Science.gov

Sample records for aquic regimes

  1. Phosphorus vertical migration in aquic brown soil and light chernozem under different phosphorous application rate: a soil column leaching experiment.

    PubMed

    Zhao, Muqiu; Chen, Xin; Shi, Yi; Zhou, Quanlai; Lu, Caiyan

    2009-01-01

    A soil column leaching experiment was conducted to study the vertical migration of phosphorus in aquic brown soil and light chernozem under different phosphorus fertilization rates. The results showed that total dissolved phosphorus concentration in the leachates from the two soils was nearly the same, but dissolved inorganic phosphorus concentration was obviously different. In all fertilization treatments, aquic brown soil had a higher content of phosphorus in calcium chloride extracts compared with light chernozem. But Olsen phosphorus content was higher at the soil depth beneath 0-20 cm, and increased with increasing phosphorus application rate.

  2. [Effects of fertilization on aquic brown soil potassium budget and crop potassium allocation].

    PubMed

    Jiang, Zishao; Yu, Wantai; Zhang, Lu

    2006-12-01

    Through a consecutive 15 years field trial on the aquic brown soil in Shenyang suburb of Northeast China, this paper studied the soil potassium budget and crop potassium allocation under effects of different fertilization systems. The results indicated that applying nitrogen or nitrogen plus phosphorous without potassium application accelerated the deficit of soil potassium. The potassium concentration in soybean grain and stalk was higher under potassium application than with no potassium supply, while that in maize grain had no significant difference in different fertilization treatments. The reutilization of recycled nutrients in farming system could mitigate the deficit of soil potassium budget, and such reutilization assorted with appropriate amount of potassium fertilization could not only produce high crop yield, but also balance soil potassium budget.

  3. Using magnetic susceptibility to discriminate between soil moisture regimes in selected loess and loess-like soils in northern Iran

    NASA Astrophysics Data System (ADS)

    Valaee, Morteza; Ayoubi, Shamsollah; Khormali, Farhad; Lu, Sheng Gao; Karimzadeh, Hamid Reza

    2016-04-01

    This study used discriminant analysis to determine the efficacy of magnetic measures for discriminating between four soil moisture regimes in northern Iran. The study area was located on loess deposits and loess-like soils containing similar parent material. Four soil moisture regimes including aridic, xeric, udic, and aquic were selected. A total of 25 soil profiles were drug from each regime and composite soil samples were collected within the moisture control section. A set of magnetic measures including magnetic susceptibility at low (χlf) and high (χhf) frequencies, frequency-dependent magnetic susceptibility (χfd), saturation isothermal remnant magnetization (SIRM), and isothermal remnant magnetization (IRM100 mT, IRM 20 mT) were measured in the laboratory. Dithionite citrate bicarbonate (Fed) and acid oxalate (Feo) contents of all soil samples were also determined. The lowest and highest χlf and χhf were observed in aquic and udic moisture regimes, respectively. A similar trend was obtained for Fed and Fed-Feo. The significant positive correlation between Fed and SIRM (r = 0.60; P < 0.01) suggested the formation of stable single domains (SSD) due to pedogenic processes. The results of discriminant analysis indicated that a combination of magnetic measures could successfully discriminate between the selected moisture regimes in the study area (average accuracy = 80%). It can thus be concluded that magnetic measures could be applied as a powerful indicator for differentiation of soil moisture regimes in the study area.

  4. [Effects of long-term fertilization on pH buffer system of sandy loam calcareous fluvor-aquic soil].

    PubMed

    Wang, Ji-Dong; Qi, Bing-Jie; Zhang, Yong-Chun; Zhang, Ai-Jun; Ning, Yun-Wang; Xu, Xian-Ju; Zhang, Hui; Ma, Hong-Bo

    2012-04-01

    Soil samples (0-80 cm) were collected from a 30-year fertilization experimental site in Xuzhou, Jiangsu Province of East China to study the variations of the pH, calcium carbonate and active calcium carbonate contents, and pH buffer capacity of sandy loam calcareous fluvor-aquic soil under different fertilization treatments. Thirty-year continuous application of different fertilizers accelerated the acidification of topsoil (0-20 cm), with the soil pH decreased by 0.41-0.70. Under different fertilization, the soil pH buffer capacity (pHBC) varied from 15.82 to 21.96 cmol x kg(-1). As compared with no fertilization, single N fertilization decreased the pHBC significantly, but N fertilization combined with organic fertilization could significantly increase the pHBC. The soil pHBC had significant positive correlations with soil calcium carbonate and active calcium carbonate contents, but less correlation with soil organic matter content and soil cation exchange capacity, suggesting that after a long-term fertilization, the sandy loam calcareous fluvor-aquic soil was still of an elementary calcium carbonate buffer system, and soil organic matter and cation exchange capacity contributed little to the buffer system. The soil calcium carbonate and active calcium carbonate contents were greater in 0-40 cm than in 40-80 cm soil layer. Comparing with soil calcium carbonate, soil active calcium carbonate was more sensitive to reflect the changes of soil physical and chemical properties, suggesting that the calcium carbonate buffer system could be further classified as soil active calcium carbonate buffer system.

  5. Effects of slow-release urea fertilizers on urease activity, microbial biomass, and nematode communities in an aquic brown soil.

    PubMed

    Jiao, Xiaoguang; Liang, Wenju; Chen, Lijun; Zhang, Haijun; Li, Qi; Wang, Peng; Wen, Dazhong

    2005-05-01

    A field experiment was carried out at the Shenyang Experimental Station of Ecology (CAS) in order to study the effects of slow-release urea fertilizers high polymer-coated urea (SRU1), SRU1 mixed with dicyandiamide DCD (SRU2), and SRU1 mixed with calcium carbide CaC2 (SRU3) on urease activity, microbial biomass C and N, and nematode communities in an aquic brown soil during the maize growth period. The results demonstrated that the application of slow-release urea fertilizers inhibits soil urease activity and increases the soil NH4+-N content. Soil available N increment could promote its immobilization by microorganisms. Determination of soil microbial biomass N indicated that a combined application of coated urea and nitrification inhibitors increased the soil active N pool. The population of predators/omnivores indicated that treatment with SRU2 could provide enough soil NH4+-N to promote maize growth and increased the food resource for the soil fauna compared with the other treatments.

  6. Ammonia-oxidation as an engine to generate nitrous oxide in an intensively managed calcareous Fluvo-aquic soil

    PubMed Central

    Huang, Tao; Gao, Bing; Hu, Xiao-Kang; Lu, Xing; Well, Reinhard; Christie, Peter; Bakken, Lars R.; Ju, Xiao-Tang

    2014-01-01

    We combine field observations, microcosm, stoichiometry, and molecular and stable isotope techniques to quantify N2O generation processes in an intensively managed low carbon calcareous fluvo-aquic soil. All the evidence points to ammonia oxidation and linked nitrifier denitrification (ND) being the major processes generating N2O. When NH4+-based fertilizers are applied the soil will produce high N2O peaks which are inhibited almost completely by adding nitrification inhibitors. During ammonia oxidation with high NH4+ concentrations (>80 mg N kg−1) the soil matrix will actively consume oxygen and accumulate high concentrations of NO2−, leading to suboxic conditions inducing ND. Calculated N2O isotopomer data show that nitrification and ND accounted for 35–53% and 44–58% of total N2O emissions, respectively. We propose that slowing down nitrification and avoiding high ammonium concentrations in the soil matrix are important measures to reduce N2O emissions per unit of NH4+-based N input from this type of intensively managed soil globally. PMID:24492201

  7. Linkage between N2O emission and functional gene abundance in an intensively managed calcareous fluvo-aquic soil.

    PubMed

    Yang, Liuqing; Zhang, Xiaojun; Ju, Xiaotang

    2017-02-24

    The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. We investigated the abundance of bacterial amoA for nitrification and narG, nirS, nirK, and nosZ for denitrification by in situ soil sampling to determine how the abundance of these genes changes instantly during N fertilization events and is related to high N2O emission peaks. We also investigated how long-term incorporated straw and/or manure affect(s) the abundance of these genes based on a seven-year field experiment. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. A significant correlation between annual N2O emissions and narG, nirS, and nirK gene numbers indicates that the abundance of these genes is related to N2O emission under conditions for denitrification, thus partly contributing to the annual N2O emissions. These findings will help to draw up appropriate measures for mitigation of N2O emissions in this 'hotspot' region.

  8. [Profile distribution of exchangeable calcium and magnesium in an aquic brown soil as affected by land use type].

    PubMed

    Zhang, Yu-ge; Liang, Wen-ju; Jiang, Yong

    2008-04-01

    A comparative study was made on the profile distribution of exchangeable Ca and Mg and Ca/Mg ratio at the depth of 0-150 cm in an aquic brown soil under four land use patterns, i. e., paddy field, maize field, fallow field, and woodland. The results showed that less difference was observed in the soil exchangeable Ca content and storage among different land use patterns. For soil exchangeable Mg, it was significantly higher in woodland than in paddy field, and its storage was in the sequence of woodland > maize field > fallow field > paddy field (P <0.05). The exchangeable Ca/Mg ratio tended to decrease with soil depth, and was significantly lower in paddy field than in other three land use patterns in the soil layers below 40 cm (P <0.05). The preferential retention of Mg in soil ecosystem, soil management practices, and plant characteristics, e. g., biomass cycling rate, biomass above- and below-ground allocation, root distribution, and maximum rooting depth) might play important roles in shaping soil exchangeable Ca and Mg profiles and in reconstructing soil exchangeable Ca and Mg pools.

  9. Linkage between N2O emission and functional gene abundance in an intensively managed calcareous fluvo-aquic soil

    NASA Astrophysics Data System (ADS)

    Yang, Liuqing; Zhang, Xiaojun; Ju, Xiaotang

    2017-02-01

    The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. We investigated the abundance of bacterial amoA for nitrification and narG, nirS, nirK, and nosZ for denitrification by in situ soil sampling to determine how the abundance of these genes changes instantly during N fertilization events and is related to high N2O emission peaks. We also investigated how long-term incorporated straw and/or manure affect(s) the abundance of these genes based on a seven-year field experiment. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. A significant correlation between annual N2O emissions and narG, nirS, and nirK gene numbers indicates that the abundance of these genes is related to N2O emission under conditions for denitrification, thus partly contributing to the annual N2O emissions. These findings will help to draw up appropriate measures for mitigation of N2O emissions in this ‘hotspot’ region.

  10. Linkage between N2O emission and functional gene abundance in an intensively managed calcareous fluvo-aquic soil

    PubMed Central

    Yang, Liuqing; Zhang, Xiaojun; Ju, Xiaotang

    2017-01-01

    The linkage between N2O emissions and the abundance of nitrifier and denitrifier genes is unclear in the intensively managed calcareous fluvo-aquic soils of the North China Plain. We investigated the abundance of bacterial amoA for nitrification and narG, nirS, nirK, and nosZ for denitrification by in situ soil sampling to determine how the abundance of these genes changes instantly during N fertilization events and is related to high N2O emission peaks. We also investigated how long-term incorporated straw and/or manure affect(s) the abundance of these genes based on a seven-year field experiment. The overall results demonstrate that the long-term application of urea-based fertilizer and/or manure significantly enhanced the number of bacterial amoA gene copies leading to high N2O emission peaks after N fertilizer applications. These peaks contributed greatly to the annual N2O emissions in the crop rotation. A significant correlation between annual N2O emissions and narG, nirS, and nirK gene numbers indicates that the abundance of these genes is related to N2O emission under conditions for denitrification, thus partly contributing to the annual N2O emissions. These findings will help to draw up appropriate measures for mitigation of N2O emissions in this ‘hotspot’ region. PMID:28233823

  11. Long-term fertilization of organic manure led to the succession of Bacillus community in an alluvial-aquic soil

    NASA Astrophysics Data System (ADS)

    Chen, Ruirui; Lin, Xiangui; Feng, Youzhi; Hu, Junli; Wang, Ruirui

    2014-05-01

    Long-term fertilization inevitably influences soil physic-chemical and biological properties. Our previous studies with a long-term fertilization experiment on an alluvial-aquic have revealed that specific Bacillus spp. was observed in organic manure-fertilized soils. The current study investigated the effects of long-term fertilization on the succession of Bacillus community in soils and their functions. The experiment included three fertilizer treatments: organic manure (OM), mineral fertilizers (NPK) and the control (without fertilizers). The results showed that long-term application of chemical fertilizers didn't increase the quantity of soil microbial population as much as organic fertilizers did, but it played an important role in maintaining the diversity and community structure of indigenous Bacilli. Correspondingly, long-term application of organic manure significantly increased the quantity while significantly decreased the diversity of Bacilli community. The ratio of Bacilli/bacteria was more constant in OM treatment than NPK indicating the stability of the response to long-term organic fertilizers. PCR-DGGE and clone library revealed the succession of Bacillus community after long-term application of organic manure and the dominant Bacillus spp occurred in the treatmen OM was Bacillus asahii. Our results also proved that Bacillus asahii was not derived from exogenous organic manure, but one of indigenous bacteria in the soil. Bacillus asahii was induced by the substrate after the application of organic manure, and gradually evolved into dominant Bacillus after 4 to 5 years. With an enzyme assay test of pure species and a soil incubation experiment, we came to a preliminary judgment, that the dominant Bacillus asahii didn't significantly influence the decomposition rate of cellulose and protein in the soil, but it promoted the decomposition of lipids, and could also improve the transformation process from fresh organic matter to humus. Applied organic

  12. Effects of dicyandiamide and acetylene on N2O emissions and ammonia oxidizers in a fluvo-aquic soil applied with urea.

    PubMed

    Wang, Qing; Zhang, Li-Mei; Shen, Ju-Pei; Du, Shuai; Han, Li-Li; He, Ji-Zheng

    2016-11-01

    Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are crucial for N2O emission as they carry out the key step of nitrification. Dicyandiamide (DCD) and acetylene (C2H2) are typical nitrification inhibitors (NIs), while the comparative effects of these NIs on N2O production and ammonia oxidizers' (AOB and AOA) growth are unclear. Four treatments including a control, urea, urea + DCD, and urea + C2H2 were set up to investigate their effect of inhibiting soil nitrification, nitrification-related N2O emission as well as the growth of ammonia oxidizers with a fluvo-aquic soil using microcosms for 28 days. N2O emission and net nitrification rate increased after the application of urea, but were significantly restrained in urea + NI treatments, while C2H2 was more effective in reducing N2O emission and nitrification rate than DCD. The abundance of AOB, which was significantly correlated with N2O emission and net nitrification rate, was more inhibited by C2H2 than DCD. Furthermore, the application of urea in all the soils had little impact on the AOA community, while obvious shifts of AOB community structure were found compared with the control. All AOB sequences fell within Nitrosospira cluster 3, and the AOA community was clustered to group 1.1b. Collectively, it indicated that application of urea combined with NIs (DCD or C2H2) could potentially alter N2O emission, mainly through regulating the growth of AOB but not AOA in this fluvo-aquic soil.

  13. [Effects of long-term application of organic fertilizer and superphosphate on accumulation and leaching of Olsen-P in Fluvo-aquic soil].

    PubMed

    Huang, Shao-Min; Guo, Dou-Dou; Zhang, Shui-Qing

    2011-01-01

    Based on a 20-year experiment of fertilization with organic and chemical fertilizers on a Fluvo-aquic soil under wheat-corn cropping system, this paper studied the relationships between Olsen-P concentration in plough layer and crop yields as well as the accumulation and vertical translocation of Olsen-P in soil profile. The results showed that when the Olsen-P concentration in plough layer maintained at 10-40 mg x kg(-1), the grain yields of wheat and corn were higher, whereas when the concentration of Olsen-P in plough layer was higher than 40 mg x kg(-1), it started to leach, which meant that in light loam Fluvo-aquic soil, the threshold value for P leaching might be 40 mg x kg(-1). In the treatments of chemical fertilization (NPK) and corn straw returning (SNPK) with the P application rate of 77-90 kg x hm(-2), the Olsen-P concentration in plough layer was increased by 0.63-0.72 mg x kg(-1) per 100 kg x hm(-2) of applied P, with an annual increment of 0.49-0.65 mg x kg(-1) and needed 45-60 years for reaching the threshold value for P leaching. In the treatments of chemical fertilization combined with manure application (MNPK, MNPK2, and 1.5MNPK), the formula of Olsen-P accumulation in 0-20 cm soil layer were Y(MNPK) = 3.1097x + 6.9615 (R2 = 0.8562), Y(MNPK2) = 2.4765x + 13.563 (R2 = 0.9307), and Y1.5MNPK = 4.506x + 6.4464 (R2 = 0.8862). It might take 8 years to reach the threshold value for Olsen-P leaching when the P application rate in treatment 1.5MNPK was 210 kg x hm(-2), 11 years when the P application rate in treatments MNPK2 and MNPK was 125 and 140 kg x hm(-2). Organic fertilization combined with chemical fertilization increased the Olsen-P accumulation rate being 2.5 times higher than chemical fertilization. Excessive application of organic fertilizer could increase the accumulation and leaching of Olsen-P in soil profile.

  14. Characteristics of maize biochar with different pyrolysis temperatures and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil.

    PubMed

    Wang, Xiubin; Zhou, Wei; Liang, Guoqing; Song, Dali; Zhang, Xiaoya

    2015-12-15

    In this study, the characteristics of maize biochar produced at different pyrolysis temperatures (300, 450 and 600°C) and its effects on organic carbon, nitrogen and enzymatic activities after addition to fluvo-aquic soil were investigated. As pyrolysis temperature increased, ash content, pH, electrical conductivity, surface area, pore volume and aromatic carbon content of biochar increased while yield, ratios of oxygen:carbon and hydrogen: carbon and alkyl carbon content decreased. During incubation, SOC, total N, and ammonium-N contents increased in all biochar-amended treatments compared with the urea treatment; however, soil nitrate-N content first increased and then decreased with increasing pyrolysis temperature of the applied biochar. Extracellular enzyme activities associated with carbon transformation first increased and then decreased with biochars pyrolyzed at 450 and 600°C. Protease activity markedly increased with increased pyrolysis temperatures, whereas pyrolysis temperature had limited effect on soil urease activity. The results indicated that the responses of extracellular enzymes to biochar were dependent on the pyrolysis temperature, the enzyme itself and incubation time as well.

  15. [Estimation of organic matter content of north fluvo-aquic soil based on the coupling model of wavelet transform and partial least squares].

    PubMed

    Wang, Yan-Cang; Yang, Gui-Jun; Zhu, Jin-Shan; Gu, Xiao-He; Xu, Peng; Liao, Qin-Hong

    2014-07-01

    For improving the estimation accuracy of soil organic matter content of the north fluvo-aquic soil, wavelet transform technology is introduced. The soil samples were collected from Tongzhou district and Shunyi district in Beijing city. And the data source is from soil hyperspectral data obtained under laboratory condition. First, discrete wavelet transform efficiently decomposes hyperspectral into approximate coefficients and detail coefficients. Then, the correlation between approximate coefficients, detail coefficients and organic matter content was analyzed, and the sensitive bands of the organic matter were screened. Finally, models were established to estimate the soil organic content by using the partial least squares regression (PLSR). Results show that the NIR bands made more contributions than the visible band in estimating organic matter content models; the ability of approximate coefficients to estimate organic matter content is better than that of detail coefficients; The estimation precision of the detail coefficients fir soil organic matter content decreases with the spectral resolution being lower; Compared with the commonly used three types of soil spectral reflectance transforms, the wavelet transform can improve the estimation ability of soil spectral fir organic content; The accuracy of the best model established by the approximate coefficients or detail coefficients is higher, and the coefficient of determination (R2) and the root mean square error (RMSE) of the best model for approximate coefficients are 0.722 and 0.221, respectively. The R2 and RMSE of the best model for detail coefficients are 0.670 and 0.255, respectively.

  16. Effect of application of dairy manure, effluent and inorganic fertilizer on nitrogen leaching in clayey fluvo-aquic soil: A lysimeter study.

    PubMed

    Fan, Jianling; Xiao, Jiao; Liu, Deyan; Ye, Guiping; Luo, Jiafa; Houlbrooke, David; Laurenson, Seth; Yan, Jing; Chen, Lvjun; Tian, Jinping; Ding, Weixin

    2017-08-15

    Dairy farm manure and effluent are applied to cropland in China to provide a source of plant nutrients, but there are concerns over its effect on nitrogen (N) leaching loss and groundwater quality. To investigate the effects of land application of dairy manure and effluent on potential N leaching loss, two lysimeter trials were set up in clayey fluvo-aquic soil in a winter wheat-summer maize rotation cropping system on the North China Plain. The solid dairy manure trial included control without N fertilization (CK), inorganic N fertilizer (SNPK), and fresh (RAW) and composted (COM) dairy manure. The liquid dairy effluent trial consisted of control without N fertilization (CF), inorganic N fertilizer (ENPK), and fresh (FDE) and stored (SDE) dairy effluent. The N application rate was 225kgNha(-1) for inorganic N fertilizer, dairy manure, and effluent treatments in both seasons. Annual N leaching loss (ANLL) was highest in SNPK (53.02 and 16.21kgNha(-1) in 2013/2014 and 2014/2015, respectively), which were 1.65- and 2.04-fold that of COM, and 1.59- and 1.26-fold that of RAW. In the effluent trial (2014/2015), ANLL for ENPK and SDE (16.22 and 16.86kgNha(-1), respectively) were significantly higher than CF and FDE (6.3 and 13.21kgNha(-1), respectively). NO3(-) contributed the most (34-92%) to total N leaching loss among all treatments, followed by dissolved organic N (14-57%). COM showed the lowest N leaching loss due to a reduction in NO3(-) loss. Yield-scaled N leaching in COM (0.35kgNMg(-1) silage) was significantly (P<0.05) lower than that in the other fertilization treatments. Therefore, the use of composted dairy manure should be increased and that of inorganic fertilizer decreased to reduce N leaching loss while ensuring high crop yield in the North China Plain.

  17. Arctic circulation regimes.

    PubMed

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L

    2015-10-13

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability.

  18. Arctic circulation regimes

    PubMed Central

    Proshutinsky, Andrey; Dukhovskoy, Dmitry; Timmermans, Mary-Louise; Krishfield, Richard; Bamber, Jonathan L.

    2015-01-01

    Between 1948 and 1996, mean annual environmental parameters in the Arctic experienced a well-pronounced decadal variability with two basic circulation patterns: cyclonic and anticyclonic alternating at 5 to 7 year intervals. During cyclonic regimes, low sea-level atmospheric pressure (SLP) dominated over the Arctic Ocean driving sea ice and the upper ocean counterclockwise; the Arctic atmosphere was relatively warm and humid, and freshwater flux from the Arctic Ocean towards the subarctic seas was intensified. By contrast, during anticylonic circulation regimes, high SLP dominated driving sea ice and the upper ocean clockwise. Meanwhile, the atmosphere was cold and dry and the freshwater flux from the Arctic to the subarctic seas was reduced. Since 1997, however, the Arctic system has been under the influence of an anticyclonic circulation regime (17 years) with a set of environmental parameters that are atypical for this regime. We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from the Arctic Ocean and Greenland impact environmental conditions and interrupt their decadal variability. PMID:26347536

  19. Detecting spatial regimes in ecosystems

    EPA Science Inventory

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological ...

  20. Cloud regimes as phase transitions

    NASA Astrophysics Data System (ADS)

    Stechmann, Samuel N.; Hottovy, Scott

    2016-06-01

    Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes -- open versus closed cells -- fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. With this new conceptual viewpoint, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions.

  1. Hall effect in hopping regime

    NASA Astrophysics Data System (ADS)

    Avdonin, A.; Skupiński, P.; Grasza, K.

    2016-02-01

    A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO.

  2. Detecting spatial regimes in ecosystems

    USGS Publications Warehouse

    Sundstrom, Shana M.; Eason, Tarsha; Nelson, R. John; Angeler, David G.; Barichievy, Chris; Garmestani, Ahjond S.; Graham, Nicholas A.J.; Granholm, Dean; Gunderson, Lance; Knutson, Melinda; Nash, Kirsty L.; Spanbauer, Trisha; Stow, Craig A.; Allen, Craig R.

    2017-01-01

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological potential (i.e. potential vegetation), and often fail to account for ongoing changes due to stressors such as land use change and climate change and their effects on plant and animal communities. We use Fisher information, an information theory-based method, on both terrestrial and aquatic animal data (U.S. Breeding Bird Survey and marine zooplankton) to identify ecological boundaries, and compare our results to traditional early warning indicators, conventional ecoregion maps and multivariate analyses such as nMDS and cluster analysis. We successfully detected spatial regimes and transitions in both terrestrial and aquatic systems using Fisher information. Furthermore, Fisher information provided explicit spatial information about community change that is absent from other multivariate approaches. Our results suggest that defining spatial regimes based on animal communities may better reflect ecological reality than do traditional ecoregion maps, especially in our current era of rapid and unpredictable ecological change.

  3. Flow regimes during immiscible displacement

    DOE PAGES

    Armstrong, Ryan T.; Mcclure, James; Berrill, Mark A.; ...

    2017-02-01

    Fractional ow of immiscible phases occurs at the pore scale where grain surfaces and phases interfaces obstruct phase mobility. However, the larger scale behavior is described by a saturation-dependent phenomenological relationship called relative permeability. As a consequence, pore-scale parameters, such as phase topology and/ or geometry, and details of the flow regime cannot be directly related to Darcy-scale flow parameters. It is well understood that relative permeability is not a unique relationship of wetting-phase saturation and rather depends on the experimental conditions at which it is measured. Herein we use fast X-ray microcomputed tomography to image pore-scale phase arrangements duringmore » fractional flow and then forward simulate the flow regimes using the lattice-Boltzmann method to better understand the underlying pore-scale flow regimes and their influence on Darcy-scale parameters. We find that relative permeability is highly dependent on capillary number and that the Corey model fits the observed trends. At the pore scale, while phase topologies are continuously changing on the scale of individual pores, the Euler characteristic of the nonwetting phase (NWP) averaged over a sufficiently large field of view can describe the bulk topological characteristics; the Euler characteristic decreases with increasing capillary number resulting in an increase in relative permeability. Lastly, we quantify the fraction of NWP that flows through disconnected ganglion dynamics and demonstrate that this can be a significant fraction of the NWP flux for intermediate wetting-phase saturation. Furthermore, rate dependencies occur in our homogenous sample (without capillary end effect) and the underlying cause is attributed to ganglion flow that can significantly influence phase topology during the fractional flow of immiscible phases.« less

  4. Overview of the regimes: CWC

    SciTech Connect

    1995-12-31

    The Chemical Weapons Convention`s (CWC) seeks to eradicate an entire category of catastrophic weapons and to ensure their continued non-production. Unlike the Non-Proliferation Treaty`s (NPT), the CWC requires disarmament. States Parties having chemical weapons (CW) must destroy them. The CWC has not adopted the NPT distinction between weapons and non-weapons states; the CWC`s prohibitions and obligations will apply identically to all States parties. In most other respects, the two treaties establish similar regimes with similar approaches. Included are objectives and primary obligations, legal bases, institutional oversight, trade restrictions, protection of information, penal consequences, and role of the United Nations.

  5. The New English Quality Assurance Regime

    ERIC Educational Resources Information Center

    Brown, Roger

    2011-01-01

    England is developing a new quality assurance regime that will come into effect in October 2011. A new funding regime will operate from the following year, together with new rules to ease the participation of private higher education providers. This article describes and analyses the new quality and funding regimes. It argues that the greater…

  6. Adaptation in Collaborative Governance Regimes

    NASA Astrophysics Data System (ADS)

    Emerson, Kirk; Gerlak, Andrea K.

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  7. Adaptation in collaborative governance regimes.

    PubMed

    Emerson, Kirk; Gerlak, Andrea K

    2014-10-01

    Adaptation and the adaptive capacity of human and environmental systems have been of central concern to natural and social science scholars, many of whom characterize and promote the need for collaborative cross-boundary systems that are seen as flexible and adaptive by definition. Researchers who study collaborative governance systems in the public administration, planning and policy literature have paid less attention to adaptive capacity specifically and institutional adaptation in general. This paper bridges the two literatures and finds four common dimensions of capacity, including structural arrangements, leadership, knowledge and learning, and resources. In this paper, we focus on institutional adaptation in the context of collaborative governance regimes and try to clarify and distinguish collaborative capacity from adaptive capacity and their contributions to adaptive action. We posit further that collaborative capacities generate associated adaptive capacities thereby enabling institutional adaptation within collaborative governance regimes. We develop these distinctions and linkages between collaborative and adaptive capacities with the help of an illustrative case study in watershed management within the National Estuary Program.

  8. Fire regime in Mediterranean ecosystem

    NASA Astrophysics Data System (ADS)

    Biondi, Guido; Casula, Paolo; D'Andrea, Mirko; Fiorucci, Paolo

    2010-05-01

    The analysis of burnt areas time series in Mediterranean regions suggests that ecosystems characterising this area consist primarily of species highly vulnerable to the fire but highly resilient, as characterized by a significant regenerative capacity after the fire spreading. In a few years the area burnt may once again be covered by the same vegetation present before the fire. Similarly, Mediterranean conifer forests, which often refers to plantations made in order to reforest the areas most severely degraded with high erosion risk, regenerate from seed after the fire resulting in high resilience to the fire as well. Only rarely, and usually with negligible damages, fire affects the areas covered by climax species in relation with altitude and soil types (i.e, quercus, fagus, abies). On the basis of these results, this paper shows how the simple Drossel-Schwabl forest fire model is able to reproduce the forest fire regime in terms of number of fires and burned area, describing whit good accuracy the actual fire perimeters. The original Drossel-Schwabl model has been slightly modified in this work by introducing two parameters (probability of propagation and regrowth) specific for each different class of vegetation cover. Using model selection methods based on AIC, the model with the optimal number of classes with different fire behaviour was selected. Two different case studies are presented in this work: Regione Liguria and Regione Sardegna (Italy). Both regions are situated in the center of the Mediterranean and are characterized by a high number of fires and burned area. However, the two regions have very different fire regimes. Sardinia is affected by the fire phenomenon only in summer whilst Liguria is affected by fires also in winter, with higher number of fires and larger burned area. In addition, the two region are very different in vegetation cover. The presence of Mediterranean conifers, (Pinus Pinaster, Pinus Nigra, Pinus halepensis) is quite spread in

  9. Propagation Regime of Iron Dust Flames

    NASA Technical Reports Server (NTRS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew J.

    2012-01-01

    A flame propagating through an iron-dust mixture can propagate in two asymptotic regimes. When the characteristic time of heat transfer between particles is much smaller than the characteristic time of particle combustion, the flame propagates in the continuum regime where the heat released by reacting particles can be modelled as a space-averaged function. In contrast, when the characteristic time of heat transfer is much larger than the particle reaction time, the flame can no longer be treated as a continuum due to dominating effects associated with the discrete nature of the particle reaction. The discrete regime is characterized by weak dependence of the flame speed on the oxygen concentration compared to the continuum regime. The discrete regime is observed in flames propagating through an iron dust cloud within a gas mixture containing xenon, while the continuum regime is obtained when xenon is substituted with helium.

  10. Regimes of DNA confined in a nanochannel

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Doyle, Patrick

    2014-03-01

    Scaling regimes for polymers confined to tubular channels are well established when the channel cross-sectional dimension is either very small (Odjik regime) or large (classic de Gennes regime) relative to the polymer Kuhn length. In the literature, there is no clear consensus regarding the intermediate region and if subregimes even exist to connect these two classic bounding regimes. The confluence of emerging single DNA mapping technologies and a resurged interest in the fundamental properties of confined polymers has led to extensive research in this area using DNA as a model system. Due to the DNA molecule's properties and limitations of nanofabrication, most experiments are performed in this intermediate regime with channel dimensions of a few Kuhn lengths. Here we use simulations and theory to reconcile conflicting theories and show that there are indeed extended de Gennes, partial alignment and hairpin regimes located between the two classic regimes. Simulations results for both chain extension and free energy support the existence of these regimes. This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's research program in BioSystems and Micromechanics, the National Science Foundation (CBET-1335938).

  11. FISHER INFORMATION AND ECOSYSTEM REGIME CHANGES

    EPA Science Inventory

    Following Fisher’s work, we propose two different expressions for the Fisher Information along with Shannon Information as a means of detecting and assessing shifts between alternative ecosystem regimes. Regime shifts are a consequence of bifurcations in the dynamics of an ecosys...

  12. Three regimes of relativistic beam - plasma interaction

    SciTech Connect

    Muggli, P.; Allen, B.; Fang, Y.; Yakimenko, V.; Babzien, M.; Kusche, K.; Fedurin, M.; Vieira, J.; Martins, J.; Silva, L.

    2012-12-21

    Three regimes of relativistic beam - plasma interaction can in principle be reached at the ATF depending on the relative transverse and longitudinal size of the electron bunch when compared to the cold plasma collisionless skin depth c?{omega}{sub pe}: the plasma wakefield accelerator (PWFA), the self-modulation instability (SMI), and the current filamentation instability (CFI) regime. In addition, by choosing the bunch density, the linear, quasi-nonlinear and non linear regime of the PWFA can be reached. In the case of the two instabilities, the bunch density determines the growth rate and therefore the occurrence or not of the instability. We briefly describe these three regimes and outline results demonstrating that all these regime have or will be reached experimentally. We also outline planned and possible follow-on experiments.

  13. 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.

  14. Distinct Turbulence Saturation Regimes in Stellarators

    NASA Astrophysics Data System (ADS)

    Plunk, G. G.; Xanthopoulos, P.; Helander, P.

    2017-03-01

    In the complex 3D magnetic fields of stellarators, ion-temperature-gradient turbulence is shown to have two distinct saturation regimes, as revealed by petascale numerical simulations and explained by a simple turbulence theory. The first regime is marked by strong zonal flows and matches previous observations in tokamaks. The newly observed second regime, in contrast, exhibits small-scale quasi-two-dimensional turbulence, negligible zonal flows, and, surprisingly, a weaker heat flux scaling. Our findings suggest that key details of the magnetic geometry control turbulence in stellarators.

  15. Earth Regime Network Evolution Study (ERNESt)

    NASA Technical Reports Server (NTRS)

    Menrad, Bob

    2016-01-01

    Speaker and Presenter at the Lincoln Laboratory Communications Workshop on April 5, 2016 at the Massachusetts Institute of Technology Lincoln Laboratory in Lexington, MA. A visual presentation titled Earth Regimes Network Evolution Study (ERNESt).

  16. Prolonged instability prior to a regime shift.

    PubMed

    Spanbauer, Trisha L; 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.

  17. Electron transport fluxes in potato plateau regime

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1997-12-01

    Electron transport fluxes in the potato plateau regime are calculated from the solutions of the drift kinetic equation and fluid equations. It is found that the bootstrap current density remains finite in the region close to the magnetic axis, although it decreases with increasing collision frequency. This finite amount of the bootstrap current in the relatively collisional regime is important in modeling tokamak startup with 100{percent} bootstrap current. {copyright} {ital 1997 American Institute of Physics.}

  18. Iranian Regime Reform: Opportunities and Consequences

    DTIC Science & Technology

    2010-12-01

    formal political access to mitigate the adverse effects of . . . the deterioration of quality of life .”70 Three broad sets of factors outlined by...demanding changes in the Iranian regime that mesh with U.S.. national interests. However, the Green Movement may not be successful in effecting change...viable threat to the Iranian regime. This thesis used game theory as a tool because game theory outcomes very often reflect real- life outcomes

  19. Greenland Meltwater and Arctic Circulation Regimes

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, D. S.; Proshutinsky, A. Y.; Timmermans, M. L.; Myers, P. G.; Platov, G.

    2015-12-01

    Between 1948 and 1996, wind-driven components of ice drift and surface ocean currents experienced a well-pronounced decadal variability alternating between anticyclonic and cyclonic circulation regimes. During cyclonic regimes, low sea level atmospheric pressure dominated over the Arctic Ocean driving sea ice and the upper ocean clockwise; the Arctic atmosphere was relatively warm and humid and freshwater flux from the Arctic Ocean toward the sub-Arctic seas was intensified. During anticylonic circulation regimes, high sea level pressure dominated over the Arctic driving sea ice and ocean counter-clockwise; the atmosphere was cold and dry and the freshwater flux from the Arctic to the sub-Arctic seas was reduced. Since 1997, however, the Arctic system has been dominated by an anticyclonic circulation regime with a set of environmental parameters that are atypical for these regimes. Of essential importance is to discern the causes and consequences of the apparent break-down in the natural decadal variability of the Arctic climate system, and specifically: Why has the well-pronounced decadal variability observed in the 20th century been replaced by relatively weak interannual changes under anticyclonic circulation regime conditions in the 21st century? We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from Greenland impact environmental conditions and interrupt their decadal variability. In order to test this hypothesis, numerical experiments with several FAMOS (Forum for Arctic Modeling & Observational Synthesis) ice-ocean coupled models have been conducted. In these experiments, Greenland melt freshwater is tracked by passive tracers being constantly released along the Greenland coast. Propagation pathways and time scales of Greenland meltwater within the sub-Arctic seas are discussed.

  20. Identifying natural flow regimes using fish communities

    NASA Astrophysics Data System (ADS)

    Chang, Fi-John; Tsai, Wen-Ping; Wu, Tzu-Ching; Chen, Hung-kwai; Herricks, Edwin E.

    2011-10-01

    SummaryModern water resources management has adopted natural flow regimes as reasonable targets for river restoration and conservation. The characterization of a natural flow regime begins with the development of hydrologic statistics from flow records. However, little guidance exists for defining the period of record needed for regime determination. In Taiwan, the Taiwan Eco-hydrological Indicator System (TEIS), a group of hydrologic statistics selected for fisheries relevance, is being used to evaluate ecological flows. The TEIS consists of a group of hydrologic statistics selected to characterize the relationships between flow and the life history of indigenous species. Using the TEIS and biosurvey data for Taiwan, this paper identifies the length of hydrologic record sufficient for natural flow regime characterization. To define the ecological hydrology of fish communities, this study connected hydrologic statistics to fish communities by using methods to define antecedent conditions that influence existing community composition. A moving average method was applied to TEIS statistics to reflect the effects of antecedent flow condition and a point-biserial correlation method was used to relate fisheries collections with TEIS statistics. The resulting fish species-TEIS (FISH-TEIS) hydrologic statistics matrix takes full advantage of historical flows and fisheries data. The analysis indicates that, in the watersheds analyzed, averaging TEIS statistics for the present year and 3 years prior to the sampling date, termed MA(4), is sufficient to develop a natural flow regime. This result suggests that flow regimes based on hydrologic statistics for the period of record can be replaced by regimes developed for sampled fish communities.

  1. 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.

  2. Dynamic treatment regimes: technical challenges and applications

    PubMed Central

    Lizotte, Daniel J.; Qian, Min; Pelham, William E.; Murphy, Susan A.

    2014-01-01

    Dynamic treatment regimes are of growing interest across the clinical sciences because these regimes provide one way to operationalize and thus inform sequential personalized clinical decision making. Formally, a dynamic treatment regime is a sequence of decision rules, one per stage of clinical intervention. Each decision rule maps up-to-date patient information to a recommended treatment. We briefly review a variety of approaches for using data to construct the decision rules. We then review a critical inferential challenge that results from nonregularity, which often arises in this area. In particular, nonregularity arises in inference for parameters in the optimal dynamic treatment regime; the asymptotic, limiting, distribution of estimators are sensitive to local perturbations. We propose and evaluate a locally consistent Adaptive Confidence Interval (ACI) for the parameters of the optimal dynamic treatment regime. We use data from the Adaptive Pharmacological and Behavioral Treatments for Children with ADHD Trial as an illustrative example. We conclude by highlighting and discussing emerging theoretical problems in this area. PMID:25356091

  3. Gradual regime shifts in fairy circles

    PubMed Central

    Zelnik, Yuval R.; Meron, Ehud; Bel, Golan

    2015-01-01

    Large responses of ecosystems to small changes in the conditions—regime shifts—are of great interest and importance. In spatially extended ecosystems, these shifts may be local or global. Using empirical data and mathematical modeling, we investigated the dynamics of the Namibian fairy circle ecosystem as a case study of regime shifts in a pattern-forming ecosystem. Our results provide new support, based on the dynamics of the ecosystem, for the view of fairy circles as a self-organization phenomenon driven by water–vegetation interactions. The study further suggests that fairy circle birth and death processes correspond to spatially confined transitions between alternative stable states. Cascades of such transitions, possible in various pattern-forming systems, result in gradual rather than abrupt regime shifts. PMID:26362787

  4. Massive superstring scatterings in the Regge regime

    SciTech Connect

    He Song; Lee, Jen-Chi; Takahashi, Keijiro; Yang Yi

    2011-03-15

    We calculate four classes of high-energy massive string scattering amplitudes of fermionic string theory at arbitrary mass levels in the Regge regime (RR). We show that all four leading order amplitudes in the RR can be expressed in terms of the Kummer function of the second kind. Based on the summation algorithm of a set of extended signed Stirling number identities, we show that all four ratios calculated previously by the method of decoupling of zero-norm states among scattering amplitudes in the Gross regime can be extracted from this Kummer function in the RR. Finally, we conjecture and give evidence that the existence of these four Gross regime ratios in the RR persists to subleading orders in the Regge expansion of all high-energy fermionic string scattering amplitudes.

  5. Gradual regime shifts in fairy circles.

    PubMed

    Zelnik, Yuval R; Meron, Ehud; Bel, Golan

    2015-10-06

    Large responses of ecosystems to small changes in the conditions--regime shifts--are of great interest and importance. In spatially extended ecosystems, these shifts may be local or global. Using empirical data and mathematical modeling, we investigated the dynamics of the Namibian fairy circle ecosystem as a case study of regime shifts in a pattern-forming ecosystem. Our results provide new support, based on the dynamics of the ecosystem, for the view of fairy circles as a self-organization phenomenon driven by water-vegetation interactions. The study further suggests that fairy circle birth and death processes correspond to spatially confined transitions between alternative stable states. Cascades of such transitions, possible in various pattern-forming systems, result in gradual rather than abrupt regime shifts.

  6. 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.

  7. On the regimes of charge reversal.

    PubMed

    Jiménez-Angeles, Felipe; Lozada-Cassou, Marcelo

    2008-05-07

    Charge reversal of the planar electrical double layer is studied by means of a well known integral equation theory. By a numerical analysis, a diagram is constructed with the onset points of charge reversal in the space of the fundamental variables of the system. Within this diagram, two regimes of charge reversal are identified, which are referred to as oscillatory and nonoscillatory. We found that these two regimes can be distinguished through a simple formula. Furthermore, a symmetry between electrostatic and size correlations in charge reversal is exhibited. Agreement of our results with other theories and molecular simulations data is discussed.

  8. Statistical regimes of random laser fluctuations

    SciTech Connect

    Lepri, Stefano; Cavalieri, Stefano; Oppo, Gian-Luca; Wiersma, Diederik S.

    2007-06-15

    Statistical fluctuations of the light emitted from amplifying random media are studied theoretically and numerically. The characteristic scales of the diffusive motion of light lead to Gaussian or power-law (Levy) distributed fluctuations depending on external control parameters. In the Levy regime, the output pulse is highly irregular leading to huge deviations from a mean-field description. Monte Carlo simulations of a simplified model which includes the population of the medium demonstrate the two statistical regimes and provide a comparison with dynamical rate equations. Different statistics of the fluctuations helps to explain recent experimental observations reported in the literature.

  9. Supercurrent in the quantum Hall regime.

    PubMed

    Amet, F; Ke, C T; Borzenets, I V; Wang, J; Watanabe, K; Taniguchi, T; Deacon, R S; Yamamoto, M; Bomze, Y; Tarucha, S; Finkelstein, G

    2016-05-20

    A promising route for creating topological states and excitations is to combine superconductivity and the quantum Hall (QH) effect. Despite this potential, signatures of superconductivity in the QH regime remain scarce, and a superconducting current through a QH weak link has been challenging to observe. We demonstrate the existence of a distinct supercurrent mechanism in encapsulated graphene samples contacted by superconducting electrodes, in magnetic fields as high as 2 tesla. The observation of a supercurrent in the QH regime marks an important step in the quest for exotic topological excitations, such as Majorana fermions and parafermions, which may find applications in fault-tolerant quantum computing.

  10. Light focusing in the Anderson regime

    NASA Astrophysics Data System (ADS)

    Leonetti, Marco; Karbasi, Salman; Mafi, Arash; Conti, Claudio

    2014-07-01

    Anderson localization is a regime in which diffusion is inhibited and waves (also electromagnetic waves) get localized. Here we exploit adaptive optics to achieve focusing in disordered optical fibres in the Anderson regime. By wavefront shaping and optimization, we observe the generation of a propagation-invariant beam, where light is trapped transversally by disorder, and show that Anderson localizations can be also excited by extended speckled beams. We demonstrate that disordered fibres allow a more efficient focusing action with respect to standard fibres in a way independent of their length, because of the propagation-invariant features and cooperative action of transverse localizations.

  11. Convective Regimes in Crystallizing Basaltic Magma Chambers

    NASA Astrophysics Data System (ADS)

    Gilbert, A. J.; Neufeld, J. A.; Holness, M. B.

    2015-12-01

    Cooling through the chamber walls drives crystallisation in crustal magma chambers, resulting in a cumulate pile on the floor and mushy regions at the walls and roof. The liquid in many magma chambers, either the bulk magma or the interstitial liquid in the mushy regions, may convect, driven either thermally, due to cooling, or compositionally, due to fractional crystallization. We have constructed a regime diagram of the possible convective modes in a system containing a basal mushy layer. These modes depend on the large-scale buoyancy forcing characterised by a global Rayleigh number and the proportion of the chamber height constituting the basal mushy region. We have tested this regime diagram using an analogue experimental system composed of a fluid layer overlying a pile of almost neutrally buoyant inert particles. Convection in this system is driven thermally, simulating magma convection above and within a porous cumulate pile. We observe a range of possible convective regimes, enabling us to produce a regime diagram. In addition to modes characterised by convection of the bulk and interstitial fluid, we also observe a series of regimes where the crystal pile is mobilised by fluid motions. These regimes feature saltation and scouring of the crystal pile by convection in the bulk fluid at moderate Rayleigh numbers, and large crystal-rich fountains at high Rayleigh numbers. For even larger Rayleigh numbers the entire crystal pile is mobilised in what we call the snowglobe regime. The observed mobilisation regimes may be applicable to basaltic magma chambers. Plagioclase in basal cumulates crystallised from a dense magma may be a result of crystal mobilisation from a plagioclase-rich roof mush. Compositional convection within such a mush could result in disaggregation, enabling the buoyant plagioclase to be entrained in relatively dense descending liquid plumes and brought to the floor. The phenocryst load in porphyritic lavas is often interpreted as a

  12. Atmospheric weather regimes over tropical South America

    NASA Technical Reports Server (NTRS)

    Connors, Vickie S.; Garstang, Michael; Nolf, Scott R.

    1991-01-01

    Infrared radiance measurements by the GOES-6 satellite during April 1986 through April 1987 were used to characterize and identify distinct regimes of persistent large-scale cloudiness patterns over the Amazon Basin. It is suggested that the energetics of the tropical troposphere over the Amazon Basin can be directly related to the GOES large-scale cloudiness patterns. The geometry and persistence of the cloud patterns are influenced by shifts in general circulation features and are likely modulated by 4- to 5-day and 40- to 60-day waves. Diurnal forcing effects are more pronounced during weather regimes characterized by prominently clear skies over land areas.

  13. Markovian quantum master equation beyond adiabatic regime.

    PubMed

    Yamaguchi, Makoto; Yuge, Tatsuro; Ogawa, Tetsuo

    2017-01-01

    By introducing a temporal change time scale τ_{A}(t) for the time-dependent system Hamiltonian, a general formulation of the Markovian quantum master equation is given to go well beyond the adiabatic regime. In appropriate situations, the framework is well justified even if τ_{A}(t) is faster than the decay time scale of the bath correlation function. An application to the dissipative Landau-Zener model demonstrates this general result. The findings are applicable to a wide range of fields, providing a basis for quantum control beyond the adiabatic regime.

  14. Markovian quantum master equation beyond adiabatic regime

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Makoto; Yuge, Tatsuro; Ogawa, Tetsuo

    2017-01-01

    By introducing a temporal change time scale τA(t ) for the time-dependent system Hamiltonian, a general formulation of the Markovian quantum master equation is given to go well beyond the adiabatic regime. In appropriate situations, the framework is well justified even if τA(t ) is faster than the decay time scale of the bath correlation function. An application to the dissipative Landau-Zener model demonstrates this general result. The findings are applicable to a wide range of fields, providing a basis for quantum control beyond the adiabatic regime.

  15. Supercurrent in the quantum Hall regime

    NASA Astrophysics Data System (ADS)

    Amet, F.; Ke, C. T.; Borzenets, I. V.; Wang, J.; Watanabe, K.; Taniguchi, T.; Deacon, R. S.; Yamamoto, M.; Bomze, Y.; Tarucha, S.; Finkelstein, G.

    2016-05-01

    A promising route for creating topological states and excitations is to combine superconductivity and the quantum Hall (QH) effect. Despite this potential, signatures of superconductivity in the QH regime remain scarce, and a superconducting current through a QH weak link has been challenging to observe. We demonstrate the existence of a distinct supercurrent mechanism in encapsulated graphene samples contacted by superconducting electrodes, in magnetic fields as high as 2 tesla. The observation of a supercurrent in the QH regime marks an important step in the quest for exotic topological excitations, such as Majorana fermions and parafermions, which may find applications in fault-tolerant quantum computing.

  16. Delinating Thermohaline Double-Diffusive Rayleigh Regimes

    NASA Astrophysics Data System (ADS)

    Graf, T.; Walther, M.; Kolditz, O.; Liedl, R.

    2013-12-01

    In natural systems, convective flow induced from density differences may occur in near-coastal aquifers, atmospheric boundary layers, oceanic streams or within the earth crust. Whether an initially stable, diffusive regime evolves into a convective (stable or chaotic) regime, or vice versa, depends on the system's framing boundary conditions. A conventional parameter to express the relation between diffusive and convective forces of such a density-driven regime is Rayleigh number (Ra). While most systems are mainly dominated by only a single significant driving force (i.e. only temperature or salinity), some systems need to consider two boundary processes (e.g. deep, thus warm, haline flow in porous media). In that case, a two-dimensional, 'double-diffusive' Rayleigh system can be defined. Nield (1998) postulated a boundary between diffusive and convective regime at RaT + RaC = 4pi^2 in the first quadrant (Q1), with Rayleigh numbers for temperature and concentration respectively. The boundary in the forth quadrant (Q4) could not exactly be determined, yet the approximate position estimated. Simulations with HydroGeoSphere (Therrien, 2010) using a vertical, quadratic, homogeneous, isotropic setup confirmed the existence of the 4pi^2-boundary and revealed additional regimes (diffusive, single-roll, double-roll, chaotic) in Q1. Also, non-chaotic, oscillating patterns could be identified in Q4. More detailed investigations with OpenGeoSys (Kolditz, 2012) confirmed the preceding HGS results, and, using a 1:10-scaled domain (height:length), uncovered even more distinctive regimes (diffusive, minimum ten roles, supposely up to 25 roles, and chaotic?) in Q1, while again, oscillating patterns were found in the transition zone between diffusive and chaotic regimes in Q4. Output of numerical simulations from Q1 and Q4 show the mentioned regimes (diffusive, stable-convective, stable-oscillatory, chaotic) while results are displayed in context of a possible delination between

  17. Regimes of turbulence without an energy cascade

    NASA Astrophysics Data System (ADS)

    Barenghi, C. F.; Sergeev, Y. A.; Baggaley, A. W.

    2016-10-01

    Experiments and numerical simulations of turbulent 4He and 3He-B have established that, at hydrodynamic length scales larger than the average distance between quantum vortices, the energy spectrum obeys the same 5/3 Kolmogorov law which is observed in the homogeneous isotropic turbulence of ordinary fluids. The importance of the 5/3 law is that it points to the existence of a Richardson energy cascade from large eddies to small eddies. However, there is also evidence of quantum turbulent regimes without Kolmogorov scaling. This raises the important questions of why, in such regimes, the Kolmogorov spectrum fails to form, what is the physical nature of turbulence without energy cascade, and whether hydrodynamical models can account for the unusual behaviour of turbulent superfluid helium. In this work we describe simple physical mechanisms which prevent the formation of Kolmogorov scaling in the thermal counterflow, and analyze the conditions necessary for emergence of quasiclassical regime in quantum turbulence generated by injection of vortex rings at low temperatures. Our models justify the hydrodynamical description of quantum turbulence and shed light into an unexpected regime of vortex dynamics.

  18. Regimes of turbulence without an energy cascade

    PubMed Central

    Barenghi, C. F.; Sergeev, Y. A.; Baggaley, A. W.

    2016-01-01

    Experiments and numerical simulations of turbulent 4He and 3He-B have established that, at hydrodynamic length scales larger than the average distance between quantum vortices, the energy spectrum obeys the same 5/3 Kolmogorov law which is observed in the homogeneous isotropic turbulence of ordinary fluids. The importance of the 5/3 law is that it points to the existence of a Richardson energy cascade from large eddies to small eddies. However, there is also evidence of quantum turbulent regimes without Kolmogorov scaling. This raises the important questions of why, in such regimes, the Kolmogorov spectrum fails to form, what is the physical nature of turbulence without energy cascade, and whether hydrodynamical models can account for the unusual behaviour of turbulent superfluid helium. In this work we describe simple physical mechanisms which prevent the formation of Kolmogorov scaling in the thermal counterflow, and analyze the conditions necessary for emergence of quasiclassical regime in quantum turbulence generated by injection of vortex rings at low temperatures. Our models justify the hydrodynamical description of quantum turbulence and shed light into an unexpected regime of vortex dynamics. PMID:27761005

  19. A Global Classification of Contemporary Fire Regimes

    NASA Astrophysics Data System (ADS)

    Norman, S. P.; Kumar, J.; Hargrove, W. W.; Hoffman, F. M.

    2014-12-01

    Fire regimes provide a sensitive indicator of changes in climate and human use as the concept includes fire extent, season, frequency, and intensity. Fires that occur outside the distribution of one or more aspects of a fire regime may affect ecosystem resilience. However, global scale data related to these varied aspects of fire regimes are highly inconsistent due to incomplete or inconsistent reporting. In this study, we derive a globally applicable approach to characterizing similar fire regimes using long geophysical time series, namely MODIS hotspots since 2000. K-means non-hierarchical clustering was used to generate empirically based groups that minimized within-cluster variability. Satellite-based fire detections are known to have shortcomings, including under-detection from obscuring smoke, clouds or dense canopy cover and rapid spread rates, as often occurs with flashy fuels or during extreme weather. Such regions are free from preconceptions, and the empirical, data-mining approach used on this relatively uniform data source allows the region structures to emerge from the data themselves. Comparing such an empirical classification to expectations from climate, phenology, land use or development-based models can help us interpret the similarities and differences among places and how they provide different indicators of changes of concern. Classifications can help identify where large infrequent mega-fires are likely to occur ahead of time such as in the boreal forest and portions of the Interior US West, and where fire reports are incomplete such as in less industrial countries.

  20. Climatic regimes of tropical convection and rainfall

    SciTech Connect

    Wang, Bin )

    1994-07-01

    Annual distribution and phase propagation of tropical convection are delineated using harmonic and amplitude-phase characteristics analysis of climatological pentad mean outgoing longwave radiation and monthly frequencies of highly reflective cloud. An annual eastward propagation of peak rainy season along the equator from the central Indian Ocean (60[degrees]E) to Arafura Sea (130[degrees]E) is revealed. This indicates a transition from the withdrawal of the Indian summer monsoon to the onset of the Australian summer monsoon. Significant bimodal variations are found around major summer monsoon regions. These variations originate from the interference of two adjacent regimes. The convergence zones over the eastern North Pacific, the South Pacific, and the southwest Indian Ocean are identified as a marine monsoon regime that is characterized by a unimodal variation with a concentrated summer rainfall associated with the development of surface westerlies equatorward of a monsoon trough. Conversely, the central North Pacific and North Atlantic convergence zones between persistent northeast and southeast trades are classified as trade-wind convergence zones; which differ from the marine monsoon regime by their persistent rainy season and characteristic bimodal variation with peak rainy seasons occurring in late spring and fall. The roles of the annual march of sea surface temperature in the phase propagation and formation of various climatic regimes of tropical convection are also discussed. 34 refs., 8 figs., 1 tab.

  1. Knowledge Regimes and Contradictions in Education Reforms

    ERIC Educational Resources Information Center

    Aasen, Petter; Prøitz, Tine Sophie; Sandberg, Nina

    2014-01-01

    The article outlines a theoretical framework for understanding education policy and education reforms based on the concept of knowledge regimes. The concept refers to understandings and definitions of governance and procedural aspects, manners of governing and curriculum issues, thus it comprises contents, structures, and processes of education…

  2. Impacts of different hydrodynamic regimes on flocculation

    NASA Astrophysics Data System (ADS)

    Ramirez-Mendoza, Rafael; Souza, Alejandro; Amoudry, Laurent

    2014-05-01

    A number of activities carried out in coastal zones and estuaries are affected by sediment transport. Therefore, good knowledge of the processes involved is necessary to adequately manage these areas. Flocculation is a key process on fine sediment dynamics, which affects the effective particle size and settling velocity. The process is further complicated under the combined effect of currents and waves. This research seeks to improve our understanding of the flocculation process under the combined effect of currents and waves. The study site is the Dee Estuary located in Liverpool Bay, United Kingdom. Measurements of volume concentration, grain size and current velocities near the sea bed were obtained from a mooring deployed between 12 February 2008 and 9 March 2008. Turbulent properties could also be calculated because of the fast sampling rate used for current velocities. Water samples were taken from a research vessel during the first two days of the study in order to calibrate moored instruments and convert volume to mass concentration. The observations almost covered two fortnightly periods and three different dynamic regimes can be distinguished: currents-only, combined waves and currents, and wave dominated. During the currents-only regime, floc aggregation and breakup coincide with periods of low and high turbulent stress respectively. The combination of waves and spring tide currents makes the second regime and the floc breakup is most dominant when waves are higher than one meter and small flocs are found even with low turbulent stress from both waves and currents. The third regime is identified as wave-dominant during neap tides with current speed less than 0.25 m/s and waves of 1-2 meters height. In this regime the wave effect takes large sediment into suspension at the same time as small particle sizes from floc breakup. In this case the median particle size is strongly related to the wave height which means that a slight particle aggregation is still

  3. Regime Dependant Microphysical Variability in Darwin, Australia

    NASA Astrophysics Data System (ADS)

    Dolan, B.; Rutledge, S. A.; Lang, T. J.

    2010-12-01

    Of utmost importance for global precipitation estimates from satellites such as TRMM and the upcoming Global Precipitation Measurement (GPM) is to understand processes that lead to variability in precipitation on sub-seasonal, seasonal, and climatological scales. Many studies have linked differences in rainfall characteristics such as mean diameter (D0) to sub-seasonal regime variability forced by large scale wind shifts, topography, and continental and maritime convection, across various regions of the globe. Several analyses have tied differences between regimes to differing microphysical processes that drive changes in the drop-size distributions occurring in convective rainfall. For example, decreased ice mass aloft and smaller mean diameters are indicative of warm rain processes, while vigorous ice formation leads to large, melting ice to create large drops. If the microphysical variability in different regimes is characterized and understood, the results could be used to improve satellite precipitation algorithms. The polarimetric, Doppler C-band radar, CPOL, located near Darwin, Australia provides a unique platform to study differences in microphysics between land and ocean, as well as variability between monsoon and break periods. The focus of this study is to examine the microphysical processes occurring in four distinct regimes around Darwin (monsoon-land, monsoon-ocean, break-land, break-ocean), using polarimetric data from CPOL. Analyses such as contoured frequency by altitude (CFADs) diagrams, cumulative distribution functions, and mean profiles of precipitation water mass, precipitation ice mass, reflectivity, differential reflectivity and specific differential phase will aide in understanding the physics of precipitation in these regimes. The formation of precipitation ice aloft, warm rain processes, and the contributions of warm rain and cold cloud processes including melting of ice into large drops, will be linked to differences in D0, rain

  4. Regime Shifts in the Anthropocene: Drivers, Risks, and Resilience

    PubMed Central

    Rocha, Juan Carlos; Peterson, Garry D.; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers. PMID:26267896

  5. Regime shifts in the anthropocene: drivers, risks, and resilience.

    PubMed

    Rocha, Juan Carlos; Peterson, Garry D; Biggs, Reinette

    2015-01-01

    Many ecosystems can experience regime shifts: surprising, large and persistent changes in the function and structure of ecosystems. Assessing whether continued global change will lead to further regime shifts, or has the potential to trigger cascading regime shifts has been a central question in global change policy. Addressing this issue has, however, been hampered by the focus of regime shift research on specific cases and types of regime shifts. To systematically assess the global risk of regime shifts we conducted a comparative analysis of 25 generic types of regime shifts across marine, terrestrial and polar systems; identifying their drivers, and impacts on ecosystem services. Our results show that the drivers of regime shifts are diverse and co-occur strongly, which suggests that continued global change can be expected to synchronously increase the risk of multiple regime shifts. Furthermore, many regime shift drivers are related to climate change and food production, whose links to the continued expansion of human activities makes them difficult to limit. Because many regime shifts can amplify the drivers of other regime shifts, continued global change can also be expected to increase the risk of cascading regime shifts. Nevertheless, the variety of scales at which regime shift drivers operate provides opportunities for reducing the risk of many types of regime shifts by addressing local or regional drivers, even in the absence of rapid reduction of global drivers.

  6. Dominant takeover regimes for genetic algorithms

    NASA Technical Reports Server (NTRS)

    Noever, David; Baskaran, Subbiah

    1995-01-01

    The genetic algorithm (GA) is a machine-based optimization routine which connects evolutionary learning to natural genetic laws. The present work addresses the problem of obtaining the dominant takeover regimes in the GA dynamics. Estimated GA run times are computed for slow and fast convergence in the limits of high and low fitness ratios. Using Euler's device for obtaining partial sums in closed forms, the result relaxes the previously held requirements for long time limits. Analytical solution reveal that appropriately accelerated regimes can mark the ascendancy of the most fit solution. In virtually all cases, the weak (logarithmic) dependence of convergence time on problem size demonstrates the potential for the GA to solve large N-P complete problems.

  7. Flamelet Regime Diagram for Turbulent Combustion Simulations

    NASA Astrophysics Data System (ADS)

    Chan, Wai Lee; Ihme, Matthias; Kolla, Hemanth; Chen, Jacqueline

    2016-11-01

    The flamelet model has been widely used in numerical combustion investigations, particularly for the closure of large-eddy simulations (LES) of turbulent reacting flows. In most cases, the simulation results demonstrated good agreements with their experimental counterparts. However, a systematic analysis of the flamelet model's applicability, as well as its potential limitations, is seldom conducted, and the model performance is usually based only on a-posteriori comparisons. The objective of this work is to derive a metric that can formally quantify the suitability of the flamelet model in different flame configurations. For this purpose, a flamelet regime diagram has been developed and studied in the context of direct numerical simulations (DNS) of a turbulent lifted jet flame. The implementation of the regime diagram in LES has been investigated through explicit filtering of the DNS results.

  8. Photoelectron circular dichroism in different ionization regimes

    NASA Astrophysics Data System (ADS)

    Wollenhaupt, Matthias

    2016-12-01

    Photoelectron circular dichroism (PECD) describes an asymmetry in the photoelectron angular distribution (PAD) from photoionization of randomly oriented enantiomers with circularly polarized light. Baulieu et al present a comprehensive set of measured PADs from multiphoton ionization of limonene and fenchone in different ionization regimes (multiphoton and tunneling) and analyze the resulting PECD (Baulieu et al 2016 New J. Phys. 18 102002). From their observations the authors conclude that the PECD is universal in the sense that the molecular chirality is encoded in the PAD independent of the ionization regime. The analysis is supplemented by a classical model based on electron scattering in a chiral potential. The paper presents beautiful data and is an important step towards a more complete physical picture of PECD. The results and their interpretation stimulate the ongoing vivid debate on the role of resonances in multiphoton PECD.

  9. Steady and transient regimes in hydropower plants

    NASA Astrophysics Data System (ADS)

    Gajic, A.

    2013-12-01

    Hydropower plant that has been in operation for about 30 years has to be reconstructed. They have already installed 12 Kaplan turbines, the largest in the world at that time. The existing CAM relationship was determined based on hydraulic model tests and checked by efficiency on-site tests. It was also tested based on turbine bearing vibrations. In order to discover vibrations and long cracks on stay vanes detailed on-site measurements were performed. Influence of the modification of the trailing edges on the dynamic stresses of the stay vanes is also shown. In order to improve power output transient regimes were analyzed, both experimentally and numerically. Reversible hydropower plant, a pioneer in Europe since it was the first Pump storage power plant constructed with the highest head pump-turbines in the world. Analyses of transient regimes discover some problems with S-shaped characteristics coupled with non-symmetrical penstock.

  10. Economic Performance and North Korean Regime Legitimacy

    DTIC Science & Technology

    2014-06-01

    PERFORMANCE AND NORTH KOREAN REGIME LEGITIMACY by Patrick J. Moore June 2014 Thesis Advisor: Naazneen Barma Second Reader: Robert Weiner THIS...Advisor Dr. Robert Weiner Second Reader Dr. Mohammed Hafez Chair, Department of National Security Affairs iv THIS PAGE...offers a view of success, the country outside the capital is a much different situation. Victor Cha writes that even in Kaesong, the second -largest city

  11. A Regime Legitimacy Explanation of African Peacekeeping

    DTIC Science & Technology

    2011-09-01

    peacekeeping in a U-shaped curve, meaning that states attempting to increase their legitimacy participate at a higher-than-expected level. Likewise, the...distribution is unlimited A REGIME LEGITIMACY EXPLANATION OF AFRICAN PEACEKEEPING Matthew Ross Second Lieutenant, United States Air Force...B.S., Political Science, United States Air Force Academy, 2010 Submitted in partial fulfillment of the requirements for the degree of

  12. Maxwellian distribution in non-classical regime

    NASA Astrophysics Data System (ADS)

    Mohazzabi, Pirooz; L. Helvey, Shannon; McCumber, Jeremy

    2002-12-01

    A molecular dynamics investigation shows that the assumption of molecular chaos remains valid in the non-classical regime. Consequently, the velocity distribution function of an extremely dense system of spinless particles relaxes into Maxwellian, even in the presence of arbitrary interactions between the particles of the system. Systems with densities exceeding 30 times solid densities are investigated using a soft Lennard-Jones interparticle potential energy function.

  13. The nuclear non-proliferation treaty regime

    SciTech Connect

    1995-12-31

    The Non-Proliferation Treaty (NPT) regime, including national safeguards agreements and the International Atomic Energy Agency (IAEA) Statute, embodies the international effort to ban illicit transfers of nuclear material and acquisition or transfer of nuclear weaponry. Included are objectives and primary obligations, legal bases, institutional oversight, trade restrictions, protection of information, penal consequences, and role of the United Nations. Regional agreements supplement the NPT.

  14. Proliferation Control Regimes: Background and Status

    DTIC Science & Technology

    2012-10-25

    the further spread of nuclear weapons, several challenges to the regime have arisen in recent years: India and Pakistan tested nuclear weapons in 1998...States and other countries to India , a non-party to the NPT with nuclear weapons, has raised questions about what benefits still exist for non... India , Pakistan, North Korea, and Israel are not members of the NPT. Apart from diplomatic questions about how to treat their status as states with

  15. Bose polarons in the strongly interacting regime

    NASA Astrophysics Data System (ADS)

    Kedar, Dhruv; Hu, Ming-Guang; van de Graaff, Michael; Corson, John; Cornell, Eric; Jin, Deborah

    2016-05-01

    Impurities immersed in and interacting with a Bose-Einstein condensate (BEC) are predicted to form quasiparticle excitations called Bose polarons. I will present experimental evidence of Bose polarons in cold atoms obtained using radio-frequency spectroscopy to measure the excitation spectrum of fermionic K-40 impurities interacting with a BEC of Rb-87 atoms. We use an interspecies Feshbach resonance to tune the interactions between the impurities and the bosons, and we take data in the strongly interacting regime.

  16. Utilizing Surface Sensors to Identify Wake Regimes

    NASA Astrophysics Data System (ADS)

    Wang, Mengying; Hemati, Maziar S.

    2016-11-01

    Marine swimmers often exploit external flow structures to reduce locomotive effort. To achieve this advantage, these swimmers utilize mechanosensory organs on the surface of their bodies to detect hydrodynamic signals from the surrounding fluid, which can then be used to inform the control task. Recently, there has been a growing interest in developing similar flow sensing systems to achieve enhanced propulsive efficiency and maneuverability in human-engineered underwater vehicles. In particular, much attention has been given to the problem of wake sensing; however, these investigations have concentrated on a restricted class of wakes-i.e., Kármán-type vortex streets-whereas more complicated wake structures can arise in practice. In this talk, we will explore the possibility of identifying wake regimes through the use of surface sensors. Potential flow theory is adopted to simulate the interactions of various wakes with a fish-like body. Wakes in different dynamical regimes impart distinct hydrodynamic signatures on the body, which permits these regimes to be distinguished from one another in an automated fashion. Our results can provide guidance for improving flow sensing capabilities in human-engineered systems and hint at how marine swimmers may sense their hydrodynamic surroundings.

  17. Partial accretion regime of accreting millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Eksi, Kazim

    2016-07-01

    The inner parts of the disks around neutron stars in low mass X-ray binaries may become geometrically thick due to inhibition of accretion at the disk mid-plane when the central object is rotating rapidly. In such a case matter inflowing through the disk may keep accreting onto the poles of the neutron star from the parts of the disk away from the disk mid-plane while the matter is propelled at the disk mid-plane. An important ingredient of the evolution of millisecond pulsars is then the fraction of the inflowing matter that can accrete onto the poles in the fast rotation regime depending on the fastness parameter. This ``soft'' propeller regime may be associated with the rapid decay stage observed in the light curves of several accreting millisecond pulsars. To date only a few studies considered the partial accretion regime. By using geometrical arguments we improve the existing studies and test the model by reproducing the lightcurves of millisecond X-ray pulsars via time dependent simulations of disk evolution. We also present analytical solutions that represent disks with partial accretion.

  18. Dynamical Response of Continuum Regime Langmuir Probe

    NASA Astrophysics Data System (ADS)

    Rappaport, H. L.

    2009-11-01

    Probe dynamic response is sometimes used as a way to increase the amount of information obtained from Langmuir probes [1]. In this poster, the effects of frequency dependent probe capacitance and coupling of probe fields to damped Langmuir waves and damped ion acoustic waves are considered. In the continuum regime, with small Debye length to spherical probe radius ratio, the probe DC current vs. voltage characteristic displays a hard saturation at sufficiently large probe potential [2]. In this regime, the sheath thickness varies little with the applied voltage although the plasma response can still be measured. A goal of the present investigation is to show that the probe dynamical response is richer as a result of modulation of sheath thickness or shielding particularly in the larger Debye length to probe radius ratio regime. Inertia inhibits ion response at sufficiently high frequency and deviation from the DC characteristic is shown.[4pt] [1] D. N. Walker, R.F. Fernsler, D.D. Blackwell, and W.E. Amatucci, Phys. Plasmas 15, 123506 (2008).[0pt] [2] E. Baum and R.L. Chapkis, AIAA J. 8, 1073 (1970).

  19. Constructing an interdisciplinary flow regime recommendation

    USGS Publications Warehouse

    Bartholow, J.M.

    2010-01-01

    It is generally agreed that river rehabilitation most often relies on restoring a more natural flow regime, but credibly defining the desired regime can be problematic. I combined four distinct methods to develop and refine month-by-month and event-based flow recommendations to protect and partially restore the ecological integrity of the Cache la Poudre River through Fort Collins, Colorado. A statistical hydrologic approach was used to summarize the river's natural flow regime and set provisional monthly flow targets at levels that were historically exceeded 75% of the time. These preliminary monthly targets were supplemented using results from three Poudre-specific disciplinary studies. A substrate maintenance flow model was used to better define the high flows needed to flush accumulated sediment from the river's channel and help sustain the riparian zone in this snowmelt-dominated river. A hydraulic/habitat model and a water temperature model were both used to better define the minimum flows necessary to maintain a thriving cool water fishery. The result is a range of recommended monthly flows and daily flow guidance illustrating the advantage of combining a wide range of available disciplinary information, supplemented by judgment based on ecological principles and a general understanding of river ecosystems, in a highly altered, working river. ?? 2010 American Water Resources Association.

  20. Lubrication regimes in lumbar total disc arthroplasty.

    PubMed

    Shaheen, A; Shepherd, D E T

    2007-08-01

    A number of total disc arthroplasty devices have been developed. Some concern has been expressed that wear may be a potential failure mode for these devices, as has been seen with hip arthroplasty. The aim of this paper was to investigate the lubrication regimes that occur in lumbar total disc arthroplasty devices. The disc arthroplasty was modelled as a ball-and-socket joint. Elastohydrodynamic lubrication theory was used to calculate the minimum film thickness of the fluid between the bearing surfaces. The lubrication regime was then determined for different material combinations, size of implant, and trunk velocity. Disc arthroplasties with a metal-polymer or metal-metal material combination operate with a boundary lubrication regime. A ceramic-ceramic material combination has the potential to operate with fluid-film lubrication. Disc arthroplasties with a metal-polymer or metal-metal material combination are likely to generate wear debris. In future, it is worth considering a ceramic-ceramic material combination as this is likely to reduce wear.

  1. Detecting spatial regimes in ecosystems | Science Inventory ...

    EPA Pesticide Factsheets

    Research on early warning indicators has generally focused on assessing temporal transitions with limited application of these methods to detecting spatial regimes. Traditional spatial boundary detection procedures that result in ecoregion maps are typically based on ecological potential (i.e. potential vegetation), and often fail to account for ongoing changes due to stressors such as land use change and climate change and their effects on plant and animal communities. We use Fisher information, an information theory based method, on both terrestrial and aquatic animal data (US Breeding Bird Survey and marine zooplankton) to identify ecological boundaries, and compare our results to traditional early warning indicators, conventional ecoregion maps, and multivariate analysis such as nMDS (non-metric Multidimensional Scaling) and cluster analysis. We successfully detect spatial regimes and transitions in both terrestrial and aquatic systems using Fisher information. Furthermore, Fisher information provided explicit spatial information about community change that is absent from other multivariate approaches. Our results suggest that defining spatial regimes based on animal communities may better reflect ecological reality than do traditional ecoregion maps, especially in our current era of rapid and unpredictable ecological change. Use an information theory based method to identify ecological boundaries and compare our results to traditional early warning

  2. THE DYNAMIC REGIME CONCEPT FOR ECOSYSTEM MANAGEMENT AND RESTORATION

    EPA Science Inventory

    Dynamic regimes of ecosystems are multidimensional basis of attraction, characterized by particular species communities and ecosystems processes. Ecosystem patterns and processes rarely respond linerarly to disturbances, and the nonlinear cynamic regime concept offers a more real...

  3. Toward a dynamical understanding of planetary-scale flow regimes.

    NASA Astrophysics Data System (ADS)

    Marshall, J.; Molteni, F.

    1993-06-01

    A strategy for diagnosing and interpreting flow regimes that is firmly rooted in dynamical theory is presented and applied to the study of observed and modeled planetary-scale regimes of the wintertime circulation in the Northern Hemisphere.

  4. FISHER INFORMATION OF DYNAMIC REGIME TRANSITIONS IN ECOLOGICAL SYSTEMS

    EPA Science Inventory

    Ecosystems often exhibit transitions between multiple dynamic regimes (or steady states). As ecosystems experience perturbations of varying regularity and intensity, they may either remain within the state space neighborhood of the current regime, or ?flip? into the neighborhood ...

  5. River Flow Regimes and Effective Discharge

    NASA Astrophysics Data System (ADS)

    Basso, S.; Sprocati, R.; Frascati, A.; Marani, M.; Schirmer, M.; Botter, G.

    2015-12-01

    The concept of effective discharge is widespread in geomorphology and river engineering and restoration. For example, it is used to design the most stable channel configuration, to estimate sedimentation rate and lifespan of reservoirs and to characterize the hydrologic forcing in models studying long-term evolution of rivers. Accordingly, the effective discharge has been the focus of countless empirical, theoretical and numerical studies, which found it to vary among catchments as a function of climate, landscape and river morphology, type of transport (dissolved, suspended or bedload), and of streamflow variability. The heterogeneity of the effective discharge values observed in different catchments challenges a thorough understanding of its pivotal drivers, and a consistent framework which explains observations carried out in different geographic areas is still lacking. In the present work, the observed diversity is explained in terms of the underlying heterogeneity of river flow regimes, by linking effective discharge to attributes of the sediment rating curve and to streamflow variability, as resulting from climatic and landscape drivers. An analytic expression of the effective ratio (i.e. the ratio between effective discharge and mean streamflow) is provided, which captures observed values of effective discharge for suspended sediment transport in a set of catchments of the continental United States. The framework disentangles hydrologic and landscape controls on effective discharge, and highlights distinct effective ratios of persistent and erratic hydrologic regimes (respectively characterized by low and high flow variability), attributable to intrinsically different streamflow dynamics. Clusters of river catchments characterized by similar streamflow dynamics can be identified. The framework provides an opportunity for first-order estimates of effective discharge in rivers belonging to different areas, based on the type of flow regime.

  6. The discrete regime of flame propagation

    NASA Astrophysics Data System (ADS)

    Tang, Francois-David; Goroshin, Samuel; Higgins, Andrew

    The propagation of laminar dust flames in iron dust clouds was studied in a low-gravity envi-ronment on-board a parabolic flight aircraft. The elimination of buoyancy-induced convection and particle settling permitted measurements of fundamental combustion parameters such as the burning velocity and the flame quenching distance over a wide range of particle sizes and in different gaseous mixtures. The discrete regime of flame propagation was observed by substitut-ing nitrogen present in air with xenon, an inert gas with a significantly lower heat conductivity. Flame propagation in the discrete regime is controlled by the heat transfer between neighbor-ing particles, rather than by the particle burning rate used by traditional continuum models of heterogeneous flames. The propagation mechanism of discrete flames depends on the spa-tial distribution of particles, and thus such flames are strongly influenced by local fluctuations in the fuel concentration. Constant pressure laminar dust flames were observed inside 70 cm long, 5 cm diameter Pyrex tubes. Equally-spaced plate assemblies forming rectangular chan-nels were placed inside each tube to determine the quenching distance defined as the minimum channel width through which a flame can successfully propagate. High-speed video cameras were used to measure the flame speed and a fiber optic spectrometer was used to measure the flame temperature. Experimental results were compared with predictions obtained from a numerical model of a three-dimensional flame developed to capture both the discrete nature and the random distribution of particles in the flame. Though good qualitative agreement was obtained between model predictions and experimental observations, residual g-jitters and the short reduced-gravity periods prevented further investigations of propagation limits in the dis-crete regime. The full exploration of the discrete flame phenomenon would require high-quality, long duration reduced gravity environment

  7. Laboratory Exploration of Multiple Zonal Jet Regimes

    NASA Astrophysics Data System (ADS)

    Smith, C. A.; Speer, K. G.; Griffiths, R. W.

    2012-12-01

    The differentially heated, rotating annulus has classically been used to study wave interactions within a single, baroclinic jet. At high rotation rates, the baroclinic instability of the flow leads to a transition to a turbulent, eddy-dominated regime. In the presence of a topographic beta effect, the flow has been observed to produce multiple, meandering zonal jets that are qualitatively similar to those found in planetary atmospheres and in the Antarctic Circumpolar Current (ACC). Our study builds on previous annulus experiments [1] by making observations further within this new regime. We observe with PIV and other techniques how the structure of the flow responds to changes in various parameters such as tank geometry, gradient in the Coriolis parameter, rotation rate, and differential thermal forcing. By not employing the more typical direct forcing of small scales, but by applying a large scale forcing over the annulus gap width, this study allows the varying effects of eddy scale selection, enstrophy cascade, etc. to naturally generate flow that more closely resembles planetary atmospheres and the ACC. We seek nondimensional parameters that significantly control zonation in a real fluid. These observations will provide a metric for the comparison of various theoretical models for multiple zonal jet formation. Other properties of the jets, such as their migration, meandering, bifurcation, and merging, can also be observed in an idealized situation and compared to numerical simulations. Ultimately, this will aid the testing and development of sub-grid-scale parameterizations for the multiple zonal jet regime that remain robust in the face of multiple forcing parameters. [1] Wordsworth, R. D., Read, P. L., & Yamazaki, Y. H. (2008). Turbulence, waves, and jets in a differentially heated rotating annulus experiment Physics of Fluids, 20(12), 126602.Streak photograph of suspended particles visualizing the flow representative of multiple zonal jets

  8. Potential vorticity regimes over East Asia during winter

    NASA Astrophysics Data System (ADS)

    Huang, Wenyu; Chen, Ruyan; Wang, Bin; Wright, Jonathon S.; Yang, Zifan; Ma, Wenqian

    2017-02-01

    Nine potential vorticity (PV) regimes over East Asia are identified by applying a Self-Organizing Map and Hierarchical Ascendant Classification regime analysis to the daily PV reanalysis fields on the 300 K isentropic surface for December-March 1948-2014. According to the surface temperature anomalies over East Asia, these nine regimes are further classified into three classes, i.e., cold class (three regimes), warm class (four regimes), and neutral class (two regimes). The PV-based East Asian winter monsoon index (EAWMI) is used to study the relationship between PV distributions and the temperature anomalies. The magnitude of cold (warm) anomalies over the land areas of East Asia increases (decreases) quasi-linearly with the EAWMI. Regression analysis reveals that cold temperature anomalies preferentially occur when the EAWMI exceeds a threshold at ˜0.2 PVU (where 1 PVU ≡ 10-6 m2 K kg-1 s-1). PV inversion uncovers the mechanisms behind the relationships between the PV regimes and surface temperature anomalies and reveals that cold (warm) PV regimes are associated with significant warming (cooling) in the upper troposphere and lower stratosphere. On average, cold regimes have longer durations than warm regimes. Interclass transition probabilities are much higher for paths from warm/neutral regimes to cold regimes than for paths from cold regimes to warm/neutral regimes. Besides, intraclass transitions are rare within the warm or neutral regimes. The PV regime analysis provides insight into the causes of severe cold spells over East Asia, with blocking circulation patterns identified as the primary factor in initiating and maintaining these cold spells.

  9. Imperfect relativistic mirrors in the quantum regime

    SciTech Connect

    Mendonça, J. T.; Serbeto, A.; Galvão, R. M. O.

    2014-05-15

    The collective backscattering of intense laser radiation by energetic electron beams is considered in the relativistic quantum regime. Exact solutions for the radiation field are obtained, for arbitrary electron pulse shapes and laser intensities. The electron beams act as imperfect nonlinear mirrors on the incident laser radiation. This collective backscattering process can lead to the development of new sources of ultra-short pulse radiation in the gamma-ray domain. Numerical examples show that, for plausible experimental conditions, intense pulses of gamma-rays, due to the double Doppler shift of the harmonics of the incident laser radiation, can be produced using the available technology, with durations less than 1 as.

  10. Efficiency of Rectification: Reversible vs. Irreversible Regimes

    NASA Astrophysics Data System (ADS)

    Sokolov, I. M.

    2002-11-01

    Both man-made locomotive devices and molecular motors use gears to transform a reciprocating motion into a directed one. One of the most common gears is a rectifier, a mechanically irreversible appliance. The maximal energetic efficiency of an isothermic gear is bounded by unity, as a consequence of the Second Law. However, approaching this ideal efficiency does not imply approaching reversibility. We discuss what properties of a rectifier mostly influence the transduction efficiency and show that an appliance which locks under backward force is just the one which can approach the ideal efficiency either in the reversible or in the irreversible regime.

  11. Bose Polarons in the Strongly Interacting Regime

    NASA Astrophysics Data System (ADS)

    Hu, Ming-Guang; Van de Graaff, Michael J.; Kedar, Dhruv; Corson, John P.; Cornell, Eric A.; Jin, Deborah S.

    2016-07-01

    When an impurity is immersed in a Bose-Einstein condensate, impurity-boson interactions are expected to dress the impurity into a quasiparticle, the Bose polaron. We superimpose an ultracold atomic gas of 87Rb with a much lower density gas of fermionic 40 impurities. Through the use of a Feshbach resonance and radio-frequency spectroscopy, we characterize the energy, spectral width, and lifetime of the resultant polaron on both the attractive and the repulsive branches in the strongly interacting regime. The width of the polaron in the attractive branch is narrow compared to its binding energy, even as the two-body scattering length diverges.

  12. Ultracold Molecules: Physics in the Quantum Regime

    SciTech Connect

    Doyle, John

    2014-11-17

    Our research encompasses approaches to the trapping of diatomic molecules at low temperature plus the cooling and detection of polyatomic molecules in the kelvin temperature regime. We have cooled and trapped CaF and/or CaH molecules, loaded directly from a molecular beam. As part of this work, we are continuing to develop an important trapping technique, optical loading from a buffer-gas beam. This method was invented in our lab. We are also studying cold polyatomic molecules and their interactions with cold atoms.

  13. Global oscillation regime change by gated inhibition.

    PubMed

    Romeo, August; Supèr, Hans

    2016-10-01

    The role of sensory inputs in the modelling of synchrony regimes is exhibited by means of networks of spiking cells where the relative strength of the inhibitory interaction is controlled by the activation of a linear unit working as a gating variable. Adaptation to stimulus size is determined by the value of a changing length scale, modelled by the time-varying radius of a circular receptive field. In this set-up, 'consolidation' time intervals relevant to attentional effects are shown to depend on the dynamics governing the evolution of the introduced length scale.

  14. The relationship between void waves and flow regime transition

    SciTech Connect

    Lahey, R.T. Jr.; Drew, D.A.; Kalkach-Navarro, S.; Park, J.W.

    1992-12-31

    The results of an extensive experimental and analytical study on the relationship between void waves and flow regime transition are presented, in particular, the bubbly/slug flow regime transition. It is shown that void wave instability signals a flow regime transition.

  15. 22 CFR 120.29 - Missile Technology Control Regime.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Missile Technology Control Regime. 120.29... DEFINITIONS § 120.29 Missile Technology Control Regime. (a) For purposes of this subchapter, Missile Technology Control Regime (MTCR) means the policy statement between the United States, the United...

  16. 22 CFR 120.29 - Missile Technology Control Regime.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 22 Foreign Relations 1 2011-04-01 2011-04-01 false Missile Technology Control Regime. 120.29... DEFINITIONS § 120.29 Missile Technology Control Regime. (a) For purposes of this subchapter, Missile Technology Control Regime (MTCR) means the policy statement between the United States, the United...

  17. Pulse regime in formation of fractal fibers

    NASA Astrophysics Data System (ADS)

    Smirnov, B. M.

    2016-11-01

    The pulse regime of vaporization of a bulk metal located in a buffer gas is analyzed as a method of generation of metal atoms under the action of a plasma torch or a laser beam. Subsequently these atoms are transformed into solid nanoclusters, fractal aggregates and then into fractal fibers if the growth process proceeds in an external electric field. We are guided by metals in which transitions between s and d-electrons of their atoms are possible, since these metals are used as catalysts and filters in interaction with gas flows. The resistance of metal fractal structures to a gas flow is evaluated that allows one to find optimal parameters of a fractal structure for gas flow propagation through it. The thermal regime of interaction between a plasma pulse or a laser beam and a metal surface is analyzed. It is shown that the basic energy from an external source is consumed on a bulk metal heating, and the efficiency of atom evaporation from the metal surface, that is the ratio of energy fluxes for vaporization and heating, is 10-3-10-4 for transient metals under consideration. A typical energy flux ( 106 W/cm2), a typical surface temperature ( 3000 K), and a typical pulse duration ( 1 μs) provide a sufficient amount of evaporated atoms to generate fractal fibers such that each molecule of a gas flow collides with the skeleton of fractal fibers many times.

  18. Variety of synchronous regimes in neuronal ensembles.

    PubMed

    Komarov, M A; Osipov, G V; Suykens, J A K

    2008-09-01

    We consider a Hodgkin-Huxley-type model of oscillatory activity in neurons of the snail Helix pomatia. This model has a distinctive feature: It demonstrates multistability in oscillatory and silent modes that is typical for the thalamocortical neurons. A single neuron cell can demonstrate a variety of oscillatory activity: Regular and chaotic spiking and bursting behavior. We study collective phenomena in small and large arrays of nonidentical cells coupled by models of electrical and chemical synapses. Two single elements coupled by electrical coupling show different types of synchronous behavior, in particular in-phase and antiphase synchronous regimes. In an ensemble of three inhibitory synaptically coupled elements, the phenomenon of sequential synchronous dynamics is observed. We study the synchronization phenomena in the chain of nonidentical neurons at different oscillatory behavior coupled with electrical and chemical synapses. Various regimes of phase synchronization are observed: (i) Synchronous regular and chaotic spiking; (ii) synchronous regular and chaotic bursting; and (iii) synchronous regular and chaotic bursting with different numbers of spikes inside the bursts. We detect and study the effect of collective synchronous burst generation due to the cluster formation and the oscillatory death.

  19. Distinct transport regimes for two elastically coupled molecular motors.

    PubMed

    Berger, Florian; Keller, Corina; Klumpp, Stefan; Lipowsky, Reinhard

    2012-05-18

    Cooperative cargo transport by two molecular motors involves an elastic motor-motor coupling, which can reduce the motors' velocity and/or enhance their unbinding from the filament. We show theoretically that these interference effects lead, in general, to four distinct transport regimes. In addition to a weak coupling regime, kinesin and dynein motors are found to exhibit a strong coupling and an enhanced unbinding regime, whereas myosin motors are predicted to attain a reduced velocity regime. All of these regimes, which we derive by explicit calculations and general time scale arguments, can be explored experimentally by varying the elastic coupling strength.

  20. Option pricing with regime switching by trinomial tree method

    NASA Astrophysics Data System (ADS)

    Yuen, Fei Lung; Yang, Hailiang

    2010-02-01

    We present a fast and simple tree model to price simple and exotic options in Markov Regime Switching Model (MRSM) with multi-regime. We modify the trinomial tree model of Boyle (1986) [12] by controlling the risk neutral probability measure in different regime states to ensure that the tree model can accommodate the data of all different regimes at the same time preserving its combining tree structure. In MRSM, the market might not be complete, therefore we provide some ideas and discussions on managing the regime switching risk in support of our results.

  1. Cointegration and causal linkages in fertilizer markets across different regimes

    NASA Astrophysics Data System (ADS)

    Lahmiri, Salim

    2017-04-01

    Cointegration and causal linkages among five different fertilizer markets are investigated during low and high market regimes. The database includes prices of rock phosphate (RP), triple super phosphate (TSP), diammonium phosphate (DAP), urea, and potassium chloride (PC). It is found that fertilizer markets are closely linked to each other during low and high regimes; and, particularly during high regime (after 2007 international financial crisis). In addition, there is no evidence of bidirectional linear relationship between markets during low and high regime time periods. Furthermore, all significant linkages are only unidirectional. Moreover, some causality effects have emerged during high regime. Finally, the effect of an impulse during high regime time period persists longer and is stronger than the effect of an impulse during low regime time period (before 2007 international financial crisis).

  2. Stable operating regime for traveling wave devices

    DOEpatents

    Carlsten, Bruce E.

    2000-01-01

    Autophase stability is provided for a traveling wave device (TWD) electron beam for amplifying an RF electromagnetic wave in walls defining a waveguide for said electromagnetic wave. An off-axis electron beam is generated at a selected energy and has an energy noise inherently arising from electron gun. The off-axis electron beam is introduced into the waveguide. The off-axis electron beam is introduced into the waveguide at a second radius. The waveguide structure is designed to obtain a selected detuning of the electron beam. The off-axis electron beam has a velocity and the second radius to place the electron beam at a selected distance from the walls defining the waveguide, wherein changes in a density of the electron beam due to the RF electromagnetic wave are independent of the energy of the electron beam to provide a concomitant stable operating regime relative to the energy noise.

  3. Dynamic Recrystallization: The Dynamic Deformation Regime

    NASA Astrophysics Data System (ADS)

    Murr, L. E.; Pizaña, C.

    2007-11-01

    Severe plastic deformation (PD), especially involving high strain rates (>103 s 1), occurs through solid-state flow, which is accommodated by dynamic recrystallization (DRX), either in a continuous or discontinuous mode. This flow can be localized in shear instability zones (or adiabatic shear bands (ASBs)) with dimensions smaller than 5 μ, or can include large volumes with flow zone dimensions exceeding centimeters. This article illustrates these microstructural features using optical and electron metallography to examine a host of dynamic deformation examples: shaped charge jet formation, high-velocity and hypervelocity impact crater formation, rod penetration into thick targets (which includes rod and target DRX flow and mixing), large projectile-induced target plug formation and failure, explosive welding, and friction-stir welding and processing. The DRX is shown to be a universal mechanism that accommodates solid-state flow in extreme (or severe) PD regimes.

  4. Diffusive Transport Properties Across Coupling Regimes

    NASA Astrophysics Data System (ADS)

    Dharuman, G.; Murillo, M. S.; Verboncoeur, J.; Christlieb, A.

    2014-10-01

    Transport properties are poorly known across coupling regimes, therefore understanding them is of importance for theoretical and practical reasons. A useful tool is an ultracold plasma system because of the experimental capability to tune the system to attain Coulomb coupling Γ ranging from 0.1 to 1 to 10 with the screening parameter κ ranging from 0 to 4 to 8, spanning the regions of the phase diagram from weak to moderate to strongly coupled and screened systems. Strong coupling is possible if Disorder Induced Heating is mitigated which requires a correlated initial ion state. Of particular interest is Rydberg blockaded gas of ultracold atoms where the local blockade effect results in correlations. Predictions of higher coupling in ultracold plasma created from a Rydberg blockaded gas have been reported. In this work we examine the diffusive transport properties of ultracold plasma system using molecular dynamics simulations for experimentally realizable values of Γ and κ as discussed above.

  5. Evolution of the water regime of Phobos

    SciTech Connect

    Fanale, F.P.; Salvail, J.R. )

    1990-12-01

    In the present model of Phobos water regime evolution, a time-dependent solar insolation is influenced by both decreasing solar output over geologic time and the Mars and Phobos cycles of eccentricity and obliquity, which vary over 100,000-1,000,000 year time scales. The results presented address model cases which assume (1) a homogeneous distribution of water ice, and (2) a driving of water ice toward the surface by the internal thermal gradient near the poles. A two-dimensional model is used to compute temperatures, heat and vapor fluxes, and ice removal/deposition rates, for the case of uniform ice distribution throughout Phobos. The results obtained indicate that a substantial amount of vapor is produced within 1 km of the surface. 15 refs.

  6. Capillary underwater discharges in repetitive pulse regime

    NASA Astrophysics Data System (ADS)

    de Baerdemaeker, F.; Monte, M.; Leys, C.

    2004-03-01

    In this study a capillary underwater discharge, that is sustained with AC (50 Hz) voltages up to 7.5 kV, is investigated. In a capillary discharge scheme, the current is, at some point along its path between two submerged electrodes, flowing through a narrow elongated bore in a dielectric material. When the current density is sufficiently high, local boiling and subsequent vapour breakdown results in the formation of a plasma within this capillary. At the same time the capillary emits an intense jet of vapour bubbles. Time-dependent electrical current, voltage and light emission curves are recorded for discharges in solutions of NaCl in distilled water and reveal different discharge regimes, depending on the conductivity and the excitation voltage, ranging from repetitive microsecond discharge pulses to a quasi-continuous discharge with a glow-like voltage-current characteristic.

  7. Nonlinear regimes of forced magnetic reconnection

    SciTech Connect

    Vekstein, G.; Kusano, K.

    2015-09-15

    This letter presents a self-consistent description of nonlinear forced magnetic reconnection in Taylor's model of this process. If external boundary perturbation is strong enough, nonlinearity in the current sheet evolution becomes important before resistive effects come into play. This terminates the current sheet shrinking that takes place at the linear stage and brings about its nonlinear equilibrium with a finite thickness. Then, in theory, this equilibrium is destroyed by a finite plasma resistivity during the skin-time, and further reconnection proceeds in the Rutherford regime. However, realization of such a scenario is unlikely because of the plasmoid instability, which is fast enough to develop before the transition to the Rutherford phase occurs. The suggested analytical theory is entirely different from all previous studies and provides proper interpretation of the presently available numerical simulations of nonlinear forced magnetic reconnection.

  8. Multimode optomechanical system in the quantum regime.

    PubMed

    Nielsen, William Hvidtfelt Padkær; Tsaturyan, Yeghishe; Møller, Christoffer Bo; Polzik, Eugene S; Schliesser, Albert

    2017-01-03

    We realize a simple and robust optomechanical system with a multitude of long-lived (Q > 10(7)) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry-Perot resonator detects these modes' motion with a measurement rate (96 kHz) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures (10 K). Reaching this quantum regime entails, inter alia, quantum measurement backaction exceeding thermal forces and thus strong optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to -2.4 dB (-3.6 dB if corrected for detection losses) and bandwidths ≲90 kHz. The multimode nature of the membrane and Fabry-Perot resonators will allow multimode entanglement involving electromagnetic, mechanical, and spin degrees of freedom.

  9. Multimode optomechanical system in the quantum regime

    NASA Astrophysics Data System (ADS)

    Hvidtfelt Padkær Nielsen, William; Tsaturyan, Yeghishe; Møller, Christoffer Bo; Polzik, Eugene S.; Schliesser, Albert

    2017-01-01

    We realize a simple and robust optomechanical system with a multitude of long-lived (Q > 107) mechanical modes in a phononic-bandgap shielded membrane resonator. An optical mode of a compact Fabry–Perot resonator detects these modes’ motion with a measurement rate (96 kHz) that exceeds the mechanical decoherence rates already at moderate cryogenic temperatures (10 K). Reaching this quantum regime entails, inter alia, quantum measurement backaction exceeding thermal forces and thus strong optomechanical quantum correlations. In particular, we observe ponderomotive squeezing of the output light mediated by a multitude of mechanical resonator modes, with quantum noise suppression up to ‑2.4 dB (‑3.6 dB if corrected for detection losses) and bandwidths ≲90 kHz. The multimode nature of the membrane and Fabry–Perot resonators will allow multimode entanglement involving electromagnetic, mechanical, and spin degrees of freedom.

  10. The Great Lakes' regional climate regimes

    NASA Astrophysics Data System (ADS)

    Sugiyama, Noriyuki

    For the last couple of decades, the Great Lakes have undergone rapid surface warming. In particular, the magnitude of the summer surface-warming trends of the Great Lakes have been much greater than those of surrounding land (Austin and Colman, 2007). Among the Great Lakes, the deepest Lake Superior exhibited the strongest warming trend in its annual, as well as summer surface water temperature. We find that many aspects of this behavior can be explained in terms of the tendency of deep lakes to exhibit multiple regimes characterized, under the same seasonally varying forcing, by the warmer and colder seasonal cycles exhibiting different amounts of wintertime lake-ice cover and corresponding changes in the summertime lake-surface temperatures. In this thesis, we address the problem of the Great Lakes' warming using one-dimensional lake modeling to interpret diverse observations of the recent lake behavior. (Abstract shortened by ProQuest.).

  11. Environment Flow Assessment with Flow Regime Transition

    NASA Astrophysics Data System (ADS)

    Su, J.; Ho, C. C.; Chang, L. C.

    2015-12-01

    To avoid worsen river and estuarine ecosystems cause by overusing water resources, environmental flows conservation is applied to reduce the impact of river environment. Environmental flows refer to water provided within a river, wetland or coastal zone to sustain ecosystems and benefits to human wellbeing. Environment flow assessment is now widely accepted that a naturally variable flow regime, rather than just a minimum low flow. In this study, we propose four methods, experience method, Tenant method, hydraulic method and habitat method to assess the environmental flow of base flow, flush flow and overbank flow with different discharge, frequency and occurrence period. Dahan River has been chosen as a case to demonstrate the assessment mechanism. The alternatives impact analysis of environment and human water used provides a reference for stakeholders when holding an environmental flow consultative meeting.

  12. Regime Changes in California Temperature Trends

    NASA Astrophysics Data System (ADS)

    Cordero, E. C.; Kessomkiat, W.; Mauget, S.

    2008-12-01

    Annual and seasonal temperature trends are analyzed for California using surface data from the US Historical Climate Network and the larger COOP network. While trends in Tmax and Tmin both show warming over the last 50 years, the temporal and spatial structure of these trends is quite different. An analysis using Mann Whitney U statistics reveals that the patterns of warming and cooling from individual stations have a distinct temporal signature that differs between Tmax and Tmin. Significant cooling trends in Tmin are found between 1920-1958, while significant warming only starts after the 1970s. In contrast, Tmax trends show a more variable pattern of warming and cooling between 1920-1980, with California wide warming only occurring after 1980. These results suggest regime changes in California temperature trends that could only occur through large scale forcing. A discussion of the various forcing mechanisms contributing to California trends and their spatial and temporal variability will be presented.

  13. Anomalous Transport in the Superfluid Fluctuation Regime

    NASA Astrophysics Data System (ADS)

    Uchino, Shun; Ueda, Masahito

    2017-03-01

    Motivated by a recent experiment in ultracold atoms [S. Krinner et al., Proc. Natl. Acad. Sci. U.S.A. 113, 8144 (2016), 10.1073/pnas.1601812113], we analyze transport of attractively interacting fermions through a one-dimensional wire near the superfluid transition. We show that in a ballistic regime where the conductance is quantized in the absence of interaction, the conductance is renormalized by superfluid fluctuations in reservoirs. In particular, the particle conductance is strongly enhanced, and the conductance plateau is blurred by emergent bosonic pair transport. For spin transport, in addition to the contact resistance, the wire itself is resistive, leading to a suppression of the measured spin conductance. Our results are qualitatively consistent with the experimental observations.

  14. Supercurrent in the quantum Hall regime

    NASA Astrophysics Data System (ADS)

    Wei, Ming-Tso; Amet, François; Ke, Chung-Ting; Borzenets, Ivan; Wang, Jiyingmei; Watanabe, Keji; Taniguchi, Takashi; Deacon, Russell; Yamamoto, Michihisa; Bomze, Yuriy; Tarucha, Seigo; Finkelstein, Gleb

    Combining superconductivity and the quantum Hall (QH) effect is a promising route for creating new types of topological excitations. Despite this potential, signatures of superconductivity in the quantum Hall regime remain scarce, and a superconducting current through a QH weak link has so far eluded experimental observation. Here we demonstrate the existence of a novel type of Josephson coupling through a QH region at magnetic fields as high as 2 Tesla. The supercurrent is mediated by states encompassing QH edge channels, which are flowing on opposite sides of the sample. The edges are coupled together by the hybrid electron-hole modes at the interfaces between the QH region and the superconducting contacts. These chiral modes, which share some features with Majorana modes, are formed when electron and hole edge states are mixed by the superconductor.

  15. Deterministic-random separation in nonstationary regime

    NASA Astrophysics Data System (ADS)

    Abboud, D.; Antoni, J.; Sieg-Zieba, S.; Eltabach, M.

    2016-02-01

    In rotating machinery vibration analysis, the synchronous average is perhaps the most widely used technique for extracting periodic components. Periodic components are typically related to gear vibrations, misalignments, unbalances, blade rotations, reciprocating forces, etc. Their separation from other random components is essential in vibration-based diagnosis in order to discriminate useful information from masking noise. However, synchronous averaging theoretically requires the machine to operate under stationary regime (i.e. the related vibration signals are cyclostationary) and is otherwise jeopardized by the presence of amplitude and phase modulations. A first object of this paper is to investigate the nature of the nonstationarity induced by the response of a linear time-invariant system subjected to speed varying excitation. For this purpose, the concept of a cyclo-non-stationary signal is introduced, which extends the class of cyclostationary signals to speed-varying regimes. Next, a "generalized synchronous average'' is designed to extract the deterministic part of a cyclo-non-stationary vibration signal-i.e. the analog of the periodic part of a cyclostationary signal. Two estimators of the GSA have been proposed. The first one returns the synchronous average of the signal at predefined discrete operating speeds. A brief statistical study of it is performed, aiming to provide the user with confidence intervals that reflect the "quality" of the estimator according to the SNR and the estimated speed. The second estimator returns a smoothed version of the former by enforcing continuity over the speed axis. It helps to reconstruct the deterministic component by tracking a specific trajectory dictated by the speed profile (assumed to be known a priori).The proposed method is validated first on synthetic signals and then on actual industrial signals. The usefulness of the approach is demonstrated on envelope-based diagnosis of bearings in variable

  16. Antecedents of Teachers Fostering Effort within Two Different Management Regimes: An Assessment-Based Accountability Regime and Regime without External Pressure on Results

    ERIC Educational Resources Information Center

    Christophersen, Knut-Andreas; Elstad, Eyvind; Turmo, Are

    2012-01-01

    This article focuses on the comparison of organizational antecedents of teachers' fostering of students' effort in two quite different accountability regimes: one management regime with an external-accountability system and one with no external accountability devices. The methodology involves cross-sectional surveys from two different management…

  17. Rheological equations in asymptotic regimes of granular flow

    USGS Publications Warehouse

    Chen, C.-L.; Ling, C.-H.

    1998-01-01

    This paper assesses the validity of the generalized viscoplastic fluid (GVF) model in light of the established constitutive relations in two asymptotic flow regimes, namely, the macroviscous and grain-inertia regimes. A comprehensive review of the literature on constitutive relations in both regimes reveals that except for some material constants, such as the coefficient of restitution, the normalized shear stress in both regimes varies only with the grain concentration, C. It is found that Krieger-Dougherty's relative viscosity, ??*(C), is sufficiently coherent among the monotonically nondecreasing functions of C used in describing the variation of the shear stress with C in both regimes. It not only accurately represents the C-dependent relative viscosity of a suspension in the macroviscous regime, but also plays a role of the radial distribution function that describes the statistics of particle collisions in the grain-inertia regime. Use of ??*(C) alone, however, cannot link the two regimes. Another parameter, the shear-rate number, N, is needed in modelling the rheology of neutrally buoyant granular flows in transition between the two asymptotic regimes. The GVF model proves compatible with most established relations in both regimes.

  18. Characterization of fire regime in Sardinia (Italy)

    NASA Astrophysics Data System (ADS)

    Bacciu, V. M.; Salis, M.; Mastinu, S.; Masala, F.; Sirca, C.; Spano, D.

    2012-12-01

    In the last decades, a number of Authors highlighted the crucial role of forest fires within Mediterranean ecosystems, with impacts both negative and positive on all biosphere components and with reverberations on different scales. Fire determines the landscape structure and plant composition, but it is also the cause of enormous economic and ecological damages, beside the loss of human life. In Sardinia (Italy), the second largest island of the Mediterranean Basin, forest fires are perceived as one of the main environmental and social problems, and data are showing that the situation is worsening especially within the rural-urban peripheries and the increasing number of very large forest fires. The need for information concerning forest fire regime has been pointed out by several Authors (e.g. Rollins et al., 2002), who also emphasized the importance of understanding the factors (such as weather/climate, socio-economic, and land use) that determine spatial and temporal fire patterns. These would be used not only as a baseline to predict the climate change effect on forest fires, but also as a fire management and mitigation strategy. The main aim of this paper is, thus, to analyze the temporal and spatial patterns of fire occurrence in Sardinia (Italy) during the last three decades (1980-2010). For the analyzed period, fire statistics were provided by the Sardinian Forest Service (CFVA - Corpo Forestale e di Vigilanza Ambientale), while weather data for eight weather stations were obtained from the web site www.tutiempo.it. For each station, daily series of precipitation, mean, maximum and minimum temperature, relative humidity and wind speed were available. The present study firstly analyzed fire statistics (burned area and number of fires) according to the main fire regime characteristics (seasonality, fire return interval, fire incidence, fire size distribution). Then, fire and weather daily values were averaged to obtain monthly, seasonal and annual values, and

  19. Evaluating temperature regimes for protection of brown trout

    USGS Publications Warehouse

    Armour, Carl L.

    1994-01-01

    Geographic distribution and population success of brown trout (Salmo trutta) are affected by temperature regimes. Concepts are presented for evaluating alternative temperature regimes for brown trout based on published temperature information and professional judgment. Temperature information from the literature is included for spawning runs, spawning, egg and larval development, growth, and other subjects. The objective is to aid biologists in evaluating alternative temperature regimes so as to select those that will protect and enhance environmental quality for brown trout.

  20. Shearing box simulations in the Rayleigh unstable regime

    NASA Astrophysics Data System (ADS)

    Nauman, Farrukh; Blackman, Eric G.

    2017-01-01

    We study the stability properties of Rayleigh unstable flows both in the purely hydrodynamic and magnetohydrodynamic (MHD) regimes for two different values of the shear q = 2.1, 4.2 (q = -dln Ω/dln r) and compare it with the Keplerian case q = 1.5. We find that the q > 2 regime is unstable both in the hydrodynamic and in the MHD limit (with an initially weak magnetic field). In this regime, the velocity fluctuations dominate the magnetic fluctuations. In contrast, in the q < 2 (magnetorotational instability (MRI)) regime the magnetic fluctuations dominate. This highlights two different paths to MHD turbulence implied by the two regimes, suggesting that in the q > 2 regime the instability produces primarily velocity fluctuations that cause magnetic fluctuations, with the causality reversed for the q < 2 MRI unstable regime. We also find that the magnetic field correlation is increasingly localized as the shear is increased in the Rayleigh unstable regime. In calculating the time evolution of spatial averages of different terms in the MHD equations, we find that the q > 2 regime is dominated by terms which are nonlinear in the fluctuations, whereas for q < 2, the linear terms play a more significant role.

  1. Film thickness for different regimes of fluid-film lubrication

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.

    1980-01-01

    Film thickness equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic lubrication of low-elastic-modulus materials (soft EHL), or isoviscous-elastic; and elastohydrodynamic lubrication of high-elastic-modulus materials (hard EHL), or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The results are presented as a map of the lubrication regimes, with film thickness contours on a log-log grid of the viscosity and elasticity for three values of the ellipticity parameter.

  2. Varying Inundation Regimes Differentially Affect Natural and ...

    EPA Pesticide Factsheets

    Climate change is altering sea-level rise rates and precipitation patterns worldwide. Coastal wetlands are vulnerable to these changes. System responses to stressors are important for resource managers and environmental stewards to understand in order to best manage them. Thin layer sand or sediment application to drowning and eroding marshes is one approach to build elevation and resilience. The above- and below-ground structure, soil carbon dioxide emissions, and pore water constituents in vegetated natural marsh sediments and sand-amended sediments were examined at varying inundation regimes between mean sea level and mean high water (0.82 m NAVD88 to 1.49 m NAVD88) in a field experiment at Laws Point, part of the Plum Island Sound Estuary (MA). Significantly lower salinities, pH, sulfides, phosphates, and ammonium were measured in the sand-amended sediments than in the natural sediments. In natural sediments there was a pattern of increasing salinity with increasing elevation while in the sand-amended sediments the trend was reversed, showing decreasing salinity with increasing elevation. Sulfide concentrations generally increased from low to high inundation with highest concentrations at the highest inundation (i.e., at the lowest elevations). High pore water phosphate concentrations were measured at low elevations in the natural sediments, but the sand-amended treatments had mostly low concentrations of phosphate and no consistent pattern with elevation. A

  3. RF Profile Control for Sustained Plasma Regimes

    NASA Astrophysics Data System (ADS)

    Hosea, J.; Bernabei, S.; Leblanc, B.; Majeski, R.; Menard, J.; Ono, M.; Phillips, C. K.; Schilling, G.; Wilson, J. R.

    1999-11-01

    For advancing plasma operation regimes for AT tokamaks and steady state concepts, as well as for forming and sustaining alternate concepts, it is necessary to provide control of the spatial profiles for the important plasma parameters - pressure, current, etc.. RF techniques offer considerable promise for providing this control and should be further developed as rapidly as possible within the well established tokamak program for forming a basis for application to all confinement concepts. Notably, IBW promises to provide internal transport barrier control if the coupling physics can be understood and efficient antenna coupling to the Bernstein wave can be developed. We will review the IBW experience and discuss possible explanations and solutions for the coupling problems encountered. In particular, the competing roles of parametric decay instability and surface mode excitation will be examined in order to elucidate the increase in surface power losses for the larger devices DIII-D and TFTR. Also, issues which need to be understood for employing ICRF and LH techniques to best advantage, such as antenna bombardment and energetic electron excitation, respectively, will be outlined.

  4. On spinfoam models in large spin regime

    NASA Astrophysics Data System (ADS)

    Han, Muxin

    2014-01-01

    We study the semiclassical behavior of Lorentzian Engle-Pereira-Rovelli-Livine (EPRL) spinfoam model, by taking into account the sum over spins in the large spin regime. We also employ the method of stationary phase analysis with parameters and the so-called, almost analytic machinery, in order to find the asymptotic behavior of the contributions from all possible large spin configurations in the spinfoam model. The spins contributing the sum are written as Jf = λjf, where λ is a large parameter resulting in an asymptotic expansion via stationary phase approximation. The analysis shows that at least for the simplicial Lorentzian geometries (as spinfoam critical configurations), they contribute the leading order approximation of spinfoam amplitude only when their deficit angles satisfy \\gamma \\mathring{\\Theta }_f\\le \\lambda ^{-1/2} mod 4\\pi {Z}. Our analysis results in a curvature expansion of the semiclassical low energy effective action from the spinfoam model, where the UV modifications of Einstein gravity appear as subleading high-curvature corrections.

  5. Cluster analysis of multiple planetary flow regimes

    NASA Technical Reports Server (NTRS)

    Mo, Kingtse; Ghil, Michael

    1987-01-01

    A modified cluster analysis method was developed to identify spatial patterns of planetary flow regimes, and to study transitions between them. This method was applied first to a simple deterministic model and second to Northern Hemisphere (NH) 500 mb data. The dynamical model is governed by the fully-nonlinear, equivalent-barotropic vorticity equation on the sphere. Clusters of point in the model's phase space are associated with either a few persistent or with many transient events. Two stationary clusters have patterns similar to unstable stationary model solutions, zonal, or blocked. Transient clusters of wave trains serve as way stations between the stationary ones. For the NH data, cluster analysis was performed in the subspace of the first seven empirical orthogonal functions (EOFs). Stationary clusters are found in the low-frequency band of more than 10 days, and transient clusters in the bandpass frequency window between 2.5 and 6 days. In the low-frequency band three pairs of clusters determine, respectively, EOFs 1, 2, and 3. They exhibit well-known regional features, such as blocking, the Pacific/North American (PNA) pattern and wave trains. Both model and low-pass data show strong bimodality. Clusters in the bandpass window show wave-train patterns in the two jet exit regions. They are related, as in the model, to transitions between stationary clusters.

  6. TBT causes regime shift in shallow lakes.

    PubMed

    Sayer, Carl D; Hoare, Daniel J; Simpson, Gavin L; Henderson, Andrew C G; Liptrot, Eleanor R; Jackson, Michael J; Appleby, Peter G; Boyle, John F; Jones, I Iwan; Waldock, Mike J

    2006-09-01

    Tributyltin (TBT) is an organotin compound used since the early 1960s as a biocide in boat antifouling paints. Its use has been linked to a host of negative effects in marine ecosystems including malformations and imposex in Mollusca and acute toxicity in many other aquatic animals. Yet, the consequences of TBT use in freshwaters are largely unknown. Here, for the first time we reveal that TBT may have caused hitherto unsuspected damage to freshwater ecosystems. Through an analysis of dated sediment cores collected from a system of recreationally boated, shallow lakes, we show that first evidence of TBT is associated with a dramatic loss of submerged vegetation and associated diverse animal communities. Cause and effect are difficult to unravel in our study. However, we hypothesize that TBT, through reducing populations of grazing organisms in lakes already affected by eutrophication, promoted the replacement of macrophytes by phytoplankton, ultimately leading to a regime shift in the ecosystem. Our findings may have parallels in freshwater ecosystems all over the world.

  7. Global fishery prospects under contrasting management regimes

    PubMed Central

    Costello, Christopher; Ovando, Daniel; Clavelle, Tyler; Strauss, C. Kent; Hilborn, Ray; Melnychuk, Michael C.; Branch, Trevor A.; Gaines, Steven D.; Szuwalski, Cody S.; Cabral, Reniel B.; Rader, Douglas N.; Leland, Amanda

    2016-01-01

    Data from 4,713 fisheries worldwide, representing 78% of global reported fish catch, are analyzed to estimate the status, trends, and benefits of alternative approaches to recovering depleted fisheries. For each fishery, we estimate current biological status and forecast the impacts of contrasting management regimes on catch, profit, and biomass of fish in the sea. We estimate unique recovery targets and trajectories for each fishery, calculate the year-by-year effects of alternative recovery approaches, and model how alternative institutional reforms affect recovery outcomes. Current status is highly heterogeneous—the median fishery is in poor health (overfished, with further overfishing occurring), although 32% of fisheries are in good biological, although not necessarily economic, condition. Our business-as-usual scenario projects further divergence and continued collapse for many of the world’s fisheries. Applying sound management reforms to global fisheries in our dataset could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual. We also find that, with appropriate reforms, recovery can happen quickly, with the median fishery taking under 10 y to reach recovery targets. Our results show that commonsense reforms to fishery management would dramatically improve overall fish abundance while increasing food security and profits. PMID:27035953

  8. CSDP: The seismology of continental thermal regimes

    SciTech Connect

    Aki, K.

    1990-05-01

    This is a progress report for the past one year of research (year 3 of 5-year project) under the project titled CSDP: Seismology of Continental Thermal Regime'', in which we proposed to develop seismological interpretation theory and methods applicable to complex structures encountered in continental geothermal areas and apply them to several candidate sites for the Continental Scientific Drilling Project. The past year has been extremely productive especially in the area of interpretation theory, including the following two major break-throughs. One is the derivation of an integral equation for time-dependent power spectra, which unified all the existing theories on seismic scattering (including the radiative transfer theory for total energy and single and multiple scattering theories based on the ray approach) and offers more complete and economical solutions to the problems of seismic scattering and attenuation. The other is the new formula for synthetic seismograms for layered media with irregular interfaces, combining the T-matrix method for an arbitrary shaped inclusion and the method of global generalized reflection/transmission coefficients for layered media. Both breakthroughs will enable us to deal with seismic observations in complex earth structures more efficiently and accurately. In the area of experimental studies, we discovered seismic guided waves trapped in the San Andreas fault near Parkfield, California. 54 refs., 14 figs.

  9. The seismology of geothermal regimes. Final report

    SciTech Connect

    Aki, K.

    1997-04-01

    The authors have been developing seismological interpretation theory and methods applicable to complex structures encountered in geothermal areas for a better understanding of the earth`s geothermal regimes. The questions the y have addressed in their research may be summarized as ``What is going on in the earth`s crust under tectonically active regions; what are the structures and processes responsible for such activities as earthquakes and volcanic eruptions; and how can one capture their essence effectively by means of seismological studies?`` First, the authors found clear evidence for localization of scattered seismic energy in the deep magmatic system of the volcano on the island of Reunion in the Indian Ocean. The seismic coda of local earthquakes show concentrated energy in the intrusive zones as late as 30 to 40 seconds after the origin time. This offers a very effective method for defining a zone of strong heterogeneity on a regional scale, complementary to the high resolution study using trapped modes as pursued in the past project. Secondly, the authors identified about 700 long-period events with various frequencies and durations from the data collected during the past 5 years which included three episodes of eruption. They are applying a finite-element method to the simplest event with the longest period and the shortest duration in order to find the location, geometry and physical properties of their source deterministically. The preliminary result described here suggests that their sources may be a horizontally lying magma-filled crack at a shallow depth under the summit area. In addition to the above work on the Reunion data, they have continued the theoretical and observational studies of attenuation and scattering of seismic waves.

  10. CSDP: Seismology of continental thermal regime

    SciTech Connect

    Aki, K.

    1989-04-01

    This is a progress report for the past one year of research (year 2 of 5-year project) under the project titled CSDP: Seismology of Continental Thermal Regime'', in which we proposed to develop seismological interpretation theory and methods applicable to complex structures encountered in continental geothermal areas and apply them to several candidate sites for the Continental Scientific Drilling Project. During the past year, two Ph.D. thesis works were completed under the present project. One is a USC thesis on seismic wave propagation in anisotropic media with application to defining fractures in the earth. The other is a MIT thesis on seismic Q and velocity structure for the magma-hydrothermal system of the Valles Caldera, New Mexico. The P.I. co-organized the first International Workshop on Volcanic Seismology at Capri, Italy in October 1988, and presented the keynote paper on the state-of-art of volcanic seismology''. We presented another paper at the workshop on Assorted Seismic Signals from Kilauea Volcano, Hawaii. Another international meeting, namely, the Chapman Conference on seismic anisotropy in the earth's crust at Berkeley, California in May 1988, was co-organized by the co-P.I. (P.C.L), and we presented our work on seismic waves in heterogeneous and anisotropic media. Adding the publications and presentations made in the past year to the list for the preceding year, the following table lists 21 papers published, submitted or presented in the past two years of the present project. 65 refs., 334 figs., 1 tab.

  11. Extractive Regimes: Toward a Better Understanding of Indonesian Development

    ERIC Educational Resources Information Center

    Gellert, Paul K.

    2010-01-01

    This article proposes the concept of an extractive regime to understand Indonesia's developmental trajectory from 1966 to 1998. The concept contributes to world-systems, globalization, and commodity-based approaches to understanding peripheral development. An extractive regime is defined by its reliance on extraction of multiple natural resources…

  12. A Tale of Two Regimes: Instrumentality and Commons Access

    ERIC Educational Resources Information Center

    Toly, Noah J.

    2005-01-01

    Technical developments have profound social and environmental impacts. Both are observed in the implications of regimes of instrumentality for commons access regimes. Establishing social, material, ecological, intellectual, and moral infrastructures, technologies are partly constitutive of commons access and may militate against governance…

  13. Disciplinary Regimes of "Care" and Complementary Alternative Education

    ERIC Educational Resources Information Center

    Thomson, Pat; Pennacchia, Jodie

    2016-01-01

    In schools, the notion of "care" is often synonymous with welfare and disciplinary regimes. Drawing on Foucault, and a study of alternative education (AE) across the UK, and looking in depth at two cases of complementary AE, we identify three types of disciplinary regimes at work in schools: (1) dominant performative reward and…

  14. FISHER INFORMATION AS A METRIC FOR SUSTAINABLE SYSTEM REGIMES

    EPA Science Inventory

    The important question in sustainability is not whether the world is sustainable, but whether a humanly acceptable regime of the world is sustainable. We propose Fisher Information as a metric for the sustainability of dynamic regimes in complex systems. The quantity now known ...

  15. Detection and Assessment of Ecosystem Regime Shifts from Fisher Information

    EPA Science Inventory

    Ecosystem regime shifts, which are long-term system reorganizations, have profound implications for sustainability. There is a great need for indicators of regime shifts, particularly methods that are applicable to data from real systems. We have developed a form of Fisher info...

  16. Water use regimes: Characterizing direct human interaction with hydrologic systems

    USGS Publications Warehouse

    Weiskel, P.K.; Vogel, R.M.; Steeves, P.A.; Zarriello, P.J.; DeSimone, L.A.; Ries, Kernell G.

    2007-01-01

    [1] The sustainability of human water use practices is a rapidly growing concern in the United States and around the world. To better characterize direct human interaction with hydrologic systems (stream basins and aquifers), we introduce the concept of the water use regime. Unlike scalar indicators of anthropogenic hydrologic stress in the literature, the water use regime is a two-dimensional, vector indicator that can be depicted on simple x-y plots of normalized human withdrawals (hout) versus normalized human return flows (hin). Four end-member regimes, natural-flow-dominated (undeveloped), human-flow-dominated (churned), withdrawal-dominated (depleted), and return-flow-dominated (surcharged), are defined in relation to limiting values of hout and hin. For illustration, the water use regimes of 19 diverse hydrologic systems are plotted and interpreted. Several of these systems, including the Yellow River Basin, China, and the California Central Valley Aquifer, are shown to approach particular end-member regimes. Spatial and temporal regime variations, both seasonal and long-term, are depicted. Practical issues of data availability and regime uncertainty are addressed in relation to the statistical properties of the ratio estimators hout and hin. The water use regime is shown to be a useful tool for comparative water resources assessment and for describing both historic and alternative future pathways of water resource development at a range of scales. Copyright 2007 by the American Geophysical Union.

  17. Plasma Physics Regimes in Tokamaks with Li Walls

    SciTech Connect

    L.E. Zakharo; N.N. Gorelenkov; R.B. White; S.I. Krasheninnikov; G.V. Pereverzev

    2003-08-21

    Low recycling regimes with a plasma limited by a lithium wall surface suggest enhanced stability and energy confinement, both necessary for tokamak reactors. These regimes could make ignition feasible in compact tokamaks. Ignited Spherical Tokamaks (IST), self-sufficient in the bootstrap current, are introduced as a necessary step for development of the physics and technology of power reactors.

  18. Global regime shift dynamics of catastrophic sea urchin overgrazing

    PubMed Central

    Ling, S. D.; Scheibling, R. E.; Rassweiler, A.; Johnson, C. R.; Shears, N.; Connell, S. D.; Salomon, A. K.; Norderhaug, K. M.; Pérez-Matus, A.; Hernández, J. C.; Clemente, S.; Blamey, L. K.; Hereu, B.; Ballesteros, E.; Sala, E.; Garrabou, J.; Cebrian, E.; Zabala, M.; Fujita, D.; Johnson, L. E.

    2015-01-01

    A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

  19. IDENTIFICATION OF REGIME SHIFTS IN TIME SERIES USING NEIGHBORHOOD STATISTICS

    EPA Science Inventory

    The identification of alternative dynamic regimes in ecological systems requires several lines of evidence. Previous work on time series analysis of dynamic regimes includes mainly model-fitting methods. We introduce two methods that do not use models. These approaches use state-...

  20. FISHER INFORMATION AS A METRIC FOR SUSTAINABLE REGIMES

    EPA Science Inventory

    The important question in sustainability is not whether the world is sustainable, but whether a humanly acceptable regime of the world is sustainable. We propose Fisher Information as a metric for the sustainability of dynamic regimes in complex systems. The quantity now known ...

  1. Conditional heteroscedasticity as a leading indicator of ecological regime shifts.

    PubMed

    Seekell, David A; Carpenter, Stephen R; Pace, Michael L

    2011-10-01

    Regime shifts are massive, often irreversible, rearrangements of nonlinear ecological processes that occur when systems pass critical transition points. Ecological regime shifts sometimes have severe consequences for human well-being, including eutrophication in lakes, desertification, and species extinctions. Theoretical and laboratory evidence suggests that statistical anomalies may be detectable leading indicators of regime shifts in ecological time series, making it possible to foresee and potentially avert incipient regime shifts. Conditional heteroscedasticity is persistent variance characteristic of time series with clustered volatility. Here, we analyze conditional heteroscedasticity as a potential leading indicator of regime shifts in ecological time series. We evaluate conditional heteroscedasticity by using ecological models with and without four types of critical transition. On approaching transition points, all time series contain significant conditional heteroscedasticity. This signal is detected hundreds of time steps in advance of the regime shift. Time series without regime shifts do not have significant conditional heteroscedasticity. Because probability values are easily associated with tests for conditional heteroscedasticity, detection of false positives in time series without regime shifts is minimized. This property reduces the need for a reference system to compare with the perturbed system.

  2. Magnetised Kelvin-Helmholtz instability in the intermediate regime between subsonic and supersonic regimes

    SciTech Connect

    Henri, P.; Califano, F.; Pegoraro, F.; Faganello, M.

    2012-07-15

    The understanding of the dynamics at play at the Earth's Magnetopause, the boundary separating the Earth's magnetosphere and the solar wind plasmas, is of primary importance for space plasma modeling. We focus our attention on the low latitude flank of the magnetosphere where the velocity shear between the magnetosheath and the magnetospheric plasmas is the energetic source of Kelvin-Helmholtz instability. On the shoulder of the resulting vortex chain, different secondary instabilities are at play depending on the local plasma parameters and compete with the vortex pairing process. Most important, secondary instabilities, among other magnetic reconnection, control the plasma mixing as well as the entry of solar wind plasma in the magnetosphere. We make use of a two-fluid model, including the Hall term and the electron mass in the generalized Ohm's law, to study the 2D non-linear evolution of the Kelvin-Helmholtz instability at the magnetosheath-magnetosphere interface, in the intermediate regime between subsonic and supersonic regimes. We study the saturation mechanisms, depending on the density jump across the shear layer and the magnetic field strength in the plane. In the presence of a weak in-plane magnetic field, the dynamics of the Kelvin-Helmholtz rolled-up vortices self-consistently generates thin current sheets where reconnection instability eventually enables fast reconnection to develop. Such a system enables to study guide field multiple-island collisionless magnetic reconnection as embedded in a large-scale dynamic system, unlike the classical static, ad hoc reconnection setups. In this regime, reconnection is shown to inhibit the vortex pairing process. This study provides a clear example of nonlinear, cross-scale, collisionless plasma dynamics.

  3. Transition from column to micropinch regime in Z-pinches

    SciTech Connect

    Engel, A.; Lebert, R.; Koshelev, K. N.; Sidelnikov, Yu. V.; Gavrilescu, C.; Neff, W.

    1997-05-05

    Plasma focus and Z-pinches are known to be intensive sources of K-ion radiation. This radiation is observed in two different regimes of compression: column and micropinch. Appearance of these regimes depends on combination of discharge circuit parameter and element composition of plasma. Column regime is typical for low current discharges operating in low Z gases. Micropinch regime, which represents a development of ''neck'' type instabilities in a presence of strong radiation losses, is typical for heavy ion plasma, i.e. vacuum spark or plasma focus with admixture of heavy gases. Transition from column to micropinch mode has been investigated experimentally. It was found that appearance of either regime can be quantitatively described by a distinction parameter depending on pinch current, particle density and used element.

  4. Investigation of the regimes of mixing of superconducting tunneling structures

    NASA Astrophysics Data System (ADS)

    Kalashnikov, K. V.; Artanov, A. A.; Filippenko, L. V.; Koshelets, V. P.

    2016-11-01

    The regimes of operation of a superconductor-insulator-superconductor tunnel junction based on three-layer structures Nb/AlOx/Nb and Nb/AlN/NbN as a harmonic mixer (for frequencies of the order of 600 and 20 GHz, respectively) and a frequency up-converter (in the frequency range from 0.1 to 5.0 GHz) have been investigated experimentally. The quasiparticle and Josephson mixing regimes have been compared. It has been shown that, in some practical applications, such as the use of the superconductor-insulator-superconductor junction as a cryogenic harmonic phase detector, the Josephson mixing regime is more preferable, because it can provide a higher signal and a greater signal-to-noise ratio as compared to the quasiparticle mixing regime. It has also been demonstrated that the Josephson mixing regime is promising for the use in signal multiplexing systems for superconducting detectors.

  5. Mercury's thermal evolution and core crystallization regime

    NASA Astrophysics Data System (ADS)

    Rivoldini, A.; Van Hoolst, T.; Dumberry, M.; Steinle-Neumann, G.

    2015-10-01

    Unlike the Earth, where the liquid core isentrope is shallower than the core liquidus, at the lower pressures inside Mercury's core the isentrope can be steeper than the melting temperature. As a consequence, upon cooling, the isentrope may first enter a solid stability field near the core mantle boundary and produce ironrich snow that sinks under gravity and produces buoyant upwellings of iron depleted fluid. Similar to bottom up crystallization, crystallization initiated near the top might generate sufficient buoyancy flux to drive magnetic field generation by compositional convection.In this study we model Mercury's thermal evolution by taking into account the formation of iron-rich snow to assess when the conditions for an internally magnetic field can be satisfied. We employ a thermodynamic consistent description of the iron high-pressure phase diagram and thermoelastic properties of iron alloys as well as the most recent data about the thermal conductivity of core materials. We use a 1-dimensional parametrized thermal evolution model in the stagnant lid regime for the mantle (e.g. [1]) that is coupled to the core. The model for the mantle takes into account the formation of the crust due to melting at depth. Mantle convection is driven by heat producing radioactive elements, heat loss from secular cooling and from the heat supplied by the core. The heat generated inside the core is mainly provided from secular cooling, from the latent heat released at iron freezing, and from gravitational energy resulting form the release of light elements at the inner core-outer core boundary as well as from the sinking of iron-rich snow and subsequent upwellings of light elements in the snow zone. If the heat flow out of the core is smaller than the heat transported along the core isentrope a thermal boundary will from at the top of the outer core. To determine the extension of the convecting region inside the liquid core we calculate the convective power [2]. Finally, we

  6. Human influence on California fire regimes

    USGS Publications Warehouse

    Syphard, A.D.; Radeloff, V.C.; Keeley, J.E.; Hawbaker, T.J.; Clayton, M.K.; Stewart, S.I.; Hammer, R.B.

    2007-01-01

    Periodic wildfire maintains the integrity and species composition of many ecosystems, including the mediterranean-climate shrublands of California. However, human activities alter natural fire regimes, which can lead to cascading ecological effects. Increased human ignitions at the wildland-urban interface (WUI) have recently gained attention, but fire activity and risk are typically estimated using only biophysical variables. Our goal was to determine how humans influence fire in California and to examine whether this influence was linear, by relating contemporary (2000) and historic (1960-2000) fire data to both human and biophysical variables. Data for the human variables included fine-resolution maps of the WUI produced using housing density and land cover data. Interface WUI, where development abuts wildland vegetation, was differentiated from intermix WUI, where development intermingles with wildland vegetation. Additional explanatory variables included distance to WUI, population density, road density, vegetation type, and ecoregion. All data were summarized at the county level and analyzed using bivariate and multiple regression methods. We found highly significant relationships between humans and fire on the contemporary landscape, and our models explained fire frequency (R2 = 0.72) better than area burned (R2 = 0.50). Population density, intermix WUI, and distance to WUI explained the most variability in fire frequency, suggesting that the spatial pattern of development may be an important variable to consider when estimating fire risk. We found nonlinear effects such that fire frequency and area burned were highest at intermediate levels of human activity, but declined beyond certain thresholds. Human activities also explained change in fire frequency and area burned (1960-2000), but our models had greater explanatory power during the years 1960-1980, when there was more dramatic change in fire frequency. Understanding wildfire as a function of the

  7. Constraints on flow regimes in wide-aperture fractures

    SciTech Connect

    Ghezzehei, Teamrat A.

    2004-02-28

    In recent years, significant advances have been made in our understanding of the complex flow processes in individual fractures, aided by flow visualization experiments and conceptual modeling efforts. These advances have led to the recognition of several flow regimes in individual fractures subjected to different initial and boundary conditions. Of these, the most important regimes are film flow, rivulet flow, and sliding of droplets. The existence of such significantly dissimilar flow regimes has been a major hindrance in the development of self-consistent conceptual models of flow for single fractures that encompass all the flow regimes. The objective of this study is to delineate the existence of the different flow regimes in individual fractures. For steady-state flow conditions, we developed physical constraints on the different flow regimes that satisfy minimum energy configurations, which enabled us to segregate the wide range of fracture transmissivity (volumetric flow rate per fracture width) into several flow regimes. These are, in increasing order of flow rate, flow of adsorbed films, flow of sliding drops, rivulet flow, stable film flow, and unstable (turbulent) film flow. The scope of this study is limited to wide-aperture fractures with the flow on the opposing sides of fracture being independent.

  8. River flow regimes and vegetation dynamics along a river transect

    NASA Astrophysics Data System (ADS)

    Doulatyari, Behnam; Basso, Stefano; Schirmer, Mario; Botter, Gianluca

    2014-11-01

    Ecohydrological processes occurring within fluvial landscapes are strongly affected by natural streamflow variability. In this work the patterns of vegetation biomass in two rivers characterized by contrasting flow regimes were investigated by means of a comprehensive stochastic model which explicitly couples catchment-scale hydroclimatic processes, morphologic attributes of the river transect and in-stream bio-ecological features. The hydrologic forcing is characterized by the probability distribution (pdf) of streamflows and stages resulting from stochastic precipitation dynamics, rainfall-runoff transformation and reach scale morphologic attributes. The model proved able to reproduce the observed pdf of river flows and stages, as well as the pattern of exposure/inundation along the river transect in both regimes. Our results suggest that in persistent regimes characterized by reduced streamflow variability, mean vegetation biomass is chiefly controlled by the pattern of groundwater availability along the transect, leading to a marked transition between aquatic and terrestrial environments. Conversely, erratic regimes ensure wider aquatic-terrestrial zones in which optimal elevation ranges for species with different sensitivity to flooding and access to groundwater are separated. Patterns of mean biomass in erratic regimes were found to be more sensitive to changes in the underlying hydroclimatic conditions, notwithstanding the reduced responsiveness of the corresponding flow regimes. The framework developed highlights the important role played by streamflow regimes in shaping riverine environments, and may eventually contribute to identifying the influence of landscape, climate and morphologic features on in-stream ecological dynamics.

  9. An Examination of the Nature of Global MODIS Cloud Regimes

    NASA Technical Reports Server (NTRS)

    Oreopoulos, Lazaros; Cho, Nayeong; Lee, Dongmin; Kato, Seiji; Huffman, George J.

    2014-01-01

    We introduce global cloud regimes (previously also referred to as "weather states") derived from cloud retrievals that use measurements by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard the Aqua and Terra satellites. The regimes are obtained by applying clustering analysis on joint histograms of retrieved cloud top pressure and cloud optical thickness. By employing a compositing approach on data sets from satellites and other sources, we examine regime structural and thermodynamical characteristics. We establish that the MODIS cloud regimes tend to form in distinct dynamical and thermodynamical environments and have diverse profiles of cloud fraction and water content. When compositing radiative fluxes from the Clouds and the Earth's Radiant Energy System instrument and surface precipitation from the Global Precipitation Climatology Project, we find that regimes with a radiative warming effect on the atmosphere also produce the largest implied latent heat. Taken as a whole, the results of the study corroborate the usefulness of the cloud regime concept, reaffirm the fundamental nature of the regimes as appropriate building blocks for cloud system classification, clarify their association with standard cloud types, and underscore their distinct radiative and hydrological signatures.

  10. Toward a Physical Characterization of Raindrop Collision Outcome Regimes

    NASA Technical Reports Server (NTRS)

    Testik, F. Y.; Barros, Ana P.; Bilven, Francis L.

    2011-01-01

    A comprehensive raindrop collision outcome regime diagram that delineates the physical conditions associated with the outcome regimes (i.e., bounce, coalescence, and different breakup types) of binary raindrop collisions is proposed. The proposed diagram builds on a theoretical regime diagram defined in the phase space of collision Weber numbers We and the drop diameter ratio p by including critical angle of impact considerations. In this study, the theoretical regime diagram is first evaluated against a comprehensive dataset for drop collision experiments representative of raindrop collisions in nature. Subsequently, the theoretical regime diagram is modified to explicitly describe the dominant regimes of raindrop interactions in (We, p) by delineating the physical conditions necessary for the occurrence of distinct types of collision-induced breakup (neck/filament, sheet, disk, and crown breakups) based on critical angle of impact consideration. Crown breakup is a subtype of disk breakup for lower collision kinetic energy that presents distinctive morphology. Finally, the experimental results are analyzed in the context of the comprehensive collision regime diagram, and conditional probabilities that can be used in the parameterization of breakup kernels in stochastic models of raindrop dynamics are provided.

  11. Marine regime shifts: drivers and impacts on ecosystems services

    PubMed Central

    Rocha, J.; Yletyinen, J.; Biggs, R.; Blenckner, T.; Peterson, G.

    2015-01-01

    Marine ecosystems can experience regime shifts, in which they shift from being organized around one set of mutually reinforcing structures and processes to another. Anthropogenic global change has broadly increased a wide variety of processes that can drive regime shifts. To assess the vulnerability of marine ecosystems to such shifts and their potential consequences, we reviewed the scientific literature for 13 types of marine regime shifts and used networks to conduct an analysis of co-occurrence of drivers and ecosystem service impacts. We found that regime shifts are caused by multiple drivers and have multiple consequences that co-occur in a non-random pattern. Drivers related to food production, climate change and coastal development are the most common co-occurring causes of regime shifts, while cultural services, biodiversity and primary production are the most common cluster of ecosystem services affected. These clusters prioritize sets of drivers for management and highlight the need for coordinated actions across multiple drivers and scales to reduce the risk of marine regime shifts. Managerial strategies are likely to fail if they only address well-understood or data-rich variables, and international cooperation and polycentric institutions will be critical to implement and coordinate action across the scales at which different drivers operate. By better understanding these underlying patterns, we hope to inform the development of managerial strategies to reduce the risk of high-impact marine regime shifts, especially for areas of the world where data are not available or monitoring programmes are not in place.

  12. Boundary between stable and unstable regimes of accretion. Ordered and chaotic unstable regimes

    NASA Astrophysics Data System (ADS)

    Blinova, A. A.; Romanova, M. M.; Lovelace, R. V. E.

    2016-07-01

    We present a new study of the Rayleigh-Taylor unstable regime of accretion on to rotating magnetized stars in a set of high grid resolution three-dimensional magnetohydrodynamic simulations performed in low-viscosity discs. We find that the boundary between the stable and unstable regimes is determined almost entirely by the fastness parameter ωs = Ω⋆/ΩK(rm), where Ω⋆ is the angular velocity of the star and ΩK(rm) is the angular velocity of the Keplerian disc at the disc-magnetosphere boundary r = rm. We found that accretion is unstable if ωs ≲ 0.6. Accretion through instabilities is present in stars with different magnetospheric sizes. However, only in stars with relatively small magnetospheres, rm/R⋆ ≲ 7, do the unstable tongues produce chaotic hotspots on the stellar surface and irregular light curves. At even smaller values of the fastness parameter, ωs ≲ 0.45, multiple irregular tongues merge, forming one or two ordered unstable tongues that rotate with the angular frequency of the inner disc. This transition occurs in stars with even smaller magnetospheres, rm/R⋆ ≲ 4.2. Most of our simulations were performed at a small tilt of the dipole magnetosphere, Θ = 5°, and a small viscosity parameter α = 0.02. Test simulations at higher α values show that many more cases become unstable, and the light curves become even more irregular. Test simulations at larger tilts of the dipole Θ show that instability is present, however, accretion in two funnel streams dominates if Θ ≳ 15°. The results of these simulations can be applied to accreting magnetized stars with relatively small magnetospheres: Classical T Tauri stars, accreting millisecond X-ray pulsars, and cataclysmic variables.

  13. AN APPROACH FOR CLASSIFYING TIDAL REGIMES BASED ON TIDAL CONSTITUENTS

    EPA Science Inventory

    Tidal fluctuations can be one of the dominant physical processes in estuaries. This paper presents a numerical classification of tidal regimes that can be used to summarize local conditions and facilitate comparisons among locations. Tide predictions are customarily calculated ...

  14. Stochastic regimes in very-low-frequency fluidic oscillator

    NASA Astrophysics Data System (ADS)

    Tesař, Václav

    2016-03-01

    Paper discusses interesting unexpected stochastic regimes discovered in a fluidic oscillator designed for operation at very low oscillation frequencies - without the inconvenience of the long feedback loops needed in standard low-frequency oscillator designs. The new oscillator contains a pair of bistable turn-down active valves operating in anti-parallel — essentially analogous to Abraham & Bloch electric "multibrateur" invented in 1919. Three different self-excited oscillation regimes were found. In the order of increasing supplied flow rate, these regimes are characterised by: (A) generation of stochastic-duration multi-pulse packs, (B) generation of individual pulses with a degree of periodicity, and (C) regime with randomly appearing flow pulses separated by intervals of the order of seconds.

  15. 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.

  16. Fixed points, stable manifolds, weather regimes, and their predictability

    DOE PAGES

    Deremble, Bruno; D'Andrea, Fabio; Ghil, Michael

    2009-10-27

    In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model’s fixed points in phase space. The model dynamics is characterized by the coexistence of multiple ''weather regimes.'' To investigate the transitions from one regime to another, we focus on the identification of stable manifolds associated with fixed points. We show that these manifolds act as separatrices between regimes. We track each manifold by making use of two local predictability measures arising from the meteorological applications of nonlinear dynamics, namely, ''bred vectors'' and singular vectors. These results are then verified in the framework of ensemblemore » forecasts issued from clouds (ensembles) of initial states. The divergence of the trajectories allows us to establish the connections between zones of low predictability, the geometry of the stable manifolds, and transitions between regimes.« less

  17. The effect of refrigerants in the mixed lubrication regime

    SciTech Connect

    Mizuhara, Kazuyuki; Tomimoto, Makoto

    1997-12-31

    Because of environmental concerns, CFC (chlorofluorocarbon) refrigerants must be replaced with HFCs (hydrofluorocarbons). As a result, many tribological problems are caused especially in rotary piston compressors. To solve the problem, the effects of refrigerants on friction and wear characteristics of the oil and refrigerant mixtures at the mixed lubrication regime are investigated. The difference in refrigerants are clearly observed not only in boundary but also in the mixed lubrication regime. The effects of operating conditions on sliding conditions and experimental results are also discussed. It is concluded that for practical application where long life is essential, experiments must be conducted under the mixed lubrication regime. Also, the importance of defining the lubrication regime in terms of film parameter is emphasized.

  18. Spacetime-noncommutativity regime of loop quantum gravity

    NASA Astrophysics Data System (ADS)

    Amelino-Camelia, Giovanni; Da Silva, Malú Maira; Ronco, Michele; Cesarini, Lorenzo; Lecian, Orchidea Maria

    2017-01-01

    A recent study by Bojowald and Paily [M. Bojowald and G. M. Paily, Phys. Rev. D 87, 044044 (2013)., 10.1103/PhysRevD.87.044044] provided a path toward the identification of an effective quantum-spacetime picture of loop quantum gravity, applicable in the "Minkowski regime," the regime where the large-scale (coarse-grained) spacetime metric is flat. A pivotal role in the analysis is played by loop-quantum-gravity-based modifications to the hypersurface deformation algebra, which leave a trace in the Minkowski regime. We here show that the symmetry-algebra results reported by Bojowald and Paily are consistent with a description of spacetime in the Minkowski regime given in terms of the κ -Minkowski noncommutative spacetime, whose relevance for the study of the quantum-gravity problem had already been proposed for independent reasons.

  19. Fixed points, stable manifolds, weather regimes, and their predictability

    SciTech Connect

    Deremble, Bruno; D'Andrea, Fabio; Ghil, Michael

    2009-10-27

    In a simple, one-layer atmospheric model, we study the links between low-frequency variability and the model’s fixed points in phase space. The model dynamics is characterized by the coexistence of multiple ''weather regimes.'' To investigate the transitions from one regime to another, we focus on the identification of stable manifolds associated with fixed points. We show that these manifolds act as separatrices between regimes. We track each manifold by making use of two local predictability measures arising from the meteorological applications of nonlinear dynamics, namely, ''bred vectors'' and singular vectors. These results are then verified in the framework of ensemble forecasts issued from clouds (ensembles) of initial states. The divergence of the trajectories allows us to establish the connections between zones of low predictability, the geometry of the stable manifolds, and transitions between regimes.

  20. Analysis of light regime in continuous light distributions in photobioreactors.

    PubMed

    Brindley, Celeste; Fernández, F G Acién; Fernández-Sevilla, J M

    2011-02-01

    Maximum photobioreactor (PBR) efficiency is a must in applications such as the obtention of microalgae-derived fuels. Improving PBR performance requires a better understanding of the "light regime", the varying irradiance that microalgal cells moving in a dense culture are exposed to. We propose a definition of light regime that can be used consistently to describe the continuously varying light patterns in PBRs as well as in light/dark cycles. Equivalent continuous and light/dark regimes have been experimentally compared and the results show that continuous variations are not well represented by light/dark cycles, as had been widely accepted. It has been shown that a correct light regime allows obtaining photosynthetic rates higher than the corresponding to continuous light, the so-called "flashing light effect" and that this is possible in commercial PBRs. A correct PBR operation could result in photosynthetic efficiency close to the optimum eight quanta per O(2).

  1. Regime change and oscillation thresholds in recorder-like instruments.

    PubMed

    Auvray, Roman; Fabre, Benoît; Lagrée, Pierre-Yves

    2012-02-01

    Based on results from the literature, a description of sound generation in a recorder is developed. Linear and non-linear analysis are performed to study the dependence of the frequency on the jet velocity. The linear analysis predicts that the frequency is a function of the jet velocity. The non-linear resolution provides information about limit cycle oscillation and hysteretic regime change thresholds. A comparison of the frequency between linear theory and experiments on a modified recorder shows good agreement except at very low jet velocities. Although the predicted threshold for the onset of the first regime shows an important deviation from experiments, the hysteresis of threshold to higher regimes is accurately estimated. Furthermore, a qualitative analysis of the influence of different parameters in the model on the sound generation and regime changes is presented.

  2. FISHER INFORMATION AND DYNAMIC REGIME CHANGES IN ECOLOGICAL SYTEMS

    EPA Science Inventory

    Ecosystems often exhibit transitions between dynamic regimes (or steady states), such as the conversion of oligotrophic to eutrophic conditions and associated aquatic ecological communities, due to natural (or increasingly) anthropogenic disturbances. As ecosystems experience per...

  3. Plasma confinement regimes and collective modes characterizing them

    SciTech Connect

    Coppi, B.; Zhou, T.

    2012-10-15

    A unified theory is presented for the modes that are excited at the edge of the plasma column and are important signatures of the advanced confinement regimes into which magnetically confined plasmas can be driven. In particular, the so-called EDA H-Regime, the Elmy H-Regime, and the I-Regime are considered. The modes that are identified theoretically have characteristics that are consistent with or have anticipated those of the modes observed experimentally for each of the investigated regimes. The phase velocities, the produced transport processes, the frequencies, the wavelengths, and the consistency with the direction of spontaneous rotation are the factors considered for comparison with the relevant experiments. The quasi-coherent mode [I. Cziegler, Ph.D. dissertation, Massachusetts Institute of Technology, Cambridge, MA, 2011] that is present in the EDA H-Regime has a phase velocity in the direction of the ion diamagnetic velocity in the plasma reference frame. Consequently, this is identified as a ballooning mode near finite Larmor radius marginal stability involving the effects of transverse ion viscosity and other dissipative effects. In this regime, impurities are driven outward by the combined effects of the local temperature gradients of the impurities and their thermal conductivity, while in the Elmy H-Regime impurities are driven toward the center of the plasma column. In the I-Regimes, the excited 'Heavy Particle' modes [B. Coppi and T. Zhou, Phys. Plasmas 19, 012302 (2012); Phys. Lett. A 375, 2916 (2011)] are not of the ballooning kind and are shown to expel the impurities toward the plasma edge in the presence of significant fluctuations. These modes can have a finite frequency of oscillation with a phase velocity in the direction of the electron diamagnetic velocity or they can be nearly purely growing, explaining why there are I-Regimes where fluctuations are not observed. Instead, the modes considered for the Elmy H-Regime are of the ballooning

  4. Equatorial atmospheric weather regimes: Their structure and role

    SciTech Connect

    Connors, V.S.

    1991-01-01

    Infrared radiance measurements by the Geostationary Operational Environmental Satellite (GOES-6) from April 1986 through April 1987 are used to characterize and identify distinct regimes of persistent, large-scale cloudiness patterns over the Amazon Basin. These tropical weather regimes are responsible for the continental-scale atmospheric processes that transport air, trace gases, and heat from the Amazon Basin. The cloud patterns are represented by both scene-scale parameters, such as the cloud-free area and the value of the 'clear sky peak' in a histogram, and textural measures, such as contrast of cloudy area and homogeneity or cloudy area. Correlation analyses of the attribute arrays determined that only 9 of the original 15 cloud pattern descriptors are required for the cluster analyses. Seventy-six percent of the satellite images are classified into 1 of 14 weather regimes which persist for periods that range from 3 to 15 days each. The dominant weather regimes are described by the recurrence and duration of the events, by the rainfall produced and energy released to the tropical atmosphere, and by the composite kinematic and thermodynamic analyses. While the classification analyses identified a range of organized weather conditions in the Amazon Basin, two weather regimes, each occurring in separate seasons, dominate the year. The prominent dry season regime (A) occurs 11 times, persists for 25 percent of the year, produces 81 percent of the dry season rainfall, and 7 percent of the energy export necessary to balance the global heat budget. The prominent wet season regime (B) occurs 8 times, persists for 18 percent of the year, delivers about 30 percent of the wet season rainfall, and 16 percent of the energy export requirement. Because the dry season regime (A) draws nearly half of its water vapor supply from local sources, a vital link may exist between the rainforest ecosystem and the dry season rainfall.

  5. Distributed Low Temperature Combustion: Fundamental Understanding of Combustion Regime Transitions

    DTIC Science & Technology

    2016-09-07

    study is to bring fundamental understanding of the impact of the chemical (Tau_c) and flow (Tau_f) timescales on combustion regime transitions in...reaction zone regime. The choice of DME is partly due to the potential practical relevance, but also due to the fundamentally different chemical ... chemical mechanisms for the considered fuels (e.g. DME) to establish their ability to reproduce laminar flame and auto-ignition properties. The

  6. Synchronous marine pelagic regime shifts in the Northern Hemisphere

    PubMed Central

    Beaugrand, G.; Conversi, A.; Chiba, S.; Edwards, M.; Fonda-Umani, S.; Greene, C.; Mantua, N.; Otto, S. A.; Reid, P. C.; Stachura, M. M.; Stemmann, L.; Sugisaki, H.

    2015-01-01

    Regime shifts are characterized by sudden, substantial and temporally persistent changes in the state of an ecosystem. They involve major biological modifications and often have important implications for exploited living resources. In this study, we examine whether regime shifts observed in 11 marine systems from two oceans and three regional seas in the Northern Hemisphere (NH) are synchronous, applying the same methodology to all. We primarily infer marine pelagic regime shifts from abrupt shifts in zooplankton assemblages, with the exception of the East Pacific where ecosystem changes are inferred from fish. Our analyses provide evidence for quasi-synchronicity of marine pelagic regime shifts both within and between ocean basins, although these shifts lie embedded within considerable regional variability at both year-to-year and lower-frequency time scales. In particular, a regime shift was detected in the late 1980s in many studied marine regions, although the exact year of the observed shift varied somewhat from one basin to another. Another regime shift was also identified in the mid- to late 1970s but concerned less marine regions. We subsequently analyse the main biological signals in relation to changes in NH temperature and pressure anomalies. The results suggest that the main factor synchronizing regime shifts on large scales is NH temperature; however, changes in atmospheric circulation also appear important. We propose that this quasi-synchronous shift could represent the variably lagged biological response in each ecosystem to a large-scale, NH change of the climatic system, involving both an increase in NH temperature and a strongly positive phase of the Arctic Oscillation. Further investigation is needed to determine the relative roles of changes in temperature and atmospheric pressure patterns and their resultant teleconnections in synchronizing regime shifts at large scales.

  7. Evaluation of interregional variability in MODIS cloud regimes

    NASA Astrophysics Data System (ADS)

    Leinonen, J. S.; Lebsock, M. D.; Oreopoulos, L.; Cho, N.

    2015-12-01

    Clustering techniques have been used in the last few decades to classify cloud types automatically from satellite observations, most commonly using cloud top pressure and cloud optical depth. The underlying assumption is that the resulting clusters, called "cloud regimes" or "weather states", represent some type of basic states of the atmosphere, and thus that their occurrence can be used as a proxy for related variables such as radiative balance or precipitation. We have examined the validity of these assumptions by using independent measurements from the CloudSat and CALIPSO satellites. The CloudSat radar yields a reflectivity product that is sensitive to many aspects of the physics of the clouds, while CloudSat together with the CALIPSO lidar can retrieve the vertical structure of the cloud column, including multi-layer clouds. These observations have been separated into groups according to the recently published cloud regimes based on data from the MODIS instrument, deployed on the Aqua satellite orbiting in the same constellation with CloudSat and CALIPSO. The distributions of these observations have been constructed both globally and in a number of regions in different parts of the Earth. By analyzing the differences in the distributions between these regions, we can evaluate the usefulness of the cloud regimes as a proxy for the measured variables. Some cloud regimes have been found to be rather stable between regions, while others display considerable variability. Moreover, some cloud regimes appear much more similar to each other in CloudSat observations than they do using the MODIS regimes. We analyze the implications of these differences for the usability of the cloud regimes as climate indicators. We also explore various filtering techniques and different clustering methods that can potentially be used to reduce these differences, and thus to improve the universality of the cloud regimes.

  8. Ignition Regime for Fusion in a Degenerate Plasma

    SciTech Connect

    Son, S.; Fisch, N.J.

    2005-12-01

    We identify relevant parameter regimes in which aneutronic fuels can undergo fusion ignition in hot-ion degenerate plasma. Because of relativistic effects and partial degeneracy, the self-sustained burning regime is considerably larger than previously calculated. Inverse bremsstrahlung plays a major role in containing the reactor energy. We solve the radiation transfer equation and obtain the contribution to the heat conductivity from inverse bremsstrahlung.

  9. Assessing the Institution of the Nuclear Nonproliferation Regime

    SciTech Connect

    Toomey, Christopher

    2010-05-14

    The nuclear nonproliferation regime is facing a crisis of effectiveness. During the Cold War, the regime was relatively effective in stemming the proliferation of nuclear weapons and building an institutional structure that could, under certain conditions, ensure continued success. However, in the evolving global context, the traditional approaches are becoming less appropriate. Globalization has introduced new sets of stresses on the nonproliferation regime, such as the rise of non-state actors, broadening extensity and intensity of supply chains, and the multipolarization of power. This evolving global context demands an analytical and political flexibility in order to meet future threats. Current institutional capabilities established during the Cold War are now insufficient to meet the nonproliferation regime’s current and future needs. The research was based on information gathered through interviews and reviews of the relevant literature, and two dominant themes emerged. First, that human security should be integrated into the regime to account for the rise of non-state actors and networked violence. Second, confidence in the regime’s overall effectiveness has eroded at a time where verification-based confidence is becoming more essential. The research postulates that a critical analysis of the regime that fully utilizes institutional theory, with its focus on rules, normative structures, and procedures will be essential to adapting the regime to the current global context, building mechanisms for generating trust, creating better enforcement, and providing flexibility for the future.

  10. Modeling of a Two-Regime Crystallization in a Multicomponent

    SciTech Connect

    Mazzanti, G.; Marangoni, A; Idziak, S

    2008-01-01

    The kinetics of phase transitions of milk fat triacylglycerols, as model multicomponent lipid systems, were studied under shear in a Couette cell at 17 C, 17.5 C and 20 C under shear rates ranging from 0 to 2880s-1 using synchrotron X-ray diffraction. Two-dimensional diffraction patterns were captured during the crystallization process. No effect of shear on onset time for phase a from the liquid was observed. Afterwards a two-regime crystallization process was observed. During the first regime, as observed in other systems, shear reduced the onset time of the phase transition from phase a to 2880s-. The model previously developed for palm oil (ODE model) worked well to describe this regime, confirming the general value of the proposed ODE model. However, the ODE model did not satisfactorily describe the second regime. We found that, as the system gets closer to equilibrium, the growth regime becomes controlled by diffusion, manifested by the kinetics following a {radical}t dependence. This regime was found to be consistent with a mechanism combining step growth at a kink with progressive selection of the crystallizing moieties. This mechanism is in agreement with the displacement of the diffraction peak positions, which revealed how increased shear rate promotes the crystallization of the higher melting fraction affecting the composition of the crystallites.

  11. O-regime dynamics and modeling in Tore Supra

    NASA Astrophysics Data System (ADS)

    Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Ségui, J.-L.

    2009-06-01

    The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Équipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r ) and the electron temperature Te(r) where the equation coefficients are functions of j and Te themselves. Both the integrated modeling code CRONOS [V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r ) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

  12. O-regime dynamics and modeling in Tore Supra

    SciTech Connect

    Turco, F.; Giruzzi, G.; Imbeaux, F.; Udintsev, V. S.; Artaud, J. F.; Barana, O.; Dumont, R.; Mazon, D.; Segui, J.-L.

    2009-06-15

    The regime of nonlinear temperature oscillations (O-regime), characteristic of noninductive discharges on Tore Supra [Equipe Tore Supra, Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, France, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 1, p. 9], is investigated in its triggering and suppressing mechanism. This regime can be described by two nonlinearly coupled equations for the current density j(r) and the electron temperature T{sub e}(r) where the equation coefficients are functions of j and T{sub e} themselves. Both the integrated modeling code CRONOS[V. Basiuk et al., Nucl. Fusion 43, 822 (2003)] and a two-patch predator-prey system with diffusion and noise have been used and results have been compared to the experimental observations of the O-regime. A database of discharges is analyzed which features monotonic, flat, and reversed safety factor (q) profiles in order to characterize the action of external actuators on the regime dynamics with the widest generality. Electron cyclotron current drive and neutral beam injections have been used in order to induce localized perturbations in the total current profile j(r) as well as to change the plasma confinement conditions in the central region. Magnetic shear perturbations and modifications of the heat transport turn out to be the central parameters governing the dynamics of the O-regime.

  13. Triggered dynamics in a model of different fault creep regimes

    PubMed Central

    Kostić, Srđan; Franović, Igor; Perc, Matjaž; Vasović, Nebojša; Todorović, Kristina

    2014-01-01

    The study is focused on the effect of transient external force induced by a passing seismic wave on fault motion in different creep regimes. Displacement along the fault is represented by the movement of a spring-block model, whereby the uniform and oscillatory motion correspond to the fault dynamics in post-seismic and inter-seismic creep regime, respectively. The effect of the external force is introduced as a change of block acceleration in the form of a sine wave scaled by an exponential pulse. Model dynamics is examined for variable parameters of the induced acceleration changes in reference to periodic oscillations of the unperturbed system above the supercritical Hopf bifurcation curve. The analysis indicates the occurrence of weak irregular oscillations if external force acts in the post-seismic creep regime. When fault motion is exposed to external force in the inter-seismic creep regime, one finds the transition to quasiperiodic- or chaos-like motion, which we attribute to the precursory creep regime and seismic motion, respectively. If the triggered acceleration changes are of longer duration, a reverse transition from inter-seismic to post-seismic creep regime is detected on a larger time scale. PMID:24954397

  14. Do family policy regimes matter for children's well-being?

    PubMed

    Engster, Daniel; Stensöta, Helena Olofsdotter

    2011-01-01

    Researchers have studied the impact of different welfare state regimes, and particularly family policy regimes, on gender equality. Very little research has been conducted, however, on the association between different family policy regimes and children's well-being. This article explores how the different family policy regimes of twenty OECD countries relate to children's well-being in the areas of child poverty, child mortality, and educational attainment and achievement. We focus specifically on three family policies: family cash and tax benefits, paid parenting leaves, and public child care support. Using panel data for the years 1995, 2000, and 2005, we test the association between these policies and child well-being while holding constant for a number of structural and policy variables. Our analysis shows that the dual-earner regimes, combining high levels of support for paid parenting leaves and public child care, are strongly associated with low levels of child poverty and child mortality. We find little long-term effect of family policies on educational achievement, but a significant positive correlation between high family policy support and higher educational attainment. We conclude that family policies have a significant impact on improving children's well-being, and that dual-earner regimes represent the best practice for promoting children's health and development.

  15. Regime-Switching Bivariate Dual Change Score Model.

    PubMed

    Chow, Sy-Miin; Grimm, Kevin J; Filteau, Guillaume; Dolan, Conor V; McArdle, John J

    2013-07-01

    Mixture structural equation model with regime switching (MSEM-RS) provides one possible way of representing over-time heterogeneities in dynamic processes by allowing a system to manifest qualitatively or quantitatively distinct change processes conditional on the latent "regime" the system is in at a particular time point. Unlike standard mixture structural equation models such as growth mixture models, MSEM-RS allows individuals to transition between latent classes over time. This class of models, often referred to as regime-switching models in the time series and econometric applications, can be specified as regime-switching mixture structural equation models when the number of repeated measures involved is not large. We illustrate the empirical utility of such models using one special case-a regime-switching bivariate dual change score model in which two growth processes are allowed to manifest regime-dependent coupling relations with one another. The proposed model is illustrated using a set of longitudinal reading and arithmetic performance data from the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 study (ECLS-K; U.S. Department of Education, National Center for Education Statistics, 2010).

  16. Dynamic regime marginal structural mean models for estimation of optimal dynamic treatment regimes, Part II: proofs of results.

    PubMed

    Orellana, Liliana; Rotnitzky, Andrea; Robins, James M

    2010-03-03

    In this companion article to "Dynamic Regime Marginal Structural Mean Models for Estimation of Optimal Dynamic Treatment Regimes, Part I: Main Content" [Orellana, Rotnitzky and Robins (2010), IJB, Vol. 6, Iss. 2, Art. 7] we present (i) proofs of the claims in that paper, (ii) a proposal for the computation of a confidence set for the optimal index when this lies in a finite set, and (iii) an example to aid the interpretation of the positivity assumption.

  17. Dynamic Regime Marginal Structural Mean Models for Estimation of Optimal Dynamic Treatment Regimes, Part II: Proofs of Results*

    PubMed Central

    Orellana, Liliana; Rotnitzky, Andrea; Robins, James M.

    2010-01-01

    In this companion article to “Dynamic Regime Marginal Structural Mean Models for Estimation of Optimal Dynamic Treatment Regimes, Part I: Main Content” [Orellana, Rotnitzky and Robins (2010), IJB, Vol. 6, Iss. 2, Art. 7] we present (i) proofs of the claims in that paper, (ii) a proposal for the computation of a confidence set for the optimal index when this lies in a finite set, and (iii) an example to aid the interpretation of the positivity assumption. PMID:20405047

  18. North Sea wind climate in changing weather regimes

    NASA Astrophysics Data System (ADS)

    Anders, Ivonne; Rockel, Burkhardt

    2015-04-01

    Results from regional climate models (RCMs) are getting more and more important in future wind climate assessment. From RCMs often only the daily wind speed is available, but no information on prevailing wind direction of each day. Weather regime classification can close this gap and models ability of simulating surface wind speed can be analysed in detail. Several objective regime classifications have been investigated to be a sufficient diagnostic tool to evaluate the present wind climate at the German and Dutch coastal area of the North Sea. The classification by Jenkinson and Collison (1977) uses values for mean sea level pressure at 16 locations centered over the North Sea. Beside the predefined 8 prevailed wind directions and the two possibilities on cyclonic or anticyclonic turbulence, 2x8 hybrid weather types can be defined. In this way 27 different regimes can be distinguished including a class of non-classifiable cases. The 27 regimes could be reduced to a number of 11 by allotting the hybrid types to the directional or the centered types. As the classification is carried out for the North Sea based on ERA40 mean sea level pressure the different regimes clearly reflect the mean wind characteristics at the stations. Comparing the wind roses for the individual observations leads to the assumption that the regime classification described before fits the requirements to carry out the regime dependent evaluation of the RCMs with a focus on the German and Dutch coast. Trends in the occurrence of the regimes in the winter period of 1961 to 2000 show an increase of the regimes with Western and Southwestern wind directions and a decrease of wind events from Eastern directions in the North Sea. The trend is dominated by the strong positive phase of the NAO especially in the months January to March starting in the beginning of the 1980s. Due to the applied method ERA40 and the RCMs do not necessarily show the same regime at each day. The agreement among the RCM

  19. AN INDEX TO DETECT EXTERNALLY-FORCED DYNAMIC REGIME SHIFTS IN ECOSYSTEMS

    EPA Science Inventory

    The concept of dynamic regimes, and nonlinear shifts between regimes, has gained acceptance and importance in ecosystem research. Regimes in ecosystems are identified as states with characteristic species abundances and abiotic conditions. Ecosystems are maintained in particular ...

  20. USING FISHER INFORMATION TO DETECT GRADUAL AND RAPID ECOSYSTEM REGIME SHIFTS

    EPA Science Inventory

    As ecosystems experience perturbations of varying regularity and intensity, they may either remain within the state space neighborhood of the current regime, or "flip" into the neighborhood of a regime with different characteristics. Although the possibility of such regime shifts...

  1. Regime shifts in North Sea and Baltic Sea: A comparison

    NASA Astrophysics Data System (ADS)

    Dippner, Joachim W.; Möller, Caroline; Hänninen, Jari

    2012-12-01

    The ICES subdivisions in the North Sea (SD IIIa, SD IVa, and SD IVb) and the subdivisions in the Baltic Sea (SD 29, SD 27/28-2, and SD 25/26) are selected to compare the response in long term monitoring data (1970-2000) with respect to climate regime shifts. A modified AMOEBA model is applied to the data sets to identify the status and development of the North Sea and Baltic Sea system during two recent regime shifts. Biological regime shifts can be identified 1989/1990 in SD IIIa in the North Sea and in SD 25/26 in the Baltic Sea. A synchronous appearance of regime shifts could only be identified in the central and southern Baltic Sea for both regime shifts 1975/76 and 1989/90 where the AMOEBA model indicated a high similarity in ecosystem response. A clear difference was identified in the response of the North Sea and the Baltic Sea. Inter-annual and inter-decadal variability as well as regime shifts are driven in the Baltic Sea by direct atmospheric forcing only. In contrast, the changes in the North Sea are influenced by both the direct atmospheric forcing and the indirect forcing from the changes in North Atlantic. The fact that regime shifts as well as their synchronous appearance can be identified with the AMOEBA model might be of major interest for the management of sustainable use of ecosystem goods and services, the development of ecosystem approach to management and the implementation of the Marine Strategy Framework Directive (MSFD) of the European Union (EU).

  2. Transient response of Salix cuttings to changing water level regimes

    NASA Astrophysics Data System (ADS)

    Gorla, L.; Signarbieux, C.; Turberg, P.; Buttler, A.; Perona, P.

    2015-03-01

    Sustainable water management requires an understanding of the effects of flow regulation on riparian ecomorphological processes. We investigated the transient response of Salix viminalis by examining the effect of water-level regimes on its above-ground and below-ground biomass. Four sets of Salix cuttings, three juveniles (in the first growing season) and one mature (1 year old), were planted and initially grown under the same water-level regime for 1 month. We imposed three different water-level regime treatments representing natural variability, a seasonal trend with no peaks, and minimal flow (characteristic of hydropower) consisting of a constant water level and natural flood peaks. We measured sap flux, stem water potential, photosynthesis, growth parameters, and final root architecture. The mature cuttings were not affected by water table dynamics, but the juveniles displayed causal relationships between the changing water regime, plant growth, and root distribution during a 2 month transient period. For example, a 50% drop in mean sap flux corresponded with a -1.5 Mpa decrease in leaf water potential during the first day after the water regime was changed. In agreement with published field observations, the cuttings concentrated their roots close to the mean water table of the corresponding treatment, allowing survival under altered conditions and resilience to successive stress events. Juvenile development was strongly impacted by the minimum flow regime, leading to more than 60% reduction of both above-ground and below-ground biomass, with respect to the other treatments. Hence, we suggest avoiding minimum flow regimes where Salix restoration is prioritized.

  3. Liquid drop spreading on surfaces: Initial regimes revisited

    NASA Astrophysics Data System (ADS)

    Mitra, Surjyasish; Mitra, Sushanta

    2016-11-01

    Liquid drop spreading on a given surface is fundamental towards technological processes like coating and paints, inkjet printing, surface characterization, etc. Though, the underlying dynamics is well understood, we have revisited this problem through experiments conducted on surfaces kept in air as well as immersed in water. It was found that the two key parameters that dictated the spreading process were drop-surrounding medium viscosity ratio and the characteristic viscous length scale. It was observed that irrespective of the drop liquid and surrounding liquid medium (air and water in this case), spreading always began in a regime dominated by drop viscosity, where the spreading radius scales as r t . However, the prefactor of the scaling observed was different for air (of the order of unity) and under-water (much less than unity). Following this initial regime, a second intermediate regime dominated by drop inertia (typically found for water drops spreading in air) was observed only when the characteristic viscous length scale favored such a transition. In this regime as well, a non-universal prefactor was noted for the scaling law, i.e., r t1/2. In all cases considered, the spreading process terminated in the Tanner's regime where the spreading radius scaled as r t1/10.

  4. Differentially Rotating White Dwarfs I: Regimes of Internal Rotation

    NASA Astrophysics Data System (ADS)

    Ghosh, Pranab; Wheeler, J. Craig

    2017-01-01

    Most viable models of Type Ia supernovae (SNe Ia) require the thermonuclear explosion of a carbon/oxygen white dwarf that has evolved in a binary system. Rotation could be an important aspect of any model for SNe Ia, whether single or double degenerate, with the white dwarf mass at, below, or above the Chandrasekhar limit. Differential rotation is specifically invoked in attempts to account for the apparent excess mass in the super-Chandrasekhar events. Some earlier work has suggested that only uniform rotation is consistent with the expected mechanisms of angular momentum transport in white dwarfs, while others have found pronounced differential rotation. We show that if the baroclinic instability is active in degenerate matter and the effects of magnetic fields are neglected, both nearly uniform rotation and strongly differential rotation are possible. We classify rotation regimes in terms of the Richardson number, Ri. At small values of Ri ≤slant 0.1, we find both the low-viscosity Zahn regime with a nonmonotonic angular velocity profile and a new differential rotation regime for which the viscosity is high and scales linearly with the shear, σ. Employment of Kelvin–Helmholtz viscosity alone yields differential rotation. Large values of Ri ≫ 1 produce a regime of nearly uniform rotation for which the baroclinic viscosity is of intermediate value and scales as {σ }3. We discuss the gap in understanding of the behavior at intermediate values of Ri and how observations may constrain the rotation regimes attained by nature.

  5. Regimes of Internal Rotation in Differentially Rotating White Dwarfs

    NASA Astrophysics Data System (ADS)

    Wheeler, J. Craig; Ghosh, Pranab

    2017-01-01

    Most viable models of Type Ia supernovae (SN Ia) require the thermonuclear explosion of a carbon/oxygen white dwarf that has evolved in a binary system. Rotation could be an important aspect of any model for SN Ia, whether single or double degenerate, with the white dwarf mass at, below, or above the Chandrasekhar limit. Differential rotation is specifically invoked in attempts to account for the apparent excess mass in the super--Chandrasekhar events. Some earlier work has suggested that only uniform rotation is consistent with the expected mechanisms of angular momentum transport in white dwarfs, while others have found pronounced differential rotation. We show that if the baroclinic instability is active in degenerate matter and the effects of magnetic fields are neglected, both nearly-uniform and strongly-differential rotation are possible. We classify rotation regimes in terms of the Richardson number, Ri. At small values of Ri < 0.1, we find both the low-viscosity Zahn regime with a non-monotonic angular velocity profile and a new differential rotation regime for which the viscosity is high and scales linearly with the shear, σ. Employment of Kelvin-Helmholtz viscosity alone yields differential rotation. Large values of Ri >> 1 produce a regime of nearly-uniform rotation for which the baroclinic viscosity is of intermediate value and scales as σ3. We discuss the gap in understanding of the behavior at intermediate values of Ri and how observations may constrain the rotation regimes attained by nature.

  6. THE IMPACT OF THE GLOBAL NUCLEAR SAFETY REGIME IN BRAZIL

    SciTech Connect

    Almeida, C.

    2004-10-06

    A turning point of the world nuclear industry with respect to safety occurred due to the accident at Chernobyl, in 1986. A side from the tragic personal losses and the enormous financial damage, the Chernobyl accident has literally demonstrated that ''a nuclear accident anywhere is an accident everywhere''. The impact was felt immediately by the nuclear industry, with plant cancellations (e.g. Austria), elimination of national programs (e.g. Italy) and general construction delays. However, the reaction of the nuclear industry was equally immediate, which led to the proposal and establishment of a Global Nuclear Safety Regime. This regime is composed of biding international safety conventions, globally accepted safety standard, and a voluntary peer review system. In a previous work, the author has presented in detail the components of this Regime, and briefly discussed its impact in the Brazilian nuclear power organizations, including the Regulatory Body. This work, on the opposite, briefly reviews the Global Nuclear Safety Regime, and concentrates in detail in the discussion of its impact in Brazil, showing how it has produced some changes, and where the peer pressure regime has failed to produce real results.

  7. Early regimes of water capillary flow in slit silica nanochannels.

    PubMed

    Oyarzua, Elton; Walther, Jens H; Mejía, Andrés; Zambrano, Harvey A

    2015-06-14

    Molecular dynamics simulations are conducted to investigate the initial stages of spontaneous imbibition of water in slit silica nanochannels surrounded by air. An analysis is performed for the effects of nanoscopic confinement, initial conditions of liquid uptake and air pressurization on the dynamics of capillary filling. The results indicate that the nanoscale imbibition process is divided into three main flow regimes: an initial regime where the capillary force is balanced only by the inertial drag and characterized by a constant velocity and a plug flow profile. In this regime, the meniscus formation process plays a central role in the imbibition rate. Thereafter, a transitional regime takes place, in which, the force balance has significant contributions from both inertia and viscous friction. Subsequently, a regime wherein viscous forces dominate the capillary force balance is attained. Flow velocity profiles identify the passage from an inviscid flow to a developing Poiseuille flow. Gas density profiles ahead of the capillary front indicate a transient accumulation of air on the advancing meniscus. Furthermore, slower capillary filling rates computed for higher air pressures reveal a significant retarding effect of the gas displaced by the advancing meniscus.

  8. Similarity in Neuronal Firing Regimes across Mammalian Species

    PubMed Central

    Mochizuki, Yasuhiro; Onaga, Tomokatsu; Shimazaki, Hideaki; Shimokawa, Takeaki; Tsubo, Yasuhiro; Kimura, Rie; Saiki, Akiko; Sakai, Yutaka; Isomura, Yoshikazu; Fujisawa, Shigeyoshi; Shibata, Ken-ichi; Hirai, Daichi; Furuta, Takahiro; Kaneko, Takeshi; Takahashi, Susumu; Nakazono, Tomoaki; Ishino, Seiya; Sakurai, Yoshio; Kitsukawa, Takashi; Lee, Jong Won; Lee, Hyunjung; Jung, Min Whan; Babul, Cecilia; Maldonado, Pedro E.; Takahashi, Kazutaka; Arce-McShane, Fritzie I.; Ross, Callum F.; Sessle, Barry J.; Hatsopoulos, Nicholas G.; Brochier, Thomas; Riehle, Alexa; Chorley, Paul; Grün, Sonja; Nishijo, Hisao; Ichihara-Takeda, Satoe; Funahashi, Shintaro; Shima, Keisetsu; Mushiake, Hajime; Yamane, Yukako; Tamura, Hiroshi; Fujita, Ichiro; Inaba, Naoko; Kawano, Kenji; Kurkin, Sergei; Fukushima, Kikuro; Kurata, Kiyoshi; Taira, Masato; Tsutsui, Ken-Ichiro; Ogawa, Tadashi; Komatsu, Hidehiko; Koida, Kowa; Toyama, Keisuke; Richmond, Barry J.

    2016-01-01

    The architectonic subdivisions of the brain are believed to be functional modules, each processing parts of global functions. Previously, we showed that neurons in different regions operate in different firing regimes in monkeys. It is possible that firing regimes reflect differences in underlying information processing, and consequently the firing regimes in homologous regions across animal species might be similar. We analyzed neuronal spike trains recorded from behaving mice, rats, cats, and monkeys. The firing regularity differed systematically, with differences across regions in one species being greater than the differences in similar areas across species. Neuronal firing was consistently most regular in motor areas, nearly random in visual and prefrontal/medial prefrontal cortical areas, and bursting in the hippocampus in all animals examined. This suggests that firing regularity (or irregularity) plays a key role in neural computation in each functional subdivision, depending on the types of information being carried. SIGNIFICANCE STATEMENT By analyzing neuronal spike trains recorded from mice, rats, cats, and monkeys, we found that different brain regions have intrinsically different firing regimes that are more similar in homologous areas across species than across areas in one species. Because different regions in the brain are specialized for different functions, the present finding suggests that the different activity regimes of neurons are important for supporting different functions, so that appropriate neuronal codes can be used for different modalities. PMID:27225764

  9. Weather Regimes: The Challenge in Extended-Range Forecasting

    NASA Astrophysics Data System (ADS)

    Reinhold, Brian

    1987-01-01

    A hypothesis to explain the low-frequency (10- to 90-day) variance of the mid-latitude atmosphere is presented. In this hypothesis it is proposed that the planetary-scale waves forced by topography or other zonal inhomogeneities and the day-to-day weather disturbances (synoptic scales) influence each other to generate weather regimes. These quasi-stable flow configurations are responsible for short-range climate anomalies such as droughts, heat waves, deep freezes, and excessive precipitation, as the weather-producing disturbances are organized into storm tracks. Onset and disruption of the weather regimes may be induced by the anomalous development of perhaps a single cyclonic disturbance, which can throw the quasi equilibrium out of balance. Thus, rapid changes in flow regimes can occur almost at random. The development and transition of weather regimes may then be purely internal (that is, depending only upon the properties of the fluid motions themselves) to the atmospheric dynamics. This internal quality suggests that the chaotic, abrupt short-range climatic behavior of the mid-latitudes is a natural behavior of the system that requires no assistance from the outside. The weather regime concept presents a different view of the extended-range atmospheric behavior than the stimulus-response model, such as the atmospheric response to the El Nino.

  10. Regime switching model for financial data: Empirical risk analysis

    NASA Astrophysics Data System (ADS)

    Salhi, Khaled; Deaconu, Madalina; Lejay, Antoine; Champagnat, Nicolas; Navet, Nicolas

    2016-11-01

    This paper constructs a regime switching model for the univariate Value-at-Risk estimation. Extreme value theory (EVT) and hidden Markov models (HMM) are combined to estimate a hybrid model that takes volatility clustering into account. In the first stage, HMM is used to classify data in crisis and steady periods, while in the second stage, EVT is applied to the previously classified data to rub out the delay between regime switching and their detection. This new model is applied to prices of numerous stocks exchanged on NYSE Euronext Paris over the period 2001-2011. We focus on daily returns for which calibration has to be done on a small dataset. The relative performance of the regime switching model is benchmarked against other well-known modeling techniques, such as stable, power laws and GARCH models. The empirical results show that the regime switching model increases predictive performance of financial forecasting according to the number of violations and tail-loss tests. This suggests that the regime switching model is a robust forecasting variant of power laws model while remaining practical to implement the VaR measurement.

  11. Nonlinear regime-switching state-space (RSSS) models.

    PubMed

    Chow, Sy-Miin; Zhang, Guangjian

    2013-10-01

    Nonlinear dynamic factor analysis models extend standard linear dynamic factor analysis models by allowing time series processes to be nonlinear at the latent level (e.g., involving interaction between two latent processes). In practice, it is often of interest to identify the phases--namely, latent "regimes" or classes--during which a system is characterized by distinctly different dynamics. We propose a new class of models, termed nonlinear regime-switching state-space (RSSS) models, which subsumes regime-switching nonlinear dynamic factor analysis models as a special case. In nonlinear RSSS models, the change processes within regimes, represented using a state-space model, are allowed to be nonlinear. An estimation procedure obtained by combining the extended Kalman filter and the Kim filter is proposed as a way to estimate nonlinear RSSS models. We illustrate the utility of nonlinear RSSS models by fitting a nonlinear dynamic factor analysis model with regime-specific cross-regression parameters to a set of experience sampling affect data. The parallels between nonlinear RSSS models and other well-known discrete change models in the literature are discussed briefly.

  12. Soil magnetic susceptibility reflects soil moisture regimes and the adaptability of tree species to these regimes

    USGS Publications Warehouse

    Wang, J.-S.; Grimley, D.A.; Xu, C.; Dawson, J.O.

    2008-01-01

    Flooded, saturated or poorly drained soils are frequently anaerobic, leading to dissolution of the strongly magnetic minerals, magnetite and maghemite, and a corresponding decrease in soil magnetic susceptibility (MS). In this study of five temperate deciduous forests in east-central Illinois, USA, mean surface soil MS was significantly higher adjacent to upland tree species (31 ?? 10-5 SI) than adjacent to floodplain or lowland tree species (17 ?? 10-5 SI), when comparing regional soils with similar parent material of loessal silt. Although the sites differ in average soil MS for each tree species, the relative order of soil MS means for associated tree species at different locations is similar. Lowland tree species, Celtis occidentalis L., Ulmus americana L., Acer saccharinum L., Carya laciniosa (Michx. f.) Loud., and Fraxinus pennsylvanica Marsh. were associated with the lowest measured soil MS mean values overall and at each site. Tree species' flood tolerance rankings increased significantly, as soil MS values declined, the published rankings having significant correlations with soil MS values for the same species groups. The three published classifications of tree species' flood tolerance were significantly correlated with associated soil MS values at all sites, but most strongly at Allerton Park, the site with the widest range of soil drainage classes and MS values. Using soil MS measurements in forests with soil parent material containing similar initial levels of strongly magnetic minerals can provide a simple, rapid and quantitative method to classify soils according to hydric regimes, including dry conditions, and associated plant composition. Soil MS values thus have the capacity to quantify the continuum of hydric tolerances of tree species and guide tree species selection for reforestation. ?? 2007 Elsevier B.V. All rights reserved.

  13. 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.

  14. The history of research into improved confinement regimes

    NASA Astrophysics Data System (ADS)

    Wagner, F.

    2017-01-01

    Increasing the pressure by additional heating of magnetically confined plasmas had the consequence that turbulent processes became more violent and plasma confinement degraded. Since this experience from the early 1980ies, fusion research was dominated by the search for confinement regimes with improved properties. It was a gratifying experience that toroidally confined plasmas are able to self-organise in such a way that turbulence diminishes, resulting in a confinement with good prospects to reach the objectives of fusion R&D. The understanding of improved confinement regimes revolutionized the understanding of turbulent transport in high-temperature plasmas. In this paper the story of research into improved confinement regimes will be narrated starting with 1980.

  15. Suspended-sediment concentration regimes in Tennessee biological reference streams

    USGS Publications Warehouse

    Diehl, Timothy H.; Wolfe, William J.

    2010-01-01

    Suspended-sediment-concentration (SSC) regimes of five biological reference streams in Tennessee were characterized from 15-minute SSC records spanning 1 to 4 water years (October 1 through September 30) between 2004 and 2008. These streams represent least disturbed conditions for their respective ecoregions and have exceptional biodiversity in terms of fish or aquatic invertebrates. SSC regimes in streams, when plotted in terms of duration above a given SSC at a given annual frequency such as the annual maximum or the annual tenth longest duration, can be compared directly to published biological impairment thresholds derived from experimental trials. Based on such comparison, the SSC regimes of all five reference streams reached published impairment thresholds at least 10 times per water year for all years of record. The results suggest that the published impairment thresholds are not directly applicable to streams in Tennessee and, by extension, the southeastern United States.

  16. Two-phase flow regime map predictions under microgravity

    SciTech Connect

    Karri, S.B.R.; Mathur, V.K.

    1988-01-01

    In this paper, the widely used models of Taitel-Dukler and Weisman et al. are extrapolated to microgravity levels to compare predicted flow pattern boundaries for horizontal and vertical flows. Efforts have been made to analyze how the two-phase flow models available in the literature predict flow regime transitions in microgravity. The models of Taitel-Dukler and Weisman et al. have been found to be more suitable for extrapolation to a wide range of system parameters than the other two-phase flow regime maps available in the literature. The original criteria for all cases are used to predict the transition lines, except for the transition to dispersed flow regime in case of the Weisman model for horizontal flow. The constant 0.97 on the righthand side of this correlation should be two times that value, i.e., 1.94, in order to match this transition line in their original paper.

  17. Adaptive management of ecosystem services across different land use regimes.

    PubMed

    Ruhl, J B

    2016-12-01

    Using adaptive management to manage desired flows of ecosystem services may seem on the surface to be a good fit, but many social, economic, environmental, legal, and political factors influence how good a fit. One strongly influential factor is the land use regime within which the profile of ecosystem services is being managed. Shaped largely by legal mandates, market forces, and social and cultural practices, different land use regimes present different opportunities for and constraints on goals for ecosystem services and pose different decision making environments. Even where all other conditions appear amenable to using adaptive management, therefore, it is essential to consider the constraining (or liberating) effects of different land use regimes when deciding whether to adopt adaptive management to achieve those goals and, if so, how to implement it.

  18. Hydrodynamic interaction of swimming organisms in an inertial regime

    NASA Astrophysics Data System (ADS)

    Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M.

    2016-11-01

    We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re˜O (0.1 -100 ) , where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.

  19. Supercurrent in the quantum Hall regime, part II

    NASA Astrophysics Data System (ADS)

    Amet, Francois; Ke, Chung Ting; Borzenets, Ivan; Wang, Jiyingmei; Watanabe, Kenji; Taniguchi, Takashi; Deacon, Russel; Yamamoto, Michihisa; Bomze, Yuriy; Tarucha, Seigo; Finkelstein, Gleb

    A novel promising route for creating topological states and excitations is to combine superconductivity and the quantum Hall effect. Despite this potential, signatures of superconductivity in the quantum Hall regime remain scarce, and a superconducting current through a Landau-quantized two-dimensional electron gas has so far eluded experimental observation. High-mobility graphene/BN heterostructures exhibit the quantum Hall effect at relatively low field and are therefore particularly suitable to study the fate of the Josephson effect in that regime. Here, we report the observation of a superconducting current through graphene at fields as high as 2 Tesla. In that regime, the normal-state resistance is quantized but pockets of superconductivity still persist at small current bias. We will describe their bias and temperature dependence. Magnetic field interference patterns in the supercurrent inform on possible mechanisms mediating this supercurrent.

  20. Theoretical study of the crossover into hydrodynamic regime in graphene

    NASA Astrophysics Data System (ADS)

    Ho, Derek; Yudhistira, Indra; Hu, Ben Yu-Kuang; Adam, Shaffique

    Experiments on graphene have recently succeeded in entering the hydrodynamic regime, as demonstrated by successful observations of strong violation of Wiedemann-Franz law, the Gurzhi effect and electronic Poiseuille flow. It is known that electronic systems enter the hydrodynamic regime when electron-electron scattering dominates over electron-impurity and electron-phonon scattering. However, a quantitative study of this transition from the Fermi liquid to hydrodynamic regime is still lacking. In view of this, we quantitatively analyze the electron-electron, electron-impurity and electron-phonon scattering rates as a function of temperature, charge doping and disorder (charge puddle) strength. This yields a quantitative understanding of the onset of hydrodynamic electronic behavior in graphene samples. This work is supported by the National Research Foundation of Singapore under its Fellowship program (NRF-NRFF2012-01) and by the Singapore Ministry of Education and Yale-NUS College through Grant No. R-607-265-01312.

  1. Living dangerously on borrowed time during slow, unrecognized regime shifts.

    PubMed

    Hughes, Terry P; Linares, Cristina; Dakos, Vasilis; van de Leemput, Ingrid A; van Nes, Egbert H

    2013-03-01

    Regime shifts from one ecological state to another are often portrayed as sudden, dramatic, and difficult to reverse. Yet many regime shifts unfold slowly and imperceptibly after a tipping point has been exceeded, especially at regional and global scales. These long, smooth transitions between equilibrium states are easy to miss, ignore, or deny, confounding management and governance. However, slow responses by ecosystems after transgressing a dangerous threshold also affords borrowed time - a window of opportunity to return to safer conditions before the new state eventually locks in and equilibrates. In this context, the most important challenge is a social one: convincing enough people to confront business-as-usual before time runs out to reverse unwanted regime shifts even after they have already begun.

  2. Hydrodynamic interaction of swimming organisms in an inertial regime.

    PubMed

    Li, Gaojin; Ostace, Anca; Ardekani, Arezoo M

    2016-11-01

    We numerically investigate the hydrodynamic interaction of swimming organisms at small to intermediate Reynolds number regimes, i.e., Re∼O(0.1-100), where inertial effects are important. The hydrodynamic interaction of swimming organisms in this regime is significantly different from the Stokes regime for microorganisms, as well as the high Reynolds number flows for fish and birds, which involves strong flow separation and detached vortex structures. Using an archetypal swimmer model, called a "squirmer," we find that the inertial effects change the contact time and dispersion dynamics of a pair of pusher swimmers, and trigger hydrodynamic attraction for two pullers. These results are potentially important in investigating predator-prey interactions, sexual reproduction, and the encounter rate of marine organisms such as copepods, ctenophora, and larvae.

  3. The Self-energy Of Growing Aggregates: "Strength Regime"

    NASA Astrophysics Data System (ADS)

    Guimaraes, Ana H. F.; Spahn, F.; Seiss, M.; Brilliantov, N. V.

    2009-09-01

    The vivid appearance of the outer regions of Saturn's rings points to a balance of ongoing fragmentation and coagulation processes. This idea finds support especially in the F-ring, where collisional processes occur on an almost daily basis stirred by perturbations of the satellites Prometheus and Pandora, and in addition due the presence of putative moonlets. In order to quantify this balance in a kinetic theory we propose to calculate the resistivity of small agglomerates ("dynamic ephemeral bodies") against rupture due collisional processes and tidal pull. Earlies studies have shown that the resistivity of an aggregate is divided into two phases: "strength regime" and "gravitational regime". Early in their formation, small agglomerates are supported basically by their "glue" between the particles (adhesion) - "strength regime". For larger agglomerates the "gravitational regime" takes over provided their sizes to be bigger than a threshold in which the self-gravitational energy exceeds the adhesive binding energy, in this case the cluster's constituents are held together gravitationally. We calculated the self-energy caused by adhesion and gravity of ring's aggregates which has been considered as the threshold of impact energy or of tidal work to disrupt the agglomerate. Using a Ballistic Particle Cluster Aggregate Model (BPCA) we varied the densities of the aggregates and the size distribution of their constituents (1-10cm), calculated their self-energy and identified the transition between the "strength" to "gravitational regime". The transition between the regimes occurs at house-size aggregates (diameter of approximately 20m), a fact, that fits to the cut-off on the dense rings' main population (cm - 5m in size). Acknowledgments: A.H.F.G. thanks Dr. E. Vieira-Neto for the discussions, and also the DAAD and Uni-Potsdam for the financial support of this project.

  4. The Isolated Bubble Regime in Pool Nucleate Boiling

    NASA Technical Reports Server (NTRS)

    Buyevich, Y. A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    We consider an isolated bubble boiling regime in which vapour bubbles are intermittently produced at a prearranged set of nucleation site on an upward facing overheated wall plane. In this boiling regime, the bubbles depart from the wall and move as separate entities. Except in the matter of rise velocity, the bubbles do not interfere and are independent of one another. However, the rise velocity is dependent on bubble volume concentration in the bulk. Heat transfer properties specific to this regime cannot be described without bubble detachment size, and we apply our previously developed dynamic theory of vapour bubble growth and detachment to determine this size. Bubble growth is presumed to be thermally controlled. Two limiting cases of bubble evolution are considered: the one in which buoyancy prevails in promoting bubble detachment and the one in which surface tension prevails. We prove termination of the isolated regime of pool nucleate boiling to result from one of the four possible causes, depending on relevant parameters values. The first cause consists in the fact that the upward flow of rising bubbles hampers the downward liquid flow, and under certain conditions, prevents the liquid from coming to the wall in an amount that would be sufficient to compensate for vapour removal from the wall. The second cause is due to the lateral coalescence of growing bubbles that are attached to their corresponding nucleation sites, with ensuing generation of larger bubbles and extended vapour patches near the wall. The other two causes involve longitudinal coalescence either 1) immediately in the wall vicinity, accompanied by the establishment of the multiple bubble boiling regime, or 2) in the bulk, with the formation of vapour columns. The longitudinal coalescence in the bulk is shown to be the most important cause. The critical wall temperature and the heat flux density associated with isolated bubble regime termination are found to be functions of the physical and

  5. The legacy of large regime shifts in shallow lakes.

    PubMed

    Ramstack Hobbs, Joy M; Hobbs, William O; Edlund, Mark B; Zimmer, Kyle D; Theissen, Kevin M; Hoidal, Natalie; Domine, Leah M; Hanson, Mark A; Herwig, Brian R; Cotner, James B

    2016-12-01

    Ecological shifts in shallow lakes from clear-water macrophyte-dominated to turbid-water phytoplankton-dominated are generally thought of as rapid short-term transitions. Diatom remains in sediment records from shallow lakes in the Prairie Pothole Region of North America provide new evidence that the long-term ecological stability of these lakes is defined by the legacy of large regime shifts. We examine the modern and historical stability of 11 shallow lakes. Currently, four of the lakes are in a clear-water state, three are consistently turbid-water, and four have been observed to change state from year to year (transitional). Lake sediment records spanning the past 150-200 yr suggest that (1) the diatom assemblage is characteristic of either clear or turbid lakes, (2) prior to significant landscape alteration, all of the lakes existed in a regime of a stable clear-water state, (3) lakes that are currently classified as turbid or transitional have experienced one strong regime shift over the past 150-200 yr and have since remained in a regime where turbid-water predominates, and (4) top-down impacts to the lake food-web from fish introductions appear to be the dominant driver of strong regime shifts and not increased nutrient availability. Based on our findings we demonstrate a method that could be used by lake managers to identify lakes that have an ecological history close to the clear-turbid regime threshold; such lakes might more easily be returned to a clear-water state through biomanipulation. The unfortunate reality is that many of these lakes are now part of a managed landscape and will likely require continued intervention.

  6. Terahertz Quantum Plasmonics of Nanoslot Antennas in Nonlinear Regime.

    PubMed

    Kim, Joon-Yeon; Kang, Bong Joo; Park, Joohyun; Bahk, Young-Mi; Kim, Won Tae; Rhie, Jiyeah; Jeon, Hyeongtag; Rotermund, Fabian; Kim, Dai-Sik

    2015-10-14

    Quantum tunneling in plasmonic nanostructures has presented an interesting aspect of incorporating quantum mechanics into classical optics. However, the study has been limited to the subnanometer gap regime. Here, we newly extend quantum plasmonics to gap widths well over 1 nm by taking advantage of the low-frequency terahertz regime. Enhanced electric fields of up to 5 V/nm induce tunneling of electrons in different arrays of ring-shaped nanoslot antennas of gap widths from 1.5 to 10 nm, which lead to a significant nonlinear transmission decrease. These observations are consistent with theoretical calculations considering terahertz-funneling-induced electron tunneling across the gap.

  7. Thermal regime of ventilation shafts and its regulation

    SciTech Connect

    Petrov, N.N.; Timoshenko, N.I.

    1986-03-01

    This paper evaluates the regime of air flow through a ventilation shaft and the nondimensional heat-exchange criteria. It is shown that the air temperature in the shaft is affected more by the walls than by the reinforcement structure metal and that the heat released by internal combustion engines could be an alternative source for heating the air. High bypass aircraft turbojet engines decommissioned after their maximum surface life on planes could be used for this purpose. The study of the thermal regime in the shaft in the case of a sudden change of air temperature such as occurs during ventilation reversals has established the requirements for air heating equipment.

  8. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Technical Reports Server (NTRS)

    Oglesby, Robert; Arnold, James E. (Technical Monitor); Hoffman, Forrest; Hargrove, W. W.; Erickson, D.

    2002-01-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and time

  9. Geothermal regimes at Clearlake California: A preliminary review

    SciTech Connect

    Burns, K.L.; Potter, R.M.; Zyvoloski, G.

    1992-08-01

    Three distinct geothermal regimes are inferred in the vicinity of the city of Clearlake, California. The first is a conductive heat flow regime, the second is a fault-controlled hot spring flow of ``magmatic`` fluids, and the third is a resurgent flow of meteoric warm water. The conductive heat flow results in flat, horizontal isotherms. The hot spring generates a localized spike in the isotherms. The advective disturbance carries heat laterally to a fault-line resurgence, lowering the apparent heat flow at the surface.

  10. Champagne experiences various rhythmical bubbling regimes in a flute.

    PubMed

    Liger-Belair, Gérard; Tufaile, Alberto; Jeandet, Philippe; Sartorelli, José-Carlos

    2006-09-20

    Bubble trains are seen rising gracefully from a few points on the glass wall (called nucleation sites) whenever champagne is poured into a glass. As time passes during the gas-discharging process, the careful observation of some given bubble columns reveals that the interbubble distance may change suddenly, thus revealing different rhythmical bubbling regimes. Here, it is reported that the transitions between the different bubbling regimes of some nucleation sites during gas discharging is a process which may be ruled by a strong interaction between tiny gas pockets trapped inside the nucleation site and/or also by an interaction between the tiny bubbles just blown from the nucleation site.

  11. Strong and moderate nonlinear El Niño regimes

    NASA Astrophysics Data System (ADS)

    Takahashi, Ken; Dewitte, Boris

    2016-03-01

    It has been previously proposed that two El Niño (EN) regimes, strong and moderate, exist but the historical observational record is too short to establish this conclusively. Here, 1200 years of simulations with the GFDL CM2.1 model allowed us to demonstrate their existence in this model and, by showing that the relevant dynamics are also evident in observations, we present a stronger case for their existence in nature. In CM2.1, the robust bimodal probability distribution of equatorial Pacific sea surface temperature (SST) indices during EN peaks provides evidence for the existence of the regimes, which is also supported by a cluster analysis of these same indices. The observations agree with this distribution, with the EN of 1982-1983 and 1997-1998 corresponding to the strong EN regime and all the other observed EN to the moderate regime. The temporal evolution of various indices during the observed strong EN agrees very well with the events in CM2.1, providing further validation of this model as a proxy for nature. The two regimes differ strongly in the magnitude of the eastern Pacific warming but not much in the central Pacific. Observations and model agree in the existence of a finite positive threshold in the SST anomaly above which the zonal wind response to warming is strongly enhanced. Such nonlinearity in the Bjerknes feedback, which increases the growth rate of EN events if they reach sufficiently large amplitude, is very likely the essential mechanism that gives rise to the existence of the two EN regimes. Oceanic nonlinear advection does not appear essential for the onset of strong EN. The threshold nonlinearity could make the EN regimes very sensitive to stochastic forcing. Observations and model agree that the westerly wind stress anomaly in the central equatorial Pacific in late boreal summer has a substantial role determining the EN regime in the following winter and it is suggested that a stochastic component at this time was key for the

  12. Ocean Wave Energy Regimes of the Circumpolar Coastal Zones

    NASA Astrophysics Data System (ADS)

    Atkinson, D. E.

    2004-12-01

    Ocean wave activity is a major enviromental forcing agent of the ice-rich sediments that comprise large sections of the arctic coastal margins. While it is instructive to possess information about the wind regimes in these regions, direct application to geomorphological and engineering needs requires knowledge of the resultant wave-energy regimes. Wave energy information has been calculated at the regional scale using adjusted reanalysis model windfield data. Calculations at this scale are not designed to account for local-scale coastline/bathymetric irregularities and variability. Results will be presented for the circumpolar zones specified by the Arctic Coastal Dynamics Project.

  13. Using Clustering to Establish Climate Regimes from PCM Output

    NASA Astrophysics Data System (ADS)

    Hoffman, F.; Oglesby, R.; Hargrove, W. W.; Erickson, D.

    2002-12-01

    A multivariate statistical clustering technique--based on the k-means algorithm of Hartigan--has been used to extract patterns of climatological significance from 200 years of general circulation model (GCM) output. Originally developed and implemented on a Beowulf-style parallel computer constructed by Hoffman and Hargrove from surplus commodity desktop PCs, the high performance parallel clustering algorithm was previously applied to the derivation of ecoregions from map stacks of 9 and 25 geophysical conditions or variables for the conterminous U.S. at a resolution of 1 sq km. Now applied both across space and through time, the clustering technique yields temporally-varying climate regimes predicted by transient runs of the Parallel Climate Model (PCM). Using a business-as-usual (BAU) scenario and clustering four fields of significance to the global water cycle (surface temperature, precipitation, soil moisture, and snow depth) from 1871 through 2098, the authors' analysis shows an increase in spatial area occupied by the cluster or climate regime which typifies desert regions (i.e., an increase in desertification) and a decrease in the spatial area occupied by the climate regime typifying winter-time high latitude perma-frost regions. The patterns of cluster changes have been analyzed to understand the predicted variability in the water cycle on global and continental scales. In addition, representative climate regimes were determined by taking three 10-year averages of the fields 100 years apart for northern hemisphere winter (December, January, and February) and summer (June, July, and August). The result is global maps of typical seasonal climate regimes for 100 years in the past, for the present, and for 100 years into the future. Using three-dimensional data or phase space representations of these climate regimes (i.e., the cluster centroids), the authors demonstrate the portion of this phase space occupied by the land surface at all points in space and

  14. Orbital magnetoconductance in the variable-range-hopping regime

    NASA Technical Reports Server (NTRS)

    Sivan, U.; Entin-Wohlman, O.; Imry, Y.

    1988-01-01

    The orbital magnetoconductance (MC) in the variable-range-hopping (VRH) regime is evaluated by use of a model which approximately takes into account the interference among random paths in the hopping process. Instead of logarithmic averaging the MC is obtained by the critical percolating resistor method. The small-field MC is quadratic in H; it is positive deep in the VRH regime and changes sign when the zero-field conductivity is high enough. This behavior (except for the sign change) and the relevant magnetic field scale are in agreement with recent experiments. The calculated MC is always positive for strong fields and is predicted to saturate at sufficiently large fields.

  15. Improving Mesoscale Prediction of Shallow Convection and Cloud Regime Transitions in NRL COAMPS

    DTIC Science & Technology

    2013-09-30

    continuum of cloud regimes from stratocumulus to trade cumulus , with particular emphasis on cloud regime transitions. OBJECTIVES Accurate prediction...of cloud -topped marine boundary layers regional forecast models is currently hindered the ability of the models to represent shallow cumulus ... cloud regime transitions, exist in between stratocumulus and trade cumulus . These cloud regimes are typically characterized by one of the following

  16. Civic Capacity in Educational Reform Efforts: Emerging and Established Regimes in Rust Belt Cities

    ERIC Educational Resources Information Center

    Mitra, Dana L.; Frick, William C.

    2011-01-01

    Using urban regime theory, the article examines two Rust Belt cities that tried to break the cycle of social reproduction in their communities by reforming their schools. The article contributes to the development of urban regime theory by comparing an "emerging" regime to an "established" regime. The comparison highlights the interdependent…

  17. Production regimes for Self-Interacting Dark Matter

    SciTech Connect

    Bernal, Nicolás; Chu, Xiaoyong; Garcia-Cely, Camilo; Hambye, Thomas; Zaldivar, Bryan E-mail: xchu@ictp.it E-mail: thambye@ulb.ac.be

    2016-03-01

    In the context of Self-Interacting Dark Matter as a solution for the small-scale structure problems, we consider the possibility that Dark Matter could have been produced without being in thermal equilibrium with the Standard Model bath. We discuss one by one the following various dark matter production regimes of this kind: freeze-in, reannihilation and dark freeze-out. We exemplify how these mechanisms work in the context of the particularly simple Hidden Vector Dark Matter model. In contrast to scenarios where there is thermal equilibrium with the Standard Model bath, we find two regimes which can easily satisfy all the laboratory and cosmological constraints. These are dark freeze-out with 3-to-2 annihilations and freeze-in via a light mediator. In the first regime, different temperatures in the visible and the Dark Matter sectors allow us to avoid the constraints coming from cosmic structure formation as well as the use of non-perturbative couplings to reproduce the observed relic density. For the second regime, different couplings are responsible for Dark Matter relic density and self-interactions, permitting to surpass BBN, X-ray, CMB and direct detection constraints.

  18. 22 CFR 120.29 - Missile Technology Control Regime.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 22 Foreign Relations 1 2014-04-01 2014-04-01 false Missile Technology Control Regime. 120.29 Section 120.29 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND... amendments thereto. (c) List of all items on the MTCR Annex. Section 71(a) of the Arms Export Control Act...

  19. 22 CFR 120.29 - Missile Technology Control Regime.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 22 Foreign Relations 1 2013-04-01 2013-04-01 false Missile Technology Control Regime. 120.29 Section 120.29 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND... thereto; (c) List of all items on the MTCR Annex. Section 71(a) of the Arms Export Control Act (22...

  20. 22 CFR 120.29 - Missile Technology Control Regime.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 22 Foreign Relations 1 2012-04-01 2012-04-01 false Missile Technology Control Regime. 120.29 Section 120.29 Foreign Relations DEPARTMENT OF STATE INTERNATIONAL TRAFFIC IN ARMS REGULATIONS PURPOSE AND... thereto; (c) List of all items on the MTCR Annex. Section 71(a) of the Arms Export Control Act (22...

  1. Dynamic Financial Constraints: Distinguishing Mechanism Design from Exogenously Incomplete Regimes*

    PubMed Central

    Karaivanov, Alexander; Townsend, Robert M.

    2014-01-01

    We formulate and solve a range of dynamic models of constrained credit/insurance that allow for moral hazard and limited commitment. We compare them to full insurance and exogenously incomplete financial regimes (autarky, saving only, borrowing and lending in a single asset). We develop computational methods based on mechanism design, linear programming, and maximum likelihood to estimate, compare, and statistically test these alternative dynamic models with financial/information constraints. Our methods can use both cross-sectional and panel data and allow for measurement error and unobserved heterogeneity. We estimate the models using data on Thai households running small businesses from two separate samples. We find that in the rural sample, the exogenously incomplete saving only and borrowing regimes provide the best fit using data on consumption, business assets, investment, and income. Family and other networks help consumption smoothing there, as in a moral hazard constrained regime. In contrast, in urban areas, we find mechanism design financial/information regimes that are decidedly less constrained, with the moral hazard model fitting best combined business and consumption data. We perform numerous robustness checks in both the Thai data and in Monte Carlo simulations and compare our maximum likelihood criterion with results from other metrics and data not used in the estimation. A prototypical counterfactual policy evaluation exercise using the estimation results is also featured. PMID:25246710

  2. Optimal ranking regime analysis of TreeFlow dendrohydrological reconstructions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Optimal Ranking Regime (ORR) method was used to identify 6-100 year time windows containing significant ranking sequences in 55 western U.S. streamflow reconstructions, and reconstructions of the level of the Great Salt Lake and San Francisco Bay salinity during 1500-2007. The method’s ability t...

  3. Welfare Attitudes and Social Expenditure: Do Regimes Shape Public Opinion?

    ERIC Educational Resources Information Center

    Jakobsen, Tor Georg

    2011-01-01

    This article examines the link between regime types, social expenditure, and welfare attitudes. By employing data on 19 countries taken from the World Values Survey, the main aim is to see to what degree the institutions of a country affect the attitudes of its citizens. According to Esping-Andersen ("The three worlds of welfare…

  4. Towards an Orderly Exit Regime in English Higher Education

    ERIC Educational Resources Information Center

    Fisher, Andrew

    2016-01-01

    In a competitive market, the exit of those suppliers who cannot offer an attractive product at an attractive price is seen as desirable. However, the consequences for consumers when their own supplier leaves the market in an unplanned or disorderly way may be undesirable. Exit regimes exist in regulated markets to ensure that consumers are not…

  5. ECOLOGICALLY-RELEVANT QUANTIFICATION OF STREAMFLOW REGIMES IN WESTERN STREAMS

    EPA Science Inventory

    This report describes the rationale for and application of a protocol for estimation of ecologically-relevant streamflow metrics that quantify streamflow regime for ungaged sites subject to a range of human impact. The analysis presented here is focused on sites sampled by the U....

  6. Welfare Regimes and Educational Inequality: A Cross-National Exploration

    ERIC Educational Resources Information Center

    Peter, Tracey; Edgerton, Jason D.; Roberts, Lance W.

    2010-01-01

    Research on welfare state regimes and research on educational policy share a common concern for the reduction of social inequality. On one hand, welfare state research is typically designed within a comparative approach where scholars investigate similarities and differences in social institutions across selected countries. On the other hand, the…

  7. Two regimes in the regularity of sunspot number

    SciTech Connect

    Shapoval, A.; Shnirman, M.

    2013-12-20

    Sunspot numbers WN display quasi-periodical variations that undergo regime changes. These irregularities could indicate a chaotic system and be measured by Lyapunov exponents. We define a functional λ (an 'irregularity index') that is close to the (maximal) Lyapunov exponent for dynamical systems and well defined for series with a random component: this allows one to work with sunspot numbers. We compute λ for the daily WN from 1850 to 2012 within 4 yr sliding windows: λ exhibit sharp maxima at solar minima and secondary maxima at solar maxima. This pattern is reflected in the ratio R of the amplitudes of the main versus secondary peaks. Two regimes have alternated in the past 150 yr, R1 from 1850 to 1915 (large λ and R values) and R2 from 1935 to 2005 (shrinking difference between main and secondary maxima, R values between 1 and 2). We build an autoregressive model consisting of Poisson noise plus an 11 yr cycle and compute its irregularity index. The transition from R1 to R2 can be reproduced by strengthening the autocorrelation a of the model series. The features of the two regimes are stable for model and WN with respect to embedding dimension and delay. Near the time of the last solar minimum (∼2008), the irregularity index exhibits a peak similar to the peaks observed before 1915. This might signal a regime change back from R2 to R1 and the onset of a significant decrease of solar activity.

  8. Connectivity, regime shifts and the resilience of coral reefs

    NASA Astrophysics Data System (ADS)

    Elmhirst, Toby; Connolly, Sean R.; Hughes, Terry P.

    2009-12-01

    Connectivity of larvae among metapopulations in open marine systems can be a double-edged sword, allowing for the colonization and replenishment of both desirable and undesirable elements of interacting species-rich assemblages. This article studies the effect of recruitment by coral and macroalgae on the resilience of grazed reef ecosystems. In particular, we focus on how larval connectivity affects regime shifts between alternative assemblages that are dominated either by corals or by macroalgae. Using a model with bistability dynamics, we show that recruitment of coral larvae erodes the resilience of a macroalgae-dominated ecosystem when grazing is high, but has negligible effect when grazing is low. Conversely, recruitment by macroalgae erodes the resilience of a coral-dominated ecosystem when grazing is low, leading to a regime shift to macroalgae. Thus, spillover of coral recruits from highly protected areas will not restore coral cover or prevent flips to macroalgae in the surrounding seascape if grazing levels in these areas are depleted, but may be pivotal for re-building coral populations if grazing is high. Fishing restrictions and the re-introduction of herbivores should therefore be a prime conservation objective for preventing undesirable regime shifts. Connectivity by some components of coral reef assemblages (e.g., macroalgae, pathogens, crown-of-thorns starfish) may be detrimental to sustaining reefs, especially where overfishing and other drivers have eroded their resilience, making them more vulnerable to a regime shift.

  9. Root response of Jerusalem artichoke genotypes to different water regimes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to determine effects of drought on selected root growth parameters and develop relationships between root parameters and tuber yield for selected Jerusalem artichoke (JA) genotypes. Three water regimes (Field capacity, 50% available water (AW) and 25% AW) and five JA...

  10. Regime Change the Old Fashioned Way: US Support to Insurgencies

    DTIC Science & Technology

    2008-04-23

    attributed the failure to poor direction and coordination, and created a special structure to oversee Operation MONGOOSE , a second covert program...against the Castro regime in Cuba. To ensure unity of effort, Kennedy designated Brigadier General Edward Lansdale in writing as the 7 MONGOOSE

  11. The rainfall regime and its uncertainty in Valencia and Larnaca

    NASA Astrophysics Data System (ADS)

    Reiser, H.; Kutiel, H.

    2007-08-01

    The Most Expected Rainfall Regime - MERR in a certain region is composed of various parameters regarding the annual rainfall regime in that region. The present study examines several parameters of the MERR, such as: the rainfall TOTAL, the Date of Accumulated Percentage-DAP, the Rainy Season Length-RSL, the Number of Rain-Spells-NRS, the Rain-Spell Yield-RSY, the ratio between Average and Median rainfall-AMED, the relationship between accumulated precipitation and the number of rain-spells and the Dry-Spell Distribution-DSD. Two stations at the two sides of the Mediterranean basin, Valencia and Larnaca, have been used to illustrate the distribution of the above parameters across the Mediterranean. The main conclusion of the study is that the rainfall regime at Larnaca is less uncertain as compared with the regime in Valencia. This is probably due to the fact that rainfalls are completely absent during the summer in Larnaca, which better suits the definition of a Mediterranean climate than that of Valencia.

  12. Multi-Fluid Modeling of Low-Recycling Divertor Regimes

    SciTech Connect

    Smirnov, R. D.; Pigarov, A. Y.; Krasheninnikov, S. I.; Rognlien, T. D.; Soukhanovskii, V. A.; Rensink, M. E.; Maingi, Rajesh; Skinner, C. H.; Stotler, D. P.; Bell, R. E.; Kugel, H. W.

    2010-01-01

    The low-recycling regimes of divertor operation in a single-null NSTX magnetic configuration are studied using computer simulations with the edge plasma transport code UEDGE. The edge plasma transport properties pertinent to the low-recycling regimes are demonstrated. These include the flux-limited character of the parallel heat transport and the high plasma temperatures with the flattened profiles in the scrape-off-layer. It is shown that to maintain the balance of particle fluxes at the core interface the deuterium gas puffing rate should increase as the divertor recycling coefficient decreases. The radial profiles of the heat load to the outer divertor plate, the upstream radial plasma profiles, and the effects of the cross-field plasma transport in the low-recycling regimes are discussed. It is also shown that recycling of lithium impurities evaporating from the divertor plate at high surface temperatures can reverse the low-recycling divertor operational regime to the high-recycling one and may cause thermal instability of the divertor plate. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

  13. Institutional Regimes and Induced Dependency in Homes for the Aged.

    ERIC Educational Resources Information Center

    Booth, Tim

    1986-01-01

    Reports effects of institutional regimes on levels of dependency among residents of public homes for the elderly in England. Differences in management practices and caring routines did not affect the creation or reduction of dependency among residents. Questions the rationale that informs some current notions of good practice in residential work.…

  14. Politics, welfare regimes, and population health: controversies and evidence.

    PubMed

    Muntaner, Carles; Borrell, Carme; Ng, Edwin; Chung, Haejoo; Espelt, Albert; Rodriguez-Sanz, Maica; Benach, Joan; O'Campo, Patricia

    2011-09-01

    In recent years, a research area has emerged within social determinants of health that examines the role of politics, expressed as political traditions/parties and welfare state characteristics, on population health. To better understand and synthesise this growing body of evidence, the present literature review, informed by a political economy of health and welfare regimes framework, located 73 empirical and comparative studies on politics and health, meeting our inclusion criteria in three databases: PubMed (1948-), Sociological Abstracts (1953-), and ISI Web of Science (1900-). We identified two major research programmes, welfare regimes and democracy, and two emerging programmes, political tradition and globalisation. Primary findings include: (1) left and egalitarian political traditions on population health are the most salutary, consistent, and substantial; (2) the health impacts of advanced and liberal democracies are also positive and large; (3) welfare regime studies, primarily conducted among wealthy countries, find that social democratic regimes tend to fare best with absolute health outcomes yet consistently in terms of relative health inequalities; and (4) globalisation defined as dependency indicators such as trade, foreign investment, and national debt is negatively associated with population health. We end by discussing epistemological, theoretical, and methodological issues for consideration for future research.

  15. Regimes of flow induced vibration for tandem, tethered cylinders

    NASA Astrophysics Data System (ADS)

    Nave, Gary; Stremler, Mark

    2015-11-01

    In the wake of a bluff body, there are a number of dynamic response regimes that exist for a trailing bluff body depending on spacing, structural restoring forces, and the mass-damping parameter m* ζ . For tandem cylinders with low values of m* ζ , two such regimes of motion are Gap Flow Switching and Wake Induced Vibration. In this study, we consider the dynamics of a single degree-of-freedom rigid cylinder in the wake of another in these regimes for a variety of center-to-center cylinder spacings (3-5 diameters) and Reynolds numbers (4,000-11,000). The system consists of a trailing cylinder constrained to a circular arc around a fixed leading cylinder, which, for small angle displacements, bears a close resemblance to the transversely oscillating cylinders found more commonly in existing literature. From experiments on this system, we compare and contrast the dynamic response within these two regimes. Our results show sustained oscillations in the absence of a structural restoring force in all cases, providing experimental support for the wake stiffness assumption, which is based on the mean lift toward the center line of flow.

  16. Ranking Regime and the Future of Vernacular Scholarship

    ERIC Educational Resources Information Center

    Ishikawa, Mayumi

    2014-01-01

    World university rankings and their global popularity present a number of far-reaching impacts for vernacular scholarship. This article employs a multidimensional approach to analyze the ranking regime's threat to local scholarship and knowledge construction through a study of Japanese research universities. First, local conditions that have led…

  17. Notion of time and the semiclassical regime of quantum gravity

    SciTech Connect

    Castagnino, M.A.; Mazzitelli, F.D. Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab 1, 1428 Buenos Aires )

    1990-07-15

    Using the notion of {ital probabilistic} {ital time} introduced in a previous work, we analyze the perturbed minisuperspace models of quantum gravity. For Robertson-Walker minisuperspace we show that it is possible to derive the so-called self-consistent cosmology in the semiclassical regime. The generalization to models with several semiclassical variables is also discussed.

  18. Observed trends in the hydrologic regime of Alpine catchments

    NASA Astrophysics Data System (ADS)

    Bard, Antoine; Renard, Benjamin; Lang, Michel

    2010-05-01

    A European trans-national project, AdaptAlp, has been set up since 2008 in order to study the impacts of climate change in the Alps and to assess adaptation strategies. One of the objectives of this project is to study past and present changes in the hydrologic regime of Alpine rivers. This poster presents preliminary results of a trend analysis over the whole Alpine area. A new dataset of more than two hundred discharge time series has been collected over the six countries of the alpine space: Switzerland, Italy, Germany, Austria, Slovenia and France. These series are made up of at least forty years of daily record and are related to undisturbed catchments. This dataset covers the whole spectrum of hydrological regimes existing in the Alps (from glacier- to mixed rainfall/snow regimes). In a second step, a set of hydrologic indices has been defined to characterize the hydrologic regime in terms of low, medium and high flows. In particular, these indices describe the drought severity (in terms of duration, intensity and volume deficit) and seasonality, the volume and timing of snowmelt, floods intensity and seasonality. A statistical trend test is finally applied for each hydrologic indice at each site. Consistent trends affecting the timing of snowmelt-dominated streamflow are found all over the Alps. Spring floods appear earlier in the season and tend to be longer in duration. Winter droughts tend to be shorter and less severe in terms of volume deficit.

  19. Syria: The Consolidation of the Asad Regime, 1970-1975.

    ERIC Educational Resources Information Center

    Olson, Robert W.

    1982-01-01

    Up to 1975-76, Syria's Hafiz al-Asad was successful in consolidating his power, securing the maintenance of his regime, and broadening his base of political power. His system started weakening in 1975 due to increased opposition stemming from Syria's intervention in the Lebanese civil war. (AM)

  20. Morphodynamic regime and long-term evolution of meandering rivers

    NASA Astrophysics Data System (ADS)

    Frascati, Alessandro; Lanzoni, Stefano

    2009-06-01

    In the present contribution we focus our attention on the long-term behavior of meandering rivers, a very common pattern in nature. This class of dynamical systems is driven by the coexistence of various intrinsically nonlinear mechanisms which determine the possible occurrence of two different morphodynamic regimes: the subresonant and the superresonant regimes. Investigating the full range of morphodynamic conditions, we objectively compare the morphologic characteristics exhibited by synthetically generated and observed planimetric patterns. The analysis is carried out examining, through principal component analysis, a suitable set of morphological variables. We show that even in the presence of the strong filtering action exerted by cutoff processes, a closer, although not yet complete, similarity with natural meandering planforms can be achieved only by adopting a flow field model which accounts for the full range of morphodynamic regimes. We also introduce a new morphodynamic length scale, ?m, associated with spatially oscillating disturbances. Once normalized with this length scale, the relevant morphologic features of the simulated long-term patterns (e.g., the probability density function of local curvature and the geometric characteristics of oxbow lakes) tend to collapse on two distinct behaviors, depending on the dominant morphologic regime.

  1. Political Regime and Human Capital: A Cross-Country Analysis

    ERIC Educational Resources Information Center

    Klomp, Jeroen; de Haan, Jakob

    2013-01-01

    We examine the relationship between different dimensions of the political regime in place and human capital using a two-step structural equation model. In the first step, we employ factor analysis on 16 human capital indicators to construct two new human capital measures (basic and advanced human capital). In the second step, we estimate the…

  2. Regime-based analysis of aerosol-cloud interactions

    NASA Astrophysics Data System (ADS)

    Gryspeerdt, Edward; Stier, Philip

    2012-11-01

    Previous global satellite studies into the indirect aerosol effect have relied on determining the sensitivity of derived Cloud Droplet Number Concentration (Nd) to co-located Aerosol Optical Depth (AOD). These studies generally find a positive Nd sensitivity to AOD changes over ocean, but some find a negative sensitivity over land, in contrast to that predicted by models and theory. Here we investigate the Nd sensitivity to AOD in different cloud regimes, determined using a k-means clustering process on retrieved cloud properties. We find the strongest positive Nd sensitivity in the stratiform regimes over both land and ocean, providing the majority of the total sensitivity. The negative sensitivity previously observed over land is generated by the low cloud fraction regimes, suggesting that it is due to the difficulty of retrieving Nd at low cloud fractions. When considering a mean sensitivity, weighted by liquid cloud fraction to account for sampling biases, we find an increased sensitivity over land, in some regions becoming positive. This highlights the importance of regime based analysis when studying aerosol indirect effects.

  3. Search Regimes and the Industrial Dynamics of Science

    ERIC Educational Resources Information Center

    Bonaccorsi, Andrea

    2008-01-01

    The article addresses the issue of dynamics of science, in particular of new sciences born in twentieth century and developed after the Second World War (information science, materials science, life science). The article develops the notion of search regime as an abstract characterization of dynamic patterns, based on three dimensions: the rate of…

  4. Nonlinear transport processes in tokamak plasmas. I. The collisional regimes

    NASA Astrophysics Data System (ADS)

    Sonnino, Giorgio; Peeters, Philippe

    2008-06-01

    An application of the thermodynamic field theory (TFT) to transport processes in L-mode tokamak plasmas is presented. The nonlinear corrections to the linear ("Onsager") transport coefficients in the collisional regimes are derived. A quite encouraging result is the appearance of an asymmetry between the Pfirsch-Schlüter (P-S) ion and electron transport coefficients: the latter presents a nonlinear correction, which is absent for the ions, and makes the radial electron coefficients much larger than the former. Explicit calculations and comparisons between the neoclassical results and the TFT predictions for Joint European Torus (JET) plasmas are also reported. It is found that the nonlinear electron P-S transport coefficients exceed the values provided by neoclassical theory by a factor that may be of the order 102. The nonlinear classical coefficients exceed the neoclassical ones by a factor that may be of order 2. For JET, the discrepancy between experimental and theoretical results for the electron losses is therefore significantly reduced by a factor 102 when the nonlinear contributions are duly taken into account but, there is still a factor of 102 to be explained. This is most likely due to turbulence. The expressions of the ion transport coefficients, determined by the neoclassical theory in these two regimes, remain unaltered. The low-collisional regimes, i.e., the plateau and the banana regimes, are analyzed in the second part of this work.

  5. Microgravity Flow Regime Data: Buoyancy and Mixing Apparatus Effects

    NASA Astrophysics Data System (ADS)

    Shephard, Adam; Best, Frederick

    2010-01-01

    Zero-g two-phase flow data set qualification and flight experiment design have not been standardized and as a result, agreement among researchers has not been reached regarding what experimental conditions adequately approximate those of microgravity. The effects of buoyancy forces and mixing apparatus on the flow regime transitions are presented in this study. The gravity conditions onboard zero-g aircraft are at best 10-3 g which is used to approximate the 10-5 g conditions of microgravity, thus the buoyancy forces present on zero-g aircraft can become significantly large and unrepresentative of microgravity. When buoyancy forces approach those of surface tension forces, buoyancy induced coalescence occurs. When discussing flow regime transitions, these large buoyancy forces lead to flow regime transitions which otherwise would not occur. The buoyancy attributes of the two-phase flow data sets available in the literature are evaluated to determine which data sets exhibit buoyancy induced transitions. Upon comparison of the representative data sets, the affects of different mixing apparatus can be seen in the superficial velocity flow regime maps.

  6. FISHER INFORMATION AND DYNAMIC REGIME CHANGES IN ECOLOGICAL SYSTEMS

    EPA Science Inventory

    Fisher Information and Dynamic Regime Changes in Ecological Systems
    Abstract for the 3rd Conference of the International Society for Ecological Informatics
    Audrey L. Mayer, Christopher W. Pawlowski, and Heriberto Cabezas

    The sustainable nature of particular dynamic...

  7. Effects of two long-term mowing regimes on vegetation

    USGS Publications Warehouse

    Perry, M.C.; Deller, A.S.

    2000-01-01

    Wildlife managers have for many years been interested in the role of mowing as a management technique to benefit wildlife. Two long-term mowing regimes (60 years of similar management) were evaluated at Patuxent Research Refuge during the summer of 1997 to better understand the influence of mowing on vegetation communities. Mowing ceased in 1997 due to reduction in maintenance funds, which facilitated the identification of mature grasses. The previous mowing regimes included (1) lawn areas that had been mowed with rotary mowers approximately every 24 weeks and (2) meadow areas that had been mowed approximately once a year with a brushhog. Each regime had two replications. Vegetation was sampled in 20, 1 m2 plots per area (n=80) and percent cover visually estimated by species. The percent ground cover of the dominant vegetation on the lawn area was 40.0% red fescue (Festuca rubra), 26.5% white clover (Trifolium repens), and 18.0% Kentucky blue grass (Poa pratensis). The percent ground cover of the dominant vegetation in the meadow area was 33.2% meadow fescue (Festuca elatior), 9.9% sweet vernal grass (Anthoxanthum odoratum), 9.2% orchard grass (Dactylis glomerata), 6.3% Japanese honeysuckle (Lonicera japonica), and 5.2% red fescue. The sites were sampled again in 1999 with the major difference being the absence of white clover in the lawn areas, believed to be a result of the drought conditions in recent years. All percent ground covers for the dominant vegetation were significantly different (P<0.01) between the two mowing regimes. Species richness was higher in both years in the meadow regime (74, 62) versus the lawn regime (33, 23). Frequently mowed lawn areas may provide better grazing forage for herbivores, such as geese, rabbits, and deer, however, meadow areas may provide greater plant biomass (232 vs. 63 g/m2) and greater diversity of plant species. The meadow regime also appeared to have greater seed production and cover, which is favored by a wider

  8. TRMM Observations of Convective Regimes in the Amazon

    NASA Technical Reports Server (NTRS)

    Petersen, W. A.; Nesbitt, S. W.; Blakeslee, Robert J.; Hein, P.; Cifelli, R.; Rutledge, S. A.; Arnold, James E. (Technical Monitor)

    2001-01-01

    This study utilizes TRMM satellite precipitation radar, lightning imaging sensor, and passive microwave imager data together with ground-based lightning data to investigate the vertical structure, lightning, and rainfall characteristics of Amazonian and central South American convection for three separate wet-seasons. These characteristics are partitioned as a function of 850 mb zonal wind direction, motivated by observations collected during the six-week TRMM-LBA field campaign. The TRMM-LBA field campaign observations suggest that systematic variations in Amazonian convective vertical structure, lightning, and rainfall are all linked to bimodal variations in the low-level zonal wind (e.g., easterly and westerly regimes). The more spatially and temporally comprehensive TRMM dataset used in this study extends the TRMM-LBA observations by examining regime variability in Amazonian and South American convective structure over a continental scale domain. On a continental-scale, patterns of east and west regime 850 mb winds combined with LIS lightning flash densities suggest the presence of synoptic-scale controls (e.g., intrusion of extratropical frontal systems and interaction with the SACZ) on regional-scale variability in convective vertical structure. TRMM PR, TMI and ground-based lightning data suggest that regional variability in wet-season convective structure is most evident over the southern Amazon, Mato Grosso, Altiplano, southern Brazil, and eastern coastal regions of central and southern South America. Convective vertical structure, rain fall rates, and lightning activity are all more pronounced during easterly (westerly) regimes over the southern Amazon and Mato Grosso (Altiplano, and southern Brazil). Importantly, when considered with case-study results from TRMM-LBA, the systematic differences in convective structure that occur as a function of regime suggest that associated regime-differences may exist in the vertical distribution of diabatic heating

  9. Classification of river regimes: A context for hydroecology

    USGS Publications Warehouse

    Osterkamp, W.R.; Friedman, J.M.

    2000-01-01

    Over the past 30 years, ecologists have demostrated the importance of flow and temperature as primary variables in driving running water, riparian and floodplain ecosystems. As it is important to assess the size and timing of discharge variations in relation to those in temperature, a method is proposed that uses multivariate techniques to separately classify annual discharge and temperature regimes according to their 'shape' and 'magnitude', and which then combines the classifications. This paper: (i) describes a generally applicable method; (ii) tests the method by applying it to riparian systems on four British rivers using a 20-year record (1977-97) of flow and air temperature: (iii) proposes a hydroecological interpretation of the classification; (iv) considers the degree to which the methodology might provide information to support the design of ecologically acceptable flow regimes. 'Regimes' are defined for discharge and air temperature using monthly mean data. The results of applying the classification procedure to four British rivers indicates that the 'typical' regimes for each of the four catchments are composite features produced by a small number of clearly defined annual types that reflect interannual variability in hydroclimatological conditions. Annual discharge patterns are dominated by three 'shape' classes (accounting for 94% of the station years: class A, early (November) peak; class B, intermediate (December-January) peak; and class C, late (March) peak) and one 'magnitude' class (70% of the station years fall into class 3, intermediate), with two subordinate 'magnitude' classes: low-flow years (18%) and high flow years (12%). For air temperature, annual patterns are classified evenly into three 'shape' and four 'magnitude' classes. It is argued that this variety of flow-temperature patterns is important for sustaining ecosystem integrity and for establishing benchmark flow regimes and associated frequencies to aid river management. Copyright

  10. Early warning of atmospheric regime transitions using transfer operators

    NASA Astrophysics Data System (ADS)

    Tantet, Alexis; Dijkstra, Henk

    2015-04-01

    The existence of persistent midlatitude atmospheric regimes, such as blocking events, with time scales larger than 5-10 days and indications of preferred transition paths between them motivates the development of early-warning indicators of regime transitions. Here, we use a barotropic model of the northern midlatitudes winter flow to study such meta-stable regimes. We look at estimates of transfer operators acting on densities evolving on a reduced phase space spanned by the first Empirical Orthogonal Functions of the streamfunction and develop an early-warning indicator of zonal to blocked flow transition. The study of the spectra of transfer operators estimated for different lags reveals a multi-level structure in the flow as well as the effect of memory on the reduced dynamics due to past interactions between the resolved and unresolved variables. The slowest motions in the reduced phase space are thereby found to have time scales larger than 8 days and to behave as Markovian for larger lags. These motions are associated with meta-stable regimes and their transitions and can be detected as almost-invariant sets of the transfer operator. The early-warning indicator is based on the action on an initial density of products of the transfer operators estimated for sufficiently long lags, making use of the semi-group property of these operators and shows relatively good Peirce skill score. From the energy budget of the model, we are able to explain the meta-stability of the regimes and the existence of preferred transition paths as the manifestation of barotropic instability. Finally, even though the model is highly simplified, the skill of the early warning indicator is promising, suggesting that the transfer operator approach can be used in parallel to an operational deterministic model for stochastic prediction or to assess forecast uncertainty.

  11. The human dimension of fire regimes on Earth

    USGS Publications Warehouse

    Bowman, David M.J.S.; Balch, Jennifer; Artaxo, Paulo; Bond, William J.; Cochrane, Mark A.; D'Antonio, Carla M.; DeFries, Ruth; Johnston, Fay H.; Keeley, Jon E.; Krawchuk, Meg A.; Kull, Christian A.; Michelle, Mack; Moritz, Max A.; Pyne, Stephen; Roos, Christopher I.; Scott, Andrew C.; Sodhi, Navjot S.; Swetnam, Thomas W.

    2011-01-01

    Humans and their ancestors are unique in being a fire-making species, but 'natural' (i.e. independent of humans) fires have an ancient, geological history on Earth. Natural fires have influenced biological evolution and global biogeochemical cycles, making fire integral to the functioning of some biomes. Globally, debate rages about the impact on ecosystems of prehistoric human-set fires, with views ranging from catastrophic to negligible. Understanding of the diversity of human fire regimes on Earth in the past, present and future remains rudimentary. It remains uncertain how humans have caused a departure from 'natural' background levels that vary with climate change. Available evidence shows that modern humans can increase or decrease background levels of natural fire activity by clearing forests, promoting grazing, dispersing plants, altering ignition patterns and actively suppressing fires, thereby causing substantial ecosystem changes and loss of biodiversity. Some of these contemporary fire regimes cause substantial economic disruptions owing to the destruction of infrastructure, degradation of ecosystem services, loss of life, and smoke-related health effects. These episodic disasters help frame negative public attitudes towards landscape fires, despite the need for burning to sustain some ecosystems. Greenhouse gas-induced warming and changes in the hydrological cycle may increase the occurrence of large, severe fires, with potentially significant feedbacks to the Earth system. Improved understanding of human fire regimes demands: (1) better data on past and current human influences on fire regimes to enable global comparative analyses, (2) a greater understanding of different cultural traditions of landscape burning and their positive and negative social, economic and ecological effects, and (3) more realistic representations of anthropogenic fire in global vegetation and climate change models. We provide an historical framework to promote understanding

  12. Quantifying Floods of a Flood Regime in Space and Time

    NASA Astrophysics Data System (ADS)

    Whipple, A. A.; Fleenor, W. E.; Viers, J. H.

    2015-12-01

    Interaction between a flood hydrograph and floodplain topography results in spatially and temporally variable conditions important for ecosystem process and function. Individual floods whose frequency and dimensionality comprise a river's flood regime contribute to that variability and in aggregate are important drivers of floodplain ecosystems. Across the globe, water management actions, land use changes as well as hydroclimatic change associated with climate change have profoundly affected natural flood regimes and their expression within the floodplain landscape. Homogenization of riverscapes has degraded once highly diverse and productive ecosystems. Improved understanding of the range of flood conditions and spatial variability within floodplains, or hydrospatial conditions, is needed to improve water and land management and restoration activities to support the variable conditions under which species adapted. This research quantifies the flood regime of a floodplain site undergoing restoration through levee breaching along the lower Cosumnes River of California. One of the few lowland alluvial rivers of California with an unregulated hydrograph and regular floodplain connectivity, the Cosumnes River provides a useful test-bed for exploring river-floodplain interaction. Representative floods of the Cosumnes River are selected from previously-established flood types comprising the flood regime and applied within a 2D hydrodynamic model representing the floodplain restoration site. Model output is analyzed and synthesized to quantify and compare conditions in space and time, using metrics such as depth and velocity. This research establishes methods for quantifying a flood regime's floodplain inundation characteristics, illustrates the role of flow variability and landscape complexity in producing heterogeneous floodplain conditions, and suggests important implications for managing more ecologically functional floodplains.

  13. The human dimension of fire regimes on Earth.

    PubMed

    Bowman, David M J S; Balch, Jennifer; Artaxo, Paulo; Bond, William J; Cochrane, Mark A; D'Antonio, Carla M; Defries, Ruth; Johnston, Fay H; Keeley, Jon E; Krawchuk, Meg A; Kull, Christian A; Mack, Michelle; Moritz, Max A; Pyne, Stephen; Roos, Christopher I; Scott, Andrew C; Sodhi, Navjot S; Swetnam, Thomas W; Whittaker, Robert

    2011-12-01

    Humans and their ancestors are unique in being a fire-making species, but 'natural' (i.e. independent of humans) fires have an ancient, geological history on Earth. Natural fires have influenced biological evolution and global biogeochemical cycles, making fire integral to the functioning of some biomes. Globally, debate rages about the impact on ecosystems of prehistoric human-set fires, with views ranging from catastrophic to negligible. Understanding of the diversity of human fire regimes on Earth in the past, present and future remains rudimentary. It remains uncertain how humans have caused a departure from 'natural' background levels that vary with climate change. Available evidence shows that modern humans can increase or decrease background levels of natural fire activity by clearing forests, promoting grazing, dispersing plants, altering ignition patterns and actively suppressing fires, thereby causing substantial ecosystem changes and loss of biodiversity. Some of these contemporary fire regimes cause substantial economic disruptions owing to the destruction of infrastructure, degradation of ecosystem services, loss of life, and smoke-related health effects. These episodic disasters help frame negative public attitudes towards landscape fires, despite the need for burning to sustain some ecosystems. Greenhouse gas-induced warming and changes in the hydrological cycle may increase the occurrence of large, severe fires, with potentially significant feedbacks to the Earth system. Improved understanding of human fire regimes demands: (1) better data on past and current human influences on fire regimes to enable global comparative analyses, (2) a greater understanding of different cultural traditions of landscape burning and their positive and negative social, economic and ecological effects, and (3) more realistic representations of anthropogenic fire in global vegetation and climate change models. We provide an historical framework to promote understanding

  14. Climate change and future fire regimes: Examples from California

    USGS Publications Warehouse

    Keeley, Jon E.; Syphard, Alexandra D.

    2016-01-01

    Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation trajectories, as well as

  15. Vegetation management with fire modifies peatland soil thermal regime.

    PubMed

    Brown, Lee E; Palmer, Sheila M; Johnston, Kerrylyn; Holden, Joseph

    2015-05-01

    Vegetation removal with fire can alter the thermal regime of the land surface, leading to significant changes in biogeochemistry (e.g. carbon cycling) and soil hydrology. In the UK, large expanses of carbon-rich upland environments are managed to encourage increased abundance of red grouse (Lagopus lagopus scotica) by rotational burning of shrub vegetation. To date, though, there has not been any consideration of whether prescribed vegetation burning on peatlands modifies the thermal regime of the soil mass in the years after fire. In this study thermal regime was monitored across 12 burned peatland soil plots over an 18-month period, with the aim of (i) quantifying thermal dynamics between burned plots of different ages (from <2 to 15 + years post burning), and (ii) developing statistical models to determine the magnitude of thermal change caused by vegetation management. Compared to plots burned 15 + years previously, plots recently burned (<2-4 years) showed higher mean, maximum and range of soil temperatures, and lower minima. Statistical models (generalised least square regression) were developed to predict daily mean and maximum soil temperature in plots burned 15 + years prior to the study. These models were then applied to predict temperatures of plots burned 2, 4 and 7 years previously, with significant deviations from predicted temperatures illustrating the magnitude of burn management effects. Temperatures measured in soil plots burned <2 years previously showed significant statistical disturbances from model predictions, reaching +6.2 °C for daily mean temperatures and +19.6 °C for daily maxima. Soil temperatures in plots burnt 7 years previously were most similar to plots burned 15 + years ago indicating the potential for soil temperatures to recover as vegetation regrows. Our findings that prescribed peatland vegetation burning alters soil thermal regime should provide an impetus for further research to understand the consequences of thermal regime

  16. Stochastic Parametrisations and Regime Behaviour of Atmospheric Models

    NASA Astrophysics Data System (ADS)

    Arnold, Hannah; Moroz, Irene; Palmer, Tim

    2013-04-01

    The presence of regimes is a characteristic of non-linear, chaotic systems (Lorenz, 2006). In the atmosphere, regimes emerge as familiar circulation patterns such as the El-Nino Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO) and Scandinavian Blocking events. In recent years there has been much interest in the problem of identifying and studying atmospheric regimes (Solomon et al, 2007). In particular, how do these regimes respond to an external forcing such as anthropogenic greenhouse gas emissions? The importance of regimes in observed trends over the past 50-100 years indicates that in order to predict anthropogenic climate change, our climate models must be able to represent accurately natural circulation regimes, their statistics and variability. It is well established that representing model uncertainty as well as initial condition uncertainty is important for reliable weather forecasts (Palmer, 2001). In particular, stochastic parametrisation schemes have been shown to improve the skill of weather forecast models (e.g. Berner et al., 2009; Frenkel et al., 2012; Palmer et al., 2009). It is possible that including stochastic physics as a representation of model uncertainty could also be beneficial in climate modelling, enabling the simulator to explore larger regions of the climate attractor including other flow regimes. An alternative representation of model uncertainty is a perturbed parameter scheme, whereby physical parameters in subgrid parametrisation schemes are perturbed about their optimal value. Perturbing parameters gives a greater control over the ensemble than multi-model or multiparametrisation ensembles, and has been used as a representation of model uncertainty in climate prediction (Stainforth et al., 2005; Rougier et al., 2009). We investigate the effect of including representations of model uncertainty on the regime behaviour of a simulator. A simple chaotic model of the atmosphere, the Lorenz '96 system, is used to study

  17. The case for regime-based water quality standards

    USGS Publications Warehouse

    Poole, Geoffrey C.; Dunham, J.B.; Keenan, D.M.; Sauter, S.T.; McCullough, D.A.; Mebane, Christopher; Lockwood, Jeffrey C.; Essig, Don A.; Hicks, Mark P.; Sturdevant, Debra J.; Materna, E.J.; Spalding, M.; Risley, John; Deppman, Marianne

    2004-01-01

    Conventional water quality standards have been successful in reducing the concentration of toxic substances in US waters. However, conventional standards are based on simple thresholds and are therefore poorly structured to address human-caused imbalances in dynamic, natural water quality parameters, such as nutrients, sediment, and temperature. A more applicable type of water quality standarda??a a??regime standarda??a??would describe desirable distributions of conditions over space and time within a stream network. By mandating the protection and restoration of the aquatic ecosystem dynamics that are required to support beneficial uses in streams, well-designed regime standards would facilitate more effective strategies for management of natural water quality parameters.

  18. Nondiffusive transport regimes for suprathermal ions in turbulent plasmas.

    PubMed

    Bovet, A; Fasoli, A; Ricci, P; Furno, I; Gustafson, K

    2015-04-01

    The understanding of the transport of suprathermal ions in the presence of turbulence is important for fusion plasmas in the burning regime that will characterize reactors, and for space plasmas to understand the physics of particle acceleration. Here, three-dimensional measurements of a suprathermal ion beam in the toroidal plasma device TORPEX are presented. These measurements demonstrate, in a turbulent plasma, the existence of subdiffusive and superdiffusive transport of suprathermal ions, depending on their energy. This result stems from the unprecedented combination of uniquely resolved measurements and first-principles numerical simulations that reveal the mechanisms responsible for the nondiffusive transport. The transport regime is determined by the interaction of the suprathermal ion orbits with the turbulent plasma dynamics, and is strongly affected by the ratio of the suprathermal ion energy to the background plasma temperature.

  19. Disorder-assisted quantum transport in suboptimal decoherence regimes.

    PubMed

    Novo, Leonardo; Mohseni, Masoud; Omar, Yasser

    2016-01-04

    We investigate quantum transport in binary tree structures and in hypercubes for the disordered Frenkel-exciton Hamiltonian under pure dephasing noise. We compute the energy transport efficiency as a function of disorder and dephasing rates. We demonstrate that dephasing improves transport efficiency not only in the disordered case, but also in the ordered one. The maximal transport efficiency is obtained when the dephasing timescale matches the hopping timescale, which represent new examples of the Goldilocks principle at the quantum scale. Remarkably, we find that in weak dephasing regimes, away from optimal levels of environmental fluctuations, the average effect of increasing disorder is to improve the transport efficiency until an optimal value for disorder is reached. Our results suggest that rational design of the site energies statistical distributions could lead to better performances in transport systems at nanoscale when their natural environments are far from the optimal dephasing regime.

  20. Scalable quantum memory in the ultrastrong coupling regime.

    PubMed

    Kyaw, T H; Felicetti, S; Romero, G; Solano, E; Kwek, L-C

    2015-03-02

    Circuit quantum electrodynamics, consisting of superconducting artificial atoms coupled to on-chip resonators, represents a prime candidate to implement the scalable quantum computing architecture because of the presence of good tunability and controllability. Furthermore, recent advances have pushed the technology towards the ultrastrong coupling regime of light-matter interaction, where the qubit-resonator coupling strength reaches a considerable fraction of the resonator frequency. Here, we propose a qubit-resonator system operating in that regime, as a quantum memory device and study the storage and retrieval of quantum information in and from the Z2 parity-protected quantum memory, within experimentally feasible schemes. We are also convinced that our proposal might pave a way to realize a scalable quantum random-access memory due to its fast storage and readout performances.

  1. Quantum Theory as a Critical Regime of Language Dynamics

    NASA Astrophysics Data System (ADS)

    Grinbaum, Alexei

    2015-10-01

    Some mathematical theories in physics justify their explanatory superiority over earlier formalisms by the clarity of their postulates. In particular, axiomatic reconstructions drive home the importance of the composition rule and the continuity assumption as two pillars of quantum theory. Our approach sits on these pillars and combines new mathematics with a testable prediction. If the observer is defined by a limit on string complexity, information dynamics leads to an emergent continuous model in the critical regime. Restricting it to a family of binary codes describing `bipartite systems,' we find strong evidence of an upper bound on bipartite correlations equal to 2.82537. This is measurably different from the Tsirelson bound. The Hilbert space formalism emerges from this mathematical investigation as an effective description of a fundamental discrete theory in the critical regime.

  2. Spectator effects during Leptogenesis in the strong washout regime

    SciTech Connect

    Garbrecht, Björn; Schwaller, Pedro E-mail: pedro.schwaller@cern.ch

    2014-10-01

    By including spectator fields into the Boltzmann equations for Leptogenesis, we show that partially equilibrated spectator interactions can have a significant impact on the freeze-out value of the asymmetry in the strong washout regime. The final asymmetry is typically increased, since partially equilibrated spectators ''hide'' a part of the asymmetry from washout. We study examples with leptonic and non-leptonic spectator processes, assuming thermal initial conditions, and find up to 50% enhanced asymmetries compared to the limit of fully equilibrated spectators. Together with a comprehensive overview of the equilibration temperatures for various Standard Model processes, the numerical results indicate the ranges when the limiting cases of either fully equilibrated or negligible spectator fields are applicable and when they are not. Our findings also indicate an increased sensitivity to initial conditions and finite density corrections even in the strong washout regime.

  3. Regimes of strong light-matter coupling under incoherent excitation

    SciTech Connect

    Valle, E. del; Laussy, F. P.

    2011-10-15

    We study a two-level system (atom, superconducting qubit, or quantum dot) strongly coupled to a single photonic mode of a cavity, in the presence of incoherent pumping and including detuning and dephasing. This system displays a striking quantum-to-classical transition. On the grounds of several approximations that reproduce to various degrees exact results obtained numerically, we separate five regimes of operations, that we term ''linear,''''quantum,''''lasing,''''quenching,'' and ''thermal.'' In the fully quantized picture, the lasing regime arises as a condensation of dressed states and manifests itself as a Mollow triplet structure in the direct emitter photoluminescence spectrum, which embeds fundamental features of the full-field quantization description of light-matter interaction.

  4. Giant magnetoresistance in the variable-range hopping regime

    SciTech Connect

    Ioffe, L. B.; Spivak, B. Z.

    2013-09-15

    We predict the universal power-law dependence of the localization length on the magnetic field in the strongly localized regime. This effect is due to the orbital quantum interference. Physically, this dependence shows up in an anomalously large negative magnetoresistance in the hopping regime. The reason for the universality is that the problem of the electron tunneling in a random media belongs to the same universality class as the directed polymer problem even in the case of wave functions of random sign. We present numerical simulations that prove this conjecture. We discuss the existing experiments that show anomalously large magnetoresistance. We also discuss the role of localized spins in real materials and the spin polarizing effect of the magnetic field.

  5. Multi-band metamaterial absorber topology for infrared frequency regime

    NASA Astrophysics Data System (ADS)

    Mulla, Batuhan; Sabah, Cumali

    2017-02-01

    In this paper, a new multiband metamaterial absorber design is proposed and the numerical characterization is carried out. The design is composed of three layers with differently sized quadruplets in which the interaction among them causes the multiband absorption response in the infrared frequency regime. In order to characterize the absorber and explain the multiband topology, some parametric studies with respect to the dimensions of the structure are carried out and the contributions of the quadruplets to the absorption spectrum are analyzed. According to the results, it is found that the proposed metamaterial absorber has five bands in the infrared frequency regime with the absorption levels of: 98.90%, 99.39%, 86.46%, 92.80% and 97.96%. Moreover, the polarization dependency of the structure is examined and it is found that the design operates well as a perfect absorber with polarization independency in the studied frequency range.

  6. Supercontinuum pulse shaping in the few-cycle regime.

    PubMed

    Hagemann, Franz; Gause, Oliver; Wöste, Ludger; Siebert, Torsten

    2013-03-11

    The synthesis of nearly arbitrary supercontinuum pulse forms is demonstrated with sub-pulse structures that maintain a temporal resolution in the few-cycle regime. Spectral broadening of the 35 fs input pulses to supercontinuum bandwidths is attained in a controlled two-stage sequential filamentation in air at atmospheric pressure, facilitating a homogeneous power density over the full spectral envelope in the visible to near infrared spectral range. Only standard optics and a liquid crystal spatial light modulator (LC-SLM) are employed for achieving pulse compression to the sub 5 fs regime with pulse energies of up to 60 μJ and a peak power of 12 GW. This constitutes the starting point for further pulse form synthesis via phase modulation within the sampling limit of the pulse shaper. Transient grating frequency-resolved optical gating (TG-FROG) allows for the characterization of pulse forms that extend over several hundred femtoseconds with few-cycle substructures.

  7. Optically Pumped NMR in the Fractional Quantum Hall Regime

    NASA Astrophysics Data System (ADS)

    Barrett, S. E.; Kuzma, N. N.; Khandelwal, P.; Pfeiffer, L. N.; West, K. W.

    1998-03-01

    Optically Pumped Nuclear Magnetic Resonance measurements are a local probe of the electron spin degree of freedom in n-type GaAs quantum wells.(S.E.Barrett et al.,Phys.Rev.Lett.72),1368(1994).^, footnote S. E. Barrett et al., Phys. Rev. Lett. 74, 5112 (1995)^, footnote R. Tycko et al., Science 268, 1460 (1995). We have recently shown that this OPNMR technique can be carried out in fields up to B=12 Tesla and temperatures down to T=0.3 K, making this technique a viable new probe of the Fractional Quantum Hall regime. We will discuss our latest measurements in these conditions, and compare our new results with previous measurements and the existing theoretical models for this regime.

  8. Scalable quantum memory in the ultrastrong coupling regime

    PubMed Central

    Kyaw, T. H.; Felicetti, S.; Romero, G.; Solano, E.; Kwek, L.-C.

    2015-01-01

    Circuit quantum electrodynamics, consisting of superconducting artificial atoms coupled to on-chip resonators, represents a prime candidate to implement the scalable quantum computing architecture because of the presence of good tunability and controllability. Furthermore, recent advances have pushed the technology towards the ultrastrong coupling regime of light-matter interaction, where the qubit-resonator coupling strength reaches a considerable fraction of the resonator frequency. Here, we propose a qubit-resonator system operating in that regime, as a quantum memory device and study the storage and retrieval of quantum information in and from the Z2 parity-protected quantum memory, within experimentally feasible schemes. We are also convinced that our proposal might pave a way to realize a scalable quantum random-access memory due to its fast storage and readout performances. PMID:25727251

  9. Flow regimes and parameter dependence in nanochannel flows.

    PubMed

    Liu, Chong; Li, Zhigang

    2009-09-01

    Nanoscale fluid flow systems involve both microscopic and macroscopic parameters, which compete with each another and lead to different flow regimes. In this work, we investigate the interactions of four fundamental parameters, including the fluid-fluid, fluid-wall binding energies, temperature of the system, and driving force, and their effects on the flow motion in nanoscale Poiseuille flows. By illustrating the fluid flux as a function of a dimensionless number, which represents the effective surface effect on the fluid, we show that the fluid motion in nanochannels falls into different regimes, each of which is associated with a distinct mechanism. The mechanisms in different situations reveal the effects of the parameters on the fluid dynamics.

  10. Modeling of drop breakup in the bag breakup regime

    NASA Astrophysics Data System (ADS)

    Wang, C.; Chang, S.; Wu, H.; Xu, J.

    2014-04-01

    Several analytic models for predicting the drop deformation and breakup have been developed over the last three decades, but modeling drop breakup in the bag-type regime is less reported. In this Letter, a breakup model has been proposed to predict the drop deformation length and breakup time in the bag-type breakup regime in a more accurate manner. In the present model, the drop deformation which is approximately as the displacement of the centre of mass (c. m.) along the axis located at the centre of the drop, and the movement of c. m. is obtained by solving the pressure balance equation. The effects of the drop deformation on the drop external aerodynamic force are considered in this model. Drop breakup occurs when the deformation length reaches the maximum value and the maximum deformation length is a function of Weber number. The performance and applicability of the proposed breakup model are tested against the published experimental data.

  11. Ring-diffusion mediated homogeneous melting in the superheating regime

    NASA Astrophysics Data System (ADS)

    Bai, Xian-Ming; Li, Mo

    2008-04-01

    Homogeneous melting in the superheating regime is investigated by using molecular dynamics simulation of a Lennard-Jones model system. We show that the commonly observed catastrophic melting at the superheating limit is caused by fast heating rate. By keeping the system isothermally at temperatures below the superheating limit, we observe intense self-diffusion motions as the precursor of melting. The highly correlated atomic motions are related to the self-diffusion loops or rings. Two types of loops are observed, closed loop and open loop, where the latter is directly related to the homogeneous nucleation of the liquid phase. Homogeneous melting occurs when the number density of diffusion loops reaches a critical value. Our results suggest that homogeneous melting in the superheating regime is a first-order thermodynamic phase transition triggered by the self-diffusion loops when the kinetic constraint imposed by heating rate is lessened.

  12. Disorder-assisted quantum transport in suboptimal decoherence regimes

    PubMed Central

    Novo, Leonardo; Mohseni, Masoud; Omar, Yasser

    2016-01-01

    We investigate quantum transport in binary tree structures and in hypercubes for the disordered Frenkel-exciton Hamiltonian under pure dephasing noise. We compute the energy transport efficiency as a function of disorder and dephasing rates. We demonstrate that dephasing improves transport efficiency not only in the disordered case, but also in the ordered one. The maximal transport efficiency is obtained when the dephasing timescale matches the hopping timescale, which represent new examples of the Goldilocks principle at the quantum scale. Remarkably, we find that in weak dephasing regimes, away from optimal levels of environmental fluctuations, the average effect of increasing disorder is to improve the transport efficiency until an optimal value for disorder is reached. Our results suggest that rational design of the site energies statistical distributions could lead to better performances in transport systems at nanoscale when their natural environments are far from the optimal dephasing regime. PMID:26726133

  13. Computer Language Choices in Arms Control and Nonproliferation Regimes

    SciTech Connect

    White, G K

    2005-06-10

    The U.S. and Russian Federation continue to make substantive progress in the arms control and nonproliferation transparency regimes. We are moving toward an implementation choice for creating radiation measurement systems that are transparent in both their design and in their implementation. In particular, the choice of a programming language to write software for such regimes can decrease or significantly increase the costs of authentication. In this paper, we compare procedural languages with object-oriented languages. In particular, we examine the C and C++ languages; we compare language features, code generation, implementation details, and executable size and demonstrate how these attributes aid or hinder authentication and backdoor threats. We show that programs in lower level, procedural languages are more easily authenticated than are object-oriented ones. Potential tools and methods for authentication are covered. Possible mitigations are suggested for using object-oriented programming languages.

  14. Study of a spur gear dynamic behavior in transient regime

    NASA Astrophysics Data System (ADS)

    Khabou, M. T.; Bouchaala, N.; Chaari, F.; Fakhfakh, T.; Haddar, M.

    2011-11-01

    In this paper the dynamic behavior of a single stage spur gear reducer in transient regime is studied. Dynamic response of the single stage spur gear reducer is investigated at different rotating velocities. First, gear excitation is induced by the motor torque and load variation in addition to the fluctuation of meshing stiffness due to the variation of input rotational speed. Then, the dynamic response is computed using the Newmark method. After that, a parameter study is made on spur gear powered in the first place by an electric motor and in the second place by four strokes four cylinders diesel engine. Dynamic responses come to confirm a significant influence of the transient regime on the dynamic behavior of a gear set, particularly in the case of engine acyclism condition.

  15. Impact of Export Control and Technology Transfer Regimes: International Perspectives

    DTIC Science & Technology

    2012-01-07

    Impact of Export Control and Technology Transfer Regimes: International Perspectives 7 January 2012 by BGen (Ret.) Raymond E. Franck ...contact: NPS Acquisition Research Program Attn: James B. Greene, RADM, USN, (Ret.) Acquisition Chair Graduate School of Business and Public Policy...k^s^i=mlpqdo^ar^qb=p`elli= About the Authors Raymond (Chip) Franck , PhD, Senior Lecturer, Graduate School of Business & Public Policy, Naval

  16. Far-from-equilibrium superconductor in fluctuational regime.

    SciTech Connect

    Petkovic, A.; Chtchelkatchev, N. M.; Vinokur, V. M.

    2011-08-19

    We derive Ginzburg-Landau-type action for a two-dimensional disordered superconductor under far-from-equilibrium conditions in a fluctuational regime. Then, utilizing it, we calculate fluctuation-induced density of states and Maki-Thomson- and Aslamazov-Larkin-type contributions to the in-plane electrical conductivity. We apply our approach to a thin superconducting film sandwiched between a gate and a substrate, which have different temperatures and different electrochemical potentials.

  17. Study of the Transition Flow Regime using Monte Carlo Methods

    NASA Technical Reports Server (NTRS)

    Hassan, H. A.

    1999-01-01

    This NASA Cooperative Agreement presents a study of the Transition Flow Regime Using Monte Carlo Methods. The topics included in this final report are: 1) New Direct Simulation Monte Carlo (DSMC) procedures; 2) The DS3W and DS2A Programs; 3) Papers presented; 4) Miscellaneous Applications and Program Modifications; 5) Solution of Transitional Wake Flows at Mach 10; and 6) Turbulence Modeling of Shock-Dominated Fows with a k-Enstrophy Formulation.

  18. The Thermal Regime Around Buried Submarine High-Voltage Cables

    NASA Astrophysics Data System (ADS)

    Emeana, C. J.; Dix, J.; Henstock, T.; Gernon, T.; Thompson, C.; Pilgrim, J.

    2015-12-01

    The expansion of offshore renewable energy infrastructure and the desire for "trans-continental shelf" power transmission, all require the use of submarine High Voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70oC and are typically buried at depths of 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the thermal properties of near surface shelf sediments are poorly understood and this increases the uncertainty in determining the required cable current ratings, cable reliability and the potential effects on the sedimentary environments. We present temperature measurements from a 2D laboratory experiment, designed to represent a buried, submarine HV cable. We used a large (2.5 m-high) tank, filled with water-saturated ballotini and instrumented with 120 thermocouples, which measured the time-dependent 2D temperature distributions around the heat source. The experiments use a buried heat source to represent a series of realistic cable surface temperatures with the aim for identifying the thermal regimes generated within typical non-cohesive shelf sediments: coarse silt, fine sand and very coarse sand. The steady state heat flow regimes, and normalised and radial temperature distributions were assessed. Our results show that at temperatures up to 60°C above ambient, the thermal regimes are conductive for the coarse silt sediments and convective for the very coarse sand sediments even at 7°C above ambient. However, the heat flow pattern through the fine sand sediment shows a transition from conductive to convective heat flow at a temperature of approximately 20°C above ambient. These findings offer an important new understanding of the thermal regimes associated with submarine HV cables buried in different substrates and has huge impacts on cable ratings as the IEC 60287 standard only considers conductive heat flow as well as other potential near surface impacts.

  19. Development of the Regimes of Semiautomatic Contact Soldering

    NASA Astrophysics Data System (ADS)

    Shtennikov, V. N.

    2015-01-01

    The influence of the soldering rod length on the contact soldering temperature has been studied. The results of investigations were taken as a basis for incorporating a high-speed semiautomatic regime of soldering integrated circuits with planar leads to multilayer printed circuit boards. It has been established that to ensure an optimum soldering temperature it is necessary to take account of the temperature of the soldering rod before soldering, its length and diameter, and the soldering time when the rod is short.

  20. An infrared spectral sequence into the brown dwarf regime

    NASA Astrophysics Data System (ADS)

    Jones, H. R. A.

    2000-05-01

    A spectral sequence from mid-type M dwarfs into the brown dwarf regime is presented. These spectra cover the wavelength range 0.8 to 2.4 microns and measure the peak of the spectral energy distribution for these extremely red objects. The spectra were taken with the Hubble Space Telescope and represent an infrared spectra of M dwarfs and brown dwarfs which are free from the problems of correcting for the terrestial atmospheric absorption.

  1. MCNP/X Transport in the Tabular Regime

    NASA Astrophysics Data System (ADS)

    Hughes, H. Grady

    2007-03-01

    We review the transport capabilities of the MCNP and MCNPX Monte Carlo codes in the energy regimes in which tabular transport data are available. Giving special attention to neutron tables, we emphasize the measures taken to improve the treatment of a variety of difficult aspects of the transport problem, including unresolved resonances, thermal issues, and the availability of suitable cross sections sets. We also briefly touch on the current situation in regard to photon, electron, and proton transport tables.

  2. Signature candidate of quantum chaos far from the semiclassical regime

    SciTech Connect

    Li, Shang-Bin Xu, Zhengyuan

    2014-03-15

    We numerically investigated the entanglement product in the simplest coupled kicked top model with the spin j = 1. Different from the dynamical pattern of entanglement in the semiclassical regime, two similar initial states may have discordant entanglement oscillations. A candidate of the quantum signature of this classical chaotic system was proposed. The potential antimonotonic relation between the rank correlation coefficient qualifying the concordant of two entanglement evolutions and the stationary entanglement was preliminarily revealed.

  3. Cascade frequency generation regime in an optical parametric oscillator

    SciTech Connect

    Kolker, D B; Dmitriev, Aleksandr K; Gorelik, P; Vong, Franko; Zondy, J J

    2009-05-31

    In a parametric oscillator of a special two-sectional design based on a lithium niobate periodic structure, a cascade frequency generation regime was observed in which a signal wave pumped a secondary parametric oscillator, producing secondary signal and idler waves. The secondary parametric oscillator can be tuned in a broad range of {approx}200 nm with respect to a fixed wavelength of the primary idler wave. (nonlinear optical phenomena)

  4. Statistical instability of barrier microdischarges operating in townsend regime

    SciTech Connect

    Nagorny, V. P.

    2007-01-15

    The dynamics of barrier microdischarges operating in a Townsend regime is studied analytically and via kinetic particle-in-cell/Monte Carlo simulations. It is shown that statistical fluctuations of the number of charged particles in the discharge gap strongly influence the dynamics of natural oscillations of the discharge current and may even lead to a disruption of the discharge. Analysis of the statistical effects based on a simple model is suggested. The role of external sources in stabilizing microdischarges is clarified.

  5. 2D Melting of Plasma Crystals: Equilibrium and Nonequilibrium Regimes

    SciTech Connect

    Nosenko, V.; Zhdanov, S. K.; Ivlev, A. V.; Knapek, C. A.; Morfill, G. E.

    2009-07-03

    Comprehensive experimental investigations of melting in two-dimensional complex plasmas were carried out. Different experiments were performed in steady and unsteady heating regimes. We demonstrate an Arrhenius dependence of the defect concentration on the kinetic temperature in steady-state experiments, and show the evidence of metastable quenching in unsteady experiments, where the defect concentration follows a power-law temperature scaling. In all experiments, independent indicators suggest a grain-boundary-induced melting scenario.

  6. Regime and Periphery in Northern Yemen: The Huthi Phenomenon

    DTIC Science & Technology

    2010-01-01

    for Primary Sa‘da Crops . . . . . . . . . . . . . . . . . . . . . 32 1.5. Weapons Estimates for Conflict Governorates, 2004...Huthi’s criti- cism of the Saleh regime began to target the latter’s readiness to close ranks with the United States. Husayn focused in particular on the...Huthi actions, and sympathetic Zaydis in the community—driven to greater affiliation with the Huthis? How do we inter- pret the readiness of groups

  7. Nano-plasmonic antennas in the near infrared regime.

    PubMed

    Berkovitch, N; Ginzburg, P; Orenstein, M

    2012-02-22

    Plasmonic nano-antennas constitute a central research topic in current science and engineering with an enormous variety of potential applications. Here we review the recent progress in the niche of plasmonic nano-antennas operating in the near infrared part of the spectrum which is important for a variety of applications. Tuning of the resonance into the near infrared regime is emphasized in the perspectives of fabrication, measurement, modeling, and analytical treatments, concentrating on the vast recent achievements in these areas.

  8. Vibration analysis of a hydro generator for different operating regimes

    NASA Astrophysics Data System (ADS)

    Haţiegan, C.; Pădureanu, I.; Jurcu, M.; Nedeloni, M. D.; Hamat, C. O.; Chioncel, C. P.; Trocaru, S.; Vasile, O.; Bădescu, O.; Micliuc, D.; (Filip Nedeloni, L.; Băra, A.; (Barboni Haţiegan, L.

    2017-01-01

    Based on experimental measurements, this paper presents the vibration analysis of a hydro generator that equips a Kaplan hydraulic turbine of a Hydropower plant in Romania. This analysis means vibrations measurement to different operating regimes of the hydro generator respectively before installing it and into operation, namely putting off load mode (unexcited and excited) respectively putting on load mode. By comparing, through the experimental results obtained before and after the operation of hydro aggregates are observed vibrations improvements.

  9. MCNP/X TRANSPORT IN THE TABULAR REGIME

    SciTech Connect

    HUGHES, H. GRADY

    2007-01-08

    The authors review the transport capabilities of the MCNP and MCNPX Monte Carlo codes in the energy regimes in which tabular transport data are available. Giving special attention to neutron tables, they emphasize the measures taken to improve the treatment of a variety of difficult aspects of the transport problem, including unresolved resonances, thermal issues, and the availability of suitable cross sections sets. They also briefly touch on the current situation in regard to photon, electron, and proton transport tables.

  10. Plasma regimes in high power pulsed magnetron sputtering

    NASA Astrophysics Data System (ADS)

    de Los Arcos, Teresa

    2013-09-01

    High Power Pulsed Magnetron Sputtering (HPPMS) is a relatively recent variation of magnetron sputtering where high power is applied to the magnetron in short pulses. The result is the formation of dense transient plasmas with a high fraction of ionized species, ideally leading to better control of film growth through substrate bias. However, the broad range of experimental conditions accessible in pulsed discharges results in bewildering variations in current and voltage pulse shapes, pulse power densities, etc, which represent different discharge behaviors, making it difficult to identify relevant deposition conditions. The complexity of the plasma dynamics is evident. Within each pulse, plasma characteristics such as plasma composition, density, gas rarefaction, spatial distribution, degree of self-sputtering, etc. vary with time. A recent development has been the discovery that the plasma emission can self-organize into well-defined regions of high and low plasma emissivity above the racetrack (spokes), which rotate in the direction given by the E ×B drift and that significantly influence the transport mechanisms in HPPMS. One seemingly universal characteristic of HPPMS plasmas is the existence of well defined plasma regimes for different power ranges. These regimes are clearly differentiated in terms of plasma conductivity, plasma composition and spatial plasma self-organization. We will discuss the global characteristics of these regimes in terms of current-voltage characteristics, energy-resolved QMS and OES analysis, and fast imaging. In particular we will discuss how the reorganization of the plasma emission into spokes is associated only to specific regimes of high plasma conductivity. We will also briefly discuss the role of the target in shaping the characteristics of the HPPMS plasma, since sputtering is a surface-driven process. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) within the framework of the SFB-TR87.

  11. Maritime Security Regime Concept: A Global Approach to Regional Challenges

    DTIC Science & Technology

    2012-09-27

    issue-area.” Krasner , Stephen D . (ed.) 1983. International Regimes, Ithaca, NY: Cornell University Press. Page 1. 3 This Concept was developed...political will to address a specific problem. • Disputes and Legal Interpretations: the clash of interests between coastal states who aim for increased...S) AND ADDRESS (ES) JOINT STAFF-MN//ACT Integration 116 Lakeview Parkway Suffolk, VA 23435 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING

  12. Steady state plasma operation in RF dominated regimes on EAST

    SciTech Connect

    Zhang, X. J.; Zhao, Y. P.; Gong, X. Z.; Hu, C. D.; Liu, F. K.; Hu, L. Q.; Wan, B. N. Li, J. G.

    2015-12-10

    Significant progress has recently been made on EAST in the 2014 campaign, including the enhanced CW H&CD system over 20MW heating power (LHCD, ICRH and NBI), more than 70 diagnostics, ITER-like W-monoblock on upper divertor, two inner cryo-pumps and RMP coils, enabling EAST to investigate long pulse H mode operation with dominant electron heating and low torque to address the critical issues for ITER. H-mode plasmas were achieved by new H&CD system or 4.6GHz LHCD alone for the first time. Long pulse high performance H mode has been obtained by LHCD alone up to 28s at H{sub 98}∼1.2 or by combing of ICRH and LHCD, no or small ELM was found in RF plasmas, which is essential for steady state operation in the future Tokamak. Plasma operation in low collision regimes were implemented by new 4.6GHz LHCD with core Te∼4.5keV. The non-inductive scenarios with high performance at high bootstrap current fraction have been demonstrated in RF dominated regimes for long pulse operation. Near full non-inductive CD discharges have been achieved. In addition, effective heating and decoupling method under multi-transmitter for ICRF system were developed in this campaign, etc. EAST could be in operation with over 30MW CW heating and current drive power (LHCD ICRH NBI and ECRH), enhanced diagnostic capabilities and full actively-cooled metal wall from 2015. It will therefore allow to access new confinement regimes and to extend these regimes towards to steady state operation.

  13. Steady state plasma operation in RF dominated regimes on EAST

    NASA Astrophysics Data System (ADS)

    Zhang, X. J.; Zhao, Y. P.; Gong, X. Z.; Hu, C. D.; Liu, F. K.; Hu, L. Q.; Wan, B. N.; Li, J. G.

    2015-12-01

    Significant progress has recently been made on EAST in the 2014 campaign, including the enhanced CW H&CD system over 20MW heating power (LHCD, ICRH and NBI), more than 70 diagnostics, ITER-like W-monoblock on upper divertor, two inner cryo-pumps and RMP coils, enabling EAST to investigate long pulse H mode operation with dominant electron heating and low torque to address the critical issues for ITER. H-mode plasmas were achieved by new H&CD system or 4.6GHz LHCD alone for the first time. Long pulse high performance H mode has been obtained by LHCD alone up to 28s at H98˜1.2 or by combing of ICRH and LHCD, no or small ELM was found in RF plasmas, which is essential for steady state operation in the future Tokamak. Plasma operation in low collision regimes were implemented by new 4.6GHz LHCD with core Te˜4.5keV. The non-inductive scenarios with high performance at high bootstrap current fraction have been demonstrated in RF dominated regimes for long pulse operation. Near full non-inductive CD discharges have been achieved. In addition, effective heating and decoupling method under multi-transmitter for ICRF system were developed in this campaign, etc. EAST could be in operation with over 30MW CW heating and current drive power (LHCD ICRH NBI and ECRH), enhanced diagnostic capabilities and full actively-cooled metal wall from 2015. It will therefore allow to access new confinement regimes and to extend these regimes towards to steady state operation.

  14. Non-gaussianity in the strong regime of warm inflation

    SciTech Connect

    Moss, Ian G.; Yeomans, Timothy E-mail: timothy.yeomans@ncl.ac.uk

    2011-08-01

    The bispectrum of scalar mode density perturbations is analysed for the strong regime of warm inflationary models. This analysis generalises previous results by allowing damping terms in the inflaton equation of motion that are dependent on temperature. A significant amount of non-gaussianity emerges with constant (or local) non-linearity parameter f{sub NL} ∼ 20, in addition to the terms with non-constant f{sub NL} which are characteristic of warm inflation.

  15. The effect of holidays on a token economy regime.

    PubMed

    Elliott, P A

    1977-05-01

    This preliminary study investigates the effect on patients' performance of a set time off, in the form of a short holiday, from a strict reinforcement (token economy) regime. Assessment was by the patients' mean token earnings before and after the holiday and their self-care and work performance throughout. The results suggest that a holiday from a token economy has beneficial effects for patients.

  16. Fishbone mode excitation in the ion kinetic regime

    SciTech Connect

    Shi, B.; Sui, G. |

    1997-08-01

    By solving the dispersion relation in the ion kinetic regime, it is found that the threshold of the plasma beta value for exciting the ion-fishbone mode is lowered. Thus, for most of the present-day tokamaks where the Bussac criterion [Bussac {ital et al.}, Phys. Rev. Lett. {bold 35}, 1638 (1975)] is not satisfied, it will still be possible to excite the ion-fishbone mode. {copyright} {ital 1997 American Institute of Physics.}

  17. Kolmogorov and scalar spectral regimes in numerical turbulence

    NASA Technical Reports Server (NTRS)

    Kerr, R. M.

    1985-01-01

    Velocity and passive-scalar spectra for turbulent fields generated by a forced three-dimensional simulation and Taylormicroscale Reynolds numbers up to 83 are shown to have distinct spectral regimes, including a Kolmogorov inertial subrange. Both one- and three-dimensional spectra are shown for comparison with experiment and theory, respectively. When normalized by the Kolmogorov dissipation scales velocity spectra collapse to a single curve and a high-wavenumber bulge is seen. The bulge leads to an artificially high Kolmogorov constant, but is consistent with recent measurements of the velocity spectrum in the dissipation regime and the velocity-derivative skewness. Scalar spectra, when normalized by the Oboukov-Corrsin scales, collapse to curves which depend only on Prandtl number and show a universal inertial-convective subrange, independent of Prandtl number. When normalized by the Batchelor scales, the scalar spectra show a universal dissipation regime which is independent of Prandtl numbers from 0.1 to 1.0. The time development of velocity spectra is illustrated by energy-transfer spectra in which distinct pulses propagate to high wavenumbers.

  18. Background and mass extinctions: the alternation of macroevolutionary regimes.

    PubMed

    Jablonski, D

    1986-01-10

    Comparison of evolutionary patterns among Late Cretaceous marine bivalves and gastropods during times of normal, background levels of extinction and during the end-Cretaceous mass extinction indicates that mass extinctions are neither an intensification of background patterns nor an entirely random culling of the biota. During background times, traits such as planktotrophic larval development, broad geographic range of constituent species, and high species richness enhanced survivorship of species and genera. In contrast, during the, end-Cretaceous and other mass extinctions these factors were ineffectual, but broad geographic deployment of an entire lineage, regardless of the ranges of its constituent species, enhanced survivorship. Large-scale evolutionary patterns are evidently shaped by the alternation of these two macroevolutionary regimes, with rare but important mass extinctions driving shifts in the composition of the biota that have little relation to success during the background regime. Lineages or adaptations can be lost during mass extinctions for reasons unrelated to their survival values for organisms or species during background times, and long-term success would require the chance occurrence within a single lineage of sets of traits conducive to survivorship under both regimes.

  19. Theoretical issues of gender in the transition from socialist regimes.

    PubMed

    Grapard, U

    1997-09-01

    This article applies a gender perspective to a consideration of the recent economic and political reforms in Eastern and Central Europe. After an introduction and a brief overview of recent empirical studies of the impact of women's economic, political, and social status, the paper explores the difficulties inherent in attempts to create an East-West dialogue on women's interests. The article proposes that these difficulties can be articulated by 1) identifying whether a political regime uses an essentialist (men and women have fundamentally different biological natures) or a social constructionist (most observed differences between men and women are socially created) view to define the nature of women; 2) identifying how these distinct views of gender relations are articulated in the philosophical underpinnings of the two political regimes (the liberal Western system that strictly separates the public and private spheres while assigning different activities for men and women and the socialistic/communistic system that subordinates social reproduction to the sphere of production); and 3) comparing how these views have been articulated in social and institutional arrangements of gender relations in the two regimes. The article then claims that an understanding of the interaction between gender relations, political theory, and social practices in both the West and the East is essential for understanding the problems involved in discussions of the political-economic transition and how it affects men and women.

  20. Identifying Biologically Relevant Cues in the Hydrologic Regime

    NASA Astrophysics Data System (ADS)

    Lovellford, R. M.; Flitcroft, R.; Santelmann, M. V.; Grant, G. E.; Safeeq, M.; Lewis, S.

    2012-12-01

    Seasonal variation in hydrologic discharge and temperature defines the availability, connectivity, and quality of lentic habitats. Native aquatic species are adapted to local hydrologic regimes , eg. magnitudes and rates of change . In recent decades, biologically relevant hydrologic conditions have been identified that are necessary to maintain habitat conditions for aquatic obligate species. Another element of hydrologic regimes important to aquatic species are the cues that inform individuals of seasonal changes that precipitate important physiological or behavioral alterations. There is a need for hydrologists, biologists, and ecologists, to define biologically significant cues within the hydrologic regime. Coho salmon (Onchorhynchus kisutch), an anadromous species of Pacific salmon, offers an example of sensitivity to environmental cues. Examinations of the run-timing of mature adult coho salmon on the North Umpqua River, OR, indicate that migration timing coincides with decreasing fall water temperatures prior to increasing winter discharge. For this species, adults leave the ocean ready to spawn. Adults need to spawn in small headwater streams prior to the onset of intense storm conditions that prohibit effective deposition or fertilization of eggs in redds (salmon nests).Therefore, the timing of spawning must be carefully executed. Understanding the cues that trigger specific behaviors gives insight to the processes that provide ecosystem stability and flexibility over time. Improved understanding of these cues may help us protect freshwater ecosystems and improve management for endangered species.

  1. Comparison of algorithms for determination of solar wind regimes

    NASA Astrophysics Data System (ADS)

    Neugebauer, Marcia; Reisenfeld, Daniel; Richardson, Ian G.

    2016-09-01

    This study compares the designation of different solar wind flow regimes (transient, coronal hole, and streamer belt) according to two algorithms derived from observations by the Solar Wind Ion Composition Spectrometer, the Solar Wind Electron Proton Alpha Monitor, and the Magnetometer on the ACE spacecraft, with a similar regime determination performed on board the Genesis spacecraft. The comparison is made for the interval from late 2001 to early 2004 when Genesis was collecting solar wind ions for return to Earth. The agreement between hourly regime assignments from any pair of algorithms was less than two thirds, while the simultaneous agreement between all three algorithms was only 49%. When the results of the algorithms were compared to a catalog of interplanetary coronal mass ejection events, it was found that almost all the events in the catalog were confirmed by the spacecraft algorithms. On the other hand, many short transient events, lasting 1 to 13 h, that were unanimously selected as transient like by the algorithms, were not included in the catalog.

  2. Osmotic adaptation in Ulva lactuca under fluctuating salinity regimes.

    PubMed

    Dickson, D M; Wyn Jones, R G; Davenport, J

    1982-09-01

    A study has been made of the osmotic responses of the green intertidal alga, Ulva lactuca, under two fluctuating salinity regimes; sinusoidal and square-wave fluctuations between 30 and 100% sea water in a 12 h cycle. These regimes closely resemble the tidal fluctuation of salinity encountered by the alga in its natural estuarine habitat. Data on changes in the inorganic ions, potassium, sodium, chloride and sulphate; in the organic solute, dimethylsulphoniopropionate; in the total sugar levels and estimated osmotic and turgor pressures under the two salinity regimes are reported. Significant differences in the solute responses under these different conditions were detected. In general, better control of ion fluxes appeared to be exercised under the sinusoidal conditions which also buffered changes in dimethylsulphoniopropionate levels. Influxes of potassium were highly light-dependent. Chloride levels conspicuously failed to reach the steady-state levels in the 6-h-hyper-osmotic part of either the abrupt or gradual cycle. The possible significance of these data, which may better reflect osmotic changes in the natural environment, and some of the problems encountered, particularly in accounting for charge balance under some conditions, are discussed.

  3. Unsustainable Groundwater Exploitation and Stochastic Regime Shifts: Converging Management Constraints

    NASA Astrophysics Data System (ADS)

    Rao, Suresh; Park, Jeryang

    2014-05-01

    Increasing water security concerns arise from projected increases in competing freshwater demands, resulting from rapid urbanization, growing affluent population, and the need for increased production of food and bio-energy. These global trends in concert with the convergence of three groups of threats are likely to exacerbate freshwater security issues: (1) increasing dependency on effectively non-renewable groundwater ("peak water"); (2) increasing groundwater quality impairment("land-use intensification") from larger contaminant loads delivered from the vadose zone and surface water; and (3) increasing uncertainties in groundwater demand/supply from climate change ("stochastic risks"). Here, we present a conceptual framework for exploring water security threats, with a consideration of aquifers as complex hydrological systems with two stable states. Regime shifts in groundwater pumping -- from "sufficient" to "insufficient" -- result from changes in both internal system dynamics and external forcing from stochastic divers (non-stationary demands, hydro-climatic patterns). Examples from recent related work, in groundwater and surface water systems and ecosystems, are briefly reviewed as a prelude to presentation of model simulations of hypothetical scenarios of regime-shifts (tipping points) involving groundwater quantity and quality constraints. In addition to three types of widely recognized tipping points, we introduce a new type, stochastic tipping, that contributes to unexpected, undesirable regime shifts, resulting in inability to meet groundwater pumping needs, even when the perceived precariousness is small and the system is far from bifurcation point (deterministic tipping). Implications to sustainable groundwater management are discussed.

  4. Analysis of thermionic bare tether operation regimes in passive mode

    NASA Astrophysics Data System (ADS)

    Sanmartín, J. R.; Chen, Xin; Sánchez-Arriaga, G.

    2017-01-01

    A thermionic bare tether (TBT) is a long conductor coated with a low work-function material. In drag mode, a tether segment extending from anodic end A to a zero-bias point B, with the standard Orbital-motion-limited current collection, is followed by a complex cathodic segment. In general, as bias becomes more negative in moving from B to cathodic end C, one first finds space-charge-limited (SCL) emission covering up to some intermediate point B*, then full Richardson-Dushman (RD) emission reaching from B* to end C. An approximate analytical study, which combines the current and voltage profile equations with results from asymptotic studies of the Vlasov-Poisson system for emissive probes, is carried out to determine the parameter domain covering two limit regimes, which are effectively controlled by just two dimensionless parameters involving ambient plasma and TBT material properties. In one such limit regime, no point B* is reached and thus no full RD emission develops. In an opposite regime, SCL segment BB* is too short to contribute significantly to the current balance.

  5. Globalization, marine regime shifts and the Soviet Union

    PubMed Central

    Österblom, Henrik; Folke, Carl

    2015-01-01

    Regime shifts have been observed in marine ecosystems around the world, with climate and fishing suggested as major drivers of such shifts. The global and regional dynamics of the climate system have been studied in this context, and efforts to develop an analogous understanding of fishing activities are developing. Here, we investigate the timing of pelagic marine regime shifts in relation to the emergence of regional and global fishing activities of the Soviet Union. Our investigation of official catch statistics reflects that the Soviet Union was a major fishing actor in all large marine ecosystems where regime shifts have been documented, including in ecosystems where overfishing has been established as a key driver of these changes (in the Baltic and Black Seas and the Scotian Shelf). Globalization of Soviet Union fishing activities pushed exploitation to radically new levels and triggered regional and global governance responses for improved management. Since then, exploitation levels have remained and increased with new actors involved. Based on our exploratory work, we propose that a deeper understanding of the role of global fishing actors is central for improved management of marine ecosystems.

  6. Early regimes of water imbibition in nanoslit silica channels

    NASA Astrophysics Data System (ADS)

    Oyarzua, Elton; Zambrano, Harvey; Walther, Jens Honore; Mejia, Andres

    2014-11-01

    Capillarity is currently subject to a significant research interest. Attention is mainly paid to the late stage of the imbibition when a developed flow is reached and the Laplace pressure is balanced by the viscosity. Nevertheless, as the miniaturization of devices is reaching the nanoscale a thorough understanding of fluid flow in nanoconfinement is required. In nanofluidics, short timescales and surface characteristics dominate the flows. In this study, molecular simulations are conducted to investigate the early stage of water imbibition in silica nanochannels with heights of 4 to 10 nm. Results indicate that nanoscale imbibition is divided in three regimes. An initial regime with imbibition linearly dependent of time, where the capillary force is mainly balanced by inertia. Thereafter, a period, in which, the balance has contributions from both inertia and viscosity and, subsequently, a final regime, wherein, viscosity dominates the capillary force balance. Velocity profiles confirm the passage from an inviscid flow to a developed Poisseuille flow. The meniscus position as a function of time and air accumulation in front of the advancing meniscus are computed for different air pressures, the results reveal a systematic retarding effect of gas pressurization on the imbibition. We acknowledge support from Fondecyt Project No 11130559.

  7. Sustainability of Transient Kinetic Regimes and Origins of Death.

    PubMed

    Zubarev, Dmitry Yu; Pachón, Leonardo A

    2016-02-08

    It is generally recognized that a distinguishing feature of life is its peculiar capability to avoid equilibration. The origin of this capability and its evolution along the timeline of abiogenesis is not yet understood. We propose to study an analog of this phenomenon that could emerge in non-biological systems. To this end, we introduce the concept of sustainability of transient kinetic regimes. This concept is illustrated via investigation of cooperative effects in an extended system of compartmentalized chemical oscillators under batch and semi-batch conditions. The computational study of a model system shows robust enhancement of lifetimes of the decaying oscillations which translates into the evolution of the survival function of the transient non-equilibrium regime. This model does not rely on any form of replication. Rather, it explores the role of a structured effective environment as a contributor to the system-bath interactions that define non-equilibrium regimes. We implicate the noise produced by the effective environment of a compartmentalized oscillator as the cause of the lifetime extension.

  8. Models of warm and cold regimes of the winter stratosphere

    NASA Astrophysics Data System (ADS)

    Guryanov, Vladimir

    Research of fields of geopotential height, temperature, zonal and meridional wind in stratosphere was carried out using the Met Office data for winter seasons from 1991/1992 to 2006-2007. The above analyzes shows that change within season thermodynamic values at high latitudes during the winter is higher than seasonal or longitudinal change. Hence the average models of the cold periods of high latitudes and average monthly values have a limited applicability. In 1982 International Standard Organization (ISO) also acknowledged the necessity for creating of special models for "warm" and "cold" regimes of the high latitude winter stratosphere. Warm and cold stratosphere states were distinguished by the presence or absence of stratospheric warmings of variable intensity exceeding 10 hPa. Special maps and latitude-longitude cuts of mean values and mean square deviations of the geopotential height, temperature, zonal and meridional wind have been created for these regimes. Models of "warm" and "cold" regimes also included zonal harmonics with wave numbers 1 and 2 for all observed meteorological fields

  9. Sustainability of Transient Kinetic Regimes and Origins of Death

    PubMed Central

    Zubarev, Dmitry Yu.; Pachón, Leonardo A.

    2016-01-01

    It is generally recognized that a distinguishing feature of life is its peculiar capability to avoid equilibration. The origin of this capability and its evolution along the timeline of abiogenesis is not yet understood. We propose to study an analog of this phenomenon that could emerge in non-biological systems. To this end, we introduce the concept of sustainability of transient kinetic regimes. This concept is illustrated via investigation of cooperative effects in an extended system of compartmentalized chemical oscillators under batch and semi-batch conditions. The computational study of a model system shows robust enhancement of lifetimes of the decaying oscillations which translates into the evolution of the survival function of the transient non-equilibrium regime. This model does not rely on any form of replication. Rather, it explores the role of a structured effective environment as a contributor to the system-bath interactions that define non-equilibrium regimes. We implicate the noise produced by the effective environment of a compartmentalized oscillator as the cause of the lifetime extension. PMID:26853459

  10. Socioecological regime shifts in the setting of complex social interactions

    NASA Astrophysics Data System (ADS)

    Sugiarto, Hendrik Santoso; Chung, Ning Ning; Lai, Choy Heng; Chew, Lock Yue

    2015-06-01

    The coupling between social and ecological system has become more ubiquitous and predominant in the current era. The strong interaction between these systems can bring about regime shifts which in the extreme can lead to the collapse of social cooperation and the extinction of ecological resources. In this paper, we study the occurrence of such regime shifts in the context of a coupled social-ecological system where social cooperation is established by means of sanction that punishes local selfish act and promotes norms that prescribe nonexcessive resource extraction. In particular, we investigate the role of social networks on social-ecological regimes shift and the corresponding hysteresis effects caused by the local ostracism mechanism under different social and ecological parameters. Our results show that a lowering of network degree reduces the hysteresis effect and also alters the tipping point, which is duly verified by our numerical results and analytical estimation. Interestingly, the hysteresis effect is found to be stronger in scale-free network in comparison with random network even when both networks have the same average degree. These results provide deeper insights into the resilience of these systems, and can have important implications on the management of coupled social-ecological systems with complex social interactions.

  11. Sustainability of Transient Kinetic Regimes and Origins of Death

    NASA Astrophysics Data System (ADS)

    Zubarev, Dmitry Yu.; Pachón, Leonardo A.

    2016-02-01

    It is generally recognized that a distinguishing feature of life is its peculiar capability to avoid equilibration. The origin of this capability and its evolution along the timeline of abiogenesis is not yet understood. We propose to study an analog of this phenomenon that could emerge in non-biological systems. To this end, we introduce the concept of sustainability of transient kinetic regimes. This concept is illustrated via investigation of cooperative effects in an extended system of compartmentalized chemical oscillators under batch and semi-batch conditions. The computational study of a model system shows robust enhancement of lifetimes of the decaying oscillations which translates into the evolution of the survival function of the transient non-equilibrium regime. This model does not rely on any form of replication. Rather, it explores the role of a structured effective environment as a contributor to the system-bath interactions that define non-equilibrium regimes. We implicate the noise produced by the effective environment of a compartmentalized oscillator as the cause of the lifetime extension.

  12. Recovery of SINIS turnstile accuracy in a strongly nonequilibrium regime

    NASA Astrophysics Data System (ADS)

    Khaymovich, I. M.; Basko, D. M.

    2016-10-01

    We perform a theoretical study of nonequilibrium effects in charge transport through a hybrid single-electron transistor based on a small normal metal (N) island with the gate-controlled number of electrons, tunnel-coupled to voltage-biased superconducting (S) electrodes (SINIS). Focusing on the turnstile mode of the transistor operation with the gate voltage driven periodically, and electrons on the island being out of equilibrium, we find that the current quantization accuracy is a nonmonotonic function of the relaxation rate ΓF of the distribution function F (ɛ ) on the island due to tunneling, as compared to the drive frequency f , electron-electron 1 /τe e , and electron-phonon 1 /τe p h relaxation rates. Surprisingly, in the strongly nonequilibrium regime, f ≫ΓF≫τee -1,τep h -1 , the turnstile current plateau is recovered, similarly to the ideal equilibrium regime, τep h -1≫ΓF . The plateau is destroyed in the quasiequilibrium regime when the electron-electron relaxation is faster than tunneling.

  13. 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.

  14. Environmental sampling: Issues for the cut-off regime

    SciTech Connect

    Fearey, B.L.

    1995-09-01

    The fissile material cut-off treaty (FMCT) initiative under the Conference on Disarmament mandate is envisioned to include certain aspects of environmental sampling and monitoring. One of the intents of this treaty is to bring certain non-NPT signatories (e.g., threshold states) under this treaty agreement along with the nuclear weapon states (NWSs). This paper provides a brief overview of some of the relevant issues that may be involved in the implementation and use of environmental monitoring for (1) verification of the cut-off regime declarations, (2) the detection of undeclared activities, and, (3) application in non-routine inspections. The intent is to provide backstopping information important for treaty negotiators. Specific issues addressed within this paper include signature sampling, differences in the proposed detection regime, potential signature integrators, specific examples and spoofing concerns. Many of these issues must be carefully considered and weighed in order to create a credibly verifiable inspection regime. Importantly, the cut-off treaty must enable nondiscriminatory implementation, while carefully assuring that nonproliferation treaty requirements are maintained (i.e., preventing unintentional release of critical weapons design information--potentially through environmental sampling and analysis).

  15. Idiosyncratic responses of high Arctic plants to changing snow regimes.

    PubMed

    Rumpf, Sabine B; Semenchuk, Philipp R; Dullinger, Stefan; Cooper, Elisabeth J

    2014-01-01

    The Arctic is one of the ecosystems most affected by climate change; in particular, winter temperatures and precipitation are predicted to increase with consequent changes to snow cover depth and duration. Whether the snow-free period will be shortened or prolonged depends on the extent and temporal patterns of the temperature and precipitation rise; resulting changes will likely affect plant growth with cascading effects throughout the ecosystem. We experimentally manipulated snow regimes using snow fences and shoveling and assessed aboveground size of eight common high arctic plant species weekly throughout the summer. We demonstrated that plant growth responded to snow regime, and that air temperature sum during the snow free period was the best predictor for plant size. The majority of our studied species showed periodic growth; increases in plant size stopped after certain cumulative temperatures were obtained. Plants in early snow-free treatments without additional spring warming were smaller than controls. Response to deeper snow with later melt-out varied between species and categorizing responses by growth forms or habitat associations did not reveal generic trends. We therefore stress the importance of examining responses at the species level, since generalized predictions of aboveground growth responses to changing snow regimes cannot be made.

  16. Fire regime in a Mexican forest under indigenous resource management.

    PubMed

    Fulé, Peter Z; Ramos-Gómez, Mauro; Cortés-Montaño, Citlali; Miller, Andrew M

    2011-04-01

    The Rarámuri (Tarahumara) people live in the mountains and canyons of the Sierra Madre Occidental of Chihuahua, Mexico. They base their subsistence on multiple-use strategies of their natural resources, including agriculture, pastoralism, and harvesting of native plants and wildlife. Pino Gordo is a Rarámuri settlement in a remote location where the forest has not been commercially logged. We reconstructed the forest fire regime from fire-scarred trees, measured the structure of the never-logged forest, and interviewed community members about fire use. Fire occurrence was consistent throughout the 19th and 20th centuries up to our fire scar collection in 2004. This is the least interrupted surface-fire regime reported to date in North America. Studies from other relict sites such as nature reserves in Mexico or the USA have all shown some recent alterations associated with industrialized society. At Pino Gordo, fires recurred frequently at the three study sites, with a composite mean fire interval of 1.9 years (all fires) to 7.6 years (fires scarring 25% or more of samples). Per-sample fire intervals averaged 10-14 years at the three sites. Approximately two-thirds of fires burned in the season of cambial dormancy, probably during the pre-monsoonal drought. Forests were dominated by pines and contained many large living trees and snags, in contrast to two nearby similar forests that have been logged. Community residents reported using fire for many purposes, consistent with previous literature on fire use by indigenous people. Pino Gordo is a valuable example of a continuing frequent-fire regime in a never-harvested forest. The Rarámuri people have actively conserved this forest through their traditional livelihood and management techniques, as opposed to logging the forest, and have also facilitated the fire regime by burning. The data contribute to a better understanding of the interactions of humans who live in pine forests and the fire regimes of these

  17. The human dimension of fire regimes on Earth

    PubMed Central

    Bowman, David M J S; Balch, Jennifer; Artaxo, Paulo; Bond, William J; Cochrane, Mark A; D'Antonio, Carla M; DeFries, Ruth; Johnston, Fay H; Keeley, Jon E; Krawchuk, Meg A; Kull, Christian A; Mack, Michelle; Moritz, Max A; Pyne, Stephen; Roos, Christopher I; Scott, Andrew C; Sodhi, Navjot S; Swetnam, Thomas W; Whittaker, Robert

    2011-01-01

    Humans and their ancestors are unique in being a fire-making species, but ‘natural’ (i.e. independent of humans) fires have an ancient, geological history on Earth. Natural fires have influenced biological evolution and global biogeochemical cycles, making fire integral to the functioning of some biomes. Globally, debate rages about the impact on ecosystems of prehistoric human-set fires, with views ranging from catastrophic to negligible. Understanding of the diversity of human fire regimes on Earth in the past, present and future remains rudimentary. It remains uncertain how humans have caused a departure from ‘natural’ background levels that vary with climate change. Available evidence shows that modern humans can increase or decrease background levels of natural fire activity by clearing forests, promoting grazing, dispersing plants, altering ignition patterns and actively suppressing fires, thereby causing substantial ecosystem changes and loss of biodiversity. Some of these contemporary fire regimes cause substantial economic disruptions owing to the destruction of infrastructure, degradation of ecosystem services, loss of life, and smoke-related health effects. These episodic disasters help frame negative public attitudes towards landscape fires, despite the need for burning to sustain some ecosystems. Greenhouse gas-induced warming and changes in the hydrological cycle may increase the occurrence of large, severe fires, with potentially significant feedbacks to the Earth system. Improved understanding of human fire regimes demands: (1) better data on past and current human influences on fire regimes to enable global comparative analyses, (2) a greater understanding of different cultural traditions of landscape burning and their positive and negative social, economic and ecological effects, and (3) more realistic representations of anthropogenic fire in global vegetation and climate change models. We provide an historical framework to promote

  18. INTERFACIAL AREA TRANSPORT AND REGIME TRANSITION IN COMBINATORIAL CHANNELS

    SciTech Connect

    Seugjin Kim

    2011-01-28

    . This study investigates the geometric effects of 90-degree vertical elbows and flow configurations in two-phase flow. The study shows that the elbows make a significant effect on the transport characteristics of two-phase flow, which includes the changes in interfacial structures, bubble interaction mechanisms and flow regime transition. The effect of the elbows is characterized for global and local two-phase flow parameters. The global two-phase flow parameters include two-phase pressure, interfacial structures and flow regime transition. In order to characterize the frictional pressure drop and minor loss across the vertical elbows, pressure measurements are obtained across the test section over a wide range of flow conditions in both single-phase and two-phase flow conditions. A two-phase pressure drop correlation analogous to Lockhart-Martinelli correlation is proposed to predict the minor loss across the elbows. A high speed camera is employed to perform extensive flow visualization studies across the elbows in vertical upward, horizontal and vertical downward sections and modified flow regime maps are proposed. It is found that modified flow regime maps immediately downstream of the vertical upward elbow deviate significantly from the conventional flow regime map. A qualitative assessment of the counter-current flow limitation characteristics specific to the current experimental facility is performed. A multi-sensor conductivity probe is used to measure local two-phase flow parameters such as: void fraction, bubble velocity, interfacial area concentration and bubble frequency. The local measurements are obtained for six different flow conditions at ten measurement locations along axial direction of the test section. Both the vertical-upward and vertical-downward elbows have a significant impact on bubble distribution, resulting in, a bimodal distribution along the horizontal radius of the tube cross-section and migration of bubbles towards the inside of the

  19. Fire regimes of quaking aspen in the Mountain West

    USGS Publications Warehouse

    Shinneman, Douglas J.; Baker, William L.; Rogers, Paul C.; Kulakowski, Dominik

    2013-01-01

    Quaking aspen (Populus tremuloides Michx.) is the most widespread tree species in North America, and it is found throughout much of the Mountain West (MW) across a broad range of bioclimatic regions. Aspen typically regenerates asexually and prolifically after fire, and due to its seral status in many western conifer forests, aspen is often considered dependent upon disturbance for persistence. In many landscapes, historical evidence for post-fire aspen establishment is clear, and following extended fire-free periods senescing or declining aspen overstories sometimes lack adequate regeneration and are succeeding to conifers. However, aspen also forms relatively stable stands that contain little or no evidence of historical fire. In fact, aspen woodlands range from highly fire-dependent, seral communities to relatively stable, self-replacing, non-seral communities that do not require fire for persistence. Given the broad geographic distribution of aspen, fire regimes in these forests likely co-vary spatially with changing community composition, landscape setting, and climate, and temporally with land use and climate – but relatively few studies have explicitly focused on these important spatiotemporal variations. Here we reviewed the literature to summarize aspen fire regimes in the western US and highlight knowledge gaps. We found that only about one-fourth of the 46 research papers assessed for this review could be considered fire history studies (in which mean fire intervals were calculated), and all but one of these were based primarily on data from fire-scarred conifers. Nearly half of the studies reported at least some evidence of persistent aspen in the absence of fire. We also found that large portions of the MW have had little or no aspen fire history research. As a result of this review, we put forth a classification framework for aspen that is defined by key fire regime parameters (fire severity and probability), and that reflects underlying biophysical

  20. Hydrological regime modifications induced by climate change in Mediterranean area

    NASA Astrophysics Data System (ADS)

    Pumo, Dario; Caracciolo, Domenico; Viola, Francesco; Valerio Noto, Leonardo

    2015-04-01

    The knowledge of river flow regimes has a capital importance for a variety of practical applications, in water resource management, including optimal and sustainable use. Hydrological regime is highly dependent on climatic factors, among which the most important is surely the precipitation, in terms of frequency, seasonal distribution and intensity of rainfall events. The streamflow frequency regime of river basins are often summarized by flow duration curves (FDCs), that offer a simple and comprehensive graphical view of the overall historical variability associated with streamflow, and characterize the ability of the basin to provide flows of various magnitudes. Climate change is likely to lead shifts in the hydrological regime, and, consequently, in the FDCs. Staring from this premise, the primary objective of the present study is to explore the effects of potential climate changes on the hydrological regime of some small Mediterranean basins. To this aim it is here used a recent hydrological model, the ModABa model (MODel for Annual flow duration curves assessment in ephemeral small BAsins), for the probabilistic characterization of the daily streamflows in small catchments. The model has been calibrated and successively validated in a unique small catchment, where it has shown a satisfactory accuracy in reproducing the empirical FDC starting from easily derivable parameters arising from basic ecohydrological knowledge of the basin and commonly available climatic data such as daily precipitation and temperatures. Thus, this work also represents a first attempt to apply the ModABa to basins different from that used for its preliminary design in order to testing its generality. Different case studies are selected within the Sicily region; the model is first calibrated at the sites and then forced by future climatic scenarios, highlighting the principal differences emerging from the current scenario and future FDCs. The future climate scenarios are generated using

  1. Human impacts on river ice regime in the Carpathian Basin

    NASA Astrophysics Data System (ADS)

    Takács, Katalin; Nagy, Balázs; Kern, Zoltán

    2014-05-01

    River ice is a very important component of the cryosphere, and is especially sensitive to climatic variability. Historical records of appearance or disappearance and timing of ice phenomena are useful indicators for past climatic variations (Williams, 1970). Long-term observations of river ice freeze-up and break-up dates are available for many rivers in the temperate or cold region to detect and analyze the effects of climate change on river ice regime. The ice regime of natural rivers is influenced by climatic, hydrological and morphological factors. Regular ice phenomena observation mostly dates back to the 19th century. During this long-term observation period, the human interventions affecting the hydrological and morphological factors have become more and more intensive (Beltaos and Prowse, 2009). The anthropogenic effects, such as river regulation, hydropower use or water pollution causes different changes in river ice regime (Ashton, 1986). To decrease the occurrence of floods and control the water discharge, nowadays most of the rivers are regulated. River regulation changes the morphological parameters of the river bed: the aim is to create solid and equable bed size and stream gradient to prevent river ice congestion. For the satisfaction of increasing water demands hydropower is also used. River damming results a condition like a lake upstream to the barrage; the flow velocity and the turbulence are low, so this might be favourable for river ice appearance and freeze-up (Starosolsky, 1990). Water pollution affects ice regime in two ways; certain water contaminants change the physical characteristics of the water, e.g. lessens the freezing point of the water. Moreover the thermal stress effect of industrial cooling water and communal wastewater is also important; in winter these water sources are usually warmer, than the water body of the river. These interventions result different changes in the characteristic features of river ice regime. Selected

  2. Film thickness for different regimes of fluid-film lubrication. [elliptical contacts

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Dowson, D.

    1983-01-01

    Mathematical formulas are presented which express the dimensionless minimum film thickness for the four lubrication regimes found in elliptical contacts: isoviscous-rigid regime; piezoviscous-rigid regime; isoviscous-elastic regime; and piezoviscous-elastic regime. The relative importance of pressure on elastic distortion and lubricant viscosity is the factor that distinguishes these regimes for a given conjunction geometry. In addition, these equations were used to develop maps of the lubrication regimes by plotting film thickness contours on a log-log grid of the dimensionless viscosity and elasticity parameters for three values of the ellipticity parameter. These results present a complete theoretical film thickness parameter solution for elliptical constants in the four lubrication regimes. The results are particularly useful in initial investigations of many practical lubrication problems involving elliptical conjunctions.

  3. Rheology of cohesive granular materials across multiple dense-flow regimes.

    PubMed

    Gu, Yile; Chialvo, Sebastian; Sundaresan, Sankaran

    2014-09-01

    We investigate the dense-flow rheology of cohesive granular materials through discrete element simulations of homogeneous, simple shear flows of frictional, cohesive, spherical particles. Dense shear flows of noncohesive granular materials exhibit three regimes: quasistatic, inertial, and intermediate, which persist for cohesive materials as well. It is found that cohesion results in bifurcation of the inertial regime into two regimes: (a) a new rate-independent regime and (b) an inertial regime. Transition from rate-independent cohesive regime to inertial regime occurs when the kinetic energy supplied by shearing is sufficient to overcome the cohesive energy. Simulations reveal that inhomogeneous shear band forms in the vicinity of this transition, which is more pronounced at lower particle volume fractions. We propose a rheological model for cohesive systems that captures the simulation results across all four regimes.

  4. North Atlantic weather regimes: A synoptic study of phase space. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Orrhede, Anna Karin

    1990-01-01

    In the phase space of weather, low frequency variability (LFV) of the atmosphere can be captured in a large scale subspace, where a trajectory connects consecutive large scale weather maps, thus revealing flow changes and recurrences. Using this approach, Vautard applied the trajectory speed minimization method (Vautard and Legras) to atmospheric data. From 37 winters of 700 mb geopotential height anomalies over the North Atlantic and the adjacent land masses, four persistent and recurrent weather patterns, interpreted as weather regimes, were discernable: a blocking regime, a zonal regime, a Greenland anticyclone regime, and an Atlantic regime. These regimes are studied further in terms of maintenance and transitions. A regime survey unveils preferences regarding event durations and precursors for the onset or break of an event. The transition frequencies between regimes vary, and together with the transition times, suggest the existence of easier transition routes. These matters are more systematically studied using complete synoptic map sequences from a number of events.

  5. Characteristics of Whipple Shield Performance in the Shatter Regime

    NASA Technical Reports Server (NTRS)

    Ryan, Shannon; Bjorkman, Michael; Christiansen, Eric L.

    2009-01-01

    Between the onset of projectile fragmentation and the assumption of rear wall failure due to an impulsive load, multi-wall ballistic limit equations are linearly interpolated to provide reasonable yet conservative predictions of perforation thresholds with conveniently simple mathematics. Although low velocity and hypervelocity regime predictions are based on analytical expressions, there is no such scientific foundation for predictions in the intermediate (or shatter) regime. As the debris flux in low earth orbit (LEO) becomes increasingly dominated by manmade pollution, the profile of micrometeoroid and orbital debris (MMOD) risk shifts continually towards lower velocities. For the International Space Station (ISS), encounter velocities below 7 km/s now constitute approximately 50% of the penetration risk. Considering that the transition velocity from shatter to hypervelocity impact regimes described by common ballistic limit equations (e.g. new non-optimum Whipple shield equation [1]) occurs at 7 km/s, 50% of station risk is now calculated based on failure limit equations with little analytical foundation. To investigate projectile and shield behavior for impact conditions leading to projectile fragmentation and melt, a series of hypervelocity impact tests have been performed on aluminum Whipple shields. In the experiments projectile diameter, bumper thickness, and shield spacing were kept constant, while rear wall thickness was adjusted to determine spallation and perforation limits at various impact velocities and angles. The results, shown in Figure 1 for normal and 45 impacts, demonstrated behavior that was not sufficiently described by the simplified linear interpolation of the NNO equation (also shown in Figure 1). Hopkins et al. [2] investigated the performance of a nominally-identical aluminum Whipple shield, identifying the effects of phase change in the shatter regime. The results (conceptually represented in Figure 2) were found to agree well with

  6. Investigating Satellite Microwave observations of Precipitation in Different Climate Regimes

    NASA Astrophysics Data System (ADS)

    Wang, N.; Ferraro, R. R.

    2013-12-01

    Microwave satellite remote sensing of precipitation over land is a challenging problem due to the highly variable land surface emissivity, which, if not properly accounted for, can be much greater than the precipitation signal itself, especially in light rain/snow conditions. Additionally, surfaces such as arid land, deserts and snow cover have brightness temperature characteristics similar to precipitation Ongoing work by GPM microwave radiometer team is constructing databases through a variety of means, however, there is much uncertainty as to what is the optimal information needed for the wide array of sensors in the GPM constellation, including examination of regional conditions. The original data sets will focus on stratification by emissivity class, surface temperature and total perceptible water. We'll perform sensitivity studies to determine the potential role of ancillary data (e.g., land surface temperature, snow cover/water equivalent, etc.) to improve precipitation estimation over land in different climate regimes, including rain and snow. In other words, what information outside of the radiances can help describe the background and subsequent departures from it that are active precipitating regions? It is likely that this information will be a function of the various precipitation regimes. Statistical methods such as Principal Component Analysis (PCA) will be utilized in this task. Databases from a variety of sources are being constructed. They include existing satellite microwave measurements of precipitating and non-precipitating conditions, ground radar precipitation rate estimates, surface emissivity climatology from satellites, surface temperature and TPW from NWP reanalysis. Results from the analysis of these databases with respect to the microwave precipitation sensitivity to the variety of environmental conditions in different climate regimes will be discussed.

  7. Environmental controls on food web regimes: A fluvial perspective

    NASA Astrophysics Data System (ADS)

    Power, Mary E.

    2006-02-01

    Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of

  8. On the fast magnetic rotator regime of stellar winds

    NASA Astrophysics Data System (ADS)

    Johnstone, C. P.

    2017-01-01

    Aims: We study the acceleration of the stellar winds of rapidly rotating low mass stars and the transition between the slow magnetic rotator and fast magnetic rotator regimes. We aim to understand the properties of stellar winds in the fast magnetic rotator regime and the effects of magneto-centrifugal forces on wind speeds and mass loss rates. Methods: We extend a solar wind model to 1D magnetohydrodynamic simulations of the winds of rotating stars. We test two assumptions for how to scale the wind temperature to other stars and assume the mass loss rate scales as dot{M_star ∝ R_star2 Ω_star1.33 M_star-3.36}, in the unsaturated regime, as estimated from observed rotational evolution. Results: For 1.0 M⊙ stars, the winds can be accelerated to several thousand km s-1, and the effects of magneto-centrifugal forces are much weaker for lower mass stars. We find that the different assumptions for how to scale the wind temperature to other stars lead to significantly different mass loss rates for the rapid rotators. If we assume a constant temperature, the mass loss rates of solar mass stars do not saturate at rapid rotation, which we show to be inconsistent with observed rotational evolution. If we assume the wind temperatures scale positively with rotation, the mass loss rates are only influenced significantly at rotation rates above 75 Ω⊙. We suggest that models with increasing wind speed for more rapid rotators are preferable to those that assume a constant wind speed. If this conclusion is confirmed by more sophisticated wind modelling. it might provide an interesting observational constraint on the properties of stellar winds. All of the codes and output data used in this paper can be downloaded from http://https://zenodo.org/record/160052#.V_y6drWkVC1 or obtained by contacting the author.

  9. Petrologic Regime Diagrams: Parameterizing Kinetic Controls on Vesiculation and Crystallization

    NASA Astrophysics Data System (ADS)

    Cashman, K. V.

    2014-12-01

    Regime diagrams are commonly employed in geophysical fluid dynamics to classify experimental results and, ideally, to define non-dimensional parameters that allow those results to be applied to natural systems. Petrologic experiments, in contrast, are typically run to mimic a specific natural system, and to infer conditions of magma storage, cooling or decompression. This approach has produced important insight into specific volcanoes, but the results are difficult to generalize. Additionally, very few experimental studies evaluate the vesiculation, crystallization and degassing histories of the same sample suite, an omission that is understandable given the time-consuming nature of the experiments and analysis, but which leaves important gaps in our general understanding of the interplay between gas exsolution, crystal formation and eruption dynamics. One way to bridge these gaps is to construct a regime diagram for conditions of vesiculation and crystallization. As both are controlled by the effective supercooling experienced by the magma during cooling or decompression, one key parameter is supersaturation, although in practice, decompression rate (cooling rate) are commonly used as proxies for supersaturation. Vesiculation and crystallization are also modulated by diffusion (dependent on individual species and melt viscosity), which can be simply approximated by melt composition. Using these parameters and published data for water-saturated decompression experiments, the following fields can be (partially) defined: (1) non-equilibrium volatile exsolution, (2) equilibrium volatile exsolution, and (3) exsolution accompanied by crystallization. Melt compositions, volatile contents and crystal textures of natural samples can be measured, and thus related (crudely) to the regime diagram. Additional information required for fully linking experiments and volcanic pyroclasts includes phase proportions (crystallization efficiency), pyroclast textures (phase change

  10. Hydrodynamic Regimes Affect Coral Reef Resilience to Ocean Acidification

    NASA Astrophysics Data System (ADS)

    Teneva, L. T.; Dunbar, R. B.; Koseff, J. R.; Fleischfresser, J. D.; Koweek, D.

    2013-05-01

    Caribbean reefs hold tremendous value as sources of food, income, coastal protection, in addition to their cultural significance. Recently, studies showed that Caribbean reef growth has been surpassed in places by excessive rates of erosion due to climate change. The rates of coral reef response to ocean pH changes and warming and the implications for ecosystem resilience remain largely unknown. One way to investigate the potential structural resilience of reefs to climate change is to measure the physical oceanographic conditions in the area. Determining the hydrodynamic regimes and residence time of water in a particular reef environment is crucial to understanding the rates of future warming and acidification a reef site would experience. Our work on Pacific Islands' hydrodynamics - Central Equatorial Pacific, Great Barrier Reef, and Western Pacific -- would be of interest to Caribbean physical oceanographers and coral reef scientists. We use a combination of Acoustic Doppler Current Profilers, Acoustic Doppler Velocimeters, temperature and salinity sensors, and pressure sensors to characterize reef hydrodynamic regimes. Our work indicates that shallower, more protected reef habitats are characterized by longer residence times, their biological signals are strongly tidally modulated, essentially subjecting such habitats to higher rates of warming and acidification in the future. Reef crest environments and fore reef habitats, on the other hand, are well-mixed with open-ocean water. The hydrodynamic regimes there condition such reef sites to more attenuated temperature and pH ranges, conditions more typical of the open ocean. Our work suggests that investigating the geomorphology and resulting localized hydrodynamics in a reef area can provide insights into the relative rates at which a reef could resist or succumb to impacts of ocean acidification. Such information for different reef islands, in the Pacific or Caribbean basins, could provide helpful insights

  11. A Safety-Case Regime for Commercial Human Spaceflight

    NASA Astrophysics Data System (ADS)

    Sgobba, T.; Trujillo, M.

    2012-01-01

    Currently the commercial human spaceflight community seems to be embracing the obsolete design principles of "fly-fix-fly", and betting on public acceptance of risks comparable to those of the early times of aviation industry. The nascent space tourism industry maintains that early safety regulations (apart public safety) would kill industry and that such regulations could be developed only later when substantial operational experience is gained. Truly, most of current commercial aviation safety regulations are based on prescriptive requirements (i.e. explicitly required design solution for an implicit goal), which have been incrementally developed over more than a half century of mass transportation by air, and cannot be in general directly applied to innovative systems. However modern complex safety-critical systems cannot risk catastrophic failures while their operational experience is being accumulated, for such reason they are developed through the so called safety-case regime. ESA is currently drafting a safety standard for its future human rated transportation systems that is based on such regime. Such standard can be easily tailored with few modifications and applied to the development of a sub-orbital commercial space vehicle. In any case, because the safety-case regime makes extensive use of generically formulated requirements, the support of skilled safety engineers fully integrated into the design team is required since the very beginning. Furthermore the safety certification team needs also to be experienced in the review of safety-case based designs. Finally a quantitative safety target needs to be included and verified as the ultimate "prove of goodness" of system design.

  12. Evolution of human-driven fire regimes in Africa.

    PubMed

    Archibald, Sally; Staver, A Carla; Levin, Simon A

    2012-01-17

    Human ability to manipulate fire and the landscape has increased over evolutionary time, but the impact of this on fire regimes and consequences for biodiversity and biogeochemistry are hotly debated. Reconstructing historical changes in human-derived fire regimes empirically is challenging, but information is available on the timing of key human innovations and on current human impacts on fire; here we incorporate this knowledge into a spatially explicit fire propagation model. We explore how changes in population density, the ability to create fire, and the expansion of agropastoralism altered the extent and seasonal distribution of fire as modern humans arose and spread through Africa. Much emphasis has been placed on the positive effect of population density on ignition frequency, but our model suggests this is less important than changes in fire spread and connectivity that would have occurred as humans learned to light fires in the dry season and to transform the landscape through grazing and cultivation. Different landscapes show different limitations; we show that substantial human impacts on burned area would only have started ~4,000 B.P. in open landscapes, whereas they could have altered fire regimes in closed/dissected landscapes by ~40,000 B.P. Dry season fires have been the norm for the past 200-300 ky across all landscapes. The annual area burned in Africa probably peaked between 4 and 40 kya. These results agree with recent paleocarbon studies that suggest that the biomass burned today is less than in the recent past in subtropical countries.

  13. Effects of disturbance regime on carbohydrate reserves in meadow plants

    PubMed Central

    Janeček, Štěpán; Bartušková, Alena; Bartoš, Michael; Altman, Jan; de Bello, Francesco; Doležal, Jiří; Latzel, Vít; Lanta, Vojtěch; Lepš, Jan; Klimešová, Jitka

    2015-01-01

    Carbohydrate storage enables plants to tolerate both seasonally unfavourable conditions and recover from disturbance. Although short-term changes in storage levels due to disturbance are fairly well known, less is known about long-term changes in storage levels, especially in response to cessation of repeated disturbance. Additionally, whereas it is presumably the total amount (pool) of storage carbohydrate reserves that is of importance, typically carbohydrate concentrations are measured instead, as a proxy. We assessed changes in carbohydrate concentrations and pools in storage organs and changes in above- versus belowground biomass in response to mowing cessation in nine herbs from two meadows (dry and wet) at the (June) peak of vegetation development and the (October) growing season end 1 and 3 years after the change in the disturbance regime. We tested three hypotheses: (1) storage will increase with abandonment of mowing only in the first year after disturbance cessation, but not further increase subsequently, as high storage would hinder competitive ability; (2) storage will increase towards the end of the season in both disturbed and undisturbed plants; and (3) changes in carbohydrate concentrations are accurate predictors of changes in pools. Although species-specific changes in carbohydrate reserves occurred in the wet meadow, more general trends appeared in the dry meadow. There, plants accumulated higher carbohydrate reserves at the end of the season, especially in unmown plots. However, the reserves for plants in both disturbance regimes were the same at the growing season peak (June) in both examined years. The increase in storage of carbohydrates on unmown plots in October was manifested by increases of both storage organ biomass and carbohydrate concentration, whereas in mown plots, it was due only to increased carbohydrate concentration. Although concentrations and pools represent different aspects of plant carbohydrate economy, concentrations will

  14. Characteristics of Whipple Shield Performance in the Shatter Regime

    NASA Technical Reports Server (NTRS)

    Ryan, S.; Bjorkman, M.; Christiansen, E. L.

    2010-01-01

    Ballistic limit equations define the failure of metallic Whipple shields in three parts: low velocity, shatter, and hypervelocity. Failure limits in the shatter regime are based on a linear interpolation between the onset of projectile fragmentation, and impulsive rupture of the shield rear wall. A series of hypervelocity impact tests have been performed on aluminum alloy Whipple shields to investigate failure mechanisms and performance limits in the shatter regime. Test results demonstrated a more rapid increase in performance than predicted by the latest iteration of the JSC Whipple shield BLE following the onset of projectile fragmentation. This increase in performance was found to level out between 4.0-5.0 km/s, with a subsequent decrease in performance for velocities up to 6.0 km/s. For a detached spall failure criterion, the failure limit was found to continually decrease up to a velocity of 7.0 km/s, substantially varying from the BLE, while for perforation-based failure an increase in performance was observed. An existing phenomenological ballistic limit curve was found to provide a more accurate reproduction of shield behavior that the BLE, however a number of underlying assumptions such as the occurrence of complete projectile fragmentation and the effect on performance of incipient projectile melt were found to be inaccurate. A cratering relationship based on the largest residual fragment size has been derived for application at velocities between 3.0-4.0 km/s, and was shown to accurately reproduce the trends of the experimental data. Further investigation is required to allow a full analytical description of shatter regime performance for metallic Whipple shields.

  15. CONTROL OF LASER RADIATION PARAMETERS: Evolution of transient oscillation regimes in monolithic ring lasers

    NASA Astrophysics Data System (ADS)

    Kravtsov, Nikolai V.; Chekina, S. N.

    2005-07-01

    The evolution of the regions of existence and stability of quasi-periodic and chaotic oscillation regimes in a monolithic ring Nd:YAG laser caused by changing the pump power is studied experimentally. It is shown that the dynamic chaos regime appearing upon modulation of the pump power is alternated by windows in which different quasi-periodic lasing regimes take place. A scenario of the passage from the self-modulation lasing regime to dynamic chaos is considered.

  16. Regime shifts in the Humboldt Current ecosystem [review article

    NASA Astrophysics Data System (ADS)

    Alheit, Jürgen; Niquen, Miguel

    2004-02-01

    Of the four major eastern boundary currents, the Humboldt Current (HC) stands out because it is extremely productive, dominated by anchovy dynamics and subject to frequent direct environmental perturbations of the El Niño Southern Oscillation (ENSO). The long-term dynamics of the HC ecosystem are controlled by shifts between alternating anchovy and sardine regimes that restructure the entire ecosystem from phytoplankton to the top predators. These regime shifts are caused by lasting periods of warm or cold temperature anomalies related to the approach or retreat of warm subtropical oceanic waters to the coast of Peru and Chile. Phases with mainly negative temperature anomalies parallel anchovy regimes (1950-1970; 1985 to the present) and the rather warm period from 1970 to 1985 was characterized by sardine dominance. The transition periods (turning points) from one regime to the other were 1968-1970 and 1984-1986. Like an El Nino, the warm periods drastically change trophic relationships in the entire HC ecosystem, exposing the Peruvian anchovy to a multitude of adverse conditions. Positive temperature anomalies off Peru drive the anchovy population close to the coast as the coastal upwelling cells usually offer the coolest environment, thereby substantially decreasing the extent of the areas of anchovy distribution and spawning. This enhances the effects of negative density-dependent processes such as egg and larval cannibalism and dramatically increases its catchability. Increased spatial overlap between anchovies and the warmer water preferring sardines intensifies anchovy egg mortality further as sardines feed heavily on anchovy eggs. Food sources for juvenile and adult anchovies which prey on a mixed diet of phyto- and zooplankton are drastically reduced because of decreased plankton production due to restricted upwelling in warm years, as demonstrated by lower zooplankton and phytoplankton volumes and the diminution of the fraction of large copepods, their

  17. Spectral effectiveness of engineered thermal cloaks in the frequency regime

    PubMed Central

    Petiteau, David; Guenneau, Sebastien; Bellieud, Michel; Zerrad, Myriam; Amra, Claude

    2014-01-01

    We analyse basic thermal cloaks designed via different geometric transforms applied to thermal cloaking. We evaluate quantitatively the effectiveness of these heterogeneous anisotropic thermal cloaks through the calculation of the standard deviation of the isotherms. The study addresses the frequency regime and we point out the cloak's spectral effectiveness. We find that all these cloaks have comparable effectiveness irrespective of whether or not they have singular conductivity at their inner boundary. However, approximate cloaking with multi-layered cloak critically depends upon the homogenization algorithm and it is shown that the standard deviation varies linearly with the inverse of the number of layers. PMID:25486981

  18. Analysis of micro-fluidic tweezers in the Stokes regime

    NASA Astrophysics Data System (ADS)

    Zhao, Longhua; Ding, Yang

    2016-11-01

    Nanowire fluidic tweezers have been developed to capture and manipulate micro objects. The fluidic trapping force and the fluid field are important to achieve accurate control, but have not been fully understood yet. Utilizing singularity method, we construct the exact velocity field to analyze flows induced by a spheroid nanowire tumbling in the Stokes regime. To further explore the trapping, we analyze the trajectories of rigid or deformable microspheres near the tumbling nanowire using regularized Stokeslet method. The fluid structure, the trapping phenomenon and mechanism, and precise relation about trapping with the geometry will be presented. YD is sponsored by the Recruitment Program of Global Young Experts (China).

  19. A second-order impact model for forest fire regimes.

    PubMed

    Maggi, Stefano; Rinaldi, Sergio

    2006-09-01

    We present a very simple "impact" model for the description of forest fires and show that it can mimic the known characteristics of wild fire regimes in savannas, boreal forests, and Mediterranean forests. Moreover, the distribution of burned biomasses in model generated fires resemble those of burned areas in numerous large forests around the world. The model has also the merits of being the first second-order model for forest fires and the first example of the use of impact models in the study of ecosystems.

  20. Aerothermodynamic Characteristics in the Hypersonic Continuum-Rarefied Transitional Regime

    NASA Technical Reports Server (NTRS)

    Glass, Christopher, E.; Moss, James N.

    2001-01-01

    Stagnation pressure and heating for cylinders and spheres representative of wing leading edges and nose sections for small-scale space transportation vehicles are presented for various Knudsen numbers at Earth entry conditions that bridge from the free molecular to continuum regimes. CFD, DSMC, and collisionless DSMC are used to span Knudsen numbers from 0.001 to 100 with the CFD/DSMC overlap at a Knudsen number of 0.01 and the DSMC/collisionless DSMC overlap at 10. The present results include density contours, density and temperature along the stagnation streamline for all cases, and stagnation pressure and heat transfer coefficient as a function of Knudsen number.

  1. The efficiency of Raman amplification in the wavebreaking regime

    SciTech Connect

    Edwards, Matthew R. Mikhailova, Julia M.; Toroker, Zeev; Fisch, Nathaniel J.

    2015-07-15

    We compare previous analytic predictions, Vlasov-Maxwell simulations, and particle-in-cell results with a new set of comprehensive one and two dimensional particle-in-cell simulations in an effort to clarify apparent discrepancies between the predictions of different models for the efficiency of Raman amplification in the wavebreaking regime. We find reasonable agreement between our particle-in-cell simulations and previous results from Vlasov-Maxwell simulations and analytic work, suggesting a monotonic decrease in conversion efficiency for increased pump intensities past the wavebreaking threshold.

  2. Laser ablation dynamics in metals: The thermal regime

    SciTech Connect

    Mezzapesa, F. P.; Brambilla, M.; Dabbicco, M.; Scamarcio, G.; Columbo, L. L.; Ancona, A.; Sibillano, T.

    2012-07-02

    We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

  3. Ion holes in the hydrodynamic regime in ultracold neutral plasmas

    SciTech Connect

    McQuillen, P.; Castro, J.; Strickler, T.; Bradshaw, S. J.; Killian, T. C.

    2013-04-15

    We describe the creation of localized density perturbations, or ion holes, in an ultracold neutral plasma in the hydrodynamic regime, and show that the holes propagate at the local ion acoustic wave speed. We also observe the process of hole splitting, which results from the formation of a density depletion initially at rest in the plasma. One-dimensional, two-fluid hydrodynamic simulations describe the results well. Measurements of the ion velocity distribution also show the effects of the ion hole and confirm the hydrodynamic conditions in the plasma.

  4. Metastable and scaling regimes of one-dimensional Kawasaki dynamics.

    PubMed

    Albarracín, F A Gómez; Rosales, H D; Grynberg, M D

    2016-04-01

    We investigate the large-time scaling regimes arising from a variety of metastable structures in a chain of Ising spins with both first- and second-neighbor couplings while subject to Kawasaki dynamics. Depending on the ratio and sign of these former, different dynamic exponents are suggested by finite-size scaling analyses of relaxation times. At low but nonzero temperatures these are calculated via exact diagonalizations of the evolution operator in finite chains under several activation barriers. In the absence of metastability the dynamics is always diffusive.

  5. Metastable and scaling regimes of one-dimensional Kawasaki dynamics

    NASA Astrophysics Data System (ADS)

    Albarracín, F. A. Gómez; Rosales, H. D.; Grynberg, M. D.

    2016-04-01

    We investigate the large-time scaling regimes arising from a variety of metastable structures in a chain of Ising spins with both first- and second-neighbor couplings while subject to Kawasaki dynamics. Depending on the ratio and sign of these former, different dynamic exponents are suggested by finite-size scaling analyses of relaxation times. At low but nonzero temperatures these are calculated via exact diagonalizations of the evolution operator in finite chains under several activation barriers. In the absence of metastability the dynamics is always diffusive.

  6. Experimental Bullard-von Karman dynamo: MHD saturated regimes

    NASA Astrophysics Data System (ADS)

    Miralles, Sophie; Plihon, Nicolas; Pinton, Jean-François

    2014-05-01

    The dynamo instability, converting kinetic energy into magnetic energy, creates the magnetic fields of many astrophysical bodies for which the flows are highly turbulent. Those turbulent fluctuations restricts the range of parameters of numerical and theoretical predictions. As laboratory experiments are closer from natural parameters, this approach is favored in this work. In the past decades, dynamo action has been observed in experiments involving laminar flows [1] or fully turbulent flows [2] in liquid sodium. Nevertheless, the saturation of the velocity field by the Lorentz force due to the dynamo magnetic field is weak in those experiment because the control parameter is always close to the threshold of the instability (which is not the case in astrophysical situations). The details of the mechanism of the back reaction of Lorentz force on the flow are not known. We present here an experimental semi-synthetic dynamo, for which a fluid turbulent induction mechanism ('omega' effect) is associated to an external amplification applying a current into a pair of coils. The flow, called von-Karman, is produced by the counter rotation of two coaxial propellers in a cylindrical tank filled with liquid gallium. The resulting flow is highly turbulent (Re > 10 ^ 5). The amplification, mimicking a turbulent 'alpha' effect, allow to observe the dynamo instability at low magnetic Reynolds number (Rm ~ 2), far below the threshold of natural homogeneous dynamo. This experiment reaches non linear regimes, for which the saturation is a MHD process, at control parameter several times the critical value. The instability grows through an on-off intermittent regime evolving into a full MHD saturated regime for which the Lorentz force is in balance with the inertial one. The power budget is strongly modified by the dynamo magnetic field and we give an insight of the estimated rate of conversion of kinetic energy into magnetic one from experimental data. Very rich regimes such as

  7. Nonlinear emission of semiconductor microcavities in the strong coupling regime

    PubMed

    Houdre; Weisbuch; Stanley; Oesterle; Ilegems

    2000-09-25

    We report on the nonlinear laserlike emission from semiconductor microcavities in the strong coupling regime. Under resonant continuous wave excitation we observe a highly emissive state. The energy, dispersion, and spatial extent of this state is measured and is found to be dispersionless and spatially localized. This state coexists with luminescence that follows the usual cavity-polariton dispersion. It is attributed to the amplification of luminescence by a parametric gain due to cavity-polariton scattering. Despite the resonant excitation at 1.6 K, we observe no sign of Bose-Einstein condensation nor Boser action.

  8. Inhomogeneities in an expanding universe: the nonlinear and relativistic regimes

    NASA Astrophysics Data System (ADS)

    East, William

    2017-01-01

    I will discuss the dynamics, and observational consequences of inhomogeneities in an expanding universe. In particular, I will concentrate on how the tools of numerical relativity can be used to study this problem in a fully general-relativistic setting, where traditionally employed approximations may break down. I will show how this can be used to explore and quantify the cosmological regime where the evolution of the inhomogeneities becomes nonlinear, and where relativistic effects may become important. This includes applications to primordial black hole formation, as well as other settings in the early universe where strong-field gravity plays a role.

  9. Inelastic transport through Aharonov-Bohm interferometer in Kondo regime

    SciTech Connect

    Yoshii, Ryosuke; Eto, Mikio; Sakano, Rui; Affleck, Ian

    2013-12-04

    We formulate elastic and inelastic parts of linear conductance through an Aharonov-Bohm (AB) ring with an embedded quantum dot in the Kondo regime. The inelastic part G{sub inel} is proportional to T{sup 2} when the temperature T is much smaller than the Kondo temperature T{sub K}, whereas it is negligibly small compared with elastic part G{sub el} when T ≫ T{sub K}. G{sub inel} weakly depends on the magnetic flux penetrating the AB ring, which disturbs the precise detection of G{sub el}/(G{sub el}+G{sub inel}) by the visibility of AB oscillation.

  10. Fast Magnetic Reconnection in the Plasmoid-Dominated Regime

    SciTech Connect

    Uzdensky, D. A.; Loureiro, N. F.; Schekochihin, A. A.

    2010-12-03

    A conceptual model of resistive magnetic reconnection via a stochastic plasmoid chain is proposed. The global reconnection rate is shown to be independent of the Lundquist number. The distribution of fluxes in the plasmoids is shown to be an inverse-square law. It is argued that there is a finite probability of emergence of abnormally large plasmoids, which can disrupt the chain (and may be responsible for observable large abrupt events in solar flares and sawtooth crashes). A criterion for the transition from the resistive magnetohydrodynamic to the collisionless regime is provided.

  11. Limits of Strong Field Rescattering in the Relativistic Regime

    NASA Astrophysics Data System (ADS)

    Klaiber, M.; Hatsagortsyan, K. Z.; Wu, J.; Luo, S. S.; Grugan, P.; Walker, B. C.

    2017-03-01

    Recollision for a laser driven atomic system is investigated in the relativistic regime via a strong field quantum description and Monte Carlo semiclassical approach. We find the relativistic recollision energy cutoff is independent of the ponderomotive potential Up , in contrast to the well-known 3.2 Up scaling. The relativistic recollision energy cutoff is determined by the ionization potential of the atomic system and achievable with non-negligible recollision flux before entering a "rescattering free" interaction. The ultimate energy cutoff is limited by the available intensities of short wavelength lasers and cannot exceed a few thousand Hartree, setting a boundary for recollision based attosecond physics.

  12. [The regulatory regime and the health insurance industry in Brazil].

    PubMed

    Costa, Nilson do Rosário

    2008-01-01

    This paper analyzes the regulatory regime for health insurance and prepayment schemes in Brazil. It describes the ideas that have influenced the creation of the Agência Nacional de Saúde Suplementar-ANS (National Agency of Supplementary Health) in 2000, showing that the independent agency model was a direct result of the privatization process and of the induction of new competition mechanisms in a natural state monopoly. The paper concludes that the prepayment firms in Brazil are facing a new institutional environment as refers to their market entry or exit conditions.

  13. Space-charge-limited flow in quantum regime

    NASA Astrophysics Data System (ADS)

    Ang, Lay Kee

    2005-10-01

    Space-charge-limited (SCL) flow has been an area of active research in the development of non-neutral plasma physics, high current diodes, high power microwave sources, vacuum microelectronics and sheath physics. According to the classical Child-Langmuir (CL) law for the planar diodes, the current density scales as 3/2's power of gap voltage and to the inverse squared power of gap spacing. In the past decade, there have been renewed interests in extending the classical CL law to multi-dimensional models both numerically and analytically. The study of SCL flow in quantum regime has also attracted considerable interests in the past 3 years [1-3]. With the recent advances in nanotechnology, electron beam with very high current density may be transported in a nano-scale gap with a relatively low gap voltage. In this new operating regime, where the electron wavelength is comparable or larger than the gap spacing, the quantum effects become important. In this talk, the quantum theory of CL law will be introduced to reveal that the classical CL law is enhanced by a large factor due to electron tunneling and exchange-correlation effects, and there is a new quantum scaling for the current density, which is proportional to the 1/2's power of gap voltage, and to the inverse fourth-power of gap spacing [1-2]. Quasi-2D and 3D models with finite emission area will be shown [3]. We will also show that the classical properties of the SCL flow such as bipolar flow, beam-loaded capacitance, transit time and noise will require a complete revision in the quantum regime. The implications of the emission law of Fowler-Nordheim in the presence of intense space charge over the nanometer scale will be discussed.[1] L. K. Ang, T. J. T. Kwan, and Y. Y. Lau, ``New Scaling of Child-Langmuir Law in the Quantum Regime,'' Phys. Rev. Lett. 91, 208303 (2003). [2] L. K. Ang, Y. Y. Lau, and T. J. T. Kwan, ``Simple Derivation of Quantum Scaling in Child-Langmuir law,'' IEEE Trans Plasma Sci. 32, 410

  14. Burnett Simulations of Gaseous Flows in Transition Regime

    NASA Astrophysics Data System (ADS)

    Wang, J. X.; Bao, F. B.; Lin, J. Z.

    2011-09-01

    Burnett equations with the slip boundary conditions are used to study the three-dimensional gaseous flow in slip and transition regime. The results were first compared with those of DSMC method and good agreements were achieved. The effects of inlet to outlet pressure ratios and Knudsen numbers on flow characteristics were analyzed. The compressible effect increases the pressure nonlinear distribution while the rarefied effect reduces the nonlinear trend. With the same pressure ratio and cross-section area, the flow rate decreases with the increase of aspect ratio.

  15. Experimental classification of dynamical regimes in optically injected lasers.

    PubMed

    O'Shea, D; Osborne, S; Blackbeard, N; Goulding, D; Kelleher, B; Amann, A

    2014-09-08

    We present a reliable and fast technique to experimentally categorise the dynamical state of optically injected two mode and single mode lasers. Based on the experimentally obtained time-traces locked, unlocked and chaotic states are distinguished for varying injection strength and detuning. For the two mode laser, the resulting experimental stability diagram provides a map of the various single mode and two mode regimes and the transitions between them. This stability diagram is in strong agreement with the theoretical predictions from low-dimensional dynamical models for two mode lasers. We also apply our method to the single mode laser and retain the close agreement between theory and experiment.

  16. Climate-driven regime shift of a temperate marine ecosystem.

    PubMed

    Wernberg, Thomas; Bennett, Scott; Babcock, Russell C; de Bettignies, Thibaut; Cure, Katherine; Depczynski, Martial; Dufois, Francois; Fromont, Jane; Fulton, Christopher J; Hovey, Renae K; Harvey, Euan S; Holmes, Thomas H; Kendrick, Gary A; Radford, Ben; Santana-Garcon, Julia; Saunders, Benjamin J; Smale, Dan A; Thomsen, Mads S; Tuckett, Chenae A; Tuya, Fernando; Vanderklift, Mathew A; Wilson, Shaun

    2016-07-08

    Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests.

  17. Negative thermophoresis of nanoparticles in the free molecular regime.

    PubMed

    Wang, Jun; Li, Zhigang

    2012-07-01

    Negative thermophoresis is a phenomenon of particle transport induced by a temperature gradient, by which small particles migrate from low to high temperatures. In gas media, it depends strongly on the gas-particle interaction and temperature. In this paper, we show that negative thermophoresis is possible in the free molecular regime and a theoretical criterion is derived. On the basis of a general gas-particle interaction potential, an empirical necessary condition for negative thermophoresis that the potential parameters should satisfy is also obtained. Finally, the temperature ranges for the occurrence of negative thermophoresis are determined for a series of gas-particle interaction parameters.

  18. A Quasispecies Continuous Contact Model in a Critical Regime

    NASA Astrophysics Data System (ADS)

    Kondratiev, Yuri; Pirogov, Sergey; Zhizhina, Elena

    2016-04-01

    We study a new non-equilibrium dynamical model: a marked continuous contact model in d-dimensional space (d ge 3). We prove that for certain values of rates (the critical regime) this system has the one-parameter family of invariant measures labelled by the spatial density of particles. Then we prove that the process starting from the marked Poisson measure converges to one of these invariant measures. In contrast with the continuous contact model studied earlier in Kondratiev (Infin Dimens Anal Quantum Probab Relat Top 11(2):231-258, 2008), now the spatial particle density is not a conserved quantity.

  19. Femtosecond nonlinear fiber optics in the ionization regime.

    PubMed

    Hölzer, P; Chang, W; Travers, J C; Nazarkin, A; Nold, J; Joly, N Y; Saleh, M F; Biancalana, F; Russell, P St J

    2011-11-11

    By using a gas-filled kagome-style photonic crystal fiber, nonlinear fiber optics is studied in the regime of optically induced ionization. The fiber offers low anomalous dispersion over a broad bandwidth and low loss. Sequences of blueshifted pulses are emitted when 65 fs, few-microjoule pulses, corresponding to high-order solitons, are launched into the fiber and undergo self-compression. The experimental results are confirmed by numerical simulations which suggest that free-electron densities of ∼10(17) cm(-3) are achieved at peak intensities of 10(14) W/cm(2) over length scales of several centimeters.

  20. Semiconductor cavity QED with squeezed light: Nonlinear regime

    SciTech Connect

    Sete, Eyob A.; Eleuch, H.; Das, Sumanta

    2011-11-15

    We present a study of semiconductor cavity QED effects with squeezed light. We investigate the effects of external squeezed light produced by a subthreshold optical parametric down conversion on the quantum features of the cavity as well as output radiation in the presence of exciton-exciton scattering. It turns out that the width of the spectrum of the cavity field strongly depends on the degree of squeezing. This effect is observed both in weak- and strong-coupling regimes. Moreover, we show that the external squeezed light has a profound effect on the amount of squeezing of the output field.

  1. Higher Education Policy in Authoritarian Regimes: Comparative Perspectives on the Chilean Case.

    ERIC Educational Resources Information Center

    Levy, Daniel

    A Chilean case study of higher education under an authoritarian regime is presented. The study restricts itself to the most prevalent sub-type of the authoritarian regime which is "bureaucratic-authoritarianism" (BA). The BA designation refers to regimes which exert considerable repressive control over societies that have undergone…

  2. Optimal ranking regime analysis of U.S. climate variablility. Part II: Precipitation and streamflow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In a preceding companion paper the Optimal Ranking Regime (ORR) method was used to identify intra- to multi-decadal (IMD) regimes in U.S. climate division temperature data during 1896-2012. Here, the method is used to test for annual and seasonal precipitation regimes during that same period. In add...

  3. Urbanization, regime type and durability, and environmental degradation in Ghana.

    PubMed

    Adams, Samuel; Adom, Philip Kofi; Klobodu, Edem Kwame Mensah

    2016-12-01

    This study examines the effect of urbanization, income, trade openness, and institutional quality (i.e., regime type and durability) on environmental degradation in Ghana over the period 1965-2011. Using the bounds test approach to cointegration and the Fully Modified Phillip-Hansen (FMPH) technique, the findings show that urbanization, income, trade openness, and institutional quality have long-run cointegration with environmental degradation. Further, the results show that income, trade openness, and institutional quality are negatively associated with environmental degradation. This suggests that income, trade openness, and institutional quality enhance environmental performance. Urbanization, however, is positively related to environmental degradation. Additionally, long-run estimates conditioned on institutional quality reveal that the extent to which trade openness and urbanization enhance environmental performance is largely due to the presence of quality institutions (or democratic institutions). Finally, controlling for structural breaks, we find that trade openness, urbanization, and regime type (i.e., democracy) improve environmental performance significantly after the 1970s except for income.

  4. Transition boiling heat transfer and the film transition regime

    NASA Technical Reports Server (NTRS)

    Ramilison, J. M.; Lienhard, J. H.

    1987-01-01

    The Berenson (1960) flat-plate transition-boiling experiment has been recreated with a reduced thermal resistance in the heater, and an improved access to those portions of the transition boiling regime that have a steep negative slope. Tests have been made in Freon-113, acetone, benzene, and n-pentane boiling on horizontal flat copper heaters that have been mirror-polished, 'roughened', or teflon-coated. The resulting data reproduce and clarify certain features observed by Berenson: the modest surface finish dependence of boiling burnout, and the influence of surface chemistry on both the minimum heat flux and the mode of transition boiling, for example. A rational scheme of correlation yields a prediction of the heat flux in what Witte and Lienhard (1982) previously identified as the 'film-transition boiling' region. It is also shown how to calculate the heat flux at the boundary between the pure-film, and the film-transition, boiling regimes, as a function of the advancing contact angle.

  5. Evolution and resilience of the nuclear nonproliferation regime

    NASA Astrophysics Data System (ADS)

    Pregenzer, Arian L.

    2014-05-01

    This paper introduces the concept of systems resilience as a new framework for thinking about the future of the nonproliferation regime. Resilience refers to the ability of a system to maintain its vital functions in the face of continuous and unpredictable change. First, I make the case that the nonproliferation regime can be viewed as a complex system. Next, I discuss key themes from the literature on systems resilience and apply them to the nonproliferation system: the difference between resilience and stability; the need for evolution to maintain function; the importance of functional diversity; and the concept of the adaptive cycle. I show that most existing nonproliferation strategies are aimed at stability rather than resilience and that the current nonproliferation system may be over-constrained by the cumulative evolution of strategies. According to the literature on systems resilience, this increases its vulnerability to collapse. I argue that the resilience of the nonproliferation system can be enhanced by increasing international participation in setting the nonproliferation agenda, developing general international response capabilities, focusing on non-coercive approaches to decreasing demand, and applying systems thinking more rigorously to nonproliferation.

  6. Three Distinct Exoplanet Regimes Inferred From Host Star Metallicities

    NASA Astrophysics Data System (ADS)

    Buchhave, Lars A.; Bizzarro, Martin; Latham, David W.; Sasselov, Dimitar D.

    2014-06-01

    The occurrence rate of exoplanets smaller than 4 Earth radii (RE) in short orbits is ~50%. Despite their sheer abundance, the compositions of planets populating this regime are largely unknown. The available evidence suggests the existence of a compositional range, from small high-density rocky planets to low-density planets consisting of rocky cores surrounded by thick H/He gas envelopes. Understanding the transition from the gaseous planets to Earth-like rocky worlds is important to estimate the number of potentially habitable planets in our Galaxy and provide constraints on planet formation theories. Here, we report the abundances of heavy elements (metallicities) of over 400 stars hosting 600 exoplanet candidates discovered by the Kepler Mission and find that the exoplanets can be categorized into three populations defined by statistically distinct 4.5σ) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (RP < 1.7 RE), gas-dwarf planets with rocky cores and H/He envelopes (1.7 < RP < 3.9 RE) and ice/gas-giant planets (RP > 3.9 RE). These transitions resonate well with those inferred from dynamical mass estimates, implying that host-star metallicity - a proxy for the initial solid inventory of the protoplanetary disk - is a key ingredient regulating the structure of planetary systems.

  7. Crossing regimes of temperature dependence in animal movement.

    PubMed

    Gibert, Jean P; Chelini, Marie-Claire; Rosenthal, Malcolm F; DeLong, John P

    2016-05-01

    A pressing challenge in ecology is to understand the effects of changing global temperatures on food web structure and dynamics. The stability of these complex ecological networks largely depends on how predator-prey interactions may respond to temperature changes. Because predators and prey rely on their velocities to catch food or avoid being eaten, understanding how temperatures may affect animal movement is central to this quest. Despite our efforts, we still lack a mechanistic understanding of how the effect of temperature on metabolic processes scales up to animal movement and beyond. Here, we merge a biomechanical approach, the Metabolic Theory of Ecology and empirical data to show that animal movement displays multiple regimes of temperature dependence. We also show that crossing these regimes has important consequences for population dynamics and stability, which depend on the parameters controlling predator-prey interactions. We argue that this dependence upon interaction parameters may help explain why experimental work on the temperature dependence of interaction strengths has so far yielded conflicting results. More importantly, these changes in the temperature dependence of animal movement can have consequences that go well beyond ecological interactions and affect, for example, animal communication, mating, sensory detection, and any behavioral modality dependent on the movement of limbs. Finally, by not taking into account the changes in temperature dependence reported here we might not be able to properly forecast the impact of global warming on ecological processes and propose appropriate mitigation action when needed.

  8. Molecular dynamics of fluid flows in the Knudsen regime

    NASA Astrophysics Data System (ADS)

    Cieplak, Marek

    2000-03-01

    Novel technological applications often involve fluid flows in the Knudsen regime in which the mean free path is comparable to the system size. The boundary conditions at the wall-fluid interface are studied. The wall is modelled by atoms tethered to a lattice that interact by Lennard-Jones forces with the fluid atoms. Monoatomic and polymeric Lennard-Jones fluids are considered and Couette and gravity-driven flows are studied. The scenarios of behavior envisioned by J. C. Maxwell are found not to be valid in general. For instance, there are novel effects related to a non-zero residence time of the fluid molecules in the wall vicinity. In the limiting case of strongly attractive fluid-wall interactions, the velocity distribution of the outcoming atoms is indeed thermal. However, when the attractive tail in the fluid-wall interactions is weak, there are significant deviations from Maxwell's hypothesis. Striking many body effects are found as one interpolates between the dilute gas and the dense fluid regime. The molecular nature of the viscous and thermal slip phenomena are elucidated.

  9. Political Regime and Human Capital: A Cross-Country Analysis.

    PubMed

    Klomp, Jeroen; de Haan, Jakob

    2013-03-01

    We examine the relationship between different dimensions of the political regime in place and human capital using a two-step structural equation model. In the first step, we employ factor analysis on 16 human capital indicators to construct two new human capital measures (basic and advanced human capital). In the second step, we estimate the impact of our political variables on human capital, using a cross-sectional structural model for some 100 countries. We conclude that democracy is positively related to basic human capital, while regime instability has a negative link with basic human capital. Governance has a positive relationship with advanced human capital, while government instability has a negative link with advanced human capital. Finally, we also find an indirect positive effect of governance and democracy on both types of human capital through their effect on income. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11205-011-9983-6) contains supplementary material, which is available to authorized users.

  10. Sludge reduction using aquatic worms under different aeration regimes.

    PubMed

    Cai, Lu; Gao, Ding; Wang, Kan; Liu, Hong-Tao; Wan, Xiao-Ming

    2017-03-01

    Adding aquatic worms to a wastewater treatment system can reduce sludge production through predation. The aeration level is crucial for success. To evaluate aeration impacts on sludge reduction and determine an optimal aeration regime, this study investigated the processes of in-situ sludge reduction, using aquatic worms exposed to different aeration levels. The experiment also compared treatment results between a conventional reactor and an aquatic worm reactor (WR). Results indicated that the recommended concentration of dissolved oxygen (DO) was 2.5 mg L(-1). The removal rate of chemical oxygen demand remained steady at 80% when the DO concentration was higher than 2.5 mg L(-1), while the removal rate of ammonia nitrogen continued to moderately increase. Increasing the DO concentration to 5 mg L(-1) did not improve sludge reduction, and consumed more power. With a DO concentration of 2.5 mg L(-1) and a power of 0.19 kWh t(-1) water, the absolute sludge reduction and relative sludge reduction rates in the WR were 60.0% and 45.7%, respectively, and the daily aquatic worm growth rate was 0.150 d(-1) during the 17-d test. Therefore, at the recommended aeration regime, aquatic worms reduced the sludge without increasing the power consumption or deteriorating the effluent.

  11. Approaches to defining reference regimes for river restoration planning

    NASA Astrophysics Data System (ADS)

    Beechie, T. J.

    2014-12-01

    Reference conditions or reference regimes can be defined using three general approaches, historical analysis, contemporary reference sites, and theoretical or empirical models. For large features (e.g., floodplain channels and ponds) historical data and maps are generally reliable. For smaller features (e.g., pools and riffles in small tributaries), field data from contemporary reference sites are a reasonable surrogate for historical data. Models are generally used for features that have no historical information or present day reference sites (e.g., beaver pond habitat). Each of these approaches contributes to a watershed-wide understanding of current biophysical conditions relative to potential conditions, which helps create not only a guiding vision for restoration, but also helps quantify and locate the largest or most important restoration opportunities. Common uses of geomorphic and biological reference conditions include identifying key areas for habitat protection or restoration, and informing the choice of restoration targets. Examples of use of each of these three approaches to define reference regimes in western USA illustrate how historical information and current research highlight key restoration opportunities, focus restoration effort in areas that can produce the largest ecological benefit, and contribute to estimating restoration potential and assessing likelihood of achieving restoration goals.

  12. 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

  13. Available Climate Regimes Drive Niche Diversification during Range Expansion.

    PubMed

    Wüest, Rafael O; Antonelli, Alexandre; Zimmermann, Niklaus E; Linder, H Peter

    2015-05-01

    Climate is a main predictor of biodiversity on a global scale, yet how climate availability affects niche evolution remains poorly explored. Here we assess how intercontinental climate differences may affect the evolution of climate niches and suggest three possible processes: niche truncation along major environmental gradients, intercontinental differences in available climate causing differences in selective regimes, and niche shifts associated with long-distance dispersals leading to a pattern of punctuated evolution. Using the globally distributed danthonioid grasses, we show significant niche differentiation among continents and several instances of niche truncation. The comparison of inferred selective regimes with differences in available climatic space among continents demonstrates adaptation resulting from opportunistic evolution toward available climatic space. Our results suggest that niche evolution in this clade is punctuated, consistent with accelerated niche evolution after long-distance dispersal events. Finally, we discuss how intrinsic constraints (genetic, developmental, or functional) and biotic interactions could have interacted with these three processes during range expansion. Integrating these mechanisms could improve predictions for invasive taxa and long-term evolutionary responses of expanding clades to climate change.

  14. Electron plasma wave filamentation in the kinetic regime

    NASA Astrophysics Data System (ADS)

    Lushnikov, Pavel; Rose, Harvey; Silantyev, Denis

    2016-10-01

    We consider nonlinear electron plasma wave (EPW) dynamics in the kinetic wavenumber regime, 0.25 < kλD < 0.45 , which is typical for current high temperature laser-plasma interaction experiments, where k is the EPW wavenumber and λD is the electron Debye length. In this kinetic regime, EPW frequency reduction due to electron trapping may dominate the ponderomotive frequency shift. Previous 3D PIC simulations showed that the trapped electron EPW filamentation instability can saturate stimulated Raman backscatter by reducing the EPWs coherence but multidimensional Vlasov simulations [1] are needed to address that saturation in details. We performed nonlinear, non-equilibrium 2D Vlasov simulations to study the EPW filamentation. The initial conditions are created either by external forcing or by constructing the appropriate 1D travelling Bernstein-Greene-Kruskal (BGK) mode. Transverse perturbations of any of these initial conditions grow with time eventually producing strongly nonlinear filamentation followed by plasma turbulence. We compared these simulations with the theoretical results on growth rates of the transverse instability BGK mode showing the satisfactory agreement. Supported by the New Mexico Consortium and NSF DMS-1412140.

  15. Intermittent flow regimes near the convection threshold in ferromagnetic nanofluids.

    PubMed

    Krauzina, Marina T; Bozhko, Alexandra A; Putin, Gennady F; Suslov, Sergey A

    2015-01-01

    The onset and decay of convection in a spherical cavity filled with ferromagnetic nanofluid and heated from below are investigated experimentally. It is found that, unlike in a single-component Newtonian fluid where stationary convection sets in as a result of supercritical bifurcation and where convection intensity increases continuously with the degree of supercriticality, convection in a multicomponent ferromagnetic nanofluid starts abruptly and has an oscillatory nature. The hysteresis is observed in the transition between conduction and convection states. In moderately supercritical regimes, the arising fluid motion observed at a fixed temperature difference intermittently transitions from quasiharmonic to essentially irregular oscillations that are followed by periods of a quasistationary convection. The observed oscillations are shown to result from the precession of the axis of a convection vortex in the equatorial plane. When the vertical temperature difference exceeds the convection onset value by a factor of 2.5, the initially oscillatory convection settles to a steady-state regime with no intermittent behavior detected afterward. The performed wavelet and Fourier analyses of thermocouple readings indicate the presence of various oscillatory modes with characteristic periods ranging from one hour to several days.

  16. Hydroperiod regime controls the organization of plant species in wetlands.

    PubMed

    Foti, Romano; del Jesus, Manuel; Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio

    2012-11-27

    With urban, agricultural, and industrial needs growing throughout the past decades, wetland ecosystems have experienced profound changes. Most critically, the biodiversity of wetlands is intimately linked to its hydrologic dynamics, which in turn are being drastically altered by ongoing climate changes. Hydroperiod regimes, e.g., percentage of time a site is inundated, exert critical control in the creation of niches for different plant species in wetlands. However, the spatial signatures of the organization of plant species in wetlands and how the different drivers interact to yield such signatures are unknown. Focusing on Everglades National Park (ENP) in Florida, we show here that cluster sizes of each species follow a power law probability distribution and that such clusters have well-defined fractal characteristics. Moreover, we individuate and model those signatures via the interplay between global forcings arising from the hydroperiod regime and local controls exerted by neighboring vegetation. With power law clustering often associated with systems near critical transitions, our findings are highly relevant for the management of wetland ecosystems. In addition, our results show that changes in climate and land management have a quantifiable predictable impact on the type of vegetation and its spatial organization in wetlands.

  17. Oscillations in the bistable regime of neuronal networks

    NASA Astrophysics Data System (ADS)

    Roxin, Alex; Compte, Albert

    2016-07-01

    Bistability between attracting fixed points in neuronal networks has been hypothesized to underlie persistent activity observed in several cortical areas during working memory tasks. In network models this kind of bistability arises due to strong recurrent excitation, sufficient to generate a state of high activity created in a saddle-node (SN) bifurcation. On the other hand, canonical network models of excitatory and inhibitory neurons (E-I networks) robustly produce oscillatory states via a Hopf (H) bifurcation due to the E-I loop. This mechanism for generating oscillations has been invoked to explain the emergence of brain rhythms in the β to γ bands. Although both bistability and oscillatory activity have been intensively studied in network models, there has not been much focus on the coincidence of the two. Here we show that when oscillations emerge in E-I networks in the bistable regime, their phenomenology can be explained to a large extent by considering coincident SN and H bifurcations, known as a codimension two Takens-Bogdanov bifurcation. In particular, we find that such oscillations are not composed of a stable limit cycle, but rather are due to noise-driven oscillatory fluctuations. Furthermore, oscillations in the bistable regime can, in principle, have arbitrarily low frequency.

  18. Blow-up regimes in failure of rock specimens

    NASA Astrophysics Data System (ADS)

    Smolin, I. Yu.; Kulkov, A. S.; Makarov, P. V.; Eremin, M. O.; Bakeev, R. A.; Krasnoveykin, V. A.

    2016-11-01

    For damage evaluation, the stage of superfast catastrophic failure of a medium and its mechanical behavior in a state of self-organized criticality prior to the onset of a blow-up fracture mode is of great interest for identification of its precursors. In this work, the data of experimental and numerical investigations of mechanical behavior of a medium before its catastrophic failure and the onset of a blow-up fracture mode are presented. Rock samples and ceramic specimens are subjected to three-point bending and uniaxial compression testing. Surface velocities of the loaded specimens are registered using a laser Doppler vibrometer. The blow-up regime duration is measured to be about 10-20 ms. The specimens' mechanical behavior is numerically simulated under experimental conditions, including the regime of catastrophic fracture. The model parameters of damage accumulation are determined from a comparison with the experimental data. A number of features of the material mechanical response before the catastrophic fracture are identified, which could be treated as failure precursors.

  19. Global patterns of change in discharge regimes for 2100

    NASA Astrophysics Data System (ADS)

    Sperna Weiland, F. C.; van Beek, L. P. H.; Kwadijk, J. C. J.; Bierkens, M. F. P.

    2012-04-01

    This study makes a thorough global assessment of the effects of climate change on hydrological regimes and their accompanying uncertainties. Meteorological data from twelve GCMs (SRES scenarios A1B and control experiment 20C3M) are used to drive the global hydrological model PCR-GLOBWB. This reveals in which regions of the world changes in hydrology can be detected that have a high likelihood and are consistent amongst the ensemble of GCMs. New compared to existing studies is: (1) the comparison of spatial patterns of regime changes and (2) the quantification of notable consistent changes calculated relative to the GCM specific natural variability. The resulting consistency maps indicate in which regions the likelihood of hydrological change is large. Projections of different GCMs diverge widely. This underscores the need of using a multi-model ensemble. Despite discrepancies amongst models, consistent results are revealed: by 2100 the GCMs project consistent decreases in discharge for southern Europe, southern Australia, parts of Africa and southwestern South-America. Discharge decreases strongly for most African rivers, the Murray and the Danube while discharge of monsoon influenced rivers slightly increases. In the Arctic regions river discharge increases and a phase-shift towards earlier peaks is observed. Results are comparable to previous global studies, with a few exceptions. Globally we calculated an ensemble mean discharge increase of more than ten percent. This increase contradicts previously estimated decreases, which is amongst others caused by the use of smaller GCM ensembles and different reference periods.

  20. Global patterns of change in discharge regimes for 2100

    NASA Astrophysics Data System (ADS)

    Sperna Weiland, F. C.; van Beek, L. P. H.; Kwadijk, J. C. J.; Bierkens, M. F. P.

    2011-12-01

    This study makes a thorough global assessment of the effects of climate change on hydrological regimes and their accompanying uncertainties. Meteorological data from twelve GCMs (SRES scenarios A1B, and control experiment 20C3M) are used to drive the global hydrological model PCR-GLOBWB. We reveal in which regions of the world changes in hydrology can be detected that are significant and consistent amongst the ensemble of GCMs. New compared to existing studies is: (1) the comparison of spatial patterns of regime changes and (2) the quantification of consistent significant change calculatesd relative to both the natural variability and the inter-model spread. The resulting consistency maps indicate in which regions likelihood of hydrological change is large. Projections of different GCMs diverge widely. This underscores the need of using a multi-model ensemble. Despite discrepancies amongst models, consistent results are revealed: by 2100 the GCMs project consistent decreases in discharge for southern Europe, southern Australia, parts of Africa and southwestern South-America. Discharge decreases are large for most African rivers, the Murray and the Danube. While discharge of Monsoon influenced rivers slightly increases. In the Arctic regions river discharge increases and a phase-shift towards earlier peaks is observed. Results are comparable to previous global studies, with a few exceptions. Globally we calculated an ensemble mean discharge increase of more than ten percent. This increase contradicts previously estimated decreases, which is amongst others caused by the use of smaller GCM ensembles and different reference periods.

  1. Flood regimes in a changing world: What do we know?

    NASA Astrophysics Data System (ADS)

    Bloeschl, G.

    2015-12-01

    There has been a surprisingly large number of major floods in the last years around the world which suggests that floods may have increased and will continue to increase in the next decades. However, the realism of such changes is still hotly discussed in the literature. In this presentation I will argue that a fresh look is needed at the flood change problem in terms of the causal factors including river training, land use changes and climate variability. Analysing spatial patterns of dynamic flood characteristics helps learn form the rich diversity of flood processes across the landscape. I will present a number of examples across Europe to illustrate the range of flood generation processes and the causal factors of changes in the flood regime. On the basis of these examples, I will demonstrate how comparative hydrology can assist in learning from the differences of flood characteristics between catchments both for present and future conditions. Focus on the interactions of the natural and human water system will be instrumental in making meaningful statements about future floods in a changing world. References Hall et al. (2014) Understanding Flood Regime Changes in Europe: A state of the art assessment. Hydrol. Earth Sys. Sc., 18, 2735-2772. Blöschl et al. (2015) Increasing river floods: fiction or reality? Wiley Interdisciplinary Reviews: Water. doi: 10.1002/wat2.1079

  2. Evolution and resilience of the nuclear nonproliferation regime

    SciTech Connect

    Pregenzer, Arian L.

    2014-05-09

    This paper introduces the concept of systems resilience as a new framework for thinking about the future of the nonproliferation regime. Resilience refers to the ability of a system to maintain its vital functions in the face of continuous and unpredictable change. First, I make the case that the nonproliferation regime can be viewed as a complex system. Next, I discuss key themes from the literature on systems resilience and apply them to the nonproliferation system: the difference between resilience and stability; the need for evolution to maintain function; the importance of functional diversity; and the concept of the adaptive cycle. I show that most existing nonproliferation strategies are aimed at stability rather than resilience and that the current nonproliferation system may be over-constrained by the cumulative evolution of strategies. According to the literature on systems resilience, this increases its vulnerability to collapse. I argue that the resilience of the nonproliferation system can be enhanced by increasing international participation in setting the nonproliferation agenda, developing general international response capabilities, focusing on non-coercive approaches to decreasing demand, and applying systems thinking more rigorously to nonproliferation.

  3. Nonlinear wave interaction and spin models in the magnetohydrodynamic regime

    NASA Astrophysics Data System (ADS)

    Brodin, G.; Lundin, J.; Zamanian, J.; Stefan, M.

    2011-08-01

    Here we consider the influence on the electron spin in the magnetohydrodynamic (MHD) regime. Recently developed models that include spin-velocity correlations are taken as the starting point. A theoretical argument is presented, suggesting that in the MHD regime a single-fluid electron model with spin correlations is equivalent to a model with spin-up and spin-down electrons constituting different fluids, but where the spin-velocity correlations are omitted. Three-wave interaction of two shear Alfvén waves and a compressional Alfvén wave is then taken as a model problem to evaluate the asserted equivalence. The theoretical argument turns out to be supported, because the predictions of the two models agree completely. Furthermore, the three-wave coupling coefficients obey the Manley-Rowe relations, which further support the soundness of the models and the validity of the assumptions made in the derivation. Finally, we point out that the proposed two-fluid model can be incorporated in standard particle-in-cell schemes with only minor modifications.

  4. Fano-Andreev effect in Quantum Dots in Kondo regime

    NASA Astrophysics Data System (ADS)

    Orellana, Pedro; Calle, Ana Maria; Pacheco, Monica; Apel, Victor

    In the present work, we investigate the transport through a T-shaped double quantum dot system coupled to two normal leads and to a superconducting lead. We study the role of the superconducting lead in the quantum interferometric features of the double quantum dot and by means of a slave boson mean field approximation at low temperature regime. We inquire into the influence of intradot interactions in the electronic properties of the system as well. Our results show that Fano resonances due to Andreev bound states are exhibited in the transmission from normal to normal lead as a consequence of quantum interference and proximity effect. This Fano effect produced by Andreev bound states in a side quantum dot was called Fano-Andreev effect, which remains valid even if the electron-electron interaction are taken into account, that is, the Fano-Andreev effect is robust against e-e interactions even in Kondo regime. We acknowledge the financial support from FONDECYT program Grants No. 3140053 and 11400571.

  5. Regimes in secondary atomization of shear thinning inelastic drops

    NASA Astrophysics Data System (ADS)

    Kulkarni, Varun; Rocha, Jonathan; Sojka, Paul

    2016-11-01

    Secondary atomization plays a key role in the determining the eventual drop size distribution of a spray from an injector. Studies until recently have primarily focused on drops made of Newtonian or viscoelastic fluids. However, little is known about the breakup of single drop made of a shear thinning fluid subjected to cross flow of air. In this study we attempt to classify, experimentally, the regimes of breakup and morphology of an inelastic, shear thinning drop. Six different CMC water/glycerine based solutions are tested. The morphological patterns are classified on a We/Oh2 - 1/Oh2 plot using the zero shear rate viscosity where We denotes the Weber number and Oh is the Ohnesorge number. The regime boundaries for the various breakup patterns are juxtaposed with their Newtonian counterparts to highlight the differences. We observe a dependence on the Carreau number, Cu and power law index, n. The results converge to the Newtonian limit for particular cases of Cu and n.

  6. Climate-driven regime shifts in Arctic marine benthos.

    PubMed

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

    2012-08-28

    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.

  7. An assessment of thermal regime in and around Japan

    NASA Astrophysics Data System (ADS)

    Tanaka, Akiko

    2016-04-01

    Terrestrial surface heat flow provides a direct means to estimate the crustal thermal structure. However, the number of heat flow data is limited and spatially very inhomogeneous and even in regions with measurements the data quality varies. To provide an attempt at a higher resolution map of heat flow, we newly measured and acquired thermal conductivity data from existing samples and data. 122 core samples from 42 sites at 37 Japanese volcanoes [Coordinating Committee for Prediction of Volcanic Eruption core analysis group, 2011] were measured for thermal conductivity, thermal capacity, and bulk density, which may be used to improve the thermal regime of volcanoes. Also, to estimate the heat flow using geothermal gradient data, the closest thermal conductivity data is used for each gradient data [Tanaka et al., 2004]. This approach does not take into account geological and hydrodynamical models to use the thermal conductivity, but this assumption works well enough to provide rough estimates of heat flow from geothermal gradient. On the other hand, the depth of magnetic sources based on spectrum analysis of magnetic anomaly data [e.g., Spector and Grant, 1970] is one of several proxies for estimating thermal regime at depth. This analysis is still controversial, however, good correlation between estimated depths of crustal magnetic sources and heat flow suggests that this depth may reflect the broad average temperature. We discuss some of the limitations and possible uses for various data sources.

  8. Managing Disagreement: A Defense of “Regime Bias”

    PubMed Central

    2010-01-01

    Stein Ringen’s theory of democratic purpose cannot do the work expected of it. Ringen’s own criteria oscillate between being too vague to be useful (i.e. “freedom”) or, when specified more fully, conflicting, so that almost all democracies will seem to be potentially at cross-purposes with themselves rather than their purposes or sub-purposes being mutually reinforcing. This reflects a bigger and more theoretical problem. Disagreement about the purpose of democracy is built into democracy itself. The whole point of many (perhaps all) of our democratic institutions is to arrive at conditionally legitimate decisions in spite of such disagreement. So-called regime bias, i.e. the tendency to assess democracies according to the form and stability of their institutions rather than their results or their ability to serve certain purposes, does not in fact arise from bias. It arises on the contrary from a determination to avoid the bias inherent in giving some—inevitably partisan—ideals of what democracies should do pride of place over others in a scheme of measurement or evaluation. And even a regime-based definition of democracy must itself make simplifying assumptions that elide possible normative controversies over how the democratic game is best played. Vindicating one’s preferred set of democratic ideals against alternatives is a completely legitimate enterprise and lends richness to debates within and across democracies. But it is an inherently ideological and political enterprise, not a neutral or scholarly one. PMID:21258438

  9. Hydroperiod regime controls the organization of plant species in wetlands

    PubMed Central

    Foti, Romano; del Jesus, Manuel; Rinaldo, Andrea; Rodriguez-Iturbe, Ignacio

    2012-01-01

    With urban, agricultural, and industrial needs growing throughout the past decades, wetland ecosystems have experienced profound changes. Most critically, the biodiversity of wetlands is intimately linked to its hydrologic dynamics, which in turn are being drastically altered by ongoing climate changes. Hydroperiod regimes, e.g., percentage of time a site is inundated, exert critical control in the creation of niches for different plant species in wetlands. However, the spatial signatures of the organization of plant species in wetlands and how the different drivers interact to yield such signatures are unknown. Focusing on Everglades National Park (ENP) in Florida, we show here that cluster sizes of each species follow a power law probability distribution and that such clusters have well-defined fractal characteristics. Moreover, we individuate and model those signatures via the interplay between global forcings arising from the hydroperiod regime and local controls exerted by neighboring vegetation. With power law clustering often associated with systems near critical transitions, our findings are highly relevant for the management of wetland ecosystems. In addition, our results show that changes in climate and land management have a quantifiable predictable impact on the type of vegetation and its spatial organization in wetlands. PMID:23150589

  10. Testing QCD in the non-perturbative regime

    SciTech Connect

    A.W. Thomas

    2007-01-01

    This is an exciting time for strong interaction physics. We have a candidate for a fundamental theory, namely QCD, which has passed all the tests thrown at it in the perturbative regime. In the non-perturbative regime it has also produced some promising results and recently a few triumphs but the next decade will see enormous progress in our ability to unambiguously calculate the consequences of non-perturbative QCD and to test those predictions experimentally. Amongst the new experimental facilities being constructed, the hadronic machines at JPARC and GSI-FAIR and the 12 GeV Upgrade at Jefferson Lab, the major new electromagnetic facility worldwide, present a beautifully complementary network aimed at producing precise new measurements which will advance our knowledge of nuclear systems and push our ability to calculate the consequences of QCD to the limit. We will first outline the plans at Jefferson Lab for doubling the energy of CEBAF. The new facility presents some wonderful opportunities for discovery in strong interaction physics, as well as beyond the standard model. Then we turn to the theoretical developments aimed at extracting precise results for physical hadron properties from lattice QCD simulations. This discussion will begin with classical examples, such as the mass of the nucleon and ?, before dealing with a very recent and spectacular success involving information extracted from modern parity violating electron scattering.

  11. Oscillations in the bistable regime of neuronal networks.

    PubMed

    Roxin, Alex; Compte, Albert

    2016-07-01

    Bistability between attracting fixed points in neuronal networks has been hypothesized to underlie persistent activity observed in several cortical areas during working memory tasks. In network models this kind of bistability arises due to strong recurrent excitation, sufficient to generate a state of high activity created in a saddle-node (SN) bifurcation. On the other hand, canonical network models of excitatory and inhibitory neurons (E-I networks) robustly produce oscillatory states via a Hopf (H) bifurcation due to the E-I loop. This mechanism for generating oscillations has been invoked to explain the emergence of brain rhythms in the β to γ bands. Although both bistability and oscillatory activity have been intensively studied in network models, there has not been much focus on the coincidence of the two. Here we show that when oscillations emerge in E-I networks in the bistable regime, their phenomenology can be explained to a large extent by considering coincident SN and H bifurcations, known as a codimension two Takens-Bogdanov bifurcation. In particular, we find that such oscillations are not composed of a stable limit cycle, but rather are due to noise-driven oscillatory fluctuations. Furthermore, oscillations in the bistable regime can, in principle, have arbitrarily low frequency.

  12. A frequency tunable relativistic magnetron with a wide operation regime

    NASA Astrophysics Data System (ADS)

    Shi, Di-Fu; Qian, Bao-Liang; Wang, Hong-Gang; Li, Wei; Du, Guang-Xing

    2017-02-01

    A frequency tunable relativistic magnetron (RM) with a wide operation regime is proposed. With the all cavity-magnetron axial extraction technique, the RM can output TEM mode with the operating frequency of 4.3 GHz, which is demonstrated as the dominating output mode by theoretical analysis, cold simulations and hot simulations respectively, corresponding to the output power of 466 MW and the power conversion efficiency of 56.4 %. It also can achieve a wide frequency tuning with the bandwidth of 0.96 GHz and the relative bandwidth of 20.8 %, corresponding to the output power of above 400 MW and the power conversion efficiency of above 40 %. Further simulation results show that the RM has strong performance robustness to the perturbations of the electrical parameters and almost all structural parameters except the cathode radius, anode radius and cavity radius, however two methods proposed in this paper can be taken to further improve the RM performance. The performance robustness enables the RM to operate with a wide parameter regime while keeping a good performance. In addition, a GW-level RM with the power conversion efficiency of 55.9 % also can be obtained.

  13. [Temperature regime of biological tissue under photodynamic therapy].

    PubMed

    Barun, V V; Ivanov, A P

    2012-01-01

    An analytical model is proposed to calculate heating of human skin cover under laser light action of photodynamic therapy. A photosensitizer of "Fotolon" is taken as an example. Temperatures of skin surface and of deep dermis regions are studied as a function of time under pulsed and stationary irradiation of skin surface at the wavelength of 665 nm corresponding to the maximum of the photosensitizer absorption band. It is shown that, under the action of a short light pulse, the photosensitizer can lead to an essential temperature rise of dermis due to a considerable increase in its absorption coefficient. However, this rise does not destruct tissue cells because of the short action. Under stationary irradiation, the photosensitizer concentration has a low effect on the temperature regime of tissue. This is related with the specific features in heating of the medium by red light, where the main thermal process in skin is heat transfer over tissue volume from epidermis having a substantially larger absorption coefficient than that of dermis in the said spectral range. The role of blood perfusion in dermis and its effect on the temperature regime of tissue are evaluated.

  14. All-regime combined-cycle plant: Engineering solutions

    NASA Astrophysics Data System (ADS)

    Berezinets, P. A.; Tumanovskii, G. G.; Tereshina, G. E.; Krylova, I. N.; Markina, V. N.; Migun, E. N.

    2016-12-01

    The development of distributed power generation systems as a supplement to the centralized unified power grid increases the operational stability and efficiency of the entire power generation industry and improves the power supply to consumers. An all-regime cogeneration combined-cycle plant with a power of 20-25 mW (PGU-20/25T) and an electrical efficiency above 50% has been developed at the All-Russia Thermal Engineering Institute (ATEI) as a distributed power generation object. The PGU-20/25T two-circuit cogeneration plant provides a wide electrical and thermal power adjustment range and the absence of the mutual effect of electrical and thermal power output regimes at controlled frequency and power in a unified or isolated grid. The PGU-20/25T combined-cycle plant incorporates a gas-turbine unit (GTU) with a power of 16 MW, a heat recovery boiler (HRB) with two burners (before the boiler and the last heating stage), and a cogeneration steam turbine with a power of 6/9 MW. The PGU-20/25T plant has a maximum electrical power of 22 MW and an efficiency of 50.8% in the heat recovery regime and a maximum thermal power output of 16.3 MW (14 Gcal/h) in the cogeneration regime. The use of burners can increase the electrical power to 25 MW in the steam condensation regime at an efficiency of 49% and the maximum thermal power output to 29.5 MW (25.4 Gcal/h). When the steam turbine is shut down, the thermal power output can grow to 32.6 MW (28 Gcal/h). The innovative equipment, which was specially developed for PGU-20/25T, improves the reliability of this plant and simplifies its operation. Among this equipment are microflame burners in the heat recovery boiler, a vacuum system based on liquid-ring pumps, and a vacuum deaerator. To enable the application of PGU-20/25T in water-stressed regions, an air condenser preventing the heat-transfer tubes from the risk of covering with ice during operation in frost air has been developed. The vacuum system eliminates the need for

  15. Discharge regimes in an intermediate-pressure gas with runaway electrons

    SciTech Connect

    Kolbychev, G.V.; Ptashnik, I.V.

    1985-09-01

    It is shown experimentally that there exist two transition discharge regimes that generate beams of runaway electrons. The first regime, previously unknown, prevails during sufficiently intense ultraviolet illumination and appears immediately after the breakdown of the gap. In this regime, the discharge current is determined solely by the photoelectron emission from the cathode caused by the external ultraviolet light and consists of current runaway electrons. The second regime is a hindered glow discharge; it either follows the photoelectron regime or, if the ultraviolet illumination is not sufficiently intense, arises directly during the breakdown. 6 references.

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

    PubMed

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

    2009-01-20

    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.

  17. Intense electron-beam transport in the ion-focused regime through the collision-dominated regime

    SciTech Connect

    Sanford, T.W.L.; Poukey, J.W.; Welch, D.R.; Mock, R.C.

    1993-12-31

    This paper reviews the transport of the 19-MeV, 700-kA, 25-ns Hermes-III electron beam in long gas cells filled with N{sub 2} gas spanning six decades in pressure from 10{sup 3} to {approximately}10{sup 3} Torr. We show through measurements and theoretical analyses that the beam has two windows of stable transport: a low-pressure window (between {approximately}1 and {approximately}100 mTorr) that is dominated by propagation in the semi-collisionless IFR (ion-focused regime), and a high-pressure window (between {approximately}1 and {approximately}100 Torr) that is dominated by propagation in the resistive CDR (collision-dominated regime). In the CDR, 79{plus_minus}1.5% of the beam energy is transported over 11 m at 20 Torr. In the IFR, we show that intense radiation fields with controllable rise times and pulse widths can be generated on axis at a bremsstrahlung target. In summary, the measurements and analyses presented here provide a quantitative description of the Hermes-III beam transport over six decades in pressure.

  18. Historical thermal regimes define limits to coral acclimatization.

    PubMed

    Howells, Emily J; Berkelmans, Ray; van Oppen, Madeleine J H; Willis, Bette L; Bay, Line K

    2013-05-01

    Knowledge of the degree to which corals undergo physiological acclimatization or genetic adaptation in response to changes in their thermal environment is crucial to the success of coral reef conservation strategies. The potential of corals to acclimatize to temperatures exceeding historical thermal regimes was investigated by reciprocal transplantation of Acropora millepora colonies between the warm central and cool southern regions of the Great Barrier Reef (GBR) for a duration of 14 months. Colony fragments retained at native sites remained healthy, whereas transplanted fragments, although healthy over initial months when temperatures remained within native thermal regimes, subsequently bleached and suffered mortality during seasonal temperature extremes. Corals hosting Symbiodinium D transplanted to the southern GBR bleached in winter and the majority suffered whole (40%; n=20 colonies) or partial (50%) mortality at temperatures 1.1 degrees C below their 15-year native minimum. In contrast, corals hosting Symbiodinium C2 transplanted to the central GBR bleached in summer and suffered whole (50%; n=10 colonies) or partial (42%) mortality at temperatures 2.5 degrees C above their 15-year native maximum. During summer bleaching, the dominant Symbiodinium type changed from C2 to D within corals transplanted to the central GBR. Corals transplanted to the cooler, southern GBR grew 74-80% slower than corals at their native site, and only 50% of surviving colonies reproduced, at least partially because of cold water bleaching of transplants. Despite the absence of any visual signs of stress, corals transplanted to the warmer, central GBR grew 52-59% more slowly than corals at their native site before the summer bleaching (i.e., from autumn to spring). Allocation of energy to initial acclimatization or reproduction may explain this pattern, as the majority (65%) of transplants reproduced one month earlier than portions of the same colonies retained at the southern

  19. Smooth Horizonless Geometries Deep Inside the Black-Hole Regime.

    PubMed

    Bena, Iosif; Giusto, Stefano; Martinec, Emil J; Russo, Rodolfo; Shigemori, Masaki; Turton, David; Warner, Nicholas P

    2016-11-11

    We construct the first family of horizonless supergravity solutions that have the same mass, charges, and angular momenta as general supersymmetric rotating D1-D5-P black holes in five dimensions. This family includes solutions with arbitrarily small angular momenta, deep within the regime of quantum numbers and couplings for which a large classical black hole exists. These geometries are well approximated by the black-hole solution, and in particular exhibit the same near-horizon throat. Deep in this throat, the black-hole singularity is resolved into a smooth cap. We also identify the holographically dual states in the N=(4,4) D1-D5 orbifold conformal field theory (CFT). Our solutions are among the states counted by the CFT elliptic genus, and provide examples of smooth microstate geometries within the ensemble of supersymmetric black-hole microstates.

  20. Spin-torque driven ferromagnetic resonance in a nonlinear regime

    NASA Astrophysics Data System (ADS)

    Chen, W.; de Loubens, G.; Beaujour, J.-M. L.; Sun, J. Z.; Kent, A. D.

    2009-10-01

    Spin-valve based nanojunctions incorporating Co form="infix">∣Ni multilayers with perpendicular anisotropy were used to study spin-torque driven ferromagnetic resonance (ST-FMR) in a nonlinear regime. Perpendicular field swept resonance lines were measured under a large amplitude microwave current excitation, which produces a large angle precession of the Co form="infix">∣Ni layer magnetization. With increasing rf power the resonance lines broaden and become asymmetric, with their peak shifting to lower applied field. A nonhysteretic step jump in ST-FMR voltage signal was also observed at high powers. The results are analyzed in terms of the foldover effect of a forced nonlinear oscillator and compared to macrospin simulations. The ST-FMR nonhysteretic step response may have applications in frequency and amplitude tunable nanoscale field sensors.

  1. Characterization of transcritical and supercritical droplet vaporization regimes using computations

    NASA Astrophysics Data System (ADS)

    Govindaraju, Pavan; Banuti, Daniel; Ma, Peter; Raju, Muralikrishna; Ihme, Matthias

    2016-11-01

    Mixing of liquid fuel with ambient gases plays an important role in engine combustion efficiency and emissions. The situation of cold liquid fuel injected into gas at very high pressure and temperature conditions creates special challenges for prediction of combustion characteristics. Among them, the important question is how the interface between cold liquid fuel and hot ambient responds at the pressures and temperatures specific to engines. The presentation will elaborate on the computational procedure used to simulate the injection of n-dodecane into N2 and comparing interface characteristics with experimental data. This requires robust tools for predicting droplet evaporation, real fluid properties and molecular-dynamic simulations for validating surface tension characteristics. The effect of pyrolysis in the gas phase is considered and the influence of surface tension is examined. Finally, a comparison between theory, experiments and simulations is presented for transition in vaporization regimes. NASA.

  2. Modeling of dialogue regimes of distance robot control

    NASA Astrophysics Data System (ADS)

    Larkin, E. V.; Privalov, A. N.

    2017-02-01

    Process of distance control of mobile robots is investigated. Petri-Markov net for modeling of dialogue regime is worked out. It is shown, that sequence of operations of next subjects: a human operator, a dialogue computer and an onboard computer may be simulated with use the theory of semi-Markov processes. From the semi-Markov process of the general form Markov process was obtained, which includes only states of transaction generation. It is shown, that a real transaction flow is the result of «concurrency» in states of Markov process. Iteration procedure for evaluation of transaction flow parameters, which takes into account effect of «concurrency», is proposed.

  3. Regimes of oscillation and reed vibrations in lingual organ pipes

    NASA Astrophysics Data System (ADS)

    Cox, Eric; Rossing, Thomas D.

    2002-05-01

    We compare the sound generation in six lingual organ pipes including two trompette pipes, two oboes pipes, a krummhorn, and a rankett, the latter two of which were described in a previous paper [Cox and Rossing, paper 2aMU8, 142nd ASA meeting]. With the resonator attached, each pipe sounds in distinct regimes of oscillation, separated by discontinuities. The nominal frequencies of the pipes are generally slightly lower than the resonance frequency of the resonator but slightly higher than the natural frequency of the reed. The air mass loading of both the resonator and shallot lowers the reed frequency. Changing the blowing pressure has little effect on the sounding frequency but a modest effect on sound level.

  4. Ethnic-Based Nuptial Regimes and Marriage Behaviour

    PubMed Central

    Buttenheim, Alison M.; Nobles, Jenna

    2009-01-01

    What role do cultural norms play in shaping individual behaviour and how does this relationship change with rapid socioeconomic development? While modernization and convergence theories predict a weakened relationship between culture and behaviour as individuals rely less on family and community members for economic opportunities, recent research suggests that such norms can persist and continue to influence behaviour. We explored this question in the context of Indonesia, asking whether cultural norms for age at marriage and post-marriage residence—as articulated by local ethnic-based laws and customs known as ‘adat’—influence actual marriage behaviour. We demonstrate that adat norms are strong predictors of marriage behaviours, both over time and net of large increases in educational attainment. Our results suggest more generally that ethnic-based nuptial regimes can be critical and persistent determinants of marriage behaviours even as societies rapidly develop. PMID:19851937

  5. Flow regimes and heat transfer in vertical narrow annuli

    SciTech Connect

    Ulke, A.; Goldberg, I.

    1993-11-01

    In shell side boiling heat exchangers narrow crevices that are formed between the tubes and the tube support structure provide areas for local thermal-hydraulic conditions which differ significantly from bulk fluid conditions. Understanding of the processes of boiling and dryout in flow restricted crevices can help in designing of tube support geometries to minimize the likelihood of tube support plate and tube corrosion observed in commercial power plant steam generators. This paper describes a one dimensional thermal-hydraulic model of a vertical crevice between a tube and a support plate with cylindrical holes. The annulus formed by the support plate hole and an eccentrically located tube has been represented by vertical strips. The formation, growth and collapse of a steam bubble in each strip has been determined. Based on the bubble history, and flow regimes characterized by ``isolated`` bubbles, ``coalesced`` bubbles and liquid deficient regions have been defined.

  6. Newly discovered landscape traps produce regime shifts in wet forests

    PubMed Central

    Lindenmayer, David B.; Hobbs, Richard J.; Likens, Gene E.; Krebs, Charles J.; Banks, Samuel C.

    2011-01-01

    We describe the “landscape trap” concept, whereby entire landscapes are shifted into, and then maintained (trapped) in, a highly compromised structural and functional state as the result of multiple temporal and spatial feedbacks between human and natural disturbance regimes. The landscape trap concept builds on ideas like stable alternative states and other relevant concepts, but it substantively expands the conceptual thinking in a number of unique ways. In this paper, we (i) review the literature to develop the concept of landscape traps, including their general features; (ii) provide a case study as an example of a landscape trap from the mountain ash (Eucalyptus regnans) forests of southeastern Australia; (iii) suggest how landscape traps can be detected before they are irrevocably established; and (iv) present evidence of the generality of landscape traps in different ecosystems worldwide. PMID:21876151

  7. Fluid mobility over corrugated surfaces in the Stokes regime

    NASA Astrophysics Data System (ADS)

    Shelley, S. R.; Smith, J. D.; Hibbins, A. P.; Sambles, J. R.; Horsley, S. A. R.

    2016-08-01

    An exact solution is found for laminar fluid flow along the grooves of a family of surfaces whose shape is given by the Lambert W-function. This simple solution allows for the slip length in the direction parallel to the grooves to be calculated exactly. With this analytical model, we establish the regime of validity for a previously untested perturbation theory intended for calculating the surface mobility tensor of arbitrary periodic surfaces, finding that it compares well to the exact expression for nearly all choices of parameters of the conformal map. To test this perturbation theory further, the mobility tensor is evaluated for a simple sinusoidal surface for flow both parallel and perpendicular to the grooves, finding that the perturbation theory is less accurate in the latter of these two cases.

  8. Patterned nonadhesive surfaces: superhydrophobicity and wetting regime transitions.

    PubMed

    Nosonovsky, Michael; Bhushan, Bharat

    2008-02-19

    Nonadhesive and water-repellent surfaces are required for many tribological applications. We study mechanisms of wetting of patterned superhydrophobic Si surfaces, including the transition between various wetting regimes during microdroplet evaporation in environmental scanning electron microscopy (ESEM) and for contact angle and contact angle hysteresis measurements. Wetting involves interactions at different scale levels: macroscale (water droplet size), microscale (surface texture size), and nanoscale (molecular size). We propose a generalized formulation of the Wenzel and Cassie equations that is consistent with the broad range of experimental data. We show that the contact angle hysteresis involves two different mechanisms and how the transition from the metastable partially wetted (Cassie) state to the homogeneously wetted (Wenzel) state depends upon droplet size and surface pattern parameters.

  9. Thermophoretic force on nanocylinders in the free molecule regime

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Luo, Shuang; Xia, Guodong

    2017-03-01

    We theoretically investigate the thermophoresis of nanocylinders in the free molecule regime, wherein the nonrigid-body effect is taken into account. The analytical formulas of the thermophoretic forces on cylinders suspended in both simple gases and binary gas mixtures are derived for the two limiting collision models, i.e., specular and diffuse scatterings, based on the gas kinetic theory. In the limit of the rigid-body collision, the expressions can be reduced to the theoretical results of Garcia-Ybarra and Rosner [AIChE J. 35, 139 (1989), 10.1002/aic.690350115]. The thermophoretic velocities of the nanocylinders (including carbon nanotubes and long-chain n -alkanes) have been evaluated and it is found that the influence of the nonrigid-body effect on thermophoresis is significant for the case of small cylinder radius and low temperatures.

  10. Active tunable plasmonically induced polarization conversion in the THz regime

    NASA Astrophysics Data System (ADS)

    Ling, Furi; Yao, Gang; Yao, Jianquan

    2016-10-01

    A plasmon-induced polarization conversion (PIPC) structure based on periodically patterned graphene was demonstrated in the THz regime. By varying the Fermi level of two connected T-shape graphene strips through the electrostatic gating, the peak frequency and the group index in the transparency window can be tuned, which is good agreement with the coupled Lorentz oscillator model. Due to interference between two polarization selective graphene plasmonic resonances coexisting in the planar metamaterial, polarization conversion can be achieved. The linearly polarized THz wave can be converted to elliptically and right circularly polarized THz wave through varying the relaxation time of electrons in graphene. This novel chip-scale active terahertz device promises essential application opportunities in terahertz sensing and terahertz communications.

  11. Normal, superconducting and topological regimes of hybrid double quantum dots.

    PubMed

    Sherman, D; Yodh, J S; Albrecht, S M; Nygård, J; Krogstrup, P; Marcus, C M

    2017-03-01

    Epitaxial semiconductor-superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density. Here, we investigate double-quantum-dot structures made from InAs nanowires with a patterned epitaxial Al two-facet shell that proximitizes two gate-defined segments along the nanowire. We follow the evolution of mesoscopic superconductivity and charging energy in this system as a function of magnetic field and voltage-tuned barriers. Interdot coupling is varied from strong to weak using side gates, and the ground state is varied between normal, superconducting and topological regimes by applying a magnetic field. We identify the topological transition by tracking the spacing between successive co-tunnelling peaks as a function of axial magnetic field and show that the individual dots host weakly hybridized Majorana modes.

  12. Detector noise statistics in the non-linear regime

    NASA Technical Reports Server (NTRS)

    Shopbell, P. L.; Bland-Hawthorn, J.

    1992-01-01

    The statistical behavior of an idealized linear detector in the presence of threshold and saturation levels is examined. It is assumed that the noise is governed by the statistical fluctuations in the number of photons emitted by the source during an exposure. Since physical detectors cannot have infinite dynamic range, our model illustrates that all devices have non-linear regimes, particularly at high count rates. The primary effect is a decrease in the statistical variance about the mean signal due to a portion of the expected noise distribution being removed via clipping. Higher order statistical moments are also examined, in particular, skewness and kurtosis. In principle, the expected distortion in the detector noise characteristics can be calibrated using flatfield observations with count rates matched to the observations. For this purpose, some basic statistical methods that utilize Fourier analysis techniques are described.

  13. Thermoelectric efficiency of nanoscale devices in the linear regime

    NASA Astrophysics Data System (ADS)

    Bevilacqua, G.; Grosso, G.; Menichetti, G.; Pastori Parravicini, G.

    2016-12-01

    We study quantum transport through two-terminal nanoscale devices in contact with two particle reservoirs at different temperatures and chemical potentials. We discuss the general expressions controlling the electric charge current, heat currents, and the efficiency of energy transmutation in steady conditions in the linear regime. With focus in the parameter domain where the electron system acts as a power generator, we elaborate workable expressions for optimal efficiency and thermoelectric parameters of nanoscale devices. The general concepts are set at work in the paradigmatic cases of Lorentzian resonances and antiresonances, and the encompassing Fano transmission function: the treatments are fully analytic, in terms of the trigamma functions and Bernoulli numbers. From the general curves here reported describing transport through the above model transmission functions, useful guidelines for optimal efficiency and thermopower can be inferred for engineering nanoscale devices in energy regions where they show similar transmission functions.

  14. The two-field regime of natural inflation

    SciTech Connect

    Achúcarro, Ana; Atal, Vicente; Kawasaki, Masahiro; Takahashi, Fuminobu E-mail: atal@lorentz.leidenuniv.nl E-mail: fumi@tuhep.phys.tohoku.ac.jp

    2015-12-01

    The simplest two-field completion of natural inflation has a regime in which both fields are active and in which its predictions are within the Planck 1-σ confidence contour. We show this for the original model of natural inflation, in which inflation is achieved through the explicit breaking of a U(1) symmetry. We consider the case in which the mass coming from explicit breaking of this symmetry is comparable to that from spontaneous breaking, which we show is consistent with a hierarchy between the corresponding energy scales. While both masses are comparable when the observable modes left the horizon, the mass hierarchy is restored in the last e-foldings of inflation, rendering the predictions consistent with the isocurvature bounds. For completeness, we also study the predictions for the case in which there is a large hierarchy of masses and an initial period of inflation driven by the (heavy) radial field.

  15. Quantum tunneling at zero temperature in the strong friction regime.

    PubMed

    Bolivar, A O

    2005-01-21

    In the large damping limit we derive a Fokker-Planck equation in configuration space (the so-called Smoluchowski equation) describing a Brownian particle immersed into a thermal environment and subjected to a nonlinear external force. We quantize this stochastic system and survey the problem of escape over a double-well potential barrier. Our finding is that the quantum Kramers rate does not depend on the friction coefficient at low temperatures; i.e., we predict a superfluidity phenomenon in overdamped open systems. Moreover, at zero temperature we show that the quantum escape rate does not vanish in the strong friction regime. This result, therefore, is in contrast with the work by Ankerhold et al. [Phys. Rev. Lett. 87, 086802 (2001)

  16. Chiral Effective Field Theory Beyond the Power-Counting Regime

    SciTech Connect

    Hall, Jonathan M. M.; Leinweber, Derek B.; Young, Ross D.

    2011-05-24

    Novel techniques are presented, which identify the chiral power-counting regime (PCR), and realize the existence of an intrinsic energy scale embedded in lattice QCD results that extend outside the PCR. The nucleon mass is considered as a benchmark for illustrating this new approach. Using finite-range regularization, an optimal regularization scale can be extracted from lattice simulation results by analyzing the renormalization of the low energy coefficients. The optimal scale allows a description of lattice simulation results that extend beyond the PCR by quantifying and thus handling any scheme-dependence. Preliminary results for the nucleon magnetic moment are also examined, and a consistent optimal regularization scale is obtained. This indicates the existence of an intrinsic scale corresponding to the finite size of the source of the pion cloud.

  17. Transition from linear- to nonlinear-focusing regime in filamentation

    PubMed Central

    Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin

    2014-01-01

    Laser filamentation in gases is often carried out in the laboratory with focusing optics to better stabilize the filament, whereas real-world applications of filaments frequently involve collimated or near-collimated beams. It is well documented that geometrical focusing can alter the properties of laser filaments and, consequently, a transition between a collimated and a strongly focused filament is expected. Nevertheless, this transition point has not been identified. Here, we propose an analytical method to determine the transition, and show that it corresponds to an actual shift in the balance of physical mechanisms governing filamentation. In high-NA conditions, filamentation is primarily governed by geometrical focusing and plasma effects, while the Kerr nonlinearity plays a more significant role as NA decreases. We find the transition between the two regimes to be relatively insensitive to the intrinsic laser parameters, and our analysis agrees well with a wide range of parameters found in published literature. PMID:25434678

  18. Smooth Horizonless Geometries Deep Inside the Black-Hole Regime

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Giusto, Stefano; Martinec, Emil J.; Russo, Rodolfo; Shigemori, Masaki; Turton, David; Warner, Nicholas P.

    2016-11-01

    We construct the first family of horizonless supergravity solutions that have the same mass, charges, and angular momenta as general supersymmetric rotating D 1 -D 5 -P black holes in five dimensions. This family includes solutions with arbitrarily small angular momenta, deep within the regime of quantum numbers and couplings for which a large classical black hole exists. These geometries are well approximated by the black-hole solution, and in particular exhibit the same near-horizon throat. Deep in this throat, the black-hole singularity is resolved into a smooth cap. We also identify the holographically dual states in the N =(4 ,4 ) D 1 -D 5 orbifold conformal field theory (CFT). Our solutions are among the states counted by the CFT elliptic genus, and provide examples of smooth microstate geometries within the ensemble of supersymmetric black-hole microstates.

  19. Design of planar chiral metamaterials for near-infrared regime

    NASA Astrophysics Data System (ADS)

    Kaya, Sabri; Turkmen, Mustafa; Topaktas, Omer

    2017-01-01

    Planar chiral metamaterials (PCMs) comprising double-layer dielectric-metal-dielectric resonant structures in the shape of a windmill are presented for near-infrared regime. The circular dichroism is retrieved from transmission spectra. Effects of used materials on circular dichroism characteristics of PCM arrays are investigated for the first time. The dependence of spectral characteristics on the geometrical parameters of the PCMs is analyzed by the finite-difference time-domain method. The observations indicated that the circular dichroism characteristics of the proposed PCM arrays are strongly dependent on the type of metal and dielectric materials. Due to the enhanced chiroptical near-field response and tunable spectral behavior, proposed PCM arrays may have potential for biosensing applications of chiral biomolecules.

  20. Information causality in the quantum and post-quantum regime.

    PubMed

    Ringbauer, Martin; Fedrizzi, Alessandro; Berry, Dominic W; White, Andrew G

    2014-11-07

    Quantum correlations can be stronger than anything achieved by classical systems, yet they are not reaching the limit imposed by relativity. The principle of information causality offers a possible explanation for why the world is quantum and why there appear to be no even stronger correlations. Generalizing the no-signaling condition it suggests that the amount of accessible information must not be larger than the amount of transmitted information. Here we study this principle experimentally in the classical, quantum and post-quantum regimes. We simulate correlations that are stronger than allowed by quantum mechanics by exploiting the effect of polarization-dependent loss in a photonic Bell-test experiment. Our method also applies to other fundamental principles and our results highlight the special importance of anisotropic regions of the no-signalling polytope in the study of fundamental principles.

  1. Active tunable plasmonically induced polarization conversion in the THz regime

    PubMed Central

    Ling, Furi; Yao, Gang; Yao, Jianquan

    2016-01-01

    A plasmon-induced polarization conversion (PIPC) structure based on periodically patterned graphene was demonstrated in the THz regime. By varying the Fermi level of two connected T-shape graphene strips through the electrostatic gating, the peak frequency and the group index in the transparency window can be tuned, which is good agreement with the coupled Lorentz oscillator model. Due to interference between two polarization selective graphene plasmonic resonances coexisting in the planar metamaterial, polarization conversion can be achieved. The linearly polarized THz wave can be converted to elliptically and right circularly polarized THz wave through varying the relaxation time of electrons in graphene. This novel chip-scale active terahertz device promises essential application opportunities in terahertz sensing and terahertz communications. PMID:27734912

  2. On the Dynamical Regimes of Pattern-Accelerated Electroconvection

    PubMed Central

    Davidson, Scott M.; Wessling, Matthias; Mani, Ali

    2016-01-01

    Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states. PMID:26935925

  3. Gravity-driven soap film dynamics in subcritical regimes

    NASA Astrophysics Data System (ADS)

    Auliel, M. I.; Castro, F.; Sosa, R.; Artana, G.

    2015-10-01

    We undertake the analysis of soap-film dynamics with the classical approach of asymptotic expansions. We focus our analysis in vertical soap film tunnels operating in subcritical regimes with elastic Mach numbers Me=O(10-1) . Considering the associated set of nondimensional numbers that characterize this flow, we show that the flow behaves as a two-dimensional (2D) divergence free flow with variable mass density. When the soap film dynamics agrees with that of a 2D and almost constant mass density flow, the regions where the second invariant of the velocity gradient is non-null correspond to regions where the rate of change of film thickness is non-negligible.

  4. Light scattering regimes along the optical axis in turbid media

    NASA Astrophysics Data System (ADS)

    Campbell, S. D.; O'Connell, A. K.; Menon, S.; Su, Q.; Grobe, R.

    2006-12-01

    We inject an angularly collimated laser beam into a scattering medium of a nondairy creamer-water solution and examine the distribution of the scattered light along the optical axis as a function of the source-detector spacing. The experimental and simulated data obtained from a Monte Carlo simulation suggest four regimes characterizing the transition from unscattered to diffusive light. We compare the data also with theoretical predictions based on a first-order scattering theory for regions close to the source, and with diffusionlike theories for larger source-detector spacings. We demonstrate the impact of the measurement process and the effect of the unavoidable absorption of photons by the detection fiber on the light distribution inside the medium. We show that the range of validity of these theories can depend on the experimental parameters such as the diameter and acceptance angle of the detection fiber.

  5. Light scattering regimes along the optical axis in turbid media.

    PubMed

    Campbell, S D; O'connell, A K; Menon, S; Su, Q; Grobe, R

    2006-12-01

    We inject an angularly collimated laser beam into a scattering medium of a nondairy creamer-water solution and examine the distribution of the scattered light along the optical axis as a function of the source-detector spacing. The experimental and simulated data obtained from a Monte Carlo simulation suggest four regimes characterizing the transition from unscattered to diffusive light. We compare the data also with theoretical predictions based on a first-order scattering theory for regions close to the source, and with diffusionlike theories for larger source-detector spacings. We demonstrate the impact of the measurement process and the effect of the unavoidable absorption of photons by the detection fiber on the light distribution inside the medium. We show that the range of validity of these theories can depend on the experimental parameters such as the diameter and acceptance angle of the detection fiber.

  6. Opening-assisted coherent transport in the semiclassical regime.

    PubMed

    Zhang, Yang; Celardo, G Luca; Borgonovi, Fausto; Kaplan, Lev

    2017-02-01

    We study quantum enhancement of transport in open systems in the presence of disorder and dephasing. Quantum coherence effects may significantly enhance transport in open systems even in the semiclassical regime (where the decoherence rate is greater than the intersite hopping amplitude), as long as the disorder is sufficiently strong. When the strengths of disorder and dephasing are fixed, there is an optimal opening strength at which the coherent transport enhancement is optimized. Analytic results are obtained in two simple paradigmatic tight-binding models of large systems: the linear chain and the fully connected network. The physical behavior is also reflected in the Fenna-Matthews-Olson (FMO) photosynthetic complex, which may be viewed as intermediate between these paradigmatic models.

  7. Supercurrent in the quantum Hall regime: part I

    NASA Astrophysics Data System (ADS)

    Ke, Chung-Ting; Amet, Francois; Borzenets, Ivan; Wang, Jiyingmei; Watanabe, Keji; Taniguchi, Takashi; Deacon, Russell; Yamamoto, Michihisa; Bomze, Yuriy; Tarucha, Seigo; Finkelstein, Gleb

    The remarkable electronic quality of graphene/boron nitride heterostructures makes them an ideal medium to study induced superconductivity. Our Josephson junctions are made of encapsulated graphene demonstrate ballistic superconducting transport at the micron scale. In the hole-doped regime, a Fabry-Perot resonator is formed by PN junctions close to superconducting contacts, which causes quantum interference of the critical current. We study variations of the Fraunhofer pattern (I_C vs. B) thought the gate voltage range. At higher magnetic fields, superconducting transport across the junctions becomes profoundly non-periodic. Despite demonstrating strong fluctuations as a function of density and magnetic field, we find that supercurrent persists in a wide range of parameters.

  8. On the Dynamical Regimes of Pattern-Accelerated Electroconvection.

    PubMed

    Davidson, Scott M; Wessling, Matthias; Mani, Ali

    2016-03-03

    Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.

  9. On the Dynamical Regimes of Pattern-Accelerated Electroconvection

    NASA Astrophysics Data System (ADS)

    Davidson, Scott M.; Wessling, Matthias; Mani, Ali

    2016-03-01

    Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.

  10. Photosynthesis in chlorolichens: the influence of the habitat light regime.

    PubMed

    Piccotto, Massimo; Tretiach, Mauro

    2010-11-01

    The hypothesis that CO(2) gas exchange and chlorophyll a fluorescence (ChlaF) of lichens vary according to the light regimes of their original habitat, as observed in vascular plants, was tested by analysing the photosynthetic performance of 12 populations of seven dorsoventral, foliose lichens collected from open, south-exposed rocks to densely shaded forests. Light response curves were induced at optimum thallus water content and ChlaF emission curves at the species-specific photon flux at which the quantum yield of CO(2) assimilation is the highest and is saturating the photosynthetic process. Photosynthetic pigments were quantified in crude extracts. The results confirm that the maximum rate of gross photosynthesis is correlated with the chlorophyll content of lichens, which is influenced by light as well as by nitrogen availability. Like leaves, shade tolerant lichens emit more ChlaF than sun-loving ones, whereas the photosynthetic quantum conversion is higher in the latter.

  11. Floating production systems in a ``new economic regime``

    SciTech Connect

    Eriksen, K.; D`Souza, R.B.; Wilson, A.J.S.; Johansson, O.

    1995-12-31

    Except for a short period before, during and after the Gulf War, the oil prices have been depressed for 8--10 years. This has forced industry to be profitable at these low oil price levels. Since 1975 various floating production systems have been evaluated and used as field development solutions around the world. As technical challenges have been overcome, floating production systems have become leading contenders for traditional and deepwater field developments in this new economic regime. There are many types of Floating production systems. A few examples are--the semisubmersible Floating Production System (FPS), the monohull Floating Production, Storage and Offloading system (FPSO), the Spar Buoy and the Deep Draft Floater. As the FPS and FPSO represent proven technology and are leading contenders for several field developments in both the North Sea and the Gulf of Mexico, this paper will concentrate on these concepts.

  12. Regimes of Pulsar Pair Formation and Particle Energetics

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander G.; Zhang, Bing; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that,, while only the younger pulsars can produce pairs through CR, nearly all known radio pulsars are capable of producing pairs through non-resonant inverse-Compton scatterings. The effect of the neutron star equations of state on the pair death lines is explored. We show that pair production is facilitated in more compact stars and more a massive stars. Therefore accretion of mass by pulsars in binary systems may allow pair production in most of the millisecond purser population. We also find that two-photon pair production may be important in millisecond pursers if their surface temperatures are above approx. or equal to three million degrees K. Pursers that produce pairs through CRT wilt have their primary acceleration limited by the effect of screening of the electric field. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sup 1/2, sub rot) dependence. The acceleration voltage drop in pursers that produce pairs only through inverse-Compton emission will not be limited by electric field screening. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sub rot) dependence. Thus, older pursers will have significantly lower gamma-ray luminosity.

  13. Thermal Evolution and Crystallisation Regimes of the Martian Core

    NASA Astrophysics Data System (ADS)

    Davies, C. J.; Pommier, A.

    2015-12-01

    Though it is accepted that Mars has a sulfur-rich metallic core, its chemical and physical state as well as its time-evolution are still unconstrained and debated. Several lines of evidence indicate that an internal magnetic field was once generated on Mars and that this field decayed around 3.7-4.0 Gyrs ago. The standard model assumes that this field was produced by a thermal (and perhaps chemical) dynamo operating in the Martian core. We use this information to construct parameterized models of the Martian dynamo in order to place constraints on the thermochemical evolution of the Martian core, with particular focus on its crystallization regime. Considered compositions are in the FeS system, with S content ranging from ~10 and 16 wt%. Core radius, density and CMB pressure are varied within the errors provided by recent internal structure models that satisfy the available geodetic constraints (planetary mass, moment of inertia and tidal Love number). We also vary the melting curve and adiabat, CMB heat flow and thermal conductivity. Successful models are those that match the dynamo cessation time and fall within the bounds on present-day CMB temperature. The resulting suite of over 500 models suggest three possible crystallization regimes: growth of a solid inner core starting at the center of the planet; freezing and precipitation of solid iron (Fe- snow) from the core-mantle boundary (CMB); and freezing that begins midway through the core. Our analysis focuses on the effects of core properties that are expected to be constrained during the forthcoming Insight mission.

  14. Using Biofuel Tracers to Study Alternative Combustion Regimes

    SciTech Connect

    Mack, J H; Flowers, D L; Buchholz, B A; Dibble, R W

    2006-02-14

    Interest in the use of alternative fuels and combustion regimes is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO{sub 2} emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions, and higher noise. Noise and PM have traditionally been the obstacles toward consumer acceptance of Diesel passenger cars in North America, while NOx (a key component in photochemical smog) has been more of an engineering challenge. Diesels are lean burning (combustion with excess oxygen) and reducing NOx to N2 in an oxygen rich environment is difficult. Adding oxygenated compounds to the fuel helps reduce PM emissions, but relying on fuel alone to reduce PM is unrealistic. Keeping peak combustion temperature below 1700 K prevents NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous Charge Compression Ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to validate combustion modeling.

  15. Smith-Purcell radiation in the highly relativistic regime

    SciTech Connect

    Walsh, J.E.; Woods, K.J.; Kirk, H.G.

    1995-12-31

    An electron moving over the surface of a diffraction grating will transfer a part of its kinetic energy to radiation via a velocity synchronous coupling with a slow space harmonic component of the field. Since the phase velocity of a slow space harmonic is less than the speed of light, the slow components decay exponentially, or evanesce, with distance above the grating and the evanescence scale is determined by the product of the relative velocity, {beta}, the relative energy, {gamma}, and the wavelength {lambda}. Thus, in the relativistic regime, good electron - grating coupling can be maintained at beam heights that are greater than the emitted wavelength. In order to explore this regime a series of experiments have been carried out with moderately energetic beams and an experiment with the 70-MeV beam at the Accelerator Test Facility is in the planning stage. The work has two basic goals: the first is to explore the characteristics of the spontaneous emission produced by the beam as it moves over the grating, and the second is to evaluate the potential of grating-coupled or Smith-Purcell free electron lasers. The spontaneous emission is of direct interest. It appears on the basis of work to date that the broad spectral distribution produced by a relativistic electron beam moving over a grating is potentially an alternative source for experiments of the type now carried out on synchrotron infrared beam lines. The grating, or a system of gratings, are also a potential alternative to the magnetic undulator and thus another basic approach to free electron laser design. The presentation will include a summary of the design of the experiment which is to be carried out on the 70-MeV A.T.F. beam line and a review of the theory of Smith-Purcell radiation in the high energy limit. Gain calculations and the role of beam quality in establishing performance limits will be discussed.

  16. Landscape-scale forest disturbance regimes in southern Peruvian Amazonia.

    PubMed

    Boyd, Doreen S; Hill, Ross A; Hopkinson, Chris; Baker, Timothy R

    2013-10-01

    Landscape-scale gap-size frequency distributions in tropical forests are a poorly studied but key ecological variable. Currently, a scale gap currently exists between local-scale field-based studies and those employing regional-scale medium-resolution satellite data. Data at landscape scales but of fine resolution would, however, facilitate investigation into a range of ecological questions relating to gap dynamics. These include whether canopy disturbances captured in permanent sample plots (PSPs) are representative of those in their surrounding landscape, and whether disturbance regimes vary with forest type. Here, therefore, we employ airborne LiDAR data captured over 142.5 km2 of mature, swamp, and regenerating forests in southeast Peru to assess the landscape-scale disturbance at a sampling resolution of up to 2 m. We find that this landscape is characterized by large numbers of small gaps; large disturbance events are insignificant and infrequent. Of the total number of gaps that are 2 m2 or larger in area, just 0.45% were larger than 100 m2, with a power-law exponent (alpha) value of the gap-size frequency distribution of 2.22. However, differences in disturbance regimes are seen among different forest types, with a significant difference in the alpha value of the gap-size frequency distribution observed for the swamp/regenerating forests compared with the mature forests at higher elevations. Although a relatively small area of the total forest of this region was investigated here, this study presents an unprecedented assessment of this landscape with respect to its gap dynamics. This is particularly pertinent given the range of forest types present in the landscape and the differences observed. The coupling of detailed insights into forest properties and growth provided by PSPs with the broader statistics of disturbance events using remote sensing is recommended as a strong basis for scaling-up estimates of landscape and regional-scale carbon balance.

  17. Evaluating and optimizing horticultural regimes in space plant growth facilities

    NASA Astrophysics Data System (ADS)

    Berkovich, Y.; Chetirkin, R.; Wheeler, R.; Sager, J.

    In designing innovative Space Plant Growth Facilities (SPGF) for long duration space f ightl various limitations must be addressed including onboard resources: volume, energy consumption, heat transfer and crew labor expenditure. The required accuracy in evaluating onboard resources by using the equivalent mass methodology and applying it to the design of such facilities is not precise. This is due to the uncertainty of the structure and not completely understanding of the properties of all associated hardware, including the technology in these systems. We present a simple criteria of optimization for horticultural regimes in SPGF: Qmax = max [M · (EBI) 2 / (V · E · T) ], where M is the crop harvest in terms of total dry biomass in the plant growth system; EBI is the edible biomass index (harvest index), V is a volume occupied by the crop; E is the crop light energy supply during growth; T is the crop growth duration. The criterion reflects directly on the consumption of onboard resources for crop production. We analyzed the efficiency of plant crops and the environmental parameters by examining the criteria for 15 salad and 12 wheat crops from the data in the ALS database at Kennedy Space Center. Some following conclusion have been established: 1. The technology involved in growing salad crops on a cylindrical type surface provides a more meaningful Q-criterion; 2. Wheat crops were less efficient than leafy greens (salad crops) when examining resource utilization; 3. By increasing light intensity of the crop the efficiency of the resource utilization could decrease. Using the existing databases and Q-criteria we have found that the criteria can be used in optimizing design and horticultural regimes in the SPGF.

  18. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

    NASA Astrophysics Data System (ADS)

    Zhang, Shipeng; Wang, Minghuai; Ghan, Steven J.; Ding, Aijun; Wang, Hailong; Zhang, Kai; Neubauer, David; Lohmann, Ulrike; Ferrachat, Sylvaine; Takeamura, Toshihiko; Gettelman, Andrew; Morrison, Hugh; Lee, Yunha; Shindell, Drew T.; Partridge, Daniel G.; Stier, Philip; Kipling, Zak; Fu, Congbin

    2016-03-01

    Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascent (ω500 < -25 hPa day-1) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is close to that in subsidence regimes, which indicates that regimes with strong large-scale ascent are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (> 0.1 mm day-1) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes compared to the uncertainty in its global mean values, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes.

  19. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

    SciTech Connect

    Zhang, S.; Wang, Minghuai; Ghan, Steven J.; Ding, A.; Wang, Hailong; Zhang, Kai; Neubauer, David; Lohmann, U.; Ferrachat, S.; Takeamura, Toshihiko; Gettelman, A.; Morrison, H.; Lee, Y. H.; Shindell, D. T.; Partridge, Daniel; Stier, P.; Kipling, Z.; Fu, Congbin

    2016-03-04

    Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascend (ω500 < -25 hPa/d) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is as large as that in stratocumulus regimes, which indicates that regimes with strong large-scale ascend are as important as stratocumulus regimes in studying AIE. 42" It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (> 0.1 mm/d) contributes the most to the total aerosol indirect forcing (from 64% to nearly 100%). Results show that the uncertainty in AIE is even larger within specific dynamical regimes than that globally, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes.

  20. Welfare state regimes, health and health inequalities in adolescence: a multilevel study in 32 countries.

    PubMed

    Richter, Matthias; Rathman, Katharina; Nic Gabhainn, Saoirse; Zambon, Alessio; Boyce, William; Hurrelmann, Klaus

    2012-07-01

    Comparative research on health and health inequalities has recently started to establish a welfare regime perspective. The objective of this study was to determine whether different welfare regimes are associated with health and health inequalities among adolescents. Data were collected from the 'Health Behaviour in School-aged Children' study in 2006, including 11- to 15-year-old students from 32 countries (N = 141,091). Prevalence rates and multilevel logistic regression models were calculated for self-rated health (SRH) and health complaints. The results show that between 4 per cent and 7 per cent of the variation in both health outcomes is attributable to differences between countries. Compared to the Scandinavian regime, the Southern regime had lower odds ratios for SRH, while for health complaints the Southern and Eastern regime showed high odds ratios. The association between subjective health and welfare regime was largely unaffected by adjusting for individual socioeconomic position. After adjustment for the welfare regime typology, the country-level variations were reduced to 4.6 per cent for SRH and to 2.9 per cent for health complaints. Regarding cross-level interaction effects between welfare regimes and socioeconomic position, no clear regime-specific pattern was found. Consistent with research on adults this study shows that welfare regimes are important in explaining variations in adolescent health across countries.

  1. Analysis of weather condition influencing fire regime in Italy

    NASA Astrophysics Data System (ADS)

    Bacciu, Valentina; Masala, Francesco; Salis, Michele; Sirca, Costantino; Spano, Donatella

    2014-05-01

    Fires have a crucial role within Mediterranean ecosystems, with both negative and positive impacts on all biosphere components and with reverberations on different scales. Fire determines the landscape structure and plant composition, but it is also the cause of enormous economic and ecological damages, beside the loss of human life. In addition, several authors are in agreement suggesting that, during the past decades, changes on fire patterns have occurred, especially in terms of fire-prone areas expansion and fire season lengthening. Climate and weather are two of the main controlling agents, directly and indirectly, of fire regime influencing vegetation productivity, causing water stress, igniting fires through lightning, or modulating fire behavior through wind. On the other hand, these relationships could be not warranted in areas where most ignitions are caused by people (Moreno et al. 2009). Specific analyses of the driving forces of fire regime across countries and scales are thus still required in order to better anticipate fire seasons and also to advance our knowledge of future fire regimes. The objective of this work was to improve our knowledge of the relative effects of several weather variables on forest fires in Italy for the period 1985-2008. Meteorological data were obtained through the MARS (Monitoring Agricultural Resources) database, interpolated at 25x25 km scale. Fire data were provided by the JRC (Join Research Center) and the CFVA (Corpo Forestale e di Vigilanza Ambientale, Sardinia). A hierarchical cluster analysis, based on fire and weather data, allowed the identification of six homogeneous areas in terms of fire occurrence and climate (pyro-climatic areas). Two statistical techniques (linear and non-parametric models) were applied in order to assess if inter-annual variability in weather pattern and fire events had a significant trend. Then, through correlation analysis and multi-linear regression modeling, we investigated the

  2. An Interface between Law and Science: The Climate Change Regime

    NASA Astrophysics Data System (ADS)

    Kuleshov, Y.; Grandbois, M.; Kaniaha, S.

    2012-04-01

    Law and Science are jointly building the international climate change regime. Up to date, international law and climate science have been unable to take into consideration both regional law and Pacific climate science in this process. Under the International Climate Change Adaptation Initiative (the Australian Government Initiative to assist with high priority climate adaptation needs in vulnerable countries in the Asia-Pacific region) significant efforts were dedicated to improve understanding of climate in the Pacific through the Pacific Climate Change Science Program (PCCSP) and through the Pacific Adaptation Strategy Assistance Program (PASAP). The first comprehensive PCCSP scientific report on the South Pacific climate has been published in 2011. Under the PASAP, web-based information tools for seasonal climate prediction have been developed and now outputs from dynamical climate model are used in 15 countries of the North-West and South Pacific for enhanced prediction of rainfall, air and sea surface temperatures which reduces countries' vulnerability to climate variability in the context of a changing climate. On a regional scale, the Meteorological and Geohazards Department of Vanuatu is preparing a full report on Climate change impacts on the country. These scientific reports and tools could lead to a better understanding of climate change in the South Pacific and to a better understanding of climate change science, for lawyers and policy-makers. The International climate change regime develops itself according to science findings, and at the pace of the four scientific reports issued by the Intergovernmental Panel on Climate Change (IPCC). In return, Law is a contributing factor to climate change, a structural data in the development and perception of environmental issues and it exerts an influence on Science. Because of the dependency of law on science, the PCCSP and PASAP outcomes will also stimulate and orientate developments in law of the Pacific

  3. Nb/InAs nanowire proximity junctions from Josephson to quantum dot regimes

    NASA Astrophysics Data System (ADS)

    Gharavi, Kaveh; Holloway, Gregory W.; LaPierre, Ray R.; Baugh, Jonathan

    2017-02-01

    The superconducting proximity effect is probed experimentally in Josephson junctions fabricated with InAs nanowires contacted by Nb leads. Contact transparencies t∼ 0.7 are observed. The electronic phase coherence length at low temperatures exceeds the channel length. However, the elastic scattering length is a few times shorter than the channel length. Electrical measurements reveal two regimes of quantum transport: (i) the Josephson regime, characterised by a dissipationless current up to ∼100 nA, and (ii) the quantum dot (QD) regime, characterised by the formation of Andreev bound states (ABS) associated with spontaneous QDs inside the nanowire channel. In regime (i), the behaviour of the critical current I c versus an axial magnetic field {B}| | shows an unexpected modulation and persistence to fields > 2 T. In the QD regime, the ABS are modelled as the current-biased solutions of an Anderson-type model. The applicability of devices in both transport regimes to Majorana fermion experiments is discussed.

  4. Experimental determination of heat transfer coefficient in the slip regime and its anomalously low value

    NASA Astrophysics Data System (ADS)

    Demsis, Anwar; Verma, Bhaskar; Prabhu, S. V.; Agrawal, Amit

    2009-07-01

    In this paper, the measurement of the heat transfer coefficient in rarefied gases is presented; these are among the first heat transfer measurements in the slip flow regime. The experimental setup is validated by comparing friction factor in the slip regime and heat transfer coefficient in the continuum regime. Experimental results suggest that the Nusselt number is a function of Reynolds and Knudsen numbers in the slip flow regime. The measured values for Nusselt numbers are smaller than that predicted by theoretical or simulation results, and can become a few orders of magnitude smaller than the theoretical values in the continuum regime. The results are repeatable and expected to be useful for further experimentation and modeling of flow in the slip and transition regimes.

  5. Flow regime and deposition pattern of evaporating binary mixture droplet suspended with particles.

    PubMed

    Zhong, Xin; Duan, Fei

    2016-02-01

    The flow regimes and the deposition pattern have been investigated by changing the ethanol concentration in a water-based binary mixture droplet suspended with alumina nanoparticles. To visualize the flow patterns, Particle Image Velocimetry (PIV) has been applied in the binary liquid droplet containing the fluorescent microspheres. Three distinct flow regimes have been revealed in the evaporation. In Regime I, the vortices and chaotic flows are found to carry the particles to the liquid-vapor interface and to promote the formation of particle aggregation. The aggregates move inwards in Regime II as induced by the Marangoni flow along the droplet free surface. Regime III is dominated by the drying of the left water and the capillary flow driving particles radially outward is observed. The relative weightings of Regimes I and II, which are enhanced with an increasing load of ethanol, determine the motion of the nanoparticles and the formation of the final drying pattern.

  6. The operating regimes and basic control principles of SNPS Topaz''. [Cs

    SciTech Connect

    Makarov, A.N.; Volberg, M.S.; Grayznov, G.M.; Zhabotinsky, E.E.; Serbin, V.I. )

    1991-01-05

    The basic operating regimes of space nuclear power system (SNPS) Topaz'' are considered. These regimes include: prelaunch preparation and launch into working orbit, SNPS start-up to obtain desired electric power, nominal regime, SNPS shutdown. The main requirements for SNPS at different regimes are given, and the control algorithms providing these requirements are described. The control algorithms were chosen on the basis of theoretical studies and ground power tests of the SNPS prototypes. Topaz'' successful ground and flight tests allow to conclude that for SNPS of this type control algorithm providing required thermal state of cesium vapor supply system and excluding any possibility of discharge processes in current conducting elements is the most expedient at the start-up regime. At the nominal regime required electric power should be provided by maintenance of reactor current and fast-acting voltage regulator utilization. The limitation of the outlet coolant temperature should be foreseen also.

  7. Zonal flow regimes in rotating anelastic spherical shells (Invited)

    NASA Astrophysics Data System (ADS)

    Gastine, T.; Wicht, J.; Aurnou, J. M.; Heimpel, M. H.

    2013-12-01

    The surface zonal winds observed in the giant planets form a complex jet pattern with alternating prograde and retrograde direction. While the main equatorial band is prograde on the gas giants, both ice giants have a pronounced retrograde equatorial jet. The depth of these jets is however poorly known and highly debated. Theoretical scenarios range from "shallow models", that assume that these zonal flows are restricted to the outer stably stratified layer; to "deep models" that hypothesise that the surface winds are the signature of deep-seated convection. Most of the numerical models supporting the latter idea employed the Boussinesq approximation where compressibility effects are ignored. While this approximation is suitable for modelling the liquid iron core of terrestrial planets, this becomes questionable in the gas giants interiors, where density increases by several orders of magnitude. To tackle this problem, several numerical models using the "anelastic approximation" have been recently developed to study the compressibility effects while filtering out the fast acoustic waves. Here, we consider such anelastic models of rapidly-rotating spherical shells to explore the properties of the zonal winds in different regimes where either rotation or buoyancy dominates the force balance. We conduct several parameter studies to quantify the dependence of zonal flows on the background density stratification and the driving of convection. We find that the direction of the equatorial wind is controlled by the ratio of buoyancy and Coriolis force. The prograde equatorial band maintained by Reynolds stresses is found in the rotation-dominated regime. At low Ekman numbers, several alternating jets form at high latitude in a similar way to some previous Boussinesq calculations. In cases where buoyancy dominates Coriolis force, the angular momentum per unit mass is homogenised and the equatorial band is retrograde, reminiscent to those observed in the ice giants

  8. Weather regimes and orographic circulation around New Caledonia.

    PubMed

    Lefèvre, Jérôme; Marchesiello, Patrick; Jourdain, Nicolas C; Menkes, Christophe; Leroy, Anne

    2010-01-01

    The local climate and island-scale circulation around New Caledonia is investigated using a 4-km resolution mesoscale atmospheric model in concert with QuikSCAT scatterometer winds at 12.5-km resolution. The mesoscale atmospheric weather regimes are first examined through an objective classification applied to the remote sensed winds for nine warm seasons from 1999 to 2008. Four main weather types are identified. Their corresponding synoptic-scale circulation reveals that they are strongly discernable through the position and intensity of the South Pacific Convergence zone (SPCZ), the mid-latitude systems, and the subtropical jet stream. The link between the mesoscale weather types and the two dominant large-scale modes of variability, namely the Madden-Julian Oscillation (MJO) and the El Niño-Southern Oscillation (ENSO), is also described in terms of their influence on the occurrence of each weather type. It shows that their occurrence is significantly controlled by both MJO and ENSO, through modulation of the SPCZ. The large-scale modes of variability are scaled down to island-scale circulation through synoptic and mesoscale regimes, and are eventually modulated by orographic and thermal control. The island-scale circulation is inferred in this study by applying the compositing method to both observed and simulated winds. Their comparison clearly shows the ability of the mesoscale model to capture the local circulation and its spatial and temporal variability. A scaling analysis conducted from the simulated atmospheric parameters shows that the mountain range of New Caledonia is hydrodynamically steep. As a result of trade-wind obstruction by the mountainous island, the flow is shaped by coastally trapped mesoscale responses, i.e., blocking, flow splitting and corner winds, with a spatial scale of about 150 km. Two main obstacles, Mont Panié and Mont Humboldt play a significant role on the dynamical behavior of the low-level flow, while the diurnal heating

  9. Passive scalar scaling regimes in a rapidly decorrelating turbulent flow

    NASA Astrophysics Data System (ADS)

    Kramer, Peter Roland

    This thesis is concerned with some issues pertaining to the small scale structure of a passive scalar field advected by a turbulent flow, and driven by external stochastic pumping and/or interaction with a background passive scalar gradient. We analyze and apply two previously developed simplified mathematical models: the Simple Shear Model of Andrew Majda and Marco Avellaneda, and the Rapid Decorrelation in Time (RDT) Model of Robert Kraichnan. The fundamental representation of the passive scalar statistics in these models is presented from a consideration of Lagrangian tracer trajectories. This permits an easy extension of the Simple Shear Model to incorporate driving, and an alternative derivation of the governing mathematical equations in the RDT Model. Using a Simple Shear Poisson Blob Model of Majda and Avellaneda, we provide an example in which the correlation time of the velocity field becomes very small, but the passive scalar statistics do not converge to those of the RDT model. The RDT Model therefore only describes passive scalar advection for a velocity field with short correlation time in a certain sense. We next apply the RDT Model to investigate scaling regimes in the spectral density of a random passive scalar field advected by a turbulent flow. First, we rigorously derive three scaling regimes, and test some physical theories against these exact results. We find most predictions to succeed, but indicate an apparent gap in the reasoning behind the inertial-diffusive theory of Carl Gibson. Next, motivated by a recent experimental controversy, we consider whether, in the RDT Model, anisotropies in the external pumping could disrupt the k-1 viscous- convective scaling law at high Schmidt number. We find that the k-1 law persists. Finally, we test two asymptotic procedures, the Intermediate Asymptotic (IA) approach as described by G. I. Barenblatt and the Renormalization Group (RG) method of Lin-Yuan Chen et al. on an exactly solvable ODE arising in

  10. Modeling Gamma Ray Bursts in the Megnetically Dominated Regime

    NASA Astrophysics Data System (ADS)

    Zhang, Bing

    Recent observations of broad-band prompt emission spectra of gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Telescope suggest that they do not comply with the predictions of the standard fireball internal shock model. Several independent observations (including detections of high polarization degree of gamma-ray emission and early optical emission of some GRBs, as well as non-detection of PeV neutrinos from GRBs by IceCube) support or are consistent with the hypothesis that at least some GRBs have magnetically dominated jets. This calls for serious, detailed investigations of GRB models in the magnetically dominated regime, which interpret GRB emission as dissipation of strong magnetic fields entrained in the ejecta. On the other hand, because of their complexity, magnetic models are so far much less developed than the baryonic fireball models. Here we propose to tackle this difficult problem, aiming at making solid progress in this direction through a set of numerical investigations. Specifically, we propose to carry out the following simulations. (1) Using a relativistic MHD code, we will perform a global simulation to investigate whether efficient magnetic dissipation would occur when two high-σ magnetic blobs collide with a relativistic speed. (2) We will perform a local simulation of the relativistic collisions between two high-σ fluids, and track the evolution of magnetic field configuration in the colliding region and the interplay between magnetic reconnection and development of magnetic turbulence. (3) Through injecting test particles in the simulation box, we will study how electrons get accelerated in the turbulent reconnection regions. (4) Built upon the above-mentioned numerical simulation results, along with a Monte Carlo code and a synchrotron radiation code developed in our group before, we will develop a full numerical model to simulate lightcurves, time-dependent spectra, and polarization properties of GRB prompt emission within the framework of

  11. Emergent Phototactic Responses of Cyanobacteria under Complex Light Regimes.

    PubMed

    Chau, Rosanna Man Wah; Bhaya, Devaki; Huang, Kerwyn Casey

    2017-03-07

    Environmental cues can stimulate a variety of single-cell responses, as well as collective behaviors that emerge within a bacterial community. These responses require signal integration and transduction, which can occur on a variety of time scales and often involve feedback between processes, for example, between growth and motility. Here, we investigate the dynamics of responses of the phototactic, unicellular cyanobacterium Synechocystis sp. PCC6803 to complex light inputs that simulate the natural environments that cells typically encounter. We quantified single-cell motility characteristics in response to light of different wavelengths and intensities. We found that red and green light primarily affected motility bias rather than speed, while blue light inhibited motility altogether. When light signals were simultaneously presented from different directions, cells exhibited phototaxis along the vector sum of the light directions, indicating that cells can sense and combine multiple signals into an integrated motility response. Under a combination of antagonistic light signal regimes (phototaxis-promoting green light and phototaxis-inhibiting blue light), the ensuing bias was continuously tuned by competition between the wavelengths, and the community response was dependent on both bias and cell growth. The phototactic dynamics upon a rapid light shift revealed a wavelength dependence on the time scales of photoreceptor activation/deactivation. Thus, Synechocystis cells achieve exquisite integration of light inputs at the cellular scale through continuous tuning of motility, and the pattern of collective behavior depends on single-cell motility and population growth.IMPORTANCE The photosynthetic cyanobacterium Synechocystis sp. exhibits phototaxis that is dependent on the incident light wavelength through the action of various photoreceptors. In natural environments, cells experience a set of highly dynamic and complex light inputs, yet how cells transduce

  12. A new fast reconnection model in a collisionless regime

    SciTech Connect

    Tsiklauri, David

    2008-11-15

    Based on the first principles [i.e., (i) by balancing the magnetic field advection with the term containing electron pressure tensor nongyrotropic components in the generalized Ohm's law; (ii) using the conservation of mass; and (iii) assuming that the weak magnetic field region width, where electron meandering motion supports electron pressure tensor off-diagonal (nongyrotropic) components, is of the order of electron Larmor radius] a simple model of magnetic reconnection in a collisionless regime is formulated. The model is general, resembling its collisional Sweet-Parker analog in that it is not specific to any initial configuration, e.g., Harris-type tearing unstable current sheet, X-point collapse or otherwise. In addition to its importance from the fundamental point of view, the collisionless reconnection model offers a much faster reconnection rate [M{sub c{sup '}}{sub less}=(c/{omega}{sub pe}){sup 2}/(r{sub L,e}L)] than Sweet-Parker's classical one (M{sub sp}=S{sup -1/2}). The width of the diffusion region (current sheet) in the collisionless regime is found to be {delta}{sub c{sup '}}{sub less}=(c/{omega}{sub pe}){sup 2}/r{sub L,e}, which is independent of the global reconnection scale L and is only prescribed by microphysics (electron inertial length, c/{omega}{sub pe}, and electron Larmor radius, r{sub L,e}). Amongst other issues, the fastness of the reconnection rate alleviates, e.g., the problem of interpretation of solar flares by means of reconnection, as for the typical solar coronal parameters the obtained collisionless reconnection time can be a few minutes, as opposed to Sweet-Parker's equivalent value of less than a day. The new theoretical reconnection rate is compared to the Magnetic Reconnection Experiment device experimental data by Yamada et al. [Phys. Plasmas 13, 052119 (2006)] and Ji et al. [Geophys. Res. Lett. 35, 13106 (2008)], and a good agreement is obtained.

  13. Assessing water quality trends in catchments with contrasting hydrological regimes

    NASA Astrophysics Data System (ADS)

    Sherriff, Sophie C.; Shore, Mairead; Mellander, Per-Erik

    2016-04-01

    Environmental resources are under increasing pressure to simultaneously achieve social, economic and ecological aims. Increasing demand for food production, for example, has expanded and intensified agricultural systems globally. In turn, greater risks of diffuse pollutant delivery (suspended sediment (SS) and Phosphorus (P)) from land to water due to higher stocking densities, fertilisation rates and soil erodibility has been attributed to deterioration of chemical and ecological quality of aquatic ecosystems. Development of sustainable and resilient management strategies for agro-ecosystems must detect and consider the impact of land use disturbance on water quality over time. However, assessment of multiple monitoring sites over a region is challenged by hydro-climatic fluctuations and the propagation of events through catchments with contrasting hydrological regimes. Simple water quality metrics, for example, flow-weighted pollutant exports have potential to normalise the impact of catchment hydrology and better identify water quality fluctuations due to land use and short-term climate fluctuations. This paper assesses the utility of flow-weighted water quality metrics to evaluate periods and causes of critical pollutant transfer. Sub-hourly water quality (SS and P) and discharge data were collected from hydrometric monitoring stations at the outlets of five small (~10 km2) agricultural catchments in Ireland. Catchments possess contrasting land uses (predominantly grassland or arable) and soil drainage (poorly, moderately or well drained) characteristics. Flow-weighted water quality metrics were calculated and evaluated according to fluctuations in source pressure and rainfall. Flow-weighted water quality metrics successfully identified fluctuations in pollutant export which could be attributed to land use changes through the agricultural calendar, i.e., groundcover fluctuations. In particular, catchments with predominantly poor or moderate soil drainage

  14. The thermal regime around buried submarine high-voltage cables

    NASA Astrophysics Data System (ADS)

    Emeana, C. J.; Hughes, T. J.; Dix, J. K.; Gernon, T. M.; Henstock, T. J.; Thompson, C. E. L.; Pilgrim, J. A.

    2016-08-01

    The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine high-voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70 °C and are typically buried 1-2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near-surface sediments are poorly understood. We present temperature measurements from a 2-D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments—coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m2) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples to measure the time-dependent 2-D temperature distributions. The observed and corresponding Finite Element Method simulations of the steady state heat flow regimes and normalized radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10 °C up to 40 cm from the source of 60 °C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between cf. 20 and 36 °C above ambient, with >10 °C heat increases occurring over a metre from the source of 55 °C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (cf. 7 °C) operating temperatures and reaching temperatures of up to 18 °C above ambient at a metre from the source at surface temperatures of only 18 °C. These findings are important for the surrounding near

  15. Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

    SciTech Connect

    Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.

    1992-01-01

    FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime.

  16. Two-phase interfacial area and flow regime modeling in FLOWTRAN-TF code

    SciTech Connect

    Smith, F.G. III; Lee, S.Y.; Flach, G.P.; Hamm, L.L.

    1992-12-31

    FLOWTRAN-TF is a new two-component, two-phase thermal-hydraulics code to capture the detailed assembly behavior associated with loss-of-coolant accident analyses in multichannel assemblies of the SRS reactors. The local interfacial area of the two-phase mixture is computed by summing the interfacial areas contributed by each of three flow regimes. For smooth flow regime transitions, the code uses an interpolation technique in terms of component void fraction for each basic flow regime.

  17. Stemming the Flow of Improvised Explosive Device Making Materials through Global Export Control Regimes

    DTIC Science & Technology

    2012-09-01

    IED Making Material and Efforts to Counter Them Finally, understanding the current global export and weapons control regimes identifies factors that...the history and perceived effectiveness of these regimes and efforts, he then explores six factors for regime effectiveness. These factors are...to their other interests  Capability for capacity-building The hypothesis is that these six variables directly affect the feasibility of a global

  18. Reconciliation in Cambodia: thirty years after the terror of the Khmer Rouge regime.

    PubMed

    Bockers, Estelle; Stammel, Nadine; Knaevelsrud, Christine

    2011-01-01

    During the Khmer Rouge regime one quarter of the Cambodian population was killed as a result of malnutrition, overwork and mass killings. Although the regime ended 30 years ago, its legacy continues to affect Cambodians. Mental health problems as well as feelings of anger and revenge resulting from traumatic events experienced during the Khmer Rouge regime are still common in Cambodia. These conditions continue to impede social coexistence and the peace-building process in society. Thirty years after the Khmer Rouge regime this article gives an overview on the status of the country's current reconciliation process and recommends potential future steps.

  19. Radiation build-up in laminar and turbulent regimes in quasi-CW Raman fiber laser.

    PubMed

    Smirnov, Sergey V; Tarasov, Nikita; Churkin, Dmitry V

    2015-10-19

    We study the radiation build-up in laminar and turbulent generation regimes in quasi-CW Raman fiber laser. We found the resulted spectral shape and generation type is defined by the total spectral broadening/narrowing balance over laser cavity round-trip, which is substantially different in different regimes starting from first round-trips of the radiation build-up. In turbulent regime, the steady-state is reached only after a few round-trips, while in the laminar regime the laser approaches the equilibrium spectrum shape asymptotically.

  20. Predicting transport regime and local electrostatic environment from Coulomb blockade diamond sizes

    NASA Astrophysics Data System (ADS)

    Olsen, Stine T.; Hansen, Thorsten; Mikkelsen, Kurt V.

    2017-03-01

    Electron transport through a molecule is often described in one of the two regimes: the coherent tunnelling regime or the Coulomb blockade regime. The twilight zone of the two regimes still possesses many unsolved questions. A theoretical analysis of the oligophenylenevinylene OPV3 experiments by Bjørnholm and co-workers is performed. The experiments showed how two OPV3 derivatives performed very differently despite the strong similarity of the molecular structure, hence the experimental data showed two different transport mechanisms. The different transport mechanisms of the two OPV3 derivatives are explained from quantum mechanical calculations of the molecular redox energies and from the experimentally accessible window size.

  1. Observational evidence of preferred flow regimes in the Northern Hemisphere winter stratosphere

    NASA Technical Reports Server (NTRS)

    Pierce, R. B.; Fairlie, T. D. A.

    1993-01-01

    Ten years of stratospheric geopotential height data are analyzed in an attempt to determine whether there are preferred flow regimes in the Northern Hemisphere winter stratosphere. The data are taken from Stratospheric Sounding Units on board NOAA satellites. The probability density estimate of the amplitude of the wavenumber 1 10-mb height is found to be bimodal. The density distribution is composed of a dominant large-amplitude mode and a less frequent low-amplitude mode. When the wavenumber 1 10-mb height data are projected onto the phase plane defined by the 10-mb zonal-mean winds and wavenumber 1 100-mb heights, three preferred regimes are evident. The small-amplitude mode separates into a strong zonal wind-weak wave regime and a weak zonal wind-weak wave regime. The large-amplitude mode is an intermediate zonal wind-strong wave regime. Transitions between the large-amplitude regime and the weak zonal wind-weak wave regime are found to be associated with major stratospheric warmings. The clustering of the stratospheric data into the preferred flow regimes is interpreted in light of the bifurcation properties of the Holton and Mass model. The interannual variability of the Northern Hemisphere winter stratosphere is interpreted in terms of the relative frequency of the observed preferred regimes.

  2. Political economy of family life: couple's earnings, welfare regime and union dissolution.

    PubMed

    Kaplan, Amit; Stier, Haya

    2017-01-01

    This study examines how institutional settings moderate the relation of couples' relative and absolute earnings to the likelihood of union dissolution. Based on ECHP data, it covers 12 countries in four welfare regimes. The relationship between a couple's economic dependence and the likelihood of union dissolution were found to differ across regimes. With regard to relative earnings, equality in earnings lowered the risk of separation only in regimes characterized by a high degree of defamilialization, through either the state or the market. As for absolute earnings, women's and men's earnings were significantly related to the risk of union dissolution only in regimes where state defamilialization is low.

  3. Reaching the hydrodynamic regime in a Bose-Einstein condensate by suppression of avalanches

    SciTech Connect

    Stam, K. M. R. van der; Meppelink, R.; Vogels, J. M.; Straten, P. van der

    2007-03-15

    We report the realization of a Bose-Einstein condensate (BEC) in the hydrodynamic regime. The hydrodynamic regime is reached by evaporative cooling at a relatively low density suppressing the effect of avalanches. With the suppression of avalanches a BEC containing more than 10{sup 8} atoms is produced. The collisional opacity can be tuned from the collisionless regime to a collisional opacity of more than 2 by compressing the trap after condensation. In the collisional opaque regime a significant heating of the cloud at time scales shorter than half of the radial trap period is measured, which is a direct proof that the BEC is hydrodynamic.

  4. New Statistical Learning Methods for Estimating Optimal Dynamic Treatment Regimes

    PubMed Central

    Zhao, Ying-Qi; Zeng, Donglin; Laber, Eric B.; Kosorok, Michael R.

    2014-01-01

    Dynamic treatment regimes (DTRs) are sequential decision rules for individual patients that can adapt over time to an evolving illness. The goal is to accommodate heterogeneity among patients and find the DTR which will produce the best long term outcome if implemented. We introduce two new statistical learning methods for estimating the optimal DTR, termed backward outcome weighted learning (BOWL), and simultaneous outcome weighted learning (SOWL). These approaches convert individualized treatment selection into an either sequential or simultaneous classification problem, and can thus be applied by modifying existing machine learning techniques. The proposed methods are based on directly maximizing over all DTRs a nonparametric estimator of the expected long-term outcome; this is fundamentally different than regression-based methods, for example Q-learning, which indirectly attempt such maximization and rely heavily on the correctness of postulated regression models. We prove that the resulting rules are consistent, and provide finite sample bounds for the errors using the estimated rules. Simulation results suggest the proposed methods produce superior DTRs compared with Q-learning especially in small samples. We illustrate the methods using data from a clinical trial for smoking cessation. PMID:26236062

  5. Spinning-Down of Moving Magnetars in the Propeller Regime

    NASA Astrophysics Data System (ADS)

    Toropina, O. D.; Romanova, M. M.; Lovelace, R. V. E.

    2006-08-01

    We use axisymmmetric magnetohydrodynamic simulations to investigate the spinning-down of magnetars rotating in the propeller regime and moving supersonically through the interstellar medium. The star loses its angular momentum due to direct interaction of the rotating magnetosphere with the non-rotating interstellar medium. The simulations indicate that magnetars spin-down rapidly due to this interaction, much faster than for the case of a non-moving star. A magnetar with a surface magnetic field of 1013 - 1015 G is found to spin-down to a period P > 10^5-10^6 s in 10^4 - 10^5 yr. This may explain, why a number of soft gamma-repeaters is so small: because only a tiny fraction of all magnetars rotate sufficiently fast to be identified with the neutron stars. From many simulation runs we have derived an approximate scaling law for the angular momentum loss rate, dot{L} ∝ - ρ0.8μ0.6Ω_*1.5/v0.4, where ρ is the density of the interstellar medium, μ is the star's magnetic moment, Ω_* is its angular velocity, and v is velocity of motion.

  6. The water regime of the lake Kolon watersystem

    NASA Astrophysics Data System (ADS)

    Zellei, L.; Tamás, E. A.; Sziebert, J.; Tóth, Sz.

    2009-04-01

    Lake Kolon is one of the important freshwater marshes of Hungary, with its extensive reedbeds, meadows and forests. The natural development process of the lake was interrupted in 1930. The events which happened later give a typical cross-section of Hungarian water management practices. The interventions started with draining a considerable part of the lake and taking it into agricultural usage. In order to get the waters of the Danube floodplains under control, the building of the Danube-Valley Channel started in 1912. The channel, which is 107 kms long, was ready in 1929, and the subordinated channel system was established in the beginning of the 1930's. Connected to these works, the lake Kolon was declared as an excess water reservoir after its draining in 1927-28. So the reservoir had to be kept on minimal waterlevel in order to be able to host the arriving waters any time. This kind of management has changed from 1987 to 1996 for a more preferable management which is ruled by the actual conditions in order to maintain the water resources. With the analysis of the water resources of the lake we showed that there is a significant supply from subsurface runoff, and we determined the statistical characteristics of the quantitative indices of the water regime. The high waterlevel which is favourable from the viewpoint of nature conservation has proven to be sustainable even if the receiver is in its design status.

  7. Grain size evolution and convection regimes of the terrestrial planets

    NASA Astrophysics Data System (ADS)

    Rozel, A.; Golabek, G. J.; Boutonnet, E.

    2011-12-01

    A new model of grain size evolution has recently been proposed in Rozel et al. 2010. This new approach stipulates that the grain size dynamics is governed by two additive and simultaneous processes: grain growth and dynamic recrystallization. We use the usual normal grain growth laws for the growth part. For dynamic recrystallization, reducing the mean grain size increases the total area of grain boundaries. Grain boundaries carry some surface tension, so some energy is required to decrease the mean grain size. We consider that this energy is available during mechanical work. It is usually considered to produce some heat via viscous dissipation. A partitioning parameter f is then required to know what amount of energy is dissipated and what part is converted in surface tension. This study gives a new calibration of the partitioning parameter on major Earth materials involved in the dynamic of the terrestrial planets. Our calibration is in adequation with the published piezometric relations available in the literature (equilibrium grain size versus shear stress). We test this new model of grain size evolution in a set of numerical computations of the dynamics of the Earth using stagYY. We show that the grain size evolution has a major effect on the convection regimes of terrestrial planets.

  8. Small Seed Black Hole Growth in Various Accretion Regimes

    NASA Astrophysics Data System (ADS)

    Gerling-Dunsmore, Hannalore J.; Hopkins, Philip F.

    2016-03-01

    Observational evidence indicates a population of super massive black holes (SMBHs) (~109 -1010M⊙) formed within 1 Gyr after the Big Bang. One proposed means of SMBH formation is accretion onto small seed black holes (BHs) (~ 100M⊙). However, the existence of SMBHs within 1 Gyr requires rapid growth, but conventional models of accretion fail to grow the seed BHs quickly enough. Super Eddington accretion (Ṁ >ṀEddington) may aid in improving growth efficiency. We study small seed BH growth via accretion in 3D, using the magneto-hydrodynamics+gravity code GIZMO. In particular, we consider a BH in a high density turbulent star-forming cloud, and ask whether or not the BH can capture sufficient gas to grow rapidly. We consider both Eddington-limited and super Eddington regimes, and resolve physics on scales from 0.1 pc to 1 kpc while including detailed models for stellar feedback physics, including stellar winds, supernovae, radiation pressure, and photo-ionization. We present results on the viability of different small seed BHs growing into SMBH candidates.

  9. Plasmonic control of extraordinary optical transmission in the infrared regime

    NASA Astrophysics Data System (ADS)

    Sangiao, S.; Freire, F.; de León-Pérez, F.; Rodrigo, S. G.; De Teresa, J. M.

    2016-12-01

    We demonstrate that the spectral location of extraordinary optical transmission (EOT) resonances in metallic arrays of rectangular holes can be plasmonically tuned in the near and mid-infrared ranges. The experiments have been performed on patterned gold films. We focus on a subset of localized resonances occurring close to the cut-off wavelength of the holes, λ c. Metals are usually regarded as perfect electric conductors in the infrared regime, with an EOT cut-off resonance found around λ c = 2 L for rectangular holes (L being the long edge). For real metals, the penetration of the electromagnetic fields is simply seen as effectively enlarging L. However, by changing the hole short edge, we have found that λ c varies due to the excitation of gap surface plasmon polaritons. Finite-element calculations confirm that in these high aspect ratio rectangles with short edges two important aspects have to be taken into account in order to explain the experiments: the finite conductivity of the metal and the excitation of gap-surface plasmons inside the nanoholes.

  10. Study of Operational Regimes of the VASIMR Helicon Plasma Source

    NASA Astrophysics Data System (ADS)

    Batishchev, O.; Molvig, K.

    2000-10-01

    Effective plasma production by a plasma source is crucial for the overall > 50% efficiency of the VASIMR plasma rocket. Primary propellant H (D) - enters the helicon source as cold molecular gas and leaves it as a hot gas-plasma mix. We present an analysis that shows the following plasma composition: e, H_2, H, H^+, H_2^+, H_3^+. Mass and energy balance is described by the 14 non-linear plasma chemistry equations for the species concentrations and temperatures. Their numerical solution shows agreement with the measured electron temperature ~ 6 eV, and density ~ 10^12 cm-3 for both H and D discharges. Simulation shows also that the Ly-α radiation may account for 25%, while Frank-Condon neutrals for 15% of the total input power ~ 1 kW. Gas ionization fraction is ~ 3 - 5% with sizable amount of H_2^+ and H_3^+ ions. However, mass-flow ratio neutral gas/plasma is close to 1 due to the huge difference in the exhaust velocities. A separate numerical analysis of the pure gas flow in the gas inlet - quartz tube - magnet bore channel shows very good agreement with the gas pressure measurements. Modeling indicates that gas flow in the mixed viscous - free molecular regime (Kn ~ 0.5 - 2) is very subsonic with V ~ 0.02 - 0.1 C_S. We discuss effects of gas pre-heating and residual vacuum tank pressure, and importance of baffles.

  11. Two dynamic regimes in the human gut microbiome.

    PubMed

    Gibbons, Sean M; Kearney, Sean M; Smillie, Chris S; Alm, Eric J

    2017-02-01

    The gut microbiome is a dynamic system that changes with host development, health, behavior, diet, and microbe-microbe interactions. Prior work on gut microbial time series has largely focused on autoregressive models (e.g. Lotka-Volterra). However, we show that most of the variance in microbial time series is non-autoregressive. In addition, we show how community state-clustering is flawed when it comes to characterizing within-host dynamics and that more continuous methods are required. Most organisms exhibited stable, mean-reverting behavior suggestive of fixed carrying capacities and abundant taxa were largely shared across individuals. This mean-reverting behavior allowed us to apply sparse vector autoregression (sVAR)-a multivariate method developed for econometrics-to model the autoregressive component of gut community dynamics. We find a strong phylogenetic signal in the non-autoregressive co-variance from our sVAR model residuals, which suggests niche filtering. We show how changes in diet are also non-autoregressive and that Operational Taxonomic Units strongly correlated with dietary variables have much less of an autoregressive component to their variance, which suggests that diet is a major driver of microbial dynamics. Autoregressive variance appears to be driven by multi-day recovery from frequent facultative anaerobe blooms, which may be driven by fluctuations in luminal redox. Overall, we identify two dynamic regimes within the human gut microbiota: one likely driven by external environmental fluctuations, and the other by internal processes.

  12. Slow Wave Excitation in the ICRF and HHFW Regimes

    SciTech Connect

    Phillips, C. K.; Valeo, E. J.; Hosea, J. C.; LeBlanc, B. P.; Wilson, J. R.; Jaeger, E. F.; Berry, L. A.; Ryan, P. M.; Bonoli, P. T.; Wright, J. C.; Smithe, D. N.

    2011-12-23

    Theoretical considerations and high spatial resolution numerical simulations of radio frequency (rf) wave heating in tokamaks and in spherical toruses (ST) indicate that fast waves launched into tokamaks in the ion cyclotron range of frequencies (ICRF) or into spherical toruses in the high harmonic fast wave (HHFW) regime may excite a short wavelength slow mode inside of the plasma discharge due to the presence of hot electrons that satisfy the condition {omega}

  13. Changing disturbance regimes, ecological memory, and forest resilience

    USGS Publications Warehouse

    Johnstone, Jill F.; Allen, Craig D.; Franklin, Jerry F.; Frelich, Lee E.; Harvey, Brian J.; Higuera, Philip E.; Mack, Michelle C.; Meentemeyer, Ross K.; Metz, Margaret R.; Perry, George LW; Schoennagel, Tania; Turner, Monica G.

    2016-01-01

    Ecological memory is central to how ecosystems respond to disturbance and is maintained by two types of legacies – information and material. Species life-history traits represent an adaptive response to disturbance and are an information legacy; in contrast, the abiotic and biotic structures (such as seeds or nutrients) produced by single disturbance events are material legacies. Disturbance characteristics that support or maintain these legacies enhance ecological resilience and maintain a “safe operating space” for ecosystem recovery. However, legacies can be lost or diminished as disturbance regimes and environmental conditions change, generating a “resilience debt” that manifests only after the system is disturbed. Strong effects of ecological memory on post-disturbance dynamics imply that contingencies (effects that cannot be predicted with certainty) of individual disturbances, interactions among disturbances, and climate variability combine to affect ecosystem resilience. We illustrate these concepts and introduce a novel ecosystem resilience framework with examples of forest disturbances, primarily from North America. Identifying legacies that support resilience in a particular ecosystem can help scientists and resource managers anticipate when disturbances may trigger abrupt shifts in forest ecosystems, and when forests are likely to be resilient.

  14. Assessing the extreme overwash regime along an embayed urban beach

    NASA Astrophysics Data System (ADS)

    Silveira, Tanya M.; Taborda, Rui; Carapuço, Mafalda M.; Andrade, César; Freitas, Maria C.; Duarte, João F.; Psuty, Norbert P.

    2016-12-01

    Coastal overwash is one of the most important hazards affecting the coastal zone and therefore has been the focus of several studies related to the establishment of setback lines. However, studies of extreme overwash (EO) events along urban beaches backed by a seawall or structure are scarce, and reveal the difficulties associated with its assessment, measurement and validation. The Nazaré coastal urban area (located on the west coast of Portugal) is developed adjacent to an embayed reflective beach and is subject to frequent and localized inundation due to EO events capable of overtopping the protection seawall. The current work develops a methodological approach to simulate total water levels (TWL) and seawall overtopping occurrences in time and space, with the ultimate goal of identifying the factors that govern the extreme overwash regime. The method uses multi-decadal time series of site-specific wave and tide, and high-resolution topo-bathymetric data, and recreates the TWL time series for a 36-year period. The model is successfully validated against video imagery and maximum swash line data that provide information on the reach of the water levels measured during modal and extreme TWL conditions along the studied beach. This study establishes the importance of the interaction of the modal and extreme hydrodynamic processes with the beach and backshore morphology. The Nazaré embayment is in equilibrium with the alongshore-varying modal wave conditions, resulting in higher vulnerability of the most sheltered sector during extreme events.

  15. Microbial biogeochemistry of coastal upwelling regimes in a changing ocean

    NASA Astrophysics Data System (ADS)

    Capone, Douglas G.; Hutchins, David A.

    2013-09-01

    Coastal upwelling regimes associated with eastern boundary currents are the most biologically productive ecosystems in the ocean. As a result, they play a disproportionately important role in the microbially mediated cycling of marine nutrients. These systems are characterized by strong natural variations in carbon dioxide concentrations, pH, nutrient levels and sea surface temperatures on both seasonal and interannual timescales. Despite this natural variability, changes resulting from human activities are starting to emerge. Carbon dioxide derived from fossil fuel combustion is adding to the acidity of upwelled low-pH waters. Low-oxygen waters associated with coastal upwelling systems are growing in their extent and intensity as a result of a rise in upper ocean temperatures and productivity. And nutrient inputs to the coastal ocean continue to grow. Coastal upwelling systems may prove more resilient to changes resulting from human activities than other ocean ecosystems because of their ability to function under extremely variable conditions. Nevertheless, shifts in primary production, fish yields, nitrogen gain and loss, and the flux of climate-relevant gases could result from the perturbation of these highly productive and dynamic ecosystems.

  16. Evaluating and optimizing horticultural regimes in space plant growth facilities

    NASA Technical Reports Server (NTRS)

    Berkovich, Y. A.; Chetirkin, P. V.; Wheeler, R. M.; Sager, J. C.

    2004-01-01

    In designing innovative space plant growth facilities (SPGF) for long duration space flight, various limitations must be addressed including onboard resources: volume, energy consumption, heat transfer and crew labor expenditure. The required accuracy in evaluating on board resources by using the equivalent mass methodology and applying it to the design of such facilities is not precise. This is due to the uncertainty of the structure and not completely understanding the properties of all associated hardware, including the technology in these systems. We present a simple criteria of optimization for horticultural regimes in SPGF: Qmax = max [M x (EBI)2/(V x E x T], where M is the crop harvest in terms of total dry biomass in the plant growth system; EBI is the edible biomass index (harvest index), V is volume occupied by the crop; E is the crop light energy supply during growth; T is the crop growth duration. The criterion reflects directly on the consumption of onboard resources for crop production. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

  17. Dynamic Onset of Feynman Relation in the Phonon Regime

    PubMed Central

    Li, Y.; Zhu, C. J.; Hagley, E. W.; Deng, L.

    2016-01-01

    The Feynman relation, a much celebrated condensed matter physics gemstone for more than 70 years, predicts that the density excitation spectrum and structure factor of a condensed Bosonic system in the phonon regime drops linear and continuously to zero. Until now, this widely accepted monotonic excitation energy drop as the function of reduced quasi-momentum has never been challenged in a spin-preserving process. We show rigorously that in a light-matter wave-mixing process in a Bosonic quantum gas, an optical-dipole potential arising from the internally-generated field can profoundly alter the Feynman relation and result in a new dynamic relation that exhibits an astonishing non-Feynman-like onset and cut-off in the excitation spectrum of the ground state energy of spin-preserving processes. This is the first time that a nonlinear optical process is shown to actively and significantly alter the density excitation response of a quantum gas. Indeed, this dynamic relation with a non-Feynman onset and cut-off has no correspondence in either nonlinear optics of a normal gas or a phonon-based condensed matter Bogoliubov theory. PMID:27157438

  18. Community dynamics of Pleistocene coral reefs during alternative climatic regimes.

    PubMed

    Tager, Danika; Webster, Jody M; Potts, Donald C; Renema, Willem; Braga, Juan C; Pandolfi, John M

    2010-01-01

    Reef ecosystems built during successive periods of Pleistocene sea level rise have shown remarkable persistence in coral community structure, but little is known of the ecological characteristics of reef communities during periods of low sea stands or sea level falls. We sampled the relative species abundance of coral, benthic foraminifera, and calcareous red algae communities from eight submerged coral reefs in the Huon Gulf, Papua New Guinea, which formed during successive sea level fall and lowstand periods over the past approximately kyr. We found that dissimilarity in coral species composition increased significantly with increasing time between reef-building events. However, neither coral diversity nor the taxonomic composition of benthic foraminifera and calcareous red algae assemblages varied significantly over time. The taxonomic composition of coral communities from lowstand reefs was significantly different from that of highstand reefs previously reported from the nearby Huon Peninsula. We interpret the community composition and temporal dynamics of lowstand reefs as a result of shifting energy regimes in the Huon Gulf, and differences between low and highstand reefs as a result of differences in the interaction between biotic and environmental factors between the Huon Gulf and Huon Peninsula. Regardless of the exact processes driving these trends, our study represents the first glimpse into the ecological dynamics of coral reefs during low sea level stands when climatic conditions for reef growth were much different and less optimal than during previously studied highstand periods.

  19. Properties and regimes of vertisols with gilgai microtopography (a review)

    NASA Astrophysics Data System (ADS)

    Khitrov, N. B.

    2016-03-01

    Data on the morphology and spatial distribution of slickensides and cracks, particle-size distribution, the organic carbon content, the content and forms of carbonate concentrations, and physical and physicochemical properties of Vertisols with the gilgai microtopography are systematized. Relatively scarce information on the functioning regimes of gilgai soil complexes (their temperature and moisture conditions, redox potential, vertical and horizontal deformations, and soil density changes) is discussed. Common properties of gilgai soils are the clayey texture of their profiles and the high portion of smectitic minerals specifying the high shrink-swell capacity of the soil material. The most important specificity of soils with the gilgai microtopography is a significant horizontal differentiation of the soil profiles with alternation of bowl-shaped morphostructures with a thick dark layer without carbonates in microlows and diapiric morphostructures composed of the rising material of the lower layers with diverse carbonate concentrations on microhighs. Data on the spatial distribution of soil properties within the gilgai microcatenas can be applied in the studies of the genesis and evolution stages of the gilgai soil complexes.

  20. Using biofuel tracers to study alternative combustion regimes

    NASA Astrophysics Data System (ADS)

    Mack, J. H.; Flowers, D. L.; Buchholz, B. A.; Dibble, R. W.

    2007-06-01

    Interest in the use of alternative fuels and engines is increasing as the price of petroleum climbs. The inherently higher efficiency of Diesel engines has led to increased adoption of Diesels in Europe, capturing approximately 40% of the new passenger car market. Unfortunately, lower CO2 emissions are countered with higher nitrogen oxides (NOx) and particulate matter (PM) emissions and higher noise. Adding oxygenated compounds to the fuel helps reduce PM emissions. However, relying on fuel alone to reduce PM is unrealistic due to economic constraints and difficult due to the emerging PM standards. Keeping peak combustion temperature below 1700 K inhibits NOx formation. Altering the combustion regime to burn at temperatures below the NOx threshold and accept a wide variety of fuels seems like a promising alternative for future engines. Homogeneous charge compression ignition (HCCI) is a possible solution. Fuel and air are well mixed prior to intake into a cylinder (homogeneous charge) and ignition occurs by compression of the fuel-air mixture by the piston. HCCI is rapid and relatively cool, producing little NOx and PM. Unfortunately, it is hard to control since HCCI is initiated by temperature and pressure instead of a spark or direct fuel injection. We investigate biofuel HCCI combustion, and use intrinsically labeled biofuels as tracers of HCCI combustion. Data from tracer experiments are used to improve our combustion modeling.

  1. Regime for a Self-ionizing Raman Laser Amplifier

    SciTech Connect

    D.S. Clark; N.J. Fisch

    2001-10-04

    Backward Raman amplification and compression at high power might occur if a long pumping laser pulse is passed through a plasma to interact resonantly with a counter-propagating short seed pulse [V.M. Malkin, et al., Phys. Rev. Lett. 82 (1999) 4448-4451]. One critical issue, however, is that the pump may be unacceptably depleted due to spontaneous Raman backscatter from intrinsic fluctuations in the amplifying plasma medium prior to its useful interaction with the seed. Premature backscatter may be avoided, however, by employing a gaseous medium with pump intensities too low to ionize the medium, and using the intense seed to produce the plasma by rapid photoionization as it is being amplified [V.M. Malkin, et al., Phys. Plasmas (2001)]. In addition to allowing that only rather low power pumps be used, photoionization introduces a damping of the short pulse which must be overcome by the Raman growth rate for net amplification to occur. The parameter space of gas densities, laser wavelengths, and laser intensities is surveyed to identify favorable regimes for this effect. Output laser intensities of 10(superscript ''17'') W/cm(superscript ''2'') for 0.5 mm radiation are found to be feasible for such a scheme using a pump of 10(superscript ''13'') W/cm(superscript ''2'') and an initial seed of 5 x 10(superscript ''14'') W/cm(superscript ''2'') over an amplification length of 5.6 cm in hydrogen gas.

  2. Intermittent Flow Regimes in Unsaturated Fractured Porous Media

    NASA Astrophysics Data System (ADS)

    Ghezzehei, T. A.; Or, D.

    2001-12-01

    Flow regimes in unsaturated fractured rocks are significantly influenced by interplay between gravitational and capillary forces and by abrupt changes in media pore space properties. These interactions give rise to complex flow mechanisms that are not amenable to representation by standard continuum theories. Even when the flux of water into the fracture is uniform, actual flow of liquid occurs through preferential pathways. We developed a model for interactions between a uniform flux and local variations in fracture aperture, leading to fragmentation of the liquid into discrete elements (bridges) and subsequent initiation of avalanches. Liquid bridges form and grow in local asperities along the preferential pathways, with subsequent breakup of the bridges at a critical bridge size. The detached bridge has a potential of sweeping other bridges along the pathway downhill from the initiation point, creating an avalanche of growing mass. Consequently, the outflow at the end of the fracture occurs as a series of discrete discharge events. The size and interval of the discharge events depend on the flux of liquid into the fracture and the fracture geometry on the pathway (e.g., number of apertures and aperture sizes). Such complex flow structure was observed in other studies involving gravity-driven unsaturated flow.

  3. Cloud Microphysics Budget in the Tropical Deep Convective Regime

    NASA Technical Reports Server (NTRS)

    Li, Xiao-Fan; Sui, C.-H.; Lau, K.-M.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Cloud microphysics budgets in the tropical deep convective regime are analyzed based on a 2-D cloud resolving simulation. The model is forced by the large-scale vertical velocity and zonal wind and large-scale horizontal advections derived from TOGA COARE for a 20-day period. The role of cloud microphysics is first examined by analyzing mass-weighted mean heat budget and column-integrated moisture budget. Hourly budgets show that local changes of mass-weighted mean temperature and column-integrated moisture are mainly determined by the residuals between vertical thermal advection and latent heat of condensation and between vertical moisture advection and condensation respectively. Thus, atmospheric thermodynamics depends on how cloud microphysical processes are parameterized. Cloud microphysics budgets are then analyzed for raining conditions. For cloud-vapor exchange between cloud system and its embedded environment, rainfall and evaporation of raindrop are compensated by the condensation and deposition of supersaturated vapor. Inside the cloud system, the condensation of supersaturated vapor balances conversion from cloud water to raindrop, snow, and graupel through collection and accretion processes. The deposition of supersaturated vapor balances conversion from cloud ice to snow through conversion and riming processes. The conversion and riming of cloud ice and the accretion of cloud water balance conversion from snow to graupel through accretion process. Finally, the collection of cloud water and the melting of graupel increase raindrop to compensate the loss of raindrop due to rainfall and the evaporation of raindrop.

  4. Optically Pumped Nuclear Magnetic Resonance in the Quantum Hall Regimes

    NASA Astrophysics Data System (ADS)

    Barrett, S. E.; Khandelwal, P.; Kuzma, N. N.; Pfeiffer, L. N.; West, K. W.

    1997-03-01

    Optical pumping enables the direct detection of the nuclear magnetic resonance signal of ^71Ga nuclei located in an electron doped GaAs quantum well.footnote S. E. Barrett et al., Phys. Rev. Lett. 72, 1368 (1994) Using this technique, measurements of the Knight shift (K_S)footnote S. E. Barrett et al., Phys. Rev. Lett. 74, 5112 (1995) and spin-lattice relaxation time (T_1)footnote R. Tycko et al., Science 268, 1460 (1995) have been carried out in the Quantum Hall regimes. This talk will focus on our latest measurements of KS and T1 near Landau level filling ν=1, which extend our earlier results to higher magnetic fields (B=12 Tesla) and lower temperatures (T < 1 Kelvin). We will compare these results to the theoretical predictionsfootnote S. L. Sondhi et al., Phys. Rev. B 47, 16419 (1993); H. A. Fertig et al., Phys. Rev. B 50, 11018 (1994) that the charged excitations of the ν = 1 ground state are novel spin textures called skyrmions. The current status of this picture will be discussed.

  5. Multivalent Lipid--DNA Complexes: Distinct DNA Compaction Regimes

    NASA Astrophysics Data System (ADS)

    Evans, Heather M.; Ahmad, A.; Ewert, K.; Safinya, C. R.

    2004-03-01

    Cationic liposomes (CL), while intrinsically advantageous in comparison to viruses, still have limited success for gene therapy and require more study. CL spontaneously self-assemble with DNA via counterion release, forming small particles approximately 200nm in diameter. X-ray diffraction reveals CL-DNA structures that are typically a multilamellar organization of lipids with DNA intercalated between the layers. We explore the structural properties of CL-DNA complexes formed with new multivalent lipids (Ewert et al, J. Med. Chem. 2002; 45:5023) that range from 2+ to 16+. Contrary to a simple prediction for the DNA interaxial spacing d_DNA based on a geometrical space-filling model, these lipids show dramatic DNA compaction, down to d_DNA ˜ 25 ÅVariations in the membrane charge density, σ _M, lead to distinct spacing regimes. We propose that this DNA condensation is controlled by a unique locking mechanism between the DNA double helix and the large, multivalent lipid head groups. Funded by NSF DMR-0203755 and NIH GM-59288.

  6. A new regime of Pauli-spin blockade

    NASA Astrophysics Data System (ADS)

    Perron, Justin K.; Stewart, M. D.; Zimmerman, Neil M.

    2016-04-01

    Pauli-spin blockade (PSB) is a transport phenomenon in double quantum dots that allows for a type of spin to charge conversion often used to probe fundamental physics such as spin relaxation and singlet-triplet coupling. In this paper, we theoretically explore Pauli-spin blockade as a function of magnetic field B applied parallel to the substrate. In the well-studied low magnetic field regime, where PSB occurs in the forward (1, 1) → (0, 2) tunneling direction, we highlight some aspects of PSB that are not discussed in detail in existing literature, including the change in size of both bias triangles measured in the forward and reverse biasing directions as a function of B. At higher fields, we predict a crossover to "reverse PSB" in which current is blockaded in the reverse direction due to the occupation of a spin singlet as opposed to the traditional triplet blockade that occurs at low fields. The onset of reverse PSB coincides with the development of a tail like feature in the measured bias triangles and occurs when the Zeeman energy of the polarized triplet equals the exchange energy in the (0, 2) charge configuration. In Si quantum dots, these fields are experimentally accessible; thus, this work suggests a way to observe a crossover in magnetic field to qualitatively different behavior.

  7. Periodic Partial Extinction Regime in Acoustically Coupled Fuel Droplet Combustion

    NASA Astrophysics Data System (ADS)

    Plascencia Quiroz, Miguel; Bennewitz, John; Vargas, Andres; Sim, Hyung Sub; Smith, Owen; Karagozian, Ann

    2016-11-01

    This experimental study investigates the response of burning liquid fuel droplets exposed to standing acoustic waves, extending prior studies quantifying mean and temporal flame response to moderate acoustic excitation. This investigation explores alternative fuels exposed to a range of acoustic forcing conditions (frequencies and amplitudes), with a focus on ethanol and JP-8. Three fundamental flame regimes are observed: sustained oscillatory combustion, periodic partial extinction and reignition (PPER), and full extinction. Phase-locked OH* chemiluminescence imaging and local temporal pressure measurements allow quantification of the combustion-acoustic coupling through the local Rayleigh index G. As expected, PPER produces negative G values, despite having clear flame oscillations. PPER is observed to occur at low-frequency, high amplitude excitation, where the acoustic time scales are large compared with kinetic/reaction times scales for diffusion-limited combustion processes. These quantitative differences in behavior are determined to depend on localized fluid mechanical strain created by the acoustic excitation as well as reaction kinetics. Supported by AFOSR Grant FA9550-15-1-0339.

  8. Operating regimes for multivalued single-electron tunneling phase logic

    NASA Astrophysics Data System (ADS)

    Li, Tan; Kiehl, Richard A.

    2003-06-01

    The dc bias range and the logic-state lifetime for multivalued single-electron tunneling phase logic are examined in computer simulations. Results for quaternary operation, which is of particular interest for compact logic circuitry, are compared with those for ternary and binary logic. Quaternary logic is shown to exhibit a rotation rule similar to binary and ternary logic and to have an optimized dc bias range of 14%, compared with 20 and 37 % for ternary and binary logic, respectively. The effects of shot noise and Nyquist noise on the logic-state lifetime are strongly influenced by the number of logic states. The ratio of tunnel resistance to series resistance required to suppress the effects of shot noise below those of Nyquist noise depends on the number of logic states. To obtain a lifetime equal to 1000 phase-locked cycles together with a maximum dc bias operating range, the ratio of Coulomb energy to thermal energy Ec/kBT must be 400, 1650, and 2830 for two, three, and four states, respectively. This corresponds to a rapid drop in the maximum operating temperature with the number of states, which can be related to an exponential dependence of lifetime on the activation energy for a thermally activated escape process. The implications of these results on the trade-offs between the operating regimes for dc bias, temperature, and junction size are discussed.

  9. Power counting regime of chiral effective field theory and beyond

    SciTech Connect

    Hall, J. M. M.; Leinweber, D. B.; Young, R. D.

    2010-08-01

    Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.

  10. Evolution of Plasmonic Metamolecule Modes in the Quantum Tunneling Regime.

    PubMed

    Scholl, Jonathan A; Garcia-Etxarri, Aitzol; Aguirregabiria, Garikoitz; Esteban, Ruben; Narayan, Tarun C; Koh, Ai Leen; Aizpurua, Javier; Dionne, Jennifer A

    2016-01-26

    Plasmonic multinanoparticle systems exhibit collective electric and magnetic resonances that are fundamental for the development of state-of-the-art optical nanoantennas, metamaterials, and surface-enhanced spectroscopy substrates. While electric dipolar modes have been investigated in both the classical and quantum realm, little attention has been given to magnetic and other "dark" modes at the smallest dimensions. Here, we study the collective electric, magnetic, and dark modes of colloidally synthesized silver nanosphere trimers with varying interparticle separation using scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). This technique enables direct visualization and spatially selective excitation of individual trimers, as well as manipulation of the interparticle distance into the subnanometer regime with the electron beam. Our experiments reveal that bonding electric and magnetic modes are significantly impacted by quantum effects, exhibiting a relative blueshift and reduced EELS amplitude compared to classical predictions. In contrast, the trimer's electric dark mode is not affected by quantum tunneling for even Ångström-scale interparticle separations. We employ a quantum-corrected model to simulate the effect of electron tunneling in the trimer which shows excellent agreement with experimental results. This understanding of classical and quantum-influenced hybridized modes may impact the development of future quantum plasmonic materials and devices, including Fano-like molecular sensors and quantum metamaterials.

  11. Two dynamic regimes in the human gut microbiome

    PubMed Central

    Smillie, Chris S.; Alm, Eric J.

    2017-01-01

    The gut microbiome is a dynamic system that changes with host development, health, behavior, diet, and microbe-microbe interactions. Prior work on gut microbial time series has largely focused on autoregressive models (e.g. Lotka-Volterra). However, we show that most of the variance in microbial time series is non-autoregressive. In addition, we show how community state-clustering is flawed when it comes to characterizing within-host dynamics and that more continuous methods are required. Most organisms exhibited stable, mean-reverting behavior suggestive of fixed carrying capacities and abundant taxa were largely shared across individuals. This mean-reverting behavior allowed us to apply sparse vector autoregression (sVAR)—a multivariate method developed for econometrics—to model the autoregressive component of gut community dynamics. We find a strong phylogenetic signal in the non-autoregressive co-variance from our sVAR model residuals, which suggests niche filtering. We show how changes in diet are also non-autoregressive and that Operational Taxonomic Units strongly correlated with dietary variables have much less of an autoregressive component to their variance, which suggests that diet is a major driver of microbial dynamics. Autoregressive variance appears to be driven by multi-day recovery from frequent facultative anaerobe blooms, which may be driven by fluctuations in luminal redox. Overall, we identify two dynamic regimes within the human gut microbiota: one likely driven by external environmental fluctuations, and the other by internal processes. PMID:28222117

  12. Rehabilitation regimes based upon psychophysical studies of prosthetic vision

    NASA Astrophysics Data System (ADS)

    Chen, S. C.; Suaning, G. J.; Morley, J. W.; Lovell, N. H.

    2009-06-01

    Human trials of prototype visual prostheses have successfully elicited visual percepts (phosphenes) in the visual field of implant recipients blinded through retinitis pigmentosa and age-related macular degeneration. Researchers are progressing rapidly towards a device that utilizes individual phosphenes as the elementary building blocks to compose a visual scene. This form of prosthetic vision is expected, in the near term, to have low resolution, large inter-phosphene gaps, distorted spatial distribution of phosphenes, restricted field of view, an eccentrically located phosphene field and limited number of expressible luminance levels. In order to fully realize the potential of these devices, there needs to be a training and rehabilitation program which aims to assist the prosthesis recipients to understand what they are seeing, and also to adapt their viewing habits to optimize the performance of the device. Based on the literature of psychophysical studies in simulated and real prosthetic vision, this paper proposes a comprehensive, theoretical training regime for a prosthesis recipient: visual search, visual acuity, reading, face/object recognition, hand-eye coordination and navigation. The aim of these tasks is to train the recipients to conduct visual scanning, eccentric viewing and reading, discerning low-contrast visual information, and coordinating bodily actions for visual-guided tasks under prosthetic vision. These skills have been identified as playing an important role in making prosthetic vision functional for the daily activities of their recipients.

  13. Power counting regime of chiral effective field theory and beyond.

    SciTech Connect

    Hall, J. M.M.; Leinweber, D. B.; Young, R. D.; Physics; Univ. of Adelaide

    2010-08-10

    Chiral effective field theory ({chi}EFT) complements numerical simulations of quantum chromodynamics (QCD) on a space-time lattice. It provides a model-independent formalism for connecting lattice simulation results at finite volume and a variety of quark masses to the physical world. The asymptotic nature of the chiral expansion places the focus on the first few terms of the expansion. Thus, knowledge of the power-counting regime (PCR) of {chi}EFT, where higher-order terms of the expansion may be regarded as negligible, is as important as knowledge of the expansion itself. Through the consideration of a variety of renormalization schemes and associated parameters, techniques to identify the PCR where results are independent of the renormalization scheme are established. The nucleon mass is considered as a benchmark for illustrating this general approach. Because the PCR is small, the numerical simulation results are also examined to search for the possible presence of an intrinsic scale which may be used in a nonperturbative manner to describe lattice simulation results outside of the PCR. Positive results that improve on the current optimistic application of chiral perturbation theory ({chi}PT) beyond the PCR are reported.

  14. Tunneling and percolation transport regimes in segregated composites.

    PubMed

    Nigro, B; Grimaldi, C; Ryser, P

    2012-01-01

    We consider the problem of electron transport in segregated conductor-insulator composites in which the conducting particles are connected to all others via tunneling conductances, thus forming a global tunneling-connected resistor network. Segregation is induced by the presence of large insulating particles, which forbid the much smaller conducting fillers from occupying uniformly the three-dimensional volume of the composite. By considering both colloidal-like and granular-like dispersions of the conducting phase, modeled respectively by dispersions in the continuum and in the lattice, we evaluate by Monte Carlo simulations the effect of segregation on the composite conductivity σ, and show that an effective-medium theory applied to the tunneling network reproduces accurately the Monte Carlo results. The theory clarifies that the main effect of segregation in the continuum is that of reducing the mean interparticle distances, leading to a strong enhancement of the conductivity. In the lattice-segregation case the conductivity enhancement is instead given by the lowering of the percolation thresholds for first and beyond-first nearest neighbors. Our results generalize to segregated composites the tunneling-based description of both the percolation and hopping regimes introduced previously for homogeneous disordered systems.

  15. Progress in LHCD: a tool for advanced regimes on ITER

    NASA Astrophysics Data System (ADS)

    Tuccillo, A. A.; Barbato, E.; Bae, Y. S.; Becoulet, A.; Bernabei, S.; Bibet, P.; Calabrò, G.; Cardinali, A.; Castaldo, C.; Cesario, R.; Cho, M. H.; Cirant, S.; Crisanti, F.; Ekedahl, A.; Eriksson, L.-G.; Farina, D.; Giruzzi, G.; Goniche, M.; Granucci, G.; Ide, S.; Imbeaux, F.; Karttunen, S.; Litaudon, X.; Mailloux, J.; Mazon, D.; Mirizzi, F.; Moreau, D.; Nowak, S.; Namkung, W.; Panaccione, L.; Pericoli-Ridolfini, V.; Peysson, Y.; Petrzilka, V.; Podda, S.; Rantamaki, K.; Santini, F.; Saveliev, A.; Schneider, M.; Sozzi, C.; Suzuki, T.

    2005-12-01

    The recent success in coupling lower hybrid (LH) waves in high performance plasmas at JET together with the first demonstration on FTU of the coupling capability of the new passive active multijunction launcher removed major concerns on the possibility of using LH on ITER. LH exhibits the highest experimental current drive (CD) efficiency at low plasma temperature thus making it the natural candidate for off-axis CD on ITER where current profile control will help in maintaining burning performance on a long-time scale. We review recent LH results: long internal transport barrier obtained in JET with current profile sustained and controlled by LH acting under real time feedback together with first LH control of flat q-profile in a hybrid regime with Te ~ Ti. Minutes long fully non-inductive LH driven discharges on Tore Supra (TS). High CD efficiency with electron cyclotron in synergy with LH obtained in FTU and TS opening the possibility of interesting scenarii on ITER for MHD stabilization. Preliminary results of LH modelling for ITER are also reported. A brief overview of ITER LH system is reported together with some indication of new coming LH experiments, in particular KSTAR where CW klystrons at the foreseen ITER frequency of 5 GHz are being developed.

  16. Regime-based evaluation of cloudiness in CMIP5 models

    NASA Astrophysics Data System (ADS)

    Jin, Daeho; Oreopoulos, Lazaros; Lee, Dongmin

    2017-01-01

    The concept of cloud regimes (CRs) is used to develop a framework for evaluating the cloudiness of 12 fifth Coupled Model Intercomparison Project (CMIP5) models. Reference CRs come from existing global International Satellite Cloud Climatology Project (ISCCP) weather states. The evaluation is made possible by the implementation in several CMIP5 models of the ISCCP simulator generating in each grid cell daily joint histograms of cloud optical thickness and cloud top pressure. Model performance is assessed with several metrics such as CR global cloud fraction (CF), CR relative frequency of occurrence (RFO), their product [long-term average total cloud amount (TCA)], cross-correlations of CR RFO maps, and a metric of resemblance between model and ISCCP CRs. In terms of CR global RFO, arguably the most fundamental metric, the models perform unsatisfactorily overall, except for CRs representing thick storm clouds. Because model CR CF is internally constrained by our method, RFO discrepancies yield also substantial TCA errors. Our results support previous findings that CMIP5 models underestimate cloudiness. The multi-model mean performs well in matching observed RFO maps for many CRs, but is still not the best for this or other metrics. When overall performance across all CRs is assessed, some models, despite shortcomings, apparently outperform Moderate Resolution Imaging Spectroradiometer cloud observations evaluated against ISCCP like another model output. Lastly, contrasting cloud simulation performance against each model's equilibrium climate sensitivity in order to gain insight on whether good cloud simulation pairs with particular values of this parameter, yields no clear conclusions.

  17. Effective Potential Theory for Transport Coefficients across Coupling Regimes

    NASA Astrophysics Data System (ADS)

    Baalrud, Scott D.

    2013-10-01

    Plasmas in several modern experiments, including dense, ultracold and dusty plasmas, can reach strong coupling where the Coulomb potential energy of interacting particles exceeds their average kinetic energy. Understanding how the many-body physics of correlations affects plasma transport properties in this regime is interesting both from a basic physics standpoint and as a practical matter. Transport coefficients are essential input required for accurate hydrodynamic modeling of these systems, which can include weakly coupled and strongly coupled components simultaneously. We discuss a physically motivated extension of plasma transport theory that is computationally efficient and versatile enough that it can be applied to essentially any transport property. Like conventional plasma theories, ours is based on a binary collision picture, but where particles interact via an effective potential that accounts for average affects of the intervening medium. This includes both correlations and screening. Hypernetted chain (HNC) theory, which is a well-established approximation for the pair correlation function, is used to derive the effective potential. The theory is shown to compare well with ion velocity relaxation in an ultracold plasma experiment, as well as classical molecular dynamics simulations of temperature relaxation in electron-ion plasmas, and diffusion in both one-component plasmas and ionic mixtures. This research was conducted in collaboration with Jerome Daligault and was supported by a Richard P. Feynman Postdoctoral Fellowship and the LDRD program at Los Alamos National Laboratory.

  18. Emergent Phototactic Responses of Cyanobacteria under Complex Light Regimes

    PubMed Central

    Chau, Rosanna Man Wah

    2017-01-01

    ABSTRACT Environmental cues can stimulate a variety of single-cell responses, as well as collective behaviors that emerge within a bacterial community. These responses require signal integration and transduction, which can occur on a variety of time scales and often involve feedback between processes, for example, between growth and motility. Here, we investigate the dynamics of responses of the phototactic, unicellular cyanobacterium Synechocystis sp. PCC6803 to complex light inputs that simulate the natural environments that cells typically encounter. We quantified single-cell motility characteristics in response to light of different wavelengths and intensities. We found that red and green light primarily affected motility bias rather than speed, while blue light inhibited motility altogether. When light signals were simultaneously presented from different directions, cells exhibited phototaxis along the vector sum of the light directions, indicating that cells can sense and combine multiple signals into an integrated motility response. Under a combination of antagonistic light signal regimes (phototaxis-promoting green light and phototaxis-inhibiting blue light), the ensuing bias was continuously tuned by competition between the wavelengths, and the community response was dependent on both bias and cell growth. The phototactic dynamics upon a rapid light shift revealed a wavelength dependence on the time scales of photoreceptor activation/deactivation. Thus, Synechocystis cells achieve exquisite integration of light inputs at the cellular scale through continuous tuning of motility, and the pattern of collective behavior depends on single-cell motility and population growth. PMID:28270586

  19. Dynamic Onset of Feynman Relation in the Phonon Regime.

    PubMed

    Li, Y; Zhu, C J; Hagley, E W; Deng, L

    2016-05-09

    The Feynman relation, a much celebrated condensed matter physics gemstone for more than 70 years, predicts that the density excitation spectrum and structure factor of a condensed Bosonic system in the phonon regime drops linear and continuously to zero. Until now, this widely accepted monotonic excitation energy drop as the function of reduced quasi-momentum has never been challenged in a spin-preserving process. We show rigorously that in a light-matter wave-mixing process in a Bosonic quantum gas, an optical-dipole potential arising from the internally-generated field can profoundly alter the Feynman relation and result in a new dynamic relation that exhibits an astonishing non-Feynman-like onset and cut-off in the excitation spectrum of the ground state energy of spin-preserving processes. This is the first time that a nonlinear optical process is shown to actively and significantly alter the density excitation response of a quantum gas. Indeed, this dynamic relation with a non-Feynman onset and cut-off has no correspondence in either nonlinear optics of a normal gas or a phonon-based condensed matter Bogoliubov theory.

  20. Metallic Strip Gratings in the Sub-Subwavelength Regime

    PubMed Central

    Savin, Adriana; Steigmann, Rozina; Bruma, Alina

    2014-01-01

    Metallic strip gratings (MSG) have different applications, ranging from printed circuits to filters in microwave domains. When they are under the influence of an electromagnetic field, evanescent and/or abnormal modes appear in the region between the traces, their utilization leading to the development of new electromagnetic nondestructive evaluation methods. This paper studies the behavior of MSGs in the sub-subwavelength regime when they are excited with TEz or TMz polarized plane waves and the slits are filled with different dielectrics. The appearance of propagating, evanescent and abnormal modes is emphasized using an electromagnetic sensor with metamaterials lens realized with two conical Swiss rolls, which allows the extraction of the information carried by the guided evanescent waves. The evanescent waves, manipulated by the electromagnetic sensor with metamaterial lenses, improve the electromagnetic images so that a better spatial resolution is obtained, exceeding the limit imposed by diffraction. Their theoretical and experimental confirmation opens the perspective for development of new types of sensors working in radio and microwave frequencies. PMID:24999714