Sample records for abrupt negative shift

  1. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    NASA Astrophysics Data System (ADS)

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  2. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models

    PubMed Central

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-01-01

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change. PMID:26460042

  3. Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models.

    PubMed

    Drijfhout, Sybren; Bathiany, Sebastian; Beaulieu, Claudie; Brovkin, Victor; Claussen, Martin; Huntingford, Chris; Scheffer, Marten; Sgubin, Giovanni; Swingedouw, Didier

    2015-10-27

    Abrupt transitions of regional climate in response to the gradual rise in atmospheric greenhouse gas concentrations are notoriously difficult to foresee. However, such events could be particularly challenging in view of the capacity required for society and ecosystems to adapt to them. We present, to our knowledge, the first systematic screening of the massive climate model ensemble informing the recent Intergovernmental Panel on Climate Change report, and reveal evidence of 37 forced regional abrupt changes in the ocean, sea ice, snow cover, permafrost, and terrestrial biosphere that arise after a certain global temperature increase. Eighteen out of 37 events occur for global warming levels of less than 2°, a threshold sometimes presented as a safe limit. Although most models predict one or more such events, any specific occurrence typically appears in only a few models. We find no compelling evidence for a general relation between the overall number of abrupt shifts and the level of global warming. However, we do note that abrupt changes in ocean circulation occur more often for moderate warming (less than 2°), whereas over land they occur more often for warming larger than 2°. Using a basic proportion test, however, we find that the number of abrupt shifts identified in Representative Concentration Pathway (RCP) 8.5 scenarios is significantly larger than in other scenarios of lower radiative forcing. This suggests the potential for a gradual trend of destabilization of the climate with respect to such shifts, due to increasing global mean temperature change.

  4. Causes and projections of abrupt climate-driven ecosystem shifts in the North Atlantic.

    PubMed

    Beaugrand, Grégory; Edwards, Martin; Brander, Keith; Luczak, Christophe; Ibanez, Frederic

    2008-11-01

    Warming of the global climate is now unequivocal and its impact on Earth' functional units has become more apparent. Here, we show that marine ecosystems are not equally sensitive to climate change and reveal a critical thermal boundary where a small increase in temperature triggers abrupt ecosystem shifts seen across multiple trophic levels. This large-scale boundary is located in regions where abrupt ecosystem shifts have been reported in the North Atlantic sector and thereby allows us to link these shifts by a global common phenomenon. We show that these changes alter the biodiversity and carrying capacity of ecosystems and may, combined with fishing, precipitate the reduction of some stocks of Atlantic cod already severely impacted by exploitation. These findings offer a way to anticipate major ecosystem changes and to propose adaptive strategies for marine exploited resources such as cod in order to minimize social and economic consequences.

  5. Climate Stability: Pathway to understand abrupt glacial climate shifts

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Knorr, G.; Barker, S.; Lohmann, G.

    2017-12-01

    Glacial climate is marked by abrupt, millennial-scale climate changes known as Dansgaard-Oeschger (DO) cycles that have been linked to variations in the Atlantic meridional overturning circulation (AMOC). The most pronounced stadial coolings, Heinrich Stadials (HSs), are associated with massive iceberg discharges to the North Atlantic. This motivates scientists to consider that the North Atlantic freshwater perturbations is a common trigger of the associated abrupt transitions between weak and strong AMOC states. However, recent studies suggest that the Heinrich ice-surging events are triggered by ocean subsurface warming associated with an AMOC slow-down. Furthermore, the duration of ice-rafting events does not systematically coincide with the beginning and end of the pronounced cold conditions during HSs. In this context, we show that both, changes in atmospheric CO2 and ice sheet configuration can provide important control on the stability of the AMOC, using a coupled atmosphere-ocean model. Our simulations reveal that gradual changes in Northern Hemisphere ice sheet height and atmospheric CO2 can act as a trigger of abrupt glacial/deglacial climate changes. The simulated global climate responses—including abrupt warming in the North Atlantic, a northward shift of the tropical rain belts, and Southern Hemisphere cooling related to the bipolar seesaw—are generally consistent with empirical evidence. We further find that under a delicate configuration of atmospheric CO2 and ice sheet height the AMOC can be characterized by a self-oscillation (resonance) feature (Hopf Bifucation) with a 1000-year cycle that is comparable with observed small DO events during the MIS 3. This provides an alternative explanation for millennial-scale DO variability during glacial periods.

  6. Abrupt glacial climate shifts controlled by ice sheet changes.

    PubMed

    Zhang, Xu; Lohmann, Gerrit; Knorr, Gregor; Purcell, Conor

    2014-08-21

    During glacial periods of the Late Pleistocene, an abundance of proxy data demonstrates the existence of large and repeated millennial-scale warming episodes, known as Dansgaard-Oeschger (DO) events. This ubiquitous feature of rapid glacial climate change can be extended back as far as 800,000 years before present (BP) in the ice core record, and has drawn broad attention within the science and policy-making communities alike. Many studies have been dedicated to investigating the underlying causes of these changes, but no coherent mechanism has yet been identified. Here we show, by using a comprehensive fully coupled model, that gradual changes in the height of the Northern Hemisphere ice sheets (NHISs) can alter the coupled atmosphere-ocean system and cause rapid glacial climate shifts closely resembling DO events. The simulated global climate responses--including abrupt warming in the North Atlantic, a northward shift of the tropical rainbelts, and Southern Hemisphere cooling related to the bipolar seesaw--are generally consistent with empirical evidence. As a result of the coexistence of two glacial ocean circulation states at intermediate heights of the ice sheets, minor changes in the height of the NHISs and the amount of atmospheric CO2 can trigger the rapid climate transitions via a local positive atmosphere-ocean-sea-ice feedback in the North Atlantic. Our results, although based on a single model, thus provide a coherent concept for understanding the recorded millennial-scale variability and abrupt climate changes in the coupled atmosphere-ocean system, as well as their linkages to the volume of the intermediate ice sheets during glacials.

  7. Early Heritage-Language Education and the Abrupt Shift to a Dominant-Language Classroom: Impact on the Personal and Collective Esteem of Inuit Children in Arctic Quebec

    ERIC Educational Resources Information Center

    Bougie, Evelyne; Wright, Stephen C.; Taylor, Donald M.

    2003-01-01

    This research explored the impact of the abrupt shift from heritage-language to dominant-language education on Inuit children's personal and collective self-esteem. Specifically, the following question was addressed: will early heritage-language education serve as an inoculation against the potential negative impact of being submerged in a…

  8. Abrupt climate shift in the Western Mediterranean Sea.

    PubMed

    Schroeder, K; Chiggiato, J; Bryden, H L; Borghini, M; Ben Ismail, S

    2016-03-11

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected.

  9. Abrupt climate shift in the Western Mediterranean Sea

    PubMed Central

    Schroeder, K.; Chiggiato, J.; Bryden, H. L.; Borghini, M.; Ben Ismail, S.

    2016-01-01

    One century of oceanographic measurements has evidenced gradual increases in temperature and salinity of western Mediterranean water masses, even though the vertical stratification has basically remained unchanged. Starting in 2005, the basic structure of the intermediate and deep layers abruptly changed. We report here evidence of reinforced thermohaline variability in the deep western basin with significant dense water formation events producing large amounts of warmer, saltier and denser water masses than ever before. We provide a detailed chronological order to these changes, giving an overview of the new water masses and following their route from the central basin interior to the east (toward the Tyrrhenian) and toward the Atlantic Ocean. As a consequence of this climate shift, new deep waters outflowing through Gibraltar will impact the North Atlantic in terms of salt and heat input. In addition, modifications in the Mediterranean abyssal ecosystems and biogeochemical cycles are to be expected. PMID:26965790

  10. Extrinsic regime shifts drive abrupt changes in regeneration dynamics at upper treeline in the Rocky Mountains, U.S.A.

    PubMed

    Elliott, Grant P

    2012-07-01

    Given the widespread and often dramatic influence of climate change on terrestrial ecosystems, it is increasingly common for abrupt threshold changes to occur, yet explicitly testing for climate and ecological regime shifts is lacking in climatically sensitive upper treeline ecotones. In this study, quantitative evidence based on empirical data is provided to support the key role of extrinsic, climate-induced thresholds in governing the spatial and temporal patterns of tree establishment in these high-elevation environments. Dendroecological techniques were used to reconstruct a 420-year history of regeneration dynamics within upper treeline ecotones along a latitudinal gradient (approximately 44-35 degrees N) in the Rocky Mountains. Correlation analysis was used to assess the possible influence of minimum and maximum temperature indices and cool-season (November-April) precipitation on regional age-structure data. Regime-shift analysis was used to detect thresholds in tree establishment during the entire period of record (1580-2000), temperature variables significantly Correlated with establishment during the 20th century, and cool-season precipitation. Tree establishment was significantly correlated with minimum temperature during the spring (March-May) and cool season. Regime-shift analysis identified an abrupt increase in regional tree establishment in 1950 (1950-1954 age class). Coincident with this period was a shift toward reduced cool-season precipitation. The alignment of these climate conditions apparently triggered an abrupt increase in establishment that was unprecedented during the period of record. Two main findings emerge from this research that underscore the critical role of climate in governing regeneration dynamics within upper treeline ecotones. (1) Regional climate variability is capable of exceeding bioclimatic thresholds, thereby initiating synchronous and abrupt changes in the spatial and temporal patterns of tree establishment at broad

  11. Could gradual changes in Holocene Saharan landscape have caused the observed abrupt shift in North Atlantic dust deposition?

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2017-09-01

    The abrupt change in North Atlantic dust deposition found in sediment records has been associated with a rapid large scale transition of Holocene Saharan landscape. We hypothesize that gradual changes in the landscape may have caused this abrupt shift in dust deposition either because of the non-linearity in dust activation or because of the heterogeneous distribution of major dust sources. To test this hypothesis, we investigate the response of North Atlantic dust deposition to a prescribed 1) gradual and spatially homogeneous decrease and 2) gradual southward retreat of North African vegetation and lakes during the Holocene using the aerosol-climate model ECHAM-HAM. In our simulations, we do not find evidence of an abrupt increase in dust deposition as observed in marine sediment records along the Northwest African margin. We conclude that such gradual changes in landscape are not sufficient to explain the observed abrupt changes in dust accumulation in marine sediment records. Instead, our results point to a rapid large-scale retreat of vegetation and lakes in the area of significant dust sources.

  12. Analysis of abrupt transitions in ecological systems

    USDA-ARS?s Scientific Manuscript database

    The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the l...

  13. Anticipating abrupt shifts in temporal evolution of probability of eruption

    NASA Astrophysics Data System (ADS)

    Rohmer, J.; Loschetter, A.

    2016-04-01

    Estimating the probability of eruption by jointly accounting for different sources of monitoring parameters over time is a key component for volcano risk management. In the present study, we are interested in the transition from a state of low-to-moderate probability value to a state of high probability value. By using the data of MESIMEX exercise at the Vesuvius volcano, we investigated the potential for time-varying indicators related to the correlation structure or to the variability of the probability time series for detecting in advance this critical transition. We found that changes in the power spectra and in the standard deviation estimated over a rolling time window both present an abrupt increase, which marks the approaching shift. Our numerical experiments revealed that the transition from an eruption probability of 10-15% to > 70% could be identified up to 1-3 h in advance. This additional lead time could be useful to place different key services (e.g., emergency services for vulnerable groups, commandeering additional transportation means, etc.) on a higher level of alert before the actual call for evacuation.

  14. Abrupt shift in the observed runoff from the southwestern Greenland ice sheet

    PubMed Central

    Ahlstrøm, Andreas P.; Petersen, Dorthe; Langen, Peter L.; Citterio, Michele; Box, Jason E.

    2017-01-01

    The recent decades of accelerating mass loss of the Greenland ice sheet have arisen from an increase in both surface meltwater runoff and ice flow discharge from tidewater glaciers. Despite the role of the Greenland ice sheet as the dominant individual cryospheric contributor to sea level rise in recent decades, no observational record of its mass loss spans the 30-year period needed to assess its climatological state. We present for the first time a 40-year (1975–2014) time series of observed meltwater discharge from a >6500-km2 catchment of the southwestern Greenland ice sheet. We find that an abrupt 80% increase in runoff occurring between the 1976–2002 and 2003–2014 periods is due to a shift in atmospheric circulation, with meridional exchange events occurring more frequently over Greenland, establishing the first observation-based connection between ice sheet runoff and climate change. PMID:29242827

  15. Discrepancy and Disliking Do Not Induce Negative Opinion Shifts

    PubMed Central

    Flache, Andreas; Mäs, Michael

    2016-01-01

    Both classical social psychological theories and recent formal models of opinion differentiation and bi-polarization assign a prominent role to negative social influence. Negative influence is defined as shifts away from the opinion of others and hypothesized to be induced by discrepancy with or disliking of the source of influence. There is strong empirical support for the presence of positive social influence (a shift towards the opinion of others), but evidence that large opinion differences or disliking could trigger negative shifts is mixed. We examine positive and negative influence with controlled exposure to opinions of other individuals in one experiment and with opinion exchange in another study. Results confirm that similarities induce attraction, but results do not support that discrepancy or disliking entails negative influence. Instead, our findings suggest a robust positive linear relationship between opinion distance and opinion shifts. PMID:27333160

  16. Slowing down as an early warning signal for abrupt climate change.

    PubMed

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-09-23

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective.

  17. Slowing down as an early warning signal for abrupt climate change

    PubMed Central

    Dakos, Vasilis; Scheffer, Marten; van Nes, Egbert H.; Brovkin, Victor; Petoukhov, Vladimir; Held, Hermann

    2008-01-01

    In the Earth's history, periods of relatively stable climate have often been interrupted by sharp transitions to a contrasting state. One explanation for such events of abrupt change is that they happened when the earth system reached a critical tipping point. However, this remains hard to prove for events in the remote past, and it is even more difficult to predict if and when we might reach a tipping point for abrupt climate change in the future. Here, we analyze eight ancient abrupt climate shifts and show that they were all preceded by a characteristic slowing down of the fluctuations starting well before the actual shift. Such slowing down, measured as increased autocorrelation, can be mathematically shown to be a hallmark of tipping points. Therefore, our results imply independent empirical evidence for the idea that past abrupt shifts were associated with the passing of critical thresholds. Because the mechanism causing slowing down is fundamentally inherent to tipping points, it follows that our way to detect slowing down might be used as a universal early warning signal for upcoming catastrophic change. Because tipping points in ecosystems and other complex systems are notoriously hard to predict in other ways, this is a promising perspective. PMID:18787119

  18. An abrupt slowdown of Atlantic Meridional Overturning Circulation during 1915-1935 induced by solar forcing in a coupled GCM

    NASA Astrophysics Data System (ADS)

    Lin, P.; Song, Y.; Yu, Y.; Liu, H.

    2014-06-01

    In this study, we explore an abrupt change of Atlantic Meridional Overturning Circulation (AMOC) apparent in the historical run simulated by the second version of the Flexible Global Ocean-Atmosphere-Land System model - Spectral Version 2 (FGOALS-s2). The abrupt change is noted during the period from 1915 to 1935, in which the maximal AMOC value is weakened beyond 6 Sv (1 Sv = 106 m3 s-1). The abrupt signal first occurs at high latitudes (north of 46° N), then shifts gradually to middle latitudes (∼35° N) three to seven years later. The weakened AMOC can be explained in the following. The weak total solar irradiance (TIS) during early twentieth century decreases pole-to-equator temperature gradient in the upper stratosphere. The North polar vortex is weakened, which forces a negative North Atlantic Oscillation (NAO) phase during 1905-1914. The negative phase of NAO induces anomalous easterly winds in 50-70° N belts, which decrease the release of heat fluxes from ocean to atmosphere and induce surface warming over these regions. Through the surface ice-albedo feedback, the warming may lead to continuously melting sea ice in Baffin Bay and Davis Strait, which results in freshwater accumulation. This can lead to salinity and density reductions and then an abrupt slowdown of AMOC. Moreover, due to increased TIS after 1914, the enhanced Atlantic northward ocean heat transport from low to high latitudes induces an abrupt warming of sea surface temperature or upper ocean temperature in mid-high latitudes, which can also weaken the AMOC. The abrupt change of AMOC also appears in the PiControl run, which is associated with the lasting negative NAO phases due to natural variability.

  19. Banning Fisheries Discards Abruptly Has a Negative Impact on the Population Dynamics of Charismatic Marine Megafauna.

    PubMed

    Fondo, Esther N; Chaloupka, Milani; Heymans, Johanna J; Skilleter, Greg A

    2015-01-01

    Food subsidies have the potential to modify ecosystems and affect the provision of goods and services. Predictable Anthropogenic Food Subsidies (PAFS) modify ecosystems by altering ecological processes and food webs. The global concern over the effects of PAFS in ecosystems has led to development of environmental policies aimed at curbing the production or ultimately banning of PAFS. However, the effects of reducing or banning PAFS are not known. We explore the consequences of PAFS removal in a marine ecosystem under two scenarios: 1) gradual reduction, or 2) an abrupt ban, using a mass balance model to test these hypotheses-The reduction or loss of PAFS will: i) modify trophic levels and food webs through effects on foraging by opportunistic species, ii) increase the resilience of opportunistic species to food shortages, and iii) modify predator-prey interactions through shifts in prey consumption. We found that PAFS lower the trophic levels of opportunistic scavengers and increase their food pathways. Scavengers are able to switch prey when PAFS are reduced gradually but they decline when PAFS are abruptly banned. PAFS reduction to a certain minimal level causes a drop in the ecosystem's stability. We recommend gradual reduction of PAFS to a minimal level that would maintain the ecosystem's stability and allow species exploiting PAFS to habituate to the food subsidy reduction.

  20. Thyroperoxidase and thyroglobulin antibodies in early pregnancy and placental abruption.

    PubMed

    Haddow, James E; McClain, Monica R; Palomaki, Glenn E; Neveux, Louis M; Lambert-Messerlian, Geralyn; Canick, Jacob A; Malone, Fergal D; Porter, T Flint; Nyberg, David A; Bernstein, Peter S; D'Alton, Mary E

    2011-02-01

    To estimate the relationship between thyroid antibodies and placental abruption. This cohort study assesses thyroperoxidase and thyroglobulin antibodies in relation to placental abruption among 10,062 women with singleton viable pregnancies (from the First and Second Trimester Risk of Aneuploidy [FaSTER] trial). A thyroperoxidase antibody cutoff of 50 international units/mL is used for comparison with published data from another cohort. Women with elevated thyroperoxidase antibody levels in the first and second trimesters have a higher rate of placental abruption than antibody-negative women. This relationship is less strong in the first trimester (1.51% compared with 0.83%; odds ratio [OR], 1.83; 95% confidence interval [CI], 0.99-3.37) than in the second trimester (1.78% compared with 0.82%; OR, 2.20; 95% CI, 1.21-3.99). A similar, but weaker, relationship is present for thyroglobulin antibodies. Sixty-four of 782 thyroperoxidase antibody-positive pregnancies without abruption become negative by the second trimester; one pregnancy with abruption becomes antibody-positive. Odds ratios for pregnancies with both thyroperoxidase and thyroglobulin antibody elevations are also higher (first trimester: OR, 2.10; 95% CI, 0.91-4.86; second trimester: OR, 2.73; 95% CI, 1.17-6.33). The present data confirm an association between thyroid antibody elevations and placental abruption described in a recent report. These findings, however, do not provide support for recommending routine testing for thyroid antibodies during pregnancy. II.

  1. Aversive properties of negative incentive shifts in Fischer 344 and Lewis rats

    PubMed Central

    Brewer, Adam; Johnson, Patrick; Stein, Jeff; Schlund, Michael; Williams, Dean C.

    2018-01-01

    Research on incentive contrast highlights that reward value is not absolute but rather is based upon comparisons we make to rewards we have received and expect to receive. Both human and nonhuman studies on incentive contrast show that shifting from a larger more-valued reward to a smaller less-valued reward is associated with long periods of nonresponding—a negative contrast effect. In this investigation, we used two different genetic rat strains, Fischer 344 and Lewis rats that putatively differ in their sensitivity to aversive stimulation, to assess the aversive properties of large-to-small reward shifts (negative incentive shifts). Additionally, we examined the extent to which increasing cost (fixed-ratio requirements) modulates negative contrast effects. In the presence of a cue that signaled the upcoming reward magnitude, lever pressing was reinforced with one of two different magnitudes of food (large or small). This design created two contrast shifts (small-to-large, large-to-small) and two shifts used as control conditions (small-to-small, large-to-large). Results showed a significant interaction between rat strain and cost requirements only during the negative incentive shift with the emotionally reactive Fischer 344 rats exhibiting significantly longer response latencies with increasing cost, highlighting greater negative contrast. These findings are more consistent with emotionality accounts of negative contrast and results of neurophysiological research that suggests shifting from a large to a small reward is aversive. Findings also highlight how subjective reward value and motivation is a product of gene-environment interactions. PMID:27864048

  2. Negative symptom domain prevalence across diagnostic boundaries: The relevance of diagnostic shifts.

    PubMed

    Lyne, John; Renwick, Laoise; O'Donoghue, Brian; Kinsella, Anthony; Malone, Kevin; Turner, Niall; O'Callaghan, Eadbhard; Clarke, Mary

    2015-08-30

    Negative symptoms are included in diagnostic manuals as part of criteria for schizophrenia spectrum psychoses only, however some studies have found their presence in other diagnoses. This study sought to clarify negative symptom domain prevalence across diagnostic categories, while investigating whether negative symptoms predicted diagnostic shift over time. Scale for the Assessment of Negative Symptoms (SANS) data were collected at first presentation in 197 individuals presenting with first episode psychosis and again at one year follow-up assessment. Negative symptoms were highest among individuals with schizophrenia and among those whose diagnosis shifted from non-schizophrenia spectrum at baseline to schizophrenia spectrum at follow-up. In a non-schizophrenia spectrum group negative symptoms at baseline were not a significant predictor of diagnostic shift to schizophrenia spectrum diagnoses. The study suggests negative symptoms can present among individuals with non-schizophrenia spectrum diagnoses, although this is most relevant for individuals following diagnostic shift from non-schizophrenia spectrum to schizophrenia spectrum diagnoses. The findings support introduction of a negative symptom dimension when describing a range of psychotic illnesses, and indicate that further research investigating the evolution of negative symptoms in non-schizophrenia diagnoses is needed. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  3. High-resolution Greenland ice core data show abrupt climate change happens in few years.

    PubMed

    Steffensen, Jørgen Peder; Andersen, Katrine K; Bigler, Matthias; Clausen, Henrik B; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Arny E; Svensson, Anders; White, James W C

    2008-08-01

    The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.

  4. Climate-driven shifts in continental net primary production implicated as a driver of a recent abrupt increase in the land carbon sink

    NASA Astrophysics Data System (ADS)

    Buermann, Wolfgang; Beaulieu, Claudie; Parida, Bikash; Medvigy, David; Collatz, George J.; Sheffield, Justin; Sarmiento, Jorge L.

    2016-03-01

    The world's ocean and land ecosystems act as sinks for anthropogenic CO2, and over the last half century their combined sink strength grew steadily with increasing CO2 emissions. Recent analyses of the global carbon budget, however, have uncovered an abrupt, substantial ( ˜ 1 PgC yr-1) and sustained increase in the land sink in the late 1980s whose origin remains unclear. In the absence of this prominent shift in the land sink, increases in atmospheric CO2 concentrations since the late 1980s would have been ˜ 30 % larger than observed (or ˜ 12 ppm above current levels). Global data analyses are limited in regards to attributing causes to changes in the land sink because different regions are likely responding to different drivers. Here, we address this challenge by using terrestrial biosphere models constrained by observations to determine if there is independent evidence for the abrupt strengthening of the land sink. We find that net primary production significantly increased in the late 1980s (more so than heterotrophic respiration), consistent with the inferred increase in the global land sink, and that large-scale climate anomalies are responsible for this shift. We identify two key regions in which climatic constraints on plant growth have eased: northern Eurasia experienced warming, and northern Africa received increased precipitation. Whether these changes in continental climates are connected is uncertain, but North Atlantic climate variability is important. Our findings suggest that improved understanding of climate variability in the North Atlantic may be essential for more credible projections of the land sink under climate change.

  5. Abrupt warming of the Red Sea

    NASA Astrophysics Data System (ADS)

    Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

    2011-07-01

    Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

  6. Extensive wildfires, climate change, and an abrupt state change in subalpine ribbon forests, Colorado.

    PubMed

    Calder, W John; Shuman, Bryan

    2017-10-01

    Ecosystems may shift abruptly when the effects of climate change and disturbance interact, and landscapes with regularly patterned vegetation may be especially vulnerable to abrupt shifts. Here we use a fossil pollen record from a regularly patterned ribbon forest (alternating bands of forests and meadows) in Colorado to examine whether past changes in wildfire and climate produced abrupt vegetation shifts. Comparing the percentages of conifer pollen with sedimentary δ 18 O data (interpreted as an indicator of temperature or snow accumulation) indicates a first-order linear relationship between vegetation composition and climate change with no detectable lags over the past 2,500 yr (r = 0.55, P < 0.001). Additionally, however, we find that the vegetation changed abruptly within a century of extensive wildfires, which were recognized in a previous study to have burned approximately 80% of the surrounding 1,000 km 2 landscape 1,000 yr ago when temperatures rose ~0.5°C. The vegetation change was larger than expected from the effects of climate change alone. Pollen assemblages changed from a composition associated with closed subalpine forests to one similar to modern ribbon forests. Fossil pollen assemblages then remained like those from modern ribbon forests for the following ~1,000 yr, providing a clear example of how extensive disturbances can trigger persistent new vegetation states and alter how vegetation responds to climate. © 2017 by the Ecological Society of America.

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

    PubMed

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

    2016-04-01

    In two national samples, we examined the influence of interracial exposure in one's local environment on the dynamic process underlying race perception and its evaluative consequences. Using a mouse-tracking paradigm, we found in Study 1 that White individuals with low interracial exposure exhibited a unique effect of abrupt, unstable White-Black category shifting during real-time perception of mixed-race faces, consistent with predictions from a neural-dynamic model of social categorization and computational simulations. In Study 2, this shifting effect was replicated and shown to predict a trust bias against mixed-race individuals and to mediate the effect of low interracial exposure on that trust bias. Taken together, the findings demonstrate that interracial exposure shapes the dynamics through which racial categories activate and resolve during real-time perceptions, and these initial perceptual dynamics, in turn, may help drive evaluative biases against mixed-race individuals. Thus, lower-level perceptual aspects of encounters with racial ambiguity may serve as a foundation for mixed-race prejudice. © The Author(s) 2016.

  8. Finding Intervals of Abrupt Change in Earth Science Data

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Shekhar, S.; Liess, S.

    2011-12-01

    In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset reasonably fast. In earth science data (e.g., climate data), it is often observed that a persistently abrupt change in value occurs in a certain time-period or spatial interval. For example, abrupt climate change is defined as an unusually large shift of precipitation, temperature, etc, that occurs during a relatively short time period. A similar change pattern can also be found in geographical space, representing a sharp transition of the environment (e.g., vegetation between different ecological zones). Identifying such intervals of change from earth science datasets is a crucial step for understanding and attributing the underlying phenomenon. However, inconsistencies in these noisy datasets can obstruct the major change trend, and more importantly can complicate the search of the beginning and end points of the interval of change. Also, the large volume of data makes it challenging to process the dataset fast. In this work, we analyze earth science data using a novel, automated data mining approach to identify spatial/temporal intervals of persistent, abrupt change. We first

  9. Abrupt climate-independent fire regime changes

    USGS Publications Warehouse

    Pausas, Juli G.; Keeley, Jon E.

    2014-01-01

    Wildfires have played a determining role in distribution, composition and structure of many ecosystems worldwide and climatic changes are widely considered to be a major driver of future fire regime changes. However, forecasting future climatic change induced impacts on fire regimes will require a clearer understanding of other drivers of abrupt fire regime changes. Here, we focus on evidence from different environmental and temporal settings of fire regimes changes that are not directly attributed to climatic changes. We review key cases of these abrupt fire regime changes at different spatial and temporal scales, including those directly driven (i) by fauna, (ii) by invasive plant species, and (iii) by socio-economic and policy changes. All these drivers might generate non-linear effects of landscape changes in fuel structure; that is, they generate fuel changes that can cross thresholds of landscape continuity, and thus drastically change fire activity. Although climatic changes might contribute to some of these changes, there are also many instances that are not primarily linked to climatic shifts. Understanding the mechanism driving fire regime changes should contribute to our ability to better assess future fire regimes.

  10. Ecological forecasting in the presence of abrupt regime shifts

    NASA Astrophysics Data System (ADS)

    Dippner, Joachim W.; Kröncke, Ingrid

    2015-10-01

    Regime shifts may cause an intrinsic decrease in the potential predictability of marine ecosystems. In such cases, forecasts of biological variables fail. To improve prediction of long-term variability in environmental variables, we constructed a multivariate climate index and applied it to forecast ecological time series. The concept is demonstrated herein using climate and macrozoobenthos data from the southern North Sea. Special emphasis is given to the influence of selection of length of fitting period to the quality of forecast skill especially in the presence of regime shifts. Our results indicate that the performance of multivariate predictors in biological forecasts is much better than that of single large-scale climate indices, especially in the presence of regime shifts. The approach used to develop the index is generally applicable to all geographical regions in the world and to all areas of marine biology, from the species level up to biodiversity. Such forecasts are of vital interest for practical aspects of the sustainable management of marine ecosystems and the conservation of ecosystem goods and services.

  11. Paradox of the peak-PCIM (Paleocene Carbon Isotope Maxima; ~57.8Ma) and Abrupt Global Warming

    NASA Astrophysics Data System (ADS)

    Harper, D. T.; Hoenisch, B.; Zachos, J. C.

    2015-12-01

    The Paleocene Carbon Isotope Maxima (PCIM; ~57.8Ma) represents a major transition in global δ13C during the late Paleocene, when the long-term positive trend in δ13C reversed from positive to negative. The peak-PCIM (~57.7Ma) has been tightly resolved in new high-resolution, astronomically-tuned benthic isotope records from IODP Sites 1209 (Pacific) and 1262 (Atlantic), which show the final phase of δ13C enrichment as abrupt (~1‰ in <100kyrs) and coinciding with a 0.5‰ decline in benthic δ18O indicative of 2-3ºC of bottom water warming, effectively marking the onset of a gradual 8Myr long warming trend [Littler et al., EPSL 2014]. Typically, during the Paleogene on orbital time scales, warming is observed during intervals of δ13C depletion, consistent with release of isotopically light carbon to the atmosphere. This event, which has the appearance of a bifurcation in the long-term coupling of climate system and the carbon cycle, poses an interesting paradox as any rapid carbon release to the atmosphere should, in theory, create a negative excursion because all of the major carbon sources are isotopically light, whether volcanic outgassing, weathering/oxidation of organic carbon, or methane release [Dunkley-Jones et al., Phil. Trans. R. Soc. A 2010]. If global, there are several testable mechanisms that may explain the shift including increase in burial flux of light carbon, a reduction in heavy carbon burial flux, or a large-scale circulation change perhaps associated with the transition of a major oceanic gateway. Using trace metal (B/Ca and Mg/Ca) and stable isotope (δ11B, δ18O, and δ13C) geochemistry, here we establish the nature of the peak-PCIM at sites from 3 different ocean basins (IODP Sites 690, 1209, and 1262) and begin to test several of the possible mechanisms for change. Mg/Ca in mixed-layer planktonic foraminifera show 2-3°C of sea surface warming coinciding with, and abrupt as, the benthic carbon isotope enrichment at all sites. Bottom

  12. Response of the tropical Pacific to abrupt climate change 8,200 years ago

    NASA Astrophysics Data System (ADS)

    Atwood, A. R.; Battisti, D.; Bitz, C. M.; Sachs, J. P.

    2017-12-01

    The relatively stable climate of the Holocene epoch was punctuated by a period of large and abrupt climate change ca. 8,200 yr BP, when an outburst of glacial meltwater into the Labrador Sea drove large and abrupt climate changes across the globe. However, little is known about the response of the tropical Pacific to this event. We present the first evidence for large perturbations to the eastern tropical Pacific climate, based on sedimentary biomarker and hydrogen isotopic records from a freshwater lake in the Galápagos Islands. We inform these reconstructions with freshwater forcing simulations performed with the Community Climate System Model version 4. Together, the biomarker records and model simulations provide evidence for a mechanistic link between (1) a southward shift of the Intertropical Convergence Zone in the eastern equatorial Pacific and (2) decreased frequency and/or intensity of Eastern Pacific El Niño events during the 8,200 BP event. While climate theory and modeling studies support a southward shift of the ITCZ in response to a weakened AMOC, the dynamical drivers for the observed change in ENSO variability are less well developed. To explore these linkages, we perform simulations with an intermediate complexity model of the tropical Pacific. These results provide valuable insight into the controls of tropical Pacific climate variability and the mechanisms behind the global response to abrupt climate change.

  13. A holistic view of marine regime shifts

    PubMed Central

    Conversi, Alessandra; Dakos, Vasilis; Gårdmark, Anna; Ling, Scott; Folke, Carl; Mumby, Peter J.; Greene, Charles; Edwards, Martin; Blenckner, Thorsten; Casini, Michele; Pershing, Andrew; Möllmann, Christian

    2015-01-01

    Understanding marine regime shifts is important not only for ecology but also for developing marine management that assures the provision of ecosystem services to humanity. While regime shift theory is well developed, there is still no common understanding on drivers, mechanisms and characteristic of abrupt changes in real marine ecosystems. Based on contributions to the present theme issue, we highlight some general issues that need to be overcome for developing a more comprehensive understanding of marine ecosystem regime shifts. We find a great divide between benthic reef and pelagic ocean systems in how regime shift theory is linked to observed abrupt changes. Furthermore, we suggest that the long-lasting discussion on the prevalence of top-down trophic or bottom-up physical drivers in inducing regime shifts may be overcome by taking into consideration the synergistic interactions of multiple stressors, and the special characteristics of different ecosystem types. We present a framework for the holistic investigation of marine regime shifts that considers multiple exogenous drivers that interact with endogenous mechanisms to cause abrupt, catastrophic change. This framework takes into account the time-delayed synergies of these stressors, which erode the resilience of the ecosystem and eventually enable the crossing of ecological thresholds. Finally, considering that increased pressures in the marine environment are predicted by the current climate change assessments, in order to avoid major losses of ecosystem services, we suggest that marine management approaches should incorporate knowledge on environmental thresholds and develop tools that consider regime shift dynamics and characteristics. This grand challenge can only be achieved through a holistic view of marine ecosystem dynamics as evidenced by this theme issue.

  14. Regime shifts and resilience in China's coastal ecosystems.

    PubMed

    Zhang, Ke

    2016-02-01

    Regime shift often results in large, abrupt, and persistent changes in the provision of ecosystem services and can therefore have significant impacts on human wellbeing. Understanding regime shifts has profound implications for ecosystem recovery and management. China's coastal ecosystems have experienced substantial deterioration within the past decades, at a scale and speed the world has never seen before. Yet, information about this coastal ecosystem change from a dynamics perspective is quite limited. In this review, I synthesize existing information on coastal ecosystem regime shifts in China and discuss their interactions and cascading effects. The accumulation of regime shifts in China's coastal ecosystems suggests that the desired system resilience has been profoundly eroded, increasing the potential of abrupt shifts to undesirable states at a larger scale, especially given multiple escalating pressures. Policy and management strategies need to incorporate resilience approaches in order to cope with future challenges and avoid major losses in China's coastal ecosystem services.

  15. Lead-Lag relationships? Asynchrounous and Abrupt Shifts in Atmospheric Circulation, Temperature, and Vegetation during the 8.2 ka Event in the Eastern Mediterranean at Tenaghi Philippon, Greece

    NASA Astrophysics Data System (ADS)

    Niedermeyer, E. M.; Mulch, A.; Pross, J.

    2017-12-01

    The "8.2 ka event" has been an abrupt and prominent climate perturbation during the Holocene, and is characterized by an episode of generally colder and dryer conditions in the Northern Hemisphere realm. However, evidence to what extent this event has had an impact on climate in the Mediterranean region is ambiguous, in particular with respect to rainfall, temperature and vegetation change on land. Here we present a new, high-resolution record (ø 15 years during the event) of paleotemperatures from the Tenaghi Philippon peat deposit, Eastern Macedonia, Greece, using the MBT'/CBT index based on brGDGTs (branched Glycerol-Dialkyl-Glycerol-Tetraethers). Our data show fairly stable temperatures before the event, which is initiated at 8.1 ka by an abrupt and continuous cooling during the first 35 years of the event. After a short, 10-year episode of minimum temperatures, the event is ended by a similarly abrupt and continuous warming within 38 years. Comparison of our record with a previous study of the stable hydrogen isotopic composition of higher-plant waxes (δDwax) on the same core1 shows that changes in temperature occurred simultaneously with shifts in atmospherics moisture sources (Mediterranean vs Atlantic). Interestingly, further comparison of our data with a previous palynological study of the same core2 reveals that changes in vegetation associated with the 8.2 ka event precede shifts in hydrology and temperature by 100 years. This suggests either pronounced changes in seasonality of temperature and rainfall after the onset of the 8.2 ka event, i.e. at the peak of the event, or that changes in local atmospheric circulation (moisture sources) and temperature where not the initial trigger of changes in vegetation. References: Pross, J., Kotthoff, U., Müller, U.C., Peyron, O., Dormoy, I., Schmiedl, G., Kalaitzidis, S. and Smith, A.M. (2009): Massive perturbation in terrestrial ecosystems of the Eastern Mediterranean region associated with the 8.2 kyr B

  16. The nature of abrupt climate change during the last glacial period from detailed isotopic records from the NGRIP ice core

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; Svensson, A.; Steffensen, J. P.; Johnsen, S. J.; White, J. W. C.

    2009-04-01

    Isotopic and chemical impurity records from Greenland ice cores with sub-annual resolution across three fast climate transitions of the last deglacial termination reveal complex patterns of environmental change for the onset of Greenland Interstadial 1 (GI-1 or Bølling), the onset of Greenland Stadial 1 (GS-1 or Younger Dryas), and the onset of the Holocene. In the NGRIP ice core each of these transitions is initiated by a 1-3 year mode shift in deuterium excess, which is a proxy for the Greenland precipitation moisture source. These mode shifts in deuterium excess are decoupled in time from the isotopic (deuterium and oxygen-18) transitions from which they are derived. In general the abrupt isotopic transitions follow the corresponding deuterium excess shifts and span decades rather than years. Similar data from GISP2 confirms the clear deuterium excess mode shifts for transitions from cold states to warm states; however the abrupt deuterium excess transition at the onset of GS-1 is not expressed in a similar way at GISP2. Ironically, it appears that this cooling at the beginning of the Younger Dryas, for which we have theories of the triggering event, is less clearly recorded than warming events, the triggering of which is still poorly understood. Along with other available paleo-data, these results indicate that the sum of an abrupt climate change is composed of multiple responses from different parts of the climate system. These responses can be separated by as little as a single year to a few decades and the collection of these responses result in a variety of abrupt transitions giving each a unique anatomy. Here we expand this type of analysis with new isotope, deuterium excess, and accumulation rate time series from NGRIP across the abrupt transitions associated with several interstadial events of the Last Glacial period (Dansgaard-Oeschger events). Indeed the temporal phasing of deuterium excess and the isotopic content of the ice can vary from one event

  17. The abrupt onset of the modern South Asian Monsoon winds.

    PubMed

    Betzler, Christian; Eberli, Gregor P; Kroon, Dick; Wright, James D; Swart, Peter K; Nath, Bejugam Nagender; Alvarez-Zarikian, Carlos A; Alonso-García, Montserrat; Bialik, Or M; Blättler, Clara L; Guo, Junhua Adam; Haffen, Sébastien; Horozal, Senay; Inoue, Mayuri; Jovane, Luigi; Lanci, Luca; Laya, Juan Carlos; Mee, Anna Ling Hui; Lüdmann, Thomas; Nakakuni, Masatoshi; Niino, Kaoru; Petruny, Loren M; Pratiwi, Santi D; Reijmer, John J G; Reolid, Jesús; Slagle, Angela L; Sloss, Craig R; Su, Xiang; Yao, Zhengquan; Young, Jeremy R

    2016-07-20

    The South Asian Monson (SAM) is one of the most intense climatic elements yet its initiation and variations are not well established. Dating the deposits of SAM wind-driven currents in IODP cores from the Maldives yields an age of 12. 9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of particulate organic matter. A weaker 'proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  18. Game-Changing Innovations: How Culture Can Change the Parameters of Its Own Evolution and Induce Abrupt Cultural Shifts.

    PubMed

    Kolodny, Oren; Creanza, Nicole; Feldman, Marcus W

    2016-12-01

    One of the most puzzling features of the prehistoric record of hominid stone tools is its apparent punctuation: it consists of abrupt bursts of dramatic change that separate long periods of largely unchanging technology. Within each such period, small punctuated cultural modifications take place. Punctuation on multiple timescales and magnitudes is also found in cultural trajectories from historical times. To explain these sharp cultural bursts, researchers invoke such external factors as sudden environmental change, rapid cognitive or morphological change in the hominids that created the tools, or replacement of one species or population by another. Here we propose a dynamic model of cultural evolution that accommodates empirical observations: without invoking external factors, it gives rise to a pattern of rare, dramatic cultural bursts, interspersed by more frequent, smaller, punctuated cultural modifications. Our model includes interdependent innovation processes that occur at different rates. It also incorporates a realistic aspect of cultural evolution: cultural innovations, such as those that increase food availability or that affect cultural transmission, can change the parameters that affect cultural evolution, thereby altering the population's cultural dynamics and steady state. This steady state can be regarded as a cultural carrying capacity. These parameter-changing cultural innovations occur very rarely, but whenever one occurs, it triggers a dramatic shift towards a new cultural steady state. The smaller and more frequent punctuated cultural changes, on the other hand, are brought about by innovations that spur the invention of further, related, technology, and which occur regardless of whether the population is near its cultural steady state. Our model suggests that common interpretations of cultural shifts as evidence of biological change, for example the appearance of behaviorally modern humans, may be unwarranted.

  19. Game-Changing Innovations: How Culture Can Change the Parameters of Its Own Evolution and Induce Abrupt Cultural Shifts

    PubMed Central

    2016-01-01

    One of the most puzzling features of the prehistoric record of hominid stone tools is its apparent punctuation: it consists of abrupt bursts of dramatic change that separate long periods of largely unchanging technology. Within each such period, small punctuated cultural modifications take place. Punctuation on multiple timescales and magnitudes is also found in cultural trajectories from historical times. To explain these sharp cultural bursts, researchers invoke such external factors as sudden environmental change, rapid cognitive or morphological change in the hominids that created the tools, or replacement of one species or population by another. Here we propose a dynamic model of cultural evolution that accommodates empirical observations: without invoking external factors, it gives rise to a pattern of rare, dramatic cultural bursts, interspersed by more frequent, smaller, punctuated cultural modifications. Our model includes interdependent innovation processes that occur at different rates. It also incorporates a realistic aspect of cultural evolution: cultural innovations, such as those that increase food availability or that affect cultural transmission, can change the parameters that affect cultural evolution, thereby altering the population’s cultural dynamics and steady state. This steady state can be regarded as a cultural carrying capacity. These parameter-changing cultural innovations occur very rarely, but whenever one occurs, it triggers a dramatic shift towards a new cultural steady state. The smaller and more frequent punctuated cultural changes, on the other hand, are brought about by innovations that spur the invention of further, related, technology, and which occur regardless of whether the population is near its cultural steady state. Our model suggests that common interpretations of cultural shifts as evidence of biological change, for example the appearance of behaviorally modern humans, may be unwarranted. PMID:28036346

  20. Abrupt climate change and extinction events

    NASA Technical Reports Server (NTRS)

    Crowley, Thomas J.

    1988-01-01

    There is a growing body of theoretical and empirical support for the concept of instabilities in the climate system, and indications that abrupt climate change may in some cases contribute to abrupt extinctions. Theoretical indications of instabilities can be found in a broad spectrum of climate models (energy balance models, a thermohaline model of deep-water circulation, atmospheric general circulation models, and coupled ocean-atmosphere models). Abrupt transitions can be of several types and affect the environment in different ways. There is increasing evidence for abrupt climate change in the geologic record and involves both interglacial-glacial scale transitions and the longer-term evolution of climate over the last 100 million years. Records from the Cenozoic clearly show that the long-term trend is characterized by numerous abrupt steps where the system appears to be rapidly moving to a new equilibrium state. The long-term trend probably is due to changes associated with plate tectonic processes, but the abrupt steps most likely reflect instabilities in the climate system as the slowly changing boundary conditions caused the climate to reach some threshold critical point. A more detailed analysis of abrupt steps comes from high-resolution studies of glacial-interglacial fluctuations in the Pleistocene. Comparison of climate transitions with the extinction record indicates that many climate and biotic transitions coincide. The Cretaceous-Tertiary extinction is not a candidate for an extinction event due to instabilities in the climate system. It is quite possible that more detailed comparisons and analysis will indicate some flaws in the climate instability-extinction hypothesis, but at present it appears to be a viable candidate as an alternate mechanism for causing abrupt environmental changes and extinctions.

  1. Adaptation to abrupt time shifts of the oscillator(s) controlling human circadian rhythms.

    PubMed Central

    Mills, J N; Minors, D S; Waterhouse, J M

    1978-01-01

    1. Thirty-six subjects in an isolation unit were subjected to time shifts of 12 hr, or of 8 hr in either direction. 2. The rhythms of body temperature and excretion of eight urinary constituents were studied before and after the shift, both on a usual nychthemeral routine and during 24 hr when they remained under constant conditions, awake, engaged in light, mainly sedentary activity, and consuming identical food and fluid every hour. 3. The rhythms on nychthemeral routine were defined by fitting cosine curves. On constant routine the rhythm after the shift was cross-correlated with the original rhythm, either with variable delay (or advance) or with an additive mixture between this variably shifted rhythm and the unshifted or a fully shifted rhythm. The process yielding the highest correlation coefficient was accepted as the best descriptor of the nature of adaptation. 4. A combination of two rhythms was observed more often for urinary sodium, chloride and phosphate than for other variables. 5. Adaptation appeared to have proceeded further after westward than eastward shifts, and this difference was particularly noticeable for urinary potassium, sodium and chloride. 6. Partial adaptation usually involved a phase delay, even after an eastward shift when a cumulative delay of 16 hr would be needed to achieve full adaptation and re-entrainment. 7. Observations under nychthemeral conditions often gave a false idea of the degree of adaptation. In particular, after an eastward shift the phase of the rhythms appeared to shift in the appropriate direction when studied under nychthemeral conditions whereas the endogenous oscillator either showed no consistent behaviour or, in the control of urate excretion, a shift in the wrong direction. 8. The implications for people undergoing time shifts, in the course of shift work or transmeridional flights, are indicated. PMID:745108

  2. Theory of collective opinion shifts: from smooth trends to abrupt swings

    NASA Astrophysics Data System (ADS)

    Michard, Q.; Bouchaud, J.-P.

    2005-09-01

    We unveil collective effects induced by imitation and social pressure by analyzing data from three different sources: birth rates, sales of cell phones and the drop of applause in concert halls. We interpret our results within the framework of the Random Field Ising Model, which is a threshold model for collective decisions accounting both for agent heterogeneity and social imitation. Changes of opinion can occur either abruptly or continuously, depending on the importance of herding effects. The main prediction of the model is a scaling relation between the height h of the speed of variation peak and its width w of the form h ˜w-κ, with κ= 2/3 for well connected populations. Our three sets of data are compatible with such a prediction, with κ≈0.62 for birth rates, κ≈0.71 for cell phones and κ≈0.64 for clapping. In this last case, we in fact observe that some clapping samples end discontinuously (w=0), as predicted by the model for strong enough imitation.

  3. Climatic and Societal Causes for Abrupt Environmental Change in the Mediterranean During the Common Era

    NASA Astrophysics Data System (ADS)

    Mensing, S. A.; Tunno, I.; Sagnotti, L.; Florindo, F.; Noble, P. J.; Archer, C.; Zimmerman, S. R. H.; Pavón-Carrasco, F. J.; Cifnani, G.; Passigli, S.; Piovesan, G.

    2015-12-01

    We compare climatic and societal causes for abrupt environmental change for the last 2000 years in the Rieti Basin, central Italy using high-resolution sedimentary paleoenvironmental proxies, historical documents, and annually resolved independent climate reconstructions of temperature and precipitation. Pollen zones, identified from temporally constrained cluster analysis, coincide with historic periods developed from well-established ceramic sequences corresponding to the Roman Imperial through Late Antique (1 to 600 CE) Early Medieval (600 to 875 CE), Medieval through Late Medieval (875 to 1400 CE), Renaissance and Modern (1400 to 1725 CE), and Contemporary periods (1725 CE to present). Non-metric dimensional scaling (NMDS) ordination showed that each temporal period occupied a unique ecologic space suggesting that a new landscape was created during each successive historic period. During Roman time, between 1 and 500 CE, a modest decline in forest coincides with a positive phase of the North Atlantic Oscillation (NAO) and drier climate; however mesophyllous forest is preserved. Steep decline in forest cover between 850 and 950 CE coincides with positive temperature anomalies in Europe and a positive NAO. Although this would seem to suggest climate as a cause, temperature and precipitation changes are modest and the magnitude and rapidity of the vegetation change suggests climate played a small role. Archaeological evidence from across Europe identifies socioeconomic factors that produced forest clearing. In contrast, cooler temperatures and a negative NAO (increased ppt) appears to have been a catalyst for land abandonment and forest recovery in the 13th to 14th centuries. The NAO produces opposite effects on societies in the eastern and western Mediterranean with the negative phase in 1400 CE leading to cool wet climate and land abandonment in central Italy but an abrupt shift to drier conditions and change from sedentary village life to nomadism in Syria.

  4. Missed detection of significant positive and negative shifts in gentamicin assay: implications for routine laboratory quality practices.

    PubMed

    Koerbin, Gus; Liu, Jiakai; Eigenstetter, Alex; Tan, Chin Hon; Badrick, Tony; Loh, Tze Ping

    2018-02-15

    A product recall was issued for the Roche/Hitachi Cobas Gentamicin II assays on 25 th May 2016 in Australia, after a 15 - 20% positive analytical shift was discovered. Laboratories were advised to employ the Thermo Fisher Gentamicin assay as an alternative. Following the reintroduction of the revised assay on 12 th September 2016, a second reagent recall was made on 20 th March 2017 after the discovery of a 20% negative analytical shift due to erroneous instrument adjustment factor. The practices of an index laboratory were examined to determine how the analytical shifts evaded detection by routine internal quality control (IQC) and external quality assurance (EQA) systems. The ability of the patient result-based approaches, including moving average (MovAvg) and moving sum of outliers (MovSO) approaches in detecting these shifts were examined. Internal quality control data of the index laboratory were acceptable prior to the product recall. The practice of adjusting IQC target following a change in assay method resulted in the missed negative shift when the revised Roche assay was reintroduced. While the EQA data of the Roche subgroup showed clear negative bias relative to other laboratory methods, the results were considered as possible 'matrix effect'. The MovAvg method detected the positive shift before the product recall. The MovSO did not detect the negative shift in the index laboratory but did so in another laboratory 5 days before the second product recall. There are gaps in current laboratory quality practices that leave room for analytical errors to evade detection.

  5. Persistent millennial-scale shifts in moisture regimes in western Canada during the past six millennia

    PubMed Central

    Cumming, Brian F.; Laird, Kathleen R.; Bennett, Joseph R.; Smol, John P.; Salomon, Anne K.

    2002-01-01

    Inferences of past climatic conditions from a sedimentary record from Big Lake, British Columbia, Canada, over the past 5,500 years show strong millennial-scale patterns, which oscillate between periods of wet and drier climatic conditions. Higher frequency decadal- to centennial-scale fluctuations also occur within the dominant millennial-scale patterns. These changes in climatic conditions are based on estimates of changes in lake depth and salinity inferred from diatom assemblages in a well dated sediment core. After periods of relative stability, abrupt shifts in diatom assemblages and inferred climatic conditions occur approximately every 1,220 years. The correspondence of these shifts to millennial-scale variations in records of glacial expansion/recession and ice-rafting events in the Atlantic suggest that abrupt millennial-scale shifts are important to understanding climatic variability in North America during the mid- to late Holocene. Unfortunately, the spatial patterns and mechanisms behind these large and abrupt swings are poorly understood. Similar abrupt and prolonged changes in climatic conditions today could pose major societal challenges for many regions. PMID:12461174

  6. Persistent millennial-scale shifts in moisture regimes in western Canada during the past six millennia.

    PubMed

    Cumming, Brian F; Laird, Kathleen R; Bennett, Joseph R; Smol, John P; Salomon, Anne K

    2002-12-10

    Inferences of past climatic conditions from a sedimentary record from Big Lake, British Columbia, Canada, over the past 5,500 years show strong millennial-scale patterns, which oscillate between periods of wet and drier climatic conditions. Higher frequency decadal- to centennial-scale fluctuations also occur within the dominant millennial-scale patterns. These changes in climatic conditions are based on estimates of changes in lake depth and salinity inferred from diatom assemblages in a well dated sediment core. After periods of relative stability, abrupt shifts in diatom assemblages and inferred climatic conditions occur approximately every 1,220 years. The correspondence of these shifts to millennial-scale variations in records of glacial expansionrecession and ice-rafting events in the Atlantic suggest that abrupt millennial-scale shifts are important to understanding climatic variability in North America during the mid- to late Holocene. Unfortunately, the spatial patterns and mechanisms behind these large and abrupt swings are poorly understood. Similar abrupt and prolonged changes in climatic conditions today could pose major societal challenges for many regions.

  7. Climate-driven regime shifts in Arctic marine benthos

    PubMed Central

    Kortsch, Susanne; Primicerio, Raul; Beuchel, Frank; Renaud, Paul E.; Rodrigues, João; Lønne, Ole Jørgen; Gulliksen, Bjørn

    2012-01-01

    Climate warming can trigger abrupt ecosystem changes in the Arctic. Despite the considerable interest in characterizing and understanding the ecological impact of rapid climate warming in the Arctic, few long time series exist that allow addressing these research goals. During a 30-y period (1980–2010) of gradually increasing seawater temperature and decreasing sea ice cover in Svalbard, we document rapid and extensive structural changes in the rocky-bottom communities of two Arctic fjords. The most striking component of the benthic reorganization was an abrupt fivefold increase in macroalgal cover in 1995 in Kongsfjord and an eightfold increase in 2000 in Smeerenburgfjord. Simultaneous changes in the abundance of benthic invertebrates suggest that the macroalgae played a key structuring role in these communities. The abrupt, substantial, and persistent nature of the changes observed is indicative of a climate-driven ecological regime shift. The ecological processes thought to drive the observed regime shifts are likely to promote the borealization of these Arctic marine communities in the coming years. PMID:22891319

  8. Hemispheric asymmetry of ERPs and MMNs evoked by slow, fast and abrupt auditory motion.

    PubMed

    Shestopalova, L B; Petropavlovskaia, E A; Vaitulevich, S Ph; Nikitin, N I

    2016-10-01

    The current MMN study investigates whether brain lateralization during automatic discrimination of sound stimuli moving at different velocities is consistent with one of the three models of asymmetry: the right-hemispheric dominance model, the contralateral dominance model, or the neglect model. Auditory event-related potentials (ERPs) were recorded for three patterns of sound motion produced by linear or abrupt changes of interaural time differences. The slow motion (450deg/s) was used as standard, and the fast motion (620deg/s) and the abrupt sound shift served as deviants in the oddball blocks. All stimuli had the same onset/offset spatial positions. We compared the effects of the recording side (left, right) and of the direction of sound displacement (ipsi- or contralateral with reference to the side of recording) on the ERPs and mismatch negativity (MMN). Our results indicated different patterns of asymmetry for the ERPs and MMN responses. The ERPs showed a velocity-independent right-hemispheric dominance that emerged at the descending limb of N1 wave (at around 120-160ms) and could be related to overall context of the preattentive spatial perception. The MMNs elicited in the left hemisphere (at around 230-270ms) exhibited a contralateral dominance, whereas the right-hemispheric MMNs were insensitive to the direction of sound displacement. These differences in contralaterality between MMN responses produced by the left and the right hemisphere favour the neglect model of the preattentive motion processing indexed by MMN. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Understanding less than nothing: children's neural response to negative numbers shifts across age and accuracy.

    PubMed

    Gullick, Margaret M; Wolford, George

    2013-01-01

    We examined the brain activity underlying the development of our understanding of negative numbers, which are amounts lacking direct physical counterparts. Children performed a paired comparison task with positive and negative numbers during an fMRI session. As previously shown in adults, both pre-instruction fifth-graders and post-instruction seventh-graders demonstrated typical behavioral and neural distance effects to negative numbers, where response times and parietal and frontal activity increased as comparison distance decreased. We then determined the factors impacting the distance effect in each age group. Behaviorally, the fifth-grader distance effect for negatives was significantly predicted only by positive comparison accuracy, indicating that children who were generally better at working with numbers were better at comparing negatives. In seventh-graders, negative number comparison accuracy significantly predicted their negative number distance effect, indicating that children who were better at working with negative numbers demonstrated a more typical distance effect. Across children, as age increased, the negative number distance effect increased in the bilateral IPS and decreased frontally, indicating a frontoparietal shift consistent with previous numerical development literature. In contrast, as negative comparison task accuracy increased, the parietal distance effect increased in the left IPS and decreased in the right, possibly indicating a change from an approximate understanding of negatives' values to a more exact, precise representation (particularly supported by the left IPS) with increasing expertise. These shifts separately indicate the effects of increasing maturity generally in numeric processing and specifically in negative number understanding.

  10. Proprioceptive recalibration in the right and left hands following abrupt visuomotor adaptation.

    PubMed

    Salomonczyk, Danielle; Henriques, Denise Y P; Cressman, Erin K

    2012-03-01

    Previous studies have demonstrated that after reaching with misaligned visual feedback of the hand, one adapts his or her reaches and partially recalibrates proprioception, such that sense of felt hand position is shifted to match the seen hand position. However, to date, this has only been demonstrated in the right (dominant) hand following reach training with a visuomotor distortion in which the rotated cursor distortion was introduced gradually. As reach adaptation has been shown to differ depending on how the distortion is introduced (gradual vs. abrupt), we sought to examine proprioceptive recalibration following reach training with a cursor that was abruptly rotated 30° clockwise relative to hand motion. Furthermore, because the left and right arms have demonstrated selective advantages when matching visual and proprioceptive targets, respectively, we assessed proprioceptive recalibration in right-handed subjects following training with either the right or the left hand. On average, we observed shifts in felt hand position of approximately 7.6° following training with misaligned visual feedback of the hand, which is consistent with our previous findings in which the distortion was introduced gradually. Moreover, no difference was observed in proprioceptive recalibration across the left and right hands. These findings suggest that proprioceptive recalibration is a robust process that arises symmetrically in the two hands following visuomotor adaptation regardless of the initial magnitude of the error signal.

  11. Population age and initial density in a patchy environment affect the occurrence of abrupt transitions in a birth-and-death model of Taylor's law

    USGS Publications Warehouse

    Jiang, Jiang; DeAngelis, Donald L.; Zhang, B.; Cohen, J.E.

    2014-01-01

    Taylor's power law describes an empirical relationship between the mean and variance of population densities in field data, in which the variance varies as a power, b, of the mean. Most studies report values of b varying between 1 and 2. However, Cohen (2014a) showed recently that smooth changes in environmental conditions in a model can lead to an abrupt, infinite change in b. To understand what factors can influence the occurrence of an abrupt change in b, we used both mathematical analysis and Monte Carlo samples from a model in which populations of the same species settled on patches, and each population followed independently a stochastic linear birth-and-death process. We investigated how the power relationship responds to a smooth change of population growth rate, under different sampling strategies, initial population density, and population age. We showed analytically that, if the initial populations differ only in density, and samples are taken from all patches after the same time period following a major invasion event, Taylor's law holds with exponent b=1, regardless of the population growth rate. If samples are taken at different times from patches that have the same initial population densities, we calculate an abrupt shift of b, as predicted by Cohen (2014a). The loss of linearity between log variance and log mean is a leading indicator of the abrupt shift. If both initial population densities and population ages vary among patches, estimates of b lie between 1 and 2, as in most empirical studies. But the value of b declines to ~1 as the system approaches a critical point. Our results can inform empirical studies that might be designed to demonstrate an abrupt shift in Taylor's law.

  12. Fisheries portfolio diversification and turnover buffer Alaskan fishing communities from abrupt resource and market changes

    PubMed Central

    Cline, Timothy J.; Schindler, Daniel E.; Hilborn, Ray

    2017-01-01

    Abrupt shifts in natural resources and their markets are a ubiquitous challenge to human communities. Building resilient social-ecological systems requires approaches that are robust to uncertainty and to regime shifts. Harvesting diverse portfolios of natural resources and adapting portfolios in response to change could stabilize economies reliant on natural resources and their markets, both of which are prone to unpredictable shifts. Here we use fisheries catch and revenue data from Alaskan fishing communities over 34 years to test whether diversification and turnover in the composition of fishing opportunities increased economic stability during major ocean and market regime shifts in 1989. More than 85% of communities show reduced fishing revenues following these regime shifts. However, communities with the highest portfolio diversity and those that could opportunistically shift the composition of resources they harvest, experienced negligible or even positive changes in revenue. Maintaining diversity in economic opportunities and enabling turnover facilitates sustainability of communities reliant on renewable resources facing uncertain futures. PMID:28091534

  13. Abrupt recent shift in δ13C and δ15N values in Adélie penguin eggshell in Antarctica

    PubMed Central

    Emslie, Steven D.; Patterson, William P.

    2007-01-01

    Stable isotope values of carbon (δ13C) and nitrogen (δ15N) in blood, feathers, eggshell, and bone have been used in seabird studies since the 1980s, providing a valuable source of information on diet, foraging patterns, and migratory behavior in these birds. These techniques can also be applied to fossil material when preservation of bone and other tissues is sufficient. Excavations of abandoned Adélie penguin (Pygoscelis adeliae) colonies in Antarctica often provide well preserved remains of bone, feathers, and eggshell dating from hundreds to thousands of years B.P. Herein we present an ≈38,000-year time series of δ13C and δ15N values of Adélie penguin eggshell from abandoned colonies located in three major regions of Antarctica. Results indicate an abrupt shift to lower-trophic prey in penguin diets within the past ≈200 years. We posit that penguins only recently began to rely on krill as a major portion of their diet, in conjunction with the removal of baleen whales and krill-eating seals during the historic whaling era. Our results support the “krill surplus” hypothesis that predicts excess krill availability in the Southern Ocean after this period of exploitation. PMID:17620620

  14. Abrupt climate change: can society cope?

    PubMed

    Hulme, Mike

    2003-09-15

    Consideration of abrupt climate change has generally been incorporated neither in analyses of climate-change impacts nor in the design of climate adaptation strategies. Yet the possibility of abrupt climate change triggered by human perturbation of the climate system is used to support the position of both those who urge stronger and earlier mitigative action than is currently being contemplated and those who argue that the unknowns in the Earth system are too large to justify such early action. This paper explores the question of abrupt climate change in terms of its potential implications for society, focusing on the UK and northwest Europe in particular. The nature of abrupt climate change and the different ways in which it has been defined and perceived are examined. Using the example of the collapse of the thermohaline circulation (THC), the suggested implications for society of abrupt climate change are reviewed; previous work has been largely speculative and has generally considered the implications only from economic and ecological perspectives. Some observations about the implications from a more social and behavioural science perspective are made. If abrupt climate change simply implies changes in the occurrence or intensity of extreme weather events, or an accelerated unidirectional change in climate, the design of adaptation to climate change can proceed within the existing paradigm, with appropriate adjustments. Limits to adaptation in some sectors or regions may be reached, and the costs of appropriate adaptive behaviour may be large, but strategy can develop on the basis of a predicted long-term unidirectional change in climate. It would be more challenging, however, if abrupt climate change implied a directional change in climate, as, for example, may well occur in northwest Europe following a collapse of the THC. There are two fundamental problems for society associated with such an outcome: first, the future changes in climate currently being

  15. Abrupt Change in Ecological Systems: Inference and Diagnosis.

    PubMed

    Ratajczak, Zak; Carpenter, Stephen R; Ives, Anthony R; Kucharik, Christopher J; Ramiadantsoa, Tanjona; Stegner, M Allison; Williams, John W; Zhang, Jien; Turner, Monica G

    2018-05-18

    Abrupt ecological changes are, by definition, those that occur over short periods of time relative to typical rates of change for a given ecosystem. The potential for such changes is growing due to anthropogenic pressures, which challenges the resilience of societies and ecosystems. Abrupt ecological changes are difficult to diagnose because they can arise from a variety of circumstances, including rapid changes in external drivers (e.g., climate, or resource extraction), nonlinear responses to gradual changes in drivers, and interactions among multiple drivers and disturbances. We synthesize strategies for identifying causes of abrupt ecological change and highlight instances where abrupt changes are likely. Diagnosing abrupt changes and inferring causation are increasingly important as society seek to adapt to rapid, multifaceted environmental changes. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. The effect of abrupt climate changes and climate background conditions in Southern Europe during the last glacial

    NASA Astrophysics Data System (ADS)

    Knorr, Gregor; Martin-Puertas, Celia; Brauer, Achim; Lohmann, Gerrit

    2015-04-01

    The last glacial period is characterized by abrupt and large temperature shifts in Greenland and the North Atlantic realm. Pollen and sediment data from Lago Grande di Monticchio (MON) have demonstrated a clear imprint of these fluctuations operating at millennial time-scales. Interestingly, basic mean environmental condition changes with respect to temperature and precipitation occurred during MIS4, separating warm and dry conditions during MIS5 from relatively cold and humid conditions within MIS3. This general climate background shift is superposed by distinct millennial-scale variability at MON. Using a fully coupled atmosphere-ocean general circulation model applying boundary conditions at 32 ka BP and pre-industrial conditions as a surrogate for MIS3 and MIS5, we have simulated and analysed characteristic changes in Southern Europe during the last glacial. We find that changes in the mean state at MON are mainly related to a partial shift of the North Atlantic deep water (NADW) convection sites from the Nordic Seas to South of Iceland, the presence of the Fennoscandian ice sheet and lower greenhouse gas concentrations. These background characteristics provide the basis for enhanced zonal moisture transport from the eastern North Atlantic to Middle and Southern Europe. Furthermore, simulations of abrupt climate change scenarios show that a deactivation of the convection sites South of Iceland during MIS3 leads to cooler and dryer conditions at MON. Such temperature and precipitation changes are thought to provide a counter-acting effect on woody vegetation and associated pollen signals at MON. This is in contrast to the impact of abrupt climate perturbation scenarios during MIS5, where no significant precipitation changes are detected. Hence, the simulated changes and underlying mechanisms are largely consistent with the recorded proxy evidence with respect to both, mean state and millennial-scale changes.

  17. Abrupt transitions to a cold North Atlantic in the late Holocene

    NASA Astrophysics Data System (ADS)

    Geirsdóttir, Áslaug; Miller, Gifford; Larsen, Darren; Florian, Christopher; Pendleton, Simon

    2015-04-01

    The Holocene provides a time interval with boundary conditions similar to present, except for greenhouse gas concentrations. Recent high-resolution Northern Hemisphere records show general cooling related to orbital terms through the late Holocene, but also highly non-linear abrupt departures of centennial scale summer cold periods. These abrupt departures are evident within the last two millennia (the transitions between the Roman Warm Period (RWP, ~2,000 yr BP), the Dark Ages Cold Period (DACP, ~500-900 years AD), the Medieval Warm Period (MWP, 1000-1200 years AD) and the Little Ice Age (LIA, ~1300-1900 AD). A series of new, high-resolution and securely dated lake records from Iceland also show abrupt climate departures over the past 2 ka, characterized by shifts to persistent cold summers and an expanded cryosphere. Despite substantial differences in catchment-specific processes that dominate the lake records, the multi-proxy reconstructions are remarkably similar. After nearly a millennium with little evidence of significant climate shifts, the beginning of the first millennium AD is characterized by renewed summer cooling that leads to an expanding cryosphere. Slow summer cooling over the first five centuries is succeeded by widespread substantial cooling, with evidence for substantial expansion of glaciers and ice caps throughout our field areas between 530 and 900 AD, and an accompanying reduction in vegetation cover across much of Iceland that led to widespread landscape instability. These data suggest that the North Atlantic system began a transition into a new cold state early in the first millennium AD, which was amplified after 500 AD, until it was interrupted by warmer Medieval times between ~1000 and 1250 AD. Although severe soil erosion in Iceland is frequently associated with human settlement dated to 871 ±2 AD our reconstructions indicate that soil erosion began several centuries before settlement, during the DACP, whereas for several centuries

  18. Abrupt termination of Marine Isotope Stage 16 (Termination VII) at 631.5 ka in Santa Barbara Basin, Californi

    USGS Publications Warehouse

    Dean, Walter E.; Kennett, James P.; Behl, Richard J.; Nicholson, Craig; Sorlien, Christopher C.

    2015-01-01

    The Marine Isotope Stage 16–15 boundary (Termination VII) is the first deglacial warming step of the late Quaternary following the mid-Pleistocene transition (MPT), when 41 kyr climatic cycles shifted to strong 100 kyr cycles. The detailed structure of this important climatic event has remained unknown until now. Core MV0508-19JPC from Santa Barbara Basin, California, contains a decadal-scale climatic and geochemical sediment record of 4000 years duration that includes the early part of this deglacial episode. This record reveals that the climatic shift during the early deglacial occurred rapidly (<700 years), in a progression of three abrupt warming steps. The onset of Marine Isotope Stage (MIS) 15 was remarkably abrupt with 4–5°C sea surface warming in ~50 years. The deglacial sequence contains the well-dated Lava Creek tephra (631.3 ± 4 ka) from Yellowstone Caldera used to date the onset of Termination VII at 631.5 ka. The late MIS 16 and early MIS 15 interval exhibits multiple decadal-scale negative excursions in δ13C of planktic foraminifera, likely the result of repeated discharges of methane from methane hydrates associated with both ocean warming and low sea level. A warm interstadial that interrupts late MIS 16 is marked by elevated concentrations of redox-sensitive elements indicating sulfidic, oxygen-deficient bottom and pore-waters, and elevated concentrations of total organic carbon and Cd, reflecting increased surface productivity. Unlike younger sediments on the California margin, these indicators of increased productivity and low dissolved oxygen do not consistently correspond with each other or with preserved laminations, possibly reflecting instability of a still evolving ocean-atmosphere system following the MPT.

  19. Abrupt strategy change underlies gradual performance change: Bayesian hierarchical models of component and aggregate strategy use.

    PubMed

    Wynton, Sarah K A; Anglim, Jeromy

    2017-10-01

    While researchers have often sought to understand the learning curve in terms of multiple component processes, few studies have measured and mathematically modeled these processes on a complex task. In particular, there remains a need to reconcile how abrupt changes in strategy use can co-occur with gradual changes in task completion time. Thus, the current study aimed to assess the degree to which strategy change was abrupt or gradual, and whether strategy aggregation could partially explain gradual performance change. It also aimed to show how Bayesian methods could be used to model the effect of practice on strategy use. To achieve these aims, 162 participants completed 15 blocks of practice on a complex computer-based task-the Wynton-Anglim booking (WAB) task. The task allowed for multiple component strategies (i.e., memory retrieval, information reduction, and insight) that could also be aggregated to a global measure of strategy use. Bayesian hierarchical models were used to compare abrupt and gradual functions of component and aggregate strategy use. Task completion time was well-modeled by a power function, and global strategy use explained substantial variance in performance. Change in component strategy use tended to be abrupt, whereas change in global strategy use was gradual and well-modeled by a power function. Thus, differential timing of component strategy shifts leads to gradual changes in overall strategy efficiency, and this provides one reason for why smooth learning curves can co-occur with abrupt changes in strategy use. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  20. Prolonged Instability Prior to a Regime Shift

    EPA Science Inventory

    Regime shifts are generally defined as the point of ‘abrupt’ change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of th...

  1. Smoked marijuana attenuates performance and mood disruptions during simulated night shift work.

    PubMed

    Keith, Diana R; Gunderson, Erik W; Haney, Margaret; Foltin, Richard W; Hart, Carl L

    2017-09-01

    Individuals who work nonstandard schedules, such as rotating or night shifts, are more susceptible to workplace injuries, performance decrements, and reduced productivity. This population is also almost twice as likely to use illicit drugs as individuals working a standard day shift. The purpose of this study was to examine the effects of smoked marijuana on performance, mood, and sleep during simulated shift work. Ten experienced marijuana smokers completed this 23-day, within-participant residential study. They smoked a single marijuana cigarette (0, 1.9, 3.56% Δ 9 -THC) one hour after waking for three consecutive days under two shift conditions: day shift and night shift. Shifts alternated three times during the study, and shift conditions were separated by an 'off' day. When participants smoked placebo cigarettes, psychomotor performance and subjective-effect ratings were altered during the night shift compared to the day shift: performance (e.g., vigilance) and a few subjective ratings were decreased (e.g., "Self-Confident"), whereas other ratings were increased (e.g., "Tired"). Objective and subjective measures of sleep were also disrupted, but to a lesser extent. Marijuana attenuated some performance, mood, and sleep disruptions: participants performed better on vigilance tasks, reported being less miserable and tired and sleep a greater number of minutes. Limited negative effects of marijuana were noted. These data demonstrate that abrupt shift changes produce performance, mood, and sleep decrements during night shift work and that smoked marijuana containing low to moderate Δ 9 -THC concentrations can offset some of these effects in frequent marijuana smokers. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. A novel phase retrieval method from three-wavelength in-line phase-shifting interferograms based on positive negative 2π phase shifts

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming

    2018-01-01

    A new method to extract quantitative phases for each wavelength from three-wavelength in-line phase-shifting interferograms is proposed. Firstly, seven interferograms with positive negative 2π phase shifts are sequentially captured by using the phase-shifting technique. Secondly, six dc-term suppressed intensities can be achieved by the use of the algebraic algorithm. Finally, the wrapped phases at the three wavelengths can be acquired simultaneously from these six interferograms add-subtracting by employing the trigonometric function method. The surface morphology with increased ambiguity-free range at synthetic beat wavelength can be obtained, while maintaining the low noise precision of the single wavelength measurement, by combining this method with three-wavelength phase unwrapping method. We illustrate the principle of this algorithm, and the simulated experiments of the spherical cap and the HeLa cell are conducted to prove our proposed method, respectively.

  3. Controls on the abruptness of gravel-sand transitions

    NASA Astrophysics Data System (ADS)

    Venditti, J. G.; Church, M. A.; Lamb, M. P.; Domarad, N.; Rennie, C. D.

    2014-12-01

    As gravel-bedded rivers fine downstream, they characteristically exhibit an abrupt transition from gravel- to sand-bed. This is the only abrupt transition in grain-size that occurs in the fluvial system and has attracted considerable attention. A number of competing theories have been proposed to account for the abruptness of the transition, including base-level control, attrition of ~10mm gravel to produce sand, and sediment sorting processes. The prevailing theory for the emergence of abrupt transitions is size selective sorting of bimodal sediment wherein gravel deposits due to downstream declining shear stress, fining the bedload until a sand-bed emerges. We explored this hypothesis by examining grain-size, shear stress, gravel mobility and sand suspension thresholds through the gravel-sand transition (GST) of the Fraser River, British Columbia. The Fraser GST is an arrested gravel wedge with patches of gravel downstream of the wedge forming a diffuse extension. There is an abrupt change in bed slope through the transition that leads to an abrupt change in shear stress. The GST, bed-slope change and backwater caused by the ocean are all coincident spatially, which enhances the sharpness of the GST. Interestingly, the bimodal reach of the river occurs downstream of the GST and exhibits no downstream gradients in shear stress, suspended sediment flux, gravel mobility or sand suspension thresholds. This calls into question the prevailing theory for the emergence of an abrupt GST by size selective sorting. We provide evidence, both empirical and theoretical, that suggests the emergence of an abrupt GST is caused by rapid deposition of sand when fine gravel deposits. We argue that the emergence of gravel-sand transitions is a consequence of gravel-bedded rivers adopting a steeper slope than sand-bedded rivers. The abruptness arises because the bed slope required to convey the gravel load fixes the distal location of a terminal gravel wedge, and once the river has

  4. Abrupt shifts in ecosystem function and intensification of global biogeochemical cycle driven by hydroclimatic extremes

    NASA Astrophysics Data System (ADS)

    Ma, Xuanlong; Huete, Alfredo; Ponce-Campos, Guillermo; Zhang, Yongguang; Xie, Zunyi; Giovannini, Leandro; Cleverly, James; Eamus, Derek

    2016-04-01

    Amplification of the hydrologic cycle as a consequence of global warming is increasing the frequency, intensity, and spatial extent of extreme climate events globally. The potential influences resulting from amplification of the hydro-climatic cycle, coupled with an accelerating warming trend, pose great concerns on the sustainability of terrestrial ecosystems to sequester carbon, maintain biodiversity, provide ecosystem services, food security, and support human livelihood. Despite the great implications, the magnitude, direction, and carry-over effect of these extreme climate events on ecosystem function, remain largely uncertain. To address these pressing issues, we conducted an observational, interdisciplinary study using satellite retrievals of atmospheric CO2 and photosynthesis (chlorophyll fluorescence), and in-situ flux tower measures of ecosystem-atmosphere carbon exchange, to reveal the shifts in ecosystem function across extreme drought and wet periods. We further determine the factors that govern ecosystem sensitivity to hydroclimatic extremes. We focus on Australia but extended our analyses to other global dryland regions due to their significant role in global biogeochemical cycles. Our results revealed dramatic impacts of drought and wet hydroclimatic extremes on ecosystem function, with abrupt changes in vegetation productivity, carbon uptake, and water-use-efficiency between years. Drought resulted in widespread reductions or collapse in the normal patterns of vegetation growth seasonality such that in many cases there was no detectable phenological cycle during extreme drought years. We further identified a significant increasing trend (p < 0.001) in extreme wet year precipitation amounts over Australia and many other global regions, resulting in an increasing trend in magnitude of the episodic carbon sink pulses coupled to each La Niña-induced wet years. This finding is of global biogeochemical significance, with the consequence of amplifying

  5. Abrupt Impacts of Climate Change: Anticipating Surprises

    NASA Astrophysics Data System (ADS)

    White, James W. C.; Alley, Richard B.; Archer, David E.; Barnosky, Anthony D.; Dunlea, Edward; Foley, Jonathan; Fu, Rong; Holland, Marika M.; Lozier, M. Susan; Schmitt, Johanna; Smith, Laurence C.; Sugihara, George; Thompson, David W. J.; Weaver, Andrew J.; Wofsy, Steven C.

    2014-05-01

    Levels of carbon dioxide and other greenhouse gases in Earth's atmosphere are exceeding levels recorded in the past millions of years, and thus climate is being forced beyond the range of the recent geological era. Lacking concerted action by the world's nations, it is clear that the future climate will be warmer, sea levels will rise, global rainfall patterns will change, and ecosystems will be altered. However, there is still uncertainty about how we will arrive at that future climate state. Although many projections of future climatic conditions have predicted steadily changing conditions giving the impression that communities have time to gradually adapt, the scientific community has been paying increasing attention to the possibility that at least some changes will be abrupt, perhaps crossing a threshold or "tipping point" to change so quickly that there will be little time to react. This presentation will synopsize the new US National Research Council Report, Abrupt Impacts of Climate Change: Anticipating Surprises, highlighting areas of increased and decreased concern, as well as areas of new concern. Emphasis is placed on not only abrupt change in physical climate, but on abrupt changes in human and natural systems that can occur as a result of a slowly changing climate. The report calls for action now on an abrupt change early warning system (ACEWS) if societies are to be resilient to climate change.

  6. Global impacts of the 1980s regime shift.

    PubMed

    Reid, Philip C; Hari, Renata E; Beaugrand, Grégory; Livingstone, David M; Marty, Christoph; Straile, Dietmar; Barichivich, Jonathan; Goberville, Eric; Adrian, Rita; Aono, Yasuyuki; Brown, Ross; Foster, James; Groisman, Pavel; Hélaouët, Pierre; Hsu, Huang-Hsiung; Kirby, Richard; Knight, Jeff; Kraberg, Alexandra; Li, Jianping; Lo, Tzu-Ting; Myneni, Ranga B; North, Ryan P; Pounds, J Alan; Sparks, Tim; Stübi, René; Tian, Yongjun; Wiltshire, Karen H; Xiao, Dong; Zhu, Zaichun

    2016-02-01

    Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur. © 2015 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

  7. Negative hyperconjugation and red-, blue- or zero-shift in X-Z∙∙∙Y complexes.

    PubMed

    Joy, Jyothish; Jemmis, Eluvathingal D; Vidya, Kaipanchery

    2015-01-01

    A generalized explanation is provided for the existence of the red- and blue-shifting nature of X-Z bonds (Z=H, halogens, chalcogens, pnicogens, etc.) in X-Z∙∙∙Y complexes based on computational studies on a selected set of weakly bonded complexes and analysis of existing literature data. The additional electrons and orbitals available on Z in comparison to H make for dramatic differences between the H-bond and the rest of the Z-bonds. The nature of the X-group and its influence on the X-Z bond length in the parent X-Z molecule largely controls the change in the X-Z bond length on X-Z∙∙∙Y bond formation; the Y-group usually influences only the magnitude of the effects controlled by X. The major factors which control the X-Z bond length change are: (a) negative hyperconjugative donation of electron density from X-group to X-Z σ* antibonding molecular orbital (ABMO) in the parent X-Z, (b) induced negative hyperconjugation from the lone pair of electrons on Z to the antibonding orbitals of the X-group, and (c) charge transfer (CT) from the Y-group to the X-Z σ* orbital. The exchange repulsion from the Y-group that shifts partial electron density at the X-Z σ* ABMO back to X leads to blue-shifting and the CT from the Y-group to the σ* ABMO of X-Z leads to red-shifting. The balance between these two opposing forces decides red-, zero- or blue-shifting. A continuum of behaviour of X-Z bond length variation is inevitable in X-Z∙∙∙Y complexes.

  8. The economics of abrupt climate change.

    PubMed

    Perrings, Charles

    2003-09-15

    The US National Research Council defines abrupt climate change as a change of state that is sufficiently rapid and sufficiently widespread in its effects that economies are unprepared or incapable of adapting. This may be too restrictive a definition, but abrupt climate change does have implications for the choice between the main response options: mitigation (which reduces the risks of climate change) and adaptation (which reduces the costs of climate change). The paper argues that by (i) increasing the costs of change and the potential growth of consumption, and (ii) reducing the time to change, abrupt climate change favours mitigation over adaptation. Furthermore, because the implications of change are fundamentally uncertain and potentially very high, it favours a precautionary approach in which mitigation buys time for learning. Adaptation-oriented decision tools, such as scenario planning, are inappropriate in these circumstances. Hence learning implies the use of probabilistic models that include socioeconomic feedbacks.

  9. Temperature independent refractive index measurement using a fiber Bragg grating on abrupt tapered tip

    NASA Astrophysics Data System (ADS)

    Gomes, André D.; Silveira, Beatriz; Warren-Smith, Stephen C.; Becker, Martin; Rothhardt, Manfred; Frazão, Orlando

    2018-05-01

    A fiber Bragg grating was inscribed in an abrupt fiber taper using a femtosecond laser and phase-mask interferometer. The abrupt taper transition allows to excite a broad range of guided modes with different effective refractive indices that are reflected at different wavelengths according to Bragg's law. The multimode-Bragg reflection expands over 30 nm in the telecom-C-band. This corresponds to a mode-field overlap of up to 30% outside of the fiber, making the device suitable for evanescent field sensing. Refractive index and temperature measurements are performed for different reflection peaks. Temperature independent refractive index measurements are achieved by considering the difference between the wavelength shifts of two measured reflection peaks. A minimum refractive index sensitivity of 16 ± 1 nm/RIU was obtained in a low refractive index regime (1.3475-1.3720) with low influence of temperature (-0.32 ± 0.06 pm/°C). The cross sensitivity for this structure is 2.0 × 10-5 RIU/°C. The potential for simultaneous measurement of refractive index and temperature is also studied.

  10. Fire and vegetation shifts in the Americas at the vanguard of Paleoindian migration

    USGS Publications Warehouse

    Pinter, N.; Fiedel, S.; Keeley, J.E.

    2011-01-01

    Across North and South America, the final millennia of the Pleistocene saw dramatic changes in climate, vegetation, fauna, fire regime, and other local and regional paleo-environmental characteristics. Rapid climate shifts following the Last Glacial Maximum (LGM) exerted a first-order influence, but abrupt postglacial shifts in vegetation composition, vegetation structure, and fire regime also coincided with human arrival and transformative faunal extinctions in the Americas. We propose a model of post-glacial vegetation change in response to climatic drivers, punctuated by local fire regime shifts in response to megaherbivore-driven fuel changes and anthropogenic ignitions. The abrupt appearance of humans, disappearance of megaherbivores, and resulting changes in New World fire systems were transformative events that should not be dismissed in favor of climate-only interpretations of post-glacial paleo-environmental shifts in the Americas. Fire is a mechanism by which small human populations can have broad impacts, and growing evidence suggests that early anthropogenic influences on regional, even global, paleo-environments should be tested alongside other potential causal mechanisms.

  11. Fire and vegetation shifts in the Americas at the vanguard of Paleoindian migration

    NASA Astrophysics Data System (ADS)

    Pinter, Nicholas; Fiedel, Stuart; Keeley, Jon E.

    2011-02-01

    Across North and South America, the final millennia of the Pleistocene saw dramatic changes in climate, vegetation, fauna, fire regime, and other local and regional paleo-environmental characteristics. Rapid climate shifts following the Last Glacial Maximum (LGM) exerted a first-order influence, but abrupt post-glacial shifts in vegetation composition, vegetation structure, and fire regime also coincided with human arrival and transformative faunal extinctions in the Americas. We propose a model of post-glacial vegetation change in response to climatic drivers, punctuated by local fire regime shifts in response to megaherbivore-driven fuel changes and anthropogenic ignitions. The abrupt appearance of humans, disappearance of megaherbivores, and resulting changes in New World fire systems were transformative events that should not be dismissed in favor of climate-only interpretations of post-glacial paleo-environmental shifts in the Americas. Fire is a mechanism by which small human populations can have broad impacts, and growing evidence suggests that early anthropogenic influences on regional, even global, paleo-environments should be tested alongside other potential causal mechanisms.

  12. Sleep Loss and Fatigue in Shift Work and Shift Work Disorder

    PubMed Central

    Åkerstedt, Torbjörn; Wright, Kenneth P.

    2010-01-01

    Shift work is highly prevalent in industrialized societies (>20%) but, when it includes night work, it has pronounced negative effects on sleep, subjective and physiological sleepiness, performance, accident risk, as well as on health outcomes such as cardiovascular disease and certain forms of cancer. The reason is the conflict between the day oriented circadian physiology and the requirement for work and sleep at the “wrong” biological time of day. Other factors that negatively impact work shift sleepiness and accident risk include long duration shifts greater than 12 hours and individual vulnerability for phase intolerance that may lead to a diagnosis of shift work disorder; i.e., those shift workers with the greatest sleepiness and performance impairment during the biological night and insomnia during the biological day. Whereas some countermeasures may be used to ameliorate the negative impact of shift work on nighttime sleepiness and daytime insomnia (combined countermeasures may be the best available), there seems at present to be no way to eliminate most of the negative effects of shift work on human physiology and cognition. PMID:20640236

  13. Role of AlGaN/GaN interface traps on negative threshold voltage shift in AlGaN/GaN HEMT

    NASA Astrophysics Data System (ADS)

    Malik, Amit; Sharma, Chandan; Laishram, Robert; Bag, Rajesh Kumar; Rawal, Dipendra Singh; Vinayak, Seema; Sharma, Rajesh Kumar

    2018-04-01

    This article reports negative shift in the threshold-voltage in AlGaN/GaN high electron mobility transistor (HEMT) with application of reverse gate bias stress. The device is biased in strong pinch-off and low drain to source voltage condition for a fixed time duration (reverse gate bias stress), followed by measurement of transfer characteristics. Negative threshold voltage shift after application of reverse gate bias stress indicates the presence of more carriers in channel as compared to the unstressed condition. We propose the presence of AlGaN/GaN interface states to be the reason of negative threshold voltage shift, and developed a process to electrically characterize AlGaN/GaN interface states. We verified the results with Technology Computer Aided Design (TCAD) ATLAS simulation and got a good match with experimental measurements.

  14. Multiscale regime shifts and planetary boundaries.

    PubMed

    Hughes, Terry P; Carpenter, Stephen; Rockström, Johan; Scheffer, Marten; Walker, Brian

    2013-07-01

    Life on Earth has repeatedly displayed abrupt and massive changes in the past, and there is no reason to expect that comparable planetary-scale regime shifts will not continue in the future. Different lines of evidence indicate that regime shifts occur when the climate or biosphere transgresses a tipping point. Whether human activities will trigger such a global event in the near future is uncertain, due to critical knowledge gaps. In particular, we lack understanding of how regime shifts propagate across scales, and whether local or regional tipping points can lead to global transitions. The ongoing disruption of ecosystems and climate, combined with unprecedented breakdown of isolation by human migration and trade, highlights the need to operate within safe planetary boundaries. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. North Pacific deglacial hypoxic events linked to abrupt ocean warming

    USGS Publications Warehouse

    Praetorius, Summer K; Mix, Alan C.; Davies, Maureen H.; Wolhowe, Matthew D; Addison, Jason A.; Prahl, Frederick G

    2015-01-01

    Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition1, 2, 3, 4. The mechanisms driving this hypoxia remain under debate1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt warming events of 4–5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals12, 13, and enhanced 15N/14N ratio of organic matter13, collectively suggest association with high export production. A decrease in 18O/16O values of benthic foraminifera accompanying the most severe deoxygenation event indicates subsurface warming of up to about 2 degrees Celsius. We infer that abrupt warming triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to warming.

  16. Isotopic composition of ice core air reveals abrupt Antarctic warming during and after Heinrich Event 1a

    NASA Astrophysics Data System (ADS)

    Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.

    2017-12-01

    Antarctic temperature variations during Heinrich events, as recorded by δ18O­ice­, generally show more gradual changes than the abrupt warmings seen in Greenland ice. However, quantitative temperature interpretation of the water isotope temperature proxy is difficult as the relationship between δ18Oice and temperature is not constant through time. Fortunately, ice cores offer a second temperature proxy based on trapped gases. During times of surface warming, thermal fractionation of gases in the column of unconsolidated snow (firn) on top of the ice sheet results in isotopically heavier nitrogen (N2) and argon (Ar) being trapped in the ice core bubbles. During times of surface cooling, isotopically lighter gases are trapped. Measurements of δ15N and δ40Ar can therefore be used, in combination with a model for the height of the column of firn, to quantitatively reconstruct surface temperatures. In the WAIS Divide Ice Core, the two temperature proxies show a brief disagreement during Heinrich Stadial 1. Despite δ18Oice recording relatively constant temperature, the nitrogen and argon isotopes imply an abrupt warming between 16 and 15.8 kyr BP, manifest as an abrupt 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such abrupt climate change has been recorded in an Antarctic climate proxy. If confirmed by more detailed studies, this event may represent warming due to an extreme southward shift of the Earth's thermal equator (and the southern hemisphere westerly wind belt), caused by the 16.1 ka Heinrich Event.

  17. Energy transport, polar amplification, and ITCZ shifts in the GeoMIP G1 ensemble

    NASA Astrophysics Data System (ADS)

    Russotto, Rick D.; Ackerman, Thomas P.

    2018-02-01

    The polar amplification of warming and the ability of the Intertropical Convergence Zone (ITCZ) to shift to the north or south are two very important problems in climate science. Examining these behaviors in global climate models (GCMs) running solar geoengineering experiments is helpful not only for predicting the effects of solar geoengineering but also for understanding how these processes work under increased carbon dioxide (CO2). Both polar amplification and ITCZ shifts are closely related to the meridional transport of moist static energy (MSE) by the atmosphere. This study examines changes in MSE transport in 10 fully coupled GCMs in experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP), in which the solar constant is reduced to compensate for the radiative forcing from abruptly quadrupled CO2 concentrations. In G1, poleward MSE transport decreases relative to preindustrial conditions in all models, in contrast to the Coupled Model Intercomparison Project phase 5 (CMIP5) abrupt4xCO2 experiment, in which poleward MSE transport increases. We show that since poleward energy transport decreases rather than increases, and local feedbacks cannot change the sign of an initial temperature change, the residual polar amplification in the G1 experiment must be due to the net positive forcing in the polar regions and net negative forcing in the tropics, which arise from the different spatial patterns of the simultaneously imposed solar and CO2 forcings. However, the reduction in poleward energy transport likely plays a role in limiting the polar warming in G1. An attribution study with a moist energy balance model shows that cloud feedbacks are the largest source of uncertainty regarding changes in poleward energy transport in midlatitudes in G1, as well as for changes in cross-equatorial energy transport, which are anticorrelated with ITCZ shifts.

  18. Heat and pregnancy-related emergencies: Risk of placental abruption during hot weather.

    PubMed

    He, Siyi; Kosatsky, Tom; Smargiassi, Audrey; Bilodeau-Bertrand, Marianne; Auger, Nathalie

    2018-02-01

    Outdoor heat increases the risk of preterm birth and stillbirth, but the association with placental abruption has not been studied. Placental abruption is a medical emergency associated with major morbidity and mortality in pregnancy. We determined the relationship between ambient temperature and risk of placental abruption in warm seasons. We performed a case-crossover analysis of 17,172 women whose pregnancies were complicated by placental abruption in Quebec, Canada from May to October 1989-2012. The main exposure measure was the maximum temperature reached during the week before abruption. We computed odds ratios (OR) and 95% confidence intervals (CI) for the association of temperature with placental abruption, adjusted for humidity and public holidays. We assessed whether associations were stronger preterm or at term, or varied with maternal age, parity, comorbidity and socioeconomic status. Compared with 15°C, a maximum weekly temperature of 30°C was associated with 1.07 times the odds of abruption (95% CI 0.99-1.16). When the timing of abruption was examined, the associations were significantly stronger at term (OR 1.12, 95% CI 1.02-1.24) than preterm (OR 0.96, 95% CI 0.83-1.10). Relationships were more prominent at term for women who were younger than 35years old, nulliparous or socioeconomically disadvantaged, but did not vary with comorbidity. Associations were stronger within 1 and 5days of abruption. Temperature was not associated with preterm abruption regardless of maternal characteristics. Elevated temperatures in warm seasons may increase the risk of abruption in women whose pregnancies are near or at term. Pregnant women may be more sensitive to heat and should consider preventive measures such as air conditioning and hydration during hot weather. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Changing skewness: an early warning signal of regime shifts in ecosystems.

    PubMed

    Guttal, Vishwesha; Jayaprakash, Ciriyam

    2008-05-01

    Empirical evidence for large-scale abrupt changes in ecosystems such as lakes and vegetation of semi-arid regions is growing. Such changes, called regime shifts, can lead to degradation of ecological services. We study simple ecological models that show a catastrophic transition as a control parameter is varied and propose a novel early warning signal that exploits two ubiquitous features of ecological systems: nonlinearity and large external fluctuations. Either reduced resilience or increased external fluctuations can tip ecosystems to an alternative stable state. It is shown that changes in asymmetry in the distribution of time series data, quantified by changing skewness, is a model-independent and reliable early warning signal for both routes to regime shifts. Furthermore, using model simulations that mimic field measurements and a simple analysis of real data from abrupt climate change in the Sahara, we study the feasibility of skewness calculations using data available from routine monitoring.

  20. Emotional bias of sleep-dependent processing shifts from negative to positive with aging.

    PubMed

    Jones, Bethany J; Schultz, Kurt S; Adams, Sydney; Baran, Bengi; Spencer, Rebecca M C

    2016-09-01

    Age-related memory decline has been proposed to result partially from impairments in memory consolidation over sleep. However, such decline may reflect a shift toward selective processing of positive information with age rather than impaired sleep-related mechanisms. In the present study, young and older adults viewed negative and neutral pictures or positive and neutral pictures and underwent a recognition test after sleep or wake. Subjective emotional reactivity and affect were also measured. Compared with waking, sleep preserved valence ratings and memory for positive but not negative pictures in older adults and negative but not positive pictures in young adults. In older adults, memory for positive pictures was associated with slow wave sleep. Furthermore, slow wave sleep predicted positive affect in older adults but was inversely related to positive affect in young adults. These relationships were strongest for older adults with high memory for positive pictures and young adults with high memory for negative pictures. Collectively, these results indicate preserved but selective sleep-dependent memory processing with healthy aging that may be biased to enhance emotional well-being. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Supercritical flow characteristics at abrupt expansion structure

    NASA Astrophysics Data System (ADS)

    Lim, Jia Jun; Puay, How Tion; Zakaria, Nor Azazi

    2017-10-01

    When dealing with the design of a hydraulic structure, lateral expansion is often necessary for flow emerging at high velocity served as a cross-sectional transition. If the abrupt expansion structure is made to diverge rapidly, it will cause the major part of the flow fail to follow the boundaries. If the transition is too gradual, it will result in a waste of structural material. A preliminary study on the flow structure near the expansion and its relationship with flow parameter is carried out in this study. A two-dimensional depth-averaged model is developed to simulate the supercritical flow at the abrupt expansion structure. Constrained Interpolation Profile (CIP) scheme (which is of third order accuracy) is adopted in the numerical model. Results show that the flow structure and flow characteristics at the abrupt expansion can be reproduced numerically. The validation of numerical result is done against analytical studies. The result from numerical simulation showed good agreement with the analytical solution.

  2. Abrupt tropical climate change: past and present.

    PubMed

    Thompson, Lonnie G; Mosley-Thompson, Ellen; Brecher, Henry; Davis, Mary; León, Blanca; Les, Don; Lin, Ping-Nan; Mashiotta, Tracy; Mountain, Keith

    2006-07-11

    Three lines of evidence for abrupt tropical climate change, both past and present, are presented. First, annually and decadally averaged delta(18)O and net mass-balance histories for the last 400 and 2,000 yr, respectively, demonstrate that the current warming at high elevations in the mid- to low latitudes is unprecedented for at least the last 2 millennia. Second, the continuing retreat of most mid- to low-latitude glaciers, many having persisted for thousands of years, signals a recent and abrupt change in the Earth's climate system. Finally, rooted, soft-bodied wetland plants, now exposed along the margins as the Quelccaya ice cap (Peru) retreats, have been radiocarbon dated and, when coupled with other widespread proxy evidence, provide strong evidence for an abrupt mid-Holocene climate event that marked the transition from early Holocene (pre-5,000-yr-B.P.) conditions to cooler, late Holocene (post-5,000-yr-B.P.) conditions. This abrupt event, approximately 5,200 yr ago, was widespread and spatially coherent through much of the tropics and was coincident with structural changes in several civilizations. These three lines of evidence argue that the present warming and associated glacier retreat are unprecedented in some areas for at least 5,200 yr. The ongoing global-scale, rapid retreat of mountain glaciers is not only contributing to global sea-level rise but also threatening freshwater supplies in many of the world's most populous regions.

  3. An abrupt weakening of the subpolar gyre as trigger of Little Ice Age-type episodes

    NASA Astrophysics Data System (ADS)

    Moreno-Chamarro, Eduardo; Zanchettin, Davide; Lohmann, Katja; Jungclaus, Johann H.

    2017-02-01

    We investigate the mechanism of a decadal-scale weakening shift in the strength of the subpolar gyre (SPG) that is found in one among three last millennium simulations with a state-of-the-art Earth system model. The SPG shift triggers multicentennial anomalies in the North Atlantic climate driven by long-lasting internal feedbacks relating anomalous oceanic and atmospheric circulation, sea ice extent, and upper-ocean salinity in the Labrador Sea. Yet changes throughout or after the shift are not associated with a persistent weakening of the Atlantic Meridional Overturning Circulation or shifts in the North Atlantic Oscillation. The anomalous climate state of the North Atlantic simulated after the shift agrees well with climate reconstructions from within the area, which describe a transition between a stronger and weaker SPG during the relatively warm medieval climate and the cold Little Ice Age respectively. However, model and data differ in the timing of the onset. The simulated SPG shift is caused by a rapid increase in the freshwater export from the Arctic and associated freshening in the upper Labrador Sea. Such freshwater anomaly relates to prominent thickening of the Arctic sea ice, following the cluster of relatively small-magnitude volcanic eruptions by 1600 CE. Sensitivity experiments without volcanic forcing can nonetheless produce similar abrupt events; a necessary causal link between the volcanic cluster and the SPG shift can therefore be excluded. Instead, preconditioning by internal variability explains discrepancies in the timing between the simulated SPG shift and the reconstructed estimates for the Little Ice Age onset.

  4. Going, Going, Gone: Localizing Abrupt Offsets of Moving Objects

    ERIC Educational Resources Information Center

    Maus, Gerrit W.; Nijhawan, Romi

    2009-01-01

    When a moving object abruptly disappears, this profoundly influences its localization by the visual system. In Experiment 1, 2 aligned objects moved across the screen, and 1 of them abruptly disappeared. Observers reported seeing the objects misaligned at the time of the offset, with the continuing object leading. Experiment 2 showed that the…

  5. Bound eigenstate dynamics under a sudden shift of the well's wall

    NASA Astrophysics Data System (ADS)

    Granot, Er'El; Marchewka, Avi

    2010-03-01

    We investigate the dynamics of the eigenstate of an infinite well under an abrupt shift of the well’s wall. It is shown that when the shift is small compared to the initial well’s dimensions, the short-time behavior changes from the well-known t3/2 behavior to t1/2. It is also shown that the complete dynamical picture converges to a universal function, which has fractal structure with dimensionality D=1.25.

  6. Evaluation of the significance of abrupt changes in precipitation and runoff process in China

    NASA Astrophysics Data System (ADS)

    Xie, Ping; Wu, Ziyi; Sang, Yan-Fang; Gu, Haiting; Zhao, Yuxi; Singh, Vijay P.

    2018-05-01

    Abrupt changes are an important manifestation of hydrological variability. How to accurately detect the abrupt changes in hydrological time series and evaluate their significance is an important issue, but methods for dealing with them effectively are lacking. In this study, we propose an approach to evaluate the significance of abrupt changes in time series at five levels: no, weak, moderate, strong, and dramatic. The approach was based on an index of correlation coefficient calculated for the original time series and its abrupt change component. A bigger value of correlation coefficient reflects a higher significance level of abrupt change. Results of Monte-Carlo experiments verified the reliability of the proposed approach, and also indicated the great influence of statistical characteristics of time series on the significance level of abrupt change. The approach was derived from the relationship between correlation coefficient index and abrupt change, and can estimate and grade the significance levels of abrupt changes in hydrological time series. Application of the proposed approach to ten major watersheds in China showed that abrupt changes mainly occurred in five watersheds in northern China, which have arid or semi-arid climate and severe shortages of water resources. Runoff processes in northern China were more sensitive to precipitation change than those in southern China. Although annual precipitation and surface water resources amount (SWRA) exhibited a harmonious relationship in most watersheds, abrupt changes in the latter were more significant. Compared with abrupt changes in annual precipitation, human activities contributed much more to the abrupt changes in the corresponding SWRA, except for the Northwest Inland River watershed.

  7. The association between maternal smoking and placenta abruption: a meta-analysis.

    PubMed

    Shobeiri, Fatemeh; Masoumi, Seyedeh Zahra; Jenabi, Ensiyeh

    2017-08-01

    Several epidemiological studies have determined that maternal smoking can increase the risk of placenta abruption. To date, only a meta-analysis has been performed for assessing the relationship between smoking and placenta abruption. This meta-analysis was conducted to estimate the association between smoking and the risk of placenta abruption. A literature search was conducted in major databases such as PubMed, Web of Science, and Scopus from the earliest possible year to April 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random effects model. The literature search yielded 1167 publications until April 2016 with 4 309 610 participants. Based on OR estimates obtained from case-control and cohort studies, there was a significant association between smoking and placenta abruption (1.80; 95% CI: 1.75, 1.85). Based on the results of cohort studies, smoking and placenta abruption had a significant association (relative risk ratio: 1.65; 95% CI: 1.51, 1.80). Based on reports in epidemiological studies, we showed that smoking is a risk factor for placenta abruption.

  8. Prolonged instability prior to a regime shift

    USGS Publications Warehouse

    Spanbauer, Trisha; Allen, Craig R.; Angeler, David G.; Eason, Tarsha; Fritz, Sherilyn C.; Garmestani, Ahjond S.; Nash, Kirsty L.; Stone, Jeffery R.

    2014-01-01

    Regime shifts are generally defined as the point of ‘abrupt’ change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of the system. Using both univariate and multivariate statistical methods, we tested a long-term high-resolution paleoecological dataset with a known change in species assemblage for a regime shift. Analysis of this dataset with Fisher Information and multivariate time series modeling showed that there was a∼2000 year period of instability prior to the regime shift. This period of instability and the subsequent regime shift coincide with regional climate change, indicating that the system is undergoing extrinsic forcing. Paleoecological records offer a unique opportunity to test tools for the detection of thresholds and stable-states, and thus to examine the long-term stability of ecosystems over periods of multiple millennia.

  9. The association between uterine leiomyoma and placenta abruption: A meta-analysis.

    PubMed

    Jenabi, Ensiyeh; Ebrahimzadeh Zagami, Samira

    2017-11-01

    Some epidemiological studies have found that uterine leiomyoma can increase the risk of placenta abruption. To date, the meta-analysis has not been performed for assessing the relationship between uterine leiomyoma and placenta abruption. This meta-analysis was conducted to estimate the association between uterine leiomyoma and the risk of placenta abruption. A literature search was conducted out in major databases PubMed, Web of Science, and Scopus from the earliest possible year to October 2016. The heterogeneity across studies was explored by Q-test and I 2 statistic. The publication bias was assessed by Begg's and Egger's tests. The results were showed using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random-effects model. The literature search included 953 articles until October 2016 with 232,024 participants. Based on OR estimates obtained from case-control and cohort studies, there was significant association between uterine leiomyoma and placenta abruption (2.63; 95% CI: 1.38, 3.88). We showed based on reports in observational studies that uterine leiomyoma is a risk factor for placenta abruption.

  10. Early Holocene hydroclimate of Baffin Bay: Understanding the interplay between abrupt climate change events and ice sheet fluctuations

    NASA Astrophysics Data System (ADS)

    Corcoran, M. C.; Thomas, E. K.; Castañeda, I. S.; Briner, J. P.

    2017-12-01

    Understanding the causes of ice sheet fluctuations resulting in sea level rise is essential in today's warming climate. In high-latitude ice-sheet-proximal environments such as Baffin Bay, studying both the cause and the rate of ice sheet variability during past abrupt climate change events aids in predictions. Past climate reconstructions are used to understand ice sheet responses to changes in temperature and precipitation. The 9,300 and 8,200 yr BP events are examples of abrupt climate change events in the Baffin Bay region during which there were multiple re-advances of the Greenland and Laurentide ice sheets. High-resolution (decadal-scale) hydroclimate variability near the ice sheet margins during these abrupt climate change events is still unknown. We will generate a decadal-scale record of early Holocene temperature and precipitation using leaf wax hydrogen isotopes, δ2Hwax, from a lake sediment archive on Baffin Island, western Baffin Bay, to better understand abrupt climate change in this region. Shifts in temperature and moisture source result in changes in environmental water δ2H, which in turn is reflected in δ2Hwax, allowing for past hydroclimate to be determined from these compound-specific isotopes. The combination of terrestrial and aquatic δ2Hwax is used to determine soil evaporation and is ultimately used to reconstruct moisture variability. We will compare our results with a previous analysis of δ2Hwax and branched glycerol dialkyl glycerol tetraethers, a temperature and pH proxy, in lake sediment from western Greenland, eastern Baffin Bay, which indicates that cool and dry climate occurred in response to freshwater forcing events in the Labrador Sea. Reconstructing and comparing records on both the western and eastern sides of Baffin Bay during the early Holocene will allow for a spatial understanding of temperature and moisture balance changes during abrupt climate events, aiding in ice sheet modeling and predictions of future sea level

  11. Sleep Detriments Associated With Quick Returns in Rotating Shift Work: A Diary Study.

    PubMed

    Vedaa, Øystein; Mørland, Erik; Larsen, Marit; Harris, Anette; Erevik, Eilin; Sivertsen, Børge; Bjorvatn, Bjørn; Waage, Siri; Pallesen, Ståle

    2017-06-01

    We aimed to compared sleep characteristics associated with quick returns (QRs, <11 hours between shift intervals) with those associated with other common shift transitions. Sixty-seven nurses completed a 2-week work and sleep diary (94.0% female, mean age 47.7 years). A multilevel fixed effects model was used to examine the sleep in QRs compared with two consecutive night shifts, two consecutive evening shifts, and two consecutive day shifts, respectively. None of the other shift transitions studied encumbered as many detriments as QRs, which included short sleep duration (5.6 hours), slightly prolonged sleep onset latency, more abrupt ending of main sleep period, increased sleepiness, and higher level of perceived stress on the following shift. The study emphasizes the need for sufficient time for rest and recuperation between shifts.

  12. An international contrast of rates of placental abruption: an age-period-cohort analysis.

    PubMed

    Ananth, Cande V; Keyes, Katherine M; Hamilton, Ava; Gissler, Mika; Wu, Chunsen; Liu, Shiliang; Luque-Fernandez, Miguel Angel; Skjærven, Rolv; Williams, Michelle A; Tikkanen, Minna; Cnattingius, Sven

    2015-01-01

    Although rare, placental abruption is implicated in disproportionately high rates of perinatal morbidity and mortality. Understanding geographic and temporal variations may provide insights into possible amenable factors of abruption. We examined abruption frequencies by maternal age, delivery year, and maternal birth cohorts over three decades across seven countries. Women that delivered in the US (n = 863,879; 1979-10), Canada (4 provinces, n = 5,407,463; 1982-11), Sweden (n = 3,266,742; 1978-10), Denmark (n = 1,773,895; 1978-08), Norway (n = 1,780,271, 1978-09), Finland (n = 1,411,867; 1987-10), and Spain (n = 6,151,508; 1999-12) were analyzed. Abruption diagnosis was based on ICD coding. Rates were modeled using Poisson regression within the framework of an age-period-cohort analysis, and multi-level models to examine the contribution of smoking in four countries. Abruption rates varied across the seven countries (3-10 per 1000), Maternal age showed a consistent J-shaped pattern with increased rates at the extremes of the age distribution. In comparison to births in 2000, births after 2000 in European countries had lower abruption rates; in the US there was an increase in rate up to 2000 and a plateau thereafter. No birth cohort effects were evident. Changes in smoking prevalence partially explained the period effect in the US (P = 0.01) and Sweden (P<0.01). There is a strong maternal age effect on abruption. While the abruption rate has plateaued since 2000 in the US, all other countries show declining rates. These findings suggest considerable variation in abruption frequencies across countries; differences in the distribution of risk factors, especially smoking, may help guide policy to reduce abruption rates.

  13. Phase Memory Preserving Harmonics from Abruptly Autofocusing Beams.

    PubMed

    Koulouklidis, Anastasios D; Papazoglou, Dimitris G; Fedorov, Vladimir Yu; Tzortzakis, Stelios

    2017-12-01

    We demonstrate both theoretically and experimentally that the harmonics from abruptly autofocusing ring-Airy beams present a surprising property: They preserve the phase distribution of the fundamental beam. Consequently, this "phase memory" imparts to the harmonics the abrupt autofocusing behavior, while, under certain conditions, their foci coincide in space with the one of the fundamental. Experiments agree well with our theoretical estimates and detailed numerical calculations. Our findings open the way for the use of such beams and their harmonics in strong field science.

  14. Abrupt transitions of the top-down controlled Black Sea pelagic ecosystem during 1960 2000: Evidence for regime-shifts under strong fishery exploitation and nutrient enrichment modulated by climate-induced variations

    NASA Astrophysics Data System (ADS)

    Oguz, Temel; Gilbert, Denis

    2007-02-01

    Functioning of the Black Sea ecosystem has profoundly changed since the early 1970s under cumulative effects of excessive nutrient enrichment, strong cooling/warming, over-exploitation of pelagic fish stocks, and population outbreak of gelatinous carnivores. Applying a set of criteria to the long-term (1960-2000) ecological time-series data, the present study demonstrates that the Black Sea ecosystem was reorganised during this transition phase in different forms of top-down controlled food web structure through successive regime-shifts of distinct ecological properties. The Secchi disc depth, oxic-anoxic interface zone, dissolved oxygen and hydrogen sulphide concentrations also exhibit abrupt transition between their alternate regimes, and indicate tight coupling between the lower trophic food web structure and the biogeochemical pump in terms of regime-shift events. The first shift, in 1973-1974, marks a switch from large predatory fish to small planktivore fish-controlled system, which persisted until 1989 in the form of increasing small pelagic and phytoplankton biomass and decreasing zooplankton biomass. The increase in phytoplankton biomass is further supported by a bottom-up contribution due to the cumulative response to high anthropogenic nutrient load and the concurrent shift of the physical system to the "cold climate regime" following its ˜20-year persistence in the "warm climate regime". The end of the 1980s signifies the depletion of small planktivores and the transition to a gelatinous carnivore-controlled system. By the end of the 1990s, small planktivore populations take over control of the system again. Concomitantly, their top-down pressure when combined with diminishing anthropogenic nutrient load and more limited nutrient supply into the surface waters due to stabilizing effects of relatively warm winter conditions switched the "high production" regime of phytoplankton to its background "low production" regime. The Black Sea regime-shifts

  15. Influence of external forcings on abrupt millennial-scale climate changes: a statistical modelling study

    NASA Astrophysics Data System (ADS)

    Mitsui, Takahito; Crucifix, Michel

    2017-04-01

    The last glacial period was punctuated by a series of abrupt climate shifts, the so-called Dansgaard-Oeschger (DO) events. The frequency of DO events varied in time, supposedly because of changes in background climate conditions. Here, the influence of external forcings on DO events is investigated with statistical modelling. We assume two types of simple stochastic dynamical systems models (double-well potential-type and oscillator-type), forced by the northern hemisphere summer insolation change and/or the global ice volume change. The model parameters are estimated by using the maximum likelihood method with the NGRIP Ca^{2+} record. The stochastic oscillator model with at least the ice volume forcing reproduces well the sample autocorrelation function of the record and the frequency changes of warming transitions in the last glacial period across MISs 2, 3, and 4. The model performance is improved with the additional insolation forcing. The BIC scores also suggest that the ice volume forcing is relatively more important than the insolation forcing, though the strength of evidence depends on the model assumption. Finally, we simulate the average number of warming transitions in the past four glacial periods, assuming the model can be extended beyond the last glacial, and compare the result with an Iberian margin sea-surface temperature (SST) record (Martrat et al. in Science 317(5837): 502-507, 2007). The simulation result supports the previous observation that abrupt millennial-scale climate changes in the penultimate glacial (MIS 6) are less frequent than in the last glacial (MISs 2-4). On the other hand, it suggests that the number of abrupt millennial-scale climate changes in older glacial periods (MISs 6, 8, and 10) might be larger than inferred from the SST record.

  16. Elevated nonlinearity as an indicator of shifts in the dynamics of populations under stress.

    PubMed

    Dakos, Vasilis; Glaser, Sarah M; Hsieh, Chih-Hao; Sugihara, George

    2017-03-01

    Populations occasionally experience abrupt changes, such as local extinctions, strong declines in abundance or transitions from stable dynamics to strongly irregular fluctuations. Although most of these changes have important ecological and at times economic implications, they remain notoriously difficult to detect in advance. Here, we study changes in the stability of populations under stress across a variety of transitions. Using a Ricker-type model, we simulate shifts from stable point equilibrium dynamics to cyclic and irregular boom-bust oscillations as well as abrupt shifts between alternative attractors. Our aim is to infer the loss of population stability before such shifts based on changes in nonlinearity of population dynamics. We measure nonlinearity by comparing forecast performance between linear and nonlinear models fitted on reconstructed attractors directly from observed time series. We compare nonlinearity to other suggested leading indicators of instability (variance and autocorrelation). We find that nonlinearity and variance increase in a similar way prior to the shifts. By contrast, autocorrelation is strongly affected by oscillations. Finally, we test these theoretical patterns in datasets of fisheries populations. Our results suggest that elevated nonlinearity could be used as an additional indicator to infer changes in the dynamics of populations under stress. © 2017 The Author(s).

  17. [The role of sustained attention in shift-contingent change blindness].

    PubMed

    Nakashima, Ryoichi; Yokosawa, Kazuhiko

    2015-02-01

    Previous studies of change blindness have examined the effect of temporal factors (e.g., blank duration) on attention in change detection. This study examined the effect of spatial factors (i.e., whether the locations of original and changed objects are the same or different) on attention in change detection, using a shift-contingent change blindness task. We used a flicker paradigm in which the location of a to-be-judged target image was manipulated (shift, no-shift). In shift conditions, the image of an array of objects was spatially shifted so that all objects appeared in new locations; in no-shift conditions, all object images of an array appeared at the same location. The presence of visual stimuli (dots) in the blank display between the two images was.manipulated (dot, no-dot) under the assumption that abrupt onsets of these stimuli would capture attention. Results indicated that change detection performance was improved by exogenous attentional capture in the shift condition. Thus, we suggest that attention can play an important role in change detection during shift-contingent change blindness.

  18. Blue and red shifted temperature dependence of implicit phonon shifts in graphene

    NASA Astrophysics Data System (ADS)

    Mann, Sarita; Jindal, V. K.

    2017-07-01

    We have calculated the implicit shift for various modes of frequency in a pure graphene sheet. Thermal expansion and Grüneisen parameter which are required for implicit shift calculation have already been studied and reported. For this calculation, phonon frequencies are obtained using force constants derived from dynamical matrix calculated using VASP code where the density functional perturbation theory (DFPT) is used in interface with phonopy software. The implicit phonon shift shows an unusual behavior as compared to the bulk materials. The frequency shift is large negative (red shift) for ZA and ZO modes and the value of negative shift increases with increase in temperature. On the other hand, blue shift arises for all other longitudinal and transverse modes with a similar trend of increase with increase in temperature. The q dependence of phonon shifts has also been studied. Such simultaneous red and blue shifts in transverse or out plane modes and surface modes, respectively leads to speculation of surface softening in out of plane direction in preference to surface melting.

  19. Self-reported smoking habits and serum cotinine levels in women with placental abruption.

    PubMed

    Tikkanen, Minna; Surcel, Heljä-Marja; Bloigu, Aini; Nuutila, Mika; Ylikorkala, Olavi; Hiilesmaa, Vilho; Paavonen, Jorma

    2010-12-01

    smoking is an important risk factor for placental abruption with strong dose-dependency. Pregnant smokers often underreport tobacco use which can be objectively assessed by measuring serum cotinine levels. We examined the accuracy between self-reported smoking habits and early pregnancy serum cotinine levels in women with or without placental abruption. retrospective case-control study. university Hospital. a total of 175 women with placental abruption and 370 control women. serum samples collected during the first trimester were analyzed for serum cotinine levels. Cotinine concentration over 15 ng/ml was considered as the cutoff indicating active smoking. Smoking habits of the women and their partners were recorded at the same visit. placental abruption. of the cases of women with placental abruption, 27.4% reported smoking compared with 14.3% of the controls (p < 0.001). Based on serum cotinine levels, 30.3% of the case women and 17.6% of the control women were considered smokers (p = 0.003). Serum cotinine levels among smokers were higher in the abruption group than in the control group (median 229.5 ng/ml (interquartile range 169.8-418.1) vs. 153.5 ng/ml (56.6-241.4), p = 0.002). Self-reported number of cigarettes smoked daily correlated well with the cotinine levels (r = 0.68, p < 0.001). Of the women reporting as nonsmokers, approximately 7% were considered smokers based on cotinine testing. pregnant women with subsequent placental abruption are heavier smokers than pregnant control women. Self-reported smoking habits correlate well with serum cotinine levels in Finland. Therefore, self-reported smoking can be considered as a risk marker for placental abruption.

  20. The Abrupt Onset of the Modern South Asian Monsoon Winds (iodp Exp. 359)

    NASA Astrophysics Data System (ADS)

    Betzler, C.; Eberli, G. P.; Kroon, D.; Wright, J. D.; Swart, P. K.; Nath, B. N.; Reijmer, J.; Alvarez Zarikian, C. A.

    2016-12-01

    The South Asian Monson (SAM) is one of the most extreme features in Earth's climate system, yet its initiation and variations are not well established. The SAM is a seasonal reversal of winds accompanied by changes in precipitation with heavy rain during the summer monsoon. It is one of the most intense annually recurring climatic elements and of immense importance in supplying moisture to the Indian subcontinent thus affecting human population and vegetation, as well as marine biota in the surrounding seas. The seasonal precipitation change is one of the SAM elements most noticed on land, whereas the reversal of the wind regime is the dominating driver of circulation in the central and northern Indian Ocean realm. New data acquired during International Ocean Discovery Program Expedition 359 from the Inner Sea of the Maldives provide a previously unread archive that reveals an abrupt onset of the SAM-linked ocean circulation pattern and its relationship to the long term Neogene climate cooling. In particular it registers ocean current fluctuations and changes of intermediate water mass properties for the last 25 myrs that are directly related to the monsoon. Dating the deposits of SAM wind-driven currents yields an age of 12.9 Ma indicating an abrupt SAM onset, over a short period of 300 kyrs. This coincided with the Indian Ocean Oxygen Minimum Zone expansion as revealed by geochemical tracers and the onset of upwelling reflected by the sediment's content of sedimentary organic matter. A weaker `proto-monsoon' existed between 12.9 and 25 Ma, as mirrored by the sedimentary signature of dust influx. Abrupt SAM initiation favors a strong influence of climate in addition to the tectonic control, and we propose that the post Miocene Climate Optimum cooling, together with increased continentalization and establishment of the bipolar ocean circulation, i.e. the beginning of the modern world, shifted the monsoon over a threshold towards the modern system.

  1. A Developmental Shift from Positive to Negative Connectivity in Human Amygdala-Prefrontal Circuitry

    PubMed Central

    Gee, Dylan G.; Humphreys, Kathryn L.; Flannery, Jessica; Goff, Bonnie; Telzer, Eva H.; Shapiro, Mor; Hare, Todd A.; Bookheimer, Susan Y.; Tottenham, Nim

    2013-01-01

    Recent human imaging and animal studies highlight the importance of frontoamygdala circuitry in the regulation of emotional behavior and its disruption in anxiety-related disorders. While tracing studies have suggested changes in amygdala-cortical connectivity through the adolescent period in rodents, less is known about the reciprocal connections within this circuitry across human development, when these circuits are being fine-tuned and substantial changes in emotional control are observed. The present study examined developmental changes in amygdala-prefrontal circuitry across the ages of 4 to 22 years using task-based functional magnetic resonance imaging (fMRI). Results suggest positive amygdala-prefrontal connectivity in early childhood that switches to negative functional connectivity during the transition to adolescence. Amygdala-mPFC functional connectivity was significantly positive (greater than zero) among participants younger than ten, whereas functional connectivity was significantly negative (less than zero) among participants ten years and older, over and above the effect of amygdala reactivity. The developmental switch in functional connectivity was paralleled by a steady decline in amygdala reactivity. Moreover, the valence switch might explain age-related improvement in task performance and a developmentally normative decline in anxiety. Initial positive connectivity followed by a valence shift to negative connectivity provides a neurobiological basis for regulatory development and may present novel insight into a more general process of developing regulatory connections. PMID:23467374

  2. Coherent Sea Ice Variations in the Nordic Seas and Abrupt Greenland Climate Changes over Dansgaard-Oeschger Cycles

    NASA Astrophysics Data System (ADS)

    Sadatzki, H.; Berben, S.; Dokken, T.; Stein, R.; Fahl, K.; Jansen, E.

    2016-12-01

    Rapid changes in sea ice extent in the Nordic Seas may have played a crucial role in controlling the abruptness of ocean circulation and climate changes associated with Dansgaard-Oeschger (D-O) cycles during the last glacial (Li et al., 2010; Dokken et al., 2013). To investigate the role of sea ice for abrupt climate changes, we produced a sea ice record from the Norwegian Sea Core MD99-2284 at a temporal resolution approaching that of ice core records, covering four D-O cycles at ca. 32-41 ka. This record is based on the sea ice diatom biomarker IP25, open-water phytoplankton biomarker dinosterol and semi-quantitative phytoplankton-IP25 (PIP25) estimates. A detailed tephrochronology of MD99-2284 corroborates the tuning-based age model and independently constrains the GS9/GIS8 transition, allowing for direct comparison between our sediment and ice core records. For cold stadials we find extremely low fluxes of total organic carbon, dinosterol and IP25, which points to a general absence of open-water phytoplankton and ice algae production under a near-permanent sea ice cover. For the interstadials, in turn, all biomarker fluxes are strongly enhanced, reflecting a highly productive sea ice edge situation and implying largely open ocean conditions for the eastern Nordic Seas. As constrained by three tephra layers, we observe that the stadial-interstadial sea ice decline was rapid and may have induced a coeval abrupt northward shift in the Greenland precipitation moisture source as recorded in ice cores. The sea ice retreat also facilitated a massive heat release through deep convection in the previously stratified Nordic Seas, generating atmospheric warming of the D-O events. We thus conclude that rapid changes in sea ice extent in the Nordic Seas amplified oceanic reorganizations and were a key factor in controlling abrupt Greenland climate changes over D-O cycles. Dokken, T.M. et al., 2013. Paleoceanography 28, 491-502 Li, C. et al., 2010. Journ. Clim. 23, 5457-5475

  3. Expert system application for prioritizing preventive actions for shift work: shift expert.

    PubMed

    Esen, Hatice; Hatipoğlu, Tuğçen; Cihan, Ahmet; Fiğlali, Nilgün

    2017-09-19

    Shift patterns, work hours, work arrangements and worker motivations have increasingly become key factors for job performance. The main objective of this article is to design an expert system that identifies the negative effects of shift work and prioritizes mitigation efforts according to their importance in preventing these negative effects. The proposed expert system will be referred to as the shift expert. A thorough literature review is conducted to determine the effects of shift work on workers. Our work indicates that shift work is linked to demographic variables, sleepiness and fatigue, health and well-being, and social and domestic conditions. These parameters constitute the sections of a questionnaire designed to focus on 26 important issues related to shift work. The shift expert is then constructed to provide prevention advice at the individual and organizational levels, and it prioritizes this advice using a fuzzy analytic hierarchy process model, which considers comparison matrices provided by users during the prioritization process. An empirical study of 61 workers working on three rotating shifts is performed. After administering the questionnaires, the collected data are analyzed statistically, and then the shift expert produces individual and organizational recommendations for these workers.

  4. Goos-Hanchen shifts in tilted uniaxial crystals

    NASA Astrophysics Data System (ADS)

    Wu, Xiaohu

    2018-06-01

    The Goos-Hanchen shifts at the surface of the tilted uniaxial crystals have been studied with the help of the stationary phase method. It is found that the permittivity and the optical axis of the uniaxial crystal have outstanding influence on the Goos-Hanchen shift. The numerical results show that the negative Goos-Hanchen shift can occur even when the refractive index of the material is not negative. Besides, the Goos-Hanchen shift can be negative or positive infinite under certain conditions. Our results may provide useful information in manipulating the Goos-Hanchen shift in uniaxial crystals. We believe this method could find practical applications in tunable sensors and switches, which are based on Goos-Hanchen shifts.

  5. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, Thomas E.

    1998-01-01

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna.

  6. Risk of fetal death associated with maternal drug dependence and placental abruption: a population-based study.

    PubMed

    McDonald, Sarah D; Vermeulen, Marian J; Ray, Joel G

    2007-07-01

    Substance use in pregnancy is associated with placental abruption, but the risk of fetal death independent of abruption remains undetermined. Our objective was to examine the effect of maternal drug dependence on placental abruption and on fetal death in association with abruption and independent of it. To examine placental abruption and fetal death, we performed a retrospective population-based study of 1 854 463 consecutive deliveries of liveborn and stillborn infants occurring between January 1, 1995 and March 31, 2001, using the Canadian Institute for Health Information Discharge Abstract Database. Maternal drug dependence was associated with a tripling of the risk of placental abruption in singleton pregnancies (adjusted odds ratio [OR] 3.1; 95% confidence intervals [CI] 2.6-3.7), but not in multiple gestations (adjusted OR 0.88; 95% CI 0.12-6.4). Maternal drug dependence was associated with an increased risk of fetal death independent of abruption (adjusted OR 1.6: 95% CI 1.1-2.2) in singleton pregnancies, but not in multiples. Risk of fetal death was increased with placental abruption in both singleton and multiple gestations, even after controlling for drug dependence (adjusted OR 11.4 in singleton pregnancy; 95% CI 10.6-12.2, and 3.4 in multiple pregnancy; 95% CI 2.4-4.9). Maternal drug use is associated with an increased risk of intrauterine fetal death independent of placental abruption. In singleton pregnancies, maternal drug dependence is associated with an increased risk of placental abruption.

  7. Abrupt lake-level changes in the Rocky Mountains and surrounding regions since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Shuman, B. N.; Serravezza, M.

    2016-12-01

    The paleohydrologic record of western North America since the last glacial maximum reveals a wide range of hydroclimatic variability and distinctive patterns associated with abrupt climate changes. To evaluate the sequence of abrupt hydroclimatic shifts and centennial-to-millennial hydrologic variability in western North America over the past 17 ka, we reconstruct lake-level histories from two high-elevation lakes in the Beartooth and Bighorn Mountains. The lakes represent the headwaters of the Missouri River drainage in northern Wyoming, but also have the potential to capture regional hydroclimate variability that links the northern Rocky Mountains to the mid-continent, Pacific Northwest, and the Great Basin. We first discuss the stratigraphic record of lake-level changes in small mid-latitude lakes and then use ground-penetrating radar (GPR) and sediment cores to track the elevations of shoreline sediments within the lakes through time. We compare the stratigraphies to the records from four other lakes in Wyoming and Colorado, and find widespread evidence for a Terminal Pleistocene Drought from 15-11 ka, an early Holocene humid period from 11-8 ka, and a period of severe mid-Holocene aridity from 8-5.7 ka. The northern Wyoming lakes also provide evidence of high levels before ca. 15 ka, including rapid hydroclimatic changes at ca. 16.8 ka during Heinrich Event 1. We place the changes in a broad context by summarizing and mapping water-level changes from 107 additional, previously studied lakes. Important patterns include 1) extensive drying across the western U.S. after 15 ka; 2) coherent sub-regional differences during the Younger Dryas and Pleistocene-Holocene transition; 3) a north-south contrast from 9-6 ka consistent with a northward shift in storm tracks as the influence of the Laurentide Ice Sheet diminished; and 4) rapid increases in effective moisture across much of western North America from 6-4 ka.

  8. The negative ultraslow potential, electrophysiological correlate of infarction in the human cortex

    PubMed Central

    Lückl, Janos; Lemale, Coline L; Kola, Vasilis; Horst, Viktor; Khojasteh, Uldus; Oliveira-Ferreira, Ana I; Major, Sebastian; Winkler, Maren K L; Kang, Eun-Jeung; Schoknecht, Karl; Martus, Peter; Hartings, Jed A; Woitzik, Johannes

    2018-01-01

    Abstract Spreading depolarizations are characterized by abrupt, near-complete breakdown of the transmembrane ion gradients, neuronal oedema, mitochondrial depolarization, glutamate excitotoxicity and activity loss (depression). Spreading depolarization induces either transient hyperperfusion in normal tissue; or hypoperfusion (inverse coupling = spreading ischaemia) in tissue at risk for progressive injury. The concept of the spreading depolarization continuum is critical since many spreading depolarizations have intermediate characteristics, as opposed to the two extremes of spreading depolarization in either severely ischaemic or normal tissue. In animals, the spreading depolarization extreme in ischaemic tissue is characterized by prolonged depolarization durations, in addition to a slow baseline variation termed the negative ultraslow potential. The negative ultraslow potential is initiated by spreading depolarization and similar to the negative direct current (DC) shift of prolonged spreading depolarization, but specifically refers to a negative potential component during progressive recruitment of neurons into cell death in the wake of spreading depolarization. We here first quantified the spreading depolarization-initiated negative ultraslow potential in the electrocorticographic DC range and the activity depression in the alternate current range after middle cerebral artery occlusion in rats. Relevance of these variables to the injury was supported by significant correlations with the cortical infarct volume and neurological outcome after 72 h of survival. We then identified negative ultraslow potential-containing clusters of spreading depolarizations in 11 patients with aneurysmal subarachnoid haemorrhage. The human platinum/iridium-recorded negative ultraslow potential showed a tent-like shape. Its amplitude of 45.0 (39.0, 69.4) mV [median (first, third quartile)] was 6.6 times larger and its duration of 3.7 (3.3, 5.3) h was 34.9 times longer than the

  9. The negative ultraslow potential, electrophysiological correlate of infarction in the human cortex.

    PubMed

    Lückl, Janos; Lemale, Coline L; Kola, Vasilis; Horst, Viktor; Khojasteh, Uldus; Oliveira-Ferreira, Ana I; Major, Sebastian; Winkler, Maren K L; Kang, Eun-Jeung; Schoknecht, Karl; Martus, Peter; Hartings, Jed A; Woitzik, Johannes; Dreier, Jens P

    2018-06-01

    Spreading depolarizations are characterized by abrupt, near-complete breakdown of the transmembrane ion gradients, neuronal oedema, mitochondrial depolarization, glutamate excitotoxicity and activity loss (depression). Spreading depolarization induces either transient hyperperfusion in normal tissue; or hypoperfusion (inverse coupling = spreading ischaemia) in tissue at risk for progressive injury. The concept of the spreading depolarization continuum is critical since many spreading depolarizations have intermediate characteristics, as opposed to the two extremes of spreading depolarization in either severely ischaemic or normal tissue. In animals, the spreading depolarization extreme in ischaemic tissue is characterized by prolonged depolarization durations, in addition to a slow baseline variation termed the negative ultraslow potential. The negative ultraslow potential is initiated by spreading depolarization and similar to the negative direct current (DC) shift of prolonged spreading depolarization, but specifically refers to a negative potential component during progressive recruitment of neurons into cell death in the wake of spreading depolarization. We here first quantified the spreading depolarization-initiated negative ultraslow potential in the electrocorticographic DC range and the activity depression in the alternate current range after middle cerebral artery occlusion in rats. Relevance of these variables to the injury was supported by significant correlations with the cortical infarct volume and neurological outcome after 72 h of survival. We then identified negative ultraslow potential-containing clusters of spreading depolarizations in 11 patients with aneurysmal subarachnoid haemorrhage. The human platinum/iridium-recorded negative ultraslow potential showed a tent-like shape. Its amplitude of 45.0 (39.0, 69.4) mV [median (first, third quartile)] was 6.6 times larger and its duration of 3.7 (3.3, 5.3) h was 34.9 times longer than the negative DC

  10. Anticipatory adjustments to abrupt changes of opposing forces.

    PubMed

    Rapp, Katrin; Heuer, Herbert

    2015-01-01

    Anticipatory adjustments to abrupt load changes are based on task-specific predictive information. The authors asked whether anticipatory adjustments to abrupt offsets of horizontal forces are related to expectancy. In two experiments participants held a position against an opposing force or moved against it. At force offset they had to stop rapidly. Duration of the opposing force or distance moved against it varied between blocks of trials and was constant within each block, or it varied from trial to trial. These two variations resulted in opposite changes of the expectancy of force offset with the passage of time or distance. With constant force durations or distances in each block of trials, anticipatory adjustments tended to be poorest with the longest duration or distance, but with variable force durations or distances they tended to be best with the longest duration or distance. Thus anticipatory adjustments were related to expectancy rather than time or distance per se. Anticipatory adjustments resulted in shorter peak amplitudes of the involuntary movements, accompanied by longer movement times in Experiment 1 and faster movement times in Experiment 2. Thus, for different states of the limb at abrupt dynamic changes anticipatory adjustments involve different mechanisms that modulate different mechanical characteristics.

  11. Prolonged Instability Prior to a Regime Shift | Science ...

    EPA Pesticide Factsheets

    Regime shifts are generally defined as the point of ‘abrupt’ change in the state of a system. However, a seemingly abrupt transition can be the product of a system reorganization that has been ongoing much longer than is evident in statistical analysis of a single component of the system. Using both univariate and multivariate statistical methods, we tested a long-term high-resolution paleoecological dataset with a known change in species assemblage for a regime shift. Analysis of this dataset with Fisher Information and multivariate time series modeling showed that there was a∼2000 year period of instability prior to the regime shift. This period of instability and the subsequent regime shift coincide with regional climate change, indicating that the system is undergoing extrinsic forcing. Paleoecological records offer a unique opportunity to test tools for the detection of thresholds and stable-states, and thus to examine the long-term stability of ecosystems over periods of multiple millennia. This manuscript explores various methods of assessing the transition between alternative states in an ecological system described by a long-term high-resolution paleoecological dataset.

  12. Impacts of abrupt climate changes in the Levant from Last Glacial Dead Sea levels

    NASA Astrophysics Data System (ADS)

    Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai; Enzel, Yehouda

    2013-06-01

    A new, detailed lake level curve for Lake Lisan (the Last Glacial Dead Sea) reveals a high frequency of abrupt fluctuations during Marine Isotope Stage 3 (MIS3) compared to the relatively high stand characterizing MIS2, and the significantly lower Holocene lake. The lake level fluctuations reflect the hydrological conditions in the large watershed of the lake, which in turn reflects the hydro-climatic conditions in the central Levant region. The new curve shows that the fluctuations coincide on millennial timescales with temperature variations recorded in Greenland. Four patterns of correlation are observed through the last ice age: (1) maximum lake elevations were reached during MIS2, the coldest interval; (2) abrupt lake level drops to the lowest elevations coincided with the occurrence of Heinrich (H) events; (3) the lake returned to higher-stand conditions along with warming in Greenland that followed H-events; (4) significant lake level fluctuations coincided with virtually every Greenland stadial-interstadial cycle. Over glacial-interglacial time-scales, Northern Hemisphere glacial cooling induces extreme wetness in the Levant, with high lake levels reaching ˜160 m below mean sea level (mbmsl), approximately 240 m above typical Holocene levels of ˜400 mbmsl. These orbital time-scale shifts are driven by expansions of the European ice sheet, which deflect westerly storm tracks southward to the Eastern Mediterranean, resulting in increased sea-air temperature gradients that invoke increased cyclogenesis, and enhanced moisture delivery to the Levant. The millennial-scale lake level drops associated with Greenland stadials are most extreme during Heinrich stadials and reflect abrupt cooling of the Eastern Mediterranean atmosphere and sea-surface, which weaken the cyclogenic rain engine and cause extreme Levant droughts. During the recovery from the effect of Heinrich stadials, the regional climate configuration resumed typical glacial conditions, with enhanced

  13. Ultra-wideband horn antenna with abrupt radiator

    DOEpatents

    McEwan, T.E.

    1998-05-19

    An ultra-wideband horn antenna transmits and receives impulse waveforms for short-range radars and impulse time-of flight systems. The antenna reduces or eliminates various sources of close-in radar clutter, including pulse dispersion and ringing, sidelobe clutter, and feedline coupling into the antenna. Dispersion is minimized with an abrupt launch point radiator element; sidelobe and feedline coupling are minimized by recessing the radiator into a metallic horn. Low frequency cut-off associated with a horn is extended by configuring the radiator drive impedance to approach a short circuit at low frequencies. A tapered feed plate connects at one end to a feedline, and at the other end to a launcher plate which is mounted to an inside wall of the horn. The launcher plate and feed plate join at an abrupt edge which forms the single launch point of the antenna. 8 figs.

  14. Abruptness of Cascade Failures in Power Grids

    NASA Astrophysics Data System (ADS)

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into ``super-grids''.

  15. Abruptness of cascade failures in power grids.

    PubMed

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-15

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into "super-grids".

  16. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon

    PubMed Central

    Röpke, Cristhiana P.; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J. G.; Deus, Cláudia Pereira de; Pires, Tiago H. S.; Winemiller, Kirk O.

    2017-01-01

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon. PMID:28071701

  17. Simultaneous abrupt shifts in hydrology and fish assemblage structure in a floodplain lake in the central Amazon.

    PubMed

    Röpke, Cristhiana P; Amadio, Sidinéia; Zuanon, Jansen; Ferreira, Efrem J G; Deus, Cláudia Pereira de; Pires, Tiago H S; Winemiller, Kirk O

    2017-01-10

    Combined effects of climate change and deforestation have altered precipitation patterns in the Amazon. This has led to changes in the frequency of extreme events of flood and drought in recent decades and in the magnitude of the annual flood pulse, a phenomenon that influences virtually all aspects of river-floodplain ecosystem dynamics. Analysis of long-term data revealed abrupt and synchronous changes in hydrology and fish assemblage structure of a floodplain lake near the confluence of Amazon and Negro rivers. After an intense drought in 2005, the assemblage assumed a different and fairly persistent taxonomic composition and functional structure. Declines in abundance after 2005 were more pronounced for species of all sizes having equilibrium life history strategy, large species with periodic life history strategy, and for all trophic levels except primary consumers. Our results suggest that the extreme drought triggered changes in the fish assemblage and subsequent anomalous hydrological conditions have hampered assemblage recovery. These findings stress the need to account for climatic-driven hydrological changes in conservation efforts addressing aquatic biodiversity and fishery resources in the central Amazon.

  18. Abrupt Change of the Transboundary Runoff and Its Influence on Water Security of Lanstang-Mekong River

    NASA Astrophysics Data System (ADS)

    Sang, Y. F.; Xie, P.; Ziyi, W.; Jiangyan, Z.; Qianjin, D.; Xu, L.

    2017-12-01

    As a significant manifestation of hydrological variability, abrupt change will obviously impact on the water security. To analyze what does the variation bring under changing environment, abrupt change detection should be a basic task, as well as variation level evaluation and hydrological frequency analysis. However, there lacks an effective method to reach those purposes systematically. Here we derived correlation coefficient between the original series and the jump-component series which is related to the difference degree of mean value before and after the abrupt change. Based on it, we proposed the moving-correlation-coefficient-based detection method and evaluated the significance of abrupt change as different levels related to the value of correlation coefficient. Then, with the obtained results, we calculated hydrological frequency in different situation (before and after the abrupt change). The approach above was employed to investigate the transboundary runoff of Lanstang-Mekong River at some kinds of time scale. We obtained the abrupt changes from runoff series of year, flood season and dry season which are almost the same. All the abrupt changes were significant which could reach to the moderate level. Compared with the past situation (before the abrupt change), the hydrological frequency in the current situation (after the abrupt change) indicated the water security of the water supply and flood control in the lower reaches of Lanstang-Mekong River could be guaranteed better, which is owed to the construction and operation of the water conservancy projects on the upper Lanstang-Mekong River.

  19. A possible abrupt change in summer precipitation over eastern China around 2009

    NASA Astrophysics Data System (ADS)

    Ren, Yongjian; Song, Lianchun; Wang, Zunya; Xiao, Ying; Zhou, Bing

    2017-04-01

    Historical studies have shown that summer rainfall in eastern China undergoes decadal variations, with three apparent changes in the late 1970s, 1992, and the late 1990s. The present observational study indicates that summer precipitation over eastern China likely underwent a change in the late 2000s, during which the main spatial pattern changed from negative-positive-negative to positive-negative in the meridional direction. This change in summer precipitation over eastern China may have been associated with circulation anomalies in the middle/upper troposphere. A strong trough over Lake Baikal created a southward flow of cold air during 2009-15, compared with 1999-2008, while the westward recession of the western Pacific subtropical high strengthened the moisture transport to the north, creating conditions that were conducive for more rainfall in the north during this period. The phase shift of the Pacific Decadal Oscillation in the late 2000s led to the Pacific-Japan-type teleconnection wave train shifting from negative to positive phases, resulting in varied summer precipitation over eastern China.

  20. Regime Shifts in Shallow Lakes: Responses of Cyanobacterial Blooms to Watershed Agricultural Phosphorus Loading Over the Last ~100 Years.

    NASA Astrophysics Data System (ADS)

    Vermaire, J. C.; Taranu, Z. E.; MacDonald, G. K.; Velghe, K.; Bennett, E.; Gregory-Eaves, I.

    2015-12-01

    Rapid changes in ecosystem states have occurred naturally throughout Earth's history. However, environmental changes that have taken place since the start of the Anthropocene may be destabilizing ecosystems and increasing the frequency of regime shifts in response to abrupt changes in external drivers or local intrinsic dynamics. To evaluate the relative influence of these forcers and improve our understanding of the impact of future change, we examined the effects of historical catchment phosphorus loading associated with agricultural land use on lake ecosystems, and whether this caused a shift from a stable, clear-water, regime to a turbid, cyanobacteria-dominated, state. The sedimentary pigments, diatom, and zooplankton (Cladocera) records from a currently clear-water shallow lake (Roxton Pond) and a turbid-water shallow lake (Petit lac Saint-François; PSF) were examined to determine if a cyanobacteria associated pigment (i.e. echinenone) showed an abrupt non-linear response to continued historical phosphorus load index (determined by phosphorus budget) over the last ~100 years. While PSF lake is presently in the turbid-water state, pigment and diatom analyses indicated that both lakes were once in the clear-water state, and that non-linear increases in catchment phosphorus balance resulted in an abrupt transition to cyanobacteria dominated states in each record. These results show that phosphorus loading has resulted in state shifts in shallow lake ecosystems that has been recorded across multiple paleolimnological indicators preserved in the sedimentary record.

  1. Effects of pharmacological agents on subcortical resistance shifts

    NASA Technical Reports Server (NTRS)

    Klivington, K. A.

    1975-01-01

    Microliter quantities of tetrodotoxin, tetraethylammonium chloride, and picrotoxin injected into the inferior colliculus and superior olive of unanesthetized cats differentially affect the amplitude and waveform of click-evoked potentials and evoked resistance shifts. Tetrodotoxin simultaneously reduces the negative phase of the evoked potential and eliminates the evoked resistance shift. Tetraethylammonium enhances the negative evoked potential component, presumably of postsynaptic origin, without significantly altering evoked resistance shift amplitude. Picrotoxin also enhances the negative evoked potential wave but increases evoked resistance shift amplitude. These findings implicate events associated with postsynaptic membrane depolarization in the production of the evoked resistance shift.

  2. Abruptness of Cascade Failures in Power Grids

    PubMed Central

    Pahwa, Sakshi; Scoglio, Caterina; Scala, Antonio

    2014-01-01

    Electric power-systems are one of the most important critical infrastructures. In recent years, they have been exposed to extreme stress due to the increasing demand, the introduction of distributed renewable energy sources, and the development of extensive interconnections. We investigate the phenomenon of abrupt breakdown of an electric power-system under two scenarios: load growth (mimicking the ever-increasing customer demand) and power fluctuations (mimicking the effects of renewable sources). Our results on real, realistic and synthetic networks indicate that increasing the system size causes breakdowns to become more abrupt; in fact, mapping the system to a solvable statistical-physics model indicates the occurrence of a first order transition in the large size limit. Such an enhancement for the systemic risk failures (black-outs) with increasing network size is an effect that should be considered in the current projects aiming to integrate national power-grids into “super-grids”. PMID:24424239

  3. Synchronous centennial abrupt events in the ocean and atmosphere during the last deglaciation.

    PubMed

    Chen, Tianyu; Robinson, Laura F; Burke, Andrea; Southon, John; Spooner, Peter; Morris, Paul J; Ng, Hong Chin

    2015-09-25

    Antarctic ice-core data reveal that the atmosphere experienced abrupt centennial increases in CO2 concentration during the last deglaciation (~18 thousand to 11 thousand years ago). Establishing the role of ocean circulation in these changes requires high-resolution, accurately dated marine records. Here, we report radiocarbon data from uranium-thorium-dated deep-sea corals in the Equatorial Atlantic and Drake Passage over the past 25,000 years. Two major deglacial radiocarbon shifts occurred in phase with centennial atmospheric CO2 rises at 14.8 thousand and 11.7 thousand years ago. We interpret these radiocarbon-enriched signals to represent two short-lived (less than 500 years) "overshoot" events, with Atlantic meridional overturning stronger than that of the modern era. These results provide compelling evidence for a close coupling of ocean circulation and centennial climate events during the last deglaciation. Copyright © 2015, American Association for the Advancement of Science.

  4. Maternal sleep duration and complaints of vital exhaustion during pregnancy is associated with placental abruption.

    PubMed

    Qiu, Chunfang; Sanchez, Sixto E; Gelaye, Bizu; Enquobahrie, Daniel A; Ananth, Cande V; Williams, Michelle A

    2015-02-01

    Sleep disorders are associated with cardiovascular complications and preterm delivery (PTD). Insufficient sleep results in metabolic alterations and increased inflammation, both known to contribute to placental abruption (abruption), a determinant of PTD. We examined associations of abruption with sleep duration and complaints of vital exhaustion. The study included 164 abruption cases and 160 controls in a multicenter study in Peru. Data on habitual sleep duration and vital exhaustion during the first 6 months of pregnancy were elicited during interviews conducted following delivery. Women were categorized according to short, normal and long sleep duration (≤6, 7-8 and ≥9 h); and frequency of feeling exhausted. Odds ratios (OR) and 95% confidence intervals (CI) were calculated. Short and long sleep durations were associated with increased odds of abruption. The ORs of abruption in relation to short (≤6 h) and long (≥9 h) sleep duration were 2.0 (95% CI 1.1-3.7) and 2.1 (95% CI 1.1-4.1), compared with normal sleep duration (7-8 h). Complaints of vital exhaustion were also associated with abruption (OR = 2.37; 95% CI 1.46-3.85), and were independent of sleep duration. We extend the existing literature and support the thesis that maternal sleep habits and disorders should be assessed among pregnant women.

  5. [Reversible catatonia after the abrupt discontinuation of clozapine: Case report].

    PubMed

    Jaafari, M; Bout, A; Rammouz, I; Aalouane, R

    2016-12-01

    In this paper, we report the case of a patient, aged 26, with schizophrenia who was admitted to psychiatric emergencies for catatonia, one week after abrupt discontinuation of clozapine. An improvement was seen after only two days of the reintroduction of clozapine alone. This catatonia is reversible and it responds magnificently to the reintroduction of clozapine. And we conclude that patients and their caregivers need to be educated about the effects of abrupt cessation of clozapine administration. Copyright © 2016 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.

  6. Using a time-series statistical framework to quantify trends and abrupt change in US corn, soybean, and wheat yields from 1970-2016

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Ives, A. R.; Turner, M. G.; Kucharik, C. J.

    2017-12-01

    Previous studies have identified global agricultural regions where "stagnation" of long-term crop yield increases has occurred. These studies have used a variety of simple statistical methods that often ignore important aspects of time series regression modeling. These methods can lead to differing and contradictory results, which creates uncertainty regarding food security given rapid global population growth. Here, we present a new statistical framework incorporating time series-based algorithms into standard regression models to quantify spatiotemporal yield trends of US maize, soybean, and winter wheat from 1970-2016. Our primary goal was to quantify spatial differences in yield trends for these three crops using USDA county level data. This information was used to identify regions experiencing the largest changes in the rate of yield increases over time, and to determine whether abrupt shifts in the rate of yield increases have occurred. Although crop yields continue to increase in most maize-, soybean-, and winter wheat-growing areas, yield increases have stagnated in some key agricultural regions during the most recent 15 to 16 years: some maize-growing areas, except for the northern Great Plains, have shown a significant trend towards smaller annual yield increases for maize; soybean has maintained an consistent long-term yield gains in the Northern Great Plains, the Midwest, and southeast US, but has experienced a shift to smaller annual increases in other regions; winter wheat maintained a moderate annual increase in eastern South Dakota and eastern US locations, but showed a decline in the magnitude of annual increases across the central Great Plains and western US regions. Our results suggest that there were abrupt shifts in the rate of annual yield increases in a variety of US regions among the three crops. The framework presented here can be broadly applied to additional yield trend analyses for different crops and regions of the Earth.

  7. Abrupt aridities in the Levant-Sahel linked with solar activities

    NASA Astrophysics Data System (ADS)

    Stein, M.; Kushnir, Y.

    2012-04-01

    Observations of 19th and 20th century precipitation in the Dead Sea watershed region display a multidecadal, anti-phase relationship to North Atlantic (NAtl) sea surface temperature (SST) variability, such that when the NAtl is relatively cold, Jerusalem experiences higher than normal precipitation and vice versa. This association is underlined by a negative correlation to precipitation in the sub-Saharan Sahel and a positive correlation to precipitation in western North America, areas that are also affected by multidecadal NAtl SST variability. These observations are consistent with broad range of Holocene hydroclimatic fluctuations from the epochal, to the millennial and centennial time scales, as displayed by the Dead Sea and Sahelian lake levels and by direct and indirect proxy indicators of NAtl SSTs. On the epochal time scale, the gradual cooling of NAtl SSTs throughout the Holocene in response to precession-driven reduction of summer insolation is associated with previously well-studied wet-to-dry transition in the Sahel and with a general increase in Dead Sea lake levels from low stands after the Younger Dryas to higher stands in the mid- to late-Holocene. On the millennial and centennial time scales there is also evidence for an antiphase relationship between Holocene variations in the Dead Sea and Sahelian lake levels and with proxy indicators of NAtl SSTs. However, the records are punctuated by abrupt lake-level drops and extensive expansion of the desert belt at ~8.1, 5.7, 3.3 and 1.4 ka cal BP, which appear to be in-phase and which occur during previously documented abrupt major cooling events in the Northern Hemisphere. We link these cooling to solar activity variations that were identified in the North Atlantic IRD and cosmogenic isotopes records.

  8. Placental abruption possibly due to parvovirus B19 infection.

    PubMed

    Kawabe, Ayaka; Takai, Yasushi; Tamaru, Jun-Ichi; Samejima, Kouki; Seki, Hiroyuki

    2016-01-01

    There is concern about the development of anemia-associated fetal hydrops associated with maternal parvovirus B19 infection. Parvovirus B19 infection occurs via the globoside (P antigen) receptor, the main glycolipid of erythroid cells, which induces apoptosis. Similar findings have been reported for the P antigen of globoside-containing placental trophoblast cells. A 32-year-old woman was infected with human parvovirus B19 at week 32 of pregnancy, and had severe anemia at week 34. At week 37, an emergency cesarean section was performed because of sudden abdominal pain and fetal bradycardia; placental abruption was found. A live male infant was delivered with no sign of fetal hydrops or fetal infection. Placental tissue was positive for parvovirus B19 according to polymerase chain reaction. Immunohistochemical analysis using caspase-related M30 CytoDEATH monoclonal antibody revealed M30 staining of the placental villous trophoblasts. Placental trophoblasts and erythroid precursor cells have been reported to express globoside (P antigen), which is necessary for parvovirus B19 infectivity, and to show apoptotic activity as a result of infection. Placentas from three other pregnancies with documented abruption showed no M30 staining. The present case strongly suggests an association between placental abruption and apoptosis resulting from parvovirus B19 infection.

  9. Vegetation responses to abrupt climatic changes during the Last Interglacial Complex (Marine Isotope Stage 5) at Tenaghi Philippon, NE Greece

    NASA Astrophysics Data System (ADS)

    Milner, A. M.; Roucoux, K. H.; Collier, R. E. L.; Müller, U. C.; Pross, J.; Tzedakis, P. C.

    2016-12-01

    The discovery that climate variability during the Last Glacial shifted rapidly between climate states has intensified efforts to understand the distribution, timing and impact of abrupt climate change under a wide range of boundary conditions. In contribution to this, we investigate the nature of abrupt environmental changes in terrestrial settings of the Mediterranean region during the Last Interglacial Complex (Marine Isotope Stage [MIS] 5) and explore the relationships of these changes to high-latitude climate events. We present a new, temporally highly resolved (mean: 170 years) pollen record for the Last Interglacial Complex from Tenaghi Philippon, north-east Greece. The new pollen record, which spans the interval from 130,000 to 65,000 years ago, forms part of an exceptionally long polleniferous sediment archive covering the last 1.35 million years. The pollen data reveal an interglacial followed by alternating forest and steppe phases representing the interstadials and stadials of the Early Glacial. Superimposed on these millennial-scale changes is evidence of persistent sub-millennial-scale variability. We identify ten high-amplitude abrupt events in the pollen record, characterised by rapid contractions of closed forest to open steppe environment and interpreted to indicate major changes in moisture availability and temperature. The contractions in forest cover on millennial timescales appear associated with cooling events in the Mediterranean Sea, North Atlantic and Greenland regions, linked to the Dansgaard-Oeschger (DO) cycles of the Early Glacial. On sub-millennial timescales, the pattern of changes in forest cover at Tenaghi Philippon display a structure similar to the pattern of short-lived precursor and rebound-type events detected in the Greenland ice-core record. Our findings indicate that persistent, high-amplitude environmental variability occurred throughout the Early Glacial, on both millennial and submillennial timescales. Furthermore, the

  10. Detection of abrupt changes in dynamic systems

    NASA Technical Reports Server (NTRS)

    Willsky, A. S.

    1984-01-01

    Some of the basic ideas associated with the detection of abrupt changes in dynamic systems are presented. Multiple filter-based techniques and residual-based method and the multiple model and generalized likelihood ratio methods are considered. Issues such as the effect of unknown onset time on algorithm complexity and structure and robustness to model uncertainty are discussed.

  11. Phase shifting two coupled circadian pacemakers - Implications for jet lag

    NASA Technical Reports Server (NTRS)

    Gander, P. H.; Kronauer, R. E.; Graeber, R. C.

    1985-01-01

    Two Van der Pol oscillators with reciprocal linear velocity coupling are utilized to model the response of the human circadian timing system to abrupt displacements of the environmental time cues (zeitgebers). The core temperature rhythm and sleep-wake cycle simulated by the model are examined. The relationship between the masking of circadian rhythms by environmental variables and behavioral and physiological events and the rates of resynchronization is studied. The effects of zeitgeber phase shifts and zeitgeber strength on the resynchronization rates are analyzed. The influence of intrinsic pacemakers periods and coupling strength on resynchronization are investigated. The simulated data reveal that: resynchronization after a time zone shift depends on the magnitude of the shift; the time of day of the shift has little influence on resynchronization; the strength of zeitgebers affects the rate and direction of the resynchronization; the intrinsic pacemaker periods have a significant effect on resynchronization; and increasing the coupling between the oscillators results in an increase in the rate of resynchronization. The model data are compared to transmeridian flight studies data and similar resynchronization patterns are observed.

  12. Atmospheric CO2 and abrupt climate change on submillennial timescales

    NASA Astrophysics Data System (ADS)

    Ahn, Jinho; Brook, Edward

    2010-05-01

    How atmospheric CO2 varies and is controlled on various time scales and under various boundary conditions is important for understanding how the carbon cycle and climate change are linked. Ancient air preserved in ice cores provides important information on past variations in atmospheric CO2. In particular, concentration records for intervals of abrupt climate change may improve understanding of mechanisms that govern atmospheric CO2. We present new multi-decadal CO2 records that cover Greenland stadial 9 (between Dansgaard-Oeschger (DO) events 8 and 9) and the abrupt cooling event at 8.2 ka. The CO2 records come from Antarctic ice cores but are well synchronized with Greenland ice core records using new high-resolution CH4 records,precisely defining the timing of CO2 change with respect to abrupt climate events in Greenland. Previous work showed that during stadial 9 (40~38 ka), CO2 rose by about 15~20 ppm over around 2,000 years, and at the same time temperatures in Antarctica increased. Dust proxies indicate a decrease in dust flux over the same period. With more detailed data and better age controls we now find that approximately half of the CO2 increase during stadial 9 occurred abruptly, over the course of decades to a century at ~39.6 ka. The step increase of CO2 is synchronous with a similar step increase of Antarctic isotopic temperature and a small abrupt change in CH4, and lags after the onset of decrease in dust flux by ~400 years. New atmospheric CO2 records at the well-known ~8.2 ka cooling event were obtained from Siple Dome ice core, Antarctica. Our preliminary CO2 data span 900 years and include 19 data points within the 8.2 ka cooling event, which persisted for ~160 years (Thomas et al., Quarternary Sci. Rev., 2007). We find that CO2 increased by 2~4 ppm during that cooling event. Further analyses will improve the resolution and better constrain the CO2 variability during other times in the early Holocene to determine if the variations observed

  13. Shift Work and Shift Work Sleep Disorder: Clinical and Organizational Perspectives.

    PubMed

    Wickwire, Emerson M; Geiger-Brown, Jeanne; Scharf, Steven M; Drake, Christopher L

    2017-05-01

    Throughout the industrialized world, nearly one in five employees works some form of nontraditional shift. Such shift work is associated with numerous negative health consequences, ranging from cognitive complaints to cancer, as well as diminished quality of life. Furthermore, a substantial percentage of shift workers develop shift work disorder, a circadian rhythm sleep disorder characterized by excessive sleepiness, insomnia, or both as a result of shift work. In addition to adverse health consequences and diminished quality of life at the individual level, shift work disorder incurs significant costs to employers through diminished workplace performance and increased accidents and errors. Nonetheless, shift work will remain a vital component of the modern economy. This article reviews seminal and recent literature regarding shift work, with an eye toward real-world application in clinical and organizational settings. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

  14. Acute diabetes insipidus mediated by vasopressinase after placental abruption.

    PubMed

    Wallia, Amisha; Bizhanova, Aigerim; Huang, Wenyu; Goldsmith, Susan L; Gossett, Dana R; Kopp, Peter

    2013-03-01

    Postpartum, diabetes insipidus (DI) can be part of Sheehan's syndrome or lymphocytic hypophysitis in combination with anterior pituitary hormone deficiencies. In contrast, acute onset of isolated DI in the postpartum period is unusual. This patient presented at 33 weeks gestation with placental abruption, prompting a cesarean delivery of twins. Immediately after delivery, she developed severe DI. The DI could be controlled with the vasopressinase-resistant 1-deamino-8-D-arginine vasopressin (DDAVP), but not with arginine vasopressin (AVP), and it resolved within a few weeks. The aim of this study was to demonstrate that the postpartum DI in this patient was caused by the release of placental vasopressinase into the maternal bloodstream. Cells were transiently transfected with the AVP receptor 2 (AVPR2) and treated with either AVP or DDAVP in the presence of the patient's serum collected postpartum or 10 weeks after delivery. The response to the different treatments was evaluated by measuring the activity of a cAMP-responsive firefly luciferase reporter construct. The in vitro studies demonstrate that the patient's postpartum serum disrupts activation of the AVPR2 by AVP, but not by the vasopressinase-resistant DDAVP. Placental abruption can rarely be associated with acute postpartum DI caused by release of placental vasopressinase into the bloodstream. This clinical entity must be considered in patients with placental abruption and when evaluating patients presenting with DI after delivery.

  15. [Smoking abstinence rate and its associated factors between abrupt and gradual smoking cessation].

    PubMed

    Hao, R; Zhou, J P; Ni, L; Li, Q Y; Shi, G C

    2017-12-12

    Objective: To analyze and compare the abstinence rate of smoking quitting methods and its associated factors between abrupt and gradual smoking cessation in smokers with drug-based therapy. Methods: A prospective clinical study was conducted in patients undergoing quitting smoking intervention in Ruijin Hospital smoking cessation clinic between June 2013 and May 2016. All the subjects were randomized in a 1∶1 ratio into the abrupt smoking cessation group (smoking as usual over 3 weeks before a planned quit day, and then stopping smoking abruptly) and the gradual smoking cessation group (gradually reducing tobacco use over 3 weeks before a planned quit day, and then stopping smoking totally). The primary outcome was the complete abstinence rate, and the secondary outcomes included 1-month, 3-month and 6 month 7-day point prevalence of abstinence rates and 3 month sustained abstinence rates. Changes of body weight and drug adverse events were also compared. Results: A total of 314 moderate to severe nicotine-dependent patients were admitted in the study, including 157 patients in the abrupt smoking cessation and 157 patients in the gradual smoking cessation group. Fourteen patients fell off during the follow-up. For the complete abstinence rate, the gradual smoking cessation group was higher than the abrupt smoking cessation group(55.0% vs . 36.9%, χ(2)=9.841, P =0.002) .For 7-d smoking abstinence rate in the 1st, 3rd, 6th month, there was no significant difference between the 2 groups (all P >0.05). As for the 3-month sustained abstinence rate, a higher smoking quitting rate was seen in the gradual smoking cessation group compared to the abrupt smoking cessation group in the 6-month follow-up (17.9% vs .8.7%, χ(2)=5.441, P =0.020). The adverse drug reaction incidence was higher in the abrupt smoking cessation group than the gradual smoking cessation group (Gastrointestinal discomfort: 39.2% vs . 17.7%, χ(2)=12.336, P =0.000; Dreaminess: 40.2% vs . 13.3%, χ(2

  16. Early detection of ecosystem regime shifts: a multiple method evaluation for management application.

    PubMed

    Lindegren, Martin; Dakos, Vasilis; Gröger, Joachim P; Gårdmark, Anna; Kornilovs, Georgs; Otto, Saskia A; Möllmann, Christian

    2012-01-01

    Critical transitions between alternative stable states have been shown to occur across an array of complex systems. While our ability to identify abrupt regime shifts in natural ecosystems has improved, detection of potential early-warning signals previous to such shifts is still very limited. Using real monitoring data of a key ecosystem component, we here apply multiple early-warning indicators in order to assess their ability to forewarn a major ecosystem regime shift in the Central Baltic Sea. We show that some indicators and methods can result in clear early-warning signals, while other methods may have limited utility in ecosystem-based management as they show no or weak potential for early-warning. We therefore propose a multiple method approach for early detection of ecosystem regime shifts in monitoring data that may be useful in informing timely management actions in the face of ecosystem change.

  17. Early Detection of Ecosystem Regime Shifts: A Multiple Method Evaluation for Management Application

    PubMed Central

    Lindegren, Martin; Dakos, Vasilis; Gröger, Joachim P.; Gårdmark, Anna; Kornilovs, Georgs; Otto, Saskia A.; Möllmann, Christian

    2012-01-01

    Critical transitions between alternative stable states have been shown to occur across an array of complex systems. While our ability to identify abrupt regime shifts in natural ecosystems has improved, detection of potential early-warning signals previous to such shifts is still very limited. Using real monitoring data of a key ecosystem component, we here apply multiple early-warning indicators in order to assess their ability to forewarn a major ecosystem regime shift in the Central Baltic Sea. We show that some indicators and methods can result in clear early-warning signals, while other methods may have limited utility in ecosystem-based management as they show no or weak potential for early-warning. We therefore propose a multiple method approach for early detection of ecosystem regime shifts in monitoring data that may be useful in informing timely management actions in the face of ecosystem change. PMID:22808007

  18. Abrupt Late Holocene Shift in Atmospheric Circulation Recorded by Mineral Dust in the Siple Dome Ice Core, Antarctica

    NASA Astrophysics Data System (ADS)

    Koffman, B. G.; Goldstein, S. L.; Kaplan, M. R.; Winckler, G.; Bory, A. J. M.; Biscaye, P.

    2015-12-01

    Atmospheric dust directly influences Earth's climate by altering the radiative balance and by depositing micronutrients in the surface ocean, affecting global biogeochemical cycling. In addition, mineral dust particles provide observational evidence constraining past atmospheric circulation patterns. Because dust can originate from both local and distant terrestrial sources, knowledge of dust provenance can substantially inform our understanding of past climate history, atmospheric transport pathways, and differences in aerosol characteristics between glacial and interglacial climate states. Dust provenance information from Antarctic ice cores has until now been limited to sites in East Antarctica. Here we present some of the first provenance data from West Antarctica. We use Sr-Nd isotopes to characterize dust extracted from late Holocene ice (~1000-1800 C.E.) from the Siple Dome ice core. The data form a tight array in Sr-Nd isotope space, with 87Sr/86Sr ranging between ~0.7087 and 0.7102, and ɛNd ranging between ~ -7 and -16. This combination is unique for Antarctica, with low Nd and low Sr isotope ratios compared to high-elevation East Antarctic sites, requiring a dust source from ancient (Archean to early Proterozoic) and unweathered continental crust, which mixes with young volcanic material. Both components are likely sourced from Antarctica. We also observe significant, systematic variability in Sr and Nd isotopic signatures through time, reflecting changes in the mixing ratio of these sources, and hypothesize that these changes are driven by shifts in circulation patterns. A large change occurs over about 10 years at ca. 1125 C.E. (ΔɛNd = +3 and Δ87Sr/86Sr = -0.0014). This shift coincides with changes in climate proxies in Southern Hemisphere paleoclimate records reflecting variability in the Westerlies. We therefore interpret the shift in dust provenance at Siple Dome to be related to larger-scale circulation changes. In general, the observed shifts

  19. Recommended Experimental Procedures for Evaluation of Abrupt Wing Stall Characteristics

    NASA Technical Reports Server (NTRS)

    Capone, F. J.; Hall, R. M.; Owens, D. B.; Lamar, J. E.; McMillin, S. N.

    2003-01-01

    This paper presents a review of the experimental program under the Abrupt Wing Stall (AWS) Program. Candidate figures of merit from conventional static tunnel tests are summarized and correlated with data obtained in unique free-to-roll tests. Where possible, free-to-roll results are also correlated with flight data. Based on extensive studies of static experimental figures of merit in the Abrupt Wing Stall Program for four different aircraft configurations, no one specific figure of merit consistently flagged a warning of potential lateral activity when actual activity was seen to occur in the free-to-roll experiments. However, these studies pointed out the importance of measuring and recording the root mean square signals of the force balance.

  20. Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI

    DTIC Science & Technology

    2015-09-30

    Acquisition of an Underway CTD System for the Flow Encountering Abrupt Topography DRI T. M. Shaun Johnston Scripps Institution of Oceanography...westward flow in the North Equatorial Current (NEC) encounters tall, steep, submarine topography and islands. During the Flow Encountering Abrupt... Topography (FLEAT) DRI, investigators will determine: • Whether appreciable energy/momentum is lost from the large-scale NEC flow to smaller scales and

  1. The resilience of postglacial hunter-gatherers to abrupt climate change.

    PubMed

    Blockley, Simon; Candy, Ian; Matthews, Ian; Langdon, Pete; Langdon, Cath; Palmer, Adrian; Lincoln, Paul; Abrook, Ashley; Taylor, Barry; Conneller, Chantal; Bayliss, Alex; MacLeod, Alison; Deeprose, Laura; Darvill, Chris; Kearney, Rebecca; Beavan, Nancy; Staff, Richard; Bamforth, Michael; Taylor, Maisie; Milner, Nicky

    2018-05-01

    Understanding the resilience of early societies to climate change is an essential part of exploring the environmental sensitivity of human populations. There is significant interest in the role of abrupt climate events as a driver of early Holocene human activity, but there are very few well-dated records directly compared with local climate archives. Here, we present evidence from the internationally important Mesolithic site of Star Carr showing occupation during the early Holocene, which is directly compared with a high-resolution palaeoclimate record from neighbouring lake beds. We show that-once established-there was intensive human activity at the site for several hundred years when the community was subject to multiple, severe, abrupt climate events that impacted air temperatures, the landscape and the ecosystem of the region. However, these results show that occupation and activity at the site persisted regardless of the environmental stresses experienced by this society. The Star Carr population displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change. Instead, we show that local, intrinsic changes in the wetland environment were more significant in determining human activity than the large-scale abrupt early Holocene climate events.

  2. Response of seafloor ecosystems to abrupt global climate change

    PubMed Central

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-01-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mL⋅L−1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems. PMID:25825727

  3. Response of seafloor ecosystems to abrupt global climate change

    NASA Astrophysics Data System (ADS)

    Moffitt, Sarah E.; Hill, Tessa M.; Roopnarine, Peter D.; Kennett, James P.

    2015-04-01

    Anthropogenic climate change is predicted to decrease oceanic oxygen (O2) concentrations, with potentially significant effects on marine ecosystems. Geologically recent episodes of abrupt climatic warming provide opportunities to assess the effects of changing oxygenation on marine communities. Thus far, this knowledge has been largely restricted to investigations using Foraminifera, with little being known about ecosystem-scale responses to abrupt, climate-forced deoxygenation. We here present high-resolution records based on the first comprehensive quantitative analysis, to our knowledge, of changes in marine metazoans (Mollusca, Echinodermata, Arthropoda, and Annelida; >5,400 fossils and trace fossils) in response to the global warming associated with the last glacial to interglacial episode. The molluscan archive is dominated by extremophile taxa, including those containing endosymbiotic sulfur-oxidizing bacteria (Lucinoma aequizonatum) and those that graze on filamentous sulfur-oxidizing benthic bacterial mats (Alia permodesta). This record, from 16,100 to 3,400 y ago, demonstrates that seafloor invertebrate communities are subject to major turnover in response to relatively minor inferred changes in oxygenation (>1.5 to <0.5 mLṡL-1 [O2]) associated with abrupt (<100 y) warming of the eastern Pacific. The biotic turnover and recovery events within the record expand known rates of marine biological recovery by an order of magnitude, from <100 to >1,000 y, and illustrate the crucial role of climate and oceanographic change in driving long-term successional changes in ocean ecosystems.

  4. Abrupt Climate Change: the View from the Past, the Present and the Future

    NASA Astrophysics Data System (ADS)

    White, J. W. C.

    2014-12-01

    Climate is changing as humans put more and more greenhouse gases into the atmosphere. With CO2 levels today around 400ppm, we are clearly committed to far more climate change, both in the near term, and well beyond our children's future. A key question is how that change will occur. Abrupt climate changes are those that exceed our expectations, preparedness, and ability to adapt. Such changes challenge us economically, physically, and socially. This talk will draw upon results from ice core research over the past twenty years, as well as a new NRC report on abrupt climate change in order to address abrupt change, as seen in the past in ice cores, as seen today in key environmental systems upon which humans depend, and what is may be coming in the future.

  5. Abrupt change of Antarctic moisture origin at the end of Termination II

    PubMed Central

    Masson-Delmotte, V.; Stenni, B.; Blunier, T.; Cattani, O.; Chappellaz, J.; Cheng, H.; Dreyfus, G.; Edwards, R. L.; Falourd, S.; Govin, A.; Kawamura, K.; Johnsen, S. J.; Jouzel, J.; Landais, A.; Lemieux-Dudon, B.; Lourantou, A.; Marshall, G.; Minster, B.; Mudelsee, M.; Pol, K.; Röthlisberger, R.; Selmo, E.; Waelbroeck, C.

    2010-01-01

    The deuterium excess of polar ice cores documents past changes in evaporation conditions and moisture origin. New data obtained from the European Project for Ice Coring in Antarctica Dome C East Antarctic ice core provide new insights on the sequence of events involved in Termination II, the transition between the penultimate glacial and interglacial periods. This termination is marked by a north–south seesaw behavior, with first a slow methane concentration rise associated with a strong Antarctic temperature warming and a slow deuterium excess rise. This first step is followed by an abrupt north Atlantic warming, an abrupt resumption of the East Asian summer monsoon, a sharp methane rise, and a CO2 overshoot, which coincide within dating uncertainties with the end of Antarctic optimum. Here, we show that this second phase is marked by a very sharp Dome C centennial deuterium excess rise, revealing abrupt reorganization of atmospheric circulation in the southern Indian Ocean sector. PMID:20566887

  6. The affective shift model of work engagement.

    PubMed

    Bledow, Ronald; Schmitt, Antje; Frese, Michael; Kühnel, Jana

    2011-11-01

    On the basis of self-regulation theories, the authors develop an affective shift model of work engagement according to which work engagement emerges from the dynamic interplay of positive and negative affect. The affective shift model posits that negative affect is positively related to work engagement if negative affect is followed by positive affect. The authors applied experience sampling methodology to test the model. Data on affective events, mood, and work engagement was collected twice a day over 9 working days among 55 software developers. In support of the affective shift model, negative mood and negative events experienced in the morning of a working day were positively related to work engagement in the afternoon if positive mood in the time interval between morning and afternoon was high. Individual differences in positive affectivity moderated within-person relationships. The authors discuss how work engagement can be fostered through affect regulation. (c) 2011 APA, all rights reserved.

  7. The Regime Shift Associated with the 2004–2008 US Housing Market Bubble

    PubMed Central

    Cheong, Siew Ann

    2016-01-01

    The Subprime Bubble preceding the Subprime Crisis of 2008 was fueled by risky lending practices, manifesting in the form of a large abrupt increase in the proportion of subprime mortgages issued in the US. This event also coincided with critical slowing down signals associated with instability, which served as evidence of a regime shift or phase transition in the US housing market. Here, we show that the US housing market underwent a regime shift between alternate stable states consistent with the observed critical slowing down signals. We modeled this regime shift on a universal transition path and validated the model by estimating when the bubble burst. Additionally, this model reveals loose monetary policy to be a plausible cause of the phase transition, implying that the bubble might have been deflatable by a timely tightening of monetary policy. PMID:27583633

  8. The Atlantic Meridional Overturning Circulation and Abrupt Climate Change.

    PubMed

    Lynch-Stieglitz, Jean

    2017-01-03

    Abrupt changes in climate have occurred in many locations around the globe over the last glacial cycle, with pronounced temperature swings on timescales of decades or less in the North Atlantic. The global pattern of these changes suggests that they reflect variability in the Atlantic meridional overturning circulation (AMOC). This review examines the evidence from ocean sediments for ocean circulation change over these abrupt events. The evidence for changes in the strength and structure of the AMOC associated with the Younger Dryas and many of the Heinrich events is strong. Although it has been difficult to directly document changes in the AMOC over the relatively short Dansgaard-Oeschger events, there is recent evidence supporting AMOC changes over most of these oscillations as well. The lack of direct evidence for circulation changes over the shortest events leaves open the possibility of other driving mechanisms for millennial-scale climate variability.

  9. Acceptable Risk Analysis for Abrupt Environmental Pollution Accidents in Zhangjiakou City, China.

    PubMed

    Du, Xi; Zhang, Zhijiao; Dong, Lei; Liu, Jing; Borthwick, Alistair G L; Liu, Renzhi

    2017-04-20

    Abrupt environmental pollution accidents cause considerable damage worldwide to the ecological environment, human health, and property. The concept of acceptable risk aims to answer whether or not a given environmental pollution risk exceeds a societally determined criterion. This paper presents a case study on acceptable environmental pollution risk conducted through a questionnaire survey carried out between August and October 2014 in five representative districts and two counties of Zhangjiakou City, Hebei Province, China. Here, environmental risk primarily arises from accidental water pollution, accidental air pollution, and tailings dam failure. Based on 870 valid questionnaires, demographic and regional differences in public attitudes towards abrupt environmental pollution risks were analyzed, and risk acceptance impact factors determined. The results showed females, people between 21-40 years of age, people with higher levels of education, public servants, and people with higher income had lower risk tolerance. People with lower perceived risk, low-level risk knowledge, high-level familiarity and satisfaction with environmental management, and without experience of environmental accidents had higher risk tolerance. Multiple logistic regression analysis indicated that public satisfaction with environmental management was the most significant factor in risk acceptance, followed by perceived risk of abrupt air pollution, occupation, perceived risk of tailings dam failure, and sex. These findings should be helpful to local decision-makers concerned with environmental risk management (e.g., selecting target groups for effective risk communication) in the context of abrupt environmental accidents.

  10. Acceptable Risk Analysis for Abrupt Environmental Pollution Accidents in Zhangjiakou City, China

    PubMed Central

    Du, Xi; Zhang, Zhijiao; Dong, Lei; Liu, Jing; Borthwick, Alistair G. L.; Liu, Renzhi

    2017-01-01

    Abrupt environmental pollution accidents cause considerable damage worldwide to the ecological environment, human health, and property. The concept of acceptable risk aims to answer whether or not a given environmental pollution risk exceeds a societally determined criterion. This paper presents a case study on acceptable environmental pollution risk conducted through a questionnaire survey carried out between August and October 2014 in five representative districts and two counties of Zhangjiakou City, Hebei Province, China. Here, environmental risk primarily arises from accidental water pollution, accidental air pollution, and tailings dam failure. Based on 870 valid questionnaires, demographic and regional differences in public attitudes towards abrupt environmental pollution risks were analyzed, and risk acceptance impact factors determined. The results showed females, people between 21–40 years of age, people with higher levels of education, public servants, and people with higher income had lower risk tolerance. People with lower perceived risk, low-level risk knowledge, high-level familiarity and satisfaction with environmental management, and without experience of environmental accidents had higher risk tolerance. Multiple logistic regression analysis indicated that public satisfaction with environmental management was the most significant factor in risk acceptance, followed by perceived risk of abrupt air pollution, occupation, perceived risk of tailings dam failure, and sex. These findings should be helpful to local decision-makers concerned with environmental risk management (e.g., selecting target groups for effective risk communication) in the context of abrupt environmental accidents. PMID:28425956

  11. Electromigration failure mode concerning negative resistance shift of Cu interconnects buried in porous low-k dielectric

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Yin, Binfeng; Yu, Hewei; Chen, Leigang; Gao, Lin; Zhou, Ke; Kuo, Chinte

    2017-02-01

    Electromigration failure mode concerning a negative resistance shift of 4%-11% and cathode burnout was reported for Cu interconnects buried in porous low-k in this paper. Evidence for oxidation and debonding of Ta/TaN liner at high temperature was revealed, which was demonstrated to have been enabled by the unsealed porous low-k due to moisture uptake. The cathode burnout was thus attributed to severe Joule heating induced in the insulated liner after oxidation. The resistance decay of Cu also exhibited to be mainly consistent with the calculation from specularity recovery of electron scattering at the Cu/Ta interface after oxidation and debonding of the liner, although other factors like strain relaxation may also have some contribution.

  12. Differential effects of removing the glucose or saccharin components of a glucose-saccharin mixture in a successive negative contrast paradigm.

    PubMed

    Mitchell, Colin P; Flaherty, Charles F

    2005-03-31

    When rats experience an unexpected decrease in reward value, e.g., from 32% sucrose to 4% sucrose, consummatory behavior abruptly decreases to a level below control subjects that only experience the lesser reward, a phenomenon known as Successive Negative Contrast (SNC). In food deprived rats experiencing downshifts in sucrose concentration, SNC dissipates in 3-4 days, as consummatory behavior in shifted rats recovers to the level of unshifted controls. In Experiment 1 food deprived rats that were given 5 min daily access to a 2% glucose-0.15% saccharin mixture, and subsequently shifted to 2% glucose alone, displayed a dramatic SNC effect relative to rats that only received 2% glucose. This SNC effect was primarily manifested as a decrease in the number of consummatory bursts initiated. Interestingly, intake failed to recover to control levels during eight daily postshift sessions. However, in Experiment 2 subjects that were shifted from the same glucose-saccharin mixture to 0.15% saccharin alone failed to show SNC rather, intake fell to the level of control animals which only received 0.15% saccharin. The data from Experiment 1, in conjunction with previous studies utilizing non-deprived rats, quinine adulteration, or shifts from sucrose to saccharin, show that reductions in taste value can produce contrast effects, but suggest that a threshold caloric value is necessary for recovery. The data from Experiment 2 may suggest that saccharin and glucose do not contribute equally to the enhanced palatability of the mixture.

  13. Paleoecological evidence for abrupt cold reversals during peak Holocene warmth on Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Axford, Yarrow; Briner, Jason P.; Miller, Gifford H.; Francis, Donna R.

    2009-03-01

    A continuous record of insect (Chironomidae) remains preserved in lake sediments is used to infer temperature changes at a small lake in Arctic Canada through the Holocene. Early Holocene summers at the study site were characterized by more thermophilous assemblages and warmer inferred temperatures than today, presumably in response to the positive anomaly in Northern Hemisphere summer insolation. Peak early Holocene warmth was interrupted by two cold reversals between 9.5 and 8 cal ka BP, during which multiple cold-stenothermous chironomid taxa appeared in the lake. The earlier reversal appears to correlate with widespread climate anomalies around 9.2 cal ka BP; the age of the younger reversal is equivocal but it may correlate with the 8.2 cal ka BP cold event documented elsewhere. Widespread, abrupt climate shifts in the early Holocene illustrate the susceptibility of the climate system to perturbations, even during periods of enhanced warmth in the Northern Hemisphere.

  14. A steep-slope transistor based on abrupt electronic phase transition

    NASA Astrophysics Data System (ADS)

    Shukla, Nikhil; Thathachary, Arun V.; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G.; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-08-01

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep (`sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

  15. A steep-slope transistor based on abrupt electronic phase transition.

    PubMed

    Shukla, Nikhil; Thathachary, Arun V; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-08-07

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep ('sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

  16. Factor V Leiden, Prothrombin and MTHFR Mutation in Patients with Preeclamsia, Intrauterine Growth Restriction and Placental Abruption.

    PubMed

    Livrinova, Vesna; Lega, Marija Hadzi; Dimcheva, Anita Hristova; Samardziski, Igor; Isjanovska, Rozalinda

    2015-12-15

    Factor V Leiden, Prothrombin and MTHFR gene mutation, could have an influence in pregnancy with adverse outcome Preeclamsia, IUGR and Placental abruption. The aim of this study is to investigate the presence of above mentioned inherited thrombophilias and its statistical significance, distribution among the complicated and normal pregnancy, and relative risk for carrier of mutation to develop preeclampsia, IUGR and placental abruption. Prospective cohort study is implemented at University Clinic for Obstetric and Gynecology in Skopje, Republic of Macedonia. The study included 109 delivered patients: 40 with preeclapmsia, 22 with IUGR, 17 with placental abruption and 30 as control group with normal pregnancy. The amount of 3 ml venous blood has been used for detection of these point mutations using ThromboStrip -Opegen, QIAGEN kit manufactured for thrombotic risk. The highest frequency was found: in the group with preeclampsia 35% were MTHFR homozygous, IUGR -MTHFR heterozygous 45%, Placental abruption- 52.9% MTHFR heterozygous, and in the control group without thrombophilia 56.7%. There were combined thrombophilia in 3 patients. There aren`t statistical significance in presence of thrombophilia among groups (p > 0.05). Statistical significance (p < 0.05) was found between carriers of MTHFR homozygous in preeclampsia and group with placental abruption and control group. Relative risk in IUGR group for MTHFR homozygous was 5.54 (1.37abruption for Factor V Leiden heterozygous was 4.50 (0.47abruption. Further investigations with more patients are warranted.

  17. Factor V Leiden, Prothrombin and MTHFR Mutation in Patients with Preeclamsia, Intrauterine Growth Restriction and Placental Abruption

    PubMed Central

    Livrinova, Vesna; Lega, Marija Hadzi; Dimcheva, Anita Hristova; Samardziski, Igor; Isjanovska, Rozalinda

    2015-01-01

    BACKGROUND: Factor V Leiden, Prothrombin and MTHFR gene mutation, could have an influence in pregnancy with adverse outcome Preeclamsia, IUGR and Placental abruption. AIM: The aim of this study is to investigate the presence of above mentioned inherited thrombophilias and its statistical significance, distribution among the complicated and normal pregnancy, and relative risk for carrier of mutation to develop preeclampsia, IUGR and placental abruption. MATERIAL AND METHODS: Prospective cohort study is implemented at University Clinic for Obstetric and Gynecology in Skopje, Republic of Macedonia. The study included 109 delivered patients: 40 with preeclapmsia, 22 with IUGR, 17 with placental abruption and 30 as control group with normal pregnancy. The amount of 3 ml venous blood has been used for detection of these point mutations using ThromboStrip -Opegen, QIAGEN kit manufactured for thrombotic risk. RESULTS: The highest frequency was found: in the group with preeclampsia 35% were MTHFR homozygous, IUGR -MTHFR heterozygous 45%, Placental abruption- 52.9% MTHFR heterozygous, and in the control group without thrombophilia 56.7%. There were combined thrombophilia in 3 patients. There aren`t statistical significance in presence of thrombophilia among groups (p > 0.05). Statistical significance (p < 0.05) was found between carriers of MTHFR homozygous in preeclampsia and group with placental abruption and control group. Relative risk in IUGR group for MTHFR homozygous was 5.54 (1.37abruption for Factor V Leiden heterozygous was 4.50 (0.47abruption. Further investigations with more patients are warranted. PMID:27275292

  18. Volcano-induced regime shifts in millennial tree-ring chronologies from northeastern North America.

    PubMed

    Gennaretti, Fabio; Arseneault, Dominique; Nicault, Antoine; Perreault, Luc; Bégin, Yves

    2014-07-15

    Dated records of ice-cap growth from Arctic Canada recently suggested that a succession of strong volcanic eruptions forced an abrupt onset of the Little Ice Age between A.D. 1275 and 1300 [Miller GH, et al. (2012) Geophys Res Lett 39(2):L02708, 10.1029/2011GL050168]. Although this idea is supported by simulation experiments with general circulation models, additional support from field data are limited. In particular, the Northern Hemisphere network of temperature-sensitive millennial tree-ring chronologies, which principally comprises Eurasian sites, suggests that the strongest eruptions only caused cooling episodes lasting less than about 10 y. Here we present a new network of millennial tree-ring chronologies from the taiga of northeastern North America, which fills a wide gap in the network of the Northern Hemisphere's chronologies suitable for temperature reconstructions and supports the hypothesis that volcanoes triggered both the onset and the coldest episode of the Little Ice Age. Following the well-expressed Medieval Climate Anomaly (approximately A.D. 910-1257), which comprised the warmest decades of the last millennium, our tree-ring-based temperature reconstruction displays an abrupt regime shift toward lower average summer temperatures precisely coinciding with a series of 13th century eruptions centered around the 1257 Samalas event and closely preceding ice-cap expansion in Arctic Canada. Furthermore, the successive 1809 (unknown volcano) and 1815 (Tambora) eruptions triggered a subsequent shift to the coldest 40-y period of the last 1100 y. These results confirm that series of large eruptions may cause region-specific regime shifts in the climate system and that the climate of northeastern North America is especially sensitive to volcanic forcing.

  19. Volcano-induced regime shifts in millennial tree-ring chronologies from northeastern North America

    PubMed Central

    Gennaretti, Fabio; Arseneault, Dominique; Nicault, Antoine; Perreault, Luc; Bégin, Yves

    2014-01-01

    Dated records of ice-cap growth from Arctic Canada recently suggested that a succession of strong volcanic eruptions forced an abrupt onset of the Little Ice Age between A.D. 1275 and 1300 [Miller GH, et al. (2012) Geophys Res Lett 39(2):L02708, 10.1029/2011GL050168]. Although this idea is supported by simulation experiments with general circulation models, additional support from field data are limited. In particular, the Northern Hemisphere network of temperature-sensitive millennial tree-ring chronologies, which principally comprises Eurasian sites, suggests that the strongest eruptions only caused cooling episodes lasting less than about 10 y. Here we present a new network of millennial tree-ring chronologies from the taiga of northeastern North America, which fills a wide gap in the network of the Northern Hemisphere's chronologies suitable for temperature reconstructions and supports the hypothesis that volcanoes triggered both the onset and the coldest episode of the Little Ice Age. Following the well-expressed Medieval Climate Anomaly (approximately A.D. 910–1257), which comprised the warmest decades of the last millennium, our tree-ring-based temperature reconstruction displays an abrupt regime shift toward lower average summer temperatures precisely coinciding with a series of 13th century eruptions centered around the 1257 Samalas event and closely preceding ice-cap expansion in Arctic Canada. Furthermore, the successive 1809 (unknown volcano) and 1815 (Tambora) eruptions triggered a subsequent shift to the coldest 40-y period of the last 1100 y. These results confirm that series of large eruptions may cause region-specific regime shifts in the climate system and that the climate of northeastern North America is especially sensitive to volcanic forcing. PMID:24982132

  20. Contingent negative variation (CNV) associated with sensorimotor timing error correction.

    PubMed

    Jang, Joonyong; Jones, Myles; Milne, Elizabeth; Wilson, Daniel; Lee, Kwang-Hyuk

    2016-02-15

    Detection and subsequent correction of sensorimotor timing errors are fundamental to adaptive behavior. Using scalp-recorded event-related potentials (ERPs), we sought to find ERP components that are predictive of error correction performance during rhythmic movements. Healthy right-handed participants were asked to synchronize their finger taps to a regular tone sequence (every 600 ms), while EEG data were continuously recorded. Data from 15 participants were analyzed. Occasional irregularities were built into stimulus presentation timing: 90 ms before (advances: negative shift) or after (delays: positive shift) the expected time point. A tapping condition alternated with a listening condition in which identical stimulus sequence was presented but participants did not tap. Behavioral error correction was observed immediately following a shift, with a degree of over-correction with positive shifts. Our stimulus-locked ERP data analysis revealed, 1) increased auditory N1 amplitude for the positive shift condition and decreased auditory N1 modulation for the negative shift condition; and 2) a second enhanced negativity (N2) in the tapping positive condition, compared with the tapping negative condition. In response-locked epochs, we observed a CNV (contingent negative variation)-like negativity with earlier latency in the tapping negative condition compared with the tapping positive condition. This CNV-like negativity peaked at around the onset of subsequent tapping, with the earlier the peak, the better the error correction performance with the negative shifts while the later the peak, the better the error correction performance with the positive shifts. This study showed that the CNV-like negativity was associated with the error correction performance during our sensorimotor synchronization study. Auditory N1 and N2 were differentially involved in negative vs. positive error correction. However, we did not find evidence for their involvement in behavioral error

  1. Shift work and the assessment and management of shift work disorder (SWD).

    PubMed

    Wright, Kenneth P; Bogan, Richard K; Wyatt, James K

    2013-02-01

    Nearly 20% of the labor force worldwide, work shifts that include work hours outside 07:00 h to 18:00 h. Shift work is common in many occupations that directly affect the health and safety of others (e.g., protective services, transportation, healthcare), whereas quality of life, health, and safety during shift work and the commute home can affect workers in any field. Increasing evidence indicates that shift-work schedules negatively influence worker physiology, health, and safety. Shift work disrupts circadian sleep and alerting cycles, resulting in disturbed daytime sleep and excessive sleepiness during the work shift. Moreover, shift workers are at risk for shift work disorder (SWD). This review focuses on shift work and the assessment and management of sleepiness and sleep disruption associated with shift work schedules and SWD. Management strategies include approaches to promote sleep, wakefulness, and adaptation of the circadian clock to the imposed work schedule. Additional studies are needed to further our understanding of the mechanisms underlying the health risks of shift work, understanding which shift workers are at most risk of SWD, to investigate treatment options that address the health and safety burdens associated with shift work and SWD, and to further develop and assess the comparative effectiveness of countermeasures and treatment options. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. State survey of medical boards regarding abrupt loss of a prescriber of controlled substances.

    PubMed

    Sera, Leah; Brown, Micke; McPherson, Mary Lynn; Walker, Kathryn A; Klein-Schwartz, Wendy

    The purpose of the study was to evaluate states' experiences with abrupt changes in controlled substances (CS) prescribing, to determine whether states have action plans in place to manage such situations, and describe the components of any such plans. A survey of executive directors of 51 medical boards was conducted to evaluate states' experiences with abrupt changes in CS prescribing, the extent of consumer complaints attributed to these events, and the types of plans in place to manage these situations. Forty-six executive directors of medical boards responded. Twenty boards (43.5 percent) confirmed that their state had experienced abrupt loss of CS providers and 11 (55 percent) of these executive directors indicated that the loss resulted in increased consumer complaints. The majority of executive directors (86 percent) had no action plan. Six executive directors reported some type of action plan or process consisting of regulatory action, patient-provider connection, professional education, patient education, or public notice. Most states do not have operational plans in place. However, a few have key strategies that may be useful in addressing potential problems following abrupt loss of a CS prescriber. State medical boards can play a significant role in the development of comprehensive preparedness plans to mitigate damage from the loss of CS prescribers in the community.

  3. The Necessity of Awareness of Early Symptoms of Placental Abruption Among Pregnant Japanese Women

    PubMed Central

    Suzuki, Shunji; Shinmura, Hiroki

    2016-01-01

    Background In 2012, the recommendation for immediate contact and visit to obstetric institutions by pregnant women was emphasized by The Japan Obstetric Compensation System for Cerebral Palsy (JOCSC). In this study, we examined whether or not the increased awareness has led to the improvement of perinatal outcomes of placental abruption managed at private clinics. Methods We reviewed the obstetric records of 38 singleton pregnant women complicated by placental abruption that developed at home, and were managed at private clinics from April 2008 through April 2016. Results The perinatal outcomes, specifically the rate of cases with ≥ 1 hour time interval between symptom onset and clinic visit, have not changed significantly after the intervention. Conclusion The provision of information regarding the early clinical symptoms associated with placental abruption in pregnant women has not been well documented in Japan. PMID:27540442

  4. Abrupt Depletion Layer Approximation for the Metal Insulator Semiconductor Diode.

    ERIC Educational Resources Information Center

    Jones, Kenneth

    1979-01-01

    Determines the excess surface change carrier density, surface potential, and relative capacitance of a metal insulator semiconductor diode as a function of the gate voltage, using the precise questions and the equations derived with the abrupt depletion layer approximation. (Author/GA)

  5. Precise interpolar phasing of abrupt climate change during the last ice age.

    PubMed

    2015-04-30

    The last glacial period exhibited abrupt Dansgaard-Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard-Oeschger cycle and vice versa, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard-Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard-Oeschger dynamics.

  6. Investigating Flow Features Near Abrupt Topography in the Mariana Basin

    DTIC Science & Technology

    2015-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Investigating Flow Features Near Abrupt Topography in...waves generated by flow over topography and mesoscale eddies generated by flow past islands. Having identified the prime locations in the region for such

  7. The Relationship Between Shift Work and Men's Health.

    PubMed

    Deng, Nanfu; Kohn, Taylor P; Lipshultz, Larry I; Pastuszak, Alexander W

    2018-01-19

    More than 21 million Americans and nearly 20% of the U.S. workforce are shift workers. Non-standard shift work, defined as work that falls outside of 6 am-6 pm, can lead to poor diet, exercise, and sleep habits that lead to decreased productivity, increased workplace accidents, and a variety of negative health outcomes. To investigate the associations between shift work exposure and chronic medical conditions such as metabolic syndromes, cardiovascular disease, gastrointestinal disturbances, and depression as well as urologic complications including hypogonadism, male infertility, lower urinary tract symptoms, and prostate cancer with a focus on the effects of shift work sleep disorder (SWSD) on the severity of these negative health outcomes. We reviewed the literature examining effects of shift work and SWSD on general and urologic health. We produced a summary of effects of shift work on health with focus on the increased risk of negative health outcomes in non-standard shift workers, particularly those with SWSD, when compared to daytime workers or workers without SWSD. Studies have associated non-standard shift work schedules and poor health outcomes, including increased risks of diabetes mellitus, dyslipidemia, hypertension, heart disease, peptic ulcer disease, and depression, in shift workers. However, few studies have focused on the role that shift work plays in men's urologic health. Current evidence supports associations between non-standard shift work and increased hypogonadal symptoms, poor semen parameters, decreased fertility, lower urinary tract symptoms, and prostate cancer. These associations are strengthened by the presence of SWSD, which affects up to 20% of shift workers. Unfortunately, interventions, such as planned naps, timed light exposure, melatonin, and sedative hypnotics, aimed at alleviating excessive nighttime sleepiness and daytime insomnia in non-standard shift workers experiencing SWSD, are limited and lack strong evidence to support

  8. Abrupt GaP/Si hetero-interface using bistepped Si buffer

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ping Wang, Y., E-mail: yanping.wang@insa-rennes.fr; Kuyyalil, J.; Nguyen Thanh, T.

    We evidence the influence of the quality of the starting Si surface on the III-V/Si interface abruptness and on the formation of defects during the growth of III-V/Si heterogeneous crystal, using high resolution transmission electron microscopy and scanning transmission electron microscopy. GaP layers were grown by molecular beam epitaxy on vicinal Si (001). The strong effect of the Si substrate chemical preparation is first demonstrated by studying structural properties of both Si homoepitaxial layer and GaP/Si heterostructure. It is then shown that choosing adequate chemical preparation conditions and subsequent III-V regrowth conditions enables the quasi-suppression of micro-twins in the epilayer.more » Finally, the abruptness of GaP/Si interface is found to be very sensitive to the Si chemical preparation and is improved by the use of a bistepped Si buffer prior to III-V overgrowth.« less

  9. Self-assembly of electronically abrupt borophene/organic lateral heterostructures

    PubMed Central

    Liu, Xiaolong; Wei, Zonghui; Balla, Itamar; Mannix, Andrew J.; Guisinger, Nathan P.; Luijten, Erik; Hersam, Mark C.

    2017-01-01

    Two-dimensional boron sheets (that is, borophene) have recently been realized experimentally and found to have promising electronic properties. Because electronic devices and systems require the integration of multiple materials with well-defined interfaces, it is of high interest to identify chemical methods for forming atomically abrupt heterostructures between borophene and electronically distinct materials. Toward this end, we demonstrate the self-assembly of lateral heterostructures between borophene and perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA). These lateral heterostructures spontaneously form upon deposition of PTCDA onto submonolayer borophene on Ag(111) substrates as a result of the higher adsorption enthalpy of PTCDA on Ag(111) and lateral hydrogen bonding among PTCDA molecules, as demonstrated by molecular dynamics simulations. In situ x-ray photoelectron spectroscopy confirms the weak chemical interaction between borophene and PTCDA, while molecular-resolution ultrahigh-vacuum scanning tunneling microscopy and spectroscopy reveal an electronically abrupt interface at the borophene/PTCDA lateral heterostructure interface. As the first demonstration of a borophene-based heterostructure, this work will inform emerging efforts to integrate borophene into nanoelectronic applications. PMID:28261662

  10. [Burden and health effects of shift work].

    PubMed

    Heitmann, Jörg

    2010-10-01

    In Germany aprox. 15% of all employees have irregular or flexible working hours. Disturbed sleep and/or hypersomnia are direct consequences of shift work and therefore described as shift work disorder. Beyond this, shift work can also be associated with specific pathological disorders. There are individual differences in tolerance to shift work. Optimization of both shift schedules and sleep to "non-physiological" times of the day are measures to counteract the negative effects of shift work. There is still not enough evidence to recommend drugs for routine use in shift workers. © Georg Thieme Verlag Stuttgart · New York.

  11. Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics.

    PubMed

    Partin, J W; Quinn, T M; Shen, C-C; Okumura, Y; Cardenas, M B; Siringan, F P; Banner, J L; Lin, K; Hu, H-M; Taylor, F W

    2015-09-02

    Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

  12. Sleep and satisfaction in 8- and 12-h forward-rotating shift systems: Industrial employees prefer 12-h shifts.

    PubMed

    Karhula, Kati; Härmä, Mikko; Ropponen, Annina; Hakola, Tarja; Sallinen, Mikael; Puttonen, Sampsa

    2016-01-01

    Twelve-hour shift systems have become more popular in industry. Survey data of shift length, shift rotation speed, self-rated sleep, satisfaction and perceived health were investigated for the associations among 599 predominantly male Finnish industrial employees. The studied forward-rotating shift systems were 12-h fast (12fast, DDNN------, n = 268), 8-h fast (8fast, MMEENN----, n = 161) and 8-h slow (8slow, MMMM-EEEE-NNNN, n = 170). Satisfaction with shift system differed between the groups (p < 0.01) after controlling for age, gender, shift work experience and self-rated stress. In the 12fast, 98% of employees were satisfied with their shift system (75% 8fast, 54% 8slow). Negative effects on sleep and alertness were rare (8%) in the 12fast group (53% 8fast, 66% 8 slow, p < 0.01) and self-reported sleep difficulties were less frequent than in the 8fast and 8slow groups (8%, 27%, 41%, respectively, p < 0.01). The self-reported average sleep duration (12fast 7:50, 8fast 7:24, 8slow 7:15, p < 0.01), and shift-specific sleep before and between morning shifts and after first night shift were longer in the 12fast group. Perceived negative effects of the current shift system on general health (12fast 4%, 8fast 30%, 8slow 41%, p < 0.001) and work-life balance (12fast 8%, 8fast 52%, 8slow 63%, p < 0.001) differed strongly between the groups. In conclusion, the perceived effects of shift work were dependent on both shift length and shift rotation speed: employees in the 12-h rapidly forward-rotating shift system were most satisfied, perceived better work-life balance and slept better than the employees in the 8fast or especially the employees in the 8-h slowly rotating systems.

  13. Macrosegregation in Al-7Si alloy caused by abrupt cross-section change during directional solidification

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Johnson, L.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2016-09-01

    Hypoeutectic Al-7 wt .% Si alloys were directionally solidified vertically downward in cylindrical molds that incorporated an abrupt cross-section decrease (9.5 mm to 3.2 mm diameter) which, after 5 cm, reverted back to 9.5 mm diameter in a Bridgman furnace; two constant growth speeds and thermal gradients were investigated. Thermosolutal convection and cross-section-change-induced shrinkage flow effects on macrosegregation were investigated. Dendrite clustering and extensive radial macrosegregation was seen, particularly in the larger cross-sections, before contraction and after expansion, this more evident at the lower growth speed. This alloy shows positive longitudinal macrosegregation near cross-section decrease followed by negative macrosegregation right after it; the extent of macrosegregation, however, decreases with increasing growth speed. Primary dendrite steepling intensified as solidification proceeded into the narrower section and negative longitudinal macrosegregation was seen on the re-entrant shelves at expansion. A two-dimensional model accounting for both shrinkage and thermo-solutal convection was used to simulate solidification and the resulting mushy-zone steepling and macrosegregation. The experimentally observed longitudinal and radial macrosegregation associated with the cross-section changes during directional solidification of an Al-7Si alloy is well captured by the numerical simulations.

  14. Precise interpolar phasing of abrupt climate change during the last ice age

    USGS Publications Warehouse

    ,; Buizert, Christo; Adrian, Betty M.; Ahn, Jinho; Albert, Mary; Alley, Richard B.; Baggenstos, Daniel; Bauska, Thomas K.; Bay, Ryan C.; Bencivengo, Brian B.; Bentley, Charles R.; Brook, Edward J.; Chellman, Nathan J.; Clow, Gary D.; Cole-Dai, Jihong; Conway, Howard; Cravens, Eric; Cuffey, Kurt M.; Dunbar, Nelia W.; Edwards, Jon S.; Fegyveresi, John M.; Ferris, Dave G.; Fitzpatrick, Joan J.; Fudge, T. J.; Gibson, Chris J.; Gkinis, Vasileios; Goetz, Joshua J.; Gregory, Stephanie; Hargreaves, Geoffrey Mill; Iverson, Nels; Johnson, Jay A.; Jones, Tyler R.; Kalk, Michael L.; Kippenhan, Matthew J.; Koffman, Bess G.; Kreutz, Karl; Kuhl, Tanner W.; Lebar, Donald A.; Lee, James E.; Marcott, Shaun A.; Markle, Bradley R.; Maselli, Olivia J.; McConnell, Joseph R.; McGwire, Kenneth C.; Mitchell, Logan E.; Mortensen, Nicolai B.; Neff, Peter D.; Nishiizumi, Kunihiko; Nunn, Richard M.; Orsi, Anais J.; Pasteris, Daniel R.; Pedro, Joel B.; Pettit, Erin C.; Price, P. Buford; Priscu, John C.; Rhodes, Rachael H.; Rosen, Julia L.; Schauer, Andrew J.; Schoenemann, Spruce W.; Sendelbach, Paul J.; Severinghaus, Jeffrey P.; Shturmakov, Alexander J.; Sigl, Michael; Slawny, Kristina R.; Souney, Joseph M.; Sowers, Todd A.; Spencer, Matthew K.; Steig, Eric J.; Taylor, Kendrick C.; Twickler, Mark S.; Vaughn, Bruce H.; Voigt, Donald E.; Waddington, Edwin D.; Welten, Kees C.; Wendricks, Anthony W.; White, James W. C.; Winstrup, Mai; Wong, Gifford J.; Woodruff, Thomas E.

    2015-01-01

    The last glacial period exhibited abrupt Dansgaard–Oeschger climatic oscillations, evidence of which is preserved in a variety of Northern Hemisphere palaeoclimate archives1. Ice cores show that Antarctica cooled during the warm phases of the Greenland Dansgaard–Oeschger cycle and vice versa2, 3, suggesting an interhemispheric redistribution of heat through a mechanism called the bipolar seesaw4, 5, 6. Variations in the Atlantic meridional overturning circulation (AMOC) strength are thought to have been important, but much uncertainty remains regarding the dynamics and trigger of these abrupt events7, 8, 9. Key information is contained in the relative phasing of hemispheric climate variations, yet the large, poorly constrained difference between gas age and ice age and the relatively low resolution of methane records from Antarctic ice cores have so far precluded methane-based synchronization at the required sub-centennial precision2, 3,10. Here we use a recently drilled high-accumulation Antarctic ice core to show that, on average, abrupt Greenland warming leads the corresponding Antarctic cooling onset by 218 ± 92 years (2σ) for Dansgaard–Oeschger events, including the Bølling event; Greenland cooling leads the corresponding onset of Antarctic warming by 208 ± 96 years. Our results demonstrate a north-to-south directionality of the abrupt climatic signal, which is propagated to the Southern Hemisphere high latitudes by oceanic rather than atmospheric processes. The similar interpolar phasing of warming and cooling transitions suggests that the transfer time of the climatic signal is independent of the AMOC background state. Our findings confirm a central role for ocean circulation in the bipolar seesaw and provide clear criteria for assessing hypotheses and model simulations of Dansgaard–Oeschger dynamics.

  15. Ge-on-insulator tunneling FET with abrupt source junction formed by utilizing snowplow effect of NiGe

    NASA Astrophysics Data System (ADS)

    Matsumura, Ryo; Katoh, Takumi; Takaguchi, Ryotaro; Takenaka, Mitsuru; Takagi, Shinichi

    2018-04-01

    Tunneling field-effect transistors (TFETs) attract much attention for use in realizing next-generation low-power processors. In particular, Ge-on-insulator (GOI) TFETs are expected to realize low power operation with a high on-current/off-current (I on/I off) ratio, owing to their narrow bandgap. Here, to improve the performance of GOI-TFETs, a source junction with a high doping concentration and an abrupt impurity profile is essential. In this study, a snowplow effect of NiGe combined with low-energy BF2 + implantation has been investigated to realize an abrupt p+/n Ge junction for GOI n-channel TFETs. By optimizing the Ni thickness to form NiGe (thickness: 4 nm), an abrupt junction with a B profile abruptness of ˜5 nm/dec has been realized with a high doping concentration of around 1021 cm-3. The operation of GOI n-TFETs with this source junction having the abrupt B profile has been demonstrated, and the improvement of TFET properties such as the I on/I off ratio from 311 to 743 and the subthreshold slope from 368 to 239 mV/dec has been observed. This junction formation technology is attractive for enhancing the TFET performance.

  16. Involvement of human decidual cell-expressed tissue factor in uterine hemostasis and abruption.

    PubMed

    Lockwood, C J; Paidas, M; Murk, W K; Kayisli, U A; Gopinath, A; Huang, S J; Krikun, G; Schatz, F

    2009-11-01

    Vascular injury increases access and binding of plasma-derived factor VII to perivascular cell membrane-bound tissue factor (TF). The resulting TF/VIIa complex promotes hemostasis by cleaving pro-thrombin to thrombin leading to the fibrin clot. In human pregnancy, decidual cell-expressed TF prevents decidual hemorrhage (abruption). During placentation, trophoblasts remodel decidual spiral arteries into high conductance vessels. Shallow trophoblast invasion impedes decidual vascular conversion, producing an inadequate uteroplacental blood flow that elicits abruption-related placental ischemia. Thrombin induces several biological effects via cell surface protease activated receptors. In first trimester human DCs thrombin increases synthesis of sFlt-1, which elicits placental ischemia by impeding angiogenesis-related decidual vascular remodeling. During pregnacy, the fibrillar collagen-rich amnion and choriodecidua extracellular matrix (ECM) provides greater than additive tensile strength and structural integrity. Thrombin acts as an autocrine/paracrine mediator that degrades these ECMs by augmenting decidual cell expression of: 1) matrix metalloproteinases and 2) interleukin-8, a key mediator of abruption-associated decidual infiltration of neutrophils, which express several ECM degrading proteases. Among the cell types at the maternal fetal interface at term, TF expression is highest in decidual cells indicating that this TF meets the hemostatic demands of labor and delivery. TF expression in cultured term decidual cells is enhanced by progestin and thrombin suggesting that the maintenance of elevated circulating progesterone provides hemostatic protection and that abruption-generated thrombin acts in an autocrine/paracrine fashion on decidual cells to promote hemostasis via enhanced TF expression.

  17. Involvement of human decidual cell-expressed tissue factor in uterine hemostasis and abruption

    PubMed Central

    Lockwood, C.J.; Paidas, M.; Murk, W.K.; Kayisli, U.A.; Gopinath, A.; Krikun, G.; Huang, S.J.; Schatz, F.

    2009-01-01

    Vascular injury increases access and binding of plasma-derived factor VII to perivascular cell membrane-bound tissue factor (TF). The resulting TF/VIIa complex promotes hemostasis by cleaving pro-thrombin to thrombin leading to the fibrin clot. In human pregnancy, decidual cell-expressed TF prevents decidual hemorrhage (abruption). During placentation, trophoblasts remodel decidual spiral arteries into high conductance vessels. Shallow trophoblast invasion impedes decidual vascular conversion, producing an inadequate uteroplacental blood flow that elicits abruption-related placental ischemia. Thrombin induces several biological effects via cell surface protease activated receptors. In first trimester human DCs thrombin increases synthesis of sFlt-1, which elicits placental ischemia by impeding angiogenesis-related decidual vascular remodeling. During pregnacy, the fibrillar collagen-rich amnion and choriodecidua extracellular matrix (ECM) provides greater than additive tensile strength and structural integrity. Thrombin acts as an autocrine/paracrine mediator that degrades these ECMs by augmenting decidual cell expression of: 1) matrix metalloproteinases and 2) interleukin-8, a key mediator of abruption-associated decidual infiltration of neutrophils, which express several ECM degrading proteases. Our recent observations that: 1) among the cell types at the maternal fetal interface at term TF expression is highest in decidual cells indicates that this TF meets the hemostatic demands of labor and delivery; 2) TF expression in cultured term decidual cells is enhanced by progestin and thrombin suggest that maintenance of elevated circulating progesterone at term provides hemostatic protection, whereas abruption-generated thrombin can act in autocrine/paracrine fashion on DCs to promote hemostasis via enhanced TF expression. PMID:19720393

  18. Abrupt climate warming in East Antarctica during the early Holocene

    NASA Astrophysics Data System (ADS)

    Cremer, Holger; Heiri, Oliver; Wagner, Bernd; Wagner-Cremer, Friederike

    2007-08-01

    We report a centennial-scale warming event between 8600 and 8400 cal BP from Amery Oasis, East Antarctica, that is documented by the geochemical record in a lacustrine sediment sequence. The organic carbon content, the C/S ratio, and the sedimentation rate in this core have distinctly elevated values around 8500 y ago reflecting relatively warm and ice-free conditions that led to well-ventilated conditions in the lake and considerable sedimentation of both autochthonous and allochthonous organic matter on the lake bottom. This abrupt warming event occurred concurrently with reported warm climatic conditions in the Southern Ocean while the climate in central East Antarctic remained cold. The comparison of the spatial and temporal variability of warm climatic periods documented in various terrestrial, marine, and glacial archives from East Antarctica elucidates the uniqueness of the centennial-scale warming event in the Amery Oasis. We also discuss a possible correlation of the Amery warming event with the abrupt climatic deterioration around 8200 cal BP on the Northern Hemisphere.

  19. Additivity of abrupt onset effects supports nonspatial distraction, not the capture of spatial attention.

    PubMed

    Folk, Charles L; Remington, Roger W; Wu, Shu-Chieh

    2009-02-01

    In a recent article, Schreij, Owens, and Theeuwes (2008) reported that abruptly onsetting distractors produce costs in performance even when spatial-cuing effects confirm the presence of a top-down set for color. The authors argued that these results show that abruptly onsetting new objects capture attention independent of a top-down set and, thus, provide conclusive evidence against the theory that attentional capture is contingent on top-down attentional control settings (Folk, Remington, & Johnston, 1992). In the following article, we argue that, contrary to the conclusion drawn by Schreij et al., their own data (1) disconfirm the claim that their abrupt onsets captured spatial attention and (2) are consistent with nonspatial interference accounts of singleton-distractor effects. In support of the nonspatial account, we show that in a paradigm similar to Schreij et al.'s, distractors that do not capture attention can nonetheless influence responses to a target. We conclude that the results of Schreij et al. do not represent a challenge to contingent capture theory.

  20. Majority Group Members' Negative Reactions to Future Demographic Shifts Depend on the Perceived Legitimacy of Their Status: Findings from the United States and Portugal.

    PubMed

    Outten, H Robert; Lee, Timothy; Costa-Lopes, Rui; Schmitt, Michael T; Vala, Jorge

    2018-01-01

    Using concepts from social identity theory (Tajfel and Turner, 1979), we examined whether racial/ethnic majority group members' reactions to future demographic shifts is a function of the degree to which they perceive their ingroup's higher-status in society to be legitimate. In two studies, participants who varied in the degree to which they perceived their group's status to be legitimate were either exposed to real projections for 2060 (i.e., large decline in proportion of population that is the "majority" group), or fake projections for 2060-that resembled current figures (i.e., small decline). In Study 1, White Americans who perceived their status to be highly legitimate expressed greater intergroup threat, and negative feelings (anger and fear) toward minorities after exposure to projections with a large decline in the relative size of the White American population. In contrast, demographic shift condition had no effect on intergroup threat and negative feelings toward minorities among White Americans who perceived their status to be relatively illegitimate; negative feelings and threat remained low across both conditions. Similarly, in Study 2, ethnic Portuguese people in Portugal exposed to projections in which there was a large decline in the relative size of the ethnic Portuguese population experienced more intergroup threat and expressed a greater desire to engage in anti-immigration behaviors. The effect of demographic shift condition on intergroup threat and anti-immigration behaviors was stronger among ethnic Portuguese who perceived their status to be legitimate compared to ethnic Portuguese people who perceived their status to be relatively illegitimate. These results highlight that across different cultural contexts, majority group members' beliefs about the legitimacy of intergroup relations can affect their reactions to the prospect of increased diversity.

  1. Abrupt shift in δ18O values at Medicine Lake volcano (California, USA)

    USGS Publications Warehouse

    Donnelly-Nolan, J. M.

    1998-01-01

     Oxygen-isotope analyses of lavas from Medicine Lake volcano (MLV), in the southern Cascade Range, indicate a significant change in δ18O in Holocene time. In the Pleistocene, basaltic lavas with <52% SiO2 averaged +5.9‰, intermediate lavas averaged +5.7‰, and silicic lavas (≥63.0%SiO2) averaged +5.6‰. No analyzed Pleistocene rhyolites or dacites have values greater than +6.3‰. In post-glacial time, basalts were similar at +5.7‰ to those erupted in the Pleistocene, but intermediate lavas average +6.8‰ and silicic lavas +7.4‰ with some values as high as +8.5‰. The results indicate a change in the magmatic system supplying the volcano. During the Pleistocene, silicic lavas resulted either from melting of low-18O crust or from fractionation combined with assimilation of very-low-18O crustal material such as hydrothermally altered rocks similar to those found in drill holes under the center of the volcano. By contrast, Holocene silicic lavas were produced by assimilation and/or wholesale melting of high-18O crustal material such as that represented by inclusions of granite in lavas on the upper flanks of MLV. This sudden shift in assimilant indicates a fundamental change in the magmatic system. Magmas are apparently ponding in the crust at a very different level than in Pleistocene time.

  2. Ecosystem resilience to abrupt late Quaternary change in continental southern Siberia

    NASA Astrophysics Data System (ADS)

    Harding, Poppy; Mackay, Anson; Bezrukova, Elena; Shchetnikov, Alexander

    2017-04-01

    Quaternary climate variability is dominated by long term orbital forcing along with abrupt sub-Milankovitch events on the scales of millennia to centuries, driven by internal feedback mechanisms, volcanic forcing and fluctuating solar activity. Although these are well documented in the North Atlantic region, their expression is poorly understood in Siberia, particularly in relation to abrupt climatic events. Siberia has the world's highest level of continentality offering an opportunity to study changes remote from oceanic influences and improving understanding of interactions between the Siberian High and other atmospheric systems including the Aleutian Low, Arctic oscillation and Icelandic Low1 and ENSO2. Understanding of palaeoenvironmental change in Siberia is essential due to the region's high sensitivity to climatic change, with warming rates considerably higher than the global average over the past 50 years3, triggering significant environmental changes, including permafrost degradation, shifts in the forest-steppe biome, increases in forest fires and warming of seasonally ice-covered lakes. Additionally, the region provides essential palaeoenvironmental context for early hominins, for example at globally important sites such as Denisova cave4, and megafauna extinctions5. This presentation outlines ongoing work at Lake Baunt, SE Siberia including: key quaternary climate forcings, the site and its regional context, the key methods and preliminary results. These include a dated record back to ˜30ka BP (based on multiple 14C dates and Bayesian age modelling), multiproxy indicators of palaeoproductivity (e.g. biogenic silica and diatom analyses) and lake mixing regimes (inferred from diatom analyses). Together these highlight several key Quaternary fluctuations potentially correlated to events recorded in Greenland Ice Cores (GS2, GS2.1, GI1, GS1), and these are considered against key Quaternary records including those from nearby Lake Baikal and Hulu Cave in

  3. Turning back from the brink: Detecting an impending regime shift in time to avert it

    PubMed Central

    Biggs, Reinette; Carpenter, Stephen R.; Brock, William A.

    2009-01-01

    Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human economies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrelation) could potentially serve as early warning indicators of impending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy processes that enable society to respond more rapidly to information about impending regime shifts. PMID:19124774

  4. The problem of latent attentional capture: Easy visual search conceals capture by task-irrelevant abrupt onsets.

    PubMed

    Gaspelin, Nicholas; Ruthruff, Eric; Lien, Mei-Ching

    2016-08-01

    Researchers are sharply divided regarding whether irrelevant abrupt onsets capture spatial attention. Numerous studies report that they do and a roughly equal number report that they do not. This puzzle has inspired numerous attempts at reconciliation, none gaining general acceptance. The authors propose that abrupt onsets routinely capture attention, but the size of observed capture effects depends critically on how long attention dwells on distractor items which, in turn, depends critically on search difficulty. In a series of spatial cuing experiments, the authors show that irrelevant abrupt onsets produce robust capture effects when visual search is difficult, but not when search is easy. Critically, this effect occurs even when search difficulty varies randomly across trials, preventing any strategic adjustments of the attentional set that could modulate probability of capture by the onset cue. The authors argue that easy visual search provides an insensitive test for stimulus-driven capture by abrupt onsets: even though onsets truly capture attention, the effects of capture can be latent. This observation helps to explain previous failures to find capture by onsets, nearly all of which used an easy visual search. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  5. The Problem of Latent Attentional Capture: Easy Visual Search Conceals Capture by Task-Irrelevant Abrupt Onsets

    PubMed Central

    Gaspelin, Nicholas; Ruthruff, Eric; Lien, Mei-Ching

    2016-01-01

    Researchers are sharply divided regarding whether irrelevant abrupt onsets capture spatial attention. Numerous studies report that they do and a roughly equal number report that they do not. This puzzle has inspired numerous attempts at reconciliation, none gaining general acceptance. We propose that abrupt onsets routinely capture attention, but the size of observed capture effects depends critically on how long attention dwells on distractor items which, in turn, depends critically on search difficulty. In a series of spatial cuing experiments, we show that irrelevant abrupt onsets produce robust capture effects when visual search is difficult, but not when search is easy. Critically, this effect occurs even when search difficulty varies randomly across trials, preventing any strategic adjustments of the attentional set that could modulate probability of capture by the onset cue. We argue that easy visual search provides an insensitive test for stimulus-driven capture by abrupt onsets: even though onsets truly capture attention, the effects of capture can be latent. This observation helps to explain previous failures to find capture by onsets, nearly all of which employed an easy visual search. PMID:26854530

  6. Abrupt global-ocean anoxia during the Late Ordovician-early Silurian detected using uranium isotopes of marine carbonates.

    PubMed

    Bartlett, Rick; Elrick, Maya; Wheeley, James R; Polyak, Victor; Desrochers, André; Asmerom, Yemane

    2018-05-21

    Widespread marine anoxia is hypothesized as the trigger for the second pulse of the Late Ordovician (Hirnantian) mass extinction based on lithologic and geochemical proxies that record local bottom waters or porewaters. We test the anoxia hypothesis using δ 238 U values of marine limestones as a global seawater redox proxy. The δ 238 U trends at Anticosti Island, Canada, document an abrupt late Hirnantian ∼0.3‰ negative shift continuing through the early Silurian indicating more reducing seawater conditions. The lack of observed anoxic facies and no covariance among δ 238 U values and other local redox proxies suggests that the δ 238 U trends represent a global-ocean redox record. The Hirnantian ocean anoxic event (HOAE) onset is coincident with the extinction pulse indicating its importance in triggering it. Anoxia initiated during high sea levels before peak Hirnantian glaciation, and continued into the subsequent lowstand and early Silurian deglacial eustatic rise, implying that major climatic and eustatic changes had little effect on global-ocean redox conditions. The HOAE occurred during a global δ 13 C positive excursion, but lasted longer indicating that controls on the C budget were partially decoupled from global-ocean redox trends. U cycle modeling suggests that there was a ∼15% increase in anoxic seafloor area and ∼80% of seawater U was sequestered into anoxic sediments during the HOAE. Unlike other ocean anoxic events (OAE), the HOAE occurred during peak and waning icehouse conditions rather than during greenhouse climates. We interpret that anoxia was driven by global cooling, which reorganized thermohaline circulation, decreased deep-ocean ventilation, enhanced nutrient fluxes, stimulated productivity, which lead to expanded oxygen minimum zones. Copyright © 2018 the Author(s). Published by PNAS.

  7. Non-occupational physical activity levels of shift workers compared with non-shift workers

    PubMed Central

    Loef, Bette; Hulsegge, Gerben; Wendel-Vos, G C Wanda; Verschuren, W M Monique; Bakker, Marije F; van der Beek, Allard J; Proper, Karin I

    2017-01-01

    Objectives Lack of physical activity (PA) has been hypothesised as an underlying mechanism in the adverse health effects of shift work. Therefore, our aim was to compare non-occupational PA levels between shift workers and non-shift workers. Furthermore, exposure–response relationships for frequency of night shifts and years of shift work regarding non-occupational PA levels were studied. Methods Data of 5980 non-shift workers and 532 shift workers from the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) were used in these cross-sectional analyses. Time spent (hours/week) in different PA types (walking/cycling/exercise/chores) and intensities (moderate/vigorous) were calculated based on self-reported PA. Furthermore, sports were operationalised as: playing sports (no/yes), individual versus non-individual sports, and non-vigorous-intensity versus vigorous-intensity sports. PA levels were compared between shift workers and non-shift workers using Generalized Estimating Equations and logistic regression. Results Shift workers reported spending more time walking than non-shift workers (B=2.3 (95% CI 1.2 to 3.4)), but shift work was not associated with other PA types and any of the sports activities. Shift workers who worked 1–4 night shifts/month (B=2.4 (95% CI 0.6 to 4.3)) and ≥5 night shifts/month (B=3.7 (95% CI 1.8 to 5.6)) spent more time walking than non-shift workers. No exposure–response relationships were found between years of shift work and PA levels. Conclusions Shift workers spent more time walking than non-shift workers, but we observed no differences in other non-occupational PA levels. To better understand if and how PA plays a role in the negative health consequences of shift work, our findings need to be confirmed in future studies. PMID:27872151

  8. Fluid Shifts: Otoacoustical Emission Changes in Response to Posture and Lower Body Negative Pressure

    NASA Technical Reports Server (NTRS)

    Melgoza, R.; Kemp, D.; Ebert, D.; Danielson, R.; Stenger, M.; Hargens, A.; Dulchavsky, S.

    2016-01-01

    INTRODUCTION: The purpose of the NASA Fluid Shifts Study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to correlate these findings with vision changes and other elements of the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. Due to the invasive nature of direct measures of ICP, a noninvasive technique of monitoring ICP is desired for use during spaceflight. The phase angle and amplitude of otoacoustic emissions (OAEs) have been shown to be sensitive to posture change and ICP (1, 2), therefore use of OAEs is an attractive option. OAEs are low-level sounds produced by the sensory cells of the cochlea in response to auditory stimulation. These sounds travel peripherally from the cochlea, through the oval window, to the ear canal where they can be recorded. OAE transmission is sensitive to changes in the stiffness of the oval window, occurring as a result of changes in cochlear pressure. Increased stiffness of the oval window largely affects the transmission of sound from the cochlea at frequencies between 800 Hz and 1600 Hz. OAEs can be self-recorded in the laboratory or on the ISS using a handheld device. Our primary objectives regarding OAE measures in this experiment were to 1) validate this method during preflight testing of each crewmember (while sitting, supine and in head-down tilt position), and 2) determine if OAE measures (and presumably ICP) are responsive to lower body negative pressure and to spaceflight. METHODS: Distortion-product otoacoustic emissions (DPOAEs) and transient evoked otoacoustic emissions (TEOAEs) were recorded preflight using the Otoport Advance OAE system (Otodynamics Ltd., Hatfield, UK). Data were collected in four conditions (seated

  9. Revealing Abrupt and Spontaneous Ruptures of Protein Native Structure under picoNewton Compressive Force Manipulation.

    PubMed

    Chowdhury, S Roy; Cao, Jin; He, Yufan; Lu, H Peter

    2018-03-27

    Manipulating protein conformations for exploring protein structure-function relationship has shown great promise. Although protein conformational changes under pulling force manipulation have been extensively studied, protein conformation changes under a compressive force have not been explored quantitatively. The latter is even more biologically significant and relevant in revealing protein functions in living cells associated with protein crowdedness, distribution fluctuations, and cell osmotic stress. Here we report our experimental observations on abrupt ruptures of protein native structures under compressive force, demonstrated and studied by single-molecule AFM-FRET spectroscopic nanoscopy. Our results show that the protein ruptures are abrupt and spontaneous events occurred when the compressive force reaches a threshold of 12-75 pN, a force amplitude accessible from thermal fluctuations in a living cell. The abrupt ruptures are sensitive to local environment, likely a general and important pathway of protein unfolding in living cells.

  10. Conclusive evidence of abrupt coagulation inside the void during cyclic nanoparticle formation in reactive plasma

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wetering, F. M. J. H. van de; Nijdam, S.; Beckers, J.

    2016-07-25

    In this letter, we present scanning electron microscopy (SEM) results that confirm in a direct way our earlier explanation of an abrupt coagulation event as the cause for the void hiccup. In a recent paper, we reported on the fast and interrupted expansion of voids in a reactive dusty argon–acetylene plasma. The voids appeared one after the other, each showing a peculiar, though reproducible, behavior of successive periods of fast expansion, abrupt contraction, and continued expansion. The abrupt contraction was termed “hiccup” and was related to collective coagulation of a new generation of nanoparticles growing in the void using relativelymore » indirect methods: electron density measurements and optical emission spectroscopy. In this letter, we present conclusive evidence using SEM of particles collected at different moments in time spanning several growth cycles, which enables us to follow the nanoparticle formation process in great detail.« less

  11. Disentangling gaze shifts from preparatory ERP effects during spatial attention

    PubMed Central

    Kennett, Steffan; van Velzen, José; Eimer, Martin; Driver, Jon

    2007-01-01

    After a cue directing attention to one side, anterior event-related potentials (ERPs) show contralateral negativity (Anterior Directing Attention Negativity, ADAN). It is unclear whether ADAN effects are contaminated by contralateral negativity arising from residual gaze shifts. Conversely, it is possible that ADAN-related potentials contaminate the horizontal electrooculogram (HEOG), via volume conduction. To evaluate these possibilities, we used high-resolution infrared eye tracking, while recording EEG and HEOG in a cued spatial-attention task. We found that, after conventional ERP and HEOG pre-processing exclusions, small but systematic residual gaze shifts in the cued direction can remain, as revealed by the infrared measure. Nevertheless, by using this measure for more stringent exclusion of small gaze shifts, we confirmed that reliable ADAN components remain for preparatory spatial attention in the absence of any systematic gaze shifts toward the cued side. PMID:17241141

  12. Abrupt decadal-to-centennial hydroclimate changes in the Mediterranean region since the mid-Holocene

    NASA Astrophysics Data System (ADS)

    Hu, Hsun-Ming; Shen, Chuan-Chou; Jiang, Xiuyang; Wang, Yongjin; Mii, Horng-Sheng; Michel, Véronique

    2016-04-01

    A series of severe drought events in the Mediterranean region over the past two decades has posed a threat on both human society and biosystem. Holocene hydrological dynamics can offer valuable clues for understanding future climate and making proper adaption strategy. Here, we present a decadal-resolved stalagmite record documenting various hydroclimatic fluctuations in the north central Mediterranean region since the middle Holocene. The stalagmite δ18O sequence shows dramatic instability, characterized by abrupt shifts between dry and wet conditions <50 years. The timing of regional culture demises, such as the Hittite Kingdom, Mycenaean Greece, Akkadian Empire, Egyptian Old Kingdom, and Uruk, occurred during the drought events, suggesting an important role of climate impact on human civilization. The unstable hydroclimate evolution is related to transferred North Atlantic Oscillation states. Rate of rapid transfer of precipitation patterns, which can be pin-pointed by our good chronology, improves the prediction to future climate changes in North Atlantic region. We also found that a strong correlation between this stalagmite δ18O and sea surface temperatures especially in Pacific Ocean. This agreement suggests a distant interregional climate teleconnection.

  13. Coherent control of the Goos-Hänchen shift via Fano interference

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Shaopeng; Yang, Wen-Xing, E-mail: wenxingyang@seu.edu.cn; Zhu, Zhonghu

    2016-04-14

    A scheme of enhanced Goos-Hänchen (GH) shifts in reflected and transmitted light beams is exploited in a cavity, where an asymmetric double AlGaAs/GaAs quantum well structure with resonant tunneling to a common continuum is employed as the intracavity medium. With the help of Fano-type interference induced by resonant tunneling, the generated GH shifts that contain a negative lateral shift in reflected light beam and a positive lateral shift in transmitted light beam are found to be significantly enhanced. More interestingly, these GH shifts in reflected and transmitted light beams are modulated by means of a control beam and external biasmore » voltage, in which maximum negative shift of 1.86 mm and positive shift of 0.37 mm are achievable.« less

  14. Abrupt cooling over the North Atlantic in modern climate models

    PubMed Central

    Sgubin, Giovanni; Swingedouw, Didier; Drijfhout, Sybren; Mary, Yannick; Bennabi, Amine

    2017-01-01

    Observations over the 20th century evidence no long-term warming in the subpolar North Atlantic (SPG). This region even experienced a rapid cooling around 1970, raising a debate over its potential reoccurrence. Here we assess the risk of future abrupt SPG cooling in 40 climate models from the fifth Coupled Model Intercomparison Project (CMIP5). Contrary to the long-term SPG warming trend evidenced by most of the models, 17.5% of the models (7/40) project a rapid SPG cooling, consistent with a collapse of the local deep-ocean convection. Uncertainty in projections is associated with the models' varying capability in simulating the present-day SPG stratification, whose realistic reproduction appears a necessary condition for the onset of a convection collapse. This event occurs in 45.5% of the 11 models best able to simulate the observed SPG stratification. Thus, due to systematic model biases, the CMIP5 ensemble as a whole underestimates the chance of future abrupt SPG cooling, entailing crucial implications for observation and adaptation policy. PMID:28198383

  15. Cortisol, reaction time test and health among offshore shift workers.

    PubMed

    Harris, Anette; Waage, Siri; Ursin, Holger; Hansen, Ase Marie; Bjorvatn, Bjørn; Eriksen, Hege R

    2010-10-01

    The stress hormone cortisol shows a pronounced endogenous diurnal rhythm, which is affected by the sleep/wake cycle, meals and activity. Shift work and especially night work disrupts the sleep/wake cycle and causes a desynchronization of the natural biological rhythms. Therefore, different shift schedules may have different impact on performance at work and health. The purpose was to study if health, reaction time, and the cortisol rhythm were negatively affected when a group of shift workers changed their work schedule from ordinary day-night shift (fixed shift) to "swing shift". 19 healthy workers on a Norwegian oil rig participated in the study. They worked 2 weeks offshore followed by 4 weeks off work. The ordinary schedule consisted of 12-h day shift and 12-h night shift every other work period (14 days or nights=fixed shift). "Swing shift" involved 1 week of night shift, followed by 1 week of day shift during the work period. All participants worked ordinary day-night shift when baseline data were collected (questionnaires, saliva cortisol, and reaction time during work). After collection of baseline data the workers changed their work schedule to "swing shift", for every working period, and 9 months later the same data were collected. "Swing shift" did not give any negative health effects or any negative changes in reaction time during the day they shifted from night work to day work. Personnel adapted to night shift within a week regardless of schedule, but recovery from night shift took longer time. During swing shift the cortisol rhythm went back towards a normal rhythm in the second week, but it was not returned completely to normal values when they returned home for the 4 weeks off period. However, the cortisol rhythms were readapted to normal values after 1 week at home. For personnel returning home directly from 14 consecutive night shifts, cortisol adaptation was not complete after 1 week at home. We found no increase in health complaints from swing

  16. Ab initio density functional theory study on the atomic and electronic structure of GaP/Si(001) heterointerfaces

    NASA Astrophysics Data System (ADS)

    Romanyuk, O.; Supplie, O.; Susi, T.; May, M. M.; Hannappel, T.

    2016-10-01

    The atomic and electronic band structures of GaP/Si(001) heterointerfaces were investigated by ab initio density functional theory calculations. Relative total energies of abrupt interfaces and mixed interfaces with Si substitutional sites within a few GaP layers were derived. It was found that Si diffusion into GaP layers above the first interface layer is energetically unfavorable. An interface with Si/Ga substitution sites in the first layer above the Si substrate is energetically the most stable one in thermodynamic equilibrium. The electronic band structure of the epitaxial GaP/Si(001) heterostructure terminated by the (2 ×2 ) surface reconstruction consists of surface and interface electronic states in the common band gap of two semiconductors. The dispersion of the states is anisotropic and differs for the abrupt Si-Ga, Si-P, and mixed interfaces. Ga 2 p , P 2 p , and Si 2 p core-level binding-energy shifts were computed for the abrupt and the lowest-energy heterointerface structures. Negative and positive core-level shifts due to heterovalent bonds at the interface are predicted for the abrupt Si-Ga and Si-P interfaces, respectively. The distinct features in the heterointerface electronic structure and in the core-level shifts open new perspectives in the experimental characterization of buried polar-on-nonpolar semiconductor heterointerfaces.

  17. Tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer

    NASA Astrophysics Data System (ADS)

    Hernández-Arriaga, M. V.; Durán-Sánchez, M.; Ibarra-Escamilla, B.; Álvarez-Tamayo, R. I.; Santiago-Hernández, H.; Bello-Jiménez, M.; Kuzin, E. A.

    2017-11-01

    An experimental study of an all-fiber tunable thulium-doped fiber laser based on an abrupt-tapered in-fiber interferometer is presented. A microfiber filter with length of 6 mm and diameter of 20 μm is used to achieve single laser wavelength tuning in a range of 19.4 nm and dual-wavelength laser operation at 1761.8 and 1793.4 nm with a channel spacing of 31.6 nm. The abrupt-tapered structure allows multi-modal interference at the air-cladding interface. The proposed in-fiber interferometer exhibits characteristics of low cost and simple fabrication, making it suitable for practical applications in wavelength filtering and wavelength selection in all-fiber lasers.

  18. Effects of extended work shifts and shift work on patient safety, productivity, and employee health.

    PubMed

    Keller, Simone M

    2009-12-01

    It is estimated 1.3 million health care errors occur each year and of those errors 48,000 to 98,000 result in the deaths of patients (Barger et al., 2006). Errors occur for a variety of reasons, including the effects of extended work hours and shift work. The need for around-the-clock staff coverage has resulted in creative ways to maintain quality patient care, keep health care errors or adverse events to a minimum, and still meet the needs of the organization. One way organizations have attempted to alleviate staff shortages is to create extended work shifts. Instead of the standard 8-hour shift, workers are now working 10, 12, 16, or more hours to provide continuous patient care. Although literature does support these staffing patterns, it cannot be denied that shifts beyond the traditional 8 hours increase staff fatigue, health care errors, and adverse events and outcomes and decrease alertness and productivity. This article includes a review of current literature on shift work, the definition of shift work, error rates and adverse outcomes related to shift work, health effects on shift workers, shift work effects on older workers, recommended optimal shift length, positive and negative effects of shift work on the shift worker, hazards associated with driving after extended shifts, and implications for occupational health nurses. Copyright 2009, SLACK Incorporated.

  19. Shifting schedules: the health effects of reorganizing shift work.

    PubMed

    Bambra, Clare L; Whitehead, Margaret M; Sowden, Amanda J; Akers, Joanne; Petticrew, Mark P

    2008-05-01

    Approximately one fifth of workers are engaged in some kind of shift work. The harmful effects of shift work on the health and work-life balance of employees are well known. A range of organizational interventions has been suggested to address these negative effects. This study undertook the systematic review (following Quality Of Reporting Of Meta [QUORUM] analyses guidelines) of experimental and quasi-experimental studies, from any country (in any language) that evaluated the effects on health and work-life balance of organizational-level interventions that redesign shift work schedules. Twenty-seven electronic databases (medical, social science, economic) were searched. Data extraction and quality appraisal were carried out by two independent reviewers. Narrative synthesis was performed. The review was conducted between October 2005 and November 2006. Twenty-six studies were found relating to a variety of organizational interventions. No one type of intervention was found to be consistently harmful to workers. However, three types were found to have beneficial effects on health and work-life balance: (1) switching from slow to fast rotation, (2) changing from backward to forward rotation, and (3) self-scheduling of shifts. Improvements were usually at little or no direct organizational cost. However, there were concerns about the generalizability of the evidence, and no studies reported on impacts on health inequalities. This review reinforces the findings of epidemiologic and laboratory-based research by suggesting that certain organizational-level interventions can improve the health of shift workers, their work-life balance, or both. This evidence could be useful when designing interventions to improve the experience of shift work.

  20. Non-occupational physical activity levels of shift workers compared with non-shift workers.

    PubMed

    Loef, Bette; Hulsegge, Gerben; Wendel-Vos, G C Wanda; Verschuren, W M Monique; Vermeulen, Roel C H; Bakker, Marije F; van der Beek, Allard J; Proper, Karin I

    2017-05-01

    Lack of physical activity (PA) has been hypothesised as an underlying mechanism in the adverse health effects of shift work. Therefore, our aim was to compare non-occupational PA levels between shift workers and non-shift workers. Furthermore, exposure-response relationships for frequency of night shifts and years of shift work regarding non-occupational PA levels were studied. Data of 5980 non-shift workers and 532 shift workers from the European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) were used in these cross-sectional analyses. Time spent (hours/week) in different PA types (walking/cycling/exercise/chores) and intensities (moderate/vigorous) were calculated based on self-reported PA. Furthermore, sports were operationalised as: playing sports (no/yes), individual versus non-individual sports, and non-vigorous-intensity versus vigorous-intensity sports. PA levels were compared between shift workers and non-shift workers using Generalized Estimating Equations and logistic regression. Shift workers reported spending more time walking than non-shift workers (B=2.3 (95% CI 1.2 to 3.4)), but shift work was not associated with other PA types and any of the sports activities. Shift workers who worked 1-4 night shifts/month (B=2.4 (95% CI 0.6 to 4.3)) and ≥5 night shifts/month (B=3.7 (95% CI 1.8 to 5.6)) spent more time walking than non-shift workers. No exposure-response relationships were found between years of shift work and PA levels. Shift workers spent more time walking than non-shift workers, but we observed no differences in other non-occupational PA levels. To better understand if and how PA plays a role in the negative health consequences of shift work, our findings need to be confirmed in future studies. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  1. Impact of shift work on critical care nurses.

    PubMed

    Pryce, Cheryl

    2016-01-01

    Shift work is a common practice in the health care field to maintain 24-hour patient care. The purpose of this article is to recognize the negative impact of shift work on critical care nurses, and identify strategies to mitigate these effects. A review of the literature was completed, using the search terms: 'shift work, 'critical care', impact, and health. The literature revealed that shift work has an adverse effect on the health of a nurse. Some of the health implications include stress, sleep deprivation, cardiovascular disease, gastrointestinal symptoms, and mental health illnesses. Furthermore, shift work impacts a nurse's social life and may result in patient harm. Strategies to reduce the negative impact of shift work will be focused on educating critical care nurses and managers. These strategies include frontline staff maintaining a moderate amount of exercise, sustaining a well-balanced diet, using relaxation techniques, reducing the use of cigarettes, working an eight-hour work day, and napping during scheduled breaks. Recommendations for managers include implementing quiet time at the workplace, providing a safe space for staff to nap during breaks, facilitating an eight-hour work day, and encouraging a multidisciplinary team approach when managing workload.

  2. Dissociating the capture of attention from saccade activation by subliminal abrupt onsets.

    PubMed

    Schoeberl, Tobias; Ansorge, Ulrich

    2017-10-01

    Attentional capture and effects on saccade metrics by subliminal abrupt onset cues have been studied with peripheral cues at one out of several (two to four) display locations, swiftly followed by additional onsets at the other display locations. The lead time of the cue was too short to be seen. Here, we were interested in whether such subliminal onset cues influenced saccades primarily by way of attention or by way of direct saccade activation. In separate blocks, participants made speeded pro-saccades towards a black target or anti-saccades away from the target. Prior to the targets, an abrupt onset cue was presented either at the same side as the target (valid condition) or at the opposite side (invalid condition). If cues influenced performance by way of attentional capture, we expected facilitation of target processing in valid compared to invalid conditions (cueing effect) in the pro- as well as in the anti-saccade task. If the cues activated saccades in their direction, we expected the cueing effect to drop in the anti-saccade task compared to the pro-saccade task because in the anti-saccade task the invalid cue would activate the finally required response, whereas the valid cue would activate the alternative response, leading to interference. Results were in line with the former of these possibilities suggesting that subliminal abrupt onsets influenced saccades by way of attention with no or little direct activation of saccades.

  3. Reversal of orbital angular momentum arising from an extreme Doppler shift

    PubMed Central

    Toninelli, Ermes; Horsley, Simon A. R.; Hendry, Euan; Phillips, David B.; Padgett, Miles J.

    2018-01-01

    The linear Doppler shift is familiar as the rise and fall in pitch of a siren as it passes by. Less well known is the rotational Doppler shift, proportional to the rotation rate between source and receiver, multiplied by the angular momentum carried by the beam. In extreme cases the Doppler shift can be larger than the rest-frame frequency and for a red shift, the observed frequency then becomes “negative.” In the linear case, this effect is associated with the time reversal of the received signal, but it can be observed only with supersonic relative motion between the source and receiver. However, the rotational case is different; if the radius of rotation is smaller than the wavelength, then the velocities required to observe negative frequencies are subsonic. Using an acoustic source at ≈100 Hz we create a rotational Doppler shift larger than the laboratory-frame frequency. We observe that once the red-shifted wave passes into the “negative frequency” regime, the angular momentum associated with the sound is reversed in sign compared with that of the laboratory frame. These low-velocity laboratory realizations of extreme Doppler shifts have relevance to superoscillatory fields and offer unique opportunities to probe interactions with rotating bodies and aspects of pseudorelativistic frame translation. PMID:29581257

  4. Work shift duration: a review comparing eight hour and 12 hour shift systems.

    PubMed

    Smith, L; Folkard, S; Tucker, P; Macdonald, I

    1998-04-01

    Shiftwork is now a major feature of working life across a broad range of industries. The features of the shift systems operated can impact on the wellbeing, performance, and sleep of shiftworkers. This paper reviews the current state of knowledge on one major characteristic of shift rotas-namely, shift duration. Evidence comparing the relative effects of eight hour and 12 hour shifts on fatigue and job performance, safety, sleep, and physical and psychological health are considered. At the organisational level, factors such as the mode of system implementation, attitudes towards shift rotas, sickness absence and turnover, overtime, and moonlighting are discussed. Manual and electronic searches of the shiftwork research literature were conducted to obtain information on comparisons between eight hour and 12 hour shifts. The research findings are largely equivocal. The bulk of the evidence suggests few differences between eight and 12 hour shifts in the way they affect people. There may even be advantages to 12 hour shifts in terms of lower stress levels, better physical and psychological wellbeing, improved durations and quality of off duty sleep as well as improvements in family relations. On the negative side, the main concerns are fatigue and safety. It is noted that a 12 hour shift does not equate with being active for only 12 hours. There can be considerable extension of the person's time awake either side of the shift. However, the effects of longer term exposure to extended work days have been relatively uncharted in any systematic way. Longitudinal comparative research into the chronic impact of the compressed working week is needed.

  5. The Effect of Shift Work on Urogenital Disease: a Systematic Review.

    PubMed

    Deng, Nanfu; Haney, Nora M; Kohn, Taylor P; Pastuszak, Alexander W; Lipshultz, Larry I

    2018-05-28

    Non-standard shift work schedules negatively impact the overall health of shift workers, and several studies have shown that shift work, specifically, is detrimental to urogenital health. The aims of this study are to systematically review the literature and determine the effect of shift work on the outcomes of hypogonadism, male infertility, lower urinary tract symptoms, and urogenital cancers. Recent evidence supports associations between non-standard shift work and an increase in the frequency of prostate cancer and the severity of erectile dysfunction, lower urinary tract symptoms, and hypogonadal symptoms, as well as worsening of semen parameters and fertility. These associations are strengthened by the presence of shift work sleep disorder (SWSD) which affects up to 20% of shift workers. No studies have assessed the impact of shift work on the frequency or severity of nephrolithiasis, interstitial cystitis, pelvic pain, prostatitis, or urinary tract infections. Non-standard shift work has been associated with a variety of negative health outcomes and urologic complications, especially with concurrent shift work sleep disorder. Recognition of these elevated risks among shift workers can aid in more effective screening for urologic conditions.

  6. Elucidating Dynamical Processes Relevant to Flow Encountering Abrupt Topography (FLEAT)

    DTIC Science & Technology

    2015-09-30

    Encountering Abrupt Topography (FLEAT) Bo Qiu Dept of Oceanography, University of Hawaii at Manoa 1000 Pope Rd. Honolulu, HI 96822 phone: (808) 956...c) to explore relevant dynamics by using both simplified models and OGCM output with realistic topography and surface boundary conditions...scale abyssal circulation, we propose to use the Hallberg Isopycnal Model (HIM). The HIM allows sloping isopycnals to interact with bottom topography

  7. Detecting Negative Obstacles by Use of Radar

    NASA Technical Reports Server (NTRS)

    Mittskus, Anthony; Lux, James

    2006-01-01

    Robotic land vehicles would be equipped with small radar systems to detect negative obstacles, according to a proposal. The term "negative obstacles" denotes holes, ditches, and any other terrain features characterized by abrupt steep downslopes that could be hazardous for vehicles. Video cameras and other optically based obstacle-avoidance sensors now installed on some robotic vehicles cannot detect obstacles under adverse lighting conditions. Even under favorable lighting conditions, they cannot detect negative obstacles. A radar system according to the proposal would be of the frequency-modulation/ continuous-wave (FM/CW) type. It would be installed on a vehicle, facing forward, possibly with a downward slant of the main lobe(s) of the radar beam(s) (see figure). It would utilize one or more wavelength(s) of the order of centimeters. Because such wavelengths are comparable to the characteristic dimensions of terrain features associated with negative hazards, a significant amount of diffraction would occur at such features. In effect, the diffraction would afford a limited ability to see corners and to see around corners. Hence, the system might utilize diffraction to detect corners associated with negative obstacles. At the time of reporting the information for this article, preliminary analyses of diffraction at simple negative obstacles had been performed, but an explicit description of how the system would utilize diffraction was not available.

  8. Bend-imitating models of abruptly bent electron waveguides

    NASA Astrophysics Data System (ADS)

    Vakhnenko, Oleksiy O.

    2011-07-01

    The fundamentals of bend-imitating approach regarding the one-electron quantum mechanics in abruptly bent ideal electron waveguides are given. In general, the theory allows to model each particular circularlike bend of a continuous quantum wire as some effective multichannel scatterer being pointlike in longitudinal direction. Its scattering ability is determined by the bending angle, mean bending radius, lateral coordinate (or coordinates) in wire cross section, time (or electronic energy), and possibly by the applied magnetic field. In an equivalent formulation, the theory gives rise to rather simple matching rules for the electron wave function and its longitudinal derivative affecting only the straight parts of a wire and thereby permitting to bypass a detailed quantum mechanical consideration of elbow domains. The proposed technique is applicable for the analytical investigation of spectral and transport electronic properties related to the ideal abruptly bent 3D wirelike structures of fixed cross section and is adaptable to the 2D wirelike structures as well as to the wirelike structures subjected to the magnetic field perpendicular to the plane of wire bending. In the framework of bend-imitating approach, the investigation of electron scattering in a singly bent 2D quantum wire and a doubly bent 2D quantum wire with S-like bend has been made and the explicit dependences of transmission and reflection coefficients on geometrical parameters of respective structure as well as on electron energy have been obtained. The total suppression of mixing between the scattering channels of S-like bent quantum wire is predicted.

  9. History of Red Crater volcano, Tongariro Volcanic Centre (New Zealand): Abrupt shift in magmatism following recharge and contrasting evolution between neighboring volcanoes

    NASA Astrophysics Data System (ADS)

    Shane, Phil; Maas, Roland; Lindsay, Jan

    2017-06-01

    Red Crater volcano is one of several contemporaneously active vents on the Tongariro Volcanic Centre. Its history provides an opportunity to investigate the contrasting magmatic evolutionary paths of closely-spaced volcanoes. Rocks erupted at Red Crater over the last 3.4 ka display typical subduction-related trace element and isotopic signatures. Those erupted pre-1.8 ka are medium-K andesites (SiO2 59-62 wt%). They represent the most voluminous magmas and were emplaced in 5 lava flow events. An abrupt shift to the eruption of basaltic andesite (SiO2 53-54 wt%) with less radiogenic Sr-Nd-Pb isotope ratios, occurred post-1.8 ka. This period comprised 6 smaller volume, lava flow episodes and the contemporaneous development of a scoria cone. Plagioclase phenocrysts in post-1.8 ka lava flows have resorbed cores with diverse textural and compositional growth patterns, as would be expected from the disruption of a crystal mush. They are similar to phenocrysts of the pre-1.8 ka lava flows. The post-1.8 ka plagioclase is distinguished from those in the older lavas by overgrowths with elevated An ( 70-90), FeO and MgO contents, that mantle the resorbed cores ( An50-70). These rims are compositionally similar to groundmass plagioclase. This demonstrates that new mafic magma was intruded into the system, mixing with and entraining relic crystals from the older andesite system. Iron and Mg zoning patterns in the crystals are not consistent with significant re-equilibration via diffusion. Hence, the generation of eruptible magma during the last 1.8 ka required repeated mafic intrusion events. The emptying of the older andesitic magma reservoir early in the volcano's history removed buoyancy barriers to the direct eruption of more mafic magmas. This pattern of magmatism is not recorded at the contemporaneously active Ngauruhoe volcano, just 3 km to the SSW. Ngauruhoe rocks are compositionally distinct and are more heterogeneous in isotopic composition. Although mafic recharge is

  10. Triggers and maintenance of multiple shifts in the state of a natural community

    PubMed Central

    Schmitt, Russell J.; Holbrook, Sally J.

    2010-01-01

    Ecological communities can undergo sudden and dramatic shifts between alternative persistent community states. Both ecological prediction and natural resource management rely on understanding the mechanisms that trigger such shifts and maintain each state. Differentiating between potential mechanisms is difficult, however, because shifts are often recognized only in hindsight and many occur on such large spatial scales that manipulative experiments to test their causes are difficult or impossible. Here we use an approach that focuses first on identifying changes in environmental factors that could have triggered a given state change, and second on examining whether these changes were sustained (and thus potentially maintained the new state) or transitory (explaining the shift but not its persistence). We use this approach to evaluate a community shift in which a benthic marine species of filter feeding sea cucumber (Pachythyone rubra) suddenly came to dominate subtidal rocky reefs that had previously supported high abundances of macroalgae, persisted for more than a decade, then abruptly declined. We found that a sustained period without large wave events coincided with the shift to sea cucumber dominance, but that the sea cucumbers persisted even after the end of this low wave period, indicating that different mechanisms maintained the new community. Additionally, the period of sea cucumber dominance occurred when their predators were rare, and increases in the abundance of these predators coincided with the end of sea cucumber dominance. These results underscore the complex nature of regime shifts and illustrate that focusing separately on the causes and maintenance of state change can be a productive first step for analyzing these shifts in a range of systems. PMID:20526781

  11. Direct generation of abruptly focusing vortex beams using a 3/2 radial phase-only pattern.

    PubMed

    Davis, Jeffrey A; Cottrell, Don M; Zinn, Jonathan M

    2013-03-20

    Abruptly focusing Airy beams have previously been generated using a radial cubic phase pattern that represents the Fourier transform of the Airy beam. The Fourier transform of this pattern is formed using a system length of 2f, where f is the focal length of the Fourier transform lens. In this work, we directly generate these abruptly focusing Airy beams using a 3/2 radial phase pattern encoded onto a liquid crystal display. The resulting optical system is much shorter. In addition, we can easily produce vortex patterns at the focal point of these beams. Experimental results match theoretical predictions.

  12. Relationship between shift work and the onset of rheumatoid arthritis

    PubMed Central

    Hedström, Anna Karin; Åkerstedt, Torbjörn; Klareskog, Lars; Alfredsson, Lars

    2017-01-01

    Background Environmental factors play a prominent role in rheumatoid arthritis (RA) aetiology. Shift work has previously been associated with increased RA risk in females. The aim of this study was to investigate the potential association, including a dose–response association, between permanent night shift work, rotating shift work and day-oriented shift work and risk of developing anticitrullinated peptide antibodies (ACPA)-positive and ACPA-negative RA. Methods The present report is based on a population-based, case–control study with incident cases of RA (1951 cases and 2225 controls matched by age, gender and residential area). Using logistic regression, occurrence of RA among subjects who have been exposed to different kinds of shift work was compared with that among those who have never been exposed by calculating the OR with a 95% CI. Results Rotating shift work and day-oriented shift work increased the risk of developing ACPA-positive RA (OR 1.3, 95% CI 1.0 to 1.7 and OR 1.3, 95% CI 1.0 to 1.6), but not ACPA-negative RA. Permanent night shift work appeared to be a protective factor both against ACPA-positive RA (OR 0.7, 95% CI 0.6 to 0.9) and ACPA-negative RA (OR 0.8, 95% CI 0.6 to 1.0). For both subsets of RA, significant trends showed a lower risk of developing RA with increasing duration of permanent night shift work (p value for trend 0.002 vs 0.04). Conclusions Sleep restriction as a consequence of shift work is associated with several biological effects among which changes in melatonin production may be involved. The present epidemiological findings of a complex relationship between sleep patterns and different forms of RA may be of importance for increasing the understanding of the pathophysiology of RA. PMID:29225920

  13. Electric Field Induce Blue Shift and Intensity Enhancement in 2D Exciplex Organic Light Emitting Diodes; Controlling Electron-Hole Separation.

    PubMed

    Al Attar, Hameed A; Monkman, Andy P

    2016-09-01

    A simple but novel method is designed to study the characteristics of the exciplex state pinned at a donor-acceptor abrupt interface and the effect an external electric field has on these excited states. The reverse Onsager process, where the field induces blue-shifted emission and increases the efficiency of the exciplex emission as the e-h separation reduces, is discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. West African monsoon dynamics inferred from abrupt fluctuations of Lake Mega-Chad

    PubMed Central

    Armitage, Simon J.; Bristow, Charlie S.; Drake, Nick A.

    2015-01-01

    From the deglacial period to the mid-Holocene, North Africa was characterized by much wetter conditions than today. The broad timing of this period, termed the African Humid Period, is well known. However, the rapidity of the onset and termination of the African Humid Period are contested, with strong evidence for both abrupt and gradual change. We use optically stimulated luminescence dating of dunes, shorelines, and fluviolacustrine deposits to reconstruct the fluctuations of Lake Mega-Chad, which was the largest pluvial lake in Africa. Humid conditions first occur at ∼15 ka, and by 11.5 ka, Lake Mega-Chad had reached a highstand, which persisted until 5.0 ka. Lake levels fell rapidly at ∼5 ka, indicating abrupt aridification across the entire Lake Mega-Chad Basin. This record provides strong terrestrial evidence that the African Humid Period ended abruptly, supporting the hypothesis that the African monsoon responds to insolation forcing in a markedly nonlinear manner. In addition, Lake Mega-Chad exerts strong control on global biogeochemical cycles because the northern (Bodélé) basin is currently the world’s greatest single dust source and possibly an important source of limiting nutrients for both the Amazon Basin and equatorial Atlantic. However, we demonstrate that the final desiccation of the Bodélé Basin occurred around 1 ka. Consequently, the present-day mode and scale of dust production from the Bodélé Basin cannot have occurred before 1 ka, suggesting that its role in fertilizing marine and terrestrial ecosystems is either overstated or geologically recent. PMID:26124133

  15. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Laurie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Lui, J.; hide

    2015-01-01

    INTRODUCTION: Mechanisms responsible for the ocular structural and functional changes that characterize the visual impairment and intracranial pressure (ICP) syndrome (VIIP) are unclear, but hypothesized to be secondary to the cephalad fluid shift experienced in spaceflight. This study will relate the fluid distribution and compartmentalization associated with long-duration spaceflight with VIIP symptoms. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, can be predicted preflight with acute hemodynamic manipulations, and also if lower body negative pressure (LBNP) can reverse the VIIP effects. METHODS: Physiologic variables will be examined pre-, in- and post-flight in 10 International Space Station crewmembers including: fluid compartmentalization (D2O and NaBr dilution); interstitial tissue thickness (ultrasound); vascular dimensions and dynamics (ultrasound and MRI (including cerebrospinal fluid pulsatility)); ocular measures (optical coherence tomography, intraocular pressure, ultrasound); and ICP measures (tympanic membrane displacement, otoacoustic emissions). Pre- and post-flight measures will be assessed while upright, supine and during 15 deg head-down tilt (HDT). In-flight measures will occur early and late during 6 or 12 month missions. LBNP will be evaluated as a countermeasure during HDT and during spaceflight. RESULTS: The first two crewmembers are in the preflight testing phase. Preliminary results characterize the acute fluid shifts experienced from upright, to supine and HDT postures (increased stroke volume, jugular dimensions and measures of ICP) which are reversed with 25 millimeters Hg LBNP. DISCUSSION: Initial results indicate that acute cephalad fluid shifts may be related to VIIP symptoms, but also may be reversible by LBNP. The effect of a chronic fluid shift has yet to be evaluated. Learning Objectives: Current spaceflight VIIP research is described

  16. Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

    PubMed

    Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

    2012-11-01

    Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

  17. Work shift duration: a review comparing eight hour and 12 hour shift systems

    PubMed Central

    Smith, L.; Folkard, S.; Tucker, P.; Macdonald, I.

    1998-01-01

    OBJECTIVES: Shiftwork is now a major feature of working life across a broad range of industries. The features of the shift systems operated can impact on the wellbeing, performance, and sleep of shiftworkers. This paper reviews the current state of knowledge on one major characteristic of shift rotas-namely, shift duration. Evidence comparing the relative effects of eight hour and 12 hour shifts on fatigue and job performance, safety, sleep, and physical and psychological health are considered. At the organisational level, factors such as the mode of system implementation, attitudes towards shift rotas, sickness absence and turnover, overtime, and moonlighting are discussed. METHODS: Manual and electronic searches of the shiftwork research literature were conducted to obtain information on comparisons between eight hour and 12 hour shifts. RESULTS: The research findings are largely equivocal. The bulk of the evidence suggests few differences between eight and 12 hour shifts in the way they affect people. There may even be advantages to 12 hour shifts in terms of lower stress levels, better physical and psychological wellbeing, improved durations and quality of off duty sleep as well as improvements in family relations. On the negative side, the main concerns are fatigue and safety. It is noted that a 12 hour shift does not equate with being active for only 12 hours. CONCLUSIONS: There can be considerable extension of the person's time awake either side of the shift. However, the effects of longer term exposure to extended work days have been relatively uncharted in any systematic way. Longitudinal comparative research into the chronic impact of the compressed working week is needed.   PMID:9624275

  18. Reversal of orbital angular momentum arising from an extreme Doppler shift.

    PubMed

    Gibson, Graham M; Toninelli, Ermes; Horsley, Simon A R; Spalding, Gabriel C; Hendry, Euan; Phillips, David B; Padgett, Miles J

    2018-04-10

    The linear Doppler shift is familiar as the rise and fall in pitch of a siren as it passes by. Less well known is the rotational Doppler shift, proportional to the rotation rate between source and receiver, multiplied by the angular momentum carried by the beam. In extreme cases the Doppler shift can be larger than the rest-frame frequency and for a red shift, the observed frequency then becomes "negative." In the linear case, this effect is associated with the time reversal of the received signal, but it can be observed only with supersonic relative motion between the source and receiver. However, the rotational case is different; if the radius of rotation is smaller than the wavelength, then the velocities required to observe negative frequencies are subsonic. Using an acoustic source at [Formula: see text]100 Hz we create a rotational Doppler shift larger than the laboratory-frame frequency. We observe that once the red-shifted wave passes into the "negative frequency" regime, the angular momentum associated with the sound is reversed in sign compared with that of the laboratory frame. These low-velocity laboratory realizations of extreme Doppler shifts have relevance to superoscillatory fields and offer unique opportunities to probe interactions with rotating bodies and aspects of pseudorelativistic frame translation. Copyright © 2018 the Author(s). Published by PNAS.

  19. The Arctic Grand Challenge: Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Wilkniss, P. E.

    2003-12-01

    Trouble in polar paradise (Science, 08/30/02), significant changes in the Arctic environment are scientifically documented (R.E. Moritz et al. ibid.). More trouble, lots more, "abrupt climate change," (R. B. Alley, et al. Science 03/28/03). R. Corell, Arctic Climate Impact Assessment team (ACIA), "If you want to see what will happen in the rest of the world 25 years from now just look what's happening in the Arctic," (Arctic Council meeting, Iceland, 08/03). What to do? Make abrupt Arctic climate change a grand challenge for the IPY-4 and beyond! Scientifically:Describe the "state" of the Arctic climate system as succinctly as possible and accept it as the point of departure.Develop a hypothesis and criteria what constitutes "abrupt climate change," in the Arctic that can be tested with observations. Observations: Bring to bear existing observations and coordinate new investments in observations through an IPY-4 scientific management committee. Make the new Barrow, Alaska, Global Climate Change Research Facility a major U.S. contribution and focal point for the IPY-4 in the U.S Arctic. Arctic populations, Native peoples: The people of the North are living already, daily, with wrenching change, encroaching on their habitats and cultures. For them "the earth is faster now," (I. Krupnik and D. Jolly, ARCUS, 2002). From a political, economic, social and entirely realistic perspective, an Arctic grand challenge without the total integration of the Native peoples in this effort cannot succeed. Therefore: Communications must be established, and the respective Native entities must be approached with the determination to create well founded, well functioning, enduring partnerships. In the U.S. Arctic, Barrow with its long history of involvement and active support of science and with the new global climate change research facility should be the focal point of choice Private industry: Resource extraction in the Arctic followed by oil and gas consumption, return the combustion

  20. Set-shifting abilities, mood and loss of control over eating in binge eating disorder: An experimental study.

    PubMed

    Dingemans, Alexandra E; Visser, Hiske; Paul, Linda; van Furth, Eric F

    2015-12-15

    Executive functions play an important role in problem-solving and self-control. Set-shifting is an aspect of executive functioning and represents cognitive flexibility. The inability to control eating in Binge Eating Disorder (BED) may imply deficits in set-shifting which could be exacerbated by negative mood and depressive symptoms. The aim of the study was to test whether there is a causal relationship between set-shifting ability, changes in mood and loss of control over eating in BED. Seventy-five participants diagnosed with BED were randomly assigned to a negative or neutral mood induction. Set-shifting abilities, depressive symptoms, current mood and loss of control over eating were assessed. Having depressive symptoms and poorer set-shifting abilities resulted in a more negative mood after a negative mood induction, whereas this was not observed in the neutral mood induction. Post-hoc analyses revealed that individuals with poorer set-shifting abilities and more changes in negative mood, experienced more feelings of loss of control over eating than individuals whose set-shifting abilities were better and whose mood did not change. The results suggest that both depressive symptoms and deficits in set-shifting abilities may decrease an individual's ability to handle negative affect and increase loss of control over eating in individuals with BED. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  1. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M. B.; Hargens, A. R.; Dulchavsky, S. A.; Arbeille, P.; Danielson, R. W.; Ebert, D. J.; Garcia, K. M.; Johnston, S. L.; Laurie, S. S.; Lee, S. M. C.; hide

    2017-01-01

    Introduction. NASA's Human Research Program is focused on addressing health risks associated with long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but now more than 50 percent of ISS astronauts have experienced more profound, chronic changes with objective structural findings such as optic disc edema, globe flattening and choroidal folds. These structural and functional changes are referred to as the visual impairment and intracranial pressure (VIIP) syndrome. Development of VIIP symptoms may be related to elevated intracranial pressure (ICP) secondary to spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight and to determine if a relation exists with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as any VIIP-related effects of those shifts, are predicted by the crewmember's pre-flight status and responses to acute hemodynamic manipulations, specifically posture changes and lower body negative pressure. Methods. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, and calcaneus tissue thickness (by ultrasound); (3) vascular dimensions by ultrasound (jugular veins, cerebral and carotid arteries, vertebral arteries and veins, portal vein); (4) vascular dynamics by MRI (head/neck blood flow, cerebrospinal fluid

  2. Comparative analysis of European wide marine ecosystem shifts: a large-scale approach for developing the basis for ecosystem-based management.

    PubMed

    Möllmann, Christian; Conversi, Alessandra; Edwards, Martin

    2011-08-23

    Abrupt and rapid ecosystem shifts (where major reorganizations of food-web and community structures occur), commonly termed regime shifts, are changes between contrasting and persisting states of ecosystem structure and function. These shifts have been increasingly reported for exploited marine ecosystems around the world from the North Pacific to the North Atlantic. Understanding the drivers and mechanisms leading to marine ecosystem shifts is crucial in developing adaptive management strategies to achieve sustainable exploitation of marine ecosystems. An international workshop on a comparative approach to analysing these marine ecosystem shifts was held at Hamburg University, Institute for Hydrobiology and Fisheries Science, Germany on 1-3 November 2010. Twenty-seven scientists from 14 countries attended the meeting, representing specialists from seven marine regions, including the Baltic Sea, the North Sea, the Barents Sea, the Black Sea, the Mediterranean Sea, the Bay of Biscay and the Scotian Shelf off the Canadian East coast. The goal of the workshop was to conduct the first large-scale comparison of marine ecosystem regime shifts across multiple regional areas, in order to support the development of ecosystem-based management strategies. This journal is © 2011 The Royal Society

  3. Negation in Context: A Functional Approach to Suppression

    ERIC Educational Resources Information Center

    Giora, Rachel; Fein, Ofer; Aschkenazi, Keren; Alkabets-Zlozover, Inbar

    2007-01-01

    Three experiments show that, contrary to the current view, comprehenders do not unconditionally deactivate information marked by negation. Instead, they discard negated information when it is functionally motivated. In Experiment 1, comprehenders discarded negated concepts when cued by a topic shift to dampen recently processed information.…

  4. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

  5. Long-Term Phenological Shifts in Raptor Migration and Climate

    PubMed Central

    Jaffré, Mikaël; Beaugrand, Grégory; Goberville, Éric; Jiguet, Frédéric; Kjellén, Nils; Troost, Gerard; Dubois, Philippe J.; Leprêtre, Alain; Luczak, Christophe

    2013-01-01

    Climate change is having a discernible effect on many biological and ecological processes. Among observed changes, modifications in bird phenology have been widely documented. However, most studies have interpreted phenological shifts as gradual biological adjustments in response to the alteration of the thermal regime. Here we analysed a long-term dataset (1980-2010) of short-distance migratory raptors in five European regions. We revealed that the responses of these birds to climate-induced changes in autumn temperatures are abrupt and synchronous at a continental scale. We found that when the temperatures increased, birds delayed their mean passage date of autumn migration. Such delay, in addition to an earlier spring migration, suggests that a significant warming may induce an extension of the breeding-area residence time of migratory raptors, which may eventually lead to residency. PMID:24223888

  6. Abrupt climate change: Past, present and the search for precursors as an aid to predicting events in the future (Hans Oeschger Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Mayewski, Paul Andrew

    2016-04-01

    The demonstration using Greenland ice cores that abrupt shifts in climate, Dansgaard-Oeschger (D-O) events, existed during the last glacial period has had a transformational impact on our understanding of climate change in the naturally forced world. The demonstration that D-O events are globally distributed and that they operated during previous glacial periods has led to extensive research into the relative hemispheric timing and causes of these events. The emergence of civilization during our current interglacial, the Holocene, has been attributed to the "relative climate quiescence" of this period relative to the massive, abrupt shifts in climate that characterized glacial periods in the form of D-O events. But, everything is relative and climate change is no exception. The demise of past civilizations, (eg., Mesopatamian, Mayan and Norse) is integrally tied to abrupt climate change (ACC) events operating at regional scales. Regionally to globally distributed ACC events have punctuated the Holocene and extreme events have always posed significant challenges to humans and ecosystems. Current warming of the Arctic, in terms of length of the summer season, is as abrupt and massive, albeit not as extensive, as the transition from the last major D-O event, the Younger Dryas into the Holocene (Mayewski et al., 2013). Tropospheric source greenhouse gas rise and ozone depletion in the stratosphere over Antarctica are triggers for the modern advent of human emission instigated ACCs. Arctic warming and Antarctic ozone depletion have resulted in significance changes to the atmospheric circulation systems that transport heat, moisture, and pollutants in both hemispheres. Climate models offer a critical tool for assessing trends, but they cannot as yet predict ACC events, as evidenced by the inability of these models to predict the rapid onset of Arctic warming and resulting changes in atmospheric circulation; and in the model vs past analog differences in projections for

  7. Aerodynamic and acoustic effects of abrupt frequency changes in excised larynges.

    PubMed

    Alipour, Fariborz; Finnegan, Eileen M; Scherer, Ronald C

    2009-04-01

    To determine the aerodynamic and acoustic effects due to a sudden change from chest to falsetto register or vice versa. It was hypothesized that the continuous change in subglottal pressure and flow rate alone (pressure-flow sweep [PFS]) can trigger a mode change in the canine larynx. Ten canine larynges were each mounted over a tapered tube that supplied pressurized, heated, and humidified air. Glottographic signals were recorded during each PFS experiment, during which airflow was increased in a gradual manner for a period of 20-30 s. Abrupt changes in fundamental frequency (F(0)) and mode of vibration occurred during the PFS in the passive larynx without any change in adduction or elongation. The lower frequency mode of oscillation of the vocal folds, perceptually identified as the chest register, had relatively large amplitude oscillation, significant vocal fold contact, a rich spectral content, and a relatively loud audio signal. The higher frequency mode of oscillation, perceptually identified as falsetto, had little or no vocal fold contact and a dominant first partial. Relatively abrupt F(0) changes also occurred for gradual adduction changes, with the chest register corresponding to greater adduction, falsetto to less adduction.

  8. Associations between number of consecutive night shifts and impairment of neurobehavioral performance during a subsequent simulated night shift.

    PubMed

    Magee, Michelle; Sletten, Tracey L; Ferguson, Sally A; Grunstein, Ronald R; Anderson, Clare; Kennaway, David J; Lockley, Steven W; Rajaratnam, Shantha Mw

    2016-05-01

    This study aimed to investigate sleep and circadian phase in the relationships between neurobehavioral performance and the number of consecutive shifts worked. Thirty-four shift workers [20 men, mean age 31.8 (SD 10.9) years] worked 2-7 consecutive night shifts immediately prior to a laboratory-based, simulated night shift. For 7 days prior, participants worked their usual shift sequence, and sleep was assessed with logs and actigraphy. Participants completed a 10-minute auditory psychomotor vigilance task (PVT) at the start (~21:00 hours) and end (~07:00 hours) of the simulated night shift. Mean reaction times (RT), number of lapses and RT distribution was compared between those who worked 2-3 consecutive night shifts versus those who worked 4-7 shifts. Following 4-7 shifts, night shift workers had significantly longer mean RT at the start and end of shift, compared to those who worked 2-3 shifts. The slowest and fastest 10% RT were significantly slower at the start, but not end, of shift among participants who worked 4-7 nights. Those working 4-7 nights also demonstrated a broader RT distribution at the start and end of shift and had significantly slower RT based on cumulative distribution analysis (5 (th), 25 (th), 50 (th), 75 (th)percentiles at the start of shift; 75th percentile at the end of shift). No group differences in sleep parameters were found for 7 days and 24 hours prior to the simulated night shift. A greater number of consecutive night shifts has a negative impact on neurobehavioral performance, likely due to cognitive slowing.

  9. Change from an 8-hour shift to a 12-hour shift, attitudes, sleep, sleepiness and performance.

    PubMed

    Lowden, A; Kecklund, G; Axelsson, J; Akerstedt, T

    1998-01-01

    The present study sought to evaluate the effect of a change from a rotating 3-shift (8-hour) to a 2-shift shift (12 hour) schedule on sleep, sleepiness, performance, perceived health, and well-being. Thirty-two shift workers at a chemical plant (control room operators) responded to a questionnaire a few months before a change was made in their shift schedule and 10 months after the change. Fourteen workers also filled out a diary, carried activity loggers, and carried out reaction-time tests (beginning and end of shift). Fourteen day workers served as a reference group for the questionnaires and 9 were intensively studied during a week with workdays and a free weekend. The questionnaire data showed that the shift change increased satisfaction with workhours, sleep, and time for social activities. Health, perceived accident risk, and reaction-time performance were not negatively affected. Alertness improved and subjective recovery time after night work decreased. The quick changes in the 8-hour schedule greatly increased sleep problems and fatigue. Sleepiness integrated across the entire shift cycle showed that the shift workers were less alert than the day workers, across workdays and days off (although alertness increased with the 12-hour shift). The change from 8-hour to 12-hour shifts was positive in most respects, possibly due to the shorter sequences of the workdays, the longer sequences of consecutive days off, the fewer types of shifts (easier planning), and the elimination of quick changes. The results may differ in groups with a higher work load.

  10. Abrupt Decline in Kidney Function Before Initiating Hemodialysis and All-Cause Mortality: The Chronic Renal Insufficiency Cohort (CRIC) Study.

    PubMed

    Hsu, Raymond K; Chai, Boyang; Roy, Jason A; Anderson, Amanda H; Bansal, Nisha; Feldman, Harold I; Go, Alan S; He, Jiang; Horwitz, Edward J; Kusek, John W; Lash, James P; Ojo, Akinlolu; Sondheimer, James H; Townsend, Raymond R; Zhan, Min; Hsu, Chi-Yuan

    2016-08-01

    It is not clear whether the pattern of kidney function decline in patients with chronic kidney disease (CKD) may relate to outcomes after reaching end-stage renal disease (ESRD). We hypothesize that an abrupt decline in kidney function prior to ESRD predicts early death after initiating maintenance hemodialysis therapy. Prospective cohort study. The Chronic Renal Insufficiency Cohort (CRIC) Study enrolled men and women with mild to moderate CKD. For this study, we studied 661 individuals who developed chronic kidney failure that required hemodialysis therapy initiation. The primary predictor was the presence of an abrupt decline in kidney function prior to ESRD. We incorporated annual estimated glomerular filtration rates (eGFRs) into a mixed-effects model to estimate patient-specific eGFRs at 3 months prior to initiation of hemodialysis therapy. Abrupt decline was defined as having an extrapolated eGFR≥30mL/min/1.73m(2) at that time point. All-cause mortality within 1 year after initiating hemodialysis therapy. Multivariable Cox proportional hazards. Among 661 patients with CKD initiating hemodialysis therapy, 56 (8.5%) had an abrupt predialysis decline in kidney function and 69 died within 1 year after initiating hemodialysis therapy. After adjustment for demographics, cardiovascular disease, diabetes, and cancer, abrupt decline in kidney function was associated with a 3-fold higher risk for death within the first year of ESRD (adjusted HR, 3.09; 95% CI, 1.65-5.76). Relatively small number of outcomes; infrequent (yearly) eGFR determinations; lack of more granular clinical data. Abrupt decline in kidney function prior to ESRD occurred in a significant minority of incident hemodialysis patients and predicted early death in ESRD. Copyright © 2016 National Kidney Foundation, Inc. All rights reserved.

  11. The BTB-zinc Finger Transcription Factor Abrupt Acts as an Epithelial Oncogene in Drosophila melanogaster through Maintaining a Progenitor-like Cell State

    PubMed Central

    Turkel, Nezaket; Sahota, Virender K.; Bolden, Jessica E.; Goulding, Karen R.; Doggett, Karen; Willoughby, Lee F.; Blanco, Enrique; Martin-Blanco, Enrique; Corominas, Montserrat; Ellul, Jason; Aigaki, Toshiro; Richardson, Helena E.; Brumby, Anthony M.

    2013-01-01

    The capacity of tumour cells to maintain continual overgrowth potential has been linked to the commandeering of normal self-renewal pathways. Using an epithelial cancer model in Drosophila melanogaster, we carried out an overexpression screen for oncogenes capable of cooperating with the loss of the epithelial apico-basal cell polarity regulator, scribbled (scrib), and identified the cell fate regulator, Abrupt, a BTB-zinc finger protein. Abrupt overexpression alone is insufficient to transform cells, but in cooperation with scrib loss of function, Abrupt promotes the formation of massive tumours in the eye/antennal disc. The steroid hormone receptor coactivator, Taiman (a homologue of SRC3/AIB1), is known to associate with Abrupt, and Taiman overexpression also drives tumour formation in cooperation with the loss of Scrib. Expression arrays and ChIP-Seq indicates that Abrupt overexpression represses a large number of genes, including steroid hormone-response genes and multiple cell fate regulators, thereby maintaining cells within an epithelial progenitor-like state. The progenitor-like state is characterised by the failure to express the conserved Eyes absent/Dachshund regulatory complex in the eye disc, and in the antennal disc by the failure to express cell fate regulators that define the temporal elaboration of the appendage along the proximo-distal axis downstream of Distalless. Loss of scrib promotes cooperation with Abrupt through impaired Hippo signalling, which is required and sufficient for cooperative overgrowth with Abrupt, and JNK (Jun kinase) signalling, which is required for tumour cell migration/invasion but not overgrowth. These results thus identify a novel cooperating oncogene, identify mammalian family members of which are also known oncogenes, and demonstrate that epithelial tumours in Drosophila can be characterised by the maintenance of a progenitor-like state. PMID:23874226

  12. Abrupt treatments of hysteria during World War I, 1914-18.

    PubMed

    Macleod, Ad Sandy

    2018-06-01

    Case reports of the abrupt recovery of hysterical disorders during World War I (1914-18), though undoubtedly subject to publication bias, raise both aetiological and treatment issues regarding pseudo-neurological conversion symptoms. Published clinical anecdotes report circumstantial, psychotherapeutic, hypnotic, persuasive (and coercive) methods seemingly inducing recovery, and also responses to fright and alterations of consciousness. The ethics of modern medical practice would not allow many of these techniques, which were reported to be effective, even in the chronic cases.

  13. Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay.

    PubMed

    Muhonen, S; Julliand, V; Lindberg, J E; Bertilsson, J; Jansson, A

    2009-07-01

    The objective of this study was to investigate the effect of an abrupt change from grass hay (81% DM) to grass silage (36% DM) or grass haylage (55% DM), fed at similar DM intakes, and to compare the effects of silage and haylage on the composition and activities of the colon microflora. The forages were from the same swath harvested on the same day. Four adult colon-fistulated geldings were randomly assigned to diets in a crossover design. The study started with a preperiod when all 4 horses received the hay diet, followed by an abrupt feed change to the haylage diet for 2 horses and the silage diet for 2 horses. All 4 horses then had a new second preperiod of hay, followed by an abrupt feed change to the opposite haylage and silage diet. The periods were 21 d long, and the forage-only diets were supplemented with minerals and salt. The abrupt feed changes were made at 0800 h. Colon samples were taken before the abrupt feed change, 4 and 28 h after the feed change, and 8, 15, and 21 d after the feed change, all at 1200 h. Colon bacterial counts, VFA, pH, and DM concentrations were unchanged throughout the first 28 h after the abrupt feed change from hay to haylage and silage. Also, fecal pH and DM concentrations were unchanged during the first 28 h. During the weekly observations, colon lactobacilli counts increased (P = 0.023) in horses receiving the silage diet and were greater than on the haylage diet at 21 d. Streptococci counts decreased (P = 0.046) in horses receiving the haylage diet and were less than on the silage diet at 15 and 21 d. Total VFA concentrations and colon and fecal pH did not differ between diets and were unchanged throughout the weekly observations. The DM concentration of colon digesta and feces decreased (P = 0.030 and 0.049, respectively) on both diets during the weekly observations. The results suggest that in horses fed at the maintenance level of energy intake, an abrupt feed change from grass hay to grass silage or grass haylage from

  14. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change.

    PubMed

    Boulton, Chris A; Lenton, Timothy M

    2015-09-15

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency--i.e., "redder"--variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900-present), as indicated by a robust increase in autocorrelation. This "reddening" of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent "regime shifts." Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems.

  15. Abrupt skin lesion border cutoff measurement for malignancy detection in dermoscopy images.

    PubMed

    Kaya, Sertan; Bayraktar, Mustafa; Kockara, Sinan; Mete, Mutlu; Halic, Tansel; Field, Halle E; Wong, Henry K

    2016-10-06

    Automated skin lesion border examination and analysis techniques have become an important field of research for distinguishing malignant pigmented lesions from benign lesions. An abrupt pigment pattern cutoff at the periphery of a skin lesion is one of the most important dermoscopic features for detection of neoplastic behavior. In current clinical setting, the lesion is divided into a virtual pie with eight sections. Each section is examined by a dermatologist for abrupt cutoff and scored accordingly, which can be tedious and subjective. This study introduces a novel approach to objectively quantify abruptness of pigment patterns along the lesion periphery. In the proposed approach, first, the skin lesion border is detected by the density based lesion border detection method. Second, the detected border is gradually scaled through vector operations. Then, along gradually scaled borders, pigment pattern homogeneities are calculated at different scales. Through this process, statistical texture features are extracted. Moreover, different color spaces are examined for the efficacy of texture analysis. The proposed method has been tested and validated on 100 (31 melanoma, 69 benign) dermoscopy images. Analyzed results indicate that proposed method is efficient on malignancy detection. More specifically, we obtained specificity of 0.96 and sensitivity of 0.86 for malignancy detection in a certain color space. The F-measure, harmonic mean of recall and precision, of the framework is reported as 0.87. The use of texture homogeneity along the periphery of the lesion border is an effective method to detect malignancy of the skin lesion in dermoscopy images. Among different color spaces tested, RGB color space's blue color channel is the most informative color channel to detect malignancy for skin lesions. That is followed by YCbCr color spaces Cr channel, and Cr is closely followed by the green color channel of RGB color space.

  16. Quantitative phase imaging using four interferograms with special phase shifts by dual-wavelength in-line phase-shifting interferometry

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoqing; Wang, Yawei; Ji, Ying; Xu, Yuanyuan; Xie, Ming; Han, Hao

    2018-05-01

    A new approach of quantitative phase imaging using four interferograms with special phase shifts in dual-wavelength in-line phase-shifting interferometry is presented. In this method, positive negative 2π phase shifts are employed to easily separate the incoherent addition of two single-wavelength interferograms by combining the phase-shifting technique with the subtraction procedure, then the quantitative phase at one of both wavelengths can be achieved based on two intensities without the corresponding dc terms by the use of the character of the trigonometric function. The quantitative phase of the other wavelength can be retrieved from two dc-term suppressed intensities obtained by employing the two-step phase-shifting technique or the filtering technique in the frequency domain. The proposed method is illustrated with theory, and its effectiveness is demonstrated by simulation experiments of the spherical cap and the HeLa cell, respectively.

  17. Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes.

    PubMed

    Kaniewski, D; Paulissen, E; Van Campo, E; Al-Maqdissi, M; Bretschneider, J; Van Lerberghe, K

    2008-09-16

    The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100-800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C.

  18. The factor harmful to the quality of human life--shift-work.

    PubMed

    Strzemecka, Joanna; Pencuła, Marcin; Owoc, Alfred; Szot, Wojciech; Strzemecka, Ewa; Jabłoński, Mirosław; Bojar, Iwona

    2013-01-01

    The system of human activity, which is established by genetics and regulated by outer and inner factors, is associated with many characteristics which maintain the body in the best condition and ensure appropriate life quality. To evaluate of life quality among male shift-workers. Research based on a self-devised questionnaire, conducted among 700 shift-workers, followed by statistical analysis of the results. Nearly a half of respondents (43.00%) reported that shift-work influences the quality of their family life. Remarkably, such an opinion was often stated by people with children (46.01%) p<0.05, the divorced (58.22%), married people (44.74%) and bachelors (25.33%), respectively. Fathers usually indicated lack of contact with their family as well as irregular consumption of meals (66.91%). Almost every third respondent noted that their shift type of work negatively influence their sexual life (31.14%). It was shown that shift-work negatively influences the respondents' life quality in the form of deterioration of the quality of family life; the respondents, regardless of marital status, age and having children, most often complained about the lack of contact with the family and irregular eating with them; negative influence on sexual life, which was the case in one-third of respondents. In order to encourage healthy behaviour and increase the quality of life of people performing shift-work, training and programmes should be introduced. These would help shift- workers to adjust their work time to their family and social life.

  19. [Prelabour uterine torsion complicated by partial abruption and fetal death].

    PubMed

    Agar, N; Canis, M; Accoceberry, M; Bourdel, N; Lafaye, A-L; Gallot, D

    2014-06-01

    Uterine torsion is a rare obstetrical complication whose diagnosis remains challenging. We report a case of 180 degrees dextrogyre torsion at 36(+5) weeks of gestation complicated by partial abruption and in utero fetal death. Emergency cesarean section was performed through an unintentional posterior hysterotomy. Literature reports a few similar cases. Vertical hysterotomy should be advised in this context avoiding incision on lateral sides associated with increased risk of vascular or ureteral injury. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  20. Abrupt climatic events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals

    NASA Astrophysics Data System (ADS)

    Song, Yougui; Zeng, Mengxiu; Chen, Xiuling; Li, Yue; Chang, Hong; An, Zhisheng; Guo, Xiaohua

    2018-04-01

    The loess record of Central Asia provides an important archive of regional climate and environmental changes. In contrast to the widely investigated loess deposits in the Chinese Loess Plateau, Central Asian loess-paleosol sequences remain poorly understood. Here, we present an aeolian loess section in the southern Ili Basin. Based on granularity and mineralogical analyses, we reconstruct climatic changes during the last glaciation. The results indicated that most of the abrupt climatic events (such as Dansgaard-Oeschger events and Heinrich events) were imprinted in this loess section, although their amplitudes and ages showed some differences. Compared with the millennial oscillations recoded in loess and stalagmites in East Asia, the arid Central Asia responded more sensitively to the warming events than to the cooling events. The shifting trajectory of westerlies across Central Asia played an important role in dust deposition during the stadials. The North Atlantic climatic signals may have been transmitted from Central Asia to the East Asian monsoon regions via the westerlies.

  1. Shift work, light at night, and the risk of breast cancer.

    PubMed

    Reed, Virginia A

    2011-01-01

    Studies of the effect of shift work have identified several negative health outcomes, most notably breast cancer. Disruption of circadian rhythm by exposure to light at night has been identified as the mechanism likely responsible for this outcome. This article recommends that health care institutions work with occupational health nurses to develop and implement hazard communication and policies concerning shift work, exposure to light at night, and increased risk for negative health outcomes, particularly breast cancer. 2011, SLACK Incorporated.

  2. Correction to: Dissociating the capture of attention from saccade activation by subliminal abrupt onsets.

    PubMed

    Schoeberl, Tobias; Ansorge, Ulrich

    2018-01-01

    Attentional capture and effects on saccade metrics by subliminal abrupt onset cues have been studied with peripheral cues at one out of several (two to four) display locations, swiftly followed by additional onsets at the other display locations. The lead time of the cue was too short to be seen. Here, we were interested in whether such subliminal onset cues influenced saccades primarily by way of attention or by way of direct saccade activation. In separate blocks, participants made speeded pro-saccades towards a black target or anti-saccades away from the target. Prior to the targets, an abrupt onset cue was presented either at the same side as the target (valid condition) or at the opposite side (invalid condition). If cues influenced performance by way of attentional capture, we expected facilitation of target processing in valid compared to invalid conditions (cueing effect) in the pro- as well as in the anti-saccade task. If the cues activated saccades in their direction, we expected the cueing effect to drop in the anti-saccade task compared to the pro-saccade task because in the anti-saccade task the invalid cue would activate the finally required response, whereas the valid cue would activate the alternative response, leading to interference. Results were in line with the former of these possibilities suggesting that subliminal abrupt onsets influenced saccades by way of attention with no or little direct activation of saccades.

  3. Goos-Hänchen shifts of partially coherent light beams from a cavity with a four-level Raman gain medium

    NASA Astrophysics Data System (ADS)

    Ziauddin; Lee, Ray-Kuang; Qamar, Sajid

    2016-09-01

    We theoretically investigate spatial and angular Goos-Hänchen (GH) shifts (both negative and positive) in the reflected light for a partial coherent light incident on a cavity. A four-level Raman gain atomic medium is considered in a cavity. The effects of spatial coherence, beam width, and mode index of partial coherent light fields on spatial and angular GH shifts are studied. Our results reveal that a large magnitude of negative and positive GH shifts in the reflected light is achievable with the introduction of partial coherent light fields. Furthermore, the amplitude of spatial (negative and positive) GH shifts are sharply affected by the partial coherent light beam as compared to angular (negative and positive) GH shifts in the reflected light.

  4. Bilayer synergetic coupling double negative acoustic metasurface and cloak.

    PubMed

    Ma, Fuyin; Huang, Meng; Xu, Yicai; Wu, Jiu Hui

    2018-04-12

    In this paper, we propose a bilayer plate-type lightweight double negative metasurface based on a new synergetic coupling design concept, by which the perfect absorption, double negative bands, free manipulation of phase shifts with a 2π span and acoustic cloak can be successively realized. Firstly, the synergetic behavior between resonant and anti-resonant plates is presented to construct a bilayer unit in which each component respectively provides a pre-defined function in realizing the perfect absorption. Based on this bilayer structure, a double negative band with simultaneously negative effective mass density and bulk modulus is obtained, which, as a metasurface, can obtain continuous phase shifts almost completely covering a 2π range, thus facilitating the design of a three-dimensional (3D) acoustic cloak. In addition, based on this strong sound absorption concept, a two-dimensional (2D) omnidirectional broadband acoustical dark skin, covering between 800 to 6000 Hz, is also demonstrated through the proposed bilayer plate-type structure form. The proposed design concepts and metasurfaces have widespread potential application values in strong sound attenuation, filtering, superlens, imaging, cloak, and extraordinary wave steering, in which the attributes of strong absorption, double negative parameters or continuous phase shifts with full 2π span are required to realize the expected extraordinary physical features.

  5. The interplay between the kinetic nonlinear frequency shift and the flowing gradient in stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Wang, Q.; Y Zheng, C.; Liu, Z. J.; Xiao, C. Z.; Feng, Q. S.; Zhang, H. C.; He, X. T.

    2018-02-01

    The effect of the kinetic nonlinear frequency shift (KNFS) on backward stimulated Brillouin scattering (SBS) in homogeneous plasmas and inhomogeneous flowing plasmas is investigated by three-wave coupled-mode equations. When the positive contribution to the KNFS from electrons as well as the negative contribution from ions is included, the net KNFS can become positive at a large electron-ion temperature ratio {{ZT}}e/{T}i. In homogeneous plasmas, KNFS can greatly reduce the SBS reflectivity at low or large {{ZT}}e/{T}i but has a weak effect on SBS at {{ZT}}e/{T}i where the positive frequency shifts from electrons almost cancels out the negative shifts from ions. In inhomogeneous plasmas, the net negative frequency shift can enhance the backward SBS reflectivity for the negative gradient of the plasma flowing, and can suppress the reflectivity for the positive case. On the contrary, the net positive frequency can suppress the reflectivity for the negative case of the flowing gradient and enhance the reflectivity for the positive case. This indicates that the SBS in inhomogeneous flowing plasmas can be controlled by changing the sign of the nonlinear frequency shift.

  6. Students' educational experiences and interaction with residents on night shifts.

    PubMed

    Schiller, Jocelyn; Sokoloff, Max; Tendhar, Chosang; Schmidt, John; Christner, Jennifer

    2017-08-01

    The purpose of this mixed-methods study was to investigate whether increased night shifts for students on paediatric rotations had any negative impact on their overall quality of educational experiences in light of the implementation of duty-hour restrictions. Both quantitative and qualitative data were collected from 30 students on paediatric rotations during the academic year 2011/12. Students completed two questionnaires, one in response to their experiences during the day shifts and another in response to their experiences during the night shifts. Only 25 cases were retained for the final analyses. The non-parametric Wilcoxon signed-rank test was used to analyse the quantitative data, and constant comparative thematic analyses, as described by Creswell, were used to analyse the qualitative data. [Do] increased nights shifts for students … [have] any negative impact on their overall quality of educational experiences[?] RESULTS: The results indicated that students' perceived quality of experiences during the night shifts was greater, compared with their day shifts. Students reported having more time to socialise during the night shifts. They further reported that informal ways of learning, such as impromptu teaching and spontaneous discussions on clinical problems, were more beneficial, and these often occurred in abundance during the night shifts as opposed to the scheduled didactic teaching sessions that occur during the day shifts. This study documented many unanticipated benefits of night shifts. The feeling of cohesiveness of the night team deserves further exploration, as this can be linked to better performance outcomes. More consideration should be given to implementing night shifts as a regular feature of clerkships. © 2016 John Wiley & Sons Ltd and The Association for the Study of Medical Education.

  7. Evaluation of beam divergence of a negative hydrogen ion beam using Doppler shift spectroscopy diagnostics

    NASA Astrophysics Data System (ADS)

    Deka, A. J.; Bharathi, P.; Pandya, K.; Bandyopadhyay, M.; Bhuyan, M.; Yadav, R. K.; Tyagi, H.; Gahlaut, A.; Chakraborty, A.

    2018-01-01

    The Doppler Shift Spectroscopy (DSS) diagnostic is in the conceptual stage to estimate beam divergence, stripping losses, and beam uniformity of the 100 keV hydrogen Diagnostics Neutral Beam of International Thermonuclear Experimental Reactor. This DSS diagnostic is used to measure the above-mentioned parameters with an error of less than 10%. To aid the design calculations and to establish a methodology for estimation of the beam divergence, DSS measurements were carried out on the existing prototype ion source RF Operated Beam Source in India for Negative ion Research. Emissions of the fast-excited neutrals that are generated from the extracted negative ions were collected in the target tank, and the line broadening of these emissions were used for estimating beam divergence. The observed broadening is a convolution of broadenings due to beam divergence, collection optics, voltage ripple, beam focusing, and instrumental broadening. Hence, for estimating the beam divergence from the observed line broadening, a systematic line profile analysis was performed. To minimize the error in the divergence measurements, a study on error propagation in the beam divergence measurements was carried out and the error was estimated. The measurements of beam divergence were done at a constant RF power of 50 kW and a source pressure of 0.6 Pa by varying the extraction voltage from 4 kV to10 kV and the acceleration voltage from 10 kV to 15 kV. These measurements were then compared with the calorimetric divergence, and the results seemed to agree within 10%. A minimum beam divergence of ˜3° was obtained when the source was operated at an extraction voltage of ˜5 kV and at a ˜10 kV acceleration voltage, i.e., at a total applied voltage of 15 kV. This is in agreement with the values reported in experiments carried out on similar sources elsewhere.

  8. Internal shifting impairments in response to emotional information in dysphoric adolescents.

    PubMed

    Wante, Laura; Mueller, Sven C; Demeyer, Ineke; Naets, Tiffany; Braet, Caroline

    2017-12-01

    Previous studies have suggested that internal cognitive control impairments may play an important role in the development of depression. Despite a growing body of research in adults, the ability to shift internal attention between mental representations in working memory has received little attention in younger populations. This study investigated internal shifting capacity between emotional and non-emotional information in dysphoric and non-dysphoric adolescents. Twenty dysphoric and 34 non-dysphoric adolescents (10-17 years) completed an Internal Shifting Task, with pictures of angry and neutral faces, to measure the ability to shift attention between information held in working memory. Dysphoric adolescents showed specific shifting impairments when processing emotional material relative to non-dysphoric adolescents. Valence-specific analyses revealed that shifting was particularly impaired when shifting from negative to neutral information. By comparison, relative to non-dysphoric adolescents, dysphoric adolescents did not show shifting impairments when non-emotional features of the pictures had to be processed. The study is limited by the absence of a structured clinical interview as dysphoria was determined dimensionally. Furthermore, a comparison of the effects of different negative stimuli on shifting could not be made since sad stimuli were not included in the stimulus set. The results confirm the link between depressive symptoms and emotion-specific shifting impairments in adolescents and indicate that targeting shifting ability in response to emotional stimuli may be a promising avenue for prevention programs. Longitudinal research is needed to replicate results and to explore the role of internal shifting impairments in the etiology and maintenance of depression. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. The impact of shift work on the psychological and physical health of nurses in a general hospital: a comparison between rotating night shifts and day shifts.

    PubMed

    Ferri, Paola; Guadi, Matteo; Marcheselli, Luigi; Balduzzi, Sara; Magnani, Daniela; Di Lorenzo, Rosaria

    2016-01-01

    Shift work is considered necessary to ensure continuity of care in hospitals and residential facilities. In particular, the night shift is one of the most frequent reasons for the disruption of circadian rhythms, causing significant alterations of sleep and biological functions that can affect physical and psychological well-being and negatively impact work performance. The aim of this study was to highlight if shift work with nights, as compared with day work only, is associated with risk factors predisposing nurses to poorer health conditions and lower job satisfaction. This cross-sectional study was conducted from June 1, 2015 to July 31, 2015 in 17 wards of a general hospital and a residential facility of a northern Italian city. This study involved 213 nurses working in rotating night shifts and 65 in day shifts. The instrument used for data collection was the "Standard Shift Work Index," validated in Italian. Data were statistically analyzed. The response rate was 86%. The nurses engaged in rotating night shifts were statistically significantly younger, more frequently single, and had Bachelors and Masters degrees in nursing. They reported the lowest mean score in the items of job satisfaction, quality and quantity of sleep, with more frequent chronic fatigue, psychological, and cardiovascular symptoms in comparison with the day shift workers, in a statistically significant way. Our results suggest that nurses with rotating night schedule need special attention due to the higher risk for both job dissatisfaction and undesirable health effects.

  10. A Fast Framework for Abrupt Change Detection Based on Binary Search Trees and Kolmogorov Statistic

    PubMed Central

    Qi, Jin-Peng; Qi, Jie; Zhang, Qing

    2016-01-01

    Change-Point (CP) detection has attracted considerable attention in the fields of data mining and statistics; it is very meaningful to discuss how to quickly and efficiently detect abrupt change from large-scale bioelectric signals. Currently, most of the existing methods, like Kolmogorov-Smirnov (KS) statistic and so forth, are time-consuming, especially for large-scale datasets. In this paper, we propose a fast framework for abrupt change detection based on binary search trees (BSTs) and a modified KS statistic, named BSTKS (binary search trees and Kolmogorov statistic). In this method, first, two binary search trees, termed as BSTcA and BSTcD, are constructed by multilevel Haar Wavelet Transform (HWT); second, three search criteria are introduced in terms of the statistic and variance fluctuations in the diagnosed time series; last, an optimal search path is detected from the root to leaf nodes of two BSTs. The studies on both the synthetic time series samples and the real electroencephalograph (EEG) recordings indicate that the proposed BSTKS can detect abrupt change more quickly and efficiently than KS, t-statistic (t), and Singular-Spectrum Analyses (SSA) methods, with the shortest computation time, the highest hit rate, the smallest error, and the highest accuracy out of four methods. This study suggests that the proposed BSTKS is very helpful for useful information inspection on all kinds of bioelectric time series signals. PMID:27413364

  11. A Fast Framework for Abrupt Change Detection Based on Binary Search Trees and Kolmogorov Statistic.

    PubMed

    Qi, Jin-Peng; Qi, Jie; Zhang, Qing

    2016-01-01

    Change-Point (CP) detection has attracted considerable attention in the fields of data mining and statistics; it is very meaningful to discuss how to quickly and efficiently detect abrupt change from large-scale bioelectric signals. Currently, most of the existing methods, like Kolmogorov-Smirnov (KS) statistic and so forth, are time-consuming, especially for large-scale datasets. In this paper, we propose a fast framework for abrupt change detection based on binary search trees (BSTs) and a modified KS statistic, named BSTKS (binary search trees and Kolmogorov statistic). In this method, first, two binary search trees, termed as BSTcA and BSTcD, are constructed by multilevel Haar Wavelet Transform (HWT); second, three search criteria are introduced in terms of the statistic and variance fluctuations in the diagnosed time series; last, an optimal search path is detected from the root to leaf nodes of two BSTs. The studies on both the synthetic time series samples and the real electroencephalograph (EEG) recordings indicate that the proposed BSTKS can detect abrupt change more quickly and efficiently than KS, t-statistic (t), and Singular-Spectrum Analyses (SSA) methods, with the shortest computation time, the highest hit rate, the smallest error, and the highest accuracy out of four methods. This study suggests that the proposed BSTKS is very helpful for useful information inspection on all kinds of bioelectric time series signals.

  12. Turbulent Swirling Flow Downstream of an Abrupt Pipe Expansion -- Modeling and Experimental Measurements.

    DTIC Science & Technology

    1982-07-01

    aerospace engineering um~Ŕ" eqe~vswse 0engiee amp snry stem englnerlag. enI~e so ISaCW , meterI scienc Turbulent Swirling Flow Dowstreas of an Abrupt...With the horizontal test section and circumferentially local measurements, the extent of the influence of gravity -induced convection can be determined

  13. Representing Sudden Shifts in Intensive Dyadic Interaction Data Using Differential Equation Models with Regime Switching.

    PubMed

    Chow, Sy-Miin; Ou, Lu; Ciptadi, Arridhana; Prince, Emily B; You, Dongjun; Hunter, Michael D; Rehg, James M; Rozga, Agata; Messinger, Daniel S

    2018-06-01

    A growing number of social scientists have turned to differential equations as a tool for capturing the dynamic interdependence among a system of variables. Current tools for fitting differential equation models do not provide a straightforward mechanism for diagnosing evidence for qualitative shifts in dynamics, nor do they provide ways of identifying the timing and possible determinants of such shifts. In this paper, we discuss regime-switching differential equation models, a novel modeling framework for representing abrupt changes in a system of differential equation models. Estimation was performed by combining the Kim filter (Kim and Nelson State-space models with regime switching: classical and Gibbs-sampling approaches with applications, MIT Press, Cambridge, 1999) and a numerical differential equation solver that can handle both ordinary and stochastic differential equations. The proposed approach was motivated by the need to represent discrete shifts in the movement dynamics of [Formula: see text] mother-infant dyads during the Strange Situation Procedure (SSP), a behavioral assessment where the infant is separated from and reunited with the mother twice. We illustrate the utility of a novel regime-switching differential equation model in representing children's tendency to exhibit shifts between the goal of staying close to their mothers and intermittent interest in moving away from their mothers to explore the room during the SSP. Results from empirical model fitting were supplemented with a Monte Carlo simulation study to evaluate the use of information criterion measures to diagnose sudden shifts in dynamics.

  14. Flow Regime Study in a High Density Circulating Fluidized Bed Riser with an Abrupt Exit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, J.S.; Shadle, L.J.; Yue, P.C.

    2007-01-01

    Flow regime study was conducted in a 0.3 m diameter, 15.5 m height circulating fluidized bed (CFB) riser with an abrupt exit at the National Energy Technology Laboratory of the U.S. Department of Energy. Local particle velocities were measured at various radial positions and riser heights using an optical fiber probe. On-line measurement of solid circulating rate was continuously recorded by the Spiral. Glass beads of mean diameter 61 μm and particle density of 2,500 kg/m3 were used as bed material. The CFB riser was operated at various superficial gas velocities ranging from 3 to 7.6 m/s and solid massmore » flux from 20 to 550 kg/m2-s. At a constant riser gas velocity, transition from fast fluidization to dense suspension upflow (DSU) regime started at the bottom of the riser with increasing solid flux. Except at comparatively low riser gas velocity and solid flux, the apparent solid holdup at the top exit region was higher than the middle section of the riser. The solid fraction at this top region could be much higher than 7% under high riser gas velocity and solid mass flux. The local particle velocity showed downward flow near the wall at the top of the riser due to its abrupt exit. This abrupt geometry reflected the solids and, therefore, caused solid particles traveling downward along the wall. However, at location below, but near, the top of the riser the local particle velocities were observed flowing upward at the wall. Therefore, DSU was identified in the upper region of the riser with an abrupt exit while the fully developed region, lower in the riser, was still exhibiting core-annular flow structure. Our data were compared with the flow regime boundaries proposed by Kim et al. [1] for distinguishing the dilute pneumatic transport, fast fluidization, and DSU.« less

  15. Abrupt Upper-Plate Tilting Upon Slab-Transition-Zone Collision

    NASA Astrophysics Data System (ADS)

    Crameri, F.; Lithgow-Bertelloni, C. R.

    2017-12-01

    During its sinking, the remnant of a surface plate crosses and interacts with multiple boundaries in Earth's interior. The most-prominent dynamic interaction arises at the upper-mantle transition zone where the sinking plate is strongly affected by the higher-viscosity lower mantle. Within our numerical model, we unravel, for the first time, that this very collision of the sinking slab with the transition zone induces a sudden, dramatic downward tilt of the upper plate towards the subduction trench. The slab-transition zone collision sets parts of the higher-viscosity lower mantle in motion. Naturally, this then induces an overall larger return flow cell that, at its onset, tilts the upper plate abruptly by around 0.05 degrees and over around 10 Millions of years. Such a significant and abrupt variation in surface topography should be clearly visible in temporal geologic records of large-scale surface elevation and might explain continental-wide tilting as observed in Australia since the Eocene or North America during the Phanerozoic. Unravelling this crucial mantle-lithosphere interaction was possible thanks to state-of-the-art numerical modelling (powered by StagYY; Tackley 2008, PEPI) and post-processing (powered by StagLab; www.fabiocrameri.ch/software). The new model that is introduced here to study the dynamically self-consistent temporal evolution of subduction features accurate subduction-zone topography, robust single-sided plate sinking, stronger plates close to laboratory values, an upper-mantle phase transition and, crucially, simple continents at a free surface. A novel, fully-automated post-processing includes physical model diagnostics like slab geometry, mantle flow pattern, upper-plate tilt angle and trench location.

  16. Observation and analysis of abrupt changes in the interplanetary plasma velocity and magnetic field.

    NASA Technical Reports Server (NTRS)

    Martin, R. N.; Belcher, J. W.; Lazarus, A. J.

    1973-01-01

    This paper presents a limited study of the physical nature of abrupt changes in the interplanetary plasma velocity and magnetic field based on 19 day's data from the Pioneer 6 spacecraft. The period was chosen to include a high-velocity solar wind stream and low-velocity wind. Abrupt events were accepted for study if the sum of the energy density in the magnetic field and velocity changes was above a specified minimum. A statistical analysis of the events in the high-velocity solar wind stream shows that Alfvenic changes predominate. This conclusion is independent of whether steady state requirements are imposed on conditions before and after the event. Alfvenic changes do not dominate in the lower-speed wind. This study extends the plasma field evidence for outwardly propagating Alfvenic changes to time scales as small as 1 min (scale lengths on the order of 20,000 km).

  17. Observation of an abrupt electron heating mode transition in capacitive single radio frequency discharges

    NASA Astrophysics Data System (ADS)

    Wilczek, Sebastian; Trieschmann, Jan; Schulze, Julian; Brinkmann, Ralf Peter; Mussenbrock, Thomas; Derzsi, Aranka; Korolov, Ihor; Donkó, Zoltan

    2013-09-01

    The electron heating in capacitive discharges at very low pressures (~1 Pa) is dominated by stochastic heating. In this regime electrons are accelerated by the oscillating sheaths, traverse through the plasma bulk and interact with the opposite sheath. By varying the driving frequency or the gap size of the discharge, energetic electrons reach the sheath edge at different temporal phases, i.e., the collapsing or expanding phase, or the moment of minimum sheath width. This work reports numerical experiments based on Particle-In-Cell simulations which show that at certain frequencies the discharge switches abruptly from a low density mode in a high density mode. The inverse transition is also abrupt, but shows a significant hysteresis. This behavior is explained by the complex interaction of the bulk and the sheath. This work is supported by the German Research Foundation in the frame of TRR 87.

  18. Broadband one-dimensional photonic crystal wave plate containing single-negative materials.

    PubMed

    Chen, Yihang

    2010-09-13

    The properties of the phase shift of wave reflected from one-dimensional photonic crystals consisting of periodic layers of single-negative (permittivity- or permeability-negative) materials are demonstrated. As the incident angle increases, the reflection phase shift of TE wave decreases, while that of TM wave increases. The phase shifts of both polarized waves vary smoothly as the frequency changes across the photonic crystal stop band. Consequently, the difference between the phase shift of TE and that of TM wave could remain constant in a rather wide frequency range inside the stop band. These properties are useful to design wave plate or retarder which can be used in wide spectral band. In addition, a broadband photonic crystal quarter-wave plate is proposed.

  19. The risk of placental abruption and placenta previa in pregnant women with chronic hepatitis B viral infection: a systematic review and meta-analysis.

    PubMed

    Huang, Q T; Chen, J H; Zhong, M; Xu, Y Y; Cai, C X; Wei, S S; Hang, L L; Liu, Q; Yu, Y H

    2014-08-01

    Several epidemiological studies have found a positive association between chronic hepatitis B virus (CHB) infection and the risk of placental abruption and placenta previa, but various studies have reported conflicting findings. The objective was to systematically review the literature to determine a possible association between CHB infection and these two placental complications. We conducted a computerized search in electronic database through March 1, 2014, supplemented with a manual search of reference lists, to identify original published research on placental abruption and placenta previa rates in women with CHB infection. Data were independently extracted, and relative risks were calculated. The meta-analysis was performed using Stata version 10.0 software. Five studies involving 9088 placenta previa cases were identified. No significant association between CHB infection and placenta previa was identified (OR = 0.98, 95% CI = 0.60-1.62). Five studies involving 15571 placental abruption cases were identified. No significant association between CHB infection and placental abruption was identified (OR = 1.42, 95% CI, 0.93-2.15). The immune response against the virus represents a key factor in determining infection outcomes. No observation of significant increased risk of the placental complications could be partially explained by the complex immune response during CHB infection. Our meta-analysis found no evidence of significant associations between CHB infection and increased risk of placental abruption as well as placenta previa. Further well-designed studies were warranted to assess any potential association between CHB infection and increased risk of placental abruption as well as placenta previa. Copyright © 2014 Elsevier Ltd. All rights reserved.

  20. The impact of shift work and organizational work climate on health outcomes in nurses.

    PubMed

    von Treuer, Kathryn; Fuller-Tyszkiewicz, Matthew; Little, Glenn

    2014-10-01

    Shift workers have a higher rate of negative health outcomes than day shift workers. Few studies however, have examined the role of difference in workplace environment between shifts itself on such health measures. This study investigated variation in organizational climate across different types of shift work and health outcomes in nurses. Participants (n = 142) were nursing staff from a metropolitan Melbourne hospital. Demographic items elicited the type of shift worked, while the Work Environment Scale and the General Health Questionnaire measured organizational climate and health respectively. Analysis supported the hypotheses that different organizational climates occurred across different shifts, and that different organizational climate factors predicted poor health outcomes. Shift work alone was not found to predict health outcomes. Specifically, permanent night shift workers had significantly lower coworker cohesion scores compared with rotating day and evening shift workers and significantly higher managerial control scores compared with day shift workers. Further, coworker cohesion and involvement were found to be significant predictors of somatic problems. These findings suggest that differences in organizational climate between shifts accounts for the variation in health outcomes associated with shift work. Therefore, increased workplace cohesion and involvement, and decreased work pressure, may mitigate the negative health outcomes of shift workers. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  1. Theoretical surface core-level shifts for Be(0001)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Feibelman, P.J.

    1994-05-15

    Core-ionization potentials (CIP's) are computed for Be(0001). Three core features are observed in corresponding photoelectron spectra, with CIP's shifted relative to the bulk core level by [minus]0.825, [minus]0.570, and [minus]0.265 eV. The computed CIP shifts for the outer and subsurface layers, [minus]0.60 and [minus]0.29 eV, respectively, agree with the latter two of these. It is surmised that the [minus]0.825-eV shift is associated with a surface defect. The negative signs of the Be(0001) surface core-level shifts do not fit into the thermochemical picture widely used to explain CIP shifts. The reason is that a core-ionized Be atom is too small tomore » bond effectively to the remainder of the unrelaxed Be lattice.« less

  2. Leaf morphology shift linked to climate change.

    PubMed

    Guerin, Greg R; Wen, Haixia; Lowe, Andrew J

    2012-10-23

    Climate change is driving adaptive shifts within species, but research on plants has been focused on phenology. Leaf morphology has demonstrated links with climate and varies within species along climate gradients. We predicted that, given within-species variation along a climate gradient, a morphological shift should have occurred over time due to climate change. We tested this prediction, taking advantage of latitudinal and altitudinal variations within the Adelaide Geosyncline region, South Australia, historical herbarium specimens (n = 255) and field sampling (n = 274). Leaf width in the study taxon, Dodonaea viscosa subsp. angustissima, was negatively correlated with latitude regionally, and leaf area was negatively correlated with altitude locally. Analysis of herbarium specimens revealed a 2 mm decrease in leaf width (total range 1-9 mm) over 127 years across the region. The results are consistent with a morphological response to contemporary climate change. We conclude that leaf width is linked to maximum temperature regionally (latitude gradient) and leaf area to minimum temperature locally (altitude gradient). These data indicate a morphological shift consistent with a direct response to climate change and could inform provenance selection for restoration with further investigation of the genetic basis and adaptive significance of observed variation.

  3. Middle East coastal ecosystem response to middle-to-late Holocene abrupt climate changes

    PubMed Central

    Kaniewski, D.; Paulissen, E.; Van Campo, E.; Al-Maqdissi, M.; Bretschneider, J.; Van Lerberghe, K.

    2008-01-01

    The Holocene vegetation history of the northern coastal Arabian Peninsula is of long-standing interest, as this Mediterranean/semiarid/arid region is known to be particularly sensitive to climatic changes. Detailed palynological data from an 800-cm alluvial sequence cored in the Jableh plain in northwest Syria have been used to reconstruct the vegetation dynamics in the coastal lowlands and the nearby Jabal an Nuşayriyah mountains for the period 2150 to 550 B.C. Corresponding with the 4.2 to 3.9 and 3.5 to 2.5 cal kyr BP abrupt climate changes (ACCs), two large-scale shifts to a more arid climate have been recorded. These two ACCs had different impacts on the vegetation assemblages in coastal Syria. The 3.5 to 2.5 cal kyr BP ACC is drier and lasted longer than the 4.2 to 3.9 cal kyr BP ACC, and is characterized by the development of a warm steppe pollen-derived biome (1100–800 B.C.) and a peak of hot desert pollen-derived biome at 900 B.C. The 4.2 to 3.9 cal kyr BP ACC is characterized by a xerophytic woods and shrubs pollen-derived biome ca. 2050 B.C. The impact of the 3.5 to 2.5 cal kyr BP ACC on human occupation and cultural development is important along the Syrian coast with the destruction of Ugarit and the collapse of the Ugarit kingdom at ca. 1190 to 1185 B.C. PMID:18772385

  4. Rapid reduction versus abrupt quitting for smokers who want to stop soon: a randomised controlled non-inferiority trial

    PubMed Central

    Lindson, Nicola; Aveyard, Paul; Ingram, Jackie T; Inglis, Jennie; Beach, Jane; West, Robert; Michie, Susan

    2009-01-01

    Background The standard way to stop smoking is to stop abruptly on a quit day with no prior reduction in consumption of cigarettes. Many smokers feel that reduction is natural and if reduction programmes were offered, many more might take up treatment. Few trials of reduction versus abrupt cessation have been completed. Most are small, do not use pharmacotherapy, and do not meet the standards necessary to obtain a marketing authorisation for a pharmacotherapy. Design/Methods We will conduct a non-inferiority randomised trial of rapid reduction versus standard abrupt cessation among smokers who want to stop smoking. In the reduction arm, participants will be advised to reduce smoking consumption by half in the first week and to 25% of baseline in the second, leading up to a quit day at which participants will stop smoking completely. This will be assisted by nicotine patches and an acute form of nicotine replacement therapy. In the abrupt arm participants will use nicotine patches only, whilst smoking as normal, for two weeks prior to a quit day, at which they will also stop smoking completely. Smokers in either arm will have standard withdrawal orientated behavioural support programme with a combination of nicotine patches and acute nicotine replacement therapy post-cessation. Outcomes/Follow-up The primary outcome of interest will be prolonged abstinence from smoking, with secondary trial outcomes of point prevalence, urges to smoke and withdrawal symptoms. Follow up will take place at 4 weeks, 8 weeks and 6 months post-quit day. Trial Registration Current Controlled Trials ISRCTN22526020 PMID:19682359

  5. Shift schedule, work-family relationships, marital communication, job satisfaction and health among transport service shift workers.

    PubMed

    Iskra-Golec, Irena; Smith, Lawrence; Wilczek-Rużyczka, Ewa; Siemiginowska, Patrycja; Wątroba, Joanna

    2017-02-21

    Existing research has documented that shiftwork consequences may depend on the shift system parameters. Fast rotating systems (1-3 shifts of the same kind in a row) and day work have been found to be less disruptive biologically and socially than slower rotating systems and afternoon and night work. The aim of this study was to compare day workers and shift workers of different systems in terms of rotation speed and shifts worked with regard to work-family and family-work positive and negative spillover, marital communication style, job satisfaction and health. Employees (N = 168) of the maintenance workshops of transportation service working different shift systems (day shift, weekly rotating 2 and 3‑shift system, and fast rotating 3-shift system) participated in the study. They completed the Work- Family Spillover Questionnaire, Marital Communication Questionnaire, Minnesota Job Satisfaction Questionnaire and the Physical Health Questionnaire (a part of the Standard Shiftwork Index). The workers of quicker rotating 3-shift systems reported significantly higher scores of family-to-work facilitation (F(3, 165) = 4.175, p = 0.007) and a higher level of constructive style of marital communication (Engagement F(3, 165) = 2.761, p = 0.044) than the workers of slower rotating 2-shift systems. There were no differences between the groups of workers with regard to health and job satisfaction. A higher level of work-family facilitation and a more constructive style of marital communication were found among the workers of faster rotating 3-shift system when compared to the workers of a slower rotating 2-shift system (afternoon, night). This may indicate that the fast rotating shift system in contrary to the slower rotating one is more friendly for the work and family domains and for the relationship between them. Int J Occup Med Environ Health 2017;30(1):121-131. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

  6. Globally synchronous ice core volcanic tracers and abrupt cooling during the last glacial period

    USGS Publications Warehouse

    Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.

    2006-01-01

    We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial abrupt climate change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive events which dispersed material world wide. These globally coincident volcanics were associated with abrupt cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.

  7. A facilitative effect of negative affective valence on working memory.

    PubMed

    Gotoh, Fumiko; Kikuchi, Tadashi; Olofsson, Ulrich

    2010-06-01

    Previous studies have shown that negatively valenced information impaired working memory performance due to an attention-capturing effect. The present study examined whether negative valence could also facilitate working memory. Affective words (negative, neutral, positive) were used as retro-cues in a working memory task that required participants to remember colors at different spatial locations on a computer screen. Following the cue, a target detection task was used to either shift attention to a different location or keep attention at the same location as the retro-cue. Finally, participants were required to discriminate the cued color from a set of distractors. It was found that negative cues yielded shorter response times (RTs) in the attention-shift condition and longer RTs in the attention-stay condition, compared with neutral and positive cues. The results suggest that negative affective valence may enhance working memory performance (RTs), provided that attention can be disengaged.

  8. Night Shift Work and Its Health Effects on Nurses.

    PubMed

    Books, Candie; Coody, Leon C; Kauffman, Ryan; Abraham, Sam

    The purpose of this research was to study night shift work and its health effects on nurses. This was a quantitative study using descriptive design; it also incorporated three qualitative open-ended questions to complement the study. The data were collected using Survey Monkey, with an Internet-based confidential data collection tool. The population of relevance to this study was nurses employed in hospital settings in the United States. E-mail addresses and Facebook were used to recruit participants. Results indicated that there is an increased risk of sleep deprivation, family stressors, and mood changes because of working the night shift. Rotating shifts were mentioned as a major concern for night shift nurses. Respondents agreed that complaints about fatigue and fatigue-related illnesses in night shift workers were ignored. There was also a general perception among nurses working the night shift that sleep deprivation leads to negative health consequences including obesity; however, they were not as high a concern as rotating shifts or fatigue.

  9. Existence of negative differential thermal conductance in one-dimensional diffusive thermal transport

    NASA Astrophysics Data System (ADS)

    Hu, Jiuning; Chen, Yong P.

    2013-06-01

    We show that in a finite one-dimensional (1D) system with diffusive thermal transport described by the Fourier's law, negative differential thermal conductance (NDTC) cannot occur when the temperature at one end is fixed and there are no abrupt junctions. We demonstrate that NDTC in this case requires the presence of junction(s) with temperature-dependent thermal contact resistance (TCR). We derive a necessary and sufficient condition for the existence of NDTC in terms of the properties of the TCR for systems with a single junction. We show that under certain circumstances we even could have infinite (negative or positive) differential thermal conductance in the presence of the TCR. Our predictions provide theoretical basis for constructing NDTC-based devices, such as thermal amplifiers, oscillators, and logic devices.

  10. Placental Abruption and Perinatal Mortality With Preterm Delivery as a Mediator: Disentangling Direct and Indirect Effects

    PubMed Central

    Ananth, Cande V.; VanderWeele, Tyler J.

    2011-01-01

    The authors use recent methodology in causal inference to disentangle the direct and indirect effects that operate through a mediator in an exposure-response association paradigm. They demonstrate how total effects can be partitioned into direct and indirect effects even when the exposure and mediator interact. The impact of bias due to unmeasured confounding on the exposure-response association is assessed through a series of sensitivity analyses. These methods are applied to a problem in perinatal epidemiology to examine the extent to which the effect of abruption on perinatal mortality is mediated through preterm delivery. Data on over 26 million US singleton births (1995–2002) were utilized. Risks of mortality among abruption and nonabruption births were 102.7 and 6.2 per 1,000 births, respectively. Risk ratios of the natural direct and indirect (preterm delivery-mediated) effects of abruption on mortality were 10.18 (95% confidence interval: 9.80, 10.58) and 1.35 (95% confidence interval: 1.33, 1.38), respectively. The proportion of increased mortality risk mediated through preterm delivery was 28.1%, with even higher proportions associated with deliveries at earlier gestational ages. Sensitivity analyses underscore that the qualitative conclusions of some mediated effects and substantial direct effects are reasonably robust to unmeasured confounding of a fairly considerable magnitude. PMID:21430195

  11. Economic design of control charts considering process shift distributions

    NASA Astrophysics Data System (ADS)

    Vommi, Vijayababu; Kasarapu, Rukmini V.

    2014-09-01

    Process shift is an important input parameter in the economic design of control charts. Earlier control chart designs considered constant shifts to occur in the mean of the process for a given assignable cause. This assumption has been criticized by many researchers since it may not be realistic to produce a constant shift whenever an assignable cause occurs. To overcome this difficulty, in the present work, a distribution for the shift parameter has been considered instead of a single value for a given assignable cause. Duncan's economic design model for chart has been extended to incorporate the distribution for the process shift parameter. It is proposed to minimize total expected loss-cost to obtain the control chart parameters. Further, three types of process shifts namely, positively skewed, uniform and negatively skewed distributions are considered and the situations where it is appropriate to use the suggested methodology are recommended.

  12. Theoretical Investigation of Tunable Goos-Hänchen Shifts in a Four-Level Quantum System

    NASA Astrophysics Data System (ADS)

    Jafarzadeh, Hossein; Payravi, Mohammad

    2018-05-01

    Goos-Hänchen (GH) shifts in the reflected and transmitted light have been discussed in a cavity with four-level quantum system. It is realized that the refraction index of intracavity medium can be negative by manipulating the external coherent laser fields. For the negative refraction index of intracavity medium, the GH shifts of reflected and transmitted light beams have been analyzed in a parametric condition. It is found that due to modulation of laser signals and relative phase between applied fields, large and tunable GH shifts in reflected and transmitted light beams can be obtained.

  13. An Abrupt Centennial-Scale Drought Event and Mid-Holocene Climate Change Patterns in Monsoon Marginal Zones of East Asia

    PubMed Central

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0–7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different

  14. An abrupt centennial-scale drought event and mid-holocene climate change patterns in monsoon marginal zones of East Asia.

    PubMed

    Li, Yu; Wang, Nai'ang; Zhang, Chengqi

    2014-01-01

    The mid-latitudes of East Asia are characterized by the interaction between the Asian summer monsoon and the westerly winds. Understanding long-term climate change in the marginal regions of the Asian monsoon is critical for understanding the millennial-scale interactions between the Asian monsoon and the westerly winds. Abrupt climate events are always associated with changes in large-scale circulation patterns; therefore, investigations into abrupt climate changes provide clues for responses of circulation patterns to extreme climate events. In this paper, we examined the time scale and mid-Holocene climatic background of an abrupt dry mid-Holocene event in the Shiyang River drainage basin in the northwest margin of the Asian monsoon. Mid-Holocene lacustrine records were collected from the middle reaches and the terminal lake of the basin. Using radiocarbon and OSL ages, a centennial-scale drought event, which is characterized by a sand layer in lacustrine sediments both from the middle and lower reaches of the basin, was absolutely dated between 8.0-7.0 cal kyr BP. Grain size data suggest an abrupt decline in lake level and a dry environment in the middle reaches of the basin during the dry interval. Previous studies have shown mid-Holocene drought events in other places of monsoon marginal zones; however, their chronologies are not strong enough to study the mechanism. According to the absolutely dated records, we proposed a new hypothesis that the mid-Holocene dry interval can be related to the weakening Asian summer monsoon and the relatively arid environment in arid Central Asia. Furthermore, abrupt dry climatic events are directly linked to the basin-wide effective moisture change in semi-arid and arid regions. Effective moisture is affected by basin-wide precipitation, evapotranspiration, lake surface evaporation and other geographical settings. As a result, the time scales of the dry interval could vary according to locations due to different geographical

  15. [Shift and night work and mental health].

    PubMed

    Sancini, Angela; Ciarrocca, Manuela; Capozzella, Assunta; Corbosiero, Paola; Fiaschetti, Maria; Caciari, Tiziana; Cetica, Carlotta; Scimitto, Lara; Ponticiello, Barnaba Giuseppina; Tasciotti, Zaira; Schifano, Maria Pia; Andreozzit, Giorgia; Tomei, Francesco; Tomei, Gianfranco

    2012-01-01

    Aim of our study was to evaluate the influence that shift work and night work could have on mental health. A review of literary articles from 1990 to 2011 on shift work and night work was carried out. The results of this review confirmed that the shift work and night work affect mental health with the onset of neuropsychological disorders such as mood disorders, anxiety, nervousness, depressive anxiety syndromes, chronic fatigue and chronic insomnia irritability, sleep disturbances, reduction in levels of attention, cognitive impairments, alteration of circadian rhythm. Night work and shift work cause severe desynchronization of the cronobiological rhythms and a disruption of social life with negative effects on performance at work, on health and on social relationships. In the light of these results and recognizing shift work and night work as risk factors for the health of workers is necessary to implement preventive and periodic health checks by the occupational doctor to ensure the health and safety of workers taking account of the different environmental and individual factors.

  16. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, M.; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Lauriie, S.; Garcia, K.; Sargsyan, A.; Martin, D.; Ribeiro, L.; hide

    2016-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low-Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 50% of ISS astronauts experienced more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the spaceflight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration spaceflight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during spaceflight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's preflight conditions and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. METHODS: We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by

  17. Terrestrial Plant Biomarkers Preserved in Cariaco Basin Sediments: Records of Abrupt Tropical Vegetation Response to Rapid Climate Changes

    NASA Astrophysics Data System (ADS)

    Hughen, K. A.; Eglinton, T. I.; Makou, M.; Xu, L.; Sylva, S.

    2004-12-01

    versus δ 13C for Cariaco Basin and NW African leaf waxes indicate that biomarkers reflect real changes in local South American vegetation and not contamination from long-distance transport during cold windy climates. The precise temporal relationship between tropical vegetation shifts and climate changes is measured by direct comparison of terrestrial vegetation and climate proxies from the same core. Abrupt deglacial climate shifts in tropical and high-latitude North Atlantic regions were synchronous, whereas changes in tropical vegetation consistently lagged climate shifts by several decades.

  18. High resolution water stable isotope profiles of abrupt climate transitions in Greenland ice with new observations from NEEM

    NASA Astrophysics Data System (ADS)

    Popp, T. J.; White, J. W. C.; Gkinis, V.; Vinther, B. M.; Johnsen, S. J.

    2012-04-01

    In 1989 Willi Dansgaard and others, using the DYE3 ice core, showed that the abrupt termination of the Younger Dryas expressed in water stable isotope ratios and deuterium excess was completed in less than 50 years. A few years later, using the GISP2 ice core, Richard Alley and others proposed that snow accumulation at the site doubled in as little as 1-3 years across the same climate transition at the end of the Younger Dryas. Over the next two decades, in large part due to such observations from Greenland ice cores, a paradigm of linked, abrupt changes in the North Atlantic region has been developed around North Atlantic deep water formation, North Atlantic sea ice extent, and widespread atmospheric circulation changes occurring repeatedly during the last glacial period in response to changing freshwater fluxes to the region, or perhaps other causes. More recently, with the NGRIP ice core, using a suite of high resolution proxy data, and in particular deuterium excess, it was observed again that certain features in the climate system can switch modes from one year to the next, while other proxies can take from decades to centuries to completely switch modes. Thus, an event seen in the proxy records such as the abrupt end of the Younger Dryas (or other interstadial events) may comprise multiple climatic or oceanic responses with different relative timing and duration which potentially follow a predictable sequence of events, in some cases separated by only a few years. Today, the search continues for these emerging patterns through isotopic and other highly resolvable proxy data series from ice cores. With the recent completion of the drilling at NEEM, many abrupt transitions have now been measured in detail over a geographic transect with drilling sites spanning from DYE3 in Southern Greenland, GISP2 in the central summit region, and up to NGRIP and NEEM in the far north. The anatomy of abrupt climate transitions can therefore be examined both spatially and

  19. Towards Greenland Glaciation: Cumulative or Abrupt Transition?

    NASA Astrophysics Data System (ADS)

    Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.

    2014-12-01

    The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an abrupt ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an abrupt event or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428

  20. Exogenous attentional capture by subliminal abrupt-onset cues: evidence from contrast-polarity independent cueing effects.

    PubMed

    Fuchs, Isabella; Theeuwes, Jan; Ansorge, Ulrich

    2013-08-01

    In the present study, we tested whether subliminal abrupt-onset cues capture attention in a bottom-up or top-down controlled manner. For our tests, we varied the searched-for target-contrast polarity (i.e., dark or light targets against a gray background) over four experiments. In line with the bottom-up hypothesis, our results indicate that subliminal-onset cues capture attention independently of the searched-for target-contrast polarity (Experiment 1), and this effect is not stronger for targets that matched the searched-for target-contrast polarity (Experiment 2). In fact, even to-be-ignored cues associated with a no-go response captured attention in a salience-driven way (Experiment 3). For supraliminal cues, we found attentional capture only by cues with a matching contrast polarity, reflecting contingent capture (Experiment 4). The results point toward a specific role of subliminal abrupt onsets for attentional capture. 2013 APA, all rights reserved

  1. Attention capture by abrupt onsets: re-visiting the priority tag model.

    PubMed

    Sunny, Meera M; von Mühlenen, Adrian

    2013-01-01

    Abrupt onsets have been shown to strongly attract attention in a stimulus-driven, bottom-up manner. However, the precise mechanism that drives capture by onsets is still debated. According to the new object account, abrupt onsets capture attention because they signal the appearance of a new object. Yantis and Johnson (1990) used a visual search task and showed that up to four onsets can be automatically prioritized. However, in their study the number of onsets co-varied with the total number of items in the display, allowing for a possible confound between these two variables. In the present study, display size was fixed at eight items while the number of onsets was systematically varied between zero and eight. Experiment 1 showed a systematic increase in reactions times with increasing number of onsets. This increase was stronger when the target was an onset than when it was a no-onset item, a result that is best explained by a model according to which only one onset is automatically prioritized. Even when the onsets were marked in red (Experiment 2), nearly half of the participants continued to prioritize only one onset item. Only when onset and no-onset targets were blocked (Experiment 3), participants started to search selectively through the set of only the relevant target type. These results further support the finding that only one onset captures attention. Many bottom-up models of attention capture, like masking or saliency accounts, can efficiently explain this finding.

  2. Spontaneous abrupt climate change due to an atmospheric blocking-sea-ice-ocean feedback in an unforced climate model simulation.

    PubMed

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A; Livina, Valerie

    2013-12-03

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70 °N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change.

  3. Spontaneous abrupt climate change due to an atmospheric blocking–sea-ice–ocean feedback in an unforced climate model simulation

    PubMed Central

    Drijfhout, Sybren; Gleeson, Emily; Dijkstra, Henk A.; Livina, Valerie

    2013-01-01

    Abrupt climate change is abundant in geological records, but climate models rarely have been able to simulate such events in response to realistic forcing. Here we report on a spontaneous abrupt cooling event, lasting for more than a century, with a temperature anomaly similar to that of the Little Ice Age. The event was simulated in the preindustrial control run of a high-resolution climate model, without imposing external perturbations. Initial cooling started with a period of enhanced atmospheric blocking over the eastern subpolar gyre. In response, a southward progression of the sea-ice margin occurred, and the sea-level pressure anomaly was locked to the sea-ice margin through thermal forcing. The cold-core high steered more cold air to the area, reinforcing the sea-ice concentration anomaly east of Greenland. The sea-ice surplus was carried southward by ocean currents around the tip of Greenland. South of 70°N, sea ice already started melting and the associated freshwater anomaly was carried to the Labrador Sea, shutting off deep convection. There, surface waters were exposed longer to atmospheric cooling and sea surface temperature dropped, causing an even larger thermally forced high above the Labrador Sea. In consequence, east of Greenland, anomalous winds changed from north to south, terminating the event with similar abruptness to its onset. Our results imply that only climate models that possess sufficient resolution to correctly represent atmospheric blocking, in combination with a sensitive sea-ice model, are able to simulate this kind of abrupt climate change. PMID:24248352

  4. Association between the transition from unemployment to re-employment after abrupt bankruptcy and the depressive symptoms.

    PubMed

    Nagatomi, Kaori; Ishitake, Tatsuya; Hara, Kunio; Shigemoto, Akira; Hoshiko, Michiko; Tsuji, Yoshiyasu; Yamaguchi, Yoshie; Tamaki, Hideki; Furumura, Mitsuyo; Muramoto, Junko

    2010-01-01

    The study aimed to examine the effects of long-term unemployment and the transition from unemployment to re-employment after abrupt bankruptcy on the mental health of unemployed Japanese. The cases of 96 men and 54 women who were laid off by a large shoemaking company because of sudden bankruptcy in 1998, were examined for one year. The mental health of these individuals was evaluated using a 'self-rating questionnaire for depression (SRQ-D)'. The respondents were categorized by employment transition status into four groups: (1) still employed full-time, (2) unemployment to full-time employment, (3) unemployment to part-time employment, and (4) still unemployed. The prevalence rate of depressive symptoms in the 'still unemployed' group was significantly higher (adjusted odds ratio (OR) = 4.33) than in the still employed group. Moreover, high levels of depressive symptoms were observed in the individuals in the 'unemployment to part-time employment' group (adjusted OR = 4.93). There was no significant risk of depressive tendency among individuals in the 'unemployment to full-time employment' group. The results suggest that the negative effect of re-employment to part-time employment on depressive symptoms is similar to that in long-term unemployment.

  5. Nurse perceptions of workplace environment: differences across shifts.

    PubMed

    Teclaw, Robert; Osatuke, Katerine

    2015-11-01

    To evaluate whether nurse work shift affected workplace perceptions. Although the importance of work schedule in shaping work attitudes, generally (and specifically for nurses) is well accepted, much work remains in characterising how and why nurses' perceptions might differ across shifts. Using an exploratory study of observational data, we examined whether shift influenced non-supervisory nurses' job perceptions in the Veterans Health Administration All Employee Survey (n = 14057; years 2008, 2010, 2012). The size of differences in item means (95% C.I.) across shifts was evaluated graphically. Using ordinal logistic regression, we accounted for the ordinal outcome variables and controlled for the demographic and survey year effects. Nurses' perceptions of workplace climate differed across shifts. Items with the greatest differences, consistent across years and analytic methods, involved supervisors and fairness. Night and weekend shift nurse ratings were more negative than for weekday shift nurses. Off-shift nurses are less satisfied with work/life balance, their supervisors and especially fairness. Overall satisfaction and turnover intention are not affected to the same extent. These results indicate several specific areas that nurse managers can address through workforce support and communication. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

  6. Bias to negative emotions: a depression state-dependent marker in adolescent major depressive disorder.

    PubMed

    Maalouf, Fadi T; Clark, Luke; Tavitian, Lucy; Sahakian, Barbara J; Brent, David; Phillips, Mary L

    2012-06-30

    The aim of the current research was to examine for the first time the extent to which bias to negative emotions in an inhibitory control paradigm is a state or trait marker in major depressive disorder (MDD) in adolescents. We administered the affective go/no go task which measures the ability to switch attention to or away from positive or negative emotional stimuli to 40 adolescents with MDD (20 in acute episode (MDDa) and 20 in remission (MDDr)) and 17 healthy controls (HC). MDDa were significantly faster on the shift to negative target blocks as compared to shift to positive target blocks while HC and MDDr displayed the opposite pattern as measured by an "emotional bias index" (EBI=latency (shift to negative targets)-latency (shift to positive targets)). There was also a trend for an effect of group on commission errors, suggesting more impulsive responding by MDDa than both MDDr and HC independently of stimulus valence throughout the task. Negative bias was not associated with depression severity or medication status. In conclusion, bias to negative emotional stimuli appears to be present in the acute stage of MDD and absent in remission suggesting that it is a depression state-specific marker of MDD in adolescents. Latency emerges as a better proxy of negative bias than commission errors and accuracy on this inhibitory control task in adolescents with MDD. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Breaking barriers: expansion of the use of endolysins as novel antibacterials against Gram-negative bacteria.

    PubMed

    Briers, Yves; Lavigne, Rob

    2015-01-01

    The emergence and spread of antibiotic-resistant bacteria drives the search for novel classes of antibiotics to replenish our armamentarium against bacterial infections. This is particularly critical for Gram-negative pathogens, which are intrinsically resistant to many existing classes of antibiotics due to the presence of a protective outer membrane. In addition, the antibiotics development pipeline is mainly oriented to Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus. A promising novel class of antibacterials is endolysins. These enzymes encoded by bacterial viruses hydrolyze the peptidoglycan layer with high efficiency, resulting in abrupt osmotic lysis and cell death. Their potential as novel antibacterials to treat Gram-positive bacteria has been extensively demonstrated; however, the Gram-negative outer membrane has presented a formidable barrier for the use of endolysins against Gram-negatives until recently. This review reports on the most recent advances in the development of endolysins to kill Gram-negative species with a special focus on endolysin-engineered Artilysins(®).

  8. Abrupt hydroclimate disruption across the Australian arid zone 50 ka coincident with human colonization

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Fogel, M. L.; Magee, J. W.; Gagan, M. K.

    2016-12-01

    Although many studies focus on how climate change impacted ancient societies, in Australia a growing body of evidence indicates that activities of the earliest human colonizers in turn altered the Australian climate. We utilize the stable isotopes of carbon and oxygen preserved in near-continuous 100 ka time series of avian eggshell from five regions across the Australian arid zone to reconstruct ecosystem status (d13C) and effective moisture (d18O). Training sets of sub-modern samples provide the basis for the reconstructions. Together, d13C and d18O provide independent estimates of ecosystem status and climate over the past 100 ka from the same dated sample, reducing correlation uncertainties between proxies. Changes in eggshell d13C document a dramatic reduction of palatable summer-wet C4 grasses in all regions between 50 and 45 ka, that has persisted through to modern times. Continuous 100 ka records of effective moisture derived from eggshell d18O show moist conditions from 100 to 60 ka, with variable drying after 60 ka, but the strong shift toward greatest aridity is coincident with the onset of the last glacial maximum 30 ka ago, 15 ka after the observed ecosystem restructuring. Combining the d13C and d18O time-series shows that an abrupt and permanent restructuring of the moisture/ecosystem balance occurred between 50 and 45 ka. Additional studies show that most large monsoon-fed inland arid-zone lakes carried permanent water at least intermittently between 120 and 50 ka, but never experienced permanent deep-water status after 45 ka, despite a wide range of global climate states, including the early Holocene when most other monsoon systems were reinvigorated. The lack of exceptional climate shifts either locally or globally between 60 and 40 ka eliminates climate as the cause of the ecosystem restructuring and persistent lake desiccation. Collectively these data suggest the wave of human colonization across Australia in altered land surface characteristics

  9. Abrupt tectonics and rapid slab detachment with grain damage

    PubMed Central

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-01-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  10. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-03

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

  11. Australian shelf sediments reveal shifts in Miocene Southern Hemisphere westerlies

    PubMed Central

    Groeneveld, Jeroen; Henderiks, Jorijntje; Renema, Willem; McHugh, Cecilia M.; De Vleeschouwer, David; Christensen, Beth A.; Fulthorpe, Craig S.; Reuning, Lars; Gallagher, Stephen J.; Bogus, Kara; Auer, Gerald; Ishiwa, Takeshige

    2017-01-01

    Global climate underwent a major reorganization when the Antarctic ice sheet expanded ~14 million years ago (Ma) (1). This event affected global atmospheric circulation, including the strength and position of the westerlies and the Intertropical Convergence Zone (ITCZ), and, therefore, precipitation patterns (2–5). We present new shallow-marine sediment records from the continental shelf of Australia (International Ocean Discovery Program Sites U1459 and U1464) providing the first empirical evidence linking high-latitude cooling around Antarctica to climate change in the (sub)tropics during the Miocene. We show that Western Australia was arid during most of the Middle Miocene. Southwest Australia became wetter during the Late Miocene, creating a climate gradient with the arid interior, whereas northwest Australia remained arid throughout. Precipitation and river runoff in southwest Australia gradually increased from 12 to 8 Ma, which we relate to a northward migration or intensification of the westerlies possibly due to increased sea ice in the Southern Ocean (5). Abrupt aridification indicates that the westerlies shifted back to a position south of Australia after 8 Ma. Our midlatitude Southern Hemisphere data are consistent with the inference that expansion of sea ice around Antarctica resulted in a northward movement of the westerlies. In turn, this may have pushed tropical atmospheric circulation and the ITCZ northward, shifting the main precipitation belt over large parts of Southeast Asia (4). PMID:28508066

  12. Stimulus generalization, discrimination learning, and peak shift in horses.

    PubMed Central

    Dougherty, D M; Lewis, P

    1991-01-01

    Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms. PMID:1940765

  13. Reducing The Risk Of Abrupt Climate Change: Emission Corridors Preserving The Thermohaline Circulation

    NASA Astrophysics Data System (ADS)

    Zickfeld, K.

    Paleo-reconstructions have shown that large and abrupt climate changes have occurred throughout the last ice-age cycles. This evidence, supplemented by insights into the complex and nonlinear nature of the climate system, gives raise to the concern that anthropogenic forcing may trigger such events in the future. A prominent example for such a potential climatic shift is the collapse of the North Atlantic thermohaline circu- lation (THC), which would cause a major cooling of the northern North Atlantic and north-western Europe and considerable regional sea level rise, with possibly severe consequences on, e.g., fisheries, agriculture and ecosystems. In this paper we present emission corridors for the 21st century preserving the THC. Emission corridors embrace the range of future emissions beyond which either the THC collapses or the mitigation burden becomes intolerable. They are calculated along the conceptual and methodological lines of the tolerable windows approach. We investigate the sensitivity of the emission corridors to the main uncertain parame- ters (climate and North Atlantic hydrological sensitivities as well as emissions of non CO_2 greenhouse gases). Results show a high dependence of the size of the emis- sion corridors on hydrological and climate sensitivities. For the best-guess values of both parameters we find that the emission corridors are wider than the range spanned by the SRES emissions scenarios. Thus, no immediate mitigation seems necessary in order to preserve the THC. For high but still realistic values of the sensitivities, however, even the low SRES emissions scenarios transgress the corridor boundaries. These findings imply that under 'business as usual' a non-negligible risk of either a THC collapse or an intolerable mitigation burden exists.

  14. Single-resonator double-negative metamaterial

    DOEpatents

    Warne, Larry K.; Basilio, Lorena I.; Langston, William L.; Johnson, William A.; Ihlefeld, Jon; Ginn, III, James C.; Clem, Paul G.; Sinclair, Michael B.

    2016-06-21

    Resonances can be tuned in dielectric resonators in order to construct single-resonator, negative-index metamaterials. For example, high-contrast inclusions in the form of metallic dipoles can be used to shift the first electric resonance down (in frequency) to the first magnetic resonance, or alternatively, air splits can be used to shift the first magnetic resonance up (in frequency) near the first electric resonance. Degenerate dielectric designs become especially useful in infrared- or visible-frequency applications where the resonator sizes associated with the lack of high-permittivity materials can become of sufficient size to enable propagation of higher-order lattice modes in the resulting medium.

  15. Tracking the will to attend: Cortical activity indexes self-generated, voluntary shifts of attention.

    PubMed

    Gmeindl, Leon; Chiu, Yu-Chin; Esterman, Michael S; Greenberg, Adam S; Courtney, Susan M; Yantis, Steven

    2016-10-01

    The neural substrates of volition have long tantalized philosophers and scientists. Over the past few decades, researchers have employed increasingly sophisticated technology to investigate this issue, but many studies have been limited considerably by their reliance on intrusive experimental procedures (e.g., abrupt instructional cues), measures of brain activity contaminated by overt behavior, or introspective self-report techniques of questionable validity. Here, we used multivoxel pattern time-course analysis of functional magnetic resonance imaging data to index voluntary, covert perceptual acts-shifts of visuospatial attention-in the absence of instructional cues, overt behavioral indices, and self-report. We found that these self-generated, voluntary attention shifts were time-locked to activity in the medial superior parietal lobule, supporting the hypothesis that this brain region is engaged in voluntary attentional reconfiguration. Self-generated attention shifts were also time-locked to activity in the basal ganglia, a novel finding that motivates further research into the role of the basal ganglia in acts of volition. Remarkably, prior to self-generated shifts of attention, we observed early and selective increases in the activation of medial frontal (dorsal anterior cingulate) and lateral prefrontal (right middle frontal gyrus) cortex-activity that likely reflects processing related to the intention or preparation to reorient attention. These findings, which extend recent evidence on freely chosen motor movements, suggest that dorsal anterior cingulate and lateral prefrontal cortices play key roles in both overt and covert acts of volition, and may constitute core components of a brain network underlying the will to attend.

  16. Tracking the Will to Attend: Cortical Activity Indexes Self-Generated, Voluntary Shifts of Attention

    PubMed Central

    Gmeindl, Leon; Chiu, Yu-Chin; Esterman, Michael S.; Greenberg, Adam S.; Courtney, Susan M.; Yantis, Steven

    2016-01-01

    The neural substrates of volition have long tantalized philosophers and scientists. Over the past few decades, researchers have employed increasingly sophisticated technology to investigate this issue, but many studies have been limited considerably by their reliance on intrusive experimental procedures (e.g., abrupt instructional cues), measures of brain activity contaminated by overt behavior, or introspective self-report techniques of questionable validity. Here, we used multivoxel-pattern time-course analysis of functional magnetic resonance imaging data to index voluntary, covert perceptual acts—shifts of visuospatial attention—in the absence of instructional cues, overt behavioral indices, and self-report. We found that these self-generated, voluntary attention shifts were time-locked to activity in the medial superior parietal lobule, supporting the hypothesis that this brain region is engaged in voluntary attentional reconfiguration. Self-generated attention shifts were also time-locked to activity in the basal ganglia, a novel finding that motivates further research into the role of the basal ganglia in acts of volition. Remarkably, prior to self-generated shifts of attention we observed early and selective increases in activation of medial frontal (dorsal anterior cingulate) and lateral prefrontal cortex (right middle frontal gyrus)—activity that likely reflects processing related to the intention or preparation to reorient attention. These findings, which extend recent evidence on freely chosen motor movements, suggest that dorsal anterior cingulate and lateral prefrontal cortices play key roles in both overt and covert acts of volition, and may constitute core components of a brain network underlying the will to attend. PMID:27301353

  17. Validation of a Questionnaire to Screen for Shift Work Disorder

    PubMed Central

    Barger, Laura K.; Ogeil, Rowan P.; Drake, Christopher L.; O'Brien, Conor S.; Ng, Kim T.; Rajaratnam, Shantha M. W.

    2012-01-01

    Study Objective: At least 15% of the full-time work force is shift workers. Working during the overnight hours, early morning start times, and variable or rotating schedules present a challenge to the circadian system, and these shifts are associated with adverse health and safety consequences. Shift work disorder (SWD), a primary (circadian rhythm) sleep disorder indicated by excessive daytime sleepiness and/or insomnia associated with a shiftwork schedule, is under-recognized by primary care physicians. We sought to develop and validate a questionnaire to screen for high risk of SWD in a shift working population. Design: Shift workers completed a 26-item questionnaire and were evaluated by a sleep specialist (physician) who diagnosed them as either positive or negative for SWD. The physician assessment of SWD was guided by a flow chart that operationalized the ICSD-2 criteria for SWD. Setting: 18 sleep clinics in the USA. Patients or Participants: 311 shift workers. Interventions: Not applicable. Measurements and Results: Responses to the items in the questionnaire were entered into a series of discrimination function analyses to determine the diagnostic value of the items and the fewest number of questions with the best predictive value. The function was then cross-validated. A final 4-item questionnaire has 89% positive predictive value and 62% negative predictive value (sensitivity = 0.74; specificity = 0.82). Conclusions: This Shiftwork Disorder Screening Questionnaire may be appropriate for use in primary care settings to aid in the diagnosis of SWD. Citation: Barger LK; Ogeil RP; Drake CL; O'Brien CS; Ng KT; Rajaratnam SMW. Validation of a questionnaire to screen for shift work disorder. SLEEP 2012;35(12):1693–1703. PMID:23204612

  18. Fluid Shifts

    NASA Technical Reports Server (NTRS)

    Stenger, Michael; Hargens, A.; Dulchavsky, S.; Ebert, D.; Lee, S.; Sargsyan, A.; Martin, D.; Lui, J.; Macias, B.; Arbeille, P.; hide

    2014-01-01

    NASA is focusing on long-duration missions on the International Space Station (ISS) and future exploration-class missions beyond low Earth orbit. Visual acuity changes observed after short-duration missions were largely transient, but more than 30% of ISS astronauts experience more profound, chronic changes with objective structural and functional findings such as papilledema and choroidal folds. Globe flattening, optic nerve sheath dilation, and optic nerve tortuosity also are apparent. This pattern is referred to as the visual impairment and intracranial pressure (VIIP) syndrome. VIIP signs and symptoms, as well as postflight lumbar puncture data, suggest that elevated intracranial pressure (ICP) may be associated with the space flight-induced cephalad fluid shifts, but this hypothesis has not been tested. The purpose of this study is to characterize fluid distribution and compartmentalization associated with long-duration space flight, and to correlate these findings with vision changes and other elements of the VIIP syndrome. We also seek to determine whether the magnitude of fluid shifts during space flight, as well as the VIIP-related effects of those shifts, is predicted by the crewmember's pre-flight condition and responses to acute hemodynamic manipulations (such as head-down tilt). Lastly, we will evaluate the patterns of fluid distribution in ISS astronauts during acute reversal of fluid shifts through application of lower body negative pressure (LBNP) interventions to characterize and explain general and individual responses. We will examine a variety of physiologic variables in 10 long-duration ISS crewmembers using the test conditions and timeline presented in the Figure below. Measures include: (1) fluid compartmentalization (total body water by D2O, extracellular fluid by NaBr, intracellular fluid by calculation, plasma volume by CO rebreathe, interstitial fluid by calculation); (2) forehead/eyelids, tibia, calcaneus tissue thickness (by ultrasound

  19. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage.

    PubMed

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-06-10

    Extreme climatic events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050-4,400 yr BP) and Longshan (4,400-4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, abrupt changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions.

  20. The abrupt climate change near 4,400 yr BP on the cultural transition in Yuchisi, China and its global linkage

    PubMed Central

    Wang, Jianjun; Sun, Liguang; Chen, Liqi; Xu, Libin; Wang, Yuhong; Wang, Xinming

    2016-01-01

    Extreme climatic events have profound impacts on human society. Here we present the results of a study of organic biomarkers within a sedimentary section at the archaeological site of Yuchisi, eastern China, in order to reconstruct climatic variability during the Dawenkou (5,050–4,400 yr BP) and Longshan (4,400–4,000 yr BP) cultures. At ~4,400 yr BP, within the cultural transition horizon, abrupt changes in biomarkers, such as the fatty acid ratio C18:2/C18:0, 2C31/(C27 + C29), n-C18-ol and n-C30-ol, indicate the occurrence of local climate changes over the course of a few decades. These changes occurred during the transition from the Holocene warm period to a subsequent cold period which lasted for the following 600 years. This climatic shift has been recorded at numerous sites worldwide, and it is likely to have been the main cause of the widespread collapse of many isolated cultures at that time. The palaeoclimatic and archaeological data from the Yuchisi sediments may provide new insights into the relationship between climate change and prehistoric cultural transitions. PMID:27283832

  1. Polarized negative ions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Haeberli, W.

    1981-04-01

    This paper presents a survey of methods, commonly in use or under development, to produce beams of polarized negative ions for injection into accelerators. A short summary recalls how the hyperfine interaction is used to obtain nuclear polarization in beams of atoms. Atomic-beam sources for light ions are discussed. If the best presently known techniques are incorporated in all stages of the source, polarized H/sup -/ and D/sup -/ beams in excess of 10 ..mu..A can probably be achieved. Production of polarized ions from fast (keV) beams of polarized atoms is treated separately for atoms in the H(25) excited statemore » (Lamb-Shift source) and atoms in the H(1S) ground state. The negative ion beam from Lamb-Shift sources has reached a plateau just above 1 ..mu..A, but this beam current is adequate for many applications and the somewhat lower beam current is compensated by other desirable characteristics. Sources using fast polarized ground state atoms are in a stage of intense development. The next sections summarize production of polarized heavy ions by the atomic beam method, which is well established, and by optical pumping, which has recently been demonstrated to yield very large nuclear polarization. A short discussion of proposed ion sources for polarized /sup 3/He/sup -/ ions is followed by some concluding remarks.« less

  2. Continuous methane record of abrupt climate change 10-68 ka: sighting Heinrich events in the ice core record

    NASA Astrophysics Data System (ADS)

    Rhodes, Rachael; Brook, Edward; Chiang, John; Blunier, Thomas; Cheng, Hai; Edwards, R. Lawrence; Maselli, Olivia; McConnell, Joseph; Romanini, Daniele; Severinghaus, Jeffrey; Sowers, Todd; Stowasser, Christopher

    2014-05-01

    The Last Glacial period was punctuated by millennial scale abrupt climate changes - Dansgaard-Oeschger (D-O) cycles and Heinrich events. Controls on the magnitude and frequency of these climate perturbations, and how they may be inter-related, remain unclear. Specific problems include the difficulty of dating Heinrich sediment layers and local bias of key paleoclimate archives. We present a highly detailed and precise record of ice core methane (CH4), a globally integrated signal, which resolves climatic features in unprecedented resolution. Abrupt CH4 increases are resolved in Heinrich Stadials (HS) 1, 2, 4 and 5 where, in contrast to all D-O cycles, there are no concurrent abrupt changes in Greenland temperature. Using modern-day tropical rainfall variability as an analog, we propose that strong cooling in the North Atlantic severely restricted the northerly range of the Intertropical Convergence Zone (ITCZ), leading to an enhanced wet season over Southern Hemisphere tropical land areas, and consequently driving production of excess CH4 in tropical wetlands. Our findings place four Heinrich events firmly within ice core chronologies and suggest maximum durations of 778 to 1606 yr. CH4 anomalies are only associated with Heinrich events of Hudson Strait provenance, indicating that the tropical impacts of Heinrich events were not uniform.

  3. What work schedule characteristics constitute a problem to the individual? A representative study of Swedish shift workers.

    PubMed

    Åkerstedt, Torbjörn; Kecklund, Göran

    2017-03-01

    The purpose was to investigate which detailed characteristics of shift schedules that are seen as problems to those exposed. A representative national sample of non-day workers (N = 2031) in Sweden was asked whether they had each of a number of particular work schedule characteristics and, if yes, to what extent this constituted a "big problem in life". It was also inquired whether the individual's work schedules had negative consequences for fatigue, sleep and social life. The characteristic with the highest percentage reporting a big problem was "short notice (<1 month) of a new work schedule" (30.5%), <11 h off between shifts (27.8%), and split duty (>1.5 h break at mid-shift, 27.2%). Overtime (>10 h/week), night work, morning work, day/night shifts showed lower prevalences of being a "big problem". Women indicated more problems in general. Short notice was mainly related to negative social effects, while <11 h off between shifts was related to disturbed sleep, fatigue and social difficulties. It was concluded that schedules involving unpredictable working hours (short notice), short daily rest between shifts, and split duty shifts constitute big problems. The results challenge current views of what aspects of shift work need improvement, and negative social consequences seem more important than those related to health. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Mechanism of Pressure-Induced Phase Transitions, Amorphization, and Absorption-Edge Shift in Photovoltaic Methylammonium Lead Iodide.

    PubMed

    Szafrański, Marek; Katrusiak, Andrzej

    2016-09-01

    Our single-crystal X-ray diffraction study of methylammonium lead triiodide, MAPbI3, provides the first comprehensive structural information on the tetragonal phase II in the pressure range to 0.35 GPa, on the cubic phase IV stable between 0.35 and 2.5 GPa, and on the isostructural cubic phase V observed above 2.5 GPa, which undergoes a gradual amorphization. The optical absorption study confirms that up to 0.35 GPa, the absorption edge of MAPbI3 is red-shifted, allowing an extension of spectral absorption. The transitions to phases IV and V are associated with the abrupt blue shifts of the absorption edge. The strong increase of the energy gap in phase V result in a spectacular color change of the crystal from black to red around 3.5 GPa. The optical changes have been correlated with the pressure-induced strain of the MAPbI3 inorganic framework and its frustration, triggered by methylammonium cations trapped at random orientations in the squeezed voids.

  5. Abrupt variations of Indian and East Asian summer monsoons during the last deglacial stadial and interstadial

    NASA Astrophysics Data System (ADS)

    Hong, Bing; Hong, Yetang; Uchida, Masao; Shibata, Yasuyuki; Cai, Cheng; Peng, Haijun; Zhu, Yongxuan; Wang, Yu; Yuan, Linggui

    2014-08-01

    The phase relationship between the Indian summer monsoon (ISM) and the East Asian summer monsoon (EASM) during the last deglaciation remains controversial. Here, we reconstruct a 15,000-year plant cellulose δ13C proxy record for the ISM from the Yuexi peat bog in southwestern China. The record shows that the ISM abruptly decreases during the Younger Dryas (YD) stadial and abruptly increases during the Bølling-Allerød (BA) interstadial. A comparison of the Yuexi record with other related proxy climate records reveals two types of phenomena. First, the strengths of the two Asian monsoons are inversely related during the YD stadial, i.e., the ISM strength decreases and the EASM increases. During this period, the southern Chinese mainland consisted of a wide arid zone while the northern Chinese mainland was much wetter. The arid zone in southern China resulted from two different types of monsoon processes: the abnormal northward extension of the EASM rain belt, leading to less rainfall in southeast China, or an illusion that the EASM weakened. The other process is a real weakening of the ISM. Second, during the BA interstadial, the strengths of both the ISM and EASM clearly increased. However, the maximum strengths appear to have occurred in the Allerød period. During this period, the entire Chinese mainland, both northern and southern, experienced wet conditions. The abnormal climate pattern of wet in the north and dry in the south during the YD stadial occurs because of the combined effects of the strengthened EASM, intensified westerlies, and weakened ISM, which could be attributed to the response to the abrupt cooling in the high northern latitudes and to the El Niño-like activity in the equatorial Pacific. The widespread wet climate during the BA interstadial may be related to an abrupt increase in the greenhouse gases (GHGs) concentrations in the atmosphere and to the La Niña-like activity in the equatorial Pacific. These results contribute to a better

  6. Mid- to late Holocene climate-driven regime shifts inferred from diatom, ostracod and stable isotope records from Lake Son Kol (Central Tian Shan, Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Schwarz, Anja; Turner, Falko; Lauterbach, Stefan; Plessen, Birgit; Krahn, Kim J.; Glodniok, Sven; Mischke, Steffen; Stebich, Martina; Witt, Roman; Mingram, Jens; Schwalb, Antje

    2017-12-01

    Arid Central Asia represents a key region for understanding climate variability and interactions in the Northern Hemisphere. Patterns and mechanisms of Holocene climate change in arid Central Asia are, however, only partially understood. Multi-proxy data combining diatom, ostracod, sedimentological, geochemical and stable isotope analyses from a ca. 6000-year-old lake sediment core from Son Kol (Central Kyrgyzstan) show distinct and repeated changes in species assemblages. Diatom- and ostracod-inferred conductivity shifts between meso-euhaline and freshwater conditions suggest water balance and regime shifts. Organism-derived data are corroborated by stable isotope, mineralogical and geochemical records, underlining that Son Kol was affected by strong lake level fluctuations of several meters. The δ13Ccarb/δ18Ocarb correlation shows repeated switchovers from a closed to an open lake system. From 6000 to 3800 and 3250 to 1950 cal. yr BP, Son Kol was a closed basin lake with higher conductivities, increased nutrient availability and a water level located below the modern outflow. Son Kol became again a hydrologically open lake at 3800 and 1950 cal. yr BP. Comparisons to other local and regional paleoclimate records indicate that these regime shifts were largely controlled by changing intensity and position of the Westerlies and the Siberian Anticyclone that triggered changes in the amount of winter precipitation. A strong influence of the Westerlies ca. 5000-4400, 3800-3250 and since 1950 cal. yr BP enhanced the amount of precipitation during spring, autumn and winter, whereas cold and dry winters prevailed during phases with a strong Siberian Anticyclone and southward shifted Westerlies at ca. 6000-5000, 4400-3800 and 3250-1950 cal. yr BP. Similarities between variations in winter precipitation at Son Kol and records of the predominant NAO-mode further suggest a teleconnection between wet (dry) winter climate in Central Asia and a positive (negative) NAO

  7. From drought to flooding: understanding the abrupt 2010-11 hydrological annual cycle in the Amazonas River and tributaries

    NASA Astrophysics Data System (ADS)

    Carlo Espinoza, Jhan; Ronchail, Josyane; Loup Guyot, Jean; Junquas, Clementine; Drapeau, Guillaume; Martinez, Jean Michel; Santini, William; Vauchel, Philippe; Lavado, Waldo; Ordoñez, Julio; Espinoza, Raúl

    2012-06-01

    In this work we document and analyze the hydrological annual cycles characterized by a rapid transition between low and high flows in the Amazonas River (Peruvian Amazon) and we show how these events, which may impact vulnerable riverside residents, are related to regional climate variability. Our analysis is based on comprehensive discharge, rainfall and average suspended sediment data sets. Particular attention is paid to the 2010-11 hydrological year, when an unprecedented abrupt transition from the extreme September 2010 drought (8300 m3 s-1) to one of the four highest discharges in April 2011 (49 500 m3 s-1) was recorded at Tamshiyacu (Amazonas River). This unusual transition is also observed in average suspended sediments. Years with a rapid increase in discharge are characterized by negative sea surface temperature anomalies in the central equatorial Pacific during austral summer, corresponding to a La Niña-like mode. It originates a geopotential height wave train over the subtropical South Pacific and southeastern South America, with a negative anomaly along the southern Amazon and the southeastern South Atlantic convergence zone region. As a consequence, the monsoon flux is retained over the Amazon and a strong convergence of humidity occurs in the Peruvian Amazon basin, favoring high rainfall and discharge. These features are also reported during the 2010-11 austral summer, when an intense La Niña event characterized the equatorial Pacific.

  8. Abrupt plate acceleration during rifted margin formation: Cause and effect

    NASA Astrophysics Data System (ADS)

    Brune, Sascha; Williams, Simon; Butterworth, Nathaniel; Müller, Dietmar

    2017-04-01

    Extension rate is known to control key processes during rifted margin formation such as crust-mantle coupling, decompression melting, magmatism, and serpentinisation. Here we build on recent advances in plate tectonic reconstructions by quantifying the extension velocity history of Earth's major rifted margins during the last 240 million years. We find that many successful rifts start with a slow phase of extension followed by rapid acceleration that introduces a fast phase. The transition from slow to fast rifting takes place long before crustal break-up: approximately half of the present day rifted margin area was created during the slow, and the other half during the fast rift phase. We reproduce the rapid transition from slow to fast extension using analytical and numerical modelling with constant force boundary conditions. In these models, rift velocities are not imposed but instead evolve naturally in response to the changing strength of the rift. Our results demonstrate that abrupt plate acceleration during continental rifting is controlled by a rift-intrinsic strength-velocity feedback. The abruptness of rift acceleration is thereby governed by the nonlinearity of lithospheric localization. Realistic brittle and power-law rheologies lead to a speed-up duration between two and ten million years. For successful rifts that generate a new ocean basin, the duration of rift speed-up is notably almost independent of the applied extensional force. Instead, the force controls the duration of the slow phase: higher forces shorten the slow phase while lower forces prolong it. If the force is too low, however, delocalisation processes prevent the rift from reaching the point of speed-up and produce a failed rift, even if the extensional system was active for many million years.

  9. Tryptophan as key biomarker to detect gastrointestinal tract cancer using non-negative biochemical analysis of native fluorescence and Stokes Shift spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Leana; Zhou, Yan; Liu, Cheng-hui; Zhou, Lixin; He, Yong; Pu, Yang; Nguyen, Thien An; Alfano, Robert R.

    2015-03-01

    The objective of this study was to find out the emission spectral fingerprints for discrimination of human colorectal and gastric cancer from normal tissue in vitro by applying native fluorescence. The native fluorescence (NFL) and Stokes shift spectra of seventy-two human cancerous and normal colorectal (colon, rectum) and gastric tissues were analyzed using three selected excitation wavelengths (e.g. 300 nm, 320 nm and 340 nm). Three distinct biomarkers, tryptophan, collagen and reduced nicotinamide adenine dinucleotide hydrate (NADH), were found in the samples of cancerous and normal tissues from eighteen subjects. The spectral profiles of tryptophan exhibited a sharp peak in cancerous colon tissues under a 300 nm excitation when compared with normal tissues. The changes in compositions of tryptophan, collagen, and NADH were found between colon cancer and normal tissues under an excitation of 300 nm by the non-negative basic biochemical component analysis (BBCA) model.

  10. The abrupt changes in the yellowed fibril density in the Linen of Turin

    NASA Astrophysics Data System (ADS)

    Curciarello, F.; De Leo, V.; Fazio, G.; Mandaglio, G.

    2012-03-01

    The present investigation is an attempt to explain the abrupt changes in the yellowed fibril density (or image intensity) values in the dorsal part of the Shroud of Turin body image. The interested areas are the ones at the base of the shoulders and the buttocks. These rapid changes in the body image intensity are not anomalies of the linen manufacture. They can be explained with the original presence of aromas and/or burial ointments.

  11. Difficulty accepting lifestyle limitations after the abrupt onset of end-stage renal disease.

    PubMed

    Wolfson, M; Strong, C; Hamel, K; Cummings-Cosgrove, M; Brown, R

    1995-07-01

    Adjustment to the lifestyle changes imposed by end-stage renal disease is particularly difficult when the onset is abrupt and unheralded. A case of atheroembolism is presented in which living situation, dietary compliance, and family involvement are particularly problematic for the dialysis staff. Discussion by team members focuses on the evolution of a reasonable disposition through diligence and persistence, recognizing the need to compromise medical indications with individual lifestyle and available family support.

  12. Phase shifts in the Fourier spectra of phase gratings and phase grids: an application for one-shot phase-shifting interferometry.

    PubMed

    Toto-Arellano, Noel-Ivan; Rodriguez-Zurita, Gustavo; Meneses-Fabian, Cruz; Vazquez-Castillo, Jose F

    2008-11-10

    Among several techniques, phase shifting interferometry can be implemented with a grating used as a beam divider to attain several interference patterns around each diffraction order. Because each pattern has to show a different phase-shift, a suitable shifting technique must be employed. Phase gratings are attractive to perform the former task due to their higher diffraction efficiencies. But as is very well known, the Fourier coefficients of only-phase gratings are integer order Bessel functions of the first kind. The values of these real-valued functions oscillate around zero, so they can adopt negative values, thereby introducing phase shifts of pi at certain diffraction orders. Because this almost trivial fact seems to have been overlooked in the literature regarding its practical implications, in this communication such phase shifts are stressed in the description of interference patterns obtained with grating interferometers. These patterns are obtained by placing two windows in the object plane of a 4f system with a sinusoidal grating/grid in the Fourier plane. It is shown that the corresponding experimental observations of the fringe modulation, as well as the corresponding phase measurements, are all in agreement with the proposed description. A one-shot phase shifting interferometer is finally proposed taking into account these properties after proper incorporation of modulation of polarization.

  13. Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon

    NASA Astrophysics Data System (ADS)

    Chang, Ping; Zhang, Rong; Hazeleger, Wilco; Wen, Caihong; Wan, Xiuquan; Ji, Link; Haarsma, Reindert J.; Breugem, Wim-Paul; Seidel, Howard

    2008-07-01

    Abrupt changes in the African monsoon can have pronounced socioeconomic impacts on many West African countries. Evidence for both prolonged humid periods and monsoon failures have been identified throughout the late Pleistocene and early Holocene epochs. In particular, drought conditions in West Africa have occurred during periods of reduced North Atlantic thermohaline circulation, such as the Younger Dryas cold event. Here, we use an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon. Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. We therefore suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.

  14. Abrupt Holocene climate change as an important factor for human migration in West Greenland

    PubMed Central

    D’Andrea, William J.; Huang, Yongsong; Fritz, Sherilyn C.; Anderson, N. John

    2011-01-01

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation. PMID:21628586

  15. Postprandial metabolic profiles following meals and snacks eaten during simulated night and day shift work.

    PubMed

    Al-Naimi, S; Hampton, S M; Richard, P; Tzung, C; Morgan, L M

    2004-01-01

    Shift workers are known to have an increased risk of developing cardiovascular disease (CVD) compared with day workers. An important factor contributing to this increased risk could be the increased incidence of postprandial metabolic risk factors for CVD among shift workers, as a consequence of the maladaptation of endogenous circadian rhythms to abrupt changes in shift times. We have previously shown that both simulated and real shift workers showed relatively impaired glucose and lipid tolerance if a single test meal was consumed between 00:00-02:00 h (night shift) compared with 12:00-14:00 h (day shift). The objective of the present study was to extend these observations to compare the cumulative metabolic effect of consecutive snacks/meals, as might normally be consumed throughout a period of night or day shift work. In a randomized crossover study, eight healthy nonobese men (20-33 yrs, BMI 20-25kg/m2) consumed a combination of two meals and a snack on two occasions following a standardized prestudy meal, simulating night and day shift working (total energy 2500 kcal: 40% fat, 50% carbohydrate, 10% protein). Meals were consumed at 01:00/ 13:00 h and 07:00/19:00h, and the snack at 04:00/16:00 h. Blood was taken after an overnight fast, and for 8 h following the first meal on each occasion, for the measurement of glucose, insulin, triacylglycerol (TAG), and nonesterified fatty acids (NEFA). RM-ANOVA (factors time and shift) showed a significant effect of shift for plasma TAG, with higher levels on simulated night compared to day shift (p < 0.05). There was a trend toward an effect of shift for plasma glucose, with higher plasma glucose at night (p = 0.08), and there was a time-shift interaction for plasma insulin levels (p < 0.01). NEFA levels were unaffected by shift. Inspection of the area under the plasma response curve (AUC) following each meal and snack revealed that the differences in lipid tolerance occurred throughout the study, with greatest

  16. Controlling abruptly autofocusing vortex beams to mitigate crosstalk and vortex splitting in free-space optical communication.

    PubMed

    Yan, Xu; Guo, Lixin; Cheng, Mingjian; Li, Jiangting

    2018-05-14

    Orbital angular momentum (OAM) mode crosstalk induced by atmospheric turbulence is a challenging phenomenon commonly occurring in OAM-based free-space optical (FSO) communication. Recent advances have facilitated new practicable methods using abruptly autofocusing light beams for weakening the turbulence effect on the FSO link. In this work, we show that a circular phase-locked Airy vortex beam array (AVBA) with sufficient elements has the inherent ability to form an abruptly autofocusing light beam carrying OAM, and its focusing properties can be controlled on demand by adjusting the topological charge values and locations of these vortices embedded in the array elements. The performance of a tailored Airy vortex beam array (TAVBA) through atmospheric turbulence is numerically studied. In a comparison with the ring Airy vortex beam (RAVB), the results indicate that TAVBA can be a superior light source for effectively reducing the intermodal crosstalk and vortex splitting, thus leading to improvement in the FSO system performance.

  17. Shift Work and Endocrine Disorders

    PubMed Central

    Ulhôa, M. A.; Marqueze, E. C.; Burgos, L. G. A.; Moreno, C. R. C.

    2015-01-01

    The objective of this review was to investigate the impact of shift and night work on metabolic processes and the role of alterations in the sleep-wake cycle and feeding times and environmental changes in the occurrence of metabolic disorders. The literature review was performed by searching three electronic databases for relevant studies published in the last 10 years. The methodological quality of each study was assessed, and best-evidence synthesis was applied to draw conclusions. The literature has shown changes in concentrations of melatonin, cortisol, ghrelin, and leptin among shift workers. Melatonin has been implicated for its role in the synthesis and action of insulin. The action of this hormone also regulates the expression of transporter glucose type 4 or triggers phosphorylation of the insulin receptor. Therefore, a reduction in melatonin can be associated with an increase in insulin resistance and a propensity for the development of diabetes. Moreover, shift work can negatively affect sleep and contribute to sedentarism, unhealthy eating habits, and stress. Recent studies on metabolic processes have increasingly revealed their complexity. Physiological changes induced in workers who invert their activity-rest cycle to fulfill work hours include disruptions in metabolic processes. PMID:25892993

  18. Effects of Early, Abrupt Weaning on HIV-free Survival of Children in Zambia

    PubMed Central

    Kuhn, Louise; Aldrovandi, Grace M.; Sinkala, Moses; Kankasa, Chipepo; Semrau, Katherine; Mwiya, Mwiya; Kasonde, Prisca; Scott, Nancy; Vwalika, Cheswa; Walter, Jan; Bulterys, Marc; Tsai, Wei-Yann; Thea, Donald M.

    2008-01-01

    Background In low-resource settings, many programs recommend that women who are infected with the human immunodeficiency virus (HIV) stop breast-feeding early. We conducted a randomized trial to evaluate whether abrupt weaning at 4 months as compared with the standard practice has a net benefit for HIV-free survival of children. Methods We enrolled 958 HIV-infected women and their infants in Lusaka, Zambia. All the women planned to breast-feed exclusively to 4 months; 481 were randomly assigned to a counseling program that encouraged abrupt weaning at 4 months, and 477 to a program that encouraged continued breast-feeding for as long as the women chose. The primary outcome was either HIV infection or death of the child by 24 months. Results In the intervention group, 69.0% of the mothers stopped breast-feeding at 5 months or earlier; 68.8% of these women reported the completion of weaning in less than 2 days. In the control group, the median duration of breast-feeding was 16 months. In the overall cohort, there was no significant difference between the groups in the rate of HIV-free survival among the children; 68.4% and 64.0% survived to 24 months without HIV infection in the intervention and control groups, respectively (P = 0.13). Among infants who were still being breast-fed and were not infected with HIV at 4 months, there was no significant difference between the groups in HIV-free survival at 24 months (83.9% and 80.7% in the intervention and control groups, respectively; P = 0.27). Children who were infected with HIV by 4 months had a higher mortality by 24 months if they had been assigned to the intervention group than if they had been assigned to the control group (73.6% vs. 54.8%, P = 0.007). Conclusions Early, abrupt cessation of breast-feeding by HIV-infected women in a low-resource setting, such as Lusaka, Zambia, does not improve the rate of HIV-free survival among children born to HIV-infected mothers and is harmful to HIV-infected infants

  19. Cumulative exposure to shift work and sickness absence: associations in a five-year historic cohort.

    PubMed

    van Drongelen, Alwin; Boot, Cécile R L; Hlobil, Hynek; van der Beek, Allard J; Smid, Tjabe

    2017-01-11

    Exposure to shift work has been associated with negative health consequences, although the association between shift work and sickness absence remains unclear. The aim of this study is to investigate associations between cumulative exposure to shift work and sickness absence among ground staff employees of an airline company. This study used data from the MORE (Monitoring Occupational Health Risks in Employees) cohort, which is a 5-year historic cohort. The population of the present study consisted of 7562 ground staff employees. For each employee, work schedules and sickness absence days between 2005 and 2009 were obtained from company records. For the exposure to different shift schedule types and to the cumulative number of night shifts, the association with long-term sickness absence (>7 consecutive sickness absence days) and the number of sickness absence episodes during 2009, was calculated using logistic and Poisson regression analyses. Socio-demographic variables, work-related variables, job classification variables, and previous sickness absence days were regarded as confounders. After adjusting for previous sickness absence and job classification variables, only the group of employees that switched into working in a three-shift schedule, showed a significantly increased risk for long-term sickness absence (OR = 1.31, 95%CI 1.02-1.69). Night shift exposure was not significantly associated with long-term sickness absence. Exposure to shift work was negatively associated with more sickness absence episodes. Employees who were exposed to more than 46 night shifts also showed a lower risk for more sickness absence episodes. Subgroup analyses showed that single employees and employees without children had an increased risk for long-term sickness absence when exposed to a three-shift schedule, and when they had changed between shift schedule types. Cumulative exposure to shift work proved to be negatively associated with more sickness absence episodes, and

  20. Abrupt Decline in the Arctic Winter Sea Ice Cover

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.

    2007-01-01

    Maximum ice extents in the Arctic in 2005 and 2006 have been observed to be significantly lower (by about 6%) than the average of those of previous years starting in 1979. Since the winter maxima had been relatively stable with the trend being only about -1.5% per decade (compared to about -10% per decade for the perennial ice area), this is a significant development since signals from greenhouse warming are expected to be most prominent in winter. Negative ice anomalies are shown to be dominant in 2005 and 2006 especially in the Arctic basin and correlated with winds and surface temperature anomalies during the same period. Progressively increasing winter temperatures in the central Arctic starting in 1997 is observed with significantly higher rates of increase in 2005 and 2006. The Atlantic Oscillation (AO) indices correlate weakly with the sea ice and surface temperature anomaly data but may explain the recent shift in the perennial ice cover towards the western region. Results suggest that the trend in winter ice is finally in the process of catching up with that of the summer ice cover.

  1. [Night work and shift work - effects on the health of workers].

    PubMed

    Stryjewski, Piotr J; Kuczaj, Agnieszka; Domal-Kwiatkowska, Dorota; Mazurek, Urszula; Nowalany-Kozielska, Ewa

    Number of shift workers increases in developed as well as in developing countries every year and equals 15- 20% of total amount of working people in Europe, 20% of total count of workers in United States of America, 6-32% in Asian countries and 8.1% workers in Poland. This type of employment is connected with such sectors of economy as medical care, industry, mining, transportation, communication and hospitality. The literature review analyses health effects of shift work and night work in the area of gastroenterology, circulatory system, oncologic diseases, neuropsychiatric and sleep disorders. In summary shift and night work have negative impact on human health. Further investigations analyzing impact of shift and night work are needed.

  2. Coupling of equatorial Atlantic surface stratification to glacial shifts in the tropical rainbelt.

    PubMed

    Portilho-Ramos, R C; Chiessi, C M; Zhang, Y; Mulitza, S; Kucera, M; Siccha, M; Prange, M; Paul, A

    2017-05-08

    The modern state of the Atlantic meridional overturning circulation promotes a northerly maximum of tropical rainfall associated with the Intertropical Convergence Zone (ITCZ). For continental regions, abrupt millennial-scale meridional shifts of this rainbelt are well documented, but the behavior of its oceanic counterpart is unclear due the lack of a robust proxy and high temporal resolution records. Here we show that the Atlantic ITCZ leaves a distinct signature in planktonic foraminifera assemblages. We applied this proxy to investigate the history of the Atlantic ITCZ for the last 30,000 years based on two high temporal resolution records from the western Atlantic Ocean. Our reconstruction indicates that the shallowest mixed layer associated with the Atlantic ITCZ unambiguously shifted meridionally in response to changes in the strength of the Atlantic meridional overturning with a southward displacement during Heinrich Stadials 2-1 and the Younger Dryas. We conclude that the Atlantic ITCZ was located at ca. 1°S (ca. 5° to the south of its modern annual mean position) during Heinrich Stadial 1. This supports a previous hypothesis, which postulates a southern hemisphere position of the oceanic ITCZ during climatic states with substantially reduced or absent cross-equatorial oceanic meridional heat transport.

  3. Abrupt Increases in Amazonian Tree Mortality Due to Drought-Fire Interactions

    NASA Technical Reports Server (NTRS)

    Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silverio, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nobrega, Caroline C.; hide

    2014-01-01

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, longterm experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW x m(exp -1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with less than 1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

  4. Abrupt increases in Amazonian tree mortality due to drought-fire interactions.

    PubMed

    Brando, Paulo Monteiro; Balch, Jennifer K; Nepstad, Daniel C; Morton, Douglas C; Putz, Francis E; Coe, Michael T; Silvério, Divino; Macedo, Marcia N; Davidson, Eric A; Nóbrega, Caroline C; Alencar, Ane; Soares-Filho, Britaldo S

    2014-04-29

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW ⋅ m(-1)). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change.

  5. Abrupt increases in Amazonian tree mortality due to drought–fire interactions

    PubMed Central

    Brando, Paulo Monteiro; Balch, Jennifer K.; Nepstad, Daniel C.; Morton, Douglas C.; Putz, Francis E.; Coe, Michael T.; Silvério, Divino; Macedo, Marcia N.; Davidson, Eric A.; Nóbrega, Caroline C.; Alencar, Ane; Soares-Filho, Britaldo S.

    2014-01-01

    Interactions between climate and land-use change may drive widespread degradation of Amazonian forests. High-intensity fires associated with extreme weather events could accelerate this degradation by abruptly increasing tree mortality, but this process remains poorly understood. Here we present, to our knowledge, the first field-based evidence of a tipping point in Amazon forests due to altered fire regimes. Based on results of a large-scale, long-term experiment with annual and triennial burn regimes (B1yr and B3yr, respectively) in the Amazon, we found abrupt increases in fire-induced tree mortality (226 and 462%) during a severe drought event, when fuel loads and air temperatures were substantially higher and relative humidity was lower than long-term averages. This threshold mortality response had a cascading effect, causing sharp declines in canopy cover (23 and 31%) and aboveground live biomass (12 and 30%) and favoring widespread invasion by flammable grasses across the forest edge area (80 and 63%), where fires were most intense (e.g., 220 and 820 kW⋅m−1). During the droughts of 2007 and 2010, regional forest fires burned 12 and 5% of southeastern Amazon forests, respectively, compared with <1% in nondrought years. These results show that a few extreme drought events, coupled with forest fragmentation and anthropogenic ignition sources, are already causing widespread fire-induced tree mortality and forest degradation across southeastern Amazon forests. Future projections of vegetation responses to climate change across drier portions of the Amazon require more than simulation of global climate forcing alone and must also include interactions of extreme weather events, fire, and land-use change. PMID:24733937

  6. Ontogenetic shifts of heart position in snakes.

    PubMed

    Lillywhite, Harvey B; Lillywhite, Steven M

    2017-08-01

    Heart position relative to total body length (TL) varies among snakes, with anterior hearts in arboreal species and more centrally located hearts in aquatic or ground-dwelling species. Anterior hearts decrease the cardiac work associated with cranial blood flow and minimize drops in cranial pressure and flow during head-up climbing. Here, we investigate whether heart position shifts intraspecifically during ontogenetic increases in TL. Insular Florida cottonmouth snakes, Agkistrodon conanti, are entirely ground-dwelling and have a mean heart position that is 33.32% TL from the head. In contrast, arboreal rat snakes, Pantherophis obsoleta, of similar lengths have a mean heart position that is 17.35% TL from the head. In both species, relative heart position shifts craniad during ontogeny, with negative slopes = -.035 and -.021% TL/cm TL in Agkistrodon and Pantherophis, respectively. Using a large morphometric data set available for Agkistrodon (N = 192 individuals, 23-140 cm TL), we demonstrate there is an anterior ontogenetic shift of the heart position within the trunk (= 4.56% trunk length from base of head to cloacal vent), independent of head and tail allometry which are both negative. However, in longer snakes > 100 cm, the heart position reverses and shifts caudally in longer Agkistrodon but continues toward the head in longer individuals of Pantherophis. Examination of data sets for two independent lineages of fully marine snakes (Acrochordus granulatus and Hydrophis platurus), which do not naturally experience postural gravity stress, demonstrate both ontogenetic patterns for heart position that are seen in the terrestrial snakes. The anterior migration of the heart is greater in the terrestrial species, even if TL is standardized to that of the longer P. obsoleta, and compensates for about 5 mmHg gravitational pressure head if they are fully upright. © 2017 Wiley Periodicals, Inc.

  7. The slightly-enriched spectral shift control reactor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martin, W.R.; Lee, J.C.; Larsen, E.W.

    1991-11-01

    An advanced converter reactor design utilizing mechanical spectral shift control rods in a conventional pressurized water reactor configuration is under investigation. The design is based on the principle that a harder spectrum during the early part of the fuel cycle will result in large neutron captures in fertile {sup 238}U, which can then be burned in situ in a softer spectrum later in the cycle. Preliminary design calculations performed during FY 89 showed that the slightly-enriched spectral shift reactor design offers the benefit of substantially increased fuel resource utilization with the proven safety characteristics of the pressurized water reactor technologymore » retained. Optimization of the fuel design and development of fuel management strategies were carried out in FY 90, along with effort to develop and validate neutronic methodology for tight-lattice configurations with hard spectra. During FY 91, the final year of the grant, the final Slightly-Enriched Spectral Shift Reactor (SESSR) design was determined, and reference design analyses were performed for the assemblies as well as the global core configuration, both at the beginning of cycle (BOC) and with depletion. The final SESSR design results in approximately a 20% increase in the utilization of uranium resources, based on equilibrium fuel cycle analyses. Acceptable pin power peaking is obtained with the final core design, with assembly peaking factors equal to less than 1.04 for spectral shift control rods both inserted and withdrawn, and global peaking factors at BOC predicted to be 1.4. In addition, a negative Moderation Temperature Coefficient (MTC) is maintained for BOC, which is difficult to achieve with conventional advanced converter designs based on a closed fuel cycle. The SESSR design avoids the need for burnable poison absorber, although they could be added if desired to increase the cycle length while maintaining a negative MTC.« less

  8. The ability of computed tomography to diagnose placental abruption in the trauma patient.

    PubMed

    Kopelman, Tammy R; Berardoni, Nicole E; Manriquez, Maria; Gridley, Daniel; Vail, Sydney J; Pieri, Paola G; O'Neill; Pressman, Melissa A

    2013-01-01

    Fetal demise following trauma remains a devastating complication largely owing to placental injury and abruption. Our objective was to determine if abdominopelvic computed tomographic (CT) imaging can assess for placental abruption (PA) when obtained to exclude associated maternal injuries. Retrospective review of pregnant trauma patients of 20-week gestation or longer presenting to a trauma center during a 7-year period who underwent CT imaging as part of their initial evaluation. Radiographic images were reviewed by a radiologist for evidence of PA and classified based on percentage of visualized placental enhancement. Blinded to CT results, charts were reviewed by an obstetrician for clinical evidence of PA and classified as strongly positive, possibly positive, or no evidence. A total of 176 patients met inclusion criteria. CT imaging revealed evidence of PA in 61 patients (35%). As the percentage of placental enhancement decreased, patients were more likely to have strong clinical manifestations of PA, reaching statistical significance when enhancement was less than 50%. CT imaging evidence of PA was apparent in all patients who required delivery for nonassuring fetal heart tones. CT imaging evaluation of the placenta can accurately identify PA and therefore can help stratify patients at risk for fetal complications. The likelihood of requiring delivery increased as placental enhancement declined to less than 25%. Diagnostic study, level III.

  9. A Static Color Discontinuity Can Capture Spatial Attention when the Target Is an Abrupt-Onset Singleton

    ERIC Educational Resources Information Center

    Burnham, Bryan R.; Neely, James H.

    2008-01-01

    C. L. Folk, R. W. Remington, and J. C. Johnston's (1992) contingent involuntary orienting hypothesis states that a salient visual feature will involuntarily capture attention only when the observer's attentional set includes similar features. In four experiments, when the target's relevant feature was its being an abruptly onset singleton,…

  10. The characterization of GH shifts of surface plasmon resonance in a waveguide using the FDTD method.

    PubMed

    Oh, Geum-Yoon; Kim, Doo Gun; Choi, Young-Wan

    2009-11-09

    We have explicated the Goos-Hänchen (GH) shift in a mum-order Kretchmann-Raether configuration embedded in an optical waveguide structure by using the finite-difference time-domain method. For optical waveguide-type surface plasmon resonance (SPR) devices, the precise derivation of the GH shift has become critical. Artmann's equation, which is accurate enough for bulk optics, is difficult to apply to waveguide-type SPR devices. This is because Artmann's equation, based on the differentiation of the phase shift, is inaccurate at the critical and resonance angles where drastic phase changes occur. In this study, we accurately identified both the positive and the negative GH shifts around the incidence angle of resonance. In a waveguide-type Kretchmann-Raether configuration with an Au thin film of 50 nm, positive and negative lateral shifts of -0.75 and + 1.0 microm are obtained on the SPR with the incident angles of 44.4 degrees and 47.5 degrees, respectively, at a wavelength of 632.8 nm.

  11. Columnar shifts as symmetry-breaking degrees of freedom in molecular perovskites

    NASA Astrophysics Data System (ADS)

    Boström, Hanna L. B.; Hill, Joshua A.; Goodwin, Andrew L.

    We introduce columnar shifts---collective rigid-body translations---as a structural degree of freedom relevant to the phase behaviour of molecular perovskites ABX$_{\\textrm3}$ (X = molecular anion). Like the well-known octahedral tilts of conventional perovskites, shifts also preserve the octahedral coordination geometry of the B-site cation in molecular perovskites, and so are predisposed to influencing the low-energy dynamics and displacive phase transitions of these topical systems. We present a qualitative overview of the interplay between shift activation and crystal symmetry breaking, and introduce a generalised terminology to allow characterisation of simple shift distortions, drawing analogy to the "Glazer notation" for octahedral tilts. We apply our approach to the interpretation of a representative selection of azide and formate perovskite structures, and discuss the implications for functional exploitation of shift degrees of freedom in negative thermal expansion materials and hybrid ferroelectrics.

  12. Abrupt drainage cycles of the Fennoscandian Ice Sheet

    PubMed Central

    Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

    2013-01-01

    Continental ice sheets are a key component of the Earth’s climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate–lake–FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas. PMID:23569264

  13. Modeling geologically abrupt climate changes in the Miocene

    NASA Astrophysics Data System (ADS)

    Haupt, B. J.; Seidov, D.

    2010-12-01

    The gradual cooling of the Cenozoic, including the Miocene epoch, was punctuated by many geologically abrupt warming and cooling episodes - strong deviations from the cooling trend with time span of ten to hundred thousands of years. Our working hypothesis is that some of those warming episodes at least partially might have been caused by dynamics of the emerging Antarctic Ice Sheet, which, in turn, might have caused strong changes of sea surface salinity in the Miocene Southern Ocean. Feasibility of this hypothesis is explored in a series of coupled ocean-atmosphere computer experiments. The results suggest that relatively small and geologically short-lived changes in freshwater balance in the Southern Ocean could have significantly contributed to at least two prominent warming episodes in the Miocene. Importantly, the experiments also suggest that the Southern Ocean was more sensitive to the salinity changes in the Miocene than today, which can attributed to the opening of the Central American Isthmus as a major difference between the Miocene and the present-day ocean-sea geometry.

  14. Placental abruption: etiopathogenic aspects, diagnostic and therapeutic implications.

    PubMed

    Brăila, Anca Daniela; Gluhovschi, Adrian; Neacşu, Adrian; Lungulescu, Cristian Virgil; Brăila, Mihai; Vîrcan, Elena Luminiţa; Cotoi, Bogdan Virgil; Gogănău, Alexandru Marian

    2018-01-01

    The severe form of retroplacental hematoma is a serious accident in the second stage of pregnancy and at birth with frightening for the mother and fetus that often lead to death. The pathological mechanism presumes conditions for a "special ground" capital for the "efficiency" of the acute intradecidual vascular accident with the rupture of the uterus-placental arterioles. The complete clinical picture of this severe form of retroplacental hematoma - the placental abruption, observed and mentioned by the classics (vascular drama of Couvelaire) consists of five syndromes, 18 signs and symptoms, four paradoxes, phenomena not fully met in the other forms of retroplacental hematoma (minor and intermediate). The rate of incidence of retroplacental hematoma is in between 0.13-1.38% and depends on the environment, on the socio-economic and medical conditions, on the "obstetric education" and associated pathology. Our study aims at re-evaluating the clinico-paraclinical phenomenon imposed by the dramatism of the phenomenon of in utero placental apoplexy, the impact on neonatal mortality and on the functional prognosis from the point of view of surgical climax.

  15. Abrupt drainage cycles of the Fennoscandian Ice Sheet.

    PubMed

    Soulet, Guillaume; Ménot, Guillemette; Bayon, Germain; Rostek, Frauke; Ponzevera, Emmanuel; Toucanne, Samuel; Lericolais, Gilles; Bard, Edouard

    2013-04-23

    Continental ice sheets are a key component of the Earth's climate system, but their internal dynamics need to be further studied. Since the last deglaciation, the northern Eurasian Fennoscandian Ice Sheet (FIS) has been connected to the Black Sea (BS) watershed, making this basin a suitable location to investigate former ice-sheet dynamics. Here, from a core retrieved in the BS, we combine the use of neodymium isotopes, high-resolution elemental analysis, and biomarkers to trace changes in sediment provenance and river runoff. We reveal cyclic releases of meltwater originating from Lake Disna, a proglacial lake linked to the FIS during Heinrich Stadial 1. Regional interactions within the climate-lake-FIS system, linked to changes in the availability of subglacial water, led to abrupt drainage cycles of the FIS into the BS watershed. This phenomenon raised the BS water level by ∼100 m until the sill of the Bosphorus Strait was reached, flooding the vast northwestern BS shelf and deeply affecting the hydrology and circulation of the BS and, probably, of the Marmara and Aegean Seas.

  16. Prenatal vitamin C and E supplementation in smokers is associated with reduced placental abruption and preterm birth: a secondary analysis.

    PubMed

    Abramovici, A; Gandley, R E; Clifton, R G; Leveno, K J; Myatt, L; Wapner, R J; Thorp, J M; Mercer, B M; Peaceman, A M; Samuels, P; Sciscione, A; Harper, M; Saade, G; Sorokin, Y

    2015-12-01

    Smoking and pre-eclampsia (PE) are associated with increases in preterm birth, placental abruption and low birthweight. We evaluated the relationship between prenatal vitamin C and E (C/E) supplementation and perinatal outcomes by maternal self-reported smoking status focusing on outcomes known to be impacted by maternal smoking. A secondary analysis of a multi-centre trial of vitamin C/E supplementation starting at 9-16 weeks in low-risk nulliparous women with singleton gestations. We examined the effect of vitamin C/E by smoking status at randomisation using the Breslow-Day test for interaction. The trial's primary outcomes were PE and a composite outcome of pregnancy-associated hypertension (PAH) with serious adverse outcomes. Perinatal outcomes included preterm birth and abruption. There were no differences in baseline characteristics within subgroups (smokers versus nonsmokers) by vitamin supplementation status. The effect of prenatal vitamin C/E on the risk of PE (P = 0.66) or PAH composite outcome (P = 0.86) did not differ by smoking status. Vitamin C/E was protective for placental abruption in smokers (relative risk [RR] 0.09; 95% CI 0.00-0.87], but not in nonsmokers (RR 0.92; 95% CI 0.52-1.62) (P = 0.01), and for preterm birth in smokers (RR 0.76; 95% CI 0.58-0.99) but not in nonsmokers (RR 1.03; 95% CI 0.90-1.17) (P = 0.046). In this cohort of women, smoking was not associated with a reduction in PE or the composite outcome of PAH. Vitamin C/E supplementation appears to be associated with a reduction in placental abruption and preterm birth among smokers. © 2014 Royal College of Obstetricians and Gynaecologists.

  17. Abrupt Atmospheric Methane Increases Associated With Hudson Strait Heinrich Events

    NASA Astrophysics Data System (ADS)

    Rhodes, R.; Brook, E.; Chiang, J. C. H.; Blunier, T.; Maselli, O. J.; McConnell, J. R.; Romanini, D.; Severinghaus, J. P.

    2015-12-01

    The drivers of abrupt climate change during the Last Glacial Period are not well understood. While Dansgaard-Oeschger (DO) cycles are thought to be linked to variations in the strength of the Atlantic Meridional Ocean Circulation (AMOC), it is not clear how or if Heinrich Events—extensive influxes of icebergs into the North Atlantic Ocean that impacted global climate and biogeochemistry—are related. An enduring problem is the difficultly in dating iceberg rafted debris deposits that typically lack foraminifera. Here we present an ultra-high resolution record of methane from the West Antarctic Ice Sheet Divide ice core at unprecedented, continuous temporal resolution from 67.2-9.8 ka BP, which we propose constrains the timing of Heinrich events. Our methane record essentially mirrors Greenland ice core stable isotope variability across D-O events, except during Heinrich stadials 1, 2, 4 and 5. Partway through these stadials only, methane increases abruptly and rapidly, as at the onset of a D-O event but Greenland temperature exhibits no equivalent response. Speleothem records exhibit signatures of drought in the Northern extra-tropics and intensified monsoonal activity over South America at these times. We use a simple heuristic model to propose that cold air temperatures and extensive sea ice in the North, resulting from Heinrich events, caused extreme reorganization of tropical hydroclimate. This involved curtailment of the seasonal northerly migration of tropical rain belts, leading to intensification of rainfall over Southern Hemisphere tropical wetlands, thus allowing production of excess methane relative to a 'normal' Greenland stadial. We note that this mechanism can operate if AMOC is already in a slowed state when a Heinrich event occurs, as paleo-evidence suggests it was. Heinrich events and associated sea ice cover would therefore act to prolong the duration of this AMOC state. Our findings place the big four Heinrich events of Hudson Strait origin

  18. Abrupt drying events in the Caribbean related to large Laurentide meltwater pulses during the glacial-to-Holocene transition

    NASA Astrophysics Data System (ADS)

    Vieten, Rolf; Warken, Sophie; Winter, Amos; Scholz, Denis; Black, David; Zanchettin, Davide; Miller, Thomas E.

    2017-04-01

    At the end of the last deglaciation North Atlantic meltwater pulses from the retreating Laurentide ice sheet triggered a chain of oceanic and atmospheric responses including temporary slow-down of the thermohaline circulation and hemispheric-scale alterations of the atmospheric circulation. The 8.2 ka event (occurring about 8.2 ka BP) is the most pronounced meltwater pulse during the Holocene and serves as an analogue to understand how North Atlantic fresh water influxes can affect the ocean-atmosphere coupled system on a basin, hemispheric or global scale. This event left strong regional climate imprints, such as abrupt cooling reconstructed over the North Atlantic and Europe lasting 100 to 150 years and drying in the northern hemispheric tropics. However, there is a lack of high resolution proxies to learn about the event's temporal structure especially in the tropics. We present geochemical evidence from a stalagmite indicating sudden climate fluctuations towards drier conditions in the northeastern Caribbean possibly related to rapid cooling in the high northern latitudes and a southward shift of the Inter-Tropical Convergence Zone (ITCZ). Stalagmite PR-PA-1 was collected in Palco cave, Puerto Rico, and it is a remarkable record of the 8.2 ka event because 15 MC-ICPMS 230Th/U-dates produce a precise chronology of its Holocene period growing solely between 9.0 ka BP to 7.5 ka BP. Based on 240 trace element and stable isotope ratio measurement we reconstructed hydrological changes with sub-decadal resolution. Our proxy data show large and rapid climate variations before 8.0 ka. Pronounced peaks in the Mg/Ca and δ13C records indicate three major events of abrupt drying. These fluctuations towards drier conditions took place in less than 10 years and the climate remained drier than the natural range for 10 to 20 years, before it returned to pre-fluctuation conditions again. Our observations confirm previous studies suggesting that repeated meltwater pulses

  19. Anomalous positive flatband voltage shifts in metal gate stacks containing rare-earth oxide capping layers

    NASA Astrophysics Data System (ADS)

    Caraveo-Frescas, J. A.; Hedhili, M. N.; Wang, H.; Schwingenschlögl, U.; Alshareef, H. N.

    2012-03-01

    It is shown that the well-known negative flatband voltage (VFB) shift, induced by rare-earth oxide capping in metal gate stacks, can be completely reversed in the absence of the silicon overlayer. Using TaN metal gates and Gd2O3-doped dielectric, we measure a ˜350 mV negative shift with the Si overlayer present and a ˜110 mV positive shift with the Si overlayer removed. This effect is correlated to a positive change in the average electrostatic potential at the TaN/dielectric interface which originates from an interfacial dipole. The dipole is created by the replacement of interfacial oxygen atoms in the HfO2 lattice with nitrogen atoms from TaN.

  20. Integrated ecological and chemical food web accumulation modeling explains PAH temporal trends during regime shifts in a shallow lake.

    PubMed

    Kong, Xiangzhen; He, Wei; Qin, Ning; Liu, Wenxiu; Yang, Bin; Yang, Chen; Xu, Fuliu; Mooij, Wolf M; Koelmans, Albert A

    2017-08-01

    Shallow lakes can switch suddenly from a turbid situation with high concentrations of phytoplankton and other suspended solids to a vegetated state with clear water, and vice versa. These alternative stable states may have a substantial impact on the fate of hydrophobic organic compounds (HOCs). Models that are fit to simulate impacts from these complex interactions are scarce. We developed a contaminant fate model which is linked to an ecosystem model (PCLake) for shallow lakes. This integrated model was successful in simulating long-term dynamics (1953-2012) of representative polycyclic aromatic hydrocarbons (PAHs) in the main biotic and abiotic components in a large shallow lake (Chaohu in China), which has undergone regime shifts in this period. Historical records from sediment cores were used to evaluate the model. The model revealed that regime shifts in shallow lakes had a strong impact on the fate of less hydrophobic compounds due to the large storage capacity of macrophytes, which accumulated up to 55.6% of phenanthrene in the clear state. The abrupt disappearance of macrophytes after the regime shift resulted in a sudden change in phenanthrene distribution, as the sediment became the major sink. For more hydrophobic compounds such as benzo(a)pyrene, the modeled impact of the regime shift was negligible for the whole environment, yet large for biotic compartments. This study is the first to provide a full mechanistic analysis of the impact of regime shifts on the fate of PAHs in a real lake ecosystem. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Abrupt Strategy Change Underlies Gradual Performance Change: Bayesian Hierarchical Models of Component and Aggregate Strategy Use

    ERIC Educational Resources Information Center

    Wynton, Sarah K. A.; Anglim, Jeromy

    2017-01-01

    While researchers have often sought to understand the learning curve in terms of multiple component processes, few studies have measured and mathematically modeled these processes on a complex task. In particular, there remains a need to reconcile how abrupt changes in strategy use can co-occur with gradual changes in task completion time. Thus,…

  2. Accurate evaluation of fast threshold voltage shift for SiC MOS devices under various gate bias stress conditions

    NASA Astrophysics Data System (ADS)

    Sometani, Mitsuru; Okamoto, Mitsuo; Hatakeyama, Tetsuo; Iwahashi, Yohei; Hayashi, Mariko; Okamoto, Dai; Yano, Hiroshi; Harada, Shinsuke; Yonezawa, Yoshiyuki; Okumura, Hajime

    2018-04-01

    We investigated methods of measuring the threshold voltage (V th) shift of 4H-silicon carbide (SiC) metal–oxide–semiconductor field-effect transistors (MOSFETs) under positive DC, negative DC, and AC gate bias stresses. A fast measurement method for V th shift under both positive and negative DC stresses revealed the existence of an extremely large V th shift in the short-stress-time region. We then examined the effect of fast V th shifts on drain current (I d) changes within a pulse under AC operation. The fast V th shifts were suppressed by nitridation. However, the I d change within one pulse occurred even in commercially available SiC MOSFETs. The correlation between I d changes within one pulse and V th shifts measured by a conventional method is weak. Thus, a fast and in situ measurement method is indispensable for the accurate evaluation of I d changes under AC operation.

  3. Modern Prejudice and Same-Sex Parenting: Shifting Judgments in Positive and Negative Parenting Situations

    PubMed Central

    MASSEY, SEAN G.; MERRIWETHER, ANN M.; GARCIA, JUSTIN R.

    2013-01-01

    The current study compares the effects of traditional and modern anti-homosexual prejudice on evaluations of parenting practices of same-sex and opposite-sex couples. Undergraduate university student participants (N = 436) completed measures of traditional and modern anti-homosexual prejudice and responded to a vignette describing a restaurant scene in which parents react to their child’s undesirable behavior. The parents’ sexual orientation and the quality of their parenting (positive or negative quality) were varied randomly. It was predicted that participants who score higher in modern prejudice would rate the negative parenting behaviors of same-sex parents more negatively than similar behaviors in opposite-sex parents. It was also predicted that this modern prejudice effect would be most pronounced for male participants. Both hypotheses were supported. PMID:23667347

  4. CLASS Shifts in Modeling Instruction

    NASA Astrophysics Data System (ADS)

    Brewe, Eric; Kramer, Laird; O'Brien, George

    2008-10-01

    Among the most surprising findings in Physics Education Research is the lack of positive results on attitudinal measures, such as Colorado Learning Attitudes about Science Survey (CLASS) and Maryland Physics Expectations Survey (MPEX). The uniformity with which physics teaching manages to negatively shift attitudes toward physics learning is striking. Strategies which have been shown to improve learning, such as interactive engagement and studio format classes, provide more authentic science experiences for students, yet do not produce positive attitudinal results. Florida International University's Physics Education Research Group has implemented Modeling Instruction in University Physics classes. Using the CLASS as a pre/post measure has shown attitudinal improvements through both semesters of the introductory physics sequence. In this paper, we report positive shifts on the CLASS in two sections of Modeling Physics, one in Mechanics (N=30) and one in Electricity and Magnetism, (N=31) and examine how these results reflect on Modeling Instruction.

  5. Auditory Attention and Comprehension During a Simulated Night Shift: Effects of Task Characteristics.

    PubMed

    Pilcher, June J; Jennings, Kristen S; Phillips, Ginger E; McCubbin, James A

    2016-11-01

    The current study investigated performance on a dual auditory task during a simulated night shift. Night shifts and sleep deprivation negatively affect performance on vigilance-based tasks, but less is known about the effects on complex tasks. Because language processing is necessary for successful work performance, it is important to understand how it is affected by night work and sleep deprivation. Sixty-two participants completed a simulated night shift resulting in 28 hr of total sleep deprivation. Performance on a vigilance task and a dual auditory language task was examined across four testing sessions. The results indicate that working at night negatively impacts vigilance, auditory attention, and comprehension. The effects on the auditory task varied based on the content of the auditory material. When the material was interesting and easy, the participants performed better. Night work had a greater negative effect when the auditory material was less interesting and more difficult. These findings support research that vigilance decreases during the night. The results suggest that auditory comprehension suffers when individuals are required to work at night. Maintaining attention and controlling effort especially on passages that are less interesting or more difficult could improve performance during night shifts. The results from the current study apply to many work environments where decision making is necessary in response to complex auditory information. Better predicting the effects of night work on language processing is important for developing improved means of coping with shiftwork. © 2016, Human Factors and Ergonomics Society.

  6. [Sleep disorders among physicians on shift work].

    PubMed

    Schlafer, O; Wenzel, V; Högl, B

    2014-11-01

    Sleep disorders in physicians who perform shift work can result in increased risks of health problems that negatively impact performance and patient safety. Even those who cope well with shift work are likely to suffer from sleep disorders. The aim of this manuscript is to discuss possible causes, contributing factors and consequences of sleep disorders in physicians and to identify measures that can improve adaptation to shift work and treatment strategies for shift work-associated sleep disorders. The risk factors that influence the development of sleep disorders in physicians are numerous and include genetic factors (15 % of the population), age (> 50 years), undiagnosed sleep apnea,, alcohol abuse as well as multiple stress factors inherent in clinical duties (including shift work), research, teaching and family obligations. Several studies have reported an increased risk for medical errors in sleep-deprived physicians. Shift workers have an increased risk for psychiatric and cardiovascular diseases and shift work may also be a contributing factor to cancer. A relationship has been reported not only with sleep deprivation and changes in food intake but also with diabetes mellitus, obesity, hypertension and coronary heart disease. Nicotine and alcohol consumption are more frequent among shift workers. Increased sickness and accident rates among physicians when commuting (especially after night shifts) have a socioeconomic impact. In order to reduce fatigue and to improve performance, short naps during shiftwork or naps plus caffeine, have been proposed as coping strategies; however, napping during adverse circadian phases is less effective, if not impossible when unable to fall asleep. Bright and blue light supports alertness during a night shift. After shiftwork, direct sunlight exposure to the retina can be avoided by using dark sunglasses or glasses with orange lenses for commuting home. The home environment for daytime sleeping after a night shift should be

  7. Abrupt climate changes during Termination III in Southern Europe

    PubMed Central

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence

    2017-01-01

    The Late Quaternary glacial–interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium–thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I). PMID:28874530

  8. Abrupt climate changes during Termination III in Southern Europe.

    PubMed

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R Lawrence

    2017-09-19

    The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ 13 C, δ 18 O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).

  9. Abrupt climate changes during Termination III in Southern Europe

    NASA Astrophysics Data System (ADS)

    Pérez-Mejías, Carlos; Moreno, Ana; Sancho, Carlos; Bartolomé, Miguel; Stoll, Heather; Cacho, Isabel; Cheng, Hai; Edwards, R. Lawrence

    2017-09-01

    The Late Quaternary glacial-interglacial transitions represent the highest amplitude climate changes over the last million years. Unraveling the sequence of events and feedbacks at Termination III (T-III), including potential abrupt climate reversals similar to those of the last Termination, has been particularly challenging due to the scarcity of well-dated records worldwide. Here, we present speleothem data from southern Europe covering the interval from 262.7 to 217.9 kyBP, including the transition from marine isotope stage (MIS) 8 to MIS 7e. High-resolution δ13C, δ18O, and Mg/Ca profiles reveal major millennial-scale changes in aridity manifested in changing water availability and vegetation productivity. uranium-thorium dates provide a solid chronology for two millennial-scale events (S8.1 and S8.2) which, compared with the last two terminations, has some common features with Heinrich 1 and Heinrich 2 in Termination I (T-I).

  10. Detecting and isolating abrupt changes in linear switching systems

    NASA Astrophysics Data System (ADS)

    Nazari, Sohail; Zhao, Qing; Huang, Biao

    2015-04-01

    In this paper, a novel fault detection and isolation (FDI) method for switching linear systems is developed. All input and output signals are assumed to be corrupted with measurement noises. In the proposed method, a 'lifted' linear model named as stochastic hybrid decoupling polynomial (SHDP) is introduced. The SHDP model governs the dynamics of the switching linear system with all different modes, and is independent of the switching sequence. The error-in-variable (EIV) representation of SHDP is derived, and is used for the fault residual generation and isolation following the well-adopted local approach. The proposed FDI method can detect and isolate the fault-induced abrupt changes in switching models' parameters without estimating the switching modes. Furthermore, in this paper, the analytical expressions of the gradient vector and Hessian matrix are obtained based on the EIV SHDP formulation, so that they can be used to implement the online fault detection scheme. The performance of the proposed method is then illustrated by simulation examples.

  11. Abrupt shifts in phenology and vegetation productivity under climate extremes

    USDA-ARS?s Scientific Manuscript database

    Amplification of the hydrologic cycle as a consequence of global warming is predicted to increase climate variability and the frequency and severity of droughts. Predicting how ecosystems will be affected by climate change requires not only reliable forecasts of future climate, but also observationa...

  12. Outbreaks by canopy-feeding geometrid moth cause state-dependent shifts in understorey plant communities.

    PubMed

    Karlsen, Stein Rune; Jepsen, Jane Uhd; Odland, Arvid; Ims, Rolf Anker; Elvebakk, Arve

    2013-11-01

    The increased spread of insect outbreaks is among the most severe impacts of climate warming predicted for northern boreal forest ecosystems. Compound disturbances by insect herbivores can cause sharp transitions between vegetation states with implications for ecosystem productivity and climate feedbacks. By analysing vegetation plots prior to and immediately after a severe and widespread outbreak by geometrid moths in the birch forest-tundra ecotone, we document a shift in forest understorey community composition in response to the moth outbreak. Prior to the moth outbreak, the plots divided into two oligotrophic and one eutrophic plant community. The moth outbreak caused a vegetation state shift in the two oligotrophic communities, but only minor changes in the eutrophic community. In the spatially most widespread communities, oligotrophic dwarf shrub birch forest, dominance by the allelopathic dwarf shrub Empetrum nigrum ssp. hermaphroditum, was effectively broken and replaced by a community dominated by the graminoid Avenella flexuosa, in a manner qualitatively similar to the effect of wild fires in E. nigrum communities in coniferous boreal forest further south. As dominance by E. nigrum is associated with retrogressive succession the observed vegetation state shift has widespread implications for ecosystem productivity on a regional scale. Our findings reveal that the impact of moth outbreaks on the northern boreal birch forest system is highly initial-state dependent, and that the widespread oligotrophic communities have a low resistance to such disturbances. This provides a case for the notion that climate impacts on arctic and northern boreal vegetation may take place most abruptly when conveyed by changed dynamics of irruptive herbivores.

  13. Interactions with soil biota shift from negative to positive when a tree species is moved outside its native range.

    PubMed

    Gundale, Michael J; Kardol, Paul; Nilsson, Marie-Charlotte; Nilsson, Urban; Lucas, Richard W; Wardle, David A

    2014-04-01

    Studies evaluating plant-soil biota interactions in both native and introduced plant ranges are rare, and thus far have lacked robust experimental designs to account for several potential confounding factors. Here, we investigated the effects of soil biota on growth of Pinus contorta, which has been introduced from Canada to Sweden. Using Swedish and Canadian soils, we conducted two glasshouse experiments. The first experiment utilized unsterilized soil from each country, with a full-factorial cross of soil origin, tree provenance, and fertilizer addition. The second experiment utilized gamma-irradiated sterile soil from each country, with a full-factorial cross of soil origin, soil biota inoculation treatments, tree provenance, and fertilizer addition. The first experiment showed higher seedling growth on Swedish soil relative to Canadian soil. The second experiment showed this effect was due to differences in soil biotic communities between the two countries, and occurred independently of all other experimental factors. Our results provide strong evidence that plant interactions with soil biota can shift from negative to positive following introduction to a new region, and are relevant for understanding the success of some exotic forest plantations, and invasive and range-expanding native species. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  14. Sources of Cognitive Inflexibility in Set-Shifting Tasks: Insights Into Developmental Theories From Adult Data

    PubMed Central

    Dick, Anthony Steven

    2012-01-01

    Two experiments examined processes underlying cognitive inflexibility in set-shifting tasks typically used to assess the development of executive function in children. Adult participants performed a Flexible Item Selection Task (FIST) that requires shifting from categorizing by one dimension (e.g., color) to categorizing by a second orthogonal dimension (e.g., shape). The experiments showed performance of the FIST involves suppression of the representation of the ignored dimension; response times for selecting a target object in an immediately-following oddity task were slower when the oddity target was the previously-ignored stimulus of the FIST. However, proactive interference from the previously relevant stimulus dimension also impaired responding. The results are discussed with respect to two prominent theories of the source of difficulty for children and adults on dimensional shifting tasks: attentional inertia and negative priming. In contrast to prior work emphasizing one over the other process, the findings indicate that difficulty in the FIST, and by extension other set-shifting tasks, can be attributed to both the need to shift away from the previously attended representation (attentional inertia), and the need to shift to the previously ignored representation (negative priming). Results are discussed in relation to theoretical explanations for cognitive inflexibility in adults and children. PMID:23539267

  15. Sources of Cognitive Inflexibility in Set-Shifting Tasks: Insights Into Developmental Theories From Adult Data.

    PubMed

    Dick, Anthony Steven

    2012-01-01

    Two experiments examined processes underlying cognitive inflexibility in set-shifting tasks typically used to assess the development of executive function in children. Adult participants performed a Flexible Item Selection Task (FIST) that requires shifting from categorizing by one dimension (e.g., color) to categorizing by a second orthogonal dimension (e.g., shape). The experiments showed performance of the FIST involves suppression of the representation of the ignored dimension; response times for selecting a target object in an immediately-following oddity task were slower when the oddity target was the previously-ignored stimulus of the FIST. However, proactive interference from the previously relevant stimulus dimension also impaired responding. The results are discussed with respect to two prominent theories of the source of difficulty for children and adults on dimensional shifting tasks: attentional inertia and negative priming . In contrast to prior work emphasizing one over the other process, the findings indicate that difficulty in the FIST, and by extension other set-shifting tasks, can be attributed to both the need to shift away from the previously attended representation ( attentional inertia ), and the need to shift to the previously ignored representation ( negative priming ). Results are discussed in relation to theoretical explanations for cognitive inflexibility in adults and children.

  16. Effects of strain on Goos-Hänchen shifts of monolayer phosphorene

    NASA Astrophysics Data System (ADS)

    Li, Kaihui; Cheng, Fang

    2018-03-01

    We investigate the Goos-Hänchen(GH) shift for ballistic electrons (i) reflected from a step-like inhomogeneity of strain, and (ii) transmitted through a monolayer phosphoresce junction consisting of a positive strained region and two normal regions (or a normal region and two negative strained regions). Refraction occurs at the interface between the unstrained/positive-strain(negative-strain/unstrained), in analogy with optical refraction. The critical angle is different for different strengths and directions of the strains. The critical angles for electrons tunneling through unstrained/positive-strain junction can even decrease to zero when the positive strain exceeds a critical value. For the monolayer phosphorene junction consisting of a positive strain region and two normal regions (or a normal region and two negative strain regions), we find that the GH shifts resonantly depends on the middle region width. The resonant values and the plus-minus sign of the displacement can be controlled by the incident angle, incident energy and the strain. These properties will be useful for the applications in phosphorene-based electronic devices.

  17. Negative pressure darwinism: survival of the fittest paradigm.

    PubMed

    Miller, Michael; Bybordi, Farhad

    2009-07-01

    The use of negative pressure for wound healing has been based on a set of parameters and devices that until recently were combined into a single paradigm. Despite historical and more recent evidence providing viable alternative considerations, it is only recently that this paradigm and its tenets have come into question. As the understanding of the limits of the current paradigm and specific instances of its benefits and drawbacks are identified, shifts in the paradigm must take place if the therapy is to evolve, develop, and continue to be efficacious. The pertinence of the concept of survival of the fittest is used to explore the need for a paradigm shift in negative pressure wound therapy.

  18. Quantifying attention shifts in augmented reality image-guided neurosurgery.

    PubMed

    Léger, Étienne; Drouin, Simon; Collins, D Louis; Popa, Tiberiu; Kersten-Oertel, Marta

    2017-10-01

    Image-guided surgery (IGS) has allowed for more minimally invasive procedures, leading to better patient outcomes, reduced risk of infection, less pain, shorter hospital stays and faster recoveries. One drawback that has emerged with IGS is that the surgeon must shift their attention from the patient to the monitor for guidance. Yet both cognitive and motor tasks are negatively affected with attention shifts. Augmented reality (AR), which merges the realworld surgical scene with preoperative virtual patient images and plans, has been proposed as a solution to this drawback. In this work, we studied the impact of two different types of AR IGS set-ups (mobile AR and desktop AR) and traditional navigation on attention shifts for the specific task of craniotomy planning. We found a significant difference in terms of the time taken to perform the task and attention shifts between traditional navigation, but no significant difference between the different AR set-ups. With mobile AR, however, users felt that the system was easier to use and that their performance was better. These results suggest that regardless of where the AR visualisation is shown to the surgeon, AR may reduce attention shifts, leading to more streamlined and focused procedures.

  19. Shifts in Teaching Motivation and Sense of Self-as-Teacher in Initial Teacher Education

    ERIC Educational Resources Information Center

    Tang, Sylvia Y. F.; Cheng, May M. H.; Cheng, Annie Y. N.

    2014-01-01

    This article presents four student teacher cases using an examination of the nature of shifts in student teachers' motivation for choosing teaching as a career in relation to the development of their sense of self-as-teacher. The analysis relates positive and negative shifts in teaching motivation and sense of self-as-teacher to variation in…

  20. Chromophobe hepatocellular carcinoma with abrupt anaplasia: a proposal for a new subtype of hepatocellular carcinoma with unique morphological and molecular features

    PubMed Central

    Wood, Laura D; Heaphy, Christopher M; Daniel, Hubert Darius-J; Naini, Bita V; Lassman, Charles R; Arroyo, May R; Kamel, Ihab R; Cosgrove, David P; Boitnott, John K; Meeker, Alan K; Torbenson, Michael S

    2014-01-01

    Hepatocellular carcinomas exhibit heterogeneous morphologies by routine light microscopy. Although some morphologies represent insignificant variations in growth patterns, others may represent unrecognized subtypes of hepatocellular carcinoma. Identification of these subtypes could lead to separation of hepatocellular carcinomas into discrete groups with unique underlying genetic changes, prognosis, or therapeutic responses. In order to identify potential subtypes, two pathologists independently screened a cohort of 219 unselected hepatocellular carcinoma resection specimens and divided cases into potential subtypes. One of these promising candidate subtypes was further evaluated using histological and molecular techniques. This subtype was characterized by a unique and consistent set of histological features: smooth chromophobic cytoplasm, abrupt focal nuclear anaplasia (small clusters of tumor cells with marked nuclear anaplasia in a background of tumor cells with bland nuclear cytology), and scattered microscopic pseudocysts—we designate this variant as ‘chromophobe hepatocellular carcinoma with abrupt anaplasia’. Thirteen cases were identified (6% of all hepatocellular carcinomas), including 6 men and 7 women with an average age of 61 years. Six cases occurred in cirrhotic livers. Serum AFP was elevated in 6 out of 10 cases. There were a variety of underlying liver diseases, but cases were enrichment for chronic hepatitis B, P = 0.006. Interestingly, at the molecular level, this variant was strongly associated with the alternative lengthening of telomere (ALT) phenotype by telomere FISH. ALT is a telomerase-independent mechanism of telomere maintenance and is found in approximately 8% of unselected hepatocellular carcinomas. In contrast, 11/12 (92%) of the cases of chromophobe hepatocellular carcinoma with abrupt anaplasia were ALT-positive. In summary, we propose that chromophobe hepatocellular carcinoma with abrupt anaplasia represents a new subtype of

  1. Chromophobe hepatocellular carcinoma with abrupt anaplasia: a proposal for a new subtype of hepatocellular carcinoma with unique morphological and molecular features.

    PubMed

    Wood, Laura D; Heaphy, Christopher M; Daniel, Hubert Darius-J; Naini, Bita V; Lassman, Charles R; Arroyo, May R; Kamel, Ihab R; Cosgrove, David P; Boitnott, John K; Meeker, Alan K; Torbenson, Michael S

    2013-12-01

    Hepatocellular carcinomas exhibit heterogeneous morphologies by routine light microscopy. Although some morphologies represent insignificant variations in growth patterns, others may represent unrecognized subtypes of hepatocellular carcinoma. Identification of these subtypes could lead to separation of hepatocellular carcinomas into discrete groups with unique underlying genetic changes, prognosis, or therapeutic responses. In order to identify potential subtypes, two pathologists independently screened a cohort of 219 unselected hepatocellular carcinoma resection specimens and divided cases into potential subtypes. One of these promising candidate subtypes was further evaluated using histological and molecular techniques. This subtype was characterized by a unique and consistent set of histological features: smooth chromophobic cytoplasm, abrupt focal nuclear anaplasia (small clusters of tumor cells with marked nuclear anaplasia in a background of tumor cells with bland nuclear cytology), and scattered microscopic pseudocysts--we designate this variant as 'chromophobe hepatocellular carcinoma with abrupt anaplasia'. Thirteen cases were identified (6% of all hepatocellular carcinomas), including 6 men and 7 women with an average age of 61 years. Six cases occurred in cirrhotic livers. Serum AFP was elevated in 6 out of 10 cases. There were a variety of underlying liver diseases, but cases were enrichment for chronic hepatitis B, P=0.006. Interestingly, at the molecular level, this variant was strongly associated with the alternative lengthening of telomere (ALT) phenotype by telomere FISH. ALT is a telomerase-independent mechanism of telomere maintenance and is found in approximately 8% of unselected hepatocellular carcinomas. In contrast, 11/12 (92%) of the cases of chromophobe hepatocellular carcinoma with abrupt anaplasia were ALT-positive. In summary, we propose that chromophobe hepatocellular carcinoma with abrupt anaplasia represents a new subtype of

  2. Abrupt contraction flow of magnetorheological fluids

    NASA Astrophysics Data System (ADS)

    Kuzhir, P.; López-López, M. T.; Bossis, G.

    2009-05-01

    Contraction and expansion flows of magnetorheological fluids occur in a variety of smart devices. It is important therefore to learn how these flows can be controlled by means of applied magnetic fields. This paper presents a first investigation into the axisymmetric flow of a magnetorheological fluid through an orifice (so-called abrupt contraction flow). The effect of an external magnetic field, longitudinal or transverse to the flow, is examined. In experiments, the pressure-flow rate curves were measured, and the excess pressure drop (associated with entrance and exit losses) was derived from experimental data through the Bagley correction procedure. The effect of the longitudinal magnetic field is manifested through a significant increase in the slope of the pressure-flow rate curves, while no discernible yield stress occurs. This behavior, observed at shear Mason numbers 10

  3. Differences in Multi-Modal Ultrasound Imaging between Triple Negative and Non-Triple Negative Breast Cancer.

    PubMed

    Li, Ziyao; Tian, Jiawei; Wang, Xiaowei; Wang, Ying; Wang, Zhenzhen; Zhang, Lei; Jing, Hui; Wu, Tong

    2016-04-01

    The objective of this study was to identify multi-modal ultrasound imaging parameters that could potentially help to differentiate between triple negative breast cancer (TNBC) and non-TNBC. Conventional ultrasonography, ultrasound strain elastography and 3-D ultrasound (3-D-US) findings from 50 TNBC and 179 non-TNBC patients were retrospectively reviewed. Immunohistochemical examination was used as the reference gold standard for cancer subtyping. Different ultrasound modalities were initially analyzed to define TNBC-related features. Subsequently, logistic regression analysis was applied to TNBC-related features to establish models for predicting TNBC. TNBCs often presented as micro-lobulated, markedly hypo-echoic masses with an abrupt interface (p = 0.015, 0.0015 and 0.004, compared with non-TNBCs, respectively) on conventional ultrasound, and showed a diminished retraction pattern phenomenon in the coronal plane (p = 0.035) on 3-D-US. Our findings suggest that B-mode ultrasound and 3-D-US in multi-modality ultrasonography could be a useful non-invasive technique for differentiating TNBCs from non-TNBCs. Copyright © 2016 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  4. Evaluating the impact of abrupt changes in forest policy and management practices on landscape dynamics: analysis of a Landsat image time series in the Atlantic Northern Forest.

    PubMed

    Legaard, Kasey R; Sader, Steven A; Simons-Legaard, Erin M

    2015-01-01

    Sustainable forest management is based on functional relationships between management actions, landscape conditions, and forest values. Changes in management practices make it fundamentally more difficult to study these relationships because the impacts of current practices are difficult to disentangle from the persistent influences of past practices. Within the Atlantic Northern Forest of Maine, U.S.A., forest policy and management practices changed abruptly in the early 1990s. During the 1970s-1980s, a severe insect outbreak stimulated salvage clearcutting of large contiguous tracts of spruce-fir forest. Following clearcut regulation in 1991, management practices shifted abruptly to near complete dependence on partial harvesting. Using a time series of Landsat satellite imagery (1973-2010) we assessed cumulative landscape change caused by these very different management regimes. We modeled predominant temporal patterns of harvesting and segmented a large study area into groups of landscape units with similar harvest histories. Time series of landscape composition and configuration metrics averaged within groups revealed differences in landscape dynamics caused by differences in management history. In some groups (24% of landscape units), salvage caused rapid loss and subdivision of intact mature forest. Persistent landscape change was created by large salvage clearcuts (often averaging > 100 ha) and conversion of spruce-fir to deciduous and mixed forest. In groups that were little affected by salvage (56% of landscape units), contemporary partial harvesting caused loss and subdivision of intact mature forest at even greater rates. Patch shape complexity and edge density reached high levels even where cumulative harvest area was relatively low. Contemporary practices introduced more numerous and much smaller patches of stand-replacing disturbance (typically averaging <15 ha) and a correspondingly large amount of edge. Management regimes impacted different areas to

  5. Evaluating the Impact of Abrupt Changes in Forest Policy and Management Practices on Landscape Dynamics: Analysis of a Landsat Image Time Series in the Atlantic Northern Forest

    PubMed Central

    Legaard, Kasey R.; Sader, Steven A.; Simons-Legaard, Erin M.

    2015-01-01

    Sustainable forest management is based on functional relationships between management actions, landscape conditions, and forest values. Changes in management practices make it fundamentally more difficult to study these relationships because the impacts of current practices are difficult to disentangle from the persistent influences of past practices. Within the Atlantic Northern Forest of Maine, U.S.A., forest policy and management practices changed abruptly in the early 1990s. During the 1970s-1980s, a severe insect outbreak stimulated salvage clearcutting of large contiguous tracts of spruce-fir forest. Following clearcut regulation in 1991, management practices shifted abruptly to near complete dependence on partial harvesting. Using a time series of Landsat satellite imagery (1973-2010) we assessed cumulative landscape change caused by these very different management regimes. We modeled predominant temporal patterns of harvesting and segmented a large study area into groups of landscape units with similar harvest histories. Time series of landscape composition and configuration metrics averaged within groups revealed differences in landscape dynamics caused by differences in management history. In some groups (24% of landscape units), salvage caused rapid loss and subdivision of intact mature forest. Persistent landscape change was created by large salvage clearcuts (often averaging > 100 ha) and conversion of spruce-fir to deciduous and mixed forest. In groups that were little affected by salvage (56% of landscape units), contemporary partial harvesting caused loss and subdivision of intact mature forest at even greater rates. Patch shape complexity and edge density reached high levels even where cumulative harvest area was relatively low. Contemporary practices introduced more numerous and much smaller patches of stand-replacing disturbance (typically averaging <15 ha) and a correspondingly large amount of edge. Management regimes impacted different areas to

  6. Hydrological regulation drives regime shifts: evidence from paleolimnology and ecosystem modeling of a large shallow Chinese lake.

    PubMed

    Kong, Xiangzhen; He, Qishuang; Yang, Bin; He, Wei; Xu, Fuliu; Janssen, Annette B G; Kuiper, Jan J; van Gerven, Luuk P A; Qin, Ning; Jiang, Yujiao; Liu, Wenxiu; Yang, Chen; Bai, Zelin; Zhang, Min; Kong, Fanxiang; Janse, Jan H; Mooij, Wolf M

    2017-02-01

    Quantitative evidence of sudden shifts in ecological structure and function in large shallow lakes is rare, even though they provide essential benefits to society. Such 'regime shifts' can be driven by human activities which degrade ecological stability including water level control (WLC) and nutrient loading. Interactions between WLC and nutrient loading on the long-term dynamics of shallow lake ecosystems are, however, often overlooked and largely underestimated, which has hampered the effectiveness of lake management. Here, we focus on a large shallow lake (Lake Chaohu) located in one of the most densely populated areas in China, the lower Yangtze River floodplain, which has undergone both WLC and increasing nutrient loading over the last several decades. We applied a novel methodology that combines consistent evidence from both paleolimnological records and ecosystem modeling to overcome the hurdle of data insufficiency and to unravel the drivers and underlying mechanisms in ecosystem dynamics. We identified the occurrence of two regime shifts: one in 1963, characterized by the abrupt disappearance of submerged vegetation, and another around 1980, with strong algal blooms being observed thereafter. Using model scenarios, we further disentangled the roles of WLC and nutrient loading, showing that the 1963 shift was predominantly triggered by WLC, whereas the shift ca. 1980 was attributed to aggravated nutrient loading. Our analysis also shows interactions between these two stressors. Compared to the dynamics driven by nutrient loading alone, WLC reduced the critical P loading and resulted in earlier disappearance of submerged vegetation and emergence of algal blooms by approximately 26 and 10 years, respectively. Overall, our study reveals the significant role of hydrological regulation in driving shallow lake ecosystem dynamics, and it highlights the urgency of using multi-objective management criteria that includes ecological sustainability perspectives when

  7. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions.

    PubMed

    Molina, Mario; Zaelke, Durwood; Sarma, K Madhava; Andersen, Stephen O; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-12-08

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of "dangerous anthropogenic interference" (DAI). Scientific and policy literature refers to the need for "early," "urgent," "rapid," and "fast-action" mitigation to help avoid DAI and abrupt climate changes. We define "fast-action" to include regulatory measures that can begin within 2-3 years, be substantially implemented in 5-10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO(2) GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO(2) emissions.

  8. Unusual Electrical Transport Driven by the Competition between Antiferromagnetism and Ferromagnetism in Antiperovskite Mn3Zn1−xCoxN

    PubMed Central

    Chu, Lihua; Wang, Cong; Guo, Yanjiao; Liu, Zhuohai

    2018-01-01

    The magnetic, electrical transport and thermal expansion properties of Mn3Zn1−xCoxN (x = 0.2, 0.4, 0.5, 0.7, 0.9) have been systematically investigated. Co-doping in Mn3ZnN complicates the magnetic interactions, leading to a competition between antiferromagnetism and ferromagnetism. Abrupt resistivity jump phenomenon and negative thermal expansion behavior, both associated with the complex magnetic transition, are revealed in all studied cases. Furthermore, semiconductor-like transport behavior is found in sample x = 0.7, distinct from the metallic behavior in other samples. Below 50 K, resistivity minimum is observed in samples x = 0.4, 0.7, and 0.9, mainly caused by e-e scattering mechanism. We finally discussed the strong correlation among unusual electrical transport, negative thermal expansion and magnetic transition in Mn3Zn1−xCoxN, which allows us to conclude that the observed unusual electrical transport properties are attributed to the shift of the Fermi energy surface entailed by the abrupt lattice contraction. PMID:29439522

  9. ShiftNMFk 1.2

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alexandrov, Boian S.; Vesselinov, Velimir V.; Stanev, Valentin

    The ShiftNMFk1.2 code, or as we call it, GreenNMFk, represents a hybrid algorithm combining unsupervised adaptive machine learning and Green's function inverse method. GreenNMFk allows an efficient and high performance de-mixing and feature extraction of a multitude of nonnegative signals that change their shape propagating through the medium. The signals are mixed and recorded by a network of uncorrelated sensors. The code couples Non-negative Matrix Factorization (NMF) and inverse-analysis Green's functions method. GreenNMF synergistically performs decomposition of the recorded mixtures, finds the number of the unknown sources and uses the Green's function of the governing partial differential equation to identifymore » the unknown sources and their charecteristics. GreenNMF can be applied directly to any problem controlled by a known partial-differential parabolic equation where mixtures of an unknown number of sources are measured at multiple locations. Full GreenNMFk method is a subject LANL U.S. Patent application S133364.000 August, 2017. The ShiftNMFk 1.2 version here is a toy version of this method that can work with a limited number of unknown sources (4 or less).« less

  10. Shifts on reproductive phenology of tropical cerrado savanna trees and climate changes

    NASA Astrophysics Data System (ADS)

    Morellato, Patricia

    2010-05-01

    Phenology is the study of cyclic biological events and its relationship to abiotic factors. Timing of flowering, fruiting and leafing is highly correlated to environmental factors such as temperature, precipitation, irradiance and isolation. Accordingly, any change in these factors may have a direct effect on the initiation, intensity and duration of different phenophases. Tropical phenology has not contributed much for climatic change research since historical data sets are scarce and the absence of sharp seasons and distinct factors driving phenology makes difficult the detection of changes over time. One way to have insights on climate driven phenology shifts on tropical plants is through the comparison of plant phenology under different environmental conditions. Fragmentation of natural landscape has exposed plants to edge effects - the interaction between two adjacent ecosystems, when the two are separated by an abrupt transition - the edge, including both abiotic and biological changes on environmental conditions that likely affect plant phenology. The microclimatic conditions along edges have important direct biological effects on the reproductive phenology and fitness of plant species. One can expected that the abiotic edge effects on plant phenology may be similar to some extent to certain effects induced by climate change on plant phenology since both involve shifts on environmental conditions. Due to the threatened status and rich biodiversity of Brazilian Neotropical savanna, or the Brazilian Cerrado, the present study aimed to understand edge effects on cerrado savanna species. We compared micro environmental factors and phenology of several species on the edge and in the interior of cerrado savanna. Our first results indicated that shifts on the micro environmental condition may have driven changes in time, duration and intensity of species phenology and may give us insights on savanna responses to climate changes.

  11. Level shift two-components autoregressive conditional heteroscedasticity modelling for WTI crude oil market

    NASA Astrophysics Data System (ADS)

    Sin, Kuek Jia; Cheong, Chin Wen; Hooi, Tan Siow

    2017-04-01

    This study aims to investigate the crude oil volatility using a two components autoregressive conditional heteroscedasticity (ARCH) model with the inclusion of abrupt jump feature. The model is able to capture abrupt jumps, news impact, clustering volatility, long persistence volatility and heavy-tailed distributed error which are commonly observed in the crude oil time series. For the empirical study, we have selected the WTI crude oil index from year 2000 to 2016. The results found that by including the multiple-abrupt jumps in ARCH model, there are significant improvements of estimation evaluations as compared with the standard ARCH models. The outcomes of this study can provide useful information for risk management and portfolio analysis in the crude oil markets.

  12. Emergency Radiology Practice Patterns: Shifts, Schedules, and Job Satisfaction.

    PubMed

    Hanna, Tarek N; Shekhani, Haris; Lamoureux, Christine; Mar, Hanna; Nicola, Refky; Sliker, Clint; Johnson, Jamlik-Omari

    2017-03-01

    To assess the practice environment of emergency radiologists with a focus on schedule, job satisfaction, and self-perception of health, wellness, and diagnostic accuracy. A survey drawing from prior radiology and health care shift-work literature was distributed via e-mail to national societies, teleradiology groups, and private practices. The survey remained open for 4 weeks in 2016, with one reminder. Data were analyzed using hypothesis testing and logistic regression modeling. Response rate was 29.6% (327/1106); 69.1% of respondents (n = 226) were greater than 40 years old, 73% (n = 240) were male, and 87% (n = 284) practiced full time. With regard to annual overnight shifts (NS): 36% (n = 118) did none, 24.9% (n = 81) did 182 or more, and 15.6% (n = 51) did 119. There was a significant association between average NS worked per year and both perceived negative health effects (P < .01) and negative impact on memory (P < .01). There was an inverse association between overall job enjoyment and number of annual NS (P < .05). The odds of agreeing to the statement "I enjoy my job" for radiologists who work no NS is 2.21 times greater than for radiologists who work at least 119 NS, when shift length is held constant. Radiologists with 11+ years of experience who work no NS or 1 to 100 NS annually have lower odds of feeling overwhelmed when compared with those working the same number of NS with <10 years' experience. There is significant variation in emergency radiology practice patterns. Annual NS burden is associated with lower job satisfaction and negative health self-perception. Copyright © 2016 American College of Radiology. Published by Elsevier Inc. All rights reserved.

  13. The association between shift work and sick leave: a systematic review

    PubMed Central

    van Drongelen, Alwin; Holte, Kari Anne; Labriola, Merete; Lund, Thomas; van Mechelen, Willem; van der Beek, Allard J

    2012-01-01

    Shift work is associated with a number of negative health outcomes, although it is not known whether it is associated with sick leave. This systematic review therefore aimed to determine whether an association exists between shift work and sick leave. A systematic literature search was conducted in six databases on observational studies. Two reviewers independently selected relevant articles and appraised methodological quality. Data extraction was performed independently by review couples. Articles were categorised according to shift work characteristics and summarised using a levels of evidence synthesis. In total, the search strategy yielded 1207 references, of which 24 studies met the inclusion criteria. Nine studies were appraised as high quality and used in the levels of evidence synthesis. Two high quality longitudinal studies found a positive association between fixed evening shifts and longer sick leave for female healthcare workers. The evidence was assessed as strong. Evidence was inconclusive for rotating shifts, shift work including nights, for fixed night work, and for 8-hour and 12-hour shifts. The association found between evening work and sick leave in female healthcare workers implies that the association between shift work and sick leave might be schedule and population specific. To study the association further, more high quality studies are necessary that assess and adjust for detailed shift work exposure. PMID:22767871

  14. Effect of width of incident Gaussian beam on the longitudinal shifts and distortion in the reflected beam

    NASA Astrophysics Data System (ADS)

    Ziauddin; Qamar, Sajid

    2014-05-01

    Control of the longitudinal shifts, i.e., spatial and angular Goos-Hänchen (GH) shifts, is revisited to study the effect of width of incident Gaussian beam on the shifts and distortion in the reflected beam. The beam is incident on a cavity consisted of atomic medium where each four-level atom follows N-type atom-field configuration. The atom-field interaction leads to Raman gain process which has been used earlier to observe a significant enhancement of the negative group index, i.e., in the range -103 to -104 for 23Na condensate [G.S. Agarwal, S. Dasgupta, Phys. Rev. A 70 (2004) 023802]. The negative and positive longitudinal shifts could be observed in the reflected light corresponding to the anomalous and normal dispersions of the intracavity medium, respectively. It is observed that the shifts are relatively large for small range of beam width and these became small for large width of the incident beam. It is also noticed that the magnitudes of spatial and angular GH shifts behave differently when the beam width increases. Further, distortion in the reflected beam decreases with an increase in beam width.

  15. Nanotribological Properties of Positively and Negatively charged nanodiamonds as additives to solutions

    NASA Astrophysics Data System (ADS)

    Liu, Zijian; Corley, Steven; Shenderova, Olga; Brenner, Donald; Krim, Jacqueline

    2013-03-01

    Nano-diamond (ND) particles are known to be beneficial for wear and friction reduction when used as additives in liquids, but the fundamental origins of the improvement in tribological properties has not been established. In order to explore this issue, we have investigated the nanotribological properties of ND coated with self-assembled monolayers (SAM) as additives to solutions, employing gold/chrome coated quartz crystal microbalances (QCM). Measurements were performed with the QCM initially immersed in deionized water. ND particles with positively and negatively charged SAM end groups were then added to the water, while the frequency and amplitude of the QCM were monitored. Negative shifts in both the QCM frequency and amplitude were observed when ND with positively charged SAM end groups were added, while positive shifts in both the QCM frequency and amplitude were observed when ND with negatively charged ND end groups were added. The results are consistent with a lubricating effect for the negatively charged ND, but were only observed for sufficiently small negative ND particle size. Experiments on QCM surfaces with differing textures and roughness are in progress, to determine the separate contributing effects of surface roughness charge-water interactions. Funding provided by NSF DMR.

  16. Phase-shift parametrization and extraction of asymptotic normalization constants from elastic-scattering data

    NASA Astrophysics Data System (ADS)

    Ramírez Suárez, O. L.; Sparenberg, J.-M.

    2017-09-01

    We introduce a simplified effective-range function for charged nuclei, related to the modified K matrix but differing from it in several respects. Negative-energy zeros of this function correspond to bound states. Positive-energy zeros correspond to resonances and "echo poles" appearing in elastic-scattering phase-shifts, while its poles correspond to multiple-of-π phase shifts. Padé expansions of this function allow one to parametrize phase shifts on large energy ranges and to calculate resonance and bound-state properties in a very simple way, independently of any potential model. The method is first tested on a d -wave 12C+α potential model. It is shown to lead to a correct estimate of the subthreshold-bound-state asymptotic normalization constant (ANC) starting from the elastic-scattering phase shifts only. Next, the 12C+α experimental p -wave and d -wave phase shifts are analyzed. For the d wave, the relatively large error bars on the phase shifts do not allow one to improve the ANC estimate with respect to existing methods. For the p wave, a value agreeing with the 12C(6Li,d )16O transfer-reaction measurement and with the recent remeasurement of the 16Nβ -delayed α decay is obtained, with improved accuracy. However, the method displays two difficulties: the results are sensitive to the Padé-expansion order and the simplest fits correspond to an imaginary ANC, i.e., to a negative-energy "echo pole," the physical meaning of which is still debatable.

  17. Bacteremias in liver transplant recipients: shift toward gram-negative bacteria as predominant pathogens.

    PubMed

    Singh, Nina; Wagener, Marilyn M; Obman, Asia; Cacciarelli, Thomas V; de Vera, Michael E; Gayowski, Timothy

    2004-07-01

    During the 1990s, gram-positive bacteria emerged as major pathogens after liver transplantation. We sought to determine whether the pathogens associated with bacteremias in liver transplant recipients have changed. Patients included 233 liver transplant recipients transplanted between 1989 and 2003. The proportion of all infections due to bacteremias increased significantly over time (P <.0001). Of other major infections, a trend toward a decrease in fungal infections (P =.089) and a significant decrease in cytomegalovirus (CMV) disease (P =.0004) were documented. Whereas the proportion of bacteremias due to gram-negatives increased from 25% in the period of 1989-1993 to 51.8% in 1998-03, that of gram-positive bacteria decreased from 75% in the period of 1989-93 to 48.2% in the period of 1998-2003. Methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae, and Pseudomonas aeruginosa were the most frequent pathogens in bacteremic patients. The incidence of bacteremias due to MRSA and Pseudomonas aeruginosa has remained unchanged (P <.20); however, that due to enteric gram-negative bacteria, particularly Klebsiella pneumoniae has increased (P =.02). Klebsiella pneumoniae isolates in the current quartile were not clonally related. In conclusion, bacteremias as a proportion of all infections in liver transplant recipients have increased significantly over time, due in part to a decline in infections due to other major pathogens, e.g., fungi, primarily Candida species, and CMV. Gram-negative bacteria have emerged as predominant pathogens in bacteremic liver transplant recipients.

  18. Abrupt climate change and transient climates during the Paleogene: a marine perspective.

    PubMed

    Zachos, J C; Lohmann, K C; Walker, J C; Wise, S W

    1993-03-01

    Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

  19. Abrupt climate change and transient climates during the Paleogene: a marine perspective

    NASA Technical Reports Server (NTRS)

    Zachos, J. C.; Lohmann, K. C.; Walker, J. C.; Wise, S. W.

    1993-01-01

    Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.

  20. Abrupt opium discontinuation has no significant triggering effect on acute myocardial infarction.

    PubMed

    Masoomi, Mohammad; Zare, Jahangir; Nasri, Hamidreza; Mirzazadeh, Ali; Sheikhvatan, Mehrdad

    2011-04-01

    A deleterious effect of withdrawal symptoms due to abrupt discontinuation of opium on the cardiovascular system is one of the recent interesting topics in the cardiovascular field. The current study hypothesized that the withdrawal syndrome due to discontinuing opium might be an important trigger for the appearance of acute myocardial infarction. Eighty-one opium-addicted individuals who were candidates for cardiovascular clinical evaluation and consecutively hospitalized in the coronary care unit (CCU) ward of Shafa Hospital in Kerman between January and July 2009 were included in the study and categorized in the case group, including patients experiencing withdrawal symptoms within 6-12 h after the reduced or discontinued use of opium according to the Diagnostic and Statistical Manual of Mental Disorders-revised IV version (DSM-IV-R) criteria for opium dependence and withdrawal, and the control group, without opium withdrawal symptoms. The appearance of acute myocardial infarction was compared between the two groups using multivariable regression models. Acute myocardial infarction occurred in 50.0% of those with withdrawal symptoms and in 45.1% of patients without evidence of opium withdrawal (P = 0.669). Multivariable analysis showed that opium withdrawal symptoms were not a trigger for acute myocardial infarction adjusting for demographic characteristics, marital status, education level and common coronary artery disease risk profiles [odds ratio (OR) = 0.920, 95% confidence interval (CI) = 0.350-2.419, P = 0.866]. Also, daily dose of opium before reducing or discontinuing use did not predict the appearance of myocardial infarction in the presence of confounder variables (OR = 0.975, 95% CI = 0.832-1.143, P = 0.755). Withdrawal syndrome due to abrupt discontinuation of opium does not have a triggering role for appearance of acute myocardial infarction.

  1. Health consequences of shift-work: the case of iranian hospital security personnel.

    PubMed

    Abedini, Roghayeh; Soltanzadeh, Ahmad; Faghih, Mohammad Amin; Mohammadi, Heidar; Kamalinia, Mojtaba; Mohraz, Majid Habibi; Arassi, Maziyar; Veyseh, Peyman Piran; Aghaei, Hamed; Hosseini, Seyed Younes

    2015-01-01

    Shift-work, which is an ergonomics issue in workplaces, can negatively affect workers. The security personnel of medical centers in Iran have multiple responsibilities and consequently are exposed to such unwanted situations as observing patients, disputing with patient's attendants, unwanted shift schedules, and being away from family for long periods. This study assessed health problems of Iranian hospital security personnel (shift-worker personnel) using the Survey of Shift-workers (SOS) questionnaire (Persian version). This cross-sectional study was conducted in seven medical centers (4 hospitals and 3 clinics). A total of 416 workers were surveyed: shift-workers (exposed group) (n=209) and non-shift-workers (unexposed group) (n=207). The prevalence of adverse health effects was higher in shift-workers than day-workers. The level of education and mean Body Mass Index (BMI) in shift-workers were significantly higher compared with day-workers. The prevalence of gastrointestinal disorders, cardiovascular and psychological problems were also significantly higher in shift-workers compared with day-workers. Overall, the prevalence of health problems among the security personnel of medical centers was high. Hence, it is recommended that personnel be put under periodic monitoring and receive medical counseling and treatment if there is any disorder.

  2. Fluorescence spectral shift of QD films with electron injection: Dependence on counterion proximity

    NASA Astrophysics Data System (ADS)

    Lu, Meilin; Li, Bo; Zhang, Yaxin; Liu, Weilong; Yang, Yanqiang; Wang, Yuxiao; Yang, Qingxin

    2017-05-01

    Due to the promising application of quantum dot (QD) films in solar cells, LEDs and environmental detectors, the fluorescence of charged QD films has achieved much attention during recent years. In this work, we observe the spectral shift of photoluminescence (PL) in charged CdSe/ZnS QD films controlled by electrochemical potential. The spectral center under negative bias changes from red-shift to blue-shift while introducing smaller inorganic counterions (potassium ions) into the electrolyte. This repeatable effect is attributed to the enhanced electron injection with smaller cations and the electronic perturbations of QD luminescence by these excess charges.

  3. Response of the auroral electrojet indices to abrupt southward IMF turnings

    NASA Astrophysics Data System (ADS)

    Gjerloev, J. W.; Hoffman, R. A.; Ohtani, S.; Weygand, J.; Barnes, R.

    2010-05-01

    We present results from a study of the behavior of the auroral electrojet indices following abrupt southward turnings of the IMF Bz. The auroral electrojet indices are calculated from observations made by more than 100 ground based stations provided by the SuperMAG collaborators. Based on three simple criteria we selected 73 events. In each event the interval of analysis started at the time of the IMF Bz southward turning and ended 45 minutes later or at the onset of any abrupt energy unloading event in the magnetosphere, regardless of size. We refer to this period as the "pre-unloading phase". To isolate the dependence of the auroral electrojets on the solar induced ionospheric conductivity during this phase we separated the standard AU/AL indices into two new sets of indices defined by the upper and lower envelope of the north-south component for all sunlit stations (AUs/ALs) and for all stations in darkness (AUd/ALd). Based on events and statistical analyses we can conclude that following a southward turning of the IMF Bz the AUd/ALd indices show no measurable response while the AUs/ALs indices clearly intensify. The intensifications of AUs/ALs are dependent on the intensity of the solar wind driver (as measured by IMF Bz or the Akasofu ɛ parameter). The lack of AUd/ALd response does not depend on the intensity of any subsequent substorm. We find that during these isolated events the ionospheric current system is primarily confined to the sunlit ionosphere. This truncated version of the classical global DP-2 current system suggests that auroral electrojet continuity is not maintained across the terminator. Because of its conductivity dependence on the solar zenith angle, this truncated global current pattern is expected to be highly dependent on UT and season and thus can be asymmetric between hemispheres. Thus we argue that the global two-cell DP-2 current system is not a consequence only of a southward turning of the IMF but requires also the reduction of the

  4. Postglacial Human resilience and susceptibility to abrupt climate change new insights from Star Carr

    NASA Astrophysics Data System (ADS)

    Blockley, Simon; Abrook, Ashley; Bayliss, Alex; Candy, Ian; Conneller, Chantal; Darvill, Chris; Deeprose, Laura; Kearney, Rebecca; Langdon, Pete; Langdon Langdon, Cath; Lincoln, Paul; Macleod, Alison; Matthews, Ian; Palmer, Adrian; Schreve, Danielle; Taylor, Barry; Milner, Nicky

    2017-04-01

    We know little about the lives of the early humans who lived during the early Postglacial period (the Lateglacial and Early Holocene), a time characterised by abrupt climate change after 16,000, which includes a series of abrupt climatic transitions linked to the reorganisation of the global environment after the glacial maximum and the last major global warming event at the onset of the Holocene. The hunter-gatherers who lived during the early Postglacial have been characterised as highly mobile, dispersed and living within small groups, and there is much debate as to how they adapted to climatic and environmental change: did they move in response to climatic transitions (and if so what was the climatic threshold), or instead adapt their lifeways to the new environmental conditions? A key area for examining these ideas is the British Isles as it sits on the Atlantic fringe of Northwest Europe with a climate that is highly responsive to the wider climate forcing experienced in the northern Hemisphere. Furthermore, in this period, Britain is directly linked to continental Europe due to lowered global sea levels allowing for the ease of human migration in and out of this region. In general the British record has been seen as being dominated by abandonment and reoccupation in the Postglacial during periods of climatic transition with hunter-gatherer mobility being closely linked to the prevailing environment. Recent discoveries at the Early Mesolithic site of Star Carr and surrounding area, linked to local and regional climate records, based on isotopic, chironomid and pollen proxy data and dated at high chronological resolution, offer a new picture. Postglacial human occupation of the area commences at the Pleistocene/Holocene transition but is short lived and appears to end close to the Pre-Boreal Oscillation, However, this is followed by a period where hunter-gatherers occupy Star Carr and settle and invest time and effort into building huts and large scale wooden

  5. Quantifying attention shifts in augmented reality image-guided neurosurgery

    PubMed Central

    Drouin, Simon; Collins, D. Louis; Popa, Tiberiu; Kersten-Oertel, Marta

    2017-01-01

    Image-guided surgery (IGS) has allowed for more minimally invasive procedures, leading to better patient outcomes, reduced risk of infection, less pain, shorter hospital stays and faster recoveries. One drawback that has emerged with IGS is that the surgeon must shift their attention from the patient to the monitor for guidance. Yet both cognitive and motor tasks are negatively affected with attention shifts. Augmented reality (AR), which merges the realworld surgical scene with preoperative virtual patient images and plans, has been proposed as a solution to this drawback. In this work, we studied the impact of two different types of AR IGS set-ups (mobile AR and desktop AR) and traditional navigation on attention shifts for the specific task of craniotomy planning. We found a significant difference in terms of the time taken to perform the task and attention shifts between traditional navigation, but no significant difference between the different AR set-ups. With mobile AR, however, users felt that the system was easier to use and that their performance was better. These results suggest that regardless of where the AR visualisation is shown to the surgeon, AR may reduce attention shifts, leading to more streamlined and focused procedures. PMID:29184663

  6. Growth dynamics of SiGe nanowires by the vapour-liquid-solid method and its impact on SiGe/Si axial heterojunction abruptness.

    PubMed

    Pura, J L; Periwal, P; Baron, T; Jiménez, J

    2018-08-31

    The vapour-liquid-solid (VLS) method is by far the most extended procedure for bottom-up nanowire growth. This method also allows for the manufacture of nanowire axial heterojunctions in a straightforward way. To do this, during the growth process, precursor gases are switched on/off to obtain the desired change in the nanowire composition. Using this technique, axially heterostructured nanowires can be grown, which are crucial for the fabrication of electronic and optoelectronic devices. SiGe/Si nanowires are compatible with complementary metal oxide semiconductor (CMOS) technology, which improves their versatility and the possibility of integration with current electronic technologies. Abrupt heterointerfaces are fundamental for the development and correct operation of electronic and optoelectronic devices. Unfortunately, the VLS growth of SiGe/Si heterojunctions does not provide abrupt transitions because of the high solubility of group IV semiconductors in Au, with the corresponding reservoir effect that precludes the growth of sharp interfaces. In this work, we studied the growth dynamics of SiGe/Si heterojunctions based on already developed models for VLS growth. A composition map of the Si-Ge-Au liquid alloy is proposed to better understand the impact of the growing conditions on the nanowire growth process and the heterojunction formation. The solution of our model provides heterojunction profiles that are in good agreement with the experimental measurements. Finally, an in-depth study of the composition map provides a practical approach to the drastic reduction of heterojunction abruptness by reducing the Si and Ge concentrations in the catalyst droplet. This converges with previous approaches, which use catalysts aiming to reduce the solubility of the atomic species. This analysis opens new paths to the reduction of heterojunction abruptness using Au catalysts, but the model can be naturally extended to other catalysts and semiconductors.

  7. Turbulent forced convection of nanofluids downstream an abrupt expansion

    NASA Astrophysics Data System (ADS)

    Kimouche, Abdelali; Mataoui, Amina

    2018-03-01

    Turbulent forced convection of Nanofluids through an axisymmetric abrupt expansion is investigated numerically in the present study. The governing equations are solved by ANYS 14.0 CFD code based on the finite volume method by implementing the thermo-physical properties of each nanofluid. All results are analyzed through the evolutions of skin friction coefficient and Nusselt number. For each nanofluid, the effect of both volume fraction and Reynolds number on this type of flow configuration, are examined. An increase on average Nusselt number with the volume fraction and Reynolds number, are highlighted and correlated. Two relationships are proposed. The first one, determines the average Nusselt number versus Reynolds number, volume fraction and the ratio of densities of the solid particles to that of the base fluid ( \\overline{Nu}=f(\\operatorname{Re},φ, ρ_s/ρ_f) ). The second one varies according Reynolds number, volume fraction and the conductivities ratio of solid particle to that of the base fluid ( \\overline{Nu}=f(\\operatorname{Re},φ, k_s/k_f) ).

  8. Mechanical characterization of capsule properties using abrupt-step channels

    NASA Astrophysics Data System (ADS)

    Salsac, Anne-Virginie; Le Goff, Anne; Kaoui, Badr; Barthè-Biesel, Dominique; Biomechanics; Bioengineering Lab Team

    2017-11-01

    Capsules consisting of a liquid droplet enclosed by a thin polymerized membrane are commonly encountered in nature (cells) or in industrial process (pharmaceutical, cosmetic or food products). The mechanical properties of the capsule wall are essential to guarantee the particle integrity and release of the internal contents when and where necessary. The difficulty is to assess the mechanical properties of the thin membrane. We will show how abrupt-step channels can be used to identify the membrane viscoelastic properties and point of rupture. This can be achieved by using a channel presenting a step change in cross-section and inverting the direction of the flow of the capsule suspension within the tube. To deduce information on the viscoelasticity, we will exploit the relaxation of the capsules as they flow through the expansion. To study membrane rupture, we will instead invert the channel, block the capsules at the neck of the constriction and determine the pressure difference needed for breakup. All the experiments will be conducted on initially spherical capsules with a thin cross-linked protein membrane for a proof of concept.

  9. Transverse shifts of a light beam reflected from a uniaxially anisotropic chiral slab

    NASA Astrophysics Data System (ADS)

    Xu, Guoding; Li, Jun; Xiao, Yuting; Mao, Hongmin; Sun, Jian; Pan, Tao

    2015-01-01

    We study for the first time the transverse shifts of a Gaussian beam reflected from a uniaxially anisotropic chiral (UAC) slab, where the chirality appears only in one direction and the host medium is a uniaxial crystal or an electric plasma. The results indicate that the transverse shifts are closely related to the propagation behaviors of the eigenwaves in the slab. Specifically, when one or both of the eigenwaves are totally reflected at the second interface of the slab, the spatial transverse shift becomes resonances but is not enhanced; when one eigenwave is totally reflected at the first interface and the other is transmitted at the second interface, the larger and negative transverse shifts can be obtained. The propagation behaviors of the eigenwaves in the UAC slab provide more abundant information about the transverse shifts than in a single interface structure.

  10. Hydrologic impacts of past shifts of Earth's thermal equator offer insight into those to be produced by fossil fuel CO2.

    PubMed

    Broecker, Wallace S; Putnam, Aaron E

    2013-10-15

    Major changes in global rainfall patterns accompanied a northward shift of Earth's thermal equator at the onset of an abrupt climate change 14.6 kya. This northward pull of Earth's wind and rain belts stemmed from disintegration of North Atlantic winter sea ice cover, which steepened the interhemispheric meridional temperature gradient. A southward migration of Earth's thermal equator may have accompanied the more recent Medieval Warm to Little Ice Age climate transition in the Northern Hemisphere. As fossil fuel CO2 warms the planet, the continents of the Northern Hemisphere are expected to warm faster than the Southern Hemisphere oceans. Therefore, we predict that a northward shift of Earth's thermal equator, initiated by an increased interhemispheric temperature contrast, may well produce hydrologic changes similar to those that occurred during past Northern Hemisphere warm periods. If so, the American West, the Middle East, and southern Amazonia will become drier, and monsoonal Asia, Venezuela, and equatorial Africa will become wetter. Additional paleoclimate data should be acquired and model simulations should be conducted to evaluate the reliability of this analog.

  11. Reducing abrupt climate change risk using the Montreal Protocol and other regulatory actions to complement cuts in CO2 emissions

    PubMed Central

    Molina, Mario; Zaelke, Durwood; Sarma, K. Madhava; Andersen, Stephen O.; Ramanathan, Veerabhadran; Kaniaru, Donald

    2009-01-01

    Current emissions of anthropogenic greenhouse gases (GHGs) have already committed the planet to an increase in average surface temperature by the end of the century that may be above the critical threshold for tipping elements of the climate system into abrupt change with potentially irreversible and unmanageable consequences. This would mean that the climate system is close to entering if not already within the zone of “dangerous anthropogenic interference” (DAI). Scientific and policy literature refers to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to help avoid DAI and abrupt climate changes. We define “fast-action” to include regulatory measures that can begin within 2–3 years, be substantially implemented in 5–10 years, and produce a climate response within decades. We discuss strategies for short-lived non-CO2 GHGs and particles, where existing agreements can be used to accomplish mitigation objectives. Policy makers can amend the Montreal Protocol to phase down the production and consumption of hydrofluorocarbons (HFCs) with high global warming potential. Other fast-action strategies can reduce emissions of black carbon particles and precursor gases that lead to ozone formation in the lower atmosphere, and increase biosequestration, including through biochar. These and other fast-action strategies may reduce the risk of abrupt climate change in the next few decades by complementing cuts in CO2 emissions. PMID:19822751

  12. Application of the phase shifting diffraction interferometer for measuring convex mirrors and negative lenses

    DOEpatents

    Sommargren, Gary E.; Campbell, Eugene W.

    2004-03-09

    To measure a convex mirror, a reference beam and a measurement beam are both provided through a single optical fiber. A positive auxiliary lens is placed in the system to give a converging wavefront onto the convex mirror under test. A measurement is taken that includes the aberrations of the convex mirror as well as the errors due to two transmissions through the positive auxiliary lens. A second, measurement provides the information to eliminate this error. A negative lens can also be measured in a similar way. Again, there are two measurement set-ups. A reference beam is provided from a first optical fiber and a measurement beam is provided from a second optical fiber. A positive auxiliary lens is placed in the system to provide a converging wavefront from the reference beam onto the negative lens under test. The measurement beam is combined with the reference wavefront and is analyzed by standard methods. This measurement includes the aberrations of the negative lens, as well as the errors due to a single transmission through the positive auxiliary lens. A second measurement provides the information to eliminate this error.

  13. Application Of The Phase Shifting Diffraction Interferometer For Measuring Convex Mirrors And Negative Lenses

    DOEpatents

    Sommargren, Gary E.; Campbell, Eugene W.

    2005-06-21

    To measure a convex mirror, a reference beam and a measurement beam are both provided through a single optical fiber. A positive auxiliary lens is placed in the system to give a converging wavefront onto the convex mirror under test. A measurement is taken that includes the aberrations of the convex mirror as well as the errors due to two transmissions through the positive auxiliary lens. A second measurement provides the information to eliminate this error. A negative lens can also be measured in a similar way. Again, there are two measurement set-ups. A reference beam is provided from a first optical fiber and a measurement beam is provided from a second optical fiber. A positive auxiliary lens is placed in the system to provide a converging wavefront from the reference beam onto the negative lens under test. The measurement beam is combined with the reference wavefront and is analyzed by standard methods. This measurement includes the aberrations of the negative lens, as well as the errors due to a single transmission through the positive auxiliary lens. A second measurement provides the information to eliminate this error.

  14. Changes in nurses' decision making during a 12-h day shift.

    PubMed

    McClelland, L E; Switzer, F S; Pilcher, J J

    2013-01-01

    Although shift work is necessary in many health-care settings, research suggests that it can have detrimental effects on performance in health-care providers. To determine if a change in decision-making occurred across a 12-h day shift in a sample of registered nurses. The participants were nurses working a 12-h day shift (7 a.m.-7 p.m.) at a large hospital in the south-eastern USA. Participants completed a policy-capturing questionnaire, examining their likelihood of calling a physician in response to specific patient symptoms, at the beginning and end of the shift. They also completed self-report surveys on alertness, stress and sleepiness. Sixty-five nurses completed the study, an overall response rate of 41%. Participants significantly changed their decision-making policies from the beginning to the end of the work shift and also became significantly less alert and more stressed. However, there was no correlation between decision-making and reported alertness and stress. These results suggest that medical judgment in registered nurses changed from the beginning to the end of a 12-h day shift. One possible underlying mechanism responsible for the changes seen across the shift could be the ability to maintain attention, as suggested by the Controlled Attention Model. The current results expand upon previous research, indicating there are a variety of negative outcomes associated with shift work.

  15. Textile inspired flexible metamaterial with negative refractive index

    NASA Astrophysics Data System (ADS)

    Burgnies, L.; Lheurette, É.; Lippens, D.

    2015-04-01

    This work introduces metallo-dielectric woven fabric as a metamaterial for phase-front manipulation. Dispersion diagram as well as effective medium parameters retrieved from reflection and transmission coefficients point out negative values of refractive index. By numerical simulations, it is evidenced that a pair of meandered metallic wires, arranged in a top to bottom configuration, can yield to a textile metamaterial with simultaneously negative permittivity and permeability. While the effective negative permittivity stems from the metallic grid arrangement, resonating current loop resulting from the top to bottom configuration of two meandered metallic wires in near proximity produces magnetic activity with negative permeability. By adjusting the distance between pairs of metallic wires, the electric plasma frequency can be shifted to overlap the magnetic resonance. Finally, it is shown that the woven metamaterial is insensitive to the incident angle up to around 60°.

  16. The Mediterranean Sea regime shift at the end of the 1980s, and intriguing parallelisms with other European basins.

    PubMed

    Conversi, Alessandra; Fonda Umani, Serena; Peluso, Tiziana; Molinero, Juan Carlos; Santojanni, Alberto; Edwards, Martin

    2010-05-19

    Regime shifts are abrupt changes encompassing a multitude of physical properties and ecosystem variables, which lead to new regime conditions. Recent investigations focus on the changes in ecosystem diversity and functioning associated to such shifts. Of particular interest, because of the implication on climate drivers, are shifts that occur synchronously in separated basins. In this work we analyze and review long-term records of Mediterranean ecological and hydro-climate variables and find that all point to a synchronous change in the late 1980s. A quantitative synthesis of the literature (including observed oceanic data, models and satellite analyses) shows that these years mark a major change in Mediterranean hydrographic properties, surface circulation, and deep water convection (the Eastern Mediterranean Transient). We provide novel analyses that link local, regional and basin scale hydrological properties with two major indicators of large scale climate, the North Atlantic Oscillation index and the Northern Hemisphere Temperature index, suggesting that the Mediterranean shift is part of a large scale change in the Northern Hemisphere. We provide a simplified scheme of the different effects of climate vs. temperature on pelagic ecosystems. Our results show that the Mediterranean Sea underwent a major change at the end of the 1980s that encompassed atmospheric, hydrological, and ecological systems, for which it can be considered a regime shift. We further provide evidence that the local hydrography is linked to the larger scale, northern hemisphere climate. These results suggest that the shifts that affected the North, Baltic, Black and Mediterranean (this work) Seas at the end of the 1980s, that have been so far only partly associated, are likely linked as part a northern hemisphere change. These findings bear wide implications for the development of climate change scenarios, as synchronous shifts may provide the key for distinguishing local (i.e., basin

  17. The effects of double-shifts (15.5 hours) on sleep, fatigue and health.

    PubMed

    Kecklund, G; Ekstedt, M; Akerstedt, T; Dahlgren, A; Samuelson, B

    2001-12-01

    The aim of the present study was to investigate how "double-shifts" (15.5 hours) affects sleep, fatigue and self-rated health. The study was carried out on male construction workers of which 80% were long-distance commuters. The schedule involved two work periods and each work period involved two double shifts in a row. The subjects filled in a sleep/wake diary at 8 times across a year and a questionnaire at 3 times. They also wore an actigraph during one shift cycle. The results showed that sleepiness, and to a certain extent, mental fatigue increased during double shifts and accumulated across days. The short rest time (8.5 hours) between days caused insufficient sleep and approximately 5.5 hours of sleep was obtained between double shifts. Questionnaire data showed that complaints of insufficient sleep, exhaustion on awakening and pain symptoms increased across the year. It was concluded that a shift system involving double shifts has a negative effect on fatigue, recovery and health-related well-being.

  18. Is impaired set-shifting a feature of "pure" anorexia nervosa? Investigating the role of depression in set-shifting ability in anorexia nervosa and unipolar depression.

    PubMed

    Giel, Katrin E; Wittorf, Andreas; Wolkenstein, Larissa; Klingberg, Stefan; Drimmer, Eyal; Schönenberg, Michael; Rapp, Alexander M; Fallgatter, Andreas J; Hautzinger, Martin; Zipfel, Stephan

    2012-12-30

    Impaired set-shifting has been reported in patients with anorexia nervosa (AN) and in patients with affective disorders, including major depression. Due to the prevalent comorbidity of major depression in AN, this study aimed to examine the role of depression in set-shifting ability. Fifteen patients with AN without a current comorbid depression, 20 patients with unipolar depression (UD) and 35 healthy control participants were assessed using the Trail Making Test (TMT), the Wisconsin Card Sorting Test (WCST) and a Parametric Go/No-Go Test (PGNG). Set-shifting ability was intact in patients with AN without a comorbid depression. However, patients with UD performed significantly poorer in all three tasks compared to AN patients and in the TMT compared to healthy control participants. In both patient groups, set-shifting ability was moderately negatively correlated with severity of depressive symptoms, but was unrelated to BMI and severity of eating disorder symptoms in AN patients. Our results suggest a pivotal role of comorbidity for neuropsychological functioning in AN. Impairments of set-shifting ability in AN patients may have been overrated and may partly be due to comorbid depressive disorders in investigated patients. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

  19. Millivolt-scale DC shifts in the human scalp EEG: evidence for a nonneuronal generator.

    PubMed

    Voipio, Juha; Tallgren, Pekka; Heinonen, Erkki; Vanhatalo, Sampsa; Kaila, Kai

    2003-04-01

    Slow shifts in the human scalp-recorded EEG, including those related to changes in brain CO(2) levels, have been generally assumed to result from changes in the level of tonic excitation of apical dendrites of cortical pyramidal neurons. We readdressed this issue using DC-EEG shifts elicited in healthy adult subjects by hypo- or hypercapnia. A 3-min period of hyperventilation resulted in a prompt negative shift with a rate of up to 10 microV/s at the vertex (Cz) and an extremely steep dependence (up to 100 microV/mmHg) on the end-tidal Pco(2). This shift had a maximum of up to -2 mV at Cz versus the temporal derivations (T3/T4). Hyperventilation-like breathing of 5% CO(2)-95% O(2), which does not lead to a significant hypocapnia, resulted in a near-complete block of the negative DC shift at Cz. Hypoventilation, or breathing 5% CO(2) in air at normal respiratory rate, induced a positive shift. The high amplitude of the voltage gradients on the scalp induced by hyperventilation is not consistent with a neuronal origin. Instead, the present data suggest that they are generated by extracortical volume currents driven by a Pco(2)-dependent potential difference across epithelia separating the cerebrospinal fluid and blood. Since changes in respiratory patterns and, hence, in the level of brain Pco(2), are likely to occur under a number of experimental conditions in which slow EEG responses have been reported (e.g., attention shifts, preparatory states, epileptic seizures, and hypoxic episodes), the present results call for a thorough reexamination of the mechanisms underlying scalp-recorded DC-EEG responses.

  20. Unregistered health care staff's perceptions of 12 hour shifts: an interview study.

    PubMed

    Thomson, Louise; Schneider, Justine; Hare Duke, Laurie

    2017-10-01

    The purpose of the study was to explore unregistered health care staff's perceptions of 12 hour shifts on work performance and patient care. Many unregistered health care staff work 12 hour shifts, but it is unclear whether these are compatible with good quality care or work performance. Twenty five health care assistants from a range of care settings with experience of working 12 hour shifts took part in interviews or focus groups. A wide range of views emerged on the perceived impact of 12 hour shifts in different settings. Negative outcomes were perceived to occur when 12 hour shifts were combined with short-staffing, consecutive long shifts, high work demands, insufficient breaks and working with unfamiliar colleagues. Positive outcomes were perceived to be more likely in a context of control over shift patterns, sufficient staffing levels, and a supportive team climate. The perceived relationship between 12 hour shifts and patient care and work performance varies by patient context and wider workplace factors, but largely focuses on the ability to deliver relational aspects of care. Nursing managers need to consider the role of other workplace factors, such as shift patterns and breaks, when implementing 12 hour shifts with unregistered health care staff. © 2017 John Wiley & Sons Ltd.

  1. Uranium isotope evidence for the abrupt onset of oceanic anoxia during the end-Guadalupian mass extinction

    NASA Astrophysics Data System (ADS)

    Song, H.; Algeo, T. J.; Romaniello, S. J.; Tong, J.; Du, Y.; Wei, H.; Shen, S.; Anbar, A. D.

    2016-12-01

    The end-Guadalupian (Middle/Late Permian) mass extinction was one of the major crises of the Phanerozoic, resulting in the disappearance of numerous shallow-marine taxa. Several hypotheses have been proposed for this catastrophe but are still under debate. Here, we undertook a high-resolution carbonate U isotopic (δ238/235U) study of the Guadalupian-Lopingian boundary (GLB) at the Penglaitan section (Guadalupian/ Lopingian GSSP) to explore the causal relationship between ocean redox changes and the mass extinction event. The Penglaitan δ238U profile shows two abrupt negative excursions, one in the uppermost Guadalupian (Beds 6j-6k) and the other in the lowermost Lopingian (lower Bed 7). The first excursion (from ‒0.30 ‰ to ‒0.50 ‰) coincided with the main extinction event, suggesting that rapid expansion of oceanic anoxia may have been a contributor to the biotic crisis. The second, larger excursion (from ‒0.25 ‰ to ‒0.65 ‰) demonstrates that the crisis interval was marked by multiple phases of expanded oceanic anoxia. A U-isotope mass balance model shows that, during these excursions, the anoxic/euxinic sink flux increased to 40 % of the total sink flux of seawater U, which is three times of the modern ocean value of 13 %. This study thus provides circumstantial evidence for a causal relationship between expansion of oceanic anoxia and the end-Guadalupian biotic crisis.

  2. Study of chemical shift in Kα, Kβ1,3 and Kβ// X-ray emission lines of 37Rb compounds with WDXRF

    NASA Astrophysics Data System (ADS)

    Kainth, Harpreet Singh; Singh, Ranjit; Singh, Tejbir; Mehta, D.; Shahi, J. S.; Kumar, Sanjeev

    2018-05-01

    The positive and negative chemical shifts in Kα, Kβ1,3 and Kβ// X-ray emission lines of rubidium compounds were measured with high resolution WDXRF spectrometer. The measured energy shifts in Kα emission lines ranges from -2.95 eV to -3.64 eV, Kβ1,3 emission lines ranges from 1.16 eV to 1.32 eV and Kβ// emission lines ranges from 1.31 eV to 4.36 eV respectively. In the present work, it has been found that chemical shift in Kβ// X-ray emission lines were found to be larger than Kα and Kβ1,3 X-ray emission lines. To find the cause of chemical shift, various factors like effective charge, line intensity ratio, bond length and electro-negativity were calculated and correlated with the chemical shift.

  3. The Social Pathologies of Self-Realization: A Diagnosis of the Consequences of the Shift in Individualization

    ERIC Educational Resources Information Center

    Hammershoj, Lars Geer

    2009-01-01

    The aim of this article is to inquire into today's social pathologies, i.e. the negative consequences of the developmental processes of society. In a dialogue with Axel Honneth, the article asserts that a shift has occurred in individualization, a shift that implies a fundamental change in social pathologies: Social pathologies no longer derive…

  4. Acute tubular necrosis (ATN) presenting with an unusually prolonged period of marked polyuria heralded by an abrupt oliguric phase.

    PubMed

    Ramoutar, Virin; Landa, Cristian; James, Leighton R

    2014-08-22

    A 50-year-old African-American man presented with acute tubular necrosis (ATN) secondary to hypotension from non-typhoid Salmonella gastroenteritis and bacteraemia. The oliguric phase lasted only 24 h followed by prolonged polyuria for 20 days, with urine output in excess of 16 L/day at maximum. As indexed in PubMed this is only the second published case of this nature since 1974, in which an abrupt oliguric phase of 24 h or less heralded prolonged polyuria in ATN. The diagnosis is challenging as fractional excretion of sodium early in the clinical course and rapid normalisation of serum creatinine with intravenous fluids (IVF) may point towards prerenal azotaemia resulting in a premature discharge from hospital. Patients with an abrupt oliguric phase may suffer a secondary renal insult from the profound fluid loss that is to follow and may need inpatient monitoring with supplemental IVF to prevent deleterious outcomes. 2014 BMJ Publishing Group Ltd.

  5. Acute tubular necrosis (ATN) presenting with an unusually prolonged period of marked polyuria heralded by an abrupt oliguric phase

    PubMed Central

    Ramoutar, Virin; Landa, Cristian; James, Leighton R

    2014-01-01

    A 50-year-old African-American man presented with acute tubular necrosis (ATN) secondary to hypotension from non-typhoid Salmonella gastroenteritis and bacteraemia. The oliguric phase lasted only 24 h followed by prolonged polyuria for 20 days, with urine output in excess of 16 L/day at maximum. As indexed in PubMed this is only the second published case of this nature since 1974, in which an abrupt oliguric phase of 24 h or less heralded prolonged polyuria in ATN. The diagnosis is challenging as fractional excretion of sodium early in the clinical course and rapid normalisation of serum creatinine with intravenous fluids (IVF) may point towards prerenal azotaemia resulting in a premature discharge from hospital. Patients with an abrupt oliguric phase may suffer a secondary renal insult from the profound fluid loss that is to follow and may need inpatient monitoring with supplemental IVF to prevent deleterious outcomes. PMID:25150229

  6. Shift work--problems and its impact on female nurses in Udaipur, Rajasthan India.

    PubMed

    Rathore, H; Shukla, K; Singh, S; Tiwari, G

    2012-01-01

    Abstract : There is good evidence that shift work has negative effects on workers health, safety and performance. It is quite appropriate that attention is paid to this very important feature of socio-technical systems, which may adversely affect mental and physical health, social life and safety of shift workers. Research into the impact of shift work on professionals has consistently identified a range of negative outcomes in physical, psychological, and social domains (Akerstedt, 1988; Costa, Lievore, Casaletti, Gaffuri, & Folkard, 1989; Kogi, 2005; Paley & Tepas, 1994). Hospitals, the biggest employer in the health care field, employ more night shift workers than any other industry. It can therefore be inferred that in medical domain high percentage of workforce may be affected by problems related to shift work. Thus the present study will provide knowledge base for the problems faced by the female nurses. The present study was undertaken with an objective of getting an insight into the problems faced by female nurses in shift work. . It was found that the female nurses in India worked on roaster pattern of change in shift every seven days. They did not have a say in the change of duties, it could only be done on mutual grounds. Partners of younger group did not much adjust to their shift pattern this created stress among the nurses.The results showed that the female nurses in both the age groups i.e. 30-45 years and 45-60 years faced many problems related to health and well being, fatigue, social and domestic situations. They could not give much time to their children in particular. Travelling in nights was risky for them. Common problem was the insufficient sleep during night shifts. The nurses had to cater to the needs of the family, children in particular along with the adjustments to be made due to shift work. They had to sometimes do the night duties and attend social functions as a part of their duty. Children and husband in some cases did not cooperate

  7. Abrupt onset of muscle dysfunction after treatment for Grave's disease: a case report.

    PubMed

    Hernán Martínez, José; Sánchez, Alfredo; Torres, Oberto; Palermo, Coromoto; Santiago, Mónica; Figueroa, Carlos; Trinidad, Rafael; Mangual, Michelle; Gutierrez, Madeleine; González, Eva; Miranda, María de Lourdes

    2014-01-01

    Myopathy is a known complication of hypothyroidism, commonly characterized by an elevation in Creatine Kinase (CPK) due to increase capillary permeability proportional to the hypothyroid state. Thyroid hormone is important for the expression of fast myofibrillar proteins in the muscle. In hypothyroidism the expression of these proteins are deficient and there is an increase accumulation of slow myofibrillar proteins. A rapid or abrupt descend in thyroid hormones caused by radioiodine therapy after prolonged hyperthyroidism can lead to local hypothyroid state within the muscle tissue, resulting in CPK elevation and hypothyroid myopathy. Hormone replacement leads to resolution of symptoms and normalization of muscle enzymes serum levels.

  8. ON AN ALLEGED TRUTH/FALSITY ASYMMETRY IN CONTEXT SHIFTING EXPERIMENTS

    PubMed Central

    Hansen, Nat

    2012-01-01

    Keith DeRose has argued that context shifting experiments should be designed in a specific way in order to accommodate what he calls a ‘truth/falsity asymmetry’. I explain and critique DeRose's reasons for proposing this modification to contextualist methodology, drawing on recent experimental studies of DeRose's bank cases as well as experimental findings about the verification of affirmative and negative statements. While DeRose's arguments for his particular modification to contextualist methodology fail, the lesson of his proposal is that there is good reason to pay close attention to several subtle aspects of the design of context shifting experiments. PMID:25821248

  9. Control of Goos-Hänchen shift via input probe field intensity

    NASA Astrophysics Data System (ADS)

    Ziauddin; Lee, Ray-Kuang; Qamar, Sajid

    2016-11-01

    We suggest a scheme to control Goos-Hänchen (GH) shift in an ensemble of strongly interacting Rydberg atoms, which act as super-atoms due to the dipole blockade mechanism. The ensemble of three-level cold Rydberg-dressed (87Rb) atoms follows a cascade configurations where two fields, i.e, a strong control and a weak field are employed [D. Petrosyan, J. Otterbach, and M. Fleischhauer, Phys. Rev. Lett. 107, 213601 (2011)]. The propagation of probe field is influenced by two-photon correlation within the blockade distance, which are damped due to the saturation of super-atoms. The amplitude of GH shift in the reflected light depends on the intensity of probe field. We observe large negative GH shift in the reflected light for small values of the probe field intensities.

  10. Comparison of trends and abrupt changes of the South Asia high from 1979 to 2014 in reanalysis and radiosonde datasets

    NASA Astrophysics Data System (ADS)

    Shi, Chunhua; Huang, Ying; Guo, Dong; Zhou, Shunwu; Hu, Kaixi; Liu, Yu

    2018-05-01

    The South Asian High (SAH) has an important influence on atmospheric circulation and the Asian climate in summer. However, current comparative analyses of the SAH are mostly between reanalysis datasets and there is a lack of sounding data. We therefore compared the climatology, trends and abrupt changes in the SAH in the Japanese 55-year Reanalysis (JRA-55) dataset, the National Centers for Environmental Prediction Climate Forecast System Reanalysis (NCEP-CFSR) dataset, the European Center for Medium-Range Weather Forecasts Reanalysis Interim (ERA-interim) dataset and radiosonde data from China using linear analysis and a sliding t-test. The trends in geopotential height in the control area of the SAH were positive in the JRA-55, NCEP-CFSR and ERA-interim datasets, but negative in the radiosonde data in the time period 1979-2014. The negative trends for the SAH were significant at the 90% confidence level in the radiosonde data from May to September. The positive trends in the NCEP-CFSR dataset were significant at the 90% confidence level in May, July, August and September, but the positive trends in the JRA-55 and ERA-Interim were only significant at the 90% confidence level in September. The reasons for the differences in the trends of the SAH between the radiosonde data and the three reanalysis datasets in the time period 1979-2014 were updates to the sounding systems, changes in instrumentation and improvements in the radiation correction method for calculations around the year 2000. We therefore analyzed the trends in the two time periods of 1979-2000 and 2001-2014 separately. From 1979 to 2000, the negative SAH trends in the radiosonde data mainly agreed with the negative trends in the NCEP-CFSR dataset, but were in contrast with the positive trends in the JRA-55 and ERA-Interim datasets. In 2001-2014, however, the trends in the SAH were positive in all four datasets and most of the trends in the radiosonde and NCEP-CFSR datasets were significant. It is

  11. Increasing Optimism Protects Against Pain-Induced Impairment in Task-Shifting Performance.

    PubMed

    Boselie, Jantine J L M; Vancleef, Linda M G; Peters, Madelon L

    2017-04-01

    Persistent pain can lead to difficulties in executive task performance. Three core executive functions that are often postulated are inhibition, updating, and shifting. Optimism, the tendency to expect that good things happen in the future, has been shown to protect against pain-induced performance deterioration in executive function updating. This study tested whether this protective effect of a temporary optimistic state by means of a writing and visualization exercise extended to executive function shifting. A 2 (optimism: optimism vs no optimism) × 2 (pain: pain vs no pain) mixed factorial design was conducted. Participants (N = 61) completed a shifting task once with and once without concurrent painful heat stimulation after an optimism or neutral manipulation. Results showed that shifting performance was impaired when experimental heat pain was applied during task execution, and that optimism counteracted pain-induced deterioration in task-shifting performance. Experimentally-induced heat pain impairs shifting task performance and manipulated optimism or induced optimism counteracted this pain-induced performance deterioration. Identifying psychological factors that may diminish the negative effect of persistent pain on the ability to function in daily life is imperative. Copyright © 2016 American Pain Society. Published by Elsevier Inc. All rights reserved.

  12. Reliability of the anterior drawer test, the pivot shift test, and the Lachman test.

    PubMed

    Kim, S J; Kim, H K

    1995-08-01

    In 147 patients with arthroscopically proved chronic injuries of the anterior cruciate ligament, the anterior drawer test, the Lachman test, and the pivot shift test were done before operation under general or spinal anesthesia. Results of the anterior drawer test were positive in 79.6% of the patients, in 98.6% patients having the Lachman test, and in 89.8% of patients having the pivot shift test. In 19 cases (12.9%), arthroscopic examination showed reattachment of the proximally torn end of the anterior cruciate ligament to the posterior cruciate ligament. In these cases, results of the anterior drawer test were positive in 13 patients (68.4%), in 17 (89.5%) patients having the Lachman test, and in 12 patients (63.2%) having the pivot shift test. In 15 cases with a false negative pivot shift test, arthroscopy showed blockage of anterior subluxation of the lateral tibial condyle by a partially functioning portion of the anterior cruciate ligament, which was reattached to the posterior cruciate ligament in 7 cases. In 2 cases with a false negative Lachman test, there was firm reattachment of the torn end of the anterior cruciate ligament to the proximal portion of the posterior cruciate ligament combined with a bucket handle tear of the medial meniscus. The Lachman test was most sensitive in diagnosing chronic injuries of the anterior cruciate ligament. The pivot shift test was also sensitive but was influenced by many factors.

  13. Intrapartum anti-disseminated intravascular coagulation therapy leading to successful vaginal delivery following intrauterine fetal death caused by placental abruption: a case report.

    PubMed

    Honda, Michiko; Matsunaga, Shigetaka; Era, Sumiko; Takai, Yasushi; Baba, Kazunori; Seki, Hiroyuki

    2014-12-23

    Disseminated intravascular coagulation due to placental abruption with intrauterine fetal death is not uncommon. It can result in increased maternal mortality rates and the need for hysterectomy or greater transfusion volumes if the delivery is not completed within six to eight hours. However, consensus is lacking regarding the delivery approach for cases in which delivery is prolonged. A 37-year-old Japanese woman was transported to our tertiary center two and a half hours after the onset of labor because of a diagnosis of placental abruption with intrauterine fetal death at 40 weeks and three days' gestation. On arrival, although severe hypofibrinogenemia was observed, there was no external hemorrhage. Because her cervical canal dilation was good (Bishop score, 7), labor was induced using oxytocin. Anti-disseminated intravascular coagulation therapy was simultaneously started via transfusion. After her hypofibrinogenemia resolved, delivery progressed rapidly, and the fetus was delivered approximately 10 hours after the onset. To reduce postpartum hemorrhage, 6g of fibrinogen concentrate and tranexamic acid, an antifibrinolytic agent, were administered immediately before extraction of the dead fetus and placenta. Although the amount of intrapartum hemorrhage was 1824g, there was no abnormal bleeding after delivery, and our patient was discharged three days later. In cases of placental abruption complicated with disseminated intravascular coagulation, intrapartum administration of coagulation factors can simultaneously promote effective labor and correct hypofibrinogenemia, enabling minimally invasive vaginal delivery.

  14. Potential Arctic tundra vegetation shifts in response to changing temperature, precipitation and permafrost thaw

    NASA Astrophysics Data System (ADS)

    van der Kolk, Henk-Jan; Heijmans, Monique M. P. D.; van Huissteden, Jacobus; Pullens, Jeroen W. M.; Berendse, Frank

    2016-11-01

    Over the past decades, vegetation and climate have changed significantly in the Arctic. Deciduous shrub cover is often assumed to expand in tundra landscapes, but more frequent abrupt permafrost thaw resulting in formation of thaw ponds could lead to vegetation shifts towards graminoid-dominated wetland. Which factors drive vegetation changes in the tundra ecosystem are still not sufficiently clear. In this study, the dynamic tundra vegetation model, NUCOM-tundra (NUtrient and COMpetition), was used to evaluate the consequences of climate change scenarios of warming and increasing precipitation for future tundra vegetation change. The model includes three plant functional types (moss, graminoids and shrubs), carbon and nitrogen cycling, water and permafrost dynamics and a simple thaw pond module. Climate scenario simulations were performed for 16 combinations of temperature and precipitation increases in five vegetation types representing a gradient from dry shrub-dominated to moist mixed and wet graminoid-dominated sites. Vegetation composition dynamics in currently mixed vegetation sites were dependent on both temperature and precipitation changes, with warming favouring shrub dominance and increased precipitation favouring graminoid abundance. Climate change simulations based on greenhouse gas emission scenarios in which temperature and precipitation increases were combined showed increases in biomass of both graminoids and shrubs, with graminoids increasing in abundance. The simulations suggest that shrub growth can be limited by very wet soil conditions and low nutrient supply, whereas graminoids have the advantage of being able to grow in a wide range of soil moisture conditions and have access to nutrients in deeper soil layers. Abrupt permafrost thaw initiating thaw pond formation led to complete domination of graminoids. However, due to increased drainage, shrubs could profit from such changes in adjacent areas. Both climate and thaw pond formation

  15. Transverse magnetic field effect on the giant Goos–Hänchen shifts based on a degenerate two-level system

    NASA Astrophysics Data System (ADS)

    Nasehi, R.

    2018-06-01

    We study the effect of the Goos–Hänchen (GH) shifts through a cavity with degenerate two-level systems in the line of . For this purpose, we focus on the transverse magnetic field (TMF) in a Floquet frame to obtain the giant GH shifts. Physically, the collisional effects of TMF lead to increasing the population trapping in the ground state. However, we demonstrate that the population trapping generates the large negative or positive GH shifts and simultaneously switches from superluminal to subluminal (or vice versa). Also, we investigate the other optical properties such as the longitudinal magnetic field (LMF), which plays an important role in the control of the GH shifts and leads to the generation of new subsystems. In the next step, we evaluate the GH shifts beyond the multi-photon resonance condition by the control of TMF. Moreover, we compute the appearance of negative and positive GH shifts by setting the width of the incident Gaussian beams in the presence of a multi-photon resonance condition. Our results show that superluminal or subluminal light propagation can be simultaneously controlled by adjusting the rates of the TMF and LMF. The significant effects of these factors on the degenerate two-level systems provide different applications such as slow light, optical switches and quantum information storage.

  16. Trends and shifts in streamflow in Hawaii, 1913-2008

    USGS Publications Warehouse

    Bassiouni, Maoya; Oki, Delwyn S.

    2013-01-01

    This study addresses a need to document changes in streamflow and base flow (groundwater discharge to streams) in Hawai'i during the past century. Statistically significant long-term (1913-2008) downward trends were detected (using the nonparametric Mann-Kendall test) in low-streamflow and base-flow records. These long-term downward trends are likely related to a statistically significant downward shift around 1943 detected (using the nonparametric Pettitt test) in index records of streamflow and base flow. The downward shift corresponds to a decrease of 22% in median streamflow and a decrease of 23% in median base flow between the periods 1913-1943 and 1943-2008. The shift coincides with other local and regional factors, including a change from a positive to a negative phase in the Pacific Decadal Oscillation, shifts in the direction of the trade winds over Hawai'i, and a reforestation programme. The detected shift and long-term trends reflect region-wide changes in climatic and land-cover factors. A weak pattern of downward trends in base flows during the period 1943-2008 may indicate a continued decrease in base flows after the 1943 shift. Downward trends were detected more commonly in base-flow records than in high-streamflow, peak-flow, and rainfall records. The decrease in base flow is likely related to a decrease in groundwater storage and recharge and therefore is a valuable indicator of decreasing water availability and watershed vulnerability to hydrologic changes. Whether the downward trends will continue is largely uncertain given the uncertainty in climate-change projections and watershed responses to changes.

  17. Shifts in fisheries management: adapting to regime shifts

    PubMed Central

    King, Jacquelynne R.; McFarlane, Gordon A.; Punt, André E.

    2015-01-01

    For many years, fisheries management was based on optimizing yield and maintaining a target biomass, with little regard given to low-frequency environmental forcing. However, this policy was often unsuccessful. In the last two to three decades, fisheries science and management have undergone a shift towards balancing sustainable yield with conservation, with the goal of including ecosystem considerations in decision-making frameworks. Scientific understanding of low-frequency climate–ocean variability, which is manifested as ecosystem regime shifts and states, has led to attempts to incorporate these shifts and states into fisheries assessment and management. To date, operationalizing these attempts to provide tactical advice has met with limited success. We review efforts to incorporate regime shifts and states into the assessment and management of fisheries resources, propose directions for future investigation and outline a potential framework to include regime shifts and changes in ecosystem states into fisheries management.

  18. Nutrition and health in hotel staff on different shift patterns.

    PubMed

    Seibt, R; Süße, T; Spitzer, S; Hunger, B; Rudolf, M

    2015-08-01

    Limited research is available that examines the nutritional behaviour and health of hotel staff working alternating and regular shifts. To analyse the nutritional behaviour and health of employees working in alternating and regular shifts. The study used an ex post facto cross-sectional analysis to compare the nutritional behaviour and health parameters of workers with alternating shifts and regular shift workers. Nutritional behaviour was assessed with the Food Frequency Questionnaire. Body dimensions (body mass index, waist hip ratio, fat mass and active cell mass), metabolic values (glucose, triglyceride, total cholesterol and low- and high-density lipoprotein), diseases and health complaints were included as health parameters. Participants worked in alternating (n = 53) and regular shifts (n = 97). The average age of subjects was 35 ± 10 years. There was no significant difference in nutritional behaviour, most surveyed body dimensions or metabolic values between the two groups. However, alternating shift workers had significantly lower fat mass and higher active cell mass but nevertheless reported more pronounced health complaints. Sex and age were also confirmed as influencing the surveyed parameters. Shift-dependent nutritional problems were not conspicuously apparent in this sample of hotel industry workers. Health parameters did not show significantly negative attributes for alternating shift workers. Conceivably, both groups could have the same level of knowledge on the health effects of nutrition and comparable opportunities to apply this. Further studies on nutritional and health behaviour in the hotel industry are necessary in order to create validated screening programmes. © The Author 2015. Published by Oxford University Press on behalf of the Society of Occupational Medicine. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  19. Impact of night-shift work on the prevalence of erosive esophagitis in shipyard male workers.

    PubMed

    Chung, Tae Heum; Lee, Jiho; Kim, Moon Chan

    2016-08-01

    Whether night-shift work is a risk factor for gastroesophageal reflux disease is controversial. The aim of this study was to investigate the association between night-shift work and other factors, and erosive esophagitis. A cross-sectional study with 6040 male shipyard workers was performed. Esophagogastroduodenoscopic examination and a survey about night-shift work status, lifestyle, medical history, educational status, and marital status were conducted in all workers. The odds ratios of erosive esophagitis according to night-shift work status were calculated by using the logistic regression model. The prevalence of erosive esophagitis increased in the night-shift workers [odds ratio, 95 % confidence interval: 1.41 (1.03-1.94)]. According to multiple logistic regression models, night-shift work, obesity, smoking, and alcohol consumption of ≥140 g/week were significant risk factors for erosive esophagitis. By contrast, Helicobacter pylori infection was negatively associated with erosive esophagitis. Night-shift work is suggested to be a risk factor for erosive esophagitis. Avoidance of night-shift work and lifestyle modification should be considered for prevention and management of gastroesophageal reflux disease.

  20. On the calculation of turbulent heat transport downstream from an abrupt pipe expansion

    NASA Technical Reports Server (NTRS)

    Chieng, C. C.; Launder, B. E.

    1980-01-01

    A numerical study of flow and heat transfer in the separated flow region produced by an abrupt pipe explosion is reported, with emphasis on the region in the immediate vicinity of the wall where turbulent transport gives way to molecular conduction and diffusion. The analysis is based on a modified TEACH-2E program with the standard k-epsilon model of turbulence. Predictions of the experimental data of Zemanick and Dougall (1970) for a diameter ratio of 0.54 show generally encouraging agreement with experiment. At a diameter ratio of 0.43 different trends are discernable between measurement and calculation, though this appears to be due to effects unconnected with the wall region studied here.

  1. [Analysis of relationship between shift-work and occupational stress among workers from different companies].

    PubMed

    Gu, Guizhen; Yu, Shanfa; Zhou, Wenhui; Wu, Hui

    2016-01-01

    To investigate the relationship between work in shifts and occupational stress. A total of 5338 employees from 13 companies were investigated by cluster sampling, and occupational stress measuring tools, job content questionnaire, and effort-reward imbalance questionnaire were used to investigate occupational stress factors, stress reaction, and the condition of work in shifts. The employees who worked in shifts accounted for 46.6%. The condition of work in shifts varied significantly across different companies, employees with different individual features (including sex, job title, degree of education, age, working years, smoking, and drinking), and employees with different weekly working times(P<0.01 or P<0.05); health status was associated with work in shifts(P<0.01); compared with the employees who did not work in shifts, those who worked in shifts had significantly lower scores of technology utilization, work control level, psychological need, reward, social support, and job satisfaction(P<0.01 or P<0.05), as well as significantly higher scores of physical demands, effort, depressive symptoms, and negative affectivity(P<0.01). Work in shifts can affect health status, and is associated with occupational stress.

  2. Temperature-tunable lasing in negative dielectric chiral nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Wu, Ri-Na; Wu, Jie; Wu, Xiao-Jiao; Dai, Qin

    2015-05-01

    In this work, negative dielectric nematic liquid crystal SLC12V620-400, chiral dopant S811, and laser dye DCM are used to prepare dye-doped chiral nematic liquid crystal laser sample. In order to investigate temperature-tunable lasing in negative dielectric chiral nematic liquid crystal, we measure the transmission and lasing spectrum of this sample. The photonic band gap (PBG) is observed to red shift with its width reducing from 71.2 nm to 40.2 nm, and its short-wavelength band edge moves 55.3 nm while the long-wavelength band edge only moves 24.9 nm. The wavelength of output laser is found to red shift from 614.4 nm at 20 °C to 662.8 nm at 67 °C, which is very different from the previous experimental phenomena. The refractive indices, parallel and perpendicular to the director in chiral nematic liquid crystal have different dependencies on temperature. The experiment shows that the pitch of this chiral nematic liquid crystal increases with the increase of temperature. The decrease in the PBG width, different shifts of band edges, and the red shift of laser wavelength are the results of refractive indices change and pitch thermal elongation. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Outstanding Young Scholars Growth Plans of Colleges and Universities in Liaoning Province, China (Grant No. LJQ2013022), the Science and Technology Research of Liaoning Province, China (Grant No. L2010465), the Open Funds of Liaoning Province Key Laboratory of Laser and Optical Information of Shenyang Ligong University, China.

  3. Ocular Measures of Sleepiness Are Increased in Night Shift Workers Undergoing a Simulated Night Shift Near the Peak Time of the 6-Sulfatoxymelatonin Rhythm

    PubMed Central

    Ftouni, Suzanne; Sletten, Tracey L.; Nicholas, Christian L.; Kennaway, David J.; Lockley, Steven W.; Rajaratnam, Shantha M.W.

    2015-01-01

    Study Objectives: The study examined the relationship between the circadian rhythm of 6-sulphatoxymelatonin (aMT6s) and ocular measures of sleepiness and neurobehavioral performance in shift workers undergoing a simulated night shift. Methods: Twenty-two shift workers (mean age 33.4, SD 11.8 years) were tested at approximately the beginning (20:00) and the end (05:55) of a simulated night shift in the laboratory. At the time point corresponding to the end of the simulated shift, 14 participants were classified as being within range of 6-sulphatoxymelatonin (aMT6s) acrophase— defined as 3 hours before or after aMT6s peak—and 8 were classified as outside aMT6s acrophase range. Participants completed the Karolinska Sleepiness Scale (KSS) and the auditory psychomotor vigilance task (aPVT). Waking electroencephalography (EEG) was recorded and infrared reflectance oculography was used to collect ocular measures of sleepiness: positive and negative amplitude/velocity ratio (PosAVR, NegAVR), mean blink total duration (BTD), the percentage of eye closure (%TEC), and a composite score of sleepiness levels (Johns Drowsiness Scale; JDS). Results: Participants who were tested within aMT6s acrophase range displayed higher levels of sleepiness on ocular measures (%TEC, BTD, PosAVR, JDS), objective sleepiness (EEG delta power frequency band), subjective ratings of sleepiness, and neurobehavioral performance, compared to those who were outside aMT6s acrophase range. Conclusions: The study demonstrated that objective ocular measures of sleepiness are sensitive to circadian rhythm misalignment in shift workers. Citation: Ftouni S, Sletten TL, Nicholas CL, Kennaway DJ, Lockley SW, Rajaratnam SM. Ocular measures of sleepiness are increased in night shift workers undergoing a simulated night shift near the peak time of the 6-sulfatoxymelatonin rhythm. J Clin Sleep Med 2015;11(10):1131–1141. PMID:26094925

  4. Implications of Shift Work for Parent-Adolescent Relationships in Dual-Earner Families

    ERIC Educational Resources Information Center

    Davis, Kelly D.; Crouter, Ann C.; McHale, Susan M.

    2006-01-01

    This investigation examined the implications of shift work for parent-adolescent relationship quality--intimacy, conflict, parental knowledge, and involvement--in a sample of 376 dual-earner families. The findings suggested that mothers' relationships with their adolescents were not negatively impacted by their working nonstandard schedules but…

  5. Monitoring channel head erosion processes in response to an artificially induced abrupt base level change using time-lapse photography 2301

    USDA-ARS?s Scientific Manuscript database

    Headcut and channel extension in response to an abrupt base level change in 2004 of approximately 1m was studied in a 1.29 ha semiarid headwater drainage on the Walnut Gulch Experimental Watershed (WGEW) in southeastern Arizona, USA. Field observations and time-lapse photography were coupled with hy...

  6. Predictors of Perinatal Mortality Associated with Placenta Previa and Placental Abruption: An Experience from a Low Income Country

    PubMed Central

    Berhan, Yifru

    2014-01-01

    A retrospective cohort study design was used to assess predictors of perinatal mortality in women with placenta previa and abruption between January 2006 and December 2011. Four hundred thirty-two women (253 with placenta previa and 179 with placental abruption) were eligible for analysis. Binary logistic regression, Kaplan-Meier survival curve, and receiver operating characteristic (ROC) curve were used. On admission, 77% of the women were anaemic (<12 gm/dL) with mean haemoglobin level of 9.0 ± 3.0 gm/dL. The proportion of overall severe anaemia increased from about 28% on admission to 41% at discharge. There were 50% perinatal deaths (neonatal deaths of less than seven days of age and fetal deaths after 28 weeks of gestation). In the adjusted odds ratios, lengthy delay in accessing hospital care, prematurity, anaemia in the mothers, and male foetuses were independent predictors of perinatal mortality. The haemoglobin level at admission was more sensitive and more specific than prematurity in the prediction of perinatal mortality. The proportion of severe anaemia and perinatal mortality was probably one of the highest in the world. PMID:25002975

  7. Ebb and Flow in Parent-Child Interactions: Shifts from Early through Middle Childhood

    PubMed Central

    Bradley, Robert H.; Pennar, Amy; Iida, Masumi

    2015-01-01

    Objective This study documents the strength of relations between key parent and child behaviors as they occur during typical encounters for both mothers and fathers and determines whether there were shifts in the strength of relations between parent and child behaviors during early and middle childhood. Design Multivariate multi-level modeling was used to examine associations between three parent behaviors (respect for autonomy, stimulation of development, hostility) and two child behaviors (agency, negativity) as they occurred in typical parent-child activities at four time points from 54 months through 5th grade for 817 families. Results For mothers and fathers, respect for autonomy and stimulation were associated with child agency. Paternal hostility was negatively associated with child agency, but for mothers the relation became more positive with age. Parental respect for autonomy and hostility were associated with child negativity for both mothers and fathers; however, for mothers, relations between autonomy support and child negativity became more positive, and relations between hostility and child negativity became less positive. Conclusions There are clear shifts in the strength of relations between some parenting behaviors and child behaviors from early to middle childhood, indicative of a changing dialectic as children become more independent and different dialectics for mothers and fathers. Parenting behavior links to child competence and adaptive behavior, and the findings may help resolve some uncertainties about relations between parental behavior and children's developmental trajectories. PMID:26877717

  8. Abrupt increase in rat carotid blood flow induces rapid alteration of artery mechanical properties

    PubMed Central

    Monson, Kenneth L.; Matsumoto, Melissa M.; Young, William L.; Manley, Geoffrey T.; Hashimoto, Tomoki

    2010-01-01

    Vascular remodeling is essential to proper vessel function. Dramatic changes in mechanical environment, however, may initiate pathophysiological vascular remodeling processes that lead to vascular disease. Previous work by some of our group has demonstrated a dramatic rise in matrix metalloproteinase (MMP) expression shortly following an abrupt increase in carotid blood flow. We hypothesized that there would be a corresponding change in carotid mechanical properties. Unilateral carotid ligation surgery was performed to produce an abrupt, sustained increase in blood flow through the contralateral carotid artery of rats. The flow-augmented artery was harvested after sham surgery or 1, 2, or 6 days after flow augmentation. Vessel mechanical response in the circumferential direction was then evaluated through a series of pressure-diameter tests. Results show that the extent of circumferential stretch (normalized change in diameter) at in vivo pressure levels was significantly different (p<0.05) from normo-flow controls at 1 and 2 days following flow augmentation. Measurements at 1, 2, and 6 days were not significantly different from one another, but a trend in the data suggested that circumferential stretch was largest 1 day following surgery and subsequently decreased toward baseline values. Because previous work with this model indicated a similar temporal pattern for MMP-9 expression, an exploratory set of experiments was conducted where vessels were tested 1 day following surgery in animals treated with broad spectrum MMP inhibitors (either doxycycline or GM6001). Results showed a trend for the inhibitors to minimize changes in mechanical properties. Observations demonstrate that vessel mechanical properties change rapidly following flow augmentation and that alterations may be linked to expression of MMPs. PMID:21094476

  9. How time delay and network design shape response patterns in biochemical negative feedback systems.

    PubMed

    Börsch, Anastasiya; Schaber, Jörg

    2016-08-24

    Negative feedback in combination with time delay can bring about both sustained oscillations and adaptive behaviour in cellular networks. Here, we study which design features of systems with delayed negative feedback shape characteristic response patterns with special emphasis on the role of time delay. To this end, we analyse generic two-dimensional delay differential equations describing the dynamics of biochemical signal-response networks. We investigate the influence of several design features on the stability of the model equilibrium, i.e., presence of auto-inhibition and/or mass conservation and the kind and/or strength of the delayed negative feedback. We show that auto-inhibition and mass conservation have a stabilizing effect, whereas increasing abruptness and decreasing feedback threshold have a de-stabilizing effect on the model equilibrium. Moreover, applying our theoretical analysis to the mammalian p53 system we show that an auto-inhibitory feedback can decouple period and amplitude of an oscillatory response, whereas the delayed feedback can not. Our theoretical framework provides insight into how time delay and design features of biochemical networks act together to elicit specific characteristic response patterns. Such insight is useful for constructing synthetic networks and controlling their behaviour in response to external stimulation.

  10. Testing for thresholds of ecosystem collapse in seagrass meadows.

    PubMed

    Connell, Sean D; Fernandes, Milena; Burnell, Owen W; Doubleday, Zoë A; Griffin, Kingsley J; Irving, Andrew D; Leung, Jonathan Y S; Owen, Samuel; Russell, Bayden D; Falkenberg, Laura J

    2017-10-01

    Although the public desire for healthy environments is clear-cut, the science and management of ecosystem health has not been as simple. Ecological systems can be dynamic and can shift abruptly from one ecosystem state to another. Such unpredictable shifts result when ecological thresholds are crossed; that is, small cumulative increases in an environmental stressor drive a much greater change than could be predicted from linear effects, suggesting an unforeseen tipping point is crossed. In coastal waters, broad-scale seagrass loss often occurs as a sudden event associated with human-driven nutrient enrichment (eutrophication). We tested whether the response of seagrass ecosystems to coastal nutrient enrichment is subject to a threshold effect. We exposed seagrass plots to different levels of nutrient enrichment (dissolved inorganic nitrogen) for 10 months and measured net production. Seagrass response exhibited a threshold pattern when nutrient enrichment exceeded moderate levels: there was an abrupt and large shift from positive to negative net leaf production (from approximately 0.04 leaf production to 0.02 leaf loss per day). Epiphyte load also increased as nutrient enrichment increased, which may have driven the shift in leaf production. Inadvertently crossing such thresholds, as can occur through ineffective management of land-derived inputs such as wastewater and stormwater runoff along urbanized coasts, may account for the widely observed sudden loss of seagrass meadows. Identification of tipping points may improve not only adaptive-management monitoring that seeks to avoid threshold effects, but also restoration approaches in systems that have crossed them. © 2017 Society for Conservation Biology.

  11. Concurrent intraoperative uterine rupture and placenta accreta. Do preoperative chronic hypertension, preterm premature rupture of membranes, chorioamnionitis, and placental abruption provide warning to this rare occurrence?

    PubMed

    Cometa, M Anthony; Wasilko, Scott M; Wendling, Adam L

    2018-04-01

    Uterine and placental pathology can be a major cause of morbidity and mortality in the parturient and infant. When presenting alone, placental abruption, uterine rupture, or placenta accreta can result in significant peripartum hemorrhage, requiring aggressive surgical and anesthetic management; however, the presence of multiple concurrent uterine and placental pathologies can result in significant morbidity and mortality. We present the anesthetic management of a parturient who underwent an urgent cesarean delivery for non-reassuring fetal tracing in the setting of chronic hypertension, preterm premature rupture of membranes, and chorioamnionitis who was subsequently found to have placental abruption, uterine rupture, and placenta accreta.

  12. Gap solitons in a nonlinear quadratic negative-index cavity.

    PubMed

    Scalora, Michael; de Ceglia, Domenico; D'Aguanno, Giuseppe; Mattiucci, Nadia; Akozbek, Neset; Centini, Marco; Bloemer, Mark J

    2007-06-01

    We predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton.

  13. Low-loss single-layer metamaterial with negative index of refraction at visible wavelengths.

    PubMed

    García-Meca, C; Ortuño, R; Salvador, R; Martínez, A; Martí, J

    2007-07-23

    We present a structure exhibiting a negative index of refraction at visible or near infrared frequencies using a single metal layer. This contrasts with recently developed structures based on metal-dielectric-metal composites. The proposed metamaterial consists of periodically arranged thick stripes interacting with each other to give rise to a negative permeability. Improved designs that allow for a negative index for both polarizations are also presented. The structures are numerically analyzed and it is shown that the dimensions can be engineered to shift the negative index band within a region ranging from telecommunication wavelengths down to blue light.

  14. NIGHT SHIFT WORK AND FRACTURE RISK: THE NURSES’ HEALTH STUDY

    PubMed Central

    Feskanich, Diane; Hankinson, Susan E.; Schernhammer, Eva S.

    2009-01-01

    Summary Night shift work suppresses melatonin production and has been associated with an increased risk of major diseases including hormonally related tumors. Experimental evidence suggests that light at night acts through endocrine disruption, likely mediated by melatonin. To date, no observational study has addressed the effect of night work on osteoporotic fractures, another condition highly sensitive to sex steroid exposure. Our study, to our knowledge the first to address this question, supports the hypothesis that night shift work may negatively affect bone health, adding to the growing list of ailments that have been associated with shift work. Introduction We evaluated the association between night shift work and fractures at the hip and wrist in postmenopausal nurses. Methods The study population was drawn from Nurses’ Health Study participants who were working full or part time in nursing in 1988 and had reported their total number of years of rotating night shift work. Through 2000, 1,223 incident wrist and hip fractures involving low or moderate trauma were identified among 38,062 postmenopausal women. We calculated multivariate relative risks (RR) of fracture over varying lengths of follow-up in relation to years of night shift work. Results Compared with women who never worked night shifts, 20+ years of night shift work was associated with a significantly increased risk of wrist and hip fractures over eight years of follow-up (RR = 1.37, 95% confidence interval [CI], 1.04–1.80). This risk was strongest among women with a lower BMI (<24) who never used hormone replacement therapy (RR = 2.36; 95% CI, 1.33–4.20). The elevated risk was no longer apparent with twelve years of follow-up after the baseline single assessment of night shift work. Conclusions Long durations of rotating night shift work may contribute to risk of hip and wrist fractures, although the potential for unexplained confounding cannot be ruled out. PMID:18766292

  15. [NIGHT SHIFT WORK AND HEALTH DISORDER RISK IN FEMALE WORKERS].

    PubMed

    Kukhtina, E G; Solionova, L G; Fedichkina, T P; Zykova, I E

    2015-01-01

    There was evaluated the risk to health in females employed in shift work, including night shifts. According to the data of periodical medical examinations health indices of 403 females employed in shift work, including night shifts, were compared with indices of 205 females--workers of administrative units of the same enterprise. Overall relative risk (RR) for the health disorder associated with the night shift was 1.2 (95%; confidence interval (CI): 1.09-1.28). A statistically significant increase in risk was observed in relation to uterine fibroids (OR 1.3; 95% CI: 1.06-1.54), mastopathy (OR 1.4; 95% CI: 1.2-1.6), inorganic sleep disorders (OR 8.8; 95% CI 2.6-29.8). At the boundary of the statistical significance there was the increase in the risk for obesity (OR 1.2; 95% C: 0.97-1.39), hypertension (OR 1.2; 95% CI, 0.9-1.5) and endometriosis (OR 1.5; 95% CI: 0.98-2.16). There was revealed an adverse effect of night shifts on the gestation course: ectopic pregnancy in the experimental group occurred 6.6 times more frequently than in the control group (95% CI: 0.87-50.2), and spontaneous abortion--1.7 times (95% CI: 0.95-3.22). The performed study has once again confirmed the negative impact of smoking on women's reproductive health: smoking women in the experimental group compared with the control group smokers had 2.7 times increased risk of uterine fibroids (within 1.06-7.0), the risk in non-smokers was significantly lower--1.2 (0.98-1.4). The findings suggest about a wide range of health problems related to employment on shift work, including night shifts, which indicates to the need for adoption of regulatory and preventive measures aimed to this professional group.

  16. Change from slowly rotating 8-hour shifts to rapidly rotating 8-hour and 12-hour shifts using participative shift roster design.

    PubMed

    Smith, P A; Wright, B M; Mackey, R W; Milsop, H W; Yates, S C

    1998-01-01

    The study examined the impact of change, from slowly rotating continuous 8-hour shifts to more rapidly rotating continuous 8-hour and 12-hour shifts, on the health and quality of life of shift workers. Self-report survey data were collected from 72 shift workers at 3 sewage treatment plants before and several months after roster change. After the change 1 plant first worked a rapidly rotating, 8-hour shift roster and then worked a 12-hour shift roster, and the other 2 plants worked continuous 12-hour shift rosters. After the change the shift workers at each plant reported increased satisfaction with roster design, a decrease in physical and psychological circadian malaise associated with shift work, improved day sleep quality, less tiredness, and improvements in the quality of home, social and work life. A between-plant comparison of the rapidly rotating 8-hour and 12-hour shift rosters showed greater improvements had been obtained with the 12-hour shift roster, and no significant differences in tiredness or sleep quality between the redesigned 8- and 12-hour shift rosters. However, a within-plant matched-pairs comparison at the 1st plant of the rapidly rotating 8-hour shift roster and the 12-hour shift roster showed no significant differences. The results show that the prior level of support for change may best explain the impact of roster redesign on individual well-being. They lend further support to shift worker participation in roster design.

  17. Elicitation and abrupt termination of behaviorally significant catchlike tension in a primitive insect.

    PubMed

    Hoyle, G; Field, L H

    1983-07-01

    Sustained steady contractural or catchlike tension (CT) occurs in the metathoracic extensor tibiae muscle of the primitive insect the weta (Orthoptera: Stenopelmatidae) during its characteristic leg-extension defense behavior or following leg-position conditioning. Similar action occurs occasionally in semi-intact preparations and is abruptly turned off by a single peripheral inhibitory impulse. These phenomena were reproduced routinely by first infusing saline containing 10(-8) M (or stronger) octopamine into the muscle for 12 min, and then stimulating the slow excitatory motor neuron SETi with a brief burst. Direct stimulation of the dorsal unpaired median neuron, innervating the extensor tibiae (DUMETi) prior to SETi stimulation, also led to CT. Both octopamine and DUMETi markedly enhanced the tension developed in response to a burst of impulses in SETi.

  18. North Atlantic ocean circulation and abrupt climate change during the last glaciation.

    PubMed

    Henry, L G; McManus, J F; Curry, W B; Roberts, N L; Piotrowski, A M; Keigwin, L D

    2016-07-29

    The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ(13)C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean's persistent, central role in abrupt glacial climate change. Copyright © 2016, American Association for the Advancement of Science.

  19. Abrupt uplift within the past 1700 years at Southern Puget Sound, Washington

    USGS Publications Warehouse

    Bucknam, R.C.; Hemphill-Haley, E.; Leopold, E.B.

    1992-01-01

    Shorelines rose as much as 7 meters along southern Puget Sound and Hood Canal between 500 and 1700 years ago. Evidence for this uplift consists of elevated wave-cut shore platforms near Seattle and emerged, peat-covered tidal flats as much as 60 kilometers to the southwest. The uplift was too rapid for waves to leave intermediate shorelines on even the best preserved platform. The tidal flats also emerged abruptly; they changed into freshwater swamps and meadows without first becoming tidal marshes. Where uplift was greatest, it adjoined an inferred fault that crosses Puget Sound at Seattle and it probably accompanied reverse slip on that fault 1000 to 1100 years ago. The uplift and probable fault slip show that the crust of the North America plate contains potential sources of damaging earthquakes in the Puget Sound region.

  20. The effect on road safety of a modal shift from car to bicycle.

    PubMed

    Stipdonk, Henk; Reurings, Martine

    2012-01-01

    To describe and apply a method to assess the effect on road safety of a modal shift from cars to bicycles. Ten percent of all car trips shorter than 7.5 km were assumed to be replaced by bicycle trips. Single-vehicle and multivehicle crashes involving cars and/or bicycles were considered. The safety of car occupants and cyclists was taken into account as well as the safety of other road users involved in such crashes. The computations were carried out by age and gender. Assuming constant risk (casualties per distance traveled), the expected number of accidents is proportional to the mobility shift. Several types of risk were considered: the risk of being injured as a car driver or cyclist and the risk of being involved as a car driver or cyclist in a crash in which another road user is injured. The results indicated that the total gain of the modal shift was negative for fatalities, which means that there was a net increase in the number of fatalities. The modal shift was advantageous for young drivers and disadvantageous for elderly drivers. In addition, it was more positive for males than for females. The turning point was around the age of 35. For hospitalized casualties, due to the strong influence of the many hospitalized cyclists in nonmotorized vehicle crashes, there was a strong negative overall effect, and the modal shift resulted in a positive effect for 18- and 19-year-old males only. Overall, a small increase (up to 1%) in the number of cyclist fatalities and a greater increase of 3.5 percent in the number of inpatients was expected. The increase in casualties was mainly due to the proportion of single-vehicle bicycle crashes with serious injuries in relation to the total number of injured cyclists. The effect of the modal shift was shown to depend on age and gender, resulting in fewer casualties for younger drivers and for women. It is possible to provide a first approximation of the effect on road safety of a mobility shift from cars to bicycles. This

  1. Local fluid shifts and edema in humans during simulated microgravity

    NASA Technical Reports Server (NTRS)

    Hargens, Alan R.

    1991-01-01

    Local fluid shifts and edema in humans during simulated microgravity is studied. Recent results and significance and future plans on the following research topics are discussed: mechanisms of headward edema formation during head-down tilt; postural responses of head and foot microcirculations and their sensitivity to bed rest; and transcapillary fluid transport associated with lower body negative pressure (LBNP) with and without saline ingestion.

  2. A study examining the impact of 12-hour shifts on critical care staff.

    PubMed

    Richardson, Annette; Turnock, Christopher; Harris, Liz; Finley, Alison; Carson, Sarah

    2007-11-01

    Twelve-hour shifts contribute to flexible patterns of work, but the effects on delivery of direct care and staff fatigue are important topics for deeper examination. To examine the impact and implications of 12-hour shifts on critical care staff. A staged dual approach using two focus groups (n = 16) and questionnaires (n = 147) with critical care staff from three critical care units. Positive effects were found with planning and prioritizing care, improved relationships with patients/relatives, good-quality time off work and ease of travelling to work. Less favourable effects were with caring for patients in isolation cubicles and the impact on staff motivation and tiredness. Acceptable patterns of work were suggested for 'numbers of consecutive shifts' and 'rest periods between shifts'. Most participants believed 12-hour shifts should continue. The challenge is to ensure existing systems and practices develop to improve on the less positive effects of working 12-hour shifts. This study provides nurse managers with important and relevant staff views on the impact of working 12-hour shifts. In particular to those working within a critical care environment and suggests the challenge is to ensure existing systems and practices develop to improve on the less encouraging effects of working 12-hour shifts. It adds an understanding of the senior nurse's view on the positive and negative effects of managing and organizing staff off duty to safely run a department with 12-hour shifts.

  3. Positive mood on negative self-statements: paradoxical intervention in geriatric patients with major depressive disorder.

    PubMed

    Lanza, Claudia; Müller, Christine; Riepe, Matthias W

    2018-06-01

    Mood regulation is said to be age-specific. Negative self-statements (NST) are used to induce negative mood. However, little is known about NST in older persons and geriatric patients with major depressive disorder. We investigated healthy young (YC) and older (OC) control subjects and older patients with major depressive disorder (OP). Subjects were exposed to NST subsequent to baseline assessment comprising psychological and psychometric tests. Preferences for emotionally salient stimuli were measured with an eye-tracking task. Mood in YC shifted towards depressive mood or remained stable on NST. In OC and more so in OP some subjects responded paradoxically subsequent to NST with mood being more positive than at baseline. Extent and direction of mood change correlated with prevailing mood at baseline and total score in the Hamilton Depression Anxiety Scale. At baseline, YC had a preference for 'happy' stimuli. Subsequent to NST view preference shifted towards 'sad.' In contrast, OC had no preference at baseline but shifted towards 'happy' on NST. Mood change on NST is age-specific. In geriatric patients with depressive disorder, however, NST may induce a shift towards more positive mood and thus may be used in future as a therapeutic intervention.

  4. Reduced Tolerance to Night Shift in Chronic Shift Workers: Insight From Fractal Regulation.

    PubMed

    Li, Peng; Morris, Christopher J; Patxot, Melissa; Yugay, Tatiana; Mistretta, Joseph; Purvis, Taylor E; Scheer, Frank A J L; Hu, Kun

    2017-07-01

    Healthy physiology is characterized by fractal regulation (FR) that generates similar structures in the fluctuations of physiological outputs at different time scales. Perturbed FR is associated with aging and age-related pathological conditions. Shift work, involving repeated and chronic exposure to misaligned environmental and behavioral cycles, disrupts circadian coordination. We tested whether night shifts perturb FR in motor activity and whether night shifts affect FR in chronic shift workers and non-shift workers differently. We studied 13 chronic shift workers and 14 non-shift workers as controls using both field and in-laboratory experiments. In the in-laboratory study, simulated night shifts were used to induce a misalignment between the endogenous circadian pacemaker and the sleep-wake cycles (ie, circadian misalignment) while environmental conditions and food intake were controlled. In the field study, we found that FR was robust in controls but broke down in shift workers during night shifts, leading to more random activity fluctuations as observed in patients with dementia. The night shift effect was present even 2 days after ending night shifts. The in-laboratory study confirmed that night shifts perturbed FR in chronic shift workers and showed that FR in controls was more resilience to the circadian misalignment. Moreover, FR during real and simulated night shifts was more perturbed in those who started shift work at older ages. Chronic shift work causes night shift intolerance, which is probably linked to the degraded plasticity of the circadian control system. © Sleep Research Society 2017. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

  5. Demographic compensation and tipping points in climate-induced range shifts.

    PubMed

    Doak, Daniel F; Morris, William F

    2010-10-21

    To persist, species are expected to shift their geographical ranges polewards or to higher elevations as the Earth's climate warms. However, although many species' ranges have shifted in historical times, many others have not, or have shifted only at the high-latitude or high-elevation limits, leading to range expansions rather than contractions. Given these idiosyncratic responses to climate warming, and their varied implications for species' vulnerability to climate change, a critical task is to understand why some species have not shifted their ranges, particularly at the equatorial or low-elevation limits, and whether such resilience will last as warming continues. Here we show that compensatory changes in demographic rates are buffering southern populations of two North American tundra plants against the negative effects of a warming climate, slowing their northward range shifts, but that this buffering is unlikely to continue indefinitely. Southern populations of both species showed lower survival and recruitment but higher growth of individual plants, possibly owing to longer, warmer growing seasons. Because of these and other compensatory changes, the population growth rates of southern populations are not at present lower than those of northern ones. However, continued warming may yet prove detrimental, as most demographic rates that improved in moderately warmer years declined in the warmest years, with the potential to drive future population declines. Our results emphasize the need for long-term, range-wide measurement of all population processes to detect demographic compensation and to identify nonlinear responses that may lead to sudden range shifts as climatic tipping points are exceeded.

  6. FunShift: a database of function shift analysis on protein subfamilies

    PubMed Central

    Abhiman, Saraswathi; Sonnhammer, Erik L. L.

    2005-01-01

    Members of a protein family normally have a general biochemical function in common, but frequently one or more subgroups have evolved a slightly different function, such as different substrate specificity. It is important to detect such function shifts for a more accurate functional annotation. The FunShift database described here is a compilation of function shift analysis performed between subfamilies in protein families. It consists of two main components: (i) subfamilies derived from protein domain families and (ii) pairwise subfamily comparisons analyzed for function shift. The present release, FunShift 12, was derived from Pfam 12 and consists of 151 934 subfamilies derived from 7300 families. We carried out function shift analysis by two complementary methods on families with up to 500 members. From a total of 179 210 subfamily pairs, 62 384 were predicted to be functionally shifted in 2881 families. Each subfamily pair is provided with a markup of probable functional specificity-determining sites. Tools for searching and exploring the data are provided to make this database a valuable resource for protein function annotation. Knowledge of these functionally important sites will be useful for experimental biologists performing functional mutation studies. FunShift is available at http://FunShift.cgb.ki.se. PMID:15608176

  7. Concurrent intraoperative uterine rupture and placenta accreta. Do preoperative chronic hypertension, preterm premature rupture of membranes, chorioamnionitis, and placental abruption provide warning to this rare occurrence?

    PubMed Central

    Wasilko, Scott M.; Wendling, Adam L.

    2018-01-01

    Uterine and placental pathology can be a major cause of morbidity and mortality in the parturient and infant. When presenting alone, placental abruption, uterine rupture, or placenta accreta can result in significant peripartum hemorrhage, requiring aggressive surgical and anesthetic management; however, the presence of multiple concurrent uterine and placental pathologies can result in significant morbidity and mortality. We present the anesthetic management of a parturient who underwent an urgent cesarean delivery for non-reassuring fetal tracing in the setting of chronic hypertension, preterm premature rupture of membranes, and chorioamnionitis who was subsequently found to have placental abruption, uterine rupture, and placenta accreta. PMID:29756067

  8. Convection and macrosegregation in Al-19Cu alloy directionally solidified through an abrupt contraction in cross-section: A comparison with Al-7Si

    NASA Astrophysics Data System (ADS)

    Ghods, M.; Lauer, M.; Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2017-02-01

    Hypoeutectic Al-19 wt. % Cu alloys were directionally solidified in cylindrical molds that featured an abrupt cross-section decrease 9.5 to 3.2 mm in diameter). Thermo-solutal convection and cross-section-change-induced shrinkage flow effects on macrosegregation were investigated. Dendrite clustering and extensive radial macrosegregation was seen, particularly in the larger cross-section before contraction. This alloy shows positive longitudinal macrosegregation near the contraction followed by negative macrosegregation right after it; the extent of macrosegregation, however, decreases with increasing growth speed. The degree of thermo-solutal convection was compared to another study investigating directional solidification of Al-7 wt. % Si [1] in order to study the effect of solutal expansion coefficient on macrosegregation. An interesting change of the radial macrosegregation profile, attributable to the area-change-induced-shrinkage flow, was observed very close to the contraction. A two-dimensional model accounting for both shrinkage and thermo-solutal convection was used to simulate solidification, the resulting steepling as well as axial and radial macrosegregation. The experimentally observed macrosegregation associated with the contraction during directional solidification was well predicted by the numerical simulations.

  9. Suspended few-layer graphene beam electromechanical switch with abrupt on-off characteristics and minimal leakage current

    NASA Astrophysics Data System (ADS)

    Kim, Sung Min; Song, Emil B.; Lee, Sejoon; Seo, Sunae; Seo, David H.; Hwang, Yongha; Candler, R.; Wang, Kang L.

    2011-07-01

    Suspended few-layer graphene beam electro-mechanical switches (SGSs) with 0.15 μm air-gap are fabricated and electrically characterized. The SGS shows an abrupt on/off current characteristics with minimal off current. In conjunction with the narrow air-gap, the outstanding mechanical properties of graphene enable the mechanical switch to operate at a very low pull-in voltage (VPI) of 1.85 V, which is compatible with conventional complimentary metal-oxide-semiconductor (CMOS) circuit requirements. In addition, we show that the pull-in voltage exhibits an inverse dependence on the beam length.

  10. Flow Regime Study in a Circulating Fluidized Bed Riser with an Abrupt Exit: [1] High Density Suspension

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mei, J.S.; Lee, G.T.; Seachman, S.M.

    2008-05-13

    Flow regime study was conducted in a 0.3 m diameter, 15.5 m tall circulating fluidized bed (CFB) riser with an abrupt exit at the National Energy Technology Laboratory of the U. S. Department of Energy. A statistical designed test series was conducted including four (4) operating set points and a duplicated center point (therefore a total of 6 operating set points). Glass beads of mean diameter 200 μm and particle density of 2,430 kg/m3 were used as bed material. The CFB riser was operated at various superficial gas velocities ranging from 5.6 to 7.6 m/s and solid mass flux frommore » a low of 86 to a high of 303 kg/m2-s. Results of the apparent solids fraction profile as well as the radial particle velocity profile were analyzed in order to identify the presence of Dense Suspension Upflow (DSU) conditions. DSU regime was found to exist at the bottom of the riser, while the middle section of the riser was still exhibiting core-annular flow structure. Due to the abrupt geometry of the exit, the DSU regime was also found at the top of the riser. In addition the effects of the azimuthal angle, riser gas velocity, and mass solids flux on the particle velocity were investigated and are discussed in this paper.« less

  11. If it bleeds, it leads: separating threat from mere negativity

    PubMed Central

    Boshyan, Jasmine; Adams, Reginald B.; Mote, Jasmine; Betz, Nicole; Ward, Noreen; Hadjikhani, Nouchine; Bar, Moshe; Barrett, Lisa F.

    2015-01-01

    Most theories of emotion hold that negative stimuli are threatening and aversive. Yet in everyday experiences some negative sights (e.g. car wrecks) attract curiosity, whereas others repel (e.g. a weapon pointed in our face). To examine the diversity in negative stimuli, we employed four classes of visual images (Direct Threat, Indirect Threat, Merely Negative and Neutral) in a set of behavioral and functional magnetic resonance imaging studies. Participants reliably discriminated between the images, evaluating Direct Threat stimuli most quickly, and Merely Negative images most slowly. Threat images evoked greater and earlier blood oxygen level-dependent (BOLD) activations in the amygdala and periaqueductal gray, structures implicated in representing and responding to the motivational salience of stimuli. Conversely, the Merely Negative images evoked larger BOLD signal in the parahippocampal, retrosplenial, and medial prefrontal cortices, regions which have been implicated in contextual association processing. Ventrolateral as well as medial and lateral orbitofrontal cortices were activated by both threatening and Merely Negative images. In conclusion, negative visual stimuli can repel or attract scrutiny depending on their current threat potential, which is assessed by dynamic shifts in large-scale brain network activity. PMID:24493851

  12. Negative gate bias and light illumination-induced hump in amorphous InGaZnO thin film transistor.

    PubMed

    Jeon, Jae-Hong; Seo, Seung-Bum; Park, Han-Sung; Choe, Hee-Hwan; Seo, Jong-Hyun; Park, Kee-Chan; Park, Sang-Hee Ko

    2013-11-01

    While observing the transfer characteristics of a-IGZO TFTs, it was noticed that a hump occurred in the subthreshold regime after light and bias stress. This study analyzes the mechanism of the hump occurrence. It was determined that hump characteristics were related with parasitic TFTs which formed at the peripheral edges parallel with the channel direction. It seems that the negative shift of the transfer characteristics of parasitic TFTs was larger than that of the main TFT under light and bias stress. Therefore, the difference in the negative shift between the main TFT and the parasitic TFT was the origin of the hump occurrence. We investigated the instability of a-IGZO TFTs under negative gate bias with light illumination for various channel structures in order to verify the above mechanism.

  13. Choices between positive and negative reinforcement during treatment for escape-maintained behavior.

    PubMed

    DeLeon, I G; Neidert, P L; Anders, B M; Rodriguez-Catter, V

    2001-01-01

    Positive reinforcement was more effective than negative reinforcement in promoting compliance and reducing escape-maintained problem behavior for a child with autism. Escape extinction was then added while the child was given a choice between positive or negative reinforcement for compliance and the reinforcement schedule was thinned. When the reinforcement requirement reached 10 consecutive tasks, the treatment effects became inconsistent and reinforcer selection shifted from a strong preference for positive reinforcement to an unstable selection pattern.

  14. Depressed adolescents' positive and negative use of social media.

    PubMed

    Radovic, Ana; Gmelin, Theresa; Stein, Bradley D; Miller, Elizabeth

    2017-02-01

    This qualitative study examined descriptions of social media use among 23 adolescents (18 female, 5 male) who were diagnosed with depression to explore how social media use may influence and be influenced by psychological distress. Adolescents described both positive and negative use of social media. Positive use included searching for positive content (i.e. for entertainment, humor, content creation) or for social connection. Negative use included sharing risky behaviors, cyberbullying, and for making self-denigrating comparisons with others. Adolescents described three types of use in further detail including "oversharing" (sharing updates at a high frequency or too much personal information), "stressed posting" (sharing negative updates with a social network), and encountering "triggering posts." In the context of treatment, these adolescents shifted their social media use patterns from what they perceived as negative to more positive use. Implications for clinicians counseling depressed adolescents on social media use are discussed. Copyright © 2016 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.

  15. Depressed adolescents’ positive and negative use of social media

    PubMed Central

    Radovic, Ana; Gmelin, Theresa; Stein, Bradley D.; Miller, Elizabeth

    2017-01-01

    This qualitative study examined descriptions of social media use among 23 adolescents (18 female, 5 male) who were diagnosed with depression to explore how social media use may influence and be influenced by psychological distress. Adolescents described both positive and negative use of social media. Positive use included searching for positive content (i.e. for entertainment, humor, content creation) or for social connection. Negative use included sharing risky behaviors, cyberbullying, and for making self-denigrating comparisons with others. Adolescents described three types of use in further detail including “oversharing” (sharing updates at a high frequency or too much personal information), “stressed posting” (sharing negative updates with a social network), and encountering “triggering posts.” In the context of treatment, these adolescents shifted their social media use patterns from what they perceived as negative to more positive use. Implications for clinicians counseling depressed adolescents on social media use are discussed. PMID:27997851

  16. Ice-coupled wave propagation across an abrupt change in ice rigidity, density, or thickness

    NASA Astrophysics Data System (ADS)

    Barrett, Murray D.; Squire, Vernon A.

    1996-09-01

    The model of Fox and Squire [1990, 1991, 1994], which discusses the oblique propagation of surface gravity waves from the open sea into an ice sheet of constant thickness and properties, is augmented to include propagation across an abrupt transition of properties within a continuous ice sheet or across two dissimilar ice sheets that abut one another but are free to move independently. Rigidity, thickness, and/or density may change across the transition, allowing, for example, the modeling of ice-coupled waves into, across, and out of refrozen leads and polynyas, across cracks, and through coherent pressure ridges. Reflection and transmission behavior is reported for various changes in properties under both types of transition conditions.

  17. Forced-rupture of cell-adhesion complexes reveals abrupt switch between two brittle states

    NASA Astrophysics Data System (ADS)

    Toan, Ngo Minh; Thirumalai, D.

    2018-03-01

    Cell adhesion complexes (CACs), which are activated by ligand binding, play key roles in many cellular functions ranging from cell cycle regulation to mediation of cell extracellular matrix adhesion. Inspired by single molecule pulling experiments using atomic force spectroscopy on leukocyte function-associated antigen-1 (LFA-1), expressed in T-cells, bound to intercellular adhesion molecules (ICAM), we performed constant loading rate (rf) and constant force (F) simulations using the self-organized polymer model to describe the mechanism of ligand rupture from CACs. The simulations reproduce the major experimental finding on the kinetics of the rupture process, namely, the dependence of the most probable rupture forces (f*s) on ln rf (rf is the loading rate) exhibits two distinct linear regimes. The first, at low rf, has a shallow slope, whereas the slope at high rf is much larger, especially for a LFA-1/ICAM-1 complex with the transition between the two occurring over a narrow rf range. Locations of the two transition states (TSs) extracted from the simulations show an abrupt change from a high value at low rf or constant force, F, to a low value at high rf or F. This unusual behavior in which the CACs switch from one brittle (TS position is a constant over a range of forces) state to another brittle state is not found in forced-rupture in other protein complexes. We explain this novel behavior by constructing the free energy profiles, F(Λ)s, as a function of a collective reaction coordinate (Λ), involving many key charged residues and a critical metal ion (Mg2+). The TS positions in F(Λ), which quantitatively agree with the parameters extracted using the Bell-Evans model, change abruptly at a critical force, demonstrating that it, rather than the molecular extension, is a good reaction coordinate. Our combined analyses using simulations performed in both the pulling modes (constant rf and F) reveal a new mechanism for the two loading regimes observed in the

  18. Workaholism and negative work-related incidents among nurses.

    PubMed

    Andreassen, Cecilie Schou; Pallesen, Ståle; Moen, Bente E; Bjorvatn, Bjørn; Waage, Siri; Schaufeli, Wilmar B

    2018-05-15

    The present study comprised 1,781 nurses who participated in an investigation about working conditions, sleep, and health. They answered a questionnaire about age, sex, marital status, children living at home, work hours per week, number of night shifts last year, and total sleep duration and that also included a validated instrument assessing workaholism. In addition, they were asked to report on eight items concerning negative work-related incidents (dozed off at work, dozed while driving, harmed or nearly harmed self, harmed or nearly harmed patients/others, and harmed or nearly harmed equipment). Logistic regression analyses identified several predictors of these specific incidents: Low age (dozed at work, harmed and nearly harmed self, harmed and nearly harmed equipment), male sex (harmed and nearly harmed self, nearly harmed equipment), not living with children (harmed patients/others), low percentage of full-time equivalent (nearly harmed self and harmed patients/others), number of night shifts last year (dozed off at work and while driving, nearly harmed patients/others) and sleep duration (inversely related to dozed off at work and while driving, nearly harmed self). However, the most consistent predictor of negative work-related incidents was workaholism which was positively and significantly associated with all the eight incidents.

  19. Positive focal shift of gallium nitride high contrast grating focusing reflectors

    NASA Astrophysics Data System (ADS)

    He, Shumin; Wang, Zhenhai; Liu, Qifa

    2016-09-01

    We design a type of metasurfaces capable of serving as a visible-light focusing reflector based on gallium nitride (GaN) high contrast gratings (HCGs). The wavefront of the reflected light is precisely manipulated by spatial variation of the grating periods along the subwavelength ridge array to achieve light focusing. Different from conventional negative focal shift effect, a positive focal shift is observed in such focusing reflectors. Detailed investigations of the influence of device size on the focusing performance, especially the focal length, are preformed via a finite element method . The results show that all performance parameters are greatly affected by the reflector size. A more concentrated focal point, or a better focusing capability, can be achieved by larger size. With increasing reflector size, the achieved focal length decreases and gradually approaches to the design, thus the corresponding positive focal shift decreases. Our results are helpful for understanding the visible-light control of the planar HCG-based focusing reflectors.

  20. Alteration in eating habits among shift workers of a poultry processing plant in southern Brazil.

    PubMed

    de Freitas, Elisângela da Silva; Canuto, Raquel; Henn, Ruth Liane; Olinto, Beatriz Anselmo; Macagnan, Jamile Block Araldi; Pattussi, Marcos Pascoal; Busnello, Fernanda Michelin; Olinto, Maria Teresa Anselmo

    2015-08-01

    The relationship between shift work and the eatinghabits of workers was investigated in a slaughterhouse in southern Brazil. It involved a cross-sectional study with 1,206 workers of both sexes between 18 and 50 years of age. A standardized questionnaire was used to gather demographic, socioeconomic, work shift and eating habit information. The shift of work was categorized into daytime and nighttime, based on the starting and ending times of the shift. The eating habits of workers were evaluated as follows: number and type of meals eaten during the 24 hours of a normal day, the inappropriateness of the hoursof these meals and the dietaryrisk score. This was built on the risk score of the weekly consumption of 13 food items. After adjusting for potential confounders, non-Caucasian and younger male workers were more likely to manifest eating risk habits. Nighttimeshift workers consumed ahigher number of meals/day with greater inappropriateness of meal times than daytimeshift workers. The night shift can negatively influence the eating habits of workers of that shift.

  1. Infant EEG and temperament negative affectivity: Coherence of vulnerabilities to mothers' perinatal depression.

    PubMed

    Lusby, Cara M; Goodman, Sherryl H; Yeung, Ellen W; Bell, Martha Ann; Stowe, Zachary N

    2016-11-01

    Associations between infants' frontal EEG asymmetry and temperamental negative affectivity (NA) across infants' first year of life and the potential moderating role of maternal prenatal depressive symptoms were examined prospectively in infants (n = 242) of mothers at elevated risk for perinatal depression. In predicting EEG, in the context of high prenatal depressive symptoms, infant NA and frontal EEG asymmetry were negatively associated at 3 months of age and positively associated by 12 months of age. By contrast, for low depression mothers, infant NA and EEG were not significantly associated at any age. Postnatal depressive symptoms did not add significantly to the models. Dose of infants' exposure to maternal depression mattered: infants exposed either pre- or postnatally shifted from a positive association at 3 months to a negative association at 12 months; those exposed both pre- and postnatally shifted from a negative association at 3 months to a positive association at 12 months. Prenatal relative to postnatal exposure did not matter for patterns of association between NA and EEG. The findings highlight the importance of exploring how vulnerabilities at two levels of analysis, behavioral and psychophysiological, co-occur over the course of infancy and in the context of mothers' depressive symptomatology.

  2. Resilience of the Nexus of Competitive Water Consumption between Human Society and Environment Development: Regime Shifts and Early Warning Signals

    NASA Astrophysics Data System (ADS)

    Li, Z.; Liu, P.; Feng, M.; Zhang, J.

    2017-12-01

    Based on the modeling of the water supply, power generation and environment (WPE) nexus by Feng et al. (2016), a refined theoretical model of competitive water consumption between human society and environment has been presented in this study, examining the role of technology advancement and social environmental awareness growth-induced pollution mitigation to the environment as a mechanism for the establishment and maintenance of the coexistence of both higher social water consumption and improved environment condition. By coupling environmental and social dynamics, both of which are represented by water consumption quantity, this study shows the possibility of sustainable situation of the social-environmental system when the benefit of technology offsets the side effect (pollution) of social development to the environment. Additionally, regime shifts could be triggered by gradually increased pollution rate, climate change-induced natural resources reduction and breakdown of the social environmental awareness. Therefore, in order to foresee the pending abrupt regime shifts of the system, early warning signals, including increasing variance and autocorrelation, have been examined when the system is undergoing stochastic disturbance. ADDIN EN.REFLIST Feng, M. et al., 2016. Modeling the nexus across water supply, power generation and environment systems using the system dynamics approach: Hehuang Region, China. J. Hydrol., 543: 344-359.

  3. [Is It Time to Implement a 12-Hour Shift for Nurses in Taiwan?

    PubMed

    Lin, Yi-Fung; Chang, Shiow-Ru; Wang, Li-Ting

    2017-04-01

    The twelve-hour shift system, first introduced in the U.S. in 1967 to address a nursing shortage, is now the main system of shift rotation used in numerous countries. In recent years, several hospitals in Taiwan have implemented the 12-hour shift model as one initiative to improve the problems of overtime and high turnover rate among nursing staff. Under this model, nurses work only three to four days per week for 12-hour shifts per day. Despite the increase in numbers of days off, there is growing concern that long shift hours may harm both the safety of patients and the well being of the nurses. The aim of the present article is to explain the application of the 12-hour shift system and to review the potential impacts of this model. Benefits of the 12-hour shift system include improving quality of life for nursing staff, reducing the turnover rate, and increasing job satisfaction. Primary concerns regarding this system include patient safety, nurse fatigue, and the potential negative effects on the sleep quality of nurses. These findings may be referenced by policymakers considering the development / implementation of flexible work schedules in Taiwan. The government must set a ceiling on work hours allowed per week and impose limits on overtime in order to prevent burnout in nursing staff.

  4. Contributors to shift work tolerance in South Korean nurses working rotating shift.

    PubMed

    Jung, Hye-Sun; Lee, Bokim

    2015-05-01

    Shift workers have rapidly increased in South Korea; however, there is no published research exploring shift work tolerance among South Korean workers. This study aimed to investigate factors related to shift work tolerance in South Korean nurses. The sample comprised of 660 nurses who worked shifts in a large hospital in South Korea. A structured questionnaire included following comprehensive variables: demographic (age and number of children), individual (morningness and self-esteem), psychosocial (social support and job stress), lifestyle (alcohol consumption, physical activity, and BMI), and working condition factors (number of night shifts and working hours). Shift work tolerance was measured in terms of insomnia, fatigue, and depression. The results of hierarchical regressions indicate that all variables, except for three, number of children, BMI, and working hours, were related to at least one of the symptoms associated with shift work tolerance. Based on these results, we offer some practical implications to help improve shift work tolerance of workers. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. The influence of abrupt increases in seawater pCO2 on plankton productivity in the subtropical North Pacific Ocean

    PubMed Central

    Böttjer, Daniela; Letelier, Ricardo M.; Church, Matthew J.

    2018-01-01

    We conducted a series of experiments to examine short-term (2–5 days) effects of abrupt increases in the partial pressure of carbon dioxide (pCO2) in seawater on rates of primary and bacterial production at Station ALOHA (22°45’ N, 158° W) in the North Pacific Subtropical Gyre (NPSG). The majority of experiments (8 of 10 total) displayed no response in rates of primary production (measured by 14C-bicarbonate assimilation; 14C-PP) under elevated pCO2 (~1100 μatm) compared to ambient pCO2 (~387 μatm). In 2 of 10 experiments, rates of 14C-PP decreased significantly (~43%) under elevated pCO2 treatments relative to controls. Similarly, no significant differences between treatments were observed in 6 of 7 experiments where bacterial production was measured via incorporation of 3H-leucine (3H-Leu), while in 1 experiment, rates of 3H-Leu incorporation measured in the dark (3H-LeuDark) increased more than 2-fold under high pCO2 conditions. We also examined photoperiod-length, depth-dependent (0–125 m) responses in rates of 14C-PP and 3H-Leu incorporation to abrupt pCO2 increases (to ~750 μatm). In the majority of these depth-resolved experiments (4 of 5 total), rates of 14C-PP demonstrated no consistent response to elevated pCO2. In 2 of 5 depth-resolved experiments, rates of 3H-LeuDark incorporation were lower (10% to 15%) under elevated pCO2 compared to controls. Our results revealed that rates of 14C-PP and bacterial production in this persistently oligotrophic habitat generally demonstrated no or weak responses to abrupt changes in pCO2. We postulate that any effects caused by changes in pCO2 may be masked or outweighed by the role that nutrient availability and temperature play in controlling metabolism in this ecosystem. PMID:29694353

  6. Multiple shifts to different pollinators fuelled rapid diversification in sexually deceptive Ophrys orchids.

    PubMed

    Breitkopf, Hendrik; Onstein, Renske E; Cafasso, Donata; Schlüter, Philipp M; Cozzolino, Salvatore

    2015-07-01

    Episodes of rapid speciation provide unique insights into evolutionary processes underlying species radiations and patterns of biodiversity. Here we investigated the radiation of sexually deceptive bee orchids (Ophrys). Based on a time-calibrated phylogeny and by means of ancestral character reconstruction and divergence time estimation, we estimated the tempo and mode of this radiation within a state-dependent evolutionary framework. It appears that, in the Pleistocene, the evolution of Ophrys was marked by episodes of rapid diversification coinciding with shifts to different pollinator types: from wasps to Eucera bees to Andrena and other bees. An abrupt increase in net diversification rate was detected in three clades. Among these, two phylogenetically distant lineages switched from Eucera to Andrena and other bees in a parallel fashion and at about the same time in their evolutionary history. Lack of early radiation associated with the evolution of the key innovation of sexual deception suggests that Ophrys diversification was mainly driven by subsequent ecological opportunities provided by the exploitation of novel pollinator groups, encompassing many bee species slightly differing in their sex pheromone communication systems, and by spatiotemporal fluctuations in the pollinator mosaic. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  7. The effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses.

    PubMed

    Dehghan, Habibollah; Azmoon, Hiva; Souri, Shiva; Akbari, Jafar

    2014-01-01

    Psychological problems as state anxiety (SA) in the work environment has negative effect on the employees life especially shift work nurses, i.e. negative effect on mental and physical health (sleep quality, eye fatigue and comfort thermal). The purpose of this study was determination of effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses. This cross-sectional research conducted on 82 shift-work personnel of 18 nursing workstations of Isfahan hospitals in 2012. To measure the SA, sleep quality, visual fatigue and thermal comfort, Spielberger state-trait anxiety inventory, Pittsburg sleep quality index, eye fatigue questionnaire and thermal comfort questionnaire were used respectively. The data were analyzed with descriptive statistics, student test and correlation analysis. Correlation between SA and sleep quality was -0.664(P < 0001), Pearson correlation between SA and thermal comfort was -0.276(P = 0.016) and between SA and eye fatigue was 0.57 (P < 0001). Based on these results, it can be concluded that improvement of thermal conditions and reduce state anxiety level can be reduce eye fatigue and increase the sleep quality in shift work nurses.

  8. The effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses

    PubMed Central

    Dehghan, Habibollah; Azmoon, Hiva; Souri, Shiva; Akbari, Jafar

    2014-01-01

    Psychological problems as state anxiety (SA) in the work environment has negative effect on the employees life especially shift work nurses, i.e. negative effect on mental and physical health (sleep quality, eye fatigue and comfort thermal). The purpose of this study was determination of effects of state anxiety and thermal comfort on sleep quality and eye fatigue in shift work nurses. Methods: This cross-sectional research conducted on 82 shift-work personnel of 18 nursing workstations of Isfahan hospitals in 2012. To measure the SA, sleep quality, visual fatigue and thermal comfort, Spielberger state-trait anxiety inventory, Pittsburg sleep quality index, eye fatigue questionnaire and thermal comfort questionnaire were used respectively. The data were analyzed with descriptive statistics, student test and correlation analysis. Results: Correlation between SA and sleep quality was −0.664(P < 0001), Pearson correlation between SA and thermal comfort was −0.276(P = 0.016) and between SA and eye fatigue was 0.57 (P < 0001). Conclusion: Based on these results, it can be concluded that improvement of thermal conditions and reduce state anxiety level can be reduce eye fatigue and increase the sleep quality in shift work nurses. PMID:25077165

  9. [Perception of shift work, burnout and sleep disturbances: a study among call centre operators].

    PubMed

    Consiglio, Chiara; Tinelli, Erica

    2016-01-20

    Shift work is often considered to be a factor that can negatively affect health and sleep quality. However, it is usually considered as a structural factor of the job and not as a perception of a work demand. The study aimed at analyzing the relationship between perception of shift work, burnout and sleep disturbances in a potentially stressful context, namely the call centre setting. Call centre operators (N=510) completed a questionnaire encompassing the following scales: perceptions of shift work, monotony, time pressure, exhaustion, cynicism and sleep disturbances. We conducted two hierarchical regressions in order to analyze the contribution of the perception of shift work on burnout dimensions (exhaustion and cynicism), beyond the contribution of socio-demographical variables, and of two specific job stressors for call centre operators, namely monotony and time pressure. The mediating role of exhaustion and cynicism between the perception of shift work and sleep disturbances was also explored. The perception of shift work was associated with operators' burnout, beyond the effect of socio-demographic variables and other job stressors. In addition, the relationship between the perception of shift work and sleep disturbances was fully mediated by exhaustion and partially mediated by cynicism. Perceived shift work may represent a risk factor for the health of call centre operators that should be monitored and possibly managed through specific organizational interventions.

  10. Split-shift work in relation to stress, health and psychosocial work factors among bus drivers.

    PubMed

    Ihlström, Jonas; Kecklund, Göran; Anund, Anna

    2017-01-01

    Shift work has been associated with poor health, sleep and fatigue problems and low satisfaction with working hours. However, one type of shift working, namely split shifts, have received little attention. This study examined stress, health and psychosocial aspects of split-shift schedules among bus drivers in urban transport. A questionnaire was distributed to drivers working more than 70% of full time which 235 drivers in total answered. In general, drivers working split-shift schedules (n = 146) did not differ from drivers not working such shifts (n = 83) as regards any of the outcome variables that were studied. However, when individual perceptions towards split-shift schedules were taken into account, a different picture appeared. Bus drivers who reported problems working split shifts (36%) reported poorer health, higher perceived stress, working hours interfering with social life, lower sleep quality, more persistent fatigue and lower general work satisfaction than those who did not view split shifts as a problem. Moreover, drivers who reported problems with split shifts also perceived lower possibilities to influence working hours, indicating lower work time control. This study indicates that split shifts were not associated with increased stress, poorer health and adverse psychosocial work factors for the entire study sample. However, the results showed that individual differences were important and approximately one third of the drivers reported problems with split shifts, which in turn was associated with stress, poor health and negative psychosocial work conditions. More research is needed to understand the individual and organizational determinants of tolerance to split shifts.

  11. The impact of long work hours and shift work on cognitive errors in nurses.

    PubMed

    Rhéaume, Ann; Mullen, Jane

    2018-01-01

    Pilot study to examine the impact of long work hours and shift work on cognitive errors in nurses. Twelve-hour shifts are more commonly used in hospital settings and there is growing concern over the impact that extended and irregular work hours have on nurses' well-being and performance. Twenty-eight nurses working different shifts (8-hr days and 12-hr rotation) participated in this study. Nurses were assessed at the beginning of four consecutive shifts using actigraphy, a sleep diary and an after work questionnaire. Nurses working 12-hr rotations had less total sleep time and less sleep efficiency than 8-hr day nurses. Twelve-hour rotation nurses also napped more than their counterparts. There were no differences between the two groups with respect to cognitive errors. Twelve-hour rotations have a negative effect on nurses' sleep patterns. There is no evidence indicating 12-hr rotations increased errors. Nurse managers can implement specific strategies, such as greater shift work flexibility and designated quiet time, to reduce the effects of disturbed sleep patterns in nurses. © 2017 John Wiley & Sons Ltd.

  12. The role of attentional processes in children's prosocial behavior with peers: attention shifting and emotion.

    PubMed

    Wilson, Beverly J

    2003-01-01

    This study evaluated the role of attentional shifting in children's prosocial behavior with peers. Participants were 27 aggressive/rejected and 27 nonaggressive/popular kindergarten and first grade boys and girls. Children's ability to shift attention from one affective state to another was assessed during: (a) a computerized task that required shifting attention between different affective events (i.e., the Children's Attentional Shifting Task, CAST) and (b) an analogue entry task with unacquainted peers. Children's latency for sharing with peers was assessed after they experienced failure during the entry task. Aggressive/rejected children had significant difficulty shifting attention from negative to positive affect during the CAST and were slower to share after experiencing entry failure. In general, aggressive/rejected children were less able to regulate their behavior effectively after experiencing social failure. Girls, regardless of status, had less difficulty than boys shifting attention from one affective state to another during the CAST. In addition, children's social status/aggressiveness, their ability to regulate emotional behavior after social failure and to shift attention effectively on the CAST predicted approximately 31% of the variance in their latency to share. These findings suggest that the ability to shift attention between different affective states plays a significant role in children's prosocial behavior with peers.

  13. Dynamic response of desert wetlands to abrupt climate change

    PubMed Central

    Springer, Kathleen B.; Manker, Craig R.; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming. PMID:26554007

  14. Dynamic response of desert wetlands to abrupt climate change

    USGS Publications Warehouse

    Springer, Kathleen; Manker, Craig; Pigati, Jeffrey S.

    2015-01-01

    Desert wetlands are keystone ecosystems in arid environments and are preserved in the geologic record as groundwater discharge (GWD) deposits. GWD deposits are inherently discontinuous and stratigraphically complex, which has limited our understanding of how desert wetlands responded to past episodes of rapid climate change. Previous studies have shown that wetlands responded to climate change on glacial to interglacial timescales, but their sensitivity to short-lived climate perturbations is largely unknown. Here, we show that GWD deposits in the Las Vegas Valley (southern Nevada, United States) provide a detailed and nearly complete record of dynamic hydrologic changes during the past 35 ka (thousands of calibrated 14C years before present), including cycles of wetland expansion and contraction that correlate tightly with climatic oscillations recorded in the Greenland ice cores. Cessation of discharge associated with rapid warming events resulted in the collapse of entire wetland systems in the Las Vegas Valley at multiple times during the late Quaternary. On average, drought-like conditions, as recorded by widespread erosion and the formation of desert soils, lasted for a few centuries. This record illustrates the vulnerability of desert wetland flora and fauna to abrupt climate change. It also shows that GWD deposits can be used to reconstruct paleohydrologic conditions at millennial to submillennial timescales and informs conservation efforts aimed at protecting these fragile ecosystems in the face of anthropogenic warming.

  15. Changes in regional and temporal patterns of activity associated with aging during the performance of a lexical set-shifting task.

    PubMed

    Martins, Ruben; Simard, France; Provost, Jean-Sebastien; Monchi, Oury

    2012-06-01

    Some older individuals seem to use compensatory mechanisms to maintain high-level performance when submitted to cognitive tasks. However, whether and how these mechanisms affect fronto-striatal activity has never been explored. The purpose of this study was to investigate how aging affects brain patterns during the performance of a lexical analog of the Wisconsin Card Sorting Task, which has been shown to strongly depend on fronto-striatal activity. In the present study, both younger and older individuals revealed significant fronto-striatal loop activity associated with planning and execution of set-shifts, though age-related striatal activity reduction was observed. Most importantly, while the younger group showed the involvement of a "cognitive loop" during the receiving negative feedback period (which indicates that a set-shift will be required to perform the following trial) and the involvement of a "motor loop" during the matching after negative feedback period (when the set-shift must be performed), older participants showed significant activation of both loops during the matching after negative feedback period only. These findings are in agreement with the "load-shift" model postulated by Velanova et al. (Velanova K, Lustig C, Jacoby LL, Buckner RL. 2007. Evidence for frontally mediated controlled processing differences in older adults. Cereb Cortex. 17:1033-1046.) and indicate that the model is not limited to memory retrieval but also applies to executive processes relying on fronto-striatal regions.

  16. Biomonitoring of metals under the water framework directive: detecting temporal trends and abrupt changes, in relation to the removal of pollution sources.

    PubMed

    Solaun, O; Rodríguez, J G; Borja, A; González, M; Saiz-Salinas, J I

    2013-02-15

    Temporal trends in metal concentrations, i.e. Ag, Cd, Cu, Cr, Hg, Ni, Pb and Zn, measured in soft tissues of Mytilus galloprovincialis mussels and Crassostrea gigas oysters collected from estuarine waters within the Basque Country (Bay of Biscay), have been investigated to determine if actions undertaken have improved the environmental quality of rivers and estuaries. Data compiled between 1990 and 2010 have been analysed statistically, applying the Mann-Kendall and the Mann-Whitney-Wilcoxon tests. Moreover, in those cases with significant trends, the Kolmogorov-Zurbenko Adaptive (KZA) filter was applied to detect abrupt changes. Results showed significant decreasing trends for some metals, i.e. Ni, Cu, Pb and Zn, and differences between medians. Trend lines showed abrupt changes occurring between 1998 and 2002. Therefore, observed downward trends were related to increased wastewater treatment and diversions of discharges to ocean, implemented mainly during 2000-2002. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. "What Controls the Structure and Stability of the Ocean Meridional Overturning Circulation: Implications for Abrupt Climate Change?"

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fedorov, Alexey

    2013-11-23

    The central goal of this research project is to understand the properties of the ocean meridional overturning circulation (MOC) – a topic critical for understanding climate variability and stability on a variety of timescales (from decadal to centennial and longer). Specifically, we have explored various factors that control the MOC stability and decadal variability in the Atlantic and the ocean thermal structure in general, including the possibility abrupt climate change. We have also continued efforts on improving the performance of coupled ocean-atmosphere GCMs.

  18. Subclinical hypothyroidism as a risk factor for placental abruption: evidence from a low-risk primigravid population.

    PubMed

    Breathnach, Fionnuala M; Donnelly, Jennifer; Cooley, Sharon M; Geary, Michael; Malone, Fergal D

    2013-12-01

    Subclinical thyroid hypofunction in pregnancy has been shown to have an association with neurodevelopmental delay in the offspring. It is unclear whether obstetric factors may account for this observation. To establish the prevalence of subclinical hypothyroidism (SCH) in a low-risk primigravid population and to explore its association with obstetric sequelae. Nine hundred and fifty-three primigravid women had thyroid hormone indices analysed in the early second trimester. Delivery and neonatal outcomes were available for 904 women who met the criteria for inclusion in the study. Women with subclinical hypothyroidism (thyroid-stimulating hormone (TSH) values at or above the 98th percentile with a normal free thyroxine (fT4)) or isolated maternal hypothyroxinaemia (fT4 level at or below the second percentile with a normal-range TSH) were compared with biochemically euthyroid controls. Chi-squared test and analysis of variance were used for statistical analysis. The prevalence of SCH or isolated maternal hypothyroxinaemia was 4%. Positivity for antithyroid peroxidase (TPO) or antithyroglobulin (ATG) antibodies correlated with SCH status (P = 0.02). Placental abruption was observed more commonly in the setting of either SCH or isolated maternal hypothyroxinaemia when compared with euthyroid controls (P = 0.02 and 0.04, respectively). Subclinical hypothyroidism and isolated maternal hypothyroxinaemia are associated with placental abruption. The observation of these effects in this healthy low-risk population lends weight to the case for antenatal screening for diminished thyroid reserve. © 2013 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.

  19. Precipitation changes in the western tropical Pacific over the past millennium

    USGS Publications Warehouse

    Richey, Julie; Sachs, Julian P.

    2016-01-01

    Palau is linked to both meridional movement of the Intertropical Convergence Zone (ITCZ) and changes in the Pacific Walker Circula- tion (PWC) associated with the El Niño–Southern Oscillation. Thus, Palau’s hydroclimate should be sensitive to mean shifts in the ITCZ and PWC on decadal to centennial time scales. Using compound- specific hydrogen isotope ratios (δ2H) of dinosterol in lake sediments, we generated a decadal-resolution proxy record of hydroclimatic variability in Palau spanning the past 800 yr. Results indicate a dry- ing trend during the Little Ice Age in Palau, consistent with a south- ward displacement of the ITCZ. In addition to the secular drying trend, there are persistent large (~20‰) multi-decadal to centennial oscillations in the δ2H record, the most recent of which indicates an abrupt shift to drier conditions in the mid-1970s that coincides with a decadal-scale negative shift in the Southern Oscillation Index.

  20. Association of eating behaviours with diurnal preference and rotating shift work in Japanese female nurses: a cross-sectional study

    PubMed Central

    Yoshizaki, Takahiro; Kawano, Yukari; Noguchi, Osamu; Onishi, Junko; Teramoto, Reiko; Sunami, Ayaka; Yokoyama, Yuri; Tada, Yuki; Hida, Azumi; Togo, Fumiharu

    2016-01-01

    Objectives Our study examines differences in eating behaviour between day workers and rotating shift workers, and considers whether diurnal preference could explain the differences. Methods Japanese female nurses were studied (39 day workers and 123 rotating shift workers, aged 21–63 years) using self-administered questionnaires. The questionnaires assessed eating behaviours, diurnal preference and demographic characteristics. The questionnaire in the Guidelines for the management of obesity disease issued by the Japan Society for the Study of Obesity was used to obtain scores for the levels of obesity-related eating behaviours, including cognition of constitution, motivation for eating, eating as a diversion, feeling of satiety, eating style, meal contents and temporal eating patterns. The Japanese version of the Morningness–Eveningness (ME) questionnaire was used to measure self-rated preference for the degree to which people prefer to be active in the morning or the evening (ME). Results The scores for meal contents and temporal eating patterns in rotating shift workers were significantly higher than those in day workers. The ME score of rotating shift workers was significantly lower, indicating greater eveningness/less morningness among rotating shift workers. Multivariate linear regression revealed that the ME score was significantly negatively associated with temporal eating patterns and showed a negative association with the score for meal contents at a trend level, while current work shift was not significantly correlated with the scores. Conclusions These results suggest that eating behaviours for rotating shift workers are associated with a more unbalanced diet and abnormal temporal eating patterns and that the associations may be explained by diurnal preference rather than by rotating shift work. PMID:27895063

  1. Electrophysiological correlates of preparation and implementation for different types of task shifts.

    PubMed

    Hsieh, Shulan; Wu, Mengyao

    2011-11-14

    The ability to flexibly shift between tasks is central to cognitive control, but whether the same brain mechanisms mediate shifting across different tasks is unknown. In this study, we investigated whether variations in stimulus-dimensions or response-mapping might influence task switching in terms of its preparatory processes, as reflected in cue-locked event-related potentials (ERPs), and its implementation processes, as reflected in stimulus-locked ERPs. Participants judged pairs of digits as same or different in one of two conditions. In one condition, the task-relevant stimulus-dimension was either repeated or switched across trials while the response-mapping rule was kept constant. In the other condition, the task-relevant stimulus-dimension was kept constant while the response-mapping rule was repeated or switched across trials. The length of the preparatory interval was manipulated. Data revealed switch-related preparatory ERP components (including N2 and a late slow positivity) that were associated with both types of task shifting and an N400-like negativity that distinguished between the two types. Several switch-related implementation ERP components associated with both types of task shifting were found at posterior sites. Distinct frontal modulations of the N1, P2, and N2 were found to associate with the implementation of the response-mapping shift, whereas a slow positivity was associated with the implementation of the stimulus-dimension shift. Therefore, this study demonstrates that there are shared and distinct processes across different types of task shifting. Finally, because the same transition-cue was used for different task shifts, the distinct processes cannot be explained simply by differences in cue processing. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Oxidative DNA damage during night shift work.

    PubMed

    Bhatti, Parveen; Mirick, Dana K; Randolph, Timothy W; Gong, Jicheng; Buchanan, Diana Taibi; Zhang, Junfeng Jim; Davis, Scott

    2017-09-01

    We previously reported that compared with night sleep, day sleep among shift workers was associated with reduced urinary excretion of 8-hydroxydeoxyguanosine (8-OH-dG), potentially reflecting a reduced ability to repair 8-OH-dG lesions in DNA. We identified the absence of melatonin during day sleep as the likely causative factor. We now investigate whether night work is also associated with reduced urinary excretion of 8-OH-dG. For this cross-sectional study, 50 shift workers with the largest negative differences in night work versus night sleep circulating melatonin levels (measured as 6-sulfatoxymelatonin in urine) were selected from among the 223 shift workers included in our previous study. 8-OH-dG concentrations were measured in stored urine samples using high performance liquid chromatography with electrochemical detection. Mixed effects models were used to compare night work versus night sleep 8-OH-dG levels. Circulating melatonin levels during night work (mean=17.1 ng/mg creatinine/mg creatinine) were much lower than during night sleep (mean=51.7 ng/mg creatinine). In adjusted analyses, average urinary 8-OH-dG levels during the night work period were only 20% of those observed during the night sleep period (95% CI 10% to 30%; p<0.001). This study suggests that night work, relative to night sleep, is associated with reduced repair of 8-OH-dG lesions in DNA and that the effect is likely driven by melatonin suppression occurring during night work relative to night sleep. If confirmed, future studies should evaluate melatonin supplementation as a means to restore oxidative DNA damage repair capacity among shift workers. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  3. The Correlation Between Cognitive and Movement Shifting and Brain Activity in Children With ADHD.

    PubMed

    Kang, Kyoung Doo; Han, Doug Hyun; Kim, Sun Mi; Bae, Sujin; Renshaw, Perry F

    2018-05-01

    We assessed the correlation between the deficits of cognition, movement, and brain activity in children with Attention Deficit Hyperactvity Disorder (ADHD). We recruited 15 children with ADHD and 15 age- and sex-matched healthy control participants. Clinical symptoms, cognitive shifting, movement shifting, and brain activity were assessed using the Korean ADHD Rating Scale, the Wisconsin Card Sorting Test (WCST), the 7- and 14-ring drill test with hop jumps (7 HJ and 14 HJ), and 3.0 Tesla functional magnetic resonance imaging scanner, respectively. ADHD children showed an increased distance traveled and decreased speed on the 14 HJ task. In response to the WCST task, ADHD children showed decreased activation within right gyrus. Total distance on the 14 HJ task was negatively correlated with the mean β value of Cluster 2 in ADHD children. These results suggested that children with ADHD showed difficulty with attention shifting as well as with movement shifting.

  4. 'Registrar in charge shifts': learning how to run a busy emergency department.

    PubMed

    Craig, Simon; Dowling, Jonathan

    2013-04-01

    In Australasia, emergency registrars usually gain experience 'running' an ED overnight - without supervision. This paper describes the introduction of FACEM-supervised daytime 'registrar in charge' (RIC) shifts into a tertiary adult ED over a 6 month period. Each registrar was allocated at least one RIC shift during their 13 week ED term. Structured questionnaires gathered data regarding the educational impact of the shifts, any adverse effects on departmental function, changes to work practices, and perceptions of teaching and learning. Data were analysed using thematic analysis. During the study period, 16 senior ED registrars were rostered for 26 RIC shifts. Questionnaires were completed by 16/16 registrars and 13/16 emergency physicians. The RIC shifts were viewed positively by the emergency registrars - 93% reported useful feedback, felt that the shifts provided a good insight into their workplace behaviour, and that they should be rolled out across other departments. FACEMs were also positive in their evaluation, and reported little negative impact on departmental function. Major themes identified by both registrars and emergency physicians included communication skills, knowledge and experience, delegation, professionalism and organisational skills. Additional themes that were more prominent in FACEM responses included multitasking, dealing with interruptions, managing patient flow and being aware of the whole department. RIC shifts are a feasible and acceptable method to teach running the floor in the ED. Further study should assess impact on patient outcomes. © 2013 The Authors. EMA © 2013 Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.

  5. Optimal Shift Duration and Sequence: Recommended Approach for Short-Term Emergency Response Activations for Public Health and Emergency Management

    PubMed Central

    Burgess, Paula A.

    2007-01-01

    Since September 11, 2001, and the consequent restructuring of the US preparedness and response activities, public health workers are increasingly called on to activate a temporary round-the-clock staffing schedule. These workers may have to make key decisions that could significantly impact the health and safety of the public. The unique physiological demands of rotational shift work and night shift work have the potential to negatively impact decisionmaking ability. A responsible, evidence-based approach to scheduling applies the principles of circadian physiology, as well as unique individual physiologies and preferences. Optimal scheduling would use a clockwise (morning-afternoon-night) rotational schedule: limiting night shifts to blocks of 3, limiting shift duration to 8 hours, and allowing 3 days of recuperation after night shifts. PMID:17413074

  6. Advance, Retreat, and Halt of Abrupt Gravel-Sand Transitions in Alluvial Rivers

    NASA Astrophysics Data System (ADS)

    Blom, Astrid; Chavarrías, Víctor; Ferguson, Robert I.; Viparelli, Enrica

    2017-10-01

    Downstream fining of bed sediment in alluvial rivers is usually gradual, but often an abrupt decrease in characteristic grain size occurs from about 10 to 1 mm, i.e., a gravel-sand transition (GST) or gravel front. Here we present an analytical model of GST migration that explicitly accounts for gravel and sand transport and deposition in the gravel reach, sea level change, subsidence, and delta progradation. The model shows that even a limited gravel supply to a sand bed reach induces progradation of a gravel wedge and predicts the circumstances required for the gravel front to advance, retreat, and halt. Predicted modern GST migration rates agree well with measured data at Allt Dubhaig and the Fraser River, and the model qualitatively captures the behavior of other documented gravel fronts. The analysis shows that sea level change, subsidence, and delta progradation have a significant impact on the GST position in lowland rivers.

  7. Shape-Shifting Neoliberalism and World Bank Education Policy: A Response to Steven Klees

    ERIC Educational Resources Information Center

    Bergeron, Suzanne

    2008-01-01

    In his article titled "A Quarter Century of Neoliberal Thinking in Education: Misleading Analyses and Failed Policies", Steven J. Klees provides a rich account of how educational policy has been influenced by a shift towards neoliberal economic thinking since the 1980s. He also effectively demonstrates the negative impact of this experiment in…

  8. Early Stages Of Biome Shift in Boreal Alaska: Climate Sensitivity of Tree Growth and Accelerated Tree Mortality

    NASA Astrophysics Data System (ADS)

    Juday, G. P.; Grant, T.; Alix, C. M.; Spencer, D. L.; Beck, P. S.

    2012-12-01

    The boreal forest region of Alaska is characterized by a major east-west climate gradient, in addition to a widely appreciated north-south gradient. Low elevations of the eastern and central Interior experience warm summer temperatures and low annual precipitation, while coastal western Alaska has cool summer temperatures and greater precipitation. In the Interior the four dominant tree species of white and black spruce, aspen, and Alaska birch on low elevation sites nearly all register a strong negative radial growth relationship to summer temperatures, concentrated in May and July. Precipitation, particularly in late winter and midsummer, plays a supplemental role as a positive factor in growth. Floodplain white spruce along the Yukon and Kuskokwim Rivers transition from negative temperature response to positive response in western Alaska near the tree limit. Populations of white spruce on treeline sites display both negative growth response to July temperature and positive response to spring temperatures, with the negative response dominant in the east and the positive response dominant in the west. Across boreal Alaska summer temperatures increased abruptly in 1974, and have remained at historically high levels since. Correspondingly, climatic favorability for radial growth of Interior trees on most low elevation sites has been at extreme low levels particularly in the 21st century. Satellite-based NDVI coverage confirms that forest growth reduction is widespread in boreal Alaska since the 1980s. Defoliating and wood boring insects have reached outbreak population levels across most of boreal Alaska, partly from release of direct temperature control on the insects and partly from increased tree host susceptibility. Major outbreak species include aspen leaf miner, spruce engraver beetle, and spruce budworm. About a dozen tall willow species have been subjected to widespread attack by willow leaf blotch miner, and a new disease and defoliating insect have spread

  9. If it bleeds, it leads: separating threat from mere negativity.

    PubMed

    Kveraga, Kestutis; Boshyan, Jasmine; Adams, Reginald B; Mote, Jasmine; Betz, Nicole; Ward, Noreen; Hadjikhani, Nouchine; Bar, Moshe; Barrett, Lisa F

    2015-01-01

    Most theories of emotion hold that negative stimuli are threatening and aversive. Yet in everyday experiences some negative sights (e.g. car wrecks) attract curiosity, whereas others repel (e.g. a weapon pointed in our face). To examine the diversity in negative stimuli, we employed four classes of visual images (Direct Threat, Indirect Threat, Merely Negative and Neutral) in a set of behavioral and functional magnetic resonance imaging studies. Participants reliably discriminated between the images, evaluating Direct Threat stimuli most quickly, and Merely Negative images most slowly. Threat images evoked greater and earlier blood oxygen level-dependent (BOLD) activations in the amygdala and periaqueductal gray, structures implicated in representing and responding to the motivational salience of stimuli. Conversely, the Merely Negative images evoked larger BOLD signal in the parahippocampal, retrosplenial, and medial prefrontal cortices, regions which have been implicated in contextual association processing. Ventrolateral as well as medial and lateral orbitofrontal cortices were activated by both threatening and Merely Negative images. In conclusion, negative visual stimuli can repel or attract scrutiny depending on their current threat potential, which is assessed by dynamic shifts in large-scale brain network activity. © The Author (2014). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  10. Computational study of the shift of the G band of double-walled carbon nanotubes due to interlayer interactions

    NASA Astrophysics Data System (ADS)

    Popov, Valentin N.; Levshov, Dmitry I.; Sauvajol, Jean-Louis; Paillet, Matthieu

    2018-04-01

    The interactions between the layers of double-walled carbon nanotubes induce a measurable shift of the G bands relative to the isolated layers. While experimental data on this shift in freestanding double-walled carbon nanotubes has been reported in the past several years, a comprehensive theoretical description of the observed shift is still lacking. The prediction of this shift is important for supporting the assignment of the measured double-walled nanotubes to particular nanotube types. Here, we report a computational study of the G-band shift as a function of the semiconducting inner layer radius and interlayer separation. We find that with increasing interlayer separation, the G band shift decreases, passes through zero and becomes negative, and further increases in absolute value for the wide range of considered inner layer radii. The theoretical predictions are shown to agree with the available experimental data within the experimental uncertainty.

  11. Manic espisode, confusional syndrome and reversible splenial lesion after abrupt withdrawal of oxcarbazepine.

    PubMed

    Merizalde, Milton; Navalón, Pablo; González, María Fernanda; Domínguez, Alberto; Livianos, Lorenzo; Martínez, Juan Carlos

    2017-03-01

    Anticonvulsants are considered a second line option for bipolar disorder, it is known that the abrupt withdrawal is rarely related with demyelinated lesions of the splenium of the corpus callosum. Oxcarbazepine is used in bipolar disorder although it is not stated in the data sheet. We presented a case of a 50 years old woman with bipolar disorder who is treated with lithium and oxcarbazepine, she presented a manic episode and a confusional syndrome after she stopped taking the medication. The magnetic resonance showed a restricted diffusion area at the splenium of the corpus callosum and bifrontal hygromas that disappear two weeks later. The results of this study suggest that for a patient presenting with a mild encephalopathy and reversible splenial lesion, one should consider whether it is related to withdrawal of oxcarbazepine. Published by Elsevier B.V.

  12. Actigraph measures of sleep among female hospital employees working day or alternating day and night shifts.

    PubMed

    Korsiak, Jill; Tranmer, Joan; Leung, Michael; Borghese, Michael M; Aronson, Kristan J

    2017-07-14

    Sleep disturbance is common among shift workers, and may be an important factor in the effect of shift work on chronic disease development. In this cross-sectional study, we described sleep patterns of 294 female hospital workers (142 alternating day-night shift workers, 152 day workers) and determined associations between shift work and sleep duration. Rest-activity cycles were recorded with the ActiGraph GT3X+ for 1 week. Analyses were stratified by chronotype of shift workers. Using all study days to calculate average sleep duration, shift workers slept approximately 13 min less than day workers during main sleep periods, while 24-h sleep duration did not differ between day workers and shift workers. Results from age-adjusted models demonstrated that all shift workers, regardless of chronotype, slept 20-30 min less than day workers on day shifts during main and total sleep. Early and intermediate chronotypes working night shifts slept between 114 and 125 min less than day workers, both with regard to the main sleep episode and 24-h sleep duration, while the difference was less pronounced among late chronotypes. When sleep duration on free days was compared between shift workers and day workers, only shift workers with late chronotypes slept less, by approximately 50 min, than day workers during main sleep. Results from this study demonstrate how an alternating day-night shift work schedule impacts sleep negatively among female hospital workers, and the importance of considering chronotype in sleep research among shift workers. © 2017 European Sleep Research Society.

  13. Abrupt transition to heightened poliomyelitis epidemicity in England and Wales, 1947-1957, associated with a pronounced increase in the geographical rate of disease propagation.

    PubMed

    Smallman-Raynor, M R; Cliff, A D

    2014-03-01

    The abrupt transition to heightened poliomyelitis epidemicity in England and Wales, 1947-1957, was associated with a profound change in the spatial dynamics of the disease. Drawing on the complete record of poliomyelitis notifications in England and Wales, we use a robust method of spatial epidemiological analysis (swash-backwash model) to evaluate the geographical rate of disease propagation in successive poliomyelitis seasons, 1940-1964. Comparisons with earlier and later time periods show that the period of heightened poliomyelitis epidemicity corresponded with a sudden and pronounced increase in the spatial rate of disease propagation. This change was observed for both urban and rural areas and points to an abrupt enhancement in the propensity for the geographical spread of polioviruses. Competing theories of the epidemic emergence of poliomyelitis in England and Wales should be assessed in the light of this evidence.

  14. The influence of applied internal and external rotation on the pivot shift phenomenon.

    PubMed

    Kopf, Sebastian; Musahl, Volker; Perka, Carsten; Kauert, Ralf; Hoburg, Arnd; Becker, Roland

    2017-04-01

    The pivot shift test is performed in different techniques and the rotation of the tibia seems to have a significant impact on the amount of the pivot shift phenomenon. It has been hypothesised that external rotation will increase the phenomenon due to less tension at the iliotibial band in knee extension. Twenty-four patients with unilateral anterior cruciate ligament insufficiency were included prospectively. The pivot shift test was performed bilaterally in internal and external tibial rotation under general anaesthesia. Knee motion was captured using a femoral and a tibial inertial sensor. The difference between positive and negative peak values in Euclidean norm of acceleration was calculated to evaluate the amount of the pivot shift phenomenon. The pivot shift phenomenon was significantly increased in patients with ACL insufficiency when the test was performed in external [mean 5.2 ms - 2 (95% CI 4.3-6.0)] compared to internal tibial rotation [mean 4.4 ms - 2 (95% CI 3.5-5.4)] (p = 0.002). In healthy, contralateral knees did not show any difference between external [mean 4.0 ms - 2 (95% CI 3.3-4.7)] and internal tibial rotation [mean 4.0 ms - 2 (95% CI 3.4-4.6)] (ns). The pivot shift phenomenon was increased with external rotation in ACL-insufficient knees, and therefore, one should perform the pivot shift test, rather, in external rotation to easily evoke the, sometimes difficult to detect, pivot shift phenomenon. I (diagnostic study).

  15. Distribution of mean Doppler shift, spectral width, and skewness of coherent 50-MHz auroral radar backscatter

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Watermann, J.; McNamara, A.G.; Sofko, G.J.

    Some 7,700 radio aurora spectra obtained from a six link 50-MHz CW radar network set up on the Canadian prairies were analyzed with respect to the distributions of mean Doppler shift, spectral width and skewness. A comparison with recently published SABRE results obtained at 153 MHz shows substantial differences in the distributions which are probably due to different experimental and geophysical conditions. The spectra are mostly broad with mean Doppler shifts close to zero (type II spectra). The typical groupings of type I and type III spectra are clearly identified. All types appear to be in general much more symmetricmore » than those recorded with SABRE, and the skewness is only weakly dependent on the sign of the mean Doppler shift. Its distribution peaks near zero and shows a weak positive correlation with the type II Doppler shifts while the mostly positive type I Doppler shifts are slightly negatively correlated with the skewness.« less

  16. Scheduled Evening Sleep and Enhanced Lighting Improve Adaptation to Night Shift Work in Older Adults

    PubMed Central

    Chinoy, Evan D.; Harris, Michael P.; Kim, Min Ju; Wang, Wei; Duffy, Jeanne F.

    2017-01-01

    Objectives We tested whether a sleep and circadian-based treatment shown to improve circadian adaptation to night shifts and attenuate negative effects on alertness, performance, and sleep in young adults would also be effective in older adults. Methods We assessed subjective alertness, sustained attention (psychomotor vigilance task, PVT), sleep duration (actigraphy), and circadian timing (salivary dim-light melatonin onset, DLMO) in eighteen older adults (57.2±3.8 y; mean±SD) in a simulated shift work protocol. Four day shifts were followed by three night shifts in the laboratory. Participants slept at home and were randomized to either the Treatment Group (scheduled evening sleep and enhanced lighting during the latter half of night shifts), or Control Group (ad lib sleep and typical lighting during night shifts). Results Compared to day shifts, alertness and sustained attention declined on the first night shift in both groups, and was worse in the latter half of the night shifts. Alertness and attention improved on nights 2 and 3 for the Treatment Group but remained lower for the Control Group. Sleep duration in the Treatment Group remained similar to baseline (6–7 h) following night shifts, but was shorter (3–5 h) following night shifts in the Control Group. Treatment Group circadian timing advanced by 169.3±16.1 min (mean±SEM) but did not shift (−9.7±9.9 min) in the Control Group. Conclusions The combined treatment of scheduled evening sleep and enhanced lighting increased sleep duration and partially aligned circadian phase with sleep and work timing, resulting in improved night shift alertness and performance. PMID:27566781

  17. Removing the depth-degeneracy in optical frequency domain imaging with frequency shifting

    PubMed Central

    Yun, S. H.; Tearney, G. J.; de Boer, J. F.; Bouma, B. E.

    2009-01-01

    A novel technique using an acousto-optic frequency shifter in optical frequency domain imaging (OFDI) is presented. The frequency shift eliminates the ambiguity between positive and negative differential delays, effectively doubling the interferometric ranging depth while avoiding image cross-talk. A signal processing algorithm is demonstrated to accommodate nonlinearity in the tuning slope of the wavelength-swept OFDI laser source. PMID:19484034

  18. Extreme temperatures, foundation species, and abrupt ecosystem change: an example from an iconic seagrass ecosystem.

    PubMed

    Thomson, Jordan A; Burkholder, Derek A; Heithaus, Michael R; Fourqurean, James W; Fraser, Matthew W; Statton, John; Kendrick, Gary A

    2015-04-01

    Extreme climatic events can trigger abrupt and often lasting change in ecosystems via the reduction or elimination of foundation (i.e., habitat-forming) species. However, while the frequency/intensity of extreme events is predicted to increase under climate change, the impact of these events on many foundation species and the ecosystems they support remains poorly understood. Here, we use the iconic seagrass meadows of Shark Bay, Western Australia--a relatively pristine subtropical embayment whose dominant, canopy-forming seagrass, Amphibolis antarctica, is a temperate species growing near its low-latitude range limit--as a model system to investigate the impacts of extreme temperatures on ecosystems supported by thermally sensitive foundation species in a changing climate. Following an unprecedented marine heat wave in late summer 2010/11, A. antarctica experienced catastrophic (>90%) dieback in several regions of Shark Bay. Animal-borne video footage taken from the perspective of resident, seagrass-associated megafauna (sea turtles) revealed severe habitat degradation after the event compared with a decade earlier. This reduction in habitat quality corresponded with a decline in the health status of largely herbivorous green turtles (Chelonia mydas) in the 2 years following the heat wave, providing evidence of long-term, community-level impacts of the event. Based on these findings, and similar examples from diverse ecosystems, we argue that a generalized framework for assessing the vulnerability of ecosystems to abrupt change associated with the loss of foundation species is needed to accurately predict ecosystem trajectories in a changing climate. This includes seagrass meadows, which have received relatively little attention in this context. Novel research and monitoring methods, such as the analysis of habitat and environmental data from animal-borne video and data-logging systems, can make an important contribution to this framework. © 2014 John Wiley

  19. Rainfall-triggered shallow landslides at catchment scale: Threshold mechanics-based modeling for abruptness and localization

    NASA Astrophysics Data System (ADS)

    von Ruette, J.; Lehmann, P.; Or, D.

    2013-10-01

    Rainfall-induced shallow landslides may occur abruptly without distinct precursors and could span a wide range of soil mass released during a triggering event. We present a rainfall-induced landslide-triggering model for steep catchments with surfaces represented as an assembly of hydrologically and mechanically interconnected soil columns. The abruptness of failure was captured by defining local strength thresholds for mechanical bonds linking soil and bedrock and adjacent columns, whereby a failure of a single bond may initiate a chain reaction of subsequent failures, culminating in local mass release (a landslide). The catchment-scale hydromechanical landslide-triggering model (CHLT) was applied to results from two event-based landslide inventories triggered by two rainfall events in 2002 and 2005 in two nearby catchments located in the Prealps in Switzerland. Rainfall radar data, surface elevation and vegetation maps, and a soil production model for soil depth distribution were used for hydromechanical modeling of failure patterns for the two rainfall events at spatial and temporal resolutions of 2.5 m and 0.02 h, respectively. The CHLT model enabled systematic evaluation of the effects of soil type, mechanical reinforcement (soil cohesion and lateral root strength), and initial soil water content on landslide characteristics. We compared various landslide metrics and spatial distribution of simulated landslides in subcatchments with observed inventory data. Model parameters were optimized for the short but intense rainfall event in 2002, and the calibrated model was then applied for the 2005 rainfall, yielding reasonable predictions of landslide events and volumes and statistically reproducing localized landslide patterns similar to inventory data. The model provides a means for identifying local hot spots and offers insights into the dynamics of locally resolved landslide hazards in mountainous regions.

  20. Evidence for positive, but not negative, behavioral contrast with wheel-running reinforcement on multiple variable-ratio schedules.

    PubMed

    Belke, Terry W; Pierce, W David

    2016-12-01

    Rats responded on a multiple variable-ratio (VR) 10 VR 10 schedule of reinforcement in which lever pressing was reinforced by the opportunity to run in a wheel for 30s in both the changed (manipulated) and unchanged components. To generate positive contrast, the schedule of reinforcement in the changed component was shifted to extinction; to generate negative contrast, the schedule was shifted to VR 3. With the shift to extinction in the changed component, wheel-running and local lever-pressing rates increased in the unchanged component, a result supporting positive contrast; however, the shift to a VR 3 schedule in the changed component showed no evidence of negative contrast in the unaltered setting, only wheel running decreased in the unchanged component. Changes in wheel-running rates across components were consistent in showing a compensation effect, depending on whether the schedule manipulation increased or decreased opportunities for wheel running in the changed component. These findings are the first to demonstrate positive behavioral contrast on a multiple schedule with wheel running as reinforcement in both components. Copyright © 2016 Elsevier B.V. All rights reserved.