only reduces the noise but also attenuates the real signals. Here we investigate possible amplitude attenuations and phase changes of seasonal water storage variations in four drainage basins (Amazon, Mississippi, Ganges and Zamb...

  14. Spatiotemporal variability and long-term trends of ocean acidification in the California Current System

    Directory of Open Access Journals (Sweden)

    C. Hauri

    2013-01-01

    Full Text Available Due to seasonal upwelling, the upper ocean waters of the California Current System (CCS have a naturally low pH and aragonite saturation state (Ωarag, making this region particularly prone to the effects of ocean acidification. Here, we use the Regional Oceanic Modeling System (ROMS to conduct preindustrial and transient (1995–2050 simulations of ocean biogeochemistry in the CCS. The transient simulations were forced with increasing atmospheric pCO2 and increasing oceanic dissolved inorganic carbon concentrations at the lateral boundaries, as projected by the NCAR CSM 1.4 model for the IPCC SRES A2 scenario. Our results show a large seasonal variability in pH (range of ~ 0.14 and Ωarag (~ 0.2 for the nearshore areas (50 km from shore. This variability is created by the interplay of physical and biogeochemical processes. Despite this large variability, we find that present-day pH and Ωarag have already moved outside of their simulated preindustrial variability envelopes (defined by ±1 temporal standard deviation due to the rapidly increasing concentrations of atmospheric CO2. The nearshore surface pH of the northern and central CCS are simulated to move outside of their present-day variability envelopes by the mid-2040s and late 2030s, respectively. This transition may occur even earlier for nearshore surface Ωarag, which is projected to depart from its present-day variability envelope by the early- to mid-2030s. The aragonite saturation horizon of the central CCS is projected to shoal into the upper 75 m within the next 25 yr, causing near-permanent undersaturation in subsurface waters. Due to the model's overestimation of Ωarag, this transition may occur even earlier than simulated by the model. Overall, our study shows that the CCS joins the Arctic and Southern oceans as one of only a few known ocean regions presently approaching the dual threshold of

  15. Timing of clamping and factors associated with iron stores in full-term newborns

    Science.gov (United States)

    Oliveira, Fabiana de Cássia Carvalho; Assis, Karine Franklin; Martins, Mariana Campos; do Prado, Mara Rúbia Maciel Cardoso; Ribeiro, Andréia Queiroz; Sant’Ana, Luciana Ferreira da Rocha; Priore, Silvia Eloiza; Franceschini, Sylvia do Carmo Castro

    2014-01-01

    OBJECTIVE To analyze the impact of timing of clamping and obstetric, biological and socioeconomic factors on the iron stores of full-term newborns. METHODS Cross-sectional study between October 2011 and July 2012 in which hematological parameters were evaluated for newborns in Viçosa, MG, Southeastern Brazil. It involved collecting 7 mL of umbilical cord blood from 144 full-term not underweight newborns. The parameters investigated were complete blood count, serum iron, ferritin and C-reactive protein. The time of umbilical cord clamping was measured using a digital timer without interfering in the procedures of childbirth. The birth data were collected from Live Birth Certificates and other information was obtained from the mother through a questionnaire applied in the first month postpartum. Analysis of multiple linear regression was then used to estimate the influence of biological, obstetrics and socioeconomic factors on the ferritin levels at birth. RESULTS The median ferritin was 130.3 µg/L (n = 129, minimum = 16.4; maximum = 420.5 µg/L), the mean serum iron was 137.9 μg/dL (n = 144, SD = 39.29) and mean hemoglobin was 14.7 g/dL (n = 144, SD = 1.47). The median time of cord clamping was 36 seconds, ranging between 7 and 100. The bivariate analysis detected an association between ferritin levels and color of the child, timing clamping of 60 seconds, type of delivery, the presence of gestational diabetes and per capita family income. In multivariate analysis, the variables per capita income, number of antenatal visits and length at birth accounted for 22.0% of variation in ferritin levels. CONCLUSIONS Iron stores at birth were influenced by biological, obstetric and social characteristics. Tackling anemia should involve creating policies aimed at reducing social inequalities, improving the quality of antenatal care, as well as implementing a criterion of delayed clamping of the umbilical cord within the guidelines of labor. PMID:24789632

  16. Interannual and long-term sea level variability in the eastern Indian Ocean and South China Sea

    Science.gov (United States)

    Mohan, Soumya; Vethamony, P.

    2017-07-01

    Sea level anomalies (SLAs) derived from satellite observations (over a period of 22 years) and tide gauge data compiled from 66 stations from the eastern Indian Ocean and South China Sea (SCS) and western Pacific Ocean have been analyzed to study the interannual to long term variation of SLAs in the eastern Indian Ocean and SCS. Spatial patterns of sea level variability on the eastern boundary of the Indian Ocean exhibit non-coherent variability with SCS but show coherent variability with western Pacific Ocean. We find coherent variability in interannual SLAs in the Bay of Bengal, Andaman Sea, Malacca Strait and Java Strait. A large fraction of interannual SLA variations in the eastern SCS and interior SCS is linked to El Niño-Southern Oscillation (ENSO) and rest of the region is characterized by small scale interannual variations. The interannual SLAs in the SCS show seasonality with pronounced variation during winter and fall seasons. Interannual surface wind anomalies associated with Indian Ocean Dipole (IOD) and ENSO explain sea level interannual variability in the eastern Indian Ocean and SCS. The decadal sea level variability associated with Pacific Decadal Oscillation (PDO) and decadal ENSO are observed in the SCS.

  17. Response preparation and intra-individual reaction time variability in schizophrenia.

    Science.gov (United States)

    Dankinas, Denisas; Mėlynytė, Sigita; Šiurkutė, Aldona; Dapšys, Kastytis

    2016-01-01

    Background. It is important to prepare response in advance to increase the efficiency of its execution. The process of response preparation is usually studied using the precueing paradigm. In this paradigm subjects have to employ the preceding information about further imperative stimulus to perform proper response preparation, which shortens the reaction time of subsequent response execution. Previous studies detected the impairment of response preparation in schizophrenia only with the help of electroencephalographic parameters, but not with the assessing of reaction time. Therefore, in this study we attempted to find a behavioural parameter that could detect impairment in response preparation of schizophrenia patients. It was recently found that appropriate response preparation not only shortens the reaction time but also increases its stability, which is measured with the intra-individual reaction time variability. It was also revealed that response stability could better find cognitive dysfunction in some studies of schizophrenia disorder than classical behavioural parameters. Hence, the main goal of this study was to verify if intra-individual reaction time variability could detect the impairment of response preparation in schizophrenia patients. Materials and methods. In order to achieve the main purpose, we carried out a study with 14 schizophrenia patients and 14 control group subjects. We used precueing paradigm in our research, in which participants had to employ information about stimulus probability for the proper response preparation. Results. Our main result showed that despite the responses of schizophrenia patients were faster to the high-probability stimulus than to the low-probability one (F (1, 13) = 30.9, p reaction time variability did not differ in this group between the responses to more and less probable stimuli (F (1, 13) = 0.64, p = 0.44). Conclusions. Results of the study suggest that people with schizophrenia were able to use precueing

  18. Variable Valve Timing Scheduling in a 4-Stroke Internal Combustion Cylinder Utilizing Artificial Neural Networks

    Directory of Open Access Journals (Sweden)

    Sepehr Bapiri

    2017-09-01

    Full Text Available The apparently simple structure of a four-stroke internal combustion cylinder belies the complicated problem of optimizing valve operation in response to a change in crankshaft rotation speed. The objective of this study was to determine the cylinder pressure for valve event angles in order to determine the optimal strategy for the timing of valve events when independently-actuated valves are available. In this work, an artificial neural network is applied to create a prediction matrix to anticipate the best variable valve timing approach according to rotation speed.

  19. Time variability of X-ray sources in the M 31 centre field

    OpenAIRE

    Stiele, H.; Pietsch, W.; Haberl, F.; Freyberg, M.

    2008-01-01

    We present an extension to our XMM-Newton X-ray source catalogue of M 31, containing 39 newly found sources. In order to classify and identify more of the sources we search for X-ray time variability in XMM-Newton archival data of the M 31 centre field. As a source list we used our extended catalogue based on observations covering the time span from June 2000 to July 2004. We then determined the flux or at least an upper limit at the source positions for each observation. Deriving the flux ra...

  20. Continuous-time random-walk model of transport in variably saturated heterogeneous porous media.

    Science.gov (United States)

    Zoia, Andrea; Néel, Marie-Christine; Cortis, Andrea

    2010-03-01

    We propose a unified physical framework for transport in variably saturated porous media. This approach allows fluid flow and solute migration to be treated as ensemble averages of fluid and solute particles, respectively. We consider the cases of homogeneous and heterogeneous porous materials. Within a fractal mobile-immobile continuous time random-walk framework, the heterogeneity will be characterized by algebraically decaying particle retention times. We derive the corresponding (nonlinear) continuum-limit partial differential equations and we compare their solutions to Monte Carlo simulation results. The proposed methodology is fairly general and can be used to track fluid and solutes particles trajectories for a variety of initial and boundary conditions.

  1. Molecular dynamics based enhanced sampling of collective variables with very large time steps.

    Science.gov (United States)

    Chen, Pei-Yang; Tuckerman, Mark E

    2018-01-14

    Enhanced sampling techniques that target a set of collective variables and that use molecular dynamics as the driving engine have seen widespread application in the computational molecular sciences as a means to explore the free-energy landscapes of complex systems. The use of molecular dynamics as the fundamental driver of the sampling requires the introduction of a time step whose magnitude is limited by the fastest motions in a system. While standard multiple time-stepping methods allow larger time steps to be employed for the slower and computationally more expensive forces, the maximum achievable increase in time step is limited by resonance phenomena, which inextricably couple fast and slow motions. Recently, we introduced deterministic and stochastic resonance-free multiple time step algorithms for molecular dynamics that solve this resonance problem and allow ten- to twenty-fold gains in the large time step compared to standard multiple time step algorithms [P. Minary et al., Phys. Rev. Lett. 93, 150201 (2004); B. Leimkuhler et al., Mol. Phys. 111, 3579-3594 (2013)]. These methods are based on the imposition of isokinetic constraints that couple the physical system to Nosé-Hoover chains or Nosé-Hoover Langevin schemes. In this paper, we show how to adapt these methods for collective variable-based enhanced sampling techniques, specifically adiabatic free-energy dynamics/temperature-accelerated molecular dynamics, unified free-energy dynamics, and by extension, metadynamics, thus allowing simulations employing these methods to employ similarly very large time steps. The combination of resonance-free multiple time step integrators with free-energy-based enhanced sampling significantly improves the efficiency of conformational exploration.

  2. Molecular dynamics based enhanced sampling of collective variables with very large time steps

    Science.gov (United States)

    Chen, Pei-Yang; Tuckerman, Mark E.

    2018-01-01

    Enhanced sampling techniques that target a set of collective variables and that use molecular dynamics as the driving engine have seen widespread application in the computational molecular sciences as a means to explore the free-energy landscapes of complex systems. The use of molecular dynamics as the fundamental driver of the sampling requires the introduction of a time step whose magnitude is limited by the fastest motions in a system. While standard multiple time-stepping methods allow larger time steps to be employed for the slower and computationally more expensive forces, the maximum achievable increase in time step is limited by resonance phenomena, which inextricably couple fast and slow motions. Recently, we introduced deterministic and stochastic resonance-free multiple time step algorithms for molecular dynamics that solve this resonance problem and allow ten- to twenty-fold gains in the large time step compared to standard multiple time step algorithms [P. Minary et al., Phys. Rev. Lett. 93, 150201 (2004); B. Leimkuhler et al., Mol. Phys. 111, 3579-3594 (2013)]. These methods are based on the imposition of isokinetic constraints that couple the physical system to Nosé-Hoover chains or Nosé-Hoover Langevin schemes. In this paper, we show how to adapt these methods for collective variable-based enhanced sampling techniques, specifically adiabatic free-energy dynamics/temperature-accelerated molecular dynamics, unified free-energy dynamics, and by extension, metadynamics, thus allowing simulations employing these methods to employ similarly very large time steps. The combination of resonance-free multiple time step integrators with free-energy-based enhanced sampling significantly improves the efficiency of conformational exploration.

  3. Time - making the best of it! A Fieldwork Study Outlining Time in Endoscopy Facilities for Short-Term Stay

    DEFF Research Database (Denmark)

    Bundgaard, Karin; Sørensen, Erik E; Delmar, Charlotte

    2016-01-01

    participant observation, participant reports and patients and nurses semi-structured interviews. RESULTS/FINDINGS: The issue of time was an interwoven part of life in the productive endoscopy units. The understanding of time related to the main category: 'Time - making the best of it', and the sub categories......AIM: This paper focus on nursing and time in endoscopy facilities for short-term stay aiming to explore aspects of time in this setting and how expectations from the healthcare organisation, patients and nurses are expressed and met when managing nursing time. BACKGROUND: Former research primarily...... focuses on the subject of time in the understanding of duration where having more time is closely associated with the ability to deliver better quality nursing care. The main concern is the nurses' increased number of tasks and the decreased length of time at their disposal. However, few studies describe...

  4. How to reduce long-term drift in present-day and deep-time simulations?

    Science.gov (United States)

    Brunetti, Maura; Vérard, Christian

    2017-09-01

    Climate models are often affected by long-term drift that is revealed by the evolution of global variables such as the ocean temperature or the surface air temperature. This spurious trend reduces the fidelity to initial conditions and has a great influence on the equilibrium climate after long simulation times. Useful insight on the nature of the climate drift can be obtained using two global metrics, i.e. the energy imbalance at the top of the atmosphere and at the ocean surface. The former is an indicator of the limitations within a given climate model, at the level of both numerical implementation and physical parameterisations, while the latter is an indicator of the goodness of the tuning procedure. Using the MIT general circulation model, we construct different configurations with various degree of complexity (i.e. different parameterisations for the bulk cloud albedo, inclusion or not of friction heating, different bathymetry configurations) to which we apply the same tuning procedure in order to obtain control runs for fixed external forcing where the climate drift is minimised. We find that the interplay between tuning procedure and different configurations of the same climate model provides crucial information on the stability of the control runs and on the goodness of a given parameterisation. This approach is particularly relevant for constructing good-quality control runs of the geological past where huge uncertainties are found in both initial and boundary conditions. We will focus on robust results that can be generally applied to other climate models.

  5. Possible Influence of Volcanic Activity on the Decadal Potential Predictability of the Natural Variability in Near-Term Climate Predictions

    Directory of Open Access Journals (Sweden)

    Hideo Shiogama

    2010-01-01

    Full Text Available Initialization based on data assimilations using historical observations possibly improves near-term climate predictions. Significant volcanic activity in the future is unpredictable and not assumed in future climate predictions. To examine the possible influence of unpredictable future volcanic activity on the decadal potential predictability of the natural variability, we performed a 2006–2035 climate prediction experiment with the assumption that the 1991  Mt. Pinatubo eruption would take place again in 2010. The Pinatubo forcing induced not only significant cooling responses but also considerable noises in the natural variability. The errors due to the Pinatubo forcing grew faster than that arising from imperfect knowledge of the observed state, leading to a rapid reduction of the decadal potential predictability of the natural variability.

  6. EXAMINATION OF THE INAPPROPRIATE BEHAVIORS DISPLAYED BY PROSPECTIVE TEACHERS THROUGH DIGITAL DEVICES IN TERMS OF CERTAIN VARIABLES

    OpenAIRE

    SİNCAR, Mehmet

    2014-01-01

    The purpose of this study is to examine the inappropriate behaviors displayed by prospective teachers through digital devices in terms of certain variables, and to reveal the causes of these inappropriate behaviors. Employing quantitative and qualitative research methods, the study was carried out during the 2011-2012 academic year with participation of 185 prospective teachers from a faculty of education in Turkey. Quantitative data were analyzed by use of multiple linear regression analysis...

  7. Biological and physicochemical factors controlling short-term variability in phytoplankton primary production and photosynthetic parameters in a macrotidal ecosystem (eastern English Channel)

    Science.gov (United States)

    Jouenne, Fabien; Lefebvre, Sébastien; Véron, Benoît; Lagadeuc, Yvan

    2005-11-01

    Links between short-term variability of phytoplankton primary production and community structure changes have been studied rarely. This has been examined in a macrotidal ecosystem, the Baie des Veys (eastern English Channel, France), in 2003 and 2004, over the complete tidal cycle (semi-diurnal mode, 12 h). Within this area, primary production and photosynthetic parameter estimates, according to the 14C incorporation technique, were supported by an exhaustive taxonomic study and measurements of physicochemical factors to illustrate the environmental framework. Related to the river Vire discharge, daily interactions between estuarine and bay waters were demonstrated. Depth-integrated primary production P z was maximal around noon in the bay (48.7-68.0 mg C m -2 h -1) and decreased through the day in the mouth of the river. Photosynthetic parameters' variations and photoacclimation were influenced by the ecosystem variability level: short-term photoacclimation was possible in low mixing conditions. Changes in taxonomic composition according to tidal forcing led to variations in primary production levels. Large species, associated with high photosynthetic parameters, were observed in the bay, whereas small ones were present in the mouth of the river, when low primary production was measured. On a short-time scale, a positive relationship was observed between species diversity and primary production. This work emphasizes the need to focus on changes in phytoplankton community structure in order to understand short-term variability in primary production.

  8. Are changes in the mean or variability of climate signals more important for long-term stochastic growth rate?

    Directory of Open Access Journals (Sweden)

    Bernardo García-Carreras

    Full Text Available Population dynamics are affected by changes in both the mean and standard deviation of climate, e.g., changes in average temperature are likely to affect populations, but so are changes in the strength of year-to-year temperature variability. The impacts of increases in average temperature are extensively researched, while the impacts of changes in climate variability are less studied. Is the greater attention given to changes in mean environment justified? To help answer this question we developed a simple population model, explicitly linked to an environmental process. We used the model to compare the sensitivities of a population's long-term stochastic growth rate, a measure of fitness, to changes in the mean and standard deviation of the environment. Results are interpreted in light of a comparative analysis of the relative magnitudes of change in means and standard deviations of biologically relevant climate variables in the United States. Results show that changes in the variability of the environment can be more important for many populations. Changes in mean conditions are likely to have a greater impact than changes in variability on populations far from their ideal environment, for example, populations near species range boundaries and potentially of conservation concern. Populations near range centres and close to their ideal environment are more likely to be affected by changes in variability. Among pest and insect disease vectors, as well as species of commercial value, populations likely to be of greatest economic and public health significance are those near species range centers, living in a near-ideal environment for the species. Observed changes in the variability of climate variables may benefit these populations.

  9. Statistical assessment of DNA extraction reagent lot variability in real-time quantitative PCR

    Science.gov (United States)

    Bushon, R.N.; Kephart, C.M.; Koltun, G.F.; Francy, D.S.; Schaefer, F. W.; Lindquist, H.D. Alan

    2010-01-01

    Aims: The aim of this study was to evaluate the variability in lots of a DNA extraction kit using real-time PCR assays for Bacillus anthracis, Francisella tularensis and Vibrio cholerae. Methods and Results: Replicate aliquots of three bacteria were processed in duplicate with three different lots of a commercial DNA extraction kit. This experiment was repeated in triplicate. Results showed that cycle threshold values were statistically different among the different lots. Conclusions: Differences in DNA extraction reagent lots were found to be a significant source of variability for qPCR results. Steps should be taken to ensure the quality and consistency of reagents. Minimally, we propose that standard curves should be constructed for each new lot of extraction reagents, so that lot-to-lot variation is accounted for in data interpretation. Significance and Impact of the Study: This study highlights the importance of evaluating variability in DNA extraction procedures, especially when different reagent lots are used. Consideration of this variability in data interpretation should be an integral part of studies investigating environmental samples with unknown concentrations of organisms. ?? 2010 The Society for Applied Microbiology.

  10. Length of Growing Period over Africa: Variability and Trends from 30 Years of NDVI Time Series

    Directory of Open Access Journals (Sweden)

    Mohammed Y. Said

    2013-02-01

    Full Text Available The spatial distribution of crops and farming systems in Africa is determined by the duration of the period during which crop and livestock water requirements are met. The length of growing period (LGP is normally assessed from weather station data—scarce in large parts of Africa—or coarse-resolution rainfall estimates derived from weather satellites. In this study, we analyzed LGP and its variability based on the 1981–2011 GIMMS NDVI3g dataset. We applied a variable threshold method in combination with a searching algorithm to determine start- and end-of-season. We obtained reliable LGP estimates for arid, semi-arid and sub-humid climates that are consistent in space and time. This approach effectively mapped bimodality for clearly separated wet seasons in the Horn of Africa. Due to cloud contamination, the identified bimodality along the Guinea coast was judged to be less certain. High LGP variability is dominant in arid and semi-arid areas, and is indicative of crop failure risk. Significant negative trends in LGP were found for the northern part of the Sahel, for parts of Tanzania and northern Mozambique, and for the short rains of eastern Kenya. Positive trends occurred across western Africa, in southern Africa, and in eastern Kenya for the long rains. Our LGP analysis provides useful information for the mapping of farming systems, and to study the effects of climate variability and other drivers of change on vegetation and crop suitability.

  11. Spitzer Observations of Long-term Infrared Variability among Young Stellar Objects in Chamaeleon I

    Science.gov (United States)

    Flaherty, Kevin M.; DeMarchi, Lindsay; Muzerolle, James; Balog, Zoltan; Herbst, William; Megeath, S. Thomas; Furlan, Elise; Gutermuth, Robert

    2016-12-01

    Infrared variability is common among young stellar objects, with surveys finding daily to weekly fluctuations of a few tenths of a magnitude. Space-based observations can produce highly sampled infrared light curves, but are often limited to total baselines of about 1 month due to the orientation of the spacecraft. Here we present observations of the Chameleon I cluster, whose low declination makes it observable by the Spitzer Space Telescope over a 200-day period. We observe 30 young stellar objects with a daily cadence to better sample variability on timescales of months. We find that such variability is common, occurring in ˜80% of the detected cluster members. The change in [3.6]-[4.5] color over 200 days for many of the sources falls between that expected for extinction and fluctuations in disk emission. With our high cadence and long baseline we can derive power spectral density curves covering two orders of magnitude in frequency and find significant power at low frequencies, up to the boundaries of our 200-day survey. Such long timescales are difficult to explain with variations driven by the interaction between the disk and stellar magnetic field, which has a dynamical timescale of days to weeks. The most likely explanation is either structural or temperature fluctuations spread throughout the inner ˜0.5 au of the disk, suggesting that the intrinsic dust structure is highly dynamic.

  12. SPITZER OBSERVATIONS OF LONG-TERM INFRARED VARIABILITY AMONG YOUNG STELLAR OBJECTS IN CHAMAELEON I

    Energy Technology Data Exchange (ETDEWEB)

    Flaherty, Kevin M.; Herbst, William [Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); DeMarchi, Lindsay [Department of Physics and Astronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346 (United States); Muzerolle, James [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Balog, Zoltan [Max-Planck-Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg (Germany); Megeath, S. Thomas [Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States); Furlan, Elise [Infrared Processing and Analysis Center, California Institute of Technology, 770 S. Wilson Avenue, Pasadena, CA 91125 (United States); Gutermuth, Robert [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

    2016-12-10

    Infrared variability is common among young stellar objects, with surveys finding daily to weekly fluctuations of a few tenths of a magnitude. Space-based observations can produce highly sampled infrared light curves, but are often limited to total baselines of about 1 month due to the orientation of the spacecraft. Here we present observations of the Chameleon I cluster, whose low declination makes it observable by the Spitzer Space Telescope over a 200-day period. We observe 30 young stellar objects with a daily cadence to better sample variability on timescales of months. We find that such variability is common, occurring in ∼80% of the detected cluster members. The change in [3.6]–[4.5] color over 200 days for many of the sources falls between that expected for extinction and fluctuations in disk emission. With our high cadence and long baseline we can derive power spectral density curves covering two orders of magnitude in frequency and find significant power at low frequencies, up to the boundaries of our 200-day survey. Such long timescales are difficult to explain with variations driven by the interaction between the disk and stellar magnetic field, which has a dynamical timescale of days to weeks. The most likely explanation is either structural or temperature fluctuations spread throughout the inner ∼0.5 au of the disk, suggesting that the intrinsic dust structure is highly dynamic.

  13. Intelligent real-time CCD data processing system based on variable frame rate

    Science.gov (United States)

    Chen, Su-ting

    2009-07-01

    In order to meet the need of image shooting with CCD in unmanned aerial vehicles, a real-time high resolution CCD data processing system based on variable frame rate is designed. The system is consisted of three modules: CCD control module, data processing module and data display module. In the CCD control module, real-time flight parameters (e.g. flight height, velocity and longitude) should be received from GPS through UART (Universal Asynchronous Receiver Transmitter) and according to the corresponding flight parameters, the variable frame rate is calculated. Based on the calculated variable frame rate, CCD external synchronization control impulse signal is generated in the control of FPGA and then CCD data is read out. In the data processing module, data segmentation is designed to extract ROI (region of interest), whose resolution is equal to valid data resolution of HDTV standard conforming to SMPTE (1080i). On one hand, Ping-pong SRAM storage controller is designed in FPGA to real-time store ROI data. On the other hand, according to the need of intelligent observing, changeable window position is designed, and a flexible area of interest is obtained. In the real-time display module, a special video encoder is used to accomplish data format conversion. Data after storage is packeted to HDTV format by creating corresponding format information in FPGA. Through inner register configuration, high definition video analog signal is implemented. The entire system has been implemented in FPGA and validated. It has been used in various real-time CCD data processing situations.

  14. Morning versus afternoon gymnastic time and diurnal and seasonal changes in psychophysiological variables of school children.

    Science.gov (United States)

    Huguet, G; Touitou, Y; Reinberg, A

    1997-07-01

    The aims of this study were to document time-related (morning versus afternoon) effects of physical activities (gymnastics) on a set of physiological and psychological variables in school children, including diurnal changes. For the study, 61 boys and 69 girls, 6 to 11 years of age, volunteered. They were considered healthy according to routine clinical criteria. They were synchronized with diurnal activity from around 07:00 to 21:00 and nocturnal rest, time of year being taken into account. Tests were performed at school during 4 weeks of 4.5 days of school at fixed clock hours: 09:00, 11:00, 14:00, and 16:00. Gym time was randomized with regard to week order and season. Four different classes (39 boys and 38 girls) were involved in psychophysiological tests, and two different classes (22 boys and 31 girls) collected saliva samples for morning free cortisol determination. Both t-test and three-factor analysis of variance (ANOVA) were used for statistical analyses. Better performances were obtained in June than in mid-winter with reference to letter cancellation and random number addition tests. As a group phenomenon, morning (09:00 to 10:00) versus afternoon (14:00 to 15:00) gym was not an influential condition with regard to sleep duration, oral temperature, self-rated fatigue and drowsiness, letter cancellation, addition tests, or salivary cortisol. However, gym-time-related differences were observed in classes of younger subjects (e.g., 6-7 years) with regard to self-rated fatigue and the letter cancellation test. Such variability among subgroups suggests that interindividual differences are likely to exist in younger children with regard to manipulation of environmental factors. In addition, gym itself (without gym time consideration) may be an influential factor with regard to diurnal patterns of some variables (e.g., the letter cancellation test).

  15. Simulation of the time-variable gravity field by means of coupled geophysical models

    Directory of Open Access Journals (Sweden)

    Th. Gruber

    2011-10-01

    Full Text Available Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's interior. The first set of observations of monthly variations of the Earth gravity field was provided by the US/German GRACE satellite mission beginning in 2002. This mission is still providing valuable information to the science community. However, as GRACE has outlived its expected lifetime, the geoscience community is currently seeking successor missions in order to maintain the long time series of climate change that was begun by GRACE. Several studies on science requirements and technical feasibility have been conducted in the recent years. These studies required a realistic model of the time variable gravity field in order to perform simulation studies on sensitivity of satellites and their instrumentation. This was the primary reason for the European Space Agency (ESA to initiate a study on ''Monitoring and Modelling individual Sources of Mass Distribution and Transport in the Earth System by Means of Satellites''. The goal of this interdisciplinary study was to create as realistic as possible simulated time variable gravity fields based on coupled geophysical models, which could be used in the simulation processes in a controlled environment. For this purpose global atmosphere, ocean, continental hydrology and ice models were used. The coupling was performed by using consistent forcing throughout the models and by including water flow between the different domains of the Earth system. In addition gravity field changes due to solid Earth processes like continuous glacial isostatic adjustment (GIA and a sudden earthquake with co-seismic and post-seismic signals were modelled. All individual model results were combined and converted to gravity field

  16. The Galex Time Domain Survey. I. Selection And Classification of Over a Thousand Ultraviolet Variable Sources

    Science.gov (United States)

    Gezari, S.; Martin, D. C.; Forster, K.; Neill, J. D.; Huber, M.; Heckman, T.; Bianchi, L.; Morrissey, P.; Neff, S. G.; Seibert, M.; hide

    2013-01-01

    We present the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in approximately 40 deg(exp 2) of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of approximately 3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. We characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5 sigma level in at least one epoch. We measure the statistical properties of the UV variability, including the structure function on timescales of days and years. We report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. We classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). We detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to absolute value(?m) = 4.6 mag and 2.9 mag, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by dormant supermassive black hole. We calculate a surface density for variable sources in the UV with NUV less than 23 mag and absolute value(?m) greater than 0.2 mag of approximately 8.0, 7.7, and 1.8 deg(exp -2) for quasars, active galactic nuclei, and RR Lyrae stars

  17. Short-term variability on mesozooplankton community in a shallow mixed estuary (Bahía Blanca, Argentina): Influence of tidal cycles and local winds

    Science.gov (United States)

    Menéndez, María C.; Piccolo, María C.; Hoffmeyer, Mónica S.

    2012-10-01

    The short-term dynamics of zooplankton in coastal ecosystems are strongly influenced by physical processes such as tides, riverine runoff and winds. In this study, we investigated the short-term changes of the representative taxa within mesozooplankton in relation to the semidiurnal tidal cycles. Also, we evaluated the influence of local winds on this short-term variability. Sampling was carried out bimonthly from December 2004 to April 2006 in a fixed point located in the inner zone of the Bahía Blanca Estuary, Argentina. Mesozooplankton samples were taken by pumps during 14-h tidal cycles at 3-h intervals, from surface and bottom. Vertical profiles of temperature and salinity as well as water samples to determine suspended particulate matter were acquired at each sampling date. All data concerning winds were obtained from a meteorological station and water level was recorded with a tide gauge. Holoplankton dominated numerically on meroplankton and adventitious fraction. Concerning holoplanktonic abundance, the highest values were attained by the calanoid copepods Acartia tonsa and Eurytemora americana. Meroplankton occurred mainly as barnacle larvae while benthic harpacticoids and Corophium sp. dominated the adventitious component. Semidiurnal tide was the main influence on the A. tonsa variability. However, noticeable differences in the abundance pattern as function of wind intensity were detected. Meroplankton abundance did not show a clear variation along the tidal cycle. Distributional pattern of harpacticoids seemed to be mainly modulated by velocity asymmetries in the tidal currents, in the same way as suspended particulate matter. However, the Corophium sp. distribution indicated probable behavioural responses associated with tides. The obtained results show how variable the mesozooplankton community structure can be over short-term time scales in mesotidal temperate estuaries. This variability should be taken into account for any zooplankton monitoring

  18. Short-Term and Long-Term Variability of Antenna Position Due to Thermal Bending of Pillar Monument at Permanent GNSS Station

    Directory of Open Access Journals (Sweden)

    Gerhatova Lubomira

    2016-06-01

    Full Text Available The variability of daily site coordinates at permanent GNSS station is a sum of many disturbing factors influencing the actual satellite observations, data processing, and bias modelling. In the paper are analysed possibilities of monitoring the instability of GNSS antenna pillar monument by the independent observations using the precise inclination sensor. Long-term series from three different types of pillars show specific features in amplitude and temporal evolution of monument bending. Correlations with daily temperature and/or solar radiation changes were proved.

  19. Investigating Academic Self-Efficacy of University Students in Terms of Socio-Demographic Variables

    Science.gov (United States)

    Satici, Seydi Ahmet; Can, Gurhan

    2016-01-01

    In this study whether academic self-efficacy of university students differ in terms of various socio-demographic features has been investigated. The study was conducted on 1679 students who were attending Anadolu University. In the study, the Academic Self-Efficacy Scale and Personal Information Form were used as data collection tools. In the…

  20. Short-term variability of mineral dust, metals and carbon emission from road dust resuspension

    NARCIS (Netherlands)

    Amato, F.; Schaap, M.; Denier van der Gon, H.A.C.; Pandolfi, M.; Alastuey, A.; Keuken, M.; Querol, X.

    2013-01-01

    Particulate matter (PM) pollution in cities has severe impact on morbidity and mortality of their population. In these cities, road dust resuspension contributes largely to PM and airborne heavy metals concentrations. However, the short-term variation of emission through resuspension is not well

  1. A Meta-Analysis of the Impact of Short-Term Sleep Deprivation on Cognitive Variables

    Science.gov (United States)

    Lim, Julian; Dinges, David F.

    2010-01-01

    A substantial amount of research has been conducted in an effort to understand the impact of short-term (less than 48 hr) total sleep deprivation (SD) on outcomes in various cognitive domains. Despite this wealth of information, there has been disagreement on how these data should be interpreted, arising in part because the relative magnitude of…

  2. Understanding variability in time spent in selected locations for 7-12-year old children.

    Science.gov (United States)

    Xue, Jianping; McCurdy, Thomas; Spengler, John; Ozkaynak, Hâluk

    2004-05-01

    This paper summarizes a series of analyses of clustered, sequential activity/location data collected by Harvard University for 160 children aged 7-12 years in Southern California (Geyh et al., 2000). The main purpose of the paper is to understand intra- and inter-variability in the time spent by the sample in the outdoor location, the location exhibiting the most variability of the ones evaluated. The data were analyzed using distribution-free hypothesis-testing (K-S tests of the distributions), generalized linear modeling techniques, and random-sampling schemes that produced "cohorts" whose descriptive statistical characteristics were evaluated against the original dataset. Most importantly, our analyses indicate that subdividing the population into appropriate cohorts better replicates parameters of the original data, including the interclass correlation coefficient (ICC), which is a relative measure of the intra- and inter-individual variability inherent in the original data. While the findings of our analyses are consistent with previous assessments of "time budget" and physical activity data, they are constrained by the rather homogeneous sample available to us. Owing to a general lack of longitudinal human activity/location data available for other age/gender cohorts, we are unable to generalize our findings to other population subgroups.

  3. Variable Neighbourhood Search and Mathematical Programming for Just-in-Time Job-Shop Scheduling Problem

    Directory of Open Access Journals (Sweden)

    Sunxin Wang

    2014-01-01

    Full Text Available This paper presents a combination of variable neighbourhood search and mathematical programming to minimize the sum of earliness and tardiness penalty costs of all operations for just-in-time job-shop scheduling problem (JITJSSP. Unlike classical E/T scheduling problem with each job having its earliness or tardiness penalty cost, each operation in this paper has its earliness and tardiness penalties, which are paid if the operation is completed before or after its due date. Our hybrid algorithm combines (i a variable neighbourhood search procedure to explore the huge feasible solution spaces efficiently by alternating the swap and insertion neighbourhood structures and (ii a mathematical programming model to optimize the completion times of the operations for a given solution in each iteration procedure. Additionally, a threshold accepting mechanism is proposed to diversify the local search of variable neighbourhood search. Computational results on the 72 benchmark instances show that our algorithm can obtain the best known solution for 40 problems, and the best known solutions for 33 problems are updated.

  4. Long term variability of the annual hydrological regime and sensitivity to temperature phase shifts in Saxony/Germany

    Directory of Open Access Journals (Sweden)

    M. Renner

    2011-06-01

    Full Text Available Recently, climatological studies report observational evidence of changes in the timing of the seasons, such as earlier timing of the annual cycle of surface temperature, earlier snow melt and earlier onset of the phenological spring season. Also hydrological studies report earlier timing and changes in monthly streamflows. From a water resources management perspective, there is a need to quantitatively describe the variability in the timing of hydrological regimes and to understand how climatic changes control the seasonal water budget of river basins.

    Here, the timing of hydrological regimes from 1930–2009 was investigated in a network of 27 river gauges in Saxony/Germany through a timing measure derived by harmonic function approximation of annual periods of runoff ratio series. The timing measure proofed to be robust and equally applicable to both mainly pluvial river basins and snow melt dominated regimes.

    We found that the timing of runoff ratio is highly variable, but markedly coherent across the basins analysed. Differences in average timing are largely explained by basin elevation. Also the magnitude of low frequent changes in the seasonal timing of streamflow and the sensitivity to the changes in the timing of temperature increase with basin elevation. This sensitivity is in turn related to snow storage and release, whereby snow cover dynamics in late winter explain a large part of the low- and high-frequency variability.

    A trend analysis based on cumulative anomalies revealed a common structural break around the year 1988. While the timing of temperature shifted earlier by 4 days, accompanied by a temperature increase of 1 K, the timing of runoff ratio within higher basins shifted towards occurring earlier about 1 to 3 weeks. This accelerated and distinct change indicates, that impacts of climate change on the water cycle may be strongest in higher, snow melt dominated basins.

  5. Long term variability of the annual hydrological regime and sensitivity to temperature phase shifts in Saxony/Germany

    Science.gov (United States)

    Renner, M.; Bernhofer, C.

    2011-06-01

    Recently, climatological studies report observational evidence of changes in the timing of the seasons, such as earlier timing of the annual cycle of surface temperature, earlier snow melt and earlier onset of the phenological spring season. Also hydrological studies report earlier timing and changes in monthly streamflows. From a water resources management perspective, there is a need to quantitatively describe the variability in the timing of hydrological regimes and to understand how climatic changes control the seasonal water budget of river basins. Here, the timing of hydrological regimes from 1930-2009 was investigated in a network of 27 river gauges in Saxony/Germany through a timing measure derived by harmonic function approximation of annual periods of runoff ratio series. The timing measure proofed to be robust and equally applicable to both mainly pluvial river basins and snow melt dominated regimes. We found that the timing of runoff ratio is highly variable, but markedly coherent across the basins analysed. Differences in average timing are largely explained by basin elevation. Also the magnitude of low frequent changes in the seasonal timing of streamflow and the sensitivity to the changes in the timing of temperature increase with basin elevation. This sensitivity is in turn related to snow storage and release, whereby snow cover dynamics in late winter explain a large part of the low- and high-frequency variability. A trend analysis based on cumulative anomalies revealed a common structural break around the year 1988. While the timing of temperature shifted earlier by 4 days, accompanied by a temperature increase of 1 K, the timing of runoff ratio within higher basins shifted towards occurring earlier about 1 to 3 weeks. This accelerated and distinct change indicates, that impacts of climate change on the water cycle may be strongest in higher, snow melt dominated basins.

  6. Asymptotic behaviors of solutions for viscoelastic wave equation with space-time dependent damping term

    KAUST Repository

    Said-Houari, Belkacem

    2012-03-01

    In this paper, we consider a viscoelastic wave equation with an absorbing term and space-time dependent damping term. Based on the weighted energy method, and by assuming that the kernel decaying exponentially, we obtain the L2 decay rates of the solutions. More precisely, we show that the decay rates are the same as those obtained in Lin et al. (2010) [15] for the semilinear wave equation with absorption term. © 2011 Elsevier Inc.

  7. Modelling time variable and total eclipses of the millisecond pulsar PSR 1744-24A

    Science.gov (United States)

    Tavani, Marco; Brookshaw, Leigh

    1993-01-01

    The 11 ms pulsar PSR 1744-24A in the globular clusters Terzan 5 is the first and only known example of a binary eclipsing pulsar showing time-variable eclipses with irregular and nonsymmetric eclipse patterns. Occasionally, the pulsar eclipse becomes total, and no radio emission is detected for an extended period of time. We present here numerical results of a hydrodynamical model aimed at explaining the remarkable eclipse properties of PSR 1744-24A. We show that the hydrodynamic time scale for the partial or total pulsar enshrouding is of order of the orbital period for a relatively large mass loss rate, in agreement with observations. The time-variable eclipse egress positions imply that the mass loss rate from the companion varies within one orbital period. Hydrodynamic modelling of the mass outflow of PSR 1744-24A is of crucial importance for the understanding of a class of millisecond pulsars whose radio emission might be occasionally or permanently quenched by mass outflows from their companions. The properties of PSR 1744-24A suggest a new way of studying millisecond pulsars involving radio, X-ray, gamma-ray, and optical observations.

  8. Variability of Cost and Time Delivery of Educational Buildings in Nigeria

    Directory of Open Access Journals (Sweden)

    Aghimien, Douglas Omoregie

    2017-09-01

    Full Text Available Cost and time overrun in construction projects has become a reoccurring problem in construction industries around the world especially in developing countries. This situation is unhealthy for public educational buildings which are executed with limited government funds, and are in most cases time sensitive, as they need to cater for the influx of students into the institutions. This study therefore assessed the variability of cost and time delivery of educational buildings in Nigeria, using a study of selected educational buildings within the country. A pro forma was used to gather cost and time data on selected building projects, while structured questionnaire was used to harness information on the possible measures for reducing the variability from the construction participants that were involved in the delivery of these projects. Paired sample t-test, percentage, relative importance index, and Kruskal-Walis test were adopted for data analyses. The study reveals that there is a significant difference between the initial and final cost of delivering educational buildings, as an average of 4.87% deviation, with a sig. p-value of 0.000 was experienced on all assessed projects. For time delivery, there is also a significant difference between the initial estimated time and final time of construction as a whopping 130% averaged deviation with a sig. p-value of 0.000 was discovered. To remedy these problems, the study revealed that prompt payment for executed works, predicting market price fluctuation and inculcating it into the initial estimate, and owner’s involvement at the planning and design phase are some of the possible measures to be adopted.

  9. Bidecadal North Atlantic ocean circulation variability controlled by timing of volcanic eruptions.

    Science.gov (United States)

    Swingedouw, Didier; Ortega, Pablo; Mignot, Juliette; Guilyardi, Eric; Masson-Delmotte, Valérie; Butler, Paul G; Khodri, Myriam; Séférian, Roland

    2015-03-30

    While bidecadal climate variability has been evidenced in several North Atlantic paleoclimate records, its drivers remain poorly understood. Here we show that the subset of CMIP5 historical climate simulations that produce such bidecadal variability exhibits a robust synchronization, with a maximum in Atlantic Meridional Overturning Circulation (AMOC) 15 years after the 1963 Agung eruption. The mechanisms at play involve salinity advection from the Arctic and explain the timing of Great Salinity Anomalies observed in the 1970s and the 1990s. Simulations, as well as Greenland and Iceland paleoclimate records, indicate that coherent bidecadal cycles were excited following five Agung-like volcanic eruptions of the last millennium. Climate simulations and a conceptual model reveal that destructive interference caused by the Pinatubo 1991 eruption may have damped the observed decreasing trend of the AMOC in the 2000s. Our results imply a long-lasting climatic impact and predictability following the next Agung-like eruption.

  10. Time-scale characteristics of Kasai river hydrological regime variability for 1940-1999

    CERN Document Server

    Mbuebue, Jean-Marie Tshitenge; Mwamba, Vincent Lukanda; Phuati, Edmond Phuku; Bantu, Albert Kazadi Mukenga; Keto, Franck Tondozi

    2016-01-01

    The present study was undertaken with the aim of contributing to the characterization of the nonstationary variability of the hydrological regime of the Kasai River using the wavelet analysis for 1940-1999. The rainfalls and discharge over Kasai Basin have marked fluctuations with a perceptible downward trend and some shift around 1950, 1960, 1970, 1983 and 1994. The results show that rainfalls over Kasai basin and the discharge at Ilebo station patterns exhibit a strong annual oscillation and some intermittent oscillations in 2-8 years (1950-1975, 1983-1995) and 8-16 years (1970-1999) time scales. The wavelet coherence analysis reveals a weak possible connection between hydrological variables (rainfalls, discharge) and climate indices relative to sea surface temperature and atmospheric circulation over Atlantic tropical, Indian and Pacific Oceans (coherence less than 0.55).

  11. Adherence to nebulised therapies in adolescents with cystic fibrosis is best on week-days during school term-time.

    Science.gov (United States)

    Ball, Rosemary; Southern, Kevin W; McCormack, Pamela; Duff, Alistair J A; Brownlee, Keith G; McNamara, Paul S

    2013-09-01

    Treatment regimen for families of children with cystic fibrosis (CF) is considerable, particularly when nebulised therapies for chronic Pseudomonas aeruginosa airway infection are prescribed. Adherence to these regimens is variable, particularly in adolescence. Previously, we reported children to be more adherent in evenings compared to mornings, suggesting an association with time-pressure. The aim of this study was to determine whether adherence would be better in adolescent patients at weekends and during school holidays when time-pressures may be less. 24 patients (14 male, median [range] age 13.9 [11.1-16.8] years) were enrolled from two regional paediatric CF centres in the United Kingdom. Data for a full scholastic year, were downloaded openly from a breath-activated data logging nebuliser (I-neb™). Adherence (% of doses taken÷expected number) was calculated during term-times, holidays, weekends and weekdays, for each patient. Large variations in adherence were seen between patients. However, adherence during term-time was significantly better than holidays (pday, a similar number to those prescribed two daily treatments. Overall adherence to inhaled therapies was reasonable, but significantly reduced during holiday periods. This suggests a need for families to have not only time, but also structure in their daily routine to maintain optimal adherence to long-term therapies. It is important for CF teams to appreciate these factors when supporting families. Copyright © 2013 European Cystic Fibrosis Society. Published by Elsevier B.V. All rights reserved.

  12. Long-term Optical Polarization Variability and Multiwavelength Analysis of Blazar Mrk 421

    Science.gov (United States)

    Fraija, N.; Benítez, E.; Hiriart, D.; Sorcia, M.; López, J. M.; Mújica, R.; Cabrera, J. I.; de Diego, J. A.; Rojas-Luis, M.; Salazar-Vázquez, F. A.; Galván-Gámez, A.

    2017-09-01

    The results of 8 yr R-band photopolarimetric data of blazar Mrk 421 collected from 2008 February to 2016 May are presented, along with extensive multiwavelength observations covering radio to TeV γ-rays around the flares observed in 2008 May, 2010 March, and 2013 April. The most important results are found in 2013, when the source displayed in the R band a very high brightness state of 11.29 ± 0.03 mag (93.60 ± 1.53 mJy) on April 10 and a polarization degree of 11.00% ± 0.44% on May 13. The analysis of the optical data shows that the polarization variability is due to the superposition of two polarized components that might be produced in two distinct emitting regions. An intranight photopolarimetric variability study carried out over seven nights after the 2013 April maximum found flux and polarization variations on the nights of April 14, 15, 16, and 19. In addition, the flux shows a minimum variability timescale of Δt = 2.34 ± 0.12 hr, and the polarization degree presents variations of ˜1%-2% on a timescale of Δ t ˜ minutes. Also, a detailed analysis of the intranight data shows a coherence length of the large-scale magnetic field of {l}B≃ 0.3 pc, which is the same order of magnitude as the distance traveled by the relativistic shocks. This result suggests that there is a connection between the intranight polarimetric variations and spatial changes of the magnetic field. Analysis of the complete R-band data along with the historical optical light curve found for this object shows that Mrk 421 varies with a period of 16.26 ± 1.78 yr.

  13. Quasi-Periodic Long-Term Quadrature Light Variability in Early Type Interacting Binary Systems

    Science.gov (United States)

    Peters, Geraldine Joan

    2015-08-01

    Four years of Kepler observations have revealed a class of Algol-type binaries in which the relative brightness of the quadrature light varies from > 1 to trailing hemisphere) variables. Although L/T inequality in eclipsing binaries has been noted from ground-based photometry by several observers since the early 1950s, the regular or quasi-regular switching between maxima is new. Twenty L/T systems have so far been found in the Kepler database and at least three classes of L/T behavior have been identified. In this presentation I will give an update on the L/T phenomenon gleaned from the Kepler and K2 databases. The Kepler and K2 light curves are being analyzed with the 2015 version of the Wilson-Devinney (WD) program that includes major improvements in modeling star spots (i.e. spot motions due to drift and stellar rotation and spot growth and decay). The prototype L/T variable is WX Draconis (A8V + K0IV, P=1.80 d) which shows L/ T light variations of 2-3%. The primary is a delta Scuti star with a dominant pulsation period of 41 m. Preliminary analysis of the WX Dra data suggests that the L/T variability can be fit with either an accretion hot spot on the primary (T = 2.3 Tphot) that jumps in longitude or a magnetic cool spotted region on the secondary. If the latter model is correct the dark region must occupy at least 20% of the surface of the facing hemisphere of the secondary if it is completely black, or a larger area if not completely black. In both hot and cool spot scenarios magnetic fields must play a role in the activity. Support from NASA grants NNX11AC78G and NNX12AE44G and USC’s Women in Science and Engineering (WiSE) program is greatly appreciated.

  14. Multi- and monofractal indices of short-term heart rate variability.

    Science.gov (United States)

    Fischer, R; Akay, M; Castiglioni, P; Di Rienzo, M

    2003-09-01

    Indices of heart rate variability (HRV) based on fractal signal models have recently been shown to possess value as predictors of mortality in specific patient populations. To develop more powerful clinical indices of HRV based on a fractal signal model, the study investigated two HRV indices based on a monofractal signal model called fractional Brownian motion and an index based on a multifractal signal model called multifractional Brownian motion. The performance of the indices was compared with an HRV index in common clinical use. To compare the indices, 18 normal subjects were subjected to postural changes, and the indices were compared on their ability to respond to the resulting autonomic events in HRV recordings. The magnitude of the response to postural change (normalised by the measurement variability) was assessed by analysis of variance and multiple comparison testing. Four HRV indices were investigated for this study: the standard deviation of all normal R-R intervals; an HRV index commonly used in the clinic; detrended fluctuation analysis, an HRV index found to be the most powerful predictor of mortality in a study of patients with depressed left ventricular function; an HRV index developed using the maximum likelihood estimation (MLE) technique for a monofractal signal model; and an HRV index developed for the analysis of multifractional Brownian motion signals. The HRV index based on the MLE technique was found to respond most strongly to the induced postural changes (95% CI). The magnitude of its response (normalised by the measurement variability) was at least 25% greater than any of the other indices tested.

  15. Long-term changes and variability in a transient simulation with a chemistry-climate model employing realistic forcing

    Directory of Open Access Journals (Sweden)

    M. Dameris

    2005-01-01

    Full Text Available A transient simulation with the interactively coupled chemistry-climate model (CCM E39/C has been carried out which covers the 40-year period between 1960 and 1999. Forcing of natural and anthropogenic origin is prescribed where the characteristics are sufficiently well known and the typical timescales are slow compared to synoptic timescale so that the simulated atmospheric chemistry and climate evolve under a 'slowly' varying external forcing. Based on observations, sea surface temperature (SST and ice cover are prescribed. The increase of greenhouse gas and chlorofluorocarbon concentrations, as well as nitrogen oxide emissions are taken into account. The 11-year solar cycle is considered in the calculation of heating rates and photolysis of chemical species. The three major volcanic eruptions during that time (Agung, 1963; El Chichon, 1982; Pinatubo, 1991 are considered. The quasi-biennial oscillation (QBO is forced by linear relaxation, also known as nudging, of the equatorial zonal wind in the lower stratosphere towards observed zonal wind profiles. Beyond a reasonable reproduction of mean parameters and long-term variability characteristics there are many apparent features of episodic similarities between simulation and observation: In the years 1986 and 1988 the Antarctic ozone holes are smaller than in the other years of that decade. In mid-latitudes of the Southern Hemisphere ozone anomalies resemble the corresponding observations, especially in 1985, 1989, 1991/1992, and 1996. In the Northern Hemisphere, the episode between the late 1980s and the first half of the 1990s is dynamically quiet, in particular, no stratospheric warming is found between 1988 and 1993. As observed, volcanic eruptions strongly influence dynamics and chemistry, though only for few years. Obviously, planetary wave activity is strongly driven by the prescribed SST and modulated by the QBO. Preliminary evidence of realistic cause and effect relationships strongly

  16. Functional adjustments of xylem anatomy to climatic variability: insights from long-term Ilex aquifolium tree-ring series.

    Science.gov (United States)

    Rita, Angelo; Cherubini, Paolo; Leonardi, Stefano; Todaro, Luigi; Borghetti, Marco

    2015-08-01

    The present study assessed the effects of climatic conditions on radial growth and functional anatomical traits, including ring width, vessel size, vessel frequency and derived variables, i.e., potential hydraulic conductivity and xylem vulnerability to cavitation in Ilex aquifolium L. trees using long-term tree-ring time series obtained at two climatically contrasting sites, one mesic site in Switzerland (CH) and one drought-prone site in Italy (ITA). Relationships were explored by examining different xylem traits, and point pattern analysis was applied to investigate vessel clustering. We also used generalized additive models and bootstrap correlation functions to describe temperature and precipitation effects. Results indicated modified radial growth and xylem anatomy in trees over the last century; in particular, vessel frequency increased markedly at both sites in recent years, and all xylem traits examined, with the exception of xylem cavitation vulnerability, were higher at the CH mesic compared with the ITA drought site. A significant vessel clustering was observed at the ITA site, which could contribute to an enhanced tolerance to drought-induced embolism. Flat and negative relationships between vessel size and ring width were observed, suggesting carbon was not allocated to radial growth under conditions which favored stem water conduction. Finally, in most cases results indicated that climatic conditions influenced functional anatomical traits more substantially than tree radial growth, suggesting a crucial role of functional xylem anatomy in plant acclimation to future climatic conditions. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  17. Long-term seasonal variability of convection, and aviation hazard risks over Europe

    Science.gov (United States)

    Kahraman, Abdullah; Aslan, Zafer

    2017-04-01

    Deep moist convection (DMC), and related hazardous phenomena, such as turbulence, lightning, wind shear, icing, hail, tornadoes, and downbursts, are particularly important in aviation. They are responsible from a big portion of aircraft accidents related to weather. A climatology of DMC in greater European domain is prepared using ICTP SPEEDY model, including its long-range variability through decades, geographical distribution, and seasonal/diurnal behaviour. Results are compared with thunderstorm observations. DMC-related hazardous weather phenomena affecting aviation are also investigated using proper proxies from model output, in order to assess the risks.

  18. Variable Charge of Ultisols due to Phosphate Application and Incubation Time

    Directory of Open Access Journals (Sweden)

    Muhammad Mahbub

    2010-05-01

    Full Text Available The laboratoryexperiment was conducted to study the effect of phosphate (P application and its incubation time on pHo (pH at thepoint of zero charge and variable charge of ultisols . The determined parameters were pHo and variable surfacecharges.Soil samples were added by 0, 375 and 1,125 mg P kg-1 (or 0, 50 and 150% of the P sorption maximum,respectively. Then, they were incubated for 2, 4, 6 and 8 weeks. The variable surface-charges and pHo weredetermined by using the activity of potential determining ions (H+ and OH- within two salt concentrations as counterions (0.1N and 0.001N CaCl2 through a potentiometric titration method. The results were indicated that the high Psorption and 766 mg P kg-1 in maximum sorption were due to high contents in clay fractions and aluminum as well aslow pH of experimental soil. Application of P and incubation time were able to decrease pHo and to increase negativesurface-charges. Additionals of 375 and 1.125 mg P kg-1 incubated for 8 weeks gave the value of pHo 2.86 and 2.69;as well as the magnitude of negative charges 14.48 and 16.76 cmol(-.kg-1, respectively (both for 0.001N CaCl2.For pH > pHo (the characteristic of variable charge soils, the higher the salt (CaCl2 concentration and pH solution,the higher the negative surface-charge.

  19. Consistency across missions of long time series of global biophysical variables: challenges and lessons learnt

    Science.gov (United States)

    Lacaze, Roselyne; Smets, Bruno; Calvet, Jean-Christophe; Camacho, Fernando; Swinnen, Else; Verger, Aleixandre

    2017-04-01

    The Global component of the Copernicus Land Monitoring Service (CGLS) provides continuously a set of bio-geophysical variables describing the dynamics of vegetation, the energy budget at the continental surface, the water cycle and the cryosphere. Products are generated on a reliable and automatic basis from Earth Observation satellite data, at a frequency ranging from one hour to 10 days. They are accessible free of charge through the GCLS website (http://land.copernicus.eu/global/), associated with documentation describing the physical methodologies, the technical properties of products, and the quality of variables based on the results of validation exercises. The portfolio of the CGLS contains some Essential Climate Variables (ECV) like the Leaf Area Index (LAI), the Fraction of PAR absorbed by the vegetation (FAPAR), the surface albedo, and additional vegetation indices. These products were derived from SPOT/VEGETATION sensor data till December 2013, are currently derived from PROBA-V sensor data, and will be derived in the future from Sentinel-3 data. This talk will show how challenging is the transition between sensors to ensure the sustainability of the production while keeping the consistency of the time series. We will discuss the various sources of differences from input data, the impact of these differences on the biophysical variables and, in turn, on some final users' applications as such those based upon anomalies or assimilation of time series. We will present the mitigation measures taken to reduce as much as possible this impact. We will conclude with the lessons learnt and how this experience will be exploited to manage the transition towards Sentinel-3.

  20. Association Between Short-Term Systolic Blood Pressure Variability and Carotid Intima-Media Thickness in ELSA-Brasil Baseline.

    Science.gov (United States)

    Ribeiro, Adèle H; Lotufo, Paulo A; Fujita, André; Goulart, Alessandra C; Chor, Dora; Mill, José G; Bensenor, Isabela M; Santos, Itamar S

    2017-10-01

    Blood pressure (BP) is associated with carotid intima-media thickness (CIMT), but few studies have explored the association between BP variability and CIMT. We aimed to investigate this association in the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) baseline. We analyzed data from 7,215 participants (56.0% women) without overt cardiovascular disease (CVD) or antihypertensive use. We included 10 BP readings in varying positions during a 6-hour visit. We defined BP variability as the SD of these readings. We performed a 2-step analysis. We first linearly regressed the CIMT values on main and all-order interaction effects of the variables age, sex, body mass index, race, diabetes diagnosis, dyslipidemia diagnosis, family history of premature CVD, smoking status, and ELSA-Brasil site, and calculated the residuals (residual CIMT). We used partial least square path analysis to investigate whether residual CIMT was associated with BP central tendency and BP variability. Systolic BP (SBP) variability was significantly associated with residual CIMT in models including the entire sample (path coefficient [PC]: 0.046; P < 0.001), and in women (PC: 0.046; P = 0.007) but not in men (PC: 0.037; P = 0.09). This loss of significance was probably due to the smaller subsample size, as PCs were not significantly different according to sex. We found a small but significant association between SBP variability and CIMT values. This was additive to the association between SBP central tendency and CIMT values, supporting a role for high short-term SBP variability in atherosclerosis.

  1. Short-term Variability in the Moist Static Energy Budget Inferred from Satellite Observations

    Science.gov (United States)

    Masunaga, H.; L'Ecuyer, T. S.

    2013-12-01

    The thermodynamic variability of tropical atmosphere associated with the development of moist convection is investigated using satellite measurements from a range of platforms and instruments. Based on the analysis strategy devised by Masunaga (2013), the hourly to daily scale variability of moisture and moist static energy (MSE) convergences are derived from a coordination of TRMM, A-Train, and QuikSCAT sensors. Normalized gross moist stability (GMS; Neelin and Held 1987, Raymond et al. 2007) is then estimated as a measure of large-scale dynamics involving moist convection. GMS is found to decline toward zero before convection and gradually increase back to a positive value as the convection decays. To understand the observed behavior of GMS, large-scale vertical motion is derived from the observational constraint on moisture and thermal budget. The main results include: 1) the negative second baroclinic mode (congestus mode) enhances before convection, which is responsible for the initial reduction of GMS, 2) the rapid development of the first baroclinic mode (deep convection mode) follows and yields heavy precipitation, and 3) the second baroclinic mode switches its sign to positive (strartiform mode), resulting in the restoration of GMS, as deep convection diminishes.

  2. Squeezing more information out of time variable gravity data with a temporal decomposition approach

    DEFF Research Database (Denmark)

    Barletta, Valentina Roberta; Bordoni, A.; Aoudia, A.

    2012-01-01

    A measure of the Earth's gravity contains contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished both in time and space. After more than 7years, the GRACE gravity data available now support more elaborate analysis on the time series. We propose...... to design a screening algorithm to identify regions where anomalous gravity variations deserve further investigations. It also allows to raise the amount of information one can obtain exclusively from gravity data, prior and preliminary to any subsequent specifically targeted study. This approach has been...... used to assess the possibility of finding evidence of meaningful geophysical signals different from hydrology over Africa in GRACE data. In this case we conclude that hydrological phenomena are dominant and so time variable gravity data in Africa can be directly used to calibrate hydrological models....

  3. Global robust asymptotic stability of variable-time impulsive BAM neural networks.

    Science.gov (United States)

    Saylı, Mustafa; Yılmaz, Enes

    2014-12-01

    In this paper, the global robust asymptotic stability of the equilibrium point for a more general class of bidirectional associative memory (BAM) neural networks with variable time of impulses is addressed. Unlike most existing studies, the case of non-fix time impulses is focused on in the present study. By means of B-equivalence method, which was introduced in Akhmet (2003, 2005, 2009, 2010), Akhmet and Perestyuk (1990) and Akhmet and Turan (2009), we reduce these networks to a fix time impulsive neural networks system. Sufficient conditions ensuring the existence, uniqueness and global robust asymptotic stability of the equilibrium point are obtained by employing an appropriate Lyapunov function and linear matrix inequality (LMI). Finally, we give one illustrative example to show the effectiveness of the theoretical results. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Spectral variability and reverberation time delays in the Suzaku X-ray spectrum of NGC 4051

    Science.gov (United States)

    Miller, L.; Turner, T. J.; Reeves, J. N.; Lobban, A.; Kraemer, S. B.; Crenshaw, D. M.

    2010-03-01

    Long-exposure Suzaku X-ray observations of the nearby active galaxy NGC 4051 from 2005 and 2008 are analysed, in an attempt to reach a self-consistent understanding of both the spectral variability on long time-scales and the broad-band variability at high time resolution. The techniques of principal components analysis and a maximum likelihood method of power spectrum analysis are used. In common with other type I active galactic nuclei (AGN), the spectral variability is dominated by a varying-normalization power-law component together with a quasi-steady, hard-spectrum offset component that contains Fe K atomic features. NGC 4051 displays a strong excess over a power law at energies of above 20keV, some fraction of which also appears to vary with the power-law continuum. The fast time-scale power spectrum has a shape generally consistent with previous determinations, with the previously known dependence on broad-band photon energy, but in the new data significant differences are found between the low and high flux states of the source, demonstrating that the power spectrum is non-stationary. Frequency-dependent time lags between the hard and soft bands of up to 970 +/- 225s are measured. The existence of the observed time lags excludes the possibility that the hard spectral component originates as reflection from the inner accretion disc. We instead show that the time lags and their frequency and energy dependence may be explained simply by the effects of reverberation in the hard band, caused by reflection from a thick shell of material with maximum lags of about 10000s. If the reflecting material surrounds the AGN, it extends to a distance of about 1.5 × 1014cm, 600 gravitational radii, from the illuminating source and the global covering factor is Cg >~ 0.44, confirming previous suggestions that type I AGN have high covering factors of absorbing and reflecting material. Given the spectral and timing similarities with other type I AGN, we infer that this

  5. Age-Based Methods to Explore Time-Related Variables in Occupational Epidemiology Studies

    Energy Technology Data Exchange (ETDEWEB)

    Janice P. Watkins, Edward L. Frome, Donna L. Cragle

    2005-08-31

    Although age is recognized as the strongest predictor of mortality in chronic disease epidemiology, a calendar-based approach is often employed when evaluating time-related variables. An age-based analysis file, created by determining the value of each time-dependent variable for each age that a cohort member is followed, provides a clear definition of age at exposure and allows development of diverse analytic models. To demonstrate methods, the relationship between cancer mortality and external radiation was analyzed with Poisson regression for 14,095 Oak Ridge National Laboratory workers. Based on previous analysis of this cohort, a model with ten-year lagged cumulative radiation doses partitioned by receipt before (dose-young) or after (dose-old) age 45 was examined. Dose-response estimates were similar to calendar-year-based results with elevated risk for dose-old, but not when film badge readings were weekly before 1957. Complementary results showed increasing risk with older hire ages and earlier birth cohorts, since workers hired after age 45 were born before 1915, and dose-young and dose-old were distributed differently by birth cohorts. Risks were generally higher for smokingrelated than non-smoking-related cancers. It was difficult to single out specific variables associated with elevated cancer mortality because of: (1) birth cohort differences in hire age and mortality experience completeness, and (2) time-period differences in working conditions, dose potential, and exposure assessment. This research demonstrated the utility and versatility of the age-based approach.

  6. Inattention and Reaction Time Variability Are Linked to Ventromedial Prefrontal Volume in Adolescents.

    Science.gov (United States)

    Albaugh, Matthew D; Orr, Catherine; Chaarani, Bader; Althoff, Robert R; Allgaier, Nicholas; D'Alberto, Nicholas; Hudson, Kelsey; Mackey, Scott; Spechler, Philip A; Banaschewski, Tobias; Brühl, Rüdiger; Bokde, Arun L W; Bromberg, Uli; Büchel, Christian; Cattrell, Anna; Conrod, Patricia J; Desrivières, Sylvane; Flor, Herta; Frouin, Vincent; Gallinat, Jürgen; Goodman, Robert; Gowland, Penny; Grimmer, Yvonne; Heinz, Andreas; Kappel, Viola; Martinot, Jean-Luc; Paillère Martinot, Marie-Laure; Nees, Frauke; Orfanos, Dimitri Papadopoulos; Penttila, Jani; Poustka, Luise; Paus, Tomáš; Smolka, Michael N; Struve, Maren; Walter, Henrik; Whelan, Robert; Schumann, Gunter; Garavan, Hugh; Potter, Alexandra S

    2017-11-01

    Neuroimaging studies of attention-deficit/hyperactivity disorder (ADHD) have most commonly reported volumetric abnormalities in the basal ganglia, cerebellum, and prefrontal cortices. Few studies have examined the relationship between ADHD symptomatology and brain structure in population-based samples. We investigated the relationship between dimensional measures of ADHD symptomatology, brain structure, and reaction time variability-an index of lapses in attention. We also tested for associations between brain structural correlates of ADHD symptomatology and maps of dopaminergic gene expression. Psychopathology and imaging data were available for 1538 youths. Parent ratings of ADHD symptoms were obtained using the Development and Well-Being Assessment and the Strengths and Difficulties Questionnaire (SDQ). Self-reports of ADHD symptoms were assessed using the youth version of the SDQ. Reaction time variability was available in a subset of participants. For each measure, whole-brain voxelwise regressions with gray matter volume were calculated. Parent ratings of ADHD symptoms (Development and Well-Being Assessment and SDQ), adolescent self-reports of ADHD symptoms on the SDQ, and reaction time variability were each negatively associated with gray matter volume in an overlapping region of the ventromedial prefrontal cortex. Maps of DRD1 and DRD2 gene expression were associated with brain structural correlates of ADHD symptomatology. This is the first study to reveal relationships between ventromedial prefrontal cortex structure and multi-informant measures of ADHD symptoms in a large population-based sample of adolescents. Our results indicate that ventromedial prefrontal cortex structure is a biomarker for ADHD symptomatology. These findings extend previous research implicating the default mode network and dopaminergic dysfunction in ADHD. Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

  7. Short-term practice effects and variability in cognitive testing in a healthy elderly population

    DEFF Research Database (Denmark)

    Krenk, L.; Rasmussen, L.S.; Siersma, V.

    2012-01-01

    and variability in test performance. The aim of this study was to collect cognitive test results with repeated testing in an elderly healthy population. METHODS: 161 healthy controls =60years were included. Cognitive testing was performed upon entry into the study, at 1week and 3months. Practice effect......BACKGROUND: Cognitive decline in the elderly is a subject of intense focus. However, there is a lack of consensus regarding definition of significant decline in connection with repeated testing and the interpretation of cognitive tests results must take into account the practice effect...... was evaluated on 7 neuropsychological measures and reference values of clinically important changes were calculated according to z-scores above 1.96. RESULTS: Test scores improved significantly (p...

  8. Exploring the dynamics of balance data - movement variability in terms of drift and diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Gottschall, Julia [Institute of Physics, University of Oldenburg, D-26111 Oldenburg (Germany)], E-mail: julia.gottschall@uni-oldenburg.de; Peinke, Joachim [Institute of Physics, University of Oldenburg, D-26111 Oldenburg (Germany)], E-mail: peinke@uni-oldenburg.de; Lippens, Volker [Department of Human Movement, University of Hamburg, Moller Street 10, D-20148 Hamburg (Germany)], E-mail: vlippens@uni-hamburg.de; Nagel, Volker [Department of Human Movement, University of Hamburg, Moller Street 10, D-20148 Hamburg (Germany)

    2009-02-23

    We introduce a method to analyze postural control on a balance board by reconstructing the underlying dynamics in terms of a Langevin model. Drift and diffusion coefficients are directly estimated from the data and fitted by a suitable parametrization. The governing parameters are utilized to evaluate balance performance and the impact of supra-postural tasks on it. We show that the proposed method of analysis gives not only self-consistent results but also provides a plausible model for the reconstruction of balance dynamics.

  9. Discrete-time variable structure system synthesis for plants with nonminimum phase zeros

    Directory of Open Access Journals (Sweden)

    Iskrenović-Momčilović Olivera I.

    2014-01-01

    Full Text Available This paper analyzes a discrete variable structure system for control n-th order plants with nonminimum phase zeros in the input-output transfer function. The problem is solved by using the technique of stable system center. The first is a discrete mathematical model of the system in the normal canonical form for a given system. Then the synthesis of state generator and discrete 'time controller using the center of a stable system. The theoretical results are demonstrated in a numerical example.

  10. Variable Penalty Dynamic Time Warping Code for Aligning Mass Spectrometry Chromatograms in R

    Directory of Open Access Journals (Sweden)

    David Clifford

    2012-04-01

    Full Text Available Alignment of mass spectrometry (MS chromatograms is sometimes required prior to sample comparison and data analysis. Without alignment, direct comparison of chromatograms would lead to inaccurate results. We demonstrate a new method for computing a high quality alignment of full length MS chromatograms using variable penalty dynamic time warping. This method aligns signals using local linear shifts without excessive warping that can alter the shape (and area of chromatogram peaks. The software is available as the R package VPdtw on the Comprehensive R Archive Network and we highlight how one can use this package here. =

  11. Smart Device for the Determination of Heart Rate Variability in Real Time

    Directory of Open Access Journals (Sweden)

    David Naranjo-Hernández

    2017-01-01

    Full Text Available This work presents a first approach to the design, development, and implementation of a smart device for the real-time measurement and detection of alterations in heart rate variability (HRV. The smart device follows a modular design scheme, which consists of an electrocardiogram (ECG signal acquisition module, a processing module and a wireless communications module. From five-minute ECG signals, the processing module algorithms perform a spectral estimation of the HRV. The experimental results demonstrate the viability of the smart device and the proposed processing algorithms.

  12. Existential Meaning Among First-Time Full-Term and Preterm Mothers

    DEFF Research Database (Denmark)

    Prinds, Christina; Hvidtjørn, Dorte; Mogensen, Ole

    2014-01-01

    mothers who gave birth at full term and those who gave birth preterm. All first-time mothers who gave birth in Denmark in 2010 before the 32nd week of pregnancy and twice that number of full-term mothers (randomly sampled) were invited to participate in a national cross-sectional survey. Five core items...... meaning intensified to the same degree among mothers of full-term and preterm infants, with no statistically significant differences in terms of age, marital status, educational level, or birth method. Danish first-time mothers' attitudes related to existential meaning measured in 5 core items were...... intensified and almost similar, regardless of whether they gave birth full-term or preterm....

  13. Temporal and spatial variability in the Guadalquivir estuary: a challenge for real-time telemetry

    Science.gov (United States)

    Navarro, Gabriel; Gutiérrez, Francisco Javier; Díez-Minguito, Manuel; Losada, Miguel Angel; Ruiz, Javier

    2011-06-01

    Meteorological, hydrological, and hydrodynamic data for 3 years (2008-2010) have been used to document and explain the temporal and spatial variability of the physical-biogeochemical interactions in the Guadalquivir River Estuary. A real-time, remote monitoring network has been deployed along the course of the river between its mouth and Seville to study a broad range of temporal scales (semidiurnal, diurnal, fortnightly, and seasonal). This network consists of eight hydrological monitoring stations capable of measuring temperature, conductivity, dissolved oxygen, turbidity, and chlorophyll fluorescence at four depths. In addition, six stations have been deployed to study hydrodynamics, obtaining 20-cell water column current profiles, and there is a meteorological station at the river mouth providing data for understanding atmospheric interactions. Completing this data-gathering network, there are several moorings (tide gauges, current/wave sensors, and a thermistor chain) deployed in the estuary and river mouth. Various sources of physical forcing, such as wind, tide-associated currents, and river discharge, are responsible for the particular temporal and spatial patterns of turbidity and salinity found in the estuary. These variables force the distribution of biogeochemical variables, such as dissolved oxygen and chlorophyll fluorescence. In particular, episodes of elevated turbidity (when suspended particle matter concentration >3,000 mg/l) have been detected by the network, together with episodes of declining values of salinity and dissolved oxygen. All these patterns are related to river discharge and tidal dynamics (spring/neap and high/low tide).

  14. Real-time transmission of digital video using variable-length coding

    Science.gov (United States)

    Bizon, Thomas P.; Shalkhauser, Mary JO; Whyte, Wayne A., Jr.

    1993-01-01

    Huffman coding is a variable-length lossless compression technique where data with a high probability of occurrence is represented with short codewords, while 'not-so-likely' data is assigned longer codewords. Compression is achieved when the high-probability levels occur so frequently that their benefit outweighs any penalty paid when a less likely input occurs. One instance where Huffman coding is extremely effective occurs when data is highly predictable and differential coding can be applied (as with a digital video signal). For that reason, it is desirable to apply this compression technique to digital video transmission; however, special care must be taken in order to implement a communication protocol utilizing Huffman coding. This paper addresses several of the issues relating to the real-time transmission of Huffman-coded digital video over a constant-rate serial channel. Topics discussed include data rate conversion (from variable to a fixed rate), efficient data buffering, channel coding, recovery from communication errors, decoder synchronization, and decoder architectures. A description of the hardware developed to execute Huffman coding and serial transmission is also included. Although this paper focuses on matters relating to Huffman-coded digital video, the techniques discussed can easily be generalized for a variety of applications which require transmission of variable-length data.

  15. Analysis of agility, reaction time and balance variables at badminton players aged 9-14 years

    Directory of Open Access Journals (Sweden)

    Seydi Ahmet Ağaoğlu

    2017-12-01

    Full Text Available Aim: The aim of this study was investigated agility, static and dynamic balance and reaction time variables of badminton players aged between 9-14 and relate with among variables. Material and Methods: In Samsun, 19 males (sport age, 3.42±1.64 years and 12 females (3.00±1.28 years active badminton players were voluntarily participated in who are in 9-14 ages range. Agility was measured by “T” test, CSMI-Tecnobody Pk-252 isokinetic balance system measuring instrument was used to test static balance and dynamic balance and Mozart Lafayette reaction measuring instrument was used to test visual and auditory reaction times of players. Spearman correlation analysis was applied so as to correlation analysis. The level of significance was taken as p<0.05. Results: For female athletes, a positive relation was determined between the agility and the perimeter (mm used (r=0.727; p<0.01 through the static balance measure double foot and eyes are open. For male athletes, a positive relation was determined between the visual reaction time and the perimeter (mm used (r=0.725; p<0.01 through the static balance measure dominant foot and eyes are open. For male and female athletes were not found any correlation between reaction time and dynamic balance. Conclusion: It was determined that audio (ears and visual (eyes reaction time was effective on balance. While badminton players are closed eyes, audio sensors are more influence on balance test through measure dominant foot.

  16. Damage Detection Based on Cross-Term Extraction from Bilinear Time-Frequency Distributions

    Directory of Open Access Journals (Sweden)

    Ma Yuchao

    2014-01-01

    Full Text Available Abundant damage information is implicated in the bilinear time-frequency distribution of structural dynamic signals, which could provide effective support for structural damage identification. Signal time-frequency analysis methods are reviewed, and the characters of linear time-frequency distribution and bilinear time-frequency distribution typically represented by the Wigner-Ville distribution are compared. The existence of the cross-term and its application in structural damage detection are demonstrated. A method of extracting the dominant term is proposed, which combines the short-time Fourier spectrum and Wigner-Ville distribution; then two-dimensional time-frequency transformation matrix is constructed and the complete cross-term is extracted finally. The distribution character of which could be applied to the structural damage identification. Through theoretical analysis, model experiment and numerical simulation of the girder structure, the change rate of cross-term amplitude is validated to identify the damage location and degree. The effectiveness of the cross-term of bilinear time-frequency distribution for damage detection is confirmed and the analytical method of damage identification used in structural engineering is available.

  17. Effects of time-variable exposure regimes of the insecticide chlorpyrifos on freshwater invertebrate communities in microcosms

    NARCIS (Netherlands)

    Zafar, M.I.; Wijngaarden, van R.; Roessink, I.; Brink, van den P.J.

    2011-01-01

    The present study compared the effects of different time-variable exposure regimes having the same time-weighted average (TWA) concentration of the organophosphate insecticide chlorpyrifos on freshwater invertebrate communities to enable extrapolation of effects across exposure regimes. The

  18. Investigation of the Aggression Tendency Observed in University Students in Terms of Different Variables

    Directory of Open Access Journals (Sweden)

    Fatih CAMADAN

    2017-08-01

    Full Text Available This study aims to find out whether or not the observed level of aggression in university students varies according to different demographic variables. These variables include grade level, gender, perceived parenting styles, the place where students lived before the university and monthly economic income level of family. The study group consists of the students studying at seven state universities located in different regions of Turkey: Cumhuriyet University [Central Anatolia Region], Çanakkale Onsekiz Mart University [Marmara Region], Çukurova University [Mediterranean Region], Dicle University [South Eastern Anatolia Region], Dokuz Eylül University [Aegean Region], İnönü University [Eastern Anatolia Region] and Ondokuz Mayıs University [Black Sea Region]. The Buss-Perry Aggression Questionnaire was used to collect data. In order to determine the validity of the scale for this research, ‘Deterministic Finite Automat (DFA’ was recalculated again. Also, Cronbach’s alpha internal consistency coefficient was recalculated again for the reliability. The obtained results revealed that the factor structures in the original scale are validated for this study and the measurement instrument was found to be reliable for this research. In addition, the Personal Information Form was prepared and given to the participants by the researchers in order to obtain different demographics about them. Various statistical analyses were performed with the data obtained through the form and scale. As a result of the analyses, the aggression level of male students was found to be significantly higher than the females. The level of aggression of the students who perceive their parents’ attitudes as authoritarian was found to be significantly higher than those who are exposed to protective and democratic parenting attitudes. In addition, the students who perceive their fathers as indifferent yielded higher aggression scores than those perceiving their

  19. Spatial variability and long-term analysis of groundwater quality of Faisalabad industrial zone

    Science.gov (United States)

    Nasir, Muhammad Salman; Nasir, Abdul; Rashid, Haroon; Shah, Syed Hamid Hussain

    2017-10-01

    Water is the basic necessity of life and is essential for healthy society. In this study, groundwater quality analysis was carried out for the industrial zone of Faisalabad city. Sixty samples of groundwater were collected from the study area. The quality maps of deliberately analyzed results were prepared in GIS. The collected samples were analyzed for chemical parameters and heavy metals, such as total hardness, alkalinity, cadmium, arsenic, nickel, lead, and fluoride, and then, the results were compared with the WHO guidelines. The values of these results were represented by a mapping of quality parameters using the ArcView GIS v9.3, and IDW was used for raster interpolation. The long-term analysis of these parameters has been carried out using the `R Statistical' software. It was concluded that water is partially not fit for drinking, and direct use of this groundwater may cause health issues.

  20. Series Expansion for Direct and Inverse Solutions of Meridian in Terms of Different Latitude Variables

    Directory of Open Access Journals (Sweden)

    GUO Jiachun

    2016-05-01

    Full Text Available Formulas for direct solutions of meridian written by the reduced and geocentric latitudes respectively were derived by series expansion. Meanwhile, according to Lagrange inversion theorem, formulas for inverse solutions of the issue were also expressed in terms of the same latitudes. These two formulas were structurally consistent with that expressed by geodetic latitude ones. In these sets of formulas, internal connection between meridian and three different types of latitude were realized. Analysis and numerical calculation showed that the direct and inverse meridional solution with reduced latitude was of higher precision than that with geodetic latitude, and furthermore, there had a unified theory between meridian theory and classical geodetic problems expressed by reduced latitude.

  1. [Chemical variability of essential oils in peels collected in different time from Citrus reticulata 'Ponkan'].

    Science.gov (United States)

    Wang, Jian; Chen, Hong-ping; Liu, You-ping; Wei, Zheng

    2013-12-01

    To study the chemical variation of essential oils in peels collected from Citrus reticulata' Ponkan' in different time. The volatile oils were extracted by steam distillation and analyzed by GC-MS. The oil components were identified by their mass spectra and Kovats retention indices (RIs) and quantified by the area normalization method. A total of 68 compounds were identified in 6 samples harvested in different time, and the total contents of identified compounds in each sample were from 94.27% to 97.12%. The highest content compounds were d-limonene, gamma-terpinene and linalool representing 56.862%-67.728%, 9.298%-11.081% and 4.792%-7.893%, respectively. There was little difference in the chemical components between different samples, but a great variation in quantitation between the former 2 samples and the latter 4 samples. The chemical variability of essential oils from 6 Citrus reticulata 'Ponkan' peel samples presents a regularity.

  2. A hybrid disturbance rejection control solution for variable valve timing system of gasoline engines.

    Science.gov (United States)

    Xie, Hui; Song, Kang; He, Yu

    2014-07-01

    A novel solution for electro-hydraulic variable valve timing (VVT) system of gasoline engines is proposed, based on the concept of active disturbance rejection control (ADRC). Disturbances, such as oil pressure and engine speed variations, are all estimated and mitigated in real-time. A feed-forward controller was added to enhance the performance of the system based on a simple and static first principle model, forming a hybrid disturbance rejection control (HDRC) strategy. HDRC was validated by experimentation and compared with an existing manually tuned proportional-integral (PI) controller. The results show that HDRC provided a faster response and better tolerance of engine speed and oil pressure variations. © 2013 ISA Published by ISA All rights reserved.

  3. The effect of time trial cycling position on physiological and aerodynamic variables.

    Science.gov (United States)

    Fintelman, D M; Sterling, M; Hemida, H; Li, F-X

    2015-01-01

    To reduce aerodynamic resistance cyclists lower their torso angle, concurrently reducing Peak Power Output (PPO). However, realistic torso angle changes in the range used by time trial cyclists have not yet been examined. Therefore the aim of this study was to investigate the effect of torso angle on physiological parameters and frontal area in different commonly used time trial positions. Nineteen well-trained male cyclists performed incremental tests on a cycle ergometer at five different torso angles: their preferred torso angle and at 0, 8, 16 and 24°. Oxygen uptake, carbon dioxide expiration, minute ventilation, gross efficiency, PPO, heart rate, cadence and frontal area were recorded. The frontal area provides an estimate of the aerodynamic drag. Overall, results showed that lower torso angles attenuated performance. Maximal values of all variables, attained in the incremental test, decreased with lower torso angles (P aerodynamic drag and physiological functioning.

  4. Examining the Level of Internet Addiction of Adolescents in Terms of Various Variables

    Science.gov (United States)

    Ayaz, Mehmet Fatih; Karatas, Kasim

    2016-01-01

    The aim of the research is to examine the internet addiction of adolescents according to their genders, the type of their high-schools and class level, the time interval that they use internet most widely, their internet usage duration and usage purpose. For that, it is studied with 335 high-school students in Elazig city of Turkey in 2015. The…

  5. High resource of azimuthal entanglement in terms of Cartesian variables of noncollinear biphotons

    Science.gov (United States)

    Fedorov, M. V.

    2018-01-01

    Single-particle and coincidence distributions of photons are analyzed for the noncollinear frequency-degenerate type-I regime of spontaneous parametric down-conversion. Noncollinearity itself is shown to provide a new mechanism of strong broadening of the single-particle distributions in Cartesian components of the photon's transverse wave vectors. Related to this, the degree of entanglement appears to be very high in agreement with the earlier performed analysis in the formalism of spherical angles characterizing photon's wave vectors [Phys. Rev. A 93, 033830 (2016), 10.1103/PhysRevA.93.033830]. In Cartesian variables, very broad curves of single-particle distributions are found to have a rather unusual and peculiar shape. In theory, the key reason for these effects is the reduction of the total wave function of two photons over one of two orthogonal degrees of freedom. In the suggested and discussed experimental schemes this means that all photons of the emission cone have to be taken into account rather than only photons propagating in one given plane which is a common practice in many experiments.

  6. Variability in the intraspecific response of Pinus ponderosa seedlings subjected to long-term exposure to elevated CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Houpis, J.L.J.; Anschel, D.J. [Lawrence Livermore National Lab., CA (United States). Health and Ecological Assessment Div.; Pushnik, J.C. [California State Univ., Chico, CA (United States). Dept. of Biological Sciences; Anderson, P.D. [Forest Service, Rhinelander, WI (United States)

    1995-01-01

    The authors are investigating the effects of elevated CO{sub 2} and intraspecific variability on Pinus ponderosa. To analyze intraspecific variability, they included seedling source (family) as an additional treatment, using a split-plot experimental design. The three elevated CO{sub 2} treatments were ambient (approx. 350 ppm CO{sub 2}), ambient + 175 ppm CO{sub 2} and ambient +350 ppm CO{sub 2}. Their study uses the source/sink control framework at several key integrating steps, incorporating the long-term effects of elevated CO{sub 2} (insuring sufficient time for the expression of any long-term physiological and biochemical acclimation to occur) and genetics (using multiple species and multiple known genetic sources) in an attempt to ascertain the extent of overall regulation contributed by selected independent regulatory process at the physiological, biochemical and structural level. In order to assess intraspecific variability, this paper reports on the integration of measurements of photosynthesis, chlorophyll fluorescence, pigmentation, RuBPCase, SPSase to quantify the effects of elevated CO{sub 2} on the growth response of various families of the same species.

  7. Short-term heart rate variability in dogs with sick sinus syndrome or chronic mitral valve disease as compared to healthy controls.

    Science.gov (United States)

    Bogucki, Sz; Noszczyk-Nowak, A

    2017-03-28

    Heart rate variability is an established risk factor for mortality in both healthy dogs and animals with heart failure. The aim of this study was to compare short-term heart rate variability (ST-HRV) parameters from 60-min electrocardiograms in dogs with sick sinus syndrome (SSS, n=20) or chronic mitral valve disease (CMVD, n=20) and healthy controls (n=50), and to verify the clinical application of ST-HRV analysis. The study groups differed significantly in terms of both time - and frequency- domain ST-HRV parameters. In the case of dogs with SSS and healthy controls, particularly evident differences pertained to HRV parameters linked directly to the variability of R-R intervals. Lower values of standard deviation of all R-R intervals (SDNN), standard deviation of the averaged R-R intervals for all 5-min segments (SDANN), mean of the standard deviations of all R-R intervals for all 5-min segments (SDNNI) and percentage of successive R-R intervals >50 ms (pNN50) corresponded to a decrease in parasympathetic regulation of heart rate in dogs with CMVD. These findings imply that ST-HRV may be useful for the identification of dogs with SSS and for detection of dysautonomia in animals with CMVD.

  8. Implementation of a Model Output Statistics based on meteorological variable screening for short‐term wind power forecast

    DEFF Research Database (Denmark)

    Ranaboldo, Matteo; Giebel, Gregor; Codina, Bernat

    2013-01-01

    A combination of physical and statistical treatments to post‐process numerical weather predictions (NWP) outputs is needed for successful short‐term wind power forecasts. One of the most promising and effective approaches for statistical treatment is the Model Output Statistics (MOS) technique....... In this study, a MOS based on multiple linear regression is proposed: the model screens the most relevant NWP forecast variables and selects the best predictors to fit a regression equation that minimizes the forecast errors, utilizing wind farm power output measurements as input. The performance of the method...... is evaluated in two wind farms, located in different topographical areas and with different NWP grid spacing. Because of the high seasonal variability of NWP forecasts, it was considered appropriate to implement monthly stratified MOS. In both wind farms, the first predictors were always wind speeds (at...

  9. Time-Dependent Tree-Structured Survival Analysis with Unbiased Variable Selection through Permutation Tests

    Science.gov (United States)

    Wallace, M. L.

    2014-01-01

    Incorporating time-dependent covariates into tree-structured survival analysis (TSSA) may result in more accurate prognostic models than if only baseline values are used. Available time-dependent TSSA methods exhaustively test every binary split on every covariate; however, this approach may result in selection bias towards covariates with more observed values. We present a method that uses unbiased significance levels from newly proposed permutation tests to select the time-dependent or baseline covariate with the strongest relationship with the survival outcome. The specific splitting value is identified using only the selected covariate. Simulation results show that the proposed time-dependent TSSA method produces tree models of equal or greater accuracy as compared to baseline TSSA models, even with high censoring rates and large within-subject variability in the time-dependent covariate. To illustrate, the proposed method is applied to data from a cohort of bipolar youth to identify subgroups at risk for self-injurious behavior. PMID:25043382

  10. Trends and variability in streamflow and snowmelt runoff timing in the southern Tianshan Mountains

    Science.gov (United States)

    Shen, Yan-Jun; Shen, Yanjun; Fink, Manfred; Kralisch, Sven; Chen, Yaning; Brenning, Alexander

    2018-02-01

    Streamflow and snowmelt runoff timing of mountain rivers are susceptible to climate change. Trends and variability in streamflow and snowmelt runoff timing in four mountain basins in the southern Tianshan were analyzed in this study. Streamflow trends were detected by Mann-Kendall tests and changes in snowmelt runoff timing were analyzed based on the winter/spring snowmelt runoff center time (WSCT). Pearson's correlation coefficient was further calculated to analyze the relationships between climate variables, streamflow and WSCT. Annual streamflow increased significantly in past decades in the southern Tianshan, especially in spring and winter months. However, the relations between streamflow and temperature/precipitation depend on the different streamflow generation processes. Annual precipitation plays a vital role in controlling recharge in the Toxkon basin, while the Kaidu and Huangshuigou basins are governed by both precipitation and temperature. Seasonally, temperature has a strong effect on streamflow in autumn and winter, while summer streamflow appears more sensitive to changes in precipitation. However, temperature is the dominant factor for streamflow in the glacierized Kunmalik basin at annual and seasonal scales. An uptrend in streamflow begins in the 1990s at both annual and seasonal scales, which is generally consistent with temperature and precipitation fluctuations. Average WSCT dates in the Kaidu and Huangshuigou basins are earlier than in the Toxkon and Kunmalik basins, and shifted towards earlier dates since the mid-1980s in all the basins. It is plausible that WSCT dates are more sensitive to warmer temperature in spring period compared to precipitation, except for the Huangshuigou basin. Taken together, these findings are useful for applications in flood risk regulation, future hydropower projects and integrated water resources management.

  11. Earth time variable gravity from a spaceborne cold atom gravity gradiometer

    Science.gov (United States)

    Luthcke, S. B.; Rowlands, D. D.; Saif, B.; Black, A.

    2013-12-01

    A gradiometer sensor based on the light-pulse atom (LPA) interferometry provides a technological path forward to significantly improve Earth time variable gravity observations from space. We present the simulated performance of a single -axis space-based Cold Atom Gravity Gradiometer (CAGG) instrument based on the LPA measurement approach. We simulate the instrument on a nadir pointing, 3-axis stabilized satellite in multiple orbit configurations. In our analysis, the CAGG is chosen to have an interrogation time of T = 15s and baseline L=5 m, with a sensor measurement period of 30 s. We use a measurement noise spectrum of the sensor, which is essentially flat over at least the relevant frequency range for Earth applications (1mHz to 0.1 Hz) with a magnitude of 5.4×10-9 E^2/Hz or ~10^-5 E RMS in time series. This sensor noise spectrum was computed from a Monte Carlo sensor simulation analysis with the following error sources included in the model: platform angle jitter, 5 arcsec platform attitude misalignment, intrinsic random sensor phase noise, Raman beam static misalignment of 5 μrad, atom position fluctuations of 10 μm, and atomic mean velocity fluctuations of 1 μm/s. We further include the platform attitude error contribution in rotating the SBF gradient observations to an Earth Centered Fixed Frame for gravity field estimation. The gravity gradient is isolated from the centrifugal forces using a sensor unique rotational correction. We present the performance of the space-based CAGG instrument in recovering Earth time variable gravity. We explore the accuracy, and spatial and temporal resolution of surface mass change observations from several space-based implementations of the CAGG instrument, including various orbit configurations and mult-satellite/multi-orbit configurations.

  12. Identification of an unknown source term for a time fractional fourth-order parabolic equation

    Directory of Open Access Journals (Sweden)

    Sara Aziz

    2016-11-01

    Full Text Available In this article, we considered two inverse source problems for fourth-order parabolic differential equation with fractional derivative in time. Determination of a space dependent source term from the data given at some time t=T is considered in one problem while other addresses the recovery of a time dependent source term from the integral type over-determination condition. Existence and uniqueness of the solution of both inverse source problems are proved. The stability results for the inverse problems are presented.

  13. Examining the effect of Capoeira on socialization in terms of some variables

    Directory of Open Access Journals (Sweden)

    Serkan HACICAFEROĞLU

    2017-12-01

    Full Text Available Aim: This study was conducted in order to determine the level of contribution of capoeira to the social integration of athletes according to some demographic variables. Materials and Methods: Among the survey model a sample of the research using the general survey model was composed of 135 athletes, 86 of which were male and 49 of which were female. In order to collect the necessary data in the research, the ‘Social İntegration Scale’ was used in the sport which was prepared by Yılmaz, Karlı and Yetim, (2006 and consisted of seven sub-dimensions. Kolmogorov Smirnov test was used for the normal distribution of data in the analysis of data in the study. It was observed that the data did not follow a normal distribution in response to the outcome and Mann-Whitney U Test and Kruskal-Wallis H test were used in our study. Bonferroni correction from multiple comparison tests was used in the binary comparison of groups with significant differences as a result of Kruskal-Wallis H test analysis. Results: The results of the study show that the athletes in the sample have positive scores in all the subscales of social skills perceptions with their participation in capoeira sport. There was no statistically significant effect of capoeira on socializing between male and female athletes. At ages 27 and over, it was detected that the socializing effect of athletes was higher than that of other age groups. Conclusion: According to the findings, athletes who participated in the capoeira sports branch which has many parts of the music, rhythm and sports movements had high scores of social skills perceptions in all sub-dimensions. It can be said that the level of socialization of individuals who have Capoeira is high. In this case, it shows that sports activities affect the level of social integration of the individuals.

  14. Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

    DEFF Research Database (Denmark)

    Compton, Kathleen; Bennett, Richard A.; Hreinsdóttir, Sigrún

    2017-01-01

    -based observations of loading and melting within the 1 math formula confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap......As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak......-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps...

  15. Predictor variables for half marathon race time in recreational female runners

    Directory of Open Access Journals (Sweden)

    Beat Knechtle

    2011-01-01

    Full Text Available INTRODUCTION: The relationship between skin-fold thickness and running performance has been investigated from 100 m to the marathon distance, except the half marathon distance. OBJECTIVE: To investigate whether anthropometry characteristics or training practices were related to race time in 42 recreational female half marathoners to determine the predictor variables of half-marathon race time and to inform future novice female half marathoners. METHODS: Observational field study at the 'Half Marathon Basel' in Switzerland. RESULTS: In the bivariate analysis, body mass (r = 0.60, body mass index (r = 0.48, body fat (r = 0.56, skin-fold at pectoral (r = 0.61, mid-axilla (r = 0.69, triceps (r = 0.49, subscapular (r = 0.61, abdominal (r = 0.59, suprailiac (r = 0.55 medial calf (r = 0.53 site, and speed of the training sessions (r = -0.68 correlated to race time. Mid-axilla skin-fold (p = 0.04 and speed of the training sessions (p = 0.0001 remained significant after multi-variate analysis. Race time in a half marathon might be predicted by the following equation (r² = 0.71: Race time (min = 166.7 + 1.7x (mid-axilla skin-fold, mm - 6.4x (speed in training, km/h. Running speed during training was related to skinfold thickness at mid-axilla (r = -0.31, subscapular (r = -0.38, abdominal (r = -0.44, suprailiacal (r = -0.41, the sum of eight skin-folds (r = -0.36 and percent body fat (r = -0.31. CONCLUSION: Anthropometric and training variables were related to half-marathon race time in recreational female runners. Skin-fold thicknesses at various upper body locations were related to training intensity. High running speed in training appears to be important for fast half-marathon race times and may reduce upper body skin-fold thicknesses in recreational female half marathoners.

  16. Predictor variables for half marathon race time in recreational female runners.

    Science.gov (United States)

    Knechtle, Beat; Knechtle, Patrizia; Barandun, Ursula; Rosemann, Thomas; Lepers, Romuald

    2011-01-01

    The relationship between skin-fold thickness and running performance has been investigated from 100 m to the marathon distance, except the half marathon distance. To investigate whether anthropometry characteristics or training practices were related to race time in 42 recreational female half marathoners to determine the predictor variables of half-marathon race time and to inform future novice female half marathoners. Observational field study at the 'Half Marathon Basel' in Switzerland. In the bivariate analysis, body mass (r = 0.60), body mass index (r = 0.48), body fat (r = 0.56), skin-fold at pectoral (r = 0.61), mid-axilla (r = 0.69), triceps (r = 0.49), subscapular (r = 0.61), abdominal (r = 0.59), suprailiac (r = 0.55) medial calf (r = 0.53) site, and speed of the training sessions (r = -0.68) correlated to race time. Mid-axilla skin-fold (p = 0.04) and speed of the training sessions (p = 0.0001) remained significant after multi-variate analysis. Race time in a half marathon might be predicted by the following equation (r² = 0.71): Race time (min) = 166.7 + 1.7x (mid-axilla skin-fold, mm) - 6.4x (speed in training, km/h). Running speed during training was related to skinfold thickness at mid-axilla (r = -0.31), subscapular (r = -0.38), abdominal (r = -0.44), suprailiacal (r = -0.41), the sum of eight skin-folds (r = -0.36) and percent body fat (r = -0.31). Anthropometric and training variables were related to half-marathon race time in recreational female runners. Skin-fold thicknesses at various upper body locations were related to training intensity. High running speed in training appears to be important for fast half-marathon race times and may reduce upper body skin-fold thicknesses in recreational female half marathoners.

  17. Non-24-Hour Disorder in Blind Individuals Revisited: Variability and the Influence of Environmental Time Cues.

    Science.gov (United States)

    Emens, Jonathan S; Laurie, Amber L; Songer, Jeannie B; Lewy, Alfred J

    2013-07-01

    To assess the interindividual and intraindividual variability in the circadian rhythms of blind individuals with non-24-h disorder and to quantify the influence of environmental time cues in blind subjects lacking entrainment (non-24-h individuals or N-24s). An observational study of 21 N-24s (11 females and 10 males, age 9-78 years) who kept a sleep/wake schedule of their choosing. Circadian phase was determined using the melatonin onset (MO) from plasma or saliva samples that were collected every 2 weeks. Melatonin concentrations were measured by radioimmunoassay. A total of 469 MO assessments were conducted over 5,536 days of study. The rate of drift of circadian phase was calculated using a series of MOs (total number of hours the MO drifted divided by the total number of days studied). Stability of the rest/activity rhythm was calculated using chi-squared periodogram analysis of wrist actigraphy data in 19 subjects. Academic medical center. Paid volunteers. N/A. Subjects lacked entrainment such that circadian phase drifted an average (± standard deviation) of 0.39 ± 0.29 h later per day; however, there was notable intersubject and intrasubject variability in the rate of drift including relative coordination and periods of transient entrainment during which there was little to no drift in the circadian phase. A regular, reproducible, and significant oscillation in the rate of drift was detected in 14 of the 21 subjects. A significant non-24-h rest/activity rhythm was detected in 18 of 19 subjects. There was a strong correlation (r = 0.793, P = 0.0001) between the non-24-h rest/activity rhythm and the rate of drift of the circadian phase. Most N-24s are influenced by unidentified environmental time cues and the non-entrained biological clock in such N-24s is reflected in their rest/activity rhythms. These findings may have diagnostic and treatment implications: this disorder might be diagnosed with actigraphy alone, relative coordination and transient

  18. Water quality of the Neuse River, North Carolina : variability, pollution loads, and long-term trends

    Science.gov (United States)

    Harned, Douglas A.

    1980-01-01

    A water-quality study of the Neuse River, N.C., based on data collected during 1956-77 at the U.S. Geological Survey stations at Clayton and Kinston, employs statistical trend analysis techniques that provide a framework for river quality assessment. Overall, water-quality of the Neuse River is satisfactory for most uses. At Clayton, fecal coliform bacteria and nutrient levels are high, but algae and total-organic-carbon data indicate water-quality improvement in recent years, due probably to a new wastewater treatment plant located downstream from Raleigh, N.C. Pollution was determined by subtracting estimated natural loads of constituents from measured total loads. Pollution makes up approximately 50% of the total dissolved material transported by the Neuse. Two different data transformation methods allowed trends to be identified in constituent concentrations. The methods recomputed the concentrations as if they were determined at a constant discharge over the period of record. Although little change since 1956 can be seen in most constituents, large changes in some constituents, such as increases in potassium and sulfate, indicate that the water quality of the Neuse River has noticeably deteriorated. Increases in sulfate are probably largely due to increased long-term inputs of sulfur compounds from airborne pollutants. (USGS)

  19. Ecosystem variability along the estuarine salinity gradient: Examples from long-term study of San Francisco Bay

    Science.gov (United States)

    Cloern, James E.; Jassby, Alan D.; Schraga, Tara; Kress, Erica S.; Martin, Charles A.

    2017-01-01

    The salinity gradient of estuaries plays a unique and fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes. We use variability along the salinity gradient of San Francisco Bay to illustrate some lessons about the diversity of spatial structures in estuaries and their variability over time. Spatial patterns of dissolved constituents (e.g., silicate) can be linear or nonlinear, depending on the relative importance of river-ocean mixing and internal sinks (diatom uptake). Particles have different spatial patterns because they accumulate in estuarine turbidity maxima formed by the combination of sinking and estuarine circulation. Some constituents have weak or no mean spatial structure along the salinity gradient, reflecting spatially distributed sources along the estuary (nitrate) or atmospheric exchanges that buffer spatial variability of ecosystem metabolism (dissolved oxygen). The density difference between freshwater and seawater establishes stratification in estuaries stronger than the thermal stratification of lakes and oceans. Stratification is strongest around the center of the salinity gradient and when river discharge is high. Spatial distributions of motile organisms are shaped by species-specific adaptations to different salinity ranges (shrimp) and by behavioral responses to environmental variability (northern anchovy). Estuarine spatial patterns change over time scales of events (intrusions of upwelled ocean water), seasons (river inflow), years (annual weather anomalies), and between eras separated by ecosystem disturbances (a species introduction). Each of these lessons is a piece in the puzzle of how estuarine ecosystems are structured and how they differ from the river and ocean ecosystems they bridge.

  20. THE COMPACT, TIME-VARIABLE RADIO SOURCE PROJECTED INSIDE W3(OH): EVIDENCE FOR A PHOTOEVAPORATED DISK?

    Energy Technology Data Exchange (ETDEWEB)

    Dzib, Sergio A.; Rodriguez-Garza, Carolina B.; Rodriguez, Luis F.; Kurtz, Stan E.; Loinard, Laurent; Zapata, Luis A.; Lizano, Susana, E-mail: s.dzib@crya.unam.mx [Centro de Radiostronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Morelia 58089 (Mexico)

    2013-08-01

    We present new Karl G. Jansky Very Large Array (VLA) observations of the compact ({approx}0.''05), time-variable radio source projected near the center of the ultracompact H II region W3(OH). The analysis of our new data as well as of VLA archival observations confirms the variability of the source on timescales of years and for a given epoch indicates a spectral index of {alpha} = 1.3 {+-} 0.3 (S{sub {nu}}{proportional_to}{nu}{sup {alpha}}). This spectral index and the brightness temperature of the source ({approx}6500 K) suggest that we are most likely detecting partially optically thick free-free radiation. The radio source is probably associated with the ionizing star of W3(OH), but an interpretation in terms of an ionized stellar wind fails because the detected flux densities are orders of magnitude larger than expected. We discuss several scenarios and tentatively propose that the radio emission could arise in a static ionized atmosphere around a fossil photoevaporated disk.

  1. Long-Term Trends and Variability of Water Levels and Tides in Buenos Aires and Mar del Plata, Argentina

    Directory of Open Access Journals (Sweden)

    Sara Santamaria-Aguilar

    2017-11-01

    Full Text Available We present an analysis of the long-term trends and variability of extreme water and tidal levels and the main tidal constituents using long-term records from two tide gauges in the wider region of the Rio de la Plata estuary: Buenos Aires (1905–2013 and Mar del Plata (1956–2013. We find significant long-term trends in both tidal levels and the main tidal constituents (M2, S2, K1, O1, and the overtide M4 from a running harmonic analysis in both locations. The tidal range decreased on average 0.63 mm y−1, as a result of an increase of the low water levels and a decrease of the high water levels. We also find a secular decrease in the amplitude of the semi-diurnal constituents and an increase of the diurnal ones, but of different magnitudes at each location, which suggests that different processes are producing these changes. In Buenos Aires, an increase of river discharge into the estuary seems to reduce the tidal range by hampering the propagation of the tidal wave into the estuary, whereas no influence of river discharge on water and tidal levels can be detected in Mar del Plata. We believe that other factors such as thermohaline changes or the rise of mean sea-level may be responsible for the observed tidal range decrease. Despite the tidal long-term trends, we find no significant trends in the meteorological component of the tide-gauge records other than an increase in the mean sea-level. In addition, we explore teleconnections between the variability of the meteorological component of the tide-gauge records and climate drivers.

  2. North Atlantic atmospheric circulation and surface wind in the Northeast of the Iberian Peninsula: uncertainty and long term downscaled variability

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Bustamante, E.; Jimenez, P.A. [CIEMAT, Departamento de Energias Renovables, Madrid (Spain); Universidad Complutense de Madrid, Departamento de Astrofisica y CC. de la Atmosfera, Madrid (Spain); Gonzalez-Rouco, J.F. [Universidad Complutense de Madrid, Departamento de Astrofisica y CC. de la Atmosfera, Madrid (Spain); Navarro, J. [CIEMAT, Departamento de Energias Renovables, Madrid (Spain); Xoplaki, E. [University of Bern, Institute of Geography and Oeschger Centre for Climate Change Research, Bern (Switzerland); Montavez, J.P. [Universidad de Murcia, Departamento de Fisica, Murcia (Spain)

    2012-01-15

    The variability and predictability of the surface wind field at the regional scale is explored over a complex terrain region in the northeastern Iberian Peninsula by means of a downscaling technique based on Canonical Correlation Analysis. More than a decade of observations (1992-2005) allows for calibrating and validating a statistical method that elicits the main associations between the large scale atmospheric circulation over the North Atlantic and Mediterranean areas and the regional wind field. In an initial step the downscaling model is designed by selecting parameter values from practise. To a large extent, the variability of the wind at monthly timescales is found to be governed by the large scale circulation modulated by the particular orographic features of the area. The sensitivity of the downscaling methodology to the selection of the model parameter values is explored, in a second step, by performing a systematic sampling of the parameters space, avoiding a heuristic selection. This provides a metric for the uncertainty associated with the various possible model configurations. The uncertainties associated with the model configuration are considerably dependent on the spatial variability of the wind. While the sampling of the parameters space in the model set up moderately impact estimations during the calibration period, the regional wind variability is very sensitive to the parameters selection at longer timescales. This fact illustrates that downscaling exercises based on a single configuration of parameters should be interpreted with extreme caution. The downscaling model is used to extend the estimations several centuries to the past using long datasets of sea level pressure, thereby illustrating the large temporal variability of the regional wind field from interannual to multicentennial timescales. The analysis does not evidence long term trends throughout the twentieth century, however anomalous episodes of high/low wind speeds are identified

  3. Inhomogeneous Bulk Viscous Fluid Universe with Electromagnetic Field and Variable Λ-Term

    Science.gov (United States)

    Pradhan, Anirudh; Rai, Vandana; Jotania, Kanti

    2008-07-01

    Cylindrically symmetric inhomogeneous cosmological model for bulk viscous fluid distribution with electromagnetic field is obtained. The source of the magnetic field is due to an electric current produced along the z-axis. F12 is the non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion θ in the model is proportional to the shear σ. The values of cosmological constant for these models are found to be small and positive at late time, which are consistent with the results from recent supernovae Ia observations. Physical and geometric aspects of the models are also discussed in presence and absence of magnetic field.

  4. Validating Long-term Consistency of MODIS EVI Time Series Using Ground-based Radiation Flux Data

    Science.gov (United States)

    Kato, A.; Miura, T.

    2014-12-01

    The Enhanced Vegetation Index (EVI) time series from Moderate Resolution Imaging Spectrometer (MODIS) has exceeded a decade in length. It is, thus, desirable to evaluate how well the time series captures inter-annual variability of vegetation phenology. Previous studies calculated a two-band version of the EVI (EVI2) from tower radiation flux data and used it to validate satellite VI time series. Differences in view angle, bandpass, and spatial representativeness between flux and satellite data, however, may lead to landcover-dependent biases when they are compared directly. The objective of this study was to validate long-term consistency of MODIS EVI time series with radiation flux-derived EVI2 time series by comparing phenological metrics derived from these datasets. Ten years of MODIS EVI and ground-based EVI2 (Tower EVI2) were obtained for 10 AmeriFlux sites. Asymmetric double logistic functions were fitted to each of VIs, from which SOSs were derived. After the Gram-Schmidt orthogonalization of the derived SOSs, the standard deviation (SD) in horizontal direction (inter-annual variability) was compared with SD in perpendicular direction (differences) to assess consistency of MODIS EVI in tracking vegetation dynamics. Temporal profiles of MODIS EVI showed analogous patterns with those of tower EVI2 across five biomes although site specific differences were seen in the VI amplitude. Cross plots of SOS from MODIS and Tower VIs closely aligned to the 1:1 line (slope > 0.865, R2>0.896). The SD in inter-annual variability (≈ 20 days) was more than twice larger than the SD of SOS difference averaged for five biomes (≈ 9 days). MODIS consistently captured SOSs with 2.7-4.9-day differences at deciduous broad leaf forest and clopland sites, and also agreed well at a wooded savanna site (< 6 days). Grassland sites showed more than a week difference due to a failure in model fitting of the year with subtle VI amplitude and the year with multiple growing seasons

  5. Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment.

    Science.gov (United States)

    Bunce, David; Haynes, Becky I; Lord, Stephen R; Gschwind, Yves J; Kochan, Nicole A; Reppermund, Simone; Brodaty, Henry; Sachdev, Perminder S; Delbaere, Kim

    2017-06-01

    Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI) are at high risk of falling, the association between IIV and prospective falls is unknown. We conducted a longitudinal cohort study in cognitively intact (n = 271) and MCI (n = 154) community-dwelling adults aged 70-90 years. IIV was assessed through a variety of measures including simple and choice hand reaction time and choice stepping reaction time tasks (CSRT), the latter administered as a single task and also with a secondary working memory task. Logistic regression did not show an association between IIV on the hand-held tasks and falls. Greater IIV in both CSRT tasks, however, did significantly increase the risk of future falls. This effect was specific to the MCI group, with a stronger effect in persons exhibiting gait, posture, or physiological impairment. The findings suggest that increased stepping IIV may indicate compromised neural circuitry involved in executive function, gait, and posture in persons with MCI increasing their risk of falling. IIV measures have potential to assess neurobiological disturbance underlying physical and cognitive dysfunction in old age, and aid fall risk assessment and routine care in community and health care settings.

  6. Analysis of heart rate variability in the presence of ectopic beats using the heart timing signal.

    Science.gov (United States)

    Mateo, Javier; Laguna, Pablo

    2003-03-01

    The time-domain signals representing the heart rate variability (HRV) in the presence of an ectopic beat exhibit a sharp transient at the position of the ectopic beat, which corrupts the signal, particularly the power spectral density (PSD) of the HRV. Consequently, there is a need for correction of this type of beat prior to any HRV analysis. This paper deals with the PSD estimation of the HRV by means of the heart timing (HT) signal when ectopic beats are present. These beat occurrence times are modeled from a generalized, continuous time integral pulse frequency modulation model and, from this point of view, a specific method for minimizing the effect of the presence of ectopic beats is presented to work together with the HT signal. By using both, a white noise driven autoregressive model of the HRV signal with artificially introduced ectopic beats and actual heart rate series including ectopic beats, the more usual methods of HRV spectral estimation are compared. Results of the PSD estimation error function of the number of ectopic beats are presented. These results demonstrate that the proposed method has one order of magnitude lower error than usual ectopic beats removal strategies in preserving PSD, thus, this strategy better recovers the original clinical indexes of interest.

  7. Drivers of Time-Activity Budget Variability during Breeding in a Pelagic Seabird

    Science.gov (United States)

    Rishworth, Gavin M.; Tremblay, Yann; Green, David B.; Connan, Maëlle; Pistorius, Pierre A.

    2014-01-01

    During breeding, animal behaviour is particularly sensitive to environmental and food resource availability. Additionally, factors such as sex, body condition, and offspring developmental stage can influence behaviour. Amongst seabirds, behaviour is generally predictably affected by local foraging conditions and has therefore been suggested as a potentially useful proxy to indicate prey state. However, besides prey availability and distribution, a range of other variables also influence seabird behavior, and these need to be accounted for to increase the signal-to-noise ratio when assessing specific characteristics of the environment based on behavioural attributes. The aim of this study was to use continuous, fine-scale time-activity budget data from a pelagic seabird (Cape gannet, Morus capensis) to determine the influence of intrinsic (sex and body condition) and extrinsic (offspring and time) variables on parent behaviour during breeding. Foraging trip duration and chick provisioning rates were clearly sex-specific and associated with chick developmental stage. Females made fewer, longer foraging trips and spent less time at the nest during chick provisioning. These sex-specific differences became increasingly apparent with chick development. Additionally, parents in better body condition spent longer periods at their nests and those which returned later in the day had longer overall nest attendance bouts. Using recent technological advances, this study provides new insights into the foraging behaviour of breeding seabirds, particularly during the post-guarding phase. The biparental strategy of chick provisioning revealed in this study appears to be an example where the costs of egg development to the female are balanced by paternal-dominated chick provisioning particularly as the chick nears fledging. PMID:25551620

  8. Drivers of time-activity budget variability during breeding in a pelagic seabird.

    Directory of Open Access Journals (Sweden)

    Gavin M Rishworth

    Full Text Available During breeding, animal behaviour is particularly sensitive to environmental and food resource availability. Additionally, factors such as sex, body condition, and offspring developmental stage can influence behaviour. Amongst seabirds, behaviour is generally predictably affected by local foraging conditions and has therefore been suggested as a potentially useful proxy to indicate prey state. However, besides prey availability and distribution, a range of other variables also influence seabird behavior, and these need to be accounted for to increase the signal-to-noise ratio when assessing specific characteristics of the environment based on behavioural attributes. The aim of this study was to use continuous, fine-scale time-activity budget data from a pelagic seabird (Cape gannet, Morus capensis to determine the influence of intrinsic (sex and body condition and extrinsic (offspring and time variables on parent behaviour during breeding. Foraging trip duration and chick provisioning rates were clearly sex-specific and associated with chick developmental stage. Females made fewer, longer foraging trips and spent less time at the nest during chick provisioning. These sex-specific differences became increasingly apparent with chick development. Additionally, parents in better body condition spent longer periods at their nests and those which returned later in the day had longer overall nest attendance bouts. Using recent technological advances, this study provides new insights into the foraging behaviour of breeding seabirds, particularly during the post-guarding phase. The biparental strategy of chick provisioning revealed in this study appears to be an example where the costs of egg development to the female are balanced by paternal-dominated chick provisioning particularly as the chick nears fledging.

  9. Variability in glycosylated hemoglobin values in diabetic patients living in long-term care facilities.

    Science.gov (United States)

    Meyers, Roberta M; Broton, Jay C; Woo-Rippe, Kathleen W; Lindquist, Sara A; Cen, Ye-Ying

    2007-10-01

    The objectives of this study were to determine the prevalence of diabetes and mean A1C of patients in long-term care facilities (LTCFs); to determine differences in A1C values based on patient characteristics; and to examine the self-reported practices of providers regarding diabetes management goals. Twelve-month retrospective review of patient charts; survey of physicians and nurse practitioners providing care to these patients. Nursing facility practice of an urban teaching hospital. Participants included 168 diabetic patients living in 20 nursing facilities and 18 physician and nurse practitioners in one practice providing care to these patients. The prevalence of diabetes was 21.6% (168 of 778 patients). Mean A1C was 7.1% +/- 1.2%for 135 patients who had AIC values measured during the study interval. A1C varied by age, with patients younger than 65 having higher A1C values than patients older than 65. Higher A1C values were associated with insulin use, frequent glucose monitoring, and attending a diabetes clinic. Although a survey of providers identified modifying A1C target ranges for LTCF compared with ambulatory patients, they did not reach consensus on the actual target A1C. No association between provider perception of either patient health status or patient life expectancy and A1C values was found. Relatively low A1C values were obtainable in LTCF patients without diabetes specialty clinic use. Providers identified modifying target A1C values for LTCF patients, but achieved relatively low A1C values and did not agree on a target A1C value for LTCF patients.

  10. Variability of scaling time series in the Arctic sea-ice drift dynamics

    Directory of Open Access Journals (Sweden)

    A. Chmel

    2010-02-01

    Full Text Available The motion of an individual ice floe in the Arctic Ocean was monitored at the Russian research station North Pole 35 established on the ice pack in 2008. The ice floe speed (V was found to be correlated with wind speed (v in main features, such as the positions of maxima and minima of V and v. However, the fine structure of the V-variation cannot be explained by the wind forcing alone. There were periods of time when the floe drift was affected by the interactions of ice floes between each other or by the periodical forcing due to either the Coriolis inertia effect or the tidal activity. These data were compared with the "waiting times" statistics that are the distributions of time intervals between subsequent, sufficiently strong changes in the kinetic energy of drifting ice floe. These distributions were measured in several time windows differing in the average wind speed and wind direction, and/or in the mechanical state of the ice pack. The distribution functions N (t>τ, where N is the number of successive events of energy change separated by the time interval t that exceeds τ, constructed in different time windows demonstrate fractal or a multifractal nature of the time series during motion in the consolidated ice pack but were truly random when the ice floe drifted in the highly fragmented sea ice. The latter result shows the existence of a relationship between the long-range mechanical interactions in the pack and long-term memory (time scaling behaviour of the sea-ice motion.

  11. Increase of Short-Term Heart Rate Variability Induced by Blood Pressure Measurements during Ambulatory Blood Pressure Monitoring

    OpenAIRE

    Attila Frigy; Annamária Magdás; Victor-Dan Moga; Ioana Georgiana Coteț; Miklós Kozlovszky; László Szilágyi

    2017-01-01

    Objective. The possible effect of blood pressure measurements per se on heart rate variability (HRV) was studied in the setting of concomitant ambulatory blood pressure monitoring (ABPM) and Holter ECG monitoring (HM). Methods. In 25 hypertensive patients (14 women and 11 men, mean age: 58.1 years), 24-hour combined ABPM and HM were performed. For every blood pressure measurement, 2-minute ECG segments (before, during, and after measurement) were analyzed to obtain time domain parameters of H...

  12. Health care aides use of time in a residential long-term care unit: a time and motion study.

    Science.gov (United States)

    Mallidou, Anastasia A; Cummings, Greta G; Schalm, Corinne; Estabrooks, Carole A

    2013-09-01

    Organizational resources such as caregiver time use with older adults in residential long-term care facilities (nursing homes) have not been extensively studied, while levels of nurse staffing and staffing-mix are the focus of many publications on all types of healthcare organizations. Evidence shows that front-line caregivers' sufficient working time with residents is associated with performance, excellence, comprehensive care, quality of outcomes (e.g., reductions in pressure ulcers, urinary tract infections, and falls), quality of life, cost savings, and may be affiliated with transformation of organizational culture. To explore organizational resources in a long-term care unit within a multilevel residential facility, to measure healthcare aides' use of time with residents, and to describe working environment and unit culture. An observational pilot study was conducted in a Canadian urban 52-bed long-term care unit within a faith-based residential multilevel care facility. A convenience sample of seven healthcare aides consented to participate. To collect the data, we used an observational sheet (to monitor caregiver time use on certain activities such as personal care, assisting with eating, socializing, helping residents to be involved in therapeutic activities, paperwork, networking, personal time, and others), semi-structured interview (to assess caregiver perceptions of their working environment), and field notes (to illustrate the unit culture). Three hundred and eighty seven hours of observation were completed. The findings indicate that healthcare aides spent most of their working time (on an eight-hour day-shift) in "personal care" (52%) and in "other" activities (23%). One-to-three minute activities consumed about 35% of the time spent in personal care and 20% of time spent in assisting with eating. Overall, caregivers' time spent socializing was less than 1%, about 6% in networking, and less than 4% in paperwork. Re-organizing healthcare aides

  13. Variable School Start Times and Middle School Student's Sleep Health and Academic Performance.

    Science.gov (United States)

    Lewin, Daniel S; Wang, Guanghai; Chen, Yao I; Skora, Elizabeth; Hoehn, Jessica; Baylor, Allison; Wang, Jichuan

    2017-08-01

    Improving sleep health among adolescents is a national health priority and implementing healthy school start times (SSTs) is an important strategy to achieve these goals. This study leveraged the differences in middle school SST in a large district to evaluate associations between SST, sleep health, and academic performance. This cross-sectional study draws data from a county-wide surveillance survey. Participants were three cohorts of eighth graders (n = 26,440). The school district is unique because SST ranged from 7:20 a.m. to 8:10 a.m. Path analysis and probit regression were used to analyze associations between SST and self-report measures of weekday sleep duration, grades, and homework controlling for demographic variables (sex, race, and socioeconomic status). The independent contributions of SST and sleep duration to academic performance were also analyzed. Earlier SST was associated with decreased sleep duration (χ(2) = 173, p sleep (≤7 hours) among 45% of students. Students with SST before 7:45 a.m. were at increased risk of decreased sleep duration, academic performance, and academic effort. Path analysis models demonstrated the independent contributions of sleep duration, SST, and variable effects for demographic variables. This is the first study to evaluate the independent contributions of SST and sleep to academic performance in a large sample of middle school students. Deficient sleep was prevalent, and the earliest SST was associated with decrements in sleep and academics. These findings support the prioritization of policy initiatives to implement healthy SST for younger adolescents and highlight the importance of sleep health education disparities among race and gender groups. Copyright © 2017 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.

  14. Performance Comparison of Time-Frequency Distributions for Estimation of Instantaneous Frequency of Heart Rate Variability Signals

    Directory of Open Access Journals (Sweden)

    Nabeel Ali Khan

    2017-02-01

    Full Text Available The instantaneous frequency (IF of a non-stationary signal is usually estimated from a time-frequency distribution (TFD. The IF of heart rate variability (HRV is an important parameter because the power in a frequency band around the IF can be used for the interpretation and analysis of the respiratory rate but also for a more accurate analysis of heart rate (HR signals. In this study, we compare the performance of five states of the art kernel-based time-frequency distributions (TFDs in terms of their ability to accurately estimate the IF of HR signals. The selected TFDs include three widely used fixed kernel methods: the modified B distribution, the S-method and the spectrogram; and two adaptive kernel methods: the adaptive optimal kernel TFD and the recently developed adaptive directional TFD. The IF of the respiratory signal, which is usually easier to estimate as the respiratory signal is a mono-component with small amplitude variations with time, is used as a reference to examine the accuracy of the HRV IF estimates. Experimental results indicate that the most reliable estimates are obtained using the adaptive directional TFD in comparison to other commonly used methods such as the adaptive optimal kernel TFD and the modified B distribution.

  15. Evaluating methods for estimating space-time paths of individuals in calculating long-term personal exposure to air pollution

    Science.gov (United States)

    Schmitz, Oliver; Soenario, Ivan; Vaartjes, Ilonca; Strak, Maciek; Hoek, Gerard; Brunekreef, Bert; Dijst, Martin; Karssenberg, Derek

    2016-04-01

    Air pollution is one of the major concerns for human health. Associations between air pollution and health are often calculated using long-term (i.e. years to decades) information on personal exposure for each individual in a cohort. Personal exposure is the air pollution aggregated along the space-time path visited by an individual. As air pollution may vary considerably in space and time, for instance due to motorised traffic, the estimation of the spatio-temporal location of a persons' space-time path is important to identify the personal exposure. However, long term exposure is mostly calculated using the air pollution concentration at the x, y location of someone's home which does not consider that individuals are mobile (commuting, recreation, relocation). This assumption is often made as it is a major challenge to estimate space-time paths for all individuals in large cohorts, mostly because limited information on mobility of individuals is available. We address this issue by evaluating multiple approaches for the calculation of space-time paths, thereby estimating the personal exposure along these space-time paths with hyper resolution air pollution maps at national scale. This allows us to evaluate the effect of the space-time path and resulting personal exposure. Air pollution (e.g. NO2, PM10) was mapped for the entire Netherlands at a resolution of 5×5 m2 using the land use regression models developed in the European Study of Cohorts for Air Pollution Effects (ESCAPE, http://escapeproject.eu/) and the open source software PCRaster (http://www.pcraster.eu). The models use predictor variables like population density, land use, and traffic related data sets, and are able to model spatial variation and within-city variability of annual average concentration values. We approximated space-time paths for all individuals in a cohort using various aggregations, including those representing space-time paths as the outline of a persons' home or associated parcel

  16. Intraindividual variability in basic reaction time predicts middle-aged and older pilots' flight simulator performance.

    Science.gov (United States)

    Kennedy, Quinn; Taylor, Joy; Heraldez, Daniel; Noda, Art; Lazzeroni, Laura C; Yesavage, Jerome

    2013-07-01

    Intraindividual variability (IIV) is negatively associated with cognitive test performance and is positively associated with age and some neurological disorders. We aimed to extend these findings to a real-world task, flight simulator performance. We hypothesized that IIV predicts poorer initial flight performance and increased rate of decline in performance among middle-aged and older pilots. Two-hundred and thirty-six pilots (40-69 years) completed annual assessments comprising a cognitive battery and two 75-min simulated flights in a flight simulator. Basic and complex IIV composite variables were created from measures of basic reaction time and shifting and divided attention tasks. Flight simulator performance was characterized by an overall summary score and scores on communication, emergencies, approach, and traffic avoidance components. Although basic IIV did not predict rate of decline in flight performance, it had a negative association with initial performance for most flight measures. After taking into account processing speed, basic IIV explained an additional 8%-12% of the negative age effect on initial flight performance. IIV plays an important role in real-world tasks and is another aspect of cognition that underlies age-related differences in cognitive performance.

  17. Intraindividual Variability in Basic Reaction Time Predicts Middle-Aged and Older Pilots’ Flight Simulator Performance

    Science.gov (United States)

    2013-01-01

    Objectives. Intraindividual variability (IIV) is negatively associated with cognitive test performance and is positively associated with age and some neurological disorders. We aimed to extend these findings to a real-world task, flight simulator performance. We hypothesized that IIV predicts poorer initial flight performance and increased rate of decline in performance among middle-aged and older pilots. Method. Two-hundred and thirty-six pilots (40–69 years) completed annual assessments comprising a cognitive battery and two 75-min simulated flights in a flight simulator. Basic and complex IIV composite variables were created from measures of basic reaction time and shifting and divided attention tasks. Flight simulator performance was characterized by an overall summary score and scores on communication, emergencies, approach, and traffic avoidance components. Results. Although basic IIV did not predict rate of decline in flight performance, it had a negative association with initial performance for most flight measures. After taking into account processing speed, basic IIV explained an additional 8%–12% of the negative age effect on initial flight performance. Discussion. IIV plays an important role in real-world tasks and is another aspect of cognition that underlies age-related differences in cognitive performance. PMID:23052365

  18. Exploring Multidimensional Free Energy Landscapes Using Time-Dependent Biases on Collective Variables.

    Science.gov (United States)

    Hénin, Jérome; Fiorin, Giacomo; Chipot, Christophe; Klein, Michael L

    2010-01-12

    A new implementation of the adaptive biasing force (ABF) method is described. This implementation supports a wide range of collective variables and can be applied to the computation of multidimensional energy profiles. It is provided to the community as part of a code that implements several analogous methods, including metadynamics. ABF and metadynamics have not previously been tested side by side on identical systems. Here, numerical tests are carried out on processes including conformational changes in model peptides and translocation of a halide ion across a lipid membrane through a peptide nanotube. On the basis of these examples, we discuss similarities and differences between the ABF and metadynamics schemes. Both approaches provide enhanced sampling and free energy profiles in quantitative agreement with each other in different applications. The method of choice depends on the dimension of the reaction coordinate space, the height of the barriers, and the relaxation times of degrees of freedom in the orthogonal space, which are not explicitly described by the chosen collective variables.

  19. Variability and trends of carbon parameters at a time series in the eastern tropical Atlantic

    Directory of Open Access Journals (Sweden)

    Nathalie Lefèvre

    2016-05-01

    Full Text Available Hourly fCO2 is recorded at a time series at the PIRATA buoy located at 6°S 10°W in the eastern tropical Atlantic since June 2006. This site is located south and west of the seasonal Atlantic cold tongue and is affected by its propagation from June to September. Using an alkalinity–salinity relationship determined for the eastern tropical Atlantic and the observed fCO2, pH and the inorganic carbon concentration are calculated. The time series is investigated to explore the intraseasonal, seasonal and interannual timescales for these parameters, and to detect any long-term trends. At intraseasonal timescales, fCO2 and pH are strongly correlated. On seasonal timescales, the correlation still holds between fCO2 and pH and their variations are in agreement with those of sea surface salinity. At interannual timescales, some important differences appear in 2011–2012: lower fCO2 and fluxes are observed from September to December 2011 and are explained by higher advection of salty waters at the mooring, in agreement with the wind. In early 2012, the anomaly is still present and associated with lower sea surface temperatures. No significant long-term trend is detected over the period 2006–2013 on CO2 and any other physical parameter. However, as atmospheric fCO2 is increasing over time, the outgassing of CO2 is reduced over the period 2006–2013 as the flux is mainly controlled by the difference of fCO2 between the ocean and the atmosphere. A longer time series is required to determine if any significant trend exists in this region.

  20. Long-Term Persistency of Abnormal Heart Rate Variability following Long NICU Stay and Surgery at Birth

    Directory of Open Access Journals (Sweden)

    Mélanie Morin

    2014-01-01

    Full Text Available Preterm birth is associated with painful procedures during the neonatal intensive care unit (NICU stay. Full-term newborns can also experience pain, following surgery. These procedures can have long-lasting consequences. It has been shown that children born preterm show pain responses and cardiac alterations. This study aimed to explore the heart rate reactivity to pain in 107 subjects born either preterm or full-term who were between 7 and 25 years old at testing. We also evaluated the effect of pain experienced at birth, as represented by a longer NICU stay, time under ventilation, and surgery at birth. Participants were asked to immerse their right forearm in 10°C water for 2 minutes. Electrocardiograms were recorded at baseline and during the immersion procedure. Full-term subjects showed a stable increase in heart rate throughout the procedure, whereas preterm ones showed a strong increase at the beginning, which decreased over time. Also, preterm and full-term subjects who experienced pain at birth showed higher resting heart rate, stronger sympathetic activity, and lower cardiac vagal activity. Our study demonstrated a long-term impact of a long NICU stay and surgery at birth on cardiac autonomic activity. This could lead to impaired reactions to pain or stress in later life.

  1. Interindividual variability in functional connectivity as long-term correlate of temporal discounting.

    Directory of Open Access Journals (Sweden)

    Cinzia Calluso

    Full Text Available During intertemporal choice (IT future outcomes are usually devaluated as a function of the delay, a phenomenon known as temporal discounting (TD. Based on task-evoked activity, previous neuroimaging studies have described several networks associated with TD. However, given its relevance for several disorders, a critical challenge is to define a specific neural marker able to predict TD independently of task execution. To this aim, we used resting-state functional connectivity MRI (fcMRI and measured TD during economic choices several months apart in 25 human subjects. We further explored the relationship between TD, impulsivity and decision uncertainty by collecting standard questionnaires on individual trait/state differences. Our findings indicate that fcMRI within and between critical nodes of task-evoked neural networks associated with TD correlates with discounting behavior measured a long time afterwards, independently of impulsivity. Importantly, the nodes form an intrinsic circuit that might support all the mechanisms underlying TD, from the representation of subjective value to choice selection through modulatory effects of cognitive control and episodic prospection.

  2. Variable interval time/temperature (VITT) defrost-control-system evaluation

    Energy Technology Data Exchange (ETDEWEB)

    None

    1980-08-12

    Two variable-interval-time/temperature (VITT) heat pump defrost control systems are analyzed to determine if systems manufactured by Honeywell and Ranco qualify for credit for heat pumps with demand defrost control. The operation of the systems is described. VITT controls are not demand defrost control systems but utilize demand defrost control as backup systems in most Ranco models and all Honeywell models. The evaluations and results, intended to provide DOE information in making its determinations regarding credits for the control systems are discussed. The evaluation methodology utilizes a modified version of the Heat Pump Seasonal Performance Model (HPSPM) and the important modifications are discussed in Appendix A. Appendix B contains a detailed listing and discussion of the HPSPM output. (MCW)

  3. An Efficient Method for Systems of Variable Coefficient Coupled Burgers’ Equation with Time-Fractional Derivative

    Directory of Open Access Journals (Sweden)

    Hossein Aminikhah

    2013-01-01

    Full Text Available A new homotopy perturbation method (NHPM is applied to system of variable coefficient coupled Burgers' equation with time-fractional derivative. The fractional derivatives are described in the Caputo fractional derivative sense. The concept of new algorithm is introduced briefly, and NHPM is examined for two systems of nonlinear Burgers' equation. In this approach, the solution is considered as a power series expansion that converges rapidly to the nonlinear problem. The new approximate analytical procedure depends on two iteratives. The modified algorithm provides approximate solutions in the form of convergent series with easily computable components. Results indicate that the introduced method is promising for solving other types of systems of nonlinear fractional-order partial differential equations.

  4. An efficient method for systems of variable coefficient coupled Burgers' equation with time-fractional derivative.

    Science.gov (United States)

    Aminikhah, Hossein; Malekzadeh, Nasrin

    2013-01-01

    A new homotopy perturbation method (NHPM) is applied to system of variable coefficient coupled Burgers' equation with time-fractional derivative. The fractional derivatives are described in the Caputo fractional derivative sense. The concept of new algorithm is introduced briefly, and NHPM is examined for two systems of nonlinear Burgers' equation. In this approach, the solution is considered as a power series expansion that converges rapidly to the nonlinear problem. The new approximate analytical procedure depends on two iteratives. The modified algorithm provides approximate solutions in the form of convergent series with easily computable components. Results indicate that the introduced method is promising for solving other types of systems of nonlinear fractional-order partial differential equations.

  5. Development of a time-variable nuclear pulser for half life measurements

    Energy Technology Data Exchange (ETDEWEB)

    Zahn, Guilherme S.; Domienikan, Claudio; Carvalhaes, Roberto P. M.; Genezini, Frederico A. [Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP. P.O. Box 11049, Sao Paulo, 05422-970 (Brazil)

    2013-05-06

    In this work a time-variable pulser system with an exponentially-decaying pulse frequency is presented, which was developed using the low-cost, open-source Arduino microcontroler plataform. In this system, the microcontroller produces a TTL signal in the selected rate and a pulse shaper board adjusts it to be entered in an amplifier as a conventional pulser signal; both the decay constant and the initial pulse rate can be adjusted using a user-friendly control software, and the pulse amplitude can be adjusted using a potentiometer in the pulse shaper board. The pulser was tested using several combinations of initial pulse rate and decay constant, and the results show that the system is stable and reliable, and is suitable to be used in half-life measurements.

  6. Visualizing microvascular flow variation in OCTA using variable interscan time analysis (VISTA) (Conference Presentation)

    Science.gov (United States)

    Moult, Eric M.; Ploner, Stefan A.; Choi, WooJhon; Lee, ByungKun; Husvogt, Lennart A.; Lu, Chen D.; Novais, Eduardo; Cole, Emily D.; Potsaid, Benjamin M.; Duker, Jay S.; Hornegger, Joachim; Meier, Andreas K.; Waheed, Nadia K.; Fujimoto, James G.

    2017-02-01

    OCT angiography (OCTA) has recently garnered immense interest in clinical ophthalmology, permitting ocular vasculature to be viewed in exquisite detail, in vivo, and without the injection of exogenous dyes. However, commercial OCTA systems provide little information about actual erythrocyte speeds; instead, OCTA is typically used to visualize the presence and/or absence of vasculature. This is an important limitation because in many ocular diseases, including diabetic retinopathy (DR) and age-related macular degeneration (AMD), alterations in blood flow, but not necessarily only the presence or absence of vasculature, are thought to be important in understanding pathogenesis. To address this limitation, we have developed an algorithm, variable interscan time analysis (VISTA), which is capable of resolving different erythrocyte speeds. VISTA works by acquiring >2 repeated B-scans, and then computing multiple OCTA signals corresponding to different effective interscan times. The OCTA signals corresponding to different effective interscan times contain independent information about erythrocyte speed. In this study we provide a theoretical overview of VISTA, and investigate the utility of VISTA in studying blood flow alterations in ocular disease. OCTA-VISTA images of eyes with choroidal neovascularization, geographic atrophy, and diabetic retinopathy are presented.

  7. Assessing the Time Variability of Jupiter's Tropospheric Properties from 1996 to 2011

    Science.gov (United States)

    Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Simon-Miller, A. A.; Greco, J.; Wakefield, L.

    2012-01-01

    We acquired and analyzed mid-infrared images of Jupiter's disk at selected wavelengths from NASA's Infrared Telescope Facility (IRTF) from 1996 to 2011, including a period of large-scale changes of cloud color and albedo. We derived the 100-300 mbar temperature structure, together with tracers of vertical motion: the thickness of a 600- mbar cloud layer, the 300-mbar abundance of the condensable gas NH3, and the 400- mbar para- vs. ortho-H2 ratio. The biggest visual change was detected in the normally dark South Equatorial Belt (SEB) that 'faded' to a light color in 2010, during which both cloud thickness and NH3 abundance rose; both returned to their pre-fade levels in 2011, as the SEB regained its normal dark color. The cloud thickness in Jupiter's North Temperate Belt (NTB) increased in 2002, coincident with its visible brightening, and its NH3 abundance spiked in 2002-2003. Jupiter's Equatorial Zone (EZ), a region marked by more subtle but widespread color and albedo change, showed high cloud thickness variability between 2007 and 2009. In Jupiter's North Equatorial Belt (NEB), the cloud thickened in 2005, then slowly decreased to a minimum value in 2010-2011. No temperature variations were associated with any of these changes, but we discovered temperature oscillations of approx.2-4 K in all regions, with 4- or 8-year periods and phasing that was dissimilar in the different regions. There was also no detectable change in the para- vs. ortho-H2 ratio over time, leading to the possibility that it is driven from much deeper atmospheric levels and may be time-invariant. Our future work will continue to survey the variability of these properties through the Juno mission, which arrives at Jupiter in 2016, and to connect these observations with those made using raster-scanned images from 1980 to 1993 (Orton et al. 1996 Science 265, 625).

  8. Palaeoflood and floodplain records from Spain: Evidence for long-term climate variability and environmental changes

    Science.gov (United States)

    Benito, G.; Thorndycraft, V. R.; Rico, M.; Sánchez-Moya, Y.; Sopeña, A.

    2008-10-01

    Palaeoflood chronologies from seven Spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed. These fluvial records were divided in to two sub-sets, namely Atlantic (10 ka record) and Mediterranean (3 ka record) river basins, which represent distinct modern hydroclimatic conditions. In Atlantic basins floods result from intense, widespread rainfalls associated with Atlantic frontal systems transported by westerly airflow. Mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems (MCSs) during autumn months. Evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10,750-10,240; 9550-9130; 4820-4440; 2865-2350; 960-790; and 520-290 cal BP. Despite the different flood-producing weather conditions in Atlantic and Mediterranean rivers, the radiocarbon sample clusters overlap and indicate changes in large-scale atmospheric circulation and climatic conditions in the Iberian Peninsula. Comparison with proxy records of mean temperature for the Northern Hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases (e.g. the 2650 yr BP climatic event or AD 1590-1650 period of the Little Ice Age). Radiocarbon dates from aggraded floodplain sediments were clustered at 2710-2320, 2000-1830, and 910-500 cal BP. The first cluster period is in phase with the timing of slackwater deposition, whereas the third (910-500 cal BP) occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records. It is argued that the 910-500 cal BP floodplain aggradation period reflects the first post-Roman evidence of environmental change related to generalised land-use changes at the catchment scale, which produced high sediment load transported to overbank areas during high flows.

  9. ASSOCIATING LONG-TERM {gamma}-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I +61 Degree-Sign 303

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M.; Buehler, R. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Ballet, J.; Casandjian, J. M. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bonamente, E.; Cecchi, C. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Brigida, M. [Dipartimento di Fisica ' ' M. Merlin' ' dell' Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P. [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); Caliandro, G. A. [Institute of Space Sciences (IEEE-CSIC), Campus UAB, E-08193 Barcelona (Spain); Cameron, R. A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Caraveo, P. A. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica, I-20133 Milano (Italy); Cavazzuti, E. [Agenzia Spaziale Italiana (ASI) Science Data Center, I-00044 Frascati (Roma) (Italy); Chekhtman, A., E-mail: andrea.caliandro@ieec.uab.es, E-mail: hadasch@ieec.uab.es, E-mail: dtorres@ieec.uab.es [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); and others

    2013-08-20

    Gamma-ray binaries are stellar systems for which the spectral energy distribution (discounting the thermal stellar emission) peaks at high energies. Detected from radio to TeV gamma rays, the {gamma}-ray binary LS I +61 Degree-Sign 303 is highly variable across all frequencies. One aspect of this system's variability is the modulation of its emission with the timescale set by the {approx}26.4960 day orbital period. Here we show that, during the time of our observations, the {gamma}-ray emission of LS I +61 Degree-Sign 303 also presents a sinusoidal variability consistent with the previously known superorbital period of 1667 days. This modulation is more prominently seen at orbital phases around apastron, whereas it does not introduce a visible change close to periastron. It is also found in the appearance and disappearance of variability at the orbital period in the power spectrum of the data. This behavior could be explained by a quasi-cyclical evolution of the equatorial outflow of the Be companion star, whose features in